Fuzz Face Circuit Questions

[Cthross]

To start things off I have already read the Technology of the Fuzz Face article. However I still have some questions. First off I made some simple adjustments. I added a 100k pot in series to the 100k feedback resistor. As the 100k pot is brought into the circuit there is a perceived gain increase which seems to 'loosen' the feel of the fuzz. What exactly is happening to the circuit as the resistance is increased?

I also added the bias pot from the BYOC schematic. So there is a 470 ohm resistor from +ground to a 10k pot to the collector of Q2. This bias pot seems to take the fuzz from wooly to a thinner tighter sound. Again what does this do. Is there a better way to implement a bias pot? The Jimi or R.Mayer mods put a 1k resistor to a 18k resistor to the collector of Q2. Wouldn't the 1k resistor reduce the output of the circuit?

I bought the AC128's from AMZ and just want to create the best possible FF with them. They sound great already, I would just like to optimize them to sound the best. Thank you for any help.

Chris

[R.G.]

... I made some simple adjustments. I added a 100k pot in series to the 100k feedback resistor. As the 100k pot is brought into the circuit there is a perceived gain increase which seems to 'loosen' the feel of the fuzz. What exactly is happening to the circuit as the resistance is increased?

Less feedback does increase the gain. It also alters the DC bias point as it changes, as there is less DC bias available to the first transistor, turning it more off and raising the collector voltage a bit. These would change the tone, all right.

I also added the bias pot from the BYOC schematic. So there is a 470 ohm resistor from +ground to a 10k pot to the collector of Q2. This bias pot seems to take the fuzz from wooly to a thinner tighter sound. Again what does this do. Is there a better way to implement a bias pot? The Jimi or R.Mayer mods put a 1k resistor to a 18k resistor to the collector of Q2. Wouldn't the 1k resistor reduce the output of the circuit?

I'm not familiar with the byoc schematic.

[Cthross]

So as the resistance is increased from the 100k pot the bias on Q1 should be adjusted to optimize Q1? I'll work with this a bit to see what happens.

Here's the link for the BYOC schem, it is fairly standard I believe with the 8.2k resistor switched out for a pot. Here's the link to the schem.

http://www.buildyourownclone.com/board/viewtopic.php?f=23&t=6341