# L0rdGwyn's DIY Audio



## L0rdGwyn (Sep 27, 2020)

**I originally created this thread for a single amplifier project.  I am planning to pursue others, this thread will now encompass all things DIY audio *

Hey Head-Fiers,

I have decided to take on a big project, a full-sized, from scratch, single-ended triode headphone/speaker amp.  Prior to this build, I have built/modded after-market Grado-style headphones, built my own headphone cables and interconnects, completed Bottlehead kits, restored a tube tester, and made circuit modifications to my Glenn OTL.  I have learned a great deal along the way, but this will be my first time building an entire amplifier.

The amp will be heavily inspired from the SET builds done by @2359glenn and I will be leaning on him for his expert opinion as I move along, he has graciously agreed to help me out!  Doing a lot of reading on circuit design and practical building considerations as well.

While the topology is common, the tubes that will be utilized in this amp are not.  This will be the first time these tubes have been used in a SET headphone amp, but from my listening tests, I doubt it will be the last.  This family of tubes are mostly pre-WWII 4V/1A filament medium to high μ preamp tubes.

Here is the star of the show, the Marconi MH4.




While the input stage will be optimized for the MH4, it has numerous near-equivalents that will be compatible and also sound fantastic, here are a few I have in my collection with more to come:



In terms of outputs, it will utilize EL34 pentodes as well as KT66 and 6L6G beam tetrodes, all run as strapped triodes.  There is a possibility of using other tubes as well (KT77, EL33, KT63), still working through that process.  Mains and output transformers will be Lundahl.

The power supply design is a work-in-progress, but it will have a c̶e̶n̶t̶e̶r̶-̶t̶a̶p̶p̶p̶e̶d̶ ̶m̶a̶i̶n̶s̶ ̶t̶r̶a̶n̶f̶o̶r̶m̶e̶r̶ ̶f̶o̶r̶ ̶u̶s̶e̶ ̶o̶f̶ ̶a̶ ̶f̶u̶l̶l̶-̶w̶a̶v̶e̶ ̶t̶u̶b̶e̶ ̶r̶e̶c̶t̶i̶f̶i̶e̶r̶..  *Update: *while building the schematic, I discovered the original planned transformer did not have a sufficient current rating for the output tubes, so a non-center-tapped transformer will be used with a diode-tube hybrid bridge rectifier.  The amp will be able to take rectifier tubes of two different bases and filament voltage ratings in a single socket, 5V UX4 (e.g., 5Z3, 80, 274A) and European 4V B4 (e.g., U18/20, RGN2504, 45-IU, NU12).

Here are some of the rectifier and power tubes I have in my collection already, more to be added as the amp is constructed:



Part selection and planning has already been taking place for a month or two.  The amp will use teflon Yamamoto sockets, including the dual UX4-B4 rectifier socket.  The chassis is currently being built by Landfall Systems, it will be anodized in gold.  A diagram of the chassis layout is included below:





Overall, this will be a long process.  Currently in the design phase and drafting the schematic while simultaneously doing some part selection.  As of right now, I plan to prototype and test the amp before doing the final build in the chassis.  This will allow me to make modifications and optimize the circuit.  Once I have the test equipment, I will source inexpensive parts for the prototype before purchasing boutique components.  Here are some of the parts I am planning to use, some are on hand already:

Goldpoint stepped attenuator
Yamamoto teflon sockets
Lundahl mains and output transformers
Audio Note Standard and Kaisei electrolytic capacitors (power supply, cathode resistor bypass)
Jupiter copper foil coupling capacitors
Kiwame carbon film and Riken carbon composition resistors
WBT-0201 RCA sockets
DH Labs hook up wire (will likely limit this to signal path only, +/- on the idea right now)

I'll leave it there for now and update as I go along!  Very excited to be working on this project and planning to set myself up for future amp builds down the road.  Tube audio is something I have become very passionate about, time to finally unleash it


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## L0rdGwyn (Jan 10, 2020)

Since I first made this thread three days ago, with no exaggeration, I have been at it sun up to sun down working on the schematic for this amp.  I have consumed an unholy amount of information in that time, if I wasn't so excited about this I would never would have been able to keep up the pace.

But I am happy to say the power supply and amplifier schematics are complete.  Big thanks again to @2359glenn for signing off on my designs.

I'll just discuss the power supply in this post.  This gave me the biggest headache, but I finally feel it is right.  Here is the schematic:



*Transformer:*
The transformer will be a 350V 630mA Lundahl LL1650.

*High-voltage B+:*
Rectifier will be a hybrid HEXFRED diode-tube bridge.  Rectifer tubes will vary, but the bottom line is they will be able to supply around 250mA max to the tube plates.  The filter will be a capacitor input C-L-C-L-C design with an additional R-C filter for the driver tubes.  The resevoir capacitor will be an Auricap XO+ 2.2uF 600V, this cap is responsible for driving the rest of the supply and gets "topped up" by the rectifier as it is discharged.  The two L-C filters following the resevoir cap are responsible for smoothing the rectified DC before it is send out to the plates of the power tubes.  The capacitors will all be Audio Note Kaisei electrolytics.  The R-C filter before the driver tubes serves the same purpose, but also drops the B+ voltage sent to the plates of the driver tubes by ~20V.  An Audio Note Kaisei capacitor will be used here as well.

This supply was iteratively modeled in Power Supply Designer II software, a free tool that is incredibly useful for modeling supplies, used by many amp building hobbyists.  With this setup, the model indicates I will be getting 13mV of ripple on the power tube plates and 0.34mV of ripple on the driver tube plates.  Capacitor values may change in the final design after prototyping, so the ripple may go up or down a bit.

Here is the circuit in the model and a graph of the output voltage at B+ and B++.  Note that the rectifier is a full-wave tube with a center-tapped transformer.  The software cannot do a diode-tube hybrid rectifier, but the end result is the same.





*Filaments:*
The power tubes will get 6.6VAC to the filaments without any fancy filtering or regulation.

Because the MH4 driver tubes take 4V 1A to the filaments, the incoming 6.6VAC has to be dropped.  In addition, for the quietest possible input stage, the incoming current will be rectified and smoothed to DC.  After going over a few different solutions, I decided I am going to use Pete Millett's (a well known tube DIYer) regulated DC filament supply, here:



http://www.pmillett.com/DC_filament_supply.htm

This board was originally designed and intended for use for directly-heated triode tubes (i.e., tubes where the filament is directly connected to the cathode, so any AC hum can be heard on in the output signal), which require DC on the filaments for audio use.  The driver tubes for my amp are indirectly heated, so not prone to the same hum of directly-heated triodes, but it will serve the same purpose, a silent filament supply.

Total cost for the printed boards from his eBay shop and the parts from Mouser is $80.  The circuit includes a variable resistor to fine tune the output voltage to the needs of the tube filaments.

Think that's it for the power supply, now on to the amp circuit!

**Update 1/7/2020:* through iterative reevaluations of the amplifier design, the power supply has been altered, please see this post for the most recent build, the above information is no longer up-to-date.  Also, the amplifier will no longer feature direct current on the driver tube heaters.

https://www.head-fi.org/threads/l0rdgwyns-single-ended-triode-diy-amp.921105/page-5#post-15403852


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## L0rdGwyn (Jan 10, 2020)

Now the amplifier circuit.  Here is the schematic:



*Potentiometer:*
This will be a 25K Goldpoint stepped attenuator.  The volume pot acts as a voltage divider between the driver tube grid and ground.  That means turning up the volume pot will increase the resistance between the input signal and ground, so more signal is sent to the driver tube grid, resulting in increased signal and volume.  Turning down the volume pot decreases the resistance between the input signal and ground, so more of your input signal goes to ground and your volume decreases.  With the volume set to 0, all of the signal is lost to ground.

*Input stage:*
It will feature my new favorite tube, the MH4 and its cousins.  It will be cathode biased, also known as auto-biased.  Without getting into the nitty gritty details, this will alow the tube to find its own bias point based on the value of the cathode bias resistor and allows the tube to maintain that bias point as it ages.  This biasing scheme requires a cathode resistor bypass capacitor, which acts as a high-pass filter, among other things.  The value is appropriately high to allow all audible low frequencies to pass.  This will be an Audio Note Kaisei electrolytic.  The 56kohm resistor on the plate is known as, you guessed it, the plate resistor  this acts as the load for the tube and is usually 2-3 times the internal resistance of the tube.  From experimenting with GOTL modifications, I have found that changing this resistor has a very audible effect on the sound.  I will be using discontinued Japanese Riken carbon composition resistors on the MH4 plates, considered by many to be the best sounding resistors made.

I am going to briefly explain how the bias point is chosen for the input tube using "load lines".  Below is the current vs. voltage operating characteristics of the tube with the load line drawn in red.  The far right point of the line represents the maximum voltage across the tube, equal to the high voltage B++.  The far left line point represents the current flowing across the 56kohm plate resistor with zero voltage across the tube.  This load line tells us the plate current for any given voltage on the tube and our bias point will be on this line.  The curved lines on the graph represent the grid voltage, and the grid voltage at our desired bias point will determine the value of our cathode bias resistor.

For the input tube, we want to choose a _linear_ point on the load line, meaning we want to choose a point on the load line where the distance to the next nearest grid voltage line on both sides is about equal.  The tube will swing along the line right to left with the positive and negative AC input signal.

I chose to bias the MH4 with -3V on the grid, which corresponds with 145V on the plate, a plate current of about 1.75mA, and a cathode bias resistor of 2kohm.  This is the green dot on the load line.  I may adjust this in the final build to a grid voltage of -2.5 or -2 depending on the distortion measurements.



The input stage is coupled to the output stage via a Jupiter copper foil 0.47uF 630VC capacitor.  This allows only the AC output signal to pass and blocks the 145V DC from the MH4 plate.  If that DC current reached the grid of the next tube, it would "red plate" and burn up!!!

**Update 1/7/2020: *in the final design, the driver tubes will now be cascode constant current source (CCS) loaded rather than using a resistive load.  The method of drawing load lines described above only pertains to using a resistive load, not a CCS.

*Output stage:*
The output stage of this amp will feature various pentode and beam tetrode power tubes as strapped triodes.  This includes EL34, KT66, 6L6G, KT77, and the possibility of others.  A Goldpoint selector switch will be used to change the cathode bias resistor for the optimal bias point for each tube.  The switch has six possible positions, so I can add resistors for two more tubes later if I please  in reality, these tubes could probably all be used with the bias optimized for one tube and no switch.  Rarely are headphones going to require enough power to push the tubes to significant distortion at an unoptimal bias point, this is much more important for higher power uses like speakers.

But screw that!!!  I will optimize the bias of each tube and choose the appropriate resistor.  Audio Note Kaisei will be used again for the bypass capacitor.  For strapped triode mode, the screen grid is connected to the plate via a 100ohm resistor and the suppressor grid is connected directly to the cathode (in beam tetrodes, this is an internal connection as there is no true suppressor grid, the suppressor grid is actually generated by the beam of electrons flowing through the tube!!! Very cool, look it up).

Using our load lines again, we can choose the bias point for the power tubes.  However, it is a bit of a different process since we do not have a plate resistor acting as the load for the tube, the AC load is the impedance of the primary winding of the output transformer, 4.6kohm.  Also, the primary winding has a very low DC resistance, so the plate of the power tube essentially sees the entire 250VDC B+.

Like the input tube, we can draw our load line with the full B+ voltage on the right and the maximum plate current on the left, the blue line on the graph.  But our true operating point is not on this line!  We cannot choose the plate voltage since there is no plate resistor, the plate voltage is FIXED as the B+ of 250V.  If we operated the tube here, the bias point would be the far right of the load line, there would be no place for half of our input signal to go and it would be lost.

So, we have to draw additional load lines at the same slope as our initial line, up to but not exceeding the large curve at the top of the graph.  This is the maximum plate dissipation of the tube.  If we exceed this line with our operating point on the load line, the tube will melt.  We want to choose a load line that is below the maximum plate dissipation and allows for maximal left and right excursion along the load line.  The upper limit on the right side of the line this time around is where the grid curves start to get _squished_, which will cause significant 2nd harmonic distortion.  The leftmost limit is the grid voltage where the grid will begin to draw current, which is BAD.  By maximizing the equal left to right swing across the load line, which are getting the most peak-to-peak voltage out of the power stage, which means more POWER!

I will have to redo my bias points since I made changes to the power supply, but for the sake of example, here is where I might choose the bias point of the EL34, green dot on the red load line.  This point represents 250V on the plate, 85mA plate current, a grid voltage of about -14V, and a cathode bias resistor value of ~165ohm.  This will be done for each power tube to find the correct cathode bias resistor value for the switch.

Doing some quick math, at this bias point, this gives us roughly a peak-to-peak voltage of 220V, which is about 77VRMS, which means about 1.3W of undistorted output power.  If I were to push the output tubes closer to the max plate dissipation, could get something like 2.5W out of them with this output transformer.  Either way, it is way overkill.  The tubes will live a longer life at this bias point and a power output of 1.3W.



Okay, wrapping this up, the output transformer will be a Lundahl LL2765 with a 4.6kohm primary and a 32ohm secondary winding, which will be the output impedance of the amp.

Well there you have it, the amplifier circuit.  I know that is technically dense, but hopefully somewhat interesting.

Next step will be building the parts list and prototyping this bad boy!!!

BTW, this is still new to me, so please if Glenn or anyone else spots an error feel free to let me know 

**Update 1/7/2020: *for the sake of optimization and other design considerations, the output stage of the amplifier will no longer use multiple power tubes.  In fact, they have been changed altogether to the 6A5G tube, although the EL34 is a possible alternate depending on the final sound of the amp.  The above information on the output tubes is no longer up-to-date, although the method for determining the load line of an SET output stage is still relevant.  Please see this post for more information on the current power tube, the 6A5G.

https://www.head-fi.org/threads/l0rdgwyns-single-ended-triode-diy-amp.921105/page-5#post-15403852


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## maxpudding

This is exciting! Best of luck LG. Gonna follow your thread to learn more about amps


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## chrisdrop

maxpudding said:


> This is exciting! Best of luck LG. Gonna follow your thread to learn more about amps


.. what he said .
Me too!


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## BunnyNamedCraig

Very cool!!!

excited to see the progress.

Subbed btw


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## L0rdGwyn

BunnyNamedCraig said:


> Very cool!!!
> 
> excited to see the progress.
> 
> Subbed btw



Thanks!  I have been at it non-stop for days, things are coming along nicely, will have the schematic complete probably by the end of the day today, it has been approved Glenn, but I am going to make a few tweaks to the power supply.  Once it is complete, the next step will be to prototype the power supply and measure it.

Will post some updates in my reserved posts above later today, hope to make them somewhat educational on choosing bias points, tube linearity, etc. but at a high level, no maths


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## BunnyNamedCraig

L0rdGwyn said:


> Thanks!  I have been at it non-stop for days, things are coming along nicely, will have the schematic complete probably by the end of the day today, it has been approved Glenn, but I am going to make a few tweaks to the power supply.  Once it is complete, the next step will be to prototype the power supply and measure it.
> 
> Will post some updates in my reserved posts above later today, hope to make them somewhat educational on choosing bias points, tube linearity, etc. but at a high level, no maths


Nice! I hate math!!!


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## L0rdGwyn

Hey people - just updated my posts above with schematics and explanation of the circuit.  I learned this over the past three days, non-stop, has been a blast but my brain is mush.

Sort of techncially dense but I hope it interests people!  Next I will be getting parts together to prototype and test the power supply.


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## L0rdGwyn (Dec 15, 2019)

One more thing, got these beautiful Philips E424N tubes in the mail yesterday.  They are MH4 near equivalents and will be used as drivers in the amp, similar to what Glenn is using in his preamp.


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## SonicTrance

L0rdGwyn said:


> Hey people - just updated my posts above with schematics and explanation of the circuit.  I learned this over the past three days, non-stop, has been a blast but my brain is mush.
> 
> Sort of techncially dense but I hope it interests people!  Next I will be getting parts together to prototype and test the power supply.


Congrats on getting in to the hobby of building amps! It's very fun indeed! 

Schems look good. I was wondering about the high W grid stoppers though? There's no need for more than 1W, even lower is fine. I recommend to learn LT spice when you have many hours left over, lol. It's a great tool to use and it's free.

I'd run those MH4 tubes on at least 3 mA, preferably 4 mA, to get over the "knee" in the grid curves. There you have the best linearity. So it'll sound the best


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## L0rdGwyn (Dec 15, 2019)

SonicTrance said:


> Congrats on getting in to the hobby of building amps! It's very fun indeed!
> 
> Schems look good. I was wondering about the high W grid stoppers though? There's no need for more than 1W, even lower is fine. I recommend to learn LT spice when you have many hours left over, lol. It's a great tool to use and it's free.
> 
> I'd run those MH4 tubes on at least 3 mA, preferably 4 mA, to get over the "knee" in the grid curves. There you have the best linearity. So it'll sound the best



Hey thanks!  The high wattage of the grid stoppers is unnecessary, it's only because I want to use a specific brand of resistor and they are only made in 2W and 5W  just one of those neurotic things.

I started messing around with LTSpice the other day, but once I got started I realized the learning curve was going to require a lot of time, so I shelved it.  Definitely going to try it again when I have time!

And I agree with you on the MH4, I was actually thinking about this earlier today.  Will probably increase the value of the resevoir cap and/or drop the impedance on the R-C filter to get a higher B+ to work with.  I have a bunch of different cap and resistor values on my shopping list so I can optimize all this stuff when I build out the power supply.

Edit: wait I take it back, forgot the stoppers need to be non-inductive.  I'm gonna change them to 1/2W carbon comps.


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## 2359glenn

Yes the grid stoppers should be carbon composition.  No real current going through them so won't be making noise


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## L0rdGwyn (Dec 15, 2019)

I think I might have to look into having some custom chokes wound from Heyboer @2359glenn .  To get the MH4 up to >3mA on the plate like @SonicTrance suggested, need more B+ and I'm losing too much voltage on the chokes with the current draw of the power tubes.  Could go to 4H 65ohm 225mA but not great losing the filtering, think I end up with 14mV ripple on the power tubes.

Running everything at a higher voltage will increase the linearity of the MH4, but the linearity of the EL34 bias point will suffer.  Going to have to find a balance, but will favor the MH4.

Man, you change one thing in this business and everything else changes too!  Tricky tricky.

Edit: I might have to bite the bullett and lower my plate resistor.  Was hoping to keep 56kohm since I have these Riken resistors, but the tubes will be biased better at 30-40kohm.


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## mordy

HiLG,
Very interesting to read about all the particulars in building your amp, but not having any electronic background I can't say that I understand much about what you are describing.
Apart from the tubes you are using, is this a conventional type tube amp or an innovative design?


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## L0rdGwyn

mordy said:


> HiLG,
> Very interesting to read about all the particulars in building your amp, but not having any electronic background I can't say that I understand much about what you are describing.
> Apart from the tubes you are using, is this a conventional type tube amp or an innovative design?



Hey mordy - I'm sorry, it is pretty technical, maybe at some point I can try to make it a little more easy to understand.

This is a conventional design, a single-ended triode (SET) topology, also known as class A.  The aspects of it that are somewhat unconventional are the choice of driver tubes and the cathode bias resistor switch for multiple types of output tubes being run as strapped triodes rather than pentodes/beam tetrodes.  But overall, SET is a very well-known topology, good for a beginner


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## 2359glenn (Dec 15, 2019)

L0rdGwyn said:


> I think I might have to look into having some custom chokes wound from Heyboer @2359glenn .  To get the MH4 up to >3mA on the plate like @SonicTrance suggested, need more B+ and I'm losing too much voltage on the chokes with the current draw of the power tubes.  Could go to 4H 65ohm 225mA but not great losing the filtering, think I end up with 14mV ripple on the power tubes.
> 
> Running everything at a higher voltage will increase the linearity of the MH4, but the linearity of the EL34 bias point will suffer.  Going to have to find a balance, but will favor the MH4.
> 
> ...



I can send you a couple of nice 33K ohm Caddock resistors if you want them.
You are finding out everything is a compromise you have to do what affects the sound the least.  I wouldn't reduce filtering in the power supply.
You could try using a constant current source for the plate load on the MH4.  In my EL3N amp I use a CCS on the plate of the EL3N driver.
The same problem not enough B+ voltage plus the CCS rejects power supply noise. You can eliminate the last R-C in the power supply.
You can get a cascode CCS kit for cheap from K&K audio for $17.
That is what I use in the EL3N amp.
It is two more circuit boards with heat sink that you will have to squeeze under the chassis.


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## L0rdGwyn (Dec 15, 2019)

2359glenn said:


> I can send you a couple of nice 33K ohm Caddock resistors if you want them.
> You are finding out everything is a compromise you have to do what affects the sound the least.  I wouldn't reduce filtering in the power supply.
> You could try using a constant current source for the plate load on the MH4.  In my EL3N amp I use a CCS on the plate of the EL3N driver.
> The same problem not enough B+ voltage plus the CCS rejects power supply noise. You can eliminate the last R-C in the power supply.
> ...



And here I was thinking I was done with the design phase.  I think I could get away with a plate resistor load if I run the input and output tubes around 300V, would get me around 3.6mA on the MH4 plate with a 36kohm load.  Let me look into using a CCS load, those boards are small I could probably fit them in too, it's a decent sized chassis.  Might as well take my time and get this right.

Kind of ironic, these tubes are from the 1930s and yet they might have PCBs attached to nearly every pin lol.

Edit: I think I am going to do it, after I make sure I can fit two sets of boards.

Great linearity with a 6mA CCS.  Max plate dissipation of the MH4 is 2.5W, should be no problem.  Here is the E424N load line too at 6mA.


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## 2359glenn

Hi Keenan

Now you learned something!!  Not so easy to get it right. CCS are awesome and sound great.
Now you have a very old tube with transistors attached to the plate the horrors .
I know of no commercial amps that use CCS.  Other then DIY only @SonicTrance and me use them as far as I know.

Just letting you know the CCS has a pot to set the current plus the board has a place for a fixed resistor.
After getting the right current measure the pot and get the equivalent resistor. There is a jumper to cut to eliminate the POT.
I have had the pot go noisy on people's amps in the past.  Now I just put the resistor that has been measured for a EL3N.
You will also need a 10 ohm resistor in series to measure the current through the CCS


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## tomb

There are other instances of commercial and DIY amps that use CCS.  ECP Audio has used them for years.


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## L0rdGwyn (Dec 16, 2019)

2359glenn said:


> Hi Keenan
> 
> Now you learned something!!  Not so easy to get it right. CCS are awesome and sound great.
> Now you have a very old tube with transistors attached to the plate the horrors .
> ...



Not just transistors on the plates Glenn, the filaments too!  Will I ever be forgiven?

Great, I'll order the boards when I get the transformers from K&K.  Using these and the filament supplies is going to make actually building the amp a lot easier, fewer components to mount to the walls of the chassis, don't have to worry about rectifiers and filter caps for the MH4 filaments and no RC filter.

One thing I am wondering and haven't been able to find information on yet: how does a CCS load affect the output impedance of the driver stage?  I am thinking mostly about the low pass RC filter created by the output impedance of the driver stage and the input capacitance of the output stage.  With the 56kohm plate resistors I was planning on using and the input capacitance of the EL34 (with Miller capacitance), the high frequency roll off I estimated was well over 20kHz.

How does a CCS load affect this roll-off point?

Edit: For the sake of sparing those who are subscribed from a million notifications, I am consolidating posts.  Some new tubes arrived today, these are Opta Loewe REN904.  Interesting boxes, very different from others of the time period.


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## leftside

My 1101 Audio amp uses CCS.


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## SonicTrance

L0rdGwyn said:


> I started messing around with LTSpice the other day, but once I got started I realized the learning curve was going to require a lot of time, so I shelved it. Definitely going to try it again when I have time!


Yeah, it can seem like a bit much at first but is very useful once you learn the basics. You can also simulate power supplies with LTspice and make triode curves for pentode tubes if they're not displayed in the original datasheet.



L0rdGwyn said:


> Man, you change one thing in this business and everything else changes too! Tricky tricky.


Yes! There're a lot of variables to think about!



L0rdGwyn said:


> Kind of ironic, these tubes are from the 1930s and yet they might have PCBs attached to nearly every pin lol.


Oh no! SS parts in a tube amp? Are you crazy or what?? Haha!

Kidding aside it looks great! Nice work on the load lines. To be fair though you've drawn the CCS load lines too far. They should end @ B+ minus maybe 10V or so as the CCS would need some headroom.



L0rdGwyn said:


> One thing I am wondering and haven't been able to find information on yet: how does a CCS load affect the output impedance of the driver stage?


The CCS wont affect that impedance much. The plate load is there to set a load line for the tube, that's it. You need to look at the tubes internal resistance called Rp or Ra. The Rp stated in datasheets are for a specific operating point. It fluctuates some as well. There's a way to calculate the Rp of a specific operating point by looking at the grid curves. Remember, it's all about the curves!
There's also this formula that's useful.

µ = gm * Rp


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## A2029 (Dec 16, 2019)

L0rdGwyn said:


> How does a CCS load affect this roll-off point?
> 
> Edit: wait I think I got it!  The effective output impedance of the tube will be the plate voltage divided by the constant current.  So if biased for ~175V on the plate with 6mA of constant current, it would be equivalent to a 30kohm plate resistor load.  Does that sound right?  That would be no problem for high-frequency rolloff.
> 
> To get that same bias point using a resistive load would require a B+ of about 355V, but with the CCS I can get it with the 250V I want on the power tubes  so I will be get betting a higher plate current, better frequency resposne, and noise rejection.  What a huge advantage, I am sold.



I'll point you to some reading on CCS's:
https://www.bartola.co.uk/valves/2015/08/31/ccs-not-everything-that-glitters-is-gold-part-i/
https://audioxpress.com/assets/upload/files/Sources_101_P1.pdf
https://audioxpress.com/assets/upload/files/Sources_101_P2.pdf

A good way to lower the output impedance of a CCS is to use the Mu output, instead of the plate output:
https://www.bartola.co.uk/valves/2018/04/28/hybrid-mu-follower-output-impedance/
https://www.audioasylum.com/cgi/vt.mpl?f=tubediy&m=182689&VT=T


The cascode mosfet CCS that K&K sells uses the IXTP01N100D as the top device and a DN2540 as the bottom device. Using those devices in a cascode you get massive PSRR and AC impedance (up to 500Mohm or more at low frequencies!). Take the Mu output off of that board and you get very low Zout as well


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## L0rdGwyn (Dec 16, 2019)

SonicTrance said:


> Yeah, it can seem like a bit much at first but is very useful once you learn the basics. You can also simulate power supplies with LTspice and make triode curves for pentode tubes if they're not displayed in the original datasheet.
> 
> 
> Yes! There're a lot of variables to think about!
> ...



Thanks @SonicTrance , yes the upper limit of the CCS load lines is too far, I drew them hastily so I could see the linearity lol with the CCS drawing 10V and a targeted B+ of 250-275 for my power tubes, it will only swing up to 240V or so.

Good to hear the CCS won't affect the impedance much, no reason not to use them then, we are moving forward  listed Rp for the MH4 is 11kohm so I don't think it will be an issue, but I can calculate a more accurate Rp once the final bias point is chosen.

Just did some reading, I think I understand better now.  The output impedance will be the combination of the Rp of the tube in parallel with the AC resistance of the load.  For a CCS, the AC resistance is very high, on the order of 40Mohm or more.  So taking those two values in parallel:

1/((1/11k)+(1/(40,000k)) = ~10.99k.  Which is to say, the contribution of the CCS to the output impedance is basically zero.  Your post popped up as I was writing this @A2029 , would you say this this accurate?

I need to find a crash course on LTSpice, I might take the time today.  I'm a little bit wary of the accuracy of PSUD2 for modeling my power supply.


----------



## L0rdGwyn

By the way, thank you gentlemen for your input, nice to have others to bounce this stuff off of, Glenn gets enough PMs as is without me asking him all these questions


----------



## leftside

I think @A2029 also used LTSpice extensively when designing and building my amp.


----------



## L0rdGwyn

leftside said:


> I think @A2029 also used LTSpice extensively when designing and building my amp.



I am going to have to bite the bullett and dive in, I will be happy I did later.  As eager as I am to start building and testing, it would be better to take it slow and build good models.  I have a laundry list of equipment to and parts to source anyway, it's gonna take some time.


----------



## A2029

L0rdGwyn said:


> @A2029 , would you say this this accurate?



With a CCS and a capacitor bypassed cathode resistor, Zout is approx equal to Rp at your chosen operating point.



leftside said:


> I think @A2029 also used LTSpice extensively when designing and building my amp.



I did indeed, it's well worth learning to sim how the circuitry of an amp works and to get voltages and other parameters spot on.


----------



## L0rdGwyn

A2029 said:


> With a CCS and a capacitor bypassed cathode resistor, Zout is approx equal to Rp at your chosen operating point.



Perfect.  I think this will be a very positive design change.



A2029 said:


> I did indeed, it's well worth learning to sim how the circuitry of an amp works and to get voltages and other parameters spot on.



Spot on, I like the sound of that.  Well looks like my plans for the rest of the day are decided, better make a pot of coffee


----------



## A2029

L0rdGwyn said:


> Spot on, I like the sound of that.  Well looks like my plans for the rest of the day are decided, better make a pot of coffee



This will get you up and running for LTSpice: https://www.diyaudio.com/forums/sof...ce-iv-including-ltxvii-beginner-advanced.html

For vacuum tube models, do a google search for Koren tube models and Ayumi tube models. Also here: https://www.diyaudio.com/forums/tubes-valves/243950-vacuum-tube-spice-models.html

Enjoy!!


----------



## A2029

A2029 said:


> The cascode mosfet CCS that K&K sells uses the IXTP01N100D as the top device and a DN2540 as the bottom device. Using those devices in a cascode you get massive PSRR and AC impedance (up to 500Mohm or more at low frequencies!). Take the Mu output off of that board and you get very low Zout as well



*Edit:* I should specify that you want to get the kit with the IXTP01N100D and DN2540 from K&K as it has the best performance. They also sell kits with the IXTP08N100, or only DN2540's, but those kits don't give as good of performance. IXTP01N100D or IXCP10M45S as the top device gives better performance.

And this should get you close to the needed current set resistor:


----------



## L0rdGwyn

Thanks for the link and the graph @A2029 , really appreciate it.  For 6mA, looks like ~330ohm, we'll see how close it is with the variable resistor.

Coffee is done, time for LTSpice training.  Since I will be using some pretty expensive components in this build, I had originally planned to do a mock up of the power supply and circuit using inexpensive parts (cheap electrolytics, dummy load resistors, etc.).  If LTSpice is very accurate, I wonder if I can skip that I buy the parts I will actually be using for the build.  Even if I had to change out one or two boutique passive components, would still likely cost less than getting everything I would need for the prototype.  Will have to give it some thought, opinions are welcome.


----------



## A2029

If you can input all of the critical parameters into the LTspice model, the end product build should reflect what is simulated to a large degree. I usually don't breadboard my builds as long as I'm confident in the schematic and modeling. One of the main things to keep in mind is the engineers perspective: Add a safety margin on to any part rating. If you calculate a resistor will be dissipating 1 watt, get a 2-3 watt resistor minimum. If a capacitor is expected to see a max of 15V, get a capacitor rated 20+ volts, etc. Also, use diodes to protect against reverse voltage.


----------



## whirlwind

L0rdGwyn said:


> Now the amplifier circuit.  Here is the schematic:
> 
> 
> 
> ...





You sir, have been busy!

Take your time and have fun with it.

This is going to be a nice thread.


----------



## L0rdGwyn (Dec 16, 2019)

A2029 said:


> If you can input all of the critical parameters into the LTspice model, the end product build should reflect what is simulated to a large degree. I usually don't breadboard my builds as long as I'm confident in the schematic and modeling. One of the main things to keep in mind is the engineers perspective: Add a safety margin on to any part rating. If you calculate a resistor will be dissipating 1 watt, get a 2-3 watt resistor minimum. If a capacitor is expected to see a max of 15V, get a capacitor rated 20+ volts, etc. Also, use diodes to protect against reverse voltage.



Thanks, everything in the schematics has been overspec'd with that goal in mind.  If I could avoid breadboarding and instead devote that time to developing a very accurate LTSpice model, that would definitely be preferrable.  I am going to work toward that goal.

Edit: wow just found out someone created a MH4 LTSpice model, I figured there was no chance of that.  Nice!!!


----------



## L0rdGwyn (Dec 17, 2019)

Think I've reached a good stopping point on LTSpice, been at it for hours.  This program is dense, tons of functionality, just barely scratched the surface.  But the circuit is functional with a few caveats.  Not sure how to simulate a CCS, will have to work on it tomorrow, guessing I will have to build out the circuit or a similar one completely.  As a substitute, I cheated and used a magic 360VDC voltage source with a 28kohm resistive load and a 6mA bias point.  Not the same obviously, but the best I can do for now 

I was able to find a DIYer who created a Excel macro that generated transformer models based on the manufacturer specifications put into the spreadsheet.  REALLY cool and handy.  Obviously not going to be exact as they are very complicated to model accurately, just looking for an estimation.  I created a tube rectifier symbol and used a 5U4G as an appoximation to my U18/20 I will be using.  There might be a better rectifier model out there, just a placeholder for now.  Was very lucky someone created an MH4 model years ago, as well as a EL34 triode.

Here is the circuit in LTSpice.



Trying to look at a ballpark headphone listening output, used 135mV peak input, which gives a 2.14Vrms output corresponding to a power output of around 1mW into 32ohms.

THD is 0.95%.  Here is the FFT, mostly second harmonic, as you might expect.



Have to get that CCS up and running then try to optimize this thing  tons more to learn in this program.


----------



## Monsterzero

L0rdGwyn said:


> Think I've reached a good stopping point on LTSpice, been at it for hours.  This program is dense, tons of functionality, just barely scratched the surface.  But the circuit is functional with a few caveats.  Not sure how to simulate a CCS, will have to work on it tomorrow, guessing I will have to build out the circuit or a similar one completely.  As a substitute, I cheated and used a magic 360VDC voltage source with a 28kohm resistive load and a 6mA bias point.  Not the same obviously, but the best I can do for now
> 
> I was able to find a DIYer who created a Excel macro that generated transformer models based on the manufacturer specifications put into the spreadsheet.  REALLY cool and handy.  Obviously not going to be exact as they are very complicated to model accurately, just looking for an estimation.  I created a tube rectifier symbol and used a 5U4G as an appoximation to my U18/20 I will be using.  There might be a better rectifier model out there, just a placeholder for now.  Was very lucky someone created an MH4 model years ago, as well as a EL34 triode.
> 
> ...



Yo,when you can,can you please repeat that all in English?!?
Kidding aside,im really looking forward to how this amp ends up.


----------



## L0rdGwyn (Dec 17, 2019)

Monsterzero said:


> Yo,when you can,can you please repeat that all in English?!?
> Kidding aside,im really looking forward to how this amp ends up.



Haha of course!  Sorry, I have been living in technical jargon land for too long.

This program called LTSpice is used to build models of electrical circuits.  It's really handy since you can get a ton of information on the quality of the circuits you plan to build and the sound they will produce.  A whole crew of DIY tube amp builders have used the data from tube datasheets to create accurate models of specific tubes so they can be used in the program to test tube circuits.  So what I've done is built the circuit of the amp using those tube models.  It is pretty accurate as to what the final circuit is going to be as of right now, except I haven't figured out how to add a component called a "constant current source".  Constant current sources are sometimes used on the plates of vacuum tubes to allow tubes to operate at a more linear point and signifcantly reduce distortion.  I am planning to use them on the plates of the MH4 driver tubes to improve linearity and reduce distortion to get better sound out of the amp  Glenn uses them on the plates of the driver EL3N tubes in the GEL3N.  Also, the Speedball of the Bottlehead Crack + Speedball is a constant current source.  They can significantly improve the sound of an amp.

The green graph above is a plot called a Fourier transform.  With some uber math, the program takes the signal in the amp and changes it from voltage vs time to amplitude vs frequency.  Long story short, it shows you the distortion characteristics of the amp.  The biggest spike is the signal I put into the amp at 1kHz, which is the most common test tone used for looking at distortion.  The shorter prominent spikes to the right of the big spike are the harmonics, as in harmonic distortion.  In harmonic distortion, the input signal is multiplied x2, x3, x4, etc. and this gets added to the output.  Here we are just looking at the test tone of 1kHz, but the same applies for the music that goes into and out of the amp, these harmonics will be added at multiples of the input frequencies from 20Hz-20kHz.  The height of each spike gives you an idea of how much of each harmonic will be in the amp, at least at 1kHz, it will be different for different frequencies.  For instance, there might be more or less harmonic distortion at 5kHz, but people usually use 1kHz for the sake of testing.

Single-ended triode amplifiers typically have most of their distortion as second-harmonic distortion, seen on the graph as a the large second spike at 2kHz to the right of the input tone.  Second harmonic distortion is known for being easy on the ear, even pleasing to the ear, likely much of the reason we enjoy our tube amps  so the way I have the circuit set up right now, most of the distortion generated on the output of the amp will be second-harmonic.  I can now make adjustmentments and changes to the bias points of the tubes and components of the power supply in LTSpice to try and reduce the distortion and noise even further without actually having to build the amp yet, which is why LTSpice is such a powerful tool!

Anyway, hope that helps.  From now on I'll do a follow-up explanation every time I start rambling lol.  If anyone else is looking for an explanation for anything else I've posted, please let me know.


----------



## A2029

L0rdGwyn said:


> Haha of course!  Sorry, I have been living in technical jargon land for too long.
> 
> This program called LTSpice is used to build models of electrical circuits.  It's really handy since you can get a ton of information on the quality of the circuits you plan to build and the sound they will produce.  A whole crew of DIY tube amp builders have used the data from tube datasheets to create accurate models of specific tubes so they can be used in the program to test tube circuits.  So what I've done is built the circuit of the amp using those tube models.  It is pretty accurate as to what the final circuit is going to be as of right now, except I haven't figured out how to add a component called a "constant current source".  Constant current sources are sometimes used on the plates of vacuum tubes to allow tubes to operate at a more linear point and signifcantly reduce distortion.  I am planning to use them on the plates of the MH4 driver tubes to improve linearity and reduce distortion to get better sound out of the amp  Glenn uses them on the plates of the driver EL3N tubes in the GEL3N.  Also, the Speedball of the Bottlehead Crack + Speedball is a constant current source.  They can significantly improve the sound of an amp.
> 
> ...



Here ya go for the CCS model: https://easyupload.io/7n23g4


----------



## L0rdGwyn (Dec 17, 2019)

A2029 said:


> Here ya go for the CCS model: https://easyupload.io/7n23g4



You are the man!  I actually had just finished adding the models for the two MOSFETs to my library, now I can just copy and paste your schematic, thanks  I'll post some results to compare to my distortion measurements above.  Gonna try 330ohm for the current limiting resistor first based on the DN2540 plot you posted.


----------



## L0rdGwyn

Been doing some more playing around in LTSpice today, tweaking the bias points and running simulations to measure THD.

I changed the load to 300ohms since I typically listen to ZMFs or Sennheisers which cut my distortion numbers in half.  I also set up the signal input to get 1mW into 300ohms, which would be a very high listening volume.  The constant current source is up and running, putting 6mA on the plates of the MH4.  With that set and up where I have the tubes biased, the input stage by itself is putting out around 0.18% THD at 1kHz.  The floor of the distortion appears to be set by the output stage.  Messing around with the bias point of the EL34, I am getting anywhere from 0.4-0.6% THD out of the amp at 1mW into 300ohms, again mostly second harmonic.  I'm not exactly sure what would be an excellent THD figure for a single-ended triode headphone amp, but there isn't much tweaking to do other than rebiasing since it is a pretty conventional SET output stage.

One other thing I've noticed is the tube models do not seem to follow the datasheet curves, at least not exactly, or there is some other variable I am overlooking.  For instance, based on the datasheet, as I move the bias of the EL34 to what should be a more linear operating point (for example, moving to a plate voltage of 260V rather than 310V), I end up getting more distortion on the output, a difference of say 0.1%.  The model seems to think they are happier at a higher plate voltage and lower plate current, for example 320V and 47mA, whereas Mullard thinks they should be getting around 250V and 70mA.  So who do I trust, Mullard or LTSpice?  Not sure what to make of it yet.

Here is a FFT where I currently have the tubes biased in the model, also lowered the resevoir cap in the power supply to 1uF to decrease the B+ for the EL34.

MH4:
Plate current = 6mA
Plate voltage = 127V
Grid voltage = -3V

EL34:
Plate current = 70mA
Plate voltage = 285V
Grid voltage = -17V

THD = 0.48%


----------



## mordy

If I understand correctly, the LTSpice does the math once you input the numbers and then shows the distortion as a graph as well?
Is there any correlation between the values the program comes up with and how it is going to sound?
Or is it trial and error once you settle on a certain schematic and build it?


----------



## L0rdGwyn

mordy said:


> If I understand correctly, the LTSpice does the math once you input the numbers and then shows the distortion as a graph as well?
> Is there any correlation between the values the program comes up with and how it is going to sound?
> Or is it trial and error once you settle on a certain schematic and build it?



Hey mordy - yes that's right, once you build the circuit and do all of the setup, set the bias points, etc. then you can run a simulation that will tell you the distortion measurements as well as output the graph.  There is a lot more information that can be gleaned from this program, but I am only getting started 

Yes, there definitely is a correlation.  Generally less distortion is better.  If we do have distortion, even order harmonic distoriton (2, 4, 6, etc.) is better than odd order harmonics (3, 5, 7, etc.).  The distortion in this type of amp is mostly going to be second-harmonic.

The other thing we want to minimize is power supply noise.  The driver tubes will be isolated from it due to the constant current source plate load, but the power tubes will be prone.  I will likely be making some changes to the power supply components to add additional filtering.  May look into getting some custom chokes wound that will improve the performance of the power supply and have a higher maximum current rating.

There is some trial and error involved, but using the curves from the tube datasheets will get you into the ballpark for where the tube should be operating.


----------



## A2029 (Dec 17, 2019)

L0rdGwyn said:


> The model seems to think they are happier at a higher plate voltage and lower plate current, for example 320V and 47mA, whereas Mullard thinks they should be getting around 250V and 70mA.  So who do I trust, Mullard or LTSpice?  Not sure what to make of it yet.



Don't put much trust into either the datasheet or LTSpice sim. LTSpice models are usually not perfect. Tubes also vary tube by tube, and brand by brand. You can really only measure differences in distortion well when the whole circuit is put together and the amp output directly measured. In general, running higher voltage (and lower current) operating points on triode strapped pentodes/tetrodes will give you higher output power overall, but slightly greater distortion. But again, this can vary by tube...  The higher distortion at higher voltage operating points can be compensated to some degree by using output transformers with higher primary impedance (however, higher primary impedance means lower max output power, so always tradeoffs).


----------



## L0rdGwyn

A2029 said:


> Don't put much trust into either the datasheet or LTSpice sim. LTSpice models are usually not perfect. Tubes also vary tube by tube, and brand by brand. You can really only measure differences in distortion well when the whole circuit is put together and the amp output directly measured. In general, running higher voltage (and lower current) operating points on triode strapped pentodes/tetrodes will give you higher output power overall, but slightly greater distortion. But again, this can vary by tube...  The higher distortion at higher voltage operating points can be compensated to some degree by using output transformers with higher primary impedance (however, higher primary impedance means lower max output power, so always tradeoffs).



Duly noted, thanks Mischa.  Interesting I am seeing the opposite pattern, lower distortion at higher plate voltages, wonder if that is just a fault of the model.  The datasheet would seem to suggest lower distortion at lower plate voltage, so I had intended to run the power tubes around 250-275V on the plates.

In your experience, what would you say is the most useful information to pull from LTSpice before you start building?


----------



## rosgr63

Very exciting project, good luck with your build.

In my limited experience the better the power supply the better the amp.


----------



## L0rdGwyn (Dec 18, 2019)

rosgr63 said:


> Very exciting project, good luck with your build.
> 
> In my limited experience the better the power supply the better the amp.



Thanks, Stavros!  In its current iteration, I am looking at around 150 microvolts ripple on the output.  But your post has inspired me to reevaluate my design to be sure I am ticking all of the right boxes.

I have found this page to be very helpful, going to read through it again today: https://diyaudioprojects.com/Technical/Tube-Power-Supplies/

These pages are more to-the-point if anyone is interested in understanding some aspects of these power supplies:

http://www.valvewizard.co.uk/bridge.html
http://www.valvewizard.co.uk/smoothing.html


----------



## mordy

Sorry LG - when I see equations like





I just shut down.....


----------



## L0rdGwyn

mordy said:


> Sorry LG - when I see equations like
> 
> 
> 
> ...



Haha no mordy you're supposed to use the other links!!!  From Valve Wizard, they are much more digestible.  A few equations, but nothing like that.  That's why I posted those too


----------



## mordy

Ok - will give it a try.....


----------



## leftside

L0rdGwyn said:


> Thanks, Stavros!  In its current iteration, I am looking at around 150 microvolts ripple on the output.  But your post has inspired me to reevaluate my design to be sure I am ticking all of the right boxes.
> 
> I have found this page to be very helpful, going to read through it again today: https://diyaudioprojects.com/Technical/Tube-Power-Supplies/
> 
> ...


Separate power supply with umbilical cord connecting the power supply to the amp?  I have Lundahl and Hammond transformers in my power supply for the OTL amp that Mischa built. Obviously as this is an OTL amp, there are no transformers in the amp section (just caps - Clarity caps and Jupiter caps).


----------



## L0rdGwyn (Dec 18, 2019)

leftside said:


> Separate power supply with umbilical cord connecting the power supply to the amp?  I have Lundahl and Hammond transformers in my power supply for the OTL amp that Mischa built. Obviously as this is an OTL amp, there are no transformers in the amp section (just caps - Clarity caps and Jupiter caps).



I can't say the thought didn't cross my mind! But too late anyway since the chassis has been cut I like the look of the rectifier in the middle  I will be using Lundahl transformers as well with Hammond chokes as of right now, but I am probably going to look into having some custom chokes wound by Heyboer for a higher current rating, not a lot of headroom on the 200mA Hammonds I have in the circuit right now.  I looked at using a single Clarity Cap in the power supply as the resevoir capacitor, but the lowest capacitance they make is 25uF* which is too high for my tube rectifiers, so I'll be using an Auricap instead.  I guess I could think about using Clarity Caps for the filters in the power supply, but as you know they are friggin' HUGE!  I could probably fit them though, hmm...now look what you've done.


----------



## leftside

L0rdGwyn said:


> I can't say the thought didn't cross my mind! But too late anyway since the chassis has been cut I like the look of the rectifier in the middle  I will be using Lundahl transformers as well with Hammond chokes as of right now, but I am probably going to look into having some custom chokes wound by Heyboer for a higher current rating, not a lot of headroom on the 200mA Hammonds I have in the circuit right now.  I looked at using a single Clarity Cap in the power supply as the resevoir capacitor, but the lowest capacitance they make is 25uF* which is too high for my tube rectifiers, so I'll be using an Auricap instead.  I guess I could think about using Clarity Caps for the filters in the power supply, but as you know they are friggin' HUGE!  I could probably fit them though, hmm...now look what you've done.


Yes the Clarity Caps are huge. We couldn't fit them inside the amp section of my amp, so they had to go on the outside enclosed with transformer enclosures.

I see you're going with tube rectification. I wanted to go this route as I have a lot of nice rectifiers, but Mischa persuaded me otherwise. Might make for a good discussion of pros vs cons of tube rectification vs solid state rectification - as long as we stick to a technical discussion and don't start a flame war lol. But, we're all friends on here


----------



## L0rdGwyn (Dec 18, 2019)

leftside said:


> Yes the Clarity Caps are huge. We couldn't fit them inside the amp section of my amp, so they had to go on the outside enclosed with transformer enclosures.
> 
> I see you're going with tube rectification. I wanted to go this route as I have a lot of nice rectifiers, but Mischa persuaded me otherwise. Might make for a good discussion of pros vs cons of tube rectification vs solid state rectification - as long as we stick to a technical discussion and don't start a flame war lol. But, we're all friends on here



Actually they aren't as big as I thought, the Clarity Caps I would be using are about 2 inches in diameter.  I'll have quite a bit of real estate on the back panel since the driver filament rectification will be done on a PCB.  I'll probably swap out the Audio Note electrolytics in the PS for these.  Thanks @leftside !

From a purely technical standpoint, the only real advantage I know of for tube rectifiers is their "soft start" characteristic, which is easy on the power supply capacitors.  In pretty much every other way, solid-state rectifiers are better _technically_.  BUT tube rectifiers win for looks and magic of course  been hearing too much about this magic not to give it a try.


----------



## whirlwind

I remember Glenn telling me that running the tubes at 250 volt. besides the advantage of longer lasting tubes....also less distortion....so there is an advantage to not pushing these tubes to get further power.


----------



## A2029 (Dec 18, 2019)

L0rdGwyn said:


> Duly noted, thanks Mischa.  Interesting I am seeing the opposite pattern, lower distortion at higher plate voltages, wonder if that is just a fault of the model.  The datasheet would seem to suggest lower distortion at lower plate voltage, so I had intended to run the power tubes around 250-275V on the plates.
> 
> In your experience, what would you say is the most useful information to pull from LTSpice before you start building?



No problem Keenan  There are quite a few things that you can pull from LTSpice. When designing a circuit, I like to work from the load backwards; Determine the headphones/speakers/etc. that will be hooked up to the amp. You can then choose the output transformer based on the needed power into that load. Higher primary impedance usually gives lower distortion, but less power. Headphones are an easy load, so best to choose a high(er) primary impedance. Your chosen output transformer (LL2765) is a good choice for this. Then you can determine how much swing into the primary of the transformer is necessary to get the desired output power you want into the pair of headphones/speakers, and design the rest of the circuit from there (e.g. making sure that your driver tube can swing enough voltage at low enough distortion, and ditto for the power tube).

Some of the biggest things that I find LTSpice helps me check is to make sure that the power supply is built robustly. It's always good to do simulations at multiple frequencies (e.g. sim 20Hz, 40Hz, 100Hz, 1000Hz, etc.) to make sure you have low enough power supply ripple at all frequencies. You can also run a frequency sweep and check for any roll-off or abnormalities on the output (e.g. low end roll-off if the coupling cap or cathode bypass caps aren't sized right, or high-freq roll-off if the grid resistors are too high value, etc. etc.). Good to make sure that the circuit behaves how you want it to both when your wall voltage is low (as low as 110V) and that nothing will fry/blow out if wall voltage goes high for some reason (e.g. 140V). LTSpice is also good at calculating the effects of negative feedback if the tube models are good (though I don't use negative feedback myself in my designs). Also good for checking to make sure that supply voltages are always above the drop-out voltage of any linear regulators you use. Also good to check that the B+ voltage always stays above the drop-out voltage for the constant current source that you are using or there will be some major distortion from the driver stage. LTSpice is a more accurate simulation than PSUD2 for the power supply. Also good to send some transients through the circuit to look at various nodes for oscillations. This is especially important when choosing capacitor sizes and choke inductance(s) in the power supply. There are probably lots of things that I'm not remembering right now... too full of junk food from the Christmas buffet at my lab.



leftside said:


> I see you're going with tube rectification. I wanted to go this route as I have a lot of nice rectifiers, but Mischa persuaded me otherwise. Might make for a good discussion of pros vs cons of tube rectification vs solid state rectification - as long as we stick to a technical discussion and don't start a flame war lol. But, we're all friends on here





L0rdGwyn said:


> From a purely technical standpoint, the only real advantage I know of for tube rectifiers is their "soft start" characteristic, which is easy on the power supply capacitors.  In pretty much every other way, solid-state rectifiers are better _technically_.  BUT tube rectifiers win for looks and magic of course  been hearing too much about this magic not to give it a try.



Here are some factors that I've come across when choosing tube vs. ss rectification:

*Tube rectifier pros:*
- They look so cool!
- Tube rolling allows you to play around with circuit operating points
- They give the amp more of a "vintage tone" that can be very pleasant to the ear, and the tone can be varied to some degree by choice of rectification tube. (But see next section on cons)
- Less tendency to cause transformer ringing and less diode switching noise than ss rectification

*Tube rectifier cons:*
- The tone qualities from tube rectifiers is due in part to what is known as voltage "sag" when the tube rectifier is asked to provide greater current, and then the tube rectifier shows voltage "bloom" as it recovers and overshoots. This leads to less defined, slower and "woolly" bass, and less clarity/precision in high frequencies.
- Larger voltage drop across the tube
- Additional heater supply needed

*Solid State diode pros:*
- Less voltage drop
- No heater supply
- Does not show sag and bloom like tube rectifiers
- *If done right: *Can design for extremely low power supply noise & better bass and clarity in mids and high frequencies than can be achieved with tube rectification alone

*Solid State diode cons:*
- Doesn't look as good
- *If done wrong: *Can cause more transformer ringing, and current spiking/diode switching noise can reverberate throughout the power supply (and into the signal) resulting in a harsher sounding amp

How to do solid state rectification right: Employ RC transformer snubbers for transformer and supply zeta=1 ("critical") damping, use fast soft-recovery diodes (e.g. hexfreds, SiC Schottky's, etc.), bound rectifiers with resistance before and after the diode to decrease current spiking (which can cause supply ringing), and use capacitance multipliers and other Mosfet filtering techniques to bring power supply ripple down to extremely low levels. Also possible to build in soft-start without too much difficulty. An example: Leftside's amp has no electrolytic caps in the high voltage supply (lots of big 85uF oil caps with no electrolytic distortion), and B+ power supply ripple is under 30uV


----------



## L0rdGwyn

A2029 said:


> No problem Keenan  There are quite a few things that you can pull from LTSpice. When designing a circuit, I like to work from the load backwards; Determine the headphones/speakers/etc. that will be hooked up to the amp. You can then choose the output transformer based on the needed power into that load. Higher primary impedance usually gives lower distortion, but less power. Headphones are an easy load, so best to choose a high(er) primary impedance. Your chosen output transformer (LL2765) is a good choice for this. Then you can determine how much swing into the primary of the transformer is necessary to get the desired output power you want into the pair of headphones/speakers, and design the rest of the circuit from there (e.g. making sure that your driver tube can swing enough voltage at low enough distortion, and ditto for the power tube).
> 
> Some of the biggest things that I find LTSpice helps me check is to make sure that the power supply is built robustly. It's always good to do simulations at multiple frequencies (e.g. sim 20Hz, 40Hz, 100Hz, 1000Hz, etc.) to make sure you have low enough power supply ripple at all frequencies. You can also run a frequency sweep and check for any roll-off or abnormalities on the output (e.g. low end roll-off if the coupling cap or cathode bypass caps aren't sized right, or high-freq roll-off if the grid resistors are too high value, etc. etc.). Good to make sure that the circuit behaves how you want it to both when your wall voltage is low (as low as 110V) and that nothing will fry/blow out if wall voltage goes high for some reason (e.g. 140V). LTSpice is also good at calculating the effects of negative feedback if the tube models are good (though I don't use negative feedback myself in my designs). Also good for checking to make sure that supply voltages are always above the drop-out voltage of any linear regulators you use. Also good to check that the B+ voltage always stays above the drop-out voltage for the constant current source that you are using or there will be some major distortion from the driver stage. LTSpice is a more accurate simulation than PSUD2 for the power supply. Also good to send some transients through the circuit to look at various nodes for oscillations. This is especially important when choosing capacitor sizes and choke inductance(s) in the power supply. There are probably lots of things that I'm not remembering right now... too full of junk food from the Christmas buffet at my lab.
> 
> ...



Thank you for your input Mischa, very much appreciated.  As I go through this process, I am learning the true challenge of designing an amplifier is the power supply.  I am going to take this information and go back to the drawing board, but better to get it right.  I need to check my design for low frequency stability among some other concerns I have related to rectifier peak current.  Once I have it in a better place, I'll put the circuit through your gamut of tests


----------



## L0rdGwyn

Received the EL34 that will be going in this amp today (at least the first pair).  They are Philips double-o getter date code XF2 B6A4, got them for a good price.

Everything checks out testing wise.  Funny to think how much power is packed into this little guys.


----------



## L0rdGwyn (Dec 20, 2019)

Hey @A2029 , here is the question I mentioned I had for you.  I'll explain why these design considerations are important after all the technical chat afterward for others!

I've made some specific design changes to my power supply for this amp, wanted to explain why and get your $0.02 on them.  Here is a chicken-scatch schematic of the HT circuit:



The first change I made was adding 150ohm resistance between the mains transformer secondary and the rectifier.  The U18/20 datasheet states a minimum R-source value of 180ohms for a maximum input capacitor value of 16uF.  The secondary resistance of the Lundahl LL1650 mains transformer I plan to use is ~20ohm.  I've added this resistor to make up the difference to protect the rectifier and prevent arcing.  If I keep it, would not be a 150ohm resistor, more likely two 75ohm, three 50ohm etc. with the appropriate wattage.  Probably doesn't need to be quite this high since I am only using a 6.8uF input cap, but just for the sake of the example.

The second change I made was adding some series resistance across both LC filters.  I have been using Morgan Jones _Valve Amplifiers _book as a resource.  Following his method (and because I am still working on figuring out some of this functionality in LTSpice), I modeled my power supply in PSUD2 without this resistance added.  What I found is there is some minor ringing present.  Here is a plot from PSUD2 without any of the added resistance.  It is a stepped current load, increasing from 10mA to 160mA at 300ms to elucidate the ringing.  May be hard to appreciate here (doing this on my laptop so the plot is a bit squished), but there is ringing on the output in the form of capacitor voltage variations.  Note that this is without any "soft-start" enabled.  Green is the 65uF cap and blue is the 175uF cap.



From reading _Valve Amplifiers_, I understand that to provide adequate damping of this LC filter ringing, we are targeting a Q factor of 0.5.  The formula for Q factor is:

Q = 1/R * sqrt(L/C)

So to provide additional damping, we can 1) increase C 2) increase R or 3) decrease L.  Well increasing C is not preferable as these Clarity Caps are already enormous!  Likewise, decreasing L is not a great option since I am then loosing valuable ripple filtering.  Increasing R seems best and gives me the most bang for my buck.  So, by adding 150ohms in series with each LC filter, we get this:



Again, might be hard to see, but at least visually, the voltage variation is gone on the output and the ringing appears to be well-damped.  Obviously there will be a significant voltage drop from adding these resistors, but this is actually preferable for me as I have a bit too much B+ to work with, getting it down to 240-270V is a good place for where I want to bias the power tubes.  The resistance could also be added by getting custom chokes made with a higher DC resistance and max current rating.

So, by adding these resistors before the rectifier and in series with the inductors, I am trying to accomplish the following:

1) protect the rectifier from current spikes, arcing
2) decrease the Q factor of the filter section and damp any ringing
3) drop the B+ to my preferred bias point

Okay, with all of that being said, other than the obvious heat dissipation that will take place in the power supply, do you see any negative consequences of adding this resistance?


----------



## A2029

L0rdGwyn said:


> Okay, with all of that being said, other than the obvious heat dissipation that will take place in the power supply, do you see any negative consequences of adding this resistance?



Can't think of any negative consequences at this time, but if you have some time to throw together an LTSpice file of your schematic with all of the parameters for each part and send the .asc file over to me I can run a few sweeps I have in mind. I can throw it together myself, but may take some time for me to get around to it as I'm currently in the middle of a housing move that's taking most of my spare time and feels like a tornado went through my place


----------



## L0rdGwyn

A2029 said:


> Can't think of any negative consequences at this time, but if you have some time to throw together an LTSpice file of your schematic with all of the parameters for each part and send the .asc file over to me I can run a few sweeps I have in mind. I can throw it together myself, but may take some time for me to get around to it as I'm currently in the middle of a housing move that's taking most of my spare time and feels like a tornado went through my place



Fantastic, glad to hear no immediately obvious issues.  I would really appreciate you running the sweeps.  I'm out of town for the weekend so don't have access to the schematic, I'll get it prepped and send it to you next week.  Obviously no rush, especially with the holidays coming up.  Good luck with your move!

Landfall sent me a photo of the anodized chassis, looks good to me in gold


----------



## L0rdGwyn (Dec 22, 2019)

L0rdGwyn said:


> Hey @A2029 , here is the question I mentioned I had for you.  I'll explain why these design considerations are important after all the technical chat afterward for others!
> 
> I've made some specific design changes to my power supply for this amp, wanted to explain why and get your $0.02 on them.  Here is a chicken-scatch schematic of the HT circuit:
> 
> ...



Just to make good on my promise to explain why these changes are being made to the power supply (if I haven't bored everyone to death already and driven them away )

*Resistance added between mains transformer and rectifier:*
If you look at a tube rectifier datasheet, you will see a "R source" or "source resistance".  This is referring to the resistance to current flow between transformer and rectifier. If the resistance isn't suitably high, it can lead to large "inrush current" or "input surge current" when the amplifier is turned on and the first capacitor in the power supply begins to charge.  The larger the capacitor, the more current it is going to demand when the voltage on the rectifier side rises above zero.  Center-tapped mains transformers are typically used with a tube rectifier and have higher secondary winding resistance for this reason,  somewhere around 100ohm.  However, I am using a non-center tapped transformer with a 20ohm secondary winding resistance which are more commonly paired with solid state rectification. Solid state rectifiers are able to tolerate higher surge currents and don't suffer from the same fragility as tube rectifiers.  To prevent these current spikes and arcing, additional resistance needs to be placed after the transformer secondary winding to meet the R-source requirement of the tube rectifier.

*Resistance in series with L-C filter inductors:*
To keep this to the point, there is stored energy within these filter circuits passed from the inductor (filter choke) to the capacitor.  A higher resistance in the circuit will allow this energy to be released as heat.  Without this resistance, the filter acts as an oscillator and the energy is released as low frequency oscillations.  Depending on the frequency of this oscillation and its harmonics (which is dependent on the respective values of the choke's inductance and the capacitor's capacitance), can leak into the audio band and be heard, which is bad for our amplifier's performance.  The additional resistance added to this portion of the circuit damps this oscillation and allows the energy to be released as heat so it has no ill effects on the sound of the amplifier.

Did some editing, hope this makes sense.


----------



## L0rdGwyn

A beautiful pair of power tubes reached my door today, 1942 Fivre 6L6G black plates, foil getters.  Both tubes test 120%+ on my Jackson tester, looks to have been a good purchase.

  

I am sorry for not updating the thread, the power supply is undergoing some heavy revisions.  Will update when the true final design is complete.


----------



## Tjj226 Angel

L0rdGwyn said:


> A beautiful pair of power tubes reached my door today, 1942 Fivre 6L6G black plates, foil getters.  Both tubes test 120%+ on my Jackson tester, looks to have been a good purchase.
> 
> 
> 
> I am sorry for not updating the thread, the power supply is undergoing some heavy revisions.  Will update when the true final design is complete.



Uhhhhhh. These tubes will probably conflict with your overall design. Pmed.


----------



## L0rdGwyn (Jan 7, 2020)

At long last, I have some updates on the amp building front.

After NUMEROUS iterations, and with the input of @Tjj226 Angel , the power supply design is complete, for real this time.

Here are the highlights:

Lundahl LL1650 350V mains transformer
U18/20 rectification (and equivalents) in hybrid diode full wave bridge
Capacitor input CLCLC filter - first LC will consist of Lundahl LL2742 10H choke, second LC will consist of two Lundahl LL1685 17H chokes
Input capacitor will be a Clarity Cap TC2 10uF 800V
Second 100uF filler cap make and model TBD
Final supply caps will be Clarity Cap TC4 130uF 600V

The first tap in the supply at the 100uF cap will go to the MH4 CCS boards.  The second tap in the supply at the 130uF cap will go to the power tubes.  Given the size of these two chokes, the ripple on the output will be in the 10s of microvolts range.  Here is the LTSpice diagram:



Speaking of power tubes, another major change has been made.  While I will still be holding onto the EL34 for the sake of trying them out, I have abandoned the idea of a power tube biasing switch and have even changed the power tubes altogether.  Rather than using triode-strapped pentodes, I will be using a rather uncommon power tube.

It is the 6A5G, basically an indirectly-heated 6.3V version of the 2A3.  Here is an article on the tube:

http://vinylsavor.blogspot.com/2019/12/tube-of-month-6a5.html

So why the change?  With this tube, you get many of the advantages of the directly-heated triodes, mainly the linearity, but with a lower noise floor and no need for a DC filament supply.

The linearity of a vacuum tube can be assessed by the spacing between its grid curves.  The more evenly these are spaced, the less second harmonic distortion is generated by the amplifier as the voltage swings back and forth along the load line.

As an example of this linearity, here is the load line and bias point for the Philips E424N, a near equivalent of the MH4 that will be used in this amp, with its 6mA CCS load.  Please note this bias point is not optimized for the E424N, this is where it will be biased based on the chosen MH4 bias point, which is optimal, but this set of curves better illustrates my point.  Side note, the cathode bias resistor for the driver tubes will no longer have a bypass capacitor given the CCS loading.  One less cap in the signal path, yay!



And on the output, here is the load line and bias point for the 6A5G with a 3.3k load, which will be cathode biased with bypass cap (these are 2A3 curves, which are identical to the 6A5G).



Hopefully you can see that the grid curve spacing along these load lines, and especially near the bias points, are very even, which should yield low distortion and make for an excellent sounding amplifier 

That is all I have for now, I am expecting some components this week for my test bench, so I will post some updates on that front when I have them.  After the bench is ready to go, the next step will be to buy parts and finally start building!!!

Edit: correction on the 10H Lundahl choke, the LL2742, not the LL2741.


----------



## L0rdGwyn

Here is a draft of the interior chassis layout, major components only, this is a rough draft so very much subject to change, everything is to scale.  The chokes will be mounted to the side panel walls, all capacitors are mounted radially.  For the sake of drilling less holes in the chassis and less unsightly screws on top, going to try and consolidate screw holes between the bottom corners of the CCS boards and MH4 sockets, as well as the top corners of the CCS boards and the 0.47uF capacitor clamps.  We'll see how that goes.

Yes, the Clarity Caps are huge, but it all fits.


----------



## L0rdGwyn (Jan 11, 2020)

I made a thing today.

It is a switchable headphone dummy load for taking measurements.  Sure I could have just used some alligator clips and cheap resistors, but why take the easy road when I can work on a needlessly complex and frustrating project?

It has four sets of wirewound, non-inductive resistors to simulate a headphone load for the amplifier being measured, 32ohm, 80ohm, 120ohm, and 300ohm.  The wattages are way overkill, but it was what was available non-inductive.  The 1/4" TRS input is on the back and individual left and right channel BNC connectors on the front.

The the measurement chain goes like so:

Signal generator > amplifier > dummy load > signal analyzer.

Obviously this isn't a necessity, but a fun little project and it will be very convenient for future measurements.


----------



## Monsterzero

L0rdGwyn said:


> I made a thing today.
> 
> It is a switchable headphone dummy load for taking measurements.  Sure I could have just used some alligator clips and cheap resistors, but why take the easy road when I can work on a needlessly complex and frustrating project?
> 
> ...



Why do I forsee members wanting to order their own KOTL?


----------



## Zachik

Monsterzero said:


> Why do I forsee members wanting to order their own KOTL?


You mean KSET. Right?


----------



## L0rdGwyn

Monsterzero said:


> Why do I forsee members wanting to order their own KOTL?



Haha we will see!  Have to get one under my belt first.  I feel good about it though, I think this is going to be one heck of an amp.  Not sure anyone else would pay for it, there are some bonkers expensive components going in.

Might have to take out a loan for these amorphous core Lundahl transformers...and the Lundahl chokes...and the Clarity Caps...sheesh.


----------



## leftside

L0rdGwyn said:


> Haha we will see!  Have to get one under my belt first.  I feel good about it though, I think this is going to be one heck of an amp.  Not sure anyone else would pay for it, there are some bonkers expensive components going in.
> 
> Might have to take out a loan for these amorphous core Lundahl transformers...and the Lundahl chokes...and the Clarity Caps...sheesh.


Reminds me of an amp I'm familiar with. Go big or go home I say


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## L0rdGwyn (Jan 21, 2020)

I have on hand the power tubes that will be featured in this amp, a pair of Philco branded Sylvania 6A5G.  These ones are from their first year of production, 1937.  The boxes show it, I can't help but feel like I am breathing in something toxic every time I open them.  Nice looking tubes, looking forward to getting them in this amp.  I recently made some layout changes to my two-channel system to better take advantage of my room and I have rediscovered my love of stereo listening.  I am going to put some speaker binding posts on this amp and pair it with some sensitive speakers.  So the project is now more of a 3W SET speaker amp with a headphone output rather than a strict headphone amp, although the design doesn't change at all, I'll just be throwing a switch on the front panel to select speaker or headphone out.


----------



## A2029

L0rdGwyn said:


> The boxes show it, I can't help but feel like I am breathing in something toxic every time I open them.



The good old days when consumer products could be wrapped in asbestos  (joking)


----------



## L0rdGwyn

A2029 said:


> The good old days when consumer products could be wrapped in asbestos  (joking)



Between the asbestosis and the lead poisoning I'll be dead in 10 years, but I'll die with a smile on my face listening to pure class A


----------



## Tjj226 Angel

Dont forget the uranium paint.


----------



## 2359glenn

L0rdGwyn said:


> Between the asbestosis and the lead poisoning I'll be dead in 10 years, but I'll die with a smile on my face listening to pure class A



Naa  it will take longer then that.
I been doing this for 52 or more years now when all solder had led and capacitors had PCB I am still here.


----------



## L0rdGwyn

Another pair of NOS 6A5G arrived today, a decade older than the Philcos, 1947 Sylvanias.  Tubes are in great shape and test very well.  I wasn't happy with the price quotes I was getting from the few USA tube sellers who have some of these tubes, so naturally I had to go to the other bedrock market for USA-made tubes, Japan.  Seller reassured me the tubes were 100%, I am not dissappointed, they are pretty much immaculate.  Got them for a relatively good price, may go back for more.


 

I know these updates aren't sexy, some unexpected scheduling changes put the project on ice for a few weeks.  Should have some more substantial progress to post soon.


----------



## mordy

Are you able to give some links where to look for tubes in Japan? Are there things to keep in mind when buying from Japan?
Thanks


----------



## L0rdGwyn (Feb 4, 2020)

All of the parts for this build have been ordered and they are starting to arrive.  Unfortunately, Lundahl's US dealer does not have my LL1620 output transformers on hand, so they are being ordered and will arrive in late Feb.  The rest of the build can continue and they will be dropped in at the end.  I've had several delays with the chassis which was ordered in late November, hopefully will arrive next week.  Otherwise, I am going to post the parts as they come in here to show what is going into this build and why.

*Yamamoto sockets -* I posted these before, but going to consolidate here.  These are excellent sockets, B4 for the MH4 driver tubes, octal for the 6A5G output tubes, and an interesting UX4-B4 combo socket that will allow the use of European 4-volt rectifiers (U18/20, AZ50, RGN2504, FW4/500, etc.) and 5-volt rectifiers (5Z3).  Figuring out the optimum wiring for the rectifier socket has been...interesting, we'll see if I can hear the magic when I roll rectifier tubes.



*Goldpoint V47 stereo stepped attenuator -* I added one of these to my Glenn OTL and really like it, so this amp is getting one as well.



*Kiwame carbon film resistors -* these are widely used in the DIY community, relatively inexpensive, they are actually rebranded KOA Speer resistors under the Japanese Kiwame brand.  Regardless, I replaced the driver plate resistors in my Glenn OTL with these and A/B'd them against some Audio Note tantalum resistors.  To my surprise, there was a significant change in sound and I much preferred the Kiwames, so I've committed to using them in this build where applicable.



*Clarity Cap TC series filter capacitors -* using a 10uF 800V cap as the resevoir capacitor in the power supply (the first cap after the rectifier) and 130uF 600V caps in the last position of the power supply.  The 130uF caps will be in the signal path of the output stage, so these high-quality film caps were used.  The 130uF are also four-pole AKA Kelvin lead capacitors, which offer extended high-frequency noise suppression (see Morgan Jones _Valve Amplifiers_).  The middle PS cap is a 100uF 600V Nichicon which is on the way.



*Miflex KPCU-02 copper foil poly/paper in oil capacitors -* these are the coupling caps I am using between the input and output stages. These Polish capacitors are not very well known, but testimonials I have come across say they are a step above the Jupiter copper foil coupling capacitors sonically. Who knows if that's true, but it helps they are also 1/3 of the price  and radial-leaded, so much easier to mount in the chassis with a capacitor clamp.  Physically, they certainly exude quality.



*Audio Note Kaisei non-polar electrolytics -* these are what Audio Note has come up with on their quest to re-engineer the famous Black Gate capacitors with the help of Rubycon.  These are the cathode resistor bypass capacitors for the output tubes.  The driver tubes will not have bypass caps.  They are non-polar for reduced distortion.



*WBT RCA sockets and speaker binding posts - *not much to say on these, they are high-quality German-made sockets and binding posts.  A nice feature of the bindings posts is they come with a "puzzle plate system" that locks them in place so they do not twist when being tightened.  Noice.



*Apex Jr. mil-spec silver-plated copper PTFE wire -* Steve at Apex Jr. has been supplying this copper wire to DIYers for a long time.  It is good quality, inexpensive, and I didn't want to pay the audiophile markup for boutique wire.  Have some shielded single-conductor wire on the way to for the inputs. This will do nicely.



*AMR gold fuse -* that's right, I bought an audiophile fuse LOL but I didn't feel like going to the hardware store, and it wasn't expensive.  I am certain this fuse will be transformative and take me to the audiophile promised land.



The Lundahl mains transformer, chokes, and CCS kits should be here later this week, then the chassis next week, then the fun begins


----------



## Monsterzero

L0rdGwyn said:


> *Kiwame carbon film resistors -* these are widely used in the DIY community, relatively inexpensive, they are actually rebranded KOA Speer resistors under the Japanese Kiwame brand. Regardless, I replaced the driver plate resistors in my Glenn OTL with these and A/B'd them against some Audio Note tantalum resistors. To my surprise, there was a significant change in sound and I much preferred the Kiwame's, so I've committed to using them in this build where applicable.


Im curious. What changes did these make? Glenn mentioned them as a possible upgrade to do on my GOTL when it goes in for surgery.


----------



## L0rdGwyn

Monsterzero said:


> Im curious. What changes did these make? Glenn mentioned them as a possible upgrade to do on my GOTL when it goes in for surgery.



Hey D - I only compared them to the other resistor I had on hand that I was planning to put in, the Audio Note tantalums.  I talk about it in this post:

https://www.head-fi.org/threads/2359glenn-studio.600110/post-15291953

My impressions aligned very closely with what I found here, quite an old post but the point is the same: https://www.head-fi.org/threads/carbon-film-vs-metal-film-revisited.121104/


----------



## Tjj226 Angel

L0rdGwyn said:


> Hey D - I only compared them to the other resistor I had on hand that I was planning to put in, the Audio Note tantalums.  I talk about it in this post:
> 
> https://www.head-fi.org/threads/2359glenn-studio.600110/post-15291953
> 
> My impressions aligned very closely with what I found here, quite an old post but the point is the same: https://www.head-fi.org/threads/carbon-film-vs-metal-film-revisited.121104/



BTW, try NOS allen bradley resistors. You have to buy a handful of the values you need and match the right resistances, but for what ever reason they have always sounded the best to me and I have a small bin of both kimwame and audio note resistors at my disposal. 

I have a feeling its because carbon comp resistors have really low (pretty much 0) series inductance, but that's a complete shot in the dark.


----------



## L0rdGwyn (Feb 4, 2020)

Tjj226 Angel said:


> BTW, try NOS allen bradley resistors. You have to buy a handful of the values you need and match the right resistances, but for what ever reason they have always sounded the best to me and I have a small bin of both kimwame and audio note resistors at my disposal.
> 
> I have a feeling its because carbon comp resistors have really low (pretty much 0) series inductance, but that's a complete shot in the dark.



I've heard very good things about the Allen Bradleys and the discontinued Japanese Riken carbon comps too.  Thanks for the recommendation, I'll probably give the ABs a shot at some point down the road.  I'm using Riken carbon comps for my grid stoppers.


----------



## whirlwind

L0rdGwyn said:


> All of the parts for this build have been ordered and they are starting to arrive.  Unfortunately, Lundahl's US dealer does not have my LL1620 output transformers on hand, so they are being ordered and will arrive in late Feb.  The rest of the build can continue and they will be dropped in at the end.  I've had several delays with the chassis which was ordered in late November, hopefully will arrive next week.  Otherwise, I am going to post the parts as they come in here to show what is going into this build and why.
> 
> *Yamamoto sockets -* I posted these before, but going to consolidate here.  These are excellent sockets, B4 for the MH4 driver tubes, octal for the 6A5G output tubes, and an interesting UX4-B4 combo socket that will allow the use of European 4-volt rectifiers (U18/20, AZ50, RGN2504, FW4/500, etc.) and 5-volt rectifiers (5Z3).  Figuring out the optimum wiring for the rectifier socket has been...interesting, we'll see if I can hear the magic when I roll rectifier tubes.
> 
> ...




Very nice....those sockets will last forever.


----------



## L0rdGwyn (Feb 6, 2020)

whirlwind said:


> Very nice....those sockets will last forever.



At $50 each, they better!  

Some more 6A5G tubes arrived today, of different construction.  From all of the digging I have done, I have only seen these tubes in three different versions.

The early Sylvania black plate foil getter versions I have posted earlier in the thread (analogous to the "spring top" Sylvania 2A3)
The French-made black plate version manufactured by Visseaux, which I do not have yet
And the ribbed plate D getter version that I received today, made in 1953 (analogous to the "dual mono plate" Sylvania 2A3)

From the short time I have been hunting these tubes, this "dual mono plate" version seem to be much less common.  It will be interesting to see how they compare, I'd imagine the differences in sound would be nearly identical to the differences between their 2A3 cousins.


----------



## mordy

L0rdGwyn said:


> At $50 each, they better!
> 
> Some more 6A5G tubes arrived today, of different construction.  From all of the digging I have done, I have only seen these tubes in three different versions.
> 
> ...


Is this National Union 6A5G a Sylvania rebrand?



http://vinylsavor.blogspot.com/2019/12/tube-of-month-6a5.html


----------



## L0rdGwyn

mordy said:


> Is this National Union 6A5G a Sylvania rebrand?
> 
> http://vinylsavor.blogspot.com/2019/12/tube-of-month-6a5.html



Yessir, those National Union tubes are rebranded Sylvanias.  I haven't come across any evidence that these tubes were manufactured by anyone but Sylvania and Visseaux in France, likely under Sylvania licensing.

Obviously some of this is conjecture, but here is a Sylvania 6A5G datasheet, in what language?  French   

http://www.nj7p.org/Tubes/PDFs/Frank/121-Sylvania/6A5G.pdf

Interestingly, I have come across WWII Visseaux-manufactured 6A5G with German Wehrmacht branding, indicating the tubes were manufactured in France under Sylvania license during WWII German occupation!  That pair sold on eBay shortly before I was in the market, unfortunately, although it has some undesirable symbols on the tubes, if you catch my drift.


----------



## whirlwind

L0rdGwyn said:


> At $50 each, they better!
> 
> Some more 6A5G tubes arrived today, of different construction.  From all of the digging I have done, I have only seen these tubes in three different versions.
> 
> ...




Nice tubes.

I think I may have Glenn add that Yamamoto socket that allows the use of 4 and 5 volt rectifiers to my build.


----------



## L0rdGwyn (Feb 8, 2020)

Made some progress on a few things today, so thought I would post an update.

First off, I finished stuffing the attenuator board for my Linear Audio Autoranger.  I haven't talked much about this device on this thread, I have on others, but it essentially attenuates any input signal down to 1.0V (or 0.4V) such that audio measurements can be made with an audio interface (AKA sound card) without damaging it.  Using this, I will be able to crank this amp to clipping and take accurate audio measurements on my MOTU M4.

Here is a link to the device page, engineered by Jan Didden: https://linearaudio.nl/la-autoranger



By the way, this is where the amp building will be done.  It ain't sexy, but it gets the job done   space heaters required (please excuse the creepy manequin head in the corner, one of the previous owners of this home was a hair stylist and it has continued to live in the garage for...actually I don't know why it's still there).



Still have to finish the controller board on the Autoranger and finish up some wiring, but the bulk of the work is done with the attenuator board finished.

However, that has been put on the back-burner, since some items of much greater intrigue arrived today...some iron 



Got the first shipment of Lundahl parts from K&K audio.  Includes the LL1648 mains transformer, LL2742 choke, a pair of LL1685 chokes, transformer covers, and two cascode constant current source kits.  I made a very last minute decision to switch from the LL1650 to LL1648 mains transformer.  They are nearly identical, except the LL1650 has four 6.6V secondary windings for tube filaments, whereas the LL1648 has a pair of 6.6V and a pair of 5.9V filaments.  This will work better for my project as I am using dropping resistors to reduce the voltages of two of the filaments anyway, so the pair of 5.9V is better since I will not have to dissipate as much power.

One thing I wanted to get done today with the mains transformer was wiring up the primary and checking the filament voltages with my dropping resistors.  The ratings given by Lundahl are for 115V out of the wall, so they will be a little high for 120VAC in the USA.  On top of that, my wall AC runs a little high around 122V, and my isolation transformer bumps it up to 124V, so that is where I am testing (I have a second DMM attached to my variac).  Here is a pic of a Fivre 5Z3 the dropping resistors in place to get the 5.9V winding down to 5V, looking good.  Based on this, safe to say the 4V rectifier dropping resistors are good as well.



I also checked the 6.6V windings with 124VAC into the mains transformer.  Given that primary voltage, I am getting almost 7.1V on the filaments of the 6A5G off the 6.6V windings.  May even have to add some droppings resistors for them as well.  7.1V won't burn out the filaments right away, but could reduce the life of the tubes.  Have to give that some thought before I start drilling holes.

Checking the 4V driver tube dropping resistors is more tricky since the filaments are wired in parallel, will probably tackle this tomorrow with a tangled mess of alligator clips.

To be continued...


----------



## chrisdrop

L0rdGwyn said:


>


You are going to need a bigger, cozier chair if you have any hope of sitting there for long!


----------



## L0rdGwyn

chrisdrop said:


> You are going to need a bigger, cozier chair if you have any hope of sitting there for long!



You'd be surprised, it works quite well for me!  Plus, I'm always shuffling around anyway, not sitting for long.  It is my adjustable chair for my telescope, so I am used to it


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## mordy

Hi LG,
Re your mentioning of various voltages coming from the transformer windings, I am under the impression that in the tube era a 10% variation was considered within specs. Is it really that important to have the exact voltage available, especially since the mains voltage may fluctuate a little as well?


----------



## L0rdGwyn

mordy said:


> Hi LG,
> Re your mentioning of various voltages coming from the transformer windings, I am under the impression that in the tube era a 10% variation was considered within specs. Is it really that important to have the exact voltage available, especially since the mains voltage may fluctuate a little as well?



Hi mordy - yes, +/- 10% is the goal.  Closer to the specification is best since there will be mains variations.  The issue is the 5.9V and 6.6V specification for the heater windings is at 115VAC.  I am expecting 124VAC into the transformer from the wall, so those voltage ratings are low.  In reality, I am seeing 6.3V and 7.1V, respectively.  I am using dropping resistors for the two 5.9V (measured 6.3V) windings for the 4V/5V rectifiers and 4V driver tubes anyway.  The voltages do not need to be exact with the resistors, but you can get pretty close.  Without diving into the details (unless you want me to ), I am trying to hit smaller targets on the voltages so that a larger variety of tubes can be used within their +/-10% specification.

I had not planned to use resistors on the 6.6V (measured 7.1V) windings for the power tube heaters.  At 7.1V, I am about 13% above the 6.3V specification.  Not horrible but not comfortable either, likely will do something to bring it down to a happy place.


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## L0rdGwyn

Continued working on the tube heater dropping resistors today.

I wired a pair of 4V driver tubes with the heaters in parallel, MOV MHL4.  The heaters are center tapped and referenced to ground with a pair of 100ohm resistors, so this was a ton of fun with a thousand alligator clips.  Thankfully, the voltage is right where I want it ~3.9V with 124VAC into the mains transformer.



Next, I checked the voltage of the 4V rectifiers.  First, a Marconi rebranded Mullard FW4/500 which draws 3A:

 

Then a GEC U18/20, which draws 2.8A:

 

As expected, their filament voltages are slightly off due to the difference in drawn current, but they are right where I want them to be, looks great.

Last thing I did was put together one of the CCS kits.  I hooked it up to a 30VDC power supply and adjusted the trim pot until I got 6mA, the plate current for the driver tubes.  This corresponded to 395ohm on the trim pot, so I'll likely get a 400ohm set resistor. Thanks for the idea, @A2029 

 

So looks like my math was correct on the dropping resistors, now I can confidently drill holes in the chassis when it arrives.  Supposed to be finished re-plating Tuesday, hopefully will get it by Friday and the real building will begin next weekend.


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## Tjj226 Angel (Feb 9, 2020)

mordy said:


> Hi LG,
> Re your mentioning of various voltages coming from the transformer windings, I am under the impression that in the tube era a 10% variation was considered within specs. Is it really that important to have the exact voltage available, especially since the mains voltage may fluctuate a little as well?



You have the pieces, but you need to put them together.

Yes, tube's can handle 10% shifts. Yes, wall voltage will vary. However you want to center your tube around an average wall voltage so that as your wall voltage changes and shifts, the voltage around the tube is only shifting +/-10% or less.

It's also important to note that just because tubes can deal with 10% variations doesn't mean that being 10% outside of the spec is good for hi-fi use. Ideally you want to keep the parameters as stable and ideal as possible. 

If we were being super picky, what I would do is take your volt meter and monitor the wall voltage at different times of the day and on weekends. Figure out what your lowest and highest wall voltage was. Split the difference and run your amplifier off of a variac set to that average voltage. Set everything up such that you get as close to ideal voltages as humanly possible. That way your amp won't drift and wander as much in your home.

If you want an amp that you can take anywhere, just do the same thing but set it for 120v. It may or may not be ideal for your home, but it will work in darn near any wall socket in the US that wasn't built during ww2.


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## mordy

Is it possible to hear a difference if the voltage changes somewhat more than the 10%?
From personal experience I have found that late at night or on weekends my equipment may sound better, possibly because of less electric interference from all kinds of devices and machinery.


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## Tjj226 Angel

mordy said:


> Is it possible to hear a difference if the voltage changes somewhat more than the 10%?
> From personal experience I have found that late at night or on weekends my equipment may sound better, possibly because of less electric interference from all kinds of devices and machinery.



Well 10% difference would be obvious, but ideally we never get close to those kinds of differences.

But in general I would say it all depends on the circuit and what tubes you are using. I have seen some tube amps where the preamp tube is biased so close to the knees that a small change in voltage could let the tube slip into the knees and cause all sorts of havoc. 

On the flip side I have seen amps where the tubes were biased with such headroom that it can handle larger variations without falling apart. You would still probably hear a change, but it just wouldn't be enough of a change to cry about. 

But this is assuming good old fashion design. A tube with a plate resistor, cathode resistor, and cathode bypass capacitor.


----------



## leftside

L0rdGwyn said:


> Continued working on the tube heater dropping resistors today.
> 
> I wired a pair of 4V driver tubes with the heaters in parallel, MOV MHL4.  The heaters are center tapped and referenced to ground with a pair of 100ohm resistors, so this was a ton of fun with a thousand alligator clips.  Thankfully, the voltage is right where I want it ~3.9V with 124VAC into the mains transformer.
> 
> ...


@A2029  rocks


----------



## A2029

L0rdGwyn said:


> Continued working on the tube heater dropping resistors today.
> 
> I wired a pair of 4V driver tubes with the heaters in parallel, MOV MHL4.  The heaters are center tapped and referenced to ground with a pair of 100ohm resistors, so this was a ton of fun with a thousand alligator clips.  Thankfully, the voltage is right where I want it ~3.9V with 124VAC into the mains transformer.
> 
> ...



IXTP08N50D2 is an interesting choice for top device in the CCS cascode. I believe K&K used the IXTP01N100D in the past, but it's more expensive and not as hefty of a chip (but has lower capacitance values). What MOSFET is used as the bottom device on the other side of that heatsink?

Someday in the future I'll have to build a bunch of different CCS circuits and do an in depth shootout. I'll maybe build a blinding box to make it easy to switch and so that I can't see which CCS I'm listening to.


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## L0rdGwyn

A2029 said:


> IXTP08N50D2 is an interesting choice for top device in the CCS cascode. I believe K&K used the IXTP01N100D in the past, but it's more expensive and not as hefty of a chip (but has lower capacitance values). What MOSFET is used as the bottom device on the other side of that heatsink?



Hey Mischa - the top device is the chip on the opposite side of the heatsink, and it is the IXTP08N100D2.  The IXTP08N50D2 in the photo is the bottom device.  For some reason, Kevin has the bottom device marked Q1 on the board and the top device Q2.



A2029 said:


> Someday in the future I'll have to build a bunch of different CCS circuits and do an in depth shootout. I'll maybe build a blinding box to make it easy to switch and so that I can't see which CCS I'm listening to.



That would be very interesting, would be very curious to hear the results!  maybe I would make a change based on your test.


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## Tjj226 Angel

A2029 said:


> IXTP08N50D2 is an interesting choice for top device in the CCS cascode. I believe K&K used the IXTP01N100D in the past, but it's more expensive and not as hefty of a chip (but has lower capacitance values). What MOSFET is used as the bottom device on the other side of that heatsink?
> 
> Someday in the future I'll have to build a bunch of different CCS circuits and do an in depth shootout. I'll maybe build a blinding box to make it easy to switch and so that I can't see which CCS I'm listening to.



There is also the issue of thermals. The IXTP08N50D2 will only rise 2 degrees C per watt where as the IXTP01N100D will rise 5 degrees C per watt. Some tubes like the 5687 can create a few watts of dissipation across the CCS. Just 3 watts across the CCS is the difference between 6 degrees vs 15 degrees and may be the difference between bolting the mosfet to the top plate vs buying a dedicated heat sink.


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## A2029

L0rdGwyn said:


> Hey Mischa - the top device is the chip on the opposite side of the heatsink, and it is the IXTP08N100D2.  The IXTP08N50D2 in the photo is the bottom device.  For some reason, Kevin has the bottom device marked Q1 on the board and the top device Q2.



Ah okay, that makes more sense having the IXTP08N100D2 at the top for more voltage handling. Slightly lower Crss capacitance as well than the IXTP08N50D2. IXTP08N100D2 has good Vgs as well, which helps to reduce the capacitances of the lower device slightly.



L0rdGwyn said:


> That would be very interesting, would be very curious to hear the results!  maybe I would make a change based on your test.



That's if my ears are sensitive enough to reliably hear the minute changes 



Tjj226 Angel said:


> There is also the issue of thermals. The IXTP08N50D2 will only rise 2 degrees C per watt where as the IXTP01N100D will rise 5 degrees C per watt. Some tubes like the 5687 can create a few watts of dissipation across the CCS. Just 3 watts across the CCS is the difference between 6 degrees vs 15 degrees and may be the difference between bolting the mosfet to the top plate vs buying a dedicated heat sink.



Agreed, the IXTP08 parts are better for higher currents/dissipation.


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## L0rdGwyn (Feb 12, 2020)

Finished building the Linear Audio Autoranger last night, it is up and running.  I was rushing and accidentally mounted two front panel LEDs too far into the chassis, so they aren't visible, but functionally it is good to go   I'll fix the LEDs later this week.

Exterior:



And interior:

 

Why is this measurement device relevant to this project?  As I mentioned before, the Autoranger allows one to take precision audio measurements at high signal output levels using an audio interface (I use the MOTU M4 DAC/ADC).

In the photos, I am feeding a 1kHz sine wave into the Glenn OTL from my MOTU M4.  The Glenn OTL is connected to a switchable headphone dummy load I built, set to 300ohm.  The output of the dummy load feeds the single-ended input of the Autoranger.  You can see I am sending the Autoranger a 10V signal from the Glenn OTL.  If I connected this 10V output directly to my MOTU M4 instead of the Autoranger, the ADC would be very unhappy.  Instead, the Autoranger is providing 18dB of attenuation, so a very safe 1.28V signal enters the MOTU M4 and can be measured.

A 1kHz 10V signal from the Glenn OTL with this particular tube loadout corresponds to ~1% THD+N.  Don't worry though, at that output level you wouldn't be able to hear the high levels of distortion since you would be deaf (at ~1V output, the Glenn OTL puts out around 0.07% THD+N with these tubes, Mullard ECC32 and sextet of Tung-Sol 6BX7GT).



So, the utility of this setup is being able to test speaker amplifiers' high output voltages safely, and headphone amps if you want to crank it up and take measurements at unsafe listening volumes.  Really cool device, should be lots of fun to play with for years to come 

In other news, I received word that the chassis for this SET amp is FINALLY done.  There were some...technical difficulties with the anodization, but I am happy to say the end result is good and I should have it this weekend to start building.  I will have the house to myself, which means I will be living in my garage with the space heaters.


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## L0rdGwyn

At long last!  The chassis has arrived.  Time to check my planned layout, mark it up, and start drilling.  My goal for the weekend is to get the holes drilled and parts mounted.  After that, with just the wiring remaining, should come together pretty quickly.


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## L0rdGwyn

Busy day.  Marking up the chassis and finalizing the layout took a big chunk of time.  Jamming quite a bit inside, so the measurements needed to be exact.  

Nearly finished drilling as well, just need to use a step bit to drill some holes for the wires to pass from the transformers.  Wanted to finish, but it is 10° F right now!  It was time to come inside.  The cold keeps the drill bits nice and cool though 

Otherwise, drilling is done.  Tomorrow I will add the wiring holes, strip some of the anodization off for grounding and the transformer shield connection, then start mounting the components.  Should have everything mounted by the end of the day tomorrow.


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## L0rdGwyn (Feb 15, 2020)

Made some major progress today.  Thought I was going to just be doing a wee bit of drilling and mounting the components, but I had a little surprise...

I realized the panels of this chassis were not electrically connected due to the anodization.  The hardware does not link the metal panels the way it is constructed.  This is a safety issue in addition to not providing adequate shielding from the outside environment, so I had a little project on my hands.

First finished my drilling, then went to work on the chassis with my Dremel.  Had to grind away the anodization on the hardware contact points to link the four side panels, then use a wire brush attachment to remove the anodization on the corners of both the top and bottom panels, AND the corners of the side panels.  This allows a metal-to-metal connection so the entire chassis is now groundable.  An absolute PITA, but it had to be done.

 

With the drilling done and my grounding issue resolved, the prepwork for the chassis was finally complete (back panel was on backwards in this photo   ).



Last thing I did today was mount the major components.  Not everything is in there, but the major stuff is.  I'll have to take the chokes back out to wire them, but I wanted to see how everything fit together.  Good news, this is starting to resemble a tube amplifier. 

Here are some pics of the interior:

 

And a little teaser of what the amp is going to look like when complete:

 

So far so good, really like how it is looking.  Next thing will be to mount the final minor components, then start wiring!  Probably will take it easy tomorrow, been at it non-stop for two days


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## mordy

Wishing you good luck with a home run on the first try!


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## L0rdGwyn

mordy said:


> Wishing you good luck with a home run on the first try!



Thanks, mordy.  So far all of my planning has payed off, let's hope that continues!  I've invested a lot in this amp, so it better sound good (I think it will ).


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## 2359glenn

Nice job!!!
Now the fun of wiring it.
Looks like it will be done next week


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## leftside

Looking really good. Makes me appreciate the fine work that Mischa and Glenn do even more.


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## L0rdGwyn

2359glenn said:


> Nice job!!!
> Now the fun of wiring it.
> Looks like it will be done next week



Yes, the wiring is going to be interesting.  Unfortunately, it won't be completely done until early March, K&K didn't have my output transformers, they are on the way.  Should be here in the next two weeks, but with everything else done, will be very simple to drop them in


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## Tjj226 Angel

Jesus those clarity caps are a LOT bigger than I would have guessed. 

So far so good though. You lay out your stuff a hell of a lot better than I do, so Im sure you will be successful. : )


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## L0rdGwyn (Feb 19, 2020)

Between last night and this morning, I finished wiring the tube heaters.  Not trivial given the oddball tubes that are going in this amp.  Thankfully, as I've thought about it, this project is going to get easier as I go, should be over the hump on extremely tedious tasks now  

Here is the mains transformer wired.  All of the wire is PTFE insulated silver-plated copper, all twisted with a hand drill.  I ended up adding some voltage dropping resistors for the power tubes.  I opted to solder them directly onto the transformer heater pins, only dissipating 0.25W a piece and are rated for 5W.  One less thing to mount in a crowded amp and I can keep a better twist up to the heater pins without resistors in the way.



Here is a mess of mains and heater wires after mounting the transformer.  Chokes were removed for more working room and to get the heater wiring into the corners of the amp.



Here is the result.  For my layout, I had originally wanted to keep all of the AC wiring on one side of the amp, and the major signal wiring on the opposite side.  I couldn't justify sending heater wiring across the middle of the amplifier for the right output tube, so it is on the signal wiring side.  I am using shielded wire for the inputs, so shouldn't cause any hum issues.  If it does, can always move it later, I may reconsider.



Here are some of the dropping resistors, the set on the left (yellow wiring) drops the 5.9V winding down to 5V for use of 5Z3 rectifiers.  The set on the right (green wiring) drops the other 5.9V winding down to 4V for the driver tubes.  Note that it is center-tapped with a pair of 100ohm resistors.  I wasn't originally going to use any chassis-mount resistors, but decided I needed to dissipate some of heat into the chassis since it has essentially no airflow.  Together they are dissipating about 5W, with thermal compound in between the resistors and the chassis wall.



And here is the rectifier socket.  This combination socket from Yamamoto allows the use of 5V UX4-base rectifiers (for my purposes, 5Z3), as well as European 4V B4-base rectifiers (U18/20, FW4/500, 45-IU, etc.), which will be what I use primarily.  A pair of 0.2ohm resistors drops the voltage down from 5V to 4V for the B4 filament pins.



I originally wasn't going to post any finished-product-looking photos of the amp until it was actually done, but what the heck, it looks pretty cool!

In these photos are a Marconi-Osram U18/20 rectifier, Marconi-Osram CV399 driver (military MH4), and Sylvania 6A5G output tubes.

 

And as promised, it can use 5V 5Z3 rectifiers as well.  Here is a Fivre 5Z3.



That's all for now, we'll see if I have the energy to get started on the power supply today, that is the next step


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## Zachik

Looks great, and the workmanship of the wiring - I would say it is Glenn level (which I think is a big compliment)!!


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## chrisdrop

L0rdGwyn said:


> Between last night and this morning, I finished wiring the tube heaters.  Not trivial given the oddball tubes that are going in this amp.  Thankfully, as I've thought about it, this project is going to get easier as I go, should be over the hump on extremely tedious tasks now
> 
> Here is the mains transformer wired.  All of the wire is PTFE insulated silver-plated copper, all twisted with a hand drill.  I ended up adding some voltage dropping resistors for the power tubes.  I opted to solder them directly onto the transformer heater pins, only dissipating 0.25W a piece and are rated for 5W.  One less thing to mount in a crowded amp and I can keep a better twist up to the heater pins without resistors in the way.
> 
> ...


Lookin' good. Very pretty all 'round.


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## L0rdGwyn

Thank you gentlemen, much appreciated, gonna keep chugging along.  Supposedly I will have a nice sounding tube amp at the end of all this madness, we will see!


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## leftside

Going for a two box/chassis solution with external power supply?


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## L0rdGwyn

leftside said:


> Going for a two box/chassis solution with external power supply?



Not this time around, maybe on a future project!  It's all in there, just need to wire it, test it, make sure I am getting the expected voltages.  I have some high-wattage dummy resistors to approximate the tube load, so that will tell me things are looking okay before I connect any precious tubes


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## 2359glenn

L0rdGwyn said:


> Between last night and this morning, I finished wiring the tube heaters.  Not trivial given the oddball tubes that are going in this amp.  Thankfully, as I've thought about it, this project is going to get easier as I go, should be over the hump on extremely tedious tasks now
> 
> Here is the mains transformer wired.  All of the wire is PTFE insulated silver-plated copper, all twisted with a hand drill.  I ended up adding some voltage dropping resistors for the power tubes.  I opted to solder them directly onto the transformer heater pins, only dissipating 0.25W a piece and are rated for 5W.  One less thing to mount in a crowded amp and I can keep a better twist up to the heater pins without resistors in the way.
> 
> ...



Nice job Keenan


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## L0rdGwyn (Feb 21, 2020)

Moving right along...

Started putting together the power supply yesterday evening.  Rather than freezing my a$$ off in my garage (20F outside), I wired what I could indoors without soldering and made all of the necessary preparations for the morning.  Got up at the crack of dawn too excited to keep sleeping, and went out to get to work.

Well no doubt my work last night shaved off a huge chunk of time, still took me a solid four hours!  But lo and behold, the power supply is working perfectly  

Here is the interior post power supply implementation.  I also cleaned things up a bit, I'm a bit of a perfectionist (which means making work where there really is none).




Here is a closer look at the completed rectifier socket.  You can see a pair of Vishay HEXFRED diodes have been added to complete the hybrid SS-tube full-wave bridge rectifier.  The red wiring is the HT or B+ AC from the mains transformer.  The resistor across the terminals of the 10uF resevoir cap is a bleeder to discharge the capacitors when the amp is turned off.  I knew it was going to be busy, hopefully I never need to change anything on this socket, I will cry.



Up in the corner near the IEC outlet are two pairs of wirewound resistors.  These are serving a few different purposes in the power supply, but mainly they drop the ~420V B+ that is being sent to the driver tube CCS boards down to ~315V for the output tubes.  The tradeoff of course is heat, but they are appropriately rated and are tucked away as far as possible from the caps.  The values may need to be adjusted in the final design to dial in the output tube B+.  We'll see how good my math was when the amp is complete and the final voltages are checked.



In the meantime, to ensure everything was functioning as intended I picked up a pair of 5kohm 50W resistors to act as dummy loads for the supply.  They approximate the load it will see from the tubes, and they are doing it quite well!

In this photo, I have one multimeter connected to each channel, getting near perfectly matched voltages.  This is with the Mullard FW4-500, 320.5V for the output tubes.  With the Marconi-Osram U18/20, seeing ~315V, and with the Fivre 5Z3 ~305.  Will have to keep the large voltage drop in mind when using the 5Z3 in this amp.  I am aiming for 315V B+ for the output tubes which results in 250V on the plates.  These resistors may have approximated my tube load better than I expected.

I also measured the B+ off the 100uF cap at ~430V, which will be sent to the driver CCS boards.



So there you have it, power supply done.  Very satisfying to have done so much planning and have everything going off without a hitch.

We are rounding the corner now, this amp is very close to being done.  Just need to do the signal wiring, which is relatively simple, then wait for these output transformers to arrive from Sweden  the amp is getting heavier and heavier, it is going to be an absolute beast when the OPTs are in.


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## chrisdrop

Beautiful work. Really impressed!


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## leftside

One of my favorite threads on headfi


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## L0rdGwyn

chrisdrop said:


> Beautiful work. Really impressed!



Thanks, Chris 



leftside said:


> One of my favorite threads on headfi



Wow, I'm flattered!  Glad it has been entertaining.  When the amp is done I plan to do a series of measurements too: FFT, Bode plot, THD vs. frequency, square wave, etc., so hopefully I will still have something interesting to post about when it is finished.

In other news, today I received a final power tube to round out my collection, the French-made Visseaux 6A5G.  Other than Sylvania, Visseaux was the only other manufacturer of this tube, likely under Sylvania licensing, as I've mentioned before.

I am hoping the Sylvanias sound better, these were not cheap, but if my previous experience with Visseaux is any indicator, that will not be the case.  My poor wallet...beautiful tubes though.


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## L0rdGwyn (Feb 22, 2020)

Alright, yet another update.  Once I get started on this stuff, I can't stop until the job is done!  This amp is now 90% complete.

Worked on the input wiring today as well as the tube sockets.  Here is the updated interior:



First, the inputs.  The wiring is shielded 24 AWG silver-plated copper.  I soldered ground wires to each individual shield so they could be grounded at one end.  This will reduce the liklihood of any hum on this low-signal wiring and reduce the noise floor of the amp (in theory).  I keep saying this project is going to get easier, I think it will be easy when it is done  every step has its challenges.

 

Next I did the driver tube sockets.  Because they are CCS loaded, the cathode resistor does not necessarily need to be bypassed, so these simply have a cathode resistor.  It is the big blue one, a fancy schmancy Riken carbon film (now discontinued), surely these will take the amp over-the-top  who knows, but they sure look nice!  I've also used Riken for the set resistors on the CCS boards.  100ohm grid stopper resistors are Allen Bradley carbon composition, 470kohm grid leak are Kiwame carbon film.  I've said it before, but the coupling caps are Miflex KPCU-02 poly/paper in oil.



And last but not least, the output sockets.  Man space was tight, getting these parts in was a PITA, but we made it work.  Cathode resistor is a 750ohm Kiwame carbon film and the bypass caps are Audio Note Kaisei non-polar.  Grid stopper and grid leak resistors are the same as the driver sockets.



Now all that is left on this amp is the output wiring.  I may save it all for when the output transformers arrive in about a week (it is going to be a long week), we will see.  I will be going out of town for a short vacation next weekend, so the amp may not be done until the first week of March, assuming the transformers arrive by then.

By the way, I don't think I ever showed the rear panel I/O.  Here it is, German WBT RCA sockets, WBT binding posts.  The switch on the left is a Goldpoint to change from speaker to headphone output.



Okay, might be all I have for a week or more, sure hope these transformers get here soon, I'll try not to think about it every...waking...moment...


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## L0rdGwyn (Feb 23, 2020)

I guess when I said "might be all I have for a week", I lied.  Just one more thing!  I decided I would knock out the output wiring, I would be very sad to have to do it when the transformers arrive.  I want to be able to just wire them up and go.

Another interior photo, this is pretty much what the end result will look like, just a few extra wires run from the output tubes/130uF caps to the OPTs, then back in to the Goldpoint switch.



Here is the switch wiring in the back corner.  Looks complicated but it is very simple. The OPT leads will connect to the "common" connection points of each switch pole, then two outputs to the headphone jacks and speaker binding posts.  The headphone jacks and negative binding posts are grounded, such that the transformer secondary is grounded in case of a primary to secondary short.  Trying my best not to kill anyone here  I will also have some 470ohm resistors across the OPT secondaries to protect the transformers from open circuits.



Here is the headphone out wiring.  The 4-pin XLR and TRS jacks are wired in parallel.  What are those Kiwame resistors?  They are similar to a resistor network that would be implemented to use headphones on a speaker amplifier.  They are in parallel with the headphone drivers.  Why do this?  The output transformers will then essentially see the same (or very similar) load at all times no matter what impedance headphone is plugged in.  9.1ohm in parallel with my 300ohm ZMFs = 8.9ohm load on the transformer, which will translate to ~3700ohm load for the output tubes (the transformers will be wired for a 3300ohm primary and 8ohm secondary).  I may play around with different values, a higher load will translate to less distortion, less power as well, but this amp will already be way overkill for headphones power-wise, so upping the resistance may improve the sound a bit.



Here is a bonus photo of some tubes that will be used in this amp: Mullard FW4/500 rectifier, Philips E424N drivers, and Visseaux 6A5G powers.  My cat Freddy decided to jump in the pic, he can't believe it's almost done either.



Okay, that is really it until the transformers get here, should be very simple to put them in when they do, then I can get right to some quick confirmatory measurements, then hopefully get listening


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## L0rdGwyn (Mar 8, 2020)

Still no sign of the LL1620 OPTs.  To keep from going mad (or a sign of descent into madness?) I've been working on another design.  I started it just to keep busy, but it looks like it is likely going to happen.

In light of adding new projects, as well as the measurements I plan to publish, I've repurposed this thread and renamed it.  Rather than having multiple threads, I am just going to continue this one with other tube audio projects I pursue.  *You've been warned!*

Anyhow, it is premature to post the schematics and whatnot, but the new amp I am working on will be a 6J5 input 45 output parafeed design.  For those unfamiliar, parafeed is a variation of a single-ended output amplifier.  It is still class A1, the major difference is the AC and DC components of the output stage are separated.

In a typical SET design, the output tube DC plate current must pass through the primary winding of the output transformer.  In order to prevent core saturation of the OPTs, it must have an air gap, which lowers the inductance of the transformer, which means poor low frequency response.  This necessitates very large OPTs for single-ended designs.

In parafeed (AKA parallel feed), the DC plate load for the output tube is provided by either a plate choke (a more conventional parafeed design), or a constant current source.  The AC output of the tube is coupled to the output transformer via a capacitor, typically a high-quality film capacitor given it is directly in the signal path.  Here are some diagrams from Tube CAD showing each.

https://www.tubecad.com/2014/09/blog0308.htm

Conventional single-ended triode output:



Parafeed output (this design is plate choke loaded, as opposed to CCS):



Another note on the parafeed schematic above: the grounded end of the OPT is connected to the cathode of the output tube.  This wiring is known as "ultrafeed", the advantage here as I understand it is the cathode is seeing the AC signal from the input loop and output loop in equal magnitude but opposite phase.  The current is then cancelled, preventing cathode degeneration and the need for a cathode resistor bypass capacitor (although Tube CAD has still drawn the capacitor here).  Spice model agrees, one less electrolytic in the signal path.

So why use a CCS loaded parafeed over single-ended output?  Here are some of the advantages:

Can use an ungapped output transformer, meaning higher inductance, better low-end frequency response, and smaller
High power supply rejection ratio (i.e., rejection of power supply noise/hum)
Power supply capacitor is no longer in the signal path > smaller, easier to design power supply! 
The subsonic LC resonance of the parafeed capacitor and OPT primary inductance is sometimes used to "tune" and optimize the low end frequency extension
Here are some disadvantages:

Additional capacitor in signal path - quality is key for good sound - giant, expensive film capacitors
For CCS loading - inefficient power supply, given more than twice the plate voltage is necessary to get full peak-to-peak swing out of the power tube (this is less of an issue with plate choke loading, as the choke can supply additional voltage via inductance)
So anyway, my plan as of right now is to build a CCS loaded 6J5 input, CCS loaded 45 output parafeed headphone amp.  Currently working on schematic drafts, optimizing my Spice model, drafting chassis layout, etc. etc. but I will just leave it there for now as it is all subject to change.

Obviously I am still learning about this topology and compiling resources, so @Tjj226 Angel or anyone else, if I have mispoken on any part, please feel free to correct me.

The wait continues...


----------



## whirlwind

L0rdGwyn said:


> I guess when I said "might be all I have for a week", I lied.  Just one more thing!  I decided I would knock out the output wiring, I would be very sad to have to do it when the transformers arrive.  I want to be able to just wire them up and go.
> 
> Another interior photo, this is pretty much what the end result will look like, just a few extra wires run from the output tubes/130uF caps to the OPTs, then back in to the Goldpoint switch.
> 
> ...


                                                          really looks nice Kenan


----------



## L0rdGwyn

Thanks, Joe!  Still on OPT watch, getting pretty antsy...already have had some "hmm, maybe I should have done XYZ thing differently" thoughts, but hey, it's the first one, probably should give myself some leeway.  I'll update here when the transformers arrive, really hoping by this weekend.


----------



## leftside

The Lundahl transformers were the parts I had to wait the longest for when Mischa was building the V6 "Thunder".


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## L0rdGwyn (Mar 10, 2020)

Yeah end of Feb came and went, but nothing to do but wait it out.  Been keeping busy working on this other design.  Parafeed has many quirks, there is always more to learn.  I'm compiling a trove of online DIY tube resources as I go too, realized when I was looking up the same resources a dozen times I should probably start keeping track of this stuff.

Maybe I will publish a DIY tube resources page here on Head-Fi if one doesn't already exist, I haven't checked.  Much of this information is very scattered, you may find a diyAudio thread from 2005 with a link to a white paper for the exact question you are trying to answer and...the webpage no longer exists.  I feel like I need to preserve this stuff LOL what happens if some of this knowledge is lost?!  Maybe I'm crazy, it probably isn't an issue for electrical engineers, but I'm going to keep my own archive at least.


----------



## Tjj226 Angel

L0rdGwyn said:


> Yeah end of Feb came and went, but nothing to do but wait it out.  Been keeping busy working on this other design.  Parafeed has many quirks, there is always more to learn.  I'm compiling a trove of online DIY tube resources as I go too, realized when I was looking up the same resources a dozen times I should probably start keeping track of this stuff.
> 
> Maybe I will publish a DIY tube resources page here on Head-Fi if one doesn't already exist, I haven't checked.  Much of this information is very scattered, you may find a diyAudio thread from 2005 with a link to a white paper for the exact question you are trying to answer and...the webpage no longer exists.  I feel like I need to preserve this stuff LOL what happens if some of this knowledge is lost?!  Maybe I'm crazy, it probably isn't an issue for electrical engineers, but I'm going to keep my own archive at least.



Have you been in contact with Kevin? If so, has he been in contact with lundahl?


----------



## A2029

L0rdGwyn said:


> Maybe I will publish a DIY tube resources page here on Head-Fi if one doesn't already exist, I haven't checked.  Much of this information is very scattered, you may find a diyAudio thread from 2005 with a link to a white paper for the exact question you are trying to answer and...the webpage no longer exists.  I feel like I need to preserve this stuff LOL what happens if some of this knowledge is lost?!  Maybe I'm crazy, it probably isn't an issue for electrical engineers, but I'm going to keep my own archive at least.



If you're looking for an old webpage that is no longer hosted, plug it into the WaybackMachine here to see cached pages going back many years: https://archive.org/


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## L0rdGwyn (Mar 10, 2020)

Tjj226 Angel said:


> Have you been in contact with Kevin? If so, has he been in contact with lundahl?



I exchanged emails with him a little over a week ago letting him know I would be out of town last week, followed up when I returned and also emailed on something unrelated yesterday, haven't heard back.  I assume he hasn't received them yet, maybe a hold up I customs?  If they aren't stateside by this weekend, I may have to start bothering him more aggressively.



A2029 said:


> If you're looking for an old webpage that is no longer hosted, plug it into the WaybackMachine here to see cached pages going back many years: https://archive.org/



Hey thanks!  I'll have to seek out the pages I couldn't access again and see if it works  another issue I have come across is old photos containing schematics/diagrams/etc. no longer being hosted, making the written information more or less useless.


----------



## Tjj226 Angel

L0rdGwyn said:


> I exchanged emails with him a little over a week ago letting him know I would be out of town last week, followed up when I returned and also emailed on something unrelated yesterday, haven't heard back.  I assume he hasn't received them yet, maybe a hold up I customs?  If they aren't stateside by this weekend, I may have to start bothering him more aggressively.
> 
> 
> 
> Hey thanks!  I'll have to seek out the pages I couldn't access again and see if it works  another issue I have come across is old photos containing schematics/diagrams/etc. no longer being hosted, making the written information more or less useless.



Im wondering if there isn't a supply chain issue on lundahls side of things. The whole world right now is a bit bottle necked.


----------



## L0rdGwyn

Tjj226 Angel said:


> Im wondering if there isn't a supply chain issue on lundahls side of things. The whole world right now is a bit bottle necked.



I wouldn't be surprised, I'm sure Lundahl and Kevin are working on it, so I am just patiently waiting.  Obviously the world is a mess right now, my fancy transformers arriving late is not a big deal.


----------



## L0rdGwyn (Mar 15, 2020)

I've learned that K&K has the transformers, however they were part of a very large shipment from Lundahl and it is still being sorted through, so sounds like next week is the week.  Edit: apparently one of my transformers was mistakenly sent to someone else, so no idea.

In the mean time, I have continued to work on my 45 parafeed design.  I have taken a dive into pentode CCS devices as alterntaive to SS cascode CCS implementations.  I have what I think are some decent draft schematics at this point.  Here is the power supply:





Given both input and output stages are CCS loaded, the PS caps are not in the signal path directly, so 600V Nichicon electrolytics will be used.  What a relief after using Clarity Caps in the last build, sheesh...
Single rail given CCS, not very concerned about cross-talk
SS rectified, ultra-fast switching soft recovery Vishay HEXFRED diodes
Using Lundahl chokes again, LL1685 at 13H for the 45 node, LL1668 (which is typically used as a anode choke) for the 6J5 node.  Overkill given the CCS load of the 6J5, but will ensure unmeasurable ripple on the input
Here is the amplifier schematic:



6J5 biased at 200V / 8mA, with adequate headroom for the CCS (10V dropout), could push the voltage bit higher too.  Cathode resistor is not bypassed.  CCS will dissipate ~2W, K&K kit comes with a 3W heat sink
Here is where things get a little interesting...the 45 CCS load is an EL83 pentode, more on that below
45 biased at 180V / 32mA, with enough headroom on the B+ to account for the EL83 dropout voltage
Given the lower performance of the EL83 CCS, will likely bypass the 45 cathode resistor
Rod Coleman filament regulators will be used for the 45, as well as his raw DC supply
The parafeed capacitor value will need to be determined experimentally.  There are ways to calculate the value using a anode choke load, not so for the CCS.  I am going to take the advice of Paul Birkeland from Bottlehead and pick up a swatch of Solen caps, clip them into the circuit, take measurements (and listen) to determine the value.  Then if I want to upgrade to a fancy PIO type, I can do so confidently (they are expensive)
Output transformer is the Sowter 8983.  This is a full-sized parafeed OPT with 8ohm and 16ohm taps (25:1 and 17:1 winding ratios, respectively).  TBD on using resistors in parallel with the output
Okay so advantages to the EL83 CCS...like I said, this pentode can dissipate 9W on the plate maximum and get that heat out of the chassis.  I would be lying to you if I said there wasn't an aesthetic draw as well, hey what can I say, I am a tube junkie!!!  These tubes are very cheap, come in lots of nice flavors (Mullard/Philips/Valvo, Telefunken, and more).  That's about it.

Disadvantages to the EL83 CCS, there are quite a few: dropout voltage is ~60-80V, I have accounted for this in my power supply and then some.  Heaters of the EL83 will need to be elevated.  The internal resistance of the EL83 in this setup is something like 260K.  On the AC impedance side, there is an issue: the 73.6K g2 dropping resistor and 1uF bypass cap act as a shunt to the CCS, so they will largely determine the AC impedance to the 45 output signal in parallel with the OPT primary.  Now something like a 75K AC impedance from a CCS is hardly the end of the world, it will still function like a high-inductance anode choke, just not as good as the gazillion ohm impedance offered by a SS solution.

So yes, quite a few disadvantages.  I may play around with using a hybrid pentode/MOSFET cascode CCS as well, with the MOSFET setting the current.  Regardless, I want to experiment with this type of CCS - worst case scenario, I need to make some changes down the road.  If I have issues with the EL83 for any reason, my back up is the EL822 pentode, which can dissipate 12W on the plate and has similarly flat grid curves.  Here are the EL83's, I will be fixing the bias on the -3V line:



So that is the design as it stands right now.  With those components, I have been doing mockups of the chassis, 10.5" x 12" x 4.25", here is the top plate with the Sowter transformers at 90 degree angles to each other:



And here is the interior layout, left the transformers in for screw-hole considerations, all subject to change of course (note the dimensions of the mains are different, mine will fall in one of two different sizes, TBD).



Alright, that is the 6J5/45 all CCS loaded parafeed design for now.  Decent draft I think, but may change based on feedback I receive across multiple forums.

If anyone has any questions or would like me to explain anything in non-technical terms, please feel free to ask, I am more than happy to.


----------



## Tjj226 Angel

Just a heads up, since everything is using a CCS, your second choke can easily be replaced by a resistor for a CRC filter. A resistor will remove some thermal load off your preamp CCS and it will be drastically cheaper. 

I would also skip the hexfred diodes. They are great for when you are dealing with a few amps of current (filament supplies), but they are just stupid overkill for B+ supplies. I would use the ever popular UF4007 and just buy like 20 of them so that you will have a decent little supply. 

I would change the 56uf capacitor to another 100uf capacitor. When you use a SS rectifier, you capacitor input is not limited. So you might as well buy a 3rd of your 100uf caps and keep things simple. 

Lastly if you are going to get a sowter custom PSU transformer, get a center tapped transformer and use a full wave rectifier. Just remember to double your voltage. In this case you would need 700v CT.


----------



## L0rdGwyn

All good points as usual T.  I figured the second choke was overkill, feel better not using it hearing it from someone else, I'll switch to an RC filter, will save me space inside along with the cash.  Changing from a 56uF to 100uF is no problem either, I'll look into using a center-tapped and full-wave setup.

While perusing the annals of early 2000s audio forum posts, I found some giant pentodes that could _possibly_ be used in extremely high-wattage CCS', the 803 and 804. The 803 can take 1600V and 125W on the plate  problem is they are direct heated with 10V / 5A thoriated tungsten filaments.  Never said they were perfect!  804 also directly heated,1500V 50W on the plate, filaments at 7.5V / 3A.  People were talking about them in the context of DC-coupled amplifiers, no idea how practical it actually is, but would love to see it, just don't touch the top cap.

http://www.r-type.org/pdfs/803.pdf
http://www.r-type.org/pdfs/804.pdf


----------



## Tjj226 Angel

L0rdGwyn said:


> All good points as usual T.  I figured the second choke was overkill, feel better not using it hearing it from someone else, I'll switch to an RC filter, will save me space inside along with the cash.  Changing from a 56uF to 100uF is no problem either, I'll look into using a center-tapped and full-wave setup.
> 
> While perusing the annals of early 2000s audio forum posts, I found some giant pentodes that could _possibly_ be used in extremely high-wattage CCS', the 803 and 804. The 803 can take 1600V and 125W on the plate  problem is they are direct heated with 10V / 5A thoriated tungsten filaments.  Never said they were perfect!  804 also directly heated,1500V 50W on the plate, filaments at 7.5V / 3A.  People were talking about them in the context of DC-coupled amplifiers, no idea how practical it actually is, but would love to see it, just don't touch the top cap.
> 
> ...



Yeahhhh, those pentodes are far from ideal.

Here is my thinking. Pentodes are a great idea if you can find a small 9 pin tube that can handle everything you need it to do for less than 40 bucks a pair. Beyond that, you get to a break even point where a SS CCS with a heat sink is just as expensive. 

United SiC has a 1200v 33A part for 12 bucks. The thermal pads are a dollar, and I have found some heat sinks from ebay for about 20 bucks. So all in all by the time you add screws and everything else, you are looking at 50ish bucks for both channels. Maybe 70 bucks if you wanted two smaller individual heat sinks for left and right channel. 

That being said, tubes do have a very clear electrical advantage over SS. They are incredibly stable when it comes to temperature drift. 

However....I made a crappy test amp using a single 6E5P tube in triode at 40ma. I was dumping about 8 watts into each CCS and I had both CCSs bolted to the top plate (so 16 watts total into the top plate). The top plate gets pretty warm (130F or so), but it works and seems pretty darn stable over time. Sooooooo shrug? Maybe the jfets are more stable than one would guess?

When I stop coughing my lungs up, my next experiment is to try the jfets I have with a heat sink to see how stable it is and just refining the implementation overall.


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## L0rdGwyn (Mar 14, 2020)

Tjj226 Angel said:


> Yeahhhh, those pentodes are far from ideal.
> 
> Here is my thinking. Pentodes are a great idea if you can find a small 9 pin tube that can handle everything you need it to do for less than 40 bucks a pair. Beyond that, you get to a break even point where a SS CCS with a heat sink is just as expensive.
> 
> ...



Haha yes, far from ideal is probably an understatement, but amusing for me to think about.  The EL83 are inexpensive ($10-15 each), and the Russian equivalent is dirt cheap.  They are pretty nice looking to boot (which might only matter to me).  Will be interested to hear the results of your experiment, the heat sink will be a fin type on the exterior?  Was looking into this for my own design before switching to pentode.  Hope you feel better.


----------



## Zachik

L0rdGwyn said:


> They are pretty nice looking to boot (which might only matter to me)


Everyone on this (and Glenn's) thread love the looks of tubes! Definitely not just you...


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## L0rdGwyn (Mar 18, 2020)

FINALLY!  They have arrived.  Off to wire these up and get them into the amp. Will then do some confirmatory voltage checks, then _hopefully_ audio bliss (assuming there are no hiccups, you never know).

Will post in a few hours with updates.


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## L0rdGwyn (Mar 18, 2020)

Holy crap...

Okay first things first, got the transformers in the amp.  Below is the secondary wiring, 470ohm resistor across the output to protect the transformer from open circuits.



Had a few other things to finish up, nothing major.  Here is the final ciruict.



After I finished wiring, I eyeballed the whole circuit, reflowed a few solder joints, then brought the circuit up on a variac and checked voltages.  Here is what I got for the two channels using the GEC U18/20:

MH4 cathode: 2.44V / 2.47V
MH4 plate to cathode: 174.4V / 184.4V
B+ top of OPT: 312V / 312V
6A5G cathode: 44.6V / 45.5V
6A5G Plate to cathode: 247.6V / 251.5V

All of these values are within 1-2% of my targets, I was absoltuely dumbfounded that I nailed them so accurately.  That crazy Georg Ohm knew a thing or two.  Difference between the MH4 plate voltages is tube variation I am sure.

Well then there was only one more thing to do...have a listen?  NO!  Take measurements of course.  Here is the frequency response, down ~2dB at 20kHz, might investigate that, but essentially flat from 20Hz - 20kHz  



I am witholding FFT measurements until the amp settles down and have some time to mess around with different tube combinations.  Here are some beauty shots of the final product:

 

So how does it sound...with all of the bias suppression I can muster, it sounds incredible.  I braced myself for bad sound (expect the worst, hope for the best kind of thing), but it didn't come.  The soundstage is absolutely expansive, the bass is deep, full, and tight, treble is detailed, airy, and not the least bit strident.  Maybe I shouldn't be, but I am still a bit shocked it all worked out!  It is a keeper.

I have been listening for about an hour straight, the panel with some of the dropping resistors on it does get warm, but so far I think it is manageable, haven't taken any surface temperature measurements yet.  Will be adding some ventilation in the near future.

I guess that is all for now, just going to keep on listening  have quite a few different 4V drivers to try out (REN904, MH4, E424N, A4110, NR52, K1694), a few different rectifiers to try, and different makes of the 6A5G, but probably won't get to it tonight, might try one other combination.  At some point I have to get this baby in my stereo, that will be its final destination, but enjoying headphone listening for now.

So overall a rousing success I would say.  I will have more impressions and measurements to come I am sure (need to get a square wave generator...).

Big thank yous to @Tjj226 Angel , @2359glenn , and @A2029 for the input along the way.  This is the hardest DIY project I have ever taken on, learned an absolute ton in the process.  I'd imagine the first one is the hardest, should be smoother sailing from now on.


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## L0rdGwyn (Mar 18, 2020)

Here are some 1930s gold Telefunken REN904 in the amp.  These are some rare tubes, was able to make a NOS pair from two different sources.  They sound so good!  I apologize in advance if you see me posting elsewhere about this amp, I'm going to have to take a personal victory lap, sorry.


----------



## leftside

Congrats. You have every right to feel proud.


----------



## mordy

L0rdGwyn said:


> Here are some 1930s gold Telefunken REN904 in the amp.  These are some rare tubes, was able to make a NOS pair from two different sources.  They sound so good!  I apologize in advance if you see me posting elsewhere about this amp, I'm going to have to take a personal victory lap, sorry.


Congratulations on finishing your special amp! Very impressive!
Are you able to describe the sound versus the GOTL?


----------



## audiofest2018

L0rdGwyn said:


> Here are some 1930s gold Telefunken REN904 in the amp.  These are some rare tubes, was able to make a NOS pair from two different sources.  They sound so good!  I apologize in advance if you see me posting elsewhere about this amp, I'm going to have to take a personal victory lap, sorry.


Since you mention about a personal victory lap, how about a victory tour so we can get a good taste!?    Just kidding!  Congratulation.


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## L0rdGwyn (Mar 18, 2020)

mordy said:


> Congratulations on finishing your special amp! Very impressive!
> Are you able to describe the sound versus the GOTL?



Thanks, mordy!  I think it is still too early to say, the GOTL is such a changeling too, but at some point soon I will listen to them side-by-side, probably this weekend.



audiofest2018 said:


> Since you mention about a personal victory lap, how about a victory tour so we can get a good taste!?    Just kidding!  Congratulation.



Never!  But thank you  I am hoping to make it to ZMFestivus again this year though, if so I will bring this amp along and my other one if it is done by then.


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## maxpudding

This is exciting!

Congratulations on the completed build. The amp, from the way you describe its sound, is incredible. Hoping one day to get to listen to your amp


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## whirlwind

Congrats are in order here.

It looks fantastic Keenan, and I am glad that the sound matches the looks.
This has been a wonderful thread to follow...good job and I look forward to your next project.


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## L0rdGwyn

whirlwind said:


> Congrats are in order here.
> 
> It looks fantastic Keenan, and I am glad that the sound matches the looks.
> This has been a wonderful thread to follow...good job and I look forward to your next project.



Thanks, Joe!  Much appreciated.  Next project is underway, waiting to hear back on a transformer quote from Sowter UK, just no timeline given the worldwide slowdown.


----------



## chrisdrop

L0rdGwyn said:


> Holy crap...
> 
> Okay first things first, got the transformers in the amp.  Below is the secondary wiring, 470ohm resistor across the output to protect the transformer from open circuits.
> 
> ...


Absolutely beautiful. For some reason, Head-Fi stopped sending me updates for ANY threads in the past day or three. VERY glad I popped over to see some good news! ENJOY IT. Well earned.


----------



## Xcalibur255

Just found my way here for the first time and have read through it all.  I don't know how I missed it in Dec when it started..... probably forgot to follow a link at the time.

What a cool journey.  I knew watching a DIY'er come out of the egg would be a fun time, but seeing you produce a finished product that looks like you've been doing it for 20 years already is just awesome.  The detailed information is sure to be helpful to others who are interesting in following you in this journey too.

Congrats Keenan and I'm looking forward to seeing what you post here in the future.  Makes me wonder if you have any plans to do this as a side business, because you obviously have the ability for it.


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## L0rdGwyn (Mar 19, 2020)

Thank you again for the support everyone, it means a lot to me that people have enjoyed following this thread, I hope to keep it going with other interesting projects.  As of right I have no immediate plans to make amp building a side gig, but you never know what the future holds.  It is a heck of a lot of work though, I would have to give it careful consideration.

I only have a little time tonight with the amp after work, so I decided I would do something drastic and change all of the tubes, why not.  Here is an early black plate Fivre 5Z3 rectifier, another pair of Sylvania 6A5G albeit with the alternative flat plate construction, and some tubes that probably belong in a museum, metallized Marconi MH4.




I also found some interesting knick knacks inside the box of one of my Telefunken REN904.  The available datasheets for this tube are very sparse, this is the most complete one I have seen, first one I have found with full set of anode characteristic curves.  If I ever get bored, I might scan and restore it in Photoshop, it is from 1938.


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## L0rdGwyn (Mar 21, 2020)

Finally have a day off after finishing the amp.  After running some errands this morning, getting to sit down and listen.

Using the early foil getter Sylvania 6A5G, Fivre 5Z3 rectifier, and Opta REN904.  When I was messing around with these tubes in the GOTL, I had come to the conclusion the Opta REN904 was sort of a "tier 2" driver in this family.  Boy was I wrong.  Now properly biased and CCS loaded, the midrange detail and air is fantastic!

As I've mentioned before, I still love the HD650, especially for its ability to scale with upstream gear.  This might be the best I have ever heard it.  The staging, air, and midrange detail is pretty stunning considering the cost of this headphone.  Really looking forward to trying others.


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## L0rdGwyn (Mar 22, 2020)

I've been duped by Visseaux.

While working on this amp, I purchased a pair of French Visseaux 6A5G.  This is the only other tube manufacturer to make the 6A5G other than Sylvania, likely under their license.  My past experience with Visseaux tubes has been very positive, so I bit the bullet and paid a pretty penny for a NOS pair of these beauties.....

But while listening, there is an obvious audible hum, unlike the Sylvanias which are dead silent, and I immediately suspected they were not in fact indirectly heated, which was the major feature of the 6A5G over the 6B4G.

Took some measurements, and sure enough, there are 60Hz and 120Hz peaks down at something like -45dBFS!!!  I checked continuity between the heaters and cathode to see if they were center-tapped (the other difference between 6B4G and 6A5G), and they certainly are.  Very close inspection of the internals and I cannot see any obvious cathode sleeves...



So, Visseaux appears to have made a sort of hybrid between a 6B4G and 6A5G despite the labeling.  It is basically a 6B4G with center-tapped filaments, or a 6A5G without cathode sleeves.  What a bother!  It is too bad because they are _excellent _sounding tubes.  They certainly aren't unusable, the hum is only very intrusive with quiet music.  I'm hopeful it will be less obvious or even undetectable when listening with speakers.  C'mon guys!  What are you doing.  Maybe they missed the memo (although the cathode is clearly in the Sylvania datasheet written in French...).

http://www.nj7p.org/Tubes/PDFs/Frank/121-Sylvania/6A5G.pdf

Thomas Mayer over on VinylSavor did mention in his article back in December that addition of these cathode sleeves likely made assembly very difficult, so maybe they thought center-tapping the filaments was good enough.  Hey, some people swear by AC on DHT tubes, maybe it is a feature not a defect  have to wonder if any of the Visseaux 6A5G do have cathode sleeves, but I am not likely to try again to find out.

http://vinylsavor.blogspot.com/2019/12/tube-of-month-6a5.html

In other news - I placed my order for the mains and parafeed transformers from Sowter for my 45 build.  Timeline to receive them is up in the air given the ever-changing environment we are living in, we will see, I am not in any rush this time around.  Exchanging emails with Brian Sowter, an interesting subject came up.  It appears that Sowter has been acquired by Carnhill, and while he did not say it explicitly, it sounds as though Brian is planning to step away from the company after the transition and things are running "smoothly".  I have no experience with them, being new to the game, but Brian Sowter is known for being one of the premier transformer designers working today.  While I highly doubt the quality will suffer when he leaves, I certainly feel some sort of pressure to make a nice amp given these may be some of the last transformers made during his tenure with the company!  So hopefully this parafeed build is successful.

Otherwise, still listening and enjoying the 6A5G amp.  I am really blown away by the sound, I had hoped for it to be a "contender" with other tube amps I have heard, but it has truly exceeded my expectations, I hope I have a chance to share it with others in the near future.


----------



## Tjj226 Angel

L0rdGwyn said:


> I've been duped by Visseaux.
> 
> While working on this amp, I purchased a pair of French Visseaux 6A5G.  This is the only other tube manufacturer to make the 6A5G other than Sylvania, likely under their license.  My past experience with Visseaux tubes has been very positive, so I bit the bullet and paid a pretty penny for a NOS pair of these beauties.....
> 
> ...



Hmmmmmmmm. Kinda troubling news all the way around. 

Can't say I am overly thrilled about the sowter take over. If we are lucky the new company will have the cash flow required to hire some more workers and speed up production.


----------



## L0rdGwyn (Mar 22, 2020)

Tjj226 Angel said:


> Hmmmmmmmm. Kinda troubling news all the way around.
> 
> Can't say I am overly thrilled about the sowter take over. If we are lucky the new company will have the cash flow required to hire some more workers and speed up production.



Yes, he also mentioned that Sowter has had a significant backlog lately, but their capacity will greatly increase with the Carnhill takeover once they are caught up.  So looks like a changing of the guard with increased production, I'm guessing this is his retirement plan.


----------



## L0rdGwyn (Mar 24, 2020)

I performed a series of experiments today.

As I mentioned in the build log, I placed a 9.1ohm resistor in parallel with the headphone output of my 6A5G SET amp.  This gives the OPT an approximate 8ohm secondary impedance, which in turn gives the output tube its intended 3300ohm load.

Now there is no reason we have to use a 9.1ohm resistor, we can essentially adjust the primary load by adjusting the value of this resistor.  Along the way, I purchased some other values for the express purpose of this experiment.

So today, I soldered some alligator clips onto a pair of 9.1ohm resistors and a pair of 16ohm resistors.  I wanted to see the effect on the sound with an approximate 8ohm secondary, 16ohm secondary, and no parallel resistance.  With no parallel resistance, the full 300ohm impedance of my headphone is reflected across the transformer, giving the output tube a nearly flat AC load line.



Measurements with the three setups showed no effect on frequency response.  However, it did affect distortion.  The below numbers are all at ~0.5V RMS output, which I have found is close to my listening volume.

8ohm: 0.33% THD, H2 at -54dBFS, H3 -80dBFS
16ohm: 0.17% THD, H2 at -60dBFS, H3 -80dBFS
No resistance: 0.077% THD, H2 at -65dBFS, H3 -80dBFS

As expected, second harmonic varied with changes in parallel resistance while the higher order harmonics remained relatively constant.  So obviously the "no resistance" config sounded best since it had the least amount of second harmonic distortion, right?  Nope!  Subjective listening told a different story.

I listened to 15-20s loops of very familiar music and was able to quickly clip in and out different resistances for comparison.  For the most dramatic difference - and to get a grasp of the audible changes - I compared the 8ohm and "no resistance" setups first.  Removing the resistance entirely and reducing the amount of H2 resulted in a more pronounced center image and reduction in perceived lateral space and layering.  Instrument separation was lessened in this configuration, while the center image was closer and more pronounced.  There was a relative increase harshness as well.  The reduction in the sense of lateral space made several instruments in sound field lie on top of one another rather than a more spacious, wide distribution, which resulted in a perceived decrease in clarity.

Comparison of the 8ohm and 16ohm secondary configurations told a similar albeit less pronounced story - smaller soundstage, less instrument separation, more pronounced center image, a bit more harsh.  The higher H2 provides a more well-distrubted, layered, and airy sound field.  So after all of that, I ended up sticking with my original 8ohm secondary configuration LOL but hey, I wanted to see the effect.

Once again, this shows that good measurements do not beget good sound.  As Bob Katz discussed in his Innerfidelity article "Adventures in Distortion", what I suspect is happening is the increased H2 is masking the higher order harmonics, which are much more detrimental to sound.  Likely other factors in play too.

https://www.innerfidelity.com/content/katzs-corner-episode-25-adventures-distortion

Katz determined -60dBFS to be the optimal amount of H2 for a pleasing listen, however, I felt the -54dBFS config still held an advantage.  Just goes to show, we all hear it differently 

Obligatory YMMV, my subjective listening impressions, etc. etc. etc.


----------



## Tjj226 Angel

L0rdGwyn said:


> I performed a series of experiments today.
> 
> As I mentioned in the build log, I placed a 9.1ohm resistor in parallel with the headphone output of my 6A5G SET amp.  This gives the OPT an approximate 8ohm secondary impedance, which in turn gives the output tube its intended 3300ohm load.
> 
> ...



Very interesting indeed. The thing to look at would be the frequency and phase response for the varying resistance. 

One thing @johnjen mentioned to me with our experiments is that the parallel resistor will actually compensate for the headphone's rising impedance curve. In other words, the amplifier will see a near perfect resistive load on the secondary, so the primary impedance remains somewhat constant.


----------



## L0rdGwyn

Tjj226 Angel said:


> One thing @johnjen mentioned to me with our experiments is that the parallel resistor will actually compensate for the headphone's rising impedance curve. In other words, the amplifier will see a near perfect resistive load on the secondary, so the primary impedance remains somewhat constant.



Interesting...I didn't look into phase measurements, but I'll be repeating the process on the 45 amp and will measure in tandem with the FR.


----------



## L0rdGwyn (Mar 24, 2020)

Early on in the design of this amp, I had planned to put DC on the heaters and use a voltage regulator.  For that reason, I collected driver tubes in the MH4 family that have 4V 0.65A heaters, rather than 1A.  Well DC on the heaters was thrown out and I don't regret it, however I was concerned that I would not be able to use my 0.65A tubes given the heaters would be run over voltage.

Today I put them in anway and took some measurements.  Thankfully, the voltage is not as excessive as I expected, around 4.5V, I can live with that.  Great news because I can use the Mullard NR52, a fantastic driver tube.  Started playing around with different rectifiers today, no super critical A-B listening, but so far any differences are very subtle.

I know I sound like a broken record, but I'm still mindblown by how good this amp sounds, getting performance out of my headphones that I simply haven't heard before.  I keep waiting for my ears/brain to adjust and tell me it actually isn't all that great, but it just hasn't happened, the next song comes on and I get goosebumps again.


----------



## L0rdGwyn

I ordered the chassis for the 45 amp today, decided I would do myself a favor and allow my chassis maker to do more of the drilling this time around.  Here is the layout:

 

The chassis will be in silver with black hardware, matching the Sowter transformers.  Tubes will be all in a row, 6J5 on the interior, 45 on the exterior.  Going for a more understated, minimalist look.  Included some ventilation on the back of the top plate behind the parafeed transformers.  Also, the entire bottom plate will be perforated aluminum sheet metal for ventilation.

I don't think I documented this anywhere in the thread, but *I have abandoned using the EL83 pentode as the 45 plate load.*  After crunching the numbers, the pentode CCS brings along too much baggage with too little performance.  SO, we have moved back to an all solid-state, cascode CCS loaded design, on both the 6J5 and 45.  I have laid out the chassis for the use of a pair of specific heat sinks mounted to the back panel, with cutouts such that the MOSFETs can be mounted directly onto them.

On the transformer front, I won't be receiving them for 2-3 months, so they will again be the rate-determing step.  Not a problem as I am still grooving to the 6A5 amp, happy to take it slow this time.  At this point though, part selection is nearly complete, just need to dial in final values, should be a nice little amp.


----------



## L0rdGwyn (Mar 28, 2020)

Since I have a nice pair of XF2 EL34 on hand, and the pinout is somewhat similar to the 6A5G, thought I would do a little experimenting with them today.  I had originally planned to use the triode-strapped EL34 in this amp, but then I was introduced to the 6A5G, and the rest is history.  Let's see what I am missing out on!

To run these as triodes, I shorted g3 to the cathode, connected a 100ohm 1/2W resistor from g2 to the plate, and paralleled a resistor across the 6A5G cathode resistor with some alligator clips.  I had an extra pair of 750ohm 5W resistors from the build (same as the 6A5G cathode resistor), giving me a 375ohm cathode to ground resistance when placed in parallel.

Measurements with the tubes in place gave me this bias point:

Va-k: 295V
Vk: 20V
Ia (based on curves): ~70mA

Not bad!  I didn't bother center-tapping the heaters since this isn't permament, so there is a litle hum, but not a bother with music playing.

Distortion measurements show 0.68% THD with H2 at around -48dBFS with ~0.5V into 300ohm.  About twice the THD of the 6A5G, which is expected since the EL34 isn't a true triode.



So how do they sound?  Really good!  Some of the ridiculous staging and airiness of the 6A5G is lost, but the EL34 is no slouch itself.  The increased distortion gives it a warmer, smoother tonality, still very pleasing and dynamic.  A very nice sound.  Still happy with the 6A5G and I will be switching back, but I might leave these in for the day for a healthy listen (and I'm too lazy to reverse it right now ).

Gotta stay busy at home!  Fun times with tubes.


----------



## Tjj226 Angel

L0rdGwyn said:


> Since I have a nice pair of XF2 EL34 on hand, and the pinout is somewhat similar to the 6A5G, thought I would do a little experimenting with them today.  I had originally planned to use the triode-strapped EL34 in this amp, but then I was introduced to the 6A5G, and the rest is history.  Let's see what I am missing out on!
> 
> To run these as triodes, I shorted g3 to the cathode, connected a 100ohm 1/2W resistor from g2 to the plate, and paralleled a resistor across the 6A5G cathode resistor with some alligator clips.  I had an extra pair of 750ohm 5W resistors from the build (same as the 6A5G cathode resistor), giving me a 375ohm cathode to ground resistance when placed in parallel.
> 
> ...




Nope. Scrap your opinion. You are overdriving the transformer and you need to ground your filaments so that your amp doesn't hum. 

Once you bring the tubes down to 60ma and you solve the hum problem, then you should come back and edit your impressions. But right now I would suspect that the amp is not sounding anything close to what it should.


----------



## L0rdGwyn

Tjj226 Angel said:


> Nope. Scrap your opinion. You are overdriving the transformer and you need to ground your filaments so that your amp doesn't hum.
> 
> Once you bring the tubes down to 60ma and you solve the hum problem, then you should come back and edit your impressions. But right now I would suspect that the amp is not sounding anything close to what it should.



Nah that's okay, I'm aware it isn't optimal, the heaters need to be grounded and the OPT is over current, I just don't care.  It's probably closer to 65mA on the primary, just having some fun with junk box parts.


----------



## Tjj226 Angel

L0rdGwyn said:


> Nah that's okay, I'm aware it isn't optimal, the heaters need to be grounded and the OPT is over current, I just don't care.  It's probably closer to 65mA on the primary, just having some fun with junk box parts.



Ground the heater at least. I think you will be pretty shocked by how much of a sonic difference it makes.


----------



## L0rdGwyn (Mar 28, 2020)

Tjj226 Angel said:


> Ground the heater at least. I think you will be pretty shocked by how much of a sonic difference it makes.



Alright if you insist, I will ground the heaters and have another listen.  I want to check something else at the same time, curious how the AC noise on the FFT compares between the 6A5G and a more conventional indirectly heated tube like the EL34.  Obviously this wasn't going to work with the heaters floating, but now I can kill two birds with one stone


----------



## L0rdGwyn

Alright @Tjj226 Angel , I grounded the heaters.  In rapid succession, I did some critical listening, turned off the amp, cut out the center-taps, and listened again with the hum.  Was the sound improved with the heaters grounded?  Yeah I think it was, for the obvious reasons of having a blacker background and separation without the hum, but also better space and treble definition.  My initial impressions were positive, I still think they have a warmer, smoother tone than the 6A5G, but are certainly worthy of their own build, sound great in single-ended class A.  I'll have to figure out what I am going to do with them.  I know you are a proponent of an EL34 class A PP design, maybe a Q1 2021 project.


----------



## Tjj226 Angel

L0rdGwyn said:


> Alright @Tjj226 Angel , I grounded the heaters.  In rapid succession, I did some critical listening, turned off the amp, cut out the center-taps, and listened again with the hum.  Was the sound improved with the heaters grounded?  Yeah I think it was, for the obvious reasons of having a blacker background and separation without the hum, but also better space and treble definition.  My initial impressions were positive, I still think they have a warmer, smoother tone than the 6A5G, but are certainly worthy of their own build, sound great in single-ended class A.  I'll have to figure out what I am going to do with them.  I know you are a proponent of an EL34 class A PP design, maybe a Q1 2021 project.




Hmmm interesting. See when I forget to ground the heaters (even with a very similar build to yours) I always get a weird artifact in the audio. I was more concerned you had a similar artifact in your audio than I was about hum. 

But hey, if all you have to contend with is hum, then thats cool. 

Im glad that the 6A5G is working out as well as it is. If you prefer it over the EL34, then you would probably prefer it over any octal pentode tube. So that's really good news in my book considering our previous conversations.


----------



## L0rdGwyn

Tjj226 Angel said:


> Hmmm interesting. See when I forget to ground the heaters (even with a very similar build to yours) I always get a weird artifact in the audio. I was more concerned you had a similar artifact in your audio than I was about hum.
> 
> But hey, if all you have to contend with is hum, then thats cool.
> 
> Im glad that the 6A5G is working out as well as it is. If you prefer it over the EL34, then you would probably prefer it over any octal pentode tube. So that's really good news in my book considering our previous conversations.



There may have been something funky going on in the upper registers, but a back-and-forth A/B wasn't really possible.  I do think it sounded better with the heater grounded, beyond the hum.  Only reason I didn't do it initially was...laziness  I just wanted to get the flavor of the EL34.

The 6A5G are great, very happy with them.  Maybe you will get to hear this amp someday.


----------



## Xcalibur255

@A2029 mentioned he was building a KT150 triode strapped amp and I've been very eager to hear how it turns out for him.  I suspect many of the triode strapped pentodes can sound fairly close to the DHT sound if they are implemented well.


----------



## chrisdrop

This is perhaps a dumb question, but hey; home. Why did you go SET not OTL?


----------



## L0rdGwyn

Xcalibur255 said:


> @A2029 mentioned he was building a KT150 triode strapped amp and I've been very eager to hear how it turns out for him.  I suspect many of the triode strapped pentodes can sound fairly close to the DHT sound if they are implemented well.



The triode-strapped EL34 sound fantastic, if I had kept my original plan and used them rather than the 6A5G, I would have been very happy.  Being able to avoid a DC filament supply is a big plus.  I'm sure Mischa's KT150 build is going to be exceptional.



chrisdrop said:


> This is perhaps a dumb question, but hey; home. Why did you go SET not OTL?



Well the origin of this amp started with a potential Glenn build.  I already had the GOTL and a spot in Glenn's queue, and he and I were sort of exploring these driver tubes together, me with my planned amp and him with his preamp.  I figured since I had already owned a few OTLs, I would go for a SET.  I started gathering components to send to Glenn for when he was ready.  It got to a point where I thought, "well, I already have all this stuff, why don't I just build it?"  Seemed pretty simple at the time, boy was I wrong HA!  But glad I took it on.

Partway through, my mindset changed from a headphone amp to a single-ended class A speaker amp, which is really the primary purpose of this build, another plus of going SET.  It's final home is going to be in my stereo with a pair of high-sensitivity speakers.


----------



## chrisdrop

L0rdGwyn said:


> The triode-strapped EL34 sound fantastic, if I had kept my original plan and used them rather than the 6A5G, I would have been very happy.  Being able to avoid a DC filament supply is a big plus.  I'm sure Mischa's KT150 build is going to be exceptional.
> 
> 
> 
> ...


Is an OTL amp less / not appropriate for driving speakers?

What character differences sound-wise are expected in a SET amp Vs an OTL?


----------



## L0rdGwyn (Mar 30, 2020)

chrisdrop said:


> Is an OTL amp less / not appropriate for driving speakers?
> 
> What character differences sound-wise are expected in a SET amp Vs an OTL?



OTL can be used to drive speakers, but it is a more difficult design.  Output transformers are used to take the high impedance, high voltage source from the output tube and transform it to a low impedance, high current source to drive low impedance speakers.  To achieve the same in a typical OTL design requires paralleling a high number of tubes, which generates a lot of heat and requires a lot of current, and tube reliability can be a problem.  These amps can also utilize negative feedback to lower the output impedance further.  The high output impedance isn't so much of an issue with high impedance headphones and an appropriate damping ratio can be achieved with a reasonable number of output tubes.  But driving/damping an 8ohm speaker is another story.  One way around this is to use high impedance speakers, but they aren't really sold commercially, would need to be custom built.  I'm sure there is some trickery out there and unique OTL circuits to get around the issue, it isn't something I've looked into deeply.

I think the sound differences are implementation dependent, hard to say how they compare generally across the board, and I have never heard an OTL speaker amplifier.  One argument is that with an OTL, you are avoiding non-linearities generated by the output transformer of a SET and saving cost at the same time.  But if you are using quality transformers, it should not be an issue.  If you live somewhere cold, your OTL speaker amp will keep you warm in the winter too


----------



## Xcalibur255

chrisdrop said:


> Is an OTL amp less / not appropriate for driving speakers?
> 
> What character differences sound-wise are expected in a SET amp Vs an OTL?



The main purpose of an output transformer is to change impedance.  Generally tubes have an output impedance on their own that is so high you would not get any power transfer to the load with typical 8 ohm speakers.  OTL speaker amps do exist (Google the Atma-sphere monoblocks for an example) but they overcome the impedance issue by paralleling a crapload of tubes together so a huge honking amp that belches out heat from it's many many tubes is a mandatory side-effect of the situation.  OTL is a way more natural proposition for headphone use overall.


----------



## L0rdGwyn

No major updates on the 45 amp, but did start some work on it.

Figured while I am waiting on the transformers and chassis, I would start putting together some of the PCBs, there will be eight boards in this amp.  These are the 45 filament regulators, Rod Coleman's design, along with his raw DC supply.  Final transistors aren't mounted yet, they will need heatsinking, waiting for the chassis to see how much slack I will need on the leads.




These will be fed by 6.3V 5A windings on the custom mains transformer.  Dedicated filament transformers are often used in DHT builds (e.g., Hammond, AnTek) rather than running it off the HT transformer.  I discussed this with Rod, the reason for his recommending dedicated filament transformers is a concern for regulator rectifier noise coupling into the HT winding of the mains transformer.  But seeing as both amplifiication stages are going to be CCS loaded with >100dB PSRR, I'm running it off the mains without concern.  Gotta love that CCS load!  Will save me a big chunk of real estate.

The challenge of laying out this amp was balancing the size of the parafeed capacitors with my desire to keep the chassis somewhat compact.  The other challenge was mounting power supply components - since the cores of the Sowter transformers lie flush with the top of the chassis, a significant amount of hardware mounting space on the top plate is lost.  I could countersink so screws also lie flush with the top plate, but it would be an enormous PITA if I ever need to move/adjust a components position.  I needed a solution to minimize the footprint of the power supply.  I found these great capacitor clips from Cornell Dubilier, let you mount a 35mm cap on its side with a single 3mm screw!  Most capacitor clamps take two minimum, often three.  Saved me a lot of trouble and will keep the power supply footprint very small.



That's all for now, will do the CCS boards next.  Chassis is already machined and being plated.  When I get the transformers in two months or so, this amp will come together fast, should be a very quick build.  The interesting part will be testing various parafeed cap values, taking measurements, listening...then deciding what the final caps will be when the capacitance is determined.  Testing will be done with Solen caps, I'll have to see what will fit if I want to upgrade to something fancier.  I've carved out space in the layout for some big-ass axial caps.

6A5 amp is still rocking my world, I am ordering a pair of Omega speakers to pair with it, I'll post some picks of the model I am going for once the order is finalized.  They'll be around 97-98dB sensitive, very nice


----------



## L0rdGwyn (Apr 4, 2020)

Ordered some speakers today from Omega.   Louis from Omega specializes in crossoverless, high sensitivity, single-driver designs.  These are his "High Output 8" monitors.  In his high output designs, a second woofer is added and is cutoff in the midbass, frequency depending on the driver, 200Hz in this case.  They are 98dB/W sensitivity, 4-6ohms nominal impedance, Louis' recommendation based on my genre preferences, amplifier, etc.  Should really sing with my SET.  Mine will be in a real walnut veneer, "5-star walnut" I am told, not sure what that means, but sounds good to me   will look similar to the one below.  Pretty big cabinets at 20"x14"x11" and 32lbs a piece, going to get some beefy stands for them from Skylan.

I've been shopping around for some sensitive speakers to pair with this amp for a while, not sure how I missed Omega for so long, they really seem to fly under the radar and have a cult following.  Given the build quality, craftmanship, and sonic performance, they are very reasonably priced IMO.  In a lot of ways, Omega reminds me of ZMF.  Thanks for your $0.02 along the way @Xcalibur255 , 4-6 weeks lead time.


----------



## L0rdGwyn (Apr 5, 2020)

Just to see what all of the hype is about, this morning I did another experiment.

You might recall that I left the driver tube cathodes unbypassed in the 6A5 amp given the CCS load.  I had some leftover electrolytics from the build, some non-polar Audio Note Kaisei, I thought I would clip in the caps, bypass the cathodes, and see how it affected the sound.  Many tube DIYers go to great lengths to remove these electrolytics from the signal path, but how bad can it be really?

The alligator clips I'm using don't have teeth, so the caps can be very quickly removed for listening comparisons.




The difference is pretty BIG!  With the cathodes bypassed, there is a collpase in the soundstage, instrument separation suffers, there is less definition in the bass, and the high end sounds more harsh.  It isn't subtle whatsoever.  The amp doesn't sound _bad _with the cathodes bypassed, but once you've heard them unbypassed, no way you could go back.  Audio quality is all relative after all.  I did do some FFT measurements, bypassing the cathode resistors doesn't seem to affect distortion in a measurable way.

So the hype is real, keeping electrolytics out of the signal path is the way to go.  Luckily in the 45 parafeed amp, I will be leaving the 6J5 cathode resistors unbypassed, and I should be able to get away with leaving the 45 cathode resistors unbypassed as well using the "Western Electric" parafeed wiring configuration.



This setup could potentially inject some power supply noise onto the cathode, but seeing as I am back to using a MOSFET cascode CCS on the output tube (rather than the pentode CCS), I think I will get away with it.  That would leave only two capacitors in the signal path, the interstage coupling caps and the parafeed caps, which will both be high quality film types.

Since I am waiting around for parts again, the gears have started turning on an all DHT two-stage amplifier.  This is probably a 2021 project, so I won't talk about the details.  Might be collecting some tubes for it, but I'll certainly be looking into ways to avoid bypass caps in this setup too.  To be continued...

Another thing I did yesterday, which you might be able to see in my photo above, was rerouting the B+ wiring from the mains transformer to the rectifier.  A made a novice mistake routing this wiring along the periphery of the chassis originally.  Keeping this loop area small should help with power supply noise, and seems to have made a measurable difference.  Hindsight is 20/20.

TTFN!


----------



## Tjj226 Angel

L0rdGwyn said:


> No major updates on the 45 amp, but did start some work on it.
> 
> Figured while I am waiting on the transformers and chassis, I would start putting together some of the PCBs, there will be eight boards in this amp.  These are the 45 filament regulators, Rod Coleman's design, along with his raw DC supply.  Final transistors aren't mounted yet, they will need heatsinking, waiting for the chassis to see how much slack I will need on the leads.
> 
> ...



Lol. You went from "meh, I might do a 45 amp later on" to "the chassis is done" pretty darn quickly.

I should find out who does your cassis. I need top plates, but I can't get to the CNC machine because of the pandemic.


----------



## Tjj226 Angel

L0rdGwyn said:


> TTFN!



Try LED or battery bias. 

LED bias is super easy to implement, and depending on the circumstance, I like it more than an unbypassed cathode resistor. 

It greatly lowers the impedance to ground like a bypass capacitor would, but it doesn't have weird frequency and timing issues that a cap has.


----------



## L0rdGwyn (Apr 7, 2020)

Tjj226 Angel said:


> Lol. You went from "meh, I might do a 45 amp later on" to "the chassis is done" pretty darn quickly.
> 
> I should find out who does your cassis. I need top plates, but I can't get to the CNC machine because of the pandemic.



Well, other than going to work, I have literally nothing else to do lol.  It's taking so long to get transformers, had to decide if I was going to go for it well in advance.  Won't get the 45 transformers until May or June.  The chassis maker is Landfall Systems, Dave there is a great guy to work with, he does the machining and has the plating done at a separate shop.


----------



## L0rdGwyn (Apr 11, 2020)

I was originally going to post this on the 2359glenn thread, but thought I should keep my DIY ramblings here...been doing a lot of reading into A2 designs.

Anyone have any experience with the Ampsandsound Kenzie?  I've only heard the ZMF Pendant from them.  The Kenzie uses the 1626 output tube, the reason I'm curious.  These tubes are dirt cheap, plentiful, and look very nice!



Capable of being driven into A2 for better linearity, in a DC coupled design or using a FET source follower perhaps.  Only a 5W max plate dissipation, but pretty intriguing for a budget headphone amp.  Could go for a 125V 40mA A2 bias point with -7V on the grid, would just need a suitable 5K 40mA transformer.  If using the LL2765 ($125 each), could do 165V 30mA, but linearity would suffer.

125Va / 40mA Ia / -7Vg


CCS load a driver that can swing >90Vpp with decent gain and a FET source follower and this hybrid would get you a little over 1W into a 5K primary. If you can find some reasonable transformers (or go with the LL2765), bet you could make a kickass headphone amp pretty inexpensively with a regulated supply.  You can get a NOS pair of 1626 for like $30.  This might go on my short list of things to experiment with.


----------



## Xcalibur255

Once you've built all the pie in the sky projects, it might be a rewarding pursuit to go the other direction and see how much performance you can wring out of a cheap and cheerful design.  I think taking on both ends of the spectrum has a lot to teach.


----------



## L0rdGwyn

Absolutely, I'm starting to keep an eye out for more budget-friendly ideas, tubes that reasonably priced, available, and linear.  Who knows, maybe if well-implemented, something I could build for others.


----------



## Tjj226 Angel

Xcalibur255 said:


> Once you've built all the pie in the sky projects, it might be a rewarding pursuit to go the other direction and see how much performance you can wring out of a cheap and cheerful design.  I think taking on both ends of the spectrum has a lot to teach.



I have always wanted to do a youtube series on building your own hifi stereo system at costco. 

Aluminum foil capacitors. PIckle jar vacuum tubes. ect. 

I sort of had a theme where I would show people how to make hifi stuff in an apocalypse. Who knew that my idea would become so relevant?


----------



## kvik

The Darling Head Amp from Toolshed Amps also use 1626
https://www.toolshedamps.com/darling-stereo-desktopheadphone-amplifier


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## L0rdGwyn (Apr 13, 2020)

kvik said:


> The Darling Head Amp from Toolshed Amps also use 1626
> https://www.toolshedamps.com/darling-stereo-desktopheadphone-amplifier



Hmmm that's interesting...not the first I've heard of the "Darling" 1626 amplifier.  The original "Darling" was created by a guy named Bob Danielak in the late 1990s, he generated interest in this tube in the DIY community with his SET designs.  In fact, if you Google 1626 tube amp, you'll get a ton of DIY hits for "Darling" variants.  The Toolshed Darling seems to be descendant of his work, probably the only thing they have in common is they are both 1626 SET designs, class A1 I assume, seems to align with their power output specs.  Looks like it uses an 84 rectifier and 12SL7 driver, DC on the heaters.  Someone reviewed it on Head-Fi here, can check out the internals:

https://www.head-fi.org/showcase/toolshed-darling-1626-set-amplifier.23931/reviews

Looks like a lot of time and effort has gone into the chassis, not my style but the craftmanship is obvious!  Pretty expensive though at $2600.  For less than $1000, could build something pretty neat with these tubes I think.  Haven't dived into any details, but like I said, maybe DC coupled or using an interstage FET buffer to drive the 1626 into A2.  In A1, it is going to hit the knee of the grid curves very quickly on the negative peaks, but may not matter much with headphones.  Could parallel a few of these and drive some sensitive speakers   I think you might get better performance out of this tube in A2.

Pete Millett got 1.4W out of a single 1626 driving the grid with an opamp: http://www.pmillett.com/pwrop.htm


----------



## L0rdGwyn

Another interesting tube to design around might be the RFT EC360.



Not super available, but pretty cheap.  Internal resistance from the spec sheet is 120ohm! Mu of 2.5.  I'm a fan of the East German RFT brand.

Datasheet: http://tdsl.duncanamps.com/pdf/ec360.pdf

Here are some curves I was able to dig up:


----------



## Tjj226 Angel

I would look more at Shuguan and Sovtek for current production tubes that are cheap. 

The Sovtek 6H30 might make an interesting little OTL amp. If you put both halves of the triode in parallel you could probably get decent output impedance.


----------



## Xcalibur255

L0rdGwyn said:


> Hmmm that's interesting...not the first I've heard of the "Darling" 1626 amplifier.  The original "Darling" was created by a guy named Bob Danielak in the late 1990s, he generated interest in this tube in the DIY community with his SET designs.  In fact, if you Google 1626 tube amp, you'll get a ton of DIY hits for "Darling" variants.  The Toolshed Darling seems to be descendant of his work, probably the only thing they have in common is they are both 1626 SET designs, class A1 I assume, seems to align with their power output specs.  Looks like it uses an 84 rectifier and 12SL7 driver, DC on the heaters.  Someone reviewed it on Head-Fi here, can check out the internals:
> 
> https://www.head-fi.org/showcase/toolshed-darling-1626-set-amplifier.23931/reviews
> 
> ...


In a simpler chassis those amps would actually be $1000 less I bet.  That isn't a criticism of them at all, there is a place in the world for style and craftsmanship, but it does serve to highlight the advantage of DIY in terms of savings or re-directing the "bling" budget into more quality parts.


----------



## L0rdGwyn

Xcalibur255 said:


> In a simpler chassis those amps would actually be $1000 less I bet.  That isn't a criticism of them at all, there is a place in the world for style and craftsmanship, but it does serve to highlight the advantage of DIY in terms of savings or re-directing the "bling" budget into more quality parts.



Agreed, has to be the most expensive component of that amp.  The custom stuff I have done at Landfall is around $200 for machining, brushing, and anodizing.  Not cheap, but I like the customizability, minimalist look, and quality.  For me the bling is the tube loadout and iron, I prefer the other parts to be understated so as to give them the stage.  DIY definitely has its advantages with being able to allocate funds where performance matters most, but I understand those guys need to make money to run a business, it's a high-margin low-volume industry.


----------



## Xcalibur255

I think finding Landfall back in 2012 has turned out to be the most meaningful contribution I've made to all of this.  Being able to specify any X-Y-Z dimension is such a boon compared to the Chinese chassis products that are fixed dimension.


----------



## Zachik

Xcalibur255 said:


> I think finding Landfall back in 2012 has turned out to be the most meaningful contribution I've made to all of this.  Being able to specify any X-Y-Z dimension is such a boon compared to the Chinese chassis products that are fixed dimension.


I have used their great services for my new amp that Glenn has just finished building for me... A+ customer service, and Dave is the nicest guy


----------



## 2359glenn

L0rdGwyn said:


> Just to see what all of the hype is about, this morning I did another experiment.
> 
> You might recall that I left the driver tube cathodes unbypassed in the 6A5 amp given the CCS load.  I had some leftover electrolytics from the build, some non-polar Audio Note Kaisei, I thought I would clip in the caps, bypass the cathodes, and see how it affected the sound.  Many tube DIYers go to great lengths to remove these electrolytics from the signal path, but how bad can it be really?
> 
> ...



In my normal EL3N amp I use LED bias on the driver EL3Ns I feel this is a improvement in SQ
Usually you will lose gain with a unbypassed cathode resistor. It puts feedback into the cathode reducing gain.


----------



## L0rdGwyn

Xcalibur255 said:


> I think finding Landfall back in 2012 has turned out to be the most meaningful contribution I've made to all of this.  Being able to specify any X-Y-Z dimension is such a boon compared to the Chinese chassis products that are fixed dimension.



Well thank you then for discovering them, I really like the work they do.  I am expecting the 45 parafeed chassis this Thursday, looking forward to seeing how it turned out.  Then the long wait for transformers, again.



2359glenn said:


> In my normal EL3N amp I use LED bias on the driver EL3Ns I feel this is a improvement in SQ
> Usually you will lose gain with a unbypassed cathode resistor. It puts feedback into the cathode reducing gain.



I haven't given LED bias a try yet, some people seem to think it has a "sound", maybe I will experiment in the 45 amp.  I've left the cathode unbypassed on the MH4 drivers since they are CCS loaded.


----------



## L0rdGwyn

45 parafeed chassis arrived today.






Cut outs on the back for heatsinking the power tube CCS (top device).



Here is how it will look with the heat sinks.



Going to switch the hardware to black, forgot to mention it to Dave.  But very happy with the look!  Got some other goodies today too, sockets, resistors, etc.  but I'll save it for later


----------



## A2029

L0rdGwyn said:


> I haven't given LED bias a try yet, some people seem to think it has a "sound", maybe I will experiment in the 45 amp.  I've left the cathode unbypassed on the MH4 drivers since they are CCS loaded.



Another experiment you can try is to use an LED, but put a resistor of your choice in parallel with the LED. You can play around with the value of the resistor, but try a resistor value such that 70-90% of the current is going through the LED and 10-30% through the resistor. The LED sets the voltage and gives low dynamic impedance. The parallel resistor reduces dynamic impedance of the combo even further and decreases the parallel inductance of the pair. There are also some factors such as noise correlation that are mitigated, but I don't know how much difference those factors would make.



L0rdGwyn said:


> 45 parafeed chassis arrived today.
> 
> 
> 
> ...



Looks great! I like the brushed non-anodized aluminum look.


----------



## L0rdGwyn

A2029 said:


> Another experiment you can try is to use an LED, but put a resistor of your choice in parallel with the LED. You can play around with the value of the resistor, but try a resistor value such that 70-90% of the current is going through the LED and 10-30% through the resistor. The LED sets the voltage and gives low dynamic impedance. The parallel resistor reduces dynamic impedance of the combo even further and decreases the parallel inductance of the pair. There are also some factors such as noise correlation that are mitigated, but I don't know how much difference those factors would make.



Interesting!  I'll keep it in mind, that kind of tinkering is right up my alley.  Quasimodo and friends will be arriving from JLCPCB today as well


----------



## L0rdGwyn

Oh one more thing - I got a fitted perforated sheet to replace the bottom plate of the 6A5 amp.  This is going to be the approach going forward when ordering from Landfall.  Nice and neat, great for ventilation.  Will be adding some hidden vents to the top plate of the 6A5 amp some time next week, beneath the transformer shields.


----------



## Tjj226 Angel

L0rdGwyn said:


> Well thank you then for discovering them, I really like the work they do.  I am expecting the 45 parafeed chassis this Thursday, looking forward to seeing how it turned out.  Then the long wait for transformers, again.
> 
> 
> 
> I haven't given LED bias a try yet, some people seem to think it has a "sound", maybe I will experiment in the 45 amp.  I've left the cathode unbypassed on the MH4 drivers since they are CCS loaded.




Everything has a sound. However audiowize told me that there are some things you have to consider with LEDS.

1: LEDs are considered fixed bias rather than cathode auto bias, so you need to make sure your grid leak resistor is the appropriate size.

2: LEDs do cause a small amount of positive feedback into the tube. If your tube is prone to oscilations, then it might be a bad idea to use LEDS.

3: Not all LEDs are equal. Different quality LEDs will have slightly different dynamic impedance and other issues. Buying a higher quality / better build LED is important.

3.5: The other thing to point out is LED colors. Different LED colors will produce different bias voltage. It is important to buy a color that has the right voltage AND low dynamic impedance.


----------



## A2029

Also another thing to look for when selecting LEDs is that the inefficient LEDs are often best as they often have lower dynamic impedance. I often go with red or infrared LEDs as they tend to have lower dynamic impedance than other colors. I usually use HLMP-6000 LEDs (note: you want the old HLMP-6000, and not the newer HLMP-6000-E/G that is higher efficiency, and much higher dynamic impedance). An HLMP-6000 gives you around 1.6-1.7V per LED, and can take up to 10ma or so current. They can also be matched and paralleled for higher currents, and put in series to increase bias voltage. Around 5-6ohm dynamic impedance each I believe. You want their ForwardCurrent X ForwardVoltage to be as vertical as possible such as the STD RED below.


----------



## L0rdGwyn

Great information here, thank you both.  If memory serves, the HLMP-6000 is used in a few of Bottlehead's designs.  I'll give some thought to trying LED bias on the 6J5 of the 45 amp.  The plan as of right now is to use a 8mA / -5.5Vg bias point, could stack a few HLMP-6000, but I'll take a look at my other LED options as well.


----------



## L0rdGwyn (Apr 18, 2020)

Doing some checks on my planned layout this morning, here is sort of where I am going with it:



The Rod Coleman raw DC boards will be mounted to the side panels, filament regulators will be underneath, heat-sinked to the top plate.  I've run the numbers here, should be good to go without dedicated heat-sinking.  I am plus/minus on scotch-taping the raw DC boards to the side panel, we'll see how I feel about it later...

6J5 CCS boards will sit behind the octal sockets, likely will mount them with some pretty long standoffs to take advantage of the height of the chassis, tag strips will be mounted behind/underneath for the rectifier diodes, snubber resistor/capacitor, etc.  The power tube CCS will be mounted on the back panel, up and out of the way, leaving the entire area between the UX4 sockets and rear vents for the parafeed caps.  Once the value of the caps are determined (using cheap Solen stand-ins), we'll see what I can fit in there.  The pot will be another Goldpoint V47, which I haven't picked up yet.  Cramming a lot in this chassis, but it's gonna work.

Here is a little preview of how the amp will look, if you can imagine some Sowter transformers sitting behind the tubes and a big Goldpoint knob on the front.

 

Was going for a sort of compact, "strong" look for the amp (whatever that means).  It's going to be a dense little guy, can't wait to get to work on the build!  Tempted to get started, but think I better wait until the transformers are here, just in case the dimensions aren't exactly as listed on Sowter's site.


----------



## whirlwind

L0rdGwyn said:


> Doing some checks on my planned layout this morning, here is sort of where I am going with it:
> 
> 
> 
> ...



I love the look Kennan....simple look and elegant.


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## L0rdGwyn (Apr 17, 2020)

whirlwind said:


> I love the look Kennan....simple look and elegant.



Thanks, Joe!  The look is very important to me, so I spend a lot of time planning the layout, dimensions, spacing of the tubes/components, etc., hope it shows in the final product.


----------



## L0rdGwyn (Apr 18, 2020)

Time for another DIY rant...

I happen to have a week off starting Wednesday, not a vacation, just by way of scheduling (healthcare is weird like that).  I've squared away all of the 45 parafeed plans, so I am going to start working on the build in earnest.  I'm still at least a month away from having the transformers, likely two months, so I won't be doing any drilling on the top plate for fear of encroaching on transformer real estate, but I will begin working on the side panel components.

So, with all of those plans done, I am looking to the future.  The next build is going to be a real doozy and there is no timeline.  Might be crazy for planning it already, but helps keep me occupied from all of the stress at work!!!  Disclaimer: this is a "can we do it", not a "should we do it" kind of project.

Here is the plan in a nutshell: it will be an all DHT, three-stage hybrid A2 design using all thoriated tungsten filament tubes.  The gain will be supplied by an oddball DHT - the 841 / VT-51.  It is a high-gain (mu of 30) version of the 10Y / 801A with tighter grid spacing.  It will be CCS loaded and mu-output taken given its high internal resitance (62K).  Current drive to the output tube grid will be supplied by a FET source follower (device TBD, although I have a short list).  Output will be the 801A / VT-62, grid driven positive far into class A2 with a near 0V grid bias point.

Top choice for OPT right now is the Lundahl LL9202 at 50mA (100H).  This transformer can be wired for 6.5K, 11K, and 23K primaries.  My speakers are 6ohms nominal, so may end up using the 11K:8ohm wiring for something like a 8.25K:6ohm setup.  With the grid driven positive to saturation, with ~625Vpp, that would give this amp an output of 6W into 6ohms.  Would likely experiment with other turns ratios as well.

I had originally cooked up this idea using a 6BX7 cathode follower as the current gain stage.  After snooping around diyAudio and PMing a fellow who is experienced using the 841, I am convinced that a source follower is the way to go.  By happenstance, that same DIYer has built a very similar circuit to what I have in mind, so I will be using his schematic as a reference.

The major challenge of this design will be the power supply.  The 841 and A2 biased 801A will take very different plate voltages.  The most likely approach will be to use "stacked" power supplies, perhaps 300V + 300V, both Maida regulated, with the FET V- supply taken from the bottom.  I haven't dived into the details here yet, there is much to learn.  Given that all three stages will be taking DC only, one thought is to use a separate power supply chassis, such that I can run all of the DC power through an umbilical, keeping AC out of the amplifier chassis.  Given the size of the caps that will be needed here along with the dedicated filament transformers, using a separate chassis is likely a necessity.  Finding appropriate mains transformers will be another challenge, we'll see.

This will be a very challenging project, but taking on more complex designs is the way to learn.  Particularly, this will be a great opportunity to learn more about SS devices, and I will also be using it to take my utilization of LTSpice a step further.  I want to be very confident in my model before moving forward.

Okay, that's it, that's what I am working on in the background of the 45 amp.  Again, no timeline and all subject to change, but I think it will be a very interesting amplifier if I pull it off.


----------



## Xcalibur255 (Apr 20, 2020)

Keenan, sometimes I feel like you were born with about 5 normal people's worth of ambition...... 

This is both a compliment to you and an admonishment of myself who is too lazy to actually try and do any of this stuff.

I really want to hear your impressions of this after you build it.  The thoriated tubes are supposed to sound unique, people seem to struggle to describe it sometimes.


----------



## L0rdGwyn

Thanks @Xcalibur255 , I appreciate the compliment, we'll see if it beomes a reality!  This one is quite a challenge for me...the amplifier schematic is relatively straightforward, in fact I think I have a decent draft in LTSpice.  But the power supply is another story.  Very likely I will need a custom-wound mains transformer to pull it off, the DIYer I mentioned who has built a similar amplifier used a custom mains with dual secondaries, one secondary having multiple taps for the bias / source follower V- supply.  I figure if I take my time, I can work out the best approach.


----------



## Tjj226 Angel

L0rdGwyn said:


> Thanks @Xcalibur255 , I appreciate the compliment, we'll see if it beomes a reality!  This one is quite a challenge for me...the amplifier schematic is relatively straightforward, in fact I think I have a decent draft in LTSpice.  But the power supply is another story.  Very likely I will need a custom-wound mains transformer to pull it off, the DIYer I mentioned who has built a similar amplifier used a custom mains with dual secondaries, one secondary having multiple taps for the bias / source follower V- supply.  I figure if I take my time, I can work out the best approach.



..........?

Why would you need a custom mains transformer?


----------



## L0rdGwyn

B+ for the 841 is around 600V, B+ for the 801A in A2 is around 350V, then a negative bias supply for the FET source follower, 150-200V.  The way I have seen this done was with a dual secondary mains, with both secondaries stacked to get the 841 B+, the bottom having multiple taps for the -V supply.  Another approach might be to use multiple off-the-shelf transformers, but like I said, it's a work in progress, going to be looking into the options over the next week.  But I am open to suggestions


----------



## Tjj226 Angel (Apr 20, 2020)

L0rdGwyn said:


> B+ for the 841 is around 600V, B+ for the 801A in A2 is around 350V, then a negative bias supply for the FET source follower, 150-200V.  The way I have seen this done was with a dual secondary mains, with both secondaries stacked to get the 841 B+, the bottom having multiple taps for the -V supply.  Another approach might be to use multiple off-the-shelf transformers, but like I said, it's a work in progress, going to be looking into the options over the next week.  But I am open to suggestions



When you say you want 600v on the 841, I assume you mean that you are going to be using a CCS right? Have you calculated what your driver requirements are for the 801a?


----------



## L0rdGwyn

Tjj226 Angel said:


> When you say you want 600v on the 841, I assume you mean that you are going to be using a CCS right? Have you calculated what your driver requirements are for the 801a?



Yes, CCS loaded with mu-output.  The driver will need to swing 150Vpp to drive the 801A to clipping.  The 841 can do that well CCS loaded with a 450-500V bias point, 600V B+ is ballpark, could go to 625 or 650 for a higher plate voltage.  At close the plate saturation on the positive grid wing (+40-50V on the grid), the 801A could draw something like 10mA of grid current.  FET I am modeling right now is the IXYS IXTU01N100 for the buffer, source loaded with a CCS as well, right now I have to IXYS IXCP10M45S plugged in.

So yeah, figuring out a good way to configure the PS is going to be the challenge.  Maybe there is a simple way to do it, but this is new territory for me, I have a lot of homework to do.


----------



## Tjj226 Angel

I might just be crazy right now, so please double check my math.

Lets assume you have a 2v rms line input. 2Vrms is about 2.83v peak or about 3v peak. You multiply this by the gain of the tube at 30mu and you end up with 90v peak or 180v peak to peak.

Since you are going to loose some gain due to various reasons, I think hitting 150v peak to peak with a 2v input is reasonable.

As such, I wouldn't bother making the grid bias on the 841 much more than 3v at 4-5ma. Two red LEDs at that current should give you something like 3.4-3.6v of bias. ; )

Now you are talking about a plate voltage of around 300 and you might be able to push your luck and get away with a B+ of something like 450v. This might not sound like a huge deal, but it might just be enough of a reduction where you can use basic 600v power supply capacitors. 

Im not super familiar with hybrid mu followers, so maybe there is some extra math that needs to be done to get you to the 600v figure, but as far as I can tell, you ""SHOULD"" be able to get away with much lower B+


----------



## L0rdGwyn

Thanks @Tjj226 Angel , definitely something to consider.  Looking ahead the other day, I thought of using 800V DC link caps or something similar if I do end up with a high plate voltage on the 841.  If I thought I could get happy bias points with a more conventional power supply, I definitely would go for it.  Thinking that over, an alternative bias point for the 801A could be 400V / 40mA / -20Vg with a higher primary load.  Using fixed bias, would need maybe 425V at the top of the OPT.  Would be cutting it very close trying to use that same rail for the CCS loaded 841...just don't think it will work, will either be compromising the 801A bias point or the 841.  I think I am going to have to get creative with the power supply still, whether that be stacking, some sort of voltage-doubler arrangement, etc.

If I could have someone like Heyboer wind me a dual secondary traffo at a reasonable price, that might be an idea, I'm told they will do anything.  I plan to regulate both supplies, so doesn't necessarily need to be fancy.  The other appeal of doing something custom is I don't need all of the heater windings included on off-the-shelf transformers, just the B+.  If I went for dual secondaries of 250-0-250, I could stack the two supplies for 350+350VDC and run the bias supply off the bottom.  These numbers are all very rough, that might  get me around a 650V B+ for the 841, 325V B+ for the 801A, and my bias supply for the IXTU01N100.  These are just the ideas I'm throwing around and I'm probably overlooking something, but gotta start somewhere.

I had actually thought of using filament bias on the 841.  At 1.25A on the filament, a 3-5ohm 20W resistor would get me 3.75-6.25Vg.  Would have to be heat-sinked though.  I'm probably going to experiment with LEDs on the 45 amp, if that goes well maybe I will  use it on this amp rather than filament and avoid dissipating the ~10W.


----------



## Tjj226 Angel

Just use an antek transformer and have two voltage rails if it is really that big of an issue. 

https://www.antekinc.com/as-4t430-400va-430v-transformer/

Just use a choke input filter on the winding for the 801a to get you down closer to 350v and do what ever you want for regulation, and then a CRCRC filter on the other rail for your 841. 

If you don't need filament windings on the PT, then there is really no need to have one custom wound. There are plenty of options for cheap : D

------------------------------

Im also thinking this may not even work. If the 801a needs to have 10ma of current available to draw from, then the 841/mu follower would need to be biased at something higher than 10ma. 

This is one of those situations where I feel very strongly that there is some stupid simple solution to make this whole darn thing super cheap and easy to put together. We just need to find it.


----------



## L0rdGwyn (Apr 21, 2020)

@Tjj226 Angel I like your idea of using the dual secondary Antek with a choke input!  Something tells me there will be grounding headaches with the stacked supply, using two completely separate rails might be a better approach.  I was looking at Toroidy too, but their dedicated high-voltage transformers (no heater windings) are 230V input only...might just go with unused heater windings, but that kind of stuff drives me crazy.

So talking with a DIYer who knows these tubes well, even with a mu-output, the 841 cannot drive the capacitance of the 801A, so that is the reason for the FET source follower.  I was planning to cap couple the 841 to the source follower, then the SF will be direct-coupled to the 801A grid.  So the grid current will be supplied by the IXTU01N100 (or whatever other FET I end up going with, although I think this is a solid option).  I had planned to use a CCS on the IXTU01N100 source, which to my understanding must be set higher than the max possible grid current.  Increasing the drain current also increases the transconductance of the IXTU01N100, so the higher the better, within the realm of practicality.  Dropping something like 275V across the IXTU01N100 at 30mA constant current, would need to dissipate around 8W.  Still picking this stuff up, so I'll confirm in LTSpice.

If I went with something like the Antek, would need to use a capacitor coupled full-wave bias supply to get the negative voltage for the source follower.  Will have to look up some schematics, would have to be below the negative grid swing of the 801A, around -100V plus headroom for the CCS.  Like I said, I'm using the IXCP10M45S  as the CCS at the moment.  I have a week off of work starting tomorrow (!!!), I'll post a LTSpice schematic once I've messed around a bit more, should make more sense then I think.

What I am doing with the FET buffer is pretty similar to what Pete Millett has cooked up here with his "A2 buffer".  Tubelab has his own version which he calls "Powerdrive".

http://www.pmillett.com/A2_buffer.html

This will be one cyborg of a hybrid amp.  I'm probably committing some unspeakable DHT sins by going hybrid, but I have read overwhelmingly positive impressions about using a source follower rather than a cathode follower for A2 grid drive, and I'm not opposed to some sand assistance


----------



## Xcalibur255

Is the challenge in particular the thing you're going for?  It seems like choosing a different driver would be easier, but if you're super interested in the 841 that is all the reason one needs I suppose.

Have you considered just 10 squaring the amp?  That is driving the 801A with another 801A or 10Y.  It's still an all DHT TTF design but should simplify your powersupply since both tubes would have the same needs, and you should still have enough gain.


----------



## L0rdGwyn (Apr 21, 2020)

Yes @Xcalibur255 , using a different driver would make things considerably easier!  If all else fails, that will be the fallback option, but I think this can be done.  The 841 is a finicky tube, and I am certainly prone to tunnel vision, but the issue with using the 10Y as a driver is the gain just won't be enough for the 801A in A2.  With a 2V RMS input, 5.6V peak-to-peak, the 10Y will only swing something like 40-50Vpp, where the 801A in A2 will need 150Vpp to reach max output.  The 841 with its mu of 30 is just about enough gain for the 801A.  To use the 10Y, would have to add an additional gain stage or use a step-up interstage transformer to couple it to the source follower, but even then the gain likely wouldn't be enough.  I'll revisit the idea though, I have heard of people also using step-up line-input transformers to get adequate gain in all DHT amplifiers, but then the cost and added complexity starts to seem pretty comparable to what I am seeing with the 841 power supply.


----------



## Tjj226 Angel

L0rdGwyn said:


> @Tjj226 Angel I like your idea of using the dual secondary Antek with a choke input!  Something tells me there will be grounding headaches with the stacked supply, using two completely separate rails might be a better approach.  I was looking at Toroidy too, but their dedicated high-voltage transformers (no heater windings) are 230V input only...might just go with unused heater windings, but that kind of stuff drives me crazy.
> 
> So talking with a DIYer who knows these tubes well, even with a mu-output, the 841 cannot drive the capacitance of the 801A, so that is the reason for the FET source follower.  I was planning to cap couple the 841 to the source follower, then the SF will be direct-coupled to the 801A grid.  So the grid current will be supplied by the IXTU01N100 (or whatever other FET I end up going with, although I think this is a solid option).  I had planned to use a CCS on the IXTU01N100 source, which to my understanding must be set higher than the max possible grid current.  Increasing the drain current also increases the transconductance of the IXTU01N100, so the higher the better, within the realm of practicality.  Dropping something like 275V across the IXTU01N100 at 30mA constant current, would need to dissipate around 8W.  Still picking this stuff up, so I'll confirm in LTSpice.
> 
> ...



Oh ok, so you are doing a full class A2 fet follower. That will definitely help. 

With the Antek transformer, you will notice that the input side of the transformer has a second 120v winding for 240v. You can use that winding for your negative bias supply so long as you aren't using too much current from the transformer. 

You wouldn't really have stacked power supplies. You would just have multiple power supply rails. Grounding wouldn't be too bad in either case.


----------



## L0rdGwyn

Well I have my week off starting today, so I'm going to dive back in to the 801A amp design looking at some of the discussion that we've had here.  I really like the idea of using a toroid - I am planning a separate PS chassis with an umbilical, so using an internal toroid vs. a potted EI core that I have to mount on top would allow me to stack the two chassis.  My girlfriend is already wondering where the heck I'm going to put such a big amp...minor details, there is always more room 

Very exciting news today though - Sowter had originally told me 12 weeks on the 45 parafeed transformers.  Well I received a shipment notification today, it has only been a little over 3 weeks!  Not sure what changed, but the transformers will be here Friday, perfect timing.  Looks like the 45 amp is going to be built way ahead of schedule, going to be a busy weekend.


----------



## Tjj226 Angel

L0rdGwyn said:


> Well I have my week off starting today, so I'm going to dive back in to the 801A amp design looking at some of the discussion that we've had here.  I really like the idea of using a toroid - I am planning a separate PS chassis with an umbilical, so using an internal toroid vs. a potted EI core that I have to mount on top would allow me to stack the two chassis.  My girlfriend is already wondering where the heck I'm going to put such a big amp...minor details, there is always more room
> 
> Very exciting news today though - Sowter had originally told me 12 weeks on the 45 parafeed transformers.  Well I received a shipment notification today, it has only been a little over 3 weeks!  Not sure what changed, but the transformers will be here Friday, perfect timing.  Looks like the 45 amp is going to be built way ahead of schedule, going to be a busy weekend.



Ugh. Your'e making me look bad. Now I need to drag myself out of bed and find that darn drill bit I am missing to finish up my 45 build. : P


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## Xcalibur255

L0rdGwyn said:


> Yes @Xcalibur255 , using a different driver would make things considerably easier!  If all else fails, that will be the fallback option, but I think this can be done.  The 841 is a finicky tube, and I am certainly prone to tunnel vision, but the issue with using the 10Y as a driver is the gain just won't be enough for the 801A in A2.  With a 2V RMS input, 5.6V peak-to-peak, the 10Y will only swing something like 40-50Vpp, where the 801A in A2 will need 150Vpp to reach max output.  The 841 with its mu of 30 is just about enough gain for the 801A.  To use the 10Y, would have to add an additional gain stage or use a step-up interstage transformer to couple it to the source follower, but even then the gain likely wouldn't be enough.  I'll revisit the idea though, I have heard of people also using step-up line-input transformers to get adequate gain in all DHT amplifiers, but then the cost and added complexity starts to seem pretty comparable to what I am seeing with the 841 power supply.



You clearly know more than I do so I should probably stop offering my 2 cents knowing I'll have change coming.  I'm curious about this though, because people definitely do a 10Y driving another 10Y or an 801A driving another 801A and those designs don't always have step-up transformers involved.  Maybe it's because they are staying in A1 and not pushing for as much power as you're going for?


----------



## L0rdGwyn

Tjj226 Angel said:


> You're making me look bad.



This is my sole inspiration, I don't even like amplifiers.... don't worry, I'll burn myself out here pretty soon.


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## L0rdGwyn (Apr 22, 2020)

Xcalibur255 said:


> You clearly know more than I do so I should probably stop offering my 2 cents knowing I'll have change coming.  I'm curious about this though, because people definitely do a 10Y driving another 10Y or an 801A driving another 801A and those designs don't always have step-up transformers involved.  Maybe it's because they are staying in A1 and not pushing for as much power as you're going for?



No please, I appreciate the input!  Definitely staying in A1 is a contributor.  Did a quick Google search to see if I could find a schematic and failed.

My guess is they are using it as a two-stage power amp and connecting it to a preamp to get the additional gain rather than a line-level input, but there could be other factors in play.  In class A1, the 801A might need around 100Vpp into the grid to hit its max swing.  With a 5.6Vpp (2VRMS) line-level input, a 10Y can hit around 40-50Vpp output.  A 1:2 insterstage transformer would get you pretty close to max swing on the 801A, but at an A1 bias point, the 801A requires a pretty high plate load, so you only get maybe 2W output.  At A2 bias points, the internal resistance of the 801A is much lower,  so the required plate load is reduced in addition to a 50% larger peak-to-peak swing, so the power output jumps pretty dramatically to 6 or 7W  this is rough estimate math, so please forgive me if it is a bit off.

I think Lundahl makes a 18mA version of the LL1660 interstage that would be a good choice in that A1 application.  But to get that 150Vpp for A2, I would need a pretty unique interstage transformer, preamp, or some sort of other added gain.  The 841 can supply enough gain on its own, just a PITA since it takes a high plate voltage.


----------



## Tjj226 Angel

L0rdGwyn said:


> This is my sole inspiration, I don't even like amplifiers.... don't worry, I'll burn myself out here pretty soon.



Lol. This is honestly how I feel when I read crap marketing material on amps. Especially those cheap shiny silver ones cough cough cough.


----------



## Tjj226 Angel

L0rdGwyn said:


> No please, I appreciate the input!  Definitely staying in A1 is a contributor.  Did a quick Google search to see if I could find a schematic and failed.
> 
> My guess is they are using it as a two-stage power amp and connecting it to a preamp to get the additional gain rather than a line-level input, but there could be other factors in play.  In class A1, the 801A might need around 100Vpp into the grid to hit its max swing.  With a 5.6Vpp (2VRMS) line-level input, a 10Y can hit around 40-50Vpp output.  A 1:2 insterstage transformer would get you pretty close to max swing on the 801A, but at an A1 bias point, the 801A requires a pretty high plate load, so you only get maybe 2W output.  At A2 bias points, the internal resistance of the 801A is much lower,  so the required plate load is reduced in addition to a 33% larger peak-to-peak swing, so the power output jumps pretty dramatically to 6 or 7W  this is rough estimate math, so please forgive me if it is a bit off.
> 
> I think Lundahl makes a 18mA version of the LL1660 interstage that would be a good choice in that A1 application.  But to get that 150Vpp for A2, I would need a pretty unique interstage transformer, preamp, or some sort of other added gain.  The 841 can supply enough gain on its own, just a PITA since it takes a high plate voltage.



Not only that, but a step up transformer will reflect the input capacitance squared. So if you had a 1:4 input transformer with a tube that had 50pf of input capacitance, then you take the step up ratio (4/1 = 4) and you square it to get 16. You multiply 50 times 16 to get 800pf input capacitance on the primary of the transformer. 

This is kind of an extreme example, so don't be discouraged, but make sure you take this into account. 

A good way of handling something like this is to break up the job of a single transformer into two transformers. If you have an input transformer with a small step up ratio AND an interstate with a small step up ratio, then you could arguably get plenty of drive without having to deal with any noticeable penalties. 

Take a look at sakuma's articles and schematics. This is pretty much his whole gimmick.


----------



## L0rdGwyn

Tjj226 Angel said:


> Take a look at sakuma's articles and schematics. This is pretty much his whole gimmick.



Will do  I see his schematics around the diyAudio world pretty often, I'll have to find some time to read up on his work.


----------



## Xcalibur255

So the 10 can drive a 300B properly but not another 10 or 801A without help.  I clearly still have gaps in my knowledge here.


----------



## L0rdGwyn

I think you will have the same situation with the 10 driving a 300B, it is just a matter of input sensitivity.  The input voltage required to drive the amplifier to full output will be greater than a typical line-level 2VRMS from a DAC, so some sort of preamplification will be necessary to get the full output, whether that is from a dedicated preamp or in an integrated build with a preamp stage.  Hope that makes sense!


----------



## Tjj226 Angel

Xcalibur255 said:


> So the 10 can drive a 300B properly but not another 10 or 801A without help.  I clearly still have gaps in my knowledge here.


 
A 10Y can NOT drive a 300b without help. 

So here is a real down and dirty way to figure out how to build a single ended tube amp. 

1: Figure out how much power you want. 

2: Find an output tube that meets your power requirement. If you want 1 watt, then a 45 will work. If you want 100 watts, then you should get something crazy like an 832 tube. Lets pretend you want 2 watts and you want to make a cousin to lordgwyns amp. In this case a 2A3 would work. Here is the data sheet http://www.tubezone.net/pdf/2a3.pdf

3: Find the tube plate resistance. In this case its 800 ohms. To find your output transformer, take your plate resistance and multiply it by 5. This gives you 4000 ohms in this case. Now find the recommended plate current for the tube. It turns out to be 60ma. So now you know you need a 4000 ohm output transformer that needs to be able to handle 60ma of current. If we try to go find such a transformer we quickly learn that 4000 ohms is an uncommon number. The most common impedance figures in this range are 3.5K and 5K. 5K will give you less distortion, less power, and it will most likely give you earlier bass roll off. The 3.5K transformer will give you more power than 4K with slightly higher distortion (most of which is second order). Please keep in mind that these are my recommendations. Other people will tell you to use a 7K transformer for other reasons. But for the moment you need to find a 3.5K transformer that can handle 60ma of idle current. Once you found it, your output section is almost done. 

4: Find the recommended grid voltage for the 2a3 which is 45v. We are going to use cathode bias here, so to find your cathode bypass resistor, take your grid voltage and divide by your idle current. (R= V/I) 45v/0.06A = 750 ohms. To find the wattage of the resistor, multiply 45v by 60 ma to get 2.7 watts. Since 2.7 watts doesn't exist, you simply choose the next highest wattage rating which is 5 watts. So now we know we need a 5 watt 750 ohm resistor at 5 watts on the cathode of the 2A3. Then marry that resistor to the largest film capacitor you can afford (I find 100uf works most of the time) for your bypass capacitor and boom. Cathode bias is done. 

5: Find the max grid leak resistor for the 2A3. In this case since we are using cathode bias, it is 500K ohms. So shove a 500K ohm 1/8th watt resistor between the grid and ground. 

6: Now we marry everything together for the output stage. Find the recommended plate voltage (250v). The plate voltage is the voltage difference between the plate and cathode. Since the cathode is at 45v, we add the two voltages together to get ~300. Since we will have some voltage drop across the transformer, lets make this a little higher and shoot for 310v. So hook up your 3.5K output transformer primary between your plate and your 310v supply. Attach your grid leak resistor from grid to ground. Attach your cathode resistor and bypass cap to ground, and you got yourself an output stage. Taaaadaaaa. 

-----------------------

Input stage: 

7: Take your bias voltage of 45v. This is the peak voltage your driver would have to swing in order for the 2a3 to reach max output power. I like to go a little bit above the bias voltage to give myself a little bit of breathing room. So lets say we need to swing 50v peak as a minimum. 

8: Determine the input sensitivity of the amp. Do you want 1v to be able to push the amp to its maximum or do you want it to be 2V. Or maybe something crazy like 3.14159 volts. Lets choose 2vrms since that is the line output voltage of most dacs. If you take 2 and multiply it by the square root of 2 (1.41) you convert rms voltage to peak voltage. In this case we get 2.83v or about 3v. 

9: Take your 50v peak grid swing requirement and divide by our input sensitivity of 3. This gives us ~17. This is the minimum amount of gain we need out of the preamp tube to drive the 2a3. Now the advertised gain of the tube is the max theoretical gain we could see out of a tube. The gain actually realized out of the tube depends on how we load it. So with this in mind, lets give ourselves another fudge factor and round our gain requirement up to 20. This fudge factor with our last fudge factor should keep us nice and safe. So now we need to find a tube with a gain of 20. Now technically you also need to worry about low plate impedance so that you can drive the miller capacitance of the next tube and what not, but honestly, just find a tube with the right gain and a plate resistance of less than 10K and you will probably be more than fine. Lo and behold we find out that the ever popular 6sn7 has a gain of 20 and a plate resistance of about 7Kish. What a coincidence. Its almost like I planned it or something. AND the 6sn7 is a dual triode, so we only have to buy 1 preamp tube and 1 socket. How nice. 

10: Figure out what you want the plate load to be. If you are broke and you want to build something for rock bottom prices, use a plate resistor. If you can afford 30 bucks, use a CCS. We will use a ccs since you can easily buy them from Kevin at K&K audio and it makes the next part easy. 

11: Take your 6sn7 data sheet https://frank.pocnet.net/sheets/127/6/6SN7GT.pdf. Go find the tube curves. Look at the curves. Take them into your soul and become 1 with the curves. Now forget that. Look at how the curves have an exponential rise to them. The bottom rounded part of those curves are bad. Try to avoid them where possible. Go up the Y axis (plate current) until the curves to the right of them look nice and vertical. Looks to me like those curves start to straighten out at around 2ma. So we are going to choose a plate current of 3 ma to ensure that we are in a "linear region". 

12: Finding a bias point for the 6sn7. This is super easy because we have already determined what our input sensitivity needs to be. Since we know we are going to have 3v on the input, then we need to choose a grid voltage that is slightly higher than 3. 4v is perfectly reasonable, but lets kill 2 birds with 1 stone in step 13. 

13: Cathode bias for the 6sn7. We are gonna cheat here. We are going to use 2 red LEDs in series. Why? Because they are cheap, easy, and all we need to think about is the forward voltage drop of the LED. Most red LEDS are around 2v drop. To get 4v, you chuck 2 in series and attach them between your cathode and ground. Super simple. No fuss no muss. And did I mention it will cost less than a dollar to bias both tubes?

14: Plate voltage. So we need to look back at the tube curves. We decided that 3ma gives us nice linear curves. So draw an imaginary red line horizontally across the 3ma mark. Since we biased the cathode at 4v (or there about) we look to see where the 4v grid line intersects with our imaginary red line. Draw an imaginary blue dot at this point and look down to your X axis (plate voltage). Im seeing about 109v on the plate. For long technical reasons I will skip, the CCS as opposed to the transformer on our 2a3 needs to be fed twice the plate voltage. In other words, if we have 109v at the bottom of our ccs plate load, we need to feed it twice that amount at the top of our CCS. In this case its about 220v. 

15: grid leak resistor. The gird leak resistor in this case is just a volume pot. I suggest using an alps blue velvet 100K pot between grid and ground. 

16: Putting the preamp section together. For one section of the 6sn7 per channel, you have 1 half of an alps blue velvet pot going from grid to ground. You have two red LEDs in the cathode providing cathode bias. And you have a K&K ccs between your tube plate and the power supply. Taaaadaaa you have a preamp section. 

17: Marrying the preamp section and power section. Use a 0.22uf capacitor between the plate of the 6sn7 and the grid of the 2a3. That's it. In about 17 steps you have your analong section done. 

After that, all you need to do is design a power and dc filament supply for your 2a3s and slap it all together. It will look something like this.


----------



## Xcalibur255

Point #9 is where my knowledge gap was.  It helps to see the relationships here.  My understanding is, without enough gain the pre-amp stage simply cannot drive the output stage to full power.  If one is willing to accept the reduction in output I assume it will still sound fine otherwise?  So if we drive a 300B with a 10 the side-effect is we're probably only going to get may 4-5 watts out of the 300B, or is there some other more serious issue at play?


----------



## Tjj226 Angel

Xcalibur255 said:


> Point #9 is where my knowledge gap was.  It helps to see the relationships here.  My understanding is, without enough gain the pre-amp stage simply cannot drive the output stage to full power.  If one is willing to accept the reduction in output I assume it will still sound fine otherwise?  So if we drive a 300B with a 10 the side-effect is we're probably only going to get may 4-5 watts out of the 300B, or is there some other more serious issue at play?



Yes, if for what ever reason you do not want to achieve full output, you can undershoot this requirement. 

But I have a few points for you. 

Driving a 300b with a 10y will result in much less power than 5 watts. You may only be looking at 1 or 2 watts. However that is ONLY true if we are stuck with 2v on the input. If we have a dedicated separate preamp, we could arguably have 4v or higher on the input. Some dac's will actually have 4v rms from a balanced output. It certainly won't hurt anything if you only want 1 or 2 watts out of a 300b though, so if that is your goal, go for it. However as a side note, too much gain can cause clipping and noise floor issues. 

Just for full transparency, lets look at some numbers. Here is the 300b data sheet. http://www.tubebooks.org/tubedata/we300a_b.pdf

If we scroll down we see that western electric gives us a huge table of bias points to choose from. Lets have some fun and talk about my crazy 300b build. Go allllll the way to the bottom of that table and you will see my bias target of 450v at -97v of bias with 80ma on the plate. 

Following the rules set out in step 9, we find out I need something that can handle something like 105v peak in order to ensure that the tube can swing to full power. I also want an input sensitivity of 2v rms. So to find our gain requirement we take 105 and divide it by 3v of peak input signal. This gives us gain of 35. Again if we raise this requirement a bit, we get a gain of 40. 

Now a gain of 40 with low plate impedance actually isn't too difficult to find. In fact a ton of people will use the western electric 417a which has a gain above 40 and a really low impedance to drive their 300b, and it sort of keeps everything in the western electric family. 

But lets say we want to forego all reasonable preamp tubes and use something stupid like the 10y. Why would anyone do this? Because I can, thats why. 

A 10Y/801a has a gain of 8. If we take our 105 figure and divide by 8 we get 13.125v peak for our input sensitivity. 

So how do I go from 2v to 13.125? A 1:4 input step up transformer actually gets us really close to our goal. Close enough for government work. And remember that my bias point is wayyyyy out at the extreme. Most people will bias their 300b with 74v on the grid and a 1:4 step up would be MORE than enough to boost the input signal to adequate levels. 

Why am I not following my own advice and splitting the transformer's job up into two sections? Because I am crazy and will be directly coupling the 10y to the 300b. This will help reduce any inefficiencies and that 105 figure we have been using can be even closer to the original 98v. 

The other trick I have up my sleeve is that my amp will be mono blocks and I am making a 26 or a 10Y preamp to drive/control the mono blocks. So in theory I actually have a 3rd stage of gain driving the mono blocks. This is why my input transformer will have multiple taps. Tap 1 will be 1:1, tap 2 will be 1:2, and tap 3 will be 1:4. I will hook each tap up to a different RCA input. That way depending on the situation I am in or what ever the case may be, I can drive the amp from a standard dac, or I can drive it from a preamp without over driving the amp.


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## L0rdGwyn (Apr 24, 2020)

This amp is gonna come together pretty quickly...

Since I don't have the transformers until tomorrow, started work on the other panels.  I don't want to drill anything on the top panel yet until I know exactly where the transformers are going to be.

Finished the small bit (no pun intended) of drilling that needed to be done on the back panel - step bit for the RCA inputs (12mm hole), additional 3mm hole to mount the 45 CCS boards, and 3mm hole in the heat sinks for the top CCS device.



Since things needed to be aligned in three dimensions, had to mount everything to the chassis first, then finish soldering the IXTP08N100D2 to the board.  Came out nicely I think.  Fear not, I don't have the thermal pads on the heat sinks yet.  I used metal washers to align everything, but have some 1mm nylon spacers that will be placed between the heat sinks and the chassis at the screw mounting points for maximal thermal isolation.  I'll get the thermal pads on when the boards are attached permanently, they will be Keratherm Red.

  

So the back panel is done, nice.  Checked the current on the boards, around 35mA with the set resistor.  Going a little higher on the plate current since I am only targeting an anode voltage of about 200V.  Set resistor is a fancy Riken carbon film.  Haven't actually done any testing to see if the set resistor truly affects the sound, but it can't hurt and I like the shade of blue 

Drilling and mounting the Rod Coleman regulators to the side panels next.  Onward!


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## L0rdGwyn (Apr 23, 2020)

Coleman regulators are in.  Again, no thermal pads added yet, waiting until all of the drilling is done before mounting permanently.



Progress so far.



The 6J5 CCS boards are all ready to go, will mount them once the transformers are in place.



That's probably all I'm doing for today, got a lot done.  We'll see if these transformers show up tomorrow, wouldn't be surprised if it was Saturday instead.  Mouser lied to me on the dimensions of some current-limiting resistors for the power supply  shouldn't hold things up though, if need be I'll wire these massive resistors in temporarily until I get something more appropriately sized.

So if the transformers show tomorrow, next step will be determining the snubber resistor value, then mounting them, testing the filament regulators, then wiring her up!  Not as many quirks as the 6A5 amp, if all goes according to plan, this could be done by Sunday


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## Xcalibur255

@Tjj226 Angel 

So basically every amp I have seen that is 10 >>> 300B is designed with having a pre-amp driving it in mind to push the input sensitivity up.

I know the C3g is a natural choice of driver for a 300B, but I have been listening to them for 7 years now and would like something different for next time.

Thanks for your write-ups, they're helpful.  I'll never be able to do this stuff the way Keenan can (I can't really solder or do delicate assembly work due to health issues, my hands shake too much), but I like to know how it is done still.


----------



## L0rdGwyn

The cavalry has arrived.  It's going to be another busy one, here we go...


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## L0rdGwyn (Apr 24, 2020)

Used my recently built "Quasimodo" board to get my snubber resistor value for the mains transformer, courtesy of Mark Johnson over at diyAudio.  It allows one to dial in the value of the snubber resistor for their transformer math and measurement free, just need the board, your transformer, and a scope.  For zeta = 1 (critical damping), I came up with 780ohms.  Don't have that on hand, I'll order something close and put a few junk box resistors in series in the mean time.  Thanks for the tip, @A2029 .  This is with Mark Johnson's "CRC" method.


----------



## Tjj226 Angel

Xcalibur255 said:


> @Tjj226 Angel
> 
> So basically every amp I have seen that is 10 >>> 300B is designed with having a pre-amp driving it in mind to push the input sensitivity up.
> 
> ...



Basically. It either has a strong preamp behind it, or it uses step up transformer. It's possible some crazy audiophile has it setup to only put out 1 watt, but those people are the outliers. 

C3g is not a natural choice for the 300b. There are better tubes out there for the job, but I think the C3g strikes a nice balance of price, performance, and availability which is why you see it on some amps vs the D3a for example. There are also MUCH better tubes out there for stupid amounts of money. The WE437a is one such example.


----------



## Xcalibur255

So what would be your recommendation for a driver in an end-game, but not crazy exotic, 2-stage 300B integrated build?  Something top shelf in overall performance but not eye wateringly expensive or very scarce.  I've always been very interested in the 20 and 30 type tubes made by EML for a job like this, but the scary thing about them is if anything happens to EML there is no other source for obtaining them.  That, and they're very expensive but if they last a long time and the performance is there I would find it justifiable.


----------



## Tjj226 Angel

Xcalibur255 said:


> So what would be your recommendation for a driver in an end-game, but not crazy exotic, 2-stage 300B integrated build?  Something top shelf in overall performance but not eye wateringly expensive or very scarce.  I've always been very interested in the 20 and 30 type tubes made by EML for a job like this, but the scary thing about them is if anything happens to EML there is no other source for obtaining them.  That, and they're very expensive but if they last a long time and the performance is there I would find it justifiable.



Hmmmmmmm 

That depends on a crap ton of different factors. 

I would look at a triode strapped D3a. Its not too expensive, they are available, and you could directly couple the D3a to the 300b without too much issue. 

However if you would consider an input pentode (not triode strapped), the 310a and its derivatives are the closest thing you will get to a "natural choice" for a driver. The western electric 91a/b tube amp is considered to be "THE" western electric 300b tube amp and it uses the 310a.


----------



## 2359glenn

L0rdGwyn said:


> The cavalry has arrived.  It's going to be another busy one, here we go...



Make sure you mount these at 90 deg angle from the power transformer. E>I power transformers like to radiate a 60Hz magnetic field
that the output transformers can pickup that magnetic field if all mounted the same direction.
In the past I went crazy trying to find the hum in a amp I built. But it was the output transformers picking up the magnetic field of the power
transformer.
Or have a separate chassis for the power supply.




















i


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## L0rdGwyn (Apr 24, 2020)

No worries @2359glenn , I got it 

After making all of the measurements, drilled the holes in the top plate for the transformers.  Here it is with the bushings for the transformer wires.




I shouldn't have done it since they're going to have to come off, but I mounted the transformers, couldn't help myself, wanted to see the fruits of my labor.  Oh and just realized the front plate is on backwards LOL no matter.  Please ignore the state of chaos in the background.

 

Took much longer than expected, as usual.  I'm calling it a day, I'm beat, will finish the top plate drilling tomorrow then get to work on the heaters/filaments.


----------



## Tjj226 Angel

L0rdGwyn said:


> No worries @2359glenn , I got it
> 
> After making all of the measurements, drilled the holes in the top plate for the transformers.  Here it is with the bushings for the transformer wires.
> 
> ...



Let me know what capacitance value you end up using for the parafeed cap. Im looking at the price of 1KV capacitors and I m quickly learning that it might be cheaper to let you find the right value for me : P


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## johnjen (Apr 24, 2020)

I just 'found' this thread (thanks TTJ226) and I must say your dedication and attention to detail are exemplary.
And from what I understand these are your initial builds from scratch, most impressive indeed.

When we started building our 45 amp we took the 'classic' approach of using LOTS of capacitance with plenty of Big Iron and then proceeded to figure out how to dial it all together.  We used 6J5's as the drivers and tried battery, led, and fixed cathode bias resistors in various combinations along with Sowter parafeed output xfmrs.  It was a monstrously big build.

Start here and keep going…
https://www.head-fi.org/threads/the-diyrs-cookbook.781268/page-87#post-14475127

The tweaking part, ie. seeing what can be dialed in and how to achieve ever increasing degree's of SQ was and remains the 'finishing touch' as we kept refining the implementation.
We (mostly me) learned a huge amount of both what does, and perhaps more importantly, what doesn't work well, but alas that iteration of the 45amp is no longer.

So our current build, the Purp-Amp, uses Lundahl 2765 output xfmrs that are wired with 32Ω outputs, with ≈36Ω AB 2watt resistors across the output taps.
I use Sen HD800's and so I matched the total output impedance to optimize the load the output tubes see.
This was a significant improvement all by itself, mostly because it REALLY helped linearize the impedance the output tubes see, since the Senn's run from ≈325Ω to ≈680Ω. 
So by optimizing the output impedance this cut the variance of the load the 71A's see down from ≈355Ω to ≈1.7Ω.

This trick can be used in a variety of cases, especially with dynamic HP's with their characteristic wide variance of impedance by frequency.

Keep up the work as these sorts of efforts (both the builds and write ups) are always helpful, and in more ways and for more folks than one might imagine.

JJ
note:  AB resistors WILL change their values as they age, mostly always up in value.  This can be dealt with, but it isn't pretty, nor easy, nor exact…
Still they sound wonderful so the effort is usually worth it.


----------



## johnjen (Apr 24, 2020)

Deleted dup


----------



## L0rdGwyn (Apr 25, 2020)

Tjj226 Angel said:


> Let me know what capacitance value you end up using for the parafeed cap. Im looking at the price of 1KV capacitors and I m quickly learning that it might be cheaper to let you find the right value for me : P



I'm going to post FR plots for each cap value to show the differences  PB is interested in seeing the results as well, so I'll be putting it on the Bottlehead forum as a reference of sorts.  I'm hoping for my wallet's sake it isn't much more than 5.6uF...



johnjen said:


> I just 'found' this thread (thanks TTJ226) and I must say your dedication and attention to detail are exemplary.
> And from what I understand these are your initial builds from scratch, most impressive indeed.
> 
> When we started building our 45 amp we took the 'classic' approach of using LOTS of capacitance with plenty of Big Iron and then proceeded to figure out how to dial it all together.  We used 6J5's as the drivers and tried battery, led, and fixed cathode bias resistors in various combinations along with Sowter parafeed output xfmrs.  It was a monstrously big build.
> ...



Well thank you so much for the kind words, JJ!  I've perused the DIYrs Cookbook thread a bit already, but not in depth.  Once I've finished up this amplifier I'll give it an honest read, I'm sure there are many valuable insights you and others have shared there.  I will keep your results in mind, in a similar fashion I used an 9.1ohm resistor across the OPT secondary of my 6A5 build (3.3K:8ohm winding) and was very pleased with the results using my 300ohm ZMF Auteur.  I will be taking the same approach with this parafeed build as well.


----------



## johnjen (Apr 25, 2020)

L0rdGwyn said:


> I'm going to post FR plots for each cap value to show the differences  PB is interested in seeing the results as well, so I'll be putting it on the Bottlehead forum as a reference of sorts.  I'm hoping for my wallet's sake it isn't much more than 5.6uF...


When I was 'dialing in' the parafeed caps, I wound up with 5.83µf ±.01µf.
It was a build up of 3-4 caps to optimize the final amount of capacitance, all of which may not apply to any other build.
But I bet, since you're using the Sowter parafeed xfmrs and 45's it will be 'in the ball park'.
And along with the 'quality' of the caps these 2 parameters will make it fairly easy to determine what works best.

And yeah these caps can be stupid expensive if you dive deep down this rabbit hole…

JJ


----------



## johnjen

L0rdGwyn said:


> snip
> Well thank you so much for the kind words, JJ!  I've perused the DIYrs Cookbook thread a bit already, but not in depth.  Once I've finished up this amplifier I'll give it an honest read, I'm sure there are many valuable insights you and others have shared there.  I will keep your results in mind, in a similar fashion I used an 9.1ohm resistor across the OPT secondary of my 6A5 build (3.3K:8ohm winding) and was very pleased with the results using my 300ohm ZMF Auteur.  I will be taking the same approach with this parafeed build as well.


Also note, that that using the lower output Ω taps, the smaller the variance that senns etc (high Ω cans) will 'present' to the output tubes, using the impedance matching resistor trick.
A nifty trick especially for tube amps, but it also works on SS amps as well.

JJ


----------



## Tjj226 Angel

johnjen said:


> When I was 'dialing in' the parafeed caps, I wound up with 5.35µf or there abouts (I think).
> It was a build up of 3-4 caps to optimize the final amount of capacitance, all of which may not apply to any other build.
> But I bet, since you're using the Sowter parafeed xfmrs and 45's it will be 'in the ball park'.
> And along with the 'quality' of the caps these 2 parameters will make it fairly easy to determine what works best.
> ...



Sadly, things probably wont be that simple. That would just be too easy.


----------



## johnjen

True enough, especially if the output circuit is more sophisticated (direct coupled, etc.).
Even so, somewhere in 5.6µf range is probably a good place to start.

JJ


----------



## m17xr2b

You're building a 45 parafeed amp too? I've just finished mine, you're in for a treat. Testing 4V tubes with MH4 and PX4s now, a step up from 45s 6J5 for sure. 




PSU is in a different chassis with separate heater and HV switches, went with solid state rectifiers. 





Have fun, DIY is the only way.


----------



## L0rdGwyn

m17xr2b said:


> You're building a 45 parafeed amp too? I've just finished mine, you're in for a treat. Testing 4V tubes with MH4 and PX4s now, a step up from 45s 6J5 for sure.
> 
> 
> PSU is in a different chassis with separate heater and HV switches, went with solid state rectifiers.
> ...



Very cool, must be in vogue.  My 6A5 amp takes MH4 / REN904 / A4110 / AC/HL etc. natively, they are incredible drivers, so they received a dedicated build.  Yes a step above 6J5 I think, but I have an exhaustive collection of 6J5 that need an amp.  The MOV L63 can hang with the MH4 crew, but the Mullard NR52 might be the best driver I have ever heard.

Enjoy your new amp!


----------



## L0rdGwyn (Apr 25, 2020)

Alright folks, we are in business.

Because I am an obsessive psycho, I got up at 6:30 to keep working on the build.  Made some final layout adjustments, measurements, and finished all of the remaining drilling in record time.  Removed the anodization in a few spots for grounding purposes, permamently mounted the CCS and Coleman regulator MOSFETs to their respective heat sinks, then mounted all of the remaining components.

A few of them need to be removed again for wiring, but wanted to show the finalized layout.  The only things that are missing are 1) the parafeed caps (can you guess where they will go? ) and 2) the Goldpoint attenuator.  The Goldpoint was supposed to be delivered today, but looking at the tracking info, I suspect it will be delayed until Monday.  No problem, I have plenty to keep me busy until then.

Anyhow, here are some shots of the layout, starting to look like an amp.  Made a last-minute decision to have the 6J5 CCS boards float above the sockets, which gave me ample space for the two six-lug terminal strips in the center for power supply components.  I lucked out and discovered I have some 750ohm 5W Kiwame resistors left over from the last build, so looks like I have my PS snubber after all! 5W is overkill, but it'll do, and close enough to the 780ohm I determined for critical damping.  Also going to use the giant current-limiting resistors I got from Mouser that I thought were WAY too big.  We are making it work, gotta adapt.


  

And the top and rear panels.

 

Gotta run some errands and stuff, so testing the filament regs and getting started on the heater wiring will have to wait until this evening.


----------



## L0rdGwyn

Heaters / filament supplies are complete, B+ is next!


----------



## whirlwind

L0rdGwyn said:


> Heaters / filament supplies are complete, B+ is next!




You have fantastic energy Keenan....this looks very nice, very pleasing to the eye.
Look forward to listening impressions at some point down the road.


----------



## 2359glenn

L0rdGwyn said:


> Heaters / filament supplies are complete, B+ is next!



Not showing the filament wiring?


----------



## L0rdGwyn (Apr 26, 2020)

2359glenn said:


> Not showing the filament wiring?



Here you go, Glenn!  Sorry for the delay, I finished wiring up the B+ supply as well as the DC components of the tube sockets.  Everything is done except for the input wiring and output connections.  I'm sure they will sound great, but the wiring Sowter uses for their transformers leaves something to be desired, it simply does not hold a twist, pretty tricky to work with.



Here are the 6J5 sockets before mounting the CCS boards.  Pretty nice lead dress, if I do say so myself.







Currently troubleshooting an issue though, may have to ask for some opinions if I don't figure it out by tomorrow morning, probably best to call it a night anyway.


----------



## johnjen

This is a really nice build, Kudo's indeed.

A request if I might…
A couple more shots,
of your star grounding, say obliquely looking in from the direction of the choke inward,
and a shot of the choke wiring,
and a shot (or 2) of the diode bridge/filter wiring,
and lastly the termination of the pair of dark yellow wires from the mains.

Just by staring intently, (sorta like a technique I know of where you bang the details of the circuit against your head until it 'clicks' hahahahahahah),
I have most of the wiring figured, at least thus far in the build anyway.

Nicely implemented, it certainly is far more structured and neat than our PRWS®©™ technique (PsuedoRandomWiringScheme)…    hahahahahahahahahahaha

JJ


----------



## 2359glenn

L0rdGwyn said:


> Here you go, Glenn!  Sorry for the delay, I finished wiring up the B+ supply as well as the DC components of the tube sockets.  Everything is done except for the input wiring and output connections.  I'm sure they will sound great, but the wiring Sowter uses for their transformers leaves something to be desired, it simply does not hold a twist, pretty tricky to work with.
> 
> 
> 
> ...



Nice job!!
What type of capacitors are you using for parafeed??


----------



## L0rdGwyn

johnjen said:


> This is a really nice build, Kudo's indeed.
> 
> A request if I might…
> A couple more shots,
> ...



Sure JJ!  When the amp is done, I'll take a bunch of pictures of the interior.  Should be today I think, barring any unforseen obstacles.



2359glenn said:


> Nice job!!
> What type of capacitors are you using for parafeed??



Thanks, Glenn.  That is to-be-determined.  I have a bunch of Solen caps on hand so I can figure out the parafeed cap value, going to clip them in and run FR sweeps / do some listening.  Once the value is determined, then I'll figure out what kind of caps I want to use, will also be highly dependent on what can fit in the space behind the UX4 sockets all the way back to the rear ventilation.  Should be able to fit something with a diameter of 3 inches and a length of 4.5 inches or so, will have some good options assuming the capactiance isn't very high.


----------



## 2359glenn

L0rdGwyn said:


> Sure JJ!  When the amp is done, I'll take a bunch of pictures of the interior.  Should be today I think, barring any unforseen obstacles.
> 
> 
> 
> Thanks, Glenn.  That is to-be-determined.  I have a bunch of Solen caps on hand so I can figure out the parafeed cap value, going to clip them in and run FR sweeps / do some listening.  Once the value is determined, then I'll figure out what kind of caps I want to use, will also be highly dependent on what can fit in the space behind the UX4 sockets all the way back to the rear ventilation.  Should be able to fit something with a diameter of 3 inches and a length of 4.5 inches or so, will have some good options assuming the capactiance isn't very high.



I thought I was the only nut up this early.


----------



## L0rdGwyn

2359glenn said:


> I thought I was the only nut up this early.



Lol I'm switching from night shift to day shift, which means I gotta start getting up early to reset "the clock" (this is what I tell myself, but really I'm up because I need to hunt down a short in the amp).  People on the west coast are probably still up from last night!


----------



## L0rdGwyn

Also, I woke up at 4am and foolishly checked my phone, only to see this pair of tubes on Yahoo Auctions Japan, quickly snatched them up for the 801A amp I am planning.  Japan gots the dealz, $144 NOS.  My life is runs on tubes, it's sad.


----------



## L0rdGwyn

Found my short.  Despite my best efforts, the 45 CCS FETs were not isolated from their heat sinks.  Time for plan B, DC operating points coming soon.


----------



## johnjen (Apr 27, 2020)

I ran into a similar situation, only what I did was not isolate the 4-40 screw from the tab of the mosfet well enough, so the head of the screw was 'hot' (≈350vdc) WRT to the top plate.
Can you say tingly???
hahahahahah

JJ


----------



## 2359glenn

L0rdGwyn said:


> Found my short.  Despite my best efforts, the 45 CCS FETs were not isolated from their heat sinks.  Time for plan B, DC operating points coming soon.



You did use that plastic step washer under the head of the screw?
No burs in the hole and the heatsink is perfectly smooth under the thermal pad??


----------



## L0rdGwyn (Apr 30, 2020)

2359glenn said:


> You did use that plastic step washer under the head of the screw?
> No burs in the hole and the heatsink is perfectly smooth under the thermal pad??



Yessir, still having problems with it.  Think I will go to the hardware store and get some more plastic washers, need to get more excessive, the step washer doesn't seem to be cutting it and my conformal fluid did not help either.  Need to get this resolved before the Goldpoint arrives today!!!

I removed the heat sinks from the chassis and left them floating so I could check the DC operating points.  Very fortunate nothing appears to have been damaged from the short, at least not obviously.

6J5 B+: 380V
6J5 plate to cathode: 200V
6J5 cathode: 6.2V
6J5 plate current: 8.5mA

45 B+: 398V
45 plate to cathode: 206V
45 cathode: 35.5V
45 plate current: 35mA

Off to the hardware store I go


----------



## 2359glenn

L0rdGwyn said:


> Yessir, still having problems with it.  Think I will go to the hardware store and get some more plastic washers, need to get more excessive, the step washer doesn't seem to be cutting it and my conforming fluid did not help either.  Need to get this resolved before the Goldpoint arrives today!!!
> 
> I removed the heat sinks from the chassis and left them floating so I could check the DC operating points.  Very fortunate nothing appears to have been damaged from the short, at least not obviously.
> 
> ...



You might need a new thermal pad if the slightest burr would poke a hole in it.
 is the screw to fat should be a #4-40 screw or 4mm


----------



## L0rdGwyn

2359glenn said:


> You might need a new thermal pad if the slightest burr would poke a hole in it.
> is the screw to fat should be a #4-40 screw or 4mm



I fixed it Glenn, the short is gone, working on the input wiring now (least favorite part), next post and the amp will be complete


----------



## 2359glenn

L0rdGwyn said:


> I fixed it Glenn, the short is gone, working on the input wiring now (least favorite part), next post and the amp will be complete



Yes input wiring is my least favorite part too. I hate shielded cable always did even when I was a child I hated dealing with it.
Good luck finishing.
What was causing the short?


----------



## L0rdGwyn

2359glenn said:


> Yes input wiring is my least favorite part too. I hate shielded cable always did even when I was a child I hated dealing with it.
> Good luck finishing.
> What was causing the short?



YES!!! The shielding is such a pain, I hate it, but it is a necessary evil.

For some reason I read your post as "good luck fishing" and was very confused.  Short was caused by a one of the 45 CCS FETs, shorted to the heat sink.  Everything is isolated now.

Mega post incoming.....


----------



## L0rdGwyn (Apr 27, 2020)

Alright so...the amp is done.

Got the short figured out, finished up the input/output wiring, did some last minute voltage checks to be SURE the short was gone for good, and it was.


  

Here is the final ciruict.  Solen caps are clipped in as they are temporary for the sake of determining the parafeed cap value.



This amp uses the "Western Electric" output topology, a variation of parafeed.  As such, there are only two caps in the signal path, the coupling cap and the parafeed cap, obviously both film.  The coupling caps are Solen as of right now as well, they will match the parafeed caps whatever they end up being, I like it when things match 

   

Here is the frequency response, this is with 6.8uF parafeed caps clipped in.  At 20kHz it is down -1.6dB, essentially flat all the way to 15Hz.



On the FFT, distortion is almost entirely second harmonic at -58dBFS, third harmonic is at -85dBFS, higher order harmonics are lost in the noise floor.  At my listening volume, THD+N is 0.2%  There is a ground loop in the right channel only that I will need to hunt down, hopefully that doesn't prove to be a huge pain.

Amprehensive to give any overarching impressions since they are sure to change.  The capacitors will change in addition to burn in.  But I will say this - this amp is very fast and detailed with extremely articulate bass.  My first impression is that it is a brighter listen than my 6A5 amp, we'll see if that holds up over time.



Overall very pleased with it, next steps will be tracking down the source of the right channel ground loop at clipping in and out these different capacitors!  Will post FR plots and give some listening impressions with the cap trials.  But I am beat, time to take a break.


----------



## 2359glenn (Apr 27, 2020)

L0rdGwyn said:


> Alright so...the amp is done.
> 
> Got the short figured out, finished up the input/output wiring, did some last minute voltage checks to be SURE the short was gone for good, and it was.
> 
> ...



Nice job !!!!!!
Can you run up the frequency of your scope? The right channel might be oscillating at high frequency getting modulated with 60Hz.
Pull the 6J5 and see if it goes away?
These type of things can drive you crazy.


----------



## L0rdGwyn (Apr 27, 2020)

2359glenn said:


> Nice job !!!!!!
> Can you run up the frequency of your scope? The right channel might be oscillating at high frequency getting modulated with 60Hz.
> Pull the 6J5 and see if it goes away?
> These type of things can drive you crazy.



Yeah this might be tricky.  I shorted the inputs and it persists, so probably not a ground loop.  Removing the input tubes / shorting the grid to ground has no effect, so it appears to be on the output stage.  Right channel only though, will have to go through it systematically.  Hopefully I can nail it down!  It is the characteristic 60Hz buzz of a ground loop.  It is not coming from the B+, the CCS loads are nuking 120Hz noise on the FFT.  Hopefully not an issue with the filament regs.


----------



## 2359glenn

L0rdGwyn said:


> Yeah this might be tricky.  I shorted the inputs and it persists, so probably not a ground loop.  Removing the input tubes / shorting the grid to ground has no affect, so it appears to be on the output stage.  Right channel only though, will have to go through it systematically.  Hopefully I can nail it down!  It is the characteristic 60Hz buzz of a ground loop.  It is not coming from the B+, the CCS loads are nuking 120Hz noise on the FFT.  Hopefully not an issue with the filament regs.



Can you put your scope across the filament to see if it is comming from the filament regulator?


----------



## L0rdGwyn

2359glenn said:


> Can you put your scope across the filament to see if it is comming from the filament regulator?



Yeah I will probably roll my sleeves up and hunt it down tomorrow.  60Hz makes me think it is not the regulator, I would expect 120Hz noise from a DC reg, but you never know.  We'll get to the bottom of it one way or another, this cannot stand!


----------



## L0rdGwyn (Apr 27, 2020)

I suspect the 60Hz buzz is magnetic coupling from the mains transformer to the right OPT, despite the 90 degree orientation.  The hum persists even with all tubes removed, short of rebuilding the amp, I might be SOL on getting rid of it.


----------



## Tjj226 Angel

L0rdGwyn said:


> I suspect the 60Hz buzz is magnetic coupling from the mains transformer to the right OPT, despite the 90 degree orientation.  The hum persists even with all tubes removed, short of rebuilding the amp, I might be SOL on getting rid of it.



Could just be straight pickup. I would try shielding the cable for the power switch considering that wire is close to a bunch of sensitive things on the right channel


----------



## L0rdGwyn

Tjj226 Angel said:


> Could just be straight pickup. I would try shielding the cable for the power switch considering that wire is close to a bunch of sensitive things on the right channel



Except, it is next to the left channel  all of that nasty AC wiring runs on the left side including the power switch, which is noise-free.  I am going to connect in a traditional parafeed output and see what happens.


----------



## L0rdGwyn

Well good news, I swapped CCS's to feed the opposite transformer and the noise swapped sides, which would lead me to believe it is not a magnetic coupling issue.  What a relief, I guess I have more troubleshooting to do...maybe it is my short coming back for revenge 

At some point I am going to enjoy all of this work...some day...


----------



## A2029

L0rdGwyn said:


> Well good news, I swapped CCS's to feed the opposite transformer and the noise swapped sides, which would lead me to believe it is not a magnetic coupling issue.  What a relief, I guess I have more troubleshooting to do...maybe it is my short coming back for revenge
> 
> At some point I am going to enjoy all of this work...some day...



Mosfets can be fickle things when they are partially blown or have ESD damage. I had one that I accidentally shorted when measuring voltage when the circuit was powered. Luckily it didn't explode on me, but started making odd staticky sounds and pops periodically.


----------



## L0rdGwyn

A2029 said:


> Mosfets can be fickle things when they are partially blown or have ESD damage. I had one that I accidentally shorted when measuring voltage when the circuit was powered. Luckily it didn't explode on me, but started making odd staticky sounds and pops periodically.



When I solved the short issue, I replaced the top device on both boards, I did not replace the bottom.  I think that will be the next step, I just so happen to have a spare IXTP08N50D2.  Hopefully that will be the end of it!


----------



## Tjj226 Angel

A2029 said:


> Mosfets can be fickle things when they are partially blown or have ESD damage. I had one that I accidentally shorted when measuring voltage when the circuit was powered. Luckily it didn't explode on me, but started making odd staticky sounds and pops periodically.



........that kind of describes 90% of my audio issues. Hmmmmmmmmmmm maybe its time to put an order into mouser.


----------



## L0rdGwyn

L0rdGwyn said:


> Hopefully that will be the end of it!



Narrator: "It wouldn't be."

Yeah bottom device wasn't the culprit either.  That's all the energy I have for today, I'll get back at it tomorrow, this is proving to be a tricky little noise issue...

Thanks for following my thread everyone, I appreciate the support


----------



## Tjj226 Angel

L0rdGwyn said:


> Narrator: "It wouldn't be."
> 
> Yeah bottom device wasn't the culprit either.  That's all the energy I have for today, I'll get back at it tomorrow, this is proving to be a tricky little noise issue...
> 
> Thanks for following my thread everyone, I appreciate the support



Disconnect the coupling capacitor from the preamp tube and the power tube and then short the rca input. 

This should isolate the two stages and tell you if the noise is coming from the preamp section or the power section. Once you find the right section, then you can start swapping wires from the right channel to the left channel to find out which connection the noise is coming from.


----------



## raindownthunda (Apr 28, 2020)

Beautiful amp, Keenan! Truly a work of art inside and out. I'm impressed with how quickly you put this together while maintaining the attention to detail. I bet it sounds fantastic.


----------



## johnjen

It is at these stages (and more if pursued) where the full potential of the design can be realized.
But it does take much more fussing, and a generous dollop of patience and refined troubleshooting skills.

Case in point is the Purp-Amp has had a case of a noisy channel that comes, and goes, and went, and came back …
Right now, at times the amp can measure 0.000mv s/n (which is -120dB) for both channels, but the tubes are a touch noisy which throws off the numbers.
It has taken much simulated hair pulling consternation to get here.    hahahahahaha

JJ


----------



## L0rdGwyn

L0rdGwyn said:


> Except, it is next to the left channel  all of that nasty AC wiring runs on the left side including the power switch, which is noise-free.  I am going to connect in a traditional parafeed output and see what happens.





Tjj226 Angel said:


> Disconnect the coupling capacitor from the preamp tube and the power tube and then short the rca input.
> 
> This should isolate the two stages and tell you if the noise is coming from the preamp section or the power section. Once you find the right section, then you can start swapping wires from the right channel to the left channel to find out which connection the noise is coming from.



I did all of that legwork last night and isolated it to the output stage, and given the noise was present with no tubes, I figured it was a magnetic coupling issue, and I think my initial thought was right.

Swapping the parafeed cap outputs again today kept the noise on the right channel, AND injected some (to a lesser extent) into the left channel.  Maybe I made a mistake last night in my haste thinking it swapped sides.  Thinking through it today, because this is the Western Electric output, swapping the caps doesn't really change the L/R position of the CCS load since it is connected to the top of the OPT primary, it just changes which cathode the primary is grounded to.  So by swapping the caps, I was just injecting the noise of the right transformer into the cathode of the left output tube 

Here is a spice diagram showing the weird output wiring that resulted by swapping the parafeed cap positions from right to left channel.  This is why I was hearing the noise on both channels.




ANYWAY, long story short, I bypassed the cathode resistors on the 45, used some alligator clips to rewire for a "traditional" parafeed output AND...the noise is gone, wired like so.



So, the noise on the OPT primary was not being shunted to ground, I guess the Western Electric output was not meant to be, it is prone to noise issues after all.  I think I am done experimenting with it, but if you see something else to try that might remove the noise in the WE output, let me know.  Odd thing that it is only on the right side.

Bummer to add another cap in the signal path, but it sure beats a 60Hz buzz!


----------



## L0rdGwyn

raindownthunda said:


> Beautiful amp, Keenan! Truly a work of art inside and out. I'm impressed with how quickly you put this together while maintaining the attention to detail. I bet it sounds fantastic.



Thanks very much for the compliment!  Had a week off work, so this happened at the perfect time.  Can't say it was very restorative, but hey, I got the amp done 



johnjen said:


> It is at these stages (and more if pursued) where the full potential of the design can be realized.
> But it does take much more fussing, and a generous dollop of patience and refined troubleshooting skills.
> 
> Case in point is the Purp-Amp has had a case of a noisy channel that comes, and goes, and went, and came back …
> ...



Still more work to be done!  Now that the noise issue is "solved, I have to dial in the parafeed capacitor value, will likely get start on that tonight, stay tuned


----------



## L0rdGwyn

TubeCad lists this output as well, which removes the bypass cap from the signal path but still provides an AC path to ground, let's give it a try!


----------



## Tjj226 Angel (Apr 28, 2020)

L0rdGwyn said:


> I did all of that legwork last night and isolated it to the output stage, and given the noise was present with no tubes, I figured it was a magnetic coupling issue, and I think my initial thought was right.
> 
> Swapping the parafeed cap outputs again today kept the noise on the right channel, AND injected some (to a lesser extent) into the left channel.  Maybe I made a mistake last night in my haste thinking it swapped sides.  Thinking through it today, because this is the Western Electric output, swapping the caps doesn't really change the L/R position of the CCS load since it is connected to the top of the OPT primary, it just changes which cathode the primary is grounded to.  So by swapping the caps, I was just injecting the noise of the right transformer into the cathode of the left output tube
> 
> ...



You can't have the caps going to the other tube's cathode resistor. IDK if that would create a ground loop, but it would certainly create issues. This obviously isn't the cause of your issue, but im saying you shouldn't use that methodology for testing.

The western electric connection wouldn't inject 60hz noise. It would inject 120hz noise from the PSU.

I think what you have done with the bypass cap is that you have attenuated the problem, but you probably haven't fixed the problem.

EDIT: You could also try running the filaments off a couple Lithium ion batteries in series. Most lithium cells are around 1.2v, so 2 of them would be 2.4v which would be fine for testing. 

If the noise goes away with a couple batteries, then I would check the rod coleman regulators.


----------



## L0rdGwyn

Tjj226 Angel said:


> You can't have the caps going to the other tube's cathode resistor. IDK if that would create a ground loop, but it would certainly create issues. This obviously isn't the cause of your issue, but im saying you shouldn't use that methodology for testing.
> 
> The western electric connection wouldn't inject 60hz noise. It would inject 120hz noise from the PSU.
> 
> I think what you have done with the bypass cap is that you have attenuated the problem, but you probably haven't fixed the problem.



Yes, my point was to illustrate that the wiring was not acceptable...this was only done to see if the noise swapped channels, but it was not an accurate way to do so in retrospect.

Regardless of the cause, providing an AC path to ground on the primary of the OPT resolves the issue.  Using the TubeCad wiring scheme fixes the noise issue as well, I'll troubleshoot a bit more, but that is my fallback option.

I am going to swap the wiring of the regulators and see if the noise moves, that will eliminate them as the cause, thanks for the idea


----------



## L0rdGwyn

Tjj226 Angel said:


> If the noise goes away with a couple batteries, then I would check the rod coleman regulators.





L0rdGwyn said:


> I am going to swap the wiring of the regulators and see if the noise moves, that will eliminate them as the cause, thanks for the idea



It's the freaking regulator.


----------



## Tjj226 Angel

L0rdGwyn said:


> It's the freaking regulator.



You know whats funny about all this? That purple amp on JJs build has almost the exact same issue. But the problem is weirdly intermittent.


----------



## A2029 (Apr 28, 2020)

L0rdGwyn said:


> It's the freaking regulator.



You may have to end up replacing both of the mosfets on that board, as sometimes one malfunctioning can take out the other. When you have the mosfets off the board, also check that the resistance values of the gate stoppers haven't changed. A fried gate stopper can allow the mosfets to oscillate and cause problems.

Edit: If you are putting in an order to mouser for parts, it may be good to get 10 of 1N4104 zener diodes to put two in back-to-back stacks from the source to gates of each of the mosfets if there is space to do so on the boards. May not be needed, but gives extra insurance against reverse polarity.


----------



## L0rdGwyn (Apr 28, 2020)

A2029 said:


> You may have to end up replacing both of the mosfets on that board, as sometimes one malfunctioning can take out the other. When you have the mosfets off the board, also check that the resistance values of the gate stoppers haven't changed. A fried gate stopper can allow the mosfets to oscillate and cause problems.
> 
> Edit: If you are putting in an order to mouser for parts, it may be good to get 10 of 1N4104 zener diodes to put two in back-to-back stacks from the source to gates of each of the mosfets if there is space to do so on the boards. May not be needed, but gives extra insurance against reverse polarity.



I'll look into it, thanks.  I checked the gate stoppers on the CCS boards when replacing the FETs for that reason, I'll check the regulators as well.  I'm discussing it with Rod Coleman, but replacing the MOSFETs may be the ticket, we'll see what he has to say about it.

Took some measurements with my scope.  Directly across the filaments, the noise is not present, it is only measurable from the filament + to ground on the right channel.  The same measurement on the left channel yields no noise.  It is on the order of 100mV peak-to-peak.  The measurement was taken without CCS connected, very certain the regulator is causing the issue.


----------



## L0rdGwyn (Apr 28, 2020)

Well the plot continues to thicken in this fascintating tale of troubleshooting.  I was about to order a new set of transistors for the filament regulators, but thought I would check one more thing first...

I physically swapped the locations of the regulators, rather than the wiring.  And you know what?  The noise didn't switch  so so this appears to be a coupling issue, something is coupling to the regulator on the right side...HOW DEEP DOES THIS GO?

I guess the hunt continues...time to poke around inside with a stick.  I would have thought the left channel would have the coupling issue seeing as it is near the AC wiring.  Gotta get this solved before parafeed cap testing.


----------



## 2359glenn

Have you ruled out magnetic coupling between the transformers?
Disconnect the para feed cap and turn it on and see if you still have hum.
If you do it is magnetic coupling between the power transformer and output transformer.
This is why I only use Lundahl transformers now they reduce this.


----------



## L0rdGwyn (Apr 30, 2020)

2359glenn said:


> Have you ruled out magnetic coupling between the transformers?
> Disconnect the para feed cap and turn it on and see if you still have hum.
> If you do it is magnetic coupling between the power transformer and output transformer.
> This is why I only use Lundahl transformers now they reduce this.



No it isn't magnetic coupling Glenn, at least not to the OPT.  I was able to measure the noise with my scope from the cathode to ground with the plate disconnected and grid shorted to ground, so that pretty much narrowed it down to the filament regulator.  Now magnetic coupling to the components of the filament reg might be a possibility...it seems to be picking something up, can't narrow down what.  Given it is 60Hz, very well could be magnetic.  I would expect 120Hz noise from the PS rectifier pulses...I'll revisit later this week with fresh eyes.

I'm done fudging around with this for now though, I just wanna listen to some music!  I wired it up in the config from Tube CAD I linked a few posts back.  BOOM my 60Hz demon is gone and the amp sounds incredible.  Listening now with 10uF caps in, here is a FFT of the right channel at moderate listening volume.




Edit: I'll repost another FFT from my laptop, I suspect my desktop PC is contributing to the noise floor.  Here is the repeat: https://www.head-fi.org/threads/l0rdgwyns-diy-audio.921105/post-15588423

Here is the FR with the 10uF caps in.  20kHz is down about 0.7dBFS.


----------



## johnjen (Apr 28, 2020)

"HOW DEEP DOES THIS GO?"
Ya know…
This is where the "simulated hair pulling consternation" can loom larger than life… hahahahahahahahahaha

And sometimes it can be just as simple as how a ground connection is made to one portion of the circuit.
Yeah I know this isn't very helpful at the moment, especially when trying to pin point the source of the problem.
But at least it isn't intermittent…

And I was confused in that one circuit diagram, where a primary tap of the OPT was connected to the cathode circuit of the other channel.
A true head scratcher for sure, and I'm glad the amp isn't wired that way, or my head would have exploded at some point…    
Oh the horror… hahahahahahaha

Besides, the talent pool here should be able to provide some avenues for sleuthing out the noise and resolving these teething problems.

At least that is what I have been telling myself all along, while dialing in these amp projects…  hahahahahahahahahahaha

JJ


----------



## L0rdGwyn (Apr 29, 2020)

Okay, got started on the parafeed capacitor testing this evening. Over 200V on those caps, no touchy.



Here are the frequency response plots for the Solen caps I tested, 3.3uF, 4.7uF, 6.8uF, 8.2uF, and 10uF.

3.3uF



4.7uF



6.8uF



8.2uF



10uF



As you can see the effect on low end response from 20-30Hz is pretty subtle, we are talking about a difference of ~0.3dB when tripling the capacitance from 3.3uF to 10uF.

Here it is a GIF format for easier viewing of the low-frequency differences (click to view).



Okay, so we've established there is a very small difference in frequency response from 20-30Hz.  But how does the sound change subjectively?

I'm doing this after a 12-hour shift at work, so only have time to determine some sort of baseline.  I decided to compare at the extremes, 3.3uF and 10uF.  The results were somewhat unexpected...

I much preferred the sound of the 3.3uF.  Even if the low-frequency extension is marginally improved with the 10uF caps in, there is a very noticeable loss of soundstage, airiness, and detail.  The treble sounds a bit more harsh to my ears as well with 10uF.  The 3.3uF sound is much more spacious and cohesive.  Up to this point I had mostly been listening with the higher capacitance caps (6.8uF and 10uF), but the sound is much improved with 3.3uF.  In fact, the bass sounds better!!!  Better definition even if the extension is objectively slightly worse.

So there are clearly two competing factors in play here that will need to be balanced when assessing the other three caps.  I can say without a doubt I will not be using the 10uF, bigger does not appear to be better.

This is an interesting finding since using a lower value cap opens up many more possibilities in terms of the quality of caps that can be used.  I had somewhat assumed I would need a value higher than 5.6uF, so my top choice was the Rike Audio S-Cap 2 (aluminum foil paper in oil) as these caps are the appropriate size, value, and are well-reviewed for their "neutral" sound.  They are also quite affordable, pictured below.



I may still go in this direction.  Pending the results of the other subjective comparisons, if a 3.3uF cap is a legitimate possibility, something like a Jupiter Copper Foil could become an option.

If after the other comparisons are made the 3.3uF is determined to sound best, I will have to consider trying a 2.2uF, in which case something like a Jensen Copper Foil Paper in Oil becomes a possibility...at 2.2uF, the low-end dropoff may be too much, always compromises.

So, there is more listening to be done, pretty interesting results I think.  Other parafeed cap comparisons will come tomorrow or Friday!


----------



## Tjj226 Angel

One thing real quick. Try putting the 10uf in parallel with the 3.3uf. This will equal 13.3uf, which should sound worse if higher capacitance is the thing causing the sonic issues you are describing. 

However it will lower ESR, ESL, beyond that of the 3.3uf capacitor. 

So if it sounds much worse than a 10uf cap, then capacitance is the issue. If it sounds a lot better, then the quality of the capacitor is the issue.


----------



## L0rdGwyn (Apr 29, 2020)

Tjj226 Angel said:


> One thing real quick. Try putting the 10uf in parallel with the 3.3uf. This will equal 13.3uf, which should sound worse if higher capacitance is the thing causing the sonic issues you are describing.
> 
> However it will lower ESR, ESL, beyond that of the 3.3uf capacitor.
> 
> So if it sounds much worse than a 10uf cap, then capacitance is the issue. If it sounds a lot better, then the quality of the capacitor is the issue.



I'll put it on my list of things to try.  Can also parallel the 3.3uF and 4.7uF for 8uF and compare that to the singular 8.2uF.  But it will have to wait until tomorrow, another long day ahead.


----------



## Tjj226 Angel

L0rdGwyn said:


> I'll put it on my list of things to try.  Can also parallel the 3.3uF and 4.7uF for 8uF and compare that to the singular 8.2uF.  But it will have to wait until tomorrow, another long day ahead.



Yeup. Ultimately what you can do is parallel a high value cap with a high quality cap in order to simulate a more "ideal" capacitor.


----------



## johnjen

Using this 'bypass' technique is how I wound up at 5.83µf when I was dialing in my Sowter parafeed setup.
5.6 + 0.22 +0.01 all in parallel.

JJ


----------



## Xcalibur255

You might also consider the Audyn True Copper Max.  They are regarded as nearly the equal of the Jupiter Foils but are half the price and don't have any oil in them which should be a boon for long term reliability.  I think this is what I will use for coupling in any future amps.


----------



## L0rdGwyn

Xcalibur255 said:


> You might also consider the Audyn True Copper Max.  They are regarded as nearly the equal of the Jupiter Foils but are half the price and don't have any oil in them which should be a boon for long term reliability.  I think this is what I will use for coupling in any future amps.



I have read good things about the True Copper Max as well, but forgot about them.  They seem to fit the bill nicely too in terms of available capacitances and size.  I'll keep them in mind, thanks T!


----------



## A2029

Also check out the Miflex KPCU copper caps - new kid on the block in the copper cap world and they are definitely the best bang for the buck copper cap that I've seen.


----------



## L0rdGwyn

A2029 said:


> Also check out the Miflex KPCU copper caps - new kid on the block in the copper cap world and they are definitely the best bang for the buck copper cap that I've seen.



I have the KPCUs in my 6A5 amp  they sound great only problem is they are pretty massive at the capacitances I will need.  Might be able to squeeze them in if I end up using 3.9uF or less, which after the results last night might be realistic!


----------



## L0rdGwyn

Too tired to do any parafeed cap testing tonight, just going to sit back and listen (imagine that!).

Have the Fivre 6C5G in with my shouldered Sylvania 45s, 6.8uF caps (closest pair I grabbed with clips on).  The sound is excellent, very detailed and nuanced, deep bass and great air.  Very happy with it, but looking forward to how it will improve with the finalized caps.

I'm on the lookout for some globe 45s as well, waiting for the right pair


----------



## Tjj226 Angel

L0rdGwyn said:


> Too tired to do any parafeed cap testing tonight, just going to sit back and listen (imagine that!).
> 
> Have the Fivre 6C5G in with my shouldered Sylvania 45s, 6.8uF caps (closest pair I grabbed with clips on).  The sound is excellent, very detailed and nuanced, deep bass and great air.  Very happy with it, but looking forward to how it will improve with the finalized caps.
> 
> I'm on the lookout for some globe 45s as well, waiting for the right pair




Have fun trying to hunt down some blue glass arcturus 45s.


----------



## L0rdGwyn

Tjj226 Angel said:


> Have fun trying to hunt down some blue glass arcturus 45s.



I said I wanted to _listen_ to my amp, not drool on it.  That is way too much tube porn, just some plain old clear glass globes are good for me  I was outbid on a very nice pair of Tung-Sol globes the other day, bummer.  We'll see what comes along on the ol' eBay.  The Japanese market is not an option, those guys are DHT crazy.


----------



## L0rdGwyn (Apr 30, 2020)

Also, here is the repeat FFT I promised a few pages back.  PSU in my desktop is definitely adding to the noise floor, this is off my laptop.  10uF parafeed caps, MOV L63 input and Sylvania 45 output.  Sorry, I was lazy and did not measure the output voltage, but it is at a moderate listening volume into 300ohms.




You can see there are power supply spikes and their harmonics, none of which is audible on the output, so not a concern for me.  Will be interesting to see how using a separate power supply chassis affects the FFT measurements in the next build.


----------



## Tjj226 Angel

L0rdGwyn said:


> I said I wanted to _listen_ to my amp, not drool on it. That is way too much tube porn, just some plain old clear glass globes are good for me  I was outbid on a very nice pair of Tung-Sol globes the other day, bummer.  We'll see what comes along on the ol' eBay.  The Japanese market is not an option, those guys are DHT crazy.



Arcturus made some pretty good tubes. When I finish up my 45 build for jj and take it to his place, we will listen to the regular coke bottle 45 arcturus makes. If it is as good as I remember the blue glass version to be, then those are the only 45s I would get.


----------



## Tjj226 Angel

L0rdGwyn said:


> Also, here is the repeat FFT I promised a few pages back.  PSU in my desktop is definitely adding to the noise floor, this is off my laptop.  10uF parafeed caps, MOV L63 input and Sylvania 45 output.  Sorry, I was lazy and did not measure the output voltage, but it is at a moderate listening volume into 300ohms.
> 
> 
> 
> You can see there are power supply spikes and their harmonics, none of which is audible on the output, so not a concern for me.  Will be interesting to see how using a separate power supply chassis affects the FFT measurements in the next build.



I kinda doubt that is your PSU creating that noise. I think that is related to your 60hz issue and you are seeing the result of the 60hz harmonics. 

Considering the filtering, ccs loads, and everything else in between, I would expect to see your PSU noise a good 10 db lower.


----------



## L0rdGwyn (Apr 30, 2020)

Tjj226 Angel said:


> I kinda doubt that is your PSU creating that noise. I think that is related to your 60hz issue and you are seeing the result of the 60hz harmonics.
> 
> Considering the filtering, ccs loads, and everything else in between, I would expect to see your PSU noise a good 10 db lower.



Could be, although the issue was isolated to the right channel, with the bypass cap place, the noise pattern is identical across both.  Could also be coupled from the heater/filament/mains wiring which is not subject to attenuation.

I have one more lead to pursue on the 60Hz noise issue, going to look into it this weekend.  Adding the bypass cap equalized the channels, so I'm happy to leave it as is if unsuccessful.


----------



## Tjj226 Angel

L0rdGwyn said:


> Could be, although the issue was isolated to the right channel, with the bypass cap place, the noise pattern is identical across both.  Could also be coupled from the heater/filament/mains wiring which is not subject to attenuation.
> 
> I have one more lead to pursue on the 60Hz noise issue, going to look into it this weekend.  Adding the bypass cap equalized the channels, so I'm happy to leave it as is if unsuccessful.



Right, but like I said, I think the problem was attenuated which is why you are seeing it at 80db and not 60db.

I have a feeling that there is some small stupid problem with your ground that will be near impossible to spot. Maybe a cold solder joint or something.


----------



## johnjen

OK soooo, 
tube porn it is…



hahahahahahahahahahahaha

JJ


----------



## chrisdrop

L0rdGwyn said:


> Too tired to do any parafeed cap testing tonight, just going to sit back and listen (imagine that!).
> 
> Have the Fivre 6C5G in with my shouldered Sylvania 45s, 6.8uF caps (closest pair I grabbed with clips on).  The sound is excellent, very detailed and nuanced, deep bass and great air.  Very happy with it, but looking forward to how it will improve with the finalized caps.
> 
> I'm on the lookout for some globe 45s as well, waiting for the right pair


Beautifully done. I've really been enjoying the whole thread. I especially enjoyed reading the recent page+ of debugging. It sounded like how debugging a software project feels. Those are lovely Fivre 6C5Gs also ...  Enjoy final cap tweaking.


----------



## Xcalibur255

@L0rdGwyn

What did they go for?  I forgot to watch that auction.  You really don't see Tung-Sol globes like that everyday.  Most of the globes you will see on eBay are going to be RCA/Cunningham, but every once in a while something neat comes along.

If I ever see another nicely matched pair of Raytheon 4-Pillar Box plates I won't be outbid on them.  I passed on a beautiful pair once and really regret it.


----------



## L0rdGwyn

Tjj226 Angel said:


> Right, but like I said, I think the problem was attenuated which is why you are seeing it at 80db and not 60db.
> 
> I have a feeling that there is some small stupid problem with your ground that will be near impossible to spot. Maybe a cold solder joint or something.



Man I'm pretty sure I've checked and reflowed every joint in that amp lol I'm going to do it all again though with fresh eyes this weekend, maybe something will jump out.



johnjen said:


> OK soooo,
> tube porn it is…
> 
> 
> ...



Beautiful!



chrisdrop said:


> Beautifully done. I've really been enjoying the whole thread. I especially enjoyed reading the recent page+ of debugging. It sounded like how debugging a software project feels. Those are lovely Fivre 6C5Gs also ...  Enjoy final cap tweaking.



Thanks, Chris!  Probably will have another round of debugging Saturday, we'll see how it goes.



Xcalibur255 said:


> @L0rdGwyn
> 
> What did they go for?  I forgot to watch that auction.  You really don't see Tung-Sol globes like that everyday.  Most of the globes you will see on eBay are going to be RCA/Cunningham, but every once in a while something neat comes along.
> 
> If I ever see another nicely matched pair of Raytheon 4-Pillar Box plates I won't be outbid on them.  I passed on a beautiful pair once and really regret it.



They went for around $340, I figured it would be around there but I wasn't willing to go higher than $325.  We'll just have to see what comes along, I may just nab a nice pair of RCAs at some point.


----------



## johnjen

So do you have a set of schemotatics of the 'as built' for this amp?

And specifically the grounding scheme you've implemented?
I ask because when we oh so subtly changed our grounding implementation there was a subtle yet oh so important improvement.
So perhaps we can spot an alternative grounding scheme that might shed some insights etc.

Just a thought or 2.

JJ


----------



## L0rdGwyn (May 1, 2020)

johnjen said:


> So do you have a set of schemotatics of the 'as built' for this amp?
> 
> And specifically the grounding scheme you've implemented?
> I ask because when we oh so subtly changed our grounding implementation there was a subtle yet oh so important improvement.
> ...



Hey JJ - there is not an "as built" schematic, but I can type you out the star grounding scheme, it's pretty straightforward.

Each of the points below is a local star node that is tied to the chassis ground:

C2 power supply capacitor negative (all other power supply grounds are tied to this point, rectifier, C1, C3)
x2 cathode ground of 6J5 tubes (tied to 6J5 grid leak, RCA input ground)
x2 cathode ground of 45 tubes (tied to 45 grid leak)
Volume pot (grounded directly to chassis)
x2 OPT secondary (grounded after 1/4" headphone jack common to chassis)
RCA input shielding (each strip of shielded wire is tied to chassis ground at one end)
Electrostatic screen of mains transformer (grounded to chassis)

I think that's it, pretty simple, everything connects to chassis at a single point.


----------



## L0rdGwyn (May 1, 2020)

@Tjj226 Angel @A2029 what do you think of this...

The noise is being coupled in the mains transformer.  I did the last troubleshooting effort to get to the source, swapping the two 6.3 / 5A windings on the traffo while keeping the regulators / raw DC boards in place.  The noise switched sides.  So, the 60Hz that is being coupled is from within the mains transformer.

The lead Rod Coleman gave me was to check for leakage capacitance from primary to secondary of the filament winding, his concern being common mode noise being coupled across the transformer.  I haven't pursued this yet, but even if that were the case, there is not much to be done.  The Sowter mains has an electrostatic screen as well which is grounded to the chassis.  Ungrounding the screen had no effect.

Here are some measurements.

First, the left and right channels with *no cathode bypass caps*.  This is the situation in which the noise is clearly audible on one channel (the left in this case, since they windings were swapped), but the other channel is completely silent to the ear.  I think you will see why in the plots.

Left


Right



Now here are the two channels with the cathodes bypassed.

Left


Right


As you can see, the noise pattern on the right channel is unchanged while the excessive noise on the left channel is now gone.  With the cathodes bypassed, the noise pattern is now very similar across both channels.

*Another interesting observation:* switching the driver tubes alters the 60Hz (and harmonics) noise in the two channels with the cathodes bypassed.  This leads me to believe there is some degree of heater-to-cathode leakage contributing to this noise pattern and it may be unrelated to the noise being coupled within the transformer.

Edit: running the 6J5 heaters off my 30V/5A DC bench supply would be a good way to test this theory.

So, the question is, does bypassing the cathodes solve the issue, and can I move on from troubleshooting this further?  If the noise is being coupled within the traffo, short of having Sowter wind me a new one, there is no intervention, I think it is what it is.

@Tjj226 Angel our buddy audiowize seems to think bypassing the cathodes is the correct approach in parafeed regardless of the noise, which is worth noting.

I know this isn't the most interesting of topics, sorry for those who are following  but this comes with the territory, has been a good learning experience for me.

Thanks for your $0.02.


----------



## L0rdGwyn

L0rdGwyn said:


> *Another interesting observation:* switching the driver tubes alters the 60Hz (and harmonics) noise in the two channels with the cathodes bypassed.  This leads me to believe there is some degree of heater-to-cathode leakage contributing to this noise pattern and it may be unrelated to the noise being coupled within the transformer.
> 
> Edit: running the 6J5 heaters off my 30V/5A DC bench supply would be a good way to test this theory.



I did this little test, running one 6J5 on DC made little difference in the 60Hz noise and harmonics, so the leakage does not appear to be the cause of the variation from tube to tube, I suppose it is just a varying degree of coupling.


----------



## A2029

L0rdGwyn said:


> @Tjj226 Angel @A2029 what do you think of this...
> 
> The noise is being coupled in the mains transformer.  I did the last troubleshooting effort to get to the source, swapping the two 6.3 / 5A windings on the traffo while keeping the regulators / raw DC boards in place.  The noise switched sides.  So, the 60Hz that is being coupled is from within the mains transformer.
> 
> ...



Hi Keenan, what is the voltage and ripply on the output of each of the raw DC supplies just prior to the Coleman reg?

What do you have for RC snubbers on each of the 6.3V windings?

If it's noise from the power transformer getting through, my thought is just stick a very low drop out linear voltage reg between the Coleman board and the raw DC supply. Regulate the voltage to just above the dropout for the Coleman supply, and put a big electrolytic cap right near the input to the Coleman supply to make sure it doesn't drop below the dropout. That way the pre-reg kicks down the 60Hz noise, and the Coleman can still do its job as a CC filament supply.

Also stick a 0.1-0.68uF X2 rated cap (or high voltage cap that can take AC line voltage) across the primary from line to neutral. Parallel that with a cap of the same value but in series with a 10-20ohm resistor.


----------



## L0rdGwyn (May 1, 2020)

A2029 said:


> Hi Keenan, what is the voltage and ripply on the output of each of the raw DC supplies just prior to the Coleman reg?
> 
> What do you have for RC snubbers on each of the 6.3V windings?
> 
> ...



Hey Mischa - I measured the ripple on the raw DC boards the other day, both are around 150mVpp if memory serves.  The boards are Coleman's design as well, and according to his schematic, he uses a 220nF-33ohm single RC snubber for each secondary.

Let me chew on using a voltage regulator in between the raw DC board and the filament reg, space is tight but I might be able to make it work.  An CRC across the primary should be very simple to add in, I'll give that a try, thanks!

Edit: probably worth noting that I have a low interwinding capacitance isolation transformer between my wall mains and the amplifier (Topaz), adding / removing the transformer had no effect on the noise output.  These are spec'd to give 140-150dB attenuation to commode-mode noise.


----------



## L0rdGwyn

I am being told on diyAudio that I am debugging a problem that doesn't exist LOL one end of the filament regulator _needs_ to be at AC ground, which is not the case without the bypass caps.  So, back to where I was this morning, I am leaving the cathodes bypassed and moving on.  The residual AC noise at -85dBFS or less cannot be detected, the amp is dead silent at max volume with no input, so I'm not too concerned about it.

Time to get this parafeed cap situation figured out and finalize the circuit.


----------



## A2029

L0rdGwyn said:


> I am being told on diyAudio that I am debugging a problem that doesn't exist LOL one end of the filament regulator _needs_ to be at AC ground, which is not the case without the bypass caps.  So, back to where I was this morning, I am leaving the cathodes bypassed and moving on.  The residual AC noise at -85dBFS or less cannot be detected, the amp is dead silent at max volume with no input, so I'm not too concerned about it.
> 
> Time to get this parafeed cap situation figured out and finalize the circuit.



Ah right, didn't notice that. I'm used to seeing the Coleman regs used with fixed bias. Glad you got it worked out. Amp looks great and I'm sure it sounds fantastic!


----------



## L0rdGwyn (May 2, 2020)

Worked on getting the parafeed capacitance nailed down this morning.  I started by comparing the 4.7uF and 3.3uF in parallel vs. the single 8.2uF cap.  I can say without a doubt the two parallel caps sounded better.  Better sounstage, air, and detail.  Similar to what I said about the 3.3uF vs. 10uF, the singular higher capacitance cap causing something of a collapse of soundstage and more harsh treble.

Next, I compared the 4.7uF cap to the 4.7uF and 3.3uF in parallel to compare a singular lower capacitance cap with the higher capacitance combination.  Again, I felt the two parallel caps gave better detail, soundstage separation, and this is the first time I felt the bass was significantly improved between two sets of caps.  Fuller, tighter, more body.

Next, I compared two sets of parallel caps with different capacitances.  With what I had on hand, I went for the two lowest capacitance combos for the sake of practicality, 4.7uF + 3.3uF and 6.8uF + 3.3uF.  This is where differences started to get more difficult to detect...however, I did feel vocals started to get smeared a bit with the higher capacitance and focusing on other aspects of my test tracks revealed a loss of microdetail.

So, with the parallel combination of around 8uF, I was getting the best sound.  But what about the relative values of the two capacitors?  I then compared the 4.7uF + 3.3uF combination with an 8.2uF + 0.22uF combination.  Not an exact capacitive match, but close enough with the 5% tolerances.  I felt the two caps of similar size gave better nuance and vocal detail.

If two paralleled caps is good, is three better?  I put the 0.22uF cap in parallel with the 4.7uF and 3.3uF for a total of 8.22uF.  Adding this 0.22uF cap undeniably reduced the fullness and quality of the bass.

So my winning combination was the 4.7uF cap and 3.3uF cap in parallel.  From the measurements, I know that diminishing returns in the bass response start at around 6.8uF, so I will be looking to find a parallel set of caps with similar values that add to ~6.8uF, perhaps 3.3uF + 3.3uF or 3.9uF + 3.9uF.  Obviously this will make the size restriction more stringent, but I think the performance is worth it.  It's pretty incredible the gains that can be made in this topology by tuning the parafeed caps.

I did briefly drop the 0.22uF cap in parallel with my 0.47uF coupling cap to see if similar gains could be had there.  A few back-to-back comparisons was not enough to say definitively, and I was pretty fatigued at that point, so I'll revisit it.

Obligatory "my listening impressions, IMO, IME, YMMV" all that stuff.  Time to go cap shopping


----------



## L0rdGwyn

Caps are ordered, I did end up going with the Rike Audio S-Cap 2 (paper-polypropylene-aluminium-oil), 2x 3.3uF along with matching 0.47uF coupling caps.




I know, not as fancy-schmancy as the copper caps, but a pair of 3.3uF will fit easily in my dedicated space, not the case with the copper options.  By all accounts, they are very nice capacitors.  Helps that they were only 35 GBP a piece.  After finishing two amplifiers in less than two months, saving some cash is a nice feeling...


----------



## L0rdGwyn (May 2, 2020)

Now that both amps are complete (save for the finishing touches on the 45 parafeed), here they are side-by-side for some size context.



I don't have a penchant for naming my things, so my girlfriend has taken the responsibility from me.  As such, the MH4/6A5 amp is now called "The Golden Chalice" and the 6J5/45 parafeed is known as "Sergeant Surge" according to her.  LOL.

The Chalice is sporting a MOV U18/20, Opta REN904, and Visseaux 6A5G.  Surge is equipped with the Mullard 6C5G (inspired by @leftside 's tube du jour) and shouldered Sylvania 45.  Really hoping I can make it to ZMFestivus this year and bring them along, assuming it is still on.

Should have my Omega speakers within the next two weeks, can't wait.


----------



## Tjj226 Angel

Congratulations!. Very nice builds. Im currently dinking around with more DIY speakers and I have been taking some inspiration from the omegas, so I will be curious to see what you have to say about them.


----------



## L0rdGwyn

Thanks for your help along the way @Tjj226 Angel .  I'll report on the Omegas here when they arrive.  I was told 4-6 weeks and it has been four, pretty quick turnaround which is great!


----------



## Zachik

L0rdGwyn said:


> Thanks for your help along the way @Tjj226 Angel .  I'll report on the Omegas here when they arrive.  I was told 4-6 weeks and it has been four, pretty quick turnaround which is great!


Keenan - can both amps drive speakers?
Also, can you post some thoughts about sound differences between the 2 amps (with headphones), and how they compare to the former GOTL you had? (I know the GOTL is a moving target since it can support so many different tube types...)


----------



## Tjj226 Angel

Zachik said:


> Keenan - can both amps drive speakers?
> Also, can you post some thoughts about sound differences between the 2 amps (with headphones), and how they compare to the former GOTL you had? (I know the GOTL is a moving target since it can support so many different tube types...)



They can both drive speakers so long as the speakers are adequately efficient. A 6A5 is only putting about 3 watts into 8 ohms and a 45 is probably somewhere right around a watt.


----------



## L0rdGwyn (May 2, 2020)

Zachik said:


> Keenan - can both amps drive speakers?
> Also, can you post some thoughts about sound differences between the 2 amps (with headphones), and how they compare to the former GOTL you had? (I know the GOTL is a moving target since it can support so many different tube types...)



Hey Zachi - the 6A5 amp can run speakers, in fact that is its primary purpose, while the 45 parafeed amp is dedicated for headphones.  In a way, it replaces the GOTL as my desktop headphone amp.  As @Tjj226 Angel said, a 45 can drive speakers, but they need to be highly efficient.  The amp is not equipped to run speakers though, just headphones.

It's funny you should ask how the two amps compare since I was just doing a little back and forth between them  take this with a grain of salt since I can't be certain how dramatically adding in the final parafeed caps (rather than the bargain bin Solens I have in now) will affect the sound.  Maybe it will be a big change, maybe not, we will see!  The sound will likely change when I move to some globe 45s as well rather than the shouldered I am using now.

With that out of the way, I would say relative to the 6A5 amp, the 45 parafeed falls more into the "neutral" category.  It has tremendous midrange detail, good soundstage but more intimate than the 6A5 amp.  No part of the frequency spectrum comes off as accentuated, just very cohesive across the board with tight bass and a very nice tonality with my Auteurs, they suit each other very well I think.

I find the 6A5 amp more warm and lush than the 45 parafeed as it is right now, not in the "gooey" sense, as it does not lack for detail, it just has a more smooth tone.  The defining feature of the 6A5 amp though is its staging...it is insane.  I keep thinking I will get used to it, but it just hasn't happened yet.  It is absolutely expansive with very fine layering and instrument separation.  I attribute this in part to the driver tubes I am using in the amp, which I think are exceptional.  Of the two, the 6A5 amp has more of a "wow" factor going for it, but they are both great and offer two different presentations, which is perfect for me  detailed, relatively intimate, and neutral vs. warm, lush, and spacious.

Yeah the GOTL definitely is a moving target since it is so changeable.  I will say though that for OTLs in general, moving to a SET amp for me offered more in the way of airiness and detail with tighter bass, as well as a lower noise floor.  I'm sure the difference will vary from amp to amp based on the build, but that was what jumped out to me when I made the change.


----------



## leftside

L0rdGwyn said:


> Yeah the GOTL definitely is a moving target since it is so changeable.  I will say though that for OTLs in general, moving to a SET amp for me offered more in the way of airiness and detail with tighter bass, as well as a lower noise floor.  I'm sure the difference will vary from amp to amp based on the build, but that was what jumped out to me when I made the change.


Funny you should say that. As you know my 1101 Thunder is OTL, and the Glenn 300B is SET. I've compared them quite a lot. The 300B definitely has more airiness, but sometimes it doesn't quite have the bass or the depth as Thunder. I thought maybe the 300B has tighter bass, but I think the bass in Thunder is simply more defined and stronger. I love having both amps. Detail and soundstage is very similar. When I want to rock out, or just regular listening it's with Thunder. When I've had a little weed, I tend to veer towards the 300B. Using the C3g tubes in Thunder I can get it to sound more like the 300B.


----------



## Tjj226 Angel

L0rdGwyn said:


> Hey Zachi - the 6A5 amp can run speakers, in fact that is its primary purpose, while the 45 parafeed amp is dedicated for headphones.  In a way, it replaces the GOTL as my desktop headphone amp.  As @Tjj226 Angel said, a 45 can drive speakers, but they need to be highly efficient.  The amp is not equipped to run speakers though, just headphones.
> 
> It's funny you should ask how the two amps compare since I was just doing a little back and forth between them  take this with a grain of salt since I can't be certain how dramatically adding in the final parafeed caps (rather than the bargain bin Solens I have in now) will affect the sound.  Maybe it will be a big change, maybe not, we will see!  The sound will likely change when I move to some globe 45s as well rather than the shouldered I am using now.
> 
> ...




I hadn't realized you are using solens right now. 

I haven't tried riken caps, but even if they are slightly better than the solens, I would expect the sound stage to open up quite a bit. 

I am extrapolating quite a bit here, but by all accounts your 45 amp should have a bigger sound stage than the 6A5. All the good 45 amps I have heard almost don't have a sound stage. It's just ethereal.


----------



## Tjj226 Angel

leftside said:


> Funny you should say that. As you know my 1101 Thunder is OTL, and the Glenn 300B is SET. I've compared them quite a lot. The 300B definitely has more airiness, but sometimes it doesn't quite have the bass or the depth as Thunder. I thought maybe the 300B has tighter bass, but I think the bass in Thunder is simply more defined and stronger. I love having both amps. Detail and soundstage is very similar. When I want to rock out, or just regular listening it's with Thunder. When I've had a little weed, I tend to veer towards the 300B. Using the C3g tubes in Thunder I can get it to sound more like the 300B.



? 

Does anyone know which lundhal transformer glenn has in his 300b amp? Is it the one made for the elekit 300b amp?


----------



## leftside

Tjj226 Angel said:


> ?
> 
> Does anyone know which lundhal transformer glenn has in his 300b amp? Is it the one made for the elekit 300b amp?


Think its the LL1651, although we could always ask him to double check. Or I could open mine. I also use the LL1651 in the power section of my 1101 Audio V6 Thunder.


----------



## Tjj226 Angel

leftside said:


> Think its the LL1651, although we could always ask him to double check. Or I could open mine. I also use the LL1651 in the power section of my 1101 Audio V6 Thunder.



I meant the output transformer.  

I heard the glenn 300b amp at RMAF last year and something was off about it. It wasn't bad, but it wasn't quite right either. It was a weird enough issue where I felt like it deserved some investigating but sadly I couldn't listen to the amp more before I had to catch my plane back home. 

My engineering OCD kicked in and I have been trying to figure out why it sounded the way it did. 

What you just said about the bass being light makes me wonder what sort of output transformer he is using. Maybe he choose one with slightly lower inductance.


----------



## Zachik

L0rdGwyn said:


> I find the 6A5 amp more warm and lush than the 45 parafeed as it is right now, not in the "gooey" sense, as it does not lack for detail, it just has a more smooth tone. The defining feature of the 6A5 amp though is its staging...it is insane. I keep thinking I will get used to it, but it just hasn't happened yet. It is absolutely expansive with very fine layering and instrument separation. I attribute this in part to the driver tubes I am using in the amp, which I think are exceptional. Of the two, the 6A5 amp has more of a "wow" factor going for it, but they are both great and offer two different presentations, which is perfect for me  detailed, relatively intimate, and neutral vs. warm, lush, and spacious.


Thanks for the detailed answer!  
I think the 6A5 sound signature is more to my personal liking, from your description. Cannot wait to audition it (hopefully) at ZMFestivus III  



L0rdGwyn said:


> Yeah the GOTL definitely is a moving target since it is so changeable. I will say though that for OTLs in general, moving to a SET amp for me offered more in the way of airiness and detail with tighter bass, as well as a lower noise floor. I'm sure the difference will vary from amp to amp based on the build, but that was what jumped out to me when I made the change.


Comparing my GOTL to my 6EL3N - I agree that the latter is more refined, with tighter bass and definitely much lower noise floor!
(looking forward for @chrisdrop DIY dummy load plugs to take my GOTL to the next level in term of noise floor )


----------



## leftside

Tjj226 Angel said:


> I meant the output transformer.
> 
> I heard the glenn 300b amp at RMAF last year and something was off about it. It wasn't bad, but it wasn't quite right either. It was a weird enough issue where I felt like it deserved some investigating but sadly I couldn't listen to the amp more before I had to catch my plane back home.
> 
> ...


Well it's only light(er) compared to Thunder. I call Thunder "Thunder" for a reason.


----------



## whirlwind

L0rdGwyn said:


> Now that both amps are complete (save for the finishing touches on the 45 parafeed), here they are side-by-side for some size context.
> 
> 
> 
> ...




Beautiful Keenan...looks like it is time to enjoy some music  
Congrats.


----------



## L0rdGwyn (May 3, 2020)

Tjj226 Angel said:


> I hadn't realized you are using solens right now.
> 
> I haven't tried riken caps, but even if they are slightly better than the solens, I would expect the sound stage to open up quite a bit.
> 
> I am extrapolating quite a bit here, but by all accounts your 45 amp should have a bigger sound stage than the 6A5. All the good 45 amps I have heard almost don't have a sound stage. It's just ethereal.



I'm curious to find out myself.  The soundstage isn't small, it's quite large actually, but the 6A5 amp's stage is just enormous, so it's all relative.  Just have to wait and see what happens with the new caps, very happy with it either way, but the Solens aren't doing it any favors lol served their purpose well though.



leftside said:


> Funny you should say that. As you know my 1101 Thunder is OTL, and the Glenn 300B is SET. I've compared them quite a lot. The 300B definitely has more airiness, but sometimes it doesn't quite have the bass or the depth as Thunder. I thought maybe the 300B has tighter bass, but I think the bass in Thunder is simply more defined and stronger. I love having both amps. Detail and soundstage is very similar. When I want to rock out, or just regular listening it's with Thunder. When I've had a little weed, I tend to veer towards the 300B. Using the C3g tubes in Thunder I can get it to sound more like the 300B.



Interesting!  Yeah I don't doubt it, didn't mean to make a blanket statement, that's just been my experience with the 3-4 OTLs I have owned, the GOTL being the best one.  Thunder is a pretty unique amplifier, I'm not sure I can think of another OTL that has a separate-chassis power supply, I'm sure it makes a world of difference for the noise floor and definition.  It is nice to have options, and every custom amplifier is unique, so very tricky to say "X type of amplifier is better than Y".  Just gotta lay ears on 'em and see.  At some point, I would like to build an OTL myself, I do have all of these tubes after all...


----------



## L0rdGwyn (May 3, 2020)

whirlwind said:


> Beautiful Keenan...looks like it is time to enjoy some music
> Congrats.



Thanks, Joe!  That's what it's all about.

Funny yesterday I woke up and thought, "I have the day off, and I don't have to build an amplifier...AWESOME!".  Not that I don't enjoy it, but it is nice to have a break and appreciate the work that was put in.


----------



## L0rdGwyn

Zachik said:


> Thanks for the detailed answer!
> I think the 6A5 sound signature is more to my personal liking, from your description. Cannot wait to audition it (hopefully) at ZMFestivus III
> 
> 
> ...



No problem!  Like I said, subject to change since the 45 amp isn't finalized, I'll report back again on the sound once those caps are in with a picture of the final, final circuit lol.  Sure hope ZMFestivus III is on, just wait and see I s'pose.  Glad you are happy with your 6EL3N, I'm sure it sounds fantastic.


----------



## chrisdrop

If you don't mind saying of course...In _parts only_, what was the _rough cost_ of each amp. If you can separate tube costs that would be great. I think you also bought some lovely and not inexpensive tubes for each of these. 

I'd like to make a simple amp for fun, but I am sure that to make something I'd want to use, it will take a few iterations (i.e.; parts a few $k and I'd like not to screw the pooch on them!). In the US Bottlehead seems a good starter. I am a technical person, but not at all in this domain, so there are plenty of things to learn really. It looks like you are really having too much fun.


----------



## L0rdGwyn (May 3, 2020)

chrisdrop said:


> If you don't mind saying of course...In _parts only_, what was the _rough cost_ of each amp. If you can separate tube costs that would be great. I think you also bought some lovely and not inexpensive tubes for each of these.
> 
> I'd like to make a simple amp for fun, but I am sure that to make something I'd want to use, it will take a few iterations (i.e.; parts a few $k and I'd like not to screw the pooch on them!). In the US Bottlehead seems a good starter. I am a technical person, but not at all in this domain, so there are plenty of things to learn really. It looks like you are really having too much fun.



That's awesome, Chris!  I totally support people getting into DIY.  When asked in the past, I've recommended starting with something like a Bottlehead kit.  They don't necessarily teach you the innerworkings of the circuits (have to dig into that on your own), but what it will provide is experience with the hands-on skills needed to build an amplifier - i.e., soldering, working with point-to-point wiring, etc.

In terms of the costs of the two amps...

The 6A5 amp was a "no holds barred" type approach, so no expense was spared.  The Lundahl transformers/chokes/shields alone were $1200 USD, $275 for the stepped attenuator, $250 for the Yamamoto sockets, $300 for the chassis, probably another $750 or so for all the other miscellaneous parts (switches, caps, resistors, terminal strips, wiring, hardware, jacks/plugs, etc.)...so total without the overhead cost was somewhere around $2700 without the tubes.  LOTs of places where costs could have been cut though.

The 45 parafeed amp was _meant_ to be a cheaper build, and it was, but not by a whole lot in retrospect lol.  I think the total cost was around $2000 USD without the tubes now that I've ordered the parafeed caps.  The Sowter transformers were the greatest expense at $800 USD.

You can definitely cut more costs though - get rid of the Goldpoint parts, use a cheaper chassis, and a non-Lundahl choke for the PS, and you could knock off probably $4-500.


----------



## L0rdGwyn (May 3, 2020)

Okay so...we are putting the finishing touches on the 45 parafeed amp, but for the most part, it is done.  I'll be taking some time to sit back and enjoy the spoils of my work before diving into the next project...but where do we go from here?  Wanted to share the ideas I am kicking around for this thread.

I know, I know, "when the hell is this guy going to shut up?".  I'm sorry, I love talking about this stuff!  I have very few vices in my life, so this is it for me, I'm an addict...

So bear with me, here is what I am looking at.

*1) CCS loaded 841 input, 801A output, FET source follower insterstage coupled A2 SET with separate chassis power supply*

This is definitely happening.  With another two pairs of NOS Hytron 801A waiting to be shipped to me from overseas in addition to what is pictured below, you could say I am committed.




This ain't gonna be a cakewalk though, this is going to be a very intense build, beyond what I have done so far.  There are a number of design elements that are new to me and will take some time to work out.  I have a drafted LTSpice schematic and I've reached out to Heyboer who can wind me a B+ only dual secondary mains transformer if I so choose, or go with a off-the-shelf traffo from Antek.

Anyway, I will be working on this design with no particular timeline on when it will be built.  I thought of something today though - when it comes time to construct this build, when all of the design is finalized and parts are assembled, maybe I will get a GoPro or something and edit together a first-person account of what it is like to put together one of these amplifiers, I thought that might interest some people.  Just an idea!

*2) eTracer tube curve tracer / tester*

I have my Jackson 648-R that I restored, which serves me well, but this thing is so cool!  It's another DIY kit that can be bought from the site below.  It is a legit electronic curve tracer / tester with something of a crowd-sourced element to it as various users can generate / share specific tube testing parameters.  Has a ton of flexibility to test different types of tubes with lots of sockets, which is appealing to me since I have a collection of oddball 4V B4/B5 base tubes that I can't test without something like a Funke W19S.

Here is the site: https://www.essues.com/etracer/

Here is part 1 of a two-part series where Mark from the YouTube channel Blueglow Electronics discusses and builds one of these tracers.  This to me is much more appealing than something like an Amplitrex AT1000 and is way more affordable.



By the way, for those that are interested in building their own amplifiers, check out some of the SET build playlists from Blueglow.  Mark goes through an entire SET build from start to finish.  It is at a pretty basic level, but this is pretty much where I started on day 1 of trying to figure this stuff out, really puts into context what goes into a build at a high level, very nice of him to do a series on it.

*3) Amplifer prototyping bench*

Eventually, I am going to reach a point where it is no longer practical to build more amplifiers for myself.  My house is small, my girlfriend will kill me, and I value my life.  Pretty much after the 841/801A build, we are gonna have to pack it in for a while I think.

But does that mean the fun has to end?  Of course not!

I cooked up this idea, then found out this is somewhat of a common thing in the tube DIY community.  Essentially, it is a prototyping setup where one has the flexibility to wire together a flexible power supply, input and output stage, and measure/test/listen to a prototyped build before turning it into a completed amplifier.

Here is an example from Tubelab: http://tubelab.com/articles/tubelab-prototyping-system/

I discovered that Edcor makes "Tinker Box" mains transformers specifically for this purpose, check it out: https://www.edcorusa.com/tbpwr-1

I'm thinking I could put together a flexible voltage-regulated SS power supply, attach some tube sockets onto a piece of plywood, some input and output jacks, a few terminal strips to connect various components, and BOOM, you have a prototyping setup.  I already have all of the measurement gear I would need to test what I throw together.  The danger in this is I could be lost in my garage for months messing around with this stuff...but it is very appealing.

*4) Tube phono stage*

This is going at the bottom of the list since it isn't something I am super serious about at the moment, but it is very possible it could happen.  I sold my old integrated Rogue Audio amp to make room for the 6A5 amp in my stereo, which leaves me phono stageless.  I'll likely pick up something relatively cheap in the interim just so my turntable is functional again, but I would love to put together a relatively simple, small form factor tube phono stage to pair with my stereo.  I have done little to no research on this project yet, but it is in the queue so to speak.

-------------------------------------------------

That's what I have for now, I'll probably tinker with the 6A5 and 45 amps a bit, little improvements here and there, maybe experiment with some different biasing schemes, but these are the big projects I am looking forward to.

Rant over!


----------



## leftside

L0rdGwyn said:


> At some point, I would like to build an OTL myself, I do have all of these tubes after all...


At some point @A2029 will build me a SET amp. I do have all of these KT66/6L6/EL37/EL35 after all... 



L0rdGwyn said:


> In terms of the costs of the two amps...
> 
> The 6A5 amp was a "no holds barred" type approach, so no expense was spared.  The Lundahl transformers/chokes/shields alone were $1200 USD, $275 for the stepped attenuator, $250 for the Yamamoto sockets, $300 for the chassis, probably another $750 or so for all the other miscellaneous parts (switches, caps, resistors, terminal strips, wiring, hardware, jacks/plugs, etc.)...so total without the overhead cost was somewhere around $2700 without the tubes.  LOTs of places where costs could have been cut though.
> 
> ...


The 1101 Audio V6 Thunder cost of parts was similar - a little closer to the cost of the parts for the 45 parafeed amp.  The Jupiter and ClarityCap caps in the amp section, the Lundahl transformer in the power section, the meters, the chassis and the Acoustics Dimension 41 step being the most expensive parts.


----------



## Tjj226 Angel

L0rdGwyn said:


> Okay so...we are putting the finishing touches on the 45 parafeed amp, but for the most part, it is done.  I'll be taking some time to sit back and enjoy the spoils of my work before diving into the next project...but where do we go from here?  Wanted to share the ideas I am kicking around for this thread.
> 
> I know, I know, "when the hell is this guy going to shut up?".  I'm sorry, I love talking about this stuff!  I have very few vices in my life, so this is it for me, I'm an addict...
> 
> ...




I would hold off on the 801as until you get your omegas. Figure out if you like listening to headphones or your speakers more. 

If you like the headphones, then proceed with your plan. If you like the speakers, then I would suggest you think about a push pull amp with the 801as you have.


----------



## Zachik

L0rdGwyn said:


> The 6A5 amp was a "no holds barred" type approach, so no expense was spared. The Lundahl transformers/chokes/shields alone were $1200 USD, $275 for the stepped attenuator, $250 for the Yamamoto sockets, $300 for the chassis, probably another $750 or so for all the other miscellaneous parts (switches, caps, resistors, terminal strips, wiring, hardware, jacks/plugs, etc.)...so total without the overhead cost was somewhere around $2700 without the tubes. LOTs of places where costs could have been cut though.


Great info!!! 
I have a follow-up question:
Other than the obvious soldering iron, misc. tools, etc. - assuming you share the schematics of your design, what does one need to build a similar amp?
Does one need to invest in oscilloscope and other very pricey equipment? I do understand it is needed to verify the design, but what about when "copying" an existing design?


----------



## L0rdGwyn (May 3, 2020)

Tjj226 Angel said:


> I would hold off on the 801as until you get your omegas. Figure out if you like listening to headphones or your speakers more.
> 
> If you like the headphones, then proceed with your plan. If you like the speakers, then I would suggest you think about a push pull amp with the 801as you have.



Thanks, I'll consider it.  I can confidently say I will listen to both, not always practical to listen to your two-channel system, in which case having a nice headphone rig is great.  Especially because my significant other works from home and my listening room...is my living room lol.  Similar to the 6A5 amp, an 801A SET build would have a switchable headphone out.



Zachik said:


> Great info!!!
> I have a follow-up question:
> Other than the obvious soldering iron, misc. tools, etc. - assuming you share the schematics of your design, what does one need to build a similar amp?
> Does one need to invest in oscilloscope and other very pricey equipment? I do understand it is needed to verify the design, but what about when "copying" an existing design?



An oscilloscope is not a necessity, but if you have to troubleshoot something, it is very valuable.  Not having test equipment isn't a problem, until there is a problem and you need to track it down.  At a bare minimum, you need a soldering iron, a drill press (you can try using a hand drill, but it will be a tedious mess), a variac, a DMM (two is better).  Obviously you also need hardware, solder, wire, all of the necessary little bits along the way.  Very important to do your homework on proper electrical safety before taking on a tube amp build though, getting zapped on one hand (usually) won't cause any harm, but if you have two hands inside the chassis and one touches a hot wire and the other is grounded, your arms form a nice circuit that runs right through your heart, and you might get a defibrillation you didn't want!

There are probably better first projects out there to take on than copying the 6A5 amp that provide documentation and guidance along the way, e.g. Bottlehead or one of Tubelab's amplifiers.  You can buy a PCB from him, which makes the build much more straightforward.  Another Head-Fier is actually going down that path right now.

http://tubelab.com/designs/tubelab-sse/design/

Tubelab has a dedicated thread on diyAudio as well.


----------



## L0rdGwyn

leftside said:


> At some point @A2029 will build me a SET amp. I do have all of these KT66/6L6/EL37/EL35 after all...
> 
> The 1101 Audio V6 Thunder cost of parts was similar - a little closer to the cost of the parts for the 45 parafeed amp.  The Jupiter and ClarityCap caps in the amp section, the Lundahl transformer in the power section, the meters, the chassis and the Acoustics Dimension 41 step being the most expensive parts.



Tough having tubes burning a hole in your pocket, I know the feeling lol.  I'll look forward to seeing that build done.  Not having to buy OPT for an OTL build is great, can put that money into other aspects of the amplifier.  Those meters are very nice.


----------



## leftside

L0rdGwyn said:


> Tough having tubes burning a hole in your pocket, I know the feeling lol.  I'll look forward to seeing that build done.  Not having to buy OPT for an OTL build is great, can put that money into other aspects of the amplifier.  Those meters are very nice.


It will be a little while. I'm 5th in line at the moment.


----------



## Zachik

leftside said:


> It will be a little while. I'm 5th in line at the moment.


Mishca is a very busy guy!!


----------



## johnjen

My 2¢ on the parafeed caps.
I started with Mundorphs and the added bypass caps.
The results were merely ok, nothing to get excited about.

I then went with a 5.6µf Audyn Reference and added a 0.22µf Myflex KPCU and a 0.01µf Hovland Supercap for the triple stack.
This was a significant improvement, and where I stopped, while knowing the Audyn's could be improved upon but at a much higher price point.

I figure when the 45 amp gets up and running and I've added my secret sauce, THEN I'll push this aspect of the implmentation to see how high is up.
hahahahahahahaahahahahahahahaha

JJ


----------



## L0rdGwyn (May 3, 2020)

johnjen said:


> My 2¢ on the parafeed caps.
> I started with Mundorphs and the added bypass caps.
> The results were merely ok, nothing to get excited about.
> 
> ...



Noted!  We'll see how these Rike Audio caps pan out, I have read goods things.

Picked up a 30-pack HLMP-6000s.  Going to stack four of them on my 6J5 cathode instead of the 680ohm unbypassed resistor that is there now   will have to do it separately from the caps to appreciate the changes, whichever gets here first goes in first.

Edit: if the change is positive, a pair of IR LEDs would be a good choice for the MH4 cathode in the 6A5 amp at 1.2V a piece (Vg 2.4V).

Here is the IR LED I am looking at, will be run at 6mA, Vishay TSML1040, best I could find on Mouser with a Vf of ~1.2V.


----------



## johnjen

LED bias is an attractive option with many beneficial aspects over the resistor/cap method.
The Purp-Amp uses red LED's for the driver tube (6BQ7) for it's bias.
And at one point the 45 prototype amp used UV LED's on the 6J5's

Using LED's tends to really help stabilize that portion of the circuit, which can reduce the variability and number of test points that you have to keep your eyes on. 

JJ


----------



## Xcalibur255

Tjj226 Angel said:


> I would hold off on the 801as until you get your omegas. Figure out if you like listening to headphones or your speakers more.
> 
> If you like the headphones, then proceed with your plan. If you like the speakers, then I would suggest you think about a push pull amp with the 801as you have.


It's also worth mentioning that Omegas are uniquely suited to SET amps.  I drive mine with a push-pull EL84 arrangement right now and they almost sound too fast or too critically damped, but part of that comes down to my tastes too.


----------



## Tjj226 Angel

Xcalibur255 said:


> It's also worth mentioning that Omegas are uniquely suited to SET amps.  I drive mine with a push-pull EL84 arrangement right now and they almost sound too fast or too critically damped, but part of that comes down to my tastes too.



Is it a class A push pull amp or a class AB amp.


----------



## Xcalibur255

Good question.  It's a Luxman and of course they won't specify.  Into 8 ohms it only makes 8 watts per channel, if it were class AB I would think it would do a bit more than that.


----------



## Tjj226 Angel

Xcalibur255 said:


> Good question.  It's a Luxman and of course they won't specify.  Into 8 ohms it only makes 8 watts per channel, if it were class AB I would think it would do a bit more than that.



Oh? Luxman makes pretty good stuff. They actually make the only solid state amplifier I really like.


----------



## Xcalibur255

I like it, but there are huge caveats to that statement.  It has some..... odd behaviors.  But when things are sounding good they are sounding quite good, especially for something whose value was eroded by dealer and distributor markup.

The biggest gatcha was finding out the output stage is manually biased.  I was explicitly told by the dealer, and have read in multiple reviews of the amp, that it was a self-biasing design.  So I nabbed up a nice quad of vintage Sylvania 6BQ5s to change the flavor over the stock JJs and within 5 minutes they were red plating.  There is absolutely no mention of tube biasing anywhere in the manual either.  I'm going to have to call them if I ever want to find out how to re-bias it.

The other issue is the tone of the system shifts dramatically when a certain volume is reached.  Probably between 75-80dB.  It just goes to crap, taking on a very shouty and nasal tone that is unpleasant.  This behavior onsets quite suddenly which makes me strongly suspect a behavior in the amp as opposed to it being a behavior of the speakers.  I've had a little suspicion that my substitution of 5751 tubes in place of the stock 12AX7s might be causing the circuit to behave weirdly..... maybe it messes with the negative feedback circuit perhaps?  But the 5751s sound so much better at the lower volumes that they are still my pick, and the amp has way too much gain so I was trying to tame it a bit.  The entire usable range of the volume knob for me is from 8 o'clock to 8:30.  By the time the knob is at 9 o'clock it's loud and not sounding good anymore.

That said it has a nice sound when it is well warmed up and operating at the volume level it's happiest at.  Since it's a nearfield setup I don't usually need more than 70dB of loudness to be satisfied anyway.  Long term I would like to replace this amp with something custom made though, just because that's so much more fun and satisfying.  I've been living the amp building dream vicariously through Keenan here because my hands can't do this work, but luckily there are super people like Glenn and Mischa who are willing to give their time and creativity to build amps for us too.  

Do you build amps to sell to others Angel?  It seems like you have enough projects going that they wouldn't all be personal builds.  If that's an intrusive question you can leave it be of course.  I'm just curious.


----------



## Tjj226 Angel

Xcalibur255 said:


> I like it, but there are huge caveats to that statement.  It has some..... odd behaviors.  But when things are sounding good they are sounding quite good, especially for something whose value was eroded by dealer and distributor markup.
> 
> The biggest gatcha was finding out the output stage is manually biased.  I was explicitly told by the dealer, and have read in multiple reviews of the amp, that it was a self-biasing design.  So I nabbed up a nice quad of vintage Sylvania 6BQ5s to change the flavor over the stock JJs and within 5 minutes they were red plating.  There is absolutely no mention of tube biasing anywhere in the manual either.  I'm going to have to call them if I ever want to find out how to re-bias it.
> 
> ...



You have a PM coming


----------



## L0rdGwyn (May 7, 2020)

After three relaxing and restorative days at work (not), time to get back to the grind.

I got the parafeed caps!  As usual, every component is bigger than expected, but we've got this.



Drilled some 4mm holes in the top to place the zip-tie mounts I picked up for the caps, old trick I learned from doing Bottlehead mods, best way to wrangle in these big fellas.



I made some other modifications while I was in the amp.  I changed the parallel resistors on the output from 9.1ohm to 8.2ohm.  From my listening tests with the Solen caps, informed by previous experiments with altering the value of these resistors, I felt the amp could benefit from a little more H2 love while also eking out a bit more power.  Also, I changed the connection of the parafeed cap.  Previously, it was connected between the top of the cathode resistor and the ground-side of the OPT.  I moved it to the more conventional spot, between the tube plate and the OPT positive-side.  The same purpose is served, except the full DC potential is taken off the primary of the OPT in the new configuration.  Surely there are no other benefits?  I also just cleaned things up a bit, I like a tidy interior.

So, below is the final circuit, at least until we start playing with LED bias later today.

   

So how does it sound...amazing, much improved from before, and it was already quite good!  I did some A-Bing the other night with alligator clips between the Solen and Rike Audio caps, and there was a marked difference, but I must say, I think the improvement here goes beyond what I heard then.  The soundstage is larger, better air and bass definition, and improved holographic imaging.  I think changing to the 8.2ohm resistors on the output was a very good decision.  It is much more where I expected it to be now, fidelity-wise.

Now here is the interesting finding that I winky-faced about above...

Moving to the more conventional parafeed cap connection essentially eliminated my right channel 60Hz noise problem.  Below is the right channel FFT measurement, 350mV into 300ohms.



As you can see, the 60Hz peak is now at approximately -92dBFS, whereas previously it was at -80-85dBFS, and the noise floor is much improved without numerous power supply harmonics.  The left channel is identical.  Hallelujah!  Eff that noise.  Not that I could hear it, but it makes me happy inside to know that it is gone.

Edit: realized later than I mistakenly posted the L channel, and R channel 60Hz noise remains at -82dBFS 

Here is the FR with the final parafeed capacitance of 6.6uF.



I now have the full confidence to say that this amp kicks ass.  Listening now with the MOV L63 and my staple 45, the shouldered Sylvania.



A DIYer's work is never done.  Next up are experiments with LED bias in both amplifiers, using HLMP-6000s in the 45 parafeed amp and Vishay TSML1040 infrared LEDs in the 6A5 amp.


----------



## Xcalibur255

Congrats on another great build Keenan.  Would love to hear more detailed listening impressions once you spend more time with the amp.


----------



## L0rdGwyn

Xcalibur255 said:


> Congrats on another great build Keenan.  Would love to hear more detailed listening impressions once you spend more time with the amp.



Thanks @Xcalibur255 !  And sure thing, I will post some more detailed impressions here in due time.


----------



## Tjj226 Angel

Try bypassing your audionote bypass capacitors with like a 0.1uf film capacitor and do the same to the last couple PSU capacitors. I feel like you can get that PSU stuff down below 100db and really push the sound stage to an extreme.


----------



## L0rdGwyn (May 7, 2020)

Tjj226 Angel said:


> Try bypassing your audionote bypass capacitors with like a 0.1uf film capacitor and do the same to the last couple PSU capacitors. I feel like you can get that PSU stuff down below 100db and really push the sound stage to an extreme.



I'll give it a shot, I'll put it on the To-Try list.  Oddly enough, the 6A5 amp has pretty gnarly measured PS noise for a few different reasons, inaudible to ear, but the soundstage is HUGE.  Have you found there is a correlation?

Sad news though, looks like I made an error, think that is the left channel I posted above  noise is still there on the right at around -82dBFS.



Oh well, not getting back into it, I can't hear it, I just need to stop measuring stuff LOL.

Taking the HLMP-6000 for a spin on the 6J5 cathode now.


----------



## L0rdGwyn (May 7, 2020)

Well the HLMP-6000 are in, reminds me of Christmas lights.




Quite close to my previous bias point on the 6J5: cathode at 6.4V, plate at ~220V, 8.5mA.

AND...yeah I don't know, my immediate impression was that something was lost...I might have preferred my unbypassed Riken carbon film.

I'll give it some time, could do a true A-B, but I might just go back.  REVERSE! REVERSE!  The more I'm listening, this feels like a clear downgrade.  So many things can influence your brain and how you perceive sound, but I did make a point of listening to all my test tracks right before making the switch, was hoping it would be an obvious improvement - from an engineering standpoint it is - but the ears are telling a different story.  I have come across others saying they prefer an unbypassed resistor, so maybe there is something to it.

I'll sleep on it and listen in the morning, could be my brain, A-B tomorrow.


----------



## Tjj226 Angel

Why are you biasing the 6j5 at 6.4V? You are loading it with a CCS right?

I would knock off one or two of those LEDs and bring the bias down closer to 4v. That should improve the LED bias for starters, but it will also allow your 6J5 CCSs to work a bit harder and block some more PSU noise. 

My eyes are probably lying to me, but it looks like you might even get slightly more gain at 4v too.


----------



## L0rdGwyn (May 7, 2020)

Tjj226 Angel said:


> Why are you biasing the 6j5 at 6.4V? You are loading it with a CCS right?
> 
> I would knock off one or two of those LEDs and bring the bias down closer to 4v. That should improve the LED bias for starters, but it will also allow your 6J5 CCSs to work a bit harder and block some more PSU noise.
> 
> My eyes are probably lying to me, but it looks like you might even get slightly more gain at 4v too.



I can knock off one for a 4.9V bias point, I'll give it a go when I compare it with the unbypassed resistor.  The gain does look slightly higher at 4V, at least on the GEC L63 curves.  Unfortunately the majority of the power supply noise originates as coupling in the mains transformer and reaches the signal output via the filament reg.


----------



## Tjj226 Angel

L0rdGwyn said:


> I can knock off one for a 4.9V bias point, I'll give it a go when I compare it with the unbypassed resistor.  The gain does look slightly higher at 4V, at least on the GEC L63 curves.  Unfortunately the majority of the power supply noise originates as coupling in the mains transformer and reaches the signal output via the filament reg.



Hmmmm. So then each LED would be giving you 1.5 ish volts. Taking a second one off would give you 3.4v. I would try both honestly. I would also highly recommend you try a carbon comp resistor for the bias instead of a carbon film. 

BTW, you seriously gotta try some NOS allen bradley resistors in there instead of the kimwames. Once you hear them, you are going to rebuild both your 45 and 6a5 amp lololol. 

--------

Also my thought about bypassing the capacitors went right out the window when you corrected the FFT. Before hand, it looks like the new caps some how lowered the noise profile a bit. So my theory was to try to improve all the capacitors in the system to see if something strange like ESR was somehow effecting the noise profile. 

That being said, if you found out that the 60hz is due to capacitive coupling in the PSU transformer for the regulators, then I would look into replacing the resistors on the rod coleman PSU board with small chokes. As you know, chokes will give you extra filtering without sucking up any extra DC voltage from the supply. 

Why is chasing after the noise important? Well because that very next harmonic is pretty much right smack dab in the mid range. You might not hear something like that, but it will form something called inter modulation distortion. As a result little fine detail will get confused and lost. If I were in your shoes, I would try to bring that noise down closer to 100db or lower.


----------



## L0rdGwyn (May 8, 2020)

Tjj226 Angel said:


> Hmmmm. So then each LED would be giving you 1.5 ish volts. Taking a second one off would give you 3.4v. I would try both honestly. I would also highly recommend you try a carbon comp resistor for the bias instead of a carbon film.
> 
> BTW, you seriously gotta try some NOS allen bradley resistors in there instead of the kimwames. Once you hear them, you are going to rebuild both your 45 and 6a5 amp lololol.
> 
> ...



I've got a big ol' pack of 100ohm 0.5W ABs that I use for grid stoppers, the Kiwames are being used as grid leak and I've got them on the 45 since they conveniently come in 5W.  Could get away with a 3W cathode resistor there though.  I'll think over pursuing the noise further, short of replacing the mains transformer (which is not happening), taming it beyond -82dB will be a big PITA.  I need a break, so we'll see how I feel about it in a few weeks.  Given the changes I have heard in the amp through various tests, clearly there are other forces that are affecting the sound to a much greater degree than the PS noise, so we'll see, I may just let it go.  Thought about reaching out to Sowter, but I have no idea what kind of "guarantees" they can give about capacitive coupling in their custom transformers.  Plus those guys are about to leave the company LOL.

Those Riken carbon films I am using on the MH4/6J5 cathodes are discontinued as well and are very good, just saying


----------



## johnjen (May 8, 2020)

One of the lessons I have learned about 'fussing with the knobs and levers' is, to give each change sufficient time for it, and the rest of the circuit, to settle back down and into a stable set of operating parameters, _as the amp plays music_, and not just the static operating voltages.
Yes there can be an initial impression (say after the 1st +hr of operation, all the way to perhaps 20hrs), but I have found the SQ will vary thru time for a while.

And between that 20hr mark and 50-100hr mark the SQ can be ALL over the map.

Case in point is the latest mods I just made are blossoming now, bigly, as in I don't have the words to be able to describe the changes and it's still morphing/blossoming even as I type this.

Just some observations.

JJ


----------



## johnjen

L0rdGwyn said:


> snip
> 
> …Also, I changed the connection of the parafeed cap.  Previously, it was connected between the top of the cathode resistor and the ground-side of the OPT.  I moved it to the more conventional spot, between the tube plate and the OPT positive-side.  The same purpose is served, except the full DC potential is taken off the primary of the OPT in the new configuration.  Surely there are no other benefits?  I also just cleaned things up a bit, I like a tidy interior.
> snip


My thought was to NOT have a cap in the 'direct' path from the plate into the OPT, even though it is still in the direct electrical path for that portion of the circuit.
So when I did this, only in reverse, (moved the cap from the plate to the cathode portion of the circuit, I noticed a smoothing and refinement in the SQ overall.

Again my 2¢

JJ


----------



## whirlwind

L0rdGwyn said:


> After three relaxing and restorative days at work (not), time to get back to the grind.
> 
> I got the parafeed caps!  As usual, every component is bigger than expected, but we've got this.
> 
> ...




Job well done Keenan, and very tidy indeed


----------



## L0rdGwyn (May 8, 2020)

I just switched back to the Riken carbon films resistors, I don't have the energy to fuss around with the LEDs, I'm burnt out lol.  In retrospect I shouldn't have rushed into it, I know I didn't give them an fair shake, I will down the road.  With that being said...

The Riken resistors sound SO much better, it isn't even close.  It's a drastic change is presentation and tonality, there was a definite veil and thinness to the sound associated with the LEDs, the bass with the resistors is much more defined, and the soundstage and layering is vastly improved.  I know the LED setup could be optimized, but I would be shocked if I preferred it even with fewer LEDs in the stack and a different bias point.  I will say, I think the sound with the LEDs is less distorted and more "chiseled", but the resistors add a warmth that gives the sound more body, it sounds more natural, less synthetic, and dare I say, less solid state.

We'll give the LEDs another shot some time and optimize it, but I think the resistors are just more to my preference tonally.  Today my priority is listening to some good music and reviewing 801A schematics


----------



## L0rdGwyn

whirlwind said:


> Job well done Keenan, and very tidy indeed



Thanks, Joe.  That pic of Bonamassa is absolutely epic!


----------



## Xcalibur255

This is the kind of stuff that gives me neurosis personally.  The thought that there is one single component somewhere that isn't the right type or right implementation and it's completely holding everything back from sounding the way you ideally want it to.  It's enough to induce paranoia.  

I think amp building reminds me a lot of the human body, in that there is a great interconnectedness where most things have some affect or influence on most other things.  It all works together as a whole and thus a single tweak somewhere has effects in lots of other places.

I think the best way to calm down these thoughts is to just go with your gut.  If you think the resistors sound better than the LEDs, then they do.  I'm sure you can find arguments supporting both with a google search, but in the end it's your amp and your ears.


----------



## L0rdGwyn (May 8, 2020)

Well I suppose that is the nice thing about DIY @Xcalibur255 , or having your amp built by an experienced DIYer, tweaking the build along the way can help work out those kinks.  This amp is far beyond where it was when I was dialing in the parafeed capacitance, just takes the effort of tweaking, measuring, listening until it sounds right.  It can be quite fatiguing though.

Going with my gut has served me well thus far.  Listening after the LED change, I had an immediate sinking feeling and sense of dissatisfaction.  Moving back to the Riken resistors, and my satisfaction returned.  No subtlety whatsoever though, this was what I would call a drastic change in sound, pretty shocking actually.  I think I could see how someone might prefer the LEDs, but it isn't my taste.  Like I said though, I will give it another try and attempt to optimize it in the future, it may prove useful in a different design.

In other news, I am strongly considering abandoning my 6W 841/801A three-stage A2 design in favor of a simpler 3W 801A two-stage A1 design, with consideration of the Mullard ECC32 as the driver.  It would be sad to not use my horde of 841 tubes, but they can go into storage for future use (preamp?).  They are so finicky, I just don't know if I want to deal with it lol.  The ECC32 can drive the 801A in class A1 for 3-3.5W into a 16K load and perhaps make brief excursions into A2 with a mu output CCS load.  Just about everything about the design would be easier and the Omegas are very sensitive.


----------



## Tjj226 Angel

L0rdGwyn said:


> Well I suppose that is the nice thing about DIY @Xcalibur255 , or having your amp built by an experienced DIYer, tweaking the build along the way can help work out those kinks.  This amp is far beyond where it was when I was dialing in the parafeed capacitance, just takes the effort of tweaking, measuring, listening until it sounds right.  It can be quite fatiguing though.
> 
> Going with my gut has served me well thus far.  Listening after the LED change, I had an immediate sinking feeling and sense of dissatisfaction.  Moving back to the Riken resistors, and my satisfaction returned.  No subtlety whatsoever though, this was what I would call a drastic change in sound, pretty shocking actually.  I think I could see how someone might prefer the LEDs, but it isn't my taste.  Like I said though, I will give it another try and attempt to optimize it in the future, it may prove useful in a different design.
> 
> In other news, I am strongly considering abandoning my 6W 841/801A three-stage A2 design in favor of a simpler 3W 801A two-stage A1 design, with consideration of the Mullard ECC32 as the driver.  It would be sad to not use my horde of 841 tubes, but they can go into storage for future use (preamp?).  They are so finicky, I just don't know if I want to deal with it lol.  The ECC32 can drive the 801A in class A1 for 3-3.5W into a 16K load and perhaps make brief excursions into A2 with a mu output CCS load.  Just about everything about the design would be easier and the Omegas are very sensitive.



You could also try and track down a 842 tube. They are super rare, but it is a proper power tube and I think you can drive it with the 801a. 

You could also just judiciously choose a driver tube for the 801a that allows it to go into class A2 a little ways.


----------



## Xcalibur255

I've read in a bunch of places that whenever you can simply a 3-stage design into a 2-stage you should do so.  Fewer parts, fewer headaches.

Maybe a 7119 would drive the 801A okay?


----------



## L0rdGwyn

Tjj226 Angel said:


> You could also just judiciously choose a driver tube for the 801a that allows it to go into class A2 a little ways.



I think this is what I am going to explore, an A1 bias point with the ability to do a wee bit of A2 at the peaks.



Xcalibur255 said:


> I've read in a bunch of places that whenever you can simply a 3-stage design into a 2-stage you should do so.  Fewer parts, fewer headaches.
> 
> Maybe a 7119 would drive the 801A okay?



Fewer headaches is right.  The compromise is output power and fewer shiny thoriated tungsten filaments, but the simplicity and less potential for design traps is worth it I think.  I am committed to a flea-watt life 

The 7119 looks like it would do the job!  Just need a driver that can do a little over 100Vpp with a reasonably low plate resistance.  The 801A in A1 is a pretty easy load.  However, I do have some Mullard ECC32 around, two singles, and I do think they sound as good as advertised.  Based on what I have read of the 801A, I think they should compliment eachother well soundwise.

Just ideas right now anyway, the 7119 is a nice looking tube though, I'll definitely keep it in mind.

I am smitten by the meters on your 45 amp @Xcalibur255 , do you happen to have a link to the part?


----------



## Xcalibur255

They're Simpsons actually.  The model series is called Tru-Vue.

https://www.simpsonelectric.com/products/analog-panel-meters/tru-vue

I found a dealer in New York whose business is mostly instrument calibration for ISO purposes who sold them to me.  Can't remember the exact name of the company anymore.  Finding somebody actually selling Simpson products was one of the more time consuming witch hunts of my 45 build back in 2012/2013 as I recall.  Finding that particular model of power switch was another one.  Here's a fun fact I doubt any of the Glenn owners know:  that switch is a security switch and is tamper-proof.  They're designed to be used in things like elevators and vending machines.  That and the rated current handling ability are why it was so expensive.  I wasn't specifically looking for such a switch, it just turned out that gettting one that could handle the currnent, had the ring edge LED lighting, and had a physical push-lock actuation brought me to that category of product.  In the aviation world there are toggle switches that have their on/off LED embedded in the tip of the toggle.  I wanted to use that as a main power switch _so badly_  but 10 hours of searching on the internet would not yield a seller who had them in stock, something I still find weird to this day.

Actually I have an offer for you if you are interested.  The same time I bought the Tru-Vue meters I also found and bought a different pair of Simpson meters.  These were beautiful NOS meters made in the late 1930's, all metal.  They are DC ammeters with a 0-75 mA range.  They're brand new, true NOS.  I ended up not using them because the vintage look didn't jive with the rest of the amp, but they look absolutely incredible with that Art Deco look.  Glenn has them, and if he is able to find them among his collection of parts I would give them to you for free if you are interested in using them.  I'd really like to see them actually used on an amp rather than just sitting around collecting dust.  I think it's such a shame for a thing to exist, but not have a purpose.

https://reverb.com/item/20758849-vi...-panel-meter-dc-milliamperes-0-200ma-dc-range

They look almost exactly like this if memory serves, only with a 0-75 scale instead of the 0-200 you see in this photo.


----------



## L0rdGwyn

Be still, my beating heart  

Both of those meters are beautiful, you certainly have an eye for the aesthetic.  I do think the meters you ultimately used fit the Landfall design much better than the vintage meters.  I would love to use those deco style meters though!  I do have to wonder if Glenn still has them, given his upcoming move and all...

Either way, I'll think it over.  I would have to alter the aesthetic to some degree to use such a beautiful vintage part, incorporate some other deco type trimmings, otherwise I would just go with the acrylic Simpson meters.  All dependent of course on using fixed bias on the 801A, which isn't necessarily set in stone, a DC coupled design would likely necessitate cathode bias.  But hey, no rush, we'll see where this project ends up.

Thank you for the link!  You have very good taste, @Xcalibur255 .


----------



## Tjj226 Angel

L0rdGwyn said:


> I think this is what I am going to explore, an A1 bias point with the ability to do a wee bit of A2 at the peaks.
> 
> 
> 
> ...




If you ran a 6E5P in triode mode and you ran a wack ton of current through it (50ma) you could get the pace resistance down to under 1K and you would have a gain of 32 or more. They give really nice linear curves, would probably let you reach into class A2 by a bit, and they are 4 bucks a piece : D

A D3a in triode would give you a gain of 70 and would have a plate resistance of 1.2K but it would require less current to run which make or may not be advantageous.


----------



## Xcalibur255

L0rdGwyn said:


> Be still, my beating heart
> 
> Both of those meters are beautiful, you certainly have an eye for the aesthetic.  I do think the meters you ultimately used fit the Landfall design much better than the vintage meters.  I would love to use those deco style meters though!  I do have to wonder if Glenn still has them, given his upcoming move and all...
> 
> ...



Glenn still has them.  I asked recently, that's why they're so fresh in my mind.  It wouldn't have to be for your 801A build, just consider it an open offer if you ever want them for a project.


----------



## L0rdGwyn (May 8, 2020)

Tjj226 Angel said:


> If you ran a 6E5P in triode mode and you ran a wack ton of current through it (50ma) you could get the pace resistance down to under 1K and you would have a gain of 32 or more. They give really nice linear curves, would probably let you reach into class A2 by a bit, and they are 4 bucks a piece : D
> 
> A D3a in triode would give you a gain of 70 and would have a plate resistance of 1.2K but it would require less current to run which make or may not be advantageous.



The D3a is a pretty interesting tube, I was giving it a looksy the other day, I'll keep it on "the list".

Digging deeper into an A1-biased/somewhat A2 capable 801A design today, the compromises are showing themselves.  To direct couple at a 600V plate voltage on the 801A, the B+...yeah, not happening LOL.  Using an interstage traffo, the other option for A2, makes the difference in B+ for the driver and output stages an issue (say, 650V for the 801A and 300V for the driver), dropping that much voltage in the PS...no thanks.  In either case, I would probably have to back off the 600V 801A plate voltage to harness some A2, which is a stupid compromise considering the amp would spend a vast majority of its time in A1.  I am trying to migrate _away_ from the design issues of A2, not work around them, KISS approach.

CCS loading the driver stage gets around the large difference in input and output tube B+ and would work very well - I'd get my 600V on the 801A plate and enough voltage at the top of the CCS to ensure max driver swing with headroom.  I'll keep thinking it over, but I might just commit to A1 only, CCS load the driver stage, cap couple to the 801A and use fixed bias with 600V on the 801A plate.  That way I get to use pretty meters, which is obviously a top priority now 



Xcalibur255 said:


> Glenn still has them.  I asked recently, that's why they're so fresh in my mind.  It wouldn't have to be for your 801A build, just consider it an open offer if you ever want them for a project.



Fantastic!  Very generous of you.  I'll have to find some pictures of the equipment this particular style of meter was used in, maybe it will give me some stylistic ideas.


----------



## L0rdGwyn (May 8, 2020)

The curves in the RCA 801A datasheet do not show the A1 linearity very well since they also include A2, here are the curves from Vinylsavor, doesn't get much better than this.


----------



## Tjj226 Angel

L0rdGwyn said:


> To direct couple at a 600V plate voltage on the 801A, the B+...yeah, not happening LOL.



What if I told you you are getting a PM in a second.


----------



## L0rdGwyn (May 9, 2020)

Before I discovered Omega, I had my eye on a pair of vintage Snell J/II speakers, brought to my attention by @Tjj226 Angel .  These are something of a legendary speaker line, engineered by Peter Snell who died tragically at the age of 38 of a heart attack in 1984.  Peter Qvortrup of Audio Note UK, who was Snell's UK distributor at the time, bought the rights to the speaker designs.  The entire Audio Note line of speakers are an evolution of Snell's original work, with some obvious modifications, and at 10x the price.  Despite being a stand mount, people say these speakers sound like towers and compete with speakers 5x the price.  They are also pretty efficient at 92dB/W, 8ohms nominal, pretty good for low-wattage tube amps  bass is good down to about 50Hz.

Had a few opportunities to purchase some nice pairs on US Audio Mart, but the prices were pretty high and I eventually found Omega and gave up...until the other day.  A very nice pair of Snell J/II appeared on eBay, with restored speaker surrounds (the originals fall apart over time).  I thought I could get them at a good price, and I did!  $300 + shipping.  So now I have the beginnings of a speaker collection (this took some bartering with my girlfriend).

Here are some pics, this is about as good as they get in terms of cosmetic condition (pool table not included).  They'll be here on Wednesday, ahead of the Omegas which should arrive the following week.  It will be a fight to the death!!!  Based on what I know of the two speakers, I am expecting a bit more in the way of soundstage and airiness with the Snells given their wide baffle design, and a more punchy/fun listening experience with the Omegas.  Time will tell, but it would be nice if they complement each other well.  The stands I have for the Omegas will work perfectly for the Snells rotated 90 degrees.


----------



## 2359glenn

Direct


L0rdGwyn said:


> The D3a is a pretty interesting tube, I was giving it a looksy the other day, I'll keep it on "the list".
> 
> Digging deeper into an A1-biased/somewhat A2 capable 801A design today, the compromises are showing themselves.  To direct couple at a 600V plate voltage on the 801A, the B+...yeah, not happening LOL.  Using an interstage traffo, the other option for A2, makes the difference in B+ for the driver and output stages an issue (say, 650V for the 801A and 300V for the driver), dropping that much voltage in the PS...no thanks.  In either case, I would probably have to back off the 600V 801A plate voltage to harness some A2, which is a stupid compromise considering the amp would spend a vast majority of its time in A1.  I am trying to migrate _away_ from the design issues of A2, not work around them, KISS approach.
> 
> ...


----------



## L0rdGwyn

2359glenn said:


> Direct coupling can be done but not for the faint of heart
> My 300B mono blocks are direct coupled. Power supply is 0-425-850 the 300B cathode is at 425 plate at 850 the#210 driver plate is fed from
> 850 through a 25k 25 watt resistor. Bias on the 300B is set by adjusting the cathode resistor of the #210.
> No capacitors at all in the signal path. Craziness but sounds great.
> ...



It's funny you brought it up Glenn, I was gonna ask about your 300B monos just a little while ago, spotted you talking about them with Thomas Mayer on an Audio Asylum thread from 10 years ago lol.  Can you send me a picture when your system is back up and running?

Yeah not taking it lightly, seems there are somewhat "exotic" ways to go about it without using extremely high voltages, by using separate positive and negative power supplies.  Thinking it over, but also wondering if it is too much of a pain.  I want to use my 801As as powers, could drive them well in A1 in a cap coupled amp with an ECC32.  If I CCS load the ECC32 with an unbypassed cathode resistor and fixed bias on the 801A, only caps in the path would be the coupling cap and 801A PS cap.

Decisions decisions...mining the internet for schematics now.  Another idea is doing an all DHT two stage amp with a step up line input transformer instead of a preamp.  Could do 801A driving 801A, or 26 driving 801A, 10Y driving 801A...

Giving this a lot of thought, this amp is gonna be a lot of work, so have to make a good choice.


----------



## 2359glenn

Yes 850 volts seems a little high but not that bad. My SV572-3 amp runs at 1100 on that plate don’t want to get hit with that.
Making 21 watts of SET goodnes per channel.


----------



## L0rdGwyn

2359glenn said:


> Yes 850 volts seems a little high but not that bad. My SV572-3 amp runs at 1100 on that plate don’t want to get hit with that.
> Making 21 watts of SET goodnes per channel.



You gotta put up some pictures of your builds Glenn.  I'm more worried about my dumb a-s-s cats getting zapped than myself.  I'm listening to my REN904 / 6A5G amp right now, even with my 87dB/W NHT speakers and a high volume, sounds fantastic, can't wait for these efficient speakers to get here.  21W of SET, that's a heavyweight right there.


----------



## Tjj226 Angel

2359glenn said:


> Direct



How did you get the power supply capacitor out of the signal path?

I have been racking my brain for years how I might be able to build a SET without any capacitor or regulator influence on the sound. If you have a clever solution and are willing to share it, I would certainly appreciate it : D


----------



## 2359glenn (May 10, 2020)

Tjj226 Angel said:


> How did you get the power supply capacitor out of the signal path?
> 
> I have been racking my brain for years how I might be able to build a SET without any capacitor or regulator influence on the sound. If you have a clever solution and are willing to share it, I would certainly appreciate it : D



No there is a capacitor in the powersupply have two big paper in oil.
I can’t think of how to get rid of the last capacitor in the powersupply other then using battery’s
850 volts of battery’s would be quite a undertaking. Then what is the sound of the battery’s ??
Aa least I got most out of the signal path.


----------



## 2359glenn

L0rdGwyn said:


> You gotta put up some pictures of your builds Glenn.  I'm more worried about my dumb a-s-s cats getting zapped than myself.  I'm listening to my REN904 / 6A5G amp right now, even with my 87dB/W NHT speakers and a high volume, sounds fantastic, can't wait for these efficient speakers to get here.  21W of SET, that's a heavyweight right there.



How will the cats get under the chassis?
I don’t have any of my stuff hooked up yet maybe later today.


L0rdGwyn said:


> You gotta put up some pictures of your builds Glenn.  I'm more worried about my dumb a-s-s cats getting zapped than myself.  I'm listening to my REN904 / 6A5G amp right now, even with my 87dB/W NHT speakers and a high volume, sounds fantastic, can't wait for these efficient speakers to get here.  21W of SET, that's a heavyweight right there.



The problem with the SV572-3 amp is I used Hammond output transformers not the best for SQ.
Really not worth upgrading to lundahl as these tubes are unobtainable now.
Plus living in the south with the heat these tubes get hot. With there grafite plates glowing red.
300B With 8 watts is enough for me and and all direct heated direct coupled sounds great. Got to love the sound of
The #210 with thorated tungsten filament cathode.


----------



## L0rdGwyn (Jun 2, 2020)

2359glenn said:


> How will the cats get under the chassis?
> I don’t have any of my stuff hooked up yet maybe later today.



Cats are very crafty  but seriously, this amp is going to have a separate chassis for the power supply, so I'm a little skiddish about having a high voltage exiting the chassis.  I'll be taking an excess of precautions.



2359glenn said:


> The problem with the SV572-3 amp is I used Hammond output transformers not the best for SQ.
> Really not worth upgrading to lundahl as these tubes are unobtainable now.
> Plus living in the south with the heat these tubes get hot. With there grafite plates glowing red.
> 300B With 8 watts is enough for me and and all direct heated direct coupled sounds great. Got to love the sound of
> The #210 with thorated tungsten filament cathode.



Red hot graphite, that's intense.  There are some SV572-3 on eBay, price isnt too bad.

https://www.ebay.com/itm/Svetlana-F...:nvgAAOSwRE5afPuJ:sc:USPSPriority!44121!US!-1

I am hoping my all thoriated tungsten build sounds good, I will likely prototype it before it goes in a chassis since it is a somewhat complex design, at least for me.


----------



## L0rdGwyn (May 10, 2020)

Just got real dark here with a big thunderstorm rolling in, so that means time for artsy long-exposure tube glow pictures.




I finally closed up the 45 parafeed chassis today after matching the 45 CCS FETs more closely, which was my last to-do.  I know it isn't everyone's cup of tea, but I still love the HD650, most specifically for its ability to be elevated by a good amplifier.  It has become something of a litmus test for me - if the HD650 gets a significant performance bump, the sound of the amp is trending in the right direction.  With "Sergeant Surge", it pairs fantastically.  What I appreciate most about the amp so far is the body/density and midrange detail, the combination of which gives the music that level of realism and life that makes all this tube amplifier craziness worth it.


----------



## Tjj226 Angel

2359glenn said:


> No there is a capacitor in the powersupply have two big paper in oil.
> I can’t think of how to get rid of the last capacitor in the powersupply other then using battery’s
> 850 volts of battery’s would be quite a undertaking. Then what is the sound of the battery’s ??
> Aa least I got most out of the signal path.



Yeup.

I do have a crazy idea to get around the issue, but it's borderline suicide. 

If you use a very high current low voltage tube and match it with a high current high DCR transformer, then you could use that transformer in a parafeed configuration without the parafeed capacitor. 

If you load the parafeed output with a CCS, then you can draw current across the DCR of the transformer to elevate the plate of the tube at some given plate voltage. 

But this is obviously a balancing act.


----------



## Xcalibur255

L0rdGwyn said:


> It's funny you brought it up Glenn, I was gonna ask about your 300B monos just a little while ago, spotted you talking about them with Thomas Mayer on an Audio Asylum thread from 10 years ago lol.  Can you send me a picture when your system is back up and running?
> 
> Yeah not taking it lightly, seems there are somewhat "exotic" ways to go about it without using extremely high voltages, by using separate positive and negative power supplies.  Thinking it over, but also wondering if it is too much of a pain.  I want to use my 801As as powers, could drive them well in A1 in a cap coupled amp with an ECC32.  If I CCS load the ECC32 with an unbypassed cathode resistor and fixed bias on the 801A, only caps in the path would be the coupling cap and 801A PS cap.
> 
> ...



It's a small internet world.  I (re) found that very same thread last week myself.  Remember reading it 7 or 8 years ago too.

A few of these old discussion threads also bring up the 71A in highly reverential terms.  It's apparently not an easy tube to work with but some people put it on a holy grail pedestal for its unique sound.  I remember Glenn telling me a long time ago they were designed to be used in the very first battery powered radios and the filaments are fussy.


----------



## Tjj226 Angel

Xcalibur255 said:


> It's a small internet world.  I (re) found that very same thread last week myself.  Remember reading it 7 or 8 years ago too.
> 
> A few of these old discussion threads also bring up the 71A in highly reverential terms.  It's apparently not an easy tube to work with but some people put it on a holy grail pedestal for its unique sound.  I remember Glenn telling me a long time ago they were designed to be used in the very first battery powered radios and the filaments are fussy.



The 71a is unique and sounds pretty darn good, but the people who put it on a pedestal are being a bit extreme. 

Im getting potentially better results with my 4P1L tube in triode mode and I am getting more power out. But I won't know for sure until I go back to seattle and compare it to the 71a amp I made.


----------



## L0rdGwyn (May 11, 2020)

Tjj226 Angel said:


> The 71a is unique and sounds pretty darn good, but the people who put it on a pedestal are being a bit extreme.
> 
> Im getting potentially better results with my 4P1L tube in triode mode and I am getting more power out. But I won't know for sure until I go back to seattle and compare it to the 71a amp I made.



The 4P1L seems to be the darling tube of diyAudio, anyone who is anyone is using it  it is very affordable.


----------



## Tjj226 Angel

L0rdGwyn said:


> The 4P1L seems to be the darling tube of diyAudio, anyone who is anyone is using it  it is very affordable.



Yeup. And I am getting more parts today for more experiments. 

Xcalibur mentioned something about a one tube amp in a PM and I want to see how far I can push a step up transformer. I got these shure 1:15 step ups and from my half you know what experiments on the scope, it looks like they MIGHT be able to handle some abuse.


----------



## leftside

Tjj226 Angel said:


> Im getting potentially better results with my 4P1L tube in triode mode and I am getting more power out. But I won't know for sure until I go back to seattle and compare it to the 71a amp I made.


I use four 4PL1 as output tubes in my DAC. 

Didn't realize you were just down the road from me. When things return to "normal" it would be nice to say hi when I'm in your fine city again.


----------



## L0rdGwyn

Tjj226 Angel said:


> Xcalibur mentioned something about a one tube amp in a PM and I want to see how far I can push a step up transformer.



Interesting, let us know how it goes, either here or on the DIY'rs Cookbook thread.



Tjj226 Angel said:


> ..and from my half *you know what* experiments on the scope...



Head-Fi censorship strikes again, took me a minute to figure this one out lol.


----------



## Tjj226 Angel

L0rdGwyn said:


> Interesting, let us know how it goes, either here or on the DIY'rs Cookbook thread.
> 
> 
> 
> Head-Fi censorship strikes again, took me a minute to figure this one out lol.



No that was my own attempt from preventing the censor bots from waking up lol.


----------



## L0rdGwyn

Our robot overlords are training us well.  I find hyphens work, when crap just won't cut it and you have to say S-H-I-T.


----------



## johnjen

Tjj226 Angel said:


> The 71a is unique and sounds pretty darn good, but the people who put it on a pedestal are being a bit extreme.
> 
> Im getting potentially better results with my 4P1L tube in triode mode and I am getting more power out. But I won't know for sure until I go back to seattle and compare it to the 71a amp I made.



The Purp-Amp is the 71A amp to which he is referring and after extensive fussing and tweaking and dialing it in, it has surpassed the prototype 45 amps we built/rebuilt in overall SQ.  
But to be fair the prototype 45 amps never reached their full potential, at least consistently and they were the test beds to determine what does and doesn't work well.

And after the 71A amp had reached a sufficient degree of tweak, I then added my secret sauce and tweaked it some more so it currently is operating at an elevated level of performance, beyond what Tjj226 had previously experienced.

And after adding the Arcturus 71A's and the Cossor 6BQ7A tubes, which resulted in a MAJOR transformative upgrade, so much so that they 'made' this amp. 
So it will be interesting to determine the relative merits of these amps, both now and after the 'new kids' get the same 'treatment' and so they all are on equal footings.

But also keep in mind that the 71A can crank out a max of just under 0.8w, which makes it useful for headphones and little else.
And high Ω cans will benefit the most due in part to having an extra degree of dynamic range headroom.
And I figure, besides the differences in their respective sonic characteristics, the 45 tube, with ≈ double to rated wattage, will be able to take advantage of this benefit even more.

JJ


----------



## L0rdGwyn (May 13, 2020)

Got a very nice surprise this morning.  The Snells have arrived.

 

These were made in the last year of the J/II's manufacture, 1989.  Did I mention the guy I bought them from was the original owner?  They have basically been in storage since 2005.  The real walnut veneer is nearly immaculate.



The jumper pins for the binding posts were not included, so I fashioned some from some banana plugs.



Now THIS is a single-ended triode system.  No room treatments and whatnot, very limited on what I am allowed to do in the living room LOL fortunate to be able to make my stereo the centerpiece.  My gigantic 2.5kVA Topaz transformer is hiding in the corner behind a chair, wired for balanced power.  Note the gaping hole in my shelving - that is reserved for a special DAC if I ever put down the soldering iron long enough to finish the purchase.  Gotta get my turntable up and running again - my previous integrated amp was my phono stage - I am very tempted to build one, but will probably need some sort of stopgap.



Listening volume on the Golden Chalice is now at 1-2 o' clock with MH4 as the driver.  With my 87dB/W NHT speakers, it was more like 4-5 o'lock.  The sound is stunning, immense clarity, large soundstage, and very good imaging.  The bass is surprisingly deep.

This is probably the greatest eBay purchase I have ever made, to find a pair of these in such good condition from the original owner in the walnut veneer with the surrounds restored...you just don't get speakers this nice for $300, especially speakers that are 31 years old.  What's really gonna throw me is if I end up liking them better than the Omegas.  Time will tell!  But I expect they will be so different that the comparisons will be irrelevant.


----------



## Tjj226 Angel

Very nice. At some point when I get around to it, I am going to rebuild my snell speakers in a super dense birch plywood and try to mimic a lot of the tweaks that audio note made to the AN-Js. 

You can also open up the snells right now and replace the electrolytic capacitors inside with film capacitors. And you probably also need to replace the fero fluid in the tweeters. 

Also, if you want a fancy dac, then just make the dac end. http://www.audiodesignguide.com/DacEnd/

Its pretty similar to what audio note sells with their dacs. Its an 18 bit r2r dac and its probably one of the best I have heard.


----------



## L0rdGwyn

Tjj226 Angel said:


> Very nice. At some point when I get around to it, I am going to rebuild my snell speakers in a super dense birch plywood and try to mimic a lot of the tweaks that audio note made to the AN-Js.
> 
> You can also open up the snells right now and replace the electrolytic capacitors inside with film capacitors. And you probably also need to replace the fero fluid in the tweeters.
> 
> ...



Will be interesting to see how that works out, I have seen other Audio Note AN-J and AN-E mimics out there, the Audio Note markup is serious.  They are beautiful speakers though, love those blue hemp woofers.

I'll look into the cap replacements, need to ask the original owner if anything was done with the crossovers when the surrounds were replaced.  I recall reading somewhere that you should avoid messing with them unless absolutely necessary as components were very specifically chosen by Snell, could just be one of those weird purist audiophile legends though.  Will probably kick that can down the road, but I'll look into it.

The DAC in question is made by SW1X, a new kid on the block and also of the Audio Note school.  The DAC End looks interesting, I have a small deposit down on the SW1X DAC, had planned for something in his middle performance tier, but if I backed off and put my deposit toward his most entry-level model, I could probably also build the DAC End for the difference in cost...

Something to consider, I do love a good DIY.


----------



## Tjj226 Angel

L0rdGwyn said:


> Will be interesting to see how that works out, I have seen other Audio Note AN-J and AN-E mimics out there, the Audio Note markup is serious.  They are beautiful speakers though, love those blue hemp woofers.
> 
> I'll look into the cap replacements, need to ask the original owner if anything was done with the crossovers when the surrounds were replaced.  I recall reading somewhere that you should avoid messing with them unless absolutely necessary as components were very specifically chosen by Snell, could just be one of those weird purist audiophile legends though.  Will probably kick that can down the road, but I'll look into it.
> 
> ...



That is true up to a point. I went through the same anguish over swapping out the caps. What I did was I measured the capacitance with my meter and then bought the exact value parts. It worked great. Imaging was improved greatly.


----------



## L0rdGwyn

Tjj226 Angel said:


> That is true up to a point. I went through the same anguish over swapping out the caps. What I did was I measured the capacitance with my meter and then bought the exact value parts. It worked great. Imaging was improved greatly.



Nice, I'll do some homework and consider it.  The imaging on these is already pretty mind-blowing in my room.  With the room reinforcement, I can't imagine ever feeling these need a sub, the subjective impression is that they reach lower than 50Hz.  I'll probably take some measurements with a mic at some point.

The grills are also in perfect condition, I am so happy!  Wish I didn't have to work tonight, breaking my heart, could sit here and listen for hours.


----------



## Xcalibur255

I love seeing vintage items find a new home and purpose again.  Happy new speaker day!


----------



## L0rdGwyn

Thanks, @Xcalibur255 , can't wait for the weekend so I can really enjoy them, have three days of 12-hour night shifts ahead of me, yikes.  Saturday afternoon will be an extravaganza of driver tube rolling and re-experiencing my music library.

If anyone is interested in some Peter Snell info, here is a nice article of Stereophile that includes discussion of these speakers and their Audio Note contemporaries:

https://www.stereophile.com/content/listening-115

And a nice video where Andy Singer and Steve Guttenberg sit down and reminisce about their talented friend before his early passing.


----------



## 2359glenn

Tjj226 Angel said:


> Yeup.
> 
> I do have a crazy idea to get around the issue, but it's borderline suicide.
> 
> ...



I am nuts and suppos you are to 
You can make a power supply with chokes shunt regulators and powerful tubes like SV572-10
Rectifier to choke shunt regulator another choke then shunt regulator again.
The shunt regulators will chop off the peaks and energy stored in the chokes will fill in between peks.
This will work but waist allot of power and create plenty of heat.
But if we worried about waisting power we wouldn’t be using tubes in the first place.


----------



## 2359glenn

L0rdGwyn said:


> Will be interesting to see how that works out, I have seen other Audio Note AN-J and AN-E mimics out there, the Audio Note markup is serious.  They are beautiful speakers though, love those blue hemp woofers.
> 
> I'll look into the cap replacements, need to ask the original owner if anything was done with the crossovers when the surrounds were replaced.  I recall reading somewhere that you should avoid messing with them unless absolutely necessary as components were very specifically chosen by Snell, could just be one of those weird purist audiophile legends though.  Will probably kick that can down the road, but I'll look into it.
> 
> ...


----------



## 2359glenn

The Snell’s look great have you listened to them much yet ?
How do they sound?


----------



## Tjj226 Angel

L0rdGwyn said:


> Nice, I'll do some homework and consider it.  The imaging on these is already pretty mind-blowing in my room.  With the room reinforcement, I can't imagine ever feeling these need a sub, the subjective impression is that they reach lower than 50Hz.  I'll probably take some measurements with a mic at some point.
> 
> The grills are also in perfect condition, I am so happy!  Wish I didn't have to work tonight, breaking my heart, could sit here and listen for hours.



Im done messing around with projects today so now I have a moment to sit down lol. 

Im glad to hear that you like these speakers. Many people ask me for recommendations but very few ever take my advice. These are a great value. 

I have searched high and low for something as good if not better for a reasonable price (the snells would have been ~1500 in todays money). It usually takes ~4K to sound better than the snells and the speakers are usually twice the size or the efficiency is down to like 83db. 

If the omegas sound better, it will be VERY interesting. I will have to buy myself some cones and alnico magnets if that happens lolololol : P


----------



## Xcalibur255

I'm also greatly looking forward to a comparison between the Snell and Omega.  Though it won't be a comparison to an Alnico driver Omega since Keenan opted for their high output ferrite magnet based model.


----------



## L0rdGwyn

2359glenn said:


> The Snell’s look great have you listened to them much yet ?
> How do they sound?



I only got about 1.5-2 hours with them today, but I came away really impressed, very nice large soundstage, detail and clarity is excellent, was most surprised by the bass, very full and satisfying, and I put it through the wringer with some of the weird electronic music I enjoy.  They are undoubtedly a big step up from the NHT C3 three-way bookshelves I was using before, and much better for my amp at 92dB/W sensitive.



Tjj226 Angel said:


> Im done messing around with projects today so now I have a moment to sit down lol.
> 
> Im glad to hear that you like these speakers. Many people ask me for recommendations but very few ever take my advice. These are a great value.
> 
> I have searched high and low for something as good if not better for a reasonable price (the snells would have been ~1500 in todays money). It usually takes ~4K to sound better than the snells and the speakers are usually twice the size or the efficiency is down to like 83db.



They are great, first impressions were fantastic.  I have read the same elsewhere too, most who have heard them/owned them say they are as good as speakers multiple times the price, and I see why.  They are also a great lifestyle fit for me - big sound without the footprint of a tower.  They are still pretty chunky lol but fit well in my space.  Glad my other near-purchases of these fell through, this pair was my ideal find.



Tjj226 Angel said:


> If the omegas sound better, it will be VERY interesting. I will have to buy myself some cones and alnico magnets if that happens lolololol : P





Xcalibur255 said:


> I'm also greatly looking forward to a comparison between the Snell and Omega.  Though it won't be a comparison to an Alnico driver Omega since Keenan opted for their high output ferrite magnet based model.



Yes I'm very curious myself, like @Xcalibur255 said, the set I bought are the ferrite-magnet-based drivers, 8 inches with a second driver cut off at 200Hz, the "high output" model.  I wanted something with a beefy low end, in the ideal world I would have gotten the high-output model with the alnico driver, the High Output Super Alnico, but they are one of the most expensive Omega offers at $3.2K and they are pretty darn big, bigger than I could fit I decided.  The dual 8-inch ferrite driver model I bought was Louis' recommendation for me, I might be surprised, but I would expect that it will fall more into the "fun and punchy" category rather than having razor-sharp imaging and enormous staging, just based on what I have read of that particular driver and the cabinet.  I'm hoping the two speakers will complement each other well, and I can swap them out every so often to keep things fresh.  Fortunately, the stands I bought for the Omegas work great for both speakers!  A more apples-to-apples comparison between the Omegas and the J/II's would probably be the regular Super Alnico, but we will see.  It wasn't the plan, but two pairs of nice speakers that can be run on a flea-watt SET is a good problem to have.


----------



## L0rdGwyn (May 18, 2020)

Going over some old correspondence with a French tube seller I know, I came across an interesting tube he had recommended to me...the R120.

Much like the 6A5G, this is a ~3.5W class A indirectly heated power triode.  In fact, it is almost a drop-in replacement (!!!), the pinout is the same and the operating point is nearly identical, with the exception of -35V on the grid rather than -45V (250V / 60mA), same plate load, slightly higer mu of 5.4.

To use this tube in the 6A5 amp, I would simply need to drop my B+ 10-15V (easy-peasy, just use the 5Z3 instead of the U18/20), change the cathode resistor to ~580ohms, and center tap the heaters.

Here is the datasheet: https://frank.pocnet.net/sheets/084/r/R120.pdf

And curves:



They are pretty uncommon, but I am going to get a pair and give them a try, my French tube seller might be able to help me out.  Depending on how they sound, its possible the 6A5 amp might become the R120 amp, certainly would fit my esoteric European tube theme   we will see.

In other news, I took a gamble on some physically pristine but untested globe 45s from eBay, they will arrive today, we'll see if lady luck is on my side!

Edit: my seller has R120 in stock, so this operation is a go


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## L0rdGwyn (May 18, 2020)

Check this out @Xcalibur255 .

So like I said, I took a gamble on a pair of globe 45, engraved base Philco branded.  The eBayer who had them was not a tube seller, and as such, they were untested.  He told me he found them very carefully stored in a leather bag.  In terms of physical condition, they are as good as it gets for tubes this old: clean, rust-free tube pins, full intact getter flash, clear glass, clean bases without cracks.  I figured the odds of one of the two tubes working was pretty high, so if I got them at half market value for a pair (which for a pair is anywhere from $250-350), it would be worth the gamble even if only one worked.  I won the auction for $130 and asked the seller to pack them carefully, he took that took an extreme LOL I have never gotten tubes packed this well - a box full of packing material, then another box, more packing material, then bubble mailers, then each tube wrapped in bubble wrap.  Well done sir.

So I popped them in my Jackson 648-R AND...on one tube, only half the filament lit up and it was sort of pulsing.  Turned it off right away - I didn't need to use the function on the tester to know this was a short, and given the structure of these tubes, likely filament to grid, confirmed with a DMM.  That's okay!  We can work with that, I was more worried the filaments would be broken.

I have fixed shorts in valuable tubes in the past, it is a very scientific and calculated process...you WHACK the tube until the short is broken  ever so lovingly, of course.  What is there to lose?  Its already non-functional.

So I proceded to WHACK this tube against my hand, checking the short every 4-5 whacks.  First in one direction without change, then the other.  AND ITS FIXED!!!  Eff that short, it is gone.

Threw the tubes back in my Jackson tester, and they both test over 100% emission   105-110% more specifically, well matched too.

So lady luck was on my side after all, with the assistance of brute force.

 

Listening now, big time upgrade in terms of airiness, soundstage, holography, and realism.  These tubes live up to their reputation.


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## Xcalibur255

I had a feeling this would work out for you.  Congrats!  These tubes are "it" in my opinion in the NOS 45 world.

You were meant to get these tubes.  How many buyers would have junked that one tube as bad I wonder?  I bet most would.  Instead they are now a usable pair and making beautiful music.

You will not want to go back to the ST Sylvanias once you get used to these.  After another 24 hours to wake up they'll sound even better.  It's the palpable realism that's so amazing.  When you go back to the ST tubes the timbres don't seem as authentic, as though there is a bit of a plastic sheen to everything.  I think the lack of a mica making any contact with the glass is part of it, it is one less route for vibration to transfer.


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## L0rdGwyn

@Xcalibur255 they are incredible!  Immediately on first listen, I had a "woah" moment, going back to the ST 45s would be hard, not that they sound bad, but its all relative.

I have had a pretty good success rate with the ol' whack-a-tube method.  If you can visualize the internal short, its even easier as you can deduce which direction to shift the internals and if it is improving, just need a fraction of a millimeter to get the tube working again.  I was able to fix a Tung-Sol 5998 this way recently.

Realism is the word, they give a very satisfying body and "thickness" to the sound.  I'm actually just listening to the HD650 right now rather than the Auteur, they sound like a TOTL headphone with this amp, really enjoying it


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## Tjj226 Angel

L0rdGwyn said:


> @Xcalibur255 they are incredible!  Immediately on first listen, I had a "woah" moment, going back to the ST 45s would be hard, not that they sound bad, but its all relative.
> 
> I have had a pretty good success rate with the ol' whack-a-tube method.  If you can visualize the internal short, its even easier as you can deduce which direction to shift the internals and if it is improving, just need a fraction of a millimeter to get the tube working again.  I was able to fix a Tung-Sol 5998 this way recently.
> 
> Realism is the word, they give a very satisfying body and "thickness" to the sound.  I'm actually just listening to the HD650 right now rather than the Auteur, they sound like a TOTL headphone with this amp, really enjoying it



The old HD600 headphones work REALLY well for tube amps like this. The bass comes out a bit more, and they aren't as veiled as the HD650s. 

I haven't tried the massdrop 580X, but from what I am told they are a carbon copy of the HD600s


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## L0rdGwyn

I've owned them all at some point or another, the whole family is a great pairing with tubes.  I prefer the HD650, I find it a bit more refined than the HD600, not veiled when paired with a good amplifier but YMMV, they are more similar than different.  I picked up a HD58X when it was first released just to see how it compared, its good for the price but it isn't a HD600/650.  Also tried the HD660S when it came out, was pretty high on it at first and it is a nice headphone, but over time I felt the HD650 still bested it and it doesn't scale with upstream gear like the HD650 does.  You really can't go wrong with any of them though!  The fact that they are still so popular says something about the design and its staying power.


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## johnjen

L0rdGwyn said:


> Check this out @Xcalibur255 snip
> So I popped them in my Jackson 648-R AND...on one tube, only half the filament lit up and it was sort of pulsing.  Turned it off right away - I didn't need to use the function on the tester to know this was a short, and given the structure of these tubes, likely filament to grid, confirmed with a DMM.  That's okay!  We can work with that, I was more worried the filaments would be broken.
> 
> I have fixed shorts in valuable tubes in the past, it is a very scientific and calculated process...you WHACK the tube until the short is broken  ever so lovingly, of course.  What is there to lose?  Its already non-functional.
> ...


And so as it is written 'When in need, though shalt whack thine tubes with deliberacy and intent.'
Fore sooth if the proper supplication is made unto the deity of THE TUBE, and it did not causeth the collection plate to overload and glow red, thou shalt find you're good to go…

Words to live and die by for our beloved tubular collection.
hahahahahahaha

JJ


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## L0rdGwyn

Couldn't have said it better @johnjen LOL scripture to live by.

As I was staying up all night in preparation for night shift, took a nice little long-exposure of the Visseaux 6A5G which have a very pretty glow 




Despite the high cost of these rare tubes, operation R120 is underway.  After some testing, I am also planning someting of an overhaul of the 6A5 amp - I will be making some changes to the power supply.  If the R120 tubes pan out and I decide to keep them, I will feed their heaters from a single center-tapped filament winding - the 6A5 tubes each have their own.  With another winding freed up, I would add in the DC voltage regulators that I had originally planned to use in this amp, not necessarily for any benefit from the DC, but for another reason - some of these 4V tubes take 0.65A on the heaters rather than 1A, so having a voltage regulator is advantageous such that these tubes are not being run over voltage.  Many of these 4V 0.65A tubes are quite rare and it will help me sleep soundly at night.  For example, the Mullard NR52 takes 0.65A, it might be the best driver tube I have laid ears on, but I am wary to use as the amp is built right now.


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## Xcalibur255

Out of curiosity how do you come to find out about tubes like the R120 in the first place?  Just tube talk with sellers you have come to know?


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## L0rdGwyn

@Xcalibur255 yep exactly, I have a French tube seller I have bought some old 4V tubes from in the past (those very old metallized Marconi MH4).  We have discussed tubes over email, he is hip to some very obscure models, many of French manufacture, PTT-series postal tubes, and he has many of them in large quantities.  For example, another interesting tube that I have considered experimenting with is the French-made PTT100.  It is another MH4/REN904 equivalent, but they use the 7-pin postal tube base, like below.

I know it seems crazy to use such old tubes, but they are the best I have heard.


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## 2359glenn

L0rdGwyn said:


> @Xcalibur255 yep exactly, I have a French tube seller I have bought some old 4V tubes from in the past (those very old metallized Marconi MH4).  We have discussed tubes over email, he is hip to some very obscure models, many of French manufacture, PTT-series postal tubes, and he has many of them in large quantities.  For example, another interesting tube that I have considered experimenting with is the French-made PTT100.  It is another MH4/REN904 equivalent, but they use the 7-pin postal tube base, like below.
> 
> I know it seems crazy to use such old tubes, but they are the best I have heard.



With tubes the older the better they sound.
But they were originally in circuits that sounded like crap like telephone amplifiers.
Still sounded better then a modern cell phone that you are lucky to understand anything.


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## Zachik

2359glenn said:


> *With tubes the older the better* they sound.


I always knew tubes and red wine have a lot in common...


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## johnjen (May 19, 2020)

2359glenn said:


> With tubes the older the better they sound.
> But they were originally in circuits that sounded like crap like telephone amplifiers.
> Still sounded better then a modern cell phone that you are lucky to understand anything.


Back in the day they codified the SQ of the telephone service using the plosives and consonants of speech as the 'markers' of Intelligibility.

This practice has been abandoned with modern day telephony.
Such that when I ask for a cell phone that has excellent speech SQ the 'sales associate' has no idea what I'm asking for, let alone what it means.
And it always surprises me when I tell someone that it is, 1st and foremost, a cellPHONE, and this fact seems to surprise them.

However the Kyocera Dura XV cell phone I now have actually does have really good SQ which was a pleasant surprise indeed.

I have adopted this idea of Intelligibility and use it as a descriptor in my lexicon of terms to denote what is 'better' in terms of SQ, as mods and changes are made to my system.
I use it specifically as a way of being able to determine the ease of understanding the lyrics in songs.
It has always amazed me how garbled some singers voices can be in some songs, and by some bands, etc.
And it always is a delight when I instantly 'know' exactly what is being sung and can hear the inflection and intonation as it adds much more insight into the song itself.

JJ


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## 2359glenn

johnjen said:


> Back in the day they codified the SQ of the telephone service using the plosives and consonants of speech as the 'markers' of Intelligibility.
> 
> This practice has been abandoned with modern day telephony.
> Such that when I ask for a cell phone that has excellent speech SQ the 'sales associate' has no idea what I'm asking for, let alone what it means.
> ...



Modern cell phones are mini computers and do everything but work as a phone.  People just put up with this and pay $1000 for it.
I had a analog phone in the past that sounded good and drove through 4 states with my lady on the phone and it never dropped the call.
I guess all that matters now is texting nobody can communicate with each other anymore.


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## Xcalibur255

Some phones and carriers have an option to send your voice over the network as streaming audio data instead of using the legacy voice only telephony.  It will chew through your data but the quality is much higher.  Since nobody actually does voice calls anymore it's not pushed or talked about.


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## leftside

2359glenn said:


> I guess all that matters now is texting nobody can communicate with each other anymore.


Not quite true:
https://www.theverge.com/2020/4/23/...s-pandemic-security-privacy-concerns-response
https://www.theverge.com/2020/4/29/21241972/microsoft-teams-75-million-daily-active-users-stats

If this pandemic was a few years ago, I would have been let go from my current contract for sure. Microsoft Teams has been indispensable for us remote/wfh folks to be able to communicate with our co-workers. I've also had regular chats with family in Europe over Facebook messenger, WhatsApp and Zoom. We communicate more than ever because of modern technology.

But hey, on a related subject I have a tube amp for one of my mobile device 
https://www.audiophonics.fr/en/acce...tube-tubes-for-dx150-dx200-dx220-p-13983.html


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## chrisdrop

leftside said:


> Not quite true:
> https://www.theverge.com/2020/4/23/...s-pandemic-security-privacy-concerns-response
> https://www.theverge.com/2020/4/29/21241972/microsoft-teams-75-million-daily-active-users-stats
> 
> ...


I have felt like a Z-grade film star; on video all day, talking virtual-face-to-face with everyone needed. "Chat" like those apps, has been important, but the video has been essential. Our company is accustomed to having everyone physically together in one location. I can't believe how easily we have acclimatised - due in large part to those sorts of tools.


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## leftside

chrisdrop said:


> I have felt like a Z-grade film star; on video all day, talking virtual-face-to-face with everyone needed. "Chat" like those apps, has been important, but the video has been essential. Our company is accustomed to having everyone physically together in one location. I can't believe how easily we have acclimatised - due in large part to those sorts of tools.


Same. This will change the world forever. I imagine many business owners and CEO's now asking "do we really need so many expensive offices now..." Office conversions to condos will be picking up soon. Sorry @L0rdGwyn for getting so OT


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## L0rdGwyn

leftside said:


> Same. This will change the world forever. I imagine many business owners and CEO's now asking "do we really need so many expensive offices now..." Office conversions to condos will be picking up soon. Sorry @L0rdGwyn for getting so OT



Doesn't bother me in the slightest!  Feel free to discuss whatever you please.


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## 2359glenn

leftside said:


> Not quite true:
> https://www.theverge.com/2020/4/23/...s-pandemic-security-privacy-concerns-response
> https://www.theverge.com/2020/4/29/21241972/microsoft-teams-75-million-daily-active-users-stats
> 
> ...


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## 2359glenn

Those apps are great.
I am just saying that the SQ of cell phones are horrible.  Was just talking to my new boss and he sounded like he was under water.
Had a analog cell phone and it sounded pretty good. And drove through 4 states with my lady on the phone and it never dropped the call.
They should try working on the actual phone part and make it work right.  It does everything else GPS internet good just the phone
part sucks.


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## Zachik

2359glenn said:


> They should try working on the actual phone part and make it work right. It does everything else GPS internet good just the phone
> part sucks.


Glenn - most people (especially younger generation) do not use their phone to make any phone calls anymore... 
For them, it is a digital communicator by means of text, e-mail, Instagram, etc.


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## Tjj226 Angel

Zachik said:


> Glenn - most people (especially younger generation) do not use their phone to make any phone calls anymore...
> For them, it is a digital communicator by means of text, e-mail, Instagram, etc.



Nah. Im sort of in their weird middle ground in terms of age, but I do sadly count as a millennial. 

Most younger kids, people around my age, and older adults I know still make calls over texting. It just depends on the situation. For instance if I am meeting someone for a job somewhere, they might text me to let me know they are 10 minutes out. However if they get a flat tire along the way and they need help, they will call. 

I would say that texting is the new form of sticky notes more than the new form of calling someone.


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## L0rdGwyn

I have been quietly enjoying the spoils of my work, but that does not mean DIY shenanigans have ceased...I have three projects in the works.

1) Plans are taking shape on my 841/801A A2 build, to the point that I am ordering parts for a prototype.  LTSpice can only go so far - all is well and good in the models, time to test in the real world.  It will be something of a drawn out process, different than my approach in the previous two amps, but it will be necessary to work out the kinks as the design is more complex.  Very much looking forward to getting these tubes in an amplifier, they will double as a night light.




2) Still waiting for my Omega speakers - I suspect a delay as Louis told me he moved into a new workshop - no rush on my part.  Once they are in my stereo, I will be doing surgery on the Snells to re-cap, re-resistor, and re-ferrofluid.  Want to do it all in one go, just need some speakers to listen to while I tear them apart.

3) And lastly, the 6A5 revamp - R120 tubes are on the way.  When I have them, I will be making some changes to the power supply in addition to adding voltage regulators on the driver tube heaters.  All the power supply parts are on hand and the regulators are assembled.  If the changes are positive, I will be moving the amp into a new chassis with improved ventilation and layout for the additional regulator boards, correcting some oversights from my first build with more knowledge and experience under my belt.

So that's my non-update update.  I'll post again once I have something I am physically working on.


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## chrisdrop

L0rdGwyn said:


> they will double as a night light.


Perhaps as a spin-off; "_vintage artisanal lighting_". I am sure there is a market. The "quality of the light spectrum cast" is the new "quality of the tube sound".... Custom lampshades... LOL


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## L0rdGwyn (May 26, 2020)

chrisdrop said:


> Perhaps as a spin-off; "_vintage artisanal lighting_". I am sure there is a market. The "quality of the light spectrum cast" is the new "quality of the tube sound".... Custom lampshades... LOL



People on Etsy would eat it up!  As long as they can find use for a 9W light bulb lol.  That was my girlfriend's reaction...

Me: "Look at the beautiful filament glow from these rare vintage tubes!  Aren't they pretty?"
Her: "They look like light bulbs."

-_-


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## johnjen

Me: well they are and so much more.  It's a good thing too because now I can listen to music and light up the night all at the same time!!!

JJ   hahahahahahahaha


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## L0rdGwyn (Jun 2, 2020)

Starting to make some real moves on this next amp.  All of the parts for the prototype are ordered (I think...hard to keep track).  Have a massive shipment coming from Mouser tomorrow.  Usually the little passive components represent a somewhat negligible expense compared to the other parts - not the case this time around.  Lots of sand assistance in this build, so lots passive components.

For the prototype, I got these cool socket boards from Hificollective.



And everything will be built on the 2'x2' piece of plywood below, doing both channels.



This amp will have four different power supplies, Antek transformers, although I haven't ruled out switching to something else for the big guy in the middle for space saving measures since I am only using one of the two secondary windings.  The 841 B+ (via voltage doubler), 801A B+, and source follower V+ will be Maida regulated; the source follower V- / bias supply will be shunt regulated.

Rod Coleman regulators for both input and output tubes, filament bias for the 841, fixed bias for the 801A.  I was originally looking at getting some cool meters for the 801A fixed bias, but I am starting to consider using test points and current sense resistors instead for a few different reasons, one of them being space.  That is TBD, but will be the approach for the prototype.

The circuit I am using for the 801A bias as well as the constant current sink for the source follower will need to be prototyped - I have some solderable prototyping PCBs coming to build them out.  Once everything is up and running, I will put together the gerber files and order the finalized PCBs.

Yet another thing coming to me - a giant 12" x 7" x 3" heat sink.  Has something like a 0.25 C/W thermal resistance with zero airflow, going to throw all of the regulators on that bad boy for the prototype, will use it for future prototyping as well.

By the time I get this all laid out and the power supply and input stages working appropriately, the output transformers should be here.

So yeah, this is the big project right now, a monster of a 801A A2 SET amplifier, ~6-7W output into 8ohms.


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## L0rdGwyn (Jun 3, 2020)

Some more bits and pieces going into this amplifier.

Here is one of the completed Maida regulators - well sort of, the reg and FET chips are not actually soldered on yet, that will be done when attached to heat sinks.  This particular variation of the Maida is the work of @A2029 , so mad props to him, vastly simplifies the power supply, and it still isn't very simple.  This baby eats ripple for breakast and has very low output impedance across the audio band.  They will be used on the 841, source follower, and 801A supplies.



Here are the Hammond filament transformers for the input and output tubes.  Yup, one per tube, feeding the Rod Coleman regulators.  Again, a monster.



Panel mount fuse holders and fuse, protecting the 801A from thermal runaway in the event of a bias supply failure.  This is the most expensive fuse I have ever bought, but it met my spec...not even made of gold and audiophile crystals...these will go on the amplifier chassis back panel, beneath the output transformers.



Prototyping board - my source follower circuit, constant current sink, and bias circuitry will live on these before proper PCBs are made.



And the oh-so-important power switch.  I sort of have a thing for toggle switches, decided to go for it this time around.  This particular one is pretty and has very satisfying tactile feedback.  It is also waterproof, so if my living room floods and my amp is submerged, at least my switch will be spared.



More stuff on the way believe it or not.  I didn't intend it this way, but probably the best thing about this build is that it will keep me busy for quite a while.  I need to be working on something to distract me from...stuff, so I welcome the complexity this time around.


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## Xcalibur255

NKK switches are awesome.


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## L0rdGwyn

Xcalibur255 said:


> NKK switches are awesome.



Loving it so far.  Need to stop switching it back and forth, I'll wear it out before it even makes it in an amp


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## johnjen

I like using big honk'n toggle switches with their satisfying Ca-Lick, so I go for the 2 pole 20 amp rated ones with the larger baton.
A Manly Mans switch…    hahahahahahahahaha

JJ


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## Zachik

Xcalibur255 said:


> NKK switches are awesome.


I agree!
I have built a (my first audio DIY) switch box for connecting 2 amps to 1 set of speakers, and used NKK switch. VERY satisfying switch to use!!


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## L0rdGwyn (Jun 5, 2020)

Results from an evening of board stuffing: three Maida regulators, dual channel bias shunt regulator, four raw DC boards for Coleman regulators, and the four Coleman regulators.

#Regulated



Working this weekend, so I will start laying out the prototype early next week.  By then my giant heat sink will be here and the real fun will begin


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## L0rdGwyn

YES.



To be continued.


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## L0rdGwyn (Jun 8, 2020)

Made some progress today on the beast.

Heat sink is all prepped and ready for regulators, holes are drilled for three Maidas and four Rod Colemans.




Mounted the Hammond filament transformers and raw DC supplies, should be able to get the filament supply up and running tomorrow, then testing of the B+ supplies will begin.



I should build all amps on plywood!  Low stress, no worries about precise measurements, comes together quickly too


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## L0rdGwyn (Jun 9, 2020)

Made some solid progress today.



Got all of the regulator boards completed and mounted to the Heat Sink.  Maidas are all ready to go for when I get to work on the B+/bias supplies.



Tube sockets were all mounted, wired up the filament supply and got the filament voltages dialed in.  This was my goal for the day, happy I got to see the tube glow 

 

Next up will be the B+, source follower, and bias supplies.  Will get started on them this weekend, going to be a lot of work.  Just gonna take it one power supply at a time...


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## L0rdGwyn (Jun 12, 2020)

The eagle has landed, the Omega Super 8 High-Output Monitors have arrived.  The veneer is figured walnut.



They were waiting for me when I got home from work last night, of course I threw them in the stereo and gave them a quick listen despite being completely exhausted, more listening this morning and throughout the day.  Omegas are notorious for their long break-in period (or brain-in?), so I will defer giving major impressions until later, maybe past the 100-hour mark.  I will say this right off the bat - the midrange detail and vocal nuance is impressive.  They are also much more sensitive to on-axis positioning than my Snells.  From my short positional experiments, I've found they need a pretty generous toe-in.  Their sound is also more sensitive to changing tube configurations than the Snells.



From a DIY standpoint, I can now do Snell surgery.  Will have to decide where this project falls in terms of priority with the 841/801A amplifier prototype underway, but I plan to re-cap and re-resistor the crossovers and replace the tweeter ferrofluid.


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## Xcalibur255

Happy new speaker day.  

You'll want to experiment with toe-in a lot.  They're sensitive to that, and also to their distance from the back wall.  Louis seemed to have incorporated the rear port tuning into the voicing of his speakers because they change character a lot depending upon their proximity to walls.  Your position relative to them (being on, inside, or outside the imaginary "triangle" you form with their position) will affect the treble response dramatically.  The high end rolls off with increasing angle.  The aperture of the whizzer cone is actually a pretty good guide.  If you can't see the inner edge of the inside of the whizzer you're too close to them or don't have them toed enough.  I find the halfway point between that and havintg them pointed directly at you to be a nice sweet spot for treble balance, but my Alnicos might be voiced a bit differently too.


----------



## L0rdGwyn

Thanks, @Xcalibur255 .  Yes, definitely will be a period of experimentation, I began working on the toe-in and wall distance last night.  Unfortunately, due to my listening space being lived-in, I am pretty limited to how far into the room I can place the speakers, we will see.  I had expected a directly on-axis toe-in to be too aggressive, surprisingly I didn't find that to be the case, but right now I have them slightly less that direct, just outside the ears.  I'm sure that will be adjusted with break-in/brain-in.  I may also rewire the OPT of my SET - currently wired for an 8ohm secondary, whereas the Super 8 HO have a 4-6ohm nominal impedance, so damping factor is not optimal.  In the long run, my plan is to pair the 801A amplifier with the Snells and the 6A5(?) amplifier with the Omegas, due to the differences in sensitivity and power output of the amplifiers.

I got another DIY surprise today, the first of the R120 pairs has arrived.



This puts the overhaul of my 6A5 amp on the table too, three simultaneous projects.  Whoof!  I am taking it easy today and listening to the Omegas, will decide which path to go down tomorrow.


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## Xcalibur255

The top end will wake up in a few hours and you might find yourself dialing your toe-in back a bit in response to that.  I personally like to sit quite close to speakers and be "inside the triangle" so I toe-in more aggressively to compensate for that and maintain imaging stability.  This listening style makes the whole front stereo image a bit less precise but in exchange it expands field width and depth and increases immersion which I find a worthwhile trade-off.  I think what I do actually makes for a less accurate presentation, but it's what I like.  When you position yourself in the 'traditional' way (equilateral triangle between you and them), and do a half toe the stereo image is holographic and you identify instrument positions down to the millimeter in space.  Since I do nearfield listening anyway I trade a bit of that off to get more of a "there's sound everywhere" feeling instead.

In some ways the speakers can feel a bit fussy about placement, but they are also pretty forgiving in some ways too and will accommodate more than once preference if you tinker around with it.


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## L0rdGwyn

@Xcalibur255 I'll keep your notes in mind as the sound evolves!  I do have to wonder if the same rules apply between the alnico and ferrite drivers.  Considering they are from the same designer, I would think so but can't be certain, I will keep you posted.  At the time of my purchase, I was looking for something of a "well-rounded" speaker that could do well with most genres, I have a pretty eclectic taste in music.  Had I known I was going to land a pair of very nice Snell Js, which I believe fall into that category, I probably would have gone with the Super Alnico Monitor from Omega, I just wasn't sure at the time that it was going to be able to do everything I wanted.  Well hindsight is 20/20, something to keep in mind for the future 

Plans for my day changed quite dramatically and I got some time back.  I am going to do some critical listening with the 6A5G, then make the minor modifications to use the R120, see if I can make a decision on whether or not I will be moving forward with them.


----------



## L0rdGwyn

Here is the R120 in situ.  Fivre 5Z3 rectifier to drop the B+ to a happy place relative to the U18/20.

 

Yes, these are very nice sounding tubes.  Sound is a little more intimate than the 6A5G, better bass definition, a little more forward presentation overall.  The 6A5G tends toward smooth and laid back to my ears.  Could be less distortion, will have to take some measurements to be sure.  The additional gain of the R120 is noticeable on the volume knob, these tubes give me the flexibility to make some other modifications to the amp, so it is something of a multi-faceted decision.  I think this operation is a go, but going to give it some more listening time.


----------



## L0rdGwyn (Jun 12, 2020)

Been listening to the Omegas with the R120 for a few hours now.  Can't say how much is burn-in and how much is brain-in, but the sound has changed, for the better.

To be honest, on first listen last night, the speakers sounded pretty congested and the imaging was not great, really felt like I was listening to two point sources.  Granted listening after a long work shift never yields good results for me and I had Omegas really do need some break-in, so I slept on it.

Throughout the day, the imaging has drastically improved, much more cohesive and larger staging.  The treble has "woken up", as @Xcalibur255 suggested, I towed the speakers out a bit more as a result.  The bass seems to have tightened up and deepened a bit as well, but oddly enough the Snells seems to reach lower from memory and are more "full" sounding, which was unexpected, we will see how it continues to progress.

As far as strengths, right now they seem lie in the upper midrange and treble.  It just "pops", very realistic, nuanced, the human voice is extremely textured and lifelike.  Anything with female vocals or a male falsetto is electrifying.

The presentation of these speakers is very different than the Snells, will take some time to put it into words, looking forward to a more direct A-B comparison with the Snells once I'm done messing around with the crossovers.  A different flavor for sure, and I am really enjoy it


----------



## L0rdGwyn (Jun 13, 2020)

An interesting note about the R120.

It's pretty obvious from the external construction of the tube that it is a variant of the European-made ELXX series, most similar in construction to the Philips EL39 from what I have seen, it is a pentode converted to triode.  Taking a look inside, we can see there is a screen grid in place that is connected to the plate.  While there is no suppressor grid, the rods for g3 are intact and connected internally to the cathode.



So the R120 is a former pentode internally strapped to a triode, but without a suppressor grid.  What an oddity!

I am going to put together the first of the regulated supplies for the 841/801A amplifier today, most likely the source follower V+ at 150V.


----------



## L0rdGwyn (Jun 14, 2020)

It's a bit of a mess, but two of the four power supplies are up and running.



This dual secondary 150V Antek transformer feeds both the source follower V+ and source follower V- / bias supplies.

Just to recap, this amplifier will be using a transistor buffer stage between the input and output tubes.  Think of it as the transistor version of a cathode follower - unity gain, low distortion, and low output impedance, supplying enough current to drive the grid of the 801A +40V while drawing ~10mA at maximum positive swing.

The first of the two supplies is the 150V input to the source follower drain.  It will supply the grid current drawn by the 801A on positive grid excursions and is Maida regulated.  With the way I have parted the Maida, it is adjustable from 140-160V with a 1-turn pot on the board, perfect.

The second supply is an adaptation of Pete Millett's shunt-regulated bias supply.  I had to build his circuit in LTSpice and repart it for my purposes as his was original built for 300B bias with little-to-no current draw.  It is adjustable from -150-160V, it will feed the CCS providing bias current on the source of the source follower, as well as feeding the fixed bias supply of the 801A.



Everything looks good with the dummies, both supplies dialed in to +/- 150V.  Tomorrow I will get started on the big fellas, the 450V B+ supply for the 801A and the 650V B+ supply for the 841.  Watch your fingers and toes


----------



## L0rdGwyn

841 B+ supply is up, 650V Maida regulated voltage doubler.  This supply will have a low current draw from the 841 CCS load, around 18mA, using a voltage doubler allowed me to use a relatively small 250V toroid.

Nothing went up in smoke went brought up on variac, which tells me parts were well-selected 



Gonna take a break then throw together the 801A B+ supply.  If I have time today, will see if I can get my B+ time delay circuits working, I picked up some kits from K&K Audio.  They can't take the high voltage of the 801A / 841 B+, but because these are dedicated B+ supplies, they should work on the mains transformer primaries without issue.  The boards will be powered by the 6.3VAC windings of the 150V source follower mains transformer, which will not have a time delay.  The 30 second time delay in addition to the built-in soft start of the Maida regulators will give the filaments more than enough time to come up to voltage before B+ is applied.


----------



## Tjj226 Angel

L0rdGwyn said:


> 841 B+ supply is up, 650V Maida regulated voltage doubler.  This supply will have a low current draw from the 841 CCS load, around 18mA, using a voltage doubler allowed me to use a relatively small 250V toroid.
> 
> Nothing went up in smoke went brought up on variac, which tells me parts were well-selected
> 
> ...



You are a braver man than I am : D


----------



## gimmeheadroom

L0rdGwyn said:


> The eagle has landed, the Omega Super 8 High-Output Monitors have arrived.  The veneer is figured walnut.
> 
> 
> 
> ...



Beautiful wood.I would have thought it was maple though.


----------



## L0rdGwyn (Jun 14, 2020)

801A B+ supply is done now, adjustable to 450V on the Maida reg.  Change of plans on the 801A mains transformer - the toroid was just too big, swapped it out for an LL1650.



Put together one of the time delay boards as well, it works perfectly.  After ~25 seconds, the relay closes and the 120VAC hits the mains transformer.  The Maida reg then ramps up its voltage over another 10-15 seconds to ~450, more than enough time for the 841 / 801A filaments to heat.  The 801A supply will drop another 25-30V across the output transformer primary, giving me my 420V 40mA bias point.



Just have to put the other time delay kit in place and the power supply is done.  I love it when everything goes according to plan 

With the B+ supplies ready to go, next step will be putting together the source follower circuit and bias wiring on one of the proto-boards.  Have to work the next few days, so it will be a project for next weekend most likely.  This is coming together much more quickly than I expected, still another 2-3 weeks out from getting the output transformers, good thing I have other projects to work on.


----------



## L0rdGwyn (Jun 14, 2020)

Put together the second time delay board and tested it with the 650V 841 B+ supply.  All is working as intended.  It isn't very interesting to watch, but I took a one minute video of the startup characteristics of the supply.  The first "click" is me turning on the variac, set to 120VAC.  The second "click" at the 30 second mark is the time delay relay closing, you can then see the soft start of the Maida until it reaches 650V.



For those who are unfamiliar with why this delay/soft start is being implemented, it is to avoid something called cathode stripping.  At a high level, the idea is to avoid applying the B+ voltage to the plates before the DHT filaments are fully heated to avoid damage to the filament coating.  Whether or not it is actually a thing, or if a time delay/soft start mechanism is necessary below 1kV plate voltages, is debatable.  Nevertheless, the tubes going in this amplifier are rare and the filaments are delicate, so I'd rather be on the safe side and treat my tubes nicely.

With all of the alligator clips removed, here is the current state of the prototype after this weekend's work.




That's all until later this week!


----------



## 2359glenn

Nice job
Those tubes with thorated tungsten filaments heat up in a couple of seconds.  That is why I used A #10 to drive the 300B in
the direct coupled amps.  I might switch to 841s now for more gain.


----------



## L0rdGwyn (Jun 15, 2020)

2359glenn said:


> Nice job
> Those tubes with thorated tungsten filaments heat up in a couple of seconds.  That is why I used A #10 to drive the 300B in
> the direct coupled amps.  I might switch to 841s now for more gain.



Thanks, Glenn.  The filament regulators I am using have a soft start built in too, but the thoriated tungsten filaments still heat up pretty quickly, less than ten seconds.

This article talks about the 841 and has some curve tracings: http://vinylsavor.blogspot.com/2012/09/tube-of-month-841.html

For the set that I made, I paid around $70 a tube, maybe can do better if you keep an eye out.  Also, plate resistance is high, tricky to use without HF rolloff, it is around 25K.  Works in this amp with the source follower, also can take the mu-output of a CCS load for lower output impedance.


----------



## 2359glenn

L0rdGwyn said:


> Thanks, Glenn.  The filament regulators I am using have a soft start built in too, but the thoriated tungsten filaments still heat up pretty quickly, less than ten seconds.
> 
> This article talks about the 841 and has some curve tracings: http://vinylsavor.blogspot.com/2012/09/tube-of-month-841.html
> 
> For the set that I made, I paid around $70 a tube, maybe can do better if you keep an eye out.  Also, plate resistance is high, so they are difficult to use without HF rolloff, around 25K.  Works in this amp due to the source follower buffer, also can take the mu-output of a CCS load if needed for lower output impedance.



I seen that I was looking.
Guess a set of globes almost unobtainable my GE 10s are globes.


----------



## L0rdGwyn

2359glenn said:


> I seen that I was looking.
> Guess a set of globes almost unobtainable my GE 10s are globes.



There are some beautiful NIB GE VT-51 globes on eBay right now, but they are $325 a pair.  If I get this prototype up and running without issue and it sounds good, I will consider buying a pair.  I bought some of my shouldered Hytron 841 from the same seller, so I will see if he will give me a discount


----------



## L0rdGwyn (Jun 17, 2020)

Got off work early last night, so I put together the source follower / bias supply board.

The board has three things on it, the source follower, the constant current sink on the source of the source follower, and the bias circuit, both channels on one board.  I set the source follower constant current sink to 15mA.  The bias is set by a low current CCS and the voltage is generated across a resistor to ground.  Works as intended, although I will have to play with the resistor in series with the trimmer to adjust the range.  I did notice the voltage seems to be sensitive to environmental changes, will have to do some more testing and play with components over the next few days to be certain it will be consistent, could be a plywood amplifier problem.  Final design will use low temperature coefficient components.


----------



## L0rdGwyn

So, some updates.

On the issue in my last post on the fluctuation in the bias voltage, it is resolved.  Discovered that one of my two DMMs is faulty, so it will need to be replaced.  There was also a wiring issue, which was also fixed, so I am now getting consistent bias voltages with the isolated source follower board, 15mA CCS bias current.  I am expecting the 801A grid voltage to be around -20 to -24V in the final build.  The voltage on the source follower source (and thus, the 801A grid) will be about 4V lower than the gate, so shooting for rougly -18 to -20V on the gate.



Later today I might wire up the input stage and take some measurements, we will see, I've opened up another can of worms...

Started working on fixing up the Snells.  After shaving roughly 5 years off of my life disassembling the tweeter, I discovered...there is no ferrofluid  the voice coil is completely clean.  Must have been added to the J/III, which came after Snell's passing.  Either way, it saves me the trouble of taking apart the other one.



Next, I took apart the crossover.  It uses predominantly bipolar electrolytics, mostly in parallel, there is a single film cap.  The film is right on target, most of the electrolytics are around 15-20% over their rated spec.  Very well could be within spec (if they are rated for 20% tolerance), but we can do better.  Will have to decide philosophically which direction to go here, whether than means using the same type of capacitors in the crossover (i.e. bipolar electrolytics), or using as many film caps as I can instead.  I've been in correspondence with an expert on Snell crossovers, so I will be bouncing some ideas off of him.  He also recommended replacing the wirewound resistors with MOX.  Obviously the inductors will stay.

Right now I am most likely going to using film caps of the same rating with tighter tolerances.  Here some pictures with it removed from the first speaker.  Also took off as much of the old glue as I could.

 

Not sure if I will get to the other one today or work on my amp, taking the crossover out was a real PITA!


----------



## L0rdGwyn

Well, I checked the other tweeter just to be sure and...it has ferrofluid LOL.  I originally went down this path because one tweeter (the one without ferrofluid) was more lively and had more energetic treble than the other (with ferrofluid).  Seems I now know why!  If it was intentional, it is an odd way to tune a speaker, the difference is very audible and gives the impression of a channel imbalance.  Perhaps it was a mistake at the factory?  No way to know for sure.  While this particular model was engineered by Snell before he died, it was manufactured after his death (1989), maybe QA took a hit.



Here is the other crossover completely intact.  Some of the glue failed and a few of the components were hanging inside the cabinet.


----------



## A2029

L0rdGwyn said:


> Well, I checked the other tweeter just to be sure and...it has ferrofluid LOL.  I originally went down this path because one tweeter (the one without ferrofluid) was more lively and had more energetic treble than the other (with ferrofluid).  Seems I now know why!  If it was intentional, it is an odd way to tune a speaker, the difference is very audible and gives the impression of a channel imbalance.  Perhaps it was a mistake at the factory?  No way to know for sure.  While this particular model was engineered by Snell before he died, it was manufactured after his death (1989), maybe QA took a hit.
> 
> 
> 
> Here is the other crossover completely intact.  Some of the glue failed and a few of the components were hanging inside the cabinet.



I wonder if you could purchase ferrofluid and apply to that speaker yourself? Snell may have used a specialized proprietary formula however, so you may have to go searching through a patent database if they had a patent on it.


----------



## L0rdGwyn (Jun 18, 2020)

A2029 said:


> I wonder if you could purchase ferrofluid and apply to that speaker yourself? Snell may have used a specialized proprietary formula however, so you may have to go searching through a patent database if they had a patent on it.



Yes, I have ferrofluid on hand ready to go, would just need to clean the one tweeter out with blotting paper and replace it.  But the rabbit hole goes deeper, I have been discussing it with my Snell expert...the tweeters have different model numbers.  Either the speakers were tuned by ear at the factory and it was determined two different tweeter models were necesary to match the "master" speaker and they now have drifted apart over time, or at some point one of the tweeters broke and was replaced incorrectly, although they are original according to the first owner.

So I have two options - 1) put ferrofluid in both tweeters and see if they sound equivalent by ear 2) contact Atomic Hifi (seller of OEM Snell parts) and get a new pair of matched tweeters.  In either case, the crossover cannot be accurate, so I can throw the whole "maintaining the Snell tuning" out the window.


----------



## Tjj226 Angel

L0rdGwyn said:


> Well, I checked the other tweeter just to be sure and...it has ferrofluid LOL.  I originally went down this path because one tweeter (the one without ferrofluid) was more lively and had more energetic treble than the other (with ferrofluid).  Seems I now know why!  If it was intentional, it is an odd way to tune a speaker, the difference is very audible and gives the impression of a channel imbalance.  Perhaps it was a mistake at the factory?  No way to know for sure.  While this particular model was engineered by Snell before he died, it was manufactured after his death (1989), maybe QA took a hit.
> 
> 
> 
> Here is the other crossover completely intact.  Some of the glue failed and a few of the components were hanging inside the cabinet.





L0rdGwyn said:


> Well, I checked the other tweeter just to be sure and...it has ferrofluid LOL.  I originally went down this path because one tweeter (the one without ferrofluid) was more lively and had more energetic treble than the other (with ferrofluid).  Seems I now know why!  If it was intentional, it is an odd way to tune a speaker, the difference is very audible and gives the impression of a channel imbalance.  Perhaps it was a mistake at the factory?  No way to know for sure.  While this particular model was engineered by Snell before he died, it was manufactured after his death (1989), maybe QA took a hit.
> 
> 
> 
> Here is the other crossover completely intact.  Some of the glue failed and a few of the components were hanging inside the cabinet.




The way I understand it, you are saying both tweeters have a physical channel for ferro fluid, but one tweeter doesn't have fluid and the other does. 

If so, just go ahead and clean each tweeter out and put new ferrofluid in it. To be clear my tweeters did already have some ferrofluid in them. But ferro fluid does dry out over time, so I had a layer of wet-ish fluid on top with a layer of crud underneath. You might have the same issue on one tweeter, but the other tweeter might have dried out all together. 

Once I got everything squeaky clean and put new fluid in it, the highs just opened up and got a lot more clear. 

--------

If you are saying that the tweeters are physically different, then the tweeters got swapped at one point or another. It's HIGHLY unlikely that the factory made that error since they will often times use up their old supply of tweeters before they even touch their new stock. 

Tweeters do eventually die, and I have seen some people replace the original broken tweeters with all kinds of crap. It could be why the guy wanted to sell these speakers to begin with.


----------



## Tjj226 Angel

L0rdGwyn said:


> Yes, I have ferrofluid on hand ready to go, would just need to clean the one tweeter out with blotting paper and replace it.  But the rabbit hole goes deeper, I have been discussing it with my Snell expert...the tweeters have different model numbers.  Either the speakers were tuned by ear at the factory and it was determined two different tweeter models were necesary to match the "master" speaker and they now have drifted apart over time, or at some point one of the tweeters broke and was replaced incorrectly, although they are original according to the first owner.
> 
> So I have two options - 1) put ferrofluid in both tweeters and see if they sound equivalent by ear 2) contact Atomic Hifi (seller of OEM Snell parts) and get a new pair of matched tweeters.  In either case, the crossover cannot be accurate, so I can throw the whole "maintaining the Snell tuning" out the window.



Yeah, so then one tweeter died at some point and some dingus repair shop put in the wrong tweeter. 

I can pretty much promise that they didn't put in two different tweeters at the factory. Snell did do some weird schiit to their speakers, but not that weird.


----------



## leftside

Good job you are happy to experiment/play with these speakers. I'd have sent them back.


----------



## L0rdGwyn (Jun 18, 2020)

Tjj226 Angel said:


> Yeah, so then one tweeter died at some point and some dingus repair shop put in the wrong tweeter.
> 
> I can pretty much promise that they didn't put in two different tweeters at the factory. Snell did do some weird schiit to their speakers, but not that weird.



This might be the case, but there is one weird wrinkle.  The tweeter has "EII 2" written on the back, then crossed out and replaced with "JII Kit 2" in the same red factory marker used on the crossovers, the other tweeter says "JII Kit 1" in the same handwriting, so perhaps it was original and subbed at the factory.  Either way, I am replacing them with a matched pair.  My guy has a set for purchase, otherwise I'll go through Atomic Hifi.



leftside said:


> Good job you are happy to experiment/play with these speakers. I'd have sent them back.



It is a labor of love  every annoying project yields new knowledge and experience.  I already know this is the gateway to building my own speakers.


----------



## Tjj226 Angel

L0rdGwyn said:


> This might be the case, but there is one weird wrinkle.  The tweeter has "EII 2" written on the back, then crossed out and replaced with "JII Kit 2" in the same red factory marker used on the crossovers, the other tweeter says "JII Kit 1" in the same handwriting, so perhaps it was original and subbed at the factory.  Either way, I am replacing them with a matched pair.  My guy has a set for purchase, otherwise I'll go through Atomic Hifi.
> 
> 
> 
> It is a labor of love  every annoying project yields new knowledge and experience.  I already know this is the gateway to building my own speakers.



Wow. gg. 

I have never heard about a snell "kit" speaker either. I know audio note has kit speakers. Maybe they got the idea from snell???

BTW. If you have the cash, you can also order the audio note tweeters and woofers and make your own AN-J speaker. It's probably not the right time to be going down that rabbit hole, but if you ever have an issue with your drivers later on down the road, keep that in mind.


----------



## L0rdGwyn (Jun 19, 2020)

Tjj226 Angel said:


> BTW. If you have the cash, you can also order the audio note tweeters and woofers and make your own AN-J speaker. It's probably not the right time to be going down that rabbit hole, but if you ever have an issue with your drivers later on down the road, keep that in mind.



I put together the crossover in LTSpice to get a rough idea of the crossover point (2kHz), but the inductor values are not marked.  A quick Google search and I found a schematic of the AN-J crossover, yup they are still using the exact same one.  Very slightly different component values, funny the longevity of this design.

I actually emailed Peter Q asking about using his drivers in a Snell cabinet last week out of curiosity, but he recommended sticking with the originals and keeping the original crossover since they are not an exact 1:1 replacement.  Well keeping the original crossover parts is out the window now considering this tweeter condundrum, the only differences between the two crossover components are in the RC of the tweeter filter, the woofer components are identical.  I will likely choose an average and make both crossovers the same since I will be using new tweeters.  No difference between the two crossovers is going to be as audible as using two different models of tweeter.  I'll likely be using Clarity Cap ESA caps in the overhaul, pretty cheap, relatively small for films, and have all the values I will need.


----------



## L0rdGwyn

Just got off the phone with Atomic Hifi, placed an order with them.  I doubt what I will be receiving are the original J/II tweeters, likely an OEM equivalent or the J/III tweeter.  The original J and the J/II used a specific doping material on the diaphragm which dries and cracks over time, it is pretty uncommon for the doping to be in good condition like it is on my mismatched pair of tweeters, although one is starting to crack in one spot, usually they are falling apart.  Regardless of which model, they will be matched pair.  These speakers are moving away from an "original" label and moving more toward "modded" territory anyway considering what I am doing with the crossovers, but I think they are going to sound fantastic.

Speaking of crossovers, I prepped the boards for their new parts.  The original caulk was removed with a plastic razor, I will apply new caulk when putting them back together to seal the cabinets.  I reheated some of the old glue with a heat gun to afix one of the inductors that had fallen off, which worked great.  Possible I will have to completely change the layout to accomodate the Clarity Caps, we will see.


 

Here is one of the cabinets with everything taken out and caulk removed, I also polished up the veneer.  I absolutely love walnut and the grain on these speakers is just my taste, another reason I am going to such great lengths to restore them, these don't come up often in walnut.



So the stage is set, parts are ordered, should have these back together and rocking by the first week of July, very exciting!

With that taken care of, I am back at a fork in the road.  I am in a holding pattern with the 841/801A amp, just about everything is done except for the signal wiring, also waiting for some parts, I had to make some adjustments on the Coleman regs to accomodate filament bias on the 841.  I might do some minor work on it in the mean time, but much of the major work is complete.

Then there is project three...the 6A5 amp revamp.  I guess this is where I will focus some time, but I am still hung up on whether to switch to R120 as the outputs, the sound is quite different than the 6A5 and I haven't yet decided if it is more to my liking or not.  So I think I will have a cup of coffee, enjoy some music on the Omegas and do some more comparison of R120 vs. 6A5G.


----------



## Tjj226 Angel

L0rdGwyn said:


> Just got off the phone with Atomic Hifi, placed an order with them.  I doubt what I will be receiving are the original J/II tweeters, likely an OEM equivalent or the J/III tweeter.  The original J and the J/II used a specific doping material on the diaphragm which dries and cracks over time, it is pretty uncommon for the doping to be in good condition like it is on my mismatched pair of tweeters, although one is starting to crack in one spot, usually they are falling apart.  Regardless of which model, they will be matched pair.  These speakers are moving away from an "original" label and moving more toward "modded" territory anyway considering what I am doing with the crossovers, but I think they are going to sound fantastic.
> 
> Speaking of crossovers, I prepped the boards for their new parts.  The original caulk was removed with a plastic razor, I will apply new caulk when putting them back together to seal the cabinets.  I reheated some of the old glue with a heat gun to afix one of the inductors that had fallen off, which worked great.  Possible I will have to completely change the layout to accomodate the Clarity Caps, we will see.
> 
> ...




