# the CTH (Compact Tube Hybrid) Rev A thread...



## Mullet

We're finally here! Here's a little teaser...
   

   
  Thus far the build is going well. The only non-standard situation that I've run into is for the C13P and C14P film caps. I had to bend the leads outwards to fit them into position. Not a big deal though. Overall, it seems like the new and modified positions for everything in the power and heater sections is making the parts fit a bit easier. Also, as you can see, C8P is kind of hiding part of the 4 heater positions. Next step is to wire everything up and test this puppy out tomorrow sometime. I'll be sure to let everyone know my progress and any trials and tribulations of the process.
   
  When everything is verified and working a new BOM will be posted on cavalliaudio.com. Then I'll proceed to the next phase of shipping out everyone's boards from the group buy.


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## cfcubed

We owe much thanks to Mullet for doing most of the BoM revision, associated parts subbing/etc. and building out the 1st of the new rev.   For completeness:
  GB for this: "Group buy for CTH" - http://www.head-fi.org/forum/thread/536098/closed-group-buy-for-cth-compact-tube-hybrid-pcb
  Earlier  "A Very Compact Hybrid Amp" spec & build thread - http://www.head-fi.org/forum/thread/398839/a-very-compact-hybrid-amp
   
  >  The only non-standard situation that I've run into is for the C13P and C14P film caps. I had to bend the leads outwards to fit them into position
   
  This is because places were out of the 7.5mm pitch cap spec'd there so the rev'd BoM must have a 5mm pitch part #.
  No biggie but we should note this in BoM comment or ID a better sub. 
  BTW Mouser seems to be out of common parts lately (e.g. many Wima films, some common BC transistors, and the "long" hammond cases until recently, etc.)
   
  The changes in this new rev are largely ones that make building easier & should not result in sound or performance difference compared to proper earlier CTHs.   
   

 Space to better fit C3H.  Though new BoM 2026A+ 330uf part has better specs and 330uf has proved plenty to fix early CTH hum issues, a 470uf can be fitted there now at the builder's option.
  
 C1H, C2H increased to 150u taking advantage of a new series of caps (thanks to user rds).
  
 A TO225 (2N49922) Q1P that can handle much larger currents like cases where there is a short on the output of the regulator.  Though the earlier re-spec'd BC337 has proven sufficient for expected loads, this change provides even more current "headroom".
  
 More room around C4L and C4R to give you more space to tombstone other caps in that area.
  
 More room to fit the heatsink on the 24V regulator.
  
 PCB support for up to 4 heater voltages.  Base 12.6V & 6.3V plus up to two other voltages if you wish & provide a way to switch amongst them.  This was accomplished through off-board resistors in the past, and you can still support as many heater Vs as you wish using that method.
  
 Misc organization tweaks WRT some diode positions, comp spacing, etc.
   
  As Mullet indicated, runeight will update the CTH site with the various revision-related files & info once Mullet's build is proofed.
  
  For the curious, here's the last PCB spec image I have from runeight:


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## drclaw

Were you able to get any work done over the weekend?  I'm excited to get this project rolling!


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## Mullet

I know the feeling!
   
  Had some early hiccups with reversed resistors -- R1H and R2H and as a result ended up frying what looks to be the right side of the buffer output when trying to troubleshoot why I wasn't getting proper heater voltages. New parts are on the way and if everything goes smoothly with the transplant I think everything will be good to go by this weekend. Good thing we're vetting this BOM because I'm sure others would have had similar results with the heater voltages being so off.
   
  I'm pretty stoked as a whole. Here is a list of tubes that I've collected in the past few weeks in anticipation for this amp:
   
  Amperex Bugle Boy ECC88
  Amperex Bugle Boy ECC82
  Amperex USA Gold Pin JAN-6922
  Pro Comm Miniwatt PCC88
  Raytheon 6GU7
  RCA Clear Top 6CG7
  RCA Holland Gold Pin 7308
  RCA 5963 Black Plate D-Getter
  Siemens ECC82 Chrome Plate
  Siemens ECC802S
  Siemens PCC88
  Sylvania Gold Brand 5814A
  Telefunken ECC82 Smooth Plate
  ...and a variety of 4BQ7 tubes from Tung-Sol, Sylvania, DuMont, and Westinghouse.
   
  I know a few of these are generally well liked by many using the CTH. Any comments or suggestions regarding other tubes or these ones in particular? I'm trying to locate an Amperex Holland 8416 PQ if I can find one. I hear it's quite nice.


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## cfcubed

>  _New parts are on the way and if everything goes smoothly with the transplant I think everything will be good to go by this weekend. Good thing we're vetting this BOM because I'm sure others would have had similar results with the heater voltages being so off._
   
  Yes, we _think _that the new CTH rev will work w/R1H/R2H correction in the new BoM.  The errant heater V caused by the swap was precisely what would be correct for the swap.  Before I could diagnose R1H/R2H swap as the cause for low heater (1.37v) & high plate Vs, a short may have occurred trying to research things.   These occurrences, a BoM error (esp. in modified heater area) & short while diagnosing a CTH PCB, are not unexpected.  I blew an OB once taking measurements to make sure everything was OK (it was prior to me trying to confirm so
   
  In an effort to expedite things I've a new CTH PCB in hand & my parts arrive tomorrow (Wed) evening.  I should have it built & tested no later than this Saturday.
  So one way or another we'll have answers this weekend.


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## cfcubed

Well we have a working build now (mine), so I think we can call the new CTH PCB & newest BoM proofed.
   
  Been listening to it for a while & it's working well, voltage measurements are fine and it sounds good.
   

   
  Notes:

 I did not have to raise 24V reg & flip it heatsink upside down to fit it, the combo will fit snugly where it belongs if mounted properly.  But I've something strange in mind for casing so my 24V reg heatsinking is not final.
 Yes those are Gen II Sonicaps even though the BoM box caps are fine.  The "F" indicates the foil side/lead end going to the tube plates (input).  Used this to ID the foil: http://mailman.io.com/pipermail/sound/2006-October/014043.html
 Here are the 4 heater voltage/resistors I included & my results (within reason given the available resistor values):
 Voltage / parallel resistor value / my measured voltage under tube load w/25 yr old, uncalibrated DMM:
 4.2v / 3.3k / 4.2v
 6.3v / 7.15k / 6.2v
 7v / 9.31k / 6.9v
 12.6v / <none> / 12.7v

 So I've not yet confirmed these but it seems they should work & wiatrob noted no issues w/them:
 5.6v / 5.8k
 8.4v / 15.1k
 9.4v / 23.3k


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## Mullet

Awesome cfcubed! Congrats on your successful build. 

I get my new parts on Monday. I'm possibly planning on just redoing my whole buffer sand all in fell swoop. At a minimum I'll do at least the right side, which was giving issues reading 24v instead of 12. That way I don't have to pull my hair out -- only a few.

Can't wait for the CTH goodness!


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## Mullet

So I finally got my parts and have proceeded to replace a few BJTs on the ride side of my OB. Everything is testing fine with these readings...
   
   
  99.6v SG>TB+
  11.97v SG>OG
  77.8v SG>Pin 1
  77.5v SG>Pin 6
  11.97v SG>OL
  11.96v SG>OR
   
  My pin 4 to 5 readings for four different heater voltages are as follows using the 2-12 position NKK rotary switch that cfcubed recommended earlier on in the GB post...
   
  Position C - 6v = 6.04
  Position 1 - 7v = 6.87
   Position 2 - 4v = 4.058
  Position 3 - 12v = 12.58
   
  I'm not sure why they aren't in the same order as the BOM would suggest ie 12v, 6v, 7v, 4v, but it must have something to do with the way the switch works. I could reverse some wires to put it in order but I think that would just complicate things. The next step for me is to wire this puppy up and test out the audio. Then I'm on to panel drilling fun!


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## cfcubed

Sournds good Mullet - Yep, heater voltage WRT switch position can only be the installed order of resistors, their wiring to the rotary switch or the switch mechanics. 
  Of course you may move the wires on the switch's tabs to get the order you want.
  A couple voltages are a tad low, differing from mine, but are within reason I suppose.  It could be we are seeing variance in our DMMs or the resistor values, even something like a 0.2k variance in the _actual_ switcher feedback resistor values could account for this.  We'll see if we need to better target the resistor values if others report their actuals.  Note sometimes the precise resistor we'd like is not available (e.g. 7.25k).


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## Mullet

I have a quick question about wiring going to to IG and G+ on my RK27 pot.  This diagram looks like it's calling for G+ coming from my RCA jacks to be both connected to G+ and IG on the pot. Also it looks like the IG wire going from the pot to the IG pad on the PCB needs to be connected to both contacts on the pot as well. Is this correct? Can someone clarify what this diagram is calling for?


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## wiatrob

Mullet,
   
  All the input grounds get tied together. So, Left and Right input Ground can go to their respective (I might have labeled them IGL and IGR on the pot, but +G and IG in this diagram). Tie the pot ground pins together, then run a lead to IG on the PCB. DO NOT tie them to the output ground or case.
   
   
  Bill


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## Mullet

Cool, makes a little more sense now.

Just figured that I'd post an updated pic of the current status of my Rev A CTH... Almost there... Perhaps, I'll be there tomorrow... Just need to wire up the pot...


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## Mullet

Well we finally made it... FTW! For the size and cost to build, this amp really packs a punch. My K701s aren't having a tad bit of trouble. Thus far I've popped in a few select tubes and I'm enjoying every minute of it. I'm liking my Amperex ECC82 Bugle Boy the best. Furthermore, I'm already thinking of putting my La Figaro 332C up on the chopping block. Thanks to everyone who made this possible -- runeight, cfcubed, and a few select others.


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## cfcubed

Looking good... Great its up & running and you're enjoying it...
   
  >  Thanks to everyone who made this possible 
   
  And you are one of them... Handling the GB, finding subs for the BoM, and _almost_ having the _first_ working Rev A (we'll remember that pesky R1H/R2H thing)


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## wiatrob

Great to hear! And my thanks as well for your participation!


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## Br777

Just want to say i owned this amp at one time and loved it.  Glad to see its getting a "revival" so more people can experience its greatness


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## civilmonkey

I read the entire original CTH thread (man what long thread).  I read somewhere that some people were considering SIP sockets for C4 so they could try different capacitors.  Did anyone try this, and did it lead to instabilities?  I have a pair of Aerovox AFPS I would like to try vs the stock bom caps.  Maybe oneday with I decide to order sonic gen II's I would like to try those too.
   
  Any thoughts?


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## wiatrob

I have built with socketed caps. Wasn't really worth the trouble, as most of the interesting caps will need some creative lead work to get in the amp comfortably, making the sips hard to use with the previous designs spacing. Might be different with the new lead spacing.

Give it a try and let us know? 

The Soniccaps are a slam dunk, but even the stock wimas perform admirably i'n this design.


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## cfcubed

Now that we have new CTHs & some new CTH builders around, and I've fielded queries about this, maybe good to say something about experiences WRT cans & how CTH drives them.  The bottom line is that, like most gear, there are combos reported to work well together & combos reported to not work as well together.  Know that the vast majority of reports, for most all "common" & many "uncommon" dynamic cans (e.g. Sennheiser IE8s through LCD-2s), are very positive concerning the CTH's synergy.  CTH has been reported to drive cans known as difficult to drive as well.
   
  Not unexpected, but based on reports here & my own experiences, the CTH may not be the amp of choice for the "tails" of a Bell curve of sensitivity/impedance of cans (high-sensitivity/low-impedance cans @ one end, low-sensitivity/high-impedance @ the other). 
  There is some question whether cans at the high-sensitivity/low-impedance end _need_ amping, but that's another discussion.
   
  At one end we have some reports of some IEM users hearing hiss & having little usable volume pot range, and at the other end reports of its e12 circuit tripping for very loud/heavy bass passages.  For example, 96 dB sensitivity 32R & 250R DT880s receive good reports, where (stock 100R R18s) CTH driving 600R DT880s at loud/high levels begins to distort & if driven further can cause its e12 to trip (a good thing - its doing its job if clipping is present or LV supply wavers).
   
  The *R18 resistors* were introduced early on in CTH development as a way to contour/shift its wide performance swath within the Bell curve discussed above.  I believe we suggest R18 values from 0R -> 150R, with the default 100R being best with the majority of cans.  However, if you wish to target the high-sensitivity/low-impedance end consider 150R, the low-sensitivity/high-impedance end consider shorting the positions.
   
  If necessary, I suppose runeight could tweak what is said here or provide technical data (e.g. WRT Class-A regime values of CTH's TO92 OB design).  OTOH maybe this is enough said & users can use search to see others' reports.
   
*Update: * The way to alter native CTH gain is through tube choice... E.g. 12au7 has lower gain than 6922.  So consider this as well WRT your volume pot range & cans sensitivity.  With the large world of tubes that can be operated in this amp, there are other levels of (tube) gain available as well.  Here again is *a tube compatibility post *I made (there have since been a few more tubes found that work I think): 
http://www.head-fi.org/forum/thread/398839/a-very-compact-hybrid-amp/2025#post_6785071


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## Mullet

cfcubed -- that's quite a nugget of info that I'm sure will prove useful for for the newer builders. What's the deal with the heater currents with regards to 150mA/300mA? Does that mean you can safely run a given tube at both 12v and 6v? Running it at a different voltage would shorten the the tubes life, right?
   
  If you guys don't have your hands on the new CTH Rev A BoM and info yet you can get it here... http://cavalliaudio.com/diy/ctha/main.php?page=overview
   
  On another note and I think I've come across this in the *old* thread when I read through all 146 pages -- I'm using the RK27 pot for my volume control and every time I touch it I hear a buzz. It goes away when I take my finger off the pot. What was the fix for this? I think its grounding issue. Also, I do hear a slight hum/buzz with some headphones and some tubes. You can't hear it when music is playing. I was under the impression that the 470uF C3H would take care of this. My source is a gamma2 from my laptop. Any ideas?


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## cfcubed

>  What's the deal with the heater currents with regards to 150mA/300mA? Does that mean you can safely run a given tube at both 12v and 6v?
   
  The 9-pin mini tube spec for the CTH includes 3 heater-related pins; pins 4, 5 & 9.  The usual/series heater voltage & draw (using pins 4 & 5) is what we consider here *NOT* a tube's parallel heater voltage & draw (its pin 4-> 9 & 5->9 parallel specs are ignored as CTH has no electrical connection for the heater centertap pin #9).  *So 12.6v (series) heated tubes (e.g. 12au7) use CTH's 12.6v position,  6.3v (series) heated tubes (e.g. 6922) its 6.3v position.  *
  The max (series) heater draw we recommend for CTH is 600ma, unless a heatsink is fitted it LM2595 & its coils up-spec'd beyond the BoM spec 800ma rating.
   
  >  I'm using the RK27 pot for my volume control and every time I touch it I hear a buzz.
   
  Since your pot is mounted to a plastic panel, you need to ground your pot, in CTH to its IG which = its SG.  Easy on RK27 - you loosen one of its back screws & run a jumper from it to the IG pins/connection on the pot.
   
  > Also, I do hear a slight hum/buzz with some headphones and some tubes. You can't hear it when music is playing. I was under the impression that the 470uF C3H would take care of this.
   
  We believe the old heater "buzz" problem was solved in early 2009 with re-specing C3H to 330u, and we now raised this to 470u as an extra measure.  We know your 1st build has had its problems & repairs, but maybe this is a case ground problem.  You must assure your case is grounded, e.g. running a wire from SG to a contact screw in the case.
   
  Bottom line is assure your pot & case are grounded to IG/SG and double-check they are using an ohmmeter (measuring to either RCA-in jack ground).  This should solve it.


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## cfcubed

Oh and other usual remedies for DIY amp hum apply as well, like keeping A/C lines short, twisted & away from low-level/input runs, considering shielded low-level/input runs, etc.


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## rds

The unpopulated PCB.  Very nice look, and great layout!


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## wiatrob

Speaking of headphone synergies and SIPs - I have always socketed the *R18* resistors in my builds, allows you to swap in different values when you have your build up (but still pretty difficult to do when the amp's cased.) I don't want to be the nervous nellie - but* BE CAREFUL when poking around inside a built CTH,* as components are very dense, and one slip of the probes can release some Magik Blue Smoke pretty easily...
   
  I have stuck with 150R. I rotate through YH-3s, Senn 600s, and JH-13s regularly...


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## civilmonkey

Quote:


wiatrob said:


> I have built with socketed caps. Wasn't really worth the trouble, as most of the interesting caps will need some creative lead work to get in the amp comfortably, making the sips hard to use with the previous designs spacing. Might be different with the new lead spacing.
> 
> Give it a try and let us know?
> 
> ...


 

 Thanks -- I will skip the SIPs for C4.  I plan on shoe horning some Obligatto Film Cap 0.22uF / 630V from Parts Connexion as I'm also getting my tube socket from them.  Since they are Canadian it should hopefully be easier / cheaper shipping then Sonic Gen II's (despite the slam dunk) for me.
  
  Quote: 





cfcubed said:


> At one end we have some reports of some IEM users hearing hiss & having little usable volume pot range, and at the other end reports of its e12 circuit tripping for very loud/heavy bass passages.  For example, 96 dB sensitivity 32R & 250R DT880s receive good reports, where (stock 100R R18s) CTH driving 600R DT880s at loud/high levels begins to distort & if driven further can cause its e12 to trip (a good thing - its doing its job if clipping is present or LV supply wavers).
> 
> The *R18 resistors* were introduced early on in CTH development as a way to contour/shift its wide performance swath within the Bell curve discussed above.  I believe we suggest R18 values from 0R -> 150R, with the default 100R being best with the majority of cans.  However, if you wish to target the high-sensitivity/low-impedance end consider 150R, the low-sensitivity/high-impedance end consider shorting the positions.


 

  
  My current headphones are 600 ohm DT880's, so this was great information.  My plan will be to use SIP's for R18 resistors, and try shorting, maybe 50 ohms, depending how it goes.
   
  Thanks everyone.  I promise to report back, but given that I have a newborn, time is scare!  I will have 1 week end of April when I start/finish this build.


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## wiatrob

Quote: 





civilmonkey said:


> _Quote:_
> 
> _Thanks -- I will skip the SIPs for C4.  I plan on shoe horning some Obligatto Film Cap 0.22uF / 630V from Parts Connexion as I'm also getting my tube socket from them.  Since they are Canadian it should hopefully be easier / cheaper shipping then Sonic Gen II's (despite the slam dunk) for me._
> 
> ...


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## cfcubed

>  My current headphones are 600 ohm DT880's, so this was great information.
   
  Yes, the only cans I've ever found the CTH (w/100R R18s) could not drive well are my 600R DT880s.  I'm not bothering to short my R18s for the DT880s, CTH sounds great with my other cans asis.  I've a couple good SS headamps to use w/the 880s.
   
  BTW a crafty builder might try installing 120R or 150R R18s plus a DPDT switch that optionally shorts the positions.  Note though the R18s are "embedded" into the OB circuit, so I'm unsure of the impact (if any) of long leads on their pads.
   
  BTW#2 for my "fancy" CTH there was enough room to use a DPDT power switch - one side the A/C  - the other side e12 relay power (e.g. bridged a PCB trace I broke from Q3E/D3E to the relay).  This nullifies the short, sharp harmless "click" one can get at power-off.


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## Mullet

Quote: 





cfcubed said:


> >  What's the deal with the heater currents with regards to 150mA/300mA? Does that mean you can safely run a given tube at both 12v and 6v?
> 
> The 9-pin mini tube spec for the CTH includes 3 heater-related pins; pins 4, 5 & 9.  The usual/series heater voltage & draw (using pins 4 & 5) is what we consider here *NOT* a tube's parallel heater voltage & draw (its pin 4-> 9 & 5->9 parallel specs are ignored as CTH has no electrical connection for the heater centertap pin #9).  *So 12.6v (series) heated tubes (e.g. 12au7) use CTH's 12.6v position,  6.3v (series) heated tubes (e.g. 6922) its 6.3v position.  *
> The max (series) heater draw we recommend for CTH is 600ma, unless a heatsink is fitted it LM2595 & its coils up-spec'd beyond the BoM spec 800ma rating.
> ...


 
  Good info about why we can't just switch between 12 and 6v on a given tube. So if you have a 6 volt tube run it at 6v. Otherwise, I suppose the life of the tube will be diminished.
   
  Once I get back to the office on Monday I'll make the appropriate adjustment to the pot to eliminate the touch sensitive hum/buzz. With regards to the general hum/buzz that is mostly inaudible, I did run shielded belden 1505A cable from my RCAs to the RK27. I used the black lead instead of the normal ground lead. My thoughts were that wire is wire, but I could have been wrong. Also I do have SG going to a one of those washer thingies (that you can attach a lead to) attached to the case. It's supposed to be crimped, but I soldered it because I didn't have the right crimping tool. I guess a poor connection somewhere might be causing the low level hum.
   
  Another thing to note for everyone building this new revision. I found that with this PCB it was easy to destroy the solder pads when doing desoldering and subsequently resoldering. I completely lost my pads on my IG and a few other pads on the first replacement. I've read that others have destroyed pads on the previous CTH, but with repeated parts replacements. In the end, I had to resolder IG from the top of the board. Perhaps, this is where the bad joint is and is causing my low level hum issue. With my next build, I'm going to be sure to try not to desolder any wiring and hopefully not fry my OB BJTs. Also, I think I'll lower heat on my adjustable heat iron to see if that prevents the solder pads from being damaged.


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## cfcubed

Here is some timely & important part info from user *rds* (thanks!).
   
  Though a lot of work went into this new CTH rev & its BoM, when looking for parts subs (since its last rev circa 2009) by and large we didn't investigate uprating/changing parts values WRT newly available parts.  One of the (minor) compromises in original parts spec involved capacitor choice because of space limitations.
  User rds came up these parts recommendations from a new series of Panasonic caps available @ Mouser that appear very good options:
   

 *C1H, C2H   150u / 25v  # 667-EEU-FR1E151*  (100u likely used in all CTHs to date)
 *C3H   330u / 50v  #  667-EEU-FR1H331L*   (reports are that any 50v 330u or above cap works well)
   
  Although low-ESR caps are not required for C3H, the option above comes from the same new series and has better attributes than BoM 470u choice (other than its lower 330u which has been found sufficient).  Note it remains to be seen if the recommendations above yield any audible improvement or change, so don't fret if you've already ordered parts or assembled your CTH


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## runeight

New BoM posted to website.


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## Mullet

Adding a wire going from the pot to IG worked! No more hum or buzz when touching the RK27 pot! Thanks again cfcubed!
   
  I think I still heard a very very low buzz/hum with a few tubes though. It wasn't noticeable at all with other tubes. Tube heater voltage didn't matter. Some 12v had the buzz, others didn't. The 6v tube I tried out today was silent as well. Must be the particular tube then. Time to test all 15 or so tubes.


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## sachu

I will give up one of my CTH boards.  PM me only if you are going to build this amp in the next month or two. 
   
  Of the 3, i am keeping one, sending one to ujamerstand and one more is going to someone who wants to build this one of these.  
   
  Preference given to someone who hasn't built one of these before. PM me


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## civilmonkey

So, I recieved all my parts from Mouser/Digikey and am pretty excited to build the CTH Rev A.  Unfortunately, I am short one 9.31k resistor (my fault!).  Is there any chance a kind sole can purchase an extra when they place their order and put it in the snail mail for me?  Cheapest shipping from Mouser is $8, that is one expensive resistor   The part # is 71-RN55D-F-9.31K, PM if you can help out, I can paypal over the stamp and part cost.
   
  Thanks in advance


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## sachu

Just order it in from digikey.


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## Bop

I'd say that it would be easy to find 1/8W resistors at a nearby electronics store - say Radioshack, but if you feel like waiting...I can include it in my upcoming order.
   
  An alternative is to use resistors you have in parallel or series and get the resistance you want.  It would increase the power rating as well...


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## cfcubed

Bop- True but the heater circuit resistor values must be very close to their spe'd value & are tombstoned in a tight space. I've a spare 9,3k I offered to send if civilmonkey gets back to me before I leave on a trip (*<< Ha ha, he just did this minute*.
   
  Sachu -  You say just order from Digikey, do they ship for free or like $1 for a $1 part?


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## civilmonkey

Cfcubed hooked me up.  Thanks everyone. Hopefully you will see a photo or two from me sooner than later.


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## Mullet

Digi-Key has first class USPS shipping, which was like $2 for the 2 parts that are needed there as per the BOM. I'd imagine it would be the same for 1 resistor. It's better than the $6 or $8 that Mouser charges for ground shipping.


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## civilmonkey

ahhhh. yes, that would work, but I don't think it's available to Canada.  My only option seems to be Fex-Ex overnight, although to be honest, I didn't complete the checkout process 100%, only to the shipping part.


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## cobaltmute

Digikey is only FedEx to Canada at $8CDN flat rate.


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## BK_856er

Thanks to sachu I have a board on the way to me.  Actually he donated it when he learned that I'm building this up for my brother being deployed to Afghanistan.  Thanks, dude!  
	

	
	
		
		

		
			




   
  My mouser and digikey orders are on the way with expedited shipping.  Hoping to tackle this one asap.
   
  Maybe I missed it in the mega CTH threads, but where can I source some of that nice black perforated material for the top of the hammond case?
   
  BK


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## civilmonkey

I'm told the perf top is standard perforated sheet metal.  I imagine you could find a local metal supply place and buy some.  The option I'm going with is drilling a symetrical hole pattern above each heat sinks and finshing them with black nylon grommets.


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## sachu

Boards are out on their way to Ujamerstand and BK, and one black perf top to mullet.


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## Lil' Knight

Missed the group buy  Anyone has a spare board that you could sell me? Would appreciate a lot.


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## BK_856er

I purchased the following tubes for Project CTH-Kabul:
   
  6CG7 RCA Clear Top
  6DJ8 Amperex Bugle Boy Holland
  6DJ8 Mullard Great Britain
   
  Any others to consider to capture a broad spectrum?
   
  I'm also assembling grub and skeleton DACs for the care package - I'll audition and include only one.  Any creative way to shoe-horn one of those babies into the short Hammond CTH case?  That would be super cool.
   
  BK


----------



## civilmonkey

I have some questions about the mechanical fastening of the PCB and supporting the tube socket.
   
  1.  Given that the PCB can slide foward to backwards, do people use a standoff or something, potentially bolted through the bottom of the case?  Last time I did something like this I just screwed a few small screws in the track which the PCB slides to wedge it in place, but I wondered what other solutions are.
   
  2.  I read most of the previous CTH thread and it seemed like few people support the tube socket.  Maybe I missed a post or so, but wouldn't you be worried about flexing the PCB over and over as tube's are rolled?  I tend to over engineer things, but I would plan on some kind of support underneath the socket.  Thoughts?


----------



## Forte

Quote: 





civilmonkey said:


> I have some questions about the mechanical fastening of the PCB and supporting the tube socket.
> 
> 1.  Given that the PCB can slide foward to backwards, do people use a standoff or something, potentially bolted through the bottom of the case?  Last time I did something like this I just screwed a few small screws in the track which the PCB slides to wedge it in place, but I wondered what other solutions are.
> 
> 2.  I read most of the previous CTH thread and it seemed like few people support the tube socket.  Maybe I missed a post or so, but wouldn't you be worried about flexing the PCB over and over as tube's are rolled?  I tend to over engineer things, but I would plan on some kind of support underneath the socket.  Thoughts?


 
   
  1.  I built mine in the longer Hammond case and put a Bantam DAC in the rear which holds it in place nicely.
   
  2.  Should not be a problem. The board is quite narrow and well supported in the BOM Hammond cases, after two years of almost daily use and constant tube rolling I have had no problems.  If your still worried you could bolt a short nylon spacer to the bottom of the case under the tube to give additional support.


----------



## rds

Quote: 





bk_856er said:


> Any others [tubes] to consider to capture a broad spectrum?


 

  
  I'd recommend Amperex 6922 PQ if you're willing to spend the money.  Another great option that is very affordable are GE 5814a ...if you want to spend some more then RCA 5814a.
  ...and you gotta have at least one actual 12au7...


----------



## BK_856er

Quote: 





rds said:


> I'd recommend Amperex 6922 PQ if you're willing to spend the money.  Another great option that is very affordable are GE 5814a ...if you want to spend some more then RCA 5814a.
> ...and you gotta have at least one actual 12au7...


 


 Thanks for the suggestions.  Quick spot-check shows the PQ to be out of my budget for now.  Is there any significant difference between the 5814a and 5814?  I think I remember reading something in my multi-hour crash course last night, but the memory is fuzzy...
   
  BTW, got all my CTH parts today - wow, that is one impressive bag of parts for such a small amp!
   
  BK


----------



## cfcubed

Quote: 





bk_856er said:


> Thanks for the suggestions.  Quick spot-check shows the PQ to be out of my budget for now. <snip>
> 
> BTW, got all my CTH parts today - wow, that is one impressive bag of parts for such a small amp!


 
  tubes -  IMO the Amperex you already have may have a presentation similar enough to its pricier cousins (PQ, 8416), so if you think you need > the 3 tubes you have I'd go for something different.  This is opinion, but if I had the tubes you do & wanted a 12au7 class tube a bit different I recommend a Siemens circa early 60's.  The chrome/silver plate is a premium variant & my favorite alongside the PQ/BB/8416:
http://www.head-fi.org/forum/thread/398839/a-very-compact-hybrid-amp/285#post_5461087
   
  parts - Yes about 160 in a 3" x 5" space and a pretty tight fit in the small/std hammond.  One reason I was going to recommend against trying to jam a DAC in with it.  Recommend a "cable" DAC  build for that.  After I bundle things I often come around later to wishing I hadn't.  Better/different things come about, etc.  E.g. a couple years ago you'd have been looking @ little cap-coupled DACs instead of the ones you are. 
  BUT it's hard to argue against the great little combo a CTH/DAC makes, so we make our choices


----------



## BK_856er

Thanks, cfcubed - will keep that stuff in mind.
   
  I'm comtemplating upgrading the C4 coupling caps from the get-go if I can get some in time.  I understand the BOM piece is a good performer, but I guess I have upgrade-itus.
   
  What is the pn of the larger square Wima that I see in some builds??
   
  Mouser pn for the BOM piece is 505MKS2.22/11/10 (so tiny!)
   
  [size=11pt]Audience Auricap is 0.22uF / 400VDC 0.5 x 0.6" (~$13/each)[/size]
   
  [size=11pt]Sonicap Gen II is [size=11pt]0.22uF / 200VDC 0.27 x 0.73" (~$3/each)[/size][/size]
   
  BK


----------



## Mullet

BK_856er,
   
  If I was putting a DAC in the same case I'd definitely not use the BOM case or even the longer Hammond case. The longer case is tight enough as it is. However, it depends on I/O components that you choose to use though. If you were using 1/8" jacks and a RK097 on the front instead of a RK27 and 1/4" jack then that would give you more room. Also, if you wanted RCAs that would also cramp things a bit on the back. The best way to do this is go with 1/8" jacks on the front along with RK097. Then skip out on the fuse and RCA jacks on the back. That way you just have a power switch, USB for your DAC, air wired DC jack, and Heater switch. Are you going with 4 heater voltages? That NKK switch takes up a bit of space as well. Overall, if you want to accomplish a lot I would take a look at that case that cfcubed is using for his Fancy CTH. It looks to have space on the sides of the CTH board that would allow for a DAC.
   
  Civilmonkey,
   
  With regards to your worries about the PCB and it needing more support. It fits snuggly in the BOM case. The tube socket is fine too. The only thing that I'm thinking of doing is getting one of those socket savers like cfcubed uses. I hear it's a PITA to change out a tube socket if one goes bad.
   
  Perhaps, Forte can let us know if he thinks a socket saver is required for tons of tube rolling.
   
  I've got a whole list of tubes and thus far I'm liking a bunch of them. Siemens ECC802S, RCA 6CG7 Clear Top, Raytheon 6GU7 Japan, Telefunken ECC82 Smooth Plates, Sylvania Gold Brand 5814A gold pins to be specific. There are tons of others that are good as well. Tonight, I'm auditioning 4 different 4BZ7 tubes. So far I'm liking them the least. They seem to be a little shrill. And the bass seems a tad bit muddy. Perhaps, this is partly due to using my KSC-75s with this amp. I'll switch over to my K701s for comparison.


----------



## BK_856er

Thanks, Mullet.  Will see what I can squeeze in there as far as a tiny DAC goes, and if it won't fit I'll do the "cable" version.
   
  It looks like this mouser Wima would fit in the optional RevA larger 10mm lead spacing for C4:  505-MKS4.22/100/10P
   
  I think I'll pick up a couple to try.
   
  BK


----------



## Mullet

I already posted this in the group buy thread.

Something came up with one of our group buyers. So we have one board available. My only request is that the PCB goes to someone that hasn't built a CTH before. Who ever PMs me first gets the board. Good luck!


----------



## cfcubed

Hey Mullet, how about this guy   He's been asking & think it'd be his 1st CTH *(<<<  And he has one now, so still one more PCB avail AFAIK)*:
  Quote: 





lil' knight said:


> Missed the group buy  Anyone has a spare board that you could sell me? Would appreciate a lot.


----------



## BK_856er

I finished populating the board today and everything is progressing nicely.
   
  - Need to wait for my "special" coupling caps to arrive before power-up.
   
  - My ceramic tube socket is a little larger total diameter than the ones shown on p1, resulting in a small amount of interference with C1R.  Nothing a few minutes with a dremel can't solve.  Is there a preferred tube socket for this build?
   
  BK


----------



## civilmonkey

Quote:


cfcubed said:


> BTW a crafty builder might try installing 120R or 150R R18s plus a DPDT switch that optionally shorts the positions.  Note though the R18s are "embedded" into the OB circuit, so I'm unsure of the impact (if any) of long leads on their pads..


 


 For a test, I was able to put a piece of 26 awg SPC through the top side of the PCB for R18, then gentle wiggle a SIP socket also through the R18 location.  I haven't soldered it yet but that will be my plan.  I can run the wires from all R18 positions to a DPDT as receommended to short the positions.  I'll report back once it's tested out.


----------



## Mullet

Civilmonkey,
   
  Can you post pics of this when you're done so I can see what everything is supposed to look like? I might try and do this for my 2nd build. I'm finding that my in-ear phones aren't liking the BOM R18 100 ohm resistors that much and I could use 150 ohm resistors. I only get the volume up to maybe 7 or 8 o'clock before the volume is too loud. I'm also hearing  some noise and static. I'm leaving the 100 ohm resistors in on my first CTH for good.
   
  BK,
   
  What caps did you get? Wiatrob sent me some of those green Russian PIOs. They look like they might be a pain to solder in. I'm wondering how they compare to the Wimas I'm currently using in my CTH. Not sure if they're the BOM ones because I acquired them from cfcubed.
   
