I’ll throw my hat in the ring. I just finished building my Black Eye. I’ve been building for about ten years with a few tube projects thrown in there, so take that for what it’s worth. First, the thing sounds killer when you keep the gain and output under 50%. Above 50% for either the gain or output I get the high pitch squeal. Most of my parts for this build were obtained through Tayda including the NE555 chip. Everything was built in accordance with Sushi Box BOM / instructions. I’m using two JJ 12AX7’s I had in my stash. Couple of thoughts on my next try:
1. Maybe try A500K for the gain and output.
2. Try the TLC555 chip instead. I’ve read a few anecdotal reports how this helped an oscillating NE 555 chip.
3 I’m going to try all mouser parts instead.
4. Try out the 12AT7’s
There was also a question regarding NE555 oscillation here:
I'm trying to simulate an audio amplifier circuit in LTspice. I made this circuit based on the circuit I found here: https://circuits-diy.com/how-to-make-audio-amplifier-circuit-using-555-timer/ . ...
electronics.stackexchange.com
There was an interesting suggestion about placing a 100nf cap between pin 5 of the 555 chip and the collector of BC107 (in this example). Admittedly, I don’t know if it’s applicable here.
Hopefully we can figure out how to tame this beast because it’s worth taming.