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Aikido preamp: 12AU7 or 6CF7/6FQ7 ???

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greg7

I'm looking to build one of the Tubes4hifi preamp kits. The two I'm considering are based on the Aikido circuit. I can't decide between the one using 12Au7 and the one using 6CF7/6FQ7.

Which tube is preferable as far as linearity, distortion and subjective sound quality, all else being equal?

I like the 12AU7 for the much better NOS availability but I suspect the 6CF7/6FQ7 has better linearity/distortion, etc.

Follow Ups:

RE: Dumb question - amioutaline? 06:29:53 10/31/14 (1)
How did the 12AU7 get to be so common in pre-amps?

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- RE: Dumb question - Eli Duttman 08:20:05 10/31/14 (0)
  The type is inexpensive and draws 300 mA. of heater current. The linear Noval based medium mu twin triodes draw 600 mA. of heater current. Guess again, if you think the phenomenon of "bean counters" ruling the roost is of recent origin.
  
  Eli D.
RE: Aikido preamp: 12AU7 or 6CF7/6FQ7 ??? - sony6060 05:49:38 10/31/14 (0)
6CG7 by a long shot vs the 12AU7.
Neither, Use a 7N7 - mobiasloop 10:38:18 10/30/14 (8)
I'd be willing to bet the circuit boards you're using are laid out for the two you mentioned, but I would get me some heavy sockets and use 7N7 loctals. Much more linear, beffier tube. If you must use those miniature things then use the 6FQ7.6CG7. 12AU7 is a ho-hum tube IMHO. Moe Bias
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
- Agreed, 12AU7 is not linear enough for audio use . . . - Ray Moth 23:14:05 10/30/14 (5)
  . . . except maybe as a cathode follower.
  - Even as a cathode follower,... - Lew 10:51:37 10/31/14 (1)
    12FQ7 sounds much better than 12AU7 in my Quicksilver preamplifier.
    - RE: Even as a cathode follower,... - Triode_Kingdom 05:35:14 11/04/14 (0)
      "12FQ7 sounds much better than 12AU7 in my Quicksilver preamplifier."
      
      Why would that be? As a CF, the 12AU7's performance should be virtually identical. I really wish we could get a handle on this issue. How does your preamp bias that stage?
      
      --------------------------
      Buy Chinese. Bury freedom.
  - RE: Agreed, 12AU7 is not linear enough for audio use . . . - Eli Duttman 08:12:24 10/31/14 (0)
    Cathode follower and "concertina" phase splitter are the only legitimate uses of the 'U7 triode in HIFI service, as local current NFB, AKA degeneration, takes care of the type's non-linearity. The 'U7 triode is a wretched voltage amplifier.
    
    If you want this sort of medium mu triode in voltage amplifier service but can't come up with the extra 300 mA. per bottle of heater current needed to use the 6CG7, etc., use the Loctal based 7AF7. ;> )
    
    Eli D.
  - RE: Agreed, 12AU7 is not linear enough for audio use . . . - amnesiac 06:49:05 10/31/14 (1)
    and yet the Japanese diyers love them. I just dont get it.
    - RE: Agreed, 12AU7 is not linear enough for audio use . . . - Gingertube 14:34:09 11/02/14 (0)
      12AU7 is the tube DIY'ers "love to hate".
      Someone once said that they sound awfull and everyone jumped on the band waggon.
      
      12AU7 sound fine if run properly, that is, at 8.5 to 10mA anode current.
      A lot of folk ran them at 2 or 3 mA and then concluded that they sound crap when in fact it was their circuit implementation which was at fault, NOT the 12AU7.
      
      However, I do prefer the 6CG7/6FQ7.
      
      Cheers,
      Ian
- RE: The Monster Amp - Sherwood Forest 15:59:08 10/30/14 (0)
  Lots of great 6CG7s out there, I like Tung-Sol (original) personally. But they're not all that hard to find.
  
  If you do like I did in my DIY monster amp, you use octal sockets wired for 6SN7 (same as 6CG7) and make adapters for 6CG7. Now you have a very wide selection of tubes you can try out.
- RE: Neither, Use a 7N7 - lovetube 15:41:19 10/30/14 (0)
  i agree ,
  use the 6CG7 if you must .
  LT

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