Re: Vox Distortion Booster = Colorsound one knob fuzz?

Posted by nocentelli on Mar 15, 2016; 9:33pm
URL: http://guitar-fx-layouts.238.s1.nabble.com/Vox-Distortion-Booster-Colorsound-one-knob-fuzz-tp28841p28914.html

Marbles wrote

 Maybe this isn't the easiest circuit to understand since the fuzz face is a somewhat weird design with Q2 affecting Q1?


From what I can tell, there are a lot of 'standard' things to be found in almost every circuit (the ones I correctly or incorrectly mentioned above haha). Is there information to be found somewhere where it mentions those standard components that are found in every circuit?

If I can wrap my head around those, I can maybe easily put those aside in my head when looking at a schematic. I can filter those out and focus on what the other parts do. The 'magic' of the circuit if you will :D If that makes any sense whatsoever


If there is info like that, and someone knows, I'd love to hear it!

The most significant difference between [the colorsound and the amp version of the distortion booster] and the schematic is that 22k from Q2 emitter to Q1 base: Ignoring the bias resistors on the collectors (which varies slightly between fuzzface variants), the voltage feedback biasing is 100k in the standard fuzzface, is 150k in the vox amp/colorsound (and is pretty ripping), is variable up to 500k in the woolly mammoth (insane) and is a more modest 47k in the fuzzface part of a tonebender MkII (which has another single transistor boost Q1 in front of a fuzzface type Q2+3). I have made a one knob variant of this type of mkII circuit with just about 12k feedback resistor, it works quite well since the gain is maxed with the emitter bypass cap directly on the emitter, but it doesn't squeal feedback and is not extremely noisy. 12k is about the lowest it went before it choked off the input, but as you lower it the sound becomes less spongy and more responsive it that makes any sense: Higher values feel like higher gain, I suspect the reduced amount of negative feedback allows the transistors to clip much earlier. Perhaps this is why both the colorsound and the amp have the 220p cap to mitigate the extra saturation from the bigger feedback resistor value.

For circuit block information, Rg Keen's "technology of the fuzzface" is a bit much on first read, but I have returned to it many times over the years. There are many walk-throughs of common circuit arrangements in popular pedals like the LPB1, electra distortion, rangemaster, fuzzface, bmp, fuzzrite, TS, microamp, distortion+ etc which all use common transistor or opamp stages. Beavis, smallbear, rg keen, geofx, homewrecker, rog, Joe gore and many other web resources have explanations of how circuits operate, or what components tweak which characteristics, and if you look into a circuit, you will come across information and discussion from people who have trod this path before us. Perhaps the bigger drawback of choosing the venerable fuzzface to start with is not the slightly unusual voltage feedback biasing, but the sheer vast acres of shit you have to wade through on the internet, much of which appears to revolve around trying to source the perfect Ge transistors. However, with a couple of any old transistors and a breadboard, there are hours of fun to be had playing with values and deciding what you like. An input cap.blend/switch, variable resistor in that 22k spot, variable resistor from Q2 collector to the output cap all provide some cool variation.