By: Pekka Lehtonen
While RAT is a fine distortion pedal, it lacks some low end responce I want. So i decided to do some mods an my model from the year 1986.
First try was the "Ruetz RAT" mod by Philip Ruetz. This mod was not quite heavy enough to my taste and cut too much gain from the circuit. No more singing harmonics with the Ruetz RAT. Still it think it would be great mod for blues-type stuff.
Next attemp was my own take on the subject. Instead of cutting the gain from high freqs I desided to add gain to low end. The result is shown in the schematic at the top of this page. Google the full RAT schematic and you'll find that these R's and C's are in the opamp feedback circuirt (from "-"-input to ground).
This modification duobles the gain for frequecies above ~60Hz. The 220ohm trim pot allows for fine tuning of the high frequcies. I adjusted the trimmer to about 100ohms. This cut the high's a little and gave a bit darker sound.
This mod was a succes. The sound was fatter and even fuzzier at max Distortion, but cleaned up nicely when guitar volume was turned down a little. Harmonics and sustain were still there.
I assembled the mod by adding a 470ohm resistor in paraller with the 560ohm and another 4.7u in paraller with the 4.7u. I also soldered sockets for the trimmer in place of the 47ohm. For detailed pics on RAT insides go to Ruetz RAT pages. The 560ohm