RE: Replace 12ax7 with 12at7

Posted by Jim McShane (D) on April 1, 2012 at 12:23:47

In Reply to: RE: Replace 12ax7 with 12at7 posted by Michael Samra on April 1, 2012 at 04:39:23:

Well, as a cathode follower it will always be less than unity gain, so I doubt the mu difference is going to be audible.

The 12AT7 has a much higher Gm though, which may well be audible. I've never understood why Mac ran the relatively beefy tubes (12BH7, 12AU7, etc. ahead of the drivers and then used such a wimpy low transconductance tube as the driver. Especially as the signal voltage drives the power tube grids close to zero volts the drivers are called on to supply a bit of current - and a 12AT7 can do that much better than a 12AX7. The lower output impedance of a 12AT7 follower would be useful in that position I'd think.

But the amp is a classic, so?????

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Follow Ups Full Thread

Topic - Replace 12ax7 with 12at7 - pegwill 05:18:39 03/31/12 (18)

Think E80CC instead - andy evans 11:44:35 04/02/12 (0)

RE: Replace 12ax7 with 12at7 - BCR 05:35:45 04/01/12 (0)

RE: Replace 12ax7 with 12at7 - Neff 07:34:16 03/31/12 (0)

RE: Replace 12ax7 with 12at7 - Blackdog 06:01:39 03/31/12 (14)

RE: Replace 12ax7 with 12at7 - pegwill 06:12:29 03/31/12 (13)

one other thing. - Blackdog 06:41:41 03/31/12 (2)

RE: one other thing. - pegwill 06:54:37 03/31/12 (1)

RE: one other thing. - Alpha Al 20:53:13 03/31/12 (0)

RE: Replace 12ax7 with 12at7 - Blackdog 06:35:38 03/31/12 (0)

RE: Replace 12ax7 with 12at7 - FenderLover 06:35:16 03/31/12 (8)

RE: Replace 12ax7 with 12at7 - Jim McShane 11:49:48 03/31/12 (7)

RE: Replace 12ax7 with 12at7 - Michael Samra 04:39:23 04/01/12 (5)

RE: Replace 12ax7 with 12at7 - Jim McShane 12:23:47 04/01/12 (2)

RE: Replace 12ax7 with 12at7 - Cleantimestream 18:40:02 04/03/12 (0)

RE: Replace 12ax7 with 12at7 - Michael Samra 14:04:10 04/01/12 (0)

RE: Replace 12ax7 with 12at7 - Neff 05:19:01 04/01/12 (1)

RE: Replace 12ax7 with 12at7 - Michael Samra 14:04:34 04/01/12 (0)

RE: Replace 12ax7 with 12at7 - FenderLover 17:53:23 03/31/12 (0)

Follow Ups

RE: Replace 12ax7 with 12at7 - Jim McShane 12:23:47 04/01/12 (2)

RE: Replace 12ax7 with 12at7 - Cleantimestream 18:40:02 04/03/12 (0)

RE: Replace 12ax7 with 12at7 - Michael Samra 14:04:10 04/01/12 (0)

RE: Replace 12ax7 with 12at7

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