Subminiature Dual Triodes

[Howlin' Mad Mac]

I have some submini tubes lying around... some 6111's & 6112's I think which are 12v dual triodes which sounds somewhat similar to 12AU7's spec-wise. Now I know a 12AU7 yields about 1/4 the signal gain of a 12AX7. Is there a way to design a preamp stage using such a low yield tube with more 12AX7 like characteristics? If so can you point me to where I might find some example circuits I could use for research? Thanks.

[DIY_Guy]

Are those the tubes they used in old hearing aid devices? Pretty cool.

Anyway, I think those would be well suited for a tube overdrive pedal. I think it's been done many times before with decent results. A google search yielded a bunch of schematics.

[Howlin' Mad Mac]

Yeah I've seen some boost/overdrive schematics as well as used in tremolo circuits & a combined with a 5672 submini pentode in an SE amp. Was thinking though more along the line of using (2) 5672 pentodes in parallel with a reverb transformer as a power amp. I'm just trying to figure a way to design a preamp with these tubes that will saturate. As is most of these designs clipping is either from diodes or saturation is all in the output stage, not in the preamp.

[Gregg]

You can use 6112 as 12AX7 most of the time depending on the schematics and running them at lower voltages but no lower than 200V. Otherwise you'll have to rebias them.
I've used a lot of 6N17B which is the russian version of it (different pinout). These tubes are capable of some crazy high gain stuff.