Does all this effort mean that you feel like there is a potential for the snells to be better than the omegas?

I ask because my next step in DIY speaker design was to mimic the omega design of having two similar drivers in the same box. If the snells might end up being better, then Im not even going to go down that path.


----------



## L0rdGwyn (Jun 19, 2020)

Tjj226 Angel said:


> Does all this effort mean that you feel like there is a potential for the snells to be better than the omegas?
> 
> I ask because my next step in DIY speaker design was to mimic the omega design of having two similar drivers in the same box. If the snells might end up being better, then Im not even going to go down that path.



It's hard to say, I think the Omegas are still burning in and they are very different sounding speakers, different strengths.  The Omegas are mid-forward, very textured and detailed midrange, clean airy treble, that seems to be their area of strength.  The Snells (the way I received them) are relatively more neutralish in that area.  What has been the big shocker is the bass of the Snells is more impactful and full than the Omegas *so far!  *I can _feel_ the bass of the Snells more, they seem to move more air with sharper transients on the low end.  Not sure what your experience has been with them, but to my ears they reach lower than their ~50Hz rating, just may take better advantage of room reinforcement.  It has proven to be true that the Omegas do need burn in as the sound has changed quite a bit, I am probably at 20-25 hours in and the midrange and treble is fantastic, but I expected the dual 8-inch driver setup to knock me over with its bass (as much as a stand mount can), which hasn't really happened.  They have bass, but it falls off rather rapidly.  Is this a weakness of full-range designs?  I'm not sure.  Yet another confounding variable is that my 6A5G OPT are not wired ideally for the Omegas, they are wired for an 8ohm load whereas nominal of the Super 8 HO is 4-6ohm, which is very likely affecting low end performance.

So, that is a long way of saying, I don't know yet.


----------



## Tjj226 Angel

L0rdGwyn said:


> It's hard to say, I think the Omegas are still burning in and they are very different sounding speakers, different strengths.  The Omegas are mid-forward, very textured and detailed midrange, clean airy treble, that seems to be their area of strength.  The Snells (the way I received them) are relatively more neutralish in that area.  What has been the big shocker is the bass of the Snells is more impactful and full than the Omegas *so far!  *I can _feel_ the bass of the Snells more, they seem to move more air with sharper transients on the low end.  Not sure what your experience has been with them, but to my ears they reach lower than their ~50Hz rating, just may take better advantage of room reinforcement.  It has proven to be true that the Omegas do need burn in as the sound has changed quite a bit, I am probably at 20-25 hours in and the midrange and treble is fantastic, but I expected the dual 8-inch driver setup to knock me over with its bass (as much as a stand mount can), which hasn't really happened.  They have bass, but it falls off rather rapidly.  Is this a weakness of full-range designs?  I'm not sure.  Yet another confounding variable is that my 6A5G OPT are not wired ideally for the Omegas, they are wired for an 8ohm load whereas nominal of the Super 8 HO is 4-6ohm, which is very likely affecting low end performance.
> 
> So, that is a long way of saying, I don't know yet.



The bass/mid bass is why I love the snells. I was sort of hoping the omegas would actually give you more bass than the snells out of the box. 

Sadly based on what you said, I doubt the omegas will catch up through break in which means I need a different approach. 

Full range speakers very rarely have impressive bass (by my standards). And when they do, they are usually huge. Although the omegas are not a full range design no matter what they say in their marketing info. It is very much a 2 way speaker but with a little twist.


----------



## L0rdGwyn

Tjj226 Angel said:


> The bass/mid bass is why I love the snells. I was sort of hoping the omegas would actually give you more bass than the snells out of the box.
> 
> Sadly based on what you said, I doubt the omegas will catch up through break in which means I need a different approach.
> 
> Full range speakers very rarely have impressive bass (by my standards). And when they do, they are usually huge. Although the omegas are not a full range design no matter what they say in their marketing info. It is very much a 2 way speaker but with a little twist.



Agreed, the bass on the Snells is really satisfying, probably my favorite thing about them too.  Unlikely the Omegas catch them in that area, but they do have other strengths that make them very enjoyable to listen to, really digging them with jazz right now.  Funny how I expected the Snells to be somewhat bass-light and the Omegas to be bass cannons, boy was I wrong  the Omegas were ordered before I landed the Snells, so they were chosen as an "all-rounder" type of speaker.  Had I heard the Snells first and knew what they brought to the table, perhaps I would have gone with what I would consider one of Louis' more specialist type of designs, like the Super Alnico Monitor.  I am still very intrigued by that speaker.


----------



## Tjj226 Angel

L0rdGwyn said:


> Agreed, the bass on the Snells is really satisfying, probably my favorite thing about them too.  Unlikely the Omegas catch them in that area, but they do have other strengths that make them very enjoyable to listen to, really digging them with jazz right now.  Funny how I expected the Snells to be somewhat bass-light and the Omegas to be bass cannons, boy was I wrong  the Omegas were ordered before I landed the Snells, so they were chosen as an "all-rounder" type of speaker.  Had I heard the Snells first and knew what they brought to the table, perhaps I would have gone with what I would consider one of Louis' more specialist type of designs, like the Super Alnico Monitor.  I am still very intrigued by that speaker.



I have spent years trying to find an "upgrade" to the snells that didn't cost $$$$$. 

The tannoys have the upgraded sound quality I am after, but at a somewhat silly price. The frustration being that 90% of the cost is the cabinet. I know the drivers themselves don't actually cost that much. IDK why we have to pay thousands for living room art when all we really want is the sound. 

High end magnepans are pretty good too AND are reasonably priced, but our poor little tube amps would choke and burn up trying to play them. Apogee speakers are in the same boat. 

Klipsch corner horns are also really nice, but too expensive and too particular. If you don't have a room with two corners facing your listening chair, you are pretty much SOL. 

The ultimate god tier speaker on this planet is a western electric 753C. 

I just want a mini version of that. Why can't we have nice things?


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## L0rdGwyn (Jun 19, 2020)

@Tjj226 Angel I was really smitten by the Tannoy Eaton earlier this year, sound comes first but boy, I am a sucker for good looking audio gear lol I love those Tannoy cabinets!  They are almost _too_ nice, I mean let's face it, your other furniture is going to look like garbage sitting next to them.  Thinking of the Turnberry in particular.  Maybe once I transform my home into a Victorian mansion they will blend in.  A well-maintained pair of Snells is probably one of the best deals out there for low-power amplifiers.  For what Louis at Omega offers - in terms of customization, product line, veneers, build quality - the prices are very reasonable, but I can't say they are an upgrade over the Snells (at least my pair), they are in the same arena in terms of performance in my opinion.  Maybe that changes with different speakers in his line.


----------



## L0rdGwyn (Jun 21, 2020)

While waiting for crossover components, speaker drivers, filament reg parts, and output transformers, I have been working on the "revamp" of my 6A5 amp.

I love the sound of this amplifier, but there are a few things I would have done differently, so I've decided to streamline things.

First off, the power tubes.  The battle of the 3W IDHT titans, R120 vs. 6A5G.  I spent a few days evaluating these tubes, with speakers and headphones, and my ears told me the same thing in both cases, that I prefer the sound of the 6A5G.  The R120 has an interesting sound.  Not quite as airy as the 6A5G, more intimate staging, emphasized low end with dynamic impactful bass, the upper midrange is somewhat forward, very nice detailed treble, it has a very fast and dynamic sound, an attention grabber.  No doubt this sound has its place and another person might prefer it, but the airy, inviting, relaxed sound of the 6A5G is more to my taste.  It has its fair share of dynamism and low-end kick, but just the right amount, the R120 borders on aggressive.



So, the 6A5G stays, the R120 goes into the tube archives until I dig it up again.  This has consequences for the amplifier revamp.  Way back, I had wanted to use voltage regulators on the 4V drivers of this amplifier, the reason being that some of the tubes in my collection have 1A heaters, others 0.65A, being able to freely swap back and forth between the two was appealing, and it still is.  But alas, the 6A5G has one major drawback - due to its internal center-tap, each tube requires its own dedicated heater winding.
With two windings for the power tubes and one for the tube rectifier, that leaves one for the drivers, which will not work with my voltage regs.  Changing to R120 would have allowed me to parallel the heaters and use an artificial center-tap, freeing up a second winding for my driver tube voltage regs.  But the 6A5G is sticking around, so the regulators are not making it in the final build (I have weighed other options - dedicated rectifier transformer, nixing the rectifier outright, etc. - just letting it go).  No big deal, a nice to have, not a need to have.

Next issue to address is thermals.  Plan is to redo the chassis, add additional ventilation, redistribute/remove specific voltage dropping resistors, and change chassis-mount resistors to air-cooled through-hole.  I am also leaning toward removing the combination socket and committing to 4V recitifers, giving up the 5Z3.  I've found swapping rectifiers in this amplifier has subtle-to-undetectable effects on the sound.  The best is the U18/20, I can't see myself using anything else at this point, FW4-500 as backup.  I've changed the passive supply from a CLCLC to a CLCLCRC, the CCS loaded drivers have been moved from the first tap to the last, a more conventional layout, with plenty of headroom to drive the 6A5G to clipping and cover the droput voltage of the CCS.

Finally, I changed my grounding scheme from a conventional star ground to a distributed star ground.  This is a hybrid between star and bus, in which there are local star nodes that are daisy-chained from input to output.  There is a single chassis connection on the power supply cap where the two channels converge.  This made no measurable difference in power supply noise, but it is more neat, and call me crazy but I feel like it improved the clarity.  Hard to say, I'll just go with it  



So the current amp is now something of a test bed for the finalized design that will go in a new box.  These changes aren't essential, but the amp will run cooler and I feel better about the supply layout and grounding scheme.  If you feel better, the amp sounds better 

Three night shifts, then maybe I will be rebuilding the Snells, really looking forward to it.


----------



## 2359glenn

L0rdGwyn said:


> While waiting for crossover components, speaker drivers, filament reg parts, and output transformers, I have been working on the "revamp" of my 6A5 amp.
> 
> I love the sound of this amplifier, but there are a few things I would have done differently, so I've decided to streamline things.
> 
> ...



What is the problem with using one 4 volt regulator feeding both 4 volt drivers.  They are indirect heated so no problem.
Just use a 5 amp voltage regulator no problem.


----------



## L0rdGwyn

2359glenn said:


> What is the problem with using one 4 volt regulator feeding both 4 volt drivers.  They are indirect heated so no problem.
> Just use a 5 amp voltage regulator no problem.



I slept on it and I am reconsidering.  The regs I have on hand are from Pete Millett, and based on his spec, I would be running the heater windings slightly over current.  But Lundahl is conservative with their ratings, so let's go for it.  I ran it by PM too, he agreed there shouldn't be an issue.

Regulator is up and running.  This setup will allow me to safely and confidently use one of my favorite tubes, the Mullard NR52.  This tube has some of the deepest bass I have heard from a driver.



Another one that gets to hang out now is the Valvo A4110.



So looks like the DC heaters will make it in the revamped build after all.


----------



## 2359glenn

Or build your own 4 volt regulator not that hard just need a heat sink on it.


----------



## Xcalibur255

I probably didn't do a good enough job describing or maybe didn't emphasize the point well enough in our discussions on the Omegas, but there is a certain lightness to their bass response that never really goes away.  The frequency extension is there but the sense of weight and slam has a subtlety or delicateness to it that makes the bass feel less tangible.  I chalk it up to the damping properties of the driver.  It's probably not possible for a full range driver to have the amazing transient response the Omegas have which enables their nuanced mid/high rendering abilities and also provide any kind of visceral slam in the bass department.  The laws of physics probably make this a little bit of an either/or proposition in a single driver.  

Do play around with placement some more though Keenan.  The Omegas are kind of weird when it comes to placement and respond differently than most speakers to room boundaries.  I have mine very far out in the room out of necessity and it results in a very unique sound that I quite like for most things (but not everything).  The bass is totally there and actually quite deep given it has to energize a very large room, but there is no "hit" to it as though the initial energy of the note that you physically feel is just kind of missing somehow, but the sustain/decay of the note is there to be heard.  I knew going in my setup would be bass light and it is and I'm mostly okay with that, but I really thought your Super 8s would do better given how much more surface area you have on those dual drivers.

Most owners feel these speakers need a sub to be complete and they're probably right, but integrating one into what is supposed to be a "pure" nearfield stereo setup is something I wanted to avoid.  I suspect it wouldn't be to terribly hard to add an active pre-amp out to your amp to drive a sub if you wanted to go that route though.


----------



## L0rdGwyn (Jun 24, 2020)

@Xcalibur255 not a problem whatsoever Tyrell, I think you did describe the bass well to me.  I know getting that type of tactile bass slam is difficult to achieve in a full range design, they have other attributes that I love which makes them very fine speakers.  The bass is there and it is enough, but it is all relative, and the Snell Js just deliver a different level of density and kick to the bass.  But similar to how I thought "where did the bass go?" when swapping in the Super 8s, I thought "where did the midrange go?" when swapping in the Snells.  Always compromises in this hobby, I'm happy to have some variety of sound.  I'll do what I can with the placement, but I am limited unfortunately.  I just recently moved away from a 2.1 setup with a subwoofer, I have decided to remove subwoofers from my system, I am stricly a 2.0 guy now, keeps things simple.

On a related note, I finished one of the redone J/II crossovers.

Before:


After:


Clarity Cap CSA on the woofer, Clarity Cap ESA on the tweeter, resistors are NOS Mills non-inductive wirewound.  The crossover components are extremely well-matched, so I will only have to deal with variances in the driver / tweeter units.

Still waiting on parts from Atomic Hifi.  Don't say I never did anything for you, J/II.


----------



## Tjj226 Angel

Probably a stupid comment, so brace yourself. 

Have you tried looking for the tweeters on ebay? I usually find decent deals on j3 tweeters. IDK about j2 tweeters.


----------



## L0rdGwyn

Tjj226 Angel said:


> Probably a stupid comment, so brace yourself.
> 
> Have you tried looking for the tweeters on ebay? I usually find decent deals on j3 tweeters. IDK about j2 tweeters.



I haven't looked much, but at a glance it seems like J/III or OEM equivalent parts are sold pretty often on eBay.  I think the J/II tweeters are sort of hard to come by, especially in good shape since the doping eventually dries out.  Atomic Hifi is sending me some tweeters, I doubt they will be original J/II though, mabye J/III, but better than having a mismatched pair.


----------



## Tjj226 Angel

L0rdGwyn said:


> I haven't looked much, but at a glance it seems like J/III or OEM equivalent parts are sold pretty often on eBay.  I think the J/II tweeters are sort of hard to come by, especially in good shape since the doping eventually dries out.  Atomic Hifi is sending me some tweeters, I doubt they will be original J/II though, mabye J/III, but better than having a mismatched pair.



Well just as a heads up, I have like 6 pair of j3 tweeters from ebay. None of them are "matched". They all sounded different out of the box, but once I went through and refurbished them, they were all well within tolerance of one and other. 

A friend of mine has the J2s. He refurbished his tweeters and all the little different imbalances and nuances to the sound were cleaned right up.


----------



## L0rdGwyn

Tjj226 Angel said:


> Well just as a heads up, I have like 6 pair of j3 tweeters from ebay. None of them are "matched". They all sounded different out of the box, but once I went through and refurbished them, they were all well within tolerance of one and other.
> 
> A friend of mine has the J2s. He refurbished his tweeters and all the little different imbalances and nuances to the sound were cleaned right up.



Thanks, how did you refurbish besides replacing the ferrofluid?  I had mentally committed to moving on, but I might keep an eye out for a match to one of my two tweeters, would be preferable to use the originals.  From what I have gathered, one is an earlier model made by Culver that was used in the E original (cannot confirm if/when it was used in the J or J/II), Snell later switched to Tonegan when the Culver part became obsolete, which appears to be the make of my second tweeter that was used in both the J and E.  They are physically identical as far as I can see, I do have to wonder if they are equivalent parts and someone just didn't add ferrofluid to one mistakenly, hence the difference in HF response...coming up short on Google though.

Culver S-90662


 

Tonegan 94C70DS-00HD


----------



## Tjj226 Angel

L0rdGwyn said:


> Thanks, how did you refurbish besides replacing the ferrofluid?  I had mentally committed to moving on, but I might keep an eye out for a match to one of my two tweeters, would be preferable to use the originals.  From what I have gathered, one is an earlier model made by Culver that was used in the E original (cannot confirm if/when it was used in the J or J/II), Snell later switched to Tonegan when the Culver part became obsolete, which appears to be the make of my second tweeter that was used in both the J and E.  They are physically identical as far as I can see, I do have to wonder if they are equivalent parts and someone just didn't add ferrofluid to one mistakenly, hence the difference in HF response...coming up short on Google though.
> 
> Culver S-90662
> 
> ...



Ooooooookkkkkaayyyyy maybe someone at the snell factory knew something we dont?

Those two tweteers do indeed look identical. Maybe the deal is that tonegen bought culver? Maybe they are physically the same part but just with different company labels on them? 

Its super unlikely that two tweeters from two different companies would look nearly identical. There is more to this story than what we know. 

I would take a business card and soak it in some alcohol. Then insert it into the tweeter that doesn't have fluid and try cleaning out any crap in the cavity. If the card comes up with this redish brown color, then the tweeter had fluid in it at one point. I have a real funny feeling both of these tweeters take fluid, and they are identical tweeters. 

I would clean out each tweeter really well anyways. I always end up finding a surprising amount of dirt in the drivers.


----------



## L0rdGwyn

Tjj226 Angel said:


> Ooooooookkkkkaayyyyy maybe someone at the snell factory knew something we dont?
> 
> Those two tweteers do indeed look identical. Maybe the deal is that tonegen bought culver? Maybe they are physically the same part but just with different company labels on them?
> 
> ...



Yeah my thoughts exactly, pretty bizarre.  I'll see if I can dig up other information, but I'm going to clean them up, put ferrofluid in the one without and give them a try, I'll have the other tweeters as backups if things don't sound right.


----------



## L0rdGwyn

Got the input stage operational with filament bias.  Had to make some changes to account for the additional voltage dropped, changed transformers and some components on the Coleman regs.

What we ended up with is a regulated 650V B+ at the top of the CCS, 484V plate-to-cathode, a 9mA plate current and 5.15V on the filament with 4ohms resistance.



If it looks like a rat's nest, that's because it is.  I am still using alligator clips predominantly as it gives me the flexibility to choose which power supplies are connected at any one time.  Once everything is verified and semi-finalized, I'll solder it all together.

Tomorrow I am going to throw some sine waves into the 841 stage and source follower, we'll see what comes out the other side.  Theoretically, I should have the output transformers in a little over a week, that's when things will really get really interesting.  With the changes made to the filament supply, I now have an entire set of spare parts for another pair of 10Y / 801A tubes: DC supplies, Coleman regs, and filament transformers (whoops!).  Those are going to burn a large hole in my pocket, we'll have to come up with a plan for them


----------



## Tjj226 Angel

L0rdGwyn said:


> Got the input stage operational with filament bias.  Had to make some changes to account for the additional voltage dropped, changed transformers and some components on the Coleman regs.
> 
> What we ended up with is a regulated 650V B+ at the top of the CCS, 484V plate-to-cathode, a 9mA plate current and 5.15V on the filament with 4ohms resistance.
> 
> ...



Stop buying 801a tubes damn it! I need them to come down in price : P

But in all seriousness, im surprised how well this is coming together. When we were discussing this originally, I knew this design would be a huge pain in the butt, but you seem to enjoy crazy projects, so I will have to keep that in mind for our next talk lolololol. 

I can just see you trying to make an OTL speaker amp as your next project.


----------



## L0rdGwyn

Tjj226 Angel said:


> Stop buying 801a tubes damn it! I need them to come down in price : P
> 
> But in all seriousness, im surprised how well this is coming together. When we were discussing this originally, I knew this design would be a huge pain in the butt, but you seem to enjoy crazy projects, so I will have to keep that in mind for our next talk lolololol.
> 
> I can just see you trying to make an OTL speaker amp as your next project.



Yeah, this amp is a little nuts lol but it has all gone according to plan thankfully, fewer pitfalls than I expected.  I spent a lot of time running sims, researching, troubleshooting, so far it has paid off.  I experimented with every possible iteration of single-ended 801A I could find, didn't know at the beginning what a PITA tube it is to use, the 841 too, we'll see if I made the right design choices when the OPT arrive.

I don't want to build an OTL speaker amp LOL too big, too hot, too crazy.  Not sure what will be next, I've considered working on something cost-effective and not insane that I can build for other Head-Fiers, I think that might be fun, I am reaching amplifier saturation and SAF (spouse acceptance factor) is getting a little dicey.  I might have a DIY speaker build in the near future but that is TBD.


----------



## whirlwind

*SAF.....LOL!   *

Shoot me a pm, I may have a small project for you at some point


----------



## L0rdGwyn (Jun 26, 2020)

Wired up for some measurements today, specifically want to know the gain of the input stage.  I try to keep a DMM across a HV portion of the circuit at all times so I don't kill myself, yeah that's 708V across the voltage doubler resevoir cap  takes a minute or two for the caps to discharge across the bleeder.



With a 5.6Vpp input, I am getting a 164Vpp output.  This represents the maximum input signal from a typical DAC (5.6Vpp = 2Vrms, standard single-ended DAC output voltage).  I also figured out how to take screenshots on my scope instead of taking pictures of the screen like a caveman.



That puts the μ of the 841 at a little over 29 in this configuration.  Nice.  Will wire up the source follower next.


----------



## L0rdGwyn (Jun 26, 2020)

Wired up the source follower and did the same, 5.6Vpp input.  The output of this circuit will be direct-coupled to the grid of the 801A, so will provide the current drive into A2 region as well as the fixed bias.

 

As you can see, I have my approximate -25V bias for the 801A grid, this can be adjusted with one of the two trimmers on the board (this will be replaced with a full-sized potentiometer accessible from outside the chassis for bias adjustment in the final build).

Here is the output, essentially identical to the input (plot above), 164Vpp into the grid of the 801A.  This is beyond what is needed for max output swing as the 801A should hard clip at plate saturation, around +45V on the grid, roughly 130Vpp.



Everything works.  At this point, all there is to do is wire things up and wait for the OPT to arrive to set up the output stage, this prototype is nearing completion.


----------



## L0rdGwyn

I mentioned in a previous post that I was thinking about working on a (relatively) inexpensive headphone amplifier design that I could build for other Head-Fiers.

Well I sort of ran with the idea and today came up with the skeleton of a design.  The tube I penciled in for this idea way back was the 1626.  The datasheet doesn't show it very well, but this tube is very linear and a good choice for a low power SET (like a headphone amp), it is widely available, used in the Ampsandsound Kenzie as well as the Toolshed Darling headphone amps.  My idea is a little different.



With the OPT I am considering, a relatively small amount of gain would be needed to drive headphone to ear-destroying volumes.  The preliminary idea is a 1626 driving 1626 parafeed headphone amp with taps for 32, 150, and 300ohms.  Matched quads of these tubes are very easy to find.  With the tube driving itself, the distortion spectra will cancel to some degree, with a parafeed output should be a very clean sound.

I am getting ahead of myself, again, but I think I am going to prototype one of these, will be a cakewalk compared to what I have been working on!  If it sounds good, I might consider building one for real and sending it on a tour.


----------



## Zachik

L0rdGwyn said:


> If it sounds good, I might consider building one for real and sending it on a tour.


So, how do I sign up for the tour?


----------



## L0rdGwyn

Zachik said:


> So, how do I sign up for the tour?



If it comes to fruition, you just did!


----------



## audiofest2018

L0rdGwyn said:


> I mentioned in a previous post that I was thinking about working on a (relatively) inexpensive headphone amplifier design that I could build for other Head-Fiers.
> 
> Well I sort of ran with the idea and today came up with the skeleton of a design.  The tube I penciled in for this idea way back was the 1626.  The datasheet doesn't show it very well, but this tube is very linear and a good choice for a low power SET (like a headphone amp), it is widely available, used in the Ampsandsound Kenzie as well as the Toolshed Darling headphone amps.  My idea is a little different.
> 
> ...


I am signing up for its tour as well!


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## L0rdGwyn (Jun 27, 2020)

audiofest2018 said:


> I am signing up for its tour as well!



Added!  Well since there is interest, I am going to order parts to prototype, I have much of it on hand already.  I have been meaning to put together gerbers for my own CCS boards for a while now but have been lazy, this will motivate me to get it done.


----------



## Tjj226 Angel

L0rdGwyn said:


> I mentioned in a previous post that I was thinking about working on a (relatively) inexpensive headphone amplifier design that I could build for other Head-Fiers.
> 
> Well I sort of ran with the idea and today came up with the skeleton of a design.  The tube I penciled in for this idea way back was the 1626.  The datasheet doesn't show it very well, but this tube is very linear and a good choice for a low power SET (like a headphone amp), it is widely available, used in the Ampsandsound Kenzie as well as the Toolshed Darling headphone amps.  My idea is a little different.
> 
> ...



Slow your roll there and try the 1626 first. It is a pretty solid preamp tube, but it hasn't ever impressed me as a headphone amp tube. Compare the 1626 to a 6h30. They are similar in some ways, and very different in others, but the 6h30 would need a much less complex output transformer and you have two triodes per tube, so you only need 2 tube sockets. 

Also as a side note, with what you are describing, you don't actually need matched quads. You just need 2 matched pairs.


----------



## L0rdGwyn

Tjj226 Angel said:


> Slow your roll there and try the 1626 first.



I intend to, please see below.



L0rdGwyn said:


> ...I am going to order parts to *prototype*...



I owned a 6H30 OTL in the past, it was very disappointing, no doubt in part due to implementation.  I tried every available variant of the 6H30 in that amp, except for the rare 6H30P-DR, none of them did it for me, so I won't be using it in any design.  

My personal experience has been that single triodes are superior to equivalent dual triodes when it comes to soundstage and airiness, although it is not measurable and has nothing to do with THD or crosstalk (I measured them).  Morgan Jones got it wrong when he measured all those 6SN7 and 6J5, crowning the Brimar CV1988 "best" given its low THD.  I have owned and compared nearly every unobtainium 6SN7 to its equivalent 6J5, the 6J5 always wins, including the carbon glass CV1988 that Jones loves.  So, based on that experience, I will use single triodes as often as I can in place of dual triodes, unless the design specifically benefits from a dual triode.



Tjj226 Angel said:


> Also as a side note, with what you are describing, you don't actually need matched quads. You just need 2 matched pairs.



The idea of inverse complementary distortion cancellation is really an aside, the effect will not be significant with a CCS loaded driver stage; the 2H will be low enough that it is unlikely to significantly alter the 2H of the output.  The tubes are often sold in sets of four, only reason I made that comment.  The choice was made more for appropriate gain.  My simulated design will just reach the maximum 20Hz wattage of the OPT with two 5 mu stages when fed a 2Vrms input.  If I am making this amp for others, I don't want anyone to blow up the output transformer with the volume knob all the way up by mistake.


----------



## Tjj226 Angel

L0rdGwyn said:


> I intend to, please see below.



I did read, but I am also seeing people "sign up" so to speak. You don't want to have people get their hopes up while you prototype something. Trust me. Been there. Done that. Didn't go well. Don't want you to go through the same thing. 

Also, I was talking about using the 6H30 in series. Not in parallel. In other words have one half of the tube drive the other half of the tube. Im not a big fan of paralleling tubes either...however paralleling tubes can work if you put in extra effort to make sure both tubes have matched current running through both halves.


----------



## Zachik

Tjj226 Angel said:


> You don't want to have people get their hopes up while you prototype something.


Angel - I can only speak for myself here:
No matter how high my hopes are, if @L0rdGwyn builds a prototype and say it sounds bad - I will totally understand and wait patiently for his design to improve until he blesses it. I know he would not ship on a tour a crappy amp!!


----------



## L0rdGwyn

Tjj226 Angel said:


> I did read, but I am also seeing people "sign up" so to speak. You don't want to have people get their hopes up while you prototype something. Trust me. Been there. Done that. Didn't go well. Don't want you to go through the same thing.



I think I made it clear that it is hypothetical and contingent upon prototyping, there is obviously no financial commitment to receive an amplifier on a tour.  Anyway, I shouldn't have shared my intentions publicly, I think it would be best for me to take a break from this thread and go private with my projects for a while.


----------



## audiofest2018

Zachik said:


> Angel - I can only speak for myself here:
> No matter how high my hopes are, if @L0rdGwyn builds a prototype and say it sounds bad - I will totally understand and wait patiently for his design to improve until he blesses it. I know he would not ship on a tour a crappy amp!!


Agree with @Zachik!   When I signed up for this demo tour I understand that this is not a 100% sure thing (but I am confident that @L0rdGwyn will deliver.  )as things may come up, change, delay or not come through due to unforeseen reason.  Just want to have an opportunity to try out a DIY head amp and different tube amp as I have been following this thread and Glenn thread For quiet some time now.
I think my patient has been well trained through this head-fi hobby journey Of mine .  I have been waiting for my Glenn OTL to be built for almost a year now and am almost there I think.  I am most certain I have the ability to wait for this demo.

cheer!


----------



## Tjj226 Angel (Jun 27, 2020)

L0rdGwyn said:


> I think I made it clear that it is hypothetical and contingent upon prototyping, there is obviously no financial commitment to receive an amplifier on a tour.  Anyway, I shouldn't have shared my intentions publicly, I think it would be best for me to take a break from this thread and go private with my projects for a while.



Yeup. I did the exact same thing several years ago. Lets just say that no matter how clear you make your intentions, the karens of the audio world will find you.

Trust me, you can spell something out for people and they will still find a way to take advantage of you. I just dont want what happened to me happen to you. Thats all.

And just to be 1000% clear. Im not saying you shouldn't do this project. Im just saying that you should actually get a working prototype done and ready to go before you start opening yourself up to the general public.


----------



## johnjen (Jun 28, 2020)

And while finishing a prototype is step one, it may be v.3 or 4 before it can achieve your desired goals and is 'ready for prime time'.
Or not!
IOW there is no need to 'crowd' your dev process.

Case in point was our CBB (CardBoard Box) preamp, which while fulfilling our prototype requirements was a Long Way Off from being ready for 'Prime Time'.



And not to imply you would ever consider this as 'ready for prime time' by any stretch, but it is an example of a working prototype none the less.

This is a hobby, at least it is for me.
And I/we delight in seeing how close we can get to the edges of the cliff, while at the same time staying mobile and upright and not get surrounded by any miasma lurking close by.

JJ


----------



## Xcalibur255

Tjj226 Angel said:


> I did read, but I am also seeing people "sign up" so to speak. You don't want to have people get their hopes up while you prototype something. Trust me. Been there. Done that. Didn't go well. Don't want you to go through the same thing.
> 
> Also, I was talking about using the 6H30 in series. Not in parallel. In other words have one half of the tube drive the other half of the tube. Im not a big fan of paralleling tubes either...however paralleling tubes can work if you put in extra effort to make sure both tubes have matched current running through both halves.



We can certainly appreciate the wisdom of this sentiment, but this is a pretty tight knit group here so I think Keenan would have a pretty solid foundation of understanding to rest upon with this endeavor.

Now if some search index crawler grabs ahold of this thread and starts listing it in the first page of google search results for the 1626 tube then he might have a problem on his hands, but at this stage I think there's not much reason to be so wary.

I guess I just love to see enthusiasm flourish, so I'm viewing it through that lens.


----------



## leftside

L0rdGwyn said:


> I think it would be best for me to take a break from this thread and go private with my projects for a while.


Please don't.


----------



## Zachik

L0rdGwyn said:


> I shouldn't have shared my intentions publicly, I think it would be best for me to take a break from this thread and go private with my projects for a while.


Do not get discouraged by 1 pessimistic voice - there are quite a few here following your endeavors with lots of interest and curiosity!!


----------



## Tjj226 Angel

Zachik said:


> Do not get discouraged by 1 pessimistic voice - there are quite a few here following your endeavors with lots of interest and curiosity!!



Lol ok. I didn't say stop now did I? I said slow down. 

If trying to prevent a friend from learning simple lessons the hardest way possible is wrong. I don't want to be right. In fact if I hadn't followed this philosophy from the beginning in helping lordgwyn, I can pretty much promise you that this thread wouldn't be 36 pages long. 

Now thankfully, I know lordgwyn. This isn't going to stop him. He and a couple other members in this thread know who I am and what my true intentions are. I am genuinely here to help and I do consider him a friend or at the very least a fellow enthusiast. I am here to help him. Sometimes help means to be supportive from the side lines. Other times it means tapping someone on their shoulders and warning them of the danger ahead. 

And yes sometimes that ultimately means that im the bad guy, and yeah maybe everything this time around goes just right and he proves me wrong and I look like the village idiot. But ya know what. I would rather look like a fool and admit that I was wrong than have to say "I told you so". And I would MUCH rather say "I told you so" than to potentially watch him suffer having said nothing at all. 

At the end of the day I know that lordgwyn will come back to this thread and work with all of you. He isn't the type of person to give me because of my comments. If he were, then this thread wouldn't have gotten up off the ground.


----------



## L0rdGwyn

I really appreciate all of the kind words from everyone, I don't have any plans to abandon this hobby, frankly I'm addicted so I'm not sure if I could if I wanted to!

Thank you for your concern @Tjj226 Angel , I know you mean well, but don't worry yourself, I am a cautious person and I am not one to be taken advantage of.  I also have no plans to make this any type of serious business venture.  If I build amplifiers for others it will only be out of enjoyment and for friends on Head-Fi.  Maybe this 1626 amp will be a flop, we will see, if so I will find something else to build and send out for listening impressions.  At this point I've spent so much time and effort on these projects, I want to share what I've made and see what people think, more out of curiosity than anything else.  Hard to do in the COVID era and very unlikely previously planned meets will take place, so I think some sort of tour would be fun.

Anyway, I just need a mental break, in all likelihood I will probably only be able to keep myself away for a week or so, so I will post updates when I get back to work.


----------



## chrisdrop

L0rdGwyn said:


> I really appreciate all of the kind words from everyone, I don't have any plans to abandon this hobby, frankly I'm addicted so I'm not sure if I could if I wanted to!
> 
> Thank you for your concern @Tjj226 Angel , I know you mean well, but don't worry yourself, I am a cautious person and I am not one to be taken advantage of.  I also have no plans to make this any type of serious business venture.  If I build amplifiers for others it will only be out of enjoyment and for friends on Head-Fi.  Maybe this 1626 amp will be a flop, we will see, if so I will find something else to build and send out for listening impressions.  At this point I've spent so much time and effort on these projects, I want to share what I've made and see what people think, more out of curiosity than anything else.  Hard to do in the COVID era and very unlikely previously planned meets will take place, so I think some sort of tour would be fun.
> 
> Anyway, I just need a mental break, in all likelihood I will probably only be able to keep myself away for a week or so, so I will post updates when I get back to work.





Tjj226 Angel said:


> Lol ok. I didn't say stop now did I? I said slow down.
> 
> If trying to prevent a friend from learning simple lessons the hardest way possible is wrong. I don't want to be right. In fact if I hadn't followed this philosophy from the beginning in helping lordgwyn, I can pretty much promise you that this thread wouldn't be 36 pages long.
> 
> ...


You guys are great. Good advice offered in good faith. Good enthusiasm and interesting projects. I, for one, am learning and enjoying. "Text is clear as mud"; often/usually text communication is lacking on the internet. It is clear that this is an all positive engagement. Thank you guys for offering all that you are to the community.


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## L0rdGwyn (Jul 8, 2020)

So it's been over a week, and it will be a bit longer, going to get back into the swing of things this weekend.  After about five days, I had to work on something   so it wasn't a complete break.

First, I learned EasyEDA software and created my own CCS PCBs.  They are a bit larger than the kits I have been using, but they are sized to take the F series heat sinks from Ohmite.  These range from 1 inch tall at a 4.7 C/W thermal resistance to 2.5 inches tall with a 3 C/W thermal resistance.  This will allow me to use the CCS at up to 6-7W dissipation with the same board.  I also included a dedicated mu output.  They are in production at JLCPCB. 






I also drafted the source follower / bias supply boards, they will be finalized when the 841 / 801A protoype is completed and tested.  Speaking of which, these arrived today.



So that's exciting, unfortunately I am at the start of a series of night shifts, which means I will not get to finishing the build until this weekend, should have a functional prototype by Sunday I would say.  I have done a little work to wire up the build sans alligator clips which should make the task a little easier.  It has been so oppressively hot lately, let's hope for cool weather this weekend so I don't roast alive in my garage.

On the Snell J/II restoration front, I received my new tweeters and driver units from Atomic Hifi.  Well, there was a problem, the tweeters they sent me were not original Snells, as I expected, but they do not even fit in the cabinets if I wanted to use them, the magnet assemblies are 2mm too large and I am not modifying the cut-outs.  They are actually Morel MDT-29 stripped of their labels, which if bought from a typical retailer are half the price I was charged.  They sent along replacement crossover components as well, but a few caps and a resistor are not worth the premium, somewhat dishonest business practice IMO.  Regardless, they allowed me to return them, so I did not press the point.  The driver units are originals so I am very happy with them, they will replace the units in the speakers which were in need of a refoam, I decided to start fresh.



The original tweeters were sent off to my Snell restoration guy who is going to replace the diaphragms with a matched set using the original magnet assemblies, the diaphragms he has on hand are original Snells albeit of a later make without the problematic doping material.  So that is the plan, should have these done some time next week.

Let's see what else.  Over the past week, my home was in a state of chaos while the second floor was remodeled and the hardwood floors restored, original from the 1920s.  With the new digs, I was asked to put together a DIY stereo setup for my bedroom  so the project queue gets longer and longer.  My current crop will need to wrap up before I make any meaningful progress in that direction, but of course I have already started brainstorming.  What I am cooking up is a pair of DIY bass reflex full-range bookshelves for my bedroom.  Once the speakers are built, or at least the plans are concrete, I will design a small form factor amplifier to pair with them, topology TBD.  Listening levels will be low-to-moderate, so the speakers do not need to be overly sensitive.

I started fudging around in WinISD and other speaker modeling software along with some preliminary design education.  My very early plan is to use Markaudio's full-range drivers, top choices being the Alpair 10P or the Alpair 11MS.  The Alpair 11MS have some nice cabinet schematics available online optimized for high-output impedance amplifers (e.g. SET).

Alpair 10P


Alpair 11MS



Again, *this is all very preliminary and like anything in DIY is an iterative process*, something I will be digging into in the background, so plans will likely change.  Even if I end up using an existing cabinet schematic, I will go through the design process myself as it is something I am interested in learning.

I think that's it, wasn't exactly a break I guess, quite a chaotic week with the house remodel.  In non-DIY news, a very sweet stray cat showed up on my back patio on July 4th, we decided to lure him back with some stinky cat food and two days later he returned.  He is now part of the family, his name is Lucky.



My other two cats are hissing at him, but they just need time to adjust  he doesn't seem to be bothered in the slightest.

That's all until this weekend, can't wait to lay ears on my crazy A2 amplifier


----------



## chrisdrop

L0rdGwyn said:


> So it's been over a week, and it will be a bit longer, going to get back into the swing of things this weekend.  After about five days, I had to work on something   so it wasn't a complete break.
> 
> First, I learned EasyEDA software and created my own CCS PCBs.  They are a bit larger than the kits I have been using, but they are sized to take the F series heat sinks from Ohmite.  These range from 1 inch tall at a 4.7 C/W thermal resistance to 2.5 inches tall with a 3 C/W thermal resistance.  This will allow me to use the CCS at up to 6-7W dissipation with the same board.  I also included a dedicated mu output.  They are in production at JLCPCB.
> 
> ...


Welcome Lucky. My cats would hiss too, but who could resist.


----------



## Xcalibur255

Double thumbs up for the new kitty.  ^_^

I spent quite a bit of time looking into the Markaudio full range drivers myself.  Was toying with the idea of trying to build a pair of speakers for fun, but I don't really have the tools or space to do the woodworking and have grown less and less confident over time that my hands are up to the task anyway.

I have this cute little pair of ALO Audio Pandas that use a 3" Dayton audio full range driver.  I was thinking about trying to sub a similar size Markaudio driver in as an upgrade, but became fearful of wrecking the nice bamboo cabinets on a gamle that might not pay off.  At the least it's unlikely the bass port tuning would be a correct match, I would be rely somewhat on luck for it to work out.


----------



## L0rdGwyn

chrisdrop said:


> Welcome Lucky. My cats would hiss too, but who could resist.



It's just all part of the cat experience, they will be fast friends in no time, there is enough salmon pâté to go around 



Xcalibur255 said:


> Double thumbs up for the new kitty.  ^_^
> 
> I spent quite a bit of time looking into the Markaudio full range drivers myself.  Was toying with the idea of trying to build a pair of speakers for fun, but I don't really have the tools or space to do the woodworking and have grown less and less confident over time that my hands are up to the task anyway.
> 
> I have this cute little pair of ALO Audio Pandas that use a 3" Dayton audio full range driver.  I was thinking about trying to sub a similar size Markaudio driver in as an upgrade, but became fearful of wrecking the nice bamboo cabinets on a gamle that might not pay off.  At the least it's unlikely the bass port tuning would be a correct match, I would be rely somewhat on luck for it to work out.



The Markaudio drivers are very highly regarded in the DIY community, if you wanted to pursue the driver replacement, you could post your cabinet and port dimensions on diyAudio, there is a dedicated Markaudio driver thread, someone might be able to say how far off the tuning would be.  I'm not at that point yet, but I hope to be soon.


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## L0rdGwyn (Jul 12, 2020)

It's alive.  IT'S ALIVE!!!

I have tears in my eyes listening for first time, it sounds incredible, moved by the music and relieved after all of the work that went into this project.  None of these builds are easy, but this one was extra not easy.



This is a pretty frivolous post, much, much more to come today, there is a lot to say.  A gamut of measurements and comments on the final steps of the build.  I can't say it is done since there is likely more tweaking to come, but the beast lives.


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## whirlwind

Very awesome, a big congrats to you    
That is a lot of work.
Enjoy your listening and tweaking.


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## L0rdGwyn (Jul 13, 2020)

On two hours of sleep, I worked on getting the output stage of the amplifier configured all day yesterday, a tedious task, you'll know if you've ever wired a Lundahl OPT.

Finished up and got to biasing the output tubes.  This took some time as I was not about to mess around with adjusting trimmers with the amplifier on, I've been very careful while building this prototype given the 450V and 650V B+ supplies, so I had to power down and power up with each adjustment.

Finally, I hit my goal of 420V 40mA on the 801A outputs.



So our tube bias points:

841: Va 500; Ia 9mA; Vg -5
801A: Va 420V; Ia 40mA; Vg -21V

Just as the datasheet describes, love it 

Here is another boring video of the startup sequence with the 801A coming up to bias.  Again, first click is me turning on power, which immediately sends 120VAC to the filament supplies as well as the source follower / bias supplies.  The second click are the relays closing on the time delay boards.  These boards sit between the wall AC and the 841 / 801A B+ transformers, allowing the filaments to come completely up to voltage / temperature before B+ is applied.  The time delay boards are each powered by the 6.3VAC windings of the source follower transformer.  The voltage drop across a 1ohm current sense resistor on the filament of the 801A tells us how much DC current is passing through the tube by Ohm's law (1mV = 1ohm * 1mA), so we are looking for a 40mV drop across that resistor.



After doing my final voltage checks, there was only one more thing to do...listen?  No!  Measurements of course.

The amplifier starts to clip between 18.8Vpk-pk and 19.8Vpk-pk (full output) into 8ohms, making this roughly a 5.5-6W amplifier.

Here is a 1kHz sine wave at 18.8Vpk-pk.



Before the next graph, a quick recap on class A2.  Most single-ended class A designs are class A1, meaning the grid always operates at a negative voltage.  In a class A1 design, the grid will begin to draw current at the most positive swings (closest to 0V).  Without a source for that current, the amplifier will clip, this typically defines one of the two boundaries for the max output swing a tube can generate.

But what if we could supply that extra current and drive the grid positive  that is the basis of a class A2 design, which are much less common given their...peculiarities.  In this amplifier, the positive grid current is supplied by a transistor known as a source follower.  This is the transistor equivalent of a cathode follower, more commonly known to tubeheads.  Since the source follower is directly in the signal path, that makes this a hybrid amplifier with each of the respective devices doing what they do best: tubes for voltage gain, transistors for current gain.  The source follower provides an easy capacitive load for the input tube and can generate more than enough current to push the output grid - to which it is direct-coupled - far into class A2 territory.  Also worth noting that some tubes, like the 801A, were designed to operate in A2 regions.

So how far does that grid go?  Here is the full peak-to-peak swing of the grid at max output before clipping.  144Vpk-pk with its most positive peak at +46V, where it will draw roughly 10mA.



Next is the frequency response.  Good bass extension down to 20Hz, but we do have some HF rolloff.  We hit -3dB on the high end at about 16.5kHz, 20kHz is down at -4.4dB.  I did experiment with taking the plate output vs the mu output of the 841 CCS given its high plate resistance without any appreciable change, I believe this rolloff is due to output transformer parasitics.  Appropriate transformers for the 801A that will provide a sufficient output impedance are hard to come by, so this is likely a consequence of the 37:1 turns ratio.  My Lundahl LL1620 in my other amp didn't quite hit their spec either.  I will look a bit further into it and check some Bode plots along the circuit path to be sure there is not another low-pass bottleneck.  TBH though, I am not concerned, it is not at all noticeable on subjective listening and I can't hear beyond 16.5kHz anyway.



I did do some distortion measurements as well, here is what we got:

1mW into 300ohms (with paralleled 8.2ohm resistors on the output): 0.25% THD
1W into 8 ohms: 0.77% THD
Full output 5.86W into 8 ohms: 4.54% THD

I have only listened with headphones so far.  The most immediately obvious characteristic is this amp is _fast_ and the bass is very tight.  It has a very clean sound, this is not your warm and gooey type of tube amplifier, but very dynamic, airy, and well-extended in both directions (subjectively speaking ).

Once my Snells are back together, which very well could be tomorrow, I will lug this beast into my living room, quarantine my cats so they don't get fried, and give it a proper two-channel listen.

So far, I am very pleased with my monstrosity, but it is only halfway done.  Phase 2 will be getting it into a proper chassis with a separate enclosure for the power supply.  The layout is going to be an extreme challenge, but the show must go on!


----------



## Tjj226 Angel

Great job! 

Im even willing to bet your high frequency roll off is caused by something other than your transformer which means it should be fixable giving you even better performance. 

I can't wait to see this thing finalized. 

I will be curious how this sounds on the snells vs the omegas. You seemed to imply that the omegas had a different presentation than the snells, and I would bet money that this amp will accentuate those differences. It could make the omegas come to life or it could give the snells the little extra oomph they need.


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## L0rdGwyn (Jul 12, 2020)

Tjj226 Angel said:


> Great job!
> 
> Im even willing to bet your high frequency roll off is caused by something other than your transformer which means it should be fixable giving you even better performance.
> 
> ...



Thanks!  That would be nice, I will save that hunt for next weekend.  Looking forward to finalizing as well, can't wait to hide the rats nest of wires and leave four pretty thoriated tungsten DHTs on top.  I'll have to go to a meet and seek out the tube purists, I'll tell them there is a transistor in the signal path after the fact  the Omegas and Snells are pretty different, I'll do a proper head-to-head once I get the tweeters back in the J/IIs. This amp has some truly killer bass (at least on headphones) should be a good fit for the revamped Js


----------



## evonimos

Lovely!
Cats, tube projects and Snell 2way speakers.

Keep us updated.


----------



## L0rdGwyn

My prediction came true, the restored Snell J/II tweeters arrived today!

 

The original magnet assemblies were maintained, however the diaphragms were replaced.  A very nice touch that I did not expect, new faceplates with sealing foam around the perimeter (the screw holes on the original face plates were a bit tired).

The gentleman who did these for me is baco99 on Audiokarma, going to plug him since he did such a great job and has been so helpful to me, he has a company called Holt Hill Audio.  He designs and sells his own speakers, but will also restore any vintage speaker you throw at him, so if you find something you want to restore, he's your guy.  He has a large stock of these OEM Snell diaphgragms, a perfect replacement as mine were mismatched.

Holt Hill Audio: http://holthill.com/#

All there was to do was put everything back together.  Here is my revamped fancy crossover back inside the cabinet.



And the speaker just before closing.



 Oh man, these look good

 

Because I am a psycho, the only things original in the speakers are the cabinets, two out of the three inductors, and the damping material LOL they got the works.  I know its over-the-top, but I know what I like, still below MSRP in 2020 dollars 

Back where they belong.



BIG improvement across the board, the speakers are now well-matched, the treble is so much improved, I expected that but I would have been happy if it was simply balanced, better imaging, clear, articulate and detailed, the midrange too, it was quite recessed with the speakers as I received them.  Going to give them some time today and tomorrow for burn in.


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## L0rdGwyn (Jul 13, 2020)

Just one more thing.

My package from JLCPCB arrived with the CCS boards I designed.



I added some nice-to-haves, there is a dedicated mu output pad and these take the Ohmite F-series TO-220 heat sinks, same as what is pictured but they can get taller, up to 3 C/W thermal resistance at the largest size, giving these CCS to flexibility to run at highish currents.  I placed the standoff holes right at the center of the heat sink, such that a single pair of standoffs can support the largest model which are 2.5 inches tall.

These will load the 841 in the finalized A2 amplifier.  Need to finish my design of the source follower / bias supply boards next.


----------



## L0rdGwyn (Jul 14, 2020)

Sorry, I know people are probably tired of me already but I found some interesting tubes.

One of my current tube infatuations (there are several) is the Telefunken EL156, highly regarded tubes for SET or PP use, but quite pricey, go for around $400 a pair, here is a picture.



EL156 datasheet: http://frank.yueksel.org/sheets/118/e/EL156.pdf

But as I was poking around, I came across a pentode that I think is interesting and relatively inexpensive!  The Telefunken EL152 (6.3V heaters) and FL152 (12.6V heaters), I think they look rather nice!



I had never seen them before, they are descendants of the WWII era Telefunken LS50.  Interestingly the USSR reverse-engineered the LS50 during the war and created the GU50, which is popular with some folks over on diyAudio given they are still plentiful in Russian surplus and are dirt cheap.  You can get a pair of FL152 for $80, a pair of GU50 for around $20!

EL152 / FL152 datasheet: https://frank.pocnet.net/sheets/118/e/EL152.pdf

Here are the EL152 / FL152 triode curves.  The datasheet doesn't give tube constants for triode strapping, but from the curves, mu looks to be about 5, Ri around 1.5K.



Could make for a cool amplifier, looks pretty linear to me.  I have seen bias points in SET config suggested around 350V 100mA with a 40W max plate dissipation.  Doing some eyeballing, a 5K OPT and a driver that can swing ~100Vpk-pk would get you something like a 4.5-5W SET amp, could be done on the cheap using the GU50 instead of the Tele's.  Anyway, thought I'd share, I'm always on the look out for weird audio tubes to fantasize about.


----------



## L0rdGwyn (Jul 14, 2020)

I brought the beast into my house for some two-channel goodness.  I am never doing that again HA!!  Omg it is heavy.

It's...beautiful.....lol.



It sounds great with the Snells, again very clean, tight bass, very focused and dynamic.  The 6A5G amp by comparison is more soft, a little more..ethereal?  diffuse?  Hard to nail down the differences after one listen.

As promised, I threw the Omegas into the mix to compare to the new-and-improved Snell J/II.



So going low to high...the bass.  Maybe it was the amp pairing, maybe it was my room being back in its proper arrangement, but the Omegas initially surprised me in terms of the bass _quantity_, it is more than I remember, but still not as high-output as the Snells.  In terms of quality, it goes to the Snells for sure.  With the Omegas, there is bass, but what instrument am I hearing again?  The Snells do _detailed_ bass, and legitimately have usable bass down to 50Hz, I mean these things really rumble, frequency sweeps show it is even audible down to 40Hz.  What the Omegas lack in bass is detail and dynamics, there is a low end thump, but the nuance and attack just isn't there.

In the mids, it is mixed.  Replacing the Snell drivers definitely closed the gap in terms of midrange detail, which previously I would have given to the Omegas.  The Snells' midrange is very cohesive with the rest of the frequency spectrum and sounds very realistic. The Omegas are mid-forward, which lends itself very well to the human voice, they do female vocals extremely well, but due to the forward nature, they can sound disjointed at times.  For acoustic music or music with vocal emphasis (stereotypical "audiophile" music, you know what I'm talking about), the Omegas kill it, but the Snells are more well-rounded and realistic sounding.

In the treble, again, the new tweeters really closed the gap with the Snells.  Hard to say who pulls ahead here, they are both very detailed, the Snells do better with bad treble in bad recordings.  Since the Omegas are a bit more aggressive, when it sounds bad, it sounds BAD, which might be viewed as a strength, they are more revealing in that regard.  I'm going to call it a draw, the treble is very satisfying and airy in both cases, nothing to complain about here.

In terms of overall character / tone, the Snells to me have more of a "realism" to them, the Omegas have a very apparent character, it is a bit jarring going from the Snells to the Omegas, but then my ears adjust and it seems to fall away.  I am going to call it clarity, which goes to the Snells.

For imaging / soundstage, Snells again.  Those wide baffles really throw a huge stage and they have pretty darn good off-axis performance.  The Omegas are very sensitive to on-axis listening, they have a much smaller "sweet spot", which is a disadvantage considering these are in my living room and there are often others enjoying the music with me.  The Omegas have a pretty impressive stage themselves, but to a greater degree have more of a "two point source" image.  The center image is well-defined for the Omegas, but it is all relative, the Snells fill in that center image more fully.

So the verdict?  It might be obvious, I prefer the Snells.  No doubt there is some bias considering I put a lot of time and effort into these speakers.  Like I said before, it is all relative and the Omegas are very nice speakers, if I did not have the Snells I would be very happy with them.  Also worth noting this is not Omegas top-of-the-line offering as these are the ferrite magnet drivers, the alnico drivers are Omegas fanciest.  I suspect the perceived deficiencies in clarity would be gone with the alnicos.

The Snells just have a killer bass, tone, soundstage, imaging and are a great lifestyle fit for me given my space and the type of amplifiers I am building, so there it is.

Not sure if the differences could be picked up, but something I wish I had is a microphone setup such that I could get high-quality recordings of this system to post for comparison, would also allow me to take FR measurements...something to think about


----------



## Tjj226 Angel

Not bad for a pair of old speakers from the 90s.

I know this is just going to make you bang your head into a wall, but I am playing around with different tweeter upgrades on my snells. Im thinking a good planar tweeter might be a good choice.

IDK. 

I showed you those cardboard horns, and even with as ugly and messed up as they are, they DESTROY the snells and even the tannoys in mid range clarity. Its not even a competition. So needless to say I am really tempted to try and perfect the horn and use the snells as a sort of bass cabinet.


----------



## L0rdGwyn

@Tjj226 Angel not bad at all!  Well I'll be curious to hear how the tweeter experiment plays out, I am done with tweeters for a while  good luck with the horns, I'd like to experiment with them some day when I have the space and the woodworking tools, but that is a whole new can of worms.


----------



## Xcalibur255

I've had a growing suspicion that Omegas are quite finnicky about amp pairing, especially tube amp pairing.  I honestly think I got kind of lucky with mine and the Luxman SQ-N150 as I my setup mostly sounds to me the way you describe your Snells, except for the bass performance.  I can't say I have complaints about my bass *quality* though, in fact things like the pluck of an electric bass guitar string are some of the most impressive moments with the speakers because they seem so real, but the leading edge of percussion notes are definitely limp and I think that's just a characteristic of these drivers.


----------



## L0rdGwyn (Jul 16, 2020)

@Xcalibur255 I wonder the same, and to be fair this is not an optimal pairing.  Ideally the amplifier would be wired for a 4-6ohm secondary, so the output impedance is relatively high for the Super 8s and they will be poorly damped, which will definitely affect bass quality and quantity.  I also wonder about the ferrite vs. alnico magnet driver difference.  If I could do it again and I knew I was going to find the Snells, I would have purchased the Super Alnico Monitor, I guess I should have listened to your advice T!  But I was looking for an "all-rounder" type of speaker at the time and I wasn't sure if the Super Alnico was going to fulfill that need, and now the Snells do, so a more niche speaker would have been a better choice to complement to them.  Oh well, live and learn.


----------



## Xcalibur255

Worst case scenario I hear they have really good resale value, but I'm guessing the Super 8s will find a place and a use scenario with the right amp as a dance partner.  The fact that my amp is push-pull is a data point to consider too.  I haven't had the pleasure of hearing my speakers driven by an SET yet.


----------



## Zachik

Xcalibur255 said:


> I've had a growing suspicion that Omegas are quite finnicky about amp pairing, especially tube amp pairing.





L0rdGwyn said:


> I also wonder about the ferrite vs. alnico magnet driver difference. If I could do it again and I knew I was going to find the Snells, I would have purchased the Super Alnico Monitor


I have just pulled the trigger on crazy custom Omegas!  Hopefully, they would pair well with my solid-state and/or my Glenn EL3N amp... Ended up spending WAY more than planned, betting on them being end-game for me. Fingers crossed this bet will pay off


----------



## L0rdGwyn (Jul 17, 2020)

Xcalibur255 said:


> Worst case scenario I hear they have really good resale value, but I'm guessing the Super 8s will find a place and a use scenario with the right amp as a dance partner.  The fact that my amp is push-pull is a data point to consider too.  I haven't had the pleasure of hearing my speakers driven by an SET yet.



I know we've talked about it before, but I bet your 45 amp if modded would sound great with those alnico drivers, but I know it is a hassle to have done.  



Zachik said:


> I have just pulled the trigger on crazy custom Omegas!  Hopefully, they would pair well with my solid-state and/or my Glenn EL3N amp... Ended up spending WAY more than planned, betting on them being end-game for me. Fingers crossed this bet will pay off



I'm sure they will sound great! I don't mean to imply at all that Omegas are bad speakers, only that I prefer the Snells to the Super 8s specifically.  Just like your GOTL and GEL3N, I'm sure you love both, but if you had to pick one, you could   they are still great speakers, like @Xcalibur255 said, they may just be picky about amplifier pairing, who knows, they might surprise me on a future listen.


----------



## L0rdGwyn

Also @Zachik what did you end up getting?!


----------



## Zachik

L0rdGwyn said:


> Also @Zachik what did you end up getting?!


Since my setup is a near-field on computer desk (ears are 2-3 feet away from speakers) - Louis recommended the Super 3 (RS5 drivers, which are 4.5" full range).
To make sure I have enough bass - opted for the HO (2nd RS5 driver with low-pass filter).
I wanted to be 100% sure I have *plenty bass* (yeah, I am a bass head...  ) - so we added front firing powered 8" sub in each cabinet!
So, each speaker will have 3 drivers: 2 x RS5 (Super 3HO) + 1 x sub. Crazy... I know... But if that thing cannot satisfy my bass desire - I think I need to see a doctor


----------



## L0rdGwyn

@Zachik sounds awesome keep us posted


----------



## Zachik

L0rdGwyn said:


> @Zachik sounds awesome keep us posted


You know the drill... would take 6-8 weeks


----------



## Xcalibur255

It's really the solution to all this bass talk with these speakers.  Kind of makes me want to upgrade mine this way.  All it would take is another 6 inches of cabinet height to shove a pair of their deephemp sub modules into the bottom of the cabinets and voila there's bass.  The beautiful part of it is the back of the speakers will (presumably) have the sub's level and crossover controls which will allow for tuning to accomodate different rooms and placements.


----------



## Zachik

Xcalibur255 said:


> The beautiful part of it is the back of the speakers will (presumably) have the sub's level and crossover controls which will allow for tuning to accomodate different rooms and placements.


Not presumably - the back WILL have the sub's level, crossover and phase controls!


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## L0rdGwyn (Jul 19, 2020)

I'll be very interested to see how they turn out, @Zachik hopefully they satisfy your bass cravings!

I haven't done much physical work on either of my two pending projects, although I have been making some plans...

The next thing in store for the 801A A2 amp is to do some experimenting with different source follower devices.  Initially, I was going to try a few different chips, but have decided to start with just one, a high-quality SiC (silicon carbide) chip from Cree, the C2M1000170D.  From a specification standpoint, it fits the bill perfectly.  The gate-drain capacitance (Crss) of a source follower ideally will be low and constant over the voltage range at which the source follower will be operated.  The Crss is the capacitive load "seen" by the driver tube, in parallel with the load capacitance, and will form an RC filter which could cause some HF rolloff in the audio band depending on the output impedance of the previous stage.


 

The AOT1N60, the source follower chip I am currently using, has a very low Crss, around 2pF, whereas the Cree C2M1000170D has a Crss of around 1pF.  It is also much more "flat" over the voltage range it will be operating.  In _theory_, this will improve HF behavior.  I don't expect it to change the HF rolloff as changing the CCS from plate to mu output had no effect, which illustrates this is not the culprit, making the already very low input capacitance even lower will do very little .  Regardless, I will take measurements, I am interested to see if there are effects on the distortion profile and audible subjective differences when changing the devices. The Cree C2M1000170D is in a larger package than the AOT1N60, so finalization of the SF PCB is on hold until after this experiment.  I will have the C2M1000170D tomorrow, we'll see if I can get to it before work.

The other thing I have been cooking up...

While I love the chassis work Landfall does in terms of the quality of the machining and customization, the aesthetic limitations of anodized aluminum have started to bother me.  It is also a bit of a bottleneck in terms of completing amplifiers, made worse by the COVID situation, getting the parts anodized at the shops local to Landfall can take a long time and the work has been a bit inconsistent in the past.  We need a better solution.

So, I am going to try my hand at powder coating.  At home.  It is not difficult, not terribly expensive, and it opens up a HUGE number of options in terms of finishes.  When I was in college, I actually worked for a powder coating company doing R&D work during the summer, so I am quite familiar with the process 

The plan is to have Landfall machine the chassis parts to my spec, then send me the raw, unfinished, unbrushed aluminum parts.  I will do any additional drilling, then prep and powder coat the parts.  Here is my initial shopping list for the project:

1) powder coating gun
2) pancake air compressor
3) air compressor regulator
4) in-line air compressor filter
5) biggest toaster oven I can find - this is used to "bake" and cure the parts after the powder coating is applied, the larger the oven, the larger the chassis I can finish.  The one I am currently looking at has internal dimensions of 16 3/8" x 15 7/8", this seems to be the biggest on the market, so this is the largest width-depth chassis I could coat using this system.  Anything larger than that would require a larger oven or IR lamp to cure the parts, but that would be a beast of a chassis.
6) various part preparation knick-knacks
7) powder - THIS is what makes this process so intriguing.  What kinds of finish options would this open up?  Check out the options from Prismatic Powders, they claim to have the largest color selection in the world and I believe it.  It is actually a bit overwhelming LOL there are so many cool options that would look fantastic on an amplifier.

Prismatic Powders: https://www.prismaticpowders.com/shop/powder-coating-colors

Another advantage of this process is only the exterior of the chassis will need to be coated, saving me the effort of removing anodization to ground the chassis.  Special care will need to be made to ensure any holes in the chassis are not made too small with the additional coating (although typical powder coating thickness is on the order of 0.1mm), but I will plan accordingly and mask with high temperature tape.

Since I have made alterations to the 6A5 amplifier circuit and there will be some changes made to the layout, its new chassis will be the test for this project.  As of right now, I am planning to keep it gold.  To be very honest, the anodized gold I received was not exactly what I had in mind, so I can rectify it.

Spanish gold perhaps? https://www.prismaticpowders.com/shop/powder-coating-colors/EMS-0940/spanish-gold

That's more like it


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## Tjj226 Angel

Hey just as a heads up, you should simulate that mosfet in LTspice to get its curves at the voltages you want and make sure that the part is relatively linear over the voltage and current range you want. 

I have been messing around with SIC jfets and I have found out that they like to be pushed pretty hard before they calm down. It looks like that mosfet might be a similar situation. 

If that cree part manages to sort itself out with a little more voltage, that is truly an amazing part.


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## L0rdGwyn (Jul 19, 2020)

@Tjj226 Angel thanks for the heads up, I do have it in a LTSpice sim, it looks pretty good, better than the chip I am using, so I am going to give it a try 

They don't have a LTSpice model for it yet, but there is another brand new chip from Cree that is very intriguing, C3M0350120D.  I have not looked into it deeply, but at a glance for a source follower, Crss is a little higher at 3.4pF (still plenty low), but it is very well-behaved in terms of capacitance vs. voltage consistency.  In a source follower, Ciss is boostrapped and the FET can drive Coss no problem, so Crss is the critical parameter.


----------



## mordy

L0rdGwyn said:


> I'll be very interested to see how they turn out, @Zachik hopefully they satisfy your bass cravings!
> 
> I haven't done much physical work on either of my two pending projects, although I have been making some plans...
> 
> ...


Here is a suggestion for a color scheme:




-Just kidding, but I find this to be a striking design.....


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## L0rdGwyn

I love Art Deco design @mordy , not sure about the color scheme though HA!  another nice option going in the powder coating direction is a two-tone look with the top plate a different color than the side and front panels, I've very excited about the possibilities.


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## L0rdGwyn (Jul 24, 2020)

I've been doing a lot of experimenting with the 801A A2 prototype...

First, I replaced the AOTN160 source follower with the Cree C2M1000170D.  And?  I don't know HA!  I think the sound has changed, I cannot say for better or for worse but it does sound good, measurements are more or less the same, minute changes in distortion and no change in frequency response.  What I am planning to do is design a PCB that can either A) take either TO-220 or TO-247 package devices on the same board or B) design two separate boards.  This way I can easily experiment with different devices and see how they affect the sound.  With the prototype built the way it is, swapping chips on the source follower protoboard is a hassle, making any kind of listening comparisons near impossible, so further subjective tests will have to wait until I have the PCBs.

As you might recall, the amplifier as initially built had a somewhat significant HF rolloff with the -3dB point at 16.5kHz, seen below.



After much thought and listening tests, I decided this rolloff needed to be improved.  The source of the problem is twofold: 1) high internal resistance output tube (801A) and 2) high-turns-ratio OPT parasitics, namely leakage inductance and stray capacitance, the second forming a low-pass RC filter with the internal resistance of the output tube, what I suspected to be the major cause of the HF rolloff.  This was confirmed after checking the other stages of the amplifier.

I attacked this issue from two angles by experimenting with different bias points to alter the plate resistance of the 801A and...negative feedback (GASP!!!).

Yup, we are going there.  I began a series of experiments adding a small amount of feedback from the secondary of the OPT to the cathode of the 841 driver tube, just as shown in the diagram below.  This necessitated switching back from filament bias to cathode bias on the 841, including a bypass cap, more to come on that.



In this configuration, I used a 500ohm cathode resistor on the 841 with bypass cap, then a 50ohm resistor to ground, R2 in the diagram, to get my 500 / 9mA Ia / -5Vg bias point.  I then altered the value of R1 to adjust the amount of NFB from the secondary to the cathode.  I tried values of 2K, 1K, then 500ohm.

Using this feedback, I am trading gain of the 841 stage and total power output for lower output impedance, high frequency extension, and lower distortion.

*Output Impedance:*
Here we are shooting for an output impedance of 2.67ohms or less for a 3:1 damping ratio with 8ohm speakers.

No NFB: 3.95ohm (YOUCH)
R1 = 2K: 3.47ohm (better...)
R1 = 1K: 2.50ohm (me likey)
R1 = 500ohm: 1.02ohms (oooh baby)

So big improvements to be had here when it comes to output impedance, which will improve the damping factor for 8ohm speakers and tighten up the bass.

*Frequency Response:*

Result with no negative feedback is posted above, here is the rest.

R1 = 2K, 20kHz at -4.4dB



R1 = 1K, -20kHz at -3dB



R1 = 500ohm, 20kHz at -2.3dB



Again, nice improvements with increasing feedback.

*Distortion at 1W:*
No NFB: 0.78% THD
R1 = 2K 0.72% THD
R1 = 1K 0.67% THD
R1 = 500ohm 0.61% THD

Modest improvements in distortion.

*Power Output:*
As I mentioned, these improvements come with a cost, and that is gain from the driver stage, which will lower the swing of the output tube and reduce power output.

No NFB: 5.85W
R1 = 2K: 5.85W (still enough gain to drive the 801A to clipping)
R1 = 1K: 5.3W
R1 = 500ohm 4.3W

Always compromises in amp building, while the FR and low output impedance of the 500ohm configuration is appealing, power output takes a big hit.

*Adjusting the turns ratio:*

One other thing I explored was rewiring the OPT for 6.5K:8ohm.  I wanted to see if I could reduce the stray capacitance at a lower turns ratio and still get an acceptable output impedance with NFB.

Here is the FR with R1 = 1K.



The FR is more flat overall, but the rolloff is quite precipitous.  I thought about playing with this some more as adding more feedback would likely have big high frequency gains, but then I measured the output impedance....at 4.81ohms.  Adding enough NFB to get the output impedance down to an acceptable level would decimate the power output, so I decided it wasn't worth pursuing this further.

*Bias Points:*
I also tried adjusting the bias points and checking the output impedance, the logic being that the internal resistance of the 801A would fall with a higher current, lower voltage bias point.  That did not turn out to be the case!  Here are the results with R1 = 1K.

Zout at 365V 50mA: 2.95ohm
Zout at 400V 45mA: 3.22ohm
Zout at 420V 43mA: 2.50ohm

So my original bias point gave the best result.  A quick note, I also measured distortion at 1W at these bias points.  The distortion jumps rather quickly when the amp enters A2, and given the 365V and 400V bias points were closer to 0 grid volts, the 1W distortion at these bias points was poor, >1% THD.

*Subjective:*
Okay so how did the amp sound with this NFB added.  First, I bypassed the 841 cathode with an Audio Note Kaisei electrolytic.  As might be expected, it made the amp sound crappy, big step down in sound quality, congested, small sound stage, typical electrolytic stuff.  This gave me pause as I was not very enthusiastic about adding a cap to the signal path.  The biggest film cap I had lying around was 10uF, low for a typical bypass cap and I hadn't run any sims.  I thought "what the hell, maybe I can just evaluate the mids and highs", but this ended up giving me frequency extension all the way down to 20Hz.  Not only that, but I felt the original sound of the amp was well-maintained, it sounded great!  Adding a cap to the signal path made me very apprehensive about moving forward with this design, but this changed my mind, so I will be using a high-quality film on the cathode in the final build, will be doing more experimenting to determine the optimal capacitance, will try multiple caps in parallel as well.

Overall, I felt the sound of the amp was much improved with the NFB added.  Very tight bass ,detailed, great instrument separation and very noticeable increase in frequency extension and airiness.

So this is the direction I am going with the amp, unsure how much power I am willing to sacrifice yet for the gains listed above, that is TBD, but I am very happy with the initial results 

Edit: an aside, I may look into the possibility of using a pentode on the input such that proper feedback can be implemented with an excess of gain,  TBD more research to be done here...


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## Xcalibur255

I would encourage multiple long listening sessions while evaluating this.  It's been my experience over the years that these kinds of change initially hit you as very positive ones, but over time as you slowly peel the layers off the onion you start to discover downsides as well that don't bode well for long-term listening satisfaction.  Just my .02 cents.  You can put my change in the animal shelter donation plastic cat bank that's sitting on the counter over there.


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## L0rdGwyn (Jul 27, 2020)

Xcalibur255 said:


> I would encourage multiple long listening sessions while evaluating this.  It's been my experience over the years that these kinds of change initially hit you as very positive ones, but over time as you slowly peel the layers off the onion you start to discover downsides as well that don't bode well for long-term listening satisfaction.  Just my .02 cents.  You can put my change in the animal shelter donation plastic cat bank that's sitting on the counter over there.



I appreciate the $0.02  I'm coming to terms with taking this one slow, it is going to take some experimentation, I would like the measurements AND the subjective experience to pass the test before moving to a chassis, so there is much more to be done.  Initial impressions were good with the above, and it sure beats losing out on a significant amount of the high frequencies, but OPT to cathode feedback can cause instability.  I am going to give it a more thorough try with output tube plate to cathode feedback using a true pentode, the Mullard EF37A.  The 801A when used is often paired with NFB given its high internal resistance.  I was resistant to using it myself, but decided it is worth exploring given the measurements of the initial prototype.  So it's gonna be a while until this one goes in a box.


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## L0rdGwyn (Jul 28, 2020)

I am taking a break from the 801A A2 amplifier, I need it, waiting for some pentodes to arrive to apply _for real_ NFB and experiment some more.  Excited about the possibilities, in some ways moving away from the 841 might be a relief if the result is good, will make the chassis conversion much easier, we'll see.

Been dragging my feet pretty hard on my 6A5G amplifier redux, but made some meaningful progress today by finishing my plans for the new chassis layout.

So how will the new version differ from the original?  In a few minor ways.

New grounding scheme
Improved ventilation
DC voltage regulator for driver tube heaters, allowing a broader variety of 4V tubes to be used
Film bypass caps on 6A5G cathodes
XLR jack removed
4V rectifier only
Powder coated chassis
I've placed an order with Landfall for the unbrushed, unfinished aluminum chassis that I will be powder coating myself.  I would like to go with a metallic finish again, juggling around some ideas, a more gold gold vs. a copper or bronze finish.  Some finishes I am considering:

Spanish Gold: https://www.prismaticpowders.com/shop/powder-coating-colors/EMS-0940/spanish-gold
Monaco Copper: https://www.prismaticpowders.com/shop/powder-coating-colors/PPB-4520/monaco-copper
Bronze Chrome: https://www.prismaticpowders.com/shop/powder-coating-colors/PMB-4124/bronze-chrome

I'm always looking for trouble, and there is another regret I have, not including speaker binding posts on my 45 amplifier.  Since I was only shooting for headphones, I wimped out on the power supply and used a cool bias.  Rather than the 1.5W the amp is capable of, theoretically it could only put out 0.75W into 8ohms as built.  But what the hell let's try it out  with alligator clips, all things are possible.

 

It sounds great gets these speaker pretty darn loud, not going to rock the house down with this amp, but very satisfying volumes in my small room.

So I am redoing the power supply, ordering yet another chassis that I will powder coat, adding binding posts, and making this a speaker / headphone amp.  The footprint will remain the same.  I mentioned some time ago that I was going to put together a bedroom stereo, that is likely where this amp will be moved.  Which means I'll need a TRUE headphone amp, no regrets this time, which means I'll need to design one, which means it will be the basis for the "inexpensive" headphone amplifier I will be putting together, it's in the works, more to come on that.


----------



## L0rdGwyn

Here is the diagram of the new 6A5G amp chassis.  Nothing too crazy, I adjusted the position of the rectifier tube, added the ventilation around the tube sockets and removed the cutout for the XLR jack.  Should have this on hand quickly since it will be unfinished, hope is to be able to powder coat by next weekend.  Landfall is going to send me some scrap as well for testing.


----------



## Tjj226 Angel

L0rdGwyn said:


> Here is the diagram of the new 6A5G amp chassis.  Nothing too crazy, I adjusted the position of the rectifier tube, added the ventilation around the tube sockets and removed the cutout for the XLR jack.  Should have this on hand quickly since it will be unfinished, hope is to be able to powder coat by next weekend.  Landfall is going to send me some scrap as well for testing.



Are you moving the transformers underneath?


----------



## L0rdGwyn

Tjj226 Angel said:


> Are you moving the transformers underneath?



No they will be on top, but I will do that drilling myself.  I'll be making some very small changes to the interior layout, just easier to fine tune things that way.


----------



## Zachik

L0rdGwyn said:


> and removed the cutout for the XLR jack


why?!?!


----------



## L0rdGwyn

Zachik said:


> why?!?!



It isn't a connection I use, I included it on the original build for "convenience" but it just sits there unused.  I make my own cables, I like 1/4", these amps are not balanced so it is really a single-ended connection, no different thant a 1/4".  If I had a bunch of XLR headphone cables, maybe it would have stayed, but I don't so it has to go!  One less thing to wire


----------



## L0rdGwyn

In a freak accident today, I lost a Sylvania 6A5G.  Bummer.  Let's turn a negative into a positive and do an autopsy  with proper safety equipment, of course (look ma, I'm Thomas Mayer!)

Here is the tube with the envelope removed.



And the top mica.



Plate structure.

 

Grid / heater/ cathode anatomy.



And the grids by themselves.



Here are the heaters with their cathode sleeves.  You might also be able to make out the center tap at the bottom as well.  This is what makes this tube rather unique.  Around the time that indirectly-heated power tubes were becoming a thing, pentodes were all the rage, so indirectly heated power triodes never really took off.  This is why you see many DHTs used in SET amplifiers, or triode-strapped pentodes.  This is one of the few indirectly heated power triodes that was engineered, based on the 2A3.  As you can see, the internals are nearly identical to the 2A3, but Sylvania slipped cathode sleeves over the filaments (now heaters) and center tapped them for hum balance.  Sylvania and Visseaux (under Sylvania license) were the only manufacturers of this tube.



In case there was any doubt, here are the heaters separated from the cathodes.



And the remaining base with foil getter.



I've been meaning to get some more of these, so I have two more NOS pairs on the way.  One of the two that were in the amp was noisy, hopefully this was the noisy one!!!  I have a spare single with exactly matching internal structure, so it isn't too much of a tragedy ("he told himself...").


----------



## mordy

These things happen to all of us - part of the "tube mystique".......


----------



## whirlwind

L0rdGwyn said:


> In a freak accident today, I lost a Sylvania 6A5G.  Bummer.  Let's turn a negative into a positive and do an autopsy  with proper safety equipment, of course (look ma, I'm Thomas Mayer!)
> 
> Here is the tube with the envelope removed.
> 
> ...




Good Lord, great autopsy...well done...thanks for the pics!


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## L0rdGwyn (Aug 2, 2020)

With my powder coating plans finalized, 6A5G amp redux parts ordered, and my 45 parafeed revamp underway, I finally sat down and took the necessary deep dive into implementing NFB in the 801A A2 amplifier.

As I mentioned, I will be trying this out with Mullard EF37A, which are en route.  I may also play around with the 6J7G, which is a near equivalent.  LTSpice models of the 6J7 are more readily available, so that is what I simmed with.

I have been looking over the work of Gary Pimm, a tube DIYer / innovator who did a lot of work with CCS loads, pentode CCS loads, hybrid MOSFET / pentode CCS loads, among many other things.  He stepped away from the hobby unfortunately, as I recall because he was "tired of solving other peoples' audio problems".  His website is no longer up, but can be accessed using the Wayback Machine.

He came up with two clever methods to utilize a CCS load with a pentode gain stage, the first using a large value resistor in parallel to the CCS, the other using a resistance to ground, allowing the same type of PSRR you could expect using a CCS loaded triode.  Alternatively, I could just use a plate resistor 



What I mocked up in LTSpice today uses the resistance to ground method.  In my design, the open loop gain of the amplifier with a 6J7G pentode input (meaning, the gain of the amplifier with no NFB applied) is around 59dB.  With my NFB loop in place - from the 801A plate to the 6J7G cathode - I am seeing a closed loop gain of 44dB, so roughly 15dB of NFB applied.

This takes the open loop mu of the 6J7G from 165 to a closed loop mu of 32, plenty to drive the 801A to full output.  In fact, it is more than I will need, as I will be attempting to rewire the LL9202 OPT to 6.5K:8ohm and rebias to 370Va / 50mA Ia / -11Vg.  With the NFB, the output impedance will be sufficiently low for the lower turns ratio wiring.  This should also increase the power output of the amplifier, I should be able to swing 620Vpp into a 6.5K load, making this more like a 7W amplifier, in theory.  Here is the new 801A load line.



Here is the drafted pentode gain stage.  Will need to dial in the phase compensation capacitor, I penciled in 50pF.  Near the bandwidth limits of the amplifier, the phase could potentially shift to 180 degrees.  If this happens, at those frequencies the feedback will no longer be negative, it will be positive, resulting in oscillation.  That is bad!  In short, this capacitor in parallel with the 50K feedback resistor prevents that from happening and stabilizes the amplifier.



All theoretical right now, but the sims look good.  In LTSpice, I am seeing 0.25% THD at 1W, 0.56% THD at 3W.  Of course, those numbers aren't going to be terribly accurate, but would be very impressive if real life results are in that ballpark.

Going to keep tweaking this design, tubes are on the way, will report back on this front when I have some real world numbers  very excited to try this out, this is turning into quite the Frankenamp.


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## L0rdGwyn (Aug 1, 2020)

Here is the more standard pentode stage using a 100K plate load rather than the CCS + 250K to ground.  Less cool, but more practical.  With the source follower buffer stage, the low output impedance of the CCS mu output likely isn't a necessity, so taking a more KISS approach would save me some headaches.  The B+ for this stage can be taken off the 801A power supply rail, which would mean saying goodbye to my 700V B+ for the 841, oh no!


----------



## L0rdGwyn

Testing is ongoing, but I have some preliminary single-channel results using plate-to-cathode feedback with a pentode driver in the 801A A2 amplifier.

Just to recap, in the original design with the 841 and no NFB, I used a 420Va / 40mA Ia / -21Vg bias point for the 801A with an 11K:8ohm OPT wiring.  My FR started to roll off around 6-7kHz and my -3dB point was 16.5kHz, my output impedance was 4ohms, quite high for 8ohm speakers.  Here is the original FR.



For this new NFB pentode setup, I decided to try rewiring the OPT to 6.5K:8ohm for the sake of decreasing OPT parasitics (unwanted deficiencies in the OPT made worse by a higher turns ratio).  Typically, without NFB added, cutting the turns ratio in half would double the output impedance (BAD!).  However, adding the NFB will lower it.  I figured I could compensate for the increased output impedance with the NFB added and get it down to a reasonable level.  I rebiased the 801A to 360Va / 50mA Ia / -10Vg with the 6.5K primary.

The pentode I used is the Mullard EF37A, seen below drowning in a web of wires.  While I had looked into using a CCS load on the pentode driver, doing so has a complication, instability of the DC operating point given a nearly flat load line.  With the CCS loaded pentode, very small changes in cathode voltage result in drastic changes in DC operating point, so there could be quite a bit of drift.  This can be overcome using a servo circuit for stability, but I decided to take the KISS approach and use a resistive load.  Taking the resistive load approach, the open loop gain of the pentode will be lower with decreased overall NFB.  I ran several simulations in both cases in LTSpice, which showed using a resistive load and less NFB resulted in a more "SET" distribution of harmonics, meaning higher H2 and a progressive falling off of higher order harmonics.  This is desirable for the sound I would like to achieve.

So, I biased it with a 400V B+, 200K plate load, 200Va / 100Vg2 / 3.2Vg1.  NFB was taken from the plate of the 801A to the cathode of the EF37A.  



Measurements in this configuration:

Output Z: 2.8ohm
THD @ 1W: 1.2%
Power output: 4.7W into 8ohms

THD at 1W is higher than the original build given the lower primary impedance of the OPT, but overall well-behaved and does follow a more "SET" harmonics distribution as I mentioned above.  Frequency response below, vastly improved from the build with 841 driver and no NFB.  Doesn't truly start to roll off until around 16.5kHz, down 2.5dB at 20kHz.



Will continue playing with this setup over the next few days.  When the measurements look near-optimal, I will set up the other channel and have a listen.  Might give this a try with the 11K:8ohm wiring and original 801A bias point as well.

Not sure if people are interested in reading this type of technical / experimentation stuff, but I am always happy to answer questions about the topology and the "whys" as far as design changes go


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## L0rdGwyn (Aug 8, 2020)

Well I couldn't help myself, I threw the other channel together, got the other EF37A biased, and gave the amp a listen with my Auteur and...it sounds amazing, SUPER clean, dynamic, very tight bass, and great realism, I left the cathodes of the EF37A unbypassed, so no nasty electrolytics in the signal path.



I thought "this sounds pretty low distortion", I unplugged my headphones and took an FFT at my particular listening volume, which was pretty damn loud.

THD was 0.023%, with H2 at -80dB and H3 at -90dB, all other harmonics lost in the noise floor.  WOW!  The power of NFB.

I can honestly say the sound with NFB is improved over the 841 implementation, not to mention there are about ten other reasons to not use the 841.  Using it in the beginning took some convincing, but I had a lot of fun with it and learned a great deal along the way.

So the pentodes stay, the NFB stays, very happy with the outcome, more fine tuning to be done but this will be a great sounding amp


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## L0rdGwyn

I know I said I wouldn't do this again, but some work around the house placed my cats back in quarantine.  Thought this would be a good opportunity to give the new-and-improved 801A A2 amplifier a test run with some speakers.



The amp is significantly lighter without the 841 parts, which included a toroid and two filament transformers, so moving it indoors wasn't nearly as arduous as last time.

So, the sound...this is something special.  The staging and imaging of this amplifier are eerie, it takes the clarity and detail of the Snell J/IIs to a level I have not heard.  Extremely dynamic with uber tight authoritative bass.  My girlfriend and I sat down and listened to track after track, locked up cats be damned!  EDM, reggae, classical, post-punk, outlaw country, jazz, listened to a little bit of everything, a really impressive showing, it can do it all.

After an hour and a half the cats had to come back out lol but I wanted to keep listening!  

There may be a little tweaking ahead, some bias point changes, altering the amount of NFB, etc. but by and large, this is the amp, very happy with it now.  Finally getting sound proportional to how big of a PITA this project has been!!!



Dropping the 841 driver shrunk the power supply big time, still going with a separate chassis, but the layout will be much more manageable now.  Can't wait to get to work on it, have to dot the i's and cross the t's first, but what I heard today is going to be major motivation to get this one boxed up ASAP.  Now for the color...


----------



## whirlwind

Pretty impressive, congrats.


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## 2359glenn

What a fun project !
 Now that I am back to building amps have to come up with something new and fun to design. After my backlog is done.
Has to be a amp that is new but can't be to crazy I have to make a profit when selling without the price being crazy. 
Switching to a pentode with NFB is a must or you would need two stages of gain.
Direct heated tubes are a pain to use but the thorated tungsten #10 and #801 sound so special and look great.


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## L0rdGwyn (Aug 9, 2020)

2359glenn said:


> What a fun project !
> Now that I am back to building amps have to come up with something new and fun to design. After my backlog is done.
> Has to be a amp that is new but can't be to crazy I have to make a profit when selling without the price being crazy.
> Switching to a pentode with NFB is a must or you would need two stages of gain.
> Direct heated tubes are a pain to use but the thorated tungsten #10 and #801 sound so special and look great.



So glad to hear your shop is back up and running!  Can't wait to see what you put together Glenn.  DHT really are a pain but the sound is worth the effort.  I knew the 801A was a difficult output tube when I started, glad I stuck with it though, loving the sound and that TT filament glow.  This amp commits all of the sins: NFB, transistor in signal path, pentode driver, but it sounds great  I think I will work on something less crazy next, this one has been a real doozy.


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## Zachik

2359glenn said:


> Now that I am back to building amps have to come up with something new and fun to design. After my backlog is done.


Oh no!!!! my poor wallet...


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## L0rdGwyn (Aug 9, 2020)

Took some time to optimize the bias point of the EF37A and degree of NFB this morning with fantastic results.

Not sure if I mentioned this before, but what I did on the cathode of the EF37A was place two 1K 0.5W trimmers, bisected by the 50K feedback resistor.  The top of the two trimmers adjusts the bias of the EF37A without affecting the NFB, whereas the bottom trimmer adjust the amount of NFB injected into the cathode.  Because some DC current is injected into the cathode from the NFB, the bottom trimmer also affects the bias point.  Leaving the top trimmer unbypassed causes cathode degeneration, linearizing the pentode but also decreasing gain through internal NFB.  If I were to use a bypass cap here, I could get more gain and increase the degree of NFB in the amplifier, but leaving an electrolytic out of the signal path is well worth the tradeoff for less gain.  With this setup, the stage can be adjusted, tested, and optimized. 



I increased the EF37A plate load to 220K, squeezing a little more gain out of the stage.  This necessitated increasing the value of the g2 resistor to 1.2Meg.  With the trimmers where they were originally, this gave me a bias point with 220V on the plate of the EF37A and 100V on g2.

Next, I input a max signal of 2Vrms into the amplifier and adjusted the top trimmer, changing the bias of the EF37A to increase the gain, pushing the amplifier to clipping, visible on my scope.  Then, I adjusted the bottom trimmer to increase the NFB and reduce the gain, bringing the amp back out of clipping with max signal input.

This process was continued until the optimum bias and NFB was achieved with 120ohm on the top trimmer and 350ohm on the bottom.  Final bias point of the EF37A was 220V on the plate and 96V on g2.

So what does this get me?

Zout is now *0.38ohm*, giving me a damping factor of > 20 with 8 ohm speakers 

THD @ 1W is 1.18%.

Here is the FR with the additional NFB, still some marginal HF rolloff, only significant at inaudible frequencies.  With the output impedance now as low as it is, this is likely a limitation of the OPT.



Not bad  

With this setup and a 365V 50mA bias point, I am getting 17.4Vpp into 8ohms, so around 4.8W out of this amp.  With the LL9202 rewired for 6.5K:8ohm, copper losses increase from 0.5dB to 0.8dB, so power output suffers a bit.

I _should_ be able to get 5W though.  I discovered that the output stage is clipping asymmetrically at my bias point with the 6.5K primary.  Here is the output of my scope, yellow is the voltage across an 8ohm dummy load, purple is the output from the 801A plate.  As I said before, the EF37A gain / NFB has been adjusted such that the amp is just out of clipping at maximum input, so this is at 2Vrms into the EF37A.



Now watch what happens if I increase the signal input beyond 2Vrms from my signal generator, driving the output stage to clipping.  The 801A clips asymmetrically at the positive peaks.  This limits the full peak-to-peak voltage swing of the 801A and power output of the amplifier.



To optimize the stage, I will try decreasing the plate voltage from a 365V to a 350V / 50mA bias point.  This should allow the output stage to clip symmetrically, increasing the peak-to-peak swing of the 801A enough to get 5W out of the amplifier.  This will decrease the plate dissipation to 17.5W (87.5% of maximum), so will help the longevity of the 801A tubes as well.

The down side is I will need to adjust some resistor values in the Maida regulator to get the voltage down to 350V, so looks like yet another Mouser order is in my near future.

The saga continues...


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## Xcalibur255

Would love to hear your thoughts on the sonic quality differences between the previous implementation and the NFB one.  There is SO MUCH double speak and 2nd-hand parroting about what NHB sounds like that I'm convinced that 99% of people including me have false ideas about whether it is truly good or bad.  The school of thought goes that it makes an amp sound sterile and dry, and takes away the sense of layering and depth in exchange for better dynamics and a faster, cleaner sound.  I'm guessing this is all conditionally true at best depending on the details of the implementation.

I still believe, though, that any time you switch to a sound that is more dynamically "alive" the initial reaction is going to be super positive but with many more hours of listening the enthusiasm has a tendency to wane.  That's just the psychology of how our brains process sound.


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## Tjj226 Angel

Xcalibur255 said:


> Would love to hear your thoughts on the sonic quality differences between the previous implementation and the NFB one.  There is SO MUCH double speak and 2nd-hand parroting about what NHB sounds like that I'm convinced that 99% of people including me have false ideas about whether it is truly good or bad.  The school of thought goes that it makes an amp sound sterile and dry, and takes away the sense of layering and depth in exchange for better dynamics and a faster, cleaner sound.  I'm guessing this is all conditionally true at best depending on the details of the implementation.
> 
> I still believe, though, that any time you switch to a sound that is more dynamically "alive" the initial reaction is going to be super positive but with many more hours of listening the enthusiasm has a tendency to wane.  That's just the psychology of how our brains process sound.



Well just to give you some perspective, there are different types of NFB that fall into two categories being local feedback and global feedback.

Global feedback is usually what everyone talks about as being bad, and this is mostly due to it's implementation. I think global feedback is also far more widely used in tube amps because of it's use on the Williamson amplifier which a lot of people tend to copy. 

Lordgwyn is using a type of local feedback. There are tons of different ways you can achieve local feedback. Each has their own pros, cons, and tonality. For instance Ultra Linear is a type of local feedback that feeds the plate signal back to the screen grid. Using an unbypassed cathode resistor is another type of local feedback. The list goes on and on. 

Theoretically all negative feedback is "bad" in the sense that the signal is actually being damaged in the process. It is definitely not an ideal solution by any stretch of the imagination. However since we don't live in a perfect world, sometimes negative feedback is a necessity. It is the amp designers job to figure out a way to apply negative feedback in such a way that it does the least harm possible to the music while at the same time fixing the problem that required negative feedback in the first place. 

It takes a LOT of fine tuning to really nail something like this down. Most mass production amp designers simply wont take the time to do this which is why most of them fall short.


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## L0rdGwyn (Aug 10, 2020)

Xcalibur255 said:


> Would love to hear your thoughts on the sonic quality differences between the previous implementation and the NFB one.  There is SO MUCH double speak and 2nd-hand parroting about what NHB sounds like that I'm convinced that 99% of people including me have false ideas about whether it is truly good or bad.  The school of thought goes that it makes an amp sound sterile and dry, and takes away the sense of layering and depth in exchange for better dynamics and a faster, cleaner sound.  I'm guessing this is all conditionally true at best depending on the details of the implementation.
> 
> I still believe, though, that any time you switch to a sound that is more dynamically "alive" the initial reaction is going to be super positive but with many more hours of listening the enthusiasm has a tendency to wane.  That's just the psychology of how our brains process sound.



Sure thing!

I originally went with the 841 / 801A setup with no NFB given the "cool factor" of using two pairs of similar thoriated tungsten tubes, this setup also came recommended to me by a specific DIYer who had experience with a similar build.  I had other discussions on the design privately with a few different DIYers, some of which warned that I should look into using NFB if I wanted to implement the 801A as a power tube.  Using this tube is difficult due to the high internal resistance, there are basically two different approaches you can take.

1) Use a very high impedance OPT without negative feedback, something on the order of 11-16K to provide a proper load to the output tube and maintain a reasonably low output impedance for speakers.  The compromise here is high impedance transformers of this type are going to have bandwidth limitations and the output impedance will still likely be quite high.

2) Implement some form of negative feedback to decrease the output impedance, increase bandwidth, and lower distortion.  This allows the use of lower impedance transformers with better frequency extension.  The compromise here is the use of NFB, if you are averse to it or are concerned it will have a negative effect on the sound.

I moved forward with option 1 and, as I showed in the thread, the FR was compromised by the 11K OPT and the output impedance was high at 4ohm. Another warning I was given by a DIYer who is experienced with the 841 is that it produces a high degree of higher order harmonics, and this was found to be true.  The initial impressions of the amp in this configuration were "good", the sound was more clean and less "tubey", very dynamic, but as I listened more and more I realized that I could tell the HF was rolled of, losing that extra degree of airiness, microdetail, and presence the highest register provides.  The harmonic spectrum of the amplifier also did not follow a typical "SET" distribution that I have alluded to, instead with a higher degree of H3 than H2 and a signicant amount of higher order harmonics.  I felt over time this created a bit of a harsh sound to the treble.

Given this dissatisfaction, I decided option 2 with the NFB was worth investigating.  I discussed this as well with DIYers I respect across different forums, plate to cathode feedback was highly recommended, so I began playing with implementing it in LTSpice.

The concern with NFB is that it disproportionately affects the lower harmonics (H2, H3), so the issue is after adding gobs of NFB, you could be left with predominantly higher order harmonics and a sterile, harsh sounding amp.  I wanted to avoid this, so ran simulations to get an idea of the harmonic distribution.  From my testing, I found that a resistor loaded pentode results in a more SET harmonic distribution, which allows masking of harmonics by a higher H2, as well as a progressive falling off of the higher order harmonics beyond H2.  This was opposed to using a CCS loaded pentode with very high open loop gain, allowing a high degree of NFB.  This setup has its own shortcomings related to stability of DC operating point, but also leads to an undesirable distribution of harmonics.

So that is how I decided to go this direction, again while discussing design theory with DIYers in private.  I optimized the feedback circuit in LTSpice while monitoring the harmonic profile before attempting to apply it in the real world with the EF37A.  This specific pentode was made for audio use and is more tolerant of high B+ voltages than something like the 6J7G, so works well in my circuit.

Implementing NFB in the amplifier has gotten me better frequency response, extremely low output impedance, and lower distortion with a good harmonic profile.  So all of the measurements check out, save the small amount of HF rolloff that remains above 17K, which is a limitation of the LL9202 OPT.

So how about the subjective sound compared to the relatively harsh sounding 841 design?

I nearly posted about it frivolously a few times and deleted the posts, for fear of being accused of new toy syndrome, and maybe I am guilty, but since you asked...

When it comes to dynamics, transparency, soundstage, detail retrieval, and imaging...this is the best amp I have ever heard.  Maybe that doesn't mean much coming from someone who is three scratch builds into this thing, but there it is.

It is truly jaw-dropping, I did not expect it to sound this good.  No doubt the sound has a low-distortion character and is very "clean", but _so far_, it doesn't at all shift into the realm of sterile or harsh.  It is just *transparent*.  That is the best way to describe the sound of this amp now, it just sounds like real life, completely clear.  The imaging is so razor sharp, the definition of the center image shocked me on first listen.

I lugged the thing into my house again yesterday to listen with the NFB and bias point of the EF37A optimized. Again, more of the same, just insane staging, imaging, and detail, especially in the bass.  I listened to the HD650 afterward, which has sort of become a benchmark headphone for me.  I have never heard it sound that good before, it honestly turns it into a different headphone!  I might even prefer it over the Auteur paired with this amp, it scales incredibly well and takes the technical performance of the headphone somewhere I didn't know it was capable of.

So, without question, the addition of local NFB with the EF37A in place of the 841 without negative feedback was a massively positive change, WAY exceeding my expectations.

I know how hyperbolic this all must sound, but its just blowing my mind...even compared to my 6A5G and 45 amplifiers.

Given how positive the change has been, I am tempted to push things even further, specifically by trying a different OPT.  The LL9202 I have been using were purchased with the intention of using an 11K primary, and as such, they have a very high primary inductance of 100H.  The compromise of designing the transformer this way is evident in the rolloff above 17kHz.  I have had talks with two different DIYers who have designed amps using NFB with the 801A using a 0Vg bias point at around 320V 60mA with a 3K primary.  They are achieving *8W* or more in those amplifiers, so I am considering an experiment with a lower primary impedance, higher bandwidth output transformer for additional power output now that we are full steam ahead with NFB.

The OPT changeout plan above obviously assumes that the LL9202 is not significantly responsible for the fantastic sound I am getting, so purchasing a new set of OPT outright is too risky.  But it just so happens that I have a pair of perfect transformers for this experiment on hand already...in an amplifier than is currently being disassembled...the 3.3K LL1620 60mA in my 6A5G amplifier 

Throwing these OPT into my prototype will allow me to deduce if the same sound can be maintained or improved upon with a lower primary impedance to get a full 20Hz - 20kHz at a near 0V grid bias and get around 8W out of the amp.

More to come on the above, the DIY rabbit hole keeps getting deeper and deeper.


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## L0rdGwyn (Aug 10, 2020)

Sorry for the wall of text, I don't even know if anyone is reading this stuff, but just to give an idea of what I mean when I say a SET harmonics distribution, I mean like below, with a prominent H2 with progressively decreasing H3, H4, H5, etc. until they are lost in the noise floor.



This is at a little over 2mW into 300ohm with 8.2ohm resistors paralleled on the headphone output, pretty damn loud for headphones.  You'll have to excuse the power supply noise, this amp is literally built on a piece of wood LOL not to mention overly long runs of wire all over the place, it is a mess for picking up noise, it will be better in the final build with separate chassis.

It might be a little dense, but there is an interesting article that touches on this topic here: http://www.nutshellhifi.com/library/FindingCG.html

It starts pretty objective, sort of gets a little hand wavy by the end as I recall, but it is still an interesting read for those that are interested on how harmonic distortion affects our perception of frequency response changes, despite them being measurably unchanged.


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## Xcalibur255

Well, I'm reading.    You explained it very well too.  The voicing of an amp seems to have a great deal to do with the behavior of its harmonic distortion profile....... this is a fascinating subject for sure.  

You're referring to the spikes at 2k, 3k, 4k, 5k that are getting progressively smaller right?  It forms something of a bell curve to my eyes.  This is why so many push-pull amps sound dry to me, because the 2nd order is getting cancelled out but the higher order harmonics are still there.

This and the psychology behind how our subconscious mind processes sound go hand in hand for me.  Both are super deep and super interesting.

Have you tried the Omegas with this configuration yet?  I have a hunch that their strengths will get reinforced enough to give some wow factor there.  This is why I like my Alnicos so much, because the things it does so well are entrancing enough that I can mostly just forgive the things they aren't doing so well.  Mostly.  There are days when I too would like to actually have some bass in my setup.    There's always the TV system I guess.  I have a JL Audio Dominion sub in that one just to give the towers extra omph down low that they honestly didn't even need..... but that setup is just lifeless for music playback compared to my tube amps.  It's got no soul.


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## Tjj226 Angel

Xcalibur255 said:


> Well, I'm reading.    You explained it very well too.  The voicing of an amp seems to have a great deal to do with the behavior of its harmonic distortion profile....... this is a fascinating subject for sure.
> 
> You're referring to the spikes at 2k, 3k, 4k, 5k that are getting progressively smaller right?  It forms something of a bell curve to my eyes.  This is why so many push-pull amps sound dry to me, because the 2nd order is getting cancelled out but the higher order harmonics are still there.
> 
> ...



The reduction of second order harmonics does not necessarily mean that you will end up with a dry sounding amp. 

Always remember that what we ideally want to achieve is a straight wire with gain. In turn we actually do want 0 distortion. Canceling 2nd order distortion is not inherently a bad thing. The catch is that it is not inherently a good thing either. 

It is important to consider how the second order distortion is canceled. Canceling distortion through a push pull topology is theoretically better than canceling it with negative feedback. HOWEVER push pull amplifiers require special design considerations that may result in a compromise to audio quality. 

It all depends on the circuit and how it's implemented. That being said, I would also say that generally speaking there is a tendency for amp designers to hyperventilate over THD and as a result they tend to overcompensate their designs which will often times lead to a dry sounding amp. 

I need a little video of Balmer saying TOPOLOGY TOPOLOGY TOPOLOGY TOPOLOGY


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## L0rdGwyn (Aug 11, 2020)

Xcalibur255 said:


> Well, I'm reading.    You explained it very well too.  The voicing of an amp seems to have a great deal to do with the behavior of its harmonic distortion profile....... this is a fascinating subject for sure.
> 
> You're referring to the spikes at 2k, 3k, 4k, 5k that are getting progressively smaller right?  It forms something of a bell curve to my eyes.  This is why so many push-pull amps sound dry to me, because the 2nd order is getting cancelled out but the higher order harmonics are still there.
> 
> ...



I definitely think the harmonic profile is a major contributor, but of course it has to be more complex than that.  That article I posted is one of the few I have found that discussing the effect of harmonic distribution on the perception of frequency response changes.  Nelson Pass has done quite a bit of work on figuring out how harmonics affect the subjective listening experience too.  Similar to what is seen in SET amplifiers, they have found that a higher H2 and lesser H3 results in the psychoacoustic illusion of increased soundstage and space.  As a result, Pass Labs specifically designs their amplifiers such that what distortion is left over (since they are still looking to achieve low distortion) is H2 and H3 in a certain ratio.  While I am not a SS guy, I secretly would love to own one of his First Watt class A power amplifiers and pair it with a tube preamp of my design  but I digress.

I can't say specifically that the harmonic changes going from 841 with no NFB to EF37A with NFB are the soul reason for the change in character of the amplifier, but I think it is definitely a contributor.  One of the DIYers I have alluded to who is using plate-to-cathode feedback with a pentode gain stage is actually planning to implement a switch in his design that changes the pentode load from a CCS to resistive, the goal of which is to alter the sound of the amp from a high NFB typical "hifi" sound to more of a "SET" sound with a resistive load, I thought that was a pretty neat idea 

As the amp stands right now, I have optimized the gain stage for maximum NFB while maintaining maximum power output of the 801A.  What I think I will do next is reduce the NFB, while keeping the output impedance and FR at acceptable levels and see how it changes the subjective sound.  Obviously the measurements will say "more NFB is better", so we will see if the subjective experience says otherwise.

Maybe you could try one of Omegas subwoofers?  I haven't tried the Omegas with the amp yet, but you're right, they would benefit from the low output impedance.

I think tomorrow I am going to change some parts in the Maida regulator, see if I can get something near 0V bias point on the grid without changing my bias supply too dramatically, then change the OPT out for the 3.3K 60mA.  As I mentioned, somehow two different builders are getting 8W out of a 3K OPT, which does not align with any loadline I can draw on the 801A curves, there must be some magic happening at this bias


----------



## Zachik

L0rdGwyn said:


> So, without question, the addition of local NFB with the EF37A in place of the 841 without negative feedback was a massively positive change, WAY exceeding my expectations.
> 
> I know how hyperbolic this all must sound, but its just blowing my mind...even compared to my 6A5G and 45 amplifiers.


I am curious whether or not you'd lose any of the magic of this new design by replacing the EF37A tubes?
I am asking, because I have a really bad experience with top cap tubes! Tried both 6C8G and EL32, and both acted as antenna for EMI. Living in a densely populated area with 20+ WiFi networks in range is not a good idea with top cap tubes. Ferrite beads on the cable to the top cap did not help. Disconnecting my router did help a lot, though...
So, do you think different / equivalent tube type that does not use top cap could work in this design?
Also, how likely your first "community friendly" amp be using this topology / architecture?  or is it way too pricey due to expensive parts?

Just thinking out loud...


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## L0rdGwyn (Aug 11, 2020)

Zachik said:


> I am curious whether or not you'd lose any of the magic of this new design by replacing the EF37A tubes?
> I am asking, because I have a really bad experience with top cap tubes! Tried both 6C8G and EL32, and both acted as antenna for EMI. Living in a densely populated area with 20+ WiFi networks in range is not a good idea with top cap tubes. Ferrite beads on the cable to the top cap did not help. Disconnecting my router did help a lot, though...
> So, do you think different / equivalent tube type that does not use top cap could work in this design?
> Also, how likely your first "community friendly" amp be using this topology / architecture?  or is it way too pricey due to expensive parts?
> ...



Hey Zachi - I haven't had any RFI issues since adding in the EF37A, they are very quiet so far.  A properly positioned and valued grid stopper resistor should take care of it.  I suspect using adapters in the GOTL in combination with the top cap tubes likely is a contributor, as this places the grid stopper even further from the grid input.  I imagine it would be difficult to avoid RFI where you live though!  Sorry you have to deal with it.

I would have to find a pentode that is similarly linear with similar gain and no top cap to work in this design, I have not looked but there might be something out there.  One big advantage of the EF37A though is it is capable of taking up to a 450V B+ and g2 supply, whereas similar AF pentodes like the 6J7G are maxed out at a 300V supply.  Since the EF37A can take more voltage, I can easily run it off the same power supply rail as the 801A.  If I do end up moving the bias point of the 801A to closer to 320V on the plate, this would open up more driver tube possibilities.

With all of that being said, this amplifier is not a good choice for a community build.  Certainly a two-stage amp using a pentode input and NFB is possible, but it is done in this design out of necessity with the 801A output tube to improve output impedance and FR.  This is done for use with speakers, the NFB isn't necessary for headphones as they are typically a much higher impedance and good damping factors can be had even with the rather high output impedance of a SET amplifier.  This is one reason designing a headphone amp is an easier task than designing a speaker amp  this amp is also fixed bias with an A2 output stage, bias adjustment will probably be internal, so this isn't really a good one to build for other people.  It is also expensive!

I am hoping / planning to put together a simple parafeed headphone amplifier that I could potentially build for others, using the Sowter 8665 OPT, possibly a single-stage "spud" design, keeping the number of active components in the signal path to a minimum with high-quality parafeed output caps.  This idea is in the queue with the transformers ordered, but that is as much as I can say about it at the moment.  That will be the next project after I get all of this other stuff wrapped up.


----------



## Tjj226 Angel

L0rdGwyn said:


> Hey Zachi - I haven't had any RFI issues since adding in the EF37A, they are very quiet so far.  A properly positioned and valued grid stopper resistor should take care of it.  I suspect using adapters in the GOTL in combination with the top cap tubes likely is a contributor, as this places the grid stopper even further from the grid input.  I imagine it would be difficult to avoid RFI where you live though!  Sorry you have to deal with it.
> 
> I would have to find a pentode that is similarly linear with similar gain and no top cap to work in this design, I have not looked but there might be something out there.  One big advantage of the EF37A though is it is capable of taking up to a 450V B+ and g2 supply, whereas similar AF pentodes like the 6J7G are maxed out at a 300V supply.  Since the EF37A can take more voltage, I can easily run it off the same power supply rail as the 801A.  If I do end up moving the bias point of the 801A to closer to 320V on the plate, this would open up more driver tube possibilities.
> 
> ...



I wonder if you drop the output impedance of the 801a enough, could you get away with less output transformer impedance.


----------



## L0rdGwyn

I


Tjj226 Angel said:


> I wonder if you drop the output impedance of the 801a enough, could you get away with less output transformer impedance.



Yeah exactly, I am going to try it out, maybe you missed it in one of my wall of text posts, but I am going to throw my 3.3K LL1620 60mA in the prototype with a near 0Vg bias point as a test run, they are coming out of the 6A5G amp since it is being powder coated.  PB and audiowize got 8W out of an 801A A2 amp at around a 320V 60mA bias with a 3K primary.  I don't see how from the load lines I am drawing, but two different people got the same result, 8W is pretty nuts...


----------



## Tjj226 Angel

L0rdGwyn said:


> I
> 
> 
> Yeah exactly, I am going to try it out, maybe you missed it in one of my wall of text posts, but I am going to throw my 3.3K LL1620 60mA in the prototype with a near 0Vg bias point as a test run, they are coming out of the 6A5G amp since it is being powder coated.  PB and audiowize got 8W out of an 801A A2 amp at around a 320V 60mA bias with a 3K primary.  I don't see how from the load lines I am drawing, but two different people got the same result, 8W is pretty nuts...



I guess I must have missed it. Im a bit distracted these days to say the least lol.


----------



## L0rdGwyn

Tjj226 Angel said:


> I guess I must have missed it. Im a bit distracted these days to say the least lol.



I feel ya, sometimes it feels like I have two jobs working on these amps, but it keeps my mind occupied from all of the chaos.


----------



## Tjj226 Angel

L0rdGwyn said:


> I feel ya, sometimes it feels like I have two jobs working on these amps, but it keeps my mind occupied from all of the chaos.



Yeahhhh, my truck is still in the shop, so I am just flat out useless and all my projects are piling up. I HOPEFULLY get it back in a few hours, but I have had to chase after these guys more than once, so I am not holding my breath.


----------



## Zachik

L0rdGwyn said:


> If I do end up moving the bias point of the 801A to closer to 320V on the plate, this would open up more driver tube possibilities.


I am following your thread, and will most definitely keep an eye on such development 



L0rdGwyn said:


> With all of that being said, this amplifier is not a good choice for a community build.





L0rdGwyn said:


> This is done for use with speakers, the NFB isn't necessary for headphones as they are typically a much higher impedance and good damping factors can be had even with the rather high output impedance of a SET amplifier.





L0rdGwyn said:


> It is also expensive!


Does the NFB circuit make it expensive and thus not a good choice for community build?  or is it expensive regardless of NFB?
For me, having speaker taps is a clear advantage. But not a showstopper if they're not there...



L0rdGwyn said:


> I am hoping / planning to put together a simple parafeed headphone amplifier that I could potentially build for others, using the Sowter 8665 OPT, possibly a single-stage "spud" design, keeping the number of active components in the signal path to a minimum with high-quality parafeed output caps.


Interesting... which tubes would you use for such community build? 
Also, do you have a good pointer for reading on parafeed in general, and how it differs from OTL and SET amps?  Since I own Glenn's OTL and EL3N amps, I would like my next amps to sound different from them (since I do not intend to get rid of any of them )


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## whirlwind (Aug 11, 2020)

L0rdGwyn said:


> I am hoping / planning to put together a simple parafeed headphone amplifier that I could potentially build for others, using the Sowter 8665 OPT, possibly a single-stage "spud" design, keeping the number of active components in the signal path to a minimum with high-quality parafeed output caps.  This idea is in the queue with the transformers ordered, but that is as much as I can say about it at the moment.  That will be the next project after I get all of this other stuff wrapped up.



It will be interesting to see how this turns out...this should have a nice dark back round for headphone listening.

Many people love the "spud" designed amps.


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## 2359glenn (Aug 11, 2020)

I think a spud amp using a EML-20B should sound fantastic. Always wanted to build a amp with this tube.
Will be a costly build but few parts the less parts the better the sound.  KISS
http://www.emissionlabs.com/datasheets/20b-ota-1.pdf


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## L0rdGwyn (Aug 11, 2020)

Tjj226 Angel said:


> Yeahhhh, my truck is still in the shop, so I am just flat out useless and all my projects are piling up. I HOPEFULLY get it back in a few hours, but I have had to chase after these guys more than once, so I am not holding my breath.



Sorry to hear that, hopefully they get it up and running again, that can be a real mental burden.



Zachik said:


> Does the NFB circuit make it expensive and thus not a good choice for community build?  or is it expensive regardless of NFB?
> For me, having speaker taps is a clear advantage. But not a showstopper if they're not there...



The NFB circuit is not expensive, it is mostly related to the tubes themselves (the 801A is getting increasingly rare and expensive) and the sheer number of parts, this is a pretty BIG amplifier which will have a separate PS chassis, it has six transformers total.  Also, it is a fixed bias amp which is a little less user friendly than a "auto bias" amplifier, as the bias points of the tubes needs to be manually adjusted.  Since this is sort of a personal statement build, the plan right now is to have the bias adjustment on the inside.  Getting it set up to be accessible on the exterior with meters and pots present a totally new layout challenge and again, more parts and cost.  I hope that makes sense!  Just not a very user friendly design, overall, it's sort of a crazy experimental type of build.



Zachik said:


> Interesting... which tubes would you use for such community build?
> Also, do you have a good pointer for reading on parafeed in general, and how it differs from OTL and SET amps?  Since I own Glenn's OTL and EL3N amps, I would like my next amps to sound different from them (since I do not intend to get rid of any of them )



Not so sure on the tubes yet, but the Sowter 8665 has a 10K primary, which leaves open a lot of possibilities.  Max power output for that transformer is 500mW, so assuming I keep a 10K primary (depends on the secondary winding and impedance of the headphones used), that would mean using a tube that can swing a maximum 200Vpp into a 10K load, which means a gain of 35 maximum with a typical DAC 2Vrms input.  But 500mW is overkill, a lower gain tube would be fine too, there is some flexibility, my very vague plan right now is to try a bunch of different tubes out and see what sounds best!  Since I am NFB happy at the moment, maybe I will also experiment with a power pentode with cathode feedback  its just going to be a sandbox until I find a good sound.

Here is a resource that goes over what a parafeed amplifier is: http://diy.ecpaudio.com/p/parafeed-tutorial.html


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## L0rdGwyn (Aug 11, 2020)

2359glenn said:


> I think a spud amp using a EML-20B should sound fantastic. Always wanted to build a amp with this tube.
> Will be a costly build but few parts the less parts the better the sound.  KISS
> http://www.emissionlabs.com/datasheets/20b-ota-1.pdf



I have heard great things about the EML-20B Glenn, could be a good choice with a 3.3K anode resistance with a 10K OPT primary.  With a mu of 20, could get something like 150mW out of a spud headphone amp with it.  Would have to be a bit larger to house filament regulators / transformers, but it is an intriguing idea, I'll add it to the list of possibilities.  They are pricey though, youch.


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## 2359glenn

Why not just use the recommended transformer and forget about parafeed leave out that capacitor no capacitor really sounds good.


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## L0rdGwyn

2359glenn said:


> Why not just use the recommended transformer and forget about parafeed leave out that capacitor no capacitor really sounds good.



That transformer must be a custom job from Lundahl, I can't find it on their site.  Parafeed has many advantages too - smaller OPT for a more compact amp, better low frequency performance with higher primary inductance, using a cascode CCS load on the output rather than a choke will give over 100dB PSRR, which means a much simpler, smaller, and cheaper power supply with very low ripple.  The goal is to make a great sounding amp that is compact and cost effective, so a parafeed spud design fits well, I think the clarity will be very good with a single gain stage.  I think the trick is the cap setup has to be tuned by ear, getting great results in my 45 amp taking that approach.


----------



## Tjj226 Angel

2359glenn said:


> Why not just use the recommended transformer and forget about parafeed leave out that capacitor no capacitor really sounds good.



There is always a capacitor in your signal path. In a normal configuration the power supply capacitor and bypass capacitor are in series. In a parafeed configuration your parafeed cap and bypass capacitor are in series. 

At least with parafeed you get the noise floor reduction


----------



## Zachik

2359glenn said:


> I think a spud amp using a EML-20B should sound fantastic. Always wanted to build a amp with this tube.
> Will be a costly build but few parts the less parts the better the sound.  KISS
> http://www.emissionlabs.com/datasheets/20b-ota-1.pdf


Quick search yields more than $500 per tube!!! Yikes.


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## johnjen

And with a parafeed cap, what with it being a smaller value (≈5-6µfd), the suitability and availability of quality caps is much greater than power supply caps.
And yeah 'tuning it' by ear is really the only way to dial it in.
Even though high end non-polar caps in this range can be mighty expensive, at least the 'electrolytic smear' can be avoided.

JJ


----------



## Zachik

L0rdGwyn said:


> The NFB circuit is not expensive, it is mostly related to the tubes themselves (the 801A is getting increasingly rare and expensive) and the sheer number of parts, this is a pretty BIG amplifier which will have a separate PS chassis, it has six transformers total. Also, it is a fixed bias amp which is a little less user friendly than a "auto bias" amplifier, as the bias points of the tubes needs to be manually adjusted. Since this is sort of a personal statement build, the plan right now is to have the bias adjustment on the inside. Getting it set up to be accessible on the exterior with meters and pots present a totally new layout challenge and again, more parts and cost. I hope that makes sense! Just not a very user friendly design, overall, it's sort of a crazy experimental type of build.


OK. You got me convinced... not a good option for a community build, for several reasons...



L0rdGwyn said:


> Not so sure on the tubes yet, but the Sowter 8665 has a 10K primary, which leaves open a lot of possibilities. Max power output for that transformer is 500mW, so assuming I keep a 10K primary (depends on the secondary winding and impedance of the headphones used), that would mean using a tube that can swing a maximum 200Vpp into a 10K load, which means a gain of 35 maximum with a typical DAC 2Vrms input. But 500mW is overkill, a lower gain tube would be fine too, there is some flexibility, my very vague plan right now is to try a bunch of different tubes out and see what sounds best! Since I am NFB happy at the moment, maybe I will also experiment with a power pentode with cathode feedback  its just going to be a sandbox until I find a good sound.


Sounds interesting. Being a single stage amp would probably make it sound quite different from my GOTL and 6EL3N amps. Right?  and single stage would make it very low noise floor, I assume?
Do you plan on implementing parafeed for this amp?



L0rdGwyn said:


> Here is a resource that goes over what a parafeed amplifier is: http://diy.ecpaudio.com/p/parafeed-tutorial.html


Interesting read!  Thanks.


----------



## 2359glenn

Zachik said:


> Quick search yields more than $500 per tube!!! Yikes.



Not that unreasonable I paid allot more then that for 300Bs.
Might have to do something about that cathode resistor bypass capacitor and get it out of there.
My direct coupled 300B amp has no capacitors at all in the signal path except for the last capacitor in the power supply. That is a hard one to get rid of.


----------



## L0rdGwyn

Zachik said:


> Sounds interesting. Being a single stage amp would probably make it sound quite different from my GOTL and 6EL3N amps. Right?  and single stage would make it very low noise floor, I assume?
> Do you plan on implementing parafeed for this amp?



Yes, I would expect it to sound different!  Tube choice will play a large role in that, as will the parafeed capacitor configuration.  Does your 6EL3N amp have the ability to use a single stage like the GEL3N?  I know Glenn included that on some other amps, that switch essentially changes the amp to a spud amp, but not parafeed.

The noise floor should be very low yes.  I think they discuss it in that parafeed article, but you have two choices for the DC plate load of the output tube - a plate choke, or a CCS load.

The advantage of a plate choke is it allows the output tube to swing higher than your applied B+ voltage through energy stored in the choke (inductance).  The disadvantage is they are large, expensive, must have a suitabily high inductance to allow for passage of the lowest frequencies of the audio band, they also do not have the same level of PSRR (power supply rejection ratio) as the a CCS load.  You can think of PSRR as the degree to which power supply noise is squashed on the output signal.

The advantage of a CCS load is it is smaller, cheaper, gives much better PSRR to the point that the power supply does not need a significant amount of passive filtering, so it can be made very simple, small, and cheap!  The disadvantages (because there are always compromises ) is the CCS has to dissipate a significant amount of heat (the reason I have heat sinks mounted to the back of my 45 amp), you can use a pentode CCS to get this heat out of the chassis, but performance is compromised.  Also, there is no energy stored in a CCS allowing the tube to swing higher than the B+, meaning to get a full output swing, the amp requires a much higher B+, approximately equal to: 

(output tube plate voltage + cathode voltage) + 1/2*(peak-to-peak output tube voltage swing) + (CCS dropout voltage) + (headroom).  

For my 45 amp that I am reworking for speaker use, for example, I am looking at a 275V bias point on the plate.  But to get the full output swing with a CCS load, I will need something like a 500V B+!


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## L0rdGwyn (Aug 12, 2020)

Tjj226 Angel said:


> There is always a capacitor in your signal path. In a normal configuration the power supply capacitor and bypass capacitor are in series. In a parafeed configuration your parafeed cap and bypass capacitor are in series.
> 
> At least with parafeed you get the noise floor reduction





2359glenn said:


> Not that unreasonable I paid allot more then that for 300Bs.
> Might have to do something about that cathode resistor bypass capacitor and get it out of there.
> My direct coupled 300B amp has no capacitors at all in the signal path except for the last capacitor in the power supply. That is a hard one to get rid of.



Could use a Maida regulator and fixed bias.  This is what I am doing in the 801A amp, there are no capacitors in the output stage signal loop.  There is now a regulator, but the output impedance across the audio band is less than the resistance in the wires connecting it to the tube plate.  There are film caps in the signal of the driver stage though, no electrolytics!  Oh and there is a SiC transistor 

In the future, I plan to bring this amp to a meet, find the tube purist and let them listen.  Afterward I will tell them there is a transistor in the signal path and NFB, oh the horror!


----------



## Zachik

L0rdGwyn said:


> Does your 6EL3N amp have the ability to use a single stage like the GEL3N? I know Glenn included that on some other amps, that switch essentially changes the amp to a spud amp, but not parafeed.


Yes. Using this 1-stage mode, the amp becomes MUCH lower gain (obviously!), and even lower noise floor (pretty low vs. GOTL to begin with...). Work well for easy to drive dynamic driver headphones. Most of the time - I use the 2-stage mode, though.


----------



## Propagandist

This entire thread is just a wealth of wonderful, helpful information.  Thank you everyone, and especially LG, for being so descriptive and detailed in your posts.  As someone trying to design my own amp, your thoughts are extremely valuable.


----------



## L0rdGwyn

Propagandist said:


> This entire thread is just a wealth of wonderful, helpful information.  Thank you everyone, and especially LG, for being so descriptive and detailed in your posts.  As someone trying to design my own amp, your thoughts are extremely valuable.



Thanks for following along!  Happy to answer questions.  @Tjj226 Angel @2359glenn and @A2029 helped me get started, along with a handful of other DIYers on other forums, it has been a bottomless pit ever since.


----------



## Xcalibur255

I've brought up the 20B idea off and on for years now.  Basically just the same concept as the Inspire IHA-1 with a big fancy DHT in place of those 6SN7s.  The IHA-1 can't even call itself a true OTA because it has each section of the 6SN7 to work with.

Yamamoto also does their C3m single tube headphone amp.  Aside from that I can't think of many examples of this type of headphone amp off the top of my head.

I'm guessing the list of tubes that work well for this application are going to be pretty limited since you need both high enough gain and low enough Rp to get decent performance out of the OPT and it seems like those things don't often go hand in hand.


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## Xcalibur255 (Aug 12, 2020)

2359glenn said:


> Not that unreasonable I paid allot more then that for 300Bs.
> Might have to do something about that cathode resistor bypass capacitor and get it out of there.
> My direct coupled 300B amp has no capacitors at all in the signal path except for the last capacitor in the power supply. That is a hard one to get rid of.


This is the one with the 10 driver stage right?  I still want to own an integrated single chassis version of this before I die.  I have rolled idea after idea around in my head about what my "ultimate" end game amp would be, and time and time again I keep coming back to 10Y >>> 300B.  

AKA difficult and expensive.


----------



## L0rdGwyn (Aug 12, 2020)

So there seems to have been a disconnect as far as what 8W out of the 801A in A2 actually means...WARNING: wall of text.

This morning, I tried out the 3.3K OPT setup with the Lundahl LL1620 60mA.

I nixed my bias supply and just used 520K to ground, not ideal since the grid voltage isn't fine-tuneable, it is fixed by the gate-to-source voltage of my FET buffer, so -3.1V on the grid of the 801A.  I was able to adjust my bias point to some degree using the trimpot on the Maida regulator.  I dialed it in to a 335Va / 57mA / -3.1Vg bias point.

With this bias, I am getting 156V to 524V peak-to-peak swing on the 801A plate *without clipping*, hard clipping on the positive peaks starts beyond 524V.  This results in roughly 16V peak-to-peak into 8ohms, about 4W out.  This is pretty darn consistent with the datasheet if I draw out the load line, copper losses included.

Ideally, I would get to a true 0V bias point and 320V with a 3K (rather than 3.3K) primary impedance, it is doable, have to put +3V on the gate of my FET.  At that bias, if the datasheet is to be believed - and so far has been consistent with my measurements - even assuming no copper losses, that makes 5.5W into a 3K load without clipping.  Even if you did something crazy and biased at +10V on the grid at 280V on the plate, that is 400Vpp into 3K, makes a 6.4W.

Here is the 3.3K / 335V / 57mA / -3.1Vg load line.  As you can see, consistent with my measurements, the amp should clip at roughly 520-530V on the positive peaks.




So, I was very confused as I could not see how you could get 8W out of an 801A A2 amp at any 0V bias point.  Thought maybe some magic would happen if I tried it out, but it doesn't look like it.  As it turns out, the DIYers who suggested it were quoting power output from the full peak-to-peak voltage swing on the load line above, even though the 801A will hard clip on the positive peaks.  So, swinging from 70V to 524V into a 3.3K load, that does add up to about 8W.  However, the postivie signal is going to be chopped off above 524V.

That just isn't how I go about measuring power output, maybe my approach is flawed, but for me the power output is measured at peak-to-peak swing without hard clipping, so this is a 4W amplifier whereas I was getting closer to 5W with the LL9202 and my old 365V / 50mA / -10Vg bias point.

Just to see this experiment all the way through, I added additional NFB given the reduced gain needed from the driver stage, here are the measurements, FR curve below.  I believe I am hitting transformer limitations again, as the HF rolloff is nearly identical to what I am getting in the 6A5G amplifier.

Output Z: 3.4ohms
THD @ 1W 1.52%
-0.86 db at 20kHz



How about the sound going from the LL9202 50mA with a 6.5K 100H primary to the LL1620 60mA with a 3.3K 60H primary?

While the sound is still very good, my initial impression was that it took a step back, that degree of hyper-realism, airiness, and staging was lost to some extent.  I am going to give it another try later after a break.

So, while the bandwidth may have improved a tad, the output impedance is higher, we have higher distortion, more NFB, less power, and overall I feel the sound has degraded somewhat.  I am likely to return to the LL9202 and rebias the 801A at 350V for a full 5W output unclipped.


----------



## L0rdGwyn (Aug 12, 2020)

Xcalibur255 said:


> I've brought up the 20B idea off and on for years now.  Basically just the same concept as the Inspire IHA-1 with a big fancy DHT in place of those 6SN7s.  The IHA-1 can't even call itself a true OTA because it has each section of the 6SN7 to work with.
> 
> Yamamoto also does their C3m single tube headphone amp.  Aside from that I can't think of many examples of this type of headphone amp off the top of my head.
> 
> I'm guessing the list of tubes that work well for this application are going to be pretty limited since you need both high enough gain and low enough Rp to get decent performance out of the OPT and it seems like those things don't often go hand in hand.



You are exactly right @Xcalibur255 , the ideal spud tube is high gain, low plate resistance.  That is why the EL3N is a very good choice!  With a 3K plate resistance and a mu of 20, it makes for a good single stage tube.

There is something I have thought to experiment with though - it just an idea now, have not even simulated it yet - but using a cascode CCS plate load on the parafeed output, you could potentially take the mu output of the CCS as opposed to the plate, lowering the output impedance significantly.  This might make it possible to use higher Rp tubes in a spud parafeed design and get a low output impedance to adequately damp headphones.  If it works, could open up more possibilities with high Rp / mu tubes.  Maybe I will throw together another 700V PS and try it out with the 841, Rp of 25K, mu of 30   just for funsies though, not sending a 700V B+ amplifier out into the world!


----------



## Tjj226 Angel

Xcalibur255 said:


> I've brought up the 20B idea off and on for years now.  Basically just the same concept as the Inspire IHA-1 with a big fancy DHT in place of those 6SN7s.  The IHA-1 can't even call itself a true OTA because it has each section of the 6SN7 to work with.
> 
> Yamamoto also does their C3m single tube headphone amp.  Aside from that I can't think of many examples of this type of headphone amp off the top of my head.
> 
> I'm guessing the list of tubes that work well for this application are going to be pretty limited since you need both high enough gain and low enough Rp to get decent performance out of the OPT and it seems like those things don't often go hand in hand.




The list of tubes you can do this with is actually quite large. It just all depends on what you want and how you want to do it. 

First step is to figure out what headphones you are trying to drive. Lets look at the HD600/HD650 headphones as an example. I will skip the math and the technicalities and just sort of skip straight to the answers so that you can better understand what is going on without getting confused. 

A HD600 has a sensitivity of 105 db at 1 volt. In order to hit 120db peaks, we need the amplifier to provide 6v peak to peak with headroom, so we will probably want to design the amp so that it can output 7v peak to peak. We know that ohms law tells us that the current we need at 7v into a 300ohm headphone is 23.333... ma. Lets just say we need 30ma as a fudge factor. 

Since most dacs these days will output 2v RMS which is ~2.83 v, we need an amp with a total gain of about 2.5ish. Again, lets call it 3 for the sake of having plenty of margin to play with. 

Now you need to find a combination of a tube and output transformer that will yield a total gain of 3 with a bias current of 30ma (you actually don't need 30ma for a number of reasons, but as you know by know, I like have a ton of margin in my designs). 

Keep in mind that a 5K to 300ohm transformer has a voltage ratio of 4, and a 10K to 300ohm transformer has a ratio of about 6. So we need to look at tubes with a gain of somewhere in the mid teen range. A pro tip here is to choose a twin triode tube that can be paralleled. I normally don't like paralleling tubes since it is kind of a pain to find twin triodes that are well matched, but paralleling tubes will actually reduce their self noise by 3db. Considering the low winding ratio of the transformer, we need all the help we can get in order to make the amp quiet. 

The ever venerable 5687 would be the perfect tube for this application. In parallel the bias current would be above 40ma, the gain is about 17, and the plate impedance would be reduced to about 1K. 

I would use two united SIC Jfets as a CCS for the plate load (about. 15 bucks per channel), and a edcor xsm 15K to 600ohm transformer that you would be using as a 7.5K to 300 ohm transformer which would cost another 15 bucks per side. 

Alternatively, you could use tubes like the 6E5P with an unbypassed cathode resistor to reduce gain and increase plate impedance to match the same configuration as the 5687 for even less money.


----------



## 2359glenn

L0rdGwyn said:


> You are exactly right @Xcalibur255 , the ideal spud tube is high gain, low plate resistance.  That is why the EL3N is a very good choice!  With a 3K plate resistance and a mu of 20, it makes for a good single stage tube.
> 
> There is something I have thought to experiment with though - it just an idea now, have not even simulated it yet - but using a cascode CCS plate load on the parafeed output, you could potentially take the mu output of the CCS as opposed to the plate, lowering the output impedance significantly.  This might make it possible to use higher Rp tubes in a spud parafeed design and get a low output impedance to adequately damp headphones.  If it works, could open up more possibilities with high Rp / mu tubes.  Maybe I will throw together another 700V PS and try it out with the 841, Rp of 25K, mu of 30   just for funsies though, not sending a 700V B+ amplifier out into the world!



The EL3N is a really good sounding tube also. But to really use it in a spud amp  really needs a input transformer to boost the input signal to get a decent output.


----------



## 2359glenn

Xcalibur255 said:


> This is the one with the 10 driver stage right?  I still want to own an integrated single chassis version of this before I die.  I have rolled idea after idea around in my head about what my "ultimate" end game amp would be, and time and time again I keep coming back to 10Y >>> 300B.
> 
> AKA difficult and expensive.



The 10Y>300B sounds great had them for 16 years now.
But I don't think I would make this direct coupled amp for anyone as the B+ voltage is 850


----------



## L0rdGwyn (Aug 13, 2020)

I've had a breakthrough in the 801A A2 amp design, a new path forward.

But first, a mistake was made.  Remember when I said I was getting a 0.38ohm output impedance? That turned out to be false LOL I thought it was suspiciously low at the time given that I had not drastically altered the feedback fraction, those results were not reproducible, so something was off at the time.

I am more consistently getting output impedances around 2.8ohm with various feedback setups I have tried with the resistively loaded pentode stage.  This is borderline high, I am seeking a damping factor of 3 or more for 8ohm speakers, so 2.8ohms on the output ain't really gonna cut it.

So what to do.  Altering the degree of NFB via my cathode trimmers improves the output impedance, albeit marginally, but increasing it too much and the stage does not have enough gain to drive the 801A to clipping.  As I mentioned, I have left the cathode of the EF37A unbypassed / degenerated, meaning there is internal NFB, which reduces the gain.  I decided to try bypassing the cathode with a 500uF electrolytic to see what it got me...I also added a film cap to my feedback loop to take the DC current out of the equation, making the bias process of the EF37A much more straightforward.

Open loop mu of the EF37A stage jumped from 40 to 100 with the cathode bypassed.  Closed loop measurements in this setup below.

THD @ 1W 1%
Output Z: 2.8ohms
-2.4dB @ 20kHz




So we have some improvement in THD, output Z is largely the same, rolloff at 20kHz is unchanged but improved at 17kHz.

How about the subjective sound?  A step back, no question, as there is now an electrolytic in the signal path  less detail, degree of realism and space has diminished, more "smeared".

So now what?  I need more gain out of my input stage to increase NFB, lower the output impedance for proper 8ohm damping, and continue to improve bandwidth.  At this point though, I am reaching the limits of what can be done with a resistor loaded stage, using 220K on the plate of the EF37A.

I did spend all that time learning about CCS loaded pentodes...*LET'S DO IT  *

One of the difficulties with using one of these stages is dialing in the CCS to provide the anode current for the pentode in addition to the plate load resistor, which is grounded.  The benefit is the ability to use a higher resistor value that is typically practical on the plate of the pentode, continuing to flatten the load line and increase gain of the stage beyond the quoted specification.  In addition, the CCS provides the same PSRR you could expect in a CCS loaded triode stage (not that it is needed in this amp, with the Maida regulator + CCS, ripple is being crushed to the tune of >200dB PSRR!).

The disadvantage is DC bias point stability.  With a nearly flat load line, small changes in cathode voltage result in big swings in bias point, so there is the potential for bias point drift.  I figured if I used a larger plate load resistor without going nuts, I could get away with it.  I settled on 470K.

So, the CCS stage was simulated in LTSpice to get ballpark figures, and away we went.  Here is what it looks like now.  Yup it is an absolute disaster, but hey its a prototype on a piece of wood  I needed to throw a 1K resistor in series with my CCS trimmers to get the current down to EF37A levels.



After some tweaking, dialing-in of voltages / currents, we settled on the following EF37A bias with the CCS in place: CCS current 1.56mA / Va 240 / Vg2 95V / Vk 2.77V.

I measured the open loop mu of the stage *without a bypass cap, *it went from 40 to 125!!! Eff off electrolytic, I don't need you  now getting more open loop gain than with the resistively loaded stage WITH bypass.  As a result, the input was driving the 801A to clipping and then some, allowing me to further increase the feedback fraction.

So, how about the measurements...

THD @ 1W 0.44%
Output Z 2.44ohm
-1.67dB @ 20kHz



1kHz sine wave at full output, 18.06Vpp into 8ohms = 5.2W



Yeah...big gains across the board.  Now will get a >3 damping factor for 8ohm speakers, further HF extension, lower THD, and I got my 5 watts.

The sound is back to its airy, realistic, hyper-detailed state with the electrolytic out of the picture.

I monitored the plate and cathode voltages of the EF37A with music playing at varying volumes, did several shut-downs and start-ups as well - the bias does not drift, it finds its way right back to the same point every time.

So this is the way forward, keeping the CCS, more tweaking and optimization to come, but it is undoubtedly an improvement.

Just to show what further gains could be had measurements wise if the plate load resistor is further increased (which will in turn increase the gain of the stage and NFB), here are the measurements repeated with the cathode bypassed with the 500uF electrolytic with the CCS in place.

THD @ 1W 0.24%
Output Z 2.15ohm
-1.19dB @ 20kHz



Will continue to improve the design, but it's time to call it a day!


----------



## L0rdGwyn (Aug 13, 2020)

I have one more result to share.  For the above, I included a film cap in the feedback loop to block DC from the 801A plate.  However, I have seen feedback implemented without a cap.

No doubt including this capacitor degrades the sound, I was aware but didn't realize how significantly until I removed it again and got the original sound back, keeping it out of the loop and creating stable NFB without it is now imperative.  What's more, the is the first time it has been removed from the loop and the CCS pentode stage has been implemented.  I adjusted the trimmers to account for the DC current from the 801A plate, which is now part of the bias.  This rebias resulted in additional gain, and I was able to further adjust the feedback fraction.  This is my best result yet, objectively and subjectively speaking, this is the best it has ever measured or ever sounded.

THD @ 1W 0.25%
Output Z 2.14ohm

In my excitement, I didn't measure the rolloff at 20kHz, but this is the widest bandwidth I have seen, looks to me to be about -1dB at 20kHz.



The goal now is to maintain this sound while ensuring amplifier stability, there are now a few semi-exotic circuit elements in this amplifier, have to be sure they are going to play nicely together long term.


----------



## Xcalibur255

I wonder how many people would have put their first iteration into a chassis and listened to it that way for a long time.  This has been an inspirational read in so many ways, how you keep going back again and again for more improvement and keep succeeding.  In a pretty darn short period of time too I might add!


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## L0rdGwyn

Thanks @Xcalibur255 , that's very nice of you to say.  It isn't all sunshine and rainbows though unfortunately, even just today I have new issues to troubleshoot.  Many times a new change raises more questions than it answers!  So it will still be quite a while until this design is done.  But I know what it is capable of and that is motivating, just a matter of making all the pieces work in concert.  I will be happy and relieved when everything is finalized and I just have to work on the chassis, which will be a challenge in and of itself.  Have to admit getting a little fatigued, but I hope all of the posting here has been enjoyable to follow.


----------



## johnjen

The 1st iterations of our 45 amp went thru, too numerous to mention, wiring layout changes and circuit modifications.
And then we scrapped it and tried the 2nd iteration in a whole new chassis which never really gelled.
The latest iteration of the 45 amp will be considerably smaller and less cumbersome all the way around.

And the Purp-Amp 71A/6BQ7A HP amp has also gone thru numerous circuit 'enhancements' and re-wire changes.
It has taken months to dial it all in and find out what does, and does not work, and why.

And once the next generation of gear is up and running, the Purp-Amp will get 're-freshed' with new selected critical parts with even further refinements added to 'complete' the build to make it a 'finished' amp.
Right now it’s a 'hobbyist' amp, meaning it is 'fussy'. 
For me that isn't really a problem but for a usual audioist it wouldn't be considered a 'finished product'.

Although it has reached a degree of SQ that makes it suitable as a 'reference' for comparison to the up and coming new kids on the block.
Namely a 26 pre-amp, a 45 HP amp, a 300B HP/Spkr amp, and a pair of derivative Western Electric 124 mono block Spkr amps, and more.

In motorcycling it’s the journey, not the destination, that is the portion of the whole experience that is most memorable.
Audio gives us both facets, the journey and the destination, as each yields 'the gud stuff', from the whole experience.

JJ


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## L0rdGwyn

Thanks for your thoughts @johnjen , looking forward to seeing the new 45 amp come to fruition!  Certainly the experience is just as important as the destination.  This amplifier has turned into a test bed for experimenting with several new circuit elements, so no matter the outcome, I will be more knowledgeable on the other side and the better for it


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## johnjen

Learning curves are like that, you get to learn what does work, and also what works better, sorta after the fact, which can be applied in v.2.

I have found that learning what NOT to do is more than 50% of the learning curve in terms of being valuable in a build, and most of this isn't found in books nor writeups.

For instance, is it 'better' to ground each component (input connector, input xfmr, volume control etc.) separately? 
Or tie them together at a 'key' point for a single 'star' ground connection?
This example along with grounding issues and related specific design implementations have a propensity to be mostly a matter of learn by doing, and in more cases than not, on a case by case basis.

It's all FM (Fricken Magic)…
hahahahahahahahahahahahahahahaha     

JJ


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## L0rdGwyn (Aug 16, 2020)

@whirlwind your modified GOTL is done!  Sorry for the delay, when you told me the ECC32 was one of your favorites, I had to go back and be sure the new bias point with the CCS load was a subjective improvement.  I am happy to say it is, very noticeable gains in soundstage and clarity, so I think you will be pleased.  Using the CCS load will get the load line out of the "knee" of the ECC32 curves, so that is a large part of the improvement I am sure.  Obviously the amp was  not built for ECC32 it is not an exact equivalent to the 6SN7, so balancing the two bias points was the goal with the available B+, very happy with the result.

Here is the interior just before closing.



It will be on its way home tomorrow.  Since I no longer have an amp for them, had to have a listen to some very rare tubes in my collection, the Tung Sol 7802.  Sounds great with the ECC32


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## L0rdGwyn (Aug 16, 2020)

Some of my powder coating equipment is starting to arrive.  Unfortunately, seems the COVID situation has inspired many people to start powder coating, so a significant amount of the gear I purchased is backordered.  It will be another couple weeks before I can start working on it.

Here is one important part though, the largest toaster oven on the market!  From my research at least.  Has to hit 400F to bake the parts after coating.



The interior of the oven will dictate the largest dimension chassis I can coat, the reason it is so big.  Here is the top plate of the new 6A5 amplifier chassis inside, it is 15 inches wide.  I can probably go as large as 16.5in.  Works for me, I'm not very interested in building amplifiers larger than that anyway.



I have the powder as well, I ordered 1lbs of two different finishes, they will go on test parts to see the in person result before a final decision is made.

Stage Pass Bronze
https://www.prismaticpowders.com/shop/powder-coating-colors/PMB-8157/stage-pass-bronze



Yankee Gold
https://www.prismaticpowders.com/shop/powder-coating-colors/UMB-1807/yankee-gold



The Stage Pass Bronze photo doesn't really do it justice, Prismatic Powders has YouTube videos for each finish showing a part being moving around to display how it changes in different lighting, which really makes the bronze pop.


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## L0rdGwyn

So, I _thought_ it was going to be a couple weeks until I had the powder coating equipment based on an email I received, turns out it is being delivered tomorrow.  But I have to work, and will be out of town this weekend, so I probably won't get to it until late next week.

Regardless, I figured I should go ahead and get the prep work done for the new 6A5 amp chassis.  Not trivial, as the layout is changing, so I had to dismantle the old version, figure out exactly how everything was going to fit in the new version, mark up the chassis and do the drilling.  Got started yesterday evening, then worked on it another 4-5 hours today.

But it's done!  So now when I have the time, I can jump right into the coating process.

  

I will have to do some final prep work the day of the coating, buffing out some minor scratches in the raw metal, cleaning, then going over the surface with a tack cloth.  Holes will be filled with silcon plugs and certain portions masked with high temperature tape.  Will have some practice with scrap metal first.

Fortunately, when the coating is done, putting it back together should be relatively quick since a portion of the original wiring was left intact.

Very excited to get this amp back up in running, improved, and I can finally try out my Mazda AC/HL drivers.


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## Xcalibur255 (Aug 19, 2020)

Tjj226 Angel said:


> The list of tubes you can do this with is actually quite large. It just all depends on what you want and how you want to do it.
> 
> First step is to figure out what headphones you are trying to drive. Lets look at the HD600/HD650 headphones as an example. I will skip the math and the technicalities and just sort of skip straight to the answers so that you can better understand what is going on without getting confused.
> 
> ...



If you have a few minutes to spare would it be possible to walk us through another scenario like this? 

Let's assume we want to build an integrated speaker amplifier with an output impedance targeted for 8 ohm load speakers and input sensitivity appropriate for being driven by a typical 2V output DAC.  If we want to use the KT150 as an output tube in this amplifier in a triode connected application (setting aside for the moment whether or not this is a good idea and just assuming it as a fact of the design), what would we be looking for in the ideal driver stage tube assuming we want the amplifier to be *reasonably* affordable and a 2-stage design that would be comfortable driving a speaker anywhere in the 88-98dB sensitivity range to reasonable volumes?


----------



## leftside

L0rdGwyn said:


> So, I _thought_ it was going to be a couple weeks until I had the powder coating equipment based on an email I received, turns out it is being delivered tomorrow.  But I have to work, and will be out of town this weekend, so I probably won't get to it until late next week.
> 
> Regardless, I figured I should go ahead and get the prep work done for the new 6A5 amp chassis.  Not trivial, as the layout is changing, so I had to dismantle the old version, figure out exactly how everything was going to fit in the new version, mark up the chassis and do the drilling.  Got started yesterday evening, then worked on it another 4-5 hours today.
> 
> ...


Following along. Mischa and I are also considering different coating/case options. I want my next amp to have a similar coating/case/appearance as my DAC.


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## Zachik

leftside said:


> Following along. Mischa and I are also considering different coating/case options. I want my next amp to have a similar coating/case/appearance as my DAC.


Can you share some details on said next amp?
(I am sure LG won't mind "hijacking" his thread, especially since we're discussing DIY amps after all...)


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## L0rdGwyn

leftside said:


> Following along. Mischa and I are also considering different coating/case options. I want my next amp to have a similar coating/case/appearance as my DAC.



The pressure is on  hope it turns out well.  Going to a shop might get a more ideal result, but seeing as I intend to do this long term, that would definitely add up, so I felt it was very DIYable.  I'm a little concerned about coating the interior of the tube socket vents, the powder coating gun I purchased has two voltage settings, which should help (small crevices can be difficult to coat due to the Faraday effect).  So we'll see, worst case scenario you guys can see how NOT to do things, but hoping for a good result.


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## leftside

Zachik said:


> Can you share some details on said next amp?
> (I am sure LG won't mind "hijacking" his thread, especially since we're discussing DIY amps after all...)


When Mischa is ready to start the build on this amp I'll provide more details for sure. Power tubes will be based on the power tubes I already have: EL34/KT66/KT77/6L6. Driver tubes will probably be fixed at 6J5 + 6SN7. I'll post details in the 1101 thread. There is no rush on my side for this amp, so it might not be until the end of the year.


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## A2029

Xcalibur255 said:


> If you have a few minutes to spare would it be possible to walk us through another scenario like this?
> 
> Let's assume we want to build an integrated speaker amplifier with an output impedance targeted for 8 ohm load speakers and input sensitivity appropriate for being driven by a typical 2V output DAC.  If we want to use the KT150 as an output tube in this amplifier in a triode connected application (setting aside for the moment whether or not this is a good idea and just assuming it as a fact of the design), what would we be looking for in the ideal driver stage tube assuming we want the amplifier to be *reasonably* affordable and a 2-stage design that would be comfortable driving a speaker anywhere in the 88-98dB sensitivity range to reasonable volumes?



If you want to do only two stages, driver and power tube, then a driver with a gain of approx 25+ would be needed to drive the KT150s to clipping when the KT150 is biased at high voltage (I'll be running mine around 580V). This could be accomplished with a 12BY7/12HL7/12HG7/12GN7 when triode strapped and with a constant current source (what I'm using), but there are many other options for tubes with enough gain. A lower biased KT150 could get away with a driver with a gain of even 20. This opens things up to more options for the driver. A single KT150 tube per side in this scenario could give you up to 15-18W into 8 ohms, while a parallel pair per side could give you 25-30W or more (depending on how high output impedance and distortion you are okay with when choosing your output transformer) into 8 ohms.


----------



## Xcalibur255

Thanks Mischa!  So a slightly more conservative design targeting 10-12 watts could use a 6J5 driver stage then.  It's good to know my basic idea was viable.


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## Tjj226 Angel

Xcalibur255 said:


> If you have a few minutes to spare would it be possible to walk us through another scenario like this?
> 
> Let's assume we want to build an integrated speaker amplifier with an output impedance targeted for 8 ohm load speakers and input sensitivity appropriate for being driven by a typical 2V output DAC.  If we want to use the KT150 as an output tube in this amplifier in a triode connected application (setting aside for the moment whether or not this is a good idea and just assuming it as a fact of the design), what would we be looking for in the ideal driver stage tube assuming we want the amplifier to be *reasonably* affordable and a 2-stage design that would be comfortable driving a speaker anywhere in the 88-98dB sensitivity range to reasonable volumes?



@A2029 is correct as far as I can tell. The problem is that I can't seem to find any data sheet for the KT150 with the triode data on it. 

But generally speaking the way you would solve this is by finding the bias voltage of your power tube, then you divide that number by your input PEAK VOLTAGE (very important). This gives you the bare minimum amount of gain you would need to drive the KT150 into clipping under the assumption that your preamp tube will achieve maximum theoretical gain. 

Since that never happens, I would add 20% to what ever number you come up with just to be on the safe side. 

So lets assume that your bias voltage is 60v for the KT150. You first take your input voltage in RMS and convert it to peak voltage. To do that all you have to do is multiply your RMS voltage by the square root of 2 which is about 1.41. What you find is that 2v rms is about 2.83v peak. 

Then you divide 60v by 2.83 and you get about 21.2. So you need a BARE MINIMUM gain of 21.2. If you chuck on 20% you end up with right about 25. ( I tried to choose numbers that would match with A2029's example).


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## Xcalibur255 (Aug 19, 2020)

So let's say we decide to use a driver that does *not* have sufficient gain to drive the output stage to clipping.  Say for example, we're going to use a 45 to drive this KT150, consequences be damned!    What would be the most significant negative consequence of this?  Is it just a matter of the amp not achieving its theoretical best output power rating, or are there more meaningful consequences like increasing distortion or moving the output tube's operating point to somewhere undesirable?

Thanks so much guys for being willing to share your time to teach here.


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## A2029

Xcalibur255 said:


> So let's say we decide to use a driver that does *not* have sufficient gain to drive the output stage to clipping.  Say for example, we're going to use a 45 to drive this KT150, consequences be damned!    What would be the most significant negative consequence of this?  Is it just a matter of the amp not achieving its theoretical best output power rating, or are there more meaningful consequences like increasing distortion or moving the output tube's operating point to somewhere undesirable?
> 
> Thanks so much guys for being willing to share your time to teach here.



No negatives other than just not getting full potential power out of the amp


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## Tjj226 Angel

Xcalibur255 said:


> So let's say we decide to use a driver that does *not* have sufficient gain to drive the output stage to clipping.  Say for example, we're going to use a 45 to drive this KT150, consequences be damned!    What would be the most significant negative consequence of this?  Is it just a matter of the amp not achieving its theoretical best output power rating, or are there more meaningful consequences like increasing distortion or moving the output tube's operating point to somewhere undesirable?
> 
> Thanks so much guys for being willing to share your time to teach here.



Loss of power. Remember that power and volume in this case go hand in hand. An output transformer literally takes all your voltage/volume gain and steps it down as a part of the process for impedance matching. 

If you don't have enough voltage gain / volume gain / "power" on the primary side of the transformer, your amp will be realllll quiet on the other side of the transformer. 

That being said, you don't have to go for maximum power if you know that less watts will suffice. For headphones, I think this it is fairly common to see tube amps run with less than max power. But for speaker tube amps.......yeahhhhh you are going to want max power.


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## L0rdGwyn (Aug 23, 2020)

Got home early from my weekend trip, so you know what that means...powder coating time!

I got everything set up: powder coating stand, powder coating gun, pancake air compressor, toaster oven, masking materials, etc.  Most of this stuff was purchased from Eastwood who sell DIY powder coating gear.  Have to admit, the quality of some of the stuff was very suspect, but I was able to get it all working to a satisfactory degree.




Here is the rear panel after masking and coating, holes filled with silicon plugs, high temperature tape to mask some of the interior metal faces.



Then off to the oven we go!  12 minutes at 400 F, used an IR thermometer to monitor the part temperature.  I found the oven ran a little hot, so setting it to 375F got us to a real world 400F.  It was hot as hell in my garage, all the windows and door shut so as to not let in a draft for coating, plus a 400F oven, this was completely miserable work LOL.



Here is the top plate after coating.  I went pretty heavy with the powder, I wanted to be sure I got the interior of the vents and socket cut out since they are bottom mounted.



So how did it turn out?  Considering this was my first crack at this, I think pretty well.  The color is called Stage Pass Bronze.  It is a metallic and changes in different light, I really like it.

  

I was able to keep the interior relatively powder coat free with my masking job, great for grounding purposes.



I would say 3/5 parts turned out perfect, the top plate has some speckling, maybe some dust got on top after I prepped the part, maybe due to my heavy coat, I think I can live with it though.  One of the side panels was nudged by some aluminum foil in the oven, so I am going to redo it.  Not a huge blemish, but it will drive me crazy!  Still soul searching on the top plate speckling.

So there you have it, powder coating is doable.  I like the color, I will give myself a B on the job, will reorder the side panel to fix it and probably live with the blemishes on the top plate.


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## L0rdGwyn (Aug 29, 2020)

I have been very busy, two days of nonstop work...

First, valuable lessons learned in powder coating.  If anyone is insane enough to try this, I cannot stress enough how garbage the pancake air compressor from Eastwood is, do not buy!  I went ahead and replaced it with a much nicer air compressor (and quieter), which made a huge improvement in the coating process.  I bought a higher quality air pressure regulator for the powder coating gun as well.  Essentially, the gun itself was the only valuable component purchased from Eastwood.



I received the replacement parts for the 6A5 chassis from Dave at Landfall.  Side note - he seems interested in powder coating as an alternative to aluminum anodization, I am going to share my results with him, perhaps he will reach out to a powder coating shop local to him.  Anyway, I decided that the blemishes on the top plate were going to drive me crazy down the road, so I ordered a new top plate in addition to the replacement side panel.  Redid the drilling, prepped the parts, and coated once again.  Had to respray a few times, but in the end, I got what I would consider a top-notch finish on the chassis, more to come on that 

Since I did have to respray a few times, the powder on the bottom of the top plate began to build up, covering the portion that makes contact with the side panels to ground the chassis.  To clean it up and reestablish the ground connection, I sanded the top plate interior, first with 80 grit to remove the coating, the 180 grit to smooth things out.



So in the end, I got my perfect chassis   

I also learned from an earlier mistake and got a drop cloth to cover my in-progress projects in my garage, the powder gets EVERYWHERE.  Not unexpected, but it made more of a mess than I anticipated.

Anyway, so the powder coating experiment was a success, I now have a very robust setup with high quality parts for future amplifiers.

Now on to the end result...


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## L0rdGwyn (Aug 29, 2020)

Here is the new-and-improved 6A5G SET amplifier.

Most important part first, the circuit.



I think I've listed off the changes before, but here they are once more.

New grounding scheme (distributed star ground)
Additional passive filtering in power supply
4V / 5V combination rectifier socket changed to 4V only (U18/20, FW4/500, etc.)
DC heater regulator for driver tubes, allowing the use of 4V drivers of varying current rating
CCS kits swapped for boards of my design, mu-output from CCS to output stage
Clarity Cap ESA film bypass caps on 6A5G cathodes
NOS Mills MRA non-inductive wirewound resistors on 6A5G cathodes
Improved ventilation
XLR jack removed
Combination rectifer socket was replaced with a dedicated B4/B5 socket from Yamamoto.  Center pin removed as the U18/20 has a B4 base.

 

Rear panel with RCA inputs, speaker outputs, Goldpoint speaker / headphone output switch.



And some shots of the amp itself with the Mazda AC/HL driver, Philco (Sylvania) 6A5G outputs, and GEC U18/20 rectifier.

 

Back my stereo where it belongs.

 

Can finally check this one off the list, I am very happy with how it turned out.  Now back to two (or three?) projects in-progress, the 45 amp upgrade and the A2 monster...updates to come on that front.


----------



## Zachik

VERY impressive!


----------



## L0rdGwyn

Thanks, @Zachik , I appreciate it.

Just a quick update on the 801A A2 amplifier, I have been working on it in the background, troubleshooting, testing...I decided not to include all of that detail here, but I have reached a conclusion on the amplifier: the Lundahl LL9202 will need to go.  The transformers were purchased with the intention of using an 11K primary with no NFB, they were adapted to the NFB design rewired for a 6.5K primary.  While the bandwidth is improved with feedback added, it is JUST good enough, and adding any capacitance to stabilize the feedback loop leads to HF rolloff, reversing the gains made by adding feedback in the first place.

While needing to add capacitance to the feedback loop is not a foregone conclusion, I've become frustrated with the transformers being a bottleneck for the design.  While it is entirely possible they are in part responsible for the great sound I heard out of the prototype, I've decided it is worth going another direction where there is no question of bandwidth limitations or quality.

I am having a pair of custom OPT wound for me by Sowter UK, specifically for this design. They will be 5K:8ohm, 60mA DC with plenty of bandwidth to play with.  I already have another order pending with Sowter, so simple enough to keep adding on and spending my hard-earned money!  The design was discussed with Brian Sowter and he made a recommendation on the size, power output specs, etc.

This will likely mean a new bias point as well.  With a 5K primary, a 330V, 55mA bias is near ideal, it might turn into a full A2 design with a near 0V bias on the grid, we will see.

If for whatever reason the transformers don't work out in the A2 design, there are numerous possibilities with a 5K 60mA OPT.  I think I lost my mind the other day and starting looking at PX25 schematics...ABORT ABORT!

Anyway, this means some design changes, alterations to the bias and B+ supplies.  This one is a long way from being done, but we are learning a lot along the way, which is valuable.


----------



## leftside

Looks amazing! Love the color. A very clean and bold look. Bet it also sounds amazing.

How about building a preamp next? A custom preamp with emphasis on the phono stage has been my most recent purchase. Should get it by the winter. PM if interested, as I don't want to pollute your wonderful thread.


----------



## Zachik

leftside said:


> Looks amazing! Love the color. A very clean and bold look. Bet it also sounds amazing.
> 
> How about building a preamp next? A custom preamp with emphasis on the phono stage has been my most recent purchase. Should get it by the winter. PM if interested, as I don't want to pollute your wonderful thread.


Another build by Mischa?


----------



## leftside

Zachik said:


> Another build by Mischa?


Mischa is doing my next amp  This preamp is by a fellow mountain biker in Australia: http://www.supratek.com.au/. I will sell my McIntosh C500 preamp to fund this project. The Mac is a great looking preamp and it's served me well over the years, but I have the boutique/custom bug, but I don't have the hardware skills of @L0rdGwyn... This preamp has the inputs/outputs I require (off the shelf preamps always have lot's of inputs I never use) and of course it's meant to have a fabulous phono stage. Luckily, I already have most of the tubes that will go in the Supratek. I've been researching this project for a while. Supratek is not too widely known, but there is plenty of chat about these preamps on Audiogon.com and stereo.net.au.


----------



## chrisdrop

L0rdGwyn said:


> Here is the new-and-improved 6A5G SET amplifier.
> 
> Most important part first, the circuit.
> 
> ...


Congrats. It looks great inside and out. I admire the persistence to get it *exactly* how you want it. I am sure it has been personally rewarding on so many levels. I love how the drive to complete a project can take you into learning about anything that will make the project better. The best way to learn something is to just get stuck into a project and it'll take you places.


----------



## whirlwind

L0rdGwyn said:


> Here is the new-and-improved 6A5G SET amplifier.
> 
> Most important part first, the circuit.
> 
> ...



Great job!  That color looks killer. I bet it sounds as good as it looks to


----------



## L0rdGwyn

leftside said:


> Looks amazing! Love the color. A very clean and bold look. Bet it also sounds amazing.
> 
> How about building a preamp next? A custom preamp with emphasis on the phono stage has been my most recent purchase. Should get it by the winter. PM if interested, as I don't want to pollute your wonderful thread.



Thanks @leftside , it does sound great, looking forward to getting off work tonight and spending more time with it.  Designing a phono stage or phono preamp is pretty high on my list of potential projects as I am in need of a new phono stage, I'll reach out when I get serious about it and see what you've got cooking!  I am hoping for a relatively simple and predictable design, nothing crazy that will need prototyping.



chrisdrop said:


> Congrats. It looks great inside and out. I admire the persistence to get it *exactly* how you want it. I am sure it has been personally rewarding on so many levels. I love how the drive to complete a project can take you into learning about anything that will make the project better. The best way to learn something is to just get stuck into a project and it'll take you places.



You are right @chrisdrop , ultimately I wasn't content with the finish on version 1 of this amp, so a new method had to be explored!  Wasn't sure how that would end up, very relieved things went (mostly) according to plan.

I nearly had a heart attack on first listen, the amp sounded terrible and I was measuring 5% THD at 1W!!!  Turns out my test DAC was bugging out, a restart fixed the issue, went from extreme disappointment to elation in a series of minutes HA!  DIY is an emotional rollercoaster.


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## L0rdGwyn (Sep 1, 2020)

Nice to come home from a long day and unwind to some music, had a listen to some highly cherished 4V drivers from my collection, the Telefunken REN904.




Before settling in, I took a few measurements.

THD at 1W is 1.3%.  One thing I didn't expect though, this amp is putting out over 4W without hard clipping.  The 6A5G is rated at 3.75W at 5% THD in class A1, below is a 1kHz sine wave at 4.2W into 8ohm at less than 5% THD.



So the amp is a bit beefier than I expected, and with a 3.3K plate load as opposed to the 2.5K load from the spec sheet, I'll have to verify these measurements at a later date, but right now it is time to enjoy the music


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## Xcalibur255

Emotional rollercoaster describes the whole hobby.  It's worth it though.


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## JazzVinyl

L0rdGwyn said:


> Nice to come home from a long day and unwind to some music, had a listen to some highly cherished 4V drivers from my collection, the Telefunken REN904.
> 
> 
> 
> ...




Sure is a pretty amp!!


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## L0rdGwyn

Thanks @JazzVinyl , much appreciated!  I like the look of it with the Mazda AC/HL drivers, took me a long time to find those tubes and they sound great.



I rechecked the measurements I posted above after stepping away for a day, as I suspected they were inaccurate.

True to the datasheet, this is roughly a 3.75W into 8ohm amplifier at 5% THD at max output, roughly 1.5% THD at 1W into 8ohm.

Here is the frequency response, down about 1dB at 20Hz and 20kHz, similar to version 1.


----------



## L0rdGwyn (Sep 3, 2020)

With the 6A5G rebuild done, the Snell J/II restoration done, I think it is time to consider taking a little hiatus from tube DIY.  Nothing crazy, but my two pending projects are in a good place and are both in a holding pattern while waiting for an order from Sowter UK.

I have solidified plans for the 45 parafeed rebuild, it is dependent on a new custom mains transformer from Sowter to support a 1.5-2W bias point on the 45.  Once I receive notification of shipment, I can pull the trigger on the new chassis for powder coating, binding posts, speaker / headphone switch, etc.  The layout will not dramatically change, so should be a relatively straightforward rebuild.  The hardest part is choosing the color!

Also dependent on the Sowter order is the 801A A2 amplifier, I have an order pending for a pair of custom-wound 5K:8ohm 60mA OPT for the build.  I have a good understanding of the capabilities of the CCS loaded pentode stage and have a stable feedback loop without need for a phase compensation capacitor.  I am seeing stable bias voltages, but could potentially investigate a more complex screen supply.  The bias supply will need to be altered depending on my chosen bias point, but overall the prototype is in a good place, it should not be much more work before chassis plans can be made after the new OPT arrive.

An aside, I was playing around with the feedback loop yesterday and also changed the devices of my pentode CCS load, which improved stability.  I took some FFT measurements with the CCS fed EF37A with a 470K restive load to ground, 801A rebiased to 330V 50mA (in preparation for the Sowter OPT).  The spectrum is H3 dominant, from my testing I have found I prefer the sound with a more H2 dominant spectrum with less NFB added, but I couldn't help but be impressed by the distortion figures. 

1W into 8ohms.



4W into 8ohms (my test DAC only puts on 1.78Vrms, so the amplifier is not being pushed to clipping at its full 5W).



So anyway, both projects are waiting on Sowter, I expect it will be at least a month, likely more until I hear from them.  I am going to try and force myself to not look at tube DIY until the order is on its way, I think it will be a healthy break considering I have been at it nonstop for nearly 8 months.

We'll see how it goes


----------



## leftside

Might as well start on that preamp 

What made you go with Sowter? Mischa and I are looking at different transformers for the Kt66/6L6/EL34 headphone amp at the moment.


----------



## L0rdGwyn

@leftside PM in 5...4...3.....


----------



## L0rdGwyn

Have a week off beginning today, starting the day off right  fall decorations are up, never too early for Halloween!

Listening to a Marconi-branded Mullard FW4/500 rectifier, Philips E424N drivers, Philco-branded Sylvania 6A5G.



Definitely have not been reading about tube DIY, definitely have not been making plans to design a phono stage...I think I have a problem.


----------



## whirlwind

L0rdGwyn said:


> Have a week off beginning today, starting the day off right  fall decorations are up, never too early for Halloween!
> 
> Listening to a Marconi-branded Mullard FW4/500 rectifier, Philips E424N drivers, Philco-branded Sylvania 6A5G.
> 
> ...




Enjoy your week off! I am off until next Monday.
I have been quite enjoying the nice weather, walking, grilling and off course listening to music.
You have some wonderful stuff to listen to. I like the Halloween decor, one of my favorite holidays.


----------



## Tjj226 Angel

L0rdGwyn said:


> Have a week off beginning today, starting the day off right  fall decorations are up, never too early for Halloween!
> 
> Listening to a Marconi-branded Mullard FW4/500 rectifier, Philips E424N drivers, Philco-branded Sylvania 6A5G.
> 
> ...




The number 1 question when building a phonostage is how to apply the EQ. Everything else in the circuit is really simple.


----------



## L0rdGwyn

whirlwind said:


> Enjoy your week off! I am off until next Monday.
> I have been quite enjoying the nice weather, walking, grilling and off course listening to music.
> You have some wonderful stuff to listen to. I like the Halloween decor, one of my favorite holidays.



Thanks, Joe, enjoy your time off as well!  The cool weather of fall will be a welcome change, looking forward to my garage not being a sauna!  



Tjj226 Angel said:


> The number 1 question when building a phonostage is how to apply the EQ. Everything else in the circuit is really simple.



Yesirree, I am doing all-in-one passive EQ with two gain stages.  In fact, I have finished a draft schematic for a MM design, another hybrid setup with a source follower output buffer  at this point I have mentally committed, so it's going in the project queue.


----------



## 2359glenn

L0rdGwyn said:


> Have a week off beginning today, starting the day off right  fall decorations are up, never too early for Halloween!
> 
> Listening to a Marconi-branded Mullard FW4/500 rectifier, Philips E424N drivers, Philco-branded Sylvania 6A5G.
> 
> ...



You have a problem I have been doing this for 50 years.


----------



## L0rdGwyn

2359glenn said:


> You have a problem I have been doing this for 50 years.



HA!  I guess it takes one to know one, Glenn.  Maybe it is one of those good problems.  I'm trying to find other things to do with my free time, I get bored then a little voice says "Or, you could go ahead and make a phono stage, you do need one after all."  This is my problem.


----------



## Tjj226 Angel

L0rdGwyn said:


> Thanks, Joe, enjoy your time off as well!  The cool weather of fall will be a welcome change, looking forward to my garage not being a sauna!
> 
> 
> 
> Yesirree, I am doing all-in-one passive EQ with two gain stages.  In fact, I have finished a draft schematic for a MM design, another hybrid setup with a source follower output buffer  at this point I have mentally committed, so it's going in the project queue.



You are gonna hate me, but if you like hybrid source followers, have you considered an LCR EQ?


----------



## L0rdGwyn

Tjj226 Angel said:


> You are gonna hate me, but if you like hybrid source followers, have you considered an LCR EQ?



I don't even want to go there!  Lol I have come across it, but I am shooting for simplicity, low cost, and ease of layout.  I have what I feel is a nearly complete schematic and I happen to have nearly all of the major components.  If time is taken to design custom PCBs for the output buffer, I think I could have this built in a matter of weeks for pretty darn cheap.  Most expensive parts will be the Landfall chassis and output caps.


----------



## Tjj226 Angel

L0rdGwyn said:


> I don't even want to go there!  Lol I have come across it, but I am shooting for simplicity, low cost, and ease of layout.  I have what I feel is a nearly complete schematic and I happen to have nearly all of the major components.  If time is taken to design custom PCBs for the output buffer, I think I could have this built in a matter of weeks for pretty darn cheap.  Most expensive parts will be the Landfall chassis and output caps.




Simplicity! Low cost! Who are you and what have you done with lordgwyn.


----------



## Xcalibur255

Remember, it's simple and low cost by his standards, so it'll be pretty bespoke and sweet still.


----------



## leftside

Tjj226 Angel said:


> You are gonna hate me, but if you like hybrid source followers, have you considered an LCR EQ?


That's what I'm getting later this year.


----------



## L0rdGwyn (Sep 10, 2020)

Tjj226 Angel said:


> Simplicity! Low cost! Who are you and what have you done with lordgwyn.



I am changed!  Well, not really, we'll see how crazy I go with the coupling caps.  While I know LCR is the way to go, my turntable / cart just don't justify a "statement" phono stage build.  So I will make my all-in-one traditional RIAA, nice and cute and compact to go with my MM Ortofon 2M Bronze.  Whenever I get around to upgrading my turntable, maybe I will revisit the idea.  A shop local to me has a beautiful 1972 Thorens TD 125 MK II..for $900.  The thought of buying it and refinishing the plinth has taken up some real estate in my brain, but it will just have to wait.  I pulled the trigger on the Innuous Zen Mini Mk3 music server with LPSU, so all big purchases are on hold at the moment!

Here is the Thorens, I wonder if it's still there...


----------



## Tjj226 Angel

leftside said:


> That's what I'm getting later this year.



I think as far as passive filters go, LCR is the best way to go. 

Im still debating whether or not passive or active eq is the best option. I have a couple of crazy ideas for RIAA correction using local feedback instead of global like you see on most schematics. 




L0rdGwyn said:


> I am changed!  Well, not really.  While I know LCR is the way to go, my turntable / cart just don't justify a "statement" phono stage build.  So I will make my all-in-one traditional RIAA, nice and cute and compact to go with my MM Ortofon 2M Bronze.  Whenever I get around to upgrading my turntable, maybe I will revisit the idea.  A shop local to me has a beautiful 1972 Thorens TD 125 MK II..for $900.  The thought of buying it and refinishing the plinth has taken up some real estate in my brain, but it will just have to wait.  I pulled the trigger on the Innuous Zen Mini Mk3 music server with LPSU, so all big purchases are on hold at the moment!
> 
> Here is the Thorens, I wonder if it's still there...



I can tell you that the TD 125 isn't worth it. With thorens it is pretty much the 124 or bust. 

In any case, there isn't a single vintage turn table I would buy. All the good ones cost wayyyyyyy more than they should. And honestly, the project carbon tables are such a fantastic value that it is sort of hard to justify the cost of anything else. The next step up would be a Linn LP12, and now you are looking at a 3000+ price tag. 

If you are willing to do the work, just build your own turn table. 

Get yourself a smooth DC motor and build yourself a variable DC power supply based on a constant current source. Once you do that, you can couple the dc motor to the turn table platter with a belt and bob's your uncle. You now have a motor setup that is better than what most people have. By having the PSU be adjustable, you can dial in precisely how fast the platter should spin, and so long as your CCS is stable, wow and flutter pretty much go away.

Buying a platter is pretty easy. In fact if you are friends with a machine shop, they should be able to mill you out a really solid aluminum platter for relatively cheap. 

Building your own tone arm is also surprisingly easy. There is a whole thread on building your own linear tone arm. I would only use an arm that keeps the needle perfectly tangential to the grove. I built my own linear tone arm in an afternoon with spare parts and crap I found around town. Not only did it work the first time around, but it worked better than most other arms I have heard in my life. 

The last parts would be the bearings, plinth, and springs needed for mechanical damping. 

Everything else is just a matter of damping and avoiding any and all unnecessary vibrations. Oh and aesthetics


----------



## johnjen

Yeah, uh-uh, just go ahead and jump into this rabbit hole.   
The tone arm is (or can be) rube goldberg to the max and as long as the basics are covered, can get the job done (I've seen the Angel Arm, and was suitably impressed).   
And of course there is that money black hole at the end of the arm…  

But the TT is a whole nuther matter. 
Especially the main bearings and getting 'good' springs.   

And wholey schiit, $3k for the Linn?  
Dam, I didn't realize they were going for 3 large.  

Still the thrill of victory of getting a home built TT and arm working vastly outweighs the agony of the hrs. & hrs. sweating over the details.
hahahahahahahahahahahaha

JJ


----------



## Tjj226 Angel

johnjen said:


> Yeah, uh-uh, just go ahead and jump into this rabbit hole.
> The tone arm is (or can be) rube goldberg to the max and as long as the basics are covered, can get the job done (I've seen the Angel Arm, and was suitably impressed).
> And of course there is that money black hole at the end of the arm…
> 
> ...



Eh. You know..... The more I research building my own table from scratch the more I don't really think it is that much of a rabbit hole. I had such good luck with my linear tone arm and my crappy audio technica needle, that I really think the key isn't what you buy, but how you implement it. 

Based on my experience, you can put together a whole system for a couple hundred bucks that would sound far superior to systems costing 50K or more. 

It is on the list of things to do. But right now I am too busy designing a new DHT heater.


----------



## johnjen

Tjj226 Angel said:


> Eh. You know..... The more I research building my own table from scratch the more I don't really think it is that much of a rabbit hole. I had such good luck with my linear tone arm and my crappy audio technica needle, that I really think the key isn't what you buy, but how you implement it.


 I whole heartedly agree that it is the setup, but you still need really good bearings and suspension setup.
That was the Linn LP12's secret, well a couple of them anyway.



Tjj226 Angel said:


> Based on my experience, you can put together a whole system for a couple hundred bucks that would sound far superior to systems costing 50K or more.
> 
> It is on the list of things to do. But right now I am too busy designing a new DHT heater.


OOOoohhhhh pick me, pick me first…  hahahahahahahaha…

JJ


----------



## Tjj226 Angel

johnjen said:


> I whole heartedly agree that it is the setup, but you still need really good bearings and suspension setup.
> That was the Linn LP12's secret, well a couple of them anyway.
> 
> OOOoohhhhh pick me, pick me first…  hahahahahahahaha…
> ...




http://www.tubecad.com/2020/04/blog0501.htm

I don't actually think the rod coleman circuits are exactly the same as the ones described in the article, but one thing that has always bugged me is that we dont have a center tap. I really want a center tap.


----------



## johnjen

Ah yes the old center tap as a true ground reference so the filament remains more stable for the cathode feed to ground.
And I would imagine that the added stability should help other portions of the circuit as well.

JJ


----------



## Tjj226 Angel

johnjen said:


> Ah yes the old center tap as a true ground reference so the filament remains more stable for the cathode feed to ground.
> And I would imagine that the added stability should help other portions of the circuit as well.
> 
> JJ



Well IDK if stability has anything to do with it. 

However the truth "cathode" in a DHT tube IS the center of the filament. By attaching the cathode resistor on the side of the filament, it is as if you stuck something in the way of the cathode. 

If the article is correct, it also partially explains why the western electric parafeed connection didn't seem to work. If the impedance to the voltage rails on the rod coleman are only 50K, then a 1K unbypassed resistor is going to pass a fair amount of signal back to the PSU for the regulator. In the case of a direct coupled amp where that cathode resistor might be ~8K or so, now you are looking at something closer to a 1: 5 impedance ratio and your audio quality suffers.


----------



## L0rdGwyn

Tjj226 Angel said:


> If you are willing to do the work, just build your own turn table.
> 
> Get yourself a smooth DC motor and build yourself a variable DC power supply based on a constant current source. Once you do that, you can couple the dc motor to the turn table platter with a belt and bob's your uncle. You now have a motor setup that is better than what most people have. By having the PSU be adjustable, you can dial in precisely how fast the platter should spin, and so long as your CCS is stable, wow and flutter pretty much go away.
> 
> ...



It's an intriguing idea.  But I can't hold back when I work on this stuff, so it would be quite the undertaking and I'd end up spending more than if I just bought a high-end TT.  I'll throw it on top of the "potential projects" pile.  I'm trying to knock out this phono stage real quick then get back to my A2 amplifier when the Sowter OPT arrive.

Yes, the vintage TT are not a good value, but I am a sucker for aesthetics and the vintage allure.  I'm not at all a fan of the modern look of a lot of new production hifi gear, piano gloss all black everything, gross.  A vintage TT like that Thorens has a certain aesthetic appeal for me, I can't help it.

https://www.tonepublications.com/old-school/thorens-td-125-turntable/


----------



## Tjj226 Angel

L0rdGwyn said:


> It's an intriguing idea.  But I can't hold back when I work on this stuff, so it would be quite the undertaking and I'd end up spending more than if I just bought a high-end TT.  I'll throw it on top of the "potential projects" pile.  I'm trying to knock out this phono stage real quick then get back to my A2 amplifier when the Sowter OPT arrive.
> 
> Yes, the vintage TT are not a good value, but I am a sucker for aesthetics and the vintage allure.  I'm not at all a fan of the modern look of a lot of new production hifi gear, piano gloss all black everything, gross.  A vintage TT like that Thorens has a certain aesthetic appeal for me, I can't help it.
> 
> https://www.tonepublications.com/old-school/thorens-td-125-turntable/




Yeahhhhh I know what you mean. They do have that classic look that is hard to argue with. In that case check out the old AR TT. It still has the classic look, but only costs ~300 bucks. 

There are a ton of published mods, ready made upgrades for sale, and other bits of info that you can use to turn that thing into a monster. 

There is also a TD124 on ebay right now and the current bid is 1,230. But prices on the 124 keep going up, so you could argue it is a financial investment : P


----------



## leftside

L0rdGwyn said:


> It's an intriguing idea.  But I can't hold back when I work on this stuff, so it would be quite the undertaking and I'd end up spending more than if I just bought a high-end TT.  I'll throw it on top of the "potential projects" pile.  I'm trying to knock out this phono stage real quick then get back to my A2 amplifier when the Sowter OPT arrive.
> 
> Yes, the vintage TT are not a good value, but I am a sucker for aesthetics and the vintage allure.  I'm not at all a fan of the modern look of a lot of new production hifi gear, piano gloss all black everything, gross.  A vintage TT like that Thorens has a certain aesthetic appeal for me, I can't help it.
> 
> https://www.tonepublications.com/old-school/thorens-td-125-turntable/


I think exactly the opposite. I blame it from growing up in England during the 70's - which wasn't a pleasant time, so I have an aversion to most things 70's - apart from the music from 1976 onwards (punk and new wave - which one could argue was a result of those tough times). Piano black or nothing for me  Would be such a boring boring world if we all liked the same things 100% of the time.

I have total respect for those of you thinking about building your own turntable. It took me many hours of watching YouTube videos and reading the forums over at VPI to simply be able to setup my turntable and cart correctly! Aligning the zenith of that little cantilever is so important. I now not only hear differences with the tiniest of adjustments, but can also measure these differences with AnalogMagik.


----------



## L0rdGwyn

Tjj226 Angel said:


> Yeahhhhh I know what you mean. They do have that classic look that is hard to argue with. In that case check out the old AR TT. It still has the classic look, but only costs ~300 bucks.
> 
> There are a ton of published mods, ready made upgrades for sale, and other bits of info that you can use to turn that thing into a monster.
> 
> There is also a TD124 on ebay right now and the current bid is 1,230. But prices on the 124 keep going up, so you could argue it is a financial investment : P



Yeah the TD124 is out of my price range, just too much demand given its reputation.  The TD125 is well-regarded from my reading, they still have it in the shop, I might take a peak at it in person and talk to my vintage audio guy, can't hurt to look, right?  Cleveland is not a good city for hifi, that store is probably the most interesting place to look at gear, they collect and restore vintage receivers, turntables, speakers, etc.  Maybe I will spot another diamond in the rough.



leftside said:


> I think exactly the opposite. I blame it from growing up in England during the 70's - which wasn't a pleasant time, so I have an aversion to most things 70's - apart from the music from 1976 onwards (punk and new wave - which one could argue was a result of those tough times). Piano black or nothing for me  Would be such a boring boring world if we all liked the same things 100% of the time.
> 
> I have total respect for those of you thinking about building your own turntable. It took me many hours of watching YouTube videos and reading the forums over at VPI to simply be able to setup my turntable and cart correctly! Aligning the zenith of that little cantilever is so important. I now not only hear differences with the tiniest of adjustments, but can also measure these differences with AnalogMagik.



I 100% respect that!  Aesthetic preferences are totally individual, also have to take into account the environment the gear is going to be living in, to each their own.  Don't get me wrong, some aesthetic leftovers from the 70s are a disaster.  I don't know if it was just a USA thing, but that wood paneling everyone used to put up on their walls...what were they thinking.  I'm going to have to take a look at AnalogMagik when the dust settles on my turntable setup, seems to be some pretty powerful software.


----------



## L0rdGwyn

Here is the PCB I will be using for the source follower output, a similar board adapted for TO-247 will be used for the inter-stage source follower buffer in the 801A A2 amplifier.

Includes TO-220 pads for the AOT1N60 source follower, IXCP10M45S current sink on the source, trimmer / jumper / resistor to set the source follower idle current via the current sink, protection zeners, 100nF PS decoupling cap, gate stoppers...

Now that that is done, I really have nothing stopping me from working on the layout, then ordering the chassis for this phono stage.


----------



## L0rdGwyn

Are people interested in seeing a vintage turntable restored?  Asking for a friend.


----------



## leftside

L0rdGwyn said:


> Are people interested in seeing a vintage turntable restored?  Asking for a friend.


With a modern look  Just kidding  "Yes" is my shorter answer.


----------



## L0rdGwyn (Sep 11, 2020)

@leftside Ha!  I will keep that in mind  well if at least one person is interested in hearing about it...

I was going to keep this a secret for a little while if only to hide my lack of self control: I bought the Thorens TD 125 MKII I was lusting after.  I got started polishing some parts, then decided I would regret not sharing the restoration process.

Went to the shop today, told myself "I will not leave with the turntable."  I was doomed from the start.  I haggled with the shopkeeper and he knocked off a considerable amount, I examined the motor, speed control, cueing mechanism, etc.  Everything checked out, it is in excellent functional condition, someone took very good care of this turntable.

This purchase will have ramifications on my phono stage design, more on that later, here are some photos.

   

Here is the headshell and stock Thorens TP16 tonearm, button on the far right controls the cueing lever.

 

Here is the motor assembly, the top plate floats on an adjustable sprint suspension.

 

The TD 125 MKII has a built in strobe and speed adjustment to fine-tune the RPM.



Okay so there it is.  What exactly am I going to do as far as the restoration goes?  A few things...

For one, I am going to replace the smoked dust cover with a clear acrylic dust cover to show off the turntable.  I will be taking the cover to a local place on Monday that will make me an exact copy of the cover but in clear acrylic.

Next, the dustcover hinges and black strip on the rear of the turntable are not original, and they are broken.  As it turns out, I discovered these hinges are actually OEM parts for the Linn LP12 and replacements are readily available on eBay, a new pair is on the way.



Next, the I/O.  The hardwired phono connectors and ground wire will have to go.  As terrifying as it is going to be do to, I am going to drill holes in the wood plinth and install high-quality phono connectors and a ground post low-capacitance wiring.  I will likely upgrade the power cord as well.



In terms of cosmetics, the entire turntable is going to be disassembled, cleaned, and all of the raw metalwork polished.  I have a buffing wheel that I have used on other projects, so it will likely be employed for the tonearm and platter.

The internal speed control board is working as intended, so I may leave it alone depending on what I see inside, possible I will replace any suspicious looking electrolytic capacitors.

And lastly, the cartridge, there isn't one!

The headshell on this turntable is not compatible with the cartridge on my current table, so I am using this as an opportunity to "upgrade" from a MM to an MC cartridge.  This has downstream effects as my phono stage design was intended for MM.  However, I was a bit concerned about the input capacitance of my planned design, adapting the stage to MC essentially fixes my capacitance issue.

I will be adding a MC step-up transformer and the stage will be made for MC cartridges, schematic has been updated and parts are being ordered.  I have a good idea of what cart I will be getting, but I will leave that for later 

Sorry, I know that is a lot, it has been a very productive day!  I am crazy excited about where this is going.  My dad is visiting me from out of state in mid-October, one of the only people in my family who appreciates good sound, so the goal is to have this new vinyl rig up-and-running by then.

For every one project completed, two more emerge...


----------



## leftside

Check out Mick from Supratek. I think he has managed to not use a step-up transformer with his phono stage design.
http://www.supratek.com.au/guide-to-buying-a-tube-preamp.html
https://www.facebook.com/6SN7GT/pos...n-of-the-cortese-preamplifie/445707425850849/


----------



## L0rdGwyn

leftside said:


> Check out Mick from Supratek. I think he has managed to not use a step-up transformer with his phono stage design.
> http://www.supratek.com.au/guide-to-buying-a-tube-preamp.html
> https://www.facebook.com/6SN7GT/pos...n-of-the-cortese-preamplifie/445707425850849/



He builds some beautiful amplifiers, some day I will spend the cash and build an LCR phono stage.  The most common way to avoid the SUT is to use an opamp, something tells me that is not what Mick is doing LOL I'm sure his has found a low-noise method using tubes.  The primary motivator for an active solution is usually avoiding the cost of the SUT, seems Mick feels there are other advantages, but I am happy to use it as it easily adapts my MM stage for MC use and resolves a design concern.

Thomas Mayer is a big fan of LCR phono stages, the guy is an absolute junkie for iron, look how many chokes he uses between the B+ supply, heater supply, and RIAA in this D3a phono stage: http://vinylsavor.blogspot.com/2013/02/making-of-d3a-lcr-riaa-phono-preamp.html


----------



## L0rdGwyn

Here are some more details on the upcoming phono stage design.

After some discussion with Kevin at K&K Audio, step-up input transformers will be a brand new offering from Lundahl, the LL9226XL: https://www.lundahltransformers.com/new-transformer/



First gain stage will be a high gm triode-strapped pentode, the D3a.



RIAA filter will be an "all-in-one" passive approach between the two gain stages.  The second gain stage will be another low-noise triode-strapped pentode, the EF86, successor to the pentode being used in my 801A A2 amplifier, the EF37A.  Both stages will be CCS loaded and LED biased.



As I have alluded to, the output buffer will be a FET source follower, the AOT1N60 with a IXCP10M45S current sink.

Coupling and output capacitors will be copper foil Miflex KPCU-01.  The output caps are going to be 1.5uF, they are pretty big.



Those are the highlights, most parts have been ordered at this point, I will nail down the layout and chassis dimensions over the next few days, still need to decide on a color.  I will be using QQQ 9-pin sockets, I've used this brand before and I like them, great quality for the price.  I've ordered tube shields as well, we'll see if they are necessary, would love to show off the tubes assuming there is not a significant noise contribution without the shields.

For testing, I am putting together an inverse RIAA filter.  This is pretty self-explanatory, with a standard signal generator input, the output is an inverse of the RIAA equalization curve, such that the frequency response of the phono stage can be evaluated.  I will build it on a protoboard with a switch for MM vs MC output, schematic below.



I hit up some vinyl shops yesterday in anticipation of the new setup, grabbed a bunch of jazz, some minimalist techno from a local guy I like (Steve Hauschildt), and a really nice original gatefold copy of Zappa's _Hot Rats_.


----------



## leftside

L0rdGwyn said:


> Here are some more details on the upcoming phono stage design.
> 
> After some discussion with Kevin at K&K Audio, step-up input transformers will be a brand new offering from Lundahl, the LL9226XL: https://www.lundahltransformers.com/new-transformer/
> 
> ...


We should maybe talk about record cleaning. I've had great results with a DIY ultrasonic for cleaning + VPI HW-17 for rinsing, but that is getting a little OT...


----------



## L0rdGwyn (Sep 13, 2020)

Here is what I use, Squeaky Clean Vinyl MKIII, budget friendly and IME very effective: https://squeakycleanvinyl.com/products/squeakycleanvinyl-mk-iii

I use it with a small 1 gallon wet/dry vacuum.  Rather than their included brush, I use paint edger tools, like below, the little fibers easily get into all of the vinyl grooves.

 

For a solution, I use a mix of distilled water and isopropyl alcohol.  This is going to be controversial, but I also use a drop of odor / dye-free detergent in the cleaning solution to break the surface tension of the water, otherwise it floats on top of the vinyl rather than penetrating the grooves.  Did a lot of reading and research on that before I went for it, can't remember my reasoning but ultimately felt there were no negative consequences.  Everything is thoroughly rinsed with distilled water and sucked out with the vacuum.

Not as fancy as an ultrasonic cleaner, but for $150 or so, it works great!  A bit messy though.


----------



## L0rdGwyn

What DIY ultrasonic cleaner are you using, @leftside ?


----------



## leftside

L0rdGwyn said:


> Here is what I use, Squeaky Clean Vinyl MKIII, budget friendly and IME very effective: https://squeakycleanvinyl.com/products/squeakycleanvinyl-mk-iii
> 
> I use it with a small 1 gallon wet/dry vacuum.  Rather than their included brush, I use paint edger tools, like below, the little fibers easily get into all of the vinyl grooves.
> 
> ...


Very cool. It's the final stage - the rinse - that I find is a key part of the whole process. Hence the reason why I kept my old and trusty VPI HW-17.



L0rdGwyn said:


> What DIY ultrasonic cleaner are you using, @leftside ?


Earlier version of Cleaner Vinyl Pro:
https://www.cleanervinyl.com/procomponents.html 

And the cheapest US cleaner I could find. It's noisy, so I leave it to do it's work in the garage. 3 records at a time.
https://www.amazon.com/CO-Z-Professional-Ultrasonic-Instrument-Commercial/dp/B075FQPPYR/

There are literally hundreds and hundreds of pages on various forums discussing record cleaning and various formulas, but the above has worked for me now for a number of years. Harry (founder of VPI) uses the same process as above, and of course there is a very long thread on the VPI forum discussing record cleaning.


----------



## L0rdGwyn

leftside said:


> Very cool. It's the final stage - the rinse - that I find is a key part of the whole process. Hence the reason why I kept my old and trusty VPI HW-17.
> 
> Earlier version of Cleaner Vinyl Pro:
> https://www.cleanervinyl.com/procomponents.html
> ...



Very interesting, I'll have to consider it, seems to be a more streamlined approach and less messy!  Thanks for sharing.

I'm in the process of opening up the Thorens TT, will post some pictures of the interior soon.


----------



## L0rdGwyn (Sep 13, 2020)

Okay, got to work on the Thorens, here it is with the platter and belt removed.




Opened up from the bottom without issue, here is the inside.



In terms of cleanliness, corrosion, etc., it is essentially in like-new condition on the interior, there isn't much to do from that standpoint except blowing out a little dust, all of the mechanical functions are flawless, nothing sticks, all connections are free from oxidation.  The three white knobs adjust the tension of the top plate suspension system, so that will be fine-tuned when it is all put back together.

Here is the speed control board.



There are two Valvo branded electrolytics on the board.  They are surely off spec and I checked out the board with the intention of removing them.  However, it is totally working as intended, I may leave them for now, if it ain't broke don't fix it kind of thing, can always change them later if necessary.  Also, have never seen Valvo caps before, which is kinda cool.



Now here is where the work will need to be done, the tonearm wiring.  As you can see, someone changed out the phono connector wires at some point and just snipped the wire, leaving it attached, so obviously that will need to go.  The plan is to drill holes in the back of the plinth to mount permanent phono connectors and grounding post.  The ground wire is attached to the top plate, I checked continuity from the cartridge input to identify where everything was wired.



With that figured out, the tonearm wiring was desoldered and the tonearm removed.



This is the hard part, disassembling the tonearm, cleaning it, and getting it prepped for new tonearm wiring.

Why use new wiring?  Because the tonearm output is going to be wired balanced.  Yup, an application where running balanced actually has benefits!  Turntable cartridges are inherently balanced, however they are often run single-ended with their negative terminals grounded for single-ended phono stages.  The primary of the step-up transformer of my phono stage will be setup for balanced operation, whereas the secondary will be single-ended.  Since we are amplifying a very, very small signal from a MC catridge (0.5mV nominal), noise / hum cancellation across the balanced connections is a huge benefit.  TBD on what wire I will use and whether or not it will be shielded after exiting the tonearm (the grounded arm itself will act as a shield for the unshielded tonearm wiring).  So, since we are rewiring anyway, might as well update with something fancy.

After the arm tube was removed, I got to work taking apart the fastener at the end of the tube.  This was a PITA, as there is a pin that needed to be extracted before the nut could be removed.  I filed down the tip of a small nail, secured the arm, and gently tapped out the pin until it could be extracted with a pair of needle-nose pliers, with the aid of WD-40.  The resin at the end of the arm tube was removed, it will not be needed anymore.



Next, the same process was repeated for the headshell.  Luckily, the annoying pin was immediately accessible with pliers, so it wasn't much work to remove it and the resin.



With that out of the way, the new wiring will pass from the end of the arm tube into the headshell, directly attached to the cartridge.



Everything will be polished up nice and pretty.  Taking apart and cleaning the rest of the tonearm is next...


----------



## johnjen

Seeing these pics reminds me of when I owned one of these back in the early 70's.
It was a decent price for a manual TT and at the time worked well, even though the arm was not all that great.

It was later relegated to 'spare equipment' status when the 124 came out.

JJ


----------



## Tjj226 Angel

Just upgrade the arm while you have it apart. 

You can get the SME arm for 100 bucks and it keeps the vintage aesthetic because it is a vintage part that is still being produced.


----------



## johnjen (Sep 13, 2020)

AND it's a WAY better arm, having had both…

JJ


----------



## L0rdGwyn

Geez, tough crowd lol.  I am keeping the TP16 for now, changing to an SME is always an option later, will require changing out the armboard as well.

Here is the disassembled tonearm.



And reassembly after cleaning.  May have to partially disassemble again when the new tonearm wire arrives, but felt I should put it back together while the process was fresh in my mind.  Cleaned out a bunch of dust and grime, polished everything up, nice and smooth.


----------



## Tjj226 Angel

L0rdGwyn said:


> Geez, tough crowd lol.  I am keeping the TP16 for now, changing to an SME is always an option later, will require changing out the armboard as well.
> 
> Here is the disassembled tonearm.
> 
> ...



Nahhh. I just know that you will replace the arm eventually, so why not do it "while you are in there" so to speak. 

In other news I think I may have invented a new form of TT suspension. Its a super rough idea right now, so I will share ideas when they sound less stupid : P


----------



## johnjen

Another thing to consider is…
Now that you have completely disassembled the arm, including the main bearings, you just might find that getting them dialed back in 'just right' might be 'tricky'.
Micro torque adjustments can be a 'challenge'.
And that's assuming they are not 'dented' or have flat spots…

Just say'n is all…

JJ


----------



## L0rdGwyn

Tjj226 Angel said:


> Nahhh. I just know that you will replace the arm eventually, so why not do it "while you are in there" so to speak.
> 
> In other news I think I may have invented a new form of TT suspension. Its a super rough idea right now, so I will share ideas when they sound less stupid : P



Please post some pictures when you have a prototype, if it is very promising maybe you could patent it!



johnjen said:


> Another thing to consider is…
> Now that you have completely disassembled the arm, including the main bearings, you just might find that getting them dialed back in 'just right' might be 'tricky'.
> Micro torque adjustments can be a 'challenge'.
> And that's assuming they are not 'dented' or have flat spots…
> ...



Thanks for the warning, JJ.  I am confident I have the patience and dexterity to get it 'just right'.


----------



## L0rdGwyn (Sep 14, 2020)

Dropped off the TD 125 dust cover today at a plastics shop, they are making me an identical copy in clear acrylic, should have it later this week.

Parts are arriving for the phono stage, here is some of what is going in.

Antek mains transformer with steel shield.  The B+ will be Maida regulated, so going with cheap iron on the mains transformer is a great cost savings, small form factor as well since I am trying to keep this phono stage petit.



On the subject of petit, here are the Miflex KPCU-01 capacitors that will be going in the build, 0.1uF coupling and 1.5uF output caps.  Maybe could have gone with the 250V version which are a tiny bit smaller, but would have been cutting it close on the voltage rating at turn on, they will fit.



Vampire CM2FCB connectors for the inputs and outputs.  I have been looking for a good RCA for a little while, have been a little disappointed with the quality of what I have used in the past, these seem very nice, they might become a go to for other projects.



And the QQQ 9-pin sockets and aluminum tube shields.  These shields aren't as nice as some of the NOS ones I have hiding somewhere in my garage, maybe I will switch them out.  Ideally they would not be needed, but input stage is going to be sensitive to noise pickup, we will see!  Large for the D3a, small for the EF86.



Going to see if I can nail down the final details of the layout today, then place my mega Mouser order for the little bits and bobs.  Pumped!


----------



## Xcalibur255

I have the Vampires on the 45 amp, and decided to go with them again for a new project along with the complementing speaker binding posts (which are all metal and thus won't break when torqued).  If you arrived at them as the best cross-section between value (such as it is in this hobby) and cost then I feel even better about the choice now.


----------



## L0rdGwyn

@Xcalibur255 yes exactly, they seem to be high quality, I like the look, and they aren't terribly expensive, I got them from Sonic Craft.  I used WBT RCAs on my 6A5 amp, one of them is clearly off spec as standard RCA connectors are too small for it, such that only those that flex can be used which drives me...crazy, it will eventually have to be replaced.  Love the WBT binding posts though, I will use those again.  I have CMC RCAs on my 45 amp, which are pretty nice but feel a little on the cheap side, functionally much better than the WBTs though.  The Vampires feel like a nice middle ground, I will be using their ground post on the phono stage as well, nice to have things match  probably will put something fancier on the Thorens, maybe Cardas RCAs and ground post as the tonearm wire just might be Cardas as well, TBD.


----------



## L0rdGwyn (Sep 14, 2020)

Everything I said about cost-effectiveness, simplicity, ease of layout for the phono stage, throw it all out the window.  I have been working on the chassis layout and it is now going to have a separate power supply chassis.

It just makes too much sense from a design and layout standpoint and will ensure the lowest possible noise.  I will be using Neutrik speakOn cables to run the B+ and DC heater supply from the power supply chassis to the phono stage chassis.  Right now I am targeting two 8" x 8" x 3.25" square chassis that will stack.  The phono stage is going to sit next to my upcoming music streamer that has a very similar size profile and with another stacking power supply, so they will match.

In some ways this change simplifies things, but it will undoubtedly be more expensive, I am a cash cow for Dave and Landfall


----------



## Tjj226 Angel

L0rdGwyn said:


> Everything I said about cost-effectiveness, simplicity, ease of layout for the phono stage, throw it all out the window.  I have been working on the chassis layout and it is now going to have a separate power supply chassis.
> 
> It just makes too much sense from a design and layout standpoint and will ensure the lowest possible noise.  I will be using Neutrik speakOn cables to run the B+ and DC heater supply from the power supply chassis to the phono stage chassis.  Right now I am targeting two 8" x 8" x 3.25" square chassis that will stack.  The phono stage is going to sit next to my upcoming music streamer that has a very similar size profile and with another stacking power supply, so they will match.
> 
> In some ways this change simplifies things, but it will undoubtedly be more expensive, I am a cash cow for Dave and Landfall



Might as well toss in a few DHTs and an LCR network while you are at it : P


----------



## L0rdGwyn (Sep 15, 2020)

Tjj226 Angel said:


> Might as well toss in a few DHTs and an LCR network while you are at it : P



LOL right?  Just throw a couple filament transformers in there, a few regulators, a couple chokes  this thing is getting out of hand as is!  The chassis is just about done in terms of design, just trying to nail down how I am going to go about the balanced connection, re-evaluating if it is worth the extra effort.


----------



## Tjj226 Angel

L0rdGwyn said:


> LOL right?  Just throw a couple filament transformers in there, a few regulators, a couple chokes  this thing is getting out of hand as is!  The chassis is just about done in terms of design, just trying to nail down how I am going to go about the balanced connection, re-evaluating if it is worth the extra effort.



I would not do a separate PSU. The grounding scheme gets very awkward, and ground is very important in a phonostage. I would build it in a single chassis, but I would have the PSU internally separated with a shield. 

And actually you can go one step further. I would put the tubes inside the chassis on a board of some kind and then top mount all your iron. This plus an internal shield would give you two degrees of isolation which would be pretty much equivalent of having two chassis.


----------



## L0rdGwyn (Sep 18, 2020)

Tjj226 Angel said:


> I would not do a separate PSU. The grounding scheme gets very awkward, and ground is very important in a phonostage. I would build it in a single chassis, but I would have the PSU internally separated with a shield.
> 
> And actually you can go one step further. I would put the tubes inside the chassis on a board of some kind and then top mount all your iron. This plus an internal shield would give you two degrees of isolation which would be pretty much equivalent of having two chassis.



I did look at this option specifically before deciding on a separate PS chassis, it's essentially putting them side-by-side instead of on top of one another.  I feel good about the grounding scheme and the plan overall and the separate chassis has some ergonomic benefits.

The design is still a work-in-progress but it getting close to being finalized in terms of layout, chassis size / dimensions.  Should be able to place final orders this weekend.

I nailed down exactly how I am going about the balanced connection and parts are on the way.  The TP16 tonearm will be rewired with Cardas litz 33AWG tonearm wire, which comes as a 4 conductor braid, and rhodium cartridge clips.  The braid will be divided into twisted pairs down the tonearm tube, will once again become a four conductor braid as it exists the tube and makes its way through the base of the tonearm.




On the TD 125 interior, where the wire exits the tonearm, it will meet two cables made from Mogami 2549.  This is an OFC low-capacitance twisted pair with copper shield, the V+ and V- will go to the twisted pair, the shield will be continuously grounded with the tonearm.  The Mogami will then exit the chassis and terminate in two 3-pin XLR connectors which will serve as the turntable outputs.  On the other end, the phono stage will take balanced inputs with two 3-pin XLR, and the shield will serve as the chassis grounding point as opposed to a conventional ground post.  The primary of the Lundahl LL9226XL will remain floating whereas the secondary will be grounded, allowing the noise-reduction benefits of a balanced input on a single-ended phono stage.

Making that tonearm cable is going to be a PITA.  I decided to finally get a soldering pot so I don't have to shave the enamel off litz wire anymore and it can be tinned easily.  Sowter also uses an enameled wire, and with a bunch of Sowter iron on the way it will save me some headaches.

That's all for now, I will post some pictures of the finalized chassis diagrams when they are ready.  The chassis is going to be black, Stone Black specifically, a satin black from Prismatic Powders.


----------



## L0rdGwyn (Sep 19, 2020)

Here are the tubes that are going in the phono stage, Siemens D3a and EF86.  When triode strapped the D3a is a very interesting tube for audio, I suspect this won't be the last time I use it in a design.



Chassis plans are finalized.  The phono stage and power supply chassis' will both be 9" x 9" x 3.25", here are the diagrams I sent to Landfall.

Power supply chassis.  Steel shielded toroidal mains transformer will be centered on the interior, DC heater regulator will also be inside, raw B+, 0V power supply ground, DC heater voltage, and redundant safety earth will be run out of the umbilical to the phono chassis; there will be no AC in the phono chassis.  A very nice chrome NKK toggle switch will be mounted to the front plate.





Phono stage chassis.  Raw B+ will immediately hit the Maida regulator which will be heat-sinked to the chassis, dissipating ~1W.  The goal of the layout is to minimize the length of signal path and grounding connections.  As such, the signal will flow from front to back as follows:

3-pin XLR inputs > LL9226XL step-up transformer > D3a gain stage > RIAA > EF86 gain stage > source follower buffer > Miflex output caps > RCA outputs





With all of the plans finalized, all there is to do now is order the remaining parts from Mouser.  As usual, this build became more complicated than I suspected, but I think it is going to turn out well!  Very excited.


----------



## L0rdGwyn

Here are the chassis CAD diagrams from Landfall.  I told Dave I was going to get some CAD freeware and learn it some day, but just haven't gotten around to it!  The software I am using to lay out my chassis is...just good enough to use, but in many ways horrible, I will not speak its name here lol.  Also Dave and his partner are very serious about getting an in-house powder coating rig with professional equipment, so that may be on the table soon for Landfall orders.  I'll likely continue doing it myself since I went to all of the effort to set up my own and I am very OCD.

 

Mouser order is going in, here are some other parts going in the build.

Amphenol rear-mounted 3-pin XLR inputs on the front of the phono stage chassis, should make for a nice clean look.



NKK toggle power switch.



Neutrik speakOn 8-conductor connectors for the umbilical.

 

That might be it for now, LL9226XL transformers are on the way from K&K Audio, I will be taking pinout measurements and designing a PCB for them such that they are already wired and more easily mounted in the chassis.  The mounting holes in the PCB will be square such that the board can be mounted at a 90 degree rotation if there are any external coupling issues, measurable or audible, the devil is in the details.


----------



## L0rdGwyn (Sep 23, 2020)

Picked up the clear acrylic dust cover replica for the Thorens today 



I love it, big improvement, nice job by my plastic guys.  The turntable still needs some work, waiting for the replacement hinges, Mogami balanced wire for the outputs, and...a new headshell.  Realized pretty quickly after putting everything back together, the headshell I was given with the TT is not compatible with the TP16 tonearm, so I have one coming that is.

It is a NOS headshell made by Thorens, a limited edition offering for the Swiss market only, and compatible with the my tonearm, found in old stock from an ex Thorens distributor.



It's coming from Switzerland, so this appears to be the rate-limiting step.  My Cardas tonearm wire, clips, etc. have arrived, once I have the new headshell, I can proceed with the tonearm rewire and the balanced outputs via Mogami 2549 and Switchcraft 3-pin XLR.

I've decided on a cartridge, the Hana EL.  Low output MC cartridge, very highly regarded and independently recommended by different audiophiles I chat with.  It is a good match for the TP16 tonearm with a resonant frequency around 9.5Hz.



My big box of Mouser crap is here too.  At this point, I've got 90% of what I need to build the phono stage, should have the machined chassis soon, then it's really on!  I've pretty much worked for a week straight, 13 hours a day, so now I have six days off, time to go stuff some PCBs


----------



## L0rdGwyn

Got quite a bit done on the board stuffing front.

Four boards for the D3a and EF86 cascode CCS loads, two of my new source follower / current sink boards for the output buffers, one per channel, and @A2029 's very nice Maida regulator, sans the high voltage FET as it will be heat-sinked to the chassis, so will be added to the board after fine-tuning of the layout is finished.



Next up, designing a PCB for these little guys, the Lundahl MC input transformers.



These are a brand new design from Lundahl, should sound pretty darn good!


----------



## L0rdGwyn

Wrapping up the loose ends on the phono stage planning, I finished up the step-up transformer PCBs, these are ordered.  They are wired in configuration C for a 1:10 turns ratio.  I decided against the mounting holes being configured in a square, too much real-estate cost to get it done.



Also settled on the umbilical cabling - Belden 1039A.  Has four individually shielded 16 AWG twisted pairs plus an overall shield.



We're getting getting close...

In other news, way, way back I mentioned that I was setting up a small stereo in my bedroom.  Well I've taken some time on that and have settled on some speakers for it.  They need to be very compact, of good sound quality, aesthetically pleasing, and sensitive enough that they can be driven to low-to-moderate listening volumes with a flea-watt amplifier.

The Klipsch KG series was recommended to me, so that is the direction I am going, most likely the Klipsch KG 1.5.  These little speakers are rated at 90dB/W and by all accounts are excellent sounding for their size / price.  Keeping an eye on the used market, I'll probably re-cap and re-resistor the crossovers when I find a nice pair.

I tried to push for the KG 2.2 which have two woofers and are more sensitive at 93dB/W, but they are quite a bit bigger at 20" tall, wasn't gonna happen


----------



## Xcalibur255

Why not use the Omegas for this, or are they too big?


----------



## L0rdGwyn

@Xcalibur255 too big!  I am operating under very strict size regulations implemented by my girlfriend lol.  I need something very compact, the market for small relatively sensitive speakers is pretty...small.  The Klipsch check a lot of the boxes, there are some other really interesting vintage speakers from that line, like the KG2 and KG4.


----------



## Xcalibur255

I love that this is where your girlfriend is drawing the line in the sand.  Not the powder-coating equipment or amps lying around on plywood planks.


----------



## L0rdGwyn

Or the tube amps in every room, or the electronic components everywhere, or me living in my garage for three days straight...she is very tolerant of my insanity, so going with some smallish speakers in the bedroom is a small compromise haha!  She is a music lover though and is shopping for new vinyl in preparation for the Thorens setup, she benefits from my antics too


----------



## Zachik

Xcalibur255 said:


> I love that this is where your girlfriend is drawing the line in the sand.  Not the powder-coating equipment or amps lying around on plywood planks.


Wait until status changes from GF to wife... see what happens then...


----------



## L0rdGwyn

LOL she is basically my wife, going on 9 years, it just isn't "official" so to speak  who wants to pay for a wedding when you can use that money for...literally anything else!  I vote tubes and tube accessories.


----------



## Xcalibur255 (Sep 25, 2020)

L0rdGwyn said:


> Or the tube amps in every room, or the electronic components everywhere, or me living in my garage for three days straight...she is very tolerant of my insanity, so going with some smallish speakers in the bedroom is a small compromise haha!  She is a music lover though and is shopping for new vinyl in preparation for the Thorens setup, she benefits from my antics too



I was reading about the DeVore Gibbon 3XL which is nice and small, but they don't seem to be in production anymore if the website product listings are anything to go by.

They're also quite expensive, but everything from DeVore seems to be.  People rave about them, particularly the O/93 and O/96 which are high sensitivity models.  They seem like the logical thing to 'graduate' to one day in the future if upgradeitis should ever strike.


----------



## L0rdGwyn

@Xcalibur255 funny you should bring up the Gibbon 3XL, the other day I was compiling a list of sensitive bookshelf speakers on the market.  I had remembered the 3XL and checked out Devore's site to see the specs, and saw the same thing, it wasn't there!  Seems Devore is going for floorstanders only these days, unless they have a new bookshelf in the works.  I'd be interested in a used pair, if they weren't so expensive.

Here is the rest of the list I put together.  It doesn't have every Omega monitor, just some representatives.  I'm sure there are other contemporary high-efficiency monitors I did not find.

Blumenstein Orca: https://www.blumensteinaudio.com/all-products/orca-3-inch-fullrange-pair
Decware DM945: https://www.decware.com/newsite/DM945.html
Klipsch RP-600M: https://www.klipsch.com/products/rp-600m-bookshelf-speakers
Martin Logan Motion 35XTi: https://www.martinlogan.com/en/product/motion-35xti
Omega Compact Alnico Monitor: https://omegaloudspeakers.com/colle...ts/compact-alnico-monitor?variant=32172350732
Omega Super 3 High-Output: https://omegaloudspeakers.com/colle...per-3-high-output-monitor?variant=34755858700
Tekton Mini Lore Monitor: https://www.tektondesign.com/mini-lore-monitor.html 

Side note - I watched some interviews with John Devore many months ago, super cool guy.  He is into birding and collecting vinyl, so he's alright in my book


----------



## L0rdGwyn (Sep 25, 2020)

Here is the inverse RIAA filter that will be used for part of the phono stage testing.   This allows the phono stage to be tested with a standard signal generator with a flat frequency response by mimicking the RIAA frequency response seen on LP playback.  It has a little toggle switch that changes the output voltage to approximate either MM or MC cartridges.  This will primarily be used to measure the frequency response of the phono stage.


 

Here is the frequency response of the filter, excuse the 60Hz notch, I am using some really long RCAs.



Looks like the headshell from Switzerland is arriving today, that was fast!  So it will be a busier weekend than expected as I will have everything to finish rewiring the Thorens TT.


----------



## Xcalibur255

The Blumenstein Triton was the primary alternative I was considering against Omega.  In the end I couldn't get over spending that much money for a speaker that has a $5 Pioneer BOFU driver in it, but I got the impression that this guy might voice his speakers in a way I would really like so I do still wonder about it sometimes.  He interned at Feastrex for a while and apparently will make you a pair of speakers with Feastrex drivers if you ask super nicely and your pockets are deep.  The drivers themselves start at 5K a pair.


----------



## L0rdGwyn

Xcalibur255 said:


> The Blumenstein Triton was the primary alternative I was considering against Omega.  In the end I couldn't get over spending that much money for a speaker that has a $5 Pioneer BOFU driver in it, but I got the impression that this guy might voice his speakers in a way I would really like so I do still wonder about it sometimes.  He interned at Feastrex for a while and apparently will make you a pair of speakers with Feastrex drivers if you ask super nicely and your pockets are deep.



They are nice looking speakers, I've read good things about them too.  Yeah I have a similar hangup, when I look at those speakers I think, "why can't I just make that?" They are very much a DIY type of design with the birch ply and all.  Obviously he has taken the time to design the cabinets, assemble parts, etc.  Oh, I am forbidden from Baltic birch plywood speakers in my bedroom as well, so whatever I get has to be veneered!  Would love to hear the Tritons some day.



Xcalibur255 said:


> The drivers themselves start at 5K a pair.



Holy cow!  Japanese audiophiles / DIYers go hard.  I just read this on their site:

"...a tremendous amount of labor goes into the manufacture of our cones, and the uniquely formulated Japanese paper is handmade exclusively for Feastrex by an artisan who has been designated by the Japanese government as a “living national treasure,” and who represents the ninth consecutive generation of his family to carry on this traditional art."

There you have it folks, that'll be $5K please.


----------



## Xcalibur255 (Sep 25, 2020)

They're supposed to be pretty special.  A pair of those in a furniture grade bamboo cabinet are my dream speaker.  I would only consider any of the Blumensteins in the bamboo versions, the birch just looks too DIY for me.

Oh, if you are considering the Omega CAM you should do what I did and sub the Super 7 cabinet in place of the CAM cabinet.  This makes the speaker quite a bit less wide and bulky.

I think if I ever did Omega again I would do what Zachik requested and have powered subs built into the speakers so they're actually fullrange.


----------



## L0rdGwyn (Sep 25, 2020)

Oh yeah, I had moved past the idea, but nearly PM'd you about your Alnico Super 7.  I think I should at least give it some more consideration, certainly the Klipsch setup is smaller and cheaper, going with the larger Super 7 would take some convincing...if I get serious about it, you will hear from me 

Adding the subs is a nice touch, could always add a separate unit as well.


----------



## L0rdGwyn (Sep 25, 2020)

I got the replacement LP12 hinges, I can now open the dustcover of my turntable lol, great feature.



And the new headshell has arrived, I like the look, simple and clean.  Now I just need to rewire the TT for balanced, which I am very much not looking forward to.  Probably the very first involved DIY audio thing I did was build my own headphones using after-market Grado drivers.  At the time, I wired and braided my own headphone cables, I learned very quickly that I hated it HA!  It is very tedious.  Now I am going to be working with 33AWG litz wire, I can't wait.


----------



## Zachik

Xcalibur255 said:


> I think if I ever did Omega again I would do what Zachik requested and have powered subs built into the speakers so they're actually fullrange.


I do not remember if I posted an update, but the plan has changed slightly...
Initially, I have ordered a Super 3HO with built-in sub. That is 2 x 4.5" drivers plus the 8" sub all front firing.
At some point, I was thinking that having the sub kinda negates the need for 2nd (HO) driver for extra bass... so instead, the final design is:
Single Alnico driver plus built-in sub. Still both front firing. I think that would have more finesse thanks to the Alnico driver, without bass compromise thanks to the sub!  
Anyhow, speakers should be ready next week or the week after. Exciting times!!!


----------



## L0rdGwyn (Sep 25, 2020)

Can't wait to see / hear about them, @Zachik , I'm sure they will sound phenomenal.

In non-DIY news, this hunk of junk arrived today.



Innuos ZENmini Mk3 music streamer / server + linear power supply unit.  Going to have to take a short break from the analogue world to get this baby set up.  Not sure where the appropriate place to talk about it would be, but I think this is a product that would interest a lot of Head-Fiers, it has some really nice features and top marks for ease-of-use and sound quality from my research.  This particular model has a built-in DAC, which is convenient, but also sports USB + SPDIF digital outputs for use of an external DAC, which is where we are heading.


----------



## Zachik

L0rdGwyn said:


> Innuos ZENmini Mk3 music streamer / server + linear power supply unit. Going to have to take a short break from the analogue world to get this baby set up. Not sure where the appropriate place to talk about it would be, but I think this is a product that would interest a lot of Head-Fiers, it has some really nice features and top marks for ease-of-use and sound quality from my research. This particular model has a built-in DAC, which is convenient, but also sports USB + SPDIF digital outputs for use of an external DAC, which is where we are heading.


Since this is YOUR thread, I would say here is as good place as any!  

I am curious to read your take on it.  I did audition (at home) its bigger brother, the Innuos ZEN Mk3. Single (bigger) chassis with LPS built-in.


----------



## L0rdGwyn

@Zachik well I guess I could!  Not really a DIY thing, but hey why not.  Obviously since I just got it today, I'll give it some time and share some thoughts at some point down the road.  I took a look at the ZEN Mk3 as well, but liked the compact form factor of the ZENmini along with the higher degree of flexibility it offers with a built-in DAC and additional digital I/O.


----------



## whirlwind

This thread just kicks a$$


----------



## L0rdGwyn (Sep 26, 2020)

Whooooooo...I rewired the Thorens for balanced, THAT was fun.

Here is the Cardas tonearm wire before tinning.  As you can see, it is thin, delicate, and difficult to work with, so obviously I had to take this on.  Did I mention it is enamel coated too?  Good stuff.



I decided to take the plunge and go full soldering pot.  I've gotten tired of the work-arounds for litz (enamel coated) copper wire, let's just take care of it.  I got some Cardas bar solder, Cardas soldering flux, and the pot itself.  BTW, if you ever order stuff from Cardas, they send you tons of swag.

Anyway, I had to cut a chunk of the bar solder off with a hack saw to actually use it.



Here is the chunk in the pot, watching it melt was very satisfying.



I threaded the full length of wire down the tonearm after removing the arm tube, got the appropriate length determined, removed it again, tinned the ends, threaded it back down again and proceeded to solder in place the rhodium-plated Cardas cartridge clips.  I then had to thread the tonearm wire and ground wire through the base.  This may sound simple, but these little wires catch on everything, I ended up having to solder them all together just to pass them through the base 😭

Okay so the tonearm wiring was done, next the outputs.  As I mentioned, they will be a pair of 3-pin XLR with shielded Mogami 2549 cable.  Here is one of the two Switchcraft XLR connectors before closing up.



I ended up completely removing the original tag board inside the TT and replaced with three anchor points for the output wiring.  The Mogami cable itself acts as an anchor point for the tonearm wire after it exits the base, I think it turned out well, the outputs are very secure.

 

The tonearm ground and shields from the Mogami cable are connected to the TT top plate.  This same ground connection will pass through the Mogami cable to the chassis ground of the phono stage.



With the bottom closed up, it will look like so.  I am +/- on replacing the original power cord, no rush to do so whatsoever.



I used an old Ortofon MM cart to get the tonearm wire length figured out and for demonstration purposes, here are the cartridge clips in place.



While I was at it, I took my orbital buffer to the sides of the TT platter.  After polishing by hand, it was shiny.  Now it is super shiny.



That was extremely tedious, as expected, I cannot recommend it lol but glad it is done.  As far as the turntable work goes, that was the last major thing, at this point it is just a matter of setup when the new cartridge arrives.  That includes dialing in the tension of the floating deck, cartridge alignment, vertical tracking force, tonearm height. etc. etc.  It needs a more thorough exterior cleaning too, but the major technical work is done.

All of the phono stage preparations are made, just waiting for the chassis to arrive to get started.  Can't wait to get this rig up and running!


----------



## L0rdGwyn

I have some initial thoughts on the Innuos ZENmini Mk3, but first, a question for anyone who follows this thread...

Should I continue posting the specific step-by-step updates on these projects, or just cut to the completed stuff with measurements?  Not sure if people are indifferent to all of the extra info along the way.

Anyway, I've had a few days with the Innuos streamer.  Here it is on my rack, phono stage will eventually sit next to it.



Previously, I was using the relatively inexpensive Bluesound NODE 2 with my music library stored on a Synology 918+ NAS.  For the price, it was a nice setup, Bluesound has a pretty good app and integrates with Spotify, TIDAL, etc.  Ease-of-use was a high-priority since that pretty much is the deciding factor on whether or not my girlfriend will use the stereo.

The NODE 2, over time, has become pretty buggy.  Spotify Connect, the primary way my girlfriend uses the stereo, started having serious connection and dropout issues, not being able to find the streamer on the network, also had issues maintaining a connection to the shared music folder on my NAS.  I tried re-flashing the firmware, updating, all kinds of troubleshooting.  The NODE 2 served us well for a few years, but it was time to move on.

So, the Innuos ZENmini Mk3.  I was drawn to it by its minimalist aesthetic, compact size, Innuos's emphasis on ease-of-use, universal praise for its sound quality, and great digital I/O.
___________________________________________________________________________________________________________________________________________

So starting with the *ease-of-use*.  Innuos includes a very straightforward "Quick Start Guide" to get you going, includes instructions for importing your music library from a shared network folder, over USB, or from other programs like iTunes.  I really like that control of the device is done over a web browser, you simply go to my.innuos.com, the streamer is instantly detected on your network, and away you go.  Importing my entire music library from my NAS to the on-board HDD was pretty simple.  Innuos does what it can with the included metadata from your files, filling in album artwork, artist / composer / album / song names, etc.  It isn't perfect, but it is very easy to go back in and manually edit the metadata.  It also has a very handy built-in album artwork finder, showing you a variety of image choices so you can find one of good quality.  My only complaint here is saving the new album cover / metadata takes a good 10 seconds, so cruising through your music library and updating all of your albums is going to take some time, it adds up.

Primary control of the streamer, whether that be your music library, music apps, internet radio, etc. is done through a Squeezebox application.  I use Orange Squeeze for Android, Squeeze Control for Windows, and iPeng is the iPhone equivalent (which my girlfriend uses).  They are all functionally equivalent, the UI is simple and easy to use, it integrates everything into one place, which I appreciate.  I do use Spotify for discovering / sampling new music at times, but I have to say, IME the user experience is garbage.  Spotify Connect is very unreliable and is fraught with bugs and connection issues, it boggles my mind that a company as successful as Spotify can't get it together.  Using the Squeezebox apps circumvents the problem as you do not have to use Spotify Connect or Spotify's UI, it talks directly to the streamer, which is a big plus for me!

I have not used it yet, but the built in CD ripper is supposed to be phenomenally simple and efficient, so I am looking forward to that.  The streamer can do quite a bit more (can act as a Roon endpoint, for example), but the above is how I will be using it, to access my lossless music library, use streaming services, internet radio, and rip CDs.
___________________________________________________________________________________________________________________________________________

Moving on to *sound quality*.  The ZENmini has an on-board DAC, which I have been very pleased with.  Compared to the on-board Burr-Brown DAC on the Bluesound NODE 2, there is an unmistakable increase in definition, space, and separation, most notable in the bass.  Whether this is strictly a result of the DAC implementation or the low-noise streamer, I cannot say, but I'm happy to say as a stand-alone device, the sound quality of the ZENmini with the linear power supply is very good, a big improvement over the NODE 2 (as it should be, since it is roughly 4x the price). Not much else to say here, I'm at a point where I tend to skip the flowery audiophile-speak, it just sounds good.
___________________________________________________________________________________________________________________________________________

Okay, the *digital I/O*.  This was a big draw for me and a large reason why I went with the ZENmini Mk3 over its larger brother, the ZEN Mk3.  The ZEN only has USB digital output, that's it, whereas the ZEN Mini has USB, coaxial S/PDIF, and optical S/PDIF.  I like the extra flexibility, but there is another reason. Way back on another thread, I brought up my interest in purchasing a DAC from SW1X Audio Design.  I put down a deposit on one of Slawa's DACs and never finished the purchase...LOL.  Yes, it's been a long time since, I could have paid the remaining balance and had my DAC by now, but I keep finding more and more expensive DIY nonsense to get into, it's a bottomless pit...anyway, I still fully intend to finish my SW1X purchase, and Slawa deals primarily in coaxial S/PDIF, so have this digital output was a priority for me such that it can integrate easily with my future DAC.
___________________________________________________________________________________________________________________________________________

So those are my initial thoughts, the Innuos ZENmini Mk3 is easy to use, sounds good, looks good, and has great I/O, pretty much all you can ask for with a digital streamer.

Not a whole lot to report on the DIY front unfortunately, had some delays at Landfall so the phono stage chassis is just shipping today.  Dave gave me a discount for inspiring them to set up a powder coating operation, so that is really happening, DIYers rejoice!  Should make them a very attractive all-in-one chassis option.  I should be able to get going on the powder coating this weekend.  I did have to do some troubleshooting with my DC heater regulators, just barely enough voltage on my heater windings to keep the regulator above dropout, so I've ordered some very low Vf diodes to replace the ones currently on the board.  Squeezing out another 0.5V is all I will need, so should resolve the issue.  I had thought about including that troubleshooting process in the thread, but again, not sure if people are interested in that level of detail and if it is worth the effort.

Should have some real progress to report on the phono stage this weekend, we'll see how the powder coating goes.


----------



## Zachik

L0rdGwyn said:


> Should I continue posting the specific step-by-step updates on these projects


YES!



L0rdGwyn said:


> So those are my initial thoughts, the Innuos ZENmini Mk3 is easy to use, sounds good, looks good, and has great I/O, pretty much all you can ask for with a digital streamer.


So... I have compared the bigger brother ZEN mk3 (using its USB out) to my NUC based music server (running Win 10, also using USB out). 
Both were connected to a Gustard U12 (USB to SPDIF Coax / AES converter), and then high quality (and expensive) Coax cable to my Amber 3 DAC.
On my NUC, I am running JRiver Media Center software, and all my music collection is stored locally (on SSD).
Bottom line FOR ME: GUI on Media Center is way better, sound wise I could not hear ANY difference. 
My GF who did a real blind test (I swapped the USB cable between NUC and ZEN) - kept choosing the NUC as better sounding "by a very small margin"  
BTW, my NUC is in a passive case (no fan), and is substantially smaller than the ZEN. *Saved myself a lot of cash!*


----------



## L0rdGwyn (Sep 29, 2020)

Zachik said:


> So... I have compared the bigger brother ZEN mk3 (using its USB out) to my NUC based music server (running Win 10, also using USB out).
> Both were connected to a Gustard U12 (USB to SPDIF Coax / AES converter), and then high quality (and expensive) Coax cable to my Amber 3 DAC.
> On my NUC, I am running JRiver Media Center software, and all my music collection is stored locally (on SSD).
> Bottom line FOR ME: GUI on Media Center is way better, sound wise I could not hear ANY difference.
> ...



Nice!  Well I'm glad it is working out.  It's unlikely I could tell the ZENmini from another server on a blind test, and I am not a hardcore "computer audiophile", I just wanted something high-quality that is plug-and-play with streaming services integrated, along with USB + coaxial S/PDIF digital outputs in preparation for the SW1X DAC.  I considered building my own server, but I have too much to do as is!   Any sound differences I heard are more likely due to the DAC implementation than the server, but it does give me warm and fuzzies to know it has been engineered for low noise.  Maybe at some point I will compare servers with an external DAC, and probably hear no difference lol.


----------



## L0rdGwyn

The PCBs I designed for the input transformers arrived, turned out very well.


 

JLCPCB also sent me a keychain that matches one of my cats, are they spying on me?!



Chassis arrives tomorrow, will get to drilling and _maybe_ powder coating on Sunday.


----------



## bcowen

L0rdGwyn said:


> Whooooooo...I rewired the Thorens for balanced, THAT was fun.
> 
> Here is the Cardas tonearm wire before tinning.  As you can see, it is thin, delicate, and difficult to work with, so obviously I had to take this on.  Did I mention it is enamel coated too?  Good stuff.
> 
> ...



Hat's off to you on that!  Rewiring a tonearm (at least the two I've done) is not for the faint of heart.


----------



## L0rdGwyn (Oct 2, 2020)

bcowen said:


> Hat's off to you on that!  Rewiring a tonearm (at least the two I've done) is not for the faint of heart.



Sure isn't!  Up there with some of the most tedious things I've done DIY, only a true master of Zen could go back and willingly do a second lol.  Will hopefully be reaping the rewards soon 

With winter coming up, have to wrap up these projects ASAP, dawned on me that powder coating in a 15F garage probably ain't gonna work out too well  guess my poor 801A amp will have to hibernate if Sowter doesn't ship my iron soon, gotta unleash the beast!


----------



## A2029

L0rdGwyn said:


> Sure isn't!  Up there with some of the most tedious things I've done DIY, only a true maser of Zen could go back and willingly do a second lol.  Will hopefully be reaping the rewards soon
> 
> With winter coming up, have to wrap up these projects ASAP, dawned on me that powder coating in a 15F garage probably ain't gonna work out too well  guess my poor 801A amp will have to hibernate if Sowter doesn't ship my iron soon, gotta unleash the beast!







Get a bunch of these + Say sorry to the GF for the higher elec bill for that month


----------



## L0rdGwyn

A2029 said:


> Get a bunch of these + Say sorry to the GF for the higher elec bill for that month



LOL at that point, might as well just live out there!  Got everything I need, I'll work on my half-finished DIY projects to stay busy, drink from the gallon of water I use to wet the soldering sponge, cook with my powder coating oven, sleep on a pile of old Mouser boxes....yup, this is a good idea.


----------



## chrisdrop

L0rdGwyn said:


> Should I continue posting the specific step-by-step updates on these projects, or just cut to the completed stuff with measurements? Not sure if people are indifferent to all of the extra info along the way.


I like the continued updates. Great thread in general. Measurements are cool, but how the sausage is made is more interesting. That is where most of the interesting stuff is IMO actually.


----------



## bcowen

chrisdrop said:


> I like the continued updates. Great thread in general. Measurements are cool, but how the sausage is made is more interesting. That is where most of the interesting stuff is IMO actually.



I used to work for Oscar Mayer, and if that's not a known name in the UK it's a major packaged meat brand in the US. And trust me, you _*don't*_ want to know how the sausage is made. 

Apologies for hijacking your thought...I just stumbled in here yesterday but really like what I've read so far with the updates, detail and photos.


----------



## gimmeheadroom

bcowen said:


> I used to work for Oscar Mayer, and if that's not a known name in the UK it's a major packaged meat brand in the US. And trust me, you _*don't*_ want to know how the sausage is made.
> 
> Apologies for hijacking your thought...I just stumbled in here yesterday but really like what I've read so far with the updates, detail and photos.



Reminds me of the Mark Twain line that went something like "Two things people should never see being made are sausage and legislation"

And somebody else said they package "everything but the squeal"


----------



## L0rdGwyn (Oct 2, 2020)

chrisdrop said:


> I like the continued updates. Great thread in general. Measurements are cool, but how the sausage is made is more interesting. That is where most of the interesting stuff is IMO actually.



Duly noted, then I will continue my play-by-play ranting.  I am in the middle of a pretty heinous work schedule, will be able to make some progress on the chassis this Sunday, then back to work.  Next weekend though, it is on!

I mentioned that once the whether turns cold I really won't be able to powder coat any chassis unless there is a warm spell.  On order from Sowter I have a new custom mains transformer for the revamped 45 amp, the custom output transformers for the 801A amp, and a pair of parafeed headphone output transformers, the Sowter 8665.

My plan for the winter months is to prototype with the Sowter 8665 until I find something that clicks.  I've mentioned a "spud" parafeed design, the 8665 is well-suited for it, will be aiming to use a bias scheme that  makes the parafeed cap the only one in the signal path, fixed bias, battery, diode, etc.  Looking forward to experimenting with those transformers.

Ale Moglia did a gyrator-loaded 8665 spud headphone amp, 6E6P-DR biased with Cree SiC diode array and raved about it, so seems a viable approach, maybe I will pick his brain.

https://www.bartola.co.uk/valves/2019/10/26/6e6p-dr-hp-amp-part-2/


----------



## Zachik

L0rdGwyn said:


> Duly noted, then I will continue my play-by-play ranting.


Oh, so when I replied with emphatic YES, that wasn't good enough?!    
I guess I am not as special as @chrisdrop


----------



## L0rdGwyn

Lol @Zachik every Head-Fier is super special!  We were talking about digital streamers, so I was distracted  with you and @chrisdrop giving feedback, it is confirmed, I'll continue with the how-it's-made type details, just wanted to make sure I wasn't rambling along for no good reason.


----------



## Zachik

@L0rdGwyn In case it was not 100% clear - I was just giving you a hard time for the fun of it...
BTW, @chrisdrop IS a very special Head-Fi-er!!   Amazing community. Cannot wait for next CanJam so I can meet some folks again.


----------



## whirlwind

L0rdGwyn said:


> Duly noted, then I will continue my play-by-play ranting.  I am in the middle of a pretty heinous work schedule, will be able to make some progress on the chassis this Sunday, then back to work.  Next weekend though, it is on!
> 
> I mentioned that once the whether turns cold I really won't be able to powder coat any chassis unless there is a warm spell.  On order from Sowter I have a new custom mains transformer for the revamped 45 amp, the custom output transformers for the 801A amp, and a pair of parafeed headphone output transformers, the Sowter 8665.
> 
> ...



Can't wait for you to complete the spud and tell your findings....


----------



## L0rdGwyn

Here are the raw aluminum chassis for the phono stage.



With the tubes on top, it will be a pretty tall stack, I may end up making a longer umbilical to place them on separate shelves, we will see!

 

Next step is to sloppily put some of the large components in and finalize the layout, particularly all of the mounting holes for PCBs, terminal strips, capacitor mounting backets, etc.  I think it is going to look good, assuming the powder coating turns out well.


----------



## bcowen

L0rdGwyn said:


> Here are the raw aluminum chassis for the phono stage.
> 
> 
> 
> ...



Sweet!  Very nice metalwork.  But I think you should gold-plate them rather than powder coat.


----------



## L0rdGwyn

bcowen said:


> Sweet!  Very nice metalwork.  But I think you should gold-plate them rather than powder coat.



I'll just call up my gold-plating guy  wish I could take credit for the machining, that is Landfall Systems handiwork!  They do a fantastic job, love working with Dave over there.  I've looked into what it would take to machine my own chassis and, well, it's hella expensive!  Not happening any time soon, so I will remain Landfall's #1 customer lol.


----------



## Zachik

L0rdGwyn said:


> Not happening any time soon, so I will remain Landfall's #1 customer lol.


Dave is an awesome guy to work with!
We had quite a few iterations for the 6EL3N chassis, until the design was finalized. The result is very impressive, if I may say so myself...


----------



## bcowen

Zachik said:


> Dave is an awesome guy to work with!
> We had quite a few iterations for the 6EL3N chassis, until the design was finalized. The result is very impressive, if I may say so myself...



Of all people Zachi, you know the drill:  pics or it didn't happen.


----------



## Zachik

bcowen said:


> Of all people Zachi, you know the drill:  pics or it didn't happen.


Posted on Glenn's thread in April 2020 when I got it... 
Trying not to hijack Keenan's thread too much, but since we're talking about Dave's chassis handiwork - here are couple quick photos:


----------



## bcowen

Zachik said:


> Posted on Glenn's thread in April 2020 when I got it...
> Trying not to hijack Keenan's thread too much, but since we're talking about Dave's chassis handiwork - here are couple quick photos:



Oh, _*that*_ one.  Nevermind.



Seriously, that is one sweet looking amp.  I love it!


----------



## L0rdGwyn

Zachik said:


> Trying not to hijack Keenan's thread too much, but since we're talking about Dave's chassis handiwork - here are couple quick photos:



As far as I am concerned, anyone can talk about anything, anytime to any extent on this thread I won't care in the slightest!  Your conversations just might be interrupted now and then with some DIY updates


----------



## whirlwind (Oct 3, 2020)

Zachik said:


> Posted on Glenn's thread in April 2020 when I got it...
> Trying not to hijack Keenan's thread too much, but since we're talking about Dave's chassis handiwork - here are couple quick photos:



What a beautiful amp...that has to sound glorious with the looks to boot!!
I am such a fan of the EL3N tubes.

Keenan, I would love to see what you come up with using EL34/KT66/ECT. amp       You know, just sayin'


----------



## L0rdGwyn

whirlwind said:


> Keenan, I would love to see what you come up with using EL34/KT66/ECT. amp       You know, just sayin'



That's something that has been in the back of of my mind for a while, but I am brushing up against the SAF (spouse acceptance factor), especially when that 801A amp is done, it is going to be huge!  I've also been keen on trying out Electraprint's transformers, so that is probably the direction I would go, theoretically.  I do have a nice pair of XF2 EL34 that are sitting in storage...I have too many tubes not being used in storage lol.



My other dream pentode SET is one made with the Telefunken EL156.  We'll see, like I said I am reaching tube amp saturation point, any suggested new amp build is going to be met with a "where is it going to go?" response, for which I will have no answer LOL.

Let's see what the Brownies do today, Joe, think it will be a real litmus test for them.


----------



## whirlwind

L0rdGwyn said:


> That's something that has been in the back of of my mind for a while, but I am brushing up against the SAF (spouse acceptance factor), especially when that 801A amp is done, it is going to be huge!  I've also been keen on trying out Electraprint's transformers, so that is probably the direction I would go, theoretically.  I do have a nice pair of XF2 EL34 that are sitting in storage...I have too many tubes not being used in storage lol.
> 
> 
> 
> ...



Yeah, I agree this game will tell us much more about the Browns.
Hoping for good results.


----------



## L0rdGwyn

I received some more 6A5G tubes from Japan, Sylvanias to replace the one I broke and dissected.  These are true NOS, perfect condition.



After a chaotic work week, nice to ease into a short break with some relaxing tunes.



Listening to some of my favorite ambient albums.

 



Will get going on the phono stage today, but taking my time, figuring out the finalized layout and drilling is probably my least favorite part of the build process, but we gotta get it done!


----------



## L0rdGwyn (Oct 4, 2020)

Here's a little bit of how-it's-made type stuff.  One outstanding issue I had to work on before finalizing the layout of the phono stage was the dropout voltage of the DC heater regulators.  To save myself a lot of time and effort, I use Pete Millett's filament regulators, PCBs all ready to go from him.  Any time you are using solid state voltage regulators, you have to ensure the voltage drop across the regulator is sufficiently high to maintain regulation.  I knew I was going to be cutting it close on the dropout voltage to get 6.3VDC out of these regulators using the 6.3VAC windings of my mains transformer.  The Antek traffo is specc'd for a 115VAC primary (whereas US wall mains is 120VAC), so that gives a little more wiggle room as the secondary voltage will be a bit higher than 6.3VAC due to the higher primary voltage ((120/115)*6.3 = 6.57VAC).

The mains AC out of your wall outlet is not fixed at 120VAC (if you live in the USA), it is somewhat variable, so I had to be sure there was going to be enough headroom in the regulator to avoid hitting dropout with variation in the mains AC.  To test this, setup the mains transformer with the heater regulators, the D3a and EF86 tubes, and a variac.  This way, I could slowly decrease the voltage on the mains transformer primary and see when the regulators fell out of regulation, via DMM and oscilloscope.

What I found was I hit dropout at around 117VAC on the D3a, which have a slightly higher heater current draw than the EF86.  That is...not good, as 117VAC is a totally plausible voltage to see out of my wall outlet.  So we needed a solution...

What I did was find the lowest Vf (forward voltage drop) TO-220-2 package Schottky diodes on the market that would work with Pete Millett's design.  These turned out to be the ON Semiconductor MBR2515LG.

This worked out, I was able to keep the regulators happy down to a little over 113VAC, which I am comfortable with.  I could theoretically run the heaters a little low at 6.2VDC to get more wiggle room, functionally it would not make a difference, but I think 113VAC will be just fine.

I know it's not the most fascinating of topics, but important nonetheless!  Can move on to the layout now.


----------



## L0rdGwyn (Oct 5, 2020)

I finished up finalizing the layout and the drilling today.  This layout was a real challenge, it is going to be nice and cozy in there!  But it all fits, will have to be mindful of the order in which components are mounted during the build as placing some will leave others inaccessible.

Here is the top of the phono stage chassis after drilling.



I mounted the large components to be sure all of my measurements and layout checked out, was able to squeeze it all in there.  Here is a preview of where we are going with the layout.



The boards above each of the four tube sockets are the cascode CCS loads.  The boards in the center mounted to the side panels are the source follower output buffers + constant current sinks, the input transformers are near the front, Maida regulator toward the back next to the umbilical input, and I'm not sure if you can see them since they are so small, but the Miflex copper coupling and output caps are center and rear, respectively.

As I've said, this is my least favorite part of building, once those holes are drilled, that's it!  But looks like we've pulled it off.

I have to work the next four days, so won't get to the powder coating until this weekend, but that is the next step.  With ten parts to coat, it is going to be an all day affair.  Once again, will be in Stone Black from Prismatic Powders.



So that's it until this weekend!


----------



## bcowen

L0rdGwyn said:


> I finished up finalizing the layout and the drilling today.  This layout was a real challenge, it is going to be nice and cozy in there!  But it all fits, will have to be mindful of the order in which components are mounted during the build as placing some will leave others inaccessible.
> 
> Here is the top of the phono stage chassis after drilling.
> 
> ...



Nice!!  You drill good.    

How low a cartridge output will those Lundahl's handle comfortably?


----------



## L0rdGwyn

bcowen said:


> Nice!!  You drill good.
> 
> How low a cartridge output will those Lundahl's handle comfortably?



Thanks  they can be wired for 1:5, 1:10, or 1:20 step-up, Lundahl recommends specific source impedances for each winding ratio to optimize bandwidth, so theoretically you could use them wired for 1:20 with a very low output cart assuming its impedance is less than 25ohm.  I'll be using them wired 1:10 with a Hana EL (0.5mV output, 30ohm impedance), the two gain stages will get me the rest of the way there!


----------



## L0rdGwyn (Oct 9, 2020)

I have no update on the phono stage just yet, still planning to powder coat tomorrow, but I have some down time at work, something has been on my mind...

I am fan of Nelson Pass, I admire his balanced approach to designing his amplifiers that blends both objective measurements and subjective impressions.  He has also been a huge supporter of the diyAudio community, and he is just a cool dude IMO.

Obviously Nelson deals in solid state gear, and I am a self-proclaimed "tube guy", HOWEVER, I have been very intrigued by his First Watt line of amplifiers for some time as they incorporate many of the same philosophical design goals sought by tube SET nuts like myself, that being simplicity of circuitry, pure class A, and minimal NFB.

I'm sure some are already familiar with First Watt, but it is essentially Nelson's experimental playground where he designs what he wants outside of the Pass Labs brand.  Of particular interest to me are his designs that utilize static induction transistors (SIT), also known as VFETs.  What makes these devices very interesting is that their characteristic curves are much more similar to that of triodes than your typical transistor, whose curves are more similar to that of pentodes.

Why is this important?  Because triodes / SIT transistors can be operated in class A without feedback at reasonable levels of distortion, whereas pentodes / JFETs / MOSFETs are much less linear and require NFB to tame their distortion to acceptable levels when used as voltage gain devices.

Below are the curves of one of Nelson's SIT transistors, as you can see, they are much like that of a triode.



Anyway, why am I ranting about all of this...an attractive project for me is to build a tube preamp and pair it with a First Watt SIT amplifier...except the First Watt SIT models are essentially unavailable as the SIT devices were made in limited quantity, and they went for around $4,000 a piece!!!  BUT Nelson intermittently releases kits to the DIY community, and he happens to have one coming up that utilizes NOS VFETs.  I am going to try and get my hands on one when they are released, and if so, I will build it and perhaps pair it with a tube preamp.

Long story short, I might build a DIY SS power amplifier, assuming I can get one of the kits.  If not, perhaps I will build one of Nelson's other DIY designs, we will see.

Will hopefully have some powder coated phono stage chassis to show off tomorrow


----------



## Tjj226 Angel

L0rdGwyn said:


> I have no update on the phono stage just yet, still planning to powder coat tomorrow, but I have some down time at work, something has been on my mind...
> 
> I am fan of Nelson Pass, I admire his balanced approach to designing his amplifiers that blends both objective measurements and subjective impressions.  He has also been a huge supporter of the diyAudio community, and he is just a cool dude IMO.
> 
> ...



I have looked at doing the same thing a few times. Something that you might want to look into are the Russian SIT/Vfets. I haven't looked to see which parts are good and which ones are bad, but they are generally cheaper and somewhat readily available.  

Couple other things worth considering. 

1: Super triodes. If you are going to make a hybrid amp anyways, take a look at super triodes. You can get tube curves, with SS power, for a fraction of the cost of an SIT part. 

2: Feedback. There are supposedly different ways you can introduce local feedback to a mosfet to make it act like a triode. 

3: Push pull with identical parts rather than complementary parts. If you take the time to design an amp with two identical output devices, the distortion characteristics will cancel more completely than if you had used an N and P channel complementary pair. This means that the majority of your distortion will come from your single ended driver ie your tube front end. Also worth noting is that with a bipolar PSU, feedback, and DC offset, you can eliminate the output capacitor. And trust me, a DC servo circuit is WAYYYYYYYYYYY cheaper than a high quality output capacitor. 

-----------------------

A SIT amp would be cool. Any of the other options are cool too. Just want to give you some options before you see the price tag on the SIT parts : P


----------



## Xcalibur255

I wanted one of those SIT amps, but by the time I learned of them the window of opportunity had already opened and closed.  What I do not understand is why nobody seems to have any interest in doing another run of the VFET chips or designing and producing an updated one.  I don't expect any mainstream brand (which ironically would easily have the budget and manufacturing ability) to pursue it because they're all to busy re-selling the same aluminum jewelry they've been repackaging for decades now, but a boutique manufacturer would be wise to crack this nut and market it in a savvy way.  It's essentially offering something similar to a tube experience sound-wise without any of the drawbacks or care and feeding issues of actually having tubes.

Jason Stoddard at Schiit mentioned being really into Nelson Pass a couple of times so I was holding my breath for a while that he would pick this ball up and run with it (IMO they're the perfect people to implement and market something like this), but I think if it was going to happen there would have been talk of it by now.


----------



## L0rdGwyn

Tjj226 Angel said:


> I have looked at doing the same thing a few times. Something that you might want to look into are the Russian SIT/Vfets. I haven't looked to see which parts are good and which ones are bad, but they are generally cheaper and somewhat readily available.
> 
> Couple other things worth considering.
> 
> ...



Thanks for the ideas, I am pretty keen on the VFET designs in particular.  I know they are very rare and expensive now, but one thing about this Pass kit that is appealing is that he is providing the devices, unless builders already have them (some do).  According to NP, he has about 200 N channel and 200 P channel devices on hand.  Finding them on my own would be a big hassle, not sure I am ready to go down that road just yet 



Xcalibur255 said:


> I wanted one of those SIT amps, but by the time I learned of them the window of opportunity had already opened and closed.  What I do not understand is why nobody seems to have any interest in doing another run of the VFET chips or designing and producing an updated one.  I don't expect any mainstream brand (which ironically would easily have the budget and manufacturing ability) to pursue it because they're all to busy re-selling the same aluminum jewelry they've been repackaging for decades now, but a boutique manufacturer would be wise to crack this nut and market it in a savvy way.  It's essentially offering something similar to a tube experience sound-wise without any of the drawbacks or care and feeding issues of actually having tubes.
> 
> Jason Stoddard at Schiit mentioned being really into Nelson Pass a couple of times so I was holding my breath for a while that he would pick this ball up and run with it (IMO they're the perfect people to implement and market something like this), but I think if it was going to happen there would have been talk of it by now.



Right?  You would think someone else would have picked this up.  There is one company in Japan apparently that has current production SIT devices in their gear, Digital do MaiN, pretty boutique stuff from what I can tell.  Doesn't sound like NP is ready to do another batch of them himself, from my reading, he paid a very pretty penny to have them made.  I'd imagine part of the difficulty with marketing SIT amplifiers would be the power output.


----------



## Xcalibur255

Seeing how well stuff like the Schiit Aegir is doing is proof in my mind that people can be convinced that they don't actually need 250 watts per channel for their personal stereo systems, and that the quality of the first watt is what they should be caring about.  The right company speaking to the right audience could make huge waves with VFET.


----------



## Tjj226 Angel

L0rdGwyn said:


> Thanks for the ideas, I am pretty keen on the VFET designs in particular.  I know they are very rare and expensive now, but one thing about this Pass kit that is appealing is that he is providing the devices, unless builders already have them (some do).  According to NP, he has about 200 N channel and 200 P channel devices on hand.  Finding them on my own would be a big hassle, not sure I am ready to go down that road just yet
> 
> 
> 
> Right?  You would think someone else would have picked this up.  There is one company in Japan apparently that has current production SIT devices in their gear, Digital do MaiN, pretty boutique stuff from what I can tell.  Doesn't sound like NP is ready to do another batch of them himself, from my reading, he paid a very pretty penny to have them made.  I'd imagine part of the difficulty with marketing SIT amplifiers would be the power output.



I believe the Vfets are depletion mode devices. If I am correct, it is not that complicated to build a PP amp using two N channel Vfets. In fact the design looks a lot like a regular PP tube amp. 

I HIGHLY advise using two identical devices in PP. It sounds MUCH better than using a N/P complimentary pair. In fact if you dig for it, NP even has a write up about this technique.


----------



## L0rdGwyn

Xcalibur255 said:


> Seeing how well stuff like the Schiit Aegir is doing is proof in my mind that people can be convinced that they don't actually need 250 watts per channel for their personal stereo systems, and that the quality of the first watt is what they should be caring about.  The right company speaking to the right audience could make huge waves with VFET.



Good point, but Schiit are the masters of marketing  they're going against the grain "we're not like the other guys" approach has worked very well for them so far.  But I absolutely agree, marketed as a "tube sound without tubes" might go far, Pass didn't really take that approach from what I have seen, but then he has a reputation, anything he makes will sell!



Tjj226 Angel said:


> I believe the Vfets are depletion mode devices. If I am correct, it is not that complicated to build a PP amp using two N channel Vfets. In fact the design looks a lot like a regular PP tube amp.
> 
> I HIGHLY advise using two identical devices in PP. It sounds MUCH better than using a N/P complimentary pair. In fact if you dig for it, NP even has a write up about this technique.



I'll look for that writeup, in fact I think I just read it today, but it is all a blur   I'm trying to exert minimal effort on this one LOL I don't want to design my own VFET amplifier, purely looking to work on one of NPs designs, again why the upcoming kit I keep referencing is appealing.

I believe his plan is to release kits with the P channel version of the VFET first, then do a second release with the N channel, it is a single-ended amplifier with the VFET setup as a source follower with a constant current sink.  The voltage gain front end is a step up transformer, however it sounds like there will be "options" for the front end if one doesn't want to use the traffo.  These are going to sell like hot cakes so hopefully I can grab one


----------



## Tjj226 Angel

Xcalibur255 said:


> I wanted one of those SIT amps, but by the time I learned of them the window of opportunity had already opened and closed.  What I do not understand is why nobody seems to have any interest in doing another run of the VFET chips or designing and producing an updated one.  I don't expect any mainstream brand (which ironically would easily have the budget and manufacturing ability) to pursue it because they're all to busy re-selling the same aluminum jewelry they've been repackaging for decades now, but a boutique manufacturer would be wise to crack this nut and market it in a savvy way.  It's essentially offering something similar to a tube experience sound-wise without any of the drawbacks or care and feeding issues of actually having tubes.
> 
> Jason Stoddard at Schiit mentioned being really into Nelson Pass a couple of times so I was holding my breath for a while that he would pick this ball up and run with it (IMO they're the perfect people to implement and market something like this), but I think if it was going to happen there would have been talk of it by now.



Tooling. It would be one thing if you only had to pay a company to make 1000 units, but in reality you are paying for all the tooling, labor, ect that goes into making that part. Its usually a 100K+ investment to get a few thousand devices. 

Nelson pass did it because he didn't mind investing the time, energy, ect to make the gamble work. 

However this sort of an investment is usually frowned upon in the business world. In general you want to avoid having merchandise on hand as much as possible. That way you are not paying for the overhead to just warehouse stuff and your insurance is lower. Blah blah blah. 

The truth is that if you want to make these companies produce certain parts, you have to prove that they have a unique use in industry. For instance united SIC is making power Jfets again because they make for really good high power switches. If a vfet/SIT can somehow be used to replace mosfets and make a system more efficient, they will start making them in bulk for 10 cents a piece.


----------



## Xcalibur255

I'm actually fairly well versed on the subject too, and I agree with everything you just wrote.  There are two things that hang me up really:

1)  The tooling for the existing VFET NP used should exist still, if it was disposed of that was not a wise decision on somebody's part.  The investment was already made on somebody's part, so the production capacity existed, yet nobody wanted to utilize it again.  There must be more to the story we weren't told because that doesn't add up.  Possibly the tooling and fixtures encountered an obsolescence issue.....?

2)  There was supposedly a military application, or possibly a *potential* military application for these parts.  This is, without question, the best way to guarantee that the tooling and capacity will be created and will continue to exist (at least in the USA it is), yet in this case it didn't work out that way.

We do custom PCBAs where I work and nearly all of the cost is in initial tooling investment and ICT fixtures.  If nothing else it means the product needs to have a lifespan measured in years, not months, and some volume behind it to justify the cost of initial start-up, but I don't see this as a deterrent to any reasonably deep-pocketed audio company.  The world of tubes and the tube sound is really becoming a "known" thing in the high-end mainstream and the interest in a solid state product that achieves a similar result will likely be strong.


----------



## Tjj226 Angel (Oct 9, 2020)

Xcalibur255 said:


> We do custom PCBAs where I work


----------



## Xcalibur255

Your pic is broken so I'm missing out on what was potentially a good meme.   

I should clarify that by "do custom" I don't mean manufacture I mean we have them manufactured for us for the product we make.


----------



## johnjen

Tjj's response made me laugh…
But then I like to laugh and will go out of my to do so, so there is that…

JJ


----------



## Xcalibur255

Personally I think a "doesn't everybody" meme would have hit harder.  7/10


----------



## Tjj226 Angel

Xcalibur255 said:


> Personally I think a "doesn't everybody" meme would have hit harder.  7/10



I thought you had basically outed yourself as a resource for the entire DIY community. 

I figured I would point that part out so that you could edit it and hide it as quickly as possible lololol.


----------



## Xcalibur255

Tjj226 Angel said:


> I thought you had basically outed yourself as a resource for the entire DIY community.
> 
> I figured I would point that part out so that you could edit it and hide it as quickly as possible lololol.


Ohhh.  Yeah, my wording is dumb sometimes.  The products we make require custom designed and fabricated PCBAs, so I have some familiarity with the logistics and processes of that world.  I didn't mean to imply that we manufacture PCBs, though that would be an interesting job.


----------



## L0rdGwyn (Oct 10, 2020)

Xcalibur255 said:


> Ohhh.  Yeah, my wording is dumb sometimes.  The products we make require custom designed and fabricated PCBAs, so I have some familiarity with the logistics and processes of that world.  I didn't mean to imply that we manufacture PCBs, though that would be an interesting job.



Would have been disappointed if you were holding out on us this long @Xcalibur255 LOL I use JLCPCB, if you can learn to use EasyEDA (which is some sloppy software, IMO, but hey it's free!), getting some PCBs designed and fabricated is pretty simple.


----------



## L0rdGwyn

Here we go again...




Several lessons were learned the first time around, so this should go much more smoothly.  For one, I took several things out of my garage and covered the rest with tarps LOL trying to minimize the inevitable black dusting.

Two parts down.  I probably went a little heavy on this one and overcompensated and went a little light on the second.  But I am doing the parts in ascending order of aesthetic importance, so starting with the rear panels, no biggie.  Top and front plates will be the last parts coated in this process.


----------



## leftside

Looks like a scene from Dexter


----------



## L0rdGwyn

leftside said:


> Looks like a scene from Dexter



I resent that remark!  I am a very normal, non-serial killer person...but yeah it totally does 

Almost done...


----------



## A2029

L0rdGwyn said:


> Several lessons were learned the first time around, so this should go much more smoothly.  For one, I took several things out of my garage and covered the rest with tarps LOL trying to minimize the inevitable black dusting.



One thing that I read you could do is to use a big thin sheet of grounded metal a little ways away from your part to collect the overspray. I believe online they suggest even just glueing some aluminum foil onto big cardboard sheets (could use trifold presentation cardboard boards), then just run a ground wire from those sheets to earth ground. You could also potentially try adding some resistance in line with the ground to the aluminum sheets to make it less attractive than your part, so that you can tweak how much of the powder gets attracted to the part and how much wants to go to the aluminum foil.


----------



## Zachik

Crazy science time...


----------



## Zachik

L0rdGwyn said:


> I resent that remark!  I am a very normal, non-serial killer person...but yeah it totally does
> 
> Almost done...


Dexter looked very normal non-serial killer, too!  Just saying...


----------



## L0rdGwyn

Okay, done, took about...7 hours, that was a lot of parts.  DIY is...fun!

Far from perfect, but they will do.  This powder seems more prone to clumping that the last I used, so there is some speckling on parts of the finish, but undetectable from even a foot away.  I was bothered by it as I was coating, but when viewing the chassis as a whole, I think they look nice.  I am actively trying to be less of a psychopathic perfectionist lol.



They will likely go side-by-side, but can stack if there is room on the rack.  Perforated aluminum sheet metal on the bottom of both chassis.

 

I might start mounting some parts later tonight, but nothing else major today, I am beat!



A2029 said:


> One thing that I read you could do is to use a big thin sheet of grounded metal a little ways away from your part to collect the overspray. I believe online they suggest even just glueing some aluminum foil onto big cardboard sheets (could use trifold presentation cardboard boards), then just run a ground wire from those sheets to earth ground. You could also potentially try adding some resistance in line with the ground to the aluminum sheets to make it less attractive than your part, so that you can tweak how much of the powder gets attracted to the part and how much wants to go to the aluminum foil.



Thanks for the idea, maybe I will throw something together.  I might even seek out a better powder coating gun, I am starting to think it is the weak link in the setup and the reason I am getting some speckling, the powder flow and shape of the cloud is pretty inconsistent.  If I am going to keep doing this craziness, I think we can do better.


----------



## L0rdGwyn

I mounted some of the parts in preparation for getting the power supply up and running.



Starting to look like a thing.  All done, right?


----------



## Zachik

@L0rdGwyn - why did you decide to place the RCAs on top, instead of the back?  Curious about your design choice (which I am *100% sure *makes sense)...


----------



## L0rdGwyn (Oct 11, 2020)

@Zachik mostly for aesthetic reasons  when this phono was being designed, it was originally going to be single-ended input for MM cartridges.  So that meant RCA inputs with a ground post.  For the sake of minimizing the signal path / ground connections, I was planning to place the RCA inputs on the top plate at the front near the input tubes, it made sense then to place the output RCAs on top as well at the back of the top plate near the output tubes.  When I changed the design for MC cartridges and balanced input, it made more sense to place the XLR inputs on the front of the chassis rather than the top, I decided to leave the output RCAs as they were.  No fancy reason, I just like how they look!


----------



## L0rdGwyn (Oct 11, 2020)

Been moving pretty slow today on phono progress, had to run some errands, but worked out the umbilical wiring.

Here is the Belden 1039A I am using, four individually shielded 16AWG twisted pairs, with another overall shield.  Two pairs for the DC heater regulators, one pair for the B+ / PS ground, one pair for redundant chassis ground which the shields are tied to at one end.  This cable is no joke, need superhuman strength just to remove the jacket.



Here is the finished umbilical with Neutrik NL8FC connectors.

 

Wire is pretty rigid but it can be worked to lay the way you want it.  After some (American) football, I will put together the power supply


----------



## A2029

L0rdGwyn said:


> Been moving pretty slow today on phono progress, had to run some errands, but worked out the umbilical wiring.
> 
> Here is the Belden 1039A I am using, four individually shielded 16AWG twisted pairs, with another overall shield.  Two pairs for the DC heater regulators, one pair for the B+ / PS ground, one pair for redundant chassis ground which the shields are tied to at one end.  This cable is no joke, need superhuman strength just to remove the jacket.
> 
> ...


----------



## L0rdGwyn

A2029 said:


>



LOLOLOL what is happening in that pic?!  It looks...alive, I am scared.


----------



## bcowen

A2029 said:


>



ROFL!!  That reminds me of a Kimber speaker cable I saw at CES many moons ago.  Black Pearl, I think?  One 8' piece (one channel) weighed in at around 50 lbs, and the retail price on the pair was around $15k (USD).  I'm not one of those "a cable is a cable" kind of people, but even I have limits.


----------



## 2359glenn (Oct 11, 2020)

L0rdGwyn said:


> Been moving pretty slow today on phono progress, had to run some errands, but worked out the umbilical wiring.
> 
> Here is the Belden 1039A I am using, four individually shielded 16AWG twisted pairs, with another overall shield.  Two pairs for the DC heater regulators, one pair for the B+ / PS ground, one pair for redundant chassis ground which the shields are tied to at one end.  This cable is no joke, need superhuman strength just to remove the jacket.
> 
> ...



Tuff wire to work with I use it at work to feed power and signals to sensors.  High power frequency drives with a 480 volt 50amp square wave to a motor  puts out plenty of noise.
No noise pickup with 1039A double shielded cable.


----------



## 2359glenn

A2029 said:


>



Craziness.


----------



## L0rdGwyn

2359glenn said:


> Tuff wire to work with I use it at work to feed power and signals to sensors.  High power frequency drives with a 480 volt 50amp square wave to a motor  puts out plenty of noise



Yeah, that jacket is THICK.  Could stand to be a bit thinner and more flexible, but in every other way it is exactly what I need for this phono stage, so I'll take it!


----------



## 2359glenn

L0rdGwyn said:


> Yeah, that jacket is THICK.  Could stand to be a bit thinner and more flexible, but in every other way it is exactly what I need for this phono stage, so I'll take it!



Did you buy that short piece? I usually have to buy it in 100ft roles don't matter I use it all.


----------



## L0rdGwyn (Oct 11, 2020)

2359glenn said:


> Did you buy that short piece? I usually have to buy it in 100ft roles don't matter I use it all.



I found a site that will cut and sell by the foot, I bought 10 ft: https://www.wireandcableyourway.com/.


----------



## Zachik

bcowen said:


> price on the pair was around $15k (USD). I'm not one of those "a cable is a cable" kind of people, but *even I have limits*.


Yup - also called "credit card's line of credit"


----------



## Tjj226 Angel (Oct 13, 2020)

A2029 said:


>



Now there is a cable only a mother can love.


----------



## L0rdGwyn

Got some work in on the phono stage today, finished the power supply.

Heater regulators are dialed in to 6.3V, threw a dummy load on the Maida to set the B+.


 

The rest should be pretty simple, going to finish it tomorrow barring some unforeseen catastrophe.


----------



## bcowen

L0rdGwyn said:


> Got some work in on the phono stage today, finished the power supply.
> 
> Heater regulators are dialed in to 6.3V, threw a dummy load on the Maida to set the B+.
> 
> ...



Sweet!  That's a righteous looking transformer in there...


----------



## L0rdGwyn

bcowen said:


> Sweet!  That's a righteous looking transformer in there...



Thanks  it's actually a cheap Antek toroid, since the supply is regulated the mains traffo doesn't need to be anything fancy-schmancy, the black steel pot helps control leakage of magnetic flux to minimize any magnetic coupling.


----------



## L0rdGwyn

Tube socket wiring done, have to show it now, going to be buried here pretty soon!



Goal is still to finish today, onward!


----------



## bcowen

L0rdGwyn said:


> Tube socket wiring done, have to show it now, going to be buried here pretty soon!
> 
> 
> 
> Goal is still to finish today, onward!



You truly know how to do it right.   Love those carbon films....was just getting ready to swap out the cheap metal films in the Darkvoice project with these (stashed long ago):


----------



## L0rdGwyn (Oct 13, 2020)

bcowen said:


> You truly know how to do it right.   Love those carbon films....was just getting ready to swap out the cheap metal films in the Darkvoice project with these (stashed long ago):



Are those Riken Ohm carbon films?  Those are my favorites  I typically use them on tube cathodes, have them unbypassed on the driver tube cathodes of my 6A5G amplifier and the 6J5 drivers of my 45 amp.

But...sadly...those blue resistors in the phono stage are actually metal films 😭 since the goal is lowest possible noise in the phono stage, decided to go with the lowest noise resistor in most places. I have a little stash of Riken carbon films on standby though  the grid stoppers in the phono stage are Allen Bradleys.


----------



## L0rdGwyn

Checking bias points with LED bias glow...here they are.

D3a: Va 138V, Vk 1.21V, Ia 19mA
EF86: Va 120V, Vk 1.58V, Ia 4mA



Also measured the input capacitance of the EF86 as it will need to be compensated for in the RIAA filter - that is, it is part of the filter.  Measured at 240pF for one of my EF86, 260pF for the other.


----------



## bcowen

L0rdGwyn said:


> Are those Riken Ohm carbon films?  Those are my favorites  I typically use them on tube cathodes, have them unbypassed on the driver tube cathodes of my 6A5G amplifier and the 6J5 drivers of my 45 amp.
> 
> But...sadly...those blue resistors in the phono stage are actually metal films 😭 since the goal is lowest possible noise in the phono stage, decided to go with the lowest noise resistor in most places. I have a little stash of Riken carbon films on standby though  the grid stoppers in the phono stage are Allen Bradleys.



I was looking at the Allen Bradleys.  Those are carbon, yes?

And yes, mine are Riken Ohms.  Don't even know how long they've been in the stash -- probably 20 years?  Love the sound of them, but the Allen Bradleys are a good runner up (IMO).  Plans are to swap out the (cheap) metal film 6SN7 cathode bias resistors with the Rikens in the Darkvoice, but I was also planning on a cap bypass. Perhaps I should try them alone?


----------



## L0rdGwyn (Oct 13, 2020)

bcowen said:


> I was looking at the Allen Bradleys.  Those are carbon, yes?
> 
> And yes, mine are Riken Ohms.  Don't even know how long they've been in the stash -- probably 20 years?  Love the sound of them, but the Allen Bradleys are a good runner up (IMO).  Plans are to swap out the (cheap) metal film 6SN7 cathode bias resistors with the Rikens in the Darkvoice, but I was also planning on a cap bypass. Perhaps I should try them alone?



That's right!  They are carbon films, grid stoppers for preventing parasitic oscillations.

The issue with leaving the cathode resistor unbypassed (known as cathode degeneration) is it will increase the internal resistance of the tube and you will lose gain.  I don't know a ton about the Darkvoice, but I think it is a cathode follower output.  Cathode followers don't suffer from the Miller Effect and have a low input capacitance, so you MIGHT get away with it, but I would probably leave it bypassed.  Using a CCS load minimizes the above negative effects of an unbypased cathode, which is what I have done in my amplifiers.

If you really wanted to get crazy, you could CCS load the 6SN7, _then _leave the cathode unbypassed


----------



## bcowen

L0rdGwyn said:


> That's right!  They are carbon films, grid stoppers for preventing parasitic oscillations.
> 
> The issue with leaving the cathode resistor unbypassed (known as cathode degeneration) is it will increase the internal resistance of the tube and you will lose gain.  I don't know a ton about the Darkvoice, but I think it is a cathode follower output.  Cathode followers don't suffer from the Miller Effect and have a low input capacitance, so you MIGHT get away with it, but I would probably leave it bypassed.  Using a CCS load minimizes the above negative effects of an unbypased cathode, which is what I have done in my amplifiers.
> 
> If you really wanted to get crazy, you could CCS load the 6SN7, _then _leave the cathode unbypassed



Thanks!  The DV comes from the factory with only the resistor...no cap bypass.  Some guys have added 220 uF bypass caps to get rid of hum, and some have ditched the resistor and gone to an LED. I've been looking at a CCS, but unfortunately don't know enough about circuit design to know what I'm doing. I'm a parts swapper, not a doctor.  LOL!  I know adding the cap will increase gain, and that's a problem right now because the highest volume I can tolerate is at 7:00 on the volume control (where 6:00 is full counterclockwise).   I'm going to swap the pot which will take some doing, but that will hopefully give me some usable rotation and get out of the poor tracking area.  I should probably just leave the cathode bias arrangement alone until I get the new pot in. But as usual I'm always looking at the easiest thing first.


----------



## L0rdGwyn (Oct 13, 2020)

Well it took until the very end of the day, but we got it done!  The phono stage is complete.

Pics of the circuit first, here is the power supply interior, once again.

 

And the phono stage chassis interior.

  

We crammed it all in there.  Terminal strips in the center have the RIAA components, blue trimmers are high resistance (1Meg, 100K) in parallel with the RIAA resistor such that they can be trimmed to value precisely.  Caps could be better matched, at the mercy of component tolerances, might go back and match them better down the road.

And the exterior.

 

The phono chassis by itself.



Having a listen now, didn't even measure it, just threw it in the system!  Nothing like a first try success  no issues, just righteous analogue sound.

More pictures of the vinyl setup to come with phono stage in situ.


----------



## Zachik

Beautiful


----------



## L0rdGwyn

It lives below...



Thorens TD 125 MkII has been fitted with the Hana EL MC cartridge.  The turntable needs a little more work, some fine touches, but it is ready for sound.


----------



## L0rdGwyn

bcowen said:


> Thanks!  The DV comes from the factory with only the resistor...no cap bypass.  Some guys have added 220 uF bypass caps to get rid of hum, and some have ditched the resistor and gone to an LED. I've been looking at a CCS, but unfortunately don't know enough about circuit design to know what I'm doing. I'm a parts swapper, not a doctor.  LOL!  I know adding the cap will increase gain, and that's a problem right now because the highest volume I can tolerate is at 7:00 on the volume control (where 6:00 is full counterclockwise).   I'm going to swap the pot which will take some doing, but that will hopefully give me some usable rotation and get out of the poor tracking area.  I should probably just leave the cathode bias arrangement alone until I get the new pot in. But as usual I'm always looking at the easiest thing first.



Well if you get serious about adding a CCS load, let me know!  I can help out with the technical stuff, would just need to measure the B+ voltage, 6SN7 plate and cathode voltages with a DMM.  For the cost of parts and shipping, could shoot you some CCS boards ready to go


----------



## L0rdGwyn (Oct 14, 2020)

The phono stage sounds very good, spacious, smooth, very natural.  Design to build in about a month, not bad!  A new record for me.

I will take some measurements tomorrow or Thursday, take a look at the distortion, frequency response, etc.  But that is all for today, goodnight


----------



## whirlwind (Oct 14, 2020)

L0rdGwyn said:


> It lives below...
> 
> 
> 
> Thorens TD 125 MkII has been fitted with the Hana EL MC cartridge.  The turntable needs a little more work, some fine touches, but it is ready for sound.



Job very well done sir  

Go Browns!


----------



## L0rdGwyn

whirlwind said:


> Job very well done sir
> 
> Go Browns!



Thanks, Joe!  Go Browns indeed


----------



## bcowen

L0rdGwyn said:


> Well if you get serious about adding a CCS load, let me know!  I can help out with the technical stuff, would just need to measure the B+ voltage, 6SN7 plate and cathode voltages with a DMM.  For the cost of parts and shipping, could shoot you some CCS boards ready to go



Very gracious of you.  Thanks!  My next step is to get this gain issue resolved before adding even more. Hoping a pot swap will take care of it (or at least help) -- I just need to get off my butt and do it.


----------



## bcowen

L0rdGwyn said:


> It lives below...
> 
> 
> 
> Thorens TD 125 MkII has been fitted with the Hana EL MC cartridge.  The turntable needs a little more work, some fine touches, but it is ready for sound.



Beautiful visually, and with tubes and analog it _has_ to be beautiful sonically.  

Is that a clamp on the Thorens, or just a weight?  I've tried a couple clamps on the Nottingham but like it better with just a weight. The Basis that preceded it definitely preferred a clamp. But neither have a sprung suspension...


----------



## L0rdGwyn

@bcowen just a weight!  Like to keep it simple  haven't messed around with clamps much, I like being able to plop it on there and go.  I've adjusted the Thorens suspension for the extra weight too.

Getting down with some H. Hancock this morning, sounds amazing.


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## L0rdGwyn (Oct 14, 2020)

Just realized this phono stage opens a new door for tube rolling possibilities...there are a few variants of D3a out there, most of them are Siemens made though.

But the EF86...oh boy lots of options!  Might snag a pair of these Marconis, might be Mullard rebrands based on the construction, have to dig into the details of this family of tubes.


----------



## bcowen

L0rdGwyn said:


> @bcowen just a weight!  Like to keep it simple  haven't messed around with clamps much, I like being able to plop it on there and go.  I've adjusted the Thorens suspension for the extra weight too.
> 
> Getting down with some H. Hancock this morning, sounds amazing.



How's that Hana sounding?  You have it decently broken-in yet?  Nice looking cartridge, to be sure.


----------



## L0rdGwyn (Oct 14, 2020)

bcowen said:


> How's that Hana sounding?  You have it decently broken-in yet?  Nice looking cartridge, to be sure.



Sounds very, very good  only have five or six hours on the cart, it has a ways to go! The Thorens restoration and phono stage build were done simultaneously, so the first time I listened to the Hana was yesterday. Just finished up listening to Nina Simone's cover of George Harrison's "Isn't It a Pity" off _Emergency Ward_, amazing cover, the space / staging is excellent.


----------



## whirlwind

L0rdGwyn said:


> @bcowen just a weight!  Like to keep it simple  haven't messed around with clamps much, I like being able to plop it on there and go.  I've adjusted the Thorens suspension for the extra weight too.
> 
> Getting down with some H. Hancock this morning, sounds amazing.



Killer picture, thanks for posting! What a great system, I bet you are so much enjoying reaping your rewards, great album too!
Not to mention that beautiful amp on the top shelf, that must sound glorious and that color is really growing on me. Amp is drop dead gorgeous


----------



## L0rdGwyn

whirlwind said:


> Killer picture, thanks for posting! What a great system, I bet you are so much enjoying reaping your rewards, great album too!
> Not to mention that beautiful amp on the top shelf, that must sound glorious and that color is really growing on me. Amp is drop dead gorgeous



Thanks for the compliments, Joe, slowly but surely the DIY system is coming together  just a few more additions and some tweaking to be done here and there.


----------



## bcowen

L0rdGwyn said:


> Thanks for the compliments, Joe, slowly but surely the DIY system is coming together  just a few more additions and some tweaking to be done here and there.



As long as you have the proper tool for dialing in the azimuth on the Hana, you should be good to go.


----------



## L0rdGwyn

@bcowen $300!  Lol I will stick to a mirror for now 

Been spinning vinyl all day, something of a stress test I guess.  Phono stage hasn't flinched, sounds incredible and stays very cool.  My girlfriend is working elsewhere, which means I can play all of my weird dissonant electronic music  running Opta REN904 drivers in the 6A5G amp with a GEC U18/20 rectifier.



Made a GIF of my cart for funzies.





In case anyone is interested, Langrex just put up two listings for Siemens D3a tubes at good prices, around $60 a pair.  Pretty interesting tubes for audio, extremely linear triode strapped, make for good 300B drivers too, I will be buying backups


----------



## bcowen

L0rdGwyn said:


> @bcowen $300!  Lol I will stick to a mirror for now
> 
> Been spinning vinyl all day, something of a stress test I guess.  Phono stage hasn't flinched, sounds incredible and stays very cool.  My girlfriend is working elsewhere, which means I can play all of my weird dissonant electronic music  running Opta REN904 drivers in the 6A5G amp with a GEC U18/20 rectifier.
> 
> ...



I love it!  Is that the Beatles white album?  LOL!

I bought a Fozgometer many, many moons ago when I had money and lacked wisdom (the money part changed, anyway).    They were around $150 back then IIRC.  It definitely makes things easy, but you can do exactly the same thing with a DVM (or for the well heeled, an o'scope).  With a test LP that has separate left and right channel 1 KHz test tone tracks, it just compares the output between the two and once you have them outputting at exactly the same level, the azimuth is dead on. I figured that out not too long after I bought the Foz.  

https://www.musicdirect.com/vinyl/ultimate-analog-test-lp-analogue-productinos-test-vinyl-lp


----------



## L0rdGwyn

bcowen said:


> I love it!  Is that the Beatles white album?  LOL!
> 
> I bought a Fozgometer many, many moons ago when I had money and lacked wisdom (the money part changed, anyway).    They were around $150 back then IIRC.  It definitely makes things easy, but you can do exactly the same thing with a DVM (or for the well heeled, an o'scope).  With a test LP that has separate left and right channel 1 KHz test tone tracks, it just compares the output between the two and once you have them outputting at exactly the same level, the azimuth is dead on. I figured that out not too long after I bought the Foz.
> 
> https://www.musicdirect.com/vinyl/ultimate-analog-test-lp-analogue-productinos-test-vinyl-lp



Oh hey, that's easy peasy!  I have a test LP on the way that has azimuth adjustment tracks, left and right 1kHz tones, thanks for the tip  has FR sweeps as well, going to measure the full FR of the total setup, hopefully the sweep is accurate.

I got this guy: https://www.musicdirect.com/vinyl/ultimate-analog-test-lp-analogue-productinos-test-vinyl-lp

Have seen some bad reviews, but on the whole they seem pretty good.  Should be fun to measure and mess around with!


----------



## L0rdGwyn

The D3a have a more pleasing tube glow than I initially gave them credit for, doesn't come across well in photos, unfortunately.



Going to have to accelerate my new DAC purchase after putting together this vinyl setup...the gap has widened substantially, need to narrow it again, the cold digital world is a scary proposition!  Need some tube DAC love to make it warm and inviting again.


----------



## bcowen

L0rdGwyn said:


> I got this guy: https://www.musicdirect.com/vinyl/ultimate-analog-test-lp-analogue-productinos-test-vinyl-lp



LOL!  Great  minds think alike.  

I don't have that particular LP, but have the same test tones in the 2-LP Telarc Omnidisc set. Too bad those have been out of print for so long...every test you can think of and some you might not have even known about.


----------



## leftside

L0rdGwyn said:


> Going to have to accelerate my new DAC purchase after putting together this vinyl setup...the gap has widened substantially, need to narrow it again, the cold digital world is a scary proposition!  Need some tube DAC love to make it warm and inviting again.


The double edged sword of owning both a DAC and turntable  I have had quite a few instances when the DAC has leapfrogged the turntable, then the turntable leapfrogged the DAC, then.....


----------



## L0rdGwyn (Oct 15, 2020)

bcowen said:


> LOL!  Great  minds think alike.
> 
> I don't have that particular LP, but have the same test tones in the 2-LP Telarc Omnidisc set. Too bad those have been out of print for so long...every test you can think of and some you might not have even known about.



The one I picked up seems to be the "best" out there as far as new pressings go, but sounds like there have been some QC issues, maybe I should look into an old test record...we'll see how it goes.



leftside said:


> The double edged sword of owning both a DAC and turntable  I have had quite a few instances when the DAC has leapfrogged the turntable, then the turntable leapfrogged the DAC, then.....



Sounds like one of those good problems  Slawa at SW1X is seeking analogue sound when he designs his DACs, it'll be interesting to see how they compare, just have to put the soldering iron down and finish the purchase!  On that note...

I have an overabundance of 841 DHT tubes, you might say I overcommitted to them when I was designing the 801A amp LOL they didn't work out in that application so I have...a lot of them, too many, need to do something with them.  Thinking about trying them out in my spud headphone amp, working on the details.  The Sowter 8665 transformers were meant to "be driven from a cathode follower output stage via a coupling capacitor" per Sowter and co.  Never seen them used that way, more typically in a parafeed application, but it got me thinking, why not a cap coupled source follower instead of a cathode follower?

Could go something like this: CCS loaded 841 input with filament bias (resistor or SiC diode), direct-coupled to the gate of the source follower FET, cap coupled to the output tranny.  That would place a single film cap in the signal path and should yield a very low output impedance.  Just an idea right now, will definitely need a prototype, might sound horrible   I pretty much have everything on hand for what I have in mind, would be a pretty cool looking amp with just a pair of thoriated tungsten 841 tubes sticking out of the top.  Wouldn't be a powerhouse though, a little over 300mW, whereas the 8665 are rated for 500mW.


----------



## chrisdrop

L0rdGwyn said:


> Well it took until the very end of the day, but we got it done!  The phono stage is complete.
> 
> Pics of the circuit first, here is the power supply interior, once again.
> 
> ...


Congrats yet-again. Beautifully done.


----------



## L0rdGwyn (Oct 17, 2020)

Thanks, @chrisdrop !  I appreciate the compliments.

I guess since this project is done, save for a few minor background tweaks / measurements, it's back to focusing on the 801A A2 amplifier.  I reached out to Sowter for a queue update, sounds like I will be getting my order soon.  Might not be soon enough to get the prototype wrapped up and the amp in its chassis, unless there is a significant warm spell, powder coating will likely have to wait until spring.

That's okay though, as there are two particular design challenges I need to make some decisions on.  The first is how to regulate my near 0V grid bias point with the new transformers.  Going 5K:8 with the Sowters and switching to a full A2 design, meaning there will no longer be an A1 to A2 transition point, the 801A will be biased at close to 0V on the grid, so it will be in A2 95-100% of the time.  I have some ideas on how to regulate the bias point, but having the extra time to work it out will be useful.  Here is what the new load line is going to look like roughly, I have a few different options available.  With copper losses, will probably be around a 6W amplifier.



The second thing to work on is my g2 supply for the EF37A.  If I end up CCS loading the pentode, which I have experimented with and the results are intriguing, the amplifier may benefit from a regulated g2 supply for stability.  Again, have some ideas, but need to make some final decisions.

Still feels a ways away, but really looking forward to getting this one done, the few times I lugged the beast inside and put it in my system, it was very impressive!


----------



## bcowen

L0rdGwyn said:


> Thanks, @chrisdrop !  I appreciate the compliments.
> 
> I guess since this project is done, save for a few minor background tweaks / measurements, it's back to focusing on the 801A A2 amplifier.  I reached out to Sowter for a queue update, sounds like I will be getting my order soon.  Might not be soon enough to get the prototype wrapped up and the amp in its chassis, unless there is a significant warm spell, powder coating will likely have to wait until spring.
> 
> ...



Quite interested to see the play-by-play progress on that as it develops. Sounds pretty cool!

But does that mean I have to wait even longer for you to design an 300B SET headphone amp?  These KR's should provide enough power into even high impedance 'phones.


----------



## L0rdGwyn (Oct 17, 2020)

@bcowen the 801A A2 amp is quite a ways done already!  It is a plywood prototype at the moment  circuit is 90% of the way there.  This amp commits several of the SET purist sins: transistor in the signal path, pentode input tubes, local negative feedback...and it sounds great!

Here is an old post: https://www.head-fi.org/threads/l0rdgwyns-diy-audio.921105/post-15791611

I was using Lundahl LL9202 OPT at the time, but we are changing to Sowter iron very soon for a number of reasons, mostly bandwidth limitations of the Lundahls.



And as far as 300B SET goes, to be completely honest with you, I am not very interested in the 300B!  At least for myself.  Nothing against 300B fans, this is very much a personal thing, I just don't have a lot of interest in new production tubes.  I know many of them are very well-engineered and sound great, but the charm and intrigue of NOS tubes is really what does it for me, and I am not about to go and shell out $2K for a pair of Western Electric 300Bs LOL.

If I ever go for an uber expensive output tube amp, a more likely build would be based on the PX25.  Also very pricey!  But still much cheaper than the 300B, I have seen pairs go for as low as $600, mostly in Japan.  I have no concrete plans whatsoever to do that, but the idea has intrigued me.


----------



## L0rdGwyn (Oct 23, 2020)

I'm very close to finalizing one of the outstanding design questions in the 801A amplifier.

Just to reiterate, I am using a CCS loaded EF37A pentode input tube with local NFB taken from the plate of the 801A back to the cathode of the EF37A.  As the gain of the EF37A increases, the degree of NFB also increases.  By using a CCS load on the pentode, in parallel with a resistive load to ground, the gain of the pentode can be increased beyond what is possible with a typical resistive load.  More gain = more NFB = lower distortion + lower output impedance + better frequency extension.

One drawback of this approach is the CCS + high resistive load "flattens" the load line of the pentode and any small variation in cathode voltage can result in large changes in plate / screen voltage, causing some drift.  One method to overcome this is to use a DC servo.  Another method to stabilize the voltages is what I am showing below.



This is a local NFB arrangement with the g2 voltage being derived from a voltage divider taken from the mu output of the CCS.  The audio signal is dropped across an RC and the remaining DC is fed to g2 via a DN2540 source follower.

I threw this circuit on a protoboard and have tested it.  It results in VERY stable plate / screen voltages as any variation in plate voltage is communicated to the screen.  At near clipping into an 8ohm dummy load, with both real music and sine waves, I see no more than 0.3-0.4V drift in either voltage.

I know that is a lot of technical mumbo jumbo, but long story short, this arrangement makes the CCS loaded pentode setup 100% viable, which gives a ton of flexibility to dial in the degree of NFB in circuit and fine tune the final sound of the amplifier.  The NFB flexibility offered by the CCS-loaded pentode also allows me to leave the EF37A cathode unbypassed, such that the only capacitor in the signal path is the 0.47uF film coupling cap, which is a large reason for this amplifier's stunning clarity / transparency.

Next up is the 0Vg bias point regulation, along with finally putting some of these circuits onto real PCBs.  The prototype is an absolute mess of alligator clips, getting the wiring tightened up will get us closer to real-world "finalized build" performance / measurements.


----------



## L0rdGwyn (Oct 29, 2020)

More turntable shenanigans.

The TD 125 has three plastic cups on the underside that are used for adjusting the suspension.  These are somewhat notorious for stripping over time and becoming difficult to adjust.  I found that to be the case on one of the three, so I decided to replace them.



A gentleman in Italy sells machined precision replicas in a more robust plastic, they work perfectly, nice a smooth.  I like them in black too 



Next was the speed adjustment on the control board on the interior, simple turn of a few trimpots with some measured voltages, now getting perfect 16/33/45 RPM when flipping the switch on the front panel.

And the next thing - when doing the final setup of the TP16 tonearm, I found three issues.  1) the Hana EL was too light for the arm, which necessitated putting the counterweights at their minimal position.  The TP16 has a VTF adjustment, I had to go beyond the "2" grams mark on the arm to actually get my measured 2g tracking force because the cart is so light, obviously this is not ideal.  2) because the headshell I am using is not stock and has a vertical offset, it was riding a little low for comfort with the Hana cart, as little as 1-2mm of clearance to the vinyl with minor warps, not good either!  3) given the vertical offset of the headshell, in addition to the Hana being a somewhat shallow cartridge, I found that I was not getting the tonearm perfectly parallel to the vinyl in its lowest position, meaning the VTA was slightly off.

So what to do...I decided to shim it.  But not just any shim!  It can't look cheap / janky, I found the perfect solution.  A Chinese eBay seller had these very nice graphite shims for sale, adding 4mm of space between the headshell and 2g of mass as well.



Happy to say it solved all of the problems I listed above.  I now have the VTF adjustment set to 2g on the tonearm (with the "fine tune counterweight" dialing it in to a perfect 2.000g), I have plenty of clearance between the headshell and vinyl, and a nicely parallel tonearm as well.

And it looks great!  Which is very important to me, happy with the result.



Oh one more thing I nearly forgot...I bought some more vintage speakers.  They will be going in my bedroom in a small stereo setup, they are the Klipsch KG1.  These are 90dB/W sensitive sealed two-way bookshelf speakers, Klipsch's first foray into true bookshelves, made from 1990-1992, succeeded by the KG1.2, then the KG1.5.

Here is a very nice spec sheet from Klipsch, including a FR plot: http://assets.klipsch.com/product-specsheets/KG-1-Spec-Sheet.pdf

I don't have them in hand yet, seller's pictures aren't the greatest, but they are in excellent shape with the original box, just a little dusty.

 

The consensus is these little speakers punch way above their size and price, so very excited to have them, especially in a real walnut veneer.  They will be paired with my revamped 6J5 / 45 parafeed amplifier.  I am waiting for the replacement mains transformer from Sowter, then I will get a new chassis from Landfall, drill it, powder coat it, put it all back together for a real 2W 45 speaker amp.  Obviously these aren't going to bring the house down at 90dB/W, but they will get more than loud enough for a small bedroom rig.  I don't expect to do much with the crossovers, will likely replace the original bipolar electrolytics, oddball value at 25uf which is tricky, but they should otherwise be good to go.  Ferrofluid on the tweeters may need to be changed as well.  Super excited to try these out.


----------



## bcowen

L0rdGwyn said:


> A gentleman in Italy sells machined precision replicas in a more robust plastic, they work perfectly, nice a smooth.  I like them in black too



Sweet! 



L0rdGwyn said:


> And the next thing - when doing the final setup of the TP16 tonearm, I found three issues.  1) the Hana EL was too light for the arm, which necessitated putting the counterweights at their minimal position.  The TP16 has a VTF adjustment, I had to go beyond the "2" grams mark on the arm to actually get my measured 2g tracking force because the cart is so light, obviously this is not ideal.



First world problems.  This is what the rest of us use.









 



L0rdGwyn said:


> Ferrofluid on the tweeters may need to be changed as well.



How do you "change" that without destroying the tweeter?  Or are you just going to add some?  Not intended as a smart-ass question -- I'm truly interested. 

Interesting aside: the first speakers I bought were some Epicure (EPI) Model 10's back in 1976. These had what EPI marketed as the "air spring" tweeters which were basically an inverted dome -- and they had ferrofluid in them. I had no clue what ferrofluid was, but about 9.5 years later I'd popped the grilles off and saw this gooey stuff smearing down the baffles starting just below the tweeters. As the speakers had a 10 year warranty, I called EPI and the guy gave me an education on ferrofluid.    They sent me a new pair of tweeters AND a new pair of woofers at no charge (I just had to return the old ones) which I thought was pretty amazing for a pair of speakers I'd only paid $200 for new.  Installed the new drivers, and got another first education on what break-in is.  LOL!


----------



## L0rdGwyn

bcowen said:


> First world problems.  This is what the rest of us use.



LOL this would be a daily source of anxiety for me.  Yup I'm a psycho 



bcowen said:


> How do you "change" that without destroying the tweeter?  Or are you just going to add some?  Not intended as a smart-ass question -- I'm truly interested.
> 
> Interesting aside: the first speakers I bought were some Epicure (EPI) Model 10's back in 1976. These had what EPI marketed as the "air spring" tweeters which were basically an inverted dome -- and they had ferrofluid in them. I had no clue what ferrofluid was, but about 9.5 years later I'd popped the grilles off and saw this gooey stuff smearing down the baffles starting just below the tweeters. As the speakers had a 10 year warranty, I called EPI and the guy gave me an education on ferrofluid.    They sent me a new pair of tweeters AND a new pair of woofers at no charge (I just had to return the old ones) which I thought was pretty amazing for a pair of speakers I'd only paid $200 for new.  Installed the new drivers, and got another first education on what break-in is.  LOL!



So to change the ferrofluid on a tweeter, you need to do some delicate surgery lol.  Have to take apart the tweeter, remove the tweeter diaphragm from the magnet assembly (which often requires separation of old adhesive with x-acto knife).  Once they are separated, the ferrofluid sits inside the magetic field of the magnet, best way is to fish it out with some blotting paper, sold at craft stores, highly absorbent stuff that wicks the fluid out of the magnet.  Once it is all out, can do some cleanup with isopropyl alcohol, then add more fluid.  Since it is magnetic, it drops right in and redistributes itself around the magnet, then put it all back together!  Some contact cement can replace the old adhesive.  

I did this on my Snell tweeters, high stakes sheeit LOL but I talked to my vintage speaker expert guy on AK, who tells me the ferrofluid in this particular speaker rarely needs to be replaced.

Wow, that is some serious customer service, hats off to Epicure.  $200 in 1976, the internet tells me that's nearly $1K in 2020 bucks!


----------



## L0rdGwyn (Oct 29, 2020)

Oh another thing, I won an auction for a ten pack of D3a tubes, great price per tube, so I am all set for the phono for a long time  might experiment with these in other designs as well, very interesting tubes triode strapped, super linear, high gain, high transconductance, low output impedance, makes for a very nice driver if you can use the gain.



Tube of the Month article from Vinylsavor: http://vinylsavor.blogspot.com/2012/12/tube-of-month-d3a.html

Look


----------



## A2029 (Oct 29, 2020)

L0rdGwyn said:


> Tube of the Month article from Vinylsavor: http://vinylsavor.blogspot.com/2012/12/tube-of-month-d3a.html
> 
> Look



She's got some beautiful curves


----------



## L0rdGwyn (Oct 29, 2020)

A2029 said:


> She's got some beautiful curves



Aye, that she does, that she does  more linear than many triodes, pretttty noice.

Oh yet another FYI type thing - Dave at Landfall is in the process of experimenting with powder coating, shooting real parts.  He got a REALLY nice powder coating rig from Columbia Coatings, fluidizing hopper, the whole bit.  So, sooner rather than later, he is going to have some very pretty powder coating finishes to offer along with machining chassis.

Seeing how his stuff is turning out and the ease-of-use he is experiencing makes me realize what a garbage powder coating gun the Eastwood dual voltage is...in retrospect, I am shocked I was able to get a good finish on my 6A5G amplifier, even on two attempts.  The phono didn't turn out as well as I wanted, I now realize that the gun is the issue, so.....

I am going to upgrade before powder coating anything else.  Not going to go full auto shop powder coating rig, nothing that serious, but I've already invested in so much of the gear that I have to keep going LOL.  I am likely going to purchase the Red Line EZ 50 powder coating gun, it has a higher kV rating, better powder distribution and flow control.  I will probably also put together a cheap powder coating booth, something real hodgepodge, probably out of cardboard, some air filters and a box fan, really all that is needed to keep my garage from becoming a dusty mess.

I will accept nothing but perfection on the 45 and 801A amps when they are being built, I've invested too much time in them, so better to make the change and ensure that is the end result.  I am not the type to go after sellers for their bad products, writing negative reviews and all of that, but literally NOTHING I bought from Eastwood satisfied, it was all garbage, and I think I am going to make that clear on their site.  You've been warned!


----------



## bcowen

L0rdGwyn said:


> LOL this would be a daily source of anxiety for me.  Yup I'm a psycho
> 
> 
> 
> ...



Hmmmm...risky and high stakes, to be sure.    I've owned the Snell E/III's, C/IV's, and C/V's and I would have had to grow some great big balls to do surgery on those tweeters. LOL!   About the only mod I did to any of them was bypassing the tweeter level pot on the C/V's with a high quality Vishay resistor once I'd settled on the right value. Made a pretty noticeable improvement to the clarity and purity of the treble presentation.

And that $200 was even more dear at $2.90/hour (IIRC) working 3rd shift at a convenience store to help fund the college expenses. Back then it was food or speakers (not enough $$ for both), and you can see which way I went.  So there's at least 2 of us that are psychos.


----------



## L0rdGwyn

bcowen said:


> Hmmmm...risky and high stakes, to be sure.    I've owned the Snell E/III's, C/IV's, and C/V's and I would have had to grow some great big balls to do surgery on those tweeters. LOL!   About the only mod I did to any of them was bypassing the tweeter level pot on the C/V's with a high quality Vishay resistor once I'd settled on the right value. Made a pretty noticeable improvement to the clarity and purity of the treble presentation.
> 
> And that $200 was even more dear at $2.90/hour (IIRC) working 3rd shift at a convenience store to help fund the college expenses. Back then it was food or speakers (not enough $$ for both), and you can see which way I went.  So there's at least 2 of us that are psychos.



Wowee!  You've owned some nice speakers.  How do you like those Tekton Lores?  I was checking out their tiny Mini-Lore Monitor for my bedroom rig at one point.

When it comes to food vs. hifi, the answer is obvious...contrary to popular belief, as long as you have access to water, you can live without food for a very long time, 1-2 months, for future reference if you have a big purchase coming up.


----------



## A2029

L0rdGwyn said:


> Wowee!  You've owned some nice speakers.  How do you like those Tekton Lores?  I was checking out their tiny Mini-Lore Monitor for my bedroom rig at one point.
> 
> When it comes to food vs. hifi, the answer is obvious...contrary to popular belief, as long as you have access to water, you can live without food for a very long time, 1-2 months, for future reference if you have a big purchase coming up.



If you have enough body fat and take supplemental vitamins, minerals and electrolytes along with water, the human body can survive a HUGE amount of time without solid food. Check out this amazing case (note that this man was medically supervised throughout his whole fasting period): https://www.sciencealert.com/the-true-story-of-a-man-who-survived-without-any-food-for-382-days

A lot of audio gear on a year's worth of grocery money, though I'd imagine you'd be a zombie and not hear at your best during a good portion of that time


----------



## L0rdGwyn

A2029 said:


> If you have enough body fat and take supplemental vitamins, minerals and electrolytes along with water, the human body can survive a HUGE amount of time without solid food. Check out this amazing case (note that this man was medically supervised throughout his whole fasting period): https://www.sciencealert.com/the-true-story-of-a-man-who-survived-without-any-food-for-382-days
> 
> A lot of audio gear on a year's worth of grocery money, though I'd imagine you'd be a zombie and not hear at your best during a good portion of that time



Hmmm that is a lot of money saved, what would I do with it...

So all I have to do is gain 300lbs...compile a year's worth of daily vitamins and Gatorade...and not eat...then I could build a type 50 SET amp...with Tango interstage and output transformers......where do I sign?  Assuming I can still lift my arms.


----------



## bcowen

L0rdGwyn said:


> Wowee!  You've owned some nice speakers.  How do you like those Tekton Lores?  I was checking out their tiny Mini-Lore Monitor for my bedroom rig at one point.
> 
> When it comes to food vs. hifi, the answer is obvious...contrary to popular belief, as long as you have access to water, you can live without food for a very long time, 1-2 months, for future reference if you have a big purchase coming up.



I like the Lores a lot. Well, after some surgery, anyway.  They are not "audiophile" speakers (been there, done that), but they're a blast to listen to. And sensitive enough to play at rock concert levels with 20 watts of SET power. When I first got them (sound unheard), I almost put them back in the boxes to send them back. Totally unlistenable with no bass to speak of and treble that shredded my ears. But I decided to give them a chance, so I hooked them up to my HT receiver and hammered the crap out of 'em for about 50 hours. What a metamorphosis! Don't think I've ever heard such a big change with break-in out of any other speaker I've owned. Transferred them to the audio rig, and there was still some sizzle in the treble that bothered me, so I emailed Eric Alexander: "I can fix that," and after a few more emails he shipped me a new pair of crossovers. Put them in, and he had in fact fixed the treble issue, but also killed the fun factor...they were just kind of boring. A few more emails, a 2nd set of new crossovers, and bingo! He had nailed the tonal balance, dynamics, and restored the foot-tap and involvement that had made me go through the effort to begin with. These are a $1k pair of speakers using guitar amp woofers (complete with whizzer cones) that are invalidating every known law of audiophile-ism. What the hell? But even though they had become quite enjoyable and keepers for sure, my inner psycho surfaced and I just *had* to soup up the crossovers with better parts...which took them up another level. So at this point I think they're the best $5k speakers I've ever heard for (all in) about $1350. 

Factory (3rd version) crossover:




Psycho crossovers (and Neotech PCOCC copper wire):


----------



## bcowen

A2029 said:


> If you have enough body fat and take supplemental vitamins, minerals and electrolytes along with water, the human body can survive a HUGE amount of time without solid food. Check out this amazing case (note that this man was medically supervised throughout his whole fasting period): https://www.sciencealert.com/the-true-story-of-a-man-who-survived-without-any-food-for-382-days
> 
> A lot of audio gear on a year's worth of grocery money, though I'd imagine you'd be a zombie and not hear at your best during a good portion of that time



LOL!  I could do that.  Food is so, so...temporary.  

Unfortunately I have a 6'4" teenager at home that would eat (literally) whatever I saved.


----------



## Zachik

L0rdGwyn said:


> Oh yet another FYI type thing - Dave at Landfall is in the process of experimenting with powder coating, shooting real parts. He got a REALLY nice powder coating rig from Columbia Coatings, fluidizing hopper, the whole bit. So, sooner rather than later, he is going to have some very pretty powder coating finishes to offer along with machining chassis.


I am going to be one of the very first guinea pigs for the powder coating, probably as soon as this coming weekend...


----------



## mordy

When I started reading the sentence I though for a second about saving money by not eating.....


----------



## L0rdGwyn (Oct 30, 2020)

bcowen said:


> I like the Lores a lot. Well, after some surgery, anyway.  They are not "audiophile" speakers (been there, done that), but they're a blast to listen to. And sensitive enough to play at rock concert levels with 20 watts of SET power. When I first got them (sound unheard), I almost put them back in the boxes to send them back. Totally unlistenable with no bass to speak of and treble that shredded my ears. But I decided to give them a chance, so I hooked them up to my HT receiver and hammered the crap out of 'em for about 50 hours. What a metamorphosis! Don't think I've ever heard such a big change with break-in out of any other speaker I've owned. Transferred them to the audio rig, and there was still some sizzle in the treble that bothered me, so I emailed Eric Alexander: "I can fix that," and after a few more emails he shipped me a new pair of crossovers. Put them in, and he had in fact fixed the treble issue, but also killed the fun factor...they were just kind of boring. A few more emails, a 2nd set of new crossovers, and bingo! He had nailed the tonal balance, dynamics, and restored the foot-tap and involvement that had made me go through the effort to begin with. These are a $1k pair of speakers using guitar amp woofers (complete with whizzer cones) that are invalidating every known law of audiophile-ism. What the hell? But even though they had become quite enjoyable and keepers for sure, my inner psycho surfaced and I just *had* to soup up the crossovers with better parts...which took them up another level. So at this point I think they're the best $5k speakers I've ever heard for (all in) about $1350.
> 
> Factory (3rd version) crossover:
> 
> ...



Wow, very cool Eric was willing to go to those lengths to help you get the sound right, nice looking crossovers too  I've perused his speakers a few times, I'm more of a wood veneer kind of guy, maybe down the road I would give something from Tekton a shot if they could do something like this, beautiful veneer.  The market for high-sensitivity speakers just really isn't that large, so definitely worth exploring at some point methinks.



Since you mentioned breaking from audiophile norms, I don't think I am a stereotypical audiophile either, I am not looking for perfect tonal balanced or capturing "live" sound, I'm in it for musical enjoyment.  These days I categorize sound into "good" and "bad" LOL.  Just so happens that good also grabs many audiophile adjectives, like "clarity", "transparency", "full-bodied", and "spacious".  Obviously if something is way out of whack in the FR, that's undesirable, but I can handle some tonal imbalance if many of the other boxes are checked.

Obviously, for me a big part of this hobby is the DIY aspect too, been modding / tweaking my gear ever since the beginning.  Total tangent, but one of the first DIY things I got into was modding Grados / building custom headphones with after-market Grado drivers.  Been thinking about getting into the after-market stuff again, some of those drivers are really excellent, have been curious how they might sound with some of these amplifiers...

Just ranting now, but here are some of the headphones I made, the cups were lathed by the Head-Fier @fleasbaby who is a very talented woodworker, beautiful stuff.

Vintage (early 90s) Grado SR125 with black limba inner sleeves

 

Nhoord Red V2 with black limba cups

 

Symphones Magnum V8 drivers in vintage Grado low-profile cups, black limba inner sleeves (these were my favorites, soundwise)

   

Have thought about doing another pair using the most recent Symphones V9 driver.  Braiding those cables was a real pain though LOL.


----------



## fleasbaby

L0rdGwyn said:


> Wow, very cool Eric was willing to go to those lengths to help you get the sound right, nice looking crossovers too  I've perused his speakers a few times, I'm more of a wood veneer kind of guy, maybe down the road I would give something from Tekton a shot if they could do something like this, beautiful veneer.  The market for high-sensitivity speakers just really isn't that large, so definitely worth exploring at some point methinks.
> 
> 
> 
> ...



Nice to see those cups still at work! Funny you guys should be discussing speakers, and mentioning full-range drivers for them. I recently branched out a little, and using a little pre-built Class D board (which I promptly upgraded with Mundorf caps after a little time with the stock configuration), made myself a nice little 10 watt amp.

I'm now in the middle of making cabinets for some Fostex FE206En drivers I managed to get for a decent price, unused, on US Audio Mart. I am hating working with plywood though. Cheap it may be, and the recommended material, but I have been spoiled up until now, using nice hardwoods for all my headphone stuff. This is the amp. My audiophile pal dubbed it "the Elf" and said I needed to make a little pointy hat for it.



It currently runs on a wall-wart, but a linear power supply from Teradak arrived this week. Going to see if I can squeeze just a little more out of it. While I build the Fostex cabinets I have been using a pair of Klipsch Heresy 1 speakers.


----------



## L0rdGwyn

@fleasbaby looks fantastic!  Love the chassis and a beautiful Technics cassette deck.  I've dabbled with the idea of building my own speakers / cabinets as well, from my reading marine-grade plywood is the way to go in terms of overall quality, or of course Baltic birch is a popular choice.  Will they be wood veneered?  Will have to keep an eye out for when they are done.


----------



## fleasbaby

L0rdGwyn said:


> @fleasbaby looks fantastic!  Love the chassis and a beautiful Technics cassette deck.  I've dabbled with the idea of building my own speakers / cabinets as well, from my reading marine-grade plywood is the way to go in terms of overall quality, or of course Baltic birch is a popular choice.  Will they be wood veneered?  Will have to keep an eye out for when they are done.



Thanks . Every once in a while something comes out on cassette instead of vinyl, and I am not completely averse to the medium, so I'll haul out the old tank and play a few. 

I was hoping not to get into trying to veneer the speakers. Looking at the cabinets this morning after glue-up and sanding, I might just leave them unfinished, mount the drivers and see how they sound. If I like what I hear I'll buy better wood and make a second go of it. As they are right now they definitely lack "wife-appeal"...LOL

Have a look at Madisound. They have a bunch of kits and parts...I think I might be doing more of this type of thing. Its a nice change from standing at the lathe.


----------



## L0rdGwyn (Oct 30, 2020)

fleasbaby said:


> Thanks . Every once in a while something comes out on cassette instead of vinyl, and I am not completely averse to the medium, so I'll haul out the old tank and play a few.
> 
> I was hoping not to get into trying to veneer the speakers. Looking at the cabinets this morning after glue-up and sanding, I might just leave them unfinished, mount the drivers and see how they sound. If I like what I hear I'll buy better wood and make a second go of it. As they are right now they definitely lack "wife-appeal"...LOL
> 
> Have a look at Madisound. They have a bunch of kits and parts...I think I might be doing more of this type of thing. Its a nice change from standing at the lathe.



The wife-appeal is a real issue  Baltic birch, a favorite amongst DIY speaker builders, is basically forbidden in my home LOL.  If you have the knowledge and gear, why not give it a go!  The barrier for me is acquiring the woodworking equipment and learning the trade, it is a big time / money / space investment, one I would love to make, but I've already made one of those big investments recently for building tube amplifiers.  What I was considering at one point was doing a pair of bass reflex speakers using Markaudio drivers, they are pricey but very highly regarded and they have plans available on their site, like these using the Alpair 12P.  It is about 92dB/W sensitive, so could get decent volume with a little flea-watt tube amp.  Your 10W amp should be able to rock the house with those Fostex units.


----------



## puck

I just saw that fleasbaby was building a set of speakers with Fostex drivers and thought I'd share mine.  These are using FE166 drivers in a spiral baffle enclosure.  I built them probably 10 years ago now (how is it possible that it was that long ago?)  Single full range driver speakers are pretty interesting.  They sound quite good I think.

The second pic is small since I couldn't find the original and had to pull it off an old blog post I made about them.


----------



## L0rdGwyn (Oct 30, 2020)

puck said:


> I just saw that fleasbaby was building a set of speakers with Fostex drivers and thought I'd share mine.  These are using FE166 drivers in a spiral baffle enclosure.  I built them probably 10 years ago now (how is it possible that it was that long ago?)  Single full range driver speakers are pretty interesting.  They sound quite good I think.
> 
> The second pic is small since I couldn't find the original and had to pull it off an old blog post I made about them.



Beautiful!  Fantastic work, the baffles are walnut?  Really like the grills as well.  How do you find the bass response / dynamics?


----------



## puck

Thanks!  The main box is solid maple and the front baffles are walnut and maple.  I was a bit worried about going with solid maple as I had read that it can have expansion/contraction issues with environmental changes but they have been rock solid.  They have "spiral" ramps inside that act as a lot of bracing as well so that probably helps.  I designed and machined the grills myself.  I was originally intending to leave them without grills but, at the time I built them, my daughter was 2 and was very likely going poke the cones with fingers or some object so they got grills LOL.  They have much better bass than I had expected.  They are by no means bass heavy but they have good extension and seem pretty balanced.  The dynamics also seem pretty good. Full range single driver speakers are kind of their own beasts.  They do play very well with lower volumes and don't require a ton of power which is nice.   It's a bit hard for me to judge speakers well as I have a pretty average speaker amp and the room that they are in is very far from ideal.


----------



## fleasbaby

L0rdGwyn said:


> The wife-appeal is a real issue  Baltic birch, a favorite amongst DIY speaker builders, is basically forbidden in my home LOL.  If you have the knowledge and gear, why not give it a go!  The barrier for me is acquiring the woodworking equipment and learning the trade, it is a big time / money / space investment, one I would love to make, but I've already made one of those big investments recently for building tube amplifiers.  What I was considering at one point was doing a pair of bass reflex speakers using Markaudio drivers, they are pricey but very highly regarded and they have plans available on their site, like these using the Alpair 12P.  It is about 92dB/W sensitive, so could get decent volume with a little flea-watt tube amp.  Your 10W amp should be able to rock the house with those Fostex units.



I've been digging through MarkAudio's pages....they do look interesting, for sure. 



puck said:


> I just saw that fleasbaby was building a set of speakers with Fostex drivers and thought I'd share mine.  These are using FE166 drivers in a spiral baffle enclosure.  I built them probably 10 years ago now (how is it possible that it was that long ago?)  Single full range driver speakers are pretty interesting.  They sound quite good I think.
> 
> The second pic is small since I couldn't find the original and had to pull it off an old blog post I made about them.





puck said:


> Thanks!  The main box is solid maple and the front baffles are walnut and maple.  I was a bit worried about going with solid maple as I had read that it can have expansion/contraction issues with environmental changes but they have been rock solid.  They have "spiral" ramps inside that act as a lot of bracing as well so that probably helps.  I designed and machined the grills myself.  I was originally intending to leave them without grills but, at the time I built them, my daughter was 2 and was very likely going poke the cones with fingers or some object so they got grills LOL.  They have much better bass than I had expected.  They are by no means bass heavy but they have good extension and seem pretty balanced.  The dynamics also seem pretty good. Full range single driver speakers are kind of their own beasts.  They do play very well with lower volumes and don't require a ton of power which is nice.   It's a bit hard for me to judge speakers well as I have a pretty average speaker amp and the room that they are in is very far from ideal.



Those are beautifully made. I think I might be dropping the idea of plywood altogether and going back to hardwood for these. Would be cool to see what the inside of those look like.

The whole "low-watts-high-sensitivity" thing is fascinating. The sound is a little different from my main rig (A Schiit Vidar driving a pair of Magnepan LRS), but not that far off. Its more intimate, but not in the way audiophiles say intimate is. Its really nice with jazz especially, and I listen mostly to that...Blue Note, Impulse, Verve, etc...as well as spiritual and free stuff from the seventies.


----------



## Tjj226 Angel

L0rdGwyn said:


> The wife-appeal is a real issue  Baltic birch, a favorite amongst DIY speaker builders, is basically forbidden in my home LOL.  If you have the knowledge and gear, why not give it a go!  The barrier for me is acquiring the woodworking equipment and learning the trade, it is a big time / money / space investment, one I would love to make, but I've already made one of those big investments recently for building tube amplifiers.  What I was considering at one point was doing a pair of bass reflex speakers using Markaudio drivers, they are pricey but very highly regarded and they have plans available on their site, like these using the Alpair 12P.  It is about 92dB/W sensitive, so could get decent volume with a little flea-watt tube amp.  Your 10W amp should be able to rock the house with hose Fostex units.



That's why god made veneer.


----------



## fleasbaby

Tjj226 Angel said:


> That's why god made veneer.



I'm going to have to get brave and try using it. Something about gluing and clamping down layers of extremely thing wood makes me twitchy though...LOL....I see a sticky disaster on the horizon in the Wabi Sabi Workshop....oh well. Only one way to truly learn.


----------



## puck

fleasbaby said:


> I've been digging through MarkAudio's pages....they do look interesting, for sure.
> 
> 
> 
> ...



Thanks!  The original design is from Masaaki Takenaka.  I don't know if his design is still up but I actually modeled the design in order to convert it to english units since I can't get metric material.  Here's an image of the 3D model.  I actually have drawings for the parts as well.  It's technically a backloaded horn design.  The spiral creates the path length needed for the horn in a smaller enclosure. 

I agree that low watt high sensitivity systems have their own sound, especially the single driver designs.  I really got fascinated with them in the early 2000s and built something like 4 different designs. I was really into the Passlabs first watt ideas and thought that was just a really cool concept that makes a lot of sense.  These ended up being my favorites overall not in any small part for the wife appeal.  My first set were giant boxes about 6 feet tall that my wife really hated.  I thought they were kinda cool but they had to go LOL.


----------



## Tjj226 Angel

fleasbaby said:


> I'm going to have to get brave and try using it. Something about gluing and clamping down layers of extremely thing wood makes me twitchy though...LOL....I see a sticky disaster on the horizon in the Wabi Sabi Workshop....oh well. Only one way to truly learn.



Its not that bad. Its all about setup.

You don't even clamp the wood. What you do is you apply some contact cement to both the veneer and your wood and you let it sit for ~20 minutes before you apply the two pieces together. 

The glue goes from being a wet sticky mess to something that kind of reminds me of fly paper. Its super tacky, but its no longer wet. 

Then you gently lay your veneer on your wood panel using a roller to help make sure the veneer is lying flat with no air bubbles. The two tacky surfaces almost insta-bond to each other. Once your piece is on, just use your roller to smooth out the rest of the veneer. After that, you trim it to size and let it cure overnight. 

I have never had to clamp the veneer to the wood.


----------



## puck

I built a set of long horns that I veneered with mixed results.  Mostly, I think I just didn't really know what the heck I was doing.  They came out great at first but the veneer later delaminated a bit in places which really sucked.  I was able to iron it back down to some degree but it wasn't great.  Again, I just didn't do it right.  It's also hard to get a great finish if the veneer has any deeper saw marks or any flaws since you can't sand it much before you sand through it.


----------



## L0rdGwyn

fleasbaby said:


> The whole "low-watts-high-sensitivity" thing is fascinating. The sound is a little different from my main rig (A Schiit Vidar driving a pair of Magnepan LRS), but not that far off. Its more intimate, but not in the way audiophiles say intimate is. Its really nice with jazz especially, and I listen mostly to that...Blue Note, Impulse, Verve, etc...as well as spiritual and free stuff from the seventies.



It's definitely different, I am all but committed to the flea-watt life it at this point and really enjoying the change.  In an audiophile world so full of choice, it is something of a relief to narrow the playing field.  Also makes for an interesting exploration of high-sensitivity vintage options.



puck said:


> Thanks!  The original design is from Masaaki Takenaka.  I don't know if his design is still up but I actually modeled the design in order to convert it to english units since I can't get metric material.  Here's an image of the 3D model.  I actually have drawings for the parts as well.  It's technically a backloaded horn design.  The spiral creates the path length needed for the horn in a smaller enclosure.
> 
> I agree that low watt high sensitivity systems have their own sound, especially the single driver designs.  I really got fascinated with them in the early 2000s and built something like 4 different designs. I was really into the Passlabs first watt ideas and thought that was just a really cool concept that makes a lot of sense.  These ended up being my favorites overall not in any small part for the wife appeal.  My first set were giant boxes about 6 feet tall that my wife really hated.  I thought they were kinda cool but they had to go LOL.



Well done, interesting design.  Did you ever get around to running these with a First Watt style class A amp?


----------



## puck

L0rdGwyn said:


> It's definitely different, I am all but committed to the flea-watt life it at this point and really enjoying the change.  In an audiophile world so full of choice, it is something of a relief to narrow the playing field.  Also makes for an interesting exploration of high-sensitivity vintage options.
> 
> 
> 
> Well done, interesting design.  Did you ever get around to running these with a First Watt style class A amp?




I didn't.  I always wanted to build one but never got around to it.  I should sometime though as we as a family listen to music a lot now so it would be fun to use those speakers and an amp like that.  They currently have been relegated to being rear surround speakers as the wife didn't like my single driver center speaker that I had built and I didn't feel like building a new center at the time so we ended up with a Def Tech center and front speaker setup.  It's fine but it would be fun to revisit the single driver setup for music.


----------



## L0rdGwyn

puck said:


> I didn't.  I always wanted to build one but never got around to it.  I should sometime though as we as a family listen to music a lot now so it would be fun to use those speakers and an amp like that.  They currently have been relegated to being rear surround speakers as the wife didn't like my single driver center speaker that I had built and I didn't feel like building a new center at the time so we ended up with a Def Tech center and front speaker setup.  It's fine but it would be fun to revisit the single driver setup for music.



Gotcha, I bet they would sound great in that setup, or with a SET design, a 2A3 or the like.  If you want a simple and relatively cheap First Watt type amp, check out NP's Amp Camp Amp on the diyAudio store, they seem to sell out repeatedly but are up for preorder.  High praise for this little guy and comes with everything you need, just stuff the boards and mount everything in the chassis, can also grab two and run them as monos. 

Amp Camp Amp: https://diyaudiostore.com/products/amp-camp-amp-kit?variant=7072933085218


----------



## puck

L0rdGwyn said:


> Gotcha, I bet they would sound great in that setup, or with a SET design, a 2A3 or the like.  If you want a simple and relatively cheap First Watt type amp, check out NP's Amp Camp Amp on the diyAudio store, they seem to sell out repeatedly but are up for preorder.  High praise for this little guy and comes with everything you need, just stuff the boards and mount everything in the chassis, can also grab two and run them as monos.
> 
> Amp Camp Amp: https://diyaudiostore.com/products/amp-camp-amp-kit?variant=7072933085218



Nice!  Thanks for the link.  I'll check them out.


----------



## Xcalibur255

L0rdGwyn said:


> The wife-appeal is a real issue  Baltic birch, a favorite amongst DIY speaker builders, is basically forbidden in my home LOL.  If you have the knowledge and gear, why not give it a go!  The barrier for me is acquiring the woodworking equipment and learning the trade, it is a big time / money / space investment, one I would love to make, but I've already made one of those big investments recently for building tube amplifiers.  What I was considering at one point was doing a pair of bass reflex speakers using Markaudio drivers, they are pricey but very highly regarded and they have plans available on their site, like these using the Alpair 12P.  It is about 92dB/W sensitive, so could get decent volume with a little flea-watt tube amp.  Your 10W amp should be able to rock the house with those Fostex units.



If you build these you have to make a second pair for me pretty please.  

(Joking of course...... or am I?   )


----------



## fleasbaby

L0rdGwyn said:


> The wife-appeal is a real issue  Baltic birch, a favorite amongst DIY speaker builders, is basically forbidden in my home LOL.  If you have the knowledge and gear, why not give it a go!  The barrier for me is acquiring the woodworking equipment and learning the trade, it is a big time / money / space investment, one I would love to make, but I've already made one of those big investments recently for building tube amplifiers.  What I was considering at one point was doing a pair of bass reflex speakers using Markaudio drivers, they are pricey but very highly regarded and they have plans available on their site, like these using the Alpair 12P.  It is about 92dB/W sensitive, so could get decent volume with a little flea-watt tube amp.  Your 10W amp should be able to rock the house with those Fostex units.



BTW thanks for pointing the Alpair 12p out...definitely moving it up my list for more research....


----------



## whirlwind

L0rdGwyn said:


> Wow, very cool Eric was willing to go to those lengths to help you get the sound right, nice looking crossovers too  I've perused his speakers a few times, I'm more of a wood veneer kind of guy, maybe down the road I would give something from Tekton a shot if they could do something like this, beautiful veneer.  The market for high-sensitivity speakers just really isn't that large, so definitely worth exploring at some point methinks.
> 
> 
> 
> ...



Some nice Grado mods Keenan.
Grado headphones were my entry into listening with headphones and I am right with you with how something sounds....if i think it sounds good, I am happy


----------



## L0rdGwyn (Oct 31, 2020)

Xcalibur255 said:


> If you build these you have to make a second pair for me pretty please.
> 
> (Joking of course...... or am I?   )



You never know, we will see  I am thinking speaker building could be a next year type of endeavor.  Need to do a garage overhaul before I try to cram a bunch of woodworking equipment in there!  It is on the to do list.  I am trying to do a better job of working on what's in front of me though instead of creating an endless queue of projects LOL need to finish the 801A amp (the existence of that amp is your fault, by the way) and the 45 parafeed overhaul.  Just need this dang iron from Sowter...I was promised a timeline, and then they never got back to me.

One thing I like about the idea of speaker building is - in my mind at least - it is a bit simpler and cheaper than building a from-scratch tube amp!  Especially if working from a known design.  So I could build speakers for others or gift them relatively easily once I am familiar with the woodworking aspects.

Building an amp is...a PITA, to be honest HA!  Designing the circuit, makings parts lists, acquiring all of the parts, waiting forever for transformers, drafting the layout, sending layout diagrams for a chassis, then trialing said layout before coating the chassis, then drilling and coating the chassis, then all of the point-to-point wiring, getting electrocuted, testing the amplifier, tweaking it for better sound...

For full-range speakers, once the investment in the equipment is made, just need the wood, the speaker driver, some glue, damping material, binding posts, wire, contact cement and veneer!  Again, in my mind this is a much simpler process lol real life is probably different, but could be a nice change of pace.  Much more planning and complexity involved if going for your own from-scratch design.

With all of that being said, I am looking for an excuse to try out some OPT from Electra-Print.  Outside of the transformers I've already purchased, whatever amplifier comes next, I will be going through them.  They are in the USA, solid quality, and pretty reasonably priced compared to the likes of Sowter and Lundahl.



fleasbaby said:


> BTW thanks for pointing the Alpair 12p out...definitely moving it up my list for more research....



Of course!  The Alpair 10P is another popular option, but all of Markaudio's drivers from the Alpair line are highly regarded, the 12P is the most efficient from what I have seen, clocking in at around 92dB/W, I think the 10P is around 90dB/W.  The guys on the speaker forum over at diyAudio are very helpful if you have any design questions.



whirlwind said:


> Some nice Grado mods Keenan.
> Grado headphones were my entry into listening with headphones and I am right with you with how something sounds....if i think it sounds good, I am happy



Thanks, Joe!  Like I said I might do another one with the Symphones V9, really like the V8 driver.  @fleasbaby does some incredible wood cup lathing, you can check out his stuff here: https://wabisabiheadphones.wordpress.com/

If anyone wanted to make their own Grado style headphones, there is a great community of Head-Fiers to talk to about it.  The big players in after-market Grado-style drivers are Symphones, Nhoord, Elleven Acoustica (I have not actually heard these but they seem to be highly praised), and of course you can extract Grado drivers and use them too.


----------



## bcowen

L0rdGwyn said:


> Wow, very cool Eric was willing to go to those lengths to help you get the sound right, nice looking crossovers too  I've perused his speakers a few times, I'm more of a wood veneer kind of guy, maybe down the road I would give something from Tekton a shot if they could do something like this, beautiful veneer.  The market for high-sensitivity speakers just really isn't that large, so definitely worth exploring at some point methinks.



Yeah, my Lores have the basic black paint. The finish is of good quality, but the cabinets will never be confused with pieces of nice furniture.  Fortunately they're on the smallish side (for floorstanders) and don't dominate the room or call attention to themselves...at least IMO (my wife may be politely _not_ suggesting otherwise ).








L0rdGwyn said:


> Just ranting now, but here are some of the headphones I made, the cups were lathed by the Head-Fier @fleasbaby who is a very talented woodworker, beautiful stuff.



Man, those are all gorgeous!  Really nice work!


----------



## L0rdGwyn

bcowen said:


> Yeah, my Lores have the basic black paint. The finish is of good quality, but the cabinets will never be confused with pieces of nice furniture.  Fortunately they're on the smallish side (for floorstanders) and don't dominate the room or call attention to themselves...at least IMO (my wife may be politely _not_ suggesting otherwise ).
> 
> 
> 
> ...



Wow nice setup!  The Lores look great in black.  Always tricky to toe the spouse acceptance factor line lol.  My strategy is to bring up a photo of something I know is pushing the boundary and say something like "look at these ridiculous things!", which usually gets a "oh my god, those are hideous!", but if I get a mild "hmmm" or "they're not that bad", I can file them away as possibly being safe.  The original Snell Type C got a hard pass LOL admittedly they are very of their time aesthetically.

Have some spooky jams playing for the holiday, front windows open in case there are any brave trick-or-treaters out there, kiddos have never heard the Halloween Theme quite like this before


----------



## Zachik

L0rdGwyn said:


> Have some spooky jams playing for the holiday, front windows open in case there are any brave trick-or-treaters out there, kiddos have never heard the Halloween Theme quite like this before


What treats have you got for the brave trick-or-treaters?  Giving away L63 tubes by any chance? Maybe I can still get in time...


----------



## L0rdGwyn (Oct 31, 2020)

Zachik said:


> What treats have you got for the brave trick-or-treaters?  Giving away L63 tubes by any chance? Maybe I can still get in time...



Let's see...the last kid asked for Reese's...instead I gave him my NOS pair of Western Electric 421A.  I told him to hold onto them for 10 years, then sell them on eBay and buy stock in The Hershey Company with the earnings. This was not appreciated.


----------



## bcowen (Oct 31, 2020)

L0rdGwyn said:


> Let's see...the last kid asked for Reese's...instead I gave him my NOS pair of Western Electric 421A.  I told him to hold onto them for 10 years, then sell them on eBay and buy stock in The Hershey Company with the earnings. This was not appreciated.



LOL!  Do you have the kid's phone number?  I need to talk to him about 1) showing proper gratitude for a gift (any gift), and 2) see how many Reeses I need to bring in trade for those WE's.


----------



## bcowen

L0rdGwyn said:


> Wow nice setup!  The Lores look great in black.  Always tricky to toe the spouse acceptance factor line lol.  My strategy is to bring up a photo of something I know is pushing the boundary and say something like "look at these ridiculous things!", which usually gets a "oh my god, those are hideous!", but if I get a mild "hmmm" or "they're not that bad", I can file them away as possibly being safe.  The original Snell Type C got a hard pass LOL admittedly they are very of their time aesthetically.
> 
> Have some spooky jams playing for the holiday, front windows open in case there are any brave trick-or-treaters out there, kiddos have never heard the Halloween Theme quite like this before



Nice!  Seems we have similar good taste in flooring, rugs, and wall color.  And oh yeah, tubes and LP's.


----------



## Zachik

L0rdGwyn said:


> I gave him my NOS pair of Western Electric 421A


You are a bad person - you just painted a huge bullseye on this kid's back!


----------



## L0rdGwyn (Oct 31, 2020)

bcowen said:


> LOL!  Do you have the kid's phone number?  I need to talk to him about 1) showing proper gratitude for a gift (any gift), and 2) see how many Reeses I need to bring in trade for those WE's.



You know I didn't think to get it!  I was put off by the dirty looks from his parents, and some muttering about giving out "ugly yellow lightbulbs" instead of candy.



bcowen said:


> Nice!  Seems we have similar good taste in flooring, rugs, and wall color.  And oh yeah, tubes and LP's.



HA!  You are right, I didn't notice that before!  Wood floors, rugs, neutral wall tones, tubes, and LPs, a combination for the ages.



Zachik said:


> You are a bad person - you just painted a huge bullseye on this kid's back!



Uh oh, sounds like the makings of a good horror film, "Hunted by Head-Fiers"


----------



## L0rdGwyn

I have those Klipsch KG 1 speakers coming to me on Wednesday.  What I didn't mention about them is the binding posts terminals are broken on one of the speakers.  Easily replaceable, but I wanted them to be original (psycho), so I picked up a pair of KG 1 crossovers someone had for sale on eBay.



In addition to fixing the binding posts, I can remove and measure the the mylar film caps from the four crossovers and take the best matched pairs.  Maybe down the road I will upgrade them to some other fancy-schmancy film cap if I really love the speakers.  I was able to find a supplier of 25uF 100V nonpolar electrolytics (Madisound), so they will be replaced as well.

Looking forward to getting those little guys up and running!


----------



## Xcalibur255

L0rdGwyn said:


> (the existence of that amp is your fault, by the way)



So it's time to start talking about the type 50 now?


----------



## L0rdGwyn

Xcalibur255 said:


> So it's time to start talking about the type 50 now?



Lol unfortunately I am ahead of the curve on that one, I nearly lost my mind a few weeks ago and bought a NOS pair that was on sale...as you can imagine, they were still bonkers expensive.  The 50 is a bit of a pain though as it can only take a 10K grid leak resistor, necessitating either an interstage transformer or grid choke.  The 50 is already pretty nutso expensive and rare (at least NOS), add on the additional iron requirement and that would be one expensive amplifier!  Would love to do it, but not any time soon.   It is on my list of pie-in-the-sky amplifier builds to do some day, along with the PX25.  These tubes are on the verge of extinction, there are some new production models out there though...


----------



## fleasbaby

@puck looking at your speakers, you got me thinking about grills now...did a test run on a Kumiko grill using some scrap pine I had on hand after a job on the house (side note: if anyone tells you replacing a front door is easy, laugh them out of the room....if they tell you its even easier using a prehung door, kick them as you laugh them out of the room), and I think I can pull it off. 

First attempt had terrible joints (see below). Second run should be better though. I'm going to make some jigs for the angles...the speakers are in the background. I assembled them without finishing the cabinets to hear how they sound before committing more time to them. After a few hours break in I am really, really liking what I hear, so I'll be disassembling them again soon, and making those cabinets look prettier (somehow...Maple plywood just isn't pretty...).


----------



## puck

Very nice!


----------



## L0rdGwyn (Nov 6, 2020)

After five crazy nights at work, I am back to the world of the humans!  So obviously first thing I have to do is DIY.

I got the Klipsch KG1 a few days ago, cleaned up the crossovers today, replaced the 30-year-old electrolytics with 25uF nonpolar replacements, and matched the mylar film caps from the two sets of crossovers I had on hand.



Also replaced the broken binding posts on one of the speakers from the spares I purchased.  Perfect.



These speakers are in VERY good condition, better than anticipated, which is always a nice surprise.  I am a big fan of walnut veneer.

 

Here is the first draft of my bedroom stereo setup.  Have the Klipsch KG1 paired up with my 6J5 / 45 parafeed amplifier.  As I've said countless times, the amplifier is being overhauled when the replacement mains transformer arrives.  As built, it only puts out 0.75W.  Even so, it sounds great!  Drives these speakers to very satisfying volumes, even if it might be soft clipping on loud transients.  We will fix that later when it is rebuilt for 2W.



These speakers sound very nice, a perfect fit for my use.  Detailed, balanced sound, nice clarity, and satisfying bass for their size.  The low end benefits from room boundary reinforcement without a doubt, so even better given their near-wall position.  Obviously speaker positioning is not ideal, I plan to get some platforms to raise the speakers off the dresser slightly, under which I will also hide the Bluesound streamer and separate DAC.  They will likely stay where they are in terms of left-right spacing, this is a compromise for the plants LOL.  My girlfriend recently started collecting exotic plans, so this setup is an amalgamation of our two weird hobbies.

Have some new artwork coming for the wall above, so maybe that will dictate the chassis color for the revamped amp


----------



## Xcalibur255

They must be sealed cabinets judging by the proximity to the wall.  

This kind of post should honestly be a PSA to people in general on the subject of how much power they really need from an amplifier.  I'm guessing those speakers are in the high 80's for sensitivity given their small size and you're getting the listening volumes you want on a single watt of output power.


----------



## L0rdGwyn

@Xcalibur255 90dB/W!  And yes, they are sealed cabinets  plenty of volume for my bedroom, figured it would work out given my experience running the Snells off the 45 amp, transient distortion will benefit from the extra headroom when the amp is fixed up.


----------



## fleasbaby

Xcalibur255 said:


> They must be sealed cabinets judging by the proximity to the wall.
> 
> This kind of post should honestly be a PSA to people in general on the subject of how much power they really need from an amplifier.  I'm guessing those speakers are in the high 80's for sensitivity given their small size and you're getting the listening volumes you want on a single watt of output power.





L0rdGwyn said:


> @Xcalibur255 90dB/W!  And yes, they are sealed cabinets  plenty of volume for my bedroom, figured it would work out given my experience running the Snells off the 45 amp, transient distortion will benefit from the extra headroom when the amp is fixed up.



My Fostex FE206En drivers are 96bB/W, and I'm actually having trouble keeping volumes low and sensible with that little 8 Watt T-Amp I made...there are definitely lessons to be learned. I know I am taking notes and eyeing out my Schiit Vidar and Magnepan LRS setup, wondering if its worth keeping...


----------



## Xcalibur255

I think a lot of people running Vidar could and should be using Aegir instead.  They're scared off by the lower output and shouldn't be.


----------



## fleasbaby (Nov 6, 2020)

Xcalibur255 said:


> I think a lot of people running Vidar could and should be using Aegir instead.  They're scared off by the lower output and shouldn't be.



I went to the Schittr and heard both. I preferred the sound of the Vidar...hence my choice. They had both out and hooked up to a pair of LRS. I loved the combo. Went home and started hunting for a second hand Vidar and joined the waitlist for the LRS.


----------



## L0rdGwyn

fleasbaby said:


> My Fostex FE206En drivers are 96bB/W, and I'm actually having trouble keeping volumes low and sensible with that little 8 Watt T-Amp I made...there are definitely lessons to be learned. I know I am taking notes and eyeing out my Schiit Vidar and Magnepan LRS setup, wondering if its worth keeping...



Well keep us posted on what you decide to do!  Could always give those Fostex speakers a try with some tubes down the road  a few watts should get the job done.


----------



## L0rdGwyn

Some serious business rare tubes have appeared on the eBay...be still my beating heart!  These will go for big bucks...I will probably stay on the sidelines since my 801A amplifier is not actually complete yet, but woooh boy how tempting...ceramic base AND graphite plates, how can one resist?



Oddly enough, the rare 801A types are much cheaper if bought in Japan, the North American eBay markup for DHTs is a real thing.  I find it ironic that they are cheaper / more plentiful in Japan considering they were made here 😂 Japanese audiophiles love their DHT SET amplifiers.

I have been staring at this pair of 1940 ceramic-base Taylor 801A on Japanese auction for a week or so...again, cannot justify the purchase without a completed amplifier, around $300 with the exchange rate, but so purdy.


----------



## whirlwind (Nov 7, 2020)

L0rdGwyn said:


> After five crazy nights at work, I am back to the world of the humans!  So obviously first thing I have to do is DIY.
> 
> I got the Klipsch KG1 a few days ago, cleaned up the crossovers today, replaced the 30-year-old electrolytics with 25uF nonpolar replacements, and matched the mylar film caps from the two sets of crossovers I had on hand.
> 
> ...



Wow!  What a great bedroom set-up !

Those 801 tubes do look to be made rather well


----------



## fleasbaby

L0rdGwyn said:


> Well keep us posted on what you decide to do!  Could always give those Fostex speakers a try with some tubes down the road  a few watts should get the job done.



Thats what I'm thinking...any suggestions for a decent flea-watt amp for a new-ish builder?


----------



## Tjj226 Angel

L0rdGwyn said:


> Lol unfortunately I am ahead of the curve on that one, I nearly lost my mind a few weeks ago and bought a NOS pair that was on sale...as you can imagine, they were still bonkers expensive.  The 50 is a bit of a pain though as it can only take a 10K grid leak resistor, necessitating either an interstage transformer or grid choke.  The 50 is already pretty nutso expensive and rare (at least NOS), add on the additional iron requirement and that would be one expensive amplifier!  Would love to do it, but not any time soon.   It is on my list of pie-in-the-sky amplifier builds to do some day, along with the PX25.  These tubes are on the verge of extinction, there are some new production models out there though...



Those grant fidelity type 50s are like 600 a pair. It's actually kind of impressive they are that cheap considering the parts and labor that went into making them. 

Im kind of in the same boat. There is a certain draw or mystique to the type 50. I just can't justify the price of a type 50 when the 300b exists. Maybe one of these days, the chinese will make a cheap type 50.


----------



## Tjj226 Angel

fleasbaby said:


> Thats what I'm thinking...any suggestions for a decent flea-watt amp for a new-ish builder?



Try a triode strapped el84. 

Cheap, easy, great sound, and there are TONS of schematics online to choose from.


----------



## L0rdGwyn (Nov 8, 2020)

fleasbaby said:


> Thats what I'm thinking...any suggestions for a decent flea-watt amp for a new-ish builder?



Fantastic!  Sure thing.  You sort of have three options that increase in degree of complexity:

1) Build from a kit
2) Build from a vetted schematic
3) Design and build from scratch

If you wanted to work from a kit, the obvious first option is Bottlehead.  Has the advantage of including just about everything you need for the build along with detailed step-by-step instructions, just need a soldering iron, a DMM, and some wood glue (but of course, you would build a beautiful wood base I am sure @fleasbaby).  Disadvantage is they do little to help with a conceptual understanding of the circuit, the instructions are written in a very "do this, then do that" kind of way, but definitely a good way to start.  Can also be quite expensive depending on the kit.  Their cheapest stereo kit is the S.E.X. amplifier, which doubles as a headphone amp, good for 2W.  The next option of the ladder is the Stereomour II, a 2A3 integrated amplifier, which will get you around 3.5W, but the price nearly doubles.

If you want a little more independence of design and are up for delving deeper into electronics tinkering, another option is Tubelab.  The dude who runs the site, George, is very active on diyAudio and provides PCBs for single-ended amplifiers, the most popular being his "Simple Single-Ended" design.

http://tubelab.com/pc-boards/tubelab-sse/

He has areas of the site that go through the design, build process, transformer options, etc. to build out the rest of the amplifier.  There is also a dedicated area of diyAudio for his builds, where you can ask questions / get advice.

https://www.diyaudio.com/forums/tubelab/

Going with Tubelab allows you to work from a proven circuit, but choose some of your own parts (transformers, in particular) and the flexibility to design your own chassis.  Those are probably the top two options in terms of kits, but there are others out there.

The next option, as @Tjj226 Angel said, is to find a tried-and-true schematic to work from.  As usual, diyAudio is a good place to ask questions and seek advice, always happy to help here as well to the best of my ability  for single-ended, going with a triode-strapped pentode design like the EL84 is going to be the simplest approach as you can avoid worrying about filament supplies for directly-heated triodes, which add quite a bit of complexity to a build.  If you wanted to go bigger than the EL84, other indirectly-heated output tube options with tons of schematics out there are 6L6, EL34, KT66, although the tubes themselves will be more expensive.

Then the last option is to go straight to your own design, which I can tell you from experience is very challenging.  But if you are up for it, the learning experience is very valuable.  Obviously this gets you full control to do what you want with the amplifier, but lots of learning to be done and pitfalls along the way.  My top two resources I recommend in terms of tube amplifier design are Morgan Jones' _Valve Amplifiers_ (PDFs floating around online) and Merlin Blencowe's _Designing High-Fidelity Valve Preamps _(print only, but he has tons of information on his site as well: http://www.valvewizard.co.uk/).

Sorry for the book!  Hope that helps.


----------



## L0rdGwyn

Tjj226 Angel said:


> Those grant fidelity type 50s are like 600 a pair. It's actually kind of impressive they are that cheap considering the parts and labor that went into making them.
> 
> Im kind of in the same boat. There is a certain draw or mystique to the type 50. I just can't justify the price of a type 50 when the 300b exists. Maybe one of these days, the chinese will make a cheap type 50.



Those Grant Fidelity tubes look great, better than most other new production tubes IMO.  Someone is going to have to start making them cheap, NOS stocks are drying up, 50 appears to be going extinct!  It does have an allure, but it's terrifying to invest into an expensive amplifier and not know if you are going to have tubes available in the future.  EML made the 50 at one point, not sure if they still are though.


----------



## Tjj226 Angel

L0rdGwyn said:


> Those Grant Fidelity tubes look great, better than most other new production tubes IMO.  Someone is going to have to start making them cheap, NOS stocks are drying up, 50 appears to be going extinct!  It does have an allure, but it's terrifying to invest into an expensive amplifier and not know if you are going to have tubes available in the future.  EML made the 50 at one point, not sure if they still are though.



Doubtful. I mean they technically don't even make a 2a3 tube. All the chinese 2a3s are 300bs with a 2.5v filament. 

I wouldn't be a bit surprised if the same approach is used for the PX4s which would explain why they are so much cheaper than the PX25s.


----------



## bcowen

Tjj226 Angel said:


> Try a triode strapped el84.
> 
> Cheap, easy, great sound, and there are TONS of schematics online to choose from.



Since you mention the EL-84, I fondly remember this little Cary integrated using 4 EL-84's per channel in an ultralinear Class A, push-pull config. After I was kicked out of the P-P club by daring to listen to an SET it had to go, but it was a sweet sounding very musical amp regardless. Can only imagine how much better it would have been in a triode configuration.


----------



## L0rdGwyn

Chill Sunday morning with Stars of the Lid.

 



We are approaching the very cold Cleveland winter, I am thinking of shutting down garage DIY operations for the season, mostly because there are components that will not appreciate being exposed to freezing temperatures, thawed, then frozen again repeatedly.  I have no timeline on when Sowter is going to ship my transformers, there are other aspects of the amplifier I could be working on, but admittedly the motivation isn't there since I will fall short of finishing the prototype without the new transformers.  Will probably put together a makeshift soldering station indoors when they get here, I won't be able to resist, but again not sure when that is going to be.

So, might be a winter of LTSpice prototyping and amplifier build fantasies  right now I am playing around with some sort of design for the LL9202 transformers that will be left over from the first iteration of 801A prototype (EL11 SEP?), as well as a "budget" amplifier featuring the GU-50 output tube, $10 a pair Russian copy of the Telefunken LS-50 (reverse engineered by the Russians after capturing German military equipment), a popular DIY option often called the "poor man's 300B".  I really want to try some OPT from Electra-Print, not sure this will be the one but it is intriguing, maybe with a 6E5P driver for a two-stage all-Russian integrated.

The little hats on the GU-50 are growing on me.  With a 2.5K OPT primary and a 350V 100mA bias point, can get 8W out of these guys.



The other tube on the short list of amplifier builds falls somewhere between "realistic" and "pie-in-the-sky", the Telefunken EL156.  They are pretty expensive, but I have some serious tube lust for them...

Anyway, going to finish what I am working on before starting anything new for once, but it might not be until springtime.

Have a nice Sunday everyone


----------



## mordy

Personally, I would appreciate a true budget preamp - headphone amplifier using the GU-50 with off the shelf inexpensive parts.


----------



## L0rdGwyn (Nov 8, 2020)

mordy said:


> Personally, I would appreciate a true budget preamp - headphone amplifier using the GU-50 with off the shelf inexpensive parts.



Well thanks @mordy !  8W is pretty spicy for a headphone amp, I would build it for speakers with a headphone jack most likely, with parallel resistors on the headphone output.  Given that this would be pretty high-powered for a SET design, even with the parallel resistors, the headphone output would put out some decent power.

I threw together a quick LTSpice schematic to get a ballpark figure.  With the amp putting out roughly 8W into 8ohm, it would put out 200mW into a 300ohm parallel load (300ohm headphone).  Drop the headphone impedance to 32ohm and it would do 1.6W!  So plenty of power for headphones still.

Definitely would try to keep the amp design cheap, but two areas where I can't compromise are the chassis and the output transformers.  A pair of Electra-Print copper 2.5K:8ohm 100mA OPT would cost $400, which is actually affordable as far as high-quality transformers go.  So wouldn't be _super _cheap, but budget as far as a transformer-coupled amplifiers go while not compromising on sound quality.  The cost savings only go so far when you are dealing with transformers, OTL typically have the cost-advantage.



All theoretical right now, but I like the idea of this design, back to basics.  Could put this together without worrying about a prototype, it would just work!


----------



## Xcalibur255

bcowen said:


> Since you mention the EL-84, I fondly remember this little Cary integrated using 4 EL-84's per channel in an ultralinear Class A, push-pull config. After I was kicked out of the P-P club by daring to listen to an SET it had to go, but it was a sweet sounding very musical amp regardless. Can only imagine how much better it would have been in a triode configuration.


My Luxman uses this tube configuration too.  For a mainstream retail product it sounds quite nice and pairs well with my alnico speakers.  It's never been the sound quality that has been the letdown with this amp, it's how much of a misfit it is when it comes to integrating into a larger system with other components.  In addition to the known issue it has with backfeeding distortion into my DAC when it's not on, I've also recently found out that it does the same to other gear plugged into the same surge supressor.  Decent sounding or not it's not worth having to unplug the thing all the time.  If it were standalone and not sharing the DAC and power source with another amplifier there wouldn't be an issue.  Clearly Luxman assumed all its owners would have that usage scenario.


----------



## Paladin79 (Nov 9, 2020)

L0rdGwyn said:


> Chill Sunday morning with Stars of the Lid.
> 
> 
> 
> ...



I am in the process of designing an LS50 amp in order to win a bet. I need to achieve 12 watts out and use other specific parts handed to me by local engineers. I have a version breadboarded already and need to complete a cabinet before I do final assembly. This is a speaker amp.

I have also designed my own class A OTL headphone amp of course, the Incubus Elegan amp. It is a great cat warmer. That is not an adapter on the driver tube but a socket saver, native tubes are 6sn7 and 6080's. 

 Second photo is wood I will use for the LS 50 amp. In order to win the bet I need to use GU 50's with 6BX6 or equivalent drivers so I have some latitude there.


----------



## bcowen

Paladin79 said:


> I am in the process of designing an LS50 amp in order to win a bet. I need to achieve 12 watts out and use other specific parts handed to me by local engineers. I have a version breadboarded already and need to complete a cabinet before I do final assembly. This is a speaker amp.
> 
> I have also designed my own class A OTL headphone amp of course, the Incubus Elegan amp. It is a great cat warmer. Second photo is wood I will use for the LS 50 amp



Do I get royalties on the tiger maple?  

Blatantly ripping off your idea on the Schiit rack to begin with is, of course, irrelevant.


----------



## Paladin79

bcowen said:


> Do I get royalties on the tiger maple?
> 
> Blatantly ripping off your idea on the Schiit rack to begin with is, of course, irrelevant.


I have to admit you outdid me on your mini-rack after you ripped off my design.   I am still annoyed that I had to build a sideways amp so it fit on your shelf. Can you not even tell each channel is 90 degrees out of phase? Oh well, at least you have not copied my large rack design. Solid cherry and patinated copper.


----------



## L0rdGwyn (Nov 9, 2020)

Paladin79 said:


> I am in the process of designing an LS50 amp in order to win a bet. I need to achieve 12 watts out and use other specific parts handed to me by local engineers. I have a version breadboarded already and need to complete a cabinet before I do final assembly. This is a speaker amp.
> 
> I have also designed my own class A OTL headphone amp of course, the Incubus Elegan amp. It is a great cat warmer. That is not an adapter on the driver tube but a socket saver, native tubes are 6sn7 and 6080's.
> 
> Second photo is wood I will use for the LS 50 amp. In order to win the bet I need to use GU 50's with 6BX6 or equivalent drivers so I have some latitude there.



Very nice!  I see we both enjoy tube amplifiers and cats  beautiful curly wood, I am sure the amplifier will be a beauty.  I have seen your OTL reference in other threads, perhaps I will get to hear it some day.  An OTL design is in my future, unsure of the topology but I have quite the stash of OTL tubes burning a hole in my pocket.  Right now I am lost in the world of transformer-coupled single-ended class A with no end in site.  The current project is an 801A full A2 design with a 0V grid bias.  It has gone through various stages of prototyping due to circuit complexity, nearing completion at long last.

Definition of a rat's nest.  Old photo but it hasn't gotten any less ugly


----------



## bcowen

L0rdGwyn said:


>



That's gonna need a _really_ big box.


----------



## fleasbaby

L0rdGwyn said:


> Fantastic!  Sure thing.  You sort of have three options that increase in degree of complexity:
> 
> 1) Build from a kit
> 2) Build from a vetted schematic
> ...



Hmmmm...I think the sane approach would be a Bottlehead S.E.X. kit....but I want to explore the tubelab stuff a little. I might head that way instead. For my current little amp, I was fine figuring out how to wire up a power switch, set it up to take two sources and get a volume knob wired up as well. I might have the chops to make something from tubelab fly, and to greater satisfaction...



L0rdGwyn said:


> Chill Sunday morning with Stars of the Lid.
> 
> 
> 
> ...



That Stars of the Lid album is fantastic...



bcowen said:


> Do I get royalties on the tiger maple?
> 
> Blatantly ripping off your idea on the Schiit rack to begin with is, of course, irrelevant.





Paladin79 said:


> I have to admit you outdid me on your mini-rack after you ripped off my design.   I am still annoyed that I had to build a sideways amp so it fit on your shelf. Can you not even tell each channel is 90 degrees out of phase? Oh well, at least you have not copied my large rack design. Solid cherry and patinated copper.



Love these racks. A little while back I made one for my Schiit-stack as well. Its all Walnut...need to dig up pics and share. I have some on my Wabi Sabi Headphones Instagram somewhere...


----------



## L0rdGwyn

bcowen said:


> That's gonna need a _really_ big box.



It's gonna need two


----------



## bcowen

Paladin79 said:


> Oh well, at least you have not _*yet*_ copied my large rack design. Solid cherry and patinated copper.



^^^^^^^
Fixed this for you.


----------



## Paladin79 (Nov 9, 2020)

L0rdGwyn said:


> Very nice!  I see we both enjoy tube amplifiers and cats  beautiful curly wood, I am sure the amplifier will be a beauty.  I have seen your OTL reference in other threads, perhaps I will get to hear it some day.  An OTL design is in my future, unsure of the topology but I have quite the stash of OTL tubes burning a hole in my pocket.  Right now I am lost in the world of transformer-coupled single-ended class A with no end in site.  The current project is an 801A full A2 design with a 0V grid bias.  It has gone through various stages of prototyping due to circuit complexity, nearing completion at long last.
> 
> Definition of a rat's nest.  Old photo but it hasn't gotten any less ugly


In order to win this bet, I will use pentodes as triodes to accomplish a SET amp. I do not show the insides of my amps, I have received offers on my OTL design and for me to show very much is not in my best interest. Maybe one day I will build another loaner so you can check out the sound. I started that design because my local friends wanted to do a blind listen on 6sn7 equivalent tubes in four identical amps. Unfortunately everyone who heard it wanted one. The exception being one guy who is saving up lol.

You must  keep the room locked where your amp is stored lol. My cat Finnegan would have half those jumpers hidden throughout the house on the first day if I left something like that within his reach.


----------



## L0rdGwyn

fleasbaby said:


> Hmmmm...I think the sane approach would be a Bottlehead S.E.X. kit....but I want to explore the tubelab stuff a little. I might head that way instead. For my current little amp, I was fine figuring out how to wire up a power switch, set it up to take two sources and get a volume knob wired up as well. I might have the chops to make something from tubelab fly, and to greater satisfaction...
> 
> That Stars of the Lid album is fantastic...



Great!  Well keep us posted, as I said happy to answer questions and I am sure other knowledgeable folks here would be too.  Going with Tubelab will give more in the way of customizability and maybe more bang/wattage for the buck.

Doing a quick "Google Images" search, here are some nice looking "Simple Single-Ended" builds.

Also glad to find another Stars of the Lid fan  good stuff!


----------



## Paladin79 (Nov 9, 2020)

L0rdGwyn said:


> Great!  Well keep us posted, as I said happy to answer questions and I am sure other knowledgeable folks here would be too.  Going with Tubelab will give more in the way of customizability and maybe more bang/wattage for the buck.
> 
> Doing a quick "Google Images" search, here are some nice looking "Simple Single-Ended" builds.
> 
> Also glad to find another Stars of the Lid fan  good stuff!


Walnut and spalted maple on the the amp on the right perhaps?

I have a bunch of splated maple to use but I have to be pretty careful with it and may need to move equipment outside in warmer weather.
The electronics is easy for me but I need to spend more time learning woodworking. A couple of my projects.


----------



## Tjj226 Angel

L0rdGwyn said:


> Very nice!  I see we both enjoy tube amplifiers and cats  beautiful curly wood, I am sure the amplifier will be a beauty.  I have seen your OTL reference in other threads, perhaps I will get to hear it some day.  An OTL design is in my future, unsure of the topology but I have quite the stash of OTL tubes burning a hole in my pocket.  Right now I am lost in the world of transformer-coupled single-ended class A with no end in site.  The current project is an 801A full A2 design with a 0V grid bias.  It has gone through various stages of prototyping due to circuit complexity, nearing completion at long last.
> 
> Definition of a rat's nest.  Old photo but it hasn't gotten any less ugly



What is the purposed of the antek transformer? 

And btw, I am going to be experimenting with using the filament taps off the lundhal transformer to run the rod colemans sometime today. I get the feeling that the lundhal transformer might be built well enough where we might be able to get away with it. 

For the 801a you would obviously have to run the filament taps in series to get 13.2V which means you would still need filament transformers for your driver tube(s), but it would be a MUCH smaller transformer which could help improve the clutter.


----------



## L0rdGwyn

Paladin79 said:


> In order to win this bet, I will use pentodes as triodes to accomplish a SET amp. I do not show the insides of my amps, I have received offers on my OTL design and for me to show very much is not in my best interest. Maybe one day I will build another loaner so you can check out the sound. I started that design because my local friends wanted to do a blind listen on 6sn7 equivalent tubes in four identical amps. Unfortunately everyone who heard it wanted one. The exception being one guy who is saving up lol.
> 
> You must not own cats or keep the room locked where your amp is stored lol. My cat Finnegan would have half those jumpers hidden throughout the house on the first day if I left something like that within his reach.



Sure!  A wise decision if you are selling your work.  Right now I am not and have no concrete plans to, so I am not shy about showing the innards of my designs...lately I am being asked for the link to my YouTube channel, which does not exist.  The idea has been planted in my head though and I am considering it...could be fun to do a GoPro design-to-build amplifier  and by fun I mean a ton of work.

Oh my three cats were locked up for that audition LOL exposed 400VDC and cats is not a winning combination.


----------



## bcowen

L0rdGwyn said:


> Oh my three cats were locked up for that audition LOL exposed 400VDC and cats is not a winning combination.



LOL!!! 

An alternative cat warmer...and distractor.  Not feasible during the summer though.


----------



## L0rdGwyn (Nov 9, 2020)

Tjj226 Angel said:


> What is the purposed of the antek transformer?



The two secondaries feed the regulated V+ and V- supplies for the source follower such that the grid can swing from around +60 to -80V, it is being replaced with two smaller single secondary toroids, but not worried about space since the PS is in a separate chassis.  Good luck with your experiment, what DHT filaments are you powering off the Lundahl windings?


----------



## L0rdGwyn

bcowen said:


> LOL!!!
> 
> An alternative cat warmer...and distractor.  Not feasible during the summer though.



LOL in a state of rapture!  All hail the sacred cat warmer!


----------



## Tjj226 Angel

L0rdGwyn said:


> The two secondaries feed the regulated V+ and V- supplies for the source follower such that the grid can swing from around +60 to -80V, it is being replaced with two smaller single secondary toroids, but not worried about space since the PS is in a separate chassis.  Good luck with your experiment, what DHT filaments are you powering off the Lundahl windings?



71a


----------



## L0rdGwyn

Tjj226 Angel said:


> 71a



Nice, should get you right in the sweet spot!


----------



## Tjj226 Angel

L0rdGwyn said:


> Nice, should get you right in the sweet spot!



Hopefully. If not, im thinking about using a mosfet as a rectifier. 

But in any case im working to rebuild that purple amp on johns thread to be a single chassis and half the size.


----------



## Paladin79

Tjj226 Angel said:


> Hopefully. If not, im thinking about using a mosfet as a rectifier.
> 
> But in any case im working to rebuild that purple amp on johns thread to be a single chassis and half the size.


I have been asked to build amps using purpleheart wood but so far I have avoided it, maybe one day.  I have at least five sold if I ever go that route.


----------



## Tjj226 Angel

Paladin79 said:


> I have been asked to build amps using purpleheart wood but so far I have avoided it, maybe one day.  I have at least five sold if I ever go that route.



It's an incredibly dense wood. It chewed up a couple of my forstner bits. I told myself I would never build another chassis like it, and then I immediately went out and bought cocobolo. I think I secretly hate myself or I am a glutton for punishment. IDK.


----------



## Paladin79 (Nov 9, 2020)

Tjj226 Angel said:


> It's an incredibly dense wood. It chewed up a couple of my forstner bits. I told myself I would never build another chassis like it, and then I immediately went out and bought cocobolo. I think I secretly hate myself or I am a glutton for punishment. IDK.


Try honey locust sometime, I had to resort to metal cutting bits. I have worked plenty with purpleheart but no matter what you do it will turn brown one day. You can only hope to slow the process by using specific lacquers. My favorite wood to date is rainbow poplar, it is gorgeous and easy to work with, this photo does not do it justice.

And getting back to amp building, I like to use 1/8 inch copper for looks as well as conductivity and weight. Below are a couple examples. Brushed copper and patinated copper, then the rainbow poplar. Sorry if some of these photos are redundant, I will try to talk more about amp design in the future, and I will post photos of the outside of my SET amp when it is close to completion. I need to decide if I want to add current meters before I do the final cuts on the cabinet.  Oh and splines, those are something I really like to add to amp corners.


----------



## Tjj226 Angel

Paladin79 said:


> Try honey locust sometime, I had to resort to metal cutting bits. I have worked plenty with purpleheart but no matter what you do it will turn brown one day. You can only hope to slow the process by using specific lacquers. My favorite wood to date is rainbow poplar, it is gorgeous and easy to work with, this photo does not do it justice.
> 
> And getting back to amp building, I like to use 1/8 inch copper for looks as well as conductivity and weight. Below are a couple examples. Brushed copper and patinated copper, then the rainbow poplar. Sorry if some of these photos are redundant, I will try to talk more about amp design in the future, and I will post photos of the outside of my SET amp when it is close to completion. I need to decide if I want to add current meters before I do the final cuts on the cabinet.  Oh and splines, those are something I really like to add to amp corners.



I used lenmar polyurethane on the purple heart. It doesn't specifically say it is uv resistant, but I tried it on a piece of purple heart and left it outside in the sun for a few days, and there wasn't a bit of color change. After about twoish years, johns amp still looks identical. I tried a lot of different finishes and all of them turned the purple heart from a nice soft bright purple into something that looked like cheap grape jam. This lenmar stuff was the only finish that kept a lot of the original color. Time will tell, but Im pretty happy with it. 

Rainbow poplar is pretty freaking cool, but it's one of those woods that you have to buy in person so that you can choose the right piece. I used to live in VA where we could buy all sorts of cool stuff, but now I live in MT. If I want exotic wood I pretty much have to buy it online. I can't even get my hands on decent maple around here.  

The goal now is to make all metal chassis using 1/8th in. aluminum and then clad it in wood. That way I can buy a single piece of something nice online and make it last longer. Otherwise the wood would be more expensive than the transformers.


----------



## bcowen

Tjj226 Angel said:


> If not, im thinking about using a mosfet as a rectifier.



Heresy!  Heresy, I tell 'ya.

If I knew anything about electronic design I'd tell you why.  But since I don't, nevermind.


----------



## Paladin79

Tjj226 Angel said:


> I used lenmar polyurethane on the purple heart. It doesn't specifically say it is uv resistant, but I tried it on a piece of purple heart and left it outside in the sun for a few days, and there wasn't a bit of color change. After about twoish years, johns amp still looks identical. I tried a lot of different finishes and all of them turned the purple heart from a nice soft bright purple into something that looked like cheap grape jam. This lenmar stuff was the only finish that kept a lot of the original color. Time will tell, but Im pretty happy with it.
> 
> Rainbow poplar is pretty freaking cool, but it's one of those woods that you have to buy in person so that you can choose the right piece. I used to live in VA where we could buy all sorts of cool stuff, but now I live in MT. If I want exotic wood I pretty much have to buy it online. I can't even get my hands on decent maple around here.
> 
> The goal now is to make all metal chassis using 1/8th in. aluminum and then clad it in wood. That way I can buy a single piece of something nice online and make it last longer. Otherwise the wood would be more expensive than the transformers.


I have found some pretty decent wood sources, one is in Brazil Indiana not real far from me. My son lives in Vienna VA
 near Wolf Trap and he is able to find decent hardwood. He used two inch solid cherry on his bar top.


----------



## Paladin79

bcowen said:


> Heresy!  Heresy, I tell 'ya.
> 
> If I knew anything about electronic design I'd tell you why.  But since I don't, nevermind.


I actually put a solid state amp inside @bcowen's amp, the tubes light up and he has convinced himself that he is actually hearing a difference in tubes when he swaps them but I have not had the heart to tell him.


----------



## L0rdGwyn (Nov 9, 2020)

Paladin79 said:


> Try honey locust sometime, I had to resort to metal cutting bits. I have worked plenty with purpleheart but no matter what you do it will turn brown one day. You can only hope to slow the process by using specific lacquers. My favorite wood to date is rainbow poplar, it is gorgeous and easy to work with, this photo does not do it justice.
> 
> And getting back to amp building, I like to use 1/8 inch copper for looks as well as conductivity and weight. Below are a couple examples. Brushed copper and patinated copper, then the rainbow poplar. Sorry if some of these photos are redundant, I will try to talk more about amp design in the future, and I will post photos of the outside of my SET amp when it is close to completion. I need to decide if I want to add current meters before I do the final cuts on the cabinet.  Oh and splines, those are something I really like to add to amp corners.



Very nice!  Talk about whatever you please, no rules here, all DIYers and curious Head-Fiers welcome 







Edit: actually there is one rule, if you have cats, pictures are required.


----------



## bcowen

L0rdGwyn said:


> Edit: actually there is one rule, if you have cats, pictures are required.



That picture is hilarious!  Almost looks like a 2-headed cat.   

Seriously, gorgeous felines!!  Where's the 3rd one?


----------



## bcowen

Paladin79 said:


> I actually put a solid state amp inside @bcowen's amp, the tubes light up and he has convinced himself that he is actually hearing a difference in tubes when he swaps them but I have not had the heart to tell him.



Yeah, well, a mosfet doesn't light up, so my comment still applies. So there.


----------



## Paladin79

This is Woodstock and Finnegan the cat.


----------



## L0rdGwyn (Nov 9, 2020)

bcowen said:


> That picture is hilarious!  Almost looks like a 2-headed cat.
> 
> Seriously, gorgeous felines!!  Where's the 3rd one?



Freddy (left) is the cuddly one, Sassafras (right) tolerates him LOL they are brother a sister.  Notice that they sleep on TOP of the corduroy cat cave monster instead of inside of it, typical cats.

Here is the third, Lucky the black sheep, looking like an absolute doofus.


----------



## L0rdGwyn

Paladin79 said:


> This is Woodstock and Finnegan the cat.



Best friends!

Alright one more cat photo, this is one of my favorites.  Freddy doing his best "how you doin'?" cat pose.


----------



## Paladin79 (Nov 9, 2020)

Back to amps and such, I may grab these Telefunken tubes.


----------



## bcowen

L0rdGwyn said:


> Freddy (left) is the cuddly one, Sassafras (right) tolerates him LOL they are brother a sister.  Notice that they sleep on TOP of the corduroy can cave monster instead of inside of it, typical cats.
> 
> Here is the third, Lucky the black sheep, looking like an absolute doofus.



LOL!  Lucky just looks comfortable.    

Mine sleep on the dog's bed, presumably just to firmly establish who's in charge.


----------



## bcowen

Paladin79 said:


> Back to amps and such, I may grab these Telefunken tubes.



And you complain about my amp being sideways...you're gonna have to build_ that_ amp upside down.


----------



## L0rdGwyn (Nov 9, 2020)

Paladin79 said:


> Back to amps and such, I may grab these Telefunken tubes.



I saw those!  A very nice set, good seller too might I add.

If you buy them I would be curious to know how they compare to the GU50 when your amp is complete.


----------



## Paladin79

bcowen said:


> And you complain about my amp being sideways...you're gonna have to build_ that_ amp upside down.


Well bats need a warm place too you know and Finnegan has yet to climb the ceiling so far, curtains yes, but but no ceilings.


----------



## Tjj226 Angel

bcowen said:


> Yeah, well, a mosfet doesn't light up, so my comment still applies. So there.



I mean this is just for the filament supply, but I do intend on trying it some day for the B+. 

Honestly my designs these days focus on power supply rejection. So the audio really can't make it back to the rectifier in the first place.


----------



## Paladin79

L0rdGwyn said:


> I saw those!  A very nice set, good seller too might I add.
> 
> If you buy them I would be curious to know how they compare to the GU50 when your amp is complete.


Sure, I will most likely buy them after I win my bet with some of the proceeds. I like to separate funds and only spend what I take in on amps and such for more gear. It also allows me to keep track and gift amps to friends but most likely I will stop at seven.


----------



## L0rdGwyn

Tjj226 Angel said:


> Honestly my designs these days focus on power supply rejection. So the audio really can't make it back to the rectifier in the first place.



Yeah, but then how can you hear your $200 rectifier tube?  The trick is to shoot for 40dB PSRR, a nice balance, this allows the "good" rectifier tube harmonics to come through with the ripple, while the "bad" harmonics are rejected...it's science


----------



## Paladin79 (Nov 9, 2020)

One of the tube headphone racks I made. definitely a diy project.

I bought dud tubes by the pound and received many that worked or just needed pins re-soldered. I finally told the seller I really liked the looks of those with black glass and received many working tubes that way as well.


----------



## Xcalibur255

Finally!  Some quality content in this thread!

/Meow


----------



## L0rdGwyn

Doing some listening with the new bedroom setup, sounds real good, loving the KG1.  Despite the speakers having a sensitivity of 90dB/W and the specs all adding up, still had some unfounded reservations about my little 45 amp providing enough power on the transients.

I threw my scope across the speaker terminals and measured the peak-to-peak voltage in real time with bass-driven power-demanding music, increasing the volume bit by bit to see when I would hit near-clipping on the transients with the amp as-built.  I measured the SPL via phone app at my listening position (the bed) about 2 meters away.



What I found was at an SPL of 80dB, pretty much the loudest I would realistically listen in this room, the amp was not even hitting 0.75W, so I feel more confident than ever a 2W 45 amp will get the job done.  Happy day!


----------



## Paladin79

L0rdGwyn said:


> Doing some listening with the new bedroom setup, sounds real good, loving the KG1.  Despite the speakers having a sensitivity of 90dB/W and the specs all adding up, still had some unfounded reservations about my little 45 amp providing enough power on the transients.
> 
> I threw my scope across the speaker terminals and measured the peak-to-peak voltage in real time with bass-driven power-demanding music, increasing the volume bit by bit to see when I would hit near-clipping on the transients with the amp as-built.  I measured the SPL via phone app at my listening position (the bed) about 2 meters away.
> 
> ...


Very nice. Many of my builds harken back to the day of highly efficient speakers and tube amps that were inefficient and yet produced a wonderful sound. My goal is 12 watts but 4 watts might have worked. What speakers are you using? I am running some Definitive Technology bookshelf speakers but I keep waiting for a deal to appear on some Klipsch La Scalas. (I have some connections.)


----------



## Paladin79

L0rdGwyn said:


> Doing some listening with the new bedroom setup, sounds real good, loving the KG1.  Despite the speakers having a sensitivity of 90dB/W and the specs all adding up, still had some unfounded reservations about my little 45 amp providing enough power on the transients.
> 
> I threw my scope across the speaker terminals and measured the peak-to-peak voltage in real time with bass-driven power-demanding music, increasing the volume bit by bit to see when I would hit near-clipping on the transients with the amp as-built.  I measured the SPL via phone app at my listening position (the bed) about 2 meters away.
> 
> ...


Sorry I get busy and skim info, you are running Klipsch. A very good choice.


----------



## L0rdGwyn (Nov 9, 2020)

Paladin79 said:


> Very nice. Many of my builds harken back to the day of highly efficient speakers and tube amps that were inefficient and yet produced a wonderful sound. My goal is 12 watts but 4 watts might have worked. What speakers are you using? I am running some Definitive Technology bookshelf speakers but I keep waiting for a deal to appear on some Klipsch La Scalas. (I have some connections.)



Thanks!  The bedroom setup above has a pair of Klipsch KG1 paired with a 6J5 / 45 parafeed amp.  In my main system, I have a pair of Snell J/II that @Tjj226 Angel turned me onto, I re-drivered and re-crossovered them in this thread.  They are 92dB/W paired with a 3.5WPC MH4 / 6A5G SET.  Eventually, the 6W 801A amp will be rotated in.  I guess I'll have to find somewhere else to put amps and speakers (bathroom? ).

It's funny you should mention the La Scalas, it's a different love affair every week in this hobby, I have been very interested in them lately.  Realistically I have nowhere to put them, but would love to restore a pair some day when I have the space (I showed them to my girlfriend, who made the very valid point that the cats would sleep in the woofer horn).  Let me know if you end up going for them!

The other day I had some downtime at work, I watched an interview with a Klipsch employee who moved into a new house _because their old one couldn't fit their new Klipschorns_!  That is devotion.


----------



## bcowen

L0rdGwyn said:


> The other day I had some downtime at work, I watched an interview with a Klipsch employee who moved into a new house _because their old one couldn't fit their new Klipschorns_!  That is devotion.



That person should be a role model for all of us.  Hope he has cats.


----------



## Paladin79

L0rdGwyn said:


> Thanks!  The bedroom setup above has a pair of Klipsch KG1 paired with a 6J5 / 45 parafeed amp.  In my main system, I have a pair of Snell J/II that @Tjj226 Angel turned me onto, I re-drivered and re-crossovered them in this thread.  They are 92dB/W paired with a 3.5WPC MH4 / 6A5G SET.  Eventually, the 6W 801A amp will be rotated in.  I guess I'll have to find somewhere else to put amps and speakers (bathroom? ).
> 
> It's funny you should mention the La Scalas, it's a different love affair every week in this hobby, I have been very interested in them lately.  Realistically I have nowhere to put them, but would love to restore a pair some day when I have the space (I showed them to my girlfriend, who made the very valid point that the cats would sleep in the woofer horn).  Let me know if you end up going for them!
> 
> The other day I had some downtime at work, I watched an interview with a Klipsch employee who moved into a new house _because their old one couldn't fit their new Klipschorns_!  That is devotion.


Klipsch main office used to be in Hope Arkansas but now it is in Indianapolis IN, not far from my office so on occasion I catch a break.


----------



## L0rdGwyn

bcowen said:


> That person should be a role model for all of us.  Hope he has cats.



*She is their marketing director, and a hardcore audiophile who LOVES Klipschorns, how cool is that?


----------



## bcowen

L0rdGwyn said:


> *She is their marketing director, and a hardcore audiophile who LOVES Klipschorns, how cool is that?



Oooops...how sexist of me.  Hope _*she *_has cats.  LOL!!


----------



## Paladin79

These are some of my newer pieces of test equipment. As I recall I stole the 6SN7 EICO tube from the sweep generator and sold it to @bcowen as sorta NOS.


----------



## L0rdGwyn (Nov 9, 2020)

bcowen said:


> Oooops...how sexist of me.  Hope _*she *_has cats.  LOL!!



LOL let's face it, there aren't too many chicks in the hobby but they are out there!  She did a whole interview on it.  Doesn't get any more hardcore than selling your house for a pair of speakers...unless you sell your family...but no one would ever do that...right?



Paladin79 said:


> These are some of my newer pieces of test equipment. As I recall I stole the 6SN7 EICO tube from the sweep generator and sold it to @bcowen as sorta NOS.



Very cool, did they require much in the way of restoration?  The only vintage piece of test equipment I own is a Jackson 648-R, which is in need of a tune-up, at one point I had thought of picking up a vintage Wien bridge oscillator.  Everything else are modern gizmos and gadgets.  The heart of my test rig is a MOTU M4 audio interface paired with a Linear Audio Autoranger, although I learned the hard way that a sound card measurement rig is not useful for testing absolutely everything...like very low input impedance phono stages, for instance.


----------



## bcowen

Paladin79 said:


> These are some of my newer pieces of test equipment. As I recall I stole the 6SN7 EICO tube from the sweep generator and sold it to @bcowen as sorta NOS.



It actually tested better than NOS in my perfectly calibrated Hickok that needs a 1k ohm/volt impedance meter for the calibration.  So thanks.


----------



## bcowen

L0rdGwyn said:


> Doesn't get any more hardcore than selling your house for a pair of speakers...unless you sell your family...but no one would ever do that...right?



Um, no. I don't think.  Yet.  Wait...was that a question or a statement?


----------



## Paladin79 (Nov 9, 2020)

L0rdGwyn said:


> LOL let's face it, there aren't too many chicks in the hobby but they are out there!  She did a whole interview on it.  Doesn't get any more hardcore than selling your house for a pair of speakers...unless you sell your family...but no one would ever do that...right?
> 
> 
> 
> Very cool, did they require much in the way of restoration?  The only vintage piece of test equipment I own is a Jackson 648-R, which is in need of a tune-up, at one point I had thought of picking up a vintage Wien bridge oscillator.  Everything else are modern gizmos and gadgets.  The heart of my test rig is a MOTU M4 audio interface paired with a Linear Audio Autoranger, although I learned the hard way that a sound card measurement rig is not useful for testing absolutely everything...like very low input impedance phono stages, for instance.


They required very little restoration, the Variac and sweep generator were pristine.

I have access to an engineering department if I need test equipment but I still have several pieces from when I ran my own business.

Here are some DIY pieces you may or may not recognize.


----------



## Paladin79 (Nov 10, 2020)

What you see there is a highly modified Bottlehead Crack and a working Schiit Coaster amp that fits perfectly inside a magic eight ball. The Coaster amp was an attempt to do some advertising as well as offer a DIY product. Several were sent out with Bom and Schematic but there was the same error on both and I figured it out. In doing so I may well have been the first person outside of Schiit to get several going. The round design was a wonderful challenge and I mounted them in a flying saucer, round tobacco tin, a headphone rack, etc.

I knew before I received a Crack that I wanted front dual pots and meters, on the back plate I have the AC input, line in etc. I went steampunk and if you look up Steampunk Bottlehead Crack on Google images, much of my work can be found there. Matching headphones I modified, headphone rack, cables, et alia.

I believe it was the Crack design that caused Jason to send me the Coaster amp boards, then later on he became aware of a small wager @bcowen and I made over tube identification. Jason hosted a shootout with several 6sn7 I loaned him.

Also here is is an example of what my downstairs looks like when my wife is away. With some of this blind listening going on, I wanted an amp that really featured the 6sn7 and had the capability to use single triode pairs, odd shaped tubes etc. My local audiophile group became curious what might be the highest regarded 6sn7 equivalent so I built four identical amps for that purpose and the Incubus Elegan was the result.


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## L0rdGwyn

Paladin79 said:


>



I have the same signal generator 

Likely the next piece of equipment I will buy will be the "etracer".



Not cheap, but I think this is the coolest tester out there right now, a digital curve tracer with a 750V 300mA anode supply and 0 to -170V grid supply, so you can get real curves traced for high voltage transmitting tubes, DHT like the 300B, etc.  Supposedly it has an A2 mode as well.  Also comes with the ability to create your own tube testing profiles based on the spec sheets, in case you have a collection of oddball 4V European tubes for instance...or maybe you want to check out some triode-strapped pentode operating curves for which a datasheet does not exist  it's on the wish list but it's a long list, have a few other items that will come first.  It is a "kit" technically with some assembly required, mostly tedious tube socket wiring, I'll show it off here when I finally pick it up some time next year.


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## Paladin79 (Nov 11, 2020)

L0rdGwyn said:


> I have the same signal generator
> 
> Likely the next piece of equipment I will buy will be the "etracer".
> 
> ...


Interesting, I have built my own curve tracers for solid state but never tubes, I doubt I would use one enough to warrant buying one but I do like the concept. I am at the point of my career where I need to start getting ride of equipment instead of adding new pieces. 

I am going to name my current amp for @bcowen and call it simply the Cowen. Along with that I will bequeath him my entire collection of GE tubes, few men are honored in such a way.


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## Tjj226 Angel

Paladin79 said:


> Interesting, I have built my own curve tracers for solid state but never tubes, I doubt I would use one enough to warrant buying one but I do like the concept.



How well does your curve tracer work? Im thinking about building one for jfet matching, but im not sold on the idea quite yet.


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## Paladin79

Tjj226 Angel said:


> How well does your curve tracer work? Im thinking about building one for jfet matching, but im not sold on the idea quite yet.


Have you not used something like the Huntron tracker? They are great for solid state comparisons as well as troubleshooting electronic components, especially electrolytics. Mine attach to oscilloscopes so you avoid the extra cost of a built in display. There is a learning curve but they can be extremely useful.


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## L0rdGwyn (Nov 11, 2020)

I said I was feeling lazy about working on the 801A amp, well I had a spark of inspiration today to do some more experimenting, only because I saw my local Microcenter had a zener I needed for the bias supply lol.

So I picked it up and rebuilt the bias supply on a protoboard.  Previously, the supply placed the 801A with a negative grid bias such that it would begin in A1, then progress to A2 with increasing power output.  The final version of this amp is going to have a 0V grid bias point, such that it is running in A2 100% of the time.  Planned load line is below.



So how the heck to we maintain a 0V bias point and regulate it?  For the source follower that drives the 801A grid, the source is ~3.5V negative relative to the gate, so we need to place a positive voltage on the gate to reach 0V on the source.  The plan is to get that done using the regulated DC heater supply for the EF37A input tubes via a zener stabilized voltage divider.  The regulators I am using are Pete Millett's filament supplies, set to 6.3V.



I wired it up and it works.  Below are the 801A grid voltage (left) and plate voltage (right), plate current was measured as well and was right on the money at 60mA.  With real music playing, seeing around 100mV of drift on the grid, not bad.  This will need some refinement, I may design my own DC regulator for this specific purpose, but this is the general plan going forward.


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## bcowen

Paladin79 said:


> I am going to name my current amp for @bcowen and call it simply the Cowen. Along with that I will bequeath him my entire collection of GE tubes, few men are honored in such a way.



I'm honored.  I think.  Well, the first part anyway, maybe.  Perhaps I'll just throw the GE's in a box and sell the whole lot on Ebay for $5 with free shipping (and still feel sorry for the buyer).


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## Tjj226 Angel

Paladin79 said:


> Have you not used something like the Huntron tracker? They are great for solid state comparisons as well as troubleshooting electronic components, especially electrolytics. Mine attach to oscilloscopes so you avoid the extra cost of a built in display. There is a learning curve but they can be extremely useful.



Nope. Up until now I have never had a need for matched SS parts. Everything I have done solid state wise has always been single ended. Im technically not even sure I need to match these jfets since they are the united SIC units which are supposedly well made and don't have a ton of variance. 

However I am making a direct drive hybrid amp. Kind of like a son of zen amp except that it takes the output from the source rather than the drain. I figure the better matched the jfets are, the less feedback I will have to use (if any).


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## Tjj226 Angel

L0rdGwyn said:


> I said I was feeling lazy about working on the 801A amp, well I had a spark of inspiration today to do some more experimenting, only because I saw my local Microcenter had a zener I needed for the bias supply lol.
> 
> So I picked it up and rebuilt the bias supply on a protoboard.  Previously, the supply placed the 801A with a negative grid bias such that it would begin in A1, then progress to A2 with increasing power output.  The final version of this amp is going to have a 0V grid bias point, such that it is running in A2 100% of the time.  Planned load line is below.



I poked around your circuit over this past weekend. Im not quite done, so don't quote me or anything, but I think there is a MUCH better way to build this circuit. Not only should it perform better, but you can do it with half the parts.


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## Paladin79

Tjj226 Angel said:


> Nope. Up until now I have never had a need for matched SS parts. Everything I have done solid state wise has always been single ended. Im technically not even sure I need to match these jfets since they are the united SIC units which are supposedly well made and don't have a ton of variance.
> 
> However I am making a direct drive hybrid amp. Kind of like a son of zen amp except that it takes the output from the source rather than the drain. I figure the better matched the jfets are, the less feedback I will have to use (if any).


I really doubt you will have much issue, I generally use trackers to troubleshoot quickly. I get non-working audio gear all the time so the equipment generally pays for itself in no time. An ESR meter also helps.


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## L0rdGwyn (Nov 12, 2020)

Tjj226 Angel said:


> I poked around your circuit over this past weekend. Im not quite done, so don't quote me or anything, but I think there is a MUCH better way to build this circuit. Not only should it perform better, but you can do it with half the parts.



Let me test my mind-reading abilities - elevating the 801A filaments and direct-coupling the mu-output of the pentode CCS to the 801A grid, removing the need for the buffer stage and negative bias supply? 

It's a great idea in theory, working it up in LTSpice.  Going to be quirky, but if it could be made to work, there could potentially be no capacitors in the signal path...


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## L0rdGwyn

Well I don't know if what I posted above was going to be your suggestion @Tjj226 Angel , but my idea works and I have a functional LTSpice model.  Real world could be quite different, but the amplifier is now a fully direct-coupled capacitorless design with a much-simplified power supply, so thanks for getting the gears turning!  There are some practical aspects that will need to be investigated, but the concept passes the LTSpice test.  Will likely post my .asc on diyAudio to get feedback (no-pun-intended) from the big tube brains.


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## Tjj226 Angel

L0rdGwyn said:


> Let me test my mind-reading abilities - elevating the 801A filaments and direct-coupling the mu-output of the pentode CCS to the 801A grid, removing the need for the buffer stage and negative bias supply?
> 
> It's a great idea in theory, working it up in LTSpice.  Going to be quirky, but if it could be made to work, there could potentially be no capacitors in the signal path...



You are pretty much on the right track. The difference is that I would either use the buffer, or I would find a way to incorporate the buffer into the mu follower such that the preamp tube remains shielded from variations in current. 

But yes, DC coupling the amp and getting rid of the negative supply is the way to go. Not only does it get rid of the coupling capacitor, but it also eliminates the negative voltage rail from being in the audio path. If I can incorporate the buffer into the mu follower, I might also be able to eliminate the positive buffer rail from the audio path as well. Im thinking we could use something akin to a current mirror....but idk. There is a solution there I am not quite yet seeing. 

Also, I forgot, what driver tube are you using?


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## Tjj226 Angel

L0rdGwyn said:


> Well I don't know if what I posted above was going to be your suggestion @Tjj226 Angel , but my idea works and I have a functional LTSpice model.  Real world could be quite different, but the amplifier is now a fully direct-coupled capacitorless design with a much-simplified power supply, so thanks for getting the gears turning!  There are some practical aspects that will need to be investigated, but the concept passes the LTSpice test.  Will likely post my .asc on diyAudio to get feedback (no-pun-intended) from the big tube brains.



Good good. 

I can pretty much guess that Euro21 and Audiowize has been helping you along on this project, and I know they will definitely have some meaningful feedback.


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## L0rdGwyn (Nov 12, 2020)

Tjj226 Angel said:


> You are pretty much on the right track. The difference is that I would either use the buffer, or I would find a way to incorporate the buffer into the mu follower such that the preamp tube remains shielded from variations in current.
> 
> But yes, DC coupling the amp and getting rid of the negative supply is the way to go. Not only does it get rid of the coupling capacitor, but it also eliminates the negative voltage rail from being in the audio path. If I can incorporate the buffer into the mu follower, I might also be able to eliminate the positive buffer rail from the audio path as well. Im thinking we could use something akin to a current mirror....but idk. There is a solution there I am not quite yet seeing.
> 
> Also, I forgot, what driver tube are you using?



Exactly, no bias supply and given the 0V grid bias point, the 801A B+ does not need to be insanely high, around 520V with a 200V filament elevation.  I'll take a look at buffer options, I thought the same i.e. how the CCS mu-output driving the 801A grid might affect the anode current of the driver tube (EF37A), does not appear to have an ill effect and the impedance appears to be low enough to drive the grid with the NFB applied, so perhaps a separate buffer isn't even necessary, we will see...

If this can be pulled off, this design just got pretty interesting.  The transparency should be pretty nuts, it was already excellent with a single coupling cap.


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## Zachik

L0rdGwyn said:


> Will likely post my .asc on diyAudio to get feedback (no-pun-intended) from the big tube brains.


I am curious: on which thread is that brainstorming activity taking place?
Always looking for good read... even if 5% would stick - that is a win for me!


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## Tjj226 Angel

L0rdGwyn said:


> Exactly, no bias supply and given the 0V grid bias point, the 801A B+ does not need to be insanely high, around 520V with a 200V filament elevation.  I'll take a look at buffer options, I thought the same i.e. how the CCS mu-output driving the 801A grid might affect the anode current of the driver tube (EF37A), does not appear to have an ill effect and the impedance appears to be low enough to drive the grid with the NFB applied, so perhaps a separate buffer isn't even necessary, we will see...
> 
> If this can be pulled off, this design just got pretty interesting.  The transparency should be pretty nuts, it was already excellent with a single coupling cap.



What triode curves are you using for the EF37A? I thought it was similar to a 6j7 which means its similar to a 6sj7. If I look at the 6sj7 curves, I am coming up with a plate voltage of about 100 to driver the 801a to full swing.


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## L0rdGwyn

@Zachik I will send you a link.

@Tjj226 Angel EF37A is run as a CCS loaded pentode, the high gain with local NFB is a necessity to get good bandwidth and output impedance out of the 801A, especially with a 5K OPT.  It's a tricky tube to design for given its high internal resistance, the parasitics of a high primary impedance OPT make using it in a no NFB design pretty unappealing.  You either take the limitations of the high-turns-ratio OPT or run it with NFB, I've had better results with the latter.  PSE is another option, but let's be serious, I am not going to match pairs of 801A and use four filament transformers LOL.


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## Tjj226 Angel

L0rdGwyn said:


> @Zachik I will send you a link.
> 
> @Tjj226 Angel EF37A is run as a CCS loaded pentode, the high gain with local NFB is a necessity to get good bandwidth and output impedance out of the 801A, especially with a 5K OPT.  It's a tricky tube to design for given its high internal resistance, the parasitics of a high primary impedance OPT make using it in a no NFB design pretty unappealing.  You either take the limitations of the high-turns-ratio OPT or run it with NFB, I've had better results with the latter.  PSE is another option, but let's be serious, I am not going to match pairs of 801A and use four filament transformers LOL.



OHhhhhh thats right. Forgot you went to a lower impedance transformer. That explains the gain requirements.

Hold on, recalculating.

Side note: For what it's worth, if you run the 801a at ~310V at 60ma, ltspice is showing a plate impedance of ~3.6K. I have already seen NFB results in the 800ohm range on my end, however the signal on the 801a grid is screwed up because of the current and impedance shifts. 

I still think you are just going to have to use a buffer or at the very least give the 801a its own dedicated current source.


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## L0rdGwyn

I have some time off of work and it appears that I have on hand what I need to throw together a single-channel of the direct-coupled 801A A2 amplifier.  Looks like I have my activities planned for the week, let's give it a whirl


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## L0rdGwyn

Well last night I started breaking down my 801A prototype, making adjustments to the power supplies, etc.  As I was moving along and thinking through just how I was going to prototype the DC coupled version, it occurred to me that while the design has two positive effects (removal of the negative bias supply and a coupling capacitor), it also introduces a host of new complexities and design issues, to the point that I am likely to scrap the idea.  It's all hunky dory in LTSpice simulations, then you think about how it will actually need to be implemented in the real world, no free lunch in this hobby


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## Tjj226 Angel

L0rdGwyn said:


> Well last night I started breaking down my 801A prototype, making adjustments to the power supplies, etc.  As I was moving along and thinking through just how I was going to prototype the DC coupled version, it occurred to me that while the design has two positive effects (removal of the negative bias supply and a coupling capacitor), it also introduces a host of new complexities and design issues, to the point that I am likely to scrap the idea.  It's all hunky dory in LTSpice simulations, then you think about how it will actually need to be implemented in the real world, no free lunch in this hobby



Can you post your LT spice simulation? I am not seeing good results from using a mu follower without some type of separate current supply for the 801a grid.


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## L0rdGwyn (Nov 15, 2020)

@Tjj226 Angel the dedicated buffer is a necessity I've found, but that isn't the issue.  Bias stability of the 801A will be a problem, the grid voltage will be at the mercy of component variances in the pentode driver - changing driver tubes will require an internal manual adjustment.  Not only that, but bias stability of the CCS loaded pentode (and thus, if DC coupled, bias stability of the 801A) is already a problem given the very high gain and propensity to drift with small changes in cathode voltage - it's possible a DC bias servo would be needed.  Bringing the 801A up to bias safely is also a problem - with the CCS loaded pentode with the soft-start Maida regulator, the pentode plate voltage swings up to ~270V transiently before coming down to bias at 200V (that was with a 350V B+, will be higher with the new higher voltage B+ rail).  That means the grid of the 801A will momentarily be at +70V or more relative to the filament, which is likely to blow the plate fuse on startup.  There's more!  The higher B+ requirement (525V vs. 350V prior) now pushes up against the limit of 600V component tolerances, not to mention any umbilical connectors will have to be appropriately rated.  While the negative bias supply is gone, now a separate filament elevation supply is required, so the part count does not go down significantly.  Removing the V+/V- supplies also makes the power supply options for the buffer less favorable, which means significantly more excess voltage that will need to be dissipated.  All of those problems stated and it does not include the issues elevating the filament is likely to have on the stability of the feedback loop.

So, it's likely to be scrapped, it isn't a simple implementation by any means.


