Ginger Bass overdrive... 1N5818 crucial?

[CheapChip]

I don't know if it still helps, but putting a 5089 made a real difference in my build.
Unity gain at maxed volume was a problem for me, and a 5089 gave me enough headroom: unity is now at 1' or 2' on volume pot.

[cmdrfun]

Hey, I came across this thread a few weeks ago when I had the same question as the OP... but saw that the OP's question never got answered. So here is my answer:

I looked at the 1N5818 data sheet and saw that the forward voltage drop is nominally 0.3V. I have plenty of 1N60s on hand so I looked up their data sheet since I know their forward drop should be around 0.3V since they are Ge diodes. BTW, 1N60s are also Shottky diodes according to the data sheet (I just thought they were Ge signal diodes). The 1N60 forward drop is also listed as nominally 0.3V as expected. Unfortunately the 1N60P forward drop is nominally 0.5V and I couldn't remember which I had... so I measured them. The forward drop on my 1N60s was about 0.25V on average.

I also ordered some 2N5818s and then built the circuit with 1N60s while waiting for them to arrive. I really liked the sound, with the gain and bass cranked and treble anti-cranked it had a very synth-sounding distortion (with bass; with guitar it's pretty clean but nice sounding). As another experiment I plugged in some 1N914s and it resulted in some farty, unmusical distortion when the gain was cranked, probably due to JFET clipping.

My 1N5818s arrived yesterday so I got back to experimenting. First I measured the forward drop on the 1N5818s and it came in around 0.18V on average. So I expected there to be a slight drop in volume but also more crunch when replacing the 1N60s. I wired up a DPST switch so I could easily A/B the two sets of diodes. I did hear the volume drop with the 1N5818s, but  the crunch seemed to actually decrease. Between the two diodes I prefer the 1N60s. I think maybe it's the best of both worlds - a bit of soft clipping from the 1N60s plus a bit of JFET clipping, but not enough to make the farty sounds. That's my guess anyway. I could get the same sounds made with the 1N5818s by simply turning the gain down a bit.

As far as the 5088 vs 5089 goes, I've come up with three theories about why this might result in more volume, and they all revolve around the increased input impedance and decreased output impedance that comes from using a higher beta transistor in a buffer stage, but quantitatively none of them results in much of a noticeable difference, so I won't bother writing them out in gory detail. Unless you can hear a volume difference of 0.2 dB, which I can't. Another interesting experiment would be to replace the 2N5089 with a Darlington like MPSA13.