Rangemaster Biasing

[Khas Evets]

My Rangemaster is biased to 7V and sounds great. The asymmetry is a big part of the sound. I was thinking it might be nice to add a switch adjusting the bias closer to 4.5V for a more symmetrical signal (and maybe more gain and headroom?). Has anyone experimented this?

[mac]

with a 220k resistor instead of the 470k, a collector voltage of around 4.5v should be obtained, at least for germaniums with hfe=100 and Vbe=0.1 - 0.2v.
for silicons a 180k should work.
going to try.

download this helper program from
http://geocities.com/guitarfxs/english/download_eng.html
and resize bias at will.

mac

[Khas Evets]

Good idea, mac!

That made it easy to experiment with a 1M pot in parallel with the 470k resistor. I got the collector to bias at ~4.5V with a parallel resistance of ~330k (making the 470k resistor effectively 193k). I don't think the sound is louder, but it sounds more focused. It removes some of the Rangemaster 'grit', but I like the option. This is not a dramatic change, but I like the added versatility it adds to the pedal. I think I'll add a switch for this.

Let me know how it worked for you, mac.

[mac]

Instead of a switch I placed a 220k in series with a 250k pot to go from 4.5v at min to near 7V at max.
I agree with you, at 4.5v the sound is more focused and not much louder. I still prefer the original setting but the mod is a nice addition.

mac

http://geocities.com/guitarfxs