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## Paladin79

I have thought through all circuitry in my GS50 amp and did a few cuts for the cabinet but I have too many other projects I need to finish right now.  I hope to wrap up the amp in a couple weeks. I also get slowed down by my wife taking up a lot of shop space with pottery but I am having a shed built and it will be delivered in about a month.

This morn I am listening to one of my Incubus amps with a very rare Melz driver tube from 1958, Tung Sol 5998, Gungnir DAC, Focal Utopia headphones. I do not use design simulation, I design for my ears and occasionally others like the sound.  It took me a long time to find headphones that opened up the sound on the Incubus. My group uses Senn HD800's with their four amps and they are very good, for my ears, the Utopias allow the highs to progress and reach their potential.


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## Tjj226 Angel

L0rdGwyn said:


> @Tjj226 Angel the dedicated buffer is a necessity I've found, but that isn't the issue.  Bias stability of the 801A will be a problem, the grid voltage will be at the mercy of component variances in the pentode driver - changing driver tubes will require an internal manual adjustment.  Not only that, but bias stability of the CCS loaded pentode (and thus, if DC coupled, bias stability of the 801A) is already a problem given the very high gain and propensity to drift with small changes in cathode voltage - it's possible a DC bias servo would be needed.  Bringing the 801A up to bias safely is also a problem - with the CCS loaded pentode with the soft-start Maida regulator, the pentode plate voltage swings up to ~270V transiently before coming down to bias at 200V.  That means the grid of the 801A will momentarily be at +70V relative to the filament, which is likely to blow the plate fuse on startup.  There's more!  The higher B+ requirement (525V vs. 350V prior) now pushes up against the limit of 600V component tolerances, not to mention any umbilical connectors will have to be appropriately rated.  While the negative bias supply is gone, now a separate filament elevation supply is required, so the part count does not go down significantly.  Removing the V+/V- supplies also makes the power supply options for the buffer less favorable, which means significantly more excess voltage that will need to be dissipated.  All of those problems stated and it does not include the issues elevating the filament is likely to have on the stability of the feedback loop.
> 
> So, it's likely to be scrapped, it isn't a simple implementation by any means.



Yeup, I already know. Don't worry. I got you fam. Just sit tight, and wait for my signal. : P 

And if I finish my schematic and you just hate it, that's fine. I will post it anyways just in case it gives you or someone else ideas later on in life. 

I will however leave you with an idea to ponder. 

If you take the 801a bias from -10v to 0v and you raise your bias current to 60ma, your plate impedance goes down. And not by a trivial amount either. You should really define how much NFB in db you need in order to get the 801a impedance down to 2K, 1K, and ~500ohms. 2K being the maximum for a 5K load, and 500 ohms being the minimum for a 3K load. 

By knowing how much feedback in DB you need in order to achieve a particular outcome, you can better define your gain requirements. I HAVE A FUNNY FEELING THAT IF YOU DO THIS, YOU MIGHT COME UP WITH SOME NEW IDEAS!!!

NUDGE NUDGE WINK WINK


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## L0rdGwyn

Paladin79 said:


> I have thought through all circuitry in my GS50 amp and did a few cuts for the cabinet but I have too many other projects I need to finish right now.  I hope to wrap up the amp in a couple weeks. I also get slowed down by my wife taking up a lot of shop space with pottery but I am having a shed built and it will be delivered in about a month.
> 
> This morn I am listening to one of my Incubus amps with a very rare Melz driver tube from 1958, Tung Sol 5998, Gungnir DAC, Focal Utopia headphones. I do not use design simulation, I design for my ears and occasionally others like the sound.  It took me a long time to find headphones that opened up the sound on the Incubus. My group uses Senn HD800's with their four amps and they are very good, for my ears, the Utopias allow the highs to progress and reach their potential.



Nice, sounds like a lovely combination, look forward to seeing your LS50 / GU50 amplifier.  I use a combination of simulation and tuning by ear, LTSpice is a powerful tool IMO when the design warrants it.  This amplifier is quite complex, at least by my standards, so being able to do a test run in sim is very useful!


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## L0rdGwyn (Nov 15, 2020)

Tjj226 Angel said:


> Yeup, I already know. Don't worry. I got you fam. Just sit tight, and wait for my signal. : P
> 
> And if I finish my schematic and you just hate it, that's fine. I will post it anyways just in case it gives you or someone else ideas later on in life.
> 
> ...




Well thanks for putting in the time!  You may have missed it, but I am using a 0V 60mA bias point, and yes the plate resistance does fall significantly at A2 bias points.  I have trialed it using the 6.5K 50mA LL9202 (just because they are what I have on hand the moment), but the transformers coming from Sowter are 5K 60mA for that reason, that is where we are headed.  The CCS loaded pentode is highly adjustable from a gain standpoint, so the feedback can be finely dialed in by adjusting the plate load or the feedback fraction via the feedback resistors.  Leaving the pentode cathode unbypassed significantly reduces the gain due to cathode degeneration, but increases linearity and of course the sound is MUCH better sans electrolytic.  I am only adding enough NFB for a suitable output impedance anyway.  In the now broken down prototype, I have trimmers on the cathodes such that I can adjust the feedback fraction in real time and see the adjustment on scope, maximizing the degree of feedback while providing just the right amount of gain to drive the 801A to full output in A2, I've been able to get output impedances around 2ohm with a 470K resistor on the EF37A plate.  Obviously adjustments will need to be made when the 5K transformers arrive, more feedback will be necessary, but that is the beauty if the CCS loaded pentode, you can basically make the gain, and thus the feedback, whatever you want!  It's pretty nifty


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## Paladin79

L0rdGwyn said:


> Nice, sounds like a lovely combination, look forward to seeing your LS50 / GU50 amplifier.  I use a combination of simulation and tuning by ear, LTSpice is a powerful tool IMO when the design warrants it.  This amplifier is quite complex, at least by my standards, so being able to do a test run in sim is very useful!


I was just speaking for myself of course, I do use test equipment and have over 40 years of background in engineering. I studied tube theory in college but that was ages ago so it is fun to have a chance to work with it now. At the end of the day, I have to be happy with the sound and in all honesty, I could not build Incubus amps fast enough after friends heard them so I suppose others might agree on the result.  I am still working full time so amp building is just a fun hobby at this point in time. I do have an abundance of very expensive parts so I tried to use some of those up on my later builds so they might not go to waste.


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## L0rdGwyn

Paladin79 said:


> I was just speaking for myself of course, I do use test equipment and have over 40 years of background in engineering. I studied tube theory in college but that was ages ago so it is fun to have a chance to work with it now. At the end of the day, I have to be happy with the sound and in all honesty, I could not build Incubus amps fast enough after friends heard them so I suppose others might agree on the result.  I am still working full time so amp building is just a fun hobby at this point in time. I do have an abundance of very expensive parts so I tried to use some of those up on my later builds so they might not go to waste.



I bet it does sound great, would like to hear it some day, maybe a future Head-Fi meet when COVID has ended


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## L0rdGwyn (Nov 15, 2020)

Side note, if anyone feels like brainstorming ideas on ways to use a particular DHT, the 841, I know a guy who has quite a few pairs  another tricky one with a plate resistance of ~25K and mu of 30, high-gain cousin to the 801A.

This "guy" I am referring to has cooked up some crazy, inefficient ideas to use these tubes, a single-gain-stage hybrid headphone amp using SiC diode filament bias on the 841, AOT1N60 buffer, cap-coupled to a Sowter 8665 OPT, for example.  The Sowter 8665 was "designed to be driven from a cathode follower output stage via a coupling capacitor."  Replace "cathode follower" with "source follower", and there you have it.  More commonly these are used in parafeed applications, but the plate resistance of the 841 is too high to drive the output on its own.  Shown with a 32ohm load, but would likely have high-Z and low-Z taps.

I am currently making labels, boxing up my tube collection, and listening to Christmas music, so apologies for being scatter-brained


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## Tjj226 Angel

L0rdGwyn said:


> Side note, if anyone feels like brainstorming ideas on ways to use a particular DHT, the 841, I know a guy who has quite a few pairs  another tricky one with a plate resistance of ~25K and mu of 30, high-gain cousin to the 801A.
> 
> This "guy" I am referring to has cooked up some crazy, inefficient ideas to use these tubes, a single-gain-stage hybrid headphone amp using SiC diode filament bias on the 841, AOT1N60 buffer, cap-coupled to a Sowter 8665 OPT, for example.  The Sowter 8665 was "designed to be driven from a cathode follower output stage via a coupling capacitor."  Replace "cathode follower" with "source follower", and there you have it.  More commonly these are used in parafeed applications, but the plate resistance of the 841 is too high to drive the output on its own.  Shown with a 32ohm load, but would likely have high-Z and low-Z taps.
> 
> I am currently making labels, boxing up my tube collection, and listening to Christmas music, so apologies for being scatter-brained



Do you know how much AC signal that transformer can handle on the primary? I have sent a couple emails but I never got a response. 

My math says it can only handle ~100v peak to peak.


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## bcowen (Nov 15, 2020)

Quick question for the gurus here.  I'm finally getting around to replacing the volume pot in the Darkvoice, and I figured while I might as well replace the input wiring from the RCA jacks while I'm at it. I have this really nice shielded silver wire leftover from another project, but it's pretty thin gauge (like 28 gauge, maybe 30).  Is that sufficient for this application?  I know it's only carrying 2 volts (for about 10 inches) but didn't know if there was anything else to consider.  The stock wiring is substantially heavier, probably 20 gauge...and is likely an alloy of recycled auto parts.


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## L0rdGwyn

Tjj226 Angel said:


> Do you know how much AC signal that transformer can handle on the primary? I have sent a couple emails but I never got a response.
> 
> My math says it can only handle ~100v peak to peak.



Yeah it's weird, they list specs for it in a few different places, they rate it at 500mW at 20Hz, on another page 2.5W at 50Hz.  I have been operating under the assumption it can handle 500mW.


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## L0rdGwyn

bcowen said:


> Quick question for the gurus here.  I'm finally getting around to replacing the volume pot in the Darkvoice, and I figured while I might as well replace the input wiring from the RCA jacks while I'm at it. I have this really nice shielded silver wire leftover from another project, but it's pretty thin gauge (like 28 gauge, maybe 30).  Is that sufficient for this application?  I know it's only carrying 2 volts (for about 10 inches) but didn't know if there was anything else to consider.  The stock wiring is substantially heavier, probably 20 gauge...and is likely an alloy of recycled auto parts.



You should be totally fine using 28AWG or 30AWG, as long as it isn't too fragile mechanically, many people use very thin shielded coaxial cable for line level amplifier inputs.  Definitely doesn't need to be 20AWG!


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## Paladin79

bcowen said:


> Quick question for the gurus here.  I'm finally getting around to replacing the volume pot in the Darkvoice, and I figured while I might as well replace the input wiring from the RCA jacks while I'm at it. I have this really nice shielded silver wire leftover from another project, but it's pretty thin gauge (like 28 gauge, maybe 30).  Is that sufficient for this application?  I know it's only carrying 2 volts (for about 10 inches) but didn't know if there was anything else to consider.  The stock wiring is substantially heavier, probably 20 gauge...and is likely an alloy of recycled auto parts.


I generally use 24 awg shielded twisted pair or Belden 1855A when using coaxial cable. Impedance is not a factor under 1 meter in length.


----------



## bcowen

L0rdGwyn said:


> You should be totally fine using 28AWG or 30AWG, as long as it isn't too fragile mechanically, many people use very thin shielded coaxial cable for line level amplifier inputs.  Definitely doesn't need to be 20AWG!


Thanks!


----------



## bcowen

Paladin79 said:


> I generally use 24 awg shielded twisted pair or Belden 1855A when using coaxial cable. Impedance is not a factor under 1 meter in length.


Thanks!  You might recognize this particular wire from the inside of the Cary preamp.  Silver conductor with a braided silver shield. As an added bonus, it's free.


----------



## Paladin79 (Nov 16, 2020)

bcowen said:


> Thanks!  You might recognize this particular wire from the inside of the Cary preamp.  Silver conductor with a braided silver shield. As an added bonus, it's free.


Very nice, it’s been a while since I opened the Cary.  I need to work on my Cary power amp once the components for my new amp are in situ in the tiger maple.

I need to achieve as much power out of my GU50 amp as I can get so I may use larger conductor on the line in portion as well as speaker out, I like to use bonded and shielded twisted pair in some applications and I can add my own shielding to any pair.


----------



## L0rdGwyn

@Tjj226 Angel how did your Lundahl DHT filament experiment go?


----------



## Tjj226 Angel

L0rdGwyn said:


> @Tjj226 Angel how did your Lundahl DHT filament experiment go?



So far so good. But I got distracted with my new CCS boards that came in. I wanted to solder some up to test and send out to John.


----------



## L0rdGwyn

Tjj226 Angel said:


> So far so good. But I got distracted with my new CCS boards that came in. I wanted to solder some up to test and send out to John.



Awesome, I'm sure he will enjoy that.  I am going to try the same, stacking two 6.6VAC windings of a Lundahl LL1650, gives me the right amount of raw DC for the 841 with filament bias  turns out the Sowter 8665 are being delivered today, what timing!  So I am going to throw together a prototype of the headphone amp design I posted above.  I have just about everything I need for a test run, except for the SiC diodes, should be functional by this weekend.

Yeah that's right, I am going to use a 475V B+ for a 0.5W headphone amplifier, don't judge me.


----------



## bcowen

L0rdGwyn said:


> Awesome, I'm sure he will enjoy that.  I am going to try the same, stacking two 6.6VAC windings of a Lundahl LL1650, gives me the right amount of raw DC for the 841 with filament bias  turns out the Sowter 8665 are being delivered today, what timing!  So I am going to throw together a prototype of the headphone amp design I posted above.  I have just about everything I need for a test run, except for the SiC diodes, should be functional by this weekend.
> 
> Yeah that's right, I am going to use a 475V B+ for a 0.5W headphone amplifier, don't judge me.



Far from me to be judgmental, but since I'm unqualified to comment on the design I'll reserve my concerns about this slowing progress on your tube organization.   

You *did* make me look at my own mess though (guess I felt guilty), and I uncovered an unused pair of Kimber RCA jacks in my, um, stuff.  Cool...now I don't have to buy any.


----------



## L0rdGwyn

bcowen said:


> Far from me to be judgmental, but since I'm unqualified to comment on the design I'll reserve my concerns about this slowing progress on your tube organization.
> 
> You *did* make me look at my own mess though (guess I felt guilty), and I uncovered an unused pair of Kimber RCA jacks in my, um, stuff.  Cool...now I don't have to buy any.



LOL tube reorganization is just about complete   

Quick access drawers for tube rollability.


 

Then the remainder going with the others in basement hibernation.


----------



## L0rdGwyn

The most important thing about this headphone amp is that it will be pretty, sound quality be damned!  841 on the right (VT-51) with thoriated tungsten filaments.


----------



## L0rdGwyn

Arrived.



I think I've worked out a scheme to build this thing today or tomorrow, but will need to use a more typical resistor filament bias rather than SiC diode while I wait for parts.  Standby...


----------



## Tjj226 Angel

L0rdGwyn said:


> Arrived.
> 
> 
> 
> I think I've worked out a scheme to build this thing today or tomorrow, but will need to use a more typical resistor filament bias rather than SiC diode while I wait for parts.  Standby...



Oh, I hadn't realized you were actually going to build that 841 amp. 

If you could experimentally determine how much voltage these guys can take, that would be super freaking cool.


----------



## L0rdGwyn

Tjj226 Angel said:


> Oh, I hadn't realized you were actually going to build that 841 amp.
> 
> If you could experimentally determine how much voltage these guys can take, that would be super freaking cool.



I didn't either, until yesterday LOL I bought these transformer to do... something with, didn't know what.  I was pulling an all nighter recently and I threw together the schematic to kill time.  Looked at it again yesterday and thought it might actually be pretty cool.  Then these transformers showed up unannounced, now I am building it lol things change quickly.  Why can't you calculate the peak voltage based in the 500mW power rating and reflected load?  500mW with a 12:1 turns ratio and 32ohm headphone would be 132Vpk-pk, for example.


----------



## Tjj226 Angel

L0rdGwyn said:


> I didn't either, until yesterday LOL I bought these transformer to do... something with, didn't know what.  I was pulling an all nighter recently and I threw together the schematic to kill time.  Looked at it again yesterday and thought it might actually be pretty cool.  Then these transformers showed up unannounced, now I am building it lol things change quickly.  Why can't you calculate the peak voltage based in the 500mW power rating and reflected load?  500mW with a 12:1 turns ratio and 32ohm headphone would be 132Vpk-pk, for example.



Because it doesn't actually say 32 ohms on the 12:1 tap : )

It says 30 ohms to 100 ohms. 30 ohms at 500mw would be as follows. 

12*(Sqrt((0.5/0.7071)*30)) = ~55v which means thee peak to peak voltage is 110v. 

If you take the same equation and look at 100hms at 500mw, you end up with 200v peak to peak. 

It would be nice to know with some amount of certainty that the transformer can take x amount of voltage without having to second guess the spec sheet.


----------



## L0rdGwyn

Exactly, the peak voltage is not constant, it will vary depending on the load attached to the secondary.  A higher reflected impedance to the primary will result in a higher peak-to-peak voltage at the same 500mW power dissipation, so it will depend on the headphone impedance used and on which tap.


----------



## Tjj226 Angel

L0rdGwyn said:


> Exactly, the peak voltage is not constant, it will vary depending on the load attached to the secondary.  A higher reflected impedance to the primary will result in a higher peak-to-peak voltage at the same 500mW power dissipation, so it will depend on the headphone impedance used and on which tap.



That's not how that works. 

The max AC primary voltage a transformer can handle is a function of the primary coil, frequency, core geometry, core material, and any DC current that might be present. So long as frequency is constant (in our case we care about 20hz), the max ac voltage figure is more or less constant regardless of your secondary configuration. 

This is why a 70v line transformer can only take 70v RMS on its primary regardless of how you configure the secondary. 

Now normally we don't care about this spec because most output transformers are big and beefy enough to handle plenty of signal voltage. But in this case you have a smaller core and it uses a fair amount of nickel which will saturate more quickly than GOSS.


----------



## L0rdGwyn

Tjj226 Angel said:


> That's not how that works.
> 
> The max AC primary voltage a transformer can handle is a function of the primary coil, frequency, core geometry, core material, and any DC current that might be present. So long as frequency is constant (in our case we care about 20hz), the max ac voltage figure is more or less constant regardless of your secondary configuration.
> 
> ...



I'll ask Sowter for clarification on the max AC input, maybe they won't ignore me since I've given them my money lol but I have found them to be spotty when it comes to returning emails.


----------



## L0rdGwyn (Nov 16, 2020)

@Tjj226 Angel I can't seem to find it, but I remember somewhere Sowter had listed the nominal primary impedance of the 8665 at 10K, which at a 500mW power rating would be 200Vpk-pk.  Taking a guess, maybe the effects of core saturation occur beyond the pk-pk voltage at the power rating limitation, the reason they don't list it in the spec sheet?  I can guarantee one thing that isn't in the spec sheet, I would be deaf before the core saturates LOL.


----------



## L0rdGwyn (Nov 16, 2020)

There is another high-mu DHT, pretty similar in some ways to the 841, the Valvo Aa.  Mu of 30 (25 for the 841), Ri 30K (25K for the 841), 3.8V / 0.5A filament (7.5V / 1.25A for the 841), lower operating plate voltage of around 200V, don't believe the filaments are thoriated tungsten.  It has a cousin, the Ba, with a mu of 14 and a slightly lower plate resistance of 25K.  Like the 841, these tubes need some sort of buffer given their high plate resistances.  Very nice looking though  a pair will set you back around $200.



Had a busy day today, so the impractical 841 headphone amp will have to wait until tomorrow.


----------



## L0rdGwyn

Do you ever put in eBay sniper bids on tubes you think you won't win, maybe two bids on two different auctions thinking "I'll probably lose both, but maybe one will pan out", then you win both of them at prices right below your highest bid?  Welp, I will have some very choice tubes coming my way LOL.

@Tjj226 Angel Brian Sowter got back to me on the AC signal rating of the 8665, here it is from the horse's mouth:

"The power rating is referring to the saturation induction rather than the heat dissipation.  It should be ok for say 2.5W depending on your cooling."

So sounds like the core will begin to saturate beyond 500mW input, but they are good for 2.5W in terms of heat.


----------



## L0rdGwyn (Nov 17, 2020)

I built the 841 amp in my cold-ass garage! First snow of the season, what a day to decide to do this...

Prepare for ugly.  Not everything on the plank is part of the headphone amp, mind you.  Ignore the toroid, Clarity Cap, and that stuff in the background 



I stacked two pairs of 6.9VAC windings on the Lundahl LL1650 for the 841 filaments.  I used resistor filament bias on the 841, bias ended up being 370Va, 5mA Ia, 3.75Vk.  Maida regulated B+ was 460V off the 350VAC HT winding of the LL1650.  I set the bias current for the AOT1N60 source follower to 15mA.  Output capacitor is a 4.7uF polypropylene Solen.  The Sowter 8665 are wired 4:1 for use with high impedance headphones.

Distortion spectrum at 1mW into a 300ohm dummy load, left channel.



As you can see, the distortion is very low and follows a nice single-ended spectrum.  What isn't low is that 120Hz noise peak LOL.  I _suspect_ this could be due to rectifier coupling into the B+ mains winding from the filament supply, although I would suspect the Maida to squash that way down, but I will have to look into it further.  Could also be coupling due to this being built on a piece of wood with way-too-long alligator clips all over the place.  Oddly enough, the 120Hz noise is not audible while listening.  Worst case, if it is coupling from the filament supply, I will have to use dedicated filament transformers.  Would be a bummer, just means more chassis real estate.

Here is the frequency response.



Nice and flat with a smidge of rolloff at 20Hz.  Will try increasing the value of the output cap and see if we can get a full 20Hz-20kHz.

How does it sound...no joke, it sounds incredible.  Excellent clarity, soundstage, bass definition, no doubt in large part due to the very low distortion.  I like it a lot.  Also, this should be able to drive just about any headphone, 10mW of output into the HD650 is a very unhealthy listening volume, and we've got a lot of power to spare.

So yeah, this thing sounds really, really good, I am likely to take it all the way to completion once I sort out the heater winding vs. filament transformer question.  Will also be playing with the bias point some more, and will have to try out the SiC diode filament bias vs. resistor filament bias when they arrive later this week.

So purdy.


----------



## L0rdGwyn (Nov 17, 2020)

It's a good thing this amp sounds good, one of the two pairs of tubes I mentioned above are these, RCA globe 841.


----------



## L0rdGwyn

This morning, I gave the dedicated filament transformers a shot vs. running the filaments off the paralleled heater windings of my Lundahl mains transformer, FFT below.

1mW into 300ohms dummy, left channel, dedicated filament traffo.



The 120Hz peak has completely disappeared, so I think I have my answer, looks like the filament transformers will be necessary after all, bummer! The LL1650 would have been a nice all-in-one solution otherwise.

Just for fun, I pushed the amp a little bit and watched the distortion spectrum in real time. As I recall, at 300mW into 300ohms, the distortion was only 0.25%!  So it's good to know the distortion will be nearly inaudible just before I go deaf.


----------



## bcowen

L0rdGwyn said:


> Just for fun, I pushed the amp a little bit and watched the distortion spectrum in real time. As I recall, at 300mW into 300ohms, the distortion was only 0.25%!  So it's good to know the distortion will be nearly inaudible just before I go deaf.



Man, those are some beautiful tubes!  And pretty impressive end result.  

But we all know that a tube amp _can't_ sound good without at least 1% distortion, so you either need to go back to the drawing board or crank it up louder.


----------



## L0rdGwyn

bcowen said:


> Man, those are some beautiful tubes!  And pretty impressive end result.
> 
> But we all know that a tube amp _can't_ sound good without at least 1% distortion, so you either need to go back to the drawing board or crank it up louder.



LOL you are right!  Except I did crank it up and the distortion is still super low  I will have to sabotage the circuit somehow.

Here are some square waves.

1kHz




10kHz



100Hz



A little bit of ringing, but nothing sinister, looks to be out of the audio band.

Here is a 1kHz sine wave with the amp driven to full output, it clips at around 35Vpk-pk into 300ohms at the current bias point.  That's about 0.5W.


----------



## L0rdGwyn

Cree SiC diodes arrived, I will A-B SiC diode filament bias vs. resistor filament bias later today.


----------



## L0rdGwyn

Okay, I did a quick AB of the resistor filament bias and the SiC diode filament bias.  Four stacked gets about 4V of bias on the filament.

 

Honestly, it's probably too close to call, I THINK the resistor sounds better, so that's what I'm going with for now, will probably revisit it at a later date.


----------



## johnjen

Just a note in passing.
I have repeatedly noticed that it takes ≈1hr of 'on time' before I can even initially ascertain if a component swap/modification/tweak is 'better' or not.
The only exception is when it immediately smacks me up side my head that the component change is obviously 'better'.

I'm performing such a test right now with new CCS's in the Purp-Amp, and this 1hr 'settling in' criteria is being reaffirmed, yet again.

JJ


----------



## L0rdGwyn

johnjen said:


> Just a note in passing.
> I have repeatedly noticed that it takes ≈1hr of 'on time' before I can even initially ascertain if a component swap/modification/tweak is 'better' or not.
> The only exception is when it immediately smacks me up side my head that the component change is obviously 'better'.
> 
> ...



Hey JJ - thanks for the note, I am looking for big changes right off the bat, which are sometimes very obvious and makes the path forward simple.  If not, further investigation is needed.  In this particular case, it is a very simple swap going from resistor to diode filament bias, so when the amp is completed, I can do some more thorough A-Bing and decide which is the long term solution.


----------



## L0rdGwyn (Nov 19, 2020)

I've seen enough to move forward with building the 841 headphone amplifier.  I essentially have all of the parts already!  Just need a few more knick knacks and a chassis.

I will mount the filament transformers and Lundahl mains transformer on top of the chassis under steel shields.  Obviously, all of the shields need to match for aesthetic reasons, so I ordered two sets of shields from China, surprisingly they look very nice!  Was happy to come across these.  I like the rounded edge version better, but it will be a tight fit dimensions wise, so we'll see which ones pan out and I will keep the other set for a future project.

 

In terms of the chassis, I am working on a draft.  I cannot do powder coating in my garage due to the cold weather.  Also, if I do any powder coating in the future, I need to upgrade my powder coating gun and build a booth to help with the mess.  So, I will likely have Dave at Landfall powder coat this one (he has offered to do a few coating jobs for free so I can critique lol).  This makes things a bit tricky since I typically test my layout first before doing any drilling, then do the coating.  I have two options here:

1) Draft the chassis with a lot of wiggle room layout wise, such that I can confidently have Dave do all of the machining and the coating, sending the chassis to me ready to go
2) Have Dave send me the uncoated and partially machined chassis, test my layout with real parts, do the rest of the drilling myself, then send it back for coating

Not sure which approach to take yet, I'll have a better idea once I have a draft done.

With the big transformers on top of the chassis, the major space constraints will be defined by the filament supply raw DC boards and the output caps.  Given that we are going to need somewhere around 6.6-8.2uF of output capacitance, and the amplifier already sounds so good using a Solen output cap in the prototype, I might make my life easy and use polypropylene instead of PIO.  Fitting gigantic PIO caps is such a PITA, I'm sort of over it, at least for this build LOL.  Getting some high-quality polypropylene caps will make the layout 100x easier.

Let's see what else...I need to figure out the switch situation to change the turns ratio of the 8665 OPT, but that shouldn't be too tricky.

Since I only have two tubes in this amplifier, there is going to be a lot of open chassis real estate on the front half of the top plate.  For aesthetic reasons, I am going to put that to use by doing a recessed mounting of the 841 tubes, à la Yamamoto style.



Will probably mount the tubes down about half the depth of the base, should make for a cool look I think  I will leave the gap between the top plate and the recessed plate open, which will be great for ventilation purposes, will come up with a ventilation design for the top as well.

I will reorder my source follower PCBs and have a set made for a TO-247 chip to try out the Cree C2M1000170D instead of the AOTN160.  The current sink FET is going to get quite toasty in this build since it is dropping a lot of voltage, so the board will boast a pretty beefy heat sink.  The IXCP10M90S package is rated for 40W though, so shouldn't be a problem, just hot, will need to ventilate appropriately.

I think those are the major things to work on, finally building a proper headphone amp, about time I suppose


----------



## L0rdGwyn

To me, the bright glow of the thoriated tungsten tubes is reminiscent of sunlight, so I am going to do something like below, the tube sockets will be recessed, the surrounding ventilation pattern will be a sunburst.  This is a rough draft so obviously subject to change in terms of dimensions and layout.


----------



## bcowen

L0rdGwyn said:


> I've seen enough to move forward with building the 841 headphone amplifier.  I essentially have all of the parts already!  Just need a few more knick knacks and a chassis.
> 
> I will mount the filament transformers and Lundahl mains transformer on top of the chassis under steel shields.  Obviously, all of the shields need to match for aesthetic reasons, so I ordered two pairs of shields from China, surprisingly they look very nice!  Was happy to come across these.  I like the rounded edge version better, but it will be a tight fit dimensions wise, so we'll see which ones pan out and I will keep the other set for a future project.
> 
> ...



I like the transformer covers with the rounded corners, just in case you put this up for a vote at some point. 

The 'metalwork' coming from China these days is pretty darn good, depending on the source of course. I bought a chassis for a linear power supply (partial) kit a couple years ago, and I was frankly quite impressed with it, especially for the money. Nice aesthetic, all screw holes lined up and had machined threads, powder coat was flawless, etc.


----------



## L0rdGwyn (Nov 19, 2020)

bcowen said:


> I like the transformer covers with the rounded corners, just in case you put this up for a vote at some point.
> 
> The 'metalwork' coming from China these days is pretty darn good, depending on the source of course. I bought a chassis for a linear power supply (partial) kit a couple years ago, and I was frankly quite impressed with it, especially for the money. Nice aesthetic, all screw holes lined up and had machined threads, powder coat was flawless, etc.



Very nice!  Yes, there are some quality chassis from China.  The silver chassis @2359glenn uses on his GOTL are Chinese and are well made. 

I like the rounded ones too!  But I had to order both, fitting the Lundahl mains transformer inside is going to be REALLY tight, I'm not certain it will fit lol and it is the biggest one they offer in that style.


----------



## L0rdGwyn (Nov 19, 2020)

Alright, I've got the switch situation figured out for the output transformers.

The Sowter 8665 has three secondary windings.  How they are wired up determines the turns ratio of the transformer, and thus, the impedance of headphone that _should_ be connected.

From Sowter's site:

 

So, the switch has to take the three windings and change how they are stacked, series vs. parallel.

Here is my chicken scratch wiring diagram lol.



I will need a 4 pole, 3 throw, 3 deck switch, which will be from Goldpoint.  The above is for one channel, so it only shows 2 of the 4 poles, C stands for "common".  Note that the +/- wiring is opposite from Sowter's diagram on the upper right since the amplifier has a single phase-inverting stage, so the phase must be reversed on the output.

"Common" is where the transformer windings will be connected, then the C will connected to 1, 2, or 3 depending on the position of the switch.  Position 1 will put all of the windings in parallel for low impedance headphones, position 2 will put two windings in parallel and one in series for medium impedance headphones, and position 3 will put all of the windings in series for high impedance headphones.

This will be a pain to wire but the benefit is worth it  this way the amplifier will be compatible with virtually any headphone impedance.


----------



## leftside

I like the rounded corners too @A2029


----------



## L0rdGwyn (Nov 19, 2020)

leftside said:


> I like the rounded corners too @A2029



LOL nice.  The rounded edges remind me of some vintage Tango transformers.  I hope I can use them too, the width of my Lundahl mains transformer is 118mm, the interior width of the shield is 119mm!  It's gonna be a wee bit tight HA!  Probably nothing a Dremel can't fix 

I have the Auteur out the the garage for a listen...MAN this amp sounds really good.  Okay I might be biased LOL but it is super detailed, huge staging and really impressive imaging, reminds me of certain iterations of the 801A prototype that blew my mind...



I sort of overcommitted when I was trying to use the 841 as the gain stage for the 801A amp, then was filled with regret when they didn't pan out in that design.  Now I am so happy I have extra pairs!  These tubes are pretty rare, so I was snatching them up whenever they surfaced.  These kick ass in a single gain stage headphone amplifier, the distortion spectrum is very favorable.

Tomorrow the RCA globe 841 arrive, I have big expectations for them, hopefully they are quiet!  If they are good, there are some GE globe 841 on eBay, but expensive!  The seller at one point had offered me a pretty good price, maybe I can talk him down again.

They are from 1939.



I am getting a little desperate for someone else to listen to what I have made.  I was really excited to bring my gear to ZMFestivus this year, but obviously it was canceled.  I am pretty wary of sending these rare tubes long distances though, maybe I will send the amp to @whirlwind since he is local to me


----------



## leftside

L0rdGwyn said:


> LOL nice.  The rounded edges remind me of some vintage Tango transformers.  I hope I can use them too, the width of my Lundahl mains transformer is 118mm, the interior width of the shield is 119mm!  It's gonna be a wee bit tight HA!  Probably nothing a Dremel can't fix


Also great for cleaning tube pins! I honestly never realized how many different attachments you can get for these things until I purchased one.


----------



## L0rdGwyn (Nov 19, 2020)

leftside said:


> Also great for cleaning tube pins! I honestly never realized how many different attachments you can get for these things until I purchased one.



It is the best tool!  So useful, absolute essential IMO.

Just measured the output impedance of the amplifier with the high-impedance wiring, 4:1 turns ratio.

Output Z is 19.89ohms for use with 250-600ohm headphones.  Nice.

We can infer from that measurement that with the low impedance wiring, a turns ratio of 12:1, the output Z will be somewhere around 2.2ohm for use with 30-100ohm headphones.


----------



## bcowen

leftside said:


> Also great for cleaning tube pins! I honestly never realized how many different attachments you can get for these things until I purchased one.



Whoever invented the Dremel should be awarded a Nobel prize.  Along with whoever invented Magic Erasers, gas powered lawnmowers, and of course, Al Gore for inventing the internet.


----------



## Xcalibur255

Thank goodness for a series of tubes.


----------



## johnjen

I like using scotchbrite, green or maroon for the heavy corrosion and white for a good surface finish.

It removes way less material and gets down to the shiny metal underneath and the white makes for a very fine scratch free finish.

JJ


----------



## bcowen

johnjen said:


> I like using scotchbrite, green or maroon for the heavy corrosion and white for a good surface finish.
> 
> It removes way less material and gets down to the shiny metal underneath and the white makes for a very fine scratch free finish.
> 
> JJ



I like those too.  And there's even a Dremel app for that.   Just don't buy the Dremel branded ones that are close to $15 for 2 pieces.  They don't last any longer than these (ask me how I know...):

https://www.amazon.com/Abrasive-Buf...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl


----------



## Zachik

bcowen said:


> I like those too.  And there's even a Dremel app for that.   Just don't buy the Dremel branded ones that are close to $15 for 2 pieces.  They don't last any longer than these (ask me how I know...):
> 
> https://www.amazon.com/Abrasive-Buffing-Polishing-Grinding-Accessories/dp/B07T89FTYQ/ref=sr_1_1_sspa?crid=1R661I71VZNXG&dchild=1&keywords=dremel+scotchbrite+wheels&qid=1605837325&sprefix=demel+scotchbrite,aps,149&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE3Rlg1Wk02VUpQU08mZW5jcnlwdGVkSWQ9QTA0MDIxMTk4RU0wNlA2RE1QQVomZW5jcnlwdGVkQWRJZD1BMDkzMjEyMTFXRkxIUlEzR1pRSksmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl


Bill - are those good for cleaning tubes' pins? or is it going to damage the pins? (especially the skinny 12AU7 type)
I got a few tubes from eBay that I never got to clean, and I would not dare plugging those specific tubes into any amp before giving them a Spa day...


----------



## bcowen (Nov 19, 2020)

Zachik said:


> Bill - are those good for cleaning tubes' pins? or is it going to damage the pins? (especially the skinny 12AU7 type)
> I got a few tubes from eBay that I never got to clean, and I would not dare plugging those specific tubes into any amp before giving them a Spa day...



I wouldn't be worried about damaging the pins on a noval tube as you control how much pressure is applied, but these aren't going to be very effective at getting between and behind the pins.  They work decently with octal pins as there's enough room to angle the wheel to make contact with a good portion of the pins, especially after the abrasive is worn down a bit.  For novals, that Magic Eraser I mentioned works better than you'd think -- dampen the pad, and just push the pins down into the pad in different places a half-dozen times.  Won't help with really baked on crud, but for surface grime and even light oxidation it works quite well.  Some guys even use the Magic Eraser as a stylus cleaner by just dropping the stylus down onto the pad.  I haven't been brave enough to try it...yet.  

(if you try the Magic Eraser, be sure to get the name brand Mr Clean one and not a store-brand knock off)


----------



## Zachik

bcowen said:


> For novals, that Magic Eraser I mentioned works better than you'd think -- dampen the pad, and just push the pins down into the pad in different places a half-dozen times.


Something like this one?
https://www.amazon.com/STK-Extra-Th...re-Leather-Car-Steel/dp/B01CYTW58Y/ref=sr_1_7

Would it work on the octal pins as well?
I need to clean various octal and noval tubes... Next week is off work, so I am starting to line up some micro-projects / chores for me to get a good use of the time off


----------



## leftside

Zachik said:


> Bill - are those good for cleaning tubes' pins? or is it going to damage the pins? (especially the skinny 12AU7 type)
> I got a few tubes from eBay that I never got to clean, and I would not dare plugging those specific tubes into any amp before giving them a Spa day...


Regular dirty pins:
https://www.amazon.ca/gp/product/B07PJHJ893

Giving these a try next:
https://www.amazon.ca/gp/product/B07ZJBXYD7
https://www.amazon.ca/gp/product/B087RQXFZ7

This works really well on EL3N pins:


----------



## leftside

Haven't used on the little tubes like 12AX7.


----------



## bcowen

Zachik said:


> Something like this one?
> https://www.amazon.com/STK-Extra-Th...re-Leather-Car-Steel/dp/B01CYTW58Y/ref=sr_1_7
> 
> Would it work on the octal pins as well?
> I need to clean various octal and noval tubes... Next week is off work, so I am starting to line up some micro-projects / chores for me to get a good use of the time off



No, this one:

https://www.amazon.com/Mr-Clean-Cle...n+magic+eraser&qid=1605841504&s=pantry&sr=8-7

They don't work so well with octal pins. The foam is too dense to easily push the pins into.  Not an issue with the smaller, sharp points of a noval, but I haven't had much success with an octal.  For those, the bits that @leftside linked above work very well...if you have a Dremel.  If not, Deoxit and pipe cleaners is my go-to method. Just follow the directions on the Deoxit can (which most people don't )....apply it liberally, let it sit for 3-5 minutes, then reapply and scrub. The metal wire in the pipe cleaner acts as a decent scrubbing tool after the Deoxit has had time to chemically break down the crud some. I always follow the second application with an alcohol scrub just to clean off the Deoxit residue.


----------



## leftside

bcowen said:


> No, this one:
> 
> https://www.amazon.com/Mr-Clean-Cle...n+magic+eraser&qid=1605841504&s=pantry&sr=8-7
> 
> They don't work so well with octal pins. The foam is too dense to easily push the pins into.  Not an issue with the smaller, sharp points of a noval, but I haven't had much success with an octal.  For those, the bits that @leftside linked above work very well...if you have a Dremel.  If not, Deoxit and pipe cleaners is my go-to method. Just follow the directions on the Deoxit can (which most people don't )....apply it liberally, let it sit for 3-5 minutes, then reapply and scrub. The metal wire in the pipe cleaner acts as a decent scrubbing tool after the Deoxit has had time to chemically break down the crud some. I always follow the second application with an alcohol scrub just to clean off the Deoxit residue.


Couldn't agree more. Glad you mentioned the alcohol scrub/wipe at the end there.


----------



## whirlwind

L0rdGwyn said:


> LOL nice.  The rounded edges remind me of some vintage Tango transformers.  I hope I can use them too, the width of my Lundahl mains transformer is 118mm, the interior width of the shield is 119mm!  It's gonna be a wee bit tight HA!  Probably nothing a Dremel can't fix
> 
> I have the Auteur out the the garage for a listen...MAN this amp sounds really good.  Okay I might be biased LOL but it is super detailed, huge staging and really impressive imaging, reminds me of certain iterations of the 801A prototype that blew my mind...
> 
> ...



Oh wow. This would be an honor to get to listen to one of your amps. I am sure each and everyone of them sound as good as they look.
They are look killer and professionally done.

The only downside I can see is that I would probably want to buy the amp


----------



## L0rdGwyn

whirlwind said:


> Oh wow. This would be an honor to get to listen to one of your amps. I am sure each and everyone of them sound as good as they look.
> They are look killer and professionally done.
> 
> The only downside I can see is that I would probably want to buy the amp



Well you and I have already successfully shipped an amp back and forth, could be a good test run!  I'd love to hear your thoughts.  Making copies of this amp would be a little tricky since the tubes are very uncommon, as are the few other high-mu DHTs, but something like this could be made easily with a new production high-mu DHT, like the EML-20B or EML-30A and likely wouldn't need the FET buffer given the lowish plate impedance  something to keep in mind!

Got back from a very fruitful vinyl shop hop a little bit ago, a great haul!  Pretty eclectic mix, from Glenn Gould to Lead Belly, new-age, Tuareg guitar, electro funk, opera....

Needless to say the DIY rig is in full swing tonight, especially since everything is more or less shut down at the moment.

   

Definitely a good year to get into DIY and start a Head-Fi thread, ha!  Lots of time at home, that's for sure.  Thanks to everyone who has followed along and listened to all of my crazed rants.

It is Lucky's first Christmas since being abducted from the back yard, no longer a stray cat, he is not complaining so far.  He enjoys sleeping to new-age and ambient music, in particular.


----------



## bcowen

L0rdGwyn said:


> Well you and I have already successfully shipped an amp back and forth, could be a good test run!  I'd love to hear your thoughts.  Making copies of this amp would be a little tricky since the tubes are very uncommon, as are the few other high-mu DHTs, but something like this could be made easily with a new production high-mu DHT, like the EML-20B or EML-30A and likely wouldn't need the FET buffer given the lowish plate impedance  something to keep in mind!
> 
> Got back from a very fruitful vinyl shop hop a little bit ago, a great haul!  Pretty eclectic mix, from Glenn Gould to Lead Belly, new-age, Tuareg guitar, electro funk, opera....
> 
> ...



I enjoy all your crazed rants.  Even though many are well over my head, I still enjoy them and possibly might maybe somehow learn something in the process.


----------



## Zachik

bcowen said:


> I enjoy all your crazed rants.  Even though many are well over my head, I still enjoy them and possibly might maybe somehow learn something in the process.


+1


----------



## Xcalibur255

Best cat I ever had was one who just showed up on the back porch one day and then never left.

This thread is great, I hope you never tire of doing it.  It'll be even greater a couple of years from now when you are MOT and selling this stuff.


----------



## L0rdGwyn

bcowen said:


> I enjoy all your crazed rants.  Even though many are well over my head, I still enjoy them and possibly might maybe somehow learn something in the process.





Zachik said:


> +1



Well thanks gentlemen!  You have now given me the green light to keep ranting away LOL.



Xcalibur255 said:


> Best cat I ever had was one who just showed up on the back porch one day and then never left.
> 
> This thread is great, I hope you never tire of doing it.  It'll be even greater a couple of years from now when you are MOT and selling this stuff.



Awesome, that's pretty much what happened with Lucky, he just showed up and was super friendly, obviously a stray and malnourished, now he is packing on the pounds.

The only way I could see myself stopping the thread completely is if there just wasn't any interest in it, so hopefully it doesn't come to that!  The pace will probably slow down next year though...I think...

I'm still plugging away at this 841 headphone amp layout.  It's bigger than I had thought it would be, right now it is 12" x 13" x 3.25".  I am moving the power switch to the back of the amp to free up some space, since there will be a large switch on front panel.  Here is the most recent layout.  This is how I estimate where everything will go and in what orientation.




Plan right now is to use 6.8uF 600V Auricap XO on the output.



There is more work to be done on it, but we are getting there...


----------



## L0rdGwyn

I just had a birthday this past week, something that has been on my wish list for some time is a quality digital recorder.  I got some gift cards that I am going to use to get one today  most likely the Zoom H4n Pro.

Not sure if this counts as DIY, but I have a major and a minor plan for this recorder...

The major plan is this: similar to how people like to capture memories on home videos (like my dad did with a giant shoulder-mount VHS recorder in the 1990s LOL), I would like to capture soundscapes of places I visit, either my favorite places locally or while traveling.  Then I can listen to these recordings in the future and be transported to these places, completely from an auditory perspective.

That is the major draw for me, but the other is I can get decent quality audio recordings of my stereo and perhaps use the measurements to optimize speaker positioning.

We'll see how useful that is, but I will try taking an audio/video recording my system today or tomorrow and see how it goes.  If it works out, I'll post it here!

Probably something on vinyl...any genre suggestions?  I've got a little bit of everything: rock, EDM, ambient, classical, jazz, dub, opera, hip hop, post-punk, country, freak-folk, various types of ethnic music...I'll have to see where I can upload and link the video without getting in trouble!


----------



## Zachik

L0rdGwyn said:


> I'm still plugging away at this 841 headphone amp layout. It's bigger than I had thought it would be, right now it is 12" x 13" x 3.25". I am moving the power switch to the back of the amp to free up some space, since there will be a large switch on front panel. Here is the most recent layout. This is how I estimate where everything will go and in what orientation.


Keenan - I will spare you from the snarky comment about the power switch on the back, comparing it to Schiit audio, and just ask:
what is the big switch in the front for?


----------



## Zachik

L0rdGwyn said:


> I just had a birthday this past week


Happy birthday my friend!


----------



## L0rdGwyn

Zachik said:


> Keenan - I will spare you from the snarky comment about the power switch on the back, comparing it to Schiit audio, and just ask:
> what is the big switch in the front for?



LOL I thought the same thing.  It's actually advantageous in some ways since I don't need to run 120VAC from the back of the amplifier to a power switch at the front panel, which could couple into the audio signal.  The big switch on the front will be for changing the turns-ratio of the output transformers for compatibility with headphones of different impedances.  I talk about it a little bit here:

https://www.head-fi.org/threads/l0rdgwyns-diy-audio.921105/post-15986125



Zachik said:


> Happy birthday my friend!



Thanks!!!


----------



## Zachik

L0rdGwyn said:


> The big switch on the front will be for changing the turns-ratio of the output transformers for compatibility with headphones of different impedances. I talk about it a little bit here:
> 
> https://www.head-fi.org/threads/l0rdgwyns-diy-audio.921105/post-15986125


The risk of reading so many different threads here (and elsewhere...) is forgetting some details or previously read info. Thanks for the reminder


----------



## L0rdGwyn (Nov 22, 2020)

Here is a recording of my system using a Zoom digital recorder, instead of something "audiophile" I decided to go festive  'tis the season, after all.

The sound quality obviously isn't the same as in person and it is definitely more "tinny" and less full, YouTube further compresses the audio, but I THINK you can at least _sense_ that the sound quality is good.  You be the judge!  I'll try something else later today, maybe some jazz, maybe some EDM.

Chain: Thorens TD 125 MKII w/ Hana EL MC cartridge > balanced input to Lundahl LL9226XL / D3a / EF86 phono stage > MOV MH4 / Visseaux 6A5G / Lundahl LL1620 SET > Snell J/II


----------



## L0rdGwyn (Nov 22, 2020)

Here is another one.  I discovered running the output of the Zoom recorder to the audio input of the camera was degrading the sound quality and adding noise.  I recorded audio and video separately, then edited them together afterward with much better results.

Art Blakey & the Jazz Messengers - Moanin'



Here is my little stereo recording rig.


----------



## Xcalibur255

A belated happy birthday to you Keenan.


----------



## L0rdGwyn (Nov 24, 2020)

The prototyping aspect of the 841 headphone amp is done, but I did keep the prototype intact to try out these before breaking it down.



They sound great, glad I picked them up.

 

Some other nice tubes arrived today as well, ceramic base graphite plate RCA 801.



These will go in the 801A amplifier when it is done, hopefully in the next five years.

Looks like my custom mains transformer from Sowter is shipping, so I can start working on the updated 45 amplifier in the near future.  Tubes will be re-biased for 2W and binding posts added for speakers.

Lastly, I will be working on a DIY ultrasonic record cleaner relatively soon, need a better process and the markup for what is out on the market for US cleaners is too much.  Think I could get the record cleaning parts setup for less than $100, then around $150 for the US cleaner itself.  Will probably show the design here, won't be anything super fancy, really just need a way to mount the records, then a low RPM 5VDC motor.


----------



## bcowen

L0rdGwyn said:


> The prototyping aspect of the 841 headphone amp is done, but I did keep the prototype intact to try out these before breaking it down.
> 
> 
> 
> ...



I went with the Vinyl Stack.  Pricier than DIY to be sure, but it works great and I don't regret spending the money a bit.  

https://thevinylstack.com/view-cart/#!/3-Record-ULTRA-Sonic-Spin-Kit/p/51658871/category=13505423

Bought the tank (6 liter) on Ebay for $100.  It's fine, but in hindsight I should have spent the extra $30 and gone with the 10 liter.





But I didn't abandon the DIY part altogether -- the filtration qualifies.  Small pump (made for yard fountains) and a 1-micron filter canister.  I turn it on and let it filter while I'm running the just ultrasonic-ed LP's through the VPI 16.5 for a final rinse and vacuum. Is it all worth it?  Way.


----------



## Zachik

Bill, are you cleaning vinyls or distilling moonshine?!


----------



## L0rdGwyn (Nov 25, 2020)

bcowen said:


> I went with the Vinyl Stack.  Pricier than DIY to be sure, but it works great and I don't regret spending the money a bit.
> 
> https://thevinylstack.com/view-cart/#!/3-Record-ULTRA-Sonic-Spin-Kit/p/51658871/category=13505423
> 
> ...



I like it!  Honestly, the price for the Vinyl Stack isn't bad, I might just play copycat and go with it rather than the DIY route  I was looking at the prices for CleanerVinyl, which are pretty outrageous for what it is, IMO.  What makes you wish you went with the 10L, ease of use?  And how often do you typically change the filter?


----------



## bcowen

Zachik said:


> Bill, are you cleaning vinyls or distilling moonshine?!



Yes.


----------



## bcowen (Nov 25, 2020)

L0rdGwyn said:


> I like it!  Honestly, the price for the Vinyl Stack isn't bad, I might just play copycat and go with it rather than the DIY route  I was looking at the prices for CleanerVinyl, which are pretty outrageous for what it is, IMO.  What makes you wish you went with the 10L, ease of use?  And how often do you typically change the filter?



The record clamp assembly on the Vinyl Stack will accept 3 LP's at a time, and with the narrower width of the 6L tank there's barely enough room for 3.  I've done the tin foil test to see where the major cavitation activity was occurring, and with this particular tank it's pretty much in the center with not much going on near the sides so I've just resorted to doing 2 at a time.  I think the (wider) 10L tank would do a good job with 3, and that would serve my inherent laziness much better.  

I don't have any scientific process on the filter. I'm guessing somewhere around the 200 LP mark when it starts to get noticeably grimy. I haven't noticed any real difference in the flow rate which would logically be reduced if it was clogging up, but that's just a visual observation as well. Probably a lot depends on the initial condition of the LP's...most of the ones I've been cleaning are resale shop and garage sale finds, and probably cruddier on average than most. 

One thing I really like with the Vinyl Stack is the ingeniously simple clamping system for the record(s). Very easy to mount/dismount and the clamp discs not only cover the entire label area but have rubber O rings on both sides so the label is completely protected from getting wet in the process.  And the whole thing is very nicely done -- I was wowed with how every little detail was considered and addressed in a quality fashion.


----------



## bcowen

L0rdGwyn said:


> I like it!  Honestly, the price for the Vinyl Stack isn't bad, I might just play copycat and go with it rather than the DIY route  I was looking at the prices for CleanerVinyl, which are pretty outrageous for what it is, IMO.  What makes you wish you went with the 10L, ease of use?  And how often do you typically change the filter?



OK, so this filtering system option for the CleanerVinyl is pushing past the boundaries of silly:






The DIY routine:

https://www.amazon.com/gp/product/B0014C5D64/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B00D049XFQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B01G305PK0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

$55.68 from Amazon.  Add another ~$20 for the tubing/hose clamps/fittings for about $75 all in...which includes 2 _hugely_ larger filters than the teeny little ring filter that comes with the CleanerVinyl. And $19 for a single replacement filter for the CV setup? Sheesh Louish.


----------



## L0rdGwyn (Nov 25, 2020)

bcowen said:


> The record clamp assembly on the Vinyl Stack will accept 3 LP's at a time, and with the narrower width of the 6L tank there's barely enough room for 3.  I've done the tin foil test to see where the major cavitation activity was occurring, and with this particular tank it's pretty much in the center with not much going on near the sides so I've just resorted to doing 2 at a time.  I think the (wider) 10L tank would do a good job with 3, and that would serve my inherent laziness much better.
> 
> I don't have any scientific process on the filter. I'm guessing somewhere around the 200 LP mark when it starts to get noticeably grimy. I haven't noticed any real difference in the flow rate which would logically be reduced if it was clogging up, but that's just a visual observation as well. Probably a lot depends on the initial condition of the LP's...most of the ones I've been cleaning are resale shop and garage sale finds, and probably cruddier on average than most.
> 
> One thing I really like with the Vinyl Stack is the ingeniously simple clamping system for the record(s). Very easy to mount/dismount and the clamp discs not only cover the entire label area but have rubber O rings on both sides so the label is completely protected from getting wet in the process.  And the whole thing is very nicely done -- I was wowed with how every little detail was considered and addressed in a quality fashion.



Gotcha, makes sense.  What I am thinking of doing is a 10L cleaner with the 4 stack version of the Vinyl Stack and a filtration system.  While I know the post-ultrasonic rinsing step with a dedicated cleaner is the best method, I will be pushing up against SAF/WAF by going for both at once LOL.  So I think I will just have to go for the US w/ distilled + wetting agent and air drying, at least temporarily.

I was watching some video reviews of the Vinyl Stack, the clamping system and magnetic mounting seems really well thought out, me likey 



bcowen said:


> OK, so this filtering system option for the CleanerVinyl is pushing past the boundaries of silly:
> 
> 
> 
> ...



RIGHT?!  I couldn't justify the prices being asked, which is why I was initially thinking of a DIY solution, thanks for pointing out the Vinyl Stack.

Oh and for the record (no pun intended, seriously), the 132kHz ultrasonic cleaner he is selling on his site for $600 can be sourced directly from China for $279.  And he is likely getting a discount by buying in bulk, what great profit margins!


----------



## L0rdGwyn (Nov 25, 2020)

I took steps today to scale back DIY operations for the winter.  Mostly this means breaking down my 801A / 841 prototype and getting everything that will not appreciate the cold of winter out of my garage and ready for storage indoors.

Most likely any work on the 801A amplifier will be put on hold until late winter / early spring, since the prototype will need to be reassembled for further testing with the new transformers.

I will continue forward with the 45 amplifier rebuild and 841 headphone amplifier since those designs are complete, just a matter of getting the chassis details finalized.  Since I am having all of the machining and coating done by Landfall for both builds this time around, the amount of time that needs to be spent outdoors should be pretty minimal.  In theory, I will just need to mount and wire the components, which is a cakewalk compared to trialing a layout, marking a chassis, drilling, prepping parts, coating...

So, I think things are going to slow down quite a bit around here, sorry!  It has been a busy 11 months.  Looking forward to finally finishing the 45 amp and getting the 841 headamp up and running.


----------



## Xcalibur255

I"m sure there will still be things to talk about.  This is your space after all, we can talk about cats all winter and I'll be here to give a thumbs up.


----------



## L0rdGwyn

Xcalibur255 said:


> I"m sure there will still be things to talk about.  This is your space after all, we can talk about cats all winter and I'll be here to give a thumbs up.



That sounds lovely! Yes, we can talk about cats and DIY shenanigans, maybe future plans.  I will need a distraction, this is going to be a rough winter...


----------



## bcowen

L0rdGwyn said:


> That sounds lovely! Yes, we can talk about cats and DIY shenanigans, maybe future plans.  I will need a distraction, this is going to be a rough winter...



You can distract yourself by ultrasonically cleaning LP's all winter.  By spring, you'll have lots of squeaky clean vinyl.


----------



## L0rdGwyn

New 45 mains transformer is here.



Will work on getting the new chassis ordered, but will take some time, busy times at work.  I am probably going with a maroon powder coat on the new one, sort of a nod to early Marconi branding given the amplifier will most often run a pair of MOV L63 in the driver position.  As for the old mains transformer?  Since it was spec'd for the 45 with a 325VAC B+ winding and three 6.3VAC windings, can pretty easily be used for a IDHT amplifier at some point.

I lost two auctions the other day for some NOS type 50, narrowly on one auction.  If I had won, it would have solidified long-term plans to build a type 50 amplifier.  I even reached out to Emission Labs to see if they are still producing a new-production type 50...they are, with no plans to stop.  So, keeping an eye on type 50 auctions.  If the mood strikes and I pull a NOS pair, then that's that.  There is only one way to sate my unobtanium DHT tube lust.

Updates on other builds...the Sowter 801A transformers should get here any day now.  Like I've said, physical work on this amplifier is halted, but I have an abundance of data from the prototype...going to do some brainstorming on the design and see if there is anything I want to alter over the winter.

And the 841 headphone amplifier.  Been holding off on finalizing any chassis layout plans until the transformer shields get here, which is happening today, assuming the mail is delivered, getting completely snowed-in at the moment.


----------



## bcowen

L0rdGwyn said:


> New 45 mains transformer is here.
> 
> 
> 
> ...



These Cary amps I used to have were painted in Jaguar Red (a sexier name for maroon ). Beauty is in the eye of the beholder of course, but these were probably the biggest eye-candy amps I've ever owned. The gleaming chrome and gold transformer caps of my current Jota amp look nice too (IMO), but these were different-ly gorgeous.   Hard to see in the picture, but the gloss was a mile deep. The transformer covers had more of a satin sheen, but contrasted nicely with the gloss on the chassis.

I'm not well-versed on powder coating...can you do a bright gloss finish?


----------



## L0rdGwyn (Dec 1, 2020)

bcowen said:


> These Cary amps I used to have were painted in Jaguar Red (a sexier name for maroon ). Beauty is in the eye of the beholder of course, but these were probably the biggest eye-candy amps I've ever owned. The gleaming chrome and gold transformer caps of my current Jota amp look nice too (IMO), but these were different-ly gorgeous.   Hard to see in the picture, but the gloss was a mile deep. The transformer covers had more of a satin sheen, but contrasted nicely with the gloss on the chassis.
> 
> I'm not well-versed on powder coating...can you do a bright gloss finish?



Very nice, who needs a furnace when you have a pair of these bad boys?  Powder coating is very versatile, can get just about any finish you like, matte, textured, satin, high-gloss, etc.  I have been going through Prismatic Powders, tons and tons of finish options.

I'll be doing Maroon Bliss (metallic flake) or Iris Maroon (solid tone), more likely the latter.

Maroon Bliss: https://www.prismaticpowders.com/shop/powder-coating-colors/PMB-5456/maroon-bliss
Iris Maroon: https://www.prismaticpowders.com/shop/powder-coating-colors/PSB-4974/iris-maroon

Oh, and the Vinyl Stack is en route


----------



## bcowen

L0rdGwyn said:


> Very nice, who needs a furnace when you have a pair of these bad boys?  Powder coating is very versatile, can get just about any finish you like, matte, textured, satin, high-gloss, etc.  I have been doing through Prismatic Powders, tons and tons of finish options.
> 
> I'll be doing Maroon Bliss (metallic flake) or Iris Maroon (solid tone), more likely the latter.
> 
> ...



Cool!  Did you get a tank yet?


----------



## L0rdGwyn

bcowen said:


> Cool!  Did you get a tank yet?



Not yet!  Worked all weekend, need to nail down the rest of the parts for the rig today.  Gonna grab a 10L tank and then figure out the filtering mechanism.


----------



## Xcalibur255

It's rare for one of these storms to not hit here.  I'm definitely not complaining.........

You can kinda tell when it's just going to be a near-miss around here though because the wind will be blowing 60+ mph and it is doing just that.  I'd still rather go looking for my garbage can tomorrow than shovel snow.


----------



## L0rdGwyn

Xcalibur255 said:


> It's rare for one of these storms to not hit here.  I'm definitely not complaining.........
> 
> You can kinda tell when it's just going to be a near-miss around here though because the wind will be blowing 60+ mph and it is doing just that.  I'd still rather go looking for my garbage can tomorrow than shovel snow.



Seven more hours of snow to go!


----------



## Zachik

Xcalibur255 said:


> It's rare for one of these storms to not hit here.  I'm definitely not complaining.........
> 
> You can kinda tell when it's just going to be a near-miss around here though because the wind will be blowing 60+ mph and it is doing just that.  I'd still rather go looking for my garbage can tomorrow than shovel snow.





L0rdGwyn said:


> Seven more hours of snow to go!



NO idea what you guys are talking about.........


----------



## whirlwind

L0rdGwyn said:


> Seven more hours of snow to go!




I was wondering how bad you got it up there.


----------



## L0rdGwyn (Dec 1, 2020)

whirlwind said:


> I was wondering how bad you got it up there.



It's still going!  I am impressed by my bird feeders, I wonder how much snow they can hold on top...




I live on the east side of Cleveland, which is even worse for snow since we get all of the lake effect.  Sometimes we will get a downpouring over here and people on the west side get none LOL.

My 801A transformers are supposed to be delivered, but I wonder if it will actually happen, the roads are undrivable...we'll see how hardcore FedEx is.


----------



## Zachik

L0rdGwyn said:


> It's still going!  I am impressed by my bird feeders, I wonder how much snow they can hold on top...
> 
> 
> 
> ...


How deep is the snow?!   
Also, how do you get to work if the roads are undrivable?


----------



## whirlwind

L0rdGwyn said:


> It's still going!  I am impressed by my bird feeders, I wonder how much snow they can hold on top...
> 
> 
> 
> ...



Yeah man that lake effect snow can be really nasty.....stay safe.


----------



## L0rdGwyn

Zachik said:


> How deep is the snow?!
> Also, how do you get to work if the roads are undrivable?



Looks like a foot or so based on the widely accepted railing analysis.



Well I am off today and tomorrow, so I am going nowhere!  By Thursday a lot of it will probably have melted.

I had to venture out earlier today for a mandatory errand...it was an absolute mess.


----------



## bcowen

L0rdGwyn said:


> Looks like a foot or so based on the widely accepted railing analysis.
> 
> 
> 
> ...



Yuck!  Be safe, man.

I spent two winters in central Wisconsin.  My first night there (in January) the low was -26 degrees.  Seriously questioned my own sanity. LOL!

Now *this *seems like an ice-age.


----------



## Xcalibur255

@Zachik

One of you ALWAYS comes along....


----------



## L0rdGwyn (Dec 2, 2020)

Sowter iron for the 801A has arrived.  5K:8ohm 60mA for a 0Vg bias point.



I said I was going to think about things I wanted to alter on this design, one came to me while I was asleep, which is kind of weird.  Tube amps are penetrating my subconscious.

The original plan was to use a separate chassis power supply without any components mounted on top such that the two chassis could stack if need be.  As time has gone on, that idea hasn't sat well with me since mounting a mains transformer on the interior would require a _thick_ chassis.  The two stacked would be big, too big.  I also want to simplify the power supply to some extent.

So here is what I am thinking...I am going to commit to the chassis being side-by-side with the mains transformer on top, and that mains transformer will be custom wound, yet again, by Sowter.  Why?  I can include the B+ secondary in addition to a second 100VAC secondary for the V- supply on the same transformer.  One mains transformer, two filament transformers, done.

That leaves the mains transformer solo on top of the PS chassis.  I envision this as sort of a narrow chassis at the same depth as the amplifier chassis, something like 12" L x 9" W x 3.25" H.  This would leave space on the top plate near the front of the PS chassis.  What to do with it?  How about a tube rectifier?  From a pragmatic standpoint, this is stupid as it will serve essentially no functional purpose other than extending the soft start time (soft start already built into the Maida regulator), I will do away with my B+ time-delay circuitry since the 801A filaments come up to voltage very quickly.

The tube rectifier is really just for aesthetics LOL which I am a sucker for.

What rectifier?  Probably the 5Z3.  I have some very nice examples on hand already, particularly from Fivre.  Specs fit, uses a UX4 base, which I like for some reason.

Here is sort of how I see the top plate layout shaking out, from a aesthetic standpoint.  The 45 mains transformer is standing in as an example for the PS chassis.



The tube rectifier isn't a done deal, but the custom mains is in my mind.  This probably pushes the completion of this amplifier to summer 2021, there is a lot to do.  Next steps will be to finalize the amplifier circuit via prototype with the new transformers, verify the power supply requirements, then order the custom mains transformer from Sowter.


----------



## L0rdGwyn

I feel pretty strongly this is the color I am going to go with for this amplifier, Prismatic Powders British Green.  Matches the transformers too 



I am considering setting up a soldering station in my basement with a fume extractor so I can keep soldering over the winter, to be continued...


----------



## whirlwind

L0rdGwyn said:


> I feel pretty strongly this is the color I am going to go with for this amplifier, Prismatic Powders British Green.  Matches the transformers too
> 
> 
> 
> I am considering setting up a soldering station in my basement with a fume extractor so I can keep soldering over the winter, to be continued...




Really diggin that color!


----------



## L0rdGwyn

whirlwind said:


> Really diggin that color!



Thanks, Joe.  I was looking for a very deep, classy dark green, not sure how I missed this one when I was looking a few months ago, think it will look really good with the silver end bells of the Sowter transformers  can't wait to finish that amp but there is a lot of work to do, the pay off should be worth it though.

I got the round transformer shields for the 841 amp the other day, happy to say they fit the mains and filament transformers I will be using.

 

Now I can work on finalizing the layout, but first things first, going to see if I can nail down the details of the revamped 45 amplifier chassis today or tomorrow and get it ordered.  Shouldn't be drastically different from the original, but will need to change the ventilation, add cutouts for speaker binding posts, and a switch for the headphone output.


----------



## bcowen

L0rdGwyn said:


> Thanks, Joe.  I was looking for a very deep, classy dark green, not sure how I missed this one when I was looking a few months ago, think it will look really good with the silver end bells of the Sowter transformers  can't wait to finish that amp but there is a lot of work to do, the pay off should be worth it though.
> 
> I got the round transformer shields for the 841 amp the other day, happy to say they fit the mains and filament transformers I will be using.
> 
> ...



Sweet!  Those covers look classy.  You going to paint them?  Would look pretty cool to paint them with a high gloss black, or perhaps just a high gloss clear coat....you know, something that will instantly showcase every fingerprint and microscopic dust particle.


----------



## L0rdGwyn (Dec 5, 2020)

bcowen said:


> Sweet!  Those covers look classy.  You going to paint them?  Would look pretty cool to paint them with a high gloss black, or perhaps just a high gloss clear coat....you know, something that will instantly showcase every fingerprint and microscopic dust particle.



I'm going to leave them as is, I like the matte black!  I learned my lesson on crafting my own high gloss thingamajigs when I polished the aluminum top plate of one of my Bottlehead builds to a mirror finish...every imperfection and blemish pushed me closer and closer to the brink of insanity lol, never again!  It did look nice, but I have a problem with perfectionism, hence why I keep rebuilding my amplifiers, should have known it would drive me crazy 

I am going to give some high gloss powder coat finishes a shot, like that green above, but I will be putting the coating responsibilities into the hands of someone with better gear than me  not sure on the chassis color yet for that amp.

Almost done with this new 45 amp layout...


----------



## bcowen

L0rdGwyn said:


> I learned my lesson on crafting my own high gloss thingamajigs when I polished the aluminum top plate of one of my Bottlehead builds to a mirror finish...every imperfection and blemish pushed me closer and closer to the brink of insanity lol, never again!  It did look nice, but I have a problem with perfectionism, hence why I keep rebuilding my amplifiers, should have known it would drive me crazy



ROFL!  The downside of DIY:  you know where _every_ imperfection is, even if nobody else ever will.


----------



## L0rdGwyn (Dec 5, 2020)

bcowen said:


> ROFL!  The downside of DIY:  you know where _every_ imperfection is, even if nobody else ever will.



YES!  It is a problem LOL fortunately my 6A5G amp is just about perfect in my deranged mind, same with my Snells, the Thorens TT is close just need to make some minor adjustments.  My phono stage is destined for a rebuild since I've made some changes internally (now some unnecessary holes in the chassis) and I'm not happy with how the finish turned out, but that is pretty far down on the to do list.  I expect this new 45 amp will hit the mark.

Here is that Bottlehead build, think the new owner is happy with it.  Don't know what I was thinking with all of the shiny, a recipe for madness.


----------



## L0rdGwyn

I said a while back I was going to learn some CAD software to make designing chassis a more efficient process.  Today I downloaded a trial of AutoCAD, my life is changed.

In a matter of minutes, I was able to recreate the chassis design I was working on in a software whose name I will not utter here (absolute trash, but free).  AutoCAD has tons of useful tools for getting a precise arrangement and drawing just about any geometric object.

Having an idea in my head of what I wanted the ventilation to look like, below is what I had to draw in order to get a perfect hexagonal vent arrangement aligned on the edge of a circle (you can set the program to snap shapes tangent to a circle, for example).




Trim all the extra guidelines away, and you get the end result, new top plate for the 45 amp.



Using this software is going to streamline getting chassis made.  Dave at Landfall works in AutoCAD, so I can simply draw up whatever I like (within the constraints of what he is able to machine), export the files and send it over to him, no annotations necessary, easy peasy


----------



## whirlwind

L0rdGwyn said:


> YES!  It is a problem LOL fortunately my 6A5G amp is just about perfect in my deranged mind, same with my Snells, the Thorens TT is close just need to make some minor adjustments.  My phono stage is destined for a rebuild since I've made some changes internally (now some unnecessary holes in the chassis) and I'm not happy with how the finish turned out, but that is pretty far down on the to do list.  I expect this new 45 amp will hit the mark.
> 
> Here is that Bottlehead build, think the new owner is happy with it.  Don't know what I was thinking with all of the shiny, a recipe for madness.



Well, it does look classy, but I can understand all the upkeep to keep it looking that way.
I find myself always wiping my LCD-4 grills with a nice soft cloth, just because I hate the finger prints that gets on the chrome, they look great....when clean.


----------



## L0rdGwyn

whirlwind said:


> Well, it does look classy, but I can understand all the upkeep to keep it looking that way.
> I find myself always wiping my LCD-4 grills with a nice soft cloth, just because I hate the finger prints that gets on the chrome, they look great....when clean.



The chrome on the LCD-4 looks very nice.  Issue with the aluminum is it oxides quite easily and loses its luster.  It's also a soft metal, so polishing to remove the oxidation leads to visible micro-scratches.  One of things that no one else notices but eats away at you lol if I were ever to do something like that again, I would get it chromed properly at a shop.  Buffing that thing was no joke!  I'm sure the grills on the LCD-4 hold up much better being chromed.


----------



## Tjj226 Angel

L0rdGwyn said:


> I said a while back I was going to learn some CAD software to make designing chassis a more efficient process.  Today I downloaded a trial of AutoCAD, my life is changed.
> 
> In a matter of minutes, I was able to recreate the chassis design I was working on in a software whose name I will not utter here (absolute trash, but free).  AutoCAD has tons of useful tools for getting a precise arrangement and drawing just about any geometric object.
> 
> ...



Now was this other software named after a way to generate power? Or was it named after its pricing model? 

Because if it is named after a particular form of power generation that always seems to be 10 years out, then I will go download autocad right here and now. 

If it is named after how free the software is, then yeah that makes sense.


----------



## paradoxper

L0rdGwyn said:


> YES!  It is a problem LOL fortunately my 6A5G amp is just about perfect in my deranged mind, same with my Snells, the Thorens TT is close just need to make some minor adjustments.  My phono stage is destined for a rebuild since I've made some changes internally (now some unnecessary holes in the chassis) and I'm not happy with how the finish turned out, but that is pretty far down on the to do list.  I expect this new 45 amp will hit the mark.
> 
> Here is that Bottlehead build, think the new owner is happy with it.  Don't know what I was thinking with all of the shiny, a recipe for madness.


It's a disease of the soul!

Oh yes, the days of perfect mirroring: the DIY T2, and even though we used the much esteemed Headamp resources i.e. the same anodizer/polisher, we had multiple articles come back with various defects. It was quite a pain.

However, it came out real pretty although there were glove mandates during listening sessions.


I'd do it again. I'm a bit compulsive with cost-no-object builds.  

I wish you luck in showing restraint.


----------



## L0rdGwyn (Dec 5, 2020)

Tjj226 Angel said:


> Now was this other software named after a way to generate power? Or was it named after its pricing model?
> 
> Because if it is named after a particular form of power generation that always seems to be 10 years out, then I will go download autocad right here and now.
> 
> If it is named after how free the software is, then yeah that makes sense.



Oh it ain't free, the price for the full suite will make your eyes bleed.  Everyone is going to subscription models now, that way the end user owns nothing and makes payments ad infinitum.  There is an AutoCAD LT (light) version that is cheaper but not cheap, around $30/month, hurts especially when you're using the program maybe once or twice a month.  Not an issue though, I am in the process of sourcing a free alternative  lots of free CAD software out there, maybe not as feature rich as AutoCAD, definitely enough to get the job done.


----------



## L0rdGwyn

paradoxper said:


> It's a disease of the soul!
> 
> Oh yes, the days of perfect mirroring: the DIY T2, and even though we used the much esteemed Headamp resources i.e. the same anodizer/polisher, we had multiple articles come back with various defects. It was quite a pain.
> 
> ...



Very nice!  It won't be something I attempt again in the near future, I have had my fill of pretty shiny, these days I am all about simple aesthetics and that stone cold SET iron  I am salivating over my new Sowter paperweights, soon my babies...


----------



## Tjj226 Angel

L0rdGwyn said:


> Oh it ain't free, the price for the full suite will make your eyes bleed.  Everyone is going to subscription models now, that way the end user owns nothing and makes payments ad infinitum.  There is an AutoCAD LT (light) version that is cheaper but not cheap, around $30/month, hurts especially when you're using the program maybe once or twice a month.  Not an issue though, I am in the process of sourcing a free alternative



I will drop the pretense and assume you were using fusion360 for your designs?

The thing about fusion 360 is that it is both a CAD and CAM program in one. If you are running the CNC machine yourself, then fusion360 is the best piece of software you can use. 

However, since you are just sending drawings off to Landfall, then you can use any vector drawing software out there. You don't have to limit yourself to a CAD style program. The only reason most people tend to lean towards CAD programs is because you can specify dimensions a little easier. But the truth is that there are plenty of vector drawing programs that allow you to do the same thing. 

You just need to find the right program that lets you draw circles, squares, and lines with intuitive controls and easy drag and drop placement functionality.


----------



## Zachik

L0rdGwyn said:


> I am in the process of sourcing a free alternative


Please do share once you find a good (enough) free alternative!
For my last project - I have used the free software from Front Panel Express (called Front Panel Designer). Worked pretty well for me, and was very easy to learn quickly. Can export DXF files which can be imported into AutoCAD by Dave and others.


----------



## bcowen

L0rdGwyn said:


> Very nice!  It won't be something I attempt again in the near future, I have had my fill of pretty shiny, these days I am all about simple aesthetics and that stone cold SET iron  I am salivating over my new Sowter paperweights, soon my babies...



Some good, hard chrome (and gold plate) makes things easy...and results in much less shiny neurosis.


----------



## L0rdGwyn

Tjj226 Angel said:


> I will drop the pretense and assume you were using fusion360 for your designs?
> 
> The thing about fusion 360 is that it is both a CAD and CAM program in one. If you are running the CNC machine yourself, then fusion360 is the best piece of software you can use.
> 
> ...



Whoops I need to read more carefully, your allusions to Fusion 360 went right over my head lol but that wasn't it!  A vector program that truly isn't worthy of discussion.  I like the feel of the CAD software, going to stick with it.



bcowen said:


> Some good, hard chrome (and gold plate) makes things easy...and results in much less shiny neurosis.



Now THAT is some good shiny.  Chrome is the way to go!


----------



## L0rdGwyn (Dec 6, 2020)

Placed some orders for final parts for the 45 parafeed rebuild.  Will be adding these WBT binding posts.



Elma knob and Goldpoint selector for the headphone switch on the rear panel.

 

I'll be switching over to NOS Mills MRA10 wirewound resistors on the 45 cathodes and Clarity Cap CSA bypass caps.

I will be swapping out the 6J5 CCS boards (from K&K Audio) for my boards, which have a pad for the mu output. 

The 45 CCS boards mounted to the rear panel heat sinks will stay as is, they are currently (no pun intended) set for 35mA.  I am feeling lazy, going to leave them that way and use a somewhat hot bias on the 45, 265V 35mA, load line below.



Most everything else will stay as is.  I think I forgot to mention I had Sowter place additional screens to shield the 45 filament windings on the mains transformer to prevent rectifier coupling between windings.

Will do one more QC check on the chassis layout and place the order tomorrow, should have this done by Christmas


----------



## L0rdGwyn

I had a last-minute change of heart on the 45 amp color.  It will now be in a very, very dark blue, almost black, Casper Blue.



I think this will mesh better with the silver Sowter end bells and binding posts.

Chassis is ordered, now the wait begins.  Will continue planning the 841 headphone amplifier layout in the meanwhile.  Have the chassis a good part of the way done in AutoCAD, we'll see if I can finish it between today and tomorrow.


----------



## whirlwind

L0rdGwyn said:


> I had a last-minute change of heart on the 45 amp color.  It will now be in a very, very dark blue, almost black, Casper Blue.
> 
> 
> 
> ...




I like it...that is very dark and dang sexy!


----------



## Zachik

L0rdGwyn said:


> I had a last-minute change of heart on the 45 amp color. It will now be in a very, very dark blue, almost black, Casper Blue.


Personally, this dark blue is WAY nicer than the green!  
I like your change of heart


----------



## L0rdGwyn

Thanks, gents  I feel good about it too, think it will look nice.

Been plugging away at this 841 chassis.  Finally got the sunburst ventilation pattern into a workable state in AutoCAD.  This was not easy, sheesh...took me about two hours.  Had to remove the white background of the picture in Photoshop, convert the remaining line pattern to a vectorized DXF file, insert into my drawing to use as a stencil, trace the line pattern, delete the inserted DXF file, trim the lines to 1/8" outside the socket cutout, add 1/16" circles at each line end point, connect the tangents to form a 1/16" wide "pill" shape, then trim away all of the excess guidelines...this better turn out damn good!




Probably will need to be tweaked a bit later, but it's in there!  Things are coming along nicely now.


----------



## L0rdGwyn

Here is the 841 headphone amplifier layout so far, just need to figure out the power supply components, I'd say the plan is 70% of the way there.



It's all gonna fit, chassis will be 12" x 13" x 3.25".  The purple rectangles are the recessed plates on which the tube sockets will be mounted, 12mm down, so the tubes will be recessed about half the width of their bases into a 1.75" opening.  OPT are mounted on the side panels on the interior (orange), which will hit the switch on the front panel in the center to alter the turns ratio to match various headphone impedances.  Once I've 100% confirmed the layout, the part outlines will be removed, leaving only the mounting holes.  Then the hardest part...the color


----------



## bcowen

L0rdGwyn said:


> I had a last-minute change of heart on the 45 amp color.  It will now be in a very, very dark blue, almost black, Casper Blue.
> 
> 
> 
> ...




I like_ this_ blue better. Mostly because of the name.  Now if they'd introduce one called "Bcowen Sleeping With A Supermodel," I'd probably like that even better.


----------



## L0rdGwyn

bcowen said:


> I like_ this_ blue better. Mostly because of the name.  Now if they'd introduce one called "Bcowen Sleeping With A Supermodel," I'd probably like that even better.



LOL!!! I hear "Bcowen Sleeping With A Supermodel" is coming up on the 2021 product launch  projected to outperform this year's showcase powder "L0rdGwyn Cruising To Ibiza On His G6".


----------



## Zachik

L0rdGwyn said:


> I hear "Bcowen Sleeping With A Supermodel" is coming up on the 2021 product launch


...followed by "Bcowen's wife left, smashing all his tubes on her way out" on 2022 product roadmap


----------



## bcowen

Zachik said:


> ...followed by "Bcowen's wife left, smashing all his tubes on her way out" ...



I'm pretty sure that would end by sailing through the courts as justifiable homicide.


----------



## Xcalibur255

L0rdGwyn said:


> I had a last-minute change of heart on the 45 amp color.  It will now be in a very, very dark blue, almost black, Casper Blue.
> 
> 
> 
> ...



Dig the color.  One of the things that comes into play when moving away from black is how it's going to look at night when the orange glow of the tubes will be casting against it.  Orange + blue and orange + green both result in a tertiary color resembling brown, but the orange/green mix skews to more of an olive tone where as the orange/blue more of a ruddy brown.


----------



## L0rdGwyn

Xcalibur255 said:


> Dig the color.  One of the things that comes into play when moving away from black is how it's going to look at night when the orange glow of the tubes will be casting against it.  Orange + blue and orange + green both result in a tertiary color resembling brown, but the orange/green mix skews to more of an olive tone where as the orange/blue more of a ruddy brown.



Interesting!  I'll have to see how the color looks at night.  My 45s don't have a super vibrant glow, so we will see.  Hoping the blue tones come out in certain lighting.

I am finishing up the 841 chassis right now, planning to place the order today, ahead of schedule!


----------



## L0rdGwyn (Dec 8, 2020)

Here is the final top plate design for the 841 headphone amp, including the recessed tube socket plates.



I went to look at the Cree C2M1000170D FETs I plan to use in this build, holy smokes they are backorder for almost a year!  Good thing I have two left  



Haven't finalized the color choice yet, but probably going with a very pale gold metallic.


----------



## Zachik

L0rdGwyn said:


> Haven't finalized the color choice yet, but probably going with a very pale gold metallic.


What happened to the dark blue?!


----------



## L0rdGwyn

Zachik said:


> What happened to the dark blue?!



Dark blue is going on the 45 parafeed amplifier, this is a completely different build!  A dedicated headphone amp featuring the 841 DHT.  Sorry, I know I keep switching back and forth.

Here are various knick knacks for the 45 parafeed amplifier, courtesy of Hificollective.  Still have no idea how they get my packages here overnight from the UK...


----------



## Zachik

L0rdGwyn said:


> Dark blue is going on the 45 parafeed amplifier, this is a completely different build! A dedicated headphone amp featuring the 841 DHT. Sorry, I know I keep switching back and forth.


Yeah - hard to keep track with you buddy!


----------



## L0rdGwyn

Sorry!  Got my Sowter shipments which covered three different builds.  After these two are done, all that will be left in the queue is 801A amp, that will be a good feeling.


----------



## whirlwind

Zachik said:


> What happened to the dark blue?!



You need to be on your "A" game......two projects at once!


----------



## Zachik

whirlwind said:


> You need to be on your "A" game......two projects at once!


I know... Keenan is doing all the hard work, and I screw up even as a spectator    

On a separate semi-related note:
I am going to build my first DIY amp soon. Going to commit 2 sins, though... 
a. That is a solid-state amp
b. I am using someone else's design

But I should get some points back, because:
a. The designer is the great Nelson Pass. He's the Glenn of solid state speaker power amps. So, not just a design by some Joe Shmoe.
b. In the spirit of DIY, and not "settling" for anything "standard" - I am actually taking 2 separate designs (both by Nelson Pass) and combining them into 1 amp.
More details to come... 
Some of the parts should arrive next month (Jan. 2021), I hope, but I will post more info between now and then


----------



## whirlwind

Zachik said:


> I know... Keenan is doing all the hard work, and I screw up even as a spectator
> 
> On a separate semi-related note:
> I am going to build my first DIY amp soon. Going to commit 2 sins, though...
> ...



Very nice, keep everyone informed on how it is going....nothing wrong with SS by the way.


----------



## L0rdGwyn

Zachik said:


> I know... Keenan is doing all the hard work, and I screw up even as a spectator
> 
> On a separate semi-related note:
> I am going to build my first DIY amp soon. Going to commit 2 sins, though...
> ...



Very cool!  Looking forward to hearing more details as plans unfold  keep us posted.


----------



## Xcalibur255 (Dec 8, 2020)

L0rdGwyn said:


> Interesting!  I'll have to see how the color looks at night.  My 45s don't have a super vibrant glow, so we will see.  Hoping the blue tones come out in certain lighting.
> 
> I am finishing up the 841 chassis right now, planning to place the order today, ahead of schedule!


Oh, that's right, this one's the 45.  They basically don't glow at all.  Guess it depends on how much of a light show the drivers put on.  Did this one have the 6J5s and not the exotic tubes with the ceramic like coating on them?

I think my remarks about color only truly apply to the 801A in the future since the tungsten filaments produce so much light of their own.


----------



## L0rdGwyn

Xcalibur255 said:


> Oh, that's right, this one's the 45.  They basically don't glow at all.  Guess it depends on how much of a light show the drivers put on.  Did this one have the 6J5s and not the exotic tubes with the ceramic like coating on them?



Yep, this one has the 6J5 drivers, typically run either MOV L63 (which also do not glow) or the Fivre 6C5G, so not a whole lot of tube glow going on.  When it is done, I'll take some pictures in different lighting and see how it changes the color.  Who knows, it might just look black all the time LOL.


----------



## bcowen (Dec 8, 2020)

Zachik said:


> I am going to build my first DIY amp soon. Going to commit 2 sins, though...
> a. That is a solid-state amp



You are so _totally_ fired.


----------



## Zachik

bcowen said:


> You are so _totally_ fired.



I knew it... Bill has such strong principals!!   
(at least until he can spend some quality time with a super model )


----------



## fleasbaby

Whoa...check out for a hot minute and a lot happens on this thread...

Came back to post pictures of my speaker build. After making Maple plywood bass reflex cabinets for my Fostex FE206En drivers, I really wasn't happy with how they looked...I went back and rebuilt them using Poplar and Mahogany instead. 

Very happy with the result, but as is my usual habit, am thinking of the next build. Either going to make back loaded horn cabinets for these drivers, or explore open baffles with a pair of Lii Audio F15 drivers.




Driving them with an amp built around those handy little T Amp prepopulated boards you can buy on Parts Express that put out about 8 watts.


----------



## bcowen

fleasbaby said:


> Whoa...check out for a hot minute and a lot happens on this thread...
> 
> Came back to post pictures of my speaker build. After making Maple plywood bass reflex cabinets for my Fostex FE206En drivers, I really wasn't happy with how they looked...I went back and rebuilt them using Poplar and Mahogany instead.
> 
> ...



Beautiful cabinets!!!


----------



## fleasbaby

bcowen said:


> Beautiful cabinets!!!



Thanks! I just couldn't stomach how the Maple plywood looked...the Mahogany and Poplar are a lot more appealing.


----------



## L0rdGwyn

fleasbaby said:


> Whoa...check out for a hot minute and a lot happens on this thread...
> 
> Came back to post pictures of my speaker build. After making Maple plywood bass reflex cabinets for my Fostex FE206En drivers, I really wasn't happy with how they looked...I went back and rebuilt them using Poplar and Mahogany instead.
> 
> ...



Looks amazing, congrats! How do you like the sound? Looking forward to your next design. Wabi Sabi Speakers in the works?


----------



## fleasbaby

L0rdGwyn said:


> Looks amazing, congrats! How do you like the sound? Looking forward to your next design. Wabi Sabi Speakers in the works?



They are good. Still not going to displace my Magnepan LRS and Schiit Vidar combo, but I like them. Not sure I want to make speakers a product line yet, LOL...


----------



## L0rdGwyn (Dec 10, 2020)

I joked that choosing the color for the 841 amplifier chassis was the hardest part, but it really might be lol high-stakes decision.

I've explored all kinds of options.  Every time I look at something "loud", like a bright and/or pale color (e.g. a metallic white, gold), I tend to feel like it clashes with the spirit of this old technology and then fall back to a more muted color option that will not distract.

Right now I am leaning toward this, Evo Grey, a metallic dark gray.



Going to revisit some of the medium-tone gold options again, need to decide today!

Also, based on the cutters used by Landfall, I had to widen the cutouts of the sunburst pattern of the 841 vents, so they will now look like below.


----------



## L0rdGwyn

Here are the redone source follower PCBs for this amp, tweaked for TO-247 package FETs to work with the Cree C2M1000170D.



The current sink FET will need to drop a decent amount of voltage, so these will be fitted with a rather beefy Ohmite FA-T220-64E heat sink.


----------



## L0rdGwyn (Dec 10, 2020)

Evo Grey is a done deal, that's what it will be.  Just need to order a few more parts and we will be all set for these two amplifiers.

For the 841 amp, I will be using Auricap XO output caps, been wanting to try these for a while.  Could not bring myself to try and fit PIO caps in this build!  Especially at 6.8uF.  Getting 6.6uF of aluminum foil PIO caps in the 45 parafeed amp was quite a hassle.  So, we are going with a high quality metalized polypropylene this time around.


----------



## bcowen

L0rdGwyn said:


> Evo Grey is a done deal, that's what it will be.  Just need to order a few more parts and we will be all set for these two amplifiers.
> 
> For the 841 amp, I will be using Auricap XO output caps, been wanting to try these for a while.  Could not bring myself to try and fit PIO caps in this build!  Especially at 6.8uF.  Getting 6.6uF of aluminum foil PIO caps in the 45 parafeed amp was quite a hassle.  So, we are going with a high quality metalized polypropylene this time around.



FWIW, I like the Auricaps.  Like you I think a good PIO is even better, but the Auricaps strike a very nice balance between sonic quality, size, and cost.


----------



## L0rdGwyn

More parts for the two upcoming builds.

Goldpoint stuff.  Rear panel headphone / speaker switch for the 45 parafeed amplifier (left), stepped attenuator for the 841 headphone amplifier (center), output transformer turns ratio switch for the 841 headphone amplifier (right).




And for the 841 headphone amplifier, my new fave, Vampire CM2FCB RCAs, and Switchcraft 1/4" TRS headphone jack.



Chassis are being cut today.


----------



## bcowen

L0rdGwyn said:


> More parts for the two upcoming builds.
> 
> Goldpoint stuff.  Rear panel headphone / speaker switch for the 45 parafeed amplifier (left), stepped attenuator for the 841 headphone amplifier (center), output transformer turns ratio switch for the 841 headphone amplifier (right).
> 
> ...



Nice!!!  Hadn't seen that Switchcraft jack before...looks really nicely built.


----------



## L0rdGwyn

bcowen said:


> Nice!!!  Hadn't seen that Switchcraft jack before...looks really nicely built.



It is!  They are nice jacks, have four or five extras on hand for future designs.


----------



## Zachik

L0rdGwyn said:


> It is!  They are nice jacks, have four or five extras on hand for future designs.


I saw that one, and almost got it for my solid state build, but I needed one that has switches (so speaker would automatically cut-off as soon as you plug headphones) and could not find one of those that has the switches. Had to settle on the headphone jack...


----------



## bcowen

Zachik said:


> I saw that one, and almost got it for my solid state build, but I needed one that has switches (so speaker would automatically cut-off as soon as you plug headphones) and could not find one of those that has the switches. Had to settle on the headphone jack...



You could go with something like this for a solid-state build and probably not notice any difference:






Just yankin' your chain...


----------



## L0rdGwyn

Zachik said:


> I saw that one, and almost got it for my solid state build, but I needed one that has switches (so speaker would automatically cut-off as soon as you plug headphones) and could not find one of those that has the switches. Had to settle on the headphone jack...



Well I'm sure you'll appreciate the convenience of simply plugging in your headphones!

I am very much looking forward to having a quality headphone amplifier back on my desk...



bcowen said:


> You could go with something like this for a solid-state build and probably not notice any difference:
> 
> 
> 
> ...



Is that a DC barrel jack? LOL.


----------



## L0rdGwyn

I don't think I mentioned this, but I decided to go a little thick on the 841 amplifier chassis, 12" x 13" x 4.25" instead of 3.25".   This amplifier is also immune from SAF since it is on my desk  so let's go big!   This simplified the layout some and will allow for some experimentation with how deep into the chassis the tubes are mounted (half the width of the base vs. full base, for example).

Here is the full chassis design.  Power switch will be on the rear panel this time around, volume and OPT turns ratio switches on the front along with the headphone jack.


----------



## bcowen

L0rdGwyn said:


> Is that a DC barrel jack? LOL.



Maybe.  I mean does it really matter what you plug into the jack of a solid-state amp?  Coat hanger, french fries, used Q-Tips, whatever...


----------



## Zachik

bcowen said:


> Maybe.  I mean does it really matter what you plug into the jack of a solid-state amp?  Coat hanger, french fries, used Q-Tips, whatever...


Sigh... 
Good solid state beats the Schiit out of a crappy tube. Just sayin'...


----------



## L0rdGwyn

Bad amps is bad amps  definitely heard my share of both that I didn't care for.

I know project chaos is coming when the desk starts getting filled with DIY parts.



Gonna be up until 4-5AM tonight, staring at these 801A transformers is driving me nuts, so I'll start working on the various PCBs for that build, we'll see how far we get.  Want to get to a point where I have everything ready so I can throw together and measure a single channel with the new transformers.  No idea what I will do with the old ones yet.


----------



## Zachik

L0rdGwyn said:


> Very cool!  Looking forward to hearing more details as plans unfold  keep us posted.


So... I was planning on making some progress this weekend...
Mouser, had other plans for me by screwing up and sending me the wrong components. I was supposed to have ALL the components for 1st stage of my project couple days ago, but unfortunately I do not 
Will have to wait a few more days. Sigh.


----------



## L0rdGwyn

Zachik said:


> So... I was planning on making some progress this weekend...
> Mouser, had other plans for me by screwing up and sending me the wrong components. I was supposed to have ALL the components for 1st stage of my project couple days ago, but unfortunately I do not
> Will have to wait a few more days. Sigh.



I'm sure they'll resolve it, they have pretty good customer service in my experience.


----------



## Zachik

L0rdGwyn said:


> I'm sure they'll resolve it, they have pretty good customer service in my experience.


It is being resolved, but I missed my opportunity of working on it over the weekend. Not a huge deal, just disappointing...
Will work on it during the week or next weekend.


----------



## bcowen

Zachik said:


> Sigh...
> Good solid state beats the Schiit out of a crappy tube. Just sayin'...



You know (I hope) I'm just messin' with you.    Honestly, I haven't listened to a solid state amp in so long I couldn't even tell you what a good (current design) even sounds like.  So I'm quite interested to see how your project turns out.


----------



## Zachik

bcowen said:


> You know (I hope) I'm just messin' with you.    Honestly, I haven't listened to a solid state amp in so long I couldn't even tell you what a good (current design) even sounds like.  So I'm quite interested to see how your project turns out.


I know it is all in good spirit 

As for my upcoming solid state amp - I do NOT expect it to compete with Cavalli Liquid Gold... 
The headphone amp piece of it is actually a preamp with headphone out. People claim it is pretty good. I do not think anyone would sell his *good *headphone amp for that 
Mind you, the headphone out is just a bonus. Main purpose is a speaker amp, which is Nelson Pass' specialty! The initial plan, since I am customizing this design anyhow, was to remove the headphone out from the preamp. God knows the last thing I need is yet another headphone amp    but people kept writing on the intrawebs how surprisingly good it is - so I decided to keep it after all.


----------



## L0rdGwyn

Zachik said:


> I know it is all in good spirit
> 
> As for my upcoming solid state amp - I do NOT expect it to compete with Cavalli Liquid Gold...
> The headphone amp piece of it is actually a preamp with headphone out. People claim it is pretty good. I do not think anyone would sell his *good *headphone amp for that
> Mind you, the headphone out is just a bonus. Main purpose is a speaker amp, which is Nelson Pass' specialty! The initial plan, since I am customizing this design anyhow, was to remove the headphone out from the preamp. God knows the last thing I need is yet another headphone amp    but people kept writing on the intrawebs how surprisingly good it is - so I decided to keep it after all.



I'm sure it will sound great!  My thinking is that I will always at some point want to connect headphones to an amplifier, even if it is for speakers, so might as well just go ahead with the headphone jack.

Just picked these up, hope they are quiet.




I designed the PCBs for this 801A build last night - modified TO-247 source follower board, EF37A g2 supply board, 0V g1 801A bias supply board.  Going to review the work again tomorrow then order.  In the prototype, had some oscillation quirks with the g2 supply circuit, but the wiring on the protoboard was NOT ideal, long runs of wire not helping either, want to get a better idea of the performance on a nice tight PCB.  Also, the LL9202 OPT have a resonance at around 20-22kHz which was being fed into the feedback loop, I expect some of the issues I was encountering will go away with the higher quality Sowter transformers, but we will see


----------



## L0rdGwyn

I was going to be all sneaky and wait to show it until after the amp was completely done, but I am a sucker and excited.  Here is a pic from Dave at Landfall of the coated 45 amplifier chassis in Casper Blue.


----------



## L0rdGwyn

And some more parts for the 841 headphone amplifier.  Auricap XO output caps, CMC teflon UX4 sockets, and rear panel IEC with rocker switch.



Totally random, but last night I was looking at output transformers (this is surprising, I know).  One Electron had been mentioned to me in the past as a very solid budget option.  I looked into them further, they seems to be of very high quality for the price and come in a few very convenient primary impedances (1.6K, 3K, 4.8K).  I am thinking if / when I go for a "budget" SET design, I will seriously consider giving these a try, only around $110 a pop.  They have sort of a rugged, unfinished look to them too, which I kind of like for some reason.


----------



## Tjj226 Angel

IDK if you saw it or not, but those one electron transformers will soon be no more. The company is closing it's doors because of covid.


----------



## L0rdGwyn

Tjj226 Angel said:


> IDK if you saw it or not, but those one electron transformers will soon be no more. The company is closing it's doors because of covid.



Like, completely?  Man that stinks, I may buy some up before they go out of stock...


----------



## Tjj226 Angel

L0rdGwyn said:


> Like, completely?  Man that stinks, I may buy some up before they go out of stock...



That's what a lot of people are doing. Blue Glow talked about it on his youtube channel. 

Im not sure I would bother though. If you just want to have stock on hand, just go buy edcor transformers and wait the 2 months. They actually have a proper 5K transformer with a very healthy amount of inductance (50H) for 15 bucks less than one electron.


----------



## L0rdGwyn

Tjj226 Angel said:


> That's what a lot of people are doing. Blue Glow talked about it on his youtube channel.
> 
> Im not sure I would bother though. If you just want to have stock on hand, just go buy edcor transformers and wait the 2 months. They actually have a proper 5K transformer with a very healthy amount of inductance (50H) for 15 bucks less than one electron.



I'll probably buy a pair at least to try them out since they are going extinct.  Bummer!  Yeah Edcor is hanging in there, I'd have to go for some of their unfinished end bells though, the Edcor blue isn't for me.


----------



## bcowen

L0rdGwyn said:


> And some more parts for the 841 headphone amplifier.  Auricap XO output caps, CMC teflon UX4 sockets, and rear panel IEC with rocker switch.
> 
> 
> 
> Totally random, but last night I was looking at output transformers (this is surprising, I know).  One Electron had been mentioned to me in the past as a very solid budget option.  I looked into them further, they seems to be of very high quality for the price and come in a few very convenient primary impedances (1.6K, 3K, 4.8K).  I am thinking if / when I go for a "budget" SET design, I will seriously consider giving these a try, only around $110 a pop.  They have sort of a rugged, unfinished look to them too, which I kind of like for some reason.



Sweet!  I just got some of these in for another project.  Really like these sockets and the tight (but not death-grip) contact they put on the tube pins.  They're ceramic rather than teflon, but at $16.50/pair they're not priced like teflon either.


----------



## L0rdGwyn

bcowen said:


> Sweet!  I just got some of these in for another project.  Really like these sockets and the tight (but not death-grip) contact they put on the tube pins.  They're ceramic rather than teflon, but at $16.50/pair they're not priced like teflon either.



Nice!  What kind of project?  The teflon versions are pretty cheap too, only a few bucks more each than the ceramic.  Pretty good compared to Yamamoto teflon socket prices


----------



## bcowen

L0rdGwyn said:


> Nice!  What kind of project?  The teflon versions are pretty cheap too, only a few bucks more each than the ceramic.  Pretty good compared to Yamamoto teflon socket prices



Modifying a dual tube adapter.  I don't much care for the sockets that are in there, so I'm, um, upgrading.   

Where did you get the teflon ones?  I've seen the Yamamotos -- like super-extremely-awesome nice, but I (personally) can't justify spending that much on a socket.


----------



## L0rdGwyn (Dec 15, 2020)

bcowen said:


> Modifying a dual tube adapter.  I don't much care for the sockets that are in there, so I'm, um, upgrading.
> 
> Where did you get the teflon ones?  I've seen the Yamamotos -- like super-extremely-awesome nice, but I (personally) can't justify spending that much on a socket.



Cool! CMC are a good bang-for-the-buck I think.  Can usually get them direct from China on eBay or check here - https://www.hificollective.co.uk/valvebases/cmc-octal-teflon-chassis-mount-base.html

I know it's in the UK, but Hificollective has an awesome selection.  FedEx Express is around 17 GBP and gets to the USA in around two days.  I am usually buying multiple things at once, so the shipping costs is worth it.

I have Yamamoto sockets in my 6A5G amplifier, not sure if I will spring for them again, they are very expensive.

Edit: a little closer to home, Parts Connexion has something very similar here - https://www.partsconnexion.com/CONNEX-76985.html


----------



## bcowen

L0rdGwyn said:


> Cool! CMC are a good bang-for-the-buck I think.  Can usually get them direct from China on eBay or check here - https://www.hificollective.co.uk/valvebases/cmc-octal-teflon-chassis-mount-base.html
> 
> I know it's in the UK, but Hificollective has an awesome selection.  FedEx Express is around 17 GBP and gets to the USA in around two days.  I am usually buying multiple things at once, so the shipping costs is worth it.
> 
> ...



Sweet.  Thanks!


----------



## L0rdGwyn (Dec 15, 2020)

No problem!

I've been kicking around budget amplifier ideas, this is most likely where we are heading after the 801A monster is finally done.  Since the One Electron OPT are going away, unfortunately, I think my budget transformer will be from Transcendar.  These are of similar price / caliber to One Electron, another very good quality but affordable audio transformer maker.  Fun fact, they are used in Ampsandsound's amplifiers.

I reached out to Gery at Transcendar for a price list, $115 for a 15W single-ended transformer (compared to $250 for Lundahl and $300 for Sowter).  He also does custom wound mains transformers, nice!  That is big, a service that is not offered many places.  As far as what this budget SET amplifier will be (and when I say budget, I mean less than $1K for parts), I have two ideas so far: 6E5P / GU50, as I mentioned before, or perhaps a 76 / EL34.  Either way, it would be an indirectly-heated triode-strapped pentode build, fixed bias, panel meters, regulated power supply, active-loaded driver.  That's what I have in mind, for now, all theoretical.

In more practical news, I have been talking with Sowter about the custom mains I will have done for the 801A amplifier once I have confirmed the specifications via prototype.  I am very likely going to put the two 801A filament windings on the transformer.

A concern with putting DHT windings on the same core as the B+ is tainting either supply with 120Hz rectifier pulses due to electrostatic coupling, but I have had very good success running the 45 filaments on my Sowter custom mains and according to Brian Sowter, they have done it numerous times in the past with no complaints.

So what does that mean in practical terms?  In theory, I will have the B+ winding, both DHT filament windings, the bias winding, and a heater winding on the same transformer, which would significantly decrease the footprint of the power supply, like, big time.  If I go this route, I will put the whole amplifier in a single chassis, as opposed to a separate power supply chassis.

That's all for now, should hopefully be able to work on the 45 parafeed rebuild this weekend.  841 headphone amp build timeline is likely first week of January.


----------



## Zachik

bcowen said:


> Sweet!  I just got some of these in for another project.  Really like these sockets and the tight (but not death-grip) contact they put on the tube pins.  They're ceramic rather than teflon, but at $16.50/pair they're not priced like teflon either.



Bill, I have no idea how you plan on fitting those 3-legged parts to a 8-pin socket!!!   





Unless, of course, you're going to fit one of those fine creations of US innovation:


----------



## Zachik

L0rdGwyn said:


> I have two ideas so far: 6E5P / GU50, as I mentioned before, or perhaps a 76 / EL34.


Based on aesthetic of the tubes alone - I vote for the 76 / EL34 option! The other one (6E5P / GU50) would look like ugly duckling... What's with the GU50 hat?!


----------



## L0rdGwyn (Dec 15, 2020)

Zachik said:


> Based on aesthetic of the tubes alone - I vote for the 76 / EL34 option! The other one (6E5P / GU50) would look like ugly duckling... What's with the GU50 hat?!



LOL the GU50 hats have grown on me, they are actually a copy of a WWII era Telefunken tube, the LS50, if that gives those hats any more swag 

But no doubt the 76 / EL34 would look cooler, could use 37 drivers as well although they would come shy of driving the EL34 to full output.  Honestly the only reason I am considering these instead is because I have the tubes already...will look over some other pentode options as well, but they can't be unobtanium / super expensive, which sort of rules out my love affair with the Telefunken EL156.

Edit: another interesting option is the Telefunken EL152 / FL152, similar to the GU50 but without the hat  not crazy expensive but not widely available either...probably too close to extinction to be worth the effort.


----------



## Zachik

L0rdGwyn said:


> LOL the GU50 hats have grown on me, they are actually a copy of a WWII era Telefunken tube, the LS50, if that gives those hats any more swag
> 
> But no doubt the 76 / EL34 would look cooler, could use 37 drivers as well although they would come shy of driving the EL34 to full output.  Honestly the only reason I am considering these instead is because I have the tubes already...will look over some other pentode options as well, but they can't be unobtanium / super expensive, which sort of rules out my love affair with the Telefunken EL156.
> 
> Edit: another interesting option is the Telefunken EL152 / FL152, similar to the GU50 but without the hat  not crazy expensive but not widely available either...probably too close to extinction to be worth the effort.


Good points!  The 76 (from a VERY quick search) are easy to find but not very cheap... EL34 are plentiful in new production, and actually some are not bad! We cannot be NOS-snobs, especially for "entry-level-priced" tube amp.
Looks like the Russian 6E5P are dirt cheap which is good! The screw ugly ducklings (from now on: fuglings ) also seem plentiful and cheap.

So... either the ugly pair for real cheap, or the good lookers for more $ but still reasonable and with plenty NOS options.
I still vote for the 76 / EL34 personally, unless the fuglings   sound much better...


----------



## bcowen

Zachik said:


> Bill, I have no idea how you plan on fitting those 3-legged parts to a 8-pin socket!!!



I used to like you.


----------



## Zachik

@L0rdGwyn - here is your chance to snag NOS EL34 pair for the budget amp...   






I would have been all over it, if the shipping to the US wasn't that expensive...


----------



## L0rdGwyn

Zachik said:


> @L0rdGwyn - here is your chance to snag NOS EL34 pair for the budget amp...
> 
> 
> 
> I would have been all over it, if the shipping to the US wasn't that expensive...



Yikes!  Not so budget after all lol some of these tube sellers I tell ya what...

I have a nice pair of Philips XF2 EL34, think I paid 158 Euro for them.  Prices for NOS RFT EL34 aren’t bad either!


----------



## Zachik

L0rdGwyn said:


> I have a nice pair of Philips XF2 EL34, think I paid 158 Euro for them. Prices for NOS RFT EL34 aren’t bad either!


Yup. When Glenn was building my 6EL3N amp, since he did not have any EL34 tubes to test with - I sent him a holidays present in the form of RFT EL34 pair   WOW - that was a year ago! Time definitely flies...
Also, some of the new production gold lions and tung sol are getting very favorable impressions. Not too far from NOS... For entry level amp - pretty cool you can include reasonable price / sound new production, and let people "upgrade" later with NOS tubes.
Granted the fuglings  tubes are way cheaper than even new production EL34...


----------



## leftside

L0rdGwyn said:


> Yikes!  Not so budget after all lol some of these tube sellers I tell ya what...
> 
> I have a nice pair of Philips XF2 EL34, think I paid 158 Euro for them.  Prices for NOS RFT EL34 aren’t bad either!


Post up the codes. Probably made in Mullard Blackburn factory.


----------



## L0rdGwyn

leftside said:


> Post up the codes. Probably made in Mullard Blackburn factory.



I will post them tonight  I hear you are the EL34 scholar these days.


----------



## whirlwind

L0rdGwyn said:


> I will post them tonight  I hear you are the EL34 scholar these days.



Yeah, dude has a dictionary of nothing but EL34 tubes


----------



## leftside

L0rdGwyn said:


> I will post them tonight  I hear you are the EL34 scholar these days.





whirlwind said:


> Yeah, dude has a dictionary of nothing but EL34 tubes


I'm taking lessons from a very fine Italian gentleman. And like a good student I'm looking for homework


----------



## Zachik

leftside said:


> And like a good student I'm looking for homework


...while the midnight oil tube burns


----------



## L0rdGwyn

Here is your assignment @leftside.

Code XF2 B6A4


----------



## leftside

L0rdGwyn said:


> Here is your assignment @leftside.
> 
> Code XF2 B6A4


Double ring getter, welded plates, dark brown(?) base XF2 B6A4 = Mullard Blackburn plant, 1966, January, 4th week. @gibosi can you check my answer. It's only my first week studying haha.


----------



## gibosi

leftside said:


> Double ring getter, welded plates, dark brown(?) base XF2 B6A4 = Mullard Blackburn plant, 1966, January, 4th week. @gibosi can you check my answer. It's only my first week studying haha.



It looks correct to me.


----------



## L0rdGwyn

leftside said:


> Double ring getter, welded plates, dark brown(?) base XF2 B6A4 = Mullard Blackburn plant, 1966, January, 4th week. @gibosi can you check my answer. It's only my first week studying haha.



Nice!  The base is very, very dark brown, to the point of almost looking black.


----------



## leftside

gibosi said:


> It looks correct to me.


Thanks! The "black" base almost threw me until I realized it must be very dark brown.


----------



## gibosi

leftside said:


> Thanks! The "black" base almost threw me until I realized it must be very dark brown.



Well in my experience, the color of the base has no affect on the sound. Further, Philips code didn't have a digit indicating the base, whether black, brown or metal. The brown base was said to provide better isolation from RF noise, but I doubt that that is a problem in your sound room.


----------



## L0rdGwyn

Some good news and some bad news...

Bad news first - one of the filaments of my ceramic base Taylor VT-62 (801A) is broken, seemingly in transit as I have to assume it was intact when the tubes were packed.

The good news is the seller completely refunded me no questions asked and it appears I will get to keep the good tube.  Should be able to find it's mate (I have a suitor in mind).

Here is the good one.




And for fun, ceramic base graphite plate RCA 801.  These are very rare.


----------



## Zachik

leftside said:


> Double ring getter, welded plates, dark brown(?) base XF2 B6A4 = Mullard Blackburn plant, 1966, January, 4th week. @gibosi can you check my answer. It's only my first week studying haha.


55th birthday coming up soon... 
@L0rdGwyn you should gift them with a new amp!


----------



## leftside

gibosi said:


> Well in my experience, the color of the base has no affect on the sound. Further, Philips code didn't have a digit indicating the base, whether black, brown or metal. The brown base was said to provide better isolation from RF noise, but I doubt that that is a problem in your sound room.


Yep no difference in sound to my ears either. From what I've read, it seems the dark brown base were the earlier XF2, and the black base the latter XF2 from the Blackburn factory..


----------



## gibosi

leftside said:


> Yep no difference in sound to my ears either. From what I've read, it seems the dark brown base were the earlier XF2, and the black base the latter XF2 from the Blackburn factory..



I have no experience with EL34, but the ‘low loss’ brown micanol base wasn't introduced until the 1950's. And for example, GEC 6AS7G with black bases are older than those with brown bases.


----------



## leftside

gibosi said:


> I have no experience with EL34, but the ‘low loss’ brown micanol base wasn't introduced until the 1950's. And for example, GEC 6AS7G with black bases are older than those with brown bases.


Other way around with Mullard EL34. XF2 Mullard introduced in 1962 with dark brown base. Black base came in 1971. 

Thanks for the info. I didn't realize the brown base was meant to be "low loss".


----------



## L0rdGwyn

Zachik said:


> 55th birthday coming up soon...
> @L0rdGwyn you should gift them with a new amp!



We will see!  I know I keep saying "I need to finish what's in front me" but really going to try to stick to that this time, this 801A amp needs to be completed before serious work is done on a EL34 SET.

In terms of driver tubes, doesn't necessarily need to be the 76, EL34 triode strapped doesn't need a high mu driver, so lots of options available.


----------



## gibosi

leftside said:


> Other way around with Mullard EL34. XF2 Mullard introduced in 1962 with dark brown base. Black base came in 1971.
> 
> Thanks for the info. I didn't realize the brown base was meant to be "low loss".



Ah, given those dates this makes sense. By 1970, manufacturers were looking for ways to make tubes as cheaply as possible while still meeting spec. And brown miconal bases were more expensive than black composition bases. In the same way, E80CC had gold pins through the 1950's and 60's, but by 1970, gold pins were discontinued in favor of standard nickle-plated pins


----------



## Zachik

L0rdGwyn said:


> In terms of driver tubes, doesn't necessarily need to be the 76, EL34 triode strapped doesn't need a high mu driver, so lots of options available.


How about the ever so popular 6J5 tubes for drivers?
The only problem *for me*, is my 6EL3N already supports 6J5 drivers and EL34 power tubes *natively*... So this amp would be too close to what I already have (and love), but that is just me


----------



## L0rdGwyn

Zachik said:


> How about the ever so popular 6J5 tubes for drivers?
> The only problem *for me*, is my 6EL3N already supports 6J5 drivers and EL34 power tubes *natively*... So this amp would be too close to what I already have (and love), but that is just me



I expect the two amps would still each have their own unique sound given there are quite a few design differences (EL34 bias point, OPT primary impedance, cathode vs. fixed bias, power supply design, etc.).  The 6J5 would be a great choice, but I like to try new tubes, so would probably opt for something else.  The 76 came to mind, but something like the very linear triode-strapped EF86 would fit the bill nicely.


----------



## CJG888

EF86 as a driver tube works well in the Quad II   .


----------



## L0rdGwyn

CJG888 said:


> EF86 as a driver tube works well in the Quad II   .



Awesome! Nice looking amp.  Yeah the EF86 is more linear than most triodes when triode-strapped, really enjoying them in my phono stage.


----------



## Zachik

L0rdGwyn said:


> Awesome! Nice looking amp.  Yeah the EF86 is more linear than most triodes when triode-strapped, really enjoying them in my phono stage.


So the theoretical plan for the theoretical inexpensive amp would be EF86 drivers and EL34 power tubes?  Nice!
Now the challenge would be to fit the amp in a small chassis... My setup already look like a hoarder's natural habitat 
Maybe something like this (I know it is an electro stat amp, just as a form factor example):


----------



## bcowen

Zachik said:


> So the theoretical plan for the theoretical inexpensive amp would be EF86 drivers and EL34 power tubes?  Nice!
> Now the challenge would be to fit the amp in a small chassis... My setup already look like a hoarder's natural habitat
> Maybe something like this (I know it is an electro stat amp, just as a form factor example):



Well, since you asked...  The form factor itself isn't bad, but the rest is, um, how do I say "butt ugly" nicely? Cosmetically challenged? Train/dirt road analogy? LOL! Maybe with a mirror chrome main chassis and a 24k gold electroplated faceplate it could be, um, less not pretty. Not that I have an opinion or anything, of course.


----------



## Zachik

bcowen said:


> Well, since you asked...  The form factor itself isn't bad, but the rest is, um, how do I say "butt ugly" nicely? Cosmetically challenged? Train/dirt road analogy? LOL! Maybe with a mirror chrome main chassis and a 24k gold electroplated faceplate it could be, um, less not pretty. Not that I have an opinion or anything, of course.


Bill, I agree the design is not pretty, but I like the small footprint! Sorry if I was not clear - I would love the chassis' width and depth be like this one...
As for mirror chrome and 24k gold faceplates... NO!  Personally, I like matte darker colors. 
Honestly, I trust Keenan's designs. Other than his mirror chrome Bottlehead Crack, that is...


----------



## L0rdGwyn

Zachik said:


> Bill, I agree the design is not pretty, but I like the small footprint! Sorry if I was not clear - I would love the chassis' width and depth be like this one...
> As for mirror chrome and 24k gold faceplates... NO!  Personally, I like matte darker colors.
> Honestly, I trust Keenan's designs. Other than his mirror chrome Bottlehead Crack, that is...



No guarantees it will be EF86!  As you said, all just ideas right now  but it is a contender for sure.  Using a noval 9-pin tube definitely would make the footprint smaller, but no way it will be as small as the electrostatic amp!  The size limiter will be the transformers, which for a single-ended amp are necessarily large to avoid core saturation, so making a truly small form factor SET amp is tricky.  My 45 parafeed amplifier is on the smaller side (10.5" x 12" x 4.25") due to it being parafeed, smaller transformers as they do not need to support a DC current on the primary winding.  Realistically, a EL34 SET with Transcendar transformers at a minimum would probably be 12" wide, dependent on the size of the mains transformer.  Maybe something like 10" x 12" x 3.25" could be doable  time will tell, still a long ways off.


----------



## Zachik

L0rdGwyn said:


> The size limiter will be the transformers, which for a single-ended amp are necessarily large to avoid core saturation, so making a truly small form factor SET amp is tricky.


Maybe you should use AC-to-DC wallwart... Feed the amp 12V or 24V DC with a little 5.5mm / 2.1mm barrel type input


----------



## L0rdGwyn

Zachik said:


> Maybe you should use AC-to-DC wallwart... Feed the amp 12V or 24V DC with a little 5.5mm / 2.1mm barrel type input



Lol if only it were that simple.  I read recently that Tubelab (very active tube DIYer on diyAudio) is building a very high-powered amp using a bunch of stacked switched power supplies, that guy is always up to something crazy.

Today I am going to buy the eTracer tube tester that I have brought up a few times.  My Jackson 648-R died on me, think it is an issue with one of the transformers which is not fixable, so time to upgrade.  The eTracer is one of the coolest tube testers out there right now, excited to show off its capabilities here.  It is a fully functional curve tracer, which means tubes can be accurately matched, curves can be obtained for oddball tubes without widely available datasheets, strapped triode curves for pentodes, etc.  It comes with several uncommon sockets that are useful for me (e.g. B4/B5).  The test library comes with around 100 tube configuration files, but custom configuration files can be generated by the user, which I will definitely be doing for a number of the more uncommon tubes in my collection.

So, will probably end up posting a bunch of curves traces in the near future, more to come.


----------



## bcowen

L0rdGwyn said:


> Lol if only it were that simple.  I read recently that Tubelab (very active tube DIYer on diyAudio) is building a very high-powered amp using a bunch of stacked switched power supplies, that guy is always up to something crazy.
> 
> Today I am going to buy the eTracer tube tester that I have brought up a few times.  My Jackson 648-R died on me, think it is an issue with one of the transformers which is not fixable, so time to upgrade.  The eTracer is one of the coolest tube testers out there right now, excited to show off its capabilities here.  It is a fully functional curve tracer, which means tubes can be accurately matched, curves can be obtained for oddball tubes without widely available datasheets, strapped triode curves for pentodes, etc.  It comes with several uncommon sockets that are useful for me (e.g. B4/B5).  The test library comes with around 100 tube configuration files, but custom configuration files can be generated by the user, which I will definitely be doing for a number of the more uncommon tubes in my collection.
> 
> So, will probably end up posting a bunch of curves traces in the near future, more to come.



OK, as a bit of a tube tester hobbyist myself I am now officially and totally jealous.    Be very interested in your thoughts on it once you get it in play.


----------



## Tom-s

For my tube tracings I've build the utracer. Essentially the tester that's copied by the guy who now sells the e-tracer. 

Check out the utracer website! It's cheap. To be build in any form factor. Works great for me (also with B4/B5 sockets  ).

One of the best tester websites out there: https://www.dos4ever.com/uTracer3/uTracer3_pag0.html

For the much overpaid etracer kind of money; you could consider the best DIY tester imho: http://www.roehrentest.de/EnglishInfo.html

Why don't you get a new transformer made for the Jackson? It's a nice tester to complement a pulse tester like the etracer.
That's the weakness of such a tester, you don't stress the tube and can't properly test for shorts.


----------



## L0rdGwyn

Tom-s said:


> For my tube tracings I've build the utracer. Essentially the tester that's copied by the guy who now sells the e-tracer.
> 
> Check out the utracer website! It's cheap. To be build in any form factor. Works great for me (also with B4/B5 sockets  ).
> 
> ...



Thanks for the input, I wasn't aware of the RoeTest, I'll check it out!  I've bought tubes from its maker in the past.  In terms of the uTracer vs. eTracer, I like the flexible high-voltage power supply of the eTracer for high-voltage / transmitting output tubes, there is an overview of the differences on the eTracer website.  For the Jackson, at some point I will pick up a "for parts" 648 on eBay and harvest the transformer, just not up for it at the moment, I'm working a lot of overtime right now so exchanging my money for my time is a tradeoff I'm willing to make.


----------



## leftside

L0rdGwyn said:


> Lol if only it were that simple.  I read recently that Tubelab (very active tube DIYer on diyAudio) is building a very high-powered amp using a bunch of stacked switched power supplies, that guy is always up to something crazy.
> 
> Today I am going to buy the eTracer tube tester that I have brought up a few times.  My Jackson 648-R died on me, think it is an issue with one of the transformers which is not fixable, so time to upgrade.  The eTracer is one of the coolest tube testers out there right now, excited to show off its capabilities here.  It is a fully functional curve tracer, which means tubes can be accurately matched, curves can be obtained for oddball tubes without widely available datasheets, strapped triode curves for pentodes, etc.  It comes with several uncommon sockets that are useful for me (e.g. B4/B5).  The test library comes with around 100 tube configuration files, but custom configuration files can be generated by the user, which I will definitely be doing for a number of the more uncommon tubes in my collection.
> 
> So, will probably end up posting a bunch of curves traces in the near future, more to come.


Interested. I've been waiting for the Amplitrex AT1000 to come up for sale used, but they very rarely appear, and when they do someone beats me to it. I'm not paying the retail price for one of those. I need to read up on this etracer. I'm still getting through my EL34 book, and the author of the EL34 book has now sent me another 300+ page book on KT66/KT88/6550/6L6 tubes. I've got a lot of reading to do over the holidays.

Are you also getting the Sbox12?


----------



## L0rdGwyn

leftside said:


> Interested. I've been waiting for the Amplitrex AT1000 to come up for sale used, but they very rarely appear, and when they do someone beats me to it. I'm not paying the retail price for one of those. I need to read up on this etracer. I'm still getting through my EL34 book, and the author of the EL34 book has now sent me another 300+ page book on KT66/KT88/6550/6L6 tubes. I've got a lot of reading to do over the holidays.
> 
> Are you also getting the Sbox12?



Tons of information on the eTracer website on its functionality, there are also a few videos on Blueglow Electronic's YouTube channel as he goes through the build of one (it is a kit, but you can pay to have it assembled).  I am not going to go for the Sbox12, maybe something to upgrade to down the road, but it is a hefty price to remove what I would consider a pretty minor inconvenience, typically I am not testing huge batches of tubes at a time.  For someone testing a variety of tubes at high volume, like a tube seller for example, I could see how not having to switch the wiring with every tube change would be valuable.

I looked into the RoeTest @Tom-s , looks super cool, but dang that is quite a project!  Big commitment to take that on, I've requested information from the designer but will probably stick with the eTracer.  Oh, and I mistakenly thought the designer was a German tube seller I buy from, he just happens to have a RoeTest, whoops!


----------



## leftside

L0rdGwyn said:


> Tons of information on the eTracer website on its functionality, there are also a few videos on Blueglow Electronic's YouTube channel as he goes through the build of one (it is a kit, but you can pay to have it assembled).  I am not going to go for the Sbox12, maybe something to upgrade to down the road, but it is a hefty price to remove what I would consider a pretty minor inconvenience, typically I am not testing huge batches of tubes at a time.  For someone testing a variety of tubes at high volume, like a tube seller for example, I could see how not having to switch the wiring with every tube change would be valuable.
> 
> I looked into the RoeTest @Tom-s , looks super cool, but dang that is quite a project!  Big commitment to take that on, I've requested information from the designer but will probably stick with the eTracer.  Oh, and I mistakenly thought the designer was a German tube seller I buy from, he just happens to have a RoeTest, whoops!


Yes I thought the same with the Sbox12 (once I figured out what it was for). I'm ok with switching the wiring, especially as I'll be retesting the same types of tubes in batches. Thanks!


----------



## L0rdGwyn

leftside said:


> Yes I thought the same with the Sbox12 (once I figured out what it was for). I'm ok with switching the wiring, especially as I'll be retesting the same types of tubes in batches. Thanks!



No problem, I'll keep you posted!


----------



## Zachik

leftside said:


> I'm still getting through my EL34 book, and the author of the EL34 book has now sent me another 300+ page book on KT66/KT88/6550/6L6 tubes. I've got a lot of reading to do over the holidays.


I might get that ebook, too...  Did the seller send you the book on KT66/KT88/6550/6L6 tubes for free? or is it an additional purchase?


----------



## leftside

Zachik said:


> I might get that ebook, too...  Did the seller send you the book on KT66/KT88/6550/6L6 tubes for free? or is it an additional purchase?


It's an extra cost:
https://digilander.libero.it/pasqua49/THE AUDIO BEAM TETRODE/Guide to the Audio Beam Tetrode.htm


----------



## bcowen

L0rdGwyn said:


> Nice!  What kind of project?  The teflon versions are pretty cheap too, only a few bucks more each than the ceramic.  Pretty good compared to Yamamoto teflon socket prices



This didn't turn out as I'd originally envisioned -- I'd planned on the socket retainers being inside the box instead of outside, but things just wouldn't fit due to the height of these particular sockets. But it satisfies the primary goal of getting some better sockets in the adapter. Had to make it blend in with the Incubus 'cause, well, you know things need visual synergy to sound best, right?


----------



## L0rdGwyn

bcowen said:


> This didn't turn out as I'd originally envisioned -- I'd planned on the socket retainers being inside the box instead of outside, but things just wouldn't fit due to the height of these particular sockets. But it satisfies the primary goal of getting some better sockets in the adapter. Had to make it blend in with the Incubus 'cause, well, you know things need visual synergy to sound best, right?



Looks great!  I have a similar adapter from way back for 4V B4 tubes using similar sockets and came across the same issue.  Very nice you were able to get it to match the amplifier 

Hey @leftside - FYI, if you do end up buying an eTracer and have Chris build it, you might ask him to add a gas test to the tracer, discussed here.  Also adds 1K grid stoppers to the grid supply, although these should be in place either way IMO.


----------



## L0rdGwyn

While waiting for the chassis to arrive, thought I would get some small tasks done on the 841 spud amplifier.  Here are the TO-247 source follower boards and CCS boards for the 841.  Source follower FET is the SiC Cree C2M1000170D.




Super interested to check out the 841 curves on the eTracer, will be looking forward to that.


----------



## leftside

L0rdGwyn said:


> Looks great!  I have a similar adapter from way back for 4V B4 tubes using similar sockets and came across the same issue.  Very nice you were able to get it to match the amplifier
> 
> Hey @leftside - FYI, if you do end up buying an eTracer and have Chris build it, you might ask him to add a gas test to the tracer, discussed here.  Also adds 1K grid stoppers to the grid supply, although these should be in place either way IMO.


I do think I'm going to get one.


----------



## bcowen

leftside said:


> I do think I'm going to get one.



If a tester doesn't have a one-button push for testing the 2nd triode of a dual triode tube, then it's way too complicated for me.


----------



## L0rdGwyn (Dec 20, 2020)

leftside said:


> I do think I'm going to get one.



Awesome.  Mine is ordered, I have been working through some outstanding questions I had, here is a bit of info worth knowing.

1) The eTracer software does a shorts test across all supplies for every test.  If a short is detected, the test won't run and there is a pop up notification.
2) There are current-limiting circuit protection mechanism across all supplies (anode, cathode, heater / filament, screen, etc.) such that none of the circuit components will be damaged if a short is made inadvertently.  Each supply is fused as well.
3) For tubes with external electrodes (grid / plate top caps or otherwise), an adapter will need to be made to connect the appropriate supply to the external electrode.

I'll fill in other gaps as more questions come to mind.



bcowen said:


> If a tester doesn't have a one-button push for testing the 2nd triode of a dual triode tube, then it's way too complicated for me.



A single button traces both triodes simultaneously and the curves are overlaid


----------



## bcowen

L0rdGwyn said:


> A single button traces both triodes simultaneously and the curves are overlaid



Oh, just fine then.  Mine is vintage, so there.


----------



## Zachik

L0rdGwyn said:


> Awesome.  Mine is ordered, I have been working through some outstanding questions I had, here is a bit of info worth knowing.
> 
> 1) The eTracer software does a shorts test across all supplies for every test.  If a short is detected, the test won't run and there is a pop up notification.
> 2) There are current-limiting circuit protection mechanism across all supplies (anode, cathode, heater / filament, screen, etc.) such that none of the circuit components will be damaged if a short is made inadvertently.  Each supply is fused as well.
> ...


I will follow your future posts on the eTracer. You got me interested, too! My wallet hates you Keenan......

Can @bcowen use the eTracer to test his JFETs?


----------



## L0rdGwyn

bcowen said:


> Oh, just fine then.  Mine is vintage, so there.



It looks beautiful too, nothing compares to that vintage tester swag.  A week or two ago when I was looking for Jackson 648s to part out, I came across a pristine early model, nearly bid on it but stayed my hand, thing sold for a steal.  I have...regrets...


----------



## johnjen (Dec 20, 2020)

All this talk of tube testers has me wanting to haul out my Transcendent Tube Analyzer and 'fix' it so ALL of the tube sockets are functional.

They were sold as kits and the 'assembler' was rather amateurish in his kit building techniques.
IOW it looks like a 5yr old used this as a way to learn how to solder, not to mention cut wires to length, and strip off the insulation etc…  
I'm tempted to rip out all of the existing wiring and start all over again.  

Well, that is until my lazy proclivities rise up and I manage to easily repair it, so that ALL of the tube sockets actually work.   
In which case I'll leave well enough alone.  
And bemoan my procrastination for putting this project off for so long…  
hahahahahahahahahahahaha   

JJ  
Edit I just picked up one of these today for a friend…
A B&K 700 that was just calibrated and is in fairly decent shape.


The thing is neither of these testers will check 6C6 tubes which is actually where I need to test my collection the most.

To wit…

And for those who might not be familiar with that nubbin on the top of the tubes, that is the grid connection and NOT the usual plate connection.
I'll probably have to hunt down an appropriate adapter or make up a true rube goldberg collection of clippy leads and spare connectors etc.
hahahahahahahahahaha 

JJ


----------



## bcowen

Zachik said:


> Can @bcowen use the eTracer to test his JFETs?



I already put them all in a garbage bag and sent them to you.


----------



## bcowen

johnjen said:


> All this talk of tube testers has me wanting to haul out my Transcendent Tube Analyzer and 'fix' it so ALL of the tube sockets are functional.
> 
> They were sold as kits and the 'assembler' was rather amateurish in his kit building techniques.
> IOW it looks like a 5yr old used this as a way to learn how to solder, not to mention cut wires to length, and strip off the insulation etc…
> I'm tempted to rip out all of the existing wiring and start all over again.



ROFL!  Oh, the memories.  Look familiar?  (except I built mine, so it looks more like a 10 year old did it ).


----------



## L0rdGwyn

Zachik said:


> I will follow your future posts on the eTracer. You got me interested, too! My wallet hates you Keenan......



Looking forward to showing what it can do!  While tracing/testing well-known tubes is the primary goal, I'm excited to trace tubes without widely available triode curves, whether that be pentodes or transmitting triodes.

I've had some interest in this tube lately, the 3C24.  DHT, thoriated tungsten transmitting triode.  Difficult to use, A2 operation with a positive grid bias point, I will probably pick some up and trace them for fun, maybe a project will evolve down the road.  The eTracer can also trace A2 curves.


----------



## johnjen (Dec 20, 2020)

bcowen said:


> ROFL!  Oh, the memories.  Look familiar?  (except I built mine, so it looks more like a 10 year old did it ).


Ah yes I see the obligatory photo of the cat whilst it's staking it's claim to the obligatory re-appropriated walk-in linen closet.

And that MUST be an old photo since the tube collection hasn't populated the rafters, yet, not to mention it's missing the requisite 'testers chair' for those long testing/cataloging/matching sessions, along with the dedicated computer workstation with a custom SQL database to track the tube collection thru time to maintain an accurate life span history of each and every tube…
hahahahahahahahahahahahahahahaha

JJ


----------



## bcowen

johnjen said:


> Ah yes I see the obligatory photo of the cat whilst it's staking it's claim to the obligatory re-appropriated walk-in linen closet.
> 
> And that MUST be an old photo since the tube collection hasn't populated the rafters, yet, not to mention it's missing the requisite 'testers chair' for those long testing/cataloging/matching sessions, along with the dedicated computer workstation with a custom SQL database to track the tube collection thru time to maintain an accurate life span history of each and every tube…
> hahahahahahahahahahahahahahahaha
> ...



LOL!  Yes, that's an old photo from BK (Before Kid) times when I was permitted to have my own listening room...and my own toy closet.  Different house too.  I *do* remember putting together that Transcendent tester...nothing difficult conceptually, but a LOT of wiring and soldering. Worked well too although it was far more advanced than my knowledge at the time (and probably even now). I had a nicely restored and calibrated Hickok 539C that was much easier to use although it obviously didn't provide as much info as the Transcendent.  

And only for you @johnjen , but notice the original Cable Cooker on the shelf just above and to the right of the Transcendent?  I have the upgraded Anniversary Edition now...you know, progress and all.


----------



## L0rdGwyn (Dec 21, 2020)

I picked up a lot of those 3C24 triodes I mentioned above.



These oddball tubes are plentiful and cheap, no commercial amplifier manufacturer in their right mind would ever sell something designed with 3C24 - these old Eimac transmitting tubes have wire leads to the grid and plate which require finned, heat-dissipating caps to help sink heat (these typically operate in a positive grid bias region, which means the grid will also draw current).

The old Eimac heat-dissipating caps are hard to come by, but I was able to find a surplus dealer who has some NOS examples in stock.



These caps are not insulated from the plate / grid, meaning the full voltage will be across them.  No touchy  any amplifier with these tubes in it would need to have some sort of glass or polycarbonate shield around them so they are not touched by an unsuspecting person / cat, there would be around 300V on the plate cap.  Did I mention these are hard to use?  Plate resistance at a usable operating point will be on the order of 10-14K, meaning negative feedback would be a necessity.

Let me show you why I have been so interested in them.  Here they are used as input tubes in an 801A design, although I am interested in using them as output tubes.  The plates are meant to be operated at a power dissipation such that they glow red.

 

Anyway, we'll trace some curves and hold onto these for a future A2 design.  A very knowledgeable DIYer once told me that once you start messing around with transmitting tubes, you never go back.


----------



## Zachik

L0rdGwyn said:


> A very knowledgeable DIYer once told me that once you start messing around with transmitting tubes, you never go back


Once you accidentally touch the 300V - you might never go, period!


----------



## bcowen

Zachik said:


> Once you accidentally touch the 300V - you might never go, period!



LOL!  I'm betting the cat would only sniff it once.  A little moist-nose induced arc would be....interesting.


----------



## L0rdGwyn

Zachik said:


> Once you accidentally touch the 300V - you might never go, period!



300V ain't bad, it's when you get to over 400V that things start to get interesting....err, not that I would know... safety first


----------



## whirlwind

L0rdGwyn said:


> It looks beautiful too, nothing compares to that vintage tester swag.  A week or two ago when I was looking for Jackson 648s to part out, I came across a pristine early model, nearly bid on it but stayed my hand, thing sold for a steal.  I have...regrets...



Oh Lord! My dad had one of these in his TV repair shop!


----------



## L0rdGwyn

whirlwind said:


> Oh Lord! My dad had one of these in his TV repair shop!



It's a beautiful tester!  Regret not picking it up, but I was concerned it would turn into another project if it had serious issues lol.


----------



## johnjen (Dec 21, 2020)

Zachik said:


> Once you accidentally touch the 300V - you might never go, period!


300 vdc is just the entry level for acclimating to 'the tingle'.    
hahahahahhahahhahahahaha  

JJ


----------



## L0rdGwyn (Dec 24, 2020)

Wishing everyone a Merry Christmas  lots of holiday tunes being played on this puppy as of late.




Expecting more snow over the next 48 hours, a Christmas miracle!  Won't be on Head-Fi much until the new year, at which point I will have a week off and the new amplifier chassis' should be here, and maybe a curve tracer with some interesting transmitting tubes, looking forward to that.

So until then, everyone stay safe, and wear your masks if visiting with family and friends!


----------



## whirlwind

Merry Christmas back at you...stay safe.


----------



## bcowen

L0rdGwyn said:


> Wishing everyone a Merry Christmas  lots of holiday tunes being played on this puppy as of late.
> 
> 
> 
> ...



Beautiful setup, LG!  And any photo that includes LP's always gets bonus points.   

Best of wishes to you as well. Hope you have a very enjoyable holiday with your family and friends.


----------



## L0rdGwyn (Dec 26, 2020)

Well I failed at staying off Head-Fi over Christmas, but I did come up with some DIY ideas 

First off, I had a stroke of...well not genius, but a stroke of something, on the 801A amplifier.  Up this point, I have been planning on using a FET source follower to drive the 801A grid in A2.  As the design evolved, I found I did not like the direction things were going in terms of regulating 0V on the 801A grid.  This design needs the flexibility to move the 801A grid to either side of 0V due to operating variances from tube to tube.  I won't get into how I was going to do that with the FET, but I don't like it.

The situation changed when I decided I was getting yet another custom mains transformer from Sowter for this design and putting everything in one chassis.  Again, won't bore with all of the reasoning, but the long and short of it is I am going to use a cathode follower instead.  For those that don't know, this is the tube equivalent of a source follower and will serve the same purpose - low output impedance to provide grid current as the tube swings into A2 territory on the positive grid peaks.

This change will make getting a 0V bias point on the 801A much easier as the cathode follower will be grid biased and will have a current sink on the cathode.  Simply adjust the grid voltage with an external trimmer to move the cathode positive or negative to either side of 0V to hit a perfect 60mA plate current.

What makes this change even more appealing is I have a ridonkulous number of choice 6BX7 hanging around from ye olde Glenn OTL days.  Here are my favorites.



They are dual triodes, so only one tube should be needed, unless I feel the need to use two and parallel the sections.

Okay so that's thing number one on my mind, but there's more.

Next thing I am trying out - voltage regulator tubes.  I came across a build by Pete Millet where he used the VR105 to regulate the screen voltage of a pentode.  These are cold cathode tubes (no heater necessary) with an inert gas rather than a vacuum in their envelope.  They drop a fixed voltage from plate to cathode within a specific current operating range.  I am going to see how they fare regulating g2 voltages in the 801A amplifier - a much simpler approach than the somewhat complex screen feedback circuit I have in place now (this allows the screen to track variations in plate voltage).  It might be too simple and we'll have to see how it performs in terms of bias drift, but I think it's worth a try and fun!  Bonus points is that these tubes have a faint purple glow due to the inert gas.



Alright moving on to the next thing - I have picked up one more pair of transmitting triodes to play around with, the big brother to the 3C24, the 4C25.  Very similar tube but has a 50W plate dissipation and a crazy 5V 5A filament.  Will I ever build something with them?  Who knows, but they are pretty cool and that's all that matters to me  will trace curves and fantasize about a insane A2 amplifier using them.



These operating curves are not for the faint of heart.  Positive grid A2 bias point with NFB required, not so different from my 801A amplifier hmmm  



NEXT!

I discovered the Darkvoice thread over Christmas and was helping out some Head-Fiers with their modding projects.  This resulted in some modding fever, so now I am going to get a used Darkvoice and hot rod it.  This probably means active load on the 6SN7 drive, current sink on the 6080 output (making the DV similar to the Bottlehead Crack + Speedball), regulating the power supply, removing most of the power supply components to make some room in the chassis (uses a pretty chunky CRCRCRC), then see what else we can do with the space.  Just a fun little side project, I will probably sell or gift away the amplifier when it is done.



And the last thing I will simply say is I am taking a SET design to sell in 2021 very seriously, a speaker amplifier with a switchable headphone output, will provide more details as plans are finalized.


----------



## Zachik

L0rdGwyn said:


> And the last thing I will simply say is I am taking a SET design to sell in 2021 very seriously, a speaker amplifier with a switchable headphone output, will provide more details as plans are finalized.


Very cool stuff. I will follow this specific venture VERY closely - I volunteer to be your beta tester


----------



## Tjj226 Angel

Just as a fun fact, audiowize over on DIY audio has a pretty darn good 3c24 amp in his personal collection. Might be worth reaching out to him and see how he heated his filament.


----------



## L0rdGwyn

Tjj226 Angel said:


> Just as a fun fact, audiowize over on DIY audio has a pretty darn good 3c24 amp in his personal collection. Might be worth reaching out to him and see how he heated his filament.



That guy has done it all!  I'll shoot him a PM if the 3C24 stuff gets serious, thanks for the tip.


----------



## Tjj226 Angel

L0rdGwyn said:


> That guy has done it all!  I'll shoot him a PM if the 3C24 stuff gets serious, thanks for the tip.



You have no idea. 

You know who he is right? He does this kind of stuff at a near commercial level. This IS his day job.


----------



## bcowen

L0rdGwyn said:


>



Oooooohhhhhh.....I want one of these in the Darkvoice mod. Even if it doesn't do anything but sit there and glow.    

Of course if doing this would impede your progress on the 300B SET headphone amp, then nevermind,  LOL!


----------



## L0rdGwyn

bcowen said:


> Oooooohhhhhh.....I want one of these in the Darkvoice mod. Even if it doesn't do anything but sit there and glow.
> 
> Of course if doing this would impede your progress on the 300B SET headphone amp, then nevermind,  LOL!



LOL sure thing, I'll just plop one on top of the transformer shield, only needs 5mA from the power supply so you are good to go 

I will get to work on that 300B SET headphone amp, but the price for the work is a pair of NOS Western Electric 300Bs, preferably from the 1950s, you wouldn't happen to have a pair, would you?


----------



## bcowen

L0rdGwyn said:


> LOL sure thing, I'll just plop one on top of the transformer shield, only needs 5mA from the power supply so you are good to go
> 
> I will get to work on that 300B SET headphone amp, but the price for the work is a pair of NOS Western Electric 300Bs, preferably from the 1950s, you wouldn't happen to have a pair, would you?



Ouch!  Unfortunately I don't have a pair...only a matched quad, dangit.  How about my 401k instead?


----------



## mordy

L0rdGwyn said:


> LOL sure thing, I'll just plop one on top of the transformer shield, only needs 5mA from the power supply so you are good to go
> 
> I will get to work on that 300B SET headphone amp, but the price for the work is a pair of NOS Western Electric 300Bs, preferably from the 1950s, you wouldn't happen to have a pair, would you?


Here is a beginning - a 1959 WE 300B:
https://www.ebay.com/itm/Western-El...223244?hash=item2af8c4088c:g:aOAAAOSwlc1fxvmh




Don't know how, but on the same page another Western Electric item popped - the $1 freight is a real bargain - looks like a fun project....
Some of my grandchildren will not even know what it is.
https://www.ebay.com/itm/Western-El...368156?hash=item3ff0a6451c:g:uYIAAOSwRkVf3-fX


----------



## leftside

Apparently the new 300B's are now shipping:
https://www.westernelectric.com/300b


----------



## L0rdGwyn

bcowen said:


> Ouch!  Unfortunately I don't have a pair...only a matched quad, dangit.  How about my 401k instead?



Wow a matched quad, even better!  NOS 300B push pull 



mordy said:


> Here is a beginning - a 1959 WE 300B:
> https://www.ebay.com/itm/Western-El...223244?hash=item2af8c4088c:g:aOAAAOSwlc1fxvmh
> 
> Don't know how, but on the same page another Western Electric item popped - the $1 freight is a real bargain - looks like a fun project....
> ...



If it has Western Electric in the name, I'm all for it.  Surely such a beautiful phone booth would go over well with the Mrs.  maybe I will convert it into a greenhouse.



leftside said:


> Apparently the new 300B's are now shipping:
> https://www.westernelectric.com/300b



Will you be adding a pair to your collection, @leftside ?  I wonder how long they will be available.


----------



## Xcalibur255

This is why I chose a triode strapped KT150 for my upcoming amp.  Once you have a 300B you WILL end up going down the rabbit hole that is 300B tube upgrades, and it's one of the deepest holes there is.  So I decided to pour cement in it.


----------



## Zachik

As mentioned a couple weeks ago - I have been busy with my very first DIY amp.
This project is a 2-phase project, with the end result being an integrated amp (preamp + speaker amp + headphone amp all-in-one):
* Phase 1: Preamp including a headphone amp
* Phase 2: Class A speaker amp

Update:
Yesterday, I finished phase 1. Well, mostly. It is fully working, but wires and such need some tidying-up, which I will postpone until phase 2 is added...
Here is the photo of my creation:




The design is by Nelson Pass, with some tweaks and modifications 
Power supply is external brick supplying 24V DC.
So far, I have used an old DAP as the source (FiiO X3-II). After nothing blew up with my sacrificial headphones, I tested it with HD600, and this thing is mighty powerful     Sound is smooth and warm, with thunderous bass!!  
I did not save anything on cost, but this can be built relatively cheap (BOM cost $250-ish excluding the case), and IMHO can compete with solid state amps that cost WAY WAY more!

I have learned A LOT from this project, mostly related to DIY techniques, etc. This project, despite being based on a kit - was out of stock, so I had to source all the components, match JFETs, tune JFET's resistor to achieve the desired output current, etc. 

Cannot wait until I get the PCBs and parts for phase 2, although that would take several more weeks...


----------



## Tjj226 Angel

Xcalibur255 said:


> This is why I chose a triode strapped KT150 for my upcoming amp.  Once you have a 300B you WILL end up going down the rabbit hole that is 300B tube upgrades, and it's one of the deepest holes there is.  So I decided to pour cement in it.



Not even close. 

300bs are actually pretty simple. You got Russian 300bs. Chinese 300bs. And WE300bs. There are a bunch of fru fru 300bs out there, but I have never been impressed by any of them. The only two I haven't heard would be the EML and Elrog 300bs. But I have heard from multiple sources that the Elrogs needs some more tweaking. And the EML tubes are different all around. 

So you can either go cheap, or eye wateringly expensive. All the middle of the road stuff is either crap, or so expensive that you might as well buy the new production WE tubes.


----------



## UntilThen

L0rdGwyn said:


> And the last thing I will simply say is I am taking a SET design to sell in 2021 very seriously, a speaker amplifier with a switchable headphone output, will provide more details as plans are finalized.



Will be looking at this with interest. The memory of LCD-4 with Auris Nirvana 2 weeks ago is just unforgettable. Not interested in a speaker amp but strictly a headphone amp to drive any headphones.  

Nice slightly warm tone with tons of details and incredible speaker like bass.

Qutest > Auris Nirvana > Audeze LCD-4 at Minidisc where I spend 2 hours.


----------



## L0rdGwyn

Zachik said:


> As mentioned a couple weeks ago - I have been busy with my very first DIY amp.
> This project is a 2-phase project, with the end result being an integrated amp (preamp + speaker amp + headphone amp all-in-one):
> * Phase 1: Preamp including a headphone amp
> * Phase 2: Class A speaker amp
> ...



Very nice, @Zachik  !  Have a pic of the chassis?  Looks very tidy inside, well done.


----------



## bcowen

L0rdGwyn said:


> Wow a matched quad, even better!  NOS 300B push pull



Gaaaaaaahhhhh!!!!!!   The SET in me just blew up into little bitty pieces.  Hopefully I can glue everything back together.


----------



## bcowen

Zachik said:


> As mentioned a couple weeks ago - I have been busy with my very first DIY amp.
> This project is a 2-phase project, with the end result being an integrated amp (preamp + speaker amp + headphone amp all-in-one):
> * Phase 1: Preamp including a headphone amp
> * Phase 2: Class A speaker amp
> ...



I can't see the tube sockets. Can they be seen from the top?  

Seriously, nice work!


----------



## Zachik

L0rdGwyn said:


> Very nice, @Zachik  !  Have a pic of the chassis?  Looks very tidy inside, well done.


Here you go... Front and back (ignore the temporary volume "knob")


----------



## bcowen

Tjj226 Angel said:


> Not even close.
> 
> 300bs are actually pretty simple. You got Russian 300bs. Chinese 300bs. And WE300bs. There are a bunch of fru fru 300bs out there, but I have never been impressed by any of them. The only two I haven't heard would be the EML and Elrog 300bs. But I have heard from multiple sources that the Elrogs needs some more tweaking. And the EML tubes are different all around.
> 
> So you can either go cheap, or eye wateringly expensive. All the middle of the road stuff is either crap, or so expensive that you might as well buy the new production WE tubes.



And on the in-between expensive side but not WE expensive are the KR's (Krons).  The high current 300BXLS tubes sound quite good, although there's precious little besides the EML's to compare them to directly.  The standard KR 300B's are better than most, and (relatively) sanely priced.


----------



## leftside

L0rdGwyn said:


> Wow a matched quad, even better!  NOS 300B push pull
> 
> 
> 
> ...


No I won't.



Xcalibur255 said:


> This is why I chose a triode strapped KT150 for my upcoming amp.  Once you have a 300B you WILL end up going down the rabbit hole that is 300B tube upgrades, and it's one of the deepest holes there is.  So I decided to pour cement in it.


I have the Glenn 300B, I purchased the Taks, and I was done. As some of you well know, I have quite the tube collecting habit... but the price of the 300B's prevented this habit from getting even worse. 

Unfortunately, Pasquale Russo's EL34 book has added a few tubes to the wants list for next year. Only another 160 pages to go... but at least I'm through the "dangerous" Mullard, Philips, Amperex, Valvo and Telefunken sections. The sections on Tesla, Tungsram, Siemens and RFT were also quite fascinating, as the book isn't just about the EL34 tubes, it's also about the history of the manufacturers, date codes, factory codes, etc. I might try and pick up some of the early RFT if I can find them. And when this book is finished I'll be on to the KT66/KT88/6550 book. I've already skimmed through it, and I'm a little scared to read in detail...


----------



## UntilThen

@leftside, Nirvana uses EL34 and it's delicious. I think I can forget about my EL11, EL12 spez tubes.


----------



## L0rdGwyn

UntilThen said:


> Will be looking at this with interest. The memory of LCD-4 with Auris Nirvana 2 weeks ago is just unforgettable. Not interested in a speaker amp but strictly a headphone amp to drive any headphones.
> 
> Nice slightly warm tone with tons of details and incredible speaker like bass.
> 
> Qutest > Auris Nirvana > Audeze LCD-4 at Minidisc where I spend 2 hours.



I guess I didn't scare you away from the 6.5W headphone amplifier  funny is even Auris says it is too much power LOL.  If made for headphones strictly, could do a 5K primary with headphone appropriate secondary taps (32, 120, 300ohm) and get lower distortion with tons of power to spare, 3-4W guesstimated.


----------



## L0rdGwyn

leftside said:


> No I won't.
> 
> I have the Glenn 300B, I purchased the Taks, and I was done. As some of you well know, I have quite the tube collecting habit... but the price of the 300B's prevented this habit from getting even worse.
> 
> Unfortunately, Pasquale Russo's EL34 book has added a few tubes to the wants list for next year. Only another 160 pages to go... but at least I'm through the "dangerous" Mullard, Philips, Amperex, Valvo and Telefunken sections. The sections on Tesla, Tungsram, Siemens and RFT were also quite fascinating, as the book isn't just about the EL34 tubes, it's also about the history of the manufacturers, date codes, factory codes, etc. I might try and pick up some of the early RFT if I can find them. And when this book is finished I'll be on to the KT66/KT88/6550 book. I've already skimmed through it, and I'm a little scared to read in detail...



Sounds akin to browsing a shopping catalog, I'm sure the historical context adds to the allure, will be curious to see what tubes you pick up next year.  I have always thought highly of RFT-made tubes, have thought of buying some EL34 for this upcoming project.


----------



## UntilThen

L0rdGwyn said:


> I guess I didn't scare you away from the 6.5W headphone amplifier  funny is even Auris says it is too much power LOL.  If made for headphones strictly, could do a 5K primary with headphone appropriate secondary taps (32, 120, 300ohm) and get lower distortion with tons of power to spare, 3-4W guesstimated.



I don't care about the wattage. Just give me seismic and tsunami bass. I've heard LCD-4 with different amps but with Nirvana it's different. Maybe with the Glenn 300b amp it would have been just as delicious.


----------



## mordy

UntilThen said:


> I don't care about the wattage. Just give me seismic and tsunami bass. I've heard LCD-4 with different amps but with Nirvana it's different. Maybe with the Glenn 300b amp it would have been just as delicious.


If you check German eBay there are many RFT EL34 tubes for sale with prices all over the place. Looks like they made the EL34 for Siemens and others as well. It also seems that RFT marketed their own tubes under several different names.


----------



## johnjen

I just sent Pasquale Russo a request for a copy of his tetrode review.
I have a 6L6GC speaker amp with a pair of unique 6L6GC tubes I want to learn more about.

JJ


----------



## Tjj226 Angel

bcowen said:


> And on the in-between expensive side but not WE expensive are the KR's (Krons).  The high current 300BXLS tubes sound quite good, although there's precious little besides the EML's to compare them to directly.  The standard KR 300B's are better than most, and (relatively) sanely priced.



You do realize that someone bought the WE factory and is making real new production WE300bs again right? I wanna say the 300b XLS is right around the same price as the ones from WE. 

https://www.westernelectric.com/300b


----------



## Tjj226 Angel

johnjen said:


> I just sent Pasquale Russo a request for a copy of his tetrode review.
> I have a 6L6GC speaker amp with a pair of unique 6L6GC tubes I want to learn more about.
> 
> JJ



Go take pictures of those tubes and put a post up on DIY audio. 

I forgot RFT exists. It would make total sense for that tube to be an RFT tube. RFT had a habit of labeling their KT66s as 6L6s.

https://www.ebay.com/itm/2x-PREMIUM...904429?hash=item52425ff9ed:g:G7sAAOSw-lVfxj6G

Some of the older and wiser guys on DIYaudio should be able to spot some tell tale sign to confirm.


----------



## UntilThen

mordy said:


> If you check German eBay there are many RFT EL34 tubes for sale with prices all over the place. Looks like they made the EL34 for Siemens and others as well. It also seems that RFT marketed their own tubes under several different names.


Huh? What has Siemens and RFT to do with Nirvana stock tube. That amp is not supplied with those tubes.


----------



## L0rdGwyn

UntilThen said:


> Huh? What has Siemens and RFT to do with Nirvana stock tube. That amp is not supplied with those tubes.



I think that was a misquote UT, probably meant for yours truly.



Tjj226 Angel said:


> You do realize that someone bought the WE factory and is making real new production WE300bs again right?



Where do I get one of these...WE factories you speak of?


----------



## UntilThen

L0rdGwyn said:


> I guess I didn't scare you away from the 6.5W headphone amplifier  funny is even Auris says it is too much power LOL.  If made for headphones strictly, could do a 5K primary with headphone appropriate secondary taps (32, 120, 300ohm) and get lower distortion with tons of power to spare, 3-4W guesstimated.


You should know better. You are the engineer
The thing is when I sit down to listen with LCD4 and Nirvana, I did not know the specs before hand. Neither did I know the price or where it’s made. All I know is that it uses a ECC82 and a pair of EL34. So I was bobbing my head and enjoying my music for 2 hours! Only to be disappointed at the end when I was told it’s 10 grand. I thought how could an unknown amp cost that much. Then I googled when I went home and found a long list of very favourable reviews. So I wasn’t prejudiced when I started listening because I didn’t know anything about the amp at trthat point.


----------



## UntilThen

L0rdGwyn said:


> I think that was a misquote UT, probably meant for yours truly.


Ah thank you. I thought the wines getting to me from the festive cheers lol.


----------



## johnjen

Tjj226 Angel said:


> Go take pictures of those tubes and put a post up on DIY audio.
> snip
> Some of the older and wiser guys on DIYaudio should be able to spot some tell tale sign to confirm.


So your gunna make me work for it?   
Some peoples kids…  
hahahahahahahahahaahahahahahahaha  

JJ


----------



## L0rdGwyn

UntilThen said:


> You should know better. You are the engineer
> The thing is when I sit down to listen with LCD4 and Nirvana, I did not know the specs before hand. Neither did I know the price or where it’s made. All I know is that it uses a ECC82 and a pair of EL34. So I was bobbing my head and enjoying my music for 2 hours! Only to be disappointed at the end when I was told it’s 10 grand. I thought how could an unknown amp cost that much. Then I googled when I went home and found a long list of very favourable reviews. So I wasn’t prejudiced when I started listening because I didn’t know anything about the amp at trthat point.



It is an eye-catching design!  The sneeze guard is a nice touch, very considerate for the tubes during the pandemic.  There is so little in the description when it comes to the circuit or the transformers, wish they provided more information  why does it cost $6K USD?!  I am biased toward what I have found to sound good in a SET design, but I am confident what I have in mind will sound quite good for a lot less money, but there is only one way to know for sure.


----------



## UntilThen

L0rdGwyn said:


> Where do I get one of these...WE factories you speak of?



https://www.westernelectric.com/300b

_Today, the 300B is re-entering production at the Rossville Works.  _


----------



## UntilThen

L0rdGwyn said:


> It is an eye-catching design!  The sneeze guard is a nice touch, very considerate for the tubes during the pandemic.  There is so little in the description when it comes to the circuit or the transformers, wish they provided more information  why does it cost $6K USD?!  I am biased toward what I have found to sound good in a SET design, but I am confident what I have in mind will sound quite good for a lot less money, but there is only one way to know for sure.



And the best person to test your amp would be me because I can compare it with the motherlode 10k Nirvana. If yours sound better, the whole of Head-Fi will hear of it .... from my assistant @bcowen who I will pass on the encrypted review. Thereafter we will sign an agreement for me to be your sole distributor and naturally I'll get the 1st amp at 50% discount.

Are you using EL34 or KT88 tubes?


----------



## L0rdGwyn

UntilThen said:


> https://www.westernelectric.com/300b
> 
> _Today, the 300B is re-entering production at the Rossville Works.  _



Neat little video here.





UntilThen said:


> And the best person to test your amp would be me because I can compare it with the motherlode 10k Nirvana. If yours sound better, the whole of Head-Fi will hear of it .... from my assistant @bcowen who I will pass on the encrypted review. Thereafter we will sign an agreement for me to be your sole distributor and naturally I'll get the 1st amp at 50% discount.
> 
> Are you using EL34 or KT88 tubes?



Hehehe we will see  move to Ohio then I will not have to pay Australian shipping.  EL34, although this is fixed bias so there is some flexibility to adjust the grid bias for similar tubes, like KT66.  KT88 will draw significantly more plate current at the same grid voltage, it is a different animal compared to the EL34.


----------



## UntilThen

Very interesting video of how the tube is made. Looks easy. Why are they charging so much?


----------



## UntilThen

L0rdGwyn said:


> Hehehe we will see  move to Ohio then I will not have to pay Australian shipping.  EL34, although this is fixed bias so there is some flexibility to adjust the grid bias for similar tubes, like KT66.  KT88 will draw significantly more plate current at the same grid voltage, it is a different animal compared to the EL34.



I don't mind if it's just EL34 because I know how good that can sound. Smooth and yet power aplenty - to drive Susvara? 

Wait this mystery amp that you're making. Will it have tube or ss rectification.


----------



## UntilThen

Oh one more thing. Nirvana is dead quiet. And I mean dead quiet. I can't hear a thing with LCD-4 on my head. Even at max volume with no music playing. 

Can you do the same? Studio Six is the other tube amp that stays very quiet with no music playing and volume at max.


----------



## L0rdGwyn (Dec 27, 2020)

UntilThen said:


> I don't mind if it's just EL34 because I know how good that can sound. Smooth and yet power aplenty - to drive Susvara?
> 
> Wait this mystery amp that you're making. Will it have tube or ss rectification.



Solid state.  The power supply will be regulated, even if it were tube rectified any sound the tube could possibly impart would be inaudible.  In terms of noise, the goal is always to make a quiet amp, with headphones it becomes more important, might necessitate DC on the heaters if dead quiet at maximum volume without music is a high priority.


----------



## whirlwind

UntilThen said:


> Oh one more thing. Nirvana is dead quiet. And I mean dead quiet. I can't hear a thing with LCD-4 on my head. Even at max volume with no music playing.
> 
> Can you do the same? Studio Six is the other tube amp that stays very quiet with no music playing and volume at max.



Oh man...congrats on the LCD-4, what a great headphone. LCD house sound is killer to my ears.




L0rdGwyn said:


> Solid state.  The power supply will be regulated, even if it were tube rectified any sound the tube could possibly impart would be inaudible.  In terms of noise, the goal is always to make a quiet amp, with headphones it becomes more important, might necessitate DC on the heaters if dead quiet at maximum volume without music is a high priority.



Always a tough choice about SS / Tube Rectifier...SS can save some cash that your probably going to spend on some very addicting tube glow...but that glow is hard to pass up


----------



## UntilThen

whirlwind said:


> Oh man...congrats on the LCD-4, what a great headphone. LCD house sound is killer to my ears.


Eh Joe I didn’t buy the LCD4. I bought he1000se. I tried the LCD4 at the store with Nirvana. Meanwhile I still have LCD3 and LCDx and hd800.

the plan is to have just LCD4 and he1000se eventually then that’s it.


----------



## whirlwind

UntilThen said:


> Eh Joe I didn’t buy the LCD4. I bought he1000se. I tried the LCD4 at the store with Nirvana. Meanwhile I still have LCD3 and LCDx and hd800.
> 
> the plan is to have just LCD4 and he1000se eventually then that’s it.



Digging that planar sound.


----------



## L0rdGwyn

Let's hope those Browns can pull out the win today @whirlwind , we are suddenly without our top four wide receivers due to COVID!  But I still like our odds


----------



## whirlwind

L0rdGwyn said:


> Let's hope those Browns can pull out the win today @whirlwind , we are suddenly without our top four wide receivers due to COVID!  But I still like our odds



I was just reading this, guess  we will be using our TE's much more today...along with Chubb & Hunt
As bad as this year has been, the Browns are a bright spot, they have been fun to watch again!
Go Browns!


----------



## bcowen (Dec 27, 2020)

Tjj226 Angel said:


> You do realize that someone bought the WE factory and is making real new production WE300bs again right? I wanna say the 300b XLS is right around the same price as the ones from WE.
> 
> https://www.westernelectric.com/300b



Yup. This is, what, the 3rd re-issue? Or the 4th?  I lost track.  The first reissues came out in the late '90's, and they were very good.  Perhaps not exactly as good as '40's and '50's manufacture originals, but darn close. At least that's what the general talk was -- I had some of those reissues, but (at the time) didn't have any originals to compare directly to.  The KR BXLS version is roughly $1k/pair, or at least was when I bought a backup set a couple years ago. The regular ones are a little less.


----------



## bcowen

UntilThen said:


> And the best person to test your amp would be me because I can compare it with the motherlode 10k Nirvana. If yours sound better, the whole of Head-Fi will hear of it .... from my assistant @bcowen who I will pass on the encrypted review. Thereafter we will sign an agreement for me to be your sole distributor and naturally I'll get the 1st amp at 50% discount.
> 
> Are you using EL34 or KT88 tubes?



You realize marketing people (even assistants) get paid stupid amounts of money, right?  Good.  Then I'm ready.  

But if the good L0rd is making an SET, it better not be with a pentode or my feelings will be hurt.  For headphone purposes I could live with a 2A3 if the 300B rabbit hole is deemed too cavernous to venture into without military escort.


----------



## Tjj226 Angel

bcowen said:


> Yup. This is, what, the 3rd re-issue? Or the 4th?  I lost track.  The first reissues came out in the late '90's, and they were very good.  Perhaps not exactly as good as '40's and '50's manufacture originals, but darn close. At least that's what the general talk was -- I had some of those reissues, but (at the time) didn't have any originals to compare directly to.  The KR BXLS version is roughly $1k/pair, or at least was when I bought a backup set a couple years ago. The regular ones are a little less.



Hmmmm. 

You might have had a fair deal. As far as I can tell, it is roughly 1K for the regular ones, and I can't even find a price for the XLS. 

Now if you live in Europe, or you find a retailer that will ship to the US without using some stupid conversion rate, then yes, the KRs are a half decent deal. But every US retailer I know of jacks the prices up so much that they don't have much value. 

The ones I really want to play with are the ELROG 300bs. Thoriated tungsten filaments could be a kick arse modification to the 300b. I hope they get the kinks worked out soon.


----------



## bcowen

Tjj226 Angel said:


> Hmmmm.
> 
> You might have had a fair deal. As far as I can tell, it is roughly 1K for the regular ones, and I can't even find a price for the XLS.
> 
> ...



I bought them from a US (authorized) dealer that I've done business with over the years. He doesn't stock them so I just asked if he could order them and the best price he could offer. Prices have probably gone up some since then too.

https://highend-electronics.com/collections/kr-audio?page=1


----------



## UntilThen

whirlwind said:


> Digging that planar sound.


 
Yes I do. I hope it's not a mistake buying the hekse but @UsoppNoKami loves it and he's my advisor. 

I love the planar sound specifically Audeze hence my 2 LCD-3f and LCD-X but after I hear LCD-4, I'm ready to ditch all the other Audezes for the 4.


----------



## UntilThen

bcowen said:


> You realize marketing people (even assistants) get paid stupid amounts of money, right?  Good.  Then I'm ready.
> 
> But if the good L0rd is making an SET, it better not be with a pentode or my feelings will be hurt.  For headphone purposes I could live with a 2A3 if the 300B rabbit hole is deemed too cavernous to venture into without military escort.



Yes I do realise assistants are important and they get paid well like caddies in pro golf. Btw I'm looking for a caddy.

Hmmm EL34, KT88, 2A3 and 300b. I don't know. Anyone will do. I still think EL34 because they are good and cheap (er).


----------



## L0rdGwyn (Dec 27, 2020)

bcowen said:


> You realize marketing people (even assistants) get paid stupid amounts of money, right?  Good.  Then I'm ready.
> 
> But if the good L0rd is making an SET, it better not be with a pentode or my feelings will be hurt.  For headphone purposes I could live with a 2A3 if the 300B rabbit hole is deemed too cavernous to venture into without military escort.



Yes it is a triode-strapped pentode SET, an imposter!  Maybe a true triode thing will happen in the future, but the added cost, size, and complexity of using a filament supply would bring the price up significantly.  Ask me how I know 

I am only aware of two indirectly heated power triodes, the 6A5G and the R120 (although the R120 is really pentode that was strapped internally to make a triode).

Building amps for others, I think tube cost and availability is a concern, obviously 2A3 are pricey, another DHT choice that is pretty widely available and would perform similarly is the 6B4G (6.3V octal base 2A3).


----------



## L0rdGwyn

But then again, new production 2A3 will probably be available until the end of time, the same can't be said for the 6B4G (although NOS Russian models are abundant).  45 is a good choice for a pure headphone amp as well given its power output of around 1.5W.  Just thinking out loud.

Maybe I will make this EL34 SET a pure headphone amp, since that seems to be where the interest is.  Wait, this is a headphone forum?


----------



## bcowen

UntilThen said:


> Yes I do realise assistants are important and they get paid well like caddies in pro golf. Btw I'm looking for a caddy.
> 
> Hmmm EL34, KT88, 2A3 and 300b. I don't know. Anyone will do. I still think EL34 because they are good and cheap (er).



I hate golf.  Mostly because I suck at it.  I don't mind driving the cart and drinking the beer though...maybe I could be a caddy assistant?


----------



## bcowen

L0rdGwyn said:


> But then again, new production 2A3 will probably be available until the end of time, the same can't be said for the 6B4G (although NOS Russian models are abundant).  45 is a good choice for a pure headphone amp as well given its power output of around 1.5W.  Just thinking out loud.
> 
> Maybe I will make this EL34 SET a pure headphone amp, since that seems to be where the interest is.  Wait, this is a headphone forum?



I like 2A3's.  Have a few old RCA's rolling around here somewhere.  Just not much power for speakers, but more than enough for a headphone-only amp.  At least then we could still correctly refer to it as an SET, instead of an SETSP.   EL-34's....criminy. How bourgeoisie.


----------



## UntilThen

L0rdGwyn said:


> Maybe I will make this EL34 SET a pure headphone amp, since that seems to be where the interest is. Wait, this is a headphone forum?



No it's a Home Theatre forum lol. 

I have no reason to want a speaker amp because I already have one to drive most any speakers. So a headphone (and a mother lode one) is what I'm interested in. 

See here my rack. The bottom unit is my Redgum Rgi120enr black series driving my Axis Voicebox S monitors. Speakers are power hungry and the amp can dish it up easily. 



The monitors have since been move to the big desk for near field listening. Waiting for the Isoacoutics Aperta 100 stands to come. This is my accommodation away from home.


----------



## whirlwind

L0rdGwyn said:


> Let's hope those Browns can pull out the win today @whirlwind , we are suddenly without our top four wide receivers due to COVID!  But I still like our odds



Well this did not turn out as we had hoped


----------



## UntilThen

bcowen said:


> I hate golf.  Mostly because I suck at it.  I don't mind driving the cart and drinking the beer though...maybe I could be a caddy assistant?



Yup come drive my cart but you need a driver's license because there are lakes and I don't want us driven into the lakes !


----------



## UntilThen (Dec 27, 2020)

bcowen said:


> I like 2A3's.  Have a few old RCA's rolling around here somewhere.  Just not much power for speakers, but more than enough for a headphone-only amp.  At least then we could still correctly refer to it as an SET, instead of an SETSP.   EL-34's....criminy. How bourgeoisie.



How about giving me those 2A3s in case I buy an improved DNA Stratus.


----------



## L0rdGwyn

whirlwind said:


> Well this did not turn out as we had hoped



Turns out having half of your offense out is a problem!!!  Next week now essentially a must win, unless the Colts lose...


----------



## L0rdGwyn

bcowen said:


> I like 2A3's.  Have a few old RCA's rolling around here somewhere.  Just not much power for speakers, but more than enough for a headphone-only amp.  At least then we could still correctly refer to it as an SET, instead of an SETSP.   EL-34's....criminy. How bourgeoisie.





UntilThen said:


> No it's a Home Theatre forum lol.
> 
> I have no reason to want a speaker amp because I already have one to drive most any speakers. So a headphone (and a mother lode one) is what I'm interested in.
> 
> ...



I forget not everyone has committed to the flea-watt high-sensitivity speaker life.  Where do your priorities lie?!

But no 2A3 this time around, sorry  maybe in the future, but a larger, more expensive amplifier it would have to be.  Those DHTs make you work for their sound, no doubt about it.


----------



## bcowen

L0rdGwyn said:


> But no 2A3 this time around, sorry  maybe in the future, but a larger, more expensive amplifier it would have to be.  Those DHTs make you work for their sound, no doubt about it.



Dang it.  I'm driving this golf cart straight into the lake in protest.  _After_ I unload the beer, of course.


----------



## leftside

UntilThen said:


> @leftside, Nirvana uses EL34 and it's delicious. I think I can forget about my EL11, EL12 spez tubes.


Yes great tubes. Must be about 300 different EL34 variations from various manufacturers. I still really like the EL11 and EL12 - they are related to the EL34 and are ancestors. The EL11 and EL12 tend to be the go to tubes in my DAC.


----------



## UntilThen

leftside said:


> Yes great tubes. Must be about 300 different EL34 variations from various manufacturers. I still really like the EL11 and EL12 - they are related to the EL34 and are ancestors. The EL11 and EL12 tend to be the go to tubes in my DAC.


Oh really what dac is that that uses el11 and el12?

my worry in having a custom amp make for these EL tubes is that when they fail it’s hard to find replacement for these EL11 and EL12 and there is no guarantee that the tubes I have are hum free even though they are NOS


----------



## UntilThen

bcowen said:


> Dang it.  I'm driving this golf cart straight into the lake in protest.  _After_ I unload the beer, of course.


You’re not driving my cart into the lake it’s a $75000 fine.


----------



## UntilThen

L0rdGwyn said:


> I forget not everyone has committed to the flea-watt high-sensitivity speaker life. Where do your priorities lie?!


Why would I want Holly Cole speakers when I can have Cassandra Wilson speakers?


----------



## leftside

L0rdGwyn said:


> Sounds akin to browsing a shopping catalog, I'm sure the historical context adds to the allure, will be curious to see what tubes you pick up next year.  I have always thought highly of RFT-made tubes, have thought of buying some EL34 for this upcoming project.


I like the RFT tubes a lot as well. The EL11 get a lot of time in my DAC. The 1950's - 1960's RFT EL34 are meant to be the ones to have. Did you know the very early RFT EL34 didn't have a dimple in the top of the glass? RFT also made EL34 for Siemens, Telefunken, RSD, Valvo and ITT.



UntilThen said:


> I don't care about the wattage. Just give me seismic and tsunami bass. I've heard LCD-4 with different amps but with Nirvana it's different. Maybe with the Glenn 300b amp it would have been just as delicious.


Custom amps make great matches for the LCD-4 



johnjen said:


> I just sent Pasquale Russo a request for a copy of his tetrode review.
> I have a 6L6GC speaker amp with a pair of unique 6L6GC tubes I want to learn more about.
> 
> JJ


That's the book I'm reading next. It looks a great read, although both books can be bad for the pocket. I might also be able to help if you have any questions with the KT66 or KT88.


----------



## leftside

UntilThen said:


> Oh really what dac is that that uses el11 and el12?
> 
> my worry in having a custom amp make for these EL tubes is that when they fail it’s hard to find replacement for these EL11 and EL12 and there is no guarantee that the tubes I have are hum free even though they are NOS


Lampizator TRP DAC. With a EL11/EL12 to EL34 adapter. I've been finding quite a few EL11 and EL12 from German eBay sellers. Usually in singles and for quite cheap. The only problem with these tubes is finding a perfect construction match if you are buying singles. There seems to be a lot of variations....


----------



## L0rdGwyn

Yes, even though the DHTs have the sex appeal, the EL34 is a fine tube triode-strapped.  Some day I want to try it in SEP with negative feedback applied.

Speaking of pentodes, finally got my hands on a somewhat elusive one, at least true NOS, 1956 shouldered Mullard EF37A in red  these go in the 801A amplifier.


----------



## johnjen

leftside said:


> snip
> That's the book I'm reading next. It looks a great read, although both books can be bad for the pocket. I might also be able to help if you have any questions with the KT66 or KT88.


Thanks for the offer I appreciate it.

JJ


----------



## L0rdGwyn

UntilThen said:


> Why would I want Holly Cole speakers when I can have Cassandra Wilson speakers?



I'll take the Holly Cole speakers 



(I wish   )


----------



## bcowen

UntilThen said:


> You’re not driving my cart into the lake it’s a $75000 fine.



I'm sure my employer would take care of it. He's a nice guy.


----------



## bcowen

L0rdGwyn said:


> Yes, even though the DHTs have the sex appeal, the EL34 is a fine tube triode-strapped.  Some day I want to try it in SEP with negative feedback applied.
> 
> Speaking of pentodes, finally got my hands on a somewhat elusive one, at least true NOS, 1956 shouldered Mullard EF37A in red  these go in the 801A amplifier.



Man, those are cool!  All my tubes are like just totally boring looking.  Maybe I need some paint.


----------



## UntilThen

leftside said:


> Custom amps make great matches for the LCD-4



See Leftside knows what he's talking about because he lives with a LCD-4 and a Casaandra Wilson amp and a Pavarotti amp. Those amps have biceps and muscles.


----------



## johnjen (Dec 27, 2020)

So here are my 'mystery' 6L6GC's.
Yes it says Made for McIntosh by Generous Electric in the U.S.A. but, but, as we all know and bcowen has repeatedly reminded us all, GE tubes are neither fit for man nor beast.
And they even have the GE dot codes, go figure…

Except this pair (identical date codes (63-13/188-4) and measurement numbers) kick the matched sets of triads and westinghouses I have under, not just the bus, but then have been crushed under semi-trailer as well.
As in, it's not EVEN close.

I've not seen a pair of 6L6GC's like this pair, nor have I have found any reference to these.




Perhaps our very own GE expert can dig down deep into the recesses of GE history and retrieve the real meal deal about these mystery tubes.
And I'm SURE he would delight in regurgitating all of these intriguing factoids of note, after all, he is our very own GE tube historian, with his long history and fascination with America's Premier Tube Manufacturer, so I'm sure he could regale us all with the oh so intriguing pertinent technical details…
hahahahahahahahahahahaha…   

And just in case he demurs to offer up his oh so precious collection of historical, er hysterical, anecdotes I best trundle off to DIY to see if anyone has anything else resembling history to share… 
hahahahahahahahahahaha…  

JJ


----------



## L0rdGwyn

@johnjen hmmm well I am no GE historian, but the acid etching on the glass is certainly characteristic of GE tubes, which would seem to suggest they are in fact manufactured by GE.

These look to be of identical construction too.


----------



## UntilThen

leftside said:


> Lampizator TRP DAC. With a EL11/EL12 to EL34 adapter. I've been finding quite a few EL11 and EL12 from German eBay sellers. Usually in singles and for quite cheap. The only problem with these tubes is finding a perfect construction match if you are buying singles. There seems to be a lot of variations....



That's interesting the your Lampi dac can take EL11 / EL12 with adapters. No hum?   

Exactly, getting those ancient german tubes in match pairs is very hard now but I have them  I think I have 7 matched pairs of EL11 and 5 pairs of EL12 spez and several other EL12 and EL12N. I dream of 'Berlin' every month. As much as I try to 'forget' these tubes, they will resurface in my dreams and remind me of an unrealised ambition. So maybe, just maybe I might have an amp commissioned for it one day.

@L0rdGwyn was the one who has his graphic design specialist sister do this for me.  That was many moons ago.


----------



## johnjen (Dec 28, 2020)

L0rdGwyn said:


> @johnjen hmmm well I am no GE historian, but the acid etching on the glass is certainly characteristic of GE tubes, which would seem to suggest they are in fact manufactured by GE.
> 
> These look to be of identical construction too.


Yes those look nearly identicle for sure, are they 6L6GC's as well?
The thing is, did GE make these tubes just for McIntosh, because I haven't seen any mention of them making 6L6GCs in any of the 5 GE catalogs I have.

Curios'r and curios'r…

JJ
EDIT:  I may have solved my mystery.
My collection of 'old' tube catalogs may indeed be too 'old' as in the GC variant was a so to speak, 'later' version.
Mystery partially solved.


----------



## Tjj226 Angel

johnjen said:


> So here are my 'mystery' 6L6GC's.
> Yes it says Made for McIntosh by Generous Electric in the U.S.A. but, but, as we all know and bcowen has repeatedly reminded us all, GE tubes are neither fit for man nor beast.
> And they even have the GE dot codes, go figure…
> 
> ...




I think you are having a stroke there buddy. Your mystery tubes are the westinghouse tubes. Not the Mcintosh.


----------



## L0rdGwyn (Dec 27, 2020)

UntilThen said:


> @L0rdGwyn was the one who has his graphic design specialist sister do this for me.  That was many moons ago.



LOL I forgot about that, some of my finest work, I'll have a print made and framed, sent overnight express to your doorstep for the memories.

The EL11 is equivalent to the EL3N, triode curves below.



Some time ago I attempted to find triode curves for the EL12 and EL12spez, wasn't able to locate them.  I was able to find EL12N curves, which is a close relative, although it is a beam tetrode as opposed to pentode, courtesy of diyAudio.  Since these would be triode strapped, max g2 voltage per the Telefunken datasheet for EL12 is 350V, same for the plate.  18W plate dissipation.  Rp per the curve tracer of around 1K, something like 1-1.5K by my estimation.  Could do a 3.5 to 5K output transformer.  Here is a load line at 350V / 50mA / 5K OPT.



That would get you probably around a 4.5W amplifier with copper losses, more power if you went with a 3K or 3.5K transformer.

There is one issue with the EL11 driving EL12 amplifier design though, @UntilThen , the input sensitivity.

The EL11 has gain of around 20 and the EL12 around 18.  To get a full output of the EL12, the grid will need to swing only around 35V peak-to-peak.  With the gain of 20 for the first stage, 35V / 20 = 1.75V peak-to-peak input = 0.61Vrms input sensitivity, whereas a typical DAC puts out 1.5-2Vrms.

What that means is the amplifier will be driven to full output very early on the volume knob and it will get really loud really fast with a typical 2Vrms DAC.  Could put a voltage divider in front of the volume pot to lower the input voltage, or if you have a DAC capable of it, lower the output to 0.6Vrms or so.


----------



## bcowen

johnjen said:


> Perhaps our very own GE expert can dig down deep into the recesses of GE history and retrieve the real meal deal about these mystery tubes.
> And I'm SURE he would delight in regurgitating all of these intriguing factoids of note, after all, he is our very own GE tube historian, with his long history and fascination with America's Premier Tube Manufacturer, so I'm sure he could regale us all with the oh so intriguing pertinent technical details…
> hahahahahahahahahahahaha…



Yeah, what you said. Where *is* @gibosi when we need him?  

But you know, with measurements and tolerances and metallurgical science in the comparatively primitive stages it was back then, it's entirely possible GE screwed up and made a good sounding tube.  Stranger things have happened...


----------



## L0rdGwyn

bcowen said:


> Yeah, what you said. Where *is* @gibosi when we need him?
> 
> But you know, with measurements and tolerances and metallurgical science in the comparatively primitive stages it was back then, it's entirely possible GE screwed up and made a good sounding tube.  Stranger things have happened...



GE five-star 5670 is a nice little miniature triode!

There was a holiday delay, both of my Landfall chassis are now shipping.

Here is the chassis for the 841 spud headphone amplifier in Evo Grey 😍😍😍 sunburst pattern came out nicely I think.

Will have almost a week off starting Jan 1, going to be a busy week with two amps to build.


----------



## leftside

UntilThen said:


> That's interesting the your Lampi dac can take EL11 / EL12 with adapters. No hum?


No hum. Best as power tubes I think though in amps.



L0rdGwyn said:


> Some time ago I attempted to find triode curves for the EL12 and EL12spez, wasn't able to locate them.  I was able to find EL12N curves, which is a close relative, although it is a beam tetrode as opposed to pentode, courtesy of diyAudio.  Since these would be triode strapped, max g2 voltage per the Telefunken datasheet for EL12 is 350V, same for the plate.  18W plate dissipation.  Rp per the curve tracer of around 1K, something like 1-1.5K by my estimation.  Could do a 3.5 to 5K output transformer.  Here is a load line at 350V / 50mA / 5K OPT.


I have a couple of 375v EL12s.
https://www.radiomuseum.org/tubes/tube_el12375.html


----------



## L0rdGwyn (Dec 27, 2020)

leftside said:


> I have a couple of 375v EL12s.
> https://www.radiomuseum.org/tubes/tube_el12375.html



Interesting, I wonder what the screen voltage rating is, have to take it into account when triode strapping pentodes as the screen is connected to the plate typically and it has its own separate rating.  Maybe if we can dig up a Valvo EL12 datasheet 

EL12spez has a screen voltage rating of 425V with the same plate dissipaton of 18W, so could run at a higher plate voltage / lower current operating point if there was an advantage, but the load line above looks pretty symmetrical to me.


----------



## mordy

johnjen said:


> Yes those look nearly identicle for sure, are they 6L6GC's as well?
> The thing is did GE make these tubes just for McIntosh, because I haven't seen any mention of them making 6L6GCs in any of the 5 GE catalogs I have.
> 
> Curios'r and curios'r…
> ...


Why not contact McIntosh which is still in business?


----------



## mordy

leftside said:


> No hum. Best as power tubes I think though in amps.
> 
> 
> I have a couple of 375v EL12s.
> https://www.radiomuseum.org/tubes/tube_el12375.html


There are exceptions to every rule - add GE 6C5 and 5687 to the list of good sounding tubes.


----------



## L0rdGwyn (Dec 27, 2020)

L0rdGwyn said:


> LOL I forgot about that, some of my finest work, I'll have a print made and framed, sent overnight express to your doorstep for the memories.
> 
> The EL11 is equivalent to the EL3N, triode curves below.
> 
> ...



One more thing to think about @UntilThen whenever you have this amplifier built - if using EL12spez as the output tube rather than EL12, those top caps are the tube plates, meaning there is going to be around 350V there outside the chassis, not an amplifier you want to leave on unsupervised if animals or children are around (adults touching your tube gear without permission will have to learn the hard way).  If that is an issue, you could have some sort of glass or metal cage placed around the output tubes.


----------



## leftside

L0rdGwyn said:


> One more thing to think about @UntilThen whenever you have this amplifier built - if using EL12spez as the output tube rather than EL12, those top caps are the tube plates, meaning there is going to be around 350V there outside the chassis, not an amplifier you want to leave on unsupervised if animals or children are around (adults touching your tube gear without permission will have to learn the hard way).  If that is an issue, you could have some sort of glass or metal cage placed around the output tubes.


I learnt the hard way with TT21 tubes with adapters (instead of KT66 tubes) with my McIntosh MC75 amps. It was quite the shock.


----------



## L0rdGwyn

leftside said:


> I learnt the hard way with TT21 tubes with adapters (instead of KT66 tubes) with my McIntosh MC75 amps. It was quite the shock.



Oh yeah I bet, definitely something to think about if using a tube with exposed electrodes.  I am brainstorming ideas for my future transmitting triode amplifier with either 3C24 or HK54.  Even worse for these transmitting tubes, the plate caps have exposed metal since they are meant to sink heat from the plate and grid.  For me, that makes putting something around them mandatory, here is an example, could do something similar for the EL12spez, or just use EL12 instead, or run the risk of electrocution.


----------



## UntilThen

L0rdGwyn said:


> Here is the chassis for the 841 spud headphone amplifier in Evo Grey 😍😍😍 sunburst pattern came out nicely I think.



That chassis looks nice.


----------



## UntilThen

L0rdGwyn said:


> One more thing to think about @UntilThen whenever you have this amplifier built - if using EL12spez as the output tube rather than EL12, those top caps are the tube plates, meaning there is going to be around 350V there outside the chassis, not an amplifier you want to leave on unsupervised if animals or children are around (adults touching your tube gear without permission will have to learn the hard way). If that is an issue, you could have some sort of glass or metal cage placed around the output tubes.



No worries. No children or animals around me in my home away from home.  If @bcowen come and visit me, I'll make sure there's no touching from him.


----------



## johnjen

mordy said:


> Why not contact McIntosh which is still in business?


I kinda did already without all the fuss.
In looking into these GE mystery tubes it looks like they OEM'd them to a number of company's and I've found another matched set of Wurlitzer branded GE's from the 60's, so that will give me dual sets of matched pairs for the WE ƒ'-133/24 knockoff monoblock speaker amps already 'in the pipeline'.

And it looks like a matched set of 'regular' GE's should work as well.

But now I got's to get a more modern GE tube catalog, one that includes this variant of the 6L6 tube.

JJ


----------



## L0rdGwyn

I have another good GE tube entry - WWII era General Electric 841 / VT-51.  I may snag a pair of these for the sunburst spud amplifier  but not cheap for these rare globes.


----------



## bcowen

UntilThen said:


> No worries. No children or animals around me in my home away from home.  If @bcowen come and visit me, I'll make sure there's no touching from him.



Yeah, right.  Here's the more likely scenario:

"Hey Bill...check out this super-cool amp!  And what's really awesome is this tactile feedback feature -- touch this tube right _here_."
(followed by knee-slapping laughter in the background)


----------



## L0rdGwyn

Well the Eimac HR2 plate / grid caps I found are legit, true NOS, pretty cool!



Doing some light brainstorming on how I might set up the driver stage for that amplifier.  The same seller also has the compatible plate caps for the 100TH, the big fella.  Maybe I will pick up a pair of those caps, you never can know what the DIY future holds.



The eTracer is scheduled to arrive New Years Eve, so will be able to play with that very soon.  I think I will trace some EL34 triode curves on the first go around to test the functionality, then work on creating my own tube profiles for the 3C24, 4C25, and 841.

I also FINALLY bought an ultrasonic cleaner, hopefully will get that soon so I can work out the filtering mechanism.  The mail is running terribly slow at the moment, I'm sure it is a problem everywhere, really hoping these Landfall chassis make it here by Jan 2.

Been trying to decide which amplifier to build first - any thoughts on 45 parafeed rebuild vs. the new 841 spud amplifier?  Probably will only have time to do one or the other during my week off.


----------



## whirlwind

L0rdGwyn said:


> GE five-star 5670 is a nice little miniature triode!
> 
> There was a holiday delay, both of my Landfall chassis are now shipping.
> 
> ...



That chassis is quite sexy.  Sunburst pattern came out great.
Can't wait to hear your sound impressions from the spud.


----------



## bcowen

L0rdGwyn said:


> Oh yeah I bet, definitely something to think about if using a tube with exposed electrodes.  I am brainstorming ideas for my future transmitting triode amplifier with either 3C24 or HK54.  Even worse for these transmitting tubes, the plate caps have exposed metal since they are meant to sink heat from the plate and grid.  For me, that makes putting something around them mandatory, here is an example, could do something similar for the EL12spez, or just use EL12 instead, or run the risk of electrocution.



I _like_ the framework on that guard, but the chicken-wire mesh doesn't have me drooling all over the keyboard. If you could do a frame like that and then have a sunburst-type design (like your 841 top plate, minus the socket hole) for some side plates....now *that* would be cool and might make me drool.  Just another opinion, FWIW.


----------



## bcowen

L0rdGwyn said:


> Been trying to decide which amplifier to build first - any thoughts on 45 parafeed rebuild vs. the new 841 spud amplifier?  Probably will only have time to do one or the other during my week off.



The 300B SET headphone amp.  You didn't list that, so just trying to help by way of reminder.


----------



## UntilThen

bcowen said:


> The 300B SET headphone amp.  You didn't list that, so just trying to help by way of reminder.



and the Auris Nirvana contender. Don't forget.


----------



## bcowen

UntilThen said:


> and the Auris Nirvana contender. Don't forget.



My memory is good.  It's @L0rdGwyn I'm worried about, IIRC.


----------



## UntilThen

bcowen said:


> My memory is good.  It's @L0rdGwyn I'm worried about, IIRC.


----------



## Xcalibur255

Since EL34s are hot topic right now, has anybody tried these?

https://sophiaelectric.com/collections/kt88-and-el34-tubes/products/pages-se-el34


----------



## L0rdGwyn (Dec 28, 2020)

bcowen said:


> The 300B SET headphone amp.  You didn't list that, so just trying to help by way of reminder.





UntilThen said:


> and the Auris Nirvana contender. Don't forget.



300B SET?  Nirvana contender?  What in the heck are you guys talking about?  Today is transmitting tube day, maybe tomorrow I will remember 

But in all seriousness, what is nice about this winding path down Single Ended Class A Ave. is every build informs another in some way, so finishing current projects will improve future ones.


----------



## UntilThen

Xcalibur255 said:


> Since EL34s are hot topic right now, has anybody tried these?
> 
> https://sophiaelectric.com/collections/kt88-and-el34-tubes/products/pages-se-el34



Those are nice looking EL34. If I have an amp build for EL34, I'll buy those. With navy blue chassis of course.


----------



## Tjj226 Angel (Dec 28, 2020)

Just as a heads up.

Audiowize built a 810 amp that I heard right before I left seattle. That amp was really REALLY good. He originally designed it to use the 100TH tubes, but the 810s were much fuller and beefier sounding IMO.


----------



## L0rdGwyn

Tjj226 Angel said:


> Just as a heads up.
> 
> Audiowize built a 810 amp that I heard right before I left seattle. That amp was really REALLY good. He originally designed it to use the 100TH tubes, but the 810s were much fuller and beefier sounding IMO.



Awesome, thanks!  810 seems to be a rare animal though, at least a quick eBay search isn’t yielding any hits.  Looks cool though will keep it in mind  maybe a pair will pop up.


----------



## Tjj226 Angel

L0rdGwyn said:


> Awesome, thanks!  810 seems to be a rare animal though, at least a quick eBay search isn’t yielding any hits.  Looks cool though will keep it in mind  maybe a pair will pop up.



It could have a slightly different name like the 810T or some such nonsense. I only got to really see that amp for like a day or two in the midst of moving, so it was all kind of a blur. 

Ask Audiowize about it. Im sure he also has pictures. IDK if this would be offensive to him or not, but that amp was probably my favorite one of his that I was able to hear.


----------



## L0rdGwyn

Tjj226 Angel said:


> It could have a slightly different name like the 810T or some such nonsense. I only got to really see that amp for like a day or two in the midst of moving, so it was all kind of a blur.
> 
> Ask Audiowize about it. Im sure he also has pictures. IDK if this would be offensive to him or not, but that amp was probably my favorite one of his that I was able to hear.



Sounds cool, I think you were right though, 810, just can't find any anywhere!




Didn’t realize I was going to be building one of these 0Vg transmitting tube amplifiers when I hitched my cart to the 801A, but here we are.  Looking forward to messing around with the 3C24 and 4C25.


----------



## L0rdGwyn

It appears that my plans for the evening have been made for me.



Will post some curves once I get everything up and running.


----------



## Tjj226 Angel

L0rdGwyn said:


> It appears that my plans for the evening have been made for me.
> 
> 
> 
> Will post some curves once I get everything up and running.



NIIIIIIIIIIICEEE


----------



## bcowen

L0rdGwyn said:


> It appears that my plans for the evening have been made for me.
> 
> 
> 
> Will post some curves once I get everything up and running.



Sweet!!!


----------



## Zachik

L0rdGwyn said:


> It appears that my plans for the evening have been made for me.
> 
> 
> 
> Will post some curves once I get everything up and running.


I thought it comes as a kit... was I wrong?  Does it come fully assembled?


----------



## UntilThen

L0rdGwyn said:


> It appears that my plans for the evening have been made for me.
> 
> 
> 
> Will post some curves once I get everything up and running.



Is that your new Xbox ?


----------



## L0rdGwyn

Zachik said:


> I thought it comes as a kit... was I wrong?  Does it come fully assembled?



It does come as a kit, but in the true spirit of DIY, I paid to have it assembled LOL.  Money well spent IMO, putting one of these together is a lot of tedious socket wiring, which I really did not want to do.



UntilThen said:


> Is that your new Xbox ?



*Tubebox.  This bad boy is going to make all of my wildest tube fantasies come true


----------



## UntilThen

L0rdGwyn said:


> *Tubebox. This bad boy is going to make all of my wildest tube fantasies come true



Is that your new tube tester? If so I want one. Next question is how much. Next question is can you ship it to me. I've got tubes to test, specifically all my EL11, EL12, EL13, El14, etc.


----------



## L0rdGwyn

UntilThen said:


> Is that your new tube tester? If so I want one. Next question is how much. Next question is can you ship it to me. I've got tubes to test, specifically all my EL11, EL12, EL13, El14, etc.



Yes!  But not only is it a tube tester, it is a curve tracer, meaning it traces the operating curves of the tubes.  This is a very powerful tool for tube DIY as it no longer makes the user dependent on the curves made in tube datasheets - the tubes can be tested in real time and operating points evaluated.

This also allows one to create tube configuration / test files for oddball tubes without widely available triode curves, allows the tracing of pentode curves with the ability to vary screen and suppressor grid voltages, and even allows A2 curves to be trace in positive grid regions.

It is not cheap though!  Here is the product page with pricing information.  It can be purchased as a DIY kit or fully assembled.  Note that for tubes with external electrodes, like the EL12spez, adapters will have to be made to connect the tester power supplies to those external connections.

https://www.essues.com/etracer/index.php/buy

Here are the first curves...


----------



## L0rdGwyn

Since EL34 is talk of the town, thought I would test one first.




Here is a screenshot of the GUI after tracing the triode curves with measured parameters in the bottom right corner.  As you can see, this particular EL34 tests at around 89% of maximum gm, 86% of expected plate current.



I am nerding out, this thing is so cool!!!


----------



## L0rdGwyn

Next up is globe 45.  As some might recall, I got these for a song as they were untested, one had a grid-to-filament short that I was able to break by whacking the tube a few times.



I think I made out pretty well on the purchase!


----------



## Zachik

L0rdGwyn said:


> It is not cheap though! Here is the product page with pricing information. It can be purchased as a DIY kit or fully assembled. Note that for tubes with external electrodes, like the EL12spez, adapters will have to be made to connect the tester power supplies to those external connections.
> 
> https://www.essues.com/etracer/index.php/buy


Making sure I understand the pricing: (for fully built and shipped eTracer)
- PC control software USD$500 (Mandatory) 
- Built and tested PCB: USD$350 (Mandatory)
- Model-01 chassis with accessories: USD$200 (Optional)
- Mean Well EPP-200-27 power supply: USD$30 (Optional, must be bought together with the Model-01 chassis)
- Assembly service now available at USD$150 for etracer (Optional)
- Shipping rate is USD$80 to US 
- Paypal payment incurs a 6% service fee 
TOTAL: $1,310 plus paypal fee

Holy moly - that IS very expensive!!!


----------



## UntilThen

Zachik said:


> Making sure I understand the pricing: (for fully built and shipped eTracer)
> - PC control software USD$500 (Mandatory)
> - Built and tested PCB: USD$350 (Mandatory)
> - Model-01 chassis with accessories: USD$200 (Optional)
> ...



Nah piece of cake for you.   I'd buy it but I don't have enough tubes to justify buying it. Sold most of my tubes together with the sale of Elise, GOTL and Studio Six. Only enough left for Oblivion, WA22 and LF339.


----------



## L0rdGwyn

Zachik said:


> Making sure I understand the pricing: (for fully built and shipped eTracer)
> - PC control software USD$500 (Mandatory)
> - Built and tested PCB: USD$350 (Mandatory)
> - Model-01 chassis with accessories: USD$200 (Optional)
> ...



Yup, it is expensive and I honestly would not recommend this for all but the most serious tube tester enthusiasts or those that are going to use the information this tester provides for circuit development.  However, if you compare the functionality of the etracer and its price to something like the Amplitrex AT1000 or a fully restored Hickok TV-7 D/U, it might not seem so crazy (as in, this tester does a heck of a lot more and is either cheaper or the same price as those testers, roughly).  There are DIY options like the uTracer which will save cost, but the etracer does have advantages over it, most notably it boasts a 750VDC power supply.  The differences are outlined very specifically on the etracer site.


----------



## Xcalibur255

The 810 has a rather eye popping data sheet.


----------



## Xcalibur255

The eTracer is very impressive.  Certainly priced out of reach of the average enthusiast but I would love to see this get into the hands of more reputable sellers.


----------



## L0rdGwyn (Dec 29, 2020)

Okay I have the A2 functionality figured out.

Here are the curves for the 841, including both A1 (where it will be operating in my spud amplifier) as well as A2.  This tube could have some pretty interesting A2 applications.



All curves to the left of 0V are positive in increments of +5V.



Just for fun to see what a positive A2 operating point would look like in terms of tube constants, I did a quick scan at a 400V, 23mA, +5V on the grid, which yielded a Rp of 13K and mu of 21.  Interesting...


----------



## L0rdGwyn

Xcalibur255 said:


> The eTracer is very impressive.  Certainly priced out of reach of the average enthusiast but I would love to see this get into the hands of more reputable sellers.



I think Chris, the designer, is starting to reach out to internationally distributors!  He is based in Taiwan.


----------



## L0rdGwyn

This might be the last one for the night - full set of A1 + A2 curves for the Taylor 801A.  Happy to say the pair that I made match almost perfectly as far as the measurements go.


----------



## leftside

Zachik said:


> Making sure I understand the pricing: (for fully built and shipped eTracer)
> - PC control software USD$500 (Mandatory)
> - Built and tested PCB: USD$350 (Mandatory)
> - Model-01 chassis with accessories: USD$200 (Optional)
> ...


Compare to the price of the Amplitrex.



L0rdGwyn said:


> Yup, it is expensive and I honestly would not recommend this for all but the most serious tube tester enthusiasts or those that are going to use the information this tester provides for circuit development.  However, if you compare the functionality of the etracer and its price to something like the Amplitrex AT1000 or a fully restored Hickok TV-7 D/U, it might not seem so crazy (as in, this tester does a heck of a lot more and is either cheaper or the same price as those testers, roughly).  There are DIY options like the uTracer which will save cost, but the etracer does have advantages over it, most notably it boasts a 750VDC power supply.  The differences are outlined very specifically on the etracer site.


I crossed the 1000 count with tubes this month. It's time I purchased my own tube tester, although my friend has been enjoying me showing and then testing many different tubes over the years. I'll get this etracer early next year. The big thing for me with something like this or the Amplitrex is the ability to connect to a computer. The same thing with Analog Magik for setting up the turntable cart.


----------



## Zachik

Zachik said:


> Making sure I understand the pricing: (for fully built and shipped eTracer)
> - PC control software USD$500 (Mandatory)
> - Built and tested PCB: USD$350 (Mandatory)
> - Model-01 chassis with accessories: USD$200 (Optional)
> ...





L0rdGwyn said:


> Yup, it is expensive and I honestly would not recommend this for all but the most serious tube tester enthusiasts or those that are going to use the information this tester provides for circuit development.  However, if you compare the functionality of the etracer and its price to something like the Amplitrex AT1000 or a fully restored Hickok TV-7 D/U, it might not seem so crazy (as in, this tester does a heck of a lot more and is either cheaper or the same price as those testers, roughly).  There are DIY options like the uTracer which will save cost, but the etracer does have advantages over it, most notably it boasts a 750VDC power supply.  The differences are outlined very specifically on the etracer site.


Honestly, the only cost "I have a problem with" is the software license cost. ALL other costs are reasonable, IMHO. 
Even $800 is not exactly cheap, but makes sense. Again, IMHO.


----------



## bcowen

Xcalibur255 said:


> Certainly priced out of reach of the average enthusiast...



And operationally out of reach as well.    

Comparatively speaking though, the better and more capable vintage testers will cost as much and probably more (speaking mostly to the Hickok 539's, Triplett 3444's, Weston 981's, etc.). And they don't have anything close to the same capabilities, and you still have a machine that's old and if something major breaks (like a meter or transformer), you're pretty much SOL unless you can find a donor machine for cheap somewhere.  I still love the vintage testers and in the sub-$500/$600 range can still make good sense for the average tube addict, but at the $1k+ price level they no longer make a lot of sense.


----------



## UntilThen

bcowen said:


> And operationally out of reach as well.
> 
> Comparatively speaking though, the better and more capable vintage testers will cost as much and probably more (speaking mostly to the Hickok 539's, Triplett 3444's, Weston 981's, etc.). And they don't have anything close to the same capabilities, and you still have a machine that's old and if something major breaks (like a meter or transformer), you're pretty much SOL unless you can find a donor machine for cheap somewhere.  I still love the vintage testers and in the sub-$500/$600 range can still make good sense for the average tube addict, but at the $1k+ price level they no longer make a lot of sense.



What you need is a NOS tube tester. Takes a NOS tube tester to test a NOS tube to produce a NOS result.


----------



## Tjj226 Angel

UntilThen said:


> What you need is a NOS tube tester. Takes a NOS tube tester to test a NOS tube to produce a NOS result.



No. 

What we need to do is figure out how to make SS stuff not suck so that we can chuck all this crap in the dump and put all our saved money into stock or something.


----------



## UntilThen (Dec 30, 2020)

Tjj226 Angel said:


> No.
> 
> What we need to do is figure out how to make SS stuff not suck so that we can chuck all this crap in the dump and put all our saved money into stock or something.



Well spoken. I've just taken the first step and bought a Questyle CMA Twelve and it's supposed to have arrived yesterday but I will wait for it patiently today. 2021 might be when I farewell tubes and go to solid states. No hum, no hiss and no more hunting for NOS tubes.  

Oh dang, broke my promise to bcowen. This is my 4th posts today !


----------



## Tjj226 Angel

UntilThen said:


> Well spoken. I've just taken the first step and bought a Questyle CMA Twelve and it's supposed to have arrived yesterday but I will wait for it patiently today. 2021 might be when I farewell tubes and go to solid states. No hum, no hiss and no more hunting for NOS tubes.
> 
> Oh dang, broke my promise to bcowen. This is my 4th posts today !



I was REALLY surprised by the luxman SS amps. Out of all the shows, parties, music clubs, and shops I have been to, the luxman was probably the first SS amp that I heard and could actually live with. It wasn't so great that I was willing to give up my tube amps, but it was definitely a step in the right direction. 

I also made a small little BS Jfet prototype headphone amp that did actually sound better than tubes. The catch there is that it was just a buffer. It didn't have a SS gain stage. 

So it is definitely possible for SS to replace tubes. Once life settles down, I am going to dive into that topic a bit more. 

What I can say for the moment is that most SS amps are designed incorrectly for hifi. I think the key is to build amps that have as much distortion canceling as possible so that you can avoid NFB.


----------



## L0rdGwyn (Dec 30, 2020)

bcowen said:


> And operationally out of reach as well.



Yeah now that I’ve used it, very important the user understand how to interpret characteristic curves of a tube and choose operating points, especially if creating a new tube configuration file.  Chris has tons of tutorial videos that show how this is done, but you gotta get it right!


----------



## Tjj226 Angel

Oh and just because it is the holidays, I thought I would stir the pot a little. 

AHEM 

Oh lordgwyyyyyyyn......

Did you know that with class A2 tubes, you can use the grid as a plate and get really low output impedance? You can use that curve tracer to get a really good idea of how you need to setup an 801a to make that work.  

Have fuuuuunnnnn.


----------



## Galapac

UntilThen said:


> Well spoken. I've just taken the first step and bought a Questyle CMA Twelve and it's supposed to have arrived yesterday but I will wait for it patiently today. 2021 might be when I farewell tubes and go to solid states. No hum, no hiss and no more hunting for NOS tubes.
> 
> Oh dang, broke my promise to bcowen. This is my 4th posts today !


Say it ain't so!
I thought you would always have a spot for tube amps.
I think Bruc3 has one of those Questyle amps, did you try it when you sold him your extra 339?

If they would make a SS where you can dial in different tube amp sounds like some fender guitar amps with tubes that just glow pretty for no other reason then sign me up, part of my joy is that warm glow of the tubes I find intoxicating.


----------



## Zachik

Tjj226 Angel said:


> What we need to do is figure out how to make SS stuff not suck so that we can chuck all this crap in the dump and put all our saved money into stock or something.


I definitely need to spend more time with it, but my little DIY preamp that I built (posted here about it 3-4 days ago) - sounds surprisingly good!
Quick recap:
Nelson Pass design. Without the case - I estimate the BOM at $200-ish. Maybe $250 tops. So that is the price of 1 pair of EL34s... 
Obviously I am biased, being my first (non-passive) DIY audio project, but it sounds great with the HD600 that I tested it with!


----------



## Tjj226 Angel

Zachik said:


> I definitely need to spend more time with it, but my little DIY preamp that I built (posted here about it 3-4 days ago) - sounds surprisingly good!
> Quick recap:
> Nelson Pass design. Without the case - I estimate the BOM at $200-ish. Maybe $250 tops. So that is the price of 1 pair of EL34s...
> Obviously I am biased, being my first (non-passive) DIY audio project, but it sounds great with the HD600 that I tested it with!



Nelson pass definitely knows what he is doing. 

Does your preamp use Jfets?


----------



## Zachik

Tjj226 Angel said:


> Nelson pass definitely knows what he is doing.
> 
> Does your preamp use Jfets?


Yes! (to both NP knows what he is doing, and your questions about using JFETs)

I have used a different PCB design (for the same circuit basically), but the original PCB design by NP can be purchased here for $19:
https://diyaudiostore.com/collectio...s/acp-amp-camp-pre-amp?variant=31783672119369

Unfortunately, they do not sell the component kit - but was not too hard to figure it out with a little help from the DIYaudio community


----------



## Tjj226 Angel

Zachik said:


> Yes! (to both NP knows what he is doing, and your questions about using JFETs)
> 
> I have used a different PCB design (for the same circuit basically), but the original PCB design by NP can be purchased here for $19:
> https://diyaudiostore.com/collectio...s/acp-amp-camp-pre-amp?variant=31783672119369
> ...



Im literally designing a dac at the moment that uses something similar to this as the current to voltage output stage.


----------



## L0rdGwyn

Tjj226 Angel said:


> Oh and just because it is the holidays, I thought I would stir the pot a little.
> 
> AHEM
> 
> ...



Uh oh, I’ll check it out.  Let me know if you have seen a schematic somewhere.


----------



## Tjj226 Angel

L0rdGwyn said:


> Uh oh, I’ll check it out.  Let me know if you have seen a schematic somewhere.



Here is the general idea. 

http://diyaudioprojects.com/mirror/members.aol.com/sbench102/inverted.html

I haven't really messed with this before because as far as I can tell, you can't put out very much power. But it would work for headphones or a preamp.


----------



## UntilThen

Galapac said:


> Say it ain't so!
> I thought you would always have a spot for tube amps.
> I think Bruc3 has one of those Questyle amps, did you try it when you sold him your extra 339?
> 
> If they would make a SS where you can dial in different tube amp sounds like some fender guitar amps with tubes that just glow pretty for no other reason then sign me up, part of my joy is that warm glow of the tubes I find intoxicating.



I have a spot for any amps. Send me a Bakoon AMP-13R and I'll have spot on the table for it. Or I might be interested in Xi Audio Formula S driving Abyss AB-1266 Phi TC. I won't leave tube amps but I will diversify and get one capable ss amp for headphones. Another amp that has caught my attention is the Flux Lab FA-10. 

Alright enough of disrupting L0rdGwyn.


----------



## L0rdGwyn

Tjj226 Angel said:


> Here is the general idea.
> 
> http://diyaudioprojects.com/mirror/members.aol.com/sbench102/inverted.html
> 
> I haven't really messed with this before because as far as I can tell, you can't put out very much power. But it would work for headphones or a preamp.



Cool, I'll keep this in mind, maybe I will try to trace some similar curves with the 6AS7G or 6080.



UntilThen said:


> Alright enough of disrupting L0rdGwyn.



Talk about whatever you please!  I don't care 

Finally received a batch of D3a that I ordered ages ago, thought they would never arrive honestly.  Will have to solder some grid stoppers onto the etracer before tracing these, otherwise they will oscillate.




Also, @Galapac 's Darkvoice 336SE arrived, which I will be making some modifications to.  Some time this weekend I'll take some baseline measurements and post them for comparison later.

Looks like I get to bust out the ol' OTL tube collection


----------



## Xcalibur255 (Dec 30, 2020)

Tjj226 Angel said:


> I was REALLY surprised by the luxman SS amps. Out of all the shows, parties, music clubs, and shops I have been to, the luxman was probably the first SS amp that I heard and could actually live with. It wasn't so great that I was willing to give up my tube amps, but it was definitely a step in the right direction.
> 
> I also made a small little BS Jfet prototype headphone amp that did actually sound better than tubes. The catch there is that it was just a buffer. It didn't have a SS gain stage.
> 
> ...


My gut feeling is that we're just one breakthrough away from the class D stuff actually outpacing both tubes and SS and merging the worlds of subjective and objective (that is, it measures good and it sounds good to the majority of people).  That's all it is, a gut feeling.  I'm not an expert and possess only amateur knowledge on these matters.  Traditional SS probably can't get enough NFB and physical components out of the circuit to actually do what the very best tube designs do, but we might be one exotic material away from it being possible for class D. 

I do think that enthusiasm for tubes can often be self-propagating as a means unto itself and nothing else at times.  I would LOVE to get the sound of a great tube amp out of something small, light and energy efficient.  Losing the "cool" factor of the glowing glass bulbs is an acceptable price to pay.


----------



## Tjj226 Angel

Xcalibur255 said:


> My gut feeling is that we're just one breakthrough away from the class D stuff actually outpacing both tubes and SS and merging the worlds of subjective and objective (that is, it measures good and it sounds good to the majority of people).  That's all it is, a gut feeling.  I'm not an expert and possess only amateur knowledge on these matters.  Traditional SS probably can't get enough NFB and physical components out of the circuit to actually do what the very best tube designs do, but we might be one exotic material away from it being possible for class D.
> 
> I do think that enthusiasm for tubes can often be self-propagating as a means unto itself and nothing else at times.  I would LOVE to get the sound of a great tube amp out of something small, light and energy efficient.  Losing the "cool" factor of the glowing glass bulbs is an acceptable price to pay.



Maybe. There is a catch. 

Any advancement in technology that will make class D any better, SHOULD theoretically make all the other amplifier classes better as well. 

The name of the game with class D is square wave. Who ever has the nicest cleanest square wave response will make the best class D amp. Well if you want to make a nice square wave, you need a device that can switch on and off as instantaneously as possible. 

It just so happens that attribute will also benefit every other amplifier class as well. Soooooooooo you sort of end up with this leap frog scenario. 

Now that being said.......... I could also see someone designing a completely new class of amplifier that outperforms class A on merit alone. You have guys like LTA with their weird RF amplifier, so anything is possible. 

-----------------

Tubes are indeed cool, and there are plenty of situations where a tube is simply better or provides a unique solution to an engineering problem. 

My problem with tubes really has nothing to do with tubes. Transformers on the other hand are a PAIN IN THE you know what. No matter how well you build your SET circuit, no matter what crazy tricks you do, your sound quality will ALWAYS be limited by the output transformer. 

A pair of decent transformers can EASILY run you into a grand or more for a pair. And that is just for some transformers that don't completely suck. The best of the best transformers you can find, can easily run into the 5K mark PER TRANSFORMER. 

Now maybe one day we will get carbon fiber nanotube wire for cheaper than copper wire (I don't quite understand why were not there already). Then you can theoretically make a transformer that is so close to ideal, there is no point in whining about it. But for the moment, transformers kinda suck.

A decent emitter follower SHOULD sound better than a transformer any day of the week. And for the most part, I have found in my experiments that it is possible to get really good sound out of a hybrid amp in a SE configuration.


----------



## Galapac

L0rdGwyn said:


> Cool, I'll keep this in mind, maybe I will try to trace some similar curves with the 6AS7G or 6080.
> 
> 
> 
> ...


Oh crap did I leave a headphone jack adapter in it? Too funny...


----------



## UntilThen

Ok where are we with amps now?   Class A, A/B, D don't matter to me as long as it sound good and won't bbq my steak. 

So can someone in the know comment on my forthcoming Questyle CMA Twelve? If it's bad, I'll donate it to Salvation Army . If it's good, well I'll keep it of course. 

Something else that has my attention now. I have HiFiMan Arya and He1000se side by side on my desk, ready to entertain me for New Year Eve.


----------



## L0rdGwyn (Dec 31, 2020)

Had some time today so I took my measurements of the Darkvoice 336SE.  I wanted to use the stock tubes and not something completely unobtainium, I also have a very limited collection of 6SN7 now, so what's in there is a NEC 6520 and Russian 6H8C.  All measurements were done on the left channel into a 300ohm dummy load.



Here is the frequency response at 1mW into a 300ohm.  As you can see, there is some low frequency rolloff, about -2dB at 20Hz.  High frequency extension is good.



THD+N FFT plot at 1mW into 300ohm.  Distortion is exclusively 2nd harmonic at 0.22%.  Power supply noise at 60Hz at around -72dB, 120Hz at -78dB.



Same measurement at 10mW into 300ohm, 0.73% THD, now seeing a smidge of 3rd harmonic.



1kHz square wave 1mW into 300ohm.



10kHz square wave 1mW into 300ohm.



100Hz square wave 1mW into 300ohm.



The low frequency rolloff can be seen on the 1kHz square and very plain on the 100Hz square, the 10kHz square is pretty good with a hint of HF rolloff which can be seen on the FR plot.

I measured the output impedance as well at 1kHz, it is roughly 71.5ohm.

As I mess around inside the amp, I'll take repeat measurements for comparison.


----------



## A2029 (Dec 31, 2020)

L0rdGwyn said:


> Had some time today so I took my measurements of the Darkvoice 336SE.  I wanted to use the stock tubes and not something completely unobtainium, I also have a very limited collection of 6SN7 now, so what's in there is a NEC 6520 and Russian 6H8C.  All measurements were done on the left channel into a 300ohm dummy load.
> 
> 
> 
> ...



Very cool! What is the output cap value in the Darkvoice? Electrolytic?


----------



## L0rdGwyn (Dec 31, 2020)

A2029 said:


> Very cool! What is the output cap value in the Darkvoice? Electrolytic?



Thanks!  Three 10uF films in parallel actually, which would explain the LF rolloff.  Into a 300ohm dummy, that gives a f-3dB of 17Hz, right on the money.  Anything less than a 300ohm load with this amp the LF rolloff becomes pretty substantial.

I am modding the Darkvoice for a Head-Fier, probably going to throw on some current sources / sinks and perhaps regulate the power supply.  Everything is resistively loaded and the supply has a very chunky CRCRC-CRC filter with 3440uF of capacitance.


----------



## Galapac (Dec 31, 2020)

It’s like watching doctors work.  
”We can rebuild him, we have the technology.”

Very impressed as I don’t fully understand the terminology but you guys are like amp Drs.


----------



## UntilThen

Galapac said:


> It’s like watching doctors work.
> ”We can rebuild him, we have the technology.”
> 
> Very impressed as I don’t fully understand the terminology but you guys are like amp Drs.



All I know is that he is going to turn your Darkvoice into a Lightvoice while retaining the high and low voice with any headphones.


----------



## UntilThen

L0rdGwyn said:


> Thanks!  Three 10uF films in parallel actually, which would explain the LF rolloff.  Into a 300ohm dummy, that gives a f-3dB of 17Hz, right on the money.  Anything less than a 300ohm load with this amp the LF rolloff becomes pretty substantial.
> 
> I am modding the Darkvoice for a Head-Fier, probably going to throw on some current sources / sinks and perhaps regulate the power supply.  Everything is resistively loaded and the supply has a very chunky CRCRC-CRC filter with 3440uF of capacitance.



When you finish with that, can you mod my La Figaro please. I need smoother volume turning knobs.


----------



## bcowen

Galapac said:


> It’s like watching doctors work.
> ”We can rebuild him, we have the technology.”
> 
> Very impressed as I don’t fully understand the terminology but you guys are like amp Drs.



LOL!  Some of us are the ones sitting in that glassed-in mezzanine above the operating room watching the_ real _doctor perform the surgery below us.  But I'm taking notes while sipping on a cocktail up there.


----------



## UntilThen

bcowen said:


> LOL!  Some of us are the ones sitting in that glassed-in mezzanine above the operating room watching the_ real _doctor perform the surgery below us.  But I'm taking notes while sipping on a cocktail up there.



You're the intern. You will be operating next so pay very careful attention now. Don't want the amp to go into cardiac arrest.


----------



## Zachik

L0rdGwyn said:


> Had some time today so I took my measurements of the Darkvoice 336SE.  I wanted to use the stock tubes and not something completely unobtainium, I also have a very limited collection of 6SN7 now, so what's in there is a NEC 6520 and Russian 6H8C.  All measurements were done on the left channel into a 300ohm dummy load.
> 
> 
> 
> ...


Couple quick questions, since I am trying to better understand the setup (recently I invested some $$$ into test equipment as well):
1. I almost bought the exact same scope last week...  Would 2 channel scope be enough, or would you seriously consider a 4-channel scope? Just curious, since price delta is $120 or so, and I do not want to have a buyer's remorse... 
2. What is the Autoranging Attenuator thingy?
3. What is the dummy load you're referring to?  The black box under the autoranging attenuator?
4. What software are you using for the FR and THD plots? Is that the Siglent software connected to the scope?

Thanks!


----------



## L0rdGwyn (Dec 31, 2020)

Zachik said:


> Couple quick questions, since I am trying to better understand the setup (recently I invested some $$$ into test equipment as well):
> 1. I almost bought the exact same scope last week...  Would 2 channel scope be enough, or would you seriously consider a 4-channel scope? Just curious, since price delta is $120 or so, and I do not want to have a buyer's remorse...
> 2. What is the Autoranging Attenuator thingy?
> 3. What is the dummy load you're referring to?  The black box under the autoranging attenuator?
> ...



Hey Zachik,

1. I don't have much use for a four-channel scope, maybe I will some day, but two channels has been sufficient for me so far.  One functionality this scope lacks that I at one point wish it had is the ability to generate Bode plots.
2. The Linear Audio Autoranger is a device that attenuates / amplifies any input signal and changes it to roughly 1Vrms.  This is meant to be paired with a ADC / DAC sound card in a measurements system.  A typical ADC can only handle line-level voltages as it was not made for making high-voltage audio measurements.  The Autoranger allows you to measure high AC voltages (from a power amplifier, for example) without damaging the sound card.  It is a DIY kit from Linear Audio, although I believe Jan Didden will assemble it for you for a fee.
3. A dummy load is a "fake" load for the DUT for the sake of a measurement.  For example, a 300ohm resistor taking the place of a 300ohm headphone.  The black box under the Autoranger is the switchable headphone dummy load I made, can do 32, 80, 120, and 300ohms.  Makes taking output impedance measurements very simple by varying the load and measuring the output voltage.  TRS input connects to the headphone output of the amp, BNC jacks connect to the Autoranger input.  Eventually I will build something similar for speaker measurements with 4, 6, 8, and 16ohm dummy loads.


  

4. FR and FFT plots are made using either Arta or REW.  The square waves are generated on the scope in combination with a signal generator.  Note that a typical signal generator is not low enough distortion to make THD+N measurements - the generator itself with swamp out the distortion of the DUT, better to use a sound card to generate your input signal.  The limit of the measurements you can make will be determined by the distortion of the ADC / DAC of the sound card.  The MOTU M4 that I use is good down to about 0.0008% THD+N.


----------



## L0rdGwyn (Dec 31, 2020)

UntilThen said:


> When you finish with that, can you mod my La Figaro please. I need smoother volume turning knobs.



Adding some new pots should be a pretty easy change!  Might want to see if there is someone local to you to do it UT, IMO not worth shipping the amp internationally to swap the pots.

Speaking of pots, the stock pot on the Darkvoice is horrendous...did they make it with sand?  It is very rough.


----------



## UntilThen

L0rdGwyn said:


> Adding some new pots should be a pretty easy change!  Might want to see if there is someone local to you to do it UT, IMO not worth shipping the amp internationally to swap the pots.



Yup I was kidding. 

As a matter of fact, I'm going to take it to the http://www.thefactoryaudio.com/. The place that replaced all my GOTL sockets and put in some juicy caps and resistors.


----------



## bcowen

L0rdGwyn said:


> Adding some new pots should be a pretty easy change!  Might want to see if there is someone local to you to do it UT, IMO not worth shipping the amp internationally to swap the pots.
> 
> Speaking of pots, the stock pot on the Darkvoice is horrendous...did they make it with sand?  It is very rough.



Sand might be an upgrade.    And I think they applied the conductive film to the discs by pouring it out of a 5 gallon bucket. Mine was positioned so that 6:00 was max counterclockwise rotation. 7:00 was as loud as I could possibly listen. But from 7:00 to around 12:00, there was very little volume change. Then by the time you got to 3:00, your ears were blown and a serious case of carpal tunnel of the wrist had suddenly developed. OK, maybe I'm exaggerating a wee bit.   But putting the Alps pot in there was an instant and significant improvement both sonically and ergonomically.


----------



## UntilThen

L0rdGwyn said:


> Speaking of pots, the stock pot on the Darkvoice is horrendous...did they make it with sand? It is very rough.



That's what my right LF339 volume pot feels like. You think a little WD40 will help?  Surprisingly the left knob is smooth. Did they forget to lubricate the right?


----------



## L0rdGwyn (Dec 31, 2020)

Here is kind of what I am thinking for the revamped Darkvoice 336SE circuit.

First off, the power supply will be Maida regulated, meaning all of the CRCRC-CRC caps and resistors can be completely removed, which will free up space for the PCBs that will be going in.  This will allow us to increase the available B+ voltage to around 175V while obeying the dropout voltage of the regulator.

A simple cascode CCS load will go on the plate of the 6SN7 set to 3mA, putting about 80V on plate of the 6SN7 / grid of the 5998/6080.

Simple IXCP10M45S current sink on the cathode of the output tube, set tentatively in my sim to 55mA.  The Darkvoice has the output tubes biased at something like 80mA, we'll have to see what is practical in terms of heatsinking the FET.

This amp absolutely needs more capacitance on the output for better low frequency extension.  Not sure how I am going to do it from a space perspective, but 100uF of film caps would be a good place to be.

Lastly, I added a startup protection diode to the output tube, can't hurt and prevents arcing from grid to cathode as the tubes come up to bias.



Pretty simple circuit, should have significant audible benefits.  Tricky thing is going to be fitting everything inside, but we will find a way.


----------



## L0rdGwyn (Jan 1, 2021)

Happy New Year everyone  hope it is a better one.

I like the idea of the new Darkvoice circuit, but power dissipated in the FET current sink is going to limit how hard we can push the cathode follower, possible I might leave it resistively loaded, we will see how big of a heat sink I can fit.


----------



## UntilThen

L0rdGwyn said:


> Happy New Year everyone



That's 20 hours ago !


----------



## L0rdGwyn

UntilThen said:


> That's 20 hours ago !



Not for me! 3 hours


----------



## Xcalibur255

Wish everyone a good 2021.  It shouldn't be hard to outperform 2020.  

Keenan I get the feeling your affordable amp to build and sell to Head-fi members really ought to be an OTL design.  It would be ideal if the output impedance could be gotten a bit lower still, but I've used headphones as low as 24 ohm on my GOTL running 5998 (which yields an output impedance of 25 ohms in that config) and it sounded fine.  The pinch for all "affordable" tube amps is the battle of how money to put into the output transformers.  Inevitably the amp ends up no longer being cheap because we always want good performance and cheap transformers just can't do the job.

That's assuming people want an all tube design of course.  Now, I know you'll probably end up doing both eventually and you probably should as there is a place for both, but OTLs seem to deliver on cheap and cheerful more easily and seems like a natural starting point.


----------



## L0rdGwyn

Xcalibur255 said:


> Wish everyone a good 2021.  It shouldn't be hard to outperform 2020.
> 
> Keenan I get the feeling your affordable amp to build and sell to Head-fi members really ought to be an OTL design.  It would be ideal if the output impedance could be gotten a bit lower still, but I've used headphones as low as 24 ohm on my GOTL running 5998 (which yields an output impedance of 25 ohms in that config) and it sounded fine.  The pinch for all "affordable" tube amps is the battle of how money to put into the output transformers.  Inevitably the amp ends up no longer being cheap because we always want good performance and cheap transformers just can't do the job.
> 
> That's assuming people want an all tube design of course.  Now, I know you'll probably end up doing both eventually and you probably should as there is a place for both, but OTLs seem to deliver on cheap and cheerful more easily and seems like a natural starting point.



I hear you, for headphones OTL is a natural starting point.  I'll give it some thought, in either case I would need to build something first and give it a listen before moving forward.  Maybe I will try out some OTL ideas rather than going straight to the EL34 SET, I am open to that.


----------



## Paladin79

My project for today, I am down to wiring two ladder pots then it will be done. GU-50 and 6bx6 tubes soon to be traded out for Telefunken LS50's and EF 80's (6bx6).

Tiger maple and white walnut case.  15 watt, Class A SET


----------



## L0rdGwyn

Paladin79 said:


> My project for today, I am down to wiring two ladder pots then it will be done. GU-50 and 6bx6 tubes soon to be traded out for Telefunken LS50's and EF 80's (6bx6).
> 
> Tiger maple and white walnut case.  15 watt, Class A SET



Looks fantastic, congrats!


----------



## Paladin79

L0rdGwyn said:


> Looks fantastic, congrats!


Thanks I just have to remember how to wire dual ladder pots and I am done, well maybe a bottom on the amp case but that can wait. And I may play with a headphone out at some point. This is the Cowen, I have to use certain parts to win a bet then I can upgrade tubes, caps, wire etc. Then it gets a name change lol.


----------



## L0rdGwyn

Paladin79 said:


> Thanks I just have to remember how to wire dual ladder pots and I am done, well maybe a bottom on the amp case but that can wait. And I may play with a headphone out at some point. This is the Cowen, I have to use certain parts to win a bet then I can upgrade tubes, caps, wire etc. Then it gets a name change lol.



Hopefully whoever chose the parts gave you some decent transformers to work with   well it looks great, sure the sound will match.


----------



## L0rdGwyn

Chassis for my upcoming amplifiers are lost somewhere in Texas, go figure, so not sure I will be working on them as I had planned during time off, USPS is in shambles right now.

Another compelling reason to buy the etracer was to test my collection of 4V B5 base tubes, these are the drivers in my 6A5G amplifier.  Got around to it today, here are a few examples.

Marconi MH4


 

Telefunken REN904

 

Opta REN904


----------



## Paladin79 (Jan 1, 2021)

L0rdGwyn said:


> Hopefully whoever chose the parts gave you some decent transformers to work with   well it looks great, sure the sound will match.


Luckily I got to choose my own transformers, I chose some Russian military made devices. The GU and LS 50 tubes were used in German and Russian military transmitters I do believe so I decided to go old school. This is much easier than another bet I undertook involving blade switches and magic eye tubes.


----------



## Galapac

L0rdGwyn said:


> I hear you, for headphones OTL is a natural starting point.  I'll give it some thought, in either case I would need to build something first and give it a listen before moving forward.  Maybe I will try out some OTL ideas rather than going straight to the EL34 SET, I am open to that.


If you built an OTL like I hear Glenn does I’d be one of the first in line as I’m sure others would. 😉


----------



## UntilThen

L0rdGwyn said:


> Looks fantastic, congrats!



If Lord Gwyn says it's fantastic then it is.


----------



## UntilThen

Paladin79 said:


> This is the Cowen  UntilThen, I have to use certain parts to win a bet then I can upgrade tubes, caps, wire etc. Then it gets a no name change lol  and will stay that way forever.



There fixed your typo.


----------



## Paladin79

Galapac said:


> If you built an OTL like I hear Glenn does I’d be one of the first in line as I’m sure others would. 😉


I designed my own OTL but I like to concentrate on specific tubes rather than how many different tubes an amp might support. My analogy is a swiss army knife, it can get you by with some of the functions but when you design the best knife, or scissors or file you can, they tend to beat out such devices. YMMV


----------



## L0rdGwyn (Jan 1, 2021)

Galapac said:


> If you built an OTL like I hear Glenn does I’d be one of the first in line as I’m sure others would. 😉



Well Glenn uses a specific output topology in his OTL amplifier and out of respect for him, I would not build one that way without his explicit permission as it would essentially be a GOTL clone in my mind.  Unless you get into hybrid topologies, there are only so many ways to make a 6AS7G OTL amplifier, with most of them being some variation of a cathode follower.  Put a current source / cathode follower on top, you get SRPP.  Use a conventional cathode follower and load the cathode with a resistor or current sink.  Parallel the sections and get a conventional cathode follower with half the output impedance.  SRPP and something like a White cathode follower are ideally optimized for a specific load, meaning they are not optimal for varying headphone impedances, although Glenn has made it work to great effect.  John Broskie at Tube CAD has some interesting ideas omitting output caps by cancelling the DC offset on the output.  If people are interested in another 6AS7G cathode follower OTL, I'd be happy to make one, it would have my own personal influence, but it wouldn't be anything that hasn't been done before in terms of the output stage.


----------



## Paladin79 (Jan 1, 2021)

L0rdGwyn said:


> Well Glenn uses a specific output topology in his OTL amplifier and out of respect for him, I would not build one that way without his explicit permission as it would essentially be a GOTL clone in my mind.  Unless you get into hybrid topologies, there are only so many ways to make a 6AS7G OTL amplifier, with most of them being some variation of a cathode follower.  Put a current source / cathode follower on top, you get SRPP.  Use a conventional cathode follower and load the cathode with a resistor or current sink.  Parallel the sections and get a conventional cathode follower with half the output impedance.  SRPP and something like a White cathode follower are ideally optimized for a specific load, meaning they are not optimal for varying headphone impedances, although Glenn has made it work to great effect.  John Broskie at Tube CAD has some interesting ideas omitting output caps by cancelling the DC offset on the output.  If people are interested in another 6AS7G cathode follower OTL, I'd be happy to make one, it would have my own personal influence, but it wouldn't be anything that hasn't been done before in terms of the output stage.


I do not generally run an Incubus with headphones under 50 ohms but many do, 32 and less in fact. I do not discuss my design since I do not want clones or mods.

I love this Belden wire for wiring dual pots, it is molded together so you can split off what you need and each side is two conductor with ground so it is well set up for even dual gang pots.


----------



## Galapac

My comments earlier regarding GOTL was really not specific to his amps but more in a generalized “boutique“ style of amp.
I like the custom idea of amp building and not a one size fits all approach.
Apologies if my comment came across as not inteneed.


----------



## Paladin79

Galapac said:


> My comments earlier regarding GOTL was really not specific to his amps but more in a generalized “boutique“ style of amp.
> I like the custom idea of amp building and not a one size fits all approach.
> Apologies if my comment came across as not inteneed.


You are fine. Mine are somewhat boutique I suppose and they were never intended for sale. Unfortunately I let friends hear one and 50 amps later, I am still being asked to build them. All of mine are unique in cabinet design and I used a few levels of parts. My personal Incubus Elegan....


----------



## Tjj226 Angel

L0rdGwyn said:


> Well Glenn uses a specific output topology in his OTL amplifier and out of respect for him, I would not build one that way without his explicit permission as it would essentially be a GOTL clone in my mind.  Unless you get into hybrid topologies, there are only so many ways to make a 6AS7G OTL amplifier, with most of them being some variation of a cathode follower.  Put a current source / cathode follower on top, you get SRPP.  Use a conventional cathode follower and load the cathode with a resistor or current sink.  Parallel the sections and get a conventional cathode follower with half the output impedance.  SRPP and something like a White cathode follower are ideally optimized for a specific load, meaning they are not optimal for varying headphone impedances, although Glenn has made it work to great effect.  John Broskie at Tube CAD has some interesting ideas omitting output caps by cancelling the DC offset on the output.  If people are interested in another 6AS7G cathode follower OTL, I'd be happy to make one, it would have my own personal influence, but it wouldn't be anything that hasn't been done before in terms of the output stage.



PSSSSST PSSSSSSSSSSSSSSSSST

6E5P - 32 ohm cathode follower. Parallel them up and they can outperform the 6AS7G.


----------



## L0rdGwyn

Galapac said:


> My comments earlier regarding GOTL was really not specific to his amps but more in a generalized “boutique“ style of amp.
> I like the custom idea of amp building and not a one size fits all approach.
> Apologies if my comment came across as not inteneed.



Oh I hope I didn't come across as offended in any way!  Not at all, just wanted to make general comment since I have been asked about making something like Glenn's OTL before.  Sorry I am coming off of a night shift so my brain is a little discombobulated.

The point I am trying to make is that coming up with something "unique" in the world of 6AS7G headphone amplifiers isn't likely, so any amp I would build would be variation of an existing 6AS7G OTL topology.

I was laughing to myself reading the description of the Apex Teton OTL the other day, that amp is $5K.  The description reads like new heights have been reached in terms of what can be done with a 6AS7G headphone amp, but what they actually describe is...a capacitor coupled 6AS7G cathode follower, like the Bottlehead Crack, the Darkvoice, etc. etc. albeit with a much nicer chassis and better power supply, to be certain.



Tjj226 Angel said:


> PSSSSST PSSSSSSSSSSSSSSSSST
> 
> 6E5P - 32 ohm cathode follower. Parallel them up and they can outperform the 6AS7G.



But the people want the 6AS7G!!!  What I really want to do is make an OTL with these, but they are not so plentiful.  Maybe I will do it anyway.


----------



## UntilThen

There's a lot happening here today. It's a busy workshop.


----------



## Galapac

Paladin79 said:


> You are fine. Mine are somewhat boutique I suppose and they were never intended for sale. Unfortunately I let friends hear one and 50 amps later, I am still being asked to build them. All of mine are unique in cabinet design and I used a few levels of parts. My personal Incubus Elegan....


Nice! I believe I have seen your amp before in these forums somewhere. I remember because it is very unique. It must be very satisfying to build. The closest I could relate to it is building my own Crypto mining rig. This rig has helped fund my audio hobby.


----------



## Paladin79

Galapac said:


> Nice! I believe I have seen your amp before in these forums somewhere. I remember because it is very unique. It must be very satisfying to build. The closest I could relate to it is building my own Crypto mining rig. This rig has helped fund my audio hobby.


very nice.


----------



## Tjj226 Angel

Galapac said:


> Nice! I believe I have seen your amp before in these forums somewhere. I remember because it is very unique. It must be very satisfying to build. The closest I could relate to it is building my own Crypto mining rig. This rig has helped fund my audio hobby.



Did you actually make any money though. That is the REAL question.


----------



## bcowen

UntilThen said:


> If Lord Gwyn says it's fantastic then it is.



Suck up.


----------



## Galapac

Tjj226 Angel said:


> Did you actually make any money though. That is the REAL question.


I sense a skeptic?
The REAL answer is I Sure did. 😉
I’m not going to get into specifics as this forum is not for that but I’ve done alright for myself as an early adopter and still do it.


----------



## Tjj226 Angel

Galapac said:


> I sense a skeptic?
> The REAL answer is I Sure did. 😉
> I’m not going to get into specifics as this forum is not for that but I’ve done alright for myself as an early adopter and still do it.



Not a skeptic. I certainly know it's possible (I was doing it until my internet company said they would cut my service if I didn't stop), but these days it's not all that easy to turn a profit.


----------



## UntilThen

bcowen said:


> Suck up.


Off course he’s LORD Gwyn.


----------



## UntilThen

Galapac said:


> Nice! I believe I have seen your amp before in these forums somewhere. I remember because it is very unique. It must be very satisfying to build. The closest I could relate to it is building my own Crypto mining rig. This rig has helped fund my audio hobby.


My seven wonders of the world PC may not be as powerful as this but it’s nice(r) with Corsair RGB and these days you need RGB.


----------



## UntilThen

The year has just started and though I was looking forward to Gwyn’s Nirvana, I have just bought Questyle CMA 12 and v280. Let’s see if China or Germany is better.


----------



## L0rdGwyn

I think I'll prototype a 6AS7G OTL when the weather warms up, I have two different ideas in mind, I'll try both and see which sounds better.

Bummed I can't work on the 45 or 841 amplifiers, was counting on having the chassis in hand by now, but in the mean time I have been making incremental improvements to the 801A amplifier design, very excited about where it is going.  I held onto all of my 6BX7 / 6BL7 tubes from back when I had the Glenn OTL, knew they would come in handy eventually as cathode followers in some design, this will be it, replacing my previous FET source follower.  That will bring the number of tubes in this amp to six, could become seven if I have good results using the VR105 to regulate the EF37A screens.  Not exactly sure of the chassis size yet, but it is going to be big.


----------



## Paladin79

L0rdGwyn said:


> I think I'll prototype a 6AS7G OTL when the weather warms up, I have two different ideas in mind, I'll try both and see which sounds better.
> 
> Bummed I can't work on the 45 or 841 amplifiers, was counting on having the chassis in hand by now, but in the mean time I have been making incremental improvements to the 801A amplifier design, very excited about where it is going.  I held onto all of my 6BX7 / 6BL7 tubes from back when I had the Glenn OTL, knew they would come in handy eventually as cathode followers in some design, this will be it, replacing my previous FET source follower.  That will bring the number of tubes in this amp to six, could become seven if I have good results using the VR105 to regulate the EF37A screens.  Not exactly sure of the chassis size yet, but it is going to be big.


I will finish my Cowen amp tomorrow then I will make another Incubus sample, repair a few amps for friends then on to pre-amp design.

I was making an OTL a week for a long time but the woodwork slows me down, making each amp unique is never easy. They fetch $1,500 to $2,000 and maxed at $5k.


----------



## Xcalibur255 (Jan 2, 2021)

L0rdGwyn said:


> I hear you, for headphones OTL is a natural starting point.  I'll give it some thought, in either case I would need to build something first and give it a listen before moving forward.  Maybe I will try out some OTL ideas rather than going straight to the EL34 SET, I am open to that.


I mean honestly we're the peanut gallery here.  It takes nothing for us to toss these suggestions out there.  It's your time, money and energy that's going into it so whatever interests you most is obviously the way to go.  Once you make one for somebody and sell it for the first time the floodgates will be open too so it's incumbent upon the rest of us here to be considerate and remember that you don't do this for a living (yet ).


----------



## UntilThen

Lord Gwyn, just my 2 cents and I sure hate calling you lord every time. Remember though that I'm King.   

Do something you're passionate about. If it's EL34 or 300b or 45 or 2a3 then go for it. OTL amps based on the 6as7g are dime a dozen out there. Think Darkvoice, Woo Wa3, Crack, Little Dot, Elise etc. 

That's my 2 cents and it's not a lot.


----------



## Xcalibur255

L0rdGwyn said:


> I was laughing to myself reading the description of the Apex Teton OTL the other day, that amp is $5K.  The description reads like new heights have been reached in terms of what can be done with a 6AS7G headphone amp, but what they actually describe is...a capacitor coupled 6AS7G cathode follower, like the Bottlehead Crack, the Darkvoice, etc. etc. albeit with a much nicer chassis and better power supply, to be certain.
> 
> 
> 
> But the people want the 6AS7G!!!  What I really want to do is make an OTL with these, but they are not so plentiful.  Maybe I will do it anyway.



The Apex Teton drives me nuts.  Sonically my GOTL is the same amp at 1/10 the price.  Done right the price/performance ratio of OTL designs are generally good so somebody had to come along and milk it of course.....

Tubes that are hard to come by aren't so bad as long as they're not a genuine pain to find and aren't expensive.  What bothers me is being locked into a single tube and brand.  The 6E5P as mentioned above for example.  I'm sure it's an outstanding tube otherwise he wouldn't have mentioned it, but from what I saw you get exactly one option here and that's a Russian Reflektor.  If the tone ends up being just to your liking then great, but if you find yourself wishing you could tune it a bit with a different tube choice then you're flat out of luck.  I generally feel the same way as Palandin79 does here in that amps don't need to be capable of running 500 different tube types.  Of course some people love this and that's 100% okay, but I think you ultimately end up with a little bit better amp if it's specialized and targeted to work very well with a particular tube type.  What I don't like is not having any variety at all WITHIN that tube type.  This was my regret with the C3g.  I'd love to change my 45 amp to use the 6J5 actually and it's something I may pursue someday.  The 6J5 is probably a better driver for the 45 anyway as the amp will have better gain structure I'm thinking.


----------



## Xcalibur255

Galapac said:


> Nice! I believe I have seen your amp before in these forums somewhere. I remember because it is very unique. It must be very satisfying to build. The closest I could relate to it is building my own Crypto mining rig. This rig has helped fund my audio hobby.


Funny you should post this.  I just finished building my first new PC in 11 years today.  Cute little mini ITX rig.  The case has a handle in the top that folds into the chassis magnetically when it isn't needed.  It's one of those brilliant ideas that makes you wonder why everybody doesn't do it.  The old PC has been a fantastic machine but when I upgraded monitors and moved up from 1080p it finally started to struggle even though it's received graphic card updates over the years.  The real chore this weekend will be moving 11 years of my life from the old machine to the new one......


----------



## Xcalibur255

UntilThen said:


> Off course he’s LORD Gwyn.


We could change it up and go with Gwyn-sama too.


----------



## UntilThen

Xcalibur255 said:


> We could change it up and go with Gwyn-sama too.



I don't know what Gwyn-sama is but I'll go along as it will help me beat @bcowen score. 

I googled and this is what I get.


----------



## L0rdGwyn (Jan 2, 2021)

@Xcalibur255 @UntilThen well thank you gentlemen, I just don't want to push something mediocre out there, I don't expect a 6AS7G OTL will break new ground, but if I could make something pleasant and somewhat reasonably priced (while also being worth my time and effort), then I am happy to do it.  It will need to be done at some point anyway as I have a stash of 6AS7G/5998/6080 tubes burning a whole in my pocket.  We will see, I'm throwing the OTL and the EL34 SET on the To-Do List, we'll see how I feel about each project come springtime once these other personal projects are done.

LOL @UntilThen , yes Gwyn is a character from the video game Dark Souls, maybe you have heard of it.  I'm not much into video gaming these days, but if you can appreciate video games as works of art, Hidetaka Miyazaki from From Software has done some incredible work in terms of storytelling / gameplay mechanics in his games, my Head-Fi username is a reference to the character.  I originally made it as a satire of overwrought gamer tags, but it stuck!  Now I am L0rdGwyn forever.


----------



## UntilThen

L0rdGwyn said:


> @Xcalibur255 @UntilThen well thank you gentlemen, I just don't want to push something mediocre out there, I don't expect a 6AS7G OTL will break new ground, but if I could make something pleasant and somewhat reasonably priced (while also being worth my time and effort), then I am happy to do it.  It will need to be done at some point anyway as I have a stash of 6AS7G/5998/6080 tubes burning a whole in my pocket.  We will see, I'm throwing the OTL and the EL34 SET on the To-Do List, we'll see how I feel about each project come springtime once these other personal projects are done.
> 
> LOL @UntilThen , yes Gwyn is a character from the video game Dark Souls, maybe you have heard of it.  I'm not much into video gaming these days, but if you can appreciate video games as works of art, Hidetaka Miyazaki from From Software has done some incredible work in terms of storytelling / gameplay mechanics in his games, my Head-Fi username is a reference to the character.  I originally made it as a satire of overwrought gamer tags, but it stuck!  Now I am L0rdGwyn forever.



Remember the Auris Nirvana contender. That's a 10grand motherlode amp. If you can do the same wood and throw in a leather band, you're half way there.   Meanwhile what do think of my mid price amps to kick off 2021?  They are Questyle CMA Twelve and Violectric v280. The best of China and Germany.

This was Questyle statement product in 2017.
https://www.stereo.net.au/reviews/review-questyle-gold-stack-reference-system

I best remember Violectric for v281 but now they have 
https://headfonics.com/violectric-d...olectric DHA V590 is,It is priced at $3499.95.

They might be the pathway out of tube amps for me. Say goodbye to hiss and hum, zero noise floor and pitch perfect. 

Remember a lot of this is said in tongue in cheek but I'm half serious.


----------



## Xcalibur255 (Jan 2, 2021)

UntilThen said:


> I don't know what Gwyn-sama is but I'll go along as it will help me beat @bcowen score.
> 
> I googled and this is what I get.


On the 5% off chance you genuinely don't know, the -sama honorific in Japanese denotes great respect and is used when referrring to somebody of greatly superior social stature such as a...... Lord.    The images were the perfect reply though, be it on purpose or by accident.

I actually really dislike my username.  I'm one of those people who can't be clever about things like this and wish I could.  So I just fish out whatever generic crap my brain can churn up and feel bad about it afterward.


----------



## UntilThen

Xcalibur255 said:


> On the 5% off chance you genuinely don't know, the -sama honorific in Japanese denotes great respect and is used when referrring to somebody of greatly superior social stature such as a...... Lord.    The images were the perfect reply though, be it on purpose or by accident.
> 
> I actually really dislike my username.  I'm one of those people who can't be clever about things like this and wish I could.  So I just fish out whatever generic crap my brain can churn up and feel bad about it afterward.



Sama hahaha. I've been to Japan for a holiday with my family in 2010 but I don't know about sama. I do know arigato gozaimasu. That's about it and my favourite raimen soup.

Not sure why I chose UntilThen but it's a sign of my never ending quest for the next gear, particularly amp. Until maybe I leave Head-Fi. The day might come sooner than I know as I started enjoying golf more and learning not to hook or slice unless it's intentional !!! and that obligatory Hole in one of course. I shall return here as Tiger Woods.


----------



## Paladin79 (Jan 2, 2021)

Xcalibur255 said:


> I mean honestly we're the peanut gallery here.  It takes nothing for us to toss these suggestions out there.  It's your time, money and energy that's going into it so whatever interests you most is obviously the way to go.  Once you make one for somebody and sell it for the first time the floodgates will be open too so it's incumbent upon the rest of us here to be considerate and remember that you don't do this for a living (yet ).


My situation is different, I have spent over forty years in electronics and I have run my own company but now I am just trying to get back to some tube sounds I heard many years ago. I spent a lot of time with solid state but it just does not have the warmth and music appeal for me anymore. As far as OTL's, if done well, they can be remarkable. Some of my past work has been with power supply design and of course now I am GM for a company and I specialize in custom work for them, much of it involving high end wire. I only do point to point wiring and have access to some amazing components including tubes. As far as design, I have never paid a lot of attention to what others have done, I tend to think for myself. Today's EE's are taught to work as a team but it was different for me in college and so I can work on my own. Electronics is easy for me but I need goals and learning woodworking makes a nice way to combine the two. I do little things like this to keep my hand in when not building amps.

Oh and the floodgates did open for me on the Incubus amp and I hope to build a few more soon. I should note that it is not about the money so much for me, I gifted seven of them including one to @bcowen for his kindness in sharing tubes with me. It can have drawbacks but for the most part it has been a fun experience. The Incubus really shows off 6sn7 sound and I can pick out tube noise I do not hear in other amps but it was designed that way. Four will be used in a 6sn7 equivalent blind challenge including 6j5's, 7a4's, et alia.


----------



## whirlwind

L0rdGwyn said:


> I hear you, for headphones OTL is a natural starting point.  I'll give it some thought, in either case I would need to build something first and give it a listen before moving forward.  Maybe I will try out some OTL ideas rather than going straight to the EL34 SET, I am open to that.



I vote for the EL34 Set    
Just kiddin'...I love all of your projects.


----------



## bcowen

L0rdGwyn said:


> @Xcalibur255 @UntilThen well thank you gentlemen, I just don't want to push something mediocre out there, I don't expect a 6AS7G OTL will break new ground, but if I could make something pleasant and somewhat reasonably priced (while also being worth my time and effort), then I am happy to do it.  It will need to be done at some point anyway as I have a stash of 6AS7G/5998/6080 tubes burning a whole in my pocket.  We will see, I'm throwing the OTL and the EL34 SET on the To-Do List, we'll see how I feel about each project come springtime once these other personal projects are done.



There's one big hole in the current 6AS7/OTL market: one that will play well with low impedance 'phones.  Even silly-low like the 13 ohm DCA Aeons.  Now *that* would be cool.  I'm too ignorant on the design side to know if that's even possible and maybe that's why the hole exists....but it _would_ be cool.


----------



## Paladin79 (Jan 2, 2021)

bcowen said:


> There's one big hole in the current 6AS7/OTL market: one that will play well with low impedance 'phones.  Even silly-low like the 13 ohm DCA Aeons.  Now *that* would be cool.  I'm too ignorant on the design side to know if that's even possible and maybe that's why the hole exists....but it _would_ be cool.


Hell's ducks man, buy some different headphones will ya???  What are Ripper's like 20 ohms or such and he runs them on the incubus lol.

By the way, the amp formerly known as Cowen is on its maiden voyage. It works first time but I need to experiment with driver tubes lol.


----------



## Tjj226 Angel

bcowen said:


> There's one big hole in the current 6AS7/OTL market: one that will play well with low impedance 'phones.  Even silly-low like the 13 ohm DCA Aeons.  Now *that* would be cool.  I'm too ignorant on the design side to know if that's even possible and maybe that's why the hole exists....but it _would_ be cool.



Assuming you run each triode section of a 6as7g at 100ma, you would need two tubes in parallel for the Aeons to hit 110db peaks. 

If you want to hit 120b peaks, you would need 8 6as7gs in parallel per channel. Soooooo yeahhhhh.


----------



## UntilThen

whirlwind said:


> I vote for the EL34 Set
> Just kiddin'...I love all of your projects.



I voted for Gwyn-sama or was it Lord Gwyn. And of course I voted for UntilThen.


----------



## UntilThen

Tjj226 Angel said:


> If you want to hit 120b peaks, you would need 8 6as7gs in parallel per channel. Soooooo yeahhhhh.



I would love that. Watching the glow will be my Winter pastime. That and I can use my 8 x Svetlana 6h13c. Dirty and cheap. How about 8 x Fotons?


----------



## leftside

Paladin79 said:


> My situation is different, I have spent over forty years in electronics and I have run my own company but now I am just trying to get back to some tube sounds I heard many years ago. I spent a lot of time with solid state but it just does not have the warmth and music appeal for me anymore. As far as OTL's, if done well, they can be remarkable. Some of my past work has been with power supply design and of course now I am GM for a company and I specialize in custom work for them, much of it involving high end wire. I only do point to point wiring and have access to some amazing components including tubes. As far as design, I have never paid a lot of attention to what others have done, I tend to think for myself. Today's EE's are taught to work as a team but it was different for me in college and so I can work on my own. Electronics is easy for me but I need goals and learning woodworking makes a nice way to combine the two. I do little things like this to keep my hand in when not building amps.
> 
> Oh and the floodgates did open for me on the Incubus amp and I hope to build a few more soon. I should note that it is not about the money so much for me, I gifted seven of them including one to @bcowen for his kindness in sharing tubes with me. It can have drawbacks but for the most part it has been a fun experience. The Incubus really shows off 6sn7 sound and I can pick out tube noise I do not hear in other amps but it was designed that way. Four will be used in a 6sn7 equivalent blind challenge including 6j5's, 7a4's, et alia.


Great to see posts like these. Nice work.



whirlwind said:


> I vote for the EL34 Set


Incoming for me from Mischa 



bcowen said:


> There's one big hole in the current 6AS7/OTL market: one that will play well with low impedance 'phones.  Even silly-low like the 13 ohm DCA Aeons.  Now *that* would be cool.  I'm too ignorant on the design side to know if that's even possible and maybe that's why the hole exists....but it _would_ be cool.


That would be tricky...



Paladin79 said:


> Hell's ducks man, buy some different headphones will ya???


Agreed


----------



## leftside

Tjj226 Angel said:


> Assuming you run each triode section of a 6as7g at 100ma, you would need two tubes in parallel for the Aeons to hit 110db peaks.
> 
> If you want to hit 120b peaks, you would need 8 6as7gs in parallel per channel. Soooooo yeahhhhh.


6 6AS7G (or 5998) in my amp. @A2029 why didn't we do 8?! I'm sending it back for some mods haha


----------



## UntilThen

leftside said:


> Incoming for me from Mischa



That I have to see. A Auris Nirvana contender I hope.  https://audiosolace.com/2020/02/22/auris-audio-nirvana-amplifier-review/

An unforgettable experience listening to LCD-4 and Nirvana. Chocolatey syrup of the best kind.


----------



## leftside (Jan 2, 2021)

UntilThen said:


> That I have to see. A Auris Nirvana contender I hope.  https://audiosolace.com/2020/02/22/auris-audio-nirvana-amplifier-review/
> 
> An unforgettable experience listening to LCD-4 and Nirvana. Chocolatey syrup of the best kind.


What happened to the Oblivion? I really like the look of that amp.

The Auris looks nice. I just took a quick look. But, I'm sure the custom amp builders on here can build better for cheaper. No marketing or sales costs...

This is a nice feature: "The first dial allows users to select from a range of impendences to match the transducer of their choice and goes from 30 ohms all the way to 600 ohms. This allows the amplifier to work well with a plethora of headphones including the hard to drive 600 ohm Beyerdynamic DT 990 headphones". I wonder if any comprises would have been made to enable such a feature? Perhaps the amp builders on here would know?


----------



## UntilThen

leftside said:


> What happened to the Oblivion? I really like the look of that amp.
> 
> The Auris looks nice. I just took a quick look. But, I'm sure the custom amp builders on here can build better for cheaper. No marketing or sales costs...



The Oblivion is right here. Sonic just showed me pictures of his forthcoming Infinity of around 8 to 10 watts minimum driving efficient speakers and any headphones and it looks imposing and awesome. He will be posting pictures on his thread soon when he has finish it, on this Oblivion thread. Very nice chap Sonic is.

Wireless !  



My New Year's Eve setup   Complimentary cocktail.


----------



## leftside

UntilThen said:


> The Oblivion is right here. Sonic just showed me pictures of his forthcoming Infinity of around 8 to 10 watts minimum driving efficient speakers and any headphones and it looks imposing and awesome. He will be posting pictures on his thread soon when he has finish it, on this Oblivion thread. Very nice chap Sonic is.
> 
> Wireless !


Very nice!

From my notes with Mischa I see that you can get output transformers with multiple secondaries (e.g. 16, 32, 64, 128, & 300 ohm, etc), so that's what they are probably doing with the Auris. This will be a 2-4 month wait from Sowter to build such a custom transformer for my amp.


----------



## UntilThen

leftside said:


> Very nice!
> 
> From my notes with Mischa I see that you can get output transformers with multiple secondaries* (e.g. 16, 32, 64, 128, & 300 ohm, etc), so that's what they are probably doing with the Auris. *This will be a 2-4 month wait from Sowter to build such a custom transformer for my amp.



Yes on the Nirvana, there are 3 knobs on the top. Left to right:- impedance switch (32, 64, 128, 300 and I think 600 too), Volume and lastly gain switch I think... can't remember clearly now. I've heard quite a few different setups since LCD-4 and Nirvana.

I'm sure Mischa will turn out an outstanding EL34 amp for you.


----------



## L0rdGwyn

Can't spend much time on here today, maybe someone else can answer in detail, but yes, they are using multiple secondary taps on the output transformers to match the headphone impedances.  This is pretty standard with SET designs made for headphones.

Glad to hear you went with Sowter @leftside , it will be worth the wait.


----------



## Tjj226 Angel

You know what guys, here is a question for all of you. 

I am working on a speaker amp that is hopefully going to go into production. 

The problem is that it is COMPLETELY balanced from input to output. The only way you can use it with headphones is if the headphones are wired to be balanced. You can't use a single ended to balanced adapter. The headphones have to have 4 individual conductors going to the amp. Otherwise your headphones, the amp, or both might go up in smoke. 

Would that restriction be a turn off or a turn on?


----------



## UntilThen

L0rdGwyn said:


> Glad to hear you went with Sowter @leftside , it will be worth the wait.



What's wrong with Lundahl? Not good enough? I know I know there will always be better.


----------



## UntilThen

Tjj226 Angel said:


> You know what guys, here is a question for all of you.
> 
> I am working on a speaker amp that is hopefully going to go into production.
> 
> ...



Hmmm I sure wouldn't want to turn that on with my Hekse but all Hekse needs is my iPod mini !  Kidding! Hekse maybe sound good with that tiny device but it sound great properly amped.


----------



## L0rdGwyn

UntilThen said:


> What's wrong with Lundahl? Not good enough? I know I know there will always be better.



I like Lundahl, I have their MC SUT in my phono stage and LL1620 OPT in my 6A5G SET, but since a large portion of their transformer line are made with the flexibility to wire for multiple turns ratios / secondary impedances, that comes with compromises i.e. transformer parasitics leading to bandwidth limitations and ringing.  Custom transformers are a step up in quality as they will be optimized for a specific design.


----------



## bcowen

Tjj226 Angel said:


> You know what guys, here is a question for all of you.
> 
> I am working on a speaker amp that is hopefully going to go into production.
> 
> ...



You'll have to humor me first and give me a quick education on 'balanced' as it applies to headphones.  Is that simply a matter of L+, L-, R+, and R- each having a separate connection at the amp (phone jack) end?  With a typical (single-ended?) setup the L- and R- are tied together at the phone jack.  Am I on the right track here, or is there more to it?


----------



## UntilThen

bcowen said:


> You'll have to humor me first and give me a quick education on 'balanced' as it applies to headphones.  Is that simply a matter of L+, L-, R+, and R- each having a separate connection at the amp (phone jack) end?  With a typical (single-ended?) setup the L- and R- are tied together at the phone jack.  Am I on the right track here, or is there more to it?



You took the question out of my mouth. Thanks for asking on my behalf.


----------



## Zachik

Tjj226 Angel said:


> You know what guys, here is a question for all of you.
> 
> I am working on a speaker amp that is hopefully going to go into production.
> 
> ...


For me, it is neither a turn off nor turn on - most of my headphones have balanced cable with detachable adapter for SE amps.
What about the amp's inputs? I only have SE DACs, so balanced-only amp *inputs* could be a showstopper for me...


----------



## Tjj226 Angel

bcowen said:


> You'll have to humor me first and give me a quick education on 'balanced' as it applies to headphones.  Is that simply a matter of L+, L-, R+, and R- each having a separate connection at the amp (phone jack) end?  With a typical (single-ended?) setup the L- and R- are tied together at the phone jack.  Am I on the right track here, or is there more to it?



Yeup. 

Basically you have to have a true 4 pin XLR cable. You can't adapt the cable in any way.


----------



## L0rdGwyn

I am expecting big things from these, 5K:8ohm single secondary OPT for my 801A amp.  Dying to get this thing finished, but winter weather is slowing things down.


----------



## Tjj226 Angel

Zachik said:


> For me, it is neither a turn off nor turn on - most of my headphones have balanced cable with detachable adapter for SE amps.
> What about the amp's inputs? I only have SE DACs, so balanced-only amp *inputs* could be a showstopper for me...



Single ended or balanced input via an input transformer.


----------



## bcowen

Tjj226 Angel said:


> Yeup.
> 
> Basically you have to have a true 4 pin XLR cable. You can't adapt the cable in any way.



OK, then I'd just need a new HP cable so the balanced headphone situation would not be a show stopper _for me._


----------



## L0rdGwyn

Here is a interesting audio tube that I have mentioned before, E55L / 8233.  These were made by Mullard with Amperex branding.

When triode strapped, you end up with a very linear triode with a mu of 30 and a plate resistance of 600ohms, perfect driver for a two-stage amplifier or even a spud with high-efficiency speakers.


----------



## bcowen

UntilThen said:


> You took the question out of my mouth. Thanks for asking on my behalf.



Uh-oh.  We're starting to think alike?  This is a truly frightening development.....for you.


----------



## UntilThen

bcowen said:


> Uh-oh.  We're starting to think alike?  This is a truly frightening development.....for you.


----------



## Tjj226 Angel

L0rdGwyn said:


> Here is a interesting audio tube that I have mentioned before, E55L / 8233.  These were made by Mullard with Amperex branding.
> 
> When triode strapped, you end up with a very linear triode with a mu of 30 and a plate resistance of 600ohms, perfect driver for a two-stage amplifier or even a spud with high-efficiency speakers.



NO NO NO SHHHHHHHHHHHHHHHH They are already too expensive.


----------



## Paladin79

Tjj226 Angel said:


> Yeup.
> 
> Basically you have to have a true 4 pin XLR cable. You can't adapt the cable in any way.


I do not like swapping cables so I use four pin mini xlrs and pigtails. I can go to 3.5 mm or 1/4 inch TRS our four pin full size XLR quickly, and without constant plugging and unplugging on the headphone cup end. I have some separate class A amps I run and I can do a splitter to those as well.


----------



## L0rdGwyn

Tjj226 Angel said:


> NO NO NO SHHHHHHHHHHHHHHHH They are already too expensive.



ERR I mean, these are horrible no good tubes, low plate resistance and linearity is actually BAD, this is what you don't want...

Here are the curves for the D3a, another interesting audio pentode when triode strapped.  I was told these were going to oscillate in the etracer without grid stopper installed, but I didn't have an issue with it.  As I've said probably a million times, these are the input tubes in my phono stage, very nice.


----------



## bcowen

L0rdGwyn said:


> ERR I mean, these are horrible no good tubes, low plate resistance and linearity is actually BAD, this is what you don't want...
> 
> Here are the curves for the D3a, another interesting audio pentode when triode strapped.  I was told these were going to oscillate in the etracer without grid stopper installed, but I didn't have an issue with it.  As I've said probably a million times, these are the input tubes in my phono stage, very nice.



Do you have any CV4079's (GEC A2293) to trace?


----------



## L0rdGwyn

bcowen said:


> Do you have any CV4079's (GEC A2293) to trace?



I will in 2-3 weeks


----------



## Xcalibur255

bcowen said:


> There's one big hole in the current 6AS7/OTL market: one that will play well with low impedance 'phones.  Even silly-low like the 13 ohm DCA Aeons.  Now *that* would be cool.  I'm too ignorant on the design side to know if that's even possible and maybe that's why the hole exists....but it _would_ be cool.


A hybrid design could probably get it done if you don't mind an amp that isn't 100% tube output.  I think people do overthink the whole concept of low impedance headphones not being compatible with OTLs though.  It's true to some extent but it's gear dependent.  I also think in a lot of cases people don't even *try* it and if they did sometimes they might discover it sounds just fine.  I have an Ether and I don't think it sounds bad on my GOTL.  The bass is a bit soft but I think it's still beating the transformer coupled Inspire IHA-1 on that front (in fairness many amps do, bass is THE weakness of the IHA-1).


----------



## Zachik

L0rdGwyn said:


> Dying to get this thing finished, but winter weather is slowing things down


Why can't you work inside the house?
Not as comfy as the garage, I imagine, but most people (I think) do not have a dedicated "lab" or work area...


----------



## UntilThen

bcowen said:


> Do you have any CV4079's (GEC A2293) to trace?



Do you have any Telefunken EL11 or EL12 spez to trace? I'm planning to trade my EL tubes for a Pacific island.


----------



## Xcalibur255 (Jan 2, 2021)

Tjj226 Angel said:


> You know what guys, here is a question for all of you.
> 
> I am working on a speaker amp that is hopefully going to go into production.
> 
> ...


For me personally?  Yes it would be a turn off.  Nothing I have is balanced and never will be.  This is one of those divisive topics in the audiophile community.  Some people absolutely swear by it and think it performs miracles for their sound and others think it's completely pointless unless you're doing 300 foot cable runs to a studio stage.  I'm sure there are advantages to the whole signal chain being balanced from end to end but you'd have to plan and re-do your entire system around that.


----------



## UntilThen

I am with Xcalibur but I still like my balance cable. They are nice(r).


----------



## Galapac

Tjj226 Angel said:


> Yeup.
> 
> Basically you have to have a true 4 pin XLR cable. You can't adapt the cable in any way.


4.4mm Pentaconn ok?


----------



## Galapac

UntilThen said:


> I am with Xcalibur but I still like my balance cable. They are nice(r).


I think balanced gives you a bigger bump when driving headphones.


----------



## Tjj226 Angel

Xcalibur255 said:


> For me personally?  Yes it would be a turn off.  Nothing I have is balanced and never will be.  This is one of those divisive topics in the audiophile community.  Some people absolutely swear by it and think it performs miracles for their sound and others think it's completely pointless unless you're doing 300 foot cable runs to a studio stage.  I'm sure there are advantages to the whole signal chain being balanced from end to end but you'd have to plan and re-do your entire system around that.



I totally get that. This is not a balanced amp for the sake of being balanced. Here is a super simplified circuit. (Oh and if anyone wants to use this for DIY purposes, you are more than welcome to. This part of what I am showing you is not a new idea. It's just a bridged amp.)

Basically what I have done is made a speaker amp, and I am asking you guys if it is even worth it to slap a 4 pin XLR on the front of the chassis. This thing is going to be 25W class A per channel and 100W as a mono block. 

The outputs are designed in such a way that they work really well for speaker drivers of any kind. But your headphones have to be wired as if they are speakers. Otherwise things will go sparky sparky boom boom and you will be mad at me : P


----------



## Galapac

Tjj226 Angel said:


> I totally get that. This is not a balanced amp for the sake of being balanced. Here is a super simplified circuit. (Oh and if anyone wants to use this for DIY purposes, you are more than welcome to. This part of what I am showing you is not a new idea. It's just a bridged amp.)
> 
> Basically what I have done is made a speaker amp, and I am asking you guys if it is even worth it to slap a 4 pin XLR on the front of the chassis. This thing is going to be 25W class A per channel and 100W as a mono block.
> 
> The outputs are designed in such a way that they work really well for speaker drivers of any kind. But your headphones have to be wired as if they are speakers. Otherwise things will go sparky sparky boom boom and you will be mad at me : P


That reminds me of my SPL SS amp. You cannot plug in an SE without the volume turned down all the way or you can blow the amp. They have a disclaimer in the manual but people have done it, lol. It  Has a balanced input but you can plug in with no issue, no matter the volume.


----------



## L0rdGwyn

Zachik said:


> Why can't you work inside the house?
> Not as comfy as the garage, I imagine, but most people (I think) do not have a dedicated "lab" or work area...



Unfortunately, there isn't really a practical place to work in my house, and it is 25F in my garage!  I can work out there with some heaters, but leaving certain components out in freezing temperatures is out of the question.  If I were to downsize the "prototyping board" (aka a piece of plywood and a giant heatsink), I could bring it in and out as needed, although it would be a hassle...

Once the two amps I'm working on are done, I'll probably come up with a solution to work on the 801A design before the winter ends.  Necessity is the mother of invention after all.



UntilThen said:


> Do you have any Telefunken EL11 or EL12 spez to trace? I'm planning to trade my EL tubes for a Pacific island.



I do not, although the curves of the EL11 are available in the EL3 datasheet.  Would be interesting to see the triode curves of the EL12 and/or EL12spez as they are not provided in the datasheets.


----------



## UntilThen

Galapac said:


> I think balanced gives you a bigger bump when driving headphones.



yes it does when it’s a balanced amp. I’ve experienced it in Ragnarok and Questyle CMA 12. In these amps it’s more forceful and louder when using the balance rather than the se connections.


----------



## bcowen

UntilThen said:


> Do you have any Telefunken EL11 or EL12 spez to trace? I'm planning to trade my EL tubes for a Pacific island.



No.  I'm allergic to pentodes.


----------



## Tjj226 Angel

bcowen said:


> No.  I'm allergic to pentodes.



Nah. You are just allergic to pentode amps that use crappy screen supplies.


----------



## whirlwind

UntilThen said:


> I am with Xcalibur but I still like my balance cable. They are nice(r).



I always like having a balanced cable to use, even on an amp that is not balanced, but still gives you the balanced jack , that way no need for adapters.


----------



## whirlwind

L0rdGwyn said:


> I am expecting big things from these, 5K:8ohm single secondary OPT for my 801A amp.  Dying to get this thing finished, but winter weather is slowing things down.



I thought once you could not get in the garage because of winter, this thread would really slow down.
I have learned that my slow down and your  slow down are two different things.
I mean this in a very cool kind of way....you go brother!     

This thread rocks


----------



## UntilThen

bcowen said:


> No.  I'm allergic to pentodes.



When I had the Primaluna Dialogue Premium Dialogue HP, there is a switch for triode or ultra linear mode. I would prefer the sweet warm of the triode mode but occasionally I would switch to the wide bandwidth of the ultra linear mode and became one with the orchestra itself. I'm the conductor !


----------



## UntilThen

whirlwind said:


> This thread rocks



It rocks because topics could change at the speed of lightning, from Auris pretender to pentodes, to triodes, to eTracer, to custom amps, to funny jokes. 

Mostly it rocks because we all want to see Lord Qwyn .... I mean what his next creation is going to be.


----------



## whirlwind (Jan 2, 2021)

UntilThen said:


> It rocks because topics could change at the speed of lightning, from Auris pretender to pentodes, to triodes, to eTracer, to custom amps, to funny jokes.
> 
> Mostly it rocks because we all want to see Lord Qwyn .... I mean what his next creation is going to be.



Topics can change, but it is Keenan's energy and his love for experimenting and learning on the fly that make this one of my favorite threads on head-fi.
You have to love what you are doing to go on at this pace and it is a wonderful thing to see happening and especially if you are one who favors custom stuff over the stuff you buy off the shelf.


----------



## L0rdGwyn (Jan 2, 2021)

whirlwind said:


> I thought once you could not get in the garage because of winter, this thread would really slow down.
> I have learned that my slow down and your  slow down are two different things.



You got that right, I keep saying I am going to slow down and things keep speeding up!  Oh well gotta fill the hours somehow.  Big game tomorrow, BTW 



UntilThen said:


> Mostly it rocks because we all want to see Lord Qwyn .... I mean what his next creation is going to be.



If these dang chassis would get here from Texas, I could put together these two amplifiers, althought one is a rehash of an old design.  Actually just checked tracking, could get here early next week if they aren't held up in Cleveland, hooray!


----------



## UntilThen

L0rdGwyn said:


> If these dang chassis would get here from Texas, I could put together these two amplifiers, althought one is a rehash of an old design. Actually just checked tracking, could get here early next week if they aren't held up in Cleveland, hooray!



That makes 2 of us looking forward to next week. You get to work on your creation and I get the German tiger tank in the Violectric v280. Should have bought 2. One to drive each channel.


----------



## bcowen

UntilThen said:


> When I had the Primaluna Dialogue Premium Dialogue HP, there is a switch for triode or ultra linear mode. I would prefer the sweet warm of the triode mode but occasionally I would switch to the wide bandwidth of the ultra linear mode and became one with the orchestra itself. I'm the conductor !



The pentode thing was mostly a joke, but @Tjj226 Angel is correct that I've heard some crappy pentode designs.

The Cary V12i monos were some non-crappy pentode amps that also had that triode/ultralinear switch thing, and in fact you could switch each quad of output tubes independently. So you could go 1/3 triode, 2/3rd's ultralinear, or 2/3rds triode, 1/3 ultralinear, etc per amp. Honestly that particular "feature" was at best gimmicky and pretty much worthless as the amps didn't sound right unless they were in full triode or full ultralinear.  I much preferred triode for normal listening, but with 200 watts/side of tube power in ultralinear into 94 dB sensitive speakers with bass that was pretty flat into the mid-20's it was fun at times to redefine the term "pissing off the neighbors."


----------



## UntilThen

bcowen said:


> I much preferred triode for normal listening, but with 200 watts/side of tube power in ultralinear into 94 dB sensitive speakers with bass that was pretty flat into the mid-20's it was fun at times to redefine the term "pissing off the neighbors."



For me it was 'bringing down the house' in ultra linear that gave me the most satisfaction. When the insurance man came to assess the damage, he couldn't figure out what had just happened. I pointed to the switch and explain never to set it to ultra linear because triode is what you want and ultra linear is BOOM. 

He sign the papers and I got a new house. Now I'm itching to try the ultra linear mode again.......


----------



## bcowen

UntilThen said:


> For me it was 'bringing down the house' in ultra linear that gave me the most satisfaction. When the insurance man came to assess the damage, he couldn't figure out what had just happened. I pointed to the switch and explain never to set it to ultra linear because triode is what you want and ultra linear is BOOM.
> 
> He sign the papers and I got a new house. Now I'm itching to try the ultra linear mode again.......



Wow.  What headphones were you using?


----------



## UntilThen

bcowen said:


> Wow.  What headphones were you using?



Beats


----------



## Xcalibur255

Tjj226 Angel said:


> I totally get that. This is not a balanced amp for the sake of being balanced.



I know you wouldn't pursue it just because of it's audiophile buzzword value.  It's either an elegant solution to a problem, a way to get parts out of the signal chain, or both and I'm sure it will work great.  For me, an amp like that would require a lot of investment because it would mean a new DAC and new cables so the total dollar investment would be a pretty big barrier to entry.  That's all I was weighing in on, as I'm sure there are other people out there like me who will view it through that lens.


----------



## Galapac

UntilThen said:


> For me it was 'bringing down the house' in ultra linear that gave me the most satisfaction. When the insurance man came to assess the damage, he couldn't figure out what had just happened. I pointed to the switch and explain never to set it to ultra linear because triode is what you want and ultra linear is BOOM.
> 
> He sign the papers and I got a new house. Now I'm itching to try the ultra linear mode again.......


Did you get into the “special” sauce again?


----------



## Xcalibur255

bcowen said:


> The pentode thing was mostly a joke, but @Tjj226 Angel is correct that I've heard some crappy pentode designs.
> 
> The Cary V12i monos were some non-crappy pentode amps that also had that triode/ultralinear switch thing, and in fact you could switch each quad of output tubes independently. So you could go 1/3 triode, 2/3rd's ultralinear, or 2/3rds triode, 1/3 ultralinear, etc per amp. Honestly that particular "feature" was at best gimmicky and pretty much worthless as the amps didn't sound right unless they were in full triode or full ultralinear.  I much preferred triode for normal listening, but with 200 watts/side of tube power in ultralinear into 94 dB sensitive speakers with bass that was pretty flat into the mid-20's it was fun at times to redefine the term "pissing off the neighbors."



From what I understand of ultraliner the key to making it work is having the transformers optimized for it, so a feature like this seems dubious to me, but I'm not an expert either.

I asked myself more than once if it would be worth it to ask for a triode/pentode mode switch in my upcoming amp from Mischa, but for me switches like that are OCD fuel and I've learned to avoid them.  That, and the more switches and knobs an amp has the less optimized it is for doing one thing well, and I'm a big fan of things that are pure of purpose and do their one thing very well.


----------



## UntilThen

Xcalibur what amp are you getting from Mischa. Mind sharing?


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## johnjen (Jan 3, 2021)

Xcalibur255 said:


> I know you wouldn't pursue it just because of it's audiophile buzzword value.  It's either an elegant solution to a problem, a way to get parts out of the signal chain, or both and I'm sure it will work great.  For me, an amp like that would require a lot of investment because it would mean a new DAC and new cables so the total dollar investment would be a pretty big barrier to entry.  That's all I was weighing in on, as I'm sure there are other people out there like me who will view it through that lens.


Just as a casual aside…
You can run unbalanced into any balanced input, and it's usually not that big a deal.

And the outputs to speakers are automagically 'balanced', well unless there are additional circuits on the outputs that 'unbalance' these signals.
So as an experiment you could run any balanced power amp from an unbalanced signal source. providing said source could deliver the necessary input voltage to drive the amp to full power.

The one thing I rely upon is that the audio signal does NOT ride on chassis ground, as in, standard rca jack wiring.
Instead it is a differential signal.

And while this can 'complicate' setups, it also isolates and floats the audio signal so it is more independent from the signals that ground carries.
And EVERY circuit uses ground as 'the return path' for ALL of it's electronic and electrical functions.

Is this a 'must do' sorta thing?
No, not really, unless you are deliberately exploring the edges of the performance envelope.

In which case, those signals being well below 'normal' audibility, are being addressed and the changes that occur are being noted.
This is 'territory' that unbalanced is unable to travel because it uses ground as it is directly tied to the signal path coming in and going out of the amp.

But then again for most folks this is an audiophool rabbit hole that only those 'brave/phoolhardy enough to even want to venture into, would even look in this direction in the first place.

And of course there is the bling and schnaub factors, but those don't count, right?
hahahahahahaahahahahahahahahahahaa   

JJ


----------



## Tjj226 Angel

Xcalibur255 said:


> I know you wouldn't pursue it just because of it's audiophile buzzword value.  It's either an elegant solution to a problem, a way to get parts out of the signal chain, or both and I'm sure it will work great.  For me, an amp like that would require a lot of investment because it would mean a new DAC and new cables so the total dollar investment would be a pretty big barrier to entry.  That's all I was weighing in on, as I'm sure there are other people out there like me who will view it through that lens.



I definitely hear you, but it is worth mentioning that on my design, I do actually have an input transformer. 

Some balanced amps on the market require you to use balanced inputs as well as balanced outputs. Mine would simply require balanced outputs which would mean a different headphone cable. You could still use the same dac and interconnects without any issue and the transformer would take care of the rest. I would never design something that would force people to upend their whole audio chain. 

The question should maybe be rewritten to...."is rewiring your headphones a deal breaker".


----------



## Tjj226 Angel

@L0rdGwyn 

One thought comes to me with your tube tracer. Try making an adapter to parallel some tubes together and trace it. We have all been told that paralleling tubes should just halve the plate impedance, but does it? Does linearity really stay the same? Maybe it gets worse. Or maybe it gets better. Maybe it's tube dependent. 

I feel like that would be a super interesting line of research.


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## Xcalibur255 (Jan 3, 2021)

UntilThen said:


> Xcalibur what amp are you getting from Mischa. Mind sharing?



6J5 to KT150 for driving speakers.  Nothing super exotic or ambitious.  I decided on the KT150 because I have heard that, when implemented well as a triode, its performance comes close enough to a 300B that I shouldn't actually miss having 300B.  That's the idea anyway.  It also has the advantage of having better power output than a 300B even in a triode strapped single-ended application, and the 6J5 will be a good driver for it.  I really wanted to use 6J5 this time, and while you *can* use it with 300B I understand it's not ideal.  If I understand correctly using a CCS gets around the miller capacitance issue, but in the end the amp would probably only be making 5-6 watts because the 6J5 can't drive the 300B to full output.

This amp is a replacement for my Luxman SQ-N150.  Primarily because of the weird problem I have with it causing heavy distortion in whatever other amp it shares the DAC with.  I'm really tired of having to unplug the RCA jacks from it whenever I want to use the headphone amp.  I'm honestly pretty happy with how the Luxman sounds, it pairs quite well with the Omega speakers IMO.  I think the KT150 amp will outperform the Luxman though, particularly since I'm throwing a fair bit of money at the output transformers for it.  I'm hoping for a sound that's a little wetter and lusher than the Luxman with a bit more body and weight.  If it is also more resolving that would be a big win too but I could live with a break-even on that front.  As long as instrument timbres are realistic I'm happy on that front.  Since I'm making a move from an ultralinear topology to an SET one I think I'll get what I'm hoping for from the KT150.  I think the Luxman being EL84 is really what saves it from coming off as dry with its ultralinear topology.  The EL84 brings enough "cheerfulness" to the table to give the amp a nice tonal character.


----------



## UntilThen

Xcalibur255 said:


> I'm hoping for a sound that's a little wetter and lusher than the Luxman with a bit more body and weight. If it is also more resolving that would be a big win too but I could live with a break-even on that front.



Very succinctly put. Wetter, lusher, body and weight and resolving is what I hear from the Auris Nirvana through LCD-4. I'm still wet in my eyes just thinking about it. 

So this is driving your speakers? Is it also for headphones? Most of us are interested in a speakers + headphones usage. 

When I had the Primaluna Dialogue Premium HP, I was running 12ax7s and 8 x KT88s. Was almost on the verge of spending another $800 for a set of 8 x new issue Tung Sol KT150. Does your amp use a pair of KT150 or quad? Looks interesting. Can't wait to see the result and your impressions.


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## Xcalibur255 (Jan 3, 2021)

Actually, yes, it will have a 1/4" headphone jack too.  I originally wanted it to be speaker only, after all it would be sitting across the desk from an already great Glenn 45 SET headphone amp.  Sadly, though, the G45 is acting up again after my move and isn't sounding right so I decided it would be wise to make the KT150 a dual purpose amp.  Mischa thinks it will perform very well as a headphone amp.  It certainly won't lack for power, even with some being lost in the name of load impedance matching for the transformers.

The other option I asked for was a two position bias switch for KT150 and EL34.  I think a popular way to go with amps like this is to make them swiss army knives that can run EL34, 6L6, KT88, KT120, etc. and that wasn't my intention.  I was going to have it be exclusively a KT150 amp, but since I have never actually HEARD the tube before I started thinking it might be wise to give myself something to turn to that would offer a different flavor.  EL34s are warm and a known quantity so it seemed logical.  However, I fully expect to like the way the amp sounds in KT150 mode and will probably never use the EL34 option because it would offer only 1/3 the output power of the KT150 and will likely suffer from reduced transparency and resolving ability since the EL34 will have a lot more 2nd order harmonic distortion.  Some 2nd order is fine and actually probably very good for the sound I'm looking for, but there is such a thing as too much.  But the option will be there and it doesn't cost much to add it.  What matters most to me is that the operating points for the tubes are optimal.  I've seen a number of "universal" amps that let you roll all these output tubes and they basically run a single generic operating point that is a compromise and doesn't allow any one tube type to actually sound its best.  IMO that's a bad trade, to give up a single great sound so you can choose between a dozen mediocre ones instead.  Of course I've also heard there are better ways to implement this so all the tubes sound good, but having tons of choices is an OCD thing for me so I'm limiting things to 2 tube types even if more could be made to sound their best.

This is a custom build and not a part of Mischa's standard offerings.  If it turns out well I'm sure he would build another one for somebody, though I imagine some people might find the build cost a bit much for an amp that "only" uses a strapped pentode.  I decided that really good transformers was important to maximize the potential of the KT150 idea so I'm fine with it, but I could see somebody else opting for a slightly more conservative version of this build idea.

What other details....... oh, the amp is single ended so you're dealing with just four tubes.  2 x 6J5 and 2 x KT150 (or EL34).  It won't be using a tube rectifier.  So the tubing/operating cost will be pretty good with this amp.  I think that's the biggest problem with the PrimaLuna amps.  If you want to upgrade tubes there you're buying a bunch of them, though there are amps that are even worse of course.

Sorry for hijacking your thread Keenan!


----------



## UntilThen

Lol Keenan say I can talk anything as long as I call him Gwyn sama.

your choice is good. I think limiting it to KT150 and EL34 is all you need. With such an amp, you don’t really want to go nuts with tube rolling. It’s either sweet or it’s not.

interestingly the Nirvana can roll in KT88 too besides EL34. Someone did that and like the harder hitting KT88.


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## L0rdGwyn (Jan 3, 2021)

Tjj226 Angel said:


> @L0rdGwyn
> 
> One thought comes to me with your tube tracer. Try making an adapter to parallel some tubes together and trace it. We have all been told that paralleling tubes should just halve the plate impedance, but does it? Does linearity really stay the same? Maybe it gets worse. Or maybe it gets better. Maybe it's tube dependent.
> 
> I feel like that would be a super interesting line of research.



Great idea, the etracer has two outputs from each supply, so running two sections of a dual triode in parallel should be no problem.  I have a 6J5 to 6SN7 adapter hiding somewhere too, I'll try to find a reasonably matched pair of 6J5 in my collection for comparison.

@Xcalibur255 @UntilThen honestly guys, talk about whatever you want!  This thread can be a place to talk all things DIY or any type of general discussion, no qualms on my part.  Like I've said before, if the discussion moves away from DIY, you just might get interrupted by DIY shenanigan updates now and then  hijack away.

Having a chill Sunday morning with Glenn, and I don't mean @2359glenn .  It's not DIY, but my speaker stands from Sound Anchors should be arriving tomorrow, which I am pretty excited about.


----------



## Zachik

Update on my DIY NP integrated amp:
The kit for the 2nd phase of the project, the speaker amp section, has arrived early 



in fact, it arrived on Dec. 31 but I had couple busy days so never got to it...
Plan to start and finish the PCBs today. Not that many components!


----------



## L0rdGwyn

Alright @Tjj226 Angel , here is your first set of parallel triodes data.  Decided to go with the 6BX7 since it is directly related to something I am working on.



Here is a Toshiba 6BX7GT, single triode curves first, both sections overlaid.



Now I have connected both plates to the same HV supply rather than the two separate supplies to parallel the triodes.



As expected, the plate current is roughly doubled and the plate resistance is roughly halved, which can be seen on the curves as well.  Qualitatively, it _looks_ more linear, but the only way to say for sure would be to set up a common cathode amplifier stage and measure THD at equivalent operating points.


----------



## Tjj226 Angel

L0rdGwyn said:


> Alright @Tjj226 Angel , here is your first set of parallel triodes data.  Decided to go with the 6BX7 since it is directly related to something I am working on.
> 
> 
> 
> ...



VERY COOL!

I might save up for one of these..........or design my own.............why do I do this?


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## L0rdGwyn (Jan 3, 2021)

Tjj226 Angel said:


> VERY COOL!
> 
> I might save up for one of these..........or design my own.............why do I do this?



I know it is expensive, but it's a great product IMO!  Had my eye on it for a few months, it hasn't disappointed so far.

Edit: actually one thing I will say is the quality of some of the sockets is pretty poor, but they can be replaced.


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## Zachik

Quick question for the DIY-ers here:
I have read online somewhere that when soldering 3W resistors to a PCB, it is recommended to leave an air gap between the resistor and PCB. Reason: power resistors are getting hot and will (or might) discolor the PCB over time.

Do you guys also keep air gap, or do you solder it like normal 1/4W resistors with the body of the resistor (barely) touching the PCB? 
Would that discoloration, if happens, cosmetic only? or could it potentially cause a failure over time??


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## L0rdGwyn

Zachik said:


> Quick question for the DIY-ers here:
> I have read online somewhere that when soldering 3W resistors to a PCB, it is recommended to leave an air gap between the resistor and PCB. Reason: power resistors are getting hot and will (or might) discolor the PCB over time.
> 
> Do you guys also keep air gap, or do you solder it like normal 1/4W resistors with the body of the resistor (barely) touching the PCB?
> Would that discoloration, if happens, cosmetic only? or could it potentially cause a failure over time??



If I am putting a high-wattage resistor on a PCB, assuming I am expecting it to dissipate a decent amount of power, I float it above the PCB for better airflow and to get the heat away from the other components.


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## L0rdGwyn (Jan 3, 2021)

It's DIY of a different flavor, but I think it's still relevant: I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.  It's in pretty good physical condition other than some paint splotches on the underside, which shouldn't be an issue.  The bottom plate is metal so if I can't get it off, I might just strip it and repaint.  Obviously can't be seen, but I like to be thorough.  The bakelite itself is in great shape and will be thoroughly polished.

According to the seller, it turns on, lights up, but does not make sound, so will have to see what the issue is.  Could be as simple as replacing the tubes, could be a disaster (busted transformer, speaker driver).  Sort of a gamble, but this is the type of old deco style radio she is into, although it was made in the late 40s / early 50s.

Time to learn how one of these old radios works.


----------



## Galapac

L0rdGwyn said:


> It's DIY of a different flavor, but I think it's still relevant: I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.  It's in pretty good physical condition other than some paint splotches on the underside, which shouldn't be an issue.  The bottom plate is metal so if I can't get it off, I might just strip it and repaint.  Obviously can't be seen, but I like to be thorough.  The bakelite itself is in great shape and will be thoroughly polished.
> 
> According to the seller, it turns, lights up, but does not make sound, so will have to see what the issue is.  Could be as simple as replacing the tubes, could be a disaster (busted transformer, speaker driver).  Sort of a gamble, but this is the type of old deco style radio she is into, although it was made in the late 40s / early 50s.
> 
> Time to learn how one of these old radios works.


I always wanted one of those but what makes me pause is that I wouldn’t want to hear any newer music through it. I would want to listen to old radio shows and music to keep with the theme. Some big band music from the 1920’s/30’s would be ideal.


----------



## L0rdGwyn

Galapac said:


> I always wanted one of those but what makes me pause is that I wouldn’t want to hear any newer music through it. I would want to listen to old radio shows and music to keep with the theme. Some big band music from the 1920’s/30’s would be ideal.



Yeah I hear ya, doubt very much modern music will be played through this thing!  Cleveland has an excellent ad-free classical station that will probably get 80% of the air time.  Other than the college stations, FM stations around here are pretty mediocre IMO.  Haven't delved much into the AM stations, but I will now


----------



## UntilThen

L0rdGwyn said:


> I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.



Is that from @bcowen  attic?


----------



## Zachik

L0rdGwyn said:


> If I am putting a high-wattage resistor on a PCB, assuming I am expecting it to dissipate a decent amount of power, I float it above the PCB for better airflow and to get the heat away from the other components.


Thinking some more about it - I have 2 PCBs with that dilemma:
1. Current is less than 0.5A with 1R 3W resistors - so P = I^2*R = 0.25W. Not enough to cause any issue, and I am not even sure why the design calls for 3W resistors! Maybe deal with momentary spike when turning on the power??
2. Current approx 0.8A with 0.67 ohm resistors --> P = 0.8 * 0.8 * 0.67 = 0.43W. Still not going to be very hot, I don't think...

Conclusion: should not be too bad at all, and I should leave it as-is... do you agree @L0rdGwyn ?


----------



## L0rdGwyn (Jan 3, 2021)

Zachik said:


> Thinking some more about it - I have 2 PCBs with that dilemma:
> 1. Current is less than 0.5A with 1R 3W resistors - so P = I^2*R = 0.25W. Not enough to cause any issue, and I am not even sure why the design calls for 3W resistors! Maybe deal with momentary spike when turning on the power??
> 2. Current approx 0.8A with 0.67 ohm resistors --> P = 0.8 * 0.8 * 0.67 = 0.43W. Still not going to be very hot, I don't think...
> 
> Conclusion: should not be too bad at all, and I should leave it as-is... do you agree @L0rdGwyn ?



They are most likely overspecced so they stay cool.  You don't want to run the resistors anywhere near their rated wattage or they will get HOT!  You typically only want them to dissipate 1/4 of their rated wattage, maybe 1/3 tops but that is going to be a hot resistor.  Running a 3W resistor at 0.25W will be just fine, same goes for 0.43W, they shouldn't get too spicy, probably fine to leave them on the PCB but raising them up off of it even a little bit can't hurt.  Again, if there are any heat-sensitive components nearby, I would try to make some space between them otherwise they might be prone to drift or perhaps premature aging depending on the component.


----------



## bcowen (Jan 3, 2021)

UntilThen said:


> Is that from @bcowen  attic?



LOL!  No, but my wife got me this to _put_ in the attic.  The weight on that needle has to be measured in ounces, not grams.  I assume that lacquer discs were played on these things?  According to the serial number it was made in 1924, and the mainspring is still good...spins up and rotates pretty smoothly (but noisily).  Unfortunately I don't have any GE LP's to sacrifice in testing the sound quality.


----------



## L0rdGwyn

Zachik said:


> Conclusion: should not be too bad at all, and I should leave it as-is... do you agree @L0rdGwyn ?



Sorry I didn't see this last part @Zachik - I think it will be fine as is, especially if this was designed as a kit on diyAudio, they should have thought through these things already.


----------



## Tjj226 Angel

L0rdGwyn said:


> It's DIY of a different flavor, but I think it's still relevant: I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.  It's in pretty good physical condition other than some paint splotches on the underside, which shouldn't be an issue.  The bottom plate is metal so if I can't get it off, I might just strip it and repaint.  Obviously can't be seen, but I like to be thorough.  The bakelite itself is in great shape and will be thoroughly polished.
> 
> According to the seller, it turns on, lights up, but does not make sound, so will have to see what the issue is.  Could be as simple as replacing the tubes, could be a disaster (busted transformer, speaker driver).  Sort of a gamble, but this is the type of old deco style radio she is into, although it was made in the late 40s / early 50s.
> 
> Time to learn how one of these old radios works.



Just google Heterodyne radio. There are a couple of old army navy training videos out there that do a really good job of explaining how radio works. 

There is a super popular marantz radio that is hailed as being one of the best radios out there. It even has a tiny little oscilloscope tube in it to show you when you have locked onto a station. It's pretty cool. 

What I have learned about radios is that you definitely want to use SS crystals for the receiver section. Once you have your music signal demodulated from the carrier signal, you can use tubes from then on and get the best of both worlds.


----------



## Xcalibur255

L0rdGwyn said:


> It's DIY of a different flavor, but I think it's still relevant: I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.  It's in pretty good physical condition other than some paint splotches on the underside, which shouldn't be an issue.  The bottom plate is metal so if I can't get it off, I might just strip it and repaint.  Obviously can't be seen, but I like to be thorough.  The bakelite itself is in great shape and will be thoroughly polished.
> 
> According to the seller, it turns on, lights up, but does not make sound, so will have to see what the issue is.  Could be as simple as replacing the tubes, could be a disaster (busted transformer, speaker driver).  Sort of a gamble, but this is the type of old deco style radio she is into, although it was made in the late 40s / early 50s.
> 
> Time to learn how one of these old radios works.


I love art deco and gothic design.  Literally everything looked more interesting 100 years ago.

Very nice find you scored there.


----------



## Galapac

I think the one with the scope is like this one:
https://www.ebay.com/itm/Marantz-10...685171&hash=item217ff44530:g:qy4AAOSwwVZf0XpB


----------



## Zachik

L0rdGwyn said:


> probably fine to leave them on the PCB but raising them up off of it even a little bit can't hurt


The resistors in question already soldered, and leads were clipped, so not an option to lift them other than buying new resistors and replacing the ones I already soldered...
Moving forward, I will lift those in future projects, but will leave the ones that are soldered already as-is. Only soldered some of the 3W resistors, so will lift the others when I resume tomorrow.


----------



## whirlwind

L0rdGwyn said:


> It's DIY of a different flavor, but I think it's still relevant: I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.  It's in pretty good physical condition other than some paint splotches on the underside, which shouldn't be an issue.  The bottom plate is metal so if I can't get it off, I might just strip it and repaint.  Obviously can't be seen, but I like to be thorough.  The bakelite itself is in great shape and will be thoroughly polished.
> 
> According to the seller, it turns on, lights up, but does not make sound, so will have to see what the issue is.  Could be as simple as replacing the tubes, could be a disaster (busted transformer, speaker driver).  Sort of a gamble, but this is the type of old deco style radio she is into, although it was made in the late 40s / early 50s.
> 
> Time to learn how one of these old radios works.



I really wish I would have kept a few of the older bakelite radio's from my fathers old tv shop. They really seem cool now!
I remember a few that had some wild colors, not sure of all the different brands or what type of tubes they used.

*GO BROWNS!*


----------



## CJG888

L0rdGwyn said:


> It's DIY of a different flavor, but I think it's still relevant: I'll be restoring this vintage Zenith bakelite radio for my girlfriend as a birthday gift, just won at auction.  It's in pretty good physical condition other than some paint splotches on the underside, which shouldn't be an issue.  The bottom plate is metal so if I can't get it off, I might just strip it and repaint.  Obviously can't be seen, but I like to be thorough.  The bakelite itself is in great shape and will be thoroughly polished.
> 
> According to the seller, it turns on, lights up, but does not make sound, so will have to see what the issue is.  Could be as simple as replacing the tubes, could be a disaster (busted transformer, speaker driver).  Sort of a gamble, but this is the type of old deco style radio she is into, although it was made in the late 40s / early 50s.
> 
> Time to learn how one of these old radios works.


If this is an “All-American Five” design, you could be in for quite a shock!


----------



## CJG888

After all, who needs mains transformers?


----------



## L0rdGwyn

@CJG888 it is a transformerless radio like the AA5 designs, although it uses seven tubes.  Will have to see if it uses a separate ground bus or not, if it doesn't will have to modify it for safety.


----------



## L0rdGwyn

whirlwind said:


> I really wish I would have kept a few of the older bakelite radio's from my fathers old tv shop. They really seem cool now!
> I remember a few that had some wild colors, not sure of all the different brands or what type of tubes they used.
> 
> *GO BROWNS!*



Some of those old bakelite radios really were made in wild colors!  Especially the mid-century modern types, bet it was really cool growing up around all that old tech.

GO BROWNS INDEED!  18 years later, we're back.  We'll see how we fare agains the full strength Steelers next week, but should be getting some critical players back, you never know what can happen.


----------



## L0rdGwyn (Jan 5, 2021)

Well no amplifier chassis today unfortunately, but the mail man did bring me some other goodies, here are todays spoils.

Hytron VR105 cold cathode voltage regulator tubes.  Going to play with using these on the screens in the pentode gain stage of my 801A amplifier.  I'm not expecting it to replace the DC feedback circuit I have in place, but you never know, they might surprise.  Great utility tubes that I will find a reason to use at some point.




Mullard EF37A, gain stage pentode in my 801A design.  I have a few different builds of this particular tube, but this is the earliest and most hard-to-find.



Another pair of E55L.  A paid $20 for this pair as they were untested, from the estate sale of an electrician / collector.  Sometimes you gotta follow your tube gut, they test over 110% of nominal.  No idea what I am going to do with these yet, but will be bidding on a few more upcoming auctions and hording these for...something.



And my big boy speaker stands from Sound Anchors.  I had to screw in the feet so it counts as DIY.  Slim and trim, welded steel built custom for my speakers.



Maybe even more exciting than the speaker stands are these plywood planks they came mounted on for shipping.  Well there are no excuses now, I will be moving my giant heat sink to one of these to finish a single channel of my 801A prototype.  Can move it indoors and outdoors no problem with the smaller footprint, so working on that monster is back on the menu.



On that subject, I placed an order today for 801A amplfier custom mains transformer from Sowter.  Will be a long wait, but will give me time to refine a few things.  I have been working on this design for what feels like a very long time, it is rather complex as far as single-ended class A tube amplifiers go, can't wait to show it off!  Should be a real looker.

Last thing is a teaser - I have some sleeper tubes on the way, a lesser known pentode that when triode strapped makes for an excellent driver tube, I will trace them and we will see how good they actually are.  More tube hording may ensue.


----------



## L0rdGwyn

What the heck is going on when there are 80+ guests viewing this thread?  Are you people or robots?!  It's a little disconcerting, in either case.


----------



## Zachik

L0rdGwyn said:


> What the heck is going on when there are 80+ guests viewing this thread?  Are you people or robots?!  It's a little disconcerting, in either case.


95 guests just now...


----------



## L0rdGwyn

Zachik said:


> 95 guests just now...



They must be bots, unleashed by eBay tube sellers skimming the thread for their next big score...conspiracy theories abound!


----------



## Zachik

haha   

Speaking of eBay, I have been looking at (and buying) various DIY related stuff recently. That and tubes. So why do I get this recommendation???





What do these complement???


----------



## L0rdGwyn

Zachik said:


> haha
> 
> Speaking of eBay, I have been looking at (and buying) various DIY related stuff recently. That and tubes. So why do I get this recommendation???
> 
> ...



These are a favorite of DIYers, there is a dedicated Hot Tamales forum on diyAudo, haven't you heard?

Holy crap that is a lot of Hot Tamales...


----------



## A2029

Zachik said:


> haha
> 
> Speaking of eBay, I have been looking at (and buying) various DIY related stuff recently. That and tubes. So why do I get this recommendation???
> 
> ...



I don't know about you, but some people call their tubes Hot Tamales after they've been running for a couple hours


----------



## Galapac

This is just the most popular thread on Head-Fi


----------



## Zachik

A2029 said:


> I don't know about you, but some people call their tubes Hot Tamales after they've been running for a couple hours


 
At least I did not get any NSFW recommendation...


----------



## L0rdGwyn

Galapac said:


> This is just the most popular thread on Head-Fi



The bots are vastly inflating its popularity


----------



## L0rdGwyn

Looks like I will have the 45 and 841 amplifier chassis tomorrow, so will finally get to building / re-building them.  The 45 amplifier will be first, since it will be sort of a transplantation, hoping I can get it done in one day.


----------



## L0rdGwyn

Making some preparations so we can hit the ground running tomorrow.


----------



## bcowen

Zachik said:


> haha
> 
> Speaking of eBay, I have been looking at (and buying) various DIY related stuff recently. That and tubes. So why do I get this recommendation???
> 
> ...



Um, Texas BBQ?   Ooops, sorry...wrong thread.


----------



## bcowen

L0rdGwyn said:


> Well no amplifier chassis today unfortunately, but the mail man did bring me some other goodies, here are todays spoils.
> 
> Hytron VR105 cold cathode voltage regulator tubes.  Going to play with using these on the screens in the pentode gain stage of my 801A amplifier.  I'm not expecting it to replace the DC feedback circuit I have in place, but you never know, they might surprise.  Great utility tubes that I will find a reason to use at some point.
> 
> ...



Sweet!  And love those Sound Anchors.  I had a pair for some Coincident speakers a while back. Expensive, but oh so very nicely made.  And free plywood to boot?  Mine only had cardboard packaging.  Shrug.


----------



## bcowen

Galapac said:


> This is just the most popular thread on Head-Fi



I like the Ebay 'bot conspiracy theory.  Would seem to have some coincidence with prices across several threads here.


----------



## Xcalibur255

This thread's been around long enough now that I suspect people doing google searches on tube related subjects are having it come up in first page results.


----------



## bcowen

L0rdGwyn said:


> Well no amplifier chassis today unfortunately, but the mail man did bring me some other goodies, here are todays spoils.
> 
> Hytron VR105 cold cathode voltage regulator tubes.  Going to play with using these on the screens in the pentode gain stage of my 801A amplifier.  I'm not expecting it to replace the DC feedback circuit I have in place, but you never know, they might surprise.  Great utility tubes that I will find a reason to use at some point.
> 
> ...



I feel like such a pauper.  This is all *I* got in today.    

Amtrans carbon film resistors on the left.  I've never tried them, but they seem to have a good following. Love the (discontinued) Rikens, but I couldn't find any at this value so decided to give these a try.


----------



## L0rdGwyn

bcowen said:


> I feel like such a pauper.  This is all *I* got in today.
> 
> Amtrans carbon film resistors on the left.  I've never tried them, but they seem to have a good following. Love the (discontinued) Rikens, but I couldn't find any at this value so decided to give these a try.



Wow...that's all you got, really?

Lol I kid, are these going in the Darkvoice?


----------



## L0rdGwyn (Jan 4, 2021)

Xcalibur255 said:


> This thread's been around long enough now that I suspect people doing google searches on tube related subjects are having it come up in first page results.



It is sort of this surge now and then, it was up to 117 in a half hour...I remember it happening on the 2359glenn thread as well, weird.  Maybe someone is posting links to this thread on some dark web forum


----------



## bcowen

L0rdGwyn said:


> Wow...that's all you got, really?
> 
> Lol I kid, are these going in the Darkvoice?



Yup.  Replacing the cheesy metal films that are on the 6SN7 socket.  I'm holding off on any expensive, um, _renovations_ until you get done.


----------



## bcowen

L0rdGwyn said:


> It is sort of this surge now and then, it was up to 117 in a half hour...I remember it happening on the 2359glenn thread as well, weird.  Maybe someone is posting links to this thread on some dark web forum



Probably stealing all your awesome ideas.  Maybe we need a 'members only' L0rdGwyn thread.


----------



## L0rdGwyn (Jan 4, 2021)

bcowen said:


> Yup.  Replacing the cheesy metal films that are on the 6SN7 socket.  I'm holding off on any expensive, um, _renovations_ until you get done.



Nice!  IME changing the type of plate resistor does have a very audible effect on the sound, I preferred carbon films overall in my experiments (included carbon film, carbon comp, metal film, ridiculously overpriced Audio Note tantalums).  I haven't made any major strides on the Darkvoice renovations yet, but I will Wednesday night - going to design a gyrator PCB, probably someting similar to Ale Moglia's popular gyrator design.  Compared to the CCS load, it serves a similar function by showing the 6SN7 a high AC impedance, flattening the load line.  Unlike the CCS, it maintains a well-regulated voltage on the 6SN7 stage output, important if you are direct-coupling the two stages  I am working five straight night shifts starting Thursday, so I will be staying up all night Wednesday to prepare for it.  This is typically when I dive into LTSpice sims or PCB mock ups, should get it all figured out and ready to go!



bcowen said:


> Probably stealing all your awesome ideas.  Maybe we need a 'members only' L0rdGwyn thread.



Super Best DIY Guys And Friends?  SB-DGAF?


----------



## audiofest2018

Xcalibur255 said:


> This thread's been around long enough now that I suspect people doing google searches on tube related subjects are having it come up in first page results.


Pretty soon @L0rdGwyn will have his own Youtube channel on how to make  tube amp so we all can subscribe to watch!  Haha!


----------



## L0rdGwyn (Jan 4, 2021)

bcowen said:


> Probably stealing all your awesome ideas.



Oh and realistically, any good idea I've come up with is really pieced together from at least five other peoples' better ideas LOL I owe a lot to a long list of tube DIYers and electrical engineers from diyAudio.


----------



## bcowen

L0rdGwyn said:


> Nice!  IME changing the type of plate resistor does have a very audible effect on the sound, I preferred carbon films overall in my experiments (included carbon film, carbon comp, metal film, ridiculously overpriced Audio Note tantalums).  I haven't made any major strides on the Darkvoice renovations yet, but I will Wednesday night - going to design a gyrator PCB, probably someting similar to Ale Moglia's popular gyrator design.  Compared to the CCS load, it serves a similar function by showing the 6SN7 a high AC impedance, flattening the load line.  Unlike the CCS, it maintains a well-regulated voltage on the 6SN7 stage output, important if you are direct-coupling the two stages  I am working five straight night shifts starting Thursday, so I will be staying up all night Wednesday to prepare for it.  This is typically when I dive into LTSpice sims or PCB mock ups, should get it all figured out and ready to go!
> 
> 
> 
> Super Best DIY Guys And Friends?  SB-DGAF?



I've always enjoyed good carbon films over most anything else when the wattage requirement would allow.  Perhaps power supplies are better served with high quality metal films or foils, I don't know.  But the Rikens were great soldered to tube sockets because they sounded nice and didn't drift (at least as much) as older tech like the Allen Bradleys.  Was sad to see Riken go, but maybe (hopefully?) these Amtrans are a good replacement.

And for the forum, I was thinking "L0rdGwyn and Minions" or the like, with @Tjj226 Angel as chief technical advisor (of course).


----------



## Velozity (Jan 4, 2021)

L0rdGwyn said:


> Nice!  IME changing the type of plate resistor does have a very audible effect on the sound, I preferred carbon films overall in my experiments (included carbon film, carbon comp, metal film, ridiculously overpriced Audio Note tantalums).  I haven't made any major strides on the Darkvoice renovations yet, but I will Wednesday night - going to design a gyrator PCB, probably someting similar to Ale Moglia's popular gyrator design.  Compared to the CCS load, it serves a similar function by showing the 6SN7 a high AC impedance, flattening the load line.  Unlike the CCS, it maintains a well-regulated voltage on the 6SN7 stage output, important if you are direct-coupling the two stages  I am working five straight night shifts starting Thursday, so I will be staying up all night Wednesday to prepare for it.  This is typically when I dive into LTSpice sims or PCB mock ups, should get it all figured out and ready to go!
> 
> Super Best DIY Guys And Friends?  SB-DGAF?





Let me fix that for you:  *JAN*-SB-DGAF.  This _is_ a  tube thread after all


----------



## Velozity

Zachik said:


> haha
> 
> Speaking of eBay, I have been looking at (and buying) various DIY related stuff recently. That and tubes. So why do I get this recommendation???
> 
> ...





Lol, just taking a stab here, but I'd say eBay considers that typical "nerd" food.  They're stereotyping us!              ....*quietly pulls a few more chips from the bag*


----------



## Galapac

Velozity said:


> Lol, just taking a stab here, but I'd say eBay considers that typical "nerd" food.  They're stereotyping us!              ....*quietly pulls a few more chips from the bag*


Never know what I’m going to read in here, love it!
My personal favorite: https://www.amazon.com/Albanese-Che...id=1609816119&sprefix=Red+gumm,aps,170&sr=8-5


----------



## L0rdGwyn

Velozity said:


> Let me fix that for you:  *JAN*-SB-DGAF.  This _is_ a  tube thread after all



Joint Army Navy Super Best DIY Guys And Friends, man it really rolls right off the tongue doesn't it?


----------



## Tjj226 Angel (Jan 4, 2021)

bcowen said:


> I've always enjoyed good carbon films over most anything else when the wattage requirement would allow.  Perhaps power supplies are better served with high quality metal films or foils, I don't know.  But the Rikens were great soldered to tube sockets because they sounded nice and didn't drift (at least as much) as older tech like the Allen Bradleys.  Was sad to see Riken go, but maybe (hopefully?) these Amtrans are a good replacement.
> 
> And for the forum, I was thinking "L0rdGwyn and Minions" or the like, with @Tjj226 Angel as chief technical advisor (of course).



Resistors are one of those things where we use them every day, and no one knows schiit about the complex effects they impart on our stuff.

There is no reason why two resistors with similar DCR, ESL, and thermal design should sound different. But not only can they sound different, they can sound WILDLY different.

One day, I would like to dive into the theory behind resistors and see whats really going on.


----------



## L0rdGwyn

bcowen said:


> I've always enjoyed good carbon films over most anything else when the wattage requirement would allow.  Perhaps power supplies are better served with high quality metal films or foils, I don't know.  But the Rikens were great soldered to tube sockets because they sounded nice and didn't drift (at least as much) as older tech like the Allen Bradleys.  Was sad to see Riken go, but maybe (hopefully?) these Amtrans are a good replacement.
> 
> And for the forum, I was thinking "L0rdGwyn and Minions" or the like, with @Tjj226 Angel as chief technical advisor (of course).



I am a big Riken fan myself, if I am using an unbypassed cathode resistor that is my go to!  Kiwame / KOA Spear is my budget backup.


----------



## bcowen

Galapac said:


> Never know what I’m going to read in here, love it!
> My personal favorite: https://smile.amazon.com/Albanese-Cherry-Flavored-Single-Flavor-Gummies-Package/dp/B00657A1UG/ref=sr_1_5?crid=1S1GG0DZMJA0E&dchild=1&keywords=red+gummy+bears&qid=1609816119&sprefix=Red+gumm,aps,170&sr=8-5



LOL!  I would bet the promotional cost of those is paid for by dentists.


----------



## Zachik

bcowen said:


> LOL!  I would bet the promotional cost of those is paid for by dentists.


or weight watchers


----------



## johnjen (Jan 5, 2021)

Tjj226 Angel said:


> Resistors are one of those things where we use them every day, and no one knows schiit about the complex effects they impart on our stuff.
> 
> There is no reason why two resistors with similar DCR, ESL, and thermal design should sound different. But not only can they sound different, they can sound WILDLY different.
> 
> One day, I would like to dive into the theory behind resistors and see whats really going on.


I grew up with carbon comp's and figured that the newer carbon and metal film varieties were 'necessarily' better…
That is until I fussed around with using them in particular 'key' locations in the circuit, and I tried the usual suspects in a variety of ways…

The old Allen Bradley hunker buster resistors seem to impart a 'clearer' or more pure harmonic signature, at least where I use them anyway.
BUT take into account that we are talking very small differences in SQ hear.
But when the entire system has been dialed in, even these small differences can still be greatly appreciated.
And they are usually additive in the total net effect they make.

I liken this to my term of *CP*'s (Choke Points), as the limitations to the flow of music thru the circuit continue to be reduced, i.e. it gets all the more 'dialed in', the SQ changes and improves at an increasing rate as fewer *CP'*s remain, that kind of additive total net effect.

That isn't to say they are the best choice in other regards, like long term stability.
Not that they 'wear out' or crumble to dust, but they will continue to increase their measured value over and above their specified value.
It comes with the territory so to speak.

So for me, I'll keep track of them, where they are used, as they 'age', as the operating points of their related circuits move further into the 'safe zone' of operation as opposed to moving out of the 'safe zone'.

Bottom line, the old school CC Ω's beat out the new young-guy CF & MF Ω's in terms of overall SQ.
But they are fiddly, yes, quite fiddly.    

JJ


----------



## fleasbaby

L0rdGwyn said:


> What the heck is going on when there are 80+ guests viewing this thread?  Are you people or robots?!  It's a little disconcerting, in either case.



I'm still lurking...


----------



## L0rdGwyn

fleasbaby said:


> I'm still lurking...



Happy to hear it!

I am tearing down the old 45 amplifier while waiting for the new chassis to be delivered.  Barring some disaster, confident it will be finished today, will post some photos when it is done.


----------



## Zachik

Transformer question time: 
I have come across a small company this morning, that makes great looking OTL amps, using toroidal transformers so their chassis looks VERY clean. No bulky transformers on top of the chassis.
So, the question is... *what are the downsides of toroidal transformers?* Why are you not using them @L0rdGwyn in your amp designs?

Here are the amps I was referring to:
https://www.wbamp.com/headphones-tube-amplifiers/


----------



## CJG888

I’ve got a WBA Tzar on order- would be interested to hear the answer!


----------



## Tjj226 Angel

Zachik said:


> Transformer question time:
> I have come across a small company this morning, that makes great looking OTL amps, using toroidal transformers so their chassis looks VERY clean. No bulky transformers on top of the chassis.
> So, the question is... *what are the downsides of toroidal transformers?* Why are you not using them @L0rdGwyn in your amp designs?
> 
> ...



For a power supply transformer, a toroidal is probably better than an EI transformer since it radiates less EMI. 

Why don't more tube amp manufacturers use toroidal transformers? Because they usually don't have the right assortment of filament heater windings, and I have yet to find a toroid manufacturer that will custom make a transformer to accommodate. 

I use toroid transformers from antek, but I have had to change how I do things a bit to make it work.


----------



## L0rdGwyn (Jan 5, 2021)

Zachik said:


> Transformer question time:
> I have come across a small company this morning, that makes great looking OTL amps, using toroidal transformers so their chassis looks VERY clean. No bulky transformers on top of the chassis.
> So, the question is... *what are the downsides of toroidal transformers?* Why are you not using them @L0rdGwyn in your amp designs?
> 
> ...



Hey Zachik,

Nothing wrong with toroids, in fact they have many advantages, one of them being low emitted magnetic field, I have one in my phono stage.  This is just personal preference, but from an aesthetic standpoint if I have all of the transformers out on top of the chassis, I like them to match, whether that be mismatched brands / types covered in matching shields (which will be the case in my 841 headphone amp), or matched brand / and or build.  They just have to look the same or very similar to satisfy my OCD tendencies.  So I am unlikely ever to pair a toroid with a EI core output transformers in a SET design unless I can shroud them similarly.  However, since there are no OPT in an OTL and the transformer is singular, I would definitely consider using a toroid in an OTL.  In fact, I am very likely to do it at some point.   I probably have six Antek toroids in a drawer in my garage that I bought for various types of experiments over the past year, many of their off-the-shelf toroids have dual secondaries as well which is useful.


----------



## L0rdGwyn

Well the old 45 amp is completely dismantled and ready for reassembly, but the mail hasn't been delivered yet...

About to get in my car and track down my mail carrier, that's a mentally healthy and reasonable thing to do, right?


----------



## Tjj226 Angel

L0rdGwyn said:


> Well the old 45 amp is completely dismantled and ready for reassembly, but the mail hasn't been delivered yet...
> 
> About to get in my car and track down my mail carrier, that's a mentally healthy and reasonable thing to do, right?



Its what I do every other day, so its probably fine.


----------



## Zachik

L0rdGwyn said:


> About to get in my car and track down my mail carrier, that's a mentally healthy and reasonable thing to do, right?


Absolutely!


----------



## Xcalibur255

Those poor people had a rough holiday season so I would offer them as much patience as you can.


----------



## Zachik

L0rdGwyn said:


> They just have to look the same or very similar to satisfy my OCD tendencies.


Understood! But if you use toroids - they're hidden inside the chassis and the only visible "stuff" on top are the tubes. 
Much cleaner look IMHO (see the WBA link I shared before).


----------



## Zachik

CJG888 said:


> I’ve got a WBA Tzar on order


What's that?!  Cannot find it on their website...


----------



## Tjj226 Angel

Xcalibur255 said:


> Those poor people had a rough holiday season so I would offer them as much patience as you can.



I mean they are all multi billion dollar enterprises and their employees get paid good money to drive around in a truck and play kick ball with all my packages. 

I have already had two packages in the last month fly from the west coast, to the east coast, then back to the west coast, just to make it to me 2 weeks late. 

Then they have the nerve to claim covid. I swear some of these companies are standing on the graves of those who have died to save a few bucks off the operating costs.


----------



## CJG888 (Jan 5, 2021)

Zachik said:


> What's that?!  Cannot find it on their website...


Not all of their products are on the website. Both the Tzar and the flagship Electron are newish designs using the 6S41S (6C41C in Cyrillic) output tube.

Tzar:





Electron:


----------



## Zachik

CJG888 said:


> Not all of their products are on the website. Both the Tzar and the flagship Electron are newish designs using the 6S41S (6C41C in Cyrillic) output tube.
> 
> Tzar:
> 
> ...


Interesting. How did you find out and got details on the Tzar and Electron if not on their website?

The one that caught my eye was the 300B amp: (https://www.wbamp.com/product/virtus-300b-otl-single-ended-headphone-amplifier/)




@L0rdGwyn - how hard would it be to design something similar? 
This one is $1,488 - *quite a steal if it sounds good!*
Preamp out is doable (not sure how much extra they would charge for customization). I wonder if speaker taps are realistic? For efficient speakers?


----------



## CJG888

The Tzar will comfortably drive planars (and the Electron presumably Linn Isobariks...  ).

The advantages of using the 6S41S are low internal resistance, high output and low cost! OTK-rated Soviet NOS (good enough for MiGs) at 16€ a pop. I know what good 300Bs cost! Think of them as being like half a 6S33S, only with better quality and consistency.


----------



## L0rdGwyn (Jan 5, 2021)

Xcalibur255 said:


> Those poor people had a rough holiday season so I would offer them as much patience as you can.



Oh I was just joking around, I would never in a million years give a postal worker a hard time, let alone people that actually deserve it.



Zachik said:


> Interesting. How did you find out and got details on the Tzar and Electron if not on their website?
> 
> The one that caught my eye was the 300B amp: (https://www.wbamp.com/product/virtus-300b-otl-single-ended-headphone-amplifier/)
> 
> ...



Not very hard, it is a 300B OTL (notice no transformers?), I slopped together a LTSpice schematic, not optimized but output impedance of a 300B cathode follower is around 70ohm at 1kHz.  As a cathode follower, would need a modest driver tube as the input capacitance is no longer an issue.  I would probably direct-couple it, just spitballin' here.


----------



## L0rdGwyn

Since I am just killing time here, I put together a 6J5 input gyrator-loaded direct-coupled 300B OTL in LTSpice, running the 300B pretty hard, output impedance at 1kHz is 60ohm, does 2W into 300ohms with a 2Vrms input.


----------



## bcowen

L0rdGwyn said:


> Hey Zachik,
> 
> Nothing wrong with toroids, in fact they have many advantages, one of them being low emitted magnetic field, I have one in my phono stage.  This is just personal preference, but from an aesthetic standpoint if I have all of the transformers out on top of the chassis, I like them to match, whether that be mismatched brands / types covered in matching shields (which will be the case in my 841 headphone amp), or matched brand / and or build.  They just have to look the same or very similar to satisfy my OCD tendencies.  So I am unlikely ever to pair a toroid with a EI core output transformers in a SET design unless I can shroud them similarly.  However, since there are no OPT in an OTL and the transformer is singular, I would definitely consider using a toroid in an OTL.  In fact, I am very likely to do it at some point.   I probably have six Antek toroids in a drawer in my garage that I bought for various types of experiments over the past year, many of their off-the-shelf toroids have dual secondaries as well which is useful.



I believe the input tranny in the Darkvoice is a toroid.


----------



## Zachik

L0rdGwyn said:


> Not very hard, it is a 300B OTL (notice no transformers?), I slopped together a LTSpice schematic, not optimized but output impedance of a 300B cathode follower is around 70ohm at 1kHz. As a cathode follower, would need a modest driver tube as the input capacitance is no longer an issue. I would probably direct-couple it since the 300B biases at around -80V on the grid. Just spitballin' here.


Would such design be able to drive both headphones (100-300 ohms) as well as efficient (Omega) speakers? (not simultaneously... )
What about planar headphones (the downfall of most OTLs)?


----------



## bcowen

L0rdGwyn said:


> Since I am just killing time here, I put together a 6J5 input gyrator-loaded direct-coupled 300B OTL in LTSpice, running the 300B pretty hard, output impedance at 1kHz is 60ohm, does 2W into 300ohms with a 2Vrms input.



Try plugging in a 300BXLS.  And then how long before you can build one for me?


----------



## L0rdGwyn

Zachik said:


> Would such design be able to drive both headphones (100-300 ohms) as well as efficient (Omega) speakers? (not simultaneously... )
> What about planar headphones (the downfall of most OTLs)?



100% no on the speakers, the output impedance is way too high, need some sort of current gain to drive a speaker load (transformer, transistor, etc.).  Like other OTLs, high impedance headphones would be the name of the game, not sure what the market is like for high-impedance planars, but low impedance planars would be a no no.


----------



## L0rdGwyn

bcowen said:


> Try plugging in a 300BXLS.  And then how long before you can build one for me?



Woah, that thing is a beast!


----------



## Xcalibur255

Tjj226 Angel said:


> I mean they are all multi billion dollar enterprises and their employees get paid good money to drive around in a truck and play kick ball with all my packages.
> 
> I have already had two packages in the last month fly from the west coast, to the east coast, then back to the west coast, just to make it to me 2 weeks late.
> 
> Then they have the nerve to claim covid. I swear some of these companies are standing on the graves of those who have died to save a few bucks off the operating costs.



I'm not defending the system, it is in need of improvement.  But crunch time is no fun for any person working a physical job, especially one who is more aware than the average joe and laments the fact that he has to be a tiny cog in a large machine that doesn't work well.


----------



## Xcalibur255

And yes, I'm projecting just a little bit here........


----------



## bcowen

L0rdGwyn said:


> Woah, that thing is a beast!



Yeah, a bit over 21 watts/channel in the Jota amp.  And people say SET's are wimpy.  Maybe compared to a 2kw/channel Class D amp, but then that's more like comparing fine wine to dog poop.


----------



## L0rdGwyn

Finally...

Alright, back to work!


----------



## bcowen

L0rdGwyn said:


> Finally...
> 
> Alright, back to work!



You nabbed the mailmanperson?  Your talents continue to amaze me.


----------



## Zachik

L0rdGwyn said:


> 100% no on the speakers, the output impedance is way too high, need some sort of current gain to drive a speaker load (transformer, transistor, etc.).  Like other OTLs, high impedance headphones would be the name of the game, not sure what the market is like for high-impedance planars, but low impedance planars would be a no no.


So how about adding a 2nd toroid transformer (or using toroid transformer with 2 secondaries) - one for headphone out and one for the speakers? Would that work?
What is the transistor option you've mentioned above as another possible solution for the speaker load? Other than committing blasphemy - any reason not to use a transistor based solution for the speaker taps?


----------



## L0rdGwyn

Zachik said:


> So how about adding a 2nd toroid transformer (or using toroid transformer with 2 secondaries) - one for headphone out and one for the speakers? Would that work?
> What is the transistor option you've mentioned above as another possible solution for the speaker load? Other than committing blasphemy - any reason not to use a transistor based solution for the speaker taps?



So the toroid is the power transformer, not the output transformer, since we are talking about a hypothetical OTL design.  The 60ohm output impedance is without a transformer, the output is AC coupled via an output capacitor.  I was just pointing out that in order to lower the output impedance to speaker-usable levels in any amplifier, you need a way to turn voltage into current, which is typically done via a output transformer in tube designs or power transistors in solid-state designs.  It can also be done by paralleling several output tubes in a speaker OTL design.  Combining a 300B OTL and adding a power transistor for speakers, you might as well just build a 300B SET IMO.


----------



## Tjj226 Angel

L0rdGwyn said:


> So the toroid is the power transformer, not the output transformer, since we are talking about a hypothetical OTL design.  The 60ohm output impedance is without a transformer, the output is AC coupled via an output capacitor.  I was just pointing out that in order to lower the output impedance to speaker-usable levels in any amplifier, you need a way to turn voltage into current, which is typically done via a output transformer in tube designs or power transistors in solid-state designs.  It can also be done by paralleling several output tubes in a speaker OTL design.  Combining a 300B OTL and adding a power transistor for speakers, you might as well just build a 300B SET IMO.



It's also worth adding to this that no one has cracked the code on how to make really high quality audio toroid transformers quite yet. Their interwinding capacitance is usually huge compared to a cheap EI transformer.


----------



## Zachik

L0rdGwyn said:


> Combining a 300B OTL and adding a power transistor for speakers, you might as well just build a 300B SET IMO.





Tjj226 Angel said:


> It's also worth adding to this that no one has cracked the code on how to make really high quality audio toroid transformers quite yet. Their interwinding capacitance is usually huge compared to a cheap EI transformer.



So, if I go this route - I would need 1 toroid for power and 2nd toroid serving as the SET transformer?  (i.e. abandoning OTL architecture)
...and this would be quite noisy amp (due to toroid capacitance)?


----------



## Tjj226 Angel

Zachik said:


> So, if I go this route - I would need 1 toroid for power and 2nd toroid serving as the SET transformer?  (i.e. abandoning OTL architecture)
> ...and this would be quite noisy amp (due to toroid capacitance)?



You wouldn't have very good high frequency performance if you used a toroid transformer on the output of the amp due to interwinding capacitance. 

Toroid - power supply = Good. 

Toroid - output transformer = probably bad unless you find yourself a transformer winding wizard or something.


----------



## L0rdGwyn

Tjj226 Angel said:


> It's also worth adding to this that no one has cracked the code on how to make really high quality audio toroid transformers quite yet. Their interwinding capacitance is usually huge compared to a cheap EI transformer.



I know Toroidy makes single-ended output transformers, although I have read little-to-nothing about them.  Here is their 300B single-ended offering.

https://sklep.toroidy.pl/en_US/p/TTG-EL34SE-Tube-output-UL-transformer-3,2kOhm-EL34-6L6-SE/560



Zachik said:


> So, if I go this route - I would need 1 toroid for power and 2nd toroid serving as the SET transformer?  (i.e. abandoning OTL architecture)
> ...and this would be quite noisy amp (due to toroid capacitance)?



You would need a pair of output transformers for a SET design.  The issue with the capacitance is the RC formed by the output tube plate resistance and the interwinding capacitance of the output transformer, which will roll off  the high frequencies.


----------



## Tjj226 Angel

L0rdGwyn said:


> I know Toroidy makes single-ended output transformers, although I have read little-to-nothing about them.  Here is their 300B single-ended offering.
> 
> https://sklep.toroidy.pl/en_US/p/TTG-EL34SE-Tube-output-UL-transformer-3,2kOhm-EL34-6L6-SE/560
> 
> ...



I know. Look carefully at their capacitance spec for their lowest impedance transformer. It is still 7.6nf. For a 3K transformer, we really want to be down in the 2nf range and below. 

At 7.6nf, the capacitance becomes a problem somewhere in the midrange. 

This is part of the reason why transformers get so expensive. In order to achieve really good high frequency performance, you have to wind a bunch of individual coils on the bobbin and put them all in series. All the individual coil capacitances and inductances are put in series as a result. When you put inductance in series, it adds (good thing). And when you put capacitances in series, it gets smaller too (also good thing). 

Usually the better built transformers will have alternative winding layers, but toroids (for what ever reason) apparently can't have a lot of layers in series or something? I know there is an article out there that explains all of this.


----------



## L0rdGwyn

Well, since the mail ran so late, wasn't realistic to finish the 45 amplifier tonight, unless I were to stay up until 2AM.

So I will be up at the crack of dawn to finish the job.  Here is how far I got on the interior.


----------



## bcowen

L0rdGwyn said:


> Well, since the mail ran so late, wasn't realistic to finish the 45 amplifier tonight, unless I were to stay up until 2AM.
> 
> So I will be up at the crack of dawn to finish the job.  Here is how far I got on the interior.



MMMMMMM....oil caps and Rikens.  I can tell it's going to sound great before you even finish it.


----------



## L0rdGwyn

bcowen said:


> MMMMMMM....oil caps and Rikens.  I can tell it's going to sound great before you even finish it.



Wait until you see the parafeed caps, they are freakin' huge!  I was a real psycho when I built this amp the first time and even used Rikens as the current set resistors on the four CCS boards LOL.  Well they're already there so they're staying.

The color turned out really well, going to look pretty classy I think.


----------



## A2029

Tjj226 Angel said:


> I know. Look carefully at their capacitance spec for their lowest impedance transformer. It is still 7.6nf. For a 3K transformer, we really want to be down in the 2nf range and below.
> 
> At 7.6nf, the capacitance becomes a problem somewhere in the midrange.
> 
> ...



I got some Toroidy transformers custom made to test out for an amp that I've had sitting on a shelf for the past while. Told them that I'd like it to be -1dB or better at 20Khz, so I look forward to testing to see if they were able to do it. They didn't provide any specs with the transformers as it was a custom job. Guess we'll see


----------



## Zachik

A2029 said:


> I got some Toroidy transformers custom made to test out for an amp that I've had sitting on a shelf for the past while. Told them that I'd like it to be -1dB or better at 20Khz, so I look forward to testing to see if they were able to do it. They didn't provide any specs with the transformers as it was a custom job. Guess we'll see


What kind of amp is it for Mischa?


----------



## Tjj226 Angel

A2029 said:


> I got some Toroidy transformers custom made to test out for an amp that I've had sitting on a shelf for the past while. Told them that I'd like it to be -1dB or better at 20Khz, so I look forward to testing to see if they were able to do it. They didn't provide any specs with the transformers as it was a custom job. Guess we'll see



Frequency response is one thing. I would be more curious about the phase response out to 20Khz. 

I really do hope they work though. I have been eyeing the GM70 output transformers.


----------



## A2029

Zachik said:


> What kind of amp is it for Mischa?



It's a parallel KT150 single ended amp for my personal uses. 12BY7/12HL7/12HG7 driver into the KT150s. I went way overboard with polishing on it due to OCD. I even set up a rig for electropolishing the stainless steel chassis. Sides made from African Padauk wood. The whole amp is kind of an experiment in going overboard, lol. >3000uF in the high voltage supply running over 600 volts  Remote control stepped relay attenuation with programmed soft start... I'll post more on it when I have it completed and up and running.

Toroidal transformers are traditionally very poor performers when used in single ended applications as they saturate very easily when there is a DC bias present. To get around this, I believe Toroidy and some other Toroidal audio manufacturers are using powdered cores that have some inherent gap for running DC bias, but they are still not very popular on the market, and reviews are almost non-existent, so will be very interesting to hear and measure their performance.


----------



## A2029

Tjj226 Angel said:


> Frequency response is one thing. I would be more curious about the phase response out to 20Khz.
> 
> I really do hope they work though. I have been eyeing the GM70 output transformers.



I really hope so as well! Luckily the experiment with them isn't too pricey, and they would represent pretty good value if they work out well and sound good. I'll definitely be posting my findings.

To extend their bandwidth I'm also thinking of trying to semi-float their secondary using a resistor in tandem with some protection circuitry that would trigger if there was a short between the primary and secondary, shunt the HV supply current to ground, and shut down the amp. Wouldn't want 500+ volts on a speaker cable. Will have to think about how best to do this.


----------



## L0rdGwyn

A2029 said:


> It's a parallel KT150 single ended amp for my personal uses. 12BY7/12HL7/12HG7 driver into the KT150s. I went way overboard with polishing on it due to OCD. I even set up a rig for electropolishing the stainless steel chassis. Sides made from African Padauk wood. The whole amp is kind of an experiment in going overboard, lol. >3000uF in the high voltage supply running over 600 volts  Remote control stepped relay attenuation with programmed soft start... I'll post more on it when I have it completed and up and running.
> 
> Toroidal transformers are traditionally very poor performers when used in single ended applications as they saturate very easily when there is a DC bias present. To get around this, I believe Toroidy and some other Toroidal audio manufacturers are using powdered cores that have some inherent gap for running DC bias, but they are still not very popular on the market, and reviews are almost non-existent, so will be very interesting to hear and measure their performance.



I remember you mentioning this amp, can't wait to see it.  Did you get those sweet chromed transformer shields from Toroidy too?


----------



## Zachik

A2029 said:


> I went way overboard with polishing on it due to OCD. I even set up a rig for electropolishing the stainless steel chassis.


Yeah... That is the reason I prefer matte finish...


----------



## A2029

L0rdGwyn said:


> I remember you mentioning this amp, can't wait to see it.  Did you get those sweet chromed transformer shields from Toroidy too?



I opted for the cheapo non-potted versions, there was enough polished stainless and polished aluminum film caps for my liking already


----------



## L0rdGwyn (Jan 6, 2021)

Okay the 45 parafeed rebuild is done, finally.  Always takes longer than I think it will.

Here is the circuit first, there is a lot crammed inside.



Top.



Rear panel.  Speaker binding posts sit behind the output transformers.  Rear switch is for the headphone output.



Here it is with some tubes.



Bottom plate is perforated aluminum sheet for ventilation.



I like how compact this amp is, small footprint considering how much stuff is stuffed inside.  It sounds great, spinning some vinyl.



Will have to go back in at some point to finely dial in the filament supply and I may better match the 45 CCS FETs, but overall it's done, I can mark it off the list!  Will probably take some measurements later today.

841 amplifier is next...


----------



## Zachik

Beautiful Keenan!  Inside and out 
Hey - what are the PCBs connected to the rear panel heatsinks?


----------



## L0rdGwyn

Zachik said:


> Beautiful Keenan!  Inside and out
> Hey - what are the PCBs connected to the rear panel heatsinks?



Thanks, Zachi, those are the CCS boards for the 45 output tubes.  They dissipate a decent amount of power, around 7.5W, so they get their own exterior-mounted heat sinks.


----------



## bcowen

L0rdGwyn said:


> Okay the 45 parafeed rebuild is done, finally.  Always takes longer than I think it will.
> 
> Here is the circuit first, there is a lot crammed inside.
> 
> ...



Gorgeous!  And you weren't kidding about the big huge monstrous coupling caps.  Is that 2 of them stacked together on each side?  Sweet!!


----------



## L0rdGwyn

bcowen said:


> Gorgeous!  And you weren't kidding about the big huge monstrous coupling caps.  Is that 2 of them stacked together on each side?  Sweet!!



Yup, two 3.3uF in parallel!  Luckily they fit 😂 gotta work for those PIO caps.


----------



## Xcalibur255

The perforated bottom panel is a great idea.  I wonder why more people don't do that.


----------



## L0rdGwyn

I ended up swapping the 45 cathode bypass caps, they were Clarity Caps, now they are Audio Note Kaisei electrolytics.  In this particular type of parafeed output stage, the cathode bypass caps are not "in the signal path" and do not affect the frequency response as a typical cathode bypass cap would, they provide an AC path to ground.  For that reason, I thought I might be able to get away with a lower value film.  Unfortunately, this left a significant degree of 60Hz noise at the top of the cathode of the left channel 45, so I had to add more capacitance, some experimentation showed that films weren't going to cut it.

A 220uF Audio Note Kaisei buried the 60Hz noise, so that's what it's gonna be.




I have found that the bypass caps in this setup are still somewhat audible, despite being out of the signal path, but to a much lesser degree than a typical cathode biased output stage.  I'll take a small amount of bipolar electrolytic influence over a 60Hz noise, even if it is barely audible, would drive me crazy if left alone.


----------



## whirlwind

L0rdGwyn said:


> Okay the 45 parafeed rebuild is done, finally.  Always takes longer than I think it will.
> 
> Here is the circuit first, there is a lot crammed inside.
> 
> ...



Beautiful. Great idea to use the  perforated aluminum bottom.


----------



## L0rdGwyn

Here is the 45 amp's final destination, back in the bedroom stereo with the Klipsch KG 1.



Just have a cheap Topping DAC and a Bluesound streamer right now, might upgrade the DAC to something fancy at some point.  Sounds great though, very happy with the result.


----------



## bcowen

L0rdGwyn said:


> Here is the 45 amp's final destination, back in the bedroom stereo with the Klipsch KG 1.
> 
> 
> 
> Just have a cheap Topping DAC and a Bluesound streamer right now, might upgrade the DAC to something fancy at some point.  Sounds great though, very happy with the result.



You need some Sound Anchors for the Klipsch's.    

Looks great!


----------



## CJG888

Some of those old Klipsch speakers look like potential sleepers, underappreciated as they are not part of the “Heritage Series”, but sharing many of their characteristics: high sensitivity, flat 8 Ohm impedance, real wood veneer, mid-century style.


----------



## L0rdGwyn

CJG888 said:


> Some of those old Klipsch speakers look like potential sleepers, underappreciated as they are not part of the “Heritage Series”, but sharing many of their characteristics: high sensitivity, flat 8 Ohm impedance, real wood veneer, mid-century style.



The KG series is highly regarded by many!  Although many of the earlier models have a 4ohm impedance.  The KG4 is a popular vintage model, 6ohms nominal, 94dB/W.



Sort of my 10 year hifi plan is to get a pair of full-sized horns, when I move into a larger home that can take them   whether than will be something like the Klipsch La Scala, some vintage Altecs, or perhaps a DIY build using Great Plains Audio's new production 604 driver, not sure yet, just dreaming of giant speakers.


----------



## bcowen

L0rdGwyn said:


> The KG series is highly regarded by many!  Although many of the earlier models have a 4ohm impedance.  The KG4 is a popular vintage model, 6ohms nominal, 94dB/W.
> 
> 
> 
> Sort of my 10 year hifi plan is to get a pair of full-sized horns, when I move into a larger home that can take them   whether than will be something like the Klipsch La Scala, some vintage Altecs, or perhaps a DIY build using Great Plains Audio's new production 604 driver, not sure yet, just dreaming of giant speakers.



Just get a pair of these and call it a day.  1 watt will get you to rock'n'roll levels, or make it 16 watts for best probability of structural damage. 

(I wasn't even aware they were still making these)


----------



## UntilThen

L0rdGwyn said:


> What the heck is going on when there are 80+ guests viewing this thread?  Are you people or robots?!  It's a little disconcerting, in either case.



Wasn't me I was working hard. If I had been looking in that would count as 50 - just ask @bcowen .


----------



## UntilThen

Have you make my Auris Nirvana contender yet Lord Gwyn? If not I'll have to drop the Lord title and then camp myself in the 1101 thread instead.


----------



## bcowen

UntilThen said:


> Wasn't me I was working hard. If I had been looking in that would count as 50 - just ask @bcowen .



Where have you been?  You up and disappear just when we required needed wanted....well, we just wondered where you were.


----------



## UntilThen

bcowen said:


> Where have you been?  You up and disappear just when we required needed wanted....well, we just wondered where you were.



I was working... at home.. just focusing you know. Work you have to focus. Head-fi you don't have to think.   Well buddy I did think about you while I was working... about the chump I left behind in Detroit.


----------



## UntilThen

@bcowen  Detroit is very nice what are you complaining about?


----------



## L0rdGwyn

UntilThen said:


> Have you make my Auris Nirvana contender yet Lord Gwyn? If not I'll have to drop the Lord title and then camp myself in the 1101 thread instead.



Lol nope not yet, gotta finish up the projects I have in progress before officially starting on a Head-Fi community type of design.  Just completed the 45 amp, 841 should be done in the next two weeks, then will focus on the 801A A2 SET while doing Darkvoice mods on the side.  THEN I can think about EL34 SET vs some sort of OTL headphone amp, so it’s gonna be a little while.


----------



## UntilThen

I was kidding you Keenan. I'm going to take a step back and consider what I want going forward. I've been playing around with 'cheap' solid state amps a bit, just to get a taste of what their higher end counterparts are like. 

SMSL SP200 is considered to be quite similar to Benchmark HPA4 tone. Never heard HPA4 but SP200 at $260 sounds like a dynamite. Some might consider it too bright. Others will say it's neutral without adding any colouration. It has energy and impact though. I used to sneered at low cost gear that are made in China but that perception is slowly changing as I hear it for myself.

Questyle CMA Twelve isn't exactly cheap not is it too expensive. It has a lovely neutral / warm tone and a very solidly constructed dac / preamp / amp in a 10mm aviation grade aluminium chassis. Feels solid too. Questyle Golden Reference was at one time considered high end in both price and sound. Check out the reviews.

Violectric V280 is a v8 in a small form factor. It has that deep throttle appeal. Almost felt like a tube amp and that curvy sexy bottom will get your attention. This is the slim version of the v281 with almost similar power output but only a little less - just.

Woo Audio Wa22 - what can I say. Despite a lot of Woo bashing, I like it. Leftside likes it too. @bcowen likes it too. So I have numbers at my side.  

So a picture of my lockdown gear in Sydney. The rest of my gear, Oblivion, LF339, Yggdrasil are in Canberra. I'm the man of 2 cities. Sydney Carton is the hero who lays down his life... for the love of his life and his friend. What a story. What courage, what selflessness and supreme love. It's time to say goodbye to head-fi and contemplate the life of Sydney Carton.


----------



## whirlwind

L0rdGwyn said:


> Here is the 45 amp's final destination, back in the bedroom stereo with the Klipsch KG 1.
> 
> 
> 
> Just have a cheap Topping DAC and a Bluesound streamer right now, might upgrade the DAC to something fancy at some point.  Sounds great though, very happy with the result.




What a killer bedroom set-up.
My bed room set-up consist of the Hiby R3 Pro and some cheap Chi-Fi iem's.


----------



## CJG888

Did you make any modifications to the KG 1s?


----------



## L0rdGwyn

UntilThen said:


> I was kidding you Keenan. I'm going to take a step back and consider what I want going forward. I've been playing around with 'cheap' solid state amps a bit, just to get a taste of what their higher end counterparts are like.
> 
> SMSL SP200 is considered to be quite similar to Benchmark HPA4 tone. Never heard HPA4 but SP200 at $260 sounds like a dynamite. Some might consider it too bright. Others will say it's neutral without adding any colouration. It has energy and impact though. I used to sneered at low cost gear that are made in China but that perception is slowly changing as I hear it for myself.
> 
> ...



Making the change to solid state certainly would save you a lot of tube cash!  I owned the Violetric V100 at one time, that was a nice solid state amplifier, although I preferred my tubes to it  I have some interest in solid state designs, particularly those based on SIT / VFETs.  While they are solid state parts, these transistors behave similarly to triodes and can be operated without negative feedback.  I plan to build a VFET power amplifier at some point and pair it with a tube preamp.  Certainly a nice setup to have at your home away from home.



whirlwind said:


> What a killer bedroom set-up.
> My bed room set-up consist of the Hiby R3 Pro and some cheap Chi-Fi iem's.



Thanks Joe, your listening room more than makes up for it, it kicks ass!



CJG888 said:


> Did you make any modifications to the KG 1s?



I essentially kept them stock.  I was able to buy a second pair of KG 1 crossovers, I measured and found the best matched set of caps for the pair of crossovers using the four I had and also replaced the bipolar electrolytics.  So nothing crazy, wanted to keep them somewhat true to the originals!


----------



## bcowen

UntilThen said:


> Woo Audio Wa22 - what can I say. Despite a lot of Woo bashing, I like it. Leftside likes it too. @bcowen likes it too. So I have numbers at my side.



I haven't ever heard the Woo, but if _you_ say I like it I probably do. 



UntilThen said:


> It's time to say goodbye to head-fi and contemplate the life of Sydney Carton.



Oh, please.  You obviously need another cup of coffee.  I will eventually win the numbers contest of course, but winning is no fun if the other team just quits showing up.


----------



## Zachik

UntilThen said:


> I've been playing around with 'cheap' solid state amps a bit, just to get a taste of what their higher end counterparts are like.


Add to your list the HeadAmp Gilore Lite mk2 ($500 in the US) and/or its big brother the GS-X mini ($1800). Great solid state amps, IMHO. 
I own the GLmk2 (actually, 2 of them) with the cap mod (and one in stock form). You can find it used on Head-Fi for $250-300... well worth it


----------



## CJG888

The real reason for tube amps: the thrill of the chase (NOS tubes)....


----------



## UntilThen

L0rdGwyn said:


> Making the change to solid state certainly would save you a lot of tube cash! I owned the Violetric V100 at one time, that was a nice solid state amplifier, although I preferred my tubes to it  I have some interest in solid state designs, particularly those based on SIT / VFETs. While they are solid state parts, these transistors behave similarly to triodes and can be operated without negative feedback. I plan to build a VFET power amplifier at some point and pair it with a tube preamp. Certainly a nice setup to have at your home away from home.



It's not about saving on tube cash. I quite enjoy seeing parcels of tubes arriving every alternate days in the past. Make no mistake I still like tubes but solid state is very quiet and can be ultra revealing. It's just 2 polar opposite. Not saying all ss and tube amps are the same but we all know that.

I just received a pair of Mullard GZ32 rectifiers for my Wa22 yesterday and in the last month have bought quite a few tubes for LF339.


----------



## UntilThen

Zachik said:


> Add to your list the HeadAmp Gilore Lite mk2 ($500 in the US) and/or its big brother the GS-X mini ($1800). Great solid state amps, IMHO.
> I own the GLmk2 (actually, 2 of them) with the cap mod (and one in stock form). You can find it used on Head-Fi for $250-300... well worth it



I was actually contemplating the GS-X mini or it's bigger brother. Or the new Violectric V590 or Niimbus. Just one will do. While I'm toying with a number of 'cheaper' variants here, eventually will settle on one and perhaps 2 tube amps.   I doubt I will have the discipline. Amp rolling is definitely more pronounced than tube rolling. Headphones rolling is even more.


----------



## UntilThen

bcowen said:


> Oh, please. You obviously need another cup of coffee. I will eventually win the numbers contest of course, but winning is no fun if the other team just quits showing up.



I concede. You win.  I am however trying to organise a yearly Sydney Can event with the help of a headphone audio gear reviewer. So you have to move to Sydney if you want any contest.


----------



## Zachik

UntilThen said:


> I was actually contemplating the GS-X mini or it's bigger brother.


I actually liked the GS-X mini WAY more than its bigger brother! Go figure...


----------



## UntilThen

Zachik said:


> I actually liked the GS-X mini WAY more than its bigger brother! Go figure...



Good for our pockets then.  

I just bought the Schiit Mjolnir 2 to partner my Yggdrasil. After I sold off the Ragnarok and Jotunheim, I did not think about Schiit amps anymore but this sale came up and the unit is so 'new' and comes with the Amperex Orange globes. So I thought why not and went for it. To my surprise I like it. Here I have CMA12 dac > Mjolnir2 > Hekse and it's pretty good to my ears. So I won't be jumping on the GSX Mini so soon yet.


----------



## whirlwind

*HA!

HERE WE GO BROWNIES!!!

That was a lot of fun!!*


----------



## UntilThen

@bcowen  what happened? What are they looking at 'Show us your Head-Fi station??? Did you say something funny ? .


----------



## Paladin79

I decided to make another loaner Incubus amp but this time in spalted maple with purple heart splines. The amp will then go to @Ripper2860 while I do some tweaks on his amp, then on to @sam6550a to get his opinion on the amp. Nothing real fancy on this one other than the cabinet. I may loan some purple cables with it, just to set it off a bit.

Woods of choice.


----------



## bcowen

UntilThen said:


> @bcowen  what happened? What are they looking at 'Show us your Head-Fi station??? Did you say something funny ? .



I probably said something funny, but I have no idea what you're talking about.


----------



## UntilThen

Paladin79 said:


> I decided to make another loaner Incubus amp but this time in spalted maple with purple heart splines.



Love the wood. You're good at doing this. I'm just thinking of the Nirvana with the wooden enclosure. You could turn out a wooden enclosure much better. Imagine a purple heart splines enclosure.


----------



## UntilThen

bcowen said:


> I probably said something funny, but I have no idea what you're talking about.



You're blind. Can't you see 37 users and 44 guests looking in when I was giving the 'fourscore and seven years' speech at 5am. Simon and Art Garfunkel sang Sound of Silence at 3am and I sang mine at 5am.


----------



## bcowen

UntilThen said:


> You're blind. Can't you see 37 users and 44 guests looking in when I was giving the 'fourscore and seven years' speech at 5am. Simon and Art Garfunkel sang Sound of Silence at 3am and I sang mine at 5am.



So _that's_ why I woke up with a headache.


----------



## bcowen

Paladin79 said:


> I decided to make another loaner Incubus amp but this time in spalted maple with purple heart splines. The amp will then go to @Ripper2860 while I do some tweaks on his amp, then on to @sam6550a to get his opinion on the amp. Nothing real fancy on this one other than the cabinet. I may loan some purple cables with it, just to set it off a bit.
> 
> Woods of choice.



Is the spalted maple an upgrade from my cardboard?  I'm wondering if I should be feeling jealous.


----------



## UntilThen

bcowen said:


> So _that's_ why I woke up with a headache.


----------



## Paladin79

bcowen said:


> Is the spalted maple an upgrade from my cardboard?  I'm wondering if I should be feeling jealous.


Na your case is special, your amp has its own shipping carton.


----------



## L0rdGwyn

whirlwind said:


> *HA!
> 
> HERE WE GO BROWNIES!!!
> 
> That was a lot of fun!!*



GO BROWNS!!!  Wasn't able to watch unfortunately, had to work, but caught bits and followed along as I could, incredible win.  Coming off of five 13 hour night shifts in a row, my life is in shambles.  Now that I have rejoined the world of the humans, going to see if I can get some work done on the 841 amp over the next two days.  Started working on my radio restoration today, but didn't have the energy to take pics and whatnot, more to come on that front.


----------



## whirlwind (Jan 13, 2021)

L0rdGwyn said:


> GO BROWNS!!!  Wasn't able to watch unfortunately, had to work, but caught bits and followed along as I could, incredible win.  Coming off of five 13 hour night shifts in a row, my life is in shambles.  Now that I have rejoined the world of the humans, going to see if I can get some work done on the 841 amp over the next two days.  Started working on my radio restoration today, but didn't have the energy to take pics and whatnot, more to come on that front.



Thanks for all that you and many , many others do working in your field. What a terrible health crisis that we are in. I never , ever imagined anything like this.
Thanks...you people are real troopers.
Many people take the people on the front lines for granted...just think, where would we be without them all ?


----------



## CJG888

As there seem to be lots of NOS tube experts here, I have a question:

Back in the 90s, I bought a number of these ECC83s from Centre Electronics in Birmingham (UK). They are NOS (plain white boxes), apparently Yugoslavian. They have an ‘O‘-getter. I wonder if they might be Ei? Any ideas?

























Sound is both warm and detailed.

Labels wipe off very easily (in fact, it happened during photographing - see lower code)...


----------



## L0rdGwyn

whirlwind said:


> Thanks for all that you and many , many others do working in your field. What a terrible health crisis that we are in. I never , ever imagined anything like this.
> Thanks...you people are real troopers.
> Many people take the people on the front lines for granted...just think, where would we be without them all ?



Thanks Joe, I appreciate that, certainly has been interesting at work, very much looking forward to getting back to some sort of normality, hopefully later this year.



CJG888 said:


> As there seem to be lots of NOS tube experts here, I have a question:
> 
> Back in the 90s, I bought a number of these ECC83s from Centre Electronics in Birmingham (UK). They are NOS (plain white boxes), apparently Yugoslavian. They have an ‘O‘-getter. I wonder if they might be Ei? Any ideas?
> 
> ...



I'm not super familiar with internal construction of ECC83, perhaps someone else here is, but there appears to be a date code on one side of the tube, have a picture that shows it?


----------



## CJG888

Not easy to decipher, I’m afraid:


----------



## Galapac

Paladin79 said:


> You are fine. Mine are somewhat boutique I suppose and they were never intended for sale. Unfortunately I let friends hear one and 50 amps later, I am still being asked to build them. All of mine are unique in cabinet design and I used a few levels of parts. My personal Incubus Elegan....



I just recalled where I have seen your amps before....the "Guilty Pleasure Gear Pics" thread on the headphone community forum. 
The one you did in walnut/maple/copper below is pretty sweet, VU meters are a nice touch, very artistic and vintage looking.

Is that a 5998/6SN7 tube combination?


----------



## CJG888

Shades of Moth....


----------



## CJG888

Headphone jack on the side is a good idea.


----------



## CJG888

I suppose this could be the Ei logo?


----------



## CJG888 (Jan 13, 2021)

If they are Eis, they may have been made on Telefunken machinery (although maybe not to the same tolerances).

Apparently those old production lines were destroyed in the Yugoslav war...

I read somewhere that Audio Research used to fit Ei ECC83s as standard (with their own labelling, no less!).


----------



## Paladin79

Galapac said:


> I just recalled where I have seen your amps before....the "Guilty Pleasure Gear Pics" thread on the headphone community forum.
> The one you did in walnut/maple/copper below is pretty sweet, VU meters are a nice touch, very artistic and vintage looking.
> 
> Is that a 5998/6SN7 tube combination?


Yep 6sn7/ 6080 or 6as7 build. That build was pretty complex and I doubt I will do it again, just too much labor. The brushed copper especially.

I am trying to decide on a loaner to send out to friends, if I use this wood it may not make it very far, some lacewood boards I just stacked up to check look. This is a simpler build and I have a bunch of these metal plates, I cut every single hole in the copper. If I make the next one too pretty it may not make it to a lot of people, this is my Incubus Elegan amp.


----------



## Paladin79

CJG888 said:


> Headphone jack on the side is a good idea.


That has two headphone jacks, one on each side. Two sets of headphones can be used but they work best if the headphones are similar impedance. Those who understand resistance in parallel will have a pretty good idea why that is.


----------



## bcowen

Paladin79 said:


> That has two headphone jacks, one on each side. Two sets of headphones can be used but they work best if the headphones are similar impedance. Those who understand resistance in parallel will have a pretty good idea why that is.



Even those of us that don't understand resistance in parallel can only listen to one pair of headphones at a time. Well, except maybe @Ripper2860 who has like 6 ears or something...


----------



## Paladin79

bcowen said:


> Even those of us that don't understand resistance in parallel can only listen to one pair of headphones at a time. Well, except maybe @Ripper2860 who has like 6 ears or something...


Some of us allow a wife or son or daughter to listen as well. They might even return if not subjected to Marilyn Manson you know.


----------



## bcowen

Paladin79 said:


> Some of us allow a wife or son or daughter to listen as well. They might even return if not subjected to Marilyn Manson you know.



Well, *I* wear the pants in my house.


----------



## Paladin79

bcowen said:


> Well, *I* wear the pants in my house.


I always pictured you as more of a kilt man myself, or a pleated skirt if listening to Manson.


----------



## Ripper2860

bcowen said:


> Even those of us that don't understand resistance in parallel can only listen to one pair of headphones at a time. Well, except maybe @Ripper2860 who has like 6 ears or something...



I find it much easier to roll ears as opposed to HP pads.


----------



## Ripper2860

bcowen said:


> Well, *I* wear the *SPANX* in my house.



Fixed it for you.  😏


----------



## leftside

Paladin79 said:


> I always pictured you as more of a kilt man myself, or a pleated skirt if listening to Manson.


Beautiful.... People.


----------



## Tjj226 Angel

bcowen said:


> Even those of us that don't understand resistance in parallel can only listen to one pair of headphones at a time. Well, except maybe @Ripper2860 who has like 6 ears or something...



What do you not understand about resistance in parallel? 

Traffic on a one lane road will move much more slowly than traffic on a 2 lane road.


----------



## L0rdGwyn

Finally making some headway on the 841 amplifier, just been so damn busy lately!  I started mounting some of the parts.  This thing should come together pretty quickly.

The recessed socket mounting came out really well.  Not gonna lie, it looks real dope with a pair of globe 841 in place.


----------



## bcowen

Tjj226 Angel said:


> What do you not understand about resistance in parallel?
> 
> Traffic on a one lane road will move much more slowly than traffic on a 2 lane road.



It was intended as a joke.


----------



## Tjj226 Angel

bcowen said:


> It was intended as a joke.


----------



## bcowen

Paladin79 said:


> I always pictured you as more of a kilt man myself, or a pleated skirt if listening to Manson.



Marilyn Manson requires tighty whities to prevent possible interference with the air guitar.


----------



## Paladin79

bcowen said:


> Marilyn Manson requires tighty whities to prevent possible interference with the air guitar.


Thanks for sharing that.  

Today I should be receiving some LS 50 Telefunken power tubes, WW2 vintage to try in my power amp formerly known as Cowen thanks to the kindness of @Old Deaf Donkey.


----------



## Old Deaf Donkey

Paladin79 said:


> Thanks for sharing that.
> 
> Today I should be receiving some LS 50 Telefunken power tubes, WW2 vintage to try in my power amp formerly known as Cowen thanks to the kindness of @Old Deaf Donkey.


Seriously, I'd vote for keeping the name of that amp. Cowen sounds noble!


----------



## Ripper2860

My vote is to call it 'The Sorbothane Amp'.  For some reason Sorbothane is Bill's Kryptonite.


----------



## L0rdGwyn

Here are the filament and mains transformers before and after shielding.  Gives you an idea of what the final look is going to be sans tubes.


----------



## Paladin79 (Jan 14, 2021)

Special thanks go out to @Old Deaf Donkey for some 1942 Kriegsmarine Telefunken LS 50 tubes for my amp, sometimes known as the Cowen.     I will plug them in after a company Zoom meeting and see how they do. They are obviously NOS and the pins are in remarkable shape.

I won a bet using Russian tubes so now it is time to reinvest some of my winnings into the amp and to see what the Telefunkens do for it, driver and power tubes.


----------



## CJG888

U-Boot tubes...


----------



## Paladin79

Old Deaf Donkey said:


> Seriously, I'd vote for keeping the name of that amp. Cowen sounds noble!


Paulius sound much more noble, and more modest.


----------



## CJG888

The bass should go deep!


----------



## Paladin79

CJG888 said:


> U-Boot tubes...


uh huh


----------



## Paladin79

L0rdGwyn said:


> Here are the filament and mains transformers before and after shielding.  Gives you an idea of what the final look is going to be sans tubes.


I have not read back far enough to know, is that a kit or did you have the top cut for your own design?


----------



## L0rdGwyn

Paladin79 said:


> I have not read back far enough to know, is that a kit or did you have the top cut for your own design?



It is my design, the chassis and layout were done in AutoCAD then machined.  First time I've done the entire layout without the chassis in front of me, but seems to have worked out well!


----------



## UntilThen

bcowen said:


> Well, *I* wear the pants in my house.



Are you sure?


----------



## UntilThen

Old Deaf Donkey said:


> Seriously, I'd vote for keeping the name of that amp. Cowen sounds noble!



I was going to call it UntilThen but whatever.


----------



## UntilThen

L0rdGwyn said:


> Here are the filament and mains transformers before and after shielding.  Gives you an idea of what the final look is going to be sans tubes.



Woah can I have that. I'll name it UntilThen. What is this? Speaker amp or headphone amp or just a night lamp? Ok kidding but looks very nice even half finish. What is it?


----------



## Tjj226 Angel

UntilThen said:


> Woah can I have that. I'll name it UntilThen. What is this? Speaker amp or headphone amp or just a night lamp? Ok kidding but looks very nice even half finish. What is it?



That there is a high octane hand warmer for the cold ohio winters. 

BUT WAIT. THERE'S MORE!

It also has a built in headphone amp for your convenience.


----------



## UntilThen

Tjj226 Angel said:


> That there is a high octane hand warmer for the cold ohio winters.
> 
> BUT WAIT. THERE'S MORE!
> 
> It also has a built in headphone amp for your convenience.



Subscribed !


----------



## L0rdGwyn (Jan 14, 2021)

UntilThen said:


> Woah can I have that. I'll name it UntilThen. What is this? Speaker amp or headphone amp or just a night lamp? Ok kidding but looks very nice even half finish. What is it?



It's a headphone amp, a hybrid.  841 thoriated tungsten DHT for voltage gain, filament biased, Cree SiC FET for current gain, Sowter 8665 output transformers.  I prototyped it a few months ago, it sounds purdy good!



Tjj226 Angel said:


> That there is a high octane hand warmer for the cold ohio winters.
> 
> BUT WAIT. THERE'S MORE!
> 
> It also has a built in headphone amp for your convenience.



Not only that, it is also...a reading lamp!  @UntilThen nailed it.  Because let's be honest, these tubes are basically light bulbs.


----------



## CJG888

Thoriated tungsten = mildly radioactive ☢️


----------



## bcowen

UntilThen said:


> Are you sure?



Just looked.  Yup.


----------



## L0rdGwyn

CJG888 said:


> Thoriated tungsten = mildly radioactive ☢



Only a concern if ingested.  Although tempting, I do not plan to eat the filaments.


----------



## bcowen

CJG888 said:


> Thoriated tungsten = mildly radioactive ☢



Does this make them more susceptible to RFI then?


----------



## L0rdGwyn

bcowen said:


> Does this make them more susceptible to RFI then?



The gamma rays go straight from the tubes through your head right to your eardrums, ultimate transparency, no headphones necessary.  The brain cancer is worth it.


----------



## bcowen

L0rdGwyn said:


> Only a concern if ingested.  Although tempting, I do not plan to eat the filaments.



Well since that just killed tonight's dinner plans, you can always order pizza.  Most of what we have available for delivery around here resembles food, kind of.


----------



## whirlwind

L0rdGwyn said:


> Here are the filament and mains transformers before and after shielding.  Gives you an idea of what the final look is going to be sans tubes.



Nice....what sockets are those for the 841's ?


----------



## UntilThen

L0rdGwyn said:


> Not only that, it is also...a reading lamp! @UntilThen nailed it. Because let's be honest, these tubes are basically light bulbs.



I always knew I have the foresight.   Question - is this the Auris Nirvana contender? I.e at least 6 watts into 32 ohms ? How about make it 8? Got to drive those Tannoy Wesminster !


----------



## Xcalibur255

The worst part of winter isn't even the cold anymore it's the insane hurricane force straight winds that are becoming increasingly common now.  Then summer rolls around and it hails every 3 days.  I don't even complain about blizzards anymore, though being without power for 11 days when winter storm Atlas hit us was memorable......

Why do I live here again.....?


----------



## UntilThen

Come to Australia, Xcalibur and bring your KT150 amp when it's ready.


----------



## L0rdGwyn

whirlwind said:


> Nice....what sockets are those for the 841's ?



They are CMC teflon sockets, the poor man's Yamamoto  I think they are pretty nice though, for the price.



UntilThen said:


> I always knew I have the foresight.   Question - is this the Auris Nirvana contender? I.e at least 6 watts into 32 ohms ? How about make it 8? Got to drive those Tannoy Wesminster !



Nope, this amplifier will put out a measly 0.5W!  How will it power anything?  I am told certain headphones require 15W amplifiers these days to be "driven".  Maybe I am overconfident, but I think this amp will sound better than the sneeze glass amp.


----------



## Xcalibur255

I need transmitter tubes to power my IEMs, and make sure there's no hum either mister!


----------



## L0rdGwyn

I think that's all for today, didn't get super far but it's a start!  Filament supply is nearly done, will take it up again this weekend.


----------



## UntilThen

L0rdGwyn said:


> I am told certain headphones require 15W amplifiers these days to be "driven".



For those headphones, I'll use my Sansui au alpha 907mr or Redgum Rgi120enr. I'm actually not keen on a combination speaker/headphone amp. I like to keep those 2 functions separate. I.e. a dedicated integrated amp or separates for stereo and headphone amps strictly for headphones and a dap for iems but I don't use iems apart for my Senns Momentum wireless earbads.


----------



## Tjj226 Angel

CJG888 said:


> Thoriated tungsten = mildly radioactive ☢



Thorium is pretty mild all things considered. 

Try the voltage regulator tubes filled with krypton gas.


----------



## Galapac

Thought I cross post this from the 339i thread...may be interest here.

https://www.head-fi.org/threads/la-figaro-339.502306/post-16106315


----------



## Galapac

Thought I’d share another CP

Nice look inside an Eddie Current amp...real nice.

https://www.head-fi.org/threads/zmf-verite-closed-new-closed-back-zmf-flagship.911505/post-16106214


----------



## UntilThen

I've seen the internals of that ec amp before from @Liu Junyuan 's pictures and where's LJ these days?


----------



## UntilThen

Bet you haven't seen the internals of my previous GOTL. Work of art I'd say. Glenn created so many more after that. This is the Super 9.


----------



## UntilThen

I think I should get another GOTL again.


----------



## leftside

Galapac said:


> Thought I cross post this from the 339i thread...may be interest here.
> 
> https://www.head-fi.org/threads/la-figaro-339.502306/post-16106315


There's been a few pairs sell for $150 lately, but not all had slotted plates, and didn't test as high as these. Great tubes.


----------



## UntilThen

Too late the Bendix(s) are gone now.


----------



## Galapac

Without listening to both 


UntilThen said:


> Bet you haven't seen the internals of my previous GOTL. Work of art I'd say. Glenn created so many more after that. This is the Super 9.


If I were to judge on pure aesthetics I’d prefer the cleaner look of the EC but I haven’t heard either one and not sure I would prefer a does it all amp.


----------



## UntilThen (Jan 14, 2021)

Galapac said:


> Without listening to both
> 
> If I were to judge on pure aesthetics I’d prefer the cleaner look of the EC but I haven’t heard either one and not sure I would prefer a does it all amp.



It's cleaner because it uses less tubes. On GOTL there are 7 sockets. Though I haven't heard the EC, it would be hard to beat the 6 x 6BX7gt and a nice 6sn7 sound and Glenn's tuning is amazing.


----------



## Galapac

Yeah crazy what those GOTL amps can do, he definitely has a big following. He is tough to get ahold of these days. I have had only one response from him in three months. Have you heard from him?


----------



## UntilThen

I'm not talking up about how configurable it is. What impressed me is 6 x 6bx7gt or some nice pairs of 6080 / 6as7g or 6336. GOTL is very unique in it's tone and I love it. That despite hearing Studio Six, Wa22 and the other competitors. 

If you're trying to get onboard now, it's probably too late unless you're willing to wait, wait, wait. DNA Stratus has a long queue too but it's getting better to 6 months. That's what Donald told me and I'm still trying to get my hands on that Smurf.


----------



## leftside

Galapac said:


> Yeah crazy what those GOTL amps can do, he definitely has a big following. He is tough to get ahold of these days. I have had only one response from him in three months. Have you heard from him?


I have a Glenn amp and like it a lot, but you might have better luck with Mischa at the moment - although I hear his waitlist is also expanding.
https://www.head-fi.org/threads/1101-audio-custom-crafted-headphone-amps.919425/
https://www.head-fi.org/showcase/1101-audio-blue-halo-otl-tube-headphone-amplifier.24755/

I think Mischa also created another thread, but I can't seem to find it...


----------



## Galapac

@UntilThen - Did you put your order in for a DNA yet? I know you wanted one and it was on your wish list. I used to build little electronic science projects in high school and they all used that blue color box. I built a Tesla coil with one.


----------



## UntilThen

I spoke to Donald before Christmas about the Stratus and he told me that all parts of the present Stratus are spoken for with confirmed orders but he told me he's working on an improved model that sits between Stratus and Stellaris and once that is designed, waiting times will be 6 months at least. 

So I insist that the new model be call UntilThen - you hear that @bcowen and @Old Deaf Donkey ?


----------



## UntilThen

leftside said:


> I have a Glenn amp and like it a lot, but you might have better luck with Mischa at the moment - although I hear his waitlist is also expanding.
> https://www.head-fi.org/threads/1101-audio-custom-crafted-headphone-amps.919425/
> https://www.head-fi.org/showcase/1101-audio-blue-halo-otl-tube-headphone-amplifier.24755/
> 
> I think Mischa also created another thread, but I can't seem to find it...



That's why I'm trying to get to know Mischa better like add him to my Linkedin. Failing that I'll have to learn how to create my own tube amp.


----------



## Galapac

leftside said:


> I have a Glenn amp and like it a lot, but you might have better luck with Mischa at the moment - although I hear his waitlist is also expanding.
> https://www.head-fi.org/threads/1101-audio-custom-crafted-headphone-amps.919425/
> https://www.head-fi.org/showcase/1101-audio-blue-halo-otl-tube-headphone-amplifier.24755/
> 
> I think Mischa also created another thread, but I can't seem to find it...


Thank you for this. Although I am not in the market right now for a new amp I will read these threads and keep Mischa in mind.


----------



## bcowen (Jan 14, 2021)

UntilThen said:


> I spoke to Donald before Christmas about the Stratus and he told me that all parts of the present Stratus are spoken for with confirmed orders but he told me he's working on an improved model that sits between Stratus and Stellaris and once that is designed, waiting times will be 6 months at least.
> 
> So I insist that the new model be call UntilThen - you hear that @bcowen and @Old Deaf Donkey ?



Perhaps appropriate, but no audiophile worth his salt has the patience to wait _Until Then_.  6 months?  6 _days_ is a stretch for me. After 6 months I'd probably forget I'd even ordered it. Or what I ordered it for.


----------



## bcowen

UntilThen said:


> That's why I'm trying to get to know Mischa better like add him to my Linkedin. Failing that I'll have to learn how to create my own tube amp.



We'll all keep our fingers crossed that you can build on the relationship with Mischa. The alternative could cause Australia to blow up, and none of us want to see that.


----------



## UntilThen

bcowen said:


> We'll all keep our fingers crossed that you can build on the relationship with Mischa. The alternative could cause Australia to blow up, and none of us want to see that.



We're meeting half way in Guam. That way only an island will blow up.


----------



## bcowen (Jan 14, 2021)

UntilThen said:


> We're meeting half way in Guam. That way only an island will blow up.



LOL!  But wait...isn't Australia an island?  I mean a really _big_ one, of course.  But if it blows, I'll have nowhere to drive your golf cart into the lake.


----------



## UntilThen

You must know the difference between an island and a continent. You can try to drive that golf cart from Sydney to Perth if you can find charging station along the way.

and btw where's @L0rdGwyn  we're really going off topic 3 pages ago.


----------



## bcowen

UntilThen said:


> You must know the difference between an island and a continent. You can try to drive that golf cart from Sydney to Perth if you can find charging station along the way.
> 
> and btw where's @L0rdGwyn  we're really going off topic 3 pages ago.



He's probably patiently waiting for us to get back on topic, and rolling his eyes UntilThen.


----------



## Galapac

bcowen said:


> He's probably patiently waiting for us to get back on topic, and rolling his eyes UntilThen.


I think he mentioned he was doing another all nighter at work. God bless him.


----------



## L0rdGwyn

Sorry gents, have a lot going on lately, feel free to discuss whatever you please!


----------



## Xcalibur255

Starting to get the itch to get a new headphone again but I can't nail down a choice that passes the "gut feeling" test.  I was going to sell off most of my current headphones and get a Focal Clear but something makes me hesitate.  Nothing in my current collection sounds truly right to me, they all have some kind of wonky or unnatural sounding quirk in their presentation.  All my years in this hobby and I still haven't had my Goldilocks "just right" moment with headphones.


----------



## CJG888

DT48A. Seriously.


----------



## Tjj226 Angel

Xcalibur255 said:


> Starting to get the itch to get a new headphone again but I can't nail down a choice that passes the "gut feeling" test.  I was going to sell off most of my current headphones and get a Focal Clear but something makes me hesitate.  Nothing in my current collection sounds truly right to me, they all have some kind of wonky or unnatural sounding quirk in their presentation.  All my years in this hobby and I still haven't had my Goldilocks "just right" moment with headphones.



I like the LCD-3s pre fazor. 

Planar, ESL, or bust.


----------



## A2029

Xcalibur255 said:


> Starting to get the itch to get a new headphone again but I can't nail down a choice that passes the "gut feeling" test.  I was going to sell off most of my current headphones and get a Focal Clear but something makes me hesitate.  Nothing in my current collection sounds truly right to me, they all have some kind of wonky or unnatural sounding quirk in their presentation.  All my years in this hobby and I still haven't had my Goldilocks "just right" moment with headphones.



If looking for a relatively cheaper option, but one that still scales very well with the upstream gear, I often suggest the Senn HD6XX headphones. Not the most high end, and they lack in the bass department and have a few other frequency response nit-picks, but very good bang-for-the-buck.


----------



## L0rdGwyn

I am also a big fan of the HD650, really does scale well!  Of course it is not as revealing as TOTL headphones, but the tonality is on point IMO.  The gap closes significantly with a high-quality amplifier.


----------



## Xcalibur255

CJG888 said:


> DT48A. Seriously.


I think the problem there would be comfort.  Excessive clamp and pressure points are a significant issue for me.  Even my DT880 used to bother me a little before I got used to them and they're probably the most comfortable headphone you can buy.


----------



## Xcalibur255

Tjj226 Angel said:


> I like the LCD-3s pre fazor.
> 
> Planar, ESL, or bust.


I have an original LCD-2 pre fazor (not the "classic" re-issue).  Kind of a love-hate relationship with it.  I think the top end has a distinctly un-natural metallic overtone to it that I cannot unhear these days and attempting to bury it through tube rolling choices just produces an overall sound that is too unbalanced.


----------



## CJG888

Xcalibur255 said:


> I think the problem there would be comfort.  Excessive clamp and pressure points are a significant issue for me.  Even my DT880 used to bother me a little before I got used to them and they're probably the most comfortable headphone you can buy.


I would not advocate using the original solid rubber pads. They do the sound no favours, and are essentially medical equipment, designed to be easily cleaned between patients...

I fitted the latest circumaural pads to mine, which greatly improved comfort and tonal balance. At the same time, a new head pad, new hardware (sliders, nuts & bolts), and (very important, this) a FAW Claire Mk 2 cable were fitted.

You soon get used to the clamp- the pads are designed for professional monitoring applications. After a while, you forget you are wearing them.


----------



## CJG888

The main issue at the moment is that I keep hearing tape edits, oxide stripping etc.!


----------



## Xcalibur255

So I've always stayed away from the HD650 because it wouldn't play nice with the Glenn 45.  Anything that high impedance doesn't.  This is why I was interested in the Focal Clear, the overall tonal balance between it and the HD650 seems quite close, maybe a little closer to an HD600 but it's in the ballpark.  What bothers me about it is the reports of high clamp force and high weight.  Having the disadvantages of a planar in a dynamic headphone is a tough sell, especially at $1,500.  If I want something heavy on my head I might as well go planar.

I considered the Ether 2 for a long time too.  I have an original Ether.  It's not a bad headphone, but the tuning has a sense of immaturity to it with too much narrow band spotlighting in certain frequencies and a lack of smooth transition.  There's a reason why the resale value on them as dropped like a rock and I kind of regret buying them even though they're an okay listen.  What bothers me about Ether 2, and DCA in general, is how polarized everybody's opinions on them are.  They are either the BEST EVER or they are the WORST EVER and you never really see opinions in between.  This leads me to believe from my experience as a quality coordinator that they have an undiscovered ongoing manufacturing variance issue and people are getting distinctly different experiences from the same headphone.  Ether 2 is way too expensive a product for a potential dice roll like that.

I wish I could *try* the Focal, but that's part of living where I live.  Nearest dealer is many miles away.


----------



## Tjj226 Angel (Jan 15, 2021)

Xcalibur255 said:


> I have an original LCD-2 pre fazor (not the "classic" re-issue).  Kind of a love-hate relationship with it.  I think the top end has a distinctly un-natural metallic overtone to it that I cannot unhear these days and attempting to bury it through tube rolling choices just produces an overall sound that is too unbalanced.



The LCD-3 fixes that top end issue. Especially with a proper cable.

Do you have a new cable for the LCD-2? Audeze cables are utter junk.


----------



## Xcalibur255

Yeah I have a Norne Draug 3 on it.  Definitely an improvement.  I think my impressions are colored by the last time I tried to listen to it though, as that was when I found out the G45 had returned to being a "problem child" so to speak.

For years I have wondered how much of this is me and not the gear.  My hearing changes pretty wildly day to day depending on some things.  But...... there is enough repeatability to the issues I hear that I remain confident that it can't ALL be in my head.  If it is then I wish somebody would tweak the simulation for me a bit.


----------



## UntilThen

Ah you're all talking headphones here. Mistake me coming in here @bcowen . Now my post counts will sky rocket. It's already 60 today.

Strange you're all talking about the headphones I love. 

I have LCD-3f, LCD-X, HD800, He1000se, HD650 and an incoming HD800S. Al my cables are Forza Audioworks Noir Hybrid HPC, Noir HPC Mk2 and Claire Hybrid Mk2.

Love the Audeze(s) a lot. Dreaming of the LCD-4 now. However the He1000se which I had since New Year's Eve is just simply gorgeous to my ears. 

3 days ago I heard the HD800S. Have a HD800 for 4 years and still have it. 3 years ago, I heard the HD800S in a meet, back to back with a HD800. HD800S sounded awful then after switching over from HD800 immediately. However 3 days ago, a friend came over with his HD800S and I listen to it with Questyle CMA 12 and the bass surprised me. Now I'm committed to buy a HD800S and it's coming soon !

HD650 sits in the box. Occasionally I take it out and listen to it. Sounds good with all my amps. Scales well but I just can't use it when I prefer the other headphones.


----------



## bcowen

UntilThen said:


> Ah you're all talking headphones here. Mistake me coming in here @bcowen . Now my post counts will sky rocket. It's already 60 today.
> 
> Strange you're all talking about the headphones I love.
> 
> ...



Well, since you brought it up   I'm looking for a pair of high impedance closed 'phones. I need the closed for domestic tranquility, and I need the high impedance 'cause neither of my OTL amps play nicely with low impedances. 300 ohms is ideal, but probably down to 150 or so would get by. Any great ideas that don't require a 2nd mortgage? Been considering the ZMF Atticus, but I'd really like to spend not that much.


----------



## UntilThen

Bcowen if Atticus is too much, you have to get a Beats instead or a Bose Quietcomfort 35. 

However for you of aristocratic background, you have to consider ZMF Verite closed, Focal Stella, Senn hd820, etc... I dunno I don't do closed headphones. The world is my oyster and I wear only open headphones. Anything else and you're missing the experience.


----------



## Galapac

@bcowen - Focal just came out with this closed version which people have been saying good things about, if you don’t mind the Bentley logo and they look pretty sharp. You can get an open box version here for a bit cheaper or buy new with a 1 year return option, no questions asked.

https://www.headphones.com/collections/closed-back/products/focal-radiance-open-box


----------



## bcowen

UntilThen said:


> Bcowen if Atticus is too much, you have to get a Beats instead or a Bose Quietcomfort 35.
> 
> However for you of aristocratic background, you have to consider ZMF Verite closed, Focal Stella, Senn hd820, etc... I dunno I don't do closed headphones. The world is my oyster and I wear only open headphones. Anything else and you're missing the experience.



Problem is that without closed 'phones I'm also missing the experience. In totality.  With the spousal unit in close proximity, I can't get through an entire song without the "What in hell are you listening to NOW?" interruption.  With closed 'phones she can't hear it, and more importantly I can't hear her.   And me wearing the pants in this house is strangely exempt in this particular scenario.


----------



## bcowen

Galapac said:


> @bcowen - Focal just came out with this closed version which people have been saying good things about, if you don’t mind the Bentley logo and they look pretty sharp. You can get an open box version here for a bit cheaper or buy new with a 1 year return option, no questions asked.
> 
> https://www.headphones.com/collections/closed-back/products/focal-radiance-open-box



Thanks!  Love the looks of those, but they're only 35 ohm impedance which is too low I'm afraid.


----------



## UntilThen

bcowen said:


> Problem is that without closed 'phones I'm also missing the experience. In totality.  With the spousal unit in close proximity, I can't get through an entire song without the "What in hell are you listening to NOW?" interruption.  With closed 'phones she can't hear it, and more importantly I can't hear her.   And me wearing the pants in this house is strangely exempt in this particular scenario.



Ok you're beyond funny. Everyday I can post a lot of things but if I didn't have interaction with you, then I'm not getting the full experience. Whatever you do, don't leave Head-Fi.


----------



## Galapac

bcowen said:


> Thanks!  Love the looks of those, but they're only 35 ohm impedance which is too low I'm afraid.


Oh yeah, sorry about that.


----------



## UntilThen

Alright just got an email that my LCD-3f is ready for collection. See yous later !


----------



## Xcalibur255

Galapac said:


> @bcowen - Focal just came out with this closed version which people have been saying good things about, if you don’t mind the Bentley logo and they look pretty sharp. You can get an open box version here for a bit cheaper or buy new with a 1 year return option, no questions asked.
> 
> https://www.headphones.com/collections/closed-back/products/focal-radiance-open-box


See, this is the OTHER reason I'm hesitant about Focal.  Half of what you're paying is for the "audio bling" and not the performance.  I appreciate good design as much as the next guy, but if you take the Bentley logo off these and the associated license and legal costs I bet you could lower the price by $200.

I like to support the "little guys" where I can.  That's one of the things that drew me to Mr.Speakers/DCA, but they're asking for $2,200 for the Ether 2 and given their history of quality issues and consistency issues I just can't go for it.


----------



## L0rdGwyn (Jan 15, 2021)

Ooof the Bentley branding on that headphones hurts my eyes.  Reminds me of a guy in high school who took the logo off of his Chrysler 300 and replaced it with a Bentley "B".  Obviously we were all completely fooled and thought he was driving a real Bentley at the ripe age of 17, definitely not tacky!

@bcowen the Atticus would be a good choice, probably could get a pair for a decent price in the classifieds.  I haven't heard them, but a cheaper option for closed back high-impedance headphones is the Beyerdynamic DT1770.  If you wanted to go vintage, could try to find a pair of Sennheiser HD250 Linear (600 ohm) or Linear II (300ohm).  Used to have a pair, very nice and underrated vintage stuff from Sennheiser.


----------



## Xcalibur255

I should probably mentioned that when I said 'good design' I was referring to the Focal line in general, not that silly Bentley logo in particular.


----------



## Ripper2860

Galapac said:


> @bcowen - Focal just came out with this closed version which people have been saying good things about, if you don’t mind the Bentley logo and they look pretty sharp. You can get an open box version here for a bit cheaper or buy new with a 1 year return option, no questions asked.
> 
> https://www.headphones.com/collections/closed-back/products/focal-radiance-open-box



Focal Radiance - Open-Box
Open-Box items are Final Sale

*Order within 2 Days 18 Hrs 11Mins To have it shipped today!*

Wait!  So I can order it on Sunday and still get it shipped today!?  😯


----------



## Galapac

Ripper2860 said:


> Focal Radiance - Open-Box
> Open-Box items are Final Sale
> 
> *Order within 2 Days 18 Hrs 11Mins To have it shipped today!*
> ...


Woah! 😎


----------



## bcowen

Ripper2860 said:


> Focal Radiance - Open-Box
> Open-Box items are Final Sale
> 
> *Order within 2 Days 18 Hrs 11Mins To have it shipped today!*
> ...



You should ask @UntilThen since it's already tomorrow there.


----------



## Zachik

L0rdGwyn said:


> @bcowen the Atticus would be a good choice, probably could get a pair for a decent price in the classifieds. I haven't heard them, but a cheaper option for closed back high-impedance headphones is the Beyerdynamic DT1770


I own an Atticus. @L0rdGwyn I will forgive your comparison to DT1770 since you never auditioned the Atticus. Not even the same league, IMHO, and the signature of ZMF is so much more pleasing and musical


----------



## bcowen

L0rdGwyn said:


> Ooof the Bentley branding on that headphones hurts my eyes.  Reminds me of a guy in high school who took the logo off of his Chrysler 300 and replaced it with a Bentley "B".  Obviously we were all completely fooled and thought he was driving a real Bentley at the ripe age of 17, definitely not tacky!
> 
> @bcowen the Atticus would be a good choice, probably could get a pair for a decent price in the classifieds.  I haven't heard them, but a cheaper option for closed back high-impedance headphones is the Beyerdynamic DT1770.  If you wanted to go vintage, could try to find a pair of Sennheiser HD250 Linear (600 ohm) or Linear II (300ohm).  Used to have a pair, very nice and underrated vintage stuff from Sennheiser.



Thanks for that L0rd!  I'd looked at those on Drop's site, but the version they are selling is 32 ohms so I just passed them right on by.  I see the normal (non-Drop) ones are 250 ohms which would be perfect. Might be worth a try through Amazon...can send them right back if they don't blip on my preference radar.  I have the Senn HD-6XX's -- got them on one of Drop's last sales for $180.  Killer 'phones for the money IMO, and in fact really nice sounding 'phones period once you ditch the crap stock cable and add some Dekoni pads.  But my ears have more expensive tastes, unfortunately.  Might as well use them while they still work.


----------



## bcowen

Zachik said:


> I own an Atticus. @L0rdGwyn I will forgive your comparison to DT1770 since you never auditioned the Atticus. Not even the same league, IMHO, and the signature of ZMF is so much more pleasing and musical



Oh, just perfect. Now I'm all confused again.  Or as usual.


----------



## bcowen (Jan 15, 2021)

Zachik said:


> I own an Atticus. @L0rdGwyn I will forgive your comparison to DT1770 since you never auditioned the Atticus. Not even the same league, IMHO, and the signature of ZMF is so much more pleasing and musical



So how much do you want for your Atticus?  Seems like you're about due for an upgrade to a Weston 981 Type 3 tester, right?     I have a pretty one almost ready to go.


----------



## Zachik

bcowen said:


> So how much do you want for your Atticus?


Sorry buddy - I cannot let it go since I am a hoarder collector 
I would recommend contacting Zach, and ask if he has a B-stock Atticus, or maybe a unit that was on a reviewer's tour. Would make it a little cheaper if he does, but still not gonna compete with 1770...


----------



## UntilThen

bcowen said:


> You should ask @UntilThen since it's already tomorrow there.



Ask and it shall be answered. What you need to order is this end game setup I've just heard this afternoon. 

https://www.head-fi.org/threads/1101-audio-custom-crafted-headphone-amps.919425/post-16109211


----------



## L0rdGwyn

Zachik said:


> I own an Atticus. @L0rdGwyn I will forgive your comparison to DT1770 since you never auditioned the Atticus. Not even the same league, IMHO, and the signature of ZMF is so much more pleasing and musical



Oh I have heard the Atticus, in fact I used to own it, I have never heard the DT1770!  I don't doubt the Atticus is the more musical headphone, but it is also more expensive, if price is a factor.


----------



## UntilThen

I must be drunk when I sold off my Eikon and Atticus at 2/3 of the price I paid for after one year. 

My Atticus has the Padauk wood ! The cherry one is Eikon.

That's Feliks Euforia and my cray computer.


----------



## L0rdGwyn

UntilThen said:


> I must be drunk when I sold off my Eikon and Atticus at 2/3 of the price I paid for after one year.
> 
> My Atticus has the Padauk wood ! The cherry one is Eikon.
> 
> That's Feliks Euforia and my cray computer.



I have thought first edition Atticus Eikon will be collector's items in ten years, I wonder what prices they will command


----------



## L0rdGwyn

Got some more crazy transmitting triodes yesterday, Gammatron HK54.  These monsters have a 50W plate dissipation and a 5V / 5A filament, safe to say you could cook / pulverize an egg on these babies when biased to max plate dissipation.



Here is a datasheet.  Will attempt to trace these at some point although I have had some issues obtaining curves with the 3C24 thus far.

http://www.r-type.org/pdfs/hk54.pdf

It is nearly 6AM here, time go to finish the filament supply for the 841 amp.


----------



## whirlwind (Jan 16, 2021)

bcowen said:


> So how much do you want for your Atticus?  Seems like you're about due for an upgrade to a Weston 981 Type 3 tester, right?     I have a pretty one almost ready to go.



Very nice tester.   

As far as closed cans go, I agree that the Atticus is killer...warm...great bass and especially the mid bass.
Someone has already mentioned B stock, so that could be an option as well as the classifieds here. I think ZMF at some point will be coming out with a more affordable option and I would assume it would still have Zach's house sound,which is great to my ears.

You could also go with the very cheap route of Chi-Fi iems...what you get for $50 - $100 these days is pretty insane.


----------



## L0rdGwyn (Jan 16, 2021)

Filament supply is done.  This amplifier uses filament bias on the 841 tubes.  For those that aren't familiar, this is a type of fixed bias available only to DHTs.  A resistance is placed in series with the filament supply and the bias is generated by the voltage dropped across this resistance.  The enamel wirewound resistors shown are 3ohms and will generate 3.75V of bias with the 1.25A filament current of the 841.  This is really only practical with DHTs that do not require high bias voltages on the filament as the size of the resistors starts to become impractical.  Take, for example, a 300B with 70V on the filament with a 1.2A filament current.  That would require a 58ohm resistor dissipating 84W, so realistically, would need to be something like a 500W resistor, massive.



So glowy, so purdy.



B+ supply is next.


