Cascading Gain Stage

[elpops]

Out of curiosity, has anyone ever done a cascading gain stage in a 5E3, feeding the 1/2 tube from the bright channel inputs into the 1/2 tube in the normal channel? I remember reading that this is sort of what a Dumble was supposed to do, but I'd like to know if anyone has done it, can report on how it sounded, and/or offer any schematics or photos?

Seeing as how my 5E3 probably isn't going to go as an acoustic / vocal amp, I might as well take it 180 degrees in the opposite direction!

Thanks in advance!

ElPops

[Shea]

Not I. But if you try it, you might want to use separate cathode resistors & bypass caps on V1. With a shared cathode design, any AC that appears on the cathodes as a result of the second gain stage will show up as positive feedback to the first gain stage, causing an oscillation. Theoretically, the bypass cap ought to shunt that AC to ground, but it doesn't always do a perfect job. I learned this when I tried the same thing in a 5F8A Twin circuit.

You might need to put a voltage divider to attenuate the signal between the first two stages, or between the 2nd and 3rd gain stage. With a DPDT switch, you can rig it up so that in one position of the switch the output from the first gain stage passes from the volume pot through a voltage divider into the other gain stage of V1, and in the other position everything operates normally. Kind of like the "hot switch" mod on Doug Hoffman's site, but with a voltage divider between the two stages.

Shea