  On another note here's an observation that I noticed. Sometimes when I take 2 fingers, my thumb and middle finger, and rub them along the length of the CTH, I can feel friction or energy. I measured this with my DMM and I'm getting a reading of .007 VDC. After taking the reading the friction goes away then quickly comes back after a minute or so. Interesting...


----------



## Mullet

Also, no more boards left...
   
  Lil' Knight and meltdown100 got the last two.


----------



## rds

Quote: 





mullet said:


> On another note here's an observation that I noticed. Sometimes when I take 2 fingers, my thumb and middle finger, and rub them along the length of the CTH, I can feel friction or energy. I measured this with my DMM and I'm getting a reading of .007 VDC. After taking the reading the friction goes away then quickly comes back after a minute or so. Interesting...


 


  You're probably having charge build up on your case.  It should be grounded for safety, and this will solve the issue you mention.
   
  Here's how I did it:

   
  fyi the other white wire goes to the pot (to stop hum when you touch the volume knob) like so:


----------



## BK_856er

Quote: 





mullet said:


> BK,
> 
> What caps did you get? Wiatrob sent me some of those green Russian PIOs. They look like they might be a pain to solder in. I'm wondering how they compare to the Wimas I'm currently using in my CTH. Not sure if they're the BOM ones because I acquired them from cfcubed.


 

 I got the tiny BOM Wima caps with the initial parts, then later some larger Wima and Kemet (?) along with another order just because they were cheap enough.  Spearately I ordered 400V Sonicap GenII and Auricap units.  Not sure yet what I'm going to install - probably the Auricap.
   
  BK


----------



## Lil' Knight

I haven't got the boards or seen the case but you guys might want to try the Russian FT-3 teflon caps. Stunning performance, build like a tank for dirt cheap price. Look for the 200v ones which are smaller than the 600v. Used them in my tube DAC and they have almost the same performance with the Vcap and Jensen. Didn't really like the Auricap though. Russian PIO caps are also great for the value but somehow they make the sound a lil' slower, which is not my taste. 

I'll use a custom made case anyway so space is not really a trouble for me. Also thinking of putting a GrubDAC to make a small, high performance USB DAC. Any idea on about an easy to switch between RCA and USB inputs?


----------



## Mullet

rds said:


> You're probably having charge build up on your case.  It should be grounded for safety, and this will solve the issue you mention.
> 
> Here's how I did it:
> 
> ...




The weird thing is that I've grounded my case from star ground. I guess ill have to check the connecton one more time. It might be slightly loose. The only difference is that I have my pot grounded to input ground and it seems to be working with regards to fixing that annoying hum. Maybe i should switch it to SG instead.


----------



## forsakenrider

Wow, rds, you really puch those transistors low! i always thought they should be up a bit for heat disipation...


----------



## Mullet

lil' knight said:


> I haven't got the boards or seen the case but you guys might want to try the Russian FT-3 teflon caps. Stunning performance, build like a tank for dirt cheap price. Look for the 200v ones which are smaller than the 600v. Used them in my tube DAC and they have almost the same performance with the Vcap and Jensen. Didn't really like the Auricap though. Russian PIO caps are also great for the value but somehow they make the sound a lil' slower, which is not my taste.
> 
> I'll use a custom made case anyway so space is not really a trouble for me. Also thinking of putting a GrubDAC to make a small, high performance USB DAC. Any idea on about an easy to switch between RCA and USB inputs?




Hrmmmmm, now I'm thinking that I might want to try and find the wima caps I used in my first CTH. I'm not so sold on the Russian PIO caps being that they are "slower". What would be the benefits of going with them over the BOM Wima caps? What exactly does slower mean?


----------



## Lil' Knight

It's just my feeling about the sound. Some might prefer the PIO caps for tube amp, which makes the mids lusher and sweeter but speed is not fast. The green K75 caps are cheap enough so it's still worth trying to see they fit your taste or not. Hard to describe exactly the sound because I'm not really good at writing flowery stuffs. From my own experience, PIO caps like K75, Vitamin Q, Gudeman... make the sound more colored in the relaxing way, while the teflon ones bring up more details and clearer highs.


----------



## BK_856er

Here's my current CTH status.
   
  BK


----------



## Lil' Knight

The board is really cramped. Just wondering if the PCB layout will fit the CMC teflon tube socket?


----------



## rds

Quote: 





mullet said:


> The weird thing is that I've grounded my case from star ground. I guess ill have to check the connecton one more time. It might be slightly loose. The only difference is that I have my pot grounded to input ground and it seems to be working with regards to fixing that annoying hum. Maybe i should switch it to SG instead.





   
       I'm not sure what you mean by star ground since this board has a ground plane.  SG is a point on the ground plane which is connected to the power supply ground.  Also, your case and pot should be grounded to the same point unless your pot is well isolated from the case.  
  
   

  Quote: 





forsakenrider said:


> Wow, rds, you really puch those transistors low! i always thought they should be up a bit for heat disipation...


 

 Yeah... I have my reasons but they're mostly idiosyncratic 
	

	
	
		
		

		
			





   Having longer leads might reduce thermal conductivity to the board, but a 1mm space vs a 5mm space under the transistor won't do anything to increase heat dissipation in my opinion.  In fact if we assume that shorter leads increase thermal conductivity and that the board dissipates heat then short leads would increase dissipation.


----------



## forsakenrider

Good call RDS, and it opens up a little room for Volume pots and jacks! Do you pre bend them or just jam them down in there!


----------



## rds

Quote: 





forsakenrider said:


> Good call RDS, and it opens up a little room for Volume pots and jacks! Do you pre bend them or just jam them down in there!


 


  I usually bend the middle lead only


----------



## cfcubed

Opinion here...
  rds - Yep, good points WRT transistor height... I too always left room under for airflow but whether that is truly a heat-diss. advantage is unclear.
     As far as getting them that low, the PCB is designed for the "triangle" base pin TO92 layout not the in-line one (tech terms escape me  I don't pre-bend, although that may be good to do, I find the leads have enough flex to get them pretty close to the board if you want.
   
  grounds - like rds says but I'd always ground the pot if its not going into grounded metal.
   
  Lil Knight - Yep, as before the board is tight for sure & this PCB rev is better than the last in that regard.  One of the prime CTH goals was a full-featured, through-hole DIY desktop headamp in its 3" x 4.8" space (see 1st "A Very.." thread post).  When you review its features, operating points, SQ as reported by owners, etc. it seems to have met & exceeded its design goals.
   
  WRT C4 coupling caps I've heard most of the usual suspects in CTHs.  This is really IMO but I'd not obsess about this.  Reports say the amp sounds great w/any C4s used to date, but there are subtle diffs amongst them and you can find others' opinions in the "A Very.." & Tube and Tweak threads.  My own experiences & opinion echos those like Lil Knight's above.  Note: There is no reported lack of "crispness" for CTH, so IMO "slower" caps that trim upper-treble a wee bit are something to consider.  But again IMO we're splitting hairs a bit here esp when you consider the many tube-rolling possibilities to get similar effect.
   
  BTW fitting fancy caps is easier using the new PCB rev but keep in mind well-soldered & secured C4s are a must.  Here's my latest, next-to-last CTH buildup (prior board rev):


----------



## Mullet

> I'm not sure what you mean by star ground since this board has a ground plane.  SG is a point on the ground plane which is connected to the power supply ground.  Also, your case and pot should be grounded to the same point unless your pot is well isolated from the case.  
   
  I have SG connected to my case. I assumed SG on the board meant Star Ground. I could be wrong. My pot is mounted to the plastic panels that come with the Hammond case. So it is isolated. However, I was having the hum issue when I was touching the pot. Cfcubed suggested that I loosen one of the screws on my RK27 and connect a lead or wire from that to IG. I just took a piece of wire and connected it from the pot to the wire that goes my G+/IG terminals on the pot to IG on the board. The hum then went away.


----------



## ujamerstand

SG is soft ground. Usually it's isolated from the chassis ground with a ground loop breaker.


----------



## Mullet

Quote: 





lil' knight said:


> The board is really cramped. Just wondering if the PCB layout will fit the CMC teflon tube socket?


 


  Some how looking at pics of this socket online it doesn't like it would fit well. Is it made for pcb mounting? This is what I'm using on my CTHs... http://bit.ly/elHoQV They seem to work well. I still might get a socket saver to prolong the life of the socket.


----------



## Lil' Knight

Yeah, it's made for PCB but the pins are fixed, not adjustable like the ceramic socket. Those in the link looks nice, I'll order a couple of them then


----------



## BK_856er

FYI, the Alps RK097 small pot in the current RevA BOM points to the single-channel version!  I just discovered this while organizing parts to do the casework.
   
  BK


----------



## cfcubed

>  the Alps RK097 small pot in the current RevA BOM points to the single-channel version!
   
  Ack, sorry!  I've said it privately to Mullet/Runeight during the throes of our revising the BoM, building vendor-part-specific BoMs suck  Actually, revising that BoM is one of the things that _almost_ kept this latest GB from happening. 
  Perhaps better all-around to do vendor-part-specific BoMs of this size through shared/community/wiki effort (or not do 'em & just host a "parts list").
   
  I'll alert runeight to this so he changes the spreadsheet BoM.   You'll have to *search for prefix "RK097122" *(e.g. RK09712200MC) *on Mouser or just use Panasonic Digikey alternate *(cheap US shipping as discussed here).


----------



## BK_856er

Thanks, cfcubed.  And thanks also guys for all the hard work making this a reality.
   
  Out of curiosity, what is the compatible range of potentiometer resistance for this design?  The small 50k pots are hard to come by!
   
  Any practical consequences or considerations when deviating from the default 50k unit?
   
  BK


----------



## cfcubed

Quote: 





bk_856er said:


> Thanks, cfcubed.  And thanks also guys for all the hard work making this a reality.  Any practical consequences or considerations when deviating from the default 50k unit?


 
  I'm glad you asked this CTH vol pot resistance question here.  I've used 20k & 50k input vol pots in CTHs and cannot say I hear a difference (esp any that was not possibly attributable to other differences in the builds).  My understanding is that any effect this might have is relative to the source being connected.  IOW how the source reacts to CTH's input resistance (to ground) e.g. prior stage loading.  Perhaps its not as much of a concern as the quality/balance of the pot (because common sources have no trouble driving 10k/20k/50k loads)?


----------



## revolink24

Chris, you built one of these with an RK27, right? Is the case in your Mouser BOM still a tight fit with the RK27, or is it sufficiently roomy?

As someone with only a few amp projects under my belt, I like to have ample room in my case, so I might just get a bigger case and go for standoffs.


----------



## cfcubed

>  Chris, you built one of these with an RK27, right? Is the case in your Mouser BOM still a tight fit with the RK27?
   
  I've only done RK27 w/the BoM "long/longer" case, like many CTHers did, see my pics about a page back in this thread.  But someone recently was able to squeeze an RK27 in the "small" BoM case through some effort (see his post in the build Pics thread a month or so ago? - I posted there commenting on it).  I did RK097 in the "small" BoM case, as many CTHers did, like rds' pics a page or 2 back.


----------



## revolink24

Thanks, don't know how I missed that image the first time through. I have a few 50k RK27s lying around, it would be a shame not to put them to good use. The trouble I have is that the RK27s I have are all PCB mount, so I'll need to be more creative than usual in my wiring, or use a protoboard. The problem with using a protoboard is that I'm not sure it would be an ideal fit, even in the "long" Hammond case.


----------



## civilmonkey

For the socket, I picked up the generic premium gold plated $6 socket at Partsconnexcion: http://www.partsconnexion.com/socket_ceramic_prem_9pin_pcb.html
   
  My question is, what is the typical insertion force?  The socket I recieved takes almost no force to put a tube in and it seems to only 'grab' the tube pins at the bottom 20% of the pins.  That is to say, I feel very little insertion resistance until the very last 3 mm or so.  Is this typical?  I have a socket saver, and getting the tube into that feels much more like I would expect, with resistance from start to finish.  My only experience with tubes is from the Little dot MK III, and it takes must less force on the socket I bought than that amp.
   
  Thanks


----------



## Mullet

Quote: 





revolink24 said:


> Thanks, don't know how I missed that image the first time through. I have a few 50k RK27s lying around, it would be a shame not to put them to good use. The trouble I have is that the RK27s I have are all PCB mount, so I'll need to be more creative than usual in my wiring, or use a protoboard. The problem with using a protoboard is that I'm not sure it would be an ideal fit, even in the "long" Hammond case.


 


  I wouldn't even try putting a RK27 in a smaller standard BoM case. It's tight enough as it is in the longer case. I thought all RK27s were PCB mount -- at least the one that both Tangent and Amb sell.
   
  Quote: 





civilmonkey said:


> For the socket, I picked up the generic premium gold plated $6 socket at Partsconnexcion: http://www.partsconnexion.com/socket_ceramic_prem_9pin_pcb.html
> 
> My question is, what is the typical insertion force?  The socket I recieved takes almost no force to put a tube in and it seems to only 'grab' the tube pins at the bottom 20% of the pins.  That is to say, I feel very little insertion resistance until the very last 3 mm or so.  Is this typical?  I have a socket saver, and getting the tube into that feels much more like I would expect, with resistance from start to finish.  My only experience with tubes is from the Little dot MK III, and it takes must less force on the socket I bought than that amp.
> 
> Thanks


 

 I bought that ceramic pcb mountable socket that I linked to a few posts back. Insertion force seems reasonable and the grip doesn't seem to be any worse after rolling tubes about 50 to 60 times already. Like you, I bought a socket saver or two knowing that I'm going to be doing a lot more rolling for the life of this amp. I don't want to take any chances having to remove and replace a bad socket. I hear it's not a fun process.


----------



## revolink24

mullet said:


> I wouldn't even try putting a RK27 in a smaller standard BoM case. It's tight enough as it is in the longer case. I thought all RK27s were PCB mount -- at least the one that both Tangent and Amb sell.
> 
> 
> I bought that ceramic pcb mountable socket that I linked to a few posts back. Insertion force seems reasonable and the grip doesn't seem to be any worse after rolling tubes about 50 to 60 times already. Like you, I bought a socket saver or two knowing that I'm going to be doing a lot more rolling for the life of this amp. I don't want to take any chances having to remove and replace a bad socket. I hear it's not a fun process.





I'm pretty sure they are all PCB mount, I've never seen any different.

And yes, replacing sockets is a pain. I ruined a board once doing that.


----------



## BK_856er

Got my special coupling caps today.  Here's how they compare visually.  One of the GenII units is way out of spec and will need to go back.
   
  BK


----------



## Mullet

BK~
so which ones are you going to go with? I decided Im going to stick with the Russian PIOs, which are what cfcubed used in his last build -- pictured a few posts ago.

Guys, I'm still trying to wrap my head around how ground works in this amp and why certain jacks need to be isolated and why others don't. Can someone explain in a very simplistic manner how all of this works together? The different components seem to be input ground, output ground, chassis ground, and soft ground. What about floating ground or vitual ground? My head is spinning!


----------



## BK_856er

Quote: 





mullet said:


> BK~
> so which ones are you going to go with? I decided Im going to stick with the Russian PIOs, which are what cfcubed used in his last build -- pictured a few posts ago.
> ...


 

 I decided to go with the Auricap.  Bit of a pain to install, but I think it worked out OK.  Needed to trim down the wire diameter to fit the board holes, cut to length, position, etc.
   
  BK


----------



## Mullet

BK~ Looks great!
   
  I have a few goodies that I would like to offer up to anyone involved in the group buy. First and foremost, I'm offering up 2 or 3 perf boards. They might or might not come with grommets because the holes will be different sizes and I'm not sure what I have will match. They will be in silver and black. The black needs to be stripped of paint and re-painted or possibly not. Whoever PMs me first gets one of them for just S&H. The second goodie that I have are four 12AU7 type tubes. All NOS. One RCA 5814A, one RCA 6189, one Sylvania 5963, and one Sylvania 6189. I'm offering them all up for $10 plus a few bucks for shipping and handling. Finally, I have a matched pair of NOS Siemens ECC82 Silver/Chrome plates that I'm going to be putting up in the For Sale forums if I have no takers. I figure I'd offer them up here first. They are best described as very analytical or accurate. Awesome with AKG701s and Jazz or Classical. I've only popped each of them in once to test them out. I'm going to be asking $140 shipped for the pair or $70 for one. I'm thinking this is a great deal being that they go for way more on Fleabay. They really are one of the best 12AU7s. The only pic I have for now is of the Siemens chrome plates. So here goes...


----------



## civilmonkey

My board is completed but not quite working.  Green / red LED works as expected and I started the trouble shooting, but it's late and I have to work tomorrow!  Which tube pin is TB+?
   

 Measure between OG and SG. This should be very close to 12V. If it's not there might be a problem with the TLE2426 or with one of the devices in the rail splitter.
  12.11V
   

 If the OG measurment is good, measure OL and OR. They should also be very close to the voltage at OG. If they are the buffers and splitter are working.
  both 12.11V

 Set the heater switch for the heater voltage of the tube you want to insert. (no switch, 12.6 volts for 12AU7 tube)
 Insert the tube and turn on the amp again.
 Look for smoke. If there isn't any then . .
  no smoke 
   

 Measure TB+. It should be between 95V and 105V.
  what is tb+? 
   

 If TB+ is ok, measure pins 1 and 6 of the tube socket. These should be approximately 80V. If they are, and if the previous measurments are correct, then your amp is ready to go.
   78 volts at pins 1 and 6 measured against SG.
   
  Any thoughts?  I'm 100% sure that diodes are oriented correctly.  I'm off to try a different tube.
   
  Thanks


----------



## Mullet

TB+ is the hole by C10P. Measure SG to TB+. Hope that helps...


----------



## cfcubed

Quote: 





civilmonkey said:


> My board is completed but not quite working.  Green / red LED works as expected and I started the trouble shooting


 
  I didn't catch what is not working with your amp... Did you mean the e12 LED is not working/latching?
   
  I'd not worry about TB+ as that's HV & your 78V readings are good.  And your 12.X readings look good too.  If everything looks good (all Vs *including heater - pins #4 / #5*) but it doesn't go green I'd try these:
  1)  try amp w/load (test headphones).  If the amp is very close to latch sometimes this does it.
  2)  try different tube, but I'd bet this doesn't help,
  3)  try BoM box caps in C4 positions.  There has been occasional trouble w/big, fancy caps there.  We should say "*start with BoM C4 caps first*".  E.g. I'd a perfectly working CTH that when I switched in V-Cap TFTFs would not latch.


----------



## civilmonkey

Quote:


cfcubed said:


> I didn't catch what is not working with your amp... Did you mean the e12 LED is not working/latching?


  Sorry, I was not clear at 11pm last night; there is just no sound and loud buzing.  The e12 LED turns green and stays green.  I put a different tube in and the LED alternates between green and red.
   
  Quote: 





cfcubed said:


> 3)  try BoM box caps in C4 positions.  There has been occasional trouble w/big, fancy caps there.  We should say "start with BoM C4 caps first".  E.g. I'd a perfectly working CTH that when I switched in V-Cap TFTFs would not latch.


 

  
  I found TB+, not sure why I couldn't last night.  So TB+ to SG is 105 volts and all checks test out.  For C4, I have some obligatos on long leads there.  I'll put in the bom c4.  That is a good idea and hopefully the fix.


----------



## cfcubed

Quote: 





civilmonkey said:


> there is just no sound and loud buzing.  The e12 LED turns green and stays green.  I put a different tube in and the LED alternates between green and red.


 
  Switching to BoM caps _may _fix the e12 latch cycling but not likely any audio problem(s) like buzzing.  Still not a bad idea to get to std BoM baseline C4s to eliminate that variable.
  I've never had anything like a moderate/loud buzzing problem w/CTH.  Would re-check wiring esp WRT grounds & grounding.  And re-check for solder bridges, assume you've washed solder flux/resin off (I use 99% alcohol & tooth brush).
  Also remember 24VAC "floats" having no ties to any grounds, but I bet you knew that
   
  I've had low-level/soft buzzing when amps are loosely wired up on bench in PCB vise w/lots of 60hz source close by (lights, soldering iron, etc).
   
  BTW I've edited/bolded a bit of my prior post.


----------



## civilmonkey

Quote:


> Would re-check wiring esp WRT grounds & grounding.  And re-check for solder bridges, assume you've washed solder flux/resin off (I use 99% alcohol & tooth brush).



   
   My pot was wired wrong; it is correct now.  No solder bridges, I checked pretty carefully the first time around.  Yes, board was scrubbed with 99% isopropyl and a toothbrush.
   
  I ran through the initial checks again.  I still have 12.11 volts at OG,OL and OR. TB+ is 105 volts.  
   
  What has changed is that I now have 105 volts at Tube pins 1 and 6 (previously was 78 volts at each), and at heater pin #4, I have 0 volts which should be 12.6.  I'm noting that these voltages are without a tube installed. 
   
  At heater pin #5 I have 12.6 volts.  I'm pretty confident that I had correct heater voltages previously, so I wonder is someone messing up the grounds fried something.
   
  Hopefully nothing major...?


----------



## cfcubed

Make measurements w/tube in.  Heater voltage is _between_ pins 4 & 5 and 12.6v is fine for 12.6 heater switch position.  Tube pins 1 & 6 can only read properly (about 75v->85v) with tube in.
   
  So if you repeat the voltage measurements you did before with tube in & they are fine is there still something wrong w/the audio?


----------



## civilmonkey

We are close.  With a tube in, pins 1 and 6 are 78 as before, voltage drop between 4 and 5 is 12.6 volts.  The amp wouldn't latch, so I replaced my Obbligatos with bom c4, the amp latches but alternates between on and off.  
   
  Something I probably should have mentioned is that because of  the sloppy socket I received, I have another on air wired (on as short as leads as possible).  Partsconnexion has mailed me a new one, so a new socket is on the way and hopefully that solves everything.  When the amp was latched, music was playing for sure.
   
  You guys must shake you head at folks like me.  'Oh, I forgot to mention, I air wired a tube socket'  Hah.  Hopefully the new PCB mounted one fixes any remaining issues.
   
  Thanks for the help, I'll report back once I have the new socket in.


----------



## cfcubed

Tonight I had to air-wire a tube socket for the 1st time & my CTH was fine with it:
   
  .
   
  First time I tried using clear casting resin too... Should have been my 2nd time using it as I learned what sticks to what  And that it shrinks as it cures, pressing into any sockets not very well sealed in advance.
  Always learning.,  The air-wired tube is temporary of course, a socket-saver will give its life & be epoxied into the recessed tube cavity.  Other than that its working well.


----------



## Mullet

cfcubed -- what happens when you need to crack that thing open for some god forsaken reason? Looks cool though.


----------



## cfcubed

Quote: 





mullet said:


> cfcubed -- what happens when you need to crack that thing open for some god forsaken reason? Looks cool though.


 
  There will be no fixing it of course  But there's no reason to expect it to fail esp w/newer BoM revisions.  Would make an interesting paperweight if it was to stop working
  Was going to just encase an unpopulated PCB but then two things happened; someone wanted my spare PCB & it seemed we were needing a 2nd fast build-out to proof the new rev.
   
  BTW if I was to do it again I'd get it right   There were only 3 key mistakes; incorrect mold material (used release but resin fused to it), not using proper sealant (e.g. epoxy?) on parts that could be invaded, doing a 1"+ layer instead of building up thin layers (e.g. 1/4").  Maybe if I ever build a cable DAC I'd give this another try.  BUT it's not a recommended case design


----------



## civilmonkey

That's a neat case.  I was thinking of an acrylic or plexi glass top on mine.  Nice to hear the air wired tube is working.  I'm going to try my air wired tube with thicker gauge and shorter wire to see if that get's mine to latch.  I still plan on PCB mounting a socket once it arrives in the mail, but it would be interesting to see if I can get the air wired tube to work properly.


----------



## Jeroen

Quote: 





cfcubed said:


> >  Chris, you built one of these with an RK27, right? Is the case in your Mouser BOM still a tight fit with the RK27?
> 
> I've only done RK27 w/the BoM "long/longer" case, like many CTHers did, see my pics about a page back in this thread.  But someone recently was able to squeeze an RK27 in the "small" BoM case through some effort (see his post in the build Pics thread a month or so ago? - I posted there commenting on it).  I did RK097 in the "small" BoM case, as many CTHers did, like rds' pics a page or 2 back.


 
   
  I did the small case with a RK27. It will only fit if you mount the components on the front right side on the bottom side of the pcb. Caps need to be mounted flat on the pcb, the opamp dead bug style, transistors reversed, etc. It is doable, but only if you have a bit of experience.
   
  My CTH has been working well and I have not been able to notice any ill effects from bottom side mounting the components.


----------



## civilmonkey

So,
   
  My socket is no longer air wired, all voltage checks, check out (12.1 volts at og, ol, or, 78 volts at pin 1 and 6, 105 volts at tb+, 12.6 volts between pine 4 and 5).  I have bom c4 caps.
   
  Two differences from stock:
  1.  Right now R18 have SIP sockets, each also with long leads, the intention being to allow bypassing them once I hook them up to a switch.  R18 is current 121 ohms.
  2.  I have a 50k ebay knock off DACT right now
   
  The amp will latch briefly, then unlatch, and back and forth.  This happens with and without headphones plugged in.
   
  I will check the values soldered on the board carefully to make sure there are no errors, but in the meantime, anything I should be looking for?

 I tried with 2 seperate 12au7 tubes.
   
  EDIT:  I just realized I do not have a lead from IG to the PCB - I'll try this as well and report back.
   
  Thanks


----------



## cfcubed

Not sure about long leads on R18s.  You may check the actual buffer offset that's causing the relay trips by measure OG vs the channel input pins on the relay.  I'd tack little wires there for the test.
  Maybe IG -> PCB will help.  Also consider searching orig "A Very Compact.." thread for _cycle,   cycling,   latch_  for other idea.s


----------



## civilmonkey

Quote: 





cfcubed said:


> Not sure about long leads on R18s.  You may check the actual buffer offset that's causing the relay trips by measure OG vs the channel input pins on the relay.  I'd tack little wires there for the test.
> Maybe IG -> PCB will help.  Also consider searching orig "A Very Compact.." thread for _cycle,   cycling,   latch_  for other idea.s


 

  
  IG -> PCB definitly helped.  The amp lives and plays music quite nicely! The latching is a little finicky right now.  Right now, the long wires exist, but are not connected to anything, so the amp is works (gentle hum) with my ER6's.  I haven't try anything else yet, but with R18=120 ohm, if I brush the amp or anything like that it'll cycle off, but if I don't touch it, it plays fine.  I had the pot grounded to IG, and it made it worse so that anytime I touched the pot it latched off.
   
  I will play with R18 values to see if I can get the amp stable.  If so, then I'll test the bypass setting after.
   
  How much does actual temperature affect the latching?  If the tube can't get warm enough will that negatively affect it?  I ask because I'm working in my garage and it's maybe 0 to 5 degrees Celcius.
   
  Thanks very much for your help cfcubed!


----------



## cfcubed

>  anytime I touched the pot it latched off.
   
  The only time I've experienced this is when I'd a static charge & by touching something released the charge into a circuit.  Guess it could also come from the live circuit building up a charge & you grounding it by touching.  Either way I'd expect the problem to go away when boxed up & properly grounded (pot, case to SG/IG).
   
  >  How much does actual temperature affect the latching?  If the tube can't get warm enough will that negatively affect it?
   
  I'd not think you have to worry about this.  Would think hot environs would be worst than cold ones.
  BTW WRT ER6s I'd not expect CTH to be at its best w/sensitive IEMs or inefficient 600R+ impedance cans (as I posted earlier).


----------



## civilmonkey

Quote:


cfcubed said:


> > Either way I'd expect the problem to go away when boxed up & properly grounded (pot, case to SG/IG).


 
  Just to confirm, Pot and Case are grounded to both SG and IG, i.e., tied together?  On the wiring diagram I see Pot to IG and Case to SG, but in this thread from a picture earlier I see IG and SG tied together.
   
  EDIT:  As indicated by cfcubed, the problem went away when boxed up and properly grounded!  I tied Pot (IG), PCB (IG), and SG together, and bolted then all to the bom case.  No latch problems anymore.  So for my CTH, latch cycled until it was cased up. 
   
  Also, as indicated, the CTH unlatches with DT 880/600 ohms with heavy bass.  With RE0's there is a slight hum but it's not too bad.  Both were tested with R18=120 ohm.  As the DT880's are my main headphones, I have bypass wires on leads at R18 to test out.  I'll let people know how it works once I've had a chance to test.


----------



## Mullet

The way I have it is this...
   
  I have two RCA jacks. Their respective ground wires come into G+ and IG. Then I have a wire that goes across both terminals and goes to IG on the board. At first, I had problems with the amp buzzing when I'd touch the pot. Cfcubed suggested that I unscrew one of the screws of my RK27 and tie a wire from that to IG. I did just this and the buzz went away. I've also read via a post from rds that you can run a wire to your chassis from your pot and it should get rid of the hum as well. Never tried it so I don't know how it works. I'm in the camp of people who has been doing a bit of DIY for a while now, yet still doesn't really *get* the ground thing yet. I get the basic idea, but that's about it.


----------



## civilmonkey

Thanks Mullet.  The amp works and I have tied POT,IG,SG all together.
   
  I sanded the top panel with 150 grit sanding disks (needed 2 altogether) using a random orbit sander and it turned out quite nice.  I'm not completely happy with the hole layout but that's what I get for rushing / not measuring anything.   All in all it looks pretty good I think.  Inside pictures will get posted once I fix the birds nest of wires inside!


----------



## civilmonkey

I wasn't sure if I should just edit my post above, but I am considering my CTH 95% done. They last item is to replace the cheap linear 50k pot with a log 50k. I tested bypass wires on R18 and...... It works! I could detect no differences in SQ or distortion.

 Base case: BOM C4's, 120 ohms at R18 positions. Moderately heavy bass music (Orange Sky - Alexi Murdoch) at normal listening volumes causes CTH to unlatch
 BOM C4, bypass wires were 6" long each. Soldered bypass wires together, turned on amp and it latched. Played bass heavy music with DT880's. At more than satisfactory volumes, my CTH is fine with no distortion. Played Orange Sky again, LCD Soundsystem - Daft Punk Is Playing at My House, and others. Volume wise, I had the CTH at volumes which would cause hearing loss and made my ears tingle. If you really crank it up, distortion and unlatching kicks in.*  EDIT:*  The CTH does occasionally unlatch with the DT880's when I crank it up for a really good song.  In general, I find this a great amp with the DT880 and I love the sound, one just needs to use reasonable volumes*.*
 Replaced C4 with 0.22 uf MultiCaps from Partconnexion. Same result as #2, amp sounds great with DT880's. As an aside, I noticed an immediate improvement with the multicaps. To me, more details and a definite wider sound stage. I have not heard the amp with any other C4's except BOM C4s.
 Shortened bypass wires to around 3" and wired them to a switch on the front panel. Same result as #3, amp sounds great with DT880's.
   
  Final set up is R18 = 150 ohms, with a DPDT to bypass each position. I have tried both my RE0's and DT880's, and find both very great. However, I feel the synergy between the 880's and CTH better than the RE0's but a) I haven't tried many tubes, b) The linear 50k pot severely limits usable range on the POT and c) I find the RE0’s improve with amping, but you don’t need much amping. I replaced the polished top (previous post) with a clear lexan top. Material was from Homedepot. I cut it down to size and used a router with thin the length wise edges so it would fit.
   


 

 


   
  All in all, I'm very happy with this amp, and my DT880s sound great.  The only other Tube amp I can compare this to is a my Little Dot MKIII amp.  In very general terms, and with the tubes I own for each amp, the MK III is more relaxed and sounds more 'tubey' where as the CTH is more detailed, more punch, and less 'tubey'.  I guess this makes sense given that the CTH is a Hydrid amp. 
   
  I have built multiple SS amps (typical progressing from CMOY, to perf board 'maxed' CMOY, PIMETA, MINI 3, etc) and a few Alien USB DACs.  This was by far the hardest build yet.  If this is an intermediate level build, I *might* now barely be considered intermediate!
   
  Thanks again to all who made the group buy possible and the support in this thread


----------



## cfcubed

Thanks civilmonkey for the detailed feedback & great its working well & you're liking it.  So you were able to accommodate two very different headphones w/the R18s/R18 bypass.
  Nice too that you can view inside & less of a one-way street than making it one solid block of plastic 
  I wonder if you find there is enough ventilation esp. for the 24V reg... Are there any holes in the bottom?


----------



## civilmonkey

Originally Posted by *cfcubed* /img/forum/go_quote.gif


> I wonder if you find there is enough ventilation esp. for the 24V reg... Are there any holes in the bottom?


 
   
  I wonder about that too.  There are no holes in the bottom, but I thought about adding some last night and it wouldn't hurt.  My multi meter has a temperature probe on it and I thought it would be a neat test to run the amp for a while and measure inside temp near the 24V reg.  Perhaps if I manage to, I'll test before holes on bottom and after.


----------



## Lil' Knight

Just got the PCB today. What a cramped board it is! Now I have to find time to source for parts.


----------



## BK_856er

Quote: 





lil' knight said:


> Just got the PCB today. What a cramped board it is! Now I have to find time to source for parts.


 


 We prefer the term "compact"  
	

	
	
		
		

		
		
	


	



   
  It's an enjoyable build - have fun!
   
  BK


----------



## Lil' Knight

Sure it is 

Anyone knows the part number for the blue Dale resistor? Thinking of using it, the brown one is too 'boring'


----------



## ujamerstand

I remember those are Dale RN50C. I have them in the gamma-2 and the alpha20 buffers. Oh, and yeah, this IS a cramped board!


----------



## Lil' Knight

Yeah, that are also the ones in the Grub DAC. I've just taken a look at the specs, the wattage is only 1/20w but the voltage rating is 200v. Would it be fine to use?


----------



## civilmonkey

cfcubed said:


> I wonder if you find there is enough ventilation esp. for the 24V reg... Are there any holes in the bottom?


 

 I ran a small temperature test to assess interior temperatures. I checked a few specific locations for a short period of time, only one trial, a low to moderate volume, etc.  The entire aluminum side panels got quite warm, around 35 deg C as well.  Given the variability of each setup, the following may not apply to your CTH.
   
  For my setup, here are the results.  I think based on datasheets, 75 C is okay (someone please correct me if I'm wrong).  Still, lower temperatures mean more stable components and longer life, so I will add a few holes in the bottom and maybe some on the top panel to see if that affects anything.
    



