# The Christiansen "DG" 300B Amplifier Build Thread



## sceleratus

This post has been deleted because it contained the intellectual property of Neurochrome.


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## PinkLed

Excellent! Thanks for all the help by the way. 
	

	
	
		
		

		
			





 Adding this thread to my favorites, really looking forward to seeing it finished.


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## HK_sends

Subscribed!
   
  Cheers!
	

	
	
		
		

		
		
	


	



  -HK sends


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## OldSkool

Quote: 





hk_sends said:


> Subscribed!
> 
> Cheers!
> 
> ...


 

 Ditto! This should be interesting...


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## nelamvr6

Looking forward to a very interesting build.  Good luck!


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## HK_sends




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## rb2013

Really nice- good luck!


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## sceleratus

[size=16.0pt]Today I finished ordering all the components for the Damn Fine 300B with the exception of the 300B and 6N6P valves.  There are close to 150 components.  The enclosure will be custom made and it is in the design stage.[/size]
   
[size=16.0pt]I have created a Dropbox folder to put all the schematics, BOMs, Photos, and Specs.  I will update the post as I add material.  Presently there are:[/size]
   
[size=16.0pt]·      [/size][size=16.0pt]300B Schematic parts BOMs and Photos[/size]
[size=16.0pt]·      [/size][size=16.0pt]21st Century Maida Regulator Schematic, parts BOM, and photo[/size]
[size=16.0pt]·      [/size][size=16.0pt]6.3V and 5V Filament regulator Schematic, parts BOM and photo[/size]
[size=16.0pt]·      [/size][size=16.0pt]1950 Western Electric 300B valve specification[/size]
[size=16.0pt]·      [/size][size=16.0pt]Christensen Damn Good 300B Amplifier internal and external photos [/size]
[size=16.0pt]·      [/size][size=16.0pt]List of expenses.[/size]
   
[size=16.0pt]I will close with a photo of the interior.[/size]


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## sceleratus

[size=16.0pt]I finished the 21st Century Maida High Voltage Regulator while waiting for the 300B boards and components to arrive. I thought I’d show some of my soldering, I rate it ok, and provide some great soldering resources for those how don’t think they can solder.[/size]
   
[size=16.0pt]First off, if I can solder, you can solder.  Despite persistent hand tremors I got it done.  First watch the Dave Jones, EEVBLOG, 3-part video on Youtube.  They are a bit long but well worthwhile esp. if you want to solder surface mount components.  Dave has even more advanced videos as well.  Who knows, you might want to hot-rod your Lyr some day.[/size]
   
[size=16.0pt]Part 1 is about The Right Gear and Solder.  This is where I learned about 0.38mm 5 core solder. That alone made it worth watching.  I also picked up a Hakko FX-888 Solder station.  This is a can’t miss tool.  Heats up quick and amazing control and tip cleaning.  An articulated desk, arm magnifier and a small Panavise is also essential.  There is also great information on solder wick and solder suckers to correct your mistakes or remove components.  I was familiar with solder suckers but did not know about solder wick....Yes this is basic.[/size]
   
[size=16.0pt]Part 2 is basic thru-hole component soldering.  I picked up more things I didn’t know.   Prior to this, when I had to solder something, it was very hit and miss.  Cold joints.[/size]
   
[size=16.0pt]Part 3 is soldering SMD components.  I never believed I could solder a component that is 1.18mm wide.  [/size]
   
   

   

   
   
Same for LM22673 Ti switching regulators.
   

   
  They have 8 feet very close together.  Simply watch Dave’s video and you can do it.  [size=16pt]Some of my work isn’t the prettiest but I had no solder bridges.  Dave shows you how to fix them anyway.  [/size]
   
[size=16.0pt]Here’s the finished product (less heat sink):[/size]
   
   
   
   

   
Filament board.  Don't laugh,  it works..  The black spots are shadows off the shiny solder...




   
   

   
   
   
   
   
   
   
Here's what's on the way:


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## PinkLed

Looks great! I remember when I tried to custom make a PCB with ferric chloride, copper clad, and a sharpie. It was fun but looked very sloppy. Btw I have the same caliper. That thing is a great tool.


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## sceleratus

Quote: 





pinkled said:


> Looks great! I remember when I tried to custom make a PCB with ferric chloride, copper clad, and a sharpie. It was fun but looked very sloppy. Btw I have the same caliper. That thing is a great tool.


 
  Thanks,
  I'll be making a PCB for the valve tester.  It's a parallel project, but most of my attention is on the 300B.   There are some new etching techniques that appear to be better than ferric chloride.  The name of the process escapes me now.
   
  I'm using DipTrace to create the schematic (for the tester).  It produces the board trace from the schematic automatically.  I don't know that much about the circuits so I'm re-creating a few in LTspice to simulate and try to understand their function.  Again, this is more like a kit project.
   
  I could not live without a set of calipers.  I have an inexpensive set that has a 1/64th fraction table.  I use those a lot.


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## sceleratus

I'm looking for wisdom and recommendations for 300B and 6N6P valves.
If you have any experience with these I love to read about it.


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## sceleratus

[size=16.0pt]I was not going to write about my plans for the enclosure but I can’t keep a secret.  I’m really stoked and I think it will look interesting.[/size]
   
[size=16.0pt]The enclosure will be wood, have an antique style, and be made from walnut, mahogany, or rosewood.  Think “Old Cigar Humidor”.  I have a good friend that has been making custom kitchen cabinets for 30 years.  [/size]
   
[size=16.0pt]I will plate the top panel, either nickel or copper.  For the controls I did some shopping on eBay …[/size]


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## sceleratus

Boards and components arrived today.  I inventoried all the components and started to work on the driver board.
8 components mounted, 65 to go.


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## Fearless1

Quote: 





sceleratus said:


> I'm looking for wisdom and recommendations for 300B and 6N6P valves.
> If you have any experience with these I love to read about it.


 
  "Western Electric=holy grail of the 300B" according to my friend who has a Grant FidelityA535 amp.


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## sceleratus

Western Electric 300B 
The one. and only, $1,000 a pair.
Grail extra.
Thanks Fearless1
   
I have most of the 1/4 watt resisters populated.  I found an ordering error.  I ordered a 200R instead of a 220R.
At least I caught it.  This is not a cheap project, I hope it sounds like A Damn Good AMP when it's done.


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## Fearless1

Quote: 





sceleratus said:


> Western Electric 300B
> The one. and only, $1,000 a pair.
> Grail extra.
> Thanks Fearless1


 
   
  I would guess that the Full Music 300B is a decent tube as well, I like the tone of the their tubes and they are about 800 dollars cheaper then the Western Electric. (sorry to disrupt this thread, I find it fascinating!)


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## sceleratus

Quote: 





fearless1 said:


> I would guess that the Full Music 300B is a decent tube as well, I like the tone of the their tubes and they are about 800 dollars cheaper then the Western Electric. (sorry to disrupt this thread, I find it fascinating!)


 
No disruption at all.
   
I want to get all the 300B and 6N6P input I can get before I start ordering.
   
  [size=small]Any other input or suggestions are welcome.[/size]


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## sceleratus

[size=16.0pt]The driver board assembly progressed nicely.  I had to stop soldering until the correct R23 and R3 resistors arrive.  If I go further, I won’t be able to get to them. [/size]
   
[size=16.0pt]I also ordered the heat sink assembly kit for the MOSFETS.  You can see below that the heat sinks are attached but the MOSFETS are not soldered in.  When the kit arrives, I will attach the MOSFET to the heat sink and solder it to the board at the correct height.[/size]
   
[size=16.0pt]The mounting kit contains a shoulder washer, screw, nut, and a Mica insulating pad.[/size]
   
[size=16.0pt]I had a couple challenges today.  I put the 100K trimmer pots on the wrong side of the board.  I discovered this while searching for the U1 and U2 pads. I discovered both components go on the bottom of the board.  Tom neglected to put that detail in the instructions.[/size]
   
[size=16.0pt]The reason is simple.  The back side of the board faces up.  This is the side with the valve sockets.  One will want access to the trimmers for biasing.[/size]
   
[size=16.0pt]The problem was easily corrected by my solder sucker.[/size]


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## sceleratus

[size=16.0pt]Worked on a rough panel layout.  I do not have the dimensions for the output transformers because, according to Jack at Electra-Print, all the housings are custom built to the transformer specs. Wow. Thus I used the ClassicTone specifications for the output transformers.  FYI: Jack said he could wind them with silver wire but it would be about $900 for each transformer.  Wow2 [/size]
   
[size=16.0pt]When I have all the correct specifications / dimensions, I will update the layout and print an actual size print with hole centers. I will glue it to the sheet metal and take it to the drill press and see how accurate I can get it.  I am going to experiment with nickel-plating for the final finish.  I'll try a few small items first.[/size]


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## PinkLed

This thread will be the rebirth of DIY on head fi!


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## sceleratus

Quote: 





pinkled said:


> This thread will be the rebirth of DIY on head fi!


 
  gosh.
   
  Just added the DYI Nickel Plating video.


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## sceleratus

This is Jack from Electra-Fidelity.
Besides making transformers, he also make $150,000 amps.
He has  Littler ones too.
   
   
EDIT:
   
Here's a handy tip from Jack emailed me:
   
  [size=medium]..... Also, do you know about keeping the power trans and outputs out of coupling?[/size]
  [size=medium]Keep both outputs as far as you can from the power trans and the power trans[/size][size=medium][/size]
 [size=medium]should be 90 degrees, exactly in core mass centers of all transformers. Like[/size][size=medium][/size]
 [size=medium]a "T", top is one core, vertical line is other core.  If you do not do this,[/size][size=medium][/size]
 [size=medium]there will be an induced hum from the power to both output primaries, you[/size][size=medium][/size]
 [size=medium]will never get rid of it.[/size]
   
  [size=medium]I did not know that.[/size]


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## sceleratus

I'm working on the Power Board today and I thought I take a couple of annotated photos to show diode and capacitor placement on the PCB.
   
If you've built boards before ignore this post....
However, if you do have any suggestions, (other than give up, it's going to be a moulton mound of smoldering rubble),  Please post them.
   
Capacitors and Diodes:


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## sceleratus

Well they arrived.
   
Power Transformer: 14 pounds
Output Transformers: 9 pounds each
   
Lyr: 7 pounds
   
I hope sound is by the pound


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## HK_sends

So much for the "portable" option! 
	

	
	
		
		

		
		
	


	



   
  Cheers!
	

	
	
		
		

		
		
	


	



  -HK sends


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## sceleratus

Quote: 





hk_sends said:


> So much for the "portable" option!
> 
> 
> 
> ...


 
  It'll be a manly-man headphone amp.
  Not of that dainty IEM cr..


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## sceleratus

[size=16.0pt]All components have been soldered to the boards with the exception of 3 bridge rectifiers on the PSU Board.  I need to fabricate a heat sink before they can be soldered on.  I have to drill and tap the heat sink for the Maida regulator too.[/size]
   
[size=16.0pt]I have all the other components with the exception of the Volume POT (ordered) and the 300B and 6N6P valves (not ordered).  I’ve been holding off ordering them, but I guess it’s time.[/size]
   
[size=16.0pt]The next step is to lay everything out on a piece of plywood, wire it up and listen for pleasant music.  If it passes that test I will work on fabricating the panel and enclosure.[/size]
   
[size=16.0pt]I would estimate a week until Alpha Testing.[/size]
   
[size=16.0pt]Driver Board:[/size]
   

   
Driver Board Valve BIAS pots
Holes for 300B sockets
9 pin cluster each side of trim pots for 6N6P sockets.
   

   
   

   
   
PSU Board:
   

   

   
Maida High Voltage Regulator:
   

   
   
5V and 6.3V Filament Regulator:


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## sceleratus

[size=16.0pt]This is the new panel layout with the in-line transformer configuration.  Panel dimensions are 19” wide 15.75” deep.  The boards are suspended below the panel by stand-off’s.[/size]


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## HK_sends

It looks to be shaping up nicely!
   




   
  Cheers!
	

	
	
		
		

		
		
	


	



  -HK sends


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## OldSkool

32 lbs, just in transformers? 
	

	
	
		
		

		
			




   
  You might think about reinforcing your desk.


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## sceleratus

I am really phreak'd out about turning this beast on....





  Indeed.
   
I need to get a set of el Cheapo cans for the testing.  I'm not going to plug in my LCD2's.   This thing puts out a bit more power than the Lyr.  10W, 60ohm's...  Perhaps I should smoke Beats with it.


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## HPiper

From all I see you are doing an outstanding job on this build. Really very well done. I have built some amps before but nothing even close to this.


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## sceleratus

Quote: 





hpiper said:


> From all I see you are doing an outstanding job on this build. Really very well done. I have built some amps before but nothing even close to this.


 
Thanks !
   
I have tested the filament boards and they work great.  That's a start.
   
I purchased Neutrik RCA and XLR jacks.
   


   
The volume pot will be the same model in the Lyr.
   

   
The power receptacle has built in filtering.
    

   
I'm using 14 ga. stranded wire for the inter-connects.

   
[size=13pt]Speaking of wire.  Whilst configuring the board-to-board, board to transformer, transformer to jack and transformer to volume pot inter-connects, it dawned on me that it’s all 14 – 18 gauge wire.  So.. what’s the point of fancy silver Litz headphone cables if the last 6 inches to the output transformer is vanilla, 14 gauge, stranded copper wire?  That’s what the leads are that come out of the transformers.  (see black [/size]grommets)[size=13pt]  [/size]
   
[size=13.0pt]Granted, a design like the Schiit Lyr has everything mounted on the PCB.  Transformers, volume pot, and jacks.  There is no wire inside the Lyr enclosure.  But that’s not the case with designs that have external transformers like this one.  Perhaps that’s where the silver wire wound transformers come in.  Just say’n.[/size]
   
   

   
   
I contacted Brent Jesse and I will order a set of matched JJ 300B valves.
He has a set of WE co's for $3,000 each. 



 Those along with  Jack's silver wire wound output transformers will have to wait... and wait.
   
The 6N6P's are quite affordable. (Yea !)  I can also swap resistors and use ECC99's.  Down the road, I'll ask Tom if he can come up with a board mod to support ECC88's style receiving valves.


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## Fearless1

Quote: 





sceleratus said:


> He has a set of WE co's for $3,000 each.


 
  Good Lord,  you could buy a used Hyundai at that price. 
   
  Look into the Full Music tubes as well my friend says they are great budget tubes.


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## sceleratus

Found some 6N6P's
Straight from a Soviet missile silo.
8 NOS valves.  $22
We will see if I got what I paid for.  All I want is 2 good ones.
   
Here's the volume design....  I'm stoked by it.


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## sceleratus

[size=14.0pt]300B Status:[/size]
   
[size=14.0pt]All the boards are built.[/size]
   
[size=14.0pt]6.3V and 5V filament boards have been tested.[/size]
[size=14.0pt]Those and the Maida board are the hardest because they have surface mount components.  The PSU and Driver board are largely thru-hole. Today I fab’d a small copper heat sink for the PSU board.[/size]
   
[size=14.0pt]I am working on attaching the large aluminum heat sink to the high voltage Maida regulator.  It will stick out the back of the enclosure.  This will be though for me because there are 2 sets of 4 hole patterns that have to be precisely drilled for mounting.  My personal best for holes in a row is 3.[/size]
   
[size=14.0pt]I picked up a .09" 24" x 24" piece of silicon bronze for the top panel. (Nickel plate was too difficult)  Next week I will drop it off to be water cut again because of my lack of precise drilling.[/size]
   
[size=14.0pt]The following weekend I will affix the boards to the top panel using stand-offs and make the wiring harness.  Then testing without the cabinet....[/size]
   
[size=14.0pt]Example heat sink:[/size]
[size=14.0pt]I need to drill and tap holes on the perimeter of the HS for mounting.4 [/size]
   
   

   
   

   
   
**6N6P update:
Remember the great deal I got for 8 6N6P Valves ?
I forgot one small thing.  They are in Russia....
I don't think that they will be here next week.... maybe next month.
   
So the great deal isn't such a great deal because I HAVE TO BUY 2 MORE !!!!!


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## sceleratus

[size=16.0pt]Design Note:[/size]
   
[size=16.0pt]For those folks that troll the “Schiit Lyr, Tube Rolling Thread”, there was a discussion 50 pages or so back about the lack of a power switch in the front of a Lyr.  And, how it is inconvenient to have to reach back and flip the power toggle.[/size]
   
[size=16.0pt]Why did Schiit do this? One reason bantered about was running high voltage mains across the board to the front.  Well fear not!  The Damn Good 300B has a power switch in the front, and high voltage doesn’t go from front to back. How?[/size]
   
[size=16.0pt]The DG 300B will employ a SS DPST Relay.  A 3 VDC contact closure will switch the mains.  Front Switch, Low Voltage.  Since it’s solid state relay there are no coil magnetics to worry about either.[/size]


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## sceleratus

[size=16.0pt]Today I mounted the Maida regulator to the heat sink.  It took 7 holes to get 5.  In my calculations for a 3mm tap I forgot to take into consideration the run-out on my drill press.  That’s about 1mm, or Kansas.  I never learn.[/size]
   
[size=16.0pt]I still have to drill and tap the perimeter mounting holes but they are more forgiving.  Still, I’ve had enough with the drill press for one day.  The photo 2 posts up is an example.  This is mine:[/size]


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## sceleratus

Met with my cabinet friend today.
  The traditional recessed panel, humidor in the study room "look" is out.  Replaced with a very different concept, not the safest choice....  It will be love it or hate it.... I'm stoked.
  I'm keeping it under wraps until make or break.


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## sceleratus

[size=16.0pt]There’s only one vote cast on the poll.[/size]
[size=16.0pt]Come On![/size]
   
[size=16.0pt]I’m wiring the boards for the smoke test tomorrow. [/size]
[size=16.0pt]I don’t have the valves yet, but I’m going to light it up anyway.[/size]


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## HPiper

Considering all the money, time and effort you spent on this thing it had better work!! If it were me I'd probably have a break down if it blew up in front of me.


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## PinkLed

Good luck man. Never give up. Looks like a champ!


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## sceleratus

I forgot to order fuses.


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## sceleratus

Everything is here.
  Fuses, valves, sockets.
   
  I've been wiring up the headphone jack, the input jacks, and the mains.
  Those will be complete in 20 minutes.  I simple have to tin 5 wires and secure them.
   
  I wasn't expecting the 6N6P's (from Russia) the 300B's (from Brent)  and the 300B sockets from, where else,... China.
   
  It will take me a bit to terminate the sockets.
  Then triple check,
  Then clear the desk.
  And.


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## sceleratus

plugged it in.
  no tubes, no smoke....  that's the good part....
   
  put in a pair of 6N6P's and the 6.3V reg smoked.
  investigating....
   
  at the moment, Vegas likes "C".


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## sceleratus

Worked on tracing the source of the curling smoke.
   
  I did not properly affix the IC heat sink pad to the board.  It actually continued to work for a while so I could track it down.  No valves, no load, no smoke, no heat.  Add two 6N6P's  lots of heat in a hurry.
   
  It could tolerate one 6N6P for a while.... but.... my thermocouple hit 170F before I pulled the plug.  Tomorrow I'm making a new one....


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## sceleratus

[size=16.0pt]Good news today.[/size]
[size=16.0pt]I made another 6.3V filament regulator and it works like a champ.  Measured 40 C after 45 minutes.  Well within specs.  The 6N6P’s got quite hot 105 C / 115 C.  Their spec sheet says they are good to 200 C, but that’s hot.  All voltages are spot on, plate, grid, filaments for both the 300B's and the 6N6P's.  I have not tested the 300B's because........[/size]
   
[size=16.0pt]Bad news today.[/size]
[size=16.0pt]I took the 300B’s out of the box and noticed one was cracked. Never applied power to them.  I am very thankful I caught it because if it went “poof” it would be on me.  I hope Brent takes care of it.  I was hoping to hear music…  oops, shouldn’t have mentioned music.[/size]
   
[size=16.0pt]In the photo you will notice a volume control, RCA inputs, and a ¼” jack for headphones.  Wow, just like a real amp.  Stuff is bunched together for the photo.  I also need to correct the lean in the 9 pin sockets.... not easy.[/size]
   
   
   
   

   
  Crack in the glass


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## sceleratus

[size=16.0pt]I had nothing to do today due to a lack of functioning 300B’s so I did a couple things to keep me busy.[/size]
   
[size=16.0pt]As I wrote in my previous post one of the 6N6P’s was 10*° *C warmer than the other.  It was also noticeably brighter.  I decided to measure the current flow to the heaters.  The Russian spec is 750 mA [/size][size=16pt]± 70 mA.[/size]
   
[size=16pt]Sure enough, as one would expect, the valve in question drew considerably more current.[/size]
   
[size=16.0pt]Valve A   758 mA   Bingo[/size]
[size=16.0pt]Valve B   913 mA  ( 0.093 mA beyond the 820 mA limit )[/size]
[size=16.0pt]If I really knew my ***t, I’d reconcile 0.093 mA to [/size][size=16.0pt]10*° *C.[/size]
   
[size=16.0pt]I sent the measurements to Tom and I actually understood most of his response.  Tom is off the charts smart.  As in Masters in EE, Sr. circuit design engineer for TI.  He also happens to love vacuum tubes.  I usually only understand snippets of his explanations.[/size]
   
[size=16.0pt]Anyway he wasn’t too concerned.   Heater current is not a component used to match a pair of valves like gm and plate curves are.  So The Tube Store did indeed send me a matched pair of 6N6P’s.     Nonetheless they are sending a replacement.[/size]
   
[size=16.0pt]Lastly I tested my mains power switch.  (my design, not Tom’s) [/size]
   
   

   
I want to add that Tom's consulting is not free.  I'm a capitalist and I believe you get what you pay for.  He's got better things to do with his free time than tutor a numbskull for nothing.   His help and patience has been invaluable in both completing this project and understanding "some" electronics theory.  Just setting expectations if you embark on your own 300B.
   
That said,  the Damn Thing goes together pretty good.  Order the right parts and watch Dave Jones 3 part soldering tutorial on EEVBLOG and you are banked.
   
One very cool thing..... Tom's looking to see if the DG 300B can be modified to support my beloved ECC88's and variants.


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## eimis

Wow this project isn't cheap. Good luck. I'm curious on how it will turn out..


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## sceleratus

Quote: 





eimis said:


> Wow this project isn't cheap. Good luck. I'm curious on how it will turn out..


 
Yo, eimis, for sure.
It's a runaway locomotive.  I blink and it's another $25
Then there's the transformers and 300B valves.  I stopped counting the Bengies.
Just don't want to know.
   
I gained a real appreciation for companies that offer a configuration like this for what I used to think is an outrageous price.
Holy Mac Daddy, and I have no idea if it will sound as good as my Schiit Lyr.  I'm trying to rationalize it and prepare myself for the worst.
I came up with an analogy of your 8 year old child in a music recital.  She really sounds like crap, but you think it's awesome.


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## sceleratus

[size=16.0pt]I promised to itemize the project costs.  Here it is although there has to be another couple hundred in shipping or something else.  Like a new DMM and Solder Station.  Etc. etc. etc.  Those really don’t count.[/size]
   
[size=16.0pt]If I really like the sound that comes out during “desktop” testing I will have the cabinet done up right.  I have some very cool species of wood picked out.  That will be a big chunk.[/size]


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## randytsuch

Since your source is single ended (I think), wondering why you went with input tranny's instead of input coupling caps?
   
  And I know the designed said he used Solens for the interstage cap, but I used them a long time ago, and was not that impressed at the time.  I think you might want to try something else there in the future,  what's a few more $ at this point .
   
  BTW, I have a Lyr too, but matched with HE500's.  I am currently working on a new source project, but I wanted to try a DHT amp in the near future, thanks for sharing your project.
   
  Randy


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## sceleratus

Quote: 





randytsuch said:


> Since your source is single ended (I think), wondering why you went with input tranny's instead of input coupling caps?
> 
> And I know the designed said he used Solens for the interstage cap, but I used them a long time ago, and was not that impressed at the time.  I think you might want to try something else there in the future,  what's a few more $ at this point .
> 
> ...


 
   
Hi Randy,
   
For now, I'm just an idiot with a soldering iron.  I am following a design from Tom Christiansen.    Here is the link:  Tom Christiansen's web site.  Tom posts all the schematics and components including DigiKey part numbers.  He only sells the boards.  Here's some text from his site that may answer your question.
   
   
"The driver architecture is as follows: Input transformer (TR1) → Gain stage (TU1B) → Current driver (TU1A) → Output stage (TU2).
The input transformer, TR1, provides conversion from the differential input to the single ended topology of the rest of the amplifier.
For those not needing differential input, the circuit has provisions for placing an input capacitor instead of the transformer."
   
Here is is diyAudio thread where he discusses the design more.
   
   
EDIT:
   
Are you going to the LA meet?  Or does LA stand for Louisiana? 
   
  [size=small]EDIT 2:[/size]
  [size=small]I looked at Mundorf but they would not fit.  That was the only component I considered changing.  Otherwise I followed the BOM to the letter.[/size]


----------



## randytsuch

From the same website, in the 300B driver section
  The input transformer, TR1, provides conversion from the differential input to the single ended topology of the rest of the amplifier. For those not needing differential input, the circuit has provisions for placing an input capacitor instead of the transformer.
   
  LA stands for Los Angeles, live in Brentwood, work by LAX to be more exact.
   
  When/where is the LA meet?
   
  Randy


----------



## randytsuch

Nevermind the LA meet question, I saw the thread about it.


----------



## sceleratus

Quote: 





randytsuch said:


> From the same website, in the 300B driver section
> The input transformer, TR1, provides conversion from the differential input to the single ended topology of the rest of the amplifier. For those not needing differential input, the circuit has provisions for placing an input capacitor instead of the transformer.
> 
> LA stands for Los Angeles, live in Brentwood, work by LAX to be more exact.
> ...


 
Not to be snarky.....  but I put the exact same passage in my post.
   
That said, upon re-reading your question, Tom's explanation, and Wikipedia,  I have learned a bit.  More than anything this is a learning exercise for me.
Upon completion, I want to hit the books more and the soldering iron less.
Easier said than done due to learning issues.
   
I'll bring the 300B to the meet if it is worthy.


----------



## sceleratus

More on my capacitor choice.
   
Along the way I've read that caps do make a difference and discovered that there are some highly touted upgrades available.
As I said, I thought the Mundorf's looked cool but they are huge.  I then found a capacitor shootout thread (someplace)
and, as I recall, the Solen's were rated very high.  Hence, I stopped looking at other caps.
   
When the dust settles I may experiment a bit.  At the moment, I'm simply hoping to hear music.


----------



## randytsuch

Quote: 





sceleratus said:


> Not to be snarky.....  but I put the exact same passage in my post.
> 
> That said, upon re-reading your question, Tom's explanation, and Wikipedia,  I have learned a bit.  More than anything this is a learning exercise for me.
> Upon completion, I want to hit the books more and the soldering iron less.
> ...


 
   
   
  I guess I should actually read a post before replying to it. 
	

	
	
		
		

		
		
	


	



   
  It would be cool if you could bring your 300B, if it's ready.  
  If you do, would you mind if I brought my source and my HE500's to try with it?  I could also bring my K1000's.  5 watts should drive them.
   
  I don't know what the rules are, but I am guessing this won't violate the meet rules (or I won't do it if it does).
   
  Here is a REALLY long group buy thread for my current source
http://www.diyaudio.com/forums/quanghao-audio-design/228755-dac-end-r-es9018-full-assembled-board.html
   
  I use USB only for the DAC input, with the  Amanero module.  I am still working on the output stage, going to try a transformer output.
  And you have to promise not to laugh at it, it is in a case that has been reworked many times, so there are holes all over the place.
   
  Randy


----------



## randytsuch

Some capacitor reading
http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html
   
  In the beginning, he also linked to other capacitor comparisons.
   
  And I agree to get sound from your amp first before you worry about things like the best cap to use.  It's just in looking at the rest of the design and components used, IMHO a solen cap is the weakest link .
   
  Randy


----------



## sceleratus

Quote: 





randytsuch said:


> Some capacitor reading
> http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html
> 
> In the beginning, he also linked to other capacitor comparisons.
> ...


 
I'm in learning mode, and questions like yours are a great way to learn.  The whole "single ended" Class A thing is very fuzzy to me.
Tom recommended a couple of books and I'm slogging thru them.  I pick them up from time to time.  But I have retention issues.
Morgan Jones "Valve Amplifiers" and 
[size=1.7em] Designing Power Supplies for Tube Amplifiers by Merlin Blencowe[/size]   
Randy,
Please bring your source and anything else you would like.
That's the fun part,  tearing stuff apart and connecting cables.  Listening to different stuff.
I am determined to be ready for the meet but I will post if the 300B won't make it.
   
Glad I just looked up at your thread.  
My Bifrost is SPIDIF only.  I posted on the meet thread if I should upgrade to USB and if folks will be walking around with USB sources.
My plan is to bring
The Beast
The Lyr and some old glass
2 x Bifrost, one with Uber, both SPDIF
2 x LCD2's  Rev1 and Rev2
MacBook Pro and Mac Mini
   
  [size=small]General question.[/size]
  [size=small]I use the Schiit "PYST" interconnect cables for Lyr to Bifrost.[/size]
  [size=small]They are too short for The Beast.[/size]
  [size=small]I don't want to spend stupid money on interconnects.[/size]
  [size=small]What is a good 3 foot value RCA interconnect cable?[/size]
   
After all this thread and posting, it had better sound good.
   
EDIT
Getting ahead of myself on Caps.
I can always order another Driver Board for experimentation.  The components are not that expensive.
Thanks for the link.  I bookmarked it.
   
   
[size=1.7em]  [/size]


----------



## randytsuch

I mostly build my own IC's, based on a recipe Stan Warren gave me years ago, I won't pay megabucks for IC's.
   
  Whats "the Beast"?
   
  How do you generate the SPDIF signal to your dac?
   
  My dac will take SPDIF, if I add a connector to it, but as of now it's USB only.
   
  Randy


----------



## sceleratus

Quote: 





randytsuch said:


> I mostly build my own IC's, based on a recipe Stan Warren gave me years ago, I won't pay megabucks for IC's.
> 
> Whats "the Beast"?
> 
> ...


 
I call The Christiansen "Damn Good 300B" the beast.
The transformers alone are over 30 pounds.
Add a .090 metal top plate and wood enclosure and it's one tube shy of 50 lbs.
I think the enclosure will be Birdseye Maple.
   
OK.  I was incorrect. Vague at best.   SPDIF is an interconnect format and the delivery can be either optical or coax.
In the case of Macs, it's optical Toslink.  If you have a source with [size=small]toslink, you can plug into my Bifrost.[/size]
   
The headphone jack on a Mac doubles as an optical port.  Plug in a toslink cable with a little adapter and you are digital 96K Hz.  A quick setting in the "Audio Midi Setup" might be needed.


----------



## randytsuch

Maybe it's me, but I think of SPDIF as copper wires using RCA or  BNC backs.  
  For optical, I call it toslink.
   
  For my DAC to support optical/toslink, I just need to add one part, I will try to do that before the meet.
   
  BTW, my dac is pretty big, bigger than you probably expect.  Case is 16 x 16 x 5.  I bought this case for a squeezebox project a long time ago, and wanted room to experiment.
   
  Sorry if I am taking your thread off topic, but since you are waiting for tubes anyway 
   
  Randy


----------



## sceleratus

All voltages at all test point are in spec. I set the initial bias on the 300Bs. 
It's time to cable the Bifrost and plug in the LCD2s


----------



## sceleratus

IT WORKS !!!!!
 Music.
 Beautiful music.
  
 My benchmark track  [size=small]Zeppelin, "Babe I'm Gonna Leave You"[/size]
 [size=small]Is amazing.  Better than I could have expected.[/size]
  
 So much different than my Schiit Lyr.
 Rich.
 Mids in Spades.
  
 And these valves have only been cooked for and hour.
  
 I have a slight static,  at all volume levels.  Almost like listening to vinyl.
 Not unexpected because all the boards are bunched together.


----------



## randytsuch

Cool  
	

	
	
		
		

		
			




   
  Really happy for you.  It's great when you build something, and it works.  On the flip side, when it doesn't work it REALLY SUCKS.
   
  Now I really looking forward to the meet, and hearing your amp.

 Randy


----------



## sceleratus

Randy,
   
  It's a beast.   Base and Mids by the truck load


----------



## sceleratus

I was soooo phreaked out just before I flipped the switch.
  What a rush.
   
  Still in shock that it works and sounds good....
  WHo woulda thunk ???


----------



## sceleratus




----------



## holland

That's a nice amp.  I can't wait to see the enclosure.  I'm tempted to tackle a 300B build as well, but with a 6H30 or a 6SN7 input stage instead of the 6N6P.  I haven't fully read this thread, particularly the output transformers, but will when I have the time.  What z out are you going to get?  Will you have a high/low z switch of some sort?


----------



## sceleratus

Quote: 





holland said:


> That's a nice amp.  I can't wait to see the enclosure.  I'm tempted to tackle a 300B build as well, but with a 6H30 or a 6SN7 input stage instead of the 6N6P.  I haven't fully read this thread, particularly the output transformers, but will when I have the time.  What z out are you going to get?  Will you have a high/low z switch of some sort?


 
Thank you.
Not too bad for an idiot with a soldering iron....  Here's the designer's site.
   
It will support ECC99 and 12BH7A as well as the 6N6P.   Tom has finished a mod for me to support 6DJ8 / ECC88's  I have a nice collection of old glass for my Lyr.
   
The OT were made to: SK@100mA to 60Ω  10 Watts   -1Db 27Hz to 35KHz  Period.  No switch, just for my LCD2's 
   
I still can't believe I'm listening to music.


----------



## DefQon

Nice stuff there. Man was hoping it would be fairly cheap, well it is considering transformers/chokes, tubes and a chassis is always the most expensive parts of diy tube amp's if you want quality first. You've just given me more motivation to get my p-p 6p14 tube amp restored soon, considering I've just ditched the PCB and going full point-to-point wiring. Playing with 300v sounds fun .


----------



## sceleratus

Ya...  It started out, "great $165 for the boards !"
  Right.
   
  Bruce Springsteen  "It's a Death Trap, a Suicide Rap...."    6" before the volume control.
   
  I had this habit of dropping my pinky when holding the DMM probes....  I took two times to break this habit.


----------



## sceleratus

Quote: 





defqon said:


> Nice stuff there. Man was hoping it would be fairly cheap, well it is considering transformers/chokes, tubes and a chassis is always the most expensive parts of diy tube amp's if you want quality first. You've just given me more motivation to get my p-p 6p14 tube amp restored soon, considering I've just ditched the PCB and going full point-to-point wiring. Playing with 300v sounds fun .


 
  You should look at Tom's voltage regulators.
  21st Century Maida for high voltage and 6.3v and 5v filament regulators.
  They're priced nice.  Cool to build... get to do some SMD.
   
  Also,  all the schematics are on his web site if you want to adapt any to you project.


----------



## DefQon

Quote: 





sceleratus said:


> Cool to build... get to do some SMD.


 
  Love your enthusiasm for shown for SMD soldering 
	

	
	
		
		

		
			




   
  That said, I don't have much experience with SMD soldering (done a few one off repairs on mobile phones but we also had a reflow/re-work station) and I don't have a very steady hand nor a fine sized soldering tip.


----------



## sceleratus

Quote: 





defqon said:


> Love your enthusiasm for shown for SMD soldering
> 
> 
> 
> ...


 
  This was the first time I've ever done SMD.  Heck, very little soldering of any kind at all.
  And I have the shakes due to my meds.
   
  Just watch the 3 part soldering tutorial on Dave Jones EEVBLOG.  Follow his instructions.... piece of cake.
  All the SMD components are re-flow using an iron.  1) small solder pillow 2)Next, hold the component in place with tweezers 3) Heat component and pad....the tricky part... 4)Let go of the component.  5) solder the other end...6 ) go back to clean up the first.
  The components are so cheap get 4-5 extras.   One more thing.  Don't Sneeze.
   
  The one thing that made it possible for an old guy like me is a big round magnifier on an arm that lights up.
  Get that and you are banked.


----------



## randytsuch

For SMD, I have a magnifying glass that I can wear like a visor, and it works pretty well.  You need some kind of magnification to work with SMD stuff.
   
  But, as SMD goes, these boards don't look too bad, might be a good intro to SMD.  Fine pitch IC's is where it can get challenging.
   
  Pretty sure I am going to end up building a 300B amp too, although mine may have a different configuration, I started looking at the different parts of the circuit, to try to decide what to do for each.
   
  Randy


----------



## sceleratus

Modifications necessary to support ECC88 are finished.
Upgrade to Jupiter Beeswax caps is complete. 
Starting to work on longer cables.


----------



## randytsuch

I have heard good things about Jupiter caps so hopefully they sound good.
   
  One comment on wiring, when you run two wires together, where one wire is either a voltage or a signal, and the other wire is ground (or return for that voltage/signal), you should twist the two wires together for as much of the run as possible.
   
  For example, the wires from the regulators to the driver board should be "twisted pairs".
   
  Randy


----------



## holland

Thanks for the update and the link.  I'm trying not to build up too much interest, though it may be too late for that.   Your thread brought me out of a 2 year hiatus from Head-Fi.  I'm enjoying my current amps and don't have a need to build a 300B as I don't have planars, although it would be nice to have "moar power!".  I would probably design and build my own circuit, if I were going to do a 300B build, or at least something on the market with different input tubes.  Maybe something along the lines of a WA-5 with 6SN7 and 300B, or a 6SL7 and 300B variation.
   
  Since you did the mod for 6DJ8, are you able to "toggle" back easily?  Also, if you did 6DJ8, you should be able to tweak it to support 6H30 as well.  One of my amps is a Bijou, and I'm using that with 6H30 input and 6N6P drivers.  I like the 6H30 over 6DJ8/6922/ECC88 variants I've tried in the past.  You don't have to, just that I would.   It's less "tuby" than others I've tried.  My 6H30 are Sovteks.  Not the most "hifi", but I like em, so that's what I use.
   
  I don't know if you put a fuse on the AC side, but please do, use a real tight tolerance while you're building.  This way it'll trip if anything shorts.  Be wary around caps, very wary.  Drain them properly with a power resister, before you touch them.
   
  What layout are you planning on, and hopefully you won't get any magnetic coupling of the transformers.  It looks like you have it oriented properly, if you're not aware.  You may still get interference though, try it with some sensitive headphones and see if you get hum and how far apart you need to move them.  Hopefully you'll be hum free when all is said and done.  Also, if you've never built an amp, look into a star ground scheme.  I also like to separate chassis ground (earth) and signal ground with a ground loop breaker.  Personally, I use a ground bus for signal (heavy gauge copper wire, I think I use 8ga), then tie it to earth via the ground loop breaker.
   
  Do you know what the overall gain is going to be?
   
  Oh, SMD soldering.  Solder reflows on to the pads "automagically", just dab and go, and inspect with a loupe.  Use flux, when in doubt use some more, and swipe it over the pins, and it's all golden from there.  For most things, I like a wider flat tip, and swipe away from the body, in parallel with the pins.  I've tried smearing across the pins and that never really worked well for me.  I've done lots of SMD projects and they are all more or less the same technique.  An easier way is to use solder paste and bake it.  I think that's the way Twisted Pear builds their boards.  I've never done that, though, as I've never had problems with SMD work.
   
  http://www.freetronics.com/pages/surface-mount-soldering-with-a-toaster-oven#.UcTrn-tVuKA


----------



## sceleratus

Made all the cables.
 Checked the 300B bias.
 Ran a check with some crappy GE 6BQ7A's that came with my Lyr.
  
 A huge improvement over the 6N6P's
  
 I now have real-glass plugged in.
  
 1958 Amprex "tiny" Bugle Boys.  "D" getter.
 Outrageous.
  
 I still have the damn snow problem….. for now I'm just kick'n it and enjoying some incredible tunes.
  
