Switchable Pre-Amp Tubes???

[stevieb]

Just read this in the Ampeg J-20 user's manual:

Preamplifier tubes are also used to drive the power tubes. When used in this application, a 12AX7 will produce a more distorted tone than a 12AT7, which produces a clearer, sweeter sound. A 12AU7 is even cleaner and brighter than a 12AT7, giving more definition to the sound. (In some cases it is possible to change the sound by changing the type of preamp and/or driver tubes...)

Preamplifier tubes are also used to drive the power tubes. When used in this application, a 12AX7 will produce a more distorted tone than a 12AT7, which produces a clearer, sweeter sound. A 12AU7 is even cleaner and brighter than a 12AT7, giving more definition to the sound. (In some cases it is possible to change the sound by changing the type of preamp and/or driver tubes...)

And it got me wondering- could some wire in, say three sets of tube plugs, with appropiate switches, so that you could switch 12A_7's on demand? Imagine, having up to 9 12A_7 combinations to choose from-

All X's for most distortion,
All U's for the cleanest sound,
Any combination of X's, T's and U's you wanted...

Would it work? Maybe it's best application would be for a demo amp in a shop that sells tubes- a customer could plug his guitar into the demo amp, play around with different combos, and then buy the tubes that give him the sound he likes the best.

Comments?

 

[xstatic]

That is something that I have been considering building in to an amplifier. Not just for tone, but output volume as well and sensitivity

 

[dementedchord]

not terribly practical i'm afraid... and all the coupleing caps used would have to affect freq response... i've seen it done to a lesser degree by useing relays for switching...