   
  Notes:
  - Tested on April 11, 2011 with DT880/600 ohm, R18=0 ohm, tube was RCA Cleartop 12au7
  - Listening volume was moderate.  Qualitatively, louder than normal conversation (I would not have heard someone talking to me while listening), but less than a telephone dial tone.
  - Venting consists of space around tube (29 mm dia ID, minus 22 mm ID of tube saver) and 4, 7mm diameter holes above 24Vreg.
  - Beside HS = 2-3 mm away from HS fins, approx 10 mm down from top panel
  - Top of HS = temperature probe pushed against top of heat sink
  - Inside case temp = In front of tube, approx halfway between PCB and top of panel
  - I think the slight dip in temperature on the second last measurement is due to less bassy music (Alan Parsons Project came on for a song).


----------



## Forte

Holes in the bottom will help a lot, Hot air will escape much easier if there is a way for fresh air to enter the case.
  A dozen 3/8" holes spread across the base of my CTH made a noticeable difference.


----------



## stringgz301

What's the timing on production boards?  Thinking of building one with a grubdac in the same case.  Has anyone tried this before?


----------



## Mullet

This was the last run for the CTH  There was a recent group buy for this final run. Unfortunately, you missed out on this badass little amp.


----------



## Mullet

Civilmonkey, can you further explain how you had the bypass wired? I'm interested in doing something similar with my current build. I'm in the beginning stages, stuffing resistors. The only difference is that I'd maybe do 100 and 150 ohm resistors instead.
   
  With regard to buzz... Here's an interesting observation... I noticed that with 12v tubes in general I'd get a slightly noticeable hum with my Senn HD650s. If I used 6v tubes... no noticeable hum. Then I pulled the RCA jacks from my CTH and noticed the hum go away with the 12v tubes. Hrrrmmm perhaps it's my Gamma-2 DAC that is causing the issue. The Gamma-2 can either be powered over USB or external power. So I pulled the external power and went with USB power only. Now the CTH/Senn HD650 combo is completely hum free. Either something is up with the Gamma-2 or I have a bad power source. Go figure.


----------



## BK_856er

I found another problem with the BOM tonight.
   
  Got my sweet little TKD volume pot - absoutely perfect fit.  Drilled all my casework holes to perfection.  Coming together very nicely indeed and just about ready for power-up.
   
  Test fit my AC adapter to the PCB connector.  No amount of force would make it work.  What??  Back to the parts order.  The Excel BOM listing correctly shows a 2.1mm jack, but the "import" page has a 2.5mm jack instead.  ARGH!  I can't believe I didn't check this earlier.
   
  I suppose the best solution in my case is to refit the AC adapter with a 2.5mm plug, as opposed to desoldering the PCB connector.
   
  BK


----------



## ujamerstand

BK, which TKD pot did you get? the 601 or the 2511?


----------



## cfcubed

>   The Excel BOM listing correctly shows a 2.1mm jack, but the "import" page has a 2.5mm jack instead
   
  Oops.  I'll forward this correction to runeight.   Do we know if Mullet's shared Mouser BoM is correct?
  The 3-pin PCB-mount jacks can be a bear to remove if they are soldered in correctly, but I'd be tempted to swap it (I've done so before).  Seeing that shrink-wrap on your adapt cable could bother you someday
   
  >  There was a recent group buy for this final run
   
  It may be possible there is enough interest (& associated prodding someday to get runeight to do another run of these Rev A PCBs.  
  Again, incl. BoM vendor parts # revisions, esp where our error rate must be like < 1%, is one more brick in the wall against future GBs.


----------



## civilmonkey

mullet said:


> Civilmonkey, can you further explain how you had the bypass wired? I'm interested in doing something similar with my current build. I'm in the beginning stages, stuffing resistors. The only difference is that I'd maybe do 100 and 150 ohm resistors instead.


 
   
  - From the topside of the PCB, I wiggled 24 AWG silver plated copper wire from navships (ebay) and a SIP socket into each R18 location, so in total 4 wires / 4 SIP sockets.  I used the SPC because of the teflon coating, I didn't want to lose any insulation from melting when soldering and create any accidential bridges on the top side. 
  - It was a pain (very tight fit) getting the SIP and 24 AWG into the PCB.  My technique was put the wire in the PCB location (don't twist or tin the wire), then with a pair of fine needle nose pliers, gently wiggle the SIP into the PCB.  I bent a few SIP pins, so those went into the trash.
  - The advantage of the SIP is that you want try different R18 values.  I started with 120, but in the end went to 150 for my IEMs.
  - I used 24 AWG because a) it's the only teflon coated wire I had besides from 30AWG which I felt was too small, and b) I liked that it was the biggest I could fit along with a SIP socket.  I didn't know the effect of load leads at R18 would be, and thicker wire should lead to less resistance.  I would have been happier (mechanically) using 26 AWG because I wouldn't have had to force the SIP socket into place.
  - Mechanically, because of tight fit and use of slight / moderate force to get the SIP socket in, I wouldn't want to mess around with replacing resistors too many times in the SIPs.  Each time bends the SIP pin bends / moves a little (at least, when I do it).  When I did, I was careful to support the SIP socket while inserting / removing new resistors.
  - I started with around 6-8" of wire are each R18 location to make sure I had enough for wherever my DPDT was going to go.
  -From there, the 1st test was solder the R18L bypass wires together and R18R bypass wires together for a test (See my 1st post).
  -Once I knew it worked, wires were shortened to around 3" as I put the DPDT switch on the front panel.  R18L went to 2 of the 3 poles on one throw of the DPDT switch, and R18L went to the same 2 of 3 poles, but other throw of the switch.  So, when the switch is open, L/R bypass wires are not connected, when closed, R18L / R is bypassed by wires.


----------



## BK_856er

Quote: 





ujamerstand said:


> BK, which TKD pot did you get? the 601 or the 2511?


 


 I'm using the short case, so it's the small 601 pot, which is exactly 16mm cubed.  There is exactly enough room for it to fit between the front right caps and the bottom of the top groove for the perf top (a few more mm clearance if you use the hammond slide in cover due to its offset design).  I'll try to grab a pic in a day or two.  It's a nice pot.  I had to go with 10k, but 50k is apparently available if you order from asia.
   
  BK


----------



## stringgz301

I'd be happy to lead-up another group buy.  Any idea how many it takes for an order?


----------



## Mullet

I think we needed a minimum of 20 boards but ended up getting 40. I'd contact runeight to see if he wants to do another run. alex@cavalliaudio.com You'd pay for the up front cost of 20 or so boards plus shipping. Doing the group buy wasn't hard. The hardest part was going to the post office a few times. There are numerous PMs that you'd have to do with regards to keeping in contact with potential group buyers.
   
  Good Luck!


----------



## BK_856er

Quote: 





cfcubed said:


> >   The Excel BOM listing correctly shows a 2.1mm jack, but the "import" page has a 2.5mm jack instead
> 
> Oops.  I'll forward this correction to runeight.   Do we know if Mullet's shared Mouser BoM is correct?
> The 3-pin PCB-mount jacks can be a bear to remove if they are soldered in correctly, but I'd be tempted to swap it (I've done so before).  Seeing that shrink-wrap on your adapt cable could bother you someday
> ...


 

  
  I found 2.1 and 2.5mm PCB-mount power jacks locally today, as well as two different styles of 2.5mm adapters, so I'm covered for various scenarios when I sit down to address the power entry.
   
  The BOM was very solid thanks to the hard work of you guys.  The little speedbumps that I encountered were due to my choice of the shorter case and the fact that I apparently did not verify the "ancillary" parts specs until late in the game.  The total parts list is indeed a long one!
   
  I'd be up for building another one of these if stringgz can pulll together a GB.
   
  BK


----------



## lundervold

I'm in for 3 boards if we get another group buy together.


----------



## jdkJake

If there is another group buy, I am in for one.


----------



## BK_856er

Here's the small TKD pot installed.
   
  Resolved my PCB-mount power jack.  Needed to desolder it and replace it because I messed up the original one trying to make the 2.1mm AC plug fit last night.
   
  BK


----------



## cfcubed

BK - That is a nice fit for that pot & a nice pot it is. 
   
  As far as a GB I guess I'll ping runeight about what that would take.  He's quite busy right now as you can see from cavalliaudio.com


----------



## Mullet

BK~ that is indeed a nice looking build. Your bro is gonna be stoked. 

Im tempted to do something similar to civilmonkey with regards to switching the R18 resistors. The only difference is that I'd most likely not use SIP sockets because I'd be only using 100 and 150 ohm resistors. I still haven't decided on whether I'm doing this or not.

The other thing I'd want to do is use higher rated L1H and L2H so I can use a 6n6p tube among others. If anyone has spares or wants to trade for the BoM versions please PM me.


----------



## Halvor

Finally I'm getting around to build my CTH, so I have a couple of questions.
   
  - How large transformer can be used before you can't tell the difference?
   
  - I will probably have plenty of room left in my case. Will this amp benefit from bigger/additional heatsinking?
   
  Thanks


----------



## civilmonkey

No one has weighed in yet, so here are my thoughts.
  


> - How large transformer can be used before you can't tell the difference?


 
  Use the BOM 24VAC adapter.  The price is reasonable, and it's sized to work with the CTH.  I don't think a larger transformer will yield any gains.  Most people report (myself included) that with most headphones there is no hum or hiss.  Sensitive phones (e.g IEMs) do have some hiss.  With my DT880's (very hard to drive headphones), there is more punch and volume than I personally need.
  


> - I will probably have plenty of room left in my case. Will this amp benefit from bigger/additional heatsinking?


 
  My understanding is that typically, the cooler some components run, the longer the life.  How much difference there is I don't know.  I'm pretty sure I have seen on some (not all) capacitor electrolytic datasheets estimates of life and discussion of reduced life with elevated temperature.  Think laptops, they burn out much more frequently than a desktop computer which typically has better cooling.  Still, saying that, I don't think I have come across a post of anyone with a failed CTH due to temperatures, but I could be wrong, the original thread is looooong, and I might have missed bits here and there.


----------



## cfcubed

If you stick with target tube draws (< 600ma) then IIRC the amp draws 0.6A -> 0.75A (lower side for usual 300ma heaters), and you need not heatsink the LM2595.  The 24V reg does get hot & must be heat-sinked. And there should be adequate case ventilation.  So 0.8A+ 24VAC adapters are fine, unless you are shooting for higher-draw tube heaters...  In that case 1.0A+ 24VAC adapter (BoM one) is better & a small heatsink on the LM2595 makes sense.
   
  The amp's draw is relatively constant so higher-current adapters should not yield a difference/benefit (but will not hurt anything either).
   
  If you had plenty of room & felt like doing it a larger-than-spec'd heatsink on 24V reg (or two BoM ones back-to-back on the reg) could be considered.  As well as using the small heatsink on the LM2595.  But again, for the recommended use cases this is not necessary.


----------



## Mullet

I agree that the BOM 24 VAC adapter is the one to go for. There are a few tweaks that can be found here as well as the "Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread" that enhance the amp. The first and foremost are different C4 bypass caps. There are several out there that people have tried. I'm going to use those green Russian paper in oil caps for my next build. Then there is the option of using a switch and possibly SIP sockets to use different R18 resistors for headphones of varying impedance. Civilmonkey did this tweak. Finally there is the option of using higher rated amperage on your L1H and L2H to allow for the capability of using a Russian 6N6P or 6N30, which draws more than the recommended current (600mA) at 750mA+. It looks like cfcubed is saying you can get by with the BOM ac adapter for higher current tubes. The question is do you really even need to upgrade L1H and L2H for this? I've read that some builders in the past upgraded and I think some didn't and still used the 6N6P without a problem. The definitive answer is that you have to have ICH heat sinked when doing this.
   
  With regards to heat I'd say just drill a ton of holes in the case. A few on top near ICP and ICH. Then maybe 6 to 8 on each side and finally one or two on the bottom. Of course, if you can source some perforated metal then you don't need to drill any holes other than the tube hole. I found a metal hole punch works best for this. The only caveat is they're quite expensive and you need to have the right size for your hole.


----------



## Halvor

Thanks for the answers guys! Seems like there is no need for "overkill". But I would still like to stick with a toroid and have everything integrated, rather than a wallwart. So one rated 1A and 24VAC would be fine?


----------



## cfcubed

>  It looks like cfcubed is saying you can get by with the BOM ac adapter for higher current tubes.
   
  Yes, again *IIRC *from my CTH current draw measurements from 2 yrs ago or so.  It is a simple matter for builders to use a panel mount jack & measure their CTH's adapter draw under various conditions.  Just make sure your ammeter can deal with 2A+ to handle any instant/power-on draw spike.
   
  >  The question is do you really even need to upgrade L1H and L2H for this? I've read that some builders in the past upgraded and I think some didn't and still used the 6N6P without a problem. The definitive answer is that you have to have ICH heat sinked when doing this.
   
  IIRC BoM coils are rated for 800ma and its always good to have headroom.  That said my CTHs had no issues/troubles driving 750ma heater loads (w/little ICH heatsink as Mullet says), but doing so w/BoM parts is still not recommended.
   
  >  But I would still like to stick with a toroid and have everything integrated..   So one rated 1A and 24VAC would be fine?
   
  From above that rating should be fine esp. sticking w/target tube heater loads.  But experience & paranoia has me making all my builds two-box ones, providing separation between transformers and input stages/low-level stuff.  A/C adapters are a nice cheap way to get this two-box build advantage.  Anyway, if doing one-box build for this I'd be ready to allow 6" or more between transformer & input stage, use good wiring practices and test/experiment listening with transformer position/orientation/rotation prior to pining things down.


----------



## Halvor

The plans have changed in regards to my choice of case, so a wallwart might be considered. But i have yet to find one with the recommended specs in my country. Does anyone know where to find one with 230V primary?


> Anyway, if doing one-box build for this I'd be ready to allow 6" or more between transformer & input stage, use good wiring practices and test/experiment listening with transformer position/orientation/rotation prior to pining things down.

If I don't find a cheap wallwart in reasonable time, I will use a separate case for the transformer.


----------



## Mullet

So like my first CTH build what fun is it all without any problems?
   
  I stuffed all my parts, checked soldering joints, and then cleaned the board with isopropyl alcohol. Then I proceeded to wire up my power to check voltages et al. First thing I noticed is that the tube wasn't working. I tested pins 4 to 5 -- no voltage what-so-ever. Tested everything else. SG to OG 11.92v, SG to OL and OR same readings as SG to OG. SG to Pin 1 -- 107v, SG to Pin 6 on the tube -- again 107v. SG to TB+ -- 107v. Then I checked the LM2595 and I'm getting the normal readings of 33v in and 12.7v out. The only things after this in the circuit that aren't making sense are the L1H is getting 12.7v between SG and it's input, but no reading between SG and its output. Could the inductor have been bad from the get go? I tried to reflow some solder to no avail.
   
  Also, I think I might have semi-fried Q3P. When I was poking around a ring on my finger touched the board (this was two minutes after unplugging the thing) and I heard a spark pop. Now I'm getting a 97v reading on Pin 6 of the tube instead of 107. Is there supposed to be a 10v voltage drop from Q3P? Looks like I'm going to have to do another Mouser order. Any one have a spare Q3P and L1H on hand?
   
  What else should I be looking at readings wise to make sure I'm covering all bases?


----------



## civilmonkey

Has anyone tried the knock off 50K log DACTs from ebay?  I have one while waiting for a 50K Alps pot.  My experience so far is that they sound fine, the attenuation curve seems pretty reasonable, channels seemed to be matched well, and build quality is so/so  (for $10 it's just fine).  What I am experiencing though is that as I switch volumes, the click often causes the amp to unlatch for 1-2 seconds.  turning the know slower to eliminate the click reduces this, but does not eliminate it.
   
  Can anyone confirm?
   
*EDIT:  *The amp has warmed up (10 minutes of music) and I can no  longer recreate the above.


----------



## civilmonkey

Quote:


> Any one have a spare Q3P and L1H on hand?


 
  A little late but, I have one QP3 but no L1H.  PM you address if you want, I can mail it out tomorrow.


----------



## wiatrob

Quote: 





civilmonkey said:


> Has anyone tried the knock off 50K log DACTs from ebay?


 

 The Gigaworks? I plan to use one in my build, I have the case finished with the stepped attenuator mounted (but I haven't built my rev'd CTH yet).   Any further symptoms?


----------



## cfcubed

Quote: 





civilmonkey said:


> What I am experiencing though is that as I switch volumes, the click often causes the amp to unlatch for 1-2 seconds.  turning the know slower to eliminate the click reduces this, but does not eliminate it.  *EDIT:  *The amp has warmed up (10 minutes of music) and I can no  longer recreate the above.


 
  I have a guess.  I've found that if a lineout-connected iPod is turned on (wakened causing Apple logo) with CTH on & volume set it often causes e12 to cycle.  Turning CTH volume down avoids this.
  Thinking CTH is very sensitive to input offset / input offset transients.  Don't know the make/break behavior of that DACT but perhaps if you scoped what is happening when you turn it you might see spikes.  With input connected/etc so you are simulating what is being seen by the CTH input stage.
  Also think the particular C4s used may have influence on this, BoM/box caps exhibiting it less / getting earlier, more resilient lock than large, fancy caps.
   
  Having never owned / used a stepped attenuator, I'd be worried about granularity when most never go past 11am on std pots in CTH.  E.g. will I get the precise volume I want - something I'm quite picky about.  Thinking amps w/adjustable/configurable gain may be better suited as you can set/use more vol range, but again don't know much about stepped attenuators.


----------



## civilmonkey

wiatrob said:


> The Gigaworks? I plan to use one in my build, I have the case finished with the stepped attenuator mounted (but I haven't built my rev'd CTH yet).   Any further symptoms?


 

 No other symptoms.  When the amp is warmer, it seems to affect the latching less.  It still occurs occasionally but I think last night I decided I could live with it.  I'm using non bom caps.  Unfortunately ebay links die quickly, but the dact I used was $10 from Hong Kong, 21 step gold plated.
http://cgi.ebay.ca/DACT-Type-21-Stepped-Attenuator-Potentiometer-50K-300B-/200430354774?pt=LH_DefaultDomain_0&hash=item2eaa948156 

  


cfcubed said:


> I have a guess.  I've found that if a lineout-connected iPod is turned on (wakened causing Apple logo) with CTH on & volume set it often causes e12 to cycle.  Turning CTH volume down avoids this.
> .


 

 My source is an IPOD with homemade line out, but I have only connected pins 1 to 4 (not the 21 pin to ground with a 68kohm resistor).  I don't experience this luckily.
  
   


cfcubed said:


> Having never owned / used a stepped attenuator, I'd be worried about granularity when most never go past 11am on std pots in CTH.  E.g. will I get the precise volume I want - something I'm quite picky about.  Thinking amps w/adjustable/configurable gain may be better suited as you can set/use more vol range, but again don't know much about stepped attenuators.


 

 All good points.  I personally find I have enough control with the stepped attenuator but everyone is different of course.  With my DT880's I get to around 1pm on the volume knob.  Anything higher risks the amp unlatching from the load and is also pretty darn loud.  Aside,  I've found that it's not necessarily bass heavy music which will cause unlatching, rather music which is very 'full', i.e., lots of mids as well as base.  If you are familiar Alexi Murdoch - Orange Sky, that song will cause unlatching more than any electronic, heavy bass, etc.
   
  One nice thing I could say is that I can use a very low volume and still have the volume balanced in both channels.  I have never tried the alps 50k log which I understand is supposed to be pretty awesome, but other pots I've tried (the small green 10k alps for instance), usually don't balance channels at low volumes as well.


----------



## rds

Quote: 





cfcubed said:


> Having never owned / used a stepped attenuator, I'd be worried about granularity when most never go past 11am on std pots in CTH.  E.g. will I get the precise volume I want - something I'm quite picky about.  Thinking amps w/adjustable/configurable gain may be better suited as you can set/use more vol range, but again don't know much about stepped attenuators.


 
  @civilmonkey
  Another thing to consider is whether a DACT makes sense in this application.  Considering the CTH uses a single dual triode tube you will inherently have some degree of mismatch in gain between the two channels.  Using a volume control that's intended to track two channels very precisely might not have any advantage in such a circuit.
  I'd suggest a nice pot as the best choice in this application.


----------



## BK_856er

Another one lives!
   
  Final wiring was a real pita in the small case, but I think it turned out well.
   
  Sounds really great on an initial listen with a bugleboy tube and my testing headphones.  Still need to put it through its paces and do the shakedown thing, and also finish the perf top.  Mute circuit kicked in a few times when adjusting the pot up or down quickly.  Didn't get any meaningful voltage between pins 1 and 6 during the powerup tests, but the amp still seems to work fine.
   
  [edit:  So apparently I should have been measuring pin 1 and 6 separately against SG.  Brain does not function at 100% after 1AM.  Changed out the initial tube and no more issue with the e12 circuit.  Also zero hum/noise at any pot position with music paused.  Nice!]
   
  [edit#2:  The initial tube I mentioned above was getting 12.6V instead of the 6.3V that it was designed for...that probably explains the initial e12 quirks with quick volume changes...and the really bright heater filament glow.  Doh!  Everything is cool at 6.3V and the e12 circuit is now perfectly behaved.  I need to lay off the late night testing.]
   
  Here are some initial pics.
   
  BK


----------



## cfcubed

Looks good BK, like the right-angle wiring - nice way to dress it up.  Great it sounds good & works well too


----------



## Mullet

BK ~ looks great! Can't wait to see that silver perf top. Wiring looks cool as well. I guess I'm a little lazy with the wiring. Maybe it's because wiring the thing up is definitely a PITA and I just want to get the dang thing over with.
   
  Here's a pic of my latest creation. It turns out as of my last posting I had a defective L1H and I zapped my Q3P in the process of troubleshooting the L1H. Once I replaced these parts all was fine. I like the look of the silver knob/perf top better than the all black.
   

   
  I didn't want to take a pic of the back because I slightly screwed up the placement of a hole or two. *Anyways, if anyone has an extra undrilled panel or two that they don't need that would be killer. PM me.*
   
  With this build I went with the BOM caps. I had two Russian PIOs, but I couldn't get the leads correct and accidentally broke them off. What a waste. So I ended up with the BOM caps this time. *Maybe I'll get what BK put in his CTH and drop them in later on. What caps are those again? *They look easier to install than the Russian PIOs.
   
  Cfcubed... do you know if there is a difference in sound quality between the squarer and more taller Wima caps you sent me vs. the shorter and rectangular BOM Wima caps? Both are .22uF and I think 100v.


----------



## BK_856er

Quote: 





mullet said:


> With this build I went with the BOM caps. I had two Russian PIOs, but I couldn't get the leads correct and accidentally broke them off. What a waste. So I ended up with the BOM caps this time. *Maybe I'll get what BK put in his CTH and drop them in later on. What caps are those again? *They look easier to install than the Russian PIOs.
> 
> Cfcubed... do you know if there is a difference in sound quality between the squarer and more taller Wima caps you sent me vs. the shorter and rectangular BOM Wima caps? Both are .22uF and I think 100v.


 

 I have some info back on page 6 or 7.  I used Auricaps from Audience in my build.  The Sonicap GenII is going to be the easiest botique cap to install due to its relatively small size and solid leads.  I purchased both types through SonicCraft.
  
  BK


----------



## cfcubed

Quote: 





mullet said:


> Cfcubed... do you know if there is a difference in sound quality between the squarer and more taller Wima caps you sent me vs. the shorter and rectangular BOM Wima caps? Both are .22uF and I think 100v.


 
  Really doubt you'd hear a diff between those 0.22/100V WIMA Polyester Film box caps... The ones I sent are older & perhaps a different series (they're always making caps more compact).
  IMO w/my ears & music it would take a much bigger diff in cap/cap design to notice a difference.


----------



## civilmonkey

Update to DT880/600 ohm and e12 latching / unlatching:  I put in a 12BH7A tube (the tube I happened to buy was described as a RCA Black Plate).  The occurance of unlatching at high volumes has significantly reduced.  Aside, the sound is incredible and I can't stop listening to it.


----------



## Mullet

bk_856er said:


> I have some info back on page 6 or 7.  I used Auricaps from Audience in my build.  The Sonicap GenII is going to be the easiest botique cap to install due to its relatively small size and solid leads.  I purchased both types through SonicCraft.
> 
> BK




Cool... I'm thinking of going with the Sonicap Gen IIs. They look to be the most bang for the buck and I'm not looking to deal with a PITA installation. 



cfcubed said:


> Really doubt you'd hear a diff between those 0.22/100V WIMA Polyester Film box caps... The ones I sent are older & perhaps a different series (they're always making caps more compact).
> IMO w/my ears & music it would take a much bigger diff in cap/cap design to notice a difference.




I'm with you on not noticing the difference. My ears are by no means golden. And if both are made of the same type of material then that would make sense that they sound pretty much the same.



civilmonkey said:


> Update to DT880/600 ohm and e12 latching / unlatching:  I put in a 12BH7A tube (the tube I happened to buy was described as a RCA Black Plate).  The occurance of unlatching at high volumes has significantly reduced.  Aside, the sound is incredible and I can't stop listening to it.




I get similar unlatching with both my 250ohm DT880s and Senn HD650s at higher volumes. I'd say this happens at 1 o'clock or 2 o'clock on my pot. I'd never listen at these listening levels anyways. I'm using the blue velvet pot, so I'm not having it trip in the same fashion as you are.

I'm wondering about those 12BH7 tubes. I've read fantasic things in general, but nothing in terms of what's *the tube* to get. I've got a bunch of RCA tubes in general and want to try and move away from them to explore something new. I've heard pretty good things about Tung Sol, but they're typically more expensive @ $60 a pop. The RCAs are 1/3 the price. I was gaming for a pair of Brimar 12BH7, but I wasn't willing to pay $80 for the pair. I'm trying to stay lower than $30 a tube now that I've spent way more on a few select tubes like the Siemens CCa and chrome plate 12AU7s. At this point I'm looking for a good price on the Telefunken E88CC.


----------



## kiwiluke

Mouser does not have the amp CRD's (2.0 and 4.3 mA) as specified in the BOM.  Will the 2.2 mA (1N5306) and 4.7 mA (1N5314) diodes be suitable replacements?


----------



## Garage1217

Missed the buy.. DOH! Any boards left?


----------



## BK_856er

Just about have things wrapped up with this build!
   
  I swapped my EHHA RevA with particleman14's most excellent Beta-22 so we could each audition at length.  I thought the CTH size comparison below was amusing...
   
  BK


----------



## sachu

that CTH amp is a pint sized pinch hitter


----------



## cfcubed

Quote: 





kiwiluke said:


> Mouser does not have the amp CRD's (2.0 and 4.3 mA) as specified in the BOM.  Will the 2.2 mA (1N5306) and 4.7 mA (1N5314) diodes be suitable replacements?


 
  My guess is that you can go slightly under or slightly over (as above) if you must for these, but preference would be for using the spec'd values if they could somehow be found of course.
  Another guess is that if you had to use non-spec'd values, considering plate curves, go slightly under for the tube (1.8mA) and slightly over for the OB (4.7ma).
  You could ping runeight about this to see what he thinks.
   
  BTW for those using same input as output jacks consider trying to label them somehow (e.g. rub-on white lettering, a simple I & O ?). 
  Seems the CTH most often survives brief errant swapping of these but it's not something I'd bet on.


----------



## runeight

Sorry gents, I am pretty consumed right now getting the LFs out.
   
  Chris' CRD suggestion is just about right. You can use 1N5314 instead of 1N5313 and you can sub 1N5304 for the 1N5305. The 1N5306 would be second choice but probably ok too.


----------



## kiwiluke

Thanks for that.  As the 1N5304 is also not available at Mouser, the 1N5306 will have to do.


----------



## BK_856er

Picked up a couple 12BH7A tubes today locally.  Might be my new favorite!  One is a General Electric and is punchier, but has some microphonics.  The other is a little more subdued in its presentation, although still VERY nice.  It's labeled as "Made in Japan" and "Product of xxxSTROM"  where the xxx are rubbed off letters.  Anyone know the manufacturer?  No microphonics.  Killer glow from the top and bottom.  The lower amplification factor is helpful for sensitive cans.  There are a few more available if anyone (mullet?) is interested.
   
  Based on the reminder from cfcubed about inputs/outputs, and recognizing that this is going to my non-DIY brother, I added some good labeling.  In retrospect the 1/4" jack would have been a safer route.  The "reveal" is next week!
   
  BK


----------



## Mullet

Might be interested. What kind of prices are we talking? I'm looking to get a few 12BH7 in the near future. I'm local to Leeds electronics, so I might give them a try first. I've been reading that the 12BH7 is better than the 12AU7 and I'm curious to really find out. I can't stop buying tubes. I'm addicted!!! I know this typically belongs in the "tweaks" thread, but other than GE, what are some experiences/impressions? I'd figure that for the most part they'll have the manufacturers house sound ie RCA -- warm and lush; Sylvania -- detailed on top with rolled off bass, etc., etc. I'm looking for a cheaper Tung Sol 12BH7 that doesn't cost $60+.
   
  It seems to me that your mystery tube is a rebranded Raytheon or Matsutshita or maybe even Toshiba. My guess is it's Matsutshita that's rebranded. I've read on a few forums that tube manufactured by Matsutshita aren't the highest regarded 12BH7. But that's just a matter of opinion, isn't it?


----------



## Garage1217

I may have a bunch of 12bh7's at home. Will have to check tonight / nos stuff. Still have a few hundred tubes laying around lol


----------



## BK_856er

Quote: 





mullet said:


> Might be interested. What kind of prices are we talking? I'm looking to get a few 12BH7 in the near future. I'm local to Leeds electronics, so I might give them a try first. I've been reading that the 12BH7 is better than the 12AU7 and I'm curious to really find out. I can't stop buying tubes. I'm addicted!!! I know this typically belongs in the "tweaks" thread, but other than GE, what are some experiences/impressions? I'd figure that for the most part they'll have the manufacturers house sound ie RCA -- warm and lush; Sylvania -- detailed on top with rolled off bass, etc., etc. I'm looking for a cheaper Tung Sol 12BH7 that doesn't cost $60+.
> 
> It seems to me that your mystery tube is a rebranded Raytheon or Matsutshita or maybe even Toshiba. My guess is it's Matsutshita that's rebranded. I've read on a few forums that tube manufactured by Matsutshita aren't the highest regarded 12BH7. But that's just a matter of opinion, isn't it?


 

 $6.40 + tax (no box, test "good").  My two were grey plates, but there were also some black plate and non-A types available.
   
  BK


----------



## BK_856er

I'm finally declaring this one done.  I tested it extensively over the last couple of weeks and it's good to go.  Next week it heads off to Afghanistan with my brother.  I hope to get it to him in the next few days - he's still in the dark about it.  I predict that when he returns in about a year he'll take up DIY and join the head-fi community!
   
  I want to publicly thank sachu, jdkjake, mullet and cfcubed for donating key parts - thanks, guys!
   
  I've already posted way too many pics of the build progress, but here's a couple more with everything boxed up using jdkjake's killer Pelican.  The little blue box next to the transformer is a USB SkeletonDAC (emergency backup hi-fi).
   
  BK


----------



## jdkJake

Bravo Zulu BK!!


----------



## cfcubed

Wow.  Kudos on the build & case up, has a military look about it  What a nice surprise its going to make.  Down the road we'll have to hear how he likes it.


----------



## devast

Hi there!
   
  After seeing these wonderful new cths, i've got the urge to finally debug mine (it's been semi-working for a year now) 
  Can anyone measure the DC offset of his cth, when theres no tube plugged in ? How much should it fluctuate around the output ground ?
  I guess my ~ 50-60mV fluctuation (between +30mV and -30mV) is too high, but i need to confirm that, before i start messing with my dc servo 
   
  Thanks.


----------



## Mullet

I'm not sure that it's too high. I get a reading close to that. Around +/-33mV with no tube plugged in. I'm not noticing anything strange with my amp. What are your issues?


----------



## devast

My issues are the following:
  A year ago, i connected sg to og, smoke came out etc, fixed the psu part fine. After that it developed the following problem:
  e12 trips ,depending on the volume of the music. It does it with every tube, its channel independent, with or without a load (headphone) connected. Apart from that, at lower volume the unit works perfectly.
  Voltages read fine everywhere, i basically replaced the left output stage (transistors) the psu part transistors, the vreg, e12 transistors (except the mpsa14, its hard to source here), i tried it with different op amps.
  If my dc offset is fine, then i assume that my output stage is ok.
  That means, i'll try replacing the remaining stuff in the e12, particularly the mpsa14 darlington (i recently found a source), and maybe if thats no good, then the 1N4148 diodes.
  It uses bom c4s, so that can't be the problem either. I can't think of any other solution... i hope this time it will work.
   
  Thanks for the info, Mullet.


----------



## sachu

Make sure your AC line is good. If you are going off of a power strip, maybe try going off of a regulated power strip.
   
  Try different wallsockets. In my experience with the CTH and the infamous E12 trips, this could very well be a source of the problem.


----------



## cfcubed

I've a couple ideas in addition to sachu's. 
  Seems like you did cover many bases with your repairs/replacements, except maybe those right channel OB transistors & rail splitter parts.  Think I've had toast/smoke trouble twice across all my CTH builds, and they didn't happen due to OG-SG shorting, but were "fixed" shotgun style through replacement of all output buffer & rail splitter TO92s (not e12 parts).  So something to consider (replacing TO92s not already replaced).
  Also have you checked your source for offset & tried different sources?
  As a sort of last resort you could try shorting your R18 positions & that may get you more volume prior to de-latch.


----------



## Mullet

At what volume level is your CTH e12 tripping? If I go to about 1 or 2 o'clock and have a song that has some thumping bass or a loud transient hit I can get the relay to trip. This is with most tubes as well. With most of my headphones this is pretty darn loud so it doesn't really effect me. If I'm using my AKG K701s then I actually have to go to 1 o'clock to get a decent listening level so I'd have to go to a higher level on my pot to make the e12 trip.


----------



## sachu

I believe this is due to the fact that the E12 is not being used separately for each channel. The main reason however I feel is due to the use of CW multipliers on the power supply. Then again, there is no other way to get  such high voltage levels for the tube bias in such a small package.


----------



## devast

Thanks for the replies.
   
  First, it's tripping with different sources as well. My (usual) sources offset is roughly 10-12mV, but that shouldn't be a problem. It was working fine (at max volume without load connected it did not trip) before i fried it 
  I think i've replaced all transistors in the rail splitter, and the psu. The +/-12V rail and og is totally stable, (as far as my multimeters accuracy goes).
  It might be my 24V 1050mA transformer brick, but that seems to work good as well. Good voltages with or without the cth connected.
  @Mullet: Here's the tricky part: it's totattly dependant on the music i'm playing. Some songs trip at 11-12 o'clock, but most can go a bit higher like 1-2 o'clock.
  Phones are HD600.
  @sachu: i tried it with only one channel connected. The symptoms are exactly the same, even the tripping volume is the same.
  I did not touch the heater/tube part at all, and i don't think the problem will be there.
  If the e12 mpsa14 / 1N4148 diodes won't solve my problem, i think i'll try to get a new 24V brick.


