questions about tubes and gain level

[peffer343]

I have a B52 AT112 with 5 12ax7(4 pre, 1 power) and 2 6L6 (power) tubes. the tubes are mix and match assortment that are mostly not labeled as to mfgr. the problem i am having is that even at low gain settings, it is too overdriven. I am looking for a warmer bluesy sound, not heavy crunch and distortion

any suggestions? different brand of matching tubes? i talked to a guy who tole me that perhaps 12au7 tubes would make the gain control not so *hot*. anyone with experience with this?

[David Root]

You probably have the wrong amp for your desired tone, but yes, try 5751, 12AY7, they will not upset the current structure too much.

12AT7, 12AU7 will take more current and reduce plate and screen voltage, which may or may not be a bad thing either.

Alternatively/concurrently you can increase the preamp grid resistors to say 220K or even 470K.

Changing preamp volume/gain pots to lower values will reduce gain too. This may change tone a bit too, need to be careful.

You could also change the power transformer to a lower output voltage, or put a 25 Amp xxV zener diode between the power transformer center tap and ground.

Lots of stuff to consider. Bypassing a gain stage might help too, but that is a bit complex.

[peffer343]

thanks, dave.