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A Very Compact Hybrid Amp

Jul 8, 2010 at 2:55 PM Post #2,026 of 2,218
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..
 
Jul 16, 2010 at 2:18 PM Post #2,027 of 2,218
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.
 
  1. Core/main supported tube list:
    12.6v heater:
    12au7 variants
    ecc82
    6680
    6189
    5963
    7316
    5814
    12bh7
    8416 (12.6V 6922)
    6.3v heater:
    6922
    6dj8
     
  2. 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.
     
  3. 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



     
  4. Lots of tube preference/synergy opinion here on head-fi and elsewhere like:
    http://www.audioasylum.com/audio/faq/joes-tubes.html#12AU7
    http://www.audioasylum.com/audio/faq/joes-tubes.html#6DJ8
    http://db.audioasylum.com/cgi/m.mpl?forum=tubes&n=50176&highlight=sibilance&r=&session=
     
  5. 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."
 
Jul 16, 2010 at 9:33 PM Post #2,029 of 2,218
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.
 
Jul 16, 2010 at 10:31 PM Post #2,030 of 2,218
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.
 
Sep 12, 2010 at 10:13 PM Post #2,031 of 2,218
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
 
 
[size=small]Q8L, Q8R, Q3S, Q5S[/size]   [size=small]4[/size]   [size=small]BC337-25[/size]   [size=small]Mouser[/size]   [size=small]512-BC33725BU[/size]   [size=small]Digikey[/size]   [size=small]BC33725-ND[/size]
 
 
[size=small]C4H[/size]   [size=small]1[/size]   [size=small]Metalized Polyester/Polypropylene
Film Capacitor 2.2nf 35V[/size]		   [size=small]Mouser[/size]   [size=small]581-BQ014D0222JDD[/size]
 
 
[size=small]D5H[/size]   [size=small]1[/size]   [size=small]1N5820[/size]   [size=small]Mouser[/size]   [size=small]863-1N5820G[/size]   [size=small]Digikey[/size]   [size=small]1N5820FS-ND[/size]
 
 
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
 
[size=small]D1L, D1R[/size]   [size=small]2[/size]   [size=small]2.0mA CRD[/size]   [size=small]Mouser[/size]   [size=small]610-1N5305[/size]
[size=small]D2L, D2R[/size]   [size=small]2[/size]   [size=small]4.3mA CRD[/size]   [size=small]Mouser[/size]   [size=small]610-1N5313[/size]
 
 
 
Thanks in advance for any help you guys/gals can provide! It's greatly appreciated!
 
Sep 12, 2010 at 10:38 PM Post #2,032 of 2,218
replacement parts
 
 
863-BC337-25ZL1G
 863-1N5821G
 
505-FKP22200/100/5
 
The expensive CRDs deter simple cloning of the circuit by chinese markets I think.  There is no drop in replacement for it.
 
Sep 12, 2010 at 11:29 PM Post #2,033 of 2,218
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)
 
Sep 13, 2010 at 8:47 AM Post #2,035 of 2,218
Sep 13, 2010 at 9:57 AM Post #2,036 of 2,218
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.
 
Quote:
sachu said:
this should do
 
http://www.mouser.com/ProductDetail/Triad-Magnetics/WAU24-1000/?qs=sGAEpiMZZMtpkqKkT5w3uqDKK8oOgNqon7/yGA1hZqU%3d
Click to expand...

 
Sep 17, 2010 at 9:30 AM Post #2,037 of 2,218
Sep 17, 2010 at 9:46 AM Post #2,039 of 2,218


Quote:
sachu said:
umm the link is to a 1uF cap..the Vishay one i mean. The wima is for a 0.1UF
Click to expand...


Yikes, i think I need to put on my glasses this time of the morning
smily_headphones1.gif

 
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