Fuzz Face - how to manage Vc on Q2 to be 4.5V?

[yeeshkul]

Hello guys, I just pinned up my very first fuzz-face to a test-board. Following R.G.s superb article (thank you, that's a priceless one!) i made his hfe measuring tool and chosen Matsushita 2SB175 - hfe~100-120 for the moment (Q1, Q2) since i have nothing else yet.
I would like to ask if anyone know how to change bias voltage on collectoe of Q2(at the moment i am getting Vc on Q2 about 6.53V) - shall i change transistor or some of the resistors around to drag it down to 4.5?

[amz-fx]

Increase the value of the resistor directly above the collector of Q2 and it should make the voltage go down.  What is it now, 8.2K?  Then try 10k and see how that works.

regards, Jack

[JHS]

Replace the 8,2k (in most cases it's 8,2k) with a 22k trimpot, then you can adjust the voltage to the desired level.
It's not proven that 4,5V is the optimum collector voltage for Q2, most FF sound best between 4,5-5V or near 5V.

After setting the voltage w the trimpot for the "best" sound measure the actual value of the pot and replace it with a metal film resistor of equal value (resistors produce less noise and hiss than a trimpots)

If you don't want to change the trimpot secure it with a drop of laquer to prevent a drifting of the value due to vibration or other influences.

JHS

[analogmike]

Above info is correct. I guess increase the 8.2K a bit and you will be all set.

Those 2SB175 trannies are awesome, you should get a great tone, good luck!

[yeeshkul]

great, thank you very much guys!