 Thanks for the tips.....  I need to read your post and digest.   Right now I'm toast.... soldering all day....  It was worth it.  I have the ECC88 / 7308 / 6922 sound that I wanted so badly.


----------



## OldSkool

Congrats, my friend. Well done! Enjoy.


----------



## sceleratus

It's starting to settle in.
Does anyone have an opinion about Genalex Gold Lion 300B's versus the JJ 300B's ?
   
Photos.
First is the sketch of the enclosure.
   
Second  is the final Top and Rear panel cutouts.
I noticed the other day that my silicon bronze panel is warped.  This probably won't work for the water cutter.
If that's the case, I may switch to copper
   
Last is another shot of Frankenamp with cleaned up wiring and 1965 E188CC's.  Very sweet glass.
Ok.  Since it's my thread, I can post redundant photos.


----------



## sceleratus

Schematics:


----------



## holland

I was taking a closer look at his site, he's got some cool stuff, including an amp that I was thinking of (no PCB though).
   
  Thanks for the schematics, put it in the OP too (?).  Are you able to list the 6DJ8 mod in detail?


----------



## randytsuch

In one of the early threads after it started working, you said there was "slight static", like vinyl.
   
  It is still there?  Is it like low level noise?
   
  Curious.
   
  Otherwise, sounds like a winner, can't wait for the meet to hear it.
   
  Randy


----------



## sceleratus

Quote: 





holland said:


> I was taking a closer look at his site, he's got some cool stuff, including an amp that I was thinking of (no PCB though).
> 
> Thanks for the schematics, put it in the OP too (?).  Are you able to list the 6DJ8 mod in detail?


 
   
  A bit of a disclaimer.
  I asked Tom how many 300Bs are working in the field (NPI).  He said most folks don't let him know when they are working.  I was the first.
  Tom has two units, that makes mine serial  #3.  Add to that that this is the first HP implementation mine would now be serial #1.  This is not a Bottlehead build, Tom has no intention of kiting it out.  He does however provide a complete BOM that includes DigiKey part numbers.  That the guesswork out of ordering the components.
  Remember, I'm an idiot with a soldering iron… "OP" is that operating points? 
   
   If's so I don't have a clue but Tom talked about it them for the conversion to ECC88. ...
  "Modifying the circuit to try out the two different operating points identified from the data sheet, selecting the best one, and taking a few quick THD measurements took a bit over an hour. At 1 kHz, the THD comes in at about 0.2~0.3 % for 1 W out. 1 % THD happens at 9.5 W. Max output power is just shy of 11 W."
   
  ECC88 Driver Board BOM Modifications:
  Switch the LEDs D1, D3, D6, D8 for high-efficiency Vishay TLHG6400.
  R2 = 47 ohm
  R16 = 47 ohm
  D5 = Wire jumper (short circuit)
  D10 = Wire jumper (short circuit)
  TU1 = E88CC
  TU3 = E88CC
  Reworking the board was not too difficult.  A Soldapullt is mandatory.  I ordered the parts to have on hand if I wanted to take it back to 6N6P.
  Also there is a set of Driver board schematics on Tom's site for the ECC99 / 12BH7A.
   

   

   

   
  Quote: 





randytsuch said:


> In one of the early threads after it started working, you said there was "slight static", like vinyl.
> 
> It is still there?  Is it like low level noise?
> 
> ...


 
   
Randy,
The snow is still there, It's a bit north of "slight", but fades into the music.
Tom is working on it.  As you know anything shows up in a HP amp and this, as I said, is serial #1
   
Here is how the snow starts: 
Turn the power switch on.
5 seconds of slight hum..builds a bit, then
A sound like a needle across vinyl.
A slight pop…then the snow.  Like it passed gas.
It does not matter where the volume pot is set, the snow volume is constant.
   
I thought it was the 300B's.  Tom's reply:
When the tube is cold, its cathode (= filament for a directly heated triode like the 300B) doesn't emit any electrons. So no current flows. The hum you hear is probably just some induction into the output transformers or something. The needle across vinyl, I'm guessing is the output tube starting up. Its filament/cathode is now warm enough that it starts emitting electrons. The slight pop (probably occurs about 20~30 seconds after power-on) is likely the input stage starting up. That brings the hiss.
I don't recall a needle across vinyl sound in mine. But if my hypothesis is correct, that sound would really depend on how exactly the filament warms up and how the voltages stabilize. That probably varies considerably from tube to tube.
Good news is that I've found a way to reduce the hiss by almost 25 %. You'll need a 10 uF electrolytic capacitor rated for at least 25 V. Connect the capacitor at the footprint for D2. The (+) pin goes to the square pad (what would have been the cathode of D2). Short out D4 with a wire. Connect a similar 10 uF cap at D7 and short out D9. These D2, D4, D7, D9 are the empty footprints by the LEDs. They were intended for zener diodes for use with the 12BH7A, but can be repurposed for these capacitors. I was able to lower the hiss on my amp from 375 uV to 300 uV.
   
It's certainly isn't COTs, it's a work in progress.  (It also lack a UL approved sticker.





)  Don't get me wrong, I like dead-bang quiet and I hope it can get there.  All in all, I am enjoying my amp a lot. 
   
I'm hoping a set of Balanced HD800's show up at the show so I can audition them.


----------



## holland

Quote: 





sceleratus said:


> Remember, I'm an idiot with a soldering iron… "OP" is that operating points?


 
   
  Opening or original post.  It would be good to have the schematics in the first post of the thread
   
  Quote: 





> If's so I don't have a clue but Tom talked about it them for the conversion to ECC88. ...
> "Modifying the circuit to try out the two different operating points identified from the data sheet, selecting the best one, and taking a few quick THD measurements took a bit over an hour. At 1 kHz, the THD comes in at about 0.2~0.3 % for 1 W out. 1 % THD happens at 9.5 W. Max output power is just shy of 11 W."
> 
> ECC88 Driver Board BOM Modifications:
> ...


 
   
  Thanks for the info!


----------



## sceleratus

Quote: 





holland said:


> Opening or original post.  It would be good to have the schematics in the first post of the thread
> 
> 
> Thanks for the info!


 
  DONE


----------



## sceleratus

If it sucked, I would tell ya.
The hiss fades and blends into nothing.  After an hour, it's hardly there at all.  It has to be the 300B's
I still would like it to be dead bang quiet, but my hunch is it's not going to happen.  That's a plus for SS.
I'll still work on getting it there.  Upgrade the wire when I put it in the cabinet, maybe try some different 300B's
I also need to apply Tom's mod.
   
I have been afraid to listen to my Lyr for fear it would sound [size=small]superior...[/size]
  [size=small]I have a  dear friend that used to spec and oversee the construction of private theaters in mansions.[/size]
  [size=small]He's a Lynn Audio freak, God only knows how much he has in his system.[/size]
   
  [size=small]He is not a HP guy or a tube guy, per say.  Over the months I'd drop my Lyr and LCDs'2 off for him to audition. New glass, etc.[/size]
  [size=small]He thought it were pretty good.[/size]
   
  [size=small]Well today I had him over for an A/B.....  Kid you not. ... He liked the 300B hands down.  He would tell me if my kid had warts.[/size]
  [size=small]He's probably A/B'd equipment for 20 years.[/size]
  [size=small]He said the 300B was a lot bigger, esp. the base.  Fuller a lot more powerful.  I made sure he heard the hiss.....  His comment....didn't take anything away.[/size]
   
  [size=small]It is definitely coming into it's own.[/size]
  [size=small]I'm looking forward to the LA meet and getting feedback from other Head-Fiers.[/size]


----------



## tomchr

Sceleratus - thank you for posting your build thread. It's good to see that someone is enjoying the fruits of my labor (and their own too, obviously). I really appreciate you taking the time to document and share your experience. 
   
  @ Holland: Keep watching my site. Sometime in the fall, I'll be offering a Spud that'll accept a couple of different sweep tubes - both triodes and pentodes. PCBs will be available. Stay tuned...
   
  ~Tom
  ----
  Neurochrome : : Audio -- www.neurochrome.com/audio -- Engineering : : Done : : Right


----------



## sceleratus

Quote: 





tomchr said:


> Sceleratus - thank you for posting your build thread. It's good to see that someone is enjoying the fruits of my labor (and their own too, obviously). I really appreciate you taking the time to document and share your experience.
> 
> @ Holland: Keep watching my site. Sometime in the fall, I'll be offering a Spud that'll accept a couple of different sweep tubes - both triodes and pentodes. PCBs will be available. Stay tuned...
> 
> ...


 
  shucks


----------



## sceleratus

There is also a Head-Fi HUGE DIY Thread.


----------



## randytsuch

Maybe this is obvious, but have you tried moving the output tranny farther from the power tranny, and see if it helps the noise?


----------



## sceleratus

Randy.
  Yup checked that they are oriented correctly and have more than enough distance.
   
  I'm a sucker for Voodoo science.
  So to go go along with my beeswax capacitors, I ordered some "Naked" Bulk Metal Foil Resistors
   
  Besides clearing up any noise in the signal path, they will provide the US with clean power for the next 10 years.


----------



## nelamvr6

Quote: 





sceleratus said:


> Randy.
> Yup checked that they are oriented correctly and have more than enough distance.
> 
> I'm a sucker for Voodoo science.
> ...


 
  I for one appreciate it!


----------



## sceleratus

Quote: 





nelamvr6 said:


> I for one appreciate it!


 
  Wait !!!!
   
  You found the thread where those with diminished capacity troll.
  You may join.  
	

	
	
		
		

		
		
	


	



   
   
  (Inside joke)


----------



## sceleratus

I think I'll load some Porcupine TREE


----------



## OldSkool

Quote: 





sceleratus said:


> I think I'll load some Porcupine TREE


 

 In Absentia or Deadwing?


----------



## nelamvr6

Quote: 





oldskool said:


> In Absentia or Deadwing?


 
   
   
  Can't go wrong either way!


----------



## nelamvr6

Quote: 





sceleratus said:


> Wait !!!!
> 
> You found the thread where those with diminished capacity troll.
> You may join.
> ...


 
  I followed the bread crumb trail...


----------



## sceleratus

Quote: 





oldskool said:


> In Absentia or Deadwing?


 
  you may join too, but only if you can't spell obscure european cities.


----------



## OldSkool

Quote: 





sceleratus said:


> you may join too, but only if you can't spell obscure european cities.


 

 I'll take "Cities that rhyme with Ashtabula" for $200, Alex...


----------



## nelamvr6

Quote: 





oldskool said:


> I'll take "Cities that rhyme with Ashtabula" for $200, Alex...


 
  Oooh!  This might be good!


----------



## sceleratus

What is Scranton?


----------



## holland

Quote: 





tomchr said:


> @ Holland: Keep watching my site. Sometime in the fall, I'll be offering a Spud that'll accept a couple of different sweep tubes - both triodes and pentodes. PCBs will be available. Stay tuned...


 
   
  Thanks, will do.  Spud sounds cool.  Any insight on what tube and topology for the spud?  I've been meaning to put together a 12B4A amp, but haven't decided what topology I want to explore.
   
  I saw your 6J5 driver, that looks along the lines of something I was looking to do.  No PCBs though, but I'm fine with point to point.  I may just build it,


----------



## sceleratus

Back to the real purpose of the thread.
   
I dropped off the Top Panel cad file (actually AI) and a 24" x 24" x 0.090" silicon bronze to Aqua-Tech for water jet cutting.  Should be done tomorrow.  They said the bronze would work well, I scored it as a remnant for $100 and copper would be a bunch more.  The cost?  $125.
   
I think I would have spent more on hole saw bits.  Then cutting 2 square pieces that were square and 2 round pieces that were round..... out of 0.090 material.  Even if I still had my plasma cutter,  it would have looked like my pinewood derby car.
   
So we have another fingers crossed moment.  Will my 5 times checked file actually line up with the components?
It will be a miracle only a bit smaller than the one that made the amp play music.
   
Looking ahead, I'll try to put a dark patina on it, seal it, and hand it off to by cabinet friend...
   
  [size=small]*Looking for ideas *on how to pull off my wooden power button.  Now I'm not a bad McGuyver but it hasn't hit me how to secure the wood button to the switch plunger.  There are dozens of styles, plastic mechanism, steel rod with a button cap.  The button will be large, about 1" dia.[/size]
   
  [size=small]Unlike a POT / Rheo there is no shaft that you can use a bushing with a set screw.  I could secure a weld nut to the back, that would gice me threaded female, but it's the actual mating with the push buttonshaft that I haven't figured out.  Usually I can get it by crawling through McMaster Carr.[/size]
   
  [size=small]Anyway,  I'm all eyes, if you have any ideas.  Thanks in advance.[/size]


----------



## randytsuch

I am having trouble picturing your switch problem. A picture or drawing might help

Randy


----------



## sceleratus

Quote: 





randytsuch said:


> I am having trouble picturing your switch problem. A picture or drawing might help
> 
> Randy


 
Randy,
Thanks for thinking about it. The issue was/is mating a wood knob/button, like a chunk of dowel, through a wood facia and mate with a spring loaded button.  The buttons don't have a shaft, like a rotary switch.
   
Solution, scrap the push button and use a 1 stop rotary switch.  I just ordered a 1/4" shaft collar with set screws to mate the two together.
   
I picked up the top and rear panel from the AquaTech today.  I am delighted.  Everything Fits !
I have a lot of de-burring to do.  The small holes need to be cleaned up, but I'd rather have them a tad small than sloppy.  Then the finishing....  Need to watch some YouTube videos on turning a new piece of bronze into an old one.   (There are over 70 holes)
   
I have dismantled everything for safe keeping.  When the new components arrive, I'll break out the iron and give it a test.  Always a worry when you modify something that was working.


----------



## nelamvr6

Looks like they did an awesome job!


----------



## sceleratus

Quote: 





nelamvr6 said:


> Looks like they did an awesome job!


 
  It's really amazing.  Every single fixture lines up and those are 3mm holes.
  The hole saws alone would be $50 and they would shred the metal.  You'd have to pay more for a decent bit.
  Then there is the time it would take.  One off target hole and the thing looks awful.
   
  There are some serious scratches that will take some serious work.


----------



## nelamvr6

Quote: 





sceleratus said:


> It's really amazing.  Every single fixture lines up and those are 3mm holes.
> The hole saws alone would be $50 and they would shred the metal.  You'd have to pay more for a decent bit.
> Then there is the time it would take.  One off target hole and the thing looks awful.
> 
> There are some serious scratches that will take some serious work.


 
  I have faith you'll work it out...


----------



## sceleratus

I've used Scultp Nouveau patina products in the past on my home.  They are cool..... if done right.
   
I'm looking at this flat sheet of bronze and thinking "Not much character"
As such, I'm thinking about distressing it so the patina has some dimension.  It would be a real gutty move.
Like chains, ball peen hammer kinda distressing.  After the first blow, there would be no going back.  (Well try the back side of course)
   
Thoughts?  Anyone?


----------



## nelamvr6

Quote: 





sceleratus said:


> I've used Scultp Nouveau patina products in the past on my home.  They are cool..... if done right.
> 
> I'm looking at this flat sheet of bronze and thinking "Not much character"
> As such, I'm thinking about distressing it so the patina has some dimension.  It would be a real gutty move.
> ...


 
   
  What have you got to lose?  If it doesn't turn out like you envisioned, you can always break out the Rustoleum, or powdercoat it, or any number of options...


----------



## randytsuch

It also looks symetrical, so your idea of flipping it over if you don't like the outcome will work, so you get two chances, and a 2nd chance is always a good thing 
	

	
	
		
		

		
			





.
   
  For the switch, I was wondering why you couldn't drill a hole in the wood part, and then bond it the push button, but you found a solution so it doesn't matter anyway.
   
  Randy


----------



## FrankCooter

Quote: 





sceleratus said:


> I've used Scultp Nouveau patina products in the past on my home.  They are cool..... if done right.
> 
> I'm looking at this flat sheet of bronze and thinking "Not much character"
> As such, I'm thinking about distressing it so the patina has some dimension.  It would be a real gutty move.
> ...


 

 Do NOT  beat on your chassis plate with hammers, chains, etc.. You will not only warp it, but even worse, distort all your carefully machined mounting holes and recesses. If you want to add some sort of effect to your metal, try having it run through a wide belt sander or check out the many chemical treatments available for bronze. In LA (actually the San Fernando Valley) check out Industrial Metal Supply. They have a huge variety of metal treatments and surface effects. Well worth a field trip.
   
  I've been enjoying watching your progress. I do a lot of similar work. Hope to meet you at the upcoming LA meet.


----------



## sceleratus

Hi Frank,
   
  Thanks for the advice.  We have an IMS in Irvine that I've gone to for years.  It surely is a toy store for big boys with TIG welders and plasma torches. (Used to have both)  I scored the Bronze sheet from the remnant bin for $100.  It was the only piece, remnant or otherwise, in the store.  The minimum order quantity for bronze or copper would have pushed the price over the top.
   
  I picked up some Sclupt Nouveau bronze rub patina and gave it a try. I have used SN product on copper and got great results.   First, it's not the right formula, second it dawned on me that it will be too be too dark a contrast against the Birdseye maple.  I'm going to experiment to try and get more of a bottom-of-the-ocean green/blue.  That should work well against the maple and yield a mottled variegated look.  The surface is so large it needs to be broken up.
   
  We are on the same page with the rocks and chains.  The risk/reward curve is too steep.  I know how I'd like it to look, but it's not a process for first time project.


----------



## holland

Quote: 





sceleratus said:


> Hi Frank,
> 
> Thanks for the advice.  We have an IMS in Irvine that I've gone to for years.  It surely is a toy store for big boys with TIG welders and plasma torches. (Used to have both)  I scored the Bronze sheet from the remnant bin for $100.  It was the only piece, remnant or otherwise, in the store.  The minimum order quantity for bronze or copper would have pushed the price over the top.
> 
> ...


 
   
  That's good.  Chemical treatment is best, IMO, as well.
   
  Personally, I like a contrast.  Some sort of antique bronze against clear unstained highly figured maple looks good to me, with the orange glow of tubes.  I'm not sure about an oxidized look.  It might work, but I think the wood would need to look "old" as well to really pull that off.  Another option is to use cocobolo and then highly polish the bronze.  When it tarnishes, I think it would be a nice look.


----------



## sceleratus

Cool Holland.
   
  I will look into Cocobolo.  
  The unstained maple is cast in stone.  Birdseye is an amazing looking wood.
  I think you are correct, dark oxidize will not work.  Soft might.
  I have to seal it when I get it where I like it.  Thats what the patina products do, they accelerate the process and you can stop it at any point.
   
  Living in socal is helpful because there are a lot of artists.  I've asked an artist that uses metal for help.
   
  Right now I'm off to the garage to polish scratches.


----------



## sceleratus

The results from this mornings work are encouraging.
  Luckily I found some rubber bits that made short order of de-burring the edges and polishing the holes.
   
  The major and medium scratches have been removed by stepping through grit to 220.  I'm off to pick up some 400, 600, 800, then steel wool.
  It tarnishes almost immediately if you touch it.  The streaks are from wiping with acetone.


----------



## nelamvr6

Have you considered machine turning as a finish?  That can look pretty spiffy if done right:


----------



## sceleratus

Quote: 





nelamvr6 said:


> Have you considered machine turning as a finish?  That can look pretty spiffy if done right:


 
  I love it on custom cars..I was going for earthy.


----------



## sceleratus

Is this the point where I start hitting it with a hammer ?


----------



## nelamvr6

Looks lovely!


----------



## sceleratus

I'm pleased.
  180 / 220 / 400 / 600 / 1500 / Tripoli / Wenol.
  All in the direction of the grain.
   
  With each step I'm think'n  That looks pretty good, should I stop and call it the brushed look?  Next grit, same thing.  Well I should polish it.....


----------



## sceleratus

Quote: 





holland said:


> That's good.  Chemical treatment is best, IMO, as well.
> 
> Personally, I like a contrast.  Some sort of antique bronze against clear unstained highly figured maple looks good to me, with the orange glow of tubes.  I'm not sure about an oxidized look.  It might work, but I think the wood would need to look "old" as well to really pull that off.  Another option is to use cocobolo and then highly polish the bronze.  When it tarnishes, I think it would be a nice look.


 
  Holland....
   
  I just googled "cocobolo"
   
  Cocobolo is one Bad Azz wood.   Woa.
  The red is exquisite.  Seriously amazing grain.
   
  Contacting the cabinet maker.


----------



## LordShad0w

Truly amazing work and very inspirational as well. Thank you for all of your time, patience and effort in documenting it all and sharing the journey.
   
  Subscribed.


----------



## customcoco

Quote: 





sceleratus said:


> Holland....
> 
> I just googled "cocobolo"
> 
> ...


 

 Why not walnut? Or even better than cocobolo (Imo), Bloodwood.


----------



## muskyhuntr

Hi Sceleratus,
   
  You have my vote for bocote.  It is an amazing wood.  Unbelievable how it keeps a sharp edge. Used it on my M3 build and I am very happy with it. (see http://www.head-fi.org/t/85561/post-pics-of-your-builds/9135).  Sanded to 600 and finished with tung oil.  I am currently finishing up a EHHA with the same wood and a similar design.
   
  Also, based on your build, I ordered the boards for one of these amps though mine will be used to power some small speakers in a smallish room. Plan on this to be a secondary build while I finish up an Aikido pre amp and a AMB B24.  Though I did order parts for the power supply board.
   
  Keep the pictures and posts coming,
  Jim


----------



## sceleratus

Quote: 





lordshad0w said:


> Truly amazing work and very inspirational as well. Thank you for all of your time, patience and effort in documenting it all and sharing the journey.
> 
> Subscribed.


 
   
  Thanks    
	

	
	
		
		

		
			





  That is very nice.
  It really wasn't too much trouble.  I like photography and it forced me to take a lot of pictures.   I thought it would be cool to write an actual account of the build and not sugar coat anything.  The cost comes to mind.   I forgot to add the necessary tools.
  Quote: 





customcoco said:


> Why not walnut? Or even better than cocobolo (Imo), Bloodwood.


 
  @customcoco,
  Walnut was the first choice for the corner pieces and is still the leader.  The cocobolo is a very sweet exotic, but I want the birdseye maple to be the understated centerpiece of the enclosure.  It has a subtle beauty that I love.
  I'll look up bloodwood.  Many thanks for the suggestion.
  Quote: 





muskyhuntr said:


> Hi Sceleratus,
> 
> You have my vote for bocote.  It is an amazing wood.  Unbelievable how it keeps a sharp edge. Used it on my M3 build and I am very happy with it. (see http://www.head-fi.org/t/85561/post-pics-of-your-builds/9135).  Sanded to 600 and finished with tung oil.  I am currently finishing up a EHHA with the same wood and a similar design.
> 
> ...


 
  Musky !
  I used to have a home in Manitowish Waters on Rest lake.  Went after those rascals in Boulder Junction.
  A tung oil finish is where I am headed.  Your comment on holding an edge is important to this enclosure.  It seems inevitable that I round a corner during the sanding process.  I lack the patience necessary to take it slow.  This time I vow not to make that mistake. 
   
  Tom will be very pleased that you ordered boards.  He sells them for the love of the DIY community.  He's not selling dozens of boards daily and he probably only pockets lunch money.  Heck, he includes the schematics for someone to put into Diptrace and make their own boards he nets zero by doing that.
   
  EDIT:  I forgot to compliment you on you project.  It's beautiful and everything looks very tight.


----------



## sceleratus

Here is a Dropbox link that has a lot of the files for the 300 build.
   
Components, board layouts, schematic with BOMs, pictures of boards and components, Adobe Illustrator files for cutting the top and rear panel, and component data sheets.
   
300B Build Files


----------



## randytsuch

Thanks for the files.  I started downloading Adobe Illustrator but it is going to take a while, I have a slow connection right now.
   
  Looks like the panel size is 14x17.  I am thinking about using Front Panel Express or Protopanel.  Looks like they will do a 4mm thick black anodized Al plate for around $100.  And protopanel is running a sale, so they would be cheaper.  I used Protopanel for my DAC front panel, and it came out fine.
   
  IMHO, use the wood type that you want to use.  There is a bunch of exotic hardwoods out there.  FYI Rockler carries some exoctic hardwoods, and there is probably somebody around you that carries some too. 
   
  But you are the one that is going to be staring at this amp every day, so use the wood type that you like, and go for the look that works for you.
   
  Randy


----------



## sceleratus

I exported the .ai files to auto cad .dxf and .dwg  I also saved it as a .pdf
   
  The .pdf is handy because you can take it to FedEx Kinkos and print it out actual size for a few bucks.  The you can place the  boards and line it up.
  There is also a .pdf of all the schematics on one page.  Have them print this 24" x 24",  it's much easier to read the schematic.
   
  I really like to read the suggestions. You never know what is going to come up.  Cocobolo is a case in point.  I've done some woodworking in the past, as a result I've given Rockler more than a few bucks.  They are a great resource.
   
  Aquatech said the 3mm holes for the standoffs were borderline what they could do.  I had to clean them with a round file, but they are perfect.
   
  I had a great idea this morning for the front panel.  Continuing on the minimalistic theme, I am going to ditch the front wood on/off and put a heavy duty DPDT toggle in the back.
  This makes the volume knob more of the focal point....I have, what I think, is a very cool idea for the volume knob.
   
  I will post it after I draw it up.
   
  Thanks to All.


----------



## sceleratus

Quote: 





randytsuch said:


> Looks like the panel size is 14x17.


 
  I forgot to answer this question.
   
  The panel is 19" x 15.75"
  In the drawing there is a "reference" rectangle drawn to show the transformer / component setback.  It's not part of the top panel fabrication.


----------



## sceleratus

I want to scream.
   
  I have never been any good a polishing.
  I'll us a compound like Wenol or tripoli to get a glass finish.
  BUT, when I go to clean it, I'll get streaks, then spider swirls.  It's an endless loop.
   
  I tried everything. Acetone takes off all the residual compound. Leaves streaks.
  Next rubbing alcohol.
  Next distilled water.
  Next camera lens cleaner.  
	

	
	
		
		

		
			




   
  I took a propane torch to it.
  I'm going to try Barkeepers Friend.
   
  I need to google polishing.


----------



## sceleratus

Finished it to the best of my abilities.
  Went over it with Wenol again.
  By hand.  No buffer.
  With a cloth removed all the excess.
  No solvents.  Period
   
  Hung it up and sprayed a coat of lacquer.
   
  I know other could do better.  I reached my frustration limit.


----------



## randytsuch

For most things, the builder/maker/owner is much more critical than anyone else will be.  You will know the flaws, no one else will notice.  I'm sure you're looking at it at different angles, in different lighting conditions, and at just the right angle and light you see the streaks/flaws.
   
  No one else is going to do that. 
   
  And I'm sure it looks great, it looked good in the pictures and it probably looks better in real life. 
   
  For the wood, as some point I was thinking of making a Teres turntable, had a bearing and platter.  Wanted to make an exoctic wood base, but it never happened and I eventually sold off the bearing.  Analog was too much work.  But at the time, I learned about cocobola, buginga and some other exoctic hardwoods.
   
  Randy


----------



## sceleratus

Quote: 





randytsuch said:


> For most things, the builder/maker/owner is much more critical than anyone else will be.  You will know the flaws, no one else will notice.  I'm sure you're looking at it at different angles, in different lighting conditions, and at just the right angle and light you see the streaks/flaws.
> 
> No one else is going to do that.
> 
> ...


 
  +1
   
  thx


----------



## Fearless1

I am actually excited to see the finished results!  Awesome thread that is inspiring me to try a build.


----------



## sceleratus

I finished the illustrations for the enclosure.
  I just hope it's completed in time for the meet...
   
  The Neutrik XLR jacks are going to look clunky because they are meant for a metal panel.  Thus there will be these black rectangles on top of the wood face.  I already had to buy another set because I had male to begin with, but I've reached my limit.  I'm not going to spend $70 for gold Cardas jacks.


----------



## customcoco

It looks great !
   
  Even though I'd prefer a colored knob. Something along the lines of bloodwood (or even walnut), for example...


----------



## holland

It looks good.  I see you spec'd curly maple over birdseye.  I like that. 
   
  For the XLR jacks, you can use a 4-pin XLR instead of 2 3 pins, and then build adapter cables.  3 pin XLRs are very bulky, and 4-pins are lighter and more compact.
   
  You can mount the jacks behind the faceplate.  You can recess an area behind and mount them so that the opening shows the XLR only.
   
  OR
   
  You can put a designed ring around the XLR jack, from a veneer.  So, you recess on the front panel to flush mount the XLR connector externally (the black rectangle visible), then put a thin veneer of walnut around the jack so that the black is not visible.  The jack extends from the panel a small amount, especially if you get the locking ones.  You'll need to recess bolt holes as well to make it look clean.


----------



## tomchr

I would rotate the XLRs on the front 90 degrees so the "PUSH" tab faces up and recess them into the front panel such that the metal part is flush with the wood. I would also place them side by side rather than one atop the other. That'll give you more of a horizontal flow in a horizontal box.
   
  The wood is plenty thick, so I wonder if you could recess the XLRs deeper and put an inlay over them. That could be pretty sleek. If you go with, say walnut for the volume knob, you could use a walnut inlay around the XLRs... 
   
  ~Tom


----------



## sceleratus

Thanks for the ideas.
   
  The problem with the jacks is they were meant to be mounted behind a 0.106" metal panel.  To do the same with wood one would have to auger out all the wood except for 0.106"
  That would be too thin for the front.  Inlay / veneer  is an idea, however, you wouldn't be able to remove the jacks.
   
  Tom,
  Good catch on the jack orientation.  Side by side is much better.
   
  I thought about calling AquaTech to see if they saved a piece of bronze to make a bezel from. but that would probably be another $125 minimum charge.
   
  I am set on the color of the knob.  Curley Maple.  I prefer that it blend in.


----------



## sceleratus

I drew up an inlay.
  At first I was thinking the bronze material, but nixed that because I believe the naked jacks would look better.
   
  I sent this to Mike to see about either a raised or inlay plate.  There wouldn't be holes if it was inlay.
  This part may not happen in time for the meet.


----------



## sceleratus

Unless there are problems that merit posting, the next post should be the assembled working amplifier.


----------



## randytsuch

For your XLR inlay, are you sure the "push" button won't interfere with installation?


----------



## holland

Quote: 





randytsuch said:


> For your XLR inlay, are you sure the "push" button won't interfere with installation?


 
   
  No, it's fine.  Just angle it as your putting it into the plate, and it slides into place.  It's what you do to panel mount them.


----------



## sceleratus

Randy,
   
  You are correct.
  Naturally, if I surface mounted them, no problem.
  If they were mounted in a recess of the front panel, you wouldn't be able to angle the cover to nestle it into place.
  They are designed to "hook" from underneath.
  Actually, one couldn't use a raised surface plate either.
  Many thanks for that one.
   
  EDIT.  That's if you didn't want to see the two XLR jack mounting screws.
  Thin inlay might work.
   
  Rear Panel...


----------



## sceleratus

All Neutrik and Switchcraft female panel jacks have the locking button.
   
  The Cardas does not.  ($58 per pair + S&H, Canada)
  It would fix the problem.


----------



## holland

Quote: 





sceleratus said:


> EDIT.  That's if you didn't want to see the two XLR jack mounting screws.
> Thin inlay might work.


 
   
  I'm not sure I understand.  The jacks can move about and have extra wiring, so I presume it should be able to slide foward of the case.  I presume with a panel they are held in place by the panel, and the recess for which the jacks fit into, and the screws on the outer edge of the panel.  So, pull of the panel, and the jacks slide out with it, yes?  When you put the plate on, it can slide into the recess, it may take some wiggling to find the correct orientation before it slides into the slot.
   
  If an inlay, I'd imagine there's removable blocks to hold the jacks in place, on the backside.  That is screw the jack into the blocks, and slide the blocks into place and then attach them to the chassis with screws.  It's hard to visualize what you're doing with this part as there are so many possibilities.  I'm not sure how things are meant to hook from underneath, without wiggling of some sort (loose jacks).


----------



## holland

Quote: 





> Originally Posted by *sceleratus* /img/forum/go_quote.gif
> 
> The Cardas does not.  ($58 per pair + S&H, Canada)


 
   
  Amphenol too, much cheaper if you want nickel or anodized black.  Cardas looks nicer though, with the gold plating.


----------



## sceleratus

Quote: 





holland said:


> Amphenol too, much cheaper if you want nickel or anodized black.  Cardas looks nicer though, with the gold plating.


 
  I found the Cardas from a seller in PA and I bit.
  If they are surface mounted they will look decent against the maple and they would be much easier to add an inlay bezel.  Recess them and inlay can go over the top of the fasteners.
   
  The problem with the button type is the wood is 1" 1/4 thick.  The mounting flange on the jack is recessed 2.7mm 
  When you are mounting the push button type jack you must do it from Behind the Bezel, you need to tilt the jack 45 deg. into the hole of the bezel.  Metal or wood.  That could be done and the jack could nestle into a routed recess in the wood but you couldn't use screws to secure it.   It would be a whole lot of work because you'd have the jack attached to the piece you want to inlay. 
   
  Without that locking button a plate or inlay goes straight on and mounts flush.  Hence the Cardas.
   
  I looked at switchcraft  The mount was huge.


----------



## randytsuch

Always glad to help you find ways to spend more money.  
	

	
	
		
		

		
			




   
   
  Quote: 





sceleratus said:


> Randy,
> 
> You are correct.
> Naturally, if I surface mounted them, no problem.
> ...


----------



## holland

Quote: 





sceleratus said:


> Without that locking button a plate or inlay goes straight on and mounts flush.  Hence the Cardas.
> 
> I looked at switchcraft  The mount was huge.


 
   
  Meant Amphenol has non-locking jacks as well.  Neutrik does too.
   
  Anyhow, glad you went non-locking.  I dislike locking with a passion, but don't say anything because so many use them.  I'd rather have the plug disconnect on an accident than take the whole amp with it.


----------



## sceleratus

Quote: 





holland said:


> Meant Amphenol has non-locking jacks as well.  Neutrik does too.
> 
> Anyhow, glad you went non-locking.  I dislike locking with a passion, but don't say anything because so many use them.  I'd rather have the plug disconnect on an accident than take the whole amp with it.


 
  I even looked at modifying the locking jack.  They are crimped with a machine press.
   
  Honest,  I swear I looked at Neutrik catalog online and anything female had a lock.
  Moot anyway with the Cardas.
   
  I appreciate your suggestions.
   
  ANOTHER Question:
   
  Wire.
   
  What do ya'll like for output trans to XLR wire?
  Cardas, Kimber, Litz?
  Same thing RCA>Volume POT> Driver board.
   
  I decided to solder the wire directly to the board.  I removed the terminal blocks for these connections.


----------



## sceleratus

I ordered 22 ga. solid core silver wire.


----------



## sceleratus

It's killing me...
  I have nothing to work on.


----------



## tomchr

Do what I do... Start a new project. 
   
  ~Tom


----------



## sceleratus

Here's a look at my oddball vent design.
Monday all the bronze item go to a professional metal finishing company to be buffed and sealed.
   
Note:  The back fasteners are just set in.  They will be flush.
   
So... Does it look stupid?
I think with a high polish it will look ok.  I was going for Jules Verne.


----------



## randytsuch

I'm sure it will look great after you get it all put together, with the tubes glowing.  
  It's kind of hard to tell what the finished amp is going to look like though, just seeing the plate.


----------



## LordShad0w

Sceleratus,
   
  I think it will look wonderful the way you intend.
   
  I would add though that if you are able to do it I did have a small idea that might be a nice touch.
  This is of course merely one mans opinion so feel free to disregard it, but I thought that if you are getting the entire top plate polished that even if you have the raised vent sections, it will blend in to the rest.
  If you wanted a small amount of contrast, I was thinking that you could use some aluminum round stock to raise up the vent plates a touch more and either have them polished or anodized in a darker color. (perhaps black?) Then for the vent plates themselves, instead of using something like brass or copper (which tarnishes rather easily) You could keep just try to anneal them so that you get a bit of a multi-hued finish? Or perhaps anodize the top and have the bottom that faces the tubes highly polished.
   
  You could also have the entire sheet bright dipped (think of it like an acid wash that makes it incredibly bright) and then clear anodized to protect the finish and make it very durable. (Lv.3 hard anodize is a great choice for this)
   
  Just a couple ideas my friend. I know that no matter what you choose, it will look fantastic. You have already accomplished so much in this build that anything else is just the cherry on top. 
   
  Have a wonderful day.


----------



## sceleratus

Quote: 





lordshad0w said:


> Sceleratus,
> 
> I think it will look wonderful the way you intend.
> 
> ...


 
   
[size=14.0pt]Lordy,[/size]
   
[size=14.0pt]Thank you very much for posting.  You are very kind. [/size]
   
[size=14.0pt]I have been out of my mind during the project downtime and I needed the diversion.  You (anybody) don’t have to hold back any criticism. It’s all good and I’ll only cry for a bit.[/size]
   
[size=14.0pt]Example, if someone were to write that the vent’s look like sewer grates, that’s fine because I obsess over this stuff and thought to myself, “Damn, they look more like sewer grates” than a WWII pill box or some Jules Verne thing.  I usually don’t play it safe.[/size]
   
[size=14.0pt]The vent standoffs were tricky because unless you have a Proxxon mini mill (which I thought about buying) you have to use a part for something other than what was intended.[/size]
   
[size=14.0pt]I first went to DigiKey looking at board standoff’s but the 14mm brass ones I ordered were too tall and out of proportion.  So I went online to McMaster and got the 3mm x 3M SS hex in the photo because that’s the only choice for fasteners that will fit the panel hole size.[/size]
   
[size=14.0pt]I am taking everything to Normany Metal Refinishing in Costa Mesa, CA for polishing.  The owner of AquaTech (panel cutting) said they were the best around.   I was going to say polish it and seal it.  Now because of your post I can ask about Bright Dip and Lv.3  Thanks. Maybe that’s what they were going to do anyway.[/size]
   
[size=14.0pt]The sewer grates stick out enough that I will have them polished to match.  I polished and sealed everything 3 different times myself.  I would get it very bright using Tripoli and Wenol (see photo a few posts back) but when I tried to clean off the excess compound with acetone, or denatured alcohol, or distilled water it would go downhill, spraying with lacquer made it worse.[/size]
   
[size=14.0pt]So just like the hole drilling, I’m handing the panels over to someone that does it for a living.  Back to going nuts….[/size]
   
[size=14.0pt]What does any self respecting Head-Fi’r do during project downtime? [/size]
[size=14.0pt]Why they hunt unicorns of course.[/size]
   
[size=14.0pt]You become lunchmeat for voodoo component sellers.  Like 22 ga. solid core, soft annealed silver wire with slip on Teflon jackets.  (yes) Or Beeswax capacitors (yes), or silver oil Mundorf caps (no).  You purchase a 3rd set of XLR jacks because the first ones were the wrong gender and the 2nd set didn’t “look right”.  (yes) How about hand made. naked bulk metal, foil resistors? (yes)  You design a widget to accommodate very large capacitors anyway (yes).  There’s “maybe I should try some $600 higher rated 300B’s”(no)  Lastly, should I remove the tranny end caps and have them nickel-plated? (no)[/size]
   
[size=14.0pt]This is the stuff that sends the project costs to the moon.  The worst part is I dismantled everything while waiting for these parts and now I start thinking “will it sound better?”  “Will it work at all?”  Out of my mind.[/size]
   
[size=14.0pt]The best image I can post is the little bracket I made to hold the volume POT.  As you can see, I can’t line up 4 holes.  Can you imagine the results from me trying to drill 70 – 90?[/size]
   
[size=14.0pt]Does anyone want 10 x 3M x 14mm brass standoffs?[/size]


----------



## sceleratus

Downtime is very detrimental to the leather.
I'm reviewing my components box(es) and I see the extra set of Neutrik male XLR jacks that will be collecting dust.  
   
   
   
Hmmmm.. I could use them as source jacks instead of the RCA's and buy a balanced Schiit Gungnir DAC. 
   
