For those who don't want the whole Spires circuit with all the offboard wiring comes two separate öayouts for each channel. The red channel is a modified silicon fuzz face with some additional filtering and a fuzz control at the input. MPS3704 transistors seems to be not that common but a quick equivalent search reveals that they are NPN silicon transistors with a minum Hfe at 300. So 2N5088s or the BC54x family might begood subs if you don't have the stock transistors on hand.
Schematic is avaiable HERE.
Hi fuzzhead! I put the Green Channel together last night (great work!) and tried this Red one tonight (again, great work!). Per EQD, this channel used to be their discontinued Dream Crusher pedal (which was actually a germanium pedal) so I was curious about it.
ReplyDeleteThe only substitution I had to make was the 15pf (30pf was the lowest I had). I don't have any MPS3704's but tried both 2N5088's and BC547C's (so far) and it whistled like crazy in the orientation above. It works and you can almost dial in a non-whistle but still noisy fuzz if you play with the trim pot enough. However, when I flip Q1 in the opposite direction - it sounds fantastic.
I went back to the schematic and your layout looks spot on for the transistor orientation... and I double-checked the pinout on the transistors I have just to be sure. I actually really like it with the Q1 flipped but I plan to play with a few more transistors just to see if I can get this thing working per your layout.
Alright. I'm calling it a night. I would call this verified with the PN2222A's (with the existing orientation and some trim pot tweaking). I also tried MPSA18's but regardless of the transistor - it still sounds better to my ears with Q1 flipped. It's a pretty noisy circuit otherwise. The last 1/4 turn of the Fuzz pot is the sweet spot on this one and I wonder if using a different size potentiometer would make sense.
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