----------



## civilmonkey

Quote: 





devast said:


> @Mullet: Here's the tricky part: it's totattly dependant on the music i'm playing. Some songs trip at 11-12 o'clock, but most can go a bit higher like 1-2 o'clock.
> Phones are HD600.


 

 I have noticed that when using 600 ohm DT880's my CTH e12 trips anywhere from 12 to 2, depending on music.  Luckily for me, the volume is more than sufficient.  Typical bass heavy music with big hits actually trips the e12 less than a song with a full and constant spectrum of mids and bass, say like a live folk/soft rock with a nice drum line, constant bass guitar, and male vocals.


----------



## revolink24

Some ideas for replacement parts, just hoping that you guys can verify that these will work.

Fuse Holder
Replacement: http://www.mouser.com/ProductDetail/Littelfuse/03455LF2H/?qs=sGAEpiMZZMukmSYeDOiaDK82%2fMbOC9l01cigQ%2fERqRw%3d

Capacitors:

Original: http://www.mouser.com/Search/ProductDetail.aspx?R=UVR1H101MPD1TAvirtualkey64700000virtualkey647-UVR1H101MPD1TA
Replacement: http://www.mouser.com/ProductDetail/Nichicon/UKW1H101MPD/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oiucpIJyTTRQM%3d

Resistors:

Original: http://www.mouser.com/Search/ProductDetail.aspx?R=299-6.8-RCvirtualkey21980000virtualkey299-6.8-RC
Replacement: http://www.mouser.com/ProductDetail/Vishay-Dale/RN55D6R81FB14/?qs=sGAEpiMZZMsPqMdJzcrNwmmyJH8x4%252byIKMd71bZ7Q08%3D

Still looking for a heatsink replacement.

Also unsure about the relay. It should be in stock on the 30th, and though I would like to place an order today (for the meet this weekend) it wouldn't kill me to wait until then.


----------



## cfcubed

Your suggested subs look fine to me as they match value/rating/size/type/lead-spacing... I guess you've also seen the subs/corrections/suggestions for other parts in this thread (& the GB one).   The relay may be tricky to sub, but I've not tried searching yet.


----------



## cmason

Regarding: 
   
   
   Original: http://www.mouser.com/Search/ProductDetail.aspx?R=299-6.8-RCvirtualkey21980000virtualkey299-6.8-RC
 Replacement: http://www.mouser.com/ProductDetail/Vishay-Dale/RN55D6R81FB14/?qs=sGAEpiMZZMsPqMdJzcrNwmmyJH8x4%252byIKMd71bZ7Q08%3D
   
  The original part is a Carbon Film resistor, and the replacement is Metal Film.  I was struck by the fact that the these were the only Carbon Film resistors spec'ed.  Is there a big difference?
   
  -c


----------



## cmason

[size=medium]In reading on the web [1] and on headfi [2], it seems that the carbon film resistors may have more pink noise, but that this may be "pleasing."  Would anyone care to comment specifically on the CTH?  Thanks so much,
   
  -c
   
  [1] http://www.aikenamps.com/ResistorNoise.htm
  [2] http://www.head-fi.org/forum/thread/260846/metal-vs-carbon-resistors-what-is-the-difference​[/size]


----------



## wiatrob

Hopefully Alex will chime in - when I helped the original BoM, I asked this question, and I thought he said there is a reason these should be carbon for a reason. They're mighty wee little buggers...


----------



## revolink24

He's got about a day to get in here before I just give in and buy the RN55Ds, like every other resistor on the board... It could very well be a heat issue though. Carbon film resisters can tolerate higher heat, if I recall correctly. I might try these instead.


----------



## wiatrob

If you're going to use RN55s, you might as well get 1/4 watt carbon films, there are plenty available that are about the same size as RN55s:
   
http://www.mouser.com:80/ProductDetail/KOA-Speer/CF1-4CT52R6R8J/?qs=sGAEpiMZZMu61qfTUdNhG1dhquwH4o0FfRLFhWtWO%252bc%3d
   
  OR I have at least three sets of 8 - you could PM me your address and I'll mail you a set...


----------



## wiatrob

Quote:  





> _snip_ The relay may be tricky to sub, but I've not tried searching yet.


 

 I get:
   
http://www.mouser.com:80/ProductDetail/NEC/EC2-12NJ/?qs=c5n%252bvICFHOauz9TRyhaK7A%3d%3d
   
  10K in stock...
   
  EDIT Seems to be 3K today


----------



## runeight

Gents, my apologies for being slammed with work and the LF.
   
  It's ok to use metal film resistor for the 6.8R values.
   
  Also, for those of you who are having e12 trip issues, you can try increasing the value of R1E and R2E. This will desensitize the e12 and cause it to trip at higher voltages.
   
  Here's the way to approximate what will happen.
   
  The tripping voltage is approximately equal to: 600mV * R1E / R3E.
   
  With the current values this is: 600mV * 33k / 100k = 200mV.
   
  If you change R1E (and R2E) to 100k the e12 will trip at approximately 600mV.
   
  What is acceptable to you depends on your headphones.
   
  For example, 600mV with 300R headphones is only a DC current of about 2mA. This will not be a continous current because the servo will keep the DC offset near zero, but it can exist as a transient current for tens of ms before the e12 unlatches.
   
  For 32R, 600mV is more like 20mA. Most headphones can handle more than 20mA signal simply to drive them so they won't harmed by this as long as it doesn't happen continously (which it wont', again, because the servo will zero the offset and/or the e12 will cut out if the 20mA persists).
   
  Obviously, you can select any voltage that you want. 68k will trip at apprxoimately 400mV. Etc.
   
  I hope this helps with some of these problems.


----------



## revolink24

Thanks for the help!


----------



## Halvor

Does anybody know where to find a wallwart for european mains?


----------



## Lil' Knight

Just wondering if there's any (dis)advantage if I bump the C4L/C4R to 0.47uf? Just found some 0.47uf Vit Q in the parts bin and they seem to fit just fine, not really any bigger than the 0.22uf that I thought of using.


----------



## schwallman

I will receive my CTH tomorrow. I was curious if changing the in/outs to 1/4 from 1/8 jacks would be possible. I don't have any DIY skills so I'm sure it would probably be a tuff task for me. Kinda wish I would have asked more questions before I bought it but i didn't. It was built by stringgz awhile ago. Anyway, I'm still pretty excited to get it though.


----------



## jdkJake

schwallman said:


> I will receive my CTH tomorrow. I was curious if changing the in/outs to 1/4 from 1/8 jacks would be possible. I don't have any DIY skills so I'm sure it would probably be a tuff task for me. Kinda wish I would have asked more questions before I bought it but i didn't. It was built by stringgz awhile ago. Anyway, I'm still pretty excited to get it though.




http://www.radioshack.com/product/index.jsp?productId=2062467


----------



## schwallman

Yeah I have one and I guess I need to go pick up another tomorrow. I guess adapters will work for now but I will eventually want to switch them out on the cth if I can. If not I will atleast have an amp to look at and study and hopefully be able to build my own. I know it was built way before the rev a specs. Did the original cth call for the 1/8 input/output? I cant imagine why this would be the only option the original builder went with.
  Quote: 





jdkjake said:


> Quote:
> 
> 
> 
> ...


----------



## cfcubed

Quote: 





lil' knight said:


> Just wondering if there's any (dis)advantage if I bump the C4L/C4R to 0.47uf? Just found some 0.47uf Vit Q in the parts bin and they seem to fit just fine, not really any bigger than the 0.22uf that I thought of using.


 
  0.47s should work but you'd want to test this on the bench before re-boxing, e.g. the e12 latch behavior.  I tried 1ufs I'd around & my e12 latch was more touchy.  You do not nee more capacitance there tho, so you should only notice the difference in the sound of the caps (rolloff is low enough w/0.22s).
   
  Quote: 





schwallman said:


> Yeah I have one and I guess I need to go pick up another tomorrow. I guess adapters will work for now but I will eventually want to switch them out on the cth if I can. If not I will atleast have an amp to look at and study and hopefully be able to build my own. I know it was built way before the rev a specs. Did the original cth call for the 1/8 input/output? I cant imagine why this would be the only option the original builder went with.


 

 Many CTHs were built w/1/8s in & out (e.g. they were/are in the BoM) to make the fit easier in the tiny hammond target box.  It's a bit harder to fit 1/4" out + RCA in but many have done that as well (e.g. my avatar).  There's no technical reason for these diffs, only difficulty of fitment.


----------



## Lil' Knight

Thanks. I'll try both the 0.22 and 0.47 to see how the e12 responses. 
Just also ordered a GrubDAC to cramp into the case, would be a nice, tiny USB DAC/amp.


----------



## schwallman

cfcubed said:


> 0.47s should work but you'd want to test this on the bench before re-boxing, e.g. the e12 latch behavior.  I tried 1ufs I'd around & my e12 latch was more touchy.  You do not nee more capacitance there tho, so you should only notice the difference in the sound of the caps (rolloff is low enough w/0.22s).
> 
> 
> Many CTHs were built w/1/8s in & out (e.g. they were/are in the BoM) to make the fit easier in the tiny hammond target box.  It's a bit harder to fit 1/4" out + RCA in but many have done that as well (e.g. my avatar).  There's no technical reason for these diffs, only difficulty of fitment.




Ok. Ive only seen pictures of various builds. I'm really not even sure of the size since I've never seen one in person.


----------



## revolink24

So I finally "finished" my first CTH today, but it's not working (as is usually the case). The E12 LED comes on red, and doesn't change. Measuring between OG and SG seems to fluctuate between about 5v and 11v. Very strange. Does anyone have any idea what might be going on?


----------



## sachu

measure the voltages on the opamp in the rail splitter and the dual opamp in the buffer section and post your values. All wrt SG.


----------



## schwallman

Can the pcbs still be bought? Most likely from someone that got in on the last group buy I would guess.


----------



## revolink24

ICR:

Pin 1: 35 mV
Pin 2: 1.5 V
Pin 3: 1.5 V
Pin 4: 0 V
Pin 5: 36 mV
Pin 6: 1.07 V
Pin 7: 14.58 V
Pin 8: 0 V


IC1:

Pin 1: Varies, approx. 6.5-9.5V
Pin 2: 0 V
Pin 3: Varies, approx. 7.2-9.3V
Pin 4: 0 V
Pin 5: Varies, approx. 7.2-8.5
Pin 6: 0
Pin 7: Varies, 8.5-11V
Pin 8: 14.5V

Pretty strange readings....


----------



## sachu

Measure ICS..that's the rail splitter. The output of that needs to be at 12V.
   
  Measure output of the 24V regulator.


----------



## revolink24

Heh, that was silly, right you are.

Pin 1: 0.37 V
Pin 2: Varies, 6 - 9.5 V
Pin 3: 12V
Pin 4: .3V
Pin 5: 6 - 10V
Pin 6: 14.5 V
Pin 7: 14.5 V
Pin 8: 0 V


I'll have to get back to you on the 12V reg, I can't reach it without getting the board back out of the case.


----------



## revolink24

I also scoped the output, and whether the power is on or off, the output is seemingly a 60 Hz square wave. I'll check my grounds.


----------



## cfcubed

revolink24 - Could you please conduct the setup test here & let us know the voltage readings from it?:
http://www.cavalliaudio.com/diy/cth/main.php?page=setup
  Most measurements are WRT SG.  Also please let us know the heater readings (voltage bet pins #4 & #5) for both 6V & 12V heater switch positions.
  E.g. I don't see any HV in your readings.


----------



## revolink24

Okay. here goes.


Tube readings:

12.6V


Pin 4: 0 V
Pin 5: 12.7 V
Pins 1 and 6 reads 80 V.

6.3 V:

Pin 4:

4: 0V
5: 6.3V
1 and 6: 80V

Tests from site.

OG - fluctuates between 6V and up to 10.2 V
OL, OR fluctuate similarly. 

TB+ reads 105V.


----------



## sachu

wait, is Pin 1 and 6 reading with the Tube inserted?


----------



## revolink24

Nope, D'oh! They are reading 80V now with the tube inserted.

Drop across 4 and 5 also reads 12.6V.

I think there's floating AC somewhere in the circuit that is causing the E12 to trip, or at least thats the only conclusion I can think of.


----------



## revolink24

Still cant find any problems with my ground. Anyone else have any ideas?


----------



## sachu

Ok, with the tube 80V makes sense. Check output voltage of the 24V regulator next. Then measure voltages of the TLE rail splitter (be careful not to short things out when poking around there). All measurements wrt G.
   
   
  YOur HV and heater is fine. Now to cehck your LV, start from regulator, then rail splitter then buffer stage and finally E12.


----------



## Lil' Knight

Almost done populating the board but found out I missed the D1L, D1R, D2L, D2R, relay, L2H and the ICH.
Anyone happens to have those on hands? Neither Mouser nor Digikey has all of them, just don't want to make 2 orders for those small parts.


----------



## revolink24

Could someone either describe to me or show me a photo of the correct orientation of Q1P (the TO-126)? I'm a bit shaky on it, and since both my boards are exhibiting the same problems, I fear I may have accidentally reversed it.


----------



## BK_856er

Quote: 





revolink24 said:


> Could someone either describe to me or show me a photo of the correct orientation of Q1P (the TO-126)? I'm a bit shaky on it, and since both my boards are exhibiting the same problems, I fear I may have accidentally reversed it.


 


 First post, page #1, image from mullet?
   
  BK


----------



## revolink24

Sorry, can't really tell from that picture.


----------



## cfcubed

One way to do this is to ID the Emitter, Base & Collector for the device, consult the schematic:
http://www.cavalliaudio.com/diy/ctha/main.php?page=schematics/psschematic
  then look at the PCB traces to other devices.
  Another way is to see the gray dot indicator on it (top/PCB-edge) in my "last PCB spec image" on the 1st page of this thread, the device may have that dot indicator on it (hint: its the emitter).


----------



## revolink24

Thanks, that helped a lot.


----------



## Mullet

So it's been several months now since we've begun building our CTH Rev As... I'm curious as to how many people have built theirs and if you're keeping them or giving (selling) them away. I've built both of mine and have no intentions on selling or getting rid of either. The only blasphemous thing thing I'm thinking of doing is possibly building an EHHA Rev A in the next 2 years. At that point I'll decide what I intend to do with the two I've got. Other than that I have a La Figaro 332C that I'm conflicted about. It seems to have slightly more sound stage and separation over my CTH with Sonicap Gen IIs. However, I don't know if I can justify keeping it as it's taking up a bunch of desktop space and isn't really that much better than the CTH.


----------



## cfcubed

It's funny you'd post that Mullet as I've 3 CTHs now & I guess that's one too many so I will be selling one.  With 6 headamps total & an EHHA in progress think I can give one up


----------



## sinae

Im interested in building this diy but filtering all the tweak mods in forums posts might complicated for a beginner like me  

Anybody is selling kits of the new CTH revA with all added modifications?? Or at least PCBs (digikey?)

Or anybody have a list of those possible revA mods discussed on headfi.. 

Also im looking for an hybrid with total black background with no hisses,no hums, no crackles when no music is playing at mostly any volume..

also no popping..

Does any of yours CTH doing any of this..
Does the CTH has integrated ground loop protection.. if that is possible? 

Anybody thought of adding some internal 3-6 band bypassable EQs, since its an hybrid  with opamp ( or to soha II and EHHA)

On the CTH rev A plan maker 

the notes are
* Consider SIP socketing R8L & R8R, R18L & R18R for flexibility
* Consider TO92 heatsinks (e.g. Digikey HS251-ND) on BC3X7s - should not be needed
* 24V reg small heatsink do not contact case or other components
* Consider 1k resistor from VG to real ground to distribute e12/relay current across rails?
* Consider mounting holes for non-slotted case use
* DO NOT SUBSTITUTE OTHER CLASS BC DEVICES!!!!

anybody wanna comment or add to this list?


----------



## kchapdaily

Quote: 





sinae said:


> Im interested in building this diy but filtering all the tweak mods in forums posts might complicated for a beginner like me
> 
> 
> 
> ...


 

 i was considering building a cth recently. but i discovered there are no more pcb's available  you might be able to find an individual forum member willing to sell you one though


----------



## sinae

I think im gonna buy an already made cavalli hybrid amp. anybody wanna sell for good price?


----------



## Mullet

Sinae~
   
  You might be in luck finding one... It looks like cfcubed is going to be selling one of his 3... I'd send him a PM and see if one is up for sale.


----------



## sinae

just bought a SOHA II built from another headfier.. might build my own CTH revA eventually


----------



## sharkz

Does anyone currently have a finished CTH for sale? Looking to pick one up now to power my Grados and Fostexes. Please PM me if you are willing to sell one. Thanks.


----------



## sharkz

Does anyone have any opinions of a CTH with Grados? I have read nothing but good things about these amps with Fostexes, but I listen to Grados a good amount too and I am wondering if there is any synergy there as well?


----------



## schwallman

Quote: 





sharkz said:


> Does anyone currently have a finished CTH for sale? Looking to pick one up now to power my Grados and Fostexes. Please PM me if you are willing to sell one. Thanks.


 


   I have a pair of 325s that sing nicely with the CTH.


----------



## sharkz

I am admittedly not the most knowledgeable in electronics, so can anyone tell me if this amp has any DC filtering caps in the input? I will be running a DAC where the DC coupling caps have been bypassed and I want to make sure I won't be passing (or amplifying) and of the DC signal through to my headphones.
   
  Sorry if this is a stupid question.


----------



## cfcubed

CTH does not have input blocking caps: http://www.cavalliaudio.com/diy/cth/main.php?page=schematics/ipschematic
  But the design prevents harmful DC offset from making it from CTH input through to its output (headphones) due to its interstage C4 caps & integrated/modded e12: http://www.amb.org/audio/epsilon12/
   
  However it is advisable to check the output of source devices for DC in any event as it could/would cause troubles down the line.  A symptom of possible DC at input for CTH could be temperamental e12 relay latch/lock.  One CTH owner had this & we tracked it down to DC on the CTH's input from a CD transport connected to it.


----------



## sharkz

Thanks for the information cfcubed. I actually took delivery of one of your built CTH's yesterday. I am loving it with my modded Fostexes so far.


----------



## blaken

I am almost done with my original CTH. It has been shelved for almost 2 years due to moving and a new baby. I was hoping someone had an idea for a replacement multi colored LED for under the tube. I am red/green color blind so the provided one wont work. I haven't been able to find a red/blue that fits or is the right voltage. Another option is red/yellow. Green/Yellow wouldn't work for me.

My other option is to mount two very small LEDs on the front panel and just know that the top one is 12v and the bottom is 6v but I would still like one under the tube. Is there somewhere I could tap into for constant power for an LED?

Sorry I have never worked on anything near this complicated and don't want to mess it up.


----------



## cfcubed

I guess if you cannot find a dual LED with the colors you need you may need to go that 2-LED-in-front-panel route.  You could use 2 different color LEDs that you can differentiate and/or that stacked upper (green?/latched) - lower (red?/not latched) arrangement. 
  Based on CTH e12 lights here: http://www.cavalliaudio.com/diy/cth/main.php?page=schematics/e12schematic
   
  But you know the above & this still leaves out the tube LED you desire.  LEDs like about 5V IIRC & if you'd like to avoid loading one side of the rail splitter & not the other you could wire in an appropriate LED + resistor to each (- / virt gnd, virt gnd / +) but you'd have to locate PCB spots to tack in feed wires & we all know this board is tight.   I'd be tempted to try wiring the extra tube LED in parallel w/the green/latched LED & see what happens.  It may disturb the balance of the CTH e12 LED circuit, e.g. you may need play around with its resistor values or BC327 for BC560 or something. 
  If its not quick n easy I'd skip the tube LED, turn down the lights & enjoy the heater glow  And the sound.  Assuming all is working of course


----------



## Tribbs

I to have the Grado 325s and can wield a soldering iron.
  I am hoping to find a CTH printed circuit board.
   
  If anyone has a spare CTH PCB laying around please contact me.
   
  Unfortunately I'm late to the game. Any chance of another PCB group buy?


----------



## theledman

Quote: 





tribbs said:


> I to have the Grado 325s and can wield a soldering iron.
> I am hoping to find a CTH printed circuit board.
> 
> If anyone has a spare CTH PCB laying around please contact me.
> ...


 


  Echo that. I'd like to get a board as well.


----------



## frank2908

ditto, I would love to buy one, but unfortunately I live in Vietnam now. In case a group buy is not possible, what is necessary to get it custom made? Can I show the image in the first page to the custom pcb printing shop or do I need something else, like a Gerber file ( just googled it, I have no idea what it is ). Please help


----------



## cfcubed

Not a good idea & not productive to try to reproduce the CTH PCB.  Instead let me ping runeight & see if he'd get PCBs fab'd and what level of interest that might take.  With someone conducting the GB of course.  Note there is always hassle re-sourcing parts for this tiny amp (in particular the coils, LM2595 & CRDs).


----------



## Paul Clark

I am good for at least two PCBs.
   
  Have those parts always been a hassle to source?


----------



## cfcubed

Kind of, esp the CRDs in the spec'd values.  Haven't checked around for the latest BoM parts myself lately, but its something that should be done prior to committing to boards I'd think.  Seems its always taken two parts orders, e.g. Digikey & Mouser.
   
  Pinged runeight & he says he's game to make a PCB run if someone else handled everything else (e.g. the GB - $$ collection & shipping). 
  I'm considering stepping up & conducting the PCB GB (otherwise it should be a known, reliable entity around here)
  Quote: 





paul clark said:


> I am good for at least two PCBs.
> Have those parts always been a hassle to source?


----------



## Magedark

How much would it be per board? I'd be up for one board, provided we can figure out the part sourcing as well.


----------



## Paul Clark

Quote: 





> Originally Posted by *cfcubed* /img/forum/go_quote.gif
> 
> Pinged runeight & he says he's game to make a PCB run if someone else handled everything else (e.g. the GB - $$ collection & shipping).
> I'm considering stepping up & conducting the PCB GB (otherwise it should be a known, reliable entity around here)


 
   
  Once it is decided, will there be another seperate "group buy" thread started?
   
  Ref > http://www.head-fi.org/t/536098/closed-group-buy-for-cth-compact-tube-hybrid-pcb


----------



## cfcubed

>  Once it is decided, will there be another separate "group buy" thread started?
   
  Yep, so we'd carry this topic (GB, BoM sourcing, etc) over to such a thread.  Good idea.


----------



## Mullet

I did the last group buy. It went well and was not hard to set up as per the mentioned thread. We bought something like 40 boards, which came to something around $7 per board. The more you make the cheaper they are. I think in the US it was $5.30 for flat rate priority shipping. So that's like $12 for one and any extras are around $7 more.
   
  Hope that helps and I hope you guys can get another group buy off the ground.
   
  Good Luck!


----------



## schwallman

I would  grab a board.


----------



## stringgz301

I'm in for 2 boards.


----------



## cfcubed

OK, guess I'll take on a GB or straight PCB batch purchase, either way the boards would be available to builders at cost (fab, shipping, paypal fees, etc). 
  So we'd need no more commits to PCBs in this thread.
   
  BUT a quick tour of the pesky parts, at Mouser & Digikey, shows the relay (551-EC2-12NJ) unavailable <<< In stock now 11/5.  So this may be on hold until another source OR perfect sub is found... Anyone interested could try to help with that or I'd get to it over the next several days.
   
  ALSO the exact 2.0ma & 4.3ma CRDs seem unavailable but close-enough ones are.  The other past-problem parts, LM2595T-ADJ switcher & inductors are around (e.g. 1.0A  732-1429-ND).


----------



## blaken

Quote: 





cfcubed said:


>


 

 Where did you source your perforated metal from?  I need a new top for mine and that looks pretty cool.


----------



## cfcubed

Mullet found the perforated sheet where he works, tricky part is cutting it neatly incl tube hole.
   
  You can search here for perforated & maybe find some sources like http://www.onlinemetals.com/
   
  Another way to go is either scrounging around your local hardware stores for something suitable OR making neat holes (measured/center-punched) & cleaning/beveling their edges w/a deburring bit:
   
 
  
  Quote: 





blaken said:


> Where did you source your perforated metal from?  I need a new top for mine and that looks pretty cool.


----------



## Mullet

One of the original builders of the CTH came up with the idea of using perf board and I saw pics and thus my journey began. Then I found the perf board (pictured above) randomly under a raised floor in our machine room at work. I actually found two and with some trial and error I was able to extract a few smaller pieces for use on the CTH. I used metal cutters to cut smaller pieces and a metal hole punch to make the center hole. We're going through a machine room rebuild so hopefully I'll find more that I'm able to cut out and give to a few lucky head-fiers. In the meantime, I gutted an old spaceheater that had perforated metal. It's thinner than the other perf board, but should still do the trick.


----------



## blaken

Thanks guys.  I wish I had access to a drill press.  It would make casing a whole lot easier.  I have a perforated top but the tube hole is just in the wrong spot.  For now I am going to slide the top back to where the tube needs to be and then cut off the back extra with a dremel.  I will fill in the gap at the front with a piece of plexi.  It will look a little ghetto but it should work until I can find something else or get access to a press to cut my metal top. 
   
  That online metals place has some good options.  It looks like they do custom cuts too and cheap.


----------



## Ikarios

Quick question regarding the relay - the BOM calls for an NEC 12V relay - the EC2-12NJ. I have a different one that has the same pin structure. Mine is a Shinmei RSB-12-S. Can I use my part in place of the NEC relay?
   
  Also, for the specced 100nF 63V film caps (for C3L, C3R, C7L, C3P, C4E), does quality here matter much? The BOM calls for Wima MKS2 caps, but I have a set of Kemet polyesters in the same values. Will it matter much if I swap those in?
   
  Did anyone ever find a suitable Mouser alternative for L2H? I like the Kilo International knobs from Digikey so I'll probably make a small order there if I can, but if I don't need the choke from Digikey I can skip that order.
   
  I don't really understand the circuit too well, so I'd like to stick as close to the BOM as possible, but these two substitutions would save me a couple bucks in replacement parts. Thanks!


----------



## cfcubed

>  100nF 63V film caps (for C3L, C3R, C7L, C3P, C4E), does quality here matter much?
   
  Your proposed subs for those should be fine as would any 100nF 50V+ film caps that fit.  Only C4L & C4R are directly in the signal path.
   
  >  Mine is a Shinmei RSB-12-S. Can I use my part in place of the NEC relay?
   
  OK pin-out/latch type/voltage but *not* OK size/pin spacing (but _could_ try to hack/solid-core air wire).  This can be seen by comparing the datasheets, see below.  Finding a EC2-12NJ sub or alternative source *was* one thing holding up the prospect of another small batch of PCBs.  I see Mouser now has them in stock so I can re-ping runeight about the possibility.


----------



## sharkz

I have a problem with my CTH and hope someone here can help me out. After swaping some tubes around the other day, I am having problems with my amp cutting out on and off. In the middle of playing, I can hear the relay click and the LED goes from green to red. I then have to wait a minute or two again until the LED goes green. There seems to be no pattern to when it cuts out, but it has only been happening the past week or so. Anyone have any quick ideas? Thanks in advance.


----------



## cfcubed

>  There seems to be no pattern to when it cuts out, but it has only been happening the past week or so.
   
  So we'd have to relate the problem to _something_.  I can think of 2 possibilities; minor damage to the CTH somehow OR an external factor like questionable tube or offset problem in your source (e.g. a different source or source connection).
  See if gently nudging to tube while playing causes a cutout, try a known previously-working tube that did not have this problem (w/correct heater switch setting, check if your source has DC offset (DMM mV measure bet its L & G and R & G).


----------



## sharkz

cfcubed, thanks for your response. Here are two additional observations, but keep in mind these are far from scientific.
   
  First is that this problem only seemed to pop up when listening to vinyl. For the several months I have had the amp, I have listened music via a DAC from my computer almost exclusively. However my computer went down last week and I switched back to listen to some of my vinyl. The problem seemed to only pop up when listening to vinyl (Philips turntable to a cheap Behringer phono preamp). The other other observation is that using a 12v tube seems to get rid of the problem. I am not sure how stable if I were to listen to music for several hours, but using a 12AU7 tube I can get through one side of an album with no problem. Switching the three various 6v tubes I have, it seemed like there was always a cutout during the side (say ~20 mins). I am fairly sure the tubes aren't the issue because I don't think all three 6v tubes went bad at once.
   
  I do need to play around with this more, but I would appreciate hearing your thoughts. Thanks for your help.


----------



## sharkz

More observations. The issue definitely seems to be with my vinyl system as a source. Even my 12AU7 tube was cutting out tonight. Also, there isn't nearly enough gain when listening to records. Usually I listen from my DAC with my volume knob around 11 o'clock at the most. Getting my albums to a good listenable volume was taking me closer to 2 to 3 o'clock. Hopefully this information helps someone diagnose what is going on here. I am glad that everything is okay with my digital sources, but I like to listen to a good amount of vinyl so I would like to find a solution.


----------



## cfcubed

So as this seems to be related to change in source need to know results of this: _check if your source has DC offset (DMM mV measure bet its L & G and R & G)_


----------



## sharkz

I'll do this after work. Thanks.


----------



## sharkz

Alright, take this with a grain of salt because I don't totally trust my multi-meter (I know some fluctuation is normal, but I couldn't get more than a second or two of a consistent reading) but the following were the measurements from my sources using the 200mV setting on my meter:
   
  Sony SACD Player: L 3-4 R3-4
  MUSE DAC: L1.5-3 R1.5-3
  Behringer Preamp: L.3-.4 R.2-.3
   
  Again, I am not sure how accurate these readings will be. I need a better meter than the $3 Harbor Freight one I have.
   
  Hopefully this makes some sense to you.


----------



## cfcubed

Those #s look OK to me, I'd guess DC offset approaching 10mV _could_ cause a problem.
  Don't know what the problem is here, but when you say there's a 12v vs 6v heated tube diff it makes me think the gain of the tube is partly responsible for this.
  The amp's "design center" is the 12au7 + equivalents and these typically have less gain than many 6v tubes that can be used.
  You can check this theory by comparing the gain/mu/amplification factor of the tubes (e.g. google tube type + pdf for datasheets or see the tube ref I posted recently).


----------



## sharkz

Cf, thanks for your input. I will have to play around tonight and see if keeping the volume at a constant value and swapping the tubes seems to make a difference in volume. However the issue still stands that the relay is cutting out with any of my four tubes with the signal from my phono preamp. Which is weird because I haven't had trouble with any other amps I have tried coupled with the preamp.
   
  In any case I have a new preamp (Musical Fidelity V-LPS) inbound and I will give this a try when it arrives. Hopefully the step up in source signal will solve the problem. Otherwise I am completely confused, because my other sources seem fine. I listened through my DAC for several hours last night with no issues at all. In any case, I really appreciate your help.


----------



## cfcubed

BTW CTH PCBs will become available & I've created an IC thread with the info here: http://www.head-fi.org/t/581511/ic-cavalli-compact-tube-hybrid-cth-pcbs-rev-1-3-aka-rev-a
   
  Those that have posted strong interest in acquiring PCBs should read & re-post that interest in that IC thread.  Let's keep this thread for BoM & build issues & the like.


----------



## Ikarios

Got another small substitution question... for D5H, the BOM calls for a 1N582*0* diode. I have a 1N582*1* diode, which has slightly differing specs. Would it be a useable substitute? I don't know jack about diodes and don't know enough about the schematic to be sure.
   
   
  1N5820
http://www.mouser.com/ProductDetail/Vishay-Semiconductors/1N5820/?qs=sGAEpiMZZMuIUjt4yeP9czzQat3OYqJfDL9E1h5QuUY%3d
   
  1N5821
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/1N5821/?qs=sGAEpiMZZMuIUjt4yeP9c77RpzYf92T%252beUmm5gvL3b8%3d
   
  TIA!
   
  EDIT: never mind, looks like I got the 1N5820 diode after all. Now I just want to know out of curiosity/education.


----------



## Mullet

Can I use these as drop in replacements:
   
*Mouser*
  954-E-202 replacement for D1L, D1R
 954-E-452 replacement for D2L, D2R  
  
  TIA!


----------



## cfcubed

Those look like good finds to me... I'm in the midst of re-mapping CTHA 2026a BoM part #s to in-stock ones & we may change a couple/few parts values. 
  E.g. maybe raising R1E/R2E & R4E to reduce the e12's sensitivity a bit more.  More importantly I'm not sure the very last few corrections got into the Rev A BoM spreadsheet on Alex's site (e.g. stereo pot # correction [size=medium][size=10pt]*RK097122...)*[/size][/size]
   
  Thanks for helping with this, we've at least a couple weeks to get it done so there's no rush


----------



## Mullet

I have no issues with the sensitivity of the e12. I can get to around 12 o'clock on the pot before the e12 really kicks in with transients. I suppose going a little higher won't hurt though.
   
  I went through the BoM and mostly everything seems to be available along with my two new substitutes ie D1L/R and D2L/R. The RK097 is on order and won't be available til mid January. If people wanted to allow for a higher current than 800mA then they'd have to wait for 542-4608-RC to be available. DigiKey has the 1A toroid in stock - 732-1429-ND. Also, there are a few parts that are looking to be going obsolete, which means it might be a good time to find replacements at least at Mouser:
   
  512-BC560C
 512-MPSA14
 140-XRL100V22-RC
 140-XRL10V10-RC
  
  The other main parts that are out of stock have alternatives ie the Wima type caps.
   
  So it looks like most people will have to wait for a few parts at least if they're going with the RK097. The RK27 is available on eBay from some vendor in Hong Kong. I think you can also get it from Tangent's Audio shop.


----------



## kEn ViP

I'm having an issue with the initial setup. Powering it up, no smoke; LED turned from green to red after 2 minutes and the relay clicked. OG-SG measured 11.71V. OL 11.68v, OR 11.64v.
   
  Putting the tube in, TB+ only reads 68.8V. Pin 1 57v. Pin 6 0V. The E12 keeps stripping randomly. Any idea regarding this?
   
  BTW, for D1L, D1R, I'm using 2.2mA CRD instead of 2mA, and for D2L, D2R, 4.7mA CRD instead of 4.3mA. Also haven't wired up the pot to the amp,


----------



## cfcubed

>  _e12 sensitivity_ - I've never had nuisance triggers but a few CTHers have, so runeight suggested we adj things slightly.
   
