Any suggestions on what to do with an extra tube?

[Lizard King]

I'm going ahead with the Steve Ahola Blues Master mod to my bassman. When I'm all done I'll have a pre amp tube not used.

Any suggestions?


I've thought of:
1) fx loop - though I really don't think I'd use it all that much
2) add a classic reverb unit to this amp - probably need to put it in a different case.

It just kills me to have an extra tube sitting there being lazy. What would you do with it?

[Chuck H]

Are we talking about an extra tube (2xtriodes) or an extra triode (1/2 preamp tube)??

Chuck

[Lizard King]

An entire tube (both halves) is not used.

[Leka]

Tremolo?

[Chuck H]

Well then...You could just pull it out and remove all the associated circuitry and have a preamp with one less tube. And a big ol hole where it used to be.

Or you could build a pair of cathode followers after the PI to drive the power tubes. Better OD with less crossover distortion.

Or you could build a preamp stage with a low impedance output to drive the existing input. The lowered impedance would allow you to run a cord to an A/B box and back to the amp. You could have channel switching without the leds or relays.

Or you could build a post preamp OD stage with a master volume and it's own EQ.

Or you could add a trem circuit.

Or you could build a second input circuit in a different style and A/B between them for two different tones.

Or you could build one triode as a preamp overdrive and the other as a recovery/second tone control circuit ala Dumble.

A whole tube (both triodes) could do alot of things. But there are plenty of amps that have only one preamp tube. If you'll get what you need without it and any feature you can think of won't really be used, I say leave it out.

What you probably can't do is add a reverb. Because a decent reverb requires at least three triodes. One for driving the tank (two is better) one to reamplify the signal from the tank and one to balance the two signals since the "dry" portion of the signal will still be much more powerfull than the effected portion unless it is padded down to match and then both are re amplified. Another option would be to use the third triode to add more gain to the reverb signal so it matches the dry and then blend them at the PI input. Matchless added the reverb on the cathode coupled side of the PI. But this would alter the dry tone your after because it changes the gain structure and balance of the PI. Really, a good reverb needs two full preamp tubes unless you already have an effects loop in place and therefore an existing recovery stage.

Chuck

[Lizard King]

Thanks! Wow....that's a LOT of suggestions.

I had looked at some reverb drawings and saw most had multiple tubes. I have also been looking for a vibrato/tremalo schematic. I have a Line 6 tremalo box that seems to do a nice job but one less stomp box would be nice.

I also like the idea of cascading preamp sections but I wouldn't know how to draw one up. I'm pretty good at following a schematic and tweaking it but not so good on raw tube theory.

If anyone could point me to either a vibrato schematic or preamp overdrive circuit I'd appreciate it.

Thanks again.

[Lizard King]

Yes. It's a amplitude variation circuit most amp makers used to include in their amps.

[Chuck H]

You can go back to the blueguitar site and look at some of the cascade gain mods there. Some will surely correspond to your amp, or very close. Otherwise theres really nothing to it. you would build a standard gain stage similar to the input stage and put it on a switch that moves it between your guitar and the existing input. Thats a really rough explaination. But thats basically how it's done.

Since you have two triodes you could really build a gain monster if you wanted to. But consider that with a cascade preamp you will also likely need to add a master volume circuit.

Chuck

[Lizard King]

Thanks. I had found a fender vibrato circuit but now I'm going to look for a cascade gain circuit. Perhaps I'll flip a coin.

My bassman already has a master volume & the mod keeps it so I'm good to go.

Thanks again