i've just open my brother's one and its very simple but good sounding and fun mini-amp, specially with a real cab.
I haven't buid it yet so its not verified (it's my first complete vero) and be careful.
No that cap should go from pin 7 to ground and there is no filter cap for 9V on the schematics available online.
The 10n input cap isn't shown on schematics online, and that will result in a brighter sound. This circuit does not need an input cap, you can connect the input directly to pin 3
I've breadboarded this based on the commonly available schematics online, and I get the annoying fizzy decay and squealy oscillation stuff as the note dies out. I will have to try again and see if a filter cap on 9V helps. My other thought is that the 10n could possibly connect from pin 3 (input) to ground to tame high frequencies at the input.
What I really suspect is that this is just the classic decay issue that so many of us have had with 386 all along.