  >  t_iny RK097 pot for small BoM case_ - Most will opt for slightly longer (large) BoM case to make it easier to fit RK27s, 1/4" output jack & RCA ins availability of RK097s should not hold things up.
   
  >  _gunning for 1A+ coils in heater to support up to 800ma filaments_ -  The 732-1429-ND 1A L2H is a fine sub in any event & perhaps it should be the default.  There is enough flexibility with the value of L1H as part of the post ripple filter, so that M8276-ND sub would be fine as long as it fits.  Be careful bending leads on these, may even want to order an extra just in case.  And if heater draw > 500/600ma fit LM2595 w/at least part of a heatsink.
   
  And yes we should re-map to parts non-obsoleted parts & thanks a bunch Mullet for helping with this!   Looks like we should have a workable BoM before the PCBs are fabbed.
   
  ken vip - With tube in please carefully measure & let us know DC volts for TB+ / SG and tube type + heater voltage (DC between tube pins 4 & 5).


----------



## kEn ViP

Quote: 





cfcubed said:


> ken vip - With tube in please carefully measure & let us know DC volts for TB+ / SG and tube type + heater voltage (DC between tube pins 4 & 5).


 
  I'm using the Amperex 6dj8. With tube in, measurements are:
  + TB+/SG 70.8V
  + pin 4 and 5 1.9V
  + pin 1/SG 60.1V
  + pin 6/SG ~0V
  Without the tube, the e12 seems pretty stable. Putting the tube in, the LED keeps changing color.


----------



## cfcubed

All those voltages are low.  Please post these (all under load):  assuming you are using a 24VAC .75A+ A/C adapter, carefully measure it under load - its the 2 A/C jack pins in line (see PCB image), also please measure your 24V LV regulator (ICP) input & output DC voltages - that's its center pin to the right pin measurement then center pin to left pin measurement.
  So far this is a mystery to me.


----------



## kEn ViP

I got 25VAC from the jack. However measurement from the ICP seemed weird The readings kept fluctuating on both the input and output; I couldn't get a stable reading.


----------



## cfcubed

Well it seems that your A/C adapter is holding up the load but not one of your three PS sections (HV, LV, heater) is performing correctly, again they are all too low.  BTW your CRD subs should be fine.
   
  Can only think to suggest carefully re-reviewing all the parts/orientations & solder joints from the tube socket to the back of the board.  Something is affecting all 3 PS circuits: http://www.cavalliaudio.com/diy/cth/main.php?page=schematics/psschematic    If possible I'd like to know the draw on your A/C adapter but it may not be feasible to make the series amperage measurement.


----------



## Rooford

I have two boards for sale at $10 a board. I won't have time to build this amp, if anyone is interested PM me.
   
  Boards are sold.
   
  Thanks,
   
  James


----------



## flynhawaiian

Pmed you.  I’m in SF and could pick them up


----------



## cfcubed

Good news, my CTH buildup using the new BoM & PCB from latest batch is working perfectly.  We'll handle mundane payment & shipping biz in the IC thread: http://www.head-fi.org/t/581511/ic-cavalli-compact-tube-hybrid-cth-pcbs-rev-1-3-aka-rev-a , keeping this thread as its been for build info/assistance.
   
  So we'll forward the new CTH Rev A XLS BoM for hosting on CTH Rev A website, it may be called something like CTHA....Dec2011. 
  I'll forward links to a shared Mouser BoM + Digikey parts #s with my request for PCB payment.  You'll still want to make enclosure, pot, knob & jack choices at least, so carefully review things before pressing PLACE ORDER   And you'll need the little mounting & wire bits external to the PCB.
   
  Here's pics of my new PCB build up:


   
  Only variations from the std BoM IIRC are V-R gray C4 box caps (had around) and 20mm height C10P & C5P (necessitated 1000uf -> 680uf) as my planned enclosure needs 20mm max component height.

 The latest BoM raises the heater circuit L1H & L2H coils to the switcher's max current - 1A.  This allows safe operation of tube heater draws up to 800ma, since anything > 600ma requires LM2595 to get a heatsink I've added one.  Also, although entirely unnecessary, I've doubled up the 24V reg's heatsink (because my enclosure can support it & I've a thing for heatsinks  Note the bottom 2 "teeth" of the inward-facing 24v reg heatsink have been cut off & the heater switcher heatsink is upside-down with it bottom segment snipped off.  Both regulators have been soldered in as high as their leads allow, you'll need to let your enclosure fitment drive these details.


----------



## jdkJake

Nice work cfcubed! Excellent turn around time as well.
   
  Thanks for verifying the PCB and BOM. Very much appreciated!


----------



## sphinxvc

Anyone know what wattage this puts out into 38 / 50 ohm loads?


----------



## cfcubed

IIRC runeight once posted some wattage info here, perhaps dig using google search against this site.
   
  As far as gain is concerned, the only issue I recall is one of too much gain for some sensitive IEMs (little volume pot usable range, perhaps very low-level hiss).  CTH's gain is not adjustable it is dictated by the tube's gain/mu/amplification factor, we can only attenuate its gain with the volume pot + R18 resistors.  See my thoughts here: http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/15#post_7348580
   
  Since some have enjoyed CTH w/LCD-2s & orthos I think lack of drive is not a problem.
   
*One related update:*  We've desensitized CTH's e12 a smiggen more w/latest BoM.  I could not get it's e12 to trip even w/bass-boost EQ & playing my low-bass test track Chevelle's Comfortable Liar, even removed HD650s from my head & using them as speakers   So can't imagine how loud or inefficient one's cans would have to be to do so.  Leads me to think only a problem build OR problem source (w/DC offset) OR problem tube could cause nuisance trips.


----------



## cfcubed

As we've another batch of CTH builders here's some (mostly repeated) info for them.... Other than reading this whole thread & parts of the orig "A Very.." thread:
   

 *Parts ordering* - Between the Mouser Shared BoM / Digikey parts I've informed current builders of, its good to correlate that with the CTH Rev A XLS here:
http://www.cavalliaudio.com/diy/ctha/main.php?page=parts/excelbom
*The XLS BoM now hosted there is the newest one having **"Dec 2011" in its header/title.*
 Every effort has been made to assure the correctness of the BoM(s) but final responsibility lies with those who press "Place Order".  You will want to review pot, knob, enclosure, jacks, switches & other PCB-external items (e.g. fuse/fuseholder is optional*).  Things like fasteners, mounting hardware, wire are not in the BoMs.  May want to review things like the (default - see my recent posts) R18, LED & heater resistor choices (12.6, 6.3 & optionally 7v supported by default BoM R#H choices). 
*Update:  See bk_856er's steps WRT my shared Mouser BoM: http://www.head-fi.org/t/581511/ic-cavalli-compact-tube-hybrid-cth-pcbs-rev-1-3-aka-rev-a/30#post_7979379*
  
 *Assembly / Pre-pwr-up checks* - Taking your time & double-checking things cannot be over-emphasized for this compact build.  Far easier to get things right/clean @ build time then trying to diagnose build errors on this tiny, packed PCB.  Note though that IIRC it's been found that correct/working parts installed cleanly in correct locations & orientations always results in working builds.  I've mentioned how I assure all my BC* TO92 are sound by hFE testing them & its always good to double-check that Mouser put the correct parts in the bag & that we've put the right CTH parts description on them as well.  Mount resistors with their values facing up.
 There are other aids to building in the threads & off the original CTH info site:
http://www.cavalliaudio.com/diy/cth/main.php?page=overview
 Especially the *INSTRUCTION - Board assembly, Wiring & Setup links*.  CTH Rev A specific info includes:
http://www.cavalliaudio.com/diy/ctha/main.php?page=schematics/psschematic
 In particular the heater pad/switch wiring.

 I have orig CTH silkscreen, 1st three cols of BoM XLS and these images handy during the build:

 Note: A couple solder joint/pads seem too close to avoid a solder bridge & you can use above to see if a trace actually connects them.

 Hokey mod of keyid's very nice Transistor locations image:

 Misc links of good info to review (e.g. DPDT pwr/relay switch hack to eliminate pwr-off click):
http://www.head-fi.org/t/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/375#post_6146735
http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/2040#post_6951335
http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/2115#post_7106049
http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/885#post_5633376
http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/1845#post_6212177
http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/210#post_7622576
http://www.head-fi.org/t/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/555#post_7026098
http://www.head-fi.org/t/506984/ehha-rev-a-interest-thread/1215#post_7279845
  
   
     4.   In the event of *a bad part or build error* see the CTH debugging link in my sig first.
   
  * I rarely install the fuse/fuseholder in a finished CTH build... But I do use one in-line (or installed/removable in A/C adapter itself) when its on the bench.  Primarily to avoid popping the adapter prior to case-up, but note the A/C jack ohm test that's part of setup - assuring its not shorted.


----------



## Mullet

I can safely say that I have successfully completed another CTH (for sphinxvc) and everything works as expected. All voltages are normal and within range. The next step is to wait for an ALPs RK27, drill some holes for casing, and case everything up. The only snafu that I ran into was a reversed LED (green start up instead of red). It was a pain in the arse to pull that sucker out and reverse it. A couple of things to keep in mind with this build and DIY in general. The pads on this thing go quickly so beware. Also, I haven't seen this mentioned before, but it's common sense. Take off all jewelery when powering this thing up and testing. You don't want your metal touching metal and frying anything. Trust me I've done this in the past and had to replace the whole buffer. The other thing to keep in mind is that when powering up and testing and then shutting off to reflow a joint or something -- WAIT! Wait for the CTH to discharge. It takes a while -- like 5 minutes or so. When I was working on that LED, I touched solder accidentally to another part of the board and sparks were flying... actually one. But, it scared the piss outta me. Luckily, nothing was damaged and all was well with the amp.


----------



## cfcubed

Yes & proper HV safety precautions, since this project has about 100V present, is mentioned on CTH site.  Static safety precautions as well. 
  You may carefully use a low-ohm resistor to discharge the PS section caps when pwr up/down during build process.
   
  WRT LED orientation - I always brute-force test them, not soldering their leads until they've been tried first.  E.g. using just their leads' pressure to hold 'em in like in my pics above.
   
*Edit: * WRT "_The pads on this thing go quickly so beware_." - Perhaps I've developed a knack for it but I think my very 1st CTH PCB proto build (avatar) had many of it TO92s replaced _twice_ (once for not using spec'd class C/25 BCs, once for a short whilst taking measurements) & I'd no problems w/pads lifting.  But did have trouble w/C4 pads after rolling like 3 different sets of caps, some w/fat leads.
  CTH newbies may want to search for my posts WRT building if reading complete CTH threads is too much.  E.g. I tape needles to my probes, exposing only the tips/points, when measuring things on this tiny PCB.


----------



## Mullet

It looks like those D1L/R, D2L/R Semitec diodes are available again at Mouser... They strangely disappeared briefly. It's great that they are back being that they are way cheaper than the alternative.
   
  954-E-202
  and
  954-E-452


----------



## cfcubed

*WRT 954-E-202 & 954-E-452 - They look like fine subs for the 1N53* CRDs in CTH*, not only are they < 1/2 the price BUT they've closer values to the 1N53*s called for in CTH's design.  It would be great if at least one of the current builders, perhaps that's built a CTH before, give those Semitecs a try.   Again they appear great subs from their datasheet & you'd save about $6 as well.
   
*Updates:  Appears Shared Mouser Project*s may not retain the CTH parts #s descriptions that were entered for the parts *but it seems Shared Mouser Carts do not have this problem.  So I'll be PMing everyone the link to a Shared Cart copy of the Shared Mouser Project.*
  IOW users of the Shared Project may get its entered CTH parts #s substituted with those from prior project orders (if they've ordered the same part before & assigned it a name).  So if you've ordered from Mouser in the past & assigned parts #s, using the Shared Cart link I'm PMing would be more reliable (customer/CTH parts # wise).
*Also note the official CTH Rev A website is now hosting **the newest BoM XLS (has* *"Dec 2011" in its header/title).*


----------



## Mullet

CF3 ~ I can confirm that those Semitecs work. I just used them for the last two builds and as you already know the build tests fine. I was able to snag 'em before they were temporarily pulled. So I'd say builders can give it a go and save $5.


----------



## runeight

Gents, I just wanted to tell you all how much I appreciate the continued interest in the CTH. As you all can guess I am pretty busy with the new Cavalli Audio company and its new products, but I am still a DIYer at heart and I must admit, particularly fond of this little amplifier.
   
  I also want to thank Chris (cfcubed) for collaborating on its design and for taking on the support that is essential when someone has a problem (especially with this very compact and dense board). Thanks!!
   
  And I'd like to thank Mullet for doing the last group buy and helping with the support too.
   
  I hope you all like your amps. I heard one at RMAF driving a pair of LDC2s. I have to say, it sounded pretty good. 
   
  Good luck.


----------



## Tribbs

Quote:


runeight said:


> Gents, I just wanted to tell you all how much I appreciate the continued interest in the CTH. As you all can guess I am pretty busy with the new Cavalli Audio company and its new products, but I am still a DIYer at heart and I must admit, particularly fond of this little amplifier.
> 
> I also want to thank Chris (cfcubed) for collaborating on its design and for taking on the support that is essential when someone has a problem (especially with this very compact and dense board). Thanks!!
> 
> ...


 

 I also want to express my sincere thanks for giving me the opportunity to build this baby.
  Here's to hopes for another group buy for those who follow in the New Year - Cheers!
   
  HA!  My CTH PCB from Chris just arrived!  It's a good omen


----------



## Tribbs

Regarding R18 values:
   
  I will be using the 12BH7 low mu tubes with my Grado cans.
  Is 150Ω too high or should I pick a lower value?
   
  Also;
  I'll be using the small Hammond enclosure (black).  I've seen some nice, uhm, donuts (?for a lack of a better word) to decorate the tube hole in the top of the enclosure.  What are people using to make that hole look better?  I'm thinking something in chrome, brushed alum or gold finish.


----------



## cfcubed

>  Regarding R18 values
  Someone using a CTH with (your model?) Grados would have to chime in.  If all you have is 100R you can try it, just solder 'em a bit up off PCB (or use SIP sockets) so they're easy to change.  BTW at one time IIRC we said 120R max for them.
   
  > decorate the tube hole in the top
  The plastic (black) ones tend to be called grommets & somewhere I'd part number(s) for at least the middle one below.  Don't ask me for that now
  These came from my local electronics store:

   
  For metal/chrome I've used a single plate out of a (search"tube protector" off ebay.
   
  Cutting the hole is tricky, I use a greenlee step drill in a cheapo HF drill press but there are other ways.  And using any kind of perforated sheet for the top is easier then drilling neat ventilation holes like that in my avatar pic.


----------



## runeight

Quote: 





tribbs said:


> Regarding R18 values:
> 
> I will be using the 12BH7 low mu tubes with my Grado cans.
> Is 150Ω too high or should I pick a lower value?
> ...


 

 If you'd like to experiment you could try 50R first. This will drop the power in the headphones a lot. If not enough then move to 100 or 120R.


----------



## Tribbs

I thought I had read somewhere that R120Ω was large enough with Grado (32Ω Z) but am not sure.
  I'll use SIPs and experiment with different values - thanks.
   
  "Tube Protectors" - Oh man, you can tell this is my first tube amp <lol> - thanks.
   
  Next query;
   
Which specific Dual 50K POT to order?  It's not listed in the Mouser shared BoM cart.
  I may have to order the long Hammond enclosure to accomodate?


----------



## cfcubed

*10k->50k log/audio taper dual/stereo* volume pot is fine.  Little one like RK097* for small case, larger case for bigger pots like ubiquitous RK27.


----------



## BK_856er

You can also just barely fit a nice TKD pot (small 601 series) in the small case....
   
  BK


----------



## Tribbs

I was just scoping those TKDs out but can't find a 50K.
  Where did you find your 50K(?) TKD?


----------



## BK_856er

I believe mine is a 10K.  When I was looking 50K were only available from ebay/asia and I wasn't in a position to gamble on the potentially long shipping time.  You might check with the US TKD distributor (sellmark electronics).  My 10K seemed to work fine.
   
  BK


----------



## Forte

Quote: 





tribbs said:


> Also;
> I'll be using the small Hammond enclosure (black).  I've seen some nice, uhm, donuts (?for a lack of a better word) to decorate the tube hole in the top of the enclosure.  What are people using to make that hole look better?  I'm thinking something in chrome, brushed alum or gold finish.


 


  Try searching you local hardware store for a "Flush Draw Pull", something like this http://www.knobsandhardware.com/pulls/linnea-llc-rpr-65-flush-pull_g588762.html?af=1615&cse=1615
  I found one when looking for some desk draw handles, you just need to find one the right size and remove the plate at the back


----------



## Mullet

Quote: 





cfcubed said:


> > decorate the tube hole in the top
> The plastic (black) ones tend to be called grommets & somewhere I'd part number(s) for at least the middle one below.  Don't ask me for that now
> These came from my local electronics store:
> 
> ...


 
  Those black donut thingies are actually called bushings according to eagle plastics. I was recently looking for a few extras for future CTH builds and decided to look at the part # on one of my current CTH's bushing. For a 1.5 inch diameter hole you could get this one at Mouser: 561-MP15018. They have other sizes as well. Just download the spec sheet and find the right size.
   
  I agree that drilling the hole is a pain. I have found great success in finding scrap perf metal around the office. In fact my latest incarnation came from a broken space heater. You'd be amazed at what you can find if you know what to look for. I ended up using a metal hole punch found in a tool chest in my machine room at work. If I understand correctly, metal hole punches are kind of expensive.


----------



## Mullet

On another note... anyone know where I can get some of those Hammond screws? Somehow I lost mine for a build I'm doing and searching the web came up with a few results that required spending more than $10 on a credit card ie Element14 (aka Newark/Farnell) I might try going to a hardware store, but I kind of want black screws; plus I want them to be the self tapping type screw. I would need 8 of 'em.


----------



## cfcubed

Thanks for the grommets bushings correction & part #.    WRT extra black Hammond case screws, I may very well have them as I've used Allen heads in some builds.  Will look tonight & PM either way.


----------



## jdkJake

Quote: 





mullet said:


> On another note... anyone know where I can get some of those Hammond screws? Somehow I lost mine for a build I'm doing and searching the web came up with a few results that required spending more than $10 on a credit card ie Element14 (aka Newark/Farnell) I might try going to a hardware store, but I kind of want black screws; plus I want them to be the self tapping type screw. I would need 8 of 'em.


 


  Do you have a ACE hardware locally? They have them, just not sure if they are black (I think they do). They also have a selection of bushings.
   
  For sure the best local source for small hardware in all materials and sizes.


----------



## Tribbs

Man, the U.S. markup on some of this stuff -
http://www.goodcomponent.com/tube%20ring.html
http://www.goodcomponent.com/tube%20protector.html
http://www.goodcomponent.com/9-pin%20tube%20socket.html
   
  Quote:


bk_856er said:


>


 
   
*To BK_856er*:
  Were those AuriCaps a worthwhile upgrade to your CTH?
  Did you replace the C4L/R output pair? With the same values (220n)?
  What other CTH component upgrades did you find worthwhile?


----------



## BK_856er

I built it as a gift - didn't try the stock configuration/never got much time with it.  I'll defer to others regarding what's worthwhile.  Can't really go wrong with the stock setup.
   
  Next one will be all mine!
   
  BK


----------



## Mullet

I have some local yocal hardware stores I can go to along with a Home Depot. Perhaps, one of them will have something. I'm also going to try and contact Hammond directly to see if they are willing to part with 8 screws. Wish me luck. :/


----------



## Scy

Damn. I missed this one again, I assume that all the boards are gone?
  If someone has an extra board they're willing to sell, I'd be happy to take it off their hands. If not, then I guess I'll just wait for the next batch.


----------



## jdkJake

Quote: 





mullet said:


> I have some local yocal hardware stores I can go to along with a Home Depot. Perhaps, one of them will have something. I'm also going to try and contact Hammond directly to see if they are willing to part with 8 screws. Wish me luck. :/


 


  I'm telling ya, you need to hunt down an Ace Hardware store. There appears to be a couple in Brooklyn. The still excel at basic hardware and have a selection and variety unmatched for a B&M store. Home Depot only has volume, although to be fair, while they have started introducing some specialty hardware, they have a long way to go to match an Ace store.
   
  It's worth the trip.


----------



## Mullet

Good news! Hammond has been very helpful in helping to procure 8 screws. I emailed them and got a quick response. I love dealing with companies that are willing to help without an attitude.


----------



## Tribbs

Having a bit of a time finding a decent small 50K pot.  Ended up with an Alps 20K pot which is backorderd at Mouser until mid-January.
   
  In order to broaden our choice of substitutions I was wondering what, if any, audible difference is there between a 50K pot Vs 10K, 20K and 100K pots?


----------



## Mullet

I'd say go for 100k. If I remember correctly, I'd say there is no audible difference. I suspect a low ohm pot would get louder quicker and a high ohm pot would take longer to get louder. 50k is nice middle ground.


----------



## cfcubed

If you'd rather not make the $$$ stretch to TKD what about a 10k->50k small panny like the alt in the BoM:
http://search.digikey.com/scripts/DkSearch/dksus.dll?x=15&y=16&lang=en&site=us&KeyWords=P2G1203-ND&stock=1


----------



## Tribbs

My goal in this build is to limit experimenting to rolling tubes and R18 to tweak for my Grados.  Although I have plenty experience soldering PCBs (try 1980s 386 PC motherboards - component by component - nutz) I don't want to solder anything and then get the itch to replace it later. BTW, I already have my AuriCaps for C4L/R.
   
  It isn't a stretch for me to move up to a $40 TKD 2CP-601 pot but 50K isn't in stock anywhere.  But going up above that model? No way I'm going to spend $100 for a pot in this build.
   
  By the way I have corresponded with both Percy Audio and PartsConnexion.  Both say 60 days for the 50K TKD 2CP-601.  So, for the benefit of future builds you may want to send them an encouraging email to stock these.  IMO, the 50K TKD 2CP-601 would be the ideal "affordable" pot upgrade.
   
  Addendum:
  Mugdecoffee replaced a 50K Alps RK27 pot with a 100K TKD 2CP-2508 and praised it with his Grados here: http://www.head-fi.org/t/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/525
   
  Although I'm not too excited about his statement: "_One interesting effect is that the soundstage seems a little farther back which feels different especially with Grados_."  But then he goes on to say in his next post that he is using a 6DJ8 which has an amplification factor (mu) of 33.  Too hot for Grados.  Which may explain why he's stuck in "the bottom 15 degrees" with poor channel matching.  Or, is the 100K pot the culprit?


----------



## runeight

Gents, in general it is better to use a lower resistance pot. This is because the resistance of the pot is a factor in the frequency response of the amp. However, as you know, using too small of a pot can potentially load the source. Most SS sources have very low Zo, but there are a few sources with higher Zo.
   
  As a rule, MHO is that if you have to sub, go to 10k instead of 100k providing that your source has a Zo less than 1k.


----------



## Tribbs

I love definitive humble opinions - Thank you!


----------



## BK_856er

Got my mouser CTH order today.  Once again, I'm flabbergasted at the giant mountain of parts that need to go on that tiny board!  Need to remember to bring my A game for this build.  Will be fun.
   
  BK


----------



## runeight

Gents, you all may have discussed this already, but one practice that will help you if there is a problem will be to mount the resistors so that the value text on the resistor faces up so that you can read it. It's much easier to solve a problem if you can see the values. I know, because I've forgotten to do this and figuring what's wrong when you can't even determine if the right resistors are in the right places is more than a challenge.


----------



## Misterrogers

Help! 
	

	
	
		
		

		
		
	


	




 Firstly, I'm a fairly novice building (2 02 builds under my belt). I assembled my CTH off of cfcubed's bom. When I powered it up, I didn't get any sort of pop or smoke, but the LED stayed yellow/red (sorry - color blind) and didn't go to green. Started checking readings, and here's what I got:
   
   
  SG -> OG 2.8V
  SG -> OL ~6mv
  SG -> OR ~6mv
   
  Pin 1: 100.8v
  Pin 2: 0v
  Pin 3: 4.2v
  Pin 4: 0v
  Pin 5: 12.6v
  Pin 6: 100.8v
  Pin 7: 0v
  Pin 8: 4.2v
  Pin 9: ~6mv
   
  TB+: 101.6v
   
  ICP: Center -> 0: 5.7v 
  ICP: Center -> 1: 7.1v
   
  SG -> R1P: 32v/18v
   
  Q1P and Q2P both pass the Diode test
   
  Reading past threads, this pattern seems to indicate I could have a bad LM2595. How would I go about testing this IC on board? Also any/all question or questions are appreciated. Thanks in advance gang.


----------



## sachu

Nope. yourLM2595 is fine.
   
  Something's up with your ICP readings.
   
  This is throwing off the output readings as well.
   
  Tube readings are good which means heaters and HV is working fine. Just the LV and splitter section is not right.
   
  Remove ICP and measure at the pad of pin1 of ICP wrt SG. You should see about 32volts.


----------



## Misterrogers

Thanks for jumping in sachu. A couple of noob questions:
   
  To clarify, I'm trying to get ICP out of the circuit and just measure voltage at the pad? This implies it's safe to power up without ICP in?
   
  Quote: 





sachu said:


> Nope. yourLM2595 is fine.
> 
> Something's up with your ICP readings.
> 
> ...


----------



## sachu

Yes. It is safe to power up without ICP in the circuit.
   
  Alternatively, you could just measure pin1 of ICP first. It should still read 32volts. Pin3 of ICP (With ICP in the circuit) should read 24Volts wrt SG.
   
  If you are reading 24volts on the output of ICP, then measure voltages on IC1S opamp in the splitter section.


----------



## Misterrogers

I pulled ICP and measured at pin 1. 32v. I'll install a new ICP and measure output. If I get 24v, how do I measure IC1S?


----------



## Misterrogers

Also, is it ok to run without heatsinks for startup?


----------



## sachu

You should be fine with running without heatsink for startup and testing.
   
  For testing splitter.
   
  If it is working fine, then you should read 12 volts on the output of I2CS and the same ont he output of IC1S.
   
  If not, then something is wrong.
   
  What i have done in this case is replace all active components in the splitter (all transistors) with new ones, assuming the IC1S is doing its job properly (you can test this when you have all other transistors removed from the splitter section).


----------



## Misterrogers

ARg! What's the likelihood that ICP would blow if installed backwards and powered up? Man, I need more coffee


----------



## UKToecutter

Hi all,
   
  Does anybody have any unpopulated CTH Rev A boards they would like to sell?
   
  Shoot me a PM if you have.
   
  Best Regards
   
  Andy


----------



## Misterrogers

That goof seems to have set me back. Now, I only measure 24v at pin 1 of ICP. R1P now measures 34v both sides. Seems it's not resisting anymore  So what did I likely pop, or what should I test now that I'm down to 24v at pin 1? I checked the wall wort, it's still good.
  
  Quote: 





sachu said:


> You should be fine with running without heatsink for startup and testing.
> 
> For testing splitter.
> 
> ...


----------



## cfcubed

Do you mean that ICP was installed backwards from the start?   If so perhaps it (or a Q feeding it) is damaged and perhaps nothing further down the line is.
  Bad LV could be root cause of all your problems as your other measurements appear they may be ok once your LV is working.
  So I'd consider getting ahold of new ICP, Q1P and maybe Q2P and replacing them.  Measure across R1P if < 110k I circuit leave it.  I'd not run ICP w/o a heatsink & certainly for more than a few mins.
  Then you may have 24v out of ICP under load & we could take if from there (e.g. per sachu's good suggestions).  If no close elec store Digikey has a low cost shipping option.
  As per my debug link, nice pics of top and bottom might help.


----------



## Misterrogers

Happy New Year cfcubed! Thanks for checking in. No, it wasn't installed backwards from the beginning; I went to replace the first one and installed the replacement backwards 
	

	
	
		
		

		
		
	


	




. It popped R1P, which I have ordered. 
   
  I bought kit for my second board, finished yesterday, powered up, and the LED flashed green for a second, then red again! Now, this second board shares basically the same readings as what I posted above. Man, it's hard to believe that ICP, Q1P and Q2P are that fragile. Any thoughts on where I might look for shorts, etc. that would cause the pop?
   
  Also, relative to SG here's the power at the Q1P pins:
   
  Pin 1: 7.16v
  Pin 2: 32.0v
  Pin 3: 18.2v
   
  Input on ICP is 7.16v Would I be correct is assuming that Q1P is bad? It does fail the diode test. But what would make it work, then fail right away? I'll recheck my joints. Just don't want to keep feeding the board components when something else is the cause.
   
  Again and always - thanks so much for the help! I'm learning a ton.


----------



## Misterrogers

Oops, had them flipped:
   
   
  Pin 3: 7.16v (out)
  Pin 2: 32.0v
  Pin 1: 18.2v
   
  Definitely not gonna get it done. I have a spare, but it fails the diode test. Just want to clarify - should Q1P always pass the diode test? (positive to center, .7 to 1 & 3, negative to center, 0 to 1 & 3). Between my two boards, I've changed these 4 times, and my spare seems to be broken. Seems either very very sensitive, or I'm doing something very wrong.


----------



## Misterrogers

Ok. I was measuring Q1P wrong. Base is pin 3, not center - doh. So measured correctly, the installed Q1P seems to be functioning. So why is O (pin 3) only outputting 7.16v? I'm going to reflow it, but I'm confused.


----------



## cfcubed

Hey Happy New Year to you too, though I bet yours would be a bit happier w/a working CTH or two   And learning while doing with the CTH is not the easiest path...  Even "seasoned" builders like myself give a little sigh of relief when we've gotten everything right & a CTH goes green (& stays there).
   
  OK my guess as to whats wrong would be a short somewhere down the line from ICP.  Perhaps we should suggest to install ICP *last* after first checking it's *O*utput *pad* vs *SG* resistance.  So you can pull ICP & do that test and depending on the result perhaps install ICP with its *O*utput pin lifted & use 150R-> 470R *5W+* resistance (e.g. radioshack) from it to *SG*, placing a decent load & checking for 24VDC.  ICP should be able to make the resistor warm in a minute or less & still hold 24vdc across it (use ICP heatsink), if it doesn't you are back to ICP & back check/replace (and I'd suspect downstream short).
   
  BTW by strengthening Q1P (vs orig BCs) we've made it stronger in the case of a short, e.g. it may no longer be the weak link.  An improvement overall but maybe we gave up the obvious part to fail in case of a LV short.  Again it might pay to review your build very closely against Rev A pics that are around but a couple hires pics of your build(s) may help us.  
  Oh and I hope you are checking the parts values, etc, etc as you install them, not just the CTH parts desc on the bags, because as bk_856er can attest, Shared Mouser BoMs & Carts are flakey, the master list is CA's XLS.


----------



## Misterrogers

Heh, yea I know it's an advanced build. This is generally how I learn things - I throw myself in the deep end 
	

	
	
		
		

		
		
	


	




. It will be nice when I get it worked out, but I don't mind the troubleshooting. That's where we really learn what's going on. The 7.16v out from Q1P - with ICP in place, that value could be low because of resistance, correct? Hence, by pulling ICP and measuring output, we'll get the supply v. Just trying to understand . Yep, I check parts description from mouser. I also checked transistor functionality before and after installation.


----------



## cfcubed

OK I it really looks like your Q1P is reversed.  When you see a flat/wide band on a PCB image or silkscreen for a mountable device that band typically represents the mountable side of the part.  In many cases the devices (based on their TO*** type) have a section of metal tab to mate w/heatsink (see my sig CTH build info - transistor locations image).
  If I'm right & your Q1Ps were always in wrong that would certainly cause these problems.
  Just to be sure all your tombstonned diodes are band up right?   Image in http://www.cavalliaudio.com/diy/cth/main.php?page=instructions/assembly
   
  And yes too low a resistance load, like a short, would be too much for ICP or an upstream semiconductor to handle (for any length of time).
  And you need the tube in for some of the measurements of course (e.g. the 80V pin #1 & pin #6 vs SG measurements).


----------



## Misterrogers

So the the metal inset of Q1P should face the rear of the board?? Awe man. I wasn't sure - but I looked at Mullet's photo at the beginning of these thread, his seems to be facing the front. Please jump in one more time to confirm. Thanks!


----------



## Misterrogers

Also as best as I could tell, there isn't an 'orientation' band on the PCB for Q1P. It's clearly there for ICP. Also yep - tombstones diodes are band up. Thanks mate.


----------



## cfcubed

Yes the metal section of Q1P faces back of PCB.  It is difficult to see in many photos due to reflections off its plastic front.  Another indicator you will find is a mark/dot for pin #1 of such a device as you can see in my PCB closeup from the IC: thread.  And I see that the thicker Q1P line, representing its mounting side, is difficult to detect on the PCB silkscreen, so the difficult-to-see dot for its pin 1, my Transistor Locations post or a nicer completed CTH PCB pic was the way to tell.  You are not the first to do this & IIRC no parts were damaged in the other cases (but I could be wrong there).
  So good luck, maybe we'll get good news from you soon


----------



## Misterrogers

Bonehead :-| One thing I've learned with these builds - understand your components and the schematic. Don't guess, confirm. Have to say though - I suspect that if I'd installed Q1P correctly, there's a real chance that both boards would have fired up out the gate. Says something about the design/layout/bom. Ok - remove, test the part, reinstall and let's see.


----------



## Misterrogers

Works! I'm green now. Gotta install the tube socket and the heater switch, rca's, etc. and push forward with testing. Thanks so much for taking the time Chris.


----------



## cfcubed

You're welcome.  And yes Q1P orientation marking needs improvement on the PCB but there's been revision in that area of the board that makes it difficult.
  BTW there's a very nice wiring diagram up on CA.  Key is that IG = SG but OG != SG/IG.  And you may need to ground pot metal to SG or IG to avoid noise when touching pot knob.


----------



## Tribbs

Should *R13L/R *be *1/2* watt as described in BoM or a *1/4* watt as Mouser part# 71-CCF55-1.5K-E3 indicate?
   
  D'oh! - Nevermind 
	

	
	
		
		

		
			





...
   
_"Description: Metal Film Resistors - Through Hole 1/4 watt 1.5Kohms 1% Rated to 1/2 watt"_
   
  Same with R10E.


----------



## Misterrogers

What are ya'll using to attach the heatsinks?


----------



## cfcubed

Had a stash of insulated stuff + 4-40s or 6-32s around myself, but its good to isolate at least ICP with something like this (available & maybe less expensive from elsewhere):
http://www.radioshack.com/product/index.jsp?productId=2102859
  don't need a heatsink on LM2595 unless using high-draw heater tubes (> 5 or 600ma series).
*UPDATE:  Oops.... For many parts/projects its important to insulate/isolate heatsinks, but not in CTH's LV reg case as the LM78XX's tab = GND. *
    
  Quote:


misterrogers said:


> What are ya'll using to attach the heatsinks?