  [size=small]All the bronze is at the polishers and ......  he'll have it finished tomorrow afternoon![/size]
  [size=small]Stopped IMS and had them shear a piece of perforated aluminum for the bottom grill.[/size]
   
  [size=small]The 22ga silver wire and other items from Handmade Electronics arrived.  Great outfit, great products.[/size]
  [size=small]Just waiting on the Texas Components resistors and I should be hearing music again.[/size]
   
  [size=small]Looked at the Bob Parker ESR meter for testing caps.  A simple kit $80[/size]
  [size=small]It's interesting that very few of these fancy cap makers publish ESR numbers.[/size]


----------



## holland

Quote: 





sceleratus said:


> [size=14.0pt]I have been out of my mind during the project downtime and I needed the diversion.  You (anybody) don’t have to hold back any criticism. It’s all good and I’ll only cry for a bit.[/size]


 
   
  Is that the pot you're using?  Hmmm......no DACT 4 gang pot?  After those gold plated XLR jack, that pot looks.... <no comment>.  You won't see it, but you'll know it's not perfect. 
   
  Build a DAC.


----------



## sceleratus

Mike Moffat of Schiit, formerly Theta is the godfather of DAC's  I don't think I can build better.
   
  The POT is an ALPS Japan RK27112 Blue Velvet Log potentiometer.
  I used a 100K first go around.  I'll use a 10K next.
  What you see is the mounting bracket.
   
  Me not know DACT 4 gang pot


----------



## holland

Quote: 





sceleratus said:


> Mike Moffat of Schiit, formerly Theta is the godfather of DAC's  I don't think I can build better.
> 
> The POT is an ALPS Japan RK27112 Blue Velvet Log potentiometer.
> I used a 100K first go around.  I'll use a 10K next.
> ...


 
   
  re: DAC, well, you can build one for fun.  Their yggdrasil and ragnarok offerings look like it will be good.
   
  I thought I recognized the lugs on the RK27.  http://www.dact.com/html/attenuators.html .  They are expensive, but nice.  CT-2 4 gang.


----------



## sceleratus

Quote: 





holland said:


> re: DAC, well, you can build one for fun.  Their yggdrasil and ragnarok offerings look like it will be good.
> 
> I thought I recognized the lugs on the RK27.  http://www.dact.com/html/attenuators.html .  They are expensive, but nice.  CT-2 4 gang.


 
  I get the resistor "array" architecture.  Interesting.
  I am not understanding the 4 decks for balanced stereo.
  Is the "output channel" the interface to the driver board for source input?
   
   

   
  I did not see where they could be purchased in the US and those on eBay were "Type 21" not CT-2


----------



## holland

Quote: 





sceleratus said:


> I get the resistor "array" architecture.  Interesting.
> I am not understanding the 4 decks for balanced stereo.
> Is the "output channel" the interface to the driver board for source input?
> 
> ...


 
   
  It's for balanced operation and it's like a 2 gang pot for stereo.  Input relative to ground, as opposed to wiring a 2 gang for balanced operation.  You can try contacting Justin at Headamp, he used to sell them when he had extras.
   
  Here's another pot, more steps, finer control than the DACT.  http://www.khozmo.com/products_dale_shunt.html
   
  You could also not mind me, I'm just trying to spend your money.


----------



## sceleratus

Look





holland said:


> It's for balanced operation and it's like a 2 gang pot for stereo.  Input relative to ground, as opposed to wiring a 2 gang for balanced operation.  You can try contacting Justin at Headamp, he used to sell them when he had extras.
> 
> Here's another pot, more steps, finer control than the DACT.  http://www.khozmo.com/products_dale_shunt.html
> 
> You could also not mind me, I'm just trying to spend your money.




"Look! Is that a Unicorn !!"


----------



## tomchr

That volume control circuit would be useful if the XLR connectors were on the input side of the amplifier. Differential volume control. Or more like dual single-ended, actually, but that's another story.
   
  The XLRs used in this build are for the output, i.e. the connection to the headphones. This is NOT the spot for a volume control - unless you're trying to cause some whacky sound shaping effect analogous to the presence control in a guitar amp.
   
  ~Tom


----------



## holland

Quote: 





tomchr said:


> That volume control circuit would be useful if the XLR connectors were on the input side of the amplifier. Differential volume control. Or more like dual single-ended, actually, but that's another story.
> 
> The XLRs used in this build are for the output, i.e. the connection to the headphones. This is NOT the spot for a volume control - unless you're trying to cause some whacky sound shaping effect analogous to the presence control in a guitar amp.
> 
> ~Tom


 
   
  Headphone amps usually have a volume control on the input before the gain stage, especially with tubes.  They are more like a preamp in that regard.


----------



## sceleratus

[size=small]I picked the panels up from the polisher.[/size]
  [size=small]Needless to say, I am pleased.[/size]
   
  EDIT
  [size=small]Grand total for the panels:  $325[/size]
  [size=small]Not too bad.[/size]


----------



## randytsuch

Impressive  
	

	
	
		
		

		
			




   
  Can't wait to see it come together now.
   
  It is assembly time?


----------



## sceleratus

The Texas Component resistors shipped today.  I will have them tomorrow.
The only obstacle is the enclosure.   If it looks bad by the weekend I'll visit my friends table saw and radial arm saw.
   
 I asked Jack Elliano of Electra-Print what he thought the hiss noise was.  [size=medium]When I start up, there's a tiny bit of [/size][size=medium]hum for a second or two, then a brief squeak, a whoosh, then the a low level [/size][size=small]but consistent hiss.[/size]
   
I sent him this recording (300B Hiss) I made of the startup sound using a Rode stereo mic stuffed inside my LCD2 ear pads.  Ignore the [size=small]prominent noise that sounds like a motor.  I am not sure where it came from but it's not part of the hiss.[/size]
   

   
   
Here is Jack's reply.
   
  [size=medium]..."I heard the noise, I heard a 120 or maybe a 240hz tone, this could be power[/size][size=medium][/size]
 [size=medium]supply saturated filter choke.  These will double the 120hz applied to them.[/size][size=medium][/size]
 [size=medium]Use a scope to see this on B+.[/size][size=medium][/size]
 [size=medium]The hiss part does not sound like anything we have ever heard.  A tube noise[/size][size=medium][/size]
 [size=medium]is very distinct, we have dealt with tube noise all the years we worked on[/size][size=medium][/size]
 [size=medium]recording studio equipment.  I'm sure it's not resistor noise.  [/size][size=medium][/size]
 [size=medium]Anyway, try to get a picture of this hum and send it to use, if you can."[/size]
   
  [size=medium]Any guesses ?[/size]


----------



## OldSkool

Wow, that's a strange noise. Spooky, almost. 
	

	
	
		
		

		
		
	


	



   
  By chance, is your house built on an ancient burial ground?


----------



## GrindingThud

Sounds like 6n6 cathode follower hiss....are you starving it? Or maybe pot noise from the cf bias. 



oldskool said:


> Wow, that's a strange noise. Spooky, almost. :eek:
> 
> By chance, is your house built on an ancient burial ground?  :wink_face:


----------



## sceleratus

It is immediately apparent that I shouldn't have asked the question because I will not understand the answers.


----------



## GrindingThud

Vary R27 around a little and listen if hiss gets louder or softer. It's got to be noise from one of those 1st two stages...and I'm betting its the second one with the bias pot, which could be noisy. It does sound like Jack is on it though and will be able to narrow it down pretty quick. 

Edit... Reading back in the thread didn't you mention adding or increasing a capacitor that reduced the hiss a bunch? If so, that might be the stage the hiss lives in and give jack a clue where to narrow in on.


----------



## sceleratus

Quote: 





grindingthud said:


> Vary R27 around a little and listen if hiss gets louder or softer. It's got to be noise from one of those 1st two stages...and I'm betting its the second one with the bias pot, which could be noisy. It does sound like Jack is on it though and will be able to narrow it down pretty quick.
> 
> Edit... Reading back in the thread didn't you mention adding or increasing a capacitor that reduced the hiss a bunch? If so, that might be the stage the hiss lives in and give jack a clue where to narrow in on.


 
Yes.
   
Tom gave me a mod to reduce the hiss.  This was after I disassembled.  It will be implemented and tested when everything goes back together.
I will probably do another desktop build and see what the status is. .....
   
Add a 10 uF electrolytic capacitor rated for at least 25 V. Connect the capacitor at the footprint for D2. The (+) pin goes to the square pad (what would have been the cathode of D2). Short out D4 with a wire. Connect a similar 10 uF cap at D7 and short out D9. These D2, D4, D7, D9 are the empty footprints by the LEDs. They were intended for zener diodes for use with the 12BH7A, but can be repurposed for these capacitors.


----------



## sceleratus

The Driver Board resistor upgrades to Texas Components are:
   
  R22, R9 (220R)
  R6,R7,R20,R21  (2K2)
  R10, R24 (33K 3W)
   
   
EDIT:   Let's not forget the Tom is very much interested in tracking this down.  He's helped whenever I've asked.
   
EDIT 2:  That recording is about 50 x worse than the actual noise.


----------



## holland

It sounds like tube noise to me.  Let it warm up for about 30 minutes and listen again.  If still there, put a scope on it. 
   
  Nice panels, BTW.  Absolutely gorgeous.
   
  Edit: Ask Tom if he thinks it needs a cap multiplier.


----------



## sceleratus

Quote: 





holland said:


> It sounds like tube noise to me.  Let it warm up for about 30 minutes and listen again.  If still there, put a scope on it.
> 
> Nice panels, BTW.  Absolutely gorgeous.


 
  Thanks Holland.
   
  The noise is at a set volume regardless of the volume pot setting and it does not go away.
   
  What you heard was the sound when the amp is first turned on.  The sound at the end of the clip is the consistent hiss.  It stays at a fixed level regardless.  
   
  During warm up I can also hear the 300B's ... expanding?..... a single ping  .. ping.. ping like a filament it stretching /  tightening.  Microphonic but not.  That quickly goes away.
   
  The hiss plays tricks with me because I will loose it in the music most of the time, even when I stop a track.  That's just my mind adjusting to this consistent noise.  It's always there.
   
  The startup sound is very very strange.  The squeak almost sounds like a vinyl record skip.


----------



## holland

Quote: 





sceleratus said:


> Thanks Holland.
> 
> The noise is at a set volume regardless of the volume pot setting and it does not go away.
> 
> ...


 
   
  The squeak sounds like DC offset to me, let it warm up a bit before you plug in.
   
  It's after the pot, in the amp somewhere.  I have a hiss like that in one of my amps, I never tracked it down, too lazy...but it was a side project and not my real amp.  I would pull out the oscilloscope, if I were you.  I hate pulling mine out, it's gigantic and analog.  I need a smaller one that I can keep on my desk.
   
  I will need to check the schematic, but you can also ask Tom.  There should be a way to pull the gain tube, and ground the grid, and run the 300B to see if the hiss is the gain stage or the buffer stage.
   
  The pinging, ugh.  My amp at work has a ping in one channel.  It's the voltage gain tube on mine.  Mine doesn't go away, it comes and goes constantly.  I have a serious love/hate with tubes.  It's fun to work on, but it sure pisses me off at times.  Fortunately for me, I'm going back to solid state for a bit and for fun.


----------



## holland

Quote: 





sceleratus said:


> Thanks Holland.
> 
> The noise is at a set volume regardless of the volume pot setting and it does not go away.
> 
> ...


 
   
  The squeak sounds like DC offset to me, let it warm up a bit before you plug in.
   
  It's after the pot, in the amp somewhere.  I have a hiss like that in one of my amps, I never tracked it down, too lazy...but it was a side project and not my real amp.  I would pull out the oscilloscope, if I were you.  I hate pulling mine out, it's gigantic and analog.  I need a smaller one that I can keep on my desk.
   
  I will need to check the schematic, but you can also ask Tom.  There should be a way to pull the gain tube, and ground the grid, and run the 300B to see if the hiss is the gain stage or the buffer stage.
   
  The pinging, ugh.  My amp at work has a ping in one channel.  It's the voltage gain tube on mine.  Mine doesn't go away, it comes and goes constantly.  I have a serious love/hate with tubes.  It's fun to work on, but it sure pisses me off at times.  Fortunately for me, I'm going back to solid state for a bit and for fun.
   
  Edit: Oh, and if you do that,be careful.  You seem comfortable with HV, but still, would hate to hear of an accident.


----------



## sceleratus

Quote: 





holland said:


> The squeak sounds like DC offset to me, let it warm up a bit before you plug in.
> 
> It's after the pot, in the amp somewhere.  I have a hiss like that in one of my amps, I never tracked it down, too lazy...but it was a side project and not my real amp.  I would pull out the oscilloscope, if I were you.  I hate pulling mine out, it's gigantic and analog.  I need a smaller one that I can keep on my desk.
> 
> ...


 
   
  HV...
   
  Thought I posted how HV cured me from dragging my pinky when using DMM probes.   Like a gent having a spot of tea, or using chop sticks.
  J-10  Pin 1.... twice.
   
  I don't drop my pinky anymore.


----------



## holland

Quote: 





sceleratus said:


> HV...
> 
> Thought I posted how HV cured me from dragging my pinky when using DMM probes.   Like a gent having a spot of tea, or using chop sticks.
> J-10  Pin 1.... twice.
> ...


 
   
  Drain all caps with a power resistor before you touch anything.


----------



## sceleratus

Check


----------



## randytsuch

Quote: 





holland said:


> Drain all caps with a power resistor before you touch anything.


 
  I usually put a discharge resistor on my HV caps in the power supply, to drain the caps after shutdown.  I have also seen people that this might degrade sound, but I would rather be safe .
   
  With a discharge resistor, you either need a large value resistor, which will take a while to drain it, or a high power one.  You don't want the r value too low (if you go high power) because then it will draw too much power.  Power = current x voltage or v squared / r


----------



## DefQon

Bleeder resistors. This build is looking good but also very expensive.


----------



## tomchr

Folks,
   
  Wow. Lots of questions today.
  Quote: 





holland said:


> Headphone amps usually have a volume control on the input before the gain stage, especially with tubes.  They are more like a preamp in that regard.


 
   
  I know. And the schematic posted in Post #169 would be useful in that case. However in Sceleratus' build, the XLR connectors are used on the output, RCA connectors on the input. With single-ended input, there's no need for more than the 2-gang pot he already has. Should he ever convert to a differential input, the volume control schematic in Post #169 may come in handy.
   
  Quote: 





sceleratus said:


> [size=small]I picked the panels up from the polisher.[/size]
> [size=small]Needless to say, I am pleased.[/size]


 
    
  Dang!! That's nice metal work. 
   
  Quote:


sceleratus said:


> I sent him this recording (300B Hiss) I made of the startup sound using a Rode stereo mic stuffed inside my LCD2 ear pads.  Ignore the [size=small]prominent noise that sounds like a motor.  I am not sure where it came from but it's not part of the hiss.[/size]
> 
> Here is Jack's reply.
> 
> ...


 
   
  I second Jack's opinion. Get some actual measurements of this. Your recording may be entertaining, but as you already point out, other interference sources are present (motor sound). You'll need a spectrum analyzer for the measurement as an oscilloscope won't be sensitive enough. A spectrum analyzer will also tell you the spectral composition of the signal. Good news is that an external USB sound card and some software is all you need for that. I'm not aware of any spectrum analyzer software for Mac, but there's several for Windoze - including some free ones. Many people use TrueRTA. Personally, I prefer stand-alone test equipment, hence, use an HP 3562A in addition to an HP 8903A distortion analyzer.
   
  I measure 300 uV (micro volt) RMS, 80 kHz bandwidth on the output of my amp. Before I added the cap across the LED, the output measured 380 uV. The hiss does reduce as the amp warms up.
   
  It should also be mentioned that the hiss you mention was recorded on a prototype setup with rather long connections between the components, right? So layout hasn't been ruled out yet. You should be able to reproduce the performance I'm seeing in my setup once you have the parts in a shielded box and the connections tidied up.
   
  I doubt you'll find much on the B+. My 21st Century Maida Regulator takes 50 Vpp ripple and reduces it below the noise floor. I measure 20 uV RMS of noise+residual ripple/hum on the output of the regulator. If you measure this with a regular handheld DMM, it will read 0.0 mV AC. I use a 6-digit voltmeter to measure this. That said, if you do measure the B+ using a DMM and it does not read 0.0 mV AC, you should do a little debugging... 
   
  Note that measurements should be taken after at least 15 minutes of warm-up. The performance of the tubes improve significantly as they reach full operating temperature. For final test of my designs, I generally wait a good 30-60 minutes. In my 300B amp, the THD drops by about 2x (0.6 % -> 0.3 % @ 1 kHz, 1 W, 8 ohm) between cold and 15 minutes of warm-up. It settles around 0.25 %. In other tube circuits, I've seen much larger variation.
   
  You should expect a few pops and odd noises on startup. If you're concerned about these, I suggest adding a mute relay on the output. These sounds are generated by the various voltages stabilizing as the tubes start to conduct. 
   
  Quote: 





grindingthud said:


> Vary R27 around a little and listen if hiss gets louder or softer. It's got to be noise from one of those 1st two stages...and I'm betting its the second one with the bias pot, which could be noisy. It does sound like Jack is on it though and will be able to narrow it down pretty quick.


 
   
  Here's what I tried:
  1200 uF capacitor across filament on 300B: No effect
  22 nF capacitor from the wiper of R13 (bias pot) to ground: Reduced output noise by 5~10 uV RMS. Don't add too much cap here as this may cause over-current in the 300B during startup. 100 nF may be OK.
  10 uF capacitor across LED in input stage: Reduced output noise by 80 uV (from 380 uV to 300 uV RMS, 80 kHz BW). I tried bigger caps as well, but they didn't provide any improvement over the 10 uF.
   
  One thing I would like to try is to replace the LEDs with a resistor. For the E88CC, 910 ohm or 1 kohm with at least 100 uF in parallel would be a good starting point.
   
  Quote: 





holland said:


> Edit: Ask Tom if he thinks it needs a cap multiplier.


 
   
  Hey now! 
   
  ~Tom


----------



## holland

Quote: 





tomchr said:


> I know. And the schematic posted in Post #169 would be useful in that case. However in Sceleratus' build, the XLR connectors are used on the output, RCA connectors on the input. With single-ended input, there's no need for more than the 2-gang pot he already has. Should he ever convert to a differential input, the volume control schematic in Post #169 may come in handy.


 
   
  I haven't been paying too close attention, but I thought I saw XLR cutouts on his back panel, in addition to the front.  One could definitely wire balanced input to be SE input by grounding the (-) or using a transformer (Cinemag).
   
  Quote: 





> Originally Posted by *tomchr* /img/forum/go_quote.gif
> 
> Many people use TrueRTA. Personally, I prefer stand-alone test equipment, hence, use an HP 3562A in addition to an HP 8903A distortion analyzer.


 
   
  I've been meaning to get that, but something about using a sound card doesn't seem all that accurate.  I will pick it up now though, thanks for the reminder.  A stand alone analyzer is $$$$$$$ and more $$$$ on top of that.  I'd have to think a scope can pick this up though, it seems fairly loud/big and would be surprised if it's not some mV variation somewhere.  If not, there's a preamp that people have used.  An example of one is http://tangentsoft.net/elec/lnmp/


----------



## sceleratus

Tom,
   
  Thanks man.


----------



## sceleratus

Quote: 





holland said:


> I haven't been paying too close attention, but I thought I saw XLR cutouts on his back panel, in addition to the front.  One could definitely wire balanced input to be SE input by grounding the (-) or using a transformer (Cinemag).


 
  Hey Holland,
  The cutouts are for Neutrik's   They are the same for RCA and XLR.   Down the road I might make the change as I have both jacks.
  For now it's RCA.  I have to freeze the changes.
   
   



> I've been meaning to get that, but something about using a sound card doesn't seem all that accurate.  I will pick it up now though, thanks for the reminder.  A stand alone analyzer is $$$$$$$ and more $$$$ on top of that.  I'd have to think a scope can pick this up though, it seems fairly loud/big and would be surprised if it's not some mV variation somewhere.  If not, there's a preamp that people have used.  An example of one is http://tangentsoft.net/elec/lnmp/


 

   
  My Mac has Parallels and Windows 8  ("8" Don't say anything !! )
  I have been able to run Rigol virtual scope type software through the USB to my 1052.  I bet there is a good chance the spectrum analyzer software will work.
   
  Thanks for participating.
  I do appreciate it.
   
  Even if I don't understand all the answers


----------



## holland

Quote: 





sceleratus said:


> Hey Holland,
> The cutouts are for Neutrik's   They are the same for RCA and XLR.   Down the road I might make the change as I have both jacks.
> For now it's RCA.  I have to freeze the changes.


 
   
  Ah!  Got it.  You can still use the 2-gang pot for balanced volume control.  Morgan Jones has it documented in his book, and if you look at the "Monolith" thread, there's a schematic there which shows the same thing.  I was just ribbing you for going all out, except for the pot.
   
  Quote: 





> Originally Posted by *sceleratus* /img/forum/go_quote.gif
> 
> My Mac has Parallels and Windows 8  ("8" Don't say anything !! )
> I have been able to run Rigol virtual scope type software through the USB to my 1052.  I bet there is a good chance the spectrum analyzer software will work.
> ...


 
   
  You're welcome, if that was intended for me.  I'm not sure how helpful I have been, but it helps to kill the time too. 
   
  Windows + Parallels, eww!  Resource hog.  You can also use boot camp.


----------



## holland

Quote: 





holland said:


> I will need to check the schematic, but you can also ask Tom.  There should be a way to pull the gain tube, and ground the grid, and run the 300B to see if the hiss is the gain stage or the buffer stage.


 
   
  I looked, you should be able to pull it.  You might need to use a voltage divider to get the grid voltage to -80V.  Then you can check the 300B.
   
  To check the 6N6P side of things, you should be able to pull the 300B and put a cap and a resistor to ground on the input to the 300B.  The 6N6P is in a fairly basic configuration.  The amp has 3 stages.  It's a grounded cathode for the first stage (voltage gain), and a cathode follower for the second stage (current amplifier and reduces Z).  You can plug in the headphones after the cap.
   
  For the "headphones" part, you can plug in the spectrum analyzer software through a make shift jack, but first test the jack with a DMM, and also use a cheap pair of $5 headphones to double check, so you don't blow up your sound card.  Let it sit for a few minutes before plugging in, so the cap can charge.
   
  I'm a big fan of dissecting into parts and testing each section.  It's my preference, but not sure how else one would do it, especially after you diagnose the noise as rectifier noise.  Perhaps someone with more experience can chime in.  I'm not sure what the PSRR of the active components for the CCS plate loads are.  I have a feeling the hiss might be coming from the 3rd stage, the 300B stage and not the 6N6P stages due to the active components there which should offer some PSRR.
   
  Double check with Tom if it's even worth doing, and if it's correct or not.
   
   

```
6N6P Tube | | --------- 470uF to 1000uF 300V Cap (electrolytic is fine) ---------- o ---------- headphones | | | | | Resistor 33K Resistor | | | -225V Ground
```


----------



## sceleratus

Quote: 





holland said:


> Ah!  Got it.  You can still use the 2-gang pot for balanced volume control.  Morgan Jones has it documented in his book, and if you look at the "Monolith" thread, there's a schematic there which shows the same thing.  I was just ribbing you for going all out, except for the pot.
> 
> 
> You're welcome, if that was intended for me.  I'm not sure how helpful I have been, but it helps to kill the time too.
> ...


 
   
  I emailed Justin at Headamp after you suggested I check out the CT-2.  He has a balanced CT-2  $300.   I'll be waiting a couple months if I go there.
   
  I am freezing the project and working toward completing the best possible build for the meet.
  Haven't read your next post but saw 6N6P.  Tom gave me a mod to run ECC88's.
  Glancing again you are just referencing the schematic.
   
  I will read...
   
  In a few minutes I going to work on reassembly, performing all the startup validation tests, biasing the 300B's, and seeing what I have.
   
  I ordered an external sound card that had almost 5 stars out of 800 reviews on Amazon for use with RTS spectrum analyzer.  Sounds like something an amp builder should have in his quiver.
   
   
[size=1.7em] Syba SD-CM-UAUD USB Stereo Audio Adapter, C-Media Chipset[/size]   
  A month or two back Tom gave me this thread with a stepped attenuator design.  You probably know it already.
   
  I have had good luck with Parallels over the years.  I am running version 8 and I haven't had a problem.  I like that I can configure it for x amount of memory and x processors.   I close all the Mac apps, fire up Parallels and give it a bunch of resources.  Works great.
   
  I can click back to the Mac for basic apps.


----------



## sceleratus

This is my first significant electronics build and a non-kit build at that.  I've said before, I'm a solder and project.  Very weak on circuits.  What I am pretty good at is the build.  I like things done right.
   
  I started this thread to document the progress.  I also wanted to learn from the responses.
  I am delighted that so many knowledgable readers have found the thread and posted.  I've enjoyed them all and learned a few tidbits from many.  You guys are my check resource.
   
  Now I know it's a forum and ya don't know the credentials of everyone that posts, but that doesn't mean I don't want all of it.  "electronics advice is like a box of chocolates ......"
   
  I will always defer to Tom.  It's his baby.   I'm also totally stoked that he is taking the time to read everyones posts (that I don't understand) and respond.  Thats the purpose of this thread.  Exchange and learn.  That's what I see from Tom's projects.  They are there to promote tube amps and learning.  
   
  I'm blown away that Tom worked on this for several years than posts the schematics and BOMs.  Wow.  If you are a guy like me that hasn't etched a board yet, buying them from Tom, for basically "lunch money" and knowing they are correct is great.  If you are an experienced builder you get a great design for nothing.  This is the first DG 300B headphone amp.  So it's under the microscope.  I'm going to work towards making it great.
   
  Yes it's an expensive build, but I wanted to leave something to my family that looks great, works great and endures.   Or gets $50 on Craigslist.


----------



## sceleratus

Quote: 





holland said:


> I looked, you should be able to pull it.  You might need to use a voltage divider to get the grid voltage to -80V.  Then you can check the 300B.
> 
> To check the 6N6P side of things, you should be able to pull the 300B and put a cap and a resistor to ground on the input to the 300B.  The 6N6P is in a fairly basic configuration.  The amp has 3 stages.  It's a grounded cathode for the first stage (voltage gain), and a cathode follower for the second stage (current amplifier and reduces Z).  You can plug in the headphones after the cap.
> 
> ...


 
  Deferring to Tom.
  I think I get the concept.
   
  Before I retired, I owned a large networking company.  My clients were all fortune 500.
  As I grew I hired engineers, but I still knew how to troubleshoot network problems and I got a lot of great clients that way.  Many times I'd see the problem before my engineers even though I didn't have any credentials.
   
  Circuits are one or two (important steps) down the food chain from routers, switches, firewalls, and AP's.  However, troubleshooting methodology remains the same.  Isolate knowns from unknowns.


----------



## tomchr

Folks,
   
  Quote: 





sceleratus said:


> During warm up I can also hear the 300B's ... expanding?..... a single ping  .. ping.. ping like a filament it stretching /  tightening.  Microphonic but not.  That quickly goes away.


 
   
  Yep. Mine go pink ... pink for a few minutes until they're warm. That's thermal expansion of the tube. Recall the filament is probably about 500 degrees C... I've tried some FullMusic 300B/n tubes. Nice tubes!! But on those it sounded like the filament went spoinnnng as the tube heated up. They're live creatures...  Tubes and DHTs in particular are microphonic. No way around that. So any sudden relief of stress (tube going 'pink') will be picked up by the tube. In a headphone amp, it wouldn't surprise me if you could hear that. With speakers, I don't notice unless the amp is on with no music playing. Even then, it's subtle. 
   
  Quote: 





holland said:


> The squeak sounds like DC offset to me, let it warm up a bit before you plug in.


 
    
  My best guess is that it's the DC voltage on the inter-stage coupling cap that's stabilizing.
   
  Quote:


randytsuch said:


> I usually put a discharge resistor on my HV caps in the power supply, to drain the caps after shutdown.  I have also seen people that this might degrade sound, but I would rather be safe .


 
   
  There are bleeders in the design. See the schematic on my website. I put red high-efficiency LEDs in series with the bleeders to remind you to keep your paws off the high voltage. Red light --> power is on.
   
  Unless you go nuts with the bleeders and cause excessive ripple voltage (poor design choice), the bleeders won't impact the sound quality at all. I'll opt for safety any day of the week.
   
  Quote: 





defqon said:


> This build is looking good but also very expensive.


 
   
  300B tubes are not cheap. But man.... They do sound good. I absolutely love the tone of mine. I love the imaging, the detail, and the laid back natural sound. I-heart-300B.... What can I say. 
   
  A back of the envelope cost estimate reveals that you're looking at about $550ish in board and component cost for a "cost over quality" cost reduced build. A good "value" build would use Edcor CXSE-series output transformers ($80/each) and result in about $750 of board and component cost. For a high-end build, I would use Electra-Print output transformers and upgrade the 300B from JJ to FullMusic 300B/n. This increases cost quite a bit. Mostly because of the cost of the OPTs. I paid $260/each for mine because I wanted dual secondary (4, 8 ohm). So for a high-end build, you're probably looking at a bit over a grand... And you can go up from there, though, I strongly suspect you're hitting the flat part of the performance/log(price) curve at that point.
   
  Above numbers don't account for a chassis. I spent about $80 on aluminum and machined my own chassis. See the results on my website. I built two stereo amps for use in a bi-amp setup. I use them for several hours every day. /me like... 
   
  For builders who are looking for more cost effective solutions, I do have some new developments in the pipe. What I have in the lab now sounds very good but to get the golden sound of a high-end 300B amp, well..... you'll have to fork over some cash. 
   
  Quote: 





holland said:


> I looked, you should be able to pull it.  You might need to use a voltage divider to get the grid voltage to -80V.  Then you can check the 300B.
> 
> 
> 
> ...


 
   
  As Holland says, you need to add a voltage divider if you want to test the 300B alone. Pull all tubes. Solder a 39 kohm, 2 W or 3 W resistor from pin 1 to pin 3 of the small tube socket. Verify that you have about -85 V on the grid pin of the 300B socket. Turn power off and plug in the 300B. Keep an eye on the bias current of the 300B while doing this. Don't let it exceed 100 mA.
   
  I hope the "graphics" above don't get garbled. The ASCII schematic above is correct. If you're using an el-cheapo 32 ohm headphone for the test, you can get away with a 100 uF coupling cap. That's easier to find than 470 uF - 1000 uF. The cap needs to be rated for at least 300 V. 400 V would be better. Electrolytic no-name cap is fine. The resistor to ground should be a few hundred ohm. I'd use 330 ohm (10x the headphone impedance).
   
  ~Tom


----------



## sceleratus

The FX-888 is at temp.
  I am going Dark


----------



## holland

Quote: 





sceleratus said:


> Or gets $50 on Craigslist.


 
   
  Send me a PM before it gets there.  I'll even double it and give you $100 for the amp, case and parts, even if it doesn't work.  
	

	
	
		
		

		
			




   
  Quote: 





> Originally Posted by *tomchr* /img/forum/go_quote.gif
> 
> For builders who are looking for more cost effective solutions, I do have some new developments in the pipe. What I have in the lab now sounds very good but to get the golden sound of a high-end 300B amp, well..... you'll have to fork over some cash.


 
   
  I was just starting to think about a Susy and/or Circlotron build around a couple of tubes (6H30) and output transformers.  Simple, but should be good (enough for most headphones anyway).  Susy would probably be easiest.


----------



## tomchr

I'm thinking triodes or triode coupled pentodes. I really enjoy the triode sound.
   
  ~Tom


----------



## sceleratus

Quote: 





holland said:


> Send me a PM before it gets there.  I'll even double it and give you $100 for the amp, case and parts, even if it doesn't work.
> 
> 
> 
> ...


 
  Talking about my kids after I'm in the hereafter.
   
  The only resistor I have a spare is  R24 / R10   33K ohm 3W


----------



## sceleratus

Changing tips on the FX-888
   
  I have pulled the Jupiter Condensor .22uF caps and replacing them with the stock Solen .22uF cap.


----------



## tomchr

You'll have to use 39 kohm for the test. It doesn't have to be a single resistor. It could be a combination of resistors in series or parallel to give 39 kohm (+/-1 %). Otherwise, you run too much current through the 300B (bad for the tube) or too little (don't get a representative test). It would be even better if you had a potentiometer that could handle the power and be used for the test.
   
  ~Tom


----------



## tomchr

Pin 1
 |
 |
 33kohm
 |
 |
 10kohm pot ----> 300B grid
 |
 |
 Pin 3 
   
  Would work as well.
   
  ~Tom


----------



## sceleratus

Texas Component Corp. resistors


----------



## sceleratus

I have to walk away, lest I start making mistakes.
   
  Doing the tedium ALPs volume pot runs.
  Little did I know I bought the PCB version.  
	

	
	
		
		

		
		
	


	



   
  Then I'm using this soft annealed silver wire for the first time.
  "I don't know"
   
  It's tedious to measure the right lengths, thread the teflon jacket and hope you don't kink it at the connection point.
  The jacket is though... if you need to cut it back you are at risk of nicking the wire.
  "I don't know"
   
  Hope it's worth the PIA


----------



## tomchr

Teflon is a [FEMALE DOG] to work with in my experience. You really have to score the Teflon without nicking the wire and then pull it off the wire. It's real nice in high temperature applications, though. Think 100~150 C.
   
  ~Tom


----------



## sceleratus

holland said:


> Drain all caps with a power resistor before you touch anything.




Thanks Professor,

There will be no electrons flowing today. 
I need to triple check my connections in the AM and repeate the startup procedure.

I hooked up the DMM to the Texas resistors. Good to .01 They look bad azz too.


----------



## tomchr

Good call on getting some rest when you get tired. High voltage is not to be messed with while tired or under the influence.
   
  I'll see if I can take some noise spectrum measurements on my amp tonight. Will post results here.
   
  ~Tom


----------



## tomchr

My measurements show that the slight hiss (300 uV in my setup) is caused by the driver circuit - i.e. the 6N6P/E88CC/ECC99/12BH7A - and not the 300B. Using an E88CC driver tube, the circuit has a gain of about 30 V/V. This means all noise will be gained up by that much. 
   
  300 uV is actually very quiet for a speaker amp. This is also why I chose not to mess with it as the hiss is only barely audible when I stick my head right up against the tweeter in a quiet room. Sadly, this is exactly what you're doing all the time with a headphone...  Also, with a 5k:60ohm transformer, you'll also get more noise than I do with my 5k:8ohm transformer as the turns ratio is lower.
   
  There's a couple of things to try.
   
  First off, I suggest you try the 56 ohm series resistor on the output that we discussed in email.
   
  Secondly, and this is a bit more drastic, you can remove Q2 and Q4. Then connect pins 6 and 7 on the driver tubes (TU1, TU3). This removes the gain stage of the circuit. This is as quiet as the circuit can be - unless all the noise comes from the cathode follower formed by TU1A, TU3A, which I highly doubt. 
   
  ~Tom


----------



## tomchr

I tried resistor biasing by the way. 620 ohm || 470 uF in place of the stack of LEDs. The THD was slightly lower, max power slightly higher, but the noise level was unchanged.
   
  ~Tom


----------



## holland

That's good that you have it isolated.  That's bad that it's from the gain.  I was afraid gain would be too high from the start, being speaker amps need much more gain than headphones.  Orthodynamic headphones don't need that much gain, regardless of all the hype people are throwing around about needing a 5W amp.
   
  An output resistor will help, but the damping factor changes and the sound will change significantly, IMO.
   
  choices:
   
  1) Use the resistor instead of LEDs Tom mentioned above, but remove the cap for some degenerative feedback.  It will introduce non-linearity to the sound as well since it's not bypassed, not huge but different.  It may not be enough, but should affect steady state noise.
  2) Apply a negative feedback loop around the first two stages (-12dB or so from the cathode follower back to the grounded cathode input).  This will have classic feedback loop effects, but since it's a low amount should be OK.
  3) Remove the CCS on the grounded cathode stage and use a resistor and lower gain the old fashioned way, like #1 for downside.  The operating point needs to be recalculated.
  4) Use a lower mu tube, #3 recalculates and so does this.  6N6P has a mu of 23 or so.  6DJ8 has a mu of about 33.  I also mentioned that I like the 6H30, one reason is for the lower mu for OTL circuits, around 15 or so.
  5) Find the source of the originating noise and quiet it down.
   
  1-4 will affect the sound.  #2 may be the least altering, maintaining the original shape.  #5 may be hard.
   
  Anyhow, after it's fully built, the noise shape may be different.


----------



## tomchr

A little negative feedback goes a long way. It wouldn't be too difficult to add around the driver stage and cathode follower.
   
  Looking at the plate curves for the E88CC, it looks like a 47 kohm plate load would work. I'd start with 47 kohm on the plate, 620 ohm (unbypassed) in the cathode. If that doesn't reduce the gain enough, this opens up options for plate-to-plate feedback as well as regular cathode feedback.
   
  And I agree... Let's get this thing in a box before making design changes. Once the wiring is tidied up, noise, hum, and EMI are easier to control.
   
  ~Tom


----------



## sceleratus

Wow !
   
  Thanks for the recommendation and the valve amplifier lesson.  It gives me a lot to investigate.
  What's one more rush DigiKey order in the grand scheme of the project?  Then there is no rush really.
   
  Can the board get jacked up by soldering than solder sucking too much?  I know I don't want to lose the PADs, but what about the repeated heat?  I'm buying a second board anyway.
   
  The original design altered to support ECC88's with the Jupiter beeswax 0.22uF caps was the first and only listening point.  None of the mods have been auditioned.  That said.
   
  The noise was there, but not "too intrusive"  My friend has been in the audio business for eons.  The designed and built theaters for McMansions.  Big, money is no object stuff.  He has an audiophile top end Linn system.  Music is a huge thing to him.  Also named Tom.
   
  Tom listened to the 300B, as above, for quite some time A/B ing with the Lyr.  He loved the 300B and although he noticed the noise he said that in no way was it a show stopper.  "It fades into the music".  There is the psyc factor that your mind trys to pick it out and that can be annoying, but in the end it's not that significant.   
   
  I wanted to put this thing in context.  Even if it sounds the same after the 25% fix and the resistors and playing with the 56 ohm resistor, I will bring it to the meet.  All that matters is that "I like it" and I definitely do.  What ya'll already know and I just discovered, is with a DIY you can tinker endlessly.  That's cool.   I have plenty of time tryout the suggested revisions.  I'll probably order a second driver board just for that purpose.
   
  It's all good !


----------



## sceleratus

Quote: 





tomchr said:


> A little negative feedback goes a long way. It wouldn't be too difficult to add around the driver stage and cathode follower.
> 
> Looking at the plate curves for the E88CC, it looks like a 47 kohm plate load would work. I'd start with 47 kohm on the plate, 620 ohm (unbypassed) in the cathode. If that doesn't reduce the gain enough, this opens up options for plate-to-plate feedback as well as regular cathode feedback.
> 
> ...


 
  Yup.
   
  Box it !


----------



## sceleratus

Made a change to the front of the enclosure.
The wood knob wasn't going to happen.
   
I went to the drawing board and I like what cme out.  A lot.
   
3.5" hole with half round bevel to 4"
Dark Walnut back plate for the volume POT
1.75" antique knob that I purchased on eBay.
   
Bottom line the knob will be recessed and the woods will contrast.


----------



## tomchr

Quote: 





sceleratus said:


> Can the board get jacked up by soldering than solder sucking too much?  I know I don't want to lose the PADs, but what about the repeated heat?  I'm buying a second board anyway.
> 
> All that matters is that "I like it" and I definitely do.
> 
> It's all good !


 
   
  I'm glad you like it. It brings a smile to my face to know that someone out there was able to make it work well and likes the results.
   
  Now on your question about soldering. It is possible to ruin a board by repeated soldering. However, I do my best during the layout process to ensure that the boards can stand up to repeated soldering and desoldering. Compared to a commercially produced board, the pads I use for the components are oversized and the traces are much wider. This along with the through-plating and the solder mask tends to keep the pads and traces in place during the soldering. So yeah... In addition to optimizing my layouts for signal integrity and performance, I also take into account that the boards will be assembled by tinkers of varying skill levels and lay out my boards accordingly. I like to set people up for success...
   
