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FDP Forum / Fender Amps: Vintage (before 1985) / someone here will know this without looking it up - ECC82 12AU7



now even awesomer
Jun 11th, 2018 06:59 AM   Edit   Profile  

Save me some time poring over data sheets - am I right in thinking that the 12AU7 could be regarded as a lower-gain 12AT7? My Princeton Reverb II diverts the reverb drive to create an overdriven sound - could that be tamed with a 12AU7 as the reverb driver, will it handle the current OK? A bonus would be less reverb drive, as the reverb sound isn't worth much when the knob's set much above 4. Thanks in advance...

Moderator Emeritus
(with many stars)

NW Pennsylvania

Jun 11th, 2018 07:42 AM   Edit   Profile  

The 12AU7 is definitely lower on the Gain scale.

I would try a new tube of the proper spec first though.

Contributing Member

So. Cal. USA

Jun 11th, 2018 06:03 PM   Edit   Profile  

If I'm not mistaking the 12AT7 will handle more current than the 12AU7. This is the reason the 12AT7 is used in that position. It get hit pretty hard.

Contributing Member

Ooo that sandwich

is gonna get et
Jun 12th, 2018 10:36 AM   Edit   Profile  

There are other possible reasons for distorted sound in the reverb circuit. Here are the usual suspects:

Poor connections (RCA-plugs) on the reverb send and receive lines.

The tube that's in there just may be a bad tube.

The tube socket may be loose on the tube pins.

Poor ground on the reverb pot.

The reverb control pot may be damaged (cracked resistive track).


Too Near Atlanta GA

Amp Tech Emeritus
Jun 12th, 2018 04:23 PM   Edit   Profile  

In that Rivera design amp, I wouldn't replace the 12AT7 with a lower gain tube. I don't think it would render what you want out of the amp anyway. If you want to lower the gain out of that stage you might consider replacing the 1 meg resistor from pin 2 to ground on the 12AT7 with a 1 meg pot. This way you have essentially a reverb dwell control that will also reduce the drive gain when that function is chosen.


Moderator Emeritus
(with many stars)

It's all part...

of my Rock & Roll fantasy.
Jun 12th, 2018 04:31 PM   Edit   Profile  


Retired amp tech...

hard at work.



now even awesomer
Jun 18th, 2018 06:29 AM   Edit   Profile  

Thanks everyone - much appreciated as always.

FDP Forum / Fender Amps: Vintage (before 1985) / someone here will know this without looking it up - ECC82 12AU7

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