Bazz fuss biasing problem

[Martien]

I build a darlington bazz fuss with a lpb infront of it, sounds quite nice, I made a fuzz control by taking a 100k lin pot wired as a voltage divider to ground between the lpb and the fuss.
It's quite flexible but Im having some problems with the bias of the fuss, I installed a trimpot to set it right but I cant find the sweetspot, so when I slam a chord it is loud at first and less clipped and then the volume lowers a bit and the fuzz increases. Is this indeed because it is misbiased or is there another problem. Another question what is the best wat to set the bias in this case I tried the methods from the original post on biasing the bazz fuss as I said I cant find the right spot.

[kvb]

where is/are the coupling cap/s?

is there a cap in between the vol pot and the fuss?

[mac]

One thing I never mentioned about biasing is that when the BF has a drive pot at the emiter with a big bypass cap, it takes some time to reach a steady state when you change the collector resistor, ie, change bias. You need to change the trimpot in small steps.
Check my new BF, much easier to fine tune because it sounds like crap except around a tiny spot. And resistors can be estimated a priori.

http://www.diystompboxes.com/smfforum/index.php?topic=73924.0

mac

[Martien]

there are coupling cap between the stage so, 2.2 uF input then after the divider and than an output cap, here is no fuzz control on the emitter of the bazz fuss.

And mac if i try your bazz fuss with a darlington could i just add a resitor from the power rail to the diode and use the allready placed trimpot to set the bias (basicly reversing r3 and r1 in your schematic (paralel risitors interchangable right

Thank you for the tip

[Martien]

"when I slam a chord it is loud at first and less clipped and then the volume lowers a bit and the fuzz increase"
was I correct that is, is the case because of misbiassing?

[Toney]

Yes it is.
I had the same results with the first one of these I built... just couldn't get a nice balance with the 2n3904s I had.
The quickest fix?
I put an mpsa13 in there with a 10k collector resistor.
Sounds wonderful immediately, no further biasing required.

[Martien]

by the way it only acts as i discribed when the fuzz pot between the lpb and the bazz fuss is fully open, so no signal to ground only the boost directly in to the bazz fuss

[mac]

I´d try my mods in the breadboard, or if you have already soldered the circuit just add a base resistor using  a pair of "alligators".

Have you tried it without the lpb?

mac

[Martien]

I will try it without the lpb as soon as I have the time, I hope I can solve my problem then so, the fuzz will be usable on bass as well as on guitar