----------



## whirlwind

L0rdGwyn said:


> Filament supply is done.  This amplifier uses filament bias on the 841 tubes.  For those that aren't familiar, this is a type of fixed bias available only to DHTs.  A resistance is placed in series with the filament supply and the bias is generated by the voltage dropped across this resistance.  The enamel wirewound resistors shown are 3ohms and will generate 3.75V of bias with the 1.25A filament current of the 841.  This is really only practical with DHTs that do not require high bias voltages on the filament as the size of the resistors starts to become impractical.  Take, for example, a 300B with 70V on the filament with a 1.2A filament current.  That would require a 58ohm resistor dissipating 84W, so realistically, would need to be something like a 500W resistor, massive.
> 
> 
> 
> ...




Sure is a nice glow and those tubes are look to be made very rugged.


----------



## whirlwind (Jan 16, 2021)

UntilThen said:


> I must be drunk when I sold off my Eikon and Atticus at 2/3 of the price I paid for after one year.
> 
> My Atticus has the Padauk wood ! The cherry one is Eikon.
> 
> That's Feliks Euforia and my cray computer.



Great pic UT.  Wonderful collection of cans! Does not seem like that long ago.


----------



## UntilThen

That's a long time ago. Some pictures turn out better to my surprise. Like this.


----------



## L0rdGwyn

whirlwind said:


> Sure is a nice glow and those tubes are look to be made very rugged.



Thanks!  They will last an eternity where they are being biased (but of course I have like 6 extra pairs, just in case ).


----------



## A2029

L0rdGwyn said:


> Got some more crazy transmitting triodes yesterday, Gammatron HK54.  These monsters have a 50W plate dissipation and a 5V / 5A filament, safe to say you could cook / pulverize an egg on these babies when biased to max plate dissipation.
> 
> 
> 
> ...



Another connoisseur of fine tantalum plate transmitter tubes I see   

My collection of 4E27A tubes so far:


----------



## UntilThen

A2029 said:


> My collection of 4E27A tubes so far:



Mischa that is for my amp. Thanks.


----------



## L0rdGwyn

A2029 said:


> Another connoisseur of fine tantalum plate transmitter tubes I see
> 
> My collection of 4E27A tubes so far:



Very nice, any plans to build with them?  I have a batch of 3C24 and now the big brother HK54.  Tracked down some NOS Eimac heat-dissipating plate / grid caps as well, could go in a positive grid biased A2 design some day, but who knows!


----------



## A2029

L0rdGwyn said:


> Very nice, any plans to build with them?  I have a batch of 3C24 and now the big brother HK54.  Tracked down some NOS Eimac heat-dissipating plate / grid caps as well, could go in a positive grid biased A2 design some day, but who knows!



Definitely hope to do a build with them at some point, likely not for me to keep though as I already have a different personal speaker amp to keep. Only one tube per channel would be needed with these 4E27A as they have crazy high 125W max dissipation. I was originally thinking of a voltage between 1000-1200V, but I may end up sticking to something more conservative like 750-800V. One problem is the top cap that I don't feel very comfortable leaving exposed even with *only* 750V on them. I'll be looking to custom CNC some top caps that are electrically insulated with at least 3-5KV of electrical insulation capacity in case someone accidentally touches the top cap.

A1 plate curves for the triode stapped 4E27A are very nice, which got me started accumulating all of these.


----------



## L0rdGwyn (Jan 16, 2021)

A2029 said:


> Definitely hope to do a build with them at some point, likely not for me to keep though as I already have a different personal speaker amp to keep. Only one tube per channel would be needed with these 4E27A as they have crazy high 125W max dissipation. I was originally thinking of a voltage between 1000-1200V, but I may end up sticking to something more conservative like 750-800V. One problem is the top cap that I don't feel very comfortable leaving exposed even with *only* 750V on them. I'll be looking to custom CNC some top caps that are electrically insulated with at least 3-5KV of electrical insulation capacity in case someone accidentally touches the top cap.
> 
> A1 plate curves for the triode stapped 4E27A are very nice, which got me started accumulating all of these.



Awesome, nice curves!  Would be a beast of an amp in A1.  Any idea of the plate resistance triode-strapped?  Out and about or I might've eyeballed it.  I hear you on the caps, I would be looking at ~300V exposed with the 3C24.  I thought about insulating them as well, but figured the insulating material would need to posess a high thermal conductivity to maintain the cap's heatsinking function.  I didn't look into it deeply, once I found the Eimac caps I thought I would encase the tubes in glass with ventilation, so no touchy.  Who knows if it will ever happen but it's fun to hoard tubes and fantasize


----------



## Zachik

L0rdGwyn said:


> Got some more crazy transmitting triodes yesterday, Gammatron HK54. These monsters have a 50W plate dissipation and a 5V / 5A filament, safe to say you could cook / pulverize an egg on these babies when biased to max plate dissipation.





A2029 said:


> My collection of 4E27A tubes so far:


I am gonna report you guys to the DOE


----------



## A2029

L0rdGwyn said:


> Awesome, nice curves!  Would be a beast of an amp in A1.  Any idea of the plate resistance triode-strapped?  Out and about or I might've eyeballed it.  I hear you on the caps, I would be looking at ~300V exposed with the 3C24.  I thought about insulating them as well, but figured the insulating material would need to posess a high thermal conductivity to maintain the cap's heatsinking function.  I didn't look into it deeply, once I found the Eimac caps I thought I would encase the tubes in glass with ventilation, so no touchy.  Who knows if it will ever happen but it's fun to hoard tubes and fantasize



I believe plate resistance in the 1200 ohm range, so a 5K transformer would work well.

Here is my idea for the top cap, crudely drawn in paint in about 10 seconds:



Black is aluminum tubes, white would be high heat thermal epoxy in between the tubes. Innermost black tube could be copper instead of aluminum, and it gets soldered directly to a high heat, high voltage insulated copper wire. A set screw from the side holds the inner copper tube to the anode pin, and a removable plug goes in the set screw hole. The outer aluminum tube can be anodized color of choice (anodization also increases the electrical insulation), and the outermost tube could be the tallest so that the top area over the inner copper and aluminum tubes could be filled with thermal epoxy.

I may just go with glass surrounding the whole tube eventually though, not sure yet.


----------



## Galapac

A2029 said:


> I believe plate resistance in the 1200 ohm range, so a 5K transformer would work well.
> 
> Here is my idea for the top cap, crudely drawn in paint in about 10 seconds:
> 
> ...


----------



## L0rdGwyn

A2029 said:


> I believe plate resistance in the 1200 ohm range, so a 5K transformer would work well.
> 
> Here is my idea for the top cap, crudely drawn in paint in about 10 seconds:
> 
> ...



Thought that was an optical illusion when I glanced at my phone  awesome, I would love to see it!  I'd imagine the surface area would be high, another plus.  Bet you could sell these to transmitting tube heads on diyAudio.

Here is a 3C24 with the NOS Eimac HR2 caps.



These would require NFB, not unlike my 801A design.  Since these tubes would have a positive grid bias point, an interesting way to implement them is to choke load a direct-coupled cathode follower to handle the negative grid swings, removing the need for a negative bias supply.  In my mind's eye the tubes are encased in a glass cylinder with a perforated lid, I think that would look nice.


----------



## bcowen

A2029 said:


> One problem is the top cap that I don't feel very comfortable leaving exposed even with *only* 750V on them. I'll be looking to custom CNC some top caps that are electrically insulated with at least 3-5KV of electrical insulation capacity in case someone accidentally touches the top cap.



I vote for @UntilThen to get the first amp, then touch the top caps (unprotected) and let us know if it hurts.


----------



## leftside

bcowen said:


> I vote for @UntilThen to get the first amp, then touch the top caps (unprotected) and let us know if it hurts.


With his tongue haha


----------



## UntilThen

I heard my name mentioned. Did I win a prize? Or the amp...,,


----------



## bcowen

leftside said:


> With his tongue haha



LOL!  Yeah, that too.  And with bare feet on a wet floor.


----------



## bcowen

UntilThen said:


> I heard my name mentioned. Did I win a prize? Or the amp...,,



Yes.  But 'win' is a subjective term in this case.


----------



## L0rdGwyn (Jan 17, 2021)

Finished the 841 amp.

Here is the circuit.  Switch in the middle changes the turns ratio of the output transformers to accommodate different headphone impedances.  Wiring that baby was a real joy.



Here it is without the tubes.  Volume knob on the left, impedance switch in the center.



And with the 841 globes.


----------



## bcowen

L0rdGwyn said:


> Finished the 841 amp.
> 
> Here is the circuit.  Switch in the middle changes the turns ratio of the output transformers to accommodate different headphone impedances.  Wiring that baby was a real joy.
> 
> ...



Way impressive!  How does it sound?


----------



## L0rdGwyn (Jan 17, 2021)

bcowen said:


> Way impressive!  How does it sound?



It sounds phenomenal!  The bass is very deep, big soundstage and excellent transparency.  Sorry had to finish that nail-biter of a game, pictures aren't my best work either lol.  Disappointing loss but great season for the Browns.


----------



## UntilThen

L0rdGwyn said:


> It sounds phenomenal!  The bass is very deep, but soundstage and excellent transparency.  Sorry had to finish that nail-biter of a game, pictures aren't my best work either lol.  Disappointing loss but great season for the Browns.



Thanks that's my amp.


----------



## bcowen

UntilThen said:


> Thanks that's my amp.



Seriously?  I thought @L0rdGwyn had named it the "You Wish."


----------



## L0rdGwyn (Jan 17, 2021)

I'll post some better pictures of the circuit in a bit, probably some better photos of the amp too, I was rushing!

Edit: oh, and probably some measurements too.


----------



## L0rdGwyn (Jan 18, 2021)

So here's something interesting, the globe RCA 841 have super low distortion.  Like, solid state level distortion in this amplifier, especially with high impedance headphones.

THD 1mW into 32ohm (low impedance switch) - 0.017%
THD 1mW into 120ohm (medium impedance switch) - 0.007%
THD 1mW into 300ohm (high impedance switch) - 0.0054%

Whereas the shouldered Hytron 841 distortion figures are double or triple the RCA, second harmonic dominant.  This has an audible effect, the globes offer a more clean listening experience, compared to the slightly more smooth Hytrons.

With the RCA 841, this amplifier is very revealing of poor recordings, bad ones sound very bad, good ones sound incredible.  Will be interesting to see how the sound evolves.  I haven't ruled out experimenting with different output caps or even different source follower FETs.

Here is the full circuit once more, taken with my phone, my nice camera is getting a little long in the tooth and has pretty poor low light performance, hence the potato photos before.




B+ circuitry, featuring 1101 Audio's / @A2029 's exquisite HV regulator.



The output impedance switch from hell.  Thankfully I diagrammed the wiring months ago so didn't have to think about it much, but it was still a PITA to say the least.



Source follower board, CCS board, Auricap XO coupling caps, Sowter 8665A output transformers, Goldpoint V47 stepped attenuator, filament bias resistor.



And closed up.



Don't think I showed the rear panel before.



Here is a long exposure shot with the RCA 841 on my desk.


----------



## leftside

Hey @A2029, as @L0rdGwyn borrowed your exquisite HV regulator, are we borrowing his output impedance switch from hell? Are we also using those Sowter transformers?


----------



## L0rdGwyn

leftside said:


> Hey @A2029, as @L0rdGwyn borrowed your exquisite HV regulator, are we borrowing his output impedance switch from hell? Are we also using those Sowter transformers?



My guess, and I'm sure Mischa will confirm or deny, is that your custom transformers have various taps for different headphone impedances, which will be much easier to wire.  The reason these are so tricky is these are an off-the-shelf offering from Sowter with three secondary windings that can be placed in series, paralleled, or two paralleled and one in series.  Putting the windings in series or parallel on the same output makes for a trickier switch configuration compared to switching between different output taps on a custom transformer.


----------



## leftside

L0rdGwyn said:


> My guess, and I'm sure Mischa will confirm or deny, is that your custom transformers have various taps for different headphone impedances, which will be much easier to wire.  The reason these are so tricky is these are an off-the-shelf offering from Sowter with three secondary windings that can be placed in series, paralleled, or two paralleled and one in series.  Putting the windings in series or parallel on the same output makes for a trickier switch configuration compared to switching between different output taps.


You are correct - there are various taps on this custom transformer.

Your amp looks great @L0rdGwyn. I bet it must be very satisfying to put all of this together. Thanks for sharing.


----------



## L0rdGwyn

leftside said:


> You are correct - there are various taps on this custom transformer.
> 
> Your amp looks great @L0rdGwyn. I bet it must be very satisfying to put all of this together. Thanks for sharing.



Thanks!  It is, but I am friggin' exhausted, sometimes it feels like I have two jobs.  Looking forward to knocking out the remaining projects I've committed to and having a clean slate, maybe I'll even take a break!


----------



## Xcalibur255

That is darned impressive looking.  Another professional result and another interesting amp.  Congrats Keenan!


----------



## A2029

leftside said:


> Hey @A2029, as @L0rdGwyn borrowed your exquisite HV regulator, are we borrowing his output impedance switch from hell? Are we also using those Sowter transformers?





L0rdGwyn said:


> My guess, and I'm sure Mischa will confirm or deny, is that your custom transformers have various taps for different headphone impedances, which will be much easier to wire.  The reason these are so tricky is these are an off-the-shelf offering from Sowter with three secondary windings that can be placed in series, paralleled, or two paralleled and one in series.  Putting the windings in series or parallel on the same output makes for a trickier switch configuration compared to switching between different output taps on a custom transformer.





leftside said:


> You are correct - there are various taps on this custom transformer.
> 
> Your amp looks great @L0rdGwyn. I bet it must be very satisfying to put all of this together. Thanks for sharing.



@leftside We are having custom transformers made, but unfortunately not individual windings for each output. Sowter uses the following scheme of parallel and series windings to extend the frequency response of the transformer. If wiring three secondary windings for a switch was hard as @L0rdGwyn found, doing four is a real brain twister, haha  I'm doing the mental rotations now to figure out how to use a multi-pole multi-position switch to control a bank of gold plated small signal relays. The switch only controls which relays are on, and the audio signal only goes through the gold plated silver relays. Will update when I think up the exact plan.


----------



## A2029

Mental gymnastics complete 
Here are the windings and impedances for your transformers @leftside 
Z/4Z/9Z/16Z
22/88/198/352

Six relays total per transformer (U1-U6 above). For 16Z, no relays are on. For 9Z, relays U1/U2 on, for 4Z relays U1-U4 on, for Z all relays (U1-U6) on.


----------



## johnjen (Jan 18, 2021)

Just an added note that may or may not apply…

In the Purp-Amp we are using the Lundahl LL2765 HP output xfmrs to drive my HD800-Jmods.
We found that using either the 150Ω or the 600Ω output taps was much noisier than the 32Ω taps, and this to drive the 3 to 600Ω 800's.
And by using a ≈35Ω resistive load across the 32Ω output taps, along with the ≈330 to 680Ω load of the 800's, resulted in the 'best' solution for several reasons.

#1 it lowered the amount of noise (as noted), as measured and heard.
#2 it bigly reduced the range of impedance the output tubes 'see' (via reflected load) down from ≈ 330Ω - 680Ω = *350Ω variance*,
to a 33.287Ω - 31.644Ω = *1.64Ω variance*.

And no it isn't as simple as this, but the reduction in variance of the reflected load and the resultant SQ improvements using this approach are significant.

Just some food for thought.

JJ


----------



## A2029

johnjen said:


> Just an added note that may or may not apply…
> 
> In the Purp-Amp we are using the Lundahl LL2765 HP output xfmrs to drive my HD800-Jmods.
> We found that using either the 150Ω or the 600Ω output taps was much noisier than the 32Ω taps, and this to drive the 3 to 600Ω 800's.
> ...



That's very true, using the resistor trick with a lower ohm tap gives both of those benefits, but comes at the expense of lower power output for higher impedance loads. Fortunately these Sowter transformers are being paired with the LCD-4 as primary, so #2 isn't a problem due to the flat impedance of planars, and a B+ noise of under 30uV should keep the output noise very low as well


----------



## A2029

L0rdGwyn said:


> So here's something interesting, the globe RCA 841 have super low distortion.  Like, solid state level distortion in this amplifier, especially with high impedance headphones.
> 
> THD 1mW into 32ohm (low impedance switch) - 0.017%
> THD 1mW into 120ohm (medium impedance switch) - 0.007%
> ...



This is awesome Keenan! Congrats on the build!


----------



## johnjen

A2029 said:


> That's very true, using the resistor trick with a lower ohm tap gives both of those benefits, but comes at the expense of lower power output for higher impedance loads. Fortunately these Sowter transformers are being paired with the LCD-4 as primary, so #2 isn't a problem due to the flat impedance of planars, and a B+ noise of under 30uV should keep the output noise very low as well


Yeah the power available is dropped, but in my case I use 0.20mw/ch (0.08v) on average at normal listening levels (up to the mid 90dB's) and it could leap up to 0.5w/ch (4v which is ear bleed levels) peak, out of 0.75w/ch from these 71A tubes.
And this is with 14dB boost at 14hz with a Q of 0.53 (reaches ≈0dB at 100Hz) that has been added via DSP in the player, for truly thunderous bass.

I was very surprised at these numbers after playing Beethoven's 9th - 4th movement all the way thru and capturing these voltages on my fluke 289.

And all of the above wattage calcs are based upon 32Ω load.
If I were to use the 330Ω to 680Ω range, the actual wattage usage into the 800's, these numbers would drop precipitously accordingly.

JJ


----------



## whirlwind

L0rdGwyn said:


> It sounds phenomenal!  The bass is very deep, big soundstage and excellent transparency.  Sorry had to finish that nail-biter of a game, pictures aren't my best work either lol.  Disappointing loss but great season for the Browns.



It looks fantastic and the glow of those 841 globes    
It has all of the bases covered...deep bass, big stage and excellent transparency....enjoy !!

That game, oh my....we had a chance in the 4th quarter...all you can ask.
Was an enjoyable football season, the Browns and music was great in an other wise terrible year.


----------



## L0rdGwyn

A2029 said:


> Mental gymnastics complete
> Here are the windings and impedances for your transformers @leftside
> Z/4Z/9Z/16Z
> 22/88/198/352
> ...



Awesome, I didn't realize Sowter used the same secondary winding configuration in their custom transformers, my custom OPT from them are single secondary 8ohm.  Wiring a switch for four secondaries would be a real headache, great solution using the relays!



whirlwind said:


> It looks fantastic and the glow of those 841 globes
> It has all of the bases covered...deep bass, big stage and excellent transparency....enjoy !!
> 
> That game, oh my....we had a chance in the 4th quarter...all you can ask.
> Was an enjoyable football season, the Browns and music was great in an other wise terrible year.



Thanks!  Yeah the door was open in the 4th but they couldn't take advantage, oh well still a great season, I'll take it!  No reason they shouldn't be serious contenders next year too.


----------



## bcowen

L0rdGwyn said:


> Thanks!  Yeah the door was open in the 4th but they couldn't take advantage, oh well still a great season, I'll take it!  No reason they shouldn't be serious contenders next year too.



They had a great year, and honestly I think it's their time. I'm not much of a pro football fanatic, but the effort and determination they showed this year was most impressive.


----------



## Ripper2860 (Jan 18, 2021)

Deleted.  Wrong thread.


----------



## L0rdGwyn

Polished up my Auteur today and conditioned the leather, been a while since I tuned it up.  I'm back in the headphone saddle, baby!  Honestly been a while since I've listened on 'phones, been wrapped up in speaker world for a while.




I decided I did not like the Auricap XO in this amplifier, they have been temporarily swapped back to the Solen Fast-CAP MKP from the prototype.  I found they were imparting a harshness/sibilance to the upper midrange and treble.  They'll get another chance, I picked up some other caps to try out, going to have a shootout between Obbligato Gold, ClarityCap CSA, Auricap XO, and the Solens when they are all in house.


----------



## bcowen

L0rdGwyn said:


> Polished up my Auteur today and conditioned the leather, been a while since I tuned it up.  I'm back in the headphone saddle, baby!  Honestly been a while since I've listened on 'phones, been wrapped up in speaker world for a while.
> 
> 
> 
> I decided I did not like the Auricap XO in this amplifier, they have been temporarily swapped back to the Solen Fast-CAP MKP from the prototype.  I found they were imparting a harshness/sibilance to the upper midrange and treble.  They'll get another chance, I picked up some other caps to try out, going to have a shootout between Obbligato Gold, ClarityCap CSA, Auricap XO, and the Solens when they are all in house.



Obviously you need some oil caps.  Just make the chassis bigger.


----------



## A2029

bcowen said:


> Obviously you need some oil caps.  Just make the chassis bigger.



@L0rdGwyn should slot in some of these little guys:




95mm D x 220mm L


----------



## L0rdGwyn

bcowen said:


> Obviously you need some oil caps.  Just make the chassis bigger.





A2029 said:


> @L0rdGwyn should slot in some of these little guys:
> 
> 
> 95mm D x 220mm L



Even better, I'll just throw together a separate "output capacitor chassis", think those Miflex caps will need one


----------



## Xcalibur255

Are these caps for output coupling?  What are the chances you could direct couple instead?


----------



## leftside

A2029 said:


> @L0rdGwyn should slot in some of these little guys:
> 
> 
> 95mm D x 220mm L


Are we using these? 🙂


----------



## bcowen

A2029 said:


> @L0rdGwyn should slot in some of these little guys:
> 
> 
> 95mm D x 220mm L



Let me guess....those are more expensive than my house.  Each.


----------



## L0rdGwyn

Xcalibur255 said:


> Are these caps for output coupling?  What are the chances you could direct couple instead?



So in this amp, the 841 is direct-coupled to the FET which is cap coupled to the 8665A output transformers.  The 8665A were designed to be cap-coupled to a cathode follower (I used a source follower instead), can't direct couple as the OPT cannot take DC on the primary.  Since the 841 has an active load and is working into the high input impedance of the source follower, the distortion stays very low.  It's like a...filament biased parafeed spud with a FET buffer in the middle.  I had all these 841 tubes burning a hole in my pocket, and I picked up the 8665A to do something with, didn't know what, so I just slapped 'em together


----------



## A2029

bcowen said:


> Let me guess....those are more expensive than my house.  Each.



Nowhere near as costly as Duelund caps   



leftside said:


> Are we using these? 🙂



Much much smaller ones of these (0.47uF), haha


----------



## CJG888

I’ve found Obbligatos (Obbligati?) to offer most of the benefits of PIO in a smaller (and more affordable) package.

Seen here as output coupling caps in my NOS DAC (modded Teradak Chameleon):


----------



## L0rdGwyn

So turns out both changes I made between the prototype and the final version of the 841 amplifier were failures  

As I mentioned, I was hearing a certain sibilance and "bite" to the upper midrange that became somewhat fatiguing.  First I swapped the Auricap XO back to the Solens, which was an improvement, but something was still "off" compared to what I had heard in the prototype.  Did I miss this sibilance then?  The only other major change I made was swapping the source follower FET from the Alpha & Omega AOTN160 to the fancy SiC Cree C2M1000170D.  So what the heck, let's swap it back and see what happens.

Bingo.

The venerable AOTN160 fixed the sibilance, increased the soundstage, and improved the dynamics.  So, guess the SiC FET isn't the bee's knees after all.  Could be application specific as I did not notice any of these issues when messing around with the Cree chip in my 801A prototype.

So looks like I'll have to roll some different FETs in addition to the output caps, but happy with the AOTN160 for now, the sound kick's ass once again.  Maybe I can throw together some sort of modular source follower board to make A-Bing FETs easier 

Don't think I ever showed the frequency response of this amplifier.


----------



## L0rdGwyn

CJG888 said:


> I’ve found Obbligatos (Obbligati?) to offer most of the benefits of PIO in a smaller (and more affordable) package.
> 
> Seen here as output coupling caps in my NOS DAC (modded Teradak Chameleon):



Looking forward to trying them out!  Should have them Monday or Tuesday.


----------



## whirlwind

L0rdGwyn said:


> Polished up my Auteur today and conditioned the leather, been a while since I tuned it up.  I'm back in the headphone saddle, baby!  Honestly been a while since I've listened on 'phones, been wrapped up in speaker world for a while.
> 
> 
> 
> I decided I did not like the Auricap XO in this amplifier, they have been temporarily swapped back to the Solen Fast-CAP MKP from the prototype.  I found they were imparting a harshness/sibilance to the upper midrange and treble.  They'll get another chance, I picked up some other caps to try out, going to have a shootout between Obbligato Gold, ClarityCap CSA, Auricap XO, and the Solens when they are all in house.



So please tell about the sound with the Auteur....wood is killer on that headphone!


----------



## L0rdGwyn

whirlwind said:


> So please tell about the sound with the Auteur....wood is killer on that headphone!



Of course!

So, with the globe RCA 841, this is not a "tubey" amplifier due to the low distortion (although that can be tuned with the shouldered Hytron 841).  The sound is very clean, without the warmth that you might expect with a tube amplifier.  What it maintains from the tubes is excellent transparency and dynamics.  The thing that stands out most to me is the low end, it is very well-defined and hits hard!  Really great with bass-driven music like rock and EDM, pairs well with the Auteur which has a very nice low-end extension for a dynamic headphone.  Would love to pair it with the Verite at some point, we'll see how the sound changes with the cap rolling


----------



## Tjj226 Angel

Xcalibur255 said:


> Are these caps for output coupling?  What are the chances you could direct couple instead?



I just want to take a second and say that anything and everything can be directly coupled to anything else. As long as you are willing to deal with the offset voltage both positive and negative, then anything is possible. 

Just remember that with a single ended amplifier, you will almost always have some sort of capacitor in your audio path. In a direct coupled amplifier, the last power supply capacitor is in the audio path. 

So you have to be semi judicious about what you do and how you do it. All that glitters is not gold and what not.


----------



## Xcalibur255 (Jan 22, 2021)

@L0rdGwyn

I was a little surprised to see you preferring the Solen to the Auricap.  With this new discovery the Auricap might vindicate itself now.  There's nothing "wrong" with the Solens but I've heard/owned several amps that use them (still have one of them) and while they are very good at not doing anything "bad" to the music in terms of adding sibilance or bite they also make the music feel kind of dead and lifeless IMO.  Stuff like this is always a very tricky balancing act.

Then again the way you're describing the sound of the amp right now maybe the Solen has the right synergy for this particular design.


----------



## whirlwind

L0rdGwyn said:


> Of course!
> 
> So, with the globe RCA 841, this is not a "tubey" amplifier due to the low distortion (although that can be tuned with the shouldered Hytron 841).  The sound is very clean, without the warmth that you might expect with a tube amplifier.  What it maintains from the tubes is excellent transparency and dynamics.  The thing that stands out most to me is the low end, it is very well-defined and hits hard!  Really great with bass-driven music like rock and EDM, pairs well with the Auteur which has a very nice low-end extension for a dynamic headphone.  Would love to pair it with the Verite at some point, we'll see how the sound changes with the cap rolling



Thanks for this...sounds like the bass goes low and slams really well.. I like when the music has some weight and meat on the bones....sounds great.


----------



## CJG888

I‘m also not a great fan of Solens. Like Ansars (do they still make them?), they work and are better than RS Film caps. However, one of the first things I did with my Opera Consonance Cyber 20 was a „solenectomy“ followed by a transplant of a couple of Audio Note copper foils...


----------



## L0rdGwyn

Xcalibur255 said:


> @L0rdGwyn
> 
> I was a little surprised to see you preferring the Solen to the Auricap.  With this new discovery the Auricap might vindicate itself now.  There's nothing "wrong" with the Solens but I've heard/owned several amps that use them (still have one of them) and while they are very good at not doing anything "bad" to the music in terms of adding sibilance or bite they also make the music feel kind of dead and lifeless IMO.  Stuff like this is always a very tricky balancing act.
> 
> Then again the way you're describing the sound of the amp right now maybe the Solen has the right synergy for this particular design.



I suspect the major issue with the sibilance was actually the Cree FET, swapping it out for the AOT1N60 had a more significant impact than the cap swap.  Entirely possible the Auricaps had some negative synergy with the Cree and will fare better with the new chip.  I don't expect the Solens will make the final cut, but while they don't add anything, they also don't add anything, if you know what I mean.  I'll be very curious to see how the Auricaps sound with the A&O FET.  Once I have my swatch of caps in house, I will A-B them with alligator clips and declare a winner, going to just leave the Solens in for now because frankly, I'm tired of going back inside the amp lol.



CJG888 said:


> I‘m also not a great fan of Solens. Like Ansars (do they still make them?), they work and are better than RS Film caps. However, one of the first things I did with my Opera Consonance Cyber 20 was a „solenectomy“ followed by a transplant of a couple of Audio Note copper foils...



The options for compact 6.8uF 600V films are pretty limited.  The Solens, Auricaps, Claritycap CSA, and Obbligato Gold will all fit in the dedicated space.  Not sure if Ansars are still available, if anyone finds others that fit in roughly a 40mm x 56mm space, I am all ears


----------



## CJG888

I just had a look: Cricklewood Electronics still sell Ansars (limited range of values though- probably old stock).


----------



## bcowen (Jan 22, 2021)

L0rdGwyn said:


> So turns out both changes I made between the prototype and the final version of the 841 amplifier were failures
> 
> As I mentioned, I was hearing a certain sibilance and "bite" to the upper midrange that became somewhat fatiguing.  First I swapped the Auricap XO back to the Solens, which was an improvement, but something was still "off" compared to what I had heard in the prototype.  Did I miss this sibilance then?  The only other major change I made was swapping the source follower FET from the Alpha & Omega AOTN160 to the fancy SiC Cree C2M1000170D.  So what the heck, let's swap it back and see what happens.
> 
> ...



So it's like 1dB down at 20 Hz?  Sure hope you can fix that.  And I'm ignoring the ~0.3db droop at 20k because at my age I can't hear above 6k anyway. I'm pretty sure the frequency of my wife's voice is 6.1 kHz.  

Honestly that's pretty damn impressive. I mean like *way *awesome, dude. Congrats!   I'm just mad at you for even suggesting FET rolling. Like I need another rabbit hole, and I can already see @Zachik foaming at the mouth which is not a pleasant envisioning.


----------



## bcowen

CJG888 said:


> I’ve found Obbligatos (Obbligati?) to offer most of the benefits of PIO in a smaller (and more affordable) package.
> 
> Seen here as output coupling caps in my NOS DAC (modded Teradak Chameleon):



Those look very nicely made (from what I can see).  I've never tried them, but thanks for the rec!


----------



## L0rdGwyn

bcowen said:


> So it's like 1dB down at 20 Hz?  Sure hope you can fix that.  And I'm ignoring the ~0.3db droop at 20k because at my age I can't hear above 6k anyway. I'm pretty sure the frequency of my wife's voice is 6.1 kHz.
> 
> Honestly that's pretty damn impressive. I mean like *way *awesome, dude. Congrats!   I'm just mad at you for even suggesting FET rolling. Like I need another rabbit hole, and I can already see @Zachik foaming at the mouth which is not a pleasant envisioning.



That's 0.5dB at 20Hz, thank you very much!  Who knows when I'll get to messin' around with the FETs, the AOT1N60 is hard to beat, maybe I'll just kick back and enjoy the music for once  after I roll a bunch of caps of course.


----------



## Zachik

bcowen said:


> I can already see @Zachik foaming at the mouth which is not a pleasant envisioning.


 
The heart wants what the heart wants...


----------



## Paladin79

I am nearly finished with my latest Incubus build in Lacewood. I do have some wiring to finish tomorrow morn then I will begin testing before it goes out as a loaner. I never have been a fan of metal cabinets so I use hardwoods. This one is lacewood with rainbow poplar splines and it will have a tiger maple bottom plate.


----------



## L0rdGwyn

Giving the shouldered Hytron 841 a listen this morning.  These have a second harmonic dominant distortion profile in this amplifier at higher levels than the globe RCA 841, offers a bit of a different flavor, slightly more warm sounding, always nice to have options 



Working on getting my hands on a pair of globe General Electric 841, we'll see how they stack up against the others.


----------



## bcowen (Jan 24, 2021)

L0rdGwyn said:


> Working on getting my hands on a pair of globe General Electric 841, we'll see how they stack up against the others.



How much are you getting paid to take those? 

Wait.....that was a rude and improper question and certainly none of my business.  My apologies.  Let me rephrase:  I hope you're getting paid a lot to take those.


----------



## L0rdGwyn

bcowen said:


> How much are you getting paid to take those?
> 
> Wait.....that was a rude and improper question and certainly none of my business.  My apologies.  Let me rephrase:  I hope you're getting paid a lot to take those.



How dare you...

The world was a very different place in August, 1939.  On the brink of world war, with rising international demand, the engineers of General Electric were compelled, nay FORCED to make a good sounding tube, for hifi amplifiers of the future, they had no choice...I'm sure that's how it played out.


----------



## bcowen

L0rdGwyn said:


> How dare you...
> 
> The world was a very different place in August, 1939.  On the brink of world war, with rising international demand, the engineers of General Electric were compelled, nay FORCED to make a good sounding tube, for hifi amplifiers of the future, they had no choice...I'm sure that's how it played out.



That requires an assumption they knew _how_ to make a good sounding tube.  

I've actually heard a couple good sounding GE's.  They were probably out of spec and missed by quality control before shipping.  LOL!!


----------



## Galapac

I know you guys joke about the GE tubes all the time but are they really that bad? I do not own any ( I think, there may be a rougue 6SN7 somewhere) so I do not know. Are they just not known for audio quality? Were they used mainly in other applications like receivers or televisions? Were they known as a discount tube?

I am seriously asking as I do not know the history but would like to know what you can all tell me so I am “in” on the joke, so to speak.

Thanks


----------



## Zachik

Galapac said:


> I know you guys joke about the GE tubes all the time but are they really that bad? I do not own any ( I think, there may be a rougue 6SN7 somewhere) so I do not know. Are they just not known for audio quality? Were they used mainly in other applications like receivers or televisions? Were they known as a discount tube?
> 
> I am seriously asking as I do not know the history but would like to know what you can all tell me so I am “in” on the joke, so to speak.
> 
> Thanks


Actually, I think *specific tube types* by GE are actually good! 
Off hand, I think 6C5 or 6J5 all-metal tubes by GE are considered good.


----------



## L0rdGwyn

Galapac said:


> I know you guys joke about the GE tubes all the time but are they really that bad? I do not own any ( I think, there may be a rougue 6SN7 somewhere) so I do not know. Are they just not known for audio quality? Were they used mainly in other applications like receivers or televisions? Were they known as a discount tube?
> 
> I am seriously asking as I do not know the history but would like to know what you can all tell me so I am “in” on the joke, so to speak.
> 
> Thanks



Like @Zachik said, there are definitely some good GE tubes, but overall they tend to have a less than stellar reputation.  Is it deserved?  Hard to say, there some standouts in my mind as well.


----------



## L0rdGwyn (Jan 24, 2021)

So turns out I have a pair of 4.7uF 630VDC ClarityCap CSA leftover from another project, so thought I would get a head start on the cap rolling that is set to get underway tomorrow.  I am using 6.8uF output caps in the 841 amplifier, but 4.7uF is close enough to get a feel for the tonality.

First impressions...

*Solen Fast-CAP MKP* - definitely add an "artificial" character to the sound and some upper midrange / treble sibilance, but pretty good soundstage and separation though considering their price.

*Auricap XO* - better soundstage and separation than the Solens, perhaps a bit more dynamic, but still some sibiliance to the upper midrange and treble, giving the sound that "artificial" "hifi" character that I do not like, similar to what I heard when they were in the original build of the amplifier.

*ClarityCap CSA* - without a doubt, these are the best of the three.  The sibilance and artificial character is gone, the soundstage and center image are larger, the sound is more natural and less colored to my ears, better bass dynamics, just more musical overall.

So as far as I am concerned, tomorrow will just be a comparison between the Obbligato Gold and ClarityCap CSA.


----------



## L0rdGwyn

The ClarityCaps have elevated the sound of the amplifier, always amazes me how a single passive component can have such a huge impact on sound quality.




Some day, years from now, my desk won't be a disaster all the time.  I shove all of the DIY crap out of the way for the nice pictures


----------



## bcowen

L0rdGwyn said:


> The ClarityCaps have elevated the sound of the amplifier, always amazes me how a single passive component can have such a huge impact on sound quality.
> 
> 
> 
> Some day, years from now, my desk won't be a disaster all the time.  I shove all of the DIY crap out of the way for the nice pictures



Seems like the sound would be 90 degrees out of phase like that.    

Thanks for the good info on the caps!!


----------



## bcowen

Galapac said:


> I know you guys joke about the GE tubes all the time but are they really that bad? I do not own any ( I think, there may be a rougue 6SN7 somewhere) so I do not know. Are they just not known for audio quality? Were they used mainly in other applications like receivers or televisions? Were they known as a discount tube?
> 
> I am seriously asking as I do not know the history but would like to know what you can all tell me so I am “in” on the joke, so to speak.
> 
> Thanks



There are two main groups of GE tubes:  those actually made by GE, and those labeled as GE but made by someone else.  There can definitely be some treasures in the latter group.

I probably make fun of GE tubes more than most, and much of it is embellishment in the name of comedy. But there's a good bit of truth behind it too.  Obviously I haven't heard every vintage or construction type of a GE-made 6SN7, but without exception every one I _have_ heard has been 'meh' in some cases and downright awful in others.  Pretty much the same for the GE 12AU7 and 6922 families.  If they're not boring and dull and lifeless, they're screechy and fatiguing.  OTOH, a GE 211 is a wonderful tube.  And many say that the 5-star GE 5670 is a very nice sounding tube.  So I think a lot boils down to the tube type in question as well as the component it's being used in (*and* the preferences of the person listening).  I've just never been (personally) impressed with any GE-made tube I've heard, excepting the 211 (I haven't heard the 5670).  But that's one person's opinion and experience based on a very limited number of applications, so YMMV applies in spades here.


----------



## Paladin79

The lacewood Incubus is completed. I just landed a new capacitor contact in Germany, a friend of a local college professor. I will be hunting down some Telefunken tubes as well.


----------



## leftside

Used plenty of ClarityCaps in my first amp from Mischa. I think Glenn is a big fan as well.


----------



## L0rdGwyn

leftside said:


> Used plenty of ClarityCaps in my first amp from Mischa. I think Glenn is a big fan as well.



I've used them elsewhere with success, guess I should have gone with them from the get-go  shame since the Auricaps aren't really cheap, wanted to try something different, maybe they will find a home in a different application some day.


----------



## Zachik

bcowen said:


> GE 211 is a wonderful tube.


Looked those up, since I never heard of them... O M G ! ! !  Look at the example usage diagram from radiomuseum.org:




Note the 2,000 VDC    
I wonder if Keenan's cats would get curious about that one - my guess a shock would claim at least 3 of their 9 lives...


----------



## L0rdGwyn

Zachik said:


> Looked those up, since I never heard of them... O M G ! ! !  Look at the example usage diagram from radiomuseum.org:
> 
> 
> Note the 2,000 VDC
> I wonder if Keenan's cats would get curious about that one - my guess a shock would claim at least 3 of their 9 lives...



Oh yeah, transmitting triodes are no joke, they can take crazy high voltages!  Although most people are not putting 2kV on the plate of a 211, around 1kV is more typical.  If you want big power out of a single-ended class A1 amplifier, big, hot, high-voltage transmitters are the way to go...or parallel single-ended is an option if you aren't into +1kV amplifiers.


----------



## bcowen

Zachik said:


> Looked those up, since I never heard of them... O M G ! ! !  Look at the example usage diagram from radiomuseum.org:
> 
> 
> Note the 2,000 VDC
> I wonder if Keenan's cats would get curious about that one - my guess a shock would claim at least 3 of their 9 lives...



LOL!  Yeah, 2k vdc has just a bit of bite to it.  Especially with your tongue.

The 211 tubes were interchangeable with 845 tubes in (earlier) versions of both the Cary 211FE amps and the Cary 805's and I preferred 845's in both.  The 211FE amps weren't my cup of tea, but I loved the 805's (when paired with the right speaker).  Have no idea what voltages the output tubes were being run at though...I was waaaaaaaay too chicken to go poking around the insides of those amps.  

https://www.caryaudio.com/products/cad-211fe/

https://www.caryaudio.com/products/cad-805rs/


----------



## Zachik

L0rdGwyn said:


> Oh yeah, transmitting triodes are no joke, they can take crazy high voltages!  Although most people are not putting 2kV on the plate of a 211, around 1kV is more typical.  If you want big power out of a single-ended class A1 amplifier, big, hot, high-voltage transmitters are the way to go...or parallel single-ended is an option if you aren't into +1kV amplifiers.


Can you even measure over 1,000 VDC with your DMM?!  
I think most top at 1,000 VDC. Right?


----------



## L0rdGwyn

Zachik said:


> Can you even measure over 1,000 VDC with your DMM?!
> I think most top at 1,000 VDC. Right?



Mine tops out at 1kV, would have to get a bigger one  but I'm not building any 1kV amplifiers any time soon.  In fact I have just one more from-scratch amp left on the to-do list and it will only have 350-400V inside.

Waiting on another custom mains transformer from Sowter for that one, so trying to work on my vintage radio restoration and @Galapac 's modded Darkvoice in the meantime.


----------



## Zachik

L0rdGwyn said:


> Waiting on another custom mains transformer from Sowter for that one, so trying to work on my vintage radio restoration and @Galapac 's modded Darkvoice in the meantime.


I am definitely paying close attention to your DV mod... I think if that turns out to be a huge success - quite a few followers here might buy one and mod it, too


----------



## bcowen

Zachik said:


> I am definitely paying close attention to your DV mod... I think if that turns out to be a huge success - quite a few followers here might buy one and mod it, too



Just be careful if you accidentally wander over to the DV Tuberolling thread. There's already so much drool on the floor there you might slip and get hurt.  

https://www.head-fi.org/threads/darkvoice-336i-336se-tuberolling-partii.348833/


----------



## Tjj226 Angel

bcowen said:


> There are two main groups of GE tubes:  those actually made by GE, and those labeled as GE but made by someone else.  There can definitely be some treasures in the latter group.
> 
> I probably make fun of GE tubes more than most, and much of it is embellishment in the name of comedy. But there's a good bit of truth behind it too.  Obviously I haven't heard every vintage or construction type of a GE-made 6SN7, but without exception every one I _have_ heard has been 'meh' in some cases and downright awful in others.  Pretty much the same for the GE 12AU7 and 6922 families.  If they're not boring and dull and lifeless, they're screechy and fatiguing.  OTOH, a GE 211 is a wonderful tube.  And many say that the 5-star GE 5670 is a very nice sounding tube.  So I think a lot boils down to the tube type in question as well as the component it's being used in (*and* the preferences of the person listening).  I've just never been (personally) impressed with any GE-made tube I've heard, excepting the 211 (I haven't heard the 5670).  But that's one person's opinion and experience based on a very limited number of applications, so YMMV applies in spades here.



211s actually kinda suck. 

They always sound a bit too thin if I am honest. They are very spacious, and they definitely have a certain sound quality that works really well for certain genres of music, but there is always something missing from the sound. 

And honestly, there isn't even a point in using the 211 anymore. The GM70 is a better tube all around and is 1/10th the price.


----------



## bcowen

Tjj226 Angel said:


> 211s actually kinda suck.
> 
> They always sound a bit too thin if I am honest. They are very spacious, and they definitely have a certain sound quality that works really well for certain genres of music, but there is always something missing from the sound.
> 
> And honestly, there isn't even a point in using the 211 anymore. The GM70 is a better tube all around and is 1/10th the price.



Well, the GE's replaced the stock Chinese tubes, so suck is somewhat relative.   Once I got my hands on some NOS RCA 845's it was game over for the 211's.  Then 300B SET's happened...


----------



## Zachik

bcowen said:


> Just be careful if you accidentally wander over to the DV Tuberolling thread. There's already so much drool on the floor there you might slip and get hurt.
> 
> https://www.head-fi.org/threads/darkvoice-336i-336se-tuberolling-partii.348833/


More than 6,000 posts!   
Got a link to the Cliff Notes?


----------



## bcowen

Zachik said:


> More than 6,000 posts!
> Got a link to the Cliff Notes?



Here's a one-post Cliff Note from the man himself:

https://www.head-fi.org/threads/dar...erolling-partii.348833/page-409#post-16123735


----------



## L0rdGwyn

@bcowen I am working very hard right now to copy your US cleaner filtration system, I've nailed down the pump and the Pentek filter canister, royalty check is in the mail.  Have a bottle of ilfotol, the US cleaner, the Vinyl Stack, just need the filter components and the water  

Waited a long time for the US cleaner, decided in a very arbitrary kind of way that this was the best one and was worth waiting for.


----------



## bcowen

L0rdGwyn said:


> @bcowen I am working very hard right now to copy your US cleaner filtration system, I've nailed down the pump and the Pentek filter canister, royalty check is in the mail.  Have a bottle of ilfotol, the US cleaner, the Vinyl Stack, just need the filter components and the water
> 
> Waited a long time for the US cleaner, decided in a very arbitrary kind of way that this was the best one and was worth waiting for.



Sweet!  Looks like a very nice tank.  Glad I was able to return the favor even if it was only a microscopic fraction of all that you've offered us.     Be quite interested in your initial observations once you're able to US clean your first LP's.


----------



## L0rdGwyn

bcowen said:


> Sweet!  Looks like a very nice tank.  Glad I was able to return the favor even if it was only a microscopic fraction of all that you've offered us.     Be quite interested in your initial observations once you're able to US clean your first LP's.



Thanks!  I'll post some pics when it is up and running.

Battle of the titans is about to get underway.  These ClarityCaps look to be of an older vintage, hopefully that doesn't skew the results.


----------



## whirlwind

L0rdGwyn said:


> Thanks!  I'll post some pics when it is up and running.
> 
> Battle of the titans is about to get underway.  These ClarityCaps look to be of an older vintage, hopefully that doesn't skew the results.



This will be interesting.


----------



## Ripper2860

L0rdGwyn said:


> @bcowen I am working very hard right now to copy your US cleaner filtration system, I've nailed down the pump and the Pentek filter canister, royalty check is in the mail.  Have a bottle of ilfotol, the US cleaner, the Vinyl Stack, just need the filter components and the water
> 
> Waited a long time for the US cleaner, decided in a very arbitrary kind of way that this was the best one and was worth waiting for.



I have one that is similar.  It's made by Yeti.


----------



## L0rdGwyn (Jan 25, 2021)

And the winner of the compact polypropylene capacitor shootout is...the ClarityCap CSA.

*Obbligato Gold Premium* - in terms of tonality, these really do nothing wrong, they sound "neutral" (whatever that means), they don't sound overly artificial, perhaps just a touch of that somewhat harsh upper midrange, all relative to the ClarityCap CSA, but the soundstage and center image are much smaller and the bass dynamics aren't as impressive.

The ClarityCap CSA does the best job of NOT sounding like a capacitor.  They are not harsh, they remain musical, and have a serious edge in soundstage and dynamics relative to all of the other caps.  The Solens, Auricaps, and Obbligatos all seem to sound somewhat similar in character with differences in artificiality and upper midrange / treble sibilance with the Obbligatos minimizing those issues to the greatest degree.  The ClarityCaps are on a different level though, they sound like an entirely different class of capacitor.  I would rank them as follows:

ClarityCap CSA > Obbligato Gold Premium > Auricap XO > Solen Fast-CAP MKP

Now obviously there are better caps out there, but if you need a lot of capacitance in a relatively small package, the ClarityCap CSA are the best I have found so far.  It would be interesting to see how the CMR compare in a direct head-to-head to the CSA, but the size footprint goes up significantly.  I will keep these in mind for future parafeed designs if small footprint is a high priority.

Here is a disorienting photo, hope you took your Dramamine.


----------



## Zachik

L0rdGwyn said:


> Here is a disorienting photo, hope you took your Dramamine.


No joke - I was looking at the photo (before reading your text) wondering why my brain cannot comprehend what is going on there...


----------



## L0rdGwyn

Now permanent.  Will have to go back in some time soon and tighten up some of the wiring, also need to replace the source follower boards as these are an old iteration with unneeded zener pads that are jumped, so will get to that in a week or two.




Okay what's next...


----------



## leftside

L0rdGwyn said:


> @bcowen I am working very hard right now to copy your US cleaner filtration system, I've nailed down the pump and the Pentek filter canister, royalty check is in the mail.  Have a bottle of ilfotol, the US cleaner, the Vinyl Stack, just need the filter components and the water
> 
> Waited a long time for the US cleaner, decided in a very arbitrary kind of way that this was the best one and was worth waiting for.


I don't bother with a filter system, but I only clean 10-20 records at a time and most have already been pre-cleaned on a VPI HW-17.


----------



## L0rdGwyn

leftside said:


> I don't bother with a filter system, but I only clean 10-20 records at a time and most have already been pre-cleaned on a VPI HW-17.



I won't be using a dedicated cleaner, just the ultrasonic for now, would like to change the solution as infrequently as possible.


----------



## Xcalibur255

Are the cap comparisons zero hour comparisons?  You're smarter than I am so I know you've already thought of this, but I was just thinking if perhaps the ClarityCaps had previously been used elsewhere and had more hours on them that could skew results.


----------



## L0rdGwyn

Xcalibur255 said:


> Are the cap comparisons zero hour comparisons?  You're smarter than I am so I know you've already thought of this, but I was just thinking if perhaps the ClarityCaps had previously been used elsewhere and had more hours on them that could skew results.



Essentially yes, the ClarityCaps and the Obbligatos were just received brand new, although I'm sure they have been stored for some time.  The Solens and Auricaps had no more than a few hours on them.  Assuming burn in is always a positive effect and not a negative, that would give them some edge perhaps, but the gap is pretty large to my ears between the ClarityCaps and everything else, so I feel comfortable with the results.


----------



## bcowen

leftside said:


> I don't bother with a filter system, but I only clean 10-20 records at a time and most have already been pre-cleaned on a VPI HW-17.



I used the US tank for a bit before I added the filtering system. Not that the fluid appeared to be dirty visually, just got to thinking about what the US cleaner is actually doing:  exploding tiny air bubbles against the surface of the vinyl. Now if those 'bubbles' contain or are surrounded by a bit of grit (even microscopic), then exploding them on the vinyl might actually embed the particle into the groove rather than assist removing it.  I'll freely admit that's probably on the far side of anal, but 1) it didn't cost much to implement the filtering system, and 2) I'm already a homeowner in the far side of anal.    

Now some guys use ultra-pure water for their cleaning solution that's like $25/_quart_.  That requires space travel to the *planet* anal, even for me.    The $1/gallon distilled water from Food Lion is good enough as far as I'm concerned.  I also do a final distilled water rinse/vacuum on my VPI 16.5 after the US cleaning just to be sure all the US cleaning fluid is removed, and I think that provides a benefit without going (too) overboard.


----------



## Galapac

bcowen said:


> I used the US tank for a bit before I added the filtering system. Not that the fluid appeared to be dirty visually, just got to thinking about what the US cleaner is actually doing:  exploding tiny air bubbles against the surface of the vinyl. Now if those 'bubbles' contain or are surrounded by a bit of grit (even microscopic), then exploding them on the vinyl might actually embed the particle into the groove rather than assist removing it.  I'll freely admit that's probably on the far side of anal, but 1) it didn't cost much to implement the filtering system, and 2) I'm already a homeowner in the far side of anal.
> 
> Now some guys use ultra-pure water for their cleaning solution that's like $25/_quart_.  That requires space travel to the *planet* anal, even for me.    The $1/gallon distilled water from Food Lion is good enough as far as I'm concerned.  I also do a final distilled water rinse/vacuum on my VPI 16.5 after the US cleaning just to be sure all the US cleaning fluid is removed, and I think that provides a benefit without going (too) overboard.


Isn’t distilled water the purist you can get by definition? It’s distilled via steam so only the water itself is left with no impurities or minerals?


----------



## bcowen

Galapac said:


> Isn’t distilled water the purist you can get by definition? It’s distilled via steam so only the water itself is left with no impurities or minerals?



Distilled water can still have contaminants in it.  The question is whether the remaining contaminants are significant enough to justify spending big bucks on something with a few fewer contaminants.   

The link below is long and a bit old (with the prices shown affected accordingly) and probably more than you ever wanted to know about water, but the author does a pretty good job of describing the differences. Despite his conclusions though, distilled water is still good enough for me. 

https://forum.audiogon.com/discussions/finding-pure-water-for-record-cleaning-very-long#Justin_time


----------



## leftside

bcowen said:


> I used the US tank for a bit before I added the filtering system. Not that the fluid appeared to be dirty visually, just got to thinking about what the US cleaner is actually doing:  exploding tiny air bubbles against the surface of the vinyl. Now if those 'bubbles' contain or are surrounded by a bit of grit (even microscopic), then exploding them on the vinyl might actually embed the particle into the groove rather than assist removing it.  I'll freely admit that's probably on the far side of anal, but 1) it didn't cost much to implement the filtering system, and 2) I'm already a homeowner in the far side of anal.
> 
> Now some guys use ultra-pure water for their cleaning solution that's like $25/_quart_.  That requires space travel to the *planet* anal, even for me.    The $1/gallon distilled water from Food Lion is good enough as far as I'm concerned.  I also do a final distilled water rinse/vacuum on my VPI 16.5 after the US cleaning just to be sure all the US cleaning fluid is removed, and I think that provides a benefit without going (too) overboard.


 I also use a VPI vacuum cleaner for a final rinse... with ultra-pure water


----------



## bcowen

leftside said:


> I also use a VPI vacuum cleaner for a final rinse... with ultra-pure water



There's a house for sale right next door to me.


----------



## Galapac

Wow, I don’t clean my records like you guys do. I do chuck those paper sleeves and use the mofi sleeves but all I use is a spray with a microfiber brush and one of those gel things for the needle. I am more picky about my digital files and head amps. You guys are on a different level. The occasional pop or click is ok with me but I don’t have a real expensive record player setup either.


----------



## Zachik

So... reading through all the posts about record cleaning...
Can those cleaners also clean my music storage?    





Given the numerous rabbit holes in this hobby, I am grateful that vinyls is not one I went down.


----------



## bcowen (Jan 26, 2021)

Zachik said:


> So... reading through all the posts about record cleaning...
> Can those cleaners also clean my music storage?



Probably everything but the porn.   

Seriously, I fell into that rabbit hole back in the late '80's and early '90's when people were dumping their LP collections in favor of 'perfect sound forever.'  While I thoroughly enjoy what digital has become today, I found it nearly unlistenable when it was first introduced, and that with a far less accomplished and resolving system.  I think "painful" is the most descriptive term.   Probably 90% of my LP collection was purchased used for $1 or $2 a pop at resale shops and garage sales...


----------



## L0rdGwyn

Galapac said:


> Wow, I don’t clean my records like you guys do. I do chuck those paper sleeves and use the mofi sleeves but all I use is a spray with a microfiber brush and one of those gel things for the needle. I am more picky about my digital files and head amps. You guys are on a different level. The occasional pop or click is ok with me but I don’t have a real expensive record player setup either.



Right?  What a bunch of psychopaths.....oh hey my vinyl cleaning water shipped!  Nothing to see here.





Zachik said:


> Given the numerous rabbit holes in this hobby, I am grateful that vinyls is not one I went down.



It's a money pit, and then some.  The noise floor isn't as low, sure, but at least in my system, the vinyl sounds better.  Granted I am not working with a TOTL DAC at the moment, the quality of my TT and phono stage is higher.  There are very few deals to be had on vinyl these days, but it's still fun to hit your local vinyl shops and see what's in, every so often you can score a great find.  It can sometimes be painful looking through old vinyl...I don't know if it was a Cleveland thing or what, but my gawd, there is just so much garbage prog rock out there, if I have to look at one more copy of Emerson Lake & Palmer's _Trilogy_...I'll sift through five copies in a row sometimes...don't get me wrong, I like prog, but there's just too much of it in old vinyl stacks to look at a thousand times over.....what was the question again?


----------



## bcowen

L0rdGwyn said:


> Right?  What a bunch of psychopaths.....oh hey my vinyl cleaning water shipped!  Nothing to see here.
> 
> 
> 
> ...



LOL!  Just get the right tools and it's easy-peasy. 

(the Fozgometer wouldn't fit in the case)


----------



## L0rdGwyn

Put together the gyrator PCB this morning for the Darkvoice modifications.  Ordering today, we'll see how it turns out.


----------



## bcowen

L0rdGwyn said:


> Put together the gyrator PCB this morning for the Darkvoice modifications.  Ordering today, we'll see how it turns out.



Can you give us a quick explanation of what this gyrator does?


----------



## L0rdGwyn

bcowen said:


> Can you give us a quick explanation of what this gyrator does?



Absolutely!  So a gyrator is a type of active load for a tube, similar to a CCS.  The gyrator simulates and inductive load using a capacitor, but without the magnetic properties of a inductor.  The long and short of it is the gyrator provides a high AC impedance load for the tube while setting the plate _voltage _and the tube bias sets its current.  This is opposed to a CCS load which sets the plate _current_ and the tube bias sets the plate voltage.

The advantage of using a gyrator over a CCS in an amplifier like the Darkvoice is due direct coupling.  Making the plate voltage of the driver constant, as opposed to the plate current, ensures the output tube will maintain a stable bias point as its grid will be at the same voltage.


----------



## L0rdGwyn

Also, the goal is to not have to drill any holes in the Darkvoice chassis - the mounting holes of the PCB align with the mounting holes of the last CRC filter of the power supply, which will be removed once the power supply is regulated.



Think it will fit...we will see


----------



## L0rdGwyn

Oh and the end result for the listener as far as the gyrator goes is lower distortion and better power supply rejection than a resistor load.


----------



## Galapac

L0rdGwyn said:


> Also, the goal is to not have to drill any holes in the Darkvoice chassis - the mounting holes of the PCB align with the mounting holes of the last CRC filter of the power supply, which will be removed once the power supply is regulated.
> 
> 
> 
> Think it will fit...we will see


If  you need to realign things and add some holes I am not opposed to that sir. Work your magic.


----------



## bcowen

L0rdGwyn said:


> Absolutely!  So a gyrator is a type of active load for a tube, similar to a CCS.  The gyrator simulates and inductive load using a capacitor, but without the magnetic properties of a inductor.  The long and short of it is the gyrator provides a high AC impedance load for the tube while setting the plate _voltage _and the tube bias sets its current.  This is opposed to a CCS load which sets the plate _current_ and the tube bias sets the plate voltage.
> 
> The advantage of using a gyrator over a CCS in an amplifier like the Darkvoice is due direct coupling.  Making the plate voltage of the driver constant, as opposed to the plate current, ensures the output tube will maintain a stable bias point as its grid will be at the same voltage.



Ahhhhh....I see.  Now can you explain it in layman's terms? 

Just kidding.   I won't pretend to understand the _how_, but the _why_ and the end result is now clear, so thanks!


----------



## bcowen

Galapac said:


> If  you need to realign things and add some holes I am not opposed to that sir. Work your magic.



I realize that's _your_ amp, but just for the record I don't mind making _mine_ look like swiss cheese in the pursuit of better sound.


----------



## Tjj226 Angel

bcowen said:


> Well, the GE's replaced the stock Chinese tubes, so suck is somewhat relative.   Once I got my hands on some NOS RCA 845's it was game over for the 211's.  Then 300B SET's happened...



That might be true, but I am saying 211s in general are somewhat bad for music. The plate impedance is just too darn high. With a 10K to 8ohm transformer you are just shy of the 3:1 load impedance to plate impedance ratio. 

The 845, 813, and GM70 all have much lower plate impedances and will work with loads down to 7K. 

That being said, 7K transformers are still hard to find and will cost more than a good used car. 

This is why I think it is better to look at hybrid amps when you want 20watts and up.


----------



## L0rdGwyn (Jan 26, 2021)

Okay, so I wasn't planning on finalizing all of the DarkVoice modification plans today, but that's what happened, all of parts are ordered.

So here is what we are doing specifically...

1) *Maida regulated power supply.* The entire stock CRCRC-CRC filter is being excised and replaced with a 330uF reservoir cap and a Maida regulator. This regulator, again the hard work of @A2029 of 1101 Audio, has far better power supply rejection capabilities than even the biggest, clunkiest passive supplies with giant caps and chokes. It is compact and incredibly performative.

Here is the first CRCRC removed. This is where the Maida regulator will go.



It just so happens I have a regulator ready to go from another project, just have to change one or two components to adapt for this circuit. Had to get creative on how it is going to be mounted, but came up with a solution that I think will work with the existing mounting hardware, no drilling necessary. Going to attempt to get away with not using a heatsink on the TO-247 FET. Going to strap a thermocouple to it and see how hot it gets, we'll see how it goes, having to squeeze a heat sink on would make things very interesting...hoping to avoid it.



2) *Gyrator load on 6SN7.* The PCBs and parts are ordered, just a matter of waiting to get them in house for assembly. As I said, these will go in the position of the last CRC of the power supply, again using the existing mounting hardware, the PCB mounting holes will align.

The bias point of the 6SN7 will be altered slightly, so the necessary cathode resistor has been ordered as well.



3) *Output tube cathode resistor swap.* Based on simulations I have run and the new bias point of the 6SN7, in addition to the new higher available B+ supply, the bias of the output tube will also be slightly altered to maintain the 80mA plate current of the original design - keeping the 1K cathode resistors would push this to 100mA, which would be fine from a plate dissipation standpoint, but felt better not pushing the tubes harder than originally intended, especially since they are becoming quite rare (pushing 100mA through a 1K 25W resistor would get very hot too). This necessitates increasing the value of the cathode resistor slightly to 1.2K. Just for the halibut, will change them to Vishay non-inductive wirewound resistors, which fit in the same position as the originals.

4) *Output capacitance.* The DarkVoice as built has only 30uF of output capacitance, which leads to major LF rolloff with lower impedance headphones, pretty much anything under 300ohms. Have to increase it, which is challenging as the available space is very limited. I was hoping to find something that can fit on the original PCB, and I did, but it is a tight squeeze, some 33uF 250VDC TDK film caps.

Now these are thicker than the originals at 22mm, so I am not super confident that I will be able to squeeze three of them in, which would be ideal. Even if it is just two, 66uF is better than 30uF and will improve the LF performance with headphones of moderate impedance.

5) *Alps pot.* That is all.

Edit: adding another item...

6) *Heater balance.* The heaters in the stock DarkVoice do not appear to be center tapped. In addition, the leads are not a twisted pair. These two oversights are very likely the cause of the widely reported "hum" issues in this amplifier. Making both of these chances should significantly reduce the audible hum.


----------



## L0rdGwyn

That's all I'm doing for DIY today, need a mental break, going to do literally anything else but tube-related stuff this evening.


----------



## CJG888

L0rdGwyn said:


> That's all I'm doing for DIY today, need a mental break, going to do literally anything else but tube-related stuff this evening.


Basically, you’re keeping the chassis and completely redesigning the amp...


----------



## L0rdGwyn

CJG888 said:


> Basically, you’re keeping the chassis and completely redesigning the amp...



Well...the general topology is the same, it is still a direct-coupled 6AS7G OTL, but the power supply is better, the driver loading is better, and the output stage components should yield better bandwidth, I don't know if that counts as a complete redesign


----------



## adamus

i did something similar to a mates darkvoice. CCS made a big difference. Caps then helped. Power supply was icing on the cake, but least noticable after the other mods. I assume because the cascode CCS was such a brickwall to power supply noise... wouldnt stop me though!


----------



## L0rdGwyn

adamus said:


> i did something similar to a mates darkvoice. CCS made a big difference. Caps then helped. Power supply was icing on the cake, but least noticable after the other mods. I assume because the cascode CCS was such a brickwall to power supply noise... wouldnt stop me though!



Very nice!  What did you end up doing with the power supply?


----------



## adamus

L0rdGwyn said:


> Very nice!  What did you end up doing with the power supply?



Salas shunt, on horrific perfboard as none of the PCBs available fitted. Had to be sinked through the chassis from memory.


----------



## L0rdGwyn (Jan 26, 2021)

adamus said:


> Salas shunt, on horrific perfboard as none of the PCBs available fitted. Had to be sinked through the chassis from memory.



Sounds like a good DIY affair  did you find that the heaters lacked a center tap in this amplifier, no virtual center tap either?  As far as I can tell, there isn't one, which would explain all of the widely reported hum issues with this amp.


----------



## leftside

Galapac said:


> Wow, I don’t clean my records like you guys do. I do chuck those paper sleeves and use the mofi sleeves but all I use is a spray with a microfiber brush and one of those gel things for the needle. I am more picky about my digital files and head amps. You guys are on a different level. The occasional pop or click is ok with me but I don’t have a real expensive record player setup either.


One of those "gel things" are good  I've had a vinyl setup since I was 7 years old. Been upgrading and tweaking ever since  Absolutely love it. Although I do admit DACs have come a long way the last few years, and I now enjoy digital these days for "proper" listening (i.e. darkened room, etc - not just headphones in the gym, listening in the car, etc). We are totally spoilt for choice these days. It's all good.



Zachik said:


> Given the numerous rabbit holes in this hobby, I am grateful that vinyls is not one I went down.


Head on over to Computer Audiophile.....


----------



## adamus

L0rdGwyn said:


> Sounds like a good DIY affair  did you find that the heaters lacked a center tap in this amplifier, no virtual center tap either?  As far as I can tell, there isn't one, which would explain all of the widely reported hum issues with this amp.  Will dissect it further, but if not that is a big design oversight.



I can't remember if I am honest. I have a feeling I elevated the heaters , but it's probably 10 years ago, and a lot of whisky has been consumed since. 

I am currently living my 6e6p parafeed. Would be interested to see more of your gyrator PCB. Any issues with oscillation when Fed with a reg ?


----------



## L0rdGwyn (Oct 2, 2021)

adamus said:


> I can't remember if I am honest. I have a feeling I elevated the heaters , but it's probably 10 years ago, and a lot of whisky has been consumed since.
> 
> I am currently living my 6e6p parafeed. Would be interested to see more of your gyrator PCB. Any issues with oscillation when Fed with a reg ?



Ha!  Understood, no worries.  Yet to be determined on oscillation issues as I have only put together the PCB this morning, but have had no issues feeding cascode CCS in several designs with the reg.  Time will tell!  Possible it will take a few iterations, might have to add some HF decoupling if oscillation is an issue, fingers crossed.

"Revamped DarkVoice" schematic with the gyrator in place.  Reference voltage is generated by cascode LND150 CCS across 220K resistor to ground.  Have taken the output from the plate, but could take the mu output as well, depending on how the original owner feels about transistors being in the signal path


----------



## adamus

Nice. I will have a study. 

I have been playing with the IXTP08N100D2... In a CCS it sounds better than the dn2540


----------



## L0rdGwyn

adamus said:


> Nice. I will have a study.
> 
> I have been playing with the IXTP08N100D2... In a CCS it sounds better than the dn2540



I have used the IXTP08N100D2 in cascode with the IXTP08N50D2 with good success, although it was not happy in one of my designs loading a pentode that used NFB, IXCP10M90S in cascode with the DN2540 was more stable in that particular instance...

Thanks for dropping by!  Always welcome to come back to talk DIY


----------



## Tjj226 Angel

L0rdGwyn said:


> Ha!  Understood, no worries.  Yet to be determined on oscillation issues as I have only put together the PCB this morning, but have had no issues feeding cascode CCS in several designs with the reg.  Time will tell!  Possible it will take a few iterations, might have to add some HF decoupling if oscillation is an issue, fingers crossed.
> 
> The gyrator is inspired by Ale Moglia's design, here is a "Revamped DarkVoice" schematic with the gyrator in place.  Reference voltage is generated by cascode LND150 CCS across 220K resistor to ground.  Have taken the output from the plate, but could take the mu output as well, depending on how the original owner feels about transistors being in the signal path



You can easily ditch the jfet. It wouldn't be a bad idea if you had a gain stage following the gyrator, but a cathode follower will actually dampen the noise of the SS device. Not to mention that the 6080 will be way noisier than any decent mosfet you could throw at the gyrator. 

Leave the 2SK170s for the guys trying to build their phonostages 

It's also worth pointing out that if you have a CCS on the 6080 cathode, then the gyrator is a bit overkill. I know you were looking at putting a CCS on the 6080, but IDK if you made it that far or not.


----------



## L0rdGwyn

Tjj226 Angel said:


> You can easily ditch the jfet. It wouldn't be a bad idea if you had a gain stage following the gyrator, but a cathode follower will actually dampen the noise of the SS device. Not to mention that the 6080 will be way noisier than any decent mosfet you could throw at the gyrator.
> 
> Leave the 2SK170s for the guys trying to build their phonostages
> 
> It's also worth pointing out that if you have a CCS on the 6080 cathode, then the gyrator is a bit overkill. I know you were looking at putting a CCS on the 6080, but IDK if you made it that far or not.



The 2SK170 is just a stand-in for the sim, I'll be using the J310 on the first go-around.  Part of this is to experiment with this design for future use, perhaps replacing the CCS loads in my phono stage  I decided to leave the 6080 cathode resistively loaded, there isn't enough space in the DarkVoice for two gyrator boards and a heat-sinked current sink dissipating 8-10W, its too damn hot!


----------



## Tjj226 Angel

L0rdGwyn said:


> The 2SK170 is just a stand-in for the sim, I'll be using the J310 on the first go-around.  Part of this is to experiment with this design for future use, perhaps replacing the CCS loads in my phono stage  I decided to leave the 6080 cathode resistively loaded, there isn't enough space in the DarkVoice for two gyrator boards and a heat-sinked current sink dissipating 8-10W, its too damn hot!



Just put a CCS in series with the cathode resistor. 

Lets say that the 6080 cathode is at 100v at 100ma and your cathode resistor is 1000 ohms. If you don't want a CCS to deal with 10W, what you can do is split the job up between your CCS and cathode resistor. 

You drop your cathode resistor down to 500 ohms and you add a CCS at 100ma in series with the resistor. Now the CCS only has to drop 50v which means you have a dissipation of 5 watts. 

You can obviously adjust the cathode resistor and CCS values to reduce the heat on the CCS as much as possible. I would probably let the resistor handle 80% of the power and the CCS handle 20%. 

That way you actually get some current regulation on the 6080 AND you get the high impedance from the CCS in the cathode.


----------



## JazzVinyl

leftside said:


> One of those "gel things" are good  I've had a vinyl setup since I was 7 years old. Been upgrading and tweaking ever since  Absolutely love it. Although I do admit DACs have come a long way the last few years, and I now enjoy digital these days for "proper" listening (i.e. darkened room, etc - not just headphones in the gym, listening in the car, etc). We are totally spoilt for choice these days. It's all good.




Amen.  Been with vinyl a long long time, too.  As painful as it is to do, a very carefully aligned cartridge goes a long way towards eliminating  surface noise.

I clean 'bought used' records that are really dirty....with wood glue.  It's slow, it's messy, and no one believes that it works...but once you figure out how to do it right, makes all other methods seem like a waste of time.  If wood glue does not restore the vinyl, it has physical damage and there is no hope of saving it.

And agree about a darkened room!  Removing other sensory stimuli is very important in getting the most out of what your listening to.

Also agree that DAC's have come a long way!  That is sounding superb these days, too.

But, if your like me and have tons and tons of beloved vinyls' that you like to "study"....

Cheers, all!


----------



## L0rdGwyn

Apparently my fancy deionized water was destroyed in transit, so I will not be receiving it LOL.  Guess it will be the bargain buck distilled water then, not going to delay getting the ultrasonic cleaner up and running this weekend.

Hey @bcowen , what kind of filter are you using in your filtration system?  I grabbed some of these Pentek CBC-5 0.5 micron carbon filters.

https://www.filtersfast.com/Pentek-...o1DuJD-c3qWfMFipNnBkPenNy88qA91MaAhuUEALw_wcB


----------



## bcowen

L0rdGwyn said:


> Apparently my fancy deionized water was destroyed in transit, so I will not be receiving it LOL.  Guess it will be the bargain buck distilled water then, not going to delay getting the ultrasonic cleaner up and running this weekend.
> 
> Hey @bcowen , what kind of filter are you using in your filtration system?  I grabbed some of these Pentek CBC-5 0.5 micron carbon filters.
> 
> https://www.filtersfast.com/Pentek-...o1DuJD-c3qWfMFipNnBkPenNy88qA91MaAhuUEALw_wcB



You just had to one-up me, didn't you?       That's a 0.5 micron filter.....I'm using a 1 micron filter:

https://www.amazon.com/gp/product/B00D049XFQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Using this housing for it:

https://www.amazon.com/gp/product/B0014C5D64/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


----------



## L0rdGwyn

bcowen said:


> You just had to one-up me, didn't you?      That's a 0.5 micron filter.....I'm using a 1 micron filter:
> 
> https://www.amazon.com/gp/product/B00D049XFQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
> 
> ...



Well yeah, obviously!  If you were using a 0.5 micron filter, I would buy a 0.35 

My cleaning solution is just going to be distilled water and Ilfotol.  Trying to figure out is if I will run into issues with adsorption of the wetting agent if using a carbon filter.  I suspect no, but digging for definitive answers.  Any idea?


----------



## bcowen

L0rdGwyn said:


> Well yeah, obviously!  If you were using a 0.5 micron filter, I would buy a 0.35
> 
> My cleaning solution is just going to be distilled water and Ilfotol.  Trying to figure out is if I will run into issues with adsorption of the wetting agent if using a carbon filter.  I suspect no, but digging for definitive answers.  Any idea?



No idea, sorry.  The filter I'm using doesn't have any carbon in it, and I'm using a different formula for my fluid anyway.


----------



## L0rdGwyn

bcowen said:


> No idea, sorry.  The filter I'm using doesn't have any carbon in it, and I'm using a different formula for my fluid anyway.



No worries, thanks!  Should have this thing set up tomorrow night after work, I am pumped (no pun intended).


----------



## Zachik

bcowen said:


> I'm using a different formula for my fluid anyway.



Bill and his secret formula...


----------



## bcowen

Zachik said:


> Bill and his secret formula...



LOL!  No secret about it, I just copied what a _real_ chemist suggested, and it's worked quite well for me.


----------



## Zachik

bcowen said:


> I just copied what a _real_ chemist suggested, and it's worked quite well for me.


Got it. So more like...


----------



## Xcalibur255

You could set up your own R-O filtering system.  Maybe more expensive to get going but the long term costs might be better.  Or am I being naive here in my assumption that water pure enough to drink or clean corrosive parts with is still not *nearly* clean enough for vinyl?


----------



## L0rdGwyn

Remind me again of your cleaning solution, @bcowen ?



Xcalibur255 said:


> Or am I being naive here in my assumption that water pure enough to drink or clean corrosive parts with is still not *nearly* clean enough for vinyl?



I'm pretty sure there is no substance on earth that is pure enough for cleaning vinyl, but we will have to settle for what nature gave us.


----------



## Zachik

L0rdGwyn said:


> I'm pretty sure there is no substance on earth that is pure enough for cleaning vinyl


How about water from Mars?


----------



## L0rdGwyn

Zachik said:


> How about water from Mars?



Did I say earth?  I meant....*the universe.  *Water from Mars has too much sediment and adds static...


----------



## bcowen

L0rdGwyn said:


> Did I say earth?  I meant....*the universe.  *Water from Mars has too much sediment and adds static...



LOL!  And the shipping cost is kind of high.  I mean even for audiophiles.


----------



## bcowen

L0rdGwyn said:


> Remind me again of your cleaning solution, @bcowen ?



I'm using distilled water, Triton X-100 (wetting agent), Hepastat 256, and isopropyl alcohol.  Here's a handy little calculator someone came up with since your tank is bigger and the additive quantities would be different (I do not use the EDTA):

https://www.dropbox.com/sh/4ohxieumi08sbuz/AACOWoVXwIclAOOhO__lTTb1a?dl=0

The Triton is primarily a wetting agent like the ilfotol you're going to use. Doubt there's much difference between them for this application. The Hepastat not only kills any micro-bugs (like viruses and bacteria), but more importantly it acts as a de-staticizing agent (and works quite well at that). The alcohol helps dissolve organic oily stuff like fingerprints and such.  I bought some of the below to help measure as they're cheap enough to toss when you're done making up a batch so as not to risk cross-contaminating the unused liquids.

https://www.amazon.com/gp/product/B01G82SJRY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


----------



## L0rdGwyn

bcowen said:


> I'm using distilled water, Triton X-100 (wetting agent), Hepastat 256, and isopropyl alcohol.  Here's a handy little calculator someone came up with since your tank is bigger and the additive quantities would be different (I do not use the EDTA):
> 
> https://www.dropbox.com/sh/4ohxieumi08sbuz/AACOWoVXwIclAOOhO__lTTb1a?dl=0
> 
> ...



Awesome, thanks!  I think I am going to ditch the carbon filter and add isopropyl alcohol to my solution, so I will downgrading to the 1 micron sediment filter  I believe Ilfotol has anti-static properties as well, hopefully we the process right on the first try.  Need to find a particularly dirty record for a before-and-after test


----------



## Zachik

bcowen said:


> LOL!  And the shipping cost is kind of high.  I mean even for audiophiles.


I have a friend going there on a mission. Was gonna ask him to fill a bottle for me on the way back


----------



## Zachik

L0rdGwyn said:


> Need to find a particularly dirty record for a before-and-after test


That's easy - ask @bcowen for a loaner record. *Any* would do!


----------



## bcowen

Zachik said:


> I have a friend going there on a mission. Was gonna ask him to fill a bottle for me on the way back



Awesome!  Does that come with free Prime 2-day shipping?  I'm not the patient sort, you know.


----------



## bcowen

Zachik said:


> That's easy - ask @bcowen for a loaner record. *Any* would do!



Well, I haven't cleaned _*all *_my LP's yet.  I'll send @L0rdGwyn this Captain and Tenille that I was saving for you.


----------



## mordy

Zachik said:


> I have a friend going there on a mission. Was gonna ask him to fill a bottle for me on the way back


Possibly a bottle of Elmer's Glue is less expensive:

I especially liked the instruction "Go to sleep" and I learnt a new word: undry.


----------



## bcowen

mordy said:


> Possibly a bottle of Elmer's Glue is less expensive:
> 
> I especially liked the instruction "Go to sleep" and I learnt a new word: undry.




I have seen that method described several times, but have been too chicken to try it.


----------



## L0rdGwyn

The fact that this guy is squirting a giant bottle of glue above his TD 160 gives me anxiety.


----------



## bcowen

L0rdGwyn said:


> The fact that this guy is squirting a giant bottle of glue above his TD 160 gives me anxiety.



Me too.  The only place I liberally applied glue like that was to @Zachik 's tube tester.


----------



## Galapac

L0rdGwyn said:


> Awesome, thanks!  I think I am going to ditch the carbon filter and add isopropyl alcohol to my solution, so I will downgrading to the 1 micron sediment filter  I believe Ilfotol has anti-static properties as well, hopefully we the process right on the first try.  Need to find a particularly dirty record for a before-and-after test


Here's a dirty record:


----------



## bcowen

Galapac said:


> Here's a dirty record:



LOL!  I don't think even Mars water is gonna help that.


----------



## Zachik

bcowen said:


> Well, I haven't cleaned _*all *_my LP's yet.  I'll send @L0rdGwyn this Captain and Tenille that I was saving for you.


Never heard of them! But regardless, I am relived you're not risking Britney Spears in the hands of USPS...


----------



## Zachik

bcowen said:


> Me too.  The only place I liberally applied glue like that was to @Zachik 's tube tester.


At least you had the good taste of using the glue with the pink and red glitter!


----------



## L0rdGwyn

bcowen said:


> LOL!  I don't think even Mars water is gonna help that.



There is water in the atmosphere of....Uranus, maybe that will help?  Or maybe that will make it worse, hmmm


----------



## mordy

Somehow I have the idea that every serious vinyl guy has some old turntable sitting around and some records they don’t play.
Why not use the surplus stuff to test the glue method of cleaning vs the other methods?
Let your ears be the judge.


----------



## L0rdGwyn

Here are some spoils from the mail today.

GEC A2293.  I don't know why I bought these...I think I was going to consider an OTL prototype with them?  I will check them out on the curve tracer soon, two pairs.



More NIB Hytron 841, because these are cheap in Japan and you never know when they'll go extinct.



Speaking of extinct, here is a pair of 5998 I bought only because they are getting so rare!  For a good price.



And I got all kinds of DarkVoice modification knick knacks.  Output caps, Alps pot, resevoir cap and clamp, cathode resistors...I'll spare you from individual photos of all of the resistors, transistors, diodes, etc.



I am not really 100% sure those caps are going to fit.  Highly unlikely to fit three per channel, but they are a bit taller than anticipated as well, soon we will find out.

At this point I just need my gyrator PCBs to give the DarkVoice mods a test run, it will probably be another week or so but I might get the HV regulator up and running this weekend.


----------



## bcowen

L0rdGwyn said:


> Here are some spoils from the mail today.
> Speaking of extinct, here is a pair of 5998 I bought only because they are getting so rare!  For a good price.



Good price?  That's just soooooo not right.  You dawg!!!



L0rdGwyn said:


> And I got all kinds of DarkVoice modification knick knacks.  Output caps, Alps pot, resevoir cap and clamp, cathode resistors...I'll spare you from individual photos of all of the resistors, transistors, diodes, etc.



Wait....nevermind what I just said.  You the man!!!


----------



## Galapac

L0rdGwyn said:


> Here are some spoils from the mail today.
> 
> GEC A2293.  I don't know why I bought these...I think I was going to consider an OTL prototype with them?  I will check them out on the curve tracer soon, two pairs.
> 
> ...


If you don’t like those CV4079’s, I’ll take them off your hands, I really like my older A2293’s used in my 339i.


----------



## L0rdGwyn

Galapac said:


> If you don’t like those CV4079’s, I’ll take them off your hands, I really like my older A2293’s used in my 339i.



I don't know what I'm going to do with them, but like so many other tubes I will hold onto them until they find a purpose some day.  I think I was thinking of some sort of very compact OTL headphone amp using only noval 9-pin type tubes.  Glad you like them in the 339i!


----------



## Tjj226 Angel

L0rdGwyn said:


> Remind me again of your cleaning solution, @bcowen ?
> 
> 
> 
> I'm pretty sure there is no substance on earth that is pure enough for cleaning vinyl, but we will have to settle for what nature gave us.



Sure there is. It's called water. 

Seriously there is no magic in the water you used to clean a record. The reason you should use deionized water for your ultrasonic cleaner is to prevent premature damage to the machine. 

If it weren't for that you could use any basic drinking water you have on hand. 

And as a fun fact, deionized water is pretty easy to find at stores and pharmacies. You shouldn't have to order it. The catch is that they don't sell it with the drinking water. They have it in the baby isle or in the pharmacy since it is often used to clean medical equipment and what not.


----------



## Zachik

bcowen said:


> Good price? That's just soooooo not right. You dawg!!!


@L0rdGwyn never said what HE considers good price...


----------



## Xcalibur255

Every time I see somebody mention something they got from Japan I get a little jealous.  I've had stuff sitting in Japan I ordered ten months ago that's still there because of the Japan Post embargo against the USA.  The company in question won't deal with DHL/Fedex/UPS so there it sits until Japan Post decides to resume EMS service again.  Someday.  Presumably.


----------



## Zachik

Xcalibur255 said:


> I've had stuff sitting in Japan I ordered ten months ago that's still there because of the Japan Post embargo against the USA.


You have the patience of a saint!!


----------



## leftside

Tjj226 Angel said:


> Sure there is. It's called water.


Regular tap water will leave trace minerals and a residue on your records. This is why most people choose distilled water and it's pretty cheap.


----------



## L0rdGwyn

L0rdGwyn said:


> I'm pretty sure there is no substance on earth that is pure enough for cleaning vinyl, but we will have to settle for what nature gave us.





Tjj226 Angel said:


> Sure there is. It's called water.



This was a very dry joke, I have a degree in chemistry, I do know a thing or two about water


----------



## whirlwind

Xcalibur255 said:


> Every time I see somebody mention something they got from Japan I get a little jealous.  I've had stuff sitting in Japan I ordered ten months ago that's still there because of the Japan Post embargo against the USA.  The company in question won't deal with DHL/Fedex/UPS so there it sits until Japan Post decides to resume EMS service again.  Someday.  Presumably.



Wow....this is very sad to hear...hopefully sometime soon.


----------



## bcowen (Jan 29, 2021)

Tjj226 Angel said:


> Seriously there is no magic in the water you used to clean a record. The reason you should use deionized water for your ultrasonic cleaner is to prevent premature damage to the machine.



Why would using 'ionized' water cause damage to the US machine?  The tank is stainless with the transducer(s) mounted to the exterior of it. Short of using some liquid or substance that was corrosive to the stainless, I'm not understanding how the ionization (or lack of it) in the water would have any effect on the longevity of the machine?


----------



## L0rdGwyn

Xcalibur255 said:


> Every time I see somebody mention something they got from Japan I get a little jealous.  I've had stuff sitting in Japan I ordered ten months ago that's still there because of the Japan Post embargo against the USA.  The company in question won't deal with DHL/Fedex/UPS so there it sits until Japan Post decides to resume EMS service again.  Someday.  Presumably.



Sorry you are dealing with that, hopefully soon they will ease up.  I use FedEx for my shipments which definitely gets the job done.


----------



## Galapac

I have had the same problems from Germany. German post starting in late October 2021 decided to send all parcels over in shipping containers and they are all stuck at the ports in the U.S. because they are not equipped to handle small packages to USPS. Insane that I may get some Christmas presents from 2020 by Christmas 2021.


----------



## Zachik

Galapac said:


> I have had the same problems from Germany. German post starting in late October *2020 **2021* decided to send all parcels over in shipping containers and they are all stuck at the ports in the U.S. because they are not equipped to handle small packages to USPS. Insane that I may get some Christmas presents from 2020 by Christmas 2021.


Fixed it for you...
Yeah - a German eBay seller that I bought from in 2019, is banning the US. He will not sell to US buyers because according to him couple packages (sent by German post) are several months (!) late and still not arrived to the US buyers.


----------



## Tjj226 Angel

bcowen said:


> Why would using 'ionized' water cause damage to the US machine?  The tank is stainless with the transducer(s) mounted to the exterior of it. Short of using some liquid or substance that was corrosive to the stainless, I'm not understanding how the ionization (or lack of it) in the water would have any effect on the longevity of the machine?



Salt water and metal react. Even stainless steel will react overtime with salt water over time. If it didn't, the navy would build all their ships out of stainless steel. Plus not all stainless steel is created equal. 

When you talk about the "ions" in water, you are talking about the salts. Deionized water is water without the salt. 

Its total overkill to worry about this sort of stuff, because the salt in tap water is pretty darn low. 

On the other hand, these machines are usually quite expensive and deionized water is very cheap. So it makes sense to go the extra mile to take care of your machine.


----------



## miketlse

Tjj226 Angel said:


> Salt water and metal react. Even stainless steel will react overtime with salt water over time. If it didn't, the navy would build all their ships out of stainless steel. Plus not all stainless steel is created equal.
> 
> When you talk about the "ions" in water, you are talking about the salts. Deionized water is water without the salt.
> 
> ...



Dihydrogen Monoxide sounds even worse.   


Leads to corrosion and oxidation of many metals.
Contamination of electrical systems often causes short-circuits.


----------



## Zachik

miketlse said:


> Dihydrogen Monoxide sounds even worse.
> 
> 
> Leads to corrosion and oxidation of many metals.
> Contamination of electrical systems often causes short-circuits.


@bcowen - I theorize that cryogenically treating GE tubes with that substance might turn them into really awesome sounding tubes!!!


----------



## bcowen

Zachik said:


> @bcowen - I theorize that cryogenically treating GE tubes with that substance might turn them into really awesome sounding tubes!!!



You may have a great discovery there!  If the stuff totally corroded all the internal elements the tube wouldn't work, it would be very quiet as a result, and that would be a major improvement!  Good thinking, Zachi!


----------



## triod750

L0rdGwyn said:


> Here are some spoils from the mail today.
> 
> GEC A2293.  I don't know why I bought these...I think I was going to consider an OTL prototype with them?  I will check them out on the curve tracer soon, two pairs.
> 
> ...



Those A2293 sound really good with 12AU7 as driver. Powerful and relaxed.


----------



## bcowen

triod750 said:


> Those A2293 sound really good with 12AU7 as driver. Powerful and relaxed.



What 12AU7 are you using?  I've been a bit underwhelmed with the A2293's in the Darkvoice so far, but have not given them much of a chance with different driver tubes.  Going to fish my 12AU7 adapter out of the box now...


----------



## triod750

I've tried one Telefunken and two Philips. I might have a few others but I have just started to experiment. What drivers have you used?


----------



## bcowen

triod750 said:


> I've tried one Telefunken and two Philips. I might have a few others but I have just started to experiment. What drivers have you used?



I've only tried them so far with a pair of Hytron 7A4's and a Melz 1578 (6SN7).  The Darkvoice uses a 6SN7 natively as the driver tube, but I have adapters for bunches of different tubes. Have a WE 396A in the driver's seat as we speak, but not with the A2293's.


----------



## Galapac

Zachik said:


> Fixed it for you...
> Yeah - a German eBay seller that I bought from in 2019, is banning the US. He will not sell to US buyers because according to him couple packages (sent by German post) are several months (!) late and still not arrived to the US buyers.


Thanks yes, 2020. If it is the same guy I’m thinking of he has some nice 6080 Telefunkens I cannot get my hands on.


----------



## johnjen

bcowen said:


> You may have a great discovery there!  If the stuff totally corroded all the internal elements the tube wouldn't work, it would be very quiet as a result, and that would be a major improvement!  Good thinking, Zachi!


And speaking of dead/dying tubes…

Have any of you associated the last track of Daft Punks, _Random Access Memories_ album, (starting at 4min mark of Contact) with a tube amp in it's death throws? It sounds to me like section after section (input driver, output section, psu) of a tube power amp consuming itself.
It makes me laugh every time I hear it…

JJ


----------



## L0rdGwyn

Here are the operating curves for the A2293.


----------



## triod750

L0rdGwyn said:


> Here are the operating curves for the A2293.


Thanks. I'm worthless at seeing how curves sound. I even have difficulties converting notes to sound. But I enjoy the music. And I like some curves more than others.


----------



## triod750

bcowen said:


> I've only tried them so far with a pair of Hytron 7A4's and a Melz 1578 (6SN7).  The Darkvoice uses a 6SN7 natively as the driver tube, but I have adapters for bunches of different tubes. Have a WE 396A in the driver's seat as we speak, but not with the A2293's.



Please let us know the result of your experiments.


----------



## bcowen

L0rdGwyn said:


> Here are the operating curves for the A2293.



OK, so here's where things get weird with these tubes.  There is *very* little info available on the web.  Below is what I've found so far.  Not suggesting either are correct, just showing what I've found.  I have a China-made adapter (dual A2293's on top to 6SN7 socket on the bottom) that is wired (mostly) like the first diagram: Pins 1,2 and 7 are all tied together on one A2293 socket, and pins 1,2,7 and 8 are tied together on the other.  Pins 3 and 9 are tied together on both sockets. The heaters on pins 4 and 5 are the same, and the grid on pin 6 is the same and by itself.  This China adapter works fine in the Darkvoice, but does _not _work in the Incubus amp creating a very loud buzzing in both channels.  Biggest difference I see is that your tracer info shows the cathode at pin 1 (versus pin 2 in the AVO tester info), and the anode at pin 3 (instead of pin 9 in the AVO info).  Perhaps this is irrelevant since they are tied together?   What confuses me is why all the pins that have no internal element are connected together.  There's really only 5 of the 9 pins that should have (need?) a connection.


----------



## L0rdGwyn

bcowen said:


> OK, so here's where things get weird with these tubes.  There is *very* little info available on the web.  Below is what I've found so far.  Not suggesting either are correct, just showing what I've found.  I have a China-made adapter (dual A2293's on top to 6SN7 socket on the bottom) that is wired (mostly) like the first diagram: Pins 1,2 and 7 are all tied together on one A2293 socket, and pins 1,2,7 and 8 are tied together on the other.  Pins 3 and 9 are tied together on both sockets. The heaters on pins 4 and 5 are the same, and the grid on pin 6 is the same and by itself.  This China adapter works fine in the Darkvoice, but does _not _work in the Incubus amp creating a very loud buzzing in both channels.  Biggest difference I see is that your tracer info shows the cathode at pin 1 (versus pin 2 in the AVO tester info), and the anode at pin 3 (instead of pin 9 in the AVO info).  Perhaps this is irrelevant since they are tied together?   What confuses me is why all the pins that have no internal element are connected together.  There's really only 5 of the 9 pins that should have (need?) a connection.



I used the wiring diagram you posted above as a guide from Radiomuseum.  If any of the electrodes have multiple pin connections, you need only connect one, either pins 1,2, or 7 for the cathode and either pin 3 or 9 for the plate, doesn't matter which ones.  On octal tubes, the pins are often physically missing, like on a 6J5, I assume they were left in place on noval 9-pin tubes since the pins themselves are thinner and more delicate, so removing some pins might increase the physical stress imposed on the others, just a guess.  A second guess is this tube was made as a possible replacement for a competing series pass regulator tube with a 9-pin base, so maybe it was beneficial to have multiple connection alternatives.


----------



## bcowen

L0rdGwyn said:


> I used the wiring diagram you posted above as a guide from Radiomuseum.  If any of the electrodes have multiple pin connections, you need only connect one, either pins 1,2, or 7 for the cathode and either pin 3 or 9 for the plate, doesn't matter which ones.  On octal tubes, the pins are often physically missing, like on a 6J5, I assume they were left in place on noval 9-pin tubes since the pins themselves are thinner and more delicate, so removing some pins might increase the physical stress imposed on the others, just a guess.  A second guess is this tube was made as a possible replacement for a competing series pass regulator tube with a 9-pin base, so maybe it was beneficial to have multiple connection alternatives.



OK, that makes sense.  And I misspoke earlier -- the adapter is for dual A2293's to a 6080 base (although a 6080 and 6SN7 are identical on base pin connections).  I'm still wondering why this buzzing in the Incubus. I have no settings for testing these in my Hickok, so have basically plugged them into the adapter and tested them with 6080 settings. Although much lower in GM, no faults popped up while testing like that.  Do you offhand know of a (more known) tube that is similar enough electrically that the Hickok might have settings for?  Perhaps one of the two A2293 tubes has a problem that the Hickok is not indicating that is causing the issue.


----------



## triod750

Does all of your A2293 have the same getters? Round or square?


----------



## L0rdGwyn

bcowen said:


> OK, that makes sense.  And I misspoke earlier -- the adapter is for dual A2293's to a 6080 base (although a 6080 and 6SN7 are identical on base pin connections).  I'm still wondering why this buzzing in the Incubus. I have no settings for testing these in my Hickok, so have basically plugged them into the adapter and tested them with 6080 settings. Although much lower in GM, no faults popped up while testing like that.  Do you offhand know of a (more known) tube that is similar enough electrically that the Hickok might have settings for?  Perhaps one of the two A2293 tubes has a problem that the Hickok is not indicating that is causing the issue.



My question would be this: what is different about the wiring of the 6080 socket between the DarkVoice and the Incubus?  I'd imagine that would get you the answer as to why it is not working, but sounds like a short to me.  Something else you could do is put the adapter in the Incubus and check pin-to-pin continuity with a DMM to make sure there isn't a short between the electrodes of the A2293.  I'm not aware of any near-equivalents to the A2293, sorry!  I would check for shorts first and compare the pinout of the 6080 sockets between the two amps.


----------



## JazzVinyl

L0rdGwyn said:


> Awesome, thanks!  I think I am going to ditch the carbon filter and add isopropyl alcohol to my solution, so I will downgrading to the 1 micron sediment filter  I believe Ilfotol has anti-static properties as well, hopefully we the process right on the first try. Need to find a particularly dirty record for a before-and-after test



Wood Glue and patience is all you need!


----------



## L0rdGwyn (Jan 30, 2021)

First batch of ultrasonically cleaned records is done!  Waiting for them to dry to get a play test.  Trickiest part is getting arm level such that all of the grooves are submerged, padded card table is not going to work long term as the weight of the tank affects the level of the platform, so will need to swap that out.  Filtration system isn't up and running yet, package with parts was supposedly delivered but never actually made it to my doorstep.






JazzVinyl said:


> Wood Glue and patience is all you need!



Not practical for me but glad you are having success with this method!  Maybe you could stack some of those together and make a frisbee.


----------



## L0rdGwyn

Sounds great, nice and quiet.  Did twelve records, will have to refine the process but its a start.


----------



## Galapac

JazzVinyl said:


> Wood Glue and patience is all you need!


Why wood glue vs. the white stuff? Is it more flexible when hardened?


----------



## triod750

bcowen said:


> What 12AU7 are you using?  I've been a bit underwhelmed with the A2293's in the Darkvoice so far, but have not given them much of a chance with different driver tubes.  Going to fish my 12AU7 adapter out of the box now...



Listening to them with Ken-Rad 6N7 right now. Tube totally NOS and hardly warmed up but it's sounding promising.


----------



## bcowen

triod750 said:


> Does all of your A2293 have the same getters? Round or square?



They are all the same -- top round getter:


----------



## bcowen

L0rdGwyn said:


> My question would be this: what is different about the wiring of the 6080 socket between the DarkVoice and the Incubus?  I'd imagine that would get you the answer as to why it is not working, but sounds like a short to me.  Something else you could do is put the adapter in the Incubus and check pin-to-pin continuity with a DMM to make sure there isn't a short between the electrodes of the A2293.  I'm not aware of any near-equivalents to the A2293, sorry!  I would check for shorts first and compare the pinout of the 6080 sockets between the two amps.



OK, thanks!  I'll give that a try.

I did just check the tube pins with a DMM and they are fine, but I would have been very surprised if the Hickok had not indicated a short in one of them if one existed.


----------



## bcowen

L0rdGwyn said:


> Sounds great, nice and quiet.  Did twelve records, will have to refine the process but its a start.



How long did you let them spin them in the tank?


----------



## bcowen

triod750 said:


> Listening to them with Ken-Rad 6N7 right now. Tube totally NOS and hardly warmed up but it's sounding promising.



What amp are you using?

I have some long hole plate CIFTE (Mazda), RCA clear top, Mullard CV4003, and Telefunken 12AU7's pulled out to play with here in a bit...


----------



## L0rdGwyn

bcowen said:


> How long did you let them spin them in the tank?



I started at 15 min with one revolution every 5 min, increased it to 20min with four revolutions on the second and third runs, going to keep experimenting with it.


----------



## triod750

bcowen said:


> What amp are you using?
> 
> I have some long hole plate CIFTE (Mazda), RCA clear top, Mullard CV4003, and Telefunken 12AU7's pulled out to play with here in a bit...



For this I am using a humble Little Dot MKIVSE. My A2293 seems to come from the same batch as yours, bought from Langrex. With some extras from @Deyan.


----------



## JazzVinyl

L0rdGwyn said:


> First batch of ultrasonically cleaned records is done!  Waiting for them to dry to get a play test.  Trickiest part is getting arm level such that all of the grooves are submerged, padded card table is not going to work long term as the weight of the tank affects the level of the platform, so will need to swap that out.  Filtration system isn't up and running yet, package with parts was supposedly delivered but never actually made it to my doorstep.
> 
> 
> 
> ...



If you can powder coat in the house you sure as shootin' can wood glue clean records  

If you play the peel....plays backwards!


----------



## JazzVinyl

Galapac said:


> Why wood glue vs. the white stuff? Is it more flexible when hardened?



Never tried Elmers.  Titebond II is the right stuff.  The secret is to put it on thick, and let dry until completely dry.  

It's slow...but works incredibly well.


----------



## leftside

L0rdGwyn said:


> I started at 15 min with one revolution every 5 min


Same


----------



## JazzVinyl

triod750 said:


> Listening to them with Ken-Rad 6N7 right now. Tube totally NOS and hardly warmed up but it's sounding promising.



Love the metal 6N7's!  Will sound better after it cooks for 20 mins or so.  Takes the metal envelopes longer, to get a full head of steam


----------



## L0rdGwyn

JazzVinyl said:


> If you can powder coat in the house you sure as shootin' can wood glue clean records



I have three ferocious felines that say otherwise


----------



## JazzVinyl

L0rdGwyn said:


> First batch of ultrasonically cleaned records is done!  Waiting for them to dry to get a play test.  Trickiest part is getting arm level such that all of the grooves are submerged, padded card table is not going to work long term as the weight of the tank affects the level of the platform, so will need to swap that out.  Filtration system isn't up and running yet, package with parts was supposedly delivered but never actually made it to my doorstep.
> 
> 
> 
> ...



Your ultra sonic cleaning machine is very cool, LG!
I'm coming over, with a couple arm loads of LP's..


----------



## JazzVinyl

L0rdGwyn said:


> I have three ferocious felines that say otherwise



Ah yes!  Kitty rule!


----------



## bcowen

leftside said:


> Same



I'm doing 3 minutes per revolution for 15 minutes.  But I'm only doing 2 records at a time based on the pattern I got from the tin foil test (which will be _very_ tank dependent).


----------



## L0rdGwyn

Lost an influential electronic artist today, RIP SOPHIE.  She was really just getting started, sad we won't get to see what was coming next...

I'm going to US clean some more records tomorrow morning, need to experiment some more on the timing, but so far the results are good.


----------



## bcowen

L0rdGwyn said:


> I have three ferocious felines that say otherwise



Never argue with a cat.  They don't care.


----------



## johnjen

To cats, we are their support staff that they continually have to train…
Not only do they employ positive and negative reinforcement, but ignoring us is part of their clever feline plan to keep us off balance and wondering, just so they can maintain control…   
hahahahahahahahahaha   

JJ


----------



## JazzVinyl

Gang...it has been awhile since I did too much DIY electronics work.

I am seeing descriptions of parts that differ from what I remembered:

3K9 resistor

Is that what us old timers used to write as being a:

3.9K resistor?


----------



## L0rdGwyn

JazzVinyl said:


> Gang...it has been awhile since I did too much DIY electronics work.
> 
> I am seeing descriptions of parts that differ from what I remembered:
> 
> ...



They are the same!  Just different conventions.  R is used in place of a decimal point in the 3K9 method.  So 8.2Ohm = 8R2.  3,900Ohm = 3.9K = 3K9.  2.7MOhm = 2.7M = 2M7


----------



## JazzVinyl

L0rdGwyn said:


> They are the same!  Just different conventions.  R is used in place of a decimal point in the 3K9 method.  So 8.2Ohm = 8R2.  3,900Ohm = 3.9K = 3K9.  2.7MOhm = 2.7M = 2M7



Alright, got it!  Thank you, LG.


----------



## L0rdGwyn (Jan 31, 2021)

Did some more ultrasonic cleaning today.  Here is where it will live, hidden next to the water heater  padded table is gone, level is much better now.




I found I could accelerate the drying process by letting the records continue to rotate at the same speed once elevated out of the bath, so will likely do that while preparing the next batch going forward.  I'm finding the inner and outer edges of the records are not being cleaned as well as the interior, only the first and last 30 seconds of play or so, think I need to fill the tank a bit more, there is some wiggle room, to get more of the record in the center, I suspect the periphery of the tank are not as effective.

Even so, it is doing a MUCH better job than old methods, very happy so far.  My girlfriend was very proud to find this $1 copy of _The Rise and Fall of Ziggy Stardust and the Spiders from Mars_, but "Rock 'n' Roll Suicide" would skip in the middle of the track and proceed to loop the middle of the song no matter how many times it was cleaned and without a visible scratch.  Well happy to say the skip is now gone!  Hundreds of dollars and numerous hours later, we were able to save this $1 record, makes it all worth it


----------



## bcowen

L0rdGwyn said:


> Well happy to say the skip is now gone!  Hundreds of dollars and numerous hours later, we were able to save this $1 record, makes it all worth it



Sweet!  And FWIW, none of us ever doubted you had your priorities right.


----------



## leftside

L0rdGwyn said:


> Did some more ultrasonic cleaning today.  Here is where it will live, hidden next to the water heater  padded table is gone, level is much better now.
> 
> 
> 
> ...


And that's a very good record.


----------



## JazzVinyl

L0rdGwyn said:


> Well happy to say the skip is now gone!  Hundreds of dollars and numerous hours later, we were able to save this $1 record, makes it all worth it



Have had the exact same experiences with the wood glue method.  Outer most and inner most grooves hardest to get perfect.  With wood glue you make sure it is extra thick in those two areas.

Have also fixed many a skipper.

But, it is also true that sometimes there is physical damage caused by a damaged stylus and no amount of trying to save 'er works.

Have some really old and rare blues LP's that unfortunately, are indeed physically damaged.  Need to toss them in the trash, but so far have just not been able to get myself to do it


----------



## JazzVinyl

Anybody in here work on SMD?  I have a Liquid Spark that works as preamp but the headphone section has gone distorted.

Reading some posts somewhere, it was said that connecting the power with the unit turned on, will fry some SMD component that is near the relay (usually waits a long time after you press the on button for the relay to engage).  This is probably what happened to mine.

If someone is up to seeing whats what...would be interesting to see if it can be put to right.


----------



## johnjen

Step #1
What size are they?

That will determine if a hot air rework station is 'required' or not…

JJ


----------



## whirlwind

L0rdGwyn said:


> Did some more ultrasonic cleaning today.  Here is where it will live, hidden next to the water heater  padded table is gone, level is much better now.
> 
> 
> 
> ...



Good for her....that is a killer LP!
Way to bring it back from the dead.


----------



## bcowen

JazzVinyl said:


> Have had the exact same experiences with the wood glue method.  Outer most and inner most grooves hardest to get perfect.  With wood glue you make sure it is extra thick in those two areas.
> 
> Have also fixed many a skipper.
> 
> ...



Not to go too far off the path here, but this brings back memories of an un-funny funny story of my freshman year in college. Back then, LP's were the _only_ worthwhile medium...we had graduated from 8-tracks to cassettes by then, but unless you had big bucks for a Nakamichi deck, cassettes were good for the car -- but little else. A guy down the hall had this HUGE collection of LP's. I had maybe 50 or so purchased during my high school years, but this guy had closer to 2000 stacked in milk crates taking up half of his dorm room. And all these LP's were played on his little Radio Shack all-in-one system. The 'record player' part (I won't glorify it by calling it a 'turntable') had a 6 inch platter, and in order to get the needle (no, I won't call it a 'stylus' either ) to track he had 4 quarters glued to the headshell.  You could see the LP (with half of it hanging unsupported out in free air) physically bend down on the outer edge when he dropped the needle into the groove.  I shuddered every time he put on an LP knowing that after even one play on that abomination he'd likely done enough groove damage to make the LP practically worthless.  Probably well over $10k worth of LP's being systematically destroyed on this $79 (all-in) audio "system."  Ugh.  Was just hoping I'd never run across an LP he'd owned in a resale shop.


----------



## JazzVinyl

johnjen said:


> Step #1
> What size are they?
> 
> That will determine if a hot air rework station is 'required' or not…
> ...



Hello JJ...must say, I had never heard of a 'hot air station"...I must be way behind  

Here is a photo in relation to a 12AU7 tube, definitely all SMD inside,




And the Innards:


----------



## JazzVinyl

bcowen said:


> I shuddered every time he put on an LP knowing that after even one play on that abomination he'd likely done enough groove damage to make the LP practically worthless.  Probably well over $10k worth of LP's being systematically destroyed on this $79 (all-in) audio "system."  Ugh.  Was just hoping I'd never run across an LP he'd owned in a resale shop.



4 Quarters stacked up!  OMG!  Should have called the police!

I have owned many of my LP's (have about 2,500) for multiple decades, always took extreme care of them....I now realize that they will outlast me, so I just play them w/o worry


----------



## L0rdGwyn

I was pulling an all-nighter last night to prepare for night shift...this is a very dangerous time for me as I will almost always concoct a new project to pursue.

I am making some furniture changes to my two-channel system very soon and with the new real-estate will come a new DAC.  With this realization, the thought started to creep into my head "why don't I just design and build a DAC?" - I started reading up on NOS R2R designs with tube output stages and was quickly swallowed into the rabbit hole.

But I am trying to work on LESS projects, not add more to my list, and learning the intricacies of an entirely new type of audio component means money, yes, but more importantly time and energy.

How could I stop myself from taking this plunge?  Oh yeah, I could finish the DAC purchase I put a deposit down on LOL 🤦‍♂️

So that's what I am going to do, buy my DAC from SW1X finally.  I haven't completely abandoned the idea of designing a DAC some day, but in the meantime, I thought I would purchase the entry-level model from SW1X, the DAC I.  Mind you, it is still very expensive.

I really like the sound I am getting from my analog system, so it will be interesting to see how it compares to the DAC I.


----------



## JazzVinyl

L0rdGwyn said:


> I really like the sound I am getting from my analog system, so it will be interesting to see how it compares to the DAC I.



Sounds good, LG as the most precious commodity you own is your time.
I indeed love the way my analog sounds.  It is different from digital, in a very good way.

Speaking of "tube output stages" - there was an old Tube Buffer, long ago, that old timers said exceeded everything else they ever heard.  A single triode tube 12B4-A per channel. The circuit was simple, but it has some peculiarities that you had to protect for.  One wonders if a modern version of this, could be incorporated into ones digital chain as a 0 gain (or gain of 1db) to help attain that 'analog smoothness'...

https://www.vacuumtubeaudio.design/12b4-a

Cheers!


----------



## whirlwind

L0rdGwyn said:


> I was pulling an all-nighter last night to prepare for night shift...this is a very dangerous time for me as I will almost always concoct a new project to pursue.
> 
> I am making some furniture changes to my two-channel system very soon and with the new real-estate will come a new DAC.  With this realization, the thought started to creep into my head "why don't I just design and build a DAC?" - I started reading up on NOS R2R designs with tube output stages and was quickly swallowed into the rabbit hole.
> 
> ...



A  R2R dac build....very cool....this is why this is such a cool thread, LOL!  Dang, man you should be snowed in by now...how much snow do you have ?


----------



## Xcalibur255

I sense the influence of @Tjj226 Angel in this new DAC project interest. 

I'm almost tempted at this point to pursue a DAC *downgrade* to solve my problems.  No matter what I do I cannot banish a "hashy" or "reedy" sounding harshness in vocals in my system and buying more expensive and exotic stuff just doesn't feel like the right answer.  It really ruins my enjoyment of the setup and if I can't cure it then maybe going down a step in overall resolution is the answer.  But, I know deep down I won't be satisfied with that either.........


----------



## L0rdGwyn

whirlwind said:


> A  R2R dac build....very cool....this is why this is such a cool thread, LOL!  Dang, man you should be snowed in by now...how much snow do you have ?



Hmmm maybe 5 or 6 inches?  It's still coming down though!  It has been a very wintery winter this year.



Xcalibur255 said:


> I'm almost tempted at this point to pursue a DAC *downgrade* to solve my problems.  No matter what I do I cannot banish a "hashy" or "reedy" sounding harshness in vocals in my system and buying more expensive and exotic stuff just doesn't feel like the right answer.  It really ruins my enjoyment of the setup and if I can't cure it then maybe going down a step in overall resolution is the answer.  But, I know deep down I won't be satisfied with that either.........



Well it's worth a shot!  Maybe you can trial something at home?  Perhaps borrow from another Head-Fier?


----------



## bcowen

Xcalibur255 said:


> I sense the influence of @Tjj226 Angel in this new DAC project interest.
> 
> I'm almost tempted at this point to pursue a DAC *downgrade* to solve my problems.  No matter what I do I cannot banish a "hashy" or "reedy" sounding harshness in vocals in my system and buying more expensive and exotic stuff just doesn't feel like the right answer.  It really ruins my enjoyment of the setup and if I can't cure it then maybe going down a step in overall resolution is the answer.  But, I know deep down I won't be satisfied with that either.........



Here's another approach to the tube buffer @JazzVinyl mentioned.  Was quite nice with early digital players, but I don't think it's being made any longer.  Have one that's been sitting on the shelf for a good long while, and IIRC uses a pair of flying lead tubes soldered to the main board inside, so definitely not a tube rollers delight.    

https://audiophillness.com/musical-fidelity-x-10v3/


----------



## JazzVinyl

Interesting this DAC your looking at @L0rdGwyn uses the PCM1543 DAC chip(s)?  

I have a Muse quad 1543 DAC that was avail some time back.  I'm sure mine are not implemented as gracefully as the DAC your looking it...

But your welcome to borrow it,  if you have not heard the PCM1543's.


----------



## JazzVinyl

bcowen said:


> Here's another approach to the tube buffer @JazzVinyl mentioned.  Was quite nice with early digital players, but I don't think it's being made any longer.  Have one that's been sitting on the shelf for a good long while, and IIRC uses a pair of flying lead tubes soldered to the main board inside, so definitely not a tube rollers delight.



Yes, I have the Musical Fidelity X-10D that uses sockets and a pair of ECC88's, have been trying it lately, have nicer caps on order for it,  to see if it can be pushed further.  First thing I did was make it a proper power supply, that helped a lot over the wall wart supply.

It definitely adds "air and space" between instruments and gives the low notes "textures and edges".  I find it subtle, but effective.  Some say nicer caps really makes them sing.

Pretty sure you could 'recap' the v3 too?


----------



## L0rdGwyn

JazzVinyl said:


> Interesting this DAC your looking at @L0rdGwyn uses the PCM1543 DAC chip(s)?
> 
> I have a Muse quad 1543 DAC that was avail some time back.  I'm sure mine are not implemented as gracefully as the DAC your looking it...
> 
> But your welcome to borrow it,  if you have not heard the PCM1543's.



Hey JV - SW1X uses different R2R chips in each of their offerings, the chips get more exotic as you go up the line.  The DAC I uses the TDA1543 chip, the DAC II uses the a pair of PCM56 chips, and I believe the DAC III and up use the TDA1541.  Thanks for the offer, I am pretty comfortable with the purchase though, it has been a long time coming, I put down a deposit over a year ago!


----------



## Zachik

bcowen said:


> Here's another approach to the tube buffer @JazzVinyl mentioned.  Was quite nice with early digital players, but I don't think it's being made any longer.  Have one that's been sitting on the shelf for a good long while, and IIRC uses a pair of flying lead tubes soldered to the main board inside, so definitely not a tube rollers delight.
> 
> https://audiophillness.com/musical-fidelity-x-10v3/


May or may not be on the same level, but this one is a current production (and much smaller, I think):
https://ifi-audio.com/products/micro-itube2/


----------



## bcowen

JazzVinyl said:


> Yes, I have the Musical Fidelity X-10D that uses sockets and a pair of ECC88's, have been trying it lately, have nicer caps on order for it,  to see if it can be pushed further.  First thing I did was make it a proper power supply, that helped a lot over the wall wart supply.
> 
> It definitely adds "air and space" between instruments and gives the low notes "textures and edges".  I find it subtle, but effective.  Some say nicer caps really makes them sing.
> 
> Pretty sure you could 'recap' the v3 too?



Guess I should pull it out and see if it still works.  May need a re-cap of the electrolytics regardless as it's been sitting for a _very_ long time. I have a variac so can at least bring it up slowly while watching for smoke signals.


----------



## bcowen

Zachik said:


> May or may not be on the same level, but this one is a current production (and much smaller, I think):
> https://ifi-audio.com/products/micro-itube2/



I was just scrolling down the page on that and it looked pretty interesting, then this:






I am now completely a$$-less as I just laughed it all the way off.


----------



## JazzVinyl (Feb 1, 2021)

Zachik said:


> May or may not be on the same level, but this one is a current production (and much smaller, I think):
> https://ifi-audio.com/products/micro-itube2/



And this one....that takes RCA's and adds Bass/Treble:

https://www.amazon.com/gp/product/B07KMPLX9Y/


----------



## bcowen

JazzVinyl said:


> And this one....that takes RCA's and adds Bass/Treble:
> 
> https://www.amazon.com/gp/product/B07KMPLX9Y/



I'm just waiting for a pair of uber-level headphones that have a 6080/6AS7-equivalent tube amp, multibit DAC, and wi-fi streamer built in with a flip-down screen where tracks can be selected via eye movement.  Oh, and weigh less than two pounds total, of course.  I'm hoping this is on @L0rdGwyn 's project list.


----------



## leftside

L0rdGwyn said:


> I was pulling an all-nighter last night to prepare for night shift...this is a very dangerous time for me as I will almost always concoct a new project to pursue.
> 
> I am making some furniture changes to my two-channel system very soon and with the new real-estate will come a new DAC.  With this realization, the thought started to creep into my head "why don't I just design and build a DAC?" - I started reading up on NOS R2R designs with tube output stages and was quickly swallowed into the rabbit hole.
> 
> ...


Real shame we're on different sides of the continent as I came very close to purchasing a SW1X, but then along came the Lampi GA TRP on the used market. I think shipping costs would make it prohibitive for me to send you my earlier Lampi GA to compare. Maybe @Monsterzero could send you his TRP to compare? 

It will still be interesting to hear your comparison of the turntable vs the DAC. Are they at a similar price point: DAC vs turntable + cart + phono stage? The Lampi GA TRP with appropriate tubes is the closest I've heard a DAC come to my turntable setup.


----------



## L0rdGwyn

bcowen said:


> I'm just waiting for a pair of uber-level headphones that have a 6080/6AS7-equivalent tube amp, multibit DAC, and wi-fi streamer built in with a flip-down screen where tracks can be selected via eye movement.  Oh, and weigh less than two pounds total, of course.  I'm hoping this is on @L0rdGwyn 's project list.



LOL you're going to need a neck brace to hold up your head, but otherwise 10/10 on the convenience factor, I'll add it to the list  all of the parts for my Zenith 7H820Z radio are ordered and my PCBs for the DarkVoice mods should be here Thursday, so should be able to work on one or both of them next weekend!


----------



## L0rdGwyn (Feb 1, 2021)

leftside said:


> Real shame we're on different sides of the continent as I came very close to purchasing a SW1X, but then along came the Lampi GA TRP on the used market. I think shipping costs would make it prohibitive for me to send you my earlier Lampi GA to compare. Maybe @Monsterzero could send you his TRP to compare?
> 
> It will still be interesting to hear your comparison of the turntable vs the DAC. Are they at a similar price point: DAC vs turntable + cart + phono stage? The Lampi GA TRP with appropriate tubes is the closest I've heard a DAC come to my turntable setup.



I would be happy to receive any assortment of Lampizator DACs in the mail haha!  They will be well cared for  it's tricky to compare prices since the turntable is vintage (and prices seem to inflate year-by-year) with some DIY flair and the phono is completely DIY, but I would say you could probably cut some costs on both to bring the price with the cartridge to something close to the SW1X DAC I and maintain the same sound, they are probably off by a few hundred bucks, but hard to say exactly.  I'm very curious to see what SW1X brings to the table with its entry-level model.  I believe the DAC I is very similar to the early SW1X DAC @2359glenn owns.  It omits the tube rectifier of the more premium "Special" version but maintains the active I/V conversion and E182CC output stage.  I figure if I go with the DAC I, I can either upgrade later or entertain my DIY DAC aspirations.  DIY NOS R2R designs featuring the TDA1541 chip with a tube output stage are actually quite common, lots of information out there to sift through.


----------



## Xcalibur255

bcowen said:


> Here's another approach to the tube buffer @JazzVinyl mentioned.  Was quite nice with early digital players, but I don't think it's being made any longer.  Have one that's been sitting on the shelf for a good long while, and IIRC uses a pair of flying lead tubes soldered to the main board inside, so definitely not a tube rollers delight.
> 
> https://audiophillness.com/musical-fidelity-x-10v3/


I did use to have a cheap little tube buffer once upon a time.  Don't even remember what I did with it.....

I keep wondering if power condition is what I need, but that's audiophile hard mode when it comes to making informed decisions, just ahead of upgrading cables.


----------



## bcowen

Xcalibur255 said:


> I did use to have a cheap little tube buffer once upon a time.  Don't even remember what I did with it.....
> 
> I keep wondering if power condition is what I need, but that's audiophile hard mode when it comes to making informed decisions, just ahead of upgrading cables.



Speaking of power, what's the condition of the AC receptacle(s) your components are plugged into?  Are they relatively new with good clamping pressure? Or....not exactly?


----------



## Zachik

bcowen said:


> I was just scrolling down the page on that and it looked pretty interesting, then this:
> 
> 
> 
> I am now completely a$$-less as I just laughed it all the way off.


Bill, please pay attention to what you've attached here! Clearly reads: "Nothing comes close for quality." --> totally your fault for assuming they meant HIGH quality...   
Joking aside, iFi's products are pretty good (at least some / most are). Maybe it sounds good despite of the GE tube?


----------



## Zachik

L0rdGwyn said:


> my PCBs for the DarkVoice mods should be here Thursday


Just noticed today that Drop is selling the DV again for $200 (for the next few days). 
Very tempted to grab one, just to be able to replicate your mod after you declare success!


----------



## evonimos

Zachik said:


> Just noticed today that Drop is selling the DV again for $200 (for the next few days).
> Very tempted to grab one, just to be able to replicate your mod after you declare success!



Yeah. It seems to be a good value.

I like the simplicity of both the Crack and the Darkvoice.
Correct me if I'm wrong here, but I think these are basically iterations of the Aren van Waarde project (itself based on an older Rudy van Stratum schematic).

A basic topology of 2 double triodes with a 6922 (or an Octal) for input stage and a 6AS7G as a CF.
Simple as can be, no feedback, single-ended stuff.
Power supply follows suit.

So, i guess simplicity does the trick in this case and when built with quality parts, this design can really sing.

Actually, I just finished a project using a relevant PCB that found online. 
Didn't want to go all out with point to point soldering so I ended up adapting it a bit to my modifications following the same proposition.

I have to say that my experience so far with this basic, no-frills design is very positive.
Compared with my other DIY tube amp with somewhat similar design but an SRPP for signal stage I think this one takes the cake.

Here it is waiting to be finalised.









Crucial points soundwise are mainly the capacitor bank in series to the output and the power supply (both filaments and anode power).
As usual problem with any kind of mods, the problem is fitting them in a tight space when you have to use a certain enclosure.


----------



## johnjen

JazzVinyl said:


> Hello JJ...must say, I had never heard of a 'hot air station"...I must be way behind
> 
> Here is a photo in relation to a 12AU7 tube, definitely all SMD inside,
> 
> ...


From the look of it a 'skilled' DIY'r _*should*_ be able to replace the larger 'active' components using a solder iron, but a re-work station would be 'better' all the way around.
However if it's a 'smaller' component like a resistor or cap it would be MUCH trickier without a re-work station, and judging solely on your description of the behavior it does sound like a cap has ceased to capacitate…  

JJ


----------



## bcowen

johnjen said:


> ... it does sound like a cap has ceased to capacitate…
> 
> JJ



Otherwise known as decapacitated.


----------



## bcowen

Zachik said:


> Bill, please pay attention to what you've attached here! Clearly reads: "Nothing comes close for quality." --> totally your fault for assuming they meant HIGH quality...
> Joking aside, iFi's products are pretty good (at least some / most are). Maybe it sounds good despite of the GE tube?



My post was (mostly) in jest, which I realize is quite surprising and all.  

Seriously speaking, I've seen a number of people report that the GE 5670 is actually one of the better sounding tubes of that genre. If it sounds good to them, that's all that really matters.  And it _does_ stand to reason that GE had to make at least _some_ good sounding tubes, and I'm optimistic I'll run across one some day.


----------



## bcowen

Zachik said:


> Just noticed today that Drop is selling the DV again for $200 (for the next few days).
> Very tempted to grab one, just to be able to replicate your mod after you declare success!



I'll go out on a limb here and say that the Darkvoice is a great sounding little amp....for $200.  Perfect? Assault on the state-of-the-art? Superbly engineered with premium parts?  The stuff audiophile dreams are made of?  Nope, _none_ of that. It's simply a nice sounding amp for $200. I love Schiit's Vali 2, which at $150 is another great sounding little amp for the money (IMO). The Darkvoice definitely puts more "tube" on the plate than the Vali, and it's hotter and has some hum issues and coughs and farts with low impedance 'phones and all but....it's $200. Fun to play with, and if you totally blow it to pieces you're out $200, which is less than some of us have paid for a single tube.   On the budget side of HP amps the Vali is a much better choice for low impedance 'phones as its power output increases as the 'phone impedance decreases.  Exactly the opposite for the OTL Darkvoice. I wouldn't even consider using 'phones with less than 150 ohms impedance with it, at least in its stock form.


----------



## Galapac

bcowen said:


> I'll go out on a limb here and say that the Darkvoice is a great sounding little amp....for $200.  Perfect? Assault on the state-of-the-art? Superbly engineered with premium parts?  The stuff audiophile dreams are made of?  Nope, _none_ of that. It's simply a nice sounding amp for $200. I love Schiit's Vali 2, which at $150 is another great sounding little amp for the money (IMO). The Darkvoice definitely puts more "tube" on the plate than the Vali, and it's hotter and has some hum issues and coughs and farts with low impedance 'phones and all but....it's $200. Fun to play with, and if you totally blow it to pieces you're out $200, which is less than some of us have paid for a single tube.   On the budget side of HP amps the Vali is a much better choice for low impedance 'phones as its power output increases as the 'phone impedance decreases.  Exactly the opposite for the OTL Darkvoice. I wouldn't even consider using 'phones with less than 150 ohms impedance with it, at least in its stock form.


If it wasn't for the Dark Voice I probably would not have tried tube amps so it's a nice gateway drug.


----------



## Xcalibur255

bcowen said:


> Speaking of power, what's the condition of the AC receptacle(s) your components are plugged into?  Are they relatively new with good clamping pressure? Or....not exactly?


I don't think I have any issues on that front.  The PC frontend is new, which is definitely contributing something to the soup as well.  I'm slowly becoming convinced that there is no such thing as bitperfect with PC playback.  All of these hardware direct bit-perfect output methods should sound the same and they don't.  Settings that should have no effect whatosever on the sound, do.

I'm too old to fight with this stuff anymore.  I just want it to work.


----------



## JazzVinyl

I am very anxious to hear what the LG mod for the DV does...

I have owned the DV in the past.  Thought it was 'okay', if the @L0rdGwyn mod hips this baby up....might have to sign up again!


----------



## JazzVinyl

L0rdGwyn said:


> Here is kind of what I am thinking for the revamped Darkvoice 336SE circuit.
> 
> First off, the power supply will be Maida regulated, meaning all of the CRCRC-CRC caps and resistors can be completely removed, which will free up space for the PCBs that will be going in.  This will allow us to increase the available B+ voltage to around 175V while obeying the dropout voltage of the regulator.



Any guess on the cost of the LG'ing of the DV336?


----------



## chrisdrop

JazzVinyl said:


> *LG'ing*


You know you've made it when you become a verb.


----------



## L0rdGwyn

evonimos said:


> Yeah. It seems to be a good value.
> 
> I like the simplicity of both the Crack and the Darkvoice.
> Correct me if I'm wrong here, but I think these are basically iterations of the Aren van Waarde project (itself based on an older Rudy van Stratum schematic).
> ...



Looks great, nice job!  I'm curious if the Aren van Waarde schematic is the first true iteration of the 6AS7G cathode follower headphone amp, it certainly took off.


----------



## L0rdGwyn

JazzVinyl said:


> Any guess on the cost of the LG'ing of the DV336?



Don't have a number just yet, right now I am getting ready to do the mods as sort of a proof of concept.  The gyrator loads are not expensive, the major cost comes with the power supply regulator.  The regulator I am using on the first go-around is not my IP, so another might need to be substituted at a later date.  Once I've nailed down the first mods, will need to see how I can make it more cost-effective.  Another concern is the complexity of implementing the power supply regulator.  Not sure how it will all pan out yet, but I've thought maybe it would be simpler if I just did for Head-Fiers rather than sending them down a path messing around with 200VDC.


----------



## L0rdGwyn (Feb 2, 2021)

bcowen said:


> ...and has some hum issues and coughs and farts with low impedance 'phones and all...



I really think the hum issue stems from two places: 1) the heaters are not center tapped 2) the heater windings are not twisted.  Even with all of the other mods aside, fixing this should be a very simple task that anyone can do.  I just need to pull out the main PCB to see exactly what has been done.  Then everyone can remove the electrolytic bypass caps they added on


----------



## bcowen

L0rdGwyn said:


> Don't have a number just yet, right now I am getting ready to do the mods as sort of a proof of concept.  The gyrator loads are not expensive, the major cost comes with the power supply regulator.  The regulator I am using on the first go-around is not my IP, so another might need to be substituted at a later date.  Once I've nailed down the first mods, will need to see how I can make it more cost-effective.  Another concern is the complexity of implementing the power supply regulator.  Not sure how it will all pan out yet, but I've thought maybe it would be simpler if I just did for Head-Fiers rather than sending them down a path messing around with 200VDC.



I eat 200vdc for breakfast.  Give us something to be worried about.  LOL!!


----------



## L0rdGwyn

bcowen said:


> I eat 200vdc for breakfast.  Give us something to be worried about.  LOL!!



Yeah I mean for the experienced, not an impressive voltage, but for someone trying to take this on who just learned to solder and use a DMM, might be more of an issue lol. I would need to write-up step-by-step instructions with photos, which probably means modding a second DarkVoice.


----------



## bcowen (Feb 2, 2021)

Xcalibur255 said:


> I don't think I have any issues on that front.  The PC frontend is new, which is definitely contributing something to the soup as well.  I'm slowly becoming convinced that there is no such thing as bitperfect with PC playback.  All of these hardware direct bit-perfect output methods should sound the same and they don't.  Settings that should have no effect whatosever on the sound, do.
> 
> I'm too old to fight with this stuff anymore.  I just want it to work.



I get 'ya.  I'm pretty much the same way with expectations.  What DAC do you have and how are you feeding it from the PC?  If via USB, that's evil personified without some external remediation.  Schiit's (discontinued) EITR worked wonders for me prior to their introduction of the Unison USB interface.  That in itself works wonders, and is now even included in their least expensive DAC for $99.  Not trying to be a Schiit fanboy here, just that whatever they did with the Unison thing works magically on a USB signal.


----------



## bcowen

L0rdGwyn said:


> Yeah I mean for the experienced, not an impressive voltage, but for someone trying to take this on who just learned to solder and use a DMM, might be more of an issue lol. I would need to write-up step-by-step instructions with photos, which probably means modding a second DarkVoice.



I have one I can send you.  Only somewhat mangled inside.     Seriously, if you need a second one at some point I'd be most happy to send you mine.  I've replaced the RCA jacks and input wiring, the volume pot, replaced the metal films with Rikens and added the bypass caps on the 6SN7 cathodes, but haven't killed it beyond that at this point.


----------



## Xcalibur255

bcowen said:


> I get 'ya.  I'm pretty much the same way with expectations.  What DAC do you have and how are you feeding it from the PC?  If via USB, that's evil personified without some external remediation.  Schiit's (discontinued) EITR worked wonders for me prior to their introduction of the Unison USB interface.  That in itself works wonders, and is now even included in their least expensive DAC for $99.  Not trying to be a Schiit fanboy here, just that whatever they did with the Unison thing works magically on a USB signal.


DAC is an Yggdrasil, and yep it's USB.  I'm well aware of the reputation but it's necessary.  I used it on the old PC too, primarily because solutions that would have offered a coaxial or AES output always required manually changing sampling rates in the soundcard's driver control panel and ASIO over USB eliminated that hassle.  This new computer, however, I built as a mini-ITX which means it has no PCI expansion slots.  I couldn't put a soundcard in it even if I wanted to.

I honestly didn't have an issue with how USB sounded before, which makes me wonder if the 5V supply in this new PC is somehow dirtier or not regulated as well as it was in the old computer.  I used a top of the line Seasonic SGX power supply so it wasn't for lack of trying.  

My Yggy is still using Gen5 USB, I never got around to doing a Unison upgrade.  It was upgraded from Gen 2 to Gen 5 (or was it 3 to 5...?) when it got the analog2 upgrade and that got it more or less to a place where I was content with it at the time.


----------



## Xcalibur255

Thinking about this more I suspect the Unison upgrade is well worth doing, but I have kind of been hoping that a Yggy 2 announcement lands and I can just jump right onto that boat.  I know Jason is pretty vocal about supporting the platform for a long time to justify the investment, but I think we're what 6 years into Yggy now so they have to at least be thinking about their options for a follow-on product by now.


----------



## JazzVinyl

chrisdrop said:


> You know you've made it when you become a verb.



LOL...  How about:

LGified?  DVLG?  LGDV?  *L*ordy! *G*oodness_DV?


----------



## JazzVinyl

Is the DV plan to use one of these Bare Matisse High Voltage Power Supply Boards that are avail on one of these famous auction sites, as part of the power supply mod?


----------



## L0rdGwyn

JazzVinyl said:


> Is the DV plan to use one of these Bare Matisse High Voltage Power Supply Boards that are avail on one of these famous auction sites, as part of the power supply mod?



No, the DarkVoice that I am currently modding will use a high-voltage regulator designed by Mischa of 1101 Audio.  However, if all works out and others want to pursue this modification, I might recommend using the 21st Century Maida from Neurochrome as it is commercially available with SMD components pre-soldered.  The PCB is larger though so I would have to figure out if it can be mounted inside the available space inside the DarkVoice and how that would be accomplished.


----------



## bcowen

JazzVinyl said:


> Is the DV plan to use one of these Bare Matisse High Voltage Power Supply Boards that are avail on one of these famous auction sites, as part of the power supply mod?



I was hoping for something like this.  Per channel.


----------



## JazzVinyl

bcowen said:


> I was hoping for something like this.  Per channel.



The 21st Century Maida from Neurochrome has extremely wonderful specs!!!  Ka-Pow!


----------



## L0rdGwyn

Gyrator PCBs arrived today, going to try to do this DarkVoice modifications this upcoming weekend, probably Sunday into Monday.  I will pray to the oscillation gods Saturday night in preparation.



Also received all of the replacement resistors and capacitors for the Zenith radio restoration.  Replacing all of the original circuit components will be laborious, looking forward to having the circuit functional so I can focus on the fun part, which is polishing/restoring the bakelite chassis.  I will likely be using my buffing wheel to shine it up.

Let's see what else...once the DarkVoice stuff is mostly done and the radio is done, I really only have the 801A amplifier left on the big "to do" list (obviously there is an endless list of little tweaks to be done on my completed gear, but nothing super major that I have planned).

I am not rushing it as it has been a long time coming and I have huge expectations for the sound based on previous prototypes.  Right now I am playing with some simulations, ideas I have to alter the pentode input stage, more to come on that.

More fun is thinking about the final aesthetics of the amplifier.  What I think I want is to make it look more like a "vintage" SET amplifier.  Might not be for everyone, but I like the look of these Asano SET designs, sort of a high-gloss burnt reddish brown with vintage bakelite knobs and toggle power switch.



We will see if tastes change, but that is what I am liking at the moment.


----------



## evonimos (Feb 3, 2021)

Nice work there mate.
I bet you are keeping yoursefl busy and enjoying it!

Are you going to change all the resistors too?
Sorry if you have already pointed that out, but I haven't been following all previous convo.

I was just writing about resistors in another thread and I wonder what is your take on carbon composite types.
My experience is rather positive with them and they match well with tubes, especially with zero-feedback topologies.


----------



## L0rdGwyn

evonimos said:


> Nice work there mate.
> I bet you are keeping yoursefl busy and enjoying it!
> 
> Are you going to change all the resistors too?
> ...



Thanks!  I will be changing a few resistors, the cathode resistors of the 6SN7 driver tube, possibly the grid stoppers as well, and the cathode resistors of the 6080 output tube.  The power supply will no longer need the original wirewound resistors and the plate resistors of the 6SN7 won't be needed either.

I do like carbon composition resistors, but I prefer carbon films over them, there are many others though who prefer the carbon composition.  I use Allen Bradley carbon composition resistors as grid stoppers in my designs typically.


----------



## bcowen

L0rdGwyn said:


> Gyrator PCBs arrived today, going to try to do this DarkVoice modifications this upcoming weekend, probably Sunday into Monday.  I will pray to the oscillation gods Saturday night in preparation.
> 
> 
> 
> ...



Edited the picture for you, you know, just for clarity and stuff.


----------



## bcowen

JazzVinyl said:


> LOL...  How about:
> 
> LGified?  DVLG?  LGDV?  *L*ordy! *G*oodness_DV?



We _will_ need a new name. The DarkL0rd. Or if that has too negative a connotation, instead of Darkvoice 336i perhaps the Darkvoice 336LG. Or better, the 336LGv1 because we already know he'll make further improvements after the initial go 'round.


----------



## Zachik

bcowen said:


> We _will_ need a new name. The DarkL0rd. Or if that has too negative a connotation, instead of Darkvoice 336i perhaps the Darkvoice 336LG. Or better, the 336LGv1 because we already know he'll make further improvements after the initial go 'round.


Following the naming convention for Glenn's amps (GOTL / GEL3N) - it should be LG336, or with the assumption of future iterations... LG336v1


----------



## triod750

Zachik said:


> Following the naming convention for Glenn's amps (GOTL / GEL3N) - it should be LG336, or with the assumption of future iterations... LG336v1



Expecting less than immediate success is lack of confidence - thus LG336. No further versions needed.


----------



## Galapac

I do like the 336L0G (that's a zero) for the L0rdGwyn mod...and the DV is as heavy as one...

@L0rdGwyn - What are we going to call the DV mods by you?


----------



## L0rdGwyn

Galapac said:


> I do like the 336L0G (that's a zero) for the L0rdGwyn mod...and the DV is as heavy as one...
> 
> @L0rdGwyn - What are we going to call the DV mods by you?



Oh boy, I don't know!  Maybe I will wait until the modifications are done and declared a success, until then I will leave that to you guys


----------



## L0rdGwyn

I've purchased one of the 21CM boards from Neurochrome in case that becomes the path forward for future modders, might as well get it in house while I have a DarkVoice to see if/how it will mount in the chassis.

In keeping with my desire to make my 801A amplifier "vintagey", going to get some of these NOS bakelite Kurz-Kasch knobs and NOS Amphenol octal and UX4 sockets.

  

I had a slow night at work, which is very rare, brought along my laptop and went into a LTSpice deep dive on the 801A amp.  I think I have found a more elegant and simplified solution to the pentode gain stage that I am very excited about.  I believe it will be much more forgiving to the feedback loop as well, very excited to prototype it in the real world.


----------



## bcowen

L0rdGwyn said:


> Oh boy, I don't know!  Maybe I will wait until the modifications are done and declared a success, until then I will leave that to you guys



You're gonna leave that to _these_ guys? We'll have to add "brave" to your list of talents.


----------



## Galapac

I know some of you collect KT88s...these seem to be a good price but dont know the brand.
$25 a tube shipped.
https://www.head-fi.org/threads/for-sale-8-x-vintage-ram-tubeworks-kt-88-tubes.954149/


----------



## JazzVinyl

L0rdGwyn said:


> I had a slow night at work, which is very rare, brought along my laptop and went into a LTSpice deep dive on the 801A amp.  I think I have found a more elegant and simplified solution to the pentode gain stage that I am very excited about.  I believe it will be much more forgiving to the feedback loop as well, very excited to prototype it in the real world.



Very nice!  Can't wait to see what you come up with LG.

How about your 4 volt tube amps?  What was your final thoughts on those, SQ-wise?  Do you still have them?


----------



## Tjj226 Angel

L0rdGwyn said:


> Gyrator PCBs arrived today, going to try to do this DarkVoice modifications this upcoming weekend, probably Sunday into Monday.  I will pray to the oscillation gods Saturday night in preparation.
> 
> 
> 
> ...



I do really like those new age vintage amps. They look pretty freaking cool. The problem I have always ran into is that when you try to stick a bunch of film caps in an amp like this, you quickly run into problems. 

Look up the old synthesis amps. They are gorgeous and can come in some unique colors.


----------



## L0rdGwyn (Feb 4, 2021)

JazzVinyl said:


> Very nice!  Can't wait to see what you come up with LG.
> 
> How about your 4 volt tube amps?  What was your final thoughts on those, SQ-wise?  Do you still have them?



Oh yes!  The 4V tubes are alive and well, they are the drivers in my main two-channel amplifier, my 3.5WPC 6A5G SET.  I have been using the Philips E424N as input tubes for quite some time in it, they sound great, here is a photo from around Christmas time


----------



## L0rdGwyn

Tjj226 Angel said:


> I do really like those new age vintage amps. They look pretty freaking cool. The problem I have always ran into is that when you try to stick a bunch of film caps in an amp like this, you quickly run into problems.
> 
> Look up the old synthesis amps. They are gorgeous and can come in some unique colors.



Awesome I will check them out!  Does look like it could get pretty cramped in there, but as usual this will be my spin on it via Landfall chassis, so should be able to make some space.


----------



## Xcalibur255

Keenan did you ever get those meters that were supposed to come your way?


----------



## triod750

Xcalibur255 said:


> Keenan did you ever get those meters that were supposed to come your way?



I have a lot of meters here - about one thousand per kilometer. How many do you need?


----------



## bcowen

triod750 said:


> I have a lot of meters here - about one thousand per kilometer. How many do you need?



LOL!  Obviously he needs about 20 feet of them.


----------



## L0rdGwyn

Xcalibur255 said:


> Keenan did you ever get those meters that were supposed to come your way?



No sir.  Think it probably slipped Glenn's mind with all of his job and life changes going on.  No big deal though as I didn't have an immediate plan for them, but I do appreciate you offering them to me, they are beautiful.  I'll ask Glenn about it when he makes his way back to Head-Fi.

For the 801A amplifier, which will be fixed bias, I plan to use panel mount test jacks rather than a panel meter to measure voltage drop across a current sense resistor on the 801A cathode for bias adjustment, like these.  Keeps the footprint small in what will be a crowded amplifier.  In the current iteration, it is going to have seven tubes 



I have been working on this amplifier a lot this past week, making design changes via simulator and planning for real-world components.  This is the most confident I have felt about the direction, it is very nearly complete, will just need a breadboard to confirm once I have the mains transformer.  Definitely the most ambitious design I have worked on, ever since @Xcalibur255 planted the 801A seed in my brain, I hitched my horse to that cart but didn't realize the odyssey I was committing to LOL it has been extremely educational working on this amplifier.  It will put out 6-7WPC, move over 300B


----------



## Xcalibur255

Well that's a bummer.  I think I'll have to consider them lost at this point.  Would have been cool to see them become part of a vintage look build.


----------



## Xcalibur255

I have a question for the group:  is it possible for an amp's input sensitivity to be too high and if so what would that sound like in terms of a negative effect on the sound?


----------



## Zachik

L0rdGwyn said:


> Keeps the footprint small in what will be a crowded amplifier. In the current iteration, it is going to have *seven tubes*


Oh, so you're building a small amp.


----------



## L0rdGwyn

Xcalibur255 said:


> I have a question for the group:  is it possible for an amp's input sensitivity to be too high and if so what would that sound like in terms of a negative effect on the sound?



High input sensitivity as in the amp requires, for example, 3Vrms instead of 2Vrms input signal to reach full output?


----------



## L0rdGwyn

Zachik said:


> Oh, so you're building a small amp.



It's going to be a beast lol but as usual I am going to try to squeeze it into as small a chassis as I can.


----------



## Xcalibur255

L0rdGwyn said:


> High input sensitivity as in the amp requires, for example, 3Vrms instead of 2Vrms input signal to reach full output?


No, I thought that was low sensitivity.  I mean if the 2Vrms input signal is somehow *over-driving* the first tube stage.  Or is this super unlikely?


----------



## L0rdGwyn

Xcalibur255 said:


> No, I thought that was low sensitivity.  I mean if the 2Vrms input signal is somehow *over-driving* the first tube stage.  Or is this super unlikely?



Gotcha, just wanted to clarify.  So a 1Vrms input (high sensitivity) vs. a 2Vrms input (lower sensitivity).  What that would represent is too much gain in the amplifier for the source.  Assuming it is in an integrated amplifier with a variable gain stage and an power stage, the issues I see are 1) the amplifier is going to get loud very early in on the volume pot 2) the power stage can be driven to clipping / unsafe volumes more easily by accident 3) the S/N ratio of the amplifier will lower, i.e. higher noise floor for a given output voltage relative to a lower, more appropriate input sensitivity.  Maybe others can think of additional issues but that's what comes to mind for me.

As far as the over-driving concern, the 2Vrms input will be attenuated by the volume pot.  The goal of the gain stage is to swing enough voltage with some headroom at low distortion to drive the power stage to full output.  The power stage should clip well before the gain stage, if that makes sense.  If the gain stage is clipping before the power stage or the power tube is not being driven to full power output at maximum input signal, you should probably be using a higher gain input tube.  This is all assuming getting max power output out of the amplifier is the priority.  Does that answer your question?  Sorry if it doesn't, I'm a little delirious on 2 hours of sleep.


----------



## L0rdGwyn (Feb 5, 2021)

Going to keep rambling about my 801A amp since I am super hyped for it at the moment.  Like I mentioned, made some changes that are going to get the performance right where I want it to be (in theory, will need to confirm).

Here is a photo of the seven tubes going in this amplifier as it is currently designed.  This is sort of how I envision them being arranged on the top plate.


----------



## Xcalibur255

L0rdGwyn said:


> Gotcha, just wanted to clarify.  So a 1Vrms input (high sensitivity) vs. a 2Vrms input (lower sensitivity).  What that would represent is too much gain in the amplifier for the source.  Assuming it is in an integrated amplifier with a variable gain stage and an power stage, the issues I see are 1) the amplifier is going to get loud very early in on the volume pot 2) the power stage can be driven to clipping / unsafe volumes more easily by accident 3) the S/N ratio of the amplifier will lower, i.e. higher noise floor for a given output voltage relative to a lower, more appropriate input sensitivity.  Maybe others can think of additional issues but that's what comes to mind for me.
> 
> As far as the over-driving concern, the 2Vrms input will be attenuated by the volume pot.  The goal of the gain stage is to swing enough voltage with some headroom at low distortion to drive the power stage to full output.  The power stage should clip well before the gain stage, if that makes sense.  If the gain stage is clipping before the power stage or the power tube is not being driven to full power output at maximum input signal, you should probably be using a higher gain input tube.  This is all assuming getting max power output out of the amplifier is the priority.  Does that answer your question?  Sorry if it doesn't, I'm a little delirious on 2 hours of sleep.


No, it does.  I'm just theory crafting as to why my amp sounds like a replay gain experiment gone wrong half the time.  I don't think I'm on the right track with this one though.  Thanks for the help.

I do think the 50K pot in the amp should absolutely be a 100K pot instead but I doubt this alone can take credit for the trouble I have.  It does indeed get too loud too quickly.


----------



## L0rdGwyn

Xcalibur255 said:


> No, it does.  I'm just theory crafting as to why my amp sounds like a replay gain experiment gone wrong half the time.  I don't think I'm on the right track with this one though.  Thanks for the help.
> 
> I do think the 50K pot in the amp should absolutely be a 100K pot instead but I doubt this alone can take credit for the trouble I have.  It does indeed get too loud too quickly.



So the pot impedance won't affect the signal attenuation, what the pot impedance represents is the input impedance of the amplifier, what the source sees looking into the input.  Assuming a source with a low output impedance, like most DACs these days, the value of the pot isn't super critical assuming it isn't extremely low, 50K should be just fine.  What you would need to decrease the volume is a resistor voltage divider in front of the pot so it does not get the full output of the DAC.  Another option is to decrease the output voltage from the DAC if that is a feature.  I think we talked about it before, but if you haven't already, I think it is worth trying a parallel resistor on the output transformer secondary.


----------



## Xcalibur255

I don't want the resistor in the signal path, I'll be able to hear it.  The important thing is it can't explain the SQ issues, that was my main concern.


----------



## whirlwind

L0rdGwyn said:


> Going to keep rambling about my 801A amp since I am super hyped for it at the moment.  Like I mentioned, made some changes that are going to get the performance right where I want it to be (in theory, will need to confirm).
> 
> Here is a photo of the seven tubes going in this amplifier as it is currently designed.  This is sort of how I envision them being arranged on the top plate.



That is a nice layout!


----------



## L0rdGwyn

Just got home, was out of town for the weekend.  Finished up the filtration system for the ultrasonic record cleaner.  Look familiar @bcowen ? 



Tomorrow I will start the DarkVoice modifications.


----------



## bcowen

L0rdGwyn said:


> Just got home, was out of town for the weekend.  Finished up the filtration system for the ultrasonic record cleaner.  Look familiar @bcowen ?
> 
> 
> 
> Tomorrow I will start the DarkVoice modifications.



LOL!  There is a vague resemblance, to be sure.


----------



## L0rdGwyn

Cleaned one of my favorite albums to test out the new process.

At a 80dB volume level, the playback was so quiet when I dropped the stylus I thought I forgot to turn on the phono stage.



Started stuffing the gyrator boards for DarkVoice stuff tomorrow.  Will leave the leads long on the DN2540 in case there are issues, these are backordered for months, think I have about ten left.


----------



## bcowen

L0rdGwyn said:


> Cleaned one of my favorite albums to test out the new process.
> 
> At a 80dB volume level, the playback was so quiet when I dropped the stylus I thought I forgot to turn on the phono stage.
> 
> ...



Excellent choice of tunes.    

If you have True Stories, listen to the first 30 seconds of Papa Legba. If you have your cartridge azimuth dialed in _just_ perfectly, the sound effects at the very beginning start waaaaay right, go waaaay back behind the speakers, waaaay left, and then waaaay behind your listening seat before going back right and repeating. Huge, wide, 3D circle. Even though my couch (listening seat) is up against the wall, I've had people look behind them to see where the speaker is, the effect is so real. Way cool. I can tell more about cartridge alignment and setup with the beginning of that track than I can with the multitude of test LP's I have. This is only through the loudspeakers though....I cannot duplicate it with headphones. Yet.   Not that I listen to sound effects on a regular basis, just that this one is so telling of perfect cartridge alignment.


----------



## JazzVinyl

bcowen said:


> Excellent choice of tunes.
> 
> If you have True Stories, listen to the first 30 seconds of Papa Legba. If you have your cartridge azimuth dialed in _just_ perfectly, the sound effects at the very beginning start waaaaay right, go waaaay back behind the speakers, waaaay left, and then waaaay behind your listening seat before going back right and repeating. Huge, wide, 3D circle. Even though my couch (listening seat) is up against the wall, I've had people look behind them to see where the speaker is, the effect is so real. Way cool. I can tell more about cartridge alignment and setup with the beginning of that track than I can with the multitude of test LP's I have. This is only through the loudspeakers though....I cannot duplicate it with headphones. Yet.   Not that I listen to sound effects on a regular basis, just that this one is so telling of perfect cartridge alignment.



I love True Stories and the Papa Legba song!  Going to see what happens here via my trusty LP.  I also have a Weather Report LP that 'every single time'...I can make people look behind them to see a fellow who comes in with a triangle...!!!   

We play the CD and the triangle guy is clearly heard, but the 'spacial cue' is not there!

Also....the "Naked" album by Talking Heads...I only have the CD version but OMG!   Sound Quality on that one is vastly superior to my other Talking Heads CD's....Steve Lillywhite was in charge of the 'Naked' recording sessions, I believe, and on headphones...it is *really immersive*!

Cheers All...!!


----------



## L0rdGwyn

bcowen said:


> Excellent choice of tunes.
> 
> If you have True Stories, listen to the first 30 seconds of Papa Legba. If you have your cartridge azimuth dialed in _just_ perfectly, the sound effects at the very beginning start waaaaay right, go waaaay back behind the speakers, waaaay left, and then waaaay behind your listening seat before going back right and repeating. Huge, wide, 3D circle. Even though my couch (listening seat) is up against the wall, I've had people look behind them to see where the speaker is, the effect is so real. Way cool. I can tell more about cartridge alignment and setup with the beginning of that track than I can with the multitude of test LP's I have. This is only through the loudspeakers though....I cannot duplicate it with headphones. Yet.   Not that I listen to sound effects on a regular basis, just that this one is so telling of perfect cartridge alignment.



Unfortunately I don't have a copy of True Stories, just Remain in Light and Speaking in Tongues.  I passed on a nice copy of True Stories about a month ago, I am now filled with regret  maybe I'll go back and hunt it down!


----------



## bcowen

L0rdGwyn said:


> Unfortunately I don't have a copy of True Stories, just Remain in Light and Speaking in Tongues.  I passed on a nice copy of True Stories about a month ago, I am now filled with regret  maybe I'll go back and hunt it down!



Oh, then you need Little Creatures too.  I love David Byrne's voice, despite his weirdness.


----------



## L0rdGwyn

bcowen said:


> Oh, then you need Little Creatures too.  I love David Byrne's voice, despite his weirdness.



Weirdness?  I don't know what you could possibly find weird about the man.


----------



## JazzVinyl

L0rdGwyn said:


> Weirdness?  I don't know what you could possibly find weird about the man.



I have Little Creatures on LP, too...love it!

How architecture helped music evolve - David Byrne


----------



## JazzVinyl

Listening to the Little Creatures LP....I love they way the lead electric guitar is intentionally de-emphasized on this entire album.

Instead, we have:

Powerful drum rhythms, crazy sharp deep bass notes, rolled, plucked, and abrupted - also cleanly belonging to the rhythm section....many vocal harmonies and juices added via intelligent horn arrangements...keyboard arrangements lifting spirits.  Everything so very carefully orchestrated.  Nary an unneeded effort was made, by any musician, present.

One wonders how many times you had to practice these songs, to play them, this '*oh so* *p~e~r~f~e~c~t~l~y*'.

Also quite amazed at how incredibly wonderful these LP's sound, compared to their digital counterparts.

They spanked it, hard, y'all!


----------



## L0rdGwyn

Alright, phase 1 of the DarkVoice modifications is done.  Took some troubleshooting, but everything is working as intended so far.

Here is what I did:

1) Removed CRCRC-CRC filter from the power supply - replaced with single 330uF resevoir cap and HV regulator
2) Removed plate resistor load from 6SN7 input tube - replaced with DN2540 - J310 gyrator load
3) Removed 6080 1K wirewound cathode resistors - replaced with Vishay 1.2K non-inductive wirewound resistors
4) Removed 6SN7 1K cathode resistors - replaced with KOA Spear 300ohm carbon film resistors

The goal was to use the original mounting hardware and wiring as much as possible, so the regulator and gyrator PCBs are both mounted using the existing standoffs for the old electrolytic capacitors.  I used the original ground bus, but removed excess portions of it.

Here are the new tube bias points:
B+ 180VDC
6SN7: 80Va / 4.5mA / 1.4Vk
6080: 75Va / 85mA / 105Vk

This aligns very well with my simulations.  Here are some pics.


  

And now the reward 



From memory, there is a significant increase in soundstage and clarity as you might expect with an active loaded input tube, it sounds very good....granted, I only spent a short time with the stock DarkVoice, so it will be interesting to hear how it compares to the original and the La Figaro 339 when it is sent back to its owner.

Still more to do be done, phase 2 will involve fixing the heaters to hopefully get rid of the ridiculous hum issue.  Phase 2 might also include increasing the output capacitance, will also be replacing the pot and power switch.  Probably won't get to it until next weekend.


----------



## L0rdGwyn

I am very impressed by the sound coming out of this modded DarkVoice...

So I am going to throw together another pair of gyrator boards and swap them out with the CCS loads in my 841 amplifier tomorrow morning.  The dimensions and standoff mounting holes on the boards aren't suitable for the 841 layout, but if there is an audible improvement, I will put together another gyrator board that fits those dimensions, in fact it is already drafted.

I sincerely hope it doesn't sound better, otherwise it is gong to send me down a rabbit hole replacing CCS loads for gyrators in all of my gear


----------



## Zachik

L0rdGwyn said:


> I sincerely hope it doesn't sound better, otherwise it is gong to send me down a rabbit hole replacing CCS loads for gyrators in all of my gear


"*Perfect is the enemy of good*"


----------



## JazzVinyl

L0rdGwyn said:


> Alright, phase 1 of the DarkVoice modifications is done.  Took some troubleshooting, but everything is working as intended so far.



Fantastic job, LG!  Wish I could have been there for the before and after listening...!!


----------



## Tjj226 Angel

Bah, 80s music.


L0rdGwyn said:


> Alright, phase 1 of the DarkVoice modifications is done.  Took some troubleshooting, but everything is working as intended so far.
> 
> Here is what I did:
> 
> ...



All you need to do to the heaters is ground them using 2 100 ohm resistors as a center tap. 

If it is possible and you haven't already done so, I would swap out the sockets as well. I very rarely recommend screwing around with socket "upgrades" per se, but it's almost a requirement on the dark voice amps. 

Also. PSSST. PSSSSSSSSSST.......find a solution to the output capacitor. Seriously, the WE421a and 5998 tubes have twice the transconductance of the 6AS7G tube. The 5998 tubes can drive LCD2s quite nicely if given half the chance. 

The film caps in the dark voice are so chinsey that a high quality electrolytic in parallel with a high quality PIO cap, might actually sound a hell of a lot better.


----------



## L0rdGwyn

Tjj226 Angel said:


> Bah, 80s music.
> 
> 
> All you need to do to the heaters is ground them using 2 100 ohm resistors as a center tap.
> ...



Yes, a virtual center tap will be made.  The heater windings are soldered to the center PCB before they hit the tube heaters and one end appears to be grounded through a PCB trace, so it will need to be cut or the heater windings removed from the PCB and run directly to the tubes.  The wiring between the tubes is not twisted, like, at all.  Also the heaters run hot, around 15-20% above nominal, to may need some dropping resistors as well.  So yeah, not just a virtual center tap, unfortunately but nothing too tedious.  I have heard about the "hum problem" of the DarkVoice for years, it is very likely a simple heater grounding issue.  I won't be replacing the sockets, I'll leave that for other people if they want to pursue it.  I will be increasing the output capacitance with some radial TKD polypropylene film caps at 33uF a pop.


----------



## L0rdGwyn

For the sake of experimentation, I put together another set of gyrator boards to replace the 841 CCS loads in my headphone amplifier.  DN2540 was replaced with the IXTP08N100D2, increased the reference voltage resistor to put 380VDC on the plates.



Better? Worse?  The same?  I do think it is better, improvement in clarity and small increase the the staging, expectation bias be damned.  So looks like I will be ordering some gyrator boards that fit my cascode CCS PCB footprint.

Another change I made was replacing the current set resistor on the Rod Coleman regulators with NOS Mills MRA10.  A  small improvement in imaging and holography.


----------



## L0rdGwyn

I am doing a big vinyl ultrasonic cleaning session.  In between, listening to the modded DarkVoice.  Threw on a 6J5 to 6SN7 adapter and some GEC L63.

Sounds really good, but not a massive difference from the 6SN7 driver.  I've found that once the driver has an active load, it is something of an equalizer, differences between different makes of tube become more subtle.



I will eventually need to do something for all of my OTL power tubes, I might build this circuit from scratch for myself some day but in a chassis with enough space for giant output capacitors and either a choke on the 6080 cathode or a FET current sink.


----------



## bcowen

L0rdGwyn said:


> I am doing a big vinyl ultrasonic cleaning session.  In between, listening to the modded DarkVoice.  Threw on a 6J5 to 6SN7 adapter and some GEC L63.
> 
> Sounds really good, but not a massive difference from the 6SN7 driver.  I've found that once the driver has an active load, it is something of an equalizer, differences between different makes of tube become more subtle.
> 
> ...



Nice!  Really nice.

But OMG!!!!  What *is* the deal with that power cord?  Looks like the freebie that came in the box with my AM transistor radio (that runs on batteries).


----------



## L0rdGwyn (Feb 9, 2021)

bcowen said:


> Nice!  Really nice.
> 
> But OMG!!!!  What *is* the deal with that power cord?  Looks like the freebie that came in the box with my AM transistor radio (that runs on batteries).



I think that's the one that came with the amp LOL it isn't the sexiest.  I'm not huge on power cords though, at least not yet, that is like item #876 on the list of things to experiment with.  Same with interconnects, there is just to much to do 😭


----------



## JazzVinyl

L0rdGwyn said:


> I am doing a big vinyl ultrasonic cleaning session.  In between, listening to the modded DarkVoice.  Threw on a 6J5 to 6SN7 adapter and some GEC L63.
> 
> Sounds really good, but not a massive difference from the 6SN7 driver.  I've found that once the driver has an active load, it is something of an equalizer, differences between different makes of tube become more subtle.



Good!  Will keep one from falling into the 'gotta hear it" rabbit hole.

You had the Crackatowa at one time, LG?  How does LGDV336 compare to that one?


----------



## L0rdGwyn (Feb 9, 2021)

JazzVinyl said:


> Good!  Will keep one from falling into the 'gotta hear it" rabbit hole.
> 
> You had the Crackatowa at one time, LG?  How does LGDV336 compare to that one?



Oh boy, it's been a while, but I think this is better.  The Crackatwoa is a Crack + Speedball with a tube shunt-regulated power supply.  This has a better power supply regulator and I think a gyrator load is better suited for direct-coupling over the CCS load used in the Speedball as it regulates the driver tube plate voltage, and thus the output tube grid bias.  The Crackatwoa also uses LED bias on the driver, I prefer an unbypassed cathode resistor when practical.  One advantage that goes to the Crackatwoa is it uses current sink on the 6080 output tube, I can't say how big of a difference that will make vs. a resistive load, something I will explore if I rebuild this circuit from scratch.


----------



## L0rdGwyn

I made a change to my ultrasonic cleaning process.  Since I am using this as a singular cleaning step (i.e., no pre-clean or rinse), I was finding some sediment build-up on the record at the end of a clean, even while running the filter in between batches.  The solution?  Running the filter continuously while cleaning.  MASSIVE difference, this is the way.  I also marked the arm level with a permanent marker so I can quickly get it into position.


----------



## L0rdGwyn (Feb 9, 2021)

Well the vinyl is clean, so there is only one thing left to do.


----------



## bcowen

L0rdGwyn said:


> Well the vinyl is clean, so there is only one thing left to do.



De-magnetize the CD's?


----------



## JazzVinyl

L0rdGwyn said:


> Well the vinyl is clean, so there is only one thing left to do.



Spinnin' and Grinnin'...
Playing some unusual vinyls here tonight..

Pete Heycock, a solo LP (he was the guitar player for the Climax Blues Band)
and
Roger Hodgson, a solo LP...(he of Supertramp fame)

Both are very powerful albums in the olde cans...


----------



## JazzVinyl




----------



## jonathan c

bcowen said:


> De-magnetize the CD's?


De-magnetise the mc-cartridge?


----------



## CJG888

You do have that Cardas LP, I presume...


----------



## L0rdGwyn (Feb 10, 2021)

CJG888 said:


> You do have that Cardas LP, I presume...



I don't have the Cardas test LP, but I do have two others, including an old CBS STR100 test LP.


----------



## CJG888

The Cardas LP has a cartridge demagnetisation track!


----------



## bcowen

L0rdGwyn said:


> I don't have the Cardas test LP, but I do have two others, including an old CBS STR100 test LP.



This is, of course, the way.


----------



## Xcalibur255

bcowen said:


> De-magnetize the CD's?


Don't forget those special markers too.


----------



## CJG888

You can degauss your CD player. Try the Densen CD!


----------



## bcowen

Xcalibur255 said:


> Don't forget those special markers too.



And the magic rainbow foil too. No sense in going just halfway.    

http://www.pwbelectronics.co.uk/images-of-our-products


----------



## Xcalibur255 (Feb 10, 2021)

So fellas any advice on nursing a VT-231 Raytheon that's making a fairly loud and high pitch staticky/whistling noise on one side?  I took it out last week and gave it a couple of good hard smacks in the palm of my hand keeping the plates aligned to the direction of the force.  That actually fixed the tube for about a week but now the noise is back with a vengeance.  It doesn't sound like a short, there isn't much of a crackle to it.  Maybe it's leakage?  This is the "king of the 6SN7 Raytheons" the WWII era version with the extra support rods.  I'd hate to have to toss him out.


----------



## bcowen

Xcalibur255 said:


> So fellas any advice on nursing a VT-231 Raytheon that's making a fairly loud and high pitch staticky/whistling noise on one side?  I took it out last week and gave it a couple of good hard smacks in the palm of my hand keeping the plates aligned to the direction of the force.  That actually fixed the tube for about a week but now the noise is back with a vengeance.  It doesn't sound like a short, there isn't much of a crackle to it.  Maybe it's leakage?  This is the "king of the 6SN7 Raytheons" the WWII era version with the extra support rods.  I'd hate to have to toss him out.



Did you try resoldering the pins?


----------



## Xcalibur255

bcowen said:


> Did you try resoldering the pins?


Nope, I'm terrible at stuff like that.  I should just try it anyway, since it may be the only thing *to* try.  I'll probably ruin the tube trying though so I wanted to hear what people thought first.


----------



## bcowen

Xcalibur255 said:


> Nope, I'm terrible at stuff like that.  I should just try it anyway, since it may be the only thing *to* try.  I'll probably ruin the tube trying though so I wanted to hear what people thought first.



Sucking all the old solder out and replacing with new solder is the best method, but if it's not up your alley then just reheating the pins and adding a bit of solder might at least tell you if that's what's causing the problem.


----------



## L0rdGwyn

Received my globe General Electric 841 today, NIB from 1939.




These sound great, first impression is they are the highest performing of the three makes of 841 I own.  It's too bad they are so rare and expensive, I might have to buy more pairs.


----------



## Zachik

L0rdGwyn said:


> These sound great, first impression is they are the highest performing of the three makes of 841 I own. It's too bad they are so rare and expensive, I might have to buy more pairs.


Isn't that always the case? Best sounding tubes are rare and expensive?


----------



## L0rdGwyn

Zachik said:


> Isn't that always the case? Best sounding tubes are rare and expensive?



Yeah I'd say so, better sound brings higher demand which brings a higher price!  There will be a markup with these old globe DHTs too, they are pretty highly sought after, globes trigger something inside a tube junkie.


----------



## whirlwind

L0rdGwyn said:


> Yeah I'd say so, better sound brings higher demand which brings a higher price!  There will be a markup with these old globe DHTs too, they are pretty highly sought after, globes trigger something inside a tube junkie.



Ha...they absolutely do!


----------



## bcowen

Zachik said:


> Isn't that always the case? Best sounding tubes are rare and expensive?



And a good-sounding GE is rare on steroids.


----------



## Xcalibur255

It's not just talk either.  If there's a globe version of a tube it's genuinely better.  The difference isn't even subtle in my opinion.  It's interesting how they got it so right in the beginning of this technology and basically everything that followed was cost cutting.  Actually, I guess interesting isn't the word for it since that's pretty typical of most things really.....


----------



## L0rdGwyn (Feb 11, 2021)

Xcalibur255 said:


> It's not just talk either.  If there's a globe version of a tube it's genuinely better.  The difference isn't even subtle in my opinion.  It's interesting how they got it so right in the beginning of this technology and basically everything that followed was cost cutting.  Actually, I guess interesting isn't the word for it since that's pretty typical of most things really.....



That has been the case with my globe 45 and 841.  Haven't done a direct head-to-head other globes in my collection like the REN904.  I believe the move to ST shape was to allow for better support bracing to reduce microphonics, which I am sure was an improvement in certain applications.  But I am totally with you, the globes rule!  And they are pretty.


----------



## Xcalibur255

L0rdGwyn said:


> That has been the case with my globe 45 and 841.  Haven't done a direct head-to-head other globes in my collection like the REN904.  I believe the move to ST shape was to allow for better support bracing to reduce microphonics, which I am sure was an improvement in certain applications.  But I am totally with you, the globes rule!  And they are pretty.


One theory I have read is that globes possibly sound better because they generally do not have supports that make contact with the glass bulb.  This eliminates one possible route of physical transmission of vibration to the plates that can produce the low level microphonics that obscure fine details.  I'm not sure how much truth there could be to that though, it seems like the base is more than enough of a vessel for any such vibrations considering the whole plate structure is integrated with the glass stem.


----------



## L0rdGwyn

Xcalibur255 said:


> One theory I have read is that globes possibly sound better because they generally do not have supports that make contact with the glass bulb.  This eliminates one possible route of physical transmission of vibration to the plates that can produce the low level microphonics that obscure fine details.  I'm not sure how much truth there could be to that though, it seems like the base is more than enough of a vessel for any such vibrations considering the whole plate structure is integrated with the glass stem.



It would be very interesting to pick the brain of an engineer familiar with the design of these early globe tubes and get their technical input.


----------



## L0rdGwyn

Always nice coming home to more tubes, another pair of E55L, I am stocking up on these for no reason in particular, they keep popping up at good prices and have a lot of utility in audio circuits.



Maybe these will go in a spud, maybe in a LCR phono stage, maybe as a driver in a two-stage design, not sure, but I will find use for them.

Going to see if I can finish up the DarkVoice mods tomorrow morning, will work on the heater and output capacitance changes first, then see if I can get to the pot and power switch.  More importantly, I need to replace one of the woofers in my Snells due to a freak accident involving a vacuum cleaner, so some speaker surgery will come first in the early AM!


----------



## Zachik

L0rdGwyn said:


> It would be very interesting to pick the brain of an engineer familiar with the design of these early globe tubes and get their technical input.


I can recommend a great medium with good contacts in the great beyond...   
(unless you know an engineer that was part of the technical team 90+ years ago)


----------



## CJG888

It may just be the quality of the materials used on those early tubes (plus the lack of any environmental or safety regulations regarding which materials were permitted), combined with a careful, painstaking manufacturing process. 

Back in the 20s and 30s, these tubes were cutting-edge technology (and expensive)!


----------



## L0rdGwyn

Zachik said:


> I can recommend a great medium with good contacts in the great beyond...
> (unless you know an engineer that was part of the technical team 90+ years ago)



LOL I was thinking more along the lines of asking on diyAudio, but why not perform a seance and go straight to the source?  Obviously this is the most important question we could possibly ask of the dead, I am sure they are ready and waiting to be contacted on this topic.


----------



## CJG888

They used to sell rectifiers filed with mercury!

Drop one of those, and you’ll know about it...


----------



## whirlwind

L0rdGwyn said:


> That has been the case with my globe 45 and 841.  Haven't done a direct head-to-head other globes in my collection like the REN904.  I believe the move to ST shape was to allow for better support bracing to reduce microphonics, which I am sure was an improvement in certain applications.  But I am totally with you, the globes rule!  And they are pretty.



A few years back @gibosi turned me on to a Loewe Radio Mesh AZ12....I use it a lot as it sounds great and looks great


----------



## CJG888

Globes also have a certain “steampunk” appeal, and are very obvious...

One of my favourite tubes based on performance, the EL84, tends to get ignored because it is relatively modern, ubiquitous and unspectacular!


----------



## triod750

whirlwind said:


> A few years back @gibosi turned me on to a Loewe Radio Mesh AZ12....I use it a lot as it sounds great and looks great



gibosi is guilty of a lot of good advice. I am listening to a pair of Mullard Blackburn EL42 as input to a pair of Melz 6N12S as output. Those EL42 -an EL3n relative - is his idea and the Melz is mine. The lowly amp is mine too. It's producing a lovely tone though.


----------



## L0rdGwyn (Feb 12, 2021)

I finished fixing the heater situation in the DarkVoice this morning.

As I mentioned before, the heaters in the DarkVoice are not center-tapped, either at the transformer or virtually, which I suspected was a large contributor to the 60Hz noise issues numerous people are having with the amplifier.

Instead, what the designer did was ground one leg of the heaters at the 6SN7 socket here (it has been removed, but a connection was made between the 6SN7 heater and the front panel LED PCB ground connection).




So that connection was removed and a virtual center tap was made using two 100ohm resistors at the point where the heater windings hit the center PCB. The original wiring was removed and replaced with a twisted pair. I also mentioned that the tube heaters were being run over voltage, at around 7.15VAC. Just so happens I had the perfect voltage dropping resistors for the job on hand, two 130mOhm 5W wirewounds. One goes on each leg of the heaters since they are now balanced.



Now getting ~ 6.3VAC on the across the heaters (note that since the heaters are now balanced, each heater-to-ground voltage measurement will be 3.15VAC, the voltage from one heater to the other will be ~6.3VAC). Worth noting that the front panel LED is powered from the heater winding, the value of the resistor in series will need to be adjusted since the voltage has been halved, otherwise it won't light up.



So did balancing the heaters make a difference? Well, I have two 6SN7s on hand that were completely unusable in the DarkVoice due to heater-to-cathode leakage, the 60Hz noise was completely out of control. One was this black-plate Fivre 6SN7GT. I have had no problems with this tube in any other amplifier.



In terms of the hum level, the difference is massive, but there is still a low-level hum audible without music playing, took it from a 9 down to a 2. I suspect this is due to primary-to-secondary leakage in the mains transformer, which is not going to be fixed without completely replacing it, at which point you might as well just build a new amplifier. Regardless, I would still recommend this modification, center tap and balance the heaters and break the ground connection from the 6SN7 heater to the power LED ground. The hum could likely be further reduced by using a 500ohm trimpot with the wiper connected to ground instead of the two 100ohm resistors. The pot can then be adjusted to minimize the audible hum, it's called a humdinger.


----------



## Xcalibur255

CJG888 said:


> They used to sell rectifiers filed with mercury!
> 
> Drop one of those, and you’ll know about it...


I both do and do not want to own an amp one day that uses mercury vapor tubes.  They look AMAZING, but.......... mercury.


----------



## Xcalibur255

CJG888 said:


> Globes also have a certain “steampunk” appeal, and are very obvious...
> 
> One of my favourite tubes based on performance, the EL84, tends to get ignored because it is relatively modern, ubiquitous and unspectacular!



As an owner of an EL84 amp I can agree, it's a great sounding "boring" tube.


----------



## Xcalibur255

So that makes me curious, are there any ill effects from powering the switch LED off the heater supply.  Since people use LEDs for bias I assume they don't necessarily do anything bad to the supply like inject noise on their own, but this is a bit of a different thing.  Maybe they're 6V LEDs and are fed directly from the supply?


----------



## triod750

Xcalibur255 said:


> As an owner of an EL84 amp I can agree, it's a great sounding "boring" tube.


Do you think this is due to the tube or to the implementation?


----------



## L0rdGwyn

Xcalibur255 said:


> So that makes me curious, are there any ill effects from powering the switch LED off the heater supply.  Since people use LEDs for bias I assume they don't necessarily do anything bad to the supply like inject noise on their own, but this is a bit of a different thing.  Maybe they're 6V LEDs and are fed directly from the supply?



No there shouldn't be any issues powering the LED from the heater supply, it is done quite commonly, just need an appropriately sized series resistor to limit current into the LED.  The residual hum issue is most likely due to the quality of the mains transformer.  I am going to get a 500ohm trimmer and see if it can be further reduced with a humdinger.

Also, I think the EL84 is pretty highly regarded!  There are a gazillion DIY builds using it, think it is often of the first DIY tubes used by a lot of new builders since there are so many schematics available.


----------



## Xcalibur255 (Feb 12, 2021)

triod750 said:


> Do you think this is due to the tube or to the implementation?


Great sounding, boring to look at is what I meant.  I don't know why they aren't used more often in headphone amps, it seems like a good fit to me.


----------



## CJG888

Exactly! It’s the kind of tube that tends to end up inside an enclosure.

Then no one can see that you’re rocking NOS Mullards or Tungsrams!


----------



## bcowen

L0rdGwyn said:


> I finished fixing the heater situation in the DarkVoice this morning.
> 
> As I mentioned before, the heaters in the DarkVoice are not center-tapped, either at the transformer or virtually, which I suspected was a large contributor to the 60Hz noise issues numerous people are having with the amplifier.
> 
> ...



Sweet!  If there's nothing else I want to do *right now* more than anything it's to get that excess voltage off the tube filaments.  You 'da man, LG!!

A few questions:

1) I think I get it from your picture, but just to be sure:  per leg, one end of the 5 watt resistor goes into the circuit board. The other end has one of the heater wires attached as well as one end of one of the 100 ohm resistors.  The two free ends of the 100 ohm resistors are tied together and then go to ground.  Correct?  
2) With the 100 ohm resistors, what's the minimum wattage rating you'd suggest?  Is 1/2 watt enough, or does it need to be 1 watt (or even more)?  Also, does the type/quality of that resistor matter?  I think I have some 1 watt metal oxides in the stash, but is there a sonic effect to this where a good metal film (or even carbon film) would be preferable?
3) You're daisychaining the heater wires from the power tube socket to the 6SN7 socket.  No worries of voltage drop or sag? Is there any harm in running two separate pairs of wires from the circuit board to the two sockets, or is that totally unnecessary and just another avenue for noise pick up?
4) I'm assuming (and quite possibly incorrectly) that the 130 meg value for the dropping resistors you're using to get 6.3v at the sockets is somewhat dependent on your incoming AC voltage?  Mine runs pretty strong here -- usually 120v - 121v whenever I've checked it.  Is yours similar, or I guess the more pertinent question is that 130 meg value good enough regardless, so just go with it and shut up?  

And finally, I had a low level him with my DV when I first got it, regardless of the tubes in use. I found that they had not scraped away any of the powder coat where the IEC socket ground is tied to the chassis. I pulled that screw out, scraped off the paint to get a good ground connection there, and most of that background hum went away (except with, curiously, Fotons).  But it took care of it with most other tubes I tried.  Might check it on that amp and see if the same condition exists.


----------



## Zachik

L0rdGwyn said:


> The residual hum issue is most likely due to the quality of the mains transformer. I am going to get a 500ohm trimmer and see if it can be further reduced with a humdinger.


Wouldn't that trimming reduce the dynamic range of the amp? 
Wouldn't it be a lot like the impedance dongles that reduce noise floor for sensitive headphones / IEMs at the expense of dynamic range?


----------



## L0rdGwyn

bcowen said:


> Sweet!  If there's nothing else I want to do *right now* more than anything it's to get that excess voltage off the tube filaments.  You 'da man, LG!!
> 
> A few questions:
> 
> ...



1) Correct.
2) 100ohm 1/2W will work well, type doesn't matter as none of this is in in the signal path, all part of the heater supply.
3) Totally unnecessary.  If you daisy chain them or run two sets of wire from the PCB, in both cases they are in parallel.  I would daisy chain them.
4) Small m is milliohm, not mega  they are 130milliohm resistors.  Yes it will depend on how your heaters measure, I showed the calculation somewhere on the DarkVoice thread, let me see if I can find it...


----------



## L0rdGwyn

Zachik said:


> Wouldn't that trimming reduce the dynamic range of the amp?
> Wouldn't it be a lot like the impedance dongles that reduce noise floor for sensitive headphones / IEMs at the expense of dynamic range?



The trimmer is not in the signal path at all, it simply balances the noise of the heater supply such that it cancels and doesn't leak into the audio circuitry.


----------



## triod750 (Feb 12, 2021)

Xcalibur255 said:


> Great sounding, boring to look at is what I meant.  I don't know why they aren't used more often in headphone amps, it seems like a good fit to me.



I see. I have a 6B4G push-pull amp and an EL84 push-pull amp, both using 6DJ8 as input tubes. Although they sound different they both sound great. I could not put one before the other. The first one gives about 7,5w and the other one about 12w. Same designer of both of them.

(Both are loudspeaker amps).


----------



## Xcalibur255

triod750 said:


> I see. I have a 6B4G push-pull amp and an EL84 push-pull amp, both using 6DJ8 as input tubes. Although they sound different they both sound great. I could not put one before the other. The first one gives about 7,5w and the other one about 12w. Same designer of both of them.
> 
> (Both are loudspeaker amps).



The EL84 kind of has a reputation for being sweeter toned than most pentodes or tetrodes.  A well designed EL84 amp can certainly sound as nice as an SET like your 6B4G.  Both of your amps provide a great cross section of tube sound between the EL84 and 2A3 "flavors" so it sounds like you have a very nice setup.


----------



## bcowen

L0rdGwyn said:


> 1) Correct.
> 2) 100ohm 1/2W will work well, type doesn't matter as none of this is in in the signal path, all part of the heater supply.
> 3) Totally unnecessary.  If you daisy chain them or run two sets of wire from the PCB, in both cases they are in parallel.  I would daisy chain them.
> 4) Small m is milliohm, not mega  they are 130milliohm resistors.  Yes it will depend on how your heaters measure, I showed the calculation somewhere on the DarkVoice thread, let me see if I can find it...



Thanks!  And especially on #4.  I'm guessing the 130 Megohm resistors I was looking for wouldn't have worked too well.  And also explains why I was having trouble finding them in a 5 watt rating. LOL!


----------



## bcowen

CJG888 said:


> Exactly! It’s the kind of tube that tends to end up inside an enclosure.
> 
> Then no one can see that you’re rocking NOS Mullards or Tungsrams!



I had a 30 wpc integrated at one point using EL-84's.  And you're right...they were all enclosed in a standard black box chassis.   I do remember that amp sounding really good, and wish I'd never sold it.


----------



## bcowen

L0rdGwyn said:


> 1) Correct.
> 2) 100ohm 1/2W will work well, type doesn't matter as none of this is in in the signal path, all part of the heater supply.
> 3) Totally unnecessary.  If you daisy chain them or run two sets of wire from the PCB, in both cases they are in parallel.  I would daisy chain them.
> 4) Small m is milliohm, not mega  they are 130milliohm resistors.  Yes it will depend on how your heaters measure, I showed the calculation somewhere on the DarkVoice thread, let me see if I can find it...



Found your previous post in the DV thread.  I'm measuring 6.95v under load (with a test socket and tube in place) with 120.1v line voltage (which is pretty average normal for here). So if my calcs are correct I'd need a pair of 105milliOhm resistors, and they'd be dissipating 2.015 watts.  Do I get a gold star, or did I goof even this up?  


*@L0rdGwyn 's notes from DV thread:*


----------



## L0rdGwyn

Okay, so I lied about being done for the day, I put the new caps in, two TDK 33uF 250V polypropylene film caps.  I did have to removed the PCB, and it was STILL a huge PITA.  There is absolutely no slack from the transformer leads to the PCB, so getting them resoldered underneath was a true joy.

 

These are really pushing the limits in terms of what can be squeezed in here capacitance-wize.  I had hoped to put in three per channel, but it just wasn't happening.  So that gets you from 30uF stock to 66uF.  -3dB point with 300ohm headphones stock was 17Hz.  This will get you a -3dB point of 20Hz with 120ohm headphones, so drastically increases headphone flexibility.  Really using anything below 120ohm is questionable anyway since the damping factor might make the bass pretty flubby.

It sounds great, I really like it.  Really only a couple more things to do, mainly the new pot and power switch, but a couple things to experiment with as well (humdinger, higher-quality film cap on gyrator load).  Probably another week or two.


----------



## L0rdGwyn

I will get back to you soon, @bcowen !


----------



## L0rdGwyn

bcowen said:


> Found your previous post in the DV thread.  I'm measuring 6.95v under load (with a test socket and tube in place) with 120.1v line voltage (which is pretty average normal for here). So if my calcs are correct I'd need a pair of 105milliOhm resistors, and they'd be dissipating 2.015 watts.  Do I get a gold star, or did I goof even this up?
> 
> 
> *@L0rdGwyn 's notes from DV thread:*



You got it, 105mOhms per leg, you likely won't find a 105mOhm resistor so just go with 100mOhm.  Power dissipated is 2W total for both resistors, 1W per resistor.  So go with a pair of 100mOhm 5W wirewounds, could even get away with smaller 3W but they will get a wee bit hot.


----------



## bcowen

L0rdGwyn said:


> You got it, 105mOhms per leg, you likely won't find a 105mOhm resistor so just go with 100mOhm.  Power dissipated is 2W total for both resistors, 1W per resistor.  So go with a pair of 100mOhm 5W wirewounds, could even get away with smaller 3W but they will get a wee bit hot.



Perfect.  Thanks!


----------



## L0rdGwyn

Finds from record shopping today.  Both European reissues from the 80s but happy to have them, to the ultrasonic cleaner they go.



Replaced the woofer on one of my Snell Js, it was dented in with a vacuum cleaner handle LOL a true tragedy but we made it right.  Handle to replace one of the inductors on the crossover as well, but managed to do it without removing the crossover from the cabinet, so relatively painless.  They will be wearing their grills for the foreseeable future.


----------



## bcowen

L0rdGwyn said:


> Finds from record shopping today.  Both European reissues from the 80s but happy to have them, to the ultrasonic cleaner they go.
> 
> 
> 
> Replaced the woofer on one of my Snell Js, it was dented in with a vacuum cleaner handle LOL a true tragedy but we made it right.  Handle to replace one of the inductors on the crossover as well, but managed to do it without removing the crossover from the cabinet, so relatively painless.  They will be wearing their grills for the foreseeable future.



Nice!  I haven't been record shopping in a long, long time.  Back in the mid-to-late '90's it was a normal Saturday ritual to hit the used record/book stores as people were dumping their LP collections en masse for "perfect sound forever."* *  Wasn't unusual to come home with 50 LP's with a total spend of $100.  Not as easy to find used LP's that are in good condition these days, at least where I live.   

** (note: not slagging digital as I enjoy it a lot. Now. But a lot of improvements have happened in the last 20 years to make it so)

I was just listening to this one today.  2 LP set of a live performance that is _superbly_ recorded, and with the exception of Telegraph Road (where the studio version has better pyrotechnics at the end) I prefer the renditions of every song on this to any of the studio versions. I bought it when it first came out and honestly don't remember what I paid for it, but probably $20 or less. Cracked up when I looked online and saw a couple for sale at close to $300.


----------



## L0rdGwyn

I was about to order some parts from Mouser for various projects, including a trimmer to make a humdinger for the DarkVoice heater supply, then thought I should clip in some parts and elevate the heaters before I even bother.

So I did that, elevated the heaters ~55VDC above ground by connecting the virtual center tap to a 220K+100K voltage divider from the B+ supply. The smoothing cap isn't necessary with the regulated supply but I threw it on there for good measure on the first go-around.



Hum is now completely gone, goodbye! Tested on various tubes that were previously noisy. So this is the way, virtual center tap + elevated supply, no point in bothering with the humdinger, DarkVoice is now humphrey.


----------



## L0rdGwyn

I made the elevated heater change permanent. I paralleled a second 2K resistor on the power LED PCB to account for the balanced heater supply. The power LED ground has to be disconnected from the ground bus and brought to the heater center tap so the LED does not see the 50VDC offset of the heater supply. The LED now lights up again.



Very happy the hum is gone with my black plate Fivre 6SN7GT, nice and quiet. All that is left to do is swap the pot and the power switch and consider A-Bing a higher quality film cap on the gyrator.


----------



## Tjj226 Angel

Make your own OTL now and compare : )


----------



## L0rdGwyn

Yes, I think I will, don't know when, maybe an improved version of this circuit without the space limitations.  The sound is very good, surprisingly good really.

I am going to try running some 6N7 drivers in my 45 amplifier, I would like more gain on the input, I just purchased this quad of RCA 6N7G for that reason.

 

If it works out, and I think it will, that would leave me with a large pile of 6J5/6C5 without an amplifier, in addition to a pile of 6AS7G/5998/7802 without an amplifier.  They would work very nicely together in an OTL.


----------



## Xcalibur255

Isn't 6SN7/6J5 usually considered to have enough gain to drive a 45?  Since you didn't include your usual technical digression I'm all the more curious about your reasons for the change.


----------



## JazzVinyl

L0rdGwyn said:


> Finds from record shopping today.  Both European reissues from the 80s but happy to have them, to the ultrasonic cleaner they go.



I just sold "The Amazing Bud Powell Vol 2" that I found in a thrift store for 50 cents.  Poor playing condition.  
Wood glue cleaned it, then played about EX++ except for a couple spots where a few noises remained.  
Mine was a 1958 GEMA deep groove, in Mono.

New owner was thrilled with it


----------



## chrisdrop

L0rdGwyn said:


> Yes, I think I will, don't know when, maybe an improved version of this circuit without the space limitations.  The sound is very good, surprisingly good really.
> 
> I am going to try running some 6N7 drivers in my 45 amplifier, I would like more gain on the input, I just purchased this quad of RCA 6N7G for that reason.
> 
> ...


I have similar (the same date codes even maybe?) RCA 6N7Gs. They are pretty and pleasing. I don't have the original boxes however, sadly. Anyhow, I'll pop them in later today.


----------



## L0rdGwyn (Feb 16, 2021)

Xcalibur255 said:


> Isn't 6SN7/6J5 usually considered to have enough gain to drive a 45?  Since you didn't include your usual technical digression I'm all the more curious about your reasons for the change.



Well, it's close, but not ideal.  The 45 in my amplifier is biased at around -53V on the grid.  To hit the 0V grid limit, need to swing ~106Vpk-pk into it from the driver.  Assuming a perfect 6J5 with a flat load line, that would give an input sensitivity of ~1.87Vrms.  Most DACs are 2Vrms out, but many are 1.8Vrms, so we are just barely hitting full output and the pot at its maximum.  I'd like to decrease the input sensitivity, and give the input tube more headroom.  The 6N7 is a good tube for the job with its mu of 35 and an easy change since it has a similar pinout to the 6J5.  You will actually see many people use a three stage design with two halves of a 6SN7 into a 45.  A 5842 is another common 45 driver.


----------



## L0rdGwyn

JazzVinyl said:


> I just sold "The Amazing Bud Powell Vol 2" that I found in a thrift store for 50 cents.  Poor playing condition.
> Wood glue cleaned it, then played about EX++ except for a couple spots where a few noises remained.
> Mine was a 1958 GEMA deep groove, in Mono.
> 
> New owner was thrilled with it



Nice find!


----------



## L0rdGwyn

chrisdrop said:


> I have similar (the same date codes even maybe?) RCA 6N7Gs. They are pretty and pleasing. I don't have the original boxes however, sadly. Anyhow, I'll pop them in later today.



Sorta seems like slim pickings these days on 6N7s, I guess they have become quite a bit more popular since the last time I shopped for them!


----------



## JazzVinyl

L0rdGwyn said:


> Sorta seems like slim pickings these days on 6N7s, I guess they have become quite a bit more popular since the last time I shopped for them!



The Metal envelope 6N7's...Ken Rad / RCA, lack the beauty of the glow and take a while to sound their best (due to warming up the metal envelope, I think), but sure sound nice....


----------



## L0rdGwyn (Feb 16, 2021)

Alright, DarkVoice mods are done. I was able to replace the power switch without removing the front plate, then replaced the original pot with an Alps RK27. I repurposed the stock pot PCB.

So that's pretty much it, I'll probably think of something else to mess around with over the next few days, but I'm about ready to move on from this project. Will likely send it back within the next week.


----------



## Xcalibur255

L0rdGwyn said:


> Well, it's close, but not ideal.  The 45 in my amplifier is biased at around -53V on the grid.  To hit the 0V grid limit, need to swing ~106Vpk-pk into it from the driver.  Assuming a perfect 6J5 with a flat load line, that would give an input sensitivity of ~1.87Vrms.  Most DACs are 2Vrms out, but many are 1.8Vrms, so we are just barely hitting full output and the pot at its maximum.  I'd like to decrease the input sensitivity, and give the input tube more headroom.  The 6N7 is a good tube for the job with its mu of 35 and an easy change since it has a similar pinout to the 6J5.  You will actually see many people use a three stage design with two halves of a 6SN7 into a 45.  A 5842 is another common 45 driver.



So the 45 isn't quite as easy a job as I thought it was.  I wonder why triode strapped pentodes seem to be so much easier to drive in general than DHTs are, at least that's the impression I have gotten.  Differences in miller capacitance and internal plate resistance?


----------



## L0rdGwyn

Xcalibur255 said:


> So the 45 isn't quite as easy a job as I thought it was.  I wonder why triode strapped pentodes seem to be so much easier to drive in general than DHTs are, at least that's the impression I have gotten.  Differences in miller capacitance and internal plate resistance?



Well it is easy to drive in terms of being a capacitive load, more just a matter of providing enough gain on the input to drive the 45 into clipping well before the driver clips or significantly distorts.  The C3g, for example, has plenty of gain and a low output impedance, so is well-equipped to do the job (and as you know, can even drive the 300B).  Triode-strapped pentodes typically have amplification factors higher than true triodes, usually around twice the gain, so it takes less voltage on the input to drive them to clipping.


----------



## L0rdGwyn

Just rewired my 45 amplifier to take 6N7 with the sections paralleled.  Didn't even need to adjust the CCS  I replaced the Riken Ohm cathode resistors with what I had on hand that would give the appropriate bias, some nice 450ohm Allen Bradley's.



I only have one pair of matched 6N7s, some National Union 6N7GT, then a bunch of singles.



This Tung-Sol and National Union 6N7G have identical internal construction despite the smoked glass of the Tung-Sol.



This pair on the other hand...lol.  I will have to seek out their twins.



And of course, since they have similar pinouts, with the 6N7 sections paralleled, the amplifier can still take 6J5, albeit at a slightly different bias point, a win-win 



Think that's all for DIY today, time relax and get buried by snow.


----------



## L0rdGwyn

One more thing, here are some curves of the 6N7 with the sections paralleled.


----------



## triod750

Curves are wonderful when you get them straight!


----------



## whirlwind

L0rdGwyn said:


> Just rewired my 45 amplifier to take 6N7 with the sections paralleled.  Didn't even need to adjust the CCS  I replaced the Riken Ohm cathode resistors with what I had on hand that would give the appropriate bias, some nice 450ohm Allen Bradley's.
> 
> 
> 
> ...



What a simple, clean and elegant look, not to mention how much I dig that color!
We have avoided the big snow so far....how much do you have.


----------



## L0rdGwyn

whirlwind said:


> What a simple, clean and elegant look, not to mention how much I dig that color!
> We have avoided the big snow so far....how much do you have.



Thanks, Joe! We got about 8 inches on the east side of Cleveland, a lot but not the most we have seen this winter!


----------



## qingcai

L0rdGwyn said:


> I made the elevated heater change permanent. I paralleled a second 2K resistor on the power LED PCB to account for the balanced heater supply. The power LED ground has to be disconnected from the ground bus and brought to the heater center tap so the LED does not see the 50VDC offset of the heater supply. The LED now lights up again.


what are those two pcb for ? could you please share the schema ? thanks


----------



## L0rdGwyn

qingcai said:


> what are those two pcb for ? could you please share the schema ? thanks



They are active loads for the 6SN7, gyrator loads.  I am at work so cannot mine the thread, but I think I've discussed it pretty extensively and I believe I posted a schematic somewhere as well.


----------



## L0rdGwyn

Had a nice relaxing morning listening to some PG.  Swapped the input tubes in my amp to the CV399, very noice.




I thought I was done, was doing some final checks on the DarkVoice modifications this morning, decided to make some last minute changes.  I added 1K grid stoppers to the 6SN7 (there are no grid stoppers in the original design), as well as startup protection diodes from grid to cathode of the output tube.  This prevents arcing on startup before the power tube has started conducting, the diodes are out of the circuit once the grid goes negative relative to the cathode.  I also derated the mains primary fuse to 0.75A, was 1A originally.

Here is the final, final circuit.



Today, it will be stress tested on my switchable headphone dummy load.  If all checks out, it will be shipped back Monday, and that will be that, case closed!


----------



## bcowen

L0rdGwyn said:


> Had a nice relaxing morning listening to some PG.  Swapped the input tubes in my amp to the CV399, very noice.
> 
> 
> 
> ...


OK...more explanation needed (please!).  Are the diodes as simple as they look?  Basically just a diode between pins 1 and 3 and another between pins 4 and 6 (with orientation as shown)?  And what diodes are those, 1N4007's?  

I'm unclear on the grid stopper resistors....can't see clearly how those are wired in.  What do they do (in a nutshell)?

Thanks!!!


----------



## bcowen (Feb 20, 2021)

L0rdGwyn said:


> Had a nice relaxing morning listening to some PG.  Swapped the input tubes in my amp to the CV399, very noice.
> 
> 
> 
> ...


Oh, and @therremans and I were discussing the fuse earlier.  Both of our chassis' have "1 amp fuse" silkscreened on the back, yet both of ours came with 3 amp fuses installed.  LOL!   Is the 3/4 amp fuse you've put in a slo-blo or fast blow?


----------



## Galapac

bcowen said:


> Oh, and @therremans and I were discussing the fuse earlier.  Both of our chassis' have "1 amp fuse" silkscreened on the back, yet both of ours came with 3 amp fuses installed.  LOL!   Is the 3/4 amp fuse you've put in a slo-blo or fast blow?


Is the fuse going to effect anything by lowering the amperage? Will blow sooner?


----------



## L0rdGwyn

bcowen said:


> OK...more explanation needed (please!).  Are the diodes as simple as they look?  Basically just a diode between pins 1 and 3 and another between pins 4 and 6 (with orientation as shown)?  And what diodes are those, 1N4007's?
> 
> I'm unclear on the grid stopper resistors....can't see clearly how those are wired in.  What do they do (in a nutshell)?
> 
> Thanks!!!



Yup, they are 1N4007s.  Because the amp is direct-coupled, before the output tube starts conducting current, the cathode is at ground potential while the grid is at full B+ voltage (assuming no soft start, like the stock circuit), so the grid is +150V relative to the cathode.  A high grid-to-cathode voltage could potentially cause arcing, putting these diodes in place prevents that from happening.

The grid stoppers form a low pass RC filter with the input capacitance of the 6SN7.  The purpose is to cause an intentional high frequency rolloff outside of the audio band to prevent high frequency oscillation.  The stock circuit isn't likely to be prone to oscillation, but I've added transistors into the mix with the modifications, so grid stoppers are a good idea.



bcowen said:


> Oh, and @therremans and I were discussing the fuse earlier.  Both of our chassis' have "1 amp fuse" silkscreened on the back, yet both of ours came with 3 amp fuses installed.  LOL!   Is the 3/4 amp fuse you've put in a slo-blo or fast blow?



3A is way too high.  The amp should draw around 0.5A out of the wall (haven't measured directly, but based on the current draw inside).  The fuse should be rated to 1.5-2x the drawn current, some will even say 1.33.  I prefer to go 1.5 for safety as opposed to 2.  It is a slow blow, could probably use a fast blow given the soft-start built into the HV regulator, but I would definitely go with a slow blow for the stock circuit.  Inrush current will be high with all of the capacitance in the power supply.



Galapac said:


> Is the fuse going to effect anything by lowering the amperage? Will blow sooner?



It will blow sooner if there is a fault, decreasing the chance of any components being damaged.


----------



## bcowen

OK, thanks!  Pretty sure I have some 1A in the stash (not sure about 0.75A), so going to replace that 3 amp right now.  And I have a bin full of 1N4007's so will add those too.  Wonder if the arcing problems some people have noted with domino plate tubes (5998, 421A) are being caused by that?

Looking more at your picture, it appears the 1K grid stopper resistors are simply in series between the wires coming off the pot's wipers and going to the socket grid pins (1 and 4).  Do I have that right, or am I looking at it wrong?


----------



## Tjj226 Angel

L0rdGwyn said:


> 3A is way too high.  The amp should draw around 0.5A out of the wall (haven't measured directly, but based on the current draw inside).  The fuse should be rated to 1.5-2x the drawn current, some will even say 1.33.  I prefer to go 1.5 for safety as opposed to 2.  It is a slow blow, could probably use a fast blow given the soft-start built into the HV regulator, but I would definitely go with a slow blow for the stock circuit.  Inrush current will be high with all of the capacitance in the power supply.



Ah, but don't forget about the power draw from the filaments. 

Figure out the total wattage of the circuit and divide by 120.


----------



## bcowen

Also decided before I get started with everything I'd go ahead and replace the sockets too.  I really like these tapered split-contact sockets, and have used the ceramic ones for a number of adapters.  Some of them have had a lot of rolling, yet the contacts have maintained a nice firm grip without having to mess with tightening them.  Wasn't aware they were available with a teflon body, but they are so I ordered a couple for the DV.  Price is right at $22.50 a pair, just have to wait a bit for them to get here.  Couldn't reasonably justify the Admiral Yamamoto sockets which cost about half as much as the amp.    

https://www.ebay.com/itm/High-End-8...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649


----------



## L0rdGwyn

Tjj226 Angel said:


> Ah, but don't forget about the power draw from the filaments.
> 
> Figure out the total wattage of the circuit and divide by 120.



Who forgot?  I didn't.  It's the total AC VA rating of the secondaries / 120.


----------



## L0rdGwyn

bcowen said:


> OK, thanks!  Pretty sure I have some 1A in the stash (not sure about 0.75A), so going to replace that 3 amp right now.  And I have a bin full of 1N4007's so will add those too.  Wonder if the arcing problems some people have noted with domino plate tubes (5998, 421A) are being caused by that?
> 
> Looking more at your picture, it appears the 1K grid stopper resistors are simply in series between the wires coming off the pot's wipers and going to the socket grid pins (1 and 4).  Do I have that right, or am I looking at it wrong?



I have wondered the same on the 5998s, although the same issues were seen in the GOTL which is a cap coupled SRPP circuit, will have to give that some thought if a similar scenario could occur on startup.

And yes!  The grid stopper are in series, keep the leads from the resistor body to the tube pins as short as possible.  Carbon composition are best.


----------



## bcowen

L0rdGwyn said:


> I have wondered the same on the 5998s, although the same issues were seen in the GOTL which is a cap coupled SRPP circuit, will have to give that some thought if a similar scenario could occur on startup.
> 
> And yes!  The grid stopper are in series, keep the leads from the resistor body to the tube pins as short as possible.  Carbon composition are best.



I'm pretty sure I have a pair of 1K Rikens left.  They're carbon film (AFAIK) as opposed to carbon composition but assume they will be satisfactory.  1/2 watt rating is sufficient I hope?  Thanks for all the help!!


----------



## Zachik

bcowen said:


> Also decided before I get started with everything I'd go ahead and replace the sockets too.  I really like these tapered split-contact sockets, and have used the ceramic ones for a number of adapters.  Some of them have had a lot of rolling, yet the contacts have maintained a nice firm grip without having to mess with tightening them.  Wasn't aware they were available with a teflon body, but they are so I ordered a couple for the DV.  Price is right at $22.50 a pair, just have to wait a bit for them to get here.  Couldn't reasonably justify the Admiral Yamamoto sockets which cost about half as much as the amp.
> 
> https://www.ebay.com/itm/High-End-8pin-Octal-Teflon-Tube-Socket-For-EL34-KT88-5AR4-274B-GZ34-KT66-5881-x2/223597938937?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649


so... basically... modded DV is original case and transformer? EVERYTHING else is replaced?


----------



## L0rdGwyn

bcowen said:


> I'm pretty sure I have a pair of 1K Rikens left.  They're carbon film (AFAIK) as opposed to carbon composition but assume they will be satisfactory.  1/2 watt rating is sufficient I hope?  Thanks for all the help!!



I would save those Rikens, they are special!  Any run-of-the-mill carbon compostion resistor is a better choice.  The reason carbon comps are best is due to their low inductance, carbon or metal film will probably work fine but do have some inductance so are not best for damping oscillation (and like I said, the stock circuit isn't going to be very prone to oscillation, so you might not need them anyway), but carbon comp is really the right choice.  I have a big stockpile of Allen Bradley 100ohm and 1K resistors for this reason, can usually find cheap batches of them on eBay.


----------



## L0rdGwyn

bcowen said:


> Also decided before I get started with everything I'd go ahead and replace the sockets too.  I really like these tapered split-contact sockets, and have used the ceramic ones for a number of adapters.  Some of them have had a lot of rolling, yet the contacts have maintained a nice firm grip without having to mess with tightening them.  Wasn't aware they were available with a teflon body, but they are so I ordered a couple for the DV.  Price is right at $22.50 a pair, just have to wait a bit for them to get here.  Couldn't reasonably justify the Admiral Yamamoto sockets which cost about half as much as the amp.
> 
> https://www.ebay.com/itm/High-End-8pin-Octal-Teflon-Tube-Socket-For-EL34-KT88-5AR4-274B-GZ34-KT66-5881-x2/223597938937?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649



I have Yamamotos in my main SET, CRAZY expensive, I wonder if I am crazy enough to do it again, they are super nice.  I tried to get them on my 841 headamp, but Mr. Yamamoto never returned my email  it was probably for the best that I moved on LOL.


----------



## L0rdGwyn

Zachik said:


> so... basically... modded DV is original case and transformer? EVERYTHING else is replaced?



I kept the sockets  and the headphone jack!  For the record.


----------



## Tjj226 Angel

L0rdGwyn said:


> Who forgot?  I didn't.  It's the total AC VA rating of the secondaries / 120.



And you still came up with 0.5A? Wow. I would have expected something closer to 1A total draw.


----------



## L0rdGwyn (Feb 20, 2021)

The DarkVoice failed its stress test by the way.

I know much has been said of the heat this thing generates, that was the first time I had run it for any extended length of time, 4.5 hours.  The issue is the power tube cathode resistors, they are mounted on metal standoffs attached to the chassis, they are not thermally isolated.  Over time they dump 7-8W a piece into the little chassis with it acting as a heat sink, that is way too much.  I should have recognized sooner it would be problem, first hour is fine, after that it is no good, hitting close to 50C.  Not comfortable cooking all of the parts that were put inside.  That temp will significantly degrade the lifespan of the electrolytic reservoir cap as well...

So I am going to hold onto this DarkVoice another week and fix it.  Will change the resistors, either some fancy non-inductive type or wirewound enamel, increase the wattage rating, likely paralleling two or three, and allow them to cool by passive airflow only, thermally isolated from the chassis.  That will do the trick.


----------



## L0rdGwyn

Tjj226 Angel said:


> And you still came up with 0.5A? Wow. I would have expected something closer to 1A total draw.



Yup, only 0.5A!  I'll measure it directly to be sure the math checks out, but no problems running the amp on a 0.75A fuse.


----------



## bcowen

L0rdGwyn said:


> The DarkVoice failed its stress test by the way.
> 
> I know much has been said of the heat this thing generates, that was the first time I had run it for any extended length of time, 4.5 hours.  The issue is the power tube cathode resistors, they are mounted on metal standoffs attached to the chassis, they are not thermally isolated.  Over time they dump 7-8W a piece into the little chassis with it acting as a heat sink, that is way too much.  I should have recognized sooner it would be problem, first hour is fine, after that it is no good, hitting close to 50C.  Not comfortable cooking all of the parts that were put inside.  That temp will significantly degrade the lifespan of the electrolytic reservoir cap as well...
> 
> So I am going to hold onto this DarkVoice another week and fix it.  Will change the resistors, either some fancy non-inductive type or wirewound enamel, increase the wattage rating, likely paralleling two or three, and allow them to cool by passive airflow only, thermally isolated from the chassis.  That will do the trick.


So then adding a fan *was* a good move.  It was @therremans idea.  With the speed turned down it's pretty much inaudible (too loud at full voltage), but it keeps the top plate and the transformer pretty much at room temp even after several hours.  Passive would be mo' better still, so quite interested to see what you come up with.


----------



## bcowen

Zachik said:


> so... basically... modded DV is original case and transformer? EVERYTHING else is replaced?


I kept the IEC socket, fuse, power switch (for now), LED, and mine still has the 73 electrolytic caps in it 'cause it's not as advanced as @L0rdGwyn 's.


----------



## bcowen

L0rdGwyn said:


> I would save those Rikens, they are special!  Any run-of-the-mill carbon compostion resistor is a better choice.  The reason carbon comps are best is due to their low inductance, carbon or metal film will probably work fine but do have some inductance so are not best for damping oscillation (and like I said, the stock circuit isn't going to be very prone to oscillation, so you might not need them anyway), but carbon comp is really the right choice.  I have a big stockpile of Allen Bradley 100ohm and 1K resistors for this reason, can usually find cheap batches of them on eBay.


Thanks.  Found some Allen Bradley carbon comps on Ebay for $0.50 each.  Could I stop with just ordering 2?  Of course not.  There was a quantity discount, so I ordered a bunch and told my wife how much money I'd just saved.


----------



## L0rdGwyn (Feb 20, 2021)

bcowen said:


> So then adding a fan *was* a good move.  It was @therremans idea.  With the speed turned down it's pretty much inaudible (too loud at full voltage), but it keeps the top plate and the transformer pretty much at room temp even after several hours.  Passive would be mo' better still, so quite interested to see what you come up with.



I'll post the results here.  I plan to place two solder lugs where the mounting holes are for the wirewounds in the stock circuit.  Will then float two or three high wattage resistors there in parallel, there will be no metal-to-metal contact between the resistors and the chassis, that is the problem.  They will cool by airflow, but will be properly rated to dissipate the 8W or so without getting scorching hot.  The air inside the chassis will still heat up, but the chassis won't become a heatsink with an amplifier inside, should equilibrate to a much lower ambient temperature.


----------



## Zachik

bcowen said:


> There was a quantity discount, so I ordered a bunch and told my wife how much money I'd just saved.


I did the same with Christmas lights... You know, 12AU7s


----------



## bcowen

L0rdGwyn said:


> I'll post the results here.  I plan two place to solder lugs where the mounting holes are for the wirewounds in the stock circuit.  Will then float two or three high wattage resistors there in parallel, there will be no metal-to-metal contact between the resistors and the chassis, that is the problem.  They will cool by airflow, but will be properly rated to dissipate the 8W or so without getting scorching hot.  The air inside the chassis will still heat up, but the chassis won't become a heatsink with an amplifier inside, should equilibrate to a much lower ambient temperature.



Could you use a thick film resistor like this, or would it require a heatsink the size of a refrigerator?  

https://www.mouser.com/datasheet/2/427/lto30-1764098.pdf


----------



## bcowen

Zachik said:


> I did the same with Christmas lights... You know, 12AU7s



Well, I can't make fun of you (much as I'd like to ) because I did pretty much the same thing with Fotons.


----------



## johnjen

bcowen said:


> Could you use a thick film resistor like this, or would it require a heatsink the size of a refrigerator?
> 
> https://www.mouser.com/datasheet/2/427/lto30-1764098.pdf


I used a set of these in a similar (Purp-Amp) situation and it worked rather well.
The big resistors I originally used got mighty 'toasty'.

JJ


----------



## bcowen

johnjen said:


> I used a set of these in a similar (Purp-Amp) situation and it worked rather well.
> The big resistors I originally used got mighty 'toasty'.
> 
> JJ


In this application, is there any sonic difference depending on the type of resistor used?  Or is it more a matter of finding the most efficient (ie: least toasty) manner of dissipating the wattage?

There's math involved to determine the appropriate heatsink, so my brain froze and I had to go get a beer....


----------



## Zachik

bcowen said:


> Well, I can't make fun of you (much as I'd like to ) because I did pretty much the same thing with Fotons.


I was actually kidding... I saw your Fotons stash, and mine was like 10% of that...


----------



## Tom-s

bcowen said:


> Also decided before I get started with everything I'd go ahead and replace the sockets too.  I really like these tapered split-contact sockets, and have used the ceramic ones for a number of adapters.  Some of them have had a lot of rolling, yet the contacts have maintained a nice firm grip without having to mess with tightening them.  Wasn't aware they were available with a teflon body, but they are so I ordered a couple for the DV.  Price is right at $22.50 a pair, just have to wait a bit for them to get here.  Couldn't reasonably justify the Admiral Yamamoto sockets which cost about half as much as the amp.
> 
> https://www.ebay.com/itm/High-End-8pin-Octal-Teflon-Tube-Socket-For-EL34-KT88-5AR4-274B-GZ34-KT66-5881-x2/223597938937?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649



I used/build these sockets in an amplifier.
And replaced them within a week. 
They grip the pins so hard it’s impossible to get any tube in or out. A tube rollers nightmare. And well, i like tube rolling. These were too much stress on the base/pins for me. 
I like this design for my B4/5 and UX4 tubes.
With only 4/5 pins they are perfect. Also with 1920’s “not the best aligned” pins.


----------



## bcowen

Tom-s said:


> I used/build these sockets in an amplifier.
> And replaced them within a week.
> They grip the pins so hard it’s impossible to get any tube in or out. A tube rollers nightmare. And well, i like tube rolling. These were too much stress on the base/pins for me.
> I like this design for my B4/5 and UX4 tubes.
> With only 4/5 pins they are perfect. Also with 1920’s “not the best aligned” pins.


Hmmmm...interesting.  Did you use the ceramic body ones or the teflon?  I've only used the ceramic and like them a lot -- never had any issues with the grip.  But I haven't tried the teflon ones.


----------



## Tom-s

I have those EBay teflon one. Got ten pairs at once because cheap and they ended at the bottom of my sockets box.


----------



## Zachik

Tom-s said:


> They grip the pins so hard it’s impossible to get any tube in or out. A tube rollers nightmare.


I can imagine @bcowen stuck with GE tubes f...o...r...e...v...e...r.......


----------



## johnjen

bcowen said:


> In this application, is there any sonic difference depending on the type of resistor used?  Or is it more a matter of finding the most efficient (ie: least toasty) manner of dissipating the wattage?
> 
> There's math involved to determine the appropriate heatsink, so my brain froze and I had to go get a beer....


Brain Freeze aka Mush Mind and when the eye's glaze over, all are indicators of more complexity than need be.   
So what I do is throw the resistors at the wall and see if they burn a hole in the plaster 1st…  
hahahahahahahahahahaha  

But I do start out and measure the temps at the device and go from there.
This is where an IR gun comes in handy, let me tell ya…    

And I've found that the SQ seems to be more related to the stable temperature reached (Too Hot, or not), along with the means of heat dissipation, as in, is there any real (forced) air flow over, under, around the resistor, etc…
Or not.

I used Caddock MP-930 30w TO220 type, which are running at ≈110°F at the resistor face.

JJ


----------



## johnjen

I too have used the ceramic versions and like them a whole bunch.  

They are a tad more 'fussy' than the 2 finger squeeze types, which have a VERY small contact patch from the tube pin to socket contact.  
But those 2 finger squeeze sockets do allow for hard wiring the tubes…  
hahahahahahahahahahahahaha 

JJ


----------



## bcowen

johnjen said:


> I too have used the ceramic versions and like them a whole bunch.
> 
> They are a tad more 'fussy' than the 2 finger squeeze types, which have a VERY small contact patch from the tube pin to socket contact.
> But those 2 finger squeeze sockets do allow for hard wiring the tubes…
> ...



Perhaps the holes in the teflon ones (which were probably machined) aren't as big in diameter and don't allow the contacts to spread as much?  Hmmm.  Guess I'll see when they get here.  I have the ceramic ones in my Incubus amp as well as a slew of DIY adapters, and love them.  Maybe in this case the teflon is _not_ the more desirable version.  

I made the mistake of putting a NOS Amphenol octal socket in my Weston tester. The one in there was broken, and I spent a high dollar for that Amphenol because I wanted a good, durable socket.  Bad move.  Talk about a death grip.  The first couple tubes I put in I had to wedge a screwdriver between the tube base and the socket and slowly pry the dang tube out.  Great for a component where you plug in a tube and use it until it dies, but for a tube tester?  Ooops.     It loosened up a little after a few tube swaps, but still a big enough PITA I just bought a socket saver and stuck it in.  Where there's a will (and textbook laziness), there's a way.


----------



## L0rdGwyn

So, I love my Thorens turntable.  Put a lot of work into it so far and it sounds great.

I love it so much in fact that I doubled down on keeping it long term and making additional upgrades.

Won this at auction this morning.




I bought this for two reasons:

1) Spare parts long term

2) The aluminum front panel lacks the cueing switch for the stock TP16 tonearm.

Why is number 2 important?  Because I am a psycho.  If I were to replace the armboard and upgrade the tonearm, the cueing switch would be non-functional, an unusable remnant of the original tonearm, and I cannot have that.

So the plan will be to rebuild the turntable, combining parts from mine as well as the spares from this purchase.  I'll replace the armboard and upgrade the tonearm.  While I am at it, will probably get a custom wood plinth as well.

Absolutely no timeline for this, no hurry, this will be put in storage when it arrives.  Might wait until it is time to replace my cart and do everything at once.


----------



## triod750

*"Perhaps the holes in the teflon ones (which were probably machined) aren't as big in diameter and don't allow the contacts to spread as much?"*.
I have found teflon to be somewhat elastic when machining it so you may well be right. If they are cheap they might not afford to get the sizing right .


----------



## bcowen

triod750 said:


> *"Perhaps the holes in the teflon ones (which were probably machined) aren't as big in diameter and don't allow the contacts to spread as much?"*.
> I have found teflon to be somewhat elastic when machining it so you may well be right. If they are cheap they might not afford to get the sizing right .



I'll post back with a comparison when they arrive.  I'm glad @Tom-s mentioned it....I'd hate to get them all installed just to have to rip them out again.  I have a couple ceramic-bodied ones here, so if that turns out to be the case I'll just install them instead.


----------



## bcowen (Feb 21, 2021)

L0rdGwyn said:


> Absolutely no timeline for this, no hurry, this will be put in storage when it arrives.  Might wait until it is time to replace my cart and do everything at once.


I thought you just got that cartridge???  Gonna be a long wait.  LOL!

One nice benefit of US cleaning that isn't mentioned very often is that it will help the stylus last a lot longer.  The micro-grit down in the grooves of a dirty record probably chews on a stylus far more than wear from the vinyl itself.


----------



## L0rdGwyn

bcowen said:


> I thought you just got that cartridge???  Gonna be a long wait.  LOL!
> 
> One nice benefit of US cleaning that isn't mentioned very often is that it will help the stylus last a lot longer.  The micro-grit down in the grooves of a dirty record probably chews on a stylus far more than wear from the vinyl itself.



Oh yeah, it's gonna be a while, going to put that stuff in storage and wait it out.  We'll see what comes first, boredom or the cartridge replacement lol.


----------



## L0rdGwyn (Feb 21, 2021)

Did something today that has been on the to-do list for a month or so.

Might have noticed any pics of the 45 amp have not featured my globe 45s.  That is due to cathode stripping, let me explain.

The power supply in this amplifier is not regulated in any way, it is a simple CLCRC supply.  It doesn't need to be regulated because both the input and output tubes are CCS loaded, meaning the power supply rejection is extremely high, even a choke in the passive supply could be considered overkill.

Here is the problem with that though.  When the amplifier is turned on, there is no soft start, full B+ is applied immediately to the top of the CCS loads, around 525VDC.  The Rod Coleman filament regulators, on the other hand, DO have a soft start, and in any case it takes time for DHT filaments to warm up.

The result is DC current begins to flow before the 45 filaments are fully up to temperature / voltage.  They see the full B+ which begins to drop as the filaments are nearly at voltage and can supply the current the HV supply is demands.

Now cathode stripping is somewhat controversial.  Some say it doesn't exist, others say it doesn't occur until >1kV.  The idea is that if the filaments are not fully heated at the time B+ is applied, the supply will pull MORE from the areas of the filament that are at a higher temperature, hot spots, and this can potentially strip away the oxide coating of the filament, damaging and shortening the lifespan of these scarce triodes.

I wasn't very concerned about the issue in this amp until I visually observed in my globe 45 what was unmistakably cathode stripping at startup, tiny bits of glowy coating being accelerated to the plate at startup as the filaments came up to voltage. * THE HORROR* 

So obviously the globe 45s took a hiatus from the amplifier until the issue could be addressed, which happened today.

I had some time-delay kits from K&K Audio that I had originally picked up for use in my 801A amplifier.  That amplifier will no longer need the time-delay, so I figured I'd try one out in this circuit.  The board is powered from the 6.3VAC supply and provides a 30 second time delay before a relay is switched and the B+ is applied, allowing plenty of time for the 45 filaments to come up to voltage.

I alligator clipped one in, everything checked out, the filaments are immediately ready to conduct after 30 seconds.  As soon as the B+ hits, the CCS loads go to work and the 45s are brought to bias

So we made it permanent.  Had to rotate the reservoir cap and drill another hole in the chassis to mount the PCB, but it all fits nice and cozy, problem solved.





To celebrate, thought I would put the amp in the main system for the evening.  It will have to go back upstairs tonight for the routine bedtime music session  listening to some Pixies.


----------



## L0rdGwyn (Feb 21, 2021)

Oh, I also ordered the final parts for the modded DarkVoice, this is really the end of the line for that project.

Output tube cathode resistors will be non-inductive Mills MRA12, three in parallel.  Will change the Solen gyrator caps to Sonicaps.  Reservoir cap will get a capacitance bump to as well as a reliability bump to a 5000 hour Nichicon electrolytic.

That oughta exorcise the temperature demons in that amplifier.  Should have it fixed in a week.


----------



## bcowen

L0rdGwyn said:


> Oh, I also ordered the final parts for the modded DarkVoice, this is really the end of the line for that project.
> 
> Output tube cathode resistors will be non-inductive Mills MRA12, three in parallel.  Will change the Solen gyrator caps to Sonicaps.  Reservoir cap will get a capacitance bump to as well as a reliability bump to a 5000 hour Nichicon electrolytic.
> 
> That oughta exorcise the temperature demons in that amplifier.  Should have it fixed in a week.



So that will be three 3k resistors per side, correct?


----------



## L0rdGwyn (Feb 21, 2021)

bcowen said:


> So that will be three 3k resistors per side, correct?



Right, I was using 1.2K in the modded design.  Will be using three 3.9K to bring the cathode resistance to 1.3K in parallel.  In the stock circuit, 3x 3K would be equivalent.  Could also use a pair of 2K 25W vitreous enamel wirewounds if they will fit.  The Mills resistors are expensive, but high quality and compact.

This brings the total wattage rating for the resistance to 36W up from 25W.  And like I mentioned, they will not be heatsinked to the chassis.


----------



## bcowen

L0rdGwyn said:


> In the stock circuit, 3x 1K would be equivalent.  Could also use a pair of 1.5K 25W vitreous enamel wirewounds if they will fit.



Did you mean 3x *3*K for the stock circuit? (I hope?)


----------



## L0rdGwyn

bcowen said:


> Did you mean 3x *3*K for the stock circuit? (I hope?)



Yes, yes I did LOL.  Sorry brain malfunction on my way out the door, I will fix it.  3x *3K* for the stock circuit, or 2x *2K* 25W enamel wirewounds.


----------



## bcowen

L0rdGwyn said:


> Yes, yes I did LOL.  Sorry brain malfunction on my way out the door, I will fix it.  3x *3K* for the stock circuit, or 2x *2K* 25W enamel wirewounds.


Thanks!!


----------



## L0rdGwyn

bcowen said:


> Thanks!!



If you want to wait to buy anything until I have some temperature results, I should have it done in a few days, maybe Friday if everything arrives on time.  I'll be attaching a thermocouple to the chassis as well as floating it freely in the center of the interior and running the amp continuously for a few hours again.


----------



## bcowen

L0rdGwyn said:


> If you want to wait to buy anything until I have some temperature results, I should have it done in a few days, maybe Friday if everything arrives on time.  I'll be attaching a thermocouple to the chassis as well as floating it freely in the center of the interior and running the amp continuously for a few hours again.



Too late.   I was going to replace those crummy stock resistors anyway, so figured I might as well do it with some quality ones.  I about choked when I went to my usual parts haunt -- they wanted $10.75 a piece for them.  Fortunately our friends in Canada had them for a lot less.  Still expensive,  but you get what you pay for.  I was looking at some Vishay 10 watters at Mouser that were cheaper, but they're 1.5 times the length and I was scratching my head at how I'd get them to fit. The Mills will certainly make that task easier.

Is the temperature what caused the stress testing failure?  Or did something else burp in the process?


----------



## L0rdGwyn

bcowen said:


> Too late.   I was going to replace those crummy stock resistors anyway, so figured I might as well do it with some quality ones.  I about choked when I went to my usual parts haunt -- they wanted $10.75 a piece for them.  Fortunately our friends in Canada had them for a lot less.  Still expensive,  but you get what you pay for.  I was looking at some Vishay 10 watters at Mouser that were cheaper, but they're 1.5 times the length and I was scratching my head at how I'd get them to fit. The Mills will certainly make that task easier.
> 
> Is the temperature what caused the stress testing failure?  Or did something else burp in the process?



Totally temperature related, everything else was just fine, sounded great after 4.5 hours!  I just don't want to cook everything inside, would hate to send it back and have something die in a year.  High temps will reduce the life of the reservoir cap, cause bias drift in the gyrator loads, etc.  Just too hot overall, I think switching up the resistor setup will make everything happier.


----------



## bcowen (Feb 21, 2021)

L0rdGwyn said:


> Totally temperature related, everything else was just fine, sounded great after 4.5 hours!  I just don't want to cook everything inside, would hate to send it back and have something die in a year.  High temps will reduce the life of the reservoir cap, cause bias drift in the gyrator loads, etc.  Just too hot overall, I think switching up the resistor setup will make everything happier.



I had toyed around with the thought of adding some additional standoffs between the 25w wirewounds and the threaded chassis mounts (with a fiber washer in between), and then putting some heat sinks on the backside of the resistors.  There would still be some heat transmission through the screw threads, but it seems the heatsinks would keep a lot of the heat from being transferred directly into the chassis. But after looking at Vishay's specs for heatsink area on a 25w wirewound, what I had on hand would still be way short of the sink surface area specified. The stock resistors are not mounted as they should be -- they're effectively hanging in free air, so their power handling is 12.5 watts, not 25 (well, maybe 13 or 14 given the small contact area with the chassis standoffs).  And this is best case based on Vishay specs, which I'm sure exceed what's in there now. So long story a only a little longer, I liked your idea way better and put the computer parts back in the appropriate stash box.   I'm sure this is all pretty elementary to you, but I'm learning....regardless of my old dog status.  






https://www.mouser.com/datasheet/2/427/rhnh-1762472.pdf


----------



## L0rdGwyn (Feb 21, 2021)

bcowen said:


> I had toyed around with the thought of adding some additional standoffs between the 25w wirewounds and the threaded chassis mounts (with a fiber washer in between), and then putting some heat sinks on the backside of the resistors.  There would still be some heat transmission through the screw threads, but it seems the heatsinks would keep a lot of the heat from being transferred directly into the chassis. But after looking at Vishay's specs for heatsink area on a 25w wirewound, what I had on hand would still be way short of the sink surface area specified. The stock resistors are not mounted as they should be -- they're effectively hanging in free air, so their power handling is 12.5 watts, not 25 (well, maybe 13 or 14 given the small contact area with the chassis standoffs).  And this is best case based on Vishay specs, which I'm sure exceed what's in there now. So long story a only a little longer, I liked your idea way better and put the computer parts back in the appropriate stash box.   I'm sure this is all pretty elementary to you, but I'm learning....regardless of my old dog status.
> 
> 
> 
> https://www.mouser.com/datasheet/2/427/rhnh-1762472.pdf



Right!  I was so blinded by getting the more complicated aspects of the mods straightened out that I was completely blind to this heat issue, these resistors really should be heatsinked, using a more typical tubular wirewound should be a big improvement.

Here is what I am doing, four of these: https://www.mouser.com/ProductDetail/534-802/

They will mount on the standoffs built into the chassis that the wirewounds are mounted on.  The mounting hole and solder lug are not connected, so the resistors will not be thermally connected to the chassis.

This is an alternative, I have some of both on hand but not enough to do the job, I think the ones above will work better though: https://www.mouser.com/ProductDetail/534-805/

The chassis standoffs are offset and the solder lugs are offset, so should make a nice parallel connection for the resistors, if that makes sense.


----------



## bcowen

L0rdGwyn said:


> Right!  I was so blinded by getting the more complicated aspects of the mods straightened out that I was completely blind to this heat issue, these resistors really should be heatsinked, using a more typical tubular wirewound should be a big improvement.
> 
> Here is what I am doing, four of these: https://www.mouser.com/ProductDetail/534-802/
> 
> ...



Uh-oh.  I was gonna say great minds think alike but didn't want to insult you.  

I have quite a few of these, and there's no (metal) connection between the solder lug and screw lug.  If the spacing doesn't work, I have some 3-lug strips I can snip one terminal off of and end up with (effectively) what you have in the first link.  When we're done, if you show me yours I'll show you mine.


----------



## L0rdGwyn

I don't have much in the way of updates.  Waiting on a Mouser order to finish the DarkVoice modifications, likely will not document the process of my vintage radio restoration here, just the final result, that is a work-in-progress.  Once those two things are done I'll be waiting on my custom mains transformer from Sowter to prototype what I believe is the final iteration of my 801A A2 amplifier, I feel very confident in the design.  That is the final item on the to-do list as far as projects that I have committed to, everything else are just tweaks to completed designs.  I'm really looking forward to focusing all of my effort on the 801A amp, it is going to be somethin'.

With all of that being said, I have continued buying tubes for future designs.  Particularly E55L, again.

Just won this lot, the only bidder.  Six for 70 Euro + shipping?  Yes please.  Maybe the DIY world forgot about these tubes, they used to command high prices.



I now have a small stockpile of E55L, five or six pairs.  I am thinking these would go in a spud design, a popular choice for this tube, they are well-suited for the job.  Not committing to anything yet, just can't pass up these deals.


----------



## whirlwind

L0rdGwyn said:


> I don't have much in the way of updates.  Waiting on a Mouser order to finish the DarkVoice modifications, likely will not document the process of my vintage radio restoration here, just the final result, that is a work-in-progress.  Once those two things are done I'll be waiting on my custom mains transformer from Sowter to prototype what I believe is the final iteration of my 801A A2 amplifier, I feel very confident in the design.  That is the final item on the to-do list as far as projects that I have committed to, everything else are just tweaks to completed designs.  I'm really looking forward to focusing all of my effort on the 801A amp, it is going to be somethin'.
> 
> With all of that being said, I have continued buying tubes for future designs.  Particularly E55L, again.
> 
> ...



Wow. These all the same year tubes ? All look matched up in construction.


----------



## Zachik

L0rdGwyn said:


> Not committing to anything yet, just can't pass up these deals.


Keep not passing up on good deals, and your garage will end up like this:


----------



## L0rdGwyn (Feb 26, 2021)

whirlwind said:


> Wow. These all the same year tubes ? All look matched up in construction.



Yeah, a matched set!



Zachik said:


> Keep not passing up on good deals, and your garage will end up like this:



You really shouldn't post pictures of @bcowen 's garage without his permission.


----------



## whirlwind

L0rdGwyn said:


> Yeah, a matched set!


Hell yeah. Great deal, even if it is for future project. Nice matched set.


----------



## Tom-s

Here's my post on a E55L SPUD S3X i build. 
In the picture with the E55L's lined up you can see the front row has Amperex New York build E55L.
In the back row there's a bunch of Mullard E55L; those are recognized by the short exhaust tip (as the labels don't tell). 
I prefer the Mullard's sound over the Amperex build E55L. Use that amp on a regular basis.
Here's more.


----------



## bcowen

L0rdGwyn said:


> I don't have much in the way of updates.  Waiting on a Mouser order to finish the DarkVoice modifications, likely will not document the process of my vintage radio restoration here, just the final result, that is a work-in-progress.  Once those two things are done I'll be waiting on my custom mains transformer from Sowter to prototype what I believe is the final iteration of my 801A A2 amplifier, I feel very confident in the design.  That is the final item on the to-do list as far as projects that I have committed to, everything else are just tweaks to completed designs.  I'm really looking forward to focusing all of my effort on the 801A amp, it is going to be somethin'.
> 
> With all of that being said, I have continued buying tubes for future designs.  Particularly E55L, again.
> 
> ...


Sweet!  But how do you get 3 grids in a tube that small???


----------



## L0rdGwyn (Feb 26, 2021)

Tom-s said:


> Here's my post on a E55L SPUD S3X i build.
> In the picture with the E55L's lined up you can see the front row has Amperex New York build E55L.
> In the back row there's a bunch of Mullard E55L; those are recognized by the short exhaust tip (as the labels don't tell).
> I prefer the Mullard's sound over the Amperex build E55L. Use that amp on a regular basis.
> Here's more.



Very cool!  And great idea to adapt them into the S3X, bet it sounds great.  I have two more pairs of Philips / Mullard made E55L, will take a closer look at the construction when the Amperex arrive.  Unsure what direction I would go with the transformers, parafeed vs. series feed...and the biasing scheme for that matter.   Have considered using a SUT on the input as well, very early ideas right now.


----------



## bcowen

L0rdGwyn said:


> Yeah, a matched set!
> 
> 
> 
> You really shouldn't post pictures of @bcowen 's garage without his permission.


Yeah, @Zachik , what LG said.  Or at least next time get a picture of _all_ of them....that's just the small octals.


----------



## L0rdGwyn

bcowen said:


> Sweet!  But how do you get 3 grids in a tube that small???



They look small by themselves, but they are actually quite substantial, they are power output tubes and bias at 50mA triode strapped (for reference, at 2A3 biases at 60mA typically).

Here is one next to a 12AU7.


----------



## bcowen

L0rdGwyn said:


> They look small by themselves, but they are actually quite substantial, they are power output tubes and bias at 50mA triode strapped (for reference, at 2A3 biases at 60mA typically).
> 
> Here is one next to a 12AU7.


Oh, ok.  That looks mo' better.   I'm not familiar with the tube (obviously) -- looked like a noval.


----------



## bcowen

L0rdGwyn said:


> I don't have much in the way of updates.  Waiting on a Mouser order to finish the DarkVoice modifications, likely will not document the process of my vintage radio restoration here, just the final result, that is a work-in-progress.  Once those two things are done I'll be waiting on my custom mains transformer from Sowter to prototype what I believe is the final iteration of my 801A A2 amplifier, I feel very confident in the design.  That is the final item on the to-do list as far as projects that I have committed to, everything else are just tweaks to completed designs.  I'm really looking forward to focusing all of my effort on the 801A amp, it is going to be somethin'.
> 
> With all of that being said, I have continued buying tubes for future designs.  Particularly E55L, again.
> 
> ...


My DigiKey order _finally _arrived today after a week and a half in the clutches of the USPS.  Has the 100 milliohm (dropping) resistors I need for the heaters in the DV.  I usually buy from Mouser that has a good rate for FedEx ground, but Digikey had a better rate for USPS.  I guess it's worth saving a couple bucks on shipping if you don't mind waiting, but the problem is I'm not a very good waiter.    Also got the 1k AB carbon composition resistors today (for the grid stoppers), so now all I need is for a couple sockets to arrive and I'll get to work.


----------



## L0rdGwyn

bcowen said:


> My DigiKey order _finally _arrived today after a week and a half in the clutches of the USPS.  Has the 100 milliohm (dropping) resistors I need for the heaters in the DV.  I usually buy from Mouser that has a good rate for FedEx ground, but Digikey had a better rate for USPS.  I guess it's worth saving a couple bucks on shipping if you don't mind waiting, but the problem is I'm not a very good waiter.    Also got the 1k AB carbon composition resistors today (for the grid stoppers), so now all I need is for a couple sockets to arrive and I'll get to work.



Nice! Looking forward to hearing about it


----------



## bcowen

L0rdGwyn said:


> Nice! Looking forward to hearing about it


I see what you did there.  And right after "learning curve," no less.  You're on a roll!!


----------



## Galapac

bcowen said:


> I see what you did there.  And right after "learning curve," no less.  You're on a roll!!


Call him butter...😃


----------



## L0rdGwyn

Kinda spitballin' some thoughts on this E55L spud...

I like the idea of using spare parts.  If I were to parafeed it and use a CCS load rather than a choke, I have a transformer perfect for the job, old Sowter custom job from version 1 of my 45 parafeed amplifier.



Has a healthy B+ winding rated for ~100mA DC (perfect), and three 6.3VAC windings, two with high current ratings as they were originally intended for the 45.  I also have some Tent Labs DC heater regulators which I could put to use on the E55L (pictured).

Using the CCS would simplify the power supply as well given it's PSRR, so could go passive.  For soft start, could use a hybrid SS diode-tube full-wave bridge for swag, plus could use a higher Vdrop rectifier to knock off some excess voltage and save the CCS some heat.

Since I have plenty of 6.3VAC to go around and the E55L only needs perhaps -6V on the grid, could potentially use one winding for a negative bias supply and go fixed bias.  Would probably go with a 1:2 SUT as well.

The last question then becomes the output transformers.  I think I would go with a multi-tap parafeed from Electra-Print.  Have swapped emails with Jack a few times, want to try out his stuff.  If I went for a 8-32-120-300 secondary setup, would be in good shape for a flea-watt speaker amp and gobs of power for headphones.

I'm avoiding starting anything else new until I have cleared the queue, but I like this as a future project, high on the "potential projects" list.


----------



## Galapac

WOW!! Look at this! Would love to see this in person.
Pilot to bombardeer...

https://www.ebay.com/itm/B-52-Bombe...531420?hash=item2650fd3f9c:g:UJ0AAOSwH~RfsqW8


----------



## L0rdGwyn

Galapac said:


> WOW!! Look at this! Would love to see this in person.
> Pilot to bombardeer...
> 
> https://www.ebay.com/itm/B-52-Bombe...531420?hash=item2650fd3f9c:g:UJ0AAOSwH~RfsqW8



Somebody buy the $2,500 lot to use the tubes in their BHC please 😂


----------



## bcowen

Galapac said:


> WOW!! Look at this! Would love to see this in person.
> Pilot to bombardeer...
> 
> https://www.ebay.com/itm/B-52-Bombe...531420?hash=item2650fd3f9c:g:UJ0AAOSwH~RfsqW8



I'm guessing there won't be any European tubes in there...


----------



## CJG888

Full of GEs...


----------



## bcowen

CJG888 said:


> Full of GEs...


Not likely, or the US would have mistakenly dropped bombs on Hong Kong back in the '60's thinking they were over Vietnam...


----------



## L0rdGwyn (Feb 28, 2021)

So I realized I actually had the terminals I needed to make the resistor change in the DarkVoice, derp. Still need my Mouser order for the power supply changes but figured I'd go ahead and swap out the resistors.

Here is my solution to the hot resistor problem. Had to reroute the output wiring, the ground bus. Got rid of the aluminum-housed resistors, put some solder lug terminals on the standoffs instead, and used three 3.9K 12W NOS Mills non-inductive wirewounds in parallel. 1.3K cathode resistance with the 36W of rated power dissipation and they are no longer attached to the chassis by metal contact.




I have been running the amp for a little over an hour now. With the old setup, top plate was hitting around 40C and the interior of the chassis 48-50C.

Top plate still comes to around 36-37C, but floating my thermocouple on the interior of the chassis, air temperature only hits around 37-38C, that's a 12C improvement. I'll take it.



Sounds really good too with a National Union 6SN7GT and Western Electric 421A.


----------



## Tjj226 Angel

L0rdGwyn said:


> Kinda spitballin' some thoughts on this E55L spud...
> 
> I like the idea of using spare parts.  If I were to parafeed it and use a CCS load rather than a choke, I have a transformer perfect for the job, old Sowter custom job from version 1 of my 45 parafeed amplifier.
> 
> ...



Would this be just for headphones? Or for headphones and speakers?


----------



## L0rdGwyn (Mar 1, 2021)

Tjj226 Angel said:


> Would this be just for headphones? Or for headphones and speakers?



Both in theory, could do about 2W into 8ohms.  Figure if I get multitap parafeed transformers, might as well include an 8ohm tap.

But I am trying to pump the breaks on all of my ideas and be more picky.  No more simultaneous projects for me LOL one at a time from now on, it's too much work and money.  The fact that I have a mains transformer ready to go for this one makes it very appealing.  I did buy some nice NOS ceramic magnoval sockets though, just in case


----------



## L0rdGwyn (Mar 1, 2021)

I tracked down a copy of a book I have been keeping an eye out for, _Designing Power Supplies for Tube Amplifiers_ by Merlin Blencowe. I really like his preamp design book, became my leisure reading on a vacation last year LOL so I need a new one for this year. Obviously this information is available in many places and it will be a lot of review, but it's nice reading a text where everything is in the context of tube circuits. I can read about series / shunt regulators anywhere, but very few contemporary books written on TUBE series / shunt regulators  anyway, I was happy to find it.  Sort of highly sought-after in the DIY world, this book is out of print, typically listed on auction sites for insane prices.


----------



## Tjj226 Angel

L0rdGwyn said:


> I tracked down a copy of a book I have been keeping an eye out for, _Designing Power Supplies for Tube Amplifiers_ by Merlin Blencowe. I really like his preamp design book, became my leisure reading on a vacation last year LOL so I need a new one for this year. Obviously this information is available in many places and it will be a lot of review, but it's nice reading a text where everything is in the context of tube circuits. I can read about series / shunt regulators anywhere, but very few contemporary books written on TUBE series / shunt regulators  anyway, I was happy to find it.  Sort of highly sought-after in the DIY world, this book is out of print, typically listed on auction sites for insane prices.



I have seen this book from time to time. I have read a lot of Merlin's stuff on the forums, websites, and so on, so I am not too sure what this book really has to offer. If you feel like this book divulges some secrets that you can't find on the internet, please let me know. I am sort of tied up with family issues at the moment, so I am taking this time to research and read up. 

I actually just finished my first pass of "High Quality Horn Loudspeaker Systems" (which is nothing short of a kick arse book) and I am waiting for my new book to get here. 

https://www.amazon.com/Transformers-Tube-Amplifiers-INTERSTAGE-TRANSFORMERS/dp/0980622387


----------



## L0rdGwyn (Mar 2, 2021)

Tjj226 Angel said:


> I have seen this book from time to time. I have read a lot of Merlin's stuff on the forums, websites, and so on, so I am not too sure what this book really has to offer. If you feel like this book divulges some secrets that you can't find on the internet, please let me know. I am sort of tied up with family issues at the moment, so I am taking this time to research and read up.
> 
> I actually just finished my first pass of "High Quality Horn Loudspeaker Systems" (which is nothing short of a kick arse book) and I am waiting for my new book to get here.
> 
> https://www.amazon.com/Transformers-Tube-Amplifiers-INTERSTAGE-TRANSFORMERS/dp/0980622387



It goes deeper into topics he touches on on his site and has all the typical power supply type stuff, but also explores topics that I have not seen him get into elsewhere, particularly power supply regulation.  Of course you can find that info other places, but it's nice to have it in one book in the context of tube circuits.  Not sure there are any secrets, but I think it's a good read!

That book you linked is terrifying, Pandora's box, I will avert my eyes.


----------



## Galapac

I thought this was funny and wanted to share with y'all...you might relate to a few of these if not more.

_You might be a tubeneck..._
http://www.netads.com/~meo/Guitar/Tubes/tn.pl


----------



## bcowen

Tom-s said:


> I used/build these sockets in an amplifier.
> And replaced them within a week.
> They grip the pins so hard it’s impossible to get any tube in or out. A tube rollers nightmare. And well, i like tube rolling. These were too much stress on the base/pins for me.
> I like this design for my B4/5 and UX4 tubes.
> With only 4/5 pins they are perfect. Also with 1920’s “not the best aligned” pins.


Sockets came in today, and they must have heard about your death grip experience.     The contacts in these were so loose the tube would probably have fallen out if I'd turned it upside down.  Sigh.  The teflon body is nicely machined, but the contacts are terrible.  They are made differently than the ones in the ceramic sockets, and those I've really liked -- firm contact even after many tube swaps and no death grip.  Fortunately I ordered a pair of the ceramic body ones too, and ended up swapping the contacts between them.  Now I have a nice teflon body with good contacts.  Obviously pretty ridiculous to have to go to these lengths, and I'm certainly not recommending the teflon versions to anyone going forward (but I do still like the ceramic ones).

Teflon on left....with the ceramic body contacts swapped.  I re-tensioned the teflon contacts before putting them in the ceramic body(s) so they have a nice grip now....but not sure if they will stay that way or loosen back up in short order.


----------



## Paladin79

oh crap, some are heading my way too lol


----------



## bcowen

Paladin79 said:


> oh crap, some are heading my way too lol


Uh-oh.  Well, @Tom-s 's were way too tight and mine were way too loose....maybe you'll get some Goldilocks ones that are just right.


----------



## whirlwind (Mar 3, 2021)

bcowen said:


> Sockets came in today, and they must have heard about your death grip experience.     The contacts in these were so loose the tube would probably have fallen out if I'd turned it upside down.  Sigh.  The teflon body is nicely machined, but the contacts are terrible.  They are made differently than the ones in the ceramic sockets, and those I've really liked -- firm contact even after many tube swaps and no death grip.  Fortunately I ordered a pair of the ceramic body ones too, and ended up swapping the contacts between them.  Now I have a nice teflon body with good contacts.  Obviously pretty ridiculous to have to go to these lengths, and I'm certainly not recommending the teflon versions to anyone going forward (but I do still like the ceramic ones).
> 
> Teflon on left....with the ceramic body contacts swapped.  I re-tensioned the teflon contacts before putting them in the ceramic body(s) so they have a nice grip now....but not sure if they will stay that way or loosen back up in short order.


That is a shame because they look like some quality sockets.
If I get another amp I think I would splurge for Yamamoto sockets , if the amp would use multiple tubes for rolling.
May need to get rid of a kidney, but there is no denying the quality of these sockets....probably not necessary though.


----------



## bcowen

whirlwind said:


> That is a shame because they look like some quality sockets.
> If I get another amp I think I would splurge for Yamamoto sockets , if the amp would use multiple tubes for rolling.
> May need to get rid of a kidney, but there is no denying the quality of these sockets....probably not necessary though.


If I was replacing sockets or building a really nice amp, I might splurge for the Yamamotos.  Kind of overkill in the Darkvoice though.


----------



## whirlwind

bcowen said:


> If I was replacing sockets or building a really nice amp, I might splurge for the Yamamotos.  Kind of overkill in the Darkvoice though.


Yes,absolutely and understood


----------



## Zachik

bcowen said:


> If I was replacing sockets or building a really nice amp, I might splurge for the Yamamotos.  Kind of overkill in the Darkvoice though.


Did GE ever made tube sockets?


----------



## therremans

Why not stick with Belton? I have little experience with sockets but the Beltons were a great upgrade from the Chinese ceramic and Russian plastic.


----------



## Xcalibur255

Hmm, I asked Mischa to use the black composite ones for my project, but the pins look like the same style as the teflons.  I'm curious if they'll be any different.  I guess we can always switch to a different one if necessary.

I have the teflon ones in my G45 amp and they've been good, so maybe the quality changed over the years.


----------



## bcowen

therremans said:


> Why not stick with Belton? I have little experience with sockets but the Beltons were a great upgrade from the Chinese ceramic and Russian plastic.


Well, perhaps I should have just purchased them initially.  Hindsight and all, maybe.  I really *do* like the Chinese ceramic ones though, and so much so that I sent a pair to @Paladin79 to include in the build of the Incubus he made for me.  And I haven't regretted it at all, as even after a considerable amount of tube rolling they still have a nice firm grip without overdoing it. And I haven't had to even think about re-tensioning them at this point.  I was assuming (obviously incorrectly) that the teflon ones would have the same contact quality, but unfortunately they don't.


----------



## UntilThen (Mar 3, 2021)

whirlwind said:


> If I get another amp I think I would splurge for Yamamoto sockets


I just did and it cost me an apple tree.

6 Yamamoto sockets cost me as much as these GEC KT66 NOS. I sure hope the Yamamoto sockets are NOS.


----------



## bcowen

Xcalibur255 said:


> Hmm, I asked Mischa to use the black composite ones for my project, but the pins look like the same style as the teflons.  I'm curious if they'll be any different.  I guess we can always switch to a different one if necessary.
> 
> I have the teflon ones in my G45 amp and they've been good, so maybe the quality changed over the years.


I had assumed these sockets were all made by the same manufacturer, and just sold on Ebay by a number of different sellers (similar to the Chinese adapter offerings).  Perhaps there is more than one manufacturer? Or perhaps it is the same manufacturer with very inconsistent quality standards.  Hard to know for sure.


----------



## UntilThen

I even wanted to splurge on Yamamoto mA meters but Jacmusic replied that Yamamoto don't produce them anymore. At least the farm is safe.


----------



## Paladin79

https://www.ebay.com/itm/Yamamoto-S...253515?hash=item262e66e90b:g:MeoAAOSwAfhd82PO

I happened upon this, 2 watts per side and a kit. Most likely those sockets are used here.


----------



## Xcalibur255

bcowen said:


> I had assumed these sockets were all made by the same manufacturer, and just sold on Ebay by a number of different sellers (similar to the Chinese adapter offerings).  Perhaps there is more than one manufacturer? Or perhaps it is the same manufacturer with very inconsistent quality standards.  Hard to know for sure.


That was my understanding as well.  My personal experience with these sockets is from 2013 and I found them well made at that time.  From the less positive impressions that have just been shared I'm wondering if something happened between then and now.


----------



## L0rdGwyn (Mar 3, 2021)

I used CMC black composite sockets in my 45 amp, UX4 and octal.  Also used their teflon UX4 in my 841 amplifier.  They may well be the same as the other Chinese sockets, just branded.  In both cases, I found the pins were too tight, loosening them wasn't too much trouble.  You can also tighten them with a pair of fine needle nose pliers.

What I have found a little annoying with them though is the nuts on the bottom loosen quite easily and the pin will start to rotate.  Can be tightened and then soldered in place, not too much of a hassle.  But no doubt Yamamotos are the best out there.

Another good octal socket I have used before is a Japanese socket made by QQQ: https://www.angela.com/eightpintubesocketqqq.aspx

I have used their 9-pin noval too in my phono stage, which are also nice: https://www.angela.com/ninepintubesocketqqq.aspx

The other option are of course NOS sockets, Soviet mil spec, Amphenol, etc.  I am likely going this direction in my 801A amp to fit a certain aesthetic, but using Yamamotos again is also appealing, despite the cost.


----------



## L0rdGwyn

therremans said:


> Why not stick with Belton? I have little experience with sockets but the Beltons were a great upgrade from the Chinese ceramic and Russian plastic.



Beltons are very good too!  If they fit as a replacement in your application.  I used them when re-socketing @whirlwind 's GOTL for 6J5, good quality.


----------



## L0rdGwyn

Speaking of sockets, received a batch of NOS Soviet loctal sockets the other day.  These are the best out there, ceramic with silver-plated pins, very nice.  Going to use one to replace the stock loctal socket on my curve tracer.



I also picked up the sockets because I was thinking of messing around with a certain mystery pentode driver tube.  Unsure if I am going to pursue it, but they are in somewhat short supply, so I will just show some curves, I think they help communicate the intrigue


----------



## leftside

L0rdGwyn said:


> Beltons are very good too!  If they fit as a replacement in your application.  I used them when re-socketing @whirlwind 's GOTL for 6J5, good quality.


We used Belton sockets in my amp.


----------



## Zachik

L0rdGwyn said:


> Going to use one to replace the stock loctal socket on my curve tracer.


Speaking of which... Did you ever hear back from Chris with regards to a cheaper (more hobbyist friendly) version of the tracer?


----------



## L0rdGwyn

Zachik said:


> Speaking of which... Did you ever hear back from Chris with regards to a cheaper (more hobbyist friendly) version of the tracer?



Nope, was going to wait a week before accepting that my suggestion is being ignored LOL I'm guessing he is not fond of the idea.  Maybe I will be very annoying and send a follow up email, but it doesn't look promising.


----------



## whirlwind

UntilThen said:


> I just did and it cost me an apple tree.
> 
> 6 Yamamoto sockets cost me as much as these GEC KT66 NOS. I sure hope the Yamamoto sockets are NOS.



Ha! Yeah man, those sockets will rack you more than a *nice set of tubes   *
Makes it a hard decision.


----------



## L0rdGwyn

My set of NOS RCA 6N7G arrived today, just enough time for a quick listen before work.



Very nice.


----------



## whirlwind

L0rdGwyn said:


> I used CMC black composite sockets in my 45 amp, UX4 and octal.  Also used their teflon UX4 in my 841 amplifier.  They may well be the same as the other Chinese sockets, just branded.  In both cases, I found the pins were too tight, loosening them wasn't too much trouble.  You can also tighten them with a pair of fine needle nose pliers.
> 
> What I have found a little annoying with them though is the nuts on the bottom loosen quite easily and the pin will start to rotate.  Can be tightened and then soldered in place, not too much of a hassle.  But no doubt Yamamotos are the best out there.
> 
> ...



Those sure look purty sitting on that chassis .
Great idea to get the right grip you want and then solder the nut. 

Those Belton sockets you put in my amp for the 6/12J5 are dang sweet sockets. Really would never need more and if you did just replace them.

Can't wait to see the 801A.


----------



## whirlwind

leftside said:


> We used Belton sockets in my amp.



They Beltons are nice sockets.
Good Lord, if you put yamamoto's in that amp you would need to back up the Brinks truck


----------



## whirlwind

L0rdGwyn said:


> My set of NOS RCA 6N7G arrived today, just enough time for a quick listen before work.
> 
> 
> 
> Very nice.



That looks like two sets of RCA 6N7G!

Bet that sounds killer.   Those tubes look nice with those globes too!


----------



## UntilThen

L0rdGwyn said:


> Very nice.


Agree. The amp is gorgeous.


----------



## UntilThen

whirlwind said:


> They Beltons are nice sockets.
> Good Lord, if you put yamamoto's in that amp you would need to back up the Brinks truck


My Yamamoto sockets must be in there somewhere.


----------



## bcowen

UntilThen said:


> My Yamamoto sockets must be in there somewhere.



You're not worthy of Yamamoto's.  Unless, of course, you send me those Bendix.  Then you'd be worthy.


----------



## UntilThen

You mean Yamamoto is not worthy of me? How about I send you a pair of these AC/DC classic rock !



Or would you prefer imitation KT88 and KT77?


----------



## A2029

Xcalibur255 said:


> Hmm, I asked Mischa to use the black composite ones for my project, but the pins look like the same style as the teflons.  I'm curious if they'll be any different.  I guess we can always switch to a different one if necessary.
> 
> I have the teflon ones in my G45 amp and they've been good, so maybe the quality changed over the years.



Not to worry, these ones that I picked up are very good, nice grip - not too tight and not too loose.


----------



## bcowen

UntilThen said:


> You mean Yamamoto is not worthy of me? How about I send you a pair of these AC/DC classic rock !
> 
> 
> 
> Or would you prefer imitation KT88 and KT77?


Um, rectifier tubes don't sound all that good as output tubes, and t-t-t-t-t-t-tetrodes?  Arrgghhhh!  Just the thought is making me break out in hives.  I *do* appreciate the effort, but anything other than a graphite plate Bendix means you're still unworthy.


----------



## Zachik

bcowen said:


> I *do* appreciate the effort, but anything other than a graphite plate Bendix means you're still unworthy.


@UntilThen - if you really want to make @bcowen happy, try to complement his current tube stash: (I don't think he likes *GE*C... just *GE*... )


----------



## Xcalibur255

Zachik said:


> @UntilThen - if you really want to make @bcowen happy, try to complement his current tube stash: (I don't think he likes *GE*C... just *GE*... )


It's...... it's like a trainwreck.......... I want to avert my eyes but somehow I just can't.......


----------



## bcowen

Xcalibur255 said:


> It's...... it's like a trainwreck.......... I want to avert my eyes but somehow I just can't.......


I think it gave me instant cataracts.  My mother always told me doing something else would make me go blind, but she was wrong......


----------



## L0rdGwyn

Modded DarkVoice monstrosity is homeward bound.

Final circuit before closing.



I measured the current draw out of the wall, 0.59A, a bit higher than calculated, decided to go back to a 1A fuse.

Pre-out tested into my 45 SET, sounds good.



Packed up, will be back to @Galapac middle of next week (tubes not included ).


----------



## L0rdGwyn

I posted this in the DarkVoice thread, figured I'd put it here too, comparison of the stock vs. modded low-frequency rolloff with the output capacitance increased from 30uF to 66uF.

DarkVoice stock FR 1mW into 300ohms, output capacitance 30uF.



And FR into various loads on the revamped DarkVoice, 66uF output capacitance.

300ohm



120ohm



80ohm



32ohm


----------



## L0rdGwyn

Here is what I might do with the E55L spud.

Retraced the curves on my tracer, here is 170Va / 55mA bias point with 2.5K OPT.



And a draft schematic.

1:2 SUT, cathode bias with the OPT primary returned to the cathode.  Parafeed output with CCS load.  OPT would be multitap for 8ohm speakers and 32 / 120 / 300ohm headphones.



This is a very simple amplifier, low parts.  I have the mains transformer, CCS parts, and sockets already.  Power supply would be tube rectified - GZ32, GZ37, 5V4G, one of those most likely.  GZ37 has the highest Vdrop, would get some heat out of the chassis, but also the most expensive  supply would be CLCRC to drop some more voltage and spare the top CCS FET.

Would need to decide on the SUT and OPT.  Likely would do a pair of Lundahl SUT, and as I said, Electra-Print parafeed OPT.

Then the parafeed caps, that will be a hard decision.  The better the cap, the bigger and more expensive.  Might need to try and find a balance, I had thought of using Jupiter HT Beeswax / Paper.  We will see, no timeline, have to restore a radio and finish another amp first!


----------



## UntilThen

Zachik said:


> @UntilThen - if you really want to make @bcowen happy, try to complement his current tube stash: (I don't think he likes *GE*C... just *GE*... )


Did @bcowen pick these up from the recycling site? Nice boxes.


----------



## Xcalibur255 (Mar 5, 2021)

L0rdGwyn said:


> Here is what I might do with the E55L spud.
> 
> Retraced the curves on my tracer, here is 170Va / 55mA bias point with 2.5K OPT.
> 
> ...


In the IHA-1 I have developed a strong preference for the 5Y3 for rectifier duties over the other 5V options.  The 5V4G sounds awful in that amp for some reason.  Two different amps so no reason to draw comparisons of course but the 5Y3 just seems to make every amp that can use it more musical to my ears. 

If memory serves the 5V4G is indirectly heated so perhaps that is the meaningful difference.

I'm also partial to the 5R4GY.  Both have a nice low heater current draw if that is beneficial in any way.


----------



## bcowen

UntilThen said:


> Did @bcowen pick these up from the recycling site? Nice boxes.


LOL!  No, I "borrowed" them from _your_ tube stash.  Guess you didn't notice they were missing?  Or didn't care?


----------



## UntilThen

A ha the topic has changed to rectifiers. I just lost out on an auction on Brimar 5R4GY. @bcowen did you bid against me?


----------



## L0rdGwyn

Xcalibur255 said:


> In the IHA-1 I have developed a strong preference for the 5Y3 for rectifier duties over the other 5V options.  The 5V4G sounds awful in that amp for some reason.  Two different amps so no reason to draw comparisons of course but the 5Y3 just seems to make every amp that can use it more musical to my ears.
> 
> I'm also partial to the 5R4GY.  Both have a nice low heater current draw if that is beneficial in any way.



Hmmm well the 5Y3 and 5V4G have very different voltage drops, 60V vs. 25V respectively, so could be a matter of altering the bias point.  Since this amp is CCS loaded, the rectifier will be super inaudible.  It is really there for looks,  to drop some voltage in the supply and get that heat out of the chassis, and for soft start.  But who knows!  Maybe there will be some tube rectifier magic as well, we will have to see


----------



## bcowen (Mar 5, 2021)

UntilThen said:


> A ha the topic has changed to rectifiers. I just lost out on an auction on Brimar 5R4GY. @bcowen did you bid against me?


Yes.  Now I just need to buy an amp that uses them.


----------



## Xcalibur255 (Mar 5, 2021)

@L0rdGwyn

If it's mostly there for looks then my vote is 5R4GY with hanging filaments.  

You're right of course that with all the proper tricks in place the diode noise and other things that make rectifiers sound "different" are probably going to be minimized.


----------



## UntilThen

bcowen said:


> LOL!  No, I "borrowed" them from _your_ tube stash.  Guess you didn't notice they were missing?  Or didn't care?


Oh yeah I did an Spring cleaning although it's Autumn here. Decided I will dump the GEs which you send me. Thanks but I have no place to keep them. I kept these instead and they will be used in Odyssey.


----------



## UntilThen (Mar 5, 2021)

bcowen said:


> Yes.  Now I just need to buy an amp that uses them.


I know where you live, I'll be coming for that ratifier. Now don't you dare bid against me on this pair.

On 2nd thoughts you can have it. I want a new pair.

https://www.ebay.com.au/itm/EL156-T...est/324500507248?_trksid=p2485497.m4902.l9144


----------



## Xcalibur255

Haha, you guys are so fast you're catching my comments while I'm editing them.  I figured I would have 30 seconds to add a thought but nope!


----------



## therremans

UntilThen said:


> I know where you live, I'll be coming for that ratifier. Now don't you dare bid against me on this pair.
> 
> https://www.ebay.com.au/itm/EL156-T...est/324500507248?_trksid=p2485497.m4902.l9144


I’ve been searching forever for these!


----------



## UntilThen

Xcalibur255 said:


> Haha, you guys are so fast you're catching my comments while I'm editing them.  I figured I would have 30 seconds to add a thought but nope!


You need a faster rectifier when @bcowen is bidding against you. I'm putting my posts in before the day gets busy. It's moving day !


----------



## L0rdGwyn (Mar 5, 2021)

Xcalibur255 said:


> @L0rdGwyn
> 
> If it's mostly there for looks then my vote is 5R4GY with hanging filaments.
> 
> You're right of course that with all the proper tricks in place the diode noise and other things that make rectifiers sound "different" are probably going to be minimized.



Name of the game is looks, soft start, and voltage drop.  Of course all of those things can be accomplished with solid state parts (well, except for looks), but in this instance, a tube rectifier works well since I am using a spare transformer!  A 5R4GY would look very nice  but an indirect-heated rectifier is preferred for slower warm up.  Goal is to delay full application of B+ until the E55L heaters have warmed, so something like GZ32, GZ37, 5V4G would be best.  GZ34 Vdrop is too low, it is TOO good of a rectifier LOL.  GZ37 is the top candidate since it has the highest voltage drop of the indirectly-heated rectifiers, as far as I am aware.  More voltage dropped by the rectifier = less voltage drop needed by the passive supply / CCS = less heat in the chassis = happier components.


----------



## Xcalibur255

L0rdGwyn said:


> Name of the game is looks, soft start, and voltage drop.  Of course all of those things can be accomplished with solid state parts (well, except for looks), but in this instance, a tube rectifier works well since I am using a spare transformer!  A 5R4GY would look very nice  but an indirect-heated rectifier is preferred for slower warm up.  Goal is to delay full application of B+ until the E55L heaters have fully warmed, so something like GZ32, GZ37, 5V4G would be best.  GZ34 Vdrop is too low, it is TOO good of a rectifier LOL.  GZ37 is the top candidate since it has the highest voltage drop of the indirectly-heated rectifiers, as far as I am aware.  More voltage dropped by the rectifier = less voltage drop needed by the passive supply / CCS = less heat in the chassis = happier components.


Ah, I see.  Yeah if you need indirectly heated specifically then I agree GZ37 is the best fit.  They're not cheap these days though.  I think 5R4 has a pretty slow warm up time but I could be talking out my butt on that.  It's been so long since I read up on it.


----------



## UntilThen

I wouldn't have thought of 5R4GY but in talking to @gibosi about 5U4G, he told me about it. @L0rdGwyn I reckon you should use a 596 rectifer for show.


----------



## Galapac

UntilThen said:


> Oh yeah I did an Spring cleaning although it's Autumn here. Decided I will dump the GEs which you send me. Thanks but I have no place to keep them. I kept these instead and they will be used in Odyssey.


@UntilThen you are a great candidate for one of these that @telecaster raves about. Would hold all of those tubes nicely for a photo op.

https://www.ebay.com/itm/353320528483


----------



## leftside

UntilThen said:


> Oh yeah I did an Spring cleaning although it's Autumn here. Decided I will dump the GEs which you send me. Thanks but I have no place to keep them. I kept these instead and they will be used in Odyssey.


Very nice! Do you find the RFT to be a little bolder and warmer than the Telefunken? The Siemens were probably made by Philips.


----------



## CJG888

RFT can be very good value.


----------



## UntilThen

Galapac said:


> @UntilThen you are a great candidate for one of these that @telecaster raves about. Would hold all of those tubes nicely for a photo op.
> 
> https://www.ebay.com/itm/353320528483



Thanks ! I've to buy one of these. 



leftside said:


> Very nice! Do you find the RFT to be a little bolder and warmer than the Telefunken? The Siemens were probably made by Philips.



I didn't use it enough in Euforia and GOTL to remember. I certainly didn't compare the brands then, mainly using only the Telefunken EL11. In Odyssey, I'll have the chance to compare but built commence only at end of June.

You sure the Siemens were made by Philips? What about the Telefunken EL11? I check the construction of Telefunken and Siemens and they look identical.


----------



## bcowen

L0rdGwyn said:


> Name of the game is looks, soft start, and voltage drop.  Of course all of those things can be accomplished with solid state parts (well, except for looks), but in this instance, a tube rectifier works well since I am using a spare transformer!  A 5R4GY would look very nice  but an indirect-heated rectifier is preferred for slower warm up.  Goal is to delay full application of B+ until the E55L heaters have warmed, so something like GZ32, GZ37, 5V4G would be best.  GZ34 Vdrop is too low, it is TOO good of a rectifier LOL.  GZ37 is the top candidate since it has the highest voltage drop of the indirectly-heated rectifiers, as far as I am aware.  More voltage dropped by the rectifier = less voltage drop needed by the passive supply / CCS = less heat in the chassis = happier components.


You mean like these?


----------



## bcowen

UntilThen said:


> I know where you live, I'll be coming for that ratifier. Now don't you dare bid against me on this pair.
> 
> On 2nd thoughts you can have it. I want a new pair.
> 
> https://www.ebay.com.au/itm/EL156-T...est/324500507248?_trksid=p2485497.m4902.l9144


No worries.  Like you, I'm saving my pennies for a good pair of GE's.


----------



## UntilThen

I'll have that Bcowen. I'll be collecting all 5 volt rectifiers with voltage drop higher than GZ34 and of about 200mA. Gibosi has given me a list.


----------



## UntilThen

bcowen said:


> No worries.  Like you, I'm saving my pennies for a good pair of GE's.


Buy these then. 1940s !
https://www.ebay.com.au/itm/GE-RCA-...NOS/164147024948?_trksid=p2485497.m4902.l9144


----------



## bcowen

UntilThen said:


> Buy these then. 1940s !
> https://www.ebay.com.au/itm/GE-RCA-...NOS/164147024948?_trksid=p2485497.m4902.l9144


I'm holding out for a pair of 1930's.


----------



## whirlwind

L0rdGwyn said:


> Name of the game is looks, soft start, and voltage drop.  Of course all of those things can be accomplished with solid state parts (well, except for looks), but in this instance, a tube rectifier works well since I am using a spare transformer!  A 5R4GY would look very nice  but an indirect-heated rectifier is preferred for slower warm up.  Goal is to delay full application of B+ until the E55L heaters have warmed, so something like GZ32, GZ37, 5V4G would be best.  GZ34 Vdrop is too low, it is TOO good of a rectifier LOL.  GZ37 is the top candidate since it has the highest voltage drop of the indirectly-heated rectifiers, as far as I am aware.  More voltage dropped by the rectifier = less voltage drop needed by the passive supply / CCS = less heat in the chassis = happier components.


You can grab those rectifiers for not too bad of a gouge!


----------



## whirlwind

UntilThen said:


> I'll have that Bcowen. I'll be collecting all 5 volt rectifiers with voltage drop higher than GZ34 and of about 200mA. Gibosi has given me a list.



He has lots of experience rectifier rolling


----------



## UntilThen

whirlwind said:


> He has lots of experience rectifier rolling


That’s why I stalk to him. I will stick with 5 volts though. Didn’t want to use adapters.

Unfortunately I cannot use Sophia Electric 274b. That’s what my amp builder told me.


----------



## bcowen

UntilThen said:


> I'll have that Bcowen. I'll be collecting all 5 volt rectifiers with voltage drop higher than GZ34 and of about 200mA. Gibosi has given me a list.


Uncle Kev has some for a not_ too_ horrible price:

https://upscaleaudio.com/products/mullard-gz37-cv378


----------



## Xcalibur255

So LG why not just use a delay timer instead of restricting your choice of rectifier to those that have the slowest turn on?


----------



## leftside

UntilThen said:


> Thanks ! I've to buy one of these.
> 
> 
> 
> ...


Could well be. Construction can be a little difficult to see with those grey glass tubes.


----------



## L0rdGwyn

Xcalibur255 said:


> So LG why not just use a delay timer instead of restricting your choice of rectifier to those that have the slowest turn on?



Well, certainly could!  But I like that the rectifier provides the soft start and knocks off some excess voltage all in one go.  For me the rectifier isn't for sound.  With my spare Sowter mains transformer, I will have some excess voltage that will need to be dropped somewhere.  Three options for that: 1) across a tube rectifier, 2) across a resistor in the power supply, 3) across the CCS load.  Rectifier is the best option as it gets that heat out of the chassis, plus it looks cool!  I do need a time delay / soft start of some sort, so the indirectly heated rectifier checks that box as well.  So a win-win-win.  A directly heated rectifier doesn't give the same soft start benefit with a much faster warm up (indirectly heated warm up is something like 25-30s).  If for whatever reason the soft start from the indirect rectifier wasn't enough in the completed build, then I would probably add a time delay circuit and any rectifier would be fair game  trying to check all those boxes with one circuit component instead of two, we will see.


----------



## L0rdGwyn

bcowen said:


> You mean like these?



Thanks for offering these Bill.  I will only need four I think, should last me a long time, you can keep the other three, will send my address shortly.


----------



## L0rdGwyn

UntilThen said:


> I wouldn't have thought of 5R4GY but in talking to @gibosi about 5U4G, he told me about it. @L0rdGwyn I reckon you should use a 596 rectifer for show.



That rectifier is a monster, would look pretty funny next to the dinky power tubes in this amplifier.


----------



## Xcalibur255

Will they be operating as pentodes or strapped triodes in the spud?  Given how small those guys are I'm guessing they won't produce much output power as triodes.


----------



## Tjj226 Angel

Xcalibur255 said:


> Will they be operating as pentodes or strapped triodes in the spud?  Given how small those guys are I'm guessing they won't produce much output power as triodes.



They will be triodes. You can't run a tube in UL in a parafeed configuration without resorting to witchcraft. 

The only other solution would be a SEP amp. SEPs can make an ok speaker amp, but not a good headphone amp (IMO). You could theoretically have a switch to go between SET and SEP, but that would be a ton of work for something that sort of defeats the purpose of a spud amp.


----------



## L0rdGwyn (Mar 5, 2021)

Xcalibur255 said:


> Will they be operating as pentodes or strapped triodes in the spud?  Given how small those guys are I'm guessing they won't produce much output power as triodes.



They will be triode-strapped.  Into a 2.5K load, they can do about 2W, enough for a flea-watt speaker setup and any headphone.  Here is a better picture to show the scale next to a 9-pin noval tube.  They are small but beefy!


----------



## Xcalibur255

Yes, when I said pentode I was referring to SEP operation.  Why would it be okay for a speaker load and not a headphone?  Too much negative feedback required?

2W does seem fine for the application though, that's more than I would have expected from a tube that size.


----------



## L0rdGwyn

My partial Thorens TD 125 MkII arrived.



From this I am going to harvest the aluminum front panel, likely the motor (in better shape than the original in my table), and a few other spare parts.  Will be nice to have others on hand as needed.  Will get a replacement armboard for a new arm and a custom wood plinth.  Not sure which arm I will go with, SME 3009 is the classic pairing, but will take a long while to think it over before committing.

This is another long term project, but had to take it out of the box to make sure they didn't sent me a Crosley from Walmart 

I like the custom plinths from this guy's shop, might end up commissioning something custom from him.

https://www.etsy.com/shop/woodoosound?ref=simple-shop-header-name&listing_id=734791299


----------



## bcowen

L0rdGwyn said:


> My partial Thorens TD 125 MkII arrived.
> 
> 
> 
> ...


Nice!  No such thing as too many spare parts.    

That Etsy guy has some nice looking stuff.  Wonder how this sounds (and what it does to the effective mass of the arm)?  Seems like you'd want some big a$$ washers under the screw heads to prevent divots in the wood....which would add even more mass.  But way cool regardless IMO.


----------



## L0rdGwyn

bcowen said:


> Nice!  No such thing as too many spare parts.
> 
> That Etsy guy has some nice looking stuff.  Wonder how this sounds (and what it does to the effective mass of the arm)?  Seems like you'd want some big a$$ washers under the screw heads to prevent divots in the wood....which would add even more mass.  But way cool regardless IMO.



Yeah he has some interesting stuff!  Talented guy (or gal).  Maybe you can tape some pennies on top, or was it quarters?


----------



## Tjj226 Angel

Xcalibur255 said:


> Yes, when I said pentode I was referring to SEP operation.  Why would it be okay for a speaker load and not a headphone?  Too much negative feedback required?
> 
> 2W does seem fine for the application though, that's more than I would have expected from a tube that size.



Well a number of factors, but the big one is that a pentode amp would just be too much output voltage for headphones. 

You would end up having to be very careful with the volume control, or you would have to have some voltage divider network on the output to ensure that you wouldn't blow your headphones.


----------



## L0rdGwyn

Tjj226 Angel said:


> Well a number of factors, but the big one is that a pentode amp would just be too much output voltage for headphones.
> 
> You would end up having to be very careful with the volume control, or you would have to have some voltage divider network on the output to ensure that you wouldn't blow your headphones.



Or just use negative feedback


----------



## L0rdGwyn (Mar 7, 2021)

Since all that lies between me and finishing my 801A amplifier is a vintage radio (and receiving an order from Sowter), I've started collecting some parts that will go in the final build.  Here are some of them.

Vintage Amphenol octal and UX4 sockets.





Kurz-Kasch bakelite volume knobs.

 

NKK toggle power switch.



TKD 2CP-2511 volume pot (no stepped attenuator this time around).



PEC RV4LAYSA503A biasing pots.



As far as signal path components, here is what we are going with, tentatively.


Jupiter copper foil coupling caps
Mills non-inductive wirewound resistors (where applicable)
Riken Ohm carbon film capacitors (where applicable)
Allen Bradley carbon composition resistors (grid stoppers)
Sowter custom 5K:8ohm output transformers
Oh, and the tubes of course!  EF37A / 6J7G, 6BX7, 801A.



This amp is fixed bias, but there will not be any meters, instead I will include insulated test points on the chassis to place leads of a DMM.

I have to prototype one channel of the most up-to-date design before designing the chassis and layout.  There are a few question marks, but I feel good about it, the sims check out.

One thing I am trying out in this prototype is using a VR105 glow tube to regulate the EF37A / 6J7G input tube screens.  The VR105 has no heater, just a cold cathode and filled with argon gas.  Placing a voltage across it ionizes the gas, now plasma.  As the ionized gas is reduced by collisions with stray electrons, a photon is emitted, causing the tube to glow, hence the name "glow tube".  They are engineered to drop a specific voltage across a particular range of current, 105V in this case.



No reason to think it won't work, but these projects always have some hiccups.  If it doesn't work out I will regulate the screens in another form or fashion.

Let's see, anything else...think that's it for now, will have more to share once I throw the prototype together and take some measurements.  This amplifier will do 6-7W into 8ohms.


----------



## L0rdGwyn

Got some new 6N7G pairs today.

Smoked glass Radiotron - $10 + shipping.



Raytheon (although might be Sylvania based on construction) - $10 + shipping.



Mullard ECC31 - not $10 + shipping   



Mullards sound very good, as expected!  Will give the others a listen later this week.


----------



## L0rdGwyn

Oh and a few more of these.  One must always be planning for the future.


----------



## Xcalibur255

Tjj226 Angel said:


> Well a number of factors, but the big one is that a pentode amp would just be too much output voltage for headphones.
> 
> You would end up having to be very careful with the volume control, or you would have to have some voltage divider network on the output to ensure that you wouldn't blow your headphones.



Negative feedback reduces gain right?  So a ton of feedback would fix the problem but probably kill the sound at the same time.  My guess was 180 degrees off the mark.


----------



## L0rdGwyn

Xcalibur255 said:


> Negative feedback reduces gain right?  So a ton of feedback would fix the problem but probably kill the sound at the same time.  My guess was 180 degrees off the mark.



Negative feedback does reduce gain.  It is often used with pentode stages because 1) there is typically an excess of gain, 2) a high output impedance, 3) high distortion (relative to a triode).  Adding negative feedback will linearize the stage and reduce the output impedance, the amount of "extra" gain in the stage will determine how much NFB you are able to apply, you can run into stability issues if you use an excess of NFB.  In my experiments using local NFB in my 801A amplifier over the past several months, it is all about implementation.  Local NFB can vastly improve the sound of an amplifier if done right.  My initial experiments resulted in a third-harmonic dominant distortion spectrum, which resulted in a "tinny" and "thin" sound, not good.  I've made changes to achieve a second-harmonic dominant distortion spectrum with much better results sonically.

Certain prototyped versions of this amplifier I can confidently say were the best I have ever heard FWIW.  Some notable changes have been made, most significantly changing the source follower buffer stage to a cathode follower and the loading / biasing scheme of the pentode input, there are now very few transistors involved.  We'll see how it turns out!  But count me as one who is not afraid to use NFB, it just needs to be done right.


----------



## Tjj226 Angel

Xcalibur255 said:


> Negative feedback reduces gain right?  So a ton of feedback would fix the problem but probably kill the sound at the same time.  My guess was 180 degrees off the mark.



It does, but remember that at 100% plate to screen feedback would be a triode strapped pentode and the gain would still be a factor of 30. 

Even in triode mode, the amp will have a pretty hot voltage output. Let's assume that he will use a 2.5K to 32 ohm transformer for headphones. That would mean that the voltage step down ratio is about 9:1. By the time you add in losses and everything else we can say that the real world step down is 10:1 for simplicity sake. 

When you consider that lordgwyn will be using a 1:2 step up input transformer in combination with the triode strapped E55L, you end up with an effective gain of about 60. Divide that by the step down ratio of 10 and you get a theoretical gain of about 6 for the overall amplifier. With a 2V input you are getting 12v out. 

That is a pretty hot output for a headphone amp, but it isn't too crazy. High impedance headphones can benefit from such a high voltage output and 12V is manageable with a volume control. So considering that the amp is triode mode is already more than enough, imagine what an SEP amp would look like with less than 100% NFB. 

Now he could design it such that the amp would be in triode mode for 32 ohms or 8 ohms, and then have an SEP mode that is locked to 8 ohms. That way you can just run the headphones off the 8 ohm tap and let the transformer deal with the excess gain and noise floor from the pentode operation.


----------



## L0rdGwyn

When are you going to wind your own OPT @Tjj226 Angel ?  I need to live vicariously through you.


----------



## Tjj226 Angel

L0rdGwyn said:


> When are you going to wind your own OPT @Tjj226 Angel ?  I need to live vicariously through you.



By the end of march, I should be more free. The goal is to build a CNC winding machine first. I would like to build one similar to the one in this video 



The thing I like about this machine vs something you can buy off some chinese company is that the wire tensioner should be able to accept almost any gauge of wire. It's also relatively small compared to the size of the transformer you can make. Once that is all done, winding a transformer is simply a matter of doing the math for whatever transformer I want. The next step would be to wind field coil motors and make my own speaker drivers. One of my long held pasion projects is to take this speaker here... 



...and miniaturize it for desktop use. Western electric 555 compression drivers are what makes that system really shine, but they cost more than my two cars, computers, and monthly rent combined. So I have to make it from scratch.


----------



## L0rdGwyn

Tjj226 Angel said:


> By the end of march, I should be more free. The goal is to build a CNC winding machine first. I would like to build one similar to the one in this video
> 
> 
> 
> ...




To the naked eye that transformer winder looks very well-engineered, would be an incredible resource to have.  Amazing speakers, I'm sure there would be high demand for a miniaturized version.  Sounds like the makings of a profitable albeit niche business venture


----------



## bcowen

Tjj226 Angel said:


> By the end of march, I should be more free. The goal is to build a CNC winding machine first. I would like to build one similar to the one in this video
> 
> 
> 
> ...



That winding machine is way cool.  Couldn't see it in the video, but I assume there's some sort of counter or display that tracks the revolutions (which I also assume need to be precise)?


----------



## Tjj226 Angel

L0rdGwyn said:


> To the naked eye that transformer winder looks very well-engineered, would be an incredible resource to have.  Amazing speakers, I'm sure there would be high demand for a miniaturized version.  Sounds like the makings of a profitable albeit niche business venture



It is definitely a sight to behold. He has a couple videos on his channel where he shows more angles and features. The real takeaway is the wire tensioner. Everything else is fairly straightforward. To give some perspective, some wire tensioners being sold for transformer winders are friction based devices. They actually have a drag wheel that pinches your wire. This can work, but you risk damaging the insulation layer of the magnet wire. 

The better wire tensioners will work by providing feedback to a motor that will let wire go from the spool at a very particular rate, however, they cost several hundred if not thousands. This guy's feedback mechanism is that little cart connected to the spring with a piece of linear tape to the side to monitor the position of the cart. This is actually how a printer works and most of these parts can be sourced from a scrap printer to make the cost of the project a lot cheaper while still maintaining a very high degree of accuracy. 

It's pretty freaking ingenious. His design can also be made for a lot cheaper too. I get the feeling that his machine is built the way it is because he had a lot of those parts on hand. If you ditch a lot of the gears and belts by making all your motors direct drive, it should reduce the cost by quite a bit. 

The ONLY modification I would love to make is replacing that spring on the cart with a load cell or a load cell and a spring. That way I can know the amount of tension I put on the wire and dial it in for best performance. Other than that, this machine is probably about as good as it gets. 

I might end up sending you a few practice transformers for you to test considering you have more test equipment than I do : P

---------------------------------------

The speaker is a very different story. It's one thing to build that speaker. It is a completely different thing to figure out how to make it in such a way that it is easy to produce. 

The real achievement will be making a smaller than average mid range horn. That KS-6368 horn on top of the speakers I linked there is nearly flat at 220hz. I want mine to be flat at 300hz, so I should be able to downsize it a bit. That horn is about 16x11 at the mouth, and I am really hoping I can get away with 12x9. If I have a 12 inch wide horn on top of a 12 inch wide woofer cabinet with a 10 inch woofer, it should work out to being just a bit bigger than the snells with better bass extension and much better mid clarity. 

Definitely on the large side, but also doable for a large desk speaker. Or so I think.


----------



## Tjj226 Angel

bcowen said:


> That winding machine is way cool.  Couldn't see it in the video, but I assume there's some sort of counter or display that tracks the revolutions (which I also assume need to be precise)?



It's completely computer controlled, so rather than a counter, the transformer bobbin is attached to a stepper motor and a computer tells the motor to step X number of times. 

Theoretically with a bit more careful thought and engineering, you can set this up to be completely automated. If you really wanted to go crazy, you could have a multiple spindle setup and have some type of CNC taping machine in the mix so that you can slap on some bobbins and a butt load of wire at night and in the morning you would have your PSU, choke, input, output, and interstage transformers all waiting for you.


----------



## whirlwind

Tjj226 Angel said:


> By the end of march, I should be more free. The goal is to build a CNC winding machine first. I would like to build one similar to the one in this video
> 
> 
> 
> ...



This is a great video of the winding machine....cool stuff. Thanks for posting


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## L0rdGwyn (Mar 12, 2021)

Tjj226 Angel said:


> It is definitely a sight to behold. He has a couple videos on his channel where he shows more angles and features. The real takeaway is the wire tensioner. Everything else is fairly straightforward. To give some perspective, some wire tensioners being sold for transformer winders are friction based devices. They actually have a drag wheel that pinches your wire. This can work, but you risk damaging the insulation layer of the magnet wire.
> 
> The better wire tensioners will work by providing feedback to a motor that will let wire go from the spool at a very particular rate, however, they cost several hundred if not thousands. This guy's feedback mechanism is that little cart connected to the spring with a piece of linear tape to the side to monitor the position of the cart. This is actually how a printer works and most of these parts can be sourced from a scrap printer to make the cost of the project a lot cheaper while still maintaining a very high degree of accuracy.
> 
> ...



Looks great, will be excited to see where this goes, and happy to help out with testing if I have the necessary equipment  need to make some upgrades come to think of it, particularly my function generator.


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## L0rdGwyn (Mar 12, 2021)

I have been hard at work the past two days making preparations for the 801A amplifier.

Placed a mega parts order at Hificollective.  Excited to show off what is going in, will post some pics of the parts pile when it arrives.

In the meantime, here is my little pile so far.  Still need to stuff the Coleman regs.




I am finalizing one last Mouser order, then theoretically I will have everything but the mains transformer from Sowter...and some PCBs.

The bulk of the work the past two days has been designing power supply PCBs.  This amp is fixed bias, will have a Maida regulated B+ and shunt regulated negative supply.

For the shunt regulated supply, I put together a raw DC board.



Then a pair of regulator boards that will be mounted in close proximity to where they will be used in circuit.



This is definitely not a "just build it" type of design, it will need a final prototype, so that is the last step before the layout and chassis can be worked on.


----------



## m17xr2b

I already have tungsten rectifiers so no reason to get them but I though they'd work well in your 842 amp.
https://www.ebay.com/itm/PAIR-NOS-I...ON-UX-216B-GLOBE-RECTIFIER-TUBES/303857004641


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## L0rdGwyn (Mar 12, 2021)

m17xr2b said:


> I already have tungsten rectifiers so no reason to get them but I though they'd work well in your 842 amp.
> https://www.ebay.com/itm/PAIR-NOS-I...ON-UX-216B-GLOBE-RECTIFIER-TUBES/303857004641



Very cool!  Interesting rectifier.  I'm pretty committed to solid state rectification, a pair of UX216B can't quite meet the DC current demands of the design (around 181mA) but thanks for the link.  It is an 801A output rather than 842, would love to build with the 842, but that is one rare tube  my headphone amplifier is an 841 build, with 842 I could complete the trifecta


----------



## L0rdGwyn (Mar 12, 2021)

Found a much cooler vintage bakelite volume knob.  The ones I purchased I worry are too small, might look / feel too dinky on the front panel of a 3.25" thick chassis.

The skirt of this one is 2" and I like the aesthetic  10/10 projected knob feel.


----------



## bcowen

L0rdGwyn said:


> Found a much cooler vintage bakelite volume knob.  The ones I purchased I worry are too small, might look / feel too dinky on the front panel of a 3.25" thick chassis.
> 
> The skirt of this one is 2" and I like the aesthetic  10/10 projected knob feel.


Love it!  And those transformers look pretty sweet too.  They're the outputs, I presume?


----------



## L0rdGwyn (Mar 12, 2021)

bcowen said:


> Love it!  And those transformers look pretty sweet too.  They're the outputs, I presume?



Yessir!  Output transformers, custom wound by Sowter for this design, 5K:8ohm single secondary rated for 60mA on the primary.  I may bias at 55mA for tube longevity, we will see.

Here is the a 320V 55mA load line, around -3V bias on the grid.  In a "typical" single ended class A1 design, the positive portion of grid swing is not accessible and the 0V grid line represents a barrier where clipping will occur due to grid current.  However, if you supply the requested current, and the tube is made for A2 operation, you can drive the grid positive and increase output voltage swing.  At saturation (maximum swing to the left), the grids will draw 15-20mA 😯 provided by a DC-coupled cathode follower.  801A in class A1 can do about 3W with a 600Vish B+.  801A in A2 can do 7W with a 320V B+  but this type of design is not easy, which is why I have been working on it for so long, and local NFB is a must (can also use a high primary impedance OPT, but that has its own problems, compromises, compromises...).


----------



## Galapac

L0rdGwyn said:


> Yessir!  Output transformers, custom wound by Sowter for this design, 5K:8ohm single secondary rated for 60mA on the primary.  I may bias at 55mA for tube longevity, we will see.
> 
> Here is the a 320V 55mA load line, around -3V bias on the grid.  In a "typical" single ended class A1 design, the positive portion of grid swing is not accessible and the 0V grid line represents a barrier where clipping will occur due to grid current.  However, if you supply the requested current, and the tube is made for A2 operation, you can drive the grid positive and increase output voltage swing.  At saturation (maximum swing to the left), the grids will draw 15-20mA 😯 provided by a DC-coupled cathode follower.  801A in class A1 can do about 3W with a 600Vish B+.  801A in A2 can do 7W with a 320V B+  but this type of design is not easy, which is why I have been working on it for so long, and local NFB is a must (can also use a high primary impedance OPT, but that has its own problems, compromises, compromises...).


Now if only you could design your own tubes to "rectify" the compromises...


----------



## L0rdGwyn

I was taking some measurements of my 841 amplifier and came across an intermittent RF oscillation gremlin, better get rid of it.  I snuffed it out, but had to add some components to the source follower boards.  So they are getting an overhaul, here are the new ones.

 

Alright, that's it for PCB designing, now the wait.


----------



## bcowen

L0rdGwyn said:


> I was taking some measurements of my 841 amplifier and came across an intermittent RF oscillation gremlin, better get rid of it.  I snuffed it out, but had to add some components to the source follower boards.  So they are getting an overhaul, here are the new ones.
> 
> 
> 
> Alright, that's it for PCB designing, now the wait.


If you don't mind me asking, once you've drawn the board about how much does it cost to get one made (for a small one like this)?


----------



## L0rdGwyn (Mar 12, 2021)

bcowen said:


> If you don't mind me asking, once you've drawn the board about how much does it cost to get one made (for a small one like this)?



Depends on if you go with HASL vs ENIG surface finish.  For example, for a set of five of one of the boards above, going from HASL to ENIG the price jumps from $2.00 to $18.00.  Either way though, since these are manufactured in China through JLCPCB, the real cost is the shipping!

The cost isn't huge, but designing and laying out the boards is time consuming.


----------



## L0rdGwyn

Here is a little overview of HASL vs ENIG.

https://www.ourpcb.com/hasl-vs-enig.html


----------



## bcowen

L0rdGwyn said:


> Here is a little overview of HASL vs ENIG.
> 
> https://www.ourpcb.com/hasl-vs-enig.html


Thanks!!


----------



## L0rdGwyn (Mar 12, 2021)

I'm basically just messing with tube stuff all day since I don't have to work, very surprising I know.

Picked up yet another pair of 6A5G.  Don't be fooled by the branding, these were only ever made by Sylvania and Visseaux (under Sylvania license).  I have several pairs but never hurts to have one more right?  Especially at a good price.  Got this pair for $53 + shipping.



I'm just going to list off what I have on the way for the 801A amp, I can't wait, here are the parts from Hificollective and a few extras I haven't mentioned yet.

Jupiter copper foil coupling caps.  There will be two coupling caps in this amplifier (at least as currently planned), there is an element of battery bias on the pentode gain stage (it's sort of a mixed bias situation), necessitating an input capacitor, then a coupling cap between the pentode and cathode follower, so 0.22uF and 0.1uF will be used.



Removeable anode cap cable for the EF37A / 6J7G - nickel-plated top caps (might seek out something fancier), Audio Note silver-plated RCA paired with Audio Note silver-plated RCA plugs.  A removeable grid cap connection will be made using these and will connect to the chassis via RCA, if that makes sense.

  

KLE Innovations Naked Harmony binding posts.  Thought these looked cool and wanted to try them out, work with the aesthetic I am going for.



TKD 2CP-2511 50K pot.  Decided to go with a conventional potentiometer this time around as opposed to a stepped attenuator.  Of course it will pair with my new bakelite knob from above 

 

I will be RC decoupling the pentode stage from the 6BX7 cathode follower / 801A output, both the positive and negative supplies.  For that, I will be using Clarity Cap ESA caps.



Amphenol RCA jacks.  I am going to do something a bit unconventional and put them on the front of the chassis near the pot.



I will use my usual Switchcraft 152B headphone jack.



For the color, I want something vintage-ish, not flashy, not sleek, sort of boring lol contrasted by an eclectic array of parts.

One that I have had my eye on is a glossy "burnt brown" from Prismatic Powders.  I know it won't please some, but I think it would work well with what I have in mind.  Might get a small sample to spray at home so I can see it in real life before committing, still thinking this one over.



Another option might be a gloss gray (Edit: actually liking this idea more and more as I think about it...).



Part of the aesthetic inspiration is this line of Asano SET amplifiers.



That's all I can think of at the moment...should be an interesting build!  Fingers crossed on the prototype.


----------



## whirlwind

Those 6A5G's look nice.


----------



## L0rdGwyn (Mar 13, 2021)

I bought a pair of tubes I've be interested in having on hand for future experimentation, RFT EC360.  Like the 6080 / 6AS7G, the EC360 is a low mu, low Rp regulator triode.  However, it is a single triode unit as opposed to dual triode with a package similar to that of the EL34.



So let's trace some curves and see what we've got.



At the operating point listed in the datasheet, the numbers add up with a plate resistance of around 120ohm.  However, at what I would consider to be a more likely operating point (say 125-150V, 125-150mA) plate resistance is around 200ohm.  Could make for an interesting OTL headphone amplifier.


----------



## bcowen

L0rdGwyn said:


> I bought a pair of tubes I've be interested in having on hand for future experimentation, RFT EC360.  Like the 6080 / 6AS7G, the EC360 is a low mu, low Rp regulator triode.  However, it is a single triode unit as opposed to dual triode with a package similar to that of the EL34.
> 
> 
> 
> ...


Pretty tubes!  My German is a little rusty, but at least we speak the same language in Triode.    

It looks like you can run this at 12.6v (with half the current draw) on the heaters as well?


----------



## L0rdGwyn

bcowen said:


> Pretty tubes!  My German is a little rusty, but at least we speak the same language in Triode.
> 
> It looks like you can run this at 12.6v (with half the current draw) on the heaters as well?



Yup, similar to a 12AU7, 12AX7, etc.  the heaters can be run in series or parallel for 12.6V or 6.3V, respectively.


----------



## Zachik

L0rdGwyn said:


> At the operating point listed in the datasheet, the numbers add up with a plate resistance of around 120ohm. However, at what I would consider to be a more likely operating point (say 125-150V, 125-150mA) plate resistance is around 200ohm.


I am curious: why do you say that 125V to 150V is a more likely operating point for this tube?


----------



## L0rdGwyn

Zachik said:


> I am curious: why do you say that 125V to 150V is a more likely operating point for this tube?



Operating point from the datasheet is 60V 200mA with -7V on the grid for the tube's intended use as a DC regulator.  In an audio circuit as a cathode follower, the grid will need to swing the output signal from the driver, so -7V on the grid isn't going to work.  If biased at -7V, the grid will only be able to swing max 14Vpk-pk before clipping, which will make for a pretty crummy amplifier!  Needs to be biased at a point where the grid can swing the full peak-to-peak signal from the input tube.


----------



## Tjj226 Angel

bcowen said:


> Pretty tubes!  My German is a little rusty, but at least we speak the same language in Triode.
> 
> It looks like you can run this at 12.6v (with half the current draw) on the heaters as well?



You gotta be careful with that. Sometimes tubes do have an affinity for 6.3 or 12.6v operation. I doesn't make a whole lot of sense to me because half the voltage at double the amperage or double the voltage at half the amperage still equals the same amount of watts. And considering our goal with the heater is to literally heat it up, you would tend to think that the configuration of the heater almost wouldn't matter. 

And yet, there are quite a few articles and people with far more experience than me who say that some tubes have preferences for how you run the heater.


----------



## Tom-s (Mar 14, 2021)

Could you point to some reading material @Tjj226 Angel .
Most of what i've noted regarding that topic has to do with an even heating method for DHT's.
From what i take away when reading posts about heaters (as on the EML/JAC websites).
If it has a center tap. It's better to use it. The EC360 is on my radar aswel (and in the collection).
For use on my next Crack amplifier build.

Edit: What i try to say is. It doesn't seem to matter much with IDH tubes. Anyway the lowest voltage will make for the longest life (smallest dV on the heater).

Here's some reading material i refer to.
http://emissionlabs.com/Articles/TECH-BULLETIN/TB-05-Heater-Voltage/TB-05-Heater-Voltage.html
http://emissionlabs.com/Articles/APP-NOTES/AN-06-Center-tap/center-tapped-index.html


----------



## Tjj226 Angel

Tom-s said:


> Could you point to some reading material @Tjj226 Angel .
> Most of what i've noted regarding that topic has to do with an even heating method for DHT's.
> From what i take away when reading posts about heaters (as on the EML/JAC websites).
> If it has a center tap. It's better to use it. The EC360 is on my radar aswel (and in the collection).
> ...



If I don't post anything in the next 48 hours remind me to do so. I'm in the shop right now since it is finally starting to warm up. : )

And to be clear, it is not like every IDHT has a preference. Hell, most IDHTs don't have a way to configure the heater in the first place. It's just that some IDHTs seems to exhibit different emission characteristics based on how the heater is configured. 

I know there is at least one article that is easy to find online, I just gotta remember what tube they were looking at.


----------



## L0rdGwyn (Mar 17, 2021)

I have sort of an announcement to make - I've decided I will not be continuing with this thread anymore.  Furthermore, I won't be spending much time on Head-Fi going forward.

The reasoning is multifactorial, but the primary motivator is that maintaining this thread, as well as the habitual checking of Head-Fi, has become a negative influence and is consuming too much of my personal time.  Outside of this thread and two or three other tube-oriented threads, I do not engage much in the community, call me disillusioned I guess.  I'm sure it's obvious, but I am primarily interested in DIY audio, not necessarily just headphone audio.  The past few days have been sort of a trial run where I turned off all Head-Fi notifications and went cold turkey, and I can honestly say it has been nothing but positive.  I've also come to realize that I do not have the patience to build and sell amplifiers in any capacity here.

For now, I won't be doing anything as drastic as deactivating my account (assuming that is possible, I need to check with the mods) as I would be concerned this thread would disappear.  I've learned that it has become a learning resource for quite a few people, so I would like it to remain available.

So yeah, that's it, it has been a great run, thank you for everyone who followed along for the past year or so, it will make me sad to see Head-Fiers disappointed in my decision, but it is what's best for me personally.  I may check in from time-to-time and see how people are doing, I have met lots of great people on Head-Fi.  I will remain active on diyAudio I am certain, but not to the same degree that I have been active here, it just isn't that kind of forum.

Happy to explain my reasoning, but please do not try to change my mind!  I think it is time to move on.


----------



## m17xr2b

Hey, thanks for the content so far, it's been entertaining and informative, do your own thing and be happy.


----------



## bcowen (Mar 17, 2021)

L0rdGwyn said:


> I have sort of an announcement to make - I've decided I will not be continuing with this thread anymore.  Furthermore, I won't be spending much time on Head-Fi going forward.
> 
> The reasoning is multifactorial, but the primary motivator is that maintaining this thread, as well as the habitual checking of Head-Fi, has become a negative influence and is consuming too much of my personal time.  Outside of this thread and two or three other tube-oriented threads, I do not engage much in the community, call me disillusioned I guess.  I'm sure it's obvious, but I am primarily interested in DIY audio, not necessarily just headphone audio.  The past few days have been sort of a trial run where I turned off all Head-Fi notifications and went cold turkey, and I can honestly say it has been nothing but positive.  I've also come to realize that I do not have the patience to build and sell amplifiers in any capacity here.
> 
> ...


Well that's a bummer.  I've greatly enjoyed your contributions and you freely sharing your experience and knowledge, and have learned a lot along the way.  I won't try and dissuade you, only hope that you'll pop in every now and then just to say howdy if nothing else.  Best of _everything_ to you going forward!


----------



## whirlwind (Mar 17, 2021)

Thanks for all of the projects that you posted Keenan, it was much enjoyable following them. I was really interested in the EL34 build, but I totally understand.
I wish you nothing but the best brother, take care, be safe, enjoy whatever DIY stuff you get into, and thanks for everything you do in your everyday job and putting new sockets in my amp   

Kudos to you!


----------



## Zachik

@L0rdGwyn - you will be greatly missed, my friend! 
Not trying to change your mind - I truly hope to see you pop in every now and then...


----------



## CJG888

I also have to say: I understand your decision. Forums like this can be a great thief of time...

Thank you for your invaluable contribution, which has always been offbeat and interesting (and has inspired me to look at valve amplification a little “sideways”).

All the best!


----------



## Velozity

L0rdGwyn said:


> I have sort of an announcement to make - I've decided I will not be continuing with this thread anymore.  Furthermore, I won't be spending much time on Head-Fi going forward.
> 
> The reasoning is multifactorial, but the primary motivator is that maintaining this thread, as well as the habitual checking of Head-Fi, has become a negative influence and is consuming too much of my personal time.  Outside of this thread and two or three other tube-oriented threads, I do not engage much in the community, call me disillusioned I guess.  I'm sure it's obvious, but I am primarily interested in DIY audio, not necessarily just headphone audio.  The past few days have been sort of a trial run where I turned off all Head-Fi notifications and went cold turkey, and I can honestly say it has been nothing but positive.  I've also come to realize that I do not have the patience to build and sell amplifiers in any capacity here.
> 
> ...




Boooooooooo!  

  Just kidding, good luck Keenan.  Your knowledge will be missed!  Don't worry, the thread won't die.  I'll be sure to come back and bump it every St. Patrick's Day at least  .


----------



## Xcalibur255

You are 100% correct you have to take care of yourself and spend your time in the ways you feel are best.  I've enjoyed following your enthusiasm Keenan and will feel its absense but I completely understand where you are coming from.  Best wishes and I certainly do hope you are inclined to stay in touch with us at some level even if it's infrequent.


----------



## leftside

It's been a good read! Enjoy your spare time away - maybe you'll come back at some point.


----------



## mordy

Wishing you well in all your endeavors! With all the talent you have I was looking forward to the design of an inexpensive headphone amp made with off-the-shelf parts with the focus on the price/performance ratio.
Maybe one day....


----------



## A2029

Wishing you all the best in your future endeavors, my friend. You are a wonderful part of this community and will surely be missed! Hit me up at anytime if you'd like to chat


----------



## L0rdGwyn

Thank you for the well wishes everyone and for your understanding.  Have had a lot of fun with the tubehead community here, I will try not to be a complete stranger and check in now and then!


----------



## carlman14

Best wishes going forward! It's so important to take care of yourself first. I was never active here, but I followed it from the beginning and applied much of what I learned here in my own DIY efforts. Hope to see you back every now and again!


----------



## miketlse

L0rdGwyn said:


> I have sort of an announcement to make - I've decided I will not be continuing with this thread anymore.  Furthermore, I won't be spending much time on Head-Fi going forward.
> 
> The reasoning is multifactorial, but the primary motivator is that maintaining this thread, as well as the habitual checking of Head-Fi, has become a negative influence and is consuming too much of my personal time.  Outside of this thread and two or three other tube-oriented threads, I do not engage much in the community, call me disillusioned I guess.  I'm sure it's obvious, but I am primarily interested in DIY audio, not necessarily just headphone audio.  The past few days have been sort of a trial run where I turned off all Head-Fi notifications and went cold turkey, and I can honestly say it has been nothing but positive.  I've also come to realize that I do not have the patience to build and sell amplifiers in any capacity here.
> 
> ...


Hello @L0rdGwyn I remember a post from a few years ago, when I was told that very cheap valve amplifiers added distortion, but more expensive amplifiers were truly transparent. Just reading a small section of this thread, has flagged up the costs of using the appropriate tubes, plus high quality transformers, plus good quality capacitors etc.
I would be sad to see you go, but your posts represent a valuable knowledge base for future tube enthusiasts.


----------



## Ripper2860

Sad news indeed.   

Best of luck and thanks for sharing your time and efforts with the community.


----------



## UntilThen (Mar 25, 2021)

L0rdGwyn said:


> I have sort of an announcement to make - I've decided I will not be continuing with this thread anymore. Furthermore, I won't be spending much time on Head-Fi going forward.



Keenan, guess I only found out today when Joe told me. I will definitely not stop you because a decision such as this is personal. I myself have such thoughts over the years but I've given up leaving because UntilThen never leaves. It's always until then. 

Well I just want to thank you and your sister for doing this mock up for me a few years ago when I was still in the GOTL thread. I will always remember Berlin but it will be Odyssey in a few months time.

Take care and all the best. Anytime you want to catch up, just drop me a pm. Cheers UT.


----------



## bcowen

UntilThen said:


> Keenan, guess I only found out today when Joe told. I will definitely not stop you because a decision such as this is personal. I myself have such thoughts over the years but I've given up leaving because UntilThen never leaves. It's always until then.
> 
> Well I just want to thank you and your sister for doing this mock up for me a few years ago when I was still in the GOTL thread. I will always remember Berlin but it will be Odyssey in a few months time.
> 
> Take care and all the best. Anytime you want to catch up, just drop me a pm. Cheers UT.


Does the sound change any with the anode caps connected?


----------



## johnjen

bcowen said:


> Does the sound change any with the anode caps connected?


Well D'uh, of course!!!

But for the full dynamic experience, where your teeth rattle in tune with the music, you have to grab both of those connections.
That's when the music comes alive and you can't help but jerk along with the beat.  
hahahahahahahahahahahahahaha  

JJ


----------



## UntilThen

bcowen said:


> Does the sound change any with the anode caps connected?



That's Keenan's masterpiece. Don't you dare connect any cap to the top anode. I'm going to find some way to show it to him when Odyssey build is complete. Then and only then will I connect the top anode cap.

In the meantime, we've work to do. I have to win the US Master this year and you're my caddy. Fortunately or unfortunately.


----------



## bcowen

UntilThen said:


> That's Keenan's masterpiece. Don't you dare connect any cap to the top anode. I'm going to find some way to show it to him when Odyssey build is complete. Then and only then will I connect the top anode cap.
> 
> In the meantime, we've work to do. I have to win the US Master this year and you're my caddy. Fortunately or unfortunately.


No worries.  I have your driver all tuned for a fast green.  If it rains, we're screwed....but I'll get to work on the 3 wood just in case.  Putters are for babies.


----------



## UntilThen

bcowen said:


> No worries.  I have your driver all tuned for a fast green.  If it rains, we're screwed....but I'll get to work on the 3 wood just in case.  Putters are for babies.


Hahaha you're hilarous. No putters ! We go for hole in one.


----------



## bcowen (Mar 25, 2021)

UntilThen said:


> Hahaha you're hilarous. No putters ! We go for hole in one.


That's why I like being your caddy even though the pay sucks. Go for the gusto, or just don't go. Well, the Ferrari V-12 you dropped into the golf cart is an allure too (unless it gets wet).


----------



## Tjj226 Angel

Just a side note for the people who still want to learn about tubes and amplifiers in general. 

There is a book by Morgan Jones of the BBC (Morgan Jones Valve Amplifiers 4th edition) that talks all about tube amps. He talks about the electrical theory, design, testing, and tweaking tube amps to achieve the best possible sound. 

It may not be as fun as watching this thread, but when you finish reading the book, you can go start your own tube amp building thread.


----------



## Zachik

bcowen said:


> Does the sound change any with the anode caps connected?





UntilThen said:


> That's Keenan's masterpiece. Don't you dare connect any cap to the top anode. I'm going to find some way to show it to him when Odyssey build is complete. Then and only then will I connect the top anode cap.


@bcowen - this is 2021 buddy. Wireless anode caps!!


----------



## bcowen

Zachik said:


> @bcowen - this is 2021 buddy. Wireless anode caps!!



Bluetooth?  Heresy!!!


----------



## UntilThen

bcowen said:


> Bluetooth?  Heresy!!!


Bluetooth and voice activation. Apple will be making my next amp.


----------



## bcowen

UntilThen said:


> Bluetooth and voice activation. Apple will be making my next amp.


Then it'll probably be named the Granny Smith.


----------



## UntilThen

bcowen said:


> Then it'll probably be named the Granny Smith.


Mustard !  Can't spell it with a Ba...   Your employment as a caddy will be reviewed. Pay will be revised !!!!   down of course.


----------



## bcowen

UntilThen said:


> Pay will be revised !!!!   down of course.


Well that's gonna kind of suck.  Any lower and I'll be paying you.  I'm gullible and all, but my banker isn't.


----------



## UntilThen

bcowen said:


> Well that's gonna kind of suck.  Any lower and I'll be paying you.  I'm gullible and all, but my banker isn't.


I need this tooing and frooing with you each day to start my day... now I'm invigorated ... thanks mate .. ready to log on my work PC and face what comes my way. Nothing can be worst !


----------



## gibosi

L0rdGwyn said:


> I have sort of an announcement to make - I've decided I will not be continuing with this thread anymore.  Furthermore, I won't be spending much time on Head-Fi going forward.
> 
> The reasoning is multifactorial, but the primary motivator is that maintaining this thread, as well as the habitual checking of Head-Fi, has become a negative influence and is consuming too much of my personal time.  Outside of this thread and two or three other tube-oriented threads, I do not engage much in the community, call me disillusioned I guess.  I'm sure it's obvious, but I am primarily interested in DIY audio, not necessarily just headphone audio.  The past few days have been sort of a trial run where I turned off all Head-Fi notifications and went cold turkey, and I can honestly say it has been nothing but positive.  I've also come to realize that I do not have the patience to build and sell amplifiers in any capacity here.
> 
> ...



Obviously, you will be missed, but I hope you will stay in touch. 

Cheers!


----------



## leftside

@L0rdGwyn if you're still checking tube curves, I found some data here for 4654, 4699, etc:
http://www.tubebbs.com/tubedata/sheets/046/suppinfo/02/06_power-output-valves.pdf


----------



## L0rdGwyn (Mar 31, 2021)

Figured I'd pop in and say thanks to everyone I missed, so thanks!  Still won't be on regularly, but thought I'd do a quick lurker check and say hi.

Cool document @leftside , looks like only pentode curves included for the 4653, 4699, but will be very easy to trace triode curves when you get your etracer, I have been putting mine to good use.  4641 is similar to PX25, some impressive triode curves there.

I'm still chugging along DIY-wise.  I am constructing a more official workbench / soldering station at the moment, will be a big upgrade in terms of my work space.  I am also building a single-ended prototyping board, figured that I might as well make something flexible and reusable while I am bench-testing my 801A amp.  Will be used for future amplifier designs with the skeleton in place, will make throwing together an amp and listening / taking measurements relatively easy.

I've also decided what I am building after the 801A amp, another A2 transmitting triode design based on the HK54.  Will make about 15W single-ended.


----------



## bcowen

L0rdGwyn said:


> Figured I'd pop in and say thanks to everyone I missed, so thanks!  Still won't be on regularly, but thought I'd do a quick lurker check and say hi.
> 
> Cool document @leftside , looks like only pentode curves included for the 4653, 4699, but will be very easy to trace triode curves when you get your etracer, I have been putting mine to good use.  4641 is similar to PX25, some impressive triode curves there.
> 
> ...


Sweet!!  And good to see you pop back in if only briefly.  I love those external caps.  I'm going to have to find some just for the coolness factor.


----------



## UntilThen

Keenan good to see you pop in. Do that more often. I mean if you look at me, I'm still here despite Bcowen driving the cart into the lake time and again. Btw Odyssey has progressed to the 2nd phase.... orders for Sowters transfo has been made and Yamamoto sockets are just about to be made.... so yeah small baby steps but getting there.


----------



## whirlwind

Hey Keenan...nice to see you....maybe at least post a pic of each amp you build....I like to froth at the mouth  now and then.  
Hope all is well and some of the stress has left....happy building.


----------



## L0rdGwyn

bcowen said:


> Sweet!!  And good to see you pop back in if only briefly.  I love those external caps.  I'm going to have to find some just for the coolness factor.



Yeah they are pretty cool! These will need some sort of ventilated transparent shield to avoid electrocution lol likely will design something custom.



UntilThen said:


> Keenan good to see you pop in. Do that more often. I mean if you look at me, I'm still here despite Bcowen driving the cart into the lake time and again. Btw Odyssey has progressed to the 2nd phase.... orders for Sowters transfo has been made and Yamamoto sockets are just about to be made.... so yeah small baby steps but getting there.



Awesome, I'm sure it will be a great amp, the wait for Sowter is long but will be worth it!



whirlwind said:


> Hey Keenan...nice to see you....maybe at least post a pic of each amp you build....I like to froth at the mouth  now and then.
> Hope all is well and some of the stress has left....happy building.



Hey Joe- I was thinking I would do that actually, I'll at least post some pictures when I complete a project.  Definitely getting a lot done!  Been a very busy two weeks.


----------



## stasprof

Great built and some endless source of inspiration for my next DIY project! Thanks a lot L0rdGwyn!


----------



## L0rdGwyn (Apr 23, 2021)

Well it's been a couple weeks, feels like much longer, this is a lifetime in DIY years...a lot has happened so thought I would post a little update, keep it short and sweet without all the technical mumbo jumbo.

Here is the radio I am restoring, it is 95% done, just needs an IF / RF alignment, which might necessitate getting an RF signal generator that can do signal modulation...TBD on that front.  This radio is from 1948, polished up the bakelite nice and shiny.

 

I think I mentioned I was building a tube amplifier protoboard, it is done, here is a single channel of my 801A A2 amplifier built out on it.  I'll finish the other channel today.



This is a pretty complex amplifier, at least by my standards, very much a 'DIY Only' affair.  The screens of the EF37A pentode inputs are regulated by a VR105 glow tube, which makes for a very nice effect.  That is ionized argon gas, aka plasma.



You might have noticed from the other pics, I have significantly upgraded my DIY work area digs.  I built a workbench in my basement.  My DIY life is so, so, SO much better, and more efficient.



Last thing - I am going to build a solid-state power amplifier, but not just any, will use SITs, aka VFETs.  These transistors, re-popularized by Nelson Pass' First Watt line, have triode-like characteristics, can be operated in single-ended class A without use of negative feedback, or output transformers given their very low drain resistance.  They are on the verge of extinction, so figured I'd grab some while they are still available.  I have a design drafted, but realistically this is quite far away.



Here are the curves of this particular one, THF-51S.



Okay, that's all I've got!  I have been lurking here and there, hope everyone is enjoying their tube / amp rolls


----------



## whirlwind

Hey Keenan.....dang, you have been busy. 
Just wow!    

I am jelly of that damn radio...I so wish I would have kept a few of these. Now they look so damn cool!

Your new work station looks great and I don't have words for the tube amplifier protoboard.

It is great to see the projects you are working on...I hope sincerely all is well and that your job has been at least somewhat better now that some are vaccinated.


----------



## UntilThen

I see Sowter transformers in the 2nd picture.


----------



## L0rdGwyn

whirlwind said:


> Hey Keenan.....dang, you have been busy.
> Just wow!
> 
> I am jelly of that damn radio...I so wish I would have kept a few of these. Now they look so damn cool!
> ...



Hey Joe - yes, very!  I am also in the middle of a staycation, so DIY efforts have been off the rails, I have gotten a lot done.  Really happy with how the radio is turning out, sort of a bigger PITA than I anticipated, HA!  Recapping the entire thing was a LOT of fun.  It is a belated birthday gift for my girlfriend.

The situation at work is much better!  Hopefully it keeps trending that way, I think it will.  Hope you and yours are well and keeping from going stir crazy.  We'll see what those Brownies do in the draft in a few days, right in my backyard.


----------



## L0rdGwyn

UntilThen said:


> I see Sowter transformers in the 2nd picture.



That's right!  All custom work done for this amplifier, it was quite a wait.  The output transformers are 5K:8ohm, gapped for 60mA DC, but the truly impressive feat is the big mains transformer.  It has a 300V B+ winding, 100V B- winding, two 10V 4A filament windings for the 801A, a 6.3V winding for the pentode and cathode follower heaters, and three electrostatic shields.  It is a monster, and working out very well.

Just finished actually, having a listen now 

Hey look what you did @Xcalibur255 !  I finally did it, now it just needs a box.


----------



## UntilThen

L0rdGwyn said:


> That's right! All custom work done for this amplifier, it was quite a wait. The output transformers are 5K:8ohm, gapped for 60mA DC, but the truly impressive feat is the big mains transformer. It has a 300V B+ winding, 100V B- winding, two 10V 4A filament windings for the 801A, a 6.3V winding for the pentode and cathode follower heaters, and three electrostatic shields. It is a monster, and working out very well.



Very impressive indeed and I'm envious.  A little setback for me when I learn that Sowter will stop making customized power transformers. Not to be deterred, will still go ahead with Sowter output transformers and another reputable power transformer for Odyssey.

That 801A build is fascinating. Along with Odyssey being built in June, I have a 300b amp built ongoing. What say you, build me a 845 in 2023?  That is if I'm still in this world of tube amps.  

Stay well.


----------



## L0rdGwyn

UntilThen said:


> Very impressive indeed and I'm envious.  A little setback for me when I learn that Sowter will stop making customized power transformers. Not to be deterred, will still go ahead with Sowter output transformers and another reputable power transformer for Odyssey.
> 
> That 801A build is fascinating. Along with Odyssey being built in June, I have a 300b amp built ongoing. What say you, build me a 845 in 2023?  That is if I'm still in this world of tube amps.
> 
> Stay well.



I wasn't aware they had stopped, must be part of the Carnhill takeover, that is terrible news really, but very glad I had this one made beforehand.  There are very few companies still doing it at this point, I hope this isn't a trend.  I'm sure you will be happy with another mains transformer, it is really only an issue when you need oddball winding combinations.

Sounds like you have some very nice amplifiers on the way, I'm sure you will be pleased, I didn't know about the 300B.  845 is a beast, have to be okay with high voltages in your amplifiers, keep the doggies and kiddos away


----------



## L0rdGwyn

Things may change as I will likely play with increasing / decreasing the amount of negative feedback, but here are measurements of this particular iteration.

Output Z: 1.53ohm
Power: 6.2W into 8ohm

1W into 8ohm FFT



Frequency response


----------



## UntilThen

L0rdGwyn said:


> Sounds like you have some very nice amplifiers on the way, I'm sure you will be pleased, I didn't know about the 300B. 845 is a beast, have to be okay with high voltages in your amplifiers, keep the doggies and kiddos away



Known only to me but the 300b project would have gone to you but I thought you needed alone time... which we all do.  

The 845 would be a speakers only amp to drive my tower speakers. Kiddos have grown and they are getting me a LCD4... should be arriving next week. As for doggies there's only a cute cavoodle and he's trained to tube roll for me.


----------



## leftside

UntilThen said:


> Very impressive indeed and I'm envious.  A little setback for me when I learn that Sowter will stop making customized power transformers. Not to be deterred, will still go ahead with Sowter output transformers and another reputable power transformer for Odyssey.
> 
> That 801A build is fascinating. Along with Odyssey being built in June, I have a 300b amp built ongoing. What say you, build me a 845 in 2023?  That is if I'm still in this world of tube amps.
> 
> Stay well.


I'm still waiting for the Sowter output transformers for Red Dwarf. Using Lundahl for the power transformers.


----------



## UntilThen

Interesting Leftside. Any special windings on the Lundahl?


----------



## leftside

UntilThen said:


> Interesting Leftside. Any special windings on the Lundahl?


Don't think so. @A2029 would know for sure.


----------



## L0rdGwyn

I lugged the beast into my stereo.  The sound is superb, very impressive.  Will do a little more tinkering, but will begin designing the box.  The aesthetic choices are already made, just a matter of finalizing the layout and getting it in AutoCAD.


----------



## Xcalibur255

If I really did have some influence in this then I gladly accept responsibility for what has come of it.

Love the Zenith radio btw.  Now you just need to find and restore a Super Air Castle one (yes, I am obsessed with this brand name..... makes me smile every time).

Good to hear from you Keenan.


----------



## Galapac

@L0rdGwyn thanks for dropping by for an update and glad to hear you‘re happy. Keep us updated on your projects and I would love to see the beast when it has its clothes on. 😎


----------



## L0rdGwyn

Xcalibur255 said:


> If I really did have some influence in this then I gladly accept responsibility for what has come of it.
> 
> Love the Zenith radio btw.  Now you just need to find and restore a Super Air Castle one (yes, I am obsessed with this brand name..... makes me smile every time).
> 
> Good to hear from you Keenan.



Thanks!  I think it has a nice aesthetic, have to put it somewhere it will be seen  hope everything is going well with you @Xcalibur255 



Galapac said:


> @L0rdGwyn thanks for dropping by for an update and glad to hear you‘re happy. Keep us updated on your projects and I would love to see the beast when it has its clothes on. 😎



Will do @Galapac  !  I would say at least a month, probably longer before it gets its chassis.  Going to take my time with it and get it right.

After that is an amplifier on a whole new level of crazy, we'll see what happens with the HK54...another long-term type of design, but now I can play with it on my protoboard.


----------



## whirlwind (Apr 24, 2021)

L0rdGwyn said:


> Hey Joe - yes, very!  I am also in the middle of a staycation, so DIY efforts have been off the rails, I have gotten a lot done.  Really happy with how the radio is turning out, sort of a bigger PITA than I anticipated, HA!  Recapping the entire thing was a LOT of fun.  It is a belated birthday gift for my girlfriend.
> 
> The situation at work is much better!  Hopefully it keeps trending that way, I think it will.  Hope you and yours are well and keeping from going stir crazy.  We'll see what those Brownies do in the draft in a few days, right in my backyard.


Thanks for posting pics , Keenan.  Some killer stuff.

At some point I am hoping to see an EL34 amp project   

I am pretty excited about the draft. I am hoping the Clowney thing works out and maybe they can sign Richardson back.
I have no clue who they may draft...would be awesome if he was a starter though.

Great to hear from you....stay healthy and have fun.

Killer looking tubes, trannies and cans!


----------



## CJG888

Maybe I can persuade you to go down the idler wheel turntable rabbit hole next...


----------



## Zachik

By the time this amp is done - @L0rdGwyn is going to have impressive thick arms from lifting and moving all that iron around!!

Some dude: "How did you get those arms? Which gym do you go to? Who is your trainer?"
Keenan: "Gym? Trainer? I was just building a tube amp!"


----------



## bcowen

Zachik said:


> By the time this amp is done - @L0rdGwyn is going to have impressive thick arms from lifting and moving all that iron around!!
> 
> Some dude: "How did you get those arms? Which gym do you go to? Who is your trainer?"
> Keenan: "Gym? Trainer? I was just building a tube amp!"


LOL!  He's going to need a dedicated "amp swapper".  I'd volunteer, except all my time is consumed being @UntilThen 's caddy, gardener, chauffeur, and cart dryer-outer.  But hey, at $2/hour (AUD), at least I feel like I'm being unfairly compensated.  I am charging extra, however, to install the Akai in the golf cart. and even more to properly align his cartridge which is visibly off by 4 degrees in azimuth.


----------



## UntilThen

CJG888 said:


> Maybe I can persuade you to go down the idler wheel turntable rabbit hole next...



It's a most delightful rabbit hole to get into and one that can get incredibly expensive depending on how deep into the hole you want to go.



Zachik said:


> By the time this amp is done - @L0rdGwyn is going to have impressive thick arms from lifting and moving all that iron around!!
> 
> Some dude: "How did you get those arms? Which gym do you go to? Who is your trainer?"
> Keenan: "Gym? Trainer? I was just building a tube amp!"



As I progress in my head-fi journey, I develop a love for 'big' tube amps, in size and exotic design. I would never have thought that I would use HiFi racks for my head-fi gear when I started. A small desk top setup would be ok for me then. How times have changed and I can't deny that they sound so much better as I progress.

However we're seeing an overlap of head-fi and speaker amps and in some cases strictly speaker tube amps. I am just fascinated with either though.


----------



## UntilThen

bcowen said:


> LOL!  He's going to need a dedicated "amp swapper".  I'd volunteer, except all my time is consumed being @UntilThen 's caddy, gardener, chauffeur, and cart dryer-outer.  But hey, at $2/hour (AUD), at least I feel like I'm being unfairly compensated.  I am charging extra, however, to install the Akai in the golf cart. and even more to properly align his cartridge which is visibly off by 4 degrees in azimuth.



Part of my joy in this journey is meeting you. Life would not be as interesting without...  

I have upped your employment responsibilities to include changing tubes, dropping the needle on the LP and swapping the headphones for me. BUT lay off my song choices ! 

On the subject of the Akai, do you think this DBX EQ 1231 Dual EQ would be a worthwhile acquisition? I have been offered a new one at half price and it sure seem interesting to me. 31 dual bands that also have xlr inputs !!!


----------



## Zachik (Apr 24, 2021)

UntilThen said:


> On the subject of the Akai, do you think this DBX EQ 1231 Dual EQ would be a worthwhile acquisition? I have been offered a new one at half price and it sure seem interesting to me. 31 dual bands that also have xlr inputs !!!


Have you heard about Schiit's new Loki Max? Not gonna be 31 dual bands, but sound like an interesting product...
According to Jason (Schiit's CEO) - it was "released to production" which means we'll probably be able to buy it in the summer (not withstanding unforeseen supply chain issues).

Edit: @UntilThen when I refer to "summer" - that is in the northern hemisphere...   
Also, the summer prediction is MY estimate. Could be longer.


----------



## UntilThen

Zachik said:


> Have you heard about Schiit's new Loki Max? Not gonna be 31 dual bands, but sound like an interesting product...
> According to Jason (Schiit's CEO) - it was "released to production" which means we'll probably be able to buy it in the summer (not withstanding unforeseen supply chain issues).
> 
> Edit: @UntilThen when I refer to "summer" - that is in the northern hemisphere...
> Also, the summer prediction is MY estimate. Could be longer.


It's still a 4 band eq. 31 bands will be very versatile but the Akai at 12 bands is already very customizable. Kind of stumble into the world of equalization but it does help with tuning headphones... something I didn't believe in before. However there's only so much you can equalize. Not going to turn a HD800 into a LCD4.


----------



## bcowen

UntilThen said:


> Part of my joy in this journey is meeting you. Life would not be as interesting without...


Likewise, to be sure!!


UntilThen said:


> I have upped your employment responsibilities to include changing tubes, dropping the needle on the LP and swapping the headphones for me. BUT lay off my song choices !


I'll even clean the dust blob comet trail off your stylus at no charge when I get your azimuth set right for you.  No extra charge.    


UntilThen said:


> On the subject of the Akai, do you think this DBX EQ 1231 Dual EQ would be a worthwhile acquisition? I have been offered a new one at half price and it sure seem interesting to me. 31 dual bands that also have xlr inputs !!!


Oh hell no.  There aren't 25 hours in a day, which is what would be needed for me to be moving 62 sliders a micrometer at a time for you.  Besides, I still have the 72 acres of your back yard to mow.  You could perhaps consider buying me a riding lawnmower, or at least a motor-powered push mower.  And I thought *I* was cheap.


----------



## bcowen

Zachik said:


> Have you heard about Schiit's new Loki Max? Not gonna be 31 dual bands, but sound like an interesting product...
> According to Jason (Schiit's CEO) - it was "released to production" which means we'll probably be able to buy it in the summer (not withstanding unforeseen supply chain issues).
> 
> Edit: @UntilThen when I refer to "summer" - that is in the northern hemisphere...
> Also, the summer prediction is MY estimate. Could be longer.


Agree with @Zachik  (which is kind of scary ).  Wait for the Schiit Loki Max.  Even the (current) Loki Mini does less damage to the sound than any other equalizer I've heard.  The Loki Maxi will add more EQ bands as well as not getting in the way of the music (the Mini is pretty limited with only 4 EQ bands).  

(OG Loki Mini in the middle):


----------



## UntilThen

bcowen said:


> Likewise, to be sure!!
> 
> I'll even clean the dust blob comet trail off your stylus at no charge when I get your azimuth set right for you.  No extra charge.
> 
> Oh hell no.  There aren't 25 hours in a day, which is what would be needed for me to be moving 62 sliders a micrometer at a time for you.  Besides, I still have the 72 acres of your back yard to mow.  *You could perhaps consider buying me a riding lawnmower*, or at least a motor-powered push mower.  And I thought *I* was cheap.


----------



## UntilThen

bcowen said:


> Agree with @Zachik  (which is kind of scary ).  Wait for the Schiit Loki Max.  Even the (current) Loki Mini does less damage to the sound than any other equalizer I've heard.  The Loki Maxi will add more EQ bands as well as not getting in the way of the music (the Mini is pretty limited with only 4 EQ bands).
> 
> (OG Loki Mini in the middle):



No just no. For the last time, you need my Akai.


----------



## Zachik

bcowen said:


> Even the (current) Loki Mini does less damage to the sound than any other equalizer I've heard. The Loki Maxi will add more EQ bands as well as not getting in the way of the music (the Mini is pretty limited with only 4 EQ bands).


Other than price - what might make me skip the Loki Max is the size... I was hoping for something in the Lyr 3 stackable dimensions, but I think Jason confirmed the max would be in the bigger Gumby / Yggy footprint.


----------



## UntilThen

Zachik said:


> Other than price - what might make me skip the Loki Max is the size... I was hoping for something in the Lyr 3 stackable dimensions, but I think Jason confirmed the max would be in the bigger Gumby / Yggy footprint.


How many bands? Yggy's footprint has my interest. Hopefully it's also a preamp.


----------



## L0rdGwyn

CJG888 said:


> Maybe I can persuade you to go down the idler wheel turntable rabbit hole next...



It's intriguing, but no time soon!  I have doubled down on the TD125, will be doing a custom plinth and SME tonearm at some point...


----------



## L0rdGwyn

Zachik said:


> By the time this amp is done - @L0rdGwyn is going to have impressive thick arms from lifting and moving all that iron around!!
> 
> Some dude: "How did you get those arms? Which gym do you go to? Who is your trainer?"
> Keenan: "Gym? Trainer? I was just building a tube amp!"



LOL seriously though, it's no joke.  Really it's the 6A5G amp that is the beast, three transformers and three chokes, it's a PITA to move around!  And of course I must move it to a different room every few weeks or so, you know, to work out, summer will be here in no time.


----------



## Zachik

UntilThen said:


> How many bands? Yggy's footprint has my interest. Hopefully it's also a preamp.





Jason Stoddard said:


> *Lokiest. *Still not sure what to call this crazy-ass, all-LC-filtered, remote control, relay stepped, Nexus equalizer, but it’s much more than, say, a “Lokius.” It will be at least 10x the cost of a Loki Mini, so don’t get super excited. But this one is ready to rock and roll.


At some other occasion he wrote or implied it will be the big footprint (like Yggy).


----------



## CJG888

L0rdGwyn said:


> It's intriguing, but no time soon!  I have doubled down on the TD125, will be doing a custom plinth and SME tonearm at some point...


It wouldn’t need to be INSTEAD of the TD125 😀.

And, of course, a Garrard or Lenco would be too predictable! A Gates, perhaps? Complete with open gate gearshift à la Ferrari...


----------



## Xcalibur255

bcowen said:


> LOL!  He's going to need a dedicated "amp swapper".  I'd volunteer, except all my time is consumed being @UntilThen 's caddy, gardener, chauffeur, and cart dryer-outer.  But hey, at $2/hour (AUD), at least I feel like I'm being unfairly compensated.  I am charging extra, however, to install the Akai in the golf cart. and even more to properly align his cartridge which is visibly off by 4 degrees in azimuth.


The secret is to put casters under the amp instead of rubber feet.


----------



## UntilThen

UntilThen said:


> I have upped your employment responsibilities to include changing tubes, dropping the needle on the LP and swapping the headphones for me. BUT lay off my song choices !



@bcowen, remember your new additional tasks. There are many candidates vying for your job so do your best.


----------



## bcowen

UntilThen said:


> @bcowen, remember your new additional tasks. There are many candidates vying for your job so do your best.


LOL!  You walk the dog, and I'll tend to her needs.  That's what dedicated employees do.  

As a bonus, your Akai might actually help with that rig.


----------



## UntilThen

bcowen said:


> LOL!  You walk the dog, and I'll tend to her needs.  That's what dedicated employees do.
> 
> As a bonus, your Akai might actually help with that rig.



You deserve a 'like' to this reply.   

Btw the Akai will be sold for that famous painting on the wall.


----------



## L0rdGwyn (Apr 26, 2021)

Since I already made some posts about it, thought I'd update, I made changes to the input stage on the 801A amplifier, now uses a high mu triode, the 6SF5, rather than a pentode gain stage.  Now seeing THD at 0.3% at 1W into 8ohm, output impedance 1.7ohm.



Simultaneously, my SW1X DAC arrived, so they are both being listened to in my system right now.

This is simply the best it has ever sounded.  Really incredible realism, staging, bass dynamics...

I will be very happy with this pair  until the next amplifier build, that is...


----------



## Tjj226 Angel

That's one of the audio note dac clones. Should be a awesome dac. 

What do you have in it? I know these companies have a wide range of variations on a particular product.


----------



## whirlwind

L0rdGwyn said:


> Since I already made some posts about it, thought I'd update, I made changes to the input stage on the 801A amplifier, now uses a high mu triode, the 6SF5, rather than a pentode gain stage.  Now seeing THD at 0.3% at 1W into 8ohm, output impedance 1.7ohm.
> 
> 
> 
> ...


Congrats!


----------



## L0rdGwyn

Tjj226 Angel said:


> That's one of the audio note dac clones. Should be a awesome dac.
> 
> What do you have in it? I know these companies have a wide range of variations on a particular product.



It runs on a pair of Burr-Brown PCM45P-K.  B+ supply is 5Y3 rectified, CLC.  Output is a 5687.  I didn't go for a lot of the exotic stuff, stock caps for example, can change them myself if the mood strikes, although that would likely void any warranty.

SW1X obviously is running in the Audio Note vein, and Slawa doesn't hide it, he pays homage to Peter Qvortrup on his site.  Some say his stuff is better than Audio Note's, I can't say either way as I haven't heard both, but this is a very good DAC...

I locked in the price late 2019 with a deposit, I believe there have been two price increases since then, likely they will keep going up as the company grows.


----------



## bcowen

L0rdGwyn said:


> It runs on a pair of Burr-Brown PCM45P-K.  B+ supply is 5Y3 rectified, CLC.  Output is a 5687.  I didn't go for a lot of the exotic stuff, stock caps for example, can change them myself if the mood strikes, although that would likely void any warranty.
> 
> SW1X obviously is running in the Audio Note vein, and Slawa doesn't hide it, he pays homage to Peter Qvortrup on his site.  Some say his stuff is better than Audio Note's, I can't say either way as I haven't heard both, but this is a very good DAC...
> 
> I locked in the price late 2019 with a deposit, I believe there have been two price increases since then, likely they will keep going up as the company grows.


Nice!!  There's something about a tubed DAC that just make it so much more, um, better.    My speaker rig DAC uses a pair of 6922's in the output stage, although no tube rectifier.  Comparing it to the Schiit Bifrost 2 isn't fair as it retailed for 3x the price, but sonically the Bifrost doesn't compare either.


----------



## Tjj226 Angel

L0rdGwyn said:


> It runs on a pair of Burr-Brown PCM45P-K.  B+ supply is 5Y3 rectified, CLC.  Output is a 5687.  I didn't go for a lot of the exotic stuff, stock caps for example, can change them myself if the mood strikes, although that would likely void any warranty.
> 
> SW1X obviously is running in the Audio Note vein, and Slawa doesn't hide it, he pays homage to Peter Qvortrup on his site.  Some say his stuff is better than Audio Note's, I can't say either way as I haven't heard both, but this is a very good DAC...
> 
> I locked in the price late 2019 with a deposit, I believe there have been two price increases since then, likely they will keep going up as the company grows.



The audio note dac and most of SW1Xs stuff will sound different, and I could definitely understand why some people might find SW1Xs stuff better. 

Audio note uses two 5687s on their output in an SRPP configuration. This gives them really low output impedance, but SRPP does seem to have it's own "sound" to it. Some people like it, some people don't. 

SW1X is using a much more traditional approach with a regular resistor loaded anode follower. It might not be the fanciest way of doing things, but it has a sound that is much easier to enjoy IMO. 

I will also point out that I have tried those cactus capacitors on some stuff and found that I don't really like them. I would prioritize putting some miflex capacitors in there or potentially making some bigger changes and putting in a output transformer. 

What I would be really curios to find out is how much resistance are they loading the 5687 with to calculate the actual gain of the 5687. If you find out that the resistance is kind of low and you are only realizing a gain of 10 or something like that, then you could take the resistor out and swap it with a 2:1 output transformer. 

Since most of your amps have a high input impedance, the reflected load back to your 5687 would be so high that you would realize enough gain to make the step down almost negligible in terms of voltage output, and you would cut your output impedance by half. Plus if you use the WE capacitor trick, you could also lower your noise floor quite a bit. 

It would be a lot of work, and kind of a pain, but it would be a really cool upgrade.


----------



## whirlwind

@L0rdGwyn   Pretty happy with those first two draft picks!


----------



## L0rdGwyn

Tjj226 Angel said:


> The audio note dac and most of SW1Xs stuff will sound different, and I could definitely understand why some people might find SW1Xs stuff better.
> 
> Audio note uses two 5687s on their output in an SRPP configuration. This gives them really low output impedance, but SRPP does seem to have it's own "sound" to it. Some people like it, some people don't.
> 
> ...



I'll have to think it over, I'm apprehensive to make changes at all really, these DACs are not cheap!  The cap changeout is easy though, so maybe that will be done at some point, the Arizona capacitors are stock and could use an upgrade, but I was not going to pay for more expensive caps that I could put in myself lol.  Probably if I was going to the trouble to add an output transformer, I would just start from scratch and design a TDA1541 DAC, something I'd like to work on at some point, but of course I have no idea when that will be.



whirlwind said:


> @L0rdGwyn   Pretty happy with those first two draft picks!



Me too!  The rich got richer, got some real brains running the show now, Joe, these Browns are the real deal.  Should be a very exciting season with legitimate Super Bowl chances if we stay healthy.

I'm working on the 801A amplifier chassis, made some progress today, right now it is 16.5" x 13" x 3.25".  Tube sockets will be recessed with circular ventilation.  As usual, I've spent a lot of time thinking about how it is going to look, going for sort of an 'old school' aesthetic, I think it's gonna turn out well.  I use to-scale stick diagrams in AutoCAD to optimize the layout, objects in color are internal / external components.

Still a little ways to go, it's a lot of work doing this type of planning, can't miss any little detail...


----------



## Tjj226 Angel

L0rdGwyn said:


> I'll have to think it over, I'm apprehensive to make changes at all really, these DACs are not cheap!  The cap changeout is easy though, so maybe that will be done at some point, the Arizona capacitors are stock and could use an upgrade, but I was not going to pay for more expensive caps that I could put in myself lol.  Probably if I was going to the trouble to add an output transformer, I would just start from scratch and design a TDA1541 DAC, something I'd like to work on at some point, but of course I have no idea when that will be.



I can't remember if I told you about the Jlabs i2s board or not. 

I have only just started playing with it, and I can tell you that with USB it sounds a little better than spdif and I haven't even realized it's full potential yet. 

You can tie it into any of the popular R2R dac chips without any glue on logic, filters, or anything else of the sort. With this board, all you have to worry about is making a few regulator boards to supply voltage to everything and your output stage. 

I might encourage you to leave your SW1X alone and try to build your own dac first since it isn't all that hard (once you wrap your mind around it) and the results are incredible. The one my friend built for me years ago sounded much better than the audio note dacs right out of the gate.


----------



## L0rdGwyn (May 3, 2021)

Tjj226 Angel said:


> I can't remember if I told you about the Jlabs i2s board or not.
> 
> I have only just started playing with it, and I can tell you that with USB it sounds a little better than spdif and I haven't even realized it's full potential yet.
> 
> ...



It's something I'll get to eventually, just a matter of time.  Now that I have a very nice DAC in my main system, the cheapo DACs in my headphone and bedroom systems are real eye (ear?) sores.  Probably what will happen is I will try to build something semi compact for my desk to pair with my headphone amp.  Time will tell!  This 801A build has been hard work, I might be done with amplifiers for a while...at least full builds, I will play with the protoboard of course 

Finished the 801A chassis, here it is, many hours of work.  Dimensions are 3.25" x 13.5" x 16.5".

Top plate and recessed socket plates.



Front panel.



Rear panel.



Side panels.




The main chassis is going to be in a semi-gloss medium gray, the recessed socket plates will be matte black.  Have to review my color choices one more time to be certain.

There is no headphone jack on this build, it is a 7W speaker amp, didn't want to compromise on the layout to add the switch and additional wiring.  Probably what I will do at some point is build a box with binding posts on the back and a headphone jack on the front with 8ohm resistors inside, so I can listen with headphones if the need arises.


----------



## UntilThen

Me like. You get UntilThen’s approval. Looks very the good. 👍😎


----------



## UntilThen (May 3, 2021)

L0rdGwyn said:


> Finished the 801A chassis, here it is, many hours of work. Dimensions are 3.25" x 13.5" x 16.5".


Metrics please? Imperial gives me headaches 😃

ok so that’s 80 x 340 x 420

compared to Destiny 

430 x 360 x 100

Now I get a better idea how big your 801 is.


----------



## UntilThen

That’s almost the same size as my 300b amp called Destiny. Just one pic if I may without gate crashing. 😉


----------



## L0rdGwyn

@UntilThen looks nice!  6EM7 dual dissimilar triode, fun tubes to design with.  Is it a speaker or headphone amp?

Yep, about the same size, can't wait to get this one done, the sound is jaw-dropping


----------



## UntilThen

Keenan it’s both a headphone and speakers amp. 8 sweet watts. Drives my Axis LS88 4 ohms 92 dB floor standers in the lounge very well with meat and body tone at 12 o’clock on the volume.

Best part is how well it drives my Audeze LCD4 and HiFiMan He1000se.

The 6EM7/ 6AE7 driver tubes as you know is very interesting.

Another view of the amp



P/S: I’m keeping a keen eye 👁 on your amp when it finished. I know you will make it look absolutely gorgeous as well as how it will sound. Cheers.


----------



## UntilThen

Btw it uses Interstage transformers instead of capacitors and has double chokes to minimise noise.


----------



## L0rdGwyn

Very nice @UntilThen , any idea who made the transformers?  Look like they could be Transcendar.  8W with 92dB speakers will get the job done  I will have a similar pairing at 7W 92dB.

Will you be getting your other amp from Ultrasonic as well?


----------



## UntilThen

L0rdGwyn said:


> Very nice @UntilThen , any idea who made the transformers?  Look like they could be Transcendar.  8W with 92dB speakers will get the job done  I will have a similar pairing at 7W 92dB.
> 
> Will you be getting your other amp from Ultrasonic as well?


Hahaha let’s just pretend it’s Transcender shall we? It will sound better if our mind believe so. I won’t disclose the transformers but I will be getting the super duper KT88/EL34 amp from Ultrasonic Studios using old school design and Sowter transformers, Mundorf Supreme Silver oil and Yamamoto sockets.

Then I will be dying to see and hear how they compare. Granted comparing 300b and KT88/EL34 are like apples and Jack fruit !


----------



## L0rdGwyn

Why stop at Transcendar, look like vintage Tango to me  it will be interesting to compare, although not apples-to-apples like you say, DHT vs. IDHT, interstage transformers vs. cap-coupled (?), fixed vs. autobias, also a three-stage design vs. two-stage...lots of variables, but both single-ended class A1.  Good thing with tube amps, if you follow a few basic guidelines, it is hard to make a bad sounding amp, you end up with variety of nice amplifiers to listen to.


----------



## UntilThen

L0rdGwyn said:


> Why stop at Transcendar, look like vintage Tango to me  it will be interesting to compare, although not apples-to-apples like you say, DHT vs. IDHT, interstage transformers vs. cap-coupled (?), fixed vs. autobias, also a three-stage design vs. two-stage...lots of variables, but both single-ended class A1.  Good thing with tube amps,* if you follow a few basic guidelines, it is hard to make a bad sounding amp, you end up with variety of nice amplifiers to listen to.*



That last statement is so true. My amp builder say similar thing. That is that old school design has been around for decades. Ampansound Mogwai Se and Bigger Ben uses Transcendar I think. 

The builder of my 300b amp have use Hashimoto trannies for one customer before. Looks gorgeous.

Enough of my sharing. I want to see your finished 801. Cheers.


----------



## L0rdGwyn

That's right, Ampsandsound use Transcendar.  They are one of the few transformer makers still offering custom mains too.

Well the chassis is just ordered so it will be a short while before I receive it.  The rest of the month is quite busy for me, we will see if I have time to finish the build...I hope so, should come together very quickly considering it has already been built once on plywood and I don't have to do any of the machining.

I haven't talked in much detail about the final circuit since I have not been on here consistently, one change I am very pleased with is the use of 6F5 input tubes.

These are high gain (mu of 100) high internal resistance, low current triodes.  Unless they are coupled to a buffer circuit, they aren't very useful, but work very well in my design.  As such, they are plentiful and some very nicely constructed examples out there from GEC, Visseaux, Sylvania, RCA, Sovtek, and many others.  Nice to have plentiful tubes for a change.



Oh and they sound great, the curves look like this.



This amp has batteries in it too  battery bias, fixed bias, cathode bias, mixed bias, it has all the biases.


----------



## triod750

I guess you are a bit biased yourself too!


----------



## bcowen

L0rdGwyn said:


> That's right, Ampsandsound use Transcendar.  They are one of the few transformer makers still offering custom mains too.
> 
> Well the chassis is just ordered so it will be a short while before I receive it.  The rest of the month is quite busy for me, we will see if I have time to finish the build...I hope so, should come together very quickly considering it has already been built once on plywood and I don't have to do any of the machining.
> 
> ...


That brings up a question I've always had: with battery bias, what happens if the battery dies (or drops below a working voltage)?  Does the sound just get all weird, or do more un-nicer things happen?


----------



## L0rdGwyn (May 4, 2021)

bcowen said:


> That brings up a question I've always had: with battery bias, what happens if the battery dies (or drops below a working voltage)?  Does the sound just get all weird, or do more un-nicer things happen?



So the batteries simply serve as a voltage reference.  In class A1, the grid draws little-to-no current, so there is no discharge of the battery.  They simply need to be changed at the lifespan of the battery, which is 12 years for AAs, probably a good idea to check the voltage periodically.  BUT if the battery did have a load and did draw current, then it would be discharged over time and the bias would be altered.  If that is the case though, shouldn't use a battery


----------



## Tjj226 Angel

bcowen said:


> That brings up a question I've always had: with battery bias, what happens if the battery dies (or drops below a working voltage)?  Does the sound just get all weird, or do more un-nicer things happen?



That actually depends on quite a few factors. Let's assume you have a very simple resistor load on your tube and you are using your battery to bias the grid. 

If your grid bias starts to drop off, your tube will want to draw more current. The greater the current, the greater the voltage drop across the plate resistor. The lower the plate voltage, the lower the current draw. 

This tug of war between current and voltage means that the tube will find some stable operating condition based on the bias voltage on the grid. What you will ultimately observe is that your amp will probably start to clip well before reaching maximum output power. Or in other words if your amplifier needs 2V input in order to achieve max power, and your tube is only getting 1v of bias because your batteries are dying, then you will run into clipping if you try to drive your amplifier to normal levels. 

This only applies to situations where there is some type of current limiter on the tube. A resistor, or a CCS. 

If you are using a transformer, choke, or gyrator, the current would keep increasing as the bias goes down until the tube nukes itself.


----------



## L0rdGwyn

What @Tjj226 Angel is describing in the "nuke itself" scenario is referred to as thermal runaway.  Not an issue in this circuit even if a battery cell were to fail for some reason, but this is why fixed bias, aka grid bias, power amplifiers have protection mechanisms in place.  Typically there are at least two fail-safes included.

1) A mechanism by which the tube grid will be biased to the full potential of the negative supply if the bias potentiometer fails, biasing it into cutoff = no current draw
2) Fast blow fuse on the power tube plate and / or cathode

This protects the OPT primary from high current as well.  Destroying your transformers is even worse than destroying your tubes 😭


----------



## L0rdGwyn

Well actually I misspoke, the mechanism of thermal runaway is a bit different, but ultimately the death of the tube is reached by similar means, the grid becomes more and more positive, the tube conducts more current, and the internals melt.


----------



## Tjj226 Angel

L0rdGwyn said:


> Well actually I misspoke, the mechanism of thermal runaway is a bit different, but ultimately the death of the tube is reached by similar means, the grid becomes more and more positive, the tube conducts more current, and the internals melt.



Yeup. Just for clarification for everyone else, thermal runaway occurs when heat causes a part to become more conductive. The higher conductivity means the part will draw more current, which will create more heat, which will raise the conductivity, which will lead to more heat etc etc. 

It is a cascade effect that is caused by the heat itself. This is more common with BJTs which is why companies like schiit usually have some type of circuit monitoring the heat in the amp.


----------



## L0rdGwyn

I know I'm in danger of being sucked back in with how much I have been posting on this thread lately, but I am on night shift, I need every bit of dopamine I can squeeze out of the old brain.

I made some furniture changes, my two-channel system is nearing the end of my roadmap for it, all that is left is to put the 801A amp in rotation with the 6A5G SET.  There truly isn't any more room in my house for more gear, so not sure what happens when it's done, besides small tweaks to existing builds.  Maybe I'll add an addition to the house


----------



## tubebuyer2020

@L0rdGwyn in terms of sound on average are rectifiers worth bothering with or hexfred/schottky is the answer?


----------



## bcowen

L0rdGwyn said:


> I know I'm in danger of being sucked back in with how much I have been posting on this thread lately, but I am on night shift, I need every bit of dopamine I can squeeze out of the old brain.
> 
> I made some furniture changes, my two-channel system is nearing the end of my roadmap for it, all that is left is to put the 801A amp in rotation with the 6A5G SET.  There truly isn't any more room in my house for more gear, so not sure what happens when it's done, besides small tweaks to existing builds.  Maybe I'll add an addition to the house



Sweet!  Tubes, vinyl, and Snells.  Sometimes you just have to know when to stop.  LOL!

(and if you ever figure out when that is, please share )


----------



## whirlwind

L0rdGwyn said:


> I know I'm in danger of being sucked back in with how much I have been posting on this thread lately, but I am on night shift, I need every bit of dopamine I can squeeze out of the old brain.
> 
> I made some furniture changes, my two-channel system is nearing the end of my roadmap for it, all that is left is to put the 801A amp in rotation with the 6A5G SET.  There truly isn't any more room in my house for more gear, so not sure what happens when it's done, besides small tweaks to existing builds.  Maybe I'll add an addition to the house


Very nice.


----------



## L0rdGwyn (May 7, 2021)

tubebuyer2020 said:


> @L0rdGwyn in terms of sound on average are rectifiers worth bothering with or hexfred/schottky is the answer?



It's a bit controversial.  From a purely technical / design standpoint, solid-state rectification is better, there really is no advantage to using tube rectification that cannot be duplicated / improved upon with solid-state components.  Two positives going for tube rectifiers are their "soft-start" characteristics and inherent snubbing of transformer ringing due to their high internal resistance.  But, again, these two issues can be easily addressed using solid-state rectification.

One particular use case for tube rectifiers - if you are attempting to adapt a mains transformer you have on hand to a specific design and have some excess voltage that needs to be dropped in the power supply.  In that case, getting the heat outside of the chassis by dropping some voltage across a tube rectifier might be preferable to dropping it across resistors in the power supply, which will generate heat inside the chassis.

From a sound perspective, you sort of have to buy into what I will call "tube rectifier voodoo" to decide if you think it is worth doing or not.  Other than altering the bias point of the amplifying tubes using different tube rectifiers with varying Vdrop (which surely contributes to the notion that tube rectifiers can change sound), if you want to "hear" a tube rectifier, you better use a passive power supply, as opposed to voltage-regulated.  The power supply rejection of a high-performing voltage regulator will be so high that anything before the regulator in the supply will be essentially inaudible, including the rectifier.  Also, the regulator will nullify any changes in bias point due to different Vdrop of the rectifier.  So if you want to "hear" the rectifier, have to go passive (this means only RC or LC filters in the supply, resistors, capacitors, chokes).

My 6A5G amplifier has a passive power supply that is tube rectified.  I played around a bit with trying different 4V rectifiers, differences heard between them I would say were small to the point of uncertainty, but I did give the slight edge to the U18/20, plus it looks cool - this is the real benefit of tube rectifiers 

I have used solid-state rectifiers in all subsequent designs.  Here is my personal opinion - tube rectifiers look cool and give the amplifier swag, but I will not use them unless I need to drop some excess voltage using an off-the-shelf or on hand mains transformer in a design, or if I just want the amp to look a little cooler.  There are so many other aspects of an amplifier than will affect the sound more so than a tube rectifier, so my preference is to go solid-state and seek out those changes instead.

Just my opinion, opinions will vary by who is designing the amplifier and their personal experiences.



bcowen said:


> Sweet!  Tubes, vinyl, and Snells.  Sometimes you just have to know when to stop.  LOL!
> 
> (and if you ever figure out when that is, please share )



I THINK I am going to pump the brakes hard when this system is done.  The sound I am getting is goosebump generating, that's the benchmark for me, so I'm good  I'll probably make or buy some cool interconnects and stuff like that, I have a laundry list of tweaks that need to be made to the gear I've finished, so that's probably what I'll work on first.  Then there is this SIT power amplifier, the HK54 A2 amplifier, upgrades to my phono stage, custom plinth and new tonearm for my turntable, a mountain of rare 6AS7G-type OTL tubes in a box in my basement.....going to try and bury my desire to work on those things deep inside for a while lol.

I have more vinyl storage space now too, so obviously I will need to fill it ASAP


----------



## bcowen

L0rdGwyn said:


> I THINK I am going to pump the brakes hard when this system is done.  The sound I am getting is goosebump generating, that's the benchmark for me, so I'm good  I'll probably make or buy some cool interconnects and stuff like that, I have a laundry list of tweaks that need to be made to the gear I've finished, so that's probably what I'll work on first.  Then there is this SIT power amplifier, the HK54 A2 amplifier, upgrades to my phono stage, custom plinth and new tonearm for my turntable, a mountain of rare 6AS7G-type OTL tubes in a box in my basement.....going to try and bury my desire to work on those things deep inside for a while lol.
> 
> I have more vinyl storage space now too, so obviously I will need to fill it ASAP



All that extreme gorgeousness in the foreground, and then there's this hiding in the background:





Kind of like buying a Ferrari and filling it up with 80 octane gas. LOL!   Of course if you just have accessory type stuff plugged into that, then nevermind.


----------



## L0rdGwyn (May 7, 2021)

bcowen said:


> All that extreme gorgeousness in the foreground, and then there's this hiding in the background:
> 
> 
> 
> Kind of like buying a Ferrari and filling it up with 80 octane gas. LOL!   Of course if you just have accessory type stuff plugged into that, then nevermind.



How dare you!  I'll have you know that power strip is made of ivory and the wiring is silver-plated platinum...

But in all seriousness, that is a plane Jane, no internal filtering, no surge protection power strip, just wire and plugs, and it is very intentional 

The other end is connected to a 2.5kVA MGE isolation transformer, wired for balanced power +60/-60VAC, and better than any filtering in terms of common mode noise rejection, so essentially everything in the system is connected directly to the output of the transformer in parallel.  That is some ultra pure AC coming out of that crappy power strip LOL but I should probably get something that at least LOOKS sexier.  All of the wiring of the system needs an upgrade, except for the speaker cables maybe, just hasn't been a priority with so many other things going on.


----------



## bcowen

L0rdGwyn said:


> How dare you!  I'll have you know that power strip is made of ivory and the wiring is silver-plated platinum...
> 
> But in all seriousness, that is a plane Jane, no internal filtering, no surge protection power strip, just wire and plugs, and it is very intentional
> 
> The other end is connected to a 2.5kVA MGE isolation transformer, wired for balanced power +60/-60VAC, and better than any power supply filtering in terms of common mode noise rejection, so essentially everything in the system is connected directly to the output of the transformer in parallel.  That is some ultra pure AC coming out of that crappy power strip LOL but I should probably get something that at least LOOKS sexier.  All of the wiring of the system needs an upgrade, except for the speaker cables maybe, just hasn't been a priority with so many other things going on.


LOL!  I could tell by looking at it that it was ivory, but the switch looks kind of cheap.   

I'm not one of those $200 outlet kind of guys***, but I do believe that good sockets with a firm grip on the plug _do_ make a difference.  I have a chassis similar to this one in the closet, just never got around to putting it together with some good sockets and wire because I haven't had a need for it (yet).  It's all aluminum and pretty nicely machined for the money.

https://www.ebay.com/itm/274410580886?_trkparms=ispr=1&hash=item3fe4252b96:g:SIQAAOSwbDRe904g&amdata=enc:AQAFAAACgBaobrjLl8XobRIiIML1V4Imu%2Fn%2BzU5L90Z278x5ickkY3FSd4Ad8xn3oRtkVexxrKNM3NDghHC%2F7TwsFiXvuz6ATSQz4fO1Rwv5OxQeMFRmOCP9860cfFq38kQekiU6t156tUL%2Fsw2mENSOYDA5bEHwW%2F95c4B8vkiY8EpZvAKt7%2FPvt3o%2FxmpaQaQLLZbHJmkQfMtXPkSqZ%2Bdlfm19OxDKJfVMo%2FzjcaIfRGPzFam3Z6WbMEy%2BQriUw0pGSvXzaLwhUJI427RqhTqr0EB628x0LW%2FpJY5KLrvJPX8zam5LxsXRTo18CoFWzWcwdYYHbA5TaacZsrzVHbhO3A3ta0PglLuVcJRGm38Q1C81d%2FmhgpQetphaVL%2FWErxdIS133D2Bn7iLVUYCOyK76ncX9xOgdAmPCbDkJS1NJ1GOW0jahTfFmxTG4hDtY38%2BivLgjGtGnHQFAnzNbKDarhR5xJb7JjkBXf0bunbe1GeZwwoxMeEiS6c54BwKKb9AT2jZA7Wvfy0RNO0cR5brCiwYsMtwwti%2FSrIrs4EtBR14lHFLbiXFDY1oJ18F6BEvBginQXYP%2FUTqj9duKtZizuPqwJOaF0wG2erwxzJ0YQt7ycOrVgdWXJaP6wgaeR%2B3y0LA47WheXXTVdABId6tzq0uL5UEMJZVhL27hKRtBLNOl7ONHdL2y7jddClKDJu2HVxwHeVEM%2B3HjU0daRbw8%2Fq5nlwyCYDJBNlIL85nFaphZSgrc80MYC%2B6RTetouXEWhMFJVQBV5MBcMlbmVBsB6XC8d3IIk7Z0PClWiHy3pL6kIkteYTVgdfLpdMrM1Ja5tuCTm9osqtMHiyaA0OY9Ya53Dk%3D|cksum:274410580886d2864b89d31e4b89ada391aa93ca838b|ampidL_CLK|clp:2334524 






***I _do_ have one high dollar Furutech outlet that I bought mostly just to satisfy my curiosity. It is very nicely constructed and supremely high quality (which it better be for the money), but sonically? If there's a difference between it and just a good quality Leviton or P&S outlet, it's beyond my hearing capability.


----------



## Mr Trev

Works for me.


----------



## L0rdGwyn

bcowen said:


> LOL!  I could tell by looking at it that it was ivory, but the switch looks kind of cheap.
> 
> I'm not one of those $200 outlet kind of guys***, but I do believe that good sockets with a firm grip on the plug _do_ make a difference.  I have a chassis similar to this one in the closet, just never got around to putting it together with some good sockets and wire because I haven't had a need for it (yet).  It's all aluminum and pretty nicely machined for the money.
> 
> ...



I'm not one of those guys either, but that aluminum chassis you linked looks great!  Maybe I'll grab one and make the same thing, wire and sockets, but you know...not a piece of crap LOL.  Fixing up the wiring situation is high on the to-do list once all the major components are settled.  Could DIY some power cables and interconnects, but I sort of hate making cables...


----------



## bcowen

Mr Trev said:


> Works for me.


ROFL!  You've been visiting @Ripper2860 again I see.


----------



## Galapac

That’s the key power strip there, must be hot as hell, lol.
The one to power them all...


----------



## Ripper2860

bcowen said:


> ROFL!  You've been visiting @Ripper2860 again I see.


You're just jealous that I have an Active-Active/load balanced N+50 redundant surge suppressor/ power strip array.


----------



## whirlwind

L0rdGwyn said:


> It's a bit controversial.  From a purely technical / design standpoint, solid-state rectification is better, there really is no advantage to using tube rectification that cannot be duplicated / improved upon with solid-state components.  Two positives going for tube rectifiers are their "soft-start" characteristics and inherent snubbing of transformer ringing due to their high internal resistance.  But, again, these two issues can be easily addressed using solid-state rectification.
> 
> One particular use case for tube rectifiers - if you are attempting to adapt a mains transformer you have on hand to a specific design and have some excess voltage that needs to be dropped in the power supply.  In that case, getting the heat outside of the chassis by dropping some voltage across a tube rectifier might be preferable to dropping it across resistors in the power supply, which will generate heat inside the chassis.
> 
> ...



  "Tube Rectifier Voodoo"  I like that.


----------



## Zachik

whirlwind said:


> "Tube Rectifier Voodoo"  I like that.


I followed Glenn's advice (and my gut), and went for built-in HEXFRED for my 6EL3N... Even in my GOTL, I plugged in the HEXFRED "tube" rectifier and never bothered - too much tube nervosa even without tube rectifier 😰


----------



## L0rdGwyn (May 8, 2021)

Zachik said:


> I followed Glenn's advice (and my gut), and went for built-in HEXFRED for my 6EL3N... Even in my GOTL, I plugged in the HEXFRED "tube" rectifier and never bothered - too much tube nervosa even without tube rectifier 😰



There's really no right or wrong answer, but from the designer's point of view, there are a lot of compromises when using tube rectification.  If someone else is doing the design work though, then you are in good shape 

Another compromise I didn't mention - if using a capacitor input supply, there is a limit to the size of the reservoir cap that can be used, as well as a recommend minimum source resistance at the input of the rectifier, made up of the resistance of the mains transformer and any added resistance.  Failing to obey these limitations of the specific tube rectifier, typically outlined in the datasheet, risks arcing on startup and damaging the rectifier before the filaments have come up to temperature.  This means you typically must use a lower value reservoir capacitor, which means higher ripple in the supply if it isn't made up for further down the line.  There are other specifications that must be obeyed from the datasheet, but I'll leave it at that.

Something like a HEXFRED diode, however, is so overspec'd for use in a tube linear power supply that you can just chuck it in and forget it!  I have a big stash of these, Vishay VS-HFA06TB120-M3.  Here they are on the rectifier PCBs I designed, they have traces for transformer snubbing components as well


----------



## tubebuyer2020

L0rdGwyn said:


> It's a bit controversial ...



Thank you for spending time to write this up - very useful!


----------



## Xcalibur255

I use TrippLite ISOBars in my setup because I'm not comfortable at all with having it all plugged into the wall directly.  Summer is non-stop thunderstorms around here.  But, I do think they hurt the sound quality of the system (along with every other surge supressor I've used including the series mode ones), and these have a pretty good reputation as far as surge strips go.  The ones I have feature bank isolation and I do think it has an effect.  Things like monitors and such that have switching power supplies feed back noise into the strip and the bank isolation helps keep it from getting into the other components somewhat.

Maybe a real power conditioner is what I have been needing all this time to truly get the sound where I want it....... but I can't build enough confidence in a purchase to justify their high price.


----------



## whirlwind

L0rdGwyn said:


> There's really no right or wrong answer, but from the designer's point of view, there are a lot of compromises when using tube rectification.  If someone else is doing the design work though, then you are in good shape
> 
> Another compromise I didn't mention - if using a capacitor input supply, there is a limit to the size of the reservoir cap that can be used, as well as a recommend minimum source resistance at the input of the rectifier, made up of the resistance of the mains transformer and any added resistance.  Failing to obey these limitations of the specific tube rectifier, typically outlined in the datasheet, risks arcing on startup and damaging the rectifier before the filaments have come up to temperature.  This means you typically must use a lower value reservoir capacitor, which means higher ripple in the supply if it isn't made up for further down the line.  There are other specifications that must be obeyed from the datasheet, but I'll leave it at that.
> 
> Something like a HEXFRED diode, however, is so overspec'd for use in a tube linear power supply that you can just chuck it in and forget it!  I have a big stash of these, Vishay VS-HFA06TB120-M3.  Here they are on the rectifier PCBs I designed, they have traces for transformer snubbing components as well


Great post Keenan.
I am in the rectifier fan group.    the glow makes everything better.
With my GEL3N amp...Glenn says I can use about all rectifiers, a certain Brimar is a no go.
Rectifiers make the least change in the sound in my amp...but hey...they are tubes !


----------



## johnjen

Xcalibur255 said:


> I use TrippLite ISOBars in my setup because I'm not comfortable at all with having it all plugged into the wall directly.  Summer is non-stop thunderstorms around here.  But, I do think they hurt the sound quality of the system (along with every other surge supressor I've used including the series mode ones), and these have a pretty good reputation as far as surge strips go.  The ones I have feature bank isolation and I do think it has an effect.  Things like monitors and such that have switching power supplies feed back noise into the strip and the bank isolation helps keep it from getting into the other components somewhat.
> 
> Maybe a real power conditioner is what I have been needing all this time to truly get the sound where I want it....... but I can't build enough confidence in a purchase to justify their high price.


One option to at least consider are ac mains isolation xfrmrs.
They are no where near the cost of a power regen unit.
And if you're handy and a DIY'r you could either build one fairly inexpensively, or ebay has used ones for (sometimes) even less.

And for the more lower powered units (pre-amps, dacs, HP amps, etc) they are a decent improvement over not having one.

Surge suppressors and 'noise absorber' plug in strips are good for distribution but isolation xfmrs are 'better' at cleaning up the noise on the ac voltage itself.
I use a 'cheap' china toroid 500va unit for my entire system and I've been monitoring the ac mains voltage and it does help stabilize everything and does so quite well at that.
In addition my ac mains voltage is 'hot' (123 ±3vac) which 'complicates' things a tad, so I added an ac mains stepdown xfmr as well.
This dropped the mains supply to 118 ±3vac.
This is jumping even further down this rabbit hole than most, but my Purp-Amp is 'touchy' so to speak, so this helps to keep all the internal voltages dialed in.

The OP mentioned the xfmr he uses here…
https://www.head-fi.org/threads/l0rdgwyns-diy-audio.921105/page-168#post-16341342

JJ


----------



## L0rdGwyn

Xcalibur255 said:


> I use TrippLite ISOBars in my setup because I'm not comfortable at all with having it all plugged into the wall directly.  Summer is non-stop thunderstorms around here.  But, I do think they hurt the sound quality of the system (along with every other surge supressor I've used including the series mode ones), and these have a pretty good reputation as far as surge strips go.  The ones I have feature bank isolation and I do think it has an effect.  Things like monitors and such that have switching power supplies feed back noise into the strip and the bank isolation helps keep it from getting into the other components somewhat.
> 
> Maybe a real power conditioner is what I have been needing all this time to truly get the sound where I want it....... but I can't build enough confidence in a purchase to justify their high price.



I think we've talked about it before, the isolation transformer solution is a good one, but the transformers that are worth buying can be expensive and seem to be getting harder to find (Topaz, MGE, etc.), imperative that they be of low interwinding capacitance, otherwise the benefits aren't realized.  So many companies are completely vague about what is going on inside their power conditioners, I tend to get serious snake oil vibes...



whirlwind said:


> Great post Keenan.
> I am in the rectifier fan group.    the glow makes everything better.
> With my GEL3N amp...Glenn says I can use about all rectifiers, a certain Brimar is a no go.
> Rectifiers make the least change in the sound in my amp...but hey...they are tubes !



Thanks, Joe.  Just to clarify, I'm not anti tube rectifier at all, they are super cool and add a nice aesthetic to an amp, and I'm sure they are fun to collect, I have a few different types of 4V rectifiers for my 6A5G amp.  For me personally, just hard to justify designing with one when it makes things much more complicated!  I'll definitely do it again, just has to be the right project.

I actually just bought this GZ34 to put in my SW1X DAC.  The DAC runs a 5Y3 stock, which has a Vdrop of 60V whereas the GZ34 has a Vdrop of 10.



I took a look at the 5687 output stage and put together a LTSpice model, wanted to find the bias point to see how swapping in a GZ34 and increasing the B+ 50V would affect things.  This keeps the 5687 well within the SOA and will flatten the load line a smidge, so should have some small audible benefit actually!  See, rolling rectifiers is beneficial 

I also grabbed this E182CC to try in place of the 5687.  Should increase the output of the DAC around 30% at similar levels of distortion.



I won't share the details of the output stage, but it could be changed to a choke load quite easily, which would result in higher gain, lower distortion, better power supply isolation.  I probably won't do it, but it's tempting...maybe after I've had the DAC a few years.


----------



## whirlwind (May 9, 2021)

L0rdGwyn said:


> I think we've talked about it before, the isolation transformer solution is a good one, but the transformers that are worth buying can be expensive and seem to be getting harder to find (Topaz, MGE, etc.), imperative that they be of low interwinding capacitance, otherwise the benefits aren't realized.  So many companies are completely vague about what is going on inside their power conditioners, I tend to get serious snake oil vibes...
> 
> 
> 
> ...



Very nice.
I totally understand the SS rectification. Another asset is saving from going down another tube rabbit hole with rectifiers.

I bought my first tube in month's, as I have been telling myself  "you don't need more tubes"....ha, I caved.


How much do you listen to  6A5G SET amp with your headphones ?
Bet this sounds pretty glorious.


----------



## L0rdGwyn

whirlwind said:


> Very nice.
> I totally understand the SS rectification. Another asset is saving from going down another tube rabbit hole with rectifiers.
> 
> I bought my first tube in month's, as I have been telling myself  "you don't need more tubes"....ha, I caved.
> ...



That's a nice looking rectifier, looks to be in pristine condition  I listen to the 6A5G SET every so often on headphones, maybe every two weeks or so.  I spend more time listening to the 841 hybrid amplifier with 'phones since it is on my desk and it is a dedicated headamp.

I'll probably spend more time with it when that 801A amp is done, the 6A5G amp will then be in a rotation with the others, so it might go in the main system, my desk, the bedroom...really at max capacity with the amplifiers now, I am very much pushing the limits of spouse acceptance factor 😂


----------



## whirlwind

L0rdGwyn said:


> That's a nice looking rectifier, looks to be in pristine condition  I listen to the 6A5G SET every so often on headphones, maybe every two weeks or so.  I spend more time listening to the 841 hybrid amplifier with 'phones since it is on my desk and it is a dedicated headamp.
> 
> I'll probably spend more time with it when that 801A amp is done, the 6A5G amp will then be in a rotation with the others, so it might go in the main system, my desk, the bedroom...really at max capacity with the amplifiers now, I am very much pushing the limits of spouse acceptance factor 😂


Ha ha....understand that house acceptance factor thing


----------



## bcowen

L0rdGwyn said:


> ....I am very much pushing the limits of spouse acceptance factor 😂


I'm working on a spreadsheet that will calculate exactly how much more room I'd have for my stuff if I got rid of all of hers.  

I kind of don't work on it when she's around...


----------



## Tjj226 Angel (May 9, 2021)

I'm just going to through my two cents into the ring here.

Rectifiers by themselves make no difference to audio quality. What matters is how the power supply is designed. Sometimes a power supply can be designed in such a way that they require a very specific rectifier.

But there is an even bigger picture that I feel like a lot of people need to understand. Amplifiers do not amplify. Your music does not go into a tube or a mosfet and simply come out the other end with a larger wave form. What is actually happening is that your headphones are directly connected to the power supply of the amplifier and the tubes or mosfets are simply modulating that power supply in a very controlled way to produce music. Depending on how strongly you modulate the power supply determines the volume.

If your power supply design is not designed correctly, it will sound like crap no matter what you do. Period. End of story. Rectifiers just so happen to be one component in that chain. Depending on what your particular amplifier needs, will determine what kind of rectifier you should use.

In general a perfect power supply will look like a battery with zero internal resistance. If you can achieve that goal with a tube rectifier, then great. If you can do it with a SS rectifier, even better since they are a heck of a lot cheaper. The best solution I have been able to find so far is a mosfet based rectifier.


----------



## tubebuyer2020

Tjj226 Angel said:


> ... Amplifiers do not amplify ... tubes or mosfets are simply modulating that power supply in a very controlled way ...



Isn't a "weak" input signal modulating a "strong" power signal within a "black box" of an amp effectively result in an amplified output signal to an outside observer?

What is your opinion about driver/pre-amp and power tubes?


----------



## Tjj226 Angel

tubebuyer2020 said:


> Isn't a "weak" input signal modulating a "strong" power signal within a "black box" of an amp effectively result in an amplified output signal to an outside observer?
> 
> What is your opinion about driver/pre-amp and power tubes?



IDK what the official black box theory of an amplifier is, but I think you are on the right track.

I would phrase it more like this - A weak input signal modulates a DC supply which in turn creates a strong AC signal.

Your last question is kind of vague. I like tubes. I use them in most of my amplifiers. I mostly like the fact that they are very linear devices and make great voltage amplification devices. They kinda suck as current amplifiers though


----------



## Xcalibur255

L0rdGwyn said:


> I think we've talked about it before, the isolation transformer solution is a good one, but the transformers that are worth buying can be expensive and seem to be getting harder to find (Topaz, MGE, etc.), imperative that they be of low interwinding capacitance, otherwise the benefits aren't realized.  So many companies are completely vague about what is going on inside their power conditioners, I tend to get serious snake oil vibes...


I've looked for a Topaz a couple of times, but as you said they're already hard to find and usually salvage pieces that are all beat up.  I know it's also somewhat common for them to hum and that would drive me crazy since it would be right next to where I sit.  I had to return two TrippLites because they hummed as well, noises like that drive me crazy.

I view this subject the same way I view premium cables:  it's almost impossible to truly make informed choices through research alone.  So I just stay away from it.  But when something remains "not quite right" for a long time as a setup goes through it's evolutionary path it's logical to look at the things one has never addressed or changed as the most likely sources.

I thought about trying a TrippLite medical isolator but widespread reports of hum shut that down too.


----------



## chrisdrop

Xcalibur255 said:


> I've looked for a Topaz a couple of times, but as you said they're already hard to find and usually salvage pieces that are all beat up.  I know it's also somewhat common for them to hum and that would drive me crazy since it would be right next to where I sit.  I had to return two TrippLites because they hummed as well, noises like that drive me crazy.
> 
> I view this subject the same way I view premium cables:  it's almost impossible to truly make informed choices through research alone.  So I just stay away from it.  But when something remains "not quite right" for a long time as a setup goes through it's evolutionary path it's logical to look at the things one has never addressed or changed as the most likely sources.
> 
> I thought about trying a TrippLite medical isolator but widespread reports of hum shut that down too.


Gear hum also drives me up a wall. Sitting next to my gear, in a quiet environment I feel like o can hear everything. Your comments resonate with me and make me twitch !


----------



## Tjj226 Angel

Xcalibur255 said:


> I use TrippLite ISOBars in my setup because I'm not comfortable at all with having it all plugged into the wall directly.  Summer is non-stop thunderstorms around here.  But, I do think they hurt the sound quality of the system (along with every other surge supressor I've used including the series mode ones), and these have a pretty good reputation as far as surge strips go.  The ones I have feature bank isolation and I do think it has an effect.  Things like monitors and such that have switching power supplies feed back noise into the strip and the bank isolation helps keep it from getting into the other components somewhat.
> 
> Maybe a real power conditioner is what I have been needing all this time to truly get the sound where I want it....... but I can't build enough confidence in a purchase to justify their high price.



Honestly, if power is a real concern, just look for a used AC regenerator. They are expensive as sin, but the amount of money you will spend going down the clean/safe power rabbit hole is insane. So you might as well buy once and cry once.


----------



## chrisdrop

Tjj226 Angel said:


> Honestly, if power is a real concern, just look for a used AC regenerator. They are expensive as sin, but the amount of money you will spend going down the clean/safe power rabbit hole is insane. So you might as well buy once and cry once.


I got a less expensive regenerator after many issues. Sorted. No more messing about. Powerinspired regen was not crazy expensive and did the trick.


----------



## L0rdGwyn

Xcalibur255 said:


> I've looked for a Topaz a couple of times, but as you said they're already hard to find and usually salvage pieces that are all beat up.  I know it's also somewhat common for them to hum and that would drive me crazy since it would be right next to where I sit.  I had to return two TrippLites because they hummed as well, noises like that drive me crazy.
> 
> I view this subject the same way I view premium cables:  it's almost impossible to truly make informed choices through research alone.  So I just stay away from it.  But when something remains "not quite right" for a long time as a setup goes through it's evolutionary path it's logical to look at the things one has never addressed or changed as the most likely sources.
> 
> I thought about trying a TrippLite medical isolator but widespread reports of hum shut that down too.



Wiring an MGE / Topaz transformer for balanced power seems to silence the hum.  I had read reports of this on the Topaz forum here, and it was the case for me as well, my transformer is completely silent.  It is also a haven for my cats to sit on a cold day.  I was very fortunate to find the one I did, maybe keep an eye out and a good one might show up!


----------



## Xcalibur255

Tjj226 Angel said:


> Honestly, if power is a real concern, just look for a used AC regenerator. They are expensive as sin, but the amount of money you will spend going down the clean/safe power rabbit hole is insane. So you might as well buy once and cry once.


I'd be grateful for a specific recommendation if you have one, keeping in mind that my setup is more or less "budget high end" and anything deep into 4 figures is probably a bridge too far.


----------



## Tjj226 Angel

Xcalibur255 said:


> I'd be grateful for a specific recommendation if you have one, keeping in mind that my setup is more or less "budget high end" and anything deep into 4 figures is probably a bridge too far.



Just keep your eye out for a used PS audio stellar 3. I have seen them go for 800 bucks on ebay from time to time. It's a bit costly, but it solves the problem of delivering clean power vs trying to dance around the issue with isolation transformers. Or if lordgwyn and a few others want to pitch in, I'm sure we can come up with a DIY schematic.

I have thought about building an AC regenerator for the better part of a year, and I have a very general idea of what needs to be done, but there are still some issues I have a hard time wrapping my head around.

The number 1 issue I have is figuring out the output stage. You obviously want to use some type of transformer to ensure that you have no DC on the output, however if you choose a step up transformer, then you will have to deal with the fact that you loose current capability as you choose higher and higher step up ratios.

I haven't quite nailed down the right step up ratio quite yet.


----------



## Xcalibur255

Ah, I've looked the Stellar 3 actually, but I wasn't sure if it was rated for the job.  Ideally I would want everything on it since the PC is my source, but it's limited to only 300 regenerated watts.


----------



## Tjj226 Angel

Xcalibur255 said:


> Ah, I've looked the Stellar 3 actually, but I wasn't sure if it was rated for the job.  Ideally I would want everything on it since the PC is my source, but it's limited to only 300 regenerated watts.



Depending on the PC, it could work. That being said, I wouldn't put the PC or anything else with a switch mode PSU on it.


----------



## Xcalibur255

In the bit of experimenting I've done I have found that trying to get cleaner power to the PC itself when using it as source for the DAC is quite beneficial.  At least as much so as taking care of a similar source such as a CD transport in the same way.  I really shot myself in the foot when I built this PC though...... it's one of those cute little miniITX builds and it uses a front mounted PSU tray.   Meaning the power supply has an internal umbilical cable whose quality I have no control over and I've been given reason to believe the quality of that cable is crap.  I'm sure replacing this is pretty entry level DIY skill but I don't have the will to mess with it.  It feels like every time I fiddle with anything it just makes things worse so now I'm gun shy.


----------



## Tjj226 Angel

Xcalibur255 said:


> In the bit of experimenting I've done I have found that trying to get cleaner power to the PC itself when using it as source for the DAC is quite beneficial.  At least as much so as taking care of a similar source such as a CD transport in the same way.  I really shot myself in the foot when I built this PC though...... it's one of those cute little miniITX builds and it uses a front mounted PSU tray.   Meaning the power supply has an internal umbilical cable whose quality I have no control over and I've been given reason to believe the quality of that cable is crap.  I'm sure replacing this is pretty entry level DIY skill but I don't have the will to mess with it.  It feels like every time I fiddle with anything it just makes things worse so now I'm gun shy.



Sure. But by putting a switch mode psu on the same circuit, you dirty the power for your amp and dac. 

I would also argue that if doing something to your pc makes the audio better, then there are larger issues that should be addressed first. 

My guess is that you are using USB for your dac correct? What dac do you have.


----------



## Xcalibur255

Schiit Yggdrasil, and it is indeed fed with USB.  I have found that cleaner power into the computer has about the same effect as those USB decrapifiers have more or less.  The power supply in the PC has good regulation but I doubt it really filters anything that's coming into it for noise.  The CPU and critical sections will of course have their own regulation but the 5V supply that powers USB and such seems to be at the mercy of whatever is coming in from the IEC receptacle.

I realize it's not a good platform for an audiophile listening setup, but it's what I prefer.  I do all my listening while seated in front of this PC so there's no sense in having a music server or dedicated streaming device when it's all sitting right in front of me anyway.


----------



## leftside

Xcalibur255 said:


> Schiit Yggdrasil, and it is indeed fed with USB.  I have found that cleaner power into the computer has about the same effect as those USB decrapifiers have more or less.  The power supply in the PC has good regulation but I doubt it really filters anything that's coming into it for noise.  The CPU and critical sections will of course have their own regulation but the 5V supply that powers USB and such seems to be at the mercy of whatever is coming in from the IEC receptacle.
> 
> I realize it's not a good platform for an audiophile listening setup, but it's what I prefer.  I do all my listening while seated in front of this PC so there's no sense in having a music server or dedicated streaming device when it's all sitting right in front of me anyway.


You can continue to use your PC and SSD drive, but also connect something like a SoTM Ultra Neo to your router and then connect the Neo to the DAC. That's what I do anyway, but obviously there are multiple ways to try and improve computer audio. Head on over to Computer Audiophile, and all the different methods and gadgets there will make setting up a turntable and cart seem like a piece of cake.


----------



## Xcalibur255

Yeah for some reason the setup side of this stresses me out greatly.  Every once in a spell I'll get in the mood to tinker but most of the time I dig my heels in and don't want to touch it because it sets off a series of OCD episodes.

It's not like the system sounds *bad* and I've made great progress in getting rid of the hardness and tizziness I hear in the upper mids, but for the total price spent on all the components present I feel like the setup should have a greater sense of ease and flow than it has.  The system has always had a bit of a shouty "in your face" quality to it.  My Glenn OTL at work that I used for all my recent 6J5 testing doesn't have the sheer resolution of my home system, but it DOES have that sense of ease and flow to it so I find myself enjoying it more overall.

The other thing I'm messing with right now are cables.  I haven't touched them in a long time, so on the one hand there is a certain stability there but also some of the problem could be living there.  So I bought a different brand of cable at a similar price point and I've been doing some comparing.  What I'm hearing is promising, the new cable seems like an improvement, but I want to slow burn this experiment to make sure it isn't expectation bias at work.

I appreciate the input so far guys.  I'm grateful for any advice.  I get too stuck in my own head when thinking about this stuff.


----------



## Xcalibur255

@Tjj226 Angel 

I did some digging and at the 20-40% load the PSU is likely seeing it looks like it has around 12-14mV of ripple on the applicable rail.  This seems pretty good for a PC power supply.  What do you think?


----------



## Tjj226 Angel

@Xcalibur255 

No, cleaning up your PC power is not the same as a USB decrapifier. 

When you use so called synchronous USB your internal dac clock is slave to your PC. That means your Dac's jitter performance is almost entirely dependent on what is happening with your computer. 

Unfortunately no matter what you do, your PC will always be a noisy environment and your clock/jitter performance will suffer. You can improve it with better power supplies and so on, but all you are doing is putting lip stick on a pig. 

So long as you are not listening to DSD or some very high sample rate music, I would encourage you to look at using optical spdif with a better than walmart brand quality cable. Preferably a true glass cable. But if you have a M-ITX computer, I am going to take a wild guess and say you are probably limited to USB.

In which case, I would encourage you to look for some type of USB decrapifier that coverts your Synchronous USB to Asynchronous USB. Fair warning, they are very expensive and hard to find. I haven't found one that I would recommend, but I haven't looked that hard either.

With Asynchronous usb, you are just sending bits to your dac. The clock signal is actually discarded and the clock in your dac (or an external after market master clock) can take over. 

Even if you want to cheap out and find a USB decrapifier that uses some decent galvantic isolation, you would still be better off.


----------



## tubebuyer2020

Xcalibur255 said:


> Schiit Yggdrasil, and it is indeed fed with USB.  I have found that cleaner power into the computer has about the same effect as those USB decrapifiers have more or less.  The power supply in the PC has good regulation but I doubt it really filters anything that's coming into it for noise.  The CPU and critical sections will of course have their own regulation but the 5V supply that powers USB and such seems to be at the mercy of whatever is coming in from the IEC receptacle.
> 
> I realize it's not a good platform for an audiophile listening setup, but it's what I prefer.  I do all my listening while seated in front of this PC so there's no sense in having a music server or dedicated streaming device when it's all sitting right in front of me anyway.



But is Yggdrasil actually getting 5v power via USB? I had an issue with my Khadas and a Garage1217 amp where there was hum at very loud volumes. I solved it with iFi gadgets to inject clean 5v power into the USB for Khadas. The setup is now absolutely quiet at maximum volume. I doubt this is the issue you are facing, but just wanted to add my amateur 5 pence.


----------



## Xcalibur255

I am pretty much forced into USB, but forced isn't the right word for it anyway.  I was eager to get away from SPDIF output because the sample rate can't be dynamically changed.  I researched this to death and couldn't find a soundcard, even a professional one, that did.  You specify a sampling rate in the output and it's locked.  What I wanted was intelligent pass-though, that way if I play a 44.1/16 file and then the next file is 24/96 I want it to just send the appropriate sample rate to the DAC.  USB via ASIO does this, but every SPDIF output I've seen on every soundcard has you pick one from a dropdown list and that's it, it will resample to that rate if the source doesn't match.  Having to go into the driver between tracks was a hassle I wanted to do away with.

As for Yggdrasil according to what I have read its USB input is asynchronous.  I'm sure it could be improved upon of course but I didn't think I was in terrible shape on that front.


----------



## Tjj226 Angel

Xcalibur255 said:


> I am pretty much forced into USB, but forced isn't the right word for it anyway.  I was eager to get away from SPDIF output because the sample rate can't be dynamically changed.  I researched this to death and couldn't find a soundcard, even a professional one, that did.  You specify a sampling rate in the output and it's locked.  What I wanted was intelligent pass-though, that way if I play a 44.1/16 file and then the next file is 24/96 I want it to just send the appropriate sample rate to the DAC.  USB via ASIO does this, but every SPDIF output I've seen on every soundcard has you pick one from a dropdown list and that's it, it will resample to that rate if the source doesn't match.  Having to go into the driver between tracks was a hassle I wanted to do away with.
> 
> As for Yggdrasil according to what I have read its USB input is asynchronous.  I'm sure it could be improved upon of course but I didn't think I was in terrible shape on that front.



Which version of USB do you have with your Yggdrasil?


----------



## Xcalibur255

It came with Gen 3 and I upgraded it to Gen 5 a while back.

I suspect a combination of a few different minor things is to blame ultimately, but I tend to keep working on the things I know and ignore the things I don't.  Which is why I have ignored power conditioning all this time.


----------



## Tjj226 Angel

Xcalibur255 said:


> It came with Gen 3 and I upgraded it to Gen 5 a while back.
> 
> I suspect a combination of a few different minor things is to blame ultimately, but I tend to keep working on the things I know and ignore the things I don't.  Which is why I have ignored power conditioning all this time.



Is gen 5 the unison thing? I can't figure out if the unison usb implementation they have is asynch or not.


----------



## johnjen

No the unison USB is their latest itteration.
The gen 5 USB introduced galvanic isolation (they used ethernet input xfrmrs) to decouple the USB data stream.

JJ


----------



## Tjj226 Angel

johnjen said:


> No the unison USB is their latest itteration.
> The gen 5 USB introduced galvanic isolation (they used ethernet input xfrmrs) to decouple the USB data stream.
> 
> JJ



Huh. Interesting. 

If Gen 5 has true galvanic isolation (your dac does not share a ground with the PC), the USB connection is self powered, and your dac does not even look at the clock signal from the PC, then improving your pc power supply SHOULD not make a difference if we assume your PC is sending out bits with a near 0 error rate. 

Things I would do to improve your system. 

1: Get the unison upgrade. Mike Moffat designed it to be the best they have to offer, so you might as well take advantage of it. 

2: Make sure you are using a proper USB cable. I can't tell you how many times I have run across cheap USB3 cables that weren't even compliant with USB 2.0 standard. 

3: Get a better power supply for your PC. If improving your PC power makes an audible difference in your system, then the most obvious way of improving your setup is to swap power supplies. IDK what you currently have, but the seasonic prime ultra platinum power supply would cut your ripple numbers in half. Silly name for a PSU, but it has amazing performance figures. 

4: Listen for and address any coil whine in your PC. I did have a tiny bit of coil wine on my pc for a while and it was causing all kinds of weird issues with my audio. I ended up replacing the motherboard, and the audio went back to being normal.


----------



## leftside (May 14, 2021)

Tjj226 Angel said:


> seasonic prime ultra platinum power supply


That's what I have. Put one in when I assembled my media center/audio server PC a couple of years ago. One of the primary concerns for me was actually the quietness of the power supply as the PC is in the living room.


----------



## Xcalibur255 (May 14, 2021)

My PC has a SeaSonic Focus SGX.  Best power supply you can get in the SFF-L (which my ITX case required) form factor as far as I know.  I'm pretty old hat at PC building and am pretty picky about my power supplies.  

It's sounding like I have already taken the common sense steps, which makes me feel better.  I always wonder if I'm missing something I haven't stumbled across and don't know to research yet, which is why I like to have these conversations.  Sometimes somebody will drop a nugget of wisdom that is entirely new and those are invaluable.

It's worth nothing as well that I'm starting to believe more and more that at least part of my problem was the brand of interconnects I was using.  I've bought some different ones and have been experiment and so far what I'm hearing strikes me as an improvement.  I just rotated my Glenn 45 back in the system tonight so I'll do some listening tests over the next couple of weeks and see where that leads.  Maybe I can get to the point where an expensive power conditioner isn't necessary.  I suppose that's really what I'm grappling with is the high cost.  I want to try and gain some kind of reassurance that the improvement will at least somewhat be worth it, but this particular category of the audiophile world really triggers my snake oil sense.  I get a strong feeling that a lot of those fancy boxes that cost thousands of dollars only have a hundred bucks worth of parts inside.  I guess that's true of many things in life though, I've just decided to take umbrage with this particular example for some reason.


----------



## L0rdGwyn

Xcalibur255 said:


> My PC has a SeaSonic Focus SGX.  Best power supply you can get in the SFF-L (which my ITX case required) form factor as far as I know.


----------



## Xcalibur255 (May 14, 2021)

Very clean build!

I built a mini-ITX about that size for a friend last summer and I'll never do it again.  Never had such a frustrating build in my life.  It turned out well, but man EVERY single cable and connector is a battle in those.  It was one of those mini-fridge shaped ones where you work from the top of the case instead of the side.  Turns out that isn't an improvement at all when it comes to getting your fingers into places.

I kind of regret building my own machine as an ITX.  It's cute and all with its little magnetic folding carry handle and everything but it didn't actually need to be portable, I just liked the idea of it being petite.  Next time whenever that is it'll be back to the old tried and true ATX mid tower assuming they still exist at that point.

edit:  actually LG is that the Ncase M1 (or its little brother)?  If so then it is mostly the same case as mine.  Both are made by Lian Li.  Did the screwless panel clips give you any trouble?  I had to get replacements from them because they were breaking.  It's a neat idea but I don't care for the implementation, it kind of makes the case feel a bit cheap and rattly.  Having aluminum side panels instead of steel also invites more opportunities for fan vibration resonance.  Just goes to show the old ways are best sometimes just like with tubes.


----------



## Tjj226 Angel

Xcalibur255 said:


> Very clean build!
> 
> I built a mini-ITX about that size for a friend last summer and I'll never do it again.  Never had such a frustrating build in my life.  It turned out well, but man EVERY single cable and connector is a battle in those.  It was one of those mini-fridge shaped ones where you work from the top of the case instead of the side.  Turns out that isn't an improvement at all when it comes to getting your fingers into places.
> 
> ...



