Tone Bender MK1 circuit all using NPN BJTs (in reverse darlington) and negative ground. The idea of using NPN Silicon BJT as replacement of PNP Germanium BJT is based on https://blackcatbone.hatenadiary.org/entry/20080128/p1. NPN BJT is expected to be something like 2SC1815-GR (hFE=230) or so.
