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Big Muff PI (from front page)

9/2/1999 11:39 PM
From Terry Big Muff PI (from front page)
I have recently just finished a DIY big muff pi , no mistakes, exact parts, it sounds really solid state/muddy... anybody have any mods they'd like to share with me?  
I have a Muff PI (storebought) and I guess I'm one of those weirdos that loves its sound. Some don't. It's kind of a polarizer.  
Have you ever owned or tried one of these? Muddy, grinding solid state sound is pretty much the name of the game for this box. Trying to make it sound like something it's not (i.e., a Tube Screamer or even FuzzFace) will probably be a losing battle.  
Someone here once suggested a mod for using the Muff for bass, which could possibly work for guitar, if you're willing to experiment (a lot):  
Split your signal in two, one dry one wet, with a mixer circuit to recombine, sort of like a crude FX-loop. Turn the Muff's tone knob almost all the way up, blend, serve while hot. This severely limits the pedal's effect on your low-end, keeping the buzz-factor high and the mud-factor low. Visions of high-pass filters should be dancing in your head, if you're adventurous. But it still may not suit your tastes.  
Good luck, please let us know if you hit on something good.
9/3/1999 12:44 AM
Dave Chun

Here are my favorite BMP tone shaping mods:  
1) input cap to 22u, all 0.1u caps to 4.7u, all 1u caps to .22u. Replace all electros with tantalum or film.  
2) change resistors in tone section to trimmers to adjust turnover freq.  
3) make all 4 gain stages identical (ie: with caps and diodes), lots of clipping here, usually needs adjustment to taste in the tone control.  
4) change the last gain stage to a 2 stage FET (I usually use 2 cascades stages; the AMZ minibooster would probably work here as well).  
5) change vol/sus pots to 500k or 1M
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9/3/1999 1:48 AM
Terry the big muff is supposed to sound solid state.....that's wierd i've heard that its supposed to be creamy and smooth w/ pretty good bottom end(which it has)...  
I tried replacing one of the diode stes w/ in34a but it just makes it buzzy and ugly...  
Would adding another diode clipping stage increase distortion, if so would any extra buffering have to be done?  
Also, i'd really love it if i could smooth out this pedal..right now it sounds very harsh...  
9/3/1999 1:51 AM
oops.. almost forgot... for the mods u posted, what is the difference in the sound?  
Also, if someone could post a sound file somehow of the BMPI it would be much appreciated.  
9/3/1999 2:55 AM
Mark Hammer
I've got a setup just made for bringing out any latent raspiness (see my Dist+ posts), and I really like my BMP. You DO have to turn down the tone to get the "creamy" sound (as you would with any device using a similar tone setup, and many use it), but even with all brightness-enhancing features set full tilt, turning down the tone still gets you a rich woody sound.  
I haven't done anything special to mine, at least not out of choice. The transistors are 2n5088, chosen for high gain. The caps are as shown in posted schematics, with the exception of the feedback caps in the distortion stages, which are 560pf (these are sometimes shown as 510pf). The diodes are garden variety 1N914's. I may have chosen them for identical clipping thresholds, but that has little impact on the rasp factor.
9/3/1999 4:01 AM
Actually, when i turn my tone up...the highs are very ugly and buzzy...i wonder if it has something to do with the 360k instead of 390k resistor i used in the tone area...  
9/3/1999 10:07 AM
"i wonder if it has something to do with the 360k instead of 390k resistor i used in the tone area"
you might try 430k instead of 390k, which i've seen on a couple of schematics
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