  ~Tom


----------



## sceleratus




----------



## sceleratus

HD_Tracks
Remastered
We are talk'n Rolling Stones Magazine #2 Album of All Time (Out of 500).
   
  [size=medium]This amp take this album places I've never been to.[/size]
  [size=small]I can hear the drum skins ripple with the first licks of "Wouldn't it Be Nice"[/size]
   
  [size=medium]Otherworldly[/size]
   
   
   

   
   
DISCLAIMER:  ONLY OTHER HP AMP I'VE HAD IS A SCHIIT LYR.


----------



## randytsuch

So it must be back together.
   
  Pics?


----------



## sceleratus

Indeed it is.  Still looks like a Franken-amp.
  I believe it is fully cooked for the meet.  A soldering Iron will not be touching the boards for some time.
   
  I rolled some 1959 Valvo PCC88's.  D getters.
   
  I am now calling is a "light fuzz"  I swear, it's grease for the music.
  This thing has an amazing voice.  I referenced "Pet Sounds"
  That album is, IMO,  an acquired taste.  Honestly I never liked it much.
   
  The 300B is sounding so musical, I thought "well I ought to play Pet Sounds.
   
  I get it now.
   
  UPDATE:
  I visited the cabinet maker.  It's going to happen.  Wood was being cut.
  The figured / tiger maple looks amazing.  I saw a test "center volume knob" cut with a large bullnose bevel.
  Exactly what I envisioned.
  A much better design than the large wood knob.
   
  Those that posted I should make the knob contracting with walnut will be happy.  And they were right.  Was it you?  Holland?
  Anyway.  I'm pleased.
   
  After the meet, I am going to put bias test points on the back plate with some nice Vishay Dale precision pots.
  The test points will be Pomona shrouded jacks just like on a DMM.
  I will put a shaft collar with a perpendicular set screw to lock down the POT.


----------



## sceleratus

This thing loves these 59" PCC88's
   
  Like a 383 loves nitrous.


----------



## sceleratus




----------



## tomchr

Quote: 





sceleratus said:


> I rolled some 1959 Valvo PCC88's.  D getters.
> 
> The 300B is sounding so musical, I thought "well I ought to play Pet Sounds.
> 
> ...


 
   
  The driver tube makes a big difference. I really enjoyed the laid back and very musical sound of the 300B amp using PCC88 drivers. Of the ECC88-type tubes I've tried, that one is my favorite.
   
  Bias connectors are a great idea! I regret not fitting some on my amp. However, you do have to keep in mind that although the voltage difference between the two pins on the bias test point is only 850 mV, the test points are elevated to the B+ voltage (400 V). So with banana plug connectors, such as the Pomona connectors you show (nice connectors by the way!!), if someone was to stick a metal object into the connector, they'd be able to electrocute themselves. I'd go for a connector with a cap. For me, that brings associations of the MILSPEC Amphenol connectors. I couldn't find a good picture of the Amp connectors, so here are similar connectors from Clansman.
   
   

   
  They tend to be nearly indestructible, impossible to connect the wrong way, rather bulky, and very expensive. But, they're not exactly pretty... Hey... Maybe if you painted that maple box a nice olive drab and dropped it on the floor a few times those connectors would fit right in... 
	

	
	
		
		

		
			





 On a more serious note, you can sometimes find these connectors for dimes on the dollar at electronic surplus places.
   
  Anyway. Just beware that those connectors will be floating at high voltage. If you do go with the banana plugs, place them 0.750" apart. That's standard and will allow you to use various banana-to-whatever adaptors, which may come in handy.
   
  For a lockable bias pot, that's a solved problem. Allen Bradley makes some nice ones. They have slits in the collar to form fingers and a tapered nut goes on top and squeezes the fingers together to lock the shaft. It's more obvious from the pictures.
   


   
  Kinda clunky but could be made to work. Personally, I'd leave the bias pots on the board. The Bourns I specified in the BOM are quite nice. Just adjust them through a hole in the top plate as it looks like you were planning to do. The nodes around the bias pot are pretty high impedance. You're quite likely to cause issues with EMI/hum/noise if you move the pot off the board.
   
  In my amp, I put some heat shrink tubing around the pots to prevent the screwdriver from sliding off the pot during the adjustment. 
   
  ~Tom


----------



## GrindingThud

Military SMA connectors are another option. They can also be capped and look good in stainless.
http://www.pasternack.com/50-ohm-sma-male-non-shorting-cap-with-2.5-inch-chain-pe6019-p.aspx
http://www.pasternack.com/sma-female-standard-solder-cup-terminal-connector-pe4219-p.aspx



tomchr said:


> Bias connectors are a great idea! I regret not fitting some on my amp. However, you do have to keep in mind that although the voltage difference between the two pins on the bias test point is only 850 mV, the test points are elevated to the B+ voltage (400 V). So with banana plug connectors, such as the Pomona connectors you show (nice connectors by the way!!), if someone was to stick a metal object into the connector, they'd be able to electrocute themselves. I'd go for a connector with a cap. For me, that brings associations of the MILSPEC Amphenol connectors. I couldn't find a good picture of the Amp connectors, so here are similar connectors from Clansman.
> 
> 
> 
> ...


----------



## holland

Quote: 





> Originally Posted by *sceleratus* /img/forum/go_quote.gif
> 
> Those that posted I should make the knob contracting with walnut will be happy.  And they were right.  Was it you?  Holland?
> Anyway.  I'm pleased.
> ...


 
   
  Yep, it was me.  I'm glad it's working out.  Give an update on the hissing after it's built.  I pulled out my old amp that has a buzz and I think I'm going to fix that.   Cap multipliers FTW. 
   
  Bias points are neat, though I think using a multi-prong connector may be better.  Tom pointed out Amphenol.  I use those connectors for PS entry points when running a separate supply.  Anyhow, you can string them all into a jig so that you don't have to reach behind to probe.
   
  I don't like to mess with bias after it's set up.  It's a no win situation of constant fiddling.   You need to reach into the amp to adjust so I'm not entirely sure how much it saves you, other than giving you an easy way to stress out over bias.


----------



## sceleratus

Quote: 





holland said:


> Yep, it was me.  I'm glad it's working out.  Give an update on the hissing after it's built.  I pulled out my old amp that has a buzz and I think I'm going to fix that.   Cap multipliers FTW.
> 
> Bias points are neat, though I think using a multi-prong connector may be better.  Tom pointed out Amphenol.  I use those connectors for PS entry points when running a separate supply.  Anyhow, you can string them all into a jig so that you don't have to reach behind to probe.
> 
> I don't like to mess with bias after it's set up.  It's a no win situation of constant fiddling.   You need to reach into the amp to adjust so I'm not entirely sure how much it saves you, other than giving you an easy way to stress out over bias.


 
I like the elegance of using plug-to-plug DMM test leads.  I would need to convert the Amphenol jack to DMM and a "Y" adapter at that.
   
Electrocution Factor:
I believe the DMM contacts are recessed more than a standard household AC outlet and by shear numbers the outlets are always live whereas the amp is only hot when in use and likely will not be unattended when it is on.  Child with a screwdriver probability....  AC outlet high, 300B test points while on, Low.
   
Biasing.
I purchased a ceramic screwdriver for adjusting the trimmers.  The risk reward sounds too high for replacing the pots.  I wanted an opinion on that.  Thanks T.C.
Why do I like external access?  If I roll 300B's it's a snap to check the bias.  Plug, plug, tweak, tweak, done.  The [size=small]impetus came from Holland's comment that the fuzz could come from a faulty POT.  Damn-U Holland.  But then I wouldn't have had the test point idea.  Thanks Holland.[/size]
   
Fuzz.
I am now calling the hiss, fuzz.  It's is greatly reduced after 20 minutes and I can't detect it while listening to music.   Last night 's listening session was incredible with the 1958 PCC88's.  I think burn plays a significant factor.  I'm glad there's no real upside to swapping the trimmers because I don't want to take an iron to the board.  Next, for now I am keeping the 56 ohm resistors in my back pocket.  I'll tinker after the meet.   Holland, your comment about effecting the sound signature jumped off the page.  In no way do I want to neuter the sound signature.  I love it.
   
  [size=small]I didn't want to take the LCD2's off and put them away.  I keep getting those "shake your head" moments in a lot of tracks during a listening session.  The, wow, that's amazing ones  "I never heard that".  My comments on Pet Sounds album tracks is an example.  I used to only play "Good Only Knows"  and "Caroline".  Now, I like 75% of the album.  This amp just smashed my Lyr.  Disclaimer: that's the only HP amp I've owned, and maybe it's not hard to do, IMO, the DG 300B leaves it in the dust. [/size]


----------



## sceleratus

Ceramic screwdriver
   
Velleman VTCS3
   
   
   
   

   
   
   
   
   
   
DMM Jack


----------



## tomchr

Love that ceramic screwdriver! My tweaker set is in some sort of reinforced plastic. Not very useful as the plastic tends to get all mucked up during use.
   
   
  Quote: 





grindingthud said:


> Military SMA connectors are another option. They can also be capped and look good in stainless.
> http://www.pasternack.com/50-ohm-sma-male-non-shorting-cap-with-2.5-inch-chain-pe6019-p.aspx
> http://www.pasternack.com/sma-female-standard-solder-cup-terminal-connector-pe4219-p.aspx


 
   
  Except in this case, the SMAs would be floating at 400 V. So there'd be 400 V on those metallic caps. You really need a two-pin connector (or 4-pin if you want both bias points on the same connector) with a grounded shield if you're using metal connectors. 
   
  Quote: 





holland said:


> I don't like to mess with bias after it's set up.  It's a no win situation of constant fiddling.   You need to reach into the amp to adjust so I'm not entirely sure how much it saves you, other than giving you an easy way to stress out over bias.


 
   
  There's certainly some truth to that. During the development when the amp sat as exposed boards on a piece of plywood, my handheld Fluke meter was never far away and I checked the bias often. Now I don't check it unless I have the amp cracked open anyway. Once the tubes are burned in, the bias doesn't shift all that much. I would still support checking it every now and then. One or twice a year perhaps.
   
  Now if you're into tube rolling, you need more ready access to the bias points. You definitely need to readjust the bias after swapping the 300Bs and I would recommend rebiasing after rolling the driver tube as well.
   
  ~Tom


----------



## GrindingThud

Nope, cap is grounded to case, pin floats in center of connector and never touches cap. That's what the 'non shorting' version is for...keeps water out too. 
I use these all the time in radar applications. Insulation good to 1kv standoff. 

Although if you had 6 of them, I agree that using a single cannon plug with a custom adapter would be better.

This thread has me wanting to do one of these.....



tomchr said:


> Except in this case, the SMAs would be floating at 400 V. So there'd be 400 V on those metallic caps.
> 
> ~Tom


----------



## FrankCooter

Really enjoying watching the evolution of this amp and the process of your journey. Whatever physical state your amp is in, it will be a pleasure and an honor to listen to .  I can guarantee that your amp will not be the ugliest one at the meet. I'm pretty sure my electrostatic amp will have a lock on that distinction.  I'm actually a big fan of "Franken-amps". Perhaps the most awesome amp I've ever seen was the "Homeless Amp", which was built on a pair of trashed  grocery store shopping carts and displayed at a "New York Noise " festival back in the early '90's. Alas the pictures seem to have vanished from the internet, but it was an awesome thing to behold and apparently also to listen to (it gave me the idea to use mercury vapor rectifiers in some of my builds) It was the perfect antidote to the pretentiousness and indulgence that often goes with a lot of modern "high-end" audio.


----------



## sceleratus

Hi Frank, thanks for the post.
   
  I'm going to add "I'm just an idiot that knows how to solder" to my signature.
  Pretty sure my implementation of the DB300B will look a bit on the pretentious side.
  When it come to circuits there is no doubt I'm a form over substance guy.
  Thank God for Tom.
   
  I hope it's not the Bimbo amp.      (Not a chance)
   
  It's my opus.  My one hit wonder.  A new world.
   
  Electrostatic amp.......   I'll loan you a little static at the meet.
   
  I sure hope I don't let you down...


----------



## tomchr

Quote: 





grindingthud said:


> Nope, cap is grounded to case, pin floats in center of connector and never touches cap. That's what the 'non shorting' version is for...keeps water out too.


 
   
  Oh, I see what you're saying. So for the four connections needed, you'd use four SMA connectors. That's a good idea. They're available gold plated for the bling enthusiasts too. Teflon dielectric. 
   
  I use SMAs all the time at work. They're nice connectors.

   
   
  ~Tom


----------



## sceleratus

Quote: 





tomchr said:


> Oh, I see what you're saying. So for the four connections needed, you'd use four SMA connectors. That's a good idea. They're available gold plated for the bling enthusiasts too. Teflon dielectric.
> 
> I use SMAs all the time at work. They're nice connectors.
> 
> ...


 
  And how are you going to terminate to banana jack to the DMM?
   
  My amps not going in a submarine so I stuck with these nylon and gold flashed thingies.


----------



## GrindingThud

Umm, I guess it would be less convenient than a probe socket......... 



sceleratus said:


> And how are you going to terminate to banana jack to the DMM?
> 
> My amps not going in a submarine so I stuck with these nylon and gold flashed thingies.


----------



## sceleratus

Off topic and I can do this because it's my thread....
   
  Old guys:
  Back in the day.. anyone else own Advent speakers?
  Not sure why I thought of this.


----------



## sceleratus

Quote: 





tomchr said:


> Oh, I see what you're saying. So for the four connections needed, you'd use four SMA connectors. That's a good idea. They're available gold plated for the bling enthusiasts too. Teflon dielectric.
> 
> I use SMAs all the time at work. They're nice connectors.
> 
> ...


 
   
   
  The nice thing about this design is it will hold Mushu Pork, Lemon Chicken, Beef & Broccoli, Beef Chow Main, Pork Fried Rice, and Sweet and Sour Shrimp.
  Does everyone at the table get a remote?


----------



## sceleratus

For practice I did a test finish of some maple and walnut scraps.


----------



## GrindingThud

That looks sweet! I like the contrast.



sceleratus said:


> For practice I did a test finish of some maple and walnut scraps.


----------



## tomchr

/me like!


----------



## holland

It looks good!  I loves me some contrast.


----------



## sceleratus

Not much going on.
  I will be picking the enclosure up tomorrow   Wow.  Then light sanding, sanding sealer, and some satin lacquer.  I hate that part.     Then fun again... interconnects and wire management.
   
  I couldn't help myself....   Yup....  I ordered a pair of Mundorf Silver Oil  0.22uF caps. 
  Can't leave well enough alone.
   
  Last night I bought "Chicago Transit Authority"  96kHz flac from HD Tracks.    Wow.


----------



## sceleratus

Someone on the Lyr Tube thread asked how it might stack up against a "B22"  I had never heard of it.  (not a surprise)
   
  I looked it up and it's all SS.   Apples & Oranges?


----------



## sceleratus

My Large Capacitor board  "Outrigger".  Not available in any stores.
   
  Alpha version.  I made it 90 deg off....  Typical.  The cap is supposed to be parallel to the board.


----------



## ninexnine

Oh No!       I ran out of thread to read.
   
  I love this topic.


----------



## tomchr

Quote: 





sceleratus said:


> Someone on the Lyr Tube thread asked how it might stack up against a "B22"  I had never heard of it.  (not a surprise)
> 
> I looked it up and it's all SS.   Apples & Oranges?


 
   
  Well... They're both headphone amps that can be used to drive speakers (or vise versa), so there is some validity to the comparison. However, I don't see the value of speculating how they might sound different, so to me the question is irrelevant. If one had both amps and was able to set up a double/triple blind experiment one could present some scientifically valid data. 
   
  I've built some impressive 'sand' amps. My most recent one is based on an LME49811 IC and measures very well. 0.0005 % THD @ 50 W out I think it was. Max output power: 150 W (8 ohm). I have measurements that would back up claims of the amp being "fast", "high bandwidth", and other audiophile superlatives. On my speakers, it sounds very good.
  Still... The first time I plugged in a 300B amp to my system, I was completely floored. The warm and friendly bass, the openness of the midrange, and the amazing detail on metallic instruments (cymbals, guitar fret buzz and picking details) just blew me away. And this was with my first 300B design. The one I have for sale now is at least two or three iterations beyond my first design. I really like the tone of the midrange on the 300B. Voices sound natural and unstrained. The imaging is amazing - unlike anything I've ever experienced on a 'sand' amp. But.... 0.2 % THD @ 1 W, 10~12 W @ 3 % THD (soft clipping), 35 kHz bandwidth... 
   
  So that's my scientifically invalid "experiment" (N = 1, no blind). I'm obviously biased. But I know what I like. In the end, it all boils down to personal preferences. 
   
  ~Tom


----------



## sceleratus

Quote: 





tomchr said:


> The first time I plugged in a 300B amp to my system, I was completely floored. The warm and friendly bass, the openness of the midrange, and the amazing detail on metallic instruments (cymbals, guitar fret buzz and picking details) just blew me away. And this was with my first 300B design. The one I have for sale now is at least two or three iterations beyond my first design. I really like the tone of the midrange on the 300B. Voices sound natural and unstrained. The imaging is amazing - unlike anything I've ever experienced on a 'sand' amp. But.... 0.2 % THD @ 1 W, 10~12 W @ 3 % THD (soft clipping), 35 kHz bandwidth...
> 
> So that's my scientifically invalid "experiment" (N = 1, no blind). I'm obviously biased. But I know what I like. In the end, it all boils down to personal preferences.
> 
> ~Tom


 
  To that point, all that matters is that I like it and ... "I love it"   (Another redundant post.. sorry)
  Tom,  your descriptions are spot on.  I'm not good at matriculating sound  
	

	
	
		
		

		
			





.
  The voice of the DG 300B is far beyond my expectations.  My only reference point is my Lyr.... it's for sale.  
   
  I'm off to pick up the enclosure.


----------



## sceleratus

Quote: 





ninexnine said:


> Oh No!       I ran out of thread to read.
> 
> I love this topic.


 
A Giant...
	

	
	
		
		

		
		
	


	




  Thanks for the post 9x9
   
This has been a bizzare experience.
I "discovered" Tom because I needed help re-building a tube tester.
One day I returned to his site and read his introduction of the Damn Good 300B.
"Well that's a hell-of-a-lot more fun than a tester"
So I dropped the tester project faster than a hot tube.  I am swimming in components.
   
Next I had the bright idea to "share" my build experience on a thread.
Good or bad.  Call 911 for flames (I only had curling smoke once) or listen to beautiful music, I was going to post.
Dumb ideas and otherwise with lots of pictures.
Well the ante kept going up along with the project costs.
Upgrades here and there......Slippery slope in spades.
I started thinking the "looks like an idiot" factor is getting very high.
   
I compounded everything by announcing I was going to bring the DG 300B to the LA meet.  (In a milk crate)
Like all deadlines it got compressed..... the idiot potential continued to rise.
It my not appear to be the case, but I don't handle that well.
   
Not to jinx anything, but a huge load has been lifted from my shoulders.
It sounds great, I will have an enclosure.  It's going to make it.
What an experience.
   
   
EDIT:
The support I received from everyone has been incredible....


----------



## sceleratus

I have finishing work to do


----------



## sceleratus

Finishing is complete, on to assembly and test.


----------



## tomchr

I really like the contrast between the maple and the walnut legs. The grain of the maple is nicely chosen as well. The clearance along the bottom of the chassis will allow for a good airflow through the enclosure. Very nice.
   
  ~Tom


----------



## ninexnine

It's going to be beautiful.


----------



## holland

I love the case.  The contrast is great, with the maple and walnut.  I love that you went with curly maple instead of birdseye.   I love figured curly maple.  It's going to be really pretty with the polished top.  Don't scratch it assembling!


----------



## sceleratus

scratches... so far the wood isn't scratched. Small but visible. The bronze is delicate.  I know not to attempt to polish because it's sealed. 
  It's just going to happen..
   
   
  The assembly is progressing nicely.


----------



## OldSkool

Quote: 





sceleratus said:


> scratches... so far the wood isn't scratched. Small but visible. The bronze is delicate.  I know not to attempt to polish because it's sealed.
> It's just going to happen..
> 
> 
> The assembly is progressing nicely.


 

 Congrats, buddy! Can't wait to see it.
   
  While you are busy with assembly, you should be thinking about the very first song you will play thru that fully assembled, magnificent amp.
   
  It's a virgin amp and it needs a special song.


----------



## sceleratus

Time to "Light er' up"


----------



## holland

Looks sweet!  Good luck, hope there's no puff of smoke!  Got a view underneath and from the top (45 degrees)?


----------



## sceleratus

Lights are on but no one is home...
  I suspect the input wiring got switched.
   
  I am toast.... It's going to have to wait for tomorrow.


----------



## tomchr

Dang! That's nice. Good work!
   
  Don't forget to ground all metal pieces (safety ground).
   
  ~Tom


----------



## sceleratus

Quote: 





tomchr said:


> Dang! That's nice. Good work!
> 
> Don't forget to ground all metal pieces (safety ground).
> 
> ~Tom


 
  Thanks.
  Yes the top plate ties to all the transformers the backplate is ground to the power entry module both are terminated to the PSU ground lead.
   
  I'm pretty certain I mixed up the RCA input terminations on the Driver Board.
  I threw cation to the wind and sealed up the bottom prior to testing....
  I think that rule number one..


----------



## sceleratus

Notice I scraped the raised domes and went with just the bronze screen


----------



## tomchr

I like the screens. What's the red stuff under the transformers?
   
  Yeah... Rule #1: Don't close up the amp until you've verified that it works.
   
  ~Tom


----------



## muskyhuntr

Wow, that is nice!  Your craftsmanship is second to none.  Like every one else, I look forward to your posts! 
  Can't wait to get a good push on mine.  Have the 300B power supply done and the  21st Century Maida regulator 90% finished.
  I plan on using mine to drive some speakers in a small room.
   
  Jim


----------



## LordShad0w

Gorgeous work my friend. May the sound put a smile on your face.


----------



## sceleratus

Quote: 





muskyhuntr said:


> Wow, that is nice!  Your craftsmanship is second to none.  Like every one else, I look forward to your posts!
> Can't wait to get a good push on mine.  Have the 300B power supply done and the  21st Century Maida regulator 90% finished.
> I plan on using mine to drive some speakers in a small room.
> 
> Jim


 
  You da man Jim !
  Isn't the SMD stuff fun?


----------



## nelamvr6

Looks awesome!  Can't wait to hear how it sounds!


----------



## sceleratus

A am in tears......
   
  OMG !
   
  It Works
   
   It was a huge fight.  Totally freaked.
   
  First song:   James Taylor  "Country Road"   flac  HD Tracks.
   
  EDIT...
  What a difference the Mundorf Silver Oil caps made......  Wow !


----------



## randytsuch

I was worried for you, figured there must have been a problem or you would have posted.
   
  Really glad you fixed whatever it was.
   
  Those mundorf's are supposed to sound really good, one of the best.
   
  Randy


----------



## tomchr

Awesome! I'm really happy for you. BIG SMILE!
   
  ~Tom


----------



## sceleratus

[size=medium]What a struggle…..[/size][size=medium][/size]
 [size=medium]Easy to find…..  XLR's OPT were rolled.[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]No most normal people would say  "Fine switch the OPT wires… in line"[/size][size=medium][/size]
 [size=medium]No not Bozo.   I desoldered these stinking Cardas Jacks. [/size][size=medium][/size]
 [size=medium]Mid way through… and I'm not sure what I was doing a pin comes out.[/size][size=medium][/size]
 [size=medium]"He, looks modular, I'lll pull all of them"[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]They aren't modular.[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]I am certain that they have an accessory plug that the guy I bought them from didn't tell me about.[/size][size=medium][/size]
 [size=medium]Because they were a bitch to solder.  Didn't matter[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]Now it's a good thing I had a set of locking Neutrik's[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]Except, they aren't round.  They have protrusions for the locking mechanism. [/size][size=medium][/size]
 [size=medium]Off to the garaged and the grinder.  Yes grinder.  As in sparks and metallic dust.[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]They fit.  The part the covers the locking mechanism is aluminum foil thin…. but they work.[/size][size=medium][/size]
 [size=medium]Next the hole were off just a tad.  I splintered some maple and filled the holes.[/size][size=medium][/size]
 [size=medium]Next used a square and drilled the pilot holes.   Made some black screws withe a sharpie…[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]Except they are crooked… a tiny bit… but it drives me nutz.  [/size][size=medium][/size]
 [size=medium]I will fix them later.[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]The good news is I like the black sockets much better then the cheesy gold plated Cardas set.[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]More good news.  The Mundorf caps made a huge difference musically.[/size][size=medium][/size]
 [size=medium][/size]
 [size=medium]What a blasted fight.  I'm drained.  At least I have music to listen to.[/size]


----------



## sceleratus

Back


----------



## meme

Congratulations sceleratus, your amp looks wonderful!
   
  This thread has inspired me to get off my backside and get mine done.


----------



## randytsuch

Quote: 





meme said:


> Congratulations sceleratus, your amp looks wonderful!
> 
> This thread has inspired me to get off my backside and get mine done.


 
  +1
  This project inspired me to start a DHT amp.  I had been thinking about it for a little while, this gave me a push to really get it started.
   
  And I am lucky enough to live in LA, and am going to the head fi meet today to check this puppy out. 
	

	
	
		
		

		
			




   
  Randy


----------



## holland

sweetness! 
   
  and so it begins, the endless pit of building amps.


----------



## rb2013

sceleratus said:


> A am in tears......
> 
> OMG !
> 
> ...




Sweet caps...good choice!


----------



## rb2013

sceleratus said:


> Back




Love the heat sink (for the mosfet I assume) and gold plate!


----------



## sceleratus

n





rb2013 said:


> Love the heat sink (for the mosfet I assume) and gold plate!




Thanks

No gold. It's polishe silicon bronze.


----------



## rb2013

sceleratus said:


> n
> Thanks
> 
> No gold. It's polishe silicon bronze.




You mean not real gold...just kidding. It really looks 1st Class!


----------



## sceleratus

Many Thanks to @randytsuch for loaning me his Electro Harmonix 300Bs 
There is a substantial difference between them and the JJ's


----------



## muskyhuntr

Which ones did you like the best, the JJ's or the Electro Harmonex? 
  Also, did you fix the hiss/fuzz sound?
  Making a little progress on mine.  Have the main power supply board and the Maida boards done but not tested.  Parts for the filament boards are on order.
   
  jIM


----------



## tomchr

I tried the JJ and the Full Music 300B/n mesh plate. The Full Music are really nice! JJs tend to be a bit 'edgy', the Full Music sound really smooth and natural to my ears. In end-to-end measurements (i.e. measuring the speaker output with a microphone rather than the amp output), I also noticed differences in the distribution of harmonics. Specifically, the Full Music tended to be dominated by 2nd harmonic, whereas, the harmonic structure of the JJ tubes varied more with frequency - sometimes the 3rd harmonic being higher in magnitude than the 2nd.
   
  The Full Music tubes tend to run around $300/pair on [THAT AUCTION SITE]. The pair I had went back to the vendor, however. One of the tubes had issues with hot spots. Even at 390 V, 65 mA bias the plate on one of the tubes would develop cherry red spots. At 70 mA the spots were quite red, and the tube seemed to want to run away thermally. So be a bit careful and order from someone with a return policy.
   
  ~Tom


----------



## sceleratus

Well the idiot went and got himself banned from the forum.
  Thankfully the powers that be were gracious and let me back in.   I need to "just walk away" next time and after that.  I am sincerely thankful to be back because I enjoy Head-Fi.
   
  I have some updates from the LA Meet to post but I'll wait until I'm better acclimated with being back in the general population.


----------



## sceleratus

The LA Meet was amazing.... that's what it's about.  Learning and sharing in person.  Putting faces to avatars, going over all those posts.
  I was so drained, I really didn't network much.  At that point I was overwhelmed.  Yes Frank.... Holland, I'm sitting here and the iron is cold.
  How in the world am I going to justify this ?????  with the boss?
   
  The EH 300B's v. the JJ 300B's.  At first I loved the EH's ..  then after a while I'd listen to a favorite track and think  "there's something missing"  So after 2-3 days I rolled the JJ's back in and they were much bigger than the EH's.  Randy, that was really kind of you to let me try the EH's.
   
  The experiment cooled my jets a bit on buying other 300B's.   I was looking hard at Emissions Labs,  But I'm not sure they will be a bang for the buck.   I need to relax and just listen to music for a while.
   
  I my Schiit gear is gone with one exception.  I sold my Bifrost DAC and bought the Gungnir DAC.   I like that it's balanced and I will make some interconnects soon.  I have left over 20g a. silver wire.  I figured if that's what's inside might as well have it outside too.  Plus the iron will see some more action.  Which leads me to another ordering bungle.  The Neutrik XLR jacks came in yesterday.  One problem.  They are PCB.   doh
   
  I also sold my RTC E188CC 1965 valves.  Those were my "end-game" valves with the Lyr.  Not so much in the DG 300B.  The 58' Bugle Boys, 58' Valvo PCC88's and some Orange Globes made in the UK all sound great, but the interesting part is they all sound different from each other while sounding great.  This was not the case with the Lyr.  There would be one dominant set of glass.
   
  Today I received an amazing set of 1965 Amperex USN-CEP's  I've owned them before but sold them after the RTC's arrived.
  This set is immaculate NOS.  The silks and box are perfect.   Straight away with little burning in.... they sound like they will be a significant step up from the others.
   
  If anyone needs a set here is the AUDIOGON SELLER he has a few more matched sets.
   
  I paid almost $300 the first time around.  These are much better for $225.  Very good seller too.


----------



## sceleratus

What do ya'll think of a DYI Amp Build Thread for Beginners" ?
   
  It would require all you guys to get on board or it won't work.
  Circuit geeks could suggest designs to build, why you choose them and provide some explanation of the circuits and their function.
   
  My "area" of.... expertise...(that's a stretch) and others would be the physical build helping with how to order the wrong components and resources for getting the project completed.
   
  Thoughts?


----------



## Goobley

I'd be happy to provide the knowledge and advice that I can to such a thread. It's always nice to have more solder slingers building projects. I've really enjoyed following your thread over the past few weeks.


----------



## sceleratus

Quote: 





goobley said:


> I'd be happy to provide the knowledge and advice that I can to such a thread. It's always nice to have more solder slingers building projects. I've really enjoyed following your thread over the past few weeks.


 
  Cool.
   
  Amps only.
  My tastes are valve amps.   Probably tighten the discussion to valve amps.
  Then we can have discussions on the integration of valve models.
   
  And the other builders could get things going by discussing past and planned builds.  That would be the meat of the thread.  If it was just me it would be another rehash.  Yawn.  If it works it could be an amalgamation of builds similar to this thread.  All the describe all the ugly details and lots of photos.  I think talking about problems and "fail" is pretty cool.


----------



## Goobley

I think it could become useful resource. IMHO for beginners it may be a good idea to include hybrids as they are more approachable, but for your thread the decision is of course yours. I've just finished what I believe to be quite an interesting hybrid that I'd be happy to document in said thread. It should be fairly easy to build, the hard work was the design.


----------



## muskyhuntr

Interesting concept.  You have my interest.
   
  Jim


----------



## sceleratus

Ok, so as long as it has a valve 
I'll start it up today... Just have to wordsmith the opening post
No downside. Could be real popular.

Again. It will Only work if past builders step up and contribute .... Starting "first posts", not just waiting to answer questions.


----------



## sceleratus

Ya Jim, we need pic's


----------



## sceleratus

I put XLR source jack in today and I made a couple of cables (weave)  from the leftover 20g a. silver wire.
   
  I have a new noise problem and I suspect the cables are acting as an antenna.
  Backing up first.
   
  The snow noise diminishes at times with playing time, but some ECC88's make it louder than others.  My new USN-CEP 6922 seemed louder.
   
  Back to the XLR.
  I cabled up my Schiit Gungnir and immediately got a loud transformer buzz type sound.  What was interesting is (let me remember) ..... If I jacked up the volume pot to the Max, then decreased the source volume (iTunes) both noises were virtually gone.  Dead quiet when you peg the pot.
   
  Why I think there's an antenna ..... when I pull the xlr's at the Gungnir I get significant buzz.  If nothing is plugged into the XLR's lots of snow.
   
  I was very careful not to flip neg and ground.  
  On the RCA jacks I had center pin to one side of the pot, negative ring to the other side of the pot then continuing on to the board.  The pot sweeper was pos on the board.  At the board neg was jumped to shield.
   
  The volume pot is an Alps Japan Blue log 10K pot.
   
  With the XLR .... XLR Pin 2 replaced RCA Pos.  XLR 3 replaced RCA neg.  and XLR 1 went home run to the board replacing the jumper.
   
  Suggestions...
   
  Holland and Tom, remember in earlier discussions discussion on mitigation snow Tom said put in a 56 Ohm resistor on RCA pos / XLR 2.  I hadn't tried that because I wanted to get up and running.  I also remembered Holland thoughts that it might effect the sound.   Now with what's going on it may help.
   
  General question...  Is it best to "peg" the source (iTunes) volume and keep the volume pot low or the opposite, turn iTunes way down and increase the volume pot.  That is what's working now.


----------



## holland

I'm not sure about iTunes, but I would max it out unless it's amplifying.  The reason is increased signal:noise.  I don't really use it, but when I use optical out of my macbook, and there's no volume adjustment.
   
  Your cables need shielding, get some microphone cable as a cheap interconnect, until you find some shielded 3/4 conductor cable that you like (or not).  I like Mogami quad, or replicas as inexpensive cable as I'm not a $$$ cable believer.
   
  I'm not sure about your wiring for the amp.  Are you using a single ended jack to XLR wiring scheme?  The Gungnir has true balanced outs and each jack carries a differential signal and ground.  The single ended output does a differential to single ended conversion, probably with opamps or a discrete circuit.  Are you using the input transformer on your amp or are you capacitor coupled?  The amp is not differential, and shorting a wire to ground may be causing problems, unless you are transformer coupled on the input.  Also, how did you wire the signals to the potentiometer?
   
  Edit:  Can you take some pictures of the wiring, or draw out a schematic on paper and take a picture of it to post?


----------



## sceleratus

Quote: 





holland said:


> I'm not sure about iTunes, but I would max it out unless it's amplifying.  The reason is increased signal:noise.  I don't really use it, but when I use optical out of my macbook, and there's no volume adjustment.
> 
> Your cables need shielding, get some microphone cable as a cheap interconnect, until you find some shielded 3/4 conductor cable that you like (or not).  I like Mogami quad, or replicas as inexpensive cable as I'm not a $$$ cable believer.
> 
> ...


 
  Thanks Holland,
   
  Lots of things for me to look into and respond.
  It's a chore to lug 55 lgs up and down the stairs.
  Tomorrow I'll pack up the valves bring it up and dig in again.
   
  Unless I put the RCA's back I'm stuck with the bad cables until the new ones arrive.  I saw the Mogami on eBay and put them on a watch.  The seem like a nice intermediary price.  I don't want the gobs of $5 ones and I don't want $200
   
  The lower right corner of the diagram is the input wiring....J7 / J3 on the Driver Board
  I'll  get some close photos.


----------



## holland

OK, looked at your amp picture a few pages back, you do have the input transformer, so the wiring should work (to the amp board).  I'd need to see how you wired the pot, and any additional resistors you added to handle 4-channels with a 2-channel pot.  It's doable, but it's not as common.
   
  Some resistors in line, configuration B below.  Ideally, the pot would come after the input transformers for the amp.  You could point to point wire it, if it's easy to remove the transformer, or cut the trace and feed it in and out from the solder pads.


----------



## sceleratus

Many thanks....  I'll digest in the am.
   
  Tom will probably weigh in, but he's been very busy with projects at work.


----------



## sceleratus

My back is pretty jacked up from moving the amp after putting in the XLR's so I haven't moved it and opened it up again.
   
  What I found interesting is the noise come when resistance is introduced from the volume pot.  When it's wide open there isn't any resistance, correct?
  Very low signal (from the Mac), very low noise.  
  Large signal from the mac, more resistance applied by turning the volume pot down, more noise.
   
  If I understand correctly, if I bypass the input transformers  that may help.
   
  In the first tests, several weeks back, I only had toslink, now I have the Schiit USB card.  Either way I get the snow, perhaps more with USB.
   
  I think there is an error in the following volume diagram.  The wiper belongs in the center terminal and the jumper is between the two outside terminals.  As depicted in the color diagram.   That is what worked with the RCA's
  With the XLR, I kept pin 2 XLR (IN +) to the wiper, pin 3 (IN -)  to the top position of the block, and XLR pin 1 (Shield) to the bottom position.  Exactly as depicted in the color diagram.  So put the two together and that's how it's wired.


----------



## sceleratus

I just ordered the Mogami Neglex 2549 balanced cables.
  They look great.  Thanks
   
  Edit.
  I think I'll wait to make any changes until the cables arrive.  Then I'll have my ducks in order and implement possible modifications.


----------



## sceleratus

What about using Copper Braid Jackets internally?


----------



## sceleratus

Quote: 





holland said:


> OK, looked at your amp picture a few pages back, you do have the input transformer, so the wiring should work (to the amp board).  I'd need to see how you wired the pot, and any additional resistors you added to handle 4-channels with a 2-channel pot.  It's doable, but it's not as common.
> 
> Some resistors in line, configuration B below.  Ideally, the pot would come after the input transformers for the amp.  You could point to point wire it, if it's easy to remove the transformer, or cut the trace and feed it in and out from the solder pads.


 
   
   
  This is a good exercise  for me.  It makes me try to reconcile the board traces to the schematic and a diagram like yours.  Which I am only partially able to do.  It's hard to follow the top traces and the bottom traces and match them to the schematic.  I probably need the board in my hand to do that.  I found a photo I took of the driver board before the IPT's were installed.   The traces for C3A/B and C8A/B are visible.  Both are DNP on the schematic.  Obviously since they are under the IPT's
   
  I revisited the DACT site and looked at the CT2 and the CT2 Balanced.  The CT2 is configured exactly like the Alps.  I fave no Idea how to integrate the balance model.
   
  EDIT:  Why remove the IPT''s?


----------



## holland

Leave the input transformers alone for now.  You can feed into it without much of a problem.
   
  Remove the pot entirely, and wire the XLR directly to the amp board.  Control the volume with your laptop to make sure there's no problem.  There should be none.
   
  I've never wired a pot this way, just read about it.  All the circuits I've seen have an input transformer before the pot, probably because wiring it the way indicated in configuration B changes the load resistance seen to the source.  Anyway, try it without, put 2 47.5K resistors in line, and wire the pot as indicated in the diag.
   
  Here's another diagram from the monolith balanced amp, this one is without the input transformer in place.
   

   
  Here's the same amp with the input transformer.


----------



## holland

Quote: 





sceleratus said:


> I fave no Idea how to integrate the balance model.


 
   
  It is configuration A.  Balanced signals have 4 incoming signals, related to ground.  Single ended (RCA) has 2 incoming signals, related to ground.  RCA has no negative signal, only ground.  In the balanced 4-gang pot, when you make one click, it reduces the incoming signal on + and - for left and right channels the same amount.  You could replicate that by using 2 stereo volume controls.  One for left, and one for right channel.  For the left channel, as an example, you would use each gang in the pot for the + and the - signal, with the wiper being a voltage divider to ground for each gang.  That is configuration A.
   
  The amp you have is not differential, so wiring in an XLR is somewhat pointless.  The input transformer converts the signal to single ended for the amp topology.  The gungnir does the same in it's output stage.  DACs are differential in nature.
   
  If you put the pot after the input transformer, then you would have familiar wirings, dealing only with 2 signal channels, Left and Right (again there is no negative only "positive" signals which is the combined signal).
   
  Configuration B (or the schematics I posted from the Monolith amp) controls balanced signals with a stereo pot.  It alters the impedance seen by the source, however.  It is no longer a static 10K, but will vary by wiper position.  The inline resistors limit it to something manageable.  This is, in effect, what is known as the shunt mod (if you didn't have a negative signal).
   
