Here the charge pump is acting as a voltage inverter to give a "-9v" to the circuits.
I thought it would be worthwhile in case you need to daisy chain other effects.
Any reason batteries would be better for fuzz? Is it just the lower voltage? Or something complex and above my paygrade?
That's one of the mods on the next version - a voltage starve control. Works wonderfully on breadboard.
I remember reading somewhere that according to Mr ZVex, the starve pot pretty much does a spot on simulation of a battery due to the additional series resistance being characteristic of depleting batteries.
The "Stab" on the Fuzz Factory does just that - adds a 5k pot in series.
The previous "Fuzz Faceless" I used the pot as a voltage divider rather than series to shake things up.
But that's definitely just splitting hairs!
As to the HFE's, I haven't measured or experimented properly with different gains.
The AC128's I have do have the HFE's written down but I want to measure them myself when I have time.
RG Keen did a great article on it:
That was also one of features I was considering for the next version - a 3pdt/4pdt to switch between 2 transistors and respective bias trimmers.
But still gotta do some experimenting to evaluate for example:
Just switch the second transistor?
Would 2 germaniums sound significantly different to justify a switch?
A mix of silicon and germanium transistors?
Would a germanium optimized circuit sound good if a silicon was switched in?
Which transistors to use?
Oh goodness, where does it end? 🙂
You are definitely right about the rev log pot - the useful bits really bunch up at the end of the lin pot.
Perhaps the lin was just used because different tapers may have been difficult to manufacture at the time?
That's why PNP was first used - NPN was apparently tough to manufacture consistently.