# Garnet/Mann amp bias



## mrmatt1972 (Apr 3, 2008)

Did Garnet use fixed bias in his amps? I've got my hands on a beat up old Mann stencil (pics to follow). It is running on 1 power tube (yet still sounds great) and I'm wondering if I can just slot a new matched pair in there. The Tremolo and Reverb are also non-functional at this point, but it is missing a 12ax7 too, so we'll see what putting that one in does.

I seem to remember that you need to "mod" a Garnet to be able to adjust bias.

Also, there's a rectifier tube in there??!! I didn't think Gar went for those?

matt


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## Ripper (Jul 1, 2006)

mrmatt1972 said:


> Did Garnet use fixed bias in his amps? I've got my hands on a beat up old Mann stencil (pics to follow). It is running on 1 power tube (yet still sounds great) and I'm wondering if I can just slot a new matched pair in there. The Tremolo and Reverb are also non-functional at this point, but it is missing a 12ax7 too, so we'll see what putting that one in does.
> 
> I seem to remember that you need to "mod" a Garnet to be able to adjust bias.
> 
> ...


Garnets are fixed bias and Gar tended to bias his amps a little cool, so they really scream if you add the adjustable bias and warm them up a little bit.
Garnet labeled amps with rectos in them are very very rare but you do see them more often in his stencil amps. I've seen a very old rebel head that had a recto in it and a very early pro that did as well, but usually only in the stencil lines.


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## mrmatt1972 (Apr 3, 2008)

The power tube spots on this amp are labeled 6L6. Is there any potential to damage the amp if I slot in el34 tubes instead. BTW what I thought was a rectifier tube was actually, on second look, a 6v6 in the 2nd power tube spot!

Now that I've put the missing preamp tubes in and used 12au7 tubes where indicated the reverb and tremolo work well.

I'm going to try to refurbish this amp over the next little while. 1st big question: how do I remove a chassis bolt that is stripped?


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## Wild Bill (May 3, 2006)

mrmatt1972 said:


> The power tube spots on this amp are labeled 6L6. Is there any potential to damage the amp if I slot in el34 tubes instead. BTW what I thought was a rectifier tube was actually, on second look, a 6v6 in the 2nd power tube spot!
> 
> Now that I've put the missing preamp tubes in and used 12au7 tubes where indicated the reverb and tremolo work well.
> 
> I'm going to try to refurbish this amp over the next little while. 1st big question: how do I remove a chassis bolt that is stripped?


Matt, the big question about subbing in EL34's is that those tubes require TWICE the filament current to light up as a 6L6!

That's a lot to ask of a power transformer. Normally I wouldn't risk it. However, sometimes a guy like Gar would have standardized on a power trannie for both his 6L6 and EL34 models.

So you can try it, and keep feeling the power transformer. If you can't keep your fingers on it more than 20 seconds then its running too hot because of that increased current.

Or, you can check out the Garnet yahoo.group and see if someone has already checked this out and can tell you if the trannie will handle it.

Good luck!

:food-smiley-004:


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## Ripper (Jul 1, 2006)

Wild Bill is right, take the number off your power tranny and post it on the Garnet Groups, guys like Larry on there will be able to tell you which on it is. I know not all Garnets lend themselves to mods like the EL34 switch.


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