----------



## Scy

Here's some thermal pads from digikey. I've used them in my previous builds.
http://search.digikey.com/scripts/DkSearch/dksus.dll?site=us&lang=en&keywords=ber219+nd


----------



## Tribbs

Regarding *R5H* Heater Resistor:
   
  Is there a general concensus on which heater voltage 4.2v [3.3K], 5.6v [5.8K], 8.4v [15.1K], 9.4v [23.3K] is most practical (other then 6.3v, 7v, 12.6v)?
   
  I haven't spent much time researching all the various tubes.  Primarily interested in low-med mµ tubes.
  Would appreciate any opinion on which heater voltage R value to use here giving the greatest selection of tube roll options.
   
TIA.


----------



## Mullet

I'm going to say your R5H would best be 15.1k or 8.4v. You have two cheap options in tubes... 8GU7 and 8CG7. I can tell you that their cousins 6GU7 and 6CG7 are considered nice tubes. There might be more out there at 8v, but I'm not sure what they might be. There should be a list of tubes that have been known to work on the CTH tubes tweak thread, but it seems to be more geared towards 6 and 12 volt tubes with a few 4v options thrown in there.


----------



## Tribbs

Thanks again Mullet!  I need to search around some.
   
  Man, I need a break.  Don't have a good workbench and light w/mag anymore. So, need sunlight through the deck door and a handheld magnifying glass.  Being winter in this hemisphere, after 3P the light is so diminished I can no longer scrutinize my solder joints - these old eyes can't hack it any longer <LOL>
   
  Slow but sure...


----------



## sphinxvc

If anyone is interested, I am selling my CTH Rev. A, I've barely had it for any time at all (3 weeks) but I bought a DAC with a surprisingly capable HP-out, & so the CTH is wasting away.


----------



## Misterrogers

Wanted to let ya'll know that both of my CTH builds are up and running, thanks to the awesome assistance of cfcubed and mullet. I've learned a ton, and am enjoying the CTH immensely. One of them was a gift for a friend who's enjoying his first tube amp. This community continue's to amaze me - thanks again!


----------



## cfcubed

Quote: 





misterrogers said:


> Wanted to let ya'll know that both of my CTH builds are up and running, thanks to the awesome assistance of cfcubed and mullet. I've learned a ton, and am enjoying the CTH immensely. One of them was a gift for a friend who's enjoying his first tube amp. This community continue's to amaze me - thanks again!


 

 That's great news... Was wondering how they worked out.  Thanks for letting us know.
   
  After a little too much MAP gas torching of the acrylic edges, my build for Alex is now fully done and working well:
   

   
  If I was ever to do this again I might go for an acrylic bottom instead of the 1/4" solid alum plate.  And might go for a lower, longer layout.  I'll someday get to build details in the DIY Enclosures thread.
   
  As I designed this as tall & squat, with jacks, etc underneath, wanted PCB to sit as high & close to the top as reasonable.   Also wanted to avoid using a black "socket saver" to raise tube & didn't want to under-mount the > 20mm high caps.
   
  So substituted these C5P & C10P (Mouser) caps: 667-EEU-FC1H681 (680uf was 20mm H max value, instead of spec'd 1000uf) and 667-EEU-ED2C101S.  Both have 7.5mm lead pitch & needed lead bending to neatly fit PCB's 5mm pitch:
   

   
  There's an extra adjustable support as a screw threaded through the hole in the tube socket, probably unnecessary.      Like the way the whole thing came out.  Maybe I'll make one like it for myself someday


----------



## stringgz301

Need some debugging help on my new build.  Start it up and get the red LED but it never latches.  Measured voltages at the R1E and R2E and get 12.06v and .712 respectively.  Any suggestions?
   
  Other measurements:
   
  OG to SG = 12.06
  OL & OR are both close to 0 (3-5 mV)


----------



## cfcubed

Not to be a PITA but I like to start debugging by getting builders to do the steps in my "CTH debug" link in my sig. 
  IOW be sure of *all* general/basic/setup measurements first.  And a pic can help as it just did in spotting a reversed Q1P.


----------



## stringgz301

Thanks cfcubed.  Have checked all the basic measurements short of putting in the tube.  Also, picks attached.  Seems like the problem is somewhere in the right buffer.  All suggestions appreciated.


----------



## sachu

post readings of ICE opamp. And of the dual channel opamp in the buffer.
   
  And yes, very likely a buffer problem.


----------



## stringgz301

ICE Opamp:
   
  Pin2: 11.54
  Pin3: 12.04
  Pin4: 0
  Pin6: 22.28
  Pin7: 24.11
   
  IC1 Opamp:
   
  Pin1: 6.72
  Pin2: 11.91
  Pin3: 12.04
  Pin5: .958
  Pin6: 11.91
  Pin7: 1.188
  Pin8: 24.10


----------



## stringgz301

Figured it out.  Replaced the Q's in the right buffer 1 at a time.  It was Q4R.  Now have latch and all voltages check out.


----------



## tim_j_thomas

I moved this post to the "Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread".


----------



## BK_856er

Finally got my tube socket and C4 caps today, which will complete the board assembly!
   
  Quick question on the Auricaps.  The black lead indicates the Foil end on Auricaps, which should ideally connect to the tube plate side for best theorectical noise rejection, correct?  In other words, the opposite of how stringgz wired his up in the pics above if I have that right.  Maybe no practical consequence to how it's done, but why not.  Can anyone verify before I warm up the iron?
   
  BK


----------



## Mullet

I've sort of done it the way stringz has his except mine are reversed for each cap. Thus far I've not heard any noise or had any issues what so ever. I will say after having/listening to a few CTHs I like the CTH best with Sonicap Gen IIs over the Auricaps. I feel the Auricaps are more congested with my Thunderpants, which are a have a limited sound stage to begin with.


----------



## BK_856er

I have auricaps and sonicap genII on hand, but the genII are 400V type and rather long.  Too long for a vertical tombstone in the Hammond enclosure.  I initially thought I would socket C4, but the leads are way too large in diameter for my sockets.  The joys of botique caps.  If I decide to start with genII caps, what's a good mounting technique?
   
  BK


----------



## Mullet

I have them in a v-shape lying flat. The bottom of the v is towards the base of the socket. They fit in there nice and snug.
   
  On another note:
   
  I'm doing another build for a fellow head-fier who uses mostly Grado-type phones. I've read in the past that 150ohm R18s were preferred for these types of phones. Would I be fine with 100 ohms for this build and Magnums, Grados, etc.? What would be the caveat in doing so?


----------



## cfcubed

WRT foil C4 caps -  Yes there is a preferred orientation, perhaps you've googled stuff like this:
http://www.aikenamps.com/OutsideFoil.htm
  BUT since there is little EMF in the audio range in CTH (no transformers, has DC heater & minimal A/C traces) this is likely something not to sweat.  E.g. I'd not remove installed C4s just to change their orientation.
   
  The C4 connections are amongst the most critical in the amp, they should be solid & if sockets are used they should be robust.  And try to secure any big C4 caps, at least to each other.
   
WRT R18 values - We only recommend > 0R here for 2 reasons: 1) to provide some volume pot range and 2) to reduce/eliminate hiss BOTH in the case of more efficient cans (esp when also using higher mu tubes).  So we say 100R as it will cover most cans well, though the optimal value would differ between, say LCD-2s (lower) & Grados/IEMs (higher).   I've made a large related post here:
http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/15#post_7348580
  Ideally one could fit a DPDT R18 switch for say 0R & 120R (install 120R R18s & have the DPDT simply short those positions or not).
   
  I've MS-1is I got cheap here on the way to me & using them would be the 1st time I could speak 1st hand about Grados & CTH.  Till now been relying on the reports of others.


----------



## BK_856er

Thanks, guys.  Just about wrapped things up with this - fingers crossed.  Made a last-minute change and went with the Sonicap GenII instead of the Auricap.  Noticed the leads on the Sonicap are each different length, but I'm not sure if that indicates anything special.  Put an inquiry in with Sonicraft about that.  Lacking a scope, I tried to mimic CF3's orientation from pg1 based on the printing, fwiw.
   
  Drying off from the final IPA bath now.  Might get to wire it up and function test tomorrow.
   
  BK


----------



## Forte

Its on their website "The shorter lead is Shield"


----------



## Mullet

Nice build! Yes the longer lead means it's the input lead. But it doesn't "really" matter or so I was told by Jeff at Sonic Craft. By the way, they no longer have any .22uF 400v Gen IIs. For my next build, up for consideration is a set of .22uF Gen Is, that have a more neutral sound signature compared to the Gen IIs. The Auricaps are the other affordable option. Another thing to think about is that the .33uF Gen IIs are still available. With the recent adjustments made to the e12 specs, would the .33uF caps work without issues? I can say with the most recent adjustments and normal spec'd C4s I haven't had a trip yet from transients, etc. On my older CTHs I had this issue from time to time.
   
  On another note... I like the Gen IIs better than the Auricaps. The Auricaps are too meaty for me. I feel the Sonicaps have better resolution and the highs and lows are less rolled off.
   
  One more thing... anyone have any extra .22uF Gen IIs they can spare?


----------



## BK_856er

Quote: 





forte said:


> Its on their website "The shorter lead is Shield"


 

 Right you are.  I scanned the sonicraft site super quick in the midst of lead-bending and totally missed it!
   
  BK


----------



## BK_856er

Quote: 





bk_856er said:


> ....
> 
> Drying off from the final IPA bath now.  Might get to wire it up and function test tomorrow.
> 
> BK


 


 I forgot what a ton of work the final CTH drilling/wiring is.  It's 2:19AM, but the little guy is now 100% done and passes all the startup tests!  I'll give it a listen after I get some rest.  Finally a CTH all for me.....
   
  BK


----------



## Mullet

I feel like half this project is wiring and casing up. Not my favorite part to say the least. My fav part is turning that amp on for the first time and plugging phones in. 
   
  Enjoy the CTH!


----------



## BK_856er

Listening to the first tracks now.  Works/sounds awesome!
   
  Only issue is low volumne.  Hmmm, what did use for R18?  Whoops, somehow of the 3-4 various correct values I ordered, I installed the one I mistakingly ordered with a K at the end (120k instead of 120).  Glad I socketed those things for quick changes!  Will fix that and grab some pics later today.
   
  Sounding soooooo good right now.
   
  BK


----------



## BK_856er

Mission accomplished and sounding great!  Used 100-ohm for R18 this time and the volume is now abundant (doh!).
   
  From memory, I think this CTH sounds better than the one I made last year.  Maybe C4??  Thanks Mullet for swaying my final cap decision just moments prior to install.  I look forward to comparing both units next time I meet up with my bro.
   
  I went with the long case and shortened it by about 3/4" so it just barely fit the alps RK27 and AMB e27 board.  Used some solid wire for the rear power/heater connections to keep things tidy.  Regular stranded hookup wire up front.  Was going to route it under the board, but I ran into difficulty soldering from the top, so I changed plans.  One flub with a hot iron on the rear plastic hammond end piece.  Crammed in a heater switch, fuse holder, power switch and pcb input jack to the rear panel.  Still need to figure out a top piece - hopefully heavy gauge perf.
   
  Thanks to CF3 for organizing the latest group buy and for the ongoing support!
   
  BK


----------



## drtturnip

> Amperex Bugle Boy ECC88
> Amperex Bugle Boy ECC82
> Amperex USA Gold Pin JAN-6922
> Pro Comm Miniwatt PCC88
> ...


 
  That is a sweet stash of tubes. My money is on the telefunken.


----------



## cfcubed

Quote: 





drtturnip said:


> That is a sweet stash of tubes. My money is on the telefunken.


 
  Mine is on the Siemens ECC82 Chrome Plate & Amperexs, I'm a broken record skipping CD about them
   
  BK856er  - Looks good, really neat & compact.  Yes, C4 caps can make a diff, how much depends on your ears.  Haven't tried Auricaps yet, IIRC rds liked 'em.  If you've no use for them & don't want them laying around I'd buy 'em from you (PM).   BTW I've a couple "touched" plastic Hammond endplates in my past + associated curses


----------



## drtturnip

No arguments here. They are all really fiiiiine.


----------



## jdkJake

Nice work BK.
   
  Of course, that is now expected. 
	

	
	
		
		

		
			




   
  Somewhat surprised to see the alps vice a TKD. Gotta be a story lurking on that one.
   
  Let us know what you think of the genII once you compare notes with your brother's rig. I was leaning towards the genI for this build if not only for the bang for the buck, but, the advertised neutrality. Most interested in your subjective opinion of the two builds.


----------



## Mullet

That Telefunken is one of the best tubes depending on what headphones are in use. I have to agree the Siemens ECC82 Chrome is awesome too! Since that posting, I've pretty much collected every desirable or notable 12AU7/6DJ8 type tube and even some of the better ones don't "work" with certain phones. It seems the TP1s really reveal the tube more so than any other phones I own.
   
  BK~ your build looks great as usual. I'll take pics this time. I'm not going the e27 route, I'll be doing something very similar in terms of longer case, RK27, etc. I think I'm going to try Sonicap Gen 2 .15uF 600v for the C4 position because the lack of availability of .22uF Gen 2s. I'm not so much a fan of the Auricap with this amp. I think I'd rather use Wima MKP instead or the lower rated Sonicaps. I am curious about the Gen 1s too though. I would think they would be best to let the tube shine without coloring anything.
   
  I'm not going to lie, I've tapped the plastic ends with an iron on a few CTHs as well. It goes with the territory. It's like a rite of passage.
   
  For the top, I'll be using some silver colored perf metal I found on an old broken space heater. I stripped the parts and used a tin cutter to make a few pieces. The only thing I don't like about it is that it's thinner than the previous perf metal I used, but it will work fine when in the case.
   
  I'm starting the build on Sunday, so let the games begin!


----------



## sachu

Try the amp ohm PIO copper foil caps. My favorite coupling caps.
   
  The 6CG7 clear top will always be a favorite of mine in this big punching little amp. Wish I had kept one of the CTHs i built..


----------



## UKToecutter

A new batch of boards would be nice....


----------



## cfcubed

>  A new batch of boards would be nice....
   
  That may be in the works by a different member, stay tuned.
   
  So I've posted about the eliminate-power-off-click mod a few times & have been asked about it. 
  The CTH e12 implementation does a good job of protecting your cans against harmful DC offset at anytime, not just during pwr up & pwr off.  But there is the annoyance of an audible click during pwr off.
  A pretty easy brute-force way to completely eliminate the pwr-off click is to use a DPDT power switch for your CTH, using one set of poles for 24AC in latch & the other set to make/break the pwr to the relay.
   
  Using words I'd said "Re: relay interrupt:  IIRC, I just used a dremel w/small bit or X-acto knife & cut away one of the under side traces to the relay coil... Probably the Q3E/D3E junction to coil negative trace.". 
  Here's a pic of this for the Rev A PCB:
   

   
  On CTHs w/o the mod I simply remove the cans from my head prior to power down (always leaving cans plugged in, pwr off click is harmless).  No need for that w/this mod.


----------



## Misterrogers

Which ones did you use in CTH? Also, I just posted an IC on CTH Board GB. Here's your chance to get one back 
  
  Quote: 





sachu said:


> Try the amp ohm PIO copper foil caps. My favorite coupling caps.
> 
> The 6CG7 clear top will always be a favorite of mine in this big punching little amp. Wish I had kept one of the CTHs i built..


----------



## cfcubed

Though some of our tweak/caps posts belong in the Tube & Tweak thread, wanted to give a heads-up not to use these silly expensive V-Caps in a CTH:
http://www.v-cap.com/teflon-capacitors.php
  I've found out the hard way that CTH e12 relay lock is temperamental using them (e.g. locks w/some tube/can combos not others), even using the new BoM. 
  So I'll be listing a minty pair of those for use in some other amp design.  When they work they are joy though, well if you manage to forget what you paid for 'em


----------



## Mullet

i just went ahead with your advice and bought .15uF Sonicap Gen 2s ie anything from .1uF to .22uF should work in the CTH C4 position. They are the same length, but slightly thicker, so they should be just as easy to install. The guys over at Sonic Craft said that the sound signature shouldn't change a bit from .22uF to .15uF. I've tried the Wima MKP, MKS, Auricaps, and Sonicap Gen 2s and liked the Gen 2s the best. They just seem to have a bit more detail and don't roll the highs or lows like the Auricaps seem to do. The Wimas were ok with the MKP series being a tad bit better. They are coming out with a few new lines of caps later this year so I'm curious what they have up their sleeves being that the Gen 2s are a nice bang for the buck.


----------



## sachu

Anoher excellent choice are the multicap rtx


----------



## BK_856er

I couldn't find any decent perf, so I decided to hack the hammond top.  OMG, making your own perforated material with a hand drill is labor intensive!  Nearly 300 carefully placed holes later, chamfered on each side, and I think it's looking pretty darn good.  I hope the blisters heal quickly.
   
  Also added a heatsink to ICH today.  Moments later I took delivery of my new Russian 6N6P tube.  It's still early, but I like this tube!  Low amplification, very low microphonics, good sound.  Spectacular tube glow - that's worth the price of admission right there.  Hopefully I'm not stressing the CTH too much...
   
  BK


----------



## cfcubed

>  Russian 6N6P  ...  Hopefully I'm not stressing the CTH too much.
   
  Nope, 750ma +/- 50ma is fine w/the new/Dec2011 BoM 1A rated heater coils/chokes & the little ICH heatsink  (*<<< BK's ICH temp measurements were too high for comfort *- see my post below).  Agree, nice heater glow on that 6N6P.
   
  Looks great!   Man that's some patience doing those holes esp. w/a hand drill!    See the headphone 1/4" jack is clear, is that 3.5mm input below it?


----------



## BK_856er

Yep, 3.5mm input is below the 1/4" jack.  Nice and short internal wiring far away from the PS sections.  Sounding really nice with the LCD-2.
   
  Sure is toasty....after 45min my thermocouple is measuring 127C at the surface of the tube and the top rear of the case is 56C.
   
  BK


----------



## Mullet

Perf material is easy to find if you know what you're looking for. I just found an old trash bin at work that looks ripe for the pickin. It's got a diamond shape perf material to it. Just need to use tin clippers and then a hole punch and it's good to go.
   
  BK~ Great job on the holes. I definitely don't have the patience for that type of thing. Good going!


----------



## cfcubed

I also make the rounds looking for inexpensive/free materials for builds, but haven't located nice perf material myself.   And haven't ordered it through say:
http://www.onlinemetals.com/merchant.cfm?id=1002&step=2&top_cat=1
  Mullet nicely sent me a couple cut pieces when he'd spares.
   
  BK & I've been exchanging PMs about his CTH & temp readings.  He's reported alarmingly high temps for ICH specifically w/6N6P in his build, so I've edited my post above about this.
  We want to see all comps <= 85C, preferably lower.   "Standard" builds running the originally recommended max heater draw (< 600ma) have had temps measured & found to be OK.
  And though new BoM heater parts are rated 1A+, with extra draw comes extra heat. 
  When reaching for higher-draw tubes consider bottom & back plate 1/4"+ holes w/taller feet to allow cool air to enter (& hot air to exit).  May also have to get creative w/heatsinks on ICP & ICH.


----------



## schwallman

if anyone is looking for a board let me know. I got one in the last group buy and will not have the time to try and build one.


----------



## BK_856er

As CF3 mentioned above, with the 6N6P tube my ICH and ICP were running too hot.  I measured the actual component temps with a micro thermocouple.
   
  Project "COOL THE CTH" is now underway.  Supplemental big beefy custom fit heasinks and bunches of holes on the underside should help!
   
  BK


----------



## BK_856er

Added a bunch of medium holes on the bottom and several small stealth holes on the sides near ICP and ICH.  Also ten more holes near the tube to help tube ventilation (and add some style).  I'll avoid medium vent holes in the sides if I can help it - too hard to hand drill through the pcb slots with a hand drill and have it look good.  After the additional heatsinks and ventilation I should be done!  Will grab some comparison component temps later.
   
  BK


----------



## cfcubed

>  with the 6N6P tube my ICH and ICP were running too hot.
   
  Re-clarifying this, the ICH was especially hot (ICP not beyond acceptable) & its because of use of a low heater voltage (6.3v) tube having high draw (> 500/600ma).   
  This is because the heater switcher having to work harder to chop its incoming 38v or so & cut it down to 6.3v while passing more amperage. 
  Note: SMPS is far superior efficiency/heat wise then common linear methods of doing this, and CTH could not achieve anything near it's small form-factor, and have single 24VAC supply, without it.
   
  You'd not have to go to these extremes in a "standard" build targeting "recommended" tubes (see CTH tubes in my sig). 
  But it's been said many times that even standard CTHs using target tubes benefit from good ventilation.
   
  BK - Being into heat-sinks myself I have to say those are some macho sinks you have there   And though isolating thermal pads are recommended, the tabs on ICH & ICP = ground so that's not a concern.


----------



## jdkJake

BK, your either a Zen Master or a madman. 
	

	
	
		
		

		
			




   
  Eitherway, the results are impressive and way cool (pun intended).
   
  I still cannot believe you hand drilled and finished over 300 holes....


----------



## sachu

Very nice BK!! 
   
  If someone wants to upgrade their CTH, i'd recommend getting a Belleson Super regulator to replace the 24V 7xxx series one in the amp for powering the LV buffer stage.


----------



## BK_856er

Quote: 





cfcubed said:


> >  with the 6N6P tube my ICH and ICP were running too hot.
> 
> Re-clarifying this, the ICH was especially hot (ICP not beyond acceptable) & its because of use of a low heater voltage (6.3v) tube having high draw (> 500/600ma).
> This is because the heater switcher having to work harder to chop its incoming 38v or so & cut it down to 6.3v while passing more amperage.
> ...


 

 Just call me a macho zen master madman.
   
  I'm embarrased to admit that in my excitement I was using 12.6V on the 6N6P tube  
	

	
	
		
		

		
		
	


	



   
  I didn't realize the incorrect heater setting until CF3 mentioned 6.3V.  Oh well, I feel better with a special super-cooled CTH regardless.  Will grab some updated measurements and report back.
   
  BK


----------



## cfcubed

Quote: 





bk_856er said:


> I'm embarrased to admit that in my excitement I was using 12.6V on the 6N6P tube


 

 Oops  I guess that nice, bright tube glow & 120C+ tube top measurement were trying to tell us something
  Well the tube was drawing 10W+ and the CTH was holding its own.   Now it will do even better with your mods, e.g. no worries w/800ma draw tubes for you.
   
  BTW I've occasionally used the wrong heater setting for brief periods.  Dead giveaways for that are 1) 6.3v for 12.6v tube - lower-than-normal gain, 2) 12.6v for 6.3v - tube brighter-than-normal filament glow.


----------



## BK_856er

Just to close the loop on my Dec. 2011 CTH RevA temps with high heater draw 6N6P tube with the proper 6.3V heater setting.
   
  Measured with a micro-tip thermocouple snaked into lid holes after ~30min powered up:
   
  Room temperature = 23C
  Rear of case ambient just under top cover = 37C
  Tube surface at top cover height = 67C
  ICP at heatsink bolt = 71C
  ICH at heatsink bolt = 61C
   
  All is well.  
	

	
	
		
		

		
			




   
  BK


----------



## Misterrogers

I'm getting parts together for my next CTH build, and I've been shopping for some good cap upgrades. I picked up a pair of Robert Hovland Supercaps .22uF 400V. Anyone have any experience with these?


----------



## Mullet

BK~ smooth move on the heater voltage thing   ...I'm surprised the 6N6P even worked at 12v
   
  MR~ I don't have experience with the hovland supercaps. I've heard good things in general about the hovland musicaps, but not in relation to the CTH. One thing to keep in mind is cap size. You might have difficulties with installing those caps because of their size. Auricaps because of their size fit in easily. Wimas are no challenge either. The Sonicap Gen 2s that I've been using are approx. 1 inch long and just barely fit in a V orientation. The bottom of the V is facing towards the tube socket. You might be able to use a similar orientation and have success.
   
  By the way I just finished another CTH build for a fellow head-fier. Used .15uF Sonicap Gen 2s with success. I'm curious if the .33uF Gen 2s work as well. Sonic Craft is officially out of .22uF Gen 2s. CF3 mentioned to me in a PM that .1uF to .22uF (and maybe .33uF) would work in the C4 position. I'm just curious if there are sonic differences between .1uF and .22uF.
   
  The other thing that was different about this build was that I used 120ohm R18s instead of the BOM 100ohm R18s. The one difference I've noticed is that if I compared the volume dial in relation to "perfect listening level" on this CTH vs. mine I can move the dial up to 2 o'clock vs. 12 o'clock using my AKGK701s.


----------



## particleman14

Finally put together my Rev. A tonight.  I swapped my led orientation so red means good to go, green means bad  other than that I'm enjoying this amp w/ a 6922 tube (looking forward to rolling some more!).  
  However, I notice there is a solid amount of hum if I turn the volume up a bit.  the volume knob needs to be turned up to levels I wouldn't dare listen. Connecting the signal ground to the case doesn't seem to kill the hum for me.  any ideas?  otherwise I'm quite happy with this amp!
   
  here some pics..


----------



## Mullet

@particleman14
   
  I found that with my first CTH build when I touched the volume knob I'd get a hum. It would go away when I took my hand off the knob. I was told to take the input ground / ground + and tie that to the pot. So for example the RK27 has two screws on the back. I'd partially unscrew one of the screws and tie a wire from that to input ground and ground + on the pots wipers. No more hum. Not sure if this will help but give it a try.
   
  Congrats on your build.


----------



## cfcubed

WRT hum - What Mullet said plus check all input jack -> PCB wiring compared to wiring diag on CTH site (use ohmmeter to assure).
  Try different tube.   We've no hum issues in this design AFAIK except perhaps barely audible hum between songs w/ultra high efficiency can/IEMs.


----------



## particleman14

quick follow up regarding the massive hum at higher volumes.  turns out its the tubes!  after swapping in some new ones everythings' great!  still undecided on what tubes I should put in this guy... I've got 6922 JAN and russian 6n6p..


----------



## proid

I'm really interested in building a CTH. How does the parts cost (just normal build, nothing fancy)?


----------



## BK_856er

Quote: 





proid said:


> I'm really interested in building a CTH. How does the parts cost (just normal build, nothing fancy)?


 


  I had a $95 Mouser order, a $10 Digikey order (both excluding shipping) and small orders elsewhere for a tube socket and tube.  And of course the board.
   
  I'd say under $150 at the end of the day.
   
  Worth every penny!
   
  BK


----------



## cfcubed

Just another heads-up that there are handful of PCBs left in MisterRodgers IC/GB thread.  Don't know when the next one will happen.


----------



## wiatrob

Quote: 





particleman14 said:


> Finally put together my Rev. A tonight.  I swapped my led orientation so red means good to go, green means bad  other than that I'm enjoying this amp w/ a 6922 tube (looking forward to rolling some more!).
> However, I notice there is a solid amount of hum if I turn the volume up a bit.  the volume knob needs to be turned up to levels I wouldn't dare listen. Connecting the signal ground to the case doesn't seem to kill the hum for me.  any ideas?  otherwise I'm quite happy with this amp!


 


  It was nice to see this at the Bay Area Meet, sorry i didn't get to listen...


----------



## particleman14

Ya it was cool meeting you Wiatrob.  With all the awesome gear there the CTH was definitely overshadowed. I was very impressed with the liquid fire though!


----------



## Mullet

I have a few questions about this amp that I've never seen answered before...
   
  What is the output impedance of this amp? Is that directly tied to the R18 resistors?
   
  What is the voltage swing provided by this amp?
   
  What is the current this amp pushes out?
   
  Not sure if these measurements are available. I'm sure there is a way to find this out with a DMM. I can do the measurements with a little guidance. TIA.


----------



## Misterrogers

Ok gang - need some help. Working through setup with a new CTH Build (Belleson Super Regulator in ICP, and Hovland caps used in C4L/R). When I power up (it goes green), I get ~12V between SG/OG and SG/OL. When I go to test SG/OR, I go red and get ~< 12mv readings. If I hold the leads at SG/OR, it'll cycle every 4-5 seconds flip green then back to red. While cycling, my reads reset to ~0mv and tick up to ~12mv; then another cycle. Thoughts?


----------



## Misterrogers

Found it. One of the leads of the super reg was making contact with C2P. It's a bit of a tight fit.


----------



## Misterrogers

So I seem to have a gremlin. It periodically unlatches, and at times I just have the right channel, sometimes both. Got some hunting to do. I'll tell you though - when it's working, it sounds really, really nice. Very detailed and clear, with great extension top to bottom. If I can get the circuit stable, it's my best sounding CTH so far (initial impressions, etc. etc. ) I'm checking for more shorts, but any thoughts as to what I should be checking? Are there specific test points that would shed light on why it's de-latching at times?


----------



## sachu

What are you reading on pins 2, 3 and 6 of ICE opamp?


----------



## Misterrogers

~12v, ~12v and ~24v. I've also noticed that when I turn the volume all the way down it'll unlatch. Turn it up and it'll re-latch, usually with only the right channel.


----------



## cfcubed

You are in advanced territory Mr Rodgers  Perhaps obvious but If you've a spare standard ICP regulator (7824) around would try swapping that in for the Belleson Super Regulator.
   
  In hindsight it might have been good to get the "standard" build going w/7824 then try using the super reg.   Even tho the current problems may be unrelated to the reg (e.g. the usual full inspection & CTH debug steps & readings in my sig apply).
   
*Edit: * One thing to consider is your coupling caps, both for the channel in/out/loss (solder joints) & nuisance e12 trips.   I found that no matter what I could not use fancy-pants V-cap TFTFs as C4s in CTH w/o e12 trips.


----------



## sachu

I honestly would get rid of the E12 if it were for a personal amplifier. The risk you run of course is busting your drivers if the amp goes kaput.


----------



## cfcubed

Quote: 





sachu said:


> I honestly would get rid of the E12 if it were for a personal amplifier. The risk you run of course is busting your drivers if the amp goes kaput.


 

 Would not be my recommendation, if CTH is constructed properly & e12 is tripping it is just doing its job   If one wanted to limit e12's behavior to only catastrophe avoidance, nearly disabling it, they could raise the "sense" resistors (R1E, R2E) to some high value like 100k and the "speed" resistor (R4E) to say 3.3K.
  This would leave some degree of protection against build errors, shorts in case, etc.  And retain a bit of power on delay and power off DC protection.


----------



## Misterrogers

Ok. 'Downgraded' to the standard ICP and C4 caps - the good news is I'm still missing my left channel. Gotta step away, but this gives me hope that the circuit can handle one or both of my upgrades - once I sort out my channel issue. I'll start measuring when I can sit again, but I'd appreciate any direction you'll can provide.


----------



## Misterrogers

Voltages are good up to tube socket pin 1 and 6. 1 is ~94v and 6 is 77v. Setup says that either the tube opamps are bad, or I have a wrong component in. I assume the tube opamps are ICL and ICR? What voltages should I read at what pins to vet those? Thanks again for any/all help.


----------



## cfcubed

Since you have one working channel & one not this should not be so bad to debug.  Just take great care not to short things tho, using fine needle probes (I use pins taped to mine only exposing the pin tip).
   
  You are correct about the ICR/L and can use the schematic here:
http://www.cavalliaudio.com/diy/cth/main.php?page=schematics/ipschematic
  along with the opamp datasheet to discover the opamp pin functions.    You can see that the tube in conjunction w/ICR/L's influence on cathode bias is what brings the raw TB+/100v (94v in your case) down to about the 80v you should be reading on pins 1 & 6.    SO your 94v reading (your left channel) is like what we get when no tube is inserted, IOW if you pull the tube you should get about 94V->100V for both pin 1 & 6 WRT ground.
  Thus in addition to your suspicion of ICL as the culprit (e.g. swap ICR & ICL as a test?) you should re-confirm the tube socket soldering & the tube itself as good.


----------



## pabbi1

Will 6aq8 work here, or is the mu too high?
   
  Getting close on mine... maybe tomorrow.


----------



## Mullet

The 6AQ8 might work. If the pin outs are compatible and the plate voltage can accept around 80v then it might work. What mu does the 6AQ8 have?


----------



## cfcubed

6aq8's 57 mu is way too high, would probably have same probs 12at7 has - search thread.
See CTH tube info link in my sig. And with your DIY history hard to believe you don't have a 12au7 or 6922 class tube laying around


----------



## pabbi1

Honestly, I had sent all my excess tubes to friends (spring cleaning(s)), or with amp projects that found new homes, and only happened to have one of these around by accident. In searching the list, and searching that thread, I only saw a passing mention of 6n23p, and nothing on 6h30, though I hear whispers the latter is quite good (and which I have several of).
   
  The 6n1p I have found to be noisy in other amps (Bijou), that will settle down, but nowhere as good as the 6n23, so... just wondering.


----------



## sachu

I have a very nice RCA 6CG7 clear top. Will send it your way.


----------



## pabbi1

OK, e12 works fine, LED goes red to green, SG->og is 12.04v, OG to L & R out is 12.03v, TB+ is 97v, and...
   
  Pin 1 to Pin 6 is .6v - across 2 tubes... just making sure, but heater switch "ON' is 6.3v with the default resistor values, using H1 & H2?
   
  In the meantime, here is a money shot:


----------



## Mullet

That is one cool looking CTH! It might be cool to get a socket saver so the tube sticks out more. The side effect of this is the tube has more ventilation.


----------



## cfcubed

Quote: 





pabbi1 said:


> Pin 1 to Pin 6 is .6v - across 2 tubes... just making sure, but heater switch "ON' is 6.3v with the default resistor values, using H1 & H2?




 Now that's some unique casing
 We don't look for measurements between the 2 plates, we are looking for 80v or so for each of pin 1 & 6 WRT ground SG/IG.
 Yes heater switch on = 6v, open = 12v.   Your CTH seems healthy so far, maybe time for listening


----------



## pabbi1

DOH... maybe...  tonight.  
   
  Proving, once again, that there is a DIY Lowest Common Denominator - no matter how many projects you have logged.


----------



## cfcubed

Don't be so hard on yourself man,  esp for DIY things that happen later at night.
 Otherwise I might have to tell my story about dialing up VR2 on a b22 board thinking I was adjusting the offset:/


----------



## sachu

If anyone needs boards pm me. I have two


----------



## pabbi1

Yep, all fine - just need to let it burn in.


