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MXR Dist+


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8/30/1999 5:07 PM
Mark Hammer MXR Dist+
I put together one of these last week, and threw in a switch that selected between two 1N914's and a pair of 1N60's. I went with the latter because their clipping threshold was higher than the 1N34A's in my parts bin (.3V instead of .23). I also put in a DPDT footswitch.  
 
 
 
I never played one of these during my youth, and haven't tried a reissue at a retail outlet, so I have no point of comparison, but this thing is simply awful. The SI diodes have a nicer tone than the GE diodes, but neither are anything I look forward to playing. Both distort fine, but in a very abrasive way once you turn the gain up.  
 
 
 
More salient, with the GE diodes, there isn't a big volume difference from full-tilt both-knobs to bypass. The output level is fine with SI's, but my schematic (drawn from a 78-vintage pedal) indicates 1N270's as the original diodes.  
 
 
 
Since I make everything on perfboard, and cram it in ridiculously close together (I know, bad practice), there is always the possibility I have prevented myself from being able to see a simple wiring or component value error. Still, though, I'm wondering if there are errors in the schematic I am working with (Not that one couldn't deduce the components).  
 
 
 
So, does anyone know of a verifiably "perfect" schematic of this box, that will allow me to corroborate what I've done? Alteratively, is it supposed to sound this bad? I mean, we're talking the kind of distortion that sounds like the last AM station you can get on your car radio when you're in the middle of the mountains and desparately trying to keep one finger in touch with civilization.
 
8/30/1999 5:37 PM
Roger

>>Alteratively, is it supposed to sound this bad? I mean, we're talking the kind of distortion that sounds like the last AM station you can get on your car radio<<  
 
 
 
IMHO, the Dist+ suffers a lot when compared to modern, more high-tech pedals. It does sound buzzy and somewhat weak vs. recent designs. You might increase the amount of gain and see if that helps but the lack of a tone control and no frequency shaping before distortion limits its usefulness.  
 
 
 
Roger
 
8/30/1999 6:11 PM
Aron

I built the schematic linked to on my web site and it works fine. I think R.G. wrote that one up.  
 
 
 
http://members.tripod.com/~triparon/MXRDIST2.GIF  
 
 
 
Jack revised it.  
 
 
 
It's basically an op amp to clippers and that's it. Here's the deal, if you run your EQ so that unfiltered buzz sounds horrible, than obviously the MXR will be horrible. For some unknown reason, both of my amps must roll off enough high end to make most unfiltered pedals "playable".  
 
 
 
Of course it's always possible that you could have something in backwards or the wrong value cap - but it's you so it's unlikely. :-)  
 
 
 
If other unfiltered pedals sound "OK" on your equipment (Electra Distortion, Muff Fuzz etc...) then it's the MXR circuit. If they all sound bad, it's possibly your amp/eq settings - don't like unfiltered pedals.  
 
 
 
Just some guesses.  
 
 
 
Aron
 
8/30/1999 8:20 PM
Mark Hammer
Aesthetic differences I understand. The "calming" effect that 12" speakers with a 3khz rolloff have on buzzy effects I understand. What I don't understand is why the output from the unit (when using GE diodes) is so modest, even when the output volume is up full.
 
8/30/1999 10:10 PM
Hammy
How many diodes per side did you use? I have 2 per side in one of my pedals, and I'll agree the output level is low...
 
8/30/1999 8:20 PM
fet
I owned an original MXR Distortion+ for a short while in the mid-'70's. I bought it with an inadequate audition 'cause I loved my Phase 90 and DynaComp so much. But this thing was harsh, raspy, but non-sustaining - I couldn't use it - but it wasn't ugly enough to be interesting, like a Bosstone. Your description ofthe tone indicates that you probably built this thing correctly... seems to me that a treble-cut circuit might be your best bet to improve the sound (as I remember it).
 
8/30/1999 8:29 PM
Dave Chun

I have a feeling the 1N60s might be the culprit. A D+ with 1N60s was the first pedal I ever built (schem from the UofAlberta archive.) Horridly buzzy until I put a low pass filter after it (R-C with the R a trimmer) which calmed things down a bit. After I put Sis in there, it was OK sounding as a boost (gain down, volume up) but too noisy to be effective. It was damned loud with the Ge or Si, though.
 

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