trim pot in a fuzz face

lorez · Post by **lorez** » Mon Apr 12, 2010 2:44 pm

I finally finished soldering up the fuzz face kit I bought recently and am now trying to understand how the circuit works in principle. As part of the circuit there is a 10K trim pot. what is this used for and what would happen with regards to the different settings.

Cheers

Post by **Mike** » Mon Apr 12, 2010 2:52 pm

Schematic?

lorez · Post by **lorez** » Mon Apr 12, 2010 2:57 pm

Mike wrote:Schematic?

here you go, its a link to the musikding pdf

Post by **Mike** » Mon Apr 12, 2010 3:05 pm

It's a bias trimpot, you're biasing the 2nd transistor stage. The easiest thing to do is to turn it until it sounds best and doesn't splat out.

lorez · Post by **lorez** » Mon Apr 12, 2010 3:14 pm

Mike wrote:It's a bias trimpot, you're biasing the 2nd transistor stage. The easiest thing to do is to turn it until it sounds best and doesn't splat out.

OK cool thanks mike. When you say biasing, what is it biasing? Is it the amount of voltage coming out therefore balancing the amount of feedback in the loop?

I will have a play with it tonight as i didn't finish soldering until late so when i get home from work will be time to play with it before putting it in its case.

Post by **Mike** » Mon Apr 12, 2010 3:21 pm

It's setting the collector voltage and so also the relationship between the Collector , Collector-Emitter Junction and Ground, and via the Collector-base junction the voltage between the Base and Emitter which is known as the Threshold Voltage - this must be above a certain value (normally 0.6-1.7V) before a Bipolar transistor will pass signal in it's operating region.

lorez · Post by **lorez** » Mon Apr 12, 2010 3:33 pm

Cool, thanks Mike. That helps a lot.