Read in the build doc for the cosmo that Q3 can be subbed, theoretically with some other component changes. Wondering if anyone has tried it and come up with a tone they like there. Haven't breadboarded this one yet as I spent my time with another circuit:
As far as the dizzy tone, the PPCB forum came together with an NPN version of the Gnat (Buzzaround), which I like quite a bit. I was experimenting with it this weekend going through each, seeing what I could and couldn't replace with silicon.
Q1 and Q2 are just a darlington, but I still wanted to see if I could sub with equivalent low-beta with and without the resistor across C-B. Zero luck there.
Tried medium gain in Q1 (286) with no resistor. It sounded pretty decent with a low-ish gain (84) with a 2M2 across C-B. This was all still with an AC127 in Q3. Okay, but the sustain dropped off, might need to adjust a few other values, but not sure which.
However trying to replace Q3 with silicon was a dead end. Looked at some other schematics out there, tried adapting that final stage, even adding another gain stage before the final volume. Just sounds bad. Not even "different," just bad.
Seems like a similar situation with the Cosmo needing that germ in Q3... If anyone's got some insight on that one, I'd appreciate it.
IF what I'm looking for is better served up in a different circuit I'm open to direction. Just had this idea in my head to have two flavors of the same basic circuit.
What about using a mosfet for Q3?
Quote from: Aleph Null on February 04, 2026, 04:52:42 PMWhat about using a mosfet for Q3?
So something like this for the output stage?
dummy.png
Nah. Just slap a BS170 in the stock circuit and see what it does. You might have to change R12 if the bias is way off, but it probably won't be.