Workaround for the Triple fuzz gain control?

[John Lyons]

I'm re-posting this as it got lost in another similar thread.

The way this is set up there is a lot of crackle on the gain control.
Is there any work around for this?



I like the way the gain works to re bias the stage...it's just that the bias shift
really pushes the speakers when you adjust it. Very disconcerting.
There are a few nice places in the controls range so that's why I'd like to
keep the function the way it is.


John

[soggybag]

Try connecting the wiper of the 10k pot to the + lead of a 10uf or larger cap connect the negative lead to ground.

I'm not sure if this changes the sound. But it should allow you to change the gain in the same way. Image the cap as a route to ground. When the wiper is down the resistance of the pot is added to the cap. When the wiper is up the cap is connected to the emitter and acts as a route to ground.

The cap acts a resistor for AC dependent on the size of the cap. Smaller caps provide more resistance to lower frequencies. A small cap would act as a range booster providing less resistance to highs.

A 10uf cap should allow a full range of boost.

You might add a resistor from the negative lead of the cap to ground to limit the gain.

[soggybag]

Speaking the "crackle" knob. I built an SHO with the gain arrangement I described above and it worked fine, no crackle.

[John Lyons]

Mitchell
I was thinking about doing that with the cap but what is happening is the transistor's
bias is being changed when you rotate the "gain" pot.

Adding the cap as in the fuzz face like you describe will add gain but not
alter the bias as the Triple fuzz is doing.
The triple fuzz goes from a nice smooth overdrive to a splatty nasty fuzz.

I'll give it a try with the cap to see though, thanks

John

[WangoFett]

The crackle is caused by pot adjustment right?  There is no way around that is there?  The wiper is always gonna bounce a bit producing crackle.
How about using something that doesn't bounce, like a vactrol?

[soggybag]

I'm still an amateur at this. How the bias might change by adding a cap to the wiper is beyond me. I was just thinking about how a lot of other transistor circuits work and thought it might work here.

I've built the tripple Fuzz and it was actually very fun to play with. Try leaving out the diodes on the end. I found they didn't do a whole lot.

Looking at the circuit from my limited perspective. I'd just guess there wasn't anything special about the first stage, it's just a booster with enough gain to drive the second stage.

[soggybag]

I wonder if you put a 1M pot between the input cap and the base of the first stage, and removed the gain pot connecting the emitter to ground.

[John Lyons]

Wangofet
Good idea! I'll think on that. Yes, the crackle is with the gain adjustment
and is bounce...

Mitchell.
The Transistor is just boosting the second stage, correct.
The cap idea you had is a good one but that would be adding more
gain to the circuit as it's a baypass cap which is boosting a lot more than
as it is now. You could add a series resistance like you say but that's just
altering the boost level.
I may be wrong but I think that the bias shift is a variable boost as well as
giving you all the shades in between fully "on" (biased hot) and near fully misbiased
which will affect the way the circuit sounds, not just a matter of low or high gain
although it does that as well. I could be wrong though. I guess I need to audio probe
that first boost stage and see.

Thanks for the ideas though. Get ready for an apology

John

[Cliff Schecht]

My first thoughts are to take out the pot and add in an LDR that is controlled by a pot (pot simply goes from VCC to ground). Emitters are the most sensitive node on a transistor and having something like a pot down there is begging for trouble. Pots are noisy and unreliable, no good for a sensitive circuit node. Or perhaps a switch to choose between a few different emitter resistor values would work, but even then your emitter is going through a switch which is sort of a no-no in itself. The LDR trick is the most slick although it adds a slight amount of complication to a fairly simple circuit.