FAT RAT clipping mods

Z

ZeroF's

New member
Had anyone pulled the stock Ge Clipping Diode on the MOSFET Clipping circuit?

I already swapped out the "Stock" Si Diodes to White LEDs gaining much headroom. My understanding after discussion with Jack Orman is the MOSFET clipping circuit is the MOSFET body diode and a Ge diode. I'm told the MOSFET body diode FV is approx 0.7 V. I want to swap the lame Ge Diode with an LED so I get a asym clipping with more headroom.
Anyone out there tried this????
 
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I don't know a ton about the Rat circuit other than a ton of pedals are based off of it ...
I would do what PLX mentioned .... throw 3 different options on a switch ... start there .... or ... at least socket the spots you want to try different things in ... and experiment away .... different color LEDs will achieve slightly different results also ...
or if you really want to deep dive ... breadboard the stock circuit and have at it ...... there's a ton of info online with great info to Mod a Rat ..
 
I think the best mod was to change the OP amp from the original LM308 ..

I tried all the OP amps that can be used in the ProCo RAT circuit, and my favorite was the metal can IC version (UA308HC NOS Fairchild metal-can version of the LM308 op-amp).

-Motorola LM308AH (Motorola NOS metal can; soldered into 8-pin socket to be used in place of chip)
-LM308N (National Semiconductor)
- LM301AN (National Semiconductor)
-TL071CP (Texas Instruments)
- LM741CN (Texas Instruments)
- NE5534P (Texas Instruments)

I managed to find a few at SmallBearElectronics

https://smallbear-electronics.mybigcommerce.com/ic-ua308hc/

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ymmv
 
Hmm, I might try that FAT mod on mine. The RAT has always sounded a bit thin to me.

I do prefer LED clipping over the diodes.
 
PLX said:
@harddriver has one of those white ones.

:unsure:
Click to expand...
Yep the 1985 Whiteface Reissue! LUV it!

I bought one new back in 2013 and should not have sold it in 2018 but I stupidly did so I had to acquire another one! Is it any better than the new Rats with the newere OpAMP chips, I have not idea but alot of people have stated they didn't hear much of a difference...who knows????:dunno:
 
the main chip is no te sound,, its the mistake made in the original circut. wrong resister value in opamp gain stage
 
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