Yeup. Same here. I had an Itx build, but I actually built the PC on a small sheet of mdf and hung it off the back side of my monitor to make a bastardization of an Imac. 

It worked out well for a long time, but it got tiring real quick. I finally rebuilt my PC a few months ago and did a silent PC with a fractal design case and I don't intend on going back to mini itx for my main rig ever again.


----------



## L0rdGwyn

Xcalibur255 said:


> Very clean build!
> 
> I built a mini-ITX about that size for a friend last summer and I'll never do it again.  Never had such a frustrating build in my life.  It turned out well, but man EVERY single cable and connector is a battle in those.  It was one of those mini-fridge shaped ones where you work from the top of the case instead of the side.  Turns out that isn't an improvement at all when it comes to getting your fingers into places.
> 
> ...



It is the DAN Case, but manufactured by Lian Li.  Can't say if it is still true, but a few years ago, this was the smallest volume case on the market that supported a full-size graphics card.  I like that it takes up little space on my desk, and honestly there is just something fun about squeezing a ton of hardware horse power into a tiny form factor.  I haven't had any issue with the screwless side panels, it is a very well-made.

I ended up getting the smallest full copper low profile heat sink I could and mated it with a Noctua fan.  I delidded the Intel i7-8700K and applied liquid metal directly to the CPU and put it all back together.  Stays nice and cool 

Here is another nerdy picture I took at the time lol.


----------



## leftside (May 14, 2021)

Xcalibur255 said:


> my snake oil sense.  I get a strong feeling that a lot of those fancy boxes that cost thousands of dollars only have a hundred bucks worth of parts inside.  I guess that's true of many things in life though, I've just decided to take umbrage with this particular example for some reason.


Open up one of those very expensive (> $10k) branded media servers. You are just paying for a fancy box and the name. Far better off doing it yourself (no soldering - just assembling), or visiting a local PC builder and say you want premium and quiet parts for audio/media center and they will build one for you.


----------



## L0rdGwyn (May 14, 2021)

The chassis for the 801A amplifier is being powder coated this weekend, so I should have it next week some time.  Will only have two days to work on the amp since I will be out of town the last week of the month, so the build will probably spill over into June.

The chassis is going to be a medium gray, the recessed socket plates will be matte black.  I think I said so before, but this amplifier is meant to look vintage, so channeling some aesthetics from old tube test gear, which often is a flat gray.  Just trust me on this one 

Here is the gray I chose: https://www.prismaticpowders.com/shop/powder-coating-colors/PSB-6814/graphite-stone

So with the imminent arrival of the chassis, have to tie up some loose ends...

I broke down the amplifier prototype.  The protoboard is ready for the next round of insanity.




As I said, I don't really have room for more amplifiers, but that won't stop me from messing around on this thing.  I am thinking about trying something I haven't seen before - rather than doing the E55L spud idea I was bouncing around a while back, I might try it as a 500mW OTL headphone amp, assuming I can tame any oscillations.  With the whopping 50mA/V transconductance of the E55L, output impedance should be around 20ohms as a cathode follower.  As usual, I have a simulation made, we'll see.

I don't often post schematics here because honestly I am not looking for feedback, but the 801A amp design is very much finalized, maybe it will interest someone.  Here it is, over a year after the idea was conceived.  Many, many hours of subjective and objective testing went into it, and I am happy with the result.



Each channel has its own Maida regulator for B+ and shunt regulator for B-, only the rectifier / reservoir loop is shared between the power supplies of each channel.

This amplifier does around 0.3% THD at 1W into 8ohms, around 1.5% THD at 7W into 8ohms, full output at the onset of clipping.  Output impedance is around 1.7ohms.

Here is some other stuff I designed for this build.

Teeny tiny 1mA LND150 CCS boards, 1"x1" footprint.



Another small footprint effort - IXCP10M90S current sinks for the 6BX7 cathode follower.  These need to dissipate around 3W.



And the TL431 shunt regulator, one per channel, spec'd to handle the 25mA bias current of the 6BX7.



I'll post some pictures of the build as it progresses.  Who knows, maybe I can finish it in two days.


----------



## Xcalibur255

Tjj226 Angel said:


> Yeup. Same here. I had an Itx build, but I actually built the PC on a small sheet of mdf and hung it off the back side of my monitor to make a bastardization of an Imac.
> 
> It worked out well for a long time, but it got tiring real quick. I finally rebuilt my PC a few months ago and did a silent PC with a fractal design case and I don't intend on going back to mini itx for my main rig ever again.


The PC I just retired this winter was in a Fractal Define R3 case.  Gave 11 years of completely trouble-free service and was still working perfectly when I replaced it.  When I would build machines for others and they'd whine "why can't you just use a $30 power supply it's the same watts" I always point to stuff like this as my example.  The SeaSonic is a large part of the reason why nothing failed in that machine after 11 years of almost constant use.


----------



## Xcalibur255

L0rdGwyn said:


> It is the DAN Case, but manufactured by Lian Li.  Can't say if it is still true, but a few years ago, this was the smallest volume case on the market that supported a full-size graphics card.  I like that it takes up little space on my desk, and honestly there is just something fun about squeezing a ton of hardware horse power into a tiny form factor.  I haven't had any issue with the screwless side panels, it is a very well-made.
> 
> I ended up getting the smallest full copper low profile heat sink I could and mated it with a Noctua fan.  I delidded the Intel i7-8700K and applied liquid metal directly to the CPU and put it all back together.  Stays nice and cool
> 
> Here is another nerdy picture I took at the time lol.


Yeah I just don't have the patience to fight with that little guy.  I used a Lian-Li TU-150.  It's still very small for a PC case but it's probably at least 50% more internal volume than this is.  I love the clean look of it though......... everything has to be festooned with LEDs and mesh and windows and dumb logos these days.  Give me a clean looking black box please.

Congrats on locking the 801A design in btw.  I have no doubt at all it will be an incredible amplifier when it's finished.


----------



## bcowen

Xcalibur255 said:


> The PC I just retired this winter was in a Fractal Define R3 case.  Gave 11 years of completely trouble-free service and was still working perfectly when I replaced it.  When I would build machines for others and they'd whine "why can't you just use a $30 power supply it's the same watts" I always point to stuff like this as my example.  The SeaSonic is a large part of the reason why nothing failed in that machine after 11 years of almost constant use.


Speaking of retiring, how about a ~20 year old Lian Li?  A wee bit larger than an ITX case.   This one has had several different builds, initially hosting four 10k RPM WD Raptor drives in a mirrored raid array, Koolance water cooling for the CPU and graphics card, 800 watt PC Power and Cooling power supply, and yada yada.  A bit simpler now, but I only use it for web surfing and scanning mostly.  Different parts, same old case.


----------



## bcowen

L0rdGwyn said:


> The chassis for the 801A amplifier is being powder coated this weekend, so I should have it next week some time.  Will only have two days to work on the amp since I will be out of town the last week of the month, so the build will probably spill over into June.
> 
> The chassis is going to be a medium gray, the recessed socket plates will be matte black.  I think I said so before, but this amplifier is meant to look vintage, so channeling some aesthetics from old tube test gear, which often is a flat gray.  Just trust me on this one
> 
> ...


Nice!!!


----------



## Xcalibur255

@bcowen

Four Raptors?  That must have sounded like putting rocks in a blender.  Those things were so noisy while seeking.

Love the fan controller.


----------



## bcowen

Xcalibur255 said:


> @bcowen
> 
> Four Raptors?  That must have sounded like putting rocks in a blender.  Those things were so noisy while seeking.
> 
> Love the fan controller.


Those Raptors definitely had a whine to them.  But at the time (and especially in a Raid config) they were way faster than anything else out there.  Now even a cheap SSD blows them into the weeds.  They're actually still in the case, just not connected.  

I've toasted 2 motherboards over the years via the fan headers, so I opted to go with manual control for the case fans rather than plug them into the MoBo.  Only fan that's plugged into it is the CPU fan so it will spin up and down as needed.


----------



## Galapac

bcowen said:


> Speaking of retiring, how about a ~20 year old Lian Li?  A wee bit larger than an ITX case.   This one has had several different builds, initially hosting four 10k RPM WD Raptor drives in a mirrored raid array, Koolance water cooling for the CPU and graphics card, 800 watt PC Power and Cooling power supply, and yada yada.  A bit simpler now, but I only use it for web surfing and scanning mostly.  Different parts, same old case.


Geez Bill, you got tubes stacked everywhere. Even next to your PC.


----------



## bcowen

Galapac said:


> Geez Bill, you got tubes stacked everywhere. Even next to your PC.


LOL!  Just temporary, promise.  Pulled those out of the Cary Super Amp getting ready to do some cap surgery, and then other things got in the way.  And geeez...a box of parts still sitting there waiting to be put in the DarkVoice.  I need to learn how to focus. Or do things faster.  Or both.


----------



## L0rdGwyn

Here are some pics Dave sent of the powder coated chassis.


----------



## L0rdGwyn

Alright, chassis is here, going to see if I can build this thing in two days.

Here is a pic, shows what I did with the recessed socket plates.  Let's get to work.


----------



## triod750

You will paint it black when you have assembled it, won't you?


----------



## L0rdGwyn

No, that isn't a primer, the chassis is gray.


----------



## triod750

Just pulling your leg


----------



## Xcalibur255

It's a timeless color.

https://www.history.navy.mil/conten...ries/dn-sc-92-05364-uss-missouri--bb-63-.html


----------



## L0rdGwyn

Finished prepping the chassis, now mounting parts.  I like how things are looking so far, nice seeing the vision in your head come to life.  The sockets are vintage Amphenol.


----------



## Zachik

L0rdGwyn said:


> Finished prepping the chassis, now mounting parts.  I like how things are looking so far, nice seeing the vision in your head come to life.  The sockets are vintage Amphenol.


I envisioned the tube sockets being more recessed than that... Looks good, just not what *I thought* it would look like


----------



## L0rdGwyn

Zachik said:


> I envisioned the tube sockets being more recessed than that... Looks good, just not what *I thought* it would look like



You know originally that's what I had planned, recessing them further down, 1cm lower, did some experimenting and actually think this looks better!


----------



## Zachik

L0rdGwyn said:


> You know originally that's what I had planned, recessing them further down, 1cm lower, did some experimenting and actually think this looks better!


I guess I did not remember... too many things on my mind (including my next amp )...
Either way, THIS looks very good!


----------



## bcowen

L0rdGwyn said:


> Alright, chassis is here, going to see if I can build this thing in two days.
> 
> Here is a pic, shows what I did with the recessed socket plates.  Let's get to work.


Looks great!  Even though it's not Carolina Blue, I still give it two thumbs up.


----------



## triod750

bcowen said:


> Looks great!  Even though it's not Carolina Blue, I still give it two thumbs up.


Well, it isn't pretty but it is pretty pretty.

(The other leg).


----------



## L0rdGwyn

Here is progress on the interior.  Have just about everything mounted but the transformers.  Have to figure out how I am going to arrange terminal strips around the sockets, then wire it all up.


----------



## L0rdGwyn

I think I'll leave it there for today, that was a lot to do in five or six hours, will get back at it bright and early tomorrow morning


----------



## tubebuyer2020 (May 21, 2021)

L0rdGwyn said:


> Finished prepping the chassis, now mounting parts.  I like how things are looking so far, nice seeing the vision in your head come to life.  The sockets are vintage Amphenol.



It looks like mid-century scientific equipment - my favourite look! Also I like tube sockets that don't scratch the tube keyed post.



L0rdGwyn said:


> Here is progress on the interior.  Have just about everything mounted but the transformers.  Have to figure out how I am going to arrange terminal strips around the sockets, then wire it all up.



Very efficient use of vertical spaces!


----------



## L0rdGwyn

tubebuyer2020 said:


> It looks like mid-century scientific equipment - my favourite look! Also I like tube sockets that don't scratch the tube keyed post.
> 
> 
> 
> Very efficient use of vertical spaces!



Thanks!  The idea was to make the amp look somewhat vintage, so glad that worked out.  Hopefully I will be able to finish it today, we will see...


----------



## L0rdGwyn

Transformers mounted.  Now the great point-to-point wiring extravaganza.


----------



## tubebuyer2020 (Jul 15, 2021)

L0rdGwyn said:


> Thanks!  The idea was to make the amp look somewhat vintage, so glad that worked out.  Hopefully I will be able to finish it today, we will see...



I tried making a case (or a cage rather) myself some time ago; went with a laser cut + spray paint due to budget constraints mainly; it's not easy but very satisfying when/if it all comes together.


----------



## L0rdGwyn

Progress.

Power supply is pretty much done.  Definitely the fastest I've ever done a build.  Onward!


----------



## whirlwind

Looks very nice.


----------



## L0rdGwyn

whirlwind said:


> Looks very nice.



Thanks, Joe.  I might be kind to myself and finish it tomorrow instead of doing the marathon today.

I am planning to sleeve the input tube top cap wiring with a specific pattern of paracord that matches the amp, that order was delayed and won't be here until tomorrow apparently.  I can't show off the final build until it is all the way done!  Paracord and all.


----------



## L0rdGwyn

Almost done, maybe 85%, working my way from output to input.  Input stage is next.


----------



## whirlwind

You are not messing around!

Nice chassis...nice and roomy

Thats a lot of soldering.


----------



## L0rdGwyn

Yeah, it is a lot of soldering!  I did some more but I think I am done for the today, I'll wrap it up tomorrow morning


----------



## bcowen

L0rdGwyn said:


> Almost done, maybe 85%, working my way from output to input.  Input stage is next.


Very nice!  And unless I miscounted, you're going to need 7 of these.  Whew.  Getting pricey.


----------



## L0rdGwyn

bcowen said:


> Very nice!  And unless I miscounted, you're going to need 7 of these.  Whew.  Getting pricey.



LOL just five thanks very much, mains fuse, two transformer secondary fuses, and two cathode fuses on the 801A, a casual $800.  For audio nirvana, it's worth it 

Back at it this morning, going to try and finish before noon.


----------



## L0rdGwyn

Alright, it's done.

Circuit first...


----------



## L0rdGwyn

And the amp itself.  Note that the grid caps leads were meant to be sleeved in paracord, but it did not arrive in time, so just bare cable jacket for now, but have to admit I think it looks good in black.


----------



## A2029

L0rdGwyn said:


> Alright, it's done.
> 
> Circuit first...





L0rdGwyn said:


> And the amp itself.  Note that the grid caps leads were meant to be sleeved in paracord, but it did not arrive in time, so just bare cable jacket for now, but have to admit I think it looks good in black.



Beautiful! I really dig the grey chassis, reminds me of old school military gear. Congrats on the build Keenan!


----------



## Galapac

L0rdGwyn said:


> And the amp itself.  Note that the grid caps leads were meant to be sleeved in paracord, but it did not arrive in time, so just bare cable jacket for now, but have to admit I think it looks good in black.


Call it the B-19 cause it’s the Bomb! Congrats! You always amaze me that you can put these together so fast with no issue.


----------



## L0rdGwyn

A2029 said:


> Beautiful! I really dig the grey chassis, reminds me of old school military gear. Congrats on the build Keenan!



Thanks, Mischa!  That's kinda what I was going for, sort of a Hickok TV-7D/U look, glad it comes across  



Galapac said:


> Call it the B-19 cause it’s the Bomb! Congrats! You always amaze me that you can put these together so fast with no issue.



Thank you sir.  There is always at least one hiccup.  This time it was underrating the negative supply secondary fuse for inrush, which had me searching for a short that didn't exist 😂 increasing the rating slightly solved the problem.  The trick to building amplifiers quickly is doing literally nothing else for three days.


----------



## L0rdGwyn

I swapped out the Tung-Sol 6BX7 for some Japanese Toshibas.  I have pretty much every type of 6BX7 under the sun from the Glenn OTL days, these were one of my favorites.  The heaters have a very nice glow.


----------



## triod750

Is it too early to say whether you have achieved your design goals?
(Please don't paint it black).


----------



## Mr Trev

triod750 said:


> Is it too early to say whether you have achieved your design goals?
> (Please don't paint it black).


Agreed. That battleship grey looks awesome!


----------



## L0rdGwyn

triod750 said:


> Is it too early to say whether you have achieved your design goals?
> (Please don't paint it black).



I would say the design goals have been achieved!  Only able to listen for a few hours, night shift is a bummer, but of course this isn't the first time I've listened to this circuit.  The sound is the best of the amplifiers I've designed, particularly the low end, really unlocks a new level of bass potential from my Snells.


----------



## triod750 (May 22, 2021)

So it's just lacking the paracord then?

Edit: Congratulations!!


----------



## L0rdGwyn

triod750 said:


> So it's just lacking the paracord then?
> 
> Edit: Congratulations!!



Yup, just going to sleeve the grid cap leads in paracord.  I had picked out a pattern that matched the color motif of the amplifier, but now that I've seen it in black, I might just use a plain black cord.

Regardless, it won't get done any time soon!  I work all weekend then will be out of town for a week starting Tuesday, the reason I was in such a rush to get this amp built.


----------



## triod750

L0rdGwyn said:


> Yup, just going to sleeve the grid cap leads in paracord.  I had picked out a pattern that matched the color motif of the amplifier, but now that I've seen it in black, I might just use a plain black cord.
> 
> Regardless, it won't get done any time soon!  I work all weekend then will be out of town for a week starting Tuesday, the reason I was in such a rush to get this amp built.


Swift and perfect is acceptable.


----------



## whirlwind

I love the old skool look too!  Killer color for this amp and I dig the volume knob to!

I like the recessed sockets...they are recessed but not overly so.

Congrats and enjoy that beast Keenan!

Thanks for sharing the pics.


----------



## bcowen

L0rdGwyn said:


> And the amp itself.  Note that the grid caps leads were meant to be sleeved in paracord, but it did not arrive in time, so just bare cable jacket for now, but have to admit I think it looks good in black.


Totally awesome!


----------



## L0rdGwyn

Thanks again, guys.  This was a long time coming...probably the last major project I do for a long time.  Have a list of things I COULD work on, but they are all very involved, might just hit the books for a while and listen to some music.


----------



## chrisdrop

whirlwind said:


> I love the old skool look too!  Killer color for this amp and I dig the volume knob to!
> 
> I like the recessed sockets...they are recessed but not overly so.
> 
> ...


I agree with the @whirlwind - love the look; volume knob, recessed sockets, etc. 

Congrats on yet-another beautiful accomplishment. I hope completing it feels as good as the amp looks, and no doubt sounds.


----------



## L0rdGwyn

I sleeved the 6F5 grid cap leads with paracord today, gives the amp a little pizzazz.




Here how it looks with some graphite plate RCA 801A.


----------



## L0rdGwyn

Summoning @UntilThen , I finished my 801A amplifier finally, check it out


----------



## UntilThen

L0rdGwyn said:


> Summoning @UntilThen , I finished my 801A amplifier finally, check it out



Holy sheet that is an outstanding tube amp. I could turn the volume knob the whole day. Love the Sowter transformers look and I can picture how Odyssey will turn out except you have the power transformer too ! Oh well Odyssey has to make do with a Hammond power transformer and 2 Sowter output transformers.

Stick around buddy. I will have to persuade you to make me a tube amp next year. Tubes undecided but 6BX7 as drivers sound good. I still have 12 of those tubes - 2 sets. 

Are the 6f5 rectifiers?


----------



## L0rdGwyn

UntilThen said:


> Holy sheet that is an outstanding tube amp. I could turn the volume knob the whole day. Love the Sowter transformers look and I can picture how Odyssey will turn out except you have the power transformer too ! Oh well Odyssey has to make do with a Hammond power transformer and 2 Sowter output transformers.
> 
> Stick around buddy. I will have to persuade you to make me a tube amp next year. Tubes undecided but 6BX7 as drivers sound good. I still have 12 of those tubes - 2 sets.
> 
> Are the 6f5 rectifiers?



Thanks!  You will be very happy with Sowter, they are one of the best.  I was disappointed to hear they stopped custom mains, I had a long discussion with Martin there, it is possible they might bring it back in some capacity, but with higher prices and some design limitations.  I wouldn't have been able to build this as is without that custom mains, it was crucial.

6BX7 are very versatile, pretty good for a TV tube!  Make great cathode followers and drivers 

The 6F5 are high gain input tubes, sort of a cousin to the 6J5 actually, but gain of 100 with a high internal resistance.  Sort of a niche type of tube, but works very well in this circuit - the cathode follower handles the high internal resistance and the high gain is perfect for the amount of negative feedback I implemented.  They are extremely linear, low distortion, I was very happy to find them.


----------



## UntilThen

I have to stop Bcowen salary for a year to get one of your amp.

This is strictly speakers right? Which is ok...  how many watts into 8 ohms load Keenan?


----------



## L0rdGwyn

Yup, this one is strictly speakers, it does 7W into 8ohms, around 0.3% THD at 1W.  If I were ever to bring it to a Head-Fi event, I'd probably make a little box with some speaker binding posts on the back, headphone jack in the front, and some 8ohm resistors inside so that it could be listened to with headphones 

With my 92dB/W speakers, even listening at midnight position on the pot is very loud, can really rock the house with this amp-speaker combo.


----------



## UntilThen

7w is a little more than Auris Nirvana at 6.5w. More headroom is always welcome.

I have to get Eric to make me such a box for turning from speakers to headphones.


----------



## L0rdGwyn (May 23, 2021)

A box like that might be handy to have around!  Now you have a more interesting amp than Nirvana on the way 

I think the tube gods were smiling upon me the day I finished this amp, I won a pair of RCA 801A in overseas auction for a stupidly low price.

They are NIB, I paid $68 for the pair.  Meanwhile NA eBay sellers are trying to charge upwards of $300.  Score!



I was listening to those graphite plate 801A for some time today, I have my eye on another graphite pair, I think there is something to that graphite...


----------



## L0rdGwyn (May 24, 2021)

Here is how bias adjustment is done in the 801A amplifier.  There is a 1ohm resistor across the two mini banana test points on top of the chassis, connected to the 801A filament.  As such, 1mV across the resistor is equivalent to 1mA of bias, so the voltage is measured and adjusted accordingly.  I shoot for 55mA, puts the 801A at about 88% of max plate dissipation.  Any change in 801A or 6BX7 necessitates and bias adjustment since they are interdependent.  What is happening is the 6BX7 cathode voltage is being altered by adjusting its grid voltage.  The cathode is direct-coupled to the 801A grid, so altering the bias of the cathode follower adjusts the bias of the 801A.



I tried to make a comment on the performance of this amp in my last post but deleted it since it didn't come out right lol.  What I was trying to say is I think I am done with speaker amps for a while, this one is really going to be hard to top for me, anything that comes after this will have to be quite unique and that means difficult to design.

It will probably be based on the HK54, which could also run the 35TG.  From a design standpoint, if the 801A amp is crazy, the HK54 amp would be absolutely insane. 



Many of the design aspects of the 801A amp would make it into an HK54 build, but without a negative supply.  The HK54 biases at a positive grid voltage, meaning the grid is drawing current _all the time_.  Grid voltage would be positive, in A2, around 90% of the time.  This means you need a beast of a cathode follower or a MOSFET.  What I have penciled is the EL34, choke loaded, which would work well.  At my planned bias and load, the HK54 only has to swing around -20V negative to hit full output, that last bit of swing can be supplied by the choke, so a negative supply wouldn't be necessary.  Cool, so some sort of low distortion / high gain stage to apply appropriate NFB, then EL34 cathode follower direct coupled to the HK54.  This amp would need around 25dB of NFB as my draft stands, which of course is subject to change.

The HK54 has a 25W thoriated tungsten filament.  I already have the Rod Coleman regulators, but they would need to go on beefy dedicated heat sinks, externally mounted, with dedicated filament transformers.



Also, some sort of shroud would need to be designed such that the plate and grid caps are not touchable, having 450V exposed is not such a good idea.  So two filament transformers (Antek), two output transformers (Lundahl), two chokes (Lundahl), a mains transformer (Lundahl), some sort of transparent ventilated shroud (glass or plexiglass), externally mounted filament heat sinks, and even potentially active cooling, silent Noctua fans mounted on the interior bottom plate.

So what this amounts to is an absolute monstrosity of an amplifier - big, hot, 15W single-ended, and absolutely awesome, and absolutely ridiculous.

I don't know when I'll do it, but that is probably the only speaker amp I will want to build after this one.  Probably for the best that it is so crazy, might keep me from doing it for a while lol.


----------



## UntilThen

Fascinating. I woke up this morning to see the HK54 tubes.   Visually a very striking tube even just for display. 

I had forgotten we talk about amps last year in the DV336se thread.
https://www.head-fi.org/threads/darkvoice-336i-336se-tuberolling-partii.348833/post-16059674


----------



## triod750

Tom Waits; Mule Variations; 'What is he building in there'?


----------



## L0rdGwyn

UntilThen said:


> Fascinating. I woke up this morning to see the HK54 tubes.   Visually a very striking tube even just for display.
> 
> I had forgotten we talk about amps last year in the DV336se thread.
> https://www.head-fi.org/threads/darkvoice-336i-336se-tuberolling-partii.348833/post-16059674



Right now they are for display only!  I have a few pairs, but would like to find some more.  Discovered a guy on diyAudio is hoarding probably 75% of the world supply...

Unfortunately, my feelings about selling amplifiers changed pretty dramatically earlier this year.  I am really sorry for it as I know there is interest and I hate to disappoint, but it just isn't something I am up for.  Of course there are two excellent custom amp makers here on Head-Fi in @A2029 and @SonicTrance , and hopefully @2359glenn will make his way back here soon too.  Maybe another designer will emerge, you never know!


----------



## UntilThen

L0rdGwyn said:


> Unfortunately, my feelings about selling amplifiers changed pretty dramatically earlier this year. I am really sorry for it as I know there is interest and I hate to disappoint, but it just isn't something I am up for. Of course there are two excellent custom amp makers here on Head-Fi in @A2029 and @SonicTrance , and hopefully @2359glenn will make his way back here soon too. Maybe another designer will emerge, you never know!



I've been fortunate enough to have Glenn and Tomas make me tube amps. Glenn made me the super OTL amp and drove me crazy with tube rolling. Tomas made me Oblivion and will be building Odyssey next month... which is a few days time. 

Eric from the local scene made me the 300b amp just a month ago. In theory, I should retire from more tube amps but the irrational side of me say I have to sample what Mischa can do and I know he does wonderful stuff. 

Then I will coax and persuade you to do the 75th tube amp for me.  
http://vinylsavor.blogspot.com/2021/03/tube-of-month-75th.html


----------



## L0rdGwyn

Uh oh, maybe Thomas at Vinylsavor is taking plunge into the Eimac transmitter world!  It's a very interesting class of tubes, HK54 falls in this category.

Just to expound on the amp selling thing a bit more, never say never of course, but I fear selling amplifiers will feel like a second job.  I like to teach and I hope that this thread has inspired a few people to try their hand at DIY, I know of a few who have started their own projects, it really is very satisfying and I think many people could make a nice headphone amp.  I always recommend to start with a Bottlehead kit to get the feet wet on the hands-on, point-to-point wiring aspect of building, then hit the books to learn design theory.  Morgan Jones' _Valve Amplifiers_ can be found in PDF format online, which is a great resource.  I also like Merlin Blencowe's _Designing High-Fidelity Valve Preamps_, it is a little more readable than _Valve Amplifiers_, but print format only and doesn't get into power stages.  Very good chapters on power supply design, tube constants, common cathode amplification stage, cathode followers, and much more.


----------



## whirlwind

L0rdGwyn said:


> I sleeved the 6F5 grid cap leads with paracord today, gives the amp a little pizzazz.
> 
> 
> 
> Here how it looks with some graphite plate RCA 801A.


Man, is it me or is that power tranny huge!

Those RCA 801 tubes are off the scale in pretty!


----------



## L0rdGwyn

whirlwind said:


> Man, is it me or is that power tranny huge!
> 
> Those RCA 801 tubes are off the scale in pretty!



Thanks!  It is pretty big lol.  That transformer really makes the whole thing work.  It has a 300V B+ winding, 100V B- winding, two 10V filament windings for the 801A, and a 6.3V winding for the 6BX7 and 6F5.  Also has three internal electrostatic shields to prevent noise coupling between all of those windings.


----------



## UntilThen

whirlwind said:


> Man, is it me or is that power tranny huge!



It's just you.   Tomas had already ordered Sowter power and output transformers for my next amp. Then a month and a half later Sowter said they have stopped producing custom power transformers. @L0rdGwyn has the last of Sowter's custom power transformer. It's a beauty and that amp will be heavy.


----------



## Galapac

L0rdGwyn said:


> Thanks!  It is pretty big lol.  That transformer really makes the whole thing work.  It has a 300V B+ winding, 100V B- winding, two 10V filament windings for the 801A, and a 6.3V winding for the 6BX7 and 6F5.  Also has three internal electrostatic shields to prevent noise coupling between all of those windings.


Have you weighed the amp? Has it got a name yet @L0rdGwyn? You must name it and give it a custom nameplate.


----------



## L0rdGwyn

Galapac said:


> Have you weighed the amp? Has it got a name yet @L0rdGwyn? You must name it and give it a custom nameplate.



I haven't weighed it yet.  It is heavy, but believe it or not, my 6A5G amplifier is heavier - the Lundahl transformers overall are larger and it has three chokes inside!

The amp is called Prometheus.  My girlfriend code names all of my amplifiers, so it was her choice, after the Greek god who gave fire to humanity, so that is what it is called between us


----------



## L0rdGwyn

UntilThen said:


> It's just you.   Tomas had already ordered Sowter power and output transformers for my next amp. Then a month and a half later Sowter said they have stopped producing custom power transformers. @L0rdGwyn has the last of Sowter's custom power transformer. It's a beauty and that amp will be heavy.



I hope they will reconsider, I pled my case to Martin, I have been their #1 buyer for custom mains over the past year and a half lol he says they might bring them back in a more limited capacity at higher prices, but a large part of it is the fact that they have different technicians working on them since the Carnhill acquisition and the complexity is pushing the limits of their skill level.  Also, Carnhill being a larger company, there is some fear of liability given the high voltage transformers some customers are ordering.

So if they come back, likely higher prices, less complexity, lower voltages.


----------



## UntilThen

No problem. Tomas have found a Hammond power transformer with the same specs as what he would have ordered from Sowter. With chrome silver side covers, they look the works and I can't wait to see and hear the amp. 11w in triode mode and a bit more in UL. I'm not power hungry but headroom and a quiet amp is always welcome.

It's the output transformers that matters to me for SQ and still waiting for Sowter to deliver that. Should be soon.


----------



## Galapac

L0rdGwyn said:


> I haven't weighed it yet.  It is heavy, but believe it or not, my 6A5G amplifier is heavier - the Lundahl transformers overall are larger and it has three chokes inside!
> 
> The amp is called Prometheus.  My girlfriend code names all of my amplifiers, so it was her choice, after the Greek god who gave fire to humanity, so that is what it is called between us


Is the chassis powdered coated steel?


----------



## Zachik

L0rdGwyn said:


> The amp is called Prometheus. My girlfriend code names all of my amplifiers, so it was her choice, after the Greek god who gave fire to humanity, so that is what it is called between us


Maybe I should contract her services to name my upcoming amp by @A2029 
To be clear, I do have a working name, and couple others I am considering, but who knows - maybe she would have an even better name...


----------



## L0rdGwyn

Galapac said:


> Is the chassis powdered coated steel?



It is powder coated aluminum!


----------



## L0rdGwyn

UntilThen said:


> No problem. Tomas have found a Hammond power transformer with the same specs as what he would have ordered from Sowter. With chrome silver side covers, they look the works and I can't wait to see and hear the amp. 11w in triode mode and a bit more in UL. I'm not power hungry but headroom and a quiet amp is always welcome.
> 
> It's the output transformers that matters to me for SQ and still waiting for Sowter to deliver that. Should be soon.



Sounds like a perfect fit, the chrome will match the Sowter transformers well! Looking forward to seeing it completed.  11W will make your speakers and headphones sing


----------



## L0rdGwyn

Zachik said:


> Maybe I should contract her services to name my upcoming amp by @A2029
> To be clear, I do have a working name, and couple others I am considering, but who knows - maybe she would have an even better name...



Idk, my other amps have pretty goofy names LOL this one is definitely the coolest, I have no control over it.


----------



## UntilThen

Zachik said:


> Maybe I should contract her services to name my upcoming amp by @A2029
> To be clear, I do have a working name, and couple others I am considering, but who knows - maybe she would have an even better name...


Trust me. Paranoid is a good name.


----------



## Tjj226 Angel

Hey lordgwyn, I am a bit late to the party, but congrats on your most recent project. 

Looks great as always.


----------



## leftside

UntilThen said:


> No problem. Tomas have found a Hammond power transformer with the same specs as what he would have ordered from Sowter. With chrome silver side covers, they look the works and I can't wait to see and hear the amp. 11w in triode mode and a bit more in UL. I'm not power hungry but headroom and a quiet amp is always welcome.
> 
> It's the output transformers that matters to me for SQ and still waiting for Sowter to deliver that. Should be soon.


Hammond and Lundahl power transformers in the V6 Thunder. 

Apparently the Sowter output transformers are ready for delivery for Red Dwarf.


----------



## leftside

UntilThen said:


> Trust me. Paranoid is a good name.


----------



## L0rdGwyn

Tjj226 Angel said:


> Hey lordgwyn, I am a bit late to the party, but congrats on your most recent project.
> 
> Looks great as always.



Thanks @Tjj226 Angel ! Much appreciated 



leftside said:


> Hammond and Lundahl power transformers in the V6 Thunder.
> 
> Apparently the Sowter output transformers are ready for delivery for Red Dwarf.



That's exciting, going to be some very nice SET amplifiers popping up on Head-Fi very soon.  Finally your power pentode collection will be unleashed!


----------



## leftside

L0rdGwyn said:


> Thanks @Tjj226 Angel ! Much appreciated
> 
> 
> 
> That's exciting, going to be some very nice SET amplifiers popping up on Head-Fi very soon.  Finally your power pentode collection will be unleashed!


Yes a little wasted in the DAC - but still been fun trying them all.


----------



## UntilThen

leftside said:


> Hammond and Lundahl power transformers in the V6 Thunder.
> 
> Apparently the Sowter output transformers are ready for delivery for Red Dwarf.


Interesting Leftside. Why are you having both Hammond and Lundahl power transformers in your next amp?


----------



## Zachik

UntilThen said:


> Trust me. Paranoid is a good name.


----------



## Tjj226 Angel

UntilThen said:


> Interesting Leftside. Why are you having both Hammond and Lundahl power transformers in your next amp?



My guess is that there will be a low voltage and a high voltage transformer.


----------



## leftside (May 24, 2021)

UntilThen said:


> Interesting Leftside. Why are you having both Hammond and Lundahl power transformers in your next amp?


Previous/current amp. V6 Thunder had a totally separate chassis just for the power. It needed a Lundahl LL1651 and two Hammond 10V 185G20 

Lundahl power and Sowter output in the next amp. Simpler design.


----------



## UntilThen

L0rdGwyn said:


> Sounds like a perfect fit, the chrome will match the Sowter transformers well! Looking forward to seeing it completed.  11W will make your speakers and headphones sing


If they don’t sing, I will !


----------



## L0rdGwyn

I bought a bunch of 6F5GT tubes for chump change, think they were $7 each.  Thought I'd give my 6F5G a break and try some out.

Matched this pair on my curve tracer, JAN Sylvania 6F5GT from 1952.



Sound pretty good!  Will give them some time.  The grid cap leads look a little long with the more squat GT type, might consider making a shorter set for the GT and metal can 6F5.  This amp makes for a good night light.



Going to have a big shipment of 801A coming to me soon, probably five or six new pairs, including another graphite plate model, so looking forward to playing with those.


----------



## UntilThen

Keenan that's a beautiful beautiful looking old school amp.


----------



## L0rdGwyn

Thanks @UntilThen , I'm flattered  it was one year in the making, a lot of time and money invested, I'm very happy it turned out well.


----------



## UntilThen

A lot of money I'd say. Those Sowter transformers alone will cost a lot.


----------



## L0rdGwyn

@UntilThen yeah, this was a cost-no-object amplifier.  Given how long I worked on it though the cost was spread over many months, it went through several prototypes.  The knowledge and experience gained though is worth at least as much as the amplifier, a lot of new circuit elements for me, much reading, learning, experimenting.  Not sure what I am going to do next, probably best not to think out loud as it has gotten me into trouble in the past.  Time will tell!  But right now I need to repaint my porch


----------



## UntilThen

It's good to be passionate about what you do. No doubt this amp will be special to you. You have an objective and that is to make a 801 amp and it turn out superb.

I have an objective with Odyssey too and I wouldn't call it money no object but I didn't hold back much.  It's interesting to see 3 amps build pretty close to each other, using Sowter transformers. Your 801, Leftside amp and Odyssey. 

Now all I have to do is wait for Sowter to deliver the transformers. Surprisingly demand for such parts are high even in pandemic times. My tubes to Tomas is still waiting on international flights to take off. 

I spend a lot of time with Destiny, my 300b amp. It's like a perfect coupling with LCD4. Now Eric tells me he has a few confirm orders for Destiny. Jokingly ask me if I patent the name. I am glad the name stuck. It has an identity now. Not just any 300b amp but it's Destiny.


----------



## leftside

UntilThen said:


> It's good to be passionate about what you do. No doubt this amp will be special to you. You have an objective and that is to make a 801 amp and it turn out superb.
> 
> I have an objective with Odyssey too and I wouldn't call it money no object but I didn't hold back much.  It's interesting to see 3 amps build pretty close to each other, using Sowter transformers. Your 801, Leftside amp and Odyssey.
> 
> ...


My Sowter transformers have arrived in Canada


----------



## L0rdGwyn

UntilThen said:


> It's good to be passionate about what you do. No doubt this amp will be special to you. You have an objective and that is to make a 801 amp and it turn out superb.
> 
> I have an objective with Odyssey too and I wouldn't call it money no object but I didn't hold back much.  It's interesting to see 3 amps build pretty close to each other, using Sowter transformers. Your 801, Leftside amp and Odyssey.
> 
> ...



Yes, it is my baby 😭 801A is not an easy tube to use, didn't realize how far down the rabbit hole I would go when I signed up for it, but glad I did.

Sowter is hip right now  Martin from Sowter told me this is the busiest they have seen the consumer audio market in the 20 years he has worked there.  The busy times are part of the reason the custom mains line is going away.

Naming an amp certainly helps, gotta get that brand recognition, maybe Eric will join Head-Fi.



leftside said:


> My Sowter transformers have arrived in Canada



Looking forward to seeing the build!


----------



## L0rdGwyn

Here are some more 6F5GT tubes.

Quad of Adzam from Portugal.  Based on construction, I believe these are exported Sylvanias.




These ones are interesting, pair of early Tung-Sols.  These might be the best of the GT types I have tried so far, and very well-matched when traced.  Good ol' Tung-Sol QA.


----------



## UntilThen

leftside said:


> My Sowter transformers have arrived in Canada



Come on Sowter. Give me mine. Australia needs it too.  



L0rdGwyn said:


> Yes, it is my baby 😭 801A is not an easy tube to use, didn't realize how far down the rabbit hole I would go when I signed up for it, but glad I did.
> 
> Sowter is hip right now  Martin from Sowter told me this is the busiest they have seen the consumer audio market in the 20 years he has worked there. The busy times are part of the reason the custom mains line is going away.
> 
> Naming an amp certainly helps, gotta get that brand recognition, maybe Eric will join Head-Fi.



If Tomas didn't suggest Sowter, I wouldn't have known about Sowter transformers. I wanted Lundahl but they told Tomas that if custom trannies are required, will need to order 100.   One hundred !!! Might as well make it 300 - Spartacus !!!

Sowter must be wondering what happen to this crazy world suddenly ... I bet other DIY forums members are ordering their trannies too. 

I name it Destiny and when Eric heard it, he was tickled pink and like it. So he ask if he could use the name for that configuration of 300b amp that he build. I say sure why not but I charged royalty !!! Just kidding. 

Eric is a down right funny and a great guy. His jokes and statements floored me. He's very reserved though and I doubt he has time to participate in Head-Fi. Since @xtiva 's KT150 amp, he has been making amps non stop. He must be wondering why his orders has suddenly pick up.  He has taken a well deserved weekend away.

Now back to your baby - your prized 801A amp. I've no doubt that is your pride and joy ! I am on the other hand waiting on Odyssey! Getting that Greek hero to come home is a challenge.


----------



## L0rdGwyn

UntilThen said:


> If Tomas didn't suggest Sowter, I wouldn't have known about Sowter transformers. I wanted Lundahl but they told Tomas that if custom trannies are required, will need to order 100.   One hundred !!! Might as well make it 300 - Spartacus !!!
> 
> Sowter must be wondering what happen to this crazy world suddenly ... I bet other DIY forums members are ordering their trannies too.
> 
> ...



Lundahl make nice transformers, but they make some compromises in terms of bandwidth to make their transformers more flexible, allowing multiple impedance ratios.  Definitely still a good option, but if you need something more specific, custom is the way to go!  I will use Lundahl again I'm sure, in fact if I ever build that HK54 amplifier they have a good output transformer for job.

Well it's nice to hear another DIY type of amplifier maker has emerged, hopefully he isn't overwhelmed LOL headphone audio has gotten big and it seems to me tastes are trending more toward boutique amplifier designs.  I think the value proposition is much higher when you have an individual designing your amplifier as opposed to a more commercial operation.


----------



## UntilThen

L0rdGwyn said:


> it seems to me tastes are trending more toward boutique amplifier designs



It's exciting with boutique amp designs. I'm caught in the thick of action in seeing a custom KT150 (and variants) amp being build with transformers from SAC Thailand. Power transformer, output transformers, choke all from SAC and with covers. This one's a beast being able to output 20 watts in UL mode. Not sure how many in triode. 

I get to test it.  

A look at Silk transformers from their website and it's very interesting. Some of the builds in the gallery are amazing.
http://www.sacthailand.com/


----------



## bcowen

L0rdGwyn said:


> Well it's nice to hear another DIY type of amplifier maker has emerged, hopefully he isn't overwhelmed LOL headphone audio has gotten big and it seems to me tastes are trending more toward boutique amplifier designs.  I think the value proposition is much higher when you have an individual designing your amplifier as opposed to a more commercial operation.



Like any of the rest of us will ever have a chance to hear one.  @UntilThen buys everything they make.


----------



## UntilThen

bcowen said:


> Like any of the rest of us will ever have a chance to hear one.  @UntilThen buys everything they make.



Yes and now Steve got me interested in this. 10 watts !!!


----------



## bcowen

UntilThen said:


> Yes and now Steve got me interested in this. 10 watts !!!



Flea powered.

21 watts of (bona fide) SET:


----------



## UntilThen

bcowen said:


> Flea powered.
> 
> 21 watts of (bona fide) SET:



Schiit !@#$  Gimme that amp right now !


----------



## bcowen

UntilThen said:


> Schiit !@#$  Gimme that amp right now !


I'd drive it over in the golf cart, but it's not been waterproofed (the amp, I mean).


----------



## UntilThen

How about this hot rod? V12 !!!


----------



## Mr Trev

UntilThen said:


> How about this hot rod? V12 !!!


Dammit! They stole my idea! Cept, I was going to have the tubes and caps swap places.


----------



## UntilThen

Mr Trev said:


> Dammit! They stole my idea! Cept, I was going to have the tubes and caps swap places.



Sorry too late. Bcowen has installed it in the Bentley. Got to play in style !


----------



## Mr Trev

UntilThen said:


> Sorry too late. Bcowen has installed it in the Bentley. Got to play in style !


Bah, here's a proper cart.


----------



## bcowen

Mr Trev said:


> Bah, here's a proper cart.



I got so tired of @UntilThen yelling at me I made this.  No more lake handicap.


----------



## L0rdGwyn

Received a very thoughtful gift from @Galapac today, a nameplate for my 801A amp, Prometheus!  It has a magnet on the back, next time I open the amp I can put a strong magnet on the other side.  Either way, my system is completely catproof so it won't walk away.

I put my RCA 801 in hibernation, the workhorse tubes are in place now, the Hytron 801A.



I spent a large part of the day listening on headphones while working on another project.  I have a problem now though - I can't listen to any DAC but my SW1X.  This means running 25ft of RCA cable across my living room to get it to my headphone setup, perfect!  Sounds great with my Auteur and 841 amp.  Queen Sassafras bombed my photo, so on the internet she goes.


----------



## CJG888

UntilThen said:


> How about this hot rod? V12 !!!



This can (and has) been taken further:


----------



## CJG888

Do those 6550s mind being run horizontally?

A „flat four“ configuration comes to mind…

…could even work with a cooling fan!


----------



## L0rdGwyn

I was going to keep this quiet for a while, but it's been a rough week at work and I need a distraction.

I am developing a 2x 6J5 input, 2x 6AS7G-type output OTL headphone amplifier.  At this point plans for the circuit have been completed, I need to order parts and put together a prototype, likely next week.  The high-level chassis design is done as well.

There is no strict timeline and I would not consider this an official announcement, but if I feel the design is worthy of wider distribution, I may sell it.  Plans thus far have been made with that goal in mind.

As has been the case with my other designs, this is very much a "no compromises" type of build and it is being designed as if I were building for myself.  I would consider this a premium amplifier, and if the project comes to fruition, it would be priced accordingly.  Without putting out a number explicitly, as it has not been finalized, it would be on par with other premium commercial dual 6AS7G OTL amplifiers.  However, I believe the value proposition will be evident in the parts used, the circuit, and the build itself.

This is not yet set in stone and I am not taking orders, many logistical details need to be worked out and all is dependent on a successful prototype and test build, so likely a few months out at least.

Does the Head-Fi world have room for one more 6AS7G OTL?  We'll see, just FYI.


----------



## Zachik

L0rdGwyn said:


> Does the Head-Fi world have room for one more 6AS7G OTL?


Yes!


----------



## chrisdrop

Exciting times
Just when I thought I had sufficient amplification in my life ..


----------



## UntilThen

L0rdGwyn said:


> Does the Head-Fi world have room for one more 6AS7G OTL?



As soon as I check myself out of Amplifier Anonymous, there is room.


----------



## raindownthunda

That’s awesome Keenan! Can’t wait to learn more about it and see what you’ve landed on for the chassis design. There are never too many custom tube amps, especially running those families of tubes


----------



## L0rdGwyn

I'll post more details as the project progresses.  Would be nice to put these to good use again


----------



## UntilThen

How about 6bx7 ? I still have twelve.  An OTL amp with 12 x 6bx7gt ?


----------



## L0rdGwyn

UntilThen said:


> How about 6bx7 ? I still have twelve.  An OTL amp with 12 x 6bx7gt ?



That would be fun, 18A of heater current  no 6BX7 for this amplifier though, they would not be happy in this circuit!


----------



## L0rdGwyn

I put my 841 headphone amplifier on the bench (literally, it is on my workbench).  Getting reacquainted with my 6A5G amplifier with the Auteur.

Placing final orders for my OTL prototype.


----------



## leftside

UntilThen said:


> How about 6bx7 ? I still have twelve.  An OTL amp with 12 x 6bx7gt ?


Mine takes 12


----------



## UntilThen

leftside said:


> Mine takes 12


Yours is a beast. Takes 6 x 5998? Is it an OTL?


----------



## UntilThen

L0rdGwyn said:


> I put my 841 headphone amplifier on the bench (literally, it is on my workbench).  Getting reacquainted with my 6A5G amplifier with the Auteur.
> 
> Placing final orders for my OTL prototype.



What you have in the picture looks smart. Transformer coupled no doubt?


----------



## L0rdGwyn

UntilThen said:


> What you have in the picture looks smart. Transformer coupled no doubt?



Yes yes, it is a SET design!  It was my first SET, although I completely rebuilt it  that was fun.

Here is the inside.  Of the amplifiers I've made, from a design standpoint this one is most like your upcoming Odyssey in that it is a tube rectified, passive power supply with cathode bias (autobias) transformer coupled output.  Oh and Yamamoto sockets 

Three Lundahl transformers and three Lundahl chokes, this thing is super heavy...big ol' ClarityCaps too feeding the output stage.


----------



## leftside

UntilThen said:


> Yours is a beast. Takes 6 x 5998? Is it an OTL?


Yep.


----------



## UntilThen

L0rdGwyn said:


> Of the amplifiers I've made, from a design standpoint this one is most like your upcoming Odyssey in that it is a tube rectified, passive power supply with cathode bias (autobias) transformer coupled output. Oh and Yamamoto sockets



So please explain to me what is passive power supply.

Most of my tube amps use solid state rectifier so I do want to go with tube rectification on Odyssey. Just had word from Sowter that the transformers will shipped in the 1st week of July.


----------



## L0rdGwyn (Jun 18, 2021)

UntilThen said:


> So please explain to me what is passive power supply.
> 
> Most of my tube amps use solid state rectifier so I do want to go with tube rectification on Odyssey. Just had word from Sowter that the transformers will shipped in the 1st week of July.



So a passive supply is one that is filtered by passive components, the basic building blocks are RC (resistor-capacitor) and LC (choke-capacitor) filters.  These filters reduce ripple from the rectified wall AC, the goal of course is to reduce the ripple to the point of inaudibility, otherwise there will be a "buzz".  This is what you might call an "old school" supply.  It is not regulated in any form.  The output voltage will vary proportionally with variations in wall AC as this will alter the voltage seen on the high-voltage transformer secondary feeding the supply.  Also, the output voltage will depend on the current drawn by the load (the tubes) and the internal resistance of the power supply due to Ohm's law.  To achieve the desired output voltage for the amplifier, the components of the RC and LC filters must be chosen specifically for the design at the current that is expected to be drawn by the tubes.

This is all opposed to an active power supply.  This type of power supply uses active devices (e.g., transistors, tubes) to achieve regulation - line regulation, and load regulation, while simultaneously reducing output ripple.  Line regulation refers to how the power supply handles variations in wall AC.  With line regulation present, the supply will output a specific voltage even with variations in wall AC.  With load regulation present, the supply will output a specific voltage despite variations in drawn current.  In a passive supply with a changing load (varying current draw), a large increase in current drawn may decrease the output voltage of the supply due to increased voltage drop across the supply's internal resistance, and vice versa with large decreases in current drawn - this is due to Ohm's law.  An active supply with load regulation will prevent that from occurring - the output voltage will be unaffected by changes in current draw.  Load regulation isn't so critical in single-ended class A1 designs since the DC current draw is essentially constant, so the output voltage will remain relatively constant too.  You can combine passive and active components of course - you might use a passive RC filter to reduce ripple to a certain point before introducing a voltage regulator.

That's the idea at a high level!  They both have their pros and cons.


----------



## whirlwind

L0rdGwyn said:


> Yes yes, it is a SET design!  It was my first SET, although I completely rebuilt it  that was fun.
> 
> Here is the inside.  Of the amplifiers I've made, from a design standpoint this one is most like your upcoming Odyssey in that it is a tube rectified, passive power supply with cathode bias (autobias) transformer coupled output.  Oh and Yamamoto sockets
> 
> Three Lundahl transformers and three Lundahl chokes, this thing is super heavy...big ol' ClarityCaps too feeding the output stage.


Nice neat job Keenan...real nice.


----------



## L0rdGwyn (Jun 18, 2021)

whirlwind said:


> Nice neat job Keenan...real nice.



Thanks, Joe.

BTW, as it stands, the chassis for this 6AS7G OTL is rather large, comparable in size to the 6A5G SET pictured above to accommodate some very chunky film caps.


----------



## Tjj226 Angel

L0rdGwyn said:


> Thanks, Joe.
> 
> BTW, as it stands, the chassis for this 6AS7G OTL is rather large, comparable in size to the 6A5G SET pictured above to accommodate some very chunky film caps.



Are you going to employ any NFB to bring the output impedance down?


----------



## L0rdGwyn

Tjj226 Angel said:


> Are you going to employ any NFB to bring the output impedance down?



No, no feedback as the design stands, but the output will be paralleled.  I am planning on >250uF of film output capacitance, should afford good LF extension even for low impedance headphones, but typical damping factor rules will come into play.  I'll post some output impedance specs when the design is tested.


----------



## L0rdGwyn

PCBs have arrived for the 6AS7G OTL.  My parts should arrive early next week, should have the circuit built on my protoboard by Friday, so will have a good idea of the sound then.

I like to keep my chassis designs simple - IMO, the tubes provide enough aesthetic flair on a piece of gear, I don't like the chassis to distract from their inherent beauty   with that being said, I think the ventilation and layout provide an opportunity to add to the aesthetic.  If the projects continues forward, I will use the pattern below for the 6AS7G ventilation.  Similar to my 801A amplifier, the sockets will be mounted on sub-plates (large circle) and the sockets bottom-mounted.



Also, I decided this morning I am going to start working on a NOS R2R tube-output DAC design.  That will start with a lot of reading, but I'm confident I can come up with a good design.  Have some ideas of where I'd like to go with it, but will try to keep my mouth shut until I have some sort of draft completed.


----------



## Zachik

L0rdGwyn said:


> PCBs have arrived for the 6AS7G OTL. My parts should arrive early next week, should have the circuit built on my protoboard by Friday, so will have a good idea of the sound then.


I am VERY curious how your 6AS7G OTL will compare with GOTL using similar tubes (a pair of 6J5 for drivers, a pair of 6AS7G for output)...
Other than more premium parts (like caps) - how is your design differs from the GOTL topology / implementation?


----------



## L0rdGwyn (Jun 19, 2021)

Zachik said:


> I am VERY curious how your 6AS7G OTL will compare with GOTL using similar tubes (a pair of 6J5 for drivers, a pair of 6AS7G for output)...
> Other than more premium parts (like caps) - how is your design differs from the GOTL topology / implementation?



Sure no problem.  I want to be upfront about the design, I think people should be informed on what they are buying.  I don't want to say too much about what the GOTL is given Glenn is not here to speak to it, but Glenn's amplifier uses an SRPP output topology, which of course he has discussed publicly.  This amplifier will use a parallel cathode follower output topology.  There are amplifiers using a similar output topology on the commercial market - pretty much any commercially designed dual output 6AS7G is using a parallel cathode follower output.  I won't say this is "a new take" on the 6AS7G OTL output stage, there are only so many ways to use this tube - any SRPP out would be a GOTL clone in my mind.  With that being said, I think this amplifier has a few distinct advantages over what is out there already in terms of 6AS7G cathode follower OTLs.

1) It will use a dual mono, SS-rectified, voltage-regulated power supply - will give more details on that down the road.
2) The 6J5 input will be actively loaded, which will yield very high power supply isolation, and low distortion, and allow the cathode resistor to remain unbypassed, avoiding the use of an electrolytic bypass capacitor.
3) On that front, there will be no electrolytic capacitors in the signal path.
4) The 6AS7G output will use an active load as well, a bit of a challenge to implement due to heat as a parallel cathode follower 6AS7G pushes a lot of current, but this yields the best sound from a cathode follower, IMO.

Much of what I've pointed out as advantages won't be used in a commercial design due to cost and complexity.  As I've said, this amplifier must be "greenlighted" before I release it into the world.  Ideally, I will personally evaluate it against other similar designs to ensure it compares favorably to them.  Either that or the amplifier will need to be brought to an event or put on tour, although the latter isn't appealing due to shipping costs.  Lots of logistics to be figured out.


----------



## Zachik

L0rdGwyn said:


> Either that or the amplifier will need to be brought to an event or put on tour, although the latter isn't appealing due to shipping costs. Lots of logistics to be figured out.


How about a weekend meet? Unfortunately I am as far from you as possible (within CONUS), but will seriously consider flying over for a weekend.  Maybe @zach915m and @BooUrns have plans for a ZMFestivus event late this year (fingers crossed)...


----------



## whirlwind

L0rdGwyn said:


> Sure no problem.  I want to be upfront about the design, I think people should be informed on what they are buying.  I don't want to say to much about what the GOTL is given Glenn is not here to speak to it, but Glenn's amplifier uses an SRPP output topology, which of course he has discussed publicly.  This amplifier will use a parallel cathode follower output topology.  There are amplifiers using a similar output topology on the commercial market - pretty much any commercially designed dual output 6AS7G is using a parallel cathode follower output.  I won't say this is "a new take" on the 6AS7G OTL output stage, there are only so many ways to use this tube - any SRPP out would be a GOTL clone in my mind.  With that being said, I think this amplifier has a few distinct advantages over what is out there already in terms of 6AS7G cathode follower OTLs.
> 
> 1) It will use a dual mono, SS-rectified, voltage-regulated power supply - will give more details on that down the road.
> 2) The 6J5 input will be actively loaded, which will yield very high power supply isolation, and low distortion, and allow the cathode resistor to remain unbypassed, avoiding the use of an electrolytic bypass capacitor.
> ...


No capacitors in the signal path sounds good.


----------



## JazzVinyl

whirlwind said:


> No capacitors in the signal path sounds good.



I have a solid state amp that has no capacitors in the signal path and indeed, it sounds fantastic!

Can't wait to see what LG comes up with


----------



## Tjj226 Angel

JazzVinyl said:


> I have a solid state amp that has no capacitors in the signal path and indeed, it sounds fantastic!
> 
> Can't wait to see what LG comes up with



What amp is it? 

Lots of amps claim this, but most of them are dirty liars. The truth generally ends up being that they forgot to tell you about all the power supply capacitors in the signal path. 

I am actually working on an SS design that truly has no capacitors in the audio path, and it is exceedingly difficult. The trick is that in a normal SE amp, you generally have 3 audio path loops. 1 for the input, 1 for the driver, and 1 for the power/output stage. To marry all three loops without any coupling capacitors AND virtually no power supply interaction is actually impossible. 

And since most push pull amplifiers are actually just two class A amplifiers glued together, you end up with the same problem.


----------



## L0rdGwyn (Jun 19, 2021)

whirlwind said:


> No capacitors in the signal path sounds good.



Minor correction - there are caps in the signal path, kept to a minimum, but are all high quality films.  The best cap is no cap, but the real sound killers are electrolytics, which you will often see as bypass caps in cathode biased gain stages and also as output coupling caps in OTLs.  To get good low frequency extension from an OTL, you often need a decent amount of capacitance, which can get very pricey if we are talking film caps.  Designers will sometimes compromise by using a high capacity electrolytic bypassed with a smaller film.  But we are going all film for this amp, so the caps are pretty enormous


----------



## whirlwind

Glenn has told me that in one tube mode on the EL3N amp that there are no capacitors in the signal path.
The amp has always been dead silent in one tube mode, not much good for my planars but I use to love it with my 32 ohm Grado RS1


----------



## JazzVinyl

Tjj226 Angel said:


> What amp is it?
> 
> Lots of amps claim this, but most of them are dirty liars. The truth generally ends up being that they forgot to tell you about all the power supply capacitors in the signal path.
> 
> ...


Rudistor NX-03

Does have caps in the power supply.  A very low part count in each channels' amp sections.


----------



## Tjj226 Angel

L0rdGwyn said:


> Minor correction - there are caps in the signal path, kept to a minimum, but are all high quality films.  The best cap is no cap, but the real sound killers are electrolytics, which you will often see as bypass caps in cathode biased gain stages and also as output coupling caps in OTLs.  To get good low frequency extension from an OTL, you often need a decent amount of capacitance, which can get very pricey if we are talking film caps.  Designers will sometimes compromise by using a high capacity electrolytic bypassed with a smaller film.  But we are going all film for this amp, so the caps are pretty enormous



Just an addition to what LordGwyn is saying here, this approach is really only seen in Single Ended OTL amplifiers. 

The other method for an SE amp is to use a bipolar psu. This would allow you to center your 6AS7G's cathode at 0v against a CCS on the negative rail. There are pluses and minuses to both approaches. 

Push pull OTL amps can use one of the two methods mentioned for coupling your headphones/speakers to the amp, or they can use several other options such as using a circloton configuration.


----------



## leftside

L0rdGwyn said:


> Much of what I've pointed out as advantages won't be used in a commercial design due to cost and complexity.


That's the nice thing about going custom. You can splurge on the design and parts used. Commercially this wouldn't be feasible/profitable. The price the manufacturer would have to charge to make a profit would be absurd. 

I'd like to see one of you guys tear down something like a WA33 and take a a look at the design and parts used. I know when my local tech tore down my WA22 he wasn't very impressed. Said the transformers were very cheap. Even though I quite liked the sound of that amp!


----------



## Tjj226 Angel

Welp, we just moved into our new place. After being in a tiny apartment for so long, I now have a wood shop, metal shop, and electronics lab.


----------



## Tjj226 Angel

leftside said:


> That's the nice thing about going custom. You can splurge on the design and parts used. Commercially this wouldn't be feasible/profitable. The price the manufacturer would have to charge to make a profit would be absurd.
> 
> I'd like to see one of you guys tear down something like a WA33 and take a a look at the design and parts used. I know when my local tech tore down my WA22 he wasn't very impressed. Said the transformers were very cheap. Even though I quite liked the sound of that amp!



The WA33 is ok if the price were 3K or lower. For 8K, it's a piece of crap. 

A lot of money went into all the wrong components and chassis work.


----------



## bcowen (Jun 20, 2021)

Tjj226 Angel said:


> Welp, we just moved into our new place. After being in a tiny apartment for so long, I now have a wood shop, metal shop, and electronics lab.


Congrats!  But you know the drill:  pics or it didn't happen.


----------



## JazzVinyl

Tjj226 Angel said:


> Welp, we just moved into our new place. After being in a tiny apartment for so long, I now have a wood shop, metal shop, and electronics lab.



Very nice!
We want to move as well, but have a feeling that we are on the road to downsizing.  Like your deal, better   
Congrats!


----------



## L0rdGwyn

Tjj226 Angel said:


> Welp, we just moved into our new place. After being in a tiny apartment for so long, I now have a wood shop, metal shop, and electronics lab.



Awesome, can't wait to see what you work on with that space!


----------



## Tjj226 Angel

bcowen said:


> Congrats!  But you know the drill:  pics or it didn't happen.



Oh god, do you even want to know? 

Considering the insane prices these days, I bought an unfinished quonset hut home. The shed where I am setting up my electronics looks more livable than the house. 

In fact I am sitting here taking a break from hanging a door on the bathroom. We are talking THAT level of unfinished. 

But the flip side is that we have 50 acres of land here with no convenience, zoning, or anything of the sort. I can take pictures of the land, but the house is an utter dumpster fire at the moment.


----------



## JazzVinyl

Tjj226 Angel said:


> In fact I am sitting here taking a break from hanging a door on the bathroom. We are talking THAT level of unfinished.
> 
> But the flip side is that we have 50 acres of land here with no convenience, zoning, or anything of the sort. I can take pictures of the land, but the house is an utter dumpster fire at the moment.



50 Acres!  WOW!  You will have to start a "Head-Fi Boot Camp / Retreat"   
Sounds fun!  Good luck getting everything straightened out.


----------



## Tjj226 Angel

L0rdGwyn said:


> Awesome, can't wait to see what you work on with that space!



Yeah, it will still be a little while before things are setup. The first thing will be to finalize all the projects for @johnjen. I was going to a maker space to work on stuff, but when covid hit, they shut down. Even today they are still really picky about how many people are in the space at one time which makes getting stuff done a real pain. 

Once John is taken care of, then I will focus on that H bridge amp I showed you (and possibly everyone? I don't remember). The thing I am still stuck on with that amp is the driver/phase splitter stage. 

The whole idea behind the H bridge amp is to see what would happen if you try to maximize square law cancelation with two perfectly matched signals. The problem is that every phase splitter is pretty flawed. A transformer is probably the best phase splitter I know of, and it adds a pretty large amount of phase shift to the amp. Things only get worse from there. This is part of the reason GNFB is a thing. It helps "fix" the problems created by the phase splitter. 

I need to create a phase splitter that will produce equal gain with output signals that are perfectly in time with each other. I am not entirely sure this is possible


----------



## Tjj226 Angel

JazzVinyl said:


> Very nice!
> We want to move as well, but have a feeling that we are on the road to downsizing.  Like your deal, better
> Congrats!



Thanks! I hhope you figure your move out and all goes well.


----------



## L0rdGwyn (Jun 21, 2021)

All of my OTL parts arrived today, will start working on the prototype Wednesday 

In the mean time, I have been doing some deep dive reading on NOS R2R DAC design, specifically around I/V conversion stages.  Many of these DACs are current output types and are intended to work into a minimal impedance, the lower the better.  This current output needs to be converted into a workable voltage, hence the I/V conversion.  That voltage can then be amplified to line level through some sort of gain stage, ideally with a low output impedance.

The "best" I/V conversion is a bit controversial I am finding, as usual there are pros can cons to each.  The simplest, and probably most common, is a resistor - the current output from the DAC IC creates a voltage across said resistor and that voltage can then be amplified.  The value of the resistor often is tuned by measurements and ear, finding a balance between distortion, output voltage, and noise.

Another less common passive approach is to use a DAC interfacing SUT.  The transformer adds some gain to the I/V stage, allows the I/V resistor to remain low and helps match the impedance to the following gain stage, if needed.  The transformer also has the advantage of a "built in" low pass filter.  It also breaks the ground connection between the DAC and the output stage, keeping quantization noise out of the output ground.  This is pretty appealing, although opinions are mixed as whether or not it is an improvement over a resistor.

The other option is an "active" I/V stage, using a transistor or op-amp typically.  This is the approach taken by SW1X, for instance, and many sing its praises.

I think this is just going to take some experimentation!  No rush whatsoever as I have to plan the power supply anyhow, which will be the bulk of the work.  As cliché as it is, I am likely going to base this design on the famous TDA1541A.


----------



## Tjj226 Angel

L0rdGwyn said:


> All of my OTL parts arrived today, will start working on the prototype Wednesday
> 
> In the mean time, I have been doing some deep dive reading on NOS R2R DAC design, specifically around I/V conversion stages.  Many of these DACs are current output types and are intended to work into a minimal impedance, the lower the better.  This current output needs to be converted into a workable voltage, hence the I/V conversion.  That voltage can then be amplified to line level through some sort of gain stage, ideally with a low output impedance.
> 
> ...



Yeup. 

The two main goals are to make an IV stage with 0 input impedance and to keep that input at ground potential. 

I have been passively looking at IV stages for years and while all the different IV stages can be made to sound REALLY good, none of them are perfect.


----------



## Zachik

Tjj226 Angel said:


> I have been passively looking at IV stages for years and while all the different IV stages can be made to sound REALLY good, none of them are perfect.


...and I thought that sounding REALLY good is what we're all after!


----------



## Tjj226 Angel

Zachik said:


> ...and I thought that sounding REALLY good is what we're all after!



Nah. I want sound so good that you instantly achieve enlightenment when you listen to it.


----------



## L0rdGwyn

Here are the planned output caps for the 6AS7G OTL, 265uF ClarityCaps.




If all goes to plan, they will top mounted, visible on the exterior of the chassis.  Here's how they look in that orientation.


----------



## leftside

L0rdGwyn said:


> Here are the planned output caps for the 6AS7G OTL, 265uF ClarityCaps.
> 
> 
> 
> If all goes to plan, they will top mounted, visible on the exterior of the chassis.  Here's how they look in that orientation.


Nice. I went with Clarity caps as well in the V6. TC600.


----------



## L0rdGwyn (Mar 29, 2022)

Some small progress made on the OTL today, board stuffing mostly.

Active load for 6J5 input on the left (gyrator) and single-channel raw DC board on the right - there will be two.  The raw DC board includes transformer snubbing components, secondary fuse, current-limiting resistors, bleeder resistor, and reservoir cap.  Having it in front of me, one aspect of the raw DC board layout needs to be altered, this is why we prototype


----------



## L0rdGwyn (Mar 29, 2022)

OTL prototype is coming along, slowly but surely.  Power supply is just about done, should have the circuit functional tomorrow.

Testing with some Russian 6AS7G and 6J5 equivalents.

Progress has been hampered by NOS R2R DAC research LOL I am very excited about it.  I've spent many hours over the past four days poring over datasheets, schematics, learning digital front-end design, digital audio protocols, design requirements for specific chips, various I/V stages, etc.  Last night everything really started to click, I now feel quite confident I could design a DAC similar to my SW1X.  Still more to learn, but always exciting when the pieces start falling into place, conceptually.  Which chip I will use first has changed about five times and they have different requirements, so we will see, a plan is taking shape


----------



## L0rdGwyn (Mar 29, 2022)

6AS7G OTL prototype is up and running.  Tested with Russian tubes, now have some proper hifi glass in circuit, MOV L63 and Tung-Sol 5998.

Nice clean square waves, good frequency response.  Low-frequency rolloff in an OTL increases as the impedance of the load decreases, so to get good bass response in low-impedance headphones, need a hefty amount of output capacitance.  Given the 265uF output caps, FR is down -1dB at 20Hz with a 32ohm dummy load, most everything else is flat to 20Hz.

Even with a less-than-ideal source (my audio interface DAC that I use for testing), the sound is very good, I'm pleased with it.  Still some design things to figure out, but overall things are trending the right direction 

Now I will take a break and...read more about DACs LOL.

(My Cleveland Browns are coming for you NFL fans).


----------



## Tjj226 Angel

Just for my own edification since I might do an OTL as well, could you throw a high quality 0.22uf cap across your output caps to see what it does to the sound quality. 

It doesn't have to be now, but at some point if you get around to it, I would really be curious.


----------



## L0rdGwyn

Tjj226 Angel said:


> Just for my own edification since I might do an OTL as well, could you throw a high quality 0.22uf cap across your output caps to see what it does to the sound quality.
> 
> It doesn't have to be now, but at some point if you get around to it, I would really be curious.



It's funny you mention it, I thought about trying the same.  I'll give it a shot, only problem is I don't have anything fancy on hand in the 0.22-0.47uF range - just some 0.47uF polypropylene Audyn caps, some Solens.  I'll try the Audyn caps, if there is some audible improvement, maybe I'll grab some bang-for-the-buck PIO caps to try out.


----------



## L0rdGwyn

You know what, I have some old Russian military PIO caps as well, will try them too.


----------



## Tjj226 Angel

L0rdGwyn said:


> It's funny you mention it, I thought about trying the same.  I'll give it a shot, only problem is I don't have anything fancy on hand in the 0.22-0.47uF range - just some 0.47uF polypropylene Audyn caps, some Solens.  I'll try the Audyn caps, if there is some audible improvement, maybe I'll grab some bang-for-the-buck PIO caps to try out.



Same difference IMO. 

The idea is to simply have a very low ESR and ESL capacitor in parallel with the output cap.


----------



## Tjj226 Angel

L0rdGwyn said:


> You know what, I have some old Russian military PIO caps as well, will try them too.



That works.


----------



## L0rdGwyn

Tjj226 Angel said:


> Same difference IMO.
> 
> The idea is to simply have a very low ESR and ESL capacitor in parallel with the output cap.



Right, creating a more "ideal" capacitor.  Will give it a shot and report back!


----------



## L0rdGwyn (Jun 25, 2021)

@Tjj226 Angel I tried both the 0.47uf Audyn cap and a 1uF Russian PIO cap, clipped in parallel to the 265uF output caps.

In both cases, it was clearly a step down in sound quality.  The sound stage collapsed, separation was worse as a result, less dynamic.  The Audyn was the better of the two in parallel.

Thinking back to when I was working out the parallel cap config on my 45 parafeed, I bought a swatch of Solen caps to try out, did several combinations in parallel to get roughly the same capacitance.  At the time, I found the closer the two caps were in value paralleled, the better the sound was, so I ended up using a pair of 3.3uF.

Did some quick distortion measurement of this circuit with the L63 and 5998.

1mW into a 300ohm dummy load - 0.015% THD
1mW into 120ohm dummy load - 0.070% THD
1mW into 32ohm dummy load - 0.35% THD

With the 300ohm load, H2 is down to -80dBFS.


----------



## Zachik

L0rdGwyn said:


> Given the 265uF output caps, FR is down -1dB at 20Hz with a 32ohm dummy load, most everything else is flat to 20Hz.


Are you saying your OTL design, unlike most OTL designs, can work very well with low impedance headphones?
For most OTLs, the "street wisdom" is to use them only with headphones that are 150 ohm and higher, preferably just 300 ohm cans (ZMF, HD800, etc.)


----------



## L0rdGwyn (Jun 25, 2021)

Zachik said:


> Are you saying your OTL design, unlike most OTL designs, can work very well with low impedance headphones?
> For most OTLs, the "street wisdom" is to use them only with headphones that are 150 ohm and higher, preferably just 300 ohm cans (ZMF, HD800, etc.)



So it isn't so black and white what the "right" headphone impedance pairing is for an OTL.  The issue is twofold:

*1) Low frequency extension, dependent on headphone impedance and output capacitance.*

The output capacitance and the load of the amplifier (the headphone impedance) form a RC high-pass filter.  This means that for a specific output capacitance, as the impedance of the paired headphone goes down, the bass will roll off at a higher frequency.  To use a low-impedance headphone with an OTL, you must have enough output capacitance to keep that rolloff point at a very low frequency, ideally below 20Hz.

That is the purpose of having such gigantic film caps in this amplifier - if the user wants to use low-impedance headphones, they have the option.  As I said, with a 32ohm resistive load, the FR is down -1dB at 20Hz.  Many manufacturers will use electrolytics on the output to increase the output capacitance, but then you have electrolytic capacitors in the signal path, which is a sound killer.  I found these 265uF ClarityCaps are a good compromise between size, cost, and low-frequency extension with low-impedance headphones without having to resort to electrolytics.

Now the second consideration...

*2) Damping factor / ratio.*

Most are familiar with this concept, many will say a 3:1 damping ratio is the rule-of-thumb, but many commercial manufacturers will recommend a 1:1 damping ratio.

I think this is really up to the user - the definition of the bass may loosen with a lower ratio, some like it, some don't!  So its hard to say exactly what the damping ratio should be.  I would say 1:1 at a minimum.

The output impedance of this amplifier will vary to some extent depending on the output tube used as they have varying transconductances.  For instance, output impedance with a 5998 in this circuit is 28ohm.  Output impedance with a 6AS7G is closer to 50ohm.

So following a 1:1 rule, with a 5998, you could ostensibly run a 32ohm headphone knowing there will be a slight bass rolloff from 20-30Hz.  Using an 80ohm headphone would get you closer to a 3:1 damping ratio with essentially flat bass out to 20Hz.

I hope that makes sense, my intention is to include enough output capacitance such that the user could run low-impedance headphones if they so choose.  The ideal damping ratio is debatable, while having a flat frequency response from 20Hz-20kHz really isn't


----------



## Tjj226 Angel

L0rdGwyn said:


> @Tjj226 Angel I tried both the 0.47uf Audyn cap and a 1uF Russian PIO cap, clipped in parallel to the 265uF output caps.
> 
> In both cases, it was clearly a step down in sound quality.  The sound stage collapsed, separation was worse as a result, less dynamic.  The Audyn was the better of the two in parallel.
> 
> ...



iiiiiiiiiiiinteresting 

I have had some experiences where paralleling caps works out really well, and some that don’t work at all.

I really wish we knew what was really going on so that we could better take advantage of the situation.

Of course I also wish we still had layered capacitors instead of the jelly rolled ones so that we wouldn’t have to worry about esr and esl in the first place.


----------



## Tjj226 Angel

L0rdGwyn said:


> So it isn't so black and white what the "right" headphone impedance pairing is for an OTL.  The issue is twofold:
> 
> *1) Low frequency extension, dependent on headphone impedance and output capacitance.*
> 
> ...



It’s actually more black and white than you realize. Most amplifiers on the market (especially OTL amps) try to cut corners, and as a result, they limit their amps so much so that you have to run 300ohm headphones.

since you are not doing that, the answer to the question Zachik asked is simply - yes, your amp can take 33 ohm headphones given the right type of tube.


----------



## Zachik

L0rdGwyn said:


> I hope that makes sense, my intention is to include enough output capacitance such that the user could run low-impedance headphones if they so choose. The ideal damping ratio is debatable, while having a flat frequency response from 20Hz-20kHz really isn't


Yup - it does make sense!  Thanks for the explanation


----------



## whirlwind

L0rdGwyn said:


> 6AS7G OTL prototype is up and running.  Tested with Russian tubes, now have some proper hifi glass in circuit, MOV L63 and Tung-Sol 5998.
> 
> 
> 
> ...


 You bet they are...."Go Browns"


----------



## whirlwind

L0rdGwyn said:


> You know what, I have some old Russian military PIO caps as well, will try them too.


If they are the older ones I am a fan of these.


----------



## L0rdGwyn

whirlwind said:


> If they are the older ones I am a fan of these.



They're actually the caps I pulled out of the GOTL a long time ago HA!  Never know when you are gonna need a random part  they are good caps.


----------



## Zachik

L0rdGwyn said:


> They're actually the caps I pulled out of the GOTL a long time ago HA!


Does that make the GOTL de-cap-itated?


----------



## L0rdGwyn

Zachik said:


> Does that make the GOTL de-cap-itated?



Good one @Zachik ....LOL.


----------



## L0rdGwyn (Mar 29, 2022)

Doing some early morning listening with Western Electric 421A and fresh ears.  Sounds good!  Will listen with a better source today to see how it _really _sounds, maybe some vinyl.

On the DAC front, I've committed to a TDA1541A design, will be running it in simultaneous mode, USB input digital front-end.  Just the tip of the iceberg though, this is going to be a long-term project.  I plan to use passive I/V, most likely a SUT, ratio to be determined, with a tube output stage to reach line level.

Going to have to up my EE skills for this one, so I got myself a new beach read.


----------



## bcowen

L0rdGwyn said:


> Doing some early morning listening with Western Electric 421A and fresh ears.  Sounds good!  Will listen with a better source today to see how it _really _sounds, maybe some vinyl.



It'll never sound good with cheap, crappy tubes.  You should probably send the WE's to me and save your ears.


----------



## L0rdGwyn (Mar 29, 2022)

bcowen said:


> It'll never sound good with cheap, crappy tubes.  You should probably send the WE's to me and save your ears.



You're right, time to power up!  the 421As will be in the mail, or I can forward direct to the junk yard if that would be easier.


----------



## bcowen

L0rdGwyn said:


> You're right, time to power up!  the 421As will be in the mail, or I can forward direct to the junk yard if that would be easier.


Junkyard?  NOOOO! Even a used up, dying, or totally dead WE 421A should get a place on the fireplace mantle as a matter of respect.   

Those TungSols with the spring mica supports and silver top/bottom edges on the plates are very nice.  I scored a couple for way cheap a while back and was quite pleased with how good they sound.


----------



## L0rdGwyn

Got some nifty PCBs for my DAC today.  This project is moving at at a snail's pace since I am working on three or four things at once, but hey, progress!



So what the hell do these do?  This necessitates some technical explanation on digital front-end design for these old R2R DAC chips...can skip to TL;DR if it's too much mumbo jumbo.

Popular chips for these NOS R2R designs (e.g., TDA1541A, AD1865, PCM63, PCM56, etc.) are typically designed to operate with one or both of two different digital data stream protocols, PCM or I2S.  For PCM input chips, the right and left channel data streams are separated prior to the DAC input.  Later, I2S protocol was implemented, which places both left and right channels on the same serial data steam at double the clock frequency (two channels of data, twice the frequency).  The data for two channels is then divided (de-multiplexed) in the DAC integrated circuitry.

The problem comes up when you want to use a PCM input DAC (say PCM56, like my SW1X DAC II) with a digital front end that outputs I2S - the data streams for the two channels MUST be split before they hit the DAC input.  A common approach when using PCM chips with an I2S digital front end (e.g., CS8414 SPDIF receiver, like in my DAC II), is to "split" the channels using a hex-inverter, then re-align them using a shift register, otherwise there will be a very small inter-channel timing delay (although some designs just live with the delay rather than re-aligning the channels, given the delay is in the micro-second timeframe and is of questionable audibility).  Again, this is the approach in the DAC II.

Moving from the TDA1540 to the TDA1541A, Philips introduced the ability to use either PCM or I2S protocol.  To get the absolute best sound out of the TDA1541A, all reading, learning, and discussion has pointed toward operating it with PCM inputs, aka simultaneous mode.  This cuts the clock frequency in half, reduces jitter artifacts, and leads to the best subjective listening experience.

The boards above were designed for a USB digital front end solution that can be configured to output PCM, an all-in-one solution to interface with PCM input chips, and it came highly recommended.

*TL;DR - *basically these boards will let me design a USB input DAC and operate the TDA1541A in simultaneous mode for the best sound from the chip.  

Next thing for this project is to start to assess the specific needs for a low-noise voltage-regulated power supply, that is going to take some time to design.

Okay, that's enough of that...

On the OTL amplifier front, the sound is excellent and I am very happy with where it is from a sonic standpoint.  However, I am designing some ancillary circuitry before moving onto finalizing the chassis: new voltage-regulator PCBs, time-delay-switched relay boards, fine-tuning the more functional aspects of the circuit.  But the good news is the amp sounds very good, just need to finalize exactly what is going inside the box before we build one  more to come.


----------



## chrisdrop

L0rdGwyn said:


> Got some nifty PCBs for my DAC today.  This project is moving at at a snail's pace since I am working on three or four things at once, but hey, progress!
> 
> 
> 
> ...


Sounds fab
Hope it is as fun as it sounds


----------



## Zachik

L0rdGwyn said:


> Got some nifty PCBs for my DAC today. This project is moving at at a snail's pace since I am working on three or four things at once, but hey, progress!


Keenan, knowing this DAC is going to be cost-no-object for you:
I am curious whether the estimated BOM cost end up being more, less or same as buying the SW1X DAC II...


----------



## L0rdGwyn

Zachik said:


> Keenan, knowing this DAC is going to be cost-no-object for you:
> I am curious whether the estimated BOM cost end up being more, less or same as buying the SW1X DAC II...



Good question!  Assuming it doesn't become a money pit from endless experimentation, I would actually expect it to cost less.  The single most costly component, as things stand right now, will be the I/V stage transformers, next the chassis, then the TDA1541A chip itself (around $150).  A majority of the circuitry will be on a PCB, the real cost of that is the design time, but individual components won't be very expensive.  It adds up though depending on how quickly we get it "right".  It's very easy to create an oscillator when working with solid-state components, which is always a headache to troubleshoot...

But then all subsequent work on any future DAC would be much, much easier  the design phase faster, the power supply skeleton in place, PCB layout issues already troubleshot.  That is one of the nice things about DIY, you get faster and more efficient as you go!  But then the designs get more complex, and you become a tortoise again


----------



## L0rdGwyn (Jul 10, 2021)

I got a bunch of new 801A tubes 

RCA USN 801A - this is sort of the "classic" 801A, running these in my amp for now.



National Electronics 801A - NE was  rebrander, I'm not certain of the actual manufacturer on these yet, need to compare to others in my collection (Hytron perhaps).



Taylor graphite plate VT-62 - graphite plate version are pretty hard to come by for a good price, very pleased to pick these up.



National Electronics 801A - another pair of graphite plates, these were made by Taylor as well.



Most of my 801A were bought in Japan, lots of these tubes over there, I'm sure there is a historical reason for that.  As such I got these all for very good prices 

I don't have much interesting to report on my projects - of course work is ongoing, new projects are developing, I've worked out the remaining kinks on my OTL, just need to finish up some PCB design and it will be good to go in a chassis.  Excited to have some Head-Fiers give it a listen when the first one is done.


----------



## bcowen

L0rdGwyn said:


> I got a bunch of new 801A tubes
> 
> RCA USN 801-A - this is sort of the "classic" 801-A, running these in my amp for now.
> 
> ...



Sweet!  I've never heard an 801A.  Deprived childhood and all.    



L0rdGwyn said:


> I don't have much interesting to report on my projects - of course work is ongoing, new projects are developing, I've worked out the remaining kinks on my OTL, just need to finish up some PCB design and it will be good to go in a chassis.  Excited to have some Head-Fiers give it a listen when the first one is done.



Do you want me to send my address now, or wait until you're done?  LOL!!


----------



## whirlwind

Nice tubes! 
 I dig those graphite plates...interesting to hear about any differences in sound vs metal plate


----------



## L0rdGwyn

bcowen said:


> Sweet!  I've never heard an 801A.  Deprived childhood and all.



Probably because this tube is such a PITA to use lol but you are rewarded for the effort.



bcowen said:


> Do you want me to send my address now, or wait until you're done?  LOL!!



Lol I mean if people were willing to pay the shipping costs, which would be significant, I would consider doing a tour of some sort.  But big, heavy, expensive things cost a lot to ship.  Another thing I had considered was sending it to someone who is going to attend a meet / CanJam event so people could try it out.  Not making any final decisions now!  Just some ideas.



whirlwind said:


> Nice tubes!
> I dig those graphite plates...interesting to hear about any differences in sound vs metal plate



You know someone told me the graphite plates have lower distortion, and I think I confirmed that at some point...to me they sound a little more transparent.


----------



## L0rdGwyn (Jul 10, 2021)

Here are the Taylor graphite plates in situ.


----------



## Zachik

L0rdGwyn said:


> Another thing I had considered was sending it to someone who is going to attend a meet / CanJam event so people could try it out.


Did you try to contact Bevin & Zach, see if they're willing to organize another ZMFestivus? That would be THE perfect place to have multiple people with awesome ZMF headphones testing your creation!! 
IF that happens - I am 100% in   
I hear October is very nice in Chicago area... Just saying...


----------



## L0rdGwyn

Zachik said:


> Did you try to contact Bevin & Zach, see if they're willing to organize another ZMFestivus? That would be THE perfect place to have multiple people with awesome ZMF headphones testing your creation!!
> IF that happens - I am 100% in
> I hear October is very nice in Chicago area... Just saying...



I don't think they are doing it this year, @Zachik .  But  I will find a way to get ears / feedback on this OTL when it is done, rest assured!


----------



## UntilThen

L0rdGwyn said:


> Here are the Taylor graphite plates in situ.



This is a statement amp. Would love to hear it with my headphones and speakers. I have word that Sowter transformers are on it's way to Tomas for 15th July delivery.


----------



## L0rdGwyn (Jul 12, 2021)

I finished the last PCB for my OTL design today and BOY, was it a doozy!

The PCB contains power supply components for both channels of the dual mono power supply including...


Mains transformer snubbing components
Mains transformer secondary protection fuses
Current limiting resistors
Full-wave bridge rectifiers
Reservoir capacitors
Time delay circuit components
So in goes high-voltage AC, out comes time-delayed raw DC before it hits the power supply regulators.

Some minor details about the time delayed aspect - there will be ~30 second delay from the time the amplifier is turned on before the high-voltage power supply is activated.  During that 30 seconds, the tube heaters will be warming, such that the tubes are full ready to conduct at the time B+ is applied.  A soft start is also included, so in total the amplifier will not be fully powered on until ~45-60 seconds after the power switch is flipped.

Why is this beneficial?  For one, it reduces the possibility of any arcing of the 6AS7G power tubes on startup as there are never excessive grid-to-cathode voltages (a major contributor to the arcing experienced in these types of amplifiers).  It also prevents any unpleasant sounds from voltage transients as the large 265uF output capacitors charge.  And if you believe in cathode stripping, it is the gentlest way to apply power to NOS tubes.

Throughout the day as I worked on this PCB (and it did take all day), I intermittently went to my work bench to listen to this amp for motivation!  Man, I think it sounds really good, so I got it done, I can order all of the final components tonight and finalize the chassis layout.

Coming into the home stretch on this design, hopefully can build it in a few weeks, then get some ears on it.


----------



## whirlwind

Kudos on the soft start, it is a great feature    

A little peace of mind when using Tung Sol 5998....most bad things happen when the amp and tubes are being powered up.


----------



## L0rdGwyn

From a chassis design standpoint, here is what I have in store for this OTL amplifier.

Toroidal shield in the center, 265uF Clarity Caps will be mounted on the interior but protrude through the top plate (back left and right).  6J5 tubes in the front, 6AS7G types in the middle, sockets for both will be mounted on sub-plates, similar to my 801A amplifier.  I've designed a "flower" pattern for the 6AS7G ventilation.  As you can see, the amplifier will be very well-ventilated.

Small changes might be made, but it is almost done.  It is a large amp, size as it stands is 13.25" x 15.25" x 3.25".  Large caps, large amp


----------



## chrisdrop

L0rdGwyn said:


> From a chassis design standpoint, here is what I have in store for this OTL amplifier.
> 
> Toroidal shield in the center, 265uF Clarity Caps will be mounted on the interior but protrude through the top plate (back left and right).  6J5 tubes in the front, 6AS7G types in the middle, sockets for both will be mounted on sub-plates, similar to my 801A amplifier.  I've designed a "flower" pattern for the 6AS7G ventilation.  As you can see, the amplifier will be very well-ventilated.
> 
> Small changes might be made, but it is almost done.  It is a large amp, size as it stands is 13.25" x 15.25" x 3.25".  Large caps, large amp


Stop making me want more amps....


----------



## L0rdGwyn

chrisdrop said:


> Stop making me want more amps....





I'm excited to get one of these built and get some feedback on it.  I am enjoying the sound, I hope others will too.  To me, it has excellent transparency, dynamics, and detail retrieval.  With the way the circuit has been designed, I also don't think you need very rare / expensive 6J5 / 6AS7G to get very good sound from the amplifier.

I will be using a 40mm RCA fester style bakelite knob.  Have to import from Europe unfortunately.  Everything has to be the way it has to be...


----------



## mordy

L0rdGwyn said:


> I'm excited to get one of these built and get some feedback on it.  I am enjoying the sound, I hope others will too.  To me, it has excellent transparency, dynamics, and detail retrieval.  With the way the circuit has been designed, I also don't think you need very rare / expensive 6J5 / 6AS7G to get very good sound from the amplifier.
> 
> I will be using a 40mm RCA fester style bakelite knob.  Have to import from Europe unfortunately.  Everything has to be the way it has to be...


Will the new OTL have preamp capability?


----------



## L0rdGwyn

mordy said:


> Will the new OTL have preamp capability?



No, I had not planned on it.  Maybe I will consider it down the road.


----------



## mordy

L0rdGwyn said:


> No, I had not planned on it.  Maybe I will consider it down the road.


Is it possible to just connect the headphone out to RCA jacks in the back to serve as a preamp?


----------



## Tjj226 Angel

mordy said:


> Will the new OTL have preamp capability?



You can simply buy a headphone to RCA adapter and use it as a preamp. 

Although I strongly advise against using any headphone amp as a preamp. A headphone amp will usually have much more noise, distortion, and phase shift over a purpose built preamp.


----------



## L0rdGwyn (Jul 14, 2021)

mordy said:


> Is it possible to just connect the headphone out to RCA jacks in the back to serve as a preamp?



You could do it that way, but really not the best way.  A power amplifier (or whatever gear is being fed by the pre-outs) will typically have an input impedance >50K, which means the output capacitance of the pre-outs does not need to be as large as it is for driving a headphone.  For instance, a f-3dB point of 10Hz with a 50K load would only require an output capacitance of 0.32uF.  This amplifier has an output capacitance of 265uF.  Why does that matter?

On startup, these caps need to charge.  On the output, they will do that through the parallel resistance of the load (headphone or amplifier fed by the pre-outs) and a parallel resistor.  This combined parallel resistance needs to be low enough that an insignificant amount of DC voltage is generated on the output on startup / shutdown.

Say you have a 2.2K load resistor on the output in parallel with a 300ohm headphone.  On startup, the caps will charge, current will flow through the load and a DC voltage will develop transiently.  Across the parallel resistance of the headphone and the 2.2K resistor (264ohm), any DC voltage will be low enough so as to be negligible, of no harm.

Now say you connect a 50K input impedance device to the output instead of a 300ohm headphone.  In parallel with the same 2.2K load resistor, the 265uF caps will need to charge across 2.1K.  The DC voltage at startup might not be negligible anymore, it might be close to 20VDC.  If the input of the 50K device is not cap coupled itself, the input device could be exposed transiently to 20VDC.  Will it survive?  Depends on the device.

That's a long way of saying it would be better to use a separate output capacitor / load resistor combination for the pre-outs.


----------



## mordy (Jul 14, 2021)

L0rdGwyn said:


> You could do it that way, but really not the best way.  A power amplifier (or whatever gear is being fed by the pre-outs) will typically have an input impedance >50K, which means the output capacitance of the pre-outs does not need to be as large as it is for driving a headphone.  For instance, a f-3dB point of 10Hz with a 50K load would only require an output capacitance of 0.32uF.  This amplifier has an output capacitance of 265uF.  Why does that matter?
> 
> On startup, these caps need to charge.  On the output, they will do that through the parallel resistance of the load (headphone or amplifier fed by the pre-outs) and a parallel resistor.  This combined parallel resistance needs to be low enough that an insignificant amount of DC voltage is generated on the output on startup / shutdown.
> 
> ...


Is it complicated to add an output capacitor / load resistor combination for the pre-outs?
The three tube headphone amps I have all work well as preamps. Two have preamp amp out and the third has separate hi/lo impedance headphone out. The designer told me to use the low impedance output when using it as a preamp.
However, the preamp out goes through a ss preamp which is used as a tone and volume control for the ss power amp. By adjusting both the volume on the tube headphone amp and the volume control on the ss preamp I can achieve a low noise floor. My impression is that this does not detract from the sound; occasionally I will need a slight tone control adjustment, depending on the tubes used, but usually everything stays neutral.


----------



## L0rdGwyn

mordy said:


> Is it complicated to add an output capacitor / load resistor combination for the pre-outs?
> The three tube headphone amps I have all work well as preamps. Two have preamp amp out and the third has separate hi/lo impedance headphone out. The designer told me to use the low impedance output when using it as a preamp.



It isn't complicated from a technical standpoint, but not something I am likely to do at the moment since I am on the verge of ordering the prototype chassis.  If I were to do it, I would likely add a switch to change from headphone to pre-out, which means changing the layout, adding machined holes for the switch, RCAs, etc.  Like I said, maybe I will consider it in the future, sorry to disappoint.


----------



## mordy

L0rdGwyn said:


> It isn't complicated from a technical standpoint, but not something I am likely to do at the moment since I am on the verge of ordering the prototype chassis.  If I were to do it, I would likely add a switch to change from headphone to pre-out, which means changing the layout, adding machined holes for the switch, RCAs, etc.  Like I said, maybe I will consider it in the future, sorry to disappoint.


The amps I have with built-in preamp out do not have a switch - both are on all the time. I can use either headphones or speakers, or both at the same time. Glenn liked to use both headphones and speakers at the same time for better sound.


----------



## L0rdGwyn

mordy said:


> The amps I have with built-in preamp out do not have a switch - both are on all the time. I can use either headphones or speakers, or both at the same time. Glenn liked to use both headphones and speakers at the same time for better sound.



I can't speak to how it was set up in Glenn's OTL.  I believe one of the other amps you are referring to is a Feliks Audio amp, they list a "preamp safety circuit" in their feature list, likely for the reasons I listed above, to protect against DC transients given that the two outputs are in parallel, the reason both are on at the same time.  It isn't something I am interested in incorporating into this amplifier, but sounds like what you have is well-suited for your listening needs.


----------



## mordy (Jul 14, 2021)

L0rdGwyn said:


> I can't speak to how it was set up in Glenn's OTL.  I believe one of the other amps you are referring to is a Feliks Audio amp, they list a "preamp safety circuit" in their feature list, likely for the reasons I listed above, to protect against DC transients given that the two outputs are in parallel, the reason both are on at the same time.  It isn't something I am interested in incorporating into this amplifier, but sounds like what you have is well-suited for your listening needs.


Thanks. According to my understanding the safety circuit shuts off the amp in the event a tube short circuits in order to prevent damage to the amp and headphones/speakers.
I know that this safety circuit works because at one point I received a defective Chinese adapter that shorted out a power tube and it prevented the amp from blowing up - unfortunately a fate that befell another amp where I tried the same adapter. (Did not understand where the problem was at first.)


----------



## bcowen

L0rdGwyn said:


> I'm excited to get one of these built and get some feedback on it.  I am enjoying the sound, I hope others will too.  To me, it has excellent transparency, dynamics, and detail retrieval.  With the way the circuit has been designed, I also don't think you need very rare / expensive 6J5 / 6AS7G to get very good sound from the amplifier.
> 
> I will be using a 40mm RCA fester style bakelite knob.  Have to import from Europe unfortunately.  Everything has to be the way it has to be...


Your OCD-ness becomes you.


----------



## L0rdGwyn

bcowen said:


> Your OCD-ness becomes you.



It's a bit of problem, costs me a lot of money LOL.

I placed all final orders for parts today.  I paid for overnight shipping from Mouser as there is one last thing to test before I can finalize the chassis order and I want to do that this weekend, $23 well spent I think.  So hopefully Saturday the chassis will be checked off the to-do list.

I am listening to the OTL amp right now with MOV L63 and Tung-Sol 5998.  I bought a pretty nifty device on US Audio Mart, Matrix Audio X-SPDIF 2 - it's a USB to pretty-much-every-other-digital-output box, including I2S over HDMI.  It does its job well, impressive measurements over on Audio Science Review (this is a device where that really does matter).

So now I can run USB into the X-SPDIF 2 box from my laptop and then coaxial SPDIF into my SW1X DAC II, which of course means I lugged the beast into the basement for some listening.




Wasn't a secret, but the DAC in the audio interface I use for testing bottlenecks the crap out of this amplifier, with a proper source, the sound is vivid, reminds you the HD650 was the best headphone in the world at one point.

I also picked up another NOS R2R DAC on US Audio Mart for a song, one that has gotten quite a bit of hype recently, the Border Patrol SE.  From what I can tell, it's a pretty simple TDA1543 design, but people like it!  I've taken an interest in these DACs since I am designing one very, very slowly...so we will see how it sounds, might mod it.


----------



## bcowen

L0rdGwyn said:


> It's a bit of problem, costs me a lot of money LOL.
> 
> I placed all final orders for parts today.  I paid for overnight shipping from Mouser as there is one last thing to test before I can finalize the chassis order and I want to do that this weekend, $23 well spent I think.  So hopefully Saturday the chassis will be checked off the to-do list.
> 
> ...


Interesting.  Wonder how the Matrix compares to the (discontinued) Schiit EITR.  The EITR doesn't have anywhere near the conversion options, but makes a significant audible improvement isolating the USB noise and converting to S/PDIF.


----------



## L0rdGwyn (Jul 14, 2021)

bcowen said:


> Interesting.  Wonder how the Matrix compares to the (discontinued) Schiit EITR.  The EITR doesn't have anywhere near the conversion options, but makes a significant audible improvement isolating the USB noise and converting to S/PDIF.



ASR measured both, I think they did well.  The Matrix is powered off USB with a crap-ton of filtering / power supply regulation inside.  You can use an external power supply, but unless you've got some super low-noise PS laying around, better to run it off USB.  It measures well, looks pretty nice, and does it's job!  Definitely more expensive than the Eitr on the used market.  At some point I'll probably try SPDIF directly into the SW1X vs. USB to SPDIF through the Matrix.


----------



## L0rdGwyn (Jul 16, 2021)

Well my final test was a success, so I can order the chassis for this OTL amplifier, will do so today after a final check of the layout.

Here are some more random parts going in this amp, NKK power switch and QQQ octal sockets.



For this first one, the prototype so-to-speak, think I am going to do the chassis in this gloss Burgundy red, I think it will look nice with the blue Clarity Caps.


----------



## mordy

L0rdGwyn said:


> Well my final test was a success, so I can order the chassis for this OTL amplifier, will do so today after a final check of the layout.
> 
> Here are some more random parts going in this amp, NKK power switch and QQQ octal sockets.
> 
> ...


How many total amps can the transformers handle?


----------



## L0rdGwyn

mordy said:


> How many total amps can the transformers handle?



I think you're talking about the heater current - 6A total, 3A per channel, spec'd for a 6AS7G and a single triode input tube, like a 6J5 / 6C5 / 6P5, etc. with some headroom.


----------



## L0rdGwyn (Jul 16, 2021)

I have the Border Patrol SE in the house.  Did a little comparison between it and the SW1X DAC II.



Both NOS R2R designs, the Border Patrol uses the TDA1543, the SW1X DAC II the PCM56.  As far as I can tell, the Border Patrol takes the voltage output of the TDA1543, whereas the DAC II takes the current output of the PCM56, uses a transistor active I/V stage and a 5687 tube output gain stage to reach line level (a little higher, actually).  I didn't measure it, but output of the Border Patrol is low, below line level for sure, so big swing in the amplifier volume knob between the two DACs.  The Border Patrol as a switchable EZ80 tube rectifier - the front switch turns the tube rectifier on and off.  The designer recommends leaving the DAC on continuously and using the switch to turn off the tube rectifier for longevity.  Looking inside, it appears the switch changes the rectification from a EZ80-diode hybrid full-wave bridge rectifier to a diode full-wave rectifier.

Keeping it short and sweet, I like the Border Patrol, it's a good sounding DAC, very enjoyable, musical, I see why people like it.  The DAC II is on another level though when it comes to musicality, detail, and dynamics.  The knock on the DAC II is that it has a high noise floor, but overtop of the noise the music is excellent, very tangible, lifelike.

I'll put the Border Patrol on my desk or in the bedroom stereo for now.


----------



## Zachik

mordy said:


> How many total amps can the transformers handle?





L0rdGwyn said:


> I think you're talking about the heater current - 6A total, 3A per channel, spec'd for a 6AS7G and a single triode input tube, like a 6J5 / 6C5 / 6P5, etc. with some headroom.


So none of the infamous "mordy's towers"...


----------



## Zachik

L0rdGwyn said:


> Keeping it short and sweet, I like the Border Patrol, it's a good sounding DAC, very enjoyable, musical, I see why people like it. The DAC II is on another level though when it comes to musicality, detail, and dynamics. The knock on the DAC II is that it has a high noise floor, but overtop of the noise the music is excellent, very tangible, lifelike.


I would love to compare one day your designed DAC to my Lampizator Amber 3...
Interestingly, the Lampizator has the same high noise floor "issue" as your DAC II.


----------



## L0rdGwyn

Zachik said:


> I would love to compare one day your designed DAC to my Lampizator Amber 3...
> Interestingly, the Lampizator has the same high noise floor "issue" as your DAC II.



It's a long way off!  Projects keep popping up so I am making very little progress on it unfortunately.  High-level decisions have been made but I need to dive into the details of the power supply.  Whenever it's done though I will bring it along to future Head-Fi meets, maybe ZMFestivus 2022.  Slawa at SW1X attributes the high noise floor to the active I/V stage he uses in the DAC II.  It isn't audible on my stereo, but with headphones it can be heard in the background.


----------



## mordy

L0rdGwyn said:


> I think you're talking about the heater current - 6A total, 3A per channel, spec'd for a 6AS7G and a single triode input tube, like a 6J5 / 6C5 / 6P5, etc. with some headroom.





Zachik said:


> So none of the infamous "mordy's towers"...


No tube rolling


----------



## L0rdGwyn

mordy said:


> No tube rolling



That's right, this is not an amp for tube rolling, it is optimized for the tubes it was designed for, the 6J5 family.  Other 6.3V single triodes and triode-strapped pentodes that bias similarly could also be used, however.  At some point I will make a compatibility list.


----------



## whirlwind

mordy said:


> No tube rolling



mordy....you already have a killer OTL amp for tube rolling     

This amp won't be made to roll lots of power tubes...6336 for example or four 6AS7G or six 6BX/6BL7

Thing is for high impedance cans should sound great and you can still roll many 6J5 tubes for different tones.

For anyone with just high impedance headphones this should be great match.


----------



## mordy

L0rdGwyn said:


> That's right, this is not an amp for tube rolling, it is optimized for the tubes it was designed for, the 6J5 family.  Other 6.3V single triodes and triode-strapped pentodes that bias similarly could also be used, however.  At some point I will make a compatibility list.


I have tried a number of 6J7 family pentodes strapped as triodes in my amp, but even though they sound good, there are major problems with hum with many of them. I noticed that many early radios that used these tubes came with full size tube shields surrounding the entire tube.


----------



## mordy

whirlwind said:


> mordy....you already have a killer OTL amp for tube rolling
> 
> This amp won't be made to roll lots of power tubes...6336 for example or four 6AS7G or six 6BX/6BL7
> 
> ...


I am pretty much convinced that 6J5 family drivers are the best sounding I have come across.


----------



## whirlwind (Jul 16, 2021)

mordy said:


> I am pretty much convinced that 6J5 family drivers are the best sounding I have come across.


They are cheaper than than the better 6SN7 tubes...thing is the best ones  now are almost the same price, lol.....but it is easier to find NOS ones and there are still many cheap ones available for one to be able to change the sound a bit.
I bet the ZMF Auteur that Keenan has will sound really nice from this amp as would any other high impedance headphone.


----------



## L0rdGwyn

One thing to note - when using an active load like in this amplifier (or like I added to your GOTL, @whirlwind ), in my experience this closes the gap significantly between the cheapest and most sought-after 6J5.  The load line is flattened, so differences in linearity between the tubes become much smaller.


----------



## L0rdGwyn

Some other advantages to using an active load over a resistive load - higher gain, lower distortion, better power supply isolation.  If using cathode bias, the bypass capacitor can be removed from the signal path as the degenerated cathode will not significantly alter the output impedance of the stage, and the small degree of cathode degeneration will lower distortion even further.  The tradeoff is less flexibility to roll lots of different tubes with adapters since some variable of the tubes operation is now fixed by the active load.  But, in my opinion, the pros far outweigh the cons.


----------



## whirlwind (Jul 16, 2021)

L0rdGwyn said:


> One thing to note - when using an active load like in this amplifier (or like I added to your GOTL, @whirlwind ), in my experience this closes the gap significantly between the cheapest and most sought-after 6J5.  The load line is flattened, so differences in linearity between the tubes become much smaller.


I agree. The gap is much reduced.

Most people would have no need to go for GEC...Mullard...Firve.

Just enjoy the music.


----------



## UntilThen

OTL.... is there room in my stable for an OTL... let me see. How about an OTL that use 6 x GE 6bx7gt, a rectifier and 2 x L63/6J5? Yes Keenan?


----------



## UntilThen

It has to be GE tubes because no one wants them ..... gawd knows why.


----------



## L0rdGwyn

UntilThen said:


> OTL.... is there room in my stable for an OTL... let me see. How about an OTL that use 6 x GE 6bx7gt, a rectifier and 2 x L63/6J5? Yes Keenan?



Lol sorry @UntilThen , this is it for now, maybe I will have another offering down the road...


----------



## UntilThen

L0rdGwyn said:


> Lol sorry @UntilThen , this is it for now, maybe I will have another offering down the road...



What??? 



Anyhoo, Tomas had a first listen of Odyssey and he says it's big and full and authoritative ! I'm having glazed eyes now.


----------



## L0rdGwyn

UntilThen said:


> Anyhoo, Tomas had a first listen of Odyssey and he says it's big and full and authoritative ! I'm having glazed eyes now.



Excellent, can't wait to see the finished product!


----------



## UntilThen

L0rdGwyn said:


> Excellent, can't wait to see the finished product!



Well yeah I have to know what all the fuss is with Sowter transformers.


----------



## L0rdGwyn

UntilThen said:


> Well yeah I have to know what all the fuss is with Sowter transformers.



Well soon you will know  it will probably be a long time until I use their output transformers again, but I am planning to use some Sowter transformer in my DAC design, and I might pick up some Sowter chokes to direct-couple my 45 parafeed amplifier later this year...

For output transformers, I am looking stateside for my next amplifier build, will be going with Electra-Print low IMD winding.  Vegas baybay!


----------



## UntilThen

L0rdGwyn said:


> Well soon you will know  it will probably be a long time until I use their output transformers again, but I am planning to use some Sowter transformer in my DAC design, and I might pick up some Sowter chokes to direct-couple my 45 parafeed amplifier later this year...
> 
> For output transformers, I am looking stateside for my next amplifier build, will be going with Electra-Print low IMD winding.  Vegas baybay!



I just post on a custom amp name Chameleon that will use Silk transformers. Have a look here. https://www.head-fi.org/threads/oblivion-ultrasonic-studios.902926/post-16459181


----------



## bcowen

UntilThen said:


> It has to be GE tubes because no one wants them ..... gawd knows why.


Um, because they suck?  Naw, can't be that.  Nevermind.


----------



## bcowen

L0rdGwyn said:


> Well my final test was a success, so I can order the chassis for this OTL amplifier, will do so today after a final check of the layout.
> 
> Here are some more random parts going in this amp, NKK power switch and QQQ octal sockets.
> 
> ...


Awesome.  Love that color!!


----------



## UntilThen

bcowen said:


> Um, because they suck?  Naw, can't be that.  Nevermind.



My next custom amp will be name GE, in remembrance of the 1st company I work in.


----------



## L0rdGwyn

UntilThen said:


> I just post on a custom amp name Chameleon that will use Silk transformers. Have a look here. https://www.head-fi.org/threads/oblivion-ultrasonic-studios.902926/post-16459181



Cool!  Will be an interesting face-off I'm sure.


----------



## bcowen

UntilThen said:


> My next custom amp will be name GE, in remembrance of the 1st company I work in.


Add a 'C' at the end and I'll want one too.


----------



## Zachik

UntilThen said:


> It has to be GE tubes because no one wants them ..... gawd knows why.


@bcowen you just got promoted by @UntilThen (to gawd...)


----------



## Tjj226 Angel

UntilThen said:


> OTL.... is there room in my stable for an OTL... let me see. How about an OTL that use 6 x GE 6bx7gt, a rectifier and 2 x L63/6J5? Yes Keenan?



But why tho. 

I mean if we are being completely honest, a headphone amp needs around 150-200ma with about 7V RMS to drive darn near every headphone on the market with the exception of headphones like the HE-6 and K1000s. 

You can easily achieve this with 1 pair of 6BX7 tubes and a little bit of feedback. 

The only reason you would use 6 of them is if you were trying to make a speaker amp which is also kind of a waste of time. You would only get about 1 watt, and you would still need some feedback in order to get the output impedance low enough. 

Plus the 6BX7 is not the most linear tube in the world anyways. I would be looking for some TV sweep tubes to make a speaker OTL, and a high gm triode strapped pentode for a headphone OTL. 

Hell, if you really wanted to be fancy, you could make a very serviceable headphone OTL amp with some 6H30s.


----------



## bcowen

Zachik said:


> @bcowen you just got promoted by @UntilThen (to gawd...)


LOL!  Finally a promotion after all these years of being his underpaid caddy, gardener, and golf cart dryer-outer.  With all that I never had the time to properly set up his turntable (where the VTA is 20 degrees off, but at least he didn't install the cartridge backwards).


----------



## UntilThen

bcowen said:


> LOL!  Finally a promotion after all these years of being his underpaid caddy, gardener, and golf cart dryer-outer.  With all that I never had the time to properly set up his turntable (where the VTA is 20 degrees off, but at least he didn't install the cartridge backwards).



Yup you're promoted to bitter gourd.


----------



## L0rdGwyn

OTL chassis is ordered, here is the final.  Dimensions are L 13.5" x W 15.5" x H 3.25".


----------



## UntilThen

Starting to look very good. So the 2 round thingy behind are the blue clarity caps? Maroon red and blue - that's a smacko colour scheme !


----------



## L0rdGwyn

UntilThen said:


> Starting to look very good. So the 2 round thingy behind are the blue clarity caps? Maroon red and blue - that's a smacko colour scheme !



Yep, the large holes in the rear are for the Clarity Caps.  The tube socket sub-plates will be matte black.


----------



## bcowen

L0rdGwyn said:


> Yep, the large holes in the rear are for the Clarity Caps.  The tube socket sub-plates will be matte black.


Sweet!  

I'm thinking ChromaFlair would be a good choice for the maroon paint.


----------



## UntilThen

L0rdGwyn said:


> Dimensions are L 13.5" x W 15.5" x H 3.25".



Quite a big foot print. Almost as big as Oblivion but then for rack users like me, that is good.


----------



## UntilThen

Tjj226 Angel said:


> But why tho.



The short answer is I still have more than 12+ 6bx7. However that is just a passing thought as I have move on to other tube types. 

Having said that, six 6bx7 in Glenn OTL amp sounded better than just a pair. My ears of course.


----------



## L0rdGwyn

UntilThen said:


> Quite a big foot print. Almost as big as Oblivion but then for rack users like me, that is good.



Yeah it is large, but for what I wanted to do with the top-plate component layout, it had to be given the size of the output capacitors.  I spend a lot of time finding the right "balance" in terms of physical location of the top-mounted parts, I found this gave the best result despite the large size.


----------



## johnjen

bcowen said:


> LOL!  Finally a promotion after all these years of being his underpaid caddy, gardener, and golf cart dryer-outer.  With all that I never had the time to properly set up his turntable (where the VTA is 20 degrees off, but at least he didn't install the cartridge backwards).


That's just the 1st step, gett'n the cart in and close to be'n in the groove.

The next few steps can take WAY longer as micro adjustments are attempted, repeatedly, as in 'ooopps went to far', now come back, and 'went to far' the other way, try again and again, and in all 3 adjustment domains.

But when you hit THE Sweet Spot, boy howdy you just know it.
And the life lesson, learned all to painfully, to resist ALL temptations to see if this one last tweak will 'do the trick', only to, yet again, 'go to far…'

So when it sounds fabulous, LEAVE IT ALONE and just listen!!!!!!!!!!!

Such are the trials, tribulations and sage advice of a vinyl tweaker.
hahahahahahahahahahahahahahahahaha   

JJ


----------



## UntilThen

Roy Gandy sending this specialist to do my cartridge now. Bcowen will step down.. step out with no pay.


----------



## mordy

Tjj226 Angel said:


> But why tho.
> 
> I mean if we are being completely honest, a headphone amp needs around 150-200ma with about 7V RMS to drive darn near every headphone on the market with the exception of headphones like the HE-6 and K1000s.
> 
> ...


I am using a Glenn OTL headphone/preamp with six power tube sockets. Using 6N12S (0.9A), six tubes sound better than four or two.


----------



## bcowen

johnjen said:


> So when it sounds fabulous, LEAVE IT ALONE and just listen!!!!!!!!!!!


But what if you can tweak it just a bit more and make it sound _more_ fabulous? Or is that Moar?  This is what keeps me awake at night.


----------



## Tjj226 Angel

mordy said:


> I am using a Glenn OTL headphone/preamp with six power tube sockets. Using 6N12S (0.9A), six tubes sound better than four or two.



And @UntilThen 

The reason using multiple 6BX7 tubes in Glenn's amp sounds better is because the 6BX7 by itself WITH NO TRICKS (key point) can not achieve a low enough output impedance to drive most headphones well. As a result, if you run a 6BX7 as a simple cathode follower, you will have to run quite a few of them in parallel to get the output impedance low enough. 

HOWEVER!!!!!! 

If you want a boutique OTL amplifier, you are not limited to Glenn's topology. There are plenty of ways to build an OTL amp. One such example would be a white cathode follower. It's kind of like lordgwyns or Glenns design, but it adds a negative feedback loop around the cathode follower. This feedback loop greatly reduces the output impedance without the need of paralleling a bunch of tubes. 

There are plenty of other different topologies out there that would be better suited for a more targeted and specific use amplifier. 

Also, just as a fun side note. When it comes to OTL tubes, make sure you read, read, and reread the datasheet. The 6BX7 has a max plate wattage of only 10 watts per triode. However if you parallel the triodes, you only get 12 watts. 

If you use the 6BX7 in a push pull design, you would be able to get the full 20 watts out of the tube 

Most "OTL tubes" (high current, low plate resistance) always seem to have some type of weird caveat with their operating conditions. IDK why. It just seems to be a thing.


----------



## johnjen

bcowen said:


> But what if you can tweak it just a bit more and make it sound _more_ fabulous? Or is that Moar?  This is what keeps me awake at night.


Yes MOAR 4 ME.

Actually what keeps you awake at night is that last bit of tweak that goes horribly wrong and you spend the rest of the night trying to at least get back to where you started in the 1st place…
Don't ask me how I know this, nor how many times I have re-learned this tweakers trick, over, and over, and over, again and again…
hahahahahahahahahahahaha 

Oh yeah, and never, Never, NEVER, make 'adjustments' when the system sounds horribly ugly for whatever reason, as this is the perennial tweakers nightmare, since chasing bad SQ is never, Never, NEVER, going to result in improvements after the system recovers from the cooties it picked up from who knows where.

Just say'n is all…
hahahahahahahahahahahahahahaha  

JJ


----------



## UntilThen

Tjj226 Angel said:


> If you use the 6BX7 in a push pull design, you would be able to get the full 20 watts out of the tube



Believe me Angel, it's been a pretty full on day. 3 hours of badminton in the morning and I lost all my games to super girls and my ego's bruised.

Alright 20 watts did you say? Well I got 21 watts from Odyssey in UL mode now.  I ain't power hungry no more. So OTL might have to go on the back burner for a while. 2021 and most of 2022 will be spend tube rolling with Odyssey.

Then 2023 ... we shall see. I might be keen on a 2a3 / 45 amp. So that push out OTL even more. Now I need one more super headphone by early 2022.


----------



## Tjj226 Angel

UntilThen said:


> Believe me Angel, it's been a pretty full on day. 3 hours of badminton in the morning and I lost all my games to super girls and my ego's bruised.
> 
> Alright 20 watts did you say? Well I got 21 watts from Odyssey in UL mode now.  I ain't power hungry no more. So OTL might have to go on the back burner for a while. 2021 and most of 2022 will be spend tube rolling with Odyssey.
> 
> Then 2023 ... we shall see. I might be keen on a 2a3 / 45 amp. So that push out OTL even more. Now I need one more super headphone by early 2022.



It's 20 watts of thermal dissipation. Not actual power output. 

In other words let's say that we need to run a 6BX7 at 200v on the plate with 10 volts on the grid. If you run both triodes in the tube in parallel, you are limited to 12 watts of thermal dissipation. Ohms law says that if we take 12 watts and divide by our plate voltage of 200, we can only run the tube at 60ma. 

That means that for 1 tube, we can only put 60ma into our headphones. We also know that Watts = (I^2) * your headphone impedance. So for a 32 ohm headphone, we find that we get a power output of about 115mw. Not bad honestly. I would assume a majority of headphones on the market would probably work with 115mw. 

However if we use a push pull configuration, we now get 20 watts of dissipation (10 watts per triode). We can also reduce our plate voltage down to 150v on the plate and 5v on the grid since a push pull design will actually double our signal output. 

So now if we do the same math as before, we find out that 10 watts divided by 150 volts gets us about 66ma. Since a push pull design will give us an apparent current output of both triodes, we end up with 132ma of current going to the headphones. This gives us a power output into a 32 ohm load of 568mw. 

At 568mw, you can drive just about every headphone out there with 1 6BX7 per channel. 

And again, this is just an example of what you can do to get more mileage out of your tubes. There are tons of different options out there. Some of less power, but better distortion and sonic characteristics. Some have more power but a sloppier sound. Some have decent power and great sonics. 

The best thing you can do for yourself is to figure out what your end game headphones are, and then design an OTL in such a way that you will achieve enough power to drive them to 115db with the highest degree of linearity. Doing so will require a lot more math and engineering, but you are pretty much guaranteed to end up with a superior result.


----------



## UntilThen

All very interesting Angel ! However my mind now is on finding the optimum settings and tubes on my KT88 / EL34 custom amp with LCD4 and He1000se. I have in mind Abyss 1266 TC after I get Bcowen to rob a bank.


----------



## mordy

Tjj226 Angel said:


> It's 20 watts of thermal dissipation. Not actual power output.
> 
> In other words let's say that we need to run a 6BX7 at 200v on the plate with 10 volts on the grid. If you run both triodes in the tube in parallel, you are limited to 12 watts of thermal dissipation. Ohms law says that if we take 12 watts and divide by our plate voltage of 200, we can only run the tube at 60ma.
> 
> ...


I can follow what you are writing, but from the little I know I understand that every amp design involves many compromises. I am also not sure if a design that looks very good on paper is guaranteed to sound very good when built.
I cannot explain why certain tubes of the same designation sound very different from each other; one set of tubes from one manufacturer sounds dull and lifeless, another set of the same designation from a different manufacturer sounds lively and vibrant. One set is boring to listen to, and the other makes you smile and tap your feet...
And then we are told that more "modern" designs using CCS (constant current source) devices even out the differences between tubes and they all sound similar, be it a GE or GEC tube.
So I am left with a ?
The only way for me to solve the questions is to listen - to trust my ears.


----------



## UntilThen

mordy said:


> to trust my ears.



Absolutely. I will trust my elfin ears. I have Destiny. a 300b amp from McChanson and from memory of my time with a Woo Wa5le with Takatsukie tubes, Destiny will smoke the Woo any time any day. Most people don't know what treasures there are in some custom boutique tube amps. That's why I'm hooked on boutique custom amps now and I lurk here... and talk to Keenan.


----------



## Tjj226 Angel

mordy said:


> I can follow what you are writing, but from the little I know I understand that every amp design involves many compromises. I am also not sure if a design that looks very good on paper is guaranteed to sound very good when built.
> I cannot explain why certain tubes of the same designation sound very different from each other; one set of tubes from one manufacturer sounds dull and lifeless, another set of the same designation from a different manufacturer sounds lively and vibrant. One set is boring to listen to, and the other makes you smile and tap your feet...
> And then we are told that more "modern" designs using CCS (constant current source) devices even out the differences between tubes and they all sound similar, be it a GE or GEC tube.
> So I am left with a ?
> The only way for me to solve the questions is to listen - to trust my ears.



Uhhhhhh..... how much time you got? 

This idea that amp building is a total crap shoot and that a perfect amp on paper will not sound good in real life is either true or false depending on your frame of reference. There are tons of electrical engineers out there that feel like building a perfect amp involves making an amp that measures really well and nothing more. More often than not, these amplifiers are exceedingly complex, and use a huge amount of NFB. The irony is that if you really start to pick apart the measurements, you will also find out that they don't actually measure all that well in the first place. But the EE doesn't really see this. He just sees a perfect frequency response with low distortion and a decent looking square wave and calls it a day. When he realizes his amp sounds like crap, he will throw their hands up in the air and declare that a good sounding amplifier makes no sense and is a complete mystery. 

If you don't take my word for it, go ask any reputable designer out there. There is a great interview with John Curl, where he explains this issue a little bit more in depth. 

The truth is that human kind has known how to build amplifiers that are almost guaranteed to sound good since the late 30s. The rules of the road are simple. Build simple circuits with as few amplifying stages as possible. Minimize reactive components. Minimize distortion using things like load line cancelation before you use any form of NFB. Focus very heavily on making the amplifier as linear as possible. And for the love of god, make sure the power supply is of the highest quality you can possibly muster. Most EEs will fight these rules since the only thing that matters to them is coming up with a design that has perfect frequency response and low distortion. So long as they can achieve that, it doesn't matter how much NFB you use, or how many stages the amplifier has, or what other sin they need to commit in order to achieve that goal. 

However, if you follow those simple guidelines, you will build a decent sounding amplifier. It really is almost too easy which is why I get pissed off at certain companies that shall not be named for making such crappy amplifiers on an almost consistent basis. But I digress. If you want more technical information on why each one of these rules are important, Nelson Pass has several articles explaining them, or you can read the radiotron handbook. 

There are also very good reasons why different tubes sound different. Again, the radiotron handbook actually talks about how tubes are designed and why different chemistry, shape, and construction will result in different sound. I would also like to point out that the machines they used to pull vacuums back in the 40s-70s weren't exactly perfect, and just variation in the strength of the vacuum will cause tubes to sound different. 

IDK who said a CCS will even out the differences in tubes, but that isn't even a half truth. It's like a 8th truth. In a traditional design, you would normally load a tube with a resistor. Your cathode resistor would control how much current your tube would pull which would affect how much voltage would be dropped across the plate resistor. So on and so on. Well if some of your tubes were stronger than others, they might pull a little more or a little less current and they would change how the amplifier operates. A CCS will force the tubes to have a "constant" current across the anode and cathode which will make the amplifier perform in a more consistent way. 

If you have 10 pairs of the same tube, but they all test differently due to age, a CCS will allow them to play a little bit more consistently. It will even help different tubes sound a LITTLE bit closer to one and other since it removes the tube's operating conditions as a factor. 

But a CCS will actually magnify intrinsic differences in the tubes.


----------



## UntilThen

Tjj226 Angel said:


> Minimize distortion using things like load line cancelation before you use any form of NFB.



Can you please explain NFB. Negative Feedback? What does it do and why have it.


----------



## Tjj226 Angel

UntilThen said:


> Can you please explain NFB. Negative Feedback? What does it do and why have it.



Negative feedback is a process in which you take some portion of an output signal from somewhere in the amp and feed it back to the input of the amp. 

The goal is to cancel out any errors, distortion, or non linearities the amplifier may be producing. 

The problem is that your output signal is never exactly what you expect to be feeding back to the input and it isn't perfectly in time, so you get a lot of undesirable byproducts. These problems can be controlled in such a way that you get more benefits than drawbacks, but that is a science in of itself, and again, Nelson Pass has a couple talks and articles on the topic.


----------



## UntilThen

Tjj226 Angel said:


> Negative feedback is a process in which you take some portion of an output signal from somewhere in the amp and feed it back to the input of the amp.
> 
> The goal is to cancel out any errors, distortion, or non linearities the amplifier may be producing.
> 
> The problem is that your output signal is never exactly what you expect to be feeding back to the input and it isn't perfectly in time, so you get a lot of undesirable byproducts. These problems can be controlled in such a way that you get more benefits than drawbacks, but that is a science in of itself, and again, Nelson Pass has a couple talks and articles on the topic.



Thanks. Now I google a little and I get this 

*Negative feedback* makes the amp *sound* "tighter", particularly in the low end, where the speaker resonant hump *has* the most effect on amplifier output

and I can see why I might like this. On the other hand, without NFB means more distortion. 2nd harmonic distortion? Ones that some might like with characteristics of lush and holographic?


----------



## Tjj226 Angel (Jul 18, 2021)

UntilThen said:


> Thanks. Now I google a little and I get this
> 
> *Negative feedback* makes the amp *sound* "tighter", particularly in the low end, where the speaker resonant hump *has* the most effect on amplifier output
> 
> and I can see why I might like this. On the other hand, without NFB means more distortion. 2nd harmonic distortion? Ones that some might like with characteristics of lush and holographic?



That's a load of BS.

It all depends on the design topology and how the feedback is implemented. Saying NFB makes an amp sound tighter is like saying all red cars are faster than blue cars.

The goal of any amp designer is to make an amp that works really well without NFB. Then you add NFB after that to see if it improves the sound or not. In some cases NFB might actually work to your advantage, but usually in very small amounts.

As far as second order harmonics go, you can minimize 2nd order with good design. By adjusting the operating point of the tubes, you can find a "sweet spot" where the distortion actually drops a fair amount. You can take this one step further by matching the distortion characteristics of your output tube with your input tube. This will cross cancel some second order harmonics as well.

Now you might ask, why use NFB at all if it is so bad? Clearly it has to be useful for something.

NFB works really well in push pull amplifiers that use a phase splitter, or in any pentode based amplifier. Most active phase splitters in push pull amps are grossly imperfect. We ideally want a perfect differential amplifier stage to act as the phase splitter so that we have perfectly balanced gain, impedance, time alignment, phase response, and PSRR. I really don't know of any phase splitter that embodies all those attributes (but I am working on inventing one  ) . For the moment, every phase splitting circuit will cause some sort of problem with the signal. NFB can be used to help even out the damage enough so that the signals through the amp are balanced. So long as these errors are in phase, they will ultimately be canceled out. It's a pretty neat trick. However, too much of anything good isn't good anymore, so again, it's better to use less NFB than more.


----------



## leftside (Jul 18, 2021)

Tjj226 Angel said:


> The best thing you can do for yourself is to figure out what your end game headphones are, and then design an OTL in such a way that you will achieve enough power to drive them to 115db with the highest degree of linearity. Doing so will require a lot more math and engineering, but you are pretty much guaranteed to end up with a superior result.


I believe that is what Mischa did with my OTL and the LCD4. For the record: @A2029  did say I didn't need 6 power tubes, but I insisted  And then the Abyss turn up in my home after being spotted on the local used market recently. The seller asked me last week if he could buy them back...

Thanks for all the useful information in this great thread. I read as much as I can, but it's not my day job. I'm still hoping to be a professional downhill mountain biker haha. Mountain ebikes are making the climbs much easier these days, so there is more time and energy to practice the downhills for us older guys.


----------



## UntilThen

Tjj226 Angel said:


> That's a load of BS.



Wakaka BS 😂


----------



## Tjj226 Angel

leftside said:


> I believe that is what Mischa did with my OTL and the LCD4. For the record: @A2029  did say I didn't need 6 power tubes, but I insisted  And then the Abyss turn up in my home after being spotted on the local used market recently. The seller asked me last week if he could buy them back...



@A2029 is a pretty darn knowledgeable and I trust he made you a pretty cool amp.


----------



## Tjj226 Angel

UntilThen said:


> Wakaka BS 😂



I am always amazed what people find on the internet when it comes to audio. I swear to god there is some secret society posting nonsensical BS to the internet about audio with the intent of preventing everyone from making better audio gear.


----------



## mordy

Could you mention tube amps that are well designed according to your standards?


----------



## Tjj226 Angel

mordy said:


> Could you mention tube amps that are well designed according to your standards?



Hmmm that is actually a pretty interesting question. I will limit my answers to anything built from the 90s on up because I could sit here all night and write about vintage gear. 

For tube stuff, I have a lot of respect for audio note. They have an obvious dedication for their craft. Audionote UK is definitely good, but the kondo stuff is on another level. But the obvious problem with their stuff is that it is basically unobtainable. For the high end stuff, you would have to win the lotto, and take out a bank loan, and sell off your first born.

The high end bottlehead amps (kaiju) are actually pretty well built from an engineering stand point. I also have a ton of respect for any company that custom designs their own transformers. I would personally like to see them use some better capacitors, but the ones they do use are a hell of a lot better than other amps on the market.  

I used to like synthesis, but ever since they came out with their roma stuff, I haven't been all that thrilled with them. 

The new Quad 2 amplifier I heard was pretty good. 

There are several more that aren't coming to memory right now. 

----------

On the solid state side of things, it is a much shorter list. 

Parasound, Luxman, and a hand full of the nelson pass amplifiers. Everything else has been either passable, or so bad that I had to leave the room within a few minutes of entering. 

Luxman is the real wild card here since I do not know much about their design/engineering philosophy, but if someone put a gun to my head and told me to buy a SS amplifier, I would probably buy the luxman. But only the luxman amps that run pure class A.


----------



## whirlwind

Tjj226 Angel said:


> Uhhhhhh..... how much time you got?
> 
> 
> IDK who said a CCS will even out the differences in tubes, but that isn't even a half truth. It's like a 8th truth. In a traditional design, you would normally load a tube with a resistor. Your cathode resistor would control how much current your tube would pull which would affect how much voltage would be dropped across the plate resistor. So on and so on. Well if some of your tubes were stronger than others, they might pull a little more or a little less current and they would change how the amplifier operates. A CCS will force the tubes to have a "constant" current across the anode and cathode which will make the amplifier perform in a more consistent way.


OK...a 1/8 truth it is    

Love this thread and thanks for the detailed explanation!


----------



## leftside

Tjj226 Angel said:


> I am always amazed what people find on the internet when it comes to audio. I swear to god there is some secret society posting nonsensical BS to the internet about audio with the intent of preventing everyone from making better audio gear.


I don't think it's just audio... but audio certainly seems to have more than it's fair share of such posts for sure.


----------



## whirlwind

leftside said:


> I don't think it's just audio... but audio certainly seems to have more than it's fair share of such posts for sure.


So true...it is pretty much everything and we all know if it's on the internet it must be true


----------



## mordy

Tjj226 Angel said:


> Hmmm that is actually a pretty interesting question. I will limit my answers to anything built from the 90s on up because I could sit here all night and write about vintage gear.
> 
> For tube stuff, I have a lot of respect for audio note. They have an obvious dedication for their craft. Audionote UK is definitely good, but the kondo stuff is on another level. But the obvious problem with their stuff is that it is basically unobtainable. For the high end stuff, you would have to win the lotto, and take out a bank loan, and sell off your first born.
> 
> ...


Thanks for your answer. In looking through offerings for the brands and models you recommended, the price range was between $5,000-$70,000 which is too rich for me. Is there such a thing as tube headphone/preamp combination amplifiers that you can think of in a lower price range ($500-$1500) that are worth consideration? 
Even older items, although I am a little afraid of amps being 20-40 years old since I assume that they need servicing which may be costly and difficult to obtain.


----------



## Tjj226 Angel

mordy said:


> Thanks for your answer. In looking through offerings for the brands and models you recommended, the price range was between $5,000-$70,000 which is too rich for me. Is there such a thing as tube headphone/preamp combination amplifiers that you can think of in a lower price range ($500-$1500) that are worth consideration?
> Even older items, although I am a little afraid of amps being 20-40 years old since I assume that they need servicing which may be costly and difficult to obtain.



I can't think of a genuinely good tube amp for less than 1500 bucks that isn't a vintage amp, or requires some diy tricks to get it to perform well. 

However, the antique sound labs Mk3 headphone amp is pretty decent and can be found on ebay for a song (although it's kind of rare). The cool thing about it is that you can switch between OTL mode and transformer coupled mode. 

---------

As far as vintage amps go, I have a giant list for speaker amps, but not headphone amps. Now if you are interested, you can whip up an adapter box with a couple of resistors for 10 bucks or so. If you went that route, I would tell you to go look for a decent dynaco ST-70. They are common as dirt and you can find old people trying to throw them away to make space in their living rooms. Alternatively, you can find completely restored ST-70s on ebay for 600-700 bucks that would last until the heat death of the universe.


----------



## L0rdGwyn (Mar 29, 2022)

Have been working quite a bit lately, finally have some time off, preparing for OTL chassis which is in production.

Finished putting together the raw DC power supply boards for this amplifier, very happy with the result.  This is for both channels of the dual mono supply.

Tomorrow I'll put together my new power supply regulator boards and test them.  After that, just need the chassis to build the first one.


----------



## tubebuyer2020

L0rdGwyn said:


> ...



Could you please include Queen Sassafras in the next photo  ?


----------



## L0rdGwyn

tubebuyer2020 said:


> Could you please include Queen Sassafras in the next photo  ?



Lol I will do my best, she is very fussy and camera shy, have to catch her when she's asleep.


----------



## tubebuyer2020

L0rdGwyn said:


> Lol I will do my best, she is very fussy and camera shy, have to catch her when she's asleep.



Thanks, if she hangs around amplifiers and produces sounds then she is a part of audio chain!


----------



## miketlse

tubebuyer2020 said:


> Thanks, if she hangs around amplifiers and produces sounds then she is a part of audio chain!


Covered in all that sound absorbing fur, she can change the room acoustics, if she sleeps in the right locations.


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## L0rdGwyn (Aug 14, 2021)

miketlse said:


> Covered in all that sound absorbing fur, she can change the room acoustics, if she sleeps in the right locations.



It's very intentional, she sleeps where a sibilant resonance will be generated, holding me hostage until I give more cat food.

I tested my regulators, unfortunately I need to make a layout change, so one more week until the new PCBs arrive!

Another random thing - I returned my SW1X DAC II.  So it is on its way back to the UK and I am currently without a high-performing DAC, using the Border Patrol as a stand-in.

So what to do?

I was going to use the money from the return to invest in my own DAC design, I still plan to, but that is going to take a while and I can't wait months for a new DAC...

While doing research on power supply design, I came across the work of Pedja Rogic, DIYer / small business owner and really THE authority on implementation of the TDA1541A.  Reading up on his work, I have been extremely impressed by his engineering acumen, to the point that I've decided to buy one of his TDA1541A DACs rather than designing my own (based on this chip at least).

So I am going to order an Audial S5, most recent release from Rogic earlier this year.

Where does that leave my own DAC design?  I am going to simplify it to some extent by focusing on a different chip, likely the AD1865.  The power supply is a little more straightforward as it requires only a +5V / -5V bipolar (as opposed to the additional -15V supply of the TDA1541A), still operates in simultaneous mode, and the chips themselves are nowhere NEAR the price of a TDA1541A, around $25 a pop, which lends itself to more experimentation.  I'll use the S5 in my main system with the plan to put the AD1865 DAC with my headphone setup.

That's the DAC update, will give some thoughts on the S5 when it arrives.


----------



## Tjj226 Angel

L0rdGwyn said:


> Another random thing - *I returned my SW1X DAC II.*



A chip you may want to look into is the CS4328. 

i don't want to give away too many spoilers, but it is a pretty unique chip and the dacs that have used it are all on par with any NOS R2R dac I have ever heard. 

But the big kicker is that it is really easy to build a dac with it because it has a unique voltage output configuration. In fact it doesn't actually need an IV stage at all. 

The chip is cheap on ebay, it's easy to build with, and you get really solid performance from it.


----------



## L0rdGwyn

Tjj226 Angel said:


> A chip you may want to look into is the CS4328.



Cool, looks like it uses a built-in MOSFET output to generate 4Vpk-pk paired with an RC output filter, would make for a very simple and compact design.  I'm pretty well invested in PCM mode Iout chips, have a USB digital front end module I intend to use as well as some I/V transformers en route.


----------



## Zachik

L0rdGwyn said:


> will give some thoughts on the S5 when it arrives


Interesting - never heard of that DIY'er and his DACs. I wonder how the S5 would compare to my Lampizator Amber 3 (or to Schiit's Yggy)...


----------



## L0rdGwyn

Zachik said:


> Interesting - never heard of that DIY'er and his DACs. I wonder how the S5 would compare to my Lampizator Amber 3 (or to Schiit's Yggy)...



We will see!  Well, I will only be able to compare to what I have heard, but perhaps it will make it to a meet in the future if it is a hit.


----------



## L0rdGwyn (Jul 28, 2021)

Without realizing it, I've made some serious progress on my DAC design, it's actually at a point where I can put together the PCB and prototype.

It is now based on the PCM56 chip, two for stereo.  Not very different than designing for AD1865, some minor changes to the power supply.

The DAC will have five separate power supplies - analog positive and negative, logic positive and negative, and digital positive.  Furthermore, the individual supplies will be split down the way for the two channels.  As such, this PCB is going to be a lot of fun to lay out LOL here is a bird's eye view of the parts that need to be organized.




Yes...yes, this will be very fun, I love DIY...

Here is some mandatory reading for anyone thinking about designing a DAC: https://www.analog.com/media/en/training-seminars/tutorials/MT-031.pdf

Going to get started on this today, hopefully can order the PCBs within a few days.

Also got some interstage transformers in today for another project I am working on - will talk about what that project is in detail sometime in the future.  So purdy.



Machining is done for the OTL chassis, it will be coated this weekend, so likely will get it in house some time late next week, at which time I will build OTL #1  

Now onward to DAC design!


----------



## UntilThen

Me thinks you should build speakers. I want JBL or Tannoy with 15” woofers equivalent.


----------



## L0rdGwyn

UntilThen said:


> Me thinks you should build speakers. I want JBL or Tannoy with 15” woofers equivalent.



One idea I have floating around - once I move into a new home, I might consider building an Altec Stonehenge III clone using Great Plains Audio 604-8H-III drivers, but right now the the speakers I have are the right size for my room


----------



## UntilThen

L0rdGwyn said:


> One idea I have floating around - once I move into a new home, I might consider building an Altec Stonehenge III clone using Great Plains Audio 604-8H-III drivers, but right now the the speakers I have are the right size for my room



You will build one for me too right?

A Stonehenge.


----------



## Mr Trev

UntilThen said:


> You will build one for me too right?
> 
> A Stonehenge.


Just be sure not to get " and ' mixed up.


----------



## L0rdGwyn

UntilThen said:


> You will build one for me too right?
> 
> A Stonehenge.



Shipping will cost more than the speakers LOL will have to build on site.


----------



## UntilThen

Let me worry about shipping Stonehenge to Australia.


----------



## bcowen

UntilThen said:


> Let me worry about shipping Stonehenge to Australia.


May be cheaper to ship Australia to @L0rdGwyn .


----------



## bcowen

L0rdGwyn said:


>


That looks strangely similar to the work flow spaghetti diagram I did a few weeks ago at my newest place of employment.


----------



## UntilThen

bcowen said:


> May be cheaper to ship Australia to @L0rdGwyn .



I am giving you the task of getting Stonehenge to Sydney. Don’t let me down.


----------



## bcowen

UntilThen said:


> I am giving you the task of getting Stonehenge to Sydney. Don’t let me down.


Buy me this and I'll deliver them in perfect condition.  Eventually.


----------



## Tjj226 Angel

L0rdGwyn said:


> One idea I have floating around - once I move into a new home, I might consider building an Altec Stonehenge III clone using Great Plains Audio 604-8H-III drivers, but right now the the speakers I have are the right size for my room



Whatever you do, just make sure your woofer is able to play down to 40Hz without roll off. Through a lot of experimentation, I have found that the 40-50hz range contains a lot of tonal information. Getting down to 40hz and doing it well is one of the differences between a good speaker and a holy schiit speaker.


----------



## L0rdGwyn

Received the new PCBs for the OTL voltage regulators, now working as intended, yay.

So OTL will be built on schedule, although I will be out of town for a week in mid August, might not finish until late August, at which time I will make plans to send to a few people for feedback.

I am debating making a change, just an OCD thing, as there are two time delay circuits in the PS, one per each of the dual mono supplies.  There is around a 1 second delay between the two channels when the relays are switched on due to component tolerances.  Obviously this doesn't affect performance, I'm just a psycho and would prefer they switch at exactly the same time LOL I might go back in and drive both relays from one time delay circuit, shouldn't be a problem, just more heat dissipated in a single circuit.  I'll move forward with the first build as is since it is not a performance issue, but might change for the final build.  I wish I wasn't like this   

Continuing work on DAC, updates being made on a daily basis and design is being altered.  No doubt I could build it as is, but I hope to get it very close to "the mark" the first time around, so we will see, might take some time to get things where I want them to be, but the foundation of the design is done so hard part is over.  I will have to get a new audio interface to make digital measurements, so looking into the options now.

My aspirations for this DAC have gotten pretty high! It will probably have less than typical line level voltage output at the benefit of lower output impedance, but will likely be used in my headphone setup.

Will post updates as they come on all of the above.


----------



## Zachik

@L0rdGwyn when are you scheduled to receive the S5 DAC?
I am really curious about this one!


----------



## L0rdGwyn

Zachik said:


> @L0rdGwyn when are you scheduled to receive the S5 DAC?
> I am really curious about this one!



Lead time when I placed the order was 15-20 days, so probably mid August.


----------



## Zachik

L0rdGwyn said:


> Lead time when I placed the order was 15-20 days, so probably mid August.


Looking forward to read your impressions!
BTW, have you auditioned the (more expensive) Holo May DAC?
As much as I think the Lampizator Amber 3 DAC that I have is very good, I am starting to get an upgradeatitis itch...


----------



## L0rdGwyn

Zachik said:


> Looking forward to read your impressions!
> BTW, have you auditioned the (more expensive) Holo May DAC?
> As much as I think the Lampizator Amber 3 DAC that I have is very good, I am starting to get an upgradeatitis itch...



I have not, but you might talk to @chrisdrop , I believe he has laid ears on both the Amber 3 and Holo May.


----------



## L0rdGwyn (Jul 31, 2021)

Here is the most recent update on the PCM56 DAC - I made some design changes, will now run two PCM56 in parallel per channel.  Will use one PCB per channel in a dual mono design.  Each board will have separated +/- analog and digital supplies that feed the paralleled chips.  The boards will then stack in the chassis.  There will be a separate third PCB for the digital supply feeding the I2SoverUSB module.  All three will share a low impedance star ground point.  All boards will be fed in parallel by 1:1 isolation transformer running balanced power.

The I/V stage is all passive using Sowter 1465 SUT.  Will adjust the secondary I/V resistor to find a balance between output impedance and output voltage, but it will be less than typical line level.  Will likely plan for running into a 50K input impedance.

Still a draft but it is coming along, need to add snubber components to the transformer secondaries among other things, but I feel this is close to what the final design will be at a high level.


----------



## whirlwind

L0rdGwyn said:


> I have not, but you might talk to @chrisdrop , I believe he has laid ears on both the Amber 3 and Holo May.


Yes, @chrisdrop indeed has heard the May


----------



## L0rdGwyn (Aug 4, 2021)

Here is a look at the burgundy red chassis for the OTL, picture from Dave at Landfall, will have it Monday most likely, could potentially finish the prototype by Wednesday.



Holding judgment until I see it in person, but not sure how I feel about the gloss finish, has a bit of a hammered texture.  I have not gotten a chassis in a gloss powder before, usually go with low-gloss finishes.  I thought since this is a prototype, would be a good time to experiment.  So we will see, might go a different direction for the real thing.

I probably should stop talking about my DAC design since it changes on a daily basis, but I'm going to anyway since I'm excited about it LOL here is the latest.

I was looking at using all passive I/V stage for the DAC output with a Sowter SUT.  The issue with this approach is finding a balance between output impedance and output voltage.  Increasing one increases the other, the situation can be improved by paralleling additional chips.  I wasn't getting a result I felt good about with two PCM56 in parallel.  I explored using four in parallel per channel, but this would necessitate a buffer between the digital front end and DAC inputs, which complicates my layout in undesirable ways...

So I think I am going to go back to what I had in mind at the get go - Sowter SUT for I/V conversion followed by a tube gain stage.  This requires only a single PCM56.  The transformer performs I/V conversion and some voltage gain, the remainder of voltage and current gain is performed by the tube output stage.

Obviously there are numerous ways to skin this cat.  I want to keep it very simple, so I will likely do the following with a 12B4A in a common cathode gain stage, battery biased, CCS loaded.  Looked at some dual triodes and dual dissimilar triodes as well with the possibility of direct-coupling section 1 to section 2 as a cathode follower.  6EW6 and 6CS7 are good tubes for that purpose, might play with that idea at a later date.



Output impedance of this stage is around 800ohm with 2Vrms output.  Should work well with my amplifiers.

So I grabbed some 12B4A to trace, we'll see how those curves look


----------



## leftside

L0rdGwyn said:


> Here is a look at the burgundy red chassis for the OTL, picture from Dave at Landfall, will have it Monday most likely, could potentially finish the prototype by Wednesday.
> 
> 
> 
> ...


Looks great. Would be a fairly close match to my speakers and furniture. Did Dave manufacture all of that according to your specs/drawings?


----------



## Zachik

L0rdGwyn said:


> Here is a look at the burgundy red chassis for the OTL, picture from Dave at Landfall, will have it Monday most likely, could potentially finish the prototype by Wednesday.


Gorgeous!  Very timely since I am starting to work on a little DIY amp too (based on a kit, but with some mods and tweaks by me), and there is no "stock" case for this amp.
I have not made any decisions yet, but thought to myself "another black case? I need something more interesting than that!".  This red is definitely more interesting


----------



## L0rdGwyn

leftside said:


> Looks great. Would be a fairly close match to my speakers and furniture. Did Dave manufacture all of that according to your specs/drawings?



Thanks!  Yup, I do the layout and design the chassis in CAD software, then send it over to Dave for machining and coating.  He ended up putting together a nice powder coating rig inspired by my janky garage setup, so now it's a one stop shop!



Zachik said:


> Gorgeous!  Very timely since I am starting to work on a little DIY amp too (based on a kit, but with some mods and tweaks by me), and there is no "stock" case for this amp.
> I have not made any decisions yet, but thought to myself "another black case? I need something more interesting than that!".  This red is definitely more interesting



Very nice, well if you end up wanting to use this finish, it is burgundy from Columbia Coatings.


----------



## bcowen

L0rdGwyn said:


> Here is a look at the burgundy red chassis for the OTL, picture from Dave at Landfall, will have it Monday most likely, could potentially finish the prototype by Wednesday.
> 
> 
> Holding judgment until I see it in person, but not sure how I feel about the gloss finish, has a bit of a hammered texture.  I have not gotten a chassis in a gloss powder before, usually go with low-gloss finishes.  I thought since this is a prototype, would be a good time to experiment.  So we will see, *might go a different direction for the real thing.*


Nooooooooo!  Don't mess with success.  That looks awesome!!  Can't wait to see it formed up and sprouting tubes. 

I suppose beauty is in the eye of the beholder, but I'm beholdin' that as totally gorgeous.


----------



## L0rdGwyn

bcowen said:


> Nooooooooo!  Don't mess with success.  That looks awesome!!  Can't wait to see it formed up and sprouting tubes.
> 
> I suppose beauty is in the eye of the beholder, but I'm beholdin' that as totally gorgeous.



Well it sure seems like everyone likes it, so I will take that into consideration!  I will post pictures when the build is done


----------



## L0rdGwyn (Aug 6, 2021)

Here are the knobs going on the OTL, bakelite RCA fester style.




Some transformers for another design, these are made by Jack Elliano at Electra-Print.



And a big pile of Allen Bradley 10ohm 2W resistors.  Will be current-limiting resistors in my DAC power supply.  Giant piles of vintage parts warm my heart.



Should have the DAC chips next week, Sowter SUT should be shipping soon.  Just waiting to hear back from a custom toroidal company, looking into having custom mains and isolation transformers wound for this DAC.  Once that has been confirmed, can finalize and order the PCBs.


----------



## Galapac

L0rdGwyn said:


> Here are the knobs going on the OTL, bakelite RCA fester style.
> 
> 
> 
> ...





L0rdGwyn said:


> Here are the knobs going on the OTL, bakelite RCA fester style.
> 
> 
> 
> ...


Keenan put those awesome skills to good use, Upscale is looking for a headphone specialist and you may fit the bill, and in Southern California to boot, or remote.
Check out Kevin's funny vid for the position.


----------



## L0rdGwyn

Galapac said:


> Keenan put those awesome skills to good use, Upscale is looking for a headphone specialist and you may fit the bill, and in Southern California to boot, or remote.
> Check out Kevin's funny vid for the position.




That would be cool!  Think Kevin would be pretty confused if I sent him my resume though LOL would be fun but don't think I could work two jobs -_-


----------



## L0rdGwyn (Aug 9, 2021)

Back from a weekend away, more goodies for upcoming projects arrived  just some random DIY parts porn.

Vintage Amphenol phenolic 9-pin sockets. Bottom-mount version surprisingly hard to come by.



Some very nice Simpson 0-50mA DC analog meters for an amplifier I am working on. These are new production, not vintage, although they are of the vintage aesthetic.



For my DAC, PCM56P-K DAC chips are here. These were made in Japan, also picked up some Korean-made, will see if one performs better than the other.



And 12B4A tubes for my DAC output stage. I was totally duped by the photos on the eBay listing, these are totally GE manufactured LOL NOOO!!! Oh well, they are for testing anyway, and dirt cheap.



Here are the curves. Given these only need to swing 2Vrms, will use a high-current, low voltage bias point for the lowest output impedance.



OTL chassis arrives tomorrow, will do a little preparation tonight, going to try and build it between tomorrow and Wednesday, should be very doable, advantage of building on my protoboard ahead of time.


----------



## Tjj226 Angel

L0rdGwyn said:


> Back from a weekend away, more goodies for upcoming projects arrived  just some random DIY parts porn.
> 
> Vintage Amphenol phenolic 9-pin sockets. Bottom-mount version surprisingly hard to come by.
> 
> ...



Assuming your dac IV stage is going to be a step up transformer and a resistor before it gets to the tube, wouldn't you want a really low value resistor and a very high gain tube? I was kind of expecting you to use one of your D3a tubes for the dac. 

Does the PCM56 not require the same low input impedance as the PCM63?


----------



## L0rdGwyn

Tjj226 Angel said:


> Assuming your dac IV stage is going to be a step up transformer and a resistor before it gets to the tube, wouldn't you want a really low value resistor and a very high gain tube? I was kind of expecting you to use one of your D3a tubes for the dac.
> 
> Does the PCM56 not require the same low input impedance as the PCM63?



The PCM56 is actually very flexible in terms of loading, I've come across a testimonial using it with up to 500ohms I/V resistor with harmonics below -90dB with 0dB signal.  Most designs use 100ohm I/V load.  My SUT can be wired in 1:5 or 1:10,  In 1:10 with 12B4A output at 2Vrms, primary is less than 50ohm, less than 100ohm in 1:5.  We'll see where it goes, could definitely experiment with higher gain output tubes, but want to keep the output impedance below 1K.


----------



## Tjj226 Angel

Interesting. Maybe that's why people continue to use the PCM56 over the PCM63.


----------



## L0rdGwyn

First iteration of my PCM56 DAC is on the verge of completion, just need to do the routing, but PCB layout is complete.

Smaller board is the digital supply for USB front end, larger board is a single channel - two of these will be stacked.





Rather than integrating the SUT into the PCB with pads for the various leads, decided to leave it general so different I/V stages can be experimented with - outputs are Iout from the PCM56 and pad for the ground plane.  This is a four-layer PCB - internal ground plane, two power supply layers, and top signal layer.  I am leaving the transformers off the PCB - again, for flexibility.  As I mentioned, I am looking into having custom toroidals wound, matching power supply and balanced isolation transformers.  If that doesn't work out, there are off-the-shelf options I can use.  Each supply has test points to dial in the voltages.  Will leave the part leads long when testing on the first go-around in case there is an issue.

Off to run some errands, then OTL chassis should be here!


----------



## UntilThen

L0rdGwyn said:


> Here is a look at the burgundy red chassis for the OTL



That is really cool Keenan. You might get me interested in OTL again. Burgundy chassis with black bakelite knobs.


----------



## L0rdGwyn

UntilThen said:


> That is really cool Keenan. You might get me interested in OTL again. Burgundy chassis with black bakelite knobs.



That is exactly what this amplifier will have  in fact, I was able to purchase a set of eight fluted vintage bakelite knobs - limited supply of course, but will include on the first few of these amplifiers unless the buyer wants the new-production RCA fester style bakelite knob instead.

OTL chassis arrived just as I got home.  The gloss burgundy is much nicer to me in person, I like it.  The caveat of a gloss finish is there will be some imperfections - comes with the territory, but I am OCD.

Here is the top plate and a preview of where things are going with the socket subplates.



Now to go prep the chassis and start putting this thing together.  I am moving quite slow today, so we'll see if I can get it done by tomorrow, otherwise this weekend.


----------



## UntilThen

L0rdGwyn said:


> Here is the top plate and a preview of where things are going with the socket subplates.



Now you're really tempting me lol. I was hoping for a tube rectifier but this in itself looks spot on - what you have mapped out there. You might need a production assembly line now.


----------



## L0rdGwyn

UntilThen said:


> Now you're really tempting me lol. I was hoping for a tube rectifier but this in itself looks spot on - what you have mapped out there. You might need a production assembly line now.



I spend a very long time working out the arrangement of the top-mounted components, down to the 1/16".  The spacing and balance is very important to the aesthetic of a tube amplifier I think.

We will see, I have no concept of what demand will be yet, I will build it, have a listen, then will send to some friends for feedback before "go live".  I would like some ears to compare to other high-end OTLs before it is released.


----------



## L0rdGwyn

Here is the chassis assembled with subplates and sockets in place.  You'll have to excuse my workbench, it is a disaster at all times these days.


----------



## UntilThen

Wow Keenan, Odyssey hasn't even arrived and I'm thinking of buying your empty chassis.  

Why are there 3 holes in front and what are they for.


----------



## Zachik

L0rdGwyn said:


> Here is the chassis assembled with subplates and sockets in place.  You'll have to excuse my workbench, it is a disaster at all times these days.


Stunning!!!


----------



## whirlwind

L0rdGwyn said:


> Here is the chassis assembled with subplates and sockets in place.  You'll have to excuse my workbench, it is a disaster at all times these days.


Looks great Keenan  

I am up in the air on the gloss chassis...I like it...just not sure I prefer it to more of a matte look  , but that is just personal preference. I can see where any imperfections may show more on the shiny chassis, but that should not be a big deal anyway.
The layout looks great as well as the chassis design...very nice well done.
The way that you work...I'm guessing this will be done tomorrow...LOL


----------



## Zachik

UntilThen said:


> Why are there 3 holes in front and what are they for.


power switch, volume knob, headphone jack.


----------



## whirlwind

Zachik said:


> power switch, volume knob, headphone jack.


I would say you are correct , this is the same front layout as some other "Gwyn" amps


----------



## L0rdGwyn

whirlwind said:


> Looks great Keenan
> 
> I am up in the air on the gloss chassis...I like it...just not sure I prefer it to more of a matte look  , but that is just personal preference. I can see where any imperfections may show more on the shiny chassis, but that should not be a big deal anyway.
> The layout looks great as well as the chassis design...very nice well done.
> The way that you work...I'm guessing this will be done tomorrow...LOL



Definitely an experiment for me, glad it has been well-received, I typically do matte myself, but thought I would give the gloss a shot.  Gotta keep a microfiber clothes around to keep it nice and shiny  you're probably right!  I think it will be done tomorrow, will try to get a large portion done tonight.



Zachik said:


> power switch, volume knob, headphone jack.



He's got it @UntilThen !


----------



## Zachik

L0rdGwyn said:


> I typically do matte myself, but thought I would give the gloss a shot. Gotta keep a microfiber clothes around to keep it nice and shiny


Same here - all my amps and other DIY projects are matte finished, but I think your glossy red is spectacular!
Very seriously considering similar finish for my upcoming DIY headphone amp (with Korg tube). My pace is MUCH slower than yours, though


----------



## L0rdGwyn

Power supply is just about done, really the hard part is over, all down hill from here.  If I was really crazy I could finish tonight...but I probably shouldn't.

Top with mains transformer mounted.




Rear panel with Amphenol RCAs, heat sinks for the HV regulators, Schurter RFI filtered IEC inlet.


----------



## L0rdGwyn

Little PCB I made for the Alps pot.



Output caps creepin' out the top.


----------



## L0rdGwyn

That's it for tonight, will finish up in the morning


----------



## bcowen

UntilThen said:


> Why are there 3 holes in front and what are they for.


One is for sticking your finger in to see if it's on.  Tactile feedback, and no ugly LED.


----------



## bcowen

L0rdGwyn said:


> Little PCB I made for the Alps pot.


Question:  what benefit is the PCB versus soldering to the pot's pins directly?  Easier assembly (once the pot is installed in the chassis)?


----------



## L0rdGwyn

bcowen said:


> Question:  what benefit is the PCB versus soldering to the pot's pins directly?  Easier assembly (once the pot is installed in the chassis)?



Easier assembly, really no difference functionally.  Keeps things nice and neat


----------



## UntilThen

bcowen said:


> One is for sticking your finger in to see if it's on.  Tactile feedback, and no ugly LED.



Can I have an LED? I love LED. Just a tiny one will do.


----------



## Galapac

L0rdGwyn said:


> Little PCB I made for the Alps pot.
> 
> 
> 
> Output caps creepin' out the top.


Red and black is my favorite color combination. Very powerful color choice. Also my old high school colors! Nice Keenan!


----------



## Monsterzero

L0rdGwyn said:


> First iteration of my PCM56 DAC is on the verge of completion


Damn man! You're doing DACs now too?!? Color me incredibly impressed!


----------



## whirlwind

Galapac said:


> Red and black is my favorite color combination. Very powerful color choice. Also my old high school colors! Nice Keenan!


My high school colors also...Go "Coshocton Redskins"


----------



## L0rdGwyn

Monsterzero said:


> Damn man! You're doing DACs now too?!? Color me incredibly impressed!



This is the first, so we'll see how it goes


----------



## L0rdGwyn

These amplifier builds are always so much shorter in my head.

OTL is done, here is the final without tubes.






And with tubes.





I've learned from past experience my ears are very unreliable after a marathon amplifier build, could be the fumes, mental exhaustion, and malnutrition - so I will go do some yoga before passing judgment 🧘‍♂️


----------



## Tjj226 Angel

I know some people will dismiss me for saying this, but those output caps will need some hours on them before they sound their best. Keep that in mind while you are listening.


----------



## L0rdGwyn

The NKK toggle switch I used is pretty ridiculous, feels like it should be opening a castle drawbridge when you turn the amplifier on LOL the switch feel is 10/10.


----------



## L0rdGwyn

Tjj226 Angel said:


> I know some people will dismiss me for saying this, but those output caps will need some hours on them before they sound their best.



They do have some hours since they are the ones used on my protoboard, maybe 30-40 guesstimated, but duly noted  the X factor right now is my brain, gotta decompress before having a real listen.


----------



## whirlwind

Tjj226 Angel said:


> I know some people will dismiss me for saying this, but those output caps will need some hours on them before they sound their best. Keep that in mind while you are listening.


I concur


----------



## whirlwind (Aug 11, 2021)

L0rdGwyn said:


> The NKK toggle switch I used is pretty ridiculous, feels like it should be opening a castle drawbridge when you turn the amplifier on LOL the switch feel is 10/10.


It even looks to be pretty manly!

Tung Sol 5998 / GEC L63.....no use messing around with so so tubes


----------



## L0rdGwyn

whirlwind said:


> Tung Sol 5998 / GEC L63.....no use messing around with so so tubes



Nope, straight to the top!  Will try some GEC 6AS7G and Fivre 6C5G tonight


----------



## UntilThen

L0rdGwyn said:


> And with tubes.



It looks cutie-pie, hottie and purty. Turns out amazingly well. Love it.


----------



## UntilThen

whirlwind said:


> Tung Sol 5998 / GEC L63.....no use messing around with so so tubes



I agree. My mint pair of 5998 will be just perfect for it. Or even chug in a pair of Cetron 7236.


----------



## mordy

L0rdGwyn said:


> The NKK toggle switch I used is pretty ridiculous, feels like it should be opening a castle drawbridge when you turn the amplifier on LOL the switch feel is 10/10.


Why not the elevator illuminated push button switch? Can be ordered in different colors. At least one LED!


----------



## L0rdGwyn

mordy said:


> Why not the elevator illuminated push button switch? Can be ordered in different colors. At least one LED!



Not a big fan of power LEDs to be honest.  The power switch in this amp also serves a secondary function beyond turning the amp on and off.


----------



## Tjj226 Angel

mordy said:


> Why not the elevator illuminated push button switch? Can be ordered in different colors. At least one LED!



I have tried that one before and it did not go well. The best switches are the mechanical push button switches where the button recedes into the case. This protects against accidently turning on the amp when you didn't mean to.


----------



## triod750

Don't forget to try it with humble tubes. That could tell you more about your amp. Eventually.


----------



## bcowen

L0rdGwyn said:


> These amplifier builds are always so much shorter in my head.
> 
> OTL is done, here is the final without tubes.
> 
> ...


Gorgeous!!!!  Can't wait to hear your sonic evaluation.


----------



## bcowen

UntilThen said:


> Can I have an LED? I love LED. Just a tiny one will do.


No.


----------



## bcowen

Tjj226 Angel said:


> *I know some people will dismiss me* for saying this, but those output caps will need some hours on them before they sound their best. Keep that in mind while you are listening.


I won't.


----------



## mordy (Aug 11, 2021)

Tjj226 Angel said:


> I have tried that one before and it did not go well. The best switches are the mechanical push button switches where the button recedes into the case. This protects against accidently turning on the amp when you didn't mean to.


Here are a couple of switches around that I believe are all mechanical and have lights. The first one, which I like best, is on the GOTL:




I believe that it is made for heavy duty use for elevators etc. It has a dual function in the GOTL - if you put in a tube with the wrong voltage applied, it will not light up, alerting you that something is wrong (or a fuse blew, which happened once).
The next switch is on a 1980's Norwegian power amp:



That little push switch controls 220W into 2 ohm but does not feel very substantial and reassuring. It got stuck in the open position many months ago, and I used a power strip to turn on and off the amp. Then suddenly one day, there was a little click and the amp turned off. For reasons that are not clear to me, the switch started working again. Sprayed in a little WD-40 in the switch and it works fine again, but I am leery of it.
Several of my amps have rocker switches that seem to function well.



This large illuminated switch is on a Mondial Acurus amp and makes a very reassuring and loud click when turned on.
Which type is the best? Don't know, but I like the first one the best. The location of the amps makes it unlikely that they get turned on by accident.


----------



## Zachik

L0rdGwyn said:


> The power switch in this amp also serves a secondary function beyond turning the amp on and off.


Which is.....?


----------



## bcowen

Zachik said:


> Which is.....?


Well duh.  It quantum-tunnels the tubes, reverse cryo-treats all the caps and resistors, and demagnetizes the transformer.  I thought everyone knew this.


----------



## L0rdGwyn (Aug 11, 2021)

triod750 said:


> Don't forget to try it with humble tubes. That could tell you more about your amp. Eventually.



Aha!  But how could I forget when it has already been done? 

Exhibit A: box of Russian 6S2S.



Exhibit B: box of Russian 6H13C.



These are the projected "stock" tubes, so the amplifier was designed and tested using them.





Zachik said:


> Which is.....?



When the amp is turned off, a low resistance discharge path for the output capacitors is introduced.  This prevents any voltage transients / unpleasant sounds on shut down.  Time delay / soft start prevents the same on startup.


----------



## bcowen

L0rdGwyn said:


> When the amp is turned off, a low impedance discharge path for the output capacitors is introduced.  This prevents any voltage transients / unpleasant sounds on shut down.  Time delay / soft start prevents the same on startup.


Well, I was close.


----------



## raindownthunda

L0rdGwyn said:


> These amplifier builds are always so much shorter in my head.
> 
> OTL is done, here is the final without tubes.
> 
> ...


Great work! I'm getting some classic muscle car vibes with the retro knobs and the cherry red paint 



What advantage do you get from using the tube socket under-mount plates?


----------



## raindownthunda (Aug 11, 2021)

mordy said:


> Here are a couple of switches around that I believe are all mechanical and have lights. The first one, which I like best, is on the GOTL:
> 
> I believe that it is made for heavy duty use for elevators etc. It has a dual function in the GOTL - if you put in a tube with the wrong voltage applied, it will not light up, alerting you that something is wrong (or a fuse blew, which happened once).
> The next switch is on a 1980's Norwegian power amp:
> ...



I went all the way down RGB LED rabbit hole for my upcoming 1101 Audio build:


----------



## L0rdGwyn

raindownthunda said:


> Great work! I'm getting some classic muscle car vibes with the retro knobs and the cherry red paint
> 
> What advantage do you get from using the tube socket under-mount plates?



100% aesthetic, ha!  Maybe a slight increase in ventilation given there is additional space between the top plate and sub-plate.  With the sub-plate mounting screws in place, there is no shortage of places to mount terminal stripes / components / wires for each individual tube, so no additional holes need to be added, so that is a plus.


----------



## Tjj226 Angel

mordy said:


> Here are a couple of switches around that I believe are all mechanical and have lights. The first one, which I like best, is on the GOTL:
> I believe that it is made for heavy duty use for elevators etc. It has a dual function in the GOTL - if you put in a tube with the wrong voltage applied, it will not light up, alerting you that something is wrong (or a fuse blew, which happened once).
> The next switch is on a 1980's Norwegian power amp:
> That little push switch controls 220W into 2 ohm but does not feel very substantial and reassuring. It got stuck in the open position many months ago, and I used a power strip to turn on and off the amp. Then suddenly one day, there was a little click and the amp turned off. For reasons that are not clear to me, the switch started working again. Sprayed in a little WD-40 in the switch and it works fine again, but I am leery of it.
> ...



Oh. When you said elevator light switches, I thought you meant the one that barely move and simply light up when they are on. If you just want a switch with a light, then yeah, there are tons of decent options.


----------



## UntilThen

L0rdGwyn said:


> These are the projected "stock" tubes, so the amplifier was designed and tested using them.



It's a beautiful looking amp in this picture of the completed amp. Are the feet still missing?


----------



## Zachik

UntilThen said:


> It's a beautiful looking amp in this picture of the completed amp. Are the feet still missing?


@L0rdGwyn does not believe in feet...


----------



## L0rdGwyn (Aug 12, 2021)

UntilThen said:


> It's a beautiful looking amp in this picture of the completed amp. Are the feet still missing?



I don't like feet on my personal amps, but I will add them for future builds.  I might even add them to this one.


----------



## Xcalibur255

Talk of switches are one of the few subjects that will automatically trigger a de-lurk from me.

https://www.amazon.com/Twidec-Rocke...s=lighted+toggle+switch&qid=1628793422&sr=8-4

Wanted something like this on one of my amps so badly, but it's actually quite hard to find quality ones in the correct ratings for some reason.  This link is basically for the photo.


----------



## Xcalibur255

BTW, congrats on the build completion Keenan.  /re-lurk


----------



## UntilThen

L0rdGwyn said:


> I don't like feet on my personal amps, but I will add them for future builds.  I might even add them to this one.



Oh why don't you like feets on your own amps?  

My amps are arriving, probably today.


----------



## L0rdGwyn

UntilThen said:


> Oh why don't you like feets on your own amps?
> 
> My amps are arriving, probably today.



How exciting!  I like the flexibility to use different types of isolation.


----------



## L0rdGwyn

I'm so very close to being able to test my DAC!  The stage is set, just waiting for the go-ahead for some custom toroidal transformers, hopefully will be able to finalize the order today or tomorrow...

Sowter I/V transformers arrived today.




4-layer PCB layouts and routing are done.  Here is the digital supply board - I've included some additional length / mounting holes on the route as the USB module will be on standoffs above it, this will keep the connections between the two PCBs as short as possible.



And here is the DAC board.  As I've said before, two of these will be stacked as it is dual mono.



Got some Korean and Japanese made PCM56P-K to try out.  DIP-16 socket I am using lends itself to being able to remove the chips non-destructively, so can choose the pair with the best measured performance.



Over time, I have amassed a collection of spare Antek toroidal transformers from various projects - turns out I have the one I need for my tube output stage already, noice.

Sort of unusual decision for me, but I am thinking about keeping the tubes inside the chassis as opposed to top-mounting.  Assuming all performs well, this will be a 4.25" thick chassis, don't really want to add additional height on top for the tubes for space-saving reasons.

Anyway, just need to get these custom mains / isolation transformers ordered and I will pull the trigger on the PCBs and parts.


----------



## UntilThen

L0rdGwyn said:


> Sowter I/V transformers arrived today.



My eyes lit up at the mention of Sowter.  Huge respect for them now with what I'm hearing from Odyssey. What's an I/V transformer?


----------



## L0rdGwyn

UntilThen said:


> My eyes lit up at the mention of Sowter.  Huge respect for them now with what I'm hearing from Odyssey. What's an I/V transformer?



It's a bit technical but here is what it is!

Many of these old R2R type DAC chips are "current output" types, meaning rather than outputting a voltage that can be amplified directly (by a following preamp, for example), the output is a small AC current.  This current needs to be converted to a voltage signal that can be amplified.  Many of these chips have built-in circuitry to perform this function (often times opamps directly on the chip), but better performance can be achieved using a dedicated current-to-voltage (I/V) stage.

There are lots of ways to do this, the two major categories are active and passive.

Active I/V stages typically use opamps, transistors, or even tubes to perform the I/V conversion and simultaneously amplify the signal.

Passive I/V stages often use resistors to perform the I/V conversion, then the signal is amplified to line level by a following amplifier stage.  The less common passive approach is to use a I/V transformer, less common due to the need for specialty transformers and expense.

So, these are I/V step-up transformers.  They convert the AC current output of the PCM56 DAC to a voltage and simultaneously provide some voltage gain across the transformer.  The signal on the secondary of the transformer will be amplified by an additional tube gain stage to reach 2Vrms output with a suitably low output impedance.

Transformers have other advantages compared to resistor I/V - they have a built-in low-pass filter due to the transformer bandwidth which will remove high-frequency quantization noise from the output signal (if using a resistor, an additional low-pass filter must be added in circuit).  Another advantage is galvanic isolation between the DAC PCB ground and the secondary ground - keeping the grounds separated will reduce injection of noise from DAC circuitry into the output stage ground.

Low noise is a top priority, so we'll see how we did when I throw this thing together.


----------



## triod750

I almost understood this explanation, or I might have done. I wonder if I will remember it? It transforms simple current to wonderful music with the help of a tube. Simple as that.


----------



## Galapac

L0rdGwyn said:


> Got some Korean and Japanese made PCM56P-K to try out.


I have heard of those…they are the DAC chip itself, right?


----------



## L0rdGwyn (Aug 18, 2021)

Galapac said:


> I have heard of those…they are the DAC chip itself, right?



Yup, those are the DAC chips, an oldie but goodie, highly regarded for tonality among the old R2R chips, good measured performance as well.

There is an 18-bit version, the PCM61, which is a drop-in replacement for the PCM56, although testimonials point to the PCM56 being the better performer subjectively.


----------



## Tjj226 Angel

L0rdGwyn said:


> It's a bit technical but here is what it is!
> 
> Many of these old R2R type DAC chips are "current output" types, meaning rather than outputting a voltage that can be amplified directly (by a following preamp, for example), the output is a small AC current.  This current needs to be converted to a voltage signal that can be amplified.  Many of these chips have built-in circuitry to perform this function (often times opamps directly on the chip), but better performance can be achieved using a dedicated current-to-voltage (I/V) stage.
> 
> ...



Just to make sure everyone understands, it is important to note that the IV transformer is not actually doing any of the current to voltage conversion. The resistor is still doing all the work.

The key here is that generally speaking, the resistor we have to use is a very low value. Something around 100 ohms or less is preferable. If you use a 100 ohm resistor as your grid resistor on a tube, the input impedance of the tube and your grid leak resistor will form a voltage divider. Much of your signal will be shunted to ground and you won't generate a huge signal which is why you normally need a high gain tube. 

Why do you need a low value resistor? Because most dacs want a very low input impedance into the IV stage. A high value input impedance will cause distortion in the dac among other bad things. 

If you use a step up transformer, you can use a much higher value resistor on the secondary. The transformer will "reflect" the resistors impedance back to the primary by the square of the turns ratio. In other words it will make a big resistor look like a little resistor to the dac. 

The drawback is that a high quality step up transformer is very difficult to make and thus it is very expensive to buy a high quality one. They will also add their own distortion and other artifacts to the sound. 

One of the drawbacks can be viewed as a benefit though. Since the transformer can never be perfect, it will filter out some high frequency noise the dac might generate. I believe this is part of the reason dacs built like the one lordgwyn is building sounds so analog.


----------



## triod750

So there might be a lot of trial and error behind a good sounding device. And then you put it in a chain of other devices where it isn't comfortable and then you 'know' that it is bad...


----------



## L0rdGwyn (Aug 21, 2021)

I went ahead and put some feet on the OTL amp.



Here with Bendix 6080WB and Fivre 6C5G.



I am going to send this amp out on its mini tour this week to get some feedback.  Good thing too because it is getting pretty freakin' cluttered around here!  I have no space for anything, too many amps and parts...

Once this is out the door, can move forward with the other projects.  These custom toroidal guys - who came highly recommended - are taking a very long time to confirm my order, so I am going to order parts for my DAC, I am dying to build it, will use off-the-shelf transformers if I don't hear back soon.  My protoboard is vacant again for another design, will start working on the next amplifier too, it's going to be a pretty interesting one, stay tuned


----------



## L0rdGwyn (Aug 22, 2021)

All is ordered for DAC - decided to move forward with off-the-shelf transformers for now, not terribly expensive and will allow me to prototype.  If the custom transformers work out, then super.  Custom route is preferred to minimize capacitance, and thus mains-coupled noise, but the off-the-shelf option should work well.

I will use a medical-grade toroidal with primary-to-secondary electrostatic shield and hum band as my balanced isolation transformer.  Mains transformers will be itty bitty Talema 7XXXX series.  All are spec'd just so - very little headroom, again to minimize transformer capacitance.

I made some PCB's for the Talema transformers, they are tiny, 1.7" x 1.7" area.



Here are the final DAC PCBs.  White nearly doubled the price, so went with my usual black.  Four-layer PCBs are pricey, but it is the best way.





All power supply electrolytics will be long-life low ESR Rubycon.

I have some nice 9-pin tag boards that I had planned to swap into my protoboard when needed.  I think I will keep the tubes inside the DAC chassis, I have extra tag boards so will likely use a pair on the interior, like so.



Now the wait for all the parts to arrive, probably a week or so.  In uncharted territory here with digital, but I think my design is sound, we'll see how it goes!

Got some quality listening time in this morning with the OTL while working on all of this stuff.

Visseaux 6J5G and Tung-Sol 5998.



I've been on a bit of a techno kick, really like this compilation from Oliver Lieb.


----------



## Zachik

@L0rdGwyn How big do you expect the DAC chassis end up being? 
I would LOVE to A/B your DAC with my Lampi Amber 3...


----------



## L0rdGwyn

Zachik said:


> @L0rdGwyn How big do you expect the DAC chassis end up being?
> I would LOVE to A/B your DAC with my Lampi Amber 3...



Well let's make sure it makes sound first LOL.  Let me think about the dimensions, haven't gotten that far yet...

I know for a fact it will be a 4.25" tall chassis.  My isolation toroidal has a 3.3" OD and is about 1.5" tall, the tube output toroidal has a 3.6" OD and is 1.6" tall....

If I were to mount both of those on their sides, I could probably make the chassis something like 4.25" x 10" x 12" if I really squeeze things together.  Incidentally, those are the roughly dimensions of my 45 amplifier, but there would be nothing mounted on top, just a box with a button, USB input, RCA output.  I will probably add a small power LED this time, for me it fits thematically since it is a digital piece of gear.  But not too bright!


----------



## Zachik

L0rdGwyn said:


> Well let's make sure it makes sound first LOL.


I am not worried 
IF you decide to have a quick tour - PLEASE put me first... I am itching for a new DAC. 
Assuming you keep the off-the-shelf transformers - can you *estimate* the cost (including the case and everything)? ballpark number would be good. I am trying to see where it falls compared to commercial options I am willing to consider!

Also, are you still getting the DAC from the AD chip DIY design expert in Europe? Sorry, I forget the name... You mentioned it couple months ago.


----------



## L0rdGwyn

Zachik said:


> I am not worried
> IF you decide to have a quick tour - PLEASE put me first... I am itching for a new DAC.
> Assuming you keep the off-the-shelf transformers - can you *estimate* the cost (including the case and everything)? ballpark number would be good. I am trying to see where it falls compared to commercial options I am willing to consider!
> 
> Also, are you still getting the DAC from the AD chip DIY design expert in Europe? Sorry, I forget the name... You mentioned it couple months ago.



I'll have to give that some thought!  Hadn't considered a tour, well really hadn't considered selling this, no promises on that front!  Maybe as a favor.  Would be great to nail it the first time, I am cautiously optimistic, but you never know when a rogue oscillating component will ruin your day...

Well the cost of parts...most expensive are the Sowter transformers, around $365USD for the pair shipped.  Probably with a fancy Landfall chassis, the cost of parts is around $1300ish?  The chassis and the transformers make up almost half of that!

Could drop the Sowter transformers and use a resistor I/V instead with a higher gain tube output, like Russian 6E5P, would get you a 2Vrms output with a 1K output impedance, would bring the cost down to under $1K.  Would need to add a low pass filter to the I/V stage however.  Put it in a cardboard box, cost drops below $750 

If this design works out, it could be very easily adapted for PCM63 chip, fancy.


----------



## L0rdGwyn

Oh and yes @Zachik , I still have the Audial S5 on order.  I am expecting very big things from that DAC, so it will be the benchmark by which I compare my own.  It is TDA1541A-based.  Taking a little longer than expected though, it should ship to me this week.


----------



## bcowen (Aug 22, 2021)

L0rdGwyn said:


> Could drop the Sowter transformers and use a resistor I/V instead with a higher gain tube output, like Russian 6E5P, would get you a 2Vrms output with a 1K output impedance, would bring the cost down to under $1K.  Would need to add a low pass filter to the I/V stage however.  Put it in a cardboard box, cost drops below $750



Sorry, but I have the rights to the cardboard box chassis.  I suppose I could waive the royalty fee just for Zachi, but just once...   

https://www.head-fi.org/threads/sch...bable-start-up.701900/page-5268#post-16440552


----------



## L0rdGwyn

bcowen said:


> Sorry, but I have the rights to the cardboard box chassis.  I suppose I could waive the royalty fee just for Zachi, but just once...
> 
> https://www.head-fi.org/threads/sch...bable-start-up.701900/page-5268#post-16440552



(Sigh) papier-mâché it will have to be then!  I charge by the hour, this works out well for me


----------



## bcowen

L0rdGwyn said:


> (Sigh) papier-mâché it will have to be then!  I charge by the hour, this works out well for me


LOL!  There's always masonite or OSB board, or with lumber prices what they are perhaps sheetrock.  It's for Zachi, after all.


----------



## L0rdGwyn

bcowen said:


> LOL!  There's always masonite or OSB board, or with lumber prices what they are perhaps sheetrock.  It's for Zachi, after all.



The options are truly endless...for some nostalgic flair, there is also Play Doh, Lincoln Logs, or even Legos!  Truly a custom chassis, and even comes with ninjas.


----------



## Zachik

L0rdGwyn said:


> I'll have to give that some thought!  Hadn't considered a tour, well really hadn't considered selling this, no promises on that front!  Maybe as a favor.  Would be great to nail it the first time, I am cautiously optimistic, but you never know when a rogue oscillating component will ruin your day...
> 
> Well the cost of parts...most expensive are the Sowter transformers, around $365USD for the pair shipped.  Probably with a fancy Landfall chassis, the cost of parts is around $1300ish?  The chassis and the transformers make up almost half of that!
> 
> ...


Sorry to disappoint Bill, but for me - aesthetic is important. No cardboard chassis thank you very much. 
$1300 in parts is not too bad. Especially if it's as good as I hope... 

Keenan, what's the advantages of PCM63 chip? What is the audible difference according to the diy community?


----------



## Tjj226 Angel

L0rdGwyn said:


> (Sigh) papier-mâché it will have to be then!  I charge by the hour, this works out well for me



Nah nah. You go get an unfinished project box from micahels, paint it, and tell the customer how hard it was to make such a masterpiece. 

But in all reality, if you end up making more than a few chassis, I would look at send cut send for bulk work. Once you order in units of 5 at a time, your cost goes down quite a bit.


----------



## Zachik

L0rdGwyn said:


> Oh and yes @Zachik , I still have the Audial S5 on order.  I am expecting very big things from that DAC, so it will be the benchmark by which I compare my own.  It is TDA1541A-based.  Taking a little longer than expected though, it should ship to me this week.


Is that the same chip used in Yggy?
I am VERY interested in your impressions once you get it, and how it compares to your design!!


----------



## bcowen (Aug 22, 2021)

Zachik said:


> Sorry to disappoint Bill, but for me - aesthetic is important. No cardboard chassis thank you very much.
> $1300 in parts is not too bad. Especially if it's as good as I hope...


$1300 is just the parts though.  Then there's Keenan's labor (engineering *and* assembly), overhead, G&A costs, taxes, etc.  Although 'high end' audio entities are probably all over the map with pricing structures, a general rule of thumb is 5x - 6x parts cost to establish a retail price (I'll leave cable manufacturers out of that for simplicity).  So $6500 - $7800 final retail price.  Still not bad for a work of art, especially with a _real_ metal chassis.


----------



## Tjj226 Angel

Zachik said:


> Sorry to disappoint Bill, but for me - aesthetic is important. No cardboard chassis thank you very much.
> $1300 in parts is not too bad. Especially if it's as good as I hope...
> 
> Keenan, what's the advantages of PCM63 chip? What is the audible difference according to the diy community?



Greater resolution, lower noise, and so on. It is a better chip in theory. But it is a much harder chip to design for. If you compared both chips with a basic opamp IV stage, the PCM63 would sound better. 

But if you make a more specialized dac like what lordgwyn is doing, the PCM56 could end up sounding better. 

I am actually in the midst of building a PCM63 dac, so maybe lordgwyn and I will go head to head one of these days lol.


----------



## L0rdGwyn

Zachik said:


> Sorry to disappoint Bill, but for me - aesthetic is important. No cardboard chassis thank you very much.
> $1300 in parts is not too bad. Especially if it's as good as I hope...
> 
> Keenan, what's the advantages of PCM63 chip? What is the audible difference according to the diy community?



You know, I don't recall if I came across someone comparing the two chips at a granular level, I haven't read into it deeply, but most say the PCM63 is "better", but the PCM56 is not far behind, both well-regarded tonally from my reading.  The PCM63 is a 20-bit chip compared to the PCM56 which is a 16-bit.  BUT once you get down to bit 15, 16...and beyond, the DAC needs to be well-engineered otherwise noise will dominate at that bit depth, you won't hear the extra bits anyway!  So I wouldn't think the difference is due to dynamic range.  Another example - the PCM56 is generally more highly regarded than its 18-bit counterpart, the PCM61.  Notable also - the PCM63 does have better distortion specs than the PCM56.  If I get serious about messing around with PCM63, will look into the subjective differences further.

Another thing though - the PCM63 is becoming quite rare, especially the best binned "K" grade, even the "J" run almost $100 a piece, you need two, whereas the PCM56 is very available and cheap.  Better for experimenting 



Zachik said:


> Is that the same chip used in Yggy?
> I am VERY interested in your impressions once you get it, and how it compares to your design!!



I believe the Yggy uses a contemporary medical grade chip from Analog Devices.  The TDA1541A is OLD, a classic R2R chip, there is something of a cult following around it, it was found in many hifi CD players in the 80s.

Yes, I'm very curious myself.  Pedja Rogic (Audial) is truly an expert on TDA1541A, he has been designing with it for a long, long time.  He has pushed it to its performance limits, an accomplished designer whereas I am a first time schlub LOL but we have to start somewhere, will be interesting to see how they compare ONCE the DAC is working.


----------



## Tjj226 Angel

L0rdGwyn said:


> You know, I don't recall if I came across someone comparing the two chips at a granular level, I haven't read into it deeply, but most say the PCM63 is "better", but the PCM56 is not far behind, both well-regarded tonally from my reading.  The PCM63 is a 20-bit chip compared to the PCM56 which is a 16-bit.  BUT once you get down to bit 15, 16...and beyond, the DAC needs to be well-engineered otherwise noise will dominate at that bit depth, you won't hear the extra bits anyway!  So I wouldn't think the difference is due to dynamic range.  Another example - the PCM56 is generally more highly regarded than its 18-bit counterpart, the PCM61.  Notable also - the PCM63 does have better distortion specs than the PCM56.  If I get serious about messing around with PCM63, will look into the subjective differences further.
> 
> Another thing though - the PCM63 is becoming quite rare, especially the best binned "K" grade, even the "J" run almost $100 a piece, you need two, whereas the PCM56 is very available and cheap.  Better for experimenting



Batteries my son. You have to use batteries. Theoretically with batteries and low noise Jfets, you could reach down to 24bits of dynamic range. 

One of my projects before the year is done is to build an all in one headphone system that uses batteries and low noise jfets to achieve a true 24 bit system. 

Is it stupid? Yes. Why am I doing it? Because I can.


----------



## Galapac

Anyone have a use for these tubes?
NOS 6SG7GT/JAN-CNU National Union

I have 14 of them if someone can use them.
Never used in original boxes.


----------



## L0rdGwyn

Galapac said:


> Anyone have a use for these tubes?
> NOS 6SG7GT/JAN-CNU National Union
> 
> I have 14 of them if someone can use them.
> Never used in original boxes.



I personally don't have a use for them, but thank you for offering!  Maybe someone else does, I'm actually trying to buy less tubes as I have no space for them lol.  How did you end up with fourteen?!


----------



## Galapac

L0rdGwyn said:


> I personally don't have a use for them, but thank you for offering!  Maybe someone else does, I'm actually trying to buy less tubes as I have no space for them lol.  How did you end up with fourteen?!


Guy was selling them in sets of 6, I bought 2 sets and he threw in 2 extra.
I bought these by mistake last year ( I thought they were 6SJ7GT without my glasses on) and I have had them in the box since. Clearing out some clutter so offered them up to anyone interested.
I'll put them out on the classifieds....thanks


----------



## Zachik

Galapac said:


> I bought these by mistake last year ( I thought they were 6SJ7GT *without my glasses on*)


Awesome excuse!  Hope you have no copyright as I am gonna start using that one


----------



## L0rdGwyn (Aug 23, 2021)

Galapac said:


> Guy was selling them in sets of 6, I bought 2 sets and he threw in 2 extra.
> I bought these by mistake last year ( I thought they were 6SJ7GT without my glasses on) and I have had them in the box since. Clearing out some clutter so offered them up to anyone interested.
> I'll put them out on the classifieds....thanks



Gotcha, might try eBay sold as a lot, not really an audio tube so might have some trouble moving them on Head-Fi!



Zachik said:


> Awesome excuse!  Hope you have no copyright as I am gonna start using that one



I thought it was a pair of General Electric 12AU7, turns out I bought a pair of NOS Western Electric 300B, where are my damn glasses!

https://tubedepot.com/products/nos-...pfAPnTHSlj57_kKnAIP8iYY9jcKLPSrsaAoWlEALw_wcB

(P.S. I wear glasses too, so I feel your pain).


----------



## Zachik

L0rdGwyn said:


> I thought it was a pair of General Electric 12AU7, turns out I bought a pair of NOS Western Electric 300B, where are my damn glasses!
> 
> https://tubedepot.com/products/nos-...pfAPnTHSlj57_kKnAIP8iYY9jcKLPSrsaAoWlEALw_wcB


$199.95 is awesome price for those!!!!!


----------



## whirlwind

If you have a 12 volt switch on your OTL...you could use these


----------



## Zachik

whirlwind said:


> If you have a 12 volt switch on your OTL...you could use these


Joe, have you become a hoarder?


----------



## sam6550a

Zachik said:


> Joe, have you become a hoarder?


Beware @bcowen!


----------



## L0rdGwyn

I am told the Audial DAC will ship Wednesday, international express so should have it next week.  DAC parts should be here too AND I will be on a week-long staycation.  Should be a good week of DAC shenanigans!  Very excited.


----------



## bcowen

sam6550a said:


> Beware @bcowen!


Yeah.  I'm getting mad.  Or jealous.  Or something.


----------



## bcowen

L0rdGwyn said:


> Gotcha, might try eBay sold as a lot, not really an audio tube so might have some trouble moving them on Head-Fi!
> 
> 
> 
> ...


I hope you still haven't found your glasses when the credit card bill arrives.


----------



## L0rdGwyn

bcowen said:


> I hope you still haven't found your glasses when the credit card bill arrives.



LOL I think I'd go completely blind from that point forward.


----------



## Zachik

L0rdGwyn said:


> Should be a good week of DAC shenanigans! Very excited.


Right in time to help me scratch the DAC upgrade itch... 
Cannot wait to hear ALL about the S5, your DAC, and DAC shenanigans in general.


----------



## L0rdGwyn

Here are some random parts that are going in the PCM56 DAC.  I know these posts are kinda dumb but it helps me cope with the wait.

Talema 7XXXX series toroidals.  Had to order these from the UK, one for each channel, one for the digital supply.




Medical grade dual primary dual secondary toroidal, has an electrostatic shield and hum band, this will be my balanced isolation transformer for now.



Rubycon Caps, more of these to come, but this is the bulk, ZLH series low ESR long-life types.



Some transistors that will be used in the power supply positive rails.



DIP-16 socket for the PCM56 chips.



More stuff should arrive today, will probably start doing some prep work today and tomorrow, mostly around the 12B4A output stage.  In chemical kinetics terminology, the rate-limiting step is the PCB production, I am expecting those to arrive middle-to-late next week.  Will get everything else I can done in the mean time so it's simply a matter of stuffing the boards and testing!!!


----------



## triod750

Medical grade prevents headache...


----------



## L0rdGwyn

triod750 said:


> Medical grade prevents headache...



Unless you are in medical school


----------



## triod750

L0rdGwyn said:


> Unless you are in medical school


Absolutely - didn't think of that.


----------



## Zachik

Being in high-tech all my life, I have to admit I was never *exposed *to medical jokes 
(hopefully, my pun is an acceptable medical joke... )


----------



## triod750

Zachik said:


> Being in high-tech all my life, I have to admit I was never *exposed *to medical jokes
> (hopefully, my pun is an acceptable medical joke... )


At least you are .


----------



## L0rdGwyn

I did a lot of boring DIY stuff today, but it needed to be done for DAC preparation.

I put together CCS loads for the 12B4A output stage.



I determined snubber component values for all of the DAC transformers as well as the output stage transformer.



I reconfigured the digital front end module for PCM56 (it was originally set up for TDA1541A in Philips simultaneous mode).  I crimped power supply and digital data output leads.  Will crimp and terminate the other ends when most everything is set up and the lengths are determined.



I put together the final part lists, one more parts order and we are all set, will arrive before the PCBs.

Getting this stuff out of the way, the prototype should come together pretty quickly!  First step will be testing the power supply, if that checks out we should be in good shape


----------



## L0rdGwyn (Aug 27, 2021)

More boring DAC stuff.

Wired up the bottom of the 9-pin tag boards for the 12B4A.



Here are the major components of the output stage.  Sowter I/V transformers, 12V A23 battery between the transformer secondary and ground, aka battery (fixed) bias.  CCS active loads, plate current at 30-35mA, plate voltage will be somewhere between 100-130VDC, which will put the output impedance of the stage at 750-800ohm.  Heaters will be AC, elevated 40VDC above ground.

Will use some Clarity Caps I have around for testing, but will swap to some fancy type cap once all is finalized, maybe a 2.2uF 400VDC Jupiter copper foil, TBD.



Really nothing stopping me from putting this output stage together and testing it while waiting for parts and PCBs, will probably do that next.


----------



## L0rdGwyn (Aug 27, 2021)

Okay, bias of the output stage is set up and tested.



Based on the measurements, decided on a 30mA / 110VDC bias point with -12.5V on the grid provided by the batteries.

I didn't bring the I/V transformers into the mix, just the secondary resistor, will need to add the output caps as well, but this was only for biasing purposes.  Just need those dang PCBs now.


----------



## L0rdGwyn

That's all for now, not a whole lot else to do until PCBs are here.

So how about some music!  Without a top end DAC around, vinyl it is  vacant space in the rack for Audial S5 and/or DIY DAC when it is complete.


----------



## UntilThen

Nice Keenan. Vinyl with that Sowter amp with that menacing mains transformer looks the works. Speakers looks good too.


----------



## Zachik

L0rdGwyn said:


> Based on the measurements, decided on a 30mA / 110VDC bias point with -12.5V on the grid provided by the batteries.


So... how long do you expect the batteries would last?  



L0rdGwyn said:


> vacant space in the rack for Audial S5 and/or DIY DAC when it is complete.


I thought the S5 should be on its way by now... Anxiously looking forward to your impressions


----------



## bcowen

L0rdGwyn said:


> More boring DAC stuff.
> 
> Wired up the bottom of the 9-pin tag boards for the 12B4A.
> 
> ...


Sweet!  One question though:  how do you know when the batteries need replaced?  I'm guessing that losing the negative bias voltage would be a not good thing?  Or will they last long enough you just replace them once a year when you do your smoke detector batteries (being silly, but actually a serious question)?


----------



## bcowen

Zachik said:


> So... how long do you expect the batteries would last?
> 
> 
> I thought the S5 should be on its way by now... Anxiously looking forward to your impressions


Quit posting while I'm posting the same question.  Sheeez.


----------



## L0rdGwyn (Aug 27, 2021)

Zachik said:


> So... how long do you expect the batteries would last?
> 
> 
> I thought the S5 should be on its way by now... Anxiously looking forward to your impressions



The lifetime of the battery, so 5 years according to Duracell!

When using battery bias, the battery will not be drained, assuming the grid of the tube draws little-to-no current, which is the case in this circuit (and most class A1 gain stages).  Probably will check once a year to ensure the voltage hasn't drifted significantly.

The S5 is on its way!  International express, doesn't have a delivery date yet but my guess is Monday or Tuesday.

LOL @bcowen please see above


----------



## L0rdGwyn

UntilThen said:


> Nice Keenan. Vinyl with that Sowter amp with that menacing mains transformer looks the works. Speakers looks good too.



Thanks!  Hope you are still enjoying your new amp


----------



## UntilThen

L0rdGwyn said:


> Thanks!  Hope you are still enjoying your new amp



Enjoying it so much I need to check in to AA. Amps Anonymous. I've no doubt the wonderful sonics that I hear are attributed to Sowter irons.


----------



## L0rdGwyn

UntilThen said:


> Enjoying it so much I need to check in to AA. Amps Anonymous. I've no doubt the wonderful sonics that I hear are attributed to Sowter irons.



Yes but the rest is very important too!  All working in concert 

After building my 801A amp, I have no desire to design another speaker amp for a long, long time.  I still have a small collection of HK54 transmitting triodes for an even more ridiculous amplifier, but who knows if it will ever get done (still, I keep an eye out for more...).

I opened my 801A amp to make some minor adjustments yesterday, holy crap this was a complicated build!  Glad it is behind me lol.


----------



## UntilThen

L0rdGwyn said:


> Yes but the rest is very important too! All working in concert



Oh no doubt about it. Tomas did a splendid job on Odyssey. Your interior is nice and so is Odyssey's. A lot goes in there. A lot of switches... speakers, impedance, triode/UL, input selector switches, feedback on/off for EL11, 6sl7 or EL11 switches. Yamamoto's sockets looks good on the other side.  

Are those Duracell batteries in there? How often do you have to change it?


----------



## L0rdGwyn

UntilThen said:


> Oh no doubt about it. Tomas did a splendid job on Odyssey. Your interior is nice and so is Odyssey's. A lot goes in there. A lot of switches... speakers, impedance, triode/UL, input selector switches, feedback on/off for EL11, 6sl7 or EL11 switches. Yamamoto's sockets looks good on the other side.
> 
> Are those Duracell batteries in there? How often do you have to change it?



They power the whole amplifier, so every 5 minutes.

Just kidding  similar to the DAC, the batteries act as a voltage reference for biasing, they are not drained at all in ordinary use.  So only changed at the shelf life of the battery, which is 10 years for AA.

Gotta cram a lot inside of these complex amplifiers!  Getting the layout right is often the hardest part, I'm sure Thomas' layout is splendid.


----------



## triod750 (Aug 27, 2021)

UntilThen said:


> Are those Duracell batteries in there? How often do you have to change it?


I would think they are capacitors.

Edit. Was looking at Jupiter.


----------



## L0rdGwyn

All is truly ready now for the DAC prototype.

I added in the I/V transformers, output caps, RCA outputs, output protection zener diodes.  DAC isolation transformer is in place as well.



I fed a ballpark signal into the I/V transformer primary - obviously will not emulate the PCM56 current output well, but for the sake of checking that all is working as intended.

Here is a 1kHz sine wave at the RCA output, input signal to the I/V transformer is 0.19Vpeak-peak.



When the digital components are in place, will need to adjust the secondary resistor to find a balance between output distortion and output signal, aiming for 2Vrms.

From a build standpoint, really nothing else to do now but wait.  In the meantime, I'll probably nail down how I will be testing the DAC.


----------



## L0rdGwyn

Not much is going according to plan this week!

My Audial S5 as held up in US customs - I provided the paperwork and it was released, but it has not moved for two days despite my best efforts.  Hopefully it arrives by the weekend.

My PCM56 DAC PCBs have shipped, but projected arrival date is Tuesday, when I go back to work.  They have arrived early in the past, so I'm hopeful they will get here Monday and I can finish my prototype.

Some semi good news - the UK distributor from which I ordered my PCM56 DAC transformers made a mistake - they told me to keep the stock with a refund.  So I now have some spare transformers for another project.



This DAC designing business has opened up a whole can of worms - I expect I will be experimenting with DAC designs for some time.  As such, I'm going to design another one, a more simple and straightforward design compared to the PCM56, based on the Philips TDA1387T.  This is similar to the TDA1545, which itself is something of an improved TDA1543.

I bought 30 pieces for $11.



A major advantage of this chip over the TDA1543 (which is very popular in the DIY world) is its very minimal power supply requirements - around 6mA per chip, as opposed to 50mA of the TDA1543.  This keeps the power supply small without the need for heatsinking, meaning several of these chips can be paralleled.  That's what I intend to do, could also consider running them in differential mode (balanced).  Plan to run from one of the transformers above with SPDIF input (I2S protocol), the goal being to make a very compact NOS R2R DAC.

We'll see where that goes, otherwise I have been doing work on my next amplifier.

The wait continues for DAC stuff


----------



## L0rdGwyn (Sep 3, 2021)

The Audial S5 has landed.



This DAC has just about any digital input you could ask for.  Using the USB input runs the TDA1541A via Philips simultaneous data protocol, so that is the preferred connection for me.  It even has direct I2S digital inputs over HDMI, so you could potentially run the output of a I2S output compatible CD transport directly into the DAC.  You can even connect two of these DACs together for a four-channel USB setup.  There are many other nifty connection features, but I'll leave it at that.  Engineering!



Dual RCA outputs, one is cap coupled, the other is transformer coupled.  There is also a chassis ground connection if needed.

Here is the famous.  I won't show the rest of the interior (although there are many pictures of the inside from previous models online), but suffice to say it is impeccably well-built.



I have only been listening with the transformer-coupled outputs so far, over USB out of my Innuos server which operates as a Roon core, into my 801A amplifier to my Snells.



Pedja does state that the DAC will burn in over a couple of weeks, but first impressions are very good.  My immediate feeling is this DAC is very resolving and uncolored, neutral yet musical, especially compared to my former SW1X DAC II which had a warm / euphonic lean to my ears, no doubt in part due to the tube output stage.  But the S5 is completely devoid of audible noise, even with my amplifier at max volume without music playing (this would be an ear-destroying volume with 7W into the 92dB/W Snells).



This DAC is made from the marriage of subjective listening evaluation by the designer as well as sound engineering techniques and measurements - the DAC came with a slew of graphs showing its measured performance.

More listening / burning-in to be done, need to have a listen with headphones later today!


----------



## L0rdGwyn

Of course I am doing DIY stuff too - designing the power supply for my TDA1387T DAC.  Going to go with a LDO regulator approach likely using SMD components on this one, power supply design is actually nearly done, need to work on the digital front end and I/V stage next...

Oh and my PCM56 PCBs _should _arrive tomorrow, so it is going to be a busy weekend.


----------



## Zachik

L0rdGwyn said:


> I have only been listening with the transformer-coupled outputs so far, over USB out of my Innuos server which operates as a Roon core, into my 801A amplifier to my Snells.


Looking forward to more impressions!!!  Very interested to read your take on cap coupled vs. transformer coupled.
*Considering *DAC upgrade, and this one is on my short list of candidates...


----------



## L0rdGwyn

Zachik said:


> Looking forward to more impressions!!!  Very interested to read your take on cap coupled vs. transformer coupled.
> *Considering *DAC upgrade, and this one is on my short list of candidates...



For sure!  Will give it some time though for ears / parts to burn in.

Here are some really old transmitting triodes, Eimac 35TG from 1946.  This is a near-equivalent to the HK54.  I am slowly collecting these, if I ever build myself another speaker amplifier, it will be based on these transmitters, an A2 design making ~15W single ended.



The 35TG has a 5V 4A thoriated tungsten filament, the HK54 a 5V 5A filament.  This would be one crazy ass amplifier, I have no desire to work on it now lol so I will just stow away these tubes for a few years probably.


----------



## CJG888

Now those are a wee bit radioactive ☢️.

Tubes that glow even when they’re not switched on!!!

😀


----------



## L0rdGwyn

CJG888 said:


> Now those are a wee bit radioactive ☢️.
> 
> Tubes that glow even when they’re not switched on!!!
> 
> 😀



Yup, that's fluorescence from uranium glass used to make metal to glass seals.


----------



## CJG888

Plus the thoriated tungsten filaments…


----------



## L0rdGwyn

CJG888 said:


> Plus the thoriated tungsten filaments…



They are both harmless.


----------



## Mr Trev

L0rdGwyn said:


> They are both harmless.


but the question is… can it cure COVID?


----------



## L0rdGwyn

Mr Trev said:


> but the question is… can it cure COVID?



LOL I'll bring some 35TG and my bench supply to work, definitely won't get any weird looks as I hover "light bulbs" over the patients.


----------



## bcowen

L0rdGwyn said:


> But the S5 is completely devoid of audible noise, even with my amplifier at max volume without music playing (this would be an ear-destroying volume with 7W into the 92dB/W Snells).


Sweet!  Like @Zachik , greatly looking forward to more of your listening impressions as it breaks in.  

But 7W and 92dB is ear destroying?  Boy am I in trouble.  I can audibly saturate the transformers of the ~21wpc Jota into the 98 dB sensitive Tektons with bass heavy music. Loud, yes, and probably really loud, but not what I'd call rock concert volumes. Now the Cary V-12i monos at 200W (in ultralinear mode) into my previous 94dB Coincident Total Eclipses could do ear damaging (and probably structure damaging) volumes with headroom to spare.


----------



## bcowen

Mr Trev said:


> but the question is… can it cure COVID?


If it sounds good enough, maybe LG will _want_ to quarantine.


----------



## L0rdGwyn

bcowen said:


> Sweet!  Like @Zachik , greatly looking forward to more of your listening impressions as it breaks in.
> 
> But 7W and 92dB is ear destroying?  Boy am I in trouble.  I can audibly saturate the transformers of the ~21wpc Jota into the 98 dB sensitive Tektons with bass heavy music. Loud, yes, and probably really loud, but not what I'd call rock concert volumes. Now the Cary V-12i monos at 200W (in ultralinear mode) into my previous 94dB Coincident Total Eclipses could do ear damaging (and probably structure damaging) volumes with headroom to spare.



I really like it so far, the sound is very clean, uncolored and natural.  I'm thinking my PCM56 DAC will be a nice counterpoint with some tube warmth, some fun coloration to mix it up.

Yeah ear-destroying is too strong LOL uncomfortably loud is more accurate, but my room is pretty small!


----------



## UntilThen

bcowen said:


> Sweet!  Like @Zachik , greatly looking forward to more of your listening impressions as it breaks in.
> 
> But 7W and 92dB is ear destroying?  Boy am I in trouble.  I can audibly saturate the transformers of the ~21wpc Jota into the 98 dB sensitive Tektons with bass heavy music. Loud, yes, and probably really loud, but not what I'd call rock concert volumes. Now the Cary V-12i monos at 200W (in ultralinear mode) into my previous 94dB Coincident Total Eclipses could do ear damaging (and probably structure damaging) volumes with headroom to spare.



Can you hear me now? I am asking for the right iron for that fairway shot. Stop dreaming about amplifiers.


----------



## Zachik

L0rdGwyn said:


> I really like it so far, the sound is very clean, uncolored and natural. I'm thinking my PCM56 DAC will be a nice counterpoint with some tube warmth, some fun coloration to mix it up.


Now the question is:
When can I come over with my Amber 3 and have a 3-way shootout (Amber 3 vs. Audial S5 vs. LG DIY PCM56)? 
(I wish I were in driving distance from you... 2,500 miles is a little too far to drive, and I wonder how much hassle it would be to fly with the Amber 3...  )


----------



## bcowen

UntilThen said:


> Can you hear me now? I am asking for the right iron for that fairway shot. Stop dreaming about amplifiers.


I already handed you the one with the 'P' on it.  No?  Fairway, tee, green, rough....geeez, they're all made of grass, so it seems more like country club talk than logic.  It's like whoever came up with 15-love in tennis?  What's to love about being behind?


----------



## L0rdGwyn (Sep 3, 2021)

Zachik said:


> Now the question is:
> When can I come over with my Amber 3 and have a 3-way shootout (Amber 3 vs. Audial S5 vs. LG DIY PCM56)?
> (I wish I were in driving distance from you... 2,500 miles is a little too far to drive, and I wonder how much hassle it would be to fly with the Amber 3...  )



Something tells me TSA would have a thing or two to say about the Amber 3 lol.  Yeah it's tough, niche hobby in a big country.  Maybe ZMF will have an event next year!  It isn't very far off, this one has flown by...


----------



## Zachik

L0rdGwyn said:


> Something tells me TSA would have a thing or two about the Amber 3 lol.  Yeah it's tough, niche hobby in a big country.  Maybe ZMF will have an event next year!  It isn't very far off, this one has flown by...


Too long of a wait...
Joking aside - once your PCM56 DAC is done, if you're game... I am willing to make a Cleveland weekend mini-vaca out of it


----------



## L0rdGwyn

Zachik said:


> Too long of a wait...
> Joking aside - once your PCM56 DAC is done, if you're game... I am willing to make a Cleveland weekend mini-vaca out of it



We'll see how the DIY DAC turns out!  Hopefully no major hiccups.  That one I could send out if it is a success, but the timing isn't so good for a visit with the new COVID surge hitting Ohio, my life is about to get very rough once again


----------



## Zachik

L0rdGwyn said:


> We'll see how the DIY DAC turns out! Hopefully no major hiccups. That one I could send out if it is a success


Sounds like a plan!!!


----------



## whirlwind

L0rdGwyn said:


> We'll see how the DIY DAC turns out!  Hopefully no major hiccups.  That one I could send out if it is a success, but the timing isn't so good for a visit with the new COVID surge hitting Ohio, my life is about to get very rough once again


Yeah, I was really hoping for a different outcome for this year.
 I will be retired at the end of next week and I have bought quite a few tickets to see live music in a few different cities in Ohio...would not be surprised if some get cancelled since they are later in the year.


----------



## bcowen

whirlwind said:


> Yeah, I was really hoping for a different outcome for this year.
> * I will be retired at the end of next week* and I have bought quite a few tickets to see live music in a few different cities in Ohio...would not be surprised if some get cancelled since they are later in the year.


Congrats!  Not too far away myself, and while I've never really _wanted_ to be older, in this case I do....badly.


----------



## whirlwind

bcowen said:


> Congrats!  Not too far away myself, and while I've never really _wanted_ to be older, in this case I do....badly.


Congrats to you also.

I hear you about the getting older part....I guess there comes a time when enough work is enough and you just want to enjoy life 
and let the pace slow down from the everyday quick pace that working life brings.


----------



## L0rdGwyn

whirlwind said:


> Yeah, I was really hoping for a different outcome for this year.
> I will be retired at the end of next week and I have bought quite a few tickets to see live music in a few different cities in Ohio...would not be surprised if some get cancelled since they are later in the year.



Congrats, Joe, that's fantastic, well-deserved I am sure.  We will see, I'm hoping this winter is not like the last, many inpatient healthcare workers left after last year due to fatigue, so every hospital is short-staffed, making the surge even more devastating...most are feeling very burnt out, myself included.

>90% of COVID hospital admissions where I work are unvaccinated - if anyone who reads this thread isn't vaccinated, please consider getting it and encourage others to do so.  Rumors on the negative effects of the vaccine are not scientific...the vaccine protects against severe illness as well if one were to get infected with the delta variant.


----------



## whirlwind

L0rdGwyn said:


> Congrats, Joe, that's fantastic, well-deserved I am sure.  We will see, I'm hoping this winter is not like the last, many inpatient healthcare workers left after last year due to fatigue, so every hospital is short-staffed, making the surge even more devastating...most are feeling very burnt out, myself included.
> 
> >90% of COVID hospital admissions where I work are unvaccinated - if anyone who reads this thread isn't vaccinated, please consider getting it and encourage others to do so.  Rumors on the negative effects of the vaccine are not scientific...the vaccine protects against severe illness as well if one were to get infected with the delta variant.


Thanks Keenan.

I hear you, I thought once the vaccine was available that we could get back to normal.
I really don't have as much hope as I once had. I read everyday that the hospitals all around our country have mostly unvaccinated people taking up most of the beds. Numbers don't lie and especially when this is the case everywhere.
So sad our country has gotten to be this divided...I just can't see it changing at this point.
Anyway, thanks for what you do and I do understand how tiring it must be for the health workers..even though it is 
not my profession, I can still feel your pain.


----------



## bcowen

L0rdGwyn said:


> Congrats, Joe, that's fantastic, well-deserved I am sure.  We will see, I'm hoping this winter is not like the last, many inpatient healthcare workers left after last year due to fatigue, so every hospital is short-staffed, making the surge even more devastating...most are feeling very burnt out, myself included.
> 
> >90% of COVID hospital admissions where I work are unvaccinated - if anyone who reads this thread isn't vaccinated, please consider getting it and encourage others to do so.  Rumors on the negative effects of the vaccine are not scientific...the vaccine protects against severe illness as well if one were to get infected with the delta variant.


I don't know exactly what you do (and don't intend to pry), but from what you've posted along the way I think I can safely assume you're a medical professional. I can't imagine what you're having to deal with, so I'll just offer my sincere gratitude for what you and all your colleagues have done and endured (and continue to) through this dreadful thing.  Just when it appeared there was light at the end of the tunnel, it seems that it *is* an oncoming train.

I got my vaccinations as soon as I was eligible, but I have a number of people at work that have not.  Some are due to religious convictions, and I get that and respect it. Some have other reasons that I may not agree with, but can at least understand it. And then there are some that are due to the "violation of my rights" and/or conspiracy theories, and all I can do with them is feel pity for being that stupid.   Just my opinion, of course.


----------



## L0rdGwyn (Sep 4, 2021)

whirlwind said:


> Thanks Keenan.
> 
> I hear you, I thought once the vaccine was available that we could get back to normal.
> I really don't have as much hope as I once had. I read everyday that the hospitals all around our country have mostly unvaccinated people taking up most of the beds. Numbers don't lie and especially when this is the case everywhere.
> ...



Thanks, Joe.  I anticipated this would happen, it's the perfect storm with the rise of the anti-vax movement in addition to the ideological divide in America.  I have many opinions on why that divide exists, but best to keep them to myself lest I offend someone.



bcowen said:


> I don't know exactly what you do (and don't intend to pry), but from what you've posted along the way I think I can safely assume you're a medical professional. I can't imagine what you're having to deal with, so I'll just offer my sincere gratitude for what you and all your colleagues have done and endured (and continue to) through this dreadful thing.  Just when it appeared there was light at the end of the tunnel, it seems that it *is* an oncoming train.
> 
> I got my vaccinations as soon as I was eligible, but I have a number of people at work that have not.  Some are due to religious convictions, and I get that and respect it. Some have other reasons that I may not agree with, but can at least understand it. And then there are some that are due to the "violation of my rights" and/or conspiracy theories, and all I can do with them is feel pity for being that stupid.   Just my opinion, of course.



Thanks, Bill.  Unfortunately the "violation of my rights" and conspiracy theory camp are difficult to reason with, near impossible really.  What about the rights of the person they unknowingly gave COVID to in public who died on a ventilator leaving a family behind?  Or the person who had a poor outcome from a non-COVID illness because the hospital was overrun with COVID-infected conspiracy theorists and their care was delayed?  The hypocrisy is maddening.  I could talk about it all day, instead I do DIY audio stuff to cope LOL.


----------



## Tjj226 Angel

L0rdGwyn said:


> Thanks, Bill.  Unfortunately the "violation of my rights" and conspiracy theory camp are difficult to reason with, near impossible really.  What about the rights of the person they unknowingly gave COVID to in public who died on a ventilator leaving a family behind?  Or the person who had a poor outcome from a non-COVID illness because the hospital was overrun with COVID-infected conspiracy theorists and their care was delayed?  The hypocrisy is maddening.  I could talk about it all day, instead I do DIY audio stuff to cope LOL.



Yeah, I am not touching this one with a 10 foot pole. I have a policy that when someone starts to make the classic "for the greater good" argument, I just back away slowly with no sudden movements. Hopefully, I get the hell out of dodge before everyone starts to sterilize the undesirables.


----------



## L0rdGwyn

Tjj226 Angel said:


> Yeah, I am not touching this one with a 10 foot pole. I have a policy that when someone starts to make the classic "for the greater good" argument, I just back away slowly with no sudden movements. Hopefully, I get the hell out of dodge before everyone starts to sterilize the undesirables.



You just touched it.  Care to elaborate?


----------



## L0rdGwyn

Actually never mind it's better left unsaid.


----------



## Zachik

L0rdGwyn said:


> Unfortunately the "violation of my rights" and conspiracy theory camp are difficult to reason with, near impossible really.


That bring to mind someone's signature (I forget whos) that goes loosely something like this:
Never argue with an idiot because you'll have to lower yourself to his level, and he will surely beat you there!


----------



## bcowen

Zachik said:


> That bring to mind someone's signature (I forget whos) that goes loosely something like this:
> Never argue with an idiot because you'll have to lower yourself to his level, and he will surely beat you there!


LOL!  Kind of like repeatedly slamming your forehead into a brick wall because it feels so good when you stop.


----------



## tubebuyer2020

I was really hoping mask-wearing, social distancing and remote work would catch on. Because all of the flus I ever caught came from public transport and office.



L0rdGwyn said:


> I could talk about it all day, instead I do DIY audio stuff to cope LOL.



Ah, the soothing crackle of lethal voltages .


----------



## bcowen

tubebuyer2020 said:


> Ah, the soothing crackle of lethal voltages .


And the wonderful aroma of solder fumes.  Almost as intoxicating as um, uh, um........steak on the grille.  Yeah, that's it.....steak.


----------



## L0rdGwyn

tubebuyer2020 said:


> Ah, the soothing crackle of lethal voltages .



Something to be said for keeping busy!  And safety first, if you ever get zapped good by 500V+, you won't forget it LOL not saying that I have of course...I am ever so careful these days.

Sadly, I don't think my PCM56 boards will be here until Tuesday because of the holiday, bummer  I'll probably work on the prototype bit by bit (no pun intended) after work during the week.  I guess I'll see if I can finish my TDA1387T design over the weekend.


----------



## Mr Trev

L0rdGwyn said:


> Something to be said for keeping busy!  And safety first, if you ever get zapped good by 500V+, you won't forget it LOL not saying that I have of course...I am ever so careful these days.
> 
> Sadly, I don't think my PCM56 boards will be here until Tuesday because of the holiday, bummer  I'll probably work on the prototype bit by bit (no pun intended) after work during the week.  I guess I'll see if I can finish my TDA1387T design over the weekend.


~300v was my best. Camera flash bit me.

Good times…


----------



## Tjj226 Angel

L0rdGwyn said:


> You just touched it.  Care to elaborate?



Sure. There are better ways to solve the problem than to expect people to give up individual rights for the greater good. That kind of logic has always lead to more death and destruction, not less. 

I don't disagree with your train of thought. I know everything sucks right now, and you know I am dealing with my own medical nightmares at the moment (first my uncle, now my mom), but we can't let ourselves slide down that slippery slope. Nothing good will come of it.


----------



## L0rdGwyn

Tjj226 Angel said:


> Sure. There are better ways to solve the problem than to expect people to give up individual rights for the greater good. That kind of logic has always lead to more death and destruction, not less.
> 
> I don't disagree with your train of thought. I know everything sucks right now, and you know I am dealing with my own medical nightmares at the moment (first my uncle, now my mom), but we can't let ourselves slide down that slippery slope. Nothing good will come of it.



It's better not to have this conversation, I withdrew my request in the next post.


----------



## Xcalibur255 (Sep 4, 2021)

tubebuyer2020 said:


> I was really hoping mask-wearing, social distancing and remote work would catch on. Because all of the flus I ever caught came from public transport and office.
> 
> 
> 
> Ah, the soothing crackle of lethal voltages .



Remote work made me homeless last week by creating a massive housing crisis in my town.  The problem with all of these political debates is that everybody wants to cast issues as black and white so they can thereby cast people into right and wrong camps.  Makes the world seem nice and simple.  Only the world isn't actually like that.  The trend that had a majorly negative consequence for me probably also had a positive consequence for somebody else and both of these truths exist simultaneously.

Considering how difficult it is to escape all of this these days I prefer the story that's written on these pages to be about cool audio stuff personally.  Also, yes I realize it's a bit hypocritical to say that in a post I myself made on a political topic, but this one time I couldn't help myself for some reason.  Probably because I'm feeling a little raw about having all of my stuff shoved into somebody else's guest room at the moment.


----------



## L0rdGwyn

Xcalibur255 said:


> Remote work made me homeless last week by creating a massive housing crisis in my town.  The problem with all of these political debates is that everybody wants to cast issues as black and white so they can thereby cast people into right and wrong camps.  Makes the world seem nice and simple.  Only the world isn't actually like that.  The trend that had a majorly negative consequence for me probably also had a positive consequence for somebody else and both of these truths exist simultaneously.
> 
> Considering how difficult it is to escape all of this these days I prefer the story that's written on these pages to be about cool audio stuff personally.  Also, yes I realize it's a bit hypocritical to say that in a post I myself made on a political topic, but this one time I couldn't help myself for some reason.  Probably because I'm feeling a little raw about having all of my stuff shoved into somebody else's guest room at the moment.



I'm sorry you are dealing with that @Xcalibur255 , hopefully you can find a new place soon.  You are absolutely right of course, it is very easy to generalize and all of the issues are much more complex than they seem and there are no simple answers.  I'll try to avoid veering into what we call "politics", the discussion from those with opposing viewpoints is rarely productive these days.  I had an opportunity to vent on my professional life and took it when I probably shouldn't have, so sorry about that guys!


----------



## L0rdGwyn (Sep 5, 2021)

I wish I had meaningful progress to report on my PCM56 DAC to change the subject, but it won't be done until next weekend unfortunately.  I can at least talk a little bit more on the other DAC I am designing using the TDA1387T - the high level design is done, just need to do the boards (the worst part).  A little background...

The most well-known of the old Philips R2R chips are the TDA1541A (as in the Audial S5 DAC) and the TDA1543.  The TDA1543 was the "economy" chip at the time, a lower end offering from Philips with worse measurable performance than the TDA1541A, albeit with much more straightforward power supply requirements and less implementation complexity in general.

The TDA1543 is the chip used in the Border Patrol DAC actually.  Over the years, it has become a very popular chip to use in the DIY community due to its ease of implementation and it being relatively cheap.  BUT the real draw of the chip - it has a very favorable output compliance.  Many of these old R2Rchips have limitations on the voltage that can be "seen" by the chip at it's current output pin, often with protective zener diodes that will lead to signal clipping if the output voltage swing is too high.

If the TDA1543 is fed a 8V supply, a 2Vrms signal can be generated from a single chip using a passive I/V stage (single resistor).  All this adds up to a very simple and good sounding DIY DAC!  Many people have paralleled several of these chips to increase performance, run pairs of them in differential mode for a balanced output, or run stacks of them in differential mode, lots of things to try...

Here is a TDA1543.




Philips introduced two chips after the TDA1543 using a new "continuous calibration" architecture, the TDA1545A and the TDA1387T.  The major difference between these two chips is the TDA1387T is I2S data protocol compatible while the TDA1545A is not.  They also come in different packages.

A major advantage of the upgraded architecture is a tenfold decrease in the current draw of these chips over the TDA1543 - the TDA1387T is run from a single 5V supply with a 6mA current draw.  This makes paralleling more of these chips even easier (smaller power supply requirements) without the need to consider heatsinking.

The output compliance of the TDA1387T is, however, not quite so high as the TDA1543, so generating a 2Vrms signal using a passive I/V stage isn't quite achievable - it is capped at ~1.2Vrms.  Paralleling additional chips does decrease the size of the I/V resistor needed to reach 1.2Vrms, which in turn lowers the output impedance of the DAC in addition to the other advantages of paralleling multiple chips.

Here is the TDA1387T again.



This chip might become something of a test bed for DAC design so perhaps different implementations down the road, but at least initially I plan to parallel these chips (targeting six at the moment) with a passive resistor I/V stage and no output amplification - no tubes!  Going to use a SPDIF input using a I2S compatible receiver chip.  The power supply will use one of the spare transformers I now have on hand and is going to be regulated using a few high-performing chips from Analog Devices.  The goal here is "small", likely a majority of the components will be surface mount.

That's the plan, should be a very small R2R DAC.  Only 1.2Vrms output, but I think that will be fine.  If it sounds good I will box it and put it in my bedroom!  But again, might end up doing a few iterations of this circuit - could end up doing a differential design from here with an output transformer to go from balanced to single-ended, we will see


----------



## CJG888

Not tempted to use those ladder DAC boards from Soekris or Audio-gd?


----------



## leftside

Xcalibur255 said:


> Remote work made me homeless last week by creating a massive housing crisis in my town.


Really sorry to hear about your situation. Especially as we've chatted a few times and I know you haven't had the best of luck lately. I'll drop you a PM.


----------



## L0rdGwyn

CJG888 said:


> Not tempted to use those ladder DAC boards from Soekris or Audio-gd?



I wasn't aware they sold DAC modules, but they look to be completed circuits that just need a chassis and some ancillary parts.  That is a nice option, but I really prefer to try my own circuits, always something new to learn along the way.


----------



## Tjj226 Angel

CJG888 said:


> Not tempted to use those ladder DAC boards from Soekris or Audio-gd?



Unfortunately those are complete modules. You don't have a ton of freedom with those modules to make your own Dac.


----------



## L0rdGwyn

So this was unexpected - seems my PCM56 PCBs are going to be delivered today, figured they wouldn't be given the holiday.  Feel bad for the driver, but also excited to get to work on it.  Not sure if I'll be able to finish the job today, assuming there are no surprises (big assumption), should be able to if the delivery isn't late.  TBC...


----------



## L0rdGwyn

Was making preparations for an efficient DAC build when the PCBs arrived.  Here they are.



Here is one of the 12V transformers on its PCB.



I finished the digital front end power supply board and tested it, it works perfectly, a clean 5V, ripple is unmeasurable on my scope.



That bodes well for the rest of the build, now to stuff one of the DAC boards and test it!


----------



## Zachik

@L0rdGwyn - why did you go with separate mini-PCB for the transformer, and the rest of the power supply on a different PCB?  Why not have 1 PCB for the entire PSU?


----------



## L0rdGwyn (Sep 6, 2021)

Zachik said:


> @L0rdGwyn - why did you go with separate mini-PCB for the transformer, and the rest of the power supply on a different PCB?  Why not have 1 PCB for the entire PSU?



That was because I had intended to have a custom mains transformer made for the design, which would have been rather large, too large to put on a PCB, with each winding going to its respective PCB.  That didn't work out, and actually I am very happy with what I found off the shelf.  Having them separated does give some flexibility in terms of layout, and the transformers can be positioned a little further away from the board to coupling of noise radiated by the transformer.

I did try to fit the transformers on the PCBs at one point, but didn't like the effect it had on the layout.


----------



## L0rdGwyn

Okay...

The DAC boards are stuffed.  Here is one before testing.  This is for one channel, there are two boards.  There are test points on the board for all four power supplies.



Here is testing with dummy loads and dialing in power supply voltages before putting in a PCM56.



All checked out, so next with the chip.



Everything looks good, just need to do the same for the other board, then connect everything together and hopefully it will make music.


----------



## tubebuyer2020

@L0rdGwyn Aren't carbon comp resistors "noisy"? Which brand did you go for?


----------



## L0rdGwyn

tubebuyer2020 said:


> @L0rdGwyn Aren't carbon comp resistors "noisy"? Which brand did you go for?



They can be, but they are only current limiting resistors prior to all regulation, all other resistors are low noise metal films.  They are Allen Bradleys.


----------



## L0rdGwyn

The DAC is done!

It's looking pretty ugly crammed onto my protoboard, which was not designed for prototyping DACs, but it's all there.

One PCM56 DAC PCB per channel, two stacked on top of one another, and the USB digital front end in front.  All supplies are isolated from the wall mains via a 1:1 toroidal running +/- 60VAC balanced power.  The current output of the PCM56 hits a Sowter 1:5 SUT which goes into a battery biased, CCS loaded 12B4A output stage.




And no kidding, it sounds really damn good right out of the gate!  Will need to adjust the I/V resistor on the transformer secondary as it isn't quite hitting 2Vrms however.

This obviously isn't optimized for low noise sitting out on a piece of wood and the grounding / layout is nowhere near optimal.  Also, the heaters of the 12B4A aren't elevated above ground, that will come in the final build.  Even so, the noise floor is only audible at dangerous volumes without music playing.

So I guess I can mark that one off the bucket list, need to work on getting it in a chassis now.


----------



## bcowen

L0rdGwyn said:


> The DAC is done!
> 
> It's looking pretty ugly crammed onto my protoboard, which was not designed for prototyping DACs, but it's all there.
> 
> ...


Nice!


----------



## triod750

This is for you, Keenan:


----------



## Monsterzero

triod750 said:


> This is for you, Keenan:



No replacing Jon Lord!


----------



## triod750

Monsterzero said:


> No replacing Jon Lord!


At least not L0rdGwyn!


----------



## Monsterzero




----------



## triod750

Monsterzero said:


>



 What? Muppet Show????

Just kidding....


----------



## Monsterzero

triod750 said:


> What? Muppet Show????
> 
> Just kidding....


----------



## L0rdGwyn

triod750 said:


> This is for you, Keenan:




Thanks @triod750 

Here is a better photo of the tubes being used in this DAC, 12B4A.  I'll swap those ClarityCaps to something fancy in the final build.



Only got to listen to a few songs earlier when it was done since I had to eat something!  Now listening again - I really like what I'm hearing, the bass really hits hard and the soundstage is impressive.  Gotta get this in a box ASAP, sucks listening at my workbench lol.  I have a free 6.3VAC winding on the output stage transformer, going to go for a low brightness power LED this time around.

I was working on the TDA1387T DAC board when I got notice these PCBs were being delivered today.  Going all SMD parts for that one, actually have the BOM just about done, need to just squeeze it onto a board and route it all.  Just a two-layer PCB, it is going to be very small.

I think I have DAC fever...


----------



## Monsterzero

L0rdGwyn said:


> Thanks @triod750
> 
> Here is a better photo of the tubes being used in this DAC, 12B4A.  I'll swap those ClarityCaps to something fancy in the final build.
> 
> ...


Anytime you wanna send it my way I'd love to bounce it off of the TRP.


----------



## L0rdGwyn

Monsterzero said:


> Anytime you wanna send it my way I'd love to bounce it off of the TRP.



Cool!  Wouldn't mind sending it, gonna get started on chassis planning this weekend.


----------



## Zachik

Monsterzero said:


> Anytime you wanna send it my way I'd love to bounce it off of the TRP.





L0rdGwyn said:


> Cool!  Wouldn't mind sending it, gonna get started on chassis planning this weekend.


...and as mentioned before: I would LOVE to A/B it against my Amber 3. Not as fancy as MZ's TRP, though


----------



## triod750

Monsterzero said:


>



Yes, that's me, too old to learn. I've been old for ages.....or rather decades.


----------



## triod750

Monsterzero said:


>


When I was a kid I listened to this fight on our tube radio:


----------



## triod750

Our first car was one of these, DKW from 1938. We were six kids in the back. 18hp!


----------



## bcowen

triod750 said:


> Our first car was one of these, DKW from 1938. We were six kids in the back. 18hp!


You're not that old.  This was my first car.  2 Footpower.


----------



## CJG888 (Sep 8, 2021)

I presume DKWs must have been popular in Sweden at the time. After all, SAAB „inherited“ much of the powertrain…


----------



## triod750

CJG888 said:


> I presume DKWs must have been popular in Sweden at the time. After all, SAAB „inherited“ much of the powertrain…


Well, I just saw a couple of them. But the car was twenty years old when we bought it from my grandpa. In fact, my grandpa and my father rebuilt quite some part of it since much of it was made from wood. The roof was covered with faux leather called pegamoid. We used shoeshine on it regularly. I really did shine then.
And bcowen is right, I am not very old. I just look as if I was. I'm still playing though.

No doubt SAAB (Svenska Aeroplanaktiebolaget) made a good choice regarding powertrain. SAAB 92 - an early bird:


----------



## UntilThen

bcowen said:


> Congrats!  Not too far away myself, and while I've never really _wanted_ to be older, in this case I do....badly.



Where's the joy in retiring. Head-Fi needs your wallet.


----------



## UntilThen

Monsterzero said:


>




Love it !


----------



## UntilThen

bcowen said:


> You're not that old.  This was my first car.  2 Footpower.



Definitely a golf cart.


----------



## L0rdGwyn

Nothing new to report, just unwinding after work.


----------



## Zachik

L0rdGwyn said:


> Nothing new to report, just unwinding after work.


Using which DAC?


----------



## L0rdGwyn

Zachik said:


> Using which DAC?



I was using the Audial S5!


----------



## Zachik

L0rdGwyn said:


> I was using the Audial S5!


Once you have a few minutes - please tell more about the S5...


----------



## L0rdGwyn

Zachik said:


> Once you have a few minutes - please tell more about the S5...



I think I need to give it more listening time, @Zachik , going to be short on personal time for a couple weeks unfortunately...but I'll let you know when I've drawn some conclusions.


----------



## L0rdGwyn

I will say this about the S5 - as pointed out by the designer, it does take some warm up to sound its best IMO.  30min-1hour after startup, the staging and separation seems to open up to a new degree.


----------



## Galapac (Sep 9, 2021)

Oh sorry you said _Audial _S5…😂


----------



## CJG888

Galapac said:


> Oh sorry you said _Audial _S5…😂


Which brings us nicely back to DKW!


----------



## CJG888

To explain: the postwar Audi brand grew out of DKW. The DKW F102 received a four-stroke engine and became the F103, and then the Audi 60…


----------



## triod750

This was a modern DKW. My uncle had two of these. They were awesome.


----------



## CJG888

Also built in Brazil as Vemag Belcar until 1967…


----------



## CJG888

And there was a convertible which looked a bit like a shrunken T-Bird!


----------



## CJG888




----------



## CJG888

It’s a pity about the clouds of blue smoke, though…


----------



## Xcalibur255

One of my bucket list things used to be owning a Volvo P1800 (or really any small classic coupe in this style) with 3 pedals, but my clutch leg is no good anymore.  

Actually the newly updated 2022 Subaru BRZ and Toyota 86 twins are quite desirable too.


----------



## L0rdGwyn

Ahh I've come up for air!  I have a three day weekend, nice.

Did some listening to the Audial S5 last night after work with headphones, then followed up with my PCM56 DAC this morning.  I find it is easier to tease out what a component "is" by comparing it to others.

Using my 6A5G amp.



And lugged the protoboard up out of the basement.



My immediate thoughts are that these two DACs are in similar performance categories _subjectively_.  I am finding the S5 is more "clean" and probably more "precise" while remaining very musical, whereas the PCM56 DAC offers a more warm, smooth, laid-back presentation, probably more of an "analog" sound.  A very early comparison, I really enjoy both.  I think the performance of the PCM56 DAC will actually improve further once it is put in a chassis with proper layout, grounding, etc.

I've decided rather than using AC on the heaters of the 12B4A, I am going to run them on DC without the heater elevation.  I've designed a 12.6VDC heater regulator for that purpose for the lowest possible coupled noise.  As I've said, even built on a piece of wood, the noise floor is far, far below the audibility threshold.  Interested to see how far down it can go when the build is done.

I probably won't get whole lot done this weekend DIY-wise, I really just need some R & R.  Hopefully that includes a Browns' win in tomorrow's game


----------



## Zachik

L0rdGwyn said:


> My immediate thoughts are that these two DACs are in similar performance categories _subjectively_. I am finding the S5 is more "clean" and probably more "precise" while remaining very musical, whereas the PCM56 DAC offers a more warm, smooth, laid-back presentation, probably more of an "analog" sound. A very early comparison, I really enjoy both. I think the performance of the PCM56 DAC will actually improve further once it is put in a chassis with proper layout, grounding, etc.


At some point, after the PCM56 is all done and in a nice case, I will have to bribe you to get you to ship both S5 and PCM56 to me for a 3-way shootout with my Amber 3...


----------



## L0rdGwyn (Sep 13, 2021)

I took some quick measurements of the PCM56 DAC today.

THD at -6dB 1kHz undithered sine wave - 0.07%
THD at -20dB 1kHz undithered sine wave - 0.02%
THD at -60dB 1kHz undithered sine wave - 1.3%

Harmonic spectrum is H2 dominant, I suspect it originates mostly from the 12B4A output stage. All other harmonics are at or below -100dB using a -6dB fundamental.

Here is a -6dB FR sweep of the left channel - this is straight out of the DAC, so a 220K load with 4.7uF output caps.

Relative to midband, HF response is down roughly 0.9dB at 20kHz.


----------



## Tjj226 Angel

R2R dacs have a second order dominate distortion. NOS dacs regardless of architecture have the same distortion characteristics. 

Since the tube will produce a signal 180 degrees out of phase with the dac signal, you can try and balance out the distortion between the dac and the tube.


----------



## L0rdGwyn

I'm going to see if I can get a majority of the layout done today in AutoCAD.  I was going to keep the tubes inside the chassis originally, but decided it would be too tedious to open the chassis every time they needed to be changed.  Will help with a more compact layout as well as I can mount components underneath the tag boards, they will protrude maybe half of their total height.

I like the raw brushed aluminum with white LED look on DACs right now (maybe because I have the Audial DAC around), just seems like it fits a digital component.  Might do the same on this one, similar to the chassis of 45 amp version 1 but with silver hardware, have to think it over, powder coat of course is the alternative...it will be a 4.25" chassis like below, going to try and keep it as compact as possible, but will probably need to be wider.


----------



## Zachik

L0rdGwyn said:


> I'm going to see if I can get a majority of the layout done today in AutoCAD. I was going to keep the tubes inside the chassis originally, but decided it would be too tedious to open the chassis every time they needed to be changed. Will help with a more compact layout as well as I can mount components underneath the tag boards, they will protrude maybe half of their total height.


Do you plan to tube-roll in the PCM56 DAC?!  My personal recommendation, from my own experience and limited space:
When there is no reason to tube-roll, place the tubes inside! That enables stacking or in case of a rack - less vertical space needed.


----------



## L0rdGwyn

Zachik said:


> Do you plan to tube-roll in the PCM56 DAC?!  My personal recommendation, from my own experience and limited space:
> When there is no reason to tube-roll, place the tubes inside! That enables stacking or in case of a rack - less vertical space needed.



No, no tube rolling, only for the ease of replacing them.  Okay I will reconsider it, I actually want them inside!  I imagined being annoyed having to remove the top plate...but they should not need to be replaced frequently.


----------



## Zachik

L0rdGwyn said:


> No, no tube rolling, only for the ease of replacing them.  Okay I will reconsider it, I actually want them inside!  I imagined being annoyed having to remove the top plate...but they should not need to be replaced frequently.


Thanks for re-considering 
BTW, I have seen several manufacturers mounting internal tubes horizontally, to keep the chassis height lower... Just an idea...


----------



## Monsterzero

L0rdGwyn said:


> I imagined being annoyed having to remove the top plate...but they should not need to be replaced frequently.


Yeah, that would be me, annoyed. I do like tube roll on my DAC though.


----------



## Zachik

Monsterzero said:


> I do like tube roll on my DAC though.


Your DAC was designed for tube-rolling. The PCM56 DAC by @L0rdGwyn is NOT designed to be a tube roller's DAC... 
Replacing the tubes in 5-10 years - that annoyance is negligible


----------



## Monsterzero

Zachik said:


> Your DAC was designed for tube-rolling. The PCM56 DAC by @L0rdGwyn is NOT designed to be a tube roller's DAC...
> Replacing the tubes in 5-10 years - that annoyance is negligible


Yup I read that tube rolling isnt intended. FWIW Ive gone thru 5 rectifiers in 2 years as up until last month my DAC was on 14-16 hours daily. 

My new house has built in speakers throughout as well as on the front and back porches so my Lampi only gets used a few hours daily now. Using a Modi MB for the whole house system.


----------



## L0rdGwyn

Right, this isn't really a DAC for tube rolling!  Pretty much designed for a specific tube.  However, they won't last 5-10 years!  Unless you are using the DAC very little, but they should last a long time, long enough that it shouldn't be too much of a nuisance.

I've decided I'm going to try one more thing on the output stage before I finalize the chassis - rather than using a low gain, low resistance output tube, can instead use a high-gm pentode strapped as a triode.  Gain of the tube will be higher, so must lower the I/V resistor on the transformer secondary to still hit 2Vrms.  Linearity of the tube will be higher, so H2 output distortion will go down.  The tradeoff here is a higher output impedance, likely on the order of 1-1.2K rather than ~750ohm of the 12B4A.  Most importantly will need to see which setup sounds better.  Probably won't finish this today, but going to go get the batteries I need for biasing.


----------



## Zachik

L0rdGwyn said:


> Right, this isn't really a DAC for tube rolling! Pretty much designed for a specific tube. However, they won't last 5-10 years! Unless you are using the DAC very little, but they should last a long time, long enough that it shouldn't be too much of a nuisance.


I am curious: how long would you estimate the tubes last?
Also, how do you know when it is time to replace them? Would the DAC stop working (i.e. no sound coming from the RCAs)?


----------



## Monsterzero

Zachik said:


> Also, how do you know when it is time to replace them?


Not sure if this applies to all DACs and amps for that matter, but I lose dynamics and staging depth on my TRP when a tube needs to be replaced.


----------



## Zachik

Monsterzero said:


> Not sure if this applies to all DACs and amps for that matter, but I lose dynamics and staging depth on my TRP when a tube needs to be replaced.


I guess the challenge is: if that deterioration is slow and gradual - there is no "right moment" to replace then...


----------



## triod750

Is the deterioration of tubes frequency linear? Or do you lose more gain in the treble end?


----------



## Monsterzero

triod750 said:


> Is the deterioration of tubes frequency linear? Or do you lose more gain in the treble end?


again, speaking only about my experiences with my DAC, the gain hasnt really suffered but the bass response def suffers as does the holographic presentation. YMMV depending upon your gear.


----------



## bcowen

Zachik said:


> *When there is no reason to tube-roll...*


I've heard of this phenomenon, but thought it was just another urban legend.


----------



## Zachik

bcowen said:


> I've heard of this phenomenon, but thought it was just another urban legend.


Some tubes, like the 4W one in my freezer, only need to be rolled when they burn out


----------



## L0rdGwyn (Sep 13, 2021)

HMMMMMM. Hmm.

Well I had to try the triode-strapped *tetrodes in the DAC tonight.

The big reveal!  It's the 6E6P-DR.




Very linear when triode-strapped, mu of 33, plate resistance 1.2K.

Wired up another pair of tag boards, ferrite beads on all electrodes to discourage oscillation.  Thought I'd do a whole new pair of tag boards in case the change isn't to my liking.



There it is.  I/V resistor reduced for the same output voltage, batteries changed from 12V to 1.2V, CCS loads reduced from 30mA to 25mA for my chosen bias point.



So what does this do for us - well the THD came down significantly - with a -6dB undithered 1kHz sine (again), THD is 0.018% compared to 0.07% with the 12B4A.

I haven't measured it yet, but the output impedance will increase from ~750ohm to ~1.2K, but really not an issue.

The high frequency response, however, is more rolled off in this setup.  This is likely due to the increased input capacitance of the 6E6P-DR relative to the 12B4A.

20kHz is down -2.7dB relative to midband compared to -0.9dB using the 12B4A.



Subjectively though, I do think the clarity and detail retrieval increased quite nicely.  I really don't get the impression the top end is rolled off.  Tonally I would say the change shifts the sound of the DAC more toward neutral if I were to call the 12B4A setup warm.  In addition, the noise floor is lower and the 6E6P-DR is less microphonic than the 12B4A.

Despite the measurements, I would call it an improvement.  I think I will leave it as is for now without making a final decision and listen for a few days.  I still have the 12B4A tag boards, so could switch back for another listen, which I will likely do!


----------



## Zachik

L0rdGwyn said:


> Subjectively though, I do think the clarity and detail retrieval increased quite nicely. I really don't get the impression the top end is rolled off. Tonally I would say the change shifts the sound of the DAC more toward neutral if I were to call the 12B4A setup warm. In addition, the noise floor is lower and the 6E6P-DR is less microphonic than the 12B4A.
> 
> Despite the measurements, I would call it an improvement. I think I will leave it as is for now without making a final decision and listen for a few days. I still have the 12B4A tag boards, so could switch back for another listen, which I will likely do!


From my experience, often I preferred a worse-measuring piece of gear compared to a better measuring alternative. 
I mean isn't that what tubes is all about?? Solid state measures often better, but is not as much fun or as musical.


----------



## L0rdGwyn

Zachik said:


> From my experience, often I preferred a worse-measuring piece of gear compared to a better measuring alternative.
> I mean isn't that what tubes is all about?? Solid state measures often better, but is not as much fun or as musical.



Agreed, and the rolloff isn't so egregious that it is a true issue.  I can't hear beyond 16-17kHz anyway   the distortion is lower, which is likely contributing to the increased clarity.

I won't make any final call right now, will give it some time, then switch back to 12B4A maybe next weekend and see how I feel about going back.


----------



## Zachik

L0rdGwyn said:


> Agreed, and the rolloff isn't so egregious that it is a true issue.


I think it is usually the distortion, not roll-off, that measures worse but sounds subjectively better. 



L0rdGwyn said:


> I can't hear beyond 16-17kHz anyway


If I had to *take a guess*, I would say my hearing *probably* rolls-off at 13-14kHz 
In 15 years - you'll likely experience the same...


----------



## L0rdGwyn

Zachik said:


> I think it is usually the distortion, not roll-off, that measures worse but sounds subjectively better.
> 
> 
> If I had to *take a guess*, I would say my hearing *probably* rolls-off at 13-14kHz
> In 15 years - you'll likely experience the same...



Yeah I'm sure it's coming!  NOS DACs often have a rolled off top end, but that doesn't stop people from feeling they sound more musical


----------



## triod750

Most music takes place below the top actually, so the quality there is of utmost importance.


----------



## Zachik

triod750 said:


> Most music takes place below the top actually, so the quality there is of utmost importance.


I only care about 250 Hz and below   
(just kidding! or am I...)


----------



## L0rdGwyn

I had a listen to the DAC in my main system with the 6E6P-DR in place, I think it sounds pretty darn good, really a step up in terms of clarity and imaging.  I would be surprised if I went back to the 12B4A, but you never know!  It does have a nice euphonic tonality I think.

Gotta work in the AM, so DIY back on hold, to be continued...


----------



## Monsterzero

Zachik said:


> From my experience, often I preferred a worse-measuring piece of gear compared to a better measuring alternative.
> I mean isn't that what tubes is all about?? Solid state measures often better, but is not as much fun or as musical.


When distortion is reduced to near nil 2nd order harmonics are also removed, giving excellent measuring gear a sterile sound.
2nd order harmonics is what tubes inject into our music that we all love and adore.

I picked up a new solid state amp that measures 0.1 distortion, which on paper hasnt been seen in a solid state amp since the 1970s. The damn thing sounds quite tube like, even though on paper it should sound like garbage. 

Probably why I enjoy vintage receivers so much as the 2nd order harmonics havent been stripped away like modern gear has.


----------



## Tjj226 Angel

Monsterzero said:


> When distortion is reduced to near nil 2nd order harmonics are also removed, giving excellent measuring gear a sterile sound.
> 2nd order harmonics is what tubes inject into our music that we all love and adore.
> 
> I picked up a new solid state amp that measures 0.1 distortion, which on paper hasnt been seen in a solid state amp since the 1970s. The damn thing sounds quite tube like, even though on paper it should sound like garbage.
> ...



Maybe yes, maybe no. It all depends. 

The issue here is that ALL forms of distortion is actually bad. 2nd order just so happens to be the least bad sounding distortion.

The catch is, when you try to fix second order distortion, you generally end up creating more higher order distortion, phase angle distortion, IM distortion, or a whole host of other problems.

There are ways of trying to reduce 2nd order harmonic distortion in a more natural way. Sakuma style amplifiers are one such example.


----------



## L0rdGwyn

Here is an FFT of the right channel of the PCM56 DAC with the 6E6P-DR in place, -6dB undithered 1kHz sine wave, THD 0.014%.




Noise floor is generally below -100dB.  The 60Hz and 120Hz noise should improve in the final build with proper grounding and DC regulator heating the output tubes, right now they are on AC.  Given the PSRR of both the DAC and B+ supplies, the 120Hz is not ripple, more likely coupling from 120Hz current pulses through transformer-rectifier-reservoir cap loop.  To say the layout on the protoboard is not ideal would be a huge understatement.  It is also very easy to pick up 60Hz noise and its harmonics from your own home at these levels.  The "quietest" room in my house is upstairs, I didn't feel like dragging the prototype up there just for these measurements.

The degree of THD varies in the four 6E6P-DR I have on hand, namely the degree of H2, as low as 0.0095% in the best one.

Getting a feel for how this DAC is going to be laid out - I think I was very optimistic in how compact I thought I could make it.  It is more likely going to be a full sized component, probably around 4.25" x 11" x 16".  Things start to get very crowded when you put everything on the inside.


----------



## Galapac

Hey @L0rdGwyn, how did that old radio restore turn out?
I remember you getting one awhile back but not sure if you ever posted any pics of it.


----------



## L0rdGwyn

Galapac said:


> Hey @L0rdGwyn, how did that old radio restore turn out?
> I remember you getting one awhile back but not sure if you ever posted any pics of it.



It is on the shelf! Literally.  I finished re-capping / re-resistoring it and it is functional, I also finished cleaning up the chassis.



The last bit of work is the alignment - when I was adjusting one of the RF transformers, the adjustment screw crumbled into pieces.  So now I have to transplant the same transformer from the spare radio I bought for parts, then work on the alignment.  I hit that road bump around the time of my 801A build I just haven't gotten back to it.

I don't have the ideal equipment to do a proper IF / RF alignment, haven't decided what approach I am going to take just yet.  There is a guy in Cleveland who restores vintage audio gear, including radios, so I am considering having him do the alignment after I replace the transformer to save me the time and trouble.


----------



## L0rdGwyn (Sep 20, 2021)

After two recovery days, had the energy to work on some DIY.

I changed the configuration of the output of the DAC - rather than taking the output from the plate of the 6E6P-DR, it was taken from the source of the lower CCS device with the aim of lowering the output impedance.  That was accomplished, along with other performance benefits.

Output impedance was reduced from 1150ohm to 275ohm.

Below is an FFT of the right channel again, 1kHz -6dB undithered sine wave.



THD is the same with slightly higher gain, now with a higher H2 and no H3. Higher order harmonics are now visible since the noise floor is reduced from -110dB to -125dB, all are below -100dB.

I took another sweep of the left channel for comparison, the high frequency rolloff seen before is gone, -0.3dB at 20kHz relative to midband.



Now a flat response from this NOS DAC, not bad.  I wondered if the HF rolloff was a measurement artifact as a result of the higher output impedance prior to the change, but taking the same measurement with the Linear Audio Autoranger (which is essentially a buffer for taking soundcard measurements) resulted in the same HF attenuation.

I believe the sound has benefitted from the change as well, it sounds great!

Pretty far along into the layout now, heater regulator PCB for the 6E6P-DR is designed, getting close to being able to order the chassis.


----------



## Tjj226 Angel

Those higher order harmonics are interesting. Theoretically everything beyond your 3rd order harmonics should be virtually unmeasurable. Getting rid of 7th order harmonics in particular will make a massive difference in sound quality / listener fatigue.


----------



## L0rdGwyn (Sep 21, 2021)

Here's a peek at the completed DC heater regulator PCB.  Getting a well-regulated 6.3VDC from a 6.3VAC winding is a challenge, as you can see it uses both 6.3VAC windings off the mains transformer.  It will supply the power LED as well.  The mains transformer for the tube output stage is rated for 115VAC which helps.  This regulator is essentially ripple free, overkill really, could heat a DHT off of it!  It will maintain regulation down to about 106VAC out of the wall, so no issues with dropout.





Here is where I am headed with the chassis, subject to change of course.  About as minimalist as it gets - all of the components will be mounted on the bottom panel, so no hardware will be visible besides the screws for the top plate.  Dimensions are 4.25" x 11" x 17", it will be in brushed, silver, anodized aluminum with silver feet.  Just a silver power button and low luminosity white power LED on the front panel.  IEC inlet, USB in, and RCA out on the back panel.  That's it!



There are some parts I have on order that I would like to inspect for dimensions in person, so that is going to delay things somewhat, but better safe than sorry.


----------



## triod750

L0rdGwyn said:


> low luminosity white power LED


Loverly - I hate blue LED.


----------



## L0rdGwyn (Sep 21, 2021)

triod750 said:


> Loverly - I hate blue LED.



I'm with you there!  Don't want it to stand out much, more for function.

Side note, I got my 30-pack of TDA1387T, teeny tiny little DACs, so darn cute.



No shortage of these to experiment with.  I think I am going to change my design though - still a small form factor DAC board with SMD parts, but I think I am going to abandon the resistor I/V stage and do something more creative, going to use tube active I/V.  I have a functional schematic using two TDA1387T in parallel per channel with one tube per channel - line level output with a 500ohm output impedance.  Will be larger needing a tube mains transformer, but still quite compact I think.  No timeline on this one, just brainstorming.  Gotta wrap up plans for the PCM56 DAC then build an amplifier.


----------



## triod750

'Guess how many decisions I can make in a second'.   You remind me of Al Di Meola, Paco de Lucia and who was the third guy; guess how many notes I can play in a second.
They were also creative.


----------



## CJG888

John McLaughlin


----------



## L0rdGwyn

Listening to the PCM56 DAC last night and today while working on the layout.  Using my 6A5G amp and some ZMFs.

Gotta enjoy that tube glow now, soon it will be hidden!




I'm really happy with the sound.  Nice detail, soundstage, and clarity, non-fatiguing and smooth.  Will be fun to see how it stacks up to some other fancy tube output DACs.

I finished the interior layout, seen below.  Green are component outlines for the sake of arranging parts.



I am going to use Clarity Cap CMR for the output caps, 3.3uF 400VDC.  That will give a f-3dB point of 1Hz with a 50K load.

I am making another change - given the CCS loads are not dissipating a significant amount of power (due to the 2Vrms voltage swing of the output tubes), I am going to use my smaller form factor CCS PCBs.  The bottom FET on these boards is TO-92-3 package - I will switch to the DN2540 for the bottom device.  It has a higher transconductance than the IXTP08N50D2 at the bias current of the output tubes, as such the output impedance should drop to around 200ohms.

There are actually a few different DAC chips that can be used in this circuit without any changes, all of the following are compatible: PCM56, PCM61, AD1851, AD1860, AD1861.  I'm in no hurry, but at some point I'll probably try some out.  The AD1861 is the most intriguing.  I also have spare PCM56 - seven I think - so it would behoove me to take measurements to find the best stereo pair.

I was going to wait to measure one part in person, but I think it will be fine.  Goal for the day is checking my work, then placing the chassis order.


----------



## L0rdGwyn (Sep 22, 2021)

Took quite a few hours to go through everything all over again, but the DAC chassis order is in.

As I said, it will be in plain / silver brushed anodized aluminum.

Below is the final, didn't bother showing the side panels as they are completely plain.  The vast majority of the machining is on the bottom panel, but it won't be visible obviously.  Included ventilation on the bottom panel to promote airflow around the "hot" components, although nothing in this build gets very hot - the tubes are the hottest thing inside but only dissipating 2.75W, can place a finger on top of them comfortably while the DAC is on and warmed up.





Need to organize a final parts order for a few things, but this was the rate-determining step, so wanted to get the order in.  I have a week off in early October, would be great if I had the chassis by then and could finish the build.  I don't expect it will take long given most everything is already constructed (although I say that every time...).  One thing that is nice about everything being on the bottom plate is I don't have to put the whole chassis together to do a majority of the build - will do 90% with just the bottom plate, which will make getting to hard-to-reach places much easier, then plop the rest on top.


----------



## whirlwind

L0rdGwyn said:


> Took quite a few hours to go through everything all over again, but the DAC chassis order is in.
> 
> As I said, it will be in plain / silver brushed anodized aluminum.
> 
> ...


Done in a day if your heads right


----------



## L0rdGwyn

whirlwind said:


> Done in a day if your heads right



Oh yeah, first day I have off with everything ready it will be done LOL a marathon as usual!


----------



## Monsterzero

Stupid Question of The Day:

Would it be possible to incorporate a "trap door" into the chassis for when the tube needs to be replaced for those of us who are too lazy/ blind to take apart the whole top of the DAC? Or would that be too much work or compromise the sound?


----------



## L0rdGwyn

Monsterzero said:


> Stupid Question of The Day:
> 
> Would it be possible to incorporate a "trap door" into the chassis for when the tube needs to be replaced for those of us who are too lazy/ blind to take apart the whole top of the DAC? Or would that be too much work or compromise the sound?



Well if I were to build a copy of this for someone and they wanted the tube to be accessible, probably the easiest way would be to just have the top plate made with holes for the tubes, then just use taller standoffs on the tag boards so the tubes poke out of the top, if that makes sense.

Oh and these tubes are rated for 10,000 hours!


----------



## Monsterzero

L0rdGwyn said:


> Oh and these tubes are rated for 10,000 hours!


pffft... that would last me a week.


----------



## whirlwind

Monsterzero said:


> pffft... that would last me a week.


----------



## Galapac (Sep 23, 2021)

L0rdGwyn said:


> Well if I were to build a copy of this for someone and they wanted the tube to be accessible, probably the easiest way would be to just have the top plate made with holes for the tubes, then just use taller standoffs on the tag boards so the tubes poke out of the top, if that makes sense.
> 
> Oh and these tubes are rated for 10,000 hours!


I like the standoff idea or a chasis could be designed so it just slides off (a wrap around)  with a fasterner/clip in the back or just one thumb screw, like the old desktop PCs.

Is the top of the DAC going to have vent holes in the top for heat and light to show through?
Is that this portion?


----------



## L0rdGwyn

Galapac said:


> I like the standoff idea or a chasis could be designed so it just slides off (a wrap around)  with a fasterner/clip in the back or just one thumb screw, like the old desktop PCs.
> 
> Is the top of the DAC going to have vent holes in the top for heat and light to show through?
> Is that this portion?



That's actually intake ventilation on the bottom plate, top plate will look like so.



Could spot the tubes through the vents, but I wasn't really prioritizing making the tubes visible since they are on the interior.  The interior layout is optimized for low noise.  I originally had the vents running the full front-to-back length of the top plate, I'm considering going back to that before it goes into production.

There is intake ventilation directly below the tube tag boards on the bottom plate.



If the tubes were to be raised up to poke out of the top, would make some changes to the top ventilation pattern.


----------



## L0rdGwyn

After @Galapac 's question and looking it over again, I went back to full front-to-back ventilation on the top panel.  Widened the slots from 1/8" to 1/6".  Did the same on the bottom panel and increased ventilation there as well.

Now it's perfect!  Well, until I look at it again.  Night shift starting tonight, so no DIY for a few days.


----------



## tubebuyer2020

@L0rdGwyn are designs you are using all self-biasing? I was recently thinking of using a VU-meter for visualising transistor bias in a guitar pedal. It kind of works on a breadboard with a resistor in series, but I have concerns about precision and the idea in general. I also have a headphone amp with adjustable bias where you set a jumper and turn a trimpot until a LED (per channel) turns off.


----------



## L0rdGwyn

tubebuyer2020 said:


> @L0rdGwyn are designs you are using all self-biasing? I was recently thinking of using a VU-meter for visualising transistor bias in a guitar pedal. It kind of works on a breadboard with a resistor in series, but I have concerns about precision and the idea in general. I also have a headphone amp with adjustable bias where you set a jumper and turn a trimpot until a LED (per channel) turns off.



Hey @tubebuyer2020 - these days I like to stick to fixed bias when I can.  The tubes in the DAC are fixed bias via battery.  I am a big fan of battery bias, the tricky aspect is a DC blocking component is needed on the input - it works really well in the output stage of this DAC given there is a step up transformer between the DAC output and tube grid.

If using autobias in a gain stage, like in a two-stage amplifier, and I can afford to have a slightly higher output impedance from that stage, I prefer to use an active load (CCS or gyrator) and leave the cathode resistor unbypassed.  Usually the goal here is to keep a bypass capacitor out of the signal path if possible.  The quality of the unbypassed resistor becomes important here as it does have an audible effect on the sound.  I prefer carbon film.

And very cool, I didn't know you dabbled in DIY.  What is your amp with the adjustable bias?


----------



## tubebuyer2020 (Sep 24, 2021)

L0rdGwyn said:


> ...
> And very cool, I didn't know you dabbled in DIY.  What is your amp with the adjustable bias?



Thank you for the explanation - I have a lot to learn! No, I am only starting with some audio effects for now - one step at a time. The adjustable bias amp is one of Garage1217 ones (schematic is here http://www.mediafire.com/file/06g72zyu2d32gp6/Sunrise_3.1_schematic.pdf/file).


----------



## leftside

@L0rdGwyn I ended up ordering one of these. To cut a long story short - I found a distributor here in Canada.
http://www.tsakiridis-devices.com/test_evaluation_daedalos.html

I'll report back... maybe create a thread on here about tube testers? I still wouldn't mind getting a vintage one as well.


----------



## Zachik

leftside said:


> @L0rdGwyn I ended up ordering one of these. To cut a long story short - I found a distributor here in Canada.
> http://www.tsakiridis-devices.com/test_evaluation_daedalos.html


Looks interesting... Please report back once you get it and play with it 
BTW, how expensive are they?


----------



## whirlwind

Keenan, was up your way Saturday evening. The Jacobs Pavilion At Nautica.

Great place and I will go back. Right around the corner from here we had a couple of cock tails at Cleveland's oldest bar Harbor Inn Cafe 

Great evening of music...The Allman Betts Band and Blackberry Smoke


----------



## leftside

Zachik said:


> Looks interesting... Please report back once you get it and play with it
> BTW, how expensive are they?


I will. 1600 euros is the list price.


----------



## L0rdGwyn

leftside said:


> @L0rdGwyn I ended up ordering one of these. To cut a long story short - I found a distributor here in Canada.
> http://www.tsakiridis-devices.com/test_evaluation_daedalos.html
> 
> I'll report back... maybe create a thread on here about tube testers? I still wouldn't mind getting a vintage one as well.



Excellent!  Looks to be a nice tester, and built like a tank, looking forward to your thoughts on it.  It's actually quite odd to think there isn't a tube tester thread yet, I would be happy to contribute if you were to make one.


----------



## L0rdGwyn

whirlwind said:


> Keenan, was up your way Saturday evening. The Jacobs Pavilion At Nautica.
> 
> Great place and I will go back. Right around the corner from here we had a couple of cock tails at Cleveland's oldest bar Harbor Inn Cafe
> 
> Great evening of music...The Allman Betts Band and Blackberry Smoke



Awesome Joe, it's a nice outdoor venue right on the river, glad you had a good time!  Cleveland has a great bar scene, lots of great things actually, but we will continue the narrative of it being one of the worst places to live in America, keeps the cost of living low


----------



## L0rdGwyn (Sep 28, 2021)

I decided it was time to clean up my workbench / DIY crap today.  Went through everything to get an inventory of parts, did a bunch of reorganization, etc.  Capped that off with listening to my DAC prototype with my 841 amplifier.  That amp has been lying dormant for months!  I simply have too many amplifiers.  Turns out it still sounds pretty darn good, even better than I remember now paired with a nice DAC.




What inspired me to clean is the feedback I have gotten so far on my OTL design which is on a short tour, it has been very positive.  Hopefully that continues, if so I anticipate it will be greenlighted very soon, so I needed to make things nice and neat.

Otherwise, my DAC chassis is in production, in fact the machining is probably done at this point and it will be sent for anodization soon, very pumped about that.

So I am turning my attention to the next amplifier I am working on in the meantime, which will be an interstage transformer-coupled, fixed bias, type 45 headphone amplifier.  I have a majority of the parts, need to place some final orders and prototype, should be an interesting build.


----------



## Galapac

L0rdGwyn said:


> I decided it was time to clean up my workbench / DIY crap today.  Went through everything to get an inventory of parts, did a bunch of reorganization, etc.  Capped that off with listening to my DAC prototype with my 841 amplifier.  That amp has been lying dormant for months!  I simply have too many amplifiers.  Turns out it still sounds pretty darn good, even better than I remember now paired with a nice DAC.
> 
> 
> 
> ...


If you need to offload any amps let me know. 😉


----------



## Monsterzero

L0rdGwyn said:


> my OTL design which is on a short tour


----------



## whirlwind

L0rdGwyn said:


> Awesome Joe, it's a nice outdoor venue right on the river, glad you had a good time!  Cleveland has a great bar scene, lots of great things actually, but we will continue the narrative of it being one of the worst places to live in America, keeps the cost of living low


Much safer than Columbus, Ohio these days and it has Play House Square and five historical theaters in that square....love that place!


----------



## L0rdGwyn

whirlwind said:


> Much safer than Columbus, Ohio these days and it has Play House Square and five historical theaters in that square....love that place!



Playhouse Square is excellent!  Lots of things I love here, but for me personally, Cleveland's biggest asset is the Cleveland Orchestra.  I go to Blossom Music Center in the summer to see them play outdoors (think I went five or six times this year), then back to Severance Hall this winter  having a world class orchestra within 15 minutes drive of your home is something special, the music will bring you to tears   

Then there's the Cleveand Museum of Art, another top US institution, which is free, the Cleveland Metroparks, Cuyahoga Valley National Park, Holden Arboretum, Cleveland's excellent library system, excellent hospital system (might be a little biased on that one), and let us not forget, the Cleveland Browns!!! LOL.  I can legitimately say that now.


----------



## whirlwind (Sep 28, 2021)

L0rdGwyn said:


> Playhouse Square is excellent!  Lots of things I love here, but for me personally, Cleveland's biggest asset is the Cleveland Orchestra.  I go to Blossom Music Center in the summer to see them play outdoors (think I went five or six times this year), then back to Severance Hall this winter  having a world class orchestra within 15 minutes drive of your home is something special, the music will bring you to tears
> 
> Then there's the Cleveand Museum of Art, another top US institution, which is free, the Cleveland Metroparks, Cuyahoga Valley National Park, Holden Arboretum, Cleveland's excellent library system, excellent hospital system (might be a little biased on that one), and let us not forget, the Cleveland Browns!!! LOL.  I can legitimately say that now.


Feels great not to be the laughing stock of football...we willingly pass that torch to Jacksonville or Jets   

I have been to Blossom many times over the years, but never to see the Cleveland Orchestra


----------



## tubebuyer2020 (Sep 28, 2021)

L0rdGwyn said:


> Excellent!  Looks to be a nice tester, and built like a tank, looking forward to your thoughts on it.  It's actually quite odd to think there isn't a tube tester thread yet, I would be happy to contribute if you were to make one.



It would be interesting to know, if there are any affordable options in that area worth considering like Little Imp Tube Tester or Orange Valve Tester, or maybe this unfortunately *named newcomer:

https://www.ebay.co.uk/itm/234188446152
https://www.facebook.com/pg/Dummy-Tube-Tester-User-Group-1804152399665939/posts/?ref=page_internal





* Can you imagine, listing a tube on eBay "Tested as NOS on my Dummy Tube Tester"


----------



## Xcalibur255

L0rdGwyn said:


> So I am turning my attention to the next amplifier I am working on in the meantime, which will be an interstage-coupled, fixed bias, type 45 headphone amplifier.  I have a majority of the parts, need to place some final orders and prototype, should be an interesting build.


So, my amp?  Interesting.  

Though I'm guessing you won't be using the C3g as a driver like mine has, maybe a 6J5?  Rectification will probably be different too, not the 6BY5 disaster I signed myself up for.  It might be interesting to use the "classic" option here:  the 80/5Y3.  That's what I wish I had done.


----------



## L0rdGwyn

Xcalibur255 said:


> So, my amp?  Interesting.
> 
> Though I'm guessing you won't be using the C3g as a driver like mine has, maybe a 6J5?  Rectification will probably be different too, not the 6BY5 disaster I signed myself up for.  It might be interesting to use the "classic" option here:  the 80/5Y3.  That's what I wish I had done.



Oh does your amplifier use interstage transformers?  I hadn't considered the similarities, really just set out to make my best 45 headphone amp.

This amplifier will use custom nickel-core interstages from Intact Audio, custom multi-tap headphone output transformers from Electra-Print (300ohm, 120ohm, 32ohm taps).  Drivers are the same 6E6P-DR going in my DAC, the reason I had them on hand in the first place.  SS rectified and regulated B+ and bias supplies, Rod Coleman filament regulators.

This one isn't for me, it is being built for a friend, a certain friend who also makes bespoke wooden headphones.


----------



## Xcalibur255

Oh, I didn't pick up that interstage meant transformer interstage for some reason.  No, mine is cap coupled.

Pretty cool.  I imagine your friend could have an amp built by pretty much anybody he wanted to.  You'll have to take advantage of the opportunity on this one and get a huge chromed L0rdGwyn badge to slap on the front of it for publicity.


----------



## L0rdGwyn

Xcalibur255 said:


> Oh, I didn't pick up that interstage meant transformer interstage for some reason.  No, mine is cap coupled.
> 
> Pretty cool.  I imagine your friend could have an amp built by pretty much anybody he wanted to.  You'll have to take advantage of the opportunity on this one and get a huge chromed L0rdGwyn badge to slap on the front of it for publicity.



I was thinking I would just have the chassis made in the likeness of my avatar so there is no question LOL JK of course, but I think it will look very nice with what I have in mind.


----------



## Zachik

Your friend is an awesome dude!! Missed him (and his lovely wife) at CanJam couple days ago...


----------



## L0rdGwyn

Zachik said:


> Your friend is an awesome dude!! Missed him (and his lovely wife) at CanJam couple days ago...



Well hey, this amp might be coming to a post-COVID CanJam near you down the road, perhaps in the year 2029 lol.


----------



## whirlwind

Zachik said:


> Your friend is an awesome dude!! Missed him (and his lovely wife) at CanJam couple days ago...



Yes he is, and they are running a successful business in hard times.
They deserve it.


----------



## L0rdGwyn

I think a lot of companies are still being precautious and don't want to put their employees at risk, even if it means losing a sale, it's an admirable thing to do.


----------



## L0rdGwyn

Just placed the final parts order for the ZMF 45 amp.  Since the cat's out of the bag, here are the major components going in.

Vintage Amphenol Ux4 and 9-pin noval sockets
Vintage fluted bakelite knob (will need to polish that baby up a little bit)
Simpson DC milliammeters
Hammond dual-bobbin filament transformers (for the 45 filaments)
Lundahl LL1649 mains transformer and matching shield
Intact Audio nickel-core interstage transformers, custom for this design
ClarityCap TC 2 series film caps feeding the interstage transformers
Electra-Print low IMD output transformers, multitap for various headphone impedances (300ohm, 120ohm, 32ohm)




I won't bore with all of the PCBs I've made, I'll just say that the input tube heaters, 45 filaments, B+, and bias supplies will all be regulated.

And the tubes.



I'm excited to start building, I think this will be a very special amplifier.


----------



## bcowen

L0rdGwyn said:


> Just placed the final parts order for the ZMF 45 amp.  Since the cat's out of the bag, here are the major components going in.
> 
> Vintage Amphenol Ux4 and 9-pin noval sockets
> Vintage fluted bakelite knob (will need to polish that baby up a little bit)
> ...


Wait...the 'ZMF' 45 amp?  You can 't let a cat just part way out of the bag.  That would defy physics.


----------



## L0rdGwyn

L0rdGwyn said:


> This one isn't for me, it is being built for a friend, a certain friend who also makes bespoke wooden headphones.



Here ya go @bcowen 

And here is an actual cat for good measure.



Trust me, this one isn't defying any laws of physics, physics has her very well planted to the ground.


----------



## bcowen

L0rdGwyn said:


> Here ya go @bcowen
> 
> And here is an actual cat for good measure.
> 
> ...


OK, so I'm a little slow.  But looking stupid was worth it for a cool cat picture.


----------



## Monsterzero

whirlwind said:


> Great evening of music...The Allman Betts Band and Blackberry Smoke





whirlwind said:


> Great evening of music...The Allman Betts Band and Blackberry Smoke


Blackberry Smoke makes every evening great! My fav modern band.

#spreadthesmoke


----------



## whirlwind

Monsterzero said:


> Blackberry Smoke makes every evening great! My fav modern band.
> 
> #spreadthesmoke



First time seeing them live for me....Charlie Starr is a great front man.
At the end The Allman Betts band joined them on stage and they all jammed to Whipping Post.
Blackberry Smoke was on stage for 3 hours total as they played with both other bands besides their own 2 hour set.
I need more days like that


----------



## Xcalibur255

Definitely got the right meters there Keenan.  Thumbs up.  They're exactly the same as the pair I was trying to get sent to you aside from the scale.  I really wish the meters on my amp were 0-50 scale.  Since the amp originally had a 2A3 mode I bought 0-100 meters to accomodate the 60mA current of a 2A3 but then that whole feature ended up getting removed from the amp.

Gauges that have unnecessarily large scales are kind of a general pet peeve of mine actually.  Like how ALL cars have 0-160 MPH speedometers starting about 20 years ago.  Why?


----------



## raindownthunda

Xcalibur255 said:


> Definitely got the right meters there Keenan.  Thumbs up.  They're exactly the same as the pair I was trying to get sent to you aside from the scale.  I really wish the meters on my amp were 0-50 scale.  Since the amp originally had a 2A3 mode I bought 0-100 meters to accomodate the 60mA current of a 2A3 but then that whole feature ended up getting removed from the amp.
> 
> Gauges that have unnecessarily large scales are kind of a general pet peeve of mine actually.  Like how ALL cars have 0-160 MPH speedometers starting about 20 years ago.  Why?


What is the purpose of the mA meters? Do different mA values provide meaningful information?


----------



## L0rdGwyn (Sep 29, 2021)

Xcalibur255 said:


> Definitely got the right meters there Keenan.  Thumbs up.  They're exactly the same as the pair I was trying to get sent to you aside from the scale.  I really wish the meters on my amp were 0-50 scale.  Since the amp originally had a 2A3 mode I bought 0-100 meters to accomodate the 60mA current of a 2A3 but then that whole feature ended up getting removed from the amp.
> 
> Gauges that have unnecessarily large scales are kind of a general pet peeve of mine actually.  Like how ALL cars have 0-160 MPH speedometers starting about 20 years ago.  Why?



Thanks, T.  The "rectangular" series (which these are) have that vintage look but they are actually new production!  Think this design has been made by Simpson since the beginning, I think yours are vintage?  There was a lead time of a few weeks, but not too bad.

Totally makes sense that you would have gone with the 100mA meters for the 2A3, but since this amp will be 45 only, 0-50mA is perfect.  The tubes will bias at around 34mA, but could be reduced to 30mA or so for tube longevity.



raindownthunda said:


> What is the purpose of the mA meters? Do different mA values provide meaningful information?



This is a fixed bias design, meaning the bias of the tubes can and must be manually adjusted via a potentiometer that will mount on top of the chassis.  The milliammeters are in series with the tube cathodes, so they indicate the bias current of the tubes.  The scale of the meters isn't critical, but it's good to use one of appropriate range so smaller adjustments can be made to the bias point.


----------



## Tjj226 Angel

Xcalibur255 said:


> So, my amp?  Interesting.
> 
> Though I'm guessing you won't be using the C3g as a driver like mine has, maybe a 6J5?  Rectification will probably be different too, not the 6BY5 disaster I signed myself up for.  It might be interesting to use the "classic" option here:  the 80/5Y3.  That's what I wish I had done.



or my first attempt at a 45 for @johnjen. We ended up finding out that the direct coupling sounded a lot better.

I also wouldn’t do tube rectification for a 45. The 45 is so detailed and airy that the voltage sag you can run into with tube rectification kind of detracts from the 45 sound.

There are more exotic ways to rectify a circuit that I have yet to play with that would be even better than either a tube or a diode, such as mosfet rectification. You can even use triodes as rectifiers but idk if there is any real advantage to it


----------



## whirlwind

L0rdGwyn said:


> This is a fixed bias design, meaning the bias of the tubes can and must be manually adjusted via a potentiometer that will mount on top of the chassis.  The milliammeters are in series with the tube cathodes, so they indicate the bias current of the tubes.  The scale of the meters isn't critical, but it's good to use one of appropriate range so smaller adjustments can be made to the bias point.


Nice.  You can run them at the max or back off if you like the sound....maybe tube life extends ?


----------



## Xcalibur255 (Sep 30, 2021)

L0rdGwyn said:


> Thanks, T.  The "rectangular" series (which these are) have that vintage look but they are actually new production!  Think this design has been made by Simpson since the beginning, I think yours are vintage?  There was a lead time of a few weeks, but not too bad.
> 
> Totally makes sense that you would have gone with the 100mA meters for the 2A3, but since this amp will be 45 only, 0-50mA is perfect.  The tubes will bias at around 34mA, but could be reduced to 30mA or so for tube longevity.



Yes the ones I had were actual NOS, probably made in the 40's.  Looked brand new still.  I especially love the clover shaped pointers on the needle, everything from that time period had such great design.  These were actually 0-75mA scale in increments of 15.  Would have worked well for a 2A3 design.

You're going to run 250 plate volts then I assume?  Mine is setup for 275 (which I don't like anymore, all it's really doing is wearing tubes out faster) so ideal bias for me is 36mA but I usually de-bias a bit to 34 when I have my precious globes in and only run the ST tubes at 36.  I actually can hear the difference, but it's subtle.  There is a general feeling of a hint of veil when you lower the bias.


----------



## Xcalibur255

Tjj226 Angel said:


> or my first attempt at a 45 for @johnjen. We ended up finding out that the direct coupling sounded a lot better.
> 
> I also wouldn’t do tube rectification for a 45. The 45 is so detailed and airy that the voltage sag you can run into with tube rectification kind of detracts from the 45 sound.
> 
> There are more exotic ways to rectify a circuit that I have yet to play with that would be even better than either a tube or a diode, such as mosfet rectification. You can even use triodes as rectifiers but idk if there is any real advantage to it


So the 6BY5s ended up producing so much high frequency whine that I asked Glenn to make HEXFRED diode adapters to replace them back in 2014.  They have literally never been taken out of the amp since the day they went in, and they also improved the sound of the amp.  No downside at all except the amp now effectively has no tube glow, what with the C3g being shielded and the 45 filament doesn't exactly produce a light show.


----------



## Xcalibur255

whirlwind said:


> Nice.  You can run them at the max or back off if you like the sound....maybe tube life extends ?


45 tubes are tough as nails.  You can run them over max dissipation and they still last a long time.  I personally prefer the sound of high bias on these tubes.  A well designed 45 amp has a very fast and detailed sound to it and running the tubes under bias just reduces those strengths and makes everything a bit softer.  You don't want a "soft" 45 amp because then you more or less have a 300B without the big bloomy wall of sound experience people like about 300B.  The 45 flavor is more about holographic precision and focus while still never sounding etched or forced.  Folks who want a romantic tube flavor won't find it in the 45, at least not in a good design.


----------



## L0rdGwyn

whirlwind said:


> Nice.  You can run them at the max or back off if you like the sound....maybe tube life extends ?



Yup, can back off a bit running them at a cooler bias which will extend their life.



Xcalibur255 said:


> Yes the ones I had were actual NOS, probably made in the 40's.  Looked brand new still.  I especially love the clover shaped pointers on the needle, everything from that time period had such great design.  These were actually 0-75mA scale in increments of 15.  Would have worked well for a 2A3 design.
> 
> You're going to run 250 plate volts then I assume?  Mine is setup for 275 (which I don't like anymore, all it's really doing is wearing tubes out faster) so ideal bias for me is 36mA but I usually de-bias a bit to 34 when I have my precious globes in and only run the ST tubes at 36.  I actually can hear the difference, but it's subtle.  There is a general feeling of a hint of veil when you lower the bias.



Very cool.  And yes, 250V bias, really don't need to eek out that last 0.25W for a headphone amp.  Not sure if Zach will grab some globes, but if he does, want those to have a nice long life.


----------



## Xcalibur255

EML makes a limited edition 45 Mesh Globe, I think TubesUSA might still have some.  I've never had a cool grand just lying around to be able to buy a pair sadly, but every person who has bought them says they're worth it and genuinely better than NOS tubes.


----------



## L0rdGwyn

Xcalibur255 said:


> EML makes a limited edition 45 Mesh Globe, I think TubesUSA might still have some.  I've never had a cool grand just lying around to be able to buy a pair sadly, but every person who has bought them says they're worth it and genuinely better than NOS tubes.



I've heard really good things about the EML 45s myself, some say they are better than the NOS globes.  For looks and swag though, you can't beat those NOS globes!  My girlfriend uses my 45 amp in the bedroom more than I do, so I put the globes away lol ST Sylvanias it is for now.  At some point I am going to overhaul that amplifier.


----------



## bcowen

L0rdGwyn said:


> I've heard really good things about the EML 45s myself, some say they are better than the NOS globes.  For looks and swag though, you can't beat those NOS globes! * My girlfriend uses my 45 amp in the bedroom* more than I do, so I put the globes away lol ST Sylvanias it is for now.  At some point I am going to overhaul that amplifier.


I'm gonna leave that one alone.


----------



## Zachik

L0rdGwyn said:


> At some point I am going to overhaul that amplifier.


If it ain't broken, don't..... Nevermind - who am I kidding?! 
What are you going to improve in the 45 amp? Asking for a curious friend...


----------



## L0rdGwyn

Zachik said:


> If it ain't broken, don't..... Nevermind - who am I kidding?!
> What are you going to improve in the 45 amp? Asking for a curious friend...



It's a parafeed design with CCS loads on the 45 output.  At some point I am likely going to switch to a choke load in place of the CCS and direct-couple the input and output stages.  Right now they are cap-coupled, choke load is a prereq for the direct-couple though.  I might consider changing the input tubes as well, right now they are 6N7 or 6J5, but haven't gotten that far.  I'll likely regulate the power supply too, right now it is passive.  Those are the major things!


----------



## Xcalibur255

I wanted to do direct stage coupling on my amp but for some reason Glenn did not and was pretty opaque as to why so I let it go.  I do recall a mention of their not being room for any chokes in the chassis.  It's a considerably larger chassis than the one you used for your 45 so you can make them fit mine should accomodate it as well I would think.


----------



## L0rdGwyn (Oct 1, 2021)

Xcalibur255 said:


> I wanted to do direct stage coupling on my amp but for some reason Glenn did not and was pretty opaque as to why so I let it go.  I do recall a mention of their not being room for any chokes in the chassis.  It's a considerably larger chassis than the one you used for your 45 so you can make them fit mine should accomodate it as well I would think.



The tricky aspect of doing direct coupling is it requires a significantly higher B+.  The reason - rather than the output tube grid being at ground potential, as in cathode bias, or biased negatively by a dedicated bias supply, as in fixed bias, it is at a positive potential equal to the input tube's plate voltage.  You still need to maintain a negative grid-to-cathode voltage on the output tube, so that means you need to jack up the cathode voltage to whatever positive voltage is placed on the grid by the input tube PLUS the bias voltage.

For the 45, say the input tube is biased with 150V on the plate, meaning the 45 has 150V on its grid.  You still need -50V grid-to-cathode, so the cathode needs to be 200V above ground (50V + 150V).  Okay, so 150V on the grid, 200V on the cathode.  But we still need 250V plate to cathode to properly bias the 45.  So you are looking at a B+ of 250V + 200V = 450V plus whatever is dropped across the output transformer primary DC resistance or plate choke (in parafeed) as opposed to 250-300V of a non-direct-coupled 45 design.

So that's a design challenge, can't say why Glenn wasn't up to it though, his 10Y-300B monoblocks are direct-coupled, and that's MUCH crazier lol as you can imagine when doing the same but at 300B voltages.

Fortunately, in my 45 parafeed amp, I needed a lot of voltage headroom to use CCS rather than chokes to load the 45, so the custom mains transformer is actually perfectly suited for a choke loaded direct-coupled 45 parafeed amp.


----------



## L0rdGwyn (Oct 1, 2021)

I've been doing a little DIY before work, got my DC heater regulator up and running.  Need to make one change to the layout for stability, but with that change all is functioning as intended.  Will use this reg for the tube heaters in both my PCM56 DAC and the ZMF 45 amp, although there are some minors differences between the two based on mains transformer heater winding specs.




Essentially ripple free, buried in the RF noise picked up by my scope.



After tonight I am off for nine days, so will get some real work done on the 45 amp.  Maybe I will even be able to build my DAC if I get the chassis in that span of time.


----------



## bpiotrow13

Xcalibur255 said:


> The 45 flavor is more about holographic precision and focus while still never sounding etched or forced. Folks who want a romantic tube flavor won't find it in the 45, at least not in a good design.


Very true i own a 45 tube amp (Ayon Ha3) and use with verite open. Seems to be really good pairing. My VO's are brand new so needs burning in but even now sound really nice with 45'.

Fingers crossed for ZMFs 45 amp. Will it be comercially available?


----------



## L0rdGwyn

bpiotrow13 said:


> Very true i own a 45 tube amp (Ayon Ha3) and use with verite open. Seems to be really good pairing. My VO's are brand new so needs burning in but even now sound really nice with 45'.
> 
> Fingers crossed for ZMFs 45 amp. Will it be comercially available?



TBD on that front.  There is potential to offer some iteration of this amplifier.  As this one is being built though, given the quality of the components, it would be very, very expensive.  Some circuit changes could be made to bring down the price.  Can't commit to it right now, but we will see.


----------



## L0rdGwyn (Apr 18, 2022)

**THIS AMPLIFIER IS NO LONGER FOR SALE, sorry :/*

The time has come to release my OTL amplifier.

I wanted to name the amplifier after something of personal significance, given the time in my life when this amplifier was developed, it will be called the *Airmid* after the Gaelic goddess of healing and resurrection.

The price is $2,600 USD.

Here is a photo of the amplifier with the stock tubes, however feet have been added in the final build.  I will post additional photos when the amplifier is back from its tour.




Here is a list of the main features of the amp:

Pair 6J5 / 6C5 input tubes – equivalents like 7A4 can be used with adapters
Pair of 6AS7G / 6080 / 5998 / 421A / 7236 / 7802 output tubes
Stock tubes are Russian 6S2S (6J5 equivalent) and 6H13C (6AS7G equivalent) – there will be a discount if the buyer does not want stock tubes included
HEXFRED diode rectified dual mono power supply
30-second built-in time delay and soft start, allowing all tube heaters to fully warm before application of B+
Separate high-voltage super regulators for each channel, the topology of which was first shared with me by @A2029 of 1101 Audio.  I credit him with launching my own interest and exploration of voltage regulator design which will be prominently featured in my work going forward.  Please check out 1101 Audio’s excellent amplifier line as well 
Active loading of both 6J5 inputs and 6AS7G outputs for highest detail retrieval, lowest distortion and noise
Signal path free of electrolytic capacitors for the highest degree of clarity and transparency
Large ClarityCap film output capacitors allowing for use of low impedance headphones with good low-frequency extension
50ohm output impedance with 6AS7G / 6080; 30ohm output impedance with 5998 / 421A
Powder-coated or anodized aluminum chassis courtesy of Landfall Systems
In terms of ordering, Head-Fiers can private message me and we can talk further details.  I'm very happy and excited to share something I've made on Head-Fi finally!  I'm not sure what the demand will be, unlikely I will be able to keep up with high volume if it comes to it, but I will do my best.

There is a forthcoming review from @Monsterzero .  @zach915m and the peeps at ZMF also spent time with the amplifier, so he may share some thoughts as well.


----------



## Monsterzero

Since the cat is officially out of the bag, here are a couple photos ive taken of Airmid. Note the Airmid has a considerably larger footprint vs.  the GOTL and is nearly the same size as my TRP.


----------



## chrisdrop

L0rdGwyn said:


> The time has come to release my OTL amplifier.
> 
> I wanted to name the amplifier after something of personal significance, given the time in my life when this amplifier was developed, it will be called the *Airmid* after the Gaelic goddess of healing and resurrection.
> 
> ...


Looks fab. Well done.


----------



## bpiotrow13

We are waiting for the reviews than. Any indication when we can expect it?


----------



## raindownthunda (Oct 3, 2021)

L0rdGwyn said:


> The time has come to release my OTL amplifier.
> 
> I wanted to name the amplifier after something of personal significance, given the time in my life when this amplifier was developed, it will be called the *Airmid* after the Gaelic goddess of healing and resurrection.
> 
> ...


Congrats Keenan! It’s been a blast following your DIY journey. This is a huge milestone! Can’t wait to hear impressions from trusted ears on the forum. Also what a perfect name. Music can be such a great way to heal and recover from the trials and tribulations of life. It will surely be special knowing your creation will be “amplifying the healing” for those fortunate enough to acquire one!


----------



## Monsterzero

bpiotrow13 said:


> We are waiting for the reviews than. Any indication when we can expect it?


I should have the review prepped, filmed and uploaded on my Youtube channel within the next 7-14 days. I will post the review in this thread.


----------



## leftside

L0rdGwyn said:


> The time has come to release my OTL amplifier.
> 
> I wanted to name the amplifier after something of personal significance, given the time in my life when this amplifier was developed, it will be called the *Airmid* after the Gaelic goddess of healing and resurrection.
> 
> ...


Congratulations! It's amazing how far you've come in such a short period of time.


----------



## L0rdGwyn

Thanks everyone!  I really appreciate the kind words.  Looking forward to getting the Airmid out into the wild.

In other news, sounds like my DAC chassis will ship tomorrow, so looks like I will be able to build it before the end of the week


----------



## A2029

L0rdGwyn said:


> The time has come to release my OTL amplifier.
> 
> I wanted to name the amplifier after something of personal significance, given the time in my life when this amplifier was developed, it will be called the *Airmid* after the Gaelic goddess of healing and resurrection.
> 
> ...



Congrats Keenan on the launch of Airmid! Looks fantastic!


----------



## whirlwind

L0rdGwyn said:


> The time has come to release my OTL amplifier.
> 
> I wanted to name the amplifier after something of personal significance, given the time in my life when this amplifier was developed, it will be called the *Airmid* after the Gaelic goddess of healing and resurrection.
> 
> ...



Congrats Keenan. 

A job very well done.


----------



## carlman14

This is really cool, Keenan! Your progress is inspiring. It seems like yesterday you were just starting to fiddle around with your bottlehead crackatwoa!


----------



## L0rdGwyn

carlman14 said:


> This is really cool, Keenan! Your progress is inspiring. It seems like yesterday you were just starting to fiddle around with your bottlehead crackatwoa!



Thanks, Carl!  Yeah it has been quite a journey.


----------



## Zachik

Looking forward to (and fearing) the review by @Monsterzero 
I know he is going to compare to his GOTL (which I also own).

Grabbing a notebook and pen, start writing 500 times: "I do not need yet another amp"...


----------



## triod750

Zachik said:


> Looking forward to (and fearing) the review by @Monsterzero
> I know he is going to compare to his GOTL (which I also own).
> 
> Grabbing a notebook and pen, start writing 500 times: "I do not need yet another amp"...


You always need just one more and you know this. Just one more...


----------



## whirlwind

Zachik said:


> Looking forward to (and fearing) the review by @Monsterzero
> I know he is going to compare to his GOTL (which I also own).
> 
> Grabbing a notebook and pen, start writing 500 times: "I do not need yet another amp"...


In the words of Tom Petty..."Too Much Ain't Enough"


----------



## Zachik

triod750 said:


> You always need just one more and you know this. Just one more...


I know!



whirlwind said:


> In the words of Tom Petty..."Too Much Ain't Enough"


My limitation at this point is my rack space. No room for a 3rd rack (I have a giant one where all the amps live, and a baby one for my music server, NAS, and couple other components).
Tube amps take a ton of space... GOTL and 6EL3N amps already take a disproportional vertical space in my giant rack...

Maybe I should move to a house... $2600 for the amp + $1.3M ~ $1.5M for a house (in my area)... hmmm......


----------



## whirlwind

Zachik said:


> I know!
> 
> 
> My limitation at this point is my rack space. No room for a 3rd rack (I have a giant one where all the amps live, and a baby one for my music server, NAS, and couple other components).
> ...


Ouch.


----------



## L0rdGwyn (Oct 4, 2021)

Zachik said:


> Looking forward to (and fearing) the review by @Monsterzero
> I know he is going to compare to his GOTL (which I also own).
> 
> Grabbing a notebook and pen, start writing 500 times: "I do not need yet another amp"...



We'll see how they stack up!  Looking forward to it myself.

With my DAC chassis shipping today, I broke down the prototype on my protoboard to get started on the 45 amp prototype.

Before I did that, I made the change I mentioned on the output stage loading, swapped in the DN2540 as the bottom FET using my small form factor CCS PCBs.  Running the stage as a hybrid mu follower, I expected further improvement in output impedance and that was the case, measured at 135ohm.




A few final random parts going in, got some nice plain silver feet and silver Amphenol RCA connectors to go with the silver chassis.  I will be using ClarityCaps TOTL CMR series caps on the output.



Time to get to work on the 45 amp prototype!


----------



## zach915m

I got a chance to have the "Airmid" in house for a week or so - and I without a doubt can highly recommend it for ZMF's.    I know @L0rdGwyn told me that it can change a bit in impedance output with different tubes, but the two sets I tried in it (6080 Amperex and the stock tubes) both sounded fantastic.  

The one thing that that Airmid does right that stands it in front of the pack - is that is has a holographic, dimensional and forward mid range, that is coupled with resolution and low end weight.  All of this works together in harmony to produce a cohesive and exciting sound, and I didn't have to work hard at tube rolls to find it.  None of these strengths gets in the way of each other - which is also rare!  While you can get to that spot with other amps many times, it can be after spending a lot on tubes and/or find the right headphone combo.  The Airmid did this throughout the ZMF line-up really well, and quickly was a shop favorite among our other audiophile staff members.  

We had the amp lined up with the Euforia and Glenn OTL.  And while I definitely can never get into comparisons that say "one is better than the other" I can without a doubt recommend the Airmid among those amps, and I think out of the three, it's the easiest one to achieve a "ceiling" of sound that performs on the highest level of OTL amps.  

So anyways - @L0rdGwyn is already building me a 45 based amp that I'm super excited for that he has mentioned here, if he wasn't, I'd already have put an order in for one of these as it's just that good!  I really couldn't get over the "segmenting" of sounds that adds to the "3-d-ish-ness" of our headphones.  It just makes you want to keep listening.


----------



## Zachik

zach915m said:


> We had the amp lined up with the Euforia and Glenn OTL. And while I definitely can never get into comparisons that say "one is better than the other" I can without a doubt recommend the Airmid among those amps, and I think out of the three, it's the easiest one to achieve a "ceiling" of sound that performs on the highest level of OTL amps.


Zach - can you elaborate a bit on the Airmid vs. GOTL?
Also, did you use the same tubes for both amps in the comparison, to make it more apples-to-apples? 
(I know the GOTL uses 1 x 6SN7 vs. Airmid 2 x 6J5, but with an adapter it is easy to use 2 x 6J5 with the GOTL...)


----------



## Monsterzero (Oct 5, 2021)

Zachik said:


> can you elaborate a bit on the Airmid vs. GOTL?


I compared them using the same rolls. There are some very obvious differences between the two.
I have used: 
Kenrad 6j5+Bendix 6080
Sylvania green label metal base+ 5998
Tung Sol black plate+ 5998
GEC L63+ 5998


----------



## Zachik

Monsterzero said:


> I compared them using the same rolls. There are some very obvious differences between the two.


Awesome!  Something to look forward to...


----------



## L0rdGwyn

zach915m said:


> I got a chance to have the "Airmid" in house for a week or so - and I without a doubt can highly recommend it for ZMF's.    I know @L0rdGwyn told me that it can change a bit in impedance output with different tubes, but the two sets I tried in it (6080 Amperex and the stock tubes) both sounded fantastic.
> 
> The one thing that that Airmid does right that stands it in front of the pack - is that is has a holographic, dimensional and forward mid range, that is coupled with resolution and low end weight.  All of this works together in harmony to produce a cohesive and exciting sound, and I didn't have to work hard at tube rolls to find it.  None of these strengths gets in the way of each other - which is also rare!  While you can get to that spot with other amps many times, it can be after spending a lot on tubes and/or find the right headphone combo.  The Airmid did this throughout the ZMF line-up really well, and quickly was a shop favorite among our other audiophile staff members.
> 
> ...



Thanks for the feedback Zach!  Much appreciated.

Speaking of the 45 amp, I cleared my DAC circuit off my protoboard yesterday, spent the whole morning stuffing PCBs for the ancillary circuitry for the 45 build.

With all of that out of the way, the rest will come together quickly, should be able to have a listen either tonight or by midday tomorrow at the latest.


----------



## zach915m

Zachik said:


> Zach - can you elaborate a bit on the Airmid vs. GOTL?
> Also, did you use the same tubes for both amps in the comparison, to make it more apples-to-apples?
> (I know the GOTL uses 1 x 6SN7 vs. Airmid 2 x 6J5, but with an adapter it is easy to use 2 x 6J5 with the GOTL...)





Monsterzero said:


> I compared them using the same rolls. There are some very obvious differences between the two.
> I have used:
> Kenrad 6j5+Bendix 6080
> Sylvania green label metal base+ 5998
> ...



Probably best to defer to Monster for roll comparisons as I didn't have the exact same tubes in both at the same time and listened more for enjoyment than comparison. 

The Gotl and airmid are alike in their effortless portrayal of sound via an OTL vehicle.  You wouldn't be able to go wrong with either, I think the airmid is quieter and less suseptable to noise than my gotl, the gotl I have does have more tube choices but I'm not sure thats always a good thing!


----------



## L0rdGwyn (Oct 7, 2021)

I got the ZMF 45 amplifier prototype up and running.  It's a mess of alligator clips, sort of a complex build.



Nothing is ever perfect the first time though, have a left channel hum to troubleshoot in the morning.  Sometimes a side effect of poor layout when building on a piece of plywood.

Brought my Audial DAC downstairs for a listen.  Best word I can use to describe this amplifier is holographic, expansive three-dimensional soundstage.  Really impressive on first listen, will be better when all is quiet though


----------



## Xcalibur255

My advice to Zach is to start scouring eBay for the right unicorn pair of globe 45s now.    They are unquestionably worth it, and the things they do better than their ST counterparts will probably play to the strengths of ZMF headphones too.  The only reason I take my Ken-Rad UX245s out of my amp is so I can have that incredible "wow" moment again when they go back in.


----------



## L0rdGwyn (Oct 6, 2021)

Xcalibur255 said:


> My advice to Zach is to start scouring eBay for the right unicorn pair of globe 45s now.    They are unquestionably worth it, and the things they do better than their ST counterparts will probably play to the strengths of ZMF headphones too.  The only reason I take my Ken-Rad UX245s out of my amp is so I can have that incredible "wow" moment again when they go back in.



Once I track down the hum gremlin I will try my globe Sylvanias!


----------



## L0rdGwyn (Oct 6, 2021)

Okay, hum gremlin found.  As expected, it is due to the layout of my protoboard, magnetic field from the mains / bias / filament transformers being picked up by the left input tube, long alligator clip cathode leads not helping LOL.  I ruled out all other causes first moving along each stage of the amplifier - also put DC on the heaters of the input tubes, which will be in the final build, I was running them on AC for convenience in the prototype.

But ultimately picking up the left input tube socket with the connections attached and moving it around revealed the problem.  Interestingly, the little bias supply transformer puts out a hefty magnetic field.  I moved it further away and rotated it 90 degrees, which got the hum down to near inaudible levels.  It will be killed completely in the final build in which the layout will be optimized for low noise.

So in go the globe 45s.



Holy moly, it's going to be very hard not to build one of these for myself.


----------



## L0rdGwyn (Oct 6, 2021)

Whoops, duplicate post  my test subject (aka girlfriend), was very impressed, she said something along the lines of "the imaging is amazing", nailed it!


----------



## Zachik

All this amp talk makes the wait so hard until @A2029 finally start working on MY amp!!!
Just couple more parts, and couple more people ahead of me in the queue...........


----------



## L0rdGwyn

Zachik said:


> All this amp talk makes the wait so hard until @A2029 finally start working on MY amp!!!
> Just couple more parts, and couple more people ahead of me in the queue...........



Good things come to those who wait!


----------



## Zachik

L0rdGwyn said:


> Good things come to those who wait!


GREAT things come to those who wait for a long time!


----------



## triod750

Zachik said:


> GREAT things come to those who wait for a long time!


So you are hoping for a longer wait then? That's great!


----------



## L0rdGwyn (Oct 6, 2021)

One cool thing about this amp for tube design nerds  - the amp is not designed necessarily to run in class A2, but given the low output impedance of the input stage as well as the interstage transformers, it can make excursions into A2 for additional power output.

Quick review - most single-ended class A tube amplifiers run strictly in class A1 where the grid is biased negatively and remains negative throughout the AC voltage swing.  Once that AC wave swings the grid close to 0V, the grid's impedance will rapidly drop and it will begin to draw grid current.  Most designs cannot supply this current to drive the grid positive, so the 0V grid line represents a clipping boundary in most single-ended class A designs.

If the design CAN supply that grid current however, the AC wave can swing the grid positive beyond 0V for additional power output.  My 801A amplifier is designed to run in class A2 nearly 100% of the time as the grid current is supplied by a cathode follower.  In this 45 amplifier, grid current is supplied by the transformer-coupled input stage.

The 45 is typically a 1.5 to 1.75W tube running in class A1.

But here is a 2W sine wave into a 300ohm dummy driving it into class A2 in this design.




And the voltage swing on the grid, it is being driven positive 26V!!!



Obviously these are very distorted waveforms and this is not a kind thing to do to your 45 grids for a prolonged period of time with a signal generator.  And, in reality, 2W into a 300ohm headphone is truly a deafening volume (would be roughly 130dB with the ZMF Auteur).  So maybe just academic, but if a very power hungry headphone is being used in this amp, the 45 can swing all the way to 0V and slightly beyond without a problem if necessary.


----------



## triod750

"What is he building in there"?

Tom Waits


----------



## Zachik

triod750 said:


> So you are *hoping *for a longer wait then? That's great!


Not a matter of hoping, but already is... 
Between REALLY long lead-times to everything (especially those Sowter OPTs), and Mischa being a busy guy (with previous commitments) - it just takes time!
My gut is telling me this coming winter break - either I will be busy enjoying the new amp, or Mischa will be busy finishing it up... hopefully, the former


----------



## leftside

Zachik said:


> GREAT things come to those who wait for a long time!


Agreed. 

I wouldn't recommend a custom amp as a first amp - the wait would be too long. You definitely already need a decent amp and something to listen to while you wait. And then patience  Yes parts - especially transformers - are also an issue right now.


----------



## L0rdGwyn

Save for a few minor component changes, this 45 amp is done, time to design the box.  I have a draft underway thankfully.  Very excited people will get to hear this at future CanJam events!

Before I take down the prototype, I'll try a cap-coupled version with active load on the driver tubes for future reference.  The interstage transformers in this amp are very high quality, so very expensive.

My DAC chassis is supposed to arrive Friday, maybe if I'm lucky it will get here tomorrow, so looks like the DIY party is going to keep on rolling.  Why travel when you're on PTO when you can build tube gear in your basement like a hermit?


----------



## whirlwind

L0rdGwyn said:


> Save for a few minor component changes, this 45 amp is done, time to design the box.  I have a draft underway thankfully.  Very excited people will get to hear this at future CanJam events!
> 
> Before I take down the prototype, I'll try a cap-coupled version with active load on the driver tubes for future reference.  The interstage transformers in this amp are very high quality, so very expensive.


Look forward to your impressions of the cap-coupled version.


----------



## L0rdGwyn

whirlwind said:


> Look forward to your impressions of the cap-coupled version.



I was going to try it out today, but I think I will just keep listening  I need one of those fancy Herman Miller chairs at my workbench, not the most comfortable place to listen lol.

Speaking of listening...

I haven't talked a whole lot about my Audial S5 DAC.  I was told by the designer that it required some burn in.  At the time I received it I was also building my PCM56 DAC prototype, so it was a whole lot of DAC to handle at one time.  I did a brief A-B listening session in my main two channel system with the S5 and my prototyped PCM56 DAC, at the time I actually preferred my own creation, which surprised me.

Since I broke down my prototype in anticipation of the final build, I have been listening to the S5 exclusively.  The other night I was at my desk listening with my 6A5G amp while designing some PCBs, and it sort of dawned on me that the S5 is really an incredible DAC - not sure if it reached burn-in maturation or if it was my ears that burned it, but it has excellent transparency, staging, and dynamics, very musical.  That burn in was the real deal, turns out Mr. Rogic knows a thing or two about his own designs!

I also did some brief A-Bing of the capacitor vs. transformer-coupled outputs (which are optional) and pretty quickly concluded that I preferred the transformer-coupled outputs, just a higher degree of realism and a bit more air.

So, the S5 is now even better than I remember it on first listen, so I think my own DAC now has some very stiff competition, one will go in my headphone system, the other in my two-channel system, will be interesting to see how they compare when the PCM56 DAC is in a chassis.


----------



## Zachik

L0rdGwyn said:


> Speaking of listening...
> 
> I haven't talked a whole lot about my Audial S5 DAC. I was told by the designer that it required some burn in. At the time I received it I was also building my PCM56 DAC prototype, so it was a whole lot of DAC to handle at one time. I did a brief A-B listening session in my main two channel system with the S5 and my prototyped PCM56 DAC, at the time I actually preferred my own creation, which surprised me.
> 
> ...


Thanks Keenan - very interesting, and I will keep following closely. 
As mentioned before, *please *keep me in mind when you finally feel your DAC is ready for public evaluation


----------



## Monsterzero

The Airmid review is live.


----------



## paradoxper

Monsterzero said:


> The Airmid review is live.



Where is the higher output version for something like a Susvara or TC?


----------



## Zachik

Monsterzero said:


> The Airmid review is live.


Excellent review!
I knew I would want an Airmid... If only I had room for "just one more amp"


----------



## jaboki

paradoxper said:


> Where is the higher output version for something like a Susvara or TC?


I wonder, could the Airmid be used as a pre-amp to the CFA3?


----------



## paradoxper

jaboki said:


> I wonder, could the Airmid be used as a pre-amp to the CFA3?


Sure. I'd likely request he build around an RK50 in that case though.


----------



## Monsterzero

jaboki said:


> I wonder, could the Airmid be used as a pre-amp to the CFA3?


I will let Keenan answer that officially, but in its current configuration there are no output jacks. There is only a pair of RCA inputs and a power cable socket in the rear.


----------



## raindownthunda

Monsterzero said:


> The Airmid review is live.



Thanks for the fantastic review @Monsterzero! Seems like the VO was a hit with the Airmid due to the better staging/imaging. Do you think you prefer the VO on the Airmid over the VC?


----------



## Monsterzero

raindownthunda said:


> Thanks for the fantastic review @Monsterzero! Seems like the VO was a hit with the Airmid due to the better staging/imaging. Do you think you prefer the VO on the Airmid over the VC?


I would say I prefer the VO more than the VC on the Airmid. Another one of the traits I failed to mention in the review was the airiness of the Airmid, which accentuates an already strong trait of the VO. Its simply a brilliant pairing.

With the VC, I prefer to enhance the dynamics of it, and due to the fact that I can insert a six pack of 6bx7s into my GOTL, the Airmid simply cant replicate that sonic bombardment. Its important to stress though that the Airmid slams just as hard, if not harder than the GOTL when using identical tube rolls.

I was listening to my Sennheiser HD250 ( my fav non-ZMF headphone) while spending time in my psy trance folder, and the Airmid/HD250 combo was great, in fact id say the Airmid had slighty better sub bass control vs. GOTL, where the HD250 can sound a bit flabby on occasion.


----------



## whirlwind

Monsterzero said:


> The Airmid review is live.



Nice job as always MZ.


----------



## L0rdGwyn

Monsterzero said:


> The Airmid review is live.




Thanks for the review @Monsterzero , very well done.  RIP my free time?  I guess we'll see lol.

@jaboki sorry at this time no pre-outs are being offered on the amp.  If you are looking for a tube input to your CFA3, you'd probably be better served using something that outputs a line level voltage, like a DAC with tube output stage / buffer.


----------



## SonicTrance

Congrats on Airmid @L0rdGwyn ! Looks really good and I bet it sounds great as well!


----------



## L0rdGwyn

SonicTrance said:


> Congrats on Airmid @L0rdGwyn ! Looks really good and I bet it sounds great as well!



Thanks @SonicTrance , much appreciated


----------



## L0rdGwyn

I've included a link to the Airmid information post in my signature.

BTW @Monsterzero , last night I woke up at 1AM, couldn't fall back asleep, then saw your review, then REALLY couldn't sleep, now I'm running on fumes and I blame you LOL.


----------



## Zachik

L0rdGwyn said:


> BTW @Monsterzero , last night I woke up at 1AM, couldn't fall back asleep, then saw your review, then REALLY couldn't sleep, now I'm running on fumes and I blame you LOL.


Always blame @Monsterzero - cannot go wrong with this strategy!


----------



## L0rdGwyn (Oct 7, 2021)

Not good for much that requires physical effort today, so I am working on the chassis for @zach915m 's 45 amp.  Done in CAD software so I don't have to move 

For inspiration, I dragged the prototype out of my basement and to my desk upstairs.  45s lost in a sea of alligator clips.




Layout for this amp is a challenge, a lot to fit in the box.

I can say at least that the front panel is done, will look like so - knob center, panel meters, RCA inputs will be on the front panel (left), TRS jack (right).



We'll see how far I get today.  Will be building a DAC tomorrow.  Once that is done along with the 45 amp, can focus entirely on Airmid.


----------



## triod750

L0rdGwyn said:


> Once that is done along with the 45 amp, can focus entirely on *50* Airmid.


----------



## Zachik

L0rdGwyn said:


> RCA inputs will be on the front panel (left)


Zach's request or your design choice? Just curious...


----------



## L0rdGwyn

Zachik said:


> Zach's request or your design choice? Just curious...



My design choice, but of course I ran it by him first.  All part of a low-noise layout.


----------



## zach915m

L0rdGwyn said:


> Not good for much that requires physical effort today, so I am working on the chassis for @zach915m 's 45 amp.  Done in CAD software so I don't have to move
> 
> For inspiration, I dragged the prototype out of my basement and to my desk upstairs.  45s lost in a sea of alligator clips.
> 
> ...





L0rdGwyn said:


> My design choice, but of course I ran it by him first.  All part of a low-noise layout.



I'm fine with a huge chassis if that's what the design calls for ahhahah! 

RCA on front panel fine with me if it makes the sonics optimized!  Already seems to be a good conversation starter 😂


----------



## Zachik

zach915m said:


> Already seems to be a good conversation starter 😂


As if you need incentives for starting conversations...


----------



## L0rdGwyn (Oct 7, 2021)

zach915m said:


> I'm fine with a huge chassis if that's what the design calls for ahhahah!
> 
> RCA on front panel fine with me if it makes the sonics optimized!  Already seems to be a good conversation starter 😂



Lol I'm going to make it as compact as possible!  Right now I am targeting 16.5" L x 13" W x 4.25" H, so it will be longer than it is wide with all of the noisy AC in the rear of the chassis.

Here is the current draft of the top plate, no ventilation or anything yet and it will undoubtedly change, colored boxes are internal components.




I think I mentioned it, but my 801A amplifier has RCAs on the front panel.  I like these Silver Pulse interconnects from DH Labs, nice and flexible, look pretty good too!


----------



## L0rdGwyn

Also, I freaking love this 45 amplifier...this is going to be a problem.


----------



## johnjen

Ah I see that the magic of the 45 has snared yet another victim.
Bhhhhahahahahahahahahahahahahahaha

JJ


----------



## L0rdGwyn (Oct 7, 2021)

johnjen said:


> Ah I see that the magic of the 45 has snared yet another victim.
> Bhhhhahahahahahahahahahahahahahaha
> 
> JJ



Yup, snared me for the second time in fact lol two 45 amps in this household right now.  Edit: oh right, Zach is the victim here, I knew that   

Made some real good progress on the chassis today, going to shelve it for the night, then build my PCM56 DAC tomorrow!


----------



## zach915m

L0rdGwyn said:


> Lol I'm going to make it as compact as possible!  Right now I am targeting 16.5" L x 13" W x 4.25" H, so it will be longer than it is wide with all of the noisy AC in the rear of the chassis.
> 
> Here is the current draft of the top plate, no ventilation or anything yet and it will undoubtedly change, colored boxes are internal components.
> 
> ...





johnjen said:


> Ah I see that the magic of the 45 has snared yet another victim.
> Bhhhhahahahahahahahahahahahahahaha
> 
> JJ



The bigger the better!

The RCA cables on the front will be a good chance for us to show off those blingy cables.

I've actually never heard a 45 amp before so it's very exciting.  And having an excuse to look for tubes to buy is always fun.


----------



## L0rdGwyn

zach915m said:


> I've actually never heard a 45 amp before so it's very exciting.  And having an excuse to look for tubes to buy is always fun.



I'm excited for you to hear it!  I think I should have it to you by the end of November at the latest.  I have been listening to it for the past 4-5 hours, really pleased with this circuit.


----------



## Xcalibur255

Just a thought Keenan, you might want to consider keeping the meters on the same surface in close proximity to the trim pots.  I think it's easier to both adjust and watch the bias at the same time this way.  If the meters are on the front it's more awkward to keep an eye while adjusting the set screw.


----------



## L0rdGwyn

Xcalibur255 said:


> Just a thought Keenan, you might want to consider keeping the meters on the same surface in close proximity to the trim pots.  I think it's easier to both adjust and watch the bias at the same time this way.  If the meters are on the front it's more awkward to keep an eye while adjusting the set screw.



Thanks for the input T, I'll keep that in mind.  BTW - do you have your finger on the pulse of the NOS 45 market?  I feel like prices went up since last I checked, which was probably almost a year ago.  Seems like $150 for a pair of NOS ST shaped is pretty commonplace, I was getting much better prices last year.


----------



## Xcalibur255 (Oct 7, 2021)

They're up quite a bit in the last year, yes.  I'm seeing globes that test poorly and don't match well going for the same prices that good NOS testing pairs went for just a couple of years ago.  Since the T/J factory that made the Fullmusic tubes in China doesn't seem to be operating anymore the only semi-reasonably priced new production 45 is also going up in price and getting hard to find.

It does make me wonder how much longer we have before they start to become genuinely hard to find like a 10 or 50 is now.  For the globes at least, I have no doubt the ST tubes will be readily attainable on eBay for quite some time still.

This amp you are building deserves to have a nice pair of globes in it, especially with those interstages I'm sure it'll be crazy transparent.


----------



## L0rdGwyn

Xcalibur255 said:


> They're up quite a bit in the last year, yes.  I'm seeing globes that test poorly and don't match well going for the same prices that good NOS testing pairs went for just a couple of years ago.  Since the T/J factory that made the Fullmusic tubes in China doesn't seem to be operating anymore the only semi-reasonably priced new production 45 is also going up in price and getting hard to find.
> 
> It does make me wonder how much longer we have before they start to become genuinely hard to find like a 10 or 50 is now.  For the globes at least, I have no doubt the ST tubes will be readily attainable on eBay for quite some time still.
> 
> This amp you are building deserves to have a nice pair of globes in it, especially with those interstages I'm sure it'll be crazy transparent.



Okay, so I'm not crazy!  I wonder the same, every so often I have a mini panic about the availability of my favorite NOS tubes and have to hold back from buying whatever is available.  The transparency and 3D-ism with the globes in this amp might be the best I have ever heard, hopefully Zach can find a good pair of globes for a decent price.  Cooling off the bias in this amp doesn't cause a significant drop off in sound quality, so running at 28-30mA or so and a pair of globes should last a very long time.


----------



## Xcalibur255

For sure, a genuinely solid pair of globes will last darn near forever at 250V/30mA bias.  My beloved KenRads see 275/34 and they're not showing any significant signs of weakening after 7 years of intermittent use.  As long as something unlucky doesn't happen I would say one good pair will take care of it.  45s generally aren't prone to becoming noisy over time but it does happen.

I can keep my eyes peeled.  Or I'm possibly being presumptous there.  Maybe Zach is old hat at tube hunting.


----------



## Zachik

L0rdGwyn said:


> BTW - do you have your finger on the pulse of the NOS 45 market? I feel like prices went up since last I checked, which was probably almost a year ago. Seems like $150 for a pair of NOS ST shaped is pretty commonplace, I was getting much better prices last year.


Yup - good 45 ST pairs seem to go for $150-200, and globes for twice as much!


----------



## jgwtriode (Oct 7, 2021)

zach915m said:


> I got a chance to have the "Airmid" in house for a week or so - and I without a doubt can highly recommend it for ZMF's.    I know @L0rdGwyn told me that it can change a bit in impedance output with different tubes, but the two sets I tried in it (6080 Amperex and the stock tubes) both sounded fantastic.
> 
> The one thing that that Airmid does right that stands it in front of the pack - is that is has a holographic, dimensional and forward mid range, that is coupled with resolution and low end weight.  All of this works together in harmony to produce a cohesive and exciting sound, and I didn't have to work hard at tube rolls to find it.  None of these strengths gets in the way of each other - which is also rare!  While you can get to that spot with other amps many times, it can be after spending a lot on tubes and/or find the right headphone combo.  The Airmid did this throughout the ZMF line-up really well, and quickly was a shop favorite among our other audiophile staff members.
> 
> ...


Good for you Zach!   45's are absolutely gorgeous to listen to.  Had VAIC cobalt meshplates with magnequest cobalt transformers(bottlehead paraglows) for a couple of years.  Never heard a more musical engaging amplifier.   Will be hoot to hear further about the results.

Happy listening,

jgwtriode


----------



## johnjen

And just as a teaser…

Ya know what tube is a lot like the 45 in just about every way, except has ≈ 1/2 the power?




wait for it…





the 71A…
buuhhhahahahahahahahahahahahahahaha…

JJ


----------



## L0rdGwyn

jgwtriode said:


> Good for you Zach!   45's are absolutely gorgeous to listen to.  Had VAIC cobalt meshplates with magnequest cobalt transformers(bottlehead paraglows) for a couple of years.  Never heard a more musical engaging amplifier.   Will be hoot to hear further about the results.
> 
> Happy listening,
> 
> jgwtriode



Just to clarity, the amplifier Zach demo'd is an OTL I designed called the Airmid, but I am working on a custom 45 amplifier for him


----------



## whirlwind

Zachik said:


> Yup - good 45 ST pairs seem to go for $150-200, and globes for twice as much!


They seem to be a bit pricey, but most good tubes are.


----------



## Xcalibur255

Wasn't the 71A originally designed for battery powered radios?  I hear it's a fussy tube to work with but has an interesting sound to it.


----------



## L0rdGwyn (Oct 8, 2021)

Got my DAC chassis.  Going to go prep it and build the DAC, need to remove the anodization from grounding points.  Should only take a few hours to put the whole thing together.  Photo taken mere moments before a cat jumped on it and ruined my beautiful chassis arrangement


----------



## triod750 (Oct 8, 2021)

Shortest Way 51+ has a cat on the front plate.


----------



## bcowen

whirlwind said:


> They seem to be a bit pricey, but most good tubes are.


Has anyone tried the KR or Emission Labs 45's?  Pricey.  Very.  Just wonder how they stack up against the NOS gems.

http://www.emissionlabs.com/datasheets/EML45.html

https://www.tubeampdoctor.com/en/kr-audio-45-matched-pair-2-matched-tubes


----------



## L0rdGwyn

I'm always optimistic about how much I can get done in one sitting, it's going to take a second to finish this DAC.

It is about 85% of the way there though, not much more left.


----------



## L0rdGwyn

bcowen said:


> Has anyone tried the KR or Emission Labs 45's?  Pricey.  Very.  Just wonder how they stack up against the NOS gems.
> 
> http://www.emissionlabs.com/datasheets/EML45.html
> 
> https://www.tubeampdoctor.com/en/kr-audio-45-matched-pair-2-matched-tubes



I haven't tried either, but the EML 45s are very highly regarded, most say they are better sounding than NOS globes.  I personally don't like how they look though, that's a barrier for me lol but the KR are quite nice looking, have that NOS aesthetic.


----------



## johnjen

Xcalibur255 said:


> Wasn't the 71A originally designed for battery powered radios?  I hear it's a fussy tube to work with but has an interesting sound to it.


Yep it was and certainly can be fussy and microphonic which is a non-issue for headphones since there is no acoustic sound field to modulate them in the 1st place.
It's taken 'a while' to dial these bad boys in, but the end results are Most gratifying.

The 71A's don't quite have the same degree of 'heft' of the 45 but in terms of inner detail, resolution, and bass extension and leading edge dynamic impact etc. they can hold their own.
But that midrange, where the music lives…
Is enticing to say the least.

And granted with only ≈0.8w/ch, high Ω cans are the 'perfect' load for them.

You can kinda think of them as 1/2 of a 45 sorta-kinda.

JJ


----------



## johnjen

bcowen said:


> Has anyone tried the KR or Emission Labs 45's?  Pricey.  Very.  Just wonder how they stack up against the NOS gems.
> 
> http://www.emissionlabs.com/datasheets/EML45.html
> 
> https://www.tubeampdoctor.com/en/kr-audio-45-matched-pair-2-matched-tubes


I've kept my eyes on them as well as the few chinese varients for when I start tweaking my 45 amp and it gets to the point of needing tweako tubes to push it (the amp) over the top, right along with tweako OPT's…

JJ


----------



## jgwtriode

What an incredibly gorgeous color choice on the Amp!  A regal luxurious vibrant red.  Layout is gorgeous.  Like the choice of clarity caps.  And the tube choices sound potentially excellent.  I have drained the piggy sadly over the last few months, but at the price point this looks remarkable.  I have posted your photo on my desktop for
inspiration!  It may be a while, but will try to figure out how to afford one.

Out of curiosity and a look at a more absolute reference, Just how would a 2A3 based amp with your approach to it compare.  Saw Zach's commision and well just have 
to ask!

Thanks and happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> What an incredibly gorgeous color choice on the Amp!  A regal luxurious vibrant red.  Layout is gorgeous.  Like the choice of clarity caps.  And the tube choices sound potentially excellent.  I have drained the piggy sadly over the last few months, but at the price point this looks remarkable.  I have posted your photo on my desktop for
> inspiration!  It may be a while, but will try to figure out how to afford one.
> 
> Out of curiosity and a look at a more absolute reference, Just how would a 2A3 based amp with your approach to it compare.  Saw Zach's commision and well just have
> ...



Thank you!  Certainly let me know if / when you become interested in having one built 

And do you mean a 2A3 amplifier vs. the Airmid OTL, or a 2A3 amplifier vs. Zach's 45 design?


----------



## L0rdGwyn

Okay I finished my DAC.

This is a NOS R2R DAC based on the vintage Burr-Brown PCM56 chip with Sowter SUT I/V stage and a battery biased common cathode tube output stage, setup as a hybrid mu follower.

Here is the circuit.





And the chassis closed.







Going to put it in my main two-channel system for now.  Will be out and about today, later I will take some measurements and do some headphone listening 



It sounds very nice in my stereo


----------



## chrisdrop

L0rdGwyn said:


> Okay I finished my DAC.
> 
> This is a NOS R2R DAC based on the vintage Burr-Brown PCM56 chip with Sowter SUT I/V stage and a battery biased common cathode tube output stage, setup as a hybrid mu follower.
> 
> ...


Congrats on the milestone
It looks beautiful


----------



## Galapac

L0rdGwyn said:


> Okay I finished my DAC.
> 
> This is a NOS R2R DAC based on the vintage Burr-Brown PCM56 chip with Sowter SUT I/V stage and a battery biased common cathode tube output stage, setup as a hybrid mu follower.
> 
> ...


Looks beautiful! You are an amazing designer @L0rdGwyn. How proud you must be of your creations.
Is that a textured powder coat finish in the DAC?


----------



## L0rdGwyn

Thanks @chrisdrop and @Galapac !

It is brushed anodized aluminum, I thought the aluminum would go better with the minimalist aesthetics.


----------



## triod750

L0rdGwyn said:


> Okay I finished my DAC.
> 
> This is a NOS R2R DAC based on the vintage Burr-Brown PCM56 chip with Sowter SUT I/V stage and a battery biased common cathode tube output stage, setup as a hybrid mu follower.
> 
> ...


And that nice LED.


----------



## L0rdGwyn

triod750 said:


> And that nice LED.



Lol it's still a little bright for me, might take it down a bit more.


----------



## bcowen

L0rdGwyn said:


> Okay I finished my DAC.
> 
> This is a NOS R2R DAC based on the vintage Burr-Brown PCM56 chip with Sowter SUT I/V stage and a battery biased common cathode tube output stage, setup as a hybrid mu follower.
> 
> ...


Nice!


----------



## CJG888

Just one (rather geeky) question on the DAC: can it recognise CDs recorded with pre-emphasis and correct the same?


----------



## L0rdGwyn

CJG888 said:


> Just one (rather geeky) question on the DAC: can it recognise CDs recorded with pre-emphasis and correct the same?



Not sure, I'll look into it!


----------



## Zachik

CJG888 said:


> Just one (rather geeky) question on the DAC: can it recognise CDs recorded with pre-emphasis and correct the same?





L0rdGwyn said:


> Not sure, I'll look into it!


How about recognize _Marilyn Manson_ vocals, and correct it to sound smooth and pleasant?


----------



## L0rdGwyn (Oct 9, 2021)

Took some measurements to evaluate the noise performance.  In a small signal device, like a DAC, low noise is a top priority.  Power supply and layout were designed with this in mind.

Here is a -6dB 1kHz FFT of the left channel.  Looks pretty darn good, no low frequency junk above 105dB and only harmonic above 100dB is H2.




Noise performance in the right channel is even better.  Distortion is higher however - this is dominated by the output tube.  The one I have in the right channel right now isn't the best performer, I will have to swap it out.



But looks like we did well from a noise standpoint, nice and quiet, no hum or other audible junk!!!


----------



## bcowen

Zachik said:


> How about recognize _Marilyn Manson_ vocals, and correct it to sound smooth and pleasant?


Dangit.  I forgot how to spell 'Bite Me.'


----------



## jgwtriode

L0rdGwyn said:


> Thank you!  Certainly let me know if / when you become interested in having one built
> 
> And do you mean a 2A3 amplifier vs. the Airmid OTL, or a 2A3 amplifier vs. Zach's 45 design?


Yes interested in the differences between all of them.  If all goes well maybe 3 to 5 months I could do the Airmid, which looks amazing.  But I love the sound of 2A3's  Played with Vaic Monoplates, Classic RCA blackplates and finally Vaic Cobalt meshplates with my bottlehead paraglows a number of years back..    So really curious what you could do with a 2A3 and what kind of a price and performance difference that would be.   Kinda lusting after an Ampsandsound Rockwell from what I saw of and have read about it.

Thanks in advance,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Yes interested in the differences between all of them.  If all goes well maybe 3 to 5 months I could do the Airmid, which looks amazing.  But I love the sound of 2A3's  Played with Vaic Monoplates, Classic RCA blackplates and finally Vaic Cobalt meshplates with my bottlehead paraglows a number of years back..    So really curious what you could do with a 2A3 and what kind of a price and performance difference that would be.   Kinda lusting after an Ampsandsound Rockwell from what I saw of and have read about it.
> 
> Thanks in advance,
> 
> jgwtriode



I will shoot you a PM tomorrow, @jgwtriode !


----------



## L0rdGwyn

Starting doing some A-B testing of my PCM56 DAC and the Audial S5 with my 6A5G amplifier.



Going to take some time to tease out the differences, I'm actually surprised at how similar they are.  Will also swap in a different amplifier to be sure it isn't masking any differences.

I will say this, the noise floor of the PCM56 DAC is lower than the Audial S5, using the tried and true "turn-the-volume-knob-all-the-way-up-without-music-playing" methodology.  Both are very quiet though, you'd go deaf turning up the volume before you heard the noise floor of the S5.


----------



## L0rdGwyn

Tubes in action!


----------



## jgwtriode

L0rdGwyn said:


> I will shoot you a PM tomorrow, @jgwtriode !


Awesome, thanks so much,

jgwtriode


----------



## Zachik

L0rdGwyn said:


> Starting doing some A-B testing of my PCM56 DAC and the Audial S5


I am at the edge of my seat... 



L0rdGwyn said:


> Going to take some time to tease out the differences, I'm actually surprised at how similar they are. Will also swap in a different amplifier to be sure it isn't masking any differences.


Which headphones are you testing with?


----------



## Xcalibur255

CJG888 said:


> Just one (rather geeky) question on the DAC: can it recognise CDs recorded with pre-emphasis and correct the same?


I had never even heard of this before now, and from what I just read it seems to only be a concern for some very early CDs from the 80's.


----------



## CJG888

80s and 90s. More of an issue for classical fans. It does, however, affect such august labels as BIS, Denon and Delos…


----------



## whirlwind

Xcalibur255 said:


> I had never even heard of this before now, and from what I just read it seems to only be a concern for some very early CDs from the 80's.


I have never heard of this either.....interesting.


----------



## L0rdGwyn (Oct 10, 2021)

Zachik said:


> I am at the edge of my seat...
> 
> 
> Which headphones are you testing with?



The usual, ZMFs 

These two DACs are pretty darn close in terms of performance I would say, the differences are quite subtle actually.

Similar to what I thought when I was comparing the PCM56 DAC prototype - I think the Audial S5 gives slightly more in the way of airiness, cleanliness, staging / imaging.  It is the more "clean" sounding of the two DACs.  The PCM56 DAC however gives more in the way of smooth tonality, body, and perhaps sounds slightly more...natural?  Maybe the term is more "analog" sounding.  But again, we are talking subtle differences.  Slightly lower noise floor in the PCM56 DAC, but would never be an audible problem in either one.  Both NOS R2R so I expect that is contributing to the similar character, but I am still surprised given they use different chips, different power supplies, different I/V stages (active vs. passive), tube vs. transimpedance amplifier, different output coupling.  The S5 though is more feature rich that my DAC - it has tons of digital I/O options and also gives you the option of cap vs. transformer output coupling.  Also it has a small footprint, height-wise.

If I were to recommend one vs. the other to you, the slightly better staging of the S5 is probably more impressive for headphone use, it is a kick ass DAC.  And given all of the extra features, it is more consumer friendly than my DAC.  I am most likely going to keep the S5 in my headphone setup and put the PCM56 DAC in my stereo.  Might A-B them there as well, but during the prototyping phase, I liked the slightly more warm tone of the PCM56 DAC in my two-channel setup.  That's where I listen to vinyl too, so it will fit the theme better 

Also should mention I am using the transformer coupled outputs of the S5.


----------



## Zachik

Thanks Keenan!  Very helpful


----------



## tubebuyer2020

@L0rdGwyn another noob question if you don't mind: when ordering PCBs are you forced to buy a small (e.g. 50) batch or do you have a way of getting just a few?


----------



## L0rdGwyn

tubebuyer2020 said:


> @L0rdGwyn another noob question if you don't mind: when ordering PCBs are you forced to buy a small (e.g. 50) batch or do you have a way of getting just a few?



I use JLCPCB, the minimum order there is 5 boards.  Usually it is not much more expensive to buy duplicates (unless you are talking about a four-layer design), the cost really goes up when ordering multiple designs.


----------



## L0rdGwyn

I ended up moving the S5 to my stereo for now, want to spend some more time on headphones with the PCM56 DAC.  So on my desk it stays, also doubling as a monitor stand lol.  It will be fun to bring this DAC to a Head-Fi event some day, I'm really happy with the sound and especially happy about the low noise performance as I put a lot of effort into that aspect of the design.




Going back to work tomorrow, so the marathon run of DIY is coming to an end.  Will be back at it on Wednesday though, the priority this week will be finishing the chassis design for Zach's 45 amplifier and getting it ordered.  I have some powder coat swatches on the way for a few colors I have in mind, we'll see how they look in person, then will run the ideas by the wooden headphone master himself.


----------



## tubebuyer2020

L0rdGwyn said:


> I use JLCPCB, the minimum order there is 5 boards.  Usually it is not much more expensive to buy duplicates (unless you are talking about a four-layer design), the cost really goes up when ordering multiple designs.



Interesting, thank you - not super-cheap but affordable.


----------



## maxpudding

I am a bit late in congratulating @L0rdGwyn for his new new OTL amp, it’s really nice to see new products from these great amp builders.


----------



## zach915m

L0rdGwyn said:


> I ended up moving the S5 to my stereo for now, want to spend some more time on headphones with the PCM56 DAC.  So on my desk it stays, also doubling as a monitor stand lol.  It will be fun to bring this DAC to a Head-Fi event some day, I'm really happy with the sound and especially happy about the low noise performance as I put a lot of effort into that aspect of the design.
> 
> 
> 
> Going back to work tomorrow, so the marathon run of DIY is coming to an end.  Will be back at it on Wednesday though, the priority this week will be finishing the chassis design for Zach's 45 amplifier and getting it ordered.  I have some powder coat swatches on the way for a few colors I have in mind, we'll see how they look in person, then will run the ideas by the wooden headphone master himself.



Heyhey don't worry too much about me, I'm just along for the ride!  

DAC looks awesome! Can't wait to hear it someday!


----------



## L0rdGwyn

zach915m said:


> Heyhey don't worry too much about me, I'm just along for the ride!
> 
> DAC looks awesome! Can't wait to hear it someday!



LOL no way I'm making the final choice on color!  But I have some ideas, first swatches I got didn't impress, more on the way 

Maybe I can make the drive to CanJam Chicago next year if COVID allows, would be cool to bring along some of my gear for a meet!


----------



## L0rdGwyn

Gonna work on the 45 amp layout some more over the next few days.

Also, like I said, I want to try a cap coupled version of it while I have the prototype made up for future reference.  Thinking ahead, this circuit could be easily adapted for 2A3 with changes to the filament supply and different output transformers, although the full power output of the 2A3 for headphones is quite a lot.

But both the 45 and 2A3 do not like to see a high DC resistance on their grids in fixed bias, especially early models with relatively poor vacuum, like 45 globes.  The grid resistor loads the input stage, so using a 50K resistor (limit for 2A3) or 100K resistor (limit for 45) won't fully maximize gain and keep distortion at a minimum.

The answer to the problem for the cap-coupled version is to use a grid choke to load the stage instead - maintains a low DC resistance for the grids, but a high AC impedance to the signal due to the inductive reactance of the choke.  So I've reached out to my buddy Kevin and K&K Audio (who is probably on his way to buying a vacation home with how much of my money he has gotten over the past two years LOL), going to grab a pair of Lundahl grid chokes to give this a try before taking down the prototype.


----------



## whirlwind

L0rdGwyn said:


> LOL no way I'm making the final choice on color!  But I have some ideas, first swatches I got didn't impress, more on the way
> 
> Maybe I can make the drive to CanJam Chicago next year if COVID allows, would be cool to bring along some of my gear for a meet!


I would love to be able to come to this...listen to your amps and Zach's headphones and meet you guys in person and maybe I could visit some blues clubs.
This sounds like a couple of nice enjoyable days   

Hopefully the world will get better as far as covid goes...I have my fingers crossed for this to be the case.


----------



## L0rdGwyn

whirlwind said:


> I would love to be able to come to this...listen to your amps and Zach's headphones and meet you guys in person and maybe I could visit some blues clubs.
> This sounds like a couple of nice enjoyable days
> 
> Hopefully the world will get better as far as covid goes...I have my fingers crossed for this to be the case.



Will keep my fingers crossed!  Going to keep these dates circled on my calendar for next year.


----------



## bcowen

whirlwind said:


> I would love to be able to come to this...listen to your amps and Zach's headphones and meet you guys in person and maybe I could visit some blues clubs.
> This sounds like a couple of nice enjoyable days
> 
> Hopefully the world will get better as far as covid goes...I have my fingers crossed for this to be the case.


I think we should do a virtual meet.  Zach sends everyone a pair of headphones, and Keenan sends everyone an amp.  Then we could listen and chat from the comfort of our comfy chairs.

Everyone who's in sign below:


----------



## Xcalibur255

Sponsored by GE.


----------



## L0rdGwyn

Busy busy busy.

I put some final touches on my DAC - replaced the secondary I/V resistors with Riken Ohm (had to order from Hong Kong on eBay as the usual sources didn't have the value I needed).  Also replaced the DC heater regulator board with a new one - had to make a layout and component change to kill a 30mVrms 2MHz oscillation - of course this wasn't audible since it is in the heater circuit, but I KNEW it was there, so it had to go.  I also replaced the current limiting resistor on the power LED so it is nice and dim.

So the DAC is truly all the way done now.  It's on my workbench at the moment as I was listening to the 45 prototype with it.  No more blinding LED.




Continuing to work on the layout for the 45 amplifier.  It is a challenge, but almost there.  Still targeting 16" L x 13" W x 4.25" H.  Another day or two of work and it should be done.

I also have @Monsterzero 's GOTL in house.  Going to be swapping out the old sockets, replacing the loctal C3g sockets with octals set up for dual 6J5 / 12J5.  Might also be adding a CCS load to the input tubes, but that is an ongoing discussion.



That's not all!  Getting parts orders put together for the first Airmid build.  It will be in the anthracite gray below.



Moving pretty slow this week, trying to rally and get some of these items checked off the to-do list!


----------



## triod750

L0rdGwyn said:


> I also replaced the current limiting resistor on the power LED so it is nice and dim.


Good to see that you have your priorities right. You are a star!


----------



## L0rdGwyn

triod750 said:


> Good to see that you have your priorities right. You are a star!



Lol of course!  It was aggressively bright, now it is just right 

After a lot of experimenting, this is the ventilation pattern I am going with for the 45 amplifier.  Sockets bottom-mounted, as usual.  Almost done.


----------



## mordy

L0rdGwyn said:


> Lol of course!  It was aggressively bright, now it is just right
> 
> After a lot of experimenting, this is the ventilation pattern I am going with for the 45 amplifier.  Sockets bottom-mounted, as usual.  Almost done.


How do you determine the ventilation pattern? Aesthetics, air flow, ease of manufacturing?


----------



## L0rdGwyn

mordy said:


> How do you determine the ventilation pattern? Aesthetics, air flow, ease of manufacturing?



It's an opportunity to add some aesthetic flair to the amp, obviously needs to have adequate airflow as well.  I know the limitations of what can be machined by Landfall, so have to make sure the design doesn't violate any of those tolerances too.


----------



## mordy

L0rdGwyn said:


> It's an opportunity to add some aesthetic flair to the amp, obviously needs to have adequate airflow as well.  I know the limitations of what can be machined by Landfall, so have to make sure the design doesn't violate any of those tolerances too.


Thanks - I conjured up an image of fans blowing and a wind tunnel and air flow meters lol...


----------



## maxpudding

Heat sensors, anemometers, some CFD analysis…

Das Amp


----------



## L0rdGwyn

Here is a look at the final layout for the ZMF 45 amp.  Final dimensions are 16.5" L x 13.5" W x 4.25" H.

Lundahl mains and filament transformers will be in the back, output transformers in the center.  Potentiometers for bias adjustment in the front (left and right holes).  Hole on the bottom right near the front is the output impedance switch for 300ohm, 120ohm, 32ohm output taps.  The interstage transformers will be on the interior, along with five separate regulated power supplies (B+, bias, DC heater, 2x filament).  The left and right channels each have their own dedicated B+ and bias supply regulators.



I've shown the front panel layout before, but here it is one more time.  Volume knob center, bias milliammeters on left and right, TRS jack on the far right, RCA inputs on the far left.



Since ZMF headphones tend to have warm tones, to accent them well we are going across the color wheel, it will be coated in Distant Blue.



This color reminds me of vintage JBL speaker baffles.  Got the stamp of approval from the ZMF crew.



I will go through the whole layout at least one more time to be sure all is sound, then will place the order along with anthracite gray Airmid chassis.  Should have this 45 amp done in maybe 2-3 weeks.


----------



## triod750

So it will soon be zachrified...?


----------



## Monsterzero

L0rdGwyn said:


> Here is a look at the final layout for the ZMF 45 amp.  Final dimensions are 16.5" L x 13.5" W x 4.25" H.
> 
> Lundahl mains and filament transformers will be in the back, output transformers in the center.  Potentiometers for bias adjustment in the front (left and right holes).  Hole on the bottom right near the front is the output impedance switch for 300ohm, 120ohm, 32ohm output taps.  The interstage transformers will be on the interior, along with five separate regulated power supplies (B+, bias, DC heater, 2x filament).  The left and right channels each have their own dedicated B+ and bias supply regulators.
> 
> ...


Love those JBLs! Do you restore vintage solid state amps and receivers as well?


----------



## L0rdGwyn

Monsterzero said:


> Love those JBLs! Do you restore vintage solid state amps and receivers as well?



I am all tube right now!  Well I do have some VFET transistors around here somewhere, I am going to build a Nelson Pass First Watt style class A amp at some point, but I have no idea when.  I have a schematic somewhere.

Here's one, they are starting to dwindle in numbers, so I grabbed some before extinction.



Also, those aren't my JBLs, I wish!!!  I don't have space for mega vintage speakers right now.  A larger listening space will be a priority though when I move into a new house in 4-5 years.  Then I'll get something ridiculous, like some Altec 604s, La Scalas, JBLs, something BIG and efficient.


----------



## Monsterzero

L0rdGwyn said:


> I am going to build a Nelson Pass First Watt style class A amp


Will it weigh 175 lbs like a real one?


L0rdGwyn said:


> Also, those aren't my JBLs, I wish!!! I don't have space for mega vintage speakers right now. A larger listening space will be a priority though when I move into a new house in 4-5 years. Then I'll get something ridiculous, like some Altec 604s, La Scalas, JBLs, something BIG and efficient.


I have a pair of Rectilinear Highboys in very, very nice condition. They are quite large and heavy. Hard to find too.


----------



## L0rdGwyn

Monsterzero said:


> Will it weigh 175 lbs like a real one?



I think I was planning on loading the output transistors with a pair of massive filament chokes, so the answer is a definite yes lol.



Monsterzero said:


> I have a pair of Rectilinear Highboys in very, very nice condition. They are quite large and heavy. Hard to find too.



Awesome, I'd love to hear them.  Something very appealing about giant vintage speakers.

These JBL 4343s are a thing of beauty, something about that blue and walnut goes so well together.



I mentioned it hear before, but one of my "endgame" speaker ideas is to do a Altec Stonehenge III clone using Great Plains Audio's contemporary 604 driver.

The Klipsch La Scala also is appealing to me.  One of the only real hifi stores in Cleveland is a legit Klipsch Heritage dealer, they have a pair of La Scala AL5s there.  One day I am going to ask the owner if I can bring my own gear to play on them


----------



## triod750

L0rdGwyn said:


> One day I am going to ask the owner if I can bring my own gear to play on them


Excellent idea that you eventually might regret.


----------



## bcowen

L0rdGwyn said:


> Here is a look at the final layout for the ZMF 45 amp.  Final dimensions are 16.5" L x 13.5" W x 4.25" H.
> 
> Lundahl mains and filament transformers will be in the back, output transformers in the center.  Potentiometers for bias adjustment in the front (left and right holes).  Hole on the bottom right near the front is the output impedance switch for 300ohm, 120ohm, 32ohm output taps.  The interstage transformers will be on the interior, along with five separate regulated power supplies (B+, bias, DC heater, 2x filament).  The left and right channels each have their own dedicated B+ and bias supply regulators.
> 
> ...


Love the color!  Zach should provide you with some wood side caps to really dress it to the nines.  Your amp, his wood....the stuff dreams are made of.  

 Bargain basement representation below, but gets across the basic thought:






This wood is totally drop-dead gorgeous and would complement the blue nicely:


----------



## L0rdGwyn

triod750 said:


> Excellent idea that you eventually might regret.



Yeah I probably would!  But it's okay, a lot of prerequisites need to be met before gigantic speakers enter my home lol.



bcowen said:


> Love the color!  Zach should provide you with some wood side caps to really dress it to the nines.  Your amp, his wood....the stuff dreams are made of.
> 
> Bargain basement representation below, but gets across the basic thought:
> 
> ...



I'll probably pick up woodworking at some point, then maybe I can add some wood vibes to my designs!


----------



## triod750

L0rdGwyn said:


> Even now I can add some good vibes to my designs!


FTFY


----------



## Xcalibur255

You could just include standoffs on the sides of the chassis so he could add a wood flair from his own stock to personalize the amp.


----------



## L0rdGwyn (Oct 16, 2021)

Yeah the wood side panel is something that needs special planning to be done well IMO.  Ideally the top plate would be perfectly flush with the wood panel, at least the way I envision it, and there are components that need to be mounted on the side panel, would not want hardware visible externally on the wood, so would use a metal interior panel with screw holes counterbored to use flat head hardware such that the wood panel is flush when mounted to the side.  So the chassis would need to be made specifically for that purpose and tolerances on the wood components would be small to get the sleek, flush result, which is challenging without the ability to cut the wood to size and alter it if necessary.  I have a big garage overhaul project on the horizon, after which I might take the plunge / investment into woodworking equipment, could then incorporate it into chassis designs.


----------



## Monsterzero

L0rdGwyn said:


> Ideally the top plate would be perfectly flush with the wood panel,


There's something about a non-flush wood case that adds a vintage appeal IMHO


----------



## triod750

L0rdGwyn said:


> Yeah the wood side panel is something that needs special planning to be done well IMO.  Ideally the top plate would be perfectly flush with the wood panel, at least the way I envision it, and there are components that need to be mounted on the side panel, would not want hardware visible externally on the wood, so would use a metal interior panel with screw holes counterbored to use flat head hardware such that the wood panel is flush when mounted to the side.  So the chassis would need to be made specifically for that purpose and tolerances on the wood components would be small to get the sleek, flush result, which is challenging without the ability to cut the wood to size and alter it if necessary.  I have a big garage overhaul project on the horizon, after which I might take the plunge / investment into woodworking equipment, could then incorporate it into chassis designs.


No KISS for you then?


----------



## L0rdGwyn

triod750 said:


> No KISS for you then?



No!  Everything must be convoluted, expensive, and time-consuming.


----------



## bcowen

L0rdGwyn said:


> No!  Everything must be convoluted, expensive, and time-consuming.


ROFL!  My boss would agree with you to the letter.    

I was thinking something along these lines. The inserts go into the wood, and the screws would go out from the inside of the side panels to fasten it.  Probably overly simplistic, but once I leave work I always want things simpler than they have to be.


----------



## Xcalibur255

L0rdGwyn said:


> No!  Everything must be convoluted, expensive, and time-consuming.


Could I interest you in any number of corporate middle-management positions sir?


----------



## whirlwind

L0rdGwyn said:


> Here is a look at the final layout for the ZMF 45 amp.  Final dimensions are 16.5" L x 13.5" W x 4.25" H.
> 
> Lundahl mains and filament transformers will be in the back, output transformers in the center.  Potentiometers for bias adjustment in the front (left and right holes).  Hole on the bottom right near the front is the output impedance switch for 300ohm, 120ohm, 32ohm output taps.  The interstage transformers will be on the interior, along with five separate regulated power supplies (B+, bias, DC heater, 2x filament).  The left and right channels each have their own dedicated B+ and bias supply regulators.
> 
> ...


That distant blue may be my favorite color yet, blue but not too blue.....will it be matte finish or glossy...I am a sucker for matte finish.


----------



## L0rdGwyn

whirlwind said:


> That distant blue may be my favorite color yet, blue but not too blue.....will it be matte finish or glossy...I am a sucker for matte finish.



It will be a gloss.  Matte powders aren't offered very many places, the options are very limited unfortunately.


----------



## Galapac

L0rdGwyn said:


> It will be a gloss.  Matte powders aren't offered very many places, the options are very limited unfortunately.


That’s True. I tried to find a company around here that works with Prismacolors powder coats because they have some really cool metallic powder coats but no such luck. They are a 2 step process and the main guys don’t want to touch them.


----------



## L0rdGwyn (Oct 18, 2021)

Well I might have to amend my previous statements on the Audial S5 vs. my PCM56 DAC.

I said I was going to try the comparison again with a different amp.  For clarity, detail, soundstage, imaging, etc., the 45 amp for Zach / ZMF is the best I have, so I brought both DACs to my workbench.



I came away with a completely different set of observations.  Was it burn in of my DAC?  Was it the final changes I made to the circuit?  Or the amp pairing?

It was clear to me comparing the two that the PCM56 DAC has the larger soundstage, slightly better clarity, and better imaging.  The "warmth" I heard on my 6A5G amp was gone.  The sound is more three-dimensional with better vertical staging over the S5, which is itself no slouch.  With this pairing, the PCM56 DAC seems to have a more forward / pronounced midrange as well, whereas the S5 is more even across the spectrum, at least that is my initial impression.  Again, for technical performance, the S5 is close, but the PCM56 won out in this setup.

I will say this though - the pairing of the Audial S5 with the 45 amp is a little more relaxed and perhaps easier for a long listening session.  The combination of the PCM56 DAC with the 45 amp is insane.  The midrange clarity, imaging, soundstage...the detail retrieval is so high that it _demands_ your attention.  The pairing will pick apart a recording too - you can hear _every_ minute detail.  Another one of those cliché "I heard things I've never heard before" type of things.  An example - on the electronic album _Proto_ by Holly Herndon (which I was listening to this morning), on the track "Frontier" which is a mostly choral track with Gregorian-chant-esque vocals, between the first and second vocal sections of the track, the noise floor of the recording "cuts out", which made clear to me that the two sections were recorded separately and spliced together in production as opposed to being recorded in a single continuous take.  I had never heard the noise floor of the recording so clearly, having listened to this track numerous times.  The movement and breath and vocal detail in the opening section of the track "Extreme Love", along with the definition of the following bass line, was also pretty mind blowing.

I'll have to try the DAC comparison again with my 6A5G amp to see if my DAC has undergone some change or if it is pairing dependent, perhaps the 6A5G is imparting more of its sound on when paired with the PCM56 DAC.  The 45 amp is the most technically impressive one I have, so seems it would get closer to the "truth" of the upstream gear.

So I guess in summary, I'm again very happy with how my PCM56 DAC turned out.  I sought out a massive amount of NOS DAC design information and made what I felt were sound engineering decisions, but I still did not expect a result this good.  And I cannot wait for someone else to lay ears on this 45 amp and confirm or deny my impressions, not too much longer.


----------



## jgwtriode

Sounds amazing.  How close does the Airmid get to Zach's 45?  I had to ask, to guestimate whether the difference in what it would cost would be worth waiting a good bit longer for?

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Sounds amazing.  How close does the Airmid get to Zach's 45?  I had to ask, to guestimate whether the difference in what it would cost would be worth waiting a good bit longer for?
> 
> Happy listening,
> 
> jgwtriode



It's hard for me to say as I have not compared them directly and with the same gear!  The Airmid prototype is on its way back to me, so I will be able to listen to them side-by-side for the first time.  Given one is a SET design and the other an OTL, the two are drastically different so it would not be an apples-to-apples comparison really.

But I do have to reiterate that I haven't offered this 45 build up for public purchase as it was a one-off custom design.  I haven't ruled that out yet, it is something I have to think on, not a casual tube amp to own lol and requires some care on the part of the user given it is fixed bias.  It would be very expensive too - for reference, there are eight transformers in this amplifier, two pairs of which are custom (OPT and interstage).  The cost of the transformers alone is roughly $1,500, so the price jump from Airmid to the 45 amp, in theory, would be significant.  I mentioned that I'd like to try a cap-coupled version of it, but I am having some trouble getting in contact with Kevin at K&K Audio.  Hopefully I can get a pair of grid chokes in house in time to try it out.


----------



## jgwtriode

I will certainly keep in touch, cap coupled sounds like it might be a worthwhile compromise.  That's how my Bottlehead Paraglows we're done back in the day!

jgwtriode


----------



## L0rdGwyn

Kevin at K&K must have heard me talking about him, grid chokes are on the way, so will be able to try that out before breaking down the prototype for the final build.


----------



## Galapac (Oct 18, 2021)

*The Airmid by L0rdGwyn
”The Ferrari of amps”*





I was given the opportunity to listen to this amp and it left me speechless with a BIG smile on my face.

L0rdGwyn was gracious enough to loan the Airmid to me for a few days to take it out for a test drive, and like it’s race car colors, this amp is beautiful and fast.
The power switch just beckons you to turn it on with a forceful ‘click’ as the ‘engine’ warms up the pair of included 6J5 input tubes alongside a pair of my 5998 output tubes to be taken on a glorious ride.

I ran it this weekend with my ZMF Verite Open and Closed and my Focal Utopias and really enjoyed it most with my VCs.
The synergy between the VCs and this amp we’re match to behold and made my VCs seem as if they were an open set of headphones.

What I think separates the Airmid amp from others are twofold:

The separation of instruments with detail retrieval
The huge soundstage
I could not get over how big the soundstage is, one of the biggest I have heard from an amp!
With other amps I feel I get the impression of a cozy nightclub but with the Airmid the stage was the size of a concert hall!
Quite impressive and I was floored!

Also the detail is amazing and must be what Monsterzero was referring to In his review of the veil lifting, the clean television analogy.

This amp just begs for great sound recordings. I found the better the recording, the more I got from the Airmid.
If the original recording is not up to snuff, it will show, not in a bad way, but it will not sound ideal as the better quality recordings.
Only serious recordings need apply.
You wouldn’t put cheap gas in a _Ferrari_, would you?

It’s also worth noting that the Airmid is dead quiet when turned on/no music playing.
All of that under the hood, pedal to the floor, and…ZERO NOISE!

This is a very important aspect that is sometimes overlooked in tube amps which adds that clarity and detail that you don’t get from lesser quality builds.
I believe that is part of L0rdGwyn’s “magic” and why his Airmid amp has outstanding detail retrieval and clarity.

This amp is not for the feint of heart and is a beast. It needs to be to house those dual Clarity Caps that remind me of 2 pistons busting out of a car hood.

I really enjoyed giving the Airmid amp a test drive and thank L0rdGywn for giving me the opportunity to audition one of his latest creations.

If you are considering a new amp and have been looking for a quality, made in the USA amp, look no further and get yourself an Airmid, you will not regret it.
I would have ‘stolen’ this one from L0rdGwyn but I just recently bought an amp just prior to his release. 😁
Get in the queue now before the wait becomes too long and prices rise due to sourcing.


----------



## jgwtriode

Wow almost ready to say the hell with it and just say this amp might be enough.  But a part of me just has to know how it compares with that 45 Zach ordered.  Maybe a cap couple get just enough more right to be worth doing a bit more, that's of course if LOrdGwyn  approves of making it at least available on a custom basis.  But Hot Damn that truly does look and sound potentially it could be pretty hard to beat for anything under 4K.     Oh well saving for 1st quarter of next year.

Awesome truly awesome, thanks for sharing,

jgwtriode


----------



## Xcalibur255 (Oct 19, 2021)

Have you been able to listen to both a transformer coupled and OTL type tube amp before?  They sound quite different and honestly I don't think words entirely do those differences justice.  Each imparts the music with a different kind of soul.  It's not really about one being better than the other either, but you might find that one aligns to your personal ideal sound better.  I find a lot to like about both, but my ears have spent more time listening to OTLs over the years.  There is an effortless quality to their clarity that makes them so easy to listen to.

Also, I don't want to speak for Keenan at all, but I'm guessing that even a cap coupled version of the 45 would probably be north of that 4K figure you mentioned.  It's a pretty "no expense spared" type build and amps that have this level of parts cost are in somewhat rare air.


----------



## jgwtriode (Oct 19, 2021)

Oh indeed I know. I had $3500 dollars into my Bottlehead 2A3's back about 10 to 12 years ago.  Magnequest cobalt trannies and Vaic 2A3 Meshplates, Custom coin silver potentiometers with tantulum resistors and the best Aeon Caps I could find bypassed with some even crazier ones I fail to remember now.  They were quite amazing for a DIY 2A3.  Never have forgotten how magically musical and spacious they were.  But no I have never listened to an OTL.  Harmonic structure, PRAT and staging is what really pushes my buttons.

I do have my VC leopard woods sounding pretty good.  I drive them a really crazily modded oppo from EVS tweak shop running a femto clock and a custom built pure class A high current output stage Rick dropped into it for me.   I get crazy staging with it and I tweak the hell out of my system to get it close, it is more triode tube like than any other solid state system I have run, but its still not quite a triode.  

Happy listening,

jgwtriode


----------



## Xcalibur255

I personally consider OTL amps to be exceptionally good at all three of those things, but we each have our own preferences regarding what's ideal of course.


----------



## jgwtriode (Oct 19, 2021)

As  Artie Johnson used to say!  MMMM! Very Interesting.   Okay I look forward to Keenan's comparison's in the near future!  
But thanks for info.   I will be following this thread quite seriously over the next few months as I fill the piggy!  What are you running
if may ask?

Happy listening,
jgwtriode.


----------



## Xcalibur255

I have a pair of Glenn made amps, both OTL and 45 SET.


----------



## jgwtriode

So what differences do you find between them.  I'm certainly not in a position to do both anywhere in the future.  It would be one or the other.  I like the idea of it costing less but am willing to wait if potentially a 45 would be the better long term choice.  At this point from everything I have seen read and considered I think LOrdGwyn's offer the best option  for what I am trying to accomplish.  I looked seriously at ampsandsound and I like Justin's approach, but I think Keenan's offer move value for the dollar.   Anyhow, it won't be until February or March of next year, but am planning it out now.   Wish I could have one of each an OTL and a 45 SET, but one will have to do!

Happy listening,

jgwtriode


----------



## bpiotrow13

jgwtriode said:


> So what differences do you find between them.  I'm certainly not in a position to do both anywhere in the future.  It would be one or the other.  I like the idea of it costing less but am willing to wait if potentially a 45 would be the better long term choice.  At this point from everything I have seen read and considered I think LOrdGwyn's offer the best option  for what I am trying to accomplish.  I looked seriously at ampsandsound and I like Justin's approach, but I think Keenan's offer move value for the dollar.   Anyhow, it won't be until February or March of next year, but am planning it out now.   Wish I could have one of each an OTL and a 45 SET, but one will have to do!
> 
> Happy listening,
> 
> jgwtriode


I would be extremly interested in OTL/45 SET comparison as well. I understand these are different designs but maybe there are also some general differences in sound signature that can be described.


----------



## chrisdrop

… taking a lot of willpower to not order an Airmid. Good luck to the first int the queue !


----------



## leftside

All this talk of 45's got me thinking about bringing out some of my old 7" records and spinning a few singles...

Not DIY, but very custom - I think Mick from Supratek is going to build me a linestage/preamp. This time DHT based that can take 300B, 45 or PX4 tubes. I've had the Glenn 300B amp for a few years now, and not once have I been tempted to tube roll. Hopefully the same will stay true with this linestage. I've been very impressed with the Cortese preamp he built me last year. As it gets closer to completion (project for next year) I'll ask for some 45 or PX4 tube recommendations.


----------



## L0rdGwyn

chrisdrop said:


> … taking a lot of willpower to not order an Airmid. Good luck to the first int the queue !



That reminds me - I need to grab a 120VAC to 230VAC / 240VAC step up transformer for testing purposes, thanks


----------



## L0rdGwyn (Oct 21, 2021)

leftside said:


> All this talk of 45's got me thinking about bringing out some of my old 7" records and spinning a few singles...
> 
> Not DIY, but very custom - I think Mick from Supratek is going to build me a linestage/preamp. This time DHT based that can take 300B, 45 or PX4 tubes. I've had the Glenn 300B amp for a few years now, and not once have I been tempted to tube roll. Hopefully the same will stay true with this linestage. I've been very impressed with the Cortese preamp he built me last year. As it gets closer to completion (project for next year) I'll ask for some 45 or PX4 tube recommendations.



Very cool, that should be fun.  With NOS DHTs, I have with tube rolling the differences are quite small, so I just pop the tubes in that I like to look at most.

I like the look of the graphite plate 801As.  I've posted this pic before, but I like how it turned out.






Thanks to a tip from @tubebuyer2020 , I have some MOV 6F5GT variants on the way, the H63.  I've had my eye out for a pair of these for a reasonable price, but they are very uncommon.  Owe @tubebuyer2020 for pointing out a killer listing for me, five NOS Marconi H63 en route from Italy, they have black bases however unlike the photo below.


----------



## Velozity

Lol, I'm three weeks late to the party but congrats Keenan!  When you're ready to send that DAC on tour holla at me!


----------



## L0rdGwyn

Velozity said:


> Lol, I'm three weeks late to the party but congrats Keenan!  When you're ready to send that DAC on tour holla at me!



Thanks!  And I'll let you know!  Doing a lot of testing / listening at the moment, so it's all DACs on deck right now, but once things settle down I will consider a tour.  Unlikely this DAC is something I would put out there for general purchase in any sort of "official" capacity, but if the feedback was positive, I might consider doing one-off builds.


----------



## L0rdGwyn (Oct 21, 2021)

Still in the middle of a heinous work schedule, so not a whole lot of work getting done, but I did get my Lundahl grid chokes today.



Might not get to trying the cap-coupled version this weekend, probably next week.

While I have the prototype up, I am also going to take another input tube for a test drive, the famous 5687.  With the two sections in parallel it makes a suitable driver in a interstage transformer coupled amplifier.  However, it has lower gain than the 6E6P, less linear, and more demanding heater requirements.  Regardless, want to see how it compares while the prototype is built, so that should be interesting.  I have a single E182CC, which is a near equivalent, but no pair of these tubes, so I picked up some Tung-Sols which should be here Monday, maybe this weekend.


----------



## Xcalibur255

How about the 7119?


----------



## L0rdGwyn

Xcalibur255 said:


> How about the 7119?



Oh yeah, the 7119 is equivalent to the E182CC, which is a near-equivalent to the 5687, so they could be used interchangeably.


----------



## L0rdGwyn (Oct 22, 2021)

Once I'm caught up on a few things (well, a lot of things), I might make a little parafeed spud amplifier using the Sowter 8665 output transformers, might even harvest them from my 841 amplifier.  Sad reality is that amp is just sitting unused.  Not comfortable selling it given the voltages inside, tubes used, and a few other reasons.  I am thinking about breaking it down and re-using the parts.

What tubes for this spud?  I am considering EL83.  I have some on hand from a different project I was working on a while back.  They are affordable, plentiful, quite linear, with good gain for a spud design with a mu of 24 triode-strapped, plate resistance a little less than 2K which works well with the Sowter 8665.

Nice thing is I could pretty well guarantee this would be a good sounding amplifier without messing around with a prototype.  Could just design the chassis and build the thing.  It would also be very compact.  Could also swap the tubes to something with higher gain if need be very easily.

Once I get the 45 amp and first few Airmids out the door, will probably work on this next.


----------



## triod750

L0rdGwyn said:


> Once I'm caught up on a few things (well, a lot of things), I might make a little parafeed spud amplifier using the Sowter 8665 output transformers, might even harvest them from my 841 amplifier.  Sad reality is that amp is just sitting unused.  Not comfortable selling it given the voltages inside, tubes used, and a few other reasons.  I am thinking about breaking it down and re-using the parts.
> 
> What tubes for this spud?  I am considering EL83.  I have some on hand from a different project I was working on a while back.  They are affordable, plentiful, quite linear, with good gain for a spud design with a mu of 24 triode-strapped, plate resistance a little less than 2K which works well with the Sowter 8665.
> 
> ...


The 'Like' wasn't for breaking down the 841, that would be a sad thing to do. But building a spud would be a nice project. Many people talk about but nobody does it. I have always wanted to listen to one. I still do. So: Like!


----------



## L0rdGwyn (Oct 22, 2021)

Listening to the cap-coupled version of the 45 amplifier at the moment.

In this version, the input tubes have active loads, the two-stages are capacitor coupled, and the DC path to ground for the 45 grids is provided by the chokes as opposed to the interstage transformer secondaries.  The inductive reactance of the chokes load the input stages in parallel to the active loads on the plates.  Also, the amplifier can no longer sneak in some A2 voltage swing given the cap-coupling - the input stage can no longer provide grid current to the 45.

This change reduces the cost by around $400.



The sound is still excellent I would say, but the hyper clarity and imaging of the interstage-coupled version is noticeably reduced.  I would say it is still "very good" whereas the interstage-coupled version is "superb".  The overall tonal character is maintained, perhaps a bit more smoothed without the extra detail when interstage-coupled.

So both good, but the extra cost of the interstage transformers does have yields in terms of staging, clarity, and detail retrieval.

Now that that's finally done, I can break down this prototype in anticipation of the final build.


----------



## L0rdGwyn

Got the Airmid prototype back today too, thanks @Galapac !  First time listening to it with the PCM56 DAC.  Sounds purdy darn good!


----------



## triod750

L0rdGwyn said:


> Got the Airmid prototype back today too, thanks @Galapac !  First time listening to it with the PCM56 DAC.  Sounds purdy darn good!


My dac is much smaller than your dac. I could live in Tokyo!


----------



## L0rdGwyn

triod750 said:


> My dac is much smaller than your dac. I could live in Tokyo!



This is more of a "rural farmlands of the USA" type of DAC.


----------



## jgwtriode

Awe very nice, looking forward to some comparisons and opinions about the Airmid vs. the 45.  More I think about it the Aimid is a far more realistic choice but I want to feel like it's close enough to 45, albeit cathode coupled, to make me okay with spend a few thousand less.  Money is an issue, but sound quality is just as much so, 
Thanks and happy listening,

jgwtriode


----------



## L0rdGwyn (Oct 22, 2021)

jgwtriode said:


> Awe very nice, looking forward to some comparisons and opinions about the Airmid vs. the 45.  More I think about it the Aimid is a far more realistic choice but I want to feel like it's close enough to 45, albeit cathode coupled, to make me okay with spend a few thousand less.  Money is an issue, but sound quality is just as much so,
> Thanks and happy listening,
> 
> jgwtriode



Hi jgwtriode - hard to say exactly how they differ, I think everyone hears different things when comparing gear and they are dissimilar topologies.  In general, the Airmid finds a great balance between tube euphony, musicality, smooth character associated with OTLs while bringing with it a great deal of what I would call technical characteristics like soundstage, clarity, detail retrieval.  The two balance really well.  What you get more of from a high-end fixed bias SET design, like this 45 amp, is more of those technical characteristics, but the overall tonal character and how the music is presented between SET and OTL goes beyond that - I find difficult to put into words, something that I think does need to be heard.  Both are very good in their respective categories, but if you crave the utmost in soundstage, clarity, airiness, etc. a SET design has a higher ceiling in that regard, in my experience, whereas the OTL topology brings much in the way of euphony and musicality for significantly less money and is no slouch when it comes to technical prowess.  Hope that helps.


----------



## Xcalibur255

If we were talking about OTL vs. SET as though they are instruments then I would say they each have their own unique "timbre" that defines their character.  You can't totally quantify this with technical descriptors like soundstage and such.  There are also differences in PRAT that are difficult to put into words, as LG says you kind of have to hear both to quantify it for yourself.


----------



## L0rdGwyn (Oct 23, 2021)

I was breaking down the 45 prototype this morning and thought of an easy way to try this spud idea without too much effort.

Since I already have the 9-pin sockets of my protoboard set up for 6E6P, a simple way to try the spud was to leave the output stage components of my 841 amp in the chassis but disconnect them from the circuit and connect them to the 6E6P stage on my protoboard.  Took all of about 15 minutes.

The truth is I've had some trouble getting this 841 design to sound the way I'd like it to, I have better amps so it has been sitting.  After a lot of testing, I know the fix, but requires more PCB design, circuit changes, etc. and I'm a bit fatigued on working on it.  I also have too many amps, so converting it into something I could potentially sell with confidence is appealing, as is shrinking it down to a more reasonable size.

So anyway, I gave this a shot, took about 5 minutes for me to realize my spud circuit with the 6E6P sounds really good and I will be building it.  Will try it with the EL83 too and build what I feel is the better sounding of the two.

As built, it uses Sowter output transformers, Goldpoint attenuator, Goldpoint impedance selector switch, Clarity Caps, so not cheap given the quality of the components, but will investigate the total cost to reproduce it - would be a very compact and great sounding design to potentially offer for public sale.


----------



## whirlwind

The spud could be a great option for people needing a smaller footprint.
Small footprint and big sound.


----------



## Mr Trev

L0rdGwyn said:


> Once I'm caught up on a few things (well, a lot of things), I might make a little parafeed spud amplifier using the Sowter 8665 output transformers, might even harvest them from my 841 amplifier.  Sad reality is that amp is just sitting unused.  Not comfortable selling it given the voltages inside, tubes used, and a few other reasons.  I am thinking about breaking it down and re-using the parts.
> 
> What tubes for this spud?  I am considering EL83.  I have some on hand from a different project I was working on a while back.  They are affordable, plentiful, quite linear, with good gain for a spud design with a mu of 24 triode-strapped, plate resistance a little less than 2K which works well with the Sowter 8665.
> 
> ...


Care to enlighten a dullard like me… what exactly is a spud amp? I've heard of parafeed (Hagerman Tuba is one of the amps on my list)


----------



## Zachik

L0rdGwyn said:


> would be a very compact and great sounding design to potentially offer for public sale.


Keenan, how would a spud amp sound in comparison to an SET design? I assume that is the closest to compare to? I personally love tubey sound (as opposed to something that would sound too close to solid-state).
Also, how compact is compact? 
I have been toying with an idea of a small tube amp for use "outside my audio setup" arear. Probably on a side table in the living room, and mostly / probably with IEMs... 
Which brings another question: how quiet do you think the background / noise floor would be? Being a 1-stage amp, I am thinking probably pretty low noise floor?


----------



## L0rdGwyn

Mr Trev said:


> Care to enlighten a dullard like me… what exactly is a spud amp? I've heard of parafeed (Hagerman Tuba is one of the amps on my list)



A "spud" is a tube amp that only uses one tube per channel, typically transformer coupled, either in a SET output stage or parafeed.  Given there is only a single tube, these are usually low power designs, but work very well as headphone amplifiers.  Tubes for spud designs need to have both high gain and low plate resistance, so are usually high transconductance types.



Zachik said:


> Keenan, how would a spud amp sound in comparison to an SET design? I assume that is the closest to compare to? I personally love tubey sound (as opposed to something that would sound too close to solid-state).
> Also, how compact is compact?
> I have been toying with an idea of a small tube amp for use "outside my audio setup" arear. Probably on a side table in the living room, and mostly / probably with IEMs...
> Which brings another question: how quiet do you think the background / noise floor would be? Being a 1-stage amp, I am thinking probably pretty low noise floor?



A spud is really a single stage SET or parafeed amplifier, there is basically just a high-gain transformer-coupled output stage without an input stage.  Since headphones don't need a lot of power, spud designs make a lot of sense - keeps the signal path short with few components which lends itself well to big soundstage and high degree of clarity.  Won't be huge on power, likely around 500mW (max rating for the Sowter 8665 transformers), but that is plenty for the vast majority of headphones.  I don't know exactly how compact yet, I actually started drafting a chassis design the other day - going to start with 8" L x 10" W x 2.25" H and see where it goes.

I tried the EL83 - both sound good, not sure which direction I will go.  The EL83 is a good looking tube.




I have a bunch of E55L tubes which are a popular spud choice, but I am saving those for a LCR phono stage


----------



## Zachik

L0rdGwyn said:


> Won't be huge on power, likely around 500mW (max rating for the Sowter 8665 transformers), but that is plenty for the vast majority of headphones.


500mW is plenty, especially for IEMs.  Any idea how well it would behave with sensitive IEMs? Low noise floor and all?



L0rdGwyn said:


> going to start with 8" L x 10" W x 2.25" H and see where it goes.


I was hoping to hear 6" x 8" 
(but 8x10 is not a showstopper...)



L0rdGwyn said:


> I tried the EL83 - both sound good, not sure which direction I will go. The EL83 is a good looking tube.


EL83 looks good and is not expensive, too!


----------



## L0rdGwyn

Zachik said:


> 500mW is plenty, especially for IEMs.  Any idea how well it would behave with sensitive IEMs? Low noise floor and all?
> 
> 
> I was hoping to hear 6" x 8"
> ...



Could maybe pull off 8"x8", we'll see, still need room for three transformers!  No timeline on this though just figured I'd try it out while it's convenient, have to catch up on other stuff first.  I would expect a low noise floor yes.  Both 6E6P and EL83 are affordable, whichever one goes in the final build.  Will eyeball some other options too.


----------



## whirlwind

L0rdGwyn said:


> A "spud" is a tube amp that only uses one tube per channel, typically transformer coupled, either in a SET output stage or parafeed.  Given there is only a single tube, these are usually low power designs, but work very well as headphone amplifiers.  Tubes for spud designs need to have both high gain and low plate resistance, so are usually high transconductance types.
> 
> 
> 
> ...


Kind of like the GEL3N in one tube mode ?


----------



## L0rdGwyn

whirlwind said:


> Kind of like the GEL3N in one tube mode ?



Exactly!  One tube GEL3N is basically a spud.


----------



## Zachik

L0rdGwyn said:


> Exactly!  One tube GEL3N is basically a spud.


Cool. I thought I do not have a potato amp, but apparently - I do!!!


----------



## A2029

Zachik said:


> Cool. I thought I do not have a potato amp, but apparently - I do!!!








Potato amplifier  With filaments run off a potato power supply:


----------



## bcowen

A2029 said:


> Potato amplifier  With filaments run off a potato power supply:


LOL!  And once the potatoes die, you can still make french fries out of them.


----------



## Zachik

A2029 said:


> Potato amplifier  With filaments run off a potato power supply:


Up until now, I thought my next amp will be in a rectangle chassis... 
Mischa, how many transformers can you fit inside a Mr. Potato Head?


----------



## Xcalibur255

What's the advantage of the EL83 over the EL84?


----------



## L0rdGwyn

Xcalibur255 said:


> What's the advantage of the EL83 over the EL84?



It has a little more gain than the EL84 with similar plate resistance.  But if I am being honest, I think the high gm Russian tetrodes probably sound better, will do one more A-B, but more likely to go that direction.


----------



## tubebuyer2020

triod750 said:


> My dac is much smaller than your dac. I could live in Tokyo!



I don't know, Tokyo guys are on a whole other level:



> Normal electricity just wouldn’t do anymore. To tap into what Mr. Morita calls “pure” power, he paid $10,000 to plant a 40-foot-tall concrete pole in his front yard. On it perches his own personal transformer—that thing shaped like a cylindrical metal garbage can—which feeds power more directly from the grid.
> ...
> “It’s completely beyond my understanding,” says his wife, Reiko, 57. “But if I take it away from him, he will lose the motivation to live.”



https://www.wsj.com/articles/a-gift...ave-it-all-a-personal-utility-pole-1471189463


----------



## Mr Trev

L0rdGwyn said:


> A "spud" is a tube amp that only uses one tube per channel, typically transformer coupled, either in a SET output stage or parafeed.  Given there is only a single tube, these are usually low power designs, but work very well as headphone amplifiers.  Tubes for spud designs need to have both high gain and low plate resistance, so are usually high transconductance types.
> 
> 
> 
> ...


I take it then it wouldn't come close to enough current to drive planars?


----------



## L0rdGwyn (Oct 23, 2021)

Mr Trev said:


> I take it then it wouldn't come close to enough current to drive planars?



Probably depends on the planar and its sensitivity, output impedance of around 10ohms on the low-impedance tap if using 6E6P or 6E5P.  I don't own any real power hungry planars so I cannot test subjectively, but I've picked up around Head-Fi people like to use high-wattage amplifiers with their planars, even if they are using less than 1% of the total power!  Seems like overkill to me, but lots of people are doing it so maybe there is something to it.  In theory, even 250mW would drive any planar to unlistenable volumes.  250mW should get the HE-6 to 108dB peaks (going purely by the spec sheet).  500mW should be enough for any headphone, but like I said, I hear people like to drive their planars with massive amounts of unused power on tap and feel there is some advantage there, but I haven't tried it myself.

If high power is needed, a more traditional two-stage SET design is probably the way to go over a spud.


----------



## bcowen

L0rdGwyn said:


> Probably depends on the planar and its sensitivity, output impedance of around 10ohms on the low-impedance tap if using 6E6P or 6E5P.  I don't own any real power hungry planars so I cannot test subjectively, but I've picked up around Head-Fi people like to use high-wattage amplifiers with their planars, even if they are using less than 1% of the total power!  Seems like overkill to me, but lots of people are doing it so maybe there is something to it.  In theory, even 250mW would drive any planar to unlistenable volumes.  250mW should get the HE-6 to 108dB peaks (going purely by the spec sheet).  500mW should be enough for any headphone, but like I said, I hear people like to drive their planars with massive amounts of unused power on tap and feel there is some advantage there, but I haven't tried it myself.
> 
> If high power is need, a more traditional two-stage SET design is probably the way to go over a spud.


The Schiit Lyr 3 puts out a little over 9 watts into the DCA Aeon 2's.  I felt it was pretty sufficient.


----------



## L0rdGwyn

I actually feel pretty confident this spud is done, 6E6P it is.  It's basically the input stage of my cap-coupled 45 SET build, except instead of a 45 output stage, there is just an output transformer!  Bigger coupling cap too, for parafeed.

Around 9-10 o'clock on the spud is pretty darn loud for a 97dB/mW 300ohm headphone.  Full tilt on the pot hits over 500mW in the low, medium, and high impedance settings into 32ohms, 120ohms, 300ohms, respectively with a 2Vrms input.

Square waves look good, THD at 1mW into 300ohms is 0.048% H2 dominant.


----------



## Xcalibur255

I'm going to bring my annual tradition of mentioning that somebody should do an EML 30A or 20B spud over to this thread.  Because there's a chance Keenan just might do it someday.    I suspect 30A is the harder reach because of the higher resistance but it's the only one that really seems like it has enough gain too.


----------



## Xcalibur255

L0rdGwyn said:


> Probably depends on the planar and its sensitivity, output impedance of around 10ohms on the low-impedance tap if using 6E6P or 6E5P.  I don't own any real power hungry planars so I cannot test subjectively, but I've picked up around Head-Fi people like to use high-wattage amplifiers with their planars, even if they are using less than 1% of the total power!  Seems like overkill to me, but lots of people are doing it so maybe there is something to it.  In theory, even 250mW would drive any planar to unlistenable volumes.  250mW should get the HE-6 to 108dB peaks (going purely by the spec sheet).  500mW should be enough for any headphone, but like I said, I hear people like to drive their planars with massive amounts of unused power on tap and feel there is some advantage there, but I haven't tried it myself.
> 
> If high power is needed, a more traditional two-stage SET design is probably the way to go over a spud.


My personal theory about this has always been that the high power design ends up offering some secondary benefits such as improved dynamics (due to the robust power supply) and possibly good compatibility with difficult loads because it has ample reserves.  I agree with you though, the groupthink around "needing" lots of power just doesn't jive with the science behind how all this stuff works.  500mW is adequate for any headphone on Earth if the entire design is good, unless the goal is to give yourself hearing damage quickly.


----------



## Mr Trev

L0rdGwyn said:


> Probably depends on the planar and its sensitivity, output impedance of around 10ohms on the low-impedance tap if using 6E6P or 6E5P.  I don't own any real power hungry planars so I cannot test subjectively, but I've picked up around Head-Fi people like to use high-wattage amplifiers with their planars, even if they are using less than 1% of the total power!  Seems like overkill to me, but lots of people are doing it so maybe there is something to it.  In theory, even 250mW would drive any planar to unlistenable volumes.  250mW should get the HE-6 to 108dB peaks (going purely by the spec sheet).  500mW should be enough for any headphone, but like I said, I hear people like to drive their planars with massive amounts of unused power on tap and feel there is some advantage there, but I haven't tried it myself.
> 
> If high power is needed, a more traditional two-stage SET design is probably the way to go over a spud.


Fair enough.
Send a spud my way and I'll let you know how it works out


----------



## L0rdGwyn

Xcalibur255 said:


> I'm going to bring my annual tradition of mentioning that somebody should do an EML 30A or 20B spud over to this thread.  Because there's a chance Keenan just might do it someday.    I suspect 30A is the harder reach because of the higher resistance but it's the only one that really seems like it has enough gain too.



That could be fun, only tricky part - those tubes have pretty high plate resistance, lowest on the 20B at 3K3.  That means you are looking at a output transformer with a primary impedance of 10K or more.  Transformer parasitics and bandwidth can become issues with a high primary impedance.  Transformers would probably have to be custom and still unlikely to get a nice flat response.  But if you can sacrifice all that, it could be done!  I actually have some LL9202 50mA transformers sitting around here somewhere, can be wired for 11K, could work but the HF would probably roll off around 15kHz based on what I've seen.  They are good sounding transformers, even so.  Gain also is an issue with an amplification factor of 20 using a high impedance OPT, for all that probably would get less than 250mW with a 11K load - probably would necessitate a step-up transformer to swing some voltage on the 20B grid.  Could use some local negative feedback to improve the bandwidth and output impedance, but again, already limited on available gain.  Then there's the filament supply, and with a  SUT, another place to potentially couple magnetic noise.  Things start to get complicated pretty fast lol it hurts the brain.  Could definitely be done, but wouldn't be easy peasy.


----------



## L0rdGwyn

Mr Trev said:


> Fair enough.
> Send a spud my way and I'll let you know how it works out



If / when I build one, will probably send on a short tour


----------



## triod750

L0rdGwyn said:


> If / when I build one, will probably send on a short tour


Since when was Sweden a short tour?
Ah, yes, from Norway it is. Stupid me.


----------



## Xcalibur255

L0rdGwyn said:


> That could be fun, only tricky part - those tubes have pretty high plate resistance, lowest on the 20B at 3K3.  That means you are looking at a output transformer with a primary impedance of 10K or more.  Transformer parasitics and bandwidth can become issues with a high primary impedance.  Transformers would probably have to be custom and still unlikely to get a nice flat response.  But if you can sacrifice all that, it could be done!  I actually have some LL9202 50mA transformers sitting around here somewhere, can be wired for 11K, could work but the HF would probably roll off around 15kHz based on what I've seen.  They are good sounding transformers, even so.  Gain also is an issue with an amplification factor of 20 using a high impedance OPT, for all that probably would get less than 250mW with a 11K load - probably would necessitate a step-up transformer to swing some voltage on the 20B grid.  Could use some local negative feedback to improve the bandwidth and output impedance, but again, already limited on available gain.  Then there's the filament supply, and with a  SUT, another place to potentially couple magnetic noise.  Things start to get complicated pretty fast lol it hurts the brain.  Could definitely be done, but wouldn't be easy peasy.


Yeah I think most people who do it use a 2:1 or 4:1 step-up.  I'm sure it would be an expensive build to get right.  A guy can dream though.


----------



## Monsterzero

L0rdGwyn said:


> I've picked up around Head-Fi people like to use high-wattage amplifiers with their planars, even if they are using less than 1% of the total power!





Xcalibur255 said:


> My personal theory about this has always been that the high power design ends up offering some secondary benefits such as improved dynamics (due to the robust power supply) and possibly good compatibility with difficult loads because it has ample reserves. I agree with you though, the groupthink around "needing" lots of power just doesn't jive with the science behind how all this stuff works. 500mW is adequate for any headphone on Earth if the entire design is good, unless the goal is to give yourself hearing damage quickly.


I love my vintage receivers as headphone amps. They can drive the difficult -to-drive K240 sextett and K340 without breaking a sweat. Similarly on the OG LCD2.1 as well as the HE500, no probs. However the HE6 was woefully undertpowered on the same receivers and I only understood the hype on the HE6 once I got a speaker tap cable for it.
I used everything from a 55 watt Sansui to a 125 watt Kenwood to drive the HE6, and the difference between speaker taps and headphone jack was the obligatory night/day difference.


----------



## bpiotrow13

L0rdGwyn said:


> That could be fun, only tricky part - those tubes have pretty high plate resistance, lowest on the 20B at 3K3.  That means you are looking at a output transformer with a primary impedance of 10K or more.  Transformer parasitics and bandwidth can become issues with a high primary impedance.  Transformers would probably have to be custom and still unlikely to get a nice flat response.  But if you can sacrifice all that, it could be done!  I actually have some LL9202 50mA transformers sitting around here somewhere, can be wired for 11K, could work but the HF would probably roll off around 15kHz based on what I've seen.  They are good sounding transformers, even so.  Gain also is an issue with an amplification factor of 20 using a high impedance OPT, for all that probably would get less than 250mW with a 11K load - probably would necessitate a step-up transformer to swing some voltage on the 20B grid.  Could use some local negative feedback to improve the bandwidth and output impedance, but again, already limited on available gain.  Then there's the filament supply, and with a  SUT, another place to potentially couple magnetic noise.  Things start to get complicated pretty fast lol it hurts the brain.  Could definitely be done, but wouldn't be easy peasy.


I think Emission Labs's distributor in Europe published some schematics related to 20b amplifier, including headphone one.

http://www.jacmusic.com/kits/pre-amp/20B-V4-Low-Noise/20B-V4-index.htm

And, pardon my ignorance, if output transformer is a problem, could't be an OTL design? The more i listen ro my Verite the more I like this design.


----------



## L0rdGwyn (Oct 24, 2021)

Xcalibur255 said:


> Yeah I think most people who do it use a 2:1 or 4:1 step-up.  I'm sure it would be an expensive build to get right.  A guy can dream though.



Yeah totally doable, but hard to say how good the result would be.  My 841 amplifier is sort of a DHT spud, except there is a transistor buffer between the tube and the parafeed capacitor.  Since the very linear 841 is working into an active load and a source follower buffer, is achieves super low distortion and very low output impedance.  Was a pie in the sky build and it works!  But like I said, the sound isn't perfect.  What I've found gets the best sound is to feed the buffer circuit directly from the power supply voltage regulator while the active load of the 841 is RC decoupled with a high quality film power supply cap, like a ClarityCap TC series.  The type of cap there matters enormously, which was very surprising.  With a 30uF ClarityCap TC2, the sound is excellent, but I have no room for that cap lol could maybe squeeze in a 10uF TC2, but then the question becomes, is it worth revising the circuit again?  Getting the source follower buffer to sound its best was quite a task, I must have revised that circuit five times.  And the more straightforward, smaller, less complex 6E6P spud sounds excellent.  So I guess the point I am making is at some point there are diminishing returns on design complexity, even if it looks good on paper.



Monsterzero said:


> I love my vintage receivers as headphone amps. They can drive the difficult -to-drive K240 sextett and K340 without breaking a sweat. Similarly on the OG LCD2.1 as well as the HE500, no probs. However the HE6 was woefully undertpowered on the same receivers and I only understood the hype on the HE6 once I got a speaker tap cable for it.
> I used everything from a 55 watt Sansui to a 125 watt Kenwood to drive the HE6, and the difference between speaker taps and headphone jack was the obligatory night/day difference.



Well in that case, I'm guessing a 500mW spud likely isn't going to get the job done lol but hey might be fun to try 



bpiotrow13 said:


> I think Emission Labs's distributor in Europe published some schematics related to 20b amplifier, including headphone one.
> 
> http://www.jacmusic.com/kits/pre-amp/20B-V4-Low-Noise/20B-V4-index.htm
> 
> And, pardon my ignorance, if output transformer is a problem, could't be an OTL design? The more i listen ro my Verite the more I like this design.



The 20B headphone amplifier is pretty much what I described, I wonder if he ever built it!

Well some of the same problems exist even if trying to build an OTL - it isn't the transformer that is the issue, it is using a transformer with the particular characteristics of the tube, and the issues are similar in OTL.  If wired as a cathode follower (most common OTL topology), the output impedance is going to be roughly 1/gm (transconductance).  The 20B has a transconductance of 5.9mA/V, so you are looking at an output impedance of roughly 170ohms in that case, that's pretty high!  Also the cathode follower does not provide any gain, so it would have to be a two-stage design with a gain stage before the 20B cathode follower.  One thing that could be investigated - transformer coupling a cathode follower to lower the output impedance and increase current gain further.  If you could put maybe a 4:1 transformer on the cathode of the 20B, could get the output impedance down to a suitable place for headphones, but that is pretty unusual.  Typically tubes with high gm are used to get the output impedance down further without using a transformer, or paralleling multiple tubes.  This is why tubes like the 5998 are often used in OTL designs, it has almost three times the transconductance of the 20B.


----------



## triod750

L0rdGwyn said:


> Yeah totally doable, but hard to say how good the result would be.  My 841 amplifier is sort of a DHT spud, except there is a transistor buffer between the tube and the parafeed capacitor.  Since the very linear 841 is working into an active load and a source follower buffer, is achieves super low distortion and very low output impedance.  Was a pie in the sky build and it works!  But like I said, the sound isn't perfect.  What I've found gets the best sound is to feed the buffer circuit directly from the power supply voltage regulator while the active load of the 841 is RC decoupled with a high quality film power supply cap, like a ClarityCap TC series.  The type of cap there matters enormously, which was very surprising.  With a 30uF ClarityCap TC2, the sound is excellent, but I have no room for that cap lol could maybe squeeze in a 10uF TC2, but then the question becomes, is it worth revising the circuit again?  Getting the source follower buffer to sound its best was quite a task, I must have revised that circuit five times.  And the more straightforward, smaller, less complex 6E6P spud sounds excellent.  So I guess the point I am making is at some point there are diminishing returns on design complexity, even if it looks good on paper.
> 
> 
> 
> ...


I guess both Bogdan and I understood every word of what you wrote. The difficulties come when adding them together and trying to get a grip on what it adds up to. But my translation is 'this is complex and doubtful if it is worth doing'. Am I close?


----------



## bpiotrow13

L0rdGwyn said:


> I wonder if he ever built it!


I see no trace of that. However i see some 20b amplifiers built by his customers.

https://www.jacmusic.com/html/diversen/guestbk-all-text2.html

I may be wrong but judging from the picture one may be headphone amplifier.


----------



## bpiotrow13

triod750 said:


> I guess both Bogdan and I understood every word of what you wrote. The difficulties come when adding them together and trying to get a grip on what it adds up to. But my translation is 'this is complex and doubtful if it is worth doing'. Am I close?


Straight to the point Stefan


----------



## L0rdGwyn

triod750 said:


> I guess both Bogdan and I understood every word of what you wrote. The difficulties come when adding them together and trying to get a grip on what it adds up to. But my translation is 'this is complex and doubtful if it is worth doing'. Am I close?



That's pretty much the gist of it!  I'm not really doing custom builds, maybe in the future, but that would have to be something someone commissioned and financially committed to, not really one that just "makes sense" to try.


----------



## bpiotrow13

L0rdGwyn said:


> That's pretty much the gist of it!  I'm not really doing custom builds, maybe in the future, but that would have to be something someone commissioned and financially committed to, not really one that just "makes sense" to try.


I guess it will be more or less a guess how such amplifier would sound. It is hard to find information on how 20b sounds.


----------



## L0rdGwyn

bpiotrow13 said:


> I guess it will be more or less a guess how such amplifier would sound. It is hard to find information on how 20b sounds.



Well, I'm sure the tube sounds good when implemented well, it is very linear, here are the 20B curves:




The tube doesn't make the circuit however!  A lot goes into the sound of the amplifier beyond just the tubes used.  Biasing, signal path components, interstage coupling, quality of the power supply, noise performance are all critical.  Good tubes in a bad circuit with low quality parts will sound bad.  The question when implementing 20B is do the work arounds to implement it in a spud design detract from the sound to the point that it is no longer worth using?  Only way to know is to try or ask someone who already has.


----------



## whirlwind (Oct 24, 2021)

L0rdGwyn said:


> Probably depends on the planar and its sensitivity, output impedance of around 10ohms on the low-impedance tap if using 6E6P or 6E5P.  I don't own any real power hungry planars so I cannot test subjectively, but I've picked up around Head-Fi people like to use high-wattage amplifiers with their planars, even if they are using less than 1% of the total power!  Seems like overkill to me, but lots of people are doing it so maybe there is something to it.  In theory, even 250mW would drive any planar to unlistenable volumes.  250mW should get the HE-6 to 108dB peaks (going purely by the spec sheet).  500mW should be enough for any headphone, but like I said, I hear people like to drive their planars with massive amounts of unused power on tap and feel there is some advantage there, but I haven't tried it myself.
> 
> If high power is needed, a more traditional two-stage SET design is probably the way to go over a spud.


I agree with not needing all the extra power for planars.....it seems since the HE-6 needed it , now everybody thinks all planars need it.
I am totally in your camp...seems like overkill on 90% of all headphones.

