Post by vonFrenchie on Jun 14, 2016 22:17:22 GMT -5
I recently sold my Mastotron. I was looking at building a new fuzz pedal and I couldn't decide which pedal to build. I realize that with a few wiring tricks I could make an extremely versatile fuzz pedal. I am basing my pedal off the Multi-Face, but I would like to find a way to add a few features from the Mastotron. I was fairly fond of the Relax/Push knob and the subs switch. The one difference between the Multi-Face build and this pedal is the addition of 2 rotary switches controlling the transistors at Q1 and Q2, a DP3T switch for C in, and a DPDT switch for C out.
I have a few obstacles to deal with first. Would I have to completely isolate each transistor or just the center lead of each transistor? I don't want any unnecessary noise coming from improperly isolated transistors.
Secondly, how would I go about adding the subs switch and the Relax/Push potentiometer? I have a feeling that the subs switch on the Mastotron and the C out have fairly similar functions, but that is just going off the perfboard layouts. I have no idea how the Relax/Push pot works.
Post by vonFrenchie on Jun 16, 2016 1:14:52 GMT -5
Thanks! Everything is going well. So well that I haven't had time to work on any music related projects. I'm in the process of restoring a motorcycle. It seems like the forum is fairly dead these days. Every time I've checked for responses I was the only one on. What happened? Also, how is everything on your end going?
I'm sorry to say that thing is all messed up. I'm not sure what it'll do, but it won't be what you intended.
You've got the Multiface wrong to begin with. The bias trimmer/gain structure is shorted, so it can't do anything, and that second transistor will pretty much just run flat out all the time. It should be biased somewhere near the middle of the battery just from being DC coupled to the previous stage, so it should "work", but... Move that 100K resistor to the ground node, and snip that wire from ground to where the 100K hits now.
Your frankenstein thing is all wrong. The Trim/Gain structure won't affect bias or gain, but it will mess with the action of your tone control in somewhat complex ways. You can't share that cap, even though it's the same value. They're not supposed to connect to the same place.
The way this should work is that the trimmer sits between the bottom of Q2 and ground, and sets the DC bias/gain, and is used to adjust the symmetry of the clipping action. The gain pot in series with the cap is in parallel with that trim pot. They allow higher frequencies to bypass the trim pot and have more gain than the DC/lower frequencies.
I honestly haven't checked much of the rest of the circuit because really none of the rest matters until you fix this bias/gain structure.
Edit - after reviewing this pefboard layout, which is almost just a schematic on perf, I changed my recommendation on how to fix your scheme.
Last Edit: Jun 21, 2016 11:49:38 GMT -5 by ashcatlt
Post by vonFrenchie on Jun 26, 2016 16:34:08 GMT -5
That was a complete brain fart on my part. I drew that 100K resistor wrong once and never went back to check my work. So I can't connect the 22 uf cap to the 5.1k resistor. Should just ditch the connection, add a cap and connect it to the other side of the gain pot, or will there need to be a completely different connection?
Thanks for the critique. I'm going to draw up another draft.