----------



## Misterrogers

Ok gang - need your experience and wisdom. While trouble-shooting why I was missing my left channel, I attempted a measurement between pins 4 & 5 of the tube socket. At that moment, I figured out that I shouldn't do that  Wasn't sure if readings should have been taken relative to SG, or between 4 & 5. As a result, I no longer go green. I still measure 12V at OG, but no longer at OL and OR. In reading/studying the diagrams, It seems likely that I popped the BJT's in the rail splitter. Any help in the steps to track down the problem would as always, be greatly appreciated.
   
  And another newbie question. When doing the diode test on the BJT's, should it ALWAYS read 0 with black lead center red L/R when the transistor is installed in a non-powered board?


----------



## Misterrogers

Went to order some parts at Mouser, and found this out of stock:
   
  71-RN55D-F-22.1/R
  R9L+R,R10+R,R2S,R3S
 71-RN55D-F-22.1/R
 1/8watt 22.1ohms
   
  Any suggestions on a replacement? It's not coming back in stock till May.


----------



## MisterX

71-RN55C-F-22.1
  
  +/- 50 PPM/°C ("C spec") instead of +/- 100 PPM/°C ("D spec") and bulk package instead of reel package (/R) but otherwise interchangeable.


----------



## cfcubed

http://www.head-fi.org/t/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/630#post_8133807   and before for someone else's buffer repair.
  
 BTW you are supposed to measure V between tube heater pins 4 & 5 that's part of the diag instructions from my sig.
 But you aren't supposed to short something while doing it.  Taping your probes tips such that only a mm or so is exposed helps.
. Meter resistance won't cause problems in voltage setting BUT amperage setting would for example.


----------



## Misterrogers

Thanks for the clarification. My pins are taped and I really thought I got in without shorting, but apparently not. I was testing V. Any suggestions on where to start if OL and OR are not up to V?
  
  Quote: 





cfcubed said:


> http://www.head-fi.org/t/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/630#post_8133807   and before for someone else's buffer repair.
> 
> BTW you are supposed to measure V between tube heater pins 4 & 5 that's part of the diag instructions from my sig.
> But you aren't supposed to short something while doing it.  Taping your probes tips such that only a mm or so is exposed helps.
> . Meter resistance won't cause problems in voltage setting BUT amperage setting would for example.


----------



## Misterrogers

Thanks MisterX!
  
  Quote: 





misterx said:


> 71-RN55C-F-22.1
> 
> +/- 50 PPM/°C ("C spec") instead of +/- 100 PPM/°C ("D spec") and bulk package instead of reel package (/R) but otherwise interchangeable.


----------



## Misterrogers

Hey all - t I could really use your help. My CTH is output 24V from the reg, but I have no output on OL and OR.I'm trying to learn the CTH circuit and electronics, and I've hit a wall. 
   
  Here's some readings that seem interesting to me, and may be of help to you.
   
  K1E (Relay)
   
  Pin 1: ~24V
  Pin 2: ~23.4V
  Pin 3: ~23.4V
  Pin 4: ~
   
  Pin 5: ~24V
  Pin 6: ~12V
  Pin 7: ~12V
  Pin 8: ~
   
  IC1
   
  Pin 1: ~6.8V
  Pin 2: ~12V
  Pin 3: ~12V
  Pin 4: ~
  Pin 5: ~24V
  Pin 6: ~20V
  Pin 7: ~11.8V
  Pin 8: 23V
   
  IC1S
  Pin 1: ~203mv
  Pin 2: ~12V
  Pin 3: ~12V
  Pin 4: ~
  Pin 5: ~203mv
  Pin 6: ~24V
  Pin 7: ~12.7V
  Pin 8: ~
   
  Any help or direction would be greatly appreciated.


----------



## Misterrogers

Anyone?


----------



## cfcubed

Well prior to the apparent mishap during your heater measurement I suggested some things in this post:
http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/405#post_8196001

Now that you also seem to have problems in your railsplitter and/or output buffer, using the shotgun approach, I'd replace all the BC* TO92s in both. If a full-on inspection showed no wrong devices, orientations or solder joints.
Others could suggest likely parts to replace in order of replacement but that can lead to frustration so I've done the above and ended up happy.


----------



## Misterrogers

Thanks cfcubed. May end up just doing that. I'm trying to learn what I can about the circuit so I can be more targeted in my efforts. But yea, it is frustrating. May be time to shot gun it. Sachu is pretty dialed in with troubleshooting, so I'm hoping he'll chime in.


----------



## Mullet

I'm the not the best when it comes to troubleshooting this amp, but I'll second the idea of taking the kitchen sink approach. You could test each BJT with a diode test. Look up how to test a BJT on the net and whatever BJTs fail pull those. But that might not solve the problem. So pulling all the BJTs out should do the trick.


----------



## Scy

I'm pretty much finished with mine, here it is:









   
  Pretty much a standard build, other than the odd board placement and a few of the components. Made the acrylic parts myself, as you can see.  
  The potentiometer has a switch in it, thought about using it as a power switch, but didn't. Maybe I could use it with the relay to avoid that pop when turning off?


----------



## Misterrogers

Very nice build!


----------



## Mullet

Scy -- cool build. One more the more interesting builds I've seen thus far. What did you use to cut the plexiglass?
   
  Hey Mr R did you ever finish your build? The shotgun approach is definitely the way to go when fixing this amp. You might have a misplaced part somewhere. It's easy to do.


----------



## Misterrogers

No, not yet Mullet. I changed Q4S, Q6S, Q3S and Q5S yesterday - no luck. I've got 24V out of the reg, but no output on OL or OR. Any suggestions on where to shotgun next?


----------



## Scy

Thank you for your comments.
  Quote: 





mullet said:


> Scy -- cool build. One more the more interesting builds I've seen thus far. What did you use to cut the plexiglass?


 

 Nothing fancy really, a micro drill and a drill press, files and sanding paper. It's quite laborious to get anything done this way though, I might get a small compound table if I find enough use for it.


----------



## Mullet

What about the IC2S? I think CF3 also suggested taking out all of the BJTs from Q4L/R to Q9L/R. I know it sucks. Been there before. But taking them all out and replacing them with known good BJTs *might* work. WIsh I knew more about this to help you dial in on the problem. Like you said before hopefully Sachu can jump in and assist.


----------



## Misterrogers

All good suggestions Mullet. It's actually not so bad. I've gotten a lot better at BJT removal than I ever wanted


----------



## mrhk13

I've finally started my build, so far there's not enough on the board to do any testing, so it must be going great! 
	

	
	
		
		

		
		
	


	



   
  As I was looking for various things, I realised I didn't get R5H. I'm probably missing something on the CTH website or in this thread - but what value should it be? I understand it changes the voltage on the tube, but which one, the 6.3 V or the 12.6 V? And what resistor do I need to maintain the 6.3/12.6 choice?
   
  Thanks!
   
  mrhk13


----------



## Mullet

R4H and R5H only need to be populated if you intend to have more than 2 heater voltages. R1H is fixed. R2H and R3H usually are 9.31kΩ and 7.15kΩ for 12v and 6.3v.


----------



## mrhk13

Thanks Mullet... This morning I checked RevA schematics rather than the original schematics on the Cavalli Audio site and d'oh! I feel a bit of an idiot. It makes more sense now. I need to look back at my board: more possible voltages must mean more pads to connect a three-way/four-way switch. Completely missed that last night.
   
  Clearly, I shouldn't have posted the message, but rather gone to bed, let the lead-fumes clear and look again with fresh eyes. Lesson learned.
   
  Humbly-
  mrhk13


----------



## pistolsnipe

does anyone know where boards are currently avaliable for this project?
   
  thanks


----------



## Mullet

Just curious about cleaning the board after soldering is done. Normally, I'd just use 99% alcohol and a tooth brush. Then I'd let it dry and that's it. The board would be kind of sticky, but I ignored that. Recently, I built a GrubDAC and it was suggested to also run some hot water on the board to clean off the excess stickyness. The person said it was safe to do so. However, I've also read that you wouldn't want to do this with certain parts installed like a pot, or devices like a mosfet. What about the BJTs that are installed on the CTH, or Q1P, ICP, and ICH? Is it safe to put the whole board with all parts installed in an alcohol bath and then run the board under hot, soapy water to fully clean the board?


----------



## jdkJake

If it is still sticky, then you have not cleaned off all of the flux.

Break out the alcohol...

Rinse and repeat, rinse and repeat, ....


----------



## Mullet

More like... fun fUn FuN...


----------



## KimLaroux

Quote: 





jdkjake said:


> If it is still sticky, then you have not cleaned off all of the flux.
> Break out the alcohol...
> Rinse and repeat, rinse and repeat, ....


 
   
  Or use a higher concentration alcohol. I use 70% USP isopropyl alcohol, aka rubbing alcohol, and I rarely have to use it twice. It's strong enough to remove paint.
   
  Also make sure your toothbrush is clean. If you used it to clean your bicycle's rear cassette, then it's probably leaving more grease on the circuit board than anything. (speaking from experience 
	

	
	
		
		

		
		
	


	




 )


----------



## Mullet

That's strange I'm using 99% isopropyl alcohol. I guess there's so much flux residue that it's hard to break up especially on a board where there are so many parts. I'll give it as many tries as it takes to get this board cleaned.


----------



## jdkJake

Most stores only carry 91% isopropyl alcohol. I have never seen anything stronger than 97%. Where did you find 99%? 

You can leave it stand on the board for a short period to allow the solution to work. The key is to get the flux residual disolved into the liquid so that it can be poured off or wiped off/absorbed with a cloth or paper towel. If you used liquid flux in addition to the flux in the solder, it can take a fair amount of work to dissolve all of the residual. 

As Kim pointed out, be sure to clean the toothbrush as well. The bristles can hold a fair amount of gunk. I actually use a couple of them during the process. Rotate them to keep them clean and effective.


----------



## Mullet

Maybe it's 97%. It's from work. I work at a video post house as their in-house engineer and it was left by my predecessor. I typically use it to clean the heads on VTRs (Decks). Yup, we still use those.
   
  In the past I've always just done 2 passes on the board and like I said it was still sticky. Perhaps, I was just too eager to fire the bad boy up. This time I'll clean it over a few days. The recommendations you guys have given all sound like excellent ideas. I'll definitely use multiple tooth brushes and I'll try and do as many passes as it takes. Also, it's only the flux that is contained in the rosin core of the solder. No liquid flux needed for this project.


----------



## KimLaroux

Quote: 





jdkjake said:


> Most stores only carry 91% isopropyl alcohol. I have never seen anything stronger than 97%. Where did you find 99%?
> *You can leave it stand on the board for a short period to allow the solution to work. The key is to get the flux residual disolved into the liquid so that it can be poured off or wiped off/absorbed with a cloth or paper towel. If you used liquid flux in addition to the flux in the solder, it can take a fair amount of work to dissolve all of the residual.*
> As Kim pointed out, be sure to clean the toothbrush as well. The bristles can hold a fair amount of gunk. I actually use a couple of them during the process. Rotate them to keep them clean and effective.


 
   
*+1 *to that! I actually forgot this part. It might make a big difference. Although alcohol dries fast, so it might not give you much "soaking" time. Alcohol is, after all, a solvent. The idea is to dissolve the sticky stuff into the alcohol and then pull it away. Simply brushing will move it around and spread it evenly on the board, but it won't remove it. This is why contact cleaner is so effective in aerosol spray cans. It soaks the whole part, making the dirt drips away. The pressure of the spray helps dislodge and push away the rest.
   
  So yeah, toothbrush might be good to dislodge rough stuff, but it won't remove it from the board.


----------



## Mullet

check it...
   
  99.953% isopropyl... this crap is hardcore.


----------



## jdkJake

You can say that again! That's the kind right there. And a gallon of it no less! 
   
  Every hardcore bum in America is drooling at that sight... 
	

	
	
		
		

		
		
	


	



   
  Seriously, after an initial soak and scrub you probably can pour it over and off the tilted surface of the board for final removal of just about anything.


----------



## Mullet

I think I got a little somethin' somethin' from those fumes 
   
  Cleaning the board at an angle did the trick. I used my trusty pana-vice and put it at an angle and let the excess alcohol drip off. After 3 or 4 applications all that was left was a hazy greyish film. It's all good though.


----------



## mrhk13

Another satisfied customer! I finished the build (finally!) last night and had nice sound from the left, and a loud hum from the right. Turns out my wire at IR had broken during boxing it up. D'oh! Fixed that earlier today and now there's sweet music. First impressions are that it sounds wonderful! Have to roll some tubes but man, a revelation! Silky smooth, nice and detailed, not too warm. My only observation is that the gain is high for the headphones I've tried: I don't think I'll be listening much beyond 9 o'clock on the pot. That may be due to the headphones, they're old and probably not-very-good Panasonics. I'm starting to work on the wife to let me buy some new headphones  And then I need to start thinking about the next project, of course 
	

	
	
		
		

		
		
	


	



  
  Once I've tidied up the build (and figured out a way to dril a 1" hole for the tube!) I'll post some pics.


----------



## Misterrogers

Congrats mrhk13! It's one hell of a little amp. I just finished a another pimped CTH build. Yep, it's the same one I've been seeking troubleshooting help with on the last couple of pages. I picked up a Belleson 24V super reg and some Hovland caps for this build, and I made the error of building it first time with these parts. Right channel fine, no left. I start poking around months ago trying to figure out the problem, and in the process I shorted out a bunch of BJT's. Being stubborn, I spend a couple of months studying the circuit and tracking down the offending transistors (Q4*). I put in stock reg and caps, fired it up - right channel no left. I checked ICL, and I wasn't getting the output I should so I changed ICL. Right channel, no left. Frustrated, I pressed down on ICL and my left channel switched in!!! Hmmm. Powered down, flipped the board and re, re, re checked my joints. Damn. One pin of ICL I DIDN'T SOLDER! Can't tell you how many times I looked at that. Soldered, fired it up, all is well. I then proceed to swap in my new reg and caps one at a time. The circuit took them just fine.
   
  So here's what I want to leave you with. If you're using a non-standard case and have the room, you MUST swap out the 24V reg with a Belleson. The sonic improvement is huge. With the Belleson and the caps, this little amp has push aside my Lyr with my HE-500's. Very, very, very good.


----------



## BK_856er

Quote: 





misterrogers said:


> Congrats mrhk13! It's one hell of a little amp. I just finished a another pimped CTH build. Yep, it's the same one I've been seeking troubleshooting help with on the last couple of pages. I picked up a Belleson 24V super reg and some Hovland caps for this build, and I made the error of building it first time with these parts. Right channel fine, no left. I start poking around months ago trying to figure out the problem, and in the process I shorted out a bunch of BJT's. Being stubborn, I spend a couple of months studying the circuit and tracking down the offending transistors (Q4*). I put in stock reg and caps, fired it up - right channel no left. I checked ICL, and I wasn't getting the output I should so I changed ICL. Right channel, no left. Frustrated, I pressed down on ICL and my left channel switched in!!! Hmmm. Powered down, flipped the board and re, re, re checked my joints. Damn. One pin of ICL I DIDN'T SOLDER! Can't tell you how many times I looked at that. Soldered, fired it up, all is well. I then proceed to swap in my new reg and caps one at a time. The circuit took them just fine.
> 
> So here's what I want to leave you with. If you're using a non-standard case and have the room, you MUST swap out the 24V reg with a Belleson. The sonic improvement is huge. With the Belleson and the caps, this little amp has push aside my Lyr with my HE-500's. Very, very, very good.


 
   
  Did we ever get pics of your setup?
   
  I usually rotate my amps about once a month.  Started using the CTH again yesterday.  Very satisfying indeed!
   
  BK


----------



## Misterrogers

Not yet - I'm waiting for some standoff's to arrive to anchor the board. Once I fasten it, I'll upload some picture. Yes - very very satisfying. A friend (LFF) just ordered a Belleson for his just completed CTH. Nice upgrade.


----------



## Mullet

I've always wanted to do the regulator upgrade but never used a case that was suitable for it. I'm a fan of the smaller BOM case because a lack of desktop space. Maybe some day ill crack one of my two CTHs open and re-case it up with the belleson upgrade. In what way does the belleson super regulator improve the sound? Also what is the part number? Finally, at this point, do you like the CTH better than Project Sunrise 2?


----------



## Misterrogers

The one you want, is the SPJ78, 24V. Detail is increased, low's, mids and highs are quicker and more 'solid'. Essentially, the amp never starves in transients, and has the current 'headroom' needed to present a cleaner, clearer sonic image. Sound stage is improved - I believe largely due to the extremely stable/ripple free regulation. Yes - without a doubt. Truthfully, I always slightly preferred a stock CTH house sound over Sunrise, but now - well, let's just say that I'm constantly left wanting to hear more. At ~$60 it's not a cheap upgrade, but to me it was well worth it. I'm very interested in hearing your impression (and others), should you dive in.


----------



## mrhk13

Here are some pics of my stock CTH. Front shows on/off switch, voltage switch. And yes, I did do a fuse and on/off switch: I'm not yet that confident in my soldering skills! I'm annoyed I mis-measured the hole for the power plug. I still need to drill holes in the top plate, mostly trying to figure out how to drill a hole big enough for the tube! So that will come later. Tomorrow night the wife is out and I have a hot date with an iron (not of the soldering kind, sadly!) but plenty of time standing in one spot means I'll be able to listen to the amp for a goodly while.
   
  MisterRogers, I'll consider the upgrade. In the short time I've listened it's sounding much better than my other option (my first DIY amp: a cmoy), so I cannot imagine upgrading it just yet. Plus, I have a feeling the bottleneck is elsewhere: my cans. But as the Lowes website says: "never stop improving".


----------



## BK_856er

Looking good, mrhk13!  
	

	
	
		
		

		
			




   
  Cmoy to CTH is a huge step up in terms of build complexity and SQ.
   
  Options for the center tube hole are a greenlee type hole punch, a uni-bit. or a dremel and lots of patience.  The hole punch makes the cleanest hole, which can be important if you don't plan to "finish" with a trim ring.  Strategic vent holes or mesh top is always a good idea to keep the temps down.
   
  BK


----------



## Misterrogers

nice work mrhk13! When you do decide to try the Super Regulator, you'll probably need to switch cases. While pin compatible, the high current (2A) super reg needs a bit more room than is available in the stock case. I'll upload some photos of my install in a day or so and you can see my approach. Essentially, I used 3 pin connectors to mount the reg horizontally off to the side. This gave plenty of vertical space for my heat sink. I second the hole punch. It was easy (though I finished with a tube ring) to punch a 1in whole.
   
  Btw all - sachu suggested this awhile back somewhere in some thread; track down an RCA Clear Top 6CG7. Clear Top + Super Reg + good caps =


----------



## Mullet

No joke. You got the Lyr for sale. 
   
  I'm so tempted to crack open one of my CTHs to do some cosmetic surgery and add a Super Regulator. I always use a perforated metal top for ventilation so it wouldn't be hard to cut a small hole in that area and let the Super Regulator pop out. It may look ugly, but it won't sound ugly. Dimensionally, is it taller or taller and wider?
   
  On another note I'm about to build "The Wire" and after that I have an EHHA Rev A on deck (clearing some desk space will make this happen sooner) so perhaps I'll be less likely to want to go mucking around with my CTHs.


----------



## Misterrogers

Since a handful of you are considering adding the Belleson, here's a top down of my build. The larger case obviously helps here with the reg and caps. Mullet - mounting the reg vertically is a bit tight with the smaller caps right next to it on the board. Rather than figure out how to get it in there without shorting, I used some 3 pin male/female connectors and went horizontal.


----------



## Mullet

Back again... After building so many CTH's I'm finally having an issue with my latest build. Everything checks out fine with regard to OL, OR, OG. My TB+ is fine. Pin 6 is fine at 77.8v. Pin 1 is where I'm having an issue. I was originally getting 100v, but after some probing around I shorted something out and now I'm getting close to 35v on Pin 1. If I pull my 12v tube I get a reading of 105v on both pins 1 and 6. If I take the opamp out I get pretty good reading somewhere in the 70s. I've checked to make sure I have the right parts in the right places and they all appear to be fine. I could swap the TL081 but I'm worried I might damage it. I'm about to start ordering parts for the whole left input stage. Besides the opamp any ideas on what would cause this?


----------



## Mullet

Here are some measurements that I took with both the tube in and out...
   
  ICL without tube = pin 2 3.141v; pin 3 .115v; pin 6 .026v; pin 7 23.99v
 ICL with tube = pin 2 1.025v; pin 3 .150v; pin 6 .148v; pin 7 23.99v
 ICR with tube = pin 2 2.343v; pin 3 2.373v; pin 6 3.091vl; pin 7 24.02v
   
  Don't necessarily want to jump the gun and order...
  Q4P, R3L, R4L, R5L, R6L, R7L, R8L, ICL just yet...


----------



## Mikael109

Anyone know where I can pick up one of these PCB's?
   
  I'm looking to build this for my first DIY amp. (Cmoy seems like just board population and I've done that before.. I'm not feeling too confident in attempting a SOHA II though)
   
  I can't read the schematic on CA's Rev A power supply, but I'll only be using the 2-position heater.. So I imagine I can just use the "wiring diagram" on CA's CTH section, and the BoM to correctly populate which cap/resistor/ect goes where on the PCB?


----------



## Mullet

@Mikael109 -- Looks like another group buy is in order. I've done one before for this amp and I can tell you -- there needs to be enough interest of at least 30-40 boards to make it worth it. And yes you should be able to populate the board with double checking the BoM. Knowing how to read the schematic is good for troubleshooting. The hardest part is making it fit into that small hammond case. 
   
  By the way I fixed my issues. Just did the shot gun approach and replaced most of the left side input stage.
   
  On a side note -- I've been looking into the whole question of output impedance of the CTH in conjunction with using LCD-2s and Thunderpants (orthodynamic headphones). The CTH has a default output impedance of 104 ohms. 100 ohms comes from R18 and 4 ohms come from the CTH's output impedance without R18 installed. This impedance of 104 ohms is way too high if going by the 1/8 damping ratio ie your output impedance of your amp shouldn't be any higher than 1/8 of your headphone impedance. From my understanding, R18 is used to offset the high gain of your 12au7 or 6dj8 tube(s) -- respectively 17 or 33 mu -- especially for highly efficient cans like Grados, Denon, etc. This way your volume doesn't get too high too fast. However, if we're using this amp with orthos in mind is it better practice to jumper R18? Do we also need to raise a higher ohm pot like 100k instead of 50k? At this point, I have R18 set to its default at 100R. I'm using a 50k pot and my orthos are driven well at 12 o'clock on the pot. But are they driven, correctly? CTH Orthoheads how are you dealing with R18?


----------



## Avro_Arrow

I think you can get boards here now.


----------



## Mikael109

Quote: 





mullet said:


> @Mikael109 -- Looks like another group buy is in order. I've done one before for this amp and I can tell you -- there needs to be enough interest of at least 30-40 boards to make it worth it. And yes you should be able to populate the board with double checking the BoM. Knowing how to read the schematic is good for troubleshooting. The hardest part is making it fit into that small hammond case.


 
   
  Perfect!
   
  Thanks! The only issue I see is that I wouldn't be able to ground the case from the Star Ground pad because the case will be made of wood. I'm thinking this should be fine though because a wood case shouldn't build up charge like a metal one would.
   
  I still have one last arcade stick to finish and sell off, so hopefully there will be a GB sometime in the near future  If not I'll snag a board from the link above.


----------



## Mullet

@Avro_Arrow -- That's great to know that boards are easily accessible. Props to MisterRogers for hooking it up.
   
  ...still wondering about my output impedance query... 
   
  If you're using a wooden case I don't think you have to worry much about SG. I could be wrong, but logic tells me you'll be ok.


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## mmayer167

Thanks again Misterrogers for making more boards appear!


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## Misterrogers

More than happy to help Gents! It's a fantastic little amp that many should be able to build.


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## kchapdaily

quick question. im not sure if this is the best place to ask, but i figured it would be better than starting a new thread.
   
  i have a set of hifiman he-4's in the mail. ive heard the cth is a good amp for them.
   
  until i build a new amp, i will be driving them with my starving student. it should be fine for now, but an upgrade might be in order.
  i would like to roll tubes, so im stuck between a cth rev a and a soha II. would the cth match better? and would i have to make any modifications to the bom to drive the he-4 specifically?


----------



## Misterrogers

I drive my HE-5's every day with a slightly modded CTH, and it has the chops (P->P) to wake it up quite nicely, so I think you'll be fine with the HE-4. SOHA II is a very nice amp too - seems it's primarily a cost choice.


----------



## kchapdaily

thanks for the advice. im leaning toward the cth i think. do i need to change any components to match the impedance of the amp to my
  he-4's? and if i do go with the soha II, would i need to change anything on its bom either? im not quite clear on impedance matching, but my understanding is that if my amps impedance is greater than my headphones, thats bad. he-4 is a low impedance can, and i havent found anything on the output impedance of either the cth or soha II


----------



## Mullet

The CTH has an output impedance of 104ohms with R18. R18 = 100ohms. The natural output impedance with a "jumpered" R18 is 4ohms. Thus 104 ohms with R18 in place. If you're after the lowest output impedance possible then jumper R18L and R18R with two leads. R18 was designed to counter the super high gain of the amp. A 6DJ8 has 33 mu and a 12AU7 has a mu of 18. If you used high sensitivity headphones with a CTH with no R18 then you wouldn't get past 8 or 9 o'clock on your pot without the volume being too high.
   
  Furthermore, my current understanding of planar magnetic headphones is that their damping factor isn't really effected by an amps output impedance because their impedance and phase doesn't change over the frequency spectrum. Thus no bass loss or weird frequency response. I can say that I'm fine with the defaults of the CTH R18. I guess you could always jumper them first and if it works for you then stick with it. Or conversely throw in the default value of 100ohms for R18 and if you don't like it take 'em out.


----------



## kchapdaily

ok perfect. if i go with the cth, i will set it up in the standard configuration, and if it doesnt sound right, i will jumper R18. i appreciate the response, very helpful!


----------



## BK_856er

Goes without saying, but socketing those positions makes changing the R18 values quick & easy and low risk.
   
  The little CTH drives my LCD-2 very nicely.  Certainly not lacking in the bass department.  Pretty sure I'm using the default R18 value or something close to it.  Sounds so good I haven't been motivated to go back in!
   
  BK


----------



## kchapdaily

thats definitely good to hear. the he-4's wont sound quite as nice as the lcd-2's though 
	

	
	
		
		

		
			





. does anyone have a basis for comparison between the cth and the soha II? also, is this the best place to get the board for the cth? http://joeaudiophile.com/?product=compact-tube-hybrid-amplifier-printed-circuit-board


----------



## cfcubed

You could search here (or use google to) and look for SOHA II vs CTH impressions, there may have been some.  That link you posted is the _only_ place to get the board


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## Misterrogers

And rumor has it, that that place (Joe Audio) will soon have full kits up, with some awesome custom, predrilled aluminum cases with hand rubbed cherry wood end caps


----------



## mmayer167

^ this. Very cool


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## kchapdaily

wow a kit would make this a whole lot easier, but maybe not as fun 
	

	
	
		
		

		
		
	


	




. i think i was going to go with a metal body and wooden endcaps for this case anyway, so that would certainly be cool. any idea what kind of timetable they have for release?
   
  also cfcubed: i thought i searched a while ago, but turns out i forgot what i found. searched again, and answered my question. soha II wins, but marginally, and its more expensive to build. its also got a larger footprint. going to build the cth first, but will eventually be building the soha II anyway.


----------



## Misterrogers

heh - to each their own; I never found the sourcing of parts that fun  I'll let you know when I have some photos of the cases. Cases should be available in a week or so, kits about the same timeframe.


----------



## BK_856er

I've never heard the SOHAII, but the CTH has tremendous grins/$ and grins/cm2, and it holds its own against many larger and high-dollar setups.  The component density can be challenging, but it's a very satisfying project that you can literally "hold in your hand" and admire.  In a lot of ways it's my favorite amp.  Go for it!
   
  BK


----------



## mrhk13

Quick question for Mullet on gain of the CTH. I'm using Sony MDR-SA3000 headphones, 70 Ohm impedance, sensitivity of 100 dB/mW. I find that with the 12AU7 tubes I barely make it to 9 o'clock on the volume; with the 6-series I can just about do 8 o'clock. Based on your last post, should I increase the value of R18 to lower the CTH gain and so get more fine control over the volume? If so, any suggestions on the value for R18? Thanks!


----------



## kchapdaily

@misterrogers: beautiful. depending on price, i will certainly be ordering one of those kits. if i can avoid sourcing parts right now, i would like to. im a busy college student, and i dont have as much time as id like for projects unfortunately.
   
  @BK: glad to hear you enjoy the cth so much! im looking forward to putting one together


----------



## Mullet

Quote: 





mrhk13 said:


> Quick question for Mullet on gain of the CTH. I'm using Sony MDR-SA3000 headphones, 70 Ohm impedance, sensitivity of 100 dB/mW. I find that with the 12AU7 tubes I barely make it to 9 o'clock on the volume; with the 6-series I can just about do 8 o'clock. Based on your last post, should I increase the value of R18 to lower the CTH gain and so get more fine control over the volume? If so, any suggestions on the value for R18? Thanks!


 
   

 High sensitivity headphones would benefit from higher R18 values. I'd say try 150-200 ohms to get more out of your pot. Keep in mind with 1/8 damping factor you'd want way less than even 104ohm output impedance. 70/8=8.75ohm output impedance is what you'd want if you were going by the book. I guess at that point you'd have to decide if the damping factor really means anything to you and your ears.
   
  Otherwise, you could up your pot to 100k and see if that helps. I'm not sure what the input impedance of the CTH is though. I'd assume 50k was picked for a reason. From what I know with other amps like "The Wire" I had to up the input impedance to 500k ohms to match a 50k pot. It was advised to not use the pot to correct gain problems. Hopefully, someone else will chime in with more info on if changing the pot to a higher value will help or is correct in this situation.
   
  Most of my headphones (orthos) are at the 12 o'clock range with a 50k pot and 12AU7 tube. My 32ohm Magnums are maybe at 11 o'clock or a tiny bit less.


----------



## mrhk13

Hm, that all makes sense, especially since I ended up using a 10k pot - couldn't find the 50k one. I'll see what I have left in terms of resistors - or get a few at 200 or so. And when next I feel brave enough to take the whole thing apart again... Thanks Mullet!


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## jdkJake

mrhk13 said:


> Hm, that all makes sense, especially since I ended up using a 10k pot - couldn't find the 50k one. I'll see what I have left in terms of resistors - or get a few at 200 or so. And when next I feel brave enough to take the whole thing apart again... Thanks Mullet!




Changing from a 10k to a 50k pot without adding a series resistor will not change the input attenuation of the signal into the amp. The 50k will only make the amp an easier load on the source components.


----------



## jdkJake

mullet said:


> Otherwise, you could up your pot to 100k and see if that helps. I'm not sure what the input impedance of the CTH is though. I'd assume 50k was picked for a reason. From what I know with other amps like "The Wire" I had to up the input impedance to 500k ohms to match a 50k pot. It was advised to not use the pot to correct gain problems. Hopefully, someone else will chime in with more info on if changing the pot to a higher value will help or is correct in this situation.




With your "Wire" build, you did not up you input impedance to 500k, rather you made it 50k when you put the 50k pot in front of it. 

The "Wire" circuit featured a fixed attenuation circuit at it's front end that made the amp look like a 10k load to the source components. When you added an attenuator without "retuning" this circuit, an excessive amount of attenuation was introduced thereby causing your gain to appear to be an issue when it was the attenuation that was causing the apparent lack of amplification. There was never a gain problem per se.

The choice of a 500k (or a 1M) resistor tied to ground at the amp input provides a safety in case the pot wipers or wiring fails. This insures the input finds a path to ground and does not go full rail and toast your cans with a spectacular burst of power. Take a look at the CTH schematic , you will see a similar safety.

If you wish to add additional attenuation in front of the amp, a appropriate series resistor after the pot and before the 1M safety will form a simple voltage divider that will further attenuate the signal prior to the amp doing it's thing. IMHO, you would be better served adjusting the gain of the amp at that point, but, it will most likely change the sound signature and might even make the amp unstable without resizing the compensation capacitors. Unlike the "Wire", which is mainly a current buffer by design, I doubt the CTH can be made to run unity gain stable without significant effort.


----------



## Misterrogers

Guys - I'm working out the last bits of the BOM, and the MPSA14 seems to be obsolete at Mouser. There's plenty of replacements that match up fine - except for maximum DC collector current. The 512-MPSA14 was 1.2 a, most of the replacements are 500ma. Is this critical?


----------



## jdkJake

misterrogers said:


> Guys - I'm working out the last bits of the BOM, and the MPSA14 seems to be obsolete at Mouser. There's plenty of replacements that match up fine - except for maximum DC collector current. The 512-MPSA14 was 1.2 a, most of the replacements are 500ma. Is this critical?




The bulk pack are out of stock, but the reel and ammo pack are still very much available.

 http://www.mouser.com/Search/Refine.aspx?Keyword=512-mpsa14

Might want to buy them soon though, they are EOL as well.


----------



## kchapdaily

how are the kits coming? ive gotta say, im very exited


----------



## kchapdaily

not sure if i am stealing anyones thunder on this, but if anyone else is as exited about these kits as i am, they should know that images of the cases have been posted at joeaudiophile! and they look absolutely stunning!


----------



## Misterrogers

Yea, they kinda do - don't they?


----------



## KimLaroux

Woha! Those look amazing! Now I want to build a CTH just to have this sitting on my desk. 
	

	
	
		
		

		
		
	


	




 Is this brushed aluminum? <3
   
  Can't wait for a price now. Being able to buy a full kit makes this build even more interesting. It's fun sometimes not having to spend days sourcing parts from different suppliers. Hoping the full kit will be reasonably priced, but those enclosures alone are hinting at a high price tag.


----------



## kchapdaily

any news on the kits Misterrogers?


----------



## Misterrogers

I'll be posting an update on the site tomorrow


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## kchapdaily

great! cant wait!


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## kchapdaily

Misterrogers, any chance of the kits being available before christmas? i dont mean to be pushy, and i really appreciate how much effort goes into an endeavor like this, but i want to have a cth up and running before christmas, and i need to know if i can wait on ordering my own parts or not.
   
  Also, if you need help testing the kits, or are just looking for some early builders, id be happy to purchase an early kit.


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## mosshorn

CTH kit? Ok, subbed and you have my attention.


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## nonamodnar

Same here. Would be great to have a kit anytime soon.
  Do you think I can build it as a second project? My first was Project Sunrise 2.


----------



## Misterrogers

I do think it's possible nonamodnar! I would definitely consider the CTH kit an intermediate build, but it was my second build after an O2, and it was a success. If you're deliberate and careful, it's an enjoyable build. One great thing about this kit, is how complete it is. Unlike the Sunrise, CTH required wiring, drilling, etc.


----------



## nonamodnar

That would definitely make my learning curve more interesting. Thank you Misterrogers.
  I'm fine with wiring, but say, how much drilling is required for the CTH? I've drilled several woody goodies but I've never attempted on a PCB. How different would that be?


----------



## Misterrogers

With the CTH Kit, none  All you do is assemble. Traditionally, you must drill the case. Wiring is also preassembled, you just need to solder to the board. But definitely, no drilling the PCB itself


----------



## nonamodnar

Haha, I made a fool of myself. Let us know when you have the kit ready for shipping. It would pair marvelously with my ODAC and LFF's Paradox. + great learning experience too.


----------



## Lil' Knight

Any suggestion for a 6f8g adaptor that will work straight away without any modification?


----------



## Misterrogers

Hey all - Kits will be up at joeaudiophile.com today or tomorrow. Those of you that have been waiting - thanks for your patience! This run is limited (we have 4 left), but we're assembling more kits; should have them available in a couple of weeks. What we've tried to do with Joe's CTH Kit is address all of the tedium that goes along with a build of this complexity. Finding an attractive case, measuring and drilling, vetting thermals... all takes time and isn't cheap. Wiring is the part I dread; It can be fiddly and time consuming to do it right. We do it all for you; including disconnects that allow you to break down your case without desoldering the board. Standoffs, tie wraps, all there. The BOM for this kit is stock. The time, effort and expense went into quality components that make up the fit/finish of an amp. While the CTH is without a doubt an intermediate build, we chose it as our first kit because it's awesome amp that more should experience. We wanted to keep it alive and thriving. If you're a relative beginner, CTH is still quite doable. My first CTH was my second build ever. Go slow, take your time, study and ask questions. 
   
  In the near future, we'll have Case Upgrade kits available for existing CTH owners that like our case work. They'll come as kits, because as you can imagine - the case has been designed around specific connectors, wiring, etc. That's it for now. Keep and eye on Joe's site for more to follow. I suggest that you contact us directly for questions regarding the kit. We shouldn't hijack this build support thread. Very soon I'll start up a Joe Kit construction thread in the DIY section.


----------



## Lil' Knight

Anyone experienced a pop when turning off the amp? Mine made quite a loud noise... Also the e12 is overly sensitive, the LED keeps switching colors while I went through the setup. In some ways, I really want to skip this e12 thing...

Great sound though, nice dynamic.. I much prefer the CTH to the O2, which imo, is a big hype, never lives up to the expectation. Can't ask more for a $30 toy though.


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## cfcubed

The CTH pop-at-pwr-off has been discussed, I give some info about it & a hack to avoid it here:
http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/360#post_8100335
   
  Yes the CTH e12 implementation is sensitive & I'd expect it to cycle when probing around/doing setup measurements.  Also when turning on/off connected source.  But hopefully not under normal usage/while listening to music.


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## Lil' Knight

Thanks, I missed that mod.

Now the e12 brings up more headache for me... i have been listening for 2 hours straight, turned off to go have lunch, got back and turned the amp on. Now the e12 keeps tripping like hell... I suppose the Rev A already has revised resistors' values to reduce the e12's sensity... My output caps do have long and uneven leads though.


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## cfcubed

It sounds like you know where to start to diag your CTH's e12 tripping problem.  There is of course something wrong because even before minor Rev A BoM changes the large majority of CTHs were working fine.  I've a CTH diag/debug link in my sig - you could *carefully* double-check & post your operating points.
  But guesses are any non-std C4/coupling cap arrangement, possibly the tube, assuring the source has no DC offset, assuring adequate ventilation.  If nothing yields help search my posts for e12 resistor / sensitivity values & check yours against those/newest CTH BoM.
   
  N.B.  A subtle but important distinction has & must be made between amb's e12 excellent design & revisions and the behavior of derivative implementations.  CTH's & SOHA II's e12s are derivative works based on earlier e12 designs, and their behavior in those headamps is unique to headamps themselves.  IOW the experience/behavior of CTH/SOHA II/etc e12 implementations is unique to those headamps.
  IMO & practice, I'd not be comfortable using a tube hybrid w/o muting delay + DC offset protection, unless tests measurements showed it could not pass harmful DC to headphones.  Things like this:
http://www.head-fi.org/t/562736/what-causes-this-amp-related
  could be happening w/o the user being aware it is.  IOW a harmless albeit annoying click is preferable over volts of DC undulating your drivers.  BTW think Schitt retrofitted a relay or something into the amps in that link.


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## Lil' Knight

Thanks! I fooled around with the resistors and swapped different tube, the amp is making sound again.. Hopefully it will be stable this time.

I haven't cased up the amp, SG is not connected to the chassis. There is a slight background noise during the music, especially when touching the pot, I guess this will be solved when I finally put it in the chassis?


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## cfcubed

I'd expect that noise to go away w/proper casing, grounding incl grounding the pot.


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## Lil' Knight

Great. 

Just wondering, is this the right adaptor for using the 6f8g? Is there any necessary modification to use it?
http://www.ebay.com/itm/TWO-6F8G-6C8G-plug-adapters-12AX7-12AU7-ECC82-tubes-adapters-/260719362017?pt=Vintage_Electronics_R2&hash=item3cb415bfe1


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## cfcubed

What I know about it is found by searching for my posts for 6f8g. 
Trying them is advanced/DIY/YouAreLargelyOnYourOwn IMO


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## mink70

I've been driving the LCD-2s with my CTH/Bugle Boy ECC82 with pretty nice results, but have been wondering whether it's possible to do better. (CTH is my only amp at the moment). How ultimately good is this amp compared to commercial hybrids and transformer-coupled tube amps? For example, has anyone heard both the CTH and the Schiit Lyr and compared the sound quality?


----------



## Lil' Knight

cfcubed said:


> I'd expect that noise to go away w/proper casing, grounding incl grounding the pot.



So I got some spare time to put the amp into case. The buzz is a bit more silent but still there whenever I touch the volume knob. 
When you said ground the pot, does that mean I should connect it to the case too? It's isolated now.


----------



## cfcubed

If the case is metal I'd connect it to SG (which = IG input ground).  And if the volume pot is not mounted to grounded metal then you should run a small ground wire to it.
  On the RK27s I loosen one of the 2 little screws on back, slip a small/thin wire under it, screw it back in & run that to IG/SG/case ground.  One way or another grounding that knob.


----------



## Lil' Knight

I'm using the Hammond case with plastic panel so the pot is totally isolated. Also, the pot used is TKD 601 which does not have the screws like those of the RK27. Looks like I should just connect the ground pin to SG then.


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## Mullet

I had this issue exclusively with CTHs. Earlier on in this thread cfcubed suggested the same thing about tying the pot to input ground or SG -- either one works. After loosening the screw on the RK27 and making a small lead going to IG the buzz went away completely. With my "Wire" amp I don't have the same issue. No need to tie the pot to GND.


----------



## cfcubed

The need to ground the pot when using a metal knob is not uncommon and more a standard practice.  Don't want it being an antenna for noise or a path for static shocks to go directly to your input stage.
  It's no big deal to do it either, if there's no easy way just solder (file, flux, solder) a ground wire to a thin big washer or sheetmetal cutout & thread it onto inner side of pot shaft.


----------



## Ikarios

I picked up a set of new headphones recently and it turns out that I have a 60Hz or 120Hz hum (don't really have a way of figuring out what it is, exactly - can't find any good comparison sounds on youtube) in my CTH that I could not hear with the K501 (due to the headphones' low sensitivity). I've ensured that it is not my source introducing this hum. The case of my volume pot isn't grounded to anything and nothing changes when I touch the volume pot so I don't think that's anything. I'm using the Rev. A version of the BoM so C3H is an updated 330uF. I have noticed that the buzz gets a little more noticeable at 6.3V heater supply (6CG7). My other tubes are a 12AU7 and a 12BH7. I have tried using a surge protector and running it straight out of the wall. Disconnecting inputs doesn't change anything. I'm pretty clueless when it comes to troubleshooting so that's about as far as I got. Any help?


----------



## cfcubed

>  a set of new headphones recently and it turns out that I have a 60Hz or 120Hz hum
   
  It's been a long time since we've had a report of this with CTH...  Hum using newer BoM parts and possibly not related to grounding.
   
  Exactly what/which are your new headphones?
  You say touching the vol knob has no impact, does touching its (metal?) case have any?
  About where is the vol knob in its rotation when you notice the hum & do you only notice the hum between music passages/during the quietest parts (or is it more noticeable than that)?
   
  If this is not a ground issue then you seem to be on the right track WRT C3H, which was raised to suppress such noise.  
  R18 values also have some impact here - I wonder what value yours are & if they are std BoM/100R.


----------



## Ikarios

Quote: 





cfcubed said:


> >  a set of new headphones recently and it turns out that I have a 60Hz or 120Hz hum
> 
> It's been a long time since we've had a report of this with CTH...  Hum using newer BoM parts and possibly not related to grounding.
> 
> ...


 
   
  I believe I adhered to the CTH Rev. A BoM for all resistor/cap values, apart from the LED. The headphones I hear the hum on are HD700s, which are, from the specs, much more sensitive than my K501. I hear the hum at all rotations of the volume knob, even at the lowest, although it's pretty faint, and difficult to pick out if music is playing. It's similar to the faint drone of an air conditioner in another room, or a buzzing fluorescent light. If I get to about 12 o'clock in the rotation the amp starts to get noisy, with some DAC noise, but that's at almost unlistenably loud levels. I listen at around 9/10 o'clock at most. I've tried touching pretty much every exposed piece of metal on the outside of the case - RCA grounds, headphone jack, volume knob, exposed area of metal case, all to no avail. The only thing that changes the hum a bit is fiddling with the AC jack's nut (loosening and tightening) but my back panel is pretty tight back there and I don't want anything accidentally bridging. I suppose I'll have to take it apart and take pictures anyway, though.


----------



## flynhawaiian

How do I wire up an LED under the Tube?  What pads do I use for it?
   
  Thanks


----------



## cfcubed

You can use PCB's embedded e12 green/on/latch LED pads.  If you're already using it _think_ the circuit will still behave if you parallel in another LED (test this).
  Think I had to enlarge the PCB hole under the tube socket (e.g. w/a reamer), shrink-wrap LED leads & glued LED in socket's hole.


----------



## flynhawaiian

Thanks.  Still waiting on a part from ups, and then I can finish it up


----------



## civilmonkey

I search and searched and maybe I just missed it, but is there any information on how much power the CTH can put out?  I'm looking into using it for some HE-500s and I've read that people are doing this successfully.  I'm just curious if we have ballpark numbers.  The HE-500's supposedly need 2 watts at 32 ohms.


----------



## cfcubed

IIRC runeight made a post about that within the last few years, e.g. how many mW CTH's buffer should put out before leavhing class A.  Guess you can use google search against this site or consider pinging him about it.
   
  I've HE-500s myself & prefer my 2-channel b22 to CTH for them, O2 if something smaller is required (e.g. @ work).  Same for when I'd owned LCD-2s.  IMO & to my ears these orthos do not need warmness that tubes can impart, they benefit more from the drive of something like any b22.  When I do sometimes miss the option to color/contour the sound w/tube swapping I swap in the CTH & use a tube w/sparkle like chrome plate Siemens (and it performs well & sounds quite nice).


----------



## holland

Wow, CTH.  This brings back memories, what a great little amp with some neat features like the self zeroing output diamond buffer.
   
  Anyhow, I'm not Alex, but the CTH uses a class AB diamond buffer with approximately 20mA idle.  It should peak out around 40mA before exiting class A.  I am not sure what the voltage swing is, but for the HE-500 it shouldn't matter, it will be current limited.
   
  I would guess the voltage swing should be about 13Vp-p, roughly 5Vrms.  I'm guessing roughly 185mW rms.  Heat in the small enclosure is a constant battle, I'm not sure it can sustain that.  Note, no calculations done, and no measurements taken.  I'm not really sure if it can hit that before it clips.  Anyhow, for 38ohm you're likely looking at around 60mW of class A.  That should land you around 105dB-ish before coming out of class A.
   
  Depending on how much SPL headroom you actually need or want to target, should dictate your headphone amp requirements.  I guess if you need 120dB peak out of your HE-500, then the popular DIY amps out there are EHHA and Beta22.  The SOHA2 should land you around 112dB, in stock form.  You can get more with a bigger heatsink.
   
  Edit: keep in mind, it's all theoretical.  One would need to bench the amp to see where it lands in terms of THD to determine what's acceptable or not.


----------



## gurubhai

I was looking for a substitute for 220uH inductor (L2H) which is available at mouser since I won't want to place an order from farnell just for a single item.
  Would this one work :
http://in.mouser.com/ProductDetail/ABRACON/AIUR-02H-221K/?qs=C7smiywbPwWHRe3jq6sAEA==


----------



## cfcubed

It should work, IIRC I used a ferrite core coil like that for L2H in one of my builds & had no issue with it.
  The spec'd air core toroid is a "better" part (e.g. lower DCR), but I still say try it.


----------



## gurubhai

^Thanks.
   
  Finished my CTH build and it seems to be working fine except that I am getting some clipping/distortion if I crank it up.The TB+ is about 86V instead of the suggested 95-105V and the pin 1 & 6 of the tubes measure around 79.5V.
  I double checked the PS caps and diodes and they are all correctly oriented. Any suggestions would be appreciated.


----------



## KimLaroux

I had a similar problem with my MSSH recently. Turns out the plate current was so low, there was not enough voltage drop across the cathode resistor. This made the grid so close to ground, any input voltage exceeding it made the tube clip and distort.
   
  Check what voltage you get at Vk (across the cathode resistor). It's supposed to be around 2.4V.


----------



## holland

Quote: 





gurubhai said:


> ^Thanks.
> 
> Finished my CTH build and it seems to be working fine except that I am getting some clipping/distortion if I crank it up.The TB+ is about 86V instead of the suggested 95-105V and the pin 1 & 6 of the tubes measure around 79.5V.
> I double checked the PS caps and diodes and they are all correctly oriented. Any suggestions would be appreciated.


 
   
  TB+ is with or without the tube?  Try without the tube first.  Also measure the AC coming in without the tube.  Then do the same with the tube.  If it's fine without the tube, your transformer may have problems handling the load.
   
  If it is the same voltage without the tube as it is with the tube, it's the multiplier, check the diodes and caps again.


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## gurubhai

TB+ is the same both with and without the tube at around 85-86V.
   
  I checked the transistors and diodes of the multiplier and they seem to be okay and the cap orientation is correct. No loose joint either.


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## holland

Quote: 





gurubhai said:


> TB+ is the same both with and without the tube at around 85-86V.
> 
> I checked the transistors and diodes of the multiplier and they seem to be okay and the cap orientation is correct. No loose joint either.


 
   
  What's your AC voltage?


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## gurubhai

getting 23.8 vac out of the adapter .


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## holland

Quote: 





gurubhai said:


> getting 23.8 vac out of the adapter .


 
   
  I just looked at the schematics.  It looks like a 2.5x multiplier, which should land it around 85V.  I can't recall what mine is at.  I'll have to take a measure some time later in the week.


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## KimLaroux

Quote: 





gurubhai said:


> TB+ is the same both with and without the tube at around 85-86V.
> 
> I checked the transistors and diodes of the multiplier and they seem to be okay and the cap orientation is correct. No loose joint either.


 
   
  Seems like the tubes are not even loading the rail. Have you checked that the CCS is working correctly? It's easy to verify, just check the voltage across the cathode resistor. It should be around 2.4 V. I'm guessing it's not.


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## gurubhai

Quote: 





kimlaroux said:


> Seems like the tubes are not even loading the rail. Have you checked that the CCS is working correctly? It's easy to verify, just check the voltage across the cathode resistor. It should be around 2.4 V. I'm guessing it's not.


 

 R3L = 3.6 V
  R3R = 3.48V
   
  CRD is semitec E-202 and the tube is a 12fq7.


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## cfcubed

gurubhai said:


> CRD is semitec E-202 and the tube is a 12fq7.



Haven't looked at your CRD specs compared to spec'd BUT I'm unsure of that tube.
Years ago we started enumerating compatible tubes (see CTH info in my sig and 
http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/2025#post_6785071)
And that tube is not green/tested/recommended, so could you please try a sure-thing tube like a 12au7 (or other in my typed compatible list) and report back.


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## gurubhai

I tried both ECC82 and E88C as well. Same issue, infact the clipping was worst with e88cc.
  I think it might be a wallwart issue, will change it and report back.


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## holland

Quote: 





gurubhai said:


> getting 23.8 vac out of the adapter .


 
   
  Quote: 





gurubhai said:


> I tried both ECC82 and E88C as well. Same issue, infact the clipping was worst with e88cc.
> I think it might be a wallwart issue, will change it and report back.


 
   
  You're probably right.  It is a bit low, unloaded.  I can check mine, if I can find it.


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## holland

27.3vac unloaded.
   
  BTW, I've used 12FQ7.  I thought it was good.  I currently have a 6GU7 set aside for the CTH.
   
  Edit: My heater is not stock.  I reworked it for more current.  I can't recall the original specs.


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## gurubhai

Followup : Connected a 24V/ 2A transformer and the TB+ is now 95.9V. Currently have a BEL ECC82 plugged in listening to a T50RP, no clipping and its whisper quiet. Sounds pretty darned good too.
	

	
	
		
		

		
			




  Thanks for the help guys.


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## cfcubed

gurubhai said:


> Followup : Connected a 24V/ 2A transformer and the TB+ is now 95.9V. Currently have a BEL ECC82 plugged in listening to a T50RP, no clipping and its whisper quiet. Sounds pretty darned good too.
> Thanks for the help guys.



That's good news. So holland was on right track WRT low A/C - TB+. What was the quoted voltage and amperage of the first adapter that didn't work?
Of course these A/C adapters are just transformers in a box, no active accomodation of load and direct relation to line voltage.
BTW I've had good results, perhaps w/easier to drive cans, with 0.8+A adapters and we spec 1+A IIRC.


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## gurubhai

The other adapter was 24V, 1A ac so it should have worked but it didn't. Unloaded, it was outputting about 23.5VAC unlike holland's adapter which is closer to 27VAC. My current trafo outputs around 25VAC unloaded and seems to be working fine unless the mains dip too low.


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## civilmonkey

Quote: 





cfcubed said:


> ...
> I've HE-500s myself & prefer my 2-channel b22 to CTH for them, O2 if something smaller is required (e.g. @ work).  Same for when I'd owned LCD-2s.  IMO & to my ears these orthos do not need warmness that tubes can impart, they benefit more from the drive of something like any b22.  When I do sometimes miss the option to color/contour the sound w/tube swapping I swap in the CTH & use a tube w/sparkle like chrome plate Siemens (and it performs well & sounds quite nice).


 
   
  Quote: 





holland said:


> Wow, CTH.  This brings back memories, what a great little amp with some neat features like the self zeroing output diamond buffer.
> 
> Anyhow, I'm not Alex, but the CTH uses a class AB diamond buffer with approximately 20mA idle.  It should peak out around 40mA before exiting class A.  I am not sure what the voltage swing is, but for the HE-500 it shouldn't matter, it will be current limited.
> 
> ...


 
   
  To close this loop, I got my HE-500's yesterday.  I'm quite happy with the HE-500's on the CTH but think it is current starved.  The bass thumps and extends, don't get me wrong, and details in the mids and highs are wonderful, but bass can loose some slight details.  IMO we are talking minor, but still.  At reasonable to moderate loud volume levels I find it quite nice (volume control at 12pm).  Saying that, I also ran the HE-500's from an old 20 watt speaker amp headphone out (Sanyo JA-220), and the speaker amp's power is able to drive the HE-500's to incredible detail from lows to highs.  So, I also prefer the HE-500 with something with more power, but the CTH and HE-500  sounds great enough that if it was my only option, I don't think I'd worry too much about upgrading.  It would be the last 10-20% type upgrade only.


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## jilldwr

Just finishing off my CTH build, had the board for awhile but a few other projects got in the way. I have a question regarding the transformer hookup, my plug is off board, mounted to the back panel. I've noticed in a few pictures of others builds, they've wired their off board AC-in jacks to S1 and S2 instead of the sockets provided for the BOM listed PCB mount jack. 
  
 My question is: Am I ok to wire the center pin of the jack to the rear socket, and outer rim to the front socket, so I can keep the switch?


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## cfcubed

Yes, A/C has no polarity.


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## jilldwr

Well, fired up my CTH last night without any sparks, but that was the only good news.
 Did all the startup measurements and everything seemed fine, so hooked it up to a source and some old 600 ohm cans, Nothing!
 No output at all! Spent hours verifying all the components, everything looks good, no solder bridges either, checked with a loupe.
 Retook the measurements:
 OG -> SG = 11.98v
 OL -> SG = 11.97v
 OR -> SG = 12.00v
 TB+ -> SG = 98.8v
 P1 -> SG = 77.9v
 P6 -> SG = 78.v
 P4 -> P5 = 6v
  
 On turn on, Relay snatches at about 20 seconds.
 I'm using a new 6DJ8 Amperex.
  
 Not really sure where to look next, all my measurements thus far look pretty good?
 It's gotta be a circuit unrelated to the ones I've already checked. 
  
 Any suggestions??


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## jilldwr

Ooops! Wired up the output jack to the pins that disconnect when the plug is in! DOH!
 Man does this thing sound sweet!


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## Misterrogers

NIce! Glad to see this wonderful amp is still being built. Congrats!


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## Misterrogers

Hey gang, does anyone know the 'ma' load on ICP the 24V reg? I want to try out one of Bellesons new mini regs, but it only supports 225ma load. TIA!


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## cfcubed

Off the cuff I'd say a big no to an ICP w/225ma load rating.  It's powering output buffer, rail splitter + e12/relay in CTH and gets (very?) warm at its 1A rating.
 The best way to know its draw would be to lift its output pin & bridge back using an ammeter (> 1A capable).


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## Misterrogers

Hey Guys - need a little help. I'm trying to troubleshoot a CTH; here's what I have.
  
 OL, OR, OG   - ~12V
  
 I latch fine.
  
 Right channel has proper output, no output on the left channel. Tube pin 1 is ~95V. TB is ~95V check component values, and the left channel op amp. Pot is soldered correctly. Thoughts?


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## jilldwr

What is tube pin 6? Is this a new build ?


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## cfcubed

misterrogers said:


> Right channel has proper output, no output on the left channel. Tube pin 1 is ~95V. TB is ~95V check component values, and the left channel op amp. Pot is soldered correctly. Thoughts?


 
 Well you know where to look (pin 1) & the bad symptom (TB+ should be 95V - 105V and plate pins 1 & 6 about 80V.)   So we know you are up to here in CTH's setup instructions:

_If TB+ is good but pins 1 and 6 are far from 80V the tube opamps may be bad or a component value may be wrong.
 If everything in the tube circuit tests good but the plate voltages are still far off, the tube is bad._
  
 I find the problem curious because its a "no sound" problem, IIRC more often you get some sort of sound even if these measurements are off...  But it's been a long while since I've debugged/helped debug something like this.
 I assume your right-channel/pin 6 measurements are proper (e.g. plate about 80V). 
 If so you've probably done this but swapping ICR & ICL to see if problem follows & of course trying different tubes.  Then crawling though the left vs right input stage components & being extremely careful making/comparing live board measurements.  Maybe 1st comparing resistances at places between them on non-live board would show something.  And of course searching CTH threads for the plate pins measuring same as TB+ problem.


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## kytuphicanh

I am beginning to gather parts for the CTH build. My main 'phones would be the Koss KSC35 (60ohms @ 101db) and the only tube I am going to use is the 6f8g. 
Any suggestions regarding parts choice for this build? 

Also, which one of these would be the correct adapter? I think the 6f8g->6ca7 was mentioned before, just want to make sure I got the correct one.

http://www.ebay.com/itm/201099416430?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

http://www.ebay.com/itm/191197575305?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


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## Mullet

I believe those adapters should work.
  
 I know it's up to you but why not try any of the 6DJ8 or 12AU7 variants that the amp was designed around?
  
 Also, curious why you need an amp for the KSC35s? Aren't they fairly efficient phones to begin with?
  
 Parts wise... I'd suggest using the longer Hammond case... you can fit in the Alps RK27 pot and 1/4" jack with the longer case. Also go for the upgraded the 732-1429-ND 1A L2H. This will all up to 800mA filaments e.g. 6N6P tube. Slap on at least a partial heatsink on the LM2595 if you're going to run the 6N6P. Also, get a multi-rotary switch like this 633-MRK206A-RO. This will allow you to use more than 2 heater voltages. Both of my CTHs have 4,6,8, and12v heater voltages. I think most people just do two - 6 and 12v so it's up to you.


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## flynhawaiian

I need an alternative to the Q3E 512-MPSA14 since it is no longer made.  Does anyone know of the alternative?  Is it the 610-MPSA14?


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## cfcubed

Reviewed what info I could find and that looks like a decent sub to me for what it's used for in the CTH (relay latch).

Only issue would be (unwarranted?) suspicion of it in a build that had output relay latch issues.... Which is a symptom of many things that could be wrong with a build. If it was me I'd try that sub.


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## flynhawaiian

Sweet.  One last thing...  Which way does Q1P go?  I’m a little confused on the orientation


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## Misterrogers

The metal part should face the rear of the board (power connector, etc.)


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## flynhawaiian

Thanks.  So the "black part with the paper or cardboard" faces the top of the board?


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## Misterrogers

Take take/upload a picture when I get home this evening


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## flynhawaiian

That would be great.  I’m having problems seeing it in the other pictures.


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## Pilou

Hey Guys - need a little help.
 Does anyone know the alternative to C1L , C1R ( Aluminium Electrolytic 10u 10v) and an alternative to the Ic1 (TL082)?  since it is no longer made.
 Thanks for helping, I'd really like to do this little amp.


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## cfcubed

A post I made about TL08X alternatives:  http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/2205#post_11422879
  
 For the cap(s) bet a search for "Aluminum Electrolytic 10uF 10volt" or similar would turn up some (16 volt is OK too of course).  Nothing special about C1L & C1R but (try to) match the lead spacing & watch the diameter for fitment.


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## Mullet

Couldn't you just use a TL082CP instead? It has slightly different specs, but I'd think it should work fine.


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## cfcubed

mullet said:


> Couldn't you just use a TL082CP instead? It has slightly different specs, but I'd think it should work fine


 
 Agreed... That's what I meant in the post I linked to, that TI's TL08xCPs are suitable subs for STMicro TL08xCNs part #s in the BoM. 
 Part #s in BoM XLS are/were for ordering convenience of parts from Description field (e.g. TL081, TL082, etc).


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## Pilou

Thanks for your fast answer, I have an other little question : wich resistor are the best for R5H, 3.3k, 5.8k, 15.1k or 23.3k?


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## cfcubed

R4H & R5H are resistors you'd only purchase & use if you wanted to support more than (popular) 12.6v & 6.3v heated tubes. 
 Most builders use a SPDT toggle 12.6v/6.3v (thus not needing R4H & R5H).  See also: http://cavalliaudio.com/diy/cth/main.php?page=schematics/psschematic


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## Mullet

I've added in the extra resistors to allow for 4v and 8v tubes and I barely use them. I mainly use 6v and 12v based tubes. There are a few 8v variants of 6v/12v tubes like 8CG7 or 8GU7 that are super cheap options that most like will sound just like their 12v or 6v equivalents. If you wanted the extra heater voltages, you'd need a rotary switch like this one...
  
 Mouser Part # 633-MRK206A


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## Pilou

Thanks again, do you think this: http://www.digikey.com/product-detail/en/BC547CBU/BC547CBU-ND/975543 is a good alternative to the BC550C?


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## cfcubed

No, use the base part & classes specified (e.g. BC550 - class C).  E.g. in the case you ask about either BC550CTA (ammo/tape) or BC550CBU (bulk/loose).
  
 Curious, how many builds do you have under your belt?   The CTH is an intermediate level build, *lots* of parts in a tiny space, and misplacement / misalignment of any can ruin your day.  IOW IMO would not recommend CTH as a first project.


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## Pilou

I only have two builds has my belt: a Cmoy and a O2 amp!
 However this is not the construction that worried me but right choice of components
	

	
	
		
		

		
			





.


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## cfcubed

Sorry I did not mean to offend, sounds good - an O2 build is a good warm-up
  
 Good to confirm any questionable sub parts as you are doing.  But concentrate on Description field value in CTH XLS BoM when an exact part # is not available from your source(s).  E.g. in the Digikey BC550CGOS-ND EOL case see they suggest BC547C as direct substitute but would first search for sub using "BC550C" (from Description).


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## hpamdr

I'm enjoying a lot my CTH and got a box of russian tubes with inside some submini tube (6N16B-V). I've seen than on the proto board, you started with it !
 Does this tube can still be used  with Rev A design?
 Do you have an optimal socket conversion cabling ?   (from filament to noval skipping pin 9)


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## cfcubed

Had to go back in my archives for this one
  
 First off I suppose your CTH has a regular 9-pin socket installed....  So maybe use a "9 PIN TUBE SOCKET SAVER FOR 12AX7" or "9 pin Machine made tube socket 12AX7" (w/o center pin) from fleabay to wire the pencil tube into so it can be inserted in CTH 9-pin socket.
  
 Attaching my chicken-scratch sheets from when used 6N16B (6.3v heater) in the proto, to help you map its pinout.  Yes leave pin 9 unconnected.
  

  

  
 N.B.  Of course use something like small dia. heat shrink tubing on 6N16B leads if there's any chance of them shorting.  If you do this please post back your results/impressions.


----------



## hpamdr

Thanks this is quite helpful !
 I will do it when i will receive some socket saver and try to do an adapter.
  
 For now i also got some russian 6N6P (6н6п) i like the "airy" sound even if at first it seems to be not very fast. The gain is not very high but all is ok to power HD650 and T1.
 The tube after 30 minutes of (active) burning  is more dynamic and i like a lot the sound of the CTH with it specially for pop, small ensemble.


----------



## rds

Bumping this thread to say thanks to Dr. Cavalli, cfcubed, and everyone else involved in creating this great little buffered tube amp. It's travelled with me to three different cities and is a fond reminder of my head-fi diy days. Here it sits on my night-table in Switerland, far from my hometown of Vancouver - more than 6 years after I originally built it.


----------



## cfcubed

Thanks for the post rds, good to hear your CTH is still serving you well.  Though I listen mostly to speakers these days, I do rotate a CTH in every now & then when using cans & still enjoy it.


----------



## emilio84

Just finished reading this and pretty much any other CTH thread I could find. I'd very much like to build one of these amps. Tossed the BOM into Mouser's BOM tool and while there are approx 13-15 components that have been end of life'd it seems there are comparable current products available. The biggest unknown is obviously the PCB and after some digging I found and ordered one from what now appears to be an abandoned site (joeaudiophile) as after almost a week I haven't received any sort of shipping notification even though the order was processed. Emails to the site haven't been responded to either unfortunately. 

Is there any chance anyone has a spare pcb or kit kicking around? I'd even go as far as having a pcb (or batch) made if someone would be willing to supply me with the gerber file. 

The design seems so well received that it would be a shame to have it disappear into the archives.


----------



## Misterrogers

Hey!
  
 Apologies - Not sure what's going on communication wise. I sent you an email a couple of days ago asking for your shipping address. Also, just checked my junk folder; nothing in there from you (or anyone) unanswered. Anyway, glad yo posted here. Please verify you're emailing to mike@joeaudiophile.com. Or, you can provide your shipping address via message hear at Head-Fi. As soon as I get a shipping address I'll send one off.


----------



## emilio84

misterrogers said:


> Hey!
> 
> Apologies - Not sure what's going on communication wise. I sent you an email a couple of days ago asking for your shipping address. Also, just checked my junk folder; nothing in there from you (or anyone) unanswered. Anyway, glad yo posted here. Please verify you're emailing to mike@joeaudiophile.com. Or, you can provide your shipping address via message hear at Head-Fi. As soon as I get a shipping address I'll send one off.




Guess who just found your email in HIS junk folder.... Yeah... It's me. Anyway, for those of you following along at home, Mike did reach out to me and all is well. Really excited to get my build going!


----------



## wolfield

Does anybody have the schematics still laying around? Would someone be kind enough to share?


----------



## javaboju

I might still have these somewhere on a computer.
Let me do some digging.


----------



## wolfield

javaboju said:


> I might still have these somewhere on a computer.
> Let me do some digging.


Have you found anything at all?


----------



## proid

Does anyone have the schematic for CTH? I can no longer find it.


----------



## jilldwr

Here you go!


----------



## proid

jilldwr said:


> Here you go!



can you repost it, i can't see the schematic


----------



## Mullet (Dec 28, 2019)

Here's what I have...


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## Mr Trev

I know I'm waaay late to this party, but I like what I've been reading so far.

I'm thinking about trying to get one of these as a better tube rolling option to my current Vali 2. Anybody that still watches this thread have any opinions?


----------



## cfcubed

I still watch this thread.  Time flies.  Noticed your WTB post, hopefully you'll get a hit.  

BTW I own both a nice DIY CTH and a Massdrop CTH and rotate both in from time to time.  DIY CTH gets play because of its greater tube rolling (voicing) options; I've lots to choose from and find that fun.  But my "budget" β22 is my mainstay.

Good luck on your quest.


----------



## Mr Trev

Hope I get a hit too, but I imagine its a long shot.
If I had a clue what I was doing I'd take the schematic and do a build either point to point or with breadboard. The "compact" part really isn't a factor for me, it'll be for home desktop (bedroom) usage only.

My Vali2 is a decent enough amp, but really doesn't showcase the tubes, probably due to negative feedback. Does the CTH use negative feedback? I haven't read anything saying one way or the other.

What's this  "budget" β22 you mentioned? I tried clicking the link in your sig, but it's dead.


----------



## cfcubed (Mar 1, 2021)

Thanks for letting me know.  Updated a few of the links in my sig. 
I've built and heard a lot of headphone amps.  Part of the reason I stopped building; Too much audio gear & not enough space (or ears  Though I do plan to someday build out a Bruce Heran 6DJ8 Headwatt I bought the parts for years ago.  Assuming I can create a work area somewhere in the condo we moved to.

Anyway, based on my ears & listening prefs I couldn't easily discern diff amongst 2-, 3- & 4-channel β22s so sold most & paired down to a bare-bones, non-traditional, cheapo 2-channel β22... Plus AMB γ2, a few sets of cans & DIY CTH & Massdrop CTH in rotation.  As you may have read, tube rolling has a lot of effect in the DIY CTH design, IOW it permits tube choice to color its sound more than many other amps.  Hopefully one will popup sometime for you to try.  Maybe setup an alert somehow for new FS Headamp posts.


----------