  I hope this helps.  It's a bit confusing.
   
  Morgan Jones has this in his books too.  I can see if I can dig out the text and photocopy it, but it might be a few days or weeks before I get to it.


----------



## sceleratus

Thanks Holland,
  I have more to digest.
   
  I have the Morgan Jones book so you don't have to go through that exercise.
   
  I am not going to do anything until mid week when the cables come in from eBay.... prob later I think they are in MN.
  Truth be told with all my swapping and grinding output jacks the only think I was left with for the XLR inputs was a set of Neutrik Male ports.
  So the homemade XLR cables are the nonexistent F/F.   Thus I ordered a set of Neutrik Female jacks.
   
  I will look through all the input you have provided and see if I can understand it.   I did make some progress with the schematic.
   
  I thought about bypassing the volume pot entirely and using the source software control, but I got sad that the focal point of the enclosure, the volume knob, would be useless.
  Form over function.
   
  Thanks again,  I will do some studying.


----------



## tomchr

Yeah, work's been kicking my bee-hind lately. Such is life in the tech industry, though.
   
  I bet you've created a ground loop, hence, get some 60 Hz hum. You can't 'mod' your way out of this. Fix the ground loop.
   
  The DG300B Amp was designed as a power amp, hence, the assumption was made that any volume control was handled in a preamp of sorts. With a single ended input (think RCA), it's trivial to add a volume control. With differential inputs (XLR), it becomes more tricky. You can design a differential volume control (see below) but now you need a 4-gang pot with audio/logarithmic taper for a stereo volume control. These are available.
   
   

  If you want a differential input, but don't want to spend on a 4-gang pot, your best option (aside from building a differential preamp) is to insert a volume control at the junction between R7 and R8. Like this:
   
   

  My favorite XLR interconnects are the ones by GLS Audio. I love the multicolored cables. It makes hookup much easier when you're dealing with a fully differential, biamped system with active crossovers... I don't bother making my own interconnects. It's less expensive to let someone else do it. But then, I'm also not a believer of megabuck interconnect cables either. 
   
  Re. DIY Valve Amp Beginner Thread: One of the first posts (if not the first post) needs to be on high-voltage safety.
   
  ~Tom


----------



## sceleratus

Quote: 





holland said:


> It is configuration A.  Balanced signals have 4 incoming signals, related to ground.  Single ended (RCA) has 2 incoming signals, related to ground.  RCA has no negative signal, only ground.  In the balanced 4-gang pot, when you make one click, it reduces the incoming signal on + and - for left and right channels the same amount.  You could replicate that by using 2 stereo volume controls.  One for left, and one for right channel.  For the left channel, as an example, you would use each gang in the pot for the + and the - signal, with the wiper being a voltage divider to ground for each gang.  That is configuration A.
> 
> The amp you have is not differential, so wiring in an XLR is somewhat pointless.  The input transformer converts the signal to single ended for the amp topology.  The gungnir does the same in it's output stage.  DACs are differential in nature.
> 
> ...


 
  Getting pieces of this.
   
  Differential?
  The Gungnir is differential.
  If I am connected prior to the input trans, I'm not differential.  As you said, it's pointless.  Is that because you need differential to differential..... bear in mind, I need to understand "differential".
  Would it become differential if the pot was inserted after the input transformers?
   
  If not I should control the volume from the source and abandon the volume POT.  This scenario is almost noiseless, snow or hum.  If I do this should I revert to "RCA"
  Remember the schematic calls out XLR input wiring as the first choice.


----------



## sceleratus

Here's a DACT audio 4 gang pot.
  I think it's the CT-2 Balanced.
  If it is the best solution and fixes the problem I will probably go in that direction.  I'm at the 2 yard line.
   
  I'm going to do more testing but it's very interesting that when the 10K Alps POT is pegged wide open and the source is nearly off it sounds magnificent.
  If I pause the track I'm sure it's 80% quieter....
   
  I will test again and report.


----------



## sceleratus

I have read about ground loops before while trying to help others.
  Cutting the ground pin is NOT attractive.
   
   
  I have a Furman AC215-A
   
  I thought that would eliminate any potential ground loop.


----------



## sceleratus

This is a cool ground loop document from Jensen transformers published on MIT.edu
http://web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf


----------



## sceleratus

Hum issue
 The DG 300B and The Gungnir are plugged into a Furman AC-215A Conditioner with ground contamination circuitry.
  
 No hum was present when the input cables/interface was RCA.  That's a red flag that I did something wrong.
  
 Since the design utilizes Jensen input transformers how can ground loop hum "jump" this?
  
 Yet there is noise associated with mains power.
  
 I performed the following tests.  
 All tests had HP's plugged in.
 1 = minimum setting on volume pot
 10 =max setting on volume pot
  
 1)  Nothing connected to the amp inputs:  1 = loud snow 10 = less snow  I believe the snow was less with RCA's but I don't think the volume pot had any effect.
  
 2) Plug the homemade XLR cables into the amp only. 1 = loud snow  10 = some snow slight hum
  
 3) Plug XLR's into both amp and Gungnir (powered off)  1= Low snow  10 = same amount
  
 4) Same as #3 except the Gungnir is powered on. 1= Med. Hum plus snow 10 = Very small hum / snow
  
 5) If the Gungnir is plugged into a different outlet on the same circuit the Hum is very loud at 1.  Perhaps because the amp is in the Furman and the Gungnir is straight in an outlet.
  
 Thinking outloud:
  
 Again.  Wouldn't the IPT's isolate ground noise?
 Again. I didn't have this problem with RCA's.  Perhaps I flipped input terminal pins 1 & 3 at the driver board.  The were jumped with RCA.
  
 I know the cables are OK because I ohm'd out the pins.
  
 I can't ignore #5 that must be a ground loop, however in practice I am using the same outlet. #4  The loop occurs if gear is on different outlets one of which has a contaminated ground.  Even so if the ground is contaminated by voltage it can cause problems.
  
 I won't know more until I open the amp up next week.


----------



## tomchr

The document by Jensen Transformers that you linked to earlier is actually a pretty good description of what's going on. Differential signaling is also described here: http://en.wikipedia.org/wiki/Differential_signalling
   
  Your XLR cable should connect pin 1 to pin 1, 2 to 2, and 3 to 3 in the XLR connectors. Pin 1 may be connected by the shield of the cable. Commonly, this is done with a mic cable that has two conductors plus a braid or foil shield. Pins 2 and 3 use the two conductors. Pin 1 use the shield. There should be no connections between pin 1 and 2,3 anywhere. 
   
  Pins 1, 2, and 3 of the XLR connector should go to the appropriate pins on connectors J3 and J7 of the driver board. If you want volume control, you either need to implement a differential volume control and insert it between the XLR connector and the driver board - or you can use the hack I provided and put it between R7, R8.
   
  There should be no hum if the XLR is connected directly to the driver board. 
   
  If you accidentally flipped the connections between pins 1 and 3 on the input connectors, you'd get hum for sure. Use your ohmmeter to ring it out.
   
  ~Tom


----------



## sceleratus

Quote: 





tomchr said:


> The document by Jensen Transformers that you linked to earlier is actually a pretty good description of what's going on. Differential signaling is also described here: http://en.wikipedia.org/wiki/Differential_signalling
> 
> Your XLR cable should connect pin 1 to pin 1, 2 to 2, and 3 to 3 in the XLR connectors. Pin 1 may be connected by the shield of the cable. Commonly, this is done with a mic cable that has two conductors plus a braid or foil shield. Pins 2 and 3 use the two conductors. Pin 1 use the shield. There should be no connections between pin 1 and 2,3 anywhere.
> 
> ...


 
  Thanks Tom,
   
  When I open it u I'll see if I can fit a stepped attenuator in.  I can do it by hook or crook using a flexible shaft.
   
  I like the Goldpoint Mini-V out of Sunnyvale CA.
  If I choose a 2 deck I have to go back to RCA, correct?
   
  A 4 deckk would give me what I wanted to have.
   
  I've read that some users don't like the detent clicks.  I don't think it would bother me and I really like the concept.  It's much more precise with *[size=small]0.1%[/size]*[size=small] tolerance, 25ppm, Thin Film, 0805 [/size]*[size=small]SMD[/size]* vs a 5% pot.
   
   
  Still the ground loop has me baffled.


----------



## tomchr

Quote: 





sceleratus said:


> If I choose a 2 deck I have to go back to RCA, correct?
> 
> A 4 deckk would give me what I wanted to have.
> 
> I've read that some users don't like the detent clicks.  I don't think it would bother me and I really like the concept.  It's much more precise with *[size=small]0.1%[/size]*[size=small] tolerance, 25ppm, Thin Film, 0805 [/size]*[size=small]SMD[/size]* vs a 5% pot.


 
   
  An attenuator is basically a potentiometer with steps instead of linear travel. The number of sections needed for a volume control doesn't change just because it's labeled "attenuator" rather than "potentiometer". Hence, for a differential volume control, you'd need an attenuator with four decks.
   
  I used to use an attenuator, but it drove me nuts. If you look at most attenuators, you'll see that to get a reasonable range on a 24-position rotary switch, the first couple of steps are *HUGE*. Like 10 dB or so. In my case, I ended up with a setup where step 3 was so low volume that I could barely hear the music, and step 4 was so loud I couldn't concentrate. 
   
  In my preamp, I use a PGA2320. -95.5 dB to +31.5 dB in 0.5 dB steps. You won't find that in a rotary attenuator.
   
  The absolute tolerance of the potentiometer may be 5 %, but really it's the tracking between channels that matter. This will improve with an attenuator. But if it isn't bothering you now, it clearly isn't an issue for you.
   
  An attenuator will not fix the hum. Fix the ground loop before you start thinking about more modifications.
   
  You had an amp that had no hum. Then you modified it and got an amp with hum. Something in the conversion went wrong and caused the hum. Trace it down and fix it. Then you can start talking about modifications.
   
  ~Tom


----------



## sceleratus

Quote: 





tomchr said:


> An attenuator is basically a potentiometer with steps instead of linear travel. The number of sections needed for a volume control doesn't change just because it's labeled "attenuator" rather than "potentiometer". Hence, for a differential volume control, you'd need an attenuator with four decks.
> 
> I used to use an attenuator, but it drove me nuts. If you look at most attenuators, you'll see that to get a reasonable range on a 24-position rotary switch, the first couple of steps are *HUGE*. Like 10 dB or so. In my case, I ended up with a setup where step 3 was so low volume that I could barely hear the music, and step 4 was so loud I couldn't concentrate.
> 
> ...


 
  Precisely
  No hum > Mod > Hum > mod fail
   
  I looked into the attenuator because of the whole differential balanced interface thing and that the amp was designed for a pre-amp and that these decked stepped attenuators are pseudo pre-amps.....  That's how I got there.
   
  Step one. get it working again.


----------



## sceleratus

Volume update:
  
 When I started this thread I said I would post the good, the bad, and the ugly.  Well….
  
 Here's ugly.
 After reading your suggestions and exchanging an email or two with Tom, I was getting the impression that what I wired up was wrong.  But I didn't know why.  Tom finally figured out what I was doing and asked "are you trying to use the volume pot with XLR"?
  
 Well, yes. 
  
 Here's a tip: RCA and XLR are fundamentally different.  Something about differential volume going in, or as Holland pointed out, move the pot to the other side of the IPT's.   I had no idea, I wasn't getting it, I now know the fix, but I can't say I understand it.  I'm not keen about munging with the board.
  
 I "get" stepped attenuators.  Simply "stepping" through resistor values that are inline with the source.  Thinking…..(while typing) that's much different than a "T" configuration in a potentiometer.  Probably why my wiring didn't work.
  
 If you have a 4 deck attenuator, it sunk in that each deck is for each side of the source connection.  A source to deck link-in and deck a to the board IPT.  2 x stereo = 4 decks.  What marries the decks?  No matter, if I go that way I'll figure it out.  Or some nice person can enlighten dopey.  (Find section in Morgan Jones)
  
 I think I'm committed to balanced XLR.  The rub is the attenuators are quite large and with my centered volume control it might run into the driver board.  If so, I found a flexible shaft extension that might mitigate that.
  
  

   
  
 The other choice that came up (my reading and Tom) was TI's PGA2320  volume control IC.  I see (NPI) that it has an RS232c interface, presumably for programming.  I also presume there is MMI software.  Parallels works with a USB Serial adapter on a Mac so I think I can run MMI.  However can I control it with a tactile knob?  Then there's  building a circuit.  Might be a good time to try to produce something with DipTrace.  Always wanted to etch a board.
  
 So there you have it, Mr. Soldering Iron has run into, as Tom would say, Physics.
  
 And lost.


----------



## sceleratus

I went to diyAudio and searched TI2320.
   
  Sounds much too complicated.
  Additional power supply and a microprocessor.
   
  That leaves.
  A) Stepped Attenuator
  B) RCA.   I am so far along and such a buck naked rookie that I don't wan to carve up the driver board.
   
  I had though about building a second Driver Board just for experimentation.  This might qualify.
   
  I love this amp.  Hell it even sounds good when it's mis-wired.


----------



## holland

I use a relay attenuator with 100 steps for my nicer builds.  It's nice, but it takes up lots and lots of space.
   
  You can wire the pot before the IPT, look at http://www.head-fi.org/t/664903/the-christiansen-dg-300b-amplifier-build-thread/300#post_9653109 for the schematic.  It adds extraneous steps, but it should work fine.  Easiest is definitely after the IPT, but if you don't want to hack the board you only have 3 options.  Back to RCA, 4-gang pot, or the above link.


----------



## sceleratus

Quote: 





holland said:


> I use a relay attenuator with 100 steps for my nicer builds.  It's nice, but it takes up lots and lots of space.
> 
> You can wire the pot before the IPT, look at http://www.head-fi.org/t/664903/the-christiansen-dg-300b-amplifier-build-thread/300#post_9653109 for the schematic.  It adds extraneous steps, but it should work fine.  Easiest is definitely after the IPT, but if you don't want to hack the board you only have 3 options.  Back to RCA, 4-gang pot, or the above link.


 
  Excellent.
  Another choice.
   
  I just ran the Driver BOM at Digikey.  It's $35 for the original parts,  I have a few changes.
  Then there's the cost of the board and the Jensen transformers.  $140
   
  But it might be nice to have, then I wouldn't be timid about changing things.  A learning tool.
  If Tom came up with some things hed like to try on an HP amp (hint) I would be good to go.


----------



## sceleratus

Quote: 





holland said:


> I use a relay attenuator with 100 steps for my nicer builds.  It's nice, but it takes up lots and lots of space.
> 
> You can wire the pot before the IPT, look at http://www.head-fi.org/t/664903/the-christiansen-dg-300b-amplifier-build-thread/300#post_9653109 for the schematic.  It adds extraneous steps, but it should work fine.  Easiest is definitely after the IPT, but if you don't want to hack the board you only have 3 options.  Back to RCA, 4-gang pot, or the above link.


 
  I didn't read your post close enough the first time.  I need to read things at least tree time due to some learning issues.
   
  In the top diagram the pot is external to the board / IPT's?   I now see the +IN and -IN notation in the schematic.
  The termination sequence of a schematic won't match the terminal wiring.. correct?  As +IN is in terminal block position #2.  Just stating what I think is obvious for peace of mind.
   
   

   
   
  This seems like a low risk, high reward, nothing to lose choice.
   
  The second choice is after the IPT's.  That I understand by the transformer icon.


----------



## sceleratus

Holland,
   
  I have a 100K Alps pot and a 10K Alps pot.
  I am using the 10K now.
   
  Since your schematic is designed for 100K that's the one I should use?


----------



## holland

Quote: 





sceleratus said:


> I didn't read your post close enough the first time.  I need to read things at least tree time due to some learning issues.
> 
> In the top diagram the pot is external to the board / IPT's?   I now see the +IN and -IN notation in the schematic.
> The termination sequence of a schematic won't match the terminal wiring.. correct?  As +IN is in terminal block position #2.  Just stating what I think is obvious for peace of mind.
> ...


 
   
  Yes, you can put the schematic before the IPTs.  The schematic is really for using an IPT or no IPT, but in your case it doesn't matter.  It will just feed into the IPT.
   
  Either pot will work, but feel free to use the 100K first.  Whichever tracks better for you.  You should also be able to take the schematic from the 2 47.5K inline resistors and then the pot, but start verbatim to be sure.
   
  Do wire the XLR without the pot first, to ensure you have no noise.  If you do have noise, then all of this is moot.  Fix the noise (if it's there without the pot), and then add the pot.


----------



## sceleratus

Quote: 





holland said:


> Yes, you can put the schematic before the IPTs.  The schematic is really for using an IPT or no IPT, but in your case it doesn't matter.  It will just feed into the IPT.
> 
> Either pot will work, but feel free to use the 100K first.  Whichever tracks better for you.  You should also be able to take the schematic from the 2 47.5K inline resistors and then the pot, but start verbatim to be sure.
> 
> Do wire the XLR without the pot first, to ensure you have no noise.  If you do have noise, then all of this is moot.  Fix the noise (if it's there without the pot), and then add the pot.


 
  This is worth trying because, as I said, it's low risk, but secondly, the smooth attenuation that a pot gives you is much nicer than steps.


----------



## sceleratus

Wow.
   
  I'm reading M. Jones section on volume control, and I'm actually understanding it.  I need to understand SNR better.
  Anyway, he hates carbon track logarithmic volume controls.  "They belong in the landfill."   "If quality is paramount, use a switched attenuator."
   
  Page 553 -554


----------



## sceleratus

Holland,
   
  Buddy..... Full Speed Ahead with your design.
  Adding a 4 deck stepped attenuator was stupid money.  Between the 4 deck Goldpoint attenuator ($275) and flexshaft extension fittings ($100) and Misumi Automation custom "L" bracket $30
  Crazy, even for me.
   
  I will report the results.
   
  Thanks


----------



## tomchr

I recommend Morgan Jones, "Valve Amplifiers", 4th ed to anyone wanting to learn about tube amps. But do keep in mind that Mr. Jones can be a bit opinionated at times. He also doesn't think highly of single-ended amplifiers - such as the DG300B. He wants power... That's not what SET is about.
   
  ~Tom


----------



## sceleratus

Just emailed Tom.
   
Eureka !
   
I wired home run from the XLR jack to the board.[size=medium]
No POT  (Hello Holland)[size=medium][/size]
 [size=medium][/size]
I swear.  The snow is gone.[size=medium][/size]
A very tiny tiny tiny bit of hum.  Undetectable while listening.[/size]
Heck, it's a valve amp[size=medium]
 [size=medium][/size]
Classical Violin.  Dead Bang Quiet ![size=medium][/size]
This amp has an absolutely incredible voice.[/size]
The best I've ever heard it.[size=medium]
 [size=medium][/size]
 [size=medium][/size]
I'm think'n a dummy knob is the way to go.[/size]
I'll use iPad Remote.
I can't complicate this, it sounds too damn good.


----------



## sceleratus

IMO
   
I will now declare "The Christensen Damn Good 300B"  a *Headphone Amp.*


----------



## sceleratus

Volume Update.
   
  I'm going in the stepped attenuator direction.
  Why, my inability to test and implement other solutions.  I can handle the attenuator.
  Plenty of connect the dots and color inside the lines stuff.
   
  Since iTunes has a 20 step volume adjustment, by my calculations, I will get 20 steps for each of the attenuators 23 steps.
   
  I figured out how to move the giant 1.25" x 3" 4 deck stack.
  I purchased a 6" flexible shaft extension.  (everyone should have one of these)
  Then I ordered a custom "L" bracket from Misumi Automation.  The bracket will sit on top of the filament regulator stack.
  The alignment was perfect.
   
  Nice Photos:


----------



## muskyhuntr

Have you considered using your current pot on a single channel at a time to see if all of this is going to work.
   
  Jim


----------



## holland

What problems did you have with the proposed schematics?
   
  You should look into reducing the gain.  You have more voltage gain than the original design, lots more.  There were a couple of mods tossed around.  You could definitely live without the pot if you do that, and add it in later.


----------



## sceleratus

Quote: 





holland said:


> What problems did you have with the proposed schematics?
> 
> You should look into reducing the gain.  You have more voltage gain than the original design, lots more.  There were a couple of mods tossed around.  You could definitely live without the pot if you do that, and add it in later.


 
   
  Hi Holland,
   
  Sorry for taking so long to answer you.  I've been feeling guilty.
  I appreciate your suggestions.  So what's my problem?  (Don't answer that)
   
  I cobbled together some interim components on a little proto solder PCB from RS.
  I also ordered all the necessary good components too.
   
  I've never "worked" with one of those copper clad boards.  What a mess.  It looked like a 3rd grader did it and this is after multiple uses of my Soldapluz.  I'm looking at it thinking, how am I going to implement this mess?  Logistically mounting the board and such.
   
  I have DipTrace and I've laid some circuits out.  Creating components, pads, and schematics, but when it comes to laying out the PCB.... even using auto function the result are sketchy at best.  I would need mounting holes, etc.  The only feasible mounting position is on the wood enclosure.  I didn't like that.
   
  Next do I try to etch the board myself of pay to have one made at a minimum qty charge.  I was thinking, if I etched my own it would look like the RS copper board.  I got to the... I want this over and done point.  Listen to music.  Short story, I whimp'd out.
   
  As such I thought the slam dunk cleanest compact approach is a Goldpoint 23 step attenuator.  I'm waiting for a custom L bracket from Misumi Automation.  If everything fits, I will order one.


----------



## sceleratus




----------



## sceleratus

Does anyone know where I can get the seat sink anodized?
  I emailed a local company but I think they only do C-130 parts.


----------



## Headampbro

Quote: 





sceleratus said:


>


 
   
  Wooww, what a beautiful beast!!! I wish I have the time and talent to build it, especially when it comes to casing.


----------



## holland

Quote: 





sceleratus said:


> Does anyone know where I can get the seat sink anodized?
> I emailed a local company but I think they only do C-130 parts.


 
   
  Try a google search in the area.  There are companies around that can do any aluminum series, according to their web sites.  Here's one, but I'm not sure it's worth shipping.  http://gmpplating1-px.rtrk.com/ There should be companies closer to you.


----------



## tomchr

Anodization is the way to go. Black anodization makes the heat sink as close to a black body radiator as you can get with a reasonable budget.
  Note that simply painting or powder coating the heat sink adds an insulating layer between the air and the heat sink, hence, makes the heat sink perform _worse_ than it would in bare aluminum.
   
  Your best bet for anodization is a local machine shop. Some of the custom wheels places offer anodization of aluminum wheels for cars. I'm sure they'd be happy to dunk your heat sink in their soup for a fee... 
   
  Anodization does add a little bit of material thickness to the aluminum, so you'll have to go back and retrace your threads when you get the heat sink back from anodization.
   
  ~Tom


----------



## sceleratus

Strike One.
   
  Danco Anodizing.
  Black, Type 2
  $70 minimum.


----------



## sceleratus

The bakelite volume knob wasn't doing it for me so I went looking for someone that could turn one out of maple for me.
Today I found a great guy.  He might even try a couple inlay options I drew up.
Here are a couple thoughts.


----------



## sceleratus

I think I have found perfection in receiving valves for the DG 300B
I found a gentleman on Audiogon with a sleeve of perfectly matched 1964 Amperex E88CC/6922 USN-CEP's
The silk screens are perfect and they all measured high 14,000 on his Hickock.  NOS plus
These are very high grade valves made for the US Navy.  As such they have much tighter tolerances than a normal ECC88, etc.  There is a "Life" spec of 10,000 hours.  The amp loves them...  This was a find and the price was right...  I bought 2 sets.
   
_UPDATE_:  Snow / Noise.  Since I switched balanced interfaces it's gone.  Not sure why, but I'm not complaining.  At this moment I am listening to an HD Tracks recording of Marianne Thorsen, Trondheim Solistene,  Mozart Violin Concerto no. 3 in G major.  There are plenty of pauses in this piece and it's dead quiet during them.


----------



## nelamvr6

The USN-CEPs were my favorite in the Lyr for the longest time also.
   
  I kick myself, I was an electronics tech in the USN for 10 years, if only I'd have known how good these would turn out to be I could've found a way to "appropriate" a couple dozen...


----------



## nelamvr6

Quote: 





sceleratus said:


>


 
   
   
  Gorgeous!


----------



## Tjj226 Angel

Now you just need some western electric 300Bs 
	

	
	
		
		

		
		
	


	



   
  Do you know if the 300B can be interchanged with a 2a3?


----------



## sceleratus

tjj226 angel said:


> Now you just need some western electric 300Bs
> 
> 
> 
> ...




WEco's. ha ha very funny guy.
2a3 is a Tom question.


----------



## tomchr

Quote: 





tjj226 angel said:


> Do you know if the 300B can be interchanged with a 2a3?


 
   
  Not without a few component substitutions. See the "Output Tube Options" section of my DG 300B site. The operating point for a 2A3 is quite different from that of a 300B.
   
  ~Tom


----------



## Tjj226 Angel

Quote: 





tomchr said:


> Not without a few component substitutions. See the "Output Tube Options" section of my DG 300B site. The operating point for a 2A3 is quite different from that of a 300B.
> 
> ~Tom


 
   
  Gotcha. 
   
  I am trying to study up on designs like these. Next summer I hope to design a 300b mono block myself and try to throw as many western electric parts at it as possible. 
   
  One big question I do have is the use of polarized capacitors. A friend of mine designs amps, and he bends over backwards to avoid using polarized caps in his designs so that he can use paper in oil capacitors. 
   
  Were polar caps just unavoidable in your build, or did you use them for a greater purpose?


----------



## tomchr

Quote: 





tjj226 angel said:


> I am trying to study up on designs like these. Next summer I hope to design a 300b mono block myself and try to throw as many western electric parts at it as possible.
> 
> One big question I do have is the use of polarized capacitors. A friend of mine designs amps, and he bends over backwards to avoid using polarized caps in his designs so that he can use paper in oil capacitors.
> 
> Were polar caps just unavoidable in your build, or did you use them for a greater purpose?


 
   
  Good luck with your design. The 300B is a very challenging tube to drive. My DG 300B is the pinnacle of about three years of research, design, simulation, and experimentation. I outline some of the challenges on my website.
   
  I tend to approach design with an engineering mindset, hence, I specify components that will work well in a given application. I try to avoid capacitors in the signal path, but if I have to use a capacitor in the signal path, I use one with polypropylene dielectric. Polypropylene has very low dielectric absorption and low voltage coefficient, hence, these caps are basically sonically transparent. 
  I use electrolytic caps in places that are out of the signal path - or where the non-idealities of electrolytics don't impact the circuit performance, but where a high capacitance/volume ratio is handy. The power supply is a good example of such an application.
   
  Feel free to have a different opinion or choose different tradeoffs in your design. That's what DIY is about... 
   
  ~Tom


----------



## tomchr

You can also find a bunch of my design musings here:
   
DeathTrap400™ : : A Pretty Damn Good 300B Amp
300B (and other DHT) Biasing Options
   
  ~Tom


----------



## sceleratus

Ya know what sux?  I'm on an island with my DG 300B.  There's nobody to compare "notes" with.
  Somebody, please build one.  You will be rewarded. 
	

	
	
		
		

		
			




  I Promise.


----------



## tomchr

"On An Island". David Gilmore. Great album!
   
  Oh... Not what you meant.  I agree. Build them amps. Let us know what you think.
   
  ~Tom


----------



## nelamvr6

Quote: 





sceleratus said:


> Ya know what sux?  I'm on an island with my DG 300B.  There's nobody to compare "notes" with.
> Somebody, please build one.  You will be rewarded.
> 
> 
> ...


 
   
   
  Why don't you build one for me?  How much for one in mahogany?


----------



## NoPants

what was the all in cost of the build if you dont mind me throwing it out there without examining the thread in detail? im curious to drive my k1000 with these but i think the opt boards and tubes are already north of 1k right? i wouldnt build this for someone for less than 3k, all things considered


----------



## sceleratus

Quote: 





nopants said:


> what was the all in cost of the build if you dont mind me throwing it out there without examining the thread in detail? im curious to drive my k1000 with these but i think the opt boards and tubes are already north of 1k right? i wouldnt build this for someone for less than 3k, all things considered


 
   
  Here's almost the "all in" costs.  I posted it many pages back.
  The cabinet doubled the cost and I upgraded to some handmade resistors and fancy caps.  Plus changing to a balanced interface added the cost of a 4 deck stepped attenuator.  I'm waiting on that and yes the valves.
   
  Not for the faint of heart.


----------



## Fearless1

Quote: 





sceleratus said:


>


 
  Absolutely beautiful! I had no clue of the size until I saw it next to that piece of Schiit.


----------



## sceleratus

Quote: 





fearless1 said:


> Absolutely beautiful! I had no clue of the size until I saw it next to that piece of Schiit.


 
  The mini LCD's are nice too.


----------



## sceleratus

Oh..... "Thank you" !


----------



## tomchr

I think it is possible to squeeze in below $1k, with only a slight reduction in sound quality. If you forego the differential input (no Jensen transformers), use output transformers from Edcor (their CXSE series is quite good bang for the buck), and machine your own chassis components, you'll land at about $1k.
   
  That said, if you're spending that kind of money why not go the extra mile and make it truly high-end as sceleratus has done. Not counting the chassis parts, it's 'only' $400 more... And note that sceleratus did find that using differential inputs did improve the sound quality (that's why I built the circuit that way). What's $400 in the HiFi world anyway. And oatmeal really is quite nutritious. The family will love it! 
   
  It's a high-end amp. This has been confirmed by the many comments on it from the LA meet. A lot of people really liked it and posted rave reviews.
   
  ~Tom


----------



## holland

Quote: 





sceleratus said:


> Ya know what sux?  I'm on an island with my DG 300B.  There's nobody to compare "notes" with.
> Somebody, please build one.  You will be rewarded.
> 
> 
> ...


 
   
  I'm thinking about it, but it'll be pretty far back in the queue of things to do.  I'm also thinking about ways to make it more "useful" to me.  That is a headphone and speaker amp.  Custom wound transformers for sure with various taps and auto-switching circuitry for headphones and speakers, with multiple taps for headphone Z.  However, I'm not sure I want to change the plate load too much on the output tube, especially since headphones vary so much in impedance the load will change by default.  That brings up problems with gain, unfortunately.
   
  So, still thinking, maybe a 2014 project.


----------



## sceleratus

Quote: 





holland said:


> I'm thinking about it, but it'll be pretty far back in the queue of things to do.  I'm also thinking about ways to make it more "useful" to me.  That is a headphone and speaker amp.  Custom wound transformers for sure with various taps and auto-switching circuitry for headphones and speakers, with multiple taps for headphone Z.  However, I'm not sure I want to change the plate load too much on the output tube, especially since headphones vary so much in impedance the load will change by default.  That brings up problems with gain, unfortunately.
> 
> So, still thinking, maybe a 2014 project.


 
  Wow.
  You are the guy to pull it off.
   
  Yup.
  Jack at Electro-Print wound these for Audeze LCD2's.  50 ohm I think.
  Jack can do Anything and although I have no experience with other OPT's I am glad I had him make them.
  Very Old School.


----------



## tomchr

Having the ability to drive both speakers and headphones would certainly be nice. I think I have found a way to do it. I just need to verify that it'll work (and what the performance is).
   
  I've seen designs where the secondary of the OPT is loaded by, say, 50~100 ohm. The speaker or headphone is connected in parallel with this load. I think that should work pretty well and would allow someone to connect a headphone to their speaker amp (or vice versa). It would, however, require that the OPTs are wound for use with speakers (4/8 ohm tap). That said, I'd like to verify the performance before recommending the circuit. Expect results by mid September...
   
  ~Tom


----------



## tomchr

Quote: 





sceleratus said:


> Jack at Electro-Print wound these for Audeze LCD2's.  50 ohm I think.
> Jack can do Anything and although I have no experience with other OPT's I am glad I had him make them.
> Very Old School.


 
   
  Jack's good people. He can do anything the laws of physics will allow. I was impressed by his honesty and interest in customer success. He's not just a product pusher. He wants you to succeed using his products. Big difference. That's my mode of operation as well.
   
Electra-Print. (No affiliation, just happy customer).
   
  ~Tom


----------



## muskyhuntr

Hi All,
   
  Looking forward to what Tom comes up with.  I was originally planning on driving a set of speakers with mine, but would add head phone functionality in a second!  As of now, I have all of my power supply boards done (only the filament boards tested) and the 300B board populated with the resistors. If I am understanding Tom correctly, we are talking only about changes to the design from the output transformers on?  Any changes on the boards?  I don't plan on putting any music through this until next year, so I have plenty of time to incorporate design changes!
   
  Jim


----------



## sceleratus

Quote: 





muskyhuntr said:


> Hi All,
> 
> Looking forward to what Tom comes up with.  I was originally planning on driving a set of speakers with mine, but would add head phone functionality in a second!  As of now, I have all of my power supply boards done (only the filament boards tested) and the 300B board populated with the resistors. If I am understanding Tom correctly, we are talking only about changes to the design from the output transformers on?  Any changes on the boards?  I don't plan on putting any music through this until next year, so I have plenty of time to incorporate design changes!
> 
> Jim


 
  NEXT YEAR !!!


----------



## holland

Quote: 





tomchr said:


> Having the ability to drive both speakers and headphones would certainly be nice. I think I have found a way to do it. I just need to verify that it'll work (and what the performance is).
> 
> I've seen designs where the secondary of the OPT is loaded by, say, 50~100 ohm. The speaker or headphone is connected in parallel with this load. I think that should work pretty well and would allow someone to connect a headphone to their speaker amp (or vice versa). It would, however, require that the OPTs are wound for use with speakers (4/8 ohm tap). That said, I'd like to verify the performance before recommending the circuit. Expect results by mid September...
> 
> ~Tom


 
   
  Yeah, I've seen that around lots.  A parallel and possibly a series network to do 2 things, bring voltage down and to reflect a load closer to 8 ohm.  Usually it's a 9-10 ohm power resistor loading the secondaries.  I'm not really a fan of that.
   
  I was, however, thinking about an interstage transformer....possibly, to bring down gain.  Possibly of a switchable auto transformer type.  I haven't worked the math to see if it's viable.  These are just musings as this is so far down on my list of things to do, after a number of other headphone amps and a power amp or two.  I'm going back to SS for a bit after I explore a balanced parafeed topology for a few months.


----------



## sceleratus

Quote: 





sceleratus said:


> The bakelite volume knob wasn't doing it for me so I went looking for someone that could turn one out of maple for me.
> Today I found a great guy.  He might even try a couple inlay options I drew up.
> Here are a couple thoughts.


 
Knob Update:
   
I found a gentleman in Vista, CA thay does wood turning.
He wasn't too keen about a metal inlay.  I asked about wood and he thought ebony would work well.
That sound good and it make sense to have a wood guy do wood.
   
  [size=small]Looking for opinions:[/size]
  [size=small]I have 3 choices.[/size]
  [size=small]1) An inlayed "dot"[/size]
  [size=small]2) An inlayed 1/8" sliver, "flush"[/size]
  [size=small]3) An inlayed 1/8" sliver  "protruding"  (See diagram)[/size]
   
  [size=small]#3 Would require the most work but the added dimension could be cool.[/size]


----------



## tomchr

I'd go with either a flush dot or a flush sliver. If you want to go with dark wood for the sliver, why not continue the walnut theme?
   
  ~Tom


----------



## sceleratus

I think ebony is harder.  It's also darker so a small piece will stand out more.


----------



## tomchr

Quote: 





holland said:


> Yeah, I've seen that around lots.  A parallel and possibly a series network to do 2 things, bring voltage down and to reflect a load closer to 8 ohm.  Usually it's a 9-10 ohm power resistor loading the secondaries.  I'm not really a fan of that.


 
   
  Triodes tend to like high-impedance loads. Higher load impedance --> higher gain, lower distortion. You just want enough load on the secondary that the inductive flyback is tamed. There is some uncertainty around how the OPT will operate under these conditions that make me want to try it out before recommending it. Yeah... I'm not a fan of burning gobs of power in a resistor to allow for use with headphones either. 
   
  ~Tom


----------



## tomchr

Quote: 





sceleratus said:


> I think ebony is harder.  It's also darker so a small piece will stand out more.


 
   
  But it'll be a different color than the walnut. Arh... Grain structures. Splitting. Issues I don't have working in metals...  Oh, well. It looks like it'll be a really nice box once you're done. I can see how that bakelite knob doesn't quite fit the high-end image. A nice solid maple knob would be much nicer.
   
  Is the indicator needed? Don't you usually turn it up until it's loud enough anyway?
   
  ~Tom


----------



## sceleratus

Quote: 





tomchr said:


> But it'll be a different color than the walnut. Arh... Grain structures. Splitting. Issues I don't have working in metals...  Oh, well. It looks like it'll be a really nice box once you're done. I can see how that bakelite knob doesn't quite fit the high-end image. A nice solid maple knob would be much nicer.
> 
> Is the indicator needed? Don't you usually turn it up until it's loud enough anyway?
> 
> ~Tom


 
  The indicator is mostly a design detail.


----------



## tomchr

Quote: 





> Originally Posted by *muskyhuntr* /img/forum/go_quote.gif
> If I am understanding Tom correctly, we are talking only about changes to the design from the output transformers on?


 
   
  Correct. The headphone mod would attach to the secondary of the output transformer. It would allow for seamless switching between headphone and speaker. I need to try it out first, though.
   
  I also need to update my design collateral with the component values for the E88CC. To change to the E88CC, one of the LEDs is shorted out and two 1/4 W resistors need to be changed to different values. It's a pretty flexible driver board. I must say that I really like the E88CC as the driver tube. The 6N6P comes in as a close second followed by ECC99. But that's my ears, my speakers. I use JJ E88CC tubes ($12/ea). Nuttin' fancy.
   
  ~Tom


----------



## holland

It would be interesting to see how the 300B reacts to a reflected load of over 30Kohms.  If it does measure the same (minus some power perhaps), then scelartus could have used a 31250:50 transformer.
   
  Also some OPTs react to it OK, others don't and would prefer to see the nominal load of it's secondaries.  Though I think actual impedances might fluctuate more than that, and the parallel resistor would normalize them (affecting sound).  Though I do still wonder about an interstage transformer between the driver and cathode follower, to knock down some voltage gain, coupled with secondaries on the OPT for impedance matching.
   
  Another note, you mentioned doing something similar before, you can also apply a series resistor after the parallel to bring the output impedance up some more.  Some people like it, some people don't.  I have to admit to being one of those that prefer output impedances of 120ohms on some headphones (Beyerdyanmic), not so much on others (HD650).


----------



## tomchr

As long as the OPT bandwidth remains the same under light load as under nominal load, I don't really foresee any issues with the light load. It should give lower THD. The higher gain would probably not be noticeable (though, probably measurable). The mu of a 300B is about 4 if my memory serves. So with the nominal load, you might get a gain of 2 out of it. With the lighter load, perhaps you get 3.5. That's about 5 dB. Not enough to write home about.
   
  ~Tom


----------



## sceleratus

The Misumi L-bracket for the volume attenuator arrived and thankfully it fits.
   
One unexpected downside is the knob is spongy when connected to a rotary switch.  The reason is the extension shaft is a very tight spring, if there is any resistance when you turn it, it needs to build up torque before it can "snap" and move the switch.  This give the knob a very strange feel.  A volume pot would not have this problem.
   
Nonetheless I am now going to order the Goldpoint 23 step attenuator.  Hopefully the detents are softer than the cheap import rotary switch I used for testing.  I don't have another option so it is....going to be this way.  I'm very happy because the clearances are on the order of 1/8".  I was lucky.
   
Note the use of a $20 filament PCB as a base for the bracket.


----------



## holland

I like to use a stiff extender, not the flex ones.  Here's an example, from a quick search on fleabay.
   
  http://www.ebay.com/itm/Extension-Shaft-Volume-Control-Potentiometer-300B-/270625009018
   
  The downside is that you need to have everything lined up or it won't work well.


