Fulltone Soul Bender Mod / Tone Improvement

[Jakub421]

I recently bought a Fulltone Soul Bender, basically a Tonebender MKIII clone, but I was not very happy with how it sounded. Way too bright, fizzy, and harsh. Alot of people say that the small box Soulbender is alot gainier and brighter than the big box, and to me it was basically unusable.

Decided to remove the board and trace the circuit. It is basically a stock 3-knob Tonebender except the smaller tone pot capacitor is 0.01uf and the Q1 base-collector bypass capacitor is 150pf. Nothing out of the ordinary for a Tonebender, but for some reason the circuit was still exceptionally bright.

Decided to replace the Q3 transistor with an old 2SB405 i had laying around (hfe: ~99, leakage: ~230ua). None of the original transistors on the board have markings, so I'm guessing they are some new production NTEs. Removed the unknown Q3 and measured it (RG Keen germanium transistor testing), came out to hfe: ~50, leakage ~70ua (bias at collector was ~2.9V with a bias resistor of ~40K), definitely not an ideal candidate.

Got the 2SB405 in the board, threw in an 18K for the bias resistor, and put in a equal leakage matched transistor as the temp stabilizing diode. Collector voltage ~2.0V with a 9.5V battery.

Huge difference. More aggresive and thick, way less bright and harsh. This is what a 3-knob tonebender should sound like.
If you're not happy with your current Soulbender, try to replace the Q3 transistor, maybe throw a socket on it and play around with it. I was about to sell it, but now I'm definitely keeping this pedal.

[Smeddling]

Hi
Would you mind sharing the schematic from your trace?

Cheers

[Steben]