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A Very Compact Hybrid Amp - Page 136

post #2026 of 2213

Yeah, I was thinking of it being a power issue.. We've been waiting for weeks to get our office cubes powered properly, and in the mean time we probably have 3 times as much load on one circuit, hanging off a bit 6 foot power bar.. Pretty bad for the IS dept of a company  :(   Actually the newer one has been better since one of my co-workers has left for the day and powered off his systems..   Still going to make the changes though..

Edited by MrSlim - 7/8/10 at 1:41pm
post #2027 of 2213

There have been questions as of late, some of which in PMs, regarding tubes compatible w/CTH. 
The information seems scattered about this thread & the CTH "Tube & tweak" thread.  I'll try to consolidate here.


Although CTH's "design center" is 12au7, it is also designed for use with other 12.6v & 6.3v (series) heater tubes having compatible pin-out/properties and has been used to good effect with them. 

IMPORTANT: You must always set the heater switch to the correct series heater voltage (6.3v or 12.6v) for the tube being used.


  • Core/main supported tube list:
    12.6v heater:
    12au7 variants
    8416 (12.6V 6922)
    6.3v heater:
  • Technically speaking, we are looking for:
    1) the 12au7 / 6922 pin-out
    2) series heater voltage of 6.3 or 12.6, prefer max series heater draw = 600ma for standard CTH builds. Tube data sheets usually list "parallel" (pins #4/#5 + #9) heater draw and "series" (pins #4 & #5 only) heater draw. Ignore the parallel figures - respect the series ones.
    3) 15 -> 40 mu (15x -> 40x amplification factor or gain). Best to stay lower e.g. < 36 mu, otherwise you may get very little volume pot range with normal/standard dynamic headphones (see also R18 info).
    4) nominal/normal plate voltage of at least 80V. Most of tubes say 100V -> 200V normal plate & that's fine.
  • Advanced/techie/you-are-on-your-own list.  We began trying to compile a complete list of tubes that function in the CTH, including one with high-current and/or multivoltage heater mods.  The full list is exceeding large & our endurance ran out trying to complete it, and we were quite happy with tubes from the "Core/main supported tube list" above.
    Below is a pic of the first draft of the full list, note there have been more found since this sheet draft & there are European (ECC*) equivalents that could be added as well.
    Dark Green rows = reported to either 1) be equivalents of known compatible tubes, or 2) been actually tested & found to work well.
    Light Green rows = might work but are not sure to work & have not been tested
    Yellow rows = only supported by the "multivoltage" heater mod
    White rows = not yet evaluated


  • Lots of tube preference/synergy opinion here on head-fi and elsewhere like:
  • Updates from CTH owners: "I can vouch for the 6N1P and 12BH7A, both worth having (especially the 12BH7A).  6N23P-EV and 6N6P also work although IIRC the 6N6P is beyond what the Heater Supply was designed for and you need to change L1H & L2H to cope.  Heat sinking ICH was also recommended."

Edited by cfcubed - 3/27/11 at 9:50am
post #2028 of 2213

^thanks for that

post #2029 of 2213

It would be great if that were added the the CTH main site.  I remember spending 30 minutes more than once trying to track down that spreadsheet and it'd be annoying to have it become buried again.

post #2030 of 2213

Good idea... I'll ping Alex about it for the CavalliAudio / CTH area.   The plan was to get it up there once complete.  The spreadsheet still isn't but the info we do have should be up there.

post #2031 of 2213

So i'm back again, every time I planned this build months ago life got in the way. So i'm back, getting my orders ready at Mouser & Digikey and am stuck on a few key parts (and had some questions about others). 


The parts that I need to find replacements for are below (no longer stocked/produced or require huge minimum quantity) - I tried finding suitable replacements using the Mouser product selector, but alas, no luck



Q8L, Q8R, Q3S, Q5S   4   BC337-25   Mouser   512-BC33725BU   Digikey  




C4H   1   Metalized Polyester/Polypropylene
Film Capacitor 2.2nf 35V




D5H   1   1N5820   Mouser   863-1N5820G   Digikey  




Additionally, can anyone point me to a good power supply that would work for this build on either Mouser or Digikey?


One last question - Is there any reason the Diode's are so expensive? Is there any suitable less expensive replacement? The ones below clock in a $4.95/each


D1L, D1R   2   2.0mA CRD   Mouser   610-1N5305
D2L, D2R   2   4.3mA CRD   Mouser   610-1N5313




Thanks in advance for any help you guys/gals can provide! It's greatly appreciated!

post #2032 of 2213

replacement parts








The expensive CRDs deter simple cloning of the circuit by chinese markets I think.  There is no drop in replacement for it.

post #2033 of 2213

Awesome, thanks a ton!!! 


Any recs on a power supply? I can run by my local electronics shop where they sell ones for ~$20, but its hard to make it there during business hours (they close at 4pm)

post #2034 of 2213
post #2035 of 2213

Rock on, thanks!!

post #2036 of 2213

Ooo.  Sachu that's a nice fine.  AFAIR I spent quite a bit of time trying to find such an animal for < $20 new & could not (except some silly ones w/screw terms - no cable).


Obvious, but just make sure the associated PCB mount jack matches the plug on the A/C adapt (see its datasheet for precise details).


BTW I've been quiet around here because I've reached my personal audio nirvana using CTH->new HD600s @ work and my budget ß22->600R-DT880s @ home. 

And getting 2X 24VAC wallwarts for < $25 helped make that budget ß22 happen.

post #2037 of 2213

Darn, the MKS2-.1/63/5 were supposed to arrive back in stock at mouser on 9/15, but now thats been pushed to December.


Is http://www.mouser.com/Search/ProductDetail.aspx?R=MKT1817510064virtualkey61310000virtualkey75-MKT1817510064 a suitable replacement for it? Or would you guys recommend anything else instead?


post #2038 of 2213

umm the link is to a 1uF cap..the Vishay one i mean. The wima is for a 0.1UF

post #2039 of 2213
Originally Posted by sachu View Post

umm the link is to a 1uF cap..the Vishay one i mean. The wima is for a 0.1UF

Yikes, i think I need to put on my glasses this time of the morning :)

post #2040 of 2213


Edited by aphexii - 9/17/10 at 6:52am
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