My GS-X mk2 has more power than my GEL3N....however it does not produce better dynamics and slam ect. than the GEL3N with my 50ohm planar or my 200 ohm planar.
They both do produce a better sound than the GOTL amp however with planars....makes me believe you need enough power to get the job done, but no need for overkill

Just the thought of having to plug a headphone into speaker taps to power it is just far to scary for me to even try, LOL.
My thought would be to get different headphones.


----------



## L0rdGwyn (Oct 24, 2021)

whirlwind said:


> I agree with not needing all the extra power for planars.....it seems since the HE-6 needed it , now everybody thinks all planars need it.
> I am totally in your camp...seems like overkill on 90% of all headphones.
> 
> My GS-X mk2 has more power than my GEL3N....however it does not produce better dynamics and slam ect. than the GEL3N with my 50ohm planar or my 200 ohm planar.
> ...



Yeah I would be very surprised if this spud couldn't drive a vast majority of planars with good dynamics.  Certainly isn't a matter of volume, something like the LCD-4 would hit 120dB peaks with 200mW on the medium impedance setting.  Will be something to try for sure!


----------



## Monsterzero

whirlwind said:


> I agree with not needing all the extra power for planars.....it seems since the HE-6 needed it , now everybody thinks all planars need it.


I tried the HE500 via speaker taps just for giggles seeing as how the HE6 and HE500 use the same interconnects. Other than a _*slight*_ improvement in clarity, I couldnt tell the difference between taps and jack.


whirlwind said:


> My thought would be to get different headphones.


Thats what I eventually did.


----------



## CJG888

Monsterzero said:


> I tried the HE500 via speaker taps just for giggles seeing as how the HE6 and HE500 use the same interconnects. Other than a _*slight*_ improvement in clarity, I couldnt tell the difference between taps and jack.
> 
> Thats what I eventually did.


Quite. The HE500 is much easier to drive than everyone seems to think…

I use an OTL (but one with output tubes of low internal resistance).


----------



## leftside

Monsterzero said:


> I tried the HE500 via speaker taps just for giggles seeing as how the HE6 and HE500 use the same interconnects. Other than a _*slight*_ improvement in clarity, I couldnt tell the difference between taps and jack.
> 
> Thats what I eventually did.


Me too 🙂 I think I got the HE-6 from you? Had to try them. Had them hooked up to a McIntosh 25 watt amp. Even then I didn’t think they came anywhere close to the LCD3 I had at the time. Didn’t hold onto them for long.


----------



## jgwtriode

L0rdGwyn said:


> I actually feel pretty confident this spud is done, 6E6P it is.  It's basically the input stage of my cap-coupled 45 SET build, except instead of a 45 output stage, there is just an output transformer!  Bigger coupling cap too, for parafeed.
> 
> Around 9-10 o'clock on the spud is pretty darn loud for a 97dB/mW 300ohm headphone.  Full tilt on the pot hits over 500mW in the low, medium, and high impedance settings into 32ohms, 120ohms, 300ohms, respectively with a 2Vrms input.
> 
> Square waves look good, THD at 1mW into 300ohms is 0.048% H2 dominant.


Well why not throw a spud in the mix as well.   So I suppose that is also worth considering,  I will be looking at doing something come tax refund time, so that will give me a goodly amount of time to figure out which makes the most sense, but this frankly also seeems pretty interesting as the VC's are 99db I believe.    Another curiostity.  Appreciatie all the diversity and inclusion.

Happy listening,

jgwtriode


----------



## L0rdGwyn (Oct 26, 2021)

I made a pretty big personal DIY investment today that will pay dividends in the future.

Some months ago, during a discussion on diyAudio, I offered to trace some curves for a member on an interesting tube, a directly-heated pentode with thoriated tungsten filaments, the HY69.  Not one many have probably heard of.

While there is some evidence of this tube being used in push pull and single ended pentode designs, there did not appear to be a set of triode curves anywhere online.  Also, like other transmitting tubes, the HY69 has A2 functionality, meaning the grid can be driven positive for additional power output in an appropriate circuit.

So I traced the triode curves and provided them.  They are...exceptional.

A1 curves.



A1 + A2 curves, grid current in green.



Given how well these operate as triodes, I thought about investigating my own design, but the tubes are pretty uncommon, only made by Hytron as far as I can tell.

Well an opportunity came up and I seized it - I came across three separate eBay listings for lots of these tubes from the same seller, 30 tubes in total, a mix of used and NOS.

I bought them all.

So I have the makings of a stockpile and I plan to add to it.  What kind of amplifier will I make with them?  We will see.  For an A1 bias point, mu of 6.5 with plate resistance of 1.8K.  For a A2 bias point, plate resistance of 1.4K.  So, a 5K or 6K output transformer for a SET design without the need for negative feedback.  In A1 only, would make a 4-5W amplifier.  In A2 without negative feedback, probably a 9W amplifier.  If I got really crazy and used negative feedback with a 3K transformer a near 0V grid bias point, could squeeze 12W out of these tubes.  But a simple A1 design without negative feedback is appealing.  I might even use interstage transformers so the tubes can be driven into A2, could probably make a 6-7W amplifier in that case.

Here are some photos of the NOS tubes from what I bought.





And a set of mixed NOS / used (all tested "good") with ceramic bases.



So anyway, I will hoard these until I figure out what I'm going to do with them, could be a long, long time as I have no need for another amplifier right now.  But I couldn't pass up 30 of these tubes.

This is going to have ramifications in terms of my own future amp projects - what becomes of my nebulous HK54 / 35T amplifier project is TBD, don't know if I can have two oddball transmitting triode designs on the horizon, we will see.


----------



## whirlwind

L0rdGwyn said:


> I made a pretty big personal DIY investment today that will pay dividends in the future.
> 
> Some months ago, during a discussion on diyAudio, I offered to trace some curves for a member on an interesting tube, a directly-heated pentode with thoriated tungsten filaments, the HY69.  Not one many have probably heard of.
> 
> ...


Oh man....great stash of tubes Keenan!  I am sure at some point these will get put into something of your liking.
The tubes looks nice and rugged    

Was sort of up your way Sunday night. Since the Browns played Thursday night, the wife and I got tickets to go see Samantha Fish at the Kent Stage.
Great small venue, 636 people max. Had a great time and was glad to see they did temperature checks at the door.
She was great live...lots of energy.


----------



## L0rdGwyn

whirlwind said:


> Oh man....great stash of tubes Keenan!  I am sure at some point these will get put into something of your liking.
> The tubes looks nice and rugged
> 
> Was sort of up your way Sunday night. Since the Browns played Thursday night, the wife and I got tickets to go see Samantha Fish at the Kent Stage.
> ...



Looks like a nice venue Joe!  Never been myself, bet it was a blast!  Hopefully the Browns can take care of business Sunday, we are banged up beyond belief, but I think they can pull it off...Chubb should be back in business


----------



## whirlwind

L0rdGwyn said:


> Looks like a nice venue Joe!  Never been myself, bet it was a blast!  Hopefully the Browns can take care of business Sunday, we are banged up beyond belief, but I think they can pull it off...Chubb should be back in business


Yup....Chubb will be back...tough division as the Bengals look to be for real.


----------



## Xcalibur255

With the tubes being tungsten filament that makes them pretty viable even with a small supply.  They pretty much last forever when operated conservatively.


----------



## L0rdGwyn (Oct 26, 2021)

Xcalibur255 said:


> With the tubes being tungsten filament that makes them pretty viable even with a small supply.  They pretty much last forever when operated conservatively.



Yeah and these are rugged tubes, used in industrial applications.  Should last a long time, but never hurts to have a lifetime supply!  Really great linearity, I think they will make a nice amplifier, probably an interstage coupled A1 biased design that can make excursions into class A2, maybe 7W without NFB.


----------



## L0rdGwyn

Been conjuring up ideas for this HY69 amplifier.  Again, won't be coming for a long, long time, maybe years, going to take my time with it and make something special.  These tubes easily meet or exceed the linearity of the famous DHTs (e.g., 45, 2A3, 50, 300B), really they are similar in a lot of ways to a type 50, but with almost _double_ the gain, and as such less demanding requirements for the driver stage.  On top of that, they have thoriated tungsten filaments and A2 functionality, so can push much more power.  They are crazy tubes, I'm in love.

Before I bought those thirty HY69 tubes (and I have five more NOS HY69 on order), I told myself "Keenan, if you buy these tubes, you are going to have to sacrifice something for them."  You just can't keep all of the amplifiers / tubes, so I have an announcement...


----------



## triod750

L0rdGwyn said:


> Been conjuring up ideas for this HY69 amplifier.  Again, won't be coming for a long, long time, maybe years, going to take my time with it and make something special.  These tubes easily meet or exceed the linearity of the famous DHTs (e.g., 45, 2A3, 50, 300B), really they are similar in a lot of ways to a type 50, but with almost _double_ the gain, and as such less demanding requirements for the driver stage.  On top of that, they have thoriated tungsten filaments and A2 functionality, so can push much more power.  They are crazy tubes, I'm in love.
> 
> Before I bought those thirty HY69 tubes (and I have five more NOS HY69 on order), I told myself "Keenan, if you buy these tubes, you are going to have to sacrifice something for them."  You just can't keep all of the amplifiers / tubes, so I have an announcement...


You only need space, you don't need money. I'm all ears...


----------



## L0rdGwyn (Oct 28, 2021)

I am looking to find a good home for my 6A5G SET amplifier.  This amplifier has immense sentimental value for me, it pains me to sell it, but it deserves better than the treatment it is getting.  I am posting it here for people who follow this thread before I go to the classifieds.  Really it is preferable to sell it to someone I know given this is not a casual purchase.

Before I go into what makes this amplifier special, this sale comes with a few disclaimers:

This is an expensive amplifier!  Just to give an idea, the cost of _parts_ for this amp was roughly $2.5K.  I will be including another $800 worth of tubes with it.  I will not be adding much in the way of labor cost, but the price will eclipse $3K.  This is truly a no compromises type of design within the confines of the topology, an enthusiast's amplifier.  I recognize that might make it hard to sell, but if purchased on the commercial market, this amplifier would cost easily over $6K.
This amp uses esoteric and rare tubes, so the buyer would be committing to collecting these tubes, but I can guarantee they will not be disappointed with their sound.
This amplifier is heavy.  It has three Lundahl chokes in the power supply, three Lundahl transformers, two big ClarityCap film caps feeding the output stage.  Long story short, it should not be put on a flimsy rack / desk.  Dropping it on yourself, someone else, or a pet would cause serious injury.
This amp, like most tube designs, has high voltages inside the chassis.  The buyer should NOT attempt to service the amplifier themselves.  If the chassis is ever opened, it NEEDS to be unplugged from the wall first and be off for 15-30 mins to ensure all power supply capacitors have fully discharged.
Alright, with all of that negativity out of the way, here are the highlights of the amp:

This is a 3.75W speaker amplifier with a rear panel switch to change to headphone outputs.  In terms of headphone power, it can do 100mW into 300ohms, 270mW into 120ohms, 350mW into 80ohms, 690mW into 32ohms.  Listening volume for ZMF dynamics is around 12 to 1 o'clock with plenty of headroom.
Input tubes for this amp are a family of 4V, European B5 base indirectly heated triodes.  There are many equivalents, the major ones being MH4, MHL4, REN904, AC/HL, A4110, E428, any many more.  I will provide a full list to the buyer of all equivalents I am aware of.  These are truly excellent input tubes, but are quite rare and expensive given their age.  They are some of the best sounding driver tubes ever made.
Output tubes are 6A5G, an indirectly-heated triode similar to 2A3.  These have the linearity of a directly-heated triode (like the 2A3, 6A3, 6B4G) without the complexity of a DC filament supply.  Indirectly heated power triodes for audio use were not common - this is why you so often see triode-strapped pentodes being used in audio amplifiers, true triodes are most often DHTs, which makes this tube truly unique amongst audio output tubes.
The power supply is all passive "old school" CLCLCRC using a hybrid full-wave bridge tube rectifier.  The rectifier is also a 4V type - it can use U18/20, AZ50, FW4-500 rectifiers.  The chokes in the supply are Lundahl.  There are no electrolytics in the signal path from the power supply - the caps feeding the 6A5G output stage are ClarityCap TC4 series film caps.  The reservoir cap is also a ClarityCap TC2.  Mains transformer is also Lundahl as you can see.
The heater supply for the 4V input tubes is DC voltage regulated - different tubes in this family have different current requirements - the DC heater regulator ensures minimal coupled AC noise into the input stage while also ensuring a clean 4V is delivered to the heater no matter what the tube's current requirements may be.
Output transformers are Lundahl LL1620 wired for 3.3K primary and 8ohm secondary.  They could be rewired for 4ohm or 16ohm if necessary.
The input stage is CCS loaded with Japanese Riken Ohm carbon film current set resistors, biased by unbypassed Riken Ohm cathode resistors.
Coupling capacitors are Miflex KPCU-02 copper foils.
The output stage is cathode / auto-biased - cathode resistors are NOS Mills MRA12 non-inductive wirewounds.  Bypass capacitors are ClarityCap ESA film capacitors.
All sockets are Yamamoto teflons.  These are the best tube sockets on the market today, cost around $50 each!
The potentiometer is a Goldpoint series stepped attenuator.  The speaker / headphone output switch is also a Goldpoint.
All wiring is mil-spec silver-plated copper.
With all of that out of the way, here are some photos.  There are a few minor blemishes on the chassis, I can send detailed photos if the buyer is at all concerned.


























As you can see, right now the amplifier has no feet - I can add them free of charge.  Also, if the input tubes are too daunting and the buyer wants to pay the cost for changing the sockets (I would recommend Yamamoto), I can change the input tubes to something more common, like 6J5.

I will be including two pairs of input tubes, two pairs of output tubes, and a rectifier with the purchase.  The buyer can purchase additional tubes from me at better than market price if they so choose - I have several pairs of 6A5G which I could package together.  I also have a collection of 4V driver tubes, however these would be priced on an individual basis, some of them are very rare.

Okay that's it, if anyone is interested, they can reach out to me and we can talk details.  I understand this is something of an intimidating purchase and may take some time to sell.  I am happy to wait to make sure this amp finds a good home, it is truly one-of-a-kind.


----------



## whirlwind (Oct 28, 2021)

L0rdGwyn said:


> I am looking to find a good home for my 6A5G SET amplifier.  This amplifier has immense sentimental value for me, it pains me to sell it, but it deserves better than the treatment it is getting.  I am posting it here for people who follow this thread before I go to the classifieds.  Really it is preferable to sell it to someone I know given this is not a casual purchase.
> 
> Before I go into what makes this amplifier special, this sale comes with a few disclaimers:
> 
> ...


Very tempting....if it only used different tubes I would take it off your hands. I only listen to headphones now days also, no need for speakers.
Love the look of those  Lundahl's sitting pretty on that chassis much better look than toroidal to my eyes.

Very nice, neat clean work.

Such a beautiful amp.....I am sure it will find a new home soon.

Maybe at some point in time I can own one of your beautiful amps


----------



## triod750

Whoever buying this amp will live in eternal happiness. My Triod750 uses 6B4G tubes and sounds absolutely wonderful. It is a much simpler version than this one, but using 'the same' tube. See http://www.r-type.org/exhib/acn0057.htm .

Thus, having the Triod750,  I don't deserve this amp. Being as old as i am, I don't deserve it either. Paired with the right speakers it must be close to nirvana. For any sensible person it would be the endgame amp. I fully understand that it is painful to the Lord to sell it.


----------



## L0rdGwyn (Oct 28, 2021)

whirlwind said:


> Very tempting....if it only used different tubes I would take it off your hands. I only listen to headphones now days also, no need for speakers.
> Love the look of those  Lundahl's sitting pretty on that chassis much better look than toroidal to my eyes.
> 
> Very nice, neat clean work.
> ...



Thanks, Joe.  I hope to keep the tube loadout as is, but like I said in the post, I would be willing to swap the input tubes to something like 6J5, would be an easy change, but would require a Yamamoto socket purchase.

If a period of time has passed and the tubes do turn out to be a significant barrier, the output tubes could also be changed - swapping to something like EL34 would be simple with a few component changes.

This amp makes a very good headphone amplifier - the way the headphone jack is set up is with a resistor in parallel with the output transformer secondary, a 9.1ohm resistor.  This resistor ensures the output tubes always see their ideal load, and the headphone is run in parallel with it.  Through listening tests with different configurations, my experience has been that this gets the best sound running high impedance headphones using speaker output transformers, but at the cost of some power given the parallel resistor load.  The power specs may look wimpy, but 100mW into a 300ohm dynamic (like the ZMF Auteur, for example) can hit 117dB peaks!  I should also probably mention the output impedance is around 2-3ohms.

With a pair of reasonably sensitive monitors, would make a great headphone / nearfield desk setup.


----------



## Xcalibur255

Somebody is going to be a lucky duck indeed.  I hope it finds its forever home.

Honestly there is something to be said for coming up with interesting, off-the-beaten-path amplifiers like this and selling them bespoke as long as the buyers fully understand what they are signing up for (and this really is the sticking point because people will say they do and then time will tell another story).  Would make for a really fascinating builder image/ideology as opposed to just making a "standard" model over and over.  Every piece is unique like a work of art and you never know what will pop up next.

Could be a way to keep the hobby fun for a long time to come.  I know Glenn started to get really burned out on building the same OTL over and over in recent years, he confessed as much to me.  The fun is in the design and problem solving state, not the soldering I would imagine.


----------



## whirlwind

Xcalibur255 said:


> Somebody is going to be a lucky duck indeed.  I hope it finds its forever home.
> 
> Honestly there is something to be said for coming up with interesting, off-the-beaten-path amplifiers like this and selling them bespoke as long as the buyers fully understand what they are signing up for (and this really is the sticking point because people will say they do and then time will tell another story).  Would make for a really fascinating builder image/ideology as opposed to just making a "standard" model over and over.  Every piece is unique like a work of art and you never know what will pop up next.
> 
> Could be a way to keep the hobby fun for a long time to come.  I know Glenn started to get really burned out on building the same OTL over and over in recent years, he confessed as much to me.  The fun is in the design and problem solving state, not the soldering I would imagine.


Glenn also stated that to me about getting tired of building the same amp over and over,but I guess he just produced what the buyer wanted.

Agree, someone is going to get a dream amp here.


----------



## Zachik

whirlwind said:


> Agree, someone is going to get a dream amp here.


If only I had room for "just 1 more amp"... 
(not joking, BTW, I have reached the limit 1 amp ago and another amp is commissioned to be built in a couple months!)


----------



## bpiotrow13

If only i could afford it.. but i wish the lucky buyer all the best


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## L0rdGwyn (Oct 29, 2021)

Here is the classifieds listing for the 6A5G amplifier:

https://www.head-fi.org/classifieds/diy-mh4-6a5g-single-ended-triode-set-amplifier.13694/

Going to be working on @Monsterzero 's GOTL today, replacing sockets, rewiring the C3g sockets for 6J5, adding CCS loads.  Got my COVID booster yesterday, so moving a little slow this morning lol.


----------



## L0rdGwyn (Oct 29, 2021)

Got some more 45 globes on the way, @Xcalibur255 .  Guy who is selling me the HY69 lot asked if I was looking for any other tubes.

Bought the four globes pictured for $250.  Three test well, the Cunningham on the far right tests "a little weak".  Thought it was worth a shot, excited to try the pair of RCAs.


----------



## UntilThen

L0rdGwyn said:


> Very cool, that should be fun. With NOS DHTs, I have with tube rolling the differences are quite small, so I just pop the tubes in that I like to look at most.
> 
> I like the look of the graphite plate 801As. I've posted this pic before, but I like how it turned out.



IMO this is your statement amp and I think it's striking. Lots happening for you Keenan since I last visited.


----------



## L0rdGwyn

UntilThen said:


> IMO this is your statement amp and I think it's striking. Lots happening for you Keenan since I last visited.



Thanks, Matt.  Oh yeah, very busy as usual, I think since last you stopped by I designed and built a NOS DAC, announced my OTL, I have a few of those builds on the horizon in addition to a type 45 amp for Zach at ZMF, will be building that one in the next two weeks, waiting on the chassis.  A few others things happening but I'll leave it at that!  Hope your Odyssey amp is still satisfying


----------



## UntilThen

L0rdGwyn said:


> Thanks, Matt.  Oh yeah, very busy as usual, I think since last you stopped by I designed and built a NOS DAC, announced my OTL, I have a few of those builds on the horizon in addition to a type 45 amp for Zach at ZMF, will be building that one in the next two weeks, waiting on the chassis.  A few others things happening but I'll leave it at that!  Hope your Odyssey amp is still satisfying



Keenly awaiting to see the Zach 45.  I went through a few pages here and saw your posts of the JBL speakers. That's the kind of speaker sound I like. Still loving my Odyssey. It's one of a kind. Only one in the world. Same goes for your amps.  

I saw in that picture of your 801 amp, a turntable next to it. A chance encounter and I manage to buy the Denon DP-47f two days ago from a friend and I cannot believe how new it still is. I've been playing this Roger Waters album to death since I open it yesterday.


----------



## L0rdGwyn

UntilThen said:


> Keenly awaiting to see the Zach 45.  I went through a few pages here and saw your posts of the JBL speakers. That's the kind of speaker sound I like. Still loving my Odyssey. It's one of a kind. Only one in the world. Same goes for your amps.
> 
> I saw in that picture of your 801 amp, a turntable next to it. A chance encounter and I manage to buy the Denon DP-47f two days ago from a friend and I cannot believe how new it still is. I've been playing this Roger Waters album to death since I open it yesterday.



Looks great, brand new really, gotta love that vintage charm!  I'm sure it pairs well with the Oblivion.  I am still using my Thorens with my DIY phono stage.  I will be doing some more work on it eventually, I would like to design an LCR phono stage at some point as well, likely using E55L tubes.  But I don't know when, for now I am just a tube hoarder.


----------



## UntilThen

L0rdGwyn said:


> I would like to design an LCR phono stage at some point as well, likely using E55L tubes.



You're talented. Can make almost anything. What's an LCR? A tube phono stage sounds interesting. For both mm & mc? Stepping into vinyl is just as bad as stepping into tubes. I'm thinking of upgrading the cartridge to Denon DL 103R.


----------



## L0rdGwyn

UntilThen said:


> You're talented. Can make almost anything. What's an LCR? A tube phono stage sounds interesting. For both mm & mc? Stepping into vinyl is just as bad as stepping into tubes. I'm thinking of upgrading the cartridge to Denon DL 103R.



Yeah, vinyl is a endless money pit and rabbit hole.  But if you commit, its great!  My phono stage is for MC, it uses Lundahl MC step up transformers.  Actually the phono stage input is wired for balanced and my tonearm was rewired for balanced, the input transformers convert from balanced to single-ended.  This keep the noise pickup between the turntable and phono stage low.

LCR phono stage is one that uses a passive RIAA equalization network made up of choke / resistors / capacitors, as opposed to more typical passive RIAA that only uses resistors / capacitors.  The idea is that using a low impedance passive RIAA network gets the best sound, and that is achieved using LCR.  But tubes in an LCR phono must have specific characteristics to make the whole thing work, and specific chokes are required as well.  Basically it is expensive to make one lol but the sound is considered the best.  @leftside has a custom LCR phono, so I'm sure he could shed some light on how it sounds.


----------



## L0rdGwyn

Here is a Wikipedia article on what I mean when I say RIAA if that isn't understood by some: https://en.wikipedia.org/wiki/RIAA_equalization

Basically there is a filter added to vinyl when the recording is pressed, so the music in the vinyl groove does not have a flat frequency response, that filter must be reversed to create a flat frequency response on the output.  The signal picked up by the phono cartridge must be amplified to line level as well.  These two things are the role of a phono stage.  They are tricky to design as low noise is paramount, especially when working with MC cartridges, very small signals with big amplification, so lots of opportunity to amplify noise.  That is the reason mine has a separate chassis power supply.


----------



## Xcalibur255 (Oct 29, 2021)

@L0rdGwyn

I've never heard the Cunningham either.  You'll have to let us know what you think of them compared to the KenRad globes.

I'm currently running a pair of Emperor 45s that my best guess are Raytheon made.  They're mid-forward compared to most other 45s and aren't making very much magic with the Ethers.  Been debating whether to unplug the Ethers or swap in different tubes for the weekend.

If you ever come into possession of a pair of globe Everready Raytheon 4-Pillars then I'm inviting myself over to your house for a listen!

I once saw a beautiful pair of DeForest Audion 445s in their original boxes some 5 or 6 years ago.  I deeply deeply regret not trying to get them.  The auction ended high but still within the realm of "worth it" given how extraordinarily rare those tubes were.  I kinda didn't feel worthy of them in a way.


----------



## L0rdGwyn

Xcalibur255 said:


> @L0rdGwyn
> 
> I've never heard the Cunningham either.  You'll have to let us know what you think of them compared to the KenRad globes.
> 
> ...



For sure I will!  I'll compare them in the 45 SET, will take some pics of them too.  Those Raytheons you mentioned are beautiful, wow.

There was a pair of NOS blue glass Arcturus 45 on eBay a year or so ago, I stayed my hand, but man, those are some beautiful tubes.  At some point you do ask yourself though, "should I be using these, or putting them in a museum?"  I feel that way about my Mazda AC/HL globes.


----------



## whirlwind

L0rdGwyn said:


> Got some more 45 globes on the way, @Xcalibur255 .  Guy who is selling me the HY69 lot asked if I was looking for any other tubes.
> 
> Bought the four globes pictured for $250.  Three test well, the Cunningham on the far right tests "a little weak".  Thought it was worth a shot, excited to try the pair of RCAs.


As always...good score!


----------



## L0rdGwyn (Oct 29, 2021)

I finished six sockets on @Monsterzero 's GOTL.  I'm usually much faster, but this COVID booster really knocked me on my ass!  I feel horrible lol.  6J5 sockets are next.  Fortunately, I think the chassis cutouts for the loctal sockets will support the new octal sockets so I won't have to widen them with that giant step bit.



I think that's it for today though.  In between sockets, I've been listening to the Airmid with PCM56 DAC, MOV L63 inputs and Tung-Sol 7802 outputs.  The 7802 sounds amazing in this circuit, really great tubes.  It's been fun listening to the Airmid again after its little road trip, can be hard to critically evaluate something you've made when you have been listening to it nonstop every day like a robot.  Nice now to just kick back and enjoy it.


----------



## whirlwind

I have yet to get the booster...the first two shots put me down for one day each time, other than that, just a slightly sore arm.


----------



## L0rdGwyn

whirlwind said:


> I have yet to get the booster...the first two shots put me down for one day each time, other than that, just a slightly sore arm.



Yeah the second dose got me with the fatigue, but I was still 90% functional.  This was a new level of fatigue and arm / back pain lol I knew it was coming though talking to coworkers, so I planned to get it when I didn't work the next day.  I am all for it though, I've seen COVID mess up some really young people with no health history, I'll take one day of feeling crappy.


----------



## UntilThen

Loving the looks of the Ferrari red amp.


----------



## Monsterzero

L0rdGwyn said:


> I finished six sockets on @Monsterzero 's GOTL.  I'm usually much faster, but this COVID booster really knocked me on my ass!  I feel horrible lol.  6J5 sockets are next.  Fortunately, I think the chassis cutouts for the loctal sockets will support the new octal sockets so I won't have to widen them with that giant step bit.
> 
> 
> 
> I think that's it for today though.  In between sockets, I've been listening to the Airmid with PCM56 DAC, MOV L63 inputs and Tung-Sol 7802 outputs.  The 7802 sounds amazing in this circuit, really great tubes.  It's been fun listening to the Airmid again after its little road trip, can be hard to critically evaluate something you've made when you have been listening to it nonstop every day like a robot.  Nice now to just kick back and enjoy it.


Looking forward to hearing my amp after you work your magic on it!


----------



## bcowen

UntilThen said:


> You're talented. Can make almost anything. What's an LCR? A tube phono stage sounds interesting. For both mm & mc? Stepping into vinyl is just as bad as stepping into tubes. I'm thinking of upgrading the cartridge to Denon DL 103R.


Get the Zu modded 103R (or even the 103).  Hugely worth it.

https://www.zuaudio.com/turntable


----------



## bcowen

L0rdGwyn said:


> Yeah, vinyl is a endless money pit and rabbit hole.  But if you commit, its great!  My phono stage is for MC, it uses Lundahl MC step up transformers.  Actually the phono stage input is wired for balanced and my tonearm was rewired for balanced, the input transformers convert from balanced to single-ended.  This keep the noise pickup between the turntable and phono stage low.
> 
> LCR phono stage is one that uses a passive RIAA equalization network made up of choke / resistors / capacitors, as opposed to more typical passive RIAA that only uses resistors / capacitors.  The idea is that using a low impedance passive RIAA network gets the best sound, and that is achieved using LCR.  But tubes in an LCR phono must have specific characteristics to make the whole thing work, and specific chokes are required as well.  Basically it is expensive to make one lol but the sound is considered the best.  @leftside has a custom LCR phono, so I'm sure he could shed some light on how it sounds.


You mean not everyone has a tube phono stage?  That's like an insult to vinyl itself.


----------



## UntilThen

bcowen said:


> Get the Zu modded 103R (or even the 103).  Hugely worth it.
> 
> https://www.zuaudio.com/turntable


Hello compatriot, how about just the standard Denon DL 103R. Why do I have to pay Zu a few dollars more?


----------



## bcowen

UntilThen said:


> Hello compatriot, how about just the standard Denon DL 103R. Why do I have to pay Zu a few dollars more?


Um, 'cause it sounds better?  Yeah, that's it.   

Seriously, the 103 has been around for, like, ever.  Very nice cartridge for the money in stock form, but the plastic body hinders what it's really capable of.  Zu went about fixing some of the weak points without disturbing its voicing or overall character. More detail, better bass heft and punch, less stridency on marginal recordings, and much larger soundstage.  Of course that's only my opinion (if I had one ).


----------



## L0rdGwyn

Here's @Monsterzero 's modded GOTL.

I swapped out all of the sockets, that was fun, and replaced all with QQQ octal sockets except for the loctal C3g sockets which were replaced with Beltons due to the wider mounting hole centers.  The two Belton sockets are now set up for 6J5, the switchable heater circuit now controls the 6SN7 and 6J5 sockets, so 12J5 can also be used in place of 6J5.

I added CCS loads to the input tubes and changed the biasing scheme from resistor / capacitor cathode bias to LED bias.  Also adjusted the B+ voltage at the top of the CCS.






Here it is with some tubes, have a GZ34 rectifier in with some Sylvania 6J5GT and Toshiba 6BX7GT.


----------



## whirlwind

L0rdGwyn said:


> Here's @Monsterzero 's modded GOTL.
> 
> I swapped out all of the sockets, that was fun, and replaced all with QQQ octal sockets except for the loctal C3g sockets which were replaced with Beltons due to the wider mounting hole centers.  The two Belton sockets are now set up for 6J5, the switchable heater circuit now controls the 6SN7 and 6J5 sockets, so 12J5 can also be used in place of 6J5.
> 
> ...


Congrats Monster....enjoy those 6/12 J5 tubes.....great way to get great drivers at less price than top of line SN7 tubes...especially since NOS tubes are far more easily found.


----------



## Monsterzero

L0rdGwyn said:


> Here's @Monsterzero 's modded GOTL.
> 
> I swapped out all of the sockets, that was fun, and replaced all with QQQ octal sockets except for the loctal C3g sockets which were replaced with Beltons due to the wider mounting hole centers.  The two Belton sockets are now set up for 6J5, the switchable heater circuit now controls the 6SN7 and 6J5 sockets, so 12J5 can also be used in place of 6J5.
> 
> ...


Looks great, Keenan!!! Drop me an email when you can so we can get it back home. Ive been making due with a solid state amp/DAC in the interim, which will remain un-named. I miss my tubes! 


whirlwind said:


> Congrats Monster....enjoy those 6/12 J5 tubes.....great way to get great drivers at less price than top of line SN7 tubes...especially since NOS tubes are far more easily found.


Thank you sir! Ive been on the j5 hype train since the get-go, but im looking forward to ditching the adapters!


----------



## UntilThen

L0rdGwyn said:


> Here's @Monsterzero 's modded GOTL.



Looks a million bucks now.


----------



## L0rdGwyn (Nov 5, 2021)

I got my big box of HY69 tubes and the quad of globe 45.  The pair of RCA 45 test well and are well-matched, the other two not so well but are still usable.  No big deal though as I was most interested in the matched pair.  The test label on them is from 1933.



Sound pretty good in my little 45 amp.  Will try them out in the 45 headphone amp when it's done.



And the 30 HY69 tubes, don't know where I'm going to store all of these yet lol.  Here is one of the ceramic base tubes while tracing curves.



Here are the A1 curves for this one.  As I pointed out before, they make very good triodes.



Also got two Airmid chassis in today.  Not the greatest photo but here are the top plates, left is Chromy Bronze, right is Anthracite Gray.



Had planned to work on Zach's 45 amp first, but I made some last minute changes on the chassis which delayed the order, so I will likely get it next week some time.  Will get started on these in the interim.


----------



## UntilThen

Nice looking 45 amp you got there.


----------



## L0rdGwyn

UntilThen said:


> Nice looking 45 amp you got there.



Thank you!

Spinning some Combat Rock this Friday evening.  Happy listening everyone


----------



## L0rdGwyn

So I have some bad news - I've decided I cannot build and sell amplifiers publicly on Head-Fi.

I know this might come as a shock considering I only just recently announced the Airmid OTL and had discussed plans for future headphone amplifiers, but after thinking it over and discussing it with my partner, it just isn't going to work for a few different reasons.

First off, I am a critical care healthcare provider and my profession is pretty demanding.  Given the current state of affairs in the critical care world and recent develops in my professional life, I don't have the time and energy to essentially work two jobs, which is what building amplifiers feels like it will become.  Also, there is a certain degree of legal liability when selling high voltage audio equipment and to fully protect myself would require a commitment to small business ownership that I am not willing to make.  I wanted to keep building amps "casual", but when there is 200V+ inside the chassis and the possibility of electrocution, it cannot be done casually without taking on some degree of risk.  And without going into great detail, doing it would make me unhappy, ultimately.  

So I will withdraw the Airmid OTL from Head-Fi.  I will finish the orders that have been placed and provide future service and support for those amplifiers, but I will not be taking any new orders.  I'm sorry to have led anyone on, I hesitated in the past at the idea of selling amplifiers, but thought I should try it out and see if it was going to work - I now know without question that it won't.  I'll continue this thread if people are still interested in learning about tube audio design and potentially working on their own projects, but I won't be offering anything I show here for sale.


----------



## L0rdGwyn

On a more positive note, Zach's 45 amplifier chassis looks very nice in Distant Blue.  I will have it later this week.


----------



## UntilThen

Totally understandable Keenan. Building amps for others is a lot of work. Although you could do like what Glenn did. Make it a selectively small scale. Boutique amp builders are a cherished lot and they should not disappear. Boutique amp builders are spurred on by their love of tube amps and that's what drives them. Profit is secondary.


----------



## L0rdGwyn

UntilThen said:


> Totally understandable Keenan. Building amps for others is a lot of work. Although you could do like what Glenn did. Make it a selectively small scale. Boutique amp builders are a cherished lot and they should not disappear. Boutique amp builders are spurred on by their love of tube amps and that's what drives them. Profit is secondary.



Yes, certainly I wasn't doing it for money, I was doing it for enjoyment, for fun, and to offer something to the community, but when there are such high demands on your time and energy, there is no fun left!  It isn't something to take lightly - with every sale you are establishing a long term relationship of caring for the amplifier you put out into the world, as that number grows it will be very difficult for one person to manage.  Much respect for those that are willing to do it, but it won't work for me unfortunately.


----------



## triod750

L0rdGwyn said:


>


I cannot decide whether this tube is hot or if it is cool. Maybe both, but nothing in between.


----------



## triod750

L0rdGwyn said:


> First off, I am a critical care healthcare provider and my profession is pretty demanding. Given the current state of affairs in the critical care world and recent develops in my professional life, I don't have the time and energy to essentially work two jobs, which is what building amplifiers feels like it will become.


You have your priorities right, here. Letting a hobby remain as a hobby is, in my opinion, a wise decision. Not least with the pressure you have upon you during these hard times.


----------



## sam6550a

L0rdGwyn said:


> So I have some bad news - I've decided I cannot build and sell amplifiers publicly on Head-Fi.
> 
> I know this might come as a shock considering I only just recently announced the Airmid OTL and had discussed plans for future headphone amplifiers, but after thinking it over and discussing it with my partner, it just isn't going to work for a few different reasons.
> 
> ...


Perhaps you might consider publishing only the schematics and parts list as an educational exercise, with the usual "at your own risk" disclaimer.


----------



## bcowen

L0rdGwyn said:


> So I have some bad news - I've decided I cannot build and sell amplifiers publicly on Head-Fi.
> 
> I know this might come as a shock considering I only just recently announced the Airmid OTL and had discussed plans for future headphone amplifiers, but after thinking it over and discussing it with my partner, it just isn't going to work for a few different reasons.
> 
> ...


Sorry to hear that, but I totally get it.  But *please* keep the thread going.  I've learned a lot (even though much of it is over my head), and mostly enjoy seeing what your projects are as they come along.


----------



## L0rdGwyn

bcowen said:


> Sorry to hear that, but I totally get it.  But *please* keep the thread going.  I've learned a lot (even though much of it is over my head), and mostly enjoy seeing what your projects are as they come along.



Thanks, I will keep it going.  I'll be working on that 45 amp soon, I think that should be a pretty interesting build!


----------



## triod750

Sharing a hobby is a completely different matter and can be relaxing and rewarding - not draining!


----------



## whirlwind

L0rdGwyn said:


> So I have some bad news - I've decided I cannot build and sell amplifiers publicly on Head-Fi.
> 
> I know this might come as a shock considering I only just recently announced the Airmid OTL and had discussed plans for future headphone amplifiers, but after thinking it over and discussing it with my partner, it just isn't going to work for a few different reasons.
> 
> ...


Totally understand.

I always say when something is not fun anymore, then it is not worth doing.

Just building stuff for yourself will always remain fun


----------



## leftside

I'd still like to follow your DIY projects on here.


----------



## UntilThen

leftside said:


> I'd still like to follow your DIY projects on here.



and all the crazy tube amp enthusiasts too.


----------



## jgwtriode

bcowen said:


> Sorry to hear that, but I totally get it.  But *please* keep the thread going.  I've learned a lot (even though much of it is over my head), and mostly enjoy seeing what your projects are as they come along.





L0rdGwyn said:


> So I have some bad news - I've decided I cannot build and sell amplifiers publicly on Head-Fi.
> 
> I know this might come as a shock considering I only just recently announced the Airmid OTL and had discussed plans for future headphone amplifiers, but after thinking it over and discussing it with my partner, it just isn't going to work for a few different reasons.
> 
> ...


Understood but obviously dissappointed,  was really looking forward to an Airmid next year as the next step forward.  Will have to ponder a bit.   May have to build something myself but not really my forte.  Did it a few years ago with the Bottleheads, but was looking forward to spending a bit more for a high value finished product.  Best of luck, Keenan with everything your doing going forward.

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Understood but obviously dissappointed,  was really looking forward to an Airmid next year as the next step forward.  Will have to ponder a bit.   May have to build something myself but not really my forte.  Did it a few years ago with the Bottleheads, but was looking forward to spending a bit more for a high value finished product.  Best of luck, Keenan with everything your doing going forward.
> 
> Happy listening,
> 
> jgwtriode



Sorry to disappoint @jgwtriode , always happy to answer questions though if you ever need tube advice.


----------



## jgwtriode

It's fine, I understand.  Probably just have to save longer and spend more, just party of reality.  Your amp was kind of a bridge to getting very close to absolute for a lot less than the otherwise going rate.   I like to flirt with above 90 percent for a whole lot less than that last litte bit but really wanting it all.  My system is pretty good right now but I really want that triode magic back in my life.   So of course I will still follow and see whats up here and try and find a workable alternative.


Thanks for everything you do, 

jgwtriode


----------



## tubebuyer2020

L0rdGwyn said:


> First off, I am a critical care healthcare provider and my profession is pretty demanding. Given the current state of affairs in the critical care world and recent develops in my professional life, I don't have the time and energy to essentially work two jobs, which is what building amplifiers feels like it will become.



Very wise!



L0rdGwyn said:


> Also, there is a certain degree of legal liability when selling high voltage audio equipment and to fully protect myself would require a commitment to small business ownership that I am not willing to make.  I wanted to keep building amps "casual", but when there is 200V+ inside the chassis and the possibility of electrocution, it cannot be done casually without taking on some degree of risk.  And without going into great detail, doing it would make me unhappy, ultimately.



I think there might be an element of liability about any electrical equipment in terms of interference it produces or being a potential fire hazard.



L0rdGwyn said:


> I will finish the orders that have been placed and provide future service and support for those amplifiers...



aka Legendary Collectibles 



L0rdGwyn said:


> I'll continue this thread if people are still interested in learning about tube audio design and potentially working on their own projects...



Yes!


----------



## leftside

jgwtriode said:


> It's fine, I understand.  Probably just have to save longer and spend more, just party of reality.  Your amp was kind of a bridge to getting very close to absolute for a lot less than the otherwise going rate.   I like to flirt with above 90 percent for a whole lot less than that last litte bit but really wanting it all.  My system is pretty good right now but I really want that triode magic back in my life.   So of course I will still follow and see whats up here and try and find a workable alternative.
> 
> 
> Thanks for everything you do,
> ...


There are other custom amp builders on here.


----------



## CJG888

tubebuyer2020 said:


> Very wise!
> 
> 
> 
> ...


Also, there are numerous compliance hurdles to be jumped over and certifications to be obtained. And, of course, the issue of recycling. 

At least that is the case here in the EU…


----------



## L0rdGwyn

leftside said:


> There are other custom amp builders on here.



Check out 1101 Audio or Ultrasonic Studios, @jgwtriode .


----------



## CJG888

Or WBA…


----------



## L0rdGwyn (Mar 29, 2022)

Here is two Airmids worth of PCBs.  HV regulators still need to be mounted to their heat sinks, but the vast majority is done.  The 45 amplifier chassis will be here tomorrow (and I will be working the next two days), so I will switch over to working on that next week.  With all of this out of the way though, assembling the two Airmids won't take long when the 45 amp is done.

You might notice there is only one Alps pot in the picture, that's because one of the two Airmids will use dual mono volume pots, Goldpoint V47 attenuators to be exact, for individual channel volume adjustment.  This was per the request of the buyer.




Going to start thinking about what I will work on once these three amplifiers are done.  With my DAC built, I don't have anything concrete planned.  May still convert the 841 amplifier to a 6E6P spud, but also have some plans to make upgrades to my turntable.  I also plan to direct-couple my 45 parafeed amplifier and work on an LCR phono stage, will have to weigh all of those options.


----------



## triod750

L0rdGwyn said:


> May still convert the 841 amplifier to a 6E6P spud


Oh no and oh yes! 

I guess that just relaxing isn't relaxing at all?


----------



## L0rdGwyn

triod750 said:


> Oh no and oh yes!
> 
> I guess that just relaxing isn't relaxing at all?



Well we will see, there is no timeline on any of those things, just a few projects I'd like to get done at some point.


----------



## L0rdGwyn

Here's what I am thinking of doing with my Thorens turntable - my plan is to get a custom wooden plinth, new arm board for a new tonearm, and a new two-switch aluminum fascia plate.

I got the fascia plate in today, it's a replica actually from Vinyl Nirvana.  The turntable came in two versions, one with the stock Thorens tonearm that included a cueing mechanism and switch, and one without the cueing switch for use with other tonearms (e.g., SME series).  Since I will be changing the tonearm, the cueing switch will be nonfunctional, so it will have to go.

Here is the replica fascia plate.  I have another original two-switch plate I bought, but it's a bit dinged up, this one looks better and is functionally the same.



As far as the plinth, I am a fan of this style.



The big question is the tonearm.  The classic pairing is an SME 3009, so that is one option.  I had considered a Jelco at one point but was really disappointed to learn they went out of business due to COVID.  So more thinking to do on this front, the cost of the arm will probably dictate how soon I make the changes.


----------



## CJG888

I like my 3009…


----------



## CJG888

Not tempted by an idler drive deck? So many good ones Stateside…


----------



## UntilThen

L0rdGwyn said:


> Here's what I am thinking of doing with my Thorens turntable



How do you like my Denon DP-47f, complete with Dire Straits and camel hair brush?


----------



## L0rdGwyn (Nov 10, 2021)

CJG888 said:


> Not tempted by an idler drive deck? So many good ones Stateside…



The idler drive tables are intriguing, but I'm going to invest in my TD 125, I like it a lot and take pride in having bought it at a local shop  we'll see but probably will end up with the 3009.

BTW @CJG888 , side note but you are a classical music fan, right?  Not sure if you like Elgar, but over the weekend I saw the Cleveland Orchestra play Elgar's cello concerto featuring a young up-and-coming cellist from the UK named Sheku Kanneh-Mason.  I've heard the piece many times, but never live and a mere 20 feet from the soloist, it was one of the most incredible live performances I have ever seen, I was in tears  there is nothing like seeing a world class orchestra live.



UntilThen said:


> How do you like my Denon DP-47f, complete with Dire Straits and camel hair brush?



Looking good   I like that brush, maybe I need to upgrade.


----------



## CJG888

L0rdGwyn said:


> The idler drive tables are intriguing, but I'm going to invest in my TD 125, I like it a lot and take pride in having bought it at a local shop  we'll see but probably will end up with the 3009.
> 
> BTW @CJG888 , side note but you are a classical music fan, right?  Not sure if you like Elgar, but over the weekend I saw the Cleveland Orchestra play Elgar's cello concerto featuring a young up-and-coming cellist from the UK named Sheku Kanneh-Mason.  I've heard the piece many times, but never live and a mere 20 feet from the soloist, it was one of the most incredible live performances I have ever seen, I was in tears  there is nothing like seeing a world class orchestra live.
> 
> ...


Funny you should mention Elgar. He is, in a sense, my local composer- we are both Worcestershire lads…
In his day, he was the British composer closest to the European (German) Romantic tradition. His Cello Concerto is a staple of the repertoire, alongside the Dvorak and the Schumann…

You absolutely must get hold of the Du Pré / Barbirolli (if you don’t have it already). This sets the standard musically, and is a first-rate audiophile recording. Also please check out the violin concerto, the second symphony (Boult), or, for a real system test, The Dream of Gerontius (Boult or Rattle).


----------



## bcowen

L0rdGwyn said:


> Here is two Airmids worth of PCBs.  HV regulators still need to be mounted to their heat sinks, but the vast majority is done.  The 45 amplifier chassis will be here tomorrow (and I will be working the next two days), so I will switch over to working on that next week.  With all of this out of the way though, assembling the two Airmids won't take long when the 45 amp is done.
> 
> 
> 
> ...


I'm ready for you to start on an all-tube phono stage.  You know, enough gain (using only tubes) to handle a .25 mV output moving coil.  That would be cool.


----------



## bcowen

L0rdGwyn said:


> The idler drive tables are intriguing, but I'm going to invest in my TD 125, I like it a lot and take pride in having bought it at a local shop  we'll see but probably will end up with the 3009.
> 
> BTW @CJG888 , side note but you are a classical music fan, right?  Not sure if you like Elgar, but over the weekend I saw the Cleveland Orchestra play Elgar's cello concerto featuring a young up-and-coming cellist from the UK named Sheku Kanneh-Mason.  I've heard the piece many times, but never live and a mere 20 feet from the soloist, it was one of the most incredible live performances I have ever seen, I was in tears  there is nothing like seeing a world class orchestra live.
> 
> ...


You have an ultrasonic cleaning rig.  Brushes are for newbies.


----------



## Mr Trev

L0rdGwyn said:


> Going to start thinking about what I will work on once these three amplifiers are done.  With my DAC built, I don't have anything concrete planned.  May still convert the 841 amplifier to a 6E6P spud, but also have some plans to make upgrades to my turntable.  I also plan to direct-couple my 45 parafeed amplifier and work on an LCR phono stage, will have to weigh all of those options.


There's only one true answer…




SPUD


----------



## L0rdGwyn

CJG888 said:


> Funny you should mention Elgar. He is, in a sense, my local composer- we are both Worcestershire lads…
> In his day, he was the British composer closest to the European (German) Romantic tradition. His Cello Concerto is a staple of the repertoire, alongside the Dvorak and the Schumann…
> 
> You absolutely must get hold of the Du Pré / Barbirolli (if you don’t have it already). This sets the standard musically, and is a first-rate audiophile recording. Also please check out the violin concerto, the second symphony (Boult), or, for a real system test, The Dream of Gerontius (Boult or Rattle).



The Du Pré / Barbirolli is my go to recording as well, but I do not have it on vinyl.  It's funny you should mention _that _as I was talking of buying a copy just yesterday  thanks for the other recommendations, I will surely check them out.


----------



## L0rdGwyn (Nov 10, 2021)

bcowen said:


> I'm ready for you to start on an all-tube phono stage.  You know, enough gain (using only tubes) to handle a .25 mV output moving coil.  That would be cool.



You mean using a tube instead of a MC step up transformer?  That is a tall order!  It could be done but at a significant noise penalty.  It would be tricky  could probably parallel a bunch of input tubes to get the noise down but still wouldn't be as good as the SUT.  I'll have to look around and see who has tried it, I'm sure someone has.



bcowen said:


> You have an ultrasonic cleaning rig.  Brushes are for newbies.



It still makes me feel good to run that brush over the LP before I play it lol old habits die hard.


----------



## L0rdGwyn

Mr Trev said:


> There's only one true answer…
> 
> 
> 
> ...



Great film!  That spud will happen, it has to.  The sad reality is it sounds better than the amplifier that will be broken down to make it, it will also be smaller, less complex, more power efficient, use cheaper and more available tubes.  I will probably put many of my 841 pairs up for sale on eBay, I have so many...


----------



## Mr Trev

L0rdGwyn said:


> Great film!  That spud will happen, it has to.  The sad reality is it sounds better than the amplifier that will be broken down to make it, it will also be smaller, less complex, more power efficient, use cheaper and more available tubes.  I will probably put many of my 841 pairs up for sale on eBay, I have so many...


To honest, I was more intrigued by the spud amp back when you were thinking about using the EL84 over the 6E6P tubes. I gotta think the rolling possibilities would be far lower with an amp based on Russkie tubes


----------



## L0rdGwyn (Nov 11, 2021)

Mr Trev said:


> To honest, I was more intrigued by the spud amp back when you were thinking about using the EL84 over the 6E6P tubes. I gotta think the rolling possibilities would be far lower with an amp based on Russkie tubes



There are maybe three or four tubes that can be used in place of a 6E6P depending on the bias point, but with differences in gain (e.g., E810F, 6J52P, D3a), 6E6P is a better tube for the job in a spud though compared to EL84, higher gain and lower plate resistance, better linearity, lower noise.  But I won't be selling the spud anymore, sorry :/

I got @zach915m 's 45 amplifier chassis in today.



I don't usually do this, but here is a little preview of what the amplifier will look like.  It's fake as the parts will come off to do prep work on the chassis, the meters aren't fully mounted and flush for instance.  You'll have to excuse the mess on my workbench too lol.

I'll get started on the build for real this weekend.


----------



## L0rdGwyn

L0rdGwyn said:


> There are maybe three or four tubes that can be used in place of a 6E6P depending on the bias point, but with differences in gain (e.g., E810F, 6J52P, D3a), 6E6P is a better tube for the job in a spud though compared to EL84, higher gain and lower plate resistance, better linearity, lower noise.  But I won't be selling the spud anymore, sorry :/
> 
> I got @zach915m 's 45 amplifier chassis in today.
> 
> ...



The switch on the front is to change headphone impedance BTW, power switch will be on the rear of the amp.


----------



## Mr Trev

L0rdGwyn said:


> There are maybe three or four tubes that can be used in place of a 6E6P depending on the bias point, but with differences in gain (e.g., E810F, 6J52P, D3a), 6E6P is a better tube for the job in a spud though compared to EL84, higher gain and lower plate resistance, better linearity, lower noise.  But I won't be selling the spud anymore, sorry :/


It's all good. Maybe I'll just buy one of your 841s and ask you to toss instructions on how to covert it in the box


----------



## CJG888 (Nov 12, 2021)

L0rdGwyn said:


> The idler drive tables are intriguing, but I'm going to invest in my TD 125, I like it a lot and take pride in having bought it at a local shop  we'll see but probably will end up with the 3009.
> 
> BTW @CJG888 , side note but you are a classical music fan, right?  Not sure if you like Elgar, but over the weekend I saw the Cleveland Orchestra play Elgar's cello concerto featuring a young up-and-coming cellist from the UK named Sheku Kanneh-Mason.  I've heard the piece many times, but never live and a mere 20 feet from the soloist, it was one of the most incredible live performances I have ever seen, I was in tears  there is nothing like seeing a world class orchestra live.
> 
> ...


So it seems you are sticking with your wobbly subchassis turntable…😀

Sorry about the comment, but I used to own a TD126 Mk IV, and was distinctly underwhelmed. However, I have read that the TD125 is probably the best subchassis deck out there, comfortably outperforming the TD126 (and the Linn LP12…). At least it doesn’t have the late 126’s profusion of low-grade plastic parts…

I wasn’t aware of how large the enthusiast scene here in Germany is! It seems that there is little that needs modification, as the deck is properly engineered from the start. On two issues, there appears to be consensus, though: it deserves a better tonearm than the TP16 which comes as stock (I agree, I had the same one on my TD126), and it benefits greatly from a new motor controller/PSU. The unit sold by Dr. Fuß appears to be popular, but I imagine you will probably develop and build your own!

https://www.diyaudio.com/forums/ana...ve-vs-sine-wave-oscillator-motor-control.html

One or two enthusiasts have replaced the springs with rubber grommets… Inspired by the original Mini, perhaps?

Arm recommendations here seem to be SME3009 (the earlier, the better!), Jelco or early Mission. I imagine an Alphason HR100S or Xenon would be absolutely perfect (if you can find one!).

I wonder if an Ittok might work (if you want to use low-compliance MCs)…

BTW, do you speak German? If so, this is a tremendous resource:

https://www.analog-forum.de

And, of course, there is always:

https://www.lencoheaven.net


----------



## L0rdGwyn (Nov 12, 2021)

CJG888 said:


> So it seems you are sticking with your wobbly subchassis turntable…😀
> 
> Sorry about the comment, but I used to own a TD126 Mk IV, and was distinctly underwhelmed. However, I have read that the TD125 is probably the best subchassis deck out there, comfortably outperforming the TD126 (and the Linn LP12…). At least it doesn’t have the late 126’s profusion of low-grade plastic parts…
> 
> ...



Yup, I'm sticking with it!  The TD 125 is well-respected, many believe it to be superior to the TD 124 when properly set up, believe it or not.  The new tonearm is the next step, but like I said, I'll be making some cosmetic upgrades as well.  I have the turntable setup for balanced output, which will be the case with the new arm too.  Jelco is out of business sadly, I'll look into the other arms you mentioned, but the 3009 is the most likely path.  I studied German in college, but that was a decade ago, I still maintain some vocabulary but no longer conversational, plan to pick it up again at some point.  The Dr. Fuß motor is interesting, perhaps he's a podiatrist on the side


----------



## bcowen

CJG888 said:


> So it seems you are sticking with your wobbly subchassis turntable…😀
> 
> Sorry about the comment, but I used to own a TD126 Mk IV, and was distinctly underwhelmed. However, I have read that the TD125 is probably the best subchassis deck out there, comfortably outperforming the TD126 (and the Linn LP12…). At least it doesn’t have the late 126’s profusion of low-grade plastic parts…
> 
> ...


Definitely agree with the motor control.  When I first got my Nottingham, I thought what's the big deal with all these motor controllers?  As long as the motor spins the platter at a constant speed, what difference could a dedicated controller possibly make?  Then a dealer-friend sent me a Wave Mechanic (kind of a de-facto for Nottinghams, although I doubt they actually made them) on approval, and I was pretty much floored.  Very substantial improvement.  I'll just say it was more expensive than it needed to be but I sent money rather than ask for a return label.   I'd bet @L0rdGwyn could make one that would trounce it for 1/4 the money....


----------



## L0rdGwyn

Making slow but steady progress on the the 45 amp, was pretty wiped out this weekend so didn't get a lot done.

Chassis is all prepped, sockets, bias pots, interstage transformers (on the interior) and front panel components mounted minus the impedance switch.  Here's a look so far.

I think the first photos I posted made the blue look lighter than it is, this is a little more accurate.

Will keep working on it today.


----------



## whirlwind

L0rdGwyn said:


> Making slow but steady progress on the the 45 amp, was pretty wiped out this weekend so didn't get a lot done.
> 
> Chassis is all prepped, sockets, bias pots, interstage transformers (on the interior) and front panel components mounted minus the impedance switch.  Here's a look so far.
> 
> ...


Looks great...diggin the color too    

Congrats Zach...this is going to be killer!

Love the old skool knob!


----------



## L0rdGwyn

Thanks, Joe.

Mounting more parts.  A ways to go but getting there, here is the interior so far.



And the top with the output transformers in place.


----------



## L0rdGwyn

Okay, think I've reached my stopping point for the day.

Got everything mounted except for the filament regulators, heater regulators, and a few terminals / lugs.



Here's another photo of the top with all eight the transformers mounted (summoning @zach915m for pics) .  I like where it's going aesthetically.





I threw in some globes to see how it would look in its final form, but I can't show that until it's actually done


----------



## bcowen

L0rdGwyn said:


> Making slow but steady progress on the the 45 amp, was pretty wiped out this weekend so didn't get a lot done.
> 
> Chassis is all prepped, sockets, bias pots, interstage transformers (on the interior) and front panel components mounted minus the impedance switch.  Here's a look so far.
> 
> ...



Kimber RCA jacks?  Dude!  My absolute favorites.  Anybody that thinks connectors don't make a difference just needs to try those.


----------



## L0rdGwyn

bcowen said:


> Kimber RCA jacks?  Dude!  My absolute favorites.  Anybody that thinks connectors don't make a difference just needs to try those.



Oh yeah!  They are nice.  It's funny, after trying multiple high end RCAs, I've found there is a correlation between increasing price and increasing crappiness lol.  The Kimber RCAs are reasonably priced, well made, and easy to use (unlike the Vampire RCAs where there is no ground tab, just a block of solid copper that is impossible to solder...).


----------



## Xcalibur255

I didn't realize the vampires were that hard to use.  I went out of my way to get them for my amps.  Of course in my case I'm not the one doing the soldering so I guess that's why I remained in the dark until now!


----------



## L0rdGwyn

Xcalibur255 said:


> I didn't realize the vampires were that hard to use.  I went out of my way to get them for my amps.  Of course in my case I'm not the one doing the soldering so I guess that's why I remained in the dark until now!



It's a specific one, the CM2FCB below.

Rather than having a tab for the ground connection, the expectation is that you will solder directly to body.  The problem is the body is a solid chunk of copper, basically a little heat sink, so heating the thing to a point that will melt solder is a problem.  The whole body of the RCA is also heated to that temperature, so you risk melting the plastic bushings, so you have to remove them and do this all without the RCA mounted.  I've also heated them when soldering to the point that the gold plating starts to flake off.  It can be done but it's a PITA, such a bad design, all they had to do was include a little ground tab.  I actually still have a few pairs of these but I won't use them lol.


----------



## L0rdGwyn

More circuit done, transformers and raw DC supplies are all wired up, filament regulators are in place.  Since everything was already set up in prototype, just need to connect it all together now, but easier said than done.



Was getting tired of wiring stuff, thought about how the last thing I would want to do when the circuit is done is polish the vintage bakelite knob I'm using, so I took a "break" and polished it up some, still has some vintage wear to it, adds to the character 



Will do some more work this evening.  I'm out of town for the weekend starting Thursday, possible but not probable I will get the circuit done before I leave, we'll see how motivated I am tomorrow, otherwise I will finish it Sunday/Monday.


----------



## Mr Trev

L0rdGwyn said:


> Was getting tired of wiring stuff, thought about how the last thing I would want to do when the circuit is done is polish the vintage bakelite knob I'm using, so I took a "break" and polished it up some, still has some vintage wear to it, adds to the character


Absolutely don't want to ruin the patina.
Out of curiosity, what's the size of those things? Might look good on my Vali2…


----------



## L0rdGwyn

Mr Trev said:


> Absolutely don't want to ruin the patina.
> Out of curiosity, what's the size of those things? Might look good on my Vali2…



I think it's 2 inches across.  It is a *KNOB.*


----------



## Mr Trev

L0rdGwyn said:


> I think it's 2 inches across.  It is a *KNOB.*


Seems like they might be comically large for the Vali. Now I do have to get one. Between that knob and the totem pole adapter stacks… the mind reels


----------



## L0rdGwyn

Filament supply is done.  The glow of the 45's oxide-coated filament is quite subtle.


----------



## L0rdGwyn

Bias supplies are done.

Each channel has its own separate regulator.  -70VDC, right where I left them.



Here is the inside with all of that done.  That's where we'll leave it for tonight, will wire up the B+ supplies and signal path wiring in the morning.


----------



## bcowen

Mr Trev said:


> Seems like they might be comically large for the Vali. Now I do have to get one. Between that knob and the totem pole adapter stacks… the mind reels


No such thing as too many adapters.  Or socket savers.  Or sense.


----------



## Mr Trev (Nov 16, 2021)

bcowen said:


> No such thing as too many adapters.  Or socket savers.  Or sense.


Now slap a huge-ass vintage bakelite volume knob on that and tell me it wouldn't be awesome


----------



## L0rdGwyn

Mr Trev said:


> Now slap a huge-ass vintage bakelite volume knob on that and tell me it wouldn't be awesome


 
You'd have to put it on stilts, pretty sure that 2 inch knob would touch the tabletop if it wasn't on a Schiit stack lol.


----------



## Mr Trev

L0rdGwyn said:


> You'd have to put it on stilts, pretty sure that 2 inch knob would touch the tabletop if it wasn't on a Schiit stack lol.


As long as it doesn't block the headphone jack, its all good (added bonus if it _does_ block the power LED)


----------



## Xcalibur255

L0rdGwyn said:


> It's a specific one, the CM2FCB below.
> 
> Rather than having a tab for the ground connection, the expectation is that you will solder directly to body.  The problem is the body is a solid chunk of copper, basically a little heat sink, so heating the thing to a point that will melt solder is a problem.  The whole body of the RCA is also heated to that temperature, so you risk melting the plastic bushings, so you have to remove them and do this all without the RCA mounted.  I've also heated them when soldering to the point that the gold plating starts to flake off.  It can be done but it's a PITA, such a bad design, all they had to do was include a little ground tab.  I actually still have a few pairs of these but I won't use them lol.


That might be the one I chose, the one that's supposed to be solid copper and not just copper plated over brass right?  Hopefully they don't give Mischa a hard time.  I do remember there is a version with and without that tab.  I can't remember which version went into the 45 years ago either.


----------



## L0rdGwyn (Nov 16, 2021)

Xcalibur255 said:


> That might be the one I chose, the one that's supposed to be solid copper and not just copper plated over brass right?  Hopefully they don't give Mischa a hard time.  I do remember there is a version with and without that tab.  I can't remember which version went into the 45 years ago either.



Yeah they are gold plated OFC.

I took one out to show you what I mean, see the arrow, the expecting place to solder the common connection of the RCA is part of the body.  Like I said it can be done, but you would want to use a large solder tip at high temperature.  The issue is the whole thing heats up and the RCA body sinks away heat given before the solder actually starts to flow, makes it difficult to get a good solder connection.  In my experience anyway, maybe Mischa will have better luck!



Interestingly, I just read the parent company of Vampire went out of business and the rights to Vampire connectors were purchased by Parts Connexion, so apparently they will continue the line in some way.


----------



## Xcalibur255

Thanks Keenan.  Yeah I read that too, Parts connexion has all the remaining inventory.  I tortured myself for way too long before finally settling on these (twice actually) so I hope they're decent parts.  I genuinely do believe these parts do contribute (or rather have the potential to take away from) to the sound but getting to a place where you feel like you are making a good choice is even harder for this stuff than it is for buying cables.  I'm sure somebody out there "connector jack rolls" to find the one they like best, but if they are out there they need to write a guide for the rest of us like that one capacitor rolling guy did years ago!


----------



## whirlwind

Mr Trev said:


> Now slap a huge-ass vintage bakelite volume knob on that and tell me it wouldn't be awesome


Ha! Those large bakelite knobs are pretty awesome.


----------



## L0rdGwyn (Nov 17, 2021)

Okay, so I didn't _quite_ finish the amp today, so I am apprehensive to show completed photos.

I did everything but the output switch and I need to add in my updated heater regulator board, I used the old one for the sake of testing the circuit as I was missing one part, which arrived today.

Here is the final circuit minus the output switch and using the old heater regulator board as a stand in.




For the sake time and of listening, I just wired up the 300ohm output taps to the headphone jack.

This amp still has the best clarity, transparency, and holography I have heard in a headphone amp, so that's good news.  Unfortunately I will need to shield the filament transformers, I had hoped to avoid it, but their magnetic field is audible without them.

I have the perfect shields on hand already, here is how they will look once I add them.  When you've done enough DIY, you often have stuff you need just lying around lol that's a headache saved.



So come Sunday /  Monday, I'll add the shields, wire up the output switch, drill holes for the feet on the bottom panel, and replace the heater regulator.

I am still considering trying out the 5687 in this circuit in place of the 6E6P for the sake of comparison, going to discuss that with Zach, so TBD!


----------



## bcowen

L0rdGwyn said:


> Okay, so I didn't _quite_ finish the amp today, so I am apprehensive to show completed photos.
> 
> I did everything but the output switch and I need to add in my updated heater regulator board, I used the old one for the sake of testing the circuit as I was missing one part, which arrived today.
> 
> ...


Nice!!! (as usual)


----------



## L0rdGwyn

bcowen said:


> Nice!!! (as usual)



Thanks!  Probably will be two more weeks of tweaking things, I am going to try the 5687 when I get home next week, but I'll post some pics with it is "aesthetically done" with the impedance switch in place, probably Monday.


----------



## Xcalibur255

Out of curiosity why not 6J5?  Driving a 45 should be right in its wheelhouse.  Or maybe you already made the comparison and decided the 6E6 was better and I'm just forgetting.....


----------



## L0rdGwyn (Nov 18, 2021)

Xcalibur255 said:


> Out of curiosity why not 6J5?  Driving a 45 should be right in its wheelhouse.  Or maybe you already made the comparison and decided the 6E6 was better and I'm just forgetting.....



Using interstage transformers puts more strict requirements on what driver tubes can be used, low plate resistance is the key parameter to get good low frequency response.  The tube and the transformer form a high pass filter, so low plate resistance paired with a good IST with a suitably high primary inductance will get good low frequency performance.  Triode strapped 6E6P have a plate resistance of around 1.2K, parallel section 5687 are similar while 6J5 are up at around 7-8K.  With the right IST, it could be done, but typically a low plate resistance driver is used to get the best bass performance.


----------



## Xcalibur255

So if you were cap coupling it would not be as critical a requirement, I see.  That makes sense now that I think about it, just like with output transformers.


----------



## triod750

L0rdGwyn said:


> Thanks!  Probably will be two more weeks of tweaking things, I am going to try the 5687 when I get home next week, but I'll post some pics with it is "aesthetically done" with the impedance switch in place, probably Monday.


Does it matter what brand of 5687 you use? In some amps they don't sound the same. Or in some heads   . (I have tried them as output tubes).


----------



## L0rdGwyn

triod750 said:


> Does it matter what brand of 5687 you use? In some amps they don't sound the same. Or in some heads   . (I have tried them as output tubes).



I don't think it should matter much, I have a pair of Tung-Sol 5687.  If I end up making the change, the amp could also use E182CC and 7044, which are near equivalents.


----------



## L0rdGwyn (Nov 20, 2021)

Heading out for the weekend, but I ordered parts to make the change to 5687.  I will heat them on AC for the trial run, but if the change is good, the heater regulator will need to be modified to operate at 12.6VDC.  I made the changes to the circuit and ordered the replacement boards, just in case.  Will get back to it on Sunday / Monday!


----------



## bpiotrow13

Since there are a lot of experienced persons here I have a question on tube amps construction. I see all magnificent @L0rdGwyn amps use two power and two driver tubes. Same as some other recognised tube amps. However, there are also OTL amps using one power and one driver tubes (although it seems these are entry level amps). 

I am currently looking for an OTL amplifier for my Verite Open. Is it it really necessary to have two power /driver tubes in an OTL amp to run Verite with full potential? Especially in terms of bas control, details revealing and soundstage? If two power/ driver tubes are not necessary that would be a great advantage given the prices of nos tubes


----------



## L0rdGwyn

bpiotrow13 said:


> Since there are a lot of experienced persons here I have a question on tube amps construction. I see all magnificent @L0rdGwyn amps use two power and two driver tubes. Same as some other recognised tube amps. However, there are also OTL amps using one power and one driver tubes (although it seems these are entry level amps).
> 
> I am currently looking for an OTL amplifier for my Verite Open. Is it it really necessary to have two power /driver tubes in an OTL amp to run Verite with full potential? Especially in terms of bas control, details revealing and soundstage? If two power/ driver tubes are not necessary that would be a great advantage given the prices of nos tubes



Sorry I am on my phone so can't answer in great detail, but OTLs that use one driver and one power tube use dual triodes, two channels in one glass envelop.  Topologies vary, but taking the most apples to apples comparison with cathode follower OTLs using 6AS7G type output tubes, using a pair of outputs with the sections paralleled has the advantage of a lower output impedance which will have performance benefits and allow the use of lower impedance headphones.  I also have found I prefer a pair of single triodes over an equivalent dual triode.  So there are performance benefits to using two tubes per channel, but it will vary from amplifier to amplifier.  That's a generalization and just my experience of course.


----------



## bpiotrow13 (Nov 20, 2021)

L0rdGwyn said:


> Sorry I am on my phone so can't answer in great detail, but OTLs that use one driver and one power tube use dual triodes, two channels in one glass envelop.  Topologies vary, but taking the most apples to apples comparison with cathode follower OTLs using 6AS7G type output tubes, using a pair of outputs with the sections paralleled has the advantage of a lower output impedance which will have performance benefits and allow the use of lower impedance headphones.  I also have found I prefer a pair of single triodes over an equivalent dual triode.  So there are performance benefits to using two tubes per channel, but it will vary from amplifier to amplifier.  That's a generalization and just my experience of course.


Many thanks for Your response. I am looking for an amp based on 6as7/6080 and 6sn7 for my Verite, which are 300 oms, so i guess need not to care about low impedance. 

Could You share a bit more thoughts about those performance benefits You mentioned? This would be very valuable. Is it about bas control and details/ soundstage? I wonder if it is possible to make hi end OTL amp specifically for ZMF Verite based on one driver and one power tube (6sn7/6as7). Or it does not make sense.


----------



## L0rdGwyn

bpiotrow13 said:


> Many thanks for Your response. I am looking for an amp based on 6as7/6080 and 6sn7 for my Verite, which are 300 oms, so i guess need not to care about low impedance.
> 
> Could You share a bit more thoughts about those performance benefits You mentioned? This would be very valuable. Is it about bas control and details/ soundstage? I wonder if it is possible to make hi end OTL amp specifically for ZMF Verite based on one driver and one power tube (6sn7/6as7). Or it does not make sense.



Yes, increased soundstage and improved imaging, detail retrieval and bass definition.  Absolutely you can build a cathode follower OTL using one 6SN7 and 6AS7G, not unlike a Darkvoice or Bottlehead Crack.  Those designs could be improved upon though, particularly their power supplies.  The Apex Teton is a "high end" OTL using these tubes, although I think it is very overpriced for what it is.


----------



## bpiotrow13

L0rdGwyn said:


> Yes, increased soundstage and improved imaging, detail retrieval and bass definition.  Absolutely you can build a cathode follower OTL using one 6SN7 and 6AS7G, not unlike a Darkvoice or Bottlehead Crack.  Those designs could be improved upon though, particularly their power supplies.  The Apex Teton is a "high end" OTL using these tubes, although I think it is very overpriced for what it is.


Many thanks! It is tempting to have an amp with one tube each. I have not known Apex. So I guess the answer is not that simple. Two tubes are better than one, but it is ultimately up to the particular design.


----------



## Tjj226 Angel

bpiotrow13 said:


> Many thanks! It is tempting to have an amp with one tube each. I have not known Apex. So I guess the answer is not that simple. Two tubes are better than one, but it is ultimately up to the particular design.



Since you live in Poland, why not use the 6c33c tube? They should be very cheap and plentiful in your country and you could easily build an OTL with 1 triode output.


----------



## L0rdGwyn (Nov 22, 2021)

No problem, @bpiotrow13 .  Yes, it's never so simple, but I would say in general the designs I have heard using a pair of tubes are better.  No doubt though you can make a very good sounding amplifier using a single 6AS7G and a 6SN7 though.  You certainly could commission someone to build a "premium" OTL amplifier for your Verite using those tubes.  Given it _should_ be a low parts count amplifier, I don't think it would be too expensive.  You could reach out to the Head-Fier Paladin79, he makes an OTL amplifier using those tubes, I have not heard it, but @bcowen has one.  Not sure if he builds for anyone who inquires, but you could ask him.  Another less expensive option would be to build or commission a Bottlehead Crack + Speedball build, many are very happy using that amplifier with their high impedance ZMFs.  I would avoid the Darkvoice.

I'll be working on the 45 amp some more today, last night I rewired the input sockets for 5687.  I like the change and will most likely be keeping it that way, parts for the 12.6VDC heater regulator are on the way.  That means the input tube options would include 5687, E182CC, 7119, 7044, and Bendix 6900 if Zach wants to take out a loan.  I will be doing some other tweaks today as well, will post some photos assuming I get everything squared away from a cosmetic standpoint.


----------



## bpiotrow13

Tjj226 Angel said:


> Since you live in Poland, why not use the 6c33c tube? They should be very cheap and plentiful in your country and you could easily build an OTL with 1 triode output.


I think this is not a big difference nowadays where You live. I have a stock of 6as7 tubes already and it is much easier to tube roll with this family. But 6c33 may be a nice option, thanks


----------



## Tjj226 Angel

bpiotrow13 said:


> I think this is not a big difference nowadays where You live. I have a stock of 6as7 tubes already and it is much easier to tube roll with this family. But 6c33 may be a nice option, thanks



Russian surplus tubes are a different story. There are warehouses of those tubes strooned throughout eastern europe. If you know where to look and who to ask, you should be able to find some for free.


----------



## bpiotrow13

L0rdGwyn said:


> No problem, @bpiotrow13 . Yes, it's never so simple, but I would say in general the designs I have heard using a pair of tubes are better. No doubt though you can make a very good sounding amplifier using a single 6AS7G and a 6SN7 though. You certainly could commission someone to build a "premium" OTL amplifier for your Verite using those tubes. Given it _should_ be a low parts count amplifier, I don't think it would be too expensive. You could reach out to the Head-Fier Paladin79, he makes an OTL amplifier using those tubes, I have not heard it, but @bcowen has one. Not sure if he builds for anyone who inquires, but you could reach out to him. Another less expensive option would be to build or commission a Bottlehead Crack + Speedball build, many are very happy using that amplifier with their high impedance ZMFs. I would avoid the Darkvoice.
> 
> I'll be working on the 45 amp some more today


Thanks again. There are at least two recognised producers of OTL amps here in Polan so no problem with finding someone. Probably the most difficult part is to determine what one wants Your thread is really helpful with this regard

I (basically) currently have two headphone amps: Woo wa2 and Ayon Ha 3 (using 45 type tubes) that I use with ZMF Verite. To me 45 type tubes are too neutral and I have just put Ayon for sale. I really enjoy OTL design with Verite. However Woo wa2 uses ecc88 driver tubes and I tend to like ecc82 or 6sn7 more. This is the reason I am contemplating custom project.

Can't wait for more pictures of Your 45 amp


----------



## triod750

L0rdGwyn said:


> No problem, @bpiotrow13 .  Yes, it's never so simple, but I would say in general the designs I have heard using a pair of tubes are better.  No doubt though you can make a very good sounding amplifier using a single 6AS7G and a 6SN7 though.  You certainly could commission someone to build a "premium" OTL amplifier for your Verite using those tubes.  Given it _should_ be a low parts count amplifier, I don't think it would be too expensive.  You could reach out to the Head-Fier Paladin79, he makes an OTL amplifier using those tubes, I have not heard it, but @bcowen has one.  Not sure if he builds for anyone who inquires, but you could ask him.  Another less expensive option would be to build or commission a Bottlehead Crack + Speedball build, many are very happy using that amplifier with their high impedance ZMFs.  I would avoid the Darkvoice.
> 
> I'll be working on the 45 amp some more today, last night I rewired the input sockets for 5687.  I like the change and will most likely be keeping it that way, parts for the 12.6VDC heater regulator are on the way.  That means the input tube options would include 5687, E182CC, 7119, 7044, and Bendix 6900 if Zach wants to take out a loan.  I will be doing some other tweaks today as well, will post some photos assuming I get everything squared away from a cosmetic standpoint.


I guess he could use Melz 6N12S too. That is my favourite tube, but I don't use it for input. It is close to the parameters of 5687 (I think - what do I know about electricity)?


----------



## L0rdGwyn (Nov 22, 2021)

Wow busy day, spent the entirety of it working on this 45 amp.  The amp is done enough to show some pictures, but first I am going to tell you what I did.

Last night I rewired the input sockets for 5687 to run on AC while I wait for heater regulator parts / PCBs, so that was done fortunately.

Next I wired up the impedance switch that will be on the front panel.  Again, the transformers are tapped for 300ohm, 120ohm, and 32ohm.

Here is the wired switch.  It is a three-position toggle, up (300ohm), middle (120ohm), down (32ohm).


 

Next I put some feet on the bottom panel, but I'm not going to show that because it's boring.

Okay, here was the real doozy...

For the original build and prototype, I used the Hammond 167 series transformers for the filament supply.  What was not obvious during the prototype and blatantly obvious after building the amp is that these transformers SUCK!!!

Up to this point I have always used Hammond 166 or 266 open bracket dual bobbin transformers for dedicated filament supplies.  The 167 series is fully enclosed rather than open bracket.  I though "well, fully closed looks better, I wonder if I can get away with leaving them unshielded for the black transformer swag".  I quickly learned that was a mistake, as these transformers emit a massive magnetic field audible even with shielding and have horrendous primary-to-secondary coupling.  Every bit of mains noise was coupled into the filament supply - noise from my PC (squeeky sounds while moving the mouse), noise from every light dimmer in my house, everything.  I actually opened one up afterward thinking perhaps that I had been duped and they weren't really dual bobbin as advertised.  They appear to be, but regardless, the coupling and magnetic field were a massive noise problem.

So I ordered an equivalent pair of 166 series open bracket transformers, which I know to be good, and went to work today to make the swap.  This was a true joy to work on.

I had to remove the mains transformer as well, then tape everything up for protection including the output transformers, then go through the tedious process of marking everything up for drilling, then out to the garage for machining.



Here are the 166 series transformers in place before I affixed the shields.  I had to trim a bit off of the ends of the brackets to fit the shields overtop.



Then put everything back together.  Wooooh.  Started working on this at around 7AM and just finished.  But all of my noise woes are taken care of and the amp sounds great.

The amp isn't _completely_ done as I am running the 5687 on AC at the moment, but it is done enough for pics, will post some shortly.


----------



## L0rdGwyn (Nov 22, 2021)

Here are some pics.  Not color accurate, but close enough.







And one in operation, again the color is off given it is a dark photo with long exposure.  Green lighting is the biasing LEDs.


----------



## jgwtriode

Impressive....love those globe 45's and all that iron has gotta be good for the music.  Just like for proper blood flow!

Happy listening,

jgwtriode


----------



## Mr Trev

L0rdGwyn said:


> Wow busy day, spent the entirety of it working on this 45 amp.  The amp is done enough to show some pictures, but first I am going to tell you what I did.
> 
> Last night I rewired the input sockets for 5687 to run on AC while I wait for heater regulator parts / PCBs, so that was done fortunately.
> 
> ...


Ironic that moving your mouse made squeeky sounds


----------



## bcowen

L0rdGwyn said:


> Here are some pics.  Not color accurate, but close enough.
> 
> 
> 
> ...


Love it!!!


----------



## triod750

L0rdGwyn said:


> For the original build and prototype, I used the Hammond 167 series transformers for the filament supply. What was not obvious during the prototype and blatantly obvious after building the amp is that these transformers SUCK!!!


My Lord, just what I expected from you! You could have asked - I'm here for you...!


----------



## Mr Trev

L0rdGwyn said:


> Here are some pics.  Not color accurate, but close enough.
> 
> 
> 
> ...


At the risk of further inflaming my amp-envy…
Does the 32ohm tap mean it'll play nicely with iems?


----------



## L0rdGwyn

Mr Trev said:


> At the risk of further inflaming my amp-envy…
> Does the 32ohm tap mean it'll play nicely with iems?



Hmmm think it would depend on the IEM, output impedance on that tap is likely around 10ohm, but very sensitive IEMs will be prone to an audible noise floor.  So I don't know!  Something like the ER4XR would probably work well, maybe Zach can give it a shot and let us know.  I am IEM-less at the moment -_-


----------



## L0rdGwyn

The blue on this amp really does look different in different kinds of light, it's hard to capture the true color on camera, especially in low light.  Here is one more pic, just a phone shot, using the globe RCA 45 I picked up a few weeks ago.  The amp looks teal lol.


----------



## CJG888

L0rdGwyn said:


> The blue on this amp really does look different in different kinds of light, it's hard to capture the true color on camera, especially in low light.  Here is one more pic, just a phone shot, using the globe RCA 45 I picked up a few weeks ago.  The amp looks teal lol.


Almost Porsche Maritimblau!


----------



## whirlwind

L0rdGwyn said:


> The blue on this amp really does look different in different kinds of light, it's hard to capture the true color on camera, especially in low light.  Here is one more pic, just a phone shot, using the globe RCA 45 I picked up a few weeks ago.  The amp looks teal lol.


Sometimes it looks lavender ...sometimes blue/gray...and here it looks the color of a DN amp.
Looks great no matter what.


----------



## whirlwind

L0rdGwyn said:


> Hmmm think it would depend on the IEM, output impedance on that tap is likely around 10ohm, but very sensitive IEMs will be prone to an audible noise floor.  So I don't know!  Something like the ER4XR would probably work well, maybe Zach can give it a shot and let us know.  I am IEM-less at the moment -_-


I am looking for a nice IEM upgrade....I feel like there is way too many to keep up with and a new one coming out every week


----------



## L0rdGwyn

whirlwind said:


> I am looking for a nice IEM upgrade....I feel like there is way too many to keep up with and a new one coming out every week



Yeah a lot of choice out there, I need a new pair myself.  I mostly use them for travel, but haven't been doing as much of that lately 😂 will have to ask around when I'm ready to pull the trigger.  Just had a birthday, thought about asking for some new IEMs, but instead I asked for books on winding transformers


----------



## L0rdGwyn

Tried out the pair of low testing globe 45 I bought a few weeks ago, had to adjust the bias of course, but still sound great, totally usable.


----------



## Xcalibur255

Are the 5687 tubes staying in the final build?


----------



## L0rdGwyn

Xcalibur255 said:


> Are the 5687 tubes staying in the final build?



Yup, just need to confirm with Zach.  Doing it for a few different reasons:

-Around half the gain of the 6E6P, which is a more appropriate amount for a headphone amp.  The volume knob was quite sensitive with the 6E6P
-Easier to test on Zach's Hickok tester, which would not have settings for 6E6P.  I had planned to try testing 6E6P with settings of a near equivalent western tube, but had not yet confirmed it would work out
-More variety of tubes to try out as there were many manufacturer's of 5687 along with different variants (5687WA, 5687WB), in addition to being able to use E182CC / 7119 and 7044.  Could even use the unobtainium Bendix 6900!  And a few other tubes with adapters
-Less prone to oscillation than 6E6P.  Measures were taken to avoid it, but you can never be certain that a bad egg won't turn up

So yeah I think overall it makes sense from a design and practicality standpoint while adding more tube rollability.


----------



## leftside

whirlwind said:


> I am looking for a nice IEM upgrade....I feel like there is way too many to keep up with and a new one coming out every week


Yeah those things are nuts. My buddy collects them like I collect tubes  Just get a good set and then ignore every IEM thread on here.


----------



## L0rdGwyn

I think I will miss this amp when it's gone...maybe I will find "problems" and "important tests" to run for, oh, a few more months 

Don't think I showed it with ST shaped 45s.  This is actually the closest to the real color I have photographed.



Did some boring tests today, checking fuse ratings, adjusting trimmers, etc.  Placing one final order for a few components, extra fuses and such, rounding the corner to the finish.  I'm tempted to buy a pair of E182CC to see how they sound in this amp (I only have a single).

Once I get this shipped off, it will be back to working on the two Airmids!


----------



## L0rdGwyn

Curiosity got the better of me, grabbed a few different 5687 to try, bronze plate RCA and GE 5 star, as well as a pair of Amperex E182CC.  Will get to take them for a test run before I ship the amp, they'll come in handy some day I'm sure.


----------



## whirlwind

L0rdGwyn said:


> Curiosity got the better of me, grabbed a few different 5687 to try, bronze plate RCA and GE 5 star, as well as a pair of Amperex E182CC.  Will get to take them for a test run before I ship the amp, they'll come in handy some day I'm sure.


Ha.....this was bound to happen.....you need to make one for yourself


----------



## Xcalibur255

I would think that the 801A would be on the same footing performance-wise.  Maybe a different flavor but still good.


----------



## 2359glenn

Hi Everybody

Happy Thanksgiving

Been gone for awhile due to health issues 

Have a great weekend


----------



## Galapac

Happy Thanksgiving everyone!

@L0rdGwyn I know you wanted to see my finished Elekit TU-8200R DX that I had painted in a special powder coated red but need to take photos of the inside using the Lundahl transformers as I was so psyched to get it built, it was together before I finished taking pics of the inside. Will share on the Elekit thread later at some point.

I can’t stop listening to this new amp!


----------



## GDuss

Galapac said:


> Happy Thanksgiving everyone!
> 
> @L0rdGwyn I know you wanted to see my finished Elekit TU-8200R DX that I had painted in a special powder coated red but need to take photos of the inside using the Lundahl transformers as I was so psyched to get it built, it was together before I finished taking pics of the inside. Will share on the Elekit thread later at some point.
> 
> I can’t stop listening to this new amp!


I built one of these earlier this year with Lundahl OPT's and also can't stop listening to it.  Highly recommended for anyone interested in it, and the build was not that difficult.  Here is a photo of the insides, although most of the fun parts are under the main board:


----------



## gibosi

2359glenn said:


> Hi Everybody
> 
> Happy Thanksgiving
> 
> ...


Hope you are on the mend and enjoying your turkey day!


----------



## L0rdGwyn

2359glenn said:


> Hi Everybody
> 
> Happy Thanksgiving
> 
> ...



Hope you are doing better my friend, Happy Thanksgiving!


----------



## L0rdGwyn

Galapac said:


> Happy Thanksgiving everyone!
> 
> @L0rdGwyn I know you wanted to see my finished Elekit TU-8200R DX that I had painted in a special powder coated red but need to take photos of the inside using the Lundahl transformers as I was so psyched to get it built, it was together before I finished taking pics of the inside. Will share on the Elekit thread later at some point.
> 
> I can’t stop listening to this new amp!



Looks excellent and bet it sounds great, well done, seems like a nice kit to get your hands on a SET amplifier with quality transformers.


----------



## GDuss

L0rdGwyn said:


> Looks excellent and bet it sounds great, well done, seems like a nice kit to get your hands on a SET amplifier with quality transformers.



LG, you should sell an Airmid DIY kit.  Put together some instructions, source all the parts and sell them in a bundle, include as much profit for yourself as needed to make it worth your time.  I’d buy it.


----------



## whirlwind

GDuss said:


> LG, you should sell an Airmid DIY kit.  Put together some instructions, source all the parts and sell them in a bundle, include as much profit for yourself as needed to make it worth your time.  I’d buy it.


Make it an SET kit instead


----------



## triod750

Or maybe a kitty kit...?


----------



## L0rdGwyn

I'll keep those ideas in mind guys!

Long day at work, worked the holiday too, and through the weekend!  A five day marathon, that's a lot for me.

Luckily had something to look forward to when I got home, got the first of my 5687s to compare, RCA bronze plate, here next to the Tung-Sol 5687WA I've been using in Zach's amp.



I wanted to test the viability of rolling input tubes on changing the tone of the amp, happy to say the effect is very noticeable.  I felt the amp sounded a bit "dry" since changing to 5687, but I happened to read a few comments describing the Tung-Sol 5687WA as having a dry character.  The RCAs, by comparison, are more full and smooth without the dryness.  I would say I prefer them! Glad the amp can be tuned a bit using these tubes.  Still waiting on the GE 5-star (which, believe it or not GE haters, have rave reviews) and Amperex E182CC, should have those early next week.

Waiting for some final parts, so figured out do some tube research for Zach in the meantime.


----------



## Galapac

L0rdGwyn said:


> I'll keep those ideas in mind guys!
> 
> Long day at work, worked the holiday too, and through the weekend!  A five day marathon, that's a lot for me.
> 
> ...


Quite the glow going on in that amp, blue phosphorescence from the tubes, green gamma glow from within…you need to take a pic with the lights off when it’s ready.


----------



## jgwtriode

Gorgeous!  Looks very impressive, no doubt sounds even better than it looks.

Happy listening,

jgwtriode


----------



## whirlwind

L0rdGwyn said:


> I'll keep those ideas in mind guys!
> 
> Long day at work, worked the holiday too, and through the weekend!  A five day marathon, that's a lot for me.
> 
> ...



Love this picture of it.   

Maybe make an amp for some stats    

I love the EL34 tubes... the Blue Hawaii with some nice stats is a sound I would like to hear.  I really am not a fan of just the most detail that I can get, but I hear this sound is pretty incredible.

I am assuming here, but I am guessing any nice capable amp will sound pretty good with a nice stat headphone.


----------



## UntilThen

L0rdGwyn said:


> Tried out the pair of low testing globe 45 I bought a few weeks ago, had to adjust the bias of course, but still sound great, totally usable.



Stunning just stunning.


----------



## triod750

L0rdGwyn said:


> Still waiting on the GE 5-star (which, believe it or not GE haters, have rave reviews)


Mordy recommended these to me a few years ago and I was sceptic, even before I had 'met' bcowen, but I have often since had reasons to take Mordy's recommendations seriously. They are not bad at all. He neither.


----------



## bcowen

triod750 said:


> Mordy recommended these to me a few years ago and I was sceptic, even before I had 'met' bcowen, but I have often since had reasons to take Mordy's recommendations seriously. They are not bad at all. He neither.


LOL! 

Despite a multitude of prior protestations, I really _wanted_ to like these because they are plentiful and cheap.  And I'd also heard that the GE's were well thought of in this tube type.  I'll say they don't suck, but it's not like they're getting close to top-tier either.

I've never tried a GE 5687.


----------



## UntilThen

bcowen said:


> I'll say they don't suck, but it's not like they're getting close to top-tier either.



Wait till you hear my top tier GE rectifier.


----------



## bcowen

UntilThen said:


> Wait till you hear my* top tier GE rectifier.*


That's a four word oxymoron.


----------



## triod750

bcowen said:


> I've never tried a GE 5687.


I have, so I will try to trust your GEneral opinion. I will try hard. They don't sound anywhere close to 6N12S but not many tubes do. I tried them (GE 5687) as an alternative to 6N6P and 6N30Pi and while I liked their tone better, I found the soundstage to be too distant. I might not have run them long enough, to be fair. Then I found 6N12S and lost interest. Fast forward, I found a pair of Lorenz manufactured - not just branded - C3g at a good price and tested these with different power tubes. With GE 5687 they took care of the soundstage issue. If I had tried this combination from the start I might have lived with it for a while. But I had moved on so it was just a test.


----------



## bcowen

triod750 said:


> I have, so I will try to trust your GEneral opinion. I will try hard. They don't sound anywhere close to 6N12S but not many tubes do. I tried them (GE 5687) as an alternative to 6N6P and 6N30Pi and while I liked their tone better, I found the soundstage to be too distant. I might not have run them long enough, to be fair. Then I found 6N12S and lost interest. Fast forward, I found a pair of Lorenz manufactured - not just branded - C3g at a good price and tested these with different power tubes. With GE 5687 they took care of the soundstage issue. If I had tried this combination from the start I might have lived with it for a while. But I had moved on so it was just a test.


Have a pair of round plate Melz 6N12S, but no application for them at present. Can't tell you if they're good....or not.   






The soundstage is also the biggest issue I have with the 6C4's right now.  Nice and wide, but no depth to speak of.  I like these Lansdale-branded ones best so far.  Not sure who made them, as to my knowledge Lansdale was only a testing/grading operation and never manufactured tubes themselves.   Probably the hardest hitting bass and most dynamic tube I've subbed for a 6SN7 to date.


----------



## triod750

bcowen said:


> Have a pair of round plate Melz 6N12S, but no application for them at present. Can't tell you if they're good....or not.


With no application they are absolutely useless. Imported from Slovakia? I can trade my GE FIVE STAR, and then some, 5687 for those. (It wasn't easy to find partners for 6N12S).

Have you tried any GEC 6C4/CV133?


----------



## bcowen

triod750 said:


> With no application they are absolutely useless. Imported from Slovakia? I can trade my GE FIVE STAR, and then some, 5687 for those. (It wasn't easy to find partners for 6N12S).
> 
> Have you tried any GEC 6C4/CV133?


I got the Melz a while back...don't remember where I bought them right off.

Haven't tried the GEC's yet.  The few I've seen were pretty pricey.  Have you tried them, and if so are they worth it? 

I just got a pair of Brimars in though.  Better soundstage depth (but still comparatively lacking), and noticeably livelier up top.  But missing the sledgehammer bass of the Lansdales.


----------



## triod750

Are these from the Swiss Army?

I have a pair of KB/Z that are very lively up top. I haven't used them long enough to say something more about them. I am comparing other tubes now.

KB/FD ; STC Rochester?

Couldn't you have a sledgehammer and knock yourself on the head. That would be cheaper...


----------



## bcowen

triod750 said:


> Are these from the Swiss Army?
> 
> I have a pair of KB/Z that are very lively up top. I haven't used them long enough to say something more about them. I am comparing other tubes now.
> 
> ...


Don't know about any military designation.  They are STC Rochester.  Too bad they aren't FB's out of the Footscray plant.  

Using a sledgehammer on my head would feel really good when I stop I suppose.


----------



## L0rdGwyn

bcowen said:


> LOL!
> 
> Despite a multitude of prior protestations, I really _wanted_ to like these because they are plentiful and cheap.  And I'd also heard that the GE's were well thought of in this tube type.  I'll say they don't suck, but it's not like they're getting close to top-tier either.
> 
> I've never tried a GE 5687.



I'll let you know how they stack up 

On a sleep, eat, work, try new tubes, repeat schedule.  Tonight it is the Amperex E182CC / 7119.



These are a near-equivalent to 5687, not exact, but generally can be used in the same circuit.  Of the three pairs of input tubes I've tried so far, these seem to have the highest degree of holography.  Not sure if I prefer them over the RCAs yet, will need to A-B, but I won't have time until next week.


----------



## Velozity (Nov 27, 2021)

bcowen said:


> Have a pair of round plate Melz 6N12S, but no application for them at present. Can't tell you if they're good....or not.
> 
> 
> 
> The soundstage is also the biggest issue I have with the 6C4's right now.  Nice and wide, but no depth to speak of.  I like these Lansdale-branded ones best so far.  Not sure who made them, as to my knowledge Lansdale was only a testing/grading operation and never manufactured tubes themselves.   Probably the hardest hitting bass and most dynamic tube I've subbed for a 6SN7 to date.




I've used quite a few tubes in this family when I was doing exploring prior to switching over to 6C5/6J5.  Can I see a frontal shot of the Landsdale's plates?  Also, I posted several 6C4 impressions somewhere in the 6J5 thread, like a couple years ago.  I was quite fond of the GE 5-star in my application, but the MOV CV133 are still the best.  Particularly the unobtanium welded-plate versions.


----------



## Xcalibur255

Maybe it's false equivalency at work, but I always feel that the tubes with the longest/largest plates within a specific type and family tend to be the most resolving.


----------



## Tjj226 Angel

Xcalibur255 said:


> Maybe it's false equivalency at work, but I always feel that the tubes with the longest/largest plates within a specific type and family tend to be the most resolving.



All things being equal, bigger plates are better.


----------



## bcowen

Velozity said:


> I've used quite a few tubes in this family when I was doing exploring prior to switching over to 6C5/6J5.  Can I see a frontal shot of the Landsdale's plates?  Also, I posted several 6C4 impressions somewhere in the 6J5 thread, like a couple years ago.  I was quite fond of the GE 5-star in my application, but the MOV CV133 are still the best.  Particularly the unobtanium welded-plate versions.


Sure.  Below, Lansdale on the left and GE on the right:





The Lansdales look very similar to these Amperex branded ones, but I don't know for sure that Amperex actually made them.


----------



## triod750

https://www.dos4ever.com/EF50/EF50.html
There is a lot of intrigueing valve/tube history to be found on this link. Never mind the EF50 in itself. If you are bored one rainy day, or don't have the money to scoure eBay, take a look at this.


----------



## L0rdGwyn

I got my GE 5687, but I think I made a mistake...they are not the 5-star variety, seem to be just regular GEs...duhn duhn DUHN!!!



Yeah, they sound pretty bad LOL.

The E182CC are my favorites in the 45 amp so far, then the RCA 5687.  I won an auction for thirteen RCA 7044, another near-equivalent in this family, more similar to the E182CC, hoping to try those out before I ship the amp to Zach so I can make some recommendations.

Otherwise, just getting slaughtered in NE Ohio with COVID, so haven't been posting with the usual vigor or getting much done DIY-wise.  I'll be getting the final parts for the 45 amp heater regulator tomorrow, once that's in the amp will actually be done, so it will be shipping soon.  Then the Airmids are next which will come together quickly, after that I think I'll need a break from DIY to regroup, do some inventory, sell some spare tubes / parts, it's getting pretty crowded around here.


----------



## Xcalibur255

bcowen thumbs upping this post about accidentally buying bad sounding GE tubes........... not sure what to make of that.


----------



## bcowen

Xcalibur255 said:


> bcowen thumbs upping this post about accidentally buying bad sounding GE tubes........... not sure what to make of that.


LOL!  I'd never wish bad sounding tubes on anyone.  Well, except maybe @UntilThen because he only pays me $1.25 per hour...


----------



## Xcalibur255

Please tell me that wage is in exchange for recommending GE tubes to him all day long?


----------



## UntilThen

bcowen said:


> LOL!  I'd never wish bad sounding tubes on anyone.  Well, except maybe @UntilThen because he only pays me $1.25 per hour...



Don't complain. Some get less than that.

Look at the GE tube - Progress is Our Most Important Product. Don't you forget that.


----------



## UntilThen

More importantly what chair are you using.


----------



## jgwtriode

Ah that is clever, gave me a good laugh.

jgwtriode


----------



## chrisdrop

I _really_ like the (_5670_) 5-star GE tubes (For me > Bendix, WE equivalents)


----------



## L0rdGwyn

chrisdrop said:


> I _really_ like the (_5670_) 5-star GE tubes (For me > Bendix, WE equivalents)



Oh yeah, those are really great!  One of the best 5670.  The Bendix was pretty lackluster from what I remember, I did like the WE 396A however.  At one point I had a big collection of those tubes, all gone now!


----------



## L0rdGwyn

Going to ship @zach915m 's 45 amp today, figured I'd take some last minute photos.

Here are the tubes I'm sending with it, a little starter pack with one set of each type of driver the amp can take.  From left to right - 5687, E182CC / 7119, and 7044.



And of course a pair of Tung-Sol ST-shaped 45 (Sylvania manufactured).



Here is the final interior circuit.  Been making some tweaks here and there over the past two weeks, but now it's done.



Here is the amp with the Tung-Sol 45 and 7044.  I ended up double shielding the mains transformer to reduce the noise floor.  Now all the back row shields match, which makes me happy.





Back panel with power switch.



One more listen with my Philco globe 45 and E182CC.



Time to pack it up.


----------



## bcowen

L0rdGwyn said:


> Going to ship @zach915m 's 45 amp today, figured I'd take some last minute photos.
> 
> Here are the tubes I'm sending with it, a little starter pack with one set of each type of driver the amp can take.  From left to right - 5687, E182CC / 7119, and 7044.
> 
> ...


Wow!  Really, _really_ nice!


----------



## Mr Trev

L0rdGwyn said:


> Going to ship @zach915m 's 45 amp today, figured I'd take some last minute photos.
> 
> Here are the tubes I'm sending with it, a little starter pack with one set of each type of driver the amp can take.  From left to right - 5687, E182CC / 7119, and 7044.
> 
> ...


Damn, that's looking good.
I have to ask though… why the RCA inputs on the front?


----------



## zach915m

L0rdGwyn said:


> Going to ship @zach915m 's 45 amp today, figured I'd take some last minute photos.
> 
> Here are the tubes I'm sending with it, a little starter pack with one set of each type of driver the amp can take.  From left to right - 5687, E182CC / 7119, and 7044.
> 
> ...


Wowoow

Can't remember the last time I've been so excite. 

Will report.


----------



## jgwtriode

L0rdGwyn said:


> Going to ship @zach915m 's 45 amp today, figured I'd take some last minute photos.
> 
> Here are the tubes I'm sending with it, a little starter pack with one set of each type of driver the amp can take.  From left to right - 5687, E182CC / 7119, and 7044.
> 
> ...


Stunning Keenan.  Gorgeous shade of blue!  Love the way you lay out your amps.  Very artistic top and bottom!   Zach is a lucky man.
So in the end how does it actually sound  and if I may ask how close is the Airmid capable of getting to it with GEC's and Tungsols?

Amazing job, looks like you have been doing this for years. Every bit as pleasing or more so to look at then anything I have seen on
the market.

Impressive and happy listening,

jgwtriode


----------



## L0rdGwyn

Mr Trev said:


> Damn, that's looking good.
> I have to ask though… why the RCA inputs on the front?



Putting the RCAs on the front keeps the low level signal wiring short to minimize noise pickup between the RCA and the pot.  Lots of AC in the back of this amp, so it helps reduce the noise floor.



jgwtriode said:


> Stunning Keenan.  Gorgeous shade of blue!  Love the way you lay out your amps.  Very artistic top and bottom!   Zach is a lucky man.
> So in the end how does it actually sound  and if I may ask how close is the Airmid capable of getting to it with GEC's and Tungsols?
> 
> Amazing job, looks like you have been doing this for years. Every bit as pleasing or more so to look at then anything I have seen on
> ...



Thanks @jgwtriode , I've been very short on time lately due to work so did not get around to a true A-B test, I'll give the Airmid a listen perhaps tonight or Tuesday and see how I think they stack up.

As far as the 45 amp though, I would say its main characteristics are its transparency and holographic soundstage, I think it has the best clarity / imaging of any tube headphone amp I have heard.  The sound changes a bit depending on the input tubes used however.  The most impressive in terms of staging / imaging is the E182CC by my ears, the 7044 is slightly less spacious but I believe has the best bass definition of the three, the 5687 is more intimate but offers a more forward and exciting sound.  Also many variations of the 5687 to try and I did find there were very obvious differences in tonality between the three pairs I tried with the RCAs I am sending Zach being the best of the three.


----------



## L0rdGwyn

Also got some interesting tubes last night for my two-channel amp, MWT H63.  These are the British equivalent to the 6F5, but have dramatically different internal construction.



First set I bought from Italy got lost in the mail.  I ended up getting someone else's vintage nautical sextant instead, but that's another story.  Fortunately Langrex suddenly has a large stock of H63, hooray!  I'll probably stock up while they're available.


----------



## jgwtriode

L0rdGwyn said:


> Also got some interesting tubes last night for my two-channel amp, MWT H63.  These are the British equivalent to the 6F5, but have dramatically different internal construction.
> 
> 
> 
> First set I bought from Italy got lost in the mail.  I ended up getting someone else's vintage nautical sextant instead, but that's another story.  Fortunately Langrex suddenly has a large stock of H63, hooray!  I'll probably stock up while they're available.


Definitely curious about these Keenan!  How do they stack up against the GEC's?   Hopefully close and a bit more affordable!


Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Definitely curious about these Keenan!  How do they stack up against the GEC's?   Hopefully close and a bit more affordable!
> 
> 
> Happy listening,
> ...



They actually are GECs!  MWT / GEC / Marconi-Osram are one and the same, so the internal construction is identical  these are high gain triodes, mu of 100, with a plate resistance of around 66K, so not really useful in a lot of headphone circuits with all of that gain and the high plate resistance, but my speaker amplifier uses a little local negative feedback, they work really well in that circuit, very linear tubes too.


----------



## jgwtriode

So how do these compare sonically with the GEC 6J5's that Monster talks about on his review. I see them going for quite a bit less money!

Thanks,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> So how do these compare sonically with the GEC 6J5's that Monster talks about on his review. I see them going for quite a bit less money!
> 
> Thanks,
> 
> jgwtriode



Ahh but they cannot be compared!  As they cannot be used effectively in the same circuit, they will not work in the Airmid, sadly.  The GEC L63 / 6J5 and H63 are very different tubes in terms of the operating characteristics.  Because of its high gain, the H63 is more of a specialist type of tube, it needs to be used in a more specific type of circuit, whereas the GEC L63 / 6J5 is very adaptable in many different audio circuits, the reason they are so popular.  But in general they are both very linear and GEC-made tubes are of the highest quality, each tube is excellent its respective use case.  I can highly recommend the GEC L63 for the Airmid or any other amplifier than can use 6J5 types, they are expensive but one of the best in that family.


----------



## jgwtriode (Dec 5, 2021)

Very good, always trying to find a way to get more value, but understand sometimes you just have to pay the price to get what you want.  So thats fine, I figured I would be throwing in another 700 plus to get tubes that are really what I want.  I am going to throw a fair amount of money into an interconnect as well, although I have a couple of temporaries that will be okay until I can get what I want.  After that will tinker with a higher quality power cord.  The Wywires platinum stuff has me gobsmacked right now.  But interconnect and tubes first.   It never ends, there is always another thing to be improved.  But I am getting there.  And of course isolation of the amp comes into play as well.  I will do basic initially, withmy airbladder ikea composite table sandwich with brass cone/ceramic,  works quite well.  All good, main thing is I have the core of a phenomenal end game triode headphone amplifier to work from.  Estimate by the last quarter of next year all that will be done.  Then I can look to some very serious power line conditioning.  Right now its just a 1000Watt Hospital grade triplite that runs my Computer and DAC amp on seperate circuits.

If only I had an extra 5 to 10,000 a year to throw at this hobby.   But I manage and I am quite pleased.  It's all good and have run into some amazing people and learned a hell of a lot. 

And my system just keep sounding better which makes me a very happy listener.


Thanks again to you and everyone on this thread,  awesome people

jgwtriode


----------



## L0rdGwyn

Now that I'm not doing aggressive critical listening at my desk every day, I can put my DIY DAC in its true home, in my two channel system.






Did some post 45 amp cleanup today, will get back to work on the two Airmid builds tomorrow.


----------



## jgwtriode

Ah very nice!  What speakers are those Keenan, if you don't mind me asking?

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Ah very nice!  What speakers are those Keenan, if you don't mind me asking?
> 
> Happy listening,
> 
> jgwtriode



They are Snell J/II.  Last year I bought a used pair, replaced the drivers, rebuilt the crossovers.


----------



## CJG888

Of course you could conceivably try Audio Note crossovers…


----------



## L0rdGwyn (Dec 8, 2021)

CJG888 said:


> Of course you could conceivably try Audio Note crossovers…



And their drivers, although they are 6ohms nominal whereas the original Vifa drivers are 8ohms.  You can also buy replacement foam surrounds from Audio Note too when the originals wear out.  I had exchanged a few emails with Peter Qvortrup when I was deciding on what direction to go, but decided to replace the woofers with OEM parts from Atomic Hifi.  Replacing the tweeters was more challenging but was able to get some assistance with OEM diaphragms from a gentleman I met on Audiokarma.  Some say you shouldn't touch a Snell crossover as they were factory matched, but the electrolytics in the crossovers had drifted very, very far off of spec in thirty years.  Also I found I had two different tweeter models and the HF response was way out of balance in the two speakers, so I threw the crossover matching out the window LOL.  This pair was made in 1992 I believe, the last year of manufacture of the J/II, this was the last iteration of the Snell J to be overseen by Snell himself before his death in 1984.  I measured all of the components and matched them to the best of my ability.

Here is one of the crossovers.  I used film caps, Mills MRA wirewounds.  The speakers sound great!


----------



## CJG888

Looks impressive! I’ve had some good results with ICW caps in the past (ICW in Wrexham are the company behind Clarity Caps). I don’t recognise the silver ones, though…


----------



## L0rdGwyn

CJG888 said:


> Looks impressive! I’ve had some good results with ICW caps in the past (ICW in Wrexham are the company behind Clarity Caps). I don’t recognise the silver ones, though…



Those are also ClarityCaps, just a different series, ESA whereas the purple caps are CSA.  IME with polypropylene film cap brands, ClarityCaps are best.  That includes Audience Auricaps, Solens, Audyn, Mundorf, Sonicaps, Obbligato...probably forgetting one or two, but ClarityCaps are my go to when capacitance and size limitations necessitate a polypropylene cap versus a PIO, copper foil, aluminum foil, etc.  Some DIYers I talk to hold the NOS Soviet teflon caps in very high regard, so I will be trying them in the near future, nearly bought some recently for a project but I can't remember where I had planned to use them


----------



## leftside

I see we're on page 242.


----------



## jgwtriode

L0rdGwyn said:


> And their drivers, although they are 6ohms nominal whereas the original Vifa drivers are 8ohms.  You can also buy replacement foam surrounds from Audio Note too when the originals wear out.  I had exchanged a few emails with Peter Qvortrup when I was deciding on what direction to go, but decided to replace the woofers with OEM parts from Atomic Hifi.  Replacing the tweeters was more challenging but was able to get some assistance with OEM diaphragms from a gentleman I met on Audiokarma.  Some say you shouldn't touch a Snell crossover as they were factory matched, but the electrolytics in the crossovers had drifted very, very far off of spec in thirty years.  Also I found I had two different tweeter models and the HF response was way out of balance in the two speakers, so I threw the crossover matching out the window LOL.  This pair was made in 1992 I believe, the last year of manufacture of the J/II, this was the last iteration of the Snell J to be overseen by Snell himself before his death in 1984.  I measured all of the components and matched them to the best of my ability.
> 
> Here is one of the crossovers.  I used film caps, Mills MRA wirewounds.  The speakers sound great!


Impressive indeed.  Having sold Snell speakers years ago I know that had take make a huge improvement over what is stock on that crossovers.  Never was really that impressed by the J's.  Their bigger Snells were okay.  I preferred the Theils in terms of what we had or possibly Revel.  But I always had speakers from Tierry Budge who worked for Wilson Audio.  He designed the The Watt3 Puppy 2 or I say should reworked that particular model.  He also designed all the Talon Audio and Escalante stuff.  Back when I was selling at an Audio store he was just building stuff out of his garage.  I owned about 4 variants of his speakers.  The last one was similar to the Escalante's but not as refined.   After that I went to work for Talon Audio and had a prototype Khorus and then one of theirs in a dark red mahogany.  

I used to mod Near's crossovers for customers who wanted an improvement when I worked in the store.  Upgraded caps and resistors.  I did that because even when they
blew drivers we could just swap drivers from manufacter so effectively modding them didn't void customers warranty.  Did about 15 pairs of their speakers.  Just using Solens upscale caps.  Name escapes me at the moment.


That is a pretty damn serious crossover.

jgwtriode


----------



## L0rdGwyn (Dec 9, 2021)

jgwtriode said:


> Impressive indeed.  Having sold Snell speakers years ago I know that had take make a huge improvement over what is stock on that crossovers.  Never was really that impressed by the J's.  Their bigger Snells were okay.  I preferred the Theils in terms of what we had or possibly Revel.  But I always had speakers from Tierry Budge who worked for Wilson Audio.  He designed the The Watt3 Puppy 2 or I say should reworked that particular model.  He also designed all the Talon Audio and Escalante stuff.  Back when I was selling at an Audio store he was just building stuff out of his garage.  I owned about 4 variants of his speakers.  The last one was similar to the Escalante's but not as refined.   After that I went to work for Talon Audio and had a prototype Khorus and then one of theirs in a dark red mahogany.
> 
> I used to mod Near's crossovers for customers who wanted an improvement when I worked in the store.  Upgraded caps and resistors.  I did that because even when they
> blew drivers we could just swap drivers from manufacter so effectively modding them didn't void customers warranty.  Did about 15 pairs of their speakers.  Just using Solens upscale caps.  Name escapes me at the moment.
> ...



The Snell Js are great for my space and system, but tastes will differ.  The system has changed since I made the recording below, most significantly the amplifier is not the 6A5G SET in the video but now my 801A SET, which is more refined.  Made with a field recorder so not the greatest quality, I need to do an updated version with better equipment.



Also did this festive recording


----------



## bcowen

jgwtriode said:


> Impressive indeed.  Having sold Snell speakers years ago I know that had take make a huge improvement over what is stock on that crossovers.  Never was really that impressed by the J's.  Their bigger Snells were okay.  I preferred the Theils in terms of what we had or possibly Revel.  But I always had speakers from Tierry Budge who worked for Wilson Audio.  He designed the The Watt3 Puppy 2 or I say should reworked that particular model.  He also designed all the Talon Audio and Escalante stuff.  Back when I was selling at an Audio store he was just building stuff out of his garage.  I owned about 4 variants of his speakers.  The last one was similar to the Escalante's but not as refined.   After that I went to work for Talon Audio and had a prototype Khorus and then one of theirs in a dark red mahogany.
> 
> I used to mod Near's crossovers for customers who wanted an improvement when I worked in the store.  Upgraded caps and resistors.  I did that because even when they
> blew drivers we could just swap drivers from manufacter so effectively modding them didn't void customers warranty.  Did about 15 pairs of their speakers.  Just using Solens upscale caps.  Name escapes me at the moment.
> ...


My gateway drug speakers to this addiction were the E III's.  Had those for about 4 years then got C IV's, and then C V's.  Enjoyed them all.  Only mod I did to both of the C's was to replace that crappy wirewound tweeter pot with a good film resistor which made a pretty substantial improvement.


----------



## L0rdGwyn

Do you still sell hifi, @jgwtriode ?


----------



## jgwtriode (Dec 9, 2021)

bcowen said:


> My gateway drug speakers to this addiction were the E III's.  Had those for about 4 years then got C IV's, and then C V's.  Enjoyed them all.  Only mod I did to both of the C's was to replace that crappy wirewound tweeter pot with a good film resistor which made a pretty substantial improvement.


We had A's setup at the store in one of the main listening rooms.  They were actually quite good!  Just not quite as impressive as the upscale Theils but those did sound quite good.  We Sold a lot of Snells for upscale Theatre systems, especially their woofers, particularly the 18 inch ones.  My last pair of really good speakers was the Talon Audio Khourus it's final derivation before they sold the company to Rives Audio and just before Mike did the balanced crossover.  More hype than anything significant.  I prefered Tierry Budge's crossover in them.  Rives changed the whole thing over.  Heard the Thunderbirds with all the Accuton, a lot of boom and sizzle, but not nearly as musical.  The Esclante Freemont using the Scanspeak Revelator tweeter was damn impressive.  Thing could go up to 50k and could do a slamming 18 HZ with the double 12 woofers, one internally loaded,  worked as active compensation for the front 12.  Basically a 2 and a half way loudspeaker.  One crossover point between the 12 which used the dustcap for midrange and then the revelator was just blended in.  Not to many speakers I have heard outperform that.  Got suprising results out of some John Sweensen inspired Bazookas
later using Fostex 206 with planet 10 wood center cones, cut open the dust caps.  Just a cap and a baffle step circuit ala John Swenson.  Concrete form tubes, 8 inch inside a 12 inch to create a 7 foot long folded transmission line in a four foot tube.  Pretty weird,  John ran it with Lowther DX 4's and got amazing results.  His favorite loading of those drivers.  Ran them with Bottlehead Paraglows, with Vaic Cobalt Meshplate 2A3's and Magnequest cobalt trannies.  Pretty remarkable sound!

Happy Listening,

jgwtriode


----------



## jgwtriode

L0rdGwyn said:


> Do you still sell hifi, @jgwtriode ?


No was years ago.  I worked at a store in Salt Lake City for a couple of years and then was in charge of technical support at Kimber Kable.  Then worked at Talon for about a year in their direct sales and dealer support.   Then bailed on the whole thing.
Some real crap went on at Talon before they unloaded it to Rives Audio.  Some real cuthroat Crap, egos and politics of high end companies.  Tierry moved on to start Escalante, which was another story of much the same thing.  Very sad.

jgwtriode


----------



## L0rdGwyn (Dec 10, 2021)

jgwtriode said:


> No was years ago.  I worked at a store in Salt Lake City for a couple of years and then was in charge of technical support at Kimber Kable.  Then worked at Talon for about a year in their direct sales and dealer support.   Then bailed on the whole thing.
> Some real crap went on at Talon before they unloaded it to Rives Audio.  Some real cuthroat Crap, egos and politics of high end companies.  Tierry moved on to start Escalante, which was another story of much the same thing.  Very sad.
> 
> jgwtriode



Gosh, well I'm sorry it ended poorly, but it must've been exciting to work in the industry you are so passionate about, if nothing else must have been great to try all of those amazing speakers!


----------



## jgwtriode (Dec 10, 2021)

L0rdGwyn said:


> Gosh, well I'm sorry it ended poorly, but it must've been exciting to work in the industry you are so passionate about, if nothing else must have been great to try all of those amazing speakers!


It was while it lasted, it was never like I was actually working, it was like playing all day long and I loved sharing tips, stories, music and just getting to know different people in the industry.  Most of the Guys doing serious audio in Utah I know to some degree or another.  Some have gone on to significant things.  I know John Giolas of Wilson Audio reasonably well, Dick Diamond of YG acoustic I worked with for years.  I took over  Sean Casey of Zu Audio's secondary job at Kimber Kable.  Know Dave Evett of Evett & Shaw, out of business.  Clayton owns and runs Spatial Audio now.  Used to have discussion with Eric Alexander who designs and owns Tekton Loudspeakers.  Of course I know Ray Kimber fairly well.  Somehow it just never quite worked out.  I have gone through a hell of a lot of equipment over some 40 years of playing.  Due to divorces, moving and financial setback, and of course career changes.  I have had to scale back.  But it's all been a blast.  Over the last 5 years space and moving forced into headphones and so I have learned to enjoy that.  It's more practical.  I have been learning, buying tweaking modifying and fiddling for all those 5 years. 

First serious headphone was Paradox Slant.  Then had some issues with my pair and a bit of a falling out with the owner.  Got into Sennie HD 650's and SBAF forum.  Did every conceivable mod and created some of my own.  Someone on that site due to my of Shun Mook pucks on the sides named them the Frankenheisers based on where i placed those pucks for tuning.  My son now owns them w/o pucks.  I got those to outperform the slants.  They were significantly better than Stock sennies.  Then Blackwood Auteurs, which I still have, they are modded with Second Skin isodamp pro on the front baffles and felt rings over the top.  They sound in between stock Auteur and Verite Closed.  They are more neutral than Auteurs also a bit more detailed, open and perhaps a hint faster.  I found some discs I use on input connectors from Mad Scientist, still use those on Leopardwood VC's. It looks weird and I also use a pair of Shun Mooks on the cups.  It's not huge difference but ever so noticeably more alive sounding, with those mods.

Played with a lot of electronics over the years.  Even did a Linn/Naim Isobarik system for a few years.  Played with modded Acoustats and Vandersteins.  Tierry Budges speakers always performed better than any of those and finally just started having him build them for me.   For a few years I ran Audio Research stuff.     But all in all the best amps I ever had were My Bottlehead Paraglows with Meshplates 2A3's and Cobalt transformers.

Wanted to get back to a triode for a long time.   So as I stated I am beyond grateful to be getting the Airmid from you and look forward to tweaking it with better tubes cables and various isolation schemes I have in mind.

Best cables I have ever heard are Wywires.  Running Platinum, except for my Diamond USB cable. 

My speakers now are Swan M 200 M IIIS.  I have tweaked them with isodamp pro on the frames, brass non magnetic screws and wool baffle material to minimize edge diffraction.  They look odd but sound noticeably better than they did originally.  They sit on my cinder block speaker stands on either side of my computer monitor. 

Anyhow I look forward to an entirely new chapter with the Airmid in my system.

jgwtriode


----------



## bcowen (Dec 10, 2021)

jgwtriode said:


> It was while it lasted, it was never like I was actually working, it was like playing all day long and I loved sharing tips, stories, music and just getting to know different people in the industry.  Most of the Guys doing serious audio in Utah I know to some degree or another.  Some have gone on to significant things.  I know John Giolas of Wilson Audio reasonably well, Dick Diamond of YG acoustic I worked with for years.  I took over  Sean Casey of Zu Audio's secondary job at Kimber Kable.  Know Dave Evett of Evett & Shaw, out of business.  Clayton owns and runs Spatial Audio now.  Used to have discussion with Eric Alexander who designs and owns Tekton Loudspeakers.  Of course I know Ray Kimber fairly well.  Somehow it just never quite worked out.  I have gone through a hell of a lot of equipment over some 40 years of playing.  Due to divorces, moving and financial setback, and of course career changes.  I have had to scale back.  But it's all been a blast.  Over the last 5 years space and moving forced into headphones and so I have learned to enjoy that.  It's more practical.  I have been learning, buying tweaking modifying and fiddling for all those 5 years.
> 
> First serious headphone was Paradox Slant.  Then had some issues with my pair and a bit of a falling out with the owner.  Got into Sennie HD 650's and SBAF forum.  Did every conceivable mod and created some of my own.  Someone on that site due to my of Shun Mook pucks on the sides named them the Frankenheisers based on where i placed those pucks for tuning.  My son now owns them w/o pucks.  I got those to outperform the slants.  They were significantly better than Stock sennies.  Then Blackwood Auteurs, which I still have, they are modded with Second Skin isodamp pro on the front baffles and felt rings over the top.  They sound in between stock Auteur and Verite Closed.  They are more neutral than Auteurs also a bit more detailed, open and perhaps a hint faster.  I found some discs I use on input connectors from Mad Scientist, still use those on Leopardwood VC's. It looks weird and I also use a pair of Shun Mooks on the cups.  It's not huge difference but ever so noticeably more alive sounding, with those mods.
> 
> ...


Eric Alexander is quite the guy.  When I first got my Tekton Lores, there was a lot to like about them but there was a bite in the lower treble that I just couldn't get past (and that was with an SET tube amp driving them to boot). I blasted the crap out of them for 50+ hours hoping that would help if not cure it, but it didn't. Emailed Eric about returning them, and after I explained what was bothering me he said "I can fix that."  A few more emails with me explaining I could swap the crossovers myself (and avoid shipping the speakers back and forth), and a new set of crossovers landed on my doorstep.  He *did* fix that problem, but also killed all the life and energy which was what I liked most about them to begin with. Another email exchange, and a second pair of crossovers arrived at my front door.  Bingo.  Life back, bite gone.  Didn't charge me a penny for any of it, only asked that I return the old crossovers.  How many manufacturers would go to those lengths, and especially go to those lengths on a $1k pair of speakers?  Yup, I was impressed...and happy.  Still get goosebumps cranking 'em to 11...and rock concert SPL's with a whole 22 watts/ch of tube power.


----------



## L0rdGwyn

Happy to report the 45 amp made it to Zach and he is very happy with it.


----------



## bcowen

L0rdGwyn said:


> Happy to report the 45 amp made it to Zach and he is very happy with it.


Awesome!


----------



## jgwtriode (Dec 11, 2021)

bcowen said:


> Eric Alexander is quite the guy.  When I first got my Tekton Lores, there was a lot to like about them but there was a bite in the lower treble that I just couldn't get past (and that was with an SET tube amp driving them to boot). I blasted the crap out of them for 50+ hours hoping that would help if not cure it, but it didn't. Emailed Eric about returning them, and after I explained what was bothering me he said "I can fix that."  A few more emails with me explaining I could swap the crossovers myself (and avoid shipping the speakers back and forth), and a new set of crossovers landed on my doorstep.  He *did* fix that problem, but also killed all the life and energy which was what I liked most about them to begin with. Another email exchange, and a second pair of crossovers arrived at my front door.  Bingo.  Life back, bite gone.  Didn't charge me a penny for any of it, only asked that I return the old crossovers.  How many manufacturers would go to those lengths, and especially go to those lengths on a $1k pair of speakers?  Yup, I was impressed...and happy.  Still get goosebumps cranking 'em to 11...and rock concert SPL's with a whole 22 watts/ch of tube power.


Agreed Eric is and was one of the most genuine guys back when he used to hang out at Ray Kimber's place.  Ray had him consulting on stuff and playing with loudspeakers long before Tekton.  He had some online business he was running with low cost alternative speakers.  Ray had another guy hanging out with us who was an RF engineer from Hill Air Force base.  Can't remember his name but the three of us used to sit around and brainstorm.  He had a lot to do with some of the refinement in the Kimber Select line.

But Eric was into some pretty Clever stuff and he implemented some of Curtis cabinet tuning ideas into his stuff.   One of these days I may have to run down to Provo and let him know I am back in Utah.  Nice to see him succeeding and building very good reasonably priced loudspeakers.  The Moab's are one of the speakers I would seriously consider if I got back into it again.

So have you had a chance to hear Zach's new 45?

Happy listening,
jgwtriode


----------



## Tjj226 Angel

bcowen said:


> Eric Alexander is quite the guy.  When I first got my Tekton Lores, there was a lot to like about them but there was a bite in the lower treble that I just couldn't get past (and that was with an SET tube amp driving them to boot). I blasted the crap out of them for 50+ hours hoping that would help if not cure it, but it didn't. Emailed Eric about returning them, and after I explained what was bothering me he said "I can fix that."  A few more emails with me explaining I could swap the crossovers myself (and avoid shipping the speakers back and forth), and a new set of crossovers landed on my doorstep.  He *did* fix that problem, but also killed all the life and energy which was what I liked most about them to begin with. Another email exchange, and a second pair of crossovers arrived at my front door.  Bingo.  Life back, bite gone.  Didn't charge me a penny for any of it, only asked that I return the old crossovers.  How many manufacturers would go to those lengths, and especially go to those lengths on a $1k pair of speakers?  Yup, I was impressed...and happy.  Still get goosebumps cranking 'em to 11...and rock concert SPL's with a whole 22 watts/ch of tube power.



I love it when people in the audio world still do stuff like that.


----------



## L0rdGwyn

Finished chassis prep work for the two OTLs I am working on.

Here is the one in Anthracite Grey.




Here is the one in Chromy Bronze.



Also did the machining of the power supply regulator heat sinks.  PCBs are already done, so now just need to mount parts and wire them up.  Got hit with a migraine today though, so will get back to it tomorrow.


----------



## CJG888

L0rdGwyn said:


> Finished chassis prep work for the two OTLs I am working on.
> 
> Here is the one in Anthracite Grey.
> 
> ...


The second one looks like it should have a Leak logo…😀


----------



## Galapac

L0rdGwyn said:


> Finished chassis prep work for the two OTLs I am working on.
> 
> Here is the one in Anthracite Grey.
> 
> ...


Will one of them have independent volume per channel? I see 2 holes possibly…


----------



## L0rdGwyn

Galapac said:


> Will one of them have independent volume per channel? I see 2 holes possibly…



Yup, the gray one will have two Goldpoint V47 mono stepped attenuators for individual channel adjustment, requested by the buyer.


----------



## jgwtriode

L0rdGwyn said:


> Finished chassis prep work for the two OTLs I am working on.
> 
> Here is the one in Anthracite Grey.
> 
> ...





L0rdGwyn said:


> Finished chassis prep work for the two OTLs I am working on.
> 
> Here is the one in Anthracite Grey.
> 
> ...


They look great...partial to red of course...but that Bronze is particularly nice looking!

jgwtriode


----------



## bcowen

L0rdGwyn said:


> Finished chassis prep work for the two OTLs I am working on.
> 
> Here is the one in Anthracite Grey.
> 
> ...


Sweet!

Sorry to hear about the migraine, but I have certainly felt your pain.  Suffered with them since I was a kid, and a couple different doctors told me (after doing a battery of tests) that they would become less frequent and eventually stop altogether as I got older.  Seems they were right as I haven't had one in 5+ years.  They never said exactly how old, just old*er*....which I suppose I am.


----------



## L0rdGwyn

bcowen said:


> Sweet!
> 
> Sorry to hear about the migraine, but I have certainly felt your pain.  Suffered with them since I was a kid, and a couple different doctors told me (after doing a battery of tests) that they would become less frequent and eventually stop altogether as I got older.  Seems they were right as I haven't had one in 5+ years.  They never said exactly how old, just old*er*....which I suppose I am.



I get them maybe once or twice a year, it's gotten less frequent as time has gone on.  It's annoying, but since they occur so infrequently, I haven't seen a specialist about it. It's really only a major problem if it happens while I'm at work as I get an "aura" at the onset lasting around an hour and lose nearly half of my vision.  This is not ideal in an emergency situation LOL.


----------



## triod750

bcowen said:


> They never said exactly how old, just old*er*....which I suppose I am.


Everyone is older, all the time, until a radical change happens. Doctors!


----------



## L0rdGwyn (Dec 12, 2021)

Today is the two year anniversary of starting this thread.  Time has flown by, it's been quite the journey, thanks for everyone who has followed along.  I thought it might be fun to go through the pictures I've taken over the last two years and post the ones I liked most.  Here's what I found.


----------



## bcowen

L0rdGwyn said:


> Today is the two year anniversary of starting this thread.  Time has flown by, it's been quite the journey, thanks for everyone who has followed along.  I thought it might be fun to go through the pictures I've taken over the last two years and post the ones I liked most.  Here's what I found.


That's the best audio porn centerfold I've seen in a good while.  

I haven't been following for all of the 2 years I don't think, but I've sure enjoyed the time I have spent here...and learned a lot too.  Many, many thanks for sharing all that you do.


----------



## chrisdrop

L0rdGwyn said:


> Today is the two year anniversary of starting this thread.  Time has flown by, it's been quite the journey, thanks for everyone who has followed along.  I thought it might be fun to go through the pictures I've taken over the last two years and post the ones I liked most.  Here's what I found.


Really beautiful. You are glass, wire and metalworks artist.


----------



## L0rdGwyn

chrisdrop said:


> Really beautiful. You are glass, wire and metalworks artist.



Thank you!  Obviously two of the pictured amplifiers are Glenn's, I like the photos


----------



## Galapac

You build great amps and also have an eye for great composition in your photos. That seems to go hand in hand in our hobby with a lot of folks.


----------



## whirlwind (Dec 14, 2021)

L0rdGwyn said:


> Today is the two year anniversary of starting this thread.  Time has flown by, it's been quite the journey, thanks for everyone who has followed along.  I thought it might be fun to go through the pictures I've taken over the last two years and post the ones I liked most.  Here's what I found.



Great pics. It has been fun following all of your builds and learned a lot too.

It sure does not seem like two years, but man, how time flies.

Hope your migraines settle down. I got my booster last week and I did not have any ill effects other than sore arm.
The first two shots put me down for a day each. I feel better getting the booster, since I have been seeing quite a bit of live music
and the protocol's seem to be all over the place for each venue.

If you would not have had to stop building for the public, which I do fully understand, I probably would have been a future buyer of something.

I really like the looks of your builds....old skool at its finest.

I hope your work is going well....seems to be that time of year again where the covid is the most severe.
Stay safe and thanks for all you do.


----------



## L0rdGwyn

whirlwind said:


> Great pics. It has been fun following all of your builds and learned a lot too.
> 
> It sure does not seem like two years, but man, how time flies.
> 
> ...



Thanks, Joe, time has flown by, work isn't going well but so it goes, the surge in Ohio is very bad.  That booster really knocked me out, and it's expected the CDC will recommend additional boosters, not looking forward to that, but even if someone who is vaccinated gets a breakthrough case, the data shows the vaccine protects against severe illness and hospital admission.  That is the real key, as our healthcare system is completely overburdened and cannot sustain this, something's gotta give!  Pfizer has a new antiviral medication they think will reduce hospitalization rates, if people are willing to take it, that may help.  But who knows, the future of inpatient healthcare is very uncertain right now, critical care healthcare workers are completely burnt out and leaving in droves, I'll just keep taking the beating and build some tube gear to keep occupied when I'm home!


----------



## L0rdGwyn

But anyway, got some time off coming up which will be nice.  Won't get a lot done on the two Airmid OTLs until after the holidays, but will surely post progress when I get back to it.  Also have some really rare globe MH4 triodes on the way to me from Billington that I'm pretty excited about  also still considering throwing together that spud amplifier, started drafting a chassis for it.


----------



## leftside

L0rdGwyn said:


> Thanks, Joe, time has flown by, work isn't going well but so it goes, the surge in Ohio is very bad.  That booster really knocked me out, and it's expected the CDC will recommend additional boosters, not looking forward to that, but even if someone who is vaccinated gets a breakthrough case, the data shows the vaccine protects against severe illness and hospital admission.  That is the real key, as our healthcare system is completely overburdened and cannot sustain this, something's gotta give!  Pfizer has a new antiviral medication they think will reduce hospitalization rates, if people are willing to take it, that may help.  But who knows, the future of inpatient healthcare is very uncertain right now, critical care healthcare workers are completely burnt out and leaving in droves, I'll just keep taking the beating and build some tube gear to keep occupied when I'm home!


Yep double vaccinated here, but still got a mild dose of Covid. Very thankful I had both vaccines and I'll be lining up for my booster in January. The medical workers are working wonders here. I lined up for only 20 mins for a walk in test. Tiny little tube stuck up my nostril and then I had the results late evening. First felt sick 8 days ago but almost back to my usual self now.



L0rdGwyn said:


> But anyway, got some time off coming up which will be nice.  Won't get a lot done on the two Airmid OTLs until after the holidays, but will surely post progress when I get back to it.  Also have some really rare globe MH4 triodes on the way to me from Billington that I'm pretty excited about  also still considering throwing together that spud amplifier, started drafting a chassis for it.


Aha - you are ordering British tubes from Martin, and I've just put in an order for some US tubes


----------



## L0rdGwyn

leftside said:


> Yep double vaccinated here, but still got a mild dose of Covid. Very thankful I had both vaccines and I'll be lining up for my booster in January. The medical workers are working wonders here. I lined up for only 20 mins for a walk in test. Tiny little tube stuck up my nostril and then I had the results late evening. First felt sick 8 days ago but almost back to my usual self now.



Glad it was a mild case, that's pretty typical for someone who is vaccinated.  Unfortunately there are vaccinated but immunosuppressed patients with breakthrough cases who don't fare well.  Other than that, the vast majority of severe cases are unvaccinated.



leftside said:


> Aha - you are ordering British tubes from Martin, and I've just put in an order for some US tubes



There was a little note in their Christmas newsletter about having a quad of "balloon shape" MH4.  These things are super rare, not cheap, but a song compared to what you might see them going for on eBay, so I bought them  what US tubes did you buy?  I haven't bought any tubes from Martin in a long while, mostly I am hoarding HY69 from anywhere I can find them for some crazy future amplifier.


----------



## leftside

L0rdGwyn said:


> Glad it was a mild case, that's pretty typical for someone who is vaccinated.  Unfortunately there are vaccinated but immunosuppressed patients with breakthrough cases who don't fare well.  Other than that, the vast majority of severe cases are unvaccinated.
> 
> 
> 
> There was a little note in their Christmas newsletter about having a quad of "balloon shape" MH4.  These things are super rare, not cheap, but a song compared to what you might see them going for on eBay, so I bought them  what US tubes did you buy?  I haven't bought any tubes from Martin in a long while, mostly I am hoarding HY69 from anywhere I can find them for some crazy future amplifier.


Yes I saw that too and actually thought of your amps! Glad you got them. I ordered some Sylvania and RCA. I'll reveal which ones next year over on the The Reference Pentode and Beam Tetrode Thread.


----------



## Zachik

L0rdGwyn said:


> There was a little note in their Christmas newsletter


I wonder why I do not receive their newsletter... 
Bought tubes from them couple times in the past.


----------



## triod750

Zachik said:


> I wonder why I do not receive their newsletter...
> Bought tubes from them couple times in the past.


Maybe it's because you have to be nice in order to get them  ?


----------



## Zachik

triod750 said:


> Maybe it's because you have to be nice in order to get them  ?


I sign up (again?) today. Maybe I never did before? 
We'll see if I start getting them...


----------



## leftside

And extra nice to get one of these. The only problem with this calendar is that  occasionally the pictures make me homesick.


----------



## L0rdGwyn

leftside said:


> And extra nice to get one of these. The only problem with this calendar is that  occasionally the pictures make me homesick.



I'm a big fan, goes up on the side of my refrigerator every year.


----------



## triod750

leftside said:


> And extra nice to get one of these. The only problem with this calendar is that  occasionally the pictures make me homesick.


En rödhake...


----------



## Zachik

L0rdGwyn said:


> I'm a big fan, goes up on the side of my refrigerator every year.


Hopefully, not with a nail...


----------



## bcowen

Zachik said:


> Hopefully, not with a nail...


Epoxy.  Duh.   😇


----------



## whirlwind

leftside said:


> And extra nice to get one of these. The only problem with this calendar is that  occasionally the pictures make me homesick.


  It is nice to see some people still use these.    

I spent pretty much my whole life as an offset printer, before retiring this past September, during my 45 years I would have no idea how many different calendars that 
I have printed.

I can say that this business is nothing like it was even 25 years ago....people just don't use them as much. The times we live in I guess.

It was a great way to make a living, fun and you came home from work feeling like you made something pretty cool everyday.

Met some people I probably would never have met. In the 80's Jack Nicklaus made his way to the shop for a color OK on one of his calendars.
That was a fun talk and one of my sports heroes.

Anyway I like it when I see companies still passing these out...it keeps printers in work.

Carry on


----------



## L0rdGwyn (Dec 22, 2021)

Well I have no DIY stuff to report, just venting lol off of work finally and have six days off, which is nice, I'll be out of town though, so no tube shenanigans for a while.

I got home from five grueling days at work to find one of my cats decided to make a scratching post out of the foam surrounds of my Snells, putting a hole in one.  The surround of the other speaker is also clawed, but not punctured.

What to do...I could replace the punctured driver, again, which means also replacing an inductor in the crossover.  The VIFA woofers are not cheap and it's a PITA to do.  To ensure it doesn't happen again, I would also need to get custom metal grills for the speakers...aesthetically, I don't love that idea.

Rather than dealing with all of that hassle, I am seriously considering a speaker change.  I love those Snells, they sound great, so it hurts to get rid of them, especially after investing so much into them, but they are delicate and the parts are no longer in production.  Having such cumbersome speakers in the territory of a very destructive force (house cats) is probably going to cause me more headaches down the road.

I've been weighing my options.  A speaker I'm interested in but is way outside of my budget is the Fleetwood Deville.  Maybe something to aspire toward, but not now.

A more realistic option, and the direction I am likely to go, is the Klipsch Forte IV.  I was pretty interested in the Forte III a few years ago, glad I didn't get them at the time as Klipsch upgraded the speaker in a very short period of time, much to the chagrin of Forte III owners.  The midrange horn driver was changed, the crossover reworked, and the tweeter phase plugged altered.

So why the Forte IV?  They are really the perfect fit for my very specific use case:

Moving from the 92dB/W Snells to a 99dB/W horn is a better fit for my low-wattage SET amplifiers
Stock grills are metal mesh, meaning there is a limited amount of destruction a cat can do to them
The metal grills are also magnetized, so if a cat pulls too hard on them, they will fall off and scare them away (cats hate this type of thing), which will deter further attempts
Klipsch recommends 2"-10" placement from the back wall to augment the low end bass production of the rear 15" passive radiator, which is a good fit for my room - the close rear wall placement will also protect the passive radiators from, you guessed it, cats
Better bass extension (38Hz) relative to the Snell J/II (50Hz)
A contemporary, mainstream speaker without the headache of sourcing vintage / OEM components
There is a Klipsch Heritage dealer in Cleveland, I've reached out to them for a quote.  I would get them in American Walnut.

 

So anyway, that's what I'm thinking.  Selling the Snells will be a hassle, I may have to replace the driver anyway to sell them and they will be packaged with the Sound Anchors stands.  Honestly would consider selling them relatively cheap if I felt they were getting a good home and the buyer was willing to do local pickup.

In other news, @zach915m got himself some globe 45s  shared a pic, amp is looking good, very happy the project was a success.

Will update amp things when I get back to work on the OTLs after the holidays.


----------



## L0rdGwyn

Here is the guilty party, at his leisure.  Love him to death, but he is on the naughty list this year.


----------



## triod750

L0rdGwyn said:


> Here is the guilty party, at his leisure.  Love him to death, but he is on the naughty list this year.


Looks like a DIY type of cat. If nobody else takes care of the Snell there is only one thing to do.
My cat crashed a perfectly set up turntable rig, trying to escape from our two deerhounds. I feel your pain.
If those loudspeakers also sound good they might be a good alternative...


----------



## jgwtriode (Dec 20, 2021)

He looks quite defiant as many cats do.  After all those were for his entertainment not yours.  I used to  have a cat that would steal center position on the couch when I wanted to listen to my system, back when I had loudspeakers.  He would get quite irritated with me, but skulk on back and sit next to me to listen.  He also liked watching television quite frequently.  And of course the one evil black cat many years ago that made fuzzies on my double knit Acoustat grille  socks.  And he would proudly sit on top of them once he had
 climbed them.  Of course I would turn them on and at the first bass note he would scurry away!

Pets, I do miss having them,

jgwtriode


----------



## L0rdGwyn

I love my cats more than my hifi obviously, so we're gonna find a way for them to coexist!  He is a very good cat otherwise.


----------



## jgwtriode

I truly miss not having cats.  My landlord feeds a couple of strays that either ignore me or run when I try to approach them.  Some vicarious fun with her Yorkie, who demands cuddling every time I come up the, stairs.

jgwtriode


----------



## whirlwind

L0rdGwyn said:


> I love my cats more than my hifi obviously, so we're gonna find a way for them to coexist!  He is a very good cat otherwise.



Speaker grills, but I understand it is not the best eye-candy.

A mans gotta do what a mans gotta do


----------



## L0rdGwyn

whirlwind said:


> Speaker grills, but I understand it is not the best eye-candy.
> 
> A mans gotta do what a mans gotta do



The full story is my girlfriend whacked one of the drivers with a broom while cleaning, which led me to replace the first one.  I then put the speaker grills on to protect them, which made the speakers more appealing to be scratched by my cat.  He started scratching the grills, so I took them off again and hopes that he would stop since they were being shredded.  Only took one day of them being off to claw up the surrounds.  So that means replacing a driver and getting custom metal grills, but at this point I'm ready to move on lol.


----------



## triod750

You haven't thought of replacing the girlfriend who started it...?


----------



## Monsterzero

L0rdGwyn said:


> Stock grills are metal mesh, meaning there is a limited amount of destruction a cat can do to them


----------



## bpiotrow13

Monsterzero said:


>


This cat will eat metal mesh grills for breakfast


----------



## Xcalibur255

L0rdGwyn said:


> Here is the guilty party, at his leisure.  Love him to death, but he is on the naughty list this year.


Oh he knows what he did.  And he doesn't care either.  

Also, what KIND of globe 45s did Zach get?


----------



## Xcalibur255




----------



## L0rdGwyn

Xcalibur255 said:


> Oh he knows what he did.  And he doesn't care either.
> 
> Also, what KIND of globe 45s did Zach get?



Lol oh yeah, totally.  They are Philco branded, look to be the same build as mine from the photo, but might have to ask him for a better pic.


----------



## Xcalibur255

He'll love them then.  None of my ST 45 tubes even come close.


----------



## Galapac

Xcalibur255 said:


>


That’s a _Smooth_ Criminal 🤣


----------



## gibosi

I've been enjoying lurking here for some time, but unfortunately, I don't see any tube rectifiers, so...   lol


----------



## L0rdGwyn

gibosi said:


> I've been enjoying lurking here for some time, but unfortunately, I don't see any tube rectifiers, so...   lol



Sorry Ken, one of my amplifiers is tube rectified, but it's been a while lol admittedly I gravitate toward designing with SS rectifiers, maybe I'll use a tube again soon.


----------



## L0rdGwyn

Visiting some family friends.  Spotted this guy hiding in the basement closet.  Maybe it's my Christmas gift.


----------



## Galapac

I see a lot of mention of the 45 tube on this thread, although I have no experience with this tube, has anyone tried this new version from Sophia Elec.?
https://sophiaelectric.com/collections/frontpage/products/pages-se-45


----------



## CJG888

At last! We


L0rdGwyn said:


> Visiting some family friends.  Spotted this guy hiding in the basement closet.  Maybe it's my Christmas gift.



At last! Welcome to the dark side….


----------



## CJG888 (Dec 21, 2021)

Of course, now you need a 3009. or go all the way down the rabbit hole (Decca London International plus the Decca cartridge of your choice…).

I recommend a visit to www.lencoheaven.net


----------



## CJG888

Presumably that’s an old Weathers arm on there.


----------



## bpiotrow13 (Dec 21, 2021)

Galapac said:


> I see a lot of mention of the 45 tube on this thread, although I have no experience with this tube, has anyone tried this new version from Sophia Elec.?
> https://sophiaelectric.com/collections/frontpage/products/pages-se-45


I considered this tube and was just about to order the above, but decided to sell my 45 amp. This new design is a bit worse than princess shape tube, at least I was told that by the distributor. In any case If You want them better hurry, as I understand 45 types are no longer produced by Sophia/Fillmusic due to constructor"s death.


----------



## triod750

L0rdGwyn said:


> Visiting some family friends.  Spotted this guy hiding in the basement closet.  Maybe it's my Christmas gift.


Do I spot a Discwasher brush there?


----------



## CJG888

With a properly-sorted Garrard front end and a pair of classic Klipsch speakers (frankly, I wonder if you might prefer the Cornwall to the Forte), you will be able to take that system to the next level 😀.

Merry Christmas


----------



## CJG888

You may want to build a plinth for two arms (I wish I had, in retrospect). The Weathers can be used for a dedicated mono cartridge (if you’re into that kind of thing). Anything from a GE RPX or (preferably) VR to an A-T MONO 3/LP (what I use) or a Miyajima….


----------



## L0rdGwyn

CJG888 said:


> At last! Welcome to the dark side….



As much as I would welcome it, sadly it isn't for me @CJG888 , only joking.  It is my friends father's, an Englishman like yourself. It is used seldomly, not sure he realizes how these have appreciated in value.  I wouldn't be surprised if it was gifted to me some day however.


----------



## whirlwind

Monsterzero said:


>



Ha!


----------



## bcowen

gibosi said:


> I've been enjoying lurking here for some time, but unfortunately, I don't see any tube rectifiers, so...   lol


Here you go @gibosi .  The thread has been made whole.


----------



## CJG888

GZ37s?


----------



## bcowen

CJG888 said:


> GZ37s?


Yup.  Good eye!  Being Mullards they're marked as CV378's, but same thing.


----------



## gibosi

L0rdGwyn said:


> Sorry Ken, one of my amplifiers is tube rectified, but it's been a while lol admittedly I gravitate toward designing with SS rectifiers, maybe I'll use a tube again soon.



If and when you do, I would encourage you to use circuitry similar to what Glenn uses. That is, I can roll a 3-volt rectifier (3dg4), as well as 4- and 5- volt rectifiers.


----------



## L0rdGwyn

CJG888 said:


> With a properly-sorted Garrard front end and a pair of classic Klipsch speakers (frankly, I wonder if you might prefer the Cornwall to the Forte), you will be able to take that system to the next level 😀.
> 
> Merry Christmas



I might prefer the Cornwall, my partner would not haha.  Interestingly, most say the Forte has the more visceral bass, I may ask to demo both in store just for the heck of it. 
 Are you running a two channel system as well, or straight headphone?



gibosi said:


> If and when you do, I would encourage you to use circuitry similar to what Glenn uses. That is, I can roll a 3-volt rectifier (3dg4), as well as 4- and 5- volt rectifiers.



I'll keep that in mind!  The reason I don't use them regularly, despite how cool they are, is they conflict with my penchant for using regulated B+ supplies, which have a lot of sonic benefits.  You can use them together, but it doesn't make a lot of sense from a design standpoint.


----------



## CJG888

L0rdGwyn said:


> I might prefer the Cornwall, my partner would not haha.  Interestingly, most say the Forte has the more visceral bass, I may ask to demo both in store just for the heck of it.
> Are you running a two channel system as well, or straight headphone?
> 
> 
> ...


In addition to the headphone rig(s), I’m running SME10A / Ortofon Jubilee / Musical Fidelity XLP2 monoblock phono stage / Krell KAV-500i / Martin-Logan Vantage for classical, Garrard 301 / SME3009 / A-T VM740ML or Townshend Rock / Roksan Tabriz / A-T MONO 3/LP / Pro-Ject Tube Box DS with linear PSU / Opera Consonance Reference 5.5 Mk.2 (Telefunken ECC81 / TJ Full Music 12BH7 / Gold Lion 300B) / Aurum Cantus Leshen Mini for jazz…


----------



## leftside

L0rdGwyn said:


> I might prefer the Cornwall, my partner would not haha.  Interestingly, most say the Forte has the more visceral bass, I may ask to demo both in store just for the heck of it.
> Are you running a two channel system as well, or straight headphone?
> 
> 
> ...


@A2029 We already have a CCS/RES switch, a 60mA/30mA power tube switch, and a 6J5/6SN7 switch. Need another switch for tube rectification/ss rectification


----------



## whirlwind

CJG888 said:


> GZ37s?



yeah, look like skinny GZ37's


----------



## L0rdGwyn

CJG888 said:


> In addition to the headphone rig(s), I’m running SME10A / Ortofon Jubilee / Musical Fidelity XLP2 monoblock phono stage / Krell KAV-500i / Martin-Logan Vantage for classical, Garrard 301 / SME3009 / A-T VM740ML or Townshend Rock / Roksan Tabriz / A-T MONO 3/LP / Pro-Ject Tube Box DS with linear PSU / Opera Consonance Reference 5.5 Mk.2 (Telefunken ECC81 / TJ Full Music 12BH7 / Gold Lion 300B) / Aurum Cantus Leshen Mini for jazz…



Nice systems.  Is there a third for listening to your polka collection?  Just kidding  I'll have to pick your brain if I can coerce my friend into giving me the 401.  I'm going to demo the Forte IV on Thursday.


----------



## Xcalibur255

Galapac said:


> I see a lot of mention of the 45 tube on this thread, although I have no experience with this tube, has anyone tried this new version from Sophia Elec.?
> https://sophiaelectric.com/collections/frontpage/products/pages-se-45


The problem with the Sophias is that they are close enough in price to the EML 45 that you might as well just get the EML 45.  It's a shame they aren't a little lower in price because the world needs a non-NOS 45 alternative at this point that isn't exorbitantly priced.  Sophia tubes from this generation, generally speaking, are nice tubes though.  They're rebranded TJ Full Music tubes which are generally better sounding tubes than their Shuguang and Psvane counterparts in China.  A shame that factory isn't really operating anymore after their founder passed away.


----------



## Xcalibur255

CJG888 said:


> GZ37s?


Truly cool cats know to buy GZ33s instead.


----------



## A2029

leftside said:


> @A2029 We already have a CCS/RES switch, a 60mA/30mA power tube switch, and a 6J5/6SN7 switch. Need another switch for tube rectification/ss rectification



I'm with Keenan; there are just too many benefits for using SS rectification combined with regulated B+ that using tube rectification would be a step backwards (other than the beautiful glow of another tube ). You can also mimic all of the positive aspects of a tube rectifier using resistors and snubbers when combined with SS rectification, and don't get the negative aspects of tube rectifiers.


----------



## Zachik

A2029 said:


> I'm with Keenan; there are just too many benefits for using SS rectification combined with regulated B+ that using tube rectification would be a step backwards (other than the beautiful glow of another tube ). You can also mimic all of the positive aspects of a tube rectifier using resistors and snubbers when combined with SS rectification, and don't get the negative aspects of tube rectifiers.


Sounds like the perfect solution would be:
Solid state rectification, plus socket for a rectifier tube that will *only* provide voltage to make it glow...


----------



## bcowen

Zachik said:


> Sounds like the perfect solution would be:
> Solid state rectification, plus socket for a rectifier tube that will *only* provide voltage to make it glow...


Oh great.  Another tube rolling rabbit hole trying to find just the right glow....


----------



## Xcalibur255

If it's just for the glow you want one of those mercury vapor tubes.


----------



## Monsterzero

L0rdGwyn said:


> I'll keep that in mind! The reason I don't use them regularly, despite how cool they are, is they conflict with my penchant for using regulated B+ supplies, which have a lot of sonic benefits. You can use them together, but it doesn't make a lot of sense from a design standpoint.





A2029 said:


> I'm with Keenan; there are just too many benefits for using SS rectification combined with regulated B+ that using tube rectification would be a step backwards (other than the beautiful glow of another tube ). You can also mimic all of the positive aspects of a tube rectifier using resistors and snubbers when combined with SS rectification, and don't get the negative aspects of tube rectifiers.


Perhaps other factors are involved, but tubes that are noisy on my tube rectified GOTL were dead quiet on Keenan's amp.


----------



## gibosi

Fortunately, I guess, I am poor and my ears are old, so I'm very comfortable with a tube-rectified GOTL. And given that I've got something like 75 tube rectifiers, I am too deep into that rabbit hole to ever be able to escape. lol


----------



## leftside

bcowen said:


> Oh great.  Another tube rolling rabbit hole trying to find just the right glow....


Also need a dimmer switch/knob. Problem resolved.


----------



## whirlwind

A2029 said:


> I'm with Keenan; there are just too many benefits for using SS rectification combined with regulated B+ that using tube rectification would be a step backwards (other than the beautiful glow of another tube ). You can also mimic all of the positive aspects of a tube rectifier using resistors and snubbers when combined with SS rectification, and don't get the negative aspects of tube rectifiers.



Yeah man, that warm, cozy glow of another tube...too much ain't enough


----------



## Tjj226 Angel

I always find it funny that people put so much time and attention into rectifiers. They all suck.

A really well designed PSU acts like a battery with infinite charge. We are literally doing nothing more than trying to make sure that the last PSU capacitor that feeds each tube/mosfet/bjt/etc can be instantaneously charged back up after an impulse. 

In other words we are trying to make a PSU that converts AC to pure DC with an instantaneous response time. 

Tube rectifiers have one big benefit which is that they conduct all the time whereas diodes will switch on and off. However tubes also have a massive draw back. If you draw large amounts of current, the psu voltage will droop or "sag". This is great for guitar amps where we want lots of distortion, but its pretty terrible for hifi. 

I am grossly oversimplifying here, but the point remains the same. ALL rectifiers suck for audio. The good news is that we can do better. We simply need to build our own rectifier.


----------



## CJG888

whirlwind said:


> Yeah man, that warm, cozy glow of another tube...too much ain't enough


On a more festive note: 6111s as Christmas tree lights anyone?


----------



## jgwtriode (Dec 22, 2021)

bcowen said:


> Here you go @gibosi .  The thread has been made whole.


Oh yeah....Art Audio, gorgeous stuff.  Got the opportunity to play with their PX 4 amp a few years back when I worked for Talon audio.  Loved that Amp and the chrome is very nice as well!  Joe Fratus let me borrow it for a little while at one of the shows.


jgwtriode


----------



## whirlwind

bcowen said:


> Here you go @gibosi .  The thread has been made whole.


Oh man...if the OCD kicked in a guy could be polishing more than listening to music


----------



## bcowen

whirlwind said:


> Oh man...if the OCD kicked in a guy could be polishing more than listening to music


LOL!  I just use a Swiffer duster on it every couple weeks, no polishing required.  But now that I look at the photo closely I see a spot.....back after a bit.


----------



## Xcalibur255

Golden transformer = golden tone?


----------



## jgwtriode

Merry Listening and some happy new gear to everyone.   Happy holidays and the all the best for the new year.  Looking forward to even better audio and enjoying this hobby even more.  Thanks to all on this site for making it a better year.


jgwtriode


----------



## bcowen

jgwtriode said:


> Merry Listening and some happy new gear to everyone.   Happy holidays and the all the best for the new year.  Looking forward to even better audio and enjoying this hobby even more.  Thanks to all on this site for making it a better year.
> 
> 
> jgwtriode


And to you as well.  Nice pic, man!  I have some EH KT-88's, but they've got no fluorescence at all.


----------



## L0rdGwyn

jgwtriode said:


> Merry Listening and some happy new gear to everyone.   Happy holidays and the all the best for the new year.  Looking forward to even better audio and enjoying this hobby even more.  Thanks to all on this site for making it a better year.
> 
> jgwtriode



Merry listening and happy new gear indeed, hopefully a better new year!  I have been away from work and DIY for a week which has been healthy, ran a half marathon this morning which was nice.  I did go to my Klipsch dealer this week and demo the Forte IV.  I love them, sounded excellent and out of a Sony receiver, will be even better in my system methinks.  I intend to buy them, but there is a catch: the grills are not metal, and I need to get metal grills to meet WAF.  I am looking into my options; I've asked Klipsch if they would make me a metal grill, otherwise there are third party grill manufacturers, last resort is DIY but I don't think it will come to that.  Anyway, hope everyone is having a good holiday.  Please get vaccinated and boosted and encourage others to do so for your safety and the sanity of healthcare workers.


----------



## whirlwind (Dec 25, 2021)

L0rdGwyn said:


> Merry listening and happy new gear indeed, hopefully a better new year!  I have been away from work and DIY for a week which has been healthy, ran a half marathon this morning which was nice.  I did go to my Klipsch dealer this week and demo the Forte IV.  I love them, sounded excellent and out of a Sony receiver, will be even better in my system methinks.  I intend to buy them, but there is a catch: the grills are not metal, and I need to get metal grills to meet WAF.  I am looking into my options; I've asked Klipsch if they would make me a metal grill, otherwise there are third party grill manufacturers, last resort is DIY but I don't think it will come to that.  Anyway, hope everyone is having a good holiday.  Please get vaccinated and boosted and encourage others to do so for your safety and the sanity of healthcare workers.



Merry Christmas Keenan.

Vaccinated and boosted here.  I am glad you are getting a little break from all of the chaos.

Listening to some new music that my wife gifted me this morning.

Music makes life better.


----------



## CJG888

Same here 😀

Beethoven piano concerti with Mitsuko Uchida, Simon Rattle and the Berlin Philharmonic. No. 4 is a particular highlight!


----------



## L0rdGwyn

Got home from Christmas vacation to some presents.

My globe Marconi MH4 arrived, except they aren't Marconi MH4.  Billington got it wrong, they are Mazda VR37, an alternative construction Mazda AC/HL.  That's okay though, this is another rare one that I didn't have in my collection, the price was fair.



Love those big plates.  One of the four had a partially broken heater pin, which was a little disappointing, but nothing a little solder couldn't fix.



Listening now, they sound great, very linear, spacious.  90-year-old tubes.



More HY69 arrived.  Will just show one pair, but now have around forty of these tubes.  I put together a triode LTSpice model for these including A2 curves, so I have a few schematics I'm playing with.  Long term goal is a lifetime supply for a special speaker amplifier.  I have a special one already, so just going to hold onto these and scheme...



While I am figuring out the metal grill situation for the Forte IV, the plan for the Snells is to order another VIFA woofer to replace the one that was punctured.  Once that's fixed, going to bring them to a local shop that does consignment of vintage hifi gear.  Will package them together with the Sound Anchors stands.  Not sure how much I will ask for them yet, but it will be a good find for someone, price will be reasonable given what the custom stands cost, not to mention the souped-up crossovers and brand new drivers.  If nothing else, putting them on sale will get them out of the house to make room for the Fortes  looking forward to getting those into my system, they will sing with these flea-watt amps.


----------



## L0rdGwyn

Back to reality tomorrow, it's going to hit hard, two days then a breather.  Will try and get some more OTL work done this week!  Normally would have those amps done, just bad timing with the surge and the holidays.


----------



## L0rdGwyn (Dec 28, 2021)

Wanted to share a bit of history from my friend's father, owner of that Garrard 401 I pictured a few pages back.  Even more interesting than the turntable is the tonearm!  A design with an articulating headshell, meant to maintain parallel alignment to the vinyl groove through the entirety of the record playback.



This is a very obscure arm, invented in the 1950s by James Worden, patented, then advertised by his son, Wilfred.  According to my friend's father - who had some connection to Wilfred Worden through a series of acquaintances - Wilfred attempted to sell the design to major turntable manufacturers, including Garrard, but no one picked it up.  Then at a later date, Garrard released their own articulating tonearm design!  Seems it was a suspected copycat situation.

Anyway, I've attached some documents he provided to me if anyone is interested in reading about it.
















Worden also designed some horn loaded speakers under the name Panosonic.  My friend's dad wants me to recreate them for him lol easier said than done!  But apparently they have been discussed to some extent on diyAudio, one of the pictures below is from a restoration.


----------



## CJG888

And when did Matsushita start using „Panasonic“? Did he register the trademark?

Could have been an opportunity…😀


----------



## L0rdGwyn

CJG888 said:


> And when did Matsushita start using „Panasonic“? Did he register the trademark?
> 
> Could have been an opportunity…😀



It's Pan*O*sonic, big difference!!!


----------



## L0rdGwyn

I love a good tube deal, nailed one today, got a lot of eighteen NIB Amperex E182CC today at $22 per tube with free shipping.  Here are six of them.


----------



## CJG888

L0rdGwyn said:


> I love a good tube deal, nailed one today, got a lot of eighteen NIB Amperex E182CC today at $22 per tube with free shipping.  Here are six of them.


Where???


----------



## L0rdGwyn

CJG888 said:


> Where???



Where what?


----------



## Monsterzero

CJG888 said:


> Where???





L0rdGwyn said:


> Where what?


----------



## L0rdGwyn

Oh @CJG888 you're asking where I found them, sorry I'm a little slow today lol I thought maybe the photo wasn't visible.  eBay of course!  I asked a seller if they would combine three listings at a discount, then they threw in free shipping to boot!  For context these tubes regularly sell for $100 each.  78% off ain't bad!


----------



## Zachik

L0rdGwyn said:


> I love a good tube deal, nailed one today


I have spent sooooooo much money due to that exact same reason...


----------



## bpiotrow13

L0rdGwyn said:


> Oh @CJG888 you're asking where I found them, sorry I'm a little slow today lol I thought maybe the photo wasn't visible.  eBay of course!  I asked a seller if they would combine three listings at a discount, then they threw in free shipping to boot!  For context these tubes regularly sell for $100 each.  78% off ain't bad!


A couple od days ago somebody won an ebay auction for ten (10) 5998 type tubes for around eur500. Quite a nice deal as well.


----------



## bcowen

Zachik said:


> I have spent sooooooo much money due to that exact same reason...


This would infer that there is a such a thing as a _bad_ tube deal.  With the exception of just getting a bad tube, I think that's an oxymoron.


----------



## triod750

Please share your (good) GE tube deals with us. (Bad tube isn't working).


----------



## gibosi

L0rdGwyn said:


> I love a good tube deal, nailed one today, got a lot of eighteen NIB Amperex E182CC today at $22 per tube with free shipping.  Here are six of them.



That's a great deal! I've got a bunch of these, including a pair manufactured at Heerlen in 1958. (Notice the pinched-waist.) I think the 7119 / E182CC are very good tubes, but they are often overlooked in the audio community. Of course, having a non-standard pin-out doesn't help.


----------



## L0rdGwyn

gibosi said:


> That's a great deal! I've got a bunch of these, including a pair manufactured at Heerlen in 1958. (Notice the pinched-waist.) I think the 7119 / E182CC are very good tubes, but they are often overlooked in the audio community. Of course, having a non-standard pin-out doesn't help.



Very nice!  I like the pinched waist  very classy, I'll have to keep an eye out for that one.  Yes they are good sounding tubes, I am adding them to a stash of thirteen RCA 7044, a near equivalent.  Long term I will likely use them in a SET design, with the E182CC/7044 interstage transformer coupled to a triode strapped HY69 for around 6W output with a partial A2 grid swing.


----------



## triod750

L0rdGwyn said:


> with a partial A2 grid swing.


Must be good for jazz!!


----------



## L0rdGwyn (Dec 31, 2021)

triod750 said:


> Must be good for jazz!!



Oh yeah, and everything else!  

I've also started drafting schematics when I've had an hour here or there for an LCR phono stage, have a working draft in LTSpice.  That's another complex and long term project, but I figure best to get the gears turning now so I'm ready when I want to move forward with it.  Will have lots of inductors though, will be an expensive project.  Also building and measuring an MC phono stage is a real PITA as I found out on the first go around lol.  Probably upgrades to my TT will come first as I am very pleased with the sound of my current phono, but one must always be planning for the future.

The priority is finishing the OTL amplifiers though.  I have a chunk of time off next week, going to see if I can get one of them all the way done.


----------



## UntilThen

L0rdGwyn said:


> Today is the two year anniversary of starting this thread. Time has flown by, it's been quite the journey, thanks for everyone who has followed along. I thought it might be fun to go through the pictures I've taken over the last two years and post the ones I liked most. Here's what I found.



Happy New Year 2022 Keenan. What a 2 years it has been. May there be lots more to come.


----------



## bpiotrow13

The Best Is Yet To Come! Best for Everyone! It has been a real pleasure to read this thread. Many thanks! Bogdan


----------



## L0rdGwyn

UntilThen said:


> Happy New Year 2022 Keenan. What a 2 years it has been. May there be lots more to come.





bpiotrow13 said:


> The Best Is Yet To Come! Best for Everyone! It has been a real pleasure to read this thread. Many thanks! Bogdan



Thanks Matt, Happy New Year!  And thank you Bogdan, glad you have enjoyed reading this thread!  Hopefully will have some cool new projects to show off this year.


----------



## L0rdGwyn (Jan 2, 2022)

Have some time off, listening to the Mazda VR37, Sylvania 6A5G, and GEC U18/20 *tube rectifier* (@gibosi )



These tubes sound great, really hit the spot in terms of looks / build for me too.



Here are the operating curves.



Tomorrow afternoon I am gonna get back on the amp building horse and make some real progress on those two Airmid OTLs, think I should be able to get one or both of them done or darn close this week.

Still working on figuring out the grill situation for the Forte IV.  I'm waiting for Klipsch customer service to get back to me, they have been unreachable by phone and email, which I assume is mostly due to the busy holiday season.  Going to give them another ring tomorrow.  Plan is to see if they will build me a pair of metal grills, if not I will ask to buy the magnetic grill substrates from them without the cloth and either make my own or send them to a custom grill maker.  I'm thinking I am probably going to make some changes to the Forte IV whenever I do get them, maybe not right away but at some point.  Probably will make some upgrades in the crossover, add some damping to the horns at the very least.  Could get a little more aggressive and add some bracing to the cabinets, we'll see, I think there are some improvements that could be made.

Another thing I am excited about - as part of the deal for the 45 amp I built Zach, he is working on some custom headphones for me, probably will have them by Feb.  I will finally be joining the Vérité Closed club   mine will be made in black and white ebony.


----------



## gibosi

Excellent! The GEC U18/20 is one of my favorites. And who knows?  Maybe there is a chance that you might grow into a tube rectifier aficionado


----------



## gibosi

L0rdGwyn said:


> Could get a little more aggressive and add some bracing to the cabinets,



Back in the day, I used to apply a thick layer of an Elmers white glue and sand mixture to the inside surfaces to brace speaker cabinets.


----------



## Monsterzero

gibosi said:


> The GEC U18/20 is one of my favorites.


+1


----------



## L0rdGwyn

gibosi said:


> Excellent! The GEC U18/20 is one of my favorites. And who knows?  Maybe there is a chance that you might grow into a tube rectifier aficionado



I pretty much use the U18/20 exclusively in this amp!  Fist version could also run 5Z3 with a combo socket, but ended up switching to 4V B4 base rectifiers only.  Have a Marconi-branded FW4-500 around here somewhere...but I think the U18/20 sounds a little better.  And it looks cool, most importantly.



gibosi said:


> Back in the day, I used to apply a thick layer of an Elmers white glue and sand mixture to the inside surfaces to brace speaker cabinets.



If it works, it works!  If I do add some bracing, will probably try to do something reversible, at least at first, and take some measurements.


----------



## gibosi

And a friend used to build his speakers using Corian, the kitchen countertop material. Very dense. And of course, concrete works well too. lol


----------



## jgwtriode

L0rdGwyn said:


> Have some time off, listening to the Mazda VR37, Sylvania 6A5G, and GEC U18/20 *tube rectifier* (@gibosi )
> 
> 
> 
> ...


Very nice!  Sounds exciting,!   Particularly that you will be getting a pair of Verite Closed.  Should be amazing in ebony!  Love leopard wood  VC's.  Truelly amazing how they scale.Was doing software tweaking over the holidays, most specifically with latest majiority clean and lemonade in combination with the other packages that work very well with Jplay femto.  Stunning how much more realistic that made them sound.  The Verites easily compare with very good loudspeakers but present more subtle details and texture across the frequency spectrum.  Can't wait to see what the Airmid will bring to the table!  It's looking like a very good New year!

Very happy listening,

jgwtriode


----------



## whirlwind (Jan 4, 2022)

L0rdGwyn said:


> Have some time off, listening to the Mazda VR37, Sylvania 6A5G, and GEC U18/20 *tube rectifier* (@gibosi )
> 
> 
> 
> ...



That rectifier socket will use 4 or 5 volt rectifiers with no adapters.....correct ?

Congrats on getting the VC also.  Black & White Ebony, can't wait to see it and for you to get to hear it.
It is pretty dang spectacular.  With all of your gear, wow...great times ahead.

*PS   *My patience is running thin with Baker Mayfield......kid has turned my life upside down the last few weeks


----------



## L0rdGwyn

whirlwind said:


> That rectifier socket will use 4 or 5 volt rectifiers with no adapters.....correct ?
> 
> Congrats on getting the VC also.  Black & White Ebony, can't wait to see it and for you to get to hear it.
> It is pretty dang spectacular.  With all of your gear, wow...great times ahead.
> ...



Just 4V on the rectifier Joe, I had a combo socket in the first version of the amp so that both 4V and 5V rectifiers could be used (specifically the 5Z3).  But then I was pretty much only using 4V rectifiers, so I ended up removing the combo socket when I rebuilt the amp.  Now it just uses U18/20, AZ50, FW4-500, etc.

Yeah I can't wait for that headphone!  Really looking forward to that.

As far as Baker...yeah, I don't know, he looked good before the shoulder injury and it has been a mess ever since!  I'm guessing he plays out the last year of his contract then they'll have to make a big decision.  It's too bad, makes you wish he would have just sat out and gotten the surgery from the start.


----------



## whirlwind

L0rdGwyn said:


> Just 4V on the rectifier Joe, I had a combo socket in the first version of the amp so that both 4V and 5V rectifiers could be used (specifically the 5Z3).  But then I was pretty much only using 4V rectifiers, so I ended up removing the combo socket when I rebuilt the amp.  Now it just uses U18/20, AZ50, FW4-500, etc.
> 
> Yeah I can't wait for that headphone!  Really looking forward to that.
> 
> As far as Baker...yeah, I don't know, he looked good before the shoulder injury and it has been a mess ever since!  I'm guessing he plays out the last year of his contract then they'll have to make a big decision.  It's too bad, makes you wish he would have just sat out and gotten the surgery from the start.



Thanks for the info...I thought you had a socket for both at one point.

Baker is a tough kid, maybe too much for his own good.


----------



## L0rdGwyn

Been working on the Airmid OTL for @pravous , not quite done yet, but almost there.  Will do a little more work on it tonight, think I will be able to finish it tomorrow.  Please ignore my very messy workbench.


----------



## pravous

Looks awesome.   Very excited to listen to it!   Not going to lie the week has been going very slow since you told me maybe this week.


----------



## L0rdGwyn

pravous said:


> Looks awesome.   Very excited to listen to it!   Not going to lie the week has been going very slow since you told me maybe this week.



Excited for you to hear it!  Assuming I don't get called into work overnight (I am on call, but odds are I won't), should finish the circuit tomorrow morning, test, then add some feet to the bottom panel, and it will be done.


----------



## pravous

This week is like Christmas all over again.  First I manage to score a 7802 and then the Airmid nears completion.  I might have to go out and buy a lottery ticket.


----------



## Monsterzero

pravous said:


> First I manage to score a 7802


I saw a 7802 on eBay a week or two ago. First ive seen in several years of looking, but it was just one. I'm too old to wait for another to pop up. Congrats on getting it though


----------



## pravous

Yeah it happened to be listed on Christmas morning and I was on my phone sending pictures to family.  Dumb luck more than anything.


----------



## jgwtriode

L0rdGwyn said:


> Been working on the Airmid OTL for @pravous , not quite done yet, but almost there.  Will do a little more work on it tonight, think I will be able to finish it tomorrow.  Please ignore my very messy workbench.


----------



## jgwtriode

Looks gorgeous!  Nice color combo.  That deep grey contrasting with the Clarity Caps.

jgwtriode


----------



## L0rdGwyn (Jan 4, 2022)

Heater supply and B+ delay circuitry is up and running.  Think that's where I'll leave it for tonight.




@jgwtriode looks like some text might be missing from your last post! (Edit: oh never mind, you saw).  BTW, I have the feet for the red Airmid to replace those with missing O-rings.  I will also be putting new gyrator PCBs in that amp before I send it to you, the most updated have an additional safety zener, better safe than sorry


----------



## jgwtriode

L0rdGwyn said:


> Heater supply and B+ delay circuitry is up and running.  Think that's where I'll leave it for tonight.
> 
> 
> 
> @jgwtriode looks like some text might be missing from your last post! (Edit: oh never mind, you saw).  BTW, I have the feet for the red Airmid to replace those with missing O-rings.  I will also be putting new gyrator PCBs in that amp before I send it to you, the most updated have an additional safety zener, better safe than sorry


Thanks so much Keenan, appreciate that.  Looking forward to it.  Will get another payment off to you around mid month and hopefully by Mid February depending.  Otherwise will throw some tax return money at it.

jgwtriode


----------



## L0rdGwyn (Mar 29, 2022)

Back at it this morning, almost done actually.  All working as intended, DC operating points are dialed in.

Just need to do the input and output wiring, which won't take long, then put some feet on the bottom.  But first, lunch!


----------



## L0rdGwyn (Jan 5, 2022)

All done, here is @pravous Airmid OTL in Anthracite Grey with dual mono Goldpoint attenuators.







And with some tubes, sort of a brutalist aesthetic with those Soviet tubes in.





Now for the burn in  sounds good to me, and dead quiet.  I kind of like the mono attenuators, really makes the amp dual mono from start to finish, pretty neat.  Works great for channel balancing, @pravous.


----------



## Monsterzero

L0rdGwyn said:


> All done, here is @pravous Airmid OTL in Anthracite Grey with dual mono Goldpoint attenuators.
> 
> 
> 
> ...


Lovely.
The second tube amp I owned was the La Figaro 339, which is also a dual mono design. If I ever have another custom amp built, I might go in that direction again.


----------



## L0rdGwyn

Taking things up a few notches with the all GEC squad.


----------



## gibosi

L0rdGwyn said:


> Taking things up a few notches with the all GEC squad.



It's a great looking amp. But I don't see a tube rectifier, C3g sockets and and one 6SN7 socket with 6/12/24 volts? So I don't think it's finished? Is it?  lol


----------



## triod750

L0rdGwyn said:


> I kind of like the mono attenuators, really makes the amp dual mono from start to finish, pretty neat. Works great for channel balancing, @pravous.


I like that too and wonder why it isn't more common...


----------



## L0rdGwyn

gibosi said:


> It's a great looking amp. But I don't see a tube rectifier, C3g sockets and and one 6SN7 socket with 6/12/24 volts? So I don't think it's finished? Is it?  lol



Lol I see what you did there  different from the GOTL in a whole lot of ways.


----------



## pravous

Really looking forward to listening to this.  Especially with the GEC quad.


----------



## pravous

As far as the dual mono goes, I have a slight hearing imbalance due to a career in the trades.  In short hearing in my left ear is weaker than the right.  I figured with dual mono I could adjust to what sounds right to me.  Might also be useful for an unbalanced set of tubes as well.  Regardless should be a big upgrade from my current self built BHC.  Seems I am out of the greys so heres a picture of my current set up.





And a close up of the 7802wb I just aquired.


----------



## L0rdGwyn

pravous said:


> As far as the dual mono goes, I have a slight hearing imbalance due to a career in the trades.  In short hearing in my left ear is weaker than the right.  I figured with dual mono I could adjust to what sounds right to me.  Might also be useful for an unbalanced set of tubes as well.  Regardless should be a big upgrade from my current self built BHC.  Seems I am out of the greys so heres a picture of my current set up.
> 
> 
> 
> And a close up of the 7802wb I just aquired.



Looks nice!  That is one rare tube.  If you can snag a second one, they are excellent in this OTL.

I am listening with the HD650 right now, which I think is your headphone @pravous , pairs very well, I think you will enjoy it.


----------



## pravous

My set up is pretty simply.  Flac>Node 2i>BHC>HD650.  Have some upgrades planned for the future but I want to wait till things settle down so I can try the amp/tubes I like with some other headphones and then probably a new DAC.


----------



## L0rdGwyn

pravous said:


> My set up is pretty simply.  Flac>Node 2i>BHC>HD650.  Have some upgrades planned for the future but I want to wait till things settle down so I can try the amp/tubes I like with some other headphones and then probably a new DAC.



Nice, I have a Node 2 up in my bedroom setup, its very convenient.  Great feature is it has digital outputs, so you can pair a new DAC with it whenever you decide to upgrade but keep the convenience of the streamer.


----------



## triod750

pravous said:


> In short hearing in my left ear is weaker than the right. I figured with dual mono I could adjust to what sounds right to me. Might also be useful for an unbalanced set of tubes as well.


I am riding that same horse.


----------



## Xcalibur255

gibosi said:


> It's a great looking amp. But I don't see a tube rectifier, C3g sockets and and one 6SN7 socket with 6/12/24 volts? So I don't think it's finished? Is it?  lol


What, no ice cube maker?


----------



## Xcalibur255

The red/black combo had pop to it, but this grey tone that leans just a bit toward blue really works.  I like it better and better with every new photo.


----------



## L0rdGwyn

Thanks @Xcalibur255 , credit goes to @pravous for choosing the color, I'm a fan of gray tube amps myself.

Will be shipping this out tomorrow, so last listen tonight, have to break out something fancy.  Got the Fivre 6C5G and a pair of Western Electric 421A going.




On the speaker front, finally got a hold of Klipsch customer service after nearly two weeks, guess they've been backed up.  Anyway, they are sending me a pair of Forte IV grills, going to remove the grill cloth then and either A) send them to Speakerworks for a professional metal grill fitting or B) DIY it.  Either way, once I have plans finalized, will order the Forte IV.

Next week I will build the bronze Airmid.


----------



## Xcalibur255

I'm very curious how metal grill covers might change the sound of the speaker.  Won't you get reflection off the internal side of the metal portions and cause some cancellation or other interaction right in front of the baffle?


----------



## L0rdGwyn

Xcalibur255 said:


> I'm very curious how metal grill covers might change the sound of the speaker.  Won't you get reflection off the internal side of the metal portions and cause some cancellation or other interaction right in front of the baffle?



Yeah there will be some effect, no doubt.  Speakerworks describes the grill material they use as "transparent", they go in a lot of hifi systems and feedback is very positive, but I'm sure there will be some contribution from the grill.  Even the stock grills have an effect on the FR - without, there is a bit of a peak at 6kHz which is tamed with the grills on.  I have no choice though based on WAF lol if I want the speakers, they need the metal grills!  I'm not particularly fussy about a perfectly flat FR, I'm something of a purist, not into EQ and all that jazz, something has to be really egregious to get me worked up about it.  Based on what I heard when I demo'd them, I think it will be a good fit.


----------



## Xcalibur255

Yeah, that's the other thought I was having.  Some speakers are tuned to be netural with the grill on and will have weird peaks when they are off.  I would expect a fabric to have more of a pure attenuating behavior, affecting a specific frequency range depending on the weave and thickness of the fabric.  The metal grills on the other hand will be passing MOST of the sound through with no filtering/attenuating at all but a small portion of it is going to reflect and locally cancel right in front of the speaker cone.

My guess is that the attenuation effect of a metal grill might be more wideband than that of a cloth one, affecting a wider frequency range but with a lesser attenuation effect.  It might have the effect of giving the speaker a very slight bass shelf because the mids and low treble range might be broadly attenuated just slightly.   I haven't really thought about it much since I'm a "grills off" guy but that's the theory that comes to mind from a bit of pondering.  That actually sounds like it would be a good thing IMO.


----------



## L0rdGwyn

Xcalibur255 said:


> Yeah, that's the other thought I was having.  Some speakers are tuned to be netural with the grill on and will have weird peaks when they are off.  I would expect a fabric to have more of a pure attenuating behavior, affecting a specific frequency range depending on the weave and thickness of the fabric.  The metal grills on the other hand will be passing MOST of the sound through with no filtering/attenuating at all but a small portion of it is going to reflect and locally cancel right in front of the speaker cone.
> 
> My guess is that the attenuation effect of a metal grill might be more wideband than that of a cloth one, affecting a wider frequency range but with a lesser attenuation effect.  It might have the effect of giving the speaker a very slight bass shelf because the mids and low treble range might be broadly attenuated just slightly.   I haven't really thought about it much since I'm a "grills off" guy but that's the theory that comes to mind from a bit of pondering.  That actually sounds like it would be a good thing IMO.



Yeah I hadn't given it much thought beyond the making it happen and keeping it aesthetically pleasing given that I have no choice, but the grill should act like low pass filter to some extent and attenuate higher frequencies based on the size of the grill holes.  I think the overall effect will be subtle though.  I'll ask Speakerworks for their $0.02 when I call them.  I'm likely going to mod the speakers (I just can't help myself), which at the minimum means I will upgrade the crossover.  If I go any further than that, I will get a mic to take measurements with each change, if so I'll do a with and without metal grills test and we will get to the bottom of it


----------



## Monsterzero

L0rdGwyn said:


> Thanks @Xcalibur255 , credit goes to @pravous for choosing the color, I'm a fan of gray tube amps myself.
> 
> Will be shipping this out tomorrow, so last listen tonight, have to break out something fancy.  Got the Fivre 6C5G and a pair of Western Electric 421A going.
> 
> ...


There seems to be a bit of conflicting reports on the WE421 vs. 5998. Some say there's an audible difference, others say theyre identical. Whats your view, Keenan?

Also, on my GOTL, the 6C5 can be used in the 6J5 socket w/o adapter, yes?


----------



## L0rdGwyn (Jan 5, 2022)

Monsterzero said:


> There seems to be a bit of conflicting reports on the WE421 vs. 5998. Some say there's an audible difference, others say theyre identical. Whats your view, Keenan?
> 
> Also, on my GOTL, the 6C5 can be used in the 6J5 socket w/o adapter, yes?



Yessir, can totally use 6C5 in place of 6J5.

As far as 5998 vs. 421A, structurally they are identical, which would lead you to think there is no difference.  IME, it depends, as I've found there are audible differences even between different constructions of 5998, I owned a ton of these tubes at one time, sold off most of them.  I have a pair of 5998 with copper grid rods that sound significantly better than their steel grid rod counterparts.  Why?  No idea, but they do and are right there with the 421A.  I did all that listening a long time ago though so hard to say if I was delirious at the time or not, but for me it went 421A = 5998 (copper grid rod) > 5998 (steel grid rod).


----------



## bcowen (Jan 5, 2022)

L0rdGwyn said:


> Yeah I hadn't given it much thought beyond the making it happen and keeping it aesthetically pleasing given that I have no choice, but the grill should act like low pass filter to some extent and attenuate higher frequencies based on the size of the grill holes.  I think the overall effect will be subtle though.  I'll ask Speakerworks for their $0.02 when I call them.  I'm likely going to mod the speakers (I just can't help myself), *which at the minimum means I will upgrade the crossover. * If I go any further than that, I will get a mic to take measurements with each change, if so I'll do a with and without metal grills test and we will get to the bottom of it


What I did to my Tekton Lores.  Didn't change any values, just got mo' better parts.  Made a pretty nice improvement (Neotech PCOCC wire too).  They are a $1k pair of speakers (new), so did it make sense to spend $300 on better caps and wire?  *Yes*.   


Original crossover:





New ones:


----------



## L0rdGwyn

bcowen said:


> What I did to my Tekton Lores.  Didn't change any values, just got mo' better parts.  Made a pretty nice improvement (Neotech PCOCC wire too).  They are a $1k pair of speakers (new), so did it make sense to spend $300 on better caps and wire?  *Yes*.
> 
> 
> Original crossover:
> ...



Nice!!!  Did you feel it was a big upgrade sonically?  That's what I'm looking to do - replace the sand cast resistors with Mills MRA wirewounds, replace the inductors with nice air core types, and MAYBE replace the caps, but options will be limited as Klipsch uses some real oddball values in the Forte IV crossover, so have to wonder if the replacements (which would not be top-of-the-line) would really be an improvement over the originals, which are also films.


----------



## L0rdGwyn

Here is the Forte IV crossover, guy on Audiokarma took some pics and catalogued all the values (except for the inductors, which will probably need to be measured).

It will be a big pain to upgrade, but such is DIY.


----------



## leftside

L0rdGwyn said:


> Yessir, can totally use 6C5 in place of 6J5.
> 
> As far as 5998 vs. 421A, structurally they are identical, which would lead you to think there is no difference.  IME, it depends, as I've found there are audible differences even between different constructions of 5998, I owned a ton of these tubes at one time, sold off most of them.  I have a pair of 5998 with copper grid rods that sound significantly better than their steel grid rod counterparts.  Why?  No idea, but they do and are right there with the 421A.  I did all that listening a long time ago though so hard to say if I was delirious at the time or not, but for me it went 421A = 5998 (copper grid rod) > 5998 (steel grid rod).


Also made over a period of over 30 years. Lots of different construction types during that time. Only Western Electric made them in the 1970’s and 1980’s tho as TungSol wasn’t around by then. They all sound good. Would have to listen/compare again tho to see if I could hear any differences.


----------



## L0rdGwyn (Jan 5, 2022)

leftside said:


> Also made over a period of over 30 years. Lots of different construction types during that time. Only Western Electric made them in the 1970’s and 1980’s tho as TungSol wasn’t around by then. They all sound good. Would have to listen/compare again tho to see if I could hear any differences.



Yeah when it comes down to it, they all sound good, no one would be disappointed with any pair.  And they seem to be getting more scarce at an accelerating rate thanks to all the idiots making amps that use them.


----------



## UntilThen

L0rdGwyn said:


> Taking things up a few notches with the all GEC squad.



Incredible. Where do I sign?


----------



## Xcalibur255

L0rdGwyn said:


> Yessir, can totally use 6C5 in place of 6J5.
> 
> As far as 5998 vs. 421A, structurally they are identical, which would lead you to think there is no difference.  IME, it depends, as I've found there are audible differences even between different constructions of 5998, I owned a ton of these tubes at one time, sold off most of them.  I have a pair of 5998 with copper grid rods that sound significantly better than their steel grid rod counterparts.  Why?  No idea, but they do and are right there with the 421A.  I did all that listening a long time ago though so hard to say if I was delirious at the time or not, but for me it went 421A = 5998 (copper grid rod) > 5998 (steel grid rod).


I consider your comment on copper vs. steel grid rods to be true generally for all tubes, not just the 5998.  I learned the hard way to watch out for this back when I was still buying 6SN7s.......... there are a lot of "matched pairs" out there where one tube will be copper and the other steel.  I noticed it a lot on BGRP TS pairs sadly.


----------



## CJG888

L0rdGwyn said:


> Yeah I hadn't given it much thought beyond the making it happen and keeping it aesthetically pleasing given that I have no choice, but the grill should act like low pass filter to some extent and attenuate higher frequencies based on the size of the grill holes.  I think the overall effect will be subtle though.  I'll ask Speakerworks for their $0.02 when I call them.  I'm likely going to mod the speakers (I just can't help myself), which at the minimum means I will upgrade the crossover.  If I go any further than that, I will get a mic to take measurements with each change, if so I'll do a with and without metal grills test and we will get to the bottom of it


There’s always the Gale 301 approach:


----------



## jgwtriode

L0rdGwyn said:


> Thanks @Xcalibur255 , credit goes to @pravous for choosing the color, I'm a fan of gray tube amps myself.
> 
> Will be shipping this out tomorrow, so last listen tonight, have to break out something fancy.  Got the Fivre 6C5G and a pair of Western Electric 421A going.
> 
> ...


That is just plain gorgeous, much as I love the red airmid and am quite happy with that.  This thing has a sense of anchored timeless dark stone just waiting to come to life. Almost like a cross between Marble and steel.  Oh my gosh. Wow!

Happy listening indeed,

jgwtriode


----------



## L0rdGwyn

Okay, the gray Airmid is away.  I had the perfect shipping box, but it was full of my stash of HY69 tubes.  I transplanted them into different boxes, came across some interesting things when I did that.

For one, these old Hytron HY69 boxes are beautiful.



The seller also included an old CBS tube manual.  Neat.



Lastly, I had forgotten the seller told me he was including a few other random tubes with the purchase.  One of them is actually quite interesting...

It's the Hytron HY65, another thoriated tungsten filament directly heated pentode.  Built like a tank, an oddball tube for sure.  They are rare, datasheets are scarce, but I managed to find enough info to trace some triode curves.



They are pretty darn linear!  Which means they are suitable for audio use.



I have a pair, but the tubes are really too uncommon to seriously consider designing something with.  At a 375V 35mA bias point, plate resistance is around 2.3K with a mu of 5.8, so could conceivably design a single-ended class A amplifier using a 6.5-7K output transformer to make around 2-2.5W.   Could also consider a single-ended pentode design.  Would make a cool headphone amp  anyway, fun to trace random tubes and think about what you could build with them.


----------



## Xcalibur255

That's one of my favorite vintage box designs.  I have a pair of Hytron 45s (Sylvania manufactured) with this box art.  They still had the original sealing staples in them and were true NOS.  The trouble with tubes this nice is you don't want to use them.


----------



## pravous

This is my favorite original box and rebranded tube.


----------



## L0rdGwyn

Xcalibur255 said:


> That's one of my favorite vintage box designs.  I have a pair of Hytron 45s (Sylvania manufactured) with this box art.  They still had the original sealing staples in them and were true NOS.  The trouble with tubes this nice is you don't want to use them.



I know what you mean, some tubes it feels criminal to even use them...but I do anyway lol.



pravous said:


> This is my favorite original box and rebranded tube.



Very nice 5998 / 421A.  National rebranded a lot of different tubes, I have quite a few National 801A.  They go for good prices, I've gotten them for around $100 a pair.  Based on the construction, they are more often Taylor or Hytron rebrands, you can't beat the price.


----------



## L0rdGwyn (Jan 6, 2022)

Since I am getting rid of my Snells, I had to replace the punctured surround of the one speaker before I could put them up for sale.  Did that tonight, took about an hour-and-a-half.

Here is the hole before I got started.



Surround removed, this was the most tedious part, removing without damaging the cone.  Scraped as much glue / foam residue as I could from the frame as well.



And the new surround applied, good as new, sorta.



Will bring these to a local shop next week that does vintage hifi consignment.  They will be a nice find for someone, in a good home hopefully.


----------



## L0rdGwyn

The foam of the replacement surround is noticeably stiffer than the original, which will affect the FR, I'll have to replace the surround on the other speaker as well so they match.  But that will have to be done another day, that's all the DIY I have in me for now, back to work tomorrow.


----------



## Xcalibur255

Increased damping and more polite bass response?


----------



## L0rdGwyn (Jan 6, 2022)

Xcalibur255 said:


> Increased damping and more polite bass response?



Yes likely, it will definitely affect the resonant frequency.  They're pretty far off stock already though given the crossovers.  The foams had been replaced on the original drivers when I first received the speakers, still sounded very good.  Priority for me is to make sure they match reasonably well for the next owner, I can't in good conscience put them up for sale with what would essentially be two different driver units with one surround replaced.  It will be a bargain regardless, I won't be asking much for them, just want the speakers to be used by someone who will appreciate them.


----------



## bcowen (Jan 6, 2022)

L0rdGwyn said:


> Nice!!!  Did you feel it was a big upgrade sonically?  That's what I'm looking to do - replace the sand cast resistors with Mills MRA wirewounds, replace the inductors with nice air core types, and MAYBE replace the caps, but options will be limited as Klipsch uses some real oddball values in the Forte IV crossover, so have to wonder if the replacements (which would not be top-of-the-line) would really be an improvement over the originals, which are also films.


Yes, it was an easily audible improvement all the way around.  Treble sounds cleaner and faster, bass is more extended, but I think the biggest change was in macrodynamics that scale from soft to loud more quickly and with greater contrast.  Can't honestly tell you exactly what contributed the most (caps, wire, etc.) because I did it all at once, but I can't help but think getting rid of that stock electrolytic had to be a big factor.  I spent stupid money on the Dueland resistors...don't think I'd do that again, but the caps were relatively sane moneywise.  I had no way to measure the stock inductors and rather than mess around and spend a bunch of money getting things wrong I just cut the board around the stock ones and used them. Maybe better inductors would be even mo' better, but at times there's nothing wrong with blissful ignorance.  😆


----------



## pravous

Airmid has arrived safely.  First roll 5998 and l63 since they were the ones in Monsterzeros review.  I am sure you will all be shocked to hear that this is a huge step up from my BHC. Dead quiet. Separation, imaging and soundstage are unreal.  Can’t thank Keenan enough.  This is a work of art sonically and aesthetically.


----------



## whirlwind

pravous said:


> Airmid has arrived safely.  First roll 5998 and l63 since they were the ones in Monsterzeros review.  I am sure you will all be shocked to hear that this is a huge step up from my BHC. Dead quiet. Separation, imaging and soundstage are unreal.  Can’t thank Keenan enough.  This is a work of art sonically and aesthetically.


Congrats pal....that amp will last you a life time


----------



## Monsterzero

Ive noticed that on most, if not all OTLs, that the power button/switch is always located on the left hand side of the front face plate, and jack is on the right.

Is that by necessity based upon design ?


----------



## L0rdGwyn

Monsterzero said:


> Ive noticed that on most, if not all OTLs, that the power button/switch is always located on the left hand side of the front face plate, and jack is on the right.
> 
> Is that by necessity based upon design ?



Not at all, sides could be reversed and work just fine!


----------



## Monsterzero

L0rdGwyn said:


> Not at all, sides could be reversed and work just fine!


Thats good to know. I will let my amp builder know to swap the two.


----------



## jgwtriode

Monsterzero said:


> Thats good to know. I will let my amp builder know to swap the two.


Oh that Lampizator of yours,  Not that I can afford it right now but the new Baltic looks beyond sweet and the review seems to indicate it is quite easily worth it  6K pricing.   My ridiculously modded Oppo however is still offering improvement with each upgrade of my system.  Latest software changes with Majiority Clean and Hungry Bears MC Installer, just took it noticeably farther.  But after finishing paying Keenan for the Airmid, need GEC's and Tung Sol's.  But after that it's starting a Lampi Piggy 
Bank.

Happy Listening!

jgwtriode


----------



## cdanguyen08 (Jan 10, 2022)

jgwtriode said:


> Oh that Lampizator of yours,  Not that I can afford it right now but the new Baltic looks beyond sweet and the review seems to indicate it is quite easily worth it  6K pricing.   My ridiculously modded Oppo however is still offering improvement with each upgrade of my system.  Latest software changes with Majiority Clean and Hungry Bears MC Installer, just took it noticeably farther.  But after finishing paying Keenan for the Airmid, need GEC's and Tung Sol's.  But after that it's starting a Lampi Piggy
> Bank.
> 
> Happy Listening!
> ...


I'm looking at the Baltic 3 as well! I emailed Rob about sending in a used GA TRP I found online to be updated and he highly recommended Baltic 3. Regardless, after my amp purchase, I'd like to upgrade my DAC.


----------



## Monsterzero

jgwtriode said:


> Oh that Lampizator of yours,  Not that I can afford it right now but the new Baltic looks beyond sweet and the review seems to indicate it is quite easily worth it  6K pricing.   My ridiculously modded Oppo however is still offering improvement with each upgrade of my system.  Latest software changes with Majiority Clean and Hungry Bears MC Installer, just took it noticeably farther.  But after finishing paying Keenan for the Airmid, need GEC's and Tung Sol's.  But after that it's starting a Lampi Piggy
> Bank.
> 
> Happy Listening!
> ...


You know how you have truly, absolutely reached Game Over territory? When you stop looking at other gear, and are blissfully enjoying the music.
I'm so in that position, I wasnt even aware there was a Baltic 3 out. LOL!

So a quick look at the specs, says it comes both SE and balanced. Wow that is interesting. One negative I noticed is the option to add in a preamp isnt even available as an option on it. I use the hell out of my preamp function on my TRP. I set both my speaker amp and GOTL to a certain gain, and control the volume from my recliner with the Lampizator remote.

A thread @jgwtriode and @cdanguyen08 might be interested in following is here. The Lampi owners over there tube roll like madmen, so its a handy reference guide for when yall join the Lampi club.

BTW, one of the N. American Lampizator reps, Fred, is a member here. Drop @Gopher a message and he can help guide you guys on which DAC to get. Honestly, any of their DACs are killer, and the Baltic 3 should be no different. Now, if anyone wants to buy me their new flagship, The Horizon, I wont be mad at you.


----------



## Smallpie (Jan 10, 2022)

I used to have a Atlantic SE+ and bought a Spring and at first definitely liked the spring more as they both have a way different sound signature. Now after selling the Atlantic I’m sadly missing the musicality of that Dac. The midrange had the most realistic sound quality to it but the topend could be soft at times (only compared to other dacs like the spring.) . If I could go back I’d maybe swap back to the Atlantic.

The reason why I switched because my turntable setup did what the Lampizator did but better where the Spring sounded totally different and it complimented each other better than the tt/lampi combo. Still I miss it and would love to keep the spring AND a lampi down the road. The Spring does digital really well in its own way and I like the topend a bit more than the lampi but that is the only place it succeeds it where the lampi dominates in the midrange greatly! 

If I owned everything on vinyl I wouldn’t need the lampi but that will never happen so hopefully down the road I’ll grab a used one again and keep both. I’d greatly miss the Spring if I sold it and not making the same mistake twice.

I agree @Monsterzero. If I can muster up a spring/lampi combo I too will be in game over territory because the rest of my gear I’m totally happy with beside a wood change on a Zmf here and there.
I really tried to get into OTL based amps but DNA amps/Zmf cans are without a doubt my endgame. My 2 ch. system has been the same for years and I don’t bat an eye about changing anything there as it’s perfect in my eyes! 

Enjoy your tube rolling on the TRP and don’t look at pictures of the Golden Gate or others. Lol


----------



## L0rdGwyn

I'm curious what DAC chips Lampizator uses, my understanding is they used to use R2R but switch to delta-sigma.


----------



## Monsterzero

L0rdGwyn said:


> I'm curious what DAC chips Lampizator uses, my understanding is they used to use R2R but switch to delta-sigma.


That is how it was explained to me, although, at least on the TRP, you could request a R2R version. Im not sure if they are still doing that.


----------



## L0rdGwyn

Monsterzero said:


> That is how it was explained to me, although, at least on the TRP, you could request a R2R version. Im not sure if they are still doing that.



I've only ever heard the Amber 3, I wonder how the higher end models stack up.  I like my PCM56 DAC, would be cool to compare at a meet some day.


----------



## cdanguyen08

Monsterzero said:


> You know how you have truly, absolutely reached Game Over territory? When you stop looking at other gear, and are blissfully enjoying the music.
> I'm so in that position, I wasnt even aware there was a Baltic 3 out. LOL!
> 
> So a quick look at the specs, says it comes both SE and balanced. Wow that is interesting. One negative I noticed is the option to add in a preamp isnt even available as an option on it. I use the hell out of my preamp function on my TRP. I set both my speaker amp and GOTL to a certain gain, and control the volume from my recliner with the Lampizator remote.
> ...


I was looking to get the preamp option as well. But from emailing with NA Lampizator, they can add that option which checks the box for me.

I was looking to add a speaker setup as well. What speakers setup are you running?


----------



## Monsterzero

cdanguyen08 said:


> I was looking to get the preamp option as well. But from emailing with NA Lampizator, they can add that option which checks the box for me.


Interesting. On their website, it states preamp as not an option.


cdanguyen08 said:


> I was looking to add a speaker setup as well. What speakers setup are you running?


I use Focal Aria 905 bookshelf speakers w/ a SVS SV 1000 sub for nearfield and GoldenEar T2s for big listening. Those image and stage like rockstars, but can be a bit beamy, meaning the sweet spot is a bit small.


----------



## cdanguyen08

Monsterzero said:


> Interesting. On their website, it states preamp as not an option.
> 
> I use Focal Aria 905 bookshelf speakers w/ a SVS SV 1000 sub for nearfield and GoldenEar T2s for big listening. Those image and stage like rockstars, but can be a bit beamy, meaning the sweet spot is a bit small.


I saw that on their website as well. I was confused at first but then I went to the Baltic 3 whatsbestforum and had seen someone else get that option. 

I'll take a look at them Focals! I'll have to pitch the living room for big listening to the wife.


----------



## bcowen

Monsterzero said:


> Ive noticed that on most, if not all OTLs, that the power button/switch is always located on the left hand side of the front face plate, and jack is on the right.
> 
> Is that by necessity based upon design ?


My OTL has the power switch right and HP jack left.


----------



## Monsterzero

cdanguyen08 said:


> I'll take a look at them Focals!


Theyre discontinued, replaced by the 906, IIRC.

They were the highest rated for the price, at the time, so if your budget is north of 1k, im sure theyre are better out there, but they do the trick for me.


bcowen said:


> My OTL has the power switch right and HP jack left.


I'm diggin' the rusted, vintage look. Very cool!


----------



## jgwtriode

bcowen said:


> My OTL has the power switch right and HP jack left.


Would love to see photos of the Jota.   Loved the sound of their PX-25, which I got to play with years ago.  Had a number of customers using Jotas on the Talon Khorus back in the day when I used to work for them.  Wonderful Amps!

jgwtriode


----------



## Tjj226 Angel

L0rdGwyn said:


> I'm curious what DAC chips Lampizator uses, my understanding is they used to use R2R but switch to delta-sigma.



Yeup. But I have heard tons of lampizator dacs, and I have never been all that impressed with them. I would fully expect your dac to sound better.


----------



## Smallpie

Monsterzero said:


> That is how it was explained to me, although, at least on the TRP, you could request a R2R version. Im not sure if they are still doing that.


Your TRP is not R2R? I wonder why they switched? I’ll definitely have to read into it. I thought my Atlantic was R2R but I never looked inside to see what chip was used.

I just looked at their website and it’s very vague. Just says d/a chip in the technology info. Is all the version 2’s the new chip?


----------



## Monsterzero (Jan 11, 2022)

Akiravelvet said:


> Your TRP is not R2R?


If im not mistaken, Lampizator abandoned R2R design across all of their DACs about 3-4 years ago. As I said before, they were offering to still do a R2R implementation upon request, but default is now d/s. So no, my TRP is not R2R.

Interesting story:

Fred dropped off a loaner TRP at my old place, as he lived close by. I had it for a week, and it blew my mind. Only after giving it back to Fred did I learn that it was a d/s DAC. As a devout R2R guy, I told Fred that if I had known prior that it wasnt a R2R DAC I wouldnt have been interested in hearing it.


----------



## L0rdGwyn

Monsterzero said:


> If im not mistaken, Lampizator abandoned R2R design across all of their DACs about 3-4 years ago. As I said before, they were offering to still do a R2R implementation upon request, but default is now d/s. So no, my TRP is not R2R.
> 
> Interesting story:
> 
> Fred dropped off a loaner TRP at my old place, as he lived close by. I had it for a week, and it blew my mind. Only after giving it back to Fred did I learn that it was a d/s DAC. As a devout R2R guy, I told Fred that if I had known prior that it wasnt a R2R DAC I wouldnt have been interested in hearing it.



I put a lot of stock in what is happening in the DIY world, I might be crazy but I think some of the best gear is being made by DIYers / engineers in that arena, and quite a few people over on diyAudio are designing D/S DACs to much acclaim, so I'm sure it can be done well.


----------



## L0rdGwyn

I've returned from COVID hell, back to DIY.  I've pretty much exhausted my options for these metal grills covers for the Klipsch Forte IV.  I reached out to Speakerworks for custom grills but wasn't really impressed with what they had to say, so of course I am going to DIY it.

There is an advantage to making them myself - I can make them look cool.  Right now my vague plan is to order the speakers along with a pair of spare grills from Klipsch.  Once I get the dimensions, I am going to order some cut-to-size perforated metal sheets (lots of dealers online).  I'll remove the original plastic grill cloth, likely apply a cloth grill material (potentially a colored type, for additional swag).  I'll then paint / coat the cut perforated sheets (probably black), then apply them in front of the grill cloth, probably screwed down to the grill substrate.

What I like about this idea is having control of how they look.  Just as an example, I could do a maroon grill cloth with this type of perforated metal sheet over top of it, primed and painted black.




Other patterns are available, this one just jumped out to me, could give the speakers that vintage Altec Valencia type of look, which I think would be nice.



Anyway, going to try and finalize these plans today.  Will be replacing the second Snell driver surround and working on the bronze Airmid today.


----------



## Mr Trev

L0rdGwyn said:


> I've returned from COVID hell, back to DIY.  I've pretty much exhausted my options for these metal grills covers for the Klipsch Forte IV.  I reached out to Speakerworks for custom grills but wasn't really impressed with what they had to say, so of course I am going to DIY it.
> 
> There is an advantage to making them myself - I can make them look cool.  Right now my vague plan is to order the speakers along with a pair of spare grills from Klipsch.  Once I get the dimensions, I am going to order some cut-to-size perforated metal sheets (lots of dealers online).  I'll remove the original plastic grill cloth, likely apply a cloth grill material (potentially a colored type, for additional swag).  I'll then paint / coat the cut perforated sheets (probably black), then apply them in front of the grill cloth, probably screwed down to the grill substrate.
> 
> ...


I vote for the bottom picture - that's a damn good looking loudspeaker!


----------



## L0rdGwyn

Mr Trev said:


> I vote for the bottom picture - that's a damn good looking loudspeaker!



That's the inspiration, what I'm going to do most likely is the pattern above painted matte black and will mount it in front of a colored grill cloth.

So this gothic pattern in matte black.



Mounted in front of this burgundy grill cloth.



On this speaker.



Might change my mind on the color, could do a green or black on black, we'll see, going to call to order the speakers today!


----------



## Xcalibur255

The gothic pattern is very sharp looking.


----------



## L0rdGwyn

Xcalibur255 said:


> The gothic pattern is very sharp looking.



Thanks, I think so too!  It's a 58% open pattern so it will work well, the diamonds are probably a little less than 1" across from side to side.  There is enough space on the "X" areas to drill holes, that is how I will mount it to the magnetic grill substrate.  I am thinking I will do black on black actually.  Depending on what the cuts cost, might order one extra to experiment with different coats / colors.


----------



## miketlse

cdanguyen08 said:


> I saw that on their website as well. I was confused at first but then I went to the Baltic 3 whatsbestforum and had seen someone else get that option.
> 
> I'll take a look at them Focals! I'll have to pitch the living room for big listening to the wife.


I tried the Focal Aria 936 driven by a Chord Hugo 2, at approx half power.
They turned out to be amongst my best experiences for listening to quietish jazz, but with low powered amps.
Overall - there is no need to use mega-powered amps, so plenty of opportunity for those happy to explore lower powered amps.


----------



## Mr Trev

L0rdGwyn said:


> That's the inspiration, what I'm going to do most likely is the pattern above painted matte black and will mount it in front of a colored grill cloth.
> 
> So this gothic pattern in matte black.
> 
> ...


I do like the pattern on the Altec better, but they're your speakers
What material is the grille made of? Something that could be blued? Don't know why, but I'm a sucker for bluing


----------



## L0rdGwyn

Mr Trev said:


> I do like the pattern on the Altec better, but they're your speakers
> What material is the grille made of? Something that could be blued? Don't know why, but I'm a sucker for bluing



Yeah the Altec pattern isn't going to be available commercially since those speakers are 55-years-old, there is another gothic pattern that is interesting, could consider it, but the size of the holes is larger, nearly 1.5" across, so have to weigh that against the cat protection they will offer since that is the primary purpose of the project.  The material is cold rolled steel.

Here is the other gothic pattern.


----------



## jgwtriode

Sweet deal!   Just out of curiosity how good are the stock crossovers, wiring and connectors at this level of Klipsch.   So I trust you will be redoing the crossover and wiring.  How do their drivers compare with other high end  audio speaker manufacturers.   When I was in college I thought Klipsch corner horns were the ultimate.  Then I had a friend get Infinity RS 4.5s and the high end game started for me at the age of 21. Some 40 years later still at it!

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Sweet deal!   Just out of curiosity how good are the stock crossovers, wiring and connectors at this level of Klipsch.   So I trust you will be redoing the crossover and wiring.  How do their drivers compare with other high end  audio speaker manufacturers.   When I was in college I thought Klipsch corner horns were the ultimate.  Then I had a friend get Infinity RS 4.5s and the high end game started for me at the age of 21. Some 40 years later still at it!
> 
> Happy listening,
> 
> jgwtriode



The stock crossovers will need some work, they use sandcast resistors (ew), film caps, iron core inductors.  Will most definitely be swapping out the resistors, likely the inductors, and MAYBE the caps if I can find equivalent values at better quality (the crossovers use some very oddball cap values).  All of the Klipsch drivers are proprietary, can't say how they compare to other designers specifically, but I will say the most recent iteration of their Heritage line (version IV) has been very well received.  I've seen members on Audiokarma say they would take the new Heritage line over vintage Altecs like the model 19 and many old JBLs.  Pretty hard to find a bad review of these speakers, specifically the Forte IV and Cornwall IV, most everyone seems to say they are a knockout.  The horn speaker / high-sensitivity speaker market is pretty small, I've signed onto living in that niche given I am running single-ended class A tube amps.  My 801A amp is a beastly 7-watter  the 99dB in room sensitivity of the Forte IV is a good match, loved what I heard from them when demo'd.  Other players in the high-sensitivity market that aren't ultra expensive are Volti Audio, Zu Audio, Omega, Fern & Roby...open baffle is another option but again, not great having exposed wires / drivers with cats.  Klipsch is a nice choice since they are a mainstream brand that isn't bonkers expensive, I don't have to cry if something breaks, I can just get it replaced without too much stress.


----------



## Xcalibur255

1.5" is MORE than enough to allow access for mischievous paws.

Best part of all is he'll be watching you the whole time you're working on them with that "YES HUMAN TOIL FOR ME" expression we all love so much.


----------



## bcowen

jgwtriode said:


> Would love to see photos of the Jota.   Loved the sound of their PX-25, which I got to play with years ago.  Had a number of customers using Jotas on the Talon Khorus back in the day when I used to work for them.  Wonderful Amps!
> 
> jgwtriode


Mine is the high current version requiring high current 300B's (300BXLS). Limits the tube rolling options for sure, but it gets almost 22wpc out of an SET.  I've had a lot of amps pass through my hands over the years, and this one remains my favorite.


----------



## bcowen

L0rdGwyn said:


> The stock crossovers will need some work, they use sandcast resistors (ew), film caps, iron core inductors.  Will most definitely be swapping out the resistors, likely the inductors, and MAYBE the caps if I can find equivalent values at better quality (the crossovers use some very oddball cap values).  All of the Klipsch drivers are proprietary, can't say how they compare to other designers specifically, but I will say the most recent iteration of their Heritage line (version IV) has been very well received.  I've seen members on Audiokarma say they would take the new Heritage line over vintage Altecs like the model 19 and many old JBLs.  Pretty hard to find a bad review of these speakers, specifically the Forte IV and Cornwall IV, most everyone seems to say they are a knockout.  The horn speaker / high-sensitivity speaker market is pretty small, I've signed onto living in that niche given I am running single-ended class A tube amps.  My 801A amp is a beastly 7-watter  the 99dB in room sensitivity of the Forte IV is a good match, loved what I heard from them when demo'd.  Other players in the high-sensitivity market that aren't ultra expensive are Volti Audio, Zu Audio, Omega, Fern & Roby...open baffle is another option but again, not great having exposed wires / drivers with cats.  Klipsch is a nice choice since they are a mainstream brand that isn't bonkers expensive, I don't have to cry if something breaks, I can just get it replaced without too much stress.


Add Tekton to the list -- my Lores are 98dB sensitive and rock the house with 22 watts.  Rather unconventional design by audiophile standards (whizzer cone guitar amp drivers, anybody?  ) but they're a lot of fun and pretty cheap to boot.


----------



## L0rdGwyn

bcowen said:


> Add Tekton to the list -- my Lores are 98dB sensitive and rock the house with 22 watts.  Rather unconventional design by audiophile standards (whizzer cone guitar amp drivers, anybody?  ) but they're a lot of fun and pretty cheap to boot.



Oh yeah, totally forgot Tekton Design!  Right there with the rest of them sensitivity-wise.  Decware also has some pretty high-sensitivity designs.


----------



## L0rdGwyn

Zach sends me unfinished black and white ebony VC cup photo.  Will be finished in a gloss, should make the contrast pop.


----------



## bcowen

L0rdGwyn said:


> Zach sends me unfinished black and white ebony VC cup photo.  Will be finished in a gloss, should make the contrast pop.


OK, I'm officially jealous.  That's gorgeous!


----------



## Mr Trev

L0rdGwyn said:


> Zach sends me unfinished black and white ebony VC cup photo.  Will be finished in a gloss, should make the contrast pop.


hmmm… with no finish, it kind of looks like a giant oyster shell
mmmm… oysters…


----------



## Nicolas Yance

L0rdGwyn said:


> Zach sends me unfinished black and white ebony VC cup photo.  Will be finished in a gloss, should make the contrast pop.


That's the wood I always dream of for a VO, I even asked Zack if he would be able to take a custom order but he denied because of workload, this was in 2020.


----------



## L0rdGwyn

Nicolas Yance said:


> That's the wood I always dream of for a VO, I even asked Zack if he would be able to take a custom order but he denied because of workload, this was in 2020.



Yes, he is quite busy all the time these days!  
 Especially after the ZMF November event. 
 This was in exchange for the custom amplifier I made him recently.


----------



## jgwtriode

bcowen said:


> Mine is the high current version requiring high current 300B's (300BXLS). Limits the tube rolling options for sure, but it gets almost 22wpc out of an SET.  I've had a lot of amps pass through my hands over the years, and this one remains my favorite.


Hot Damn that is one sweet amp.  I really wanted to get an Art Audio Amp was close to getting one on incentive pricing.  Just didn't quite work out.  But I talked to 4 or 5 customers that swore by this high current version on thier Talon Audio speakers.  I will bet that thing looks ridiculous in the dark when it switched on.   

Thanks for sharing,

jgwtriode


----------



## jgwtriode (Jan 11, 2022)

Nicolas Yance said:


> That's the wood I always dream of for a VO, I even asked Zack if he would be able to take a custom order but he denied because of workload, this was in 2020.


OMGosh that is stunning.  I really like darker wood.  My Auteurs in Blackwood and my VC's in Leopard dark stain,  but wow really nice for a lighter colored wood.

jgwtriode.


----------



## Xcalibur255

L0rdGwyn said:


> Oh yeah, totally forgot Tekton Design!  Right there with the rest of them sensitivity-wise.  Decware also has some pretty high-sensitivity designs.



I've been curious about Decware's horn and slot loaded designs.  It's interesting how Omega, Zu and Tekton all get pretty different voicing out of similar full range drivers.


----------



## whirlwind

L0rdGwyn said:


> Zach sends me unfinished black and white ebony VC cup photo.  Will be finished in a gloss, should make the contrast pop.



Those are going to look killer, Keenan.

Zach told me if he hits the cups with a wipe of alcohol, you can see what they are going to look like to a certain extent.

I bet you can already picture them, right beside one of you amps


----------



## Nicolas Yance

L0rdGwyn said:


> Yes, he is quite busy all the time these days!
> Especially after the ZMF November event.
> This was in exchange for the custom amplifier I made him recently.


Please post some pictures when you get the final product.


----------



## L0rdGwyn

Nicolas Yance said:


> Please post some pictures when you get the final product.



I sure will.  Here is a pic of the bookmatched cups before sanding.



Worked on the bronze Airmid today, made some good progress, think that will be all for now, off to do some yoga 🧘‍♂️


----------



## raindownthunda

L0rdGwyn said:


> I sure will.  Here is a pic of the bookmatched cups before sanding.
> 
> 
> 
> Worked on the bronze Airmid today, made some good progress, think that will be all for now, off to do some yoga 🧘‍♂️


Two museum pieces in the making. My jaw is already dropping with how that layered grain looks on your VC. They are going to look unreal once finished.


----------



## jgwtriode (Jan 13, 2022)

Wow he even almost  bookmatched them oh my gosh, that is truely amazing looking.  Very unique.  Might aruguably be the most unique pair of ZMF headphones out there.  That bronze Airmid looks very impressive as well!

jgwtriode


----------



## L0rdGwyn

I replaced the surround of the other Snell J/II, now matched.




Having a final listen.  Rather than selling them, tomorrow I am going to gift them to a friend.  I think they're worth more than I could sell them for, so I'll live happier knowing they are being used by him.  He isn't an audiophile...yet.  I am planting the seed 



Have a buyer for the Sound Anchors, will get that done this weekend.  Forte IV are shipped and on the way, will probably have them next week, but they will stay in the boxes until I finish modifying the grills.

Busy week, back to the bronze Airmid build now.


----------



## Xcalibur255

I like to gift stuff when I can.  It's more satisfying than selling.


----------



## L0rdGwyn

Agreed!  I'd only make a few hundred bucks if sold, IMO that isn't worth it, better to infect a friend with my interests.


----------



## Zachik

L0rdGwyn said:


> Agreed!  I'd only make a few hundred bucks if sold, IMO that isn't worth it, better to infect a friend with my interests.


I wish I had friends like you, Keenan!!!


----------



## bcowen

L0rdGwyn said:


> Agreed!  I'd only make a few hundred bucks if sold, IMO that isn't worth it, better to infect a friend with my interests.


Yeah, so are you doing him a favor, or cursing him with something that will continuously drain his wallet until the end of time?   🤣🤣


----------



## L0rdGwyn

bcowen said:


> Yeah, so are you doing him a favor, or cursing him with something that will continuously drain his wallet until the end of time?   🤣🤣



I'll make him one of us, it's a shared curse, we all most bear it lol.  He probably won't fall too far down the hole though, he has his own obsessive hobbies, coffee roasting and expensive vintage Italian espresso machines.  We will see


----------



## CJG888

Then he needs to get into tube amps. Same aesthetic!


----------



## L0rdGwyn

@CJG888 we'll see how committed he is, if he asks me about tube amps, I'll know I've got him 

I listened to these speakers for a few hours last night, makes me sad to see them go, but the new setup will be better.  I've started investigating what it will take to upgrade the crossover in the Forte IV.  If done to my usual standards, it will be very expensive.  Eight inductors, four resistors, nine film caps per crossover, that adds up to big bucks when you are talking audiophile grade parts.  I'll probably still do it, but unsure of the timeline.


----------



## L0rdGwyn

Nothing major to report, just sharing a pic of the finished black and white ebony VC ear cups.  Finish is gloss lacquer.


----------



## jgwtriode

Gorgeous woodworking art!  Congrats again Keenan! Zach has created a masterpiece!


jgwtriode


----------



## Smallpie

L0rdGwyn said:


> Nothing major to report, just sharing a pic of the finished black and white ebony VC ear cups.  Finish is gloss lacquer.


Hopefully they have enough wood for a Ltd run of this. Looks amazing!


----------



## L0rdGwyn

Akiravelvet said:


> Hopefully they have enough wood for a Ltd run of this. Looks amazing!



Thanks!  I'm sorry to say doing a run with this wood isn't practical.  It is hard to find, takes years to dry it out, large quantities just aren't available unfortunately.


----------



## Monsterzero

I used to have a pair of GradoMagnums with zebrawood cups that looked similar. Ironically, when I first met Zach I asked him to make a pair of Atticus in heavily contrasted zebrawood, but his blanks didnt have the high contrast stripes to them.


----------



## L0rdGwyn

Monsterzero said:


> I used to have a pair of GradoMagnums with zebrawood cups that looked similar. Ironically, when I first met Zach I asked him to make a pair of Atticus in heavily contrasted zebrawood, but his blanks didnt have the high contrast stripes to them.



Zebrawood would be a good alternative with a similar aesthetic for sure.


----------



## jgwtriode

Akiravelvet said:


> Hopefully they have enough wood for a Ltd run of this. Looks amazing!


Well I think the point here is that this is kind of a unique one off thing.   And rightfully so, it should be!  Something unique, especially the book matching,  in return for something as unique and special as that 45 Zach now has.   So honestly I kind of hope not.  



Happy listening,

jgwtriode


----------



## Nicolas Yance

L0rdGwyn said:


> Nothing major to report, just sharing a pic of the finished black and white ebony VC ear cups.  Finish is gloss lacquer.


Amazing congratulations!


L0rdGwyn said:


> Thanks!  I'm sorry to say doing a run with this wood isn't practical.  It is hard to find, takes years to dry it out, large quantities just aren't available unfortunately.


I´m sad now but I can understand the reason. You both trade it unique pieces of audio gear.


----------



## bcowen

L0rdGwyn said:


> Nothing major to report, just sharing a pic of the finished black and white ebony VC ear cups.  Finish is gloss lacquer.


Damn.  That's just plain gorgeous.  Honestly, I was a bit underwhelmed with the first pictures of the unfinished cups, but the gloss, contrast, and depth of grain now that they're finished has me totally 'whelmed'.


----------



## jgwtriode (Jan 18, 2022)

Indeed well glossed wood is gorgeous, very showy.  But there is something about the feel, touch and earthy richness of raw wood that does get lost.  I have some well figured waterfall bubinga and a moderate size piece of Wenge that I was going to use for  a project.  Basically small pieces of sheet lumber.  I just love looking at them in there raw but cut and sanded form!

Happy listening,

jgwtriode


----------



## triod750

I like to look at and touch wood, as a wonder of nature...


----------



## andypat

L0rdGwyn said:


> Just need to do the input and output wiring, which won't take long, then put some feet on the bottom.  But first, lunch!



This is awesome! What wiring method did you end up using for the input and output: shielded or twisted pair?

Cheers!


----------



## L0rdGwyn

andypat said:


> This is awesome! What wiring method did you end up using for the input and output: shielded or twisted pair?
> 
> Cheers!



Both! I use shielded twisted pair for the input wiring to reduce noise pickup.


----------



## andypat

L0rdGwyn said:


> Both! I use shielded twisted pair for the input wiring to reduce noise pickup.



Best of both worlds! Thanks


----------



## whirlwind

L0rdGwyn said:


> Nothing major to report, just sharing a pic of the finished black and white ebony VC ear cups.  Finish is gloss lacquer.



What a gorgeous set of cups


----------



## L0rdGwyn

whirlwind said:


> What a gorgeous set of cups



Thanks, Joe, looking forward to getting them, should be soon.

Sorry I haven't been updating here, very busy at work, won't let up any time soon.  Going to try and finish this other Airmid over the weekend.  Will be picking up my Klipsch speakers on Monday, then will finalize plans of the metal grills and order materials.  When I've had time, I've been playing with the idea of building a high-power amplifier (by my standards).  Just ideas at the moment, poring over schematics, building sims, etc.  If I do it, will go one of two different directions.

A) Triode push-pull class A design using 6336 or 6528.

B) Solid state single-ended class A design using the THF-51S V-FETs.

My girlfriend uses the stereo in my bedroom often, and truth be told, the 1.5W that 45 amplifier is putting out isn't ideal for the 90dB/W Klipsch KG1s I have up there.  For low-level listening it's fine, but she has admitted it would be nice to turn it up now and then, and the low-end performance would benefit.  I want to rebuild that 45 amplifier, so in theory this high-power design would replace it while I do the rebuild.

Think I still have a pair of 6336 around here for option A.  With two sections per tube, would only need a pair.  Design would go input gain stage > long-tailed pair > 6528 / 6336.  For the input stage, gain requirements would be low without using NFB, but could either use a high-gain triode or pentode input and play with adding some GNFB.

Option B is a little more approachable as I have a functional schematic for a THF-51S power amplifier, still need to work on the power supply.  It would either need a preamp stage to make it an integrated or be paired with a dedicated preamp.  Messing with solid state preamp stages this morning, but could also throw together a simple tube pre.  My power amplifier design as it stands right now (in simulation) can do something like 40W at less than 1% THD.

So anyway, that's sort of what I've been working on in the background, making some plans.  Will post some pics of the bronze Airmid when I finish it.


----------



## jgwtriode

Did Zach make a second set of these?  I see 4 cups in this picture.  So is making himself a pair from this wood as well?  Would not blame him at all for doing so!

Very curious!

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Did Zach make a second set of these?  I see 4 cups in this picture.  So is making himself a pair from this wood as well?  Would not blame him at all for doing so!
> 
> Very curious!
> 
> ...



Yup, the other pair is his.  In fact, the black and white ebony was his idea.


----------



## jgwtriode

Sweet deal!  Zach definitely has an incredibly artistic sensibility.  I think that carries over into everything he does.  You can actually  hear it in his headphone tuning.  No other headphones I have listened to are as musical or organic sounding.  And as good as The Paradox Slant was in that regard and my super tweaked HD 650.  The Auteur clobbered either of them particularly in that way.  The VC is even more so.  All though it is not as lush as the Auteur, but even in the midrange it actually sounds more like real instrument and voices  playing together.   The Auteur is about 80 to 85% of that with a wonderfully euphonic tonality and richness that is hard to walk away from. But, when the VC is fully broken in and your system is tuned to exploit what it does; then you know that the VC is, in fact,  not just technically better but also musically and emotionally a much more satisfying headphone.   The best part of the VC is how it balances tone, harmonic structure and both instrumental and vocal textures so incredibly well.

Happy listening,

jgwtriode


----------



## bcowen

L0rdGwyn said:


> Sorry I haven't been updating here, very busy at work, won't let up any time soon.  Going to try and finish this other Airmid over the weekend.  Will be picking up my Klipsch speakers on Monday, then will finalize plans of the metal grills and order materials.  When I've had time, I've been playing with the idea of building a high-power amplifier (by my standards).  Just ideas at the moment, poring over schematics, building sims, etc.  If I do it, will go one of two different directions.
> 
> A) Triode push-pull class A design using 6336 or 6528.
> 
> *B) Solid state single-ended class A design using the THF-51S V-FETs.*


This is a family friendly forum.  Please don't swear, even if it _is _your thread.

😂🤣😂


----------



## L0rdGwyn (Jan 22, 2022)

bcowen said:


> This is a family friendly forum.  Please don't swear, even if it _is _your thread.
> 
> 😂🤣😂



Lol well I've already used a bunch of hybrid circuits here, I'm not averse to the ways of the sand  this wouldn't be your typical solid state affair though, these VFETs behave like triodes, but can push a lot more current.  I'm a little afraid of how good the amp might sound actually...

Thinking it over some more, I am going to go the solid state VFET route rather than the tube class A push pull, I did spend a few hundred bucks on these transistors after all, they are on the verge of extinction.  I went down this deep rabbit hole of designing a VFET amplifier a while back, looks like I was pretty serious about it LOL I have a nice draft of the power amplifier circuit with a JFET input buffer, using some Lundahl grid and filament chokes in the design too.

On the front end, probably going to pair it with a type 37 / type 76 linestage and design the two chassis to stack.  So it will go type 37 gain stage > JFET buffer > THF-51S output stage.  Probably will back off the bias current on the THF-51S from my original design though to make the heatsinking and chassis size more manageable.  So maybe a 30W amplifier, single-ended, class A, no negative feedback.

Here are the transistors.  I only need two but for some reason I bought six...the two strapped together are a closely matched pair, will use the roughly matched quad for testing.




At the time I was planning this, I bought some really nice custom made insulating pads from a guy on diyAudio.  First time I have looked at them.



I have some nice engraved base Sylvania and mesh plate Silvertone type 37 for the linestage.  Could take type 76 as well as I mentioned.



I'll sorta work on this in the background, but could be a cool project.


----------



## jgwtriode (Jan 24, 2022)

So better to spend 500 plus on NOS 5998 Tung sols.  How many hours can they have on them and still be considered worth buying.  Saw some for about $400 with 500 to 600 hours on them.  Better to just pay more and get NOS when possible.  Found some GEC L63's from India NOS matched and tested for $ 200.00 which seems almost reasonable.  Just looking at where the tax return dollars are going after final payment for the Airmid.


*Up for Sale 1Matched Pair (2Pcs.)
NOS 6J5G L63 GEC 
The Photos are actual Photos of tubes you are buying
Made in England
Black coated glass
Black Base, Clear Glass
New in Original GVT Box
Tested Advance Digital Tube Tester Amplitrex AT1000*
          Sr.No.2660004 T1=la=10.8ma  Gm=2800
                                       Sr.No.2660003 T1=la=10.0ma  Gm=2800                   

*NOS Gm Specification*​*2600*​Tube 1 Test Results​2800 (107.69%)​Tube 2 Test Results​2800 (107.69%)​
What do you think Keenan?     

One other thing what Kind of life expectancy do these and the tungsols have in the Airmid?


Thanks,

jgwtriode


----------



## pravous

Another place you might want to check is Billington Export Limited.  I bought a pair of l63 from them and was quite happy.


----------



## jgwtriode

pravous said:


> Another place you might want to check is Billington Export Limited.  I bought a pair of l63 from them and was quite happy.


Thanks I will check there.  Appreciate it.


----------



## jgwtriode

Just messing around making a logo sticker.  I like doing that.  Was thinking could make a transfer sticker or even a T shirt.  Just got on Zazzle and was fiddling.


----------



## L0rdGwyn

jgwtriode said:


> So better to spend 500 plus on NOS 5998 Tung sols.  How many hours can they have on them and still be considered worth buying.  Saw some for about $400 with 500 to 600 hours on them.  Better to just pay more and get NOS when possible.  Found some GEC L63's from India NOS matched and tested for $ 200.00 which seems almost reasonable.  Just looking at where the tax return dollars are going after final payment for the Airmid.
> 
> 
> *Up for Sale 1Matched Pair (2Pcs.)
> ...



Hey @jgwtriode - it's hard to put an exact number on how long the tubes will last, I've personally never used a pair of 5998s to the point of being unusable.  I think it's common for OTL users to have a few different output tubes they like to rotate in, so spreading the use around keeps them all going for years.  Also, both the input and output tubes are not being operated anywhere near their maximum plate dissipation.  In addition, the heaters are brought up to temperature before the soft-start B+ is applied, this is the gentlest way to bring the tubes up to operation and should help extend their life.

The seller whose listing you showed above is trustworthy, his prices can sometimes be on the higher end but he has a good selection of tubes and fast international shipping times in my experience.

With all of that being said, you might want to wait and try it with the stock tubes first.  I was listening last night to the bronze Airmid (which is nearly done, just one change to make in circuit and some feet added to the chassis).  The stock Russian tubes sound quite good.  Of course there are more gains to be had with 5998, but I thought to myself "one could be happy with these affordable tubes for a long time."  Also worth noting when Zach had the amp, he only listened with the stock tubes.  So just depends on if you want to try the "best" or spend some time with the stock tubes and see if you feel the need to upgrade.


----------



## jgwtriode

L0rdGwyn said:


> Hey @jgwtriode - it's hard to put an exact number on how long the tubes will last, I've personally never used a pair of 5998s to the point of being unusable.  I think it's common for OTL users to have a few different output tubes they like to rotate in, so spreading the use around keeps them all going for years.  Also, both the input and output tubes are not being operated anywhere near their maximum plate dissipation.  In addition, the heaters are brought up to temperature before the soft-start B+ is applied, this is the gentlest way to bring the tubes up to operation and should help extend their life.
> 
> The seller whose listing you showed above is trustworthy, his prices can sometimes be on the higher end but he has a good selection of tubes and fast international shipping times in my experience.
> 
> With all of that being said, you might want to wait and try it with the stock tubes first.  I was listening last night to the bronze Airmid (which is nearly done, just one change to make in circuit and some feet added to the chassis).  The stock Russian tubes sound quite good.  Of course there are more gains to be had with 5998, but I thought to myself "one could be happy with these affordable tubes for a long time."  Also worth noting when Zach had the amp, he only listened with the stock tubes.  So just depends on if you want to try the "best" or spend some time with the stock tubes and see if you feel the need to upgrade.


Appreciate that insight Keenan, will have to think about that.  Found Tungsols but at 550 to 600 a pair ouch for slightly used that seem to measure well.   

Checking another supplier who has some GEC L63.  His price is a bit better.  He has a pair that match within 10% is that close enough  for proper channel matching?


Thanks,

James


----------



## Xcalibur255

Both Keenan and I have bought from the seller in India.  They're the real deal and a safe source of L63 tubes.  They also have quite a few of the Brimars too which are also a fine choice.

Are NOS 5998s really selling for $500 now?  That's insane.  I'm almost a little tempted to sell my backup pair at those prices, but somewhere down the line I'll probably wish I still had them........


----------



## Xcalibur255

L0rdGwyn said:


> Lol well I've already used a bunch of hybrid circuits here, I'm not averse to the ways of the sand  this wouldn't be your typical solid state affair though, these VFETs behave like triodes, but can push a lot more current.  I'm a little afraid of how good the amp might sound actually...
> 
> 
> I'll sorta work on this in the background, but could be a cool project.



I've been growing more and more interested in this route too, wondering if one can match or exceed the performance of a Pass Labs INT-25 for a fraction of the price.  No doubt the answer is yes given the how much money is sunk by their distributor markup and fancy casework.


----------



## jgwtriode

Just one other question.  Current measurement does that matter?  i see anywhere from 6ma up to around 11ma on the test data.  Is that important?

Thanks


----------



## Xcalibur255

Unless your amp requires you to manually bias this gain stage you generally don't have to worry about it too much.  A new 6J5 should pull around 9mA.  A substantially lower number can be one indication of tube age and usable life remaining.  It's fairly uncommon to even have this piece of info as no vintage tube testers are able to check/report it.  That's an advantage of the Amplitrex system and some of the newer curve tracers out there.


----------



## L0rdGwyn

jgwtriode said:


> Checking another supplier who has some GEC L63.  His price is a bit better.  He has a pair that match within 10% is that close enough  for proper channel matching?



Most likely, yes.  Unfortunately, the measurements made by sellers do not tell you about mu, the gain of the tube.  That is what is ultimately responsible for proper channel matching, but conventional tube testers do not test for it.  Generally, if the tubes test reasonably close to NOS, the mu should be close enough to not cause a noticeable channel imbalance.



jgwtriode said:


> Just one other question.  Current measurement does that matter?  i see anywhere from 6ma up to around 11ma on the test data.  Is that important?



It depends on the tested operating point, but if using the operating points from the datasheet, which is often the case, 9mA would indicate a NOS value.


----------



## L0rdGwyn

Xcalibur255 said:


> I've been growing more and more interested in this route too, wondering if one can match or exceed the performance of a Pass Labs INT-25 for a fraction of the price.  No doubt the answer is yes given the how much money is sunk by their distributor markup and fancy casework.



There is quite a following for Firswatt style amplifiers in the DIY world, so no doubt there is something to it!  The cost would be lower than a new Firstwatt design for sure.  I am going to do this project, have a few schematics drafted, should sound pretty good.


----------



## L0rdGwyn

It is finally a new speaker day for me, horn style 

I ended up having to make two trips to dealer, the Forte IV boxes are huge.  Made one trip yesterday, but of course it has been snowing in NE Ohio for like a week straight, so after yet another blizzard, I went and picked up the second one today (couldn't fit both in my car, my girlfriend's hatchback has a tire leak, go figure).

First thing I did was rip apart one of the stock grills and take measurements.  Kept the badges in case I want to put them on my modded grills.



Will sand off the residual glue, drill holes for mounting the perforated metal front plate, apply new grill cloth (black), then attach the perforated metal grill on the front.  I found an architectural grill company to make the metal grills for me.  They are going to machine them to my spec in aluminum, with mounting holes, then anodize them in black satin.  Here are the dimensions, blank center is where the pattern will be, which I obviously could not build out in CAD.  Gothic pattern I chose on the right (not to scale).

 

Going to be a six week lead time given the anodization.  How to stop those dastardly cats from destroying the speakers for six weeks when I can't supervise?  A genius invention.



Magnetic cardboard, that'll stop them.

Before listening to the speakers, I swapped out the garbage jumpers included for some nice DH Labs jumpers.



So that's it, plans are made for the DIY grills, in the meantime I'll put the cardboard grills on when not in use.

Now we can listen 



But just for a bit, gotta finish off that Airmid today, just one hour of work left...


----------



## Xcalibur255

Those are really the binding post jumpers they came with?  These speakers are going to sound 1000% better when you're done with them.


----------



## bcowen (Jan 25, 2022)

Xcalibur255 said:


> Both Keenan and I have bought from the seller in India.  They're the real deal and a safe source of L63 tubes.  They also have quite a few of the Brimars too which are also a fine choice.
> 
> Are NOS 5998s really selling for $500 now?  That's insane.  I'm almost a little tempted to sell my backup pair at those prices, but somewhere down the line I'll probably wish I still had them........


I picked this one up recently for $100.  IBM branded, true blue TungSol 5998.  Tests quite well with nicely balanced triodes and GM over bogey.  Seller had some pairs up for auction at the same time...they went for less than $250 (pair) IIRC.  Timing maybe, or perhaps some potential buyers thinking an IBM labeled tube wasn't a Tung Sol.

Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago.  I love the 5998, but the Chatham is my favorite 6AS7G.


----------



## bcowen

L0rdGwyn said:


> It is finally a new speaker day for me, horn style
> 
> I ended up having to make two trips to dealer, the Forte IV boxes are huge.  Made one trip yesterday, but of course it has been snowing in NE Ohio for like a week straight, so after yet another blizzard, I went and picked up the second one today (couldn't fit both in my car, my girlfriend's hatchback has a tire leak, go figure).
> 
> ...


Nice!!  And not too huge for the space.


----------



## L0rdGwyn (Jan 26, 2022)

Here is the bronze Airmid.  Took me a little longer than expected as I had to troubleshoot an oscillating component.  Think I tracked it down, but still need to do some more testing to be certain.  So I'm gonna call it 99% done.  I already took the pictures though, so here they are.











Sounds pretty good to me!


----------



## L0rdGwyn

Xcalibur255 said:


> Those are really the binding post jumpers they came with?  These speakers are going to sound 1000% better when you're done with them.



Yeah those jumpers are pretty crappy!  Might end up changing the binding posts too.  I hope so, upgrading the crossover will be a project, likely will add damping to the horns as well.  That's pretty much what I have planned for them long term - modded grills, new binding posts, upgraded crossover, horn / driver damping.


----------



## jgwtriode

Yeah wow, could have at least done copper buss bars!


----------



## bpiotrow13 (Jan 26, 2022)

bcowen said:


> I picked this one up recently for $100.  IBM branded, true blue TungSol 5998.  Tests quite well with nicely balanced triodes and GM over bogey.  Seller had some pairs up for auction at the same time...they went for less than $250 (pair) IIRC.  Timing maybe, or perhaps some potential buyers thinking an IBM labeled tube wasn't a Tung Sol.
> 
> Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago.  I love the 5998, but the Chatham is my favorite 6AS7G.


Nice, I got the IBM/Tung Sol 5998 pair from the same seller I believe he sold two pairs and two single 5998 at the same time.

Chatham is the same as Tung Sol I believe.


----------



## bpiotrow13

Xcalibur255 said:


> Are NOS 5998s really selling for $500 now? That's insane. I'm almost a little tempted to sell my backup pair at those prices, but somewhere down the line I'll probably wish I still had them........


I started buying 5998 and some other tubes so that I have a couple of spare pairs. In a year or two I may not be able to afford them...

Somebody really needs to start current production..


----------



## whirlwind

bcowen said:


> I picked this one up recently for $100.  IBM branded, true blue TungSol 5998.  Tests quite well with nicely balanced triodes and GM over bogey.  Seller had some pairs up for auction at the same time...they went for less than $250 (pair) IIRC.  Timing maybe, or perhaps some potential buyers thinking an IBM labeled tube wasn't a Tung Sol.
> 
> Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago.  I love the 5998, but the Chatham is my favorite 6AS7G.



Oh wow....I would buy the Chatham 6AS7G for $29 all day long, LOL.


----------



## Xcalibur255

bpiotrow13 said:


> I started buying 5998 and some other tubes so that I have a couple of spare pairs. In a year or two I may not be able to afford them...
> 
> Somebody really needs to start current production..



I suspect the large and plentiful supply of Russian made 6AS7 tubes would have to be mostly dried up before any current tube factory would take an interest in this.  OTL amplifiers are still quite a bit less common too so there isn't enough money to be chased.


----------



## Xcalibur255

bcowen said:


> Also snagged an excellent testing Chatham 6AS7G for $29 a couple weeks ago.  I love the 5998, but the Chatham is my favorite 6AS7G.


Love my Chatham 6520s.  I rarely use them because I have only the one pair.  That classic tube conundrum of not wanting to use the ones you like the most.

The funny part is I almost gave up on them because they were NOISY the first time I ran them.  24 hours later they settled down and stayed quiet after that.


----------



## jgwtriode (Jan 26, 2022)

JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 (78/102ma) - JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts 1956
JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 in white box 1 section) 78ma Gm=4850 1...

What do you thinks of these  Are they worth $59 each?

jgwtriode


----------



## L0rdGwyn

Got the oscillation situation all worked out, bad batch of FETs, swapped to a near-equivalent part, functionally the same, bingo.

So now 100% done.

And I'm off to work!


----------



## bcowen

jgwtriode said:


> JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 (78/102ma) - JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts 1956
> JAN-CAHG-6AS7G Chatham by Tungsol black plates copper grid posts like new 1956 in white box 1 section) 78ma Gm=4850 1...
> 
> What do you thinks of these  Are they worth $59 each?
> ...


Not the best triode balance, but not that bad either.  $59 is a good price...most times I see these on Ebay they are going for $75+.  Finding an excellent testing one for $29 like I did is pretty rare and pure luck these days.


----------



## bcowen

bpiotrow13 said:


> Nice, I got the IBM/Tung Sol 5998 pair from the same seller I believe he sold two pairs and two single 5998 at the same time.
> 
> Chatham is the same as Tung Sol I believe.


Cool!  Do you have a way of testing them?  Hopefully they are as good as the one I got. I debated getting a pair, but my amp only uses a single....and I'm cheap.


----------



## L0rdGwyn

I recently took some repeat measurements of the red Airmid, inputs were the Russian 6S2S (6J5GT) here are the results if anyone is interested in this type of stuff.

*Russian 6AS7G*
Output Z - 50ohm
1mW into 300ohm - 0.11% THD
1mW into 120ohm - 0.22% THD
1mW into 80ohm - 0.31% THD
1mW into 32ohm - 0.67% THD

*Tung-Sol 5998*
Output Z - 30ohm
1mW into 300ohm - 0.032% THD
1mW into 120ohm - 0.094% THD
1mW into 80ohm - 0.15% THD
1mW into 32ohm - 0.38% THD

Frequency response at the two extremes.

300ohm



32ohm



1mW into 300ohm square waves.

1kHz



10kHz



100Hz



1kHz sine wave into 300ohm dummy load just before the onset of clipping. So just about 1W out.


----------



## bcowen

L0rdGwyn said:


> I recently took some repeat measurements of the red Airmid, inputs were the Russian 6S2S (6J5GT) here are the results if anyone is interested in this type of stuff.
> 
> *Russian 6AS7G*
> Output Z - 50ohm
> ...


Pardon my oscilloscope ignorance, but what do the sloping waves at 100Hz indicate (versus the flat waves at 1kHz and 10kHz)?


----------



## L0rdGwyn

bcowen said:


> Pardon my oscilloscope ignorance, but what do the sloping waves at 100Hz indicate (versus the flat waves at 1kHz and 10kHz)?



Sure!  The sloping of the waves gives info on high and low FR.  The curved (as opposed to sharp) leading edge of the 10kHz square wave indicates HF rolloff.  The downward slope of the 100Hz square wave indicates LF rolloff.  It gives some quick qualitative info on FR, but also will show ringing in the circuit, like a bell being rung by the test signal, and often will tease out any potential oscillations that could lead to amplifier instability.


----------



## L0rdGwyn

Here is a good article on square wave testing.

https://sound-au.com/articles/squarewave.htm


----------



## bcowen

L0rdGwyn said:


> Here is a good article on square wave testing.
> 
> https://sound-au.com/articles/squarewave.htm


Thanks!


----------



## L0rdGwyn

Bronze Airmid is away to a friend of Zach's, not sure if he has a Head-Fi account, I guess we'll find out!

I finished up the work on that Zenith radio FINALLY.  But it needs an alignment and I'm not buying an RF signal generator, sent it to a radio dude in Dayton today to do the job for me.

Been loving the Forte IV, they sound great, excellent clarity, body, and totally fill the room.  The fancy grills I concocted are in production, here is how they will look.




Now that I'm caught up on Airmids, taking a break from doing any hardcore amp building for a little bit, got some life stuff to do and need to catch up on some small projects that have been bothering me (e.g., replacing the terrible sockets in my curve tracer).

Always planning future designs too.  Since I have some new headphones on the way, and I am going to be Airmidless soon, I am going to need a headphone amp.  My 6A5G amp is always available, but it is truly a speaker amplifier.  The 841 hybrid headphone amp is going to be broken down soon (another project), so that might become a spud that I have drafted, would be a relatively easy project.

There is one other idea I am playing with though that is a little more ridiculous, an OTL using the Airmid topology but using a pair of 6336 or 6528.  Might just be a flavor of the week type of thing, but I am seriously considering it.  I haven't seen a headphone OTL that uses these tubes at their high current operating points - the 6528 has a gm of 37 mA/V per section, so running them in parallel would bring the theoretical output impedance to something like 15ohm.  This would have to be a whole new design though in terms of layout / chassis as doubling the current through the regulators, tubes, and active loads poses some heat management challenges.  Would consider active cooling using silent Noctua fans with intake below the tubes through the bottom panel.  Would probably do something crazy like 1200uF of film output capacitance too...

We'll see, might have another wild idea tomorrow.  I am on a horrible string of work shifts, eight of of nine days, night shift, thirteen hour shifts, brutal, so maybe I'm losing it lol but I think this OTL would be pretty interesting.  Will have some nice ZMF headphones at the end of the week though when I'm done with work, can't wait.


----------



## Monsterzero

L0rdGwyn said:


> Airmid topology but using a pair of 6336 or 6528.


Im not familiar with a 6528, but wouldnt an OTL that uses 6336s be rather limited when it comes to tube choices? I have two different 6336 pairs, Cetron and another Chatham (iirc) and to my ears , neither are anything special sounding.


----------



## L0rdGwyn (Feb 1, 2022)

Monsterzero said:


> Im not familiar with a 6528, but wouldnt an OTL that uses 6336s be rather limited when it comes to tube choices? I have two different 6336 pairs, Cetron and another Chatham (iirc) and to my ears , neither are anything special sounding.



It would be limited to the 6336 and 6528.  In a circuit that is optimized for them and pushing 300mA each, they would sound very good


----------



## gibosi

If I understand you correctly, while the Glenn can use the 6336 and 6528, the amp is designed around the 6AS7, and isn't optimized to run these high current tubes. I believe the Glenn pushes only 100mA through them versus 300mA per your design. If you do this, I bet it will be a beast! And I, for one, hope you go for it!!


----------



## bcowen

L0rdGwyn said:


> It would be limited to the 6336 and 6528.  In a circuit that is optimized for them and pushing 300mA each, they would sound very good


I always get ticked off when I see the Ebay ads throwing the 6528 and 6336 in as equivalents to 6080's and 6AS7G's.  Some poor newbie is going to take that at face value and end up frying their amp with twice the heater current.  

I'd love to hear an amp optimized for them though.  They're half (or less) the going price of the top tier 6080's and 6AS7's.


----------



## Monsterzero

bcowen said:


> I always get ticked off when I see the Ebay ads throwing the 6528 and 6336 in as equivalents to 6080's and 6AS7G's.  Some poor newbie is going to take that at face value and end up frying their amp with twice the heater current.
> 
> I'd love to hear an amp optimized for them though.  They're half (or less) the going price of the top tier 6080's and 6AS7's.


Glenn suggested the 6336 for driving low Z headphones, so I called Andy over at Vintagetubeservices and he mustve asked me 4-5 times if I was sure my amp could use them. He also refused any type of warranty on the 6336s.

Ive since learned that headphones like the K701 sound pretty spectacular on the GOTL, regardless of which power tube is in there.


----------



## Monsterzero

gibosi said:


> If I understand you correctly, while the Glenn can use the 6336 and 6528, the amp is designed around the 6AS7, and isn't optimized to run these high current tubes. I believe the Glenn pushes only 100mA through them versus 300mA per your design. If you do this, I bet it will be a beast! And I, for one, hope you go for it!!





L0rdGwyn said:


> It would be limited to the 6336 and 6528.  In a circuit that is optimized for them and pushing 300mA each, they would sound very good


What would the sonic benefits be of pushing the 6336 to full capacity, and would those benefits outweigh missing out on some of the more legendary 6as7g and equivalents?


----------



## gibosi

Monsterzero said:


> What would the sonic benefits be of pushing the 6336 to full capacity, and would those benefits outweigh missing out on some of the more legendary 6as7g and equivalents?



You may just have to get in line to get one of these amps to find out. 

And there might be more tube choices than just Chatham / Tung-Sol / Cetron. I'm not sure, but I think that Raytheon also manufactured these tubes. I have a pair labeled Raytheon that don't sound like my Chathams. To my ears, the Raytheons are not as good. And there is also a Thomson - CSF 6336A, made in France. Like the Thomson 6080, vocals are a bit more forward than the Chatham, but I like it with darker drivers and/or rectifiers.

Below, Chatham to the left and Thomson to the right.


----------



## L0rdGwyn

bcowen said:


> I always get ticked off when I see the Ebay ads throwing the 6528 and 6336 in as equivalents to 6080's and 6AS7G's.  Some poor newbie is going to take that at face value and end up frying their amp with twice the heater current.
> 
> I'd love to hear an amp optimized for them though.  They're half (or less) the going price of the top tier 6080's and 6AS7's.



Yeah, the circuit needs are very different!  2x the heater and bias current.  Not easy to do in a small package, likely a reason they aren't being used in a lot of headphone designs, will get scorching hot too.  The price differential is also appealing, given a fully biased 6336 has a similar gm to a 5998 at 1/4 the price.



Monsterzero said:


> What would the sonic benefits be of pushing the 6336 to full capacity, and would those benefits outweigh missing out on some of the more legendary 6as7g and equivalents?



The theoretical benefit is a higher transconductance operating point, which in a cathode follower circuit means lower output impedance and distortion.  Hard to say exactly how they compare as I have not heard them side-by-side, but I do feel there is a correlation between increasing transconductance and increasing soundstage / clarity / detail retrieval in cathode followers.  Transconductance increases as one goes from 6AS7G < 5998 < 7802.  A fully biased 6336 has similar transconductance to a 5998, whereas a fully biased 6528 has a transconductance a little over 2x that of a 5998.



gibosi said:


> You may just have to get in line to get one of these amps to find out.



I'm sorry but not an amplifier I am offering for purchase, just a theoretical DIY project that might come to fruition.  I hope what I post here entertains and maybe inspires other people to get into DIY.  I might choose to do one-off builds for Head-Fiers, but not open for business, so to speak, I just don't have the capacity for it.


----------



## L0rdGwyn (Feb 6, 2022)

I've made moves to build the the 6336 / 6528 OTL, it's happening and it's going to be a beast.

Given the power tubes require twice the heater and bias current, two of the mains transformers used in the Airmid are needed, one for each channel.  The B+ regulators will be dissipating around 12W each, so they will be mounted on a 200mm x 80mm x 40mm heat sink on the rear panel.

The real challenge comes with the increased bias current and power dissipated in the output tube loads.  With the sections paralleled, each 6336 / 6528 will be biased at 300mA, as such the load for each tube will need to dissipate around 34W as they will be dropping roughly half the B+ voltage...LOL.

How to get that done?  Big ass heat sinks.  Going to put big finned heat sinks on the sides of the chassis, 300mm x 80mm x 40mm, courtesy of the diyAudio store.



At 300mA bias, each power tube will be dissipating 24-30W.  They will get hot as hell, so I am going to actively cool them.  I already have a 5V regulated supply powering the time delay circuitry, I am going to beef up the LDO regulator in that position for higher current and add 3-pin fan headers to the PCB.  Will then run a pair of 80mm Noctua NF-A8 5V fans with intake directly below the power tubes.



Output caps are going to be 600uF 450V ClarityCap TC2.  They are huge caps, 77mm diameter by 145mm length.  Don't have a pic, but will look something like the middle cap below.



I have a general idea of the layout, but need to get the parts in, take some measurements before I can finalize.  No prototype, just going to build it.


----------



## bcowen

L0rdGwyn said:


> I've made moves to build the the 6336 / 6528 OTL, it's happening and it's going to be a beast.
> 
> Given the power tubes require twice the heater and bias current, two of the mains transformers used in the Airmid are needed, one for each channel.  The B+ regulators will be dissipating around 12W each, so they will be mounted on a 200mm x 80mm x 40mm heat sink on the rear panel.
> 
> ...


Holy cow.  Are you also going to need a dedicated 30 amp circuit for it?


----------



## triod750

This will be part of your heating system for your home, I presume. You will need some kind of medium to store the heat during summer to use it in the winter. Have you designed that yet?


----------



## L0rdGwyn

bcowen said:


> Holy cow.  Are you also going to need a dedicated 30 amp circuit for it?



Gotta watch out and make sure it doesn't make my wall AC sag LOL (just kidding, should only draw around 2A).



triod750 said:


> This will be part of your heating system for your home, I presume. You will need some kind of medium to store the heat during summer to use it in the winter. Have you designed that yet?



I am going to need it the way it's been snowing around here!  Been buried for a month straight.


----------



## triod750

That explains the 80mm Noctua NF-A8 snow blowers. But I was speaking of summer...


----------



## bcowen

triod750 said:


> That explains the 80mm Noctua NF-A8 snow blowers. But I was speaking of summer...


They need heat in Ohio in the summer too.  😂


----------



## L0rdGwyn

After some conversations, I am also fully back on board the ridiculous HK54 / 35T / 35TG class A2 amplifier design.  Very much a long term project, but I am gonna keep collecting these old triodes and plan for it.  With the parts order for the new OTL, going to grab a pair of 5V 50W SMPS to run the filaments of the HK54.  Using a switching filament supply drastically reduces the pain of running a 5V 5A DHT filament, doing it with a linear supply would be a real challenge.  Right now my design uses around 25dB local NFB, makes about 15W at 0.5% THD in simulation.


----------



## Monsterzero

bcowen said:


> Holy cow.  Are you also going to need a dedicated 30 amp circuit for it?


I have a dedicated 30a for my sound system, cuz I believe in...


----------



## bcowen

Hey @L0rdGwyn , what is this thing and what does it do?  You may recognize it from the capacitor board in the Darkvoice that I'm finally getting around to.


----------



## L0rdGwyn

bcowen said:


> Hey @L0rdGwyn , what is this thing and what does it do?  You may recognize it from the capacitor board in the Darkvoice that I'm finally getting around to.



That's a bridge rectifier.  It rectifies!


----------



## bcowen

L0rdGwyn said:


> That's a bridge rectifier.  It rectifies!


LOL!      Thanks!


----------



## sam6550a

bcowen said:


> LOL!      Thanks!


Or, if you short it out, it rectumfries.


----------



## jgwtriode

Hahahaha...very clever!


----------



## triod750

L0rdGwyn said:


> After some conversations, I am also fully back on board the ridiculous HK54 / 35T / 35TG class A2 amplifier design.  Very much a long term project, but I am gonna keep collecting these old triodes and plan for it.  With the parts order for the new OTL, going to grab a pair of 5V 50W SMPS to run the filaments of the HK54.  Using a switching filament supply drastically reduces the pain of running a 5V 5A DHT filament, doing it with a linear supply would be a real challenge.  Right now my design uses around 25dB local NFB, makes about 15W at 0.5% THD in simulation.


Being wild and crazy seems to come natural to you. Me, I enjoy the ride.


----------



## Zachik

triod750 said:


> Being wild and crazy seems to come natural to you. Me, I enjoy the ride.


Some people opt for cliff jumping or skydiving... @L0rdGwyn goes for extreme amp building!


----------



## jgwtriode (Feb 6, 2022)

So here is the final design I made for a logo.  Going to put it on the transformer can,  It's a painted metal badge basically,  with a black edge and magnetic backing.  $11.00.  Easily worth it.  just add a little extra visual pop on the Airmid.

jgwtriode


----------



## L0rdGwyn (Feb 7, 2022)

Here is what I am doing with the 6336 OTL chassis.  The 40mm heat sinks are in yellow, without them the chassis is 11" x 17.5" x 3.25", they add about 1.5" on each side.  To fit the rear heat sink, moved the IEC inlet and RCA inputs to the top panel.  Will cram two toroids inside a iron transformer shield, in blue.  Not sure of the color yet, might do it in all black, in keeping with the severe look of the heat sinks.





Might as well call this amp The Radiator, that's what it's going to look like lol reminiscent of the Pass Labs Aleph 3.


----------



## whirlwind

L0rdGwyn said:


> Bronze Airmid is away to a friend of Zach's, not sure if he has a Head-Fi account, I guess we'll find out!
> 
> I finished up the work on that Zenith radio FINALLY.  But it needs an alignment and I'm not buying an RF signal generator, sent it to a radio dude in Dayton today to do the job for me.
> 
> ...



Oh man, this will be a nice warm cozy place to sit during these cold Ohio winters!

This would also power some easier to drive planars.

Great project.


----------



## whirlwind (Feb 7, 2022)

gibosi said:


> If I understand you correctly, while the Glenn can use the 6336 and 6528, the amp is designed around the 6AS7, and isn't optimized to run these high current tubes. I believe the Glenn pushes only 100mA through them versus 300mA per your design. If you do this, I bet it will be a beast! And I, for one, hope you go for it!!



This is going to be a great project and what a nice welcome to the VC that is soon to land.


----------



## pravous

L0rdGwyn said:


> Here is what I am doing with the 6336 OTL chassis.  The 40mm heat sinks are in yellow, without them the chassis is 11" x 17.5" x 3.25", they add about 1.5" on each side.  To fit the rear heat sink, moved the IEC inlet and RCA inputs to the top panel.  Will cram two toroids inside a iron transformer shield, in blue.  Not sure of the color yet, might do it in all black, in keeping with the severe look of the heat sinks.
> 
> 
> 
> Might as well call this amp The Radiator, that's what it's going to look like lol reminiscent of the Pass Labs Aleph 3.


Curious as to what input tubes you are going with?  When choosing the inputs tubes is the only consideration heater voltages or are there more complex considerations in terms of their electrical interaction with the power tubes?


----------



## pravous

jgwtriode said:


> So here is the final design I made for a logo.  Going to put it on the transformer can,  It's a painted metal badge basically,  with a black edge and magnetic backing.  $11.00.  Easily worth it.  just add a little extra visual pop on the Airmid.
> 
> jgwtriode


Looks great.  The transformer cover does indeed cry out for some artwork.  This one fit perfectly but I haven’t committed to it permanently.


----------



## L0rdGwyn

pravous said:


> Curious as to what input tubes you are going with?  When choosing the inputs tubes is the only consideration heater voltages or are there more complex considerations in terms of their electrical interaction with the power tubes?



I will be using 6J5 inputs, just like Airmid.  When choosing the inputs in this type of design, want to use a tube that is linear, i.e., will produce little distortion, and a tube with an appropriate amount of gain, enough to make good volume with a variety of headphones, but not so much that the volume control is very sensitive and the noise floor elevated to a point of audibility.  In a direct-coupled design, the bias point of the input stage affects the bias point of the output stage, they are interdependent, so you must choose a bias point for the inputs that is linear and allows enough voltage swing while properly biasing the outputs.  It is something of a balancing act.  In this 6336 design, I may sacrifice some peak voltage swing / power output for a more ideal bias point, because in reality, no headphone needs 2W of power, no matter what people on Head-Fi say!


----------



## zach915m

Airmid in the house! Unfortunately it's not mine, but one of our guys had to have one after hearing it. He went with the bronze look, and it looks awesome! 

As usual, it sound other worldly, combining liquidity with resolve in a 3d way.  Very sad this will be going to his forever home soon. It's a great listen!


----------



## Monsterzero

L0rdGwyn said:


> no headphone needs 2W of power, no matter what people on Head-Fi say!


----------



## Xcalibur255

I would recommend you run a single 140mm Noctua instead of dual 80mm Keenan.  You can get the same airflow volume at considerably lower RPM for less noise.  In my experience you can get about 50 CFM from the 140mm in basically total silence where as the dual 80s will be slightly audible at about the same airflow.


----------



## whirlwind

Those Noctua fans are of very high quality...I am getting four of these for a new pc build, they are about as good as it gets.....rather pricey but well worth it.

https://www.amazon.com/gp/product/B09C6DQDNT/ref=ox_sc_act_title_2?smid=A1Z5H6ZGWCMTNX&psc=1


----------



## L0rdGwyn

zach915m said:


> Airmid in the house! Unfortunately it's not mine, but one of our guys had to have one after hearing it. He went with the bronze look, and it looks awesome!
> 
> As usual, it sound other worldly, combining liquidity with resolve in a 3d way.  Very sad this will be going to his forever home soon. It's a great listen!



Looks good!  Hope he enjoys it 



Xcalibur255 said:


> I would recommend you run a single 140mm Noctua instead of dual 80mm Keenan.  You can get the same airflow volume at considerably lower RPM for less noise.  In my experience you can get about 50 CFM from the 140mm in basically total silence where as the dual 80s will be slightly audible at about the same airflow.



Thanks, @Xcalibur255 , I'll keep that in mind, there is a 5V version of their 140mm fan.  The idea was for each tube to have its own dedicated fan / intake directly below it, a single 140mm would need to be placed in between them.  I have the pair of 80mm fans on the way, going to test them when they arrive.  If the noise is too much, I'll give the 140mm fan a try!

I bought this huge knob for the 6336 OTL build.  I'm very pleased with it.


----------



## bcowen

Xcalibur255 said:


> I would recommend you run a single 140mm Noctua instead of dual 80mm Keenan.  You can get the same airflow volume at considerably lower RPM for less noise.  In my experience you can get about 50 CFM from the 140mm in basically total silence where as the dual 80s will be slightly audible at about the same airflow.


That's a 140mm in the bottom of the Darkvoice.  It's a 12v and a bit loud at full voltage, so I use a cheap (computer) speed controller to turn it down to 7v where it still moves a good bit of air and is practically inaudible sitting a couple feet away.  I can make it totally silent at 5V and still get decent airflow, but it stalls on startup at that low a voltage.  I don't have a way to measure the RPM's though.


----------



## bcowen

L0rdGwyn said:


> Looks good!  Hope he enjoys it
> 
> 
> 
> ...


You will likely want to reduce the speed regardless of which size you go with.  Even the Noctua's are a bit too loud (for me) for this application at full voltage RPM.


----------



## Zachik

bcowen said:


> I can make it totally silent at 5V


...or you can just crank up the volume!


----------



## bcowen

Zachik said:


> ...or you can just crank up the volume!


Yeah, but it still might be intrusive during the quiet passages of Marilyn Manson.  🤣


----------



## L0rdGwyn

bcowen said:


> You will likely want to reduce the speed regardless of which size you go with.  Even the Noctua's are a bit too loud (for me) for this application at full voltage RPM.



Yeah probably, will need to do some testing.  Per fan the 80mm is the quietest 5V fan they make, but a single 200mm likely would be a quieter alternative and cover the area of both tubes better than the 140mm model.  We will see!


----------



## L0rdGwyn (Feb 7, 2022)

What I'm going to do is put a 100ohm potentiometer in series with the fan header on the PCB, then I can adjust the speed to taste and keep my dual fan setup, assuming the lowest voltage where the fan still operates still isn't too loud.


----------



## triod750

I'm trying to wrap my head around how you get the the taste of fan speed into your mouth. You have your ways, I suppose...


----------



## L0rdGwyn (Feb 7, 2022)

triod750 said:


> I'm trying to wrap my head around how you get the the taste of fan speed into your mouth. You have your ways, I suppose...



You have to run the fan into your face with your mouth open for at least an hour.  The taste is very plasticky, but worth it.

I was able to track down another functional pair of HK54, which is always great since these tubes are rare, the filaments are delicate, and they tend to be gassy.  Bought untested, I would say I have maybe a 50% success rate.  Finnicky, but I have it on good authority they are reliable and last years in an audio amplifier, just have to find some that work!

Think I have nine or ten now, along with a few 35T and 35TG, near equivalents.




Once I get the SMPS filament supplies, going to throw together a simple high-voltage supply, connect it to a variac, and attempt to "bake" the gassy HK54 / 35TG I have.  As you can see, these tubes have no getter.  The tantalum plate of these tubes actually functions as the getter, it glows red when the tubes are at full operation, so in order to de-gas the tubes they have to be brought up to operating voltage.

As an example, here is another tantalum plate tube in operation with its plate glowing red, a 100TH.



Here is a 35TG in operation, cousin to the HK54, which will be compatible in the planned amplifier.


----------



## L0rdGwyn

Warning, here comes some technical stuff, but I don't think I've talked in great detail about what I have planned for that HK54 amplifier.  Similar to my 801A amplifier, it is a class A2 design, meaning the grid is swinging positive and drawing current.  The interesting aspect of this amplifier however is that the grid is also _biased_ positive, so it will be drawing grid current at idle.  In fact, the voltage swing will be positive in class A2 around 80% of the time, it will only dip negative at peak swing, bottom right most area of the blue load line (thick red line is 0V), making around 15W at 0.5% THD in my simulations (I made an HK54 triode model based on my traced curves to run simulations in LTSpice).

To accomplish that, need a beefy cathode follower to drive the grid directly.  Subject to change, but right now I am planning to use the EL34...yup, as a cathode follower!  Pretty decent transconductance and can handle high voltage.  As of right now, I don't plan to have a negative bias supply - to hit that last 0V to -20V of grid swing, I am going to load the cathode follower with a big choke.  Input stage will be a high gain situation, likely pentode, with local negative feedback, around 25dB to reduce the output impedance to the point of being able to run 3K output transformers, probably in parafeed given the HK54 will be running ~100mA bias.  Might need to design a bias servo for the input stage, TBD on that front.

Here is a 3K load line I drew up on the HK54 curves months ago.  The bias point is at +40V on the grid.



So anyway, this is a weird amplifier to say the least, not your typical single-ended tube amp, but it will be pretty friggin' cool  realistically though I won't build this for a few years.


----------



## pravous

zach915m said:


> Airmid in the house! Unfortunately it's not mine, but one of our guys had to have one after hearing it. He went with the bronze look, and it looks awesome!
> 
> As usual, it sound other worldly, combining liquidity with resolve in a 3d way.  Very sad this will be going to his forever home soon. It's a great listen!


What Zmf headphones would you recommend for the Airmid?   I have heard great things about both the Verite open and closed.


----------



## triod750 (Feb 7, 2022)

L0rdGwyn said:


> Warning, here comes some technical stuff, but I don't think I've talked in great detail about what I have planned for that HK54 amplifier.  Similar to my 801A amplifier, it is a class A2 design, meaning the grid is swinging positive and drawing current.  The interesting aspect of this amplifier however is that the grid is also _biased_ positive, so it will be drawing grid current at idle.  In fact, the voltage swing will be positive in class A2 around 80% of the time, it will only dip negative at peak swing, bottom right most area of the blue load line (thick red line is 0V), making around 15W at 0.5% THD in my simulations (I made an HK54 triode model based on my traced curves to run simulations in LTSpice).
> 
> To accomplish that, need a beefy cathode follower to drive the grid directly.  Subject to change, but right now I am planning to use the EL34...yup, as a cathode follower!  Pretty decent transconductance and can handle high voltage.  As of right now, I don't plan to have a negative bias supply - to hit that last 0V to -20V of grid swing, I am going to load the cathode follower with a big choke.  Input stage will be a high gain situation, likely pentode, with local negative feedback, around 25dB to reduce the output impedance to the point of being able to run 3K output transformers, probably in parafeed given the HK54 will be running ~100mA bias.  Might need to design a bias servo for the input stage, TBD on that front.
> 
> ...


Thanks for the warning  . The tubes look like hot beans, really hot, and I don't understand much. But planning projects is very rewarding as it prevents you from doing other stupid things since you are too busy for that. In this case 'you' is me. My mind is always busy with things that never come into fruition since that isn't neccessary to make me happy and content.


----------



## Xcalibur255 (Feb 7, 2022)

They will usually tolerate 5V and shouldn't be stalling, at least for the PWM versions.  The motors might be a little different for a non-PWM fan.  One other thought is to go with dual 120mm if there is room for that, that would still permit lower RPMs for the same airflow and keep the dual fan setup.

edit:  Oh, that's right they do make that big ass 200mm, that's a good option too.  The stall speed on the motor would need to be pretty low though.


----------



## bcowen

Xcalibur255 said:


> They will usually tolerate 5V and shouldn't be stalling, at least for the PWM versions.  The motors might be a little different for a non-PWM fan.  One other thought is to go with dual 120mm if there is room for that, that would still permit lower RPMs for the same airflow and keep the dual fan setup.
> 
> edit:  Oh, that's right they do make that big ass 200mm, that's a good option too.  The stall speed on the motor would need to be pretty low though.


Mine will run fine if turned down to 5v...once it's already running.  It won't start up at 5v though from power up -- needs just under 7v to spin up on its own.

My sad attempt at a speed control box.  On the plus side, the controller was sitting in the computer parts bin, the SMPS wal-wart was picked out of the, well, wal-wart parts bin, and the box was free...clandestinely stolen from the wife's art supply stash. It's just a Darkvoice, after all.


----------



## jgwtriode

pravous said:


> Looks great.  The transformer cover does indeed cry out for some artwork.  This one fit perfectly but I haven’t committed to it permanently.


Very Nice... I like that


jgwtriode


----------



## L0rdGwyn (Feb 7, 2022)

Xcalibur255 said:


> They will usually tolerate 5V and shouldn't be stalling, at least for the PWM versions.  The motors might be a little different for a non-PWM fan.  One other thought is to go with dual 120mm if there is room for that, that would still permit lower RPMs for the same airflow and keep the dual fan setup.
> 
> edit:  Oh, that's right they do make that big ass 200mm, that's a good option too.  The stall speed on the motor would need to be pretty low though.



I have some 12V Noctua fans around, both PWM and 3-pin, I hooked one up to my bench supply, it functions down to just around 5V, any lower and it will stall.  Not sure if you saw, but I plan to use the 5V 80mm fan and put a potentiometer in series with the header on the power supply PCB, I am making revisions to it for this design anyhow.  Tested this with a 3-pin 12V Noctua fan, a 100ohm pot, and my bench supply, works like a charm.  Since I am using a regulated 5V supply running 5V fan, I'd expect to get good play down to around 2.5V using this approach, should be able to make the 80mm fans nice and quiet with adjustable speed.  Could always upgrade to 120mm too using the same method, like you mentioned.


----------



## L0rdGwyn (Feb 7, 2022)

Maybe I'll return the 80mm fans and just go 120mm @Xcalibur255 , honestly the thought of adjusting the voltage hadn't occurred to me initially, figured I could run them at a full 5V at max RPM without it bothering, but then again I was never a quiet PC guy lol shows what I know.  Going with the 120mm 5V fan and taking the same series resistance approach offers the same benefits at lower noise, current draw on the 5V supplies is the same, and I think the pair will fit.  I'll test the 80mm 5V fans first and go from there.


----------



## raindownthunda

L0rdGwyn said:


> Maybe I'll return the 80mm fans and just go 120mm @Xcalibur255 , honestly the thought of adjusting the voltage hadn't occurred to me initially, figured I could run them at a full 5V at max RPM without it bothering, but then again I was never a quiet PC guy lol shows what I know.  Going with the 120mm 5V fan and taking the same series resistance approach offers the same benefits at lower noise, current draw on the 5V supplies is the same, and I think the pair will fit.  I'll test the 80mm 5V fans first and go from there.


Noctua are great fans, I have several sizes in my PC. Not only will the 120mm be quieter and push much more air, any audible noise will be at a lower frequency and less annoying than the 80mm.


----------



## jgwtriode

L0rdGwyn said:


> Maybe I'll return the 80mm fans and just go 120mm @Xcalibur255 , honestly the thought of adjusting the voltage hadn't occurred to me initially, figured I could run them at a full 5V at max RPM without it bothering, but then again I was never a quiet PC guy lol shows what I know.  Going with the 120mm 5V fan and taking the same series resistance approach offers the same benefits at lower noise, current draw on the 5V supplies is the same, and I think the pair will fit.  I'll test the 80mm 5V fans first and go from there.


Get those 140 mm Noctua's that run Super Quiet and Still throw around 60 CFM.  Ordering some to further silence my computer.

jgwtriode


----------



## L0rdGwyn

raindownthunda said:


> Noctua are great fans, I have several sizes in my PC. Not only will the 120mm be quieter and push much more air, any audible noise will be at a lower frequency and less annoying than the 80mm.



Well I guess it's settled then!  I'll try the 120mm, thanks!


----------



## L0rdGwyn

jgwtriode said:


> Get those 140 mm Noctua's that run Super Quiet and Still throw around 60 CFM.  Ordering some to further silence my computer.
> 
> jgwtriode



Unfortunately, run as a pair the 120mm are the largest that will fit with the chassis the way I've designed it.


----------



## pravous

Love the big volume knob choice for the new OTL.  I decided the Airmid needed bigger volume knobs and found these. 




I meant to post but figured I needed to burn them in first


----------



## L0rdGwyn

pravous said:


> Love the big volume knob choice for the new OTL.  I decided the Airmid needed bigger volume knobs and found these.
> 
> I meant to post but figured I needed to burn them in first



Nice!  I have the same knob on my 801A amplifier, I imagine we picked them up from the same place, very unique.  I'm a sucker for cool vintage bakelite knobs, I have a little collection


----------



## bcowen

pravous said:


> Love the big volume knob choice for the new OTL.  I decided the Airmid needed bigger volume knobs and found these.
> 
> I meant to post but figured I needed to burn them in first


I hope you had them cryo-treated?  Too nice of an amp to be cutting corners.  🤣


----------



## CJG888 (Feb 8, 2022)

Why not run the fan at 5V and add a boost function to 7V on startup? The easiest way would be a manual „starter button“ bypassing a resistor. You could use something automotive….


----------



## L0rdGwyn

Here are the output caps I will be using for the 6336 OTL with a 6336 in between for scale.  Gotta be the biggest film caps I've ever bought.


----------



## jgwtriode (Feb 8, 2022)

L0rdGwyn said:


> Here are the output caps I will be using for the 6336 OTL with a 6336 in between for scale.  Gotta be the biggest film caps I've ever bought.


Those look about the same size as a pair of 120,000uf caps that I had a buddy of mine; from 40 years ago, mod my Hafler amp with,  to beef up the power supply.  Damn! 
 You could use those for bicep curls.

jgwtriode


----------



## Mr Trev

L0rdGwyn said:


> Here are the output caps I will be using for the 6336 OTL with a 6336 in between for scale.  Gotta be the biggest film caps I've ever bought.


Sweet. So what'd happen if you charged them up and decided to play catch with a <former>friend?


----------



## bcowen

L0rdGwyn said:


> Here are the output caps I will be using for the 6336 OTL with a 6336 in between for scale.  Gotta be the biggest film caps I've ever bought.


Sheeez Louise.  So what do you bypass them with?  A 60 uF cap?  I'm still trying to figure out how to get a pair of 47 uF caps in the Darkvoice.   🤣


----------



## L0rdGwyn

bcowen said:


> Sheeez Louise.  So what do you bypass them with?  A 60 uF cap?  I'm still trying to figure out how to get a pair of 47 uF caps in the Darkvoice.   🤣



That's a real challenge, there is no space in that amp!

I also got my 120mm 5V fans.  I went with the NF-A12x25 which are optimized for airflow whereas the NF-F12 are optimized for static pressure.  The NF-A12x25 has a higher current draw, max 350mA at 5V versus the NF-F12 which draws 150mA at 5V, still within the capabilities of the LDO regulator I am using.

I took some measurements - at 5V, they draw around 300mA.  With the voltage reduced to 4V, current draw drops to 200mA, I don't think I would be able to hear them inside an amplifier chassis at this voltage.  Going even lower to 3.5V and current draw is 150mA, no doubt they would be silent at 3.5V.  So could either use a pot for some adjustability or just use a properly rated series resistor to fix the speed.  The pot is more fun, so I'll probably go that route.


----------



## leftside

L0rdGwyn said:


> Here are the output caps I will be using for the 6336 OTL with a 6336 in between for scale.  Gotta be the biggest film caps I've ever bought.


@A2029 I thought the caps we used in the V6 were big…


----------



## CJG888

Back in the 90s, I remember seeing some absolutely massive polypropylene reservoir caps on a DIY amp. The owner told me that they are normally used to power electric fences on sheep stations in Australia…


----------



## whirlwind

L0rdGwyn said:


> Here are the output caps I will be using for the 6336 OTL with a 6336 in between for scale.  Gotta be the biggest film caps I've ever bought.



YOWZA!


----------



## whirlwind

leftside said:


> @A2029 I thought the caps we used in the V6 were big…



Big rugged caps for big rugged tubes!

Those  6336 tubes are built like a tank...6080 Bendix big brother.

My amp sits pretty close to me, sometimes a couple feet away and sometimes maybe four feet away, if I am laid back in my comfy chair.
They provided some warmth to my body.

The 6080 Bendix has turned into my favorite power tube in my OTL.


----------



## bcowen

whirlwind said:


> Big rugged caps for big rugged tubes!
> 
> Those  6336 tubes are built like a tank...6080 Bendix big brother.
> 
> ...


Graphite plates?


----------



## L0rdGwyn (Feb 9, 2022)

leftside said:


> @A2029 I thought the caps we used in the V6 were big…



Well to be fair that amp has three caps in parallel per channel!  Not sure of their value, but I'm sure it's a lot of capacitance.  I am only using a pair, one per channel.



whirlwind said:


> Big rugged caps for big rugged tubes!
> 
> Those  6336 tubes are built like a tank...6080 Bendix big brother.
> 
> ...



They are chunky tubes, very interested to see how they sound at a hotter bias point.  With the 6528 (higher gm cousin of the 6336), output impedance should be quite low, and good bass extension with those big caps.  This amplifier would make an engineer cry LOL over 50W dissipated to make a 2W-ish headphone amplifier, but we won't tell them.

My BW ebony VC are supposed to be delivered today, woot!


----------



## whirlwind

bcowen said:


> Graphite plates?


Yes


----------



## whirlwind

L0rdGwyn said:


> Well to be fair that amp has three caps in parallel per channel!  Not sure of their value, but I'm sure it's a lot of capacitance.  I am only using a pair, one per channel.
> 
> 
> 
> ...



Ha! Yeah, keep it silent from the engineers   

Can't wait to hear your impressions of your VC.  Should be a wonderful compliment to your open ZMF.
Are you keeping the Auteur also ?


----------



## L0rdGwyn

whirlwind said:


> Ha! Yeah, keep it silent from the engineers
> 
> Can't wait to hear your impressions of your VC.  Should be a wonderful compliment to your open ZMF.
> Are you keeping the Auteur also ?



I sold the Auteur!  But I think I will eventually get another open back ZMF to replace it.


----------



## bcowen

L0rdGwyn said:


> My BW ebony VC are supposed to be delivered today, woot!



Sweet!  But you know the drill -- pics or it didn't happen (which we will anxiously await).


----------



## L0rdGwyn

bcowen said:


> Sweet!  But you know the drill -- pics or it didn't happen (which we will anxiously await).



I will be picking them up after work


----------



## leftside

L0rdGwyn said:


> Well to be fair that amp has three caps in parallel per channel!  Not sure of their value, but I'm sure it's a lot of capacitance.  I am only using a pair, one per channel.


Enough capacitance for the Abyss and LCD4. Kind of ridiculous for an OTL but it keeps me warm in the winter


----------



## L0rdGwyn

leftside said:


> Enough capacitance for the Abyss and LCD4. Kind of ridiculous for an OTL but it keeps me warm in the winter



Every person who lives in a cold weather city needs a ridiculous OTL to keep them warm, it's a fact.


----------



## Zachik

L0rdGwyn said:


> Every person who lives in a cold weather city needs a ridiculous OTL to keep them warm, it's a fact.


Yup! Every time it dips below 55F outside - I power on my GOTL


----------



## bcowen

Zachik said:


> Yup! Every time it dips below 55F outside - I power on my GOTL


ROFL!  But 55?  That's brutal.  It's 58 here today and I'm freezing my butt off.


----------



## L0rdGwyn

The other day I drove to work in a snowstorm, to a hospital right on the shore of Lake Erie, with a 6"x6" area of my windshield I could see out of, nearly blown over by the wind in the parking lot.  It was 9 degrees F.  The next morning, my car was buried in snow, had to dig it out with the shovel I brought in my trunk.

Freezing your butt off builds character  makes the OTL warmth all the better when you get home.


----------



## Zachik

L0rdGwyn said:


> Freezing your butt off builds character


Hmm...... I will take your word!   



bcowen said:


> It's 58 here today and I'm freezing my butt off.


Pleasant 67F and sunny here right now


----------



## bcowen

L0rdGwyn said:


> The other day I drove to work in a snowstorm, to a hospital right on the shore of Lake Erie, with a 6"x6" area of my windshield I could see out of, nearly blown over by the wind in the parking lot.  It was 9 degrees F.  The next morning, my car was buried in snow, had to dig it out with the shovel I brought in my trunk.
> 
> Freezing your butt off builds character  makes the OTL warmth all the better when you get home.


But if your car was buried, how did you get in the trunk?    

(sorry, VIS* flare up waiting for those VC pics. )


*Voyeur Impatience Syndrome


----------



## L0rdGwyn

bcowen said:


> But if your car was buried, how did you get in the trunk?
> 
> (sorry, VIS* flare up waiting for those VC pics. )
> 
> ...



You might have to live with that VIS a little longer, somehow the headphones were on the truck for delivery, then made it all the way back to the initial location LOL nice of the driver to take them for a joy ride.  Since I wasn't going to be home to sign, I requested they be left at my local FedEx store so I could pick them up on the way home, I do this all the time, guess it was too complicated.  So maybe another try tomorrow?  Oh well, looks like I'll be tracing 6528 curves when I get home instead of listening to the VCs!


----------



## L0rdGwyn (Feb 9, 2022)

My 6528 didn't come today either, I'm striking out all over!  I think the crazy weather has thrown delivery services through a loop, I can't blame them for being behind.

I did get the large majority of the parts for 6336 OTL, but I need the heat sinks and transformer shield to finalize the chassis, so it's gonna be probably a week or two before I can order it.

Also got my SMPS filament supplies for the HK54 design.  A regulated linear power supply that can put out 5A at 5V ain't no joke in terms of heat management, size, complexity, so going with the SMPS is a massive quality of life improvement in an amplifier that is already pretty complicated.

The 35T / 35TG have a 4A filament whereas the HK54 have a 5A filament, having the SMPS handle the regulation is another mental weight lifted.  Small too, and shielded.  Noise performance is good for the application.  Don't have to worry about layout headaches that come with filament transformers either.  They just work!



Been thinking a little bit about how this amplifier would look.  Thing is, these tubes need to be enclosed since the plate caps are going to have peak voltages of around 500V on them, not something you want to be touching by mistake.  I came across an amplifier that I think is beautiful and I might draw inspiration from.  Don't think it is available anymore, it's based on a rather absurd 300W transmitter tube, the 304TL / 304TH.

Here is the tube.  These are amazing.  A DIY tube dude once told me that once you get into transmitter triodes, you never go back, they're just so cool.  Lots of these tubes still around actually, so if you are crazy enough to build an amplifier with a 300W transmitting triode, you should be all set terms of backups!



Here is the amp.  I love the vintage look, the Pyrex enclosure, the fact that it can kill you with mercury vapor rectifiers, high voltage, AND give you third degree burns, it really has it all.





Eventually I might do something like this on a smaller scale with the Pyrex casing and high walls and vintage aesthetic for the HK54 amp, really hits the spot for me.


----------



## bcowen (Feb 10, 2022)

L0rdGwyn said:


> Been thinking a little bit about how this amplifier would look.  Thing is, these tubes need to be enclosed since the plate caps are going to have peak voltages of around 500V on them, not something you want to be touching by mistake.  I came across an amplifier that I think is beautiful and I might draw inspiration from.  Don't think it is available anymore, it's based on a rather absurd 300W transmitter tube, the 304TL / 304TH.
> 
> Here is the tube.  These are amazing.  A DIY tube dude once told me that once you get into transmitter triodes, you never go back, they're just so cool.  Lots of these tubes still around actually, so if you are crazy enough to build an amplifier with a 300W transmitting triode, you should be all set terms of backups!
> 
> ...


That is totally beyond insane.  I _must_ have one.


----------



## jgwtriode

That almost looks steam punk it's so damn cool!  I mean hot! Very hot! Hot Damn!

jgwtriode


----------



## Zachik

L0rdGwyn said:


> it can kill you with mercury vapor rectifiers, high voltage, AND give you third degree burns


...and the amp shall be named "Death Trifecta"!


----------



## bcowen

Zachik said:


> ...and the amp shall be named "Death Trifecta"!


LOL!  Or Marilyn Ampson.


----------



## Zachik

bcowen said:


> LOL!  Or Marilyn Ampson.


That is a brilliant name!!!
@A2029 - too late to change the name of my upcoming amp?


----------



## jgwtriode

or maybe Triodemonous!


----------



## triod750

To me it looks like Kindergarten Killer.


----------



## whirlwind

leftside said:


> Enough capacitance for the Abyss and LCD4. Kind of ridiculous for an OTL but it keeps me warm in the winter



This has to be the biggest and craziest OTL ever.   
Low impedance cans ....no problem!

Yep, you should stay nice and toasty on cold winter evenings.


----------



## CJG888

Bring on the plasma headphones!


----------



## leftside

whirlwind said:


> This has to be the biggest and craziest OTL ever.
> Low impedance cans ....no problem!
> 
> Yep, you should stay nice and toasty on cold winter evenings.


I think @L0rdGwyn can go one step further up the craziness ladder


----------



## L0rdGwyn (Feb 10, 2022)

leftside said:


> I think @L0rdGwyn can go one step further up the craziness ladder



Lol well I think the V6 is still crazier than my OTL!

Now if you wanted to get REALLY crazy (and yes, I did legitimately consider this at one point), you could make an OTL using another pass regulator tube, a 100W monster, the 7241 or, even crazier, the 7242.  A 6.3V 7.5A heater, youch.  While a 6336 or 6528 is feasibly equivalent to 2-3 6AS7G / 6080 types, the 7241 is equivalent to four, and the higher transconductance 7242 could be considered equivalent to four 5998s in one bottle.  It has three separate cathodes run in parallel.




I was seriously looking at the practicality of making an OTL with a pair of these, but decided that it was actually too insane LOL we'd be talking about something like 500mA bias current per channel, and these things are rare and expensive.  So I settled on the 6336 / 6528 as a less insane, but still over-the-top compromise.

My VCs are ready for pickup, so I'll grab them tonight.


----------



## Xcalibur255

L0rdGwyn said:


> Every person who lives in a cold weather city needs a ridiculous OTL to keep them warm, it's a fact.


Ah, the problem is often that it's very cold in the winter but also very hot in the summer.  So we wind up needing to change amps just like changing between summer and winter wardrobes.


----------



## triod750

L0rdGwyn said:


> So I settled on the 6336 / 6528 as a less insane, but still over-the-top compromise.


But still a compromise, and a proof of that you are a sensible person in an insane world.


----------



## leftside

Xcalibur255 said:


> Ah, the problem is often that it's very cold in the winter but also very hot in the summer.  So we wind up needing to change amps just like changing between summer and winter wardrobes.


I did exactly that. V6 upstairs with all the other tube gear for the winter, and the Red Dwarf downstairs with the AC for the summer.


----------



## A2029

L0rdGwyn said:


> Lol well I think the V6 is still crazier than my OTL!
> 
> Now if you wanted to get REALLY crazy (and yes, I did legitimately consider this at one point), you could make an OTL using another pass regulator tube, a 100W monster, the 7241 or, even crazier, the 7242.  A 6.3V 7.5A heater, youch.  While a 6336 or 6528 is feasibly equivalent to 2-3 6AS7G / 6080 types, the 7241 is equivalent to four, and the higher transconductance 7242 could be considered equivalent to four 5998s in one bottle.  It has three separate cathodes run in parallel.
> 
> ...



Wow! With 3 of those per channel a person could make a pretty hefty OTL speaker amplifier 

Horrendously inefficient, lol. It would be suitable to heat the whole house for the -40C weather we got up here earlier this winter.


----------



## Xcalibur255

That kind of makes me wonder if it would have any kind of advantage over the AtmaSphere amps.  The sheer number of tubes they parallel means they've got to be right up there in heat and current too.


----------



## L0rdGwyn

The eagle has landed.  Look and sound incredible, thanks @zach915m !


----------



## bcowen

L0rdGwyn said:


> The eagle has landed.  Look and sound incredible, thanks @zach915m !


Niiiiiiiice!!!!!


----------



## raindownthunda

L0rdGwyn said:


> The eagle has landed.  Look and sound incredible, thanks @zach915m !


Stunning. Congrats! The color and grain is a great compliment to your amp. If you think they sound good now, just wait until they burn in  Mine opened up pretty dramatically in the first day or two.


----------



## jgwtriode (Feb 11, 2022)

L0rdGwyn said:


> The eagle has landed.  Look and sound incredible, thanks @zach915m !


Stunning, absolutely ridiculously gorgeous!     These arrived today from India!

jgwtriode.


----------



## whirlwind

leftside said:


> I did exactly that. V6 upstairs with all the other tube gear for the winter, and the Red Dwarf downstairs with the AC for the summer.


Amp rolling beats tube rolling all day, everyday    





L0rdGwyn said:


> The eagle has landed.  Look and sound incredible, thanks @zach915m !





L0rdGwyn said:


>


Gorgeous to say the least.

Now get going on that 6336 OTL


----------



## Xcalibur255

Wow, congrats Keenan.


----------



## Xcalibur255

jgwtriode said:


> Stunning, absolutely ridiculously gorgeous!     These arrived today from India!
> 
> jgwtriode.


I hope you have better luck than I did.  One of my Marconi L63 refuses to bias up in my 1101 Audio amp.  It must have a short or something.  It does work in the GOTL but will crackle a bit when it first comes on bias.  These tubes sound amazing in the GOTL but it's still a shame, I bought them for the new amp.


----------



## jgwtriode

Xcalibur255 said:


> I hope you have better luck than I did.  One of my Marconi L63 refuses to bias up in my 1101 Audio amp.  It must have a short or something.  It does work in the GOTL but will crackle a bit when it first comes on bias.  These tubes sound amazing in the GOTL but it's still a shame, I bought them for the new amp.


We shalll see.  I should have my tax return by the end of the month and can pay off my Airmid.   So first of next month can see how they work in it. 

Happy listening,

jgwtriode


----------



## L0rdGwyn

whirlwind said:


> Amp rolling beats tube rolling all day, everyday



This becomes a very dangerous problem when you build your own amps!

Interestingly, the hardness / density of B&W ebony is not so high as other ebonies, it has a Janka hardness of 1,780, so the headphones area actually quite light on the head, much lighter than my cocobolo Auteur were.  I was only able to listen for an hour or so last night, need to do some headband bending to perfect the fit and get them burned in this weekend.


----------



## whirlwind

L0rdGwyn said:


> This becomes a very dangerous problem when you build your own amps!
> 
> Interestingly, the hardness / density of B&W ebony is not so high as other ebonies, it has a Janka hardness of 1,780, so the headphones area actually quite light on the head, much lighter than my cocobolo Auteur were.  I was only able to listen for an hour or so last night, need to do some headband bending to perfect the fit and get them burned in this weekend.



You may end up with a dozen amps   

The Cocobolo I believe have a Janka rating of somewhere around 2950


----------



## jgwtriode (Feb 11, 2022)

On the burn in side.  I found the Auteurs pretty well settle around 250 hours, but the VC's took a bit longer.  Around 300 to maybe 320 hours before they really seemed just about right.  But even after they got better.  That was not as much the case with my Blackwood Auteurs.   I also have some fiddly tunning with Shun Mook Mpingo Discs on the cups and Mad Scientist Audio Nano Discs sample size.   These both helped flesh out the mids, lower the noise floor, increase PRAT and just make them sound more natural.

Happy Burn in,

jgwtriode


----------



## Xcalibur255

L0rdGwyn said:


> This becomes a very dangerous problem when you build your own amps!
> 
> Interestingly, the hardness / density of B&W ebony is not so high as other ebonies, it has a Janka hardness of 1,780, so the headphones area actually quite light on the head, much lighter than my cocobolo Auteur were.  I was only able to listen for an hour or so last night, need to do some headband bending to perfect the fit and get them burned in this weekend.


My understanding is that the density of the wood affects the damping and actually has some influence on the sound.  Would be interesting to compare it to a "standard" version.


----------



## Monsterzero

Xcalibur255 said:


> My understanding is that the density of the wood affects the damping and actually has some influence on the sound.  Would be interesting to compare it to a "standard" version.


Harder the wood the harder the slam and faster decay, whereas the softer wood types have less slam and have a lingering flavor and offers a slightly more romantic sound.

Based upon personal experiences, doing a side by side a/b, the differences are slight.


----------



## jgwtriode

found a pretty good price on a pair of 5998's .   test 65/65 and 65/65  on a TV 7 but that is all they are saying on the site.  Just wondering if that is enought
to get a sense of how good they are?


Thanks,

jgwtriode


----------



## bcowen (Feb 11, 2022)

jgwtriode said:


> found a pretty good price on a pair of 5998's .   test 65/65 and 65/65  on a TV 7 but that is all they are saying on the site.  Just wondering if that is enought
> to get a sense of how good they are?
> 
> 
> ...


The TV-7/U, A/U, B/U, and D/U provide minimum good values.  Using the "standard" value of minimum being 60% of the bogey (or average NOS) value, that would put a new 5998 at 67.  So yeah 65/65 is right at NOS as far as GM.  Of course this all depends on how well calibrated the tester they are using is.


----------



## jgwtriode

380 for the pair coming from China....what do you think

jgwtriode


----------



## bcowen

jgwtriode said:


> 380 for the pair coming from China....what do you think
> 
> jgwtriode


My opinion?  They look very nice, and if the tester they are using is reasonably calibrated they test nice too. On the high side price-wise, but not over the top.


----------



## jgwtriode (Feb 11, 2022)

everything else is 450.00 a pair or higher that I can find on ebay or any tube resellers.  Most are over 500 a pair!  Any suggestion where they might be any cheaper.  I need a pair for my Airmid.  Have my GEC L63's!

Here is another pair on ebay!  $450 Amplitron tested aparently.



Thanks,

jgwtriode


----------



## bcowen

jgwtriode said:


> everything else is 450.00 a pair or higher that I can find on ebay or any tube resellers.  Most are over 500 a pair!  Any suggestion where they might be any cheaper.  I need a pair for my Airmid.  Have my GEC L63's!
> 
> Here is another pair on ebay!  $450 Amplitron tested aparently.
> 
> ...


I don't see anything cheaper right now.  Prices are inflated due to this "huntandpeckauctions" selling off an estate and just throwing out Hail Mary prices on _everything_ they are selling.  A pair of National-branded Sylvania 7N7's (Frankies) for $450?  I about fell out of my chair when I saw that one.  A pair of 1990's $3 Chinese 12AX7's for $50? ROFL!  A pair of Hytron 5692's for $400? With the exception of the Taiwan listings, all but one of the current 5998 listings are theirs.  They will go away soon.  I picked up an IBM-branded Tung Sol 5998 a couple weeks ago for $100 just as an example.  It was only a single and that was a very good deal, but you should still be able to pick up a good pair for $300 or less under more normal circumstances.  It's rather hypocritical for *me* to recommend patience, but I will anyway.


----------



## bcowen

jgwtriode said:


> everything else is 450.00 a pair or higher that I can find on ebay or any tube resellers.  Most are over 500 a pair!  Any suggestion where they might be any cheaper.  I need a pair for my Airmid.  Have my GEC L63's!
> 
> Here is another pair on ebay!  $450 Amplitron tested aparently.
> 
> ...


One other idea:  put one of those 5998 pairs 'huntandpeck' has listed in your watchlist.  Don't offer anything at this point, just "watch" it.  See if they email _you_ an offer to sell for quite a bit less.  Can't say they will, but it happens to me from other sellers quite often.


----------



## jgwtriode

bcowen said:


> One other idea:  put one of those 5998 pairs 'huntandpeck' has listed in your watchlist.  Don't offer anything at this point, just "watch" it.  See if they email _you_ an offer to sell for quite a bit less.  Can't say they will, but it happens to me from other sellers quite often.


Thanks for the advice...okay I will wait a while maybe even until after the Airmid is here in a couple week or 3.   My concern is that inventory on these is running low and that over the next few months it may be much harder to get a good match pair of NOS. 

jgwtriode


----------



## Monsterzero

bcowen said:


> I don't see anything cheaper right now.  Prices are inflated due to this "huntandpeckauctions" selling off an estate and just throwing out Hail Mary prices on _everything_ they are selling.  A pair of National-branded Sylvania 7N7's (Frankies) for $450?  I about fell out of my chair when I saw that one.  A pair of 1990's $3 Chinese 12AX7's for $50? ROFL!  A pair of Hytron 5692's for $400? With the exception of the Taiwan listings, all but one of the current 5998 listings are theirs.  They will go away soon.  I picked up an IBM-branded Tung Sol 5998 a couple weeks ago for $100 just as an example.  It was only a single and that was a very good deal, but you should still be able to pick up a good pair for $300 or less under more normal circumstances.  It's rather hypocritical for *me* to recommend patience, but I will anyway.


 made an offer of 50.00 on a pair of 7236 and he accepted. He was asking 100.00
made an offer of 100.00 on a 596 rectifier. He declined. He was asking 229.00. It sold later for 160.00, so he is def accepting offers.


----------



## bcowen

jgwtriode said:


> Thanks for the advice...okay I will wait a while maybe even until after the Airmid is here in a couple week or 3.   My concern is that inventory on these is running low and that over the next few months it may be much harder to get a good match pair of NOS.
> 
> jgwtriode


FYI.  Just received this email. This is one of 'huntandpecks' listings that I added to my watchlist, not because I would ever pay anything close to that, just that I wanted to see where they end up.  From $450 to $300 just by_ looking_ at them....but now they're only 10x overpriced.


----------



## L0rdGwyn

bcowen said:


> FYI.  Just received this email. This is one of 'huntandpecks' listings that I added to my watchlist, not because I would ever pay anything close to that, just that I wanted to see where they end up.  From $450 to $300 just by_ looking_ at them....but now they're only 10x overpriced.



Not sure that guy knows what he has.  Some really nice tubes in his listings those, gorgeous pairs of PX25.


----------



## L0rdGwyn

Here is the 1948/49 Zenith tube radio I restored.  There are a few more things I need to do, there is some drift in the FM band that I think I can improve.  American FM radios from this time did not have amazing performance, so drift is somewhat common.  Tone control pot / knob are slightly off center, going to see if I can fix that too, but good enough to show a pic since it is in its forever home.


----------



## bcowen

L0rdGwyn said:


> Not sure that guy knows what he has.  Some really nice tubes in his listings those, gorgeous pairs of PX25.


Yes, he has some very nice tubes in there.  They're just all ridiculously priced.  Apparently all of this is from an audiophile in Virginia that is either selling everything off, or this is from his estate.  Hopefully the former, but it doesn't really specify.


----------



## Monsterzero

L0rdGwyn said:


> Not sure that guy knows what he has.  Some really nice tubes in his listings those, gorgeous pairs of PX25.


He knows enough to ask a  ridiculous amount for these. I know these are hard to come by, but c'mon.

https://www.ebay.com/itm/2553699578...5&toolid=10001&customid=kzkix7hubk01zlp100004


----------



## L0rdGwyn (Feb 12, 2022)

bcowen said:


> Yes, he has some very nice tubes in there.  They're just all ridiculously priced.  Apparently all of this is from an audiophile in Virginia that is either selling everything off, or this is from his estate.  Hopefully the former, but it doesn't really specify.





Monsterzero said:


> He knows enough to ask a  ridiculous amount for these. I know these are hard to come by, but c'mon.
> 
> https://www.ebay.com/itm/2553699578...5&toolid=10001&customid=kzkix7hubk01zlp100004



Whoever had that collection was hardcore!  His pricing approach must be something like - find highest selling price in the past six months, then multiply by five.  They will have to come down, no way people are buying some of these tubes, it's BangyBang tactics: "so, how about you give me $300, and in return I will give you a NOS, new-in-box, unused, unopened, pristine pair of...useless TV tubes."

Enjoying some tubes, horns, and vinyl tonight after some VC time.  My cat Freddy is also very into tubes, horns, and vinyl, the reason I picked him at the shelter.  His new favorite pastime is finding tubes in my collection still wrapped in bubble wrap, pulling them out of the boxes, and batting them around the house.  He is a very good cat.


----------



## bcowen (Feb 12, 2022)

L0rdGwyn said:


> Whoever had that collection was hardcore!  His pricing approach must be something like - find highest selling price in the past six months, then multiply by five.  They will have to come down, no way people are buying some of these tubes, it's BangyBang tactics: "so, how about you give me $300, and in return I will give you a NOS, new-in-box, unused, unopened, pristine pair of...useless TV tubes *that were made in China and re-silkscreened to whatever brand is currently going for the most money."*


🤣🤣

I'm going to put those 422A's in my watchlist and see what offer I get back.  $2500?  $2000?  Any bets?


----------



## triod750

https://www.ebay.co.uk/itm/234328609785?hash=item368f12d3f9:g:ZlAAAOSw1WNhs0QP 

Tror inte du att detta är ett Sylvania?


----------



## L0rdGwyn

triod750 said:


> https://www.ebay.co.uk/itm/234328609785?hash=item368f12d3f9:g:ZlAAAOSw1WNhs0QP
> 
> Tror inte du att detta är ett Sylvania?



Yes most likely, believe they were the only maker of the flat plate 6BL7.


----------



## L0rdGwyn

I did some work on 6336 OTL planning, nothing special, measured snubbing resistor values, matched components for the active loads, dialed in the value of the series resistors for the Noctua fans (I've decided to do a fixed resistor as opposed to a pot), tested the startup and shutdown conditions using the higher output capacitance relative to the Airmid.

Here is one of the Noctua fans hooked up to the Airmid power supply with a 4.7ohm series resistor.  Will try 4.7ohm, 3.9ohm, and 3.3ohm and choose the value that I feel gives the best balance of airflow vs. noise.  Did some preliminary testing, think 3.9ohm is going to be the best balance, but we will see when it's built.




So placing what should be the final parts order tonight.  Last thing is to get the heat sinks, which should arrive tomorrow.  Once I have their dimensions and make plans for drilling, I can finalize the chassis.  If all goes as planned, should be able to order it on Tuesday.  That is the rate-limiting step, will then order the revised PCBs and we'll be good to go 

Got NOS pairs of 6336 and 6528 ready to go.


----------



## triod750

triod750 said:


> https://www.ebay.co.uk/itm/234328609785?hash=item368f12d3f9:g:ZlAAAOSw1WNhs0QP
> 
> Tror inte du att detta är ett Sylvania?


Don't know what happened here. This question was intended as a PM to someone else. Anyway, thanks for the confirmation  .


----------



## L0rdGwyn

Here are the heat sinks for the 6336 OTL.  Long ones will go on the sides, shorter one on the rear panel.



Nice wavy pattern for increased surface area.



Will see if I can get the drilling plan and chassis finalized tomorrow.


----------



## bcowen

bcowen said:


> 🤣🤣
> 
> I'm going to put those 422A's in my watchlist and see what offer I get back.  $2500?  $2000?  Any bets?



LOL!!


----------



## L0rdGwyn

bcowen said:


> LOL!!



What a steal!!!


----------



## L0rdGwyn (Feb 15, 2022)

Here is the final chassis for the 6336 OTL, just the top plate, additional width of the heat sinks in yellow, transformer shield in blue.



It's gonna be big, total width with the heat sinks is around 13.15", depth with the rear heat sink 18.32", height is 3.25".

Going to have the chassis coated in the same Stone Black as my phono stage.  Black chassis, black heat sinks, black transformer shield, black knob, black sockets, black headphone jack...blue caps 

I am going to have to change fans, again, I was able to pare down the size of the chassis a bit with a smaller transformer shield, but the 120mm fans will no longer fit side-by-side, so will have to downsize to 92mm, no big deal.


----------



## Xcalibur255 (Feb 15, 2022)

I still would recommend running a single 140 over dual fans if you don't want to hear them running.  Actually the way to really maximize the fan would be to mount it inside the TOP plate and have it act as a puller instead of a pusher.  This creates both a chimney effect where you are working with the natural direction heat wants to travel and it also creates negative static pressure which improves the efficiency of heat removal in the interior space.  The bottom fan pushing air in does the opposite and generates positive pressure in the case, which will equalize the internal temperatures but is overall less efficient if the goal is to remove that heat.

Just sharing for informative purposes of course, I know there is no reasonable way to accommodate the vents topside without making the chassis even larger than this.

edit:  I wonder if it wouldn't be feasible to treat the couple of components that generate the most heat the way you would a computer processor and use a thermal pad and compound with a heatpipe attached to the external heatsink and draw the heat so it doesn't ever really even radiate inside the chassis.  An over complicated but fun solution.


----------



## L0rdGwyn

Xcalibur255 said:


> I still would recommend running a single 140 over dual fans if you don't want to hear them running.  Actually the way to really maximize the fan would be to mount it inside the TOP plate and have it act as a puller instead of a pusher.  This creates both a chimney effect where you are working with the natural direction heat wants to travel and it also creates negative static pressure which improves the efficiency of heat removal in the interior space.  The bottom fan pushing air in does the opposite and generates positive pressure in the case, which will equalize the internal temperatures but is overall less efficient if the goal is to remove that heat.
> 
> Just sharing for informative purposes of course, I know there is no reasonable way to accommodate the vents topside without making the chassis even larger than this.
> 
> edit:  I wonder if it wouldn't be feasible to treat the couple of components that generate the most heat the way you would a computer processor and use a thermal pad and compound with a heatpipe attached to the external heatsink and draw the heat so it doesn't ever really even radiate inside the chassis.  An over complicated but fun solution.



Thanks for the recommendation!  The goal of the fans isn't so much to remove heat from the interior of the chassis as it is to create airflow past the power tubes, more of a nice to have than a need to have, having two individual fans that are centered at the ventilation of each power tube is preferable for me for that reason.  I'm not too worried about the audibility as I can tailor the speed and noise with a series resistor.  Interior temperature isn't so much a problem as the major heat-generating components are all external to the chassis - the power supply regulators on the back panel heat sink, the power tube loads on the side heat sinks, power tubes atop the chassis.  The side panel heat sinks have a thermal resistance of 0.45C/W.  With 30W dissipated in each, the temperature of the heat sink will be raised only 13.5C above ambient, so assuming 25C ambient, measured at 38.5C, barely warm to the touch, similar for the rear panel.


----------



## L0rdGwyn (Feb 15, 2022)

This knob is amazing.  I can't believe I'm saying this, but it might actually be _too_ big lol for a 4.25" chassis it is just right for 3.25" it feels a little out of balance.  Might have to do some more knob shopping.  Using a TKD 2CP-2511 pot.

Edit: found a knob one size down of the same make / style, crisis averted.  Will save this one for a thicker chassis.



Here is my little test jig for measuring / matching / testing CCS components.  Chopped up a DIP socket so I can easily swap TO-220 parts.  The semiconductor shortage has been a real drag, resorted to buying parts off eBay, can get some great deals, but all must be tested.


----------



## triod750

Nice towel!


----------



## L0rdGwyn

triod750 said:


> Nice towel!



It's a beauty.  That's my "don't-scratch-up-amplifiers-while-they're-flipped-upside-down" towel.


----------



## triod750

L0rdGwyn said:


> It's a beauty.  That's my "don't-scratch-up-amplifiers-while-they're-flipped-upside-down" towel.


Everyone needs one of these. Where did you get it?


----------



## L0rdGwyn

triod750 said:


> Everyone needs one of these. Where did you get it?



Made by Cardas, the color is sonic seaweed green.


----------



## Zachik

L0rdGwyn said:


> It's a beauty.  That's my "don't-scratch-up-amplifiers-while-they're-flipped-upside-down" towel.


Did you have a different one used when you built your DAC?


----------



## bcowen

L0rdGwyn said:


> Made by Cardas, the color is sonic seaweed green.


I sure hope it's cryo-treated, demagnetized, and quantum tunneled or I'll have to start a GoFundMe to get you properly equipped.  🤣


----------



## L0rdGwyn (Feb 15, 2022)

Zachik said:


> Did you have a different one used when you built your DAC?



Oh yeah, Cardas has a whole line, different thread count for various audio gears.  NOS tube DAC version is Egyptian cotton.  Solid state amplifier version is steel wool.  I think they're trying to communicate something...


----------



## Xcalibur255

L0rdGwyn said:


> Thanks for the recommendation!  The goal of the fans isn't so much to remove heat from the interior of the chassis as it is to create airflow past the power tubes, more of a nice to have than a need to have, having two individual fans that are centered at the ventilation of each power tube is preferable for me for that reason.  I'm not too worried about the audibility as I can tailor the speed and noise with a series resistor.  Interior temperature isn't so much a problem as the major heat-generating components are all external to the chassis - the power supply regulators on the back panel heat sink, the power tube loads on the side heat sinks, power tubes atop the chassis.  The side panel heat sinks have a thermal resistance of 0.45C/W.  With 30W dissipated in each, the temperature of the heat sink will be raised only 13.5C above ambient, so assuming 25C ambient, measured at 38.5C, barely warm to the touch, similar for the rear panel.



Gotcha.  I'll be curious to see if you can get an 80 or 92 spinning slow enough to be silent without it stalling.  The threshhold of audibility for all of these PC cooling fans is generally around 600RPM in my experience, this is why everybody goes big.  If you can't increase the RPM you increase the fan diameter to move more air.  At 600RPM 80mm (or 92 for that matter) fans really don't push very much air though, so you might have to live with some noise to get the airflow you want from those smaller fans.

Artic Cooling used to make a nice little 80mm fluid dynamic bearing fan that was very well behaved and didn't stall even at very low speeds, but they've been discontinued for a long time.  If I hadn't given one away already I would rip them out of the PC they were in and send them to you.


----------



## L0rdGwyn (Feb 18, 2022)

With the 6336 OTL chassis ordered, been working on some side projects.

First off, I had a backlog of new (used) vinyl to clean.  Had some good stuff just hanging out!  Feels good to clear the queue.  Sassafras insisted on being in the photo.  She loves vent...vent warm.




Next, I swapped out the UX4, octal, and noval 9-pin sockets of my curve tracer.  Easier said than done, super PITA, but a massive quality-of-life improvement, the stock sockets are quite literally the worst I have ever come across, just absolute trash.  If I had known I was going to have to do this later, I would've just wired the sockets myself lol.



Will likely do the others later, but had to get these three done pronto, it was a crisis.  So all good now, here is an Eimac 35T that arrived today.



Got some other interesting transmitting triodes in today, will show them later once I decide whether or not I will build something with them, I think I will be the first to ever publish their operating curves.

Still need to finish my 6336 OTL PCB redesign, but no rush as the chassis will take a few weeks.


----------



## jgwtriode

Ah the vinyl takes me back to the Days when I used to order JVC supervinyl pressings of my favourite groups.  And clean them with my Nitty Gritty and treat them with LAST.  Ran a tweaked well tempered table with a rebuilt well tempered arm and a really nice Van Den Hull MC.  More mainstream audiophila in those days.  Ran Audio Research and  Vanderstein with it.    Some 800 albums that I collected.  Ah the memories!

Happy listening,,


jgwtriode


----------



## leftside

jgwtriode said:


> Ah the vinyl takes me back to the Days when I used to order JVC supervinyl pressings of my favourite groups.  And clean them with my Nitty Gritty and treat them with LAST.  Ran a tweaked well tempered table with a rebuilt well tempered arm and a really nice Van Den Hull MC.  More mainstream audiophila in those days.  Ran Audio Research and  Vanderstein with it.    Some 800 albums that I collected.  Ah the memories!
> 
> Happy listening,,
> 
> ...


Nice setup. Dare I ask what happened to those vinyl albums? I still buy a few records each year. I have something similar to a Nitty Gritty, but a lot of us also use an ultrasonic cleaner for the "first pass" of cleaning. Then something like the Nitty Gritty for the "second pass" clean/rinse.


----------



## jgwtriode (Feb 19, 2022)

Yeah the ultrasonic thing sounds like a great idea.  Was not aware of anything like that back in the day.

I sold the collectible ones. Gave away a lot, donated some and the rest just kind of lost over a number of moves as I switched over to digital.  More convenient.  And finally I had a digital setup that was at least on a par with my turntable setup.  It may seem hard to believe, but I had an adcom cd player that a very good friend modified for me.  It outperformed the 3 to 5k models I was selling at the store I worked at.  Especially with a specific Cal Audio processor I paired it up with as a transport.  I sold my Turnatable setup which I had 3 or 4 times as much money into to a customer and never looked back,

Then CAL Audio came out with a DVD player that I got on incentive since we sold them.  2500 dollar player and had my buddy rebuild that for me and there was no going back.   Then about six years ago ended up pretty much out of the whole game.    Started over decided time to go computer audio and digital files and that is where I am at now.  Moved around a lot after a couple of divorces, so headphones made more sense.   I now have the best sounding system overall I have ever had and it's about to get much better with an Airmid from Keenan and a new DAC that Ric at EVS tweaks is rebuilding for me.  Will be going with Wywires Platinum for the interconnect.  And just to spice things up will be putting the new crescent headphone band on my VC dark leopardwoods and adding copper rods to spice up the looks a bit.  Pretty exciting actually.

Also going to do Monster Zero's recommended roll on the Airmid.   Will take a little while, since the Tungsols are coming from China.


Happy listening,

jgwtriode


----------



## bpiotrow13 (Feb 21, 2022)

jgwtriode said:


> 380 for the pair coming from China....what do you think
> 
> jgwtriode


Good, i think i have bought two pairs from the same seller. It seems this buey accepts usd 300 offers for a pair.


----------



## jgwtriode

Yeah he settled on 330.00 which I am okay with.  How long did shipping take?


jgwtriode


----------



## bpiotrow13

jgwtriode said:


> Yeah he settled on 330.00 which I am okay with.  How long did shipping take?
> 
> 
> jgwtriode


Ages 

Seriously i do not remember correctly, as these are intended to be my spare pairs and i did not care much about timing. I think 1 - 2 months, but i am based in EU and it takes several weeks to go through customs. I am even waiting now for one single tube i bought from this seller on 8 January.

I decided to stock myself with Ts 5998 given the prices and have bought several pairs now, when i can afford them.


----------



## L0rdGwyn

Have no fear @jgwtriode, if the 5998 take a long time to arrive, rest assured the amplifier sounds very good even with the stock Russian tubes!


----------



## jgwtriode

Thanks Keenan....I'm a bit of an extremist, but yes I will enjoy the Airmid, knowing it gets even better!  Right now all I can listen to is My swans running off the sound card.  Actually should make an RCA and run Spdif into them from JCAT card.  That would be a ton better!

Thanks for the indirect inspiration in the moment. 

jgwtriode


----------



## whirlwind

jgwtriode said:


> Yeah he settled on 330.00 which I am okay with.  How long did shipping take?
> 
> 
> jgwtriode



Those are great tubes, but there are many great tubes that your amp can use.

After thousands of hours of listening, you can really appreciate what each bring to the table.

Even the cheapest 6/12/J5 tubes sound really good.....you can get great sound without breaking the bank.....of course, most still break the bank, just because that is what tube lovers do


----------



## jgwtriode (Feb 21, 2022)

Appreciate that...thanks.  just went for it!  I already bought an identically matched pair of GEC L63's from a seller in India on ebay.  Tubes look immaculate and came in what appear to be original boxes.  Not cheap but less than most other places selling these!

Happy listening,

jgwtriode


----------



## jgwtriode

Monster Zero is very persuasive and I am very obsessive...that is an expensive combination...lol!

jgwtriode


----------



## jgwtriode (Feb 21, 2022)

I will be throwing Wyires platinum RCA's into the mix as well.  If I really had money I would be grabbing the diamonds!   Oh well we all have our crosses to bear

jgwtriode


----------



## L0rdGwyn

I am going to see if I can ship the red Airmid later this week, have some time off starting Thursday.

I am told my 6336 OTL chassis is machined and will likely be coated today, so might have it by the weekend.  I wasn't expecting it so soon!  I need to work on the revised PCBs.  There is much work to do so I don't think the wait for the PCBs will slow thing down much.

I ordered SME cut armboard for my Thorens TT, also reached out to custom wood plinth designer, slowly making moves toward its overhaul.  Plan is for the SME 3009.

Also working on the LCR phono stage design, just preliminary at the moment, it is transformer coupled from input to output, so will be a very expensive project.  Right now it is D3a input, E55L output.  That is a project for later this year most likely.


----------



## jgwtriode

Awesome stuff.   Chinese and DHL seem to far surpass US shipping(post office and fedex particularly).   But I'm excited my DAC made it from China to US in less than a week. Hot Damn.  Got it from HIFIGO and it appears it will show up at EVS this week.   Talking to Ric at EVS about the mods.  OMG exciting stuff.  Taking the stuff he did to my Oppo and upgrading that approach to the the Gustard X 26 pro.  He will completely revamp the output stage, drastically simplifying it down to one stage instead of the three it currently has.  It is apparently not as discrete as many have described it.  He will be changing that.  Will upgrade the caps in signal path and clean up the power supply as well, get rid of the fuse and use much better regulators.  He has his own approach to heatsinking them which uses his own composite of different materials based on how it sounds.  Told me he would be tuning that to the Gustard.  My oppo Sonica was ridiculous good.  This will be much better I suspect.  Christmas in March when it all comes together.  He is going to potentially prototype a whole new approach to the output stage based on some of his own unique amplifier design stuff, which may or may not be a better approach.  If it sounds better than I may be throwing a good bit more money at it to have him implement it.  Will know that in another week or so.

Happy listening,

jgwtriode


----------



## jgwtriode (Feb 23, 2022)

So here is the finished badge for my transformer can.  3 x 1.5 inches.  May need to get a bigger one.  If I can find some place that will make a bigger one in single quantity.  No luck so far.  But I am pretty happy with the result.  Will put a magnetic backing on it.

Happy listening,

Jgwtriode


----------



## jgwtriode

Look at these beauties, showed up today out of the blue.   Thought they were weeks away.
Happy days, sweet music soon.

Happy listening,

jgwtriode


----------



## bcowen

jgwtriode said:


> Look at these beauties, showed up today out of the blue.   Thought they were weeks away.
> Happy days, sweet music soon.
> 
> Happy listening,
> ...


Nice.  They sure are pretty!


----------



## L0rdGwyn

jgwtriode said:


> Look at these beauties, showed up today out of the blue.   Thought they were weeks away.
> Happy days, sweet music soon.
> 
> Happy listening,
> ...



Very nice!  You'll be all set when the amp arrives.  Going to work on shipping plans the next two days.

I got some new tubes too, pair of 801A, another HK54, ceramic base HY69, and a pair of E182CC.


----------



## jgwtriode (Feb 23, 2022)

Those 801A's are quite shapely, gorgeous looking tubes!  Something about well shouldered triodes that just seduces the eyes, then the ears,  then the mind and then the soul!

jgwtriode


----------



## L0rdGwyn

Yes, they are nice tubes!  Somewhat difficult to design with but I would say worth the effort.

This is the pair that lives in my amplifier, Taylor with graphite plates.


----------



## jgwtriode (Feb 23, 2022)

Those are quite elegant.  Plates remind me  a bit more of 2A3's, which I really love the look of, particularly meshplates.  But I am really thrilled with these 5998's.  Feels good just to be in a room with some triodes.  Must be a Zen thing I think they are like Organites, those Resin pyramid new age thingies, they channel positive universal energy and chase the blues away.   It's been too many years without them.  Hot damn, thermionic bliss, will be fun to play with the Airmid.

jgwtriode


----------



## bpiotrow13

jgwtriode said:


> Look at these beauties, showed up today out of the blue.   Thought they were weeks away.
> Happy days, sweet music soon.
> 
> Happy listening,
> ...


Cool, Let us know how they sound. I just got delivered my next pair from the same seller. My only concern is that almost all his TS 5998 are tested at 65/65 (at least it is what he says). It seems he is increasing prices as well.


----------



## jgwtriode (Feb 25, 2022)

Yeah I wondered about that as well.  Saw his other ad where that single 5998 tested the same.  Other places are over $500 for a pair however.  What to do?  Hopefully he got a particularly good batch as opposed to just fudging the numbers.  Don't have a complete sense of how much that number actually means, other than I know it should be at least 62.  And having both sides equal is preferable.

jgwtriode


----------



## bcowen

jgwtriode said:


> Yeah I wondered about that as well.  Saw his other ad where that single 5998 tested the same.  Other places are over $500 for a pair however.  What to do?  Hopefully he got a particularly good batch as opposed to just fudging the numbers.  Don't have a complete sense of how much that number actually means, other than I know it should be at least 62.  And having both sides equal is preferable.
> 
> jgwtriode


It's possible that all the 5998's he has are _truly_ unused NOS, which would make the very similar readings make sense.  One can only hope, right?


----------



## L0rdGwyn

Red Airmid on its way to @jgwtriode , so I am again OTL-less!  Until 6336 build, couple weeks most likely.


----------



## bpiotrow13

bcowen said:


> One can only hope, right?


Exactly, we do hope


----------



## jgwtriode

I would have been fine with you keeping it another week or more.  My DAC will not be BACK for at least two weeks.


----------



## cdanguyen08

Awesome to see @L0rdGwyn  amp on ZMFs latest video!


----------



## L0rdGwyn

jgwtriode said:


> I would have been fine with you keeping it another week or more.  My DAC will not be BACK for at least two weeks.



Oh it isn't an issue whatsoever!  Happy to send it now, just haven't had an OTL-less household in a while.  Too many amps around here anyway, actually glad to have some more space lol.


----------



## L0rdGwyn

cdanguyen08 said:


> Awesome to see @L0rdGwyn  amp on ZMFs latest video!



Cool I'll have to check it out!


----------



## bcowen

L0rdGwyn said:


> Oh it isn't an issue whatsoever!  Happy to send it now, just haven't had an OTL-less household in a while.  Too many amps around here anyway, actually glad to have some more space lol.


I can loan you my Darkvoice in the interim if you like.  I can even send all the upgrade parts along with it just in case you get bored one evening.  Always happy to help a fellow audio addict.  🤣🤣🤣


----------



## jgwtriode

I would have been happy to let you keep it longer Keenan...LOL!


That's a link to Zach's Latest video where he is explaining the ZMF Process.   At 5:11 minutes in, there is the 45.  He called it the Air Mountain.  Great name.

Happy listening,

James


----------



## L0rdGwyn

bcowen said:


> I can loan you my Darkvoice in the interim if you like.  I can even send all the upgrade parts along with it just in case you get bored one evening.  Always happy to help a fellow audio addict.  🤣🤣🤣



You are very generous, but I will have to decline, I just couldn't bear the thought of the Darkvoice leaving your side!


----------



## L0rdGwyn

jgwtriode said:


> I would have been happy to let you keep it longer Keenan...LOL!
> 
> 
> That's a link to Zach's Latest video where he is explaining the ZMF Process.   At 5:11 minutes in, there is the 45.  He called it the Air Mountain.  Great name.
> ...




Air Mountain lol it is quite airy, very happy with how it turned out.


----------



## jgwtriode (Feb 25, 2022)

Very nice!  So Zach named it?  Good choice.  The transformers behind the 45's do have the appearance of a range of mountains....so it fits!  And it is in the high places where we go to transcend.  Where prophets speak to god, where Shangrila is supposed to exist.  Where the earth reaches out to and touches the heavens and draws us closer to
the stars.

I will bet it sounds transcendent, teleported to Heaven.  Zen beyond Zen.   It looks gorgeous and very technical at the same time.   No doubt a bit too pricey
for my wallet.  The Airmid will be my End game headphone Amp.  Will gradually stock up on tubes, for long term backup.   Move my Focus to AC issues and
an Ultimate DAC now.  My Highly modded Gustard X 26 pro is an interim step.  Ric at EVS explained to me how he is going to pull all the relative garbage out
of the Power Supply.  Including 5 layers of switching voltage selectors fusing and solder points.  Torroidals wired to a Furutech Inlet will be it.  He is taking the
same approach with an actual discrete single output stage.  Gustard has three in it now.   It will be a lot better than stock.  But no Lampi I am sure.  Yes Monster
you have convinced me.   I need a Lampi or the equivalent.  Any suggestions Keenan.  That will have to wait for next year.  The budget is already out the window
for this year.  But worth every penny.  Ordered Wywires Platinum RCA yesterday after a lovely chat with Alex about interconnect design and connectors.

Happy Listening,

jgwtriode


----------



## pravous

If you need something to listen to while your making the new OTL I can send you the Schiit coaster amp Airmid clone  




Clearly an upgrade over Bcowens darkvoice!


----------



## Mr Trev

pravous said:


> If you need something to listen to while your making the new OTL I can send you the Schiit coaster amp Airmid clone
> 
> Clearly an upgrade over Bcowens darkvoice!


I'll one up that. I'll send a FUBAR Little Bear P1 that you can mod to levels unknown to budget Chinese made junk audio.


----------



## jgwtriode

What in the world!  Ha Ha Ha oh my gosh.  Is that for real


----------



## pravous

Mr Trev said:


> I'll one up that. I'll send a FUBAR Little Bear P1 that you can mod to levels unknown to budget Chinese made junk audio.


That’s kind of funny.  I used the Little Bear VU meters to match tubes for the Schiit coaster amp.


----------



## bcowen

pravous said:


> That’s kind of funny.  I used the Little Bear VU meters to match tubes for the Schiit coaster amp.


And I used the Little Bear VU meters _as _an amp because they sounded better than the stock Darkvoice.  Man, this is such a small world.  😂


----------



## jgwtriode (Feb 27, 2022)

Hey Keenan what would you estimate the Airmids' power consumption at?   I am thinking about, in the near future, doing a DC to AC inverter with lithium batteries.  Had a friend discuss the concept.  He has a buddy running his audio system on an Ecoflow 3600Wh energy backup and apparently it ridiculous good.  I was thinking more like 720WH to 1000Wh.  But they have some decent pricing and are much cheaper than serious power conditioners etc.  And 3 to 4 hrs is about the max I spend even on days off listening, so one in that range might be adequate.

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Hey Keenan what would you estimate the Airmids' power consumption at?   I am thinking about, in the near future, doing a DC to AC inverter with lithium batteries.  Had a friend discuss the concept.  He has a buddy running his audio system on an Ecoflow 3600Wh energy backup and apparently it ridiculous good.  I was thinking more like 720WH to 1000Wh.  But they have some decent pricing and are much cheaper than serious power conditioners etc.  And 3 to 4 hrs is about the max I spend even on days off listening, so one in that range might be adequate.
> 
> Happy listening,
> 
> jgwtriode



At some point I measured the exact current draw from the wall, but I don't recall the measurement.  I can estimate it at 1A, so at 120VAC, that is 120W power consumption.


----------



## jgwtriode

Thanks Keenan!


----------



## L0rdGwyn (Mar 2, 2022)

Got started on the 6336 OTL today, chassis is in Stone Black, a satin black finish.

Did the chassis prep and started mounting parts, here is a look so far.




As you can see, there are large cut outs on the sides for the heat sinks.  I think it is going to look pretty cool when it's done.

That  won't be until the end of the month however, working a lot over the next two weeks, then will be out of town for another week in the middle of the month.  Still waiting for my PCBs to arrive, so it will take some time.


----------



## L0rdGwyn

Also, there's been some speculation, so I'll just throw it out there - I am building @Monsterzero an Airmid.  He had asked a ways back if I would be willing to build him an amplifier and he's decided to move forward with it.  So that will be next up after this 6336 OTL.


----------



## jgwtriode

Looks impressive as usual!  Another beauty!

jgwtriode


----------



## jgwtriode (Mar 2, 2022)

L0rdGwyn said:


> Also, there's been some speculation, so I'll just throw it out there - I am building @Monsterzero an Airmid.  He had asked a ways back if I would be willing to build him an amplifier and he's decided to move forward with it.  So that will be next up after this 6336 OTL.


Awesome!  Go Monster Zero!  Every Airmid out there makes the world a better place!  LOrdGwyn making it better, one amplifier at time!

jgwtriode


----------



## pravous

Grats Monsterzero!  I would sing the praises of the Airmid but since it was your review that pushed me to make my deposit I am sure you know what you are looking forward to.

Since my current method of testing new tube purchases is to plug them into my Bottlehead amp and cross my fingers I decided I (need?) want a tube tester.  Long story short I have ordered an Etracer and will be building it when it arrives sometime in the next two weeks.  If anyone is interested you can find out about it here: Etracer website
In preparation I have been hunting down tube data sheets for tubes that do not currently have a configuration file.  Take the 6C5 for example.  6C5 data sheet
My question for LordGwyn is when configuring the full scan voltage parameters would this be correct using the data sheet I linked?



The curve portion of the data sheet shows voltage for up to 500 for the plate, -26 for the grid but then it says a maximum plate voltage of 300.  Which is correct? 



Another question I had is how do I handle the shield pin?
Here is what I came up with for the quick scan parameters again assuming the linked data sheet is correct.



I am guessing you have done this with quite a few of your oddball tubes so I thought I would check with you before I actually try it live.


----------



## leftside

pravous said:


> Grats Monsterzero!  I would sing the praises of the Airmid but since it was your review that pushed me to make my deposit I am sure you know what you are looking forward to.
> 
> Since my current method of testing new tube purchases is to plug them into my Bottlehead amp and cross my fingers I decided I (need?) want a tube tester.  Long story short I have ordered an Etracer and will be building it when it arrives sometime in the next two weeks.  If anyone is interested you can find out about it here: Etracer website
> In preparation I have been hunting down tube data sheets for tubes that do not currently have a configuration file.  Take the 6C5 for example.  6C5 data sheet
> ...


Very nice! This eTracer was also high up on my list to buy, but I've been talking with Chris from Amplitrex the last few months, and with the amount of various different types of tubes I have, I ended up purchasing the AT1000 this week. I already have a Tsakiridis Daedalos which is a great tester, but the AT1000 tests more tubes. 

Report back on the eTracer when you have it built. I still find that device very intriguing.


----------



## Tom-s

I'll leave this here. For the most flexibility when it comes to tube testing. 

It's very moderately priced. eTracer is based on this one if i'm correct. 

https://www.dos4ever.com/uTracer3/uTracer3_pag0.html


----------



## leftside (Mar 3, 2022)

Tom-s said:


> I'll leave this here. For the most flexibility when it comes to tube testing.
> 
> It's very moderately priced. eTracer is based on this one if i'm correct.
> 
> https://www.dos4ever.com/uTracer3/uTracer3_pag0.html


Wow look what people done with that thing. Amazing. Those are all great looking projects.

And why did I think of @L0rdGwyn when I saw this picture?


----------



## L0rdGwyn (Mar 3, 2022)

pravous said:


> Grats Monsterzero!  I would sing the praises of the Airmid but since it was your review that pushed me to make my deposit I am sure you know what you are looking forward to.
> 
> Since my current method of testing new tube purchases is to plug them into my Bottlehead amp and cross my fingers I decided I (need?) want a tube tester.  Long story short I have ordered an Etracer and will be building it when it arrives sometime in the next two weeks.  If anyone is interested you can find out about it here: Etracer website
> In preparation I have been hunting down tube data sheets for tubes that do not currently have a configuration file.  Take the 6C5 for example.  6C5 data sheet
> ...



6C5 testing setup looks good, but note you will need to change the current scale on the  y-axis.  As far as the maximum voltage of 300V in the datasheet, that is referring to a bias voltage, for scanning purposes you can go higher, 500V as shown on the datasheet curves is no problem.  Just leave the shield pin disconnected.  Quick scan looks good too.


----------



## bcowen (Mar 3, 2022)

leftside said:


> Wow look what people done with that thing. Amazing. Those are all great looking projects.
> 
> *And why did I think of @L0rdGwyn when I saw this picture?*


ROFL!  And here's a picture from his youth when he first learned that a 75 watt soldering iron wasn't the best choice for circuit board work.


----------



## pravous

Tom-s said:


> I'll leave this here. For the most flexibility when it comes to tube testing.
> 
> It's very moderately priced. eTracer is based on this one if i'm correct.
> 
> https://www.dos4ever.com/uTracer3/uTracer3_pag0.html


I did seriously consider the utracer as well.  The Etracer and Utracer checked all my boxes of diy assembly, customization and computer control of voltages etc.  It came down to three small differences that pushed me to the Etracer.  For one it is a little bit of a more complete kit out of the box.  Etracer comes with a case, tube sockets, test leads and is ready to be made into a complete unit.  Utracer requires you to come up with your own case and interface between the board and tube sockets.  Two the computer interface of the Etracer is slightly more modern, usb b as compared to Utracers rs232.  Third it just so happens that LordGwyn owns an Etracer so I figured this thread would be a valuable resource if I have questions like how to make a tube configuration file.


----------



## pravous

bcowen said:


> ROFL!  And here's a picture from his youth when he first learned that a 75 watt soldering iron wasn't the best choice for circuit board work.


Despite the dubious tip size choice this was probably safer than my first third grade electrical experiments.  My teacher at school showed us how to use a coil of wire and electricity to magnetize a framing nail.  Convinced my dad to take me to radio shack and rounded up some wire, a switch and some bulb sockets.  To throw off the parents I assembled a couple of series/parallel light circuits.  Later on I decided to recreate my teachers experiment and wisely decided that the proper way to get AC mains power was to jack directly into a wall socket with stripped wire ends, even more wisely holding them in each hand.  Received my first and last taste of 120 volts that day!  Luckily the tin foil strip between two nails fuse blew as intended and I only received a brief taste.


----------



## jgwtriode

Its here Keenan.  Just opened it up and unwrapped it.  Showed up about 30 minutes ago.  On my lunch break.  It's gorgeous.  More of a Burgundy red than the pictures indicated.  I love that.  Orange red to red is not my thing for example.  But these is almost the color I would have chosen had I picked it myself.  A hint darker perhaps, but my gosh it is stunning to look at and I haven't even put the tubes in yet.

Will fire it up this evening after work.  Don't have my DAC back yet so will run it from my computer Sound card and Tidal for the time being and start running the Tara Labs Cascade Burn In to get the tubes going.  Probably about a week to 10 days away from the DAC arriving and somewhere in there my Wywires RCA will show up. Have a pretty Zenwave Flat cotton braid 10 AWG OCC power cord I can use with it.   Will eventually upgrade that as well.   

I'm in heaven, It's beggining to look a lot like Christmas


----------



## bcowen

pravous said:


> Despite the dubious tip size choice this was probably safer than my first third grade electrical experiments.  My teacher at school showed us how to use a coil of wire and electricity to magnetize a framing nail.  Convinced my dad to take me to radio shack and rounded up some wire, a switch and some bulb sockets.  To throw off the parents I assembled a couple of series/parallel light circuits.  Later on I decided to recreate my teachers experiment and wisely decided that the proper way to get AC mains power was to jack directly into a wall socket with stripped wire ends, even more wisely holding them in each hand.  Received my first and last taste of 120 volts that day!  Luckily the tin foil strip between two nails fuse blew as intended and I only received a brief taste.


LOL!  The best lessons are usually the hard ones, although with some it's amazing we're still alive.   Took me to young adulthood to learn that using your finger is *not* the best way to discharge a 1500uF, 450v cap.  I can almost still feel that.


----------



## Monsterzero

jgwtriode said:


> Its here Keenan.  Just opened it up and unwrapped it.  Showed up about 30 minutes ago.  On my lunch break.  It's gorgeous.  More of a Burgundy red than the pictures indicated.  I love that.  Orange red to red is not my thing for example.  But these is almost the color I would have chosen had I picked it myself.  A hint darker perhaps, but my gosh it is stunning to look at and I haven't even put the tubes in yet.
> 
> Will fire it up this evening after work.  Don't have my DAC back yet so will run it from my computer Sound card and Tidal for the time being and start running the Tara Labs Cascade Burn In to get the tubes going.  Probably about a week to 10 days away from the DAC arriving and somewhere in there my Wywires RCA will show up. Have a pretty Zenwave Flat cotton braid 10 AWG OCC power cord I can use with it.   Will eventually upgrade that as well.
> 
> I'm in heaven, It's beggining to look a lot like Christmas


Pics or it didn't happen!

Seriously, congrats. I hope you enjoy it as much as I did.


----------



## bcowen

jgwtriode said:


> Its here Keenan.  Just opened it up and unwrapped it.  Showed up about 30 minutes ago.  On my lunch break.  It's gorgeous.  More of a Burgundy red than the pictures indicated.  I love that.  Orange red to red is not my thing for example.  But these is almost the color I would have chosen had I picked it myself.  A hint darker perhaps, but my gosh it is stunning to look at and I haven't even put the tubes in yet.
> 
> Will fire it up this evening after work.  Don't have my DAC back yet so will run it from my computer Sound card and Tidal for the time being and start running the Tara Labs Cascade Burn In to get the tubes going.  Probably about a week to 10 days away from the DAC arriving and somewhere in there my Wywires RCA will show up. Have a pretty Zenwave Flat cotton braid 10 AWG OCC power cord I can use with it.   Will eventually upgrade that as well.
> 
> I'm in heaven, It's beggining to look a lot like Christmas


Congrats!


----------



## jgwtriode

Thanks I will post photos this evening!


----------



## L0rdGwyn

jgwtriode said:


> Its here Keenan.  Just opened it up and unwrapped it.  Showed up about 30 minutes ago.  On my lunch break.  It's gorgeous.  More of a Burgundy red than the pictures indicated.  I love that.  Orange red to red is not my thing for example.  But these is almost the color I would have chosen had I picked it myself.  A hint darker perhaps, but my gosh it is stunning to look at and I haven't even put the tubes in yet.
> 
> Will fire it up this evening after work.  Don't have my DAC back yet so will run it from my computer Sound card and Tidal for the time being and start running the Tara Labs Cascade Burn In to get the tubes going.  Probably about a week to 10 days away from the DAC arriving and somewhere in there my Wywires RCA will show up. Have a pretty Zenwave Flat cotton braid 10 AWG OCC power cord I can use with it.   Will eventually upgrade that as well.
> 
> I'm in heaven, It's beggining to look a lot like Christmas



Glad it made it there safe!  Let us know what you think


----------



## jgwtriode (Mar 3, 2022)

Okay a few quickies with phone!  The LOrdGwyn badge I had made.  And a couple of Celtic fridge magnets I have.  Triskelions with knots!  Getting some bigger ones that completely cover tops of the caps.

Later some impressions.  Funny how the color really lightens up in photos.  Looks much better in person

jgwtriode


----------



## jgwtriode (Mar 3, 2022)

Noticed another thing while I was taking quick break at work.  Work at home.  Noticed how solid that power switch is.   Much nicer than flat toggles.  Very solid and secure feel, very nice action.   And the volume pot has amazing feel to it.  Absolutely smooth but with a  pleasing sense of weight as you rotate it.  NIcest switches I have ever used.  I am impressed Keenan!

jgwtriode


----------



## jgwtriode

Hey Keenan should I be hearing noise when I first fire up the tubes. At half volume I am hearing low level pops and hisses and various odd noise.  Is that normal
Thats with my 5998's and GEC L63's.   Does that settle down or is there potentially a problem with the tubes I got

Thanks

James


----------



## L0rdGwyn

jgwtriode said:


> Hey Keenan should I be hearing noise when I first fire up the tubes. At half volume I am hearing low level pops and hisses and various odd noise.  Is that normal
> Thats with my 5998's and GEC L63's.   Does that settle down or is there potentially a problem with the tubes I got
> 
> Thanks
> ...



Most likely that is a noisy tube.  Is it heard in both channels?  If it is the tubes, they may settle down with time.  Stock tubes were not noisy when I tested them, could try them to confirm.


----------



## Zachik

jgwtriode said:


> And the volume pot has amazing feel to it. Absolutely smooth but with a pleasing sense of weight as you rotate it.


Which pot you got? I know @L0rdGwyn likes Goldpoint stepped attenuators...


----------



## L0rdGwyn

Zachik said:


> Which pot you got? I know @L0rdGwyn likes Goldpoint stepped attenuators...



It's an Alps RK27, great pot for a good price.  Power switch is made by NKK, which have become my go-to switch brand.  I have moved on from Goldpoints!  If I am using an expensive pot these days, I like to use Japanese TKD.


----------



## Zachik

L0rdGwyn said:


> It's an Alps RK27, great pot for a good price.


I have been using this one for a couple of my DIY projects. Yup - great pot for sure!


----------



## Zachik

L0rdGwyn said:


> Power switch is made by NKK, which have become my go-to switch brand.


Funny - that is the switch brand for ALL my DIY projects, too


----------



## bcowen

Zachik said:


> Funny - that is the switch brand for ALL my DIY projects, too


So great minds think alike then?  😂


----------



## jgwtriode

They do vastly improve the sound and openess of tidal straight from my computer. since I am just running it straight off my sound card and running tidal.  this frankly should not sound this good.  I have a really nice modded pair of swan S200 Mk 3+ that sound crazy good running out of my system from my old modded oppo and of course is vastly better throught the VC's especially DSD.  The Swan's DSP only do 24bit 96k. I am surprised how good they sound running tidal out of the sound card on a3.5mm to RCA silver wire I made for temporary sound.   Well feeding that to the Airmid into my VC is sound comparable to  what I was getting  when I ran my full system into the Swan's, which is nuts.  You can hear even at this level that the VC loves the Airmid.  Its like the Airmid just caresses the drivers.  It kills the sense of ease.  And the air and space is comparable right now to what I was getting out of my full system.  I mean it lacks the extremes and all of the detail, but its creating like 85% plus and tonal and harmoically its far better than it ought to be.  OMG when I get my modded DAC back in and everything running Oh my word!  This is actually enjoyable and my input is crap right now!

jgwtriode


----------



## Mr Trev

Zachik said:


> I have been using this one for a couple of my DIY projects. Yup - great pot for sure!


This has a totally different meaning when you live in a country that's legalized marijuana🤪


----------



## bcowen

Mr Trev said:


> This has a totally different meaning when you live in a country that's legalized marijuana🤪


ROFL!!!!


----------



## leftside

Mr Trev said:


> This has a totally different meaning when you live in a country that's legalized marijuana🤪


Yep great pot here


----------



## jgwtriode (Mar 4, 2022)

Keenan it's 2pm in the morning and the sound is mind boggling good already.  Noise has gotten better.  Its still there a bit.  Kind of like slightly ouder record surface noise.  The Amp is so damn naturally organically musical.  I could.  Everything is so effortless and dynamic.  This Roll just locks in with the VC and I know I am nowhere near what this thing can really do.  And as I look at it, I think I would call this color Dark Cranberry Red.  It's beautiful. a perfect compliment to the sound.

Thanks you are absolutely brilliant,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Keenan it's 2pm in the morning and the sound is mind boggling good already.  Noise has gotten better.  Its still there a bit.  Kind of like slightly ouder record surface noise.  The Amp is so damn naturally organically musical.  I could.  Everything is so effortless and dynamic.  This Roll just locks in with the VC and I know I am nowhere near what this thing can really do.  And as I look at it, I think I would call this color Dark Cranberry Red.  It's beautiful. a perfect compliment to the sound.
> 
> Thanks you are absolutely brilliant,
> 
> jgwtriode



Thanks, glad you're enjoying it.  Hopefully the tube noise will improve, my suspicion would be the L63, I have come across a few noisy ones.


----------



## bcowen

L0rdGwyn said:


> Thanks, glad you're enjoying it.  Hopefully the tube noise will improve, my suspicion would be the L63, I have come across a few noisy ones.


Possible too that it's just very tired ears at 2pm in the morning.  😂


----------



## miketlse

bcowen said:


> Possible too that it's just very tired ears at 2pm in the morning.  😂


always useful feedback for a designer.


----------



## jgwtriode

I am a bit of night owl and things always sound better at night!   I will keep burning them in.  They seem to be getting better.  May build a copper mesh faraday cage to wrap around them.  Put a couple together for my emf sensitive landlord.  We even have one of those TRI field meters here for testing.  We shall see!   It's amazing just looking at the Airmid.

Happy listening,

Jgwtriode


----------



## triod750 (Mar 4, 2022)

L0rdGwyn said:


> Thanks, glad you're enjoying it.  Hopefully the tube noise will improve, my suspicion would be the *L63, I have come across a few noisy ones.*


So have I, three out of four...


----------



## Monsterzero

jgwtriode said:


> I am a bit of night owl and things always sound better at night!


Yup. I'm guessing it has to do with less electricity usage at night, and perhaps atmospheric phenomenon, but music def sounds better at night.


----------



## triod750

We might also be more relaxed and receptive at night...


----------



## jgwtriode

I wouldn't disagree with that but I think that is a result of years of realizing that music after 11PM does sound better.  I find 2 to 3 in the morning to be the real sweet spot!  But can't always stay up that late.  But Friday nights!

jgwtriode


----------



## whirlwind

jgwtriode said:


> I am a bit of night owl and things always sound better at night!   I will keep burning them in.  They seem to be getting better.  May build a copper mesh faraday cage to wrap around them.  Put a couple together for my emf sensitive landlord.  We even have one of those TRI field meters here for testing.  We shall see!   It's amazing just looking at the Airmid.
> 
> Happy listening,
> 
> Jgwtriode



That is when my best listening time is also.

At night, kicked back in a comfy chair with a cocktail in a dark room, other than just a little tube glow


----------



## jgwtriode

i


whirlwind said:


> That is when my best listening time is also.
> 
> At night, kicked back in a comfy chair with a cocktail in a dark room, other than just a little tube glow


Indeed love turning out the lights and enjoy that warm amber orange glow accompanied by some lovely chaunteuse!

jgwtriode


----------



## jgwtriode

So the tube noise is getting lower.  But what is weird is occasional spurios odd almost whistling sounds that spike for a few seconds.  Any ideas on that!

jgwtriode


----------



## L0rdGwyn (Mar 5, 2022)

jgwtriode said:


> So the tube noise is getting lower.  But what is weird is occasional spurios odd almost whistling sounds that spike for a few seconds.  Any ideas on that!
> 
> jgwtriode



Noisy tubes.  Does a light tapping of the L63 have any effect when the noise occurs?  I have at least one L63 that does the same thing, whistles.  You could try another pair of 6J5, it is very bothersome or doesn't go away, maybe the seller would accept a return.


----------



## jgwtriode

No effect, tapping just introduces dull thunks.  It primarily happens when I turn it on or when plug the headphone jack in. It generally goes a way and it has lowered in overall volume.   So will just keep burning.   But damn this thing sounds so good.  It's nearly impossible to stop listening to it.   And what it  is doing with mediocre signal going in right now seems impossible.  And even with this you can hear it improving noticeably every 5 to 10 hours.  Just burning it through Tara Labs Cascade Burn in at and of course a few hours of Tidal every night.   Have you played at all with tuning platforms or various feet under it.  I have it sitting on 2 Mad Scientist Carbon Nano footers that use Ceramic bearings  and 1 with Tungsten Carbide.  Just my obsession. But I have found all that stuff makes a difference on most good equipment. Ordering some heavy copper wire mesh to make a faraday cage to set on top and around the tubes.  That should be a cheap way to remove any RF and EMF effects that may be affecting the tubes.

You think those Herbie's Tube Dampers might have any effect?  They aren't horribly expensive as those things tend to be far
more than what they charge.  About 40 to 50 dollars for their ones designed for triodes.

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> No effect, tapping just introduces dull thunks.  It primarily happens when I turn it on or when plug the headphone jack in. It generally goes a way and it has lowered in overall volume.   So will just keep burning.   But damn this thing sounds so good.  It's nearly impossible to stop listening to it.   And what it  is doing with mediocre signal going in right now seems impossible.  And even with this you can hear it improving noticeably every 5 to 10 hours.  Just burning it through Tara Labs Cascade Burn in at and of course a few hours of Tidal every night.   Have you played at all with tuning platforms or various feet under it.  I have it sitting on 2 Mad Scientist Carbon Nano footers that use Ceramic bearings  and 1 with Tungsten Carbide.  Just my obsession. But I have found all that stuff makes a difference on most good equipment. Ordering some heavy copper wire mesh to make a faraday cage to set on top and around the tubes.  That should be a cheap way to remove any RF and EMF effects that may be affecting the tubes.
> 
> You think those Herbie's Tube Dampers might have any effect?  They aren't horribly expensive as those things tend to be far
> more than what they charge.  About 40 to 50 dollars for their ones designed for triodes.
> ...



I would try swapping in the stock 6J5, then the stock 6AS7G to isolate the problem tubes, but I suspect it is the L63.  As I said, I have some noisy L63, a low-level whistler, but not very noticeable, comes and goes, I still use them.  An unfortunate consequence of committing to a 100-year-old dead technology.

Tube dampers might help if you find your tubes are microphonic.  Same with the isolation, will mostly affect microphonic tubes, although I haven't found many microphonic 6J5.


----------



## jgwtriode (Mar 5, 2022)

Sound's good Keenan!  Will sort it out over next few weeks!  I get the impression NOS inherently have a bit more noise than the Russian equivalents.  The L63s right now are about the same general noise level as the 6J'5s with no burn...but have a bit more random spurious noise that seems to inject itself into the mix ...pops, ticks, tapping, and Ocasional whistling.  The Russian's noise is amore consistent almost white noise...but the general levels otherwise are relatively similar right now. Obviously more burn in.  Is there a relative point when the noise settles and that's just the character of that tube!

Those are pretty balanced.  The character of both 63's is virtually identical.  Noises are mostly  centered with slight variance between channels.   Interesting stuff.  This is all seems much more pronounced on headphones, didn't mess with it in my 2A3 triodes running loudspeakers.  

Put em in and balanced the hum pots. Was using Vaic modern tubes as well!  Haven't particularly fiddled with the 6AS7's yet.

Thanks for the insights,

Jgwtriode


----------



## L0rdGwyn (Mar 5, 2022)

jgwtriode said:


> Sound's good Keenan!  Will sort it out over next few weeks!  I get the impression NOS inherently have a bit more noise than the Russian equivalents.  The L63s right now are about the same general noise level as the 6J'5s with no burn...but have a bit more random spurious noise that seems to inject itself into the mix ...pops, ticks, tapping, and Ocasional whistling.  The Russian's noise is amore consistent almost white noise...but the general levels otherwise are relatively similar right now. Obviously more burn in.  Is there a relative point when the noise settles and that's just the character of that tube!
> 
> Those are pretty balanced.  The character of both 63's is virtually identical.  Noises are mostly  centered with slight variance between channels.   Interesting stuff.  This is all seems much more pronounced on headphones, didn't mess with it in my 2A3 triodes running loudspeakers.
> 
> ...



This is at normal listening volumes?  Or volume turned up without music playing?  With the stock tubes, the amp was silent at the time of shipping.  Is the noise present with your source disconnected?


----------



## jgwtriode

Have not thought of that, interesting.  Okay I will try that and see what happens.  Could be noise from the computer right now its just Tidal running from my Sound Card.  Since my Dac is still being modded.  So I will try that and see what happens.  

Thanks,

jgwtriode


----------



## jgwtriode (Mar 5, 2022)

Omgosh, Yeah that is a ton better.  A lot of that noise is coming from the sound card.  Still coming throurgh with RCA's plugged in.  Yup pulled the 3.5mm and still hum. Then pulled the whole interconnect out at the rca's.   A tiny whisper of a hum and very tiny spurious pops at same level.  Full volume.

External noise being fed into the tubes.  They are just more sensitive to it then solid state apparently.

Wow Impressive.  These tubes are just fine.!  With the wywire RCA's this will no doubt be dead silent.  Those things are ridiculous at eliminating input noise.

Awesome,  I am thrilled!

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Omgosh, Yeah that is a ton better.  A lot of that noise is coming from the sound card.  Much more even now .  Yup pulled the 3.5mm and still hum. Then pulled the whole interconnect out at the rca's.   A tiny whisper of a hum and very tiny spurious pops at same level.  Full volume.
> 
> External noise being fed into the tubes.  They are just more sensitive to it then solid state apparently.
> 
> ...



Yes, any audio directly out of a PC is going to be prone to noise.  Also, hearing the some noise floor at full volume in a tube amplifier is normal, at anything resembling normal listening volumes it should be silent.  Full volume at 1W would be deafening, quite literally!  Even 12 o'clock with a 2Vrms line level input to this amp with the VC would be very, very loud.  So I wouldn't worry about the noise floor having any substantial effect on the audio quality, this is quite normal for a tube amp.


----------



## jgwtriode

Indeed when I am running it out my dedicated Jplay USB Card which run on its on super cap supply through Wywires best USB, the signal to the DAC is dead silent and out the DAC should be the same.  So yes it will be exceeding quiet far beyond what I need.   Wonderful!

Thanks Kennan,

James


----------



## jgwtriode (Mar 10, 2022)

What is something beyond amazing with the Airmid is the quantity and quality of Bass.  This is the best I have heard anything in the low registers sound with the VC.  First it is richer tonally and harmonically without being particularly warm.  You normally associate musical, liquid and triodes with "must be warm and possibly euphonically pleasing. Nope not at!   The Airmid does not sound that way in any aspect of how reproduces the incoming signal.   Its like it just tells whatever is heading down the chain, do your worst!  

Liquid as as anything I have owned and likely more.  It's throws immense, detailed layered stage.  It creates real size image of humans and stringed instrument.  But what's crazy how large big bass instruments sound.  I have heard little more than a handful of transducers that give you a sense of that.   This is now the second time in my life I have something that is capable of creating a fairly believable presentation of an such instrument.  Lacks somewhere between half way up from the last octave and maybe a full octave up, but within that framework it still creates a remarkably really sounding drum or tympani.  This reminds me of the first few songs I listened to.  Everything was larger and dimensionality was deeper, stage itself was about the same.  But remember I am feeding Airmid with Tidal files from the onboard soundcard.  Hopefully only another couple weeks.  The Airmid simply lets the VC know it has no choice but to serve the music and then she simply takes over.   The Verite becomes larger, more effortless, more dynamic, more lively and as a result is capable of moving beyond what you might imagine a VC was capable of.

I don't if the Goddess of healing can remake a silk purse out of a sow's ear.  But it is sure is doing it's utmost in my system.  Still a couple weeks out from all my goodies showing up New moded DAC.  New Platinum RCA and Platinum power cord from Wywires.   And will be retuning the system to fully exploit Airmid.


Sorry Monster will have to be slumming without a Lampi for at least another year or more...  But one of these days!


Happy listening everyone,

jgwtriode


----------



## Zachik

jgwtriode said:


> Sorry Monster will have to be slumming without a Lampi for at least another year or more... But one of these days!


I am selling my Lampi Amber 3... Just saying


----------



## Monsterzero

jgwtriode said:


> What is something beyond amazing with the Airmid is the quantity and quality of Bass.  This is the best I have heard anything in the low registers sound with the VC.  First it is richer tonally and harmonically without being particularly warm.  You normally associate musical, liquid and triodes with "must be warm and possibly euphonically pleasing. Nope not at!   The Airmid does not sound that way in any aspect of how reproduces the incoming signal.   Its like it just tells whatever is heading down the chain, do your worst!
> 
> Liquid as as anything I have owned and likely more.  It's throws immense, detailed layered stage.  It creates real size image of humans and stringed instrument.  But what's crazy how large big bass instruments sound.  I have heard little more than a handful of transducers that give you a sense of that.   This is now the second time in my life I have something that is capable of creating a fairly believable presentation of an such instrument.  Lacks somewhere between half way up from the last octave and maybe a full octave up, but within that framework it still creates a remarkably really sounding drum or tympani.  This reminds me of the first few songs I listened to.  Everything was larger and dimensionality was deeper, stage itself was about the same.  But remember I am feeding Airmid with Tidal files from the onboard soundcard.  Hopefully only another couple weeks.  The Airmid simply lets the VC know it has no choice but to serve the music and then she simply takes over.   The Verite becomes larger, more effortless, more dynamic, more lively and as a result is capable of moving beyond what you might imagine a VC was capable of.
> 
> ...


An end game DAC will take your system to ridiculous new heights. Whether it be a Lampizator, or something else, you've only scratched the surface of what the ZMF+Airmid combo is capable of.


----------



## leftside

Zachik said:


> I am selling my Lampi Amber 3... Just saying


Ooohhh. What are you getting? The Amber 3 is very highly rated.


----------



## Zachik

leftside said:


> Ooohhh. What are you getting? The Amber 3 is very highly rated.


I got a Holo May KTE.
To be 100% honest, the jury is still out on the Amber 3 vs. May...


----------



## jgwtriode (Mar 10, 2022)

I was lusting after a Baltic 3.  But that's at least another year a way that's around what I put into everything Since around October.  Worth every penney I spent and then some.
But know my New DAC arriving maybe within 10 days is a significantly rebuilt Gustard X 26 pro.  All the crap in the power supply is eliminated first including the Fuse.  Will have a very high quality Furutech Inlet. Will also eliminate about 8 layers of solder joints that are stock in this section.  I also know that three stage output stage will be trimmed down to 1 discreet stage.  All signal path resistors will be converted to sunumu surface mount.  A lot of the caps are replaced and/or bypassed and primary output will come through WBT Nexgen RCA's.  A lot of the rest I don't understand Ric's explanation well enough to try explain.  It will be pretty amazing but certainly no Lampi.

But it's all a process.  I did not imagine I would be at the place I am now a year ago.  I had just finished ordering VC leopardwoods on a special order from Zach at the time.  And had also just discovered Wywires and decided I needed a new harness that was less tweaky than My Crazy Mad Sci soldered in Graphene Carbon Fiber harness.

Happy listening,

jgwtriode


----------



## L0rdGwyn

Glad you are enjoying the VC + Airmid pairing @jgwtriode , will be fun to hear how it changes when you get your DAC.  Totally agree with @Monsterzero on upgrading your source, it will bring the baseline up significantly.

I almost bought a quad of PCM63 chips recently with thoughts of upgrading my DAC at some point, thankfully the seller ignored my offer and the fit of upgraditis passed lol.  Since I am looking into building an LCR phono, I've created a digital vs. analog arms race in my mind.


----------



## jgwtriode (Mar 12, 2022)

Thanks Keenan!

If I had about 5 to 6 thousand laying around it would be nice to do some records again, but I moved away from all that so many years ago.  But there is a charm and wonder in playing records that is very satisfying, even the constant cleaning and maintainence.  Used to drive my friends nuts.  But I would always run over my Nitty Gritty before playing it.  Always the first thing after pulling it out of the sleeve.  Clean it and LAST it.

Happy listening,

jgwtriode


----------



## L0rdGwyn

Whoops, never mind, guy got back to me.  So I'll be getting a quad of PCM63P-K DAC chips.  I'll redesign my DAC boards and upgrade at some point.  These chips are hard to find and expensive, had to jump on a quad from the same batch.  This is considered the top vintage R2R Burr-Brown chip, specifically the "K" grade, should be interesting.




Out of town for a week, will get moving again on the 6336 OTL when I get back, and finally put those grills on my speakers, and get things prepared for upcoming Airmid build.


----------



## jgwtriode

Hey Keenan just wondering since the 5998 is a dual triode.  Can you swap channels on the tubes after one side is used and
then use the other side.  Are the sockets wired to allow that.  Maybe not a good idea.  But I figured it was worth asking.

Thanks,

jgwtriode


----------



## L0rdGwyn

@jgwtriode the two sections are wired in parallel, so both are being used in one channel.  You don't really want to be using only one section of a dual triode as the unused section will be damaged via cathode poisoning.


----------



## whirlwind

L0rdGwyn said:


> Whoops, never mind, guy got back to me.  So I'll be getting a quad of PCM63P-K DAC chips.  I'll redesign my DAC boards and upgrade at some point.  These chips are hard to find and expensive, had to jump on a quad from the same batch.  This is considered the top vintage R2R Burr-Brown chip, specifically the "K" grade, should be interesting.
> 
> 
> 
> Out of town for a week, will get moving again on the 6336 OTL when I get back, and finally put those grills on my speakers, and get things prepared for upcoming Airmid build.



Really excited to see how the 6336 turns out  

Normally, I would also be very excited to see the Browns snag Amari Cooper, but after watching the Bengals my inner self says we need much more!


----------



## L0rdGwyn

whirlwind said:


> Really excited to see how the 6336 turns out
> 
> Normally, I would also be very excited to see the Browns snag Amari Cooper, but after watching the Bengals my inner self says we need much more!



Gonna try to get to work on it pronto when I get home!  On a little vacation 😎 have everything I need waiting for me when I get back.  Lots of precise drilling that needs to be done on the three heat sinks, that will be the bulk of the work.

Yeah Browns need some help, further away than we thought I think.  Here's hoping Baker turns it around, otherwise we are starting from scratch!


----------



## whirlwind

L0rdGwyn said:


> Gonna try to get to work on it pronto when I get home!  On a little vacation 😎 have everything I need waiting for me when I get back.  Lots of precise drilling that needs to be done on the three heat sinks, that will be the bulk of the work.
> 
> Yeah Browns need some help, further away than we thought I think.  Here's hoping Baker turns it around, otherwise we are starting from scratch!


You much deserve a vacation, and yeah, if Baker can't turn it around...we are totally screwed!


----------



## jgwtriode

L0rdGwyn said:


> @jgwtriode the two sections are wired in parallel, so both are being used in one channel.  You don't really want to be using only one section of a dual triode as the unused section will be damaged via cathode poisoning.


Thanks for the explanation,.

jgwtriode


----------



## gibosi

L0rdGwyn said:


> @jgwtriode the two sections are wired in parallel, so both are being used in one channel.  You don't really want to be using only one section of a dual triode as the unused section will be damaged via cathode poisoning.



It's my understanding that some builders wire them in series. What are the advantages you see for parallel versus series?


----------



## L0rdGwyn

gibosi said:


> It's my understanding that some builders wire them in series. What are the advantages you see for parallel versus series?



It all depends on what you are trying to accomplish with the circuit.  In this type of OTL topology which uses a cathode follower output, the output tubes provide no voltage gain, they operate at unity, gain of 1, but actually a bit less, so some voltage is lost.  The purpose of the output stage is to provide current gain, another way of putting that is to lower the output impedance.  A cathode follower is a buffer - it provides an easy resistive and capacitive load to the stage preceding it, and provides a low output impedance / high output current to the following stage.  In this case of a cathode follower OTL, that low output impedance is used for driving a headphone load without the need of an impedance matching transformer.

Putting two cathode followers in parallel will halve the output impedance, roughly, so it provides more current drive for the load.  Putting two cathode followers in series won't give any benefit as you essentially have a buffer driving a buffer and lose some current to drive the load for the second section in the series.

There are other things you can do with two sections of a dual triode however.  One thing is SRPP, which is how they are used in the Glenn OTL.  In essence, this provides some of the buffering advantages of the cathode follower while also providing some voltage gain.

Another option is to wire one section as a common cathode amplifier (aka, a voltage gain stage), then direct-couple it to the second section as a cathode follower.  Similar to SRPP, you then get some voltage gain as well as a low output impedance.  The merits of this approach vs. SRPP are often argued in DIY circles, not necessarily in the context of OTL headphone amplifiers, but in general as these circuits have utility in many different designs, in preamps for example.  Of course you can also wire both sections in cascade, two voltage gain stages in series, but this isn't so great for driving a difficult load.  Dual triodes are often used this way to attain high levels of gain in amplifiers that use global negative feedback.

In this particular circuit, that extra voltage gain isn't needed as all voltage gain is provided by the 6J5 input stage.  The best result is reached then by paralleling the two sections of the output stage to get the lowest output impedance, distortion, and highest current drive.


----------



## triod750

I understand that some ways are good and some ways are different. In what way is SEPP different and can it in any way be good?
(Really, I am just pretending to understand but you don't have to worry about that).


----------



## Monsterzero

triod750 said:


> I am just pretending to understand but you don't have to worry about that).


That's okay. My head began to hurt about half way thru the first paragraph


----------



## pravous

L0rdGwyn said:


> It all depends on what you are trying to accomplish with the circuit.  In this type of OTL topology which uses a cathode follower output, the output tubes provide no voltage gain, they operate at unity, gain of 1, but actually a bit less, so some voltage is lost.  The purpose of the output stage is to provide current gain, another way of putting that is to lower the output impedance.  A cathode follower is a buffer - it provides an easy resistive and capacitive load to the stage preceding it, and provides a low output impedance / high output current to the following stage.  In this case of a cathode follower OTL, that low output impedance is used for driving a headphone load without the need of an impedance matching transformer.
> 
> Putting two cathode followers in parallel will halve the output impedance, roughly, so it provides more current drive for the load.  Putting two cathode followers in series won't give any benefit as you essentially have a buffer driving a buffer and lose some current to drive the load for the second section in the series.
> 
> ...


How does using both triodes in parallel affect how you evaluate power tubes for matching?  Ill throw some theoretical values out there.  You have a 6AS7G that tests 6000/7000 gm.  You have another that say tests for 5000/8000 gm.  How does the Airmid see those tubes?  Do you add and divide by two or is it more complicated than that? Basically what is the effect on I, rp, gm, and mu when both halves are run in parallel?


----------



## L0rdGwyn (Mar 15, 2022)

triod750 said:


> I understand that some ways are good and some ways are different. In what way is SEPP different and can it in any way be good?
> (Really, I am just pretending to understand but you don't have to worry about that).



One advantage of SRPP (aka SEPP) is the two sections of the triode operate in push-pull, aka balanced, so even harmonic distortion can be "cancelled" if the circuit is optimized.  This optimization occurs at a fixed load chosen by the designer, meaning that when it is operating with a different load the circuit will no longer be perfectly balanced and distortion will increase.  The output impedance of SRPP is lower than that of a common cathode amplifier stage (a conventional tube gain stage) and it still provides voltage gain.  The cathode follower provides no voltage gain, but the output impedance is still lower than that of SRPP using the same tube.  Distortion is low in a cathode follower as well due to its 100% internal negative feedback, hence the operation at unity gain.  So, if you need a stage with a lowish output impedance but still require some voltage gain and the load is fixed, SRPP could be a good choice.  If you only need a buffer circuit, no voltage gain, and the lowest possible output impedance (with just a tube, no sand assistance), then the cathode follower could be a good choice.  The two circuits have different characteristics.  I haven't compared parallel cathode follower vs. SRPP in otherwise equivalent circuits, so hard to say how they differ subjectively, but for me, the lowest output impedance is desirable.



pravous said:


> How does using both triodes in parallel affect how you evaluate power tubes for matching?  Ill throw some theoretical values out there.  You have a 6AS7G that tests 6000/7000 gm.  You have another that say tests for 5000/8000 gm.  How does the Airmid see those tubes?  Do you add and divide by two or is it more complicated than that? Basically what is the effect on I, rp, gm, and mu when both halves are run in parallel?



More equal sections means more equal current sharing between the two sections when paralleled.  The tubes in Airmid aren't biased anywhere near max plate dissipation, so some unevenness of current sharing is not going to cause an issue, the sections do not need to be perfectly matched.  Generally the gm of the two sections is additive as is current, plate resistance can be treated the same as two parallel resistors ((1/Rtotal)=(1/R1)+(1/R2)), mu is the same.


----------



## triod750

How do you make the load fixed?


----------



## L0rdGwyn (Mar 14, 2022)

triod750 said:


> How do you make the load fixed?



If it is a headphone amplifier, optimize for a specific headphone load (e.g., 300ohms) then only use headphones of that impedance or accept some increase in distortion if using other impedances.  If it is is a preamp, optimize for the input impedance of the following amplifier.


----------



## triod750

Thank you, myL0rd. It's soo easy to design amplifiers - a piece of cake for children!


----------



## jgwtriode

Thanks for the explanation Keenan.   Always good to get more technical to have a better understanding about why it works so well.

jgwtriode


----------



## jgwtriode (Mar 15, 2022)

A few trinkets showed up today in the mail.   Some more mad Sci sample discs to fiddle with and their new network cable.  It's moderately pricey but not horrible.  So hooked it up from my internet router to my computer.  Still just running tidal from my
Sound card to my Airmid.  Holy Smokes!  Noticeable improvement in dynamics, kick and bottom end smack.  May have even
give me about another 5 Hz down or at least punched things up around 30 Hz on my VC's.   I may have to throw some more money into streaming.  Like a better network card. 

Have to play around with this cable, quite stiff and some really wild overdone connectors.  Not sure how long burn in is?  Do network cables burn in the same fashion as IC's?

But Wow I can hear the Airmid creating even more now.  It's crazy that a headphone is doing this kind of bass.  Not just going low.  But creating slam and impact and creating remarkable large palpable images of those instruments.  I have never heard that out of a pair of headphones before.   Hot Damn this is fun.    Everything else has improved as well. But that is what really startled me when I first hooked this network cable up.    Still waiting for my other stuff so I can really get into it again.

Happy listening,

jgwtriode


----------



## Zachik

jgwtriode said:


> A few trinkets showed up today in the mail. Some more mad Sci sample discs to fiddle with and their new network cable. It's moderately pricey but not horrible. So hooked it up from my internet router to my computer. Still just running tidal from my
> Sound card to my Airmid. Holy Smokes! Noticeable improvement in dynamics, kick and bottom end smack. May have even
> give me about another 5 Hz down or at least punched things up around 30 Hz on my VC's. I may have to throw some more money into streaming. Like a better network card.


Interesting... I have always been (and still am) skeptic about network cables. 
Unless it is used for I2S (if both source and DAC use RJ45 for I2S).


----------



## jgwtriode

I didn't really believe it either.   But Bob at Mad Scientest, told me to try it.  So he sent me one to do that with.  All I can say is yup there is definetly improvement.  Is it commensurate with the price? 

That is what I am going to determine after a couple more days of break in.   $479 for a 2M.  I'm on the edge right now but it may be necessary to
keep.  Another week or so and we shall see. 

If I keep it I suppose I will also later put in an audiophile level network card and requisite LPS or SuperCap.   There is always one more thing.

Happy listening,

jgwtriode


----------



## Zachik

@jgwtriode - I understand you're streaming from Tidal. So, your setup is something like?
<ISP provided router> Mad Scientist network cable <PC> 

No network switch or other network cables in the path?


----------



## jgwtriode

Exactly.   It's temporary.  Normally I convert everything streaned from Tidal to 24bit Flac using DrMare software and store it on a Micron SLC Sata SSD drive.  Run all of it through Jplay Femto and 3 other software packages that enhance what Jplay does all loaded from a separate drive of the same type.  That goes through A JCAT XE USB card and then to my DAC etc.  So right now I'm in holding pattern waiting to put that all back into play when my new DAC gets here.    

So really just fiddling around right now probably at least another week.   I am just simply amazed at how good this sounds and I would argue it probably shouldn't. 

jgwtriode


----------



## Tjj226 Angel

triod750 said:


> How do you make the load fixed?



You either have a fixed load or you don't. Short of running an SEPP stage into a power output tube/mosfet or using planar headphones, you are pretty much SOL.

Part of the reason SEPP does NOT make for a good OTL output stage is because most (if not all) high impedance headphones have a highly varying impedance. Worse yet, the variation usually occurs smack dab in the human vocal region. 

This is why some of the most fervent mu follower tube amp designers out there will admit that a mu follower headphone amp is a bad idea.


----------



## triod750

Tjj226 Angel said:


> You either have a fixed load or you don't.


I understand this is a design choice but that's about it. I don't understand much about these things and when I partly understand something I am very quick to forget it. Sometimes I even forget that I asked the question   .

But when someone asks a question there are probably several others that benefit from the answers so I guess I did the right thing. Thank you for your response.


----------



## Zachik

jgwtriode said:


> Exactly.   It's temporary.  Normally I convert everything streaned from Tidal to 24bit Flac using DrMare software and store it on a Micron SLC Sata SSD drive.  Run all of it through Jplay Femto and 3 other software packages that enhance what Jplay does all loaded from a separate drive of the same type.  That goes through A JCAT XE USB card and then to my DAC etc.  So right now I'm in holding pattern waiting to put that all back into play when my new DAC gets here.
> 
> So really just fiddling around right now probably at least another week.   I am just simply amazed at how good this sounds and I would argue it probably shouldn't.
> 
> jgwtriode


Interesting - I never heard of Jplay Femto nor DrMare conversion software.
I was actually curious to try HQ Player to up-sample my FLAC files (all range from 44.1K to 96K with very few at 192K). Did you ever try HQ Player? or just went with Jplay Femto?

As for your setup: since you're not really streaming in realtime from Tidal, but rather play locally stored offline files - I do not see how better ethernet cables could make ANY difference...  
I am sure there is some pseudo-scientific explanation as to why, even in this scenario, better ethernet cable would improve sound quality, but as much as I am always trying to keep an open mind - I cannot see how that could be relevant *in this offline playback scenario*!


----------



## jgwtriode

No you misunderstand me.  I am not running any of that right now.  I have a new DAC that is being rebuilt and modded.  I have nothing now.  So the only thing running is
Tidal on my computer, streaming.  No stored files.  Dont have my JCAT XE even running at the moment as a result.  My Tmobile router to Mad Sci Network cable running from
my sound card(onboard) through a modded improvise 3.5 to RCA cable into the Airmid and then my Leopardwood VC's.    Would seemingly suck as a signal source and yet 
it doesn't.   This is what I am currently running.  I thought I made that clear.   I would anticipate when my system is running as intended that improved streaming would improve my DrMare conversion potentially as well.   We shall see

Happy listening,

jgwtriode


----------



## Zachik

jgwtriode said:


> So the only thing running is
> Tidal on my computer, streaming. No stored files.


Got it. Thanks for clarifying


----------



## jgwtriode (Mar 15, 2022)

No sweat!  Still trying to figure out the whole streaming thing.  I love Jplay and have gotten quite used to it.  But HQ played with Roon and all the Sonoree stuff maybe more flexible, albeit more expensive. Have to sort that out.  DrMare software works pretty well for creating 96k 24bit Flac files from streamed Tidal files.  Store on SLC sata 2 ssd's.  But there has to be a better answer!

jgwtriode


----------



## leftside

jgwtriode said:


> No sweat!  Still trying to figure out the whole streaming thing.  I love Jplay and have gotten quite used to it.  But HQ played with Roon and all the Sonoree stuff maybe more flexible, albeit more expensive. Have to sort that out.  DrMare software works pretty well for creating 96k 24bit Flac files from streamed Tidal files.  Store on SLC sata 2 ssd's.  But there has to be a better answer!
> 
> jgwtriode


For streaming I just use Roon + Tidal. The main reason I have Tidal is not really for streaming, it's for the algorithms Roon uses in combination with "Roon Radio" and Tidal to find new music. 

Most of my music is purchased from sites like Bandcamp (where a lot of the music was originally found with "Roon Radio") This music is downloaded to a folder that I point Roon to. Roon is clever enough to make the Tidal streamed music and locally stored music all look like the same library. HQPlayer can be a worthy addition depending upon your DAC. Certainly worth a try.

My digital setup is fairly simple. SSD drive plugged into a PC. PC connected to network router. SOtM device connected to network router and DAC.


----------



## jgwtriode (Mar 17, 2022)

Mine is more than a bit carried away. JPlay Femto with Audiophile Optimizer 3.  Process Lasso latest.  I was using Audiophile Optimizer 8.8, but found Majority Clean works better without it and Process Lasso more effectively works with it that way.  Also found a particular application from Hungry Bear on JPLay forum which more effectively allows  Majority Clean to load into memory.  It is memory jitter reduction software.  Free app but a bit tweaky.  Found it on the Jplay forum.  Same guy who developed Bughead Emperor.  I run Jplay with Bubble Upn as the control point.   Use older Micron SLC drives for system and
FLAC files.  Those drives sound better to me.  I run them with 4 inch super thin wire Sata cables and use Mad Scientist Nano Sample Discs around the connections.  I run my I5 at 1100MHz using throttlestop and I also undervolt it quite a bit. USB card is a JCAT XE run on cuinas super cap ISO, which also powers the SSD's.  I run that from the JCAT to my DAC. Which I am waiting for and then out the DAC straight into my Airmid which drives my ZMF VC.  I use tidal for casual listening and to create streamed recording content for DRmare.  96K 24bit Flacs.  sound much better than CD's, not quite as good as DSD.  Mostly Blue Coast stuff.

I may go more streamed at some point but it would require a huge change if I switched over to a Roon/ Sonore/ HQ player approach.   Not ready for that yet.

Happy listening,

jgwtriode


----------



## leftside

jgwtriode said:


> Miine is more than a bit carried away. JPlay Femto with Audiophile Optimizer 3.  Process Lasso latest.  I was using Audiophile Optimizer 8.8, but found Majority Clean works better without it and Process Lasso more effectively works with it that way.  Also found a particular application from Hungry Bear on JPLay forum which more effectively allows  Majority Clean to load into memory.  It is memory jitter reduction software.  Free app but a bit tweaky.  Found it on the Jplay forum.  Same guy who developed Bughead Emperor.  I run Jplay with Bubble Upn as the control point.   Use older Micron SLC drives for system and
> FLAC files.  Those drives sound better to me.  I run them with 4 inch super thin wire Sata cables and use Mad Scientist Nano Sample Discs around the connections.  I run my I5 at 1100MHz using throttlestop and I also undervolt it quite a bit. USB card is a JCAT XE run on cuinas super cap ISO, which also power the SSD's.  I run that from the JCAT to my DAC. Which I am waiting for and then out the DAC straight into my Airmid which drives my ZMF VC.  I use tidal for casual listening and to create streamed recording content for DRmare.  96K 24bit Flacs.  sound much better than CD's, not quite as good as DSD.  Mostly Blue Coast stuff.
> 
> I may go more streamed at some point but it would require a huge change if I switched over to a Roon/ Sonore/ HQ player approach.   Not ready for that yet.
> ...


No wonder people are starting to discover vinyl again


----------



## jgwtriode (Mar 17, 2022)

Indeed that is true.  Analog was never this complicated...even with tweaking.  Just so many things effect the sound of digital files.  It's crazy!  Every single bit of that stuff I do makes a difference in how it sounds!


jgwtriode


----------



## bcowen

leftside said:


> No wonder people are starting to discover vinyl again


Very true.  With vinyl, you only need to deal with overhang, tangency, azimuth, VTA, SRA, tracking force, effective mass/cartridge compliance and antiskate before you get past the cartridge and on to the rest of the setup.  🤣🤣

Of course, many of those are trivial for those not afflicted with Analog OCD.  😂


----------



## L0rdGwyn (Mar 17, 2022)

Lol for me vinyl is WAY more complex in terms of work, making a DAC is probably the most involved project I've done so far, but now I just turn it on, and go.  Meanwhile, my vinyl setup has a laundry list of projects that just seems to get longer and longer, not to mention cleaning and maintenance of vinyl, storage space, cost, turntable setup, etc.

Flying home tomorrow, will have three more days off before going back to work, going to see how far I can get on the 6336 OTL in that timeframe.  Could probably finish it, but not as into 8-10 hour DIY sessions as I once was.  We will see!


----------



## jgwtriode

It may have been that I was simply far less obsessive about how things sounded when I was running my analog setup.  I was aware of those things but once I had the cartridge aligned with the alignment  tool, for get the name of it, I just sighted the tonearm angle in and called it good.  Tried a few different shelf structures and stands and settled on
an old VPI  turntable stand with  a composite shelf and then obsessed about keeping the records clean and preserved.  Nitty Gritty Record Cleaner and Last.  Was very content with my Well Tempered table, modified well tempered arm and a Van Den Hul One cartridge.   Until a very modified CD player and modded Cal Audio DAC actually held thier own against my analog setup.

Back in the day,

jgwtriode


----------



## bcowen

jgwtriode said:


> It may have been that I was simply far less obsessive about how things sounded when I was running my analog setup.  I was aware of those things but once I had the cartridge aligned with the alignment  tool, for get the name of it, I just sighted the tonearm angle in and called it good.  Tried a few different shelf structures and stands and settled on
> an old VPI  turntable stand with  a composite shelf and then obsessed about keeping the records clean and preserved.  Nitty Gritty Record Cleaner and Last.  Was very content with my Well Tempered table, modified well tempered arm and a Van Den Hul One cartridge.   Until a very modified CD player and modded Cal Audio DAC actually held thier own against my analog setup.
> 
> Back in the day,
> ...


Some of us go off the deep end with such most things.  

Seriously though, a lot depends on the cartridge being used. As the stylus profile gets more complex (usually as the cartridge price increases), the extreme fine tuning yields very audible sonic improvements.  Not as much of a big deal with a cartridge that has, say, a conical tip.


----------



## Zachik

bcowen said:


> Some of us go off the deep end with such most things.
> 
> Seriously though, a lot depends on the cartridge being used. As the stylus profile gets more complex (usually as the cartridge price increases), the extreme fine tuning yields very audible sonic improvements.  Not as much of a big deal with a cartridge that has, say, a conical tip.


Haha. I am re-watching the entire "24" TV series with my son, and this case looks like their "advanced interrogation kit"...


----------



## jgwtriode

Hahahahahahahhah!   That's Hilarious



jgwtriode


----------



## leftside

bcowen said:


> Some of us go off the deep end with such most things.
> 
> Seriously though, a lot depends on the cartridge being used. As the stylus profile gets more complex (usually as the cartridge price increases), the extreme fine tuning yields very audible sonic improvements.  Not as much of a big deal with a cartridge that has, say, a conical tip.


Yep that's right. I even have Analog Magik. One weekend I decided I needed to learn to setup my Benz cart properly. The magnifying glass you have in that picture is very important for lining up correctly things like the zenith. I also have a SMARTractor https://www.musicdirect.com/accessories/Acoustical-Systems-SMARTractor-Alignment-Tool.

The nice thing about Analog Magik is that when you make a change and you tell yourself "yep that sounds" better, you can measure your changes to check and see if you are delusional or not. Every time I found if "measured better" was true, then "sounds better" would also be true. It measures stuff like turntable speed, azimuth, VTF, VTA, etc. Apparently the next version would also have a zenith measurement.

Since this "experience" I am never buying a Benz cart again. They sound great, but the cantilever is so close to the cart shell that you can barely see it when making adjustments.


----------



## Zachik

jgwtriode said:


> Miine is more than a bit carried away. JPlay Femto with Audiophile Optimizer 3. Process Lasso latest. I was using Audiophile Optimizer 8.8, but found Majority Clean works better without it and Process Lasso more effectively works with it that way. Also found a particular application from Hungry Bear on JPLay forum which more effectively allows Majority Clean to load into memory. It is memory jitter reduction software. Free app but a bit tweaky. Found it on the Jplay forum. Same guy who developed Bughead Emperor. I run Jplay with Bubble Upn as the control point. Use older Micron SLC drives for system and
> FLAC files. Those drives sound better to me. I run them with 4 inch super thin wire Sata cables and use Mad Scientist Nano Sample Discs around the connections. I run my I5 at 1100MHz using throttlestop and I also undervolt it quite a bit. USB card is a JCAT XE run on cuinas super cap ISO, which also power the SSD's. I run that from the JCAT to my DAC. Which I am waiting for and then out the DAC straight into my Airmid which drives my ZMF VC. I use tidal for casual listening and to create streamed recording content for DRmare. 96K 24bit Flacs. sound much better than CD's, not quite as good as DSD. Mostly Blue Coast stuff.
> 
> I may go more streamed at some point but it would require a huge change if I switched over to a Roon/ Sonore/ HQ player approach. Not ready for that yet.


Several questions, if you do not mind...
* I have never tried ANY of the "audiophile optimizers" be it Audiophile Optimizer 3 or Fidelizer 8.8. My PC is running Win 10 and Jriver MC27 (now upgrading to the latest MC29). Did you hear ANY difference between "stock" Windows and an optimized Windows? They have really nice marketing fluff and claims on their websites, but I am often curious whether one can hear a difference? (and whether it screws up Windows such that some software, like Jriver MC, would not work properly anymore)
* Process Lasso - what did you use it for? My understanding is that its use it to be able to assign specific processes to specific cores in your PC? So what did you actually do with it? and how did it improve your sound?
* Majority Clean - I could not find this one at all... What does it do? What is "memory jitter"?! Can you share a link?
* HQ Player - you mention it as a possible change. Did you try it?  I am curious to try it, but most likely only if it can work with Jriver MC, since that is the music server / library software that I am used to (and love its interface).

Thanks!


----------



## jgwtriode (Mar 17, 2022)

http://www.mics.ne.jp/~cdorya/MajiorityClean/#download.   Here is the main thread about it. http://jplay.eu/forum/index.php?/topic/3063-pink-hq-minorityclean/page-122.
It was previously called minority clean!.

That is the fourum where I really learned about it and it is constantly being discussed.  No have never tried HQplayer.  Just heard about it.


jgwtriode


----------



## bcowen

Zachik said:


> Several questions, if you do not mind...
> * I have never tried ANY of the "audiophile optimizers" be it Audiophile Optimizer 3 or Fidelizer 8.8. My PC is running Win 10 and Jriver MC27 (now upgrading to the latest MC29). Did you hear ANY difference between "stock" Windows and an optimized Windows? They have really nice marketing fluff and claims on their websites, but I am often curious whether one can hear a difference? (and whether it screws up Windows such that some software, like Jriver MC, would not work properly anymore)
> * Process Lasso - what did you use it for? My understanding is that its use it to be able to assign specific processes to specific cores in your PC? So what did you actually do with it? and how did it improve your sound?
> * Majority Clean - I could not find this one at all... What does it do? What is "memory jitter"?! Can you share a link?
> ...


I use Fidelizer Pro to good effect.  It shuts down (or deprioritizes) a number of services that are unrelated and unnecessary for audio. Whether this would affect JRiver I can't say, although I'd be surprised if it did. I use it on a laptop prior to starting Tidal, and there is a noticeable sonic improvement.  Not night and day, but worthwhile to my ears.


----------



## Zachik

jgwtriode said:


> http://www.mics.ne.jp/~cdorya/MajiorityClean/#download. Here is the main thread about it. http://jplay.eu/forum/index.php?/topic/3063-pink-hq-minorityclean/page-122.
> It was previously called minority clean!.


Thanks. Looks like it is pretty specific for certain USB controllers. Definitely not relevant for me then...



jgwtriode said:


> No have never tried HQplayer. Just heard about it.


Same here.



bcowen said:


> I use Fidelizer Pro to good effect. It shuts down (or deprioritizes) a number of services that are unrelated and unnecessary for audio. Whether this would affect JRiver I can't say, although I'd be surprised if it did. I use it on a laptop prior to starting Tidal, and there is a noticeable sonic improvement. Not night and day, but worthwhile to my ears.


Have you ever compared to "Audiophile Optimizer 3"?
Unlike Fidelizer Pro, Audiophile Optimizer permanently changes Windows (though it can be uninstalled). May or may not be an issue, but since my music server PC is only used for that purpose - likely not an issue.
Interestingly, Fidelizer claims to be compatible with Audiophile Optimizer, so one could install both...


----------



## bcowen

Zachik said:


> Thanks. Looks like it is pretty specific for certain USB controllers. Definitely not relevant for me then...
> 
> 
> Same here.
> ...


I've never tried Audiophile Optimizer.  Since I use my laptop for things other than audio (when not listening), I like that Fidelizer only changes things when you open it. Takes about 30 seconds to do its thing, but I'm willing to live with that in trade for being able to quickly un-do everything with a reboot.  Just works out better for my personal usage requirements


----------



## triod750

Now I love my cdp even more...


----------



## jgwtriode (Mar 17, 2022)

Fidelizer Pro works great with Audiophile Optimizer, Jplay and Windows and for the most part Process Lasso.  It does apparently reinstall some of the processes you can pull out with Process Lasso.   These noticeably affect the performance of Majority Clean and prevent it from fully loading and operating in memory.  On that Jplay forum there are some explanations from Hungry Bear about this.  He also make a better installer App than what the developer uses to load it.  You don't want to just run it, although that still improves things.  You want to use an application that loads it and runs it from memory.   You also want to optimize it/s settings with process lasso.  Hungry Bear has a tutorial that he refers to on that Jplay  thread.  You can also use it with HQ player.' Ultimaty Majority Clean gives a better result without Fidelizer.  The overall effect is
best without Fidelizer in the mix.

jgwtriode


----------



## Zachik

jgwtriode said:


> Ultimaty Majority Clean gives a better result without Fidelizer


If I understand it correctly - Majiority Clean only works with specific USB controller, like the one in the JCAT USB cards.
So for me (and most others) - it just won't work...


----------



## jgwtriode

That might be true....I am not really sure.  Hadn't thought about it.  I am quite happy with how my JCAT XE works with a Wywires USB.

jgwtriode


----------



## Monsterzero (Mar 17, 2022)

edit: wrong thread


----------



## L0rdGwyn

Exciting news with the release of ZMF's Atrium, I was fortunate to have an earlier prototype of the headphone on hand during development and testing of Zach's 45 amplifier.  It is going to be a big hit.

My own personal pair of Atrium in bubinga will be shipping to me today.  Going to use it as motivation to try and finish my 6336 OTL by Monday.  Will post photos and impressions of the Atrium in the official thread once they've had some time to burn in and I've teased out differences in the final version.


----------



## whirlwind

L0rdGwyn said:


> Exciting news with the release of ZMF's Atrium, I was fortunate to have an earlier prototype of the headphone on hand during development and testing of Zach's 45 amplifier.  It is going to be a big hit.
> 
> My own personal pair of Atrium in bubinga will be shipping to me today.  Going to use it as motivation to try and finish my 6336 OTL by Monday.  Will post photos and impressions of the Atrium in the official thread once they've had some time to burn in and I've teased out differences in the final version.



That Bubinga looks killer.

Get busting on that 6336.....


----------



## L0rdGwyn

whirlwind said:


> That Bubinga looks killer.
> 
> Get busting on that 6336.....



