biasing fuzzes

[stopstopsmile]

I have never played with building a fuzz, but I would like to try.

I am not sure if I understand but say its a silicone fuzzface, how would I bias the silicone fuzzface?  Is biasing just about putting in the right value of the resistors?

[hellwood]

i found this somewhere a while back on the internet although i do it slightly differently.

With a voltmeter,
measure the voltage at the collector "c" on the first transistor.
Make this be -0.5V under ground by adjusting the 33K resistor
(replace it with a trim, for example).  With the fuzz all the
way on (the 1K pot) set the collector of the second transistor
to be at -4.5V  to -5V or so by adjusting the 8.2K the same way.
Listen to make sure you get it right.  When biased properly, the
Fuzz Face will seem to clean up and get brighter when you decrease
the volume on the guitar.  To make the pedal louder put the volume
on the pedal all the way up (the 500K pot), and increase the 470
Ohm resistor until it is about right.  In other words, use three
trims replacing the resistors in quotation marks; fiddle them back
and forth to get the voltages right, and the loudness right.

[mac]

Biasing means exactly this, finding the best resistor to make it sound good.
If you want an idea of what resistor to expect, use my calculator in the wiki area:
http://www.diystompboxes.com/biascalc/
For silicons, just set iL to zero and vbe to 0.6v.

mac

[stopstopsmile]

ok so i am understanding correctly that biasing just means adding the right value for resistor. 

I was thinking some other magical function needed to happen. 

[frankclarke]

The guitar signal wiggles about between the 0V side of the circuit and the 9V side. Biasing pulls the signal closer to one side or the other by adding a DC voltage offset to the signal.  You can push the signal off the edge of the allowed voltage, and it will get part of the signal clipped off.
So with the FF, as you vary the size of the 8.2k resistor, the signal clips differently. You can bias by ear or by voltmeter. Some fuzzes are deliberately biased close to the edge for a "sick" effect.

[mac]

If you mamma cleans your ears after you take a bath, tune the FF by ear!

mac

[Dragonfly]

Easy way to do this....

build a fuzz face....but instead of the 8k2 resistor, solder in a 10k pot...lug 3 of the pot will go to the 330 ohm resistor, lugs 2 and 1 tie together and go to the "collector" of Q2. play the fuzz through your rig, turning the pot till you find the sound that works best for YOUR NEEDS.Now, take your multimeter, set it to 20k (or a similar setting) and put the red probe on pot lug 3, black probe on pot lug 2...read the value. Now once measured that value, you can desolder the pot and replace it with a resistor that matches that value.

[stopstopsmile]

dragonfly, that seems like the easiest way to do it.   It sounds good, I think I can handle that for now.

I just need to find a tight vero of a silicone fuzzface first.  And then I am going to try this out. 

[Dragonfly]

dragonfly, that seems like the easiest way to do it.   It sounds good, I think I can handle that for now.

I just need to find a tight vero of a silicone fuzzface first.  And then I am going to try this out. 

From my gallery....