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Vintage threads from the first ten years

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5/20/1999 7:10 PM
John C.
I saw two revisions for the R.G. Keen's  
drawing of the Pro-Co Rat. One by Brad Fajardo, the other by Jack Orman.  
Which one is the original circuit (if any...)?  
Which one is suposed to sound better?  
Thank you, again.  
John C.
5/27/1999 12:02 PM
Joe Fuzz

Hi, John. The only version of the Rat schematic I've seen is the one modified by Jack Orman. This is the version I built and FWIW, I think it sounds great.  
I built it pretty much verbatim. The only major substitutions I used were a 250k pot in place of the 150k pot and 10uF caps in place of the 4.7uFs. The 250k gives it more gain (plus it's easier to find) and the 10uFs gave it more bottom end -- which you may or may not like.  
This effect really surprised me; I wasn't expecting much from a store-bought effect but it sounds great. It has a nice crunch at low gain settings and it has this "chainsaw" distortion when cranked. :-)  
As far as which one's the original schematic, I can't say.
5/27/1999 1:50 PM

Like most distortion devices, the Rat is sensitive to exactly what the devices do when really cranked. They will all sound different in some ways unless you filter them.  
The original version of the Rat I traced was years ago, and is the schematic found on the Ualberta archive. It had a couple of bugs in it. You can find a corrected version at Brad Fajardo's PCB layout web site, as well as one version of a PCB to make one.
5/27/1999 8:56 PM
John C.

Oh, thanks!  
Everybody talks about the Rat,  
so I'm afraid I'll have to build one  
for myself.  
Thank you again.
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