Gonna stuff some PCBs when I get home in a few hours!!!


----------



## Mr Trev

L0rdGwyn said:


> Gonna stuff some PCBs when I get home in a few hours!!!


Stuffin PCBs…
You know, everthing _does_ sound dirty if you say it right


----------



## jgwtriode

whirlwind said:


> That Bubinga looks killer.
> 
> Get busting on that 6336.....


Love Bubbinga.  Have some waterfall bubbinga boards I got on sale from Woodcrafters.     There is always something new to be had.   Would be great if you can do some comparisons between the Atrium's and the VC.   Sold my Auteurs to cover some other stuff I need.   So will start saving up for Atriums. probably next year barring some other
extra income showing up.

Still very happy with my VC's especially with the Airmid.  Hopefully my DAC is back within another week or two and my Wywire RCA and power cord.  

Happy listening and congrats on the Atrium,

jgwtriode


----------



## L0rdGwyn

Had enough energy to finish the main power supply PCB, revised for the 6336 OTL and including 3-pin fan headers for intake directly below the 6336.  Settled on a 7.5ohm series resistor which will drop the operating voltage of the 90mm fans a hair below 4V.  They are very quiet at this speed, but could adjust later if necessary.  Will get back to it tomorrow morning.


----------



## L0rdGwyn (Mar 19, 2022)

Got a lot done on the 6336 OTL today.  Mains transformer mounted, all PCBs are complete.  The real doozy though was the precision drilling of the three heat sinks for mounting of components.  Finished that as well, so all of the hard stuff is done at this point, now the easy (albeit tedious) point-to-point wiring of the circuit!  Will get going on that tomorrow, hopefully will finish by the evening and test, assuming there are no surprises.

Here is how the chassis looks with the two side panel heat sinks mounted.  Only thing missing from the top now are two gigantic blue capacitors.


----------



## whirlwind

L0rdGwyn said:


> Got a lot done on the 6336 OTL today.  Mains transformer mounted, all PCBs are complete.  The real doozy though was the precision drilling of the three heat sinks for mounting of components.  Finished that as well, so all of the hard stuff is done at this point, now the easy (albeit tedious) point-to-point wiring of the circuit!  Will get going on that tomorrow, hopefully will finish by the evening and test, assuming there are no surprises.
> 
> Here is how the chassis looks with the two side panel heat sinks mounted.  Only thing missing from the top now are two gigantic blue capacitors.


Dang, thing is a monster. Those are some big hunks of heat sinks  

Sounds like Baker is going to be packing his bags!


----------



## L0rdGwyn

whirlwind said:


> Dang, thing is a monster. Those are some big hunks of heat sinks
> 
> Sounds like Baker is going to be packing his bags!



I am in shock with everything that has happened in the past 24 hours!  What a whirlwind (no pun intended).


----------



## whirlwind

L0rdGwyn said:


> I am in shock with everything that has happened in the past 24 hours!  What a whirlwind (no pun intended).


 I know, right.  a guaranteed $230 million contract   ....yikes!

Hopes it all works out.


----------



## L0rdGwyn

whirlwind said:


> I know, right.  a guaranteed $230 million contract   ....yikes!
> 
> Hopes it all works out.



Yeah we'll see, hard to feel good about it given his character...Browns always find a way to stay in the news lol.


----------



## pravous

L0rdGwyn said:


> Got a lot done on the 6336 OTL today.  Mains transformer mounted, all PCBs are complete.  The real doozy though was the precision drilling of the three heat sinks for mounting of components.  Finished that as well, so all of the hard stuff is done at this point, now the easy (albeit tedious) point-to-point wiring of the circuit!  Will get going on that tomorrow, hopefully will finish by the evening and test, assuming there are no surprises.
> 
> Here is how the chassis looks with the two side panel heat sinks mounted.  Only thing missing from the top now are two gigantic blue capacitors.


Being relatively new to soldering the point to point aspect of diy is the part I find pretty relaxing.   Spent last weekend doing the Etracer build.  For me the stripping wire and making molex connectors is tedious.  For whatever reason the soldering is relaxing, probably because it is new and still fun.


----------



## L0rdGwyn

pravous said:


> Being relatively new to soldering the point to point aspect of diy is the part I find pretty relaxing.   Spent last weekend doing the Etracer build.  For me the stripping wire and making molex connectors is tedious.  For whatever reason the soldering is relaxing, probably because it is new and still fun.



It definitely can be relaxing!  But I'm always rushing these days, trying to get projects done as quickly as possible.


----------



## jgwtriode

LOrdGwyn:


Zach gave you a shout out on his most recent interview with TylerEclectic  on You Tube.   Talks about the Air Mountain being the best tube amp he has ever heard, about 25minutes in.   Pretty Awesome.  .   

Still waiting on my DAC and Wywires cables.  But even with lousy noisey source( Tidal from Asus sound card) the Airmid is still sounding better.

Happy listening

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> LOrdGwyn:
> 
> 
> Zach gave you a shout out on his most recent interview with TylerEclectic  on You Tube.   Talks about the Air Mountain being the best tube amp he has ever heard, about 25minutes in.   Pretty Awesome.  .
> ...




Hey cool!  Thanks for linking the vid, Zach has told me as much in private, it really turned out well, the clarity and holography makes your jaw drop.  But that's with eight transformers, seven power supply regulators, not a cheap or simple build, I set out to make it the best amp he owns and it was many, many hours of work, so I'm happy he likes it so much.  I think it's a good representation of what can be achieved using tubes with contemporary power supply design, I would love for some stark anti-tube objectivists to listen to it and tell me it sounds bad lol if it makes it to CanJam Chicago, I'll tell some folks on ASR to stop by the ZMF booth and give it a listen.

Going to work on my OTL again this afternoon.  Atrium is supposed to arrive too  gonna be a busy day!


----------



## L0rdGwyn

Also @jgwtriode when is your fated DAC finally going to arrive?!


----------



## jgwtriode (Mar 20, 2022)

I wish I knew!  Ric was supposed to have it done a week ago.   But other projects came up and Ric is someone who always follows his own timetable.  He also was not taking any calls from me.  Only found out by email he was working on it this weekend.  So I am hoping it will be shipping this week!

@LOrdGwyn Your welcome....thought it would be a good thing to link to your page!

Happy listening,

jgwtriode


----------



## Zachik

L0rdGwyn said:


> I'll tell some folks on ASR to stop by the ZMF booth and give it a listen.


I do not think these guys care to listen! Only measure... 
(and that is the reason I completely avoid their site now)


----------



## L0rdGwyn

Zachik said:


> I do not think these guys care to listen! Only measure...
> (and that is the reason I completely avoid their site now)



Yeah I'm not so into the ethos of the site, I think there are aspects of audio that are not well-captured by the measurements, but measurements do have their role, and there are some very knowledgeable engineers who hang out over there, so it has its value for me!  I also post my tube projects there to shake things up LOL I made a post all about my tube DAC expecting to be lambasted for it, on the contrary everyone loved it, I was shocked.


----------



## jgwtriode (Mar 20, 2022)

As the good book says! "He that hath ears, let him hear!"   I remember back in the day the words of the old "Tin Ears" himself; Julian Hirsch, editor and writer for Stereo Review.  And of course to make himself  authoritative in pseudo scientific fashion he created Hirsch Houk labs which of course made him credible in his own mind.

"It sounded as we expected it to!"  

It's all about the science, right?

LOL,

Happy listening or measuring if you prefer,

jgwtriode


----------



## smodtactical

L0rdGwyn said:


> Got a lot done on the 6336 OTL today.  Mains transformer mounted, all PCBs are complete.  The real doozy though was the precision drilling of the three heat sinks for mounting of components.  Finished that as well, so all of the hard stuff is done at this point, now the easy (albeit tedious) point-to-point wiring of the circuit!  Will get going on that tomorrow, hopefully will finish by the evening and test, assuming there are no surprises.
> 
> Here is how the chassis looks with the two side panel heat sinks mounted.  Only thing missing from the top now are two gigantic blue capacitors.



Hey man looks cool. Any chance you'll release schematics or plans of how to build this amp once your done for the DIY community (for a price of course)? Thanks


----------



## L0rdGwyn

smodtactical said:


> Hey man looks cool. Any chance you'll release schematics or plans of how to build this amp once your done for the DIY community (for a price of course)? Thanks



Thanks!  But sorry, I won't be sharing details of this design, but happy to answer questions or help if you are working on a project.


----------



## L0rdGwyn

Well as usual I got caught on a snag, bad component which sucked away 3 hours of troubleshooting.  Alas, the OTL is not done, but it's _almost_ done.  Probably have another 2-3 hours of work left to do, should have it finished by the early afternoon tomorrow.

Here is how it looks with the output caps in place.




This will give my Atrium a good 24 hours of burn in before I listen, have been running them on pink noise since they arrived.  Will post pics of the headphone and amp tomorrow when its done.


----------



## raindownthunda

L0rdGwyn said:


> Well as usual I got caught on a snag, bad component which sucked away 3 hours of troubleshooting.  Alas, the OTL is not done, but it's _almost_ done.  Probably have another 2-3 hours of work left to do, should have it finished by the early afternoon tomorrow.
> 
> Here is how it looks with the output caps in place.
> 
> ...


This is insane. I love it.


----------



## jgwtriode

Are those Clarity Caps? How big are they? Oh just out of curiosity since Monster mentioned he is doing Goldpioint pots in his Airmid.  What value is appropriate and would it improve things replacing the standard one?

Can't wait for your Atrium impressions and also how the 6336 sounds.

Happy listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Are those Clarity Caps? How big are they? Oh just out of curiosity since Monster mentioned he is doing Goldpioint pots in his Airmid.  What value is appropriate and would it improve things replacing the standard one?
> 
> Can't wait for your Atrium impressions and also how the 6336 sounds.
> 
> ...



Yes, they are ClarityCaps, TC2 series as opposed to TC4 in Airmid.  Monster is going dual mono in his Airmid, but not Goldpoint, Alps.  I use 50K, 100K is fine too.  I personally don't think there are huge gains to be had in swapping pots unless you are swapping out a very low quality one.  Could consider a stepped attenuator if you like the feel of them and stepped volume, Goldpoints are pricey though.  I haven't tried them myself, but I would expect there to be some improvement using more exotic potentiometer types, like transformer based, but they are expensive and large, unlikely to fit in an amplifier not designed for them.


----------



## whirlwind (Mar 21, 2022)

L0rdGwyn said:


> Well as usual I got caught on a snag, bad component which sucked away 3 hours of troubleshooting.  Alas, the OTL is not done, but it's _almost_ done.  Probably have another 2-3 hours of work left to do, should have it finished by the early afternoon tomorrow.
> 
> Here is how it looks with the output caps in place.
> 
> ...


What component was the culprit.

I have a stepped attenuater in one of my amps and alps in one and they seem to be of same quality.
I think most liked stepped , but I actually kind of like the alps.

I suppose if I had one with tons of steps that it would be much better   

Can't wait to see it with the glass lit up.


----------



## L0rdGwyn

whirlwind said:


> What component was the culprit.
> 
> I have a stepped attenuater in one of my amps and alps in one and they seem to be of same quality.
> I think most liked stepped , but I actually kind of like the alps.
> ...



Probably a MOSFET in one of the power supply regulators, it protects the regulator IC itself, so since the MOSFET failed, the regulator also fried.  I moved to replace both parts since it was unlikely anything else broke, and as I removed the regulator, one of the PCB traces ripped -_- so I then had to go through the painstaking process of removing all of the parts that I did not have duplicates of from the PCB to put them on another board...that's why it took three hours LOL.

Yeah my feeling is, if you like the tactile feel of the stepped attenuator, then go for it, but I have found any sonic benefit to be minimal.

Won't have to wait much longer!  Just checked DC operating points of all of the tubes and power supply regs, all is working as intended.  Just need to do the input and output wiring and it will be good to go, another hour or two.


----------



## jgwtriode

L0rdGwyn said:


> Yes, they are ClarityCaps, TC2 series as opposed to TC4 in Airmid.  Monster is going dual mono in his Airmid, but not Goldpoint, Alps.  I use 50K, 100K is fine too.  I personally don't think there are huge gains to be had in swapping pots unless you are swapping out a very low quality one.  Could consider a stepped attenuator if you like the feel of them and stepped volume, Goldpoints are pricey though.  I haven't tried them myself, but I would expect there to be some improvement using more exotic potentiometer types, like transformer based, but they are expensive and large, unlikely to fit in an amplifier not designed for them.


Very good... I will leave well enough alone then.  Just wondered if the Goldpoint might improve on the Alps pots. But no worries.

Looking forward to your impressions on the Atrium.

jgwtriode


----------



## L0rdGwyn (Mar 21, 2022)

6336 OTL is done!

Here are some pics.


----------



## L0rdGwyn (Mar 21, 2022)

Listening now with my new Atrium in curly bubinga.  Arrived yesterday, been running on pink noise for about 24 hours.

Soundstage, clarity, excellent dynamics, the amp and the headphone are both keepers.  That's all I can say right now, both need burn in!


----------



## CJG888

Those caps are BIG!


----------



## L0rdGwyn

CJG888 said:


> Those caps are BIG!



That's what 600uF of film capacitance looks like!

I want to downsize the knob, I like the style, but haven't been able to find the model one size smaller (it's vintage).

Also, fans are perhaps a little too loud, so I will have to adjust the series resistor to drop some more voltage.

I am very curious what the measurements will look like, but not today, gonna kick back and enjoy  gotta try the VC too.


----------



## CJG888

L0rdGwyn said:


> That's what 600uF of film capacitance looks like!
> 
> I want to downsize the knob, I like the style, but haven't been able to find the model one size smaller (it's vintage).
> 
> ...


Maybe a traditional Bakelite „chicken head“?


----------



## L0rdGwyn

CJG888 said:


> Maybe a traditional Bakelite „chicken head“?



I do have some chicken heads somewhere, but I like the sort of "rugged" and fluted look of the knob, I feel it matches the aesthetic of the rest of the amplifier pretty well.  It's just a tad too big for my taste, looks oversized for the chassis methinks.


----------



## Zachik

Keenan - how does the new 6336 OTL compare to your Airmid OTL? (sound wise)


----------



## triod750

L0rdGwyn said:


> gonna kick back and enjoy


Enjoy pink noise for another 24 hours? You are hard core indeed?


----------



## L0rdGwyn

Zachik said:


> Keenan - how does the new 6336 OTL compare to your Airmid OTL? (sound wise)



Hmmm that's tough, as I don't have an Airmid in house right now and I've only listened to this amp for maybe two hours.  Let me take a rain check on that one for when I have @Monsterzero 's amplifier done .  I will say the Airmid's sound is more tweakable given it can use a number of different power tubes in the 6AS7G family, whereas this amp has two flavors only, 6336 and 6528.



triod750 said:


> Enjoy pink noise for another 24 hours? You are hard core indeed?



How else am I supposed to hear all the frequencies at once?  It is the only way.


----------



## Zachik

L0rdGwyn said:


> Hmmm that's tough, as I don't have an Airmid in house right now and I've only listened to this amp for maybe two hours. Let me take a rain check on that one for when I have @Monsterzero 's amplifier done . I will say the Airmid's sound is more tweakable given it can use a number of different power tubes in the 6AS7G family, whereas this amp has two flavors only, 6336 and 6528.


Got it. Will wait for you to complete MZ's Airmid then.
Not that one can order either amp... but I am just curious as to what the non-conventional-for-OTL 6336 do to an OTL?


----------



## L0rdGwyn (Mar 21, 2022)

Zachik said:


> Got it. Will wait for you to complete MZ's Airmid then.
> Not that one can order either amp... but I am just curious as to what the non-conventional-for-OTL 6336 do to an OTL?



A 6336 can roughly be thought of as two 6AS7G in parallel in one bottle.  The 6528 can roughly be thought of as 2-3 5998 in one bottle.  So the benefit of using these tubes fully biased is similar to using a pair of 6AS7G or 5998 in parallel.  That's pretty unusual though.  The GOTL does it, but it's not quite an apples-to-apples comparison since it uses an SRPP output as opposed to a cathode follower.  @leftside 's amp is the only other that I am aware of that can parallel multiple 6AS7G / 5998.

The reason it isn't common is because it's sort of overkill lol and it causes design challenges.  Once you start paralleling multiple 6AS7G / 5998 (or using 6336 or 6528), we are talking a lot of DC bias current, which means a lot of heat that needs to be dealt with.  That gets worse if you want to use regulated power supplies and active loading of the power tubes, hence the giant heat sinks in this amplifier.  Each of those side panel heat sinks is dissipating around 32W, the tubes bias at 275mA per channel, although that will increase slightly as the components warm up.

So anyway, from a sonic standpoint, paralleling multiple tubes or using equivalents like 6336 means a lower output impedance, lower noise, better control of the driver, increased dynamics, lower distortion. 

The pattern holds for output impedance, I've just measured it in my circuit for 6336 and 6528.  For 6336 with the sections paralleled, output impedance is ~23ohm, whereas it is ~50ohm for 6AS7G in Airmid.  For 6528 with parallel sections, output impedance is ~15ohm, whereas it is ~30ohm for 5998 in Airmid.

I attempted a distortion measurement at 1mW into 300ohm with the 6528, but it is lost in the noise floor, essentially inaudible.  My audio interface I use for measurements is acting funky though, I'll have to try again at a later date.

The sound is quite good!  Got the VC out now.


----------



## pravous

Congrats on the new OTL.  Those side heat sinks are amazing. The wavy fins break up what other wise might seem like a monolithic aesthetic.


----------



## L0rdGwyn

pravous said:


> Congrats on the new OTL.  Those side heat sinks are amazing. The wavy fins break up what other wise might seem like a monolithic aesthetic.



Thanks!  Yeah I like the look with the heat sinks, they were a necessity, so had to find a way to work them into the aesthetics, I'm happy with the result.  Except the knob is too big, think I found a smaller version, that will really tie it all together for me.


----------



## L0rdGwyn

Well, I hate the term, but for me I think this is probably headphone rig endgame.  With the Audial S5 feeding this OTL paired with the Atrium and Vérité Closed, I could be content listening to this setup for the rest of my life.

(But of course I'll have to build something else at some point)


----------



## triod750

L0rdGwyn said:


> Well, I hate the term, but for me I think this is probably headphone rig endgame.  With the Audial S5 feeding this OTL paired with the Atrium and Vérité Closed, I could be content listening to this setup for the rest of my life.


I want to read this statement in the midst of a heatwave. If it was me, my life would end right there so "the rest of my life" might be appropriate after all...


----------



## L0rdGwyn

triod750 said:


> I want to read this statement in the midst of a heatwave. If it was me, my life would end right there so "the rest of my life" might be appropriate after all...



That's what the heat sinks, fans, and air conditioning are for  the chassis stays quite cool given the size of the heatsinks.  Only the tubes themselves get hot.  No touchy!


----------



## triod750

I thought the heatsinks were responsible for the air conditioning  .


----------



## bcowen

L0rdGwyn said:


> Thanks!  Yeah I like the look with the heat sinks, they were a necessity, so had to find a way to work them into the aesthetics, I'm happy with the result.  Except the knob is too big, think I found a smaller version, that will really tie it all together for me.


There's no such thing as having a knob that's too big.    

Seriously, as a ZMF fan (but not boy) I'm really interested in your thoughts on the Atriums once they're all settled in, especially in comparison to the VC's.  The VC's were my next planned upgrade at some point in the near future.


----------



## L0rdGwyn (Mar 21, 2022)

bcowen said:


> There's no such thing as having a knob that's too big.
> 
> Seriously, as a ZMF fan (but not boy) I'm really interested in your thoughts on the Atriums once they're all settled in, especially in comparison to the VC's.  The VC's were my next planned upgrade at some point in the near future.



For sure!  I'll post my thoughts on them here at some point in the next few weeks.


----------



## leftside

L0rdGwyn said:


> The reason it isn't common is because it's sort of *overkill*
> 
> So anyway, from a sonic standpoint, paralleling multiple tubes or using equivalents like 6336 means a lower output impedance, lower noise, better control of the driver, increased dynamics, lower distortion.
> 
> The pattern holds for output impedance, I've just measured it in my circuit for 6336 and 6528.  For 6336 with the sections paralleled, output impedance is ~23ohm, whereas it is ~50ohm for 6AS7G in Airmid.  For 6528 with parallel sections, output impedance is ~15ohm, whereas it is ~30ohm for 5998 in Airmid.


Lowering that output impedance certainly helps with lower impedance headphones like the Abyss.


----------



## L0rdGwyn

leftside said:


> Lowering that output impedance certainly helps with lower impedance headphones like the Abyss.




No doubt!  With a 15ohm output impedance and 600uF output caps, this new OTL should run low impedance headphones no problem.


----------



## Monsterzero (Mar 22, 2022)

leftside said:


> Lowering that output impedance certainly helps with lower impedance headphones like the Abyss.



The very first song to use double bass as a roll, thus spawning the speed and thrash metal genres!

Philthy Animal Taylor on drums!

https://www.onlinedrummer.com/drum-beats/overkill-motorhead/


----------



## L0rdGwyn

I took some quick measurements of the 6336 / 6528 OTL last night after work.

*Output Z:*
6336 - 24ohm
6528 - 15ohm

*THD w/ 6528:*
1mW into 300ohm 0.007%
1mW into 120ohm 0.013%
1mW into 80ohm 0.029%
1mW into 32ohm 0.11%

All distortion above is pure H2. Distortion measurements were largely dependent on the quality of the 6J5, I chose one that measured well.  Looking pretty good there with a 300ohm load.

*Frequency Response:*

300ohm



32ohm


----------



## jgwtriode

@LOrdGwyn are those GEC L63's, just without the sticker that is normally on them?

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> @LOrdGwyn are those GEC L63's, just without the sticker that is normally on them?
> 
> jgwtriode



Yup!  L63, that particular pair did not have the labeling when I bought them.


----------



## jgwtriode

Nice,  looks a lot cleaner and less busy without labeling....!

jgwtriode


----------



## L0rdGwyn

Yeah, I think so too!  Got my downsized vintage knob, was able to track one down, now all is in balance.


----------



## triod750

I'm lucky this isn't mine. I can't stand that kind of blue. Miles Davis' Kind of Blue was better...

(Blue leds are horrible to me).

I agree with you on the knob - much better!


----------



## L0rdGwyn

triod750 said:


> I'm lucky this isn't mine. I can't stand that kind of blue. Miles Davis' Kind of Blue was better...
> 
> (Blue leds are horrible to me).
> 
> I agree with you on the knob - much better!



I don't really see the blue since it is the chosen color of ClarityCap, a brand I hold in high regard, I only see quality audio component!  My eyes have been trained.


----------



## triod750

You are the scientific kind and I am more emotional and sensible and fragile


----------



## triod750

Actually, if the amp was mine, I wouldn't see the colour either since I close my eyes when listening.


----------



## jgwtriode

Clarity Cap Blue, a lovely shade and tone.  I remember the First Time I saw some large Blue Caps in a modified Hafler DH220.  Loved the Look of them then, still do.   And how can you not love the look of  LOrdGywn's lastest.  Stunning and those Heatsinks add an extra ferocity that makes it all the more serious looking!


jgwtriode


----------



## L0rdGwyn

triod750 said:


> You are the scientific kind and I am more emotional and sensible and fragile



I will spray paint them in magenta to appeal to your delicate sensibilities


----------



## bcowen

L0rdGwyn said:


> I will spray paint them in magenta to appeal to your delicate sensibilities


Paint them a slightly lighter shade of blue and you'd get a free season pass to Tarheel country.    

UCLA is favored to win tonight.  I choose to remain optimistic.


----------



## bcowen

bcowen said:


> Paint them a slightly lighter shade of blue and you'd get a free season pass to Tarheel country.
> 
> UCLA is favored to win tonight.  I choose to remain optimistic.


UNC 73, UCLA 67.  Perhaps optimism isn't overly overrated.  😂😂😂


----------



## leftside

Now you see them. Now you don't. I did consider leaving the covers off... but when the tubes were plugged in I thought they looked better covered up. With your amp though, I think they look better exposed.


----------



## CJG888

Clarity Caps are Welsh. They should be red…


----------



## whirlwind

For aesthetic purpose, I do like the smaller knob better


----------



## L0rdGwyn

whirlwind said:


> For aesthetic purpose, I do like the smaller knob better



Thanks!  Yeah as soon as I got that big one I was like "woah, it's huge", small knob is a better look.

I am loving this amp, it is undoubtedly a permanent resident.  Bass dynamics, staging, clarity is top notch with Atrium and VC.


----------



## whirlwind

L0rdGwyn said:


> Thanks!  Yeah as soon as I got that big one I was like "woah, it's huge", small knob is a better look.
> 
> I am loving this amp, it is undoubtedly a permanent resident.  Bass dynamics, staging, clarity is top notch with Atrium and VC.



Man, the bass dynamics should be crazy....that is like running 4 6AS7G!


----------



## triod750

L0rdGwyn said:


> clarity is top notch with Atrium and VC.


Clarity blue caps are top notch with....


----------



## L0rdGwyn

I dismantled two of my amplifiers today.  The 841 hybrid amplifier dismantling was a long time coming.  So I now have a pair of Sowter parafeed headphone transformers hanging around, going to just hold onto them for now, if I end up with a planar magnetic headphone at some point, then maybe I'll build the spud amplifier, would be an easy build, have just about everything I would need for it already and the sound is good.

I also took apart my 45 parafeed amplifier.  Over time, I decided the 1.5W of the 45 just wasn't cutting it for my speakers, and it was not optimal as a headphone amplifier either as it used speaker transformers.  Tastes have changed too and I can get better sound out of the 45 using a different topology.  So that amplifier is gone too.  Now I have some Sowter parafeed transformers along with the mains transformer on hand.  Not sure of the fate of the parafeed transformers yet, could use them in my HY69 amp if I wanted to go parafeed, TBD on that front.  But the mains transformer from the 45 amplifier is perfect for a direct-coupled 45 headphone amplifier.  So it will stick around with the potential of that becoming a project some day.  Gotta put it to use considering Sowter no longer does custom mains.

No hurry to build any other personal amps though, TBH it was becoming a pain having unused amplifiers taking up space, I am now just running the three.

801A A2 SET in my main two-channel system
6A5G SET in my little bedroom two-channel setup
6336 / 6528 OTL in the headphone setup

Nice and simple  so yeah, maybe a spud headphone amp in the future, maybe a direct-coupled 45 headphone amplifier, at some point an HY69 speaker amplifier, and at some point a HK54 speaker amplifier, no timeline on any of them.

Next up are some Airmids, promises made before I shut things down, for @Monsterzero , Zach, and friend of Zach.  Parts are starting to arrive, three sets of output caps.




As far as other upcoming personal projects, going to revamp my Thorens turntable, new tonearm new plinth, possible upgraded DC motor controller.  Also have a quad of PCM63 on the way, so I will likely upgrade my DAC from PCM56 to PCM63 later this year.  I am weighing an LCR phono design, although what I have in mind would be very costly, we'll see.  Also I am still waiting for the metal speaker grills for my Klipsch Forte IV, taking a little longer than expected.

That is all I have to report!  Will show Monster's Airmid as it comes along.

P.S. the new ZMF Atrium is absolutely kicking ass with the new OTL, absolutely love this combo.


----------



## Zachik

L0rdGwyn said:


> Next up are some Airmids, promises made before I shut things down, for @Monsterzero , Zach, and friend of Zach.


Haha. Reading this sentence got me confused for a sec... Keenan building an amp for ME?!?! YAY!!!!    
(then I realized it was Zach. Not Zachi. sigh )


----------



## L0rdGwyn

Zachik said:


> Haha. Reading this sentence got me confused for a sec... Keenan building an amp for ME?!?! YAY!!!!
> (then I realized it was Zach. Not Zachi. sigh )



LOL sorry Zachi!  I imagine that happens a lot in the ZMF threads


----------



## Zachik

Maybe 1 day you WILL build a really cool amp for me....


----------



## Mr Trev

L0rdGwyn said:


> I dismantled two of my amplifiers today.  The 841 hybrid amplifier dismantling was a long time coming.  So I now have a pair of Sowter parafeed headphone transformers hanging around, going to just hold onto them for now, if I end up with a planar magnetic headphone at some point, then maybe I'll build the spud amplifier, would be an easy build, have just about everything I would need for it already and the sound is good.


Mind elaborating on what the build might look like?
I've invested enough in planars myself, and am trying to brain out what would be my best option for getting the "tubiest" sound out of them. The majority of hybrid amps seem to be mostly voiced towards the SS spectrum and OTL are out of the question. From the bit of research I've been able to gather even OTC may not have adequate current to best drive planars ( emailed Hagerman about the Tuba and he said his Sundara do sound good, but just don't have the volume they need)


----------



## Monsterzero

Mr Trev said:


> Mind elaborating on what the build might look like?
> I've invested enough in planars myself, and am trying to brain out what would be my best option for getting the "tubiest" sound out of them. The majority of hybrid amps seem to be mostly voiced towards the SS spectrum and OTL are out of the question. From the bit of research I've been able to gather even OTC may not have adequate current to best drive planars ( emailed Hagerman about the Tuba and he said his Sundara do sound good, but just don't have the volume they need)


You may want to research the Wells Dragon. I have a level 3 here on loan, and there is plenty of tube goodness in the mids, but as you mentioned. not as much as an OTL. If that is your deciding criteria, you probably will not find it.

It can drive the Susvara & Abyss 1266 all the way down to sensitive IEMs, and everything in between, all with a very impressive black background.


----------



## bpiotrow13

Mr Trev said:


> Mind elaborating on what the build might look like?
> I've invested enough in planars myself, and am trying to brain out what would be my best option for getting the "tubiest" sound out of them. The majority of hybrid amps seem to be mostly voiced towards the SS spectrum and OTL are out of the question. From the bit of research I've been able to gather even OTC may not have adequate current to best drive planars ( emailed Hagerman about the Tuba and he said his Sundara do sound good, but just don't have the volume they need)


Maybe not the cheapest, but ear yoshino hp4 may be worth trying.


----------



## Mr Trev

Monsterzero said:


> You may want to research the Wells Dragon. I have a level 3 here on loan, and there is plenty of tube goodness in the mids, but as you mentioned. not as much as an OTL. If that is your deciding criteria, you probably will not find it.
> 
> It can drive the Susvara & Abyss 1266 all the way down to sensitive IEMs, and everything in between, all with a very impressive black background.


I'm not expecting anything near OTL levels of tubiness - I've conceded that just ain't possible. Mostly, at the moment, I'm looking for options in the "full glass" market that'll pair well with planars. The one amp I do know about is the Cayin HA-1A. But they dropped the option for running the EL84s in triode mode on the mk.II model. Granted ultralinear mode is the option for using planars, but it'b be nice to still have triode for my non-planars. Plus I haven't read much about how well it responds to rolling tubes either


----------



## L0rdGwyn

Mr Trev said:


> Mind elaborating on what the build might look like?
> I've invested enough in planars myself, and am trying to brain out what would be my best option for getting the "tubiest" sound out of them. The majority of hybrid amps seem to be mostly voiced towards the SS spectrum and OTL are out of the question. From the bit of research I've been able to gather even OTC may not have adequate current to best drive planars ( emailed Hagerman about the Tuba and he said his Sundara do sound good, but just don't have the volume they need)



Well the spud design I have in mind uses triode-strapped high gm pentodes (6E6P, E810F, D3a), these work well in the circuit due to high gain and low plate resistance, ie., a lowish output impedance when transformer coupled.

This would be around 0.5W amplifier, no planar will come close to sucking that much power, I think it could drive just about anything, but I know there is a propensity for people to want high power amplifiers for their planars.  If you were looking for something with tubes and an excess of power, probably something with a speaker amplifier tube would be up your alley, like 2A3, 300B, EL34, KT88, etc.

High current availability translates to a low output impedance, probably why people like running the headphones out of speaker amplifiers as they need to have output impedances low enough to damp 4 and 8ohms.  Could even get a speaker tube amplifier and run the planars off a speaker tap, typical output impedance for a SET speaker amplifiers is 2-3ohms on an 8ohm tap.  Output impedance will be higher if the transformers are wound for headphones as the turns ratio will be lower.


----------



## Mr Trev

So would this be something along the lines of one of those Shortest Way SW-51 amps thats been getting some hype on The-Forum-Whose-Name-Shant-Be-Mentioned


----------



## L0rdGwyn

Mr Trev said:


> So would this be something along the lines of one of those Shortest Way SW-51 amps thats been getting some hype on The-Forum-Whose-Name-Shant-Be-Mentioned



Hmm that looks to be a spud design, but can't say much else about it without a picture of the circuit or a schematic.


----------



## pravous

Excited to hear that there will be some more Airmid owners.  I have been having so much fun with mine.  Hoping to get lucky and grab a pair of Atriums tomorrow.  The ZMF pads for the hd650 were such an improvement that I just have to see what an entire ZMF package will bring to the table.  
  I have been playing around with some of the 6J5 substitutes with adaptors.  Tung Sol quad of VT-76 and 5998s are amazing in this amp.


----------



## L0rdGwyn

pravous said:


> Excited to hear that there will be some more Airmid owners.  I have been having so much fun with mine.  Hoping to get lucky and grab a pair of Atriums tomorrow.  The ZMF pads for the hd650 were such an improvement that I just have to see what an entire ZMF package will bring to the table.
> I have been playing around with some of the 6J5 substitutes with adaptors.  Tung Sol quad of VT-76 and 5998s are amazing in this amp.



Nice!  I am going to try those ZMF HD650 pads at some point, actually I think Zach was gonna send me some now that I think about it  if you manage to get an Atrium, you will love it.  I feel like a lot of different headphones have been called a "super HD650", but while the Atrium isn't exactly that, I think it does a lot of things that make the HD650 so well loved, it is extremely well rounded, warm, nice impactful bass, large soundstage, smooth euphonic mids, it's gonna be a big hit.  Atrium in on the 6336 OTL is astounding, which has much of the same DNA as Airmid, it will be a great pairing.


----------



## jgwtriode

L0rdGwyn said:


> Nice!  I am going to try those ZMF HD650 pads at some point, actually I think Zach was gonna send me some now that I think about it  if you manage to get an Atrium, you will love it.  I feel like a lot of different headphones have been called a "super HD650", but while the Atrium isn't exactly that, I think it does a lot of things that make the HD650 so well loved, it is extremely well rounded, warm, nice impactful bass, large soundstage, smooth euphonic mids, it's gonna be a big hit.  Atrium in on the 6336 OTL is astounding, which has much of the same DNA as Airmid, it will be a great pairing.


Still waiting for my new rebuilt modded DAC to properly hear my Airmid but blew me away out of my computers Sound Card streaming from Tidal.  Have A Wywires Platinum power cord and RCA cable arriving this weekend for it.  I am Running GEC L63 with my 5998's.

Happy Listening

jgwtriode


----------



## jgwtriode (Mar 31, 2022)

oops that was intended as a response to pravous.   Oh well this mild Flu has me a bit loopy!  Definetly like that Dual Mono Front Panel! And it looks great in Dark Gray! Would love a pair of Atriums...but as pretty as Bubbinga is...steel is not my first choice in metal finish and I would like a different wood.   I need to wait anyway.  My VC's are less than a year old and I have thrown more than 8K at this hobby this last 11 months..  Have to chill till next year.

jgwtriode


----------



## pravous

L0rdGwyn said:


> Nice!  I am going to try those ZMF HD650 pads at some point, actually I think Zach was gonna send me some now that I think about it  if you manage to get an Atrium, you will love it.  I feel like a lot of different headphones have been called a "super HD650", but while the Atrium isn't exactly that, I think it does a lot of things that make the HD650 so well loved, it is extremely well rounded, warm, nice impactful bass, large soundstage, smooth euphonic mids, it's gonna be a big hit.  Atrium in on the 6336 OTL is astounding, which has much of the same DNA as Airmid, it will be a great pairing.


The ZMF lambskin perforated for the hd650 are amazing.  If the stock pads lean slightly to the warm, the Zmf pads make the 650 balanced? neutral?  To me with my chain it felt like they perfectly balanced the headphone.  Treble, mid, bass all present and all distinct.   Bass is slightly tighter and sharper.  Combine all this with the Airmid and the last month has been as much fun as the first month.  One more track… That sounded great what about this album…


----------



## pravous

jgwtriode said:


> oops that was intended as a response to pravous.   Oh well this mild Flu has me a bit loopy!  Definetly like that Dual Mono Front Panel! And it looks great in Dark Gray! Would love a pair of Atriums...but as pretty as Bubbinga is...steel is not my first choice in metal finish and I would like a different wood.   I need to wait anyway.  My VC's are less than a year old and I have thrown more than 8K at this hobby this last 11 months..  Have to chill till next year.
> 
> jgwtriode


I have zero regrets going for the dual mono Goldpoint’s.  It turns out my hearing imbablance isn’t as bad as I thought.  99% of the time it takes one, at most 3 clicks to make things sound centered in my ears.  I initially had plans to make a faceplate with numbers to go behind the volume knobs but I have found I don’t need them.   For me my default is 9/46 when I turn the amp on.
   I have been considering ZMF headphones ever since I have read about them here on headfi.   I was stuck in that decision paralysis between vc/vo. For me the deciding factor was that many of the reviewers seemed to indicate that the Atrium is much kinder to lesser mastered recordings.   I am a deadhead with literal terabytes of live recordings and while most are miles above most bands some can still be pretty rough. Atrium at least as described seemed to solve my dilemma.  Best of luck to everyone tomorrow!


----------



## jgwtriode (Apr 1, 2022)

pravous said:


> I have zero regrets going for the dual mono Goldpoint’s.  It turns out my hearing imbablance isn’t as bad as I thought.  99% of the time it takes one, at most 3 clicks to make things sound centered in my ears.  I initially had plans to make a faceplate with numbers to go behind the volume knobs but I have found I don’t need them.   For me my default is 9/46 when I turn the amp on.
> I have been considering ZMF headphones ever since I have read about them here on headfi.   I was stuck in that decision paralysis between vc/vo. For me the deciding factor was that many of the reviewers seemed to indicate that the Atrium is much kinder to lesser mastered recordings.   I am a deadhead with literal terabytes of live recordings and while most are miles above most bands some can still be pretty rough. Atrium at least as described seemed to solve my dilemma.  Best of luck to everyone tomorrow!


Hope your able to get a very nice pair! You going cherry or bubbinga?

Happy listening,

jgwtriode


----------



## L0rdGwyn

pravous said:


> I have zero regrets going for the dual mono Goldpoint’s.  It turns out my hearing imbablance isn’t as bad as I thought.  99% of the time it takes one, at most 3 clicks to make things sound centered in my ears.  I initially had plans to make a faceplate with numbers to go behind the volume knobs but I have found I don’t need them.   For me my default is 9/46 when I turn the amp on.
> I have been considering ZMF headphones ever since I have read about them here on headfi.   I was stuck in that decision paralysis between vc/vo. For me the deciding factor was that many of the reviewers seemed to indicate that the Atrium is much kinder to lesser mastered recordings.   I am a deadhead with literal terabytes of live recordings and while most are miles above most bands some can still be pretty rough. Atrium at least as described seemed to solve my dilemma.  Best of luck to everyone tomorrow!



I would agree Atrium is forgiving, moreso than a lot of other TOTL headphone where what you are paying for is detail retrieval.  Atrium strikes a delicate balance between detail retrieval, natural timbre, and musicality.  It manages to sound detailed without emphasizing imperfections, IME.


----------



## pravous

jgwtriode said:


> Hope your able to get a very nice pair! You going cherry or bubbinga?
> 
> Happy listening,
> 
> jgwtriode


I am going to try for the stock cherry.  My sense from the Atrium thread is that will be the least popular option.  Ill take the discount and let the cherry age on its own.  Maybe try to get a spare set of grill covers down the line and have them powder coated to match the Airmid.


----------



## pravous

Order is in and was painless.  Whoever does ZMFs website is pretty slick.  Had my order all configured and the second it hit 11am it moved right into the cart.  Stock cherry, magnesium chassis and auteur lambskin perforated for my second set of pads.  Now the waiting begins.  Very excited to listen to a ZMF headphone on the Airmid.


----------



## jgwtriode

You will love it!  The Airmid just locks in with my VC!  You can hear it just open it up and force it to do what it is supposed to.  This despite my mediocre source of the moment.  My new rebuilt DAC currently being modified is taking far to long to be completed!  

You will have to share once it shows up!

Happy listening,

jgwtriode


----------



## heliosphann

pravous said:


> The ZMF lambskin perforated for the hd650 are amazing.  If the stock pads lean slightly to the warm, the Zmf pads make the 650 balanced? neutral?  To me with my chain it felt like they perfectly balanced the headphone.  Treble, mid, bass all present and all distinct.   Bass is slightly tighter and sharper.  Combine all this with the Airmid and the last month has been as much fun as the first month.  One more track… That sounded great what about this album…


I agree.  https://www.head-fi.org/showcase/zmf-sennheiser-6-pads-review.25732/


----------



## L0rdGwyn

pravous said:


> Order is in and was painless.  Whoever does ZMFs website is pretty slick.  Had my order all configured and the second it hit 11am it moved right into the cart.  Stock cherry, magnesium chassis and auteur lambskin perforated for my second set of pads.  Now the waiting begins.  Very excited to listen to a ZMF headphone on the Airmid.



Awesome, let us know what you think when you get them 



heliosphann said:


> I agree.  https://www.head-fi.org/showcase/zmf-sennheiser-6-pads-review.25732/



I gotta try a pair of these.


----------



## L0rdGwyn (Apr 2, 2022)

Waiting for chassis to be made for those Airmids, my grills for my Klipsch speakers will arrive tomorrow, will plan to put those together Monday.

With the quad of PCM63 on the way, I have been thinking about what I want to do with these chips.  It is a a set of four "K" grade from the same batch, not easy to find these days.

At first I had anticipated upgrading my PCM56 DAC.  As I've explored that, I've decided it may not be worth it.  The PCM56 design is good, I think it would be a shame to change it, especially as the PCM63 has some quirks that would require circuit modifications to adapt them.

So instead I think I will build a new DAC using PCM63.  The major quirk of the PCM63 is its 2mA current offset at the Iout pin.  I won't get too far into all of the technicalities, but it is something that needs to be addressed somehow in the design, many use either the on-chip bipolar offset pin (not good), or some sort of external current source or voltage reference to cancel out this unwanted DC offset.

I originally bought the four PCM63 with the thought of a single-ended DAC design and planning to have spares, but the idea had crossed my mind of doing a balanced configuration.  Of course all is subject to change, but I think this is the approach that I will take.

Specifically what I plan to do will be with...no tubes!!!  What I am thinking is a completely passive output using again Sowter I/V transformers.  I investigated this approach with parallel PCM56 when I was working on that design, but with the relatively low current output of the PCM56 (+/- 1mA), quite a few PCM56 would need to be paralleled to achieve a line level voltage output at an acceptable output impedance of the DAC.

Instead, using one pair of PCM63 balanced per channel with fully passive transformer I/V has four major benefits that I can think of off the top of my head:

1) current output of the PCM63 is double that of the PCM56 at +/- 2mA per chip, and with two running complementary, output increases to +/- 4mA per channel, equivalent to running four PCM56 in parallel, meaning a line level voltage output can be achieved with an acceptable output impedance in a fully passive configuration (i.e., no tubes)
2) running two PCM63 with the primary of the Sowter I/V transformer in balanced means the 2mA DC offset of the Iout pin of the chips will be cancelled, the current will flow from each chip in opposite polarity, meaning the avoidance of needing any output current injection or a voltage reference to cancel this DC offset and prevent magnetization of the transformer core, which means less interference of active componentry affecting the sound
3) cancellation of even order distortion on the output as well as quantization noise
4) no tubes means a smaller chassis, less complex power supply, less likelihood of power supply noise interference into signal path componentry from B+ or heater supplies.

I have more work to do on this idea, it still needs to be vetted, but if all of the boxes are checked, I would expect this to be an incredibly transparent DAC with nothing but a transformer between the Iout of the DAC chips and the RCA outs.  The transformer secondary could be wired for either balanced or single-ended outputs.

*TLDR:* I am planning to build a new DAC using PCM63 in a balanced configuration without tubes, more work to be done!


----------



## Mr Trev

L0rdGwyn said:


> Waiting for chassis to be made for those Airmids, my grills for my Klipsch speakers will arrive tomorrow, will plan to put those together Monday.
> 
> With the quad of PCM63 on the way, I have been thinking about what I want to do with these chips.  It is a a set of four "K" grade from the same batch, not easy to find these days.
> 
> ...


No tubes? @bcowen won't be happy about this


----------



## bcowen

Mr Trev said:


> No tubes? @bcowen won't be happy about this


I've been sulking and seriously questioning the meaning of life ever since I read that earlier this morning.


----------



## jgwtriode (Apr 2, 2022)

Well it would seem that Ric has been fighting his heart condition the last few weeks and that has slowed my DAC rebuild.  But on a positive note he  has done some tweaking on his transport and his test system which should allow him to better test the DAC and hear how his Analog stages are working.  So on a positive side he should be able to do now get even better sound out of the Gustard!   He also has an RF Zoebel networking idea he had for speakers that is similar to a couple of highly reviewed overpriced mods currently being sold.  Not familiar with them since I am not currently doing speakers.  But he has a surface mount resistor implementation of his approach to this, using his modified wima caps,  that  can be done on a much smaller scale and might work on headphones.  Reduced noise and possibly improving impedance curves.  May be able to implement right into the headphone cable.   Will look into it a bit more but sounds very interesting.  May have to play with it.      I love tweaks, love fiddling and tuning everything.   So maybe another one to put into the mix.


Happy listening,

jgwtriode


----------



## jgwtriode

There will be an Atrium closed.   38.30 in Zach discusses and shows an early version.    Okay well that's the new goal over the next year or so

Happy listening,

jgwtriode


----------



## bcowen

jgwtriode said:


> *There will be an Atrium closed. *  38.30 in Zach discusses and shows an early version.    Okay well that's the new goal over the next year or so
> 
> Happy listening,
> 
> jgwtriode



Cool.  I'm in.


----------



## L0rdGwyn

Custom grills I designed for my speakers arrived today.

To affix them to the magnetic MDF of my speakers, had to strip off the original cloth, sand down the residual glue on the substrates, drill new holes for mounting the grills, apply a new base black grill cloth, then affix the grills to the front with button head screws.

Here is the result.




Quite happy with it.



Funny thing is the whole point of this was to make the speakers cat proof lol well we did it, with style.


----------



## L0rdGwyn




----------



## jgwtriode

Damn those grilles looks ridiculously good.  Sweet deal!   Now your cat can just sit back and admire them!

Happy Listening,

jgwtriode










1


----------



## bcowen

L0rdGwyn said:


>


Very nice!!!!


----------



## jgwtriode (Apr 4, 2022)

Electrician came by today and rewired my room....EMF hassles with landlord....she has sensitivity to all of that.  Been a bit of a nightmare.  So Electrician drove a couple of grounding rods and isolated my room from the rest of the house.  If I was staying here more than another 6 months I may have opted for some audiophile grade outlets and better wire.  But even as it is it is, much better and lowered EMF issues with peripheral stuff upstairs that was tied to the same breaker.   Now I don't have to turn it off at nights.

Still running Tidal with no DAC straight in from Sound Card.   Been listening to a lot of old Sting stuff.   Marveling at the sound the Airmid allows the VC to pull out this mediocre source.   Stage is huge and deep, bass is tight rich and organic as hell,  Mids liquid and flowing with wonderful harmonics and liquid weight and texture.  Dynamics like a large speaker and detail that should just not be available.  Highs pure, airy and seemingly endless delicacy and resonace igniting the air with magic.  The Airmid is a musical portal that just opens its door and let whatever is there flood out into the VC unrestrained.  Never enjoyed listening to Sting this much before.   Threw on some old 2018 Reggae collaborations with Shaggy and just could not believe how much fun it was to listen to.   And then this crazy wild House remix of Roxannce called Redlight by Swedish House Mafia.  To much fun!  Swear I am listening to Full size speakers.  Crazy massive sound!

LOrdGwyn, Lord and Master of Music, Fire and Flame!!!!!

Happy Listening,

jgwtriode


----------



## L0rdGwyn (Apr 4, 2022)

Sorting through three Airmids worth of parts tonight to find the stuff specific to @Monsterzero 's which will come first.

It will have dual mono pots per his request, a pair of Alps RK27.  I made some PCBs specific for the mono pots rather than using the stereo PCBs I had on hand.



The other thing unique to this build will be the RCA inputs / outputs.  It will have a single set of RCA ins and a three-position switch, position 1 will sent the input signal to the amplifier, positions 2 and 3 will be connected to two pairs of RCA outputs.  Here is the NKK toggle switch and three pairs of Kimber RCAS.  I typically use Amphenol RCAs which I like very much, but needed something with a smaller footprint and @Monsterzero was okay with the additional cost of the Kimbers.



The chassis will be in a high gloss white, Super Mirror White.

https://www.columbiacoatings.com/S1790054.aspx



I'll be working the next few days, then will get started preparing PCBs for when the chassis arrives, which will be sometime in mid April.

After that will be Zach's, he has gone for a very unique textured powder, Gator Black.

https://www.columbiacoatings.com/gator-black.aspx



Planning is still underway for the third of the three Airmids.

I spent some more time today thinking through the new DAC idea.  I've determined DC offset of the PCM63 is actually a non-issue when transformer coupling, so rather than doing a balanced design, I am planning to do parallel single-ended.  This will maintain the advantage of using two chips to double the current output while simplifying the digital front end, going balanced comes with some headaches, a parallel design keeps things simple and my original power supply designed for the PCM56 DAC integrates very well.

I've ordered another pair of Sowter 1465 I/V transformers.  As I've mentioned, this will be a fully passive I/V stage, about as simplistic as it can get for a current output DAC.  The output signal path will go: parallel PCM63 Iout > Sowter SUT w/ secondary loading resistor > RCA outs.

Going this fully passive route is a balancing act between the load seen by the DAC (which affects distortion and noise), the desired output voltage, and the desired output impedance.

What I will probably try first is the SUT wired in 1:5 with a 2.5K secondary resistor.  This will show the PCM63 a reflected 100ohm load and result in a 1.4Vrms output voltage at 2.5K output impedance, pretty well rounded in terms of compromises.  The other approach would be to wire the SUT for 1:10 and shoot for a true line level 2Vrms (good), loading resistor would then be around 7K with a 70ohm reflected load (good), but the output impedance would be 7K (bad!), that is high for a source component and would require my increasing the input impedance of my amplifiers.  But if the sound is better, it may be worth it.  I might also consider a switch such that the loading resistor could be changed for various output impedances / voltage to suit different pre / power amplifiers.  For example, my OTL has an excess of gain, so a lower loading resistor may improve the sound at the cost of output voltage, which is not needed.  BUT my 801A speaker amplifier is designed for a 2Vrms input sensitivity, so in that case a higher loading resistor may be desired to hit 2Vrms at the cost of a higher output impedance.  Always compromises...

So, will work on that DAC on the side.  Once plans are finalized and the PCBs are made (the true work), building a testing will be very simple since there are no tubes involved.

That's all for now!


----------



## jonathan c

L0rdGwyn said:


>


They look like the cat’s meow! 🤣 (Snell Es?)


----------



## CJG888

Those Klipsch Fortes now look like vintage Altecs!


----------



## CJG888

Of course, your cats now have a perfect „ladder“ for climbing onto the turntable!

Just saying…


----------



## whirlwind

L0rdGwyn said:


> Custom grills I designed for my speakers arrived today.
> 
> To affix them to the magnetic MDF of my speakers, had to strip off the original cloth, sand down the residual glue on the substrates, drill new holes for mounting the grills, apply a new base black grill cloth, then affix the grills to the front with button head screws.
> 
> ...



Just Wow! 

Those look killer Keenan!


----------



## L0rdGwyn

jonathan c said:


> They look like the cat’s meow! 🤣 (Snell Es?)



Nice  they are Klipsch Forte IVs, 99dB/W.



CJG888 said:


> Of course, your cats now have a perfect „ladder“ for climbing onto the turntable!
> 
> Just saying…



They can jump up there actually, but they don't have much interest.  Speaker grill cloth without any barrier though is prime scratching material, not anymore!


----------



## L0rdGwyn

whirlwind said:


> Just Wow!
> 
> Those look killer Keenan!



Thanks, Joe!


----------



## bcowen

L0rdGwyn said:


> Sorting through three Airmids worth of parts tonight to find the stuff specific to @Monsterzero 's which will come first.
> 
> It will have dual mono pots per his request, a pair of Alps RK27.  I made some PCBs specific for the mono pots rather than using the stereo PCBs I had on hand.
> 
> ...


The Kimber RCA jacks are my favorite.  I never believed that RCA's could make much of a difference (assuming decent quality) until I tried the Kimbers.


----------



## Mr Trev

bcowen said:


> The Kimber RCA jacks are my favorite.  I never believed that RCA's could make much of a difference (assuming decent quality) until I tried the Kim


Barring things like mechanical grip, what exactly would make a difference?


----------



## bcowen

Mr Trev said:


> Barring things like mechanical grip, what exactly would make a difference?


Metallurgy and the dielectric (which is PTFE in the Kimbers) I suppose.  I have no better answer, just that each time I've replaced factory RCA's with Kimbers there has been an improvement to my ears.


----------



## jgwtriode

Having worked at Kimber a number of years, long ago, in technical support I can tell you Ultraplate is a unique electroless nickel that does sound diffrent than other plating.  Personally I liked the silver plated Kimber's even better.  Hard to find they haven't been produced in years.  

Kimber also distributes WBT in the USA.  The WBT NexGen are even a bit better honestly in either copper or silver.  For the dollar the NexGen copper are pretty great.  

The New KLE innovations for a few more dollars look pretty interesting, Sonic Craft has them at a healthy discount.   Lot cheaper than NexGen Silver. May have to try some of those when everything is back up and running.

Happy listening.

jgwtriode


----------



## Mr Trev

bcowen said:


> Metallurgy and the dielectric (which is PTFE in the Kimbers) I suppose.  I have no better answer, just that each time I've replaced factory RCA's with Kimbers there has been an improvement to my ears.


I'd have figured that stiffness/rigidity (ie. don't bend when plugging in) would trump anything that'd effect the sq.
On the topic of plating… I guess it does make a difference sound wise? I was under the impression that the biggest benefit for plating (gold or otherwise) was to prevent/minimize oxidation


----------



## bcowen

Mr Trev said:


> I'd have figured that stiffness/rigidity (ie. don't bend when plugging in) would trump anything that'd effect the sq.
> On the topic of plating… I guess it does make a difference sound wise? I was under the impression that the biggest benefit for plating (gold or otherwise) was to prevent/minimize oxidation


IME, the type of plating does make a difference, although it's pretty minor.  Of the four commonly used platings (that minimize oxidation), only nickel is to be avoided IMO (think glare).  Gold, silver, and rhodium all have a sound, but which sounds best probably depends on synergy and preference more than anything.


----------



## Zachik

bcowen said:


> IME, the type of plating does make a difference, although it's pretty minor.  Of the four commonly used platings (that minimize oxidation), only nickel is to be avoided IMO (think glare).  Gold, silver, and rhodium all have a sound, but which sounds best probably depends on synergy and preference more than anything.


Which one would make Marylin Manson's voice sound smooth?


----------



## Xcalibur255

Mr Trev said:


> I'd have figured that stiffness/rigidity (ie. don't bend when plugging in) would trump anything that'd effect the sq.
> On the topic of plating… I guess it does make a difference sound wise? I was under the impression that the biggest benefit for plating (gold or otherwise) was to prevent/minimize oxidation



In my experience the density of the conducting portion of the connector and the type/design of the dialectric matters more than the material.  The way the solder termination mates on the internal side matters too I am finding out.  For folks who think fancy connectors are a waste of money I always suggest exploring speaker binding posts before upgrading RCA connectors.  The difference is greater and easier to hear there.  Ironically some of the more expensive and "fancy" binding posts can actually sound quite terrible because of how thick they are.  Mass can be the enemy in this situation, and there is a trend in newer designs to greatly lower the mass of the portion of the connector actually carrying signal and make the rest of the mass of the post or connector more an insulator.


----------



## bcowen

Zachik said:


> Which one would make Marylin Manson's voice sound smooth?


Yes.

😝


----------



## L0rdGwyn

Rolled out of bed at 2PM today, gotta love that night shift!  Not capable of much movement, but I did finish my first draft of the parallel PCM63 DAC PCB before work.

Power supply is the same I designed for PCM56 with some minor adjustments, namely needing two transformers per channel instead of one due to the doubled current draw of running two chips.  This time I included the transformers on the board as opposed to separated.  The PCB is for one channel.

To keep things flexible, output from the PCB is the parallel Iout pins of the chips, so any following I/V stage can be used.  As I said, I am going to try fully passive with step-up transformer I/V, which is a battle of compromises.  If the result isn't good, I could easily change courses and do another tube output stage.  After the Airmids are done, I will build this up without a chassis, measure, listen, and make a decision.


----------



## L0rdGwyn

PCM63P-K chips arrived, the holy grail of vintage Burr-Brown R2R DACs.  These are getting very hard to find.


----------



## CJG888

L0rdGwyn said:


> PCM63P-K chips arrived, the holy grail of vintage Burr-Brown R2R DACs.  These are getting very hard to find.


DAC chips are becoming like tubes!


----------



## L0rdGwyn (Apr 8, 2022)

CJG888 said:


> DAC chips are becoming like tubes!



Lol there are definitely some similarities, these old R2R chips have similar mystique to tubes, probably why you see many NOS R2R DACs using tubes.  All I can say is I like what I've heard, so I've bought in!


----------



## Mr Trev (Apr 8, 2022)

@L0rdGwyn <or anybody else that can chime in> Do you have any familiarity with these amps: Antique Sound Lab MG-Head OTL Mark III DT
My Google-fu hasn't really been able to dig up too much credible info about them.
This is why I ask: https://www.canuckaudiomart.com/det...-mg-head-otl-mark-iii-dt-headphone-amplifier/


----------



## Monsterzero

Mr Trev said:


> @L0rdGwyn <or anybody else that can chime in> Do you have any familiarity with these amps: Antique Sound Lab MG-Head OTL Mark III DT
> My Google-fu hasn't really been able to dig up too much credible info about them.
> This is why I ask: https://www.canuckaudiomart.com/det...-mg-head-otl-mark-iii-dt-headphone-amplifier/


https://www.head-fi.org/threads/rev...2-tube-and-tube-hybrid-headphone-amps.402585/

https://www.head-fi.org/threads/antique-sound-lab-mg-head-dt-otl-mk-iii-headphone-amp.161981/


----------



## Mr Trev

Monsterzero said:


> https://www.head-fi.org/threads/rev...2-tube-and-tube-hybrid-headphone-amps.402585/
> 
> https://www.head-fi.org/threads/antique-sound-lab-mg-head-dt-otl-mk-iii-headphone-amp.161981/


I did find those threads back when, mostly generalized impressions. I was hoping for a bit more technical info like amp design, tube rolling options, moddability. You know, the usual crap I think the first thing I'd want to do is replace the 12ax7 with a 6sn7, but I'd need to know if the amp would survive the transplant


----------



## L0rdGwyn

Mr Trev said:


> @L0rdGwyn <or anybody else that can chime in> Do you have any familiarity with these amps: Antique Sound Lab MG-Head OTL Mark III DT
> My Google-fu hasn't really been able to dig up too much credible info about them.
> This is why I ask: https://www.canuckaudiomart.com/det...-mg-head-otl-mark-iii-dt-headphone-amplifier/



Sorry, I am not!  But looks like @Monsterzero rounded up some good info.  It uses 6BQ5 outputs, so EL84 could also be used.  Swapping in a 6SN7 for a 12AX7 probably won't work, those are very different tubes with very different characteristics / bias requirements.

It sounds like it has both transformer coupled and OTL output options?  If you find a picture of the circuit or a schematic, I'll take a look but a cursory Google search by me isn't bearing fruit.

This page at least has some specs and info: https://store.acousticsounds.com/d/...T_OTL_MKIII_Headphone_Amp-Headphone_Amplifier


----------



## Mr Trev

L0rdGwyn said:


> Sorry, I am not!  But looks like @Monsterzero rounded up some good info.  It uses 6BQ5 outputs, so EL84 could also be used.  Swapping in a 6SN7 for a 12AX7 probably won't work, those are very different tubes with very different characteristics / bias requirements.
> 
> It sounds like it has both transformer coupled and OTL output options?  If you find a picture of the circuit or a schematic, I'll take a look but a cursory Google search by me isn't bearing fruit.
> 
> This page at least has some specs and info: https://store.acousticsounds.com/d/...T_OTL_MKIII_Headphone_Amp-Headphone_Amplifier


That's the same problem I'm running into. A long discontinued model with little info to be had.
I suppose I could just buy it and have it sent to your place along with the promise to be your friend if you make it awesome


----------



## L0rdGwyn (Apr 8, 2022)

Mr Trev said:


> That's the same problem I'm running into. A long discontinued model with little info to be had.
> I suppose I could just buy it and have it sent to your place along with the promise to be your friend if you make it awesome



LOL but what if it _can't_ be awesome?  Honestly I am sorta done working on other people's designs, modding and whatnot, it can drive you crazy working on someone else's stuff.  Also looks like their circuits are built out on PCBs which severely limits how much it can be altered.

I'm not great for recommending tube amps these days unfortunately, my feeling is you get top quality going with A) DIY route yourself, B) DIY route by someone who does custom work.  There is so much knowledge / circuitry in the DIY arena that isn't being used by commercial amp makers, and of course they have profit margins / practicality of mass production to worry about, so you are never going to get top quality that way.  But of course the custom route means long wait times and high cost, or you can dive into the DIY deep end yourself


----------



## Mr Trev

L0rdGwyn said:


> LOL but what if it _can't_ be awesome?  Honestly I am sorta done working on other people's designs, modding and whatnot, it can drive you crazy working on someone else's stuff.  Also looks like their circuits are built out on PCBs which severely limits how much it can be altered.
> 
> I'm not great for recommending tube amps these days unfortunately, my feeling is you get top quality going with A) DIY route yourself, B) DIY route by someone who does custom work.  There is so much knowledge / circuitry in the DIY arena that isn't being used by commercial amp makers, and of course they have profit margins / practicality of mass production to worry about, so you are never going to get top quality that way.  But of course the custom route means long wait times and high cost, or you can dive into the DIY deep end yourself


What! You're L0rdGwyn, of course you could make it awesome

I guess I understand how much of a nightmare it can be trying to Frankenstein somebody else's work.
Sadly I have the EE knowledge of a potato, so the best I can DIY is having somebody tell me to put component A in slot B and hope it doesn't electrocute me
It won't stop me from living vicariously through you guys though, so keep it coming - and who knows, mebee I'll actually learn something along the way


----------



## whirlwind

L0rdGwyn said:


> I'm not great for recommending tube amps these days unfortunately, my feeling is you get top quality going with A) DIY route yourself, B) DIY route by someone who does custom work.  There is so much knowledge / circuitry in the DIY arena that isn't being used by commercial amp makers, and of course they have profit margins / practicality of mass production to worry about, so you are never going to get top quality that way.  But of course the custom route means long wait times and high cost, or you can dive into the DIY deep end yourself


No truer words have ever been spoken


----------



## Mr Trev

L0rdGwyn said:


> LOL but what if it _can't_ be awesome?  Honestly I am sorta done working on other people's designs, modding and whatnot, it can drive you crazy working on someone else's stuff.  Also looks like their circuits are built out on PCBs which severely limits how much it can be altered.
> 
> I'm not great for recommending tube amps these days unfortunately, my feeling is you get top quality going with A) DIY route yourself, B) DIY route by someone who does custom work.  There is so much knowledge / circuitry in the DIY arena that isn't being used by commercial amp makers, and of course they have profit margins / practicality of mass production to worry about, so you are never going to get top quality that way.  But of course the custom route means long wait times and high cost, or you can dive into the DIY deep end yourself


So, I'm not looking for a reccy, but a bit back you mentioned maybe I could look into getting a low power tube amp and running my planars of the speaker taps. Just wondering if this style of amp would be suitable…
https://www.musicalparadise.ca/store/index.php?route=product/product&product_id=54
I could run my dynamics from the HO and planars of the speakers


----------



## L0rdGwyn

Mr Trev said:


> So, I'm not looking for a reccy, but a bit back you mentioned maybe I could look into getting a low power tube amp and running my planars of the speaker taps. Just wondering if this style of amp would be suitable…
> https://www.musicalparadise.ca/store/index.php?route=product/product&product_id=54
> I could run my dynamics from the HO and planars of the speakers



Looks like that could get the job done!  No idea how it will sound, but it certainly has a lot of power in a small package.


----------



## pravous

Atrium were delivered this afternoon.   Sound pretty amazing with the Airmid right out of the box.  Soundstage is incredible and really liking the bass, sub bass as compared to the 650.  Happy listening.


----------



## jgwtriode

Congrats very nice indeed!

jgwtriode


----------



## bcowen

pravous said:


> Atrium were delivered this afternoon.   Sound pretty amazing with the Airmid right out of the box.  Soundstage is incredible and really liking the bass, sub bass as compared to the 650.  Happy listening.


Nice!!!


----------



## L0rdGwyn

pravous said:


> Atrium were delivered this afternoon.   Sound pretty amazing with the Airmid right out of the box.  Soundstage is incredible and really liking the bass, sub bass as compared to the 650.  Happy listening.



Awesome, enjoy!


----------



## jgwtriode (Apr 10, 2022)

Very hopeful that Ric will finish my DAC this weekend.  Aaarrrrggghhh!  Anyway have not listened to anything for a few days.  Decided back to the soundcard. Have found a better method to tack my Shun Mook Pucks onto the sides of my VC.  Little bits of double sided gorilla tape.  Does not effect the finish and sticks like mad.  Also found some real unique molecular level gel duck tape that works amazingly at keeping my mad sci nano pucks in place around connector.  I know I am nuttier than fruitcake but I love the small but definitely noticeable differences these make.  Don't even feel the added weight with the crescent pad.   Playing some electronic synth new wave and dance stuff. Particularly love OMD and Zynic.  Lots of hard driving back beat and extremely fast bouncy effects.  Big Drum Machines that kick and snap really drive that ryhthm.  As I have pointed out this really shouldn't sound this good.   But holy hell, the drive, punch, kick and extension is like a pair of well known speakers I used to own that will go down to 18HZ.  Of course the VC's can't do that.  But the VC's on the Airmid are surprisingly close.  Are getting me 90 to 95% in every way but below 30.   In terms of speed, harmonic structure, timing cues, tonal balance sheer enjoyment this is definitely better.  And I am not losing any sense of space, staging, placement or focus by comparison.  The Airmid is ridiculous at all this stuff.   This is am amp from the Gods.   I don't know if it's burned in because I haven't really tried.   But I can tell you as long as I don't hook it up to my noisy temp signal source and let the tubes settle for about 15 to 20 mins, there still is some spurious crackle in the tube for anywhere from 10 to 15 min. Then the noise is all but gone.  On the last 10% of the volume there's a hint of hum that subtley kicks in.   Of course I hear all manner of noise from the sound card but when the music's playing it doesn't really intrude,  on quiet passage just a bit.

I know the Atrium is the new ZMF soundstage King.  But on the Airmid My VC throws stage like the best planar speakers I have owned and even the 25K$ dynamic speakers I used to own and I don't have to worry about room interaction.  All this just from Tidal out of an onboard sound card.   And yes my little devices do add perhaps another 5 or more percent to all the things the VC's do.

Happy listening,

jgwtriode


----------



## whirlwind

pravous said:


> Atrium were delivered this afternoon.   Sound pretty amazing with the Airmid right out of the box.  Soundstage is incredible and really liking the bass, sub bass as compared to the 650.  Happy listening.


Wonderful.....great amp/cans/tubes....enjoy the music


----------



## Velozity

Mr Trev said:


> I did find those threads back when, mostly generalized impressions. I was hoping for a bit more technical info like amp design, tube rolling options, moddability. You know, the usual crap I think the first thing I'd want to do is replace the 12ax7 with a 6sn7, but I'd need to know if the amp would survive the transplant



I have that amp and use it at work.  It's a nice piece.  Yes you can run a 6SN7 no problem.  I also use 6V6G instead of 6BQ5.  Shown below  I'm using a Tung-Sol 6SN7 with Fivre 6V6G in the top pic and 2x Raytheon 6J5G in the bottom pic.  Adapters by way of Deyan of course.


----------



## JazzVinyl

Velozity said:


> I have that amp and use it at work.  It's a nice piece.  Yes you can run a 6SN7 no problem.  I also use 6V6G instead of 6BQ5.  Shown below  I'm using a Tung-Sol 6SN7 with Fivre 6V6G in the top pic and 2x Raytheon 6J5G in the bottom pic.  Adapters by way of Deyan of course.



I like it!!  How does she sound?


----------



## Mr Trev

Velozity said:


> I have that amp and use it at work.  It's a nice piece.  Yes you can run a 6SN7 no problem.  I also use 6V6G instead of 6BQ5.  Shown below  I'm using a Tung-Sol 6SN7 with Fivre 6V6G in the top pic and 2x Raytheon 6J5G in the bottom pic.  Adapters by way of Deyan of course.


Any chance you've had any planars plugged into it?


----------



## Velozity

JazzVinyl said:


> I like it!!  How does she sound?



Well she's certainly not a giant killer but for the price I paid I'm more than satisfied when used with my Beyerdynamic DT250 phones.  I only use the OTL mode.  It could benefit from some capacitor upgrades and such but it sounds good as-is and I can definitely tell the difference when tube rolling.  So that's certainly a win.  I would rank this above the WA3 and Bottleheads I've heard.



Mr Trev said:


> Any chance you've had any planars plugged into it?



Nope, not on this amp.


----------



## L0rdGwyn

Spent the day stuffing Airmid PCBs, three sets at once takes a long time.  I will have the chassis for the first two by the end of next week, so @Monsterzero 's amp will be done by early May.

PCBs are done and parts lists ready to go for PCM63 DAC, but I plan to hold off on ordering the bulk of the parts until I know the I/V transformers are on the way, could be another 2-3 months as they are Sowter made.

Otherwise, I have been scheming on an idea I have for a transformer-coupled 6V6-based headphone amp using a somewhat unusual output topology, will be ordering some parts to throw together a prototype and see how it sounds.

Been listening to my stereo today rather than Atrium / VC.  Of the things I have made, I think the 801A amplifier is still my favorite.  My standard loadout is GEC H63, Toshiba 6BX7GT, and graphite plate Taylor 801A.


----------



## jgwtriode (Apr 13, 2022)

My Wywires Platinum RCA's showed up this evening.  So I immediately built a 3.5mm adapter to use with the Sound Card.  Holy Hell!  Everythings improved over my old Neotech Silver Gold interconnect which used to be my headphone harness on my HD 650 Frankenheisers.  Damn, dead cold,  Noise dropped at least 70%.   Everything more detailed. Bass had more slap kick and extension. PRAT noticeably better.  High's more air and sparkle.  Stage bigger deeper and better layered.   From a sound card, what in the world.  Way to go Alex....one hell of a pair of interconnects.  Can you imagine with my modded DAC, when it arrives maybe first of next week.  and fully burned.  I am not even sure my 5998's and GEC L63's are fully burned yet, have been listening on and off.  This is much more compelling to make me want to listen despite my source limits.

 Did a bit more repositioning of the wire and was able to cut the noise level to half of what I was raving about.  And yes things are even better.

There is a sense with the Airmid, the VC and Wywires cables that the whole is greater than the sum of the parts.

It is significant that Alex told me he designs his cables around Single Ended Triodes!

Happy Listening, the fun never ends!

jgwtriode


----------



## whirlwind

Those 801's have such a lovely glow.


----------



## triod750

L0rdGwyn said:


> Otherwise, I have been scheming on an idea I have for a transformer-coupled 6V6-based headphone amp using a somewhat unusual output topology, will be ordering some parts to throw together a prototype and see how it sounds.


I can tell you right away that it sounds interesting!


----------



## L0rdGwyn (Apr 15, 2022)

While I am waiting for Airmid chassis, I have been doing some scheming....idle hands are the devil's workshop, as they say.  LTSpice is a very dangerous tool, lets me experiment with circuits and have a new design ready to go in a matter of days...not good for a tube amp addict.

Anyway, I've got another headamp design in the works, I think it's pretty interesting.  It is very much an "old school" type of design in terms of its power supply and componentry - no semiconductors!  Just resistors, capacitors, diodes, inductors (heavy emphasis on the inductors).

As it stands right now (the design changes on a daily basis), it will use the below tubes - EL34 (and its pentode / beam tetrode cousins - 6V6, 6F6, 6K6, 6L6, KT66, KT88, etc.), EF86, and GZ34 (compatible with other 5V 2A rectifiers that meet minimum current spec - 5V4, 5R4, GZ32, etc.).

What do these tubes have in common?  They are all available in new production.  Well, at least before the tube crisis of 2022, and ostensibly will be available again in the future.



Why design something using tubes that are available new?  My *HOPE* is that I could potentially get this design out into the world and available to Head-Fiers in some capacity without my having to build it.  And I mean hope, I have no guarantee that will happen and I cannot speculate further on if it will, all I can say is, we will see.

So for that reason, I will be intentionally vague on the design.  What I will say is that the output topology, which is transformer coupled, is not something I have seen done by any other headphone amplifier manufacturer and I think it has big potential.

I am prototyping a version of this circuit that really is old school though, using a choke-input, tube-rectified passive power supply.  That's about as old school as it gets from a power supply standpoint.  The version I am making definitely isn't budget friendly due to heavy use of Lundahl inductors, but will act as a proof of concept.

Working on this has been fun - I have been living in the world of semiconductor-assisted tube circuits for a while, so going back to very simple passive designs with the additional limitation of using only new-production tubes has been an interesting challenge.


----------



## whirlwind (Apr 17, 2022)

At some point these new production tubes will be available again. I think it makes amp owners feel good to know that they can buy new production tubes , makes them feel more secure if you will about spending the money for the amp.

Still waiting for that electrostat design  

Happy Easter to everybody.


----------



## L0rdGwyn (Apr 17, 2022)

whirlwind said:


> At some point these new production tubes will be available again. I think it makes amp owners feel good to know that they can buy new production tubes , makes them feel more secure if you will about spending the money for the amp.
> 
> Still waiting for that electrostat design
> 
> Happy Easter to everybody.



For sure!  But designing something completely using new production tubes is definitely a challenge.  A lot of the preamp tubes available are geared toward guitar amplifier users, not that many very linear ones to work with.  I think I came up with a good solution.  I have a version of the circuit that uses 6DJ8 / E88CC as well, but I think the pair of EF86 is better.  Also 6DJ8 are wildly expensive.

If I ever were to own an electrostat, I would have to make an amplifier for them lol better if I just don't buy one!


----------



## leftside

Hey @L0rdGwyn hope you don’t mind me posting here - but there isn’t much talk of tube testers elsewhere,

I had some time to play around with the AT1000 this afternoon. Chris from Amplitrex has been an absolute pleasure to deal with - super helpful and fast responses. Told him I had a few tubes that weren’t listed on the already extensive library of tubes that the AT1000 could test, and he produced a file I could upload. So I hooked the thing up to a laptop, read a few manuals, did some configuration and now I can test EL11, etc. 

I know the price of this tester is prohibitive, but for a tech guy like me with quite a few varied tubes it’s an absolute dream. The price has put me off for a long time, but I really should have purchased it years ago.


----------



## L0rdGwyn

leftside said:


> Hey @L0rdGwyn hope you don’t mind me posting here - but there isn’t much talk of tube testers elsewhere,
> 
> I had some time to play around with the AT1000 this afternoon. Chris from Amplitrex has been an absolute pleasure to deal with - super helpful and fast responses. Told him I had a few tubes that weren’t listed on the already extensive library of tubes that the AT1000 could test, and he produced a file I could upload. So I hooked the thing up to a laptop, read a few manuals, did some configuration and now I can test EL11, etc.
> 
> I know the price of this tester is prohibitive, but for a tech guy like me with quite a few varied tubes it’s an absolute dream. The price has put me off for a long time, but I really should have purchased it years ago.



I don't mind at all!  Very cool he was able to create a configuration file for you, I wonder if the tubes will now be included in the library with new sales.

I like the eTracer for its ability to generate operating curves, but something like the AT1000 would be nice to have for its ease and speed of testing.  It looks very well made.


----------



## whirlwind

leftside said:


> Hey @L0rdGwyn hope you don’t mind me posting here - but there isn’t much talk of tube testers elsewhere,
> 
> I had some time to play around with the AT1000 this afternoon. Chris from Amplitrex has been an absolute pleasure to deal with - super helpful and fast responses. Told him I had a few tubes that weren’t listed on the already extensive library of tubes that the AT1000 could test, and he produced a file I could upload. So I hooked the thing up to a laptop, read a few manuals, did some configuration and now I can test EL11, etc.
> 
> I know the price of this tester is prohibitive, but for a tech guy like me with quite a few varied tubes it’s an absolute dream. The price has put me off for a long time, but I really should have purchased it years ago.


Kudos to Amplitrex, that is awesome.

You are going to be busy with that tube collection of yours.  


L0rdGwyn said:


> While I am waiting for Airmid chassis, I have been doing some scheming....idle hands are the devil's workshop, as they say.  LTSpice is a very dangerous tool, lets me experiment with circuits and have a new design ready to go in a matter of days...not good for a tube amp addict.
> 
> Anyway, I've got another headamp design in the works, I think it's pretty interesting.  It is very much an "old school" type of design in terms of its power supply and componentry - no semiconductors!  Just resistors, capacitors, diodes, inductors (heavy emphasis on the inductors).
> 
> ...


How hard are you going to push the EL34 / KT66/KT88

I often wonder what the difference, if any in the sound of these tubes when pushed to their limit ?


----------



## L0rdGwyn

whirlwind said:


> How hard are you going to push the EL34 / KT66/KT88
> 
> I often wonder what the difference, if any in the sound of these tubes when pushed to their limit ?



Not hard!  They should last forever in this circuit, but it is more a side effect of how they are being used, as I mentioned it is somewhat unconventional, I will explain some time down the road.  IME, moving a tube from a cooler to a hotter bias point in the same circuit, the audible differences are very subtle.  I experimented with this quite a bit in Zach's 45 amp, I honestly could not hear a difference between running the 45s between around 70% and 100% of their max plate dissipation.  A higher bias current will increase the transconductance and gain a little bit, but like I said, I think the audible differences are pretty subtle.  YMMV of course, I know others might disagree, maybe it is circuit dependent, but that has been my experience.  It doesn't make a lot of sense to run 3W+ power tubes at a hot bias in a headphone circuit since all that power isn't needed, just wears them out faster!


----------



## whirlwind

L0rdGwyn said:


> Not hard!  They should last forever in this circuit, but it is more a side effect of how they are being used, as I mentioned it is somewhat unconventional, I will explain some time down the road.  IME, moving a tube from a cooler to a hotter bias point in the same circuit, the audible differences are very subtle.  I experimented with this quite a bit in Zach's 45 amp, I honestly could not hear a difference between running the 45s between around 70% and 100% of their max plate dissipation.  A higher bias current will increase the transconductance and gain a little bit, but like I said, I think the audible differences are pretty subtle.  YMMV of course, I know others might disagree, maybe it is circuit dependent, but that has been my experience.  It doesn't make a lot of sense to run 3W+ power tubes at a hot bias in a headphone circuit since all that power isn't needed, just wears them out faster!



Thank you, this is what I wanted to hear.

In the back of my mind I always wondered, if the EL34 sounds this nice, wonder what it could sound like with max plate voltage, lol.

Glenn told me the same as what you just said, but I still always wondered


----------



## L0rdGwyn (Apr 18, 2022)

I believe the pentode headamp circuit is just about finalized, need to test it in the real world of course.  I am like...really excited about this circuit, I think it's gonna be pretty awesome.

One aspect that is fun is the tube-rectified choke-input supply.  Choke-input is somewhat uncommon these days, capacitor-input is much more common.  Like I said, very old school.  Back in the day, high values of capacitance were not readily available, so using chokes in power supplies made more sense as they provided good filtering and better voltage regulation than a capacitor input supply.  Also, tube rectifiers are somewhat sensitive to voltage / current surges during startup conditions in capacitor input supplies due to inrush as the capacitors charge.  A choke-input supply helps tame the inrush and keeps tube rectifiers happier as they are not exposed to high ripple currents of capacitor input supplies.

Choke-input supplies do have many quirks that need to be accounted for though, and as usual there are compromises, but it makes a lot of sense for what I am trying to do in this circuit.

Compatible 5V / 2A rectifiers off the top of my head are 5AR4, 5R4, 5V4, GZ32, and 5Y3 if using lower current tubes like 6V6.

I have been window shopping for cool rectifiers, I am ready to buy into the rectifier voodoo again LOL.


----------



## L0rdGwyn

whirlwind said:


> Thank you, this is what I wanted to hear.
> 
> In the back of my mind I always wondered, if the EL34 sounds this nice, wonder what it could sound like with max plate voltage, lol.
> 
> Glenn told me the same as what you just said, but I still always wondered



Yeah honestly I think you are probably getting great sound out of those tubes as they are!  I wouldn't worry too much about driving them harder.


----------



## pravous

leftside said:


> Hey @L0rdGwyn hope you don’t mind me posting here - but there isn’t much talk of tube testers elsewhere,
> 
> I had some time to play around with the AT1000 this afternoon. Chris from Amplitrex has been an absolute pleasure to deal with - super helpful and fast responses. Told him I had a few tubes that weren’t listed on the already extensive library of tubes that the AT1000 could test, and he produced a file I could upload. So I hooked the thing up to a laptop, read a few manuals, did some configuration and now I can test EL11, etc.
> 
> I know the price of this tester is prohibitive, but for a tech guy like me with quite a few varied tubes it’s an absolute dream. The price has put me off for a long time, but I really should have purchased it years ago.


Congrats on the Amplitrex.   Looks like a pretty neat system.


----------



## L0rdGwyn

Since I am going "old school" for this pentode headamp without semiconductors, I will potentially use cathode / autobias in the input stage.  I am going to revisit my phobia of electrolytic bypass capacitors in this position and do a big shootout of different audio grade electrolytics in my prototype and see if I can find some that sound good.

Right now my shootout includes Elna Silmic II, Audio Note Kaisei, Audio Note Seiryu, Jupiter Cosmos, MOD, Nichicon FG, and Nichicon KZ.  I was considering grabbing a pair of NOS Black Gate NX series off of eBay, we'll see if curiosity gets the better of me.

There are legitimate reasons to use bypass caps this time around and I think they will do more good than harm for what I have in mind, but if I can't find one I like, then I will revert back to my fixed bias ways, likely LED biasing.  Alternatively, could investigate cramming in film bypass caps, but they would be enormous.


----------



## Xcalibur255

It really is such a missed opportunity that there isn't a simple modern tube tester that can be purchased for 250-500 dollars that can interface with a PC.  I feel like a project like this would stand a good chance of taking off really well as a Kickstarter, but I'm not the guy with enough technical knowledge to helm such a project so I sit and wait for somebody smarter and more ambitious to take a crack at it.


----------



## L0rdGwyn

Xcalibur255 said:


> It really is such a missed opportunity that there isn't a simple modern tube tester that can be purchased for 250-500 dollars that can interface with a PC.  I feel like a project like this would stand a good chance of taking off really well as a Kickstarter, but I'm not the guy with enough technical knowledge to helm such a project so I sit and wait for somebody smarter and more ambitious to take a crack at it.



The uTracer is the closest thing, but it is a DIY project: https://www.dos4ever.com/uTracer3/uTracer3_pag0.html


----------



## leftside

Xcalibur255 said:


> It really is such a missed opportunity that there isn't a simple modern tube tester that can be purchased for 250-500 dollars that can interface with a PC.  I feel like a project like this would stand a good chance of taking off really well as a Kickstarter, but I'm not the guy with enough technical knowledge to helm such a project so I sit and wait for somebody smarter and more ambitious to take a crack at it.


Totally agree. And with all the interest in tubes I was hoping such a thing would appear. But, if I pickup the AT1000 or the   Daedalos there must be some hefty expensive parts in there as these things are “amp heavy”. Also developing the software can’t be cheap. And then you have to deal with people like me and all my questions 🙂

Hopefully the high interest in tubes will continue, and technology will improve that will make a 250 - 500 tube tester viable. I’d love to see it 🤞 It would also make purchasing tubes off eBay a little “safer” if the sellers knew the buyers all owned tube testers. Heck, I’ve even received tubes from very well known tube sellers where the tubes have tested poorly (but luckily this is a rarity).

Maybe @L0rdGwyn can investigate developing one 😉


----------



## miketlse

leftside said:


> Totally agree. And with all the interest in tubes I was hoping such a thing would appear. But, if I pickup the AT1000 or the   Daedalos there must be some hefty expensive parts in there as these things are “amp heavy”. Also developing the software can’t be cheap. And then you have to deal with people like me and all my questions 🙂
> 
> Hopefully the high interest in tubes will continue, and technology will improve that will make a 250 - 500 tube tester viable. I’d love to see it 🤞 It would also make purchasing tubes off eBay a little “safer” if the sellers knew the buyers all owned tube testers. Heck, I’ve even received tubes from very well known tube sellers where the tubes have tested poorly (but luckily this is a rarity).
> 
> Maybe @L0rdGwyn can investigate developing one 😉


I take the opposing viewpoint, in that i think developing the software is the cheaper part of the project.
There must be many thousands of electronic engineering students around the world, who each year learn how to write short snippets of code for capturing/displaying data from an ADC, and conversely using tables of digital data to drive a DAC. The online resources for learning programming languages, normally contain thousands of code snippets to handle/process/display data.
Overall, this would be relatively cheap for an enthusiast to practice with and combine the snippets together.

uTracer uses a SBC at a price, that is so cheap that there is no incentive for an enthusiast to develop their own from scratch.

To my mind the expensive part of the project is connecting all the above, to a large case containing sockets, transformers, power supplies, etc.


----------



## leftside

miketlse said:


> I take the opposing viewpoint, in that i think developing the software is the cheaper part of the project.
> There must be many thousands of electronic engineering students around the world, who each year learn how to write short snippets of code for capturing/displaying data from an ADC, and conversely using tables of digital data to drive a DAC. The online resources for learning programming languages, normally contain thousands of code snippets to handle/process/display data.
> Overall, this would be relatively cheap for an enthusiast to practice with and combine the snippets together.
> 
> ...


Yeah maybe. As you say tho, the transformers, power supplies, etc are certainly not cheap. The "breakthrough" I guess would be being able to test the tubes without such parts, but I'm not sure how feasible that is.


----------



## Xcalibur255

L0rdGwyn said:


> The uTracer is the closest thing, but it is a DIY project: https://www.dos4ever.com/uTracer3/uTracer3_pag0.html


I know, but I mean a finished product.  It would reach a much larger number of people than something you need to build yourself.


----------



## L0rdGwyn

Xcalibur255 said:


> I know, but I mean a finished product.  It would reach a much larger number of people than something you need to build yourself.



I think it would be pretty tough to hit that price point and still turn a profit worth the time and effort.  Maybe if a big company with resources were to pick up the project.


----------



## L0rdGwyn

I picked up some rectifier tubes for testing purposes.

RCA 5R4GY




Sylvania 5V4G



Western Electric 274B.......



Okay, I might have imagined that last one.  You can Buy It Now on Yahoo Auctions Japan for a cool ¥500,000!! (around $4K USD).

Anyway, I already have a GZ34 and a 5Y3G, so that should cover my testing needs for 5V / 2A rectifiers in this pentode headamp.  All the iron and components are ordered for the prototype.  Now we wait.

First two Airmid chassis will finally ship today, probably will arrive by the weekend, so I will begin building on Tuesday since I will be working over the weekend.


----------



## L0rdGwyn

I also grabbed some new EF86 and a pair of E80F which should be a drop-in substitute for EF86 in this circuit.  Need to trace their curves however to get an idea of their operating point.

UK made (Mullard?) EF86



Philips Miniwatt EF86



Philips Miniwatt E80F


----------



## Xcalibur255

That reminds me of the rectifier buying spree I went on when I got my first tube amp (WA6), only the 274B was a EML tube not a WE.  Maybe it's just me but I have never liked the sound of the 5V4G in any amp I have tried it in.  Maybe it's a direct vs. indirect heating thing.  At least they were cheap back in 2008.


----------



## L0rdGwyn (Apr 19, 2022)

Xcalibur255 said:


> That reminds me of the rectifier buying spree I went on when I got my first tube amp (WA6), only the 274B was a EML tube not a WE.  Maybe it's just me but I have never liked the sound of the 5V4G in any amp I have tried it in.  Maybe it's a direct vs. indirect heating thing.  At least they were cheap back in 2008.



Yeah it will be interesting to see how they affect the sound, even more so in a choke input supply, a new variable.  These were pretty reasonably priced, I nearly went for some expensive models, but I just need something to test the circuit first and foremost.

BTW, I don't know if you caught it, but I didn't actually buy a WE 274B, I wish 😂

When I briefly had that SW1X DAC, I felt the 5Y3 sounded much better than the GZ34, even though many swear by it.  Maybe there is something to direct vs. indirectly-heated rectifiers  of course huge difference in operating points of the tubes in that circuit, and there was a lot of other weirdness going on in that DAC.  I am ready to have some fun trying different rectifiers.  If they don't end up drastically affecting the sound in this circuit, I'll just use one I think looks cool 

Brimar 5R4GY is pretty snazzy.


----------



## gibosi

L0rdGwyn said:


> Yeah it will be interesting to see how they affect the sound, even more so in a choke input supply, a new variable.  These were pretty reasonably priced, I nearly went for some expensive models, but I just need something to test the circuit first and foremost.
> 
> BTW, I don't know if you caught it, but I didn't actually buy a WE 274B, I wish 😂
> 
> ...



I don't know how sensitive your amp will be to the different GZ34 builds. It was manufactured by Mullard, M.B.L.E. Bruxelles (Mazda), Philips Sittard (Holland) and Philips Eindhoven (Holland metal). And if I'm not mistaken, in the US, GE and Sylvania. And maybe others.


----------



## whirlwind

Those Brimar's are some nice looking tubes.


----------



## Monsterzero

L0rdGwyn said:


> I picked up some rectifier tubes for testing purposes.
> 
> RCA 5R4GY
> 
> ...


I have a WWll era version of that RCA. Brent Jessee is very high on them. Never tried it in my GOTL, but it sounds nice in my DAC. Not very RCA sounding at all, airy, nice stage, but it needs to be paired with other other tubes that have mooooar bass.


----------



## L0rdGwyn

gibosi said:


> I don't know how sensitive your amp will be to the different GZ34 builds. It was manufactured by Mullard, M.B.L.E. Bruxelles (Mazda), Philips Sittard (Holland) and Philips Eindhoven (Holland metal). And if I'm not mistaken, in the US, GE and Sylvania. And maybe others.



I suppose if the GZ34 sounds best, then I will get others and find out!  Going to try representatives from the various 5V / 2A rectifiers and compare.



whirlwind said:


> Those Brimar's are some nice looking tubes.



Yeah they are, I nearly bought one but settled for the RCA 5R4GY instead.  If all goes well, I'll probably grab one, but they are a little pricey, at least $120 shipped.



Monsterzero said:


> I have a WWll era version of that RCA. Brent Jessee is very high on them. Never tried it in my GOTL, but it sounds nice in my DAC. Not very RCA sounding at all, airy, nice stage, but it needs to be paired with other other tubes that have mooooar bass.



Very cool, I'll keep that in mind.  I am very curious what conclusions I'll come to on rolling rectifiers.  While I have made one other tube-rectified amplifier, this is the first that is capable of using a variety of different types as the current and voltage demands are not high.  But 5V / 2A is the limitation, no 3A rectifiers due to specs of the transformer winding I will be using.  But I think GZ32, GZ34, 5V4, 5R4, 5Y3, 274B gives a nice variety of types to choose from.


----------



## Monsterzero

The lowly Chatham potato masher sounds killer in my DAC, and theyre dirt cheap


----------



## L0rdGwyn

Monsterzero said:


> The lowly Chatham potato masher sounds killer in my DAC, and theyre dirt cheap



I need to get me one of those mashers.  It's on the list.


----------



## Xcalibur255

The hanging filaments on the Brimars look neat.  I think the Philips 5R4GYS technically sounds a bit better than the Brimar, but the Brimar is a good step ahead of the RCAs and looks beautiful while doing it.

I have really liked the 5Y3G in every amp I've used it in.  Still easy to find cheap ones too.  I wish I hadn't tried to get fancy with the full wave bridge stuff and just asked Glenn to use a pair of these back in 2013 for my 45, it probably would have prevented years of headache and heartache.


----------



## L0rdGwyn

Xcalibur255 said:


> The hanging filaments on the Brimars look neat.  I think the Philips 5R4GYS technically sounds a bit better than the Brimar, but the Brimar is a good step ahead of the RCAs and looks beautiful while doing it.
> 
> I have really liked the 5Y3G in every amp I've used it in.  Still easy to find cheap ones too.  I wish I hadn't tried to get fancy with the full wave bridge stuff and just asked Glenn to use a pair of these back in 2013 for my 45, it probably would have prevented years of headache and heartache.



Philips 5R4GY, I'll take a look, seem somewhat uncommon.  5Y3Gs are easy to come by, they are a little light on the current handling however, 125mA DC output would work for lower current tubes like 6V6, will have to see where the bias lands for the EL34, et al., would be driving the 5Y3G pretty hard.

Full wave bridge with 5Y3Gs would be a hefty voltage drop, twice the Vdrop, would need to design the supply around that, could do a hybrid full wave bridge rectifier with a pair of SS diodes and a single 5Y3G.


----------



## Xcalibur255

So I'm going off stuff I read about nearly 10 years ago, but supposedly some people really like to do a full wave bridge using 4 tv damper diodes.  My amp uses the 6by5 whose neat trick is having two independent diodes in the same tube, so you can do the same setup using two of them instead of having 4 tv tubes.  These tubes have been completely problematic though.

I can probably guess that switching the design to use a pair of 5y3 instead of those 6by5 is probably not as simple as changing the heater voltage, but I don't know the finer points of it.

Setting aside the whole full wave bridge thing, is there some reason why it's difficult to run a *pair* of 5y3 in your design to get double the output current?


----------



## bcowen

Monsterzero said:


> The lowly Chatham potato masher sounds killer in my DAC, and theyre dirt cheap


Lowly Chatham qualifies as an oxymoron.      I've never heard a bad sounding Chatham, although I suppose they _could_ have had a dud type along the way.


----------



## L0rdGwyn (Apr 19, 2022)

Xcalibur255 said:


> Setting aside the whole full wave bridge thing, is there some reason why it's difficult to run a *pair* of 5y3 in your design to get double the output current?



So to get double the output current, you would need to have two separate supplies with separate transformer windings, one for each channel and rectified by a 5Y3, so each channel gets 125mA in a dual mono setup.  Using a pair of 5Y3 in a full wave bridge rectifier, each pair of diodes are actually in series for each half cycle of AC, so the current output remains the same, but the voltage drop is doubled.  So in a bridge configuration, using a pair of tubes means big voltage losses, unless you use something like a GZ34 which has a Vdrop of 10V or so.  If you want to use a tube rectifier but don't have a center tapped winding or want to use a full-wave bridge but don't want to use a pair of tubes, then the way to go is a hybrid tube-SS bridge rectifier, so the voltage drop is the combined drop of the tube plus a SS diode, which is typically 1V or less, instead of the voltage drop of two tubes in series.


----------



## gibosi (Apr 19, 2022)

L0rdGwyn said:


> Philips 5R4GY, I'll take a look, seem somewhat uncommon.



The Philips 5R4GY was actually manufactured by La Radiotechnique (RTC) and can also be found labeled as a Dario. And another 5R4GY you might want to consider is Fivre. The RTC tube has those very distinctive "umbrella spokes" so it is easy to recognize regardless of the brand.


----------



## L0rdGwyn

gibosi said:


> The Philips 5RAGY was actually manufactured by La Radiotechnique (RTC) and can also be found labeled as a Dario. And another 5RAGY you might want to consider is Fivre. The RTC tube has those very distinctive "umbrella spokes" so it is easy to recognize regardless of the brand.



Thanks!  Good to know, I will keep an eye out.  And for the Fivre as well.


----------



## Xcalibur255

L0rdGwyn said:


> So to get double the output current, you would need to have two separate supplies with separate transformer windings, one for each channel and rectified by a 5Y3, so each channel gets 125mA in a dual mono setup.  Using a pair of 5Y3 in a full wave bridge rectifier, each pair of diodes are actually in series for each half cycle of AC, so the current output remains the same, but the voltage drop is doubled.  So in a bridge configuration, using a pair of tubes means big voltage losses, unless you use something like a GZ34 which has a Vdrop of 10V or so.  If you want to use a tube rectifier but don't have a center tapped winding or want to use a full-wave bridge but don't want to use a pair of tubes, then the way to go is a hybrid tube-SS bridge rectifier, so the voltage drop is the combined drop of the tube plus a SS diode, which is typically 1V or less, instead of the voltage drop of two tubes in series.



That's very interesting.  I must still be missing something, or have my facts wrong about my own amplifier.  Glenn said the power supply had 350mA of rectified current because of the dual tube setup, and a 6BY5 on its own is only good for 175mA.  You just told me that they would still only 175mA because the current remains the same in a full wave bridge which is what Glenn told me this is.  

*scratches head*


----------



## L0rdGwyn (Apr 20, 2022)

Xcalibur255 said:


> That's very interesting.  I must still be missing something, or have my facts wrong about my own amplifier.  Glenn said the power supply had 350mA of rectified current because of the dual tube setup, and a 6BY5 on its own is only good for 175mA.  You just told me that they would still only 175mA because the current remains the same in a full wave bridge which is what Glenn told me this is.
> 
> *scratches head*



Well one other thing you could do is use a center tapped single transformer winding and a pair of 5Y3 (or 6BY5), then wire each 5Y3 with the two halves in parallel to create a single diode and double the current handling in a full wave two-phase (non bridge) config.  Should be less voltage drop as well.

Maybe this is what Glenn did?  But if it was a true bridge rectifier, the current handling should not be doubled as the diodes are in series.

*Edit:* just looked over the 6BY5 datasheet, it is rated for 175mA *per diode*, so a single tube is actually rated for 350mA when used as a full wave rectifier and it will be the same as a bridge rectifier.  The 125mA rating of the 5Y3 is for its use as a full wave rectifier, so each plate is only rated for 62.5mA or so.  Also, I looked at a pic you sent me a while back, those 6BY5 are definitely wired as a bridge rectifier.


----------



## L0rdGwyn

Here are some good online articles that talk about the function of a full wave two-phase rectifier and a full wave bridge rectifier.  It's in the context of SS diodes but the principles are all the same for tubes.

BTW, both a "full wave" and "full wave bridge" are full wave rectifiers, the more accurate term for what is conventionally called a full wave rectifier (i.e., one that uses a center-tapped transformer) is a full wave two-phase rectifier.

Full wave two-phase - https://www.physics-and-radio-elect...and-circuits/rectifier/fullwaverectifier.html

Full wave bridge - https://www.physics-and-radio-elect...s-and-circuits/rectifier/bridgerectifier.html


----------



## L0rdGwyn (Apr 20, 2022)

This graphic from the second article I looked nicely shows the current pathway through the positive AC half cycle in a full wave bridge rectifier.

As you can see, the diodes along the pathway are in series, the reason you suffer two voltage drops when using a pair of tubes in bridge configuration.  The current will be limited to the rating of one diode.



If you wanted to get double the current rating, would have to do some parallel setup, either dual mono as I said, or use a pair of tubes with the anodes in parallel in a full wave two-phase setup.  Here is how that would look, put together in LTSpice.


----------



## L0rdGwyn

For this pentode headamp circuit, finding a new production tube for the input stage that met my needs was a challenge.  The tube needs to be able to produce somewhat high voltage gain at low distortion with a not-too-high plate resistance.  That led me to two places - 6DJ8 and triode-strapped EF86.  I am leaning toward EF86 for a few different reasons, but I am grabbing componentry to try the 6DJ8 as well.

One turnoff is how expensive these tubes have become.  I bought this one for $80 shipped, which actually seems to be a pretty good deal.  Based on the construction, it was made by Siemens.




Just traced the curves, the sections are pretty well matched.



So we'll try this as well as EF86 and see which comes out on top.


----------



## L0rdGwyn

I suppose another advantage of using  6DJ8 input stage would be the ability to use other tubes from the 12XX7 series, namely 12AU7, 12AT7, 12AY7.  Even 12AX7 could be used, but with some significant bass rolloff.

I have a nice 12AU7 I will try when I prototype with 6DJ8, it is the Brimar CV4034.



Here are the curves from one half.



Will have to weigh performance of EF86 vs. 6DJ8 and the flexibility of tube rolling in the input stage.  Other compromises to consider as well, will be a tough decision...


----------



## triod750

But you love a challenge so I'm not that bothered...


----------



## L0rdGwyn (Apr 20, 2022)

Yeah we will see, I am not much into tube rolling, but for many people it is a high priority.

With some compromises made, a theoretical circuit with 6DJ8 input would be able to use...

Rectifier: GZ32, GZ34, 5V4, 5R4, 5Y3, 274B
Input: 6DJ8, 12AU7, 12AT7, 12AY7, 12BH7, E80CC, and more.
Output: 6V6, 6F6, 6K6, EL34, KT66, KT77, KT88, and more.

With adapters, would get even more ridiculous.


----------



## triod750

It's either amp rolling or tube rolling or both. Or neither. Pick your poison...


----------



## L0rdGwyn

triod750 said:


> It's either amp rolling or tube rolling or both. Or neither. Pick your poison...



This one is being designed with Head-Fi tube junkies in mind, so tube rolling is taking a higher priority than usual.


----------



## whirlwind

L0rdGwyn said:


> This one is being designed with Head-Fi tube junkies in mind, so tube rolling is taking a higher priority than usual.


There are Head-Fi tube junkies ?


----------



## Xcalibur255

Now I just need to learn how to read those diagrams.    The per diode current rating makes sense though and explains things.  I'm honestly quite surprised these little tubes can do this much current.  They have pretty small plates too.  Maybe the PIV rating is low in exchange?  

I was told that the full wave bridge setup was "better" so I agreed to it like the dumb consumer I am.


----------



## L0rdGwyn

Xcalibur255 said:


> Now I just need to learn how to read those diagrams.    The per diode current rating makes sense though and explains things.  I'm honestly quite surprised these little tubes can do this much current.  They have pretty small plates too.  Maybe the PIV rating is low in exchange?
> 
> I was told that the full wave bridge setup was "better" so I agreed to it like the dumb consumer I am.



I believe they have a PIV of 1400V, so not too shabby.  Tung-Sol actually specifically calls out its ratings as a rectifier in their datasheet, which is unusual for TV damper diodes.

https://frank.pocnet.net/sheets/127/6/6BY5G.pdf

Thomas Mayer discusses it in his article on them.

http://vinylsavor.blogspot.com/2012/01/tube-of-month-6by5.html

Full wave bridge is better in that makes better use of the transformer than a full wave two phase rectifier, so the transformer can be smaller and cheaper.


----------



## sam6550a

L0rdGwyn said:


> I believe they have a PIV of 1400V, so not too shabby.  Tung-Sol actually specifically calls out its ratings as a rectifier in their datasheet, which is unusual for TV damper diodes.
> 
> https://frank.pocnet.net/sheets/127/6/6BY5G.pdf
> 
> ...


Be aware--FW bridge Idc=0.62 x transformer Iac, while FW ct Idc=1.0 x transformer Iac.


----------



## L0rdGwyn

sam6550a said:


> Be aware--FW bridge Idc=0.62 x transformer Iac, while FW ct Idc=1.0 x transformer Iac.



Yes, very true.  Sowter has a nice little page that summarizes both for both cap and choke input supplies.

https://www.sowter.co.uk/rectifier-transformer-calculation.php


----------



## L0rdGwyn (Apr 20, 2022)

Just spent around four hours doing critically listening of LEDs.  I think I've cracked the code on what makes good sound from LED bias.  I rounded up a number of them after pouring through probably 100 datasheets based on my criteria.  Four came out as very good, think we have some real winners here.

So I might have to use LED bias in this circuit, I'm not expecting any of the electrolytic bypass caps will sound better, but who knows, maybe I'll be pleasantly surprised.  The 6DJ8 sounds fantastic BTW.

LED alligator clip mayhem.



Got some Belton sockets today, the plan is to design a majority of this circuit onto a PCB.


----------



## bcowen

whirlwind said:


> There are Head-Fi tube junkies ?


I'm pretty sure that's an urban legend.


----------



## leftside

You are starting to go down the same path as the tubes used my Mick at Supratek in the Cortese preamp phono section.


----------



## L0rdGwyn

leftside said:


> You are starting to go down the same path as the tubes used my Mick at Supratek in the Cortese preamp phono section.



Oh what tubes does it use?  I think I am honing in on 6DJ8 / 6922 / ECC88 as the main input tube based on what I heard today.  EF86 is appealing for its linearity and gain and will still explore it, but there are so many 6DJ8 analogues and new production models it would leave a lot of flexibility for tube rolling, not to mention the use other tubes like 12AU7, 12BH7, 12AY7, E80CC, 5670 / 2C51 (w/ adapter), and others.


----------



## Mr Trev

L0rdGwyn said:


> Just spent around four hours doing critically listening of LEDs.  I think I've cracked the code on what makes good sound from LED bias.  I rounded up a number of them after pouring through probably 100 datasheets based on my criteria.  Four came out as very good, think we have some real winners here.
> 
> So I might have to use LED bias in this circuit, I'm not expecting any of the electrolytic bypass caps will sound better, but who knows, maybe I'll be pleasantly surprised.  The 6DJ8 sounds fantastic BTW.
> 
> ...



Belton sockets good.



L0rdGwyn said:


> Oh what tubes does it use?  I think I am honing in on 6DJ8 / 6922 / ECC88 as the main input tube based on what I heard today.  EF86 is appealing for its linearity and gain and will still explore it, but there are so many 6DJ8 analogues and new production models it would leave a lot of flexibility for tube rolling, not to mention the use other tubes like 12AU7, 12BH7, 12AY7, E80CC, 5670 / 2C51 (w/ adapter), and others.


So would "others" also include 6cg7 & ecc40? Personally I find those 2 are the best sounding in my Vali2.


----------



## L0rdGwyn

Mr Trev said:


> So would "others" also include 6cg7 & ecc40? Personally I find those 2 are the best sounding in my Vali2.



Both of those would work well, the ECC40 would need an adapter though.


----------



## pravous

My daughter is currently building an EL34 12ax7 guitar practice amp.  Tube depot “Bud Guitar Amp”.  Project has been going on for over a month as she likes to solder maybe 4-5 components at a time.  Taking everything in me to not be that dad that says let’s do a project and then goes ahead and does it for them.  Paint job came out pretty nice.  She was going for a stary night/nebula look.  All I know so far is that the JJ el34/12axl tested good.


----------



## L0rdGwyn

pravous said:


> My daughter is currently building an EL34 12ax7 guitar practice amp.  Tube depot “Bud Guitar Amp”.  Project has been going on for over a month as she likes to solder maybe 4-5 components at a time.  Taking everything in me to not be that dad that says let’s do a project and then goes ahead and does it for them.  Paint job came out pretty nice.  She was going for a stary night/nebula look.  All I know so far is that the JJ el34/12axl tested good.



Wow, that's so cool!  Your daughter is on the right path  good luck with the build.


----------



## leftside

L0rdGwyn said:


> Oh what tubes does it use?  I think I am honing in on 6DJ8 / 6922 / ECC88 as the main input tube based on what I heard today.  EF86 is appealing for its linearity and gain and will still explore it, but there are so many 6DJ8 analogues and new production models it would leave a lot of flexibility for tube rolling, not to mention the use other tubes like 12AU7, 12BH7, 12AY7, E80CC, 5670 / 2C51 (w/ adapter), and others.


Tubes are 
6H23 (6N1P,6922,E88CC, 6DJ8 ok) Can also use 6H30,6N6 for lower phono gain.
E180F (6688)
6N8P/6SN7/6H8C

6N3C,6L6GC, or 5881(KT66 also ok)
274B, 5U4, 5AR4 (GZ37,GZ32,GZ34, ok)


----------



## leftside

pravous said:


> My daughter is currently building an EL34 12ax7 guitar practice amp.  Tube depot “Bud Guitar Amp”.  Project has been going on for over a month as she likes to solder maybe 4-5 components at a time.  Taking everything in me to not be that dad that says let’s do a project and then goes ahead and does it for them.  Paint job came out pretty nice.  She was going for a stary night/nebula look.  All I know so far is that the JJ el34/12axl tested good.


----------



## L0rdGwyn

leftside said:


> Tubes are
> 6H23 (6N1P,6922,E88CC, 6DJ8 ok) Can also use 6H30,6N6 for lower phono gain.
> E180F (6688)
> 6N8P/6SN7/6H8C
> ...



Nice, just goes to show how flexible some of these tubes are!  I'm sure it sounds great.


----------



## pravous

L0rdGwyn said:


> Wow, that's so cool!  Your daughter is on the right path  good luck with the build.


In a way she was the reason I got back into head-fi. At the start of Covid she basically claimed my “good” headphones a pair of Sennhieser momentum’s.  Perfect reason to upgrade.  Got some drop 6xx but had a long wait as everyone else decided to get back into headphones at the same time as me. Decided to get the Bottlehead crack and needed some warm up soldering projects.  We both built some Altoids tin phone chargers. Built the BHC on my own.  
  Last year she asked me if we could do another project which ended up in a set of 4 Schiit coaster amps. I did all the smd and she handled all the through hole.  Her first amp is driven with some 6088 sub miniatures. 
   Part of me feels guilty in introducing her to a “dying” technology.   Who knows maybe someday she will be able to upgrade to a LordGwynn schematic


----------



## L0rdGwyn

pravous said:


> In a way she was the reason I got back into head-fi. At the start of Covid she basically claimed my “good” headphones a pair of Sennhieser momentum’s.  Perfect reason to upgrade.  Got some drop 6xx but had a long wait as everyone else decided to get back into headphones at the same time as me. Decided to get the Bottlehead crack and needed some warm up soldering projects.  We both built some Altoids tin phone chargers. Built the BHC on my own.
> Last year she asked me if we could do another project which ended up in a set of 4 Schiit coaster amps. I did all the smd and she handled all the through hole.  Her first amp is driven with some 6088 sub miniatures.
> Part of me feels guilty in introducing her to a “dying” technology.   Who knows maybe someday she will be able to upgrade to a LordGwynn schematic



Sounds like she'll be an expert in no time at this rate!


----------



## whirlwind

pravous said:


> My daughter is currently building an EL34 12ax7 guitar practice amp.  Tube depot “Bud Guitar Amp”.  Project has been going on for over a month as she likes to solder maybe 4-5 components at a time.  Taking everything in me to not be that dad that says let’s do a project and then goes ahead and does it for them.  Paint job came out pretty nice.  She was going for a stary night/nebula look.  All I know so far is that the JJ el34/12axl tested good.


Very cool!

Good for her for both playing guitar, and for diving into the amp herself.

I love girls with guitar's and I know that there are some that are gearheads too...I think it's great

Encourage her


----------



## L0rdGwyn

I started building my pentode circuit onto a PCB, also have a draft of the chassis in AutoCAD.  Building a tube circuit onto a PCB is interesting, might change my life.  It will be interesting to see how quickly this design can be assembled.  Probably the most time consuming aspect will be attaching wires to the Lundahl iron, but even that will be fast.

I cannot finalize anything until the prototype circuit is fully tested, and I will not have the transformers and chokes for another month or so.  The chassis and PCB will need to be done in concert as all of the sockets, mounting holes, etc. must align perfectly.  

Pretty soon I will have done everything I can up to that point.  I will stay busy building a few amps in the meantime.


----------



## L0rdGwyn

Got some coupling caps and electrolytic bypass caps just now.

 

Not really expecting the bypass caps to outperform the LEDs I plan to use, we will see.  It will be good info for future reference either way.  Curious how the Jupiter Cosmos wet electrolytics will sound.


----------



## JazzVinyl (Apr 21, 2022)

Curious about the caps vs LED as well.  Some say bypass caps are not beneficial at all, will be interesting to examine the actual science.

Also, some say fancier caps cannot be heard in audio circuits at all....what is your opinion/expirence on that, LG?


----------



## L0rdGwyn

JazzVinyl said:


> Curious about the caps vs LED as well.  Some say bypass caps are not beneficial at all, will be interesting to examine the actual science.
> 
> Also, some say fancier caps cannot be heard in audio circuits at all....what is your opinion/expirence on that, LG?



Well, so far I can tell you the Jupiter Cosmos electrolytics blow the Audio Note Seiryu out of the water, it's a closer fight with the Audio Note Kaisei, but the Jupiters are better than them as well.

I've A-B'd a number of capacitors in prototyped circuits, alligator clips tied to the circuit so I can quickly clip in and out different components.  I believe capacitors have a sound, and bad ones can sound very bad.  LEDs have a sound as well, they are not all equal, they have varying degrees of linearity and dynamic impedance which affect the sound as well.  For the longest time I thought I just didn't like LED bias as the most popular (HLMP-6000 series) sounded bad to me.  I revisited it after a specific model was recommended to me by someone whose opinion I greatly respect, I was blown away.  I've now hunted down a host of other LEDs that I believe have similar characteristics to that one.

I'm going to pick the best of the bunch of these electrolytics and then compare to my LEDs.  These Jupiter caps are actually pretty impressive.


----------



## jgwtriode

Fascinating stuff.   Does it make sense to bypass Good film caps like the Clarity with smaller value copper foils for example?  Is there a noticeable difference in your opinion?

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Fascinating stuff.   Does it make sense to bypass Good film caps like the Clarity with smaller value copper foils for example?  Is there a noticeable difference in your opinion?
> 
> jgwtriode



I haven't experimented extensively with bypass caps, but my experience bypassing large film caps with smaller higher quality film caps is they make the sound worse.  When it comes to paralleling film caps, I've found using caps of equal value gets the best sound.


----------



## L0rdGwyn

I finished my electrolytic bypass cap shootout.  The winner is...

The Jupiter Cosmos Wet Electrolytic.  Runner up is the Elna Silmic II.

Both of these caps have very good clarity and don't tend to have the stridency some electrolytics add to the treble.  The Elna Silmic II are pretty highly respected and are dirt cheap, so a great budget option if you are trying to save a few dollars.  But the Jupiter Comos have a larger stage and better air / imaging.  I haven't heard an electrolytic bypass cap this good until now.  I actually suspect they might compete with the new LEDs, we will see this afternoon, a battle of the titans for 6DJ8 biasing supremacy!




Tier list would go something like this.

S: Jupiter Cosmos, Elna Silmic II
A: Audio Note Kaisei, Nichicon FG
B: Nichicon KZ, Vishay Sprague Atom
C: Audio Note Seiryu, MOD

It's a little vague in the middle, but the Audio Note Seiryu and MOD caps were just bad.  All of the others sounded pretty good, but the Jupiter and Elna were clearly a cut above them.


----------



## L0rdGwyn

Well I did my Jupiter Cosmos vs. LED biasing comparison, wow it is a tough one.

For the ultimate in soundstage, airiness, clarity, the LEDs win.  However...the Jupiter caps impart a very nice coloration / tonal richness that I was not expecting, and are very impressive from a staging and clarity standpoint in their own right.  Dare I say they are more musical?  I've never heard an e-lytic that actually caused a positive change...

I can't say which direction I'll go yet, it's more of a preference thing.  The LEDs are probably more "hifi" and detailed whereas the Jupiter bypass caps are more musical with a slightly more intimate stage.

I'll have to try them again when the circuit is finalized since I am doing listening tests in what is an approximation of the final circuit right now.


----------



## Monsterzero

L0rdGwyn said:


> I can't say which direction I'll go yet, it's more of a preference thing. The LEDs are probably more "hifi" and detailed whereas the Jupiter bypass caps are more musical with a slightly more intimate stage.


Why not create two versions of the amp, and allow the buyer to decide which version he/she prefers?


----------



## L0rdGwyn

Monsterzero said:


> Why not create two versions of the amp, and allow the buyer to decide which version he/she prefers?



That thought did cross my mind, could include traces for both on the PCB, or even a jumper to connect the cathodes to one or the other.  I'll keep all of that in mind.  Maybe one will reign supreme in the final version.


----------



## L0rdGwyn

I'll also add that going resistor + bypass cap (aka autobias) rather than LED bias (a form of fixed bias) helps various tubes find happier bias points, so will increase tube rolling flexibility to some degree.


----------



## Xcalibur255

Would the Jupiter be a viable upgrade for older GOTL amps with electrolytic output coupling caps?


----------



## L0rdGwyn

Xcalibur255 said:


> Would the Jupiter be a viable upgrade for older GOTL amps with electrolytic output coupling caps?



I don't recall the specs of the output caps.  I believe there is a 100uF 350VDC Jupiter so you could potentially parallel a bunch of them assuming peak voltages do not exceed 350VDC.

A simpler upgrade would be swapping out the Vishay Sprague Atom bypass caps in the input stage for Jupiters.  Easy to put back if you don't like the change too.


----------



## L0rdGwyn

L0rdGwyn said:


> I don't recall the specs of the output caps.  I believe there is a 100uF 350VDC Jupiter so you could potentially parallel a bunch of them assuming peak voltages do not exceed 350VDC.
> 
> A simpler upgrade would be swapping out the Vishay Sprague Atom bypass caps in the input stage for Jupiters.  Easy to put back if you don't like the change too.



@Xcalibur255 I looked at some old pictures, looks like they are 460uF 200VDC in the GOTL, but probably should double check yours.  So you would need four or five of the 100uF 350VDC in parallel.

They actually do make a 100uF 500VDC version as well.


----------



## carlman14

This whole bias shootout is super interesting. Would you mind also sharing which LEDs you found to be the best sounding? Or maybe what characteristics to look out for when choosing LEDs for biasing?


----------



## L0rdGwyn

carlman14 said:


> This whole bias shootout is super interesting. Would you mind also sharing which LEDs you found to be the best sounding? Or maybe what characteristics to look out for when choosing LEDs for biasing?



I'd prefer not to get into specific models since this design has the potential to become a commercial offering, but I will say that I believe the linearity of the LED's I/V curve is the strongest indicator of good sound, more so than dynamic impedance.  But even then, they still need to be auditioned.


----------



## carlman14

L0rdGwyn said:


> I'd prefer not to get into specific models since this design has the potential to become a commercial offering, but I will say that I believe the linearity of the LED's I/V curve is the strongest indicator of good sound, more so than dynamic impedance. But even then, they still need to be auditioned.



Gotcha, no worries. Excited to see what comes of this project!


----------



## Xcalibur255

L0rdGwyn said:


> @Xcalibur255 I looked at some old pictures, looks like they are 460uF 200VDC in the GOTL, but probably should double check yours.  So you would need four or five of the 100uF 350VDC in parallel.
> 
> They actually do make a 100uF 500VDC version as well.


Gotcha.  I know this particular electrolytic is considered the weakest link in this circuit.  Hence the massive blue towers of capacitor doom on your OTLs.


----------



## gibosi

L0rdGwyn said:


> @Xcalibur255 I looked at some old pictures, looks like they are 460uF 200VDC in the GOTL, but probably should double check yours.  So you would need four or five of the 100uF 350VDC in parallel.
> 
> They actually do make a 100uF 500VDC version as well.



Where are these caps located in the GOTL? I assume that they are not the black caps sitting on top of the chassis next to the inductors? Rather, I assume the ones you are talking about are inside the chassis?


----------



## L0rdGwyn

Xcalibur255 said:


> Gotcha.  I know this particular electrolytic is considered the weakest link in this circuit.  Hence the massive blue towers of capacitor doom on your OTLs.



I might have to try these caps in an OTL circuit, certainly would cut down on size.

@gibosi yes the output caps are on the interior.  The caps on top are part of the power supply.


----------



## Xcalibur255

gibosi said:


> Where are these caps located in the GOTL? I assume that they are not the black caps sitting on top of the chassis next to the inductors? Rather, I assume the ones you are talking about are inside the chassis?


Yes they are internal.  They connect the 6AS7s to the output and are mostly there for filtering purposes.  Keenan can no doubt explain better than I can.  The caps in your photo are part of the power supply, the amp is technically running off of them between A/C cycles if I remember correctly.


----------



## L0rdGwyn

Also just found out Jupiter is headquartered 30 min from my house, maybe I can swing by and convince the owner to let me try those silver foil Vitamin Q caps


----------



## Xcalibur255

L0rdGwyn said:


> Also just found out Jupiter is headquartered 30 min from my house, maybe I can swing by and convince the owner to let me try those silver foil Vitamin Q caps


That's pretty cool.  Unless it's just a corporate office and not manfacturing in which case I honestly wouldn't be surprised if they don't have their own stuff on hand in the building.


----------



## L0rdGwyn

Xcalibur255 said:


> That's pretty cool.  Unless it's just a corporate office and not manfacturing in which case I honestly wouldn't be surprised if they don't have their own stuff on hand in the building.



The address looks to be a house, maybe a home office?  No idea, maybe I'll shoot them an email and tell them how much I like their capacitors.


----------



## L0rdGwyn

@gibosi here is where the output caps were in the GOTL I had, outlined in red.

I was nuts putting 1uF 600VDC Jupiter copper foil coupling caps in this amp, way overkill, how far we have come lol.


----------



## gibosi

L0rdGwyn said:


> @gibosi here is where the output caps were in the GOTL I had, outlined in red.
> 
> I was nuts putting 1uF 600VDC Jupiter copper foil coupling caps in this amp, way overkill, how far we have come lol.



Thanks for the info. Maybe someday I will get off my a$$ and check these out.


----------



## whirlwind (Apr 22, 2022)

L0rdGwyn said:


> Also just found out Jupiter is headquartered 30 min from my house, maybe I can swing by and convince the owner to let me try those silver foil Vitamin Q caps


Ha, great....might as well set up an account....one with free delivery


----------



## L0rdGwyn

Three Airmid chassis waiting for me after work today.

Mirror white for @Monsterzero.



Gator black for @zach915m.



The third is a two tone, hammered silver top plate and a curry yellow for the front, back, and side panels.



Working tomorrow and Monday, so will get working on the white one Tuesday.


----------



## whirlwind

I kind of dig that mirror white and I usually like the flat finishes.

They all look great though.


----------



## Monsterzero

whirlwind said:


> I kind of dig that mirror white and I usually like the flat finishes.
> 
> They all look great though.


My thinking is that the sockets will offer a great contrast to the gloss white finish, which in turn should give a nice reflection to the tube glow.

Meanwhile, similar but unrelated. This might be one of the most beautiful amps I've ever seen


----------



## miketlse

Monsterzero said:


> My thinking is that the sockets will offer a great contrast to the gloss white finish, which in turn should give a nice reflection to the tube glow.
> 
> Meanwhile, similar but unrelated. This might be one of the most beautiful amps I've ever seen


Styled on a vintage coffee machine?
https://www.maxicoffee.com/machine-expresso-ariete-vintage-bleue-offre-cadeaux-p-29152.html


----------



## whirlwind

Monsterzero said:


> My thinking is that the sockets will offer a great contrast to the gloss white finish, which in turn should give a nice reflection to the tube glow.
> 
> Meanwhile, similar but unrelated. This might be one of the most beautiful amps I've ever seen


Looks like the colors of an old 50's car.


----------



## Monsterzero

whirlwind said:


> Looks like the colors of an old 50's car.


Yup, like a late 50s/early 1960s two tone Impala


----------



## L0rdGwyn (Apr 24, 2022)

I have been working on a version of my pentode headamp circuit that uses 6SL7 in the input stage.  I won't declare the change official, needs to be tested in the real world, but if the change is made it could be quite interesting.

I have a few 6SL7 and 12SL7 around, this one in particular is very nice, Tung-Sol 6SU7GTY.



Supposedly the sections were matched at the factory.  Pretty impressive, I guess they weren't lying.



We'll see if this experiment bears fruit.


----------



## Mr Trev

L0rdGwyn said:


> I have been working on a version of my pentode headamp circuit that uses 6SL7 in the input stage.  I won't declare the change official, needs to be tested in the real world, but if the change is made it could be quite interesting.
> 
> I have a few 6SL7 and 12SL7 around, this one in particular is very nice, Tung-Sol 6SU7GTY.
> 
> ...


Since you brought up 6SL7…
Other than gain, is the SL7 radically different than the SN7? Just wondering if I buy a SL7 based amp if I could swap in a SN7 without messing things up


----------



## L0rdGwyn

Mr Trev said:


> Since you brought up 6SL7…
> Other than gain, is the SL7 radically different than the SN7? Just wondering if I buy a SL7 based amp if I could swap in a SN7 without messing things up



Yeah they are very different, the high gain of the 6SL7 comes at a cost, high plate resistance of 44K.  Without getting into all the mumbo jumbo, it makes loading the tube difficult as it puts out very wimpy current.  It has different biasing needs than the 6SN7, which has a much lower plate resistance at 7.7K and takes a higher plate current and grid bias voltage.

It will be circuit dependent on whether or not they can be swapped effectively, you could probably design something that makes compromises on the biasing of both tubes but they will "work", but for the most part something that biases the two tubes ideally in the same circuit would be tricky, your typical off-the-shelf amplifier probably won't do it well.  The best option would probably be to use a CCS load with a hot bias for the 6SL7 and a cold bias for the 6SN7, but you could probably get them to bias points in their respective operating curves that wouldn't produce high distortion, voltage swing on both would be limited though.

Long story short, they each work best in circuits designed for them.


----------



## L0rdGwyn

I bought this pair of NOS RCA 6SL7GT today, will use for testing my idea in addition to the 6SL7 I have.




Also won an auction for a quad of LM Ericsson D3a.


----------



## L0rdGwyn

Nailed some good tube deals.  I buy 90% of my backup 801A outside of the USA, auction prices for them here are ridiculous, $250 a pair minimum.

By comparison I won these two pairs for $55 and $57 dollars each (by exchange rate).  Untested, but they are NOS with intact filaments (broken filaments is the major issue with these old DHTs).  Worth the gamble to me for those graphite plates at a crazy good price


----------



## L0rdGwyn (Apr 26, 2022)

Working on the white Airmid today.  Finished the chassis prep and have most of the major componentry mounted.

Here's how it's coming along.



Will take a break and do a bit more this afternoon to prepare for wiring the power supply tomorrow morning.


----------



## jgwtriode

Congrats Monster!  It looks Awesome! The contrasts are quite stunning!  The Clarity caps will also show quite nicely against the white chassis!

jgwtriode


----------



## Monsterzero

jgwtriode said:


> Congrats Monster!  It looks Awesome! The contrasts are quite stunning!  The Clarity caps will also show quite nicely against the white chassis!
> 
> jgwtriode


Thank you, Sir


----------



## pravous

L0rdGwyn said:


> Working on the white Airmid today.  Finished the chassis prep and have most of the major componentry mounted.
> 
> Here's how it's coming along.
> 
> ...



The white looks really sharp!   That mirror finish is going to reflect tube glow nicely.


----------



## pravous

My latest favorite input tubes for the Airmid.  Gec CV1135 (7193).  These are right up there with the L63.


----------



## jgwtriode

pravous said:


> My latest favorite input tubes for the Airmid.  Gec CV1135 (7193).  These are right up there with the L63.


Very interesting...how do they compare? What is pricing like for them?  The additional wire is added where?  

jgwtriode


----------



## L0rdGwyn

I usually save the input and output wiring for last, but thought I'd wire up the selector switch @Monsterzero requested now, definitely not something I'll want to do when everything else is done lol.



It's a three position toggle switch.  "UP" sends the input RCA signal to the Airmid, "CENTER" sends the signal to the first set of RCA out pass throughs, "DOWN" sends it to the second set of RCA pass throughs.  So one DAC can be plugged into the amp, then two other preamps / amps can be connected to the other two sets of RCA pass throughs.

Also got the power supply regulators mounted.



That's all for today!


----------



## L0rdGwyn

pravous said:


> My latest favorite input tubes for the Airmid.  Gec CV1135 (7193).  These are right up there with the L63.



Very cool, just be careful with those anode caps!  Around 100VDC there.


----------



## bcowen

L0rdGwyn said:


> Very cool, just be careful with those anode caps!  Around 100VDC there.


Aww, that’s just a tingle.  I’m more of a 450v DC guy myself.


----------



## L0rdGwyn

bcowen said:


> Aww, that’s just a tingle.  I’m more of a 450v DC guy myself.



Pfff, you haven't lived until you've tasted at least 600VDC, that's when things REALLY get interesting.


----------



## triod750

You have lived when you have tasted 600VDC.


----------



## pravous

I have tasted 120v ac twice in my life.  Once as a kid trying to power an electrical experiment by feeding stripped wire ends into a standard electrical outlet.  Second time was doing demolition in a warehouse in Boston.  Found wires in a wall we were removing.  Turned off all breakers in the building and was told it was safe to proceed.  Sawz all through the Romex and the blade lights up like a Christmas tree.  Turned out the building next door had cut corners and had electrical runs in the walls in our building to avoid having to patch in their building. Since that day I have always carried something like this in my tool belt. 



Just touch it to the outside of a wire and it can sense current, high or low voltage depending on the setting.


----------



## pravous

jgwtriode said:


> Very interesting...how do they compare? What is pricing like for them?  The additional wire is added where?
> 
> jgwtriode


Generally the 7193, 2c22, cv6 family are not too expensive.  You can get new nos pairs of the Ken Rad 7193 for under $50.  The gec cv variety’s can go for up to 100 a pair.  They require an adaptor that gives connections for the two top caps I got my adaptors from Deyan here on headfi.  I switched to the ceramic top caps because I liked the old school look better.   Of the three brands I have tried they are all very good.  All of them have very expansive sound stage.  Ken Rad have the nice low end, National Union are a little more mid focused.  GEC have the detail and a little more sparkle in the higher registers. Ken Rad/National Union are A to S depending on the pair and how well they match.  The two GEC pairs I have are S+. These are not for the faint of heart for tube rollers.  The two top connections are for the plate and grid.  Not sure exactly would happen but I am guessing reversing them would be bad/catastrophic. I have my plate connections with red shrink tubing and the grids with black.


----------



## L0rdGwyn

pravous said:


> Not sure exactly would happen but I am guessing reversing them would be bad/catastrophic.



I was typing up what would probably happen, but let's just summarize and say it would not be good lol.


----------



## leftside

pravous said:


> Generally the 7193, 2c22, cv6 family are not too expensive.  You can get new nos pairs of the Ken Rad 7193 for under $50.  The gec cv variety’s can go for up to 100 a pair.  They require an adaptor that gives connections for the two top caps I got my adaptors from Deyan here on headfi.  I switched to the ceramic top caps because I liked the old school look better.   Of the three brands I have tried they are all very good.  All of them have very expansive sound stage.  Ken Rad have the nice low end, National Union are a little more mid focused.  GEC have the detail and a little more sparkle in the higher registers. Ken Rad/National Union are A to S depending on the pair and how well they match.  The two GEC pairs I have are S+. These are not for the faint of heart for tube rollers.  The two top connections are for the plate and grid.  Not sure exactly would happen but I am guessing reversing them would be bad/catastrophic. I have my plate connections with red shrink tubing and the grids with black.


Can wake you up in the morning tho if you touch the top cap while the amp is on. Edit: don't do it - it can be very dangerous. Best kept out of the way of animals, small kids, and generally people who "like to touch things".


----------



## Mr Trev

L0rdGwyn said:


> Pfff, you haven't lived until you've tasted at least 600VDC, that's when things REALLY get interesting.





triod750 said:


> You have lived when you have tasted 600VDC.





pravous said:


> I have tasted 120v ac twice in my life.  Once as a kid trying to power an electrical experiment by feeding stripped wire ends into a standard electrical outlet.  Second time was doing demolition in a warehouse in Boston.  Found wires in a wall we were removing.  Turned off all breakers in the building and was told it was safe to proceed.  Sawz all through the Romex and the blade lights up like a Christmas tree.  Turned out the building next door had cut corners and had electrical runs in the walls in our building to avoid having to patch in their building. Since that day I have always carried something like this in my tool belt.
> 
> Just touch it to the outside of a wire and it can sense current, high or low voltage depending on the setting.


Huh… just as a strange aside, I was reading about the joys of fractal burning today: https://www.woodturner.org/Woodturn...spx?hkey=02ac1815-a0e5-4673-a646-741574ab3a76

BTW, my best was a 300v+ capacitor from a camera flash


----------



## pravous

Despite the dangers of the top connections the GEC variations of the 7193 also share the distinctive labels found on some of the l63.


----------



## bcowen

pravous said:


> Generally the 7193, 2c22, cv6 family are not too expensive.  You can get new nos pairs of the Ken Rad 7193 for under $50.  The gec cv variety’s can go for up to 100 a pair.  They require an adaptor that gives connections for the two top caps I got my adaptors from Deyan here on headfi.  I switched to the ceramic top caps because I liked the old school look better.   Of the three brands I have tried they are all very good.  All of them have very expansive sound stage.  Ken Rad have the nice low end, National Union are a little more mid focused.  GEC have the detail and a little more sparkle in the higher registers. Ken Rad/National Union are A to S depending on the pair and how well they match.  The two GEC pairs I have are S+. These are not for the faint of heart for tube rollers.  The two top connections are for the plate and grid.  Not sure exactly would happen but I am guessing reversing them would be bad/catastrophic. I have my plate connections with red shrink tubing and the grids with black.


I marked mine with some stickers.  Looks a little goofy I suppose, but it helps prevent goofs.


----------



## gibosi

pravous said:


> Despite the dangers of the top connections the GEC variations of the 7193 also share the distinctive labels found on some of the l63.



 10E/392  =  CV1135 VR135 and it is the Old Stores Number for this tube.

https://frank.pocnet.net/other/ServiceTypes/OldStores.html


----------



## L0rdGwyn

More progress made - mains transformer mounted, power supply is 3/4 the way done, I/O wiring is done except the output caps, easier to maneuver inside the chassis without them in place, so I typically put them in last.

 Another day or two of work and it will be done.  Will get back at it this weekend.


----------



## L0rdGwyn

My pair of RCA 6SL7GT arrived.  One wouldn't stand up, so I had to lay it on its side artistically.



Here are the curves of one with the sections paralleled, which is how I intend to use them.



Exceptional linearity, which means low distortion.  There is one outstanding question that will need to be investigated / measured when my parts arrive from Lundahl.  If that checks out, and the sound is good of course, then my pentode design will use a pair of 6SL7 on the input stage.  If the measurement or sound is bad, then likely back to 6DJ8, but we will see, I might investigate other options.  Dealing only in new production tube models is tricky, but I'm hopeful this 6SL7 experiment will have a good result.


----------



## L0rdGwyn (Apr 27, 2022)

One more thing I did today.

I figured since I liked the Jupiter Cosmos caps so much in my pentode prototype, I'd go ahead and give them a try in my 6336 OTL, which was running LED bias before in the input stage.

I paired them with some Riken Ohm carbon film resistors, the good stuff (not that they are directly in the signal path since they're bypassed, but hey why not).



How did it sound?  Absolutely horrible.  Not kidding, it was really bad, terribly harsh upper mids and treble.  Honestly, this is what I was expecting to hear when I trialed all those electrolytics in my pentode prototype.

What gives?  The bypass caps sound excellent in my other circuit, so it seems to be circuit dependent.  Perhaps in the OTL design, having two high value caps in the signal path has something to do with it, whereas the pentode circuit is transformer coupled.  Or maybe it is a testament to the quality of what I am doing in the output stage of the pentode amplifier that the input stage can be "tuned" with an electrolytic without affecting the upper midrange /  treble performance.  I have not liked using electrolytic bypass caps on the input stages of other transformer coupled designs.  There is also the possibility of parasitic oscillation, but I was not about to open up that investigation tonight.

I'll have to give it some more thought, but it appears I won't be changing all of my amplifiers over to cathode bias with Jupiter Cosmos bypass caps lol.  I expect I would get similar results with other electrolytics in the 6336 OTL circuit, but I'm happy they synergize so well in the pentode circuit.

So I removed the caps and left the Riken Ohm resistors unbypassed, which is actually how I run the bias in the Airmid input stage, albeit with Kiwame resistors.  The sound this way is great, back in business, will probably try some other LEDs at some point, but for now I'm just happy I can listen to my amp again


----------



## L0rdGwyn (Apr 27, 2022)

Like the Airmid, this 6336 OTL is very happy leaving the cathode resistor unbypassed in the input stage, I may just end up leaving it, it sounds fantastic.  With the resistor unbypassed, its quality becomes important, not all resistors sound the same!  Believe it or not.  How a tube stage is biased and what is placed in its cathode has a drastic effect on the sound quality, the reason many people go to great lengths to use fixed bias in SET designs.

Listening to some techno, had to bust out the VC.


----------



## jgwtriode (Apr 27, 2022)

What tubes are those on the input if I may ask Keenan?  And how do they sound and cost?  You familiar with the basically one man group Zynic(Peter Seimendahl)?  I believe he is somewhere in the range of Techno?    Take a listen pretty amazing stuff.  Latest pre new album cut Best before End!

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> What tubes are those on the input if I may ask Keenan?  And how do they sound and cost?
> 
> jgwtriode



Those are RFT 6J5.  They are pretty uncommon, I'm sorry to say I think sellers would price them quite high if they show on eBay.  I bought mine from an obscure German tube salesman a while back.  But you never know, maybe a deal will turn up!


----------



## bcowen

L0rdGwyn said:


> My pair of RCA 6SL7GT arrived.  One wouldn't stand up, so I had to lay it on its side artistically.
> 
> 
> 
> ...


If the 6SL7’s work out, there’s also the Melz 6N9S that are still (relatively) cheap.  If they sound as good as the Melz 1578/6N8S, that could be a thing.  I don’t have an amp currently to try them in, so can’t find out for myself.


----------



## JazzVinyl

bcowen said:


> If the 6SL7’s work out, there’s also the Melz 6N9S that are still (relatively) cheap.  If they sound as good as the Melz 1578/6N8S, that could be a thing.  I don’t have an amp currently to try them in, so can’t find out for myself.



I have a pair of Melz 6N9S inbound.  In your experience with the Melz 6N8S, what would you say I could expect from the Melz 'house sound'?

BTW, I am in hopes that the 6/12SL7's become the favored drivers of the Pentode Prototype


----------



## L0rdGwyn

bcowen said:


> If the 6SL7’s work out, there’s also the Melz 6N9S that are still (relatively) cheap.  If they sound as good as the Melz 1578/6N8S, that could be a thing.  I don’t have an amp currently to try them in, so can’t find out for myself.



Cool!  I'll keep that in mind, will definitely give them a try if they end up in the final circuit.



JazzVinyl said:


> I have a pair of Melz 6N9S inbound.  In your experience with the Melz 6N8S, what would you say I could expect from the Melz 'house sound'?
> 
> BTW, I am in hopes that the 6/12SL7's become the favored drivers of the Pentode Prototype



Me too  if my idea works out, they would really be ideal.  Time will tell, need to get some parts I've ordered in house, very eager to try it out.


----------



## bcowen (Apr 28, 2022)

JazzVinyl said:


> I have a pair of Melz 6N9S inbound.  In your experience with the Melz 6N8S, what would you say I could expect from the Melz 'house sound'?
> 
> BTW, I am in hopes that the 6/12SL7's become the favored drivers of the Pentode Prototype


Most of my experience has been with the 1578's, although I do have some regular 6N8S's  from the '50's as well.  In the Incubus amp, the 1578 along with the TungSol 5998 is probably my most favorite pairing.  The Melz is pretty linear, but leans just over the fence into warmth versus being clinical. Treble extension and purity is top notch.  Lots of air and space, and no fatigue at all even at stupid-loud levels (after break-in...they can be a little strident when totally new).  The bass is tight, tuneful, and fast with just the right weight and body when paired with the 5998. It's a bit lean down there though when paired with, say, a Chatham 6AS7G or TungSol 6080.  Soundstaging and imaging are fine, although not necessarily better than some other 6SN7's (like a KenRad black glass or tall bottle Sylvania 7N7). I only have 3 of the 1578's, but all of them are quiet as can be with no microphonics.  Two of them have almost perfectly matched triodes, and one has about a 15% difference, but it's not audible.  The regular Melz 6N8S is very much on par with the Foton 6N8S overall. They have different tunings, where the Melz is a bit leaner. The Fotons seem to have a little bump in the upper bass, and I hear this in a dozen or so I've listened to.  Not a bad thing -- in fact I like it, but when you pair it with the bass slam of a 5998 it's a bit too much.  Conversely, I like the Foton better with the Chatham for that same reason.  The 1578 is like the regular 6N8S on steroids. It's considerably more expensive, but worth it IMO.


----------



## JazzVinyl

bcowen said:


> Most of my experience has been with the 1578's, although I do have some regular 6N8S's  from the '50's as well.  In the Incubus amp, the 1578 along with the TungSol 5998 is probably my most favorite pairing.  The Melz is pretty linear, but leans just over the fence into warmth versus being clinical. Treble extension and purity is top notch.  Lots of air and space, and no fatigue at all even at stupid-loud levels (after break-in...they can be a little strident when totally new).  The bass is tight, tuneful, and fast with just the right weight and body when paired with the 5998. It's a bit lean down there though when paired with, say, a Chatham 6AS7G or TungSol 6080.



Very nice description!  I appreciate your thoughts on these,  @bcowen !!


----------



## gibosi (Apr 28, 2022)

JazzVinyl said:


> I have a pair of Melz 6N9S inbound.  In your experience with the Melz 6N8S, what would you say I could expect from the Melz 'house sound'?
> 
> BTW, I am in hopes that the 6/12SL7's become the favored drivers of the Pentode Prototype



One data point. I often run six Melz 6N12S as output tubes. And to my ears, these are quite similar to running a pair of Telefunken 6080. That is, if you like the Telefunken 'house sound', I think it is likely that you will like the Melz 'house sound'.


----------



## JazzVinyl

gibosi said:


> One data point. I often run six Melz 6N12S as output tubes. And to my ears, these are quite similar to running a pair of Telefunken 6080. That is, if you like the Telefunken 'house sound', I think it is likely that you will like the Melz 'house sound'.



Yes I think @mordy is impressed with a six pack of Melz 6N12S as well   

Appreciate!


----------



## mordy

JazzVinyl said:


> Yes I think @mordy is impressed with a six pack of Melz 6N12S as well
> 
> Appreciate!


 Personally, my six pack of Melz 6N12S are my go to power tubes. Clarity, instrument separation and tone are exemplary.
Pity that these tubes are hard to find…
Which Telefunken tubes do they sound like? EL156?


----------



## L0rdGwyn

Here is @Monsterzero 's white Airmid.


----------



## triod750

Nice in blue and white with black accents. How do the input tubes perform compared to the usual suspects?


----------



## L0rdGwyn

The Russian 6J5 aren't bad but definitely some gains to be had upgrading to fancier 6J5.

The ones in the photo are just for testing actually, I think @Monsterzero has some GEC L63 and TS 5998 waiting for the amplifier.


----------



## L0rdGwyn

RFT 6J5 and WE 421A.


----------



## L0rdGwyn

Last one.


----------



## heliosphann

L0rdGwyn said:


> Here is @Monsterzero 's white Airmid.


So fresh, so clean!


----------



## Monsterzero

L0rdGwyn said:


> Last one.





Keenan, it looks amazing! Thank you very much!


----------



## pravous

The white chassis looks amazing!  Really sets off all the features, even the screws.  Great choice Monster.  Looks like you will be stalking a tracking number in the near future.  I remember my delivery day watching the delivery truck seem to circle my house for hours till it finally showed up at 4ish in the afternoon.   Happy listening


----------



## mordy

Monsterzero said:


> Keenan, it looks amazing! Thank you very much!


Congratulations on a stunning amp! Now it needs a name...


----------



## jgwtriode

It definitely looks stunning.   Everything on it really blends together extremely well; visually, which of course is how it will sound with Monster's preferred roll.   Hot damn Monster, you will have to do an Airmid/Atrium video!  I would be very jealous, but I do love mine in red with a couple of decals over the caps to chase the white.

Congrats and very happy listening,

jgwtriode


----------



## jgwtriode (May 1, 2022)

mordy said:


> Congratulations on a stunning amp! Now it needs a name...


Keenan already took care of that, it's  named the Airmid after the Celtic Goddess of healing.  Oops  something more uniqe,   DUHHHH!


----------



## whirlwind

L0rdGwyn said:


> RFT 6J5 and WE 421A.


Looks wonderful!

Congrats @Monsterzero


----------



## Monsterzero

mordy said:


> Congratulations on a stunning amp! Now it needs a name...


Hmmmm...I'll have to give that some thought. Any suggestions?

Glacier? Yeti?


----------



## Monsterzero

jgwtriode said:


> Keenan already took care of that, it's named the Airmid after the Celtic Goddess of healing.


We all named our GOTLs. Mine was called Monster, oddly enough.   I think im gonna go with The Yeti.

My new puppy is named Taranis, the Celtic god of thunder.


----------



## bcowen

L0rdGwyn said:


> Here is @Monsterzero 's white Airmid.


Awesome!!


----------



## bcowen

Monsterzero said:


> We all named our GOTLs. Mine was called Monster, oddly enough.   I think im gonna go with The Yeti.
> 
> My new puppy is named Taranis, the Celtic god of thunder.


Yeti sounds like a beverage container.    

If you want to keep it Celtic, then I like _Cernunnos_:  Lord of the Wild Things.  LOL!


----------



## Mr Trev

Monsterzero said:


> We all named our GOTLs. Mine was called Monster, oddly enough.   I think im gonna go with The Yeti.
> 
> My new puppy is named Taranis, the Celtic god of thunder.


----------



## jgwtriode (May 1, 2022)

Okay were playing name Monster's new amp.   " Voce Di Angelo" and following that tradition I will name my Airmid.    Rìoghail,    Gaelic for Regal!

Happy listening,

jgwtriode


----------



## bcowen

jgwtriode said:


> Okay were playing name Monster's new amp.   " Voce Di Angelo" and following that tradition I will name my Airmid.    Rìoghail,    Gaelic for Regal!
> 
> Happy listening,
> 
> jgwtriode


That sure beats "HPA 3".  Or 5 or whatever.


----------



## gibosi

bcowen said:


> Awesome!!



I think this is a great name for the amp. And I might also suggest "Sublime"


----------



## leftside

That white/creme and blue gives the amp a really nice unique look.


----------



## jgwtriode (May 2, 2022)

Well doing some late listening after working out this evening.   Got My new Wywires Platinum Digital Power Cord...apparently the other was the standard High Current so Alex replaced it. 

Been burning it since Saturday afternoon on the Frig.  So thought what the heck lets see what it does on my Computer since my DAC is about two weeks away now that Ric is working on it.  Now realize what I am about to say doesn't really make any sense to me.  I have a 400 dollar Zen wave audio power cord that I was no long using after upgrading my old DAC power cord, a Wywires HC platinum.  That will now be powering the Airmid.   Anyhow its a pretty decent cord OCC stranded 11AWG cumulative neotech copper with a flat cotton braid.   Its a few years old but reasonably good.  The HC clobbered it on my old DAC.  So pulled the DigiPlat from the frig and plugged it in,  of course slathering it with and then polishing connectors with Mad Sci graphene contact enhancer.   

So reiterating my ongoing tale of frustration.   I have been waiting 8 weeks for my DAC. We won't go into all of it.   But it is finally being resolved this week.  So all of my tweak crazy computer stuff and fancy software and and JCAT stuff with tweaks have  been reduced. to onboard AZrock sound card to process Tidal streaming from it.  That is my Source.   So what difference could a power cable make, relatively huge.  Sounds like I plugged it in to a fairly good DAC.  Computer noise floor dropped to a third of what it was.  Everything got much bigger, cleaner and more dynamic, sounstage opened up and expanded.  Lyrics and details are far more inteligible and distinct.  Noticeably more relaxed and flowing and of course PRAT, knocked me on my proverbial PRAT.  Tonally richer but in that harmonically complete tonally dense weighty kind of way that is actually more neutral and yet more musical.   So of course I am now hearing even more of what the Airmid is capable of.  

Hell I feel like building a Gold plated isolation Altar, as if I could afford that,  So my current DIY will suffice,  with Rioghail looking down from on high.  Haloed in that perfect Amber orange glow.  Sacrificing some lesser solid state or inferior Vaccuum tubes from my past, and chanting Mantra's to Lordgwyn.    It's like a revelation, a moment of absolute zen transcendence anytime I do almost anything with my system now.   

 These Wywires cords get better every day for about 250 to 300 hours.  Alex recommends 200!  So more to experiment with relative to Burn in.  My Platinum RCA's are at about 120. 

Insane, crazy, audio is a Mad World of obsessive fun and discovery. 

Hot damn, nice to feel the warmth as I adjust the volume or wipe any smudges away!

Happy listening,

jgwtriode


----------



## whirlwind

Monsterzero said:


> We all named our GOTLs. Mine was called Monster, oddly enough.   I think im gonna go with The Yeti.
> 
> My new puppy is named Taranis, the Celtic god of thunder.


 You could go with the another Celtic god......."Bird"


----------



## bcowen

whirlwind said:


> You could go with the another Celtic god......."Bird"


LOL!  Or even Dave Cowens.  In name only, I like that even better.


----------



## pravous

My wife refers to the Airmid as "The other woman"


----------



## jgwtriode (May 3, 2022)

Indeed that would probably be the truth of it.   The Celtic word for bird has probably been changed to "Larreeeee"
 in the New American Celtic Dictionary!

jgwtriode


----------



## mordy

Monsterzero said:


> Hmmmm...I'll have to give that some thought. Any suggestions?
> 
> Glacier? Yeti?


How about Snow White?


----------



## L0rdGwyn

Having a last listen tonight, will ship tomorrow.  Got the Tung-Sol roll going, 6J5G and 7802.  Sounds great with the Atrium.


----------



## triod750

L0rdGwyn said:


> Sounds great with the Atrium.


Great can be many things. Can we please  have some L0rdGwyn poetry bloom?


----------



## L0rdGwyn

triod750 said:


> Great can be many things. Can we please  have some L0rdGwyn poetry bloom?



Lol I'm not much of a Head-Fi poet anymore, I leave that to the reviewers!  But what I think this amplifier does really well is it's clarity and holography, it plays to the strengths of the Atrium in that way.  The 7802 gives you a bit more of what the 5998 offers relative to a 6AS7G, more detail, airiness, bass definition.

It sounds great....


----------



## triod750

That sounds great!


----------



## Monsterzero (May 2, 2022)

L0rdGwyn said:


> I leave that to the reviewers! But what I think this amplifier does really well is it's clarity and holography, it plays to the strengths of the Atrium in that way.


Ive been really looking forward to hearing the Atrium on your amp. The Dragon is supposed to be ultra quiet and clear, but the Airmid beats it handily on both fronts. Throw in the holographic madness the Airmid throws and its going to be 3D Valhalla w/ the Atrium.

Unfortunately, I wont be able to listen for quite some time. Taranis is taking up all of my attention at the moment. He is such a daddies boy.


----------



## Monsterzero

mordy said:


> How about Snow White?


I'm torn between:

The Ice Queen
Glacier
Frost Giant


----------



## Monsterzero

whirlwind said:


> You could go with the another Celtic god......."Bird"


Since I was born and raised in Los Angeles, I grew up despising this man. However even a die hard Laker fan like myself recognizes greatness when he sees it...


----------



## jgwtriode

L0rdGwyn said:


> Lol I'm not much of a Head-Fi poet anymore, I leave that to the reviewers!  But what I think this amplifier does really well is it's clarity and holography, it plays to the strengths of the Atrium in that way.  The 7802 gives you a bit more of what the 5998 offers relative to a 6AS7G, more detail, airiness, bass definition.
> 
> It sounds great....


How does it compare tonally, harmonically and in terms of soundstaging?

jgwtriode


----------



## L0rdGwyn

Monsterzero said:


> Ive been really looking forward to hearing the Atrium on your amp. The Dragon is supposed to be ultra quiet and clear, but the Airmid beats it handily on both fronts. Throw in the holographic madness the Airmid throws and its going to be 3D Valhalla w/ the Atrium.
> 
> Unfortunately, I wont be able to listen for quite some time. Taranis is taking up all of my attention at the moment. He is such a daddies boy.



A ferocious killer!  JK, I'm sure he'll be a big softy.  Looking forward to hearing what you think of the pairing, sounds pretty good to me!



jgwtriode said:


> How does it compare tonally, harmonically and in terms of soundstaging?
> 
> jgwtriode



Tonally / harmonically I would say 7802 is similar to 5998, which many tend to describe as bright, but I think that is only because it generates lower second-harmonic distortion relative to a 6AS7G / 6080 in the same circuit.  Staging might be a tad larger, but it's been a while since I've compared them directly.  Unfortunately 7802 are super duper rare.


----------



## Monsterzero

L0rdGwyn said:


> A ferocious killer! JK, I'm sure he'll be a big softy.


Me, in a year






L0rdGwyn said:


> Unfortunately 7802 are super duper rare.


----------



## L0rdGwyn

Monsterzero said:


> Me, in a year



LOL lap dog.  I did say super DUPER, heavy emphasis on the duper.


----------



## L0rdGwyn

I got my quad of LM Ericsson D3a.  This picture doesn't do it justice, this is one fine tube.  These will go in a fancy phono stage some day.


----------



## bcowen

Monsterzero said:


> Me, in a year


Just be glad he's not_ this_ dog.


----------



## whirlwind (May 3, 2022)

Monsterzero said:


> Since I was born and raised in Los Angeles, I grew up despising this man. However even a die hard Laker fan like myself recognizes greatness when he sees it...


I was the same way with the Lakers. I hated Magic and that smile, Kareem and Worthy and all the glamour and glitz.
I did like Kurt Rambis  

Looking back, I now recognize every single one of them as great players and not the jerks that I thought they were.
Players did not get along with players on other teams as well as today's kids do.

It is hard to believe that back in the 70's the games were not even broadcasted live...the NBA has come a long way.


----------



## Monsterzero

whirlwind said:


> It is hard to believe that back in the 70's the games were not even broadcasted live...the NBA has come a long way.


On Thursday, June 3rd, 1982, a sixteen year old me went to Ticketron ( remember them?) in Pasadena, Ca and bought one ticket to Game 4 of the 1982 NBA Finals, which was being played later that night....

Today, a sixteen year old kid cannot afford a NBA Finals ticket, and certainly no tickets would remain on day of game. 

Heck a 57 year old me cannot afford a NBA Finals ticket. 



whirlwind said:


> I was the same way with the Lakers. I hated Magic and that smile, Kareem and Worthy and all the glamour and glitz.
> Looking back, I now recognize every single one of them as great players and not the jerks that I thought they were.


Never liked Worthy. 

Coop, McAdoo, Rambis, KAJ, Magic were all awesome. Big Game James, not so much.


----------



## whirlwind

Monsterzero said:


> On Thursday, June 3rd, 1982, a sixteen year old me went to Ticketron ( remember them?) in Pasadena, Ca and bought one ticket to Game 4 of the 1982 NBA Finals, which was being played later that night....
> 
> Today, a sixteen year old kid cannot afford a NBA Finals ticket, and certainly no tickets would remain on day of game.
> 
> ...



Yes, I sure do remember Ticketron.

That is the sad part about grabbing a ticket to an event like this these days...just not affordable.

To stay on topic.......great looking dog & amp...you have all you need!


----------



## L0rdGwyn (May 3, 2022)

Alright, the white Airmid is away.  Zach has offered to have his be the last one built, so looks like I will be doing the silver / curry one next.  That is for a friend of Zach, he has some specific things planned aesthetically (specific knob, hardware, etc.) so will wait to get those parts from him before I start building it.  Have some PTO coming up, so I will get started on it then.


----------



## L0rdGwyn

Got some new tubes today, nothing too exciting, I just can't pass up good tube deals.

Two more pairs of NOS HY69.  I don't even know how many of these I have now, probably 40-50.  But I am so convinced they are going to sound great, I just keep buying more when they show up.



Old datasheet inside one of the boxes.



Two more pairs of 801A, one pair with graphite plates.  I have two more pairs with graphite plates on the way.



Working for the next six days basically, so not much to be done DIY wise.  I'll get started on the next Airmid after that stretch, I'll have two weeks off  iron for my pentode headamp project is starting to ship too.  Maybe I'll hear about my Sowter I/V transformers soon so I can work on that PCM63 DAC again  oh and then there is that pesky turntable upgrade I've been slowly accumulating parts for...not to mention my VFET power amp project that has been on the backburner...so many projects, not enough time.


----------



## pravous

What a bonus to get a data sheet in the tube box.  Finally got my Etracer back up and running after a case of the mosfet flu.  Been playing around testing the different varieties of the 7193/2c22 family.   Heres a curve trace from a Ken Rad 7193.



What I have found is that there are some differences between the 7193 and the gec cv1135/vr135 and the hytron e-1148.   When I test the gec and the hytron I do not get the expected values from the 2c22 data sheet.  The GEC get somewhere around 70-80% gm and the hytron usually get around 50-60% gm.   The same pattern plays out when watching the heater current draw.  7193 draw @ .3a,  gec @ .2-.21a and the hytron draw @  .17-18a.  They all sound slightly different but the hytron seem to have noticeably less gain.  How would one go about trying to come up with expected values if you can not find a data sheet with either expected values or curves?


----------



## L0rdGwyn

pravous said:


> What a bonus to get a data sheet in the tube box.  Finally got my Etracer back up and running after a case of the mosfet flu.  Been playing around testing the different varieties of the 7193/2c22 family.   Heres a curve trace from a Ken Rad 7193.
> 
> What I have found is that there are some differences between the 7193 and the gec cv1135/vr135 and the hytron e-1148.   When I test the gec and the hytron I do not get the expected values from the 2c22 data sheet.  The GEC get somewhere around 70-80% gm and the hytron usually get around 50-60% gm.   The same pattern plays out when watching the heater current draw.  7193 draw @ .3a,  gec @ .2-.21a and the hytron draw @  .17-18a.  They all sound slightly different but the hytron seem to have noticeably less gain.  How would one go about trying to come up with expected values if you can not find a data sheet with either expected values or curves?



Without any reference material, can't really say what the engineered specifications would be.  Could dig around trying to find a datasheet online, otherwise you'll have to go with what you've measured!


----------



## leftside

I've been having "fun" with datasheets as well recently. I'm testing some ECC32 tubes that I have. Some are marked CV181, which I thought was simply a military designation of the same tube, but Chris from Amplitrex seems to think they have different data sheets and are therefore slightly different tubes. Any thoughts? Doesn't help that it seems to be tough to find data sheets that use the same settings and formats.
http://www.r-type.org/exhib/aad0139.htm
http://www.r-type.org/exhib/aac0003.htm


----------



## L0rdGwyn

leftside said:


> I've been having "fun" with datasheets as well recently. I'm testing some ECC32 tubes that I have. Some are marked CV181, which I thought was simply a military designation of the same tube, but Chris from Amplitrex seems to think they have different data sheets and are therefore slightly different tubes. Any thoughts? Doesn't help that it seems to be tough to find data sheets that use the same settings and formats.
> http://www.r-type.org/exhib/aad0139.htm
> http://www.r-type.org/exhib/aac0003.htm



I think they are the same, they have the exact same operating characteristics / tube constants according to those two datasheets.  Maybe he has some other information available?


----------



## leftside

More here:
http://www.r-type.org/pdfs/cv181.pdf
http://www.r-type.org/pdfs/ecc32.pdf


----------



## leftside

L0rdGwyn said:


> I think they are the same, they have the exact same operating characteristics / tube constants according to those two datasheets.  Maybe he has some other information available?


I always thought the same. I'll keep digging.


----------



## Tom-s (May 5, 2022)

To be precise you'd have to source the datasheet for both.
Trouble is; you won't find a datasheet on the CV181 as this is the Common Valve number equivalent for ECC32.

ECC32 is Philips tube name; a tube designed in the Mullard reseach labs. Mullard was a Philips subsidiary at the time.

For datasheet sourcing; my personal go to site is the DuncanAmps Datasheet Locator.

https://tdsl.duncanamps.com/tubesearch.php

For finding the CV number I use the amateur radio equivalent handbooks; also found online:
https://bms.isjtr.ro/other/docs/ServiceValveEqu_RSGB_1947.pdf

For the UK factory codes I use list like this pdf:
http://www.vmarsmanuals.co.uk/newsletter_articles/cv_valves.pdf

According to these sources. It's an equivalent.

Edit.
 I don't know where to source this. But Philips tube code all had a meaning. I have it in books. Need to find a source online.
For the Philips code.
Normally first letter is heater voltage or current specification. Second letter is tube type (and application from time to time). Numbers on old tubes refer to their amplification. Somewhere in the thirties or forties this changed to a series of tube; like the 80's series are all 9-pin Noval tubes.

ECC32-> E (6.3V indirectly heated AC or DC) C (triode) C (triode) 32 (English octal range, any number from 30-39).


----------



## leftside (May 5, 2022)

Tom-s said:


> To be precise you'd have to source the datasheet for both.
> Trouble is; you won't find a datasheet on the CV181 as this is the Common Valve number equivalent for ECC32.
> 
> ECC32 is Philips tube name; a tube designed in the Mullard reseach labs. Mullard was a Philips subsidiary at the time.
> ...


I did know some of that, but I didn't have those links that you provided. Thanks!

I have a PDF of all the Philips factory tube codes, and see that Philips used 'EN' to represent 'ECC32', but I wasn't how Mullard themselves came up with the codes for 'ECC32'.

I'd be very interested to know where you got this info from regarding how Mullard named the ECC32 . Edit: I see where: Section 6 of the ServiceValveEqu PDF.

Great info.


----------



## Monsterzero (May 5, 2022)

The Glacier has arrived. Unfortunately all of my audio gear is in puppy prison. Thank you @L0rdGwyn !


----------



## leftside

Monsterzero said:


> The Glacier has arrived. Unfortunately all of my audio gear is in puppy prison. Thank you @L0rdGwyn !


Lucky those tube labels align like that from an aesthetic point of view. Rare I manage to get tubes to align like that. We need a "swivel/rotate" socket feature


----------



## L0rdGwyn

Monsterzero said:


> The Glacier has arrived. Unfortunately all of my audio gear is in puppy prison. Thank you @L0rdGwyn !



You're welcome!  Let me know what you think when you're gear is set free


----------



## jgwtriode (May 6, 2022)

leftside said:


> Lucky those tube labels align like that from an aesthetic point of view. Rare I manage to get tubes to align like that. We need a "swivel/rotate" socket feature


Yeah indeed my GEC L63's  tubes test identical to each other according to the vendor.  But the labels are about 70 to 80 degrees out of alignment which does look strange.  One faces almost straight forward and the other almost completely to the right.

I will happily take the sonic benefit over the visual.  But visual matching is definitely a plus!

jgwtriode


----------



## whirlwind

Monsterzero said:


> The Glacier has arrived. Unfortunately all of my audio gear is in puppy prison. Thank you @L0rdGwyn !


That amp even looks great in jail!

Pup definitely does look like daddy's boy.





leftside said:


> I always thought the same. I'll keep digging.


Can't wait to find out if they are actually different....I always thought the CV181 was just a military version also.
If they are different I will definitely grab one.


----------



## gibosi

whirlwind said:


> Can't wait to find out if they are actually different....I always thought the CV181 was just a military version also.
> If they are different I will definitely grab one.



They are not different. CV181 is simply a British inventory number for the Mullard ECC32. And as no other company manufactured the ECC32, it is identical.

Prior to the CV numbers, the British army, navy and air force each had different numbers for the same tube. So the CV series was developed and introduced in the 1940's to simplify things. CV numbers are similar to the American VT numbers. For example, VT231 = CV1988 = 6SN7GT.

But in some cases, the CV number can refer to more than one tube. It appears that sometimes the specifications were somewhat relaxed. For example, CV378 refers to the Cossor 53KU and the Mullard GZ37. Whle the 53KU and GZ37 are similar they are not identical. But both were labeled CV378.


----------



## mordy

gibosi said:


> They are not different. CV181 is simply a British inventory number for the Mullard ECC32. And as no other company manufactured the ECC32, it is identical.
> 
> Prior to the CV numbers, the British army, navy and air force each had different numbers for the same tube. So the CV series was developed and introduced in the 1940's to simplify things. CV numbers are similar to the American VT numbers. For example, VT231 = CV1988 = 6SN7GT.
> 
> But in some cases, the CV number can refer to more than one tube. It appears that sometimes the specifications were somewhat relaxed. For example, CV378 refers to the Cossor 53KU and the Mullard GZ37. Whle the 53KU and GZ37 are similar they are not identical. But both were labeled CV378.


Can you straighten out which numbers belong where (army, navy, air force) of VR, ARP, NR and the 10E/XXXX numbers? - I think that 10E/XXXX is a RAF (Royal Air Force) reference. (Sometimes you see A M with a crown in between the letters which may mean Air Ministry.





Then you have AMERTY tubes which means American type. but I don't know if they were American made or not:



The above tube should be a Mullard made tube.
https://www.ebay.com/itm/203604991753


----------



## Tom-s (May 6, 2022)

mordy said:


> Can you straighten out which numbers belong where (army, navy, air force) of VR, ARP, NR and the 10E/XXXX numbers? - I think that 10E/XXXX is a RAF (Royal Air Force) reference. (Sometimes you see A M with a crown in between the letters which may mean Air Ministry.
> Then you have AMERTY tubes which means American type. but I don't know if they were American made or not:
> The above tube should be a Mullard made tube.
> https://www.ebay.com/itm/203604991753



VR: Royal Air Force Receiving Valve
ARP: Army Receiving Penthode
NR: Navy Receiving Valve

Another source I frequently use to search tube types UK: https://nzvrshome.files.wordpress.com/2019/07/valve-numbering-and-equivalents-radio-bygones.pdf

And the above tube you refer to is UK Brimar made; only branded Mullard.

Edit: Just noted that file also includes the European numbering system as Philips used it. From a previous post for @leftside


----------



## triod750

Tom-s said:


> And the above tube you refer to is UK Brimar made; only branded Mullard.


Typical Brimar plate.


----------



## mordy

Tom-s said:


> VR: Royal Air Force Receiving Valve
> ARP: Army Receiving Penthode
> NR: Navy Receiving Valve
> 
> ...


Thanks. Is A M an early Air Force code?


----------



## Tom-s

mordy said:


> Thanks. Is A M an early Air Force code?



All I know is this refers to Air Ministry like you said.

Here's the same same but different information 
http://www.r-type.org/articles/art-170.htm


----------



## mordy

Tom-s said:


> All I know is this refers to Air Ministry like you said.
> 
> Here's the same same but different information
> http://www.r-type.org/articles/art-170.htm


Thanks for the link. It says there that all British military tubes received a CV designation in 1941. Can I assume that a tube using only the VR or ARP code was made earlier than 1941?


----------



## gibosi

mordy said:


> Thanks for the link. It says there that all British military tubes received a CV designation in 1941. Can I assume that a tube using only the VR or ARP code was made earlier than 1941?



No. While the CV system was developed in 1941, phasing out the old numbers was a slow process. So trying to date tubes in this manner is not at all precise.


----------



## leftside

gibosi said:


> They are not different. CV181 is simply a British inventory number for the Mullard ECC32. And as no other company manufactured the ECC32, it is identical.
> 
> Prior to the CV numbers, the British army, navy and air force each had different numbers for the same tube. So the CV series was developed and introduced in the 1940's to simplify things. CV numbers are similar to the American VT numbers. For example, VT231 = CV1988 = 6SN7GT.
> 
> But in some cases, the CV number can refer to more than one tube. It appears that sometimes the specifications were somewhat relaxed. For example, CV378 refers to the Cossor 53KU and the Mullard GZ37. Whle the 53KU and GZ37 are similar they are not identical. But both were labeled CV378.


This is what I believe as well. I think Chris has some old data sheets  that might be incorrect, where one is labelled CV181 and the other ECC32, so it appears from these sheets that there are slight differences.


----------



## gibosi

mordy said:


> Can you straighten out which numbers belong where (army, navy, air force) of VR, ARP, NR and the 10E/XXXX numbers? - I think that 10E/XXXX is a RAF (Royal Air Force) reference. (Sometimes you see A M with a crown in between the letters which may mean Air Ministry.
> 
> 
> Then you have AMERTY tubes which means American type. but I don't know if they were American made or not:
> ...



It's not clear why some tubes carry the Air Ministry designation. Perhaps, as you suggest, it is an older designation, going back to the end of WWI. However, it appears to me that 10E/XXXX, 11E/XXXX, ZA/XXXX and similar inventory numbers (Old Stores Numbers) cover tubes from any and all British government users, not just the Air Ministry.

https://frank.pocnet.net/other/ServiceTypes/OldStores.html


----------



## whirlwind

gibosi said:


> They are not different. CV181 is simply a British inventory number for the Mullard ECC32. And as no other company manufactured the ECC32, it is identical.
> 
> Prior to the CV numbers, the British army, navy and air force each had different numbers for the same tube. So the CV series was developed and introduced in the 1940's to simplify things. CV numbers are similar to the American VT numbers. For example, VT231 = CV1988 = 6SN7GT.
> 
> But in some cases, the CV number can refer to more than one tube. It appears that sometimes the specifications were somewhat relaxed. For example, CV378 refers to the Cossor 53KU and the Mullard GZ37. Whle the 53KU and GZ37 are similar they are not identical. But both were labeled CV378.


Thanks for clearing that up


----------



## leftside

Tom-s said:


> VR: Royal Air Force Receiving Valve
> ARP: Army Receiving Penthode
> NR: Navy Receiving Valve
> 
> ...


Wealth of great information @Tom-s. Thanks for sharing.


----------



## mordy

gibosi said:


> No. While the CV system was developed in 1941, phasing out the old numbers was a slow process. So trying to date tubes in this manner is not at all precise.


Thanks - that's what I thought. Here is my DD tube (daily driver):




On the base it says 1002 which I think is a Mullard designation for EF39. Then it says 3U (or BU?) which I think is a date code, but what does it mean? 
July 1943?
March 1946?
Or?


----------



## gibosi (May 6, 2022)

leftside said:


> This is what I believe as well. I think Chris has some old data sheets  that might be incorrect, where one is labelled CV181 and the other ECC32, so it appears from these sheets that there are slight differences.



Edit:

> Some sources list the ECC32 as a modified ECC31.  After all, the only difference is that the cathodes are pulled out separately rather than shared between the two
> triodes. And it occurs to me that it may have taken some time to figure out what to do with this tube? Did they want to put it on the market?  And what to call it? I think
> I can safely say that no one alive knows exactly how this played out.

> Also, over time, sometimes the datasheets change. I have seen different values on early data sheets and later ones for the same tube. And it makes me wonder, did 
> the values actually change? Was there a mistake? Or was there a marketing reason to make the change? I can't know. lol  

> But in the end, I am very comfortable in claiming that the CV181 and ECC32 are identical.

