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DIY Stompboxes => Building your own stompbox => Topic started by: rousejeremy on November 17, 2012, 12:42:58 PM

Title: Piggyback Silicon transistors for germanium emulation.
Post by: rousejeremy on November 17, 2012, 12:42:58 PM
I used Ivlark's vero layout here http://tagboardeffects.blogspot.ca/2012/06/npn-silicon-fuzz-face-germanium.html?showComment=1353013918267#c897456709102690322
It sounds great, it has that germanium creaminess to it with a hint of upper octave when biased just right but the trimpot that is between Q3 and Q4 doesn't seem to do anything. Voltages don't change on any of the transistors. The trimpot between Q1 and Q2 adjusts the voltage on the collector of Q3 which helps to bias it to 4.5v. The bias pot swings hard between two unusable sounds, I tried replacing it with a 5K pot with a 3K resistor inline but I have a feeling it all has something to do with that other trimpot.
Any advice? I know this is an old circuit and I haven't seen anyone talk about it on the forum for years.
Title: Re: Piggyback Silicon transistors for germanium emulation.
Post by: LucifersTrip on November 18, 2012, 09:28:15 PM
I've never built one, but it would seem more info would be needed....

First, a clear schematic (not layout) is always helpful.

Also, in the article you linked to it says a 10 - 20K trim will be sufficient, but someone else used a 200K trim. It supposedly depends on gain...