This is one of the more recent Sola Sound MK1.5 Tone Benders built by David Main.
MK1.5 TONE BENDER: THE DIRTY HIPPIE MOD – OC75 ONLY
This has two additions to the regular circuit. A 10n cap to ground on the input and a 47k bias resistor on the base of Q1 to help stabilise the circuit when it’s a bit warmer. Some Goldies have the resistor hidden under the circuit board, but no 10n cap. Reference by Mr Main here. MK1.5s without this mod have been referred to as the ‘bear fart’ MK1.5 because of the biasing issues. reference here
The 47k resistor on the base of Q1 certainly makes a difference – the tone is the same, it just adds some extra beef. Where I live in Australia, it’s substantially warmer than England, so this mod is very handy. How much warmer? It’s winter at the moment, and it’s 22 degrees Celsius, not a cloud in the sky.
The OC84 version does not need this mod. Less leakage I guess.
SOLA SOUND “GOLDIE” TONE BENDER MK1.5 VERO LAYOUT
Here’s a nice shot care of Reverb showing the cap value to ground on the input.