I got distracted with how the ECC32 actually came about, but while that might be interesting to some, it isn't really relevant to the differences between the two datasheets referred to above.

~~~~~~~~~~~

A CV datasheet doesn't actually describe a real tube. As I mentioned earlier, the datasheet for the CV378 doesn't perfectly describe either the Cossor 53KU or the Mullard GZ37. However, the specifications detailed in the CV datasheet are loose enough to "describe" both the 53KU and the GZ37 and either will work in a circuit calling for a CV378

And similarly, the CV181 datasheet doesn't perfectly describe an ECC32. However, the specifications detailed in the CV181 datasheet are very similar to an ECC32, and again, the ECC32 will work in any circuit calling for a CV181.


----------



## gibosi

mordy said:


> On the base it says 1002 which I think is a Mullard designation for EF39. Then it says 3U (or BU?) which I think is a date code, but what does it mean?
> July 1943?
> March 1946?
> Or?



I have yet to find the key to the old Mullard codes, so your guess is as good as any.


----------



## leftside

gibosi said:


> I have yet to find the key to the old Mullard codes, so your guess is as good as any.


I’ve tried to find them too, but to no avail.


----------



## Tom-s

Tom-s said:


> VR: Royal Air Force Receiving Valve
> ARP: Army Receiving Penthode
> NR: Navy Receiving Valve
> 
> ...



I felt my previous post was somewhat incomplete. It doesn't explain the older Philips tube codes. A code system that was really convenient. As the code tells you a lot about the tube and helps to cross reference your tube to other manufacturers. This was really helpful when one needed a replacement for their radio equipment. 

Unfortunately. This information is only available in older books in my books collection. And these are in Dutch. Here's a link to the 1925 book I've pictured below named "Philips Radio": https://www.rsp-italy.it/Electronics/Databooks/Philips/_contents/Philips Tubes 1925.pdf

This old books goes in-depth explaining how to exactly use a Philips Miniwatt tube; a great little guide. It shares all needed information to build an amplifier using Philips Miniwatt tubes this era.

I've pictured page 15; chapter 11 that explains the Philips Miniwatt tube determination.
It says; loosely translated:


> "The "Miniwatt" triodes are given a certain letter and number based on a certain system.
> The heater current is given by a the letter being:
> A = heater current 0,06 - 0,08 Ampere.
> B = heater current 0,1 - 0,15 Ampere.
> ...


Even this booklet is somewhat incomplete. As I've found a first letter E valve can range till 1,6A and F is used for higher currents. Yet to find G. 

Using this system you can see how one can get an idea from what Philips tube to use.

Example US type 01A. 
Heater current: 0,25A -> C
Heater voltage: 5V -> 5
Amplification factor 9 -> 09
The Philips equivalent name is C509. Sometimes A is added for controlled heater warmup. See picture.

Example US type 27.
Heater current: 1.75A -> F
Heater voltage 2.5V -> Becomes 2 as there's no decimals in this naming system.
Amplification factor 09 -> 09
So this would be F209 -> And indeed this exists. Alternative name could be PH227.
Don't have this in my collection unfortunately. So I've pictured the next best option. An F215, same current range, same voltage, only amplification =15.
The pictured F215 shows the early solution for having an indirectly heater tube with 5 connections (with both a cathode and a heater) and only 4 pins available on the B4 European tube socket. It used a side contact connection for the cathode. In 1928 the B5 socket with 5 pins was introduced and this side contact was no longer needed.

Added an extra picture with Philips B403 from 1925/1926 time period in my preamp (In 1927 Philips changed the brown base for the newer rounded version). This preamp runs solely on battery supplies. Just as these tubes were intended to be used; almost 100 years ago.  
The right tube has "Personeel" written on it. These could only be bought by Philips employees (personeel) straight from the Philips factory at a reduced price.

I thank you for reading my brain fart.


----------



## whirlwind

gibosi said:


> I have yet to find the key to the old Mullard codes, so your guess is as good as any.


Yeah, why is this so hard. I would think there would be plenty of info available, but that does not seem to be the case.


----------



## bcowen

whirlwind said:


> Yeah, why is this so hard. *I would think there would be plenty of info available, but that does not seem to be the case.*


Tubes were replaced by transistors many years ago, so the information is no longer needed.  🤣🤣


----------



## whirlwind

bcowen said:


> Tubes were replaced by transistors many years ago, so the information is no longer needed.  🤣🤣



Ha, yeah....but info for Mullard seems much harder to find than most.


----------



## gibosi (May 7, 2022)

whirlwind said:


> Yeah, why is this so hard. I would think there would be plenty of info available, but that does not seem to be the case.



Unfortunately, when major factories were shut down, apparently no one thought it was important to keep the old records and they were simply tossed. When RCA shut down their primary factory and headquarters in Harrison, NJ, very fortunately, a number of collectors got word of it. And they pulled a huge amount of material out of the dumpsters. Otherwise, much of what we know today about RCA would be missing.


----------



## JazzVinyl

mordy said:


> Thanks - that's what I thought. Here is my DD tube (daily driver):
> 
> On the base it says 1002 which I think is a Mullard designation for EF39. Then it says 3U (or BU?) which I think is a date code, but what does it mean?
> July 1943?
> ...



That is one heck of a crusty looking tube, Mordy!   Your daily driver?


----------



## bcowen

JazzVinyl said:


> That is one heck of a *crusty looking tube*, Mordy!   Your daily driver?


----------



## JazzVinyl

At least Krusty does not have a piss yellow flesh tone, like the rest of the simpsons'....


----------



## Mr Trev

JazzVinyl said:


> That is one heck of a crusty looking tube, Mordy!   Your daily driver?


I had crusty tubes once… an ointment cleared it right up


----------



## mordy

JazzVinyl said:


> That is one heck of a crusty looking tube, Mordy!   Your daily driver?


Yes! I could remove the flaking metallic paint but what for? I love the exquisite tone and frequency range of these tubes.


----------



## mordy

gibosi said:


> I have yet to find the key to the old Mullard codes, so your guess is as good as any.


When you say old, what decade or range of years are you referring to?


----------



## leftside

mordy said:


> When you say old, what decade or range of years are you referring to?


Before 1955. Mullard adopted the Philips scheme in 1955.


----------



## leftside

The other coding scheme that is tough to crack is GEC prior to 1945. I have a bunch of the earlier KT66 from pre-1945 and the best dates I can come up with are "wartime".


----------



## JazzVinyl

mordy said:


> Yes! I could remove the flaking metallic paint but what for? I love the exquisite tone and frequency range of these tubes.



It is adapted to the SN7 socket?


----------



## mordy

JazzVinyl said:


> It is adapted to the SN7 socket?


Nyet - it is a pentode strapped as a triode and plugged into a Deyan adapter EL32 to C3g; you need two tubes.


----------



## L0rdGwyn (May 8, 2022)

mordy said:


> Thanks - that's what I thought. Here is my DD tube (daily driver):
> 
> On the base it says 1002 which I think is a Mullard designation for EF39. Then it says 3U (or BU?) which I think is a date code, but what does it mean?
> July 1943?
> ...



Interesting that you like this one mordy as it is a variable mu pentode, meaning as a triode it will have high distortion, not really an audio tube.  But given the voltage swings in headphone amplifiers are not high, maybe the distortion isn't significant.  Or you like the sound of distortion  its audio pentode cousin is the EF37A, which was the precursor to the famous EF86.


----------



## leftside

L0rdGwyn said:


> Interesting that you like this one mordy as it is a variable mu pentode, meaning as a triode it will have high distortion, not really an audio tube.  But given the voltage swings in headphone amplifiers are not high, maybe the distortion isn't significant.  Or you like the sound of distortion  it's audio pentode cousin is the EF37A, which was the precursor to the famous EF86.


Lot's of bands and artists have used distortion to good effect: https://www.roadiemusic.com/blog/the-top-10-songs-with-distortion-in-guitar-history/ I'd also add The Cramps and The Jesus and Mary Chain. Fuzz world:


----------



## Mr Trev

leftside said:


> Lot's of bands and artists have used distortion to good effect: https://www.roadiemusic.com/blog/the-top-10-songs-with-distortion-in-guitar-history/ I'd also add The Cramps and The Jesus and Mary Chain. Fuzz world:



My first impression when I read the The Jesus and Mary Chain was being reissued on DVDA… "hires distortion??"


----------



## Monsterzero

The Airmid is the most transparent amp Ive ever heard. I just spent a month with the Dragon lvl 3, which is the TOTL Dragon. Dave Hanson said the lvl 2 was one of the most transparent amps he's ever heard. The Airmid is much clearer, transparent and quieter than the lvl 3.

Impressive!


----------



## jgwtriode

The Airmid is ridiculous in terms of how much  it improves my VC!  On both counts Monster I have you to thanks for your reviews, they have altered the course
of my Audio Experience and I am beyond grateful.   Always want to check your opinions first before I consider anything.  Your are always right on the money.

Happy listening,
jgwtriode


----------



## jgwtriode

Just out of curiosity Monster what is your footer experience?   Right now I use Mad Scientist  Blackpod Nano feet in 3's under my components and single Tungsten Carbide ones Under SSD's braced to sit on a single ball to the bottom of my computer. I also use a Triad of them under my Computer.  I am thinking of getting a Set for my Airmid, once my DAC finally arrives which could be next week finally.  I do also use DIY airbladders  and Mapleshade 4" Ambrosia maple Blocks to sit those on.

thanks again,

jgwtriode


----------



## mordy

L0rdGwyn said:


> Interesting that you like this one mordy as it is a variable mu pentode, meaning as a triode it will have high distortion, not really an audio tube.  But given the voltage swings in headphone amplifiers are not high, maybe the distortion isn't significant.  Or you like the sound of distortion  its audio pentode cousin is the EF37A, which was the precursor to the famous EF86.


----------



## mordy

L0rdGwyn said:


> Interesting that you like this one mordy as it is a variable mu pentode, meaning as a triode it will have high distortion, not really an audio tube.  But given the voltage swings in headphone amplifiers are not high, maybe the distortion isn't significant.  Or you like the sound of distortion  its audio pentode cousin is the EF37A, which was the precursor to the famous EF86.


I don't hear a distorted sound; don't think I would like a distorted sound. Is there a test for distortion using your hearing since I don't have any equipment to measure with?
I like the early 50's Sylvania tall tube metal base 6J5GT, and these tubes sound similar but with better dynamics and speed.


----------



## Monsterzero (May 8, 2022)

jgwtriode said:


> Just out of curiosity Monster what is your footer experience?   Right now I use Mad Scientist  Blackpod Nano feet in 3's under my components and single Tungsten Carbide ones Under SSD's braced to sit on a single ball to the bottom of my computer. I also use a Triad of them under my Computer.  I am thinking of getting a Set for my Airmid, once my DAC finally arrives which could be next week finally.  I do also use DIY airbladders  and Mapleshade 4" Ambrosia maple Blocks to sit those on.
> 
> thanks again,
> 
> jgwtriode


I do not have much experience with footers, except for on my SVS sub, where they make a massive difference. In the past I have done a poor man's set up where I use neoprene under and over butcher block, but thats the extent of it.


----------



## gibosi

L0rdGwyn said:


> Interesting that you like this one mordy as it is a variable mu pentode, meaning as a triode it will have high distortion, not really an audio tube.  But given the voltage swings in headphone amplifiers are not high, maybe the distortion isn't significant.  Or you like the sound of distortion  its audio pentode cousin is the EF37A, which was the precursor to the famous EF86.



I assume output is certainly not linear, but is the sound actually distorted in a way that our ears can discern?


----------



## L0rdGwyn (May 8, 2022)

mordy said:


> I don't hear a distorted sound; don't think I would like a distorted sound. Is there a test for distortion using your hearing since I don't have any equipment to measure with?
> I like the early 50's Sylvania tall tube metal base 6J5GT, and these tubes sound similar but with better dynamics and speed.



Unfortunately there isn't really a way to do it in a reliable way subjectively, only way to measure is with some sort of spectrum analyzer.  If it sounds good, it sounds good!



gibosi said:


> I assume output is certainly not linear, but is the sound actually distorted in a way that our ears can discern?



It isn't linear but like I mentioned in a headphone amplifier, and especially in the GOTL since it is a two-stage amplifier with both stages providing voltage gain, the voltage that needs to be swung by the input tube is not very high.  So even with a nonlinear tube, the produced distortion might still be very low in level.  It will still have an audible effect, how audible depends on the level and harmonics produced.  Circuit changes that alter levels of distortion or change harmonic pattern are very audible.


----------



## JazzVinyl

Monsterzero said:


> The Airmid is the most transparent amp Ive ever heard. I just spent a month with the Dragon lvl 3, which is the TOTL Dragon. Dave Hanson said the lvl 2 was one of the most transparent amps he's ever heard. The Airmid is much clearer, transparent and quieter than the lvl 3.
> 
> Impressive!



You will have to start a tour of the Airmid, MZ so that we can hear what you heard.  

Otherwise, only a select few on the planet, will ever get to hear it.

Will PM my address 😊

🔊


----------



## jgwtriode (May 8, 2022)

Monsterzero said:


> I do not have much experience with footers, except for on my SVS sub, where they make a massive difference. In the past I have done a poor man's set up where I use neoprene under and over butcher block, but thats the extent of it.


Yeah I went a little nuts a few years back.  I do wheelbarrow inner tubes for airbladders.  Have 4 8" under my 16"X12" mapleshade 4" block, whic actually that sits on an ikea cardboard composite phenolic skin shelf which is what directly sits on the bladders and same thing under them and that sits on 4" 1.5 lb Mable shade brass footers. Then the Mad Sci's.  DAC in on its on stand I made from one of those Ikea  Bekvan Table/Cart.  It's about a 25 lb Birch table. Cut of the legs aout 4 inches to shorten it and threaded 4  3 lbs custom brass cones from my old Talon Speakers.  DAC sits on a similar arrangement as the computer; but uses 10" bladders, an 18" x 14"  Mapleshade and used a doubled up group of 6 Mad Sci footers with a carbon fiber/nomex composite shelf sandwiched between the cermic and tungsten carbide balls of each set.   I was thinking of something similar for the Airmid but wanted to consider other footer that might be worth playing with.   The Airmid will sit on the middle shelf, under the DAC.  Will probably just do a 2" unfinished mapleshade block at some point.  Will cut down an Ikea lack table shelf to fit and sit on probably just 3 8" bladders, unless I can find 4 6" bladders.  I sit the Airmid in a diamond arrangement to give my headphone cable a bit more slack.   When it's all done I will post a photo.   So any footer suggestions would be great.  I have been looking at the roller block variations which seem the most interesting right now.   The Ingress Audio Engineering ones,  look the most reasonable and get really good reviews.

The highest quality level 3 are  240 for a set of 3 which seems fairly reasonable.   I would probably replace the high grade steel balls with two ceramic and one tungsten carbide at some point.


Happy listening,

jgwtriode


----------



## bcowen

jgwtriode said:


> Yeah I went a little nuts a few years back.  I do wheelbarrow inner tubes for airbladders.  Have 4 8" under my 16"X12" mapleshade 4" block, whic actually that sits on an ikea cardboard composite phenolic skin shelf which is what directly sits on the bladders and same thing under them and that sits on 4" 1.5 lb Mable shade brass footers. Then the Mad Sci's.  DAC in on its on stand I made from one of those Ikea  Bekvan Table/Cart.  It's about a 25 lb Birch table. Cut of the legs aout 4 inches to shorten it and threaded 4  3 lbs custom brass cones from my old Talon Speakers.  DAC sits on a similar arrangement as the computer; but uses 10" bladders, an 18" x 14"  Mapleshade and used a doubled up group of 6 Mad Sci footers with a carbon fiber/nomex composite shelf sandwiched between the cermic and tungsten carbide balls of each set.   I was thinking of something similar for the Airmid but wanted to consider other footer that might be worth playing with.   The Airmid will sit on the middle shelf, under the DAC.  Will probably just do a 2" unfinished mapleshade block at some point.  Will cut down an Ikea lack table shelf to fit and sit on probably just 3 8" bladders, unless I can find 4 6" bladders.  I sit the Airmid in a diamond arrangement to give my headphone cable a bit more slack.   When it's all done I will post a photo.   So any footer suggestions would be great.  I have been looking at the roller block variations which seem the most interesting right now.   The Ingress Audio Engineering ones,  look the most reasonable and get really good reviews.
> 
> The highest quality level 3 are  240 for a set of 3 which seems fairly reasonable.   I would probably replace the high grade steel balls with two ceramic and one tungsten carbide at some point.
> 
> ...


Too bad the Neuance shelves aren't made any more.  I was a maple / butcher block devotee until I heard these. Ended up buying enough of them to fill both my big-rig racks.  Very light and extremely rigid.


----------



## Monsterzero

JazzVinyl said:


> You will have to start a tour of the Airmid, MZ so that we can hear what you heard.
> 
> Otherwise, only a select few on the planet, will ever get to hear it.
> 
> ...


----------



## JazzVinyl

Not sure what that reply is supposed to mean/represent.


----------



## jgwtriode (May 8, 2022)

bcowen said:


> Too bad the Neuance shelves aren't made any more.  I was a maple / butcher block devotee until I heard these. Ended up buying enough of them to fill both my big-rig racks.  Very light and extremely rigid.


That Art Audio is gorgeous.  Joe made beautiful stuff!

Okay so here is my last photo I took of My DIY Ikea Bekvam stand.  In this photo you can see how ridiculous.  This is about 5 years of fiddling with it and steadily improving it every so often.  You will note I even played with stainless steel, brass and ceramic shims, under the hard cones.  The non brass cones you see are DH ceramic cones.  I use
one one big one at the back of the base Ikea composite and one of the medium size at the front corner under the mapleshade block.   Crazy!  Most recent thing was playing with the shims which  refined the sound even further.  Tried two brass shims and ceramic.  That was most open and detailed sound I had up to that point and the liveliest, but a hint hard.  So tried stainless steel with ceramic.  Tonally better but not as open or detailed and a hint to soft and blurred.  So final thing was to do one of each and boom!  I have also recently been playing with porcelain shims under the DAC on top of the Mad Sci's tungsten carbide and ceramic balls.  Basically porcelain shower hex sheets using individual small hex tiles.  Interesting but didn't have enough time to play with them, since my DAC went Kaput!  Yup way to obsessive but  these differences are there and since these are cheap tweaks I keep fiddling.

There Is also an old Plitron 300W transformer in a steel sheilding can I sit on top of the DAC as a weight.   The Bladder's are about 1/3 full.  With all four, I have air isolation with ridiculously good stability.  If I press down as hard as I can on a corner I can get maybe a 1/8" compression.


Happy listening,

jgwtriode


----------



## raindownthunda

JazzVinyl said:


> Not sure what that reply is supposed to mean/represent.


----------



## L0rdGwyn

Monsterzero said:


> The Airmid is the most transparent amp Ive ever heard. I just spent a month with the Dragon lvl 3, which is the TOTL Dragon. Dave Hanson said the lvl 2 was one of the most transparent amps he's ever heard. The Airmid is much clearer, transparent and quieter than the lvl 3.
> 
> Impressive!



Thanks for the compliment!  Transparency / clarity / staging are a high priority for me.  When I am working on something, if those areas are improving, things are going in the right direction and the rest of the pieces fall into place.


----------



## jgwtriode

Indeed Monster Indeed!

jgwtriode


----------



## JazzVinyl

bcowen said:


> Too bad the Neuance shelves aren't made any more.  I was a maple / butcher block devotee until I heard these. Ended up buying enough of them to fill both my big-rig racks.  Very light and extremely rigid.



Need towel - to mop up drool, over your Turntable!!


----------



## JazzVinyl

L0rdGwyn said:


> Thanks for the compliment!  Transparency / clarity / staging are a high priority for me.  When I am working on something, if those areas are improving, things are going in the right direction and the rest of the pieces fall into place.



Looking forward to Pentode amp, whose schematic (hopefully) will be publicly available.


----------



## mordy

jgwtriode said:


> Yeah I went a little nuts a few years back.  I do wheelbarrow inner tubes for airbladders.  Have 4 8" under my 16"X12" mapleshade 4" block, whic actually that sits on an ikea cardboard composite phenolic skin shelf which is what directly sits on the bladders and same thing under them and that sits on 4" 1.5 lb Mable shade brass footers. Then the Mad Sci's.  DAC in on its on stand I made from one of those Ikea  Bekvan Table/Cart.  It's about a 25 lb Birch table. Cut of the legs aout 4 inches to shorten it and threaded 4  3 lbs custom brass cones from my old Talon Speakers.  DAC sits on a similar arrangement as the computer; but uses 10" bladders, an 18" x 14"  Mapleshade and used a doubled up group of 6 Mad Sci footers with a carbon fiber/nomex composite shelf sandwiched between the cermic and tungsten carbide balls of each set.   I was thinking of something similar for the Airmid but wanted to consider other footer that might be worth playing with.   The Airmid will sit on the middle shelf, under the DAC.  Will probably just do a 2" unfinished mapleshade block at some point.  Will cut down an Ikea lack table shelf to fit and sit on probably just 3 8" bladders, unless I can find 4 6" bladders.  I sit the Airmid in a diamond arrangement to give my headphone cable a bit more slack.   When it's all done I will post a photo.   So any footer suggestions would be great.  I have been looking at the roller block variations which seem the most interesting right now.   The Ingress Audio Engineering ones,  look the most reasonable and get really good reviews.
> 
> The highest quality level 3 are  240 for a set of 3 which seems fairly reasonable.   I would probably replace the high grade steel balls with two ceramic and one tungsten carbide at some point.
> 
> ...


Just for the sake of completeness, the IKEA shelf named bekväm means comfortable in Swedish.
Lol


----------



## jgwtriode

Didn't know that thanks Mordy!

jgwtriode


----------



## mordy (May 8, 2022)

Just can't come to terms with the fact I like listening to a tube that distorts... Have to be socially responsible and listen to something that measures good. Took a 6SN7 and cracked it in half and got two 6J5GT tubes. I assume that they measure good because they are featured in a recent famous custom amp.
The one with the bigger hat sounds a little better, but both sound great - a near pair of Tung Sol 6J5GT. One is from 1956 and the other rusty one says 20 on it, whatever that means.



The above is said tongue-in-cheek so don't take it too seriously. But they sound great and I hope that I don't have to worry about that dreaded d...n.
The main thing is to enjoy the music and to have fun with your stuff!


----------



## triod750

Mordy; if it sounds good, something has to be wrong about it! Or maybe you are so old that you have grown hair in your ears that filter away what might be dist...ion? I have a yummy combination of Blackburn EL42 and RCA 6BX7GT that prevents ugly treble to pass through. Only sweet treble make it to my ears and it is soothing to listen to music when using this combo. Some music/recordings benefit and so do I.


----------



## JazzVinyl

raindownthunda said:


> Charleston 'Horses' Ass' Heston on his GOD given right...!!!



Oh I see...the horses' ass, speaks...

Happiness - is a warm gun.


----------



## mordy

triod750 said:


> Mordy; if it sounds good, something has to be wrong about it! Or maybe you are so old that you have grown hair in your ears that filter away what might be dist...ion? I have a yummy combination of Blackburn EL42 and RCA 6BX7GT that prevents ugly treble to pass through. Only sweet treble make it to my ears and it is soothing to listen to music when using this combo. Some music/recordings benefit and so do I.


I was listening to an old 78 and one of my sons asked me why there is so much hiss.
But I didn’t hear it…As we age there is a high frequency roll-off, but that does not take away from the enjoyment of listening to music.
Most music is within a frequency range that older people can hear.
My impression is that the average age of people on this blog is much higher than 35…


----------



## mordy

mordy said:


> I was listening to an old 78 and one of my sons asked me why there is so much hiss.
> But I didn’t hear it…As we age there is a high frequency roll-off, but that does not take away from the enjoyment of listening to music.
> Most music is within a frequency range that older people can hear.
> My impression is that the average age of people on this blog is much higher than 35…


Or maybe 2 x 35 for some of us...(but I am not telling).


----------



## L0rdGwyn

mordy said:


> Or maybe 2 x 35 for some of us...(but I am not telling).



I guess I am bringing the average down then lol I am below average, as usual.


----------



## bcowen (May 9, 2022)

jgwtriode said:


> That Art Audio is gorgeous.  Joe made beautiful stuff!



Thanks!  I've had several dozen speaker amps in my day, and the Art remains my favorite. 



jgwtriode said:


> Okay so here is my last photo I took of My DIY Ikea Bekvam stand.  In this photo you can see how ridiculous.  This is about 5 years of fiddling with it and steadily improving it every so often.  You will note I even played with stainless steel, brass and ceramic shims, under the hard cones.  The non brass cones you see are DH ceramic cones.  I use
> one one big one at the back of the base Ikea composite and one of the medium size at the front corner under the mapleshade block.   Crazy!  Most recent thing was playing with the shims which  refined the sound even further.  Tried two brass shims and ceramic.  That was most open and detailed sound I had up to that point and the liveliest, but a hint hard.  So tried stainless steel with ceramic.  Tonally better but not as open or detailed and a hint to soft and blurred.  So final thing was to do one of each and boom!  I have also recently been playing with porcelain shims under the DAC on top of the Mad Sci's tungsten carbide and ceramic balls.  Basically porcelain shower hex sheets using individual small hex tiles.  Interesting but didn't have enough time to play with them, since my DAC went Kaput!  Yup way to obsessive but  these differences are there and since these are cheap tweaks I keep fiddling.


Some folks think I'm a bit over the top with the isolation thing, so it's nice to have some good company.  

I fell into that rabbit hole rather unintentionally.  I was using an old TV stand for my system at the time, and needed a rack just for the space.  Went to CES that year to help out some friends, and there were a couple SolidSteel racks that needed a home after the show and I was able to snag one for a great price.  Took it home and set things up, and quite honestly I was not expecting to actually hear anything different -- I was just glad to have proper support for the components.  The first tunes played resulted in one of those what!!! moments.  I can't think of any aspect of the sound that wasn't improved, some immensely.  Then I got some of the first Marigo "dots" that started out about the size of a Kennedy half-dollar.  But that's another story.   

Note that I don't hear the same levels of improvement with my HP setup.  Differences can be heard, just not as pronounced as in the big rig.  No airborne or structural vibration to contend with, I suppose.


----------



## L0rdGwyn

Wrapped up a long string of work shifts, chilling out with the Sicte 6J5GT, Cetron 6528 and the Atrium.  Got one more work errand tomorrow then I can get back to DIY.  Final parts on the way for the silver/ curry Airmid, might also do some work on the pentode prototype now that I have the output transformers.


----------



## JazzVinyl

Has to be extra satisfying, knowing you built it.  

Well done!


----------



## raindownthunda

L0rdGwyn said:


> Wrapped up a long string of work shifts, chilling out with the Sicte 6J5GT, Cetron 6528 and the Atrium.  Got one more work errand tomorrow then I can get back to DIY.  Final parts on the way for the silver/ curry Airmid, might also do some work on the pentode prototype now that I have the output transformers.


Those Sicte tubes are pretty. Haven't seen many of those pop up. Do you have any idea on who made them? The supports look kind of like Mullard.


----------



## whirlwind

Excited for the pentode prototype.

Now get those errand's run and get to work!  Just kiddin'  

Chill time is necessary after long work weeks.


----------



## gibosi

raindownthunda said:


> Those Sicte tubes are pretty. Haven't seen many of those pop up. Do you have any idea on who made them? The supports look kind of like Mullard.



It is generally believed that SICTE was founded in Pavia, Italy, in the late 1950’s by some former Fivre employees. And perhaps not surprisingly, the sound reminds me of the Fivre double triodes and rectifiers with a similar mid-range emphasis.


----------



## L0rdGwyn

raindownthunda said:


> Those Sicte tubes are pretty. Haven't seen many of those pop up. Do you have any idea on who made them? The supports look kind of like Mullard.



What @gibosi said!  Yeah they are pretty unusual as far as 6J5s go, but I agree they are similar to Fivre in terms of their flavor.


----------



## L0rdGwyn (May 13, 2022)

Even though I've been off for a few days, I haven't been able to do tube DIY, I've had to do another type of DIY, the bad kind, house DIY 🤮

Really bad weather this winter, one side of my porch skirt was torn to shreds by a wind storm, had to completely rebuild it.



From the same storm, one of the shutters was torn off my house and damaged the siding, so that had to be replaced too.  Finally having some consistently nice weather in NE Ohio, so had to take advantage.

But now I am done so I can get back to tubes 

As I said, got the parts package for the silver / curry Airmid.  The buyer is undecided on two different knobs, so we will try both and see which fit / looks better.



Going to get started on that this weekend.

I am finally taking my vinyl setup upgrades seriously.  Going to be ordering a custom wooden plinth in the coming days, along with getting a quote for a restored SME 3009 S2 Improved.  What that quote ends up being will determine whether or not I go for it versus buying one more cheaply and doing the maintenance work myself.

On that front, I am also working on a new phono stage.  I built my current phono stage at the end of 2020, funny to return to the design, I've learned quite a lot since then, so improvements have to be made.  I am leaning toward going LCR for the passive RIAA.  Originally I had a crazy design that was completely transformer coupled, but I think that is too rich for my blood right now.  Instead, going to keep it cap-coupled but go LCR for the RIAA using Dave Slagle's 7.5K RIAA inductors.

I don't post a lot of schematics here anymore, some people in the past have misinterpreted my posting them as a request for feedback, but this isn't the place, I do that in private with people I trust.  So I stopped posting them as I was sort of fed up with it, but I like my draft of this design, so I thought I'd show it.



Here is the current plan, from start to finish.

1) Balanced inputs once again (3-pin XLR), same Lundahl LL9226XL MC SUT wired for 1:10, balanced primary, single-ended secondary
2) Battery biased, triode strapped D3a or E810F first gain stage, CCS loaded and wired as a hybrid mu follower to drive the 7.5K LCR RIAA, capacitor coupled to the RIAA filter
3) Passive 7.5K LCR RIAA using Dave Slagle's inductors.  The chokes are tapped at multiple points so RIAA compliance can be measured and adjustments made
4) Cathode biased, triode strapped E55L output stage, CCS loaded and wired as a hybrid mu follower, capacitor coupled outputs.  This hybrid mu follower output stage will give the phono stage a very low output impedance.  Could experiment with leaving the cathode resistor unbypassed if it doesn't significantly increase the noise floor

As before, power supply and all AC in a separate chassis with an umbilical to the amplifying stage.

After tuning the RIAA filter, here is the output frequency response with RIAA correction in simulation, a little under 67dB of gain.  So, would start with the values in my simulation and make adjustments based on real world measurements.  Measuring phono stages is a PITA, as you need to either A) use an inverse-RIAA filter or B) take a measurement and correct for the RIAA in software, which can be done in programs like REW.



Going to mull over this design a little longer before ordering the LCR chokes, but I like where it's going.  Finally going to put those E55L to good use!

Anyway, will update turntable stuff as it comes along, but final Airmid builds come first


----------



## CJG888 (May 13, 2022)

I can heartily recommend Audio Origami‘s 3009 rebuild service. Mine has been in daily use for four years and never missed a beat.

Alas, due to a change in circumstances, all my analogue gear is now in storage while I wait for the divorce to come through (which can take another 18 months here in Germany)…


----------



## L0rdGwyn

CJG888 said:


> I can heartily recommend Audio Origami‘s 3009 rebuild service. Mine has been in daily use for four years and never missed a beat.
> 
> Alas, due to a change in circumstances, all my analogue gear is now in storage while I wait for the divorce to come through (which can take another 18 months here in Germany)…



Thanks for the recommendation, I'll check out Audio Oragami, but sorry to hear about the divorce  wish you the best in getting through it.


----------



## jgwtriode

Okay got a better phone with a better camera   So a better picture of my red Airmid with a proper tube roll and my final decals of choice.  Desided a simple triskelle on the caps best suited the Celtic inspiration and as previously stated gave it a regal/kingly name.  Rioghail, which sound most interesting of all the Celtic/Gaelic variants and it rolls nicely of the tongue.  Soon will get to hear it.  Ric is working on final tuning of my modded DAC.   Can hardly wait!

Happy listening,

jgwtriode


----------



## JazzVinyl

Looks great!!! Have it on a special regal cloth background as well?


----------



## jgwtriode

JazzVinyl said:


> Looks great!!! Have it on a special regal cloth background as well?


My bed!  Very regal indeed!  Nothing else for a decent improvised background. LOL!


----------



## L0rdGwyn

Here is a first look at the silver / curry Airmid, including the front panel hardware requested by the buyer.


----------



## L0rdGwyn

Got a pair of NIB Tung-Sol 6528 for my OTL today.  Bought untested with guaranteed return if they aren't functional, fortunately they work perfectly.  They are more squat compared to the Cetrons.



Going to see King Gizzard and the Lizard Wizard this Friday, so their new album is the jam for the day.


----------



## jgwtriode (May 16, 2022)

L0rdGwyn said:


> Here is a first look at the silver / curry Airmid, including the front panel hardware requested by the buyer.


Love the hammered silver and not a fan of yellow, but the curry contrasts quite nicely with that hammered finish.  And the front fascia looks quite striking in that combination.

jgwtriode


----------



## pravous

Great to see more Airmids getting out there. Such an amazing amp, sometimes feel guilty that I am one of the lucky few. Celebratory roll tonight.  Wife landed a job at her dream practice.  Date matched nos WE 421a with Gec cv1135 as inputs.  



Happy listening!


----------



## L0rdGwyn

pravous said:


> Great to see more Airmids getting out there. Such an amazing amp, sometimes feel guilty that I am one of the lucky few. Celebratory roll tonight.  Wife landed a job at her dream practice.  Date matched nos WE 421a with Gec cv1135 as inputs.
> 
> Happy listening!



Congrats to your wife!


----------



## jgwtriode

Would love to have a pair of Western Electrics.  Saw some on Ebay at over 600 a pair as a starting bid.  Ouch!

Congrats to both of you!

jgwtriode


----------



## L0rdGwyn

Making progress bit by bit on this silver / curry Airmid.  Trying to take a healthier approach and working a little at a time rather than multi-hour marathons.

Got the transformer and shield mounted, power supply regulators, and remaining large components.  Knob removed to keep it from being scratched during the build.





I will start the point-to-point wiring this weekend.

I ordered the new plinth for my Thorens TT.  I went with walnut, maybe it's boring but I like it, simple and classy.  Still trying to decide if I want to restore an SME 3009 myself or pay the premium to have it done for me.  My time vs. my money is always the question 

I am very excited to finish this set of upgrades.  I am reconsidering going completely transformer coupled for my LCR phono stage.  That would look something like this (schematically speaking).





This would be very expensive.  I would keep my Lundahl MC SUT as a compromise as opposed to upgrading that as well, but would still be looking at something like $1,700 USD in LCR chokes and transformers.  But if I am going through the trouble of a phono rebuild, my feeling is I might as well wait a little longer and go for the end game, which this definitely would be.  Probably would leave my digital setup in the dust, so the arms race would have to continue.  Maybe a revised plan for my quad of PCM63 chips to strike back...

Once these last two Airmids are finished, I can jump into all this craziness head first...and the pentode amplifier, and the PCM63 DAC, and all the other project I have partway done 😭😭😭


----------



## pravous

Out of curiosity what do the “v” designated components represent?  V1 is clearly a battery  but trying to figure out what kind of components v2 and v4 are.


----------



## L0rdGwyn

pravous said:


> Out of curiosity what do the “v” designated components represent?  V1 is clearly a battery  but trying to figure out what kind of components v2 and v4 are.



For the purposes of the simulation in LTSpice, they are DC voltage sources, but in the real world, V2 and V4 are the B+ supply.  In LTSpice, usually it is easier to simulate a circuit using a generic voltage source rather than the fully functional simulation of the power supply circuit combined with the amplifying circuit.  You can combine them, but it can take a very long time to run a simulation command with the complete circuit built out, especially when you are using regulated power supplies with integrated circuitry.  So for the purposes of testing an amplifier circuit, using a voltage source is easiest as a substitute.  I usually test the power supply I plan to use in a separate simulation using either a resistive load or a current source as a substitute for the current that will be drawn from the amplifying circuit.


----------



## pravous

Makes sense.  I downloaded ltspice the other week with the goal of trying to simulate the BHC circuit.   Got stuck trying to figure out how to create a transformer but this sounds like a good work around.  Thanks for the knowledge


----------



## L0rdGwyn

pravous said:


> Makes sense.  I downloaded ltspice the other week with the goal of trying to simulate the BHC circuit.   Got stuck trying to figure out how to create a transformer but this sounds like a good work around.  Thanks for the knowledge



Yeah definitely, you can add parasitics to it, but otherwise it will function as a "perfect" voltage source.  Obviously not accurate in the real world, need to know the limitations of using a simulation program, but it is an invaluable tool for prototyping circuitry without having to build it.  Note that LTSpice functions using peak voltage values as opposed to RMS.  If you want to simulate a rectified DC circuit without having to deal with the transformer primary-to-secondary coupling, can skip the primary and just use a 60Hz AC voltage source at the peak voltage value of the transformer secondary as a stand in, then follow it with the remainder of the supply.


----------



## Since1991

Really sucks I didn't get to find out about this while @L0rdGwyn was still accepting orders on custom amp builds. Those amps look great, I'm sure they sound great as well.


----------



## L0rdGwyn

Since1991 said:


> Really sucks I didn't get to find out about this while @L0rdGwyn was still accepting orders on custom amp builds. Those amps look great, I'm sure they sound great as well.



Yes, I am sorry, it was a short lived experiment.  In my excitement to share what I'd made, I thought I could balance my work, personal life, and make amplifiers on the side.  Only a few months of that reality showed me I could not as it essentially meant working two jobs, and my real job is quite taxing.  There are other talented custom amplifier makers out there though in 1101 Audio and Ultrasonic Studios, I'm sure others will show up in time too.


----------



## L0rdGwyn

After much deliberation, I made a decision on a tonearm for my upgraded Thorens TD 125 MK II.

I decided against the SME 3009 in favor of a new production arm that pairs better with my cart.  After some back and forth with Dave at Vinyl Nirvana, I went with the Sorane (formerly Abis) TA-1 (9" arm in the photo below, not the 12").




By all accounts, this is an excellent medium mass arm.  It also substitutes well for an SME, can even be used with SME armboards with an adapter.  Fantastic, as it means I can still use the very nice SME armboard I had made for the build.



The included cable is RCA, so I will have to change it to 3-pin XLR, or make a new cable.

So the tonearm is ordered, custom plinth ordered, new armboard is already here along with a new aluminum face plate without the cueing lever.  The whole turntable will need to be taken apart, so will clean things up along the way, and I will fully test the speed control board during the build and replace any suspicious componentry.  Probably will get this done some time in July.  Then the phono stage upgrade will be next


----------



## L0rdGwyn (May 22, 2022)

And I am working on the silver /curry Airmid, but there won't be much to show until it is done.  I expect to finish it next weekend*, I will post some photos then before it is shipped.


----------



## Xcalibur255

Several nice shots of Zach's 45 here.  Standing toe-to-toe with a DCS stack worth 30K and not losing any ground from what it sounds like.


----------



## zach915m (May 27, 2022)

Xcalibur255 said:


> Several nice shots of Zach's 45 here.  Standing toe-to-toe with a DCS stack worth 30K and not losing any ground from what it sounds like.



As far as amps go, if I had to keep one amp I own it would be the 45 amp for numerous reasons. It's definitely my number 1 over yes even the Lina.

I have not heard a DAC by @L0rdGwyn yet haha. The Lina dac for me is the best DAC I've heard.


----------



## ilikebananafudge

zach915m said:


> As far as amps go, if I had to keep one amp I own it would be the 45 amp for numerous reasons. It's definitely my number 1 over yes even the Lina.
> 
> I have heard a DAC by @L0rdGwyn yet haha. The Lina dac for me is the best DAC I've heard.


How would you say the Lina amp compares to the ECP DSHA-3F?


----------



## L0rdGwyn

Xcalibur255 said:


> Several nice shots of Zach's 45 here.  Standing toe-to-toe with a DCS stack worth 30K and not losing any ground from what it sounds like.






zach915m said:


> As far as amps go, if I had to keep one amp I own it would be the 45 amp for numerous reasons. It's definitely my number 1 over yes even the Lina.
> 
> I have heard a DAC by @L0rdGwyn yet haha. The Lina dac for me is the best DAC I've heard.



Very cool, thanks for the kind words, glad to hear the Air Mountain™ is hangin' in there with the Lina, maybe there's something to all this tube craziness after all  the Lina stack looks great, I'll have to give that DAC a listen some day.


----------



## zach915m

ilikebananafudge said:


> How would you say the Lina amp compares to the ECP DSHA-3F?


Need to do a direct compare of that one. I'm sure there's no loser though. 


L0rdGwyn said:


> Very cool, thanks for the kind words, glad to hear the Air Mountain™ is hangin' in there with the Lina, maybe there's something to all this tube craziness after all  the Lina stack looks great, I'll have to give that DAC a listen some day.


Tradmark that s***! 

If we hang into any of the Lina stuff you are welcome to!


----------



## jgwtriode

The Air Mountain is obviously touching the audio stratosphere.  What an amazing amplifier to look at and to think about of what it is capable.  Just out of curiosity what would you have to charge for an Air Mountain Keenan, not that your going to build another?

jgwtriode


----------



## gibosi

Found this tube and thought if you haven't seen it before you might find it interesting:

https://www.radiomuseum.org/tubes/tube_rl12p35.html

http://www.tube-classics.de/TC/Klangfilm/Projects/RL12P35/RL12P35amp.htm


----------



## L0rdGwyn (May 27, 2022)

zach915m said:


> Tradmark that s***!
> 
> If we hang into any of the Lina stuff you are welcome to!



LOL well technically you created the Air Mountain title, I'll give you first dibs on the trademark 



jgwtriode said:


> The Air Mountain is obviously touching the audio stratosphere.  What an amazing amplifier to look at and to think about of what it is capable.  Just out of curiosity what would you have to charge for an Air Mountain Keenan, not that your going to build another?
> 
> jgwtriode



I hadn't really thought about what I would've charged, but it would be very expensive given the cost of parts and the time to build.  North of $5K, but I have no doubt it outperforms most five-figure tube amplifiers on the commercial market, it's the best tube amplifier I have ever heard.  I plan to use essentially the same base circuit whenever I get around to building my HY69 speaker amplifier.  I have thought about making myself an Air Mountain some day but using 10Y / 801A as the output tube instead of 45.  But I'm in no hurry to make another speaker or headphone amp for myself, very happy with both of mine right now and other projects to work on.



gibosi said:


> Found this tube and thought if you haven't seen it before you might find it interesting:
> 
> https://www.radiomuseum.org/tubes/tube_rl12p35.html
> 
> http://www.tube-classics.de/TC/Klangfilm/Projects/RL12P35/RL12P35amp.htm



Looks like a cool tube!  Transmitting pentode with A2 capability, I would love to see what it looks like as a triode.  Surprisingly they seem to be relatively common on the eBay.  There is a link within your second link to a Lorenz push-pull design that looks interesting.  I'll have to keep these in mind, maybe I will buy a pair to test.


----------



## bcowen

zach915m said:


> As far as amps go, if I had to keep one amp I own it would be the 45 amp for numerous reasons. It's definitely my number 1 over yes even the Lina.
> 
> *I have heard a DAC by @L0rdGwyn yet haha. The Lina dac for me is the best DAC I've heard.*


Sounds like a challenge to me, Keenan.


----------



## L0rdGwyn

bcowen said:


> Sounds like a challenge to me, Keenan.



Lol what I've done in my NOS DAC is child's play compared to what dCS has engineered, they've designed their own unique DAC architecture, I've barely scratched the surface of digital design.  It is very complex, one definitely benefits from a formal engineering education, but it is surprising the quality of sound you can achieve using vintage R2R chips in NOS designs.  I would be shocked if my humble DAC came close to touching the Lina, subjectively speaking.  I use the magic of tubes to close the gap  gonna have to do something special with those PCM63 chips.


----------



## L0rdGwyn

At long last, here is the curry and silver Airmid.  Have some NEC 6520 and MOV L63 for the photo.







Sorry I've been MIA, but I've decided I'm going to significantly pare back the amount of time I spend on Head-Fi to make room for other things in my life, only logging in if I have a reason to as opposed to aimless browsing.  So I won't be on here as often as I have been or updating this thread at the same pace I have for the past 2.5 years.  If anyone has one of my amps and needs to reach me urgently, shoot me an email!

Also, if anyone is going to CanJam Chicago, Zach tells me that both the 45 amp I built him and the Airmid I built his friend will be at the ZMF table.


----------



## jgwtriode (Jun 14, 2022)

Welcome Back!  Stunning Keenan! And I really like the hammered silver finish as well!  

Will be awesome to see what people at the CanJam have to say after hearing them.

Congrats and Happy Listening,

jgwtriode





1


----------



## L0rdGwyn

Thanks @jgwtriode , yeah curious to see what people think.  Have you received your DAC yet?


----------



## jgwtriode

No unfortunately.  Ric is just dragging his feet on it.  He is far more focused on getting his Speaker RF Filters out
there right now.   Ric is older and gets to things as he gets to them.  His mods are brilliant, but he can take a while.
Just had no idea it would be this long.  He has had a few health setbacks as well.  So I keep tinkering with lowering
noise floor with some of the Mad Sci stuff.  The Carbon Graphene Nano dougnuts, discs and another large block of
the same material he sent me for a different application that I am using to make smaller blocks. I have it surrounding most
all of the connections now and the cumulative effects are quite ridiculous.  I am thing of mounting blocks of it under the
tubes to see if it has any effect.  I have my own version of the Mad Sci Tube Damper. which includes some wood Cones that
were once used as a cone center diffusor for my fostex 208 drivers designed by Planet 10 hifi. Those sit on top of the GEC L63's and the tighten the bass and slightly lower noise floor and increase space and detail slightly, plus they add just a hint
of lower mid warmth which is nice!

Got to somethin while waiting,

jgwtriode




1


----------



## jgwtriode (Jun 21, 2022)

Some nice feedback:


ZMF had a wide variety of tub amps. They were all great, but the one that stood out to me was the *Airmid*. Unfortunately, this DIY OTL amp isn't built regularly; but I hold an ounce of hope (prayer? this will change in the future. The bass on this (tested with Atrium) was magnificently resonant. Very memorable. I will be the first to get one if/whenever @zach915m can convince @L0rdGwyn to let him build them... 

Just a quick question Keenan.   How are you coupling the driver stage to the output tubes?  I don't see a cap in the signal path there.


Happy Listening

jgwtriode


----------



## zach915m

The AirMid was the star of the show for sure!


----------



## jgwtriode

I love mine!  What a remarkable amp.  Feel like it transforms my VC's into something much more.  What tubes were you running in it Zach?
I am very curious about the Closed back Atrium.   Have to wait for tax time next year.  But if all goes well.  Really want some WE 421a's but
can't really justify the cost and they are damn hard to find.

Congrats on all the excitement you created at the Can Jam.  One day I will show up to one.   

Happy  listening,

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Some nice feedback:
> 
> 
> ZMF had a wide variety of tub amps. They were all great, but the one that stood out to me was the *Airmid*. Unfortunately, this DIY OTL amp isn't built regularly; but I hold an ounce of hope (prayer? this will change in the future. The bass on this (tested with Atrium) was magnificently resonant. Very memorable. I will be the first to get one if/whenever @zach915m can convince @L0rdGwyn to let him build them...
> ...





zach915m said:


> The AirMid was the star of the show for sure!



Cool!  Good to know other people like what I like  hopefully it showed off the headphones well.

In this type of 6AS7G OTL design, the input and output stages are direct coupled, there is no capacitor in between them.

I am going to throw together my pentode headamp prototype over the next few days.  Here is the lineup of Lundahl iron going inside, a pricey little batch.  And a cat.


----------



## bcowen

jgwtriode said:


> I love mine!  What a remarkable amp.  Feel like it transforms my VC's into something much more.  What tubes were you running in it Zach?
> *I am very curious about the Closed back Atrium.  * Have to wait for tax time next year.  But if all goes well.  Really want some WE 421a's but
> can't really justify the cost and they are damn hard to find.


2nd that.


----------



## bcowen

L0rdGwyn said:


> Cool!  Good to know other people like what I like  hopefully it showed off the headphones well.
> 
> In this type of 6AS7G OTL design, the input and output stages are direct coupled, there is no capacitor in between them.
> 
> I am going to throw together my pentode headamp prototype over the next few days.  Here is the lineup of Lundahl iron going inside, a pricey little batch.  And a cat.


Totally awesome!  Oh, and I like the transformers too.


----------



## UntilThen

L0rdGwyn said:


> I am going to throw together my pentode headamp prototype over the next few days. Here is the lineup of Lundahl iron going inside, a pricey little batch. And a cat.



Looking forward to that. Pentodes as strapped triodes?


----------



## L0rdGwyn

UntilThen said:


> Looking forward to that. Pentodes as strapped triodes?



Yep, strapped as triodes.  However being used in a somewhat unusual topology, different from other transformer coupled amps using these tubes.


----------



## UntilThen

L0rdGwyn said:


> Yep, strapped as triodes.  However being used in a somewhat unusual topology, different from other transformer coupled amps using these tubes.



Interesting. I love my nos pentodes. I suppose the chassis will be as striking as Airmid or your statement amp with the Sowter transformers.


----------



## L0rdGwyn

UntilThen said:


> Interesting. I love my nos pentodes. I suppose the chassis will be as striking as Airmid or your statement amp with the Sowter transformers.



It should look pretty sharp!  I have the chassis drafted but still a work in progress.  Oh tube rectified too, I know you're a fan


----------



## UntilThen

L0rdGwyn said:


> It should look pretty sharp!  I have the chassis drafted but still a work in progress.  Oh tube rectified too, I know you're a fan



Well all your amps look sharp so I wouldn't expect anything less. I have a soft spot for tube rectification and I think there many other fans too.


----------



## UntilThen

I have always thought of this as your statement amp.


----------



## jgwtriode

L0rdGwyn said:


> Cool!  Good to know other people like what I like  hopefully it showed off the headphones well.
> 
> In this type of 6AS7G OTL design, the input and output stages are direct coupled, there is no capacitor in between them.
> 
> I am going to throw together my pentode headamp prototype over the next few days.  Here is the lineup of Lundahl iron going inside, a pricey little batch.  And a cat.


Looks like he is serious about making sure they are secure!

jgwtriode


----------



## L0rdGwyn

UntilThen said:


> I have always thought of this as your statement amp.



Thanks, that is my favorite, one year to design, I learned a great deal working on it.  The 801A is a tricky tube to work with.


----------



## UntilThen

L0rdGwyn said:


> Cool!  Good to know other people like what I like  hopefully it showed off the headphones well.
> 
> In this type of 6AS7G OTL design, the input and output stages are direct coupled, there is no capacitor in between them.
> 
> I am going to throw together my pentode headamp prototype over the next few days.  Here is the lineup of Lundahl iron going inside, a pricey little batch.  And a cat.



Show the cat Lundahl and Sowter side by side. See which he or she prefers.


----------



## whirlwind

L0rdGwyn said:


> Cool!  Good to know other people like what I like  hopefully it showed off the headphones well.
> 
> In this type of 6AS7G OTL design, the input and output stages are direct coupled, there is no capacitor in between them.
> 
> I am going to throw together my pentode headamp prototype over the next few days.  Here is the lineup of Lundahl iron going inside, a pricey little batch.  And a cat.


Great pic!

I love that you are going off the grid so to speak with the topology


----------



## L0rdGwyn

whirlwind said:


> Great pic!
> 
> I love that you are going off the grid so to speak with the topology



Thanks!  Yeah it's out of the ordinary as far as headphone amplifiers go.  I actually finished the prototype the other day, been listening to it the past three days, it worked just how I had it drawn up.  So it's tube rectified via GZ34 / 5R4 / 5V4, uses a pair of 6SL7 inputs and a pair of audio pentode outputs.  I've mostly been listening with a pair of EL34 XF2, but I've tried 6L6 and 6V6.

I've also rolled a few different rectifiers in, here is a pic of the GZ34, glad I kept one of these around.




The sound is excellent, smooth and slightly lush but with very good staging, imaging, and separation.  The low end performance is the standout for me, overall just a very dynamic sound.  No semiconductors this time around, completely "old school" design using tubes, resistors, capacitors, inductors.

So I'm moving forward with it, I have the PCB and chassis partway done, I will work on them over the remainder of the summer and build one.


----------



## bcowen

L0rdGwyn said:


> The sound is excellent, smooth and slightly lush but with very good staging, imaging, and separation.  The low end performance is the standout for me, overall just a very dynamic sound.  *No semiconductors this time around, completely "old school" design using tubes, resistors, capacitors, inductors.*
> 
> So I'm moving forward with it, I have the PCB and chassis partway done, I will work on them over the remainder of the summer and build one.


This always puts me in a happy place.  😂


----------



## whirlwind

bcowen said:


> This always puts me in a happy place.  😂


Yup, me too!


----------



## UntilThen

L0rdGwyn said:


> The sound is excellent, smooth and slightly lush but with very good staging, imaging, and separation. The low end performance is the standout for me, overall just a very dynamic sound. No semiconductors this time around, completely "old school" design using tubes, resistors, capacitors, inductors.



Sounds like what I'm hearing in Odyssey.


----------



## CJG888

L0rdGwyn said:


> Thanks!  Yeah it's out of the ordinary as far as headphone amplifiers go.  I actually finished the prototype the other day, been listening to it the past three days, it worked just how I had it drawn up.  So it's tube rectified via GZ34 / 5R4 / 5V4, uses a pair of 6SL7 inputs and a pair of audio pentode outputs.  I've mostly been listening with a pair of EL34 XF2, but I've tried 6L6 and 6V6.
> 
> I've also rolled a few different rectifiers in, here is a pic of the GZ34, glad I kept one of these around.
> 
> ...


This sort of amp is like an old VW flat four: intuitive engineering. It’s quite clear and obvious how everything works, and consequently easy to debug…


----------



## L0rdGwyn

CJG888 said:


> This sort of amp is like an old VW flat four: intuitive engineering. It’s quite clear and obvious how everything works, and consequently easy to debug…



That's true, these types of designs are quite robust too.  What I've tried to do with this circuit is make something that is free of the supply chain woes of semiconductor ICs, uses tubes that are available in new production, is relatively easy to build, but achieves a certain quality of sound that I am happy with.  I think I've accomplished that, but we'll see if my confidantes agree when one is built, it's gotten hard for me to place my circuits in the grander tube amp hierarchy as I only compare to my own designs.  The distortion as I've measured it is inaudible at normal listening volumes, around 0.007% using a 300ohm dummy load on the high Z tap, so it marries a certain lushness of sound that I associate with "old school" tube designs with impressive technicalities (soundstage, imaging, clarity, etc.).


----------



## Monsterzero

L0rdGwyn said:


> The distortion as I've measured it is inaudible at normal listening volumes, around 0.007% using a 300ohm dummy load on the high Z tap,


 With that low of a distortion are the ear pleasing 2nd order harmonics pretty much removed from the equation?


----------



## L0rdGwyn

Monsterzero said:


> With that low of a distortion are the ear pleasing 2nd order harmonics pretty much removed from the equation?



I don't really buy into the idea that there is "good" distortion and "bad" distortion these days, only more or less harmful distortion.  I think minimizing distortion is still the goal, if there is residual distortion left over, 2nd harmonic is preferable over higher order and/or odd harmonics.  The truth is lowering distortion increases the soundstage, clarity, separation, etc.  For instance, those who have heard both a CCS load and a resistive load in the same circuit almost unanimously prefer the CCS load because the distortion is lower, including 2nd harmonic.  Single-ended tube circuits produce 2nd order harmonic distortion typically, but it can be reduced to the point of inaudibility depending on the design.  So lower distortion is almost always better, but if there is anything audible, 2nd harmonic is preferred as it has the least harmful psychoacoustic effects.  That's my current feeling, maybe it will change, it can be hard to put your finger on exactly what makes an amplifier sound good to you or to another person, but at the end of the day that's all that matters, that its fun to listen to.


----------



## Zachik

L0rdGwyn said:


> I don't really buy into the idea that there is "good" distortion and "bad" distortion these days, only more or less harmful distortion.  I think minimizing distortion is still the goal, if there is residual distortion left over, 2nd harmonic is preferable over higher order and/or odd harmonics.  The truth is lowering distortion increases the soundstage, clarity, separation, etc.  For instance, those who have heard both a CCS load and a resistive load in the same circuit almost unanimously prefer the CCS load because the distortion is lower, including 2nd harmonic.  Single-ended tube circuits produce 2nd order harmonic distortion typically, but it can be reduced to the point of inaudibility depending on the design.  So lower distortion is almost always better, but if there is anything audible, 2nd harmonic is preferred as it has the least harmful psychoacoustic effects.  That's my current feeling, maybe it will change, it can be hard to put your finger on exactly what makes an amplifier sound good to you or to another person, but at the end of the day that's all that matters, that its fun to listen to.


I think it would be an interesting idea to add a knob to control (2nd harmonic) distortion. Give the amp user the choice of playing with more / less distortion and find their sweet spot. Similar idea to adding tone control...  (assuming that is design-wise feasible)


----------



## L0rdGwyn (Jun 26, 2022)

Zachik said:


> I think it would be an interesting idea to add a knob to control (2nd harmonic) distortion. Give the amp user the choice of playing with more / less distortion and find their sweet spot. Similar idea to adding tone control...  (assuming that is design-wise feasible)



Bob Katz basically did that in this article, created a circuit to add varying amounts of H2 to his audio chain and did subjective impressions: https://www.stereophile.com/content/katzs-corner-episode-25-adventures-distortion

These are hard questions to answer, people are arguing about this stuff across every audio forum in existence. I think a piece of gear sounding good or bad goes beyond just distortion, it isn't a reliable predictor of good sound IME, my approach has been to find what I like through experimentation, then apply those principles and if I can reduce the distortion along the way, that's a plus and usually an improvement.

I remember at one point when I was working on my 801A circuit, I was playing with high gain pentode input stages.  I was testing a resistively loaded pentode vs. a CCS loaded pentode.  The resistively loaded pentode had very, very high H2 (pentodes are not all that linear, so without a lot of negative feedback, distortion can be very high).  Switching to the CCS loaded pentode circuit, I was able to massively increase the open loop gain of the amplifier and apply a huge amount of negative feedback, drastically lowering distortion.  The subjective result?  The higher distortion, lower negative feedback version sounded much better.  I couldn't live with distortion that high however, so I changed approaches, but just one data point showing that distortion doesn't tell the whole story when it comes to the subjective end result.  So I apply a mix of subjective audio voodoo with a splash of objective data and try to find a balance that is pleasing to the ear but also doesn't measure horribly.


----------



## Zachik

L0rdGwyn said:


> Bob Katz basically did that in this article, created a circuit to add varying amounts of H2 to his audio chain and did subjective impressions: https://www.stereophile.com/content/katzs-corner-episode-25-adventures-distortion


Very cool - I will read later! Thanks for the link   



L0rdGwyn said:


> These are hard questions to answer, people are arguing about this stuff across every audio forum in existence.


I agree, there will never be a consensus. By giving the end-user the means to play with it, each person can find their favorable or most pleasing sound. 



L0rdGwyn said:


> I remember at one point when I was working on my 801A circuit, I was playing with high gain pentode input stages. I was testing a resistively loaded pentode vs. a CCS loaded pentode. The resistively loaded pentode had very, very high H2 (pentodes are not all that linear, so without a lot of negative feedback, distortion can be very high). Switching to the CCS loaded pentode circuit, I was able to massively increase the open loop gain of the amplifier and apply a huge amount of negative feedback, drastically lowering distortion. The subjective result? The higher distortion, lower negative feedback version sounded much better. I couldn't live with distortion that high however, so I changed approaches, but just one data point showing that distortion doesn't tell the whole story when it comes to the subjective end result.


In this case, you had 2 extreme distortion cases. IF *in theory* you could move between those 2 extremes on a scale - there is a chance you'd prefer a spot somewhere in-between. I know it is all theoretical because you switched between 2 different circuits that work differently to load the tube (R vs. CCS).



L0rdGwyn said:


> So I apply a mix of subjective audio voodoo with a splash of objective data and try to find a balance that is pleasing to the ear but also doesn't measure horribly.


Without enticing a debate here, I would only say that amps that their designers declared "test better than anyone else" - usually had me hate them almost immediately. Not due to the claims, but due to the sound that I found too sterile and cold. But that is MY taste


----------



## L0rdGwyn

Zachik said:


> Without enticing a debate here, I would only say that amps that their designers declared "test better than anyone else" - usually had me hate them almost immediately. Not due to the claims, but due to the sound that I found too sterile and cold. But that is MY taste



Yeah, that 841 DHT hybrid amplifier I made (R.I.P.) measured very well, inaudible levels of distortion in that amplifier.  Despite that, I did not like the sound, I found it a bit sterile and thin.  Eventually I found ways to improve it, but it became more of a hassle than I thought it was worth, so away it went.  Lots of "stuff" in the signal path of that design, which I think may have played a part.  Sometimes the KISS approach really is better.  On the contrary, this new pentode design also has arguably inaudible levels of distortion, but the sound is very full and dynamic, it gives excellent weight and body to the music without sounding sterile.  It pairs really well with the VC.  I actually prefer the Atrium on my OTL, but I might prefer the VC on the pentode amplifier.  I gotta get one built, the layout is giving me a headache though


----------



## jgwtriode

Just scored these as backups.  Monster shared his 6J5 guide with me an was kind of enthralled with the National Unions based on description compared to GEC L63's with
a seductive sweetness.  Eewwww!   so had to check and found these NOS from same guy in India who sold me my GEC L63's.   Very nice and for less than a quarter of what I
paid for the L63's.


----------



## Monsterzero

jgwtriode said:


> Just scored these as backups.  Monster shared his 6J5 guide with me an was kind of enthralled with the National Unions based on description compared to GEC L63's with
> a seductive sweetness.  Eewwww!   so had to check and found these NOS from same guy in India who sold me my GEC L63's.   Very nice and for less than a quarter of what I
> paid for the L63's.


 I cannot take credit for that 6J5 reference page. I believe it was @chrisdrop that put it together


----------



## jgwtriode

Well thanks anyway!.  Pretty sure those are the real deal from the photo in the guide.   My understanding is this guy in India is pretty reliable.

jgwtriode


----------



## Monsterzero

jgwtriode said:


> Well thanks anyway!.  Pretty sure those are the real deal from the photo in the guide.   My understanding is this guy in India is pretty reliable.
> 
> jgwtriode


 Rebranding isnt a forgery, so i'm not trying to disparage the seller. It was quite common for tubes to be built by one company but labled somerthing else entirely.
I have a pair of Nat U labled as Westinghouse, and another labled Nat U.

Very different from scammers slapping a GEC sticker on Russian tubes.


----------



## jgwtriode

Good to know when I am checking online.  Appreciate it.

jgwtriode


----------



## mordy

jgwtriode said:


> Good to know when I am checking online.  Appreciate it.
> 
> jgwtriode





jgwtriode said:


> Good to know when I am checking online.  Appreciate it.
> 
> jgwtriode





jgwtriode said:


> Just scored these as backups.  Monster shared his 6J5 guide with me an was kind of enthralled with the National Unions based on description compared to GEC L63's with
> a seductive sweetness.  Eewwww!   so had to check and found these NOS from same guy in India who sold me my GEC L63's.   Very nice and for less than a quarter of what I
> paid for the L63's.


Guess what? This week's daily drivers I am using is a "near" pair of National Union 6J5GT tubes that I really enjoy. One of them looks exactly like the tubes in the pictures but is labeled Super Silvertone which I think were made for the Sears dept store.
The other tube is labeled National Union but has a different internal construction. Both tubes have triple micas and and the getter flash on top and were probably made in the early 40's. 
Come to think of it, almost all my 6J5GT tubes are cleartops; the ones with the top getter flash are much less common.


----------



## jgwtriode

Really looking forward to these based on the comments in the reference guide.  If they are as good as that...then i will be ordering a backup pair as well.  Price is too good not to.

jgwtriode


----------



## mordy

The same tube may sound different in different amps, and the pairing with other tubes is extremely important in bringing out the best sound. That said, certain tubes aquit themselves very well in many different settings.
So far I have three favorite 6J5GT tubes:
1950-53 tall Sylvania tubes with metal bases. These are easy to find and there are many rebranded ones. The sound is crisp and clear overall but could be a little bright.
Tung Sol tubes are harder to find. They have very good bass punch and are harder hitting than the Sylvanias.
And now the National Union tubes, which have a softer presentation and sound in between the Sylvanias and Tung Sols.
The other NU 6J5GT tube is a sturdier metal base ladder plate military version (also says VT-94 on the tube), but the round plate black base version pictured above sounds a tad better to me.
I also enjoy Raytheon 6J5GT tubes but the above three sound a little better.
Have fun!
YMMV


----------



## Xcalibur255

Silvertones can be a number of different manufacturers, but over the years I've observed that they tend to be National Union made the most often.  So if one is hunting for an NU made tube keeping an eye out for the Silvertone branded tubes is a good thing to do.


----------



## Xcalibur255

I saw a 6J5G tube by National Union that has the same internal construction details (mica, etc.) as a National Union 45.  Sadly it was matched with a tube with a completely different kind of internals and was being sold as a pair that was matched for emissions so I passed on it, but now I'm really hoping I stumble across a properly matched pair of them because I really want to hear what they sound like.


----------



## Xcalibur255

Also, if any of you guys have been looking for a pair of Sylvania 6J5G the eBay seller named igolioto has a Zenith branded pair that looks darn near perfect right now.  My opinion of this tube improved quite a lot after hearing it on my 1101 Audio amp.  I still am not a huge fan of the extra upper midrange energy it has, but the bass slams harder from this tube than any other 6J5 I have heard and it has gobs of resolution and space between notes.


----------



## mordy

Xcalibur255 said:


> Also, if any of you guys have been looking for a pair of Sylvania 6J5G the eBay seller named igolioto has a Zenith branded pair that looks darn near perfect right now.  My opinion of this tube improved quite a lot after hearing it on my 1101 Audio amp.  I still am not a huge fan of the extra upper midrange energy it has, but the bass slams harder from this tube than any other 6J5 I have heard and it has gobs of resolution and space between notes.


Decided to look into my box of 6J5G tubes. I have several Zenith tubes, but each one is different. Then I happened to compare one Zenith tube to a NU tube - discovered that they look almost exactly the same. The only real difference is that the NU tube has a little clip above the top mica and the Zenith does not have it. Is it possible that Zenith tubes were made by National Union? (Usually I thought that Zenith sourced their tubes from Sylvania).

Then something funny happened - was going to try the pair of 6J5G NU tubes instead of the NU 6J5GT I am currently using (India version as of above somewhere).
But, since I am listening to music while I am typing this, I realized the sound was so nice that I could not get myself to switch out the tubes...
I mean, are you allowed to be happy, content, and satisfied in this hobby??
Really*? *
I must be getting old...


----------



## bcowen

mordy said:


> Decided to look into my box of 6J5G tubes. I have several Zenith tubes, but each one is different. Then I happened to compare one Zenith tube to a NU tube - discovered that they look almost exactly the same. The only real difference is that the NU tube has a little clip above the top mica and the Zenith does not have it. Is it possible that Zenith tubes were made by National Union? (Usually I thought that Zenith sourced their tubes from Sylvania).
> 
> Then something funny happened - was going to try the pair of 6J5G NU tubes instead of the NU 6J5GT I am currently using (India version as of above somewhere).
> But, since I am listening to music while I am typing this, I realized the sound was so nice that I could not get myself to switch out the tubes...
> ...


Don't worry, it will pass.


----------



## Xcalibur255

mordy said:


> Decided to look into my box of 6J5G tubes. I have several Zenith tubes, but each one is different. Then I happened to compare one Zenith tube to a NU tube - discovered that they look almost exactly the same. The only real difference is that the NU tube has a little clip above the top mica and the Zenith does not have it. Is it possible that Zenith tubes were made by National Union? (Usually I thought that Zenith sourced their tubes from Sylvania).
> 
> Then something funny happened - was going to try the pair of 6J5G NU tubes instead of the NU 6J5GT I am currently using (India version as of above somewhere).
> But, since I am listening to music while I am typing this, I realized the sound was so nice that I could not get myself to switch out the tubes...
> ...


Seriously, don't pull those tubes out if you're really digging them.  Sooner or later the mood to experiment will come around again, no point in breaking the magic before then.

Most, but not all, of the Zenith 6J5G tubes I have seen since I began keeping tabs on this type of tube have been made by Sylvania.  I don't think Sylvania exclusively made them for Zenith, but they do seem to be the most common.  My own pair of Sylvania 6J5G are Zenith branded.  The brand that really seems to be a crapshoot is Philco, I've seen at least 5 different plate styles on the Philco branded tubes.


----------



## mordy

Xcalibur255 said:


> Seriously, don't pull those tubes out if you're really digging them.  Sooner or later the mood to experiment will come around again, no point in breaking the magic before then.
> 
> Most, but not all, of the Zenith 6J5G tubes I have seen since I began keeping tabs on this type of tube have been made by Sylvania.  I don't think Sylvania exclusively made them for Zenith, but they do seem to be the most common.  My own pair of Sylvania 6J5G are Zenith branded.  The brand that really seems to be a crapshoot is Philco, I've seen at least 5 different plate styles on the Philco branded tubes.


Here are pictures of the two tubes. The first is a National Union with a date code AU - maybe from 1937 (U = one quarter of the year):



Top mica view:



Next is a Zenith with the same BRP and metal bands. Date code is N with a line under it and vertical numbers 21. Using my fingers and counting the letters from A (skipping I) M =12. Therefore N should be 1 and maybe January. 2? Maybe 1942. aNy suggestions are welcome.



The metal bands  are a different color, and the clip is absent above the top mica:



So the question is: Are both tubes made by National Union? Or one or both by Sylvania? 

_*no point in breaking the magic: *_I have noticed in the past that when I change out tubes and put the old set in again that I really liked, it takes time for my brain to adjust. And sometimes the magic does not return...Well, at least not right away...


----------



## Xcalibur255 (Jun 30, 2022)

I probably wasn't being clear about my context when I was talking about the Sylvania stuff.  Both of the tubes in your photos are 100% National Union tubes for sure.  I was just pointing out that most of the time when you see a Zenith branded 6J5G it is going to be Sylvania made, but what you have here is certainly an NU tube.  Basically just saying that what you have here is uncommon.

The oval plate and vertical mica tabs are quite unique and make the NU tubes pretty easy to ID.  The metal clip is a heat spreader and the tubes that have them would in theory have slightly longer service life.  Features like this tend to be present at the beginning of a tube's design life cycle and then they disappear over time as a cost cutting measure to make them cheaper to make.  They tend to be more common on the milspec tubes too.

This is actually a 6J5 I have not heard yet and I'd really like to.  What do you think of their sound?


----------



## mordy

Xcalibur255 said:


> I probably wasn't being clear about my context when I was talking about the Sylvania stuff.  Both of the tubes in your photos are 100% National Union tubes for sure.  I was just pointing out that most of the time when you see a Zenith branded 6J5G it is going to be Sylvania made, but what you have here is certainly an NU tube.  Basically just saying that what you have here is uncommon.
> 
> The oval plate and vertical mica tabs are quite unique and make the NU tubes pretty easy to ID.  The metal clip is a heat spreader and the tubes that have them would in theory have slightly longer service life.  Features like this tend to be present at the beginning of a tube's design life cycle and then they disappear over time as a cost cutting measure to make them cheaper to make.  They tend to be more common on the milspec tubes too.
> 
> This is actually a 6J5 I have not heard yet and I'd really like to.  What do you think of their sound?


Your comment on cost cutting got me thinking about a Wizard 6J5GT tube that only has one band on the top mica although there is room and cut-outs for two. At one point I had asked who could have manufactured this tube, but no answer was found.
There was a large chain store called Western Auto that also sold tubes under the Wizard name. They started selling radios in 1933 and at it's height had over 1800 outlets.
Now I found a 6J5GT 1940 Radiotron (RCA) tube with the same cost cutting (?) feature. Don't know what the function is of the bands, but possibly they are supports for the mica discs; two of the bands would seem to allow for a sturdier and maybe less microphonic construction. Most of the RCAs I have have two bands.




The bottom tube is a 1942(?) Wizard and the top one is the Radiotron.

Getting closer to try the NU 6J5G tubes - don't want to disturb the magic but will try them in another amp.


----------



## jgwtriode (Jul 1, 2022)

Over the last week.  I have noticed a curiously amazing something going on in my system and there is some renewed hope of my DAC showing up soon!  Ric was discussing with some circuit changes and ideas to optimize the DAC to the Airmid and squeeze even a bit more out of it than he previously thought possibly.  Here's to hoping.

Anyway I changed out the 3.5mm plug to gold plated beryllium copper and ran the shortest possible pieces of silver gold wire from my Eichman RCA's. Pretty sweet RCA to 3.5 adaptor for the onboard soundcard.  I so miss my JCAT USB XE without having an External DAC to run.  I also am having a final prototype of Mad SCi Audio's new  Ultra Black Magic USB cable sent to me by Bob.  Supposed to be a huge improvement over the older Black Magic which was a pretty amazing cable, up until I started playing with Wywires.

The gentleman who bought those Macassar Ebony Atriums from Zach talked about the way the Airmid does bass resonance and I have really began to notice that.  This allows the Airmid to create nearly real low frequency instrument size and wieght and uncanny texture.   But I have also noticed it does this throughout the entire frequency range as my system has improved and settled.  This really comes out late at night and I can tell you. truly. I have rarely heard this in any system I have heard over some 40 years of fiddling and tinkering with Audio.  Its like my system becomes a living breathing entity that can become whatever the recording requires.   It really does not sound much like I am listening to headphones anymore.

Happy listening,

jgwtriode


----------



## mordy

Xcalibur255 said:


> I probably wasn't being clear about my context when I was talking about the Sylvania stuff.  Both of the tubes in your photos are 100% National Union tubes for sure.  I was just pointing out that most of the time when you see a Zenith branded 6J5G it is going to be Sylvania made, but what you have here is certainly an NU tube.  Basically just saying that what you have here is uncommon.
> 
> The oval plate and vertical mica tabs are quite unique and make the NU tubes pretty easy to ID.  The metal clip is a heat spreader and the tubes that have them would in theory have slightly longer service life.  Features like this tend to be present at the beginning of a tube's design life cycle and then they disappear over time as a cost cutting measure to make them cheaper to make.  They tend to be more common on the milspec tubes too.
> 
> This is actually a 6J5 I have not heard yet and I'd really like to.  What do you think of their sound?


Today I took the plunge and installed the pair of octogenarian 6J5G National Union tubes. First I let them warm up a couple of minutes; who knows how irritated they will be after being woken up after a 80 year slumber?
Well, after one moderate pop - silence. Let them warm up a little more and then turned up the volume full tilt without music. Bravo! Totally silent - not bad at all; most tubes of this type make a little noise with full volume (which is way too loud for listening). 
First impression of listening is very positive. Very good low bass and an inner glow to the midrange, but need more time to have a more definitive opinion of how they sound. But it looks like a top tier tube.


----------



## gibosi

These look to be identical to NU Type 76, including the mica spacers on top. And they are among my favorite drivers.


----------



## mordy

mordy said:


> Today I took the plunge and installed the pair of octogenarian 6J5G National Union tubes. First I let them warm up a couple of minutes; who knows how irritated they will be after being woken up after a 80 year slumber?
> Well, after one moderate pop - silence. Let them warm up a little more and then turned up the volume full tilt without music. Bravo! Totally silent - not bad at all; most tubes of this type make a little noise with full volume (which is way too loud for listening).
> First impression of listening is very positive. Very good low bass and an inner glow to the midrange, but need more time to have a more definitive opinion of how they sound. But it looks like a top tier tube.


Really need to clean up the base of the NU tube - it looks like someone put on masking tape once. Problem is that the tape covers most of the writing on the tube (not seen in the picture). Is there a risk of obliterating the print if I use an alcohol swab?


----------



## Xcalibur255

gibosi said:


> These look to be identical to NU Type 76, including the mica spacers on top. And they are among my favorite drivers.


I've noticed that the really old 6J5G tubes from the late 30's during those first few years of production often tend to have the same style of plate as the type 76 preceeding it.  I have a pair of Raytheon's that I'm secretly convinced literally are 76 that were just re-branded to 6J5G because they have noticeably less gain than all of my other 6J5 tubes.  I love the way they sound too so maybe I'm a 76 tube guy and don't know it yet?


----------



## Xcalibur255

mordy said:


> Your comment on cost cutting got me thinking about a Wizard 6J5GT tube that only has one band on the top mica although there is room and cut-outs for two. At one point I had asked who could have manufactured this tube, but no answer was found.
> There was a large chain store called Western Auto that also sold tubes under the Wizard name. They started selling radios in 1933 and at it's height had over 1800 outlets.
> Now I found a 6J5GT 1940 Radiotron (RCA) tube with the same cost cutting (?) feature. Don't know what the function is of the bands, but possibly they are supports for the mica discs; two of the bands would seem to allow for a sturdier and maybe less microphonic construction. Most of the RCAs I have have two bands.
> 
> ...


The bottom tube looks the same as my pair of Ken-Rad labeled tubes, and I haven't been able to positively ID them.  They don't really sound like Ken-Rads to me, I'm doubtful that Ken-Rad actually made them.  The top tube isn't one I have had personal experience with but I've seen them from time to time in listings.  If you'd like my gut feeling I have a hunch they are RCA/GE, but that's just an intuition guess on my part.


----------



## mordy

Xcalibur255 said:


> The bottom tube looks the same as my pair of Ken-Rad labeled tubes, and I haven't been able to positively ID them.  They don't really sound like Ken-Rads to me, I'm doubtful that Ken-Rad actually made them.  The top tube isn't one I have had personal experience with but I've seen them from time to time in listings.  If you'd like my gut feeling I have a hunch they are RCA/GE, but that's just an intuition guess on my part.





The top tube is an RCA for sure - it has the RCA logo on it and the Radiotron name as well.


----------



## bcowen

mordy said:


> Really need to clean up the base of the NU tube - it looks like someone put on masking tape once. Problem is that the tape covers most of the writing on the tube (not seen in the picture). Is there a risk of obliterating the print if I use an alcohol swab?


Alcohol?  Bigger than big risk. Might depend on what ink they used on the base and I can't speak to the NU, but I wiped all the print off of a Sylvania without trying real hard.  I tried Goo-Gone on an RCA...it took out the print too.  Best I've found is Fantastic cleaner.  Liberally apply it repeatedly to the tape and let it soak in for 5 minutes or so, then you can kind of roll the tape remnants off with your fingers.  I did this on a Tung Sol 5998 that had a paper label stuck hard to it and got it all off without hurting the print at all. Took some time, but worked.


----------



## mordy

bcowen said:


> Alcohol?  Bigger than big risk. Might depend on what ink they used on the base and I can't speak to the NU, but I wiped all the print off of a Sylvania without trying real hard.  I tried Goo-Gone on an RCA...it took out the print too.  Best I've found is Fantastic cleaner.  Liberally apply it repeatedly to the tape and let it soak in for 5 minutes or so, then you can kind of roll the tape remnants off with your fingers.  I did this on a Tung Sol 5998 that had a paper label stuck hard to it and got it all off without hurting the print at all. Took some time, but worked.


Thanks - will try it


----------



## jgwtriode (Jul 5, 2022)

Wow the National Union 6J5GT's are really good with just a few hours of cursory break in.  Definitely comparable with GEC L63's.  As the guide suggested they are seductively  sweeter which is  quite nice.  After some significant burn in i will do some comparisons.    One tube is about 1/4 inch shorter.  But their specs are identical as is their construction otherwise.  Very odd????

Happy listening,

jgwtriode


----------



## mordy

jgwtriode said:


> Wow the National Union 6J5GT's are really good with just a few hours of cursory break in.  Definitely comparable with GEC L63's.  As the guide suggested they are pleasingly sweeter which is quite seductive.  After some significant burn in i will do some comparisons.    One tube is about 1/4 inch shorter.  But their specs are identical as is their construction otherwise.  Very odd????
> 
> Happy listening,
> 
> jgwtriode


Not odd at all - I have four Brimar labeled Ken-Rad 6J5GT tubes from the 40s and each one is a different size even though the internals are the same.


----------



## jgwtriode

Wild....good to know!

jgwtriode


----------



## jgwtriode (Jul 6, 2022)

They are opening up and getting more musical.  The mids through highs are gorgeous, liquid, sweet, absolutely organic.  Female voices are ethereal, sweet, seductive and stringed instrument have this wonderful bloom and halcyon sort of decay that just melts you.  Takes that ocasional brightness and subtle upper mid to treble hardness that
occassionaly shows up on some songs with the VC away!   Effortless listening.  Bass need to tighten up a bit more to compare with  the GEC in that region.  But if it does and the stage continues to open this might be my new reference roll for the Airmid. $ 48 for the pair.  

PS  Mark Knopfler is better than I have ever heard tonally and harmonically.  Can hear more of his guitar sound and voice then ever.  Horns and brass are so perfect just
the right biting sweet  burnished brass glow.  Oh his banjo.  This is absolutely what triodes are all about....OMGosh!

Happy listening.

jgwtriode


----------



## mordy

jgwtriode said:


> They are opening up and getting more musical.  The mids through highs are gorgeous, liquid, sweet, absolutely organic.  Female voices are ethereal, sweet, seductive and stringed instrument have this wonderful bloom and halcyon sort of decay that just melts you.  Takes that ocasional brightness and subtle upper mid to treble hardness that
> occassionaly shows up on some songs with the VC.   Effortless listening.  Bass need to tighten up a bit more to compare with  the GEC in that region.  But if it does and the stage continues to open this might be my new reference roll for the Airmid. $ 48 for the pair.
> 
> Happy listening.
> ...


I cannot describe the sound of the NU 6J5GT tubes the way you do, but yes, I agree! - It just feels right. My amp and power tubes are different but the impression is the same.


----------



## jgwtriode (Jul 6, 2022)

Oh my the stage is growing hour by hour as I listen and there is more ambiance and air!  Can't stop listening, so I won't! Ambiance, space and decay are magic on this tube.  These things become far more real than I can ever remember hearing on a lot of these songs I am listening to.  It's like have a softer wood without losing any speed or detail and throwing in even more tonal and harmonic integrity.   I think this tube turned my VC's into Atrium's. Staging is bigger, more open, more spacious and everything is more musical with more body and overtones.   Just needs a bit more snap and kick, which it's not quite up to the GEC L63 in that regard yet.  Bass not quite as tight yet and the tube sounds a hint soft but it's improving.   Why don't more people talk about this tube.

jgwtriode


----------



## mordy

jgwtriode said:


> Oh my the stage is growing hour by hour as I listen and there is more ambiance and air!  Can't stop listening, so I won't
> 
> jgwtriode


I have the same problem...But watch out, tomorrow is a new day and you have to get up on time!
Actually, I dug up some metal 6J5 tubes and found a pair of 1944 Tung Sol labeled tubes that were not made by RCA. Can't stop listening but for a different reason than the NU tubes. While these tubes are very good, they are not as musical as the NU tubes, but the instrument separation is spectacular. I am listening to recordings where it normally is difficult to hear each individual player clearly, but with these tubes each one stands out very clear and distinct.
Good night!


----------



## jgwtriode

mordy said:


> I have the same problem...But watch out, tomorrow is a new day and you have to get up on time!
> Actually, I dug up some metal 6J5 tubes and found a pair of 1944 Tung Sol labeled tubes that were not made by RCA. Can't stop listening but for a different reason than the NU tubes. While these tubes are very good, they are not as musical as the NU tubes, but the instrument separation is spectacular. I am listening to recordings where it normally is difficult to hear each individual player clearly, but with these tubes each one stands out very clear and distinct.
> Good night!


wow I may need to check out a pair of those.   That sounds quite worthwhile.   Thanks for the info!

jgwtriode


----------



## jgwtriode

jgwtriode said:


> wow I may need to check out a pair of those.   That sounds quite worthwhile.   Thanks for the info!
> 
> jgwtriode


Uncanny, these National Unions have a lower noise floor and are noticeably quieter than the GEC's.  Wild!
And they are getting better hour by hour.  Amazing!

Happy listening,

jgwtriode


----------



## mordy

Asked on another forum but did not get any answers - maybe someone here can help with an explanation?
I put in a pair of Brimar labeled Ken-Rad 1940's 6J5GT tubes and one of them (lower tube in picture) right away developed a foggy shadow over the heater:




Is this the beginning of anode boil-off? Looks like this (black spots over the heaters):


----------



## L0rdGwyn

I have a few days off this week, thought I'd try and make progress on some DIY things.  I'm lacking the brain power to do the next steps for my pentode amplifier today, so I'd thought I'd get started on the final Airmid for @zach915m .

Here it is after chassis prep and mounting of the major parts.  Gator chic.


----------



## L0rdGwyn

Here are some other random things I've acquired recently.

Custom walnut plinth for my turntable.  Just waiting for my new tonearm at this point, then I can rebuild it.



A pair of Sowter I/V transformers for my PCM63 DAC build.  I've sort of changed mindsets for this design, I was originally looking to do a simple passive I/V transformer coupled output.  I'll likely still give that a try, but it has compromises.  What I'm more keen on doing now is another tube output stage using E182CC with transformer coupled outputs.  TBD.



A very nice quad of NOS graphite plate 801A.  I paid around $105 dollars for this set, plus international shipping.  Absolutely ridiculous deal.


----------



## Xcalibur255

I feel like there must be some secret club where people are let in on the secret of where you find the *really* good tube scores, and I've never been able to get my jacket.


----------



## jgwtriode

Ni


L0rdGwyn said:


> I have a few days off this week, thought I'd try and make progress on some DIY things.  I'm lacking the brain power to do the next steps for my pentode amplifier today, so I'd thought I'd get started on the final Airmid for @zach915m .
> 
> Here it is after chassis prep and mounting of the major parts.  Gator chic.
> 
> Love those ha





Xcalibur255 said:


> I feel like there must be some secret club where people are let in on the secret of where you find the *really* good tube scores, and I've never been able to get my jacket.


I concur.  Feel okay about what I have...but not particularly great deals!  I would call
 them fair prices at best!

jgwtriode


----------



## whirlwind

L0rdGwyn said:


> I have a few days off this week, thought I'd try and make progress on some DIY things.  I'm lacking the brain power to do the next steps for my pentode amplifier today, so I'd thought I'd get started on the final Airmid for @zach915m .
> 
> Here it is after chassis prep and mounting of the major parts.  Gator chic.


Wow, my favorite looking chassis yet....very nice!


----------



## Wes S (Jul 12, 2022)

whirlwind said:


> Wow, my favorite looking chassis yet....very nice!


My thoughts exactly, and very fitting that it's going to Zach.  That chassis will look incredible with some Stabilized ZMF's next to it.


----------



## whirlwind

Wes S said:


> My thoughts exactly, and very fitting that it's going to Zach.  That chassis will look incredible with some Stabilized ZMF's next to it.


+1


----------



## jgwtriode

Indeed that is an amazing looking paint job.  Is that some type of hammered finish process?  Looks quite stunning!

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> Indeed that is an amazing looking paint job.  Is that some type of hammered finish process?  Looks quite stunning!
> 
> jgwtriode



It's this Gator Black powder from Columbia Coatings: https://www.columbiacoatings.com/gator-black.aspx

Turned out well I'd say!


----------



## Xcalibur255

Almost like it's wrapped in fine Corinthian leather.


----------



## jgwtriode

Very cool and unique!


----------



## jgwtriode

Xcalibur255 said:


> Almost like it's wrapped in fine Corinthian leather.


Indeed!


----------



## jgwtriode (Jul 13, 2022)

The NU's have burned and settled and I have tweaked my dampers just a bit.  Any excess warmth and veiling is gone.  The  tone is as perfect as I have heard on everything.  Gorgeously just a bit sweet with a hint of musically balanced warmth without diminishing neutrality.  Bass kicks ass but is balanced, deep,  harmonically and texturally rich in a way I have not heard even out of the GEC's.  There is a more significant sense of weight and volume to larger instruments and the resonances inherently part of their signature. The effect is completely seductive.  I am hearing details in these areas I have never heard this precisely.  Will be another late night.   Having to much fun re-listening to my favorites.  I have fiddled a bit with a few other things to push this a hint more and have a couple ideas to make some dampers using my favorite Mad Sci carbon graphene disc and doughnut material and finding a way to safely secure them to the Tungsols.   I think this will add a bit more.   Staging and focus are mesmerizing. As I suspected when I first heard them; the boundaries are no longer fuzzy or diffused, solid anchored and resonant from wall to wall.  Echo's and delays are noticeably more real.  No I still don't have my DAC back but we are getting closer, a beast to get that last bit of tuning just right according to Ric.  The price when you take a good design and start tweaking it.

Amazing,


Just a bit more!  Upper frequencies are smoother but more open and airy and the sweetness extends from the upper bass all the way up to the top and that hint of warmth.  The tonal and harmonic integration adds that ethereal magical sense of bloom to voices and accompanying strings, percussion and horns that just lets you float away.  The GEC is very close in this regard but it does not have quite this upper frequency ease.  It is just a hint thinner and slightly brighter.  There may be even a bit more detail with the NU.  But again realize this might also be the lower noise floor.  Not exactly sure.  Just grateful and enjoying what this allows.

Happy listening,

jgwtriode


----------



## Xcalibur255

jgwtriode said:


> Indeed!


Was hoping somebody would do this.  I was not disappointed.


----------



## L0rdGwyn

Some more progress.  Threw the knob on there for the pic.



Next pictures will be the finished amp, should have it done some time next week, maybe the following if something comes up.

My tonearm shipped, so I'll have my turntable to work on shortly, but I'll most likely prioritize getting the chassis and PCBs ordered for the pentode headamp, pretty psyched for that build.


----------



## jgwtriode

Xcalibur255 said:


> Was hoping somebody would do this.  I was not disappointed.


Your most welcome


----------



## jgwtriode (Jul 15, 2022)

Happy listening,

jgwtriode


----------



## L0rdGwyn

Here is the new arm I'll be putting on my Thorens.  I ended up ordering a new custom armboard for it, same Corian material as the SME board I had made, but with cuts for the TA-1.  I got my hands on an SME adapter, but the finish isn't going to work for me.



Armboard will arrive next week.  At that point I'll have just about everything to do my turntable overhaul.  Last thing to figure out is what kind of isolation I want to use, I'm considering the IsoAcoustics Orea Bronze, I could then avoid having to cut holes into the plinth.  This is going to be a lot of work, might be a bit slow moving, I'll take some pictures along the way.

Doing some more work on the gator Airmid today, hopefully will finish it this weekend.


----------



## CJG888

I recently found out that your Thorens is basically an EMT 928  

You could have put an EMT „Banana“ and „Tondose“ on it…


----------



## CJG888

Now I know why you’re not chasing the Garrard!


----------



## L0rdGwyn

CJG888 said:


> I recently found out that your Thorens is basically an EMT 928
> 
> You could have put an EMT „Banana“ and „Tondose“ on it…



Apparently EMT was involved in the development of the TD 125, so they released their own professional version, which was the EMT 928.  I didn't know that at the time of buying, but I've been quite happy with the table.  The peak performance of my analog setup outshines my digital system.  Should be even better once I'm done with the Thorens.


----------



## CJG888

Funnily enough, TD125 prices here are rising!


----------



## mordy

CJG888 said:


> Funnily enough, TD125 prices here are rising!


I picked up a Thorens TD 115 MKII turntable with some other gear I bought  - is this considered a good model? (Haven't played my records in a very long time.)


----------



## CJG888

BTW, the mounting plate of your new tonearm looks very Ortofon-like!


----------



## CJG888

mordy said:


> I picked up a Thorens TD 115 MKII turntable with some other gear I bought  - is this considered a good model? (Haven't played my records in a very long time.)


I would say that it is better than a TD150, but not as good as a TD125. You will need to clean and re-lubricate the bearing and motor bearings, replace the belt and check the suspension, though.

Which cartridge are you using?


----------



## CJG888

Che bellezza!

(No, it’s not mine!).


----------



## L0rdGwyn

CJG888 said:


> Che bellezza!
> 
> (No, it’s not mine!).



It's a cool looking table.  Definitely the guts of a TD 125, the internal electronics are different, not sure in what way, hence the mega plinth.


----------



## jgwtriode

I think the National Union 6J5Gt's are now my favorite.  Got a set of Herbie's Tube Dampers and modded them to seat my Mad Sci tube toppers above them with a bit of an additional wire frame.   Noticeably better than my improvised variant, which was better than straight tube by itself.  The NU's lack for nothing compared to the GEC L63 with the Airmid and Tungsol 5998's.  They are slightly sweeter, just as dynamic, maybe a hint faster, and maybe even slightly better at overall sense of space and staging.  If any one is
interested in my GEC's PM me.  Going to move in another direction so time to let them go if anyone is interested. 

Happy Listening,

jgwtriode


----------



## Zachik

jgwtriode said:


> Got a set of Herbie's Tube Dampers and modded them to seat my Mad Sci tube toppers above them with a bit of an additional wire frame.


Photos or it did not happen!


----------



## jgwtriode

Indeed,  I will send some over after I do some more listening.


----------



## jgwtriode (Jul 23, 2022)

Okay a quick phone photo .  That is a Mad Scientist Audio Sample disc with one of their 12Ax7/6DJ8 style tob toppers sitting in top of it with white tack between.  May crazy glue it st alatter date.  Carbon graphene expoxy material that deals with RF and electrical fields.  I use variations of these on all my connectors and other interesting places.  They make incremental differences that are worthwhile depending on how obsessive you are!  Psychosomatic perhaps but I always find when i pull them off noise floor increases a bit,. along with PRAT and musicality. System also loses a bit of intelligibility and perhaps a bit of air and space.  Color me OCD!

Happy listening,

jgwtriode


----------



## bcowen

jgwtriode said:


> Okay a quick phone photo .  That is a Mad Scientist Audio Sample disc with one of their 12Ax7/6DJ8 style tob toppers sitting in top of it with white tack between.  May crazy glue it st alatter date.


Somehow this brings up the memory of "Danger, Will Robinson, Danger!"   🤣


----------



## jgwtriode (Jul 23, 2022)

Hahaha!  True enough!  Yeah my mods are often a bit odd  and not always the cleanest.  But its all about the sound no matter how silly it may appear.   When they dont make it and you couldn't afford it even if they did; well then the imagination takes over and  dangerous things start spinning in the brain to create "what if"!   

Happy listening and modding,

Jgwtriode

jgwtriode


----------



## jgwtriode (Jul 24, 2022)

A few more observations regarding listening to the NU's vs GEC's.  The L63's do have a hint more depth and a bit more lower mid heft and they are slightly drier in overall sound with a hint more focus and absolute location specificity.  Their is slightly more air with the NU's and that is wrapped around images and instruments and the space between but it is a hair more diffused.  They do throw a wider more ambient stage albeit a bit more forward with a bit more than slightly less depth. You will definetly notice they are  sweeter and a hint more liquid.  More even in the mids and slightly more upper frequency and presence.  I would say that male voices benefit just a bit from that lower mid subtle prominence of the GEC.  Just a bit more of pleasing weight and presence to male vocals.  But female vocals are more to my liking on NU's.  Low frequencies are very comparable in all respects.  Perhaps a hint more weight with GEC's and fullness.  But a bit more speed and impact with the 6J5GT.  A Hint more overal PRAT with the NU.   Very close however all things considered.  You can listen to one and not be at all disappointed at all listening to the other  My modded Herbie tube dampers improve them to an equal degree as the NU's.  50 bucks and time spent modding well worth it.  I like the GEC more than I might have indicated, but would still if forced to choose go with the
NU.

Happy listening,

jgwtriode.


----------



## mordy

jgwtriode said:


> A few more observations regarding listening to the NU's vs GEC's.  The L63's do have a hint more depth and a bit more lower mid heft and they are slightly drier in overall sound with a hint more focus and absolute location specificity.  Their is slightly more air with the NU's and that is wrapped around images and instruments and the space between but it is a hair more diffused.  They do throw a wider more ambient stage albeit a bit more forward with a bit more than slightly less depth. You will definetly notice they are  sweeter and a hint more liquid.  More even in the mids and slightly more upper frequency and presence.  I would say that male voices benefit just a bit from that lower mid subtle prominence of the GEC.  Just a bit more of pleasing weight and presence to male vocals.  But female vocals are more to my liking on NU's.  Low frequencies are very comparable in all respects.  Perhaps a hint more weight with GEC's and fullness.  But a bit more speed and impact with the 6J5GT.  A Hint more overal PRAT with the NU.   Very close however all things considered.  You can listen to one and not be at all disappointed at all listening to the other  My modded Herbie tube dampers improve them to an equal degree as the NU's.  50 bucks and time spent modding well worth it.  I like the GEC more than I might have indicated, but would still if forced to choose go with the
> NU.
> 
> Happy listening,
> ...


I have a sweet tooth - the NU is my cup of tea! The sweetness of the NU 6J5GT wins me over...


----------



## jgwtriode (Jul 24, 2022)

Absolutely agree with you!  That might be the biggest deal about them to me.


----------



## L0rdGwyn

Here is @zach915m 's Airmid, just finished.







Running a pair of L63 and 5998s with the Atrium.  Sounds good.



I'll get this shipped out later this week, then turn my focus entirely to the pentode amplifier.  I'll get plans finalized for that, place orders, then will work on my turntable while waiting for the chassis to arrive.


----------



## CJG888

Inspired by an MGB dashboard…


----------



## jgwtriode

L0rdGwyn said:


> Here is @zach915m 's Airmid, just finished.
> 
> 
> 
> ...


Love that finish and it looks very impressive in that dark gray!
I am sure Zach will love it.



Happy listening,

jgwtriode


----------



## mordy

CJG888 said:


> Inspired by an MGB dashboard…






Glove compartment?


----------



## Monsterzero

An evening with Peter Green on the 2nd anniversary of his passing.

ZMF Auteur (OG)

NU 6J5+ GEC 6AS7G
GL KT77+ USAF 596


----------



## CJG888

mordy said:


> Glove compartment?


Crackle black finish. That, of course, is the US version. The proper one (with the steering wheel on the correct side) looks like this:


----------



## L0rdGwyn

Shipping @zach915m 's amp shortly, in addition to the stock tubes, I'm going to be selling a little NOS tube starter pack to go with it.

Tung-Sol 7802, Bendix 6080WB slotted plates.



And a pair of Sylvania VT-94D / 6J5GT.



I've been slowly selling off my OTL tubes, think I have five 7802 left.  My best pairs are accounted for, but I may be selling the last five in the near future.


----------



## L0rdGwyn

Okay, the gator Airmid is shipped.  Never say never, but that is the last one I intend to build, my foray into 6AS7G OTLs is over for now.

I was feeling ambitious today, so I thought I'd get started on my turntable.

Here is a before picture.



Interior of the table, showing the work I did a while back.



Original plinth removed.



Armboard and tonearm removed.



Subchassis removed from the top plate.  Here you can see the springs the top plate floats upon.



Here the subchassis with the new plinth added, new fascia plate.  Cleaned up everything, including the motor, strobe lens, mirror, etc.



Top plate replaced, new armboard and tonearm added on, switches replaced, everything cleaned.



Now out to the garage to polish the platter again.  This time I am going to wax it so hopefully it won't tarnish so quickly!


----------



## L0rdGwyn (Jul 29, 2022)

Turns out I don't have auto wax in my garage, oh well, I just buffed the platter by hand.

Aesthetically it is done, but still more work to be done functionally.  Need to make a 5-pin DIN to 3-pin XLR balanced cable, buy my isolation feet, level the suspended chassis, and obviously set up the tonearm.  But here's how its gonna look basically.


----------



## bcowen

L0rdGwyn said:


> Turns out I don't have auto wax in my garage, oh well, I just buffed the platter by hand.
> 
> Aesthetically it is done, but still more work to be done functionally.  Need to make a 5-pin DIN to 3-pin XLR balanced cable, buy my isolation feet, level the suspended chassis, and obviously set up the tonearm.  But here's how its gonna look basically.


Sweeeeet!!!


----------



## bcowen

L0rdGwyn said:


> Shipping @zach915m 's amp shortly, in addition to the stock tubes, I'm going to be selling a little NOS* tube starter pack to go with it.*


LOL!  With those tubes, that's like saying the Biltmore House is a starter home.


----------



## CJG888

L0rdGwyn said:


> Turns out I don't have auto wax in my garage, oh well, I just buffed the platter by hand.
> 
> Aesthetically it is done, but still more work to be done functionally.  Need to make a 5-pin DIN to 3-pin XLR balanced cable, buy my isolation feet, level the suspended chassis, and obviously set up the tonearm.  But here's how its gonna look basically.


There’s an EMT in there, just waiting to get out!


----------



## CJG888

BTW, try the Pathé Wings Panzerholz record weight. It damps and flattens the LP without putting undue mass on the suspension and bearing.

I’ve tried various heavy weights, the Souther Clever Clamp and the Michell, and settled on this one:


----------



## L0rdGwyn

CJG888 said:


> BTW, try the Pathé Wings Panzerholz record weight. It damps and flattens the LP without putting undue mass on the suspension and bearing.
> 
> I’ve tried various heavy weights, the Souther Clever Clamp and the Michell, and settled on this one:



Thanks, if I decide to make a change, I'll check it out.  Your 301 looks great.  I suspect that 401 I posted a while back will some day come into my possession, if so I'll do a full restoration.


----------



## CJG888

Thanks!

I’m having a new top plate made by Acoustand, which will move the motor unit into the exact centre of the plinth. I will then mount a NOS Ortofon AS-212 at the back, primarily for mono use (AT MONO 3/LP), but also for my cocobolo-bodied Denon 103. An SPU #1S may also be in the future.

I have already acquired and restored the necessary Denon AU-320, which offers the correct termination for both cartridges!


----------



## L0rdGwyn

CJG888 said:


> Thanks!
> 
> I’m having a new top plate made by Acoustand, which will move the motor unit into the exact centre of the plinth. I will then mount a NOS Ortofon AS-212 at the back, primarily for mono use (AT MONO 3/LP), but also for my cocobolo-bodied Denon 103. An SPU #1S may also be in the future.
> 
> I have already acquired and restored the necessary Denon AU-320, which offers the correct termination for both cartridges!



That sounds fantastic.  I'd love to have a dedicated mono arm / cart some day.  Please post some pics when it's done.


----------



## L0rdGwyn (Jul 31, 2022)

I started planning to build my balanced DIN to XLR cable and...I just can't lol I hate building cables!

So I'm gonna buy one, this one, but with a straight DIN connector.  From Audio Art Cable.  Seems nice, somewhat expensive but not insane.



Now just waiting for parts to finish the turntable job.

In the mean time, I've shifted my attention toward the pentode headamp.  I have been putting off doing the PCB for a long time, I procrasintated by building the gator Airmid and starting the turntable lol.  It's a slog, but finally sat down to do it.  It's getting there, should have a solid draft done today, then some tuning and hopefully placing the order later this week.  This is the true work of the build though, once the PCB and chassis plans are done, building this thing will be an absolute breeze.  I really like this amplifier, so very much looking forward to getting it off my protoboard and into a chassis.


----------



## Henrim

GDuss said:


> LG, you should sell an Airmid DIY kit.  Put together some instructions, source all the parts and sell them in a bundle, include as much profit for yourself as needed to make it worth your time.  I’d buy it.



Hey LG, just want to go on record saying I agree with GDuss, I'd buy your kit.


----------



## L0rdGwyn

Henrim said:


> Hey LG, just want to go on record saying I agree with GDuss, I'd buy your kit.



Well thanks, I'm flattered!  Unfortunately that amplifier really does not lend itself well to a DIY kit.  Certain aspects of it are pretty tricky to build, troubleshooting without experience would be a daunting task, and some of the critical components for it are sold out everywhere at the moment.

I've mentioned this elsewhere, but I have an idea for an accessible DIY project that I think would make an excellent OTL.  Basically the idea is to buy two BHC+SB kits, but run both the input and output stage tube sections in parallel and use them together as a pair of OTL monoblocks.  This would minimize crosstalk between the channels, cut the output impedance of the Crack circuit in half, and maintain the benefit of an actively loaded cathode follower OTL output stage, which I think is very important and few (if any) OTLs out there do this - most are resistor loaded, and I find actively loading the output stage makes a huge difference.

Probably too much to ask someone else to take this on and give it a try, but I'm tempted to.  When Cracktober rolls around and the BHC+SB kits go on sale, I might buy a pair and plan to try this out.  If I pursued it and the results were good, I would probably create a guide on how to perform the mods, probably would make some other upgrades / changes as well, and have someone make a wood base so both mono circuits could sit together in a single chassis unit.  The guide would basically start with the two completed circuits, and go from there.  I would have to give it a really stupid name too.

Just an idea right now, have some other projects that take precedence, but I think this has the potential to be very good and would be very easy for people to make.


----------



## Henrim

Wow sounds awesome! And yeah fair enough about the kit. Do you know how that design would compare to the Feliks Euforia?


----------



## CJG888

L0rdGwyn said:


> That sounds fantastic.  I'd love to have a dedicated mono arm / cart some day.  Please post some pics when it's done.


Here, at least, is the arm waiting for its big moment:


----------



## L0rdGwyn (Aug 1, 2022)

Henrim said:


> Wow sounds awesome! And yeah fair enough about the kit. Do you know how that design would compare to the Feliks Euforia?



Hard to say, could be comparable, could be better.  I think if I did this, I would send the thing out on some sort of tour to get an idea of where it stands.  But the Euforia (as far as I'm aware) uses a resistive load for its output tubes, so in that regard this design is superior.  Also this design would be dual mono throughout, whereas the Euforia uses a shared power supply.  Given it would be dual mono, would not have to worry about matching gain for tubes since the R and L channel volume would be adjusted independently. I believe the Euforia uses some sort of voltage regulation for ripple reduction in its supply, so it does have that advantage, but the Crack has enough passive filtering to reduce ripple to inaudible levels in its stock form.  Could even add chokes as part of the mod for further ripple reduction.  The Crack uses the HLMP6000 LED for biasing its input stage, there are better sounding LEDs out there, so I would probably swap that out.  Aesthetically, the top plate of one of the Cracks could be flipped such that the two side-by-side in the chassis are mirror images of each other.   I mean, even if the performance was in the same ballpark as the Euforia, it would be 1/3 of its price.


----------



## L0rdGwyn

CJG888 said:


> Here, at least, is the arm waiting for its big moment:



Very nice.  Having parts laying around for future projects is always a tease!


----------



## CJG888

L0rdGwyn said:


> That sounds fantastic.  I'd love to have a dedicated mono arm / cart some day.  Please post some pics when it's done.


Massive disadvantage of suspended subchassis turntables:

You can only fit one arm!


----------



## L0rdGwyn

CJG888 said:


> Massive disadvantage of suspended subchassis turntables:
> 
> You can only fit one arm!



Yeah that will have to wait for the 401


----------



## L0rdGwyn (Aug 1, 2022)

I ran a LTSpice simulation of my BHC+SB monoblock idea, looks good.  Stock BHC+SB output impedance is ~120ohm if memory serves, paralleling the sections brings it down to 60ohms, around 45ohms if using the 5998.  I would increase the output capacitance as well.  I'm now fond of the Jupiter Cosmos electrolytic caps, so I'd probably give those a try, likely three 100uF 350V in parallel to bring the output capacitance up to 300uF which will improve the LF response.  I think these caps sound good without having to resort to monstrous films.  As I said, would probably change the LED type in the input stage as I think there are better ones than the HLMP6000, that would have to be done experimentally, swap and listen.  Would also swap out the stock pots to a pair of 100K mono Alps RK27 like I did in @Monsterzero 's Airmid.

I'll probably think of other things to change, but I don't want to make this super complicated, the goal would be to make this a simple DIY project.  Grab two Crack+SB kits, build them (one with the plate flipped upside down so they are mirror images of each other), make a few simple mods and you're done.  I'm going to plan to buy two kits when they go on sale and do this.  Need to find someone to make me a cool wood base that can hold both units side-by-side.


----------



## Mr Trev

L0rdGwyn said:


> I'll probably think of other things to change, but I don't want to make this super complicated, the goal would be to make this a simple DIY project.  Grab two Crack+SB kits, build them (one with the plate flipped upside down so they are mirror images of each other), make a few simple mods and you're done.  I'm going to plan to buy two kits when they go on sale and do this.  *Need to find someone to make me a cool wood base that can hold both units side-by-side.*


sounds like a cue for @Paladin79 ?


----------



## Paladin79 (Aug 1, 2022)

Mr Trev said:


> sounds like a cue for @Paladin79 ?


I could do something like that down the road. I am currently building tiny radial speakers and will be making a cabinet or two for SET amps.

I have worked with BH Cracks of course and I like a nice clean top with no pots or jacks.

My take on a BH crack.  Patinated 1/8 inch copper top plate, dual single gang controls, VU meters, and IEC socket and RCA inputs and outputs on rear plate.  Cabinet is quartered oak to stay with a steampunk theme.


----------



## L0rdGwyn

Paladin79 said:


> I could do something like that down the road. I am currently building tiny radial speakers and will be making a cabinet or two for SET amps.
> 
> I have worked with BH Cracks of course and I like a nice clean top with no pots or jacks.
> 
> My take on a BH crack.  Patinated 1/8 inch copper top plate, dual single gang controls, VU meters, and IEC socket and RCA inputs and outputs on rear plate.  Cabinet is quartered oak to stay with a steampunk theme.



Looks great!  Very nice cabinets on those radial speakers, nice small footprint too.


----------



## Paladin79

L0rdGwyn said:


> I ran a LTSpice simulation of my BHC+SB monoblock idea, looks good.  Stock BHC+SB output impedance is ~120ohm if memory serves, paralleling the sections brings it down to 60ohms, around 45ohms if using the 5998.  I would increase the output capacitance as well.  I'm now fond of the Jupiter Cosmos electrolytic caps, so I'd probably give those a try, likely three 100uF 350V in parallel to bring the output capacitance up to 300uF which will improve the LF response.  I think these caps sound good without having to resort to monstrous films.  As I said, would probably change the LED type in the input stage as I think there are better ones than the HLMP6000, that would have to be done experimentally, swap and listen.  Would also swap out the stock pots to a pair of 100K mono Alps RK27 like I did in @Monsterzero 's Airmid.
> 
> I'll probably think of other things to change, but I don't want to make this super complicated, the goal would be to make this a simple DIY project.  Grab two Crack+SB kits, build them (one with the plate flipped upside down so they are mirror images of each other), make a few simple mods and you're done.  I'm going to plan to buy two kits when they go on sale and do this.  Need to find someone to make me a cool wood base that can hold both units side-by-side.


I should probably answer this directly. I could absolutely build a very nice cabinet when I have time. A couple more examples of my work....this is not a BH Crack, it is my design.


----------



## Paladin79 (Aug 1, 2022)

L0rdGwyn said:


> Looks great!  Very nice cabinets on those radial speakers, nice small footprint too.


Decware makes them and sells plans as well as the base and top sound deflector but I make all my own parts and changed the cabinet design a bit. These only need 5-7 watts and they sound better than might be expected.


----------



## L0rdGwyn

Paladin79 said:


> I should probably answer this directly. I could absolutely build a very nice cabinet when I have time. A couple more examples of my work....this is not a BH Crack, it is my design.



Thanks, I'll definitely keep that in mind when I get around to working on this!



Paladin79 said:


> Decware makes them and sells plans as well as the bass and top sound deflector but I make all my own parts and changed the cabinet design a bit. These only need 5-7 watts and they sound better than might be expected.



Very cool, would be great in a little bedroom setup, for me at least


----------



## Paladin79

L0rdGwyn said:


> Thanks, I'll definitely keep that in mind when I get around to working on this!
> 
> 
> 
> Very cool, would be great in a little bedroom setup, for me at least


I have a couple sample pairs in other peoples hands.


----------



## JazzVinyl

L0rdGwyn said:


> I ran a LTSpice simulation of my BHC+SB monoblock idea, looks good.  Stock BHC+SB output impedance is ~120ohm if memory serves, paralleling the sections brings it down to 60ohms, around 45ohms if using the 5998.  I would increase the output capacitance as well.  I'm now fond of the Jupiter Cosmos electrolytic caps, so I'd probably give those a try, likely three 100uF 350V in parallel to bring the output capacitance up to 300uF which will improve the LF response.  I think these caps sound good without having to resort to monstrous films.  As I said, would probably change the LED type in the input stage as I think there are better ones than the HLMP6000, that would have to be done experimentally, swap and listen.  Would also swap out the stock pots to a pair of 100K mono Alps RK27 like I did in @Monsterzero 's Airmid.
> 
> I'll probably think of other things to change, but I don't want to make this super complicated, the goal would be to make this a simple DIY project.  Grab two Crack+SB kits, build them (one with the plate flipped upside down so they are mirror images of each other), make a few simple mods and you're done.  I'm going to plan to buy two kits when they go on sale and do this.  Need to find someone to make me a cool wood base that can hold both units side-by-side.


@L0rdGwyn -

Does this mean the DIY Pentode amp idea is kaput?

.


----------



## Paladin79 (Aug 2, 2022)

A build I did with Russian pentodes in order to win a bet. The Germans used a similar tube during WW 2, same specs only they would not sub for each other very easily.



These Telefunken were used on German submarines in WW 2, the LS 50. Russian version was the GU 50. Built for quick change, thus the bakelite handles on the top. Plenty of Russian tubes still out there for very little money .

https://www.ebay.com/itm/254033598023?hash=item3b25951647:g:rPgAAOSwgQ9Vr3vY

I used those in conjunction with Telefunken EF 80 tubes, (6bx6).

The cabinet I made is curly maple and white walnut (butternut).


----------



## L0rdGwyn (Aug 2, 2022)

JazzVinyl said:


> @L0rdGwyn -
> 
> Does this mean the DIY Pentode amp idea is kaput?
> 
> .



Well I wouldn't call it kaput.  From the get go, it was unlikely, so I would say it still falls into that category.  The primary goal with that amplifier is to _hopefully_ have it made into a commercial product.  Once I finish building one and get some feedback, we will see if that works out.  If it doesn't, then I am going to have to make some decisions. 

I could do one of three things: 1) do nothing and sit on the design and see if there are further opportunities for commercialization down the road 2) build and sell the design myself or 3) make it into a DIY project.

Options 2 and 3 are very unpopular with my significant other.  If I were to build and sell it myself, that would require a much bigger commitment to small business ownership than I had taken previously, and I can pretty reliably say that I would not be happy doing it.  I have a good job and don't necessarily need the money, so I would really just be sacrificing my free time.  I wouldn't rule that out completely, but it's not a popular option.

Option 3, the DIY approach, is also unpopular as I would be giving away what I consider to be a pretty valuable IP.  Creating the materials to build / test the amplifier would be a big undertaking, and I would be signing myself up to be tech support for the foreseeable future.  Even so, making it into a DIY project is still appealing for certain reasons. I would love to make a high-performing amplifier accessible to everyone and it would also be satisfying to sort of shake up the commercial amplifier scene.

Sorry, I know that's probably disappointing, but that's where it stands.  I've learned along the way building amplifiers for other people is not all it's cracked up to be lol so I am being more selfish with my time and trying to make good decisions for myself.  I am trying to find a balance between making something I designed available and also not signing up for unhappiness.  An industry collaboration where my design becomes a commercially available product is the best shot at achieving that.  TBD on that front, if not then we'll see where it goes from there.


----------



## L0rdGwyn

Paladin79 said:


> A build I did with Russian pentodes in order to win a bet. The Germans used a similar tube during WW 2, same specs only they would not sub for each other very easily.
> 
> 
> 
> ...



Very nice, the GU50 is an interesting tube, very popular in the DIY world, makes a good triode or also useful in push-pull designs, or single-ended pentode, it's flexible and cheap!  I've considered building something with it.  The chassis look great.  My understanding is the Russians reverse-engineered the Telefunken LS50 design from captured German tanks during WWII.


----------



## whirlwind

L0rdGwyn said:


> Well I wouldn't call it kaput.  From the get go, it was unlikely, so I would say it still falls into that category.  The primary goal with that amplifier is to _hopefully_ have it made into a commercial product.  Once I finish building one and get some feedback, we will see if that works out.  If it doesn't, then I am going to have to make some decisions.
> 
> I could do one of three things: 1) do nothing and sit on the design and see if there are further opportunities for commercialization down the road 2) build and sell the design myself or 3) make it into a DIY project.
> 
> ...



Do what makes you and the significant other happy....just sayin'


----------



## Paladin79

L0rdGwyn said:


> Very nice, the GU50 is an interesting tube, very popular in the DIY world, makes a good triode or also useful in push-pull designs, or single-ended pentode, it's flexible and cheap!  I've considered building something with it.  The chassis look great.  My understanding is the Russians reverse-engineered the Telefunken LS50 design from captured German tanks during WWII.


That may well be true since the tubes use a different key system. They were allies for a while but Russia getting the design after the fact makes more sense.

I used the pentodes as triodes because the bet involved building a SET amp capable of 12-15 watts after I was handed a bucket of parts. I won the bet, then used higher quality parts since the amp was then for my own use.


----------



## Paladin79

L0rdGwyn said:


> Well I wouldn't call it kaput.  From the get go, it was unlikely, so I would say it still falls into that category.  The primary goal with that amplifier is to _hopefully_ have it made into a commercial product.  Once I finish building one and get some feedback, we will see if that works out.  If it doesn't, then I am going to have to make some decisions.
> 
> I could do one of three things: 1) do nothing and sit on the design and see if there are further opportunities for commercialization down the road 2) build and sell the design myself or 3) make it into a DIY project.
> 
> ...


I am retired now but for years I worked on side projects and sometimes involved my son and daughter so some of the extra electronics brought us closer together. (My son made $50 an hour working with me at age 14, he was graduated from college not owing a penny.)

My wife always supported my extra work and I always had a need to stay active, it is just how I am. Much of that came later as we had two kids and were home with them when we could be. I have run companies and owned companies but in the end I was probably happiest running a company and working on side projects as I wanted to. I keep the rights to my designs and have had a few offers. It can get very stressful when you own a company and you know something has to be built or repaired at a certain time to meet a deadline. There is also the liability factor and dealing with customers.


----------



## L0rdGwyn

Paladin79 said:


> I am retired now but for years I worked on side projects and sometimes involved my son and daughter so some of the extra electronics brought us closer together. (My son made $50 an hour working with me at age 14, he was graduated from college not owing a penny.)
> 
> My wife always supported my extra work and I always had a need to stay active, it is just how I am. Much of that came later as we had two kids and were home with them when we could be. I have run companies and owned companies but in the end I was probably happiest running a company and working on side projects as I wanted to. I keep the rights to my designs and have had a few offers. It can get very stressful when you own a company and you know something has to be built or repaired at a certain time to meet a deadline. There is also the liability factor and dealing with customers.



If I were retired, I would absolutely be building amplifiers.  Maybe I can plan to do that in say, 25 years  running a business and doing side projects seems like it could be a nice balance.  I am a critical care healthcare worker and I work rotating days / night shifts, so it can be pretty physically and mentally demanding at times, balancing that with building amplifiers for audiophiles isn't a winning formula lol.  I am also a busy body, probably this thread is evidence of that, but working on something for my own enjoyment at my own pace without strict deadlines is a different story than making something for a demanding customer.

It's great you were able to involve your family in your business ventures and pay them well for their work, these days kids would love to get their undergraduate degree without a penny owed!


----------



## bcowen

L0rdGwyn said:


> If I were retired, I would absolutely be building amplifiers.  Maybe I can plan to do that in say, 25 years  running a business and doing side projects seems like it could be a nice balance.  I am a critical care healthcare worker and I work rotating days / night shifts, so it can be pretty physically and mentally demanding at times, balancing that with building amplifiers for audiophiles isn't a winning formula lol.  I am also a busy body, probably this thread is evidence of that, but working on something for my own enjoyment at my own pace without strict deadlines is a different story than making something for a demanding customer.
> 
> It's great you were able to involve your family in your business ventures and pay them well for their work, these days kids would love to get their undergraduate degree without a penny owed!


I would love to see kids these days willing to work.


----------



## Paladin79 (Aug 2, 2022)

L0rdGwyn said:


> If I were retired, I would absolutely be building amplifiers.  Maybe I can plan to do that in say, 25 years  running a business and doing side projects seems like it could be a nice balance.  I am a critical care healthcare worker and I work rotating days / night shifts, so it can be pretty physically and mentally demanding at times, balancing that with building amplifiers for audiophiles isn't a winning formula lol.  I am also a busy body, probably this thread is evidence of that, but working on something for my own enjoyment at my own pace without strict deadlines is a different story than making something for a demanding customer.
> 
> It's great you were able to involve your family in your business ventures and pay them well for their work, these days kids would love to get their undergraduate degree without a penny owed!


I spent the majority of my career in electronics, business, and industrial management the woodworking portion is what appeals to me now. Building the same circuit over and over gets redundant. I have never made two amp cabinets the same, all are unique. Some are more unique than others, @bcowen's sideways amp lol.



I did a prototype in cardboard, his preferred medium.


----------



## bcowen

Paladin79 said:


> I spent the majority of my career in electronics, business, and industrial management the woodworking portion is what appeals to me now. Building the same circuit over and over gets redundant. I have never made two amp cabinets the same, all are unique. Some are more unique than others, @bcowen's sideways amp lol.
> 
> 
> 
> I did a prototype in cardboard, his preferred medium.


The Foton and GEC are a nice combo.  And I really like the GE warning light as it helps prevent ear damage.


----------



## L0rdGwyn

Paladin79 said:


> I spent the majority of my career in electronics, business, and industrial management the woodworking portion is what appeals to me now. Building the same circuit over and over gets redundant. I have never made two amp cabinets the same, all are unique. Some are more unique than others, @bcowen's sideways amp lol.
> 
> 
> 
> I did a prototype in cardboard, his preferred medium.



That sensitivity meter is hilarious.  Building the same thing over and over is no fun.  For me it is about trying new amplifier topologies, or new component designs altogether (DAC, phono stage).  For that, I built a prototyping board.  If I have the parts on hand, I can throw together a new amplifier circuit in an hour or two, measure it, get some subjective impressions and tweak things before designing the chassis.


----------



## Paladin79 (Aug 2, 2022)

L0rdGwyn said:


> That sensitivity meter is hilarious.  Building the same thing over and over is no fun.  For me it is about trying new amplifier topologies, or new component designs altogether (DAC, phono stage).  For that, I built a prototyping board.  If I have the parts on hand, I can throw together a new amplifier circuit in an hour or two, measure it, get some subjective impressions and tweak things before designing the chassis.


Very nice.

I set up ten friends in a PM and they helped make suggestions on Bill's cardboard amp. For the rounded corners on the real one, I bought a wood lathe, did the calculations and made a wooden cylinder that I then quartered on a table saw. That part was very difficult but I wanted to see if it could be done. The brushed copper top plate is considerable work, it is approximately the same size plate used on a BH Crack, I made all cuts on a drill press. Naturally I have to make all cabinet cuts for pots and jacks prior to assembly. I plan to make one last amp that will be prettier just to annoy Bill.


----------



## Zachik

L0rdGwyn said:


> I could do one of three things: *1) do nothing and sit on the design and see if there are further opportunities for commercialization down the road* 2) build and sell the design myself or 3) make it into a DIY project.


I *might* be able to help you out with option #1 - PM me if you're interested...


----------



## L0rdGwyn

Zachik said:


> I *might* be able to help you out with option #1 - PM me if you're interested...



Cool, I will keep that in mind


----------



## Paladin79

Some tiny radials I built,  in action. The wood is cherry and looks a little washed out in the photo but such is life.


----------



## Monsterzero

Like the diffuser. Did you make that? Question...Arent diffusers supposed to go on the opposite wall of the speakers?


----------



## Paladin79

Monsterzero said:


> Like the diffuser. Did you make that? Question...Arent diffusers supposed to go on the opposite wall of the speakers?


I did not make the diffuser but I certainly could.😜  I am not sure what other equipment this gentleman has, it may well be on the opposite wall.


----------



## Monsterzero

Paladin79 said:


> Some tiny radials I built,  in action. The wood is cherry and looks a little washed out in the photo but such is life.





Paladin79 said:


> I did not make the diffuser but I certainly could.😜  I am not sure what other equipment this gentleman has, it may well be on the opposite wall.


 Love the vintage Marantz pieces too.


----------



## bpiotrow13

I 





Paladin79 said:


> Some tiny radials I built,  in action. The wood is cherry and looks a little washed out in the photo but such is life.


I'd love to see the full system with the speakers. Though the diffusers behind the amp do not technically make sense they look great.


----------



## Paladin79

bpiotrow13 said:


> I
> I'd love to see the full system with the speakers. Though the diffusers behind the amp do not technically make sense they look great.


Well in reading the gentleman’s comments he feels they help. His house, walls, ears, and equipment. I try not to comment about what someone hears.😜


----------



## Paladin79

Monsterzero said:


> Love the vintage Marantz pieces too.


If you like older gear friends and I put together all the same gear used in the Bosch TV series. I went so far as to research the pieces from the rental company that supplied it to the show.


----------



## Monsterzero

Paladin79 said:


> If you like older gear friends and I put together all the same gear used in the Bosch TV series. I went so far as to research the pieces from the rental company that supplied it to the show.


 Nice! I dont watch much TV, but thats pretty cool.

I have a bunch of vintage pieces,

McIntosh 4100
Kenwood Eleven GX
Onkyo TX-6500 MK ll
Sansui 881
Sansui 5000a
Marantz 2226b
Akai AA-1150


----------



## Paladin79 (Aug 2, 2022)

Monsterzero said:


> Nice! I dont watch much TV, but thats pretty cool.
> 
> I have a bunch of vintage pieces,
> 
> ...


Speakers: Ohm Walsh 4, Turntable: Marantz 6300 turntable, Amp: McIntosh 240 tube amp, Preamp / tuner: McIntosh MX110

He is big into records, at one point telling his daughter he would buy her turntable and vinyl to listen to jazz.

Music from the show: “Lullaby” – Frank Morgan, “Soul Eyes” – John Coltrane, “My Funny Valentine” – Art Pepper and the Hollywood All-Stars, “My Foolish Heart” – Bill Evans, “Mood Indigo” – Frank Morgan, “For All We Know” – Sonny Rollins, “Lush Life” – Joe Henderson, “Straight Life” – Art Pepper, “Willow Weep For Me” – Clifford Brown, “What A Wonderful World” – Louis Armstrong,





Naturally we listened to a lot of Art Pepper meets the Rhythm Section and other classics when we assembled the gear. This week I am even building a couple tiny radial speakers to match the looks of some Ohm speakers. This was a fun get together with a few drinks, nothing serious like us listening to and scoring some of the top DAC's made or comparing 1500 6sn7 equivalents.    I had to repair some of the gear to bring it up to its proper level but I do my part. The McIntosh 240,,, mmmmmm.  The effort was well worth it. It is interesting to me when writers combine their love of music in their works. The great Japanese writer Haruki Murakami is that way...
https://interlude.hk/haruki-murakami-music/

I need to figure out some tops for the tiny radials so they more resemble the Ohm speakers but the angle of taper is very similar. This is DIY but you best know what you are doing to try to do these miter cuts.


----------



## bpiotrow13

Paladin79 said:


> Well in reading the gentleman’s comments he feels they help. His house, walls, ears, and equipment. I try not to comment about what someone hears.😜


It may be it helps to improve overall room's accoustics, but hard to tell, as You mentioned. In any case it looks nice


----------



## whirlwind

Paladin79 said:


> Well in reading the gentleman’s comments he feels they help. His house, walls, ears, and equipment. I try not to comment about what someone hears.😜



Ha...wise man. 

I always say that if you think it sounds better, then it sounds better


----------



## Paladin79 (Aug 3, 2022)

whirlwind said:


> Ha...wise man.
> 
> I always say that if you think it sounds better, then it sounds better


Radial speakers are interesting, especially this size. On my desktop you really feel the bass, SPL can be around 75 DB peaking to 85 or so with right at 7 watts. Since they are omnidirectional keeping reflection down when you are close to them may not be a bad thing. My computer desk has all kinds of nooks and crannies and I still get very good sound. This is just my experience and I have only listened to eight pairs thus far, in various parts of my downstairs.   I am about to make some using padauk wood, with the top sound deflector in the same material but today I will be involved with a SET amp that should be the perfect size for the little speakers.

I am sure folks here are capable of building their own tiny radial speakers but the cabinets are tricky and I can help there. If anyone has an interest just PM me and I will help with the BOM list and construction tips.  It is best that I glue the cabinets together since a spindle sander is required to get the circular opening in the top just right.


----------



## L0rdGwyn

I've been working on the pentode amplifier layout and PCB since around 9 this morning.  Pretty challenging layout with three big chokes inside, PCB dimensions have to be just right to make it all fit the way I would like it to.

Going for something simple like this for the chassis, subject to change of course.  13.5" L x 14" W x 3.25" H.  Rectifier on the left, pair of 6SL7 in the front, and pair of EL34 (or other pentode) in the back.  There will be a row of three Lundahl transformer shields in the back for the mains and output transformers.  Probably going to do it in a matte black finish.



PCB is just about done, taking a break, then just need to route all of the connections.

I also received my isolation feet for my turntable today, IsoAcoustics Orea Indigo.  Waiting for my tonearm cable and the rest of the replacement suspension parts, then I can finish the job, probably over the weekend.



As I was working on the pentode amp PCB, I went back and looked at what I had put together for that PCM63 DAC I was planning.  I had forgotten the PCBs were completely finished, woot!  So I will order those when I place orders for the pentode PCBs and plan to work on that bit by bit.  This time around I included tracings for the low voltage mains transformers onto the board which will make for a cleaner look, that no one will see  this board is for one channel, two PCM63 will run in parallel per channel.


----------



## Paladin79

I am involved in a joint effort with another engineer on an amp but I decided to order a top plate before moving on. I was also wanting to check out some exotic woods. 😜


----------



## triod750

Way back in the days we were taught that it was a no-no to use isolation feet with a suspended turntable. So that 'truth' isn't valid anymore?


----------



## CJG888

Maybe not a “no-no”, but, by definition (if the suspension is working properly), pointless!


----------



## L0rdGwyn (Aug 3, 2022)

triod750 said:


> Way back in the days we were taught that it was a no-no to use isolation feet with a suspended turntable. So that 'truth' isn't valid anymore?





CJG888 said:


> Maybe not a “no-no”, but, by definition (if the suspension is working properly), pointless!



It might be a no no, could alter the damping of the suspension system in an undesirable way.  I'll use them on my stereo amp instead and use some non-isolating feet on the turntable, have some good ones from Herbie's Audio Lab that will do the trick.


----------



## L0rdGwyn

I finished the chassis for the pentode headamp this morning, PCB is finalized as well.  Here it is as a fold out.  I trimmed the size down a smidge, so final dimensions are 13.5" L x 13.5" W x 3.25" H.  I left the transformer shield outlines in this screenshot so you can get an idea of how the top plate will look.

Again, GZ34 / 5R4 / 5V4 rectifier is on the left, pair of 6SL7 in the front, pair of EL34 (or other pentode) in the back, back row of Lundahl transformer shields (small LL1638 model).  On the front panel, toggle power switch on the far left, volume pot in the middle off-centered and aligned with the amplifying tubes, 1/4" headphone jack on the far right.  On the back panel, IEC inlet on the left, headphone impedance selector in the middle off-centered, RCA inputs on the right.




Here is one of the small Lundahl shields assembled.  With three of these, three transformers, and three chokes, this is going to be a heavy amplifier.



Black Belton sockets will be bottom mounted.  The chassis is going to be matte black, the same coating used for the Airmid socket sub-plates.  Wiring Lundahl output transformers for switchable turns ratios is a bit tricky due to their winding technique, so I have a specific headphone impedance selector switch on order from Elma.  That might slow things down a bit, but I might go ahead and place orders anyway.


----------



## L0rdGwyn

Back to turntable stuff, got the new suspension parts today.

New vs. old damping rubber washers.



I bought new springs as well, reverse engineered from the originals.  On closer inspection though, I think the originals are in good condition, I decided to keep them.  The fact that they are glued in place helped me make that decision.  I'll keep the reproductions as spares should I need them in the future.



I replaced the Valvo 1000uF electrolytic caps on the speed controller board.  I could not measure a capacitance on these.  The turntable was performing surpisingingly well considering it was probably running on unfiltered DC.



Replaced with high quality Vishay caps.  At some point I'll probably do an entire overhaul of the speed control, but that is a project unto itself.



I went ahead an re-calibrated the speed control board, did a ballpark adjustment of the suspension, and lubricated the spindle.

I'm going to do a basic setup of the tonearm, less work to do when my tonearm cable arrives.  But that's pretty much it, just need the cable so I can close up the bottom, put it back on my rack so I can fine tune the suspension and do the final setup of the arm.


----------



## Monsterzero

L0rdGwyn said:


> At some point I'll probably do an entire overhaul of the speed control, but that is a project unto itself.


 Funny, I feel the same way about getting out of bed each day


----------



## whirlwind

L0rdGwyn said:


> I finished the chassis for the pentode headamp this morning, PCB is finalized as well.  Here it is as a fold out.  I trimmed the size down a smidge, so final dimensions are 13.5" L x 13.5" W x 3.25" H.  I left the transformer shield outlines in this screenshot so you can get an idea of how the top plate will look.
> 
> Again, GZ34 / 5R4 / 5V4 rectifier is on the left, pair of 6SL7 in the front, pair of EL34 (or other pentode) in the back, back row of Lundahl transformer shields (small LL1638 model).  On the front panel, toggle power switch on the far left, volume pot in the middle off-centered and aligned with the amplifying tubes, 1/4" headphone jack on the far right.  On the back panel, IEC inlet on the left, headphone impedance selector in the middle off-centered, RCA inputs on the right.
> 
> ...


Very interested in seeing this one completed.


----------



## L0rdGwyn

whirlwind said:


> Very interested in seeing this one completed.



Thanks, me too!  First time building out a tube circuit onto a PCB.  It was a lot of work, but will make the build so simple, I think I should be able to do it in one sitting.  I'm looking forward to when I can talk about what I've done in this circuit that makes it different from other triode strapped pentode designs.


----------



## whirlwind (Aug 5, 2022)

L0rdGwyn said:


> Thanks, me too!  First time building out a tube circuit onto a PCB.  It was a lot of work, but will make the build so simple, I think I should be able to do it in one sitting.  I'm looking forward to when I can talk about what I've done in this circuit that makes it different from other triode strapped pentode designs.


I have not heard any triode strapped pentode tubes that don't sound killer.  I am not sure bad sounding one's exist


----------



## Paladin79 (Aug 5, 2022)

I agree, and naturally I have done such builds. Maybe down the road I can barter one of my cabinet builds for such a device sans tubes. I am too deep into other projects to spend a lot of time on electronics. I am working to buy my dream audio system come September so I need to build another rack in solid cherry and copper.


----------



## L0rdGwyn

whirlwind said:


> I have not heard any triode strapped pentode tubes that don't sound killer.  I am not sure bad souding one's exist



Yeah it's a great family of tubes and without the headaches that come with directly-heated triodes.  I have mostly been listening to a pair of Mullard XF2 EL34 with a Philips GZ34, but the Visseaux 6V6GT paired with a RCA 5R4GY sounds really nice too.  I don't have many other power pentodes in my tube stash, I wonder if I'll ever try some of the more sought after models a la KT66, KT88, etc.  I have to go through the list of power pentodes and pick out which will be compatible with this circuit and which won't.  Some might bias a little too hot.


----------



## Paladin79

I am about to purchase an amp that can run most anything up to a KT-150, eight power tubes, I do really like EI KT90’s.


----------



## L0rdGwyn (Aug 5, 2022)

Paladin79 said:


> I am about to purchase an amp that can run most anything up to a KT-150, eight power tubes, I do really like EI KT90’s.



Wow!  Eight KT150s, that is big time power from a tube amp, should be able to run anything.

A tube I'm going to build with at some point is the HY69.  I think I've collected 40-50 them, but I really have no reason to build another speaker amplifier right now, so they are just sitting.  They are directly-heated pentodes with thoriated tungsten filaments.  The grids are built to handle a fair amount of current so they can operate in class A2, and strapped as triodes they are easily as linear as a 45, 50, 300B etc.  And more gain!  Probably a transformer-coupled SET design, maybe 8-10W, works well with my 99dB/W Klipsch!



A1 triode curves look like this, very linear into positive grid territory as well.


----------



## Paladin79

L0rdGwyn said:


> Wow!  Eight KT150s, that is big time power from a tube amp, should be able to run anything.
> 
> A tube I'm going to build with at some point is the HY69.  I think I've collected 40-50 them, but I really have no reason to build another speaker amplifier right now, so they are just sitting.  They are directly-heated pentodes with thoriated tungsten filaments.  The grids are built to handle a fair amount of current so they can operate in class A2, and strapped as triodes they are easily as linear as a 45, 50, 300B etc.  And more gain!  Probably a transformer-coupled SET design, maybe 8-10W, works well with my 99dB/W Klipsch!
> 
> ...


Hmmm the tiny speakers I am building will handle 10 watts RMS so low power tube amps are not always relegated to efficient speakers. It would have to have an Italian name though, I am only buying gear that is Italian or sounds Italian at this time. I have no room for La Scallas but Sonus Fabers work, as does PrimaLuna, (Netherlands), Aqua La Voce, etc.   I am sort of kidding but having heard specific gear I know my likes. Now the La Voce S3 did extremely well in a DAC test friends and I conducted, I am hoping to stay with all tube gear so I am leaning toward a PrimaLuna EVO 100 DAC to go with an EVO 400 amp.


----------



## L0rdGwyn

Paladin79 said:


> Hmmm the tiny speakers I am building will handle 10 watts RMS so low power tube amps are not always relegated to efficient speakers. It would have to have an Italian name though, I am only buying gear that is Italian or sounds Italian at this time. I have no room for La Scallas but Sonus Fabers work, as does PrimaLuna, (Netherlands), Aqua La Voce, etc.   I am sort of kidding but having heard specific gear I know my likes. Now the La Voce S3 did extremely well in a DAC test friends and I conducted, I am hoping to stay with all tube gear so I am leaning toward a PrimaLuna EVO 100 DAC to go with an EVO 400 amp.



That Aqua La Voce DAC has a very elegant aesthetic, I like it.  Prima Luna EVO 100 DAC is pretty interesting with its tube master clock.  My DIY DAC has a tube output stage, but not sure I can call it a "tube DAC" if tubes aren't used in the digital front end


----------



## Zachik

L0rdGwyn said:


> not sure I can call it a "tube DAC" if tubes aren't used in the digital front end


Your design, so you can call it anything you like!


----------



## L0rdGwyn (Aug 5, 2022)

Zachik said:


> Your design, so you can call it anything you like!



Then I shall call it Philip, in honor of its DAC chip's manufacturer 

Just put together the final final thing I need before placing orders for the pentode headamp.  As I mentioned, headphone impedance selector switch using Lundahl output transformers is tricky due to their winding scheme, they have multiple secondaries that are connected in series / parallel to achieve different turns ratios.  So, to get a high and low impedance option, you need a somewhat complex switch as multiple connections are made and broken when changing the turns ratio.  Wiring a switch like this point-to-point is extremely tedious, instead I will take a simpler route seeing as the theme of this amp is "easy to build".

I have ordered the below switch from Elma with the intention of designing a PCB that will make all of the necessary transformer connections for me (side note, pretty clear to me that Elma manufactures switches for Goldpoint).




Below is the PCB.  Putting it all together will be as easy as soldering the 2x14 header to the switch, then soldering the switch to the PCB, then connecting the output transformer leads to the PCB.  Done.  I've also included secondary resistor connections so the transformer remains loaded at all times, outputs will then go right to the headphone jack.



So the amp will have a high and low headphone impedance settings.  Output impedance on the high Z tap (120ohm and up) with EL34 is roughly 16ohm, output impedance on the low Z tap (32-120ohm) is around 4ohm.  Nice low output impedance (by tube amp standards) for running planar magnetics perhaps.


----------



## JazzVinyl

"Somewhat complex" indeed!    Amazing you could figure this out!  You deserve for it to "go commercial"


----------



## L0rdGwyn

JazzVinyl said:


> "Somewhat complex" indeed!    Amazing you could figure this out!  You deserve for it to "go commercial"



Thanks!  I appreciate that.

I am doing a final listen of the prototype this morning before I place orders.  Right before I order the final components for an amp, I always go through a "but does it REALLY sound good?" phase where I temporarily doubt what I'm hearing, or hear some harshness that maybe wasn't there on the first twenty listens.  But listening again this morning has assuaged those fears, I really think this is an incredible circuit.  For those that crave soundstage, this amp has one of the largest and airiest I have heard out of a tube amplifier, larger than both the Airmid and my 6336 OTL, which both have quite large soundstages.  With the Atrium, it is a huge out-of-your-head listening experience.  I have to wonder how the soundstage compares to @zach915m 's 45 amplifier because that amp has a pretty large headstage.  This pentode amp also has some of the most full-bodied low end I have heard from a tube amp, really kicks ass with EDM.

So I'm convinced, ready to drop more money on a chassis and the PCBs!


----------



## Monsterzero

L0rdGwyn said:


> For those that crave soundstage, this amp has one of the largest and airiest I have heard out of a tube amplifier, larger than both the Airmid and my 6336 OTL,


----------



## L0rdGwyn

Monsterzero said:


>



Lol yeah the stage is really impressive!  Character of the amp is different however, a faster, more forward sound, slightly more euphonic I would say.  Good for rock too, gives electric guitars a nice bite.

Everything is ordered.  Since everything is matte black, I went ahead and grabbed a matte black Audio Note knob to match.  Kimber RCAs too.


----------



## jgwtriode (Aug 7, 2022)

Impressive stuff Keenan.  I continue to tinker with peripheral things while waiting for the eventual arrival of my DAC.  A few more health setbacks for both me and Ric.  His have set him back with my dac.  So, anyhow,  I got Herbies HALO's for 5998's.  And mounted the Medium size Mad sci doughnuts.  Same material as the sample discs.  Same approach.  Wire support structures mounted to the damper ring allowing the dougnut in this case to sit just above the tube.  A very nice result.  Again slightly lower noise floor.  More bass texture and detail, a bit more snap and transient response.  A bit more air, space and detail and a slightly larger stage.  Don't know if it really damps microphonics, but maybe.  It seems to make a slightly bigger difference then the ones I did for the National Unions, which can also sit on the top of the GEC's.   I will pull them out tomorrow and send photos.  Not particularly good looking but functional and no compromise relative to heat removal of surface area.  Might even make a slight improvement there. 

All I know is they sound better.

Even happier listening,

jgwtriode


----------



## L0rdGwyn

I put those Isoacoustics feet under my amp, hey they look pretty good I think!



I saw the Cleveland Orchestra play Grieg's piano concerto last night, so I am reliving the experience now with my favorite recording.

It looks like my tonearm cable is going to be delivered tomorrow.  Unfortunately I am working, if it's a slow day at work maybe I'll have the energy to do a quick setup when I get home, I am dying to get my turntable closed up and back on my audio rack.

All is ordered for the pentode amplifier, so unfortunately I have nothing to report, just a wait.  Once I get tired of listening to my prototype, I'll break it down and start getting things ready for the build.  Probably the rate-limiting step is the Elma switch.  I am going on vacation at the end of August, really hope I can build this thing before I leave.

I have a single Tung-Sol 6SU7GTY, I am considering picking up another single to make a pair.  This is arguably the most sought-after 6SL7 variant, so could be fun to try in the amp.


----------



## mordy

Except for looks, do the Isoacoustics feet bring an improvement?


----------



## L0rdGwyn

mordy said:


> Except for looks, do the Isoacoustics feet bring an improvement?



Yes, they seem very stable!  And improve airflow under the amp 

As far as sound, I have no idea.  The tubes in the amp are not microphonic, so no issues there.  I don't really have time to do extensive critical listening with and without to convince myself they sound better, no to mention swapping out feet from under a super heavy amp would be a real hassle.

So I'll just tell myself they sound better


----------



## JazzVinyl (Aug 7, 2022)

L0rdGwyn said:


> I put those Isoacoustics feet under my amp, hey they look pretty good I think!
> 
> 
> 
> ...



The TS 6SU7GTY is supposed to be the ultimate 6SL7. I have one and indeed it is nice.  Mine has clear glass and flat pates.  This one appears to have round plates?

May I also suggest a tube that @mordy recommended to me, an early NU 6SL7W "umbrella spoke" w/brown base.  They are rather hard to source, but if you could find a good pair, they will give the coveted Tung Sol a good run for its money.


There are also a lot of absolutely NOS 12SL7 Tung SOL BGRP's still out in the wild. Might be worth while to consider 12v for the drivers' too...cause ummm ummm ummm, they sound good, and do special things to the sound stage/image (that you have already said is 'special' in this amp).



NU 6SL7GTW - very short round-ish black pates, you can see the famed "umbrella spokes" - they appear to do the job of a Mica to prevent micro-phonics?


----------



## L0rdGwyn

JazzVinyl said:


> The TS 6SU7GTY is supposed to be the ultimate 6SL7. I have one and indeed it is nice.  Mine has clear glass and flat pates.  This one appears to have round plates?
> 
> May I also suggest a tube that @mordy recommended to me, an early NU 6SL7W "umbrella spoke" w/brown base.  They are rather had to source, but if you could find a good pair, they will give the coveted Tung Sol a good run for its money.
> 
> ...



Yes it has round plates, I haven't seen the one with flat plates.  There is a single 6SU7GTY on eBay at the moment with the same construction as mine, I messaged the seller about the test results.  "Tests strong" isn't very reassuring, hoping to get some hard numbers.  I'll keep an eye out for that NU, I have been perusing eBay but I've resisted pulling the trigger on anything yet.  That will probably change when the amp is done 

I think the spokes likely prevent the interior structure from shifting too far in any one direction as they will then make contact with the glass, I've seen similar construction in other tubes to keep the electrodes centered within the envelope.  A 12V switch would be nice, unfortunately every heater winding on the mains transformer is accounted for, so no availability to run two in series for a 12V connection.  6SL7 are available new production and still widely available NOS, so no issues with availability which was one goal of this design.

I've started jotting down tube compatibility.  6SL7 are stock input, not a ton of flexibility there, some others could be used with adapters however, like 6SC7.  12AX7, 12AY7, 12AT7 with adapters too, but performance will likely suffer.  Lots of output pentode options, most of the big players like EL34, KT66, KT88, 6550, 6V6, 6L6, etc.  Some of the lower power pentodes like 6F6, 6K6 will only work with higher Vdrop rectifiers (5R4, 5Y3), otherwise they will bias over the max plate dissipation.  Rectifiers are 5V 2A, which includes 5AR4 / GZ34, 5V4 / GZ32, 5R4, 5Y3.  Gotta be careful with the 5Y3 though, can only handle 120mA DC output current, so don't want to pair it with something like a KT88 which will push it over.  No 5V 3A rectifiers like 5U4, but still lots of 2A options.

I was listening to this combo earlier with the Vérité Closed, RCA 5Y3G and a pair of Visseaux 6V6GT, sounded really good.  To me at least, eventually we will see if other people like this amp too when I demo it.  My girlfriend says the large soundstage is good for classical when she listened to Mozart earlier today, I followed that by listening to Sabbath, so I guess it's flexible


----------



## JazzVinyl

L0rdGwyn said:


> Yes it has round plates, I haven't seen the one with flat plates.  There is a single 6SU7GTY on eBay at the moment with the same construction as mine, I messaged the seller about the test results.  "Tests strong" isn't very reassuring, hoping to get some hard numbers.  I'll keep an eye out for that NU, I have been perusing eBay but I've resisted pulling the trigger on anything yet.  That will probably change when the amp is done
> 
> I think the spokes likely prevent the interior structure from shifting too far in any one direction as they will then make contact with the glass, I've seen similar construction in other tubes to keep the electrodes centered within the envelope.  A 12V switch would be nice, unfortunately every heater winding on the mains transformer is accounted for, so no availability to run two in series for a 12V connection.  6SL7 are available new production and still widely available NOS, so no issues with availability which was one goal of this design.
> 
> ...


Pretty sure all the old timers say the 6SL7 out preforms the others mentioned, in audio circuits...

Here is my beautiful TS 6SU7GTY flat plate:



This, the aforementioned NU and TS BGRP are true top performers.  Also good are the Russian Melz 6N9S (6SL7 equiv) the other Russian branded 6SL7's also perform pretty well in a good 6SL7-as-driver circuit.  There is a Chinese 6SL7 that appears to be identical in construction to the Russian branded one, and sounds the same. China version is probably made is Russia?

As you say, still avail new is a big big plus.


----------



## L0rdGwyn (Aug 7, 2022)

JazzVinyl said:


> Pretty sure all the old timers say the 6SL7 out preforms the others mentioned, in audio circuits...
> 
> Here is my beautiful TS 6SU7GTY flat plate:
> 
> ...



That's a nice looking tube, I'll keep my eyes peeled for a pair  yes the 6SL7 is extremely linear!  More linear than the others mentioned, which means great for audio.  The 6SL7's weakness is its very high plate resistance, so it must be used carefully.   If implemented well, it has high potential and produces very low distortion.


----------



## jgwtriode

Zachik said:


> Photos or it did not happen!


Okay here are the modified Herbie's Halo's with Mad Sci carbon graphene namo doughnuts!

Happy listening,

jgwtriode


----------



## jgwtriode

L0rdGwyn said:


> Yes, they seem very stable!  And improve airflow under the amp
> 
> As far as sound, I have no idea.  The tubes in the amp are not microphonic, so no issues there.  I don't really have time to do extensive critical listening with and without to convince myself they sound better, no to mention swapping out feet from under a super heavy amp would be a real hassle.
> 
> So I'll just tell myself they sound better


Very nice....my footers of choice.  Mad Scientist  Blackpod Nano Carbon Graphene.  With Ceramic Bearings and one with Tungsten Carbide!  These improve most everything I put them under!  But have not absoloutely AB'ed with and without under the Airmid!

Happy listening,

jgwtriode


----------



## Paladin79

The start of an amp in black walnut as well as some African padauk wood in some tiny radial speakers I may well keep.


----------



## L0rdGwyn

Paladin79 said:


> The start of an amp in black walnut as well as some African padauk wood in some tiny radial speakers I may well keep.



Looks good!  I like that walnut chassis, it will be a good looking amplifier.  What tubes will it use?


----------



## Paladin79 (Aug 8, 2022)

L0rdGwyn said:


> Looks good!  I like that walnut chassis, it will be a good looking amplifier.  What tubes will it use?


Two EL 34's and a 12AX7. The walnut cabinet was used for a different purpose, I will try to bring it up to par. I cut new aluminum for the top. I had already installed an IEC connector and RCA jacks in the back so that should speed things up.  I made the cuts for a dual gang pot but I have some single gang Alps I may use. A friend used to call these Black Beauties as best I recall. I got a bunch of them in some surplus I bought.


----------



## L0rdGwyn

Paladin79 said:


> Two EL 34's and a 12AX7. The walnut cabinet was used for a different purpose, I will try to bring it up to par. I cut new aluminum for the top. I had already installed an IEC connector and RCA jacks in the back so that should speed things up.  I made the cuts for a dual gang pot but I have some single gang Alps I may use. A friend used to call these Black Beauties as best I recall. I got a bunch of them in some surplus I bought.



Nice, should pair well with your radial speakers.  Is that Alps pot vintage?  I made a last minute decision to use a TKD pot for my pentode amplifier.


----------



## Paladin79

L0rdGwyn said:


> Nice, should pair well with your radial speakers.  Is that Alps pot vintage?  I made a last minute decision to use a TKD pot for my pentode amplifier.


I am hoping the amp pairs well but in the meantime I am using a 25 year old Cary amp I like pretty well.   I have used some TKD pots in the past as well and have no complaints.
The Alps pot is indeed vintage, I still have several pairs in use in amps I built so I know how well they performed.


----------



## L0rdGwyn

Paladin79 said:


> I am hoping the amp pairs well but in the meantime I am using a 25 year old Cary amp I like pretty well.   I have used some TKD pots in the past as well and have no complaints.
> The Alps pot is indeed vintage, I still have several pairs in use in amps I built so I know how well they performed.



Very cool, I like using vintage parts, like old bakelite knobs and Amphenol sockets.  For older tube socket types like UX4 and UX5, I think the vintage Amphenol stuff is better than most if not all of the current productions sockets.  For octal and 9-pin noval, there are some good choices, still like vintage Amphenol though.  Never used a vintage pot, maybe I'll have to give that a try some day


----------



## Paladin79

L0rdGwyn said:


> Very cool, I like using vintage parts, like old bakelite knobs and Amphenol sockets.  For older tube socket types like UX4 and UX5, I think the vintage Amphenol stuff is better than most if not all of the current productions sockets.  For octal and 9-pin noval, there are some good choices, still like vintage Amphenol though.  Never used a vintage pot, maybe I'll have to give that a try some day


It is NOS and I have heard of people searching for this exact item. They are large by todays standards but I can build around most anything. I only use brands I know and trust like Amphenol, Neutrik, Switchcraft etc. I do not do boutique parts especially cables or connectors.


----------



## Zachik

jgwtriode said:


> Okay here are the modified Herbie's Halo's with Mad Sci carbon graphene namo doughnuts!
> 
> Happy listening,
> 
> jgwtriode


Haha - this is what comes to mind, seeing your contraption:


----------



## L0rdGwyn (Aug 8, 2022)

Paladin79 said:


> It is NOS and I have heard of people searching for this exact item. They are large by todays standards but I can build around most anything. I only use brands I know and trust like Amphenol, Neutrik, Switchcraft etc. I do not do boutique parts especially cables or connectors.



100% agree.  Most times with boutique connectors, you are going to pay 10x the price for something that either falls apart, is difficult to work with, or looks cheap.  I use Amphenol RCAs most often, although I do like Kimber's RCA's but that is the only boutique connector I use anymore if I'm feeling fancy.  I use Switchcraft 1/4 jacks, NKK or Schurter switches and Schurter IEC inlets.  Switchcraft or Amphenol for most other connections.

I remember a while back I bought some WBT RCAs for a build.  WBT is a German company, their site has pictures of all of these guys walking around wearing lab coats, this communicates how serious they are about their connectors, they are doing _real_ research into connector design which requires lab coats.  Well apparently they didn't think to QC those RCAs to ensure all of them were of equal diameter, one of the two was so overly thick to the point that I could not fit a standard male RCA connector over it.  I had never seen that before nor have I seen it since.  So much for the lab coats.

Or Vampire RCAs where there is no ground tab, the ground connection is on the freaking body of the RCA, which is a 1cm^3 chunk of solid copper!  How am I supposed to heat it to make a good solder connection?  It's basically a heat sink.  I heated one to the point that the gold plating started to flake off.  Just plain stupid design.


----------



## jgwtriode

Zachik said:


> Haha - this is what comes to mind, seeing your contraption:


hahaha! Indeed.   Yeah its improvised so all I care is that it improves the sound and does not look completely unsightly

jgwtriode


----------



## L0rdGwyn

Turntable is back in its home.  Still a lot of work to do setup wise, but it is a functioning turntable at this point.


----------



## bcowen

L0rdGwyn said:


> 100% agree.  Most times with boutique connectors, you are going to pay 10x the price for something that either falls apart, is difficult to work with, or looks cheap.  I use Amphenol RCAs most often, although I do like Kimber's RCA's but that is the only boutique connector I use anymore if I'm feeling fancy.  I use Switchcraft 1/4 jacks, NKK or Schurter switches and Schurter IEC inlets.  Switchcraft or Amphenol for most other connections.
> 
> I remember a while back I bought some WBT RCAs for a build.  WBT is a German company, their site has pictures of all of these guys walking around wearing lab coats, this communicates how serious they are about their connectors, they are doing _real_ research into connector design which requires lab coats.  Well apparently they didn't think to QC those RCAs to ensure all of them were of equal diameter, one of the two was so overly thick to the point that I could not fit a standard male RCA connector over it.  I had never seen that before nor have I seen it since.  So much for the lab coats.
> 
> Or Vampire RCAs where there is no ground tab, the ground connection is on the freaking body of the RCA, which is a 1cm^3 chunk of solid copper!  How am I supposed to heat it to make a good solder connection?  It's basically a heat sink.  I heated one to the point that the gold plating started to flake off.  Just plain stupid design.


I really like the Kimber RCA's.  About the only other boutique connectors I go for are Cardas binding posts on a speaker amp.  Several plating choices, not stupid expensive, and very nicely built.  

Remember the Edison Price binding posts that were all the rage 20+ years ago?  Damn, I hated those things....tighten them just a _little _too much and they would collapse.  Pretty expensive at the time too.


----------



## bcowen

L0rdGwyn said:


> Turntable is back in its home.  Still a lot of work to do setup wise, but it is a functioning turntable at this point.


Gorgeous!


----------



## L0rdGwyn (Aug 8, 2022)

bcowen said:


> I really like the Kimber RCA's.  About the only other boutique connectors I go for are Cardas binding posts on a speaker amp.  Several plating choices, not stupid expensive, and very nicely built.
> 
> Remember the Edison Price binding posts that were all the rage 20+ years ago?  Damn, I hated those things....tighten them just a _little _too much and they would collapse.  Pretty expensive at the time too.



Yeah those Kimber RCAs are well made and not crazy overpriced.  I'll have to check out the Cardas binding posts. Hmmm 20+ years ago, I remember it like it was yesterday...trading Pokémon cards with my friends...skateboarding to middle school, ERRR, I mean...trying out high end binding posts on my Snell type As and drinking fine scotch while discussing world affairs with my fellow adults.


----------



## Paladin79

L0rdGwyn said:


> Yeah those Kimber RCAs are well made and not crazy overpriced.  I'll have to check out the Cardas binding posts. Hmmm 20+ years ago, I remember it like it was yesterday...trading Pokémon cards with my friends...skateboarding to middle school, ERRR, I mean...trying out high end binding posts on my Snell type As and drinking fine scotch while discussing world affairs with my fellow adults.


As far as binding posts and associated connectors I like Pomona. Mind you many builds my employees did went to audio companies, audio engineers, and other professionals so it was best to use brands they recognized and trusted. I often refused to build with TRRS connectors because of their construction and low quality.


----------



## Paladin79

I call this a rain drop finish using gloss black lacquer and other techniques.


----------



## Xcalibur255

L0rdGwyn said:


> Or Vampire RCAs where there is no ground tab, the ground connection is on the freaking body of the RCA, which is a 1cm^3 chunk of solid copper!  How am I supposed to heat it to make a good solder connection?  It's basically a heat sink.  I heated one to the point that the gold plating started to flake off.  Just plain stupid design.


In fairness to Vampire you can get them both with and without a ground tab, though a case could probably be made that the version without probably just shouldn't exist.  Each variant has its own part and model number.


----------



## Paladin79 (Aug 9, 2022)

Xcalibur255 said:


> In fairness to Vampire you can get them both with and without a ground tab, though a case could probably be made that the version without probably just shouldn't exist.  Each variant has its own part and model number.


Each type has their purpose but I use wooden cabinets so I buy them with a solder lug.

I prefer these myself.

https://www.tecnec.com/product/nf2d-b-2/neutrik-nf2d-b-2-rca-panel-mount-jack-w-colored-isolation-washer-red

And  I really like these RCA males.

https://www.tecnec.com/product/nf2cb-2/neutrik-nf2c-b-2-rca-professional-connector-pair


----------



## CJG888

L0rdGwyn said:


> Turntable is back in its home.  Still a lot of work to do setup wise, but it is a functioning turntable at this point.


A wonderful turntable!

Nevertheless, I wonder if the mat, with its limited contact surfaces, might be holding it back.

Have you considered an Achromat or, perhaps, a copper mat?


----------



## L0rdGwyn (Aug 9, 2022)

CJG888 said:


> A wonderful turntable!
> 
> Nevertheless, I wonder if the mat, with its limited contact surfaces, might be holding it back.
> 
> Have you considered an Achromat or, perhaps, a copper mat?



Thanks, I have considered changing the mat, but not those two options specifically.
 Clearly Thorens felt there was some benefit to having minimal contact with the record with this mat design, I have to wonder what they were thinking at the time.


----------



## Paladin79

https://www.ebay.com/itm/334513496275?hash=item4de28ee0d3:g:D-cAAOSw6pZhWzNC

Here are some of the exact pots for sale that I mentioned a few days ago, for this kind of money I need to put 100 or so up for sale to help pay for the audio equipment I am buying. This would be a good time not to mention what I paid for the pots.   Maybe a joint listing for those and some black gate Rubycons lol. I thought there was serious money in holding onto Melz tubes but this is even better. I also have cases of other capacitors that a Russian friend talked me into buying, there is a good chance they will end up selling for premium prices soon enough.


----------



## Monsterzero

Conducting an Auteur Classic vs. Auteur OG shootout the last few nights. My early thoughts can be found here and here.

Running the ugly Tung Sol black cans 6J5 and Bendix 6080wb in the Airmid and Tesla El51 and USAF 596 in the rectifier slot on the Lampi


----------



## mordy

Monsterzero said:


> Conducting an Auteur Classic vs. Auteur OG shootout the last few nights. My early thoughts can be found here and here.
> 
> Running the ugly Tung Sol black cans 6J5 and Bendix 6080wb in the Airmid and Tesla El51 and USAF 596 in the rectifier slot on the Lampi


I think that the consensus is that most metal 6J5 were made by RCA. This tube and the metal 6N7 are very underrated tubes.


----------



## jgwtriode

So just how good are the RCA metal 6J5's Monster?

jgwtriode


----------



## Monsterzero (Aug 10, 2022)

jgwtriode said:


> So just how good are the RCA metal 6J5's Monster?
> 
> jgwtriode


Theyre ok, better than average but not God tier. I'm on the lookout for some ST types but they seem scarce, so these will suffice in the interim. theyre worth having but dont expect to have your world rocked like the GEC or NU did to you.

EDIT: oh wait RCA metal? No clue, I dont have a pair. Sorry I thought you were asking about the Tung Sols.
I did just pickup a pair of GE cans on the cheap due to the + comments in the 6J5 spreadshhet, but havent tried them yet.


----------



## mordy

Monsterzero said:


> Theyre ok, better than average but not God tier. I'm on the lookout for some ST types but they seem scarce, so these will suffice in the interim. theyre worth having but dont expect to have your world rocked like the GEC or NU did to you.
> 
> EDIT: oh wait RCA metal? No clue, I dont have a pair. Sorry I thought you were asking about the Tung Sols.


The Tung Sols metal 6J5 probably were made by RCA. And your description is right on.


----------



## Monsterzero

mordy said:


> I think that the consensus is that most metal 6J5 were made by RCA. This tube and the metal 6N7 are very underrated tubes.


 Thats interesting. I will have to bounce the GEs off of the TSs and see if theres a difference, though my GE cans are 6C5. Did RCA make those as well?


----------



## jgwtriode

Monsterzero said:


> Thats interesting. I will have to bounce the GEs off of the TSs and see if theres a difference, though my GE cans are 6C5. Did RCA make those as well?


Fascinating stuff, may pickup some metal cans just to play with.

Thanks

jgwtriode


----------



## CJG888

L0rdGwyn said:


> Thanks, I have considered changing the mat, but not those two options specifically.
> Clearly Thorens felt there was some benefit to having minimal contact with the record with this mat design, I have to wonder what they were thinking at the time.


Frankly, these “twin ring” mats were not primarily chosen for sound quality reasons, but to allow the easy removal of 7” singles and 10” LPs…


----------



## sam6550a

Paladin79 said:


> https://www.ebay.com/itm/334513496275?hash=item4de28ee0d3:g:D-cAAOSw6pZhWzNC
> 
> Here are some of the exact pots for sale that I mentioned a few days ago, for this kind of money I need to put 100 or so up for sale to help pay for the audio equipment I am buying. This would be a good time not to mention what I paid for the pots.   Maybe a joint listing for those and some black gate Rubycons lol. I thought there was serious money in holding onto Melz tubes but this is even better. I also have cases of other capacitors that a Russian friend talked me into buying, there is a good chance they will end up selling for premium prices soon enough.


Yikes!


----------



## L0rdGwyn

CJG888 said:


> Frankly, these “twin ring” mats were not primarily chosen for sound quality reasons, but to allow the easy removal of 7” singles and 10” LPs…



Gotcha, I'll look at replacing it at some point!


----------



## Paladin79 (Aug 10, 2022)

Monsterzero said:


> Theyre ok, better than average but not God tier. I'm on the lookout for some ST types but they seem scarce, so these will suffice in the interim. theyre worth having but dont expect to have your world rocked like the GEC or NU did to you.
> 
> EDIT: oh wait RCA metal? No clue, I dont have a pair. Sorry I thought you were asking about the Tung Sols.
> I did just pickup a pair of GE cans on the cheap due to the + comments in the 6J5 spreadshhet, but havent tried them yet.


Having done a comparison of most any 6sn7 and equivalent known to man there are a few types of Sylvania ST 6j5's I really like.

Wartime versions were the VT-192, Loktal can be quite good but I have not searched for them in a couple years so I do not know availability.


 Others by Sylvania I really like have three hole black plates like the Bad Boys so I dubbed them naughty girls. They are in the Vali 2 in the last photo. There were also some grey plates and some with two holes and bottom getters as best I recall.

The NU's did not test very well and we tried a couple NOS pairs, GEC did pretty well. None of them did well enough to finish in the top 52 tubes though in our blind testing unfortunately. We should done a different category for some of the 6j5's perhaps. GEC's finished in the top 100 so that is doing pretty well in a 1500 tube type comparison.


----------



## CJG888

L0rdGwyn said:


> Gotcha, I'll look at replacing it at some point!


The easiest thing to do might be to do what Linn did to the TD150: replace the rubber mat with a felt one. This will improve contact between LP and platter, but I don’t know how this solution hopes to control platter resonances. Maybe the „liveliness“ and „PRaT“ of the early LP12 was just due to a ringing platter!


----------



## CJG888

Running slightly too fast might help, too…

OK, I’m just being cynical now!


----------



## jgwtriode

I remember my Linn Turntable setup from years ago, a bit of nostalgia!

Happy listening,

jgwtriode


----------



## CJG888

I‘m sure a properly-sorted TD125 with a good electronic speed controller will whip the current LP12‘s a$$. Maybe a head-to-head can be arranged…


----------



## Paladin79

The last turntable I rebuilt was a Marantz 6300. I needed to keep it as stock as possible for a listening session friends and I put together.


----------



## Xcalibur255 (Aug 10, 2022)

Monsterzero said:


> Theyre ok, better than average but not God tier. I'm on the lookout for some ST types but they seem scarce, so these will suffice in the interim. theyre worth having but dont expect to have your world rocked like the GEC or NU did to you.
> 
> EDIT: oh wait RCA metal? No clue, I dont have a pair. Sorry I thought you were asking about the Tung Sols.
> I did just pickup a pair of GE cans on the cheap due to the + comments in the 6J5 spreadshhet, but havent tried them yet.


The ST glass 6J5 are kind of a double-edged sword in general.  My opinion based on my entire collection thus far: the ST glass tubes seem to generally have an advantage in resolution and overall depth of presentation, but they are also tend to be more problematic tubes with higher rates of noise and microphony issues.  So with pleasure comes pain.  I have yet to hear a 6J5GT be noisy, and some of them like the Raytheon WGT have really great build quality in general.


----------



## jgwtriode

Kind of overwhelming but the latest all out Linn LP 12 is the Klimax at 20,000 Euros.  They just reviewed it in Stereophile.  Wow!

jgwtriode


----------



## Monsterzero

Xcalibur255 said:


> The ST glass 6J5 are kind of a double-edged sword in general.  My opinion based on my entire collection thus far: the ST glass tubes seem to generally have an advantage in resolution and overall depth of presentation, but they are also tend to be more problematic tubes with higher rates of noise and microphony issues.  So with pleasure comes pain.  I have yet to hear a 6J5GT be noisy, and some of them like the Raytheon WGT have really great build quality in general.


 Keenan's amp is really quiet, like_ really _quiet. Tubes that were so noisy that they were unusable in my GOTL are silent on the Airmid. Oddly the noisiest tube on the Airmid is one of the Tung Sol black cans I used last night. That black background was one of the many reasons I decided to sell my Glenn and pick up the Airmid.

The only ST types I have are the GEC l63 smoked glass- dead silent and a pair of Zenith 6C5s. Those have a very, very faint hum in one of them.


----------



## Paladin79

Monsterzero said:


> Keenan's amp is really quiet, like_ really _quiet. Tubes that were so noisy that they were unusable in my GOTL are silent on the Airmid. Oddly the noisiest tube on the Airmid is one of the Tung Sol black cans I used last night. That black background was one of the many reasons I decided to sell my Glenn and pick up the Airmid.
> 
> The only ST types I have are the GEC l63 smoked glass- dead silent and a pair of Zenith 6C5s. Those have a very, very faint hum in one of them.


I stopped designing amps or I would have let you hear one of mine. I may build one more for myself that is prettier than the one I donated to @bcowen but that will be it for 6sn7's and the 6080 family. Tubes of choice for me were Tung Sol 5998's and some exceedingly rare Melz 6n8s from the early fifties. I own plenty of headphones and have heard most of the top of the line units made but I really prefer Focal Utopias. I do not do closed headphones anymore, they are just not for me.  My local audiophile group may do a study of power tubes down the road as well as headphone amps. Our tests groups can be fifty people or more using music that was recorded to show off 25 audio criteria. A tube might do well in several areas but not score well enough overall to be considered toward the top. It can be a little clinical but in the end it has to do with what people hear and notice in the blind studies.  In a sense applying objective thinking to a subjective subject. 

Recently we did a small and fun study of boutique fuses and fortunately four test amps I made were still very close to each other in specs using our baseline of Tung Sol 5998 tubes as well as four 6sn7's I best not talk about. Naturally I have done plenty of studies with different wire and cables, one young woman could consistently pick out types of wire in a blind study. Most are fortunate to tell copper wire from solid silver.


----------



## JazzVinyl (Aug 10, 2022)

mordy said:


> I think that the consensus is that most metal 6J5 were made by RCA. This tube and the metal 6N7 are very underrated tubes.



Agree with this.   The metal envelope tubes, never got their justice, probably because of "no glow".  They take a while to build up a full head of steam.  Much longer than their glass envelope brethren. Leave them in for an hour, then see what you think.

Don't forget the Mullard FDD20 - a beautiful "blue hue" glass envelope 12v version of the 6N7 family of tubes, in the weird European side contact mount. 
These were heavenly in FA's Elise, not so impressive in the GOTL. 

But some amps really go to town, like a pro, with them.

I have mine running today, in a Little Dot MK9 (another amp that is absolutely silent when no audio input is present).  
My example was made in Italy during early years of WWII when they were still part of the military alliance of Germany, Italy and Japan,

Count the MK9 as another amp that *likes* the FDD20.


----------



## Monsterzero

Paladin79 said:


> I best not talk about. Naturally I have done plenty of studies with different wire and cables, one young woman could consistently pick out types of wire in a blind study. Most are fortunate to tell copper wire from solid silver.


 I did a cable shootout a couple years ago...6 pairs of RCAs, 4 different USB cables and some high end power cables vs. not so high end. I did a video on my Youtube channel ( link in signature) revealing my findings. To say that I was a bit surprised, especially with the USB section, is an understatement.

I have not played around with various fuses yet, but I'd like to when funds permit. 

I do understand your hesitancy to discuss these topics in the forums though.


----------



## Xcalibur255

Monsterzero said:


> Keenan's amp is really quiet, like_ really _quiet. Tubes that were so noisy that they were unusable in my GOTL are silent on the Airmid. Oddly the noisiest tube on the Airmid is one of the Tung Sol black cans I used last night. That black background was one of the many reasons I decided to sell my Glenn and pick up the Airmid.
> 
> The only ST types I have are the GEC l63 smoked glass- dead silent and a pair of Zenith 6C5s. Those have a very, very faint hum in one of them.


Different operating points and active loading might explain the difference too.  It's fairly common for a tube to be noisy in one amp and quiet in another, and I've also found specific pairings of driver and output tubes that seem to create noise issues but each tube will independently be noise free when operated with different tube pairings.

Case in point some NU 6J5G I just bought are humming in my GOTL, but I think there's a decent chance they will be quiet in the 1101 Audio KT150 when I try them there.  At least I hope so because that's the amp I actually bought them for.    I may try a different power tube combo with them before taking them out of the GOTL too.

Glenn's amps tend to be a good worst-case scenario sanity check for noisy tubes because he often used aggressive operating points for his amps that would stress them a bit.  If a tube is quiet in the GOTL I fully expect it to be quiet in any other amp it could be inserted into, that's been my experience over the past 11 years of owning this amp.


----------



## Paladin79 (Aug 10, 2022)

Monsterzero said:


> I did a cable shootout a couple years ago...6 pairs of RCAs, 4 different USB cables and some high end power cables vs. not so high end. I did a video on my Youtube channel ( link in signature) revealing my findings. To say that I was a bit surprised, especially with the USB section, is an understatement.
> 
> I have not played around with various fuses yet, but I'd like to when funds permit.
> 
> I do understand your hesitancy to discuss these topics in the forums though.


I watched a bit of your video on cables. I build all of my own including USB with some incredible Belden cable. About the only thing I have not worked with, designed or modified has been DAC's but my preferences were very close to my group's likes except I reversed the order of two DACS compared to what was chosen by the majority.  One young lady matched the groups selection top to bottom on all 20 DACS. Some of our results are supposed to be published so I try not to go into too many specifics.

The fuse test was not real serious but a few friends went along with it.🤪


----------



## L0rdGwyn

Some of the noise issues of the GOTL stem from using high gain output tubes.  Unlike a cathode follower output, an SRPP has voltage gain, so using high gain output tubes like 6BX7 will increase the volume sensitivity as well as the noise floor.  There is no step down output transformer, so what you end up with is an excessive amount of gain for headphones in that configuration.  The amp was originally made for 6AS7G with its mu of 2 which is much more reasonable. Hope that makes sense, at work so cannot say more right now!


----------



## Paladin79

L0rdGwyn said:


> Some of the noise issues of the GOTL stem from using high gain output tubes.  Unlike a cathode follower output, an SRPP has voltage gain, so using high gain output tubes like 6BX7 will increase the volume sensitivity as well as the noise floor.  There is no step down output transformer, so what you end up with is an excessive amount of gain for headphones in that configuration.  The amp was originally made for 6AS7G with its mu of 2 which is much more reasonable. Hope that makes sense, at work so cannot say more right now!


I am so used to not being able to comment on specific products that may be advertised here I tend to back away from such discussions.😜 I got in trouble once for saying a specific headphone might be my second choice.


----------



## Monsterzero

L0rdGwyn said:


> Some of the noise issues of the GOTL stem from using high gain output tubes.  Unlike a cathode follower output, an SRPP has voltage gain, so using high gain output tubes like 6BX7 will increase the volume sensitivity as well as the noise floor.  There is no step down output transformer, so what you end up with is an excessive amount of gain for headphones in that configuration.  The amp was originally made for 6AS7G with its mu of 2 which is much more reasonable. Hope that makes sense, at work so cannot say more right now!


I do not attempt to pretend that I understand 95% of what some of you guys talk about in the diy world, but I do understand that certain tubes have a higher gain factor than others and what the pitfalls of using these tubes can present, but when I say many tubes were unlistenable on the GOTL, I'm talking about using them with 6as7g and 6080 tubes, not just 6bx7s


----------



## JazzVinyl

Monsterzero said:


> I do not attempt to pretend that I understand 95% of what some of you guys talk about in the diy world, but I do understand that certain tubes have a higher gain factor than others and what the pitfalls of using these tubes can present, but when I say many tubes were unlistenable on the GOTL, I'm talking about using them with 6as7g and 6080 tubes, not just 6bx7s


I did not have "many" tubes that were un-listenable in the GOTL.  That was quite rare for me.  But it was not what you would call "dead silent" with no input applied.

Mine had a Lindahl transformer problem as well, it made a very annoying / loud buzzing noise when some combinations of low mu (6AS7/6080) power tubes were used.  There was no cure except "not to use those tube combos". Never once did it with 6BX/BL7's...


----------



## Monsterzero

Mine had the Lundahl upgrade as well


----------



## L0rdGwyn

Paladin79 said:


> I am so used to not being able to comment on specific products that may be advertised here I tend to back away from such discussions.😜 I got in trouble once for saying a specific headphone might be my second choice.



Ahh well I don't have MOT status, so for now I can speak my mind.  The GOTL is a DIY amplifier no longer in production, I'm familiar with it as I've owned one and also done work on a few of them.  If my MOT status were to change, I'd probably have to scrub my posts, I aimed some pretty harsh criticisms at a certain 300B amplifier not too long ago, that would probably have to go D:



Monsterzero said:


> I do not attempt to pretend that I understand 95% of what some of you guys talk about in the diy world, but I do understand that certain tubes have a higher gain factor than others and what the pitfalls of using these tubes can present, but when I say many tubes were unlistenable on the GOTL, I'm talking about using them with 6as7g and 6080 tubes, not just 6bx7s



Oh okay well if they were still noisy with low gain output tubes, then it was likely heater to cathode leakage, which would be an issue inherent to the input tubes themselves.  The heater circuit in the Airmid has a DC elevation above ground, which makes that leakage a non issue.


----------



## JazzVinyl

L0rdGwyn said:


> Oh okay well if they were still noisy with low gain output tubes, then it was likely heater to cathode leakage, which would be an issue inherent to the input tubes themselves.  The heater circuit in the Airmid has a DC elevation above ground, which makes that leakage a non issue.



Agree, that is THE way to go.  I was able to cure many noise ills in the GOTL by externally heating the SN7 driver socket with clean DC.


----------



## L0rdGwyn

JazzVinyl said:


> Agree, that is THE way to go.  I was able to cure many noise ills in the GOTL by externally heating the SN7 driver socket with clean DC.



Regulated DC for heaters are definitely a good option when ultra low noise is needed (I use them in my phono stage and DAC), but this is actually AC heaters with a ground lift, the heater circuit is referenced to a positive voltage above ground.  This basically makes the heater and cathode function as a reversed bias diode, so no noisy leakage currents from the heater will enter the tube's cathode.  IME, for your average amplifier using indirectly-heated tubes, AC heaters are just fine and DC is a luxury, it's only when you are talking about small signal amplification (e.g., phono stage, DAC) with tubes that I would say DC heaters are a necessity.


----------



## Xcalibur255 (Aug 10, 2022)

Monsterzero said:


> I do not attempt to pretend that I understand 95% of what some of you guys talk about in the diy world, but I do understand that certain tubes have a higher gain factor than others and what the pitfalls of using these tubes can present, but when I say many tubes were unlistenable on the GOTL, I'm talking about using them with 6as7g and 6080 tubes, not just 6bx7s



To phrase a different way, one of the things Keenan is saying here is that some circuit designs are setup in such a way that the output tubes do not contribute any amplifying gain to the music signal at all.  I believe his Airmid is like this, where as the GOTL on the other hand uses the output tubes in a way where they do contribute gain.  Each style of circuit has its pros and cons but this is one of the reasons Airmid achieves lower noise and a blacker background over the GOTL.  This is also a major reason why the original GOTL design is so fussy with the 5998, because the original first implementation of this amp was meant specifically to use the 6080/6AS7 and the 5998 tube has 2.5x higher gain which was bringing out lots of power supply noise you were not originally meant to hear.

Things did change over time of course, some of this is only really applicable to really old versions of the GOTL like mine.


----------



## mordy

Xcalibur255 said:


> To phrase a different way, one of the things Keenan is saying here is that some circuit designs are setup in such a way that the output tubes do not contribute any amplifying gain to the music signal at all.  I believe his Airmid is like this, where as the GOTL on the other hand uses the output tubes in a way where they do contribute gain.  Each style of circuit has its pros and cons but this is one of the reasons Airmid achieves lower noise and a blacker background over the GOTL.  This is also a major reason why the original GOTL design is so fussy with the 5998, because the original first implementation of this amp was meant specifically to use the 6080/6AS7 and the 5998 tube has 2.5x higher gain which was bringing out lots of power supply noise you were not originally meant to hear.
> 
> Things did change over time of course, some of this is only really applicable to really old versions of the GOTL like mine.


As  I recall, there was a GOTL option for a 5998 switch, but the people who ordered it did not notice much of a difference.


----------



## JazzVinyl

L0rdGwyn said:


> Regulated DC for heaters are definitely a good option when ultra low noise is needed (I use them in my phono stage and DAC), but this is actually AC heaters with a ground lift, the heater circuit is referenced to a positive voltage above ground.  This basically makes the heater and cathode function as a reversed bias diode, so no noisy leakage currents from the heater will enter the tube's cathode.  IME, for your average amplifier using indirectly-heated tubes, AC heaters are just fine and DC is a luxury, it's only when you are talking about small signal amplification (e.g., phono stage, DAC) with tubes that I would say DC heaters are a necessity.



Was just reading how the elevated ground lift works.  Seems extremely easy, connect the transformers' CT to a positive DC voltage.  Why is this not the standard practice?


----------



## L0rdGwyn

JazzVinyl said:


> Was just reading how the elevated ground lift works.  Seems extremely easy, connect the transformers' CT to a positive DC voltage.  Why is this not the standard practice?



It is extremely easy and I have no idea! 🤷‍♂️


----------



## Xcalibur255 (Aug 10, 2022)

mordy said:


> As  I recall, there was a GOTL option for a 5998 switch, but the people who ordered it did not notice much of a difference.


This was my idea actually (in the GOTL amp world at least, certainly not in the larger world of tube amps).  I was teaching myself about how different tubes bias up differently in the same circuit and learned that the 5998 can and often does sound thin or lean in many circuits people use it in because it runs "cold" in those circuits.  For example an original GOTL will bias a 6080 tube at 100mA plate current, but when you drop a 5998 in there it will bias up at only 60mA.  The 5998 actually has higher max plate current and higher max dissipation ratings too so there is lots of room to go up with the plate current.

You can kind of go down a rabbit hole with this actually.  It gets debated a lot whether to run a tube hard or not, and whether it changes the sound or not.  I think it's at least partially dependent on the circuit implementation too so you probably can't apply conclusions generally across different amps.  My ears have consistently told me over the years that at a certain point where the tube is running cold (well below its maximum bias ratings) it will begin to have a skeletal sound.  Not the same thing as having thin or weak bass, it's more like the musical notes sound thin on the inside if that makes any sense.

So I convinced Glenn to rig up a switch that would change the biasing so the 5998 would draw more current and bias a bit "hotter" than it would with the 6080 bias value.  Glenn was pretty conservative about it too, he didn't want somebody to be able to red plate a 6080 if the switch was in the wrong position so it doesn't change the bias all that much, only around 20mA I think.  I know some people didn't think it made that much of a difference but I will always stand firm on my own opinion.  My ears heard a fairly big difference, a very positive one.  The 5998 to me sounds bolder and meatier and somehow more relaxed and less "in your face" at the same time with the higher bias.  Like its speaking more confidently with a smoother voice instead of trying to shout with a thin screechy one.  I'm trying to explain the sound via analogy here of course, the differences were not huge like the wording might make it seem, but I don't really have to listen that closely to hear it personally.  It's always been a big enough change that it was easy to hear for me.

A different circuit that uses a CCS for biasing might turn all of this on its head too.

edit:  cleaned up some stream of consciousness typing mistakes here and there.


----------



## JazzVinyl (Aug 10, 2022)

The GOTL allowed a dizzying array of tubes to be used.  The devout tube rollers' dream amp!


----------



## Paladin79

JazzVinyl said:


> The GOTL allowed a dizzying array or tubes to be used.  The devout tube rollers' dream amp!


lol


----------



## whirlwind

I have the 5998 switch on my GOTL.

I have not used it in quite some time though.


----------



## Xcalibur255

Honestly neither have I, but that's mostly because the 5998 is so expensive to replace now and the headphones I use with the amp these days have better synergy with tubes like the RCA 6AS7.


----------



## Paladin79

Xcalibur255 said:


> Honestly neither have I, but that's mostly because the 5998 is so expensive to replace now and the headphones I use with the amp these days have better synergy with tubes like the RCA 6AS7.


There have been some NOS GE 5998A's available for very little money. Several friends tried them and many liked the tube because of how it sounded with low frequencies. There were a couple that had to have the pins re-soldered, the gentleman selling them had no way to test them but they were new in the box. I got one for $25 and later paid around $40 each.


----------



## Xcalibur255

It was my understanding that the 5998A is not equivalent to the 5998?  It's been quite a few years now since I've been in a conversation on the subject so I can't quite recall now.


----------



## Zachik

JazzVinyl said:


> The GOTL allowed a dizzying array of tubes to be used.  The devout tube rollers' dream amp!


Yup. That drove me to create a table of compatible tubes - link is in my signature


----------



## mordy

Xcalibur255 said:


> It was my understanding that the 5998A is not equivalent to the 5998?  It's been quite a few years now since I've been in a conversation on the subject so I can't quite recall now.


From the GE 5998-A spec sheet:
"The 5998-A is a low-mu, twin triode designed for service as a series regulator in d-c power supplies. Except for the use of T-12 envelope and a different base, the 5998-A is identical to the 5998."
file:///D:/Downloads/5998A000.pdf
However, based on reading, the GE (and Sylvania) 5998-A never garnered as much enthusiasm as the TS 5998 tube.
Which leads us to the 6AS7GA tube which is supposed to be identical to the 6AS7G but with a straight glass envelope.
Again, to me it does not sound the same as the 6AS7G tube.


----------



## Paladin79

Xcalibur255 said:


> It was my understanding that the 5998A is not equivalent to the 5998?  It's been quite a few years now since I've been in a conversation on the subject so I can't quite recall now.


specs are readily available.  I use them in amps I made for 6080's and 6as7g's with no issue. I prefer the Tung Sol of course.


----------



## raindownthunda (Aug 11, 2022)

mordy said:


> From the GE 5998-A spec sheet:
> "The 5998-A is a low-mu, twin triode designed for service as a series regulator in d-c power supplies. Except for the use of T-12 envelope and a different base, the 5998-A is identical to the 5998."
> file:///D:/Downloads/5998A000.pdf
> However, based on reading, the GE (and Sylvania) 5998-A never garnered as much enthusiasm as the TS 5998 tube.
> ...


I have several Sylvania 5998A and was surprised with how good they sound. Wasn’t expecting much but they stayed in my amp for quite a while. Much more dynamic and richer than the Sylvania 6080. They do sound different to me than the TS 5998.


----------



## Paladin79

mordy said:


> From the GE 5998-A spec sheet:
> "The 5998-A is a low-mu, twin triode designed for service as a series regulator in d-c power supplies. Except for the use of T-12 envelope and a different base, the 5998-A is identical to the 5998."
> file:///D:/Downloads/5998A000.pdf
> However, based on reading, the GE (and Sylvania) 5998-A never garnered as much enthusiasm as the TS 5998 tube.
> ...


I offered it up as an alternative based on price and availability, I have not bought one for about a year. For higher gain there is always the Cetron 7236. My preferences on 6AS7G's are the Chatham bottom getters, along with some vintage Winged C's used by the Russian military. According to one friend, the military always got the best products.


----------



## sam6550a

Paladin79 said:


> I offered it up as an alternative based on price and availability, I have not bought one for about a year. For higher gain there is always the Cetron 7236. My preferences on 6AS7G's are the Chatham bottom getters, along with some vintage Winged C's used by the Russian military. According to one friend, the military always got the best products.


The only significant difference is in transconductance, with the 5998 at 14000 umho, and the 5998A at 15500 umho. I think that the 5998A is a fine, low cost alternative to other 6AS7/6080 variants. Of course, others may disagree.


----------



## Xcalibur255

mordy said:


> From the GE 5998-A spec sheet:
> "The 5998-A is a low-mu, twin triode designed for service as a series regulator in d-c power supplies. Except for the use of T-12 envelope and a different base, the 5998-A is identical to the 5998."
> file:///D:/Downloads/5998A000.pdf
> However, based on reading, the GE (and Sylvania) 5998-A never garnered as much enthusiasm as the TS 5998 tube.
> ...



Yeah, that's jogging my memory a little.  It's not a spec thing, what I meant was that people seemed to think they didn't sound as good.  I haven't compared myself so I don't have a personal opinion on it.


----------



## bcowen

Paladin79 said:


> There have been some NOS GE 5998A's available for very little money. Several friends tried them and many liked the tube because of how it sounded with low frequencies. There were a couple that had to have the pins re-soldered, the gentleman selling them had no way to test them but they were new in the box. I got one for $25 and later paid around $40 each.


I agree that the GE 5998A is a good $25 tube.   🤣  🤣


----------



## Paladin79

Xcalibur255 said:


> Yeah, that's jogging my memory a little.  It's not a spec thing, what I meant was that people seemed to think they didn't sound as good.  I haven't compared myself so I don't have a personal opinion on it.


I am talking about a minimum of ten people who have heard them and had positive comments. I can include @bcowen I suppose, if I have to.🤪
Unfortunately he has a negative expectation bias where GE is concerned.


----------



## bcowen

Paladin79 said:


> I am talking about a minimum of ten people who have heard them and had positive comments. I can include @bcowen I suppose, if I have to.🤪
> Unfortunately he has a negative expectation bias where GE is concerned.


Huh?  I don't suffer from expectation bias.  I know how things are supposed to sound before I even hear them.   🤣


----------



## Paladin79

bcowen said:


> Huh?  I don't suffer from expectation bias.  I know how things are supposed to sound before I even hear them.   🤣


I stand corrected, sort of.😁
I could send you mini radials to sample but you must already know what they sound like without hearing them.


----------



## bcowen

Paladin79 said:


> I stand corrected, sort of.😁
> I could send you mini radials to sample but you must already know what they sound like without hearing them.


Yes, of course. And I really like them!    🤣


----------



## Paladin79

bcowen said:


> Yes, of course. And I really like them!    🤣


You better or I will send people to collect the second prettiest amp I ever made.😸😸


----------



## mordy (Aug 11, 2022)

raindownthunda said:


> I have several Sylvania 5998A and was surprised with how good they sound. Wasn’t expecting much but they stayed in my amp for quite a while. Much more dynamic and richer than the Sylvania 6080. They do sound different to me than the TS 5998.


There was one make of the 5998A that people liked, but I can't remember what it was. But it was a lesser known brand.
PS: Now I remembered - the brand was Gold Aero.


----------



## jgwtriode (Aug 11, 2022)

Audio pre-cognition. Preaudience!   That actually has another meaning but hey.  Hearing before you have heard. Indeed.  Quite a talent.  LOL!

jgwtriode


----------



## bcowen

jgwtriode said:


> Audio pre-cognition. Preaudience!   That actually has another meaning but hey.  Hearing before you have heard. Indeed.  Quite a talent.  LOL!
> 
> jgwtriode


It's taken many years of training and even more years of practice, but my wife will be the first to tell you that I've constantly heard it all before.   🤣


----------



## mordy

Paladin79 said:


> I offered it up as an alternative based on price and availability, I have not bought one for about a year. For higher gain there is always the Cetron 7236. My preferences on 6AS7G's are the Chatham bottom getters, along with some vintage Winged C's used by the Russian military. According to one friend, the military always got the best products.


A Russian tube amp designer told me that the 6N5S (6H5C) is the military version of the 6H13C and made to tighter specifications.


----------



## jgwtriode

bcowen said:


> It's taken many years of training and even more years of practice, but my wife will be the first to tell you that I've constantly heard it all before.   🤣


Hilarious.   That had me rolling on the floor instead of tubes.  Thanks for that!

jgwtriode


----------



## Paladin79 (Aug 11, 2022)

I have heard various stories from my Russian contacts so that may well be true.  Many of the older Winged C’s I prefer are 6h5C. A Russian card partner introduced me to several Russian suppliers and I trust her instincts. 

Hopefully some of you know the Svetlana winged C’s are based on RCA tubes. I own plenty of both from the 50’s.

Sorry I am in several discussions, this was my response to Mordy.

I should mention my first job out of college was with RCA and a good friend’s grandfather was in tube design. I have heard some prototypes that are one of a kind and priceless.😉 We included a couple in some 6SN7 comparisons.


----------



## mordy

Paladin79 said:


> I have heard various stories from my Russian contacts so that may well be true.  Many of the older Winged C’s I prefer are 6h5C. A Russian card partner introduced me to several Russian suppliers and I trust her instincts.
> 
> Hopefully some of you know the Svetlana winged C’s are based on RCA tubes. I own plenty of both from the 50’s.
> 
> Sorry I am in several discussions, this was my response to Mordy.


I read somewhere that RCA sold a tube production line to Svetlana in the late 30's, and I always thought that the 6H13C was based on the RCA 6AS7G. I also think that the Svetlana 6H13C is the most faked tube with versions popping up monthly under all kinds of various famous names. Got to love them TFK-Haltron 6AS7G tubes - only $500/pair:
https://www.ebay.com/itm/254195578638?epid=4039142499&hash=item3b2f3cb70e:g:ZTEAAOSwdSRZ-5XN
No matter how many skillful camera angles you use, you can't hide them inverted saucer getters cups:




Reading the ad we are informed that this Western Germany production was manufactured in the UK by Marconi.

Here WE GE again...


----------



## Paladin79

mordy said:


> I read somewhere that RCA sold a tube production line to Svetlana in the late 30's, and I always thought that the 6H13C was based on the RCA 6AS7G. I also think that the Svetlana 6H13C is the most faked tube with versions popping up monthly under all kinds of various famous names. Got to love them TFK-Haltron 6AS7G tubes - only $500/pair:
> https://www.ebay.com/itm/254195578638?epid=4039142499&hash=item3b2f3cb70e:g:ZTEAAOSwdSRZ-5XN
> No matter how many skillful camera angles you use, you can't hide them inverted saucer getters cups:
> 
> ...


If I get time tomorrow I will show some early variations without inverted saucers and of course extra shielding. Russians gave me a lot of versions that just needed the solder replaced in the pins. This happens with Melz, Fotons, and even Tung Sol 5998’s. I say replace because I do not reflow solder in the tube pins. I have passed on this methodology to @bcowen and many others.


----------



## Xcalibur255

bcowen said:


> I agree that the GE 5998A is a good $25 tube.   🤣  🤣


Who are you and what have you done with Bill?


----------



## Paladin79 (Aug 12, 2022)

mordy said:


> I read somewhere that RCA sold a tube production line to Svetlana in the late 30's, and I always thought that the 6H13C was based on the RCA 6AS7G. I also think that the Svetlana 6H13C is the most faked tube with versions popping up monthly under all kinds of various famous names. Got to love them TFK-Haltron 6AS7G tubes - only $500/pair:
> https://www.ebay.com/itm/254195578638?epid=4039142499&hash=item3b2f3cb70e:g:ZTEAAOSwdSRZ-5XN
> No matter how many skillful camera angles you use, you can't hide them inverted saucer getters cups:
> 
> ...


Here are some Svetlanas from the 50's. This one was made for their navy, extra shielding at the bottom, square getter holders with a round top.



More of the same from the fifties but non-military.



Finally a military RCA from 1939, top getter but with the same lower shield as the Russian military tubes.


I should mention I have both a 6H13C and a 6H5C from 1959 and I can find no difference, they have the same inspection markings, same size logos etc and test the same.


----------



## bcowen

Xcalibur255 said:


> Who are you and what have you done with Bill?


I didn't say it was a good $30 tube.  I'm still me.  🤣


----------



## mordy

Paladin79 said:


> Here are some Svetlanas from the 50's. This one was made for their navy, extra shielding at the bottom, square getter holders with a round top.
> 
> 
> 
> ...


Interesting - the signature getter holder inverted saucers were square in the beginning, and then became round.
Do the early Svetlana tubes sound different than the later ones?
Re the RCA 6AS7G it does not seem likely that it is from 1939. The first digit(s) in the date code (not visible in the picture) should indicate the year.


----------



## Paladin79 (Aug 12, 2022)

mordy said:


> Interesting - the signature getter holder inverted saucers were square in the beginning, and then became round.
> Do the early Svetlana tubes sound different than the later ones?
> Re the RCA 6AS7G it does not seem likely that it is from 1939. The first digit(s) in the date code (not visible in the picture) should indicate the year.


I prefer the sound of the Svetlanas from the 50's myself, especially the 1955 Navy issue. I like the mids a bit better than some of the later ones. I can tell no difference in sound between two from 1959 with the two numbering schemes.

I may have gifted one to Cowen so he might be able to address the sound as well. I also gave him a prized Melz from 1954 or 1956, I dealt with a lot of Russian tubes while filling out my collections.

Somewhere I also have some bottom getter tubes made by Chatham for RCA as best I recall. Friends are starting to work on tube comparisons and I provided twenty such tubes and the Chathams may well have been in there.


----------



## bcowen

Paladin79 said:


> I prefer the sound of the Svetlanas from the 50's myself, especially the 1955 Navy issue. I like the mids a bit better than some of the later ones. I can tell no difference in sound between two from 1959 with the two numbering schemes.
> 
> I may have gifted one to Cowen so he might be able to address the sound as well. I also gave him a prized Melz from 1954 or 1956, I dealt with a lot of Russian tubes while filling out my collections.
> 
> *Somewhere I also have some bottom getter tubes made by Chatham for RCA *as best I recall. Friends are starting to work on tube comparisons and I provided twenty such tubes and the Chathams may well have been in there.


And I have some RCA's labeled as Chatham.  LOL!  

You gave me a 1958 Svetlana, but I only have one other to compare to from the late '70's IIRC (I'd have to dig it out to verify).  I like the 1958 better...has more midrange detail and harmonic nuance and deeper, punchier bass.  Not night and day, but enough to be worthwhile IMO for anyone searching these out.  I still prefer the Chatham 6AS7G to either of the Russkies, and they still pop up every now and then for mostly sane prices.  Wait....I have the pair of Amperex Made in England (or West Russia) Svetlana's too...forgot about those. 🤣   No way of telling what year they are though since all the Svetlana markings are gone.  

I've purchased a bunch of Foton 6N6P's for Folkvangr.  Have full sets of both the square dimpled getter and the (usual) round UFO getter to give both a try versus the stock tubes (which are Reflektors).  Just haven't had the time yet to compare them.


----------



## mordy

bcowen said:


> And I have some RCA's labeled as Chatham.  LOL!
> 
> You gave me a 1958 Svetlana, but I only have one other to compare to from the late '70's IIRC (I'd have to dig it out to verify).  I like the 1958 better...has more midrange detail and harmonic nuance and deeper, punchier bass.  Not night and day, but enough to be worthwhile IMO for anyone searching these out.  I still prefer the Chatham 6AS7G to either of the Russkies, and they still pop up every now and then for mostly sane prices.  Wait....I have the pair of Amperex Made in England (or West Russia) Svetlana's too...forgot about those. 🤣   No way of telling what year they are though since all the Svetlana markings are gone.
> 
> I've purchased a bunch of Foton 6N6P's for Folkvangr.  Have full sets of both the square dimpled getter and the (usual) round UFO getter to give both a try versus the stock tubes (which are Reflektors).  Just haven't had the time yet to compare them.


6N6P? Then you need the 6N6P-IR and the 6H30-DR as well to try.


----------



## bcowen

mordy said:


> 6N6P? Then you need the 6N6P-IR and the 6H30-DR as well to try.


I'm not very familiar with the 6N6P's at this point.  What's the difference with the -IR version?

6H30's are pretty pricey, and I need 8 for Folkvangr.  Stupid amps that use lots of tubes....sheeeez.


----------



## Xcalibur255

bcowen said:


> I didn't say it was a good $30 tube.  I'm still me.  🤣


I really think you might be missing out actually.  I heard through the grapevine that only GE tubes activate the special booster circuit in your amp that makes it sound its best.


----------



## pravous

Has anyone ever gone to a Hamfest?  There is one happening not to far from me and I thought it might be worth checking out as a potential source of tubes.


----------



## bcowen

Xcalibur255 said:


> I really think you might be missing out actually.  I heard through the grapevine that only GE tubes activate the special booster circuit in your amp that makes it sound its best.


I disabled that switch because it required an IC chip to work. Horrors.  Changed it over to N2O with a remote trigger.  Just don't tell @Paladin79 -- he may send Ivan and Viktor down here to repossess it.   🤣


----------



## bcowen

pravous said:


> Has anyone ever gone to a Hamfest?  There is one happening not to far from me and I thought it might be worth checking out as a potential source of tubes.


I went to several in the Raleigh area looking specifically for tubes, but that was many years ago.  There were some guys selling them along with other stuff, but it wasn't like walking into a gold mine. Mostly US tubes, very few Euro types.  Things may have changed since then though.


----------



## Paladin79

bcowen said:


> I disabled that switch because it required an IC chip to work. Horrors.  Changed it over to N2O with a remote trigger.  Just don't tell @Paladin79 -- he may send Ivan and Viktor down here to repossess it.   🤣


I could send Victoria, she is far more persuasive.


----------



## Paladin79

pravous said:


> Has anyone ever gone to a Hamfest?  There is one happening not to far from me and I thought it might be worth checking out as a potential source of tubes.


While I live in an area that was a hotbed of electronics most people I know went to huge hamfests in Ohio, I went to some of those years ago.


----------



## pravous

First time in about two weeks I have had time to sit and listen.  Airmid and Atrium with 421a and Fivre 76 does not disappoint!


----------



## L0rdGwyn

pravous said:


> Has anyone ever gone to a Hamfest?  There is one happening not to far from me and I thought it might be worth checking out as a potential source of tubes.



I haven't, but there are guys on diyAudio who go all the time to search for / swap tubes.  The "big one" is the Dayton, OH Hamvention, which draws a huge number of people every year.  I'm sure you'd find some good tubes if you made the trip  I should probably go next year


----------



## pravous

This one is in Massachusetts, crossing my fingers for some Hytron finds.


----------



## Paladin79

L0rdGwyn said:


> I haven't, but there are guys on diyAudio who go all the time to search for / swap tubes.  The "big one" is the Dayton, OH Hamvention, which draws a huge number of people every year.  I'm sure you'd find some good tubes if you made the trip  I should probably go next year


I have been to Dayton for the Hamfest. I guess because of Covid a couple near me have been canceled. I was also in Dayton for card and chess tournaments.


----------



## L0rdGwyn

Paladin79 said:


> I have been to Dayton for the Hamfest. I guess because of Covid a couple near me have been canceled. I was also in Dayton for card and chess tournaments.



Yeah I think it was cancelled in 2020 and 2021 but came back for 2022.  Should be back again for 2023, maybe I will swing by, could be fun for the spectacle if nothing else!


----------



## L0rdGwyn

I am finishing up a little tube shopping for this pentode amplifier, want a little more variety to play with when it's done.

So far I've grabbed a pair of NIB Tung-Sol 6SU7GTY ($$$), a pair of Tung-Sol 5881 outputs, a pair of Fivre 6V6G outputs, and one of those Chatham 5R4WGY potato masher rectifiers.

The last big one on my wish list is a pair of RCA 5691, they are expensive and there isn't really a pair up for sale right now that I feel is worth the price, so I will bide my time and wait to strike...


----------



## Paladin79 (Aug 12, 2022)

L0rdGwyn said:


> Yeah I think it was cancelled in 2020 and 2021 but came back for 2022.  Should be back again for 2023, maybe I will swing by, could be fun for the spectacle if nothing else!


I honestly have more tubes than I will ever use for most of my gear. The PrimaLuna I get in a month may change that though.🤪


----------



## JazzVinyl

L0rdGwyn said:


> Yeah I think it was cancelled in 2020 and 2021 but came back for 2022.  Should be back again for 2023, maybe I will swing by, could be fun for the spectacle if nothing else!



And...the HAM guys know what they are talking about when it comes to Ohm's Law, and electronics in general.  They have been around the barn, a few times.


----------



## Xcalibur255

bcowen said:


> I disabled that switch because it required an IC chip to work. Horrors.  Changed it over to N2O with a remote trigger.  Just don't tell @Paladin79 -- he may send Ivan and Viktor down here to repossess it.   🤣


Nitrous huh?  That might make it sound like something else GE makes (an MRI machine).


----------



## Xcalibur255

Paladin79 said:


> I honestly have more tubes than I will ever use for most of my gear. The PrimaLuna I get in a month may change that though.🤪


I'm curious...... as someone who seems adept at building his own amps and has probably relationships with other builders too, what made you decide to purchase a commercially available amp like the Prima Luna?


----------



## whirlwind

pravous said:


> Has anyone ever gone to a Hamfest?  There is one happening not to far from me and I thought it might be worth checking out as a potential source of tubes.


Can be a great source to find tubes.


----------



## L0rdGwyn

I have a pair of Mullard ECC32 I am going to put up for sale, I'll put them here first and see if anyone is interested.  Both purchased NIB, less than 20 hours.  $250 each + shipping, USA only for now, international shipping is a pain, sorry!

#1









#2


----------



## Paladin79 (Aug 13, 2022)

Xcalibur255 said:


> I'm curious...... as someone who seems adept at building his own amps and has probably relationships with other builders too, what made you decide to purchase a commercially available amp like the Prima Luna?


Multiple reasons.

1. I heard one with Sonus Faber speakers and wanted to own that combination.
2. I love their design, parts used, wiring scheme, etc.
3. A friend has to reduce the amount of audio gear he has so he made me an offer I cannot refuse.  The gentleman owns and has owned a lot of gear and considers the PrimaLuna the best amp he has heard and we are similar in that respect. He happens to own the Sonus Fabers I want as well along with some REL subwoofers, and a vintage tube pre-amp I am curious to hear. Other gear I may sell or donate to family members. (I have given seven headphone amps to friends and even rebuilt @bcowen's because I knew I could make him a better cabinet and improve the sound a bit.)
4. Whenever I design an amp and local friends hear it, they want one. I was building amps every weekend while running a small corporation because it was never easy for me to say no to anyone.  This way I can spend time on other hobbies and just point to ads for the PrimaLuna if they want one lol. I am retired now and want to spend more time working with Japanese high carbon steel, woodworking, literature, chess, and enjoying music. I own in excess of 65,000 albums.
5. One day my son will own all of my audio gear and he has a rather large house across the Potomac near DC,  the amp would work well in his house as well as my own.
6. When my wife retired from the local university, she was already into pottery and my gift to her was a pottery shed of her dreams. Now it is my turn to grab some gear I have wanted and  use some excess cash for myself.


----------



## bcowen

Xcalibur255 said:


> Nitrous huh?  That might make it sound like something else GE makes (an MRI machine).


LOL!  I'll give due credit to GE too for their jet engines.  I haven't yet died in a plane crash due to one of their engines failing.  At least I don't think I have....   🤣


----------



## Paladin79

bcowen said:


> LOL!  I'll give due credit to GE too for their jet engines.  I haven't yet died in a plane crash due to one of their engines failing.  At least I don't think I have....   🤣


I bought GE stock because of their work with jet engines but that purchase did not go so well. I am better off investing in one of your ideas like the DIY hot tub.



Nice hat by the way.


----------



## bcowen (Aug 13, 2022)

Paladin79 said:


> I bought GE stock because of their work with jet engines but that purchase did not go so well. I am better off investing in one of your ideas like the DIY hot tub.
> 
> 
> 
> Nice hat by the way.


LOL!  But wait until you see my newest idea.  This is just a prototype, but should be the next really big thing.  Early investors get free tassels to put on the handlebar.    🤣


----------



## JazzVinyl

I think you will find the 6SU7GTY's hard to beat.  The brown base NU Umbrella Spokes come the closest and the TS BGRP's also big winners in the 6SL7 department.   I do not have RCA 5691 but have been told "not to expect miracles" from them, especially if you already have 6SU7GTY's...was told to ignore Fivre 6SL7's too....if you already have 6SU7GTY's...

I do have pairs of NOS 12SL7 RCA's that sound nice.  In fact all the 6/12SL7's sound pretty darn good. May not be an amp for the holy tubular roller crowd...  

Will be interesting to see if that holds true in your design.


----------



## JazzVinyl

bcowen said:


> LOL!  But wait until you see my newest idea.  This is just a prototype, but should be the next really big thing.  Early investors get free tassels to put on the handlebar.    🤣



I thought I saw Bill....float by, the other day...


----------



## L0rdGwyn (Aug 14, 2022)

JazzVinyl said:


> I think you will find the 6SU7GTY's hard to beat.  The brown base NU Umbrella Spokes come the closest and the TS BGRP's also big winners in the 6SL7 department.   I do not have RCA 5691 but have been told "not to expect miracles" from them, especially if you already have 6SU7GTY's...was told to ignore Fivre 6SL7's too....if you already have 6SU7GTY's...
> 
> I do have pairs of NOS 12SL7 RCA's that sound nice.  In fact all the 6/12SL7's sound pretty darn good. May not be an amp for the holy tubular roller crowd...
> 
> Will be interesting to see if that holds true in your design.



Thanks!  Yeah I bet you're right, with the 6SU7GTY sections being factory matched (which I have verified on my tracer) they are going to be hard to beat.  But we will find out as I've purchased a trio of date-matched RCA 5691, my curiosity was too strong, and who can resist those red micanol bases.



This is the pair of 6SU7GTY I have on the way.



With that, I am done buying tubes for this amp, I think I have a pretty solid line up to play with, looks like this:

*Rectifiers:* Philips GZ34, RCA 5R4GY, Chatham 5R4WGY, Sylvania 5V4G, RCA 5Y3G
*Inputs:* RCA 6SL7GT smoked glass, Tung-Sol 6SU7GTY, RCA 5691
*Outputs:* Philips EL34, Neotron 6L6G, Tung-Sol 5881, Visseaux 6V6GT, Fivre 6V6G

The chassis is being machined and coated today, so I will probably have it in house at the end of the week.  I received my PCBs the other day, but after examining in person, I made a few adjustments, so they have been reordered, probably another week or so until I have the new design.  My Elma switch is scheduled to ship 9/5, so that is going to delay completion unfortunately, but I'll be able to get it 95% of the way done.

I am so excited to build this amp.  I have my prototype to listen to, but it's ugly as hell and huge, not to mention exposed high voltages lol.  It's very satisfying to come up with a circuit idea and have the concept translate into great sound.  I wasn't certain the result was going to be good for a few reasons, but it has far exceeded my expectations.  I will be sending it out for demo to a small group of individuals who are familiar with my other designs, very eager to hear their thoughts.


----------



## jonathan c (Aug 14, 2022)

JazzVinyl said:


> I thought I saw Bill....float by, the other day...


You _did !!_ And in a fleeting moment….


----------



## L0rdGwyn

Got one.



It sounds really good.  These things are freaking tanks.





Remember that fancy tonearm cable I bought from Audio Art Cable?  Well in classic high end cable maker fashion, the cable is wired completely wrong.  It was advertised as a balanced interconnect, I even emailed ahead to ask and be _sure _it was actually wired balanced, but the ground connections are completely wack.  This explained the completely unlistenable noise floor when I had everything connected.  It's also much stiffer / heavier than I anticipated and was affecting the suspension of my TD 125, so I am sending it back.  Honestly not sure if they are going to honor a refund, they wanted to do an exchange for a more flexible version they are working on, but I essentially said no to that given the cable would presumably be wired the same way.  I also did some...education on proper wiring of a balanced interconnect, diagrams and all free of charge.

So I'll build my own tonearm cable again, I bought the cable really out of laziness but ultimately it burned me in the end.  Hope they give me my money back!


----------



## triod750

At least they taught you a lesson, reminding you of why you are into DIY  .


----------



## L0rdGwyn

triod750 said:


> At least they taught you a lesson, reminding you of why you are into DIY  .



100% !!!  A lesson learned for me, if you want something done right...


----------



## L0rdGwyn

This is how it should be wired.




The ground connection at the tonearm and turntable chassis is continuous with the cable shield and is grounded at the phono stage end via pin 1 of the XLR connectors.

I honestly don't even know what they've done, but pin 1 of the XLR does not appear to be used, or at the very least, it is not continuous with the ground connections at the tonearm end.  Maybe they connected pin 1 to the cable shield, then left the ground connections at the turntable end separate?  Either way, it's wrong, it should be one continuous ground from end to end for maximum noise suppression.

Unlike applications where balanced connections have no real benefit, like, oh I don't know, headphone amplifiers, a balanced tonearm connection is very beneficial.  Why?  Because in small signal applications, there is a buttload of gain, something like 60-70dB in a typical MC phono stage, which means any noise picked up along the interconnect is going to be amplified big time.  And most MC phono stages use an MC step up transformers, which means it can be wired for a balanced primary and single-ended secondary.  This ensures the lowest possible noise floor.  But of course, the cable has to be wired correctly...


----------



## Paladin79

Bottlehead Cracks are going on sale August 18th.


----------



## Monsterzero

L0rdGwyn said:


> Got one.
> 
> 
> 
> ...


 Those Chathams are cheap as chips and sound very, very good in my DAC


----------



## L0rdGwyn

Paladin79 said:


> Bottlehead Cracks are going on sale August 18th.



Thanks, I saw that in the newsletter.  I think I will wait for Cracktober though, discount is $125 then vs. $66 for this sale.  Also have my hands full at the moment!


----------



## Paladin79

L0rdGwyn said:


> Thanks, I saw that in the newsletter.  I think I will wait for Cracktober though, discount is $125 then vs. $66 for this sale.  Also have my hands full at the moment!


Not a problem, I just happened to see it.
The amp I am playing around with turns out to be a perfect size for mini radial speakers, but then that was the point.🤪

Because of my background with 6SN7’s
I had to try a 1956 Melz.


----------



## L0rdGwyn (Aug 15, 2022)

Monsterzero said:


> Those Chathams are cheap as chips and sound very, very good in my DAC



Yeah sounds great to me on first listen, I'll have to compare to RCA 5R4GY for a direct head-to-head and see how audible the change is in this amp.

Chassis is on the way.


----------



## Monsterzero

L0rdGwyn said:


> Yeah sounds great to me on first listen, I'll have to compare to RCA 5R4GY for a direct head-to-head and see how audible the change is in this amp.
> 
> Chassis is on the way.


 I have a WWll RCA 5R4GY, the one that Brent Jessee calls a "WE 422a lite" . In my DAC the RCA is brighter with a wider stage and more sub bass. Very different sounding vs. The 'Masher


----------



## L0rdGwyn

Monsterzero said:


> I have a WWll RCA 5R4GY, the one that Brent Jessee calls a "WE 422a lite" . In my DAC the RCA is brighter with a wider stage and more sub bass. Very different sounding vs. The 'Masher



Gotcha, I'll keep that in mind.  I didn't do an A-B comparison, but I _felt _the masher was quite different when I listened today.  I haven't been much into tube rolling for a long time, I'm looking forward to that with this amplifier.


----------



## Xcalibur255

I haven't heard the older WWI era RCA but I did own a late 50's RCA 5R4GY and the Brimar version walked all over it IMO.  I used to have a few different 5R4 but I gave them all away except the Brimar and Philips because they sounded the best in the IHA-1.  Poor little amp has spent more time in the closet than on my desk at this point but I still can't convince myself to sell it.


----------



## L0rdGwyn

Xcalibur255 said:


> I haven't heard the older WWI era RCA but I did own a late 50's RCA 5R4GY and the Brimar version walked all over it IMO.  I used to have a few different 5R4 but I gave them all away except the Brimar and Philips because they sounded the best in the IHA-1.  Poor little amp has spent more time in the closet than on my desk at this point but I still can't convince myself to sell it.



I want to grab one of those Brimar 5R4GY, that is one good looking tube, but I'm going to be out of town in a little over a week and pretty much exclusively available in the UK, afraid I'd miss the delivery.  The poor IHA-1, buried even deeper in the closet now that you have that 1101 amp


----------



## L0rdGwyn

Got some new tubes.  Tung-Sol 6SU7GTY have arrived.



I gotta be honest, it's not like they blow the RCA 6SL7GTs I've been using out of the water by any stretch, they're just different.  Less warm, a little more laid back, a tad more airy but a little less bass heft compared to the RCAs in my amp.  Still sound great though.

Also received my pair of Tung-Sol 5881.  Good looking tubes, less airy and chiseled compared to Philips EL34, but a very nice warm, smooth tone.



Chassis is slated to arrive tomorrow, I am dying to build this.  I bought more tubes in my excitement.  This pair of Radiocoin 6L6LG (National Union?  Ken-Rad? not sure, gotta investigate).



And another pair of 6SL7, these Tung-Sol 6SL7WGT.  I bought these purely because I like how they look lol.



One more day...


----------



## Xcalibur255

I'm trying to remember if you're supposed to keep the plate oriented in a specific direction when doing the "palm whack" to try and fix a humming tube.  Could anybody help jog my memory?


----------



## L0rdGwyn

Xcalibur255 said:


> I'm trying to remember if you're supposed to keep the plate oriented in a specific direction when doing the "palm whack" to try and fix a humming tube.  Could anybody help jog my memory?



I have only ever done this to try and break a short, never to fix a hum.


----------



## Xcalibur255

L0rdGwyn said:


> I have only ever done this to try and break a short, never to fix a hum.


I can't remember where I read this.  I thought it was here but I guess not.  It's that electrical buzzing type of hum that's low level but just always there.

Since it's driving me crazy I gave it a whack because I don't have much to lose.  Didn't kill it at least, but I suspect when it warms back up it'll be buzzing again.  It's a bummer since I really wanted this pair to work out, especially after the disappointment with the KRs and the L63s.


----------



## sam6550a

Xcalibur255 said:


> I can't remember where I read this.  I thought it was here but I guess not.  It's that electrical buzzing type of hum that's low level but just always there.
> 
> Since it's driving me crazy I gave it a whack because I don't have much to lose.  Didn't kill it at least, but I suspect when it warms back up it'll be buzzing again.  It's a bummer since I really wanted this pair to work out, especially after the disappointment with the KRs and the L63s.


Try resoldering the pins. That fixes hum issues on many tubes


----------



## L0rdGwyn

Yeah @Xcalibur255, resoldering the pins may help with noise, it's worth a try if you have access to a soldering iron.


----------



## whirlwind

If resoldering does not work, I just pitch them to the side.
I really don't try anything else.


----------



## Xcalibur255 (Aug 17, 2022)

I have a wimpy 10W pencil iron that may or may not be up to the job, but I've been reluctant to try this on any of my tubes because I have no real soldering experience at all and am afraid I'll just ruin the tube in the attempt.

That, and my gut feeling is that this is something else.  It's not a huuuuuummmmmmmmm type of hum, more of that kind of warbling electric buzzing sound that varies in intensity and randomly comes and goes.  Sometimes the tube will be silent.  I have quite a few tubes that do this intermittently including a C3g tube that has done it for years in the Glenn 45 amp.  I remember reading somewhere that often times this type of noise is actually caused by a tiny amount of debris being trapped inside the grid and that a good thwack can sometimes clear it out.

Curiously enough I thwacked this tube and it didn't cure it but it DID reduce the problem by about half now that I've had it back on for a couple of hours and can judge.  I'm afraid to bang on it anymore for fear of breaking an internal wire or shifting the plate/grid so I guess this tube is just going to have to be a little noisy.


----------



## gibosi

L0rdGwyn said:


> I haven't, but there are guys on diyAudio who go all the time to search for / swap tubes.  The "big one" is the Dayton, OH Hamvention, which draws a huge number of people every year.  I'm sure you'd find some good tubes if you made the trip  I should probably go next year



A bit further east is the Kutztown Radio Show, Sept 16 and 17, in Pennsylvania. It's one of the larger shows in the US.

http://www.dvhrc.com/


----------



## UntilThen

Keenan, I've parked myself here for the unveiling of your KT88 amp. You got a name for it?


----------



## L0rdGwyn

UntilThen said:


> Keenan, I've parked myself here for the unveiling of your KT88 amp. You got a name for it?



It is called...actually no I don't have a name for it!  I'll have to think of one  somehow I want this circuit to become available to Head-Fiers, either commercial or DIY, as I've discussed ad nauseum, so it will need a proper name if that comes to pass.  If you think of one, let me know  I have made all possible preparations, my chassis and revised PCBs should be arriving imminently...


----------



## UntilThen

L0rdGwyn said:


> It is called...actually no I don't have a name for it!  I'll have to think of one  somehow I want this circuit to become available to Head-Fiers, either commercial or DIY, as I've discussed ad nauseum, so it will need a proper name if that comes to pass.  If you think of one, let me know  I have made all possible preparations, my chassis and revised PCBs should be arriving imminently...



I hate to call it KT88 amp because this amp will play with many types of power tubes and that's where the appeal is. I'm sure your chassis will be stunning so I'm waiting to see it. After naming Odyssey, I've no more inspiration for names.  I'm sure you will come up with a good one.


----------



## Monsterzero

L0rdGwyn said:


> If you think of one, let me know


apotheosis \uh-pah-thee-OH-sis\ noun. 1 a : *the perfect form or example of something* : quintessence. b : the highest or best part of something : peak. 2 : elevation to divine status : deification.


----------



## L0rdGwyn

UntilThen said:


> I hate to call it KT88 amp because this amp will play with many types of power tubes and that's where the appeal is. I'm sure your chassis will be stunning so I'm waiting to see it. After naming Odyssey, I've no more inspiration for names.  I'm sure you will come up with a good one.



I tend to go with a minimalist look, even by that standard this one is quite minimalist, but I think it is sleek, it will allow the beauty of the tubes to be front and center, which is what I like 



Monsterzero said:


> apotheosis \uh-pah-thee-OH-sis\ noun. 1 a : *the perfect form or example of something* : quintessence. b : the highest or best part of something : peak. 2 : elevation to divine status : deification.



I like it!  I will keep this on my short list which I started just now.


----------



## UntilThen

L0rdGwyn said:


> I tend to go with a minimalist look



Jony Ive agrees.


----------



## gibosi

L0rdGwyn said:


> I tend to go with a minimalist look, even by that standard this one is quite minimalist, but I think it is sleek, it will allow the beauty of the tubes to be front and center, which is what I like
> 
> 
> 
> I like it!  I will keep this on my short list which I started just now.



気高い (Kedakai) Sublime.
or 甲高い (Kandakai) Shrill

But if you don't know what these Japanese words mean, both sound great I think. lol


----------



## Zachik

UntilThen said:


> After naming Odyssey, I've no more inspiration for names.  I'm sure you will come up with a good one.


I have named 2 amps since you named your Odyssey... 
One will be unveiled soon. I hope. The other - in 6 months or so.



Monsterzero said:


> apotheosis \uh-pah-thee-OH-sis\ noun. 1 a : *the perfect form or example of something* : quintessence. b : the highest or best part of something : peak. 2 : elevation to divine status : deification.


+1 vote from me. Good name!



gibosi said:


> or 甲高い (Kandakai) Shrill


Shrill is *not *a characteristic I welcome in audio... Could be just me, though.


----------



## UntilThen

Zachik said:


> I have named 2 amps since you named your Odyssey...
> One will be unveiled soon. I hope. The other - in 6 months or so.



Alright I'm eager to see those 2 amps too.


----------



## UntilThen

Keenan, I suggest you call it Enigma because that is the LP I'm playing now.


----------



## L0rdGwyn

Alright, it's done.  I'll have pictures up shortly, sorry, UPS didn't deliver to 5:30PM!!  Pretty good though, 3.5 hours work for a build...probably 5 total including the prep I did.


----------



## pravous

Some live music for a change.  Kingfish, Kenny Wayne Shepard, Buddy Guy.


----------



## L0rdGwyn

Okay, pentode headamp is done.  I am still waiting for my impedance switch, so I wired internally for high impedance for the time being.

Without tubes.  Everything fits like a glove, first time building a tube circuit on a PCB, worked like a charm and cut build time down tremendously.



With tubes - RCA 5R4GY, Tung-Sol 6SU7GTY, Tung-Sol 5881





And in the dark.



Time to tube roll the night away with the Atrium


----------



## UntilThen

Nice, I see you're giving Lundahl some business for a change.


----------



## bcowen

pravous said:


> Some live music for a change.  Kingfish, Kenny Wayne Shepard, Buddy Guy.


Aw man, I'm jealous.  Kenny Wayne Shepard is one of my favorites.  Never had the chance to see him in concert though.


----------



## bcowen

L0rdGwyn said:


> Okay, pentode headamp is done.  I am still waiting for my impedance switch, so I wired internally for high impedance for the time being.
> 
> Without tubes.  Everything fits like a glove, first time building a tube circuit on a PCB, worked like a charm and cut build time down tremendously.
> 
> ...


Very nice, Keenan!


----------



## L0rdGwyn

UntilThen said:


> Nice, I see you're giving Lundahl some business for a change.



Yes, there is some secret sauce in this amp that makes it quite different from other pentode output amplifiers, could only be built with Lundahl inductors in fact, at least without going custom everything!


----------



## L0rdGwyn

Now Chatham potato masher and Neotron 6L6G.


----------



## UntilThen

L0rdGwyn said:


> Yes, there is some secret sauce in this amp that makes it quite different from other pentode output amplifiers, could only be built with Lundahl inductors in fact, at least without going custom everything!



Do you have power measurements for the amp?


----------



## L0rdGwyn

UntilThen said:


> Do you have power measurements for the amp?



Yup, it's a 2W amplifier.  Should be great for planar magnetics, but I don't own any lol.  Output impedance on the low Z setting will be 4-5 ohms.  I'll retake measurements once I get my output switch!


----------



## L0rdGwyn

Last pic for the night, with Philips / Mullard EL34.


----------



## UntilThen

L0rdGwyn said:


> Last pic for the night, with Philips / Mullard EL34.



Mullard EL34 is much loved by the audiophile world. So what's your thoughts of this amp driving the Atrium? Or is it too early to tell. You're just burning it in.


----------



## L0rdGwyn

UntilThen said:


> Mullard EL34 is much loved by the audiophile world. So what's your thoughts of this amp driving the Atrium? Or is it too early to tell. You're just burning it in.



I like the Mullard EL34 very much!  I've been listening to this circuit for some time on my prototyping board, so I am quite familiar by now, maybe better now that it is it a box and no alligator clips :O  it is a great pairing for Atrium.  This amplifier has an enormous soundstage and precise imaging, it still makes my jaw drop at times.  Very nice full impactful bass too.  I guess those are the stand out sound characteristics for me, big headstage and full-bodied.


----------



## UntilThen

L0rdGwyn said:


> enormous soundstage and precise imaging, full impactful bass, big headstage and full-bodied.



Lovely characteristics that I can identify with. When you say pentode amp, you're actually running it as strapped triodes right? As in single ended triodes amp.


----------



## Monsterzero

pravous said:


> Some live music for a change.  Kingfish, Kenny Wayne Shepard, Buddy Guy.


 damn, what a lineup!


----------



## L0rdGwyn

UntilThen said:


> Lovely characteristics that I can identify with. When you say pentode amp, you're actually running it as strapped triodes right? As in single ended triodes amp.



That's right, as triodes.  But different from your typical trioded pentode SET amplifier.  I haven't divulged exactly what's going on only because I don't know if this going to become a commercial design or I will sell it or DIY it.  There isn't a headphone amplifier out there doing what this one does and frankly I'm concerned someone might copy the idea.  Eventually I'll talk about the circuit though, I'd really like to.  It is 100% old school design, just tubes / resistors / capacitors/ inductors, but achieves a degree of sound that would make you think there is silicon inside.  I'm very happy with it!


----------



## whirlwind

L0rdGwyn said:


> Okay, pentode headamp is done.  I am still waiting for my impedance switch, so I wired internally for high impedance for the time being.
> 
> Without tubes.  Everything fits like a glove, first time building a tube circuit on a PCB, worked like a charm and cut build time down tremendously.
> 
> ...


 Beautiful Keenan and without a bunch of glitz! I love the chassis layout .

This amp should be great for planars , should be great for most cans!

Not sure how you did it with all pcb, but I am sure it sounds great!


----------



## whirlwind

pravous said:


> Some live music for a change.  Kingfish, Kenny Wayne Shepard, Buddy Guy.


Oh wow....I am officially jealous...looks like a killer time!!!


----------



## L0rdGwyn

whirlwind said:


> Beautiful Keenan and without a bunch of glitz! I love the chassis layout .
> 
> This amp should be great for planars , should be great for most cans!
> 
> Not sure how you did it with all pcb, but I am sure it sounds great!



Thanks Joe, yeah I'm not big on the glitz!  Tubes are the glitz  will be fun to try some planars, I'd love to show the PCB as I am proud of the work but again I feel I should be a little secretive of the details for now...but it sure makes for a very clean build inside.


----------



## whirlwind

If you want a planar to try, just say the word.


----------



## L0rdGwyn

whirlwind said:


> If you want a planar to try, just say the word.



Ooooh I'll give that some though Joe, although shipping expensive things makes me nervous!

Atrium shot.  I apologize in advance if you see this pic elsewhere lol.


----------



## UntilThen

L0rdGwyn said:


> I apologize in advance if you see this pic elsewhere lol.



That's alright. Sometimes I forget where I post a particular pic. Must have post it to Bcowen mailbox.


----------



## CJG888

As promised: behold ye the beast with two arms!


----------



## CJG888 (Aug 19, 2022)

The Ortofon arm provides the DL103 with ideal operating conditions: the extra mass ring, together with the added mass of the cocobolo body (Stanley Engineering), makes this a highish-mass arm. Tracking at 2.8g, it clears all but the 90 microns test tracks. Arm / cartridge resonance is at 8 Hz.

The signal goes to my Pro-Ject Tube Box DS (aftermarket linear PSU, NOS Mullard ECC83s) via a Denon AU-320 SUT.

This is as “103-friendly” an environment as can be found anywhere!

So far, I am getting a very punchy, dynamic sound with tremendous bass extension and a huge “wall of sound” stereo image. Everything sounds very “solid” and tangible.

In terms of absolute resolution and image depth, it loses out to the SME 3009 / AT-VM740ML combo.


----------



## L0rdGwyn

CJG888 said:


> As promised: behold ye the beast with two arms!



Looks gorgeous, congrats!


----------



## L0rdGwyn

Got some new tubes, Tung-Sol 6SL7WGT and a Redcoin 6L6G (Ken-Rad or National Union rebrand I believe).  The new 6L6G and Tung-Sol 6SU7GTY are a superb combo, the 6SL7WGT are a bit of a downgrade but not surprising.  Rectifier is a Philips GZ34.


----------



## UntilThen

L0rdGwyn said:


> Got some new tubes, Tung-Sol 6SL7WGT and a Redcoin 6L6G (Ken-Rad or National Union rebrand I believe). The new 6L6G and Tung-Sol 6SU7GTY are a superb combo, the 6SL7WGT are a bit of a downgrade but not surprising. Rectifier is a Philips GZ34.



Your amp is very versatile if it can use the lower voltage 6L6G. These are different to the higher voltage 6L6GC. I got a new pair of Ken Rad 6L6G black glass for a friend for $150 and he's happy as a child with a new toy on Christmas day.   

On another subject, turntable and tube amps are a natural pairing.


----------



## CJG888

L0rdGwyn said:


> Looks gorgeous, congrats!


Thanks!


----------



## L0rdGwyn (Aug 20, 2022)

UntilThen said:


> Your amp is very versatile if it can use the lower voltage 6L6G. These are different to the higher voltage 6L6GC. I got a new pair of Ken Rad 6L6G black glass for a friend for $150 and he's happy as a child with a new toy on Christmas day.
> 
> On another subject, turntable and tube amps are a natural pairing.



Yes, old 6L6G are no problem.  There are a few tubes that will not work, typically lower power models that will be biased over their max plate dissipation, like 6W6.  I am compiling a list.

This is one of the best sounding amps I have made, it's up there with the 45 amp I made for Zach.  It really does it all, clarity, enormous stage, dynamic, thick, impactful bass, airy detailed treble, and dead silent.  I am excited for some people to demo it.

Really love this combo, Philips GZ34, Tung-Sol 6SU7GTY, and Ken-Rad 6L6G.  I had to add some isolating pads to choke screws, temporary solution but for parts for a more elegant fix arrive.


----------



## ckhirnigs113

L0rdGwyn said:


> Yes, old 6L6G are no problem.  There are a few tubes that will not work, typically lower power models that will be biased over their max plate dissipation, like 6W6.  I am compiling a list.
> 
> This is one of the best sounding amps I have made, it's up there with the 45 amp I made for Zach.  It really does it all, clarity, enormous stage, dynamic, thick, impactful bass, airy detailed treble, and dead silent.  I am excited for some people to demo it.
> 
> Really love this combo, Philips GZ34, Tung-Sol 6SU7GTY, and Ken-Rad 6L6G.  I had to add some isolating pads to choke screws, they are beige but will change to black at some point so they blend in.


You’ve certainly peaked my interest! I’ve been reading all the great things about your amps for a while now. I know I’ve missed the boat on the Airmid. I really hope you are able to find a way to make this new project commercially available, even if on limited basis. I know I’d love to try it with my Meze Elite as well as my Auteur!


----------



## bcowen

CJG888 said:


> The Ortofon arm provides the DL103 with ideal operating conditions: the extra mass ring, together with the added mass of the cocobolo body (Stanley Engineering), makes this a highish-mass arm. Tracking at 2.8g, it clears all but the 90 microns test tracks. Arm / cartridge resonance is at 8 Hz.
> 
> The signal goes to my Pro-Ject Tube Box DS (aftermarket linear PSU, NOS Mullard ECC83s) via a Denon AU-320 SUT.
> 
> ...


The DL-103 is one of those timeless designs that has always sounded better than its price suggests, at least IMO.  I wore one out, and then went for the Zu-modded one on the second go-round.  After my Koetsu was mugged and subsequently died, I've been alternating between it and a Benz MC-Scheu.  Different sounds, but both are quite musical and enjoyable to listen to.

https://www.zuaudio.com/turntable/zudl-103


----------



## L0rdGwyn

ckhirnigs113 said:


> You’ve certainly peaked my interest! I’ve been reading all the great things about your amps for a while now. I know I’ve missed the boat on the Airmid. I really hope you are able to find a way to make this new project commercially available, even if on limited basis. I know I’d love to try it with my Meze Elite as well as my Auteur!



I hope so too!  I'll have a better idea of the direction things are heading in the next few months.  It would be an expensive amp given the cost of parts, TOTL type of design, but I have a lot of confidence in the circuit, I would happily put it up against any commercial tube amp on the market.  Who knows, maybe I'm delusional and it isn't as good as I think it is, we will see when other ears sample it.


----------



## ckhirnigs113

Can’t wait to see what others think of your new creation. I think you’ve proven you’re a pretty good judge of sound quality at this point.


----------



## UntilThen

L0rdGwyn said:


> This is one of the best sounding amps I have made, it's up there with the 45 amp I made for Zach. It really does it all, clarity, enormous stage, dynamic, thick, impactful bass, airy detailed treble, and dead silent. I am excited for some people to demo it.



I've too many amps already otherwise I'd be willing to make a financial commitment. Besides I always feel Odyssey is the finest sounding amp ever, owner bias aside.   A comparison between the 2 would be interesting.  

I wish you the best and success with this venture. More boutique amps builders will only be beneficial for the head-fi community.

P/s : just notice you displayed the Ken Rad 6L6G in the above picture. That is the tube I'm talking about.


----------



## L0rdGwyn

ckhirnigs113 said:


> Can’t wait to see what others think of your new creation. I think you’ve proven you’re a pretty good judge of sound quality at this point.



Thanks, I like to think so but you can never be certain!  When you've been listening to the same thing over and over and over, it helps to have another set of ears confirm or deny what you're hearing.  All of the critical listening also can start to cause fatigue, then my ears are useless for a few days.  But I feel good about this one, gonna be hard to see it go on its road trip.


----------



## L0rdGwyn

UntilThen said:


> I've too many amps already otherwise I'd be willing to make a financial commitment. Besides I always feel Odyssey is the finest sounding amp ever, owner bias aside.   A comparison between the 2 would be interesting.
> 
> I wish you the best and success with this venture. More boutique amps builders will only be beneficial for the head-fi community.
> 
> P/s : just notice you displayed the Ken Rad 6L6G in the above picture. That is the tube I'm talking about.



Ahhh who knows!  Would be amazing some day to have many of these boutique / custom amplifiers in one place.  I have a lot of respect for what SonicTrance is doing, so I'm sure the Odyssey is an exceptional amplifier.  From what I know of Odyssey, while the output tubes are the same, both are tube rectified and transformer coupled, that is where the similarities end, so different presentations between the two I would expect to hear.

I have been listening to those Ken-Rads the whole evening, they sound fantastic, Leonard Cohen's growl is tickling my eardrums.


----------



## UntilThen

L0rdGwyn said:


> Ahhh who knows!  Would be amazing some day to have many of these boutique / custom amplifiers in one place.  I have a lot of respect for what SonicTrance is doing, so I'm sure the Odyssey is an exceptional amplifier.  From what I know of Odyssey, while the output tubes are the same, both are tube rectified and transformer coupled, that is where the similarities end, so different presentations between the two I would expect to hear.
> 
> I have been listening to those Ken-Rads the whole evening, they sound fantastic, Leonard Cohen's growl is tickling my eardrums.



Yup total respect for Mischa and your amps. And one of Glenn 300b amp. And Eddie Current higher end offerings. Don't think the day will come for these amps to come together but I'm sure they will a total treat for the ears.

My next 300b, the Telemachus will have dual power supply. It will be switchable between regulated solid state rectifiers or unregulated tube rectification.

I smile when you mention Leonard Cohen. I thought I was the only one who enjoys his voice.


----------



## CJG888

bcowen said:


> The DL-103 is one of those timeless designs that has always sounded better than its price suggests, at least IMO.  I wore one out, and then went for the Zu-modded one on the second go-round.  After my Koetsu was mugged and subsequently died, I've been alternating between it and a Benz MC-Scheu.  Different sounds, but both are quite musical and enjoyable to listen to.
> 
> https://www.zuaudio.com/turntable/zudl-103


It also means that I am getting a decent approximation of genuine 60s broadcast sound on those old Blue Notes…


----------



## L0rdGwyn

I was wide awake at 5AM, had to come down and listen.  GZ34, EL34, 6SU7GTY.

RCA 5691 arriving today


----------



## L0rdGwyn

Here is a small tube setup, RCA 5Y3G, RCA 6SL7GT, Visseaux 6V6GT.  Despite the fact that this amp essentially has to use a pair of 6SL7 inputs (besides using adapters), I think there is still a good amount of tube rollability to mess around with.


----------



## L0rdGwyn

Here is a very nice combination I have been listening to this morning: Chatham 5R4WGY, RCA 6SL7GT, Ken-Rad 6L6G.

The timeline is going to be a little tight based on when I am supposed to receive the impedance selector switch for this build, but it's possible this amplifier will be making a trip to CanJam SoCal.  We'll see, I am going to do my best to make it happen.


----------



## L0rdGwyn

Just bought these too, Brimar CV1985 / 6SL7GTY, should sound purdy good in this amp.

Now the real question as I hunt all the fanciest 6SL7, do I consider buying a pair of ECC35?  Big bucks for a pair of those bad boys...


----------



## Mr Trev

L0rdGwyn said:


> Just bought these too, Brimar CV1985 / 6SL7GTY, should sound purdy good in this amp.
> 
> Now the real question as I hunt all the fanciest 6SL7, do I consider buying a pair of ECC35?  Big bucks for a pair of those bad boys...


You know the saying… it's better to regret something you have done, rather than something you haven't


----------



## L0rdGwyn (Aug 21, 2022)

Mr Trev said:


> You know the saying… it's better to regret something you have done, rather than something you haven't



Yeah, but man are they expensive!  If I sell my pair of ECC32, maybe I'll go for it.  Who knows, maybe I can find someone to trade me a pair of ECC35 for a pair of ECC32.  I'll add this option to my classifieds listing 

I have decided my power tube hierarchy in this amp so far goes Mullard EL34 > Ken-Rad 6L6G > Visseaux 6V6GT > Tung-Sol 5881 > Neotron 6L6G.


----------



## UntilThen

L0rdGwyn said:


> I have decided my power tube hierarchy in this amp so far goes Mullard EL34 > Ken-Rad 6L6G > Visseaux 6V6GT > Tung-Sol 5881 > Neotron 6L6G.



There are a lot more power tubes to grace your amp. Someday perhaps you should try:-

La Radiotechnique EL39
Radiotron 807
Telefunken EL12 spez

Not forgetting the usual candidates - KT88, 6550.

Yeah take it to Canjam. It's the only way to get others to sample the amp.


----------



## Zachik

L0rdGwyn said:


> it's possible this amplifier will be making a trip to CanJam SoCal.


Are you going to attend, or sending the amp with someone else (e.g. Zach)?


----------



## L0rdGwyn (Aug 21, 2022)

UntilThen said:


> There are a lot more power tubes to grace your amp. Someday perhaps you should try:-
> 
> La Radiotechnique EL39
> Radiotron 807
> ...



I am going to try!  All is dependent on Elma sending my selector switch on time, I will start bothering them about it now  it is scheduled to ship 9/5, maybe I can have them push it back a few days.

I will look over the datasheets at be sure these tubes are compatible, all about their bias point and ensuring no ratings are exceeded in my circuit.  There are a few oddball pentodes that bias too hot in this amp.  But I want to exhaust the tubes that do not need adapters first before trying others, top of the power tube shopping list right now is a pair of Tung-Sol 6550.  I would also like to try the RCA 6L6GC.  Honestly NOS KT88 are so expensive, I may not even bother.

@Zachik if the timeline is met, I will send it to Zach who will bring it with him to CanJam  not practical for me to fly out and back for one day unfortunately given my work schedule.


----------



## Zachik

L0rdGwyn said:


> not practical for me to fly out and back for one day unfortunately given my work schedule.


Yup, to do it properly - you have to arrive Friday evening and stay until Sun. night or Mon. morning 
Bummer I won't get to meet with you again this time around...


----------



## L0rdGwyn

Zachik said:


> Yup, to do it properly - you have to arrive Friday evening and stay until Sun. night or Mon. morning
> Bummer I won't get to meet with you again this time around...



Sorry!  Maybe next year I can plan ahead, or perhaps Zach will do another ZMFestivus event, Chi-town is much closer to home for me.


----------



## UntilThen

L0rdGwyn said:


> Honestly NOS KT88 are so expensive, I may not even bother.



They are expensive but I just have to sample it and when a new pair shows up, I couldn't resist. The Tung Sol 6550 too. You could try the Shuguang Black Treasures KT88-Z or Psvane KT88 Tii though. They are actually very decent.


----------



## L0rdGwyn

UntilThen said:


> They are expensive but I just have to sample it and when a new pair shows up, I couldn't resist. The Tung Sol 6550 too. You could try the Shuguang Black Treasures KT88-Z or Psvane KT88 Tii though. They are actually very decent.



Gah I'll think about it.  Probably some day I will take the plunge and go for the GEC.  I don't doubt the new production models are quite good, but I have never bought a new production tube, I am a snob.


----------



## UntilThen

L0rdGwyn said:


> Gah I'll think about it.  Probably some day I will take the plunge and go for the GEC.  I don't doubt the new production models are quite good, but I have never bought a new production tube, I am a snob.



NOS tubes drove me nuts. For all the glamour of GEC KT88, I love my 3 pairs of EL34 just as much. The smoothness of tone is like baby's bottom and soft as duck's feathers. But when you crank up the volume, that's when you wonder where that Tyson Fury come from.   

I am a snob too because I just have to have 3 of the best EL34 types.

Philips Miniwatt EL34 metal base
Philips Miniwatt EL34 double D getters brown base
Philips Miniwatt EL34 6CA7 double O getters dark brown base
I am using number 3 now, the cheapest of the 3! Having come from Shuguang Black Treasures KT88-Z, these EL34s are intoxicating and rival 300b midrange sweetness.


----------



## L0rdGwyn

UntilThen said:


> NOS tubes drove me nuts. For all the glamour of GEC KT88, I love my 3 pairs of EL34 just as much. The smoothness of tone is like baby's bottom and soft as duck's feathers. But when you crank up the volume, that's when you wonder where that Tyson Fury come from.
> 
> I am a snob too because I just have to have 3 of the best EL34 types.
> 
> ...



I'm sure those sound lovely.  I have only the Philips EL34 XF2, it is my top power tube at the moment in this amplifier, although the Ken-Rad 6L6G is a close second  I will have to dive more deeply into the EL34 lineup, if I can spot some deals, I will need backups after all.  Metal base EL34 is not in my future, but I will sample a brown base soon enough


----------



## L0rdGwyn (Aug 21, 2022)

I want to buy this pair of 6550, but I am flying out Friday to cruise in the Caribbean, and I don't trust USPS to hold the mail, I request it every time and return to stacks of letters and packages!  Maybe I will wait for a true NOS pair to come along.

https://www.ebay.com/itm/195300747963?hash=item2d78d4eabb:g:7WwAAOSwrxFjAn5h&amdata=enc:AQAHAAAAoP+6hylkevSdFkp+qtPHAG71vZizEnd6+t18eVf54McninR8gIMggqImQnaLI7jKi436q9OnjLL9QhAulAHLHLvCJQ6ecQnt3FUxHUN2E9V4NYADgabC1zz8pzC3NxP59bzrYfvdIB1h2GC0RLejXQquMMcIE9niS+YRiJDXYhBEFaCd+u768nQXSsxIVwf4gT422PbsWqSYoCStzmoeOAQ=|tkp:Bk9SR8CWka3YYA


----------



## UntilThen

L0rdGwyn said:


> I want to buy this pair of 6550, but I am flying out Friday to cruise in the Caribbean, and I don't trust USPS to hold the mail, I request it every time and return to stacks of letters and packages!  Maybe I will wait for a true NOS pair to come along.
> 
> https://www.ebay.com/itm/195300747963?hash=item2d78d4eabb:g:7WwAAOSwrxFjAn5h&amdata=enc:AQAHAAAAoP+6hylkevSdFkp+qtPHAG71vZizEnd6+t18eVf54McninR8gIMggqImQnaLI7jKi436q9OnjLL9QhAulAHLHLvCJQ6ecQnt3FUxHUN2E9V4NYADgabC1zz8pzC3NxP59bzrYfvdIB1h2GC0RLejXQquMMcIE9niS+YRiJDXYhBEFaCd+u768nQXSsxIVwf4gT422PbsWqSYoCStzmoeOAQ=|tkp:Bk9SR8CWka3YYA



Yup those are Tung Sol rebranded Leslie. 3 getters. One at the top and 2 more at the sides. Looks to be in very good condition. Mine is solid plates without the 3 holes.


----------



## gibosi

L0rdGwyn said:


> I want to buy this pair of 6550, but I am flying out Friday to cruise in the Caribbean, and I don't trust USPS to hold the mail, I request it every time and return to stacks of letters and packages!  Maybe I will wait for a true NOS pair to come along.
> 
> https://www.ebay.com/itm/195300747963?hash=item2d78d4eabb:g:7WwAAOSwrxFjAn5h&amdata=enc:AQAHAAAAoP+6hylkevSdFkp+qtPHAG71vZizEnd6+t18eVf54McninR8gIMggqImQnaLI7jKi436q9OnjLL9QhAulAHLHLvCJQ6ecQnt3FUxHUN2E9V4NYADgabC1zz8pzC3NxP59bzrYfvdIB1h2GC0RLejXQquMMcIE9niS+YRiJDXYhBEFaCd+u768nQXSsxIVwf4gT422PbsWqSYoCStzmoeOAQ=|tkp:Bk9SR8CWka3YYA



Maybe you could ask the seller to wait until you return before shipping?


----------



## Monsterzero

L0rdGwyn said:


> I have never bought a new production tube, I am a snob.


 My DAC can take EL34, in fact it shipped with Seimens EL34, they didnt sound that great, but then again the DAC wasnt burned in yet either. I keep bouncing back and forth between the NOS Tesla EL51 w/ adapters and modern Gold Lion KT77s. Both sound really nice in my DAC.

Can your amp take either of those?


----------



## L0rdGwyn

gibosi said:


> Maybe you could ask the seller to wait until you return before shipping?



I tried, he told me that eBay wants sellers to ship ASAP (it's true, you get dinged if you don't ship within a certain time period of the sale), so he can't hold them.  BUT he told me has other pairs, so message him when I get back 



Monsterzero said:


> My DAC can take EL34, in fact it shipped with Seimens EL34, they didnt sound that great, but then again the DAC wasnt burned in yet either. I keep bouncing back and forth between the NOS Tesla EL51 w/ adapters and modern Gold Lion KT77s. Both sound really nice in my DAC.
> 
> Can your amp take either of those?



I think the Siemens EL34 are pretty well-liked, so maybe the DAC needed some time?  Gold Lion KT77s for sure.  EL51 is a mystery, I will have to look at the datasheet, but probably would be fine, it's a beast of a tube with 45W plate dissipation, so unlikely to run into an issue, very likely it would work with an adapter.


----------



## Monsterzero

L0rdGwyn said:


> EL51 is a mystery, I will have to look at the datasheet, but probably would be fine, it's a beast of a tube with 45W plate dissipation,


 It's also a beast of a tube in size. Next to a 6C5 for reference


----------



## L0rdGwyn (Aug 21, 2022)

Monsterzero said:


> It's also a beast of a tube in size. Next to a 6C5 for reference



Gotta have big plates to handle big power!  Looks to be a pretty linear tube as a triode.


----------



## UntilThen

For current production, these tubes are actually very good sounding. Wish I had rotate them in more.


----------



## whirlwind

L0rdGwyn said:


> I am going to try!  All is dependent on Elma sending my selector switch on time, I will start bothering them about it now  it is scheduled to ship 9/5, maybe I can have them push it back a few days.
> 
> I will look over the datasheets at be sure these tubes are compatible, all about their bias point and ensuring no ratings are exceeded in my circuit.  There are a few oddball pentodes that bias too hot in this amp.  But I want to exhaust the tubes that do not need adapters first before trying others, top of the power tube shopping list right now is a pair of Tung-Sol 6550.  I would also like to try the RCA 6L6GC.  Honestly NOS KT88 are so expensive, I may not even bother.
> 
> @Zachik if the timeline is met, I will send it to Zach who will bring it with him to CanJam  not practical for me to fly out and back for one day unfortunately given my work schedule.



This amp will use many different power tubes that you can get decent deals on and without going the crazy route of GEC KT88, which are at insane prices, really insane. Much more money than most would spend to have in the amp daily.
There are numerous EL34 tubes that sound fantastic without going overboard and getting into the metal base variety.
At some point the price of a tube is just not worth the risk of using them, there are some tubes that are just basically in the collector's status in my opinion.
Some people may use them, but most of the people will never even bother when they can buy numerous tubes for an even lesser price.
I am sure at one point these tubes were a decent price, but not anymore.


----------



## triod750

If you buy the most expensive tubes and let them warm up continuously for a month they will sound glorious, trust me ! You won't be able to stop listening.


----------



## whirlwind

triod750 said:


> If you buy the most expensive tubes and let them warm up continuously for a month they will sound glorious, trust me ! You won't be able to stop listening.


Oh yes, you are correct, thing is the law of diminishing returns is at it's highest....most all pentode tubes sound good.


----------



## L0rdGwyn (Aug 22, 2022)

whirlwind said:


> This amp will use many different power tubes that you can get decent deals on and without going the crazy route of GEC KT88, which are at insane prices, really insane. Much more money than most would spend to have in the amp daily.
> There are numerous EL34 tubes that sound fantastic without going overboard and getting into the metal base variety.
> At some point the price of a tube is just not worth the risk of using them, there are some tubes that are just basically in the collector's status in my opinion.
> Some people may use them, but most of the people will never even bother when they can buy numerous tubes for an even lesser price.
> I am sure at one point these tubes were a decent price, but not anymore.



You're absolutely right Joe, there does come a point where the ultra rare tubes just aren't worth it.  Unless a happen across some insane deal, I will most likely pass on GEC KT88, and the metal base Mullards are out of the question.  Lots of other tubes to try.  Probably the highest up the rare tube ladder I want to go is a pair of Tung-Sol 6550, and likely some other Mullard EL34.  If the amp / circuit is good, most any tubes will sound good in it.  Right now I am listening to the Visseaux 6V6GT, they are relatively inexpensive and sound phenomenal.  I've thought about grabbing some GEC KT63 / 6F6G too, which aren't too pricey.


----------



## L0rdGwyn

Part of the reason I am interested in trying something from the KT88 / 6550 family is simply to see how they perform in the amp and take some real-world measurements.  All for the sake of science of course  I can't bring myself to buy a new production KT88 though, probably what I will eventually do is try one of the variants that is only available new production, KT90, KT120, or KT150.  Assuming they are drop in replacements for KT88 and will bias similarly, the amp should be able to use any of them, it has the heater current available to do so.  But I will check the datasheets just in case.  The KT150 would look hilariously huge in this amp though lol probably would go for the KT90 or KT120.


----------



## triod750

whirlwind said:


> Oh yes, you are correct, thing is the law of diminishing returns is at it's highest....most all pentode tubes sound good.


The more diminished the more valuable the result. Eventually one will experience something nobody else has (not) heard since they haven't yet got that far


----------



## L0rdGwyn

triod750 said:


> The more diminished the more valuable the result. Eventually one will experience something nobody else has (not) heard since they haven't yet got that far



For the cost of collecting extremely rare and valuable NOS tubes, the buyer could commission an entirely new amplifier, which would have much more drastic effects on listening experience than swapping tubes.  There is an entire 300B thread right now where people are spending thousands of dollars on 300B tubes.  Why not hold onto that money and commission a custom 300B amp as opposed to an off-the-shelf model?  Just my opinion, but the money would be better spent that way.  I think there is a misconception from tubehead audiophiles that the tube model makes the amp, but IME that is not the case, the totality of the circuit is more important and tubes are just another circuit element.  

Take a 300B amplifier with a resistor loaded cathode biased input stage, cap coupled, and cathode biased output stage with an 60Hz AC filament supply and listen to it side-by-side with a CCS or inductor loaded fixed bias input stage, cap or transformer coupled, and a fixed bias output stage with a proper DC filament supply.  There would absolutely be no comparison, the cheapest 300B tube in the latter circuit would slay the most TOTL 300B tube in the former.


----------



## triod750

I'm just joking. The designer of my Triod750 amp always said 'It's not the tube, it's the design'. Use the right tube for the design or use the right design for the tube. But what did he know?!


----------



## L0rdGwyn

triod750 said:


> I'm just joking. The designer of my Triod750 amp always said 'It's not the tube, it's the design'. Use the right tube for the design or use the right design for the tube. But what did he know?!



Oh I know you are joking!  I am agreeing with your sarcasm


----------



## L0rdGwyn (Aug 22, 2022)

I'll just add if you already own your dream amplifier and have the cash to spend on TOTL rare NOS tubes, then more power to ya  but I think there are instances where people could get better performance by changing amplifiers instead.  For many of these commercial 300B amps, I suspect the manufacturers are spending more on the cost of the chassis than they are on what's inside.


----------



## L0rdGwyn (Aug 22, 2022)

RCA 5691 have arrived.  Yeah these are good sounding tubes, and pretty to look at.  Paired with the RCA 5R4GY and Mazda 6V6GT.  I have been taking a break from the ZMFs and listening to the HD650.  It's a headphone that really scales with good amplification, can still be downright impressive and very enjoyable tone.


----------



## UntilThen

L0rdGwyn said:


> I'll just add if you already own your dream amplifier and have the cash to spend on TOTL rare NOS tubes, then more power to ya  but I think there are instances where people could get better performance by changing amplifiers instead.  For many of these commercial 300B amps, I suspect the manufacturers are spending more on the cost of the chassis than they are on what's inside.



Haha if you've not already gotten your NOS tubes then it's probably too late already unless you're willing to spend big bucks. I was fortunate to have met a private collector who owns a Leak amplifier and have amassed an amazing collection of lovely NOS tubes. We became kind of friends the more we corresponded and I bought my NOS tubes much much cheaper than on the open market or eBay. 

Was it worth buying all the NOS tubes for Odyssey? You bet. I love all of them and they add different flavors. Take for instance the EL12 spez. They are as good as the others and I have 3 pairs new in Telefunken boxes.

I'm done buying tubes for Odyssey but I'm entering a next phase with 300b amp. I look around at the commercial offerings and decided that I will still go with a custom 300b amp. If those pentode NOS tubes are expensive, good 300b tube prices will make them pale in comparison.... unless I go cheap with a pair of Psvane 300b tubes. Now I'd like to hear that it doesn't matter what 300b tubes I use, it's in the amp design but die hard 300b amp owners will tell you that's not true.


----------



## L0rdGwyn (Aug 22, 2022)

UntilThen said:


> Haha if you've not already gotten your NOS tubes then it's probably too late already unless you're willing to spend big bucks. I was fortunate to have met a private collector who owns a Leak amplifier and have amassed an amazing collection of lovely NOS tubes. We became kind of friends the more we corresponded and I bought my NOS tubes much much cheaper than on the open market or eBay.
> 
> Was it worth buying all the NOS tubes for Odyssey? You bet. I love all of them and they add different flavors. Take for instance the EL12 spez. They are as good as the others and I have 3 pairs new in Telefunken boxes.
> 
> I'm done buying tubes for Odyssey but I'm entering a next phase with 300b amp. I look around at the commercial offerings and decided that I will still go with a custom 300b amp. If those pentode NOS tubes are expensive, good 300b tube prices will make them pale in comparison.... unless I go cheap with a pair of Psvane 300b tubes. Now I'd like to hear that it doesn't matter what 300b tubes I use, it's in the amp design but die hard 300b amp owners will tell you that's not true.



It's fortunate for you to have come across such a stash,  I'm sure they are lots of fun to play with 

I think you are right to go with the custom amplifier, of course you know the quality will be better. There are certain commercial designs that are poor IMO selling for over $10K USD, but since they use 300B, like moths to the flame the audiophiles are drawn. I don't doubt for a second that there are gains to be had using higher quality 300B tubes, but I think the person willing to spend 3-4K on their commercial 300B amplifier and another 4K on 300B tubes would be better served consolidating that money into a higher quality custom amplifier and one or two good pair of 300B. Of course there is the wait time to deal with, but quality takes time.


----------



## UntilThen

L0rdGwyn said:


> I think you are right to go with the custom amplifier, of course you know the quality will be better. *There are certain commercial designs that are poor IMO selling for over $10K USD, but since they use 300B, like moths to the flame the audiophiles are drawn.* I don't doubt for a second that there are gains to be had using higher quality 300B tubes, but I think the person willing to spend 3-4K on their commercial 300B amplifier and another 4K on 300B tubes would be better served consolidating that money into a higher quality custom amplifier and one or two good pair of 300B. Of course there is the wait time to deal with, but quality takes time.



"Truer words have never been spoken".   

... and I will have at most just one pair of good 300b. The days of spending on head-fi is over. I'm going fishing !
​


----------



## triod750

UntilThen said:


> ... and I will have at most just one pair of good 300b. The days of spending on head-fi is over.


Hmmm....


----------



## Wes S (Aug 23, 2022)

L0rdGwyn said:


> For the cost of collecting extremely rare and valuable NOS tubes, the buyer could commission an entirely new amplifier, which would have much more drastic effects on listening experience than swapping tubes.  There is an entire 300B thread right now where people are spending thousands of dollars on 300B tubes.  Why not hold onto that money and commission a custom 300B amp as opposed to an off-the-shelf model?  Just my opinion, but the money would be better spent that way.  I think there is a misconception from tubehead audiophiles that the tube model makes the amp, but IME that is not the case, the totality of the circuit is more important and tubes are just another circuit element.
> 
> Take a 300B amplifier with a resistor loaded cathode biased input stage, cap coupled, and cathode biased output stage with an 60Hz AC filament supply and listen to it side-by-side with a CCS or inductor loaded fixed bias input stage, cap or transformer coupled, and a fixed bias output stage with a proper DC filament supply.  There would absolutely be no comparison, the cheapest 300B tube in the latter circuit would slay the most TOTL 300B tube in the former.


Good stuff!  Just out of curiosity, I would love to hear your thoughts on the Cayin HA300mk2 (off the shelf model) if you don't mind.  The sound is insanely good, but now you have me wondering about custom options again. . . I was looking to go custom before the purchase of the Cayin, but decided not to go that route after hearing all the good stuff Zach (ZMF) had to say about the HA300mk2.  I don't know anything about amp design, so I was not to sure about the custom route, and that was another reason I went with the Cayin.  Honestly, I am in love with the sound and I am using some Elrog ER300B and RFT 6SN7 (welded plates with ceramic spacers) and can't imagine it getting any better, but again you have me wondering. . .did I make a bad purchase?  If you or anyone in this thread thinks it can sound better than this for a similar amount of money with a custom option, I would really love to know, and thanks for your time!

I will say this from my own experience, the Cayin HA300mk2 with my upgraded NOS tubes included of which has cost me of total of around $4,800 all together, absolutely smokes my last amp the Pendant SE and it's not even close.  So, I was thinking that was a pretty good deal for what I am hearing, but again I am really interested in how a custom 300B amp would compare.


----------



## whirlwind

L0rdGwyn said:


> You're absolutely right Joe, there does come a point where the ultra rare tubes just aren't worth it.  Unless a happen across some insane deal, I will most likely pass on GEC KT88, and the metal base Mullards are out of the question.  Lots of other tubes to try.  Probably the highest up the rare tube ladder I want to go is a pair of Tung-Sol 6550, and likely some other Mullard EL34.  If the amp / circuit is good, most any tubes will sound good in it.  Right now I am listening to the Visseaux 6V6GT, they are relatively inexpensive and sound phenomenal.  I've thought about grabbing some GEC KT63 / 6F6G too, which aren't too pricey.


I have not priced KT63's for awhile. I will vouch for them being nice sounding tubes though. I am listening to a pair now. Years ago I bought some for $70 a pair then it went to $100 but I still bought more because they sounded really good, and  the bang for the buck was stellar compared to some other higher priced tubes. I am assuming @leftside will probably have every variation as he has a killer stash of tubes.


----------



## Zachik

Wes S said:


> you have me wondering. . .did I make a bad purchase?


No, you did not!
First, I auditioned the mk1 when it came out, with stock tubes, and it sounded wonderful. I bet the mk2 and with upgrade 300b tubes - sounds glorious.
Second, buying custom has its downsides too... I have one being finished as we speak, so I am not saying custom is the wrong way to go, but it is not perfect:
* Longer wait times. Much longer sometimes...
* In case of service needed (touch wood that does not happen) - well, best case it is more complicated, and worst case (e.g. Glenn amps) you're SOL.
* Unless it is a custom design that you can audition in advance, which usually it is NOT the case - it is a gamble that you'd like the sound. And you cannot return it if you do not.
* Custom amps are *usually *more expensive than commercial amps

Wes, and I know this advice usually falls on deaf ears in this hobby, since you love your amp so much - do not second guess your choice!


----------



## Xcalibur255

L0rdGwyn said:


> Part of the reason I am interested in trying something from the KT88 / 6550 family is simply to see how they perform in the amp and take some real-world measurements.  All for the sake of science of course  I can't bring myself to buy a new production KT88 though, probably what I will eventually do is try one of the variants that is only available new production, KT90, KT120, or KT150.  Assuming they are drop in replacements for KT88 and will bias similarly, the amp should be able to use any of them, it has the heater current available to do so.  But I will check the datasheets just in case.  The KT150 would look hilariously huge in this amp though lol probably would go for the KT90 or KT120.


I researched the crap out of the KT150 before committing to it for my amp.  There is a fairly solid consensus that the 150 is a substantially better tube overall than the 120.  The engineers at New Sensor had triode strapping applications in mind when designing it and it gives nice results when used in a SET application.

On a side note, I recommend you give the Sophia EL34ST (the blue glass ones) a try too.  I was honestly kind of cynical about these when I bought them and figured they would be overpriced for what they were.  It seems like the goal of most new production tubes that are entering the market now are to be "boutique" so they can be incredibly expensive.  These are absolutely worth what Sophia is charging though, I am quite in love with how they sound.  The tone is divine and they reach deep into the music with excellent layering.


----------



## L0rdGwyn (Aug 23, 2022)

Wes S said:


> Good stuff!  Just out of curiosity, I would love to hear your thoughts on the Cayin HA300mk2 (off the shelf model) if you don't mind.  The sound is insanely good, but now you have me wondering about custom options again. . . I was looking to go custom before the purchase of the Cayin, but decided not to go that route after hearing all the good stuff Zach (ZMF) had to say about the HA300mk2.  I don't know anything about amp design, so I was not to sure about the custom route, and that was another reason I went with the Cayin.  Honestly, I am in love with the sound and I am using some Elrog ER300B and RFT 6SN7 (welded plates with ceramic spacers) and can't imagine it getting any better, but again you have me wondering. . .did I make a bad purchase?  If you or anyone in this thread thinks it can sound better than this for a similar amount of money with a custom option, I would really love to know, and thanks for your time!
> 
> I will say this from my own experience, the Cayin HA300mk2 with my upgraded NOS tubes included of which has cost me of total of around $4,800 all together, absolutely smokes my last amp the Pendant SE and it's not even close.  So, I was thinking that was a pretty good deal for what I am hearing, but again I am really interested in how a custom 300B amp would compare.



Hey Wes, I'm sorry I didn't mean to make you doubt your purchase!  The Cayin HA-300MK2 is one of the most reasonably priced 300B amps out there, and it has Zach's endorsement, so I'm sure it is a great sounding amplifier.  I can't comment on the specifics of the circuit (I see no photos or specific information online), but for the price, to me it looks like you are getting quite a lot with a well-made chassis, separate tube rectified power supply unit, and other features.  And the fact that you went straight for the Elrog tubes, which have a great reputation, ultimately is saving you money long term.  I have seen some Head-Fiers collecting 300B tubes, which is an expensive endeavor unto itself, which is what motivated my comment primarily.  There are also other 300B amplifiers out there that I would say offer less than the Cayin for drastically more money (there is one in particular I find especially egregious...).  So I think you've made a good choice going for the Cayin as it isn't overpriced like some other 300B designs out there and you'll save long term going right for the best tubes.

And @Zachik 's points are all totally valid, there are drawbacks to the custom route.  The advantage is you then have access to more exotic circuit elements / topologies, but it is still a gamble, that is absolutely true.  The Telemachus seems to be the go-to custom 300B right now from Ultrasonic Studios, so maybe that is something you could investigate in the future, seems he will be making quite a few of them given the demand, maybe an audition could become available or a Head-Fier could compare it to the Cayin some day.

Sorry maybe I shouldn't be so loose lipped, I honestly did not have the Cayin in mind when making these comments, ultimately all that matters is that you are happy with your amplifier


----------



## L0rdGwyn

whirlwind said:


> I have not priced KT63's for awhile. I will vouch for them being nice sounding tubes though. I am listening to a pair now. Years ago I bought some for $70 a pair then it went to $100 but I still bought more because they sounded really good, and  the bang for the buck was stellar compared to some other higher priced tubes. I am assuming @leftside will probably have every variation as he has a killer stash of tubes.



Awesome, maybe I'll grab a pair.  $100 for a NOS pair of GEC tubes seems like a steal these days, they always have a crazy markup!


----------



## L0rdGwyn

Xcalibur255 said:


> I researched the crap out of the KT150 before committing to it for my amp.  There is a fairly solid consensus that the 150 is a substantially better tube overall than the 120.  The engineers at New Sensor had triode strapping applications in mind when designing it and it gives nice results when used in a SET application.
> 
> On a side note, I recommend you give the Sophia EL34ST (the blue glass ones) a try too.  I was honestly kind of cynical about these when I bought them and figured they would be overpriced for what they were.  It seems like the goal of most new production tubes that are entering the market now are to be "boutique" so they can be incredibly expensive.  These are absolutely worth what Sophia is charging though, I am quite in love with how they sound.  The tone is divine and they reach deep into the music with excellent layering.



Thanks, duly noted.  I am thinking I will most likely try the KT90 actually.  None of these tubes are going to be biased anywhere close to their max specs, so seems like the lowest power model is the most sane one to try.  That is the second time the Sophias have been recommended to me, so they certainly seem to have garnered a good reputation!


----------



## Deleeh

Wes S said:


> Good stuff!  Just out of curiosity, I would love to hear your thoughts on the Cayin HA300mk2 (off the shelf model) if you don't mind.  The sound is insanely good, but now you have me wondering about custom options again. . . I was looking to go custom before the purchase of the Cayin, but decided not to go that route after hearing all the good stuff Zach (ZMF) had to say about the HA300mk2.  I don't know anything about amp design, so I was not to sure about the custom route, and that was another reason I went with the Cayin.  Honestly, I am in love with the sound and I am using some Elrog ER300B and RFT 6SN7 (welded plates with ceramic spacers) and can't imagine it getting any better, but again you have me wondering. . .did I make a bad purchase?  If you or anyone in this thread thinks it can sound better than this for a similar amount of money with a custom option, I would really love to know, and thanks for your time!
> 
> I will say this from my own experience, the Cayin HA300mk2 with my upgraded NOS tubes included of which has cost me of total of around $4,800 all together, absolutely smokes my last amp the Pendant SE and it's not even close.  So, I was thinking that was a pretty good deal for what I am hearing, but again I am really interested in how a custom 300B amp would compare.


Don't misunderstand.
Just because Zach says the Cayin is good doesn't mean anything.
If Zach said something like that, I would read between the lines.
Which means that the Cayhin amplifier goes very well with the Zmf headphones.
That's all he's saying, Zach would never say it would be as good with other headphones.
Would also be counterproductive for him pessimistically.
With the Cayin amp you have, I would say you have a good one, most of the bugs from the Mk1 series have been fixed or even improved.
So no need to panic.
The Mk 1 has been slightly discredited because it was a lot of money for what it offers.
Similar to the Mcintosh mha 200 it sounds good but with the unity gain pot Mcintosh drove the amp to the wall and upset many.

Homemade amps don't necessarily sound better than the over-the-counter ones and vice versa.
It tends to depend more on the skills of the builder and the know how he has and how it was implemented.
Choice of components, type of concept, etc....
These are far more important aspects that determine how good an amplifier will be.
The result can be better, worse or the same.
But with people like Lord gwyn it is hard to say because there are only a handful of people who can enjoy his good work.
It has to be said that his parts selection, which I have roughly skimmed, is very good.
And he approaches it very differently than industrial manufacturers who go for the low cost principle.
He can afford to do that and his results speak for themselves in all areas.
Therefore, one can safely assume that a built amplifier in his range where 2500$ costs also annoys the large manufacturers who cost 5000$. The size order of the amount of money is now freely invented.
It's just to show that something like this is possible but not a must.

The best way to compare it is to have Lord gwyn's amplifier one day and compare it with your Cayhin and judge for yourself.
That would be the best and most sensible thing to do.
I wouldn't let anything else worry me now.

I also admire Lord's work and am fascinated by it and a little envious that I can't do it myself, because I would like to be able to do it.😇


----------



## L0rdGwyn

Deleeh said:


> Homemade amps don't necessarily sound better than the over-the-counter ones and vice versa.
> It tends to depend more on the skills of the builder and the know how he has and how it was implemented.
> Choice of components, type of concept, etc....
> These are far more important aspects that determine how good an amplifier will be.
> ...



I agree with many of your points, the result will depend on the designer.  I will try to stop speaking in generalities and being overly critical of commercial designs, it is really a small subset of these amplifiers that are frustrating as their prices are inflated to the point of being disingenuous, IMO, and I don't think the Cayin falls into that category.  It's true that I design from a DIYers perspective with a much more liberal budget and without the supply chain and manufacturing complexities of large volume production, so it is a little unfair to be so critical.

I am hoping to bring this pentode amplifier to a wider audience in some way as I've said, there are definitely some outlying questions as to the practicality of commercial production, supply chain, cost of manufacture, etc.  Those conversations will take place in the coming months and we will see what comes of it.  If I am able to get the amplifier to CanJam SoCal, well then Head-Fiers themselves can compare it then and there.  If no one likes it, then that will be that


----------



## Xcalibur255

L0rdGwyn said:


> Thanks, duly noted.  I am thinking I will most likely try the KT90 actually.  None of these tubes are going to be biased anywhere close to their max specs, so seems like the lowest power model is the most sane one to try.  That is the second time the Sophias have been recommended to me, so they certainly seem to have garnered a good reputation!


I haven't tried a KT90 yet either.  That would probably bias up about the same as a KT150 does in my amp in the EL34 bias setting.  I did try a KT66, which sounds fine but is my least favorite of the power tubes I have on hand.  They're very nicely made but the sound lacks the depth that the KT150 and EL34 offer.


----------



## L0rdGwyn

Xcalibur255 said:


> I haven't tried a KT90 yet either.  That would probably bias up about the same as a KT150 does in my amp in the EL34 bias setting.  I did try a KT66, which sounds fine but is my least favorite of the power tubes I have on hand.  They're very nicely made but the sound lacks the depth that the KT150 and EL34 offer.



Yeah I bet KT90 would work well in your amplifier.  Like the KT150, it is a KT88 type with a higher plate dissipation, 50W.  So maybe you would use the KT150 setting unless they KT150 are biased pretty hot, obviously Mischa would know.  Are they new production KT66?  Like the KT88, prices for NOS are a bit crazy.  I have found big differences in sound in my circuit with different 6L6 types, pretty drastic in fact.  Best one I have is the Ken-Rad 6L6G.


----------



## Wes S

Zachik said:


> No, you did not!
> First, I auditioned the mk1 when it came out, with stock tubes, and it sounded wonderful. I bet the mk2 and with upgrade 300b tubes - sounds glorious.
> Second, buying custom has its downsides too... I have one being finished as we speak, so I am not saying custom is the wrong way to go, but it is not perfect:
> * Longer wait times. Much longer sometimes...
> ...


Thanks for the info buddy!  I really appreciate the detailed response.


----------



## Wes S

L0rdGwyn said:


> Hey Wes, I'm sorry I didn't mean to make you doubt your purchase!  The Cayin HA-300MK2 is one of the most reasonably priced 300B amps out there, and it has Zach's endorsement, so I'm sure it is a great sounding amplifier.  I can't comment on the specifics of the circuit (I see no photos or specific information online), but for the price, to me it looks like you are getting quite a lot with a well-made chassis, separate tube rectified power supply unit, and other features.  And the fact that you went straight for the Elrog tubes, which have a great reputation, ultimately is saving you money long term.  I have seen some Head-Fiers collecting 300B tubes, which is an expensive endeavor unto itself, which is what motivated my comment primarily.  There are also other 300B amplifiers out there that I would say offer less than the Cayin for drastically more money (there is one in particular I find especially egregious...).  So I think you've made a good choice going for the Cayin as it isn't overpriced like some other 300B designs out there and you'll save long term going right for the best tubes.
> 
> And @Zachik 's points are all totally valid, there are drawbacks to the custom route.  The advantage is you then have access to more exotic circuit elements / topologies, but it is still a gamble, that is absolutely true.  The Telemachus seems to be the go-to custom 300B right now from Ultrasonic Studios, so maybe that is something you could investigate in the future, seems he will be making quite a few of them given the demand, maybe an audition could become available or a Head-Fier could compare it to the Cayin some day.
> 
> Sorry maybe I shouldn't be so loose lipped, I honestly did not have the Cayin in mind when making these comments, ultimately all that matters is that you are happy with your amplifier


Thanks for the info man!  I really appreciate all the info, and I am absolutely loving the amp.  The Telemachus was the one custom I was considering, but I am just going to stick with what I have as I am happy, and I am at the max of my budget anyway.

Cheers bro!


----------



## L0rdGwyn

Wes S said:


> Thanks for the info man!  I really appreciate all the info, and I am absolutely loving the amp.  The Telemachus was the one custom I was considering, but I am just going to stick with what I have as I am happy, and I am at the max of my budget anyway.
> 
> Cheers bro!



No problem!  Glad you are happy, your setup looks great


----------



## L0rdGwyn

I was able to get the ship date for the last part I need moved to 8/31, so barring some completely unexpected issue with it, CanJam SoCal should be a go for this amp  really excited about that, can't think of any better way to get some feedback on it.


----------



## Deleeh

Yes, that would be great if that could be realised.
I would be interested.
Since you are still in "development" so to speak, how about the Eu side with its 230v environment?
Would the amplifier also be compatible with the power supply?

At the CanJam SoCal you can of course get good feedback and certainly also test planar headphones and other headphones on how they do on the amplifier.
And tweak a screw or two if necessary.

Fingers crossed that it will be available as a diy kit at some point in the future,🤞🤞🤞🤞🤞🤞🤞


----------



## L0rdGwyn

Deleeh said:


> Yes, that would be great if that could be realised.
> I would be interested.
> Since you are still in "development" so to speak, how about the Eu side with its 230v environment?
> Would the amplifier also be compatible with the power supply?
> ...



230V would be no problem, the mains transformer can be wired for parallel (115/120V) or series (230/240V) primary windings to accommodate.  We'll see what happens


----------



## Xcalibur255

L0rdGwyn said:


> Yeah I bet KT90 would work well in your amplifier.  Like the KT150, it is a KT88 type with a higher plate dissipation, 50W.  So maybe you would use the KT150 setting unless they KT150 are biased pretty hot, obviously Mischa would know.  Are they new production KT66?  Like the KT88, prices for NOS are a bit crazy.  I have found big differences in sound in my circuit with different 6L6 types, pretty drastic in fact.  Best one I have is the Ken-Rad 6L6G.


No NOS power tubes for me yet.  The prices make my eyes water.  I have NOS covered on the driver side for this amp (because it's mandatory there  ) so I decided to be lazy and just buy power tubes the easy way.  The KT66 are the new sensor Gold Lions.  I think they're impressively well made, but the Sophia EL34ST and TungSol KT150 are both better in the sound department.

So, if a KT90 has a 50W rating then they'd run in the hotter KT150 bias mode.  It's pretty conservative actually at 38W.  There are so many KT tubes out there I have not looked at them all and this is one of the types I sort of just ignored.    I was going to try a KT77 but decided the Sophia EL34s kind of covered that already.

Honestly I'm still bummed out about my KR KT150 taking a dump on me.  I may try again someday (definitely not from the same seller), but I've been slowly becoming more and more uncomfortable buying the megabuck tubes and this only accelerated that attitude.  The only real listening session I got from them before they died suggested they might be a pretty sizable upgrade over the new sensor product though so the temptation is still hanging out somewhere in the back of my head.


----------



## L0rdGwyn (Aug 24, 2022)

Xcalibur255 said:


> No NOS power tubes for me yet.  The prices make my eyes water.  I have NOS covered on the driver side for this amp (because it's mandatory there  ) so I decided to be lazy and just buy power tubes the easy way.  The KT66 are the new sensor Gold Lions.  I think they're impressively well made, but the Sophia EL34ST and TungSol KT150 are both better in the sound department.
> 
> So, if a KT90 has a 50W rating then they'd run in the hotter KT150 bias mode.  It's pretty conservative actually at 38W.  There are so many KT tubes out there I have not looked at them all and this is one of the types I sort of just ignored.    I was going to try a KT77 but decided the Sophia EL34s kind of covered that already.
> 
> Honestly I'm still bummed out about my KR KT150 taking a dump on me.  I may try again someday (definitely not from the same seller), but I've been slowly becoming more and more uncomfortable buying the megabuck tubes and this only accelerated that attitude.  The only real listening session I got from them before they died suggested they might be a pretty sizable upgrade over the new sensor product though so the temptation is still hanging out somewhere in the back of my head.



Yeah the prices are crazy, I was unawares of how crazy they'd gotten, since I primarily build with DHTs, I hadn't really paid attention to the market for a few years, youch.  But at the same time its great there are so many new production options, and sounds like many of them are really good, part of the reason I went with them for this new amp, so I guess I better be willing to try them out 

38W for a 50W tube would be a good place to be, a little under 80% of maximum plate dissipation would increase tube longevity at the cost of some power output, but with your speakers being what they are and headphone use, shouldn't be an issue.

Big bummer on the KR KT150.  I can't recall, were you refunded for them?  Maybe worth trying again if there is a warranty.  Yeah it's tough with expensive and super rare tubes.  I remember at one point I was seriously considering building a PX25 amplifier and another time a type 50 amplifier with the full intention of collecting NOS tubes...not sure I'd be into that nowadays lol to spend close to $1K only to have a tube die would be tough to swallow.

Plus I have my huge stash of HY69 now, which is like a type 50 on steroids


----------



## L0rdGwyn

Coming off of a night shift, gonna power through today, listening to some Waylon Live, back on the Ken-Rad 6L6G.




For CanJam, thinking I will send along two sets of tubes - RCA 5R4GY and Philips GZ34; Tung-Sol 6SU7GTY and RCA 5691; Ken-Rad 6L6G and Philips EL34.  The GZ34 + EL34 combo has the most wow factor in terms of soundstage and airiness, while the 5R4GY + 6L6G has great tone, should be two good options.


----------



## Xcalibur255

L0rdGwyn said:


> Big bummer on the KR KT150.  I can't recall, were you refunded for them?  Maybe worth trying again if there is a warranty.  Yeah it's tough with expensive and super rare tubes.  I remember at one point I was seriously considering building a PX25 amplifier and another time a type 50 amplifier with the full intention of collecting NOS tubes...not sure I'd be into that nowadays lol to spend close to $1K only to have a tube die would be tough to swallow.
> 
> Plus I have my huge stash of HY69 now, which is like a type 50 on steroids


I did eventually get my money back.  After giving them 2 months to make things right and being completely ignored I finally filed a dispute with Paypal and the seller completely ignored THAT too it so it was decided in my favor by default.  It's the first time I've had to do such a thing and hopefully also the last.

I'm kind of surprised you haven't done anything with your HY69 stash yet!  You were pretty excited about them when you first found them and they're pretty darn cool tubes.  There's always tomorrow of course.  I'm guessing you would get power output in the same range as a 2A3 from it right?  What kind of driver tubes would suit it well?


----------



## L0rdGwyn (Aug 24, 2022)

Xcalibur255 said:


> I did eventually get my money back.  After giving them 2 months to make things right and being completely ignored I finally filed a dispute with Paypal and the seller completely ignored THAT too it so it was decided in my favor by default.  It's the first time I've had to do such a thing and hopefully also the last.
> 
> I'm kind of surprised you haven't done anything with your HY69 stash yet!  You were pretty excited about them when you first found them and they're pretty darn cool tubes.  There's always tomorrow of course.  I'm guessing you would get power output in the same range as a 2A3 from it right?  What kind of driver tubes would suit it well?



Wow!  To ignore a CC dispute is an impressive level of negligence.  Well good you got your money back, maybe you can try again with a more reputable dealer.

Yeah I'm still excited about them, but the amplifier I would build with them is similar to my 801A amplifier in terms of use, and I just don't have room for more amps right now lol also trying to be better about curbing my enthusiasm and not getting overburdened with DIY gear again.

If used only in class A1, they would get power output somewhere between a 2A3 and a 50, but since they are transmitting tubes, they have grids built to handle grid current, so if direct coupled or transformer coupled, they can swing pretty far into positive grid territory and the power output goes up to maybe 7-10W.  In terms of drivers, they have a mu of 6ish so a little higher than a DHT, so don't need a super high gain input tube.

Lots of options for them, but what I had drawn up was very similar to what I did for Zach's 45 amplifier, a transformer coupled fixed bias SET design with E182CC inputs, but for speakers instead.  I have a stash of E182CC and 7044 tubes too whenever I decide to do it.  Long term I'd also like to start winding my own transformers, so I might make that a focus of this particular build whenever the time feels right to do it.  Also need to do some sort of cage or plexiglass enclosure, not super comfortable with 450V exposed on the anode caps with my dumb cats lurking around.

Anyway, long story short it's all drawn up, just waiting to the right time to do it!


----------



## triod750

L0rdGwyn said:


> Anyway, long story short it's all drawn up, just waiting to the right time to do it!


How about next week?


----------



## L0rdGwyn

triod750 said:


> How about next week?



Next week I will be in the Bahamas


----------



## triod750

Forgot about that. I feel sorry for you and wish you better days in the future .


----------



## L0rdGwyn

triod750 said:


> Forgot about that. I feel sorry for you and wish you better days in the future .



It's a true burden, but I'm doing it for the good of humanity and world peace.


----------



## Monsterzero

L0rdGwyn said:


> Next week I will be in the Bahamas


I lived in the Bahamas, on Paradise Island for a year. The Bahamians are lovely people.
Try to get to the Turks and Caicos Islands too. Not as popular as the Bahamas, though that has changed quite a bit since I lived there (too). Better diving and less touristy.


----------



## L0rdGwyn

Monsterzero said:


> I lived in the Bahamas, on Paradise Island for a year. The Bahamians are lovely people.
> Try to get to the Turks and Caicos Islands too. Not as popular as the Bahamas, though that has changed quite a bit since I lived there (too). Better diving and less touristy.



I'm pretty sure you've lived everywhere at one point, D.


----------



## Monsterzero

L0rdGwyn said:


> I'm pretty sure you've lived everywhere at one point, D.


I've lived in many places indeed. One of the perks of being a dj for Club Med


----------



## gibosi

L0rdGwyn said:


> Next week I will be in the Bahamas



The Bahamas? Is there an audio show there?


----------



## L0rdGwyn

Monsterzero said:


> I've lived in many places indeed. One of the perks of being a dj for Club Med



That sounds like a blast!



gibosi said:


> The Bahamas? Is there an audio show there?



Only audio show there will be me with some IEMs on the beach with a good book (but I might be secretly thinking about tubes ).  I used to bring tube books on vacation, not anymore, probably a healthy choice lol.

If anyone needs a good beach read, highly recommend this one, it's a real page turner.


----------



## L0rdGwyn

Tonight's listening - Philips GZ34, Philips EL34, RCA 5691.


----------



## Zachik

L0rdGwyn said:


> If anyone needs a good beach read, highly recommend this one, it's a real page turner.


Searched audible.com, but could not find the audio version...


----------



## Xcalibur255

L0rdGwyn said:


> Wow!  To ignore a CC dispute is an impressive level of negligence.  Well good you got your money back, maybe you can try again with a more reputable dealer.


I did vet this store looking for horror stories on online forums before ordering and didn't find anything that would raise eyebrows.  They even sell the expensive limited edition RK versions of the KR tubes so there was nothing that raised any red flags.  As soon as I had a problem and needed help though I didn't exist.  Oh well, it's in the past now.

Enjoy that vacation.  Hope it's a long one that truly lets to get a breather from work.


----------



## whirlwind

L0rdGwyn said:


> Next week I will be in the Bahamas


Good for you...enjoy Keenan.


----------



## CJG888

L0rdGwyn said:


> That sounds like a blast!
> 
> 
> 
> ...


I presume you have a portable tube amp for those IEMs…


----------



## jonathan c

L0rdGwyn said:


> That sounds like a blast!
> 
> 
> 
> ...


…could the 98-lb weakling also use a 98-lb transformer to impress the Funicellos….? 🤪


----------



## L0rdGwyn

Xcalibur255 said:


> Enjoy that vacation.  Hope it's a long one that truly lets to get a breather from work.





whirlwind said:


> Good for you...enjoy Keenan.



Thanks, it is badly needed, I am experiencing black cloud syndrome at work lately lol.


----------



## cacacacaciiiiii

Hiya,

I've recently bought/built the BHC (no speedball yet) for my Atrium. First time listening to tubes, and, more, please more!

I've been eyeing the Bottlehead site; Crackatwoa, Mainline, .. not just looking for more 'tube sound' but also the build process. (looking at their products, I'm leaning more towards the Crackatwoa than the Mainline.. OTL, more 'tube'-like sound).

In my indecisiveness I would buy both of those and give them a twirl.. that got me to thinking - why don't I build one of these myself? (got some hobbyist experience in the electronics field)

Being completely new at the tube amp thing - is a DIY project from scratch a possible way to come out with a 'better' amp than the Bottlehead offering? Or will there be limitations beyond skill, time, experience coming up rather quickly? E.g. if the Crackatwoa main improvement is the power supply but such a speciality item is only available from a place like Bottlehead - defeating the point of trying anything yourself.


----------



## L0rdGwyn

Hi there - building your own amp is definitely an option, but it is a serious commitment, you have to hit the books and understand tube design before you can build your own amplifier.  The end result could be better than a Bottlehead kit definitely, depending on what you design.  There are power supply regulator kits available that will outperform the shunt regulator in the Crackatwoa and Mainline, the 21st Century Maida regulator from Neurochrome is an option, but as I said, some prerequisite electronics knowledge is required to properly implement it.  The "tube sound" you are hearing is the sound of second harmonic distortion.  The BHC is a fairly basic tube amp design and as such has somewhat high distortion.  Improvements upon it will lower distortion, which will increase clarity and soundstage.  The question then becomes do you like this less distorted sound?  Most people do.  Trying the Speedball before anything else might be a good way to assess this.  There are also numerous OTL schematics around the web, lots on diyAudio.


----------



## cacacacaciiiiii

L0rdGwyn said:


> Hi there - building your own amp is definitely an option, but it is a serious commitment, you have to hit the books and understand tube design before you can build your own amplifier.  The end result could be better than a Bottlehead kit definitely, depending on what you design.  There are power supply regulator kits available that will outperform the shunt regulator in the Crackatwoa and Mainline, the 21st Century Maida regulator from Neurochrome is an option, but as I said, some prerequisite electronics knowledge is required to properly implement it.  The "tube sound" you are hearing is the sound of second harmonic distortion.  The BHC is a fairly basic tube amp design and as such has somewhat high distortion.  Improvements upon it will lower distortion, which will increase clarity and soundstage.  The question then becomes do you like this less distorted sound?  Most people do.  Trying the Speedball before anything else might be a good way to assess this.  There are also numerous OTL schematics around the web, lots on diyAudio.


Awesome! Have been reading through this thread and saw your references to some reading material on the topic. 

Read somewhere tonality is heavily influenced by the power supply regulator, and BH having proprietary ones got me worried - but that might just be so people can’t flat out copy the schematics and go around BH in their build. Your response got me more confident to do this. 

One question on the side. With the current iteration/addons available to the Stereomour II. Any reason it wouldn’t be superior to the Mainline as a headphone amp given some tweaks and the lower noise floor through the DC filament supply upgrade? Probably a very specific question but I’ve seen you comment on some of their stuff. 

Thanks!!


----------



## L0rdGwyn (Aug 31, 2022)

cacacacaciiiiii said:


> Awesome! Have been reading through this thread and saw your references to some reading material on the topic.
> 
> Read somewhere tonality is heavily influenced by the power supply regulator, and BH having proprietary ones got me worried - but that might just be so people can’t flat out copy the schematics and go around BH in their build. Your response got me more confident to do this.
> 
> ...



I wouldn't say to tonality is most heavily influenced by the regulator, maybe others have had different experiences.  Tonality is affected by everything, tubes chosen, topology, signal path components, brand and type of capacitor and where and how capacitors are used in the signal path greatly affect tonality.  It's hard to say it is any one thing.

Yes BH, Paul Birkeland in particular, have made their own regulators.  But there are many types of voltage regulators, both tube and silicon based, and information available on their design.  The 21st Century Maida regulator I mentioned is very high performing, it is a low dropout solid state voltage regulator using a regulator integrated circuit.  That is the simplest high performing solution, but if you were feeling ambitious, you could try design your own!  Different regulators serve different purposes, the most basic function is to filter ripple, and a very simple series regulator can accomplish this.  More advanced regulators utilize negative feedback to achieve a low output impedance in addition to filtering.  Lots of options.


----------



## L0rdGwyn

Sorry I am about to get in a submarine, I'll answer re regulators and Stereomour when I resurface.


----------



## Monsterzero

L0rdGwyn said:


> Sorry I am about to get in a submarine, I'll answer re regulators and Stereomour when I resurface.


 I'm going to wager that this is the very first time in Head-Fi history that those words have been spoken.


----------



## Xcalibur255

L0rdGwyn said:


> Sorry I am about to get in a submarine, I'll answer re regulators and Stereomour when I resurface.


Museum ship or working?  Both sound fun.


----------



## Zachik

Xcalibur255 said:


> Museum ship or working?  Both sound fun.


Probably a working sub, since @L0rdGwyn mentioned he is cruising through the Bahamas


----------



## L0rdGwyn

Xcalibur255 said:


> Museum ship or working?  Both sound fun.



A working one!  At least that's what they told me before I got on...I survived!

Here is a green moray 75ft below ☠️


----------



## L0rdGwyn

@cacacacaciiiiii on the Stereomour, you could use it as a headphone amplifier, in fact I'm pretty sure this specific question has been asked in the Bottlehead forum.  It isn't necessarily ideal however as the output transformers will be tapped for speaker impedances, I think the sound would be better if dedicated headphone transformers were used and you will lose power output this way.  My guess is you would get better performance from a dedicated headamp like the Mainline, but I can't be certain.  IMO, any headphone amp using DHTs should use a DC filament supply, so you would want to include that.  I would check the Bottlehead forum for this specific question, I'm sure it has been asked.


----------



## Paladin79 (Sep 3, 2022)

L0rdGwyn said:


> Here are some other random things I've acquired recently.
> 
> Custom walnut plinth for my turntable.  Just waiting for my new tonearm at this point, then I can rebuild it.
> 
> ...


I have decided to make my own plinth for a TD 125, considering what they are fetching with decent tone arms it will be a nice small project. I have a few projects before that but I like to plan ahead.


----------



## L0rdGwyn

Paladin79 said:


> I have decided to make my own plinth for a DT 125, considering what they are fetching with decent tone arms it will be a nice small project. I have a few projects before that but I like to plan ahead.



Cool!  Always good to have more plinth options out there, please post some pics when it's done


----------



## Paladin79

L0rdGwyn said:


> Cool!  Always good to have more plinth options out there, please post some pics when it's done


I shall, I will also make a custom arm board of course. That is pretty simple stuff.


----------



## L0rdGwyn

I've also been scheming another project, as I said I can't help thinking about tubes on vacation...

I am considering a strictly community DIY project, a spud design.  I have prototyped similar circuits and the sound is very good.  However that was done with the Sowter 8665 parafeed transformers.  The wait time for Sowter is very long and frankly they aren't what they once were since being sold to Carnhill.  The 8665 are a little pricey too and require a somewhat complex switch to adjust the turns ratio...

So I've reached out to Jack at Electra-Print to commission a pair of headphone parafeed transformers along with my intention to create a DIY project, meaning potential future orders from others.  If he can provide and my plans look good, I will look to release it on Head-Fi.

That would mean PCBs, BOM, chassis CAD files, build instructions, etc.  The trick will be making it inexperienced DIYer friendly and using easily sourced parts as it will require semiconductors.  TBD, we'll see what Jack says, he can be somewhat particular about his orders.


----------



## bcowen

L0rdGwyn said:


> A working one!  At least that's what they told me before I got on...I survived!
> 
> Here is a green moray 75ft below ☠️


Did they let you drive?  Or at least fire a torpedo?


----------



## L0rdGwyn

bcowen said:


> Did they let you drive?  Or at least fire a torpedo?



Nope, I just sat there looking out the window at the reef, pouting.  Turns out they don't want some tourist crashing the sub into the coral reef for some odd reason.


----------



## Wes S

L0rdGwyn said:


> I've also been scheming another project, as I said I can't help thinking about tubes on vacation...
> 
> I am considering a strictly community DIY project, a spud design.  I have prototyped similar circuits and the sound is very good.  However that was done with the Sowter 8665 parafeed transformers.  The wait time for Sowter is very long and frankly they aren't what they once were since being sold to Carnhill.  The 8665 are a little pricey too and require a somewhat complex switch to adjust the turns ratio...
> 
> ...


This sounds awesome man!  Looking forward to hearing more about it.


----------



## Zachik

L0rdGwyn said:


> That would mean PCBs, BOM, chassis CAD files, build instructions, etc. The trick will be making it inexperienced DIYer friendly and using easily sourced parts as it will require semiconductors. TBD, we'll see what Jack says, he can be somewhat particular about his orders.


If / when you look for guinea pigs, to try out building your kit - I am in!!


----------



## L0rdGwyn (Sep 1, 2022)

Wes S said:


> This sounds awesome man!  Looking forward to hearing more about it.



Thanks yeah I will post here as thing take shape.  Once I confirm I have a source for the transformers I'll figure out the details.  Would be a dual mono power supply, CCS loaded spud circuit, parafeed output, likely Clarity Cap parafeed capacitor, LED biased.  I will subjectively test several LEDs to find the best.  I need to decide what direction to take the CCS (FET vs BJT vs current source IC) and make setting the current simple and low hazard.  Likely the supply would not require regulation given the high PSRR of the output stage, which would simplify things considerably.


----------



## Mr Trev

L0rdGwyn said:


> Thanks yeah I will post here as thing take shape.  Once I confirm I have a source for the transformers I'll figure out the details.  Would be a duo mono power supply, CCS loaded spud circuit, parafeed output, likely Clarity Cap parafeed capacitor, LED biased.  I will subjectively test several LEDs to find the best.  I need to decide what direction to take the CCS (FET vs BJT vs current source IC) and make setting the current simple and low hazard.  Likely the supply would not require regulation given the high PSRR of the output stage, which would simplify things considerably.


Bonus points if you can make it a (reasonably) cheap Chi-Fi killer. I remember watching an interview with somebody in the auto industry talking about how it was easy to make a cost-no-object luxury car, but it took serious talent to build a stand out econobox. If you can apply that to the audio realm…


----------



## L0rdGwyn (Sep 1, 2022)

Mr Trev said:


> Bonus points if you can make it a (reasonably) cheap Chi-Fi killer. I remember watching an interview with somebody in the auto industry talking about how it was easy to make a cost-no-object luxury car, but it took serious talent to build a stand out econobox. If you can apply that to the audio realm…



Well there are certain things I won't go cheap on, the chassis and the transformers,  those will be the most expensive parts, most everything else will be inexpensive.  I would guesstimate parts would cost $600-800.  Certainly it would cost less than $1K.  I'll add that Jack's transformers are very high quality and not overpriced.  I was looking into Edcor as well but they have a minimum order quantity of 25 units for custom work.  So let's hope Jack is on board.


----------



## bcowen

Zachik said:


> If / when you look for guinea pigs, to try out building your kit - I am in!!


But there's soldering involved, and probably some screws and stuff to put in.  Better leave it to me.   🤣  🤣


----------



## Wes S

L0rdGwyn said:


> Thanks yeah I will post here as thing take shape.  Once I confirm I have a source for the transformers I'll figure out the details.  Would be a dual mono power supply, CCS loaded spud circuit, parafeed output, likely Clarity Cap parafeed capacitor, LED biased.  I will subjectively test several LEDs to find the best.  I need to decide what direction to take the CCS (FET vs BJT vs current source IC) and make setting the current simple and low hazard.  Likely the supply would not require regulation given the high PSRR of the output stage, which would simplify things considerably.


Heck yeah man, that all sounds legit!  I am happy as heck with my Cayin and honestly the only other amp I would like to own would be one of your creations, so I am really pumped there might be a chance and will be following along intently.


----------



## pravous

Zachik said:


> If / when you look for guinea pigs, to try out building your kit - I am in!!


Put me down for one of the first batch as well, if and when you get there.  Any ideas what tube type you are thinking of using?


----------



## L0rdGwyn

Wes S said:


> Heck yeah man, that all sounds legit!  I am happy as heck with my Cayin and honestly the only other amp I would like to own would be one of your creations, so I am really pumped there might be a chance and will be following along intently.



No doubt it would be very different from the Cayin!  Could complement it, we will see  going to try and get it done.



pravous said:


> Put me down for one of the first batch as well, if and when you get there.  Any ideas what tube type you are thinking of using?



Cool 😎 the idea would be for me to basically provide all of the info for someone to order everything themselves, wouldn't even need to go through me - Gerber files to order PCBs, CAD files to order a chassis (although Dave at Landfall would have the files already), BOM for all of the parts and where/how to order, Excel spreadsheet denoting the part number on the PCB, then I would have to build one and take photos along the way, write instructions, etc.

The list of spud-able tubes isn't super long, have to be high transconductance types, highish gain, low plate resistance, and linear.  My top choice would be a circuit that could use the 6E6P and the E810F.  With their pinouts and bias points, a circuit could be made to use both.  The 6E6P isn't as available as it once was before the mess in Ukraine, but still obtainable.  The E810F / 7788 is still quite common and not crazy expensive.

So that's a top choice but I will review all of the options again.  Since the circuit will be built onto a PCB, I could eventually post files for different tube types as well as addended instructions so they bias correctly.


----------



## L0rdGwyn

Just won these at auction, sorry if anyone else was bidding.  @UntilThen told me I needed NOS tubes, so I am trying to live up to his standards.


----------



## bcowen

L0rdGwyn said:


> No doubt it would be very different from the Cayin!  Could complement it, we will see  going to try and get it done.
> 
> 
> 
> ...


Have you ever looked at any of AMB's stuff?  I've built a couple of their components and found them to be a lot of fun.  While you can buy some of the parts from them (if you want), most of the parts you have to buy yourself.  Not an issue at all as they provide good links on sources. They also sell the PCB which I've been most happy to buy from them.  I can buy parts all day long, but I'd be a bit leery if I had to source the board myself. Maybe that's something you'd consider stocking to sell along with the plans.  Just a thought.

https://www.amb.org/audio/sigma11/

Sigma 11 LPS. I bought the board, mosfets, and (board mounted) heat sinks from them, but purchased everything else myself:


----------



## L0rdGwyn

bcowen said:


> Have you ever looked at any of AMB's stuff?  I've built a couple of their components and found them to be a lot of fun.  While you can buy some of the parts from them (if you want), most of the parts you have to buy yourself.  Not an issue at all as they provide good links on sources. They also sell the PCB which I've been most happy to buy from them.  I can buy parts all day long, but I'd be a bit leery if I had to source the board myself. Maybe that's something you'd consider stocking to sell along with the plans.  Just a thought.
> 
> https://www.amb.org/audio/sigma11/
> 
> Sigma 11 LPS. I bought the board, mosfets, and (board mounted) heat sinks from them, but purchased everything else myself:



No I haven't seen their stuff!  I'll check it out.

Yeah this approach is something I'm considering, if I were to buy the CCS parts myself, I could test them and then specify the correct part values for the desired current, much safer than having someone test in circuit by adjusting a trimmer for example (I do this all the time, but I've accepted the risk of being shocked if I screw up).  And provide the PCB, they come in minimum quantities of 5 from most board houses, so it would be wasteful if each person had to order 5 boards when they only need one...

On the other hand, I don't really want to make a lot of work for myself, especially with international shipping.  If I do this approach I will have to add some additional cost for the time and effort.  But the goal here isn't to make money, just share the project.  I'll consider both options.


----------



## UntilThen

L0rdGwyn said:


> Just won these at auction, sorry if anyone else was bidding.  @UntilThen told me I needed NOS tubes, so I am trying to live up to his standards.



How is it? I've never tried EL37 but it ought to be good. These ones are in very good condition and rather unusual original box.


----------



## cacacacaciiiiii

L0rdGwyn said:


> I've also been scheming another project, as I said I can't help thinking about tubes on vacation...
> 
> I am considering a strictly community DIY project, a spud design.  I have prototyped similar circuits and the sound is very good.  However that was done with the Sowter 8665 parafeed transformers.  The wait time for Sowter is very long and frankly they aren't what they once were since being sold to Carnhill.  The 8665 are a little pricey too and require a somewhat complex switch to adjust the turns ratio...
> 
> ...


Oooo count me in!


----------



## L0rdGwyn

UntilThen said:


> How is it? I've never tried EL37 but it ought to be good. These ones are in very good condition and rather unusual original box.



I'll let you know in a few days!  Yes quite the interesting pair being "laboratory matched".


----------



## whirlwind (Sep 2, 2022)

L0rdGwyn said:


> Just won these at auction, sorry if anyone else was bidding.  @UntilThen told me I needed NOS tubes, so I am trying to live up to his standards.


Congrats , great looking pair of tubes. I have heard they can push 70 watts when used in a push/pull
I believe they were Mullards answer to the GEC KT66

Some of the best sounding tubes in my GEL3N amp.    
Personally I like them better than KT66 and would like to own a back up pair, the only thing preventing that is the price for a nice NOS pair.


----------



## Paladin79 (Sep 2, 2022)

L0rdGwyn said:


> I've also been scheming another project, as I said I can't help thinking about tubes on vacation...
> 
> I am considering a strictly community DIY project, a spud design.  I have prototyped similar circuits and the sound is very good.  However that was done with the Sowter 8665 parafeed transformers.  The wait time for Sowter is very long and frankly they aren't what they once were since being sold to Carnhill.  The 8665 are a little pricey too and require a somewhat complex switch to adjust the turns ratio...
> 
> ...


Sounds like a fun project, I helped a friend with one years ago, I want to say prior to 2010. The tuber.  Earliest model I can think of used television sweep tubes that were readily available at one time, not so much anymore.


----------



## L0rdGwyn

whirlwind said:


> Congrats , great looking pair of tubes. I have heard they can push 70 watts when used in a push/pull
> I believe they were Mullards answer to the GEC KT66
> 
> Some of the best sounding tubes in my GEL3N amp.
> Personally I like them better than KT66 and would like to own a back up pair, the only thing preventing that is the price for a nice NOS pair.



Thanks Joe, that's encouraging, they weren't cheap but also not outrageous, I thought it was worth it for such a nice pair!  Like the EL34, it's a true pentode, and you're right 70W in push pull.  Should sound pretty good 



Paladin79 said:


> Sounds like a fun project, I helped a friend with one years ago, I want to say prior to 2010. The tuber.  Earliest model I can think of used television sweep tubes that were readily available at one time, not so much anymore.



Cool cool, I'm sure the tuber was a good amp, maybe I'll give this one a potato themed name  a good spud circuit can really sound excellent.  Signal path is short, and in parafeed with a CCS load and LED biasing, the only capacitor in the signal path is a high quality parafeed cap.  And it will be completely dual mono, so a high degree of channel separation.  Should sound pretty good!  Especially for the price.

Maybe I can teach some people how to use a benchtop DC power supply to set the current on the CCS.  Ideally this project would become self-sustaining so anyone could build it without my involvement.


----------



## L0rdGwyn

Greetings from the Bimini islands.


----------



## UntilThen

L0rdGwyn said:


> Greetings from the Bimini islands.



Greetings Keenan. Fyi, for my next 300b amp, I will be going with Monolith Magnetics output transformers.  Enjoy your holidays !


----------



## Paladin79

L0rdGwyn said:


> Thanks Joe, that's encouraging, they weren't cheap but also not outrageous, I thought it was worth it for such a nice pair!  Like the EL34, it's a true pentode, and you're right 70W in push pull.  Should sound pretty good
> 
> 
> 
> ...




tuber

too͞′bər, tyoo͞′-
noun​
A swollen, fleshy, usually underground outgrowth of the stem or rhizome of a plant, such as the potato, bearing buds from which new plant shoots arise.
A similar outgrowth of a plant root.
A rounded projection or swelling; a tubercle.
I think it may have first been called a single tube amp or some such, then tuber, then spud.


----------



## Tjj226 Angel

UntilThen said:


> Greetings Keenan. Fyi, for my next 300b amp, I will be going with Monolith Magnetics output transformers.  Enjoy your holidays !



Be very careful with monolith. They do make some decent stuff, but you have to be very judicious and read the spec sheet carefully. For instance, their low end 300b transformer actually has more primary impedance than their higher end transformers. 

If you want a 300b transformer, look at AE europe or contact 50AE on diy audio to make you a custom 300b transformer.


----------



## bcowen

Paladin79 said:


> *A swollen, fleshy, usually underground outgrowth of the stem* or rhizome of a plant, such as the potato, bearing buds from which new plant shoots arise.
> A similar outgrowth of a plant root.
> A rounded projection or swelling; a tubercle.
> I think it may have first been called a single tube amp or some such, then tuber, then spud.


Sounds like you're describing @Ripper2860 .   🤣


----------



## UntilThen

Tjj226 Angel said:


> Be very careful with monolith. They do make some decent stuff, but you have to be very judicious and read the spec sheet carefully. For instance, their low end 300b transformer actually has more primary impedance than their higher end transformers.
> 
> If you want a 300b transformer, look at AE europe or contact 50AE on diy audio to make you a custom 300b transformer.



I will leave that to my custom amp builder. I'm just a consumer.


----------



## L0rdGwyn (Sep 2, 2022)

Paladin79 said:


> tuber
> 
> too͞′bər, tyoo͞′-
> noun​
> ...



Lol yeah that is my understanding of the origin of the name.  It has been evolving, I wonder what comes next...



UntilThen said:


> Greetings Keenan. Fyi, for my next 300b amp, I will be going with Monolith Magnetics output transformers.  Enjoy your holidays !



Thank you!  There's almost over sadly, but toward the end you start to get homesick, maybe not work sick.  MM transformers are highly regarded, I haven't used them myself, should sound great!


----------



## Ripper2860

bcowen said:


> Sounds like you're describing @Ripper2860 .   🤣


I think you're confusing me with Ron Jeremy.


----------



## L0rdGwyn

Due to some issues Jack is having, likely his services will not be available for some months.  I'll make plans in the meantime as other work will take time, I'll check in with him then.  Otherwise I'll explore an alternative.  Electra-Print would be best, so will try to hold out for him, just means it may be a while before this project is fully realized.


----------



## Zachik

L0rdGwyn said:


> Due to some issues Jack is having, likely his services will not be available for some months.  I'll make plans in the meantime as other work will take time, I'll check in with him then.  Otherwise I'll explore an alternative.  Electra-Print would be best, so will try to hold out for him, just means it may be a while before this project is fully realized.


If Electra-Print's only issue is minimum order of 25 units... I think that might be a non-issue!
I truly believe there will be enough people interested, to easily accommodate the MOQ   
(and collecting a deposit to cover the OPT cost would ensure people do not back off, leaving you high to dry)


----------



## L0rdGwyn

Zachik said:


> If Electra-Print's only issue is minimum order of 25 units... I think that might be a non-issue!
> I truly believe there will be enough people interested, to easily accommodate the MOQ
> (and collecting a deposit to cover the OPT cost would ensure people do not back off, leaving you high to dry)



Ahh that isn't the issue with Electra-Print, that is a personal thing, the minimum order quantity applies to Edcor (both E names, sorry).  But yeah you're probably right, I'll keep that in mind as a fall back option.  I think the Electra-Print transformers would be better, perhaps slightly more expensive, so I'd prefer to wait but we will see once I get far along in other plans.


----------



## L0rdGwyn (Sep 2, 2022)

I dunno, I might look into winding this parafeed transformer myself.  I have been wanting to learn to wind transformers and chokes, this might be a good time to take a crack at it.


----------



## triod750

L0rdGwyn said:


> I dunno, I might look into winding this parafeed transformer myself.  I have been wanting to learn to wind transformers and chokes, this might be a good time to take a crack at it.


That would be the least you could do to pass time...


----------



## bcowen

triod750 said:


> That would be the least you could do to pass time...


Yeah, like what else is there to do in Bimini?     🤣


----------



## L0rdGwyn (Sep 3, 2022)

Got home this afternoon, a great trip, now back to reality!  Tubes.

My Elma switch was waiting for me on the porch.  After unpacking, I excitedly got it out to put it in the pentode headamp, only to find the wiring was not what I expected when I tested it.....

Yup, Elma screwed it up!  Whoever put the switch together thought they were assembling a 2 pole x 6 throw switch when it was supposed to be a 4 pole x 3 throw.  As such, they only included two contact plates on the interior rather than four.  Fortunately, the PCB wafers were wired correctly.

I took a look inside and realized I could probably disassemble the switch and fix it by using the contacts from a spare Goldpoint switch given they are both made by Elma, so that's what I sought to do.

Here is the inside of the switch, two contacts, not four.  Lots of pictures were taken as evidence.




Here are the remains of the Goldpoint switch I sacrificed.



Four conctacts now properly aligned. 



Taking this switch completely apart and putting it back together took me almost two hours, lots of little pieces to keep track of, but I got it done, so the amp can still go to SoCal.  I'll be reaching out to Elma, not sure what they'll do about it, obviously time sensitive so I couldn't wait for a replacement, but I am out two tedious hours of repair and a Goldpoint switch.

Here is the switch inside on the PCB I designed.



Rear panel now with impedance selector switch, low for 32-150ohms, high for 150ohms and up.



Sounds purdy darn good with fresh ears.  Last thing to do before I send to Zach will be some measurements on the low impedance setting, I'll get to that some time tomorrow.


----------



## bcowen (Sep 3, 2022)

L0rdGwyn said:


> Got home this afternoon, a great trip, now back to reality!  Tubes.
> 
> My Elma switch was waiting for me on the porch.  After unpacking, I excitedly got it out to put it in the pentode headamp, only to find the wiring was not what I expected when I tested it.....
> 
> ...


Sucks to have your time wasted like that, but how fortunate you were able to fix it to get the amp done on time.  And a very nice looking amp it is!


----------



## L0rdGwyn

bcowen said:


> Sucks to have your time wasted that, but how fortunate you were able to fix it to get the amp done on time.  And a very nice looking amp it is!



Thanks!  Yeah I would've been super disappointed if I couldn't get the switch in, so in the end I'm not all that mad, curious if they will give me any kind of refund, not cheap as far as switches go.


----------



## L0rdGwyn

I've gotten serious about winding my own inductors over the past 24 hours.  It's something I've planned to do eventually, I have a few texts already, just wasn't sure when.  The time is now!!!  I spent the whole flight home reading RDH4.  It's going to take some time and lots of planning.  For now, all books, then once I feel comfortable enough to design a transformer, I'll source components, a hand crank winder most likely to start, and give it a go.  Lots of learning to do and no doubt it will be a lot of trial and error, but I think I can do it.  I like to learn by doing, in the near term I need a parafeed transformer, as I mentioned, and I'm interested in some line output step-down transformers for my PCM63 DAC, so likely those would be the focus of my early efforts.


----------



## whirlwind

^  Great idea! You go Keenan  ^


----------



## L0rdGwyn

whirlwind said:


> ^  Great idea! You go Keenan  ^



Thanks!  It should be fun, I am excited, when I get the bug for something I tend to go all in, there is no middle ground lol so I think that should help speed things along.  Was doing more reading / learning this morning.  None of my other projects are urgent (e.g, PCM63 DAC, LCR phono stage) and winding transformers could potentially help those projects along.  So it's a good time to do it, but it will take time and it will be an iterative process of improvement.

In the mean time, I took some low impedance measurements of the pentode headamp, looks good.  Mostly I wanted to see the frequency response with a 32ohm load, down 0.8dB at the frequency extremes which is good.  Just gotta figure out the packing situation.  Unlikely I'll get the Brimar CV1985 and Mullard EL37 before it hits the road, so I'll have to look forward to hearing them at a later date.

The only planar magnetic headphone I have in house is the Oppo PM-3.  26ohm impedance, 102dB/mW, so not a hard-to-drive planar.  That being said, I haven't really cared for them in the past, but this is the best I have heard them, they sound great!  And virtually hum free with volume at max without music playing, very quiet.

Maybe a good sign for other planars?  we'll see.  With GZ34 and EL34, this is a 2W amplifier, so it has the juice to handle power hungry headphones, and a relatively low output impedance for a single-ended tube headamp at around 4-5ohms.


----------



## whirlwind

Winding your own transformers will be a huge convenience for you and save loads of cash, not to mention the learning experience.   

I was going to mention this awhile back but did not think you would want to mess with it as it is bringing on quite a lot more work and time.


----------



## triod750

In a year from now, winding transformers will be a piece of cake to you. You will be able to do it in your sleep, saving both time and money  .


----------



## L0rdGwyn

whirlwind said:


> Winding your own transformers will be a huge convenience for you and save loads of cash, not to mention the learning experience.
> 
> I was going to mention this awhile back but did not think you would want to mess with it as it is bringing on quite a lot more work and time.



Yeah it really would, of course it is a big investment, but if I can manage to do a decent job of it, it would be extremely convenient.  One tricky aspect however is sourcing parts, most companies that can provide laminations have minimum order quantities that exceed DIY needs.  I am only just touching on that topic though, just a cursory look at where to source laminations so far.  Edcor can supply M6 lams at good prices which is a great option, especially for high power output and mains transformers.  For higher permeability core materials, like 50% nickel (permalloy) and 80% nickel (mumetal), sourcing it is typically from Asia with minimum order quantities of 5-10kg.  That's a few hundred bucks and a lot of material, so I'd have to feel pretty confident in what I'm doing to go for it.

Anyway, just the tip of the iceberg, I'm simultaneously reading about how to design / build and looking at the market in terms of laminations, bobbins, wire, etc.  Got a long, long way to go!



triod750 said:


> In a year from now, winding transformers will be a piece of cake to you. You will be able to do it in your sleep, saving both time and money  .



I sure hope so, time will tell


----------



## Zachik

L0rdGwyn said:


> most companies that can provide laminations have minimum order quantities that exceed DIY needs.


Well... if you wind the transformers for your DIY amp design - it will be a huge win-win!!


----------



## Xcalibur255

Are they wound by hand or with some kind of rig with a stepper motor?  I've read that tolerance consistency is important to the performance of OPTs.


----------



## L0rdGwyn

Xcalibur255 said:


> Are they wound by hand or with some kind of rig with a stepper motor?  I've read that tolerance consistency is important to the performance of OPTs.



You can do either, wind by hand with a crank winder, or some sort of motorized setup.  Some people use a modified metal lathe.  You can get a pretty high quality CNC winder for around $600-700.


----------



## triod750

L0rdGwyn said:


> You can get a pretty high quality CNC winder for around $600-700.


You can make one yourself of course. Why not?


----------



## Xcalibur255

Before we can DIY this project we have to DIY our tools so we can DIY our parts?


----------



## L0rdGwyn

triod750 said:


> You can make one yourself of course. Why not?



Lol maybe I would, if I didn't have a job.  Some things are worth buying


----------



## L0rdGwyn

Pentode headamp is on its way to @zach915m along with a nice selection of NOS tubes.  I'll be interested to see what he and other people think of it.  Due to its "old school" design, it is a warmer / more euphonic sound relative to other circuits I've recently  made, but maintains impressive technical performance.  I would still call it a prototype, subject to change based on the feedback I receive.  I've started looking into what a "new school" aka with transistors version of this circuit would look like as it would save on cost at the expense of increased complexity.  A good alternative option depending on where this project goes.

OTL monster is back in action.


----------



## jgwtriode

Oh yeah!

jgwtriode


----------



## Xcalibur255

By old skool you mean you're not using any modern silicon for power filter and regulating, but perhaps you've also come up with something more clever than the typical CLCLC filtering scheme?


----------



## L0rdGwyn

Xcalibur255 said:


> By old skool you mean you're not using any modern silicon for power filter and regulating, but perhaps you've also come up with something more clever than the typical CLCLC filtering scheme?



Nope, as built the amplifier has no silicon whatsoever, it's just tubes, resistors, capacitors, inductors.  The power supply isn't regulated, it is a passive filtered supply, nothing clever  you can do regulation with vacuum tubes, but transistor-based circuits are going to be higher performing in general.  Even a modestly performing transistor-based series regulator will outperform a gigantic choke.  They are more prone to failure however and some are becoming difficult to source reliably.  Always a balance of compromises.


----------



## JazzVinyl

Technical question for @L0rdGwyn - 

When you have an SEPP headphone amp...I have always heard that the positive and negative portions of the input are split, and amplified seperately.  
And that the output transformer's job is to rejoin the +/- portions of the output wave form, just prior to feeding the cans...

Is that in fact, what it does?


----------



## L0rdGwyn (Sep 7, 2022)

JazzVinyl said:


> Technical question for @L0rdGwyn -
> 
> When you have an SEPP headphone amp...I have always heard that the positive and negative portions of the input are split, and amplified seperately.
> And that the output transformer's job is to rejoin the +/- portions of the output wave form, just prior to feeding the cans...
> ...



What you are describing is more in line with a conventional push-pull amplifier, which is different than SEPP / SRPP.  In a push-pull design, the input signal is split into its respective positive and negative halves by a circuit element called a phase splitter (several different ways to do this), then the respective positive and negative signal are amplified and recombined at the output transformer.  This is a balanced design.

In SEPP (single ended push-pull), two triodes are stacked on top of one another and the cathode of the top triode is connected to the plate of the bottom triode with the two tubes in series.  While it looks like a single-ended circuit (not balanced), the actual function of SEPP is push pull with the resistor between the cathode and plate of the two tubes acting as a phase splitter.  Like other push pull designs, the circuit should be optimally balanced, and this is the reason why a SEPP circuit is usually designed and optimized to operate into one load impedance, as changing the load will disrupt the balance of the push-pull circuit.  It does not require an output transformer to recombine the signals and is typically capacitor coupled.

What you get out of a SEPP circuit, practically speaking, is a stage that has voltage gain (like a common cathode amplifier circuit) and a low output impedance (like a cathode follower).  So you get an increase in voltage amplification but also some output buffering.  Alternatively, you can use one of the triodes as a common cathode gain stage followed by the second triode as a cathode follower for a similar functionality without the push-pull optimization needs.  People tend to argue over which approach is better.

There is an excellent article here from TubeCAD that explains SEPP in detail, but it is a bit technical.

https://www.tubecad.com/may2000/index.html

Here is a screenshot of the general circuit.


----------



## L0rdGwyn

Rereading your question @JazzVinyl , if you have a transformer coupled SEPP headphone amplifier, then RL in the circuit above is replaced with the output transformer and the transformer primary serves the same purpose as RL, it is the load for both positive and negative halves of the output signal, so in a way the transformer does combine the two halves.


----------



## JazzVinyl

L0rdGwyn said:


> Rereading your question @JazzVinyl , if you have a transformer coupled SEPP headphone amplifier, then RL in the circuit above is replaced with the output transformer and the transformer primary serves the same purpose as RL, it is the load for both positive and negative halves of the output signal, so in a way the transformer does combine the two halves.


Yes, thanks for that 2nd look, @L0rdGwyn.

This one is SEPP, w/output transformer and also capacitor-less at  the output stage, thanks to the lack of DC there, said to be possible via a highly refined (via SS components) power supply.


----------



## Zachik

@L0rdGwyn Have you heard of that tube tester?
http://www.thebestamp.com/Testing_Equipment/AudioTubeTester-3.php

I am debating moving from the 100% manual tube tester I got, to something more modern such as that one... Amplitrex 1000 is *way *more expensive!


----------



## L0rdGwyn

JazzVinyl said:


> Yes, thanks for that 2nd look, @L0rdGwyn.
> 
> This one is SEPP, w/output transformer and also capacitor-less at  the output stage, thanks to the lack of DC there, said to be possible via a highly refined (via SS components) power supply.



Sounds like an interesting amp!


----------



## L0rdGwyn

Zachik said:


> @L0rdGwyn Have you heard of that tube tester?
> http://www.thebestamp.com/Testing_Equipment/AudioTubeTester-3.php
> 
> I am debating moving from the 100% manual tube tester I got, to something more modern such as that one... Amplitrex 1000 is *way *more expensive!



No I have not, last time I heard of this guy I was looking at his tube-based DACs years ago, I think someone recommended him to me...

Looks like an interesting tester though, pretty unusual for a tester to give you a gain reading.  Just want to be sure it's going to be able to test everything you want, I saw there is an DHT expansion module, since you have a DHT amplifier coming you definitely want to be able to test those tubes!


----------



## Zachik

L0rdGwyn said:


> Looks like an interesting tester though, pretty unusual for a tester to give you a gain reading. Just want to be sure it's going to be able to test everything you want, I saw there is an DHT expansion module, since you have a DHT amplifier coming you definitely want to be able to test those tubes!


I agree the tester looks very interesting!
IF I end up buying this one - I will most definitely get the optional DHT expansion box.
But before committing to such an expense - I am looking for (unbiased) opinions on the tester. I was hoping you (or someone else on this thread) know anything (good or bad) about this tester...


----------



## L0rdGwyn

Zachik said:


> I agree the tester looks very interesting!
> IF I end up buying this one - I will most definitely get the optional DHT expansion box.
> But before committing to such an expense - I am looking for (unbiased) opinions on the tester. I was hoping you (or someone else on this thread) know anything (good or bad) about this tester...



When I get some time, I'll take a closer look at the info page and the video and see if I can think up some pros and cons.


----------



## Zachik

L0rdGwyn said:


> When I get some time, I'll take a closer look at the info page and the video and see if I can think up some pros and cons.


Thanks - much appreciated!


----------



## L0rdGwyn

Zachik said:


> Thanks - much appreciated!



So something that comes to mind for me - this tester has a maximum 200V B+ supply.  Many tubes in their datasheets give operating parameters at higher voltages, 250V or 275V is common.  When testing, you may not have a reference value to compare the tube to since measurements will be done at lower voltages.  The gm for a tube will be different at 200V vs. 250V for example.  Practically, it's fine as you can say the tube's gm is "in the ballpark" of NOS in the datasheet and has appropriate gain, but you will not be able to use the datasheet measurement parameters directly if they are over 200V B+.  Other than that, as long as it tests all of the tubes you want to test, it has a lot of great functionality that isn't included on many tube testers, like gain measurements, sine waveform, noise testing.  Includes gas and shorts as well.


----------



## Monsterzero

Got out of the ZMF ecosystem for a change of pace last night, and donned the grossly unknown and underrated Sennheiser HD250. Man these headphones scale like mad!
The VC is more technically proficient, but if you enjoy a punchy sound with other wordly sub bass, its an amazing headphone, especially for 75 bucks shipped, lol! Still the  best bargain to date in this hobby.

Airmid- Ken Rad 6J5+Tung sol 5998
TRP-WWll era RCA 5R4GY+Sophia Electric EL34


----------



## L0rdGwyn

Monsterzero said:


> Got out of the ZMF ecosystem for a change of pace last night, and donned the grossly unknown and underrated Sennheiser HD250. Man these headphones scale like mad!
> The VC is more technically proficient, but if you enjoy a punchy sound with other wordly sub bass, its an amazing headphone, especially for 75 bucks shipped, lol! Still the  best bargain to date in this hobby.
> 
> Airmid- Ken Rad 6J5+Tung sol 5998
> TRP-WWll era RCA 5R4GY+Sophia Electric EL34



Looks awesome, yeah I sort of regret selling mine now, they really are great headphones.  I think I mentioned this before, but I had some difficulty getting a good seal with my pair, I was using ZMF universe pads at the time.  I might give them another shot someday.


----------



## JazzVinyl

Monsterzero said:


> Got out of the ZMF ecosystem for a change of pace last night, and donned the grossly unknown and underrated Sennheiser HD250. Man these headphones scale like mad!
> The VC is more technically proficient, but if you enjoy a punchy sound with other wordly sub bass, its an amazing headphone, especially for 75 bucks shipped, lol! Still the  best bargain to date in this hobby


@mordy likes the Senn HD250's too.

For me, it is Focal Elear's when I want to get out of the ZMF ecosystem.  The Focal's are very clear, high resolution / detail revealing cans.  They also have impressive, solid bass.

Highly recommended.


----------



## Zachik

L0rdGwyn said:


> So something that comes to mind for me - this tester has a maximum 200V B+ supply.  Many tubes in their datasheets give operating parameters at higher voltages, 250V or 275V is common.  When testing, you may not have a reference value to compare the tube to since measurements will be done at lower voltages.  The gm for a tube will be different at 200V vs. 250V for example.  Practically, it's fine as you can say the tube's gm is "in the ballpark" of NOS in the datasheet and has appropriate gain, but you will not be able to use the datasheet measurement parameters directly if they are over 200V B+.  Other than that, as long as it tests all of the tubes you want to test, it has a lot of great functionality that isn't included on many tube testers, like gain measurements, sine waveform, noise testing.  Includes gas and shorts as well.


I wish I could find some reviews... I hate the thought of spending $1500-ish (including the 300B module) on any tube tester, unless it is absolutely amazing!
Amplitrex 1000 which MANY swear by, is selling at $3000 for reference


----------



## Monsterzero

L0rdGwyn said:


> Looks awesome, yeah I sort of regret selling mine now, they really are great headphones.  I think I mentioned this before, but I had some difficulty getting a good seal with my pair, I was using ZMF universe pads at the time.  I might give them another shot someday.


A few others mentioned having a hard time with getting a good seal. The key is finding a pair with the original pads intact and in good shape. Even with my space goggles, I get a great seal and all the bass one can ask for.

There's a pair in the classifieds right now, but its not in the greatest shape.


JazzVinyl said:


> @mordy likes the Senn HD250's too.
> 
> For me, it is Focal Elear's when I want to get out of the ZMF ecosystem.  The Focal's are very clear, high resolution / detail revealing cans.  They also have impressive, solid bass.
> 
> Highly recommended.


I turned Mordy onto them way back when.

The Airmid is currently my only amp, so no low impedance headphones for me, but I hope to change that eventuaslly and add a second amp to the collection.


----------



## ProLoL

Monsterzero said:


> A few others mentioned having a hard time with getting a good seal. The key is finding a pair with the original pads intact and in good shape. Even with my space goggles, I get a great seal and all the bass one can ask for.
> 
> There's a pair in the classifieds right now, but its not in the greatest shape.
> 
> ...


I happen to own both pairs that are for sale, one as brand new, the other in used condition yet both have original pads and foam.
I appreciate that people recognize how good these are.


----------



## L0rdGwyn (Sep 9, 2022)

Zachik said:


> I wish I could find some reviews... I hate the thought of spending $1500-ish (including the 300B module) on any tube tester, unless it is absolutely amazing!
> Amplitrex 1000 which MANY swear by, is selling at $3000 for reference



You could ask the maker if he can get you in contact with someone he has sold the tester to.


----------



## whirlwind

Monsterzero said:


> Got out of the ZMF ecosystem for a change of pace last night, and donned the grossly unknown and underrated Sennheiser HD250. Man these headphones scale like mad!
> The VC is more technically proficient, but if you enjoy a punchy sound with other wordly sub bass, its an amazing headphone, especially for 75 bucks shipped, lol! Still the  best bargain to date in this hobby.
> 
> Airmid- Ken Rad 6J5+Tung sol 5998
> TRP-WWll era RCA 5R4GY+Sophia Electric EL34


I never owned this headphone, but I have heard it and it is very punchy indeed. The pair I listened to had very old beat up pads on them.

Nice pic!





L0rdGwyn said:


> Looks awesome, yeah I sort of regret selling mine now, they really are great headphones.  I think I mentioned this before, but I had some difficulty getting a good seal with my pair, I was using ZMF universe pads at the time.  I might give them another shot someday.


I could not get a great seal either, but the pads were pretty bad shape, the bass was fun.

Heading up to Cuyahoga to Blossom tonight to see the Black Keys....can't wait to hear Dan Auerbach's old  fuzzy Guild Thunderbird guitar.
Should be fun.


----------



## L0rdGwyn

whirlwind said:


> I could not get a great seal either, but the pads were pretty bad shape, the bass was fun.
> 
> Heading up to Cuyahoga to Blossom tonight to see the Black Keys....can't wait to hear Dan Auerbach's old  fuzzy Guild Thunderbird guitar.
> Should be fun.



That'll be awesome, have fun!  I love Blossom, I go there probably 5 or 6 times a year, mostly to see the Cleveland Orchestra  they get some big acts through there too though!


----------



## whirlwind

L0rdGwyn said:


> That'll be awesome, have fun!  I love Blossom, I go there probably 5 or 6 times a year, mostly to see the Cleveland Orchestra  they get some big acts through there too though!




Thanks.

 That is a beautiful piece of property...what a great place to hear the Cleveland Orchestra.....bet that sound's surreal there.


----------



## jgwtriode

Saw  an intereting post on Facebook at ZMF Headphones about the ZMF Caldara Planar Magnetic.   Apparently it will be at the 
SoCal Can Jam.

Is this a new flagship.  Very Curious.  My last planar was LFF Slants, so I am very curious to hear about these, especially in comparison
to the Atrium. 

jgwtriode


----------



## Monsterzero

jgwtriode said:


> Saw  an intereting post on Facebook at ZMF Headphones about the ZMF Caldara Planar Magnetic.   Apparently it will be at the
> SoCal Can Jam.
> 
> Is this a new flagship.  Very Curious.  My last planar was LFF Slants, so I am very curious to hear about these, especially in comparison
> ...


 We're drooling over it over in the VC thread. As far as pricing goes, no word yet from ZMF


----------



## L0rdGwyn

jgwtriode said:


> Saw  an intereting post on Facebook at ZMF Headphones about the ZMF Caldara Planar Magnetic.   Apparently it will be at the
> SoCal Can Jam.
> 
> Is this a new flagship.  Very Curious.  My last planar was LFF Slants, so I am very curious to hear about these, especially in comparison
> ...



Yup, that's right, it will be at CanJam SoCal.  I haven't heard it yet but Zach is very excited to release it.  I will be looking forward to reading impressions!

Unfortunately my pentode headphone amplifier will NOT be at CanJam SoCal.  Something happened to the IEC inlet during shipping, or perhaps there was an issue before shipping that I didn't realize.  In either case, the amp is on its way back to me.  We talked about shipping it directly to SoCal after I make the repair, but the logistics of that are pretty complex and the ZMF team is already going to have a lot on their plate at such a big event.

So no impressions of that amplifier.  Ultimately, I think it is for the best as I am uncertain it is complete and it felt somewhat rushed coming back from a vacation, putting in the last part, and shipping it off.  I've started to feel a transitor-based approach would make the amplifier more viable as a commercial product.  While I prioritized simplicity for the "old school" approach, the tradeoff was cost of inductors, some of which are only made by Lundahl, which limits options.

So I am likely going to investigate a "new school" version of this amp while maintaining the basic topology of the "old school" version.  Essentially three chokes will be replaced with transistor circuits, and the performance may be further improved.

But today I am reading about winding transformers  I will have the amp back tomorrow.


----------



## Xcalibur255

jgwtriode said:


> Saw  an intereting post on Facebook at ZMF Headphones about the ZMF Caldara Planar Magnetic.   Apparently it will be at the
> SoCal Can Jam.
> 
> Is this a new flagship.  Very Curious.  My last planar was LFF Slants, so I am very curious to hear about these, especially in comparison
> ...


Is this an original driver design, kind of like when MrSpeakers/DCA made the jump from Fostex modding to full design?


----------



## Monsterzero

Xcalibur255 said:


> Is this an original driver design, kind of like when MrSpeakers/DCA made the jump from Fostex modding to full design?


Yes


----------



## Xcalibur255

Monsterzero said:


> Yes


Can't wait to see what tuning approach Zach takes with it then.


----------



## jgwtriode

This should be a pretty amazing headphone considering what Zach was able to do in the past with Fostex drivers.    This should be really be something remarkable.  I really like the slightly more technical look of the grille on the Caldera!

Happy listening,

jgwtriode


----------



## jgwtriode

Found this on the reddit headphone thread for ZMF Caldera


From Zach:

Caldera is a type of massive volcano - we are using the Volcano theme because the new CAMS (caldera Asymmetrical Magnet structure) Patent Pending Magnet structure is shaped like a volcano/mountain on one side. This shape allows air to naturally spread out, and maintains a slightly asymmetric magnet force that makes the membrane more nodal, pushing a massive amount of air towards the ear and diffusing it at the same time. In concert with the also Patent Pending Atrium damping system which is also used on the Caldera, you get a linear frequency response, with a massive amount of punch, weight, and natural tones that ZMF is known for for the listener.

Aside from the new tech, we have a new earpad design for the Caldera, with what we will probably call Caldera Pads, which have a "fluting" from a smaller size on the driver size, to a larger size on the ear side. It's similar to the shape of the Audeze pads on the LCD 5, but will be more "flat" on the ear side like a volcano, This pad shape enables sound to retain air pressure on the baffle/headphone side, and for the ear cavity to still feel very open naturally. We will have three depths of these pads, and also will introduce Cowhide into one version of them, as cowhide pads can work brilliantly with planars.

The Caldera has an 80mm driver size, impedance is 65 ohms, Sensitivity is 95 dB/Mw. The baffle is made from true carbon fiber for weight, and has the asymmetrical magnets facing the front of the membrane, although different configurations could be used if warranted. Price for the stock wood will be $3499.99 with a 3199.99 release price. Stock wood is white oak. This is an open headphone utilizing the same cups as Atrium with different grille structure.

Sonically the Caldera takes a lot of the ideas that started when ZMF was a T50 modding business, which a lot of those new to ZMF may not know about. It expands on the explosive, easy going sound that the Blackwood and Ori brought to the t50 arena, except with a more evolved sound and current tech. When you think of the sound of the Caldera, it's BIG, with an adaptable stage like the Atrium, but loads of weight and control that comes with typical planar dreams, but the mid-range and treble stand out because of the ZMF damping systems and airflow of the magnets, it's more lucid and nimble, reminiscent of a great dynamic headphone. I did reference the harmon curve for parts of the tuning, specifically the 1.5 to 4khz area and made "some" decisions based on that, but I would NOT categorize this as a harmon tuned headphone, just one where I was conscious of it in regards to midrange peformance.



Happy listening,

jgwtriode


----------



## L0rdGwyn

Pentode headamp has returned.

On inspection, one of the leads from the IEC inlet to the mains transformer was broken.  I think it was only able to power on for a short period of time for @zach915m because the wire was still touching the IEC connector.  I got it to power on for a second by jiggling the power cable when it first arrived.  Not surprisingly, it sounded god awful.  I fixed the IEC, made damn sure the wires were intact, and all is fixed. 

I suspect this was an issue even before shipping, but it was likely affecting the sound to a lesser degree, perhaps the wire was partially intact.  I did not suspect / detect a problem as I did not have much time with it since I was trying to get it out the door ASAP.  Now that it is fixed, it sounds very badass and I am super bummed the Caldera won't be heard on it at CanJam  

But I do have a British invasion tube roll, so there's that.  Brimar 5R4GY, Brimar CV1985, Mullard EL37.


----------



## L0rdGwyn

Change of plans, the pentode amp is going to CanJam, just shipped it off direct to Cali


----------



## triod750

L0rdGwyn said:


> just shipped it off direct to Cali


Hmmm...
*Santiago de Cali* (Spanish pronunciation: [sanˈtjaɣo ðe ˈkali]), or *Cali*, is the capital of the Valle del Cauca department, and the most populous city in southwest Colombia,

From Wikipedia.


----------



## L0rdGwyn

triod750 said:


> Hmmm...
> *Santiago de Cali* (Spanish pronunciation: [sanˈtjaɣo ðe ˈkali]), or *Cali*, is the capital of the Valle del Cauca department, and the most populous city in southwest Colombia,
> 
> From Wikipedia.



Too late now, they're going to have to relocate CanJam.


----------



## jgwtriode

L0rdGwyn said:


> Change of plans, the pentode amp is going to CanJam, just shipped it off direct to Cali


Awesome!  Can hardly wait for the response to it with the Caldera!

jgwtriode


----------



## triod750

More of the Spanish connection: https://en.wikipedia.org/wiki/Rafael_Caldera


----------



## L0rdGwyn

triod750 said:


> More of the Spanish connection: https://en.wikipedia.org/wiki/Rafael_Caldera


----------



## L0rdGwyn

jgwtriode said:


> Awesome!  Can hardly wait for the response to it with the Caldera!
> 
> jgwtriode



Yeah I'm curious myself, Zach didn't really get a chance to audition it properly since it arrived damaged, so first listen will be at CanJam.  Hopefully people like it!  Or at the very least, don't dislike it.


----------



## L0rdGwyn

I sent along those EL37 and the Brimar 5R4GY as a secret weapon 

Continuing down the transformer winding rabbit hole. Getting more comfortable with the design aspect, still reading through resources and compiling an Excel spreadsheet for calculations. 
 Starting to feel confident I could design a decent transformer on the first attempt.  The tricky part is locating materials, but I believe I've finally found a source for M6 EI laminations.  Going down the checklist...more work to do before I can give it a whirl.


----------



## whirlwind

L0rdGwyn said:


> I sent along those EL37 and the Brimar 5R4GY as a secret weapon
> 
> Continuing down the transformer winding rabbit hole. Getting more comfortable with the design aspect, still reading through resources and compiling an Excel spreadsheet for calculations.
> Starting to feel confident I could design a decent transformer on the first attempt.  The tricky part is locating materials, but I believe I've finally found a source for M6 EI laminations.  Going down the checklist...more work to do before I can give it a whirl.


Nice secret weapon    

Can't wait to hear impressions of the amp and of Caldera.
I am much interested in the Caldera vs LCD-4 sound.


----------



## UntilThen

whirlwind said:


> I am much interested in the Caldera vs LCD-4 sound.



Curious about that too. LCD4 is unique and a lovely sounding planar.


----------



## L0rdGwyn

whirlwind said:


> Nice secret weapon
> 
> Can't wait to hear impressions of the amp and of Caldera.
> I am much interested in the Caldera vs LCD-4 sound.





UntilThen said:


> Curious about that too. LCD4 is unique and a lovely sounding planar.



We will find out soon enough!  I'm sure it will be one of the most highly sought out headphones at CanJam, lots of planar heads will have their opinions, it's going to be very interesting reading, I can't wait to demo them


----------



## UntilThen

L0rdGwyn said:


> We will find out soon enough!  I'm sure it will be one of the most highly sought out headphones at CanJam, lots of planar heads will have their opinions, it's going to be very interesting reading, I can't wait to demo them



The real test will be against Susvara, the best sounding headphone imo. This is journey's end for me.


----------



## triod750

UntilThen said:


> The real test will be against Susvara, the best sounding headphone imo. This is journey's end for me


Hmmm.....


----------



## UntilThen

triod750 said:


> Hmmm.....



Sounds like agreement to me.


----------



## jgwtriode

I think if Zach gets anywhere near that level of resolution, the musicality and spatial coherence of his tuning will take the day, maybe the weekend,  and even more so with LordGywn's amps driving it;  which significantly improves that over other amplifiers,  even very good ones.!  I can see their may need to be a certain pentode in my future because I am sure at some point when the piggy is ready to break for a Caldera I will have to start saving for that as well.

Happy listening,

jgwtriode


----------



## triod750

UntilThen said:


> Sounds like agreement to me.


You see what you want to see and hear what you want to hear....


----------



## Monsterzero

UntilThen said:


> This is journey's end for me.


 If I had 5 bucks for everytime I've seen you say this about one piece of gear or another, I'd be a very wealthy man.


----------



## jgwtriode

I don't always spend more than I should, but when I do it is for audio!

Hahahah! ROTFL

jgwtriode


----------



## Monsterzero

RE: Susvara and LCD-4, Zach has said a few times already that the Caldera is tuned unlike any other planar on the market, and @warrenpchi pretty much confirmed that sentiment.
 I should have the Caldera here soon(?) If yall want me to compare them for you in my review drop me a PM.


----------



## UntilThen

jgwtriode said:


> I can see their may need to be a certain pentode in my future



It’s just convenient to call it a pentode amp but we all know it’s strapped triodes which is where the good sounding amps are.

Keenan it has to have a name going into CANJAM and not be known as the pentode amp.


----------



## UntilThen

Monsterzero said:


> If I had 5 bucks for everytime I've seen you say this about one piece of gear or another, I'd be a very wealthy man.



I’ll just call it the journey’s beginning then. 😗


----------



## ckhirnigs113

I’ve got a nerdy name suggestion for the new amp. Since there’s excitement about pairing it with Zach’s new volcano-themed Caldera planar at CanJam, how about calling it “Orodruin”? It’s a Lord of the Rings reference. It was another name for Mount Doom. I always thought it was a cool-sounding word. On second thought, it may be too ominous for the name of a headphone amp, haha.


----------



## L0rdGwyn

UntilThen said:


> It’s just convenient to call it a pentode amp but we all know it’s strapped triodes which is where the good sounding amps are.
> 
> Keenan it has to have a name going into CANJAM and not be known as the pentode amp.



Ahh I know what you mean, but it is still in development, a prototype really as I may change the circuit.  Once you name it, it becomes "official" so it might be better to remain anonymous until it really is official.

Or I'll name it TSPA (triode-strapped pentode amp) instead of pentode amp


----------



## UntilThen

L0rdGwyn said:


> Or I'll name it TSPA (triode-strapped pentode amp) instead of pentode amp



TSPA for now sounds good.


----------



## whirlwind

UntilThen said:


> I’ll just call it the journey’s beginning then. 😗


Just call it part of the journey, because the journey only ends until the next piece of gear or next headphone......there *fixed.     *


----------



## UntilThen

whirlwind said:


> Just call it part of the journey, because the journey only ends until the next piece of gear or next headphone......there *fixed.    *



Choose your amp name wisely. I chose Odyssey because that's suppose to be journey's end when Odysseus got home. Unfortunately he had a son name Telemachus.


----------



## bcowen

L0rdGwyn said:


> Ahh I know what you mean, but it is still in development, a prototype really as I may change the circuit.  Once you name it, it becomes "official" so it might be better to remain anonymous until it really is official.
> 
> Or I'll name it TSPA (triode-strapped pentode amp) instead of pentode amp


I like Harmonia, the Greek goddess of harmony.  But with the tubes protruding like they do it may be more of a male amp, so maybe not.   🤣  🤣


----------



## L0rdGwyn

Amp made it to SoCal, looks like one of the transformers got a little banged out of alignment in transport, probably can be pushed back, but it works!  And early impressions from Zach are very good 

We will see what other people think later today.


----------



## leftside

Monsterzero said:


> RE: Susvara and LCD-4, Zach has said a few times already that the Caldera is tuned unlike any other planar on the market, and @warrenpchi pretty much confirmed that sentiment.
> I should have the Caldera here soon(?) If yall want me to compare them for you in my review drop me a PM.


That would be great. The LCD-4 are still one of my favorite headphones.


----------



## L0rdGwyn

leftside said:


> That would be great. The LCD-4 are still one of my favorite headphones.



Welcome back @leftside , haven't seen you around in a while!


----------



## whirlwind

leftside said:


> That would be great. The LCD-4 are still one of my favorite headphones.


Long time no see.

Yeah, from top to bottom the LCD-4 just delivers sweet music.


----------



## jgwtriode

BoyNamedSue said:


> Had a great time! My favorite setups, based on criteria of getting me lost in the music:
> 
> 1. ZMF Atrium (Metrum Morpheus, Airmid OTL amp). Fun, engaging, musical, punchy, great staging, and natural. Noticeably more resolving than the Auteur and Aelous I have at home. Everything sounded good. This setup has endgame potential.
> 
> ...


These comments have me really wondering whether an Atrium might not be a better choice next year than a Caldera????


----------



## Zachik

jgwtriode said:


> These comments have me really wondering whether an Atrium might not be a better choice next year than a Caldera????


Depends on whom you ask!!
I strongly prefer the Caldera. Others that I talked to - preferred the Atrium. 
(obviously, they were wrong )


----------



## Monsterzero

The Caldera and Atrium will require different amps to sound stellar. 
Although I have yet to hear the new amp that Keenan debuted at canjam. 

I will be a bit shocked if it tops the Airmid for driving high impedance headphones


----------



## jgwtriode

Zachik said:


> Depends on whom you ask!!
> I strongly prefer the Caldera. Others that I talked to - preferred the Atrium.
> (obviously, they were wrong )


What did you like better about the Caldera?  Did you hear it on Keenan's pentode?

jgwtriode


----------



## leftside

L0rdGwyn said:


> Welcome back @leftside , haven't seen you around in a while!


Thanks  It's been a busy summer on the bike, and building cupboards in the garage. 

Looking forward to the earlier darker evenings and listening again. I'm definitely more of a nighttime music listener.


----------



## Zachik

jgwtriode said:


> What did you like better about the Caldera?  Did you hear it on Keenan's pentode?
> 
> jgwtriode


Caldera had better bass (to my taste), and faster / tighter sound all around.
I did not test on Keenan's pentode - it was being used every single time I stopped by the ZMF room (and I was too busy and/or impatient to wait for it to become available).


----------



## whirlwind

Monsterzero said:


> The Caldera and Atrium will require different amps to sound stellar.
> Although I have yet to hear the new amp that Keenan debuted at canjam.
> 
> I will be a bit shocked if it tops the Airmid for driving high impedance headphones



I have never heard either of these amps from Keenan. The Airmid may very well be enough for most people for both cans as you can use the 6336B tubes which is a great plus.

Whether or not it can make the Caldera sound as full as on the pentode amp vs how the Atrium sounds on the pentode amp.

I am just guessing here, but I expect the pentode amp to be the best all around amp, so to speak. It should not have any issues powering most headphones. 

A good OTL and high impedance headphones do have a wonderful synergy going on.

I am sure Keenan will explain this all better than I can.


----------



## jgwtriode

Hey Keenan?

What would the 6336B take the Airmid's output impedance down to ?  Would that be a better choice for an output tube with the Caldera?

Thanks,

jgwtriode


----------



## Monsterzero

whirlwind said:


> I have never heard either of these amps from Keenan. The Airmid may very well be enough for most people for both cans as you can use the 6336B tubes which is a great plus.


 I could be mistaken, but I do not believe the Airmid can use the 6336. Keenan's custom 1-of- a- kind OTL Spinosaurus uses the 6336, but it's a different amp than the Airmid


----------



## L0rdGwyn

Sorry very busy week, Airmid cannot use 6336 tubes, I'll elaborate later today.


----------



## whirlwind

Monsterzero said:


> I could be mistaken, but I do not believe the Airmid can use the 6336. Keenan's custom 1-of- a- kind OTL Spinosaurus uses the 6336, but it's a different amp than the Airmid


My bad...I guess just 6AS7G....which still may power ZMF planar fine for some.

The amp that uses the 6336 tubes would probably be better.


----------



## Paladin79 (Sep 20, 2022)

A few things from my buying trip north of Philly. I spent 28 hours driving a cargo van, not all at once though.   Finnegan helped with unboxing equipment and sorting CD's, most all are Classical music.


----------



## triod750

Civilized people have their music either on cd or vinyl  or both!


----------



## Paladin79

triod750 said:


> Civilized people have their music either on cd or vinyl  or both!


I have both as well as at least 55,000 HD albums stored on hard drives. My classical music collection was lacking so I enhanced it.


----------



## L0rdGwyn

jgwtriode said:


> These comments have me really wondering whether an Atrium might not be a better choice next year than a Caldera????



Atrium is a very good pairing with Airmid, I haven't heard Caldera yet so I can't be certain exactly how they pair, sounds like a case of two different flavors to me.



Monsterzero said:


> The Caldera and Atrium will require different amps to sound stellar.
> Although I have yet to hear the new amp that Keenan debuted at canjam.
> 
> I will be a bit shocked if it tops the Airmid for driving high impedance headphones



The two amps are just different, I think each has its pros and cons, but the pentode amp does run high impedance headphones very well.  We'll just have to see what you think!



Zachik said:


> Caldera had better bass (to my taste), and faster / tighter sound all around.
> I did not test on Keenan's pentode - it was being used every single time I stopped by the ZMF room (and I was too busy and/or impatient to wait for it to become available).



Seems a lot of people listened to it, but I haven't seen / heard a peep as far as good or bad impressions other than from Zach.  Maybe they are yet to come.



whirlwind said:


> I have never heard either of these amps from Keenan. The Airmid may very well be enough for most people for both cans as you can use the 6336B tubes which is a great plus.
> 
> Whether or not it can make the Caldera sound as full as on the pentode amp vs how the Atrium sounds on the pentode amp.
> 
> ...





jgwtriode said:


> Hey Keenan?
> 
> What would the 6336B take the Airmid's output impedance down to ?  Would that be a better choice for an output tube with the Caldera?
> 
> ...



With a pair of 5998, the Airmid has an output impedance of around 30ohms, so a little over a 2:1 damping ratio with a 65ohm planar.  With 265uF output capacitance, that gives a -3dB low frequency rolloff point of around 9Hz, so low frequency extension is not an issue.  It would probably sound pretty good, but not optimal.  My 6336 OTL can hit an output impedance of 15ohms for a 4:1 damping ratio, which is better, but I still think a transformer coupled amplifier would be the best option for running a relatively low impedance planar like the Caldera.  Airmid cannot use 6336 / 6528 tubes as they draw double the heater current of a 6AS7G and bias at around double the current, so these tubes really need to have a circuit designed around them to be high performing.


----------



## triod750

Paladin79 said:


> I have both as well as at least 55,000 HD albums stored on hard drives. My classical music collection was lacking so I enhanced it.


Note to self; nobody is perfect.


----------



## Paladin79

triod750 said:


> Note to self; nobody is perfect.


I have been involved with audio since the 60’s, somewhere I still have reel to reel tapes and possibly cassette tapes. No four track or 8 track but I once owned some.

I may run two turntables after I build more racks.


----------



## triod750

Paladin79 said:


> cassette tapes


me too


----------



## Paladin79 (Sep 20, 2022)

As far as turntables and records, I still have one of these brand new in the box, sans tone arm. It is in storage with other gear about 100 miles away but I may get a tonearm and set it up.  The Pioneer PLC-590. This is just a representative photo, I would most likely mount an SME tonearm.


----------



## jgwtriode

Monsterzero said:


> I could be mistaken, but I do not believe the Airmid can use the 6336. Keenan's custom 1-of- a- kind OTL Spinosaurus uses the 6336, but it's a different amp than the Airmid


Yeah I was a bit confused for a minute about that, got temporarily excited.  But actually do remember that was the tube in the Spinosaurus.   But thought I would ask.   Oh well
I thing we are just looking at going Atrium and being happy for quite some time.   Not about to do another Amp with my budget and priorities.  If my DAC does not show up soon I may just get a stock Gustard R26, which would likely work quite well for streaming, supports roon, as well as being an R2R DAC with DSD capability.  A few folk are saying it's the best R2R under 3.5k.   Very interested even if my moded X26 pro ever does show.

Happy listening,

jgwtriode


----------



## Monsterzero

The Glenn OTL can use 6336 tubes, but iirc, it isnt optimized for the use of 6336. When I had my GOTL, planars didnt sound bad on it, but there was some grain in the sound that I knew wasn't supposed to be there.

The only low impedance headphone that blew my mind on the GOTL w/ 6336s in place was the AKG K701. That combo was absurdly good.


----------



## UntilThen

I've had a good time with GOTL with various headphones - HD800, Verite Open and LCD3. GOTL was special to me because it was my first custom amp and Glenn reach out to me whilst I was still on Euforia's thread. I spent a long time on Glenn's thread in my audio journey. I really wish him all the best where ever his is and hope all is well.

My GOTL is still with @paramesh I believe.


----------



## JazzVinyl

Paladin79 said:


> I have been involved with audio since the 60’s, somewhere I still have reel to reel tapes and possibly cassette tapes. No four track or 8 track but I once owned some.
> 
> I may run two turntables after I build more racks.


Me, three...


----------



## Xcalibur255

Monsterzero said:


> The Glenn OTL can use 6336 tubes, but iirc, it isnt optimized for the use of 6336. When I had my GOTL, planars didnt sound bad on it, but there was some grain in the sound that I knew wasn't supposed to be there.
> 
> The only low impedance headphone that blew my mind on the GOTL w/ 6336s in place was the AKG K701. That combo was absurdly good.


The K701 has a weird affinity with OTL amps that has never really made sense.  Long ago I used my GOTL exclusively with a pair until a naughty 5998 tube blew them up.

Side note:  the K712 does not have the same magic that the K701 did.  It sounds passable on the GOTL but something about the midrange rubs me the wrong way.  On my transformer coupled amps it sounds even worse.  Given it's reputation has a "fuller and warmer" K701 it really feels like I'm hearing a different headphone than those people.


----------



## L0rdGwyn (Sep 21, 2022)

A while back I talked about how I designed the pentode headamp to be easy to build, a relatively simple circuit with new production available tubes, all for the sake of either commercial or DIY viability.  A few times my thoughts have strayed to how I would build a cost-no-object version of this circuit without those constraints.  Yesterday I was on a run and the idea came back to me.  I got pretty excited about how this amp would sound, so I think I am going to build one for myself, seeing as I will have a Caldera at some point, I need a personal amplifier that can run planars.  The gist of it is it would be interstage transformer coupled as opposed to capacitor coupled, use E810F input tubes as opposed to 6SL7, LED biased instead of cathode biased, use solid state rectification and a voltage regulated power supply.  I shot an email to Dave Slagle about some transformers for this amplifier.  If he can make what I need, then I'll go for it.

Here is a pair of E810F.  These are more ideal tubes for the application, but of course they are not available new production, so I designed around 6SL7 instead.



I need to talk to Zach about how things went with the original pentode headamp at CanJam.  Don't take this as a firm decision, but I am starting to lean toward making it a DIY project.  The way it was designed, DIY makes more sense than commercial.  It would have to be redesigned with transistors to make it a commercial amplifier in my mind.  Maybe that will still happen and I can release the "old school" version as a DIY project.  It wouldn't be cheap, but relative to the price of a comparable commercial amp, it would be a steal.  Should have an answer in the next couple weeks.


----------



## Paladin79

L0rdGwyn said:


> A while back I talked about how I designed the pentode headamp to be easy to build, a relatively simple circuit with new production available tubes, all for the sake of either commercial or DIY viability.  A few times my thoughts have strayed to how I would build a cost-no-object version of this circuit without those constraints.  Yesterday I was on a run and the idea came back to me.  I got pretty excited about how this amp would sound, so I think I am going to build one for myself, seeing as I will have a Caldera at some point, I need a personal amplifier that can run planars.  The gist of it is it would be interstage transformer coupled as opposed to capacitor coupled, use E810F input tubes as opposed to 6SL7, LED biased instead of cathode biased, use solid state rectification and a voltage regulated power supply.  I shot an email to Dave Slagle about some transformers for this amplifier.  If he can make what I need, then I'll go for it.
> 
> Here is a pair of E810F.  These are more ideal tubes for the application, but of course they are not available new production, so I designed around 6SL7 instead.
> 
> ...


I have always preferred the 6sn7 over the 6sl7 and I have a few amps that run both. I did more extensive tests with 6sn7's so maybe there are some wonderful 6sl7's out there I have missed along the way.


----------



## raindownthunda

L0rdGwyn said:


> A while back I talked about how I designed the pentode headamp to be easy to build, a relatively simple circuit with new production available tubes, all for the sake of either commercial or DIY viability.  A few times my thoughts have strayed to how I would build a cost-no-object version of this circuit without those constraints.  Yesterday I was on a run and the idea came back to me.  I got pretty excited about how this amp would sound, so I think I am going to build one for myself, seeing as I will have a Caldera at some point, I need a personal amplifier that can run planars.  The gist of it is it would be interstage transformer coupled as opposed to capacitor coupled, use E810F input tubes as opposed to 6SL7, LED biased instead of cathode biased, use solid state rectification and a voltage regulated power supply.  I shot an email to Dave Slagle about some transformers for this amplifier.  If he can make what I need, then I'll go for it.
> 
> Here is a pair of E810F.  These are more ideal tubes for the application, but of course they are not available new production, so I designed around 6SL7 instead.
> 
> ...


DIY!?? Where do I sign up??  So excited to follow the progress on this project. Have you thought about chassis supply at all? Curious on whether or not it would be feasible to have a standard pre-built chassis available to order.


----------



## L0rdGwyn

Paladin79 said:


> I have always preferred the 6sn7 over the 6sl7 and I have a few amps that run both. I did more extensive tests with 6sn7's so maybe there are some wonderful 6sl7's out there I have missed along the way.



I'm certain you know this, but the 6SL7 has very different optimal requirements for loading and biasing compared to 6SN7.  I think 6SL7s are often misused in audio circuits, either they are under loaded or put in circuits with excessive amount of gain leading to a high noise floor.  There are amplifiers out there where the manufacturers say you can use either one.  Well if they are using a typical plate resistor for a 6SN7 to load a 6SL7, then the 6SL7 is grossly under loaded and distortion is going to be very high, of course it will sound bad!  If used well they have very low distortion, I believe they are actually more linear than a 6SN7, but they needed to be treated kindly with their 44K plate resistance and very high gain, they are wimpy drivers.  This circuit requires a high gain input stage, so 6SN7 won't cut it unfortunately.

Here are the traced plate curves from a Tung-Sol 6SU7GTY, doesn't get much more linear than this.  Sections were matched in the factory for this model too, seems they weren't lying!


----------



## Paladin79

L0rdGwyn said:


> I'm certain you know this, but the 6SL7 has very different optimal requirements for loading and biasing compared to 6SN7.  I think 6SL7s are often misused in audio circuits, either they are under loaded or put in circuits with excessive amount of gain leading to a high noise floor.  There are amplifiers out there where the manufacturers say you can use either one.  Well if they are using a typical plate resistor for a 6SN7 to load a 6SL7, then the 6SL7 is grossly under loaded and distortion is going to be very high, of course it will sound bad!  If used well they have very low distortion, I believe they are actually more linear than a 6SN7, but they needed to be treated kindly with their 44K plate resistance and very high gain, they are wimpy drivers.  This circuit requires a high gain input stage, so 6SN7 won't cut it unfortunately.
> 
> Here are the traced plate curves from a Tung-Sol 6SU7GTY, doesn't get much more linear than this.  Sections were matched in the factory for this model too, seems they weren't lying!


Of course, and I have amps designed for both types of tubes. I recall one of the Schiit amps or pre-amps saying it could use either but the 6sl7 would be noisier lol. I stay away from that.  I am currently comparing a bunch of 12AU7's and folks on here whom I have done favors for have been kind enough to send me matched pairs.   I only mention that since it seems to work.


----------



## L0rdGwyn

raindownthunda said:


> DIY!?? Where do I sign up??  So excited to follow the progress on this project. Have you thought about chassis supply at all? Curious on whether or not it would be feasible to have a standard pre-built chassis available to order.



Yeah no sure thing yet, but I think it might make the most sense, need to talk it over with a few people.  If I do it, I would probably release it on diyAudio and then link the post here.  That would be the best place for it to be hosted given knowledgeable members there would be able to assist those with less experience.  I've reached out to one of my diyAudio moderator pals to get his thoughts on it.  Given it is a relatively expensive project, some of the more curmudgeonly members there might poo poo it.  Oh well, we'll see what he thinks.

What I would do is release the CAD files for the chassis.  Dave at Landfall systems would have the chassis files already, so it could be ordered from him easily, ready to go, just like the one I built.  The only part that has me a little concerned is the dexterity required to solder the switch pins to the PCB I made, it's a bit of a pain to do.

I placed a very high priority on ease of building this amplifier.  With all of the parts in front of me, I could build one of these in 5-6 hours from scratch.


----------



## L0rdGwyn

Paladin79 said:


> I recall one of the Schiit amps or pre-amps saying it could use either but the 6sl7 would be noisier lol.



Exactly!  I think this problem is often overlooked in headphone amplifiers.  People want tube headphone amplifiers with 10W peak output or something crazy, then complain they can hear a hum.  Well yeah, the amp has way too much gain for a headphone!  It's going to be noisy.


----------



## Paladin79

L0rdGwyn said:


> Exactly!  I think this problem is often overlooked in headphone amplifiers.  People want tube headphone amplifiers with 10W peak output or something crazy, then complain they can hear a hum.  Well yeah, the amp has way too much gain for a headphone!  It's going to be noisy.


LOL I have not checked headphone output level on my PrimaLuna yet but it is hum free, it is of course not strictly a headphone amp and I am running 8 KT88's and 6 12au7's.


----------



## Xcalibur255

L0rdGwyn said:


> Exactly!  I think this problem is often overlooked in headphone amplifiers.  People want tube headphone amplifiers with 10W peak output or something crazy, then complain they can hear a hum.  Well yeah, the amp has way too much gain for a headphone!  It's going to be noisy.


I think people widely equate having more power with having superior dynamic qualities.  Most people don't realize that the circuit and power supply design of the amplifier mostly determines this and it doesn't need to have a dumptruck load of power to have good dynamic swing.

You can explain, but honestly people don't believe it until they hear a low power amplifier producing a big beautiful sound for themselves.


----------



## L0rdGwyn

Xcalibur255 said:


> I think people widely equate having more power with having superior dynamic qualities.  Most people don't realize that the circuit and power supply design of the amplifier mostly determines this and it doesn't need to have a dumptruck load of power to have good dynamic swing.
> 
> You can explain, but honestly people don't believe it until they hear a low power amplifier producing a big beautiful sound for themselves.



I think you are exactly right.  You can make a lower powered amplifier with those qualities.  People equate the ability of an amplifiers "drive" or ability to "power" headphones with a higher degree of dynamics / punch / bass weight and heft.  Those qualities I think are often associated with high power amplifiers, but certainly you can get those characteristics in an amplifier that only makes 1-2W.


----------



## Paladin79

It depends on the transducers of course. I have some low powered amps that work amazingly well with highly efficient speakers, it is the way it used to be in the early days of audio.


----------



## carlman14

L0rdGwyn said:


> I think you are exactly right. You can make a lower powered amplifier with those qualities. People equate the ability of an amplifiers "drive" or ability to "power" headphones with a higher degree of dynamics / punch / bass weight and heft. Those qualities I think are often associated with high power amplifiers, but certainly you can get those characteristics in an amplifier that only makes 1-2W.


This reminds me of the time I saw some of your comments over on the susvara thread. You were trying to show people that they didn't need a 200W speaker amp to drive their headphones. They weren't having any of it haha.


----------



## Paladin79 (Sep 21, 2022)

A gentleman I just visited could run Susvaras with one of the Incubus amps I designed, just over 1 watt output. (I did use more VU meters then.


----------



## L0rdGwyn

carlman14 said:


> This reminds me of the time I saw some of your comments over on the susvara thread. You were trying to show people that they didn't need a 200W speaker amp to drive their headphones. They weren't having any of it haha.



Lol I remember that.  I've tried to be better about barging in and being prescriptive about what people should or should not be doing, if it works for them then great!  I suspect it is more related to the very low output impedance of these amplifiers given they are designed for more difficult loads (speaker impedances).  Lots of people loving Susvara off of tube amps these days, which don't have tons of power on tap and very low output impedances.


----------



## whirlwind (Sep 22, 2022)

L0rdGwyn said:


> Exactly!  I think this problem is often overlooked in headphone amplifiers.  People want tube headphone amplifiers with 10W peak output or something crazy, then complain they can hear a hum.  Well yeah, the amp has way too much gain for a headphone!  It's going to be noisy.



The misconception a lot of people have is they just think or maybe just want more power. (Insert Tim "Toolman" Taylor here)

You don't need more power than you need, they are headphone's and most can be powered properly without crazy watts of power.

I can't even imagine how one's ears would feel if something went wrong when listening to headphones on a speaker amp


----------



## Paladin79

Some time ago I stopped a guy on here from using 16 gauge wire from a 100 watt speaker amp that he wanted to hook to headphones. He wanted to be sure that gauge was enough lol. I told him that hopefully the tiny wire inside the headphones would act as a fuse and save some hearing if he messed up. 
I would worry about others in his family even if he was very careful himself.


----------



## L0rdGwyn (Sep 23, 2022)

So here is my tentative plan...

As I've said, I don't think the version of the pentode headamp that I sent to CanJam is a great fit for commercial production.  While I love the simplicity of the circuit and the sound, I think the cost of the Lundahl parts is too much for commercial viability.  To make a commercial version of this circuit, I think it needs to use solid state components to replace the chokes in the design.  This poses some other design challenges that would need to be worked through.

Since I like the Lundahl iron version and it is relatively easy to build, my plan will be to release that version as a DIY project.  Note that it will be an expensive project.

Then, in the meantime, I will work on a transistor-based version of the circuit with the potential of commercial manufacture in the future.  That will take some time.

I am just waiting to hear back from Lundahl's US distributor to make sure they will be able to supply DIYers, specifically the small transformer housings were on backorder recently, I want to be sure they are going to be available in the foreseeable future before I go to the trouble of putting together materials to build this amplifier.  Likely I will have to build a second one to take photos along the way for the sake of instruction.  I will probably sell the original and the second one I build for instruction.

This project will probably be hosted on diyAudio.  I am expecting to get a mixed response there given the cost of the design (a lot of DIYers are very budget oriented).  Maybe if there are some reviews I can link to, along with some measurements, the curmudgeons will be silenced.

That is what I am thinking for now, hoping to hear back from the Lundahl distributor later today.  If so, I will probably feel it is okay to show some pictures of the interior and give an explanation of the circuit.


----------



## Paladin79

L0rdGwyn said:


> So here is my tentative plan...
> 
> As I've said, I don't think the version of the pentode headamp that I sent to CanJam is a great fit for commercial production.  While I love the simplicity of the circuit and the sound, I think the cost of the Lundahl parts is too much for commercial viability.  To make a commercially version of this circuit, I think it needs to use solid state components to replace the chokes in the design.  This poses some other design challenges that would need to be worked through.
> 
> ...



Are you talking about a headphone amp and if so what do you consider expensive?  Sorry I do not read the thread enough to keep up on the amp types.


----------



## L0rdGwyn

Paladin79 said:


> Are you talking about a headphone amp and if so what do you consider expensive?  Sorry I do not read the thread enough to keep up on the amp types.



Yes it's a headphone amp.  I have to do a final tally, but I would guesstimate to build it the way I built it here, cost of parts would be somewhere in the ballpark of $1.5K.


----------



## Paladin79

L0rdGwyn said:


> Yes it's a headphone amp.  I have to do a final tally, but I would guesstimate to build it the way I built it here, cost of parts would be somewhere in the ballpark of $1.5K.


I will watch for it, naturally I would have to make a wooden cabinet and do point to point wiring but that is just me.


----------



## L0rdGwyn

Paladin79 said:


> I will watch for it, naturally I would have to make a wooden cabinet and do point to point wiring but that is just me.



The major circuitry is all on a PCB for ease of building, but of course you can do your thang!


----------



## JazzVinyl (Sep 23, 2022)

L0rdGwyn said:


> The major circuitry is all on a PCB for ease of building, but of course you can do your thang!



I like the PCB, and the presentation it shows in the case layout that you designed.


----------



## Paladin79

Yeah I suspected that lol, I also do my own metal work, usually in copper.  I have to rush out but I was just gifted an amazing batch of 12AU7's I will have to check out when I get home. I like choices.


----------



## Paladin79

JazzVinyl said:


> I like the PCB, and the presentation it shows in the case layout that you designed.


I am sure it is well done. I spent 16 years working with custom wire and cable and have specific likes within amps I designed. I also roll a lot of tubes so I am pretty cautious about socket stability. 😀


----------



## JazzVinyl

Paladin79 said:


> I am sure it is well done. I spent 16 years working with custom wire and cable and have specific likes within amps I designed. I also roll a lot of tubes so I am pretty cautious about socket stability. 😀


If you build it point to point, I am sure it will be superbly executed!!  Wooden case would rule, too


----------



## Paladin79

JazzVinyl said:


> If you build it point to point, I am sure it will be superbly executed!!  Wooden case would rule, too


Thanks, I try.😁  I need to build an amp prettier than this one just to annoy @bcowen.


----------



## L0rdGwyn

Paladin79 said:


> Yeah I suspected that lol, I also do my own metal work, usually in copper.  I have to rush out but I was just gifted an amazing batch of 12AU7's I will have to check out when I get home. I like choices.



I typically build point-to-point, but for this particular circuit I went with PCB.  Makes for a very quick build, I could build this amp from scratch in a single day.


----------



## Paladin79

L0rdGwyn said:


> I typically build point-to-point, but for this particular circuit I went with PCB.  Makes for a very quick build, I could build this amp from scratch in a single day.


Not me, I can spent 40 hours on a cabinet and copper plate, but that is the part I enjoy. I spent nearly all my career in engineering, electronic production, and repair. 50 years worth so it can bore me at times.🤪🤪


----------



## jgwtriode (Sep 23, 2022)

L0rdGwyn said:


> Yes it's a headphone amp.  I have to do a final tally, but I would guesstimate to build it the way I built it here, cost of parts would be somewhere in the ballpark of $1.5K.


I figured it would be around that range.  That is actually quite reasonable, especially considering how well l it is likely to perform! Does that include the chassis?

jgwtriode


----------



## L0rdGwyn (Sep 23, 2022)

jgwtriode said:


> I figured it would be around that range.  That is actually quite reasonable, especially considering how well l it is likely to perform! Does that include the chassis?
> 
> jgwtriode



Yup, that's a rough figure for everything.  Not exact though, just an estimation.  I still don't have a good handle on where the amp stands in terms of subjective performance.  I know where I think it stands, but not where others do, just a few people saying it sounds great so far.  But if you figure it is a TOTL category sounding amplifier, then $1.5Kish plus a few days of labor, I think it would be worth the money and effort.  Well, I should add a fair amount of time will go into ordering parts and waiting for them to arrive, but I will try to make that as easy as I can.

Dave Slagle is going to wind the transformers for my over-the-top version of this amp.  I am going to have a custom mains wound by Monolith Magnetics with dual secondaries for a true dual mono voltage regulated power supply, because why not.


----------



## Paladin79

L0rdGwyn said:


> Yup, that's a rough figure for everything.  Not exact though, just an estimation.  I still don't have a good handle on where the amp stands in terms of subjective performance.  I know where I think it stands, but not where others do, just a few people saying it sounds great so far.  But if you figure it is a TOTL category sounding amplifier, then $1.5Kish plus a few days of labor, I think it would be worth the money and effort.  Well, I should add a fair amount of time will go into ordering parts and waiting for them to arrive, but I will try to make that as easy as I can.
> 
> Dave Slagle is going to wind the transformers for my over-the-top version of this amp.  I am going to have a custom mains wound by Monolith Magnetics with dual secondaries for a true dual mono voltage regulated power supply, because why not.


Total transformer cost? Anything else I most likely have or do not need.


----------



## L0rdGwyn

Paladin79 said:


> Total transformer cost? Anything else I most likely have or do not need.



Somewhere around $800 for the transformers and chokes, three of each.  I'll get into all of the details though soon, I want to hear back from the Lundahl distributor and be sure they can supply before I lay bare the details in public.  It is a relatively simple design, nothing innovative, but I think it has an edge over a conventional SET output topology for headphones if you can work around the design issues it presents.


----------



## Paladin79

L0rdGwyn said:


> Somewhere around $800 for the transformers and chokes, three of each.  I'll get into all of the details though soon, I want to hear back from the Lundahl distributor and be sure they can supply before I lay bare the details in public.  It is a relatively simple design, nothing innovative, but I think it has an edge over a conventional SET output topology for headphones if you can work around the design issues it presents.


Sounds good, I will wait for more info.😜


----------



## jgwtriode

Hey Keenan?

So is your all out design primarily better iron with the same components in the same pentode configuration with inter stage transformers.?  Is the driver stage coupled in the same fashion as the Airmid in the std. pentode configuration?  And how much more is the cost of the magnetics your throwing into to your all out just for reference purposes?

jgwtriode


----------



## L0rdGwyn (Sep 23, 2022)

jgwtriode said:


> Hey Keenan?
> 
> So is your all out design primarily better iron with the same components in the same pentode configuration with inter stage transformers.?  Is the driver stage coupled in the same fashion as the Airmid in the std. pentode configuration?  And how much more is the cost of the magnetics your throwing into to your all out just for reference purposes?
> 
> jgwtriode



Pretty much.  The stages in the Airmid are direct-coupled, in the standard pentode amplifier they are copper foil capacitor coupled, direct coupling doesn't make much sense in this circuit as you end up just moving the interstage coupling capacitor into the output stage as a bypass capacitor instead, which is worse.  

Major changes I am making are using custom iron (2-3x the cost of standard), solid state rectification, voltage regulated power supply, change of input tubes from 6SL7 to E810F to facilitate interstage transformer coupling, which is not doable with 6SL7, LED biasing of the E810F as opposed to cathode biasing 6SL7 in standard.  LED biasing is not objectively preferable for the 6SL7 in the standard circuit, cathode biasing was subjectively preferable as well (I tried, measured, and subjectively tested both).  The output stage topology is the commonality between the two designs, which is the most important part of the circuit and dictates the requirements of the input stage so to speak.  

These changes also add a degree of complexity that would put it outside the skill level of someone without experience to build IMO.  What I love about the original version is it achieves a very high quality of sound with a very simple design that can be built by anyone.  I tend to get the itch to "max out" a circuit idea, sort of like how I built my 6336 OTL based off the Airmid topology.  

Ever since building that 45 amp for Zach, I have thought I need to build myself a endgame level transformer coupled amplifier.  I wasn't sure what that would look like, at one point I was considering building essentially the same circuit but using the 10Y as an output instead.  I was on a run the other day and these changes to the pentode circuit popped into my head and I decided this is the one.


----------



## Paladin79

L0rdGwyn said:


> Pretty much.  The stages in the Airmid are direct-coupled, in the standard pentode amplifier they are copper foil capacitor coupled, direct coupling doesn't make much sense in this circuit as you end up just moving the interstage coupling capacitor into the output stage as a bypass capacitor instead, which is worse.
> 
> Major changes I am making are using custom iron (2-3x the cost of standard), solid state rectification, voltage regulated power supply, change of input tubes from 6SL7 to E810F to facilitate interstage transformer coupling, which is not doable with 6SL7, LED biasing of the E810F as opposed to cathode biasing 6SL7 in standard.  LED biasing is not objectively preferable for the 6SL7 in the standard circuit, cathode biasing was subjectively preferable as well (I tried, measured, and subjectively tested both).  The output stage topology is the commonality between the two designs, which is the most important part of the circuit and dictates the requirements of the input stage so to speak.
> 
> ...


All righty then,🤪🤪🤪🤪


----------



## bcowen

Paladin79 said:


> Thanks, I try.😁  I need to build an amp prettier than this one just to annoy @bcowen.


You don't have to build a new amp to annoy me.   🤣 

Besides, the only way you could make one prettier than mine is to use equally gorgeous tiger maple and then dovetail the corners.  Then I'd be annoyed.


----------



## Paladin79

bcowen said:


> You don't have to build a new amp to annoy me.   🤣
> 
> Besides, the only way you could make one prettier than mine is to use equally gorgeous tiger maple and then dovetail the corners.  Then I'd be annoyed.


Working on it, maybe.🤪🤪


----------



## jgwtriode

L0rdGwyn said:


> Pretty much.  The stages in the Airmid are direct-coupled, in the standard pentode amplifier they are copper foil capacitor coupled, direct coupling doesn't make much sense in this circuit as you end up just moving the interstage coupling capacitor into the output stage as a bypass capacitor instead, which is worse.
> 
> Major changes I am making are using custom iron (2-3x the cost of standard), solid state rectification, voltage regulated power supply, change of input tubes from 6SL7 to E810F to facilitate interstage transformer coupling, which is not doable with 6SL7, LED biasing of the E810F as opposed to cathode biasing 6SL7 in standard.  LED biasing is not objectively preferable for the 6SL7 in the standard circuit, cathode biasing was subjectively preferable as well (I tried, measured, and subjectively tested both).  The output stage topology is the commonality between the two designs, which is the most important part of the circuit and dictates the requirements of the input stage so to speak.
> 
> ...




Thanks for sharing that Keenan.  Always nice to get more insight into your designs and how specific design elements interact.
Don't always understand everything but it helps me get a better idea of why your amps sound so amazing and I always enjoy learning
more about the technical side.

jgwtriode


----------



## L0rdGwyn (Sep 24, 2022)

Alright, Lundahl distributor says we are a go for transformer availability, just a 4-5week lead time given they will mostly be made in Sweden.

Here is what I've done with this output stage in this amplifier.

Below is a conventional cathode biased SET output stage (series feed), this is what you will find in a vast majority of transformer coupled single-ended tube amplifiers.  The signal path for the output stage is comprised of the final components of the B+ supply, the output transformer, the tube, and the cathode bypass capacitor.  The transformer is always in the plate of the tube.




So what would happen if instead we put the transformer in the cathode?  It would look something like this.



The output stage signal path now consists of the B+ supply, the tube, and the output transformer.  There is no need for a bypass capacitor!!!

This is the major difference between this amplifier and other transformer coupled amps - the output stage is a transformer coupled cathode follower.  Similar to the conventional SET output stage, it is cathode biased, but rather than using a cathode resistor, we use the DC resistance of the output transformer primary winding to bias the tube along with some series resistance if need be.

So why go to the trouble?  This output topology has a number or pros over the conventional SET approach, as well as some cons.

Pros:
1) A very clean signal path in the output stage - removing a reactive component from the output stage, the bypass capacitor, has huge gains in terms of clarity, staging, dynamics, realism.  This same benefit is gained when using fixed / grid bias output stages, however they require a dedicated negative bias supply, much more complexity!  This output stage keeps the tube cathode biased without requiring a bias supply - essentially you gain the benefit of a fixed bias design without the cost / size / headache of a grid bias supply.

2) Low distortion - a cathode follower inherently is low distortion due to its internal negative feedback.  This amplifier has inaudible levels of distortion at normal listening volumes and it remains low all the way up to clipping.

3) Low output impedance and improved damping ratio - a typical SET amplifier will achieve roughly a 3:1 damping ratio.  Higher damping ratios can be accomplished using a higher turns output transformer, however this is at the cost of copper losses, a less ideal output transformer, and power output.  Using a cathode follower, and the specific tubes used in this circuit, damping ratios of 7:1 or 8:1 can be achieved, much better for driving low impedance and hard to drive planar magnetics.

Cons:
1) No voltage gain in the output stage - a cathode follower has a voltage gain of less than 1, meaning all of the voltage gain for the amplifier must be done by the input stage!  This means you need a high gain input stage that can swing big time voltages at low distortion.  Add using new production tubes into the mix and this was the hardest part of the design!  I'll discuss the input stage later...

2) Dedicated heater windings - because the entire output voltage appears on the output tube's cathode, at peak swing you risk violating the tube's maximum heater-to-cathode voltage.  If that happens, the tube could arc and it is toast!  To avoid this potential issue, each output tube MUST have its own dedicated heater winding with the heater referenced to the tube's cathode.  That means a mains transformer with at least three separate heater windings, plus a rectifier filament winding, which is not all that common.

So at a high level, this is the design of the output stage.  I was able to come up with something that works within these constraints using common tubes that sounds really excellent (in my opinion).  I'm certainly not the first person to try this, you might see bits and pieces about it on the web.  It has been discussed to a small degree on diyAudio, but in the context of speaker amplifiers where the voltage swinging requirements of the input stage become ridiculous to the point of being impractical.  But for headphones, it works quite nicely I've found


----------



## L0rdGwyn (Sep 24, 2022)

Here is the interior.


----------



## bcowen

L0rdGwyn said:


> Here is the interior.


Looks remarkably uncluttered, which I guess the PCB's contribute to a lot.

Compared to this, a 15wpc push-pull pentode (wired in triode) stereo amp.  It was a kit.


----------



## L0rdGwyn (Sep 24, 2022)

Yeah, the PCB makes the required point-to-point wiring minimal.  You can see I also included terminal blocks to make wired connection to the PCB except where a direct soldered connection is preferred, grounded connections specifically.

One thing that probably stands out are the two big chokes in the middle of the interior that the PCB is wrapped around.  These chokes load the 6SL7 input stage.  The two sections of the 6SL7 are wired in parallel to halve its internal impedance for a improved low frequency extension.  Loading a tube with a choke allows the tube's peak voltage to swing above the B+ voltage. 



This is how we get around the huge voltages needed to overcome the lack of voltage gain in the cathode follower output stage.  The 6SL7 is able to swing over 300V peak-to-peak at low distortion, essentially making up for the gain of 1 in the output.  There are very few new production high gain tubes that have excellent linearity, I felt the 6SL7 was the best choice and found a way to make it work with a ridiculous 810H 5mA anode choke, only made by Lundahl.

To keep the internal resistance of the 6SL7 as low as possible, it is cathode biased with a electrolytic bypass capacitor.  Now normally I am not a fan of electrolytics, but I knew going in an electrolytic would be the best choice to keep the bandwidth of the stage as high as possible.  Way back when, I A-B tested as many "audio grade" electrolytics as I could to try and find one I felt was worth using.  That turned out to be the Jupiter Cosmos.  Their sound is so far beyond any other electrolytic I tried, I would call them essential!  No substitutes allowed.

I told the owner of Jupiter Condenser how amazed I was with the sound he had achieved in these electrolytics, now my quote (typo and all) is immortalized on their product page, I am famous.

https://jupitercondenser.com/products/cosmos-electrolytic-axial-leads

One down side to the parallel 6SL7 stage is its very high Miller capacitance, something on the order of 400pF.  For this reason, a maximum 25K volume pot is required, otherwise the high frequency extension will suffer.


----------



## L0rdGwyn

So there you have it.  I'll get into more detail about the specifics of the schematic when I put together instructional materials.  The one part of the circuit that has me a little concerned for inexperienced builders is the output switch, it's kind of a b**** to solder, but I think I'll be able to explain the method.  I've thought about making an instructional video specifically for that task, which I think would help.

It's going to take some time, probably a few months, for me to put together all of the materials needed for an official DIY project release.  I will be making some minor changes to the PCB for ease of DIY reasons (e.g., including test points).  I will then have to build another one and take very deliberate photos along the way and compile them into a instructional PDF.

I know $1.5Kish ain't cheap, and this would be a big commitment to gather all the parts and build, but I really think people would be getting that custom / boutique amplifier sound for what I think is a pretty reasonable price.  It's really very easy to build if you have all of the right parts / equipment.  I would be very proud if people build and and love the sound, so hopefully that will be the case.


----------



## Paladin79

Friends did a similar design for a lot less money so I best pass, good luck though.


----------



## L0rdGwyn

Paladin79 said:


> Friends did a similar design for a lot less money so I best pass, good luck though.



It's all the same to me, have fun.


----------



## jgwtriode

L0rdGwyn said:


> Alright, Lundahl distributor says we are a go for transformer availability, just a 4-5week lead time given they will mostly be made in Sweden.
> 
> Here is what I've done with this output stage in this amplifier.
> 
> ...


Impressive Keenan!


----------



## jgwtriode

L0rdGwyn said:


> So there you have it.  I'll get into more detail about the specifics of the schematic when I put together instructional materials.  The one part of the circuit that has me a little concerned for inexperienced builders is the output switch, it's kind of a b**** to solder, but I think I'll be able to explain the method.  I've thought about making an instructional video specifically for that task, which I think would help.
> 
> It's going to take some time, probably a few months, for me to put together all of the materials needed for an official DIY project release.  I will be making some minor changes to the PCB for ease of DIY reasons (e.g., including test points).  I will then have to build another one and take very deliberate photos along the way and compile them into a instructional PDF.
> 
> I know $1.5Kish ain't cheap, and this would be a big commitment to gather all the parts and build, but I really think people would be getting that custom / boutique amplifier sound for what I think is a pretty reasonable price.  It's really very easy to build if you have all of the right parts / equipment.  I would be very proud if people build and and love the sound, so hopefully that will be the case.


Agreed; Keenan its around the price of a Bottlehead Mainline and you get a hell of a lot more here than in that kit.   I am really floored.  Might be later next year, but I want one.   Now hopefully we can get some impressions of it.

Happy listening,

jgwtriode


----------



## Zachik

L0rdGwyn said:


> The one part of the circuit that has me a little concerned for inexperienced builders is the output switch, it's kind of a b**** to solder, but I think I'll be able to explain the method.


Output switch?! Does the amp have headphones / speakers output??


----------



## Monsterzero

Zachik said:


> Output switch?! Does the amp have headphones / speakers output??


 output impedance switch


----------



## L0rdGwyn (Sep 25, 2022)

jgwtriode said:


> Agreed; Keenan its around the price of a Bottlehead Mainline and you get a hell of a lot more here than in that kit.   I am really floored.  Might be later next year, but I want one.   Now hopefully we can get some impressions of it.
> 
> Happy listening,
> 
> jgwtriode



Yeah that's my thinking too, and the major benefit of doing things DIY, you can make a circuit with high quality parts and it is still affordable, something equivalent would cost 4-5x as much commercially.  Could I have cut corners and made it cheaper?  Sure, I could have used Hammond chokes in the power supply with higher ripple, cheapo output transformers, a lower gain / less linear input tube at the cost of power output and maybe then I could have gone for cheaper anode chokes.  Maybe even a lower quality off-the-shelf chassis by giving up my ability to design and customize it, putting a higher burden of the prep work on the builder.  I could have avoided the steel Lundahl transformer shields at the cost of aesthetic appeal and perhaps higher magnetic coupling between mains and output transformers.  I think using the better parts is worth the cost and in some areas makes the assembly more simple, that is my style, and it shows in the end result in my opinion.  Also, being able to order all of the iron from one place is a benefit, sourcing inductors from multiple places could cut costs but the benefit would be partially lost in the extra shipping charges.  Using transistors instead of chokes is another way to cut costs, but of course this has its own compromises - the power supply would need to fundamentally change, the propensity for part failure would go up, and building the circuit would be less friendly to new DIYers.

@zach915m has the amp right now, I know he has compared it to his 45 amp and the comparison is very favorable.  @Monsterzero will have it next.  I need to come up with a name...



Zachik said:


> Output switch?! Does the amp have headphones / speakers output??





Monsterzero said:


> output impedance switch



Yeah, output impedance switch.  Low is 32-150ohms, high 150ohms and up.


----------



## carlman14

What a cool circuit! I might have to build one some day if I ever get bored of my pentode amp. You mentioned that you can get 7:1 to 8:1 damping ratio with this topology. As you know, you can also achieve a higher damping ratio by connecting higher impedance headphones to a lower impedance OPT tap... like connecting 32 ohm headphones to a 16 ohm OPT tap. Would you say that your way of achieving a higher damping ratio is any better or worse than what I described? Any pros or cons doing one vs the other?


----------



## paradoxper

L0rdGwyn said:


> Yeah that's my thinking too, and the major benefit of doing things DIY, you can make a circuit with high quality parts and it is still affordable, something equivalent would cost 4-5x as much commercially.  Could I have cut corners and made it cheaper?  Sure, I could have used Hammond chokes in the power supply with higher ripple, cheapo output transformers, a lower gain / less linear input tube at the cost of power output and maybe then I could have gone for cheaper anode chokes.  Maybe even a lower quality off-the-shelf chassis by giving up my ability to design and customize it, putting a higher burden of the prep work on the builder.  I could have avoided the steel Lundahl transformer shields at the cost of aesthetic appeal and perhaps higher magnetic coupling between mains and output transformers.  I think using the better parts is worth the cost and in some areas makes the assembly more simple, that is my style, and it shows in the end result in my opinion.  Also, being able to order all of the iron from one place is a benefit, sourcing inductors from multiple places could cut costs but the benefit would be partially lost in the extra shipping charges.  Using transistors instead of chokes is another way to cut costs, but of course this has its own compromises - the power supply would need to fundamentally change, the propensity for part failure would go up, and building the circuit would be less friendly to new DIYers.
> 
> @zach915m has the amp right now, I know he has compared it to his 45 amp and the comparison is very favorable.  @Monsterzero will have it next.  I need to come up with a name...
> 
> ...


Na, don't cut corners. DIY should represent return value not making concessions. Great job.


----------



## jgwtriode (Sep 25, 2022)

Ceridwen,. Celtic goddess of poetry and inspiration.   I think that would be an appropriate name.  If you want to switch gender; Maponus.  Celtic god of music and poetry!   Either rolls off the tongue nicely.  I love the the mythos of the Tuatha De'Danann!

Happy naming,

jgwtriode


----------



## Monsterzero

jgwtriode said:


> Ceridwen,. Celtic goddes of poetry and inspiration.   I think that would be an appropriate name.  If you want to switch gender,. Maponus.  Celtic god of music and poetry!   Either rolls of the tongue nicely.  I love the the mythos of the Tuaththa De'Danann!
> 
> Happy naming,
> 
> jgwtriode


 Sticking with the Celtic theme, you can name it 'Taranis' the Celtic God of Thunder, which also happens to be my puppy's name  He's not your normal everyday 115 lb. 7 month old pup though.


----------



## jgwtriode

Monsterzero said:


> Sticking with the Celtic theme, you can name it 'Taranis' the Celtic God of Thunder, which also happens to be my puppy's name  He's not your normal everyday 115 lb. 7 month old pup though.


In the immortal words of Scrappy Doo, "Puppy Power!"

jgwtriode


----------



## Mr Trev

L0rdGwyn said:


> I need to come up with a name...


You can always go with a confusing, albeit meaningless, alphabet soup name, ala ChiFi.
Then a couple months down the road, make a small change and re-release it as the "Pro" model


----------



## Zachik

Monsterzero said:


> Sticking with the Celtic theme, you can name it 'Taranis' the Celtic God of Thunder, which also happens to be my puppy's name  He's not your normal everyday 115 lb. 7 month old pup though.


OMG - that is a big puppy!!!
Immediately brings The Hounds of Baskerville to my mind...


----------



## L0rdGwyn

carlman14 said:


> What a cool circuit! I might have to build one some day if I ever get bored of my pentode amp. You mentioned that you can get 7:1 to 8:1 damping ratio with this topology. As you know, you can also achieve a higher damping ratio by connecting higher impedance headphones to a lower impedance OPT tap... like connecting 32 ohm headphones to a 16 ohm OPT tap. Would you say that your way of achieving a higher damping ratio is any better or worse than what I described? Any pros or cons doing one vs the other?



Thanks!

Typically a higher turns ratio output transformer is going to be less ideal than a lower turns ratio output transformer in terms of copper losses, leakage inductance, interwinding capacitance, so you are increasing the damping ratio but sacrificing some transformer performance.  For using a 32ohm headphone on 16ohm tap, not likely to be a noticeable issue, but using say a 300ohm headphone on a 16ohm tap, I think you would hear a significant difference compared to a dedicated 300ohm tap.  Obviously some power is lost doing this as well.  A while back I did some subjective comparisons using a speaker transformer for 300ohm dynamic headphones.  I used a parallel 8ohm resistor on an 8ohm tap, a parallel 16ohm resistor on an 8ohm tap, then ran the headphones right off the tap without any parallel resistance.  The 8ohm resistor on the 8ohm tap in parallel was by far the best, so I try to avoid using high Z headphones on low Z taps if I can.

One advantage of the higher turns ratio transformer is a lower noise output, but if the amplifier is well designed, the noise should be inaudible either way (this amp is dead silent on high Z).  In terms of achieving a lower output impedance, between the two I think the cathode follower approach is more effective as you are not having to compromise on transformer performance.  It is somewhat similar to using global negative feedback in a class AB push pull amplifier, the output impedance is reduced and bandwidth improve via negative feedback.  It just so happens in a cathode follower the negative feedback is happening inside the tube!

That's right folks, all your cathode follower OTLs are technically utilizing negative feedback.  Time to throw them in the trash


----------



## Monsterzero

Zachik said:


> OMG - that is a big puppy!!!
> Immediately brings The Hounds of Baskerville to my mind...


lol. We live in the middle of a forest, which is in the middle of nowhere, which is on the very, very edge of a small town that doesnt have a police force.
We do not get many visitors out this way. Taranis is our insurance policy that it remains that way.


----------



## Aleh

L0rdGwyn said:


> Yeah that's my thinking too, and the major benefit of doing things DIY, you can make a circuit with high quality parts and it is still affordable, something equivalent would cost 4-5x as much commercially. Could I have cut corners and made it cheaper? Sure, I could have used Hammond chokes in the power supply with higher ripple, cheapo output transformers, a lower gain / less linear input tube at the cost of power output and maybe then I could have gone for cheaper anode chokes. Maybe even a lower quality off-the-shelf chassis by giving up my ability to design and customize it, putting a higher burden of the prep work on the builder. I could have avoided the steel Lundahl transformer shields at the cost of aesthetic appeal and perhaps higher magnetic coupling between mains and output transformers. I think using the better parts is worth the cost and in some areas makes the assembly more simple, that is my style, and it shows in the end result in my opinion. Also, being able to order all of the iron from one place is a benefit, sourcing inductors from multiple places could cut costs but the benefit would be partially lost in the extra shipping charges. Using transistors instead of chokes is another way to cut costs, but of course this has its own compromises - the power supply would need to fundamentally change, the propensity for part failure would go up, and building the circuit would be less friendly to new DIYers.


Pls don't cut corners. Otherwise you just lose the great benefit of DIY - having the same quality for 3-4x less price.


----------



## L0rdGwyn

Aleh said:


> Pls don't cut corners. Otherwise you just lose the great benefit of DIY - having the same quality for 3-4x less price.



No I don't plan to, I was more trying to illustrate why cutting those corners isn't worth doing!  The design is final at this point.


----------



## carlman14

L0rdGwyn said:


> Thanks!
> 
> Typically a higher turns ratio output transformer is going to be less ideal than a lower turns ratio output transformer in terms of copper losses, leakage inductance, interwinding capacitance, so you are increasing the damping ratio but sacrificing some transformer performance. For using a 32ohm headphone on 16ohm tap, not likely to be a noticeable issue, but using say a 300ohm headphone on a 16ohm tap, I think you would hear a significant difference compared to a dedicated 300ohm tap. Obviously some power is lost doing this as well. A while back I did some subjective comparisons using a speaker transformer for 300ohm dynamic headphones. I used a parallel 8ohm resistor on an 8ohm tap, a parallel 16ohm resistor on an 8ohm tap, then ran the headphones right off the tap without any parallel resistance. The 8ohm resistor on the 8ohm tap in parallel was by far the best, so I try to avoid using high Z headphones on low Z taps if I can.
> 
> ...



Thanks! Informative as always. I've been using all my headphones from 32-300 ohms on a 32 ohm tap, similar to how I think some of Glenn's SET amps are implemented. Interesting that you found the parallel resistors sounded better. I would have thought that a higher secondary load (and resulting higher primary load) would sound better due to the decreased distortion. I'll have to try out some parallel resistors on the 8 ohm tap and see how that sounds!

Besides loss of power, I wonder if there's a major difference between using parallel resistors with a higher turns transformer and using a lower turns transformer with a higher ohm secondary. I suppose that wraps around to the 3:1 vs 8:1 damping ratios mentioned earlier.


----------



## raindownthunda

L0rdGwyn said:


> No I don't plan to, I was more trying to illustrate why cutting those corners isn't worth doing!  The design is final at this point.


The market has enough “someone has done it cheaper” options for people wanting to dip their toes. I would hazard a guess that a good number of us obsessed with pushing the boundaries of performance in our systems would much rather spend a good bit more for that extra 10-20% performance. I love the idea of maxing out performance with a kit that comes with the DIY labor price savings, removing the cost and time constraints of working with a custom builder. There is a satisfaction knowing this is as good as it gets, and I was able to build it while saving a good chunk of change. Are you thinking of charging a fee to purchase the plans?


----------



## Monsterzero (Sep 25, 2022)

@L0rdGwyn

Do you happen to know what the output impedance is on the Airmid with the various power tubes is?

For example, what is it when 6AS7G in place vs. 6080 vs 5998/421a vs. 7236 vs. 7802?


----------



## L0rdGwyn (Sep 25, 2022)

raindownthunda said:


> The market has enough “someone has done it cheaper” options for people wanting to dip their toes. I would hazard a guess that a good number of us obsessed with pushing the boundaries of performance in our systems would much rather spend a good bit more for that extra 10-20% performance. I love the idea of maxing out performance with a kit that comes with the DIY labor price savings, removing the cost and time constraints of working with a custom builder. There is a satisfaction knowing this is as good as it gets, and I was able to build it while saving a good chunk of change. Are you thinking of charging a fee to purchase the plans?



Nope, not planning to charge anything, it will be posted publicly.  If I end up providing any parts myself, shipping PCBs for example, I may have to charge a small fee just to cover my time and shipping costs.



Monsterzero said:


> @L0rdGwyn
> 
> Do you happen to know what the output impedance is on the Airmid with the various power tubes is?
> 
> For example, what is it when 6AS7G in place vs. 6080 vs 5998/421a vs. 7236 vs. 7802?



Output Z with 6AS7G / 6080 is 50ohms, with 5998 / 421A is 30ohms


----------



## bcowen

Mr Trev said:


> You can always go with a confusing, albeit meaningless, alphabet soup name, ala ChiFi.
> Then a couple months down the road, make a small change and re-release it as the "Pro" model


All of this naming stuff gets so confusing and bewildering.  Just call it Bob.

🤣 🤣


----------



## Monsterzero

L0rdGwyn said:


> Nope, not planning to charge anything, it will be posted publicly.  If I end up providing any parts myself, shipping PCBs for example, I may have to charge a small fee just to cover my time and shipping costs.
> 
> 
> 
> Output Z with 6AS7G / 6080 is 50ohms, with 5998 / 421A is 30ohms


With the WE 421A, the Airmid actually is pretty damn good with the Caldera. Not a tremendous amount of slam, but it's crystal clear, with no grain and sounds quite good. 

Your prototype is being shipped out to me tomorrow. 

Stay tuned


----------



## L0rdGwyn

Monsterzero said:


> With the WE 421A, the Airmid actually is pretty damn good with the Caldera. Not a tremendous amount of slam, but it's crystal clear, with no grain and sounds quite good.
> 
> Your prototype is being shipped out to me tomorrow.
> 
> Stay tuned



Nice.  Yeah with around 2:1 damping and those big output caps, should work reasonably well.

Looking forward to seeing what you think.  I think one of the output transformers sorta go bent out of alignment on the way to LA, so if it is crooked when it arrives, just ignore that lol should be a simple fix, I assume the screws anchoring it to the chassis where bent and need to be replaced.


----------



## Mr Trev

bcowen said:


> All of this naming stuff gets so confusing and bewildering.  Just call it Bob.
> 
> 🤣 🤣



Indeed. Why does everything have to have a mega/epic sounding name, why not Bob? Or even better, Lucius…


----------



## gibosi

L0rdGwyn said:


> Output Z with 6AS7G / 6080 is 50ohms, with 5998 / 421A is 30ohms



Are these calculated values or are you able to measure them?


----------



## L0rdGwyn

carlman14 said:


> Thanks! Informative as always. I've been using all my headphones from 32-300 ohms on a 32 ohm tap, similar to how I think some of Glenn's SET amps are implemented. Interesting that you found the parallel resistors sounded better. I would have thought that a higher secondary load (and resulting higher primary load) would sound better due to the decreased distortion. I'll have to try out some parallel resistors on the 8 ohm tap and see how that sounds!
> 
> Besides loss of power, I wonder if there's a major difference between using parallel resistors with a higher turns transformer and using a lower turns transformer with a higher ohm secondary. I suppose that wraps around to the 3:1 vs 8:1 damping ratios mentioned earlier.



Well hey, give it a try yourself and see what you think, maybe you'll come to a different conclusion.  Yes, Glenn ran the headphones right off the speaker tap, and I thought the same thing on the distortion.  As I recall, I measured the frequency response at the output at that time as well and there was no significant difference between the three, distortion followed the expected pattern with it being highest with the 8ohm parallel resistor and lowest with the headphones right off the 8ohm tap.  Despite that, the 8ohm parallel sounded best.  This was a while back, I swear I posted about it but I can't find it.


----------



## L0rdGwyn

gibosi said:


> Are these calculated values or are you able to measure them?



They are measured.  Well I should say they are calculated by taking some simple measurements and plugging them into a formula.


----------



## whirlwind

L0rdGwyn said:


> So there you have it.  I'll get into more detail about the specifics of the schematic when I put together instructional materials.  The one part of the circuit that has me a little concerned for inexperienced builders is the output switch, it's kind of a b**** to solder, but I think I'll be able to explain the method.  I've thought about making an instructional video specifically for that task, which I think would help.
> 
> It's going to take some time, probably a few months, for me to put together all of the materials needed for an official DIY project release.  I will be making some minor changes to the PCB for ease of DIY reasons (e.g., including test points).  I will then have to build another one and take very deliberate photos along the way and compile them into a instructional PDF.
> 
> I know $1.5Kish ain't cheap, and this would be a big commitment to gather all the parts and build, but I really think people would be getting that custom / boutique amplifier sound for what I think is a pretty reasonable price.  It's really very easy to build if you have all of the right parts / equipment.  I would be very proud if people build and and love the sound, so hopefully that will be the case.



This DIY build is a great idea IMO.     

Great project with great results can get more people hooked to build stuff, great for everyone.


----------



## Xcalibur255

L0rdGwyn said:


> No I don't plan to, I was more trying to illustrate why cutting those corners isn't worth doing!  The design is final at this point.


There's a weird sort of obsession on sites like diyaudio with making these projects as cheap as possible that I personally have never understood.  I can see why it would be fun to try and make something sound subjectively good for as little money as possible as a challenge, but not with every single build.  The penny-pinching seems to be a broadly shared mindset with that group to the point where it almost seems to be overriding the musical priorities.  I see it more the way you seem to:  rather than look for a way to get a cheaper end product it's a chance to get something at a price similar to common retail offerings that offers greatly improved performance.

Ultimately there's plenty of room for both approaches in the hobby of course.


----------



## L0rdGwyn

whirlwind said:


> This DIY build is a great idea IMO.
> 
> Great project with great results can get more people hooked to build stuff, great for everyone.



Yeah I hope so!  Who knows, maybe it will inspire someone to start working on their own designs.



Xcalibur255 said:


> There's a weird sort of obsession on sites like diyaudio with making these projects as cheap as possible that I personally have never understood.  I can see why it would be fun to try and make something sound subjectively good for as little money as possible as a challenge, but not with every single build.  The penny-pinching seems to be a broadly shared mindset with that group to the point where it almost seems to be overriding the musical priorities.  I see it more the way you seem to:  rather than look for a way to get a cheaper end product it's a chance to get something at a price similar to common retail offerings that offers greatly improved performance.
> 
> Ultimately there's plenty of room for both approaches in the hobby of course.



Agreed, there are different camps, certainly there is a group that is very bang-for-the-buck oriented, but I don't think they need to disparage those who want to spend more for quality.  We'll see how it is received on diyAudio, probably there will be a mixed response.


----------



## Mr Trev

L0rdGwyn said:


> Yeah I hope so!  Who knows, maybe it will inspire someone to start working on their own designs.
> 
> 
> 
> Agreed, there are different camps, certainly there is a group that is very bang-for-the-buck oriented, but I don't think they need to disparage those who want to spend more for quality.  We'll see how it is received on diyAudio, probably there will be a mixed response.


Isn't there some kind of saying along the lines of "you know you're on the right track when everybody's PO'd about it"


----------



## Zachik

L0rdGwyn said:


> We'll see how it is received on diyAudio, *probably there will be a mixed response*.


As opposed to Head-Fi, where we ALL always agree on everything!


----------



## Xcalibur255

Zachik said:


> As opposed to Head-Fi, where we ALL always agree on everything!


It's not about differing viewpoints (which is a good and healthy thing), but rather about some people's inability to tolerate a viewpoint that differs from their own.  I feel like the silos we live in have grown very tall in recent years.


----------



## jgwtriode

Indeed!


----------



## L0rdGwyn

Xcalibur255 said:


> It's not about differing viewpoints (which is a good and healthy thing), but rather about some people's inability to tolerate a viewpoint that differs from their own.  I feel like the silos we live in have grown very tall in recent years.



Yeah, the whole "I disagree with you, therefore I hate you" thing is getting old in general.  Who knows, maybe my project will get a warm response, I've been asked by many people on diyAudio for access to schematics / BOM etc. for personal projects I've posted there.  I've been surprised before too, I've posted several projects on ASR, the one that got the most praise was my tube DAC which I was certain would cause the most offense lol.

I finally got my hands on some 6550, won these at auction, NIB for $180.




I'm reeling from four crazy work shifts, have today and tomorrow off, gotta figure out what steps to take next on the pentode amp.


----------



## Paladin79 (Oct 2, 2022)

My DIY audio racks, solid cherry and patinated copper. I built the new rack in one day, filled it in about 15 minutes. Routing all cables will take a while. I may eventually adjust shelf heights but that is easily done.


----------



## jgwtriode

Very nicely made!  Impressive

jgwtriode


----------



## jgwtriode

At long last my Rebuilt DAC has been shipped!  Should be here Friday...and in about two weeks...fully burned I should really be able to hear what the Airmid is capable of.   Can hardly wait.   Will be resetting up and reconfiguring my system this weekend.   What a wait it has been.

Happy listening,

jgwtriode


----------



## Paladin79

I am getting back into vinyl and after many years of buying collections it is time to give the records a proper cleaning and dispose of any that are not up to par.


----------



## L0rdGwyn

jgwtriode said:


> At long last my Rebuilt DAC has been shipped!  Should be here Friday...and in about two weeks...fully burned I should really be able to hear what the Airmid is capable of.   Can hardly wait.   Will be resetting up and reconfiguring my system this weekend.   What a wait it has been.
> 
> Happy listening,
> 
> jgwtriode



Finally!  Let us know how the DAC turned out


----------



## jgwtriode

Yup I will....and how it sound with the Airmid.  Should be pretty nice.  It's running with A JCat USB XE in front of it on a Super Cap Supply, Wywires Diamond  connecting it.  And the Airmid has Wywires Platinum Power Cord and Interconnects feeding it.   Should really sound pretty damn good!  Ric says it sound quite a bit better than stock
Gustard X26 Pro.  

jgwtriode


----------



## jgwtriode (Oct 6, 2022)

Paladin79 said:


> I am getting back into vinyl and after many years of buying collections it is time to give the records a proper cleaning and dispose of any that are not up to par.


Very nice!  I remember using my Nitty Gritty Religiously back in the day.  Before ever playing, carefully removing the record from the sleeve, precleaning with a Blue soft velour/felt pad (don't remember the name).  Then the wetting process , bought the expensive fluids; then learned to make my own from a couple of recipes.  Made it by the Gallon.  Soaked the record with another soft foam brush.  Then ran the Vacuum., one side at a time.  I had the manual Nitty Gritty, which worked just fine.  Before I ever played a record I LASTed it and put in custom,, soft, clear vinyl/rice paper sleeves I bought.  to replace the crap paper sleeves record usually came in.    And then carefully positioned a Golden Last sticker on the album cover.  I would always clean the record before playing it.  And of course always clean the stylus on my cartridge before playing.    Ah the "Ceremonial Purifying Ritual of Listening to Vinyl"!

Happy listening,

jgwtriode


----------



## Monsterzero (Oct 6, 2022)

jgwtriode said:


> At long last my Rebuilt DAC has been shipped!  Should be here Friday...and in about two weeks...fully burned I should really be able to hear what the Airmid is capable of.   Can hardly wait.   Will be resetting up and reconfiguring my system this weekend.   What a wait it has been.
> 
> Happy listening,
> 
> jgwtriode


----------



## jgwtriode (Oct 6, 2022)

Monsterzero said:


>


Yes indeed! I actually thought Ric might Carc it.  He is 82 years old.  He has been modding for Decades.  LOL. 

jgwtriode


----------



## L0rdGwyn

Here are some quick and dirty measurements of the pentode headamp this morning (I swear I will try to come up with a name by this weekend, I have been swamped at work!).  These are of the right channel using Philips GZ34, Tung-Sol 6SU7GTY, and Philips EL34.  High and low Z settings used respectively.  Distortion is quite low even at higher power outputs.

FFT 1mW into 32ohm



FFT 1W into 32ohm



FFT 1mW into 300ohm



FFT 500mW into 300ohm



Frequency response 1mW into 32ohm



Frequency response 1mW into 300ohm


----------



## whirlwind

L0rdGwyn said:


> Here are some quick and dirty measurements of the pentode headamp this morning (I swear I will try to come up with a name by this weekend, I have been swamped at work!).  These are of the right channel using Philips GZ34, Tung-Sol 6SU7GTY, and Philips EL34.  High and low Z settings used respectively.  Distortion is quite low even at higher power outputs.
> 
> FFT 1mW into 32ohm
> 
> ...



Is covid ramping up pretty bad ?

I went last Thursday and got a booster...hoping to survive another winter


----------



## L0rdGwyn

whirlwind said:


> Is covid ramping up pretty bad ?
> 
> I went last Thursday and got a booster...hoping to survive another winter



Nah not at all, at least not in NE Ohio, just plain old boring critical care lately lol most COVID patients I encounter nowadays are in the hospital for other reasons and are incidentally COVID positive.


----------



## Paladin79

jgwtriode said:


> Very nice!  I remember using my Nitty Gritty Religiously back in the day.  Before ever playing, carefully removing the record from the sleeve, precleaning with a Blue soft velour/felt pad (don't remember the name).  Then the wetting process , bought the expensive fluids; then learned to make my own from a couple of recipes.  Made it by the Gallon.  Soaked the record with another soft foam brush.  Then ran the Vacuum., one side at a time.  I had the manual Nitty Gritty, which worked just fine.  Before I ever played a record I LASTed it and put in custom,, soft, clear vinyl/rice paper sleeves I bought.  to replace the crap paper sleeves record usually came in.    And then carefully positioned a Golden Last sticker on the album cover.  I would always clean the record before playing it.  And of course always clean the stylus on my cartridge before playing.    Ah the "Ceremonial Purifying Ritual of Listening to Vinyl"!
> 
> Happy listening,
> 
> jgwtriode


I bought a lot of record collections, some of which from an insurance auction, many of these I have never played. I decided to run two turntables. A direct drive that will be used for initial testing and a belt drive for those records that are in near perfect condition. I will draw up plans for a stand, plinth, and possibly a suspension system for that turntable, the other I will most likely keep in my shop.


----------



## Mr Trev

L0rdGwyn said:


> (I swear I will try to come up with a name by this weekend, I have been swamped at work!).


Tubey McAmpface?


----------



## jonathan c (Oct 6, 2022)

a)  Pentagwin

b)  Pentasaurus Rex


----------



## Xcalibur255

I wonder what the source of the small lift in 8th order harmonics is from?


----------



## L0rdGwyn

Xcalibur255 said:


> I wonder what the source of the small lift in 8th order harmonics is from?



The harmonics at 8kHz and 16kHz are artifacts, I think something is up with the ADC in my interface, they are present on loopback without the amplifier in the path. The amplifier can only take credit for the low order harmonics, I'll have to redo the measurements at some point once I've got the issue sorted out.  The noise floor is also higher than expected.  I've noticed some erratic behavior from the MOTU M4 lately, considering upgrading to the UltraLite-mk5.


----------



## L0rdGwyn (Oct 6, 2022)

Well I got the noise floor issue figured out, it was coming from my lovely mains power, now running everything off my laptop (except the amp obviously).  Still not sure about the 8kHz and 16kHz artifacts.

The measurements are actually even better with the noise issue resolved, this is a very low distortion tube amp.  Too bad about the 8kHz and 16kHz harmonics, the other harmonics are so low that the artifacts are actually making a significant contribution to THD.  In the 32ohm spectrum, the 8th harmonic is highest!

More work to be done.  Measurements are such a drag.

1mW into 32ohm




1mW into 300ohm


----------



## L0rdGwyn (Oct 6, 2022)

I came up with a solution to the 8kHz and 16kHz artifacts, I call it Microsoft Paint ADC patch.  As you can now see, the harmonics are gone and the distortion is much improved.

1mW into 32ohm


----------



## L0rdGwyn (Oct 6, 2022)

Sorry I know measurements are boring, but one more just for fun - seeing how much power is available while keeping THD < 1% for 32ohm and 300ohm loads (closest I can get to 1% THD without going over using a stepped attenuator and adjusting the DAC output).  These are obviously unlistenable volumes!

1.73W into 32ohm with 0.8% THD



864mW into 300ohm with 0.74% THD


----------



## A2029

Those are some great measurements Keenan, congrats! Low noise, low distortion and great bandwidth for an OPT coupled amp!   

For those 8 and 16 khz measurement artifacts, I get those as well with my Motu M4. I can't remember if it was changing the bit depth, sample rate, or just unplugging my laptop from mains that removed those artifacts for me. It may have also been a windows mixer issue that I'm not remembering how I solved.


----------



## L0rdGwyn

A2029 said:


> Those are some great measurements Keenan, congrats! Low noise, low distortion and great bandwidth for an OPT coupled amp!
> 
> For those 8 and 16 khz measurement artifacts, I get those as well with my Motu M4. I can't remember if it was changing the bit depth, sample rate, or just unplugging my laptop from mains that removed those artifacts for me. It may have also been a windows mixer issue that I'm not remembering how I solved.



Thanks, Mischa!  Good to know, let me mess around with some settings and see if I can get them to go away, I'll check it out tomorrow since I put away the measurement gear for the night, I will report back


----------



## L0rdGwyn

The amp came back to me for a tune up before I send it to @Monsterzero .  It got pretty banged up in transit going back and forth to the west coast, tip top now and ruggedized.  It will be heading to him this weekend.

Zach kindly gifted me a Pelican case for shipping my amps around, so I can now ship with confidence, it is a beast (cat for scale).  The postal workers thought I was shipping guns when I picked it up lol.



One perk of the amp coming back for a few days is I got to listen to these Fivre 6V6G, they sound awesome.  Have some 6550 coming tomorrow, might try to give them a quick listen before I ship the amp.


----------



## Paladin79 (Oct 7, 2022)

L0rdGwyn said:


> The amp came back to me for a tune up before I send it to @Monsterzero .  It got pretty banged up in transit going back and forth to the west coast, tip top now and ruggedized.  It will be heading to him this weekend.
> 
> Zach kindly gifted me a Pelican case for shipping my amps around, so I can now ship with confidence, it is a beast (cat for scale).  The postal workers thought I was shipping guns when I picked it up lol.
> 
> ...


Nice cat. I named my amps after some of my cats. When dealing with pedigreed cats you get a couple chances then the controlling bodies name your cats for you thus I used Latin. One of my cats was Incubus Elegans (elegant nightmare) and I used that for a headphone amp. I called him Gonzo after Gonzo journalism, think Hunter S Thompson.  Life gets complicated.


----------



## heliosphann

L0rdGwyn said:


> The amp came back to me for a tune up before I send it to @Monsterzero .  It got pretty banged up in transit going back and forth to the west coast, tip top now and ruggedized.  It will be heading to him this weekend.
> 
> Zach kindly gifted me a Pelican case for shipping my amps around, so I can now ship with confidence, it is a beast (cat for scale).  The postal workers thought I was shipping guns when I picked it up lol.
> 
> ...


Did it pass the sniff test???


----------



## L0rdGwyn (Oct 7, 2022)

heliosphann said:


> Did it pass the sniff test???



Oh yeah, it also passed the taste test, this particular cat has a knack for trying to eat the inedible.  Foam is a delicacy in her home country.


----------



## bcowen

Monsterzero said:


>


ROFL!!!


----------



## L0rdGwyn (Oct 8, 2022)

Amp is back on the road again in the Pelican case.  Yesterday I drew up some more schematicky schematics that I will include in the build document.  Placed an order for new set of Lundahl iron and shields for the instructional build, 4-5 week wait time for those so that will be the rate limiting step.  BOM document is 80% done, I will try to finish that this weekend.  Next will be adding test points to the PCB and ordering the new boards.  I am going to look over the chassis once more and make sure there is nothing I want to adjust last minute, then that will be ordered.

Remember how ELMA messed up the first switch I ordered from them?  I received the replacement.  It is the higher torque model, requires a little more force to turn compared to the first switch, thought I'd give both a try and see which is preferred.  I was a little concerned about the dexterity required to solder the 2x14 pins to the switch, but I made a little harder than I needed to on the first go around, I have a method that will make it a non issue.  Good thing, as the whole point of using a PCB-based switch was to make the work simple.  Doing point-to-point work on a complicated switch would definitely be a turn off for some people, I've really tried to make building this circuit as simple as possible.




The amplifier made it in a CanJam impressions video, my five seconds of fame.


----------



## L0rdGwyn

I'm starting a new job at the beginning of December so trying to get all of this done before then!  I've had an absolutely brutal work schedule lately, but it is much better now, should be pretty good all the way up to the end of November.  Tonight I am going to see Apollo's Fire (Grammy-winning Cleveland Baroque orchestra), then next weekend going to Detroit to see King Gizzard (yes, I am a Gizzhead), should be fun.

@A2029 I tried all kinds of stuff to try and get rid of those artifacts, no bones, not sure what the deal is, seemed to come out of nowhere.  Not the end of the world, but would like to get some semi accurate measurements to publish for this design.  Could always upgrade to the UltraLite-mk5 like I mentioned before.


----------



## A2029

L0rdGwyn said:


> @A2029 I tried all kinds of stuff to try and get rid of those artifacts, no bones, not sure what the deal is, seemed to come out of nowhere. Not the end of the world, but would like to get some semi accurate measurements to publish for this design. Could always upgrade to the UltraLite-mk5 like I mentioned before.



Hmm, last thing that I remember trying is turning the output level down by 1dB or so from the max output level in the signal generator inside of REW. Then just have to turn the amp up a bit to compensate.


----------



## L0rdGwyn

A2029 said:


> Hmm, last thing that I remember trying is turning the output level down by 1dB or so from the max output level in the signal generator inside of REW. Then just have to turn the amp up a bit to compensate.



The output level from the DAC doesn't seem to affect it on mine, its present at -20dB output all the way up to -3dB output.  I'm gonna give it one more round of thorough troubleshooting.  Maybe I'll reach out to MOTU and see if its something they've come across.


----------



## L0rdGwyn

Okay I have named the amplifier.  My partner has degrees in English literature and history so I obviously go to her for this type of thing, she gets credit for the name.

It will be called the Aegis (pronounced EE-jis).  This is the goatskin shield carried by Zeus and Athena in the Iliad, also a term meaning to be under the protection of a person or organization, as used in the phrase "under the aegis of".


----------



## triod750

So who is protected here; the designer, the builder or the amp? Or everyone and everything?


----------



## bcowen (Oct 8, 2022)

L0rdGwyn said:


> Okay I have named the amplifier.  My partner has degrees in English literature and history so I obviously go to her for this type of thing, she gets credit for the name.
> 
> It will be called the Aegis (pronounced EE-jis).  This is the goatskin shield carried by Zeus and Athena in the Iliad, also a term meaning to be under the protection of a person or organization, as used in the phrase "under the aegis of".


Cool.  I like it!  At first mention this is what comes to mind, but since it's so incredibly bad-ass that's a _good_ thing to associate. 🤣


----------



## L0rdGwyn

triod750 said:


> So who is protected here; the designer, the builder or the amp? Or everyone and everything?



The amplifier is protecting the good vibes of your music.  The designer is protecting you from getting electrocuted by the amp


----------



## bcowen

L0rdGwyn said:


> The amplifier is protecting the good vibes of your music.  The designer is protecting you from getting electrocuted by the amp


Unfortunately, nothing is protecting our wallets.   🤣 

But if it wasn't for the budgeted capital expenditure on audio, my wife would just buy more shoes...


----------



## L0rdGwyn

bcowen said:


> Unfortunately, nothing is protecting our wallets.   🤣
> 
> But if it wasn't for the budgeted capital expenditure on audio, my wife would just buy more shoes...



Lol yeah it's a pricey project, but hey, think about what an amplifier like this would cost if it wasn't DIY


----------



## triod750

Next project should be an amp with twice the sq and half the price. That would be something!

You are allowed to sleep first  ...


----------



## L0rdGwyn

triod750 said:


> Next project should be an amp with twice the sq and half the price. That would be something!
> 
> You are allowed to sleep first  ...



Probably the next DIY thing I would consider doing is the spud circuit, which I would expect to cost < $1K in parts.  For this design, I placed the highest priority on the ease with which it can be built, even if it is relatively expensive.  I think that will make it approachable even by novice DIYers.

You can save money on a tube circuit and get great sound quality by augmenting with semiconductors, but many of the great ones for tube circuits are not available right now (hopefully that changes in the near future) and the propensity for parts failure goes up.  Better to start with something easy to build and troubleshoot.


----------



## Mr Trev

L0rdGwyn said:


> Okay I have named the amplifier.  My partner has degrees in English literature and history so I obviously go to her for this type of thing, she gets credit for the name.
> 
> It will be called the Aegis (pronounced EE-jis).  This is the goatskin shield carried by Zeus and Athena in the Iliad, also a term meaning to be under the protection of a person or organization, as used in the phrase "under the aegis of".


Nice. I was going to make one final suggestion… Armando - in honour of this magnificent beast: https://manofmany.com/entertainment...-the-most-expensive-bird-ever-sold-at-auction

This way whenever the next person complains about how much you spend on audio gear you can say back… "just be thankful I'm not into pigeons"


----------



## Mr Trev

bcowen said:


> Cool.  I like it!  At first mention this is what comes to mind, but since it's so incredibly bad-ass that's a _good_ thing to associate. 🤣


Funny, that was the first thing that popped in my mind too


----------



## triod750

L0rdGwyn said:


> Better to start with something easy to build and troubleshoot.


Isn't building in itself shooting for trouble?


----------



## triod750

MyL0rd, when you have learnt to wind transformers to your liking you could start with something like this for your Thorens: https://www.whatsbestforum.com/threads/dava-fc-a1-a-field-coil-contender.30720/ Can't possibly be that difficult. Might be rewarding.


----------



## Monsterzero

triod750 said:


> MyL0rd, when you have learnt to wind transformers to your liking you could start with something like this for your Thorens: https://www.whatsbestforum.com/threads/dava-fc-a1-a-field-coil-contender.30720/ Can't possibly be that difficult. Might be rewarding.


 Head Fi's unofficial motto is "sorry about your wallet"
That sites unofficial motto is "sorry about your 401k"

Some of the member's sound systems on that site are absurd, like uber ridiculous. 
Unfortunately ( for me) that site has the best tube rolling threads for Lampizator DACs


----------



## bcowen

Monsterzero said:


> Head Fi's unofficial motto is "sorry about your wallet"
> That sites unofficial motto is "sorry about your 401k"
> 
> Some of the member's sound systems on that site are absurd, like uber ridiculous.
> Unfortunately ( for me) that site has the best tube rolling threads for Lampizator DACs


I've been sorry about my 401K since January.   🤣 

That thing weighs 26 grams?  Ooof.  I thought my dearly departed Koetsu was heavy at 10.8 grams.  Going to need a high quality gimbaled arm for that...I wouldn't even think of trying it on a unipivot.  So yeah, I probably want one anyway.


----------



## CJG888

Try an SPU. They start at around 30g and go up from there. The sound is incredible, though. Meaty, liquid midrange and plenty of speed and “snap”!


----------



## triod750

The heavier the merrier. You could add some lead to yours, @bcowen


----------



## whirlwind (Oct 9, 2022)

L0rdGwyn said:


> I'm starting a new job at the beginning of December so trying to get all of this done before then!  I've had an absolutely brutal work schedule lately, but it is much better now, should be pretty good all the way up to the end of November.  Tonight I am going to see Apollo's Fire (Grammy-winning Cleveland Baroque orchestra), then next weekend going to Detroit to see King Gizzard (yes, I am a Gizzhead), should be fun.
> 
> @A2029 I tried all kinds of stuff to try and get rid of those artifacts, no bones, not sure what the deal is, seemed to come out of nowhere.  Not the end of the world, but would like to get some semi accurate measurements to publish for this design.  Could always upgrade to the UltraLite-mk5 like I mentioned before.



Congrats on the new job   

Enjoy the trip to Detroit and the music....will be a nice little getaway.

Go Guardians!





bcowen said:


> I've been sorry about my 401K since January.   🤣
> 
> That thing weighs 26 grams?  Ooof.  I thought my dearly departed Koetsu was heavy at 10.8 grams.  Going to need a high quality gimbaled arm for that...I wouldn't even think of trying it on a unipivot.  So yeah, I probably want one anyway.


Yeah, the way things are going 401K's will be about 25 % wiped out shortly.
My retirements funds have been going south at a rapid rate and unfortunately I don't see an end in sight as of yet!


----------



## L0rdGwyn

whirlwind said:


> Congrats on the new job
> 
> Enjoy the trip to Detroit and the music....will be a nice little getaway.
> 
> Go Guardians!



Thanks!  It should be a huge quality of life improvement.


----------



## jgwtriode (Oct 11, 2022)

Well I've been fiddling with the modded Gustard x 26 Pro.  I don't have my headphone cable back from Wywires, needs a ground repair, my fault.  Alex is taking care of it.  So my Swan M 200 mk 3+ are what I am listening with.  And been tweaking and reloading windows and tweaking my computer.

Don't have Jplay up yet, but did setup AO 3, fidelizer, process lasso.  Still need to get a handle on the latest buzz with Majority clean, which has now been exceeded by Exercise Stabilizer,  and Hungry Bear's latest trusted Installer to integrate that with Process Lasso to squeeze even more out of Jplay Femto.   Will mess with that once my Wywires Platinum is back.

I did put throttlestop back on and dropped my 3.4GHz 4th Gen I5 K to 1100 MHz.  200 Hz lower than what I was previously underclocking it at.  And got it to stay stable.    Running cpu and cache -260mv undervolted.  At -265mv it freezes.   Holy Fricking crap.  With this Dac underclocking and undervolting make a substantially bigger difference.

It is much better than my rebuilt Oppo Sonica DAC which Ric also did.  It uses a variant of the same Class A high current output stage and he combines the DAC's to create a dedicated Single ended circuit called Super Single ended.  The power switch is disabled as is the Fuse and the voltage change circuitry.  The output is through WBT Copper Nexgen RCA's.

The Swan's have never sounded better.   Soundstage is at least 15 to 20% larger than ever and the speaker create images coming from the back corners of the room if it's in the recording.  focus depth and heigth are all similar improved.  Didn't know 45 HZ Bass, limit of the speaker, could have this much weight and impact.  The high frequencies air out like I have ribbon tweeters, not silk domes.  Midrange liquid, slightly warm and effortless.  PRAT and dynamics are also much improved.  But the Throttlestop tweak just made it far more effortless, organic and real.  More detail with far more ease and liquidity! More punch in the bottom, more air in the top and solidifying the boundaries.

It's litterally like the speakers more effectively couple with the air around them and the room.  They completely disappear and I only sit about 3 to 3.5 feet away from them.

They are basically very good powered desktop speakers made to serve as regular speakers.  I have them on stacked concrete block stands and they are modestly tweaked.  But I know them well enough to hear how much better this DAC is then what I had.   Very excited to put it in front of the Airmid and VC's. Hopefully by the end of the week.

If you run a PC, seriously try Underclocking and Undervolting.   I think you will be quite surprised at how much it improves the sound.

Happy listening,

jgwtriode


----------



## triod750

Your setup would drive me crazy. So much easier with a live orchestra...  
When you get bored you just change the orchestra...


----------



## JazzVinyl

jgwtriode said:


> I did put throttlestop back on and dropped my 3.4GHz 4th Gen I5 K to 1100 Hz.  200 Hz lower than what I was previously underclocking it at.  And got it to stay stable.    Running cpu and cache -260mv undervolted.  At -265mv it freezes.   Holy Fricking crap.  With this Dac underclocking and undervolting make a substantially bigger difference.



3.4 gigahertz is 3,400,000,000 hertz

But you say running at 1,100 hertz (which is 0.0000011 Giga Hertz) sounds vastly better?


----------



## leftside

jgwtriode said:


> Well I've been fiddling with the modded Gustard x 26 Pro.  I don't have my headphone cable back from Wywires, needs a ground repair, my fault.  Alex is taking care of it.  So my Swan M 200 mk 3+ are what I am listening with.  And been tweaking and reloading windows and tweaking my computer.
> 
> Don't have Jplay up yet, but did setup AO 3, fidelizer, process lasso.  Still need to get a handle on the latest buzz with Majority clean, which has now been exceed my Exercise Stabilizer and Hungry Bear's latest trusted Installer to integrate that with Process Lasso to squeeze even more out of Jplay Femto.   Will mess with that once my Wywires Platinum is back.
> 
> ...


Oh man and I thought setting up a turntable was tricky 🙂


----------



## jgwtriode (Oct 10, 2022)

leftside said:


> Oh man and I thought setting up a turntable was tricky 🙂


Yeah life was much easier with My Linn setup and then later my Well Tempered Turntable.  Many Years ago.  Far more to obsess about now with digital and streaming. 

I just left it to my dealer to periodically check the bounce of my Linn and the Well Tempered just needed a good stand under it.  With the Linn it was all dealer setup and checked.    With the Well Tempered just had to make sure my Van Den Hul was properly lined up with a very good alignment protractor and then adjust SRA and all was good.  Just keep everything records and stylus clean.  Much much simpler!

Happy listening,

jgwtriode


----------



## Xcalibur255 (Oct 11, 2022)

L0rdGwyn said:


> Okay I have named the amplifier.  My partner has degrees in English literature and history so I obviously go to her for this type of thing, she gets credit for the name.
> 
> It will be called the Aegis (pronounced EE-jis).  This is the goatskin shield carried by Zeus and Athena in the Iliad, also a term meaning to be under the protection of a person or organization, as used in the phrase "under the aegis of".


I like it......... ALTHOUGH I gotta say somebody whose name is derived from a Dark Souls reference ought to have enough RPG lore rattling around in his head to come up with Aegis on his own.


----------



## Xcalibur255

@jgwtriode How far out from the walls are your speakers?  I'm fighting with SBIR with mine since I moved into my new place.  I also suspect that having my monitor in between the speakers is also a major detractor but the entire setup is build around the PC and desk and there's no getting away from it.


----------



## jgwtriode (Oct 11, 2022)

Making the best of waiting for my repaired headphone cable.  Tweaked the digital and sound signature filters in Audiophile Optimizer to get a bit more staging and PRAT with a slightly more forward presentation.

 "Basically it's about how the OS handles CPU and Memory. This does not alter the source in any way, but there is still a difference in what you hear in the end."  Quoting Audiophil at Highend PC who markets this software optimizer for Windows.

Sure nough.  It's better.  It actually moved the stage a bit more forward without any loss of depth seemingly, that was pretty sweet!

And of course the DAC is burning in nicely and getting better every few hours.  Pretty Damn ridiculous what a 1500 dollar Chinese DAC can do with a few extra mods and some tweaking of software, computer and what's in front of it.  And this thing can be substantially bumped with Gustard's I 2S box with better 10MHZ clock oscillator that can be externally connected to the Ext Refrence connector.  Pretty Darn Happy, just need that cable and then the Airmid and the VC's enter the entire equation and OH MY GOSH!

Happy listening,

jgwtriode!


----------



## jgwtriode

JazzVinyl said:


> 3.4 gigahertz is 3,400,000,000 hertz
> 
> But you say running at 1,100 hertz (which is 0.0000011 Giga Hertz) sounds vastly better?


oops 1100 MHz typo...didn't notice!  Pardone!

jgwtriode


----------



## jgwtriode (Oct 11, 2022)

Xcalibur255 said:


> @jgwtriode How far out from the walls are your speakers?  I'm fighting with SBIR with mine since I moved into my new place.  I also suspect that having my monitor in between the speakers is also a major detractor but the entire setup is build around the PC and desk and there's no getting away from it.


I have stacked cinder blocks that my speaker sit on, about a foot outside of on either side of my monitor which sits squarely in between them on a pedstal  table with internal lamp. Kind of a mission victorian plant/lamp stand that is fairly beat, but works great for the purpose.  They sit about 3.5 feet from the side walls.  P I have the cinder blocks shimmed to keep it more rigid use coin and porcelain discs from bathroom tiling.  Stacked.  Use in lieu of cones etc.  Have larger hexagonal porcelain shims stacked at the bottom between cinder block and a marble tile floor.  The Swans image like mad and will throw significant depth and a surprising amount of width.  The monitor between does not hinder them. and I have my keyboard on a folding food table stand in front of the plant/lamp stand.  It's what I had, so I improvised.  Computer sits to the side below right speaker which sits at about 38 to 39 inches up.  I have the baffles lined with commercial grade packed lambs wool around the edges and between the drivers to limit edge diffraction.  Replaced screws with brass(non magnetic).  Some isodamp pro around the drivers.  They sound a bit better than stock with those mods and the imaging and staging improved a bit.  Everything else is just stock.


PS I did try moving the monitor back in 6 inch increments to two feet further back.  That does improve depth and imaging specificity  and evens out the midrange.  Very interesting.

Happy listening,

jgwtriode


----------



## JazzVinyl

jgwtriode said:


> oops 1100 MHz typo...didn't notice!  Pardone!
> 
> jgwtriode



I thought a serious math error had occurred.  Your not allowed to drive the spaceship anymore


----------



## L0rdGwyn (Oct 11, 2022)

Xcalibur255 said:


> I like it......... ALTHOUGH I gotta say somebody whose name is derived from a Dark Souls reference ought to have enough RPG lore rattling around in his head to come up with Aegis on his own.



Lol true, I tend to like to hear other peoples' ideas though, I'm not usually a fan of my own when it comes to naming things.


----------



## jgwtriode (Oct 11, 2022)

JazzVinyl said:


> I thought a serious math error had occurred.  Your not allowed to drive the spaceship anymore


Operator headspace as we used to say in SATCOM!


----------



## Monsterzero

Aegis arrived in one piece. Listening tonight with the ZMF Caldera.


----------



## jgwtriode

All those gorgeous tubes!

jgwtriode!


----------



## L0rdGwyn

Monsterzero said:


> Aegis arrived in one piece. Listening tonight with the ZMF Caldera.



Lookin' good


----------



## whirlwind

Monsterzero said:


> Aegis arrived in one piece. Listening tonight with the ZMF Caldera.


Are those EL34 tubes?


----------



## L0rdGwyn

whirlwind said:


> Are those EL34 tubes?



Yeah Philips / Mullard XF2.


----------



## leftside

Monsterzero said:


> Aegis arrived in one piece. Listening tonight with the ZMF Caldera.


Love it!


----------



## pravous

L0rdGwyn said:


> Probably the next DIY thing I would consider doing is the spud circuit, which I would expect to cost < $1K in parts.  For this design, I placed the highest priority on the ease with which it can be built, even if it is relatively expensive.  I think that will make it approachable even by novice DIYers.
> 
> You can save money on a tube circuit and get great sound quality by augmenting with semiconductors, but many of the great ones for tube circuits are not available right now (hopefully that changes in the near future) and the propensity for parts failure goes up.  Better to start with something easy to build and troubleshoot.


Your next project needs to be adding a headphone jack/ speaker binding posts to the etracer. 



Think of the tube rolling possibility’s!   Little modules that plug into the tube pin connections.   Heater voltage, plate and grid configured through software.  For added insanity dual mono etracers


----------



## L0rdGwyn (Oct 14, 2022)

Nothing too exciting to report as of late, Aegis work is still underway.  New set of transformers and Lundahl shields are ordered, I am finishing up some minor changes to the chassis and will place that order either today or tomorrow.

Also finishing up some final changes to the main PCB with test points included, I'll get those ordered today as well.

As of about a week ago, Dave at Landfall had around 900ft of 3.25" extrusion.  That's a lot of chassis, no worries on availability there.

I confirmed with Holger at Erhard Audio that he can supply the Lundahl parts, he says he has "plenty" of the small transformer housings.  There will be a 4-5 week wait time for the transformers / chokes since they will be made in Sweden, but if there is enough interest over time he might start holding them in stock.

Lastly, I confirmed with ELMA's U.S. sales rep that he can be reached out to directly to order the output switch, so I will provide instructions for that as well.  Another 4-5 week wait time for that part.

So, everything is on track, I'll have final orders placed over the weekend, then about a month's wait for parts, then the final build and documentation.


----------



## L0rdGwyn (Oct 14, 2022)

Here is a look at the final PCB.  I added test points for the tube heaters, plate voltages, and cathode voltages.  I also increased the hole diameter for all of the major components (I felt it was a bit tight on the first go around for some of the resistors) and increased pad sizes in certain places.  Should be easy to stuff and easy to desolder if necessary.

The idea with the test points is that the builder can clip on leads from their DMM, so no hands in the chassis while the amplifier is on.  Safety first  a few of the test points are the leads of large components (resistors, capacitors) which also can be clipped on, they have been marked on the board.

I just want you all to know that designing this PCB was a huge PITA.



I also added pads on my Alps RK27 PCB for the shield wire from the shielded twisted pair input wiring from the RCAs.  I am going to recommend a specific wire from Mogami as it has a drain wire which keeps it simple.


----------



## triod750 (Oct 14, 2022)

For discussion: https://web.archive.org/web/20120605105654/http://www.kk5dr.com/Tubes.html
What is the relevance for our use?

Example: "Every vacuum tube has an element that is known as the electron emission source usually it is either an oxide coating as in indirectly heated cathode tubes, or a treated filament as in directly heated cathodes. When the element is heated, either directly or indirectly, it emits "extra" electrons that are driven by the electro-motive force & current flow within the tube, to the anode, this is how a tube amplifies. This process is continuous, as long as the tube heater/filament is active, electrons flow, even when the tube is in standby/cut-off mode. The supply of electrons is NOT endless, every tube that is active, is on the way to the end of its life span. However, turning the tube "off" and "on" a number times unnecessarily would cause more damage than to leave the tube on for a few hours between uses. Thermal cycling is more harmful than continuous operation, but a balance of the two should be had".


----------



## EtyDave

L0rdGwyn said:


> Here is a look at the final PCB.  I added test points for the tube heaters, plate voltages, and cathode voltages.  I also increased the hole diameter for all of the major components (I felt it was a bit tight on the first go around for some of the resistors) and increased pad sizes in certain places.  Should be easy to stuff and easy to desolder if necessary.
> 
> The idea with the test points is that the builder can clip on leads from their DMM, so no hands in the chassis while the amplifier is on.  Safety first  a few of the test points are the leads of large components (resistors, capacitors) which also can be clipped on, they have been marked on the board.
> 
> ...



Pretty cool stuff.  I think I may have to build one of these.


----------



## jgwtriode

A bit of an update.  This modded Gustard X26 pro is ridiculous. Crazy how much better it sounds and of course I'm tweaking as I go.  Have throttlestop running lower than ever.  Running Audiophile Optimizer 3, Fidelizer 8.9 and the latest Process Lasso Beta.  Will reinstall Jplay and Majority Clean when I have my headphone cable back from
Alex.

The desktop swans sound amazing right now.  Done with Tidal!  Decided to take advantage of the free month and switch over to Qobuz.  Definetly better, it really lets this DAC sing.  In a couple weeks I will really know what it can do. 

Been following the Gustard thread on Head fi and am going to get the U18 DDC box for it.  Has better Clocks and I2S output conversion, as well as galvanic isolation.  Better than the Singser SU6 at a lower price and you can import the better 10Mhz clocking to the DAC using its external reference BNC.  That apparently really improves it.  And you can go whole hog latter and put better Reference Clocks into the U18.  And the there is a guy out there who mods the box to significantly improve it. 

When fully upgraded this thing apparently competes with very serious stuff.   The headfi thread is quite informative.   The sound is better in every parameter by quite noticeable margins over my previous setup.    With the U18 reclocking and reconverting the signal  I think this will be a very worthy device in front of the Airmid!

Happy listening,

jgwtriode


----------



## triod750




----------



## Marutks

EtyDave said:


> Pretty cool stuff.  I think I may have to build one of these.



I would love to build Aegis amp.   What tubes does it need?  6v6 ?


----------



## L0rdGwyn (Oct 18, 2022)

Marutks said:


> I would love to build Aegis amp.   What tubes does it need?  6v6 ?



Rectifier is GZ34, 5R4, 5V4 and a few others, 5V / 2A types.  Inputs are 6SL7 pair.  Outputs are power pentodes - EL34, 6V6, 6L6, 6550, KT88, etc.

Project isn't out yet, going to be probably another two months or so until it is.


----------



## jgwtriode

I sat here tonight staring at my system deliberating.  Thought for a few minutes about selling my VC leopardwoods, with the idea of getting an Atrium from Zach,  But I would want LTD wood and I really want an AC, so instead I went a head and order the Gustard U18 DDC and appropriate After Dark Clay Giseman Clock Cable and I2S to integrate it with my modded X 26 Pro.  7 to 10 days and more fun awaits.  


Happy listening

jgwtriode


----------



## Xcalibur255

Was saving up for an Atrium and then the Caldera came out.......... and now I'm torn between them.

  All of my headphones are old with the newest being the original MrSpeakers Ether.  I feel under-invested on the transducer side compared to what I've spent on amps, but now I have a mortage too so with every new headphone coming out costing about the same as a used car it takes some planning and saving now.  I mean it always did anyway, but now I have to be extra careful.


----------



## whirlwind

Xcalibur255 said:


> Was saving up for an Atrium and then the Caldera came out.......... and now I'm torn between them.
> 
> All of my headphones are old with the newest being the original MrSpeakers Ether.  I feel under-invested on the transducer side compared to what I've spent on amps, but now I have a mortage too so with every new headphone coming out costing about the same as a used car it takes some planning and saving now.  I mean it always did anyway, but now I have to be extra careful.



I am saving right along beside you! The Caldera is on my radar, but I may prefer the closed version.

As always, it will be sometime before I have saved enough. Other things always get in the way, I have enough stashed to get my next purchase, a family golf membership.

The good part about waiting is there will probably be some killer limited edition wood models     

Look at it this way...at least we are not slumming it.


----------



## Wes S

whirlwind said:


> I am saving right along beside you! The Caldera is on my radar, but I may prefer the closed version.
> 
> As always, it will be sometime before I have saved enough. Other things always get in the way, I have enough stashed to get my next purchase, a family golf membership.
> 
> ...


Ditto.


----------



## L0rdGwyn

Xcalibur255 said:


> Was saving up for an Atrium and then the Caldera came out.......... and now I'm torn between them.
> 
> All of my headphones are old with the newest being the original MrSpeakers Ether.  I feel under-invested on the transducer side compared to what I've spent on amps, but now I have a mortage too so with every new headphone coming out costing about the same as a used car it takes some planning and saving now.  I mean it always did anyway, but now I have to be extra careful.



I'll be getting a Caldera, one of the LTD wood models close to release.  I'm sure some good Atrium vs. Caldera comparisons will be out soon, but I can post some thoughts here when I have them both in house!


----------



## Galapac (Oct 20, 2022)

whirlwind said:


> I am saving right along beside you! The Caldera is on my radar, but I may prefer the closed version.
> 
> As always, it will be sometime before I have saved enough. Other things always get in the way, I have enough stashed to get my next purchase, a family golf membership.
> 
> ...


Same here. I always oogle over the latest offerings but eventually come to the conclusion that I should appreciate what I have, which is not bad at all.


----------



## Xcalibur255

whirlwind said:


> I am saving right along beside you! The Caldera is on my radar, but I may prefer the closed version.
> 
> As always, it will be sometime before I have saved enough. Other things always get in the way, I have enough stashed to get my next purchase, a family golf membership.
> 
> ...


Honestly I continue to be amazed at how my decade old LCD-2 continues to scale with new amps.  I see a lot of people poo-poo this old headphone as lacking in resolution but on Mischa's amp the presentation is holographic with pinpoint placement of every note and you can clearly discern the space the music was recorded in.  The headphone has some intrinsic weaknesses that no amp can truly fix, but they are easily forgotten once immersion sets in.

I definitely don't think I'm slumming it.    I just think my spending on the hobby has been lopsided for a while.


----------



## L0rdGwyn

I might go to this Head-Fi meet tomorrow, if I do I'll bring my OTL and my DIY DAC.

https://www.head-fi.org/threads/headphone-meet-in-pittsburgh-pa-october-22nd-2022.964473/

I'm expecting a lot of "What the eff is that?" reactions from the OTL lol.  Waiting to confirm my DIY thingies are welcome.


----------



## whirlwind

L0rdGwyn said:


> I might go to this Head-Fi meet tomorrow, if I do I'll bring my OTL and my DIY DAC.
> 
> https://www.head-fi.org/threads/headphone-meet-in-pittsburgh-pa-october-22nd-2022.964473/
> 
> I'm expecting a lot of "What the eff is that?" reactions from the OTL lol.  Waiting to confirm my DIY thingies are welcome.


 Nice and just a hop, skip, and jump for you to get there.


----------



## L0rdGwyn

whirlwind said:


> Nice and just a hop, skip, and jump for you to get there.



Yeah it's a quick drive!  Should be fun, no one has heard this OTL or DAC but me.  Can also answer tube questions if anyone is interested.


----------



## whirlwind

L0rdGwyn said:


> Yeah it's a quick drive!  Should be fun, no one has heard this OTL or DAC but me.  Can also answer tube questions if anyone is interested.



Great idea.

If you see any of those "Terrible Towels" lying around anywhere, give one a casual little kick for me


----------



## L0rdGwyn

Had a great time at the Pittsburgh meet!  Very cool hifi shop, cool people.  I got really positive feedback on my PCM56 DAC / OTL setup.

The big thing for me was to compare it to the Lina stack.  I A-B'd it a few times back and forth with the Atrium.  I was ready and willing to admit that the Lina was the best headphone setup I had ever heard based on its reputation, but I preferred my system over it.  The Lina does sound great.  I would call it neutralish, uncolored, very detailed, perhaps a bit airier than my chain.  But I felt my setup was more dynamic, punchy, engaging, while being neck and neck in terms of detail retrieval and with that euphonic tube tone that pulls you into the music.  By comparison, I felt the Lina stack was a bit boring to listen to, very "hifi" sounding.  Definitely could see someone preferring them the other way around, more of a different flavors type of thing, but for me DIY prevails!


----------



## jgwtriode

L0rdGwyn said:


> Had a great time at the Pittsburgh meet!  Very cool hifi shop, cool people.  I got really positive feedback on my PCM56 DAC / OTL setup.
> 
> The big thing for me was to compare it to the Lina stack.  I A-B'd it a few times back and forth with the Atrium.  I was ready and willing to admit that the Lina was the best headphone setup I had ever heard based on its reputation, but I preferred my system over it.  The Lina does sound great.  I would call it neutralish, uncolored, very detailed, perhaps a bit airier than my chain.  But I felt my setup was more dynamic, punchy, engaging, while being neck and neck in terms of detail retrieval and with that euphonic tube tone that pulls you into the music.  By comparison, I felt the Lina stack was a bit boring to listen to, very "hifi" sounding.  Definitely could see someone preferring them the other way around, more of a different flavors type of thing, but for me DIY prevails!


Not surprised at all. Who can argue with very good tube sound!   I remember the first time I listened to a really good tube preamp and of course the first time I listened to a SET amplifier.   Once you hear and feel the difference no turning back.  And as good as solid state may get some aspect of that magic is always missing.  Something in the tone, texture and harmonic structure that I have yet to hear solid state replicate!

Happy listening,

jgwtriode


----------



## jgwtriode

Okay here is a wild thang for consideration.   They are fuse crazy over on the Gustard U18 and X26 pro sites.  My U18 DDC  and After Dark I2S cable will be here Thursday night.  I decided after much reading,  going through about 50 pages on both sites,  that fuses must make a difference.  There are to many people saying the same things about how significant the improvement is.  

Can't afford to to do the latest SR purple but VH had the previous rave at a fairly reasonable price.  Since my X 26 pro is hard wired from toroids to rectifiers don't need one...but there is some evidence a real good fuse can be better than a wire bypass. 

Was thinking next year may want to throw upgrade fuses in the Airmid depending on what my experience is with the SR Orange I ordered.   

What are those fuse ratings if I may ask Keenan?  

What is insane is the QSA fuses from Hong Kong.   $1500, $5000  and $10,000 models.  Beyond belief.  But you will find some interesting commentary on what they do if you research them a bit.

It never ends.  Always another toy to throw in the box!

Happy listening,

jgwtriode


----------



## UntilThen

L0rdGwyn said:


> Okay I have named the amplifier.  My partner has degrees in English literature and history so I obviously go to her for this type of thing, she gets credit for the name.
> 
> It will be called the Aegis (pronounced EE-jis).  This is the goatskin shield carried by Zeus and Athena in the Iliad, also a term meaning to be under the protection of a person or organization, as used in the phrase "under the aegis of".



My last amp will be call Zeus. Oops I forgot that Telemachus is the last.


----------



## L0rdGwyn

jgwtriode said:


> Okay here is a wild thang for consideration.   They are fuse crazy over on the Gustard U18 and X26 pro sites.  My U18 DDC  and After Dark I2S cable will be here Thursday night.  I decided after much reading,  going through about 50 pages on both sites,  that fuses must make a difference.  There are to many people saying the same things about how significant the improvement is.
> 
> Can't afford to to do the latest SR purple but VH had the previous rave at a fairly reasonable price.  Since my X 26 pro is hard wired from toroids to rectifiers don't need one...but there is some evidence a real good fuse can be better than a wire bypass.
> 
> ...



Airmid's fuse is 2A 250VAC slow blow.

I don't buy the fuse thing, but you do you!  $1,500 for fuse is absolutely insane, which makes $10,000 incomprehensible.


----------



## Wes S (Oct 26, 2022)

jgwtriode said:


> Okay here is a wild thang for consideration.   They are fuse crazy over on the Gustard U18 and X26 pro sites.  My U18 DDC  and After Dark I2S cable will be here Thursday night.  I decided after much reading,  going through about 50 pages on both sites,  that fuses must make a difference.  There are to many people saying the same things about how significant the improvement is.
> 
> Can't afford to to do the latest SR purple but VH had the previous rave at a fairly reasonable price.  Since my X 26 pro is hard wired from toroids to rectifiers don't need one...but there is some evidence a real good fuse can be better than a wire bypass.
> 
> ...


Fuses are legit.  The SR Purple is great and the Audio Magic M1 is even better.  I have used both, and the M1 is a step up in all regards from the SR Purple of which is a step up from the Orange.  It's actually very shocking how much they can influence the sound, and I was originally a skeptic and now I am a true believer.

I have never tried or even thought of spending that crazy money on the QSA fuses though.

I feel the same way about cables too, and it was a revelation when I upgraded from my Bluejeans IC's to some Audio Envy IC's.  The BJ seemed to suck the life out of the music, and the AE made it alive.


----------



## Galapac

Wes S said:


> Fuses are legit.  The SR Purple is great and the Audio Magic M1 is even better.  I have used both, and the M1 is a step up in all regards from the SR Purple of which is a step up from the Orange.  It's actually very shocking how much they can influence the sound, and I was originally a skeptic and now I am a true believer.
> 
> I have never tried or even thought of spending that crazy money on the QSA fuses though.
> 
> I feel the same way about cables too, and it was a revelation when I upgraded from my Bluejeans IC's to some Audio Envy IC's.  The BJ seemed to suck the life out of the music, and the AE made it alive.


I'm still a skeptic but not looking to debate.

How can something that is just having current passing through it alter the sound to any degree?
@Wes S - What do you "hear" when you change the fuse? What changes exactly?

I am not willing to spend the $$$ for a fuse unless I could A/B it at a canjam or something.


----------



## L0rdGwyn

This is the second time recently fuses have come up, I really can't see how they could possibly make an audible difference from a technical standpoint, but of course I have been wrong before and I totally support anyone doing whatever they feel makes their system sound better.

I do a lot of A-B listening of my circuits as a build them out, I think I have a pretty good grasp of when there is a significant audible change or when it is falling into the gray area of possible expectation bias.  I try to maintain a healthy degree of skepticism as I know even my own ears are very changeable based on diet, sleep, stress levels, etc.

Is there a somewhat reasonably priced fuse that I can try to say once and for all that it does or does not make a difference?  The Audio Magic M1 is too rich for me to try this out.

Kind of a side note - at this recent Pittsburgh meet, the owner of the store where the meet was held was really trying to convince me that his Shunyata Research cables were the bees knees.  I told him I was cable agnostic, that I thought they made a difference to an extent, but I had not invested heavily into them because I felt my money was better spent elsewhere, in areas where I know for a fact there are audible changes.

So he insisted we demo a $600 Shunyata power cable and A-B it vs. my Audience Forte F3 power cable ($160), swapping it in my DAC.  We both listened to my PCM56 DAC / OTL / Atrium setup playing "I Want You (She’s So Heavy)" off of Abbey Road, the recent deluxe remaster.  He listened, then I listened, then the cable swap, and we both listened again.  He felt there was that "little bit of extra detail" he was looking for after the first listen.  I heard absolutely no difference, but I felt bad given how excited he was about it, so I was like "maybe there is a little more clarity, but I'd have to test it further".


----------



## ColSaulTigh

L0rdGwyn said:


> This is the second time recently fuses have come up, I really can't see how they could possibly make an audible difference from a technical standpoint, but of course I have been wrong before and I totally support anyone doing whatever they feel makes their system sound better.
> 
> I do a lot of A-B listening of my circuits as a build them out, I think I have a pretty good grasp of when there is a significant audible change or when it is falling into the gray area of possible expectation bias.  I try to maintain a healthy degree of skepticism as I know even my own ears are very changeable based on diet, sleep, stress levels, etc.
> 
> ...


I have a spare Synergistic Research Purple 3.15a T20 Slow Blow fuse I'm willing to send you for testing purposes.  Shoot me a PM with your address and I'll mail it out tomorrow.


----------



## Galapac

If anyone has a spare 5A 250VAC slow blow boutique fuse they would be willing to lend for me to demo PM me.


----------



## L0rdGwyn

ColSaulTigh said:


> I have a spare Synergistic Research Purple 3.15a T20 Slow Blow fuse I'm willing to send you for testing purposes.  Shoot me a PM with your address and I'll mail it out tomorrow.



Thanks @ColSaulTigh !  Let me check the exact current draw for my OTL from the wall tonight when I get home from work and get back to you, wanna make sure it isn't anything close to 3.15A before you go to the trouble of shipping it.


----------



## Xcalibur255

It might be worth considering if these boutique fuses actually still function properly as fuses.  It seems to me like the easiest way for a fuse to affect the sound would be for the thickness of the wire element to change.  It's entirely possible that this compromises its behavior in a fail situation and you're sacrificing protection for the circuit in the event of an accident.


----------



## L0rdGwyn

Xcalibur255 said:


> It might be worth considering if these boutique fuses actually still function properly as fuses.  It seems to me like the easiest way for a fuse to affect the sound would be for the thickness of the wire element to change.  It's entirely possible that this compromises its behavior in a fail situation and you're sacrificing protection for the circuit in the event of an accident.



Yeah I would be interested to know how well they function as fuses.  A fuse is a safety mechanism, bypassing it with a wire is asking for trouble, especially in a tube amplifier where tubes are sometimes prone to failure.  But assuming they function well as fuses, then no problems with swapping them out, I guess we'll see if they change the sound.


----------



## gibosi

L0rdGwyn said:


> Yeah I would be interested to know how well they function as fuses.  A fuse is a safety mechanism, bypassing it with a wire is asking for trouble, especially in a tube amplifier where tubes are sometimes prone to failure.  But assuming they function well as fuses, then no problems with swapping them out, I guess we'll see if they change the sound.



Yeah, fuses are designed to fail. And especially, if you roll tube rectifers as I do, how are you going to feel, when that $1,000 fuse does it's job and fails?


----------



## Galapac

gibosi said:


> Yeah, fuses are designed to fail. And especially, if you roll tube rectifers as I do, how are you going to feel, when that $1,000 fuse does it's job and fails?


Ouch, good point. I would rather have a .50 fuse blow than a costly fuse blow.


----------



## ColSaulTigh

Xcalibur255 said:


> It might be worth considering if these boutique fuses actually still function properly as fuses.  It seems to me like the easiest way for a fuse to affect the sound would be for the thickness of the wire element to change.  It's entirely possible that this compromises its behavior in a fail situation and you're sacrificing protection for the circuit in the event of an accident.





L0rdGwyn said:


> Yeah I would be interested to know how well they function as fuses.  A fuse is a safety mechanism, bypassing it with a wire is asking for trouble, especially in a tube amplifier where tubes are sometimes prone to failure.  But assuming they function well as fuses, then no problems with swapping them out, I guess we'll see if they change the sound.


When I first tested my Elrog 274B's (sent on the recommendation of the distributor because the 5U4G's were out of stock), my Synergistic Research Purple blew upon my Woo WA5-LE finishing it's "preheat" startup (if that's what it's called).  Popped immediately, and no damage to the unit whatsoever (that I can find).  It did put off a very distinctive "burnt electrical" smell though...  Said distributor was kind enough to replace it at no cost, as it was their tube recommendation that caused it to pop in the first place.  Fortunately, they're also a dealer...


----------



## whirlwind

gibosi said:


> Yeah, fuses are designed to fail. And especially, if you roll tube rectifers as I do, how are you going to feel, when that $1,000 fuse does it's job and fails?



I know right, they are suppose to fail to protect the amp.

That would be the biggest bummer ever.


----------



## LobalWarming

As chasers of sonic subtleties we auditory (nervosa) enthusiasts often are accused of using music to listen to gear. The more astute of us prefer to use gear to listen to power supplies. And the truly gifted among us employ power supplies to listen to fuses.  

I like to think that tubes make the best fuses - with the side benefit of having excellent voltage transfer functions.


----------



## leftside

gibosi said:


> Yeah, fuses are designed to fail. And especially, if you roll tube rectifers as I do, how are you going to feel, when that $1,000 fuse does it's job and fails?


Boom!


----------



## mordy

L0rdGwyn said:


> Okay I have named the amplifier.  My partner has degrees in English literature and history so I obviously go to her for this type of thing, she gets credit for the name.
> 
> It will be called the Aegis (pronounced EE-jis).  This is the goatskin shield carried by Zeus and Athena in the Iliad, also a term meaning to be under the protection of a person or organization, as used in the phrase "under the aegis of".


The Goat Shield name was already taken lol:




All metal tube shield used in early radios.


----------



## JazzVinyl

Given the notion that an expensive fuse somehow lets the AC current flow "better" to mysteriously "purify / increase fidelity" to the processed audio signal...

Then it stands to reason that REMOVING the fuse from the circuit altogether, ought to immediately cause angels to start flying out of said audio gears' arse.


----------



## bcowen

gibosi said:


> Yeah, fuses are designed to fail. And especially, if you roll tube rectifers as I do, how are you going to feel, when that $1,000 fuse does it's job and fails?


And what if that $10,000 QSA fuse blew protecting a $3000 amp?  That would suck.  

Maybe we should all stock up on amps to protect our fuses.   🤣


----------



## raindownthunda (Oct 27, 2022)

(Deleted)


----------



## jgwtriode (Oct 27, 2022)

Well surprise! My Gustard U18 showed up at lunchtime, fortunately I work from home. After Dark shipped it from Hong Kong on Monday and it was here Wednesday. One day early and they shipped it free for me. DHL international express. Impressive.  Much better than US package delivery.

It immediately sounds better and with a few hours of playing music continuously it sounds much better than at first. I am running it with a 350 dollar Zenwave Audio. Neotech flat cotton wrap OCC copper power cable that is pretty good. But I threw the 1000 dollar Wywires platinum in for a few minutes and definetly cleaner more neutral bigger stage, more dynamic. But I don't want get to carried away. That is my Airmid amp cord.

But once this system burns in and I have my wywires headphone cable back and reburned I will have to see where the better cord makes the biggest diffrence. Already have the digital version on My X pro 26 with thier Diamond USB going into the U18.

Burning the After Dark Giseman Mk2 I2S cable. I liked what they explained about the design comparable with the best DH Labs and the Audioquest in overall approach gauge and metals but has carbon fiber sheilding in it. The others didn't. I have heard carbon fiber as a conductor in some Mad Sci prototype cables and as a sheild along with graphene in the Wywires. I like what it  does for the sound and the noise floor so,  dropped some extra over the Dh Labs 2.1 IDS which I seriously considered.

The sound is much better already, noticeably more relaxed and organic, bigger stage, a bit more detail,  more air everywhere,, tighter fuller more textured bass. Sound has more weight and presence. Images are a bit more fleshed out as well. PRAT a bit better. Another 200 hours or so to really see what the fuss is about. I am impressed.  And After Dark audio was great.

And all of this on my Swam M200 Mk3+.   They don't sound anything like a 500 dollar a pair powered desktop right now!  With the Airmid and VC's I can't even imagine what it will be like.  SR orange fuse will be here Saturday...so that will be very interesting quoting Artie Johnson!

All in All the U18 is a pretty sweet deal for 500.   I2S conversion from USB, Accusilicone clocks that work throught the I2S port to reclock the X 26 pro much more accurately and galvanic isolation all in one box. Very nice!

Happy listening,

jgwtriode


----------



## Wes S (Oct 27, 2022)

Galapac said:


> I'm still a skeptic but not looking to debate.
> 
> How can something that is just having current passing through it alter the sound to any degree?
> @Wes S - What do you "hear" when you change the fuse? What changes exactly?
> ...


It's a bit a black magic with fuses, kind of like transformers.  I don't have a clue how it works, but everyone I have recommended to try them has become believers.  I heard in increase in bass (tighter and harder hitting), detail and sense of space, and it wasn't exactly subtle, and so did everyone else that has tried them.  I have yet to read of someone having one blow on them as well, so not really an issue.  The only time that comes up is from naysayers who have not actually tried them.  I used that excuse for a while as well, but finally gave in.   Tubes can go out at any second as well, and we don't bat an eye spending hundreds of dollars on those.  Some fuses have more of an effect, and the cheaper one's are a waste of time.  I would not go lower than an SR Orange if you want to get your money's worth, and the Purple is where it's for SR.  The Audio Magic M1 is a step up in all regards, but is definitely pricey.  I am saving up for the M1 to put in my Cayin, but it's gonna be a while because I just bought 3 pairs of RFT 6SN7 Welded Plates for backups (my all time favorite tube). 

As for cables, it often takes a sample size of more than two to find one that makes a considerable difference just like tubes.  Some sound similar and others are just plain better.

Not gonna beat the dead horse, but fuses are legit and so are cables. You just have to find the right one's.


----------



## L0rdGwyn

Wes S said:


> It's a bit a black magic with fuses, kind of like transformers.  I don't have a clue how it works, but everyone I have recommended to try them has become believers.  I heard in increase in bass (tighter and harder hitting), detail and sense of space, and it wasn't exactly subtle, and so did everyone else that has tried them.  I have yet to read of someone having one blow on them as well, so not really an issue.  The only time that comes up is from naysayers who have not actually tried them.  I used that excuse for a while as well, but finally gave in.   Tubes can go out at any second as well, and we don't bat an eye spending hundreds of dollars on those.  Some fuses have more of an effect, and the cheaper one's are a waste of time.  I would not go lower than an SR Orange if you want to get your money's worth, and the Purple is where it's for SR.  The Audio Magic M1 is a step up in all regards, but is definitely pricey.  I am saving up for the M1 to put in my Cayin, but it's gonna be a while because I just bought 3 pairs of RFT 6SN7 Welded Plates for backups (my all time favorite tube).
> 
> As for cables, it often takes a sample size of more than two to find one that makes a considerable difference just like tubes.  Some sound similar and others are just plain better.
> 
> Not gonna beat the dead horse, but fuses are legit and so are cables. You just have to find the right one's.



I'm definitely not a cable non believer, just included the example a few posts back to show how two people listening side-by-side can hear (or not hear) it completely differently.  I've heard differences with cables in the past, but the fuse swap will be a first to me.  I'll have a Purple fuse on the way to me today, so I will give it a serious go and see what happens!  A-Bing a fuse is going to be challenge, not exactly simple to swap it out quickly but I'll do my best.


----------



## Wes S

L0rdGwyn said:


> I'm definitely not a cable non believer, just included the example a few posts back to show how two people listening side-by-side can hear (or not hear) it completely differently.  I've heard differences with cables in the past, but the fuse swap will be a first to me.  I'll have a Purple fuse on the way to me today, so I will give it a serious go and see what happens!  A-Bing a fuse is going to be challenge, not exactly simple to swap it out quickly but I'll do my best.


Got ya on the cables and I knew that what's you were getting at.  As for the fuse, I can't wait to hear your thoughts on that one.  For me it did not really require A-Bing, as it was quite obvious the second I put the Purple in that everything got better and once I heard the improvement I did not care to put the stock fuse back in.


----------



## L0rdGwyn

Wes S said:


> Got ya on the cables and I knew that what's you were getting at.  As for the fuse, I can't wait to hear your thoughts on that one.  For me it did not really require A-Bing, as it was quite obvious the second I put the Purple in that everything got better and once I heard the improvement I did not care to put the stock fuse back in.



Gotcha, yeah I do a lot of A-B testing to be very sure, like I said I try to keep a healthy degree of skepticism even for my own listening impressions, I have been fooled by myself enough times to know that your ears cannot always be trusted, so the improvement really needs to be obvious on repeat testing for me to commit to it.  If it is knock-you-over-the-head obvious, I am going to have to do some serious thinking as to what could be going on to make such a big change with a fuse.


----------



## L0rdGwyn (Oct 27, 2022)

I've been deliberating for a long time what I'm going to do in terms of output stage for my PCM63 DAC.  If I was going to use another tube output stage, I really wanted it to be transformer coupled, and was looking at a few options of how to accomplish that.

The great thing about working on Aegis is I finally got to experiment with something I've been wanting to try for a long time, a transformer-coupled cathode follower output stage.  As I said in the Aegis post, this circuit sounds excellent at has some serious perks: low distortion, low output impedance, biasing done by the transformer itself, no cathode bypass capacitance required compared to a typical cathode biased common cathode gain stage, really great bass dynamics given the transformer is being driven by a low source impedance.

Given my PCM63 DAC is using two chips in parallel and Sowter's 1:10 I/V conversion step up transformers, a pretty significant output voltage can be generated by the transformers themselves without necessarily needing a tube gain stage.  In fact, Sowter expects people to use the transformers in this way, with the step up transformers connected directly to the output.  The problem is, the secondary resistor used to load the DAC output then becomes the DAC's output impedance essentially.  So, to get a line level voltage (2Vrms), you are looking at an output impedance of something like 8K!  That is really high for a source component.  It can be lowered at the cost of losing output voltage, so less than 2Vrms, which isn't really desirable either.

So I think I've finally figured out what I'm going to do with this DAC.  I am going to use a tube output buffer such that I can keep my 2Vrms line level voltage but use the buffer to lower the output impedance.  Now that I know how good the transformer coupled cathode follower sounds, that's exactly what I'll do.  I have a ton of E182CC and 7044 tubes, which are really excellent flexible audio triodes.  I'm going to use a pair of E182CC, each with its sections paralleled, wired as a cathode follower loaded by a transformer.

Looks like this.



Lundahl's LL2753 interstage transformer will work well it this application.  With the primary windings in series, 150ohm DCR is just the right amount to load the parallel E182CC at around 25mA bias with a 125V B+.  Secondary DCR is also 150ohm and output impedance of the parallel E182CC cathode follower is around 50ohm, so looking at around a 350-400ohm output impedance from the DAC while keeping the 2Vrms output voltage, much better than 8K without the tube buffer.

I have the PCBs for this DAC completely done, it's been a while so I'll review them one more time before ordering.  I'll probably build this early next year.


----------



## ColSaulTigh

L0rdGwyn said:


> Gotcha, yeah I do a lot of A-B testing to be very sure, like I said I try to keep a healthy degree of skepticism even for my own listening impressions, I have been fooled by myself enough times to know that your ears cannot always be trusted, so the improvement really needs to be obvious on repeat testing for me to commit to it.  If it is knock-you-over-the-head obvious, I am going to have to do some serious thinking as to what could be going on to make such a big change with a fuse.


Fuse is ready and waiting, heading to the post office at lunch to send it off.


----------



## L0rdGwyn

ColSaulTigh said:


> Fuse is ready and waiting, heading to the post office at lunch to send it off.



Sweet!  I have to place another parts order, I am going to grab the most equivalent non audiophile fuse with the order for the most apples-to-apples comparison.


----------



## Monsterzero

I've not tried high end fuses before, but I always keep an open mind about such things.

There used to be a member here ( havent seen him post in years) who would go on and on about placing various crystals and stones on and around his gear, cables and circuit breakers. To be honest I always thought he was a bit of a nutjob and while I never publicly shamed him, others did, which is probably why he no longer posts.

Anyways I ended up buying a few crystals off of eBay for a few bucks just to satisfy my own curiosity and lo and behold it did make an audible difference. It was kinda like tubes, some changes were good, others not so good and experimenting with placement and combos with other stones gave different results.

After that I experiment I always keep an open mind about various "crazy tweaks"


----------



## ColSaulTigh

I am not an electrical engineer by any stretch of the imagination.  From previous research, it seems that it has something to do with reducing vibrations in the filament combined with reducing oxygen inside the fuse (something about ozone, I think, it's been a while).

My logical brain aligns with the "naw, it can't possibly make a difference", but my real-world experimenting says otherwise.  I will say that there was a VERY dramatic difference when I put them in my Musician Pegasus DACs.  Unfortunately, with 110v, they require TWO fuses, making it cost-prohibitive unless you have a fairly unlimited amount of disposable income (which, apparently, I do, since I did it in BOTH of my Pegasuses)...

In the Woo Audio amps, I can definitely hear a difference, which I would describe as more "beefy" or "meaty" sound.  This applies to both the WA6-SEs and the WA5-LE.  Tonally, they still sound the same, but the background noise dropped to near zero (all else being equal).  On a $1,500 amp, is a $300 fuse worth it?  Probably not.  In a $6k+ amp, yeah, it is.

What I will say is this: if you've never tried them before, then please don't belittle those of us who have.  You speak from a position of no experience.  The whole "you're an idiot if you think something that small makes a difference" argument is old and tired.  I will always respond with "prove your position".  If you can, great.  If not, feel free to respectfully disagree.  But trying to be a smart-a** is just uncalled for, especially here. 

My $.02 worth, YMMV.  Hearing is believing.


----------



## L0rdGwyn

Monsterzero said:


> I've not tried high end fuses before, but I always keep an open mind about such things.
> 
> There used to be a member here ( havent seen him post in years) who would go on and on about placing various crystals and stones on and around his gear, cables and circuit breakers. To be honest I always thought he was a bit of a nutjob and while I never publicly shamed him, others did, which is probably why he no longer posts.
> 
> ...



Well it's crap to shame anyone on a forum for how they like to enjoy their system, I hope I didn't come off that way when I said a $1,500 fuse is insane.  My feeling is that even if the tweak did make a change, it's hard for me to believe it is worth $1,500, for that much you could buy some really nice transformers, or an entirely new piece of gear.

My experience has been that my ears / brain are very changeable and we are definitely prone to expectation bias, so for me a change really has to be significant and reproducible on consecutive listening tests to be considered legit.  That's not to say crystals or fuses aren't, just saying that is my approach and how I'll approach the fuse listening test.

I have been shamed myself on diyAudio and ASR for saying that changing signal path capacitors has an audible effect, usually by self-aggrandizing engineers.  Interestingly though, I've had other engineers back me up saying they cannot explain it, but there are audible differences they have heard.  This happened when I did a series of A-B tests of various electrolytic bypass capacitors for Aegis's input stage and I posted my findings on diyAudio.  And I mean, the changes in sound in these various capacitors were really knock-you-over-the-head obvious, easily discerned on a single A-B listen.  But even still, some engineers say it is impossible.

I guess the point I am trying to make is it is all relative, these engineers look at swapping capacitors probably the same way I would look at swapping a fuse or using a crystal, and I think they are very wrong.  So, I'll reserve my judgment until I have tried it myself.


----------



## Monsterzero

L0rdGwyn said:


> Well it's crap to shame anyone on a forum for how they like to enjoy their system


Agreed. I have blocked several members who mock cable believers, which is a topic I avoid like the plague these days.


L0rdGwyn said:


> I hope I didn't come off that way when I said a $1,500 fuse is insane.


No, you didn't come off that way. Frankly the only reason I havent tried fuse rolling is for economic reasons. The crystal experiment is cheap and easily reversed.


----------



## L0rdGwyn

Monsterzero said:


> Agreed. I have blocked several members who mock cable believers, which is a topic I avoid like the plague these days.
> 
> No, you didn't come off that way. Frankly the only reason I havent tried fuse rolling is for economic reasons. The crystal experiment is cheap and easily reversed.



Yeah, when it comes to tubes or capacitors, stuff like that, I don't even bother if someone gets aggro about it on diyAudio or ASR, it's not even worth having the discussion anymore since neither party is going to be convinced of the other's position.  As @ColSaulTigh said, respectful disagreement is the way, getting worked up and arguing about this stuff is a waste of energy.


----------



## jgwtriode (Oct 27, 2022)

Monsterzero said:


> I've not tried high end fuses before, but I always keep an open mind about such things.
> 
> There used to be a member here ( havent seen him post in years) who would go on and on about placing various crystals and stones on and around his gear, cables and circuit breakers. To be honest I always thought he was a bit of a nutjob and while I never publicly shamed him, others did, which is probably why he no longer posts.
> 
> ...


Indeed Monster I used to be married to a new age woman, who liked  consider herself as she described it, a "Lightworker"!

Anyway i learned all kinds of interesting thing about stones and crystals and gems; and my younger brother is a sculptor.   So I have learned a great deal and experienced first hand some of the phenomena that are ascribed to these things.  I used to think my first wife was a fruit cake when she used to play with these  I completely ignored it and let her do her thing.

At my most recent wife's suggestion, now ex,  I tried it with my audio system at the time.   About 4 years ago.  She had one of those cast resin pyramids they call organites, which channel energy and contain a mix of stones, gems and various metals like copper shavings and coils, and sometime gold or silver in specific patterns.   They are tuned supposedly to specific frequencies, 432Hz and 440Hz were generally what seemed to be the most common.   

Anyway she had one about 4 inches tall and I played with moving it in all different locations on and around my equipment and could tell no difference and then it hit me I should place it near myself while listening.   I had a particular chair high back Indian style chair I sat in to listen and I ended up finding that if I set it right between my legs in the chair 
the music became more vibrant and had more of a flow to it.  Everything was slightly improved.  Not immensely but noticeably.

Never felt the inclination to buy myself one, but that was a fascinating experience and definetly made some level of difference.

FWIW!

jgwtriode


----------



## Monsterzero

Found a thread that actually remained civil on quartz placement.

https://www.audiocircle.com/index.php?topic=94036.0


----------



## Xcalibur255

Monsterzero said:


> I've not tried high end fuses before, but I always keep an open mind about such things.
> 
> There used to be a member here ( havent seen him post in years) who would go on and on about placing various crystals and stones on and around his gear, cables and circuit breakers. To be honest I always thought he was a bit of a nutjob and while I never publicly shamed him, others did, which is probably why he no longer posts.
> 
> ...



This ties into a lot of thoughts I've had about things that alter what your brain is doing in terms of how it is processing sensory information and how much subconscious  filtering it is doing of that information before it passes whatever it sees fit to pass onto your conscious waking mind.

It could well be that science could find a way to prove definitively that some of these things don't have any actual affect on the signal, but some of us are still going to hear a difference because of the way our minds work.  And that's why it's so silly how some people get red faced and feel the need to argue about another person's preferences.  If whatever you did is helping you enjoy your hobby more and it wasn't detrimental to anybody else, then it's a good thing, and that's that.

Speaking purely for myself, there are a few rabbit holes that I have walked up to, went "mmmm, nope" and just carried along as though they don't exist.   Fuses are one of them.  Not because I don't believe they can change the sound...... I honestly don't know one way or another, but because you can drive your self insane worrying about how literally anything and everything can impact how you hear your music and at some point I just have to tell myself enough and listen to what I have.  Otherwise I'm not listening to music, I'm just building a house inside my mind that's never finished and I never truly get to live in.


----------



## Galapac

Xcalibur255 said:


> but because you can drive your self insane worrying about how literally anything and everything can impact how you hear your music and at some point I just have to tell myself enough and listen to what I have. Otherwise I'm not listening to music, I'm just building a house inside my mind that's never finished and I never truly get to live in.


I love this analogy...so true. We sometimes get so worked up in the design of the house that we forget to "live" in it. Great!


----------



## jgwtriode

Monsterzero said:


> Found a thread that actually remained civil on quartz placement.
> 
> https://www.audiocircle.com/index.php?topic=94036.0


Skimmed it!  Will have to look at that more thoroughly.  Looks very interesting!


----------



## L0rdGwyn

Xcalibur255 said:


> This ties into a lot of thoughts I've had about things that alter what your brain is doing in terms of how it is processing sensory information and how much subconscious  filtering it is doing of that information before it passes whatever it sees fit to pass onto your conscious waking mind.
> 
> It could well be that science could find a way to prove definitively that some of these things don't have any actual affect on the signal, but some of us are still going to hear a difference because of the way our minds work.  And that's why it's so silly how some people get red faced and feel the need to argue about another person's preferences.  If whatever you did is helping you enjoy your hobby more and it wasn't detrimental to anybody else, then it's a good thing, and that's that.
> 
> Speaking purely for myself, there are a few rabbit holes that I have walked up to, went "mmmm, nope" and just carried along as though they don't exist.   Fuses are one of them.  Not because I don't believe they can change the sound...... I honestly don't know one way or another, but because you can drive your self insane worrying about how literally anything and everything can impact how you hear your music and at some point I just have to tell myself enough and listen to what I have.  Otherwise I'm not listening to music, I'm just building a house inside my mind that's never finished and I never truly get to live in.



Well said.  This is roughly where I'm at with cables, I bought some entry level "audio grade" cables, mostly DH Labs stuff, seems like good quality to me, reasonably priced around $100-200 for a pair of interconnects, and I can say I'm not using absolute garbage lol.  But for me to go down the rabbit hole of trying tons and tons of cables, I just don't have the time or the energy for it!  Especially when I have so many other things to work on, I'd rather spend my time building something new and interesting, just a more fun way for me to enjoy the hobby.


----------



## L0rdGwyn

Speaking of cables...

I hadn't brought it up, but my turntable has been dormant this whole time!  Ever since I returned that tonearm cable that was wired incorrectly.  I've been super busy and just haven't had the motivation to build a proper tonearm cable.  I also just really don't like building cables, it is super tedious...

But anyway, I pushed through today and got it done.  Got the cable wired, got the suspension on my Thorens all tuned up, set up the tonearm, it is finally done.  Good thing too, I was really missing listening to vinyl.

All set up: new plinth, Sorane TA-1 tonearm, custom armboard, 5-pin DIN to dual 3-pin XLR tonearm balanced cable, new aluminum face plate, replaced rubber washers in the suspension, polished the platter, replaced the electrolytics in the speed controller...I think that's it.



Tube phono back in action.



This is my first time actually listening to it since I did all the work.  It sounds excellent, really punchy, dynamic, great clarity like you can reach out and touch the performers.

Feels good to finally wrap that up.


----------



## jgwtriode

L0rdGwyn said:


> Well said.  This is roughly where I'm at with cables, I bought some entry level "audio grade" cables, mostly DH Labs stuff, seems like good quality to me, reasonably priced around $100-200 for a pair of interconnects, and I can say I'm not using absolute garbage lol.  But for me to go down the rabbit hole of trying tons and tons of cables, I just don't have the time or the energy for it!  Especially when I have so many other things to work on, I'd rather spend my time building something new and interesting, just a more fun way for me to enjoy the hobby.


The DH labs Revelation Network Cable actually outperformed Mad Scientist cable  I had that was about 3 times the price and the Mad Sci was a much shorter length.
Was going to get their 2.1 IDS.  But I am a sucker for Carbon Fiber conductors and sheilding so I went with After Darks.

Happy listening.


----------



## UntilThen

L0rdGwyn said:


> But anyway, I pushed through today and got it done. Got the cable wired, got the suspension on my Thorens all tuned up, set up the tonearm, it is finally done. Good thing too, I was really missing listening to vinyl.



It's enjoyable listening to vinyl sometimes.


----------



## Monsterzero

UntilThen said:


> It's enjoyable listening to vinyl sometimes.


 Hendrix rules on any format!


----------



## L0rdGwyn

UntilThen said:


> It's enjoyable listening to vinyl sometimes.



Yeah I love it, honestly think my vinyl setup bests my digital setup in my stereo, maybe the gap will close with my new DAC.  I don't listen to vinyl with headphones though, just two channel.

I've also taken anti cat measures for my baby.


----------



## bcowen

jgwtriode said:


> But once this system burns in and I *have my wywires headphone cable back and reburned *I will have to see where the better cord makes the biggest diffrence. Already have the digital version on My X pro 26 with thier Diamond USB going into the U18.
> 
> 
> jgwtriode


The turbo reburner:   🤣


----------



## bcowen

L0rdGwyn said:


> Speaking of cables...
> 
> I hadn't brought it up, but my turntable has been dormant this whole time!  Ever since I returned that tonearm cable that was wired incorrectly.  I've been super busy and just haven't had the motivation to build a proper tonearm cable.  I also just really don't like building cables, it is super tedious...
> 
> ...


Looks awesome, Keenan.  How do you like the Hana?


----------



## L0rdGwyn

bcowen said:


> Looks awesome, Keenan.  How do you like the Hana?



I love it, it came highly recommended and I wasn't disappointed, been about two years now.  With the new arm, could grab a few headshells and start swapping out carts, but that is a dangerous game to play lol.  Not sure what direction I'll go when its time to make a change, maybe just an upgrade to the Hana SL.


----------



## jgwtriode

bcowen said:


> The turbo reburner:   🤣


Impressive!   I get by with Just running Tara Labs Burn in Track from my computer.  And I plug my power cord into the refrigerator with an adaptor!


----------



## mordy

jgwtriode said:


> Impressive!   I get by with Just running Tara Labs Burn in Track from my computer.  And I plug my power cord into the refrigerator with an adaptor!


Can you explain the relationship between a power cord and a refrigerator?


----------



## jgwtriode (Oct 27, 2022)

Yeah it takes current...lots of it to allow a heavy gauge cable like a power cord to fully settle.  So you buy an AES to standard plug adapter and you can attach your power cord to the end of the refrigerator cord and then plug it in the wall.  You can't ever get the current draw you need from normal components.  Maybe a 400W to 600W behemoth Amp playing 85db efficient speaker at prodigious levels might create the kind of draw needed.  But a refrigerator works quite nicely if you don't have a dedicated device or a monster amp.  You can hear what it does.  When I burn power cords I start them in the late evening after listening, let them run all day,  listen for a few hours after work and then plug them back in.  Every day they improve until they finally get there.  200 to 300 hours depending on the cord!   High powered version of the Tara labs burn in might be better but none of my components have very high current draw.

Happy listening,


----------



## mordy

jgwtriode said:


> Yeah it takes current...lots of it to allow a heavy gauge cable like a power cord to fully settle.  So you buy an AES to standard plug adapter and you can attach your power cord to the end of the refrigerator cord and then plug it in the wall.  You can't ever get the current draw you need from normal components.  Maybe a 400W to 600W behemoth Amp playing 85db efficient speaker at prodigious levels might create the kind of draw needed.  But a refrigerator works quite nicely if you don't have a dedicated device or a monster amp.  You can hear what it does.  When I burn power cords I start them in the late evening after listening, let them run all day,  listen for a few hours after work and then plug them back in.  Every day they improve until they finally get there.  200 to 300 hours depending on the cord!   High powered version of the Tara labs burn in might be better but none of my components have very high current draw.
> 
> Happy listening,


Thanks - never thought of that. With a new heavy gauge power cord I just plug it in and let it do it's job and wait. With the little experience I have I do feel that a heavier gauge "hospital grade" power cord offers some improvement over standard power cables with better bass definition.


----------



## jgwtriode

yeah gauge helps...but geometry, dielectric and the metal used can make significant differences....and then I heard Wywires power cords and realized they could make as big a diffrence as interconnects and speaker cables.   Alex will tell you they likely make the biggest difference. not sure if that is true.  But I will eventually switch all my cords over to those and better connectors, although dont think the crazy price Furutechs are worth the money, but love their solid copper plugs, what I have on my Wywires.

Happy listening,

jgwtriode


----------



## UntilThen

L0rdGwyn said:


> Yeah I love it, honestly think my vinyl setup bests my digital setup in my stereo, maybe the gap will close with my new DAC. I don't listen to vinyl with headphones though, just two channel.



I listen to speakers too. For when I want to feel the music.


----------



## CJG888

L0rdGwyn said:


> Yeah I love it, honestly think my vinyl setup bests my digital setup in my stereo, maybe the gap will close with my new DAC.  I don't listen to vinyl with headphones though, just two channel.
> 
> I've also taken anti cat measures for my baby.


That is one serious turntable! And not just because it’s the EMT 928’s long lost cousin…

I don’t know if I mentioned it before, but that mat was designed to make the handling of 7” singles easy, not to support the record properly or to maximise sound quality.

Maybe some experimentation with mats is in order (remembering to keep an eye on VTA…)?

Personally, after having tried rubber, cork, felt etc. I settled on the Funk Achromat. But then my 301’s platter is much lighter than yours.


----------



## L0rdGwyn

CJG888 said:


> That is one serious turntable! And not just because it’s the EMT 928’s long lost cousin…
> 
> I don’t know if I mentioned it before, but that mat was designed to make the handling of 7” singles easy, not to support the record properly or to maximise sound quality.
> 
> ...



Yeah, I'll likely try a new mat in the not-so-distant future, honestly it feels like this turntable is really never done lol after messing with the suspension for a long while, I actually do think it would benefit from putting in the new springs, but the surgery to remove the old ones is a little bit scary.  Also will likely do a deeper dive into the speed controller.  But right now, it is time to stop and just listen to the music, at least the mat swap is easy!


----------



## Xcalibur255

L0rdGwyn said:


> Well said.  This is roughly where I'm at with cables, I bought some entry level "audio grade" cables, mostly DH Labs stuff, seems like good quality to me, reasonably priced around $100-200 for a pair of interconnects, and I can say I'm not using absolute garbage lol.  But for me to go down the rabbit hole of trying tons and tons of cables, I just don't have the time or the energy for it!  Especially when I have so many other things to work on, I'd rather spend my time building something new and interesting, just a more fun way for me to enjoy the hobby.



I finally put my cable nervosa to bed when I started trying the Supra stuff a few years ago.  Mostly their more entry level stuff too, though I did go one step up with the analog cables and got the EFF-ISF series there because that signal connection can be so critical.  Some of the things I used to be struggling with such as having hardness or glare in the upper mids were significantly helped by the switch to Supra stuff and in a lot of cases they were actually less expensive than the cables they were replacing.  It actually feels really good to actually be content with that part of the setup.  I'm sure more resolution could be had with a higher end product but I'm happy with what I have now.


----------



## Paladin79

My start of a turntable plinth in 1 inch thick birdseye rock maple. It will be an extremely stable platform when I am done.


----------



## miketlse

Paladin79 said:


> My start of a turntable plinth in 1 inch thick birdseye rock maple. It will be an extremely stable platform when I am done.


Will you be finishing it off with wax or varnish?


----------



## Paladin79

miketlse said:


> Will you be finishing it off with wax or varnish?


Most likely linseed oil then wax. I will try a few finishes on sample pieces before I decide. I will also be building a custom dust cover with a birdseye maple frame if all goes well. Turntable is a Pro-Ject brand, solid black. the wood should really pop when it is finished.


----------



## L0rdGwyn

Xcalibur255 said:


> I finally put my cable nervosa to bed when I started trying the Supra stuff a few years ago.  Mostly their more entry level stuff too, though I did go one step up with the analog cables and got the EFF-ISF series there because that signal connection can be so critical.  Some of the things I used to be struggling with such as having hardness or glare in the upper mids were significantly helped by the switch to Supra stuff and in a lot of cases they were actually less expensive than the cables they were replacing.  It actually feels really good to actually be content with that part of the setup.  I'm sure more resolution could be had with a higher end product but I'm happy with what I have now.



Interesting!  Their cables really are affordable, maybe I'll grab a set to try at some point, lots of good testimonials out there too.


----------



## L0rdGwyn

More vinyl listening today, been a while since I took a two channel system pic.



Been doing some A-B listening of my PCM56 DAC and my vinyl rig.  I have a switch box to go between the two, drop the stylus and press play on Roon simultaneously, easy peasy.

Confirming what I already know, the vinyl edges out the PCM56 DAC, it's just a little more airy and clear, tactile.  Good thing considering how much time I've put into it.

This got me motivated to start getting a move on with the PCM63 DAC which I'm certain will be next level.  I have many of the critical components already, made sure to buy them before they all went out of stock, now just a matter of piecing together the noncritical parts.  Honestly most of the work is already done, which is great.

I was pleasantly surprised to find that my favorite voltage regulator was back in stock at Mouser along the way!  It won't last though, so I bought 50 of them  cost me a few hundred bucks, but that'll last me years.


----------



## triod750

Is the cat locked up?
(My two deerhounds was 'playing' with my cat one day. The cat escaped in a magnificent jump and landed on the turntable. The lid was on but since he crashed it, my carefully set up Moerch tonearm changed slightly and I never came back to the incredible sound I previously had).


----------



## L0rdGwyn

triod750 said:


> Is the cat locked up?
> (My two deerhounds was 'playing' with my cat one day. The cat escaped in a magnificent jump and landed on the turntable. The lid was on but since he crashed it, my carefully set up Moerch tonearm changed slightly and I never came back to the incredible sound I previously had).



Oof that stinks!  They wouldn't dare go up there when I'm around lol they know they're not supposed to.  Well trained these cats, but at night when the humans are asleep, there is no stopping them.


----------



## jgwtriode (Oct 28, 2022)

Okay fuse arrived a day early.  Just an SR orange for a bit over $100.  VH trying to clear them out basically.  Looking at the fuse makes you think this is completely ridiculous! Put it in and it sounds a bit better;  4 hours later it sounds a lot better than the basic fuse.  In literally every way.  Ultimately my system is significantly more involving.  This DAC is sounding very expensive with the Gustard DDC and this fuse in it.  And neither is even close to burned in.   Come on Alex send me my headphonecable back so I can hear this in front of the Airmid and VC's.   But oh my I can't believe all of what I am currently hearing.   Too much fun!  Isn't this a great addiction.


----------



## jgwtriode

Okay this is nuts.  I had it in the wrong way.  Switched directions.  I was reading a bit and thourght I had the S to R line up right relative to the fuse holder which is vertical looked at some standard AES inlet configurations in horizontal and realized I had it backwards between hot and neutral.  So changed and it got even better.  Crazy suff!

Happy listening,

jgwtriode


----------



## ColSaulTigh

Yes, fuses are supposedly directional.  Don't know why, but it does seem to make a difference.


----------



## jgwtriode

ColSaulTigh said:


> Yes, fuses are supposedly directional.  Don't know why, but it does seem to make a difference.


Have you heard the Audio Magic M1.   Just trying to get a sense if it may be worth waiting a bit longer and skipping the purple,  It will be next year.  My Audio budget's noticeably in the red for this year!  But my ears are very happy.  LOL!

jgwtriode


----------



## ColSaulTigh

jgwtriode said:


> Have you heard the Audio Magic M1.   Just trying to get a sense if it may be worth waiting a bit longer and skipping the purple,  It will be next year.  My Audio budget's noticeably in the red for this year!  But my ears are very happy.  LOL!
> 
> jgwtriode


Not yet.  I exclusively run SR Purple.  I'm about to invest in one to check it out, though.


----------



## bcowen (Oct 29, 2022)

L0rdGwyn said:


> Yeah, I'll likely try a new mat in the not-so-distant future, honestly it feels like this turntable is really never done lol after messing with the suspension for a long while, I actually do think it would benefit from putting in the new springs, but the surgery to remove the old ones is a little bit scary.  *Also will likely do a deeper dive into the speed controller.*  But right now, it is time to stop and just listen to the music, at least the mat swap is easy!


RE: speed controllers.  My Nottingham has an AC motor, and could be purchased with no speed controller...just plug it straight into the wall.  Speed could vary with incoming voltage though, so they sold an optional motor controller, the Wave Mechanic, for around $500 (IIRC, and that was in early '00 dollars, so not obscenely expensive but not peanuts either).  I started without it, but added it later and it made a pretty significant improvement, plus allowed you to dial in the speed exactly.  Then Lloyd Walker (may he RIP) talked me into getting his "precision motor controller".  It made a bigger improvement to the sound than the Wave Mechanic did over drinking straight from the wall.  How can this be?  The Wave Mechanic gave a very clean and steady AC signal to the motor, so how can something that (perhaps?) has a little cleaner signal make a difference?  Not like it's in the signal path, it's just turning the platter around and around.  I won't pretend to understand it, but I will say from experience that the quality of the AC going to the motor can make a pretty substantial difference.


----------



## jgwtriode

ColSaulTigh said:


> Not yet.  I exclusively run SR Purple.  I'm about to invest in one to check it out, though.


Very good... I will certainly look forward to your thought and impressions!

jgwtriode


----------



## Wes S (Oct 29, 2022)

jgwtriode said:


> Have you heard the Audio Magic M1.   Just trying to get a sense if it may be worth waiting a bit longer and skipping the purple,  It will be next year.  My Audio budget's noticeably in the red for this year!  But my ears are very happy.  LOL!
> 
> jgwtriode


Now that you have had a taste. . .The M1 is quite a bit better than the Purple of which is quite a bit better than the Orange.  Like I have been saying the M1 is where it's at, and trust me it's legit.  The M1 has stronger and tighter bass, and better balance top to bottom compared to the Purple. 

I say skip the Purple and go for the M1 or you will always be wondering how much better it can get.


----------



## L0rdGwyn

bcowen said:


> RE: speed controllers.  My Nottingham has an AC motor, and could be purchased with no speed controller...just plug it straight into the wall.  Speed could vary with incoming voltage though, so they sold an optional motor controller, the Wave Mechanic, for around $500 (IIRC, and that was in early '00 dollars, so not obscenely expensive but not peanuts either).  I started without it, but added it later and it made a pretty significant improvement, plus allowed you to dial in the speed exactly.  Then Lloyd Walker (may he RIP) talked me into getting his "precision motor controller".  It made a bigger improvement to the sound than the Wave Mechanic did over drinking straight from the wall.  How can this be?  The Wave Mechanic gave a very clean and steady AC signal to the motor, so how can something that (perhaps?) has a little cleaner signal make a difference?  Not like it's in the signal path, it's just turning the platter around and around.  I won't pretend to understand it, but I will say from experience that the quality of the signal going to the motor can make a pretty substantial difference.



Interesting, yeah it isn't something I've researched greatly so I won't pretend to be an expert on turntable and motor design, but the consistency of the platter speed and its ability to resist changes in speed with large transients as the stylus drags through the record groove is of serious concern to designers, so perhaps your precision motor controller is improving performance in that area?  For the TD 125 and the EMT 928, the electronic speed controller, driven by a Wien Bridge oscillator, was the major selling point, so it stands to reason that if its performance is optimized, the sound will be greatly improved.  It's obviously working, but I haven't tested it thoroughly enough to be sure it is working optimally, it's really a project unto itself, probably the next one in the saga of restoring this turntable.

On the subject of vinyl, you and @leftside might judge me, but I am considering buying a Degritter.  My Chinese-made ultrasonic cleaner started rusting somewhere on the interior a while back, putting all kinds of nastiness into the solution.  And TBH, the process is still a bit more work than I am happy with with somewhat suboptimal results.  And it's really loud in a small house (cats hate it).  And it's messy.  So I am apprehensive to replace the cleaner and commit to it further.  The Degritter is expensive, BUT it is so friggin' easy to use and it has pretty much universal good reviews, is much more quiet, has an automatic drying mechanism, less messy, smaller footprint, built in filter, and a big draw for me is that my partner will be able to clean her own vinyl with it given how simple it is.  A dealer told me the other day they are coming out with a new model, same price with multiple improvements.  "The bubbles are better" were his words, I am sold.


----------



## bcowen

L0rdGwyn said:


> Interesting, yeah it isn't something I've researched greatly so I won't pretend to be an expert on turntable and motor design, but the consistency of the platter speed and its ability to resist changes in speed with large transients as the stylus drags through the record groove is of serious concern to designers, so perhaps your precision motor controller is improving performance in that area?  For the TD 125 and the EMT 928, the electronic speed controller, driven by a Wien Bridge oscillator, was the major selling point, so it stands to reason that if its performance is optimized, the sound will be greatly improved.  It's obviously working, but I haven't tested it thoroughly enough to be sure it is working optimally, it's really a project unto itself, probably the next one in the saga of restoring this turntable.
> 
> On the subject of vinyl, you and @leftside might judge me, but I am considering buying a Degritter.  My Chinese-made ultrasonic cleaner started rusting somewhere on the interior a while back, putting all kinds of nastiness into the solution.  And TBH, the process is still a bit more work than I am happy with with somewhat suboptimal results.  And it's really loud in a small house (cats hate it).  And it's messy.  So I am apprehensive to replace the cleaner and commit to it further.  The Degritter is expensive, BUT it is so friggin' easy to use and it has pretty much universal good reviews, is much more quiet, has an automatic drying mechanism, less messy, smaller footprint, built in filter, and a big draw for me is that my partner will be able to clean her own vinyl with it given how simple it is.  A dealer told me the other day they are coming out with a new model, same price with multiple improvements.  "The bubbles are better" were his words, I am sold.


I hadn't seen the Degritter before. Looks to be very well thought out.  Pricey though.  No argument that the US tank/LP spinner is rather laborious. Kind of a labor of love, and if it's bothersome then it's hard to love it.  I guess the noise hasn't ever been an issue for me -- the VPI 16.5 I use for final rinse and vacuum is seriously louder.    Be interested to hear what you think of the Degritter if you end up buying one.


----------



## L0rdGwyn

bcowen said:


> I hadn't seen the Degritter before. Looks to be very well thought out.  Pricey though.  No argument that the US tank/LP spinner is rather laborious. Kind of a labor of love, and if it's bothersome then it's hard to love it.  I guess the noise hasn't ever been an issue for me -- the VPI 16.5 I use for final rinse and vacuum is seriously louder.    Be interested to hear what you think of the Degritter if you end up buying one.



Yeah, the major downer is the price, but I've committed thousands to vinyl, so it's a drop in the bucket at this point lol.  I also don't have the space for a vacuum cleaner rinse after the US clean.  The Degritter has a separate reservoir for the solution, it flows into and out of the record cleaning area when it is turned on and goes through a filter that can be cleaned and reused, it actually notifies you when the filter needs to be cleaned and when the solution needs to be replaced.  Built in fans on the interior after the solution flows out to dry the record.  Supposedly the drying mechanism is changing somehow in the upcoming new model.  They also do firmware updates.  It's a good product, IMO, pricey but seems to be of high quality.

Right now, my cleaner is in my basement.  It's a 100-year-old house with original oak floors on the first floor, and no sub floor!  Just oak planks, then the basement.  So any slight sound in the basement can be heard through the entire first floor, so the US cleaner is loud as hell.  But yeah, I've heard those VPI cleaners, they definitely are not quiet lol.

Anyway, I need to sell some stuff first before I drop the dough on the cleaner, but I'm pretty certain I'm gonna go for it.


----------



## L0rdGwyn

Not much to report Aegis wise I'm sorry to say, just waiting for transformers and chassis at this point before I can do the second build.

Parts are coming in though, here the final PCB.




And Jupiter caps, Alps pot, Audio Note knobs, going with WBT RCA's this time around.



Come Monday, I should have everything to start populating the boards, so I could at the very least get moving on those steps, doesn't necessarily have to be build in the order it will be listed in the build doc.


----------



## Paladin79 (Oct 29, 2022)

jgwtriode said:


> Very good... I will certainly look forward to your thought and impressions!
> 
> jgwtriode


I ran a blind study on those fuses compared to some that were far less expensive, I doubt you want to hear the results.  We reversed fuses just to see if any results varied, they did not. We also carefully cleaned the fuses and sockets before reinserting the fuses.

 I have always been one to listen with an open mind but at some point I like to see if a conclusion can be replicated. The same goes for cables, a few folks could tell silver from copper but once we got into silver plated copper and the like the results were not meaningful.  One young lady who is sight impaired could tell more differences than our other candidates but she was the exception.  She also participated in a DAC experiment and surprised the other 48 people involved in the blind listening.  I believe in the accuracy of large groups.

I should mention another person that did well on a blind tube study I put together, @bcowen, every once in a while I am impressed when a person can show me they do have abilities in a specific area.


----------



## bcowen

Paladin79 said:


> I should mention another person that did well on a blind tube study I put together, @bcowen, every once in a while I am impressed when a person can show me they do *have abilities in a specific area.*


So you've been looking at my OnlyFans site?  Thanks, I need the money.   🤣🤣


----------



## ColSaulTigh

Paladin79 said:


> I ran a blind study on those fuses compared to some that were far less expensive, I doubt you want to hear the results.  We reversed fuses just to see if any results varied, they did not. We also carefully cleaned the fuses and sockets before reinserting the fuses.
> 
> I have always been one to listen with an open mind but at some point I like to see if a conclusion can be replicated. The same goes for cables, a few folks could tell silver from copper but once we got into silver plated copper and the like the results were not meaningful.  One young lady who is sight impaired could tell more differences than our other candidates but she was the exception.  She also participated in a DAC experiment and surprised the other 48 people involved in the blind listening.  I believe in the accuracy of large groups.
> 
> I should mention another person that did well on a blind tube study I put together, @bcowen, every once in a while I am impressed when a person can show me they do have abilities in a specific area.


I prefer a study of one.  Perceived difference or real, the fact remains that some people (myself included) can hear a difference.  I have seen all sorts of case studies that say there's no difference, and others that say there is.  But to my ears, I can hear a difference.  Moreso in DACs than amps, but it's there nonetheless.  To my ears.

I also think there's a law of diminishing returns, like I said in my original post in this thread.  Spending a couple hundred bucks on a fuse isn't for everybody.  But if you can, and you perceived the value, then why not?

I value your opinions and thoughts on the subject, thank you for sharing.


----------



## Paladin79

bcowen said:


> So you've been looking at my OnlyFans site?  Thanks, I need the money.   🤣🤣


 And as I recall when I mentioned the results of my fuse study you said something like "as expected", as did most others I talked to.


----------



## Paladin79 (Oct 29, 2022)

ColSaulTigh said:


> I prefer a study of one.  Perceived difference or real, the fact remains that some people (myself included) can hear a difference.  I have seen all sorts of case studies that say there's no difference, and others that say there is.  But to my ears, I can hear a difference.  Moreso in DACs than amps, but it's there nonetheless.  To my ears.
> 
> I also think there's a law of diminishing returns, like I said in my original post in this thread.  Spending a couple hundred bucks on a fuse isn't for everybody.  But if you can, and you perceived the value, then why not?
> 
> I value your opinions and thoughts on the subject, thank you for sharing.


I would never argue what a person says they hear. 

One caveat on cables, we did not compare low end Chinese cables that sold for very little money.
I just go about things another way since my background is engineering. A few friends on another site brought up fuses so I conducted an experiment. I am involved with a local audiophile group who loves to get involved in such things and we have professionals working in the background to help set up said experiments. We often try to use younger college and grad students to help so we get a good cross section of listeners. Most involved are engineers, concert performers,  audio engineers, and folks in the recording field who help out when needed. We do not do pseudo-science. I am trying to choose between DACS right now and the last time we did this was a few years ago so I wanted to hear newer models. The last time we did this we used 20 DACS and my selections were off by one, I had number five and six turned around, otherwise my choices were the same as the group of fifty. The young lady I mentioned chose the final order perfectly. Results were averaged and we used 25 listening criteria. Generally when someone says I can hear this or that, I say that is wonderful!!! show me.  Mr Cowen took me up on the challenge and did very well.

There is also expectation bias, we eliminate that in any test we do. If you personally spend $1,000 for a tube because others said it was wonderful, and you compare it to a $25 tube it is not easy to be unbiased. None of our test subjects knew what we were testing. In our DAC tests, if you knew you were comparing a $6,000 DAC to a $500 DAC, same difference.


----------



## pravous

L0rdGwyn said:


> Not much to report Aegis wise I'm sorry to say, just waiting for transformers and chassis at this point before I can do the second build.
> 
> Parts are coming in though, here the final PCB.
> 
> ...


Sharp looking pcb.  What pcb design software do you use if you don't mind me asking?


----------



## L0rdGwyn

pravous said:


> Sharp looking pcb.  What pcb design software do you use if you don't mind me asking?



Thanks!  I use EasyEDA.


----------



## L0rdGwyn

Got the Caldera in house today in Kingwood.  Beautiful violet undertones to this rosewood.





Even though I have another transformer coupled amp available, my thinking is that my OTL is actually well-spec'd to run these planars and overall is the superior amplifier.  13ohms output impedance, achieves > 4:1 damping ratio and enough output capacitance to handle that planar sub bass.

I have not been disappointed, feel very confident it is driving them well.  Rich, thick, punchy, yet highly resolving and airy.  As @Monsterzero alluded to in his review, much more present treble making it a more neutral headphone relative to the Atrium, which has been my daily driver since its release.  I'll share more detailed thoughts down the road in the Caldera thread, too much pressure there right now lol this is my safe place 

Yeah this thing is the real deal, it kicks ass.


----------



## jgwtriode (Oct 30, 2022)

Quite gorgeous and no doubt they sound even better on Spinosaurus!


----------



## Xcalibur255

L0rdGwyn said:


> Interesting!  Their cables really are affordable, maybe I'll grab a set to try at some point, lots of good testimonials out there too.


The Supra Ply speaker cable is really good for the price too, and as a nice bonus it isn't the thickness and stiffness of a garden hose!


----------



## Xcalibur255

L0rdGwyn said:


> Got the Caldera in house today in Kingwood.  Beautiful violet undertones to this rosewood.
> 
> 
> 
> ...


Yep, that'll do.  Congrats!


----------



## Paladin79

Waiting on parts but I like the colors so far. Every bit of the wood will be solid maple.


----------



## L0rdGwyn

Xcalibur255 said:


> Yep, that'll do.  Congrats!



Thanks!  I did some preliminary A-B testing of Atrium and Caldera this morning.  I know that is of particular interest to a few people who follow this thread, so I will put some thoughts out there on it at some point.


----------



## L0rdGwyn

A couple vinyl finds from my local shop yesterday.


----------



## L0rdGwyn

I am patiently awaiting the arrival of the Purple fuse.  Going to start A-B testing it on my OTL, I'll use the Caldera since it is now the most revealing headphone I have here, then try it in one of my DACs.


----------



## raindownthunda

L0rdGwyn said:


> Thanks!  I did some preliminary A-B testing of Atrium and Caldera this morning.  I know that is of particular interest to a few people who follow this thread, so I will put some thoughts out there on it at some point.


Top of mind for me! I’d be curious if you have a suggestion for which headphone you’d choose for complimenting the VC (assuming proper amping for the caldera).


----------



## L0rdGwyn

raindownthunda said:


> Top of mind for me! I’d be curious if you have a suggestion for which headphone you’d choose for complimenting the VC (assuming proper amping for the caldera).



Duly noted, I'll keep that in mind!  Remind me again what are your music interests?


----------



## raindownthunda

L0rdGwyn said:


> Duly noted, I'll keep that in mind!  Remind me again what are your music interests?


Thanks! I'm all over the place with all types of electronic, rock/metal/prog, jazz/blues/folk/vocals, hip hop, strings/classical.

I had the chance to hear the Atrium a few months back and was very impressed with the vocals, staging, slam, and natural sounding string instruments. I love the speed, slam, 3d staging, and sub-bass of the VC, but find myself reaching more for my Aeolus for vocal heavy sessions or more laid back acoustic music. I was thinking the Atrium would be my next, but now I'm not quite sure. If the Caldera has just-as-good midrange/vocals as the Atrium but better details, speed, and sub-bass that seems like an obvious winner. Hopefully will get a chance to demo the Caldera at some point in the near future. Mischa is adding a "low impedance mode" option to the Blue Halo+ so should be able to drive the Caldera pretty well with his OTL design.


----------



## L0rdGwyn

raindownthunda said:


> Thanks! I'm all over the place with all types of electronic, rock/metal/prog, jazz/blues/folk/vocals, hip hop, strings/classical.
> 
> I had the chance to hear the Atrium a few months back and was very impressed with the vocals, staging, slam, and natural sounding string instruments. I love the speed, slam, 3d staging, and sub-bass of the VC, but find myself reaching more for my Aeolus for vocal heavy sessions or more laid back acoustic music. I was thinking the Atrium would be my next, but now I'm not quite sure. If the Caldera has just-as-good midrange/vocals as the Atrium but better details, speed, and sub-bass that seems like an obvious winner. Hopefully will get a chance to demo the Caldera at some point in the near future. Mischa is adding a "low impedance mode" option to the Blue Halo+ so should be able to drive the Caldera pretty well with his OTL design.



Cool cool, I will look back at this post when I do a more thorough head-to-head and let you know what I think!

Intense fuse critical listening underway...


----------



## L0rdGwyn

Purple fuse.



I first tested the fuse with my DMM to make sure it was intact (it was) then read the pamphlet.  It includes an FAQ section, the first question is "Are fuses directional?".  It states "Yes, fuses are directional.  Electricity should flow from the left to the right when you view the fuse (from the "S" to the "R").  If you do not know the direction of flow, you should listen to the fuse inserted in both directions.  One direction will sound more detailed.  This is the correct way."

Now, this is puzzling to me since this is a mains fuse, and I am guessing 99.9% of people using this fuse are using it as a mains fuse, which means it is being used for alternating current, which is NOT directional, current flows in both directions depending on the polarity of the AC waveform.

But okay, they say it is directional and I am keeping an open mind so I thought that would be a good first test - does changing the orientation of the fuse make a difference?

I spent an hour swapping the fuse back and forth listening to test tracks.  Believe it or not, I began to think there WAS a difference due to orientation, which of course made me wonder if I was really about to buy into the fuse game even though what I know from a technical standpoint, there shouldn't be a difference.  I really became nearly convinced there was a difference with more detail, staging, and airiness in one specific orientation.

I was a bit shocked at that, so given how I was nearly sure of this, I thought "well, then it should be easy to pick out blinded".  I realized I could quite easily perform a blind test since I did not need to know the orientation of the fuse to put it in place or look at it to swap orientations.

My highly scientific test went like this:
1) flop fuse around inside cupped hands to randomize initial orientation
2) listen
3) swap fuse to the other orientation without looking at it
4) listen
5) record which orientation I thought each one was.

I figured I'd do this five times to start and see how reproducible the effect was.

I immediately got it wrong on the first two runs LOL at which point I abandoned the test.

So, I don't think there is a difference due to orientation, and this just goes to show the power of expectation bias - I became convinced one orientation sounded better, then from that point forward, the opposite orientation sounded significantly worse.  As soon as I did not know the orientation, not only did the difference disappear, it became reversed.

Okay so that's the first test, took an hour and a half, taking a break then I will do the purple fuse vs. a normal fuse.  Similarly, I will listen sighted first and see if I think there is a detectable difference, then my partner has agreed to do the swapping for me to try it blinded.


----------



## LobalWarming

Great work! 

Expectation Bias: Putting the Psycho in Psychoacoustics.


----------



## L0rdGwyn

Alright, so I've been swapping these fuses back and forth in my OTL listening to the Caldera for almost an hour...

I cannot reliably pick out differences between them with sighted listening, which certainly means I wouldn't be able to hear a difference listening blinded.

But admittedly, I am pretty tired at this point.  I am going to sleep on it and give it one more go tomorrow with fresh brain / ears and see if I can hear a difference.  If I can, then I'll do a blind test to confirm.


----------



## ColSaulTigh

L0rdGwyn said:


> Alright, so I've been swapping these fuses back and forth in my OTL listening to the Caldera for almost an hour...
> 
> I cannot reliably pick out differences between them with sighted listening, which certainly means I wouldn't be able to hear a difference listening blinded.
> 
> But admittedly, I am pretty tired at this point.  I am going to sleep on it and give it one more go tomorrow with fresh brain / ears and see if I can hear a difference.  If I can, then I'll do a blind test to confirm.


Have you put it in the DAC yet?

I do appreciate your going into this with an open(ish) mind.


----------



## L0rdGwyn

ColSaulTigh said:


> Have you put it in the DAC yet?
> 
> I do appreciate your going into this with an open(ish) mind.



No, I'll try it tomorrow after I finish with the amp.


----------



## Xcalibur255

L0rdGwyn said:


> Thanks!  I did some preliminary A-B testing of Atrium and Caldera this morning.  I know that is of particular interest to a few people who follow this thread, so I will put some thoughts out there on it at some point.


Your ears are tuned pretty similar to mine I think so most definitely want to hear your thoughts on this.  Do you still have the full mesh on your Atrium?


----------



## L0rdGwyn

Xcalibur255 said:


> Your ears are tuned pretty similar to mine I think so most definitely want to hear your thoughts on this.  Do you still have the full mesh on your Atrium?



Yes!  Full mesh.  This is how it was tuned initially by Zach, he then switched to the perforated at a later date after sending out some demo units.  I want to say at this point the perforated is stock?  I'm sure someone else can confirm.


----------



## Xcalibur255

L0rdGwyn said:


> Yes!  Full mesh.  This is how it was tuned initially by Zach, he then switched to the perforated at a later date after sending out some demo units.  I want to say at this point the perforated is stock?  I'm sure someone else can confirm.


Yeah, it gets a little hazy since I think there are actually two different perf meshes, one with smaller holes that I believe is stock and one with larger holes that emerged from a discussion on SBAF that you can request.  So there are technically 4 tunings available as I understand it:  full mesh, less perf, more perf, and no mesh.


----------



## L0rdGwyn

Xcalibur255 said:


> Yeah, it gets a little hazy since I think there are actually two different perf meshes, one with smaller holes that I believe is stock and one with larger holes that emerged from a discussion on SBAF that you can request.  So there are technically 4 tunings available as I understand it:  full mesh, less perf, more perf, and no mesh.



Right, yeah I think I have the larger hole mesh somewhere around here, but never felt the urge to switch over to it.  I suppose if I had the smaller hole mesh, I'd give it a shot, but I'm pretty happy with the sound as is.


----------



## Monsterzero

L0rdGwyn said:


> I want to say at this point the perforated is stock?  I'm sure someone else can confirm.





Xcalibur255 said:


> one with smaller holes that I believe is stock


 Yep


----------



## L0rdGwyn

More fuse testing this morning.

I spent  more time A-Bing the Purple fuse and a normal fuse in my OTL.  Wide awake, freshly caffeinated and alert, I again came to the conclusion that I could not hear a difference between the two fuses.

So I'm sorry, but as far as the amplifier goes, I cannot hear it.

As promised, I then moved on to the DAC.  The testing with done with my Audial S5, a NOS R2R DAC based on the Philips TDA1541A.  Looking at the back of the DAC, it states that it takes a 4A fuse.  Drat!  Well I decided to open it up anyway and see what was inside...

Lady luck was on my side!  Inside was a 3.15A 250V slow blow fuse, same as the Purple.  Even the same brand!  Both of these fuses are made by SIBA, a German fuse manufacturer.  I felt this was worth pointing out, it seems the Purple fuse is a modified SIBA fuse, here they are side-by-side.


 

Getting the fuse in and out was much much easier with the DAC, I was able to get the swapping time down to 10 seconds for sighted listening.

I spent another hour swapping back and forth and again concluded that I could not hear a difference reliably.

I then employed my partner for another round of blind listening, and again, I could not hear a difference with her swapping the two fuses for me.  At one point she even tricked me and put the same fuse in twice, the normal fuse.  I even thought maybe there was a change between them, again expectation bias.

Interestingly, there were two instances where I thought "hmm, maybe this one does sound a little better?"  toward the end of that round of blind testing.  In both instances, I checked to see what fuse it was, and it was the normal fuse.  Further blind testing confirmed this was an anomaly and my brain tricking me than the fuse itself as I could not consistently tell them apart.

So I'm sorry guys, but I have come to the conclusion that the fuses do not make a substantial difference for me.  I think I gave this a fair shake, I even proved my lack of bias against the fuses in my initial fuse orientation testing when I thought I heard a difference, which was then proven to be false.  Again, I think whatever makes someone enjoy their system more, they should pursue, but for my system and my ears, the fuses are not making a substantive difference and any differences I thought I heard were proven to be due to expectation bias by blind testing.


----------



## ColSaulTigh

L0rdGwyn said:


> More fuse testing this morning.
> 
> I spent  more time A-Bing the Purple fuse and a normal fuse in my OTL.  Wide awake, freshly caffeinated and alert, I again came to the conclusion that I could not hear a difference between the two fuses.
> 
> ...


Couldn't ask for anything more than that.  Thank you for your time and effort into this - insightful, indeed!


----------



## Galapac

L0rdGwyn said:


> More fuse testing this morning.
> 
> I spent  more time A-Bing the Purple fuse and a normal fuse in my OTL.  Wide awake, freshly caffeinated and alert, I again came to the conclusion that I could not hear a difference between the two fuses.
> 
> ...


Thank you for this. Not sure my old ears would pick up a difference if there was one. I would not rule out that others can hear a difference and it may be their systems/ears are more sensitive to such changes.


----------



## L0rdGwyn

Galapac said:


> Thank you for this. Not sure my old ears would pick up a difference if there was one. I would not rule out that others can hear a difference and it may be their systems/ears are more sensitive to such changes.



Yeah totally, just a data point and people can use the info how they choose.  Maybe others could try it blind, or just go on enjoying the music, either way is fine!


----------



## mordy (Nov 1, 2022)

Here is an audiophile question:
Which is the less expensive alternative?
To listen to music through your equipment, or to listen to music using your equipment?


----------



## L0rdGwyn

mordy said:


> Here is an audiophile question:
> Which is the less expensive alternative?
> To listen to music through your equipment, or to listen to music using your equipment?



Might have to ask you to clarify this one mordy, not sure I am understanding the distinction between the two.


----------



## Monsterzero

L0rdGwyn said:


> Might have to ask you to clarify this one mordy, not sure I am understanding the distinction between the two.


Its an old quote from Alan Parsons:


----------



## L0rdGwyn

Monsterzero said:


> Its an old quote from Alan Parsons:



Ahh okay I'm familiar with the Parsons quote, thought maybe mordy was asking a slightly different question.

I mean, the more you listen for the enjoyability of the music and listening for what you like as opposed to listening for flaws, the better your gear will sound and the less money you'll spend.


----------



## raindownthunda

Monsterzero said:


> Its an old quote from Alan Parsons:


I would argue the two do not have to be mutually exclusive. One person can have two different modes of entertainment within the same hobby.


----------



## paradoxper

L0rdGwyn said:


> More fuse testing this morning.
> 
> I spent  more time A-Bing the Purple fuse and a normal fuse in my OTL.  Wide awake, freshly caffeinated and alert, I again came to the conclusion that I could not hear a difference between the two fuses.
> 
> ...


Need more bias.


----------



## mordy

L0rdGwyn said:


> Ahh okay I'm familiar with the Parsons quote, thought maybe mordy was asking a slightly different question.
> 
> I mean, the more you listen for the enjoyability of the music and listening for what you like as opposed to listening for flaws, the better your gear will sound and the less money you'll spend.


That is what I meant. 
I have a new inexpensive toy now (headphone amp) and I enjoy listening to it although it has flaws. 
I decided not to feel guilty about it. 
In other words, it sounds right but not perfect. 
If I put on my analytical hat I can find things that are wrong, but since I still enjoy listening to it, I don’t care. 
The sound can be too bright at times, and the tonality a little off in the midrange, but I really enjoy the overall presentation. Let the music speak for itself!
Should I feel guilty about liking something imperfect? 
Perish the thought!


----------



## L0rdGwyn (Nov 1, 2022)

Moar vinyls, newish stuff this time.







mordy said:


> That is what I meant.
> I have a new inexpensive toy now (headphone amp) and I enjoy listening to it although it has flaws.
> I decided not to feel guilty about it.
> In other words, it sounds right but not perfect.
> ...



Yeah nothing wrong with that, no such thing as perfect anyway.


----------



## jgwtriode

At long last.  I have things all together at once.  No reburning the headphone cable which Alex replaced( Wywires Platinum.    First things first.   The Airmid is dead silent with his cables.   When I plugged the headphones in with his Platinum RCA's from the DAC.  No noise.  Absolutely no noise, it was almost unsettling.  Turn the volume knob either direction it sounds the same with nothing playing.   Wow!

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> At long last.  I have things all together at once.  No reburning the headphone cable which Alex replaced( Wywires Platinum.    First things first.   The Airmid is dead silent with his cables.   When I plugged the headphones in with his Platinum RCA's from the DAC.  No noise.  Absolutely no noise, it was almost unsettling.  Turn the volume knob either direction it sounds the same with nothing playing.   Wow!
> 
> jgwtriode



I think the reason you were having noise originally was because you were using a sound card directly out of a PC.


----------



## L0rdGwyn

Just ordered my NOS parallel PCM63 PCBs.  These are four layer PCBs, so they're actually kind of expensive.  As is tradition, now that I've placed the order, I will immediately find something I want to change.

Digital front end power supply PCB for the JLSounds module.




And the DAC PCB.  Using a pair of PCM63 in parallel, so this board is one channel.  There are four separate series regulated power supplies on each board - positive digital, negative digital, positive analog, negative analog.  This time around, I included the power supply transformers on the boards themselves, that will save some space in the chassis.



The boards don't include the I/V stage, the output is the current output of the parallel DACs.  I plan to build out one of the channels and do some testing to confirm what I have in mind is going to perform the way I want it to.  If so, then I'll likely move forward with my transformer coupled tube buffer stage.

Should be an interesting DAC when it's done!


----------



## jgwtriode (Nov 1, 2022)

L0rdGwyn said:


> I think the reason you were having noise originally was because you were using a sound card directly out of a PC.


True and I got it down quite a bit by rerouting cables and the wywires were much better than what I was using.   But crazy, now there is nothing, absolutely nothing at full volume with no music playing.  No hum, no tube noise.  Sounds like the amp is not even on.  Amazing.

jgwtriode


----------



## jgwtriode (Nov 2, 2022)

Oh my word about 10 hours of burn on this headphone cable and of course DAC has at least another week to go and the DDC and it's I2S have less than half of what's on the DAC and I am speechless.  I thought the Airmid was magic previously, but this is levels and layers so much more.  While the Gustard is a pretty good DAC and arguably comparable with 3K DACs according to some folks, a few say even better than that on the thread and I am sure it is noticeably better with the mods, The U 18 transforms the daylights out of it and you can definetly hear what the SR Orange does for it also.

The silence and dynamics of the Airmid are staggering,  Bass just frankly clobbers you on Billie Eilish Hi Res Qobuz.  There is real gut punch that I have not heard out of these VC's before and liquid like I didn't know what liquid previously was.  I think my ears were previously parched by comparison.  Space, larger and more massive than I can convey.  Bigger more solid, substantial, anchored images and PRAT that has you tapping, weaving and bobbing uncontrollably. Overtones and harmonics with texturing I have never heard in my music. No brightness, hardening or etching of upper frequencies.  You can even turn up songs where Billie is virtually screaming and just enjoy it.  She has enough variety and range in her music that you could probably due a Billie Eilish Burn in disc with quite excellent results. Far greater inteligebility, easy to unravel complex lyrics and intentional slurring. 

Really good for Drab Majesty where they like to play a lot with that. Reminds me of Old early REM with a much more significant hard new wave edge.   Just too damn amazing.   And more is on the way.   I am not sure that there is a more perfect amp for ZMF Dynamics.   I may not get to bed anytime even remotely soon.  Fortunately my online job is at home and does not start until 10AM!

Another nice thing is I have been playing with qobuz settings and tweaking my computer.  I have got the software to stablize a lot more with significantly lower clock speeds and voltages.  Still significantly higher that Tidal.  But Qobuz sounds better and better with every tweak and upgrade and the diffrences beyond Tidal become even more noticeable.   But make no mistake Qubuz definitely needs better written code!   I have to occasionaly restart it.  Occasionally freezes and is usually at least a tiny bit glitchy, but when it's just running songs; especially Hi Res it is quite wonderful!

Back to the music,

Happy listening,

jgwtriode


----------



## bcowen

raindownthunda said:


> I would argue the two do not have to be mutually exclusive. One person can have two different modes of entertainment within the same hobby.


Totally agree.


----------



## LobalWarming

bcowen said:


> Totally agree.


Me too. One can have a trivially expensive mode and a seriously expensive mode. And a 3rd one - only seen in divorce court.


----------



## mordy

raindownthunda said:


> I would argue the two do not have to be mutually exclusive. One person can have two different modes of entertainment within the same hobby.


The way I understand it in my personal experience is that I keep on rolling tubes until I find the right combination, and then I stay with that one.
Until...


----------



## L0rdGwyn

I created a separate thread for the Aegis, will update there as the project progresses and the materials are finalized.

https://www.head-fi.org/threads/aegis-diy-tube-headphone-amplifier.965530/


----------



## leftside

L0rdGwyn said:


> Interesting, yeah it isn't something I've researched greatly so I won't pretend to be an expert on turntable and motor design, but the consistency of the platter speed and its ability to resist changes in speed with large transients as the stylus drags through the record groove is of serious concern to designers, so perhaps your precision motor controller is improving performance in that area?  For the TD 125 and the EMT 928, the electronic speed controller, driven by a Wien Bridge oscillator, was the major selling point, so it stands to reason that if its performance is optimized, the sound will be greatly improved.  It's obviously working, but I haven't tested it thoroughly enough to be sure it is working optimally, it's really a project unto itself, probably the next one in the saga of restoring this turntable.
> 
> On the subject of vinyl, you and @leftside might judge me, but I am considering buying a Degritter.  My Chinese-made ultrasonic cleaner started rusting somewhere on the interior a while back, putting all kinds of nastiness into the solution.  And TBH, the process is still a bit more work than I am happy with with somewhat suboptimal results.  And it's really loud in a small house (cats hate it).  And it's messy.  So I am apprehensive to replace the cleaner and commit to it further.  The Degritter is expensive, BUT it is so friggin' easy to use and it has pretty much universal good reviews, is much more quiet, has an automatic drying mechanism, less messy, smaller footprint, built in filter, and a big draw for me is that my partner will be able to clean her own vinyl with it given how simple it is.  A dealer told me the other day they are coming out with a new model, same price with multiple improvements.  "The bubbles are better" were his words, I am sold.


I really like the look of the Degritter. If I was starting over again, I’d probably consider this unit. All my vinyl has been cleaned, and I’m not buying any more, so will stick with what I have for the rare occasion when some vinyl will need another deep cleanse.


----------



## Monsterzero

My Aegis review


----------



## jgwtriode (Nov 4, 2022)

Monsterzero said:


> My Aegis review



As you stated and the Brits love to say "Brilliant"  review monster.   I think I must have one and then who knows wha willl happen with the Airmid, much as I love the Airmid.  Doesn't sound like I need both and of course,  sure there are plenty out there would would be happy to buy.   And I built Bottlehead Paraglows and a Foreplay back in the day.   So I'm game.  Will start saving and reassess where the dollars are going.   May just back off the streamer deal.   I am running a lot of my stuff straight off of qobuz with Audiophile optimizer, Fidelizer and Throttlestop and damn it sounds good!  With My JCat XE USB I could then just add the XE Network Card and another Cuinas Isopower supercap supply to run it.  Then I would likely have enough money to get parts for an Aegis!   But things here just keep sounding better as this headphone cable burns in.

Happy listening,

jgwtriode


----------



## pravous (Nov 3, 2022)

Looking forward to building one if not more Aegis.  Looking forward to seeing how it stacks up with the Airmid.


----------



## jgwtriode

L


pravous said:


> Looking forward to building one if not more Aegis.  Looking forward to seeing how it stacks up with the Airmid.


I trust Monster's ears so I think that question is already answered! I have always found him to be right on the money!

Happy listening,

jgwtriode


----------



## Paladin79 (Nov 4, 2022)

Galapac said:


> Thank you for this. Not sure my old ears would pick up a difference if there was one. I would not rule out that others can hear a difference and it may be their systems/ears are more sensitive to such changes.


Much ado about .0056 difference.🤪🤪 Better off  working on weak links in an audio chain. Oh and that was comparing purple fuses to some 20 cent fuses. $25 fuses recommended out of England showed even less difference to the purple.


----------



## Paladin79

https://ampsandsound.com/products/black-box-headphone-adapter

I picked up one of these devices and tried it on four different tube power amps and I am amazed how well it works. Basically it lets you use most any power amp as a headphone amp, you naturally have to have control over the volume level but it kept me from having to add a headphone out circuit to an amp I designed and built to win a bet.  I also had a Cary amp with a slight hum I could detect on a left channel with speakers but listening with this device really made the hum apparent. I can use it in my shop rather than hooking to a pair of speakers when I work with power amps. It is about a three minute install if I want to use it with one of my power amps in my main system.


----------



## mordy

Paladin79 said:


> https://ampsandsound.com/products/black-box-headphone-adapter
> 
> I picked up one of these devices and tried it on four different tube power amps and I am amazed how well it works. Basically it lets you use most any power amp as a headphone amp, you naturally have to have control over the volume level but it kept me from having to add a headphone out circuit to an amp I designed and built to win a bet.  I also had a Cary amp with a slight hum I could detect on a left channel with speakers but listening with this device really made the hum apparent. I can use it in my shop rather than hooking to a pair of speakers when I work with power amps. It is about a three minute install if I want to use it with one of my power amps in my main system.


Found cheaper alternatives from Australia:
https://www.ebay.com/sch/i.html?_fr...kw=black+box+headphone+adapter#item3dd7122ba7


----------



## Paladin79 (Nov 4, 2022)

mordy said:


> Found cheaper alternatives from Australia:
> https://www.ebay.com/sch/i.html?_fr...kw=black+box+headphone+adapter#item3dd7122ba7


I like this brand and the quality of components used, I am cautious about hooking an unknown device to amps that are worth thousands. It was owned by a good friend who had already tested it.

 Also I do not pay for electronics, a little labor on my part covers anything I buy.


----------



## mordy

Paladin79 said:


> I like this brand and the quality of components used, I am cautious about hooking an unknown device to amps that are worth thousands. It was owned by a good friend who had already tested it.
> 
> Also I do not pay for electronics, a little labor on my part covers anything I buy.


In the 70s I bought a set of Audio Technica headphones that you plugged into the speaker terminals of a power amp via a little box in between. Wonder if that was the same idea as the adapter mentioned above. However, those AT headphones never worked well, and I blew one of the headphone drivers.


----------



## Paladin79

mordy said:


> In the 70s I bought a set of Audio Technica headphones that you plugged into the speaker terminals of a power amp via a little box in between. Wonder if that was the same idea as the adapter mentioned above. However, those AT headphones never worked well, and I blew one of the headphone drivers.


I may look inside this one when time allows I have to switch between electronics, knife making and woodworking and today it is woodworking so all audio gear in my shop is covered.   A friend gave me an assortment of high end 12AU7's (12 pairs) so I am building him a couple things as a thank you. I also have local friends begging me for something like this..

Luckily Finnegan helps.🙀🙀


----------



## triod750

Is he doing QC on a GU50 amp or 4P1L or something like that?


----------



## Paladin79

LS-50.  GU-50. The amp will handle either with some mods I made. I do not run them as often but I have 1942 Kriegsmarine Telefunken LS-50s, NOS located in France. GU-50’s are plentiful.

I won a bet using parts given to me then I liked the amp so much I upgraded it and kept it. 10 watts per channel so I wanted headphone capabilities. 

I did own efficient speakers but I upgraded to Sonus Faber and the amp got little use other than running these.


----------



## triod750

I bet it passed his QC


----------



## Paladin79

triod750 said:


> I bet it passed his QC


One can only hope lol. Finnegan is always in the shop with me.
He particularly likes helping with single bevel Japanese knives.


----------



## miketlse

Paladin79 said:


> One can only hope lol. Finnegan is always in the shop with me.
> He particularly likes helping with single bevel Japanese knives.


Curiousity killed the cat, or maybe the human instead


----------



## jgwtriode

miketlse said:


> Curiousity killed the cat, or maybe the human instead


He appears to be pondering what he intends to do with them!

jgwtriode


----------



## jgwtriode

Paladin79 said:


> I may look inside this one when time allows I have to switch between electronics, knife making and woodworking and today it is woodworking so all audio gear in my shop is covered.   A friend gave me an assortment of high end 12AU7's (12 pairs) so I am building him a couple things as a thank you. I also have local friends begging me for something like this..
> 
> Luckily Finnegan helps.🙀🙀


An Audio Kitty, The one we had when i was still  with my second wife. used to fight me for the middle seat of the couch when I turned on my system to listen.   If he was in the living room and he saw me about to listen he would dart immediatly to it.  Sometimes I would just let him have that location.  But either way he would sit there with me and listen the entire time.  

jgwtriode!


----------



## triod750

My deerhounds just kept me company when I was listening to jazz in my loudspeaker system. Other music made them leave...


----------



## Paladin79

jgwtriode said:


> An Audio Kitty, The one we had when i was still  with my second wife. used to fight me for the middle seat of the couch when I turned on my system to listen.   If he was in the living room and he saw me about to listen he would dart immediatly to it.  Sometimes I would just let him have that location.  But either way he would sit there with me and listen the entire time.
> 
> jgwtriode!


Often Finnegan will come downstairs and meow at me if it is late at night cause he is ready for bed. If I head upstairs I see a favorite chair of mine rock a bit as he jumps out to allow me to sit down if I want lol. He then lays on the floor on his back with his paws up wanting to play.


----------



## bcowen

triod750 said:


> I bet it passed his QC


Yeah, but then he isn't very picky.  He'll even play with GE tubes.


----------



## Paladin79 (Nov 5, 2022)

bcowen said:


> Yeah, but then he isn't very picky.  He'll even play with GE tubes.




GE, GEC practically the same thing right?


----------



## bcowen

Paladin79 said:


> GE, GEC practically the same thing right?


LOL!  He was _really_ wanting your attention.  "Pet me, or the GEC is toast."   🤣  🤣


----------



## mordy

Paladin79 said:


> GE, GEC practically the same thing right?


Not uncommon for sellers on eBay to list a GE tube as GEC (General Electric Corporation) .


----------



## triod750

GECus!!


----------



## L0rdGwyn (Nov 6, 2022)

I ordered all the parts for my PCM63 DAC, aside from the I/V stage.  I'll work on it on the side while getting things set up for Aegis.

Second Aegis chassis will arrive Tuesday, just need the transformers for the second build, should get them by the end of the month.  I took a week off between my job change, so should be able to get a chunk done then assuming the transformers get here on time.

Bought some cool tubes for my 801A amp, been keeping an eye out for these, metal base GEC H63, NOS quad.



Also a pair of Mullard ECC35 to try in Aegis.



I've been on a vinyl shopping spree too since I fixed up my turntable.  Spoils from the other day.















Interesting factoid from vinyl shop guy - that Bach LP is the second ever 12" LP ever produced, ML 4002, the very first being ML 4001 (works by Mendelssohn).

Now I just need the Degritter.  Funny story - I asked Degritter the upcoming new model one of their dealers told me about, to which they told me they couldn't disclose information and that it was confidential between them and their dealers.  Oh, and they asked if I would be willing to tell them which dealer told me that?  I was like, uh, no LOL I don't want you to axe the dealer on my account.  So clearly it is true, I'll just wait it out until they announce the new version.


----------



## mordy (Nov 6, 2022)

Metal base tubes - vinyl. Let's speak about metal base vinyl/shellac... When the 78s were produced, they were pressed from a metal master. Somebody discovered a couple of metal masters that hadn't been destroyed and used them to make recordings.
The sound quality from this 1928 Louis Armstrong recording from the metal master is astounding compared to the (often scratchy sounding) original 78s:


----------



## jgwtriode (Nov 10, 2022)

The Airmid is definetly sensitive to footers as is all good equipment.  I refuse to pay crazy money for a stand because I think what I have created works incredibly well.  Not cheap but not nearly what some of those solutions cost.

I was going to throw my favorite Mad Scientist Blackpod Nanos underneath it.  But they make a bigger diffrence under the Gustard U18DDC I2S converter, reclocker into my moded X26Pro.  They make a diffrence that is pretty comparable or maybe even better than the Fuse change from standard to SR Orange. I was using ceramic and Brass cones in combination prior to which I thought was pretty good.

It already has numerous layers of isolation under it sitting atop the X26Pro with One of Mad SCi's prototype Roon NUC platforms made of carbon graphene nano cermaic material.  It's a 9 x 12 approx.  3/4" thick plate with three bearing to sit whatever on top of.   I never liked it under my DAC.  Used the Blackpod footers.  Works better on top of the DAC and I pull the top for cooling.  It isolates noise RF and spurious fields.    I Don't pretend to understand exactly why or how.

But the DDC was sitting a top that on brass and ceramic cones.  Softer devices did not sound as good.  The new set of blackpods smoked that, which brings up the Airmid. 

So back to the cones and Navcom's and Isopod hard rubber ball delrin bases.   What was the best combo of what I had left.   Two Oak cones.  Fostex FE 208 center plug mods to improve their response and DH Cone large cone shimmed wih Porcelain Tile hexes to create proper height.   The diffrences between various combos was not subtle.

And of course my Airmid was already sitting on the middle shelf of  my Modded Ikea Bekvan with 2 lb threaded Brass spikes.  It sits in the middle rotated 45 degrees to a fit a Mainstays phenolic wood over cardboard, composite shelf sittin on 4 8 inch air bladder filled 1/3 full.  That required the shelf corners sticking out,45 degree rotation.  It also allows the harness length to be closer to listening position as well.  

But fiddling and tunning and playing with tubes and tube dampers  all of which I have done and then to find that the feet make comparable diffrences in most cases more. 

So Bob has another set of Blackpod Nano's with my name on it.  Sadly Bob will probably be making these only special order in the future.  Says they are a PITA.  Apparently in addition to the Carbon and Graphene, they also use a substantial amount of diamond powder in the material mix, which completely ruins hardened drill bits.  Has to replace every set he makes.  Crazy!

System keeps getting better and the Airmid and VC's are better than ever.  Hard to explain how much better.  Music is much more real, more analog sounding, more involving.  As always there is always something that can be improved.

The joy and curse of audi0philia,

jgwtriode


----------



## jgwtriode (Nov 11, 2022)

http://jplay.eu/forum/index.php?/topic/3063-pink-hq-minorityclean/page-197

There is a link for those of you who utilize a windows computer system to stream or playback your stored files.   Most particularly if you use Process Lasso, Fidelizer and
Audiphile Optimizer.  It discusses Hungry Bear's latest software for loading and optimizing 3 specific software programs that can be used together or seperately to control
and reduce jitter in computer memory.  They are designed by a gentleman who goes by Orya!   He is constantly improving them and they are available for free.
Trusted Controller loads them and optimizes them to work with PL, Fidelizer and AO to improve what they do.  It will allow you to load 1 or all 3.  Excercise Stabilizer in it's 35th iteration,  Majiority Clean 288th iteration and Lemonade in its 50th iteration. 

Running it now with Qobuz and just starting out with ES 35 tonight.   Comparable to the SR orange fuse change or my footer change over and above just runnin PL, fidelizer and A0.   Check it out if you do windows as part of your system.  I imagine it will work just fine with HQ player as well as Jplay even thought most of these guys are hardcore Jplay folk.  Will be reinstalling Jplay Femto in the next couple of days,  but am strongly thinking of adding HQplayer, since you can now directly stream Qobuz with it, no longer neeeding Roon.   It may even be better without.

Happy listening,

jgwtriode


----------



## jgwtriode (Nov 12, 2022)

Found it! Magic.

Found a Combo of these memory jitter reduction programs that sings. Its like adding another layer of National Union 6J5GT's to my sound.  Music, just plain music.  Tone, harmonic, texture, sweet airy spacious with wonderful PRAT and layering and focus in spades.  And it just wrings emotion out of the performances, the main reason I loved my first triode amplifiers.

Despite all I have done with my tweaking this created that kind of difference all over again.  Just so damn involving in every aspect.  Oh does it bring the Airmid and VC's to life in a way I have never heard to this degree!  There is no trace of hardness or edge, everything flows.  VC's have never had quite this gorgeous, neutral sweetness and it's top to bottom.  Funny thing is even this software seems to require burn in.

I am told 24 hours is about right.  I am at 2 hours after fiddling most of this evening.

One kind gentlman on the forumn suggested the combo I am using was his favorite.   So sure why not, easy enought to quickly swap install profiles.   OMG!

With this kind of sound there is no immediate reason to pursue Atriums.  Maybe I will just slow down and eventually over the next year work my way to Caldera's,  But Goldwerger's comments in his Caldera review about  the VC being a blend of both the Atrium and the Caldera; his choice if he could only have one ZMF!

I have heard less than a couple handful of systems in all my years that sound this enjoyable.   Just had a thought!  Maybe in another year to a year and a halft Zach may apply the Atrium technology to an improved vriant of the VC,  A VC classic!    Now that might just be perfection and worth waiting for!


Happy listening,

jgwtriode


----------



## JazzVinyl

mordy said:


> Metal base tubes - vinyl. Let's speak about metal base vinyl/shellac... When the 78s were produced, they were pressed from a metal master. Somebody discovered a couple of metal masters that hadn't been destroyed and used them to make recordings.
> The sound quality from this 1928 Louis Armstrong recording from the metal master is astounding compared to the (often scratchy sounding) original 78s:



Most stampers employed in USA record plants were used until they were worn out.  I assume this particular stamper was never used to stamp any vinyl records?   Did not pass QA standards...(they are inspected under a microscope) and why it wasn't used, perhaps?

https://www.doctormix.com/blog/how-to-press-vinyl-records-complete-guide

.


----------



## mordy

JazzVinyl said:


> Most stampers employed in USA record plants were used until they were worn out.  I assume this particular stamper was never used to stamp any vinyl records?   Did not pass QA standards...(they are inspected under a microscope) and why it wasn't used, perhaps?
> 
> https://www.doctormix.com/blog/how-to-press-vinyl-records-complete-guide
> 
> .


You may be right - these metal stampers were mailed from the US to German Odeon and there are pictures of the mailing packages; perhaps they weren't used for some reason.


----------



## Monsterzero

jgwtriode said:


> Maybe in another year to a year and a halft Zach may apply the Atrium technology to an improved vriant of the VC, A VC classic! Now that might just be perfection and worth waiting for!


 Don't hold your breath. Zach told me he is " happy with how the Verites sound"


----------



## mordy

Monsterzero said:


> Don't hold your breath. Zach told me he is " happy with how the Verites sound"


Let's face it, how many people on these threads are happy with what they have and don't feel the need to search for more stuff?
My guess is - very few. Most people, including myself, are always looking for more audio perfection...
Well, sometimes you really appreciate what you have and are happy with it.


Until the upgrade bug bites you again..

It never ends...

Wife: Honey, how come you have so many of those glass thingamajigs?
Husband: I am looking for audio perfection.


----------



## jgwtriode

Monsterzero said:


> Don't hold your breath. Zach told me he is " happy with how the Verites sound"


Oh well it's my justification I guess or rationalization mixed with some level of hope!   Shift perspectives a bit and try and work on my front end for a while and or my power and grounding.  And need to sort out the best software and streamer solution for my system.  Much as I love what JPlay does with stored files I am not convinced it is the best answer for streaming Qobuz.  So shifting my focus for a while!

Happy listening,

jgwtriode


----------



## jgwtriode

Touched up a few spots with GCE contact enhancer, including that SR orange fuse I threw into the DDC, I forgot to treat it.  I have also been running some straight burn in all day without listening at all!  I also  added an additional one of Orya's jitter reduction software apps for computer memory.  I now run 3 of his most recent itterations!  Sound is even better! More vibrant, more resolved, more air, space and dynamics...it's just amazing how much more emotional and alive the Airmid and VC's sound!

Trying to put money away for the next significant upgrade!

Happy listening,

jgwtriode


----------



## Xcalibur255

https://www.ebay.com/itm/125614456625?hash=item1d3f347f31:g:20MAAOSwZFhiiT7b&amdata=enc:AQAHAAAAoCKg3qXKKrlWVDTHzQbe043xhwjkTvSE9KBpPOESI4vupf5wQ6LKERTPVO6WC23L/9YmbvEp7sVEKGGfta08VE70ILHK5cSdya9fDNH4zWqJLia/rLqKEicNt1Jz6qEiAgC2z3Gy9UYE2p44ZJvqE+xdpPiSihhekhAYvPHcqVn56kLCbdwJo07+Z2QpJHHjnLSjrynLpxceuHGC7SCwd/4=|tkp:Bk9SR8KQ3fCPYQ

Had to share this here.  It's not often I come across tubes that make me go "wow" anymore but these did.

Out of Danvers, Mass. of all places....... just too cool.


----------



## paradoxper

Xcalibur255 said:


> https://www.ebay.com/itm/125614456625?hash=item1d3f347f31:g:20MAAOSwZFhiiT7b&amdata=enc:AQAHAAAAoCKg3qXKKrlWVDTHzQbe043xhwjkTvSE9KBpPOESI4vupf5wQ6LKERTPVO6WC23L/9YmbvEp7sVEKGGfta08VE70ILHK5cSdya9fDNH4zWqJLia/rLqKEicNt1Jz6qEiAgC2z3Gy9UYE2p44ZJvqE+xdpPiSihhekhAYvPHcqVn56kLCbdwJo07+Z2QpJHHjnLSjrynLpxceuHGC7SCwd/4=|tkp:Bk9SR8KQ3fCPYQ
> 
> Had to share this here.  It's not often I come across tubes that make me go "wow" anymore but these did.
> 
> Out of Danvers, Mass. of all places....... just too cool.


What makes these wow-y? I'm a big fan of the 45 but have not tried these yet.


----------



## jgwtriode

Xcalibur255 said:


> https://www.ebay.com/itm/125614456625?hash=item1d3f347f31:g:20MAAOSwZFhiiT7b&amdata=enc:AQAHAAAAoCKg3qXKKrlWVDTHzQbe043xhwjkTvSE9KBpPOESI4vupf5wQ6LKERTPVO6WC23L/9YmbvEp7sVEKGGfta08VE70ILHK5cSdya9fDNH4zWqJLia/rLqKEicNt1Jz6qEiAgC2z3Gy9UYE2p44ZJvqE+xdpPiSihhekhAYvPHcqVn56kLCbdwJo07+Z2QpJHHjnLSjrynLpxceuHGC7SCwd/4=|tkp:Bk9SR8KQ3fCPYQ
> 
> Had to share this here.  It's not often I come across tubes that make me go "wow" anymore but these did.
> 
> Out of Danvers, Mass. of all places....... just too cool.


OMG indeed! Incredible! Gorgeous! Never owned a 45, but I have spoken to those who have!  Takes your breath away!

jgwtriode!


----------



## Xcalibur255

paradoxper said:


> What makes these wow-y? I'm a big fan of the 45 but have not tried these yet.


A brand I've never heard of before and the pristine condition mostly.


----------



## mordy

Expectation bias department?




Just switched the regular computer power cord to may headphone amp for this hospital grade 14awg power cord. The amp sounds better, more everything (you fill it in)...
Definitively worth the $13 from Amazon...
A hi-fi salesman told me many years ago that thicker cables are better (and dual thick speaker cables are even better!). I asked him why. He said: Imagine a narrow corridor with a lot of people - nobody can move that fast. But if the corridor is very wide, people can move much faster. The same thing with electrons - they can move much faster in thick cables for improved dynamics etc etc.
Not sure if these statements hold up to scientific scrutiny, but it seems to me that the sound really is better.
Better and deeper bass with better definition and detail.
More clarity.
I don't think I am imagining.


----------



## Monsterzero

mordy said:


> Expectation bias department?
> 
> Just switched the regular computer power cord to may headphone amp for this hospital grade 14awg power cord. The amp sounds better, more everything (you fill it in)...
> Definitively worth the $13 from Amazon...
> ...


I bought these power cables back in 2018 and to my ears the bass was definitely improved. Had one for my amp and DAC. Then I was sent C-Marc Lessloss braided power cables ( dont gag on the price) to try in my system back when I did that cable shootout on my Youtube channel. to my ears those were a huge improvement over the previous upgraded cables, with even better bass and a very noticeable improvement in staging and 3Dness.

To be honest, I really wish I heard no difference, because frankly spending money on cables is the most boring way to drain one's wallet in this hobby.


----------



## Xcalibur255

That's how I feel about power cables:  I wish I didn't hear a difference but once you do I feel I need to make at least a conservative effort to address it.  I like and use the entry level Supra LoRad power cables, for the same or slightly less money I preferred them over the Pangea AC-14, though I do still have the Pangea and use it on the GOTL.


----------



## paradoxper

Xcalibur255 said:


> A brand I've never heard of before and the pristine condition mostly.


This is what I assumed. I'm half tempted to pick them up but I'm really quite happy with the Perryman 45.


----------



## mordy

Xcalibur255 said:


> That's how I feel about power cables:  I wish I didn't hear a difference but once you do I feel I need to make at least a conservative effort to address it.  I like and use the entry level Supra LoRad power cables, for the same or slightly less money I preferred them over the Pangea AC-14, though I do still have the Pangea and use it on the GOTL.


I shall remain blissfully ignorant being happy with $13 cables instead of $2000 or $100 cables.
If good is good, isn't better better?
Yes, but at what cost?


----------



## jgwtriode

Once you let the genie out of the bottle you can't put it back.  If you listen to better cables, be prepared.  I had reasonably good Zenwave Audio OCC neotech copper cotton flat braid that were really an improvement.  Then I took Alex at Wywires at his word when he said I might find a bigger diffrence with power cords than either his USB cables or Interconnects.  He has very solid money back on the fact that his customers will and yes I did hear exactly what he said I would and then some.  So just be prepared if you indulge your curiosity!

Happy listening,

jgwtriode


----------



## jonathan c

mordy said:


> I shall remain blissfully ignorant being happy with $13 cables instead of $2000 or $100 cables.
> If good is good, isn't better better?^^
> Yes, but at what cost?


^^ “better better be better”…😠🤪…


----------



## pravous

My cables and power cords are all the best you can buy (of the mono price brand)   Once I figure out what DAC I want and I can see how it all fits together I plan on making my own interconnects and power cords.  My latest upgrade was a ZMF diy cable kit.  



Can’t objectively say whether it sounds better than the stock cable but subjectively I enjoy the fact that I made it myself.


----------



## mordy

jonathan c said:


> ^^ “better better be better”…😠🤪…


UnfortunatleyI   *it never ends! *
Decided to jump off the train to avoid the rabbit hole, or whatever the saying goes...


----------



## mordy

pravous said:


> My cables and power cords are all the best you can buy (of the mono price brand)   Once I figure out what DAC I want and I can see how it all fits together I plan on making my own interconnects and power cords.  My latest upgrade was a ZMF diy cable kit.
> 
> Can’t objectively say whether it sounds better than the stock cable but subjectively I enjoy the fact that I made it myself.


I wish I could make my own cables - would probably save a ton of money, but I don't have the ability to do it.


----------



## Galapac

pravous said:


> My cables and power cords are all the best you can buy (of the mono price brand)   Once I figure out what DAC I want and I can see how it all fits together I plan on making my own interconnects and power cords.  My latest upgrade was a ZMF diy cable kit.
> 
> Can’t objectively say whether it sounds better than the stock cable but subjectively I enjoy the fact that I made it myself.


Yeah I made one of those recently with the MICHANIKÓS silver cable and quad braided it myself.
Once you learn the technique it was fun to braid and it all came together nicely.

I used to be in the camp that headphone cables do not matter but with the ZMF DIY cable I can definitely hear a difference and it may be because my other cables, either bought or made, consisted mostly of copper but I can hear this MICHANIKÓS cable as actually being brighter so there is some truth to the silver/copper cables and how they present the audio.

Just not sure I like the brighter presentation that the MICHANIKÓS cable gives but like you, I enjoyed making it myself.


----------



## jgwtriode (Nov 16, 2022)

jonathan c said:


> ^^ “better better be better”…😠🤪…


In the immortal words of Roger Daltrey, "You better, You better, you bet!

jgwtriode


----------



## pravous

Galapac said:


> Yeah I made one of those recently with the MICHANIKÓS silver cable and quad braided it myself.
> Once you learn the technique it was fun to braid and it all came together nicely.
> 
> I used to be in the camp that headphone cables do not matter but with the ZMF DIY cable I can definitely hear a difference and it may be because my other cables, either bought or made, consisted mostly of copper but I can hear this MICHANIKÓS cable as actually being brighter so there is some truth to the silver/copper cables and how they present the audio.
> ...


Don’t envy you the task of soldering the thicker wire to the mini xlr connectors.  It took some helping hands and a one off jig to hold them in place while soldering.  I have not tried any silver cables but tend to prefer warmer/darker tonality so I am glad I went with copper.   The braiding was intimidating at first but once I got going it became pretty simple.


----------



## mordy

Galapac said:


> Yeah I made one of those recently with the MICHANIKÓS silver cable and quad braided it myself.
> Once you learn the technique it was fun to braid and it all came together nicely.
> 
> I used to be in the camp that headphone cables do not matter but with the ZMF DIY cable I can definitely hear a difference and it may be because my other cables, either bought or made, consisted mostly of copper but I can hear this MICHANIKÓS cable as actually being brighter so there is some truth to the silver/copper cables and how they present the audio.
> ...


Beautiful picture!


----------



## Xcalibur255

mordy said:


> I shall remain blissfully ignorant being happy with $13 cables instead of $2000 or $100 cables.
> If good is good, isn't better better?
> Yes, but at what cost?


I found the jump from the $13 stuff to the $100 stuff to be worth the investment, but after that I also made a conscious decision to stop and not explore further.  There's also a question of whether one is experimenting to solve a problem or experimenting to seek new performance heights.  I was motivated more by the former than the latter and once I got my problems sorted out (harshness in the sound) I've been content ever since.  Maybe I'm just getting old but I find that actually being content is something I really value these days.


----------



## triod750

You need to go all in and make the copper yourself. Everything else is pointless .


----------



## Galapac

pravous said:


> Don’t envy you the task of soldering the thicker wire to the mini xlr connectors.  It took some helping hands and a one off jig to hold them in place while soldering.  I have not tried any silver cables but tend to prefer warmer/darker tonality so I am glad I went with copper.   The braiding was intimidating at first but once I got going it became pretty simple.


The key there is to have some good magnifying specs when soldering the wires to the pins and pre-tinning the connectors also helps.
I use two flexible holding hands and get them as close as possible before connecting them and it takes all of a couple of seconds, no more.


----------



## pravous

Galapac said:


> The key there is to have some good magnifying specs when soldering the wires to the pins and pre-tinning the connectors also helps.
> I use two flexible holding hands and get them as close as possible before connecting them and it takes all of a couple of seconds, no more.


My problem was my version of the helping hands had the jaws too far apart.  I ended up making a clamp with some wood scraps for the connector side and using the helping hands to hold the wire which I had pre tinned along with the connector barrel.  Came out good in the end but took a few tries to come up with a good process.


----------



## pravous

triod750 said:


> You need to go all in and make the copper yourself. Everything else is pointless .


My wife already thinks I am crazy enough.  I can only imagine what she would say if I started melting down pennies in a home made forge in the back yard


----------



## triod750

pravous said:


> My wife already thinks I am crazy enough.  I can only imagine what she would say if I started melting down pennies in a home made forge in the back yard


She is probably right


----------



## raindownthunda

pravous said:


> My wife already thinks I am crazy enough.  I can only imagine what she would say if I started melting down pennies in a home made forge in the back yard


1914 Lincoln pennies sound the best. Prove me wrong.


----------



## mordy

raindownthunda said:


> 1914 Lincoln pennies sound the best. Prove me wrong.



*MELT VALUE: $0.0250* 1914 Lincoln Penny


----------



## LobalWarming

raindownthunda said:


> 1914 Lincoln pennies sound the best. Prove me wrong.


I remember a time when pennies made the best sounding fuses - way back before fuses were cryo-treated in quantum tunnels to preserve extravagant sound profit margins.


----------



## mordy

LobalWarming said:


> I remember a time when pennies made the best sounding fuses - way back before fuses were cryo-treated in quantum tunnels to preserve extravagant sound profit margins.


And I remember when you were supposed to put coins near the front edge of speakers for better sound...
Remember coloring the edges of CDs with a green marker?


----------



## Mr Trev

LobalWarming said:


> I remember a time when pennies made the best sounding fuses - way back before fuses were cryo-treated in quantum tunnels to preserve extravagant sound profit margins.


Pennies? I thought it was .22LR. At least you _knew_ when those fuses blew


----------



## LobalWarming

Mr Trev said:


> Pennies? I thought it was .22LR. At least you _knew_ when those fuses blew


Used by those who valued SLAM and IMPACT more than blood contamination on the stylus


----------



## pravous

LobalWarming said:


> I remember a time when pennies made the best sounding fuses - way back before fuses were cryo-treated in quantum tunnels to preserve extravagant sound profit margins.


I remember that the floor guys used to jam coins directly into the house mains fuse blades to power the floor sanders back in the day doing renovations in Boston.  A lot of the older houses had the light bulb threaded fuses  and couldn’t handle the 20a floor sanders so they would jack straight into the fuse rails coming into the houses. For extra safety they would then clip jumper cable alligator leads onto the coins.  That being said what they could do with 100 plus year old heart of pine floors was amazing.


----------



## funch (Nov 17, 2022)

Best fuse: None?  Shown with custom high dollar fuse puller.


----------



## ColSaulTigh

Y'all must not remember the handyman special:


----------



## Mr Trev (Nov 17, 2022)

ColSaulTigh said:


> Y'all must not remember the handyman special:


I remember watching a video online where the guys were using crowbars and socket extensions as booster cables


----------



## JazzVinyl

jgwtriode said:


> In the immortal words of Roger Daltrey, "You better, You better, you bet!
> 
> jgwtriode



Roger sang it, but Pete wrote it !!!


----------



## L0rdGwyn

Finished building out one channel of my PCM63 DAC, here it is.



I have to test the power supplies with dummy loads before I put my precious PCM63 chips in.

I also had an idea for a choke loaded EL84 OTL headamp while I was on vacation, 6922 input, ordered parts while I was away.  I grabbed a nice quad of Amperex EL84, some Hammond chokes, and 100uF Jupiter Cosmos electrolytics to try as output caps.  Grabbed six so I could experiment with paralleling capacitance.



I'm planning to experiment with some negative feedback in this circuit.  Stability will be the key, especially in a circuit using choke loads.  Assuming it works out, I am seeing around 60ohm output impedance without negative feedback and around 19ohm output impedance with negative feedback.  Could potentially have a switch to turn the negative feedback on and off, assuming it doesn't cause instability.  Should sound quite different with and without and support different types of headphones.  I have no plan for what to do with this circuit, just something I am going to experiment with for now.


----------



## LobalWarming

L0rdGwyn said:


> Finished building out one channel of my PCM63 DAC, here it is.
> 
> 
> 
> ...


I'm not one to pick sides on the whole positive/negative polarized debate... but wouldn't you have to use 2 polarized caps (reversed polarity connected) where 1 non-polarized would do? Or is the secret  sauce just letting the positive voltage mojo get through - keeping the negative nelly volts at bay?


----------



## L0rdGwyn

LobalWarming said:


> I'm not one to pick sides on the whole positive/negative polarized debate... but wouldn't you have to use 2 polarized caps (reversed polarity connected) where 1 non-polarized would do? Or is the secret  sauce just letting the positive voltage mojo get through - keeping the negative nelly volts at bay?



Well, if I am understanding your question, capacitors are DC blocking, the orientation of the +/- of a polarized capacitor is a requirement for its functionality, not a question of which voltage passes through.  Capacitors will pass AC and block DC.  If you connect a polarized capacitor in the opposite orientation, it will be damaged.  For example, in a cathode follower OTL, you would want to connect the positive end of the capacitor to the output tube's cathode and the negative end to the headphone output, which is at DC ground potentional.

Film caps are inherently non-polar.  They do make non-polarized electrolytics, but as I recall there is some data out there that shows they produce higher distortion than equivalent polarized electrolytics, so polarized are preferred for signal path applications unless a non-polarized cap is needed.

It's true you can create a non-polar capacitor by connecting two polarized caps with reverse polarity connected, but capacitance in series would be halved and it isn't needed for a capacitor coupled OTL.  Capacitance in parallel is additive, so I intended to parallel some of these Jupiter electrolytics, which will give a better low frequency response with low impedance headphones.


----------



## JazzVinyl

And there exist few amps that present no DC to the headphone output and therefore require no capacitor prior to the headphone out.  I have such amps...one is a tube amp, the other, solid state.

I has been many years since I attended electronics classes, but I do remember the teacher always stating that in audio circuit, regarding the output...that the best cap, would always be: no cap.


----------



## LobalWarming

L0rdGwyn said:


> Well, if I am understanding your question, capacitors are DC blocking, the orientation of the +/- of a polarized capacitor is a requirement for its functionality, not a question of which voltage passes through.  Capacitors will pass AC and block DC.  If you connect a polarized capacitor in the opposite orientation, it will be damaged.  For example, in a cathode follower OTL, you would want to connect the positive end of the capacitor to the output tube's cathode and the negative end to the headphone output, which is at DC ground potentional.
> 
> Film caps are inherently non-polar.  They do make non-polarized electrolytics, but as I recall there is some data out there that shows they produce higher distortion than equivalent polarized electrolytics, so polarized are preferred for signal path applications unless a non-polarized cap is needed.
> 
> It's true you can create a non-polar capacitor by connecting two polarized caps with reverse polarity connected, but capacitance in series would be halved and it isn't needed for a capacitor coupled OTL.  Capacitance in parallel is additive, so I intended to parallel some of these Jupiter electrolytics, which will give a better low frequency response with low impedance headphones.


Excellent explanation. Thank you. Not that I've joined the film cap cabal after spending hundreds on big Clarity Caps  - highly recommended around here - for my OTL. Only to discover that  it seems cheap polarized 'Lytics could have sufficed. Nope, not joining that cap cabal, at all.


----------



## bcowen

JazzVinyl said:


> And there exist few amps that present no DC to the headphone output and therefore require no capacitor prior to the headphone out.  I have such amps...one is a tube amp, the other, solid state.
> 
> I has been many years since I attended electronics classes, but I do remember the teacher always stating that in audio circuit, regarding the output...that the best cap, would always be: no cap.


This is one of the claims to fame of Schiit's Folkvangr HP amp.  OTL _and_ OCL (output capacitor-less).


----------



## Mr Trev

bcowen said:


> This is one of the claims to fame of Schiit's Folkvangr HP amp.  OTL _and_ OCL (output capacitor-less).


And apparently it can double duty as a hotplate


----------



## bcowen

Mr Trev said:


> And apparently it can double duty as a hotplate


Yes, but on the bright side I won't need to turn on the heat in the house this winter.   🤣


----------



## L0rdGwyn (Nov 26, 2022)

JazzVinyl said:


> And there exist few amps that present no DC to the headphone output and therefore require no capacitor prior to the headphone out.  I have such amps...one is a tube amp, the other, solid state.
> 
> I has been many years since I attended electronics classes, but I do remember the teacher always stating that in audio circuit, regarding the output...that the best cap, would always be: no cap.



Yeah, totally can be done, special care needs to be taken to ensure there is no DC on the output obviously as it will damage transducers.  John Broskie over at TubeCAD has written numerous articles on output capacitorless circuits, lots of hybrid stuff.  The gist of it is you need positive and negative supply rails such that they balance to 0V at the output.  Not something I have looked into deeply, just hasn't piqued my interest yet, would probably want some sort of protection circuit on the output just in case.



bcowen said:


> This is one of the claims to fame of Schiit's Folkvangr HP amp.  OTL _and_ OCL (output capacitor-less).



Pretty obvious they were like "WTH do we do with all these extra tubes?" "Just make an amp that uses all of them".


----------



## Mr Trev

bcowen said:


> Yes, but on the bright side I won't need to turn on the heat in the house this winter.   🤣


and who wouldn't want to toast marshmallows while you listen to music


----------



## L0rdGwyn (Nov 27, 2022)

Finished both channels of my PCM63 DAC and the digital front end power supply board.




The PCM63 is the Holy Grail of vintage Burr-Brown R2R chips.  Each board uses two of them in parallel, the two boards will stack on top of each other, similar to my PCM56 DAC.  The output of each board are the current output pins of the parallel chips.  I will again be using a Sowter step up transformer for the I/V stage.

I am again planning a tube output stage, but a different flavor this time around.  I have a healthy stock of NOS E182CC tubes, a very good sounding audio dual triode.  Each section has a relatively high gm of 15mA/V.  I'd like to use a pair of E182CC on the output with the sections wired in parallel in a transformer coupled cathode follower output buffer with a 1:1 output transformer, something like this.



Being completely transformer coupled and with a triode well suited for buffer service, I am expecting very good results with this setup.  However, since a cathode follower has no voltage gain, the Sowter step up transformers will be responsible for converting the current output of the DAC to a line level output voltage.  

Without getting too heavy into the technical details, these current output DACs perform best if presented with a low impedance load.  Generally, less than 100ohms is best for PCM63, otherwise it will start generating audible harmonic distortion.  To reach 2Vrms output with a 1:10 step up and parallel PCM63, roughly an 8.2K resistor will be needed on the secondary of the step up transformer, presenting the DAC chips with an ~82ohm primary impedance.

This should work well in theory, but I plan to measure the distortion on the secondary of the step up transformers with a dummy load before committing to this I/V stage.  If the measurements look good, then I'll order parts for the output buffer and design the chassis.  This time around, I plan to include some tube aesthetics with the E182CC buffer tubes sticking partway out of the top plate, should look pretty cool.

I have next week off before starting my new job, going to test this and also devote some time to the Aegis project.


----------



## heliosphann

L0rdGwyn said:


> Finished both channels of my PCM63 DAC and the digital front end power supply board.
> 
> 
> 
> ...


Pictures pretty. Rest makes my head hurt.


----------



## L0rdGwyn (Nov 26, 2022)

heliosphann said:


> Pictures pretty. Rest makes my head hurt.



Trust me, it makes my head hurt too lol.  Designing a DAC, even a relatively simple one, is no cakewalk.  But I did most of the brain work on my PCM56 DAC, so I've been able to lean on that work for the second build.  Ultimately, I wanted to build something with the PCM63, but given they run around $150 a chip, needed to be confident in my design before committing to it, and I am very happy with my PCM56 build.


----------



## jgwtriode

How will this one compare to the one you brought with you to the last dealer/enthusiast meet and put up against the DCS!   That was 
a very impressive result btw and perhaps a bit surprising, but not really knowing how incredibly well designed your projects are and
your knack for making things sound amazing!

jgwtriode


----------



## L0rdGwyn

jgwtriode said:


> How will this one compare to the one you brought with you to the last dealer/enthusiast meet and put up against the DCS!   That was
> a very impressive result btw and perhaps a bit surprising, but not really knowing how incredibly well designed your projects are and
> your knack for making things sound amazing!
> 
> jgwtriode



The digital front end is the same for both, the power supply topology is also the same, however some adjustments have been made to account for the higher current draw of parallel PCM63 vs a single PCM56 per channel.  PCM63 is a higher performing chip compared to PCM56, lower distortion and noise, higher theoretical bit depth as well - it is a 20-bit chip vs 16-bit for the PCM56.  Both use Sowter step up transformer I/V conversion, however the PCM56 DAC uses a tube voltage gain stage on its output, CCS loaded and capacitor coupled, as such the Sowter I/V transformers are only wired for 1:5 step up ratio.  The PCM63 DAC instead will use a 1:10 step up ratio and a transformer coupled tube output buffer as opposed to a voltage gain stage.  Given the PCM63 output stage is completely transformer coupled and uses a tube buffer, it should in theory generate less distortion, have better clarity, realism, and excellent low end dynamics.

So basically, the new DAC uses a higher performing DAC chip, two in parallel, and an output stage with a cleaner signal path and lower theoretical distortion.  We'll see if the measurements match expectations.


----------



## George Hincapie

L0rdGwyn said:


> The digital front end is the same for both, the power supply topology is also the same, however some adjustments have been made to account for the higher current draw of parallel PCM63 vs a single PCM56 per channel.  PCM63 is a higher performing chip compared to PCM56, lower distortion and noise, higher theoretical bit depth as well - it is a 20-bit chip vs 16-bit for the PCM56.  Both use Sowter step up transformer I/V conversion, however the PCM56 DAC uses a tube voltage gain stage on its output, CCS loaded and capacitor coupled, as such the Sowter I/V transformers are only wired for 1:5 step up ratio.  The PCM63 DAC instead will use a 1:10 step up ratio and a transformer coupled tube output buffer as opposed to a voltage gain stage.  Given the PCM63 output stage is completely transformer coupled and uses a tube buffer, it should in theory generate less distortion, have better clarity, realism, and excellent low end dynamics.
> 
> So basically, the new DAC uses a higher performing DAC chip, two in parallel, and an output stage with a cleaner signal path and lower theoretical distortion.  We'll see if the measurements match expectations.


Forgive my newbie question; is the intention, if all works as you hope, to build some of these DACs to sell, or is this a personal project only?


----------



## L0rdGwyn

George Hincapie said:


> Forgive my newbie question; is the intention, if all works as you hope, to build some of these DACs to sell, or is this a personal project only?



Sorry, but this is a personal project only.


----------



## George Hincapie

L0rdGwyn said:


> Sorry, but this is a personal project only.



I wish you the best of luck with it; those boards look like art!


----------



## L0rdGwyn

I scored a pretty sweet deal on some tubes the other day, guy from Italy had a box of 100 NOS D3a, selling them in sets of 10.  He accepted my offer for 125 Euro per lot, so I grabbed 30 of them.  12.50 Euro per tube is a crazy good deal for D3a, these are becoming more and more rare and expensive, I was stoked when this listing showed up  one of the best audio tubes ever made IMO.

I have an LCR phono stage build on the horizon, these oughta keep me well stocked for a decade or two.


----------



## Zachik

L0rdGwyn said:


> I scored a pretty sweet deal on some tubes the other day, guy from Italy had a box of 100 NOS D3a, selling them in sets of 10. He accepted my offer for 125 Euro per lot, so I grabbed 30 of them. 12.50 Euro per tube is a crazy good deal for D3a


Uh oh... @L0rdGwyn is becoming a @bcowen


----------



## L0rdGwyn

Zachik said:


> Uh oh... @L0rdGwyn is becoming a @bcowen



Well I only hoard certain tubes, @bcowen hoards all of them


----------



## Zachik

L0rdGwyn said:


> Well I only hoard certain tubes, @bcowen hoards all of them


Actually, @bcowen only hoards GE tubes, telling us they're crap so he can buy them all by the pound!


----------



## whirlwind

L0rdGwyn said:


> I scored a pretty sweet deal on some tubes the other day, guy from Italy had a box of 100 NOS D3a, selling them in sets of 10.  He accepted my offer for 125 Euro per lot, so I grabbed 30 of them.  12.50 Euro per tube is a crazy good deal for D3a, these are becoming more and more rare and expensive, I was stoked when this listing showed up  one of the best audio tubes ever made IMO.
> 
> I have an LCR phono stage build on the horizon, these oughta keep me well stocked for a decade or two.


Great score


----------



## pravous

L0rdGwyn said:


> Well I only hoard certain tubes, @bcowen hoards all of them


You are all too late I have already cornered the @bcowen market for the Aegis market!


----------



## bcowen

L0rdGwyn said:


> Well I only hoard certain tubes, @bcowen hoards all of them


LOL!  Except your 'certain' tube hoard collection probably outnumbers my 'all' tube hoard collection by a factor of 10.   🤣


----------



## bcowen

pravous said:


> You are all too late I have already cornered the @bcowen market for the Aegis market!


Use of GE tubes in Aegis will probably void the warranty.  🤣🤣


----------



## raindownthunda

pravous said:


> You are all too late I have already cornered the @bcowen market for the Aegis market!


Mullard XF2? You've got to give GE _some _credit for doing something right by buying another manufacturer's tubes rather than attempting to make their own!


----------



## L0rdGwyn (Nov 29, 2022)

Decided to go ahead and get my DAC testing done.

I configured the JLSounds I2SoverUSB module for PCM63, made connectors from the module to its power supply PCB and the left and right channel DAC boards.

Then I connected everything up in a janky way for the sake of testing.  Since these PCM63 chips are pretty old, I put them in one at a time and tested along the way to ensure I would know if one was bad.  Thankfully, they are all good to go.

Here is my sloppy test setup on a box.  My desk is a disaster from so many simultaneous projects, but it is what it is.




I dialed in all of the 5V supplies, everything is working as intended.

For the sake of testing, rather than rigging up the Sowter I/V transformers, I just soldered in 68ohm dummy load.  This would represent the primary impedance of the transformer in theory, which in the I/V stage schematic I posted a page back would be closer to 82ohms, but 68ohms is close enough for testing purposes.

Here is a 1kHz sine wave at -3dBFS at a 96kHz sample rate across the 68ohm I/V resistor.  You can see there is quantization noise, a feature of NOS R2R DACs as there is no oversampling involved.  A large portion of that will be filtered out by the I/V transformers.



I figured I might as well take a measurement across that 68ohm I/V resistor, it's pretty close to my intended 82ohm primary impedance and will give me an idea of what the noise floor looks like.

So I set that up, here is a 1kHz FFT at -6dBFS output from the DAC at 96kHz sample rate.



Holy crap!!!  That is pretty damn good, no low frequency mains noise to be found and THD at 0.0048% and almost entirely second harmonic.  This is going to be a sweet DAC.

Next will be testing with the Sowter I/V transformers to get an idea of what the distortion and noise is going to look like going into the grid of my tube buffer stage.


----------



## L0rdGwyn (Nov 30, 2022)

Did some more DAC testing with the Sowter I/V transformers in place.

Unfortunately, with the 8.2K resistors on the secondary of the transformers, meaning a 8.2K output impedance, my measurement setup with its 100K input impedance is loading down the transformers to some extent, meaning I cannot get very accurate distortion figures.  By comparison, the input impedance of a tube grid is in the megaohm range, so that will be higher performing.  I am going to have to use the measurements taken above using the 68ohm I/V dummy load as a surrogate.

So, that means I am moving on to the tube buffer stage.  As I've said before, the buffer has no voltage gain, all of the voltage has to be generated by the I/V transformers.  Now one feature of the PCM63 is that it has clamping zener diodes on its output to protect it from excessive output voltage, they clamp the voltage at 0.7V peak-to-peak.  So, on the primary side of the I/V transformers, you don't want your signal to come anywhere close to this clamping voltage or the signal will clip.

With the two PCM63 in parallel, this clamping voltage is additive to a maximum of 1.4V peak-to-peak on the primary side of the transformer.  I confirmed this on my scope by increasing the secondary I/V resistor to 27K and ramping up the output voltage until the signal clipped, seen below.



To get a 2Vrms (5.6V peak-to-peak) line level output voltage, I only need around 0.247Vrms (0.7V peak-to-peak) on the primary side of the transformer, so good to know there is plenty of headroom.

So with all of that tested, I think I am comfortable ordering the transformers for the tube buffer.  I am going to use an interstage transformer in the cathode of the E182CC actually, Lundahl's recently released LL2753.  It has a 150ohm DC resistance primary and secondary, so with the parallel E182CC cathode follower, I would be looking at an output impedance of roughly 350ohms for the DAC.

Not sure if I am going to go with amorphous core or not yet.  I've reached out the Erhard Audio to see if Holger has any variants in stock.

Anyway, DAC is coming along nicely, off to run some errands.  Between today and tomorrow, going to sit down and try to get a chunk of the Aegis documentation done.


----------



## DenverW

I’m just happy to know I have the same soldering iron as @L0rdGwyn.  Clearly I am doing something right.


----------



## ColSaulTigh

DenverW said:


> I’m just happy to know I have the same soldering iron as @L0rdGwyn.  Clearly I am doing something right.


I almost bought that multimeter - it was like 40% off for Black Friday on Amazon!  But I didn't pull the trigger, so I'll never reach the same pinnacle of greatness that is @L0rdGwyn


----------



## L0rdGwyn (Nov 30, 2022)

DenverW said:


> I’m just happy to know I have the same soldering iron as @L0rdGwyn.  Clearly I am doing something right.



It's a great iron!



ColSaulTigh said:


> I almost bought that multimeter - it was like 40% off for Black Friday on Amazon!  But I didn't pull the trigger, so I'll never reach the same pinnacle of greatness that is @L0rdGwyn



And a great multimeter!  Honestly think I just needed one in a pinch and got what was at Home Depot, but I was so happy with it I got a second one from the same brand (smaller footprint and lower max voltage).  So yeah definitely can recommend it, don't need a Fluke to do what I'm doing.


----------



## pravous

“With the two PCM63 in parallel, this clamping voltage is additive to a maximum of 1.4V peak-to-peak on the primary side of the transformer.”
Was this the sole reason to use two chips in parallel or were there other considerations?


----------



## L0rdGwyn

pravous said:


> “With the two PCM63 in parallel, this clamping voltage is additive to a maximum of 1.4V peak-to-peak on the primary side of the transformer.”
> Was this the sole reason to use two chips in parallel or were there other considerations?



That is one reason!  With these current output R2R DACs, generally the lower the I/V resistance for the voltage conversion, the better the performance.  With two DACs in parallel, you get double the voltage for the same I/V resistance (or impedance if using a step-up transformer).  

At the start, I wasn't sure what kind of output stage I was going with, I knew I wanted it to be completely transformer coupled and there was a thought to use a tube buffer without voltage gain.  After experimenting with the transformer-coupled cathode follower in Aegis, I went all in on the idea.

However, if using a single chip, I would not be able to use my tube buffer as designed and get 2Vrms output, the voltage at the primary winding of the I/V would come too close to the 0.7V limit for a single chip, at peak output it would distort.  I would either have to design for a lower than 2Vrms output or use a tube stage with voltage gain.  Using two chips in parallel solves that problem.  Also, in the ideal R2R DAC, the internal resistors are impeccably matched.  Real life might be slightly different, paralleling two DACs results in a sort of error correction for small differences in resistor matching by averaging the outputs of the two chips (at least in theory).

And subjectively speaking, there are a lot of people out there who claim paralleling R2R chips improves subjective performance, so there is definitely a not-so-sophisticated "one is good, two is better" mindset if I'm being honest.


----------



## ColSaulTigh

L0rdGwyn said:


> That is one reason!  With these current output R2R DACs, generally the lower the I/V resistance for the voltage conversion, the better the performance.  With two DACs in parallel, you get double the voltage for the same I/V resistance (or impedance if using a step-up transformer).
> 
> At the start, I wasn't sure what kind of output stage I was going with, I knew I wanted it to be completely transformer coupled and there was a thought to use a tube buffer without voltage gain.  After experimenting with the transformer-coupled cathode follower in Aegis, I went all in on the idea.
> 
> ...


Wait, so this is going to be a tube based R2R DAC?!?!?!?!

Sign me up!


----------



## L0rdGwyn

ColSaulTigh said:


> Wait, so this is going to be a tube based R2R DAC?!?!?!?!
> 
> Sign me up!



Sorry to disappoint @ColSaulTigh but this is just a one time personal project :/


----------



## pravous

“Also, in the ideal R2R DAC, the internal resistors are impeccably matched”.  
The age old production versus perfection dilemma!
I got some resistors to make the test leads to calibrate the etracer high/low resistance settings.   Not because it was needed but more as a little diy project.  Not sure how many decimals a good versus a bad meter goes out to but I was surprised that the resistors I ordered were within 1/1000 of an ohm, at least according to my multi meter.  I plugged the results into the config file and then retested some known tubes and it didn’t change the values.  All being said it was fun taking a little deeper dive and increased my trust in the testers results/design.


----------



## L0rdGwyn

pravous said:


> “Also, in the ideal R2R DAC, the internal resistors are impeccably matched”.
> The age old production versus perfection dilemma!
> I got some resistors to make the test leads to calibrate the etracer high/low resistance settings.   Not because it was needed but more as a little diy project.  Not sure how many decimals a good versus a bad meter goes out to but I was surprised that the resistors I ordered were within 1/1000 of an ohm, at least according to my multi meter.  I plugged the results into the config file and then retested some known tubes and it didn’t change the values.  All being said it was fun taking a little deeper dive and increased my trust in the testers results/design.



Glad to hear it is well calibrated!  The eTracer is fantastic, I use it all the time.


----------



## L0rdGwyn

Made some interesting observations on my DAC this morning.

For the sake of testing, I decided I wanted to connect the DAC output to some sort of buffer and do some listening / measurements.  I mentioned a few pages back I had an idea for a choke-loaded EL84 OTL headamp, I decided I could kill two birds with one stone if I built out the output stage for that amp, which is a tube buffer, and connected my DAC to it.

So that's what I did.  I'm not going to show a picture since it's an absolute rats' nest!  But basically I used an 8.2K secondary resistor on my I/V transformers, then ran that into my choke loaded EL84 cathode follower.

There is some good news and some bad news.

The good news is, my choke-loaded EL84 output stage looks pretty good in terms of bandwidth.  Need to do some distortion measurements and finish building out the 6922 input stage and listen to it as an actual headamp as opposed to a DAC output stage.  I will probably do that later today.

The bad news is I think I need to rework my DAC output stage.  As I've discussed, something like a 6.8-8.2K secondary resistor is needed across the Sowter I/V transformer secondary to get a 2Vrms line level voltage.  Unfortunately, what I am seeing is the transformers don't quite have enough inductance to get a fully extended low frequency response with a secondary resistor in that range.  With an 8.2K secondary, frequency response is down 2.5dB at 20Hz, with 6.8K down around 2dB at 20Hz.  Now that isn't horrendous, but it is down less than 1dB with a lesser secondary resistor in the 1-2K range.

Perhaps more importantly, I listened to the DAC with an 8.2K secondary and a 1K secondary.  Of course I had to crank up the potentiometer on my OTL headphone amp to almost max to get a listenable volume with the 1K secondary, but even so, the sound was much better with the lower secondary resistor value.  This is consistent with what I've said about performance improving with a lower primary impedance seen by the Iout pins of the parallel DACs.

I am going to give it one more listen with the 8.2K setup, but my thinking now is I am going to change approaches and use a lower secondary resistor and switch to a transformer coupled tube gain stage.  What that will be I'm not sure yet, I'll have to go back to the drawing board and come up with something cool.


----------



## L0rdGwyn

I did some A-Bing of the DAC + EL84 buffer with the 8.2K secondary I/V resistor and alligator clipped in and out a parallel 1K resistor, which makes an effective secondary I/V of 890ohms.

It's pretty clear the sound is much better with the 890ohm secondary, but that means I will need a tube gain stage as I said.

It's a bit of a tough call, either harm the signal more on the DAC side and use a higher performing tube output stage (the tube buffer), or use the lower I/V resistor for improved performance on the DAC side and accept that there will be slightly higher distortion on the tube side using the gain stage.

I think I am going to opt for the latter as I'm not comfortable with what's coming out of the I/V transformers with the 8.2K secondary, I think ultimately keeping the I/V resistance low and making up for the extra gain with a linear tube stage is going to make for a better end result.

But what tube?!  I am going to have to do some soul searching.  Going to have to find some tube line output transformers as well.  Back to the drawing board it is.

What the heck, here is the rats' nest.  This is what it looks like when you put a entire tube circuit together in an hour lol.



Now that the decision is made, going to turn this into an OTL headamp.


----------



## triod750

It looks exactly as my EL84 PP loudspeaker amp but for the missing tubes...


----------



## whirlwind

L0rdGwyn said:


> I did some A-Bing of the DAC + EL84 buffer with the 8.2K secondary I/V resistor and alligator clipped in and out a parallel 1K resistor, which makes an effective secondary I/V of 890ohms.
> 
> It's pretty clear the sound is much better with the 890ohm secondary, but that means I will need a tube gain stage as I said.
> 
> ...



This pic makes me dizzy


----------



## L0rdGwyn

whirlwind said:


> This pic makes me dizzy



Lol got another one coming up here in a second!  Hold onto your chair.


----------



## L0rdGwyn (Dec 1, 2022)

Okay, I think I made a cool thing.

Got the EL84 OTL all wired up.  It uses a CCS loaded 6922 input stage, cathode biased but without a bypass cap.  It is cap coupled via Jupiter copper foil caps to the output stage.  Output stage is a triode-strapped EL84 cathode follower with a choke loading its cathode.  Output caps are Jupiter Cosmos electrolytics.

Here is the rats' nest again.




So I mentioned that I was going to try some negative feedback in this circuit, settled on around 11dB.  I listened first without feedback and it sounds really good with the HD650!  That's my test headphone.

Here is 1mW into a 300ohm dummy load, THD 0.15%.  You'll have to ignore those high frequency harmonics, they are an artifact of my sound card, haven't worked out how to get rid of them yet.



And the frequency response of the amplifier without negative feedback.



Okay then I listened again with feedback and...it sound really good again!  Less tubey and lush, more clear and clean as you might expect.

Here is 1mW into 300ohm dummy load with negative feedback, THD 0.0092%.



And the frequency response with negative feedback.  As you can see, the bandwidth is improved, but it is quite good with or without feedback.



No instability whatsoever that I have been able to detect.  I can even clip in and clip out the feedback resistor while the circuit is running with no issues, which means you could have a switch built in that turns the feedback on and off.  Only problem that might pose is 11dB is a big difference in volume, so if you were listening with the feedback on, then turned it off suddenly, it would get super loud, like oh s*** loud.

But hey that's something to think about later.  I'll have to measure the output impedance of this circuit, my simulations said 60ohms without feedback and 19ohms with it, I suspect that will be pretty accurate.

So yeah, have another OTL in my back pocket, dirt chip as far as parts go too.  I will mull over what to do with it, have to focus on Aegis work now.


----------



## L0rdGwyn

I spent some more time listening to the EL84 OTL.  I mentioned few pages back I bought six of those Jupiter Cosmos 100uF electrolytic caps to try some parallel output capacitance.  I did some A-B testing of just 100uF, then 200uF, then all three for 300uF.  Not surprisingly, the sound is significantly improved with each additional parallel cap, better clarity and improved bass definition and dynamics.

With the negative feedback in place, I even tried out the Caldera (~20ohm output impedance with negative feedback), and it sounded pretty darn good!  I also went back and forth with and without negative feedback.  I think I prefer it with the feedback, the sound is smoother and with better clarity.  Maybe the dynamics are a touch more visceral without the feedback, need to do a little more listening to be sure.  The feedback circuit represents a parallel load to the output tube, I would also like to increase the values of the feedback resistors while maintaining the same feedback fraction to lighten the load of the feedback circuit and see if that effects the sound / dynamics.

Anyway, quite pleased with how this amp sounds, especially given how simple the circuit is and with inexpensive parts.


----------



## raindownthunda

L0rdGwyn said:


> I spent some more time listening to the EL84 OTL.  I mentioned few pages back I bought six of those Jupiter Cosmos 100uF electrolytic caps to try some parallel output capacitance.  I did some A-B testing of just 100uF, then 200uF, then all three for 300uF.  Not surprisingly, the sound is significantly improved with each additional parallel cap, better clarity and improved bass definition and dynamics.
> 
> With the negative feedback in place, I even tried out the Caldera (~20ohm output impedance with negative feedback), and it sounded pretty darn good!  I also went back and forth with and without negative feedback.  I think I prefer it with the feedback, the sound is smoother and with better clarity.  Maybe the dynamics are a touch more visceral without the feedback, need to do a little more listening to be sure.  The feedback circuit represents a parallel load to the output tube, I would also like to increase the values of the feedback resistors while maintaining the same feedback fraction to lighten the load of the feedback circuit and see if that effects the sound / dynamics.
> 
> Anyway, quite pleased with how this amp sounds, especially given how simple the circuit is and with inexpensive parts.


Very cool experiment! Awesome reading about OTL‘a that sound good with the Caldera since that’s an especially controversial topic right now. I’m curious about the output cap choice being electrolytic. I’ve always seen the messaging that film caps are “best”. Does it not actually matter as much as forums have led me to believe?


----------



## L0rdGwyn

raindownthunda said:


> Very cool experiment! Awesome reading about OTL‘a that sound good with the Caldera since that’s an especially controversial topic right now. I’m curious about the output cap choice being electrolytic. I’ve always seen the messaging that film caps are “best”. Does it not actually matter as much as forums have led me to believe?



It depends on who you talk to, but based on my experience, I used to make a point of avoiding electrolytics as a signal path cap. 
 But when I was designing Aegis, I was forced to use an electrolytic bypass capacitor in the input stage.  That's when I rounded up a bunch of audio grade electrolytics and did a shootout.  The top two caps from that roundup were the Elna Silmic II and the Jupiter Cosmos, but the Elna was much closer in performance to the rest of the pack than the Jupiter, it really blew the rest of them away and sounded GOOD, better even than the LEDs I was comparing it to.

Since I was so impressed, I figured I'd give them a shot as output caps in an OTL.  They certainly save on size and cost!  So far I've been really impressed with the sound overall, so I have no reason to think they're detracting from it.  Unfortunately I don't have any spare high capacitance film caps around to compare them to directly.


----------



## Mr Trev

L0rdGwyn said:


> It depends on who you talk to, but based on my experience, I used to make a point of avoiding electrolytics as a signal path cap.
> But when I was designing Aegis, I was forced to use an electrolytic bypass capacitor in the input stage.  That's when I rounded up a bunch of audio grade electrolytics and did a shootout.  The top two caps from that roundup were the Elna Silmic II and the Jupiter Cosmos, but the Elna was much closer in performance to the rest of the pack than the Jupiter, it really blew the rest of them away and sounded GOOD, better even than the LEDs I was comparing it to.
> 
> Since I was so impressed, I figured I'd give them a shot as output caps in an OTL.  They certainly save on size and cost!  So far I've been really impressed with the sound overall, so I have no reason to think they're detracting from it.  Unfortunately I don't have any spare high capacitance film caps around to compare them to directly.


So does this mean I should think about replacing all the caps in my Vali2 with Jupiters?


----------



## L0rdGwyn (Dec 1, 2022)

Mr Trev said:


> So does this mean I should think about replacing all the caps in my Vali2 with Jupiters?



I mean, you could consider it if they'll fit.  I don't know the circuit so I can't make any firm recommendations.  If there are output coupling caps, that would be the place to start.


----------



## bcowen

Mr Trev said:


> So does this mean I should think about replacing all the caps in my Vali2 with Jupiters?


Yes.


----------



## bcowen

L0rdGwyn said:


> No instability whatsoever that I have been able to detect.  I can even clip in and clip out the feedback resistor while the circuit is running with no issues, which means you could have a switch built in that turns the feedback on and off.  Only problem that might pose is 11dB is a big difference in volume, so if you were listening with the feedback on, then turned it off suddenly, it would get super loud, like oh s*** loud.


Could you put a pot in there instead of a switch so that 1) the volume would be gradually ramped up (or down), and 2) play around with feedback levels between 0dB and 11dB on the fly?  Remembering the Cary 805 amps that had adjustable feedback that was kinda fun to play with.


----------



## jonathan c

Mr Trev said:


> So does this mean I should think about replacing all the caps in my Vali2 with Jupiters?


…like this?       

  …oh, not VW but similar?…🤷🏻‍♂️🤣


----------



## L0rdGwyn

bcowen said:


> Could you put a pot in there instead of a switch so that 1) the volume would be gradually ramped up (or down), and 2) play around with feedback levels between 0dB and 11dB on the fly?  Remembering the Cary 805 amps that had adjustable feedback that was kinda fun to play with.



That's an idea!  The only downside of just doing a pot is that the feedback loop would essentially always be connected, so even if the pot set to its maximum value, there would still be some small amount of feedback.  Without breaking the loop, it wouldn't be turned off entirely.  However, I sort of envisioned this amplifier as having negative feedback, so being able to adjust it from a minimum to maximum would be a cool feature.  A 100K pot in series with a 10K resistor to cap the feedback at 11dB would make it adjustable from around 2dB to 11dB.


----------



## Mr Trev

L0rdGwyn said:


> I mean, you could consider it if they'll fit.  I don't know the circuit so I can't make any firm recommendations.  If there are output coupling caps, that would be the place to start.


Seeing some of the adapter totem poles out there, why not a couple tombstoned output caps sticking out the top too


----------



## Xcalibur255

I totally get testing with Caldera to see what it's capable of doing with lower Z phones but I'm a little surprised you're not listening with the Atrium Keenan.


----------



## L0rdGwyn

Xcalibur255 said:


> I totally get testing with Caldera to see what it's capable of doing with lower Z phones but I'm a little surprised you're not listening with the Atrium Keenan.



Oh I did!  Mostly with the Atrium actually.


----------



## bcowen

Mr Trev said:


> Seeing some of the adapter totem poles out there, why not a couple tombstoned output caps sticking out the top too


Totem poles are cool.   🤣


----------



## Mr Trev

bcowen said:


> Totem poles are cool.   🤣


See. Now imagine some monster caps poking out next to it


----------



## whirlwind

bcowen said:


> Totem poles are cool.   🤣



LOL!


----------



## L0rdGwyn (Dec 3, 2022)

Just some random updates and thoughts.

I spent some time listening to the EL84 OTL against my 6528 OTL with the Atrium.  Obviously the 6528 OTL is better, it's the best OTL I have heard.  It has improved clarity and realism, but it also costs significantly more to build and is much more complex, whereas the EL84 OTL is very simple and uses new production available tubes and easy to acquire parts.  I still find it really enjoyable and it holds up well against the 6528 OTL.  Not certain of where it stands in the hierarchy of commercial OTLs, but my feeling is it will easily outperform all entry level options and likely competes in the more middle to high end space.  There are things I like about the sound without negative feedback and things I like with the 11dB of negative feedback.  Probably there is a happy medium somewhere in the middle.  I am going to table it for now, but at some point I will try the 100K pot to adjust the feedback to taste.

I've spent some more time thinking about the tube gain stage in my PCM63 DAC.  Given the 1:10 step up ratio of the I/V transformers, the tube used for the gain stage needs to be chosen carefully as the Miller capacitance of the tube will be reflected across the transformer to the DAC x100.  Given the parallel PCM63, my calculations say I would not want to go over 100-150pF Miller capacitance.  Investigating what tubes that rules in and rules out now.  Once an option is chosen, I'll pick out some line output transformers.

The new Degritter MKII ultrasonic cleaner was announced, I put down a down payment, will probably get it in January.

I am also now officially in the queue for some transformers / inductors from Dave Slagle.  I mentioned a while back I was going to build a personalized super version of the Aegis circuit.  It will use E810F input tubes interstage transformer coupled to the triode strapped output stage.  Output transformer will also be custom wound by Dave with brass end bells.  I have some time to think it over, but trying to decide if I am going to go with a more old school approach with a passive filtered power supply and tube rectification, similar to the Aegis, or go the more complex route with voltage regulation.  Not sure yet.  I will likely order a custom mains transformer from Monolith Magnetics for the amp when the time comes to build it.

I also ordered a set of
LCR inductors from Dave for a future LCR phono I have designed.

Lastly, I am now focused on Aegis documentation.  I have the skeleton of the build document made, schematics and BOM are done, now just a matter of building it bit by bit, inserting instructions and photos along the way.  Still going to take some time, but it is fully underway.


----------



## Mr Trev

L0rdGwyn said:


> Just some random updates and thoughts.
> 
> I spent some time listening to the EL84 OTL against my 6528 OTL with the Atrium.  Obviously the 6528 OTL is better, it's the best OTL I have heard.  It has improved clarity and realism, but it also costs significantly more to build and is much more complex, whereas the EL84 OTL is very simple and uses new production available tubes and easy to acquire parts.  I still find it really enjoyable and it holds up well against the 6528 OTL.  Not certain of where it stands in the hierarchy of commercial OTLs, but my feeling is it will easily outperform all entry level options and likely competes in the more middle to high end space.  There are things I like about the sound without negative feedback and things I like with the 11dB of negative feedback.  Probably there is a happy medium somewhere in the middle.  I am going to table it for now, but at some point I will try the 100K pot to adjust the feedback to taste.
> 
> ...


Sounds like the EL84 OTL could make for a nice DIY kit <hint, hint>


----------



## LobalWarming

Mr Trev said:


> Sounds like the EL84 OTL could make for a nice DIY kit <hint, hint>


B-b-but, he's already released the full DIY tabletop kit - in artful chaos schematic form. Alligator clips probably not included.


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## bcowen

LobalWarming said:


> B-b-but, he's already released the full DIY tabletop kit - in artful chaos schematic form. *Alligator clips probably not included. *


LOL!  Or instructions.


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## DenverW

bcowen said:


> LOL!  Or instructions.


No need, just follow the pictures!


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## L0rdGwyn (Dec 4, 2022)

I did some more messing around this morning, I couldn't leave the EL84 OTL or my DAC project alone with work undone.

First, I wired up a 100K Alps pot in series with the 10K resistor in the feedback loop of the EL84 OTL.  As I said, doing this allows the feedback to be adjustable from around 2dB to 11dB.  The Alps is a logarithmic taper, a linear pot would be better for this purpose, but it's what I have around and it got the job done.

I did some listening while adjusting the feedback around.  Generally, with the feedback minimized, the sound is a little more harsh, but very dynamic and punchy with a large full stage.  Increasing the feedback to maximum smooths out the sound significantly, but the stage becomes smaller and the sound loses some of its dynamism.  I found that around 4-5dB of feedback was a nice medium between the two, nicely smoothed out but still with a large stage and maintaining that punch.  Listening was done with the Atrium.

So good to know for future reference.  Again, I don't know what I will do with this circuit, sure it could potentially be a DIY project, but let's just see how the first one goes before adding another.  With all of that done, I broke down the circuit for my next test.

I wanted to close the loop on what I am going to do with my PCM63 DAC output stage.  I was originally concerned I would not be able to use my stash of E182CC / 7044 tubes given the sections would be paralleled which would effectively double the Miller capacitance.  Fortunately, I made an error in my original calculations, fixing it revealed that the Miller capacitance is not problematic.

Just to be certain, after breaking down the EL84 OTL, I threw together a parallel section E182CC gain stage.  Since I was only interested in the high frequency performance, I loaded it with a 5K resistor.

Another masterpiece.  Nothing like soldering a 5K 50W resistor right to the tag board, pure art.



I used a 2.2K resistor on the I/V transformer secondary, fixed bias with two AA batteries in series for -3.3V on the grid and the cathodes grounded, output was cap coupled.

The high frequency performance is excellent, it is essentially that of the I/V transformer, meaning the I/V transformer is limiting bandwidth, not the tube stage, as it should be.

So with that figured out, I can move forward with my parallel E182CC output stage.  Schematically, it is going to look like this.



I/V resistor has been reduced to 1.5K, meaning a 15ohm reflected primary seen by the PCM63 Iout pins.  2x AA batteries between the I/V transformer secondary and ground for fixed bias.  Parallel E182CC which will have an effective plate resistance of around 1.2K.  Loading the E182CC will be a Sowter 9705 line output transformer.  The 9705 has a 40H primary and a 4:1 step down ratio.  Output impedance of the DAC should be somewhere around 170ohm in this configuration.  Other than the power supply, no capacitors in the signal path of the I/V stage, completely transformer coupled from the DAC to the output.

Sowter transformer are ordered, probably will be 2-3 months to receive them, so I will have to design the chassis in the meantime.  I plan to mount the Sowter transformers on top and also have the tubes projecting out of the top plate for easy swappability and tube feng shui.


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## triod750

L0rdGwyn said:


> and tube feng shui.


That's the way to do it. Show it to the world!


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## GumbyDammit223

bcowen said:


> Totem poles are cool.   🤣


Guess ya don't have to worry about that chassis getting too hot because of an embedded tube!


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## jgwtriode (Dec 11, 2022)

Oh so very nice to have such an extremely revealing backend on my setup.  Been fiddling with fine tuning my computer now that Qobuz seems to be stabilizing a lot more.
May have helped throwing in the DX engineering RF Filters on either end of the network cable.  For the $50 invested it may be the best value I have gotten out of that spending level.  Really improved things.

But I am finding now that I can drop the clock speed another 400mhz and cache and cpu voltages by anot 25mv or so.  This may not sound like a big deal but oh my you should hear how details start jumping out of the mix and the sound gains layers of dimension and sweetness.  It simultaneously becomes move involving and more relaxing and noticeably more emotional.   

I have read a few thing on Audiophile style and computer audio over the last few years about what this does.  No real scientific explanation other than it may lower thermal noise in the CPU.  You can see the core temps drop a degree or two in the software meter in Throttlestop.

I would like to drop it another 400mhz  which is as far as you can take it without complete loss of stability but I am not sure Qobuz can handle that.  Previously I could not run it any less than 2100 MHz and tonight it is working beautifully at 1700MHz at voltage offset of -245mV on cache and CPU.      And the Airmid and VC almost become a new beastie.  As almost perfectly neutrally sweetly balanced as the Airmid is with National Unions 6J5GT'sand 5998's it has become noticeably better from this change.  The staging, layer and focus become even more realistic, not just larger, more layered and more detailed.   Realize some of this was improvement in the jitter reduction software I use, that is a continuously upgraded thing with Orya on the Majiority Clean thread.  

But the real jump was the clock and voltage  drop.   Always so much fun to find refining the tweaks you have already been working on can be made even better.    This is all supporting bringing the signal directly from Qobuz.   Have not got it to sound this good using the BubbleUPN approach with Jplay Femto.  My stored stuff sounds incredibe through Jplay, but right now streaming is better  with all my stuff just assisting qobuz!

Happy listening,

jgwtriode


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## triod750

I have to thank you for making the difficult adjustment of a vinyl cartridge seem like a breeze...  
And I think we share the same passion but are very different in application...


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## L0rdGwyn

I've been drinking from the fire hose of knowledge at the new job over the past week, finally have a break to catch my breath, not much has happened in the DIY world since then obviously.

I did get my Sowter transformers for my PCM63 DAC, much faster than I anticipated, so that was a nice surprise.  Only thing left to do is finalize the chassis and order the remaining parts.



Since I have the new Degritter coming to me in a week or two, I am going to sell my Vinyl Stack, this is an accessory that let's you clean vinyl with an off-the-shelf ultrasonic cleaner, it's a great budget option and is now discontinued since the creator retired.  If anyone is interested, let me know and I'll come up with an asking price.


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## leftside

L0rdGwyn said:


> I've been drinking from the fire hose of knowledge at the new job over the past week, finally have a break to catch my breath, not much has happened in the DIY world since then obviously.
> 
> I did get my Sowter transformers for my PCM63 DAC, much faster than I anticipated, so that was a nice surprise.  Only thing left to do is finalize the chassis and order the remaining parts.
> 
> ...


Also show folks the US cleaner to use with this attachment. 

Guys, if you have vinyl and you've never done a US clean before, this is well worth it. Don't need to get fancy with exotic cleaning solutions. Just distilled water will give you great results with a US cleaner.


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## jgwtriode (Dec 15, 2022)

Indeed.  High purity distilled water,  a little bit of high purity isopropyl and some photoflow; as a wetting agent,  always worked for me back in the day.. I  visited  the local lab supplies store and would buy enough to make 5 gallons at a time.  Gave some away to friends also.  Don't remember the exact mix anymore but it worked just as well as any of the name brand cleaning fluids!  Used it with my nitty gritty, a zero stat, and a nitty gritty applicator! 

Those were very halcyon days back in the 80's and 90's.  My Linn setup was heaven, and then my system was stolen!  With insurance payoff I  setup a Well Tempered Turntable with the arm modded by a Ford Aerospace engineer, that came within a gnats whisker of a Wheaton Triplanar.  A Van Den Hul MC ONE.  Rewired the arm with silver litz soldered directly to Audioquest Lapis Cable .   That was a sweet setup that I still reminisce about.  Sold it to a friend who was one of my customers when I took the Digital plunge.

jgwtriode


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## bcowen

leftside said:


> Also show folks the US cleaner to use with this attachment.
> 
> Guys, if you have vinyl and you've never done a US clean before, this is well worth it. Don't need to get fancy with exotic cleaning solutions. Just distilled water will give you great results with a US cleaner.


2nd all of that.

I'll also add that the Vinyl Stack is very nicely made, and of far higher quality than many of the cheaper plastic devices out there.  I've been using mine for around 5 years now, and see no reason why it won't still be cleaning records 20 years from now (although I probably won't be ).


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## triod750

Whenever you are ready for it, myL0rd:


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## jgwtriode

Damn that is impressive to watch!


jgwtriode


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## triod750

Meet L0rdGwyn, 30 years from now:


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## jgwtriode

That is off the charts amazing...what a brilliant,  simple idea for a linear tracking arm and the bearing design....holy smokes!   Wow makes me wish I had gotten into machining back in the day.


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## bpiotrow13

triod750 said:


> Whenever you are ready for it, myL0rd:



Wow, impressive Is it You making it, Stefan?


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## triod750

I wish I had his work shop and tools...


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## LobalWarming

triod750 said:


> I wish I had his work shop and tools...and _*skillz ™ *_


FTFY…[ ® ™ ℠; © bcowen: 2021-2023.]


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## triod750

I wouldn't even dream about skills .


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## CJG888

I just love the way he has all the latest Festo pro equipment, but uses an old wax tin to mark out the corner radii. Could only be British!

Reminds me of how the TVR Chimaera allegedly got its indicators…


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## CJG888

Apparently, Peter Wheeler had finished the 1:1 polystyrene design model of the car, and was at a loss as to where to position the front indicators. No problem, as later his dog bit a piece out of the nose, and that’s where the indicator went…


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## L0rdGwyn

triod750 said:


> Whenever you are ready for it, myL0rd:




Nice!  I saw this video around a year ago, it's great work, but the aesthetic is not my taste.

I will be getting a Garrard 401 handed down to my down the road, so my turntable upgrade path is set.  It will need some restoration as well and a new plinth.


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## L0rdGwyn

I finished the chassis for my PCM63 DAC, order has been placed, foldout below.




Total chassis dimensions will be 18.25" x 13" x 3.25".  E182CC / 5687 tubes will protrude through the top plate, Sowter line output transformers will be back right mounted on top.  Simple front panel with an amber LED in the center, the chassis will be matte black.


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## L0rdGwyn

Anyone who has followed here knows I love triode-strapped high gm pentodes, here are some recent acquisitions.

Lot of Mullard E810F, untested and bought for around $125.  These will be used in transformer-coupled super Aegis build.




Lot of 30 NIB D3a, which will go in my LCR phono stage.



I traded some tubes with the wonderful @Tom-s , got some more pairs of Mullard E55L, again for my LCR phono stage.



And a nice set of E180F.  Unclear what I will do with these, but I'm sure they'll come in handy someday.  @Tom-s also sent me this cat.


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## whirlwind

Killer haul!


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## CJG888 (Jan 6, 2023)

L0rdGwyn said:


> Nice!  I saw this video around a year ago, it's great work, but the aesthetic is not my taste.
> 
> I will be getting a Garrard 401 handed down to my down the road, so my turntable upgrade path is set.  It will need some restoration as well and a new plinth.


Congratulations, and welcome to the Garrard rabbit hole. It goes deep…

I presume you will be doing your own strip-down and rebuild (remember to strip off all the cadmium plating!). I have found, after trying several alternatives, that the new rubber Classic Turntable Company idler wheel is the quietest by some margin.

There are really two schools of thought regarding plinths. There is the high mass approach (as shown in the video), and there is the Loricraft approach of a light, rigid top plate suspended on four sorbothane hemispheres on top of a solid wood frame. I tend to prefer the latter approach, finding that it preserves the typical Garrard “drive” and “pace”, albeit possibly at the expense of ultimate bass extension.

As far as arms are concerned, I would tend towards something vintage. I used to swear by my SME 3009 Series 2 Improved, these days I tend to spend most of my time listening to the Ortofon AS-212 / SPU combo.


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## CJG888

Of course, you could do something to support the Ukrainian economy and go for the Karmadon tonearm. It is quite a fascinating design, being basically a modern reinterpretation of the fluid-damped Gray unipivot. Sorely tempting, and just the thing for Denon 103s etc. Alas, it has a fixed headshell, so no G-shell SPUs!


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## CJG888

BTW, I’m currently moving into a new flat. First thing in is the Garrard!


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## triod750

L0rdGwyn said:


> Nice!  I saw this video around a year ago, it's great work, but the aesthetic is not my taste.
> 
> I will be getting a Garrard 401 handed down to my down the road, so my turntable upgrade path is set.  It will need some restoration as well and a new plinth.


Not to my taste either, in spite of not being clarity blue...


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## L0rdGwyn

CJG888 said:


> Congratulations, and welcome to the Garrard rabbit hole. It goes deep…
> 
> I presume you will be doing your own strip-down and rebuild (remember to strip off all the cadmium plating!). I have found, after trying several alternatives, that the new rubber Classic Turntable Company idler wheel is the quietest by some margin.
> 
> ...





CJG888 said:


> BTW, I’m currently moving into a new flat. First thing in is the Garrard!



Looks like a very nice place!  It will be some years likely until the 401 is handed down to me, I may come calling for your advice when that time comes


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## L0rdGwyn

Oh and this arrived today.



Man, so easy to use.  Sample size of one and I am totally sold.


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## Galapac

L0rdGwyn said:


> Oh and this arrived today.
> 
> 
> 
> Man, so easy to use.  Sample size of one and I am totally sold.


Is it much quieter?


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## L0rdGwyn

Galapac said:


> Is it much quieter?



Oh yeah, it's super quiet!  The drying fan is louder than the ultrasonic cleaner, and the fan power is adjustable.  Great product but it is expensive.


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