I don’t know what it is, I never build it before, quite recently I heard about it first time. It’s called Harmon Booster, but AFAIK it’s more like overdrive.
Guys on interwebz says it’s cross between Tube Screamer with Big Muff voicing. Cool description! It may be fun.
The real one was build on PNP silicon BC318C. I did my layout with offboard wiring for negative ground powering instead.
Up to you how you’ll wire it up.
Also LED limiting resistor was added on board, and 3PDT switch wiring is showed
Report back how you like it, I miss your emails 🙂
Big thumbs up and credits to SonicIV for schematic