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.
(https://i.postimg.cc/fVd0Jzhw/BF.png) (https://postimg.cc/fVd0Jzhw)
Quote from: bzblues on February 20, 2023, 05:14:32 AM
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?
(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQ31gs0mBHpH__q6TmTEQs0zVBNMwck2Br0PNt7FuY8lIAngCZrmoOkYEeYCFcfEz1l3S4&usqp=CAU)
Also keep in mind that it's a gain
reduction control, in case you were looking for more instead of less.
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:
(https://i.postimg.cc/hJ89C9Mz/Sin-t-tulo.png) (https://postimg.cc/hJ89C9Mz)
Yup, that should do it.
Are you saying it acts more like a volume control or sounding misbiased?
As long as there is enough board space, I'd wire a 10μF to 22μF cap between pot wiper and GND..
Quote from: FiveseveN on February 20, 2023, 06:21:07 AM
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
Quote from: antonis on February 20, 2023, 06:33:30 AM
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?
Yes, a polarized cap with its negative leg towards GND..
It shouldn't "solve" any problem, further than FiveseveN's suggestion.. :icon_wink:
(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 (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=100813.0)
https://www.diystompboxes.com/smfforum/index.php?topic=64906.0 (https://www.diystompboxes.com/smfforum/index.php?topic=64906.0)
https://www.diystompboxes.com/smfforum/index.php?topic=112626.0 (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 (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)
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:
(https://preview.redd.it/3jvknx9hj0g51.png?width=1748&format=png&auto=webp&v=enabled&s=8cc7d6359cd31b7b974e7764739326f94a2ef489)
You might also like the other additions.
ΙΜΗΟ, BC547 should be of C classification.. :icon_wink:
That kind of circuit DOES need a BJT of as high as possible current gain..
Quote from: FiveseveN on February 20, 2023, 07:43:48 AMRight, 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:
(https://preview.redd.it/3jvknx9hj0g51.png?width=1748&format=png&auto=webp&v=enabled&s=8cc7d6359cd31b7b974e7764739326f94a2ef489)
You might also like the other additions.
what is R3 doing there? does the 100k to ground help lower pregain volume?
With SW2 open, Q1 needs bias somehow, doesn't it..?? :icon_wink:
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.