the CTH (Compact Tube Hybrid) Rev A thread... - Page 19

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.

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

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

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.

Nice work cfcubed! Excellent turn around time as well.

Thanks for verifying the PCB and BOM. Very much appreciated!

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

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.

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:

1. 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
    
2. 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:
   
3. 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.

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.

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 Projects 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).

Quote:

Originally Posted by 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.

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 :-)