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need mutron-III schematic

9/8/1996 4:52 AM
Ethan need mutron-III schematic
I want one, can't afford one, so need to build one.  
I've perused some of the obvious FX schem sources on  
the net, but had no luck.  
9/12/1996 12:42 PM
Mark Hammer

Don't have the Mutron III schematic, but if you can find one for the Univox  
envelope-controlled filter that came out in the late 70's, it's a very close  
facsimile (up/down sweep, filter-type, resonance, etc.), and has that overdriven  
sound that many liked about the Mutron.  
I DO have the schematic for the MXR envelope-filter, and a PC mask. It doesn't  
do everything the Mutron does, but has a very pleasing "Moog-ish" sound, and  
the variable attack time is effective and musically useful. I'll try and  
cough up a GIF of each of these in the near future and post them. Those of  
you who are technically inclined might be interested to know that the Envelope Filter was probably the only commercially available unit to use switched  
capacitor filters, as opposed to the conventional FET or optoisolator-based  
sweepable filter.  
If you own one of these units, the range of the unit can be altered by swapping two capacitors. If you pop open the unit and look at the component side of the board, you'll see two 4069 hex-inverter chips and a 4066 quad-switch chip. The 4069 beside the 4066 houses the filter sections. On either side of the chip is a .001uf cap (probably ceramic). The filter range is set by these two. I  
replaced mine with two 510pf caps and wired up a dpdt 3-position toggle to giveme either the 510 caps alone, the 510caps PLUS two other 510 caps in parallel (yielding the original .001 value, or close to it), and the 510 caps plus 1000pf caps in parallel. These yield three very distinct sweep ranges and make the unit a little more maleable. The choice of caps is entirely up to you, but I found these worked just fine. The 500k pots for sensitivity and attack can also be replaced with 1meg pots to give a little more attack time when you want it and reduce the sensitivity a bit more for following line-level outputs (or very hot distortion boxes).  
If you do find the Mutron III or Univox schematic, let us know where!  
Mark Hammer
9/14/1996 3:11 PM
Ethan emeson

Someone was kind enough to say they'd send me a mutron III schematic via snail  
mail if I sent a SASE. If you want a copy (assuming I get it), send me some email. Also, the mxr has been the only other unit I considered owning, so if you do find the schem please forward.  

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