----------



## sceleratus

Quote: 





holland said:


> I like to use a stiff extender, not the flex ones.  Here's an example, from a quick search on fleabay.
> 
> http://www.ebay.com/itm/Extension-Shaft-Volume-Control-Potentiometer-300B-/270625009018
> 
> The downside is that you need to have everything lined up or it won't work well.


 
  Thanks for hunting that down Holland.
   
  eBay.  Who would have thought?  As you noted it has to line up.  Perhaps a drive shaft knuckle... not cheap.
   
  I had the hardest time finding a knurled shaft collar with a set screw for the wood volume knob.  I ended up a getting  shaft extension, non-knurled, with 2 set screws, as pictured in the eBay ad and cutting it in two.  I will use a long set screw to prevent it from pivoting should the glue give out.
   
   
  If the attenuator is "softer" than this rotary switch, I think it will be fine.
   
  I always appreciate your suggestions.


----------



## sceleratus

Next project:
   
  I thinkI can handle this one and not spend a fortune.
   
  Restore an antique valve radio.
  Y/N ?


----------



## NoPants

If there was high-leveraging of leftover parts then I might see a point but it seems pretty orthogonal otherwise. 
   
  Of course if you want to no one's going to stop you


----------



## tomchr

Quote: 





sceleratus said:


> Next project:
> 
> I thinkI can handle this one and not spend a fortune.
> 
> ...


 
   
  Depends... It could be a good learning experience or a money pit. Depending on your goals, initial state of the radio, and how much of the iron you can reuse.
   
  Definitely get a schematic and alignment procedure for the radio before you tear into it. Get it to work with as many of the original components as possible. Don't perform any modifications before you have the radio working. It's nearly impossible to diagnose a problem if you've modified the circuit (been there, done that - many years ago).
   
  ~Tom


----------



## holland

Radio?  Does that still exist?  
   
  +1 on getting the schematic.  Reverse engineer probably, if you can't find one.  Some of the old stuff is like a rat's nest, so it may be hard to trace correctly.  You'll probably want to note down every single capacitor type and voltage rating.  Those will need to be replaced, so build a list of parts as you go along and building a schematic.
   
  I'd bet it's full of dust and heavily oxidized.  The sockets need a good cleaning, possibly replace tubes.  Tighter tolerance resistors, and replace every cap and replace wires.  It doesn't sound cheap for sure.


----------



## sceleratus

holland said:


> Radio?  Does that still exist?
> 
> +1 on getting the schematic.  Reverse engineer probably, if you can't find one.  Some of the old stuff is like a rat's nest, so it may be hard to trace correctly.  You'll probably want to note down every single capacitor type and voltage rating.  Those will need to be replaced, so build a list of parts as you go along and building a schematic.
> 
> I'd bet it's full of dust and heavily oxidized.  The sockets need a good cleaning, possibly replace tubes.  Tighter tolerance resistors, and replace every cap and replace wires.  It doesn't sound cheap for sure.




And that's the beauty!


----------



## sceleratus

The attenuator sb in saturday's mail.
  I hope I have some hearing left.


----------



## tomchr

Quote: 





holland said:


> I'd bet it's full of dust and heavily oxidized.  The sockets need a good cleaning, possibly replace tubes.  Tighter tolerance resistors, and replace every cap and replace wires.  It doesn't sound cheap for sure.


 
   
  If it was designed with +/-20 % tolerance resistors, it'll still work with +/-20 % tolerance resistors. You can put in +/-1 % tolerance resistors, but that's not going to make it work any better. The receiver sensitivity will be limited by the Q of the IF filter.
   
  Any electrolytic cap in there is likely to have dried out. Any PIO caps or wax dielectric caps are suspect as well. But they might work.
   
  Be really careful when you power up that radio. Build a lightbulb tester. Use it. Wear safety glasses. Seriously! The old parts did not have any means of pressure relief, so when they blow they really BLOW!
  Repair the radio first. Leave as many original components in there as possible. Once the radio is working, you can start the restoration process. Personally, I'd leave it as original as possible. Unless, you need to sandblast the chassis or something. Then you might as well rebuild it with modern components. Save all IF and RF transformers as well as variable capacitors. Those are basically irreplaceable. 
   
  ~Tom


----------



## holland

Quote: 





tomchr said:


> If it was designed with +/-20 % tolerance resistors, it'll still work with +/-20 % tolerance resistors. You can put in +/-1 % tolerance resistors, but that's not going to make it work any better. The receiver sensitivity will be limited by the Q of the IF filter.


 
   
  It's psychological.   Plus, I like operating points to be precise.  Tubes auto-adjust, so yeah, it'll work.


----------



## Tjj226 Angel

Quote: 





tomchr said:


> You can also find a bunch of my design musings here:
> 
> DeathTrap400™ : : A Pretty Damn Good 300B Amp
> 300B (and other DHT) Biasing Options
> ...


 
  Very nice, thanks. 
   
  My friend is able to get james audio push pull transformers for dirt cheap, so now I actually need to kind of get my act together before I start soldering. This will really help


----------



## sceleratus

It's cool how the thread has become a bit of a builders hangout.    
	

	
	
		
		

		
		
	


	



   
  After reading the posts RE my antique radio musing, it's apparent there's no real product at the end (@NoPants), other than a cool wood or bakelite enclosure.
  I'd probably turn it on twice and look at the dial glow.
   
  Moving up the food chain..... I've seen a big following of mid to late seventies receivers.  Sansui and such...
  I could probably get schematics for those.  
   
  That said, probably smart to stay the course and build a "little" HP amp.
  A Tom, Holland, or Frank issue.  Scratch built gives a lot more satisfaction than being a repair man.


----------



## nelamvr6

Quote: 





sceleratus said:


> It's cool how the thread has become a bit of a builders hangout.
> 
> 
> 
> ...


 
   
   
  Have you thought about refurbing a classic tube power amp?  Something like a McIntosh 275?


----------



## sceleratus

Wh





nelamvr6 said:


> Have you thought about refurbing a classic tube power amp?  Something like a McIntosh 275?


 Whoa ...... Work O' Art


----------



## nelamvr6

Marantz had some sweet amps too:
   

   
   

   
   
  And the Dynaco ST-70 was a true classic:


----------



## sceleratus

nelamvr6 said:


> Marantz had some sweet amps too:
> 
> 
> 
> ...



I need a tissue!
Would these reside at the nelamvr6 residence?


----------



## nelamvr6

I wish!  
	

	
	
		
		

		
			




   
  They reside at Google Images...


----------



## holland

It looks like fun.
   
  So, what are you planning on doing?  Restoring a high wattage power amp?
   
  I think you need to get the LCD-3 first, to sit with that 300b amp.


----------



## sceleratus

holland said:


> It looks like fun.
> 
> So, what are you planning on doing?  Restoring a high wattage power amp?
> 
> I think you need to get the LCD-3 first, to sit with that 300b amp. :etysmile:




They look cool but no.
I might build another amp for some Thiel CS1.5 that are wasting away as front surround speakers. Replace them with in wall. 
Looking to overtake a study that my college kid uses as a man cave on breaks. It's a sty. 

Then build and amp and power the Thiels. 
Another DG 300B is the most practical because I bought extras of everything. Most everything but the tranny's and 300B' No exotic enclosure this time. 
But where's the fun?


----------



## Tjj226 Angel

PFFFFFFFFFFFFFFFFFFFFFFFFFFFFTTTTTTTTTTTTTTTTTTTTTT!!!!!!!!!!!!!!!!!
   
  Screw these weak amps. Just the other night my friend (same guy who built the amp I linked to the show your project thread) listened to this amp with some western horns and a jensen imperial bass driver.


----------



## sceleratus

Quote: 





tjj226 angel said:


> PFFFFFFFFFFFFFFFFFFFFFFFFFFFFTTTTTTTTTTTTTTTTTTTTTT!!!!!!!!!!!!!!!!!
> 
> Screw these weak amps. Just the other night my friend (same guy who built the amp I linked to the show your project thread) listened to this amp with some western horns and a jensen imperial bass driver.


 
  My wife would go for the relay rack in the family room if it were blue..... NOT !!!!


----------



## sceleratus

I think this Norman bel Geddes design be a bitch'n model for an amp enclosure.   (There goes the budget)
   
   

   
   
  This concept too..


----------



## Tjj226 Angel

Quote: 





sceleratus said:


> My wife would go for the relay rack in the family room if it were blue..... NOT !!!!


 
   
  She would if she realized what that was. Those are all western electric amps, a Thorens record player with a custom plinth, and some dac that we didn't bother to use. That rack literally costs more than my house, and we don't live in a poor neighborhood. 
   
  Just think that the power tubes are WE 300B tubes and that the transformers cost 20 times more than the tubes do. 
   
  I WANT IT!!!!!!!!!!!!


----------



## Tjj226 Angel

Quote: 





sceleratus said:


> I think this Norman bel Geddes design be a bitch'n model for an amp enclosure.   (There goes the budget)
> 
> 
> 
> ...


 
   
 
   
  I think the little radio would be cool. You could knock out the dial screen and make a little window to put tubes behind. Then rip out the speaker inside and use the area to vent any heat. IDK if it would be big enough or sturdy enough to actually support any type of large power transformer though. If it is a sturdy radio, it can be done. 
   
  The bottom one....eh. I have no idea how I feel about it.


----------



## sceleratus

Quote: 





tjj226 angel said:


> I think the little radio would be cool. You could knock out the dial screen and make a little window to put tubes behind. Then rip out the speaker inside and use the area to vent any heat. IDK if it would be big enough or sturdy enough to actually support any type of large power transformer though. If it is a sturdy radio, it can be done.
> 
> The bottom one....eh. I have no idea how I feel about it.


 
  They are broad "concepts" for a larger enclosure.
  Just looking at lines, curves, &  flow.


----------



## Tjj226 Angel

Quote: 





sceleratus said:


> They are broad "concepts" for a larger enclosure.
> Just looking at lines, curves, &  flow.


 
   
   
  I know, but I think it would actually be cool just to use the little radio and just mod it a bit. 
   
  As for what ever is in the second picture.... wellll.. I can not make up my mind. It either reminds me of the whole "futuristic" look of the 50's or it reminds me of some of the crappier cars of the 80's. 
   
  What about a straight steam punk amp? The tube sockets can be made to look like little copper gears and the volume knob can be a little hand crank. 
   
  Heck, you could also shrink the amp. Generally speaking, you can find someone who will make you something with a 3D printer in your area or online. Simply make your chassis so that all the parts are form fitting. Then, just use REALLY fine grit sand paper to smooth everything out. Paint it black with a spray can/gun and then add a clear coat to give it a piano black look. 
   
  IDK, I like to build more theme oriented things. I try not to do anything too crazy because I usually end up spending a lot of money on something that looks like crap in the long run.


----------



## sceleratus

I posted a bit back my concern that the volume control would be spongy due to the extension shaft.
I received the Goldpoint Attenuator today, and although the extension is with the woodturner, the control will not be a problem.
   
  [size=small]The action on the Godpoint Elna switch mechanism is fantastic.  As you will see I've put the knob inside until the shaft and new knob arrive.[/size]
  [size=small]Now my ears can heal.[/size]
   

   
  [size=small] [/size]


----------



## nelamvr6

Looks pretty damn impressive!


----------



## sceleratus

Ok.  I was worried that by adding this thing to the signal path the sound quality would degrade.
Was I wrong !
   
  [size=medium]I truly wish ya'll could listen to this.  It has never sounded better. Very clean very crisp with a huge voice.[/size]
   
  [size=medium]When I completed the demo build (without an enclosure) you will recall I was concerned about some snow.  Didn't detract from most tracks.  At that time Tom recommended I put a 56 ohm resistor in.   Cant remember if it what side it was on.  I never did this and 95 % of it disappeared when I went to a balanced I/O.  I'm thinking that some resistance on the input side has actually added to the quality of the sound.[/size]
   
  [size=medium]Again, I'm clueless.  I solder.[/size]
   
  [size=medium]The wiring is temporary until some braided shield comes in next week.[/size]


----------



## sceleratus

Cannibals  !!!


----------



## catfish

Does this amp have a black background?  Any buzz or hum with sensitive phones like Grados?  Did you have to use dropping resistors on the OPT secondary ?


----------



## sceleratus

I won't say it's dead-bang black.  There is a faint "something" when nothing is playing, but I can't detect it once play is pressed.  Even in classical string tracks where there are dramatic transitions.
  
 As an example:
 Marianne Thorsen, TrondheimSolistene, Mozart Violin Concerto no. 3 in G major (KV 216) Allegro
  
 I have Audeze LCD2 rev 2's  I listened with HD800 at the LA meet for a brief period, however I wasn't able to "zone in" for a good listening session.  Can't comment on the Grado's.   I did NOT implement a dropping resistor on the OPT.
  
 In the schematic below are modification Tom provided to help with early noise mitigation as well as support the ECC88 variety valves.  It helped significantly.
  
 Next I upgraded some resistors to Texas Components TX2575 bulk metal foil 0.1% and the .22mF capacitors to Mundorf silver oil as noted.  I converted the input and output interfaces to balanced / differential 3-pin XLR.  That required me to replace the ALPS Japan volume POT with a stepped attenuator.  I did this yesterday.
  
 Mid- week I will re-wire the inputs with a silk wrapped 26ga. silver wire and a copper braided shield around it.  The final touch will be to install the flexible shaft and turned figured maple knob.  Done.
  
 I guess this will be the end of the journey and the thread unless there is something significant to report…… Like putting in insane Royal Princess 300B's or the Takatsuki TA-300B.
  
 I wouldn't be that stupid.  nah.
  
 EDIT:  The longer it's turned on, the quieter it gets. As in black.


----------



## sceleratus

I am Immensely excited.
  
 My friend has a huge vinyl collection with rare stuff.  He's been putting most of his efforts into organizing a larger digital collection.  He has a top tier Lynn system.
  
 He had tried to digitize the vinyl a few months back and didn't like the results.
  
 Yesterday I took my Mac, a MOTU Microbook, and Logic Express over to give it a go.  The results are stunning!  He hasn't got the test tracks scanned into the Lynn library...  I think he will be very happy.
  
 The test cuts are.  Miles Davis Kinda Blue, Tracy Champman Revolution, and Beatles Get Back.
  
 Logic Express uses "Bounce" mode and writes 24 bit 192K .aif files on the fly.  I think it's as good as any digital recording I have and it has that nice stylus on vinyl quality.


----------



## sceleratus

I now know what I want to build next....  Phono Preamp.
  Doable?
   
  The recordings I captured were stunning.
  A/B comparisons to ripped CD's were hands down better.
  I am dumbfounded.


----------



## randytsuch

Quote: 





sceleratus said:


> I now know what I want to build next....  Phono Preamp.
> Doable?
> 
> The recordings I captured were stunning.
> ...


 
http://hagtech.com/cornet2.html


----------



## sceleratus

Quote: 





randytsuch said:


> http://hagtech.com/cornet2.html


 
  Thanks Randy


----------



## sceleratus

Full speed ahead learning how to rip vinyl to digital.
  
 Here's the analog source equipment:
 LP12 Turntable
 Akiva Cartridge
 Ekos2 Tone Arm
 Keel Sub-chassis
 Lingo Power Supply
 Linto Phono Pre-amp 
 Pre-Amp Linn Klimax Kontrol
 Amplifiers Linn 6100 and Linn 4200
 With Aktiv Crossovers 
 Speakers Linn Akurate 242MK 1
 Two Linn Melodik Subwoofers
  Digital Linn Akurate DS Streamer
  
 Recording equipment:
 MacBook Pro Retina SSD
 MOTU Microbook
  
 Software Choices:
 Logic Express 9
 MOTU AudioDesk
 Audacity
  
 The three tracks I captured were done with a whole 20 minutes of seat of the pants learning on Logic Express.  I need to learn how to set input/output recording levels so they don't clip.  Perhaps AudioDesk or Audacity is a better way to go.  ?
  
 For a beta test the results were impressing.  I found them far superior to CD recordings of the same material.  However they were not as good as the direct vinyl.  Especially when the volume was cranked.  The clipping was revealed on the Linn system.  It's good, but I think it can be better if I know what I'm doing.


----------



## sceleratus

Roger's Woodturning finished the knob and sent me a photo.  I should have it tomorrow.
  I really like it.  It should look amazing when it's on the amp.


----------



## m2man

sceleratus said:


> Full speed ahead learning how to rip vinyl to digital.
> 
> 
> 
> ...



Don't you just want an ADC before his pre-amp? Then you don't lose anything going to speaker and back through the mic. At least it sounds like you are using a mic with the Microbook...


----------



## sceleratus

The MOTO Microbook is an ADC.  It has balanced Line In.  That's where the phono pre-amp is connected.
  No Mics.  Using MOTU AudioDesk and QueMix FX software.
   
  The results are amazing.  A lot of that can be attributed to an amazing cartridge.
   
  Logic Express was horrible.


----------



## sceleratus

Completed the attenuator re-cable using shields.  It passed the DMM test......now for music.   When the maple knob arrives this afternoon the project will be complete.


----------



## nelamvr6

Awesome!


----------



## sceleratus

Exactly how I wanted it to look.
Needs a touch of lacquer.


----------



## sceleratus

It feels sooo good to not have to add/fix/change something.
   
Out


----------



## nelamvr6

Quote: 





sceleratus said:


> Exactly how I wanted it to look.
> Needs a touch of lacquer.


 
   
  Gorgeous!


----------



## holland

It looks great.  The knob is definitely better.


----------



## sceleratus

Thanks.
  It's an entirely different look.
  I put a coat of lacquer on it last night and the grain popped.  It matches the sides now.  I am very happy.
   
  EDIT:  I really like the attenuator.  The step clicks are very smooth and the sound is great.


----------



## holland

That's great.  I was just wondering about the attenuator.  To be honest, I cannot hear differences in pots, or perhaps it's just that I don't know what to listen for.


----------



## sceleratus

I'm not sure I can tell the difference either.  They are very close.  I'm just pleased that it sounds good; very clean.  I also like the tactile clicks. I was worried about that but I think I like it better than a pot.


----------



## tomchr

That's a sweet looking amp. Nice execution. Thanks for sharing your experience.
   
  ~Tom


----------



## sceleratus

Beauty shot with finished knob...


----------



## catfish

Quote: 





tomchr said:


> That's a sweet looking amp. Nice execution. Thanks for sharing your experience.
> 
> ~Tom


 
   
  How much power is this estimated at,  could it handle 5W the HE-6's ?


----------



## sceleratus

Quote: 





catfish said:


> How much power is this estimated at,  could it handle 5W the HE-6's ?


 
  This is the OPT specs from Jack Elliano at Electra-Print


----------



## tomchr

Quote: 





catfish said:


> How much power is this estimated at,  could it handle 5W the HE-6's ?


 
   
  The DG 300B Amp delivers 10 W into an 8 ohm load (1 % THD). Clipping (3 % THD) happens at about 12 W. 
   
  ~Tom


----------



## catfish

Quote: 





tomchr said:


> The DG 300B Amp delivers 10 W into an 8 ohm load (1 % THD). Clipping (3 % THD) happens at about 12 W.
> 
> ~Tom


 
   
  This is fantastic.  My only concerns are sceleratus's comments that there is some noise.  What makes a great headphone amp is a simple test.
   
  Play music on your most sensitive/efficient headphones about as loud as you like.
   
  Then play a "silence" tack which is basically just digital null.   If you hear any noise it affects the SQ.  Its a better test of a headphone amp than any THD,IMD, FFT, etc.
   
  I suspect this amp would pass the test with flying colors for orthos but may not for Grados and Senns,  which is fine really we all need more than one amp 
	

	
	
		
		

		
			




   
  I want to build something similar,  I really like the Madia regulator as I think it is a great step toward a black background SET.  But I am a little apprehiensive about the smps DHT heat.?


----------



## tomchr

Quote: 





catfish said:


> This is fantastic.  My only concerns are sceleratus's comments that there is some noise.  What makes a great headphone amp is a simple test.
> 
> I suspect this amp would pass the test with flying colors for orthos but may not for Grados and Senns,  which is fine really we all need more than one amp
> 
> ...


 
   
  I seem to recall that Sceleratus reported that using differential inputs took care of the noise. It's possible there was a ground loop in his first setup...
  Regardless, I have some experiments underway for using output transformers with higher turns ratio for driving headphones. This should dramatically reduce any noise. I'll be testing this with my Sennheiser HD650.
   
  I understand that some people fear switchers. I'm not really sure why. I compared a linear lab supply versus a switching supply for the 300B filament supply in an earlier 300B design of mine. You can see the results here: 300B Switchmode Filament Supply. I am not able to measure any significant difference between a linear supply and my switchmode supply. But the switchers are so much easier on cost and on the thermal budget.
   
  ~Tom


----------



## holland

Quote: 





> Originally Posted by *tomchr* /img/forum/go_quote.gif
> 
> I understand that some people fear switchers. I'm not really sure why.


 
   
  Audiophile BS, that's why.


----------



## tomchr

That is my suspicion as well. But as my measurements show (see link above), the fear is rather irrational.
   
  ~Tom


----------



## Dubstep Girl

So does DG stand for dubstep girl?


----------



## sceleratus

Quote: 





dubstep girl said:


> So does DG stand for dubstep girl?


 
  Well I guess it could.
  Right now it's "Damn Good"


----------



## nikongod

I thought DG was Regal's initials.


----------



## Chromako

I've read through this entire more monster thread, and have to say, AWESOME!

I thought I'd submit a little tip, if you don't mind? (I promise that I'm not trying to be pedantic.)

In my electronics experience, my motto is that "you can never have too much EM shielding." Okay...that comes after "always turn off the all the power supplies before fiddling," and "don't bypass the Earthing prong, even if you really really want to," and "50 kV HVDC arcing to your earthed meatbag &%£#ing hurts!" But you get the picture.

If you are paranoid about EMI giving background static and stuff, like me, you can line the inside of your nonconductive case panels with (grounded) metal mesh to make a Faraday cage. And always verify that your top and bottom panels are also grounded (just in case- cheesy pun intended  ) If it were me making this amazing creation of yours (which I couldn't), I'd be doing that shielding, just to be absolutely sure I got the ultimate inky black backgrounds. Naturally, YMMV.

There's a reason why so much HiFi equipment is in metal casings, besides cosmetics, and why your interconnects (and your internal wiring now- bravo!) are shielded, and why some expensive units have separate PSU enclosures. (And why plastic cased laptops have those blasted aluminium sheets in them that make them so hard to repair....argh) Everything conductive, even the legs on an integrated circuit, can be an antenna.

But you knew all that already.  

Then again, it might not make an -audible- difference given your already extensive shielding mods,but it can't hurt. It's cheap as aluminium sheets or even aluminium kitchen foil is sufficient. (Then you can use the rest of your roll to make stylin' Illuminati hats). Or aluminium metal window screen from hardware stores (that's what I use). Or you can get fancy with copper or bronze fine mesh or braiding because it looks awesome. Just make sure your new shielding is earthed  I check my work by putting my cell phone inside, plugging the device in to earth it, and calling. It should go to right to voicemail.


----------



## muskyhuntr

Interesting way to test shielding.  Good tip!
  
 Jim


----------



## sceleratus

Very interesting you should bring up noise.
 Why?
  
 I said I'd post the good, the bad, and the ugly.  As much as I don't want to, this is an Ugly Post.
  
 Out of nowhere, or maybe it's been there and slowly built up, I have developed a hum.  60Hz to be exact.  It's a bit of a moving target but it is very dominant on the left side.
  
 Not kinda, sorta, might be able to ignore it.  It's there.  Right side this morning was quiet, but I know I've heard it, but much softer.  Left always.
  
 What have I done to isolate it?
  

 Roll the glass. nothing.
 Turn everything off to see if it's a ground loop.  Power conditioning is from both the power entry module and a Furman 215-AC.   Nothing
 Purchase an Ebtech HumEx.   Nothing
 Yank the inputs to the driver board, thinking there might be an antenna.  Nothing
 I broke out the scope and made a 50Ω shunt for the HP jack.  I put a 100Hz tone and then a 30Hz tone through the inputs.  They looked fine at the HP jack and the attenuator, as expected, varied the amplitude of the sine wave.  One interesting thing.  I put the tone one one channel only.  I see the wave at normal volume on that side and nothing on the channel with no tone.  However if I crank the volume all the way up a small wave appears on the channel without a tone on the input.  (see "bleed" image.)
 I swapped the OPT on the Driver board.  Very interesting, the scope showed 60Hz sine wave at the HP jack…. CORRECTION pins 2 & 3
 I pulled both OPT inputs off the  board.  The only connection the OPT's had was to the HP XLR jack.  The scope showed a nice 60Hz sine wave on both jacks, CORRECTION pins 2 & 3.
 The sine wave was changing phase about once a second.   (see jumprope picture)
 The OPT's are mounted 2" from the Power Trans face-to-face.  I pulled the mounting bolts and moved them another inch further out.  No change.
 I put a small fire extinguisher between an OPT and the Power Trans.  No change.
 I did what your never supposed to do….  I pulled the mains ground lead from the power entry module for 15 sec.  Nothing.
 I'm contemplating a suggestion to terminate the grounds in a star configuration anyplace I can.
 Before I moved the OPT's outboard more I was certain I had a bad Power Trans.  Now I'm not so sure.
 





  
 60Hz picked up on disconnected OPT's with phase shift.


----------



## sceleratus

scouting out tall buildings.


----------



## sceleratus

Question:
 The scope picks up a 32Hz tone that I feed into the input when an output jack is probed. (See photo)  The setting are 10V / 10ms
 With nothing connected to the inputs the scope picks up 60Hz at 200mV and 2 ms.
  
 Shouldn't I have seen the 60Hz wave superimposed on the 32Hz wave?
  
 Also, with the shunts in I measure
 60Hz with 42mV Vrms on the left side. This is the noisier channel.
 60Hz with 72mV Vrms on the right side.
  
 Next I disconnect the OPT's from the driver board
 I can hear hum through the HP's but not as loud.  Both sides.  In this setup I measure:
 60Hz with 70mV Vrms on the left side. 
 60Hz with 157mV Vrms on the right side.
  
 If I clip the probe on the disconnected input leads of the OPT I measure:
  
  60Hz with 95mV Vrms on the left side. 
  60Hz with 140mV Vrms on the right side.
   
  Since the OPT's are isolated from the circuits this tells me the Power Trans has a noise problem.  
   
  Yet there are certain inconsistencies.
  Such as after testing, if I pull the power plug out entirely I will still see 60Hz and 100mV Vrms on the scope.  My DMM measures about 20mV
  Is this from the caps?
   
  I clearly don't know what I'm doing.


----------



## GrindingThud

Do you have a high impedance probe? You should look at the noise at the tube grids, the heaters, anodes, and B+....try and track down where it's coming from. Does the output noise change amplitude when you short the input?


----------



## sceleratus

I do not believe so.
  I have the Rigol DS1052E
  The stock probe is 10M ohm at 10X since it's measuring DC that would be the impedance with zero phase angle (As I understand it from Wikidedia)
   
  Not that I'm not going to look at the grid, because that was recommended by someone else as well, But If I'm picking up 60 Hz hum, both audible and with a scope, on the outputs when the OPT is disconnected from the board entirely, it can't come from the grid or anything else on the board since it's not connected. ... Unless completely misunderstand or I'm doing something wrong.
   
  The output noise does not change amplitude when the inputs are shorted.  The attenuator has no effect either.  I played music while probing at the outputs.  Turning the volume off eliminated the music wave form as expected and left the 60Hz.


----------



## GrindingThud

I missed the OPT disconnect part, sorry. That one puzzles me too....maybe induced? 



sceleratus said:


> But If I'm picking up 60 Hz hum, both audible and with a scope, on the outputs when the OPT is disconnected from the board entirely, it can't come from the grid or anything else on the board since it's not connected. ... Unless completely misunderstand or I'm doing something wrong.


----------



## sceleratus

Has to be induced from the power trans.   There's no external hum.
  It is so bizarre. 
  The waveform amplitude is higher on the right side, but that's not nearly as loud as the left, whose wave is almost flat at the same settings.
   
  It's getting worse too.


----------



## sceleratus

Quote: 





grindingthud said:


> I missed the OPT disconnect part, sorry. That one puzzles me too....maybe induced?


 
  I have to be doing something wrong with the scope.
   
  I clip to mains ground and probe XLR Pin 2 (+).
  The XLR jack has a plug with a R50 20W across Pins 3 and 2.


----------



## sceleratus

Ather problem with probing the Grids or the OPT inputs is the Scope's specification for maximum input voltage is
   

 [size=10.5px] 400V (DC＋AC Peak, 1MΩ input impedance) [/size]

   
That is exactly the voltage going into the OPT's
   
I had probed there when they are connected to the driver board and I couldn't understand why I wasn't seeing anything.  The I probed with my DMM and got 399VDC
I check the scope manual and sure enough.
   
I need the current so I can calculate the voltage diver.  I'm thinking an R1.5K should get it close to 100VDC


----------



## GrindingThud

Yes, that makes it hard to probe. You'll eventually find it....looks like you have a good set of test equipment.



sceleratus said:


> Ather problem with probing the Grids or the OPT inputs is the Scope's specification for maximum input voltage is
> 
> 
> 
> ...


----------



## sceleratus

Thanks !
  I need the encouragement.
   
  I'm looking at plate chokes as one thought......
  But if a trans is jacked up, I want it out.  I just don't want to spend the money until I am certain it's the power trans.


----------



## holland

Did you disconnect the output XLR jack from ground and use a ground loop breaker for that?  I also thought you said you move the OPT out of the chassis a bit with no impact?  Try "shielding" with aluminum foil?  It's not ideal, but just to see if the noise changes.
   
  Re: max voltage. There are 2 that you need to be concerned with.  One is the max of the scope itself, it says 400V, which should be using a 1x probe.  The other is the max voltage of the probe.  The 10x probe will attenuate the voltage, but it should spec a max voltage.


----------



## sceleratus

I ride on the short bus. What's a ground loop breaker?


----------



## holland

A 10 ohm 5W resistor in parallel with a 0.1uF 250VAC/500VDC capacitor.  This connects to mains ground, and then you connect the output XLR to it.  If the buzzing goes away, then you know you've got ground loops and we can try to fix it.  The ground loop breaker is generally a patch, but it works.  The is allows the voltages between the 2 grounds to be different.  You can also wire 2 1000V diodes in opposite directions in parallel to these as well.


----------



## sceleratus

Excellent !
Thanks.
I will see what I can put together.


----------



## sceleratus

Holland,
   
  Is there a preference?
   
  I have three large 3R3 10W and the 0.1uF 630VDC cap
  It will be an ugly assembly.... Or I can build it outboard on a Proto-Board
   
  I also have two general purpose axial diodes.  1000V 1A  DO41


----------



## holland

Quote: 





sceleratus said:


> Is there a preference?


 
   
  No.  You can just use the resistors and cap right now.  IT doesn't need to be pretty, just a quick test right now.


----------



## sceleratus

I just this moment finished using the 100V diodes, reversed, in parallel.
   
  There was not improvement.


----------



## sceleratus

I'm making the Cap / Res config now.


----------



## sceleratus

I have reached Max-Q of my abilities.





  Shipping it to an expert.


----------



## randytsuch

I guess this is too late to help you, but since it used to work OK, and then a hum started, I would have looked for cold solder joints and/or any bad connection.  I would guess something came slightly loose, or you have a bad joint somewhere, and the temperature cycles made it open up.
   
  I think the noise you are seeing with the scope isn't the real problem, since you see the noise with things disconnected, sound more like a measurement issue which is diverting your attention.
   
  Randy


----------



## sceleratus

randytsuch said:


> I guess this is too late to help you, but since it used to work OK, and then a hum started, I would have looked for cold solder joints and/or any bad connection.  I would guess something came slightly loose, or you have a bad joint somewhere, and the temperature cycles made it open up.
> 
> I think the noise you are seeing with the scope isn't the real problem, since you see the noise with things disconnected, sound more like a measurement issue which is diverting your attention.
> 
> Randy


 
 Perhaps,
  
 I certainly checked the wire connections as well as the board work.  Nothing looks suspect.
 The noise comes on fro the moment the power is thrown then the left escalates after the valves have energized.  I have been looking at this for a week.  Regardless of if it's on the scope or not I'm still in the same place.... not being able to identify it.
  
 I thought it might be the power transformer but I'm told it's a stinking mess when one goes bad.  That's not the case.
  
  
 Whatever it takes, it's going to be fixed.


----------



## FrankCooter

If it worked once, it will work again.

Put away the scope. You may be mistaking problems of measurement technique for amplifier issues. 

Randytsuch had exellent suggestions. I'd reflow every solder joint in the left channel.

Get a can of electronics freeze spray. While listening through your headphones, follow the left channel from beginning to end with the spray. If the hum changes when you spray a particular area, you've found the problem.

Get a small wooden dowel or chopstick. While listening to your headphones, use the dowel to move wiring around to see if the hum changes.

Simplify the signal wiring by going back to a single-ended signal path. You may be inducing a ground loop by your pseudo-balanced signal path.

I doubt the power transformer is an issue. It would affect both channels equally and would probably have shown up right from the start. If you think it might be.disconnect one output transformer and remove it from the chassis. With the output transformer attached only to the headphones, move the output transformer around the energized power transformer and listen for induced hum.

Put the whole project away for a few days and don't think about it. When you return, you'll have a completely different frame of mind and will see things that previously eluded you.

The design is good, it worked before, and you will fix it. When you do you'll feel a sense of triumph and accomplisment that is much greater than if everything had simply fallen effortlessly into place.


----------



## holland

I may have misread, but it was my understanding that he disconnected the output transformers from tube output and b+ (only connected on the secondaries to the headphones and to mains ground via a ground loop breaker), and he was still getting the same noise.  If that's the case, I don't think reflowing is going to do much.


----------



## randytsuch

I'm not sure about what happened with the output tranny's disconnected.
  
 In general, I agree with Frank, I would concentrate on the left channel, and reflow all the solder joints, even if the look good.
 I was also going to suggest pulling on wires to test wired connections, but if you reflow the joints then maybe you can skip this step.  But, I always do a "pull test" after soldering a wire down, found more bad connections than I care to admit with this method.
  
 Another test I wanted to suggest is to swap left and right circuits.  For instance, you could swap the left and right inputs to the driver board, to make sure the problem is not before the driver board.  Eliminates some connectors and the stepped atten from the mix.  You could also swap the heater boards (I think I remember separate left and right heaters).  With this kind of troubleshooting, you don't need to worry about looks and such, just make sure you have good connections and no shorts, and see what happens.  I think you already swapped the output trannys?
  
 Randy


----------



## FrankCooter

randytsuch said:


> Another test I wanted to suggest is to swap left and right circuits.  For instance, you could swap the left and right inputs to the driver board, to make sure the problem is not before the driver board.  Eliminates some connectors and the stepped atten from the mix.  You could also swap the heater boards (I think I remember separate left and right heaters).  With this kind of troubleshooting, you don't need to worry about looks and such, just make sure you have good connections and no shorts, and see what happens.  I think you already swapped the output trannys?
> 
> Randy




X2


----------



## tomchr

If the issue is only present in one channel, then it is NOT anything in the power supply so bias circuit as those are shared between the two channels. 
  
 No amount of shielding will do anything for 60 Hz hum induction. Unless we're talking shielding using µ-metal. EMI is not likely to downconvert to 60 Hz by chance. 
  
 With all the messing and custom silver wiring that's been going on the the input end of the amp, I bet you have a broken wire or cold solder joint somewhere in the left side. 
  
 Turn the volume all the way down. Measure the anode voltage (pin 6) of the input tube in the left channel using your o'scope (high-impedance inout, AC coupled). If you have hum there (compare with the corresponding voltage in the right channel), then the hum comes in through the input of the left channel.
  
 If it worked before, it'll work again. The two amps I built of that design have hundreds of hours on them by now. And that doesn't account for the time they spent in the DeathTrap prototyping stage (i.e. point-to-point wiring on a piece of plywood). But then, I haven't done all sorts of modding on mine either. I do that during the prototyping stage.
  
 ~Tom


----------



## Chromako

tomchr said:


> INo amount of shielding will do anything for 60 Hz hum induction. Unless we're talking shielding using µ-metal. EMI is not likely to downconvert to 60 Hz by chance.


 
 Nice that you mention that, with my obsession with EM shielding... I agree with you. Not 60Hz. That'd be a ridiculous coincidence. Unless you've got a poltergeist in the electrical grid.
  
 Hmm... now that I think of it... have you tried doing an exorcism? 
	

	
	
		
		

		
			




  
 Of course, this is all moot as he's sent it out already to get a second set of eyes, but it's fun to "armchair solder."
  
 But yes, it worked before. It'll work again!


----------



## holland

In my experience, 60Hz is usually a grounding problem, and/or mains noise coming in somewhere.  The noise is probably on both channels, but different voltage levels.  You'd probably hear it very loud with IEMs.  I'm not convinced the noise was never there.  I think it always was, just not heard as loudly.
  
 Assuming the disconnected transformer noise is a red herring....perhaps try grounding the primaries of the OPT and see if the noise is there still there.
  
 Switching the wiring for output tubes might be a start, but I would look at the input transformer as well.  IIRC, the board is a single board for both channels with wires for the 300B.  Also, another IIRC, the DC heaters are floating, perhaps ground them if they aren't already.
  
 I also believe there was prior discussion about pulling the driver tube and using a resistor divider to set the grid voltage for the 300B, can play with that again.
  
 The cold spray is an interesting recommendation, I've not tried that one before.
  
 If he sent it to Electra-Print, I'm sure Jack will find the problem.


----------



## sceleratus

holland said:


> If he sent it to Electra-Print, I'm sure Jack will find the problem.


 
 Winner, winner, chicken dinner.


----------



## sceleratus

In no way do I think the design is bad.  Frank, Randy, and I have heard how nice it can sound and I believe it sounded better after the "pseudo balance" (Frank) inputs.   I greatly appreciate everyone's suggestions and support.
  
 I am lacking the expertise to find all but an obvious problem.  
  
 I check for shorts, loose wires, implementing ground isolation, purchased a 3rd party ground loop product,  disconnecting all inputs from the driver board, disconnecting the OPT's from the driver board.  I checked the capacitance values of the "off brand" caps.  They are exactly the value called out in the BOM.  I did not deviate from any component values in the BOM.   The build wiring diagram specifically shows XLR's for the inputs.  I followed the output wiring diagram and tied XLR Pin-1's together and to mains ground.  I have rolled everything possible to roll.  I have moved the OPT's an additional inch further out from the power transformer.
  
 The box is still hear.  The dense foam packing materials arrive from U-Line today.  Jack told me not to change anything.  Just send it to him.  He has been very kind by exchanging many emails with suggestions.  Strike that "directions" as well as "what are you trying to do, knucklehead"  Yet he hung in there.  He said he's going to take a wall of gear and print it before and after.  I couldn't resist having that done.
  
 Then when some one asks how quiet it is or what's the spec.  I will have it.
  
 Tom,
 You designed one hell of an amp.  Something went south, either organically or do to an error on my part.  So much of this baffles me as it hasn't produced the expected results from my testing and I am reticent to dive into the board.  My scope is maxed out at 400V and I don't know if I can probe with a resistor.
  
 All I know the left side has escalated to "Bug Zapper' without the bugs.


----------



## sceleratus

holland said:


> In my experience, 60Hz is usually a grounding problem, and/or mains noise coming in somewhere.  The noise is probably on both channels, but different voltage levels.  You'd probably hear it very loud with IEMs.  I'm not convinced the noise was never there.  I think it always was, just not heard as loudly.


 
   
  
 That is a real possibility.
  
 Quote:


holland said:


> In my experience, 60Hz is usually a grounding problem, and/or mains noise coming in somewhere.  The noise is probably on both channels, but different voltage levels.  You'd probably hear it very loud with IEMs.  I'm not convinced the noise was never there.  I think it always was, just not heard as loudly.
> 
> Assuming the disconnected transformer noise is a red herring....perhaps try grounding the primaries of the OPT and see if the noise is there still there.
> 
> ...


