BAZZ FUSS Gain pot added

[bzblues]

Hi guys!

I've built the awesome little Bazz Fuss. This version I found online and it sounds killer. The thing is I wanted to add a gain knob and, after investigating, I read that you should wire a 1k pot to the Emiter of the transistor (check the layout)

I've tried but it doesn't work out. When I turn the knob the signal just fades away and comes back. Should I try other pot values or is it because of the layout?

Thanks a lot!

Brian.

[FiveseveN]

check the layout

A schematic would be more useful, plus that layout is not entirely clear with your black lead overlapping a black package. Is this what you did?



Also keep in mind that it's a gain reduction control, in case you were looking for more instead of less.

[bzblues]

Hi, thanks for the response.

Yes, I meant readuction in gain to make it more dinamic to use. The pot wiring to the emiter would be something like this:

[FiveseveN]

Yup, that should do it.
Are you saying it acts more like a volume control or sounding misbiased?

[antonis]

As long as there is enough board space, I'd wire a 10μF to 22μF cap between pot wiper and GND..

[bzblues]

Yup, that should do it.
Are you saying it acts more like a volume control or sounding misbiased?

Lets say I move the wiper just (up or down, it makes no difference) and the signal gets cut off completly. Then it comes back on its own, so its not acting as a volume pot or gain redution, it is acting very strange. I try several 1k pots and the result is the same

[bzblues]

As long as there is enough board space, I'd wire a 10μF to 22μF cap between pot wiper and GND..

You mean a polarized cap? (sorry, I'm very new at this) you say that will solve the problem?

[antonis]

Yes, a polarized cap with its negative leg towards GND..

It shouldn't "solve" any problem, further than FiveseveN's suggestion..
(it should improve transistor bias due to Emitter resistor fix value while you'll be able to reduce stage gain..)

http://www.home-wrecker.com/bazz.html
https://www.diystompboxes.com/smfforum/index.php?topic=100813.0
https://www.diystompboxes.com/smfforum/index.php?topic=64906.0
https://www.diystompboxes.com/smfforum/index.php?topic=112626.0

https://www.google.com/search?client=firefox-b-d&q=bazz+fuss+gain+control&tbm=isch&source=univ&fir=jEop9oEWtauQAM%252CYIVr5Ye3F12aiM%252C_%253Ba6oq_X7Do2yd-M%252C-MIZeqMJnCXflM%252C_%253Bb1Dirt8c4R-y_M%252Cl2jSyWCKln-yVM%252C_%253BSwRsG42gbkjF9M%252CM-TCwjGCfdW8cM%252C_%253BlZQSHiu_lR84KM%252CjG8KMC3YFre8MM%252C_%253BrJ5OEFR885FEYM%252CNSNiARbKAwND6M%252C_%253BcJKzznalJd6RJM%252CUGXGEjRb2Tt6FM%252C_%253By90WVkxQwGdQvM%252ClsoXuMkK8YS4_M%252C_%253BMeuqVOOmEhFrCM%252Ce5PTap3VB4MzrM%252C_%253BvOZMpLkduWTxOM%252CsND7TywzyKCuDM%252C_&usg=AI4_-kQwLN4cEvDnn0tyyzT0nusdNWyuCA&sa=X&ved=2ahUKEwjL_4K8jqT9AhVcQfEDHbz5DiAQjJkEegQIHhAC&biw=1400&bih=925&dpr=1

[FiveseveN]

Right, it cuts out because that simple gain control changes the bias and it takes a second to settle into the new conditions. Only an issue if you want to change the control while playing.
And like antonis said a better way to do it is to vary the AC feedback while leaving DC bias alone, it only takes an extra cap. See how it's implemented here:



You might also like the other additions.

[antonis]

ΙΜΗΟ, BC547 should be of C classification..

That kind of circuit DOES need a BJT of as high as possible current gain..

[mayoayox]

Right, it cuts out because that simple gain control changes the bias and it takes a second to settle into the new conditions. Only an issue if you want to change the control while playing.
And like antonis said a better way to do it is to vary the AC feedback while leaving DC bias alone, it only takes an extra cap. See how it's implemented here:



You might also like the other additions.

what is R3 doing there? does the 100k to ground help lower pregain volume?

[antonis]

With SW2 open, Q1 needs bias somehow, doesn't it..??

[mark2]

100k on the collector isn't enough for the 2N3904. Increase that to 500k'ish and you'll get a smooth gain control.

Failing that, increase the pot to 10k. I use that combination with great success.