 
  
 I think I'm just going to box it.  Why?   I'm sending it to Jack regardless and if I mung up something else during testing will just make it more difficult to find.  I'm sure he'll find it.  Then I will report back and end the speculation (Best case scenario)
  
 I don't care if I have to order another Driver Board and built it from scratch.  Hell, depending on the outcome, I might do just that, so I have a stock board and board for modding. It's gonna get fixed.  Then I'm going to listen to music for quite some time.


----------



## sceleratus

Question for educational purpose.
  
I want to revisit the screen captures below.  It's odd, to me, and I'd like to understand what might be happening.
  
I put a 114Hz tone on the left input, turned the attenuator to medium, probed the left output with the scope and captured the wave pictured 10.0V at 5.00ms.  Right and Left XLR outputs had an  R50 25W "Load Plugs" across pins 2-3.
  
I moved the probe to the right side, keeping the signal on the left input.  I got nothing until I turned the volume all the way up and captured the small wave in the other picture.  Is there a reason for this?
  


  
  
 [size=medium]Next question:[/size]
Why can I capture a 60Hz sine wave (below) with nothing connected to the inputs, yet when I put 114Hz  freq (Image above) on the input, the 60Hz is not visible?  The 114Hz is perfect.  Is it because the 144Hz tone is at 10.0V and the 60Hz noise is at 200mV?  Also the phase shifts about every second.  I setup my camera to capture this..  Thanks

  
​


----------



## tomchr

How are you grounding your scope probe? The 60 Hz pictures you post look like the scope either isn't triggering properly or you forgot to ground the scope probe.
  
 ~Tom


----------



## sceleratus

J6 P3-4


----------



## tomchr

holland said:


> Also, another IIRC, the DC heaters are floating, perhaps ground them if they aren't already.
> 
> I also believe there was prior discussion about pulling the driver tube and using a resistor divider to set the grid voltage for the 300B, can play with that again.


 
  
 The heater supplies for the 300B are grounded. The heater for the small-signal tubes are biased by a resistive divider to about -100 V. Do NOT change this as the Vhk spec of the little tube will be violated. The heater is at AC ground through a 100 nF cap.
  
 I suggest pulling the 300B and measuring the voltage of the grid pin. That'll tell you if the hum gets in before or after the 300B.
  
 My money is on:
 1) Bad connection
 2) Missing ground
 or 3) ground loop.
  
 I'd say 90 % chance of 1). 9.9 % chance of 2), and 0.1 % chance of 3).
  
 ~Tom


----------



## tomchr

sceleratus said:


> J6 P3-4


 
  
 What happens if you use J4 (or J8) pin 1 of the driver board? You can also use 300B pin 1.
  
 ~Tom


----------



## sceleratus

tomchr said:


> What happens if you use J4 (or J8) pin 1 of the driver board? You can also use 300B pin 1.
> 
> ~Tom


 
 I will set up in a few minutes and let you know.
 When I use the scope I terminate  a lead to J6 P3 ground and clip the probe to that.
  
 With a DMM I use the probes an touch the terminal block screws.


----------



## sceleratus

tomchr said:


> The heater supplies for the 300B are grounded. The heater for the small-signal tubes are biased by a resistive divider to about -100 V. Do NOT change this as the Vhk spec of the little tube will be violated. The heater is at AC ground through a 100 nF cap.
> 
> I suggest pulling the 300B and measuring the voltage of the grid pin. That'll tell you if the hum gets in before or after the 300B.
> 
> ...


 
 What about TU1 and TU3, pull those as well?
 I can't tell you how many times I have tugged on leads tied down to the blocks.
 Can't tell you about solder connections.  
 The candidate for most sensitive are loops from the board to TU2 and TU4.
 Followed by upgrades / reworks of C4A C9A   R6, R7, R20, R21.   R9,R23.   R10 R24


----------



## sceleratus

Without the valves there is a quite hum. Both sides are equal.  Nothing like the loud buzz/hum with them in.
  
 I will take measurements


----------



## tomchr

sceleratus said:


> Without the valves there is a quite hum. Both sides are equal.  Nothing like the loud buzz/hum with them in.


 
  
 There's hum in the headphones even with all the valves unplugged? That makes no sense at all. I suppose it could be coupling from the power transformer to the output transformers. Regardless, I'm not sure it's relevant as you won't be operating the amp with the OPTs disconnected.
  
 ~Tom


----------



## sceleratus

J4 / J8 Pin1 works fine as a ground with the DMM
With both sets of tubes pulled...
 [size=medium]All voltage measurements for TU1, TU3, TU2, TU4  conform with the correct values in the startup procedure.[/size]
 [size=medium]OPT input voltage is 400V[/size]


----------



## sceleratus

tomchr said:


> There's hum in the headphones even with all the valves unplugged? That makes no sense at all.
> 
> ~Tom


 
 Very light. A background hum.  Faint, certainly compared to with them in.


----------



## tomchr

sceleratus said:


> What about TU1 and TU3, pull those as well?


 
  No. The whole point is to let the small-signal tube amplify whatever hum may be on its input so you can measure it. 
  
 ~Tom


----------



## sceleratus

WIth the OPT shunts in,
With the DMM in Max/Min/Ave mode probes to left and right chan P2 will start at 60mV and drop quickly to 20mV continuing to  drop from 15mV but slowly.  Pulling the probe resets the sequence.   I [size=medium]presume this is a cap activity.[/size]


----------



## sceleratus

tomchr said:


> No. The whole point is to let the small-signal tube amplify whatever hum may be on its input so you can measure it.
> 
> ~Tom


 
 ok


----------



## sceleratus

WIth TU1 and TU3 in the Grid voltage on TU2 and TU4 rose from -232V (spec) to -76V
  
 EDIT:
  
 Reading the startup procedure this is the correct voltage for TU2/TU4 Grids when TU1 / TU3 is insertyed.
  
 There is still a faint hum.


----------



## sceleratus

With valves TU1 and TU3 in, I clipped to the J8 ground on the Driver Board and probed Pin 2 of the output jacks.
The image of the higher amplitude wave is the Right Channel.  Multiple exposures were taken to catch the wave phase shift.   If these are of any use at all...
 
 

 

 
 
​


----------



## tomchr

Suggestion: Use the line trigger on the o'scope. If the hum really is 60 Hz (or harmonics), the scope should show a clear image.
  
 ~Tom


----------



## sceleratus

I ride the short bus.  My o'scope has these triggers:
  
 Edge, Pulse Width, Video, Slope, Alternate, Pattern and Duration Trigger 
  
  
 I'll see what I can find on YouTube


----------



## sceleratus

Probably a good idea....
 I get the exact same wave form when the amp is OFF


----------



## nikongod

sceleratus said:


> Very light. A background hum.  Faint, certainly compared to with them in.


 
  
 Magnetic coupling.


----------



## sceleratus

Couldn't get a grasp on triggers after several YouTube tutorials....
Magnetic coupling must be really strong since I moved the OPT's an additional 1" to 1.5" further from the face of the power trans.
Hard to imagine this popped up now after testing in death trap mode and running production for over a month.   I also looked at transformer positioning of the Electra-Fidelity Silver 45.  Eyeballing it my distances are equivalent to greater.

  
  


  
  
  
  
Reached Max-Q of my abilities.  I'm in "box up" mode now.


----------



## holland

nikongod said:


> Magnetic coupling.


 
  
 It might be, or it might be environmental though I think flourescent lights should show up as 120Hz.
  
 Suggestion, move to a different room.  Also, add extra wire (2 feet) to the output transformers and move that away in an aggressive manner.  Move the output XLR jacks with the transformer.  Solder the wires, and scotch electrical tape (rated to 600V) to wrap.  I'm not sure about generics.
  


tomchr said:


> Suggestion: Use the line trigger on the o'scope. If the hum really is 60 Hz (or harmonics), the scope should show a clear image.
> 
> ~Tom


 
  
 I would like to see a single cycle as well, but this is probably good enough.
  


sceleratus said:


> I ride the short bus.  My o'scope has these triggers:
> 
> Edge, Pulse Width, Video, Slope, Alternate, Pattern and Duration Trigger
> 
> ...


 
  
 Just hit all of them, to experiment.  Start with Duration, trigger on high (not sure if there is a voltage level to set, but if so, set to something like 1mV), and capture about 60ms of data.
  
 The noise pictures you are posting is the same as what was on the output.  Was this with the input connected to the input XLR?  Can you disconnect it and ground the inputs to the driver board?
  
 Also, can you probe the input XLR jack?  I think you may have done this already, I forget.


----------



## sceleratus

> Just hit all of them, to experiment.  Start with Duration, trigger on high (not sure if there is a voltage level to set, but if so, set to something like 1mV), and capture about 60ms of data.
> 
> The noise pictures you are posting is the same as what was on the output.  Was this with the input connected to the input XLR?  Can you disconnect it and ground the inputs to the driver board?
> 
> Also, can you probe the input XLR jack?  I think you may have done this already, I forget.


 
 Tried many different scope trigger configuration.  I didn't know what I was looking at.
  
 I probed the driver board with all the inputs removed.
  
 Doesn't matter now.  It's in a box
  
 Thanks to everyone for the suggestions and encouragement.  Wish I could have figured it out on my own.


----------



## tomchr

Damn... I'm curious to hear what Jack finds out.
  
 ~Tom


----------



## sceleratus

tomchr said:


> Damn... I'm curious to hear what Jack finds out.
> 
> ~Tom


 
  
 you have no idea........ actually you do.


----------



## holland

follow up would be great, very curious myself.


----------



## sceleratus

I just checked FedEx status.  Jack will have them today.
  
 He said the following:
 "We will spec the amp before and after so you will have a record of what it is capable of."
 I'll have a Blueprinted amp when it comes home.
  
 Nervous......


----------



## holland

> Originally Posted by *sceleratus* /img/forum/go_quote.gif
> 
> "We will spec the amp before and after so you will have a record of what it is capable of."
> I'll have a Blueprinted amp when it comes home.
> ...


 
  
 Yeah, I would be too.


----------



## sceleratus

First and foremost, I want it to sound like it did before it became a bug zapper.   I love listening to my baby sing.
  
 But everyone here Loves Numbers.  Having a benchmark from an independent source with a good reputation is cool.   Like taking your 57' Chevy with a 383 stroker to the track.  If it's a dog, ya still love her.   (No self respecting rodder would ever send their ride out for someone to repair it....  I failed.)
  
 It'll be fun to post them.
  
 Nervous...


----------



## muskyhuntr

I don't know that you failed.  You have designed and built one of the nicest enclosures on this forum, period!  Also note that you are diving into some what uncharted territory by converting an amp designed for speakers and modifying it for head phone use.  Not an easy task, even for the most skilled builders.  Indeed, I just finished reading through a rather long and interesting thread where a number of individuals are attempting to scratch design from scratch, something similar.  I believe they spent about 30 pages just discussing the output transformer and even had a number of mfg's joining in the discussion.  Not easy!   Both you and the people on that other forum are aiming for the best that can be accomplished.  I think you both will succeed.
  
 Jim
 PS. I admire your perseverance,


----------



## sceleratus

muskyhuntr said:


> I don't know that you failed.  You have designed and built one of the nicest enclosures on this forum, period!  Also note that you are diving into some what uncharted territory by converting an amp designed for speakers and modifying it for head phone use.  Not an easy task, even for the most skilled builders.  Indeed, I just finished reading through a rather long and interesting thread where a number of individuals are attempting to scratch design from scratch, something similar.  I believe they spent about 30 pages just discussing the output transformer and even had a number of mfg's joining in the discussion.  Not easy!   Both you and the people on that other forum are aiming for the best that can be accomplished.  I think you both will succeed.
> 
> Jim
> PS. I admire your perseverance,


 
 Thanks Jim.
  
 Tom Christensen deserves the lions share of the credit.


----------



## holland

sceleratus said:


> Thanks Jim.
> 
> Tom Christensen deserves the lions share of the credit.


 
  
 A build is very personal.  It's multiple things all lumped together.  The circuit is a part of it, everything else is not.  Don't sell yourself short.  It was a good build, and as you have seen, the build can make or break a design.
  
 It'll all work out.  Everything in the box is replaceable.


----------



## sceleratus

Thanks Holland,
  
 My minds going in 10 directions wondering where the problem lies.
 I'm hoping for "stupid simple", or will I have to build a new board.  No matter.
  
 I'm very pleased that I was able to pull this build off.  I fancy myself good at design (enclosure) and logistics.  It really did come together and the sound was fantastic.


----------



## sceleratus

The problem:
  
Something failed on the Maida regulator that produced the buzz/hum.  I do not know specifically what it was.  I did look through my build and saw that I used the wrong value for R-3.  I used 10Ω.  It should have been 15Ω
  
Jack measured the amp prior to working on it and sent me the following:
  
"Distortion specs at 2 watts into 50 ohm load, 2khz at 2.2v input, 
.194% THD IMD at 2.2v input, 2.4%, this is very good.
4.43v to 8.48 watts symmetrical clipping. This is a good amp."
 
Post fix he sent me the following:
 
"We just dived into the amp and its much better and the hum is gone and draws 1/2 an amp less from the line. 
The - 50-53db noise floor, is now -55-56 db with the choke and caps.  
 
This is the limit for this circuit due to this -56db is the top of the switching noise, so can't go lower than that.  Switching noise is a hiss,  this can be heard now if you strain your ears."
 
I decided to have Jack re-work the OPT's so they will support speakers as well as HP's.
  
I am looking into some high efficiency speakers that are 85dB / 1W / 1m.  I am just learning about them but Jack said they will work great with the amp.  (Solist, LINN, Zu)  When he finishes modifying the OPT's to 8Ω, I will put an R12 in parallel and an R50 in series to the HP outputs and switch between speaker plugs.  Since I'm a nonconformist I like the Neutrik "SpeakOn" speaker connection system.
  
I hope to have the amp back by the end of the week.
  
I've been converting my friends vinyl collection to digital.  I really like the sound and am smitten with his turntable.  I'd like to build the phono pre amp and I am looking at designs.  This one from GlassWare Audio Design looks interesting but I wouldn't know a good one from a bad one.  I think the only reason I like it is that it has 8 valves, so it must be better.
  
When I recut the back panel I will put input jacks for a phono pre amp and a 4pole rotary.


----------



## holland

That's great news!  85dB isn't too sensitive, but should be good enough with 10W.  I have 89dB bookshelf speakers on a 5W amp, and it's loud enough but might not be so for high dynamic range pieces.
  
 I heard some of your clips, they came out great!  It makes me want to delve into vinyl as well.
  
 Choke and cap?  He updated the regulator and added a choke?  Chokes are nice, but can be big.  With output resistors you won't hear the noise with headphones, in addition to additional reduction going to 8 ohms on the OPT.
  
 Glassware/TubeCad makes good stuff.


----------



## sceleratus

As you all know Jack is Old School.  I think they invented the term after him.
  
He said the problem was in the regulator and as such I built another one.  However he preferred a "simpler approach" and replace it with caps and a choke.  He had the amp, I know practically nothing, I deferred to him and said do it.  My understanding is there isn't a HV regulator anymore.
  
Speakers:
The Zu Audio "Soul" are 99dB. The Sonist Recital3's are 93dB and the LINN Majik 109's are 88dB  That's where I've been looking so far.  Also found "The Horn Shoppe"  interesting and thrifty.   The speakers will be in a "music room" of which I am in the acquisition negotiation process.  The room is 19' x 15' with a 11' vaulted ceiling.... along the long edge.  I think nice clarity is the most important criteria for me.
  
I am dying without that amp.


----------



## muskyhuntr

Great news!  Glad it's all sorted out.  Do you have any specifics as to what happened to the regulator?  What part/parts?  
I am very interested in the sound with the 8 ohm transformers and how your phones sound with the resistor network.  Looking forward to a full report.
  
 I cannot comment on the Tubecad phono boards.  I will say that I am in the process of casing up one of his preamp designs.  This is going to be a 2 case dual mono design.  I am not far enough along to comment on the sound, but I have run square, triangle, and sine waves through and they look very good on the scope.  His boards are about the best I have seen offered.  Thick and rugged.  Most are adaptable to different tubes, voltages, caps, etc.  If you decide to go this route, also consider his power supplies, also first rate. 
  
 An update on my DG 300b.  All power supply boards are now built and tested.  Amp board is also built but I installed 2 resistors of the wrong value and need to replace them.  Have the 6n6p tubes.
 Unfortunately, I am going to have to put this project on hold for a while, at least until I finish up a few other projects.
  
 Jim


----------



## tomchr

sceleratus said:


> The problem:
> 
> Something failed on the Maida regulator that produced the buzz/hum.  I do not know specifically what it was.  I did look through my build and saw that I used the wrong value for R-3.  I used 10Ω.  It should have been 15Ω
> 
> ...


 
  
 In the Maida Regulator, R3 = 10 Ω is the correct value. This is listed on the top level assembly schematic. If you install a higher value here, you'll get hum for sure as the current limiter will start to kick in.
  
 Which changes did he make that resulted in a 2x reduction in power consumption? Did he dial back the bias current in the 300Bs to 50~60 mA?
  
 What switching noise is he measuring? May I see the spectrum? The only noise I measure on the output of my amp is 60 Hz and harmonics thereof induced by coupling from the power transformer to the output transformers.
  

 The noise floor is -110 dBV. The highest spurious is below -80 dBV. The only thing in the amp that switches at audio frequencies is the rectifier bridges, so I'm curious to see a spectrum measurement of the noise.
  
 ~Tom


----------



## sceleratus

Here's a Post I made on "Post Pictures of your Build"
  
I'm going to have my back panel re-cut to accommodate some changes.  Rather than 0.09" silicon bronze I'll use 0.07 T6061  AL-LEW_MINI-YUM
  
Aquatech water cuts the panels straight from my Adobe Illustrator file.  They have a fixed fee for anything up to 24" x 48".    Since I only need 6" x 16" I was going to buy a 24" x 24" piece.  I guess I could cut 3 more, but why.
  
So why am I posting?  I thought if any of ya'll might want a panel cut it would only cost the postage if it'll fit in the remainder of 24x24 otherwise add the difference between the cost of a 24x24 and a 24x48 AL sheet.  I have not purchased the material yet.  The pieces in the photo below were from a 24x24.  I'm only cutting the small one.  Including the perimeter, there are close to 90 things cutout.
  
Or if a couple guys have small pieces we could do that...
  
PM me if interested.  If needed, I'll help with getting your layout into Illustrator.


----------



## sceleratus

Unless I hear something, I will have the panel cut Tuesday.
 I could hold off a few days if there is interest.


----------



## tomchr

Aluminium is a bit more user friendly than bronze - at least judging by your experience polishing bronze. The only thing with aluminum is that it sometimes can be a bit hard to get paint to stick to it. If you use an etching primer, it's no problem. I find the Rustoleum rattle cans work quite well for this. Just don't sand the aluminum with sand paper finer than 320 grit. You want some surface roughness for the primer (or clear coat) to grip onto.
  
 Spray painting with rattle cans can be a royal pain, though. It took me nearly two weeks to get acceptable results on my 300B build. I think next time, I'll look into anodization. 
  
 Of course, if you have access to a bead blaster, you're in phat city. Bead blasted aluminum with a clear coat can look really good.
  
 ~Tom


----------



## sceleratus

Hi T,
  
 Correct-a-mundo.
  
 1) Get it anodized.  I'll probably have a couple panels cut.  With the heat sinks I'll still be at some minimum anodize charge.  Best
 2) Use my buffing wheel and compound and try to make it look billet...   Cheap and I can do it in my garage in a day.**  Trouble is I don't think T6061 sheet is the same as T6061 that's CNC'd.   I miss my 57 Chevy.  sniff
 3) Powder coat.  There are places that will do that cheap.
 4) Paint.  From my hot rod days I have some bad az industrial metal primer.  Yup.  Need that for sure.  Hot liking the paint option.
  
 **Tip I found that's great.  Get a hard rubber cone bit.  Not only does it remove the burrs in an instant, it'll give the cutouts a mirror finish.
 It's best to get an inexpensive pneumatic hand held grinder from Harbor Freight for a couple bucks, but a drill will do.


----------



## tomchr

6061-T6 aluminum is 6061-T6 regardless of how you machine it. It machines really well. 
  
 For the surface prep, I'd ask the anodizing shop for advice. They may do their own prep anyway, so you might be wasting your time getting that mirror finish on the parts. If you're responsible for the prep, definitely do a good job as any imperfection will show.
  
 Don't powder coat the heat sink. Powder coating (or painting) adds an insulating layer of paint. This increases the thermal resistance (i.e. makes it harder for the heat sink to get rid of the heat). Only black anodizing will help getting rid of the heat. Black anodized aluminum is pretty close to a black body radiator - the most efficient radiator out there. Black anode is what you want.
  
 ~Tom


----------



## sceleratus

tomchr said:


> 6061-T6 aluminum is 6061-T6 regardless of how you machine it. It machines really well.
> 
> For the surface prep, I'd ask the anodizing shop for advice. They may do their own prep anyway, so you might be wasting your time getting that mirror finish on the parts. If you're responsible for the prep, definitely do a good job as any imperfection will show.
> 
> ...


 
  
  
  Thanks for making sure, I wasn't going to powder coat the heat sink.  I would only anodize it.  
 For the back plate I'm going to polish it using Dico TC6 Tripoli and a bonnet.  It should produce close to a mirror finish.


----------



## sceleratus

I'm looking into the single driver speakers using either a Fostex or Markaudio driver.  There are a number of builders that offer either plans, make [size=small]flat-paks, or complete speakers.   I could easily assemble a flat-pak but I'd have to have someone put on the veneer.  It's not something I'd like to do for the first project and I'm sure there are special tools needed to make the job look professional.[/size]
  
 [size=small]I found a gentleman that will take his Markaudio M10 design and modify his enclosure to match the amp design.  Just adding dead space instead of using stands.[/size]
  
 [size=small] I'm just not sure the one driver designs will fit my listening tastes.  I like classic R&R more on the mellow acoustic side.   Dylan, The Dead, Knopfler, but I do like vintage Stones and Zeppelin.[/size]
  
 [size=small]For two drivers, I'm looking at ZuAudio, but they leave me with the impression of form and marketing over substance.  There's also a small builder named Sonist that Jack likes a lot.  They're a two driver configuration but I'm not liking the cabinet and they need stands.  I don't like stands.   This is where the Zu Omen fits better for me aesthetically.[/size]
  
 [size=small]Here's the modified layout for a Bob Brines M10-A10 speaker that would match the amp.  This too may be aesthetics vs what the overall best speaker would be, but it would be great to match the amp.[/size]
  
  

  
  
  
  
 [size=small] [/size]


----------



## sceleratus

Can sub woofer circuit could be added? YES

I found this circuit. I like it because it's on the output from one OPT, rather than some I saw that had op-amps on the input side....
Any preamp would mung up the headphones as well.

Any other design suggestions of this type would be appreciated. If I could add a Sub, I'd me more incline to try a single driver speaker model.




Reading the description further,

Voltage divider R1-R2-P1 is designed for use with the output signal of an average output amplifier of around d 50 W. The crossover frequency of the network may be varied between 50 Hz and 160 Hz with P2. The values of R3, P2, and C1, are calculated on the assumption that the subwoofer amplifier to be connected to K1 has a standard input resistance of 47 kΩ.

Will this work with 8W-10W ?

EDIT:
Forget the above. It's too much BS for my needs. Circuit....separate Sub, sub amp.
If a single driver won't do it, I'll go with a two driver speaker...


----------



## tomchr

With a mass loaded transmission line (MLTL) design, you can get rather extreme bass with a full range driver. No need for a sub. I ran a sim with a 5" TangBand speaker (W5-1611SA) and was able to push it to about 38~40 Hz -3 dB.
  
 Designing a speaker is more than just putting a driver in a box. Much, much more. Don't design your own unless you want to experiment and learn. Either build a kit, use known-good plans, or buy a speaker.
  
 ~Tom


----------



## sceleratus

tomchr said:


> With a mass loaded transmission line (MLTL) design, you can get rather extreme bass with a full range driver. No need for a sub. I ran a sim with a 5" TangBand speaker (W5-1611SA) and was able to push it to about 38~40 Hz -3 dB.
> 
> Designing a speaker is more than just putting a driver in a box. Much, much more. Don't design your own unless you want to experiment and learn. Either build a kit, use known-good plans, or buy a speaker.
> 
> ~Tom


 
  
 Yup,
  
 I wouldn't dream of designing my own.  I picked up on the fact that it's not just a box with a six inch hole but one acoustically engineered for a specific driver.
 Good to know about the bass on an MLT.  That's one of the designs I was looking at.  It's built for the Markaudio A10.  That option is now back in play.
  
 Thanks for watching out for me.


----------



## nikongod

Unless specifically designed for it, modern speakers with crossovers may not play nice with the Zo of your amp. 
  
 Stick with single drivers. There are plenty of designs about.


----------



## tomchr

As long as the impedance curve of the speaker is reasonably flat, there won't be a problem driving it with a tube amp. That goes for any speaker, actually. The impedance curve of a full range driver in an enclosure is not perfectly flat either...
  
 With a 2-way design, the XO frequency tends to be around 1-2 kHz. So you get a directivity change right where the ear is the most sensitive. The XO frequency is a compromise between getting decent SPL out of the tweeter (sets the low limit) and avoiding cone breakup of the woofer (sets the high limit). With the low slopes of passive XO filters, this tradeoff becomes very hard and nearly all 2-way speakers will exhibit some amount of woofer cone break-up (rude sounds in the midrange) as a result. Using electronic line-level crossovers (digital or analog) will help as the filter slope can be made much steeper, hence, the amount of rude sounds emitted by the woofer can be minimized and the XO frequency increased slightly to allow the tweeter to operate closer to its comfort zone.
  
 In a full range speaker, the tradeoffs are mostly tied to the driver size. A smaller size driver will have better performance in the highs, but won't be able to produce low bass loudly. And vise versa for a big driver. Getting a small driver to produce low bass is a game of tuned loads and peak excursion. So basically, expect a full ranger to be able to produce low bass in the right enclosure, but don't expect it to rock the house off its foundation. For DIY speakers, the TABAQ is a good place to start. Pete Millet's design based on the Jordan JX92S is another interesting one. I do have some concerns about the Jordan drivers. Specifically, that the diaphragm is made from insanely thin aluminum foil and dents really easily. Personally, I'm also not a fan of metal speakers as they tend to accentuate the cone break-up, resulting in harsh highs.
  
 ~Tom


----------



## sceleratus

Dave at Planet 10 sent me the Fonken-167.  Based on the discontinued Fostex FE-167e.
 The bottom of the cabinet is a sealed void.  In the photo I  noticed a version with a woofer.  Would that be on a passive crossover? 
 I found this source with many crossovers to choose from.


----------



## tomchr

sceleratus said:


> Dave at Planet 10 sent me the Fonken-167.  Based on the discontinued Fostex FE-167e.
> The bottom of the cabinet is a sealed void.  In the photo I  noticed a version with a woofer.  Would that be on a passive crossover?


 
  
 It could be a passive radiator. So basically a speaker diaphragm without a voice coil driven by the pressure inside the cabinet. But I don't know. I'm sure Dave will be able to answer that question.
  
 ~Tom


----------



## sceleratus

He did. Needs an amp and an input channel.
 The 167 is obsolete so the plans are obsolete.  They were provided as an example.
  
 There are a dozen other plans.  Pick a driver and take your chances.


----------



## tomchr

sceleratus said:


> There are a dozen other plans.  Pick a driver and take your chances.


 
  
 Pretty much. I've listened to Dave's designs as well as some where his enclosures were used with other drivers. They all sounded good. The only driver I didn't like so much was the Mark Audio CHR70 as it tended to suffer from a rather harsh cone break-up (pretty evident in its response curves as well). That's another driver with a diaphragm made from Reynolds Foil. Me no like.
  
 ~Tom


----------



## sceleratus

I dropped off the materials to have a new rear panel cut from T6061-T6  0.08" AL-LOU-MINI_YUM
Since the cost of materials and cutting for a 24" x 48" was the same as a 24" x 24", I had extra panels cut.
  
I moved the filament stack from the center to the left and reduced the depth by 1.50" 
  
If anyone wants a set it will only be the cost of postage.
  
  
UPDATE:  I picked them up today and they look great.
I polished the rear plate I am going to use.


----------



## sceleratus

Speakers.
 I pulled the trigger on a pair of ZuAudio Soul speakers.
 Their web site is overflowing with marketing speak, like no other I've seen.  I get skeptical when I see that.
  
 What I liked is the 60 day return policy.  I wouldn't have that option with MLT's and such.
 I also read some posts from owners on AudioKarma.  Not like an owner is going to bash his speakers.....
 They are very efficient at 99dB/w/m and they are 8 ohm.   Of all the speakers I looked at none published a 2 - 200 watt range.
 That makes m comfortable.
 Lastly, I got a deal on a demo set.  I retained the return privilege.  (If only I had an amp.)
  
*Soul Mk.II Quick Specs*​ Height: 31.5” [80cm]
 Footprint: 12.14 x 12.14” [30.8 x 30.8cm]
 Weight: 42 pounds [19kg] each. 53 pounds [24kg] packaged
 Bandwidth: 45 – 22kHz
 Efficiency: 99 dB SPL 1W, 1m
 Impedance: 8 ohm
 Power Amp Range: 2 – 200 watt
 Made In Ogden, Utah—U.S.A.​


----------



## tomchr

Technically, that's a 2-way speaker, but the tweeter only kicks in above 12 kHz. Most tweeters in 2-way systems kick in in the low kHz, so this Soul speaker should sound more like a full ranger than a 2-way speaker. What impresses me is that they were able to get a 10" driver to produce sound up to 12 kHz... It'll be interesting to hear your review.
  
 I do agree on the marketing speek, though. "Old school rooted, yet state of the art". Mmm yeah.
  
 99 dB/W/m is *sensitive*. You'll hear the grass grow with those speakers... 
  
 ~Tom


----------



## OJNeg

tomchr said:


> Technically, that's a 2-way speaker, but the tweeter only kicks in above 12 kHz. Most tweeters in 2-way systems kick in in the low kHz, so this Soul speaker should sound more like a full ranger than a 2-way speaker. *What impresses me is that they were able to get a 10" driver to produce sound up to 12 kHz*... It'll be interesting to hear your review.
> 
> I do agree on the marketing speek, though. "Old school rooted, yet state of the art". Mmm yeah.
> 
> ...


 
  
 I'm betting that's where the cone breakup is. Probably rolls off fast after that.


----------



## tomchr

> I'm betting that's where the cone breakup is. Probably rolls off fast after that.


 
  
 No doubt. That's why they have the tweeter taking over at that point. It's a coaxial driver...

 It is possible to make larger drivers make noise at higher frequencies. Check out the Mark Audio Alpair 10P-A. I'm toying with the idea of building a MLTL full range speaker based on that driver. A quick check says I should be able to get down to about 28~30 Hz (-3 dB).
  
 ~Tom


----------



## sceleratus

MLT with the 10P
  
 Bob Brines is a cool dude.


----------



## tomchr

Bob Brines is indeed cool. I've never met him, but from his posts he seems knowledgable and plugged in. His speakers use the metal cone version of the Alpair 10. I'd rather use the paper version.
  
 ~Tom


----------



## sceleratus

Not Good, and don't ask.


----------



## Tjj226 Angel

tomchr said:


> Bob Brines is indeed cool. I've never met him, but from his posts he seems knowledgable and plugged in. His speakers use the metal cone version of the Alpair 10. I'd rather use the paper version.
> 
> ~Tom


 
 Nah, if you are going to build speakers, go with an altec 755 driver.


----------



## sceleratus

tjj226 angel said:


> Nah, if you are going to build speakers, go with an altec 755 driver.




Will you quantify that?


----------



## sceleratus

Yesterday I joined the I blew up a board with a DMM probe club.
I guess there really is high voltage coarsing through the traces.
  
Silicon carnage:


----------



## nikongod

What were those things supposed to do, and how did they get busted?
 Short to ground?


----------



## sceleratus

nikongod said:


> What were those things supposed to do, and how did they get busted?
> Short to ground?


----------



## GrindingThud

Wow, snappy!



sceleratus said:


> Yesterday I joined the I blew up a board with a DMM probe club.
> I guess there really is high voltage coarsing through the traces.
> 
> Silicon carnage:


----------



## tomchr

Welcome to high-energy circuits...  Sucks with the blown components, though.
  
 When I designed my 21st Century Maida Regulator, one of the goals was to make the circuit resistant to common issues such as loose connections in output tube sockets. A sparking connection puts some rather nasty high ∂i/∂t spikes (i.e. rapid change in current vs time) into the regulator circuit. So I torture tested the regulator with a light bulb load where I wiggled one of the bulbs. I exploded a few TO-247 packages before getting all the kinks out. The end result was a very rugged regulator!
  
 Wear safety goggles!
  
 ~Tom


----------



## randytsuch

On my DMM probes, I have a set with heat shrink that covers most of the probe, leaving just the tip exposed.
  
 I use these where there is a change to short the probes against other parts of the circuit.
  
 Randy


----------



## sceleratus

me too.
 the probe skated
  
 i had to use the stupid, huge. 0.22uF Mundorf caps and it covered the 9 pin socket points.
 pin one is under the cap, close to Q3 and the heat sink.  I had to guide the probe straight down. i couldn't see it but im pretty sure i shorted Q3 and it incinerated everything around it.
 for good measure i replaced Q1-4, U1&2 and 8 surrounding resistors.
  
 i just this minute finished putting humpty back together again.  i will light the mains in a few minutes.


----------



## sceleratus

I am happy beyond belief.  It's been an ordeal, but I now have *MUSIC.*
  
 I have yet to hook up the resistive circuit necessary for HP's  The amp is dead bang quiet.  Zero as in zero noise.
 I started with Zu Audio Soul's.  They aren't as efficient as I expected.  You need to peg the POT and it's loud but at times I think I'd like another 10%
  
 BTW.  I am using the SE board with a pair of large Mundorf 0.22 uF in place of the input transformers.
  
 I thought there was no way this amp could drive my Thiel CS 1.5's.  Spec says they need 50W.
 Guess what, they sound amazing.
 So amazing in fact that the Zu Audio Soul's are going back,   Just a much more complete voice.'
  
 Tomorrow.... get the HP's working.
 I can't wait to hear if they are as quiet as I think they will be.


----------



## sceleratus

My speaker / headphone switch works great.
 The Audeze LCD2 R2's sound amazing !
 Zero static / fuzz / snow / hum.
 Stop the music and they're as quiet as a dead church mouse.


----------



## sceleratus

Now that Humpty Dumpty is rock'n again, I'll take him to the San Diego Meet on Sat Nov 2nd


----------



## tomchr

"Minimum power needed: 50 W" 
  
 Most of the time for casual listening you're probably driving them with 10~100 mW. Yes 0.01~0.1 W. Maybe even less. 
  
 Marketing is a funny discipline. 
  
 ~Tom


----------



## sceleratus

Here are photos of the current guts.
 The  input trans have been switched to the driver board build option that uses 22 mF caps.  I'm back to the 100 ohm Alps Blue pot instead of the stepped attenuator.  RCA jacks replaced the XLR's  (different from photo)  The headphone / Speaker rotary switch works great.
  
 It is still quieter than a dead church mouse and my 15 year old Thiel CS 1.5's sound great.  The Audeze LCD2's are amazing  esp. with some old vinyl that I ripped.  I love to hear the needle drop.
  
 I'm going to enjoy the music for a few months.  After that, if I get antsy I might implement a differential configuration using the Jensen JT-11P4-1 input trans that Tom drew up.  The recording level of the vinyl rips is lower than digital sources.  It is my understanding that differential will give me a 4V input instead of 2V on the RCA's  A boost to speaker volume would be nice.  Since I made a new assembly for single ended, I can easily switch them.
  
 I also came up with matching furniture for the music room.  I'll have to see if it's in the budget.
 Other items on the wish list are KR 300B's, Goertz speaker wire, and LCD3's.   I listened to them at the San Diego meet and they are smooth as silk.  It defies logic.


----------



## tomchr

Dude!! Suggestion: You really aught to pull the speakers away from the wall. Due to the Haas effect, reflections from the wall will be largely ignored by the ear/brain combo if they arrive after 5~10 ms. Hence, the total round-trip time from the front of the speaker to the wall and back to the front of the speaker should be at least 5~10 ms. This means your speakers should be 340*0.005/2 ~ 340*0.01/2 = 0.85 ~ 1.7 m away from the walls. That's 3~6 feet in 'Merican units. 
  
 ~Tom


----------



## sceleratus

Since that photo the speakers have been moved forward. 

With your information I will experiment further. 
Many thanks


----------



## Tjj226 Angel

sceleratus said:


> Will you quantify that?


 
 Sorry, I have been extremely busy with school. 
  
 What do you mean by this?


----------



## sceleratus

tjj226 angel said:


> Sorry, I have been extremely busy with school.
> 
> What do you mean by this?


 
Below is the definition:
I was asking if you would empirically backup a subjective opinion with something that can be measured.
 
Empirical evidence is information that justifies a belief in the truth.
 
quan·ti·fy
 ˈkwäntəˌfī/
_verb_
 

 *1*.
  express or measure the quantity of.
 
"it's very hard to quantify the cost"


 *2*.
LOGIC
 define the application of (a term or proposition) by the use of _all_, _some_, etc., e.g., “for all _x_ if _x_ is A then _x_ is B.”.


----------



## sceleratus

tomchr said:


> Dude!! Suggestion: You really aught to pull the speakers away from the wall. Due to the Haas effect, reflections from the wall will be largely ignored by the ear/brain combo if they arrive after 5~10 ms. Hence, the total round-trip time from the front of the speaker to the wall and back to the front of the speaker should be at least 5~10 ms. This means your speakers should be 340*0.005/2 ~ 340*0.01/2 = 0.85 ~ 1.7 m away from the walls. That's 3~6 feet in 'Merican units.
> 
> ~Tom


 
 Yo! Professor Dude,
 If I move the speakers forward, away from the front wall, and closer to the listener and the back wall, won't it take less time for the sound to get back to the front of the speaker?
  
 EDIT:
 THE RT60 of my room is 0.50
 2700 cu. ft.


----------



## sceleratus

Do I have this right?
 If my normal listening volume is  > ~45 dB, I won't have a reverb problem
 with the source 10ft from the listener.
  
 I take it this is w/o RT60 factor being applied.


----------



## Tjj226 Angel

sceleratus said:


> Below is the definition:
> I was asking if you would empirically backup a subjective opinion with something that can be measured.
> 
> Empirical evidence is information that justifies a belief in the truth.
> ...


 
  
  
 1 : The driver is very old. They did not have testing equipment for speakers in the 1950s
  
 2: Experience > data Don't believe me? How are the highs on the LCD2 (or 3?)? Pretty good right? A little roll off, but they still sound really smooth and clear. Now go look at a frequency response graph and ask yourself if the graph really reflects your personal experience.


----------



## sceleratus

tomchr said:


> Dude!! Suggestion: You really aught to pull the speakers away from the wall. Due to the Haas effect, reflections from the wall will be largely ignored by the ear/brain combo if they arrive after 5~10 ms. Hence, the total round-trip time from the front of the speaker to the wall and back to the front of the speaker should be at least 5~10 ms. This means your speakers should be 340*0.005/2 ~ 340*0.01/2 = 0.85 ~ 1.7 m away from the walls. That's 3~6 feet in 'Merican units.
> 
> ~Tom


 
 This like it would help the situation.
48" x 48" Sound Panels


----------



## tomchr

Moving the speakers out from the wall beats wall treatment on price every day of the week. The same is true for the reflection off the back wall. If the couch (listening position, I assume) is up against a wall, you may benefit from moving it away from the wall a bit. Just so your ears receive the wall reflection at least 5~10 ms after the incident sound.
  
 Rather than adding fancy wall treatments, I'd stick a ficus in the corner for diffusion. It looks prettier than the acoustic foam too.
  
 ~Tom


----------



## tomchr

These panels are supposedly quite good as well. $30 at Home Cheapo.  I strongly suspect they're the same material as the Pro panels which are pretty well spec'ed.
  
 ~Tom


----------



## sceleratus

My speakers are 89" c-to-c and the face is 28" off the wall.
 I'm at max cable length.  I am putting off buying new, but I will have to because I want the amp next to or in front of the sofa.  The good news is I won't need a long headphone cable in this position.
  
 Thanks for the sound panel referrals.  The price is indeed much better, however the Sonex have a HPC coating to make cleaning easier.
 I kinda like that. I need to find a guide for panel spacing.  I'm estimating 8" apart. 2' x 2' or 2' x 4" covering 10' behind the sofa.  Not that the room sounds bad, but I think your idea will be a nice upgrade.  The vaulted ceiling helps too.


----------



## tomchr

Before you spend megabucks on sound treatment, try hanging a heavy rug behind the couch. I've been known to prop up a sleeping bag and a down comforter on a pair of hockey sticks to experiment with various reflection mitigations. See if it makes a difference.
  
 There are basically two approaches: You can stuff the room such that reflections don't happen. Or you can position yourself and your speakers such that your ear/brain combo doesn't perceive the reflections. Usually you want some combination of these two extremes. In most cases you can get good results by just having a few rugs on the walls and some furniture around.
  
 ~Tom


----------



## sceleratus

tomchr said:


> Before you spend megabucks on sound treatment, try hanging a heavy rug behind the couch. I've been known to prop up a sleeping bag and a down comforter on a pair of hockey sticks to experiment with various reflection mitigations. See if it makes a difference.
> 
> There are basically two approaches: You can stuff the room such that reflections don't happen. Or you can position yourself and your speakers such that your ear/brain combo doesn't perceive the reflections. Usually you want some combination of these two extremes. In most cases you can get good results by just having a few rugs on the walls and some furniture around.
> 
> ~Tom


 
 I have an oriental rug someplace.  I was looking to do that a couple weeks before posting.
I just stumbled upon these.
  
 Aesthetics in this room is important to me.  I don't want to just put stuff in the room.  Didn't really love the cmc foam either.
  
 This product descriptin  really caught my eye (ear)
  
 The Auralex WaveLens scatters and redirects acoustical energy and can be an effective alternative to absorbing reflections. The WaveLens can be beneficial in numerous applications: creating a* “large sound” in a small room,* optimizing absorption panels by redirecting energy so that they are more efficient, or using the acoustical properties of an adjacent space to enhance your listening or recording environment. The WaveLens is sized to drop into a suspended ceiling grid or can be installed using the supplied mechanical fasteners.


----------



## nikongod

A nice rug would really tie that room together. 
  
 As an idea - have you considered getting sound-foam and putting it in a frame with a colorful border? Its not a sound absorption panel, its modern art. WAF of room treatments can be pretty high, if you do it well.


----------



## sceleratus

nikongod said:


> A nice rug would really tie that room together.
> 
> As an idea - have you considered getting sound-foam and putting it in a frame with a colorful border? Its not a sound absorption panel, its modern art. WAF of room treatments can be pretty high, if you do it well.


 
 The bamboo product also have these panels with circular cutouts that go in front of acoustic squares.   Overall, I really like the wood concept.  I don't know if I'd benefit more from absorption or diffusion.


----------



## nikongod

I'm not sure if you need absorption or diffusion either, mostly just saying that although these are very utilitarian things there is no reason not to spice it up a bit.


----------



## sceleratus

Here's a thought for the wood look....
 Stack these at various heights... Might be cheaper.
 EDIT:  It's not..


----------



## tomchr

Diffusers are pretty easy to build. As are absorbers. For the 3D diffusers, just use one of the programs/websites available for calculating the lengths and sequence of the wood blocks.
  
http://www.diyaudio.com/forums/construction-tips/232178-how-make-diy-acoustic-panels.html
  
 ~Tom


----------



## sceleratus

very cool
  
 I was just looking into making something.
  
 What freq. do I want to diffuse?
 The software has you set the value.


----------



## tomchr

See post #7 in the DIY Audio thread I link to above. 
  
 ~Tom


----------



## sceleratus

tomchr said:


> See post #7 in the DIY Audio thread I link to above.
> 
> ~Tom


 
 I've been using the software, but I'm not sure what "design" freq. to plug in.
 I thought about cutting bamboo stalks into the specified lengths and bonding them together.


----------



## tomchr

I really don't know. I suggest looking at the documentation for the software. You may also be able to find a thread by someone who uses the software. You can also try to model a commercially available panel to see what they're designed for. 
 My experience with room acoustics is limited to what I can measure and solve by moving the speakers and furniture around. I've never designed a diffuser. 
  
 ~Tom


----------



## sceleratus

Tom,
Just ordered the Goertz  MI 1 Center Stage speaker cable and 2' x 2' x 3" acoustic panels from The Home Depot.
I appreciate the advice.
  
  
As you pointed out Goertz, is one of the few speaker cable companies that publishes specifications for resistance, capacitance, and inductance.  That's where the rubber meets the road.  I kept going back to the article you sent.  Although Goertz is more expensive, I justify the MI 1 because I don't know the specifications of, say, AudioQuest X-2 bulk cable. At half the cost I was strongly considering this cable.  However, if it has the same specs as Home Depot zip line, I'm wasting $200.
  
The other wire/cable I was considering was "AntiCable"  (Magnet Wire)   This is what you ran in the simulation against Goertz.
  
Tom's simulation Goertz "MI 2" vs AntiCable using the specifications published by "AntiCable": 
  
AntiCable Level 2 Reference Series Speaker Wire Electrical Specifications ($6/ft.) Resistance = 0.0032 Ohms/foot run
Inductance = 0.0003mH/foot run  (300 nH)
Capacitance = 0.048nF/foot run

AntiCable Level 3 Reference Series Speaker Wire Electrical Specifications ($18/ft.) Resistance = 0.0016 Ohms/foot run
 Inductance = 0.00026mH/foot run  (260 nH)
 Capacitance = 0.044nF/foot run

Goertz MI 2 Veracity ($14/ft)

Resistance = 0.0022 ohms/ft​ Capacitance = 0.95nF/ft​ Inductance = 6nH/ft​
Goertz MI 1 Center Stage   ($8/ft)  This is the cable I purchased​
Resistance = 0.0044 ohms/ft  ​
Capacitance = 0.5nF/ft ​
Inductance = 10nH/ft ​


----------



## Mihis

Hey!
  
 I have Goertz cables in my stereo set. I had already forgotten the name
  
 Awesome thread btw. and really gorgeous piece of gear that you've build!
  
 I started listening a lot more with headphones after I moved and realized my room acoustics went south so it got tiring to listen for a longer periods.


----------



## sceleratus

mihis said:


> Hey!
> 
> I have Goertz cables in my stereo set. I had already forgotten the name
> 
> ...


 
 Cool.
  
 Do you like the wire?


----------



## Mihis

I like it It transmits sound and it looks nice Actually it had reasonable explanation for the shape and not just some weird marketing speech behind it.
  
 I haven't tested any other cables on my system, so can't say if they make a different or not.


----------



## Tjj226 Angel

@tom: 
  
 I got a potentially weird question for you. 
  
 First let me say that my mom really likes plants. The tropical ones that she collects all need a fair amount of humidity. I recently learned that steam is a pretty good sound absorbent medium. 
  
 Is it possible to build a giant humidifier and put it along a wall to absorb sound waves AND help my moms plants grow? I realize it would be a pretty big undertaking, but hey, I would be killing two birds with one stone. : )


----------



## sceleratus

tjj226 angel said:


> @tom:
> 
> I got a potentially weird question for you.
> 
> ...



Yes.
Move the plants and hi-Fi gear to the bathroom.
Beethoven Symphony No. 6, 1st. movement will be especially enjoyable.


----------



## Tjj226 Angel

Nah, my mom wants me to build her a green house in the spare room. I will vent it and everything. However, I have some special equipment and tools that might make it suitable for a listening room.


----------



## sceleratus

I can't leave well enough alone.
 I just ordered 2 Jensen Transformers JT-11p4-1, Neutrik F-XLR, a couple 24K9's,  and 10 nF caps.
 Going to give XLR's a whir again.
  
 The DMM measures1.49VAC output from the Gungnir RCA for both RCA and XLR* when a 1kHz tone is playing.  I expected 2V from the RCA and 4V from the XLR.  I’m guessing this is due to the recording level of the 1kHz tone file.
  
 *This was with an RCA to XLR cable where Pin 1 and Pin3 on the RCA are tied together.
  
 When I put an external input transformer “PVA” Jack sent me, the voltage drops to 0.8 VAC.  When I peg it I get 2.76 V RMS from the O’ Scope.


----------



## sceleratus

Put in some Jensen Line Input Transformers.
 Now I can use the Balanced XLR's on my Gungnir.  I got about a 20% boost in power.  Not measured just by feel.  This is just what I needed with my ripped LP's that are recorded at a lower level.


----------



## sceleratus

Have a set of Sophia Electric™ Princess Mesh 300B sometime this week.


----------



## sceleratus

There's no free lunch.
 This was an expensive experiment.  Distortion.  Lots.
 Two days putting it in.  20 minutes reverting back to SE.
 Sounds great.  The volume is what it is.
 I'm done.


----------



## 00940

Well, there isn't anything clearly wrong with your schematic.
  
 I can't say I like the physical implementation much though. You might try to strictly follow this:
  

  
 Orange arrows show where the wires should be twisted together right up to the components' pin.
  
 I jumpered the caps as suggested by SE. You're still using leds for bias, right ?


----------



## sceleratus

00940 said:


> Well, there isn't anything clearly wrong with your schematic.
> 
> I can't say I like the physical implementation much though. You might try to strictly follow this:
> 
> ...


 
 The components are all board mounted.
 ECC88 Pin 9 goes to ground via a string of diodes.
 All are board mounted.
  
  

  

  
 The input transformers have been replaced with 220nF caps.  (See Schematic Option on Left)


----------



## Steve Eddy

00940 said:


> Well, there isn't anything clearly wrong with your schematic.
> 
> I can't say I like the physical implementation much though. You might try to strictly follow this:
> 
> ...




Why are you taking the can and the shield to the chassis instead of signal ground?

se


----------



## Steve Eddy

sceleratus said:


> Do you mean break the grounds between L/R ?




No. In the schematic you showed in the other thread, it had the input transformer AND a 220nF coupling cap. I was suggesting you jumper across the caps, but now it seems that you didn't have those caps in the circuit at the same time you had the transformers. Is that correct?



> I have not checked the Gungnir outputs.
> Is that simply looking for DC voltage on the outputs with a DMM or scope?




Yeah, just look for any DC voltage across pins 2 and 3.

se


----------



## sceleratus

Sorry for all the confusion.  I've run 3 different configurations.
  
 1) Jensen Transformers on the Driver board (no caps).  1a) with a POT and RCA inputs.  1b) with XLR and a Goldpoint 4-deck attenuator  (Schema Option)
 2) Removed Jensen input transformers from the board and replaced them with Mundorf Silver 220nF Caps.  RCA inputs  (Schema Option)
 3) Most recently and briefly added the "outboard" Jensen trans in the diagram intron t of the driver board still with the 220nF caps.
  
 I am now listening to configuration number 2 and that's where I'm staying.  It's quiet as a dead church mouse and very musical.  As I type, I'm 4 songs into the Sophia Electric 300B mesh princess.
 They are a big step up from the JJ's.
  
 I don't see an upside to working on the outboard trans configuration again.  Sure I'd like a little more punch but I don't want to screw up what I have.   There's a lot more source RCA out's than XLR.
 I'll probably mung with the meter Steve and get a value on the Gungnir.   Can't take her apart because I have got to get 100 hours on this glass


----------



## Steve Eddy

Don't have to take the Gungnir apart. Just measure between pins 2 and 3 on its output jacks.

se


----------



## sceleratus

steve eddy said:


> Don't have to take the Gungnir apart. Just measure between pins 2 and 3 on its output jacks.
> 
> se


 
 yup...
 I mean't take the amp apart, but I appreciate your concern.
 I'll check tomorrow.
  
 Thanks


----------



## sceleratus

No DC voltage across Gungnir XLR output pins 2 & 3


----------



## 00940

steve eddy said:


> Why are you taking the can and the shield to the chassis instead of signal ground?
> 
> se


 
  
 My bad, I was a bit quick on that. Ideally, can should be run to chassis, internal shield to signal ground (though chassis is a common practice). Might be difficult with the wooden case, I just realize.
  
 Anyone interested in the finer details could have a look here
  
  


> No DC voltage across Gungnir XLR output pins 2 & 3


 
  
 Thx for measuring.   I must say, short of being with you with a scope and signal generator, it's difficult to see any obvious problems.
	

	
	
		
		

		
			





 
  
 If it works correctly and silently with rca... maybe leave well enough alone.


----------



## tomchr

sceleratus said:


> Have a set of Sophia Electric™ Princess Mesh 300B sometime this week.


 
  
 Dude!! Good find. I've been looking for a US vendor of the 300B mesh plate tubes. 
  
 I tried the Full-Music 300B/n mesh plate tubes a while back. They are very nice sounding tubes. However, one of the "matched pair" I received had issues with run-away. The plate would develop hotspots even at 380 V, 65~70 mA (27 W dissipation, the tube is rated for 40 W). I patted myself on the back from buying from an eBay vendor with a return policy. 
  
 Did you get the input transformer circuit working? It was my impression from your email that you did... 
  
 ~Tom


----------



## sceleratus

Yup.
 Got lucky again.  They sound amazing. They are in the sweet spot of the price/performance curve.  US made with a one year warranty and come in a black base.
  
 Let's not go into the input trans situation/train wreck/nightmare.  If I'm itching for a project down the road I might try it again.  Honestly my heart wasn't in it.  I wanted to listen to music more than troubleshoot a problem.


----------



## sceleratus

Here is an SPL graph for my music room as measured by FuzzMeasure Pro3 with a Røde mic.
 Volume was set to max and the mic was placed head high in the center listening position.
  
 It's pretty flat... but not quite my Audeze LCD2 R2's.  
 I don't think I want absorption panels because I don't have the power to compensate.  Also don't have the knowledge.
 Perhaps a bass trap near the speaker corners.....  I think.


----------



## sceleratus

Using this cool tool, and looking back on Tom's post ohm Haas Effect here's FuzzMeasure reverberation calculations and graphs from the Haas article.
 The room is 2700 cu ft.  At 62 ms I'm somewhere between an auditorium and an opera house.  I'f I'm reading it correctly.
 However it looks like times below 35 ms aren't good as they are close to direct sound.
  
 This is cool stuff. Time to get that physics degree.


----------



## sceleratus

Amp measurement to clipping.
  
 3.12 VAC to amp inputs.
 10.20 VAC on binding post where the sine wave starts to flatten.  Measured using DMM
 There was a 10 ohm 10W resister across the binding posts.


----------



## sceleratus

This is a duplicate post I made in "Show pictures of your Build"
  
 Does anyone have a design recommendation for a high pass filter?
  
 I put in a sub that I had doing nothing.  I cabled it straight off the second RCA's on the Schiit Gungnir DAC.
 It works great.  Because I only have 10W max from my 300B, it only required a tiny fraction of volume.  I used FuzzMeasure Pro to capture the room freq levels with the sub and my Thiel CS1.5's  Turns out that 100-120Hz is about right.
  
 The High Pass.  It is my understanding that a filter on the Thiels will make them more efficient.  That would be good for me.
  
 Any input  will be appreciated.  The BLUE is the room without the sub.
 The GREEN is after dialing in the volume, freq, and phase of the sub.
  
 This software is a lot of fun.  It recognized my speakers are Thiels from, I guess, the sound signature.
  
 EDIT:   Is this just a matter of calculating one resister and one cap?  Where 110Hz is 150 ohm and 10uF ?


----------



## sceleratus

I need a Preamp...
  
 Update.  Tried my friends LINN Preamp.  Sending 1.7V to the amp.
 HUGE difference.
  
 I bought an Adcom GFP 565 on Audiogon.


----------



## tomchr

It looks like you have a measurement error in the plot without sub (blue trace). The straight line from 3 kHz to the ADC/DAC roll-off at 22 kHz doesn't look real.
  
 Getting good in-room measurements is tricky business. 
  
 ~Tom


----------



## sceleratus

Hope everyone is having a wonderful and safe Holiday.
  
 Getting off track a bit, again,  (I can do that because it's my thread)  I got into woodworking mode.....  specifically attempting veneering and marquetry.
 I've ordered the parts to make a veneer press and my first project is a shelf for the music room.   The structure is complete and I'm waiting the arrival of the veneer
  
 If it comes off, I'll tackle a rack for the amp and gear.


----------



## randytsuch

sceleratus said:


> Hope everyone is having a wonderful and safe Holiday.
> 
> Getting off track a bit, again,  (I can do that because it's my thread)  I got into woodworking mode.....  specifically attempting veneering and marquetry.
> I've ordered the parts to make a veneer press and my first project is a shelf for the music room.   The structure is complete and I'm waiting the arrival of the veneer
> ...


 
  
 Cool.  Are you going to make a vacuum press?  I looked into veneering a little, but haven't tried it.
  
 Nice job on the shelves.  How did you make the curved cuts?  Making curves that nice is beyond my ability.
  
 I'm making a couple of cases for my 300b amp project out of curly maple.  I have one partially completed, had a few issues but it looks pretty nice now.  It's going to take a lot longer to make the cases than to build the amp, but I am enjoying the process.  I finally broke down and bought a table saw, which has been very useful.
  
 Randy


----------



## sceleratus

Happy New Year Randy,
  
It’s pretty easy to make curves.  I’ve done bending and clamping a thin wood sandwich around a jig but for this project I used a router with a template bushing in the base plate.  It will work for hardwood and mdf.
  
Make a template of the curve you want using a jigsaw and sanding it to refine the edge.  I use double sided tape to make a 3 part sandwich on the bench.  1) A sacrificial piece of MDF. 2) I rough cut one of the pieces to be duplicated with a jig saw. 3) Affix the template on the top allowing for the offset of the bushing.
  
Glide your router bushing along the template.  Repeat as many times as necessary.  I use a rubber roller to spread the glue and clamp everything together.  Rule #1.  You can never own enough clamps.
  
I use the Krieg Pocket Screw Jig to put it all together.
  
I am building a venturi based press from Joe Woodworker
  
I’m going to section the platen so I can use a large bag for smaller projects.  My veneer project is ambitious.  I discovered Paul Schurch.  He’s a master builder.  I went nuts and got his videos and signed up for his 5 day workshop in November.  Take a look at his portfolio.  Amazing.
  
I can't call it furniture but I'm working up to that for an equipment rack.
Keeping my fingers crossed.


----------



## sceleratus

Randy.
  
 As you can guess, I'm very fond of curly maple.  Be sure to post some pictures here. 
  
  
 Everybody else too.  !


----------



## randytsuch

So this is still a work in progress, but I am VERY happy with the outcome so far
  

  
  

  

  
 Only thing is that the face on the first pic is the nicest, and it's the back.  Obviously didn't plan well 
 The 2nd pic is the front of this, last one is one side.  The other side, not included, is my least favorite, doesn't have much figuring.
 It even looks better in person, there is a pretty cool almost 3d holographic effect.
  
 This is the Power supply part of my project, will house the high voltage power transformer, rectifier tube, smoothing caps, and two smaller transformers and associated circuits to generate the raw heater voltage.
  
 I'll build a 2nd box to house the main part of the amp.  I already have the piece of curly maple for that box.
  
 Finishing so far has been Dark Vintage Maple Transtint diluted with water.  Applied lots of the mixture to the wood, and then sanded down to 320 grit.
 Applied one coat Sealcoat dewaxed shellac, mixed 50/50 with denatured alcohol and one coat of Sealcoat at full strength.
  
 I am going to add dovetail miter keys to the corner, and then apply a final finish over the top of the shellac.


----------



## sceleratus

That's one fine looking cabinet.


----------



## sceleratus

Here's the shelf structure.


----------



## randytsuch

sceleratus said:


> Here's the shelf structure.


 
 How big is your shelf?
  
 I didn't really notice before, it looks huge.
  
 BTW, thanks for the idea about making a router pattern.
  
 On the sides of my box, I made a couple of "slots" on the bottom for air flow, plus they will make it easier to pick up the box, but I didn't really like how they turned out.  I'll try making a template out of scrap wood and see how that goes.
  
 Randy


----------



## sceleratus

It's 75" long 11.5" wide 3" deep.

You can use either 1/2" MDF or 1/4" Masonite hardboard. The Masonite is nice but you need to make sure you get a shallow bushing. Rocker calls them "sign" templates. They fit a standard 1 1/4 " Hole in a router sole.


----------



## tomchr

Veneering the concave curves will be interesting. It's probably "just" a matter of clamping in the right places, but I'm curious how you get the veneer to follow the curve.
  
 Neat project regardless. I really like the contrast of light-dark wood in your work. Like the walnut corners and maple sides on your 300B amp.
  
 ~Tom


----------



## sceleratus

Happy New Year Tom,
  
I made a "complimentary clamping curve" with tangent plateaus for the clamps.  There are parallel plateaus on the backside of the base curve.
However, I shouldn't need it since I'm building a vacuum press.  The system will generate 1,800 Lb/sq. inch, so it should conform to the curves nicely.
I will give it a test press first.


----------



## randytsuch

Any progress to report?
  
 I just bought a flat pack for a small, desktop speaker project, and an looking at veneering it.
  
 Considering building a vacuum press, wondering what you built?
  
 Seems like the joewoodworker stuff is the safe way to go with this.
  
 Randy


----------



## sceleratus

I have 3 - 4 projects going.  I refinished a cherry table.  Install new chair legs from Rogers Woodturning to replace broken ones.  Making raised panel window valences. And.. the shelf.
 I completed the Joe Woodworker V2 plus but I haven't tested it.  Today I will complete the modular platen then I'll give it a go.
  
 I purchased a bunch of Festool equipment.  I've had the plunge saw and rail for many years.  I added the CT-Midi dust extractor, 1400 OF router and 150/5 orbital sander.  Wow.  What a pleasure.
 Since my space is limited, I will probably get the Festool portable router table.  I like what I saw on YouTube.   I also bought the Excalibur EX-16 scroll saw.    Check out the "Wood Whisperer".
  
 Yesterday I had some Skype consulting from Paul Schurch.  Amazing.
  
 I'm days away from starting some these veneer samples.


----------



## sceleratus

It works


----------



## randytsuch

Festool, I'm jealous.
  
 I also have bought a bunch of tools in the last 6 months or so.
  
 New ROS, a Milwaukee and some Mirka Abranet sandpaper and "interface pads"  The pads are simply hook on one side, loop on the other, protects the sander pad.
 The Mirka is pretty cool sandpaper, a little expensive but lasts a long time and doesn't get clogged like normal paper when sanding finishes.
  
 Used Bosch Jigsaw to replace a Hitachi one.
  
 Dewalt Table Saw, the little one, DW745.
  
 A Rockler Router table top for my little, Bosch laminate router.
  
 Inexpensive HVLP sprayer that I haven't used yet.
  
  
 You vacuum setup looks cool, I was thinking about buying one of his vacuums, but decided against it for now.  The speakers I am going to veneer are small, so I just plan to use clamps and pressure to do the job.
  
 Here's a project update.
  

  
 After installing the dovetail keys, I had to resand, redye, and shellac the outside again.
 I then used rattle can Deft lacquer, 4 coats so far.
  
 Turns out the screen I want to install on top sags in the middle, so I need to add some more supports in the middle of the walls, you can see a couple on the inside corners in the pics.  Using same wood as the keys.
  
 Randy


----------



## sceleratus

Very Cool.
 I love how the maple pops when you apply finish.  Just amazing.
  
 I'm selling my Bosch 1617EVA router with collets and template rings.
 Also my beefy Porter Cable 6931 plunge router.
  
 I have some nice Rosewood PVA backed.  2' x 8'   This will be very easy for you.
 Also a nice strip of figured maple paper backed.  
  
 If interested, make me an offer.  It'll be friends pricing.
 I'll photograph the maple if you are interested.
  
 Don't forget you need a backing veneer.  I have a bunch I'll give you.
 If you want to come south and press it, let me know.
 I'm pressing a simple picture frame today, just to get my toes wet.
  
 I have not forgotten this is an audiophile DIY thread.....
 My "grand Plan" is to make a nice cabinet/rack/stand for the amp and the Schiit gear.


----------



## randytsuch

Thanks for the offer on the veneer, but I have my eye on some nice figured raw veneer.  I am starting to buy the stuff to make hot hide glue to try hammer veneering.
  
 Bigger router would be nice, but its not a priority at this time.
  
 Randy


----------



## sceleratus

Getting closer to a real project.
 I just finished a making a mockup veneer panel that I will use to make a table top.
 Then the music room shelf.  Then tackle an equipment cabinet as a furniture project.


----------



## GrindingThud

Attractive layout of color and grain.


----------



## sceleratus

Completed the majority of the woodworking.  I have a few worts to fix before finishing.
 I promise I'll get back to relevant content in the future.  Just on an audio sabbatical.


----------



## randytsuch

I'm impressed.
  
 Looks great so far.


----------



## sceleratus

OK, here's something Audio.
 [size=small]I started re-covering my friends LINN Subwoofer in a cherry veneer.  He has two.   I am working on matching the orange brown flat lacquer finish on his other LINN speakers.  They are cherry too.[/size]
  
Both subs will have the same grain pattern on the same faces as each pieces is a consecutive slices from the same log.
  
Since the layup is very straightforward and the sub would not fit in my bag, I had the veneer backed with a PSA peel-n-stick adhesive.  That stuff is very tough.  You had best lay it down right the first time.
  
 [size=small]That said the process is pretty easy.  What you see took yesterday afternoon. Masking, sanding, cut, apply, and trim.  Cost for veneer and backing $220.  Add stain and finish.[/size]
  
If anyone is interested in more details on how to recover your speakers send me a PM.
  
I think I'll post in-process photos of the second sub.
  
You only need a couple tools and steady hands.   Bosch trim router ($99) and a flush cut spiral "down cut" router bit ($35).  Both on Amazon.


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## sceleratus

Second sub is prepped for veneer.


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## sceleratus

Twin subs ready for finishing.


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## sceleratus

Finished staining one and put 3 coats of sanding sealer on.
 Satin top coats and it's "finished"
 Hard to photograph in the garage.  The finish is even despite the glare.


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## sceleratus

One done.  One to go.


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## sceleratus

Here's a great tip on staining wood and veneer.
  
 Often species like cherry and maple will blotch the stain, masking the grain with nondescript patches.   The cherry veneer I used was very susceptible to blotching.
 Charles Neil's "Pre-Color Conditioner" is amazing at controlling this.  However, veneers being only 1/32 thick have an additional challenge as to not oversaturate the stain and put the dried conditioner back into solution.  If this happens and you are too aggressive wiping or brushing you'll pull the combined mix off the veneer.   Not good.  The benefits far outweigh the potential problems and if you know this going into a project you'll be fine.
  
 I used General Finishes Water Based Dye/Stain.  They are great.  You get a much deeper color than oil based stains.
  
 The result was a crystal clear stained grain pattern.
  
 Charles is a Hoot !
  
 I'm working up some design ideas for the equipment rack/shelf/cabinet.
 One idea is to combine Marc Spagnolo's stool design into an "open front door" cabinet  (image is video capture) perhaps with a mica or Japanese paper backing.
  
 Rough concept.


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## tomchr

Gorgeous work! What kind of surface prep did you do?
  
 ~Tom


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## sceleratus

tomchr said:


> Gorgeous work! What kind of surface prep did you do?
> 
> ~Tom


 
 Thanks
  
 I sand the raw veneer with 320g.  Very lightly as the veneer is 1/32" thick.
 I applied Charles Neil's Pre-Color Conditioner.  Two coats following the directions.
 I shot a mixture of General Finishes Water Based Dye, orange and light brown.
 Shot the entire sub then lightly wiped down with a cloth rag.
  
 I used General Finishes Enduro water based Sanding Sealer and water based lacquer.
 I lightly sand between coats of SS with 320g. I use 600g for the top coats.
 If I want a satin or semi-gloss finish I apply two coats of "gloss" first, then finish with satin or semi-gloss.
  
 Wait two weeks then rub it out with 1000-1500g and soapy water.
  
 Below is the second sub waiting for the satin finish.


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## tomchr

Sorry. I didn't express myself clearly there... What surface prep do you do before applying the veneer? Sanding + Bondo? 
  
 ~Tom


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## sceleratus

Of course...
Prep:
You want to sand the "core" surface so the glue has more surface area to adhere to. If the existing veneer is loose tack it down with Gorilla Glue. Bondo repairs as needed.  I didn't need Bondo and I didn't prime.  Sand the existing veneer or paint and clean the dust with air / rag / then lightly with a tack cloth.
  
Cutting the pieces:
Cut the piece of veneer with an overhang no greater than 1/4".  Less is better.  This is because a 1/4" flush trim bit will get clogged by the glue if the excess exceeds the bit diameter.  I had a 1/4” bit in a Bosch Colt but switched to a 1/2" bit in my Festool 1400 because I had to stop and clean the 1/4” bit often.  The trade off is router control.  The Colt is nimble.  I did have a table widener on my OF 1400 that helped a lot.   1/4” trim bits are more common and cost a little less.  Plus they are better for tight corners.   I suppose if you let the glue dry before cutting it wouldn't be a problem, but it would take 5 days to complete cutting.  Be sure to get a down cut "bearing" bit.   Whiteside has great bits at a good price.  The spiral bits are nice, however I have an Amana 1/2" down cut non spiral bit that worked nicely and I found it for $20.
  
Applying the veneer:
You don't get a second chance to position the PSA veneer.  It sticks immediately.  If you pull it away it will tear / crack the veneer.  (Trust me).  Index the center of each side of the speaker with a mark.  Do the same with the piece of veneer for positioning.  I had the speaker up on a bench and applied the veneer to a vertical surface.  Same for the top.  Turn the speaker on it's side to apply the top. 
To apply a panel pull the backing paper down 1" to 2" exposing the glue and lightly crease the paper.  Position and set the top edge of the piece. Next reach behind and pull the paper all the way off but hold the piece out by the edges until all the paper is off. Using a stiff plastic scraper with dull corners set the piece top to bottom Down The Center.  Scrape from the middle out, center left then center right, until you reach the bottom. This worked very well for me and takes the drama out of setting a piece.
  
Sanding:
I bought a 25 piece box of Mirka “MirlonTotal” sanding pads.  I thought they were pricey at $24.  However they are larger than the 3M foam pads and those cost a lot more.  3M has a lesser grade for a buck a pad.  That said….  These pads are amazing. One pad lasted for 5 between coat sandings of one speaker…… and it’s still going strong.  I doesn’t clog either.  They are a totally redesigned Brillo type pad.
CORRECTION:
I did NOT sand the raw veneer.  Don't know what I was thinking when I posted.  The Charles Neil Pre-Color Conditioner is magic, especially with water based dyes.  Works with oils as well.   I tried a 1 1/2 lb cut of shellac.  It didn't come close to producing the color and consistency. 
  
As Always:  There are numerous spelling and grammatical error in this post.  Sorry about dat.


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## sceleratus

I hope Ya'll find these posts interesting / helpful.  I see that the read count keeps going up.....so I guess it's so.
  
 Audio wise I just don't have much to add.  I love my DG 300B, my Gungnir, and I love my LCD2's.
 This will be static for a long time.  I don't have a burning desire to build other components.
  
 As such the thread will stay quirky.
 Thanks for reading.
  
 S


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## tomchr

Very cool. Thank you for the detailed write-up. I think I may just attempt veneering when I build my speakers. The cherry looks very nice.
  
 ~Tom


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## sceleratus

Table Finished...
 Back to completing music room shelf.  Then I'll purchase a Festool DF500 Q Domino Joiner and tackle the audio cabinet.


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## sceleratus

Festool Domino 500 arrived and the music room shelf is complete. Soon l will tackle the amp cabinet.
 I came up with a very unique design based on an iconic shape.  I hope I can pull it off.  It will be wild.
 The room will be painted a different color as well.


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## sceleratus

Been gone for a while.
  
 During which I made a set of Bob Brines M10-A10 Mass Loaded Transmission line speakers using the MarkAudio Alpair 10M driver.
  
 I am very pleased with how they sound with the 300B.  I built them on a leaf-of-faith and I’m very surprised with the results.  The bass far exceeded my expectations.  Naturally I’m not going around listening to other speakers.  Ignorance is bliss and easy on the wallet.
  
 Currently building a preamp and phono preamp.


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## DejanM

Hi Sceleratus,
  
 I like very much what you have done here. Using 300B in SET seems to be ultimate solution for a headphone amp. I am trying to read through your posts here but somewhere I've got stuck .... What I am interested is to find out what changes to the original scheme of Damn Good 300B you've made in order to make a headphone amp ? Did you used the original DG PCBs and then did some modifications ?
  
 I am thinking of going the same path you did but I would like to find out first what I can expect in terms of already existing DG PCBs ... ?


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## Misterrogers

Not Sceleratus, but I'm pretty confident he (and Tom, the designer provider of this information) wouldn't mind. I've built the same amp, and Sceleratus and I but implemented the same basic 'LPAD' circuit that Tom provided. I've attached it below. This allows us to switch between speaker taps and headphone out. I've been running mine with Mills resistors, but just yesterday rolled in Path Audio resistors. The mills sounded great, but these PA resistors are ridiculous. Clean, smooth, fast, better macro / micro detail (less phase shift / smear) and better separation. Not cheap, but they're not coming out.


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## sceleratus

dejanm said:


> Hi Sceleratus,
> 
> I like very much what you have done here. Using 300B in SET seems to be ultimate solution for a headphone amp. I am trying to read through your posts here but somewhere I've got stuck .... What I am interested is to find out what changes to the original scheme of Damn Good 300B you've made in order to make a headphone amp ? Did you used the original DG PCBs and then did some modifications ?
> 
> I am thinking of going the same path you did but I would like to find out first what I can expect in terms of already existing DG PCBs ... ?


 

 Hi Dejan,
 Misterrogers is spot on.  Has nothing to do with the PCB.  It's all about the output transformers.  The windings and resistor values you specify to match your headphone and speaker specs.  If you only want to use HP's have the OPT's made to match.  Mine are  Audeze LCD2 and  MTL speakers with Alpair drivers.
  
 I'm building a case for Misterrogers DG300B. Why?   Cuz I didn't build my case and I wanted to see if I could build a better one.  Unfinished woodworking business.  Being an insufferable show-off here's where it stands.  We are finalizing the top and back plates.  We've also come up with some cool tricks which will be revealed if they actually work. 
	

	
	
		
		

		
			





  Gotta update my other thread.


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## Misterrogers

^ What he said 
  
 Glad you mentioned the case - didn't want to 'out' your efforts; cause if I was reading this, building this amp, and you weren't making it for me.... I'd be dogging ya!


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## DejanM

So if I understand you correctly guys, no changes to the original PCBs and component values except for the output transformer ... is that correct ?
  
 What do you thing about Lundahl LL2765 as an output transformer ?
  
http://www.lundahl.se/wp-content/uploads/datasheets/2765.pdf


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## Misterrogers

There are a handful of things that can be swapped or upgraded (output resistors / caps come to mind). You don't need to (the amp is well designed, and the BOM is solid), but you can if you want to squeeze more out of it. I went with custom Silk power and output transformers - c-core. Don't have experience with LL2765.


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## tomchr

dejanm said:


> So if I understand you correctly guys, no changes to the original PCBs and component values except for the output transformer ... is that correct ?


 
  
 Correct. 
  
 If you use the circuit shown in Post #634, you won't need to change the output transformer either. Just build according to the instructions and you'll be fine.
  
 Tom


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## Heffa

dejanm said:


> What do you thing about Lundahl LL2765 as an output transformer ?
> 
> http://www.lundahl.se/wp-content/uploads/datasheets/2765.pdf



DejanM - did you build the DG300B using the Lundahl LL2765? 

I'm really interested in building a DG300B for powering my Audeze LCD-2 as well, and beeing Swedish I would like to use the Lundahl OPT if possible. As far as my very limited understanding tells me the LL2765 would work...


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## tomchr

As far as I can tell from the data sheet, the LL2765 should work.
  
 Tom


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## Heffa

Thanks for the feedback Tom!


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## jh4db536 (Jun 2, 2017)

Dropping by to give Tom the well deserved praise for designing such a wonderful amp. It fired up on first try and sounds great, worked out perfectly to power my high efficiency system. I configured the amp to run 6DJ8/PCC88 driver tubes, 300b output tubes, mundorf and jantzen superior coupling caps, and electraprint silver output transformers.  Driver tubes are Siemens PCC88 and Genalex 300b.

The speakers are BK20 BLH with 8" F208EZ sigmas. Approx 97dB/w.


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## Heffa

Wow, that looks sweet!


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## jh4db536

A little more on the 300B build and BK20








Initial check and biasing




I think this is possibly understated


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## rellik

wow, that is a complex build. Some of the joints seem to be floating on the semi-pliable glue.

---Could you recommend a glue that stays compliant when used to create a strain relief void?


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## jh4db536 (Jun 2, 2017)

There's nothing floating on glue, all joints that are supposed to be glued are flush. I used Titebond2 and 3 from homedepot and would recommend Titebond2 if i had to do it again (faster cure).

With these flatpacks, everything is position a piece at a time, glue, align the other side, and clamp. It's very easy, a caveman could do it.






To fill voids (3 sections in each cabinet), i used a mixture of sand and liquid foam.


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## rellik

"Happy Days". I like your profile picture.

BTW, I must be mistaken about the voids, must be angles or something. Thanks for the glue recommendations.


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## tomchr

Last Call: The DG300B will be discontinued once the current stock of 15 board sets runs out. I'm spread too thin and will focus on my solid-state designs going forward.

Thanks,

Tom


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## tomchr

One board set left.

Thanks,

Tom


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## Paladin79

tomchr said:


> One board set left.
> 
> Thanks,
> 
> Tom



 I am doing a build as well as a couple friends and it certainly looks like a well documented project.


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## sceleratus

Another Box.   Don’t think I posted this One.   Made it for Mike. 
birdseye maple and Purple Heart contoured with French Polish finish.
This will be the last for me because I have tinnitus in the hearing.  Everything is fuzzy.  Sometimes my brain makes it sound like a distant radio station.  Weird. Then... I can’t build fine motor skilled things because I have tremors in my hands  Probing with a DMM is I’ll advised. The 300B. Isn’t working.  I paid a guy in a guitar shop $300 he was lost.   So I’m just do-n woodworking.  I’m fine with that. 
you guys n gals are Great
peace
luke


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## randytsuch

sceleratus said:


> Another Box.   Don’t think I posted this One.   Made it for Mike.
> birdseye maple and Purple Heart contoured with French Polish finish.
> This will be the last for me because I have tinnitus in the hearing.  Everything is fuzzy.  Sometimes my brain makes it sound like a distant radio station.  Weird. Then... I can’t build fine motor skilled things because I have tremors in my hands  Probing with a DMM is I’ll advised. The 300B. Isn’t working.  I paid a guy in a guitar shop $300 he was lost.   So I’m just do-n woodworking.  I’m fine with that.
> you guys n gals are Great
> ...



Sorry to see that you have tinnitus, and about the hand tremors.  Getting old sucks.  And yeah, stay away from high voltages.

Take care.

Randy


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## sceleratus

Thanks Randy
whatca gonna do....I don’t have the franchise for problems everybody has something

my son is a nuclear engineer and works for Cymer they make lasers or power source for EUV. Chip lithography machines that the parent company  AMSL makes.  Super cool all the chip makers, Intel  Samsung, etc etc buy from ASML because nobody else makes the machines. They are $100M each

I bring this up because if you watch the 10 min clip it’s pretty incredible the 70yr jump from single circuit tube to IC
Extreme Ultraviolet Lithography


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## tomchr

Now available, unsupported, for DIY use only. Licensing for commercial use is available.

https://neurochrome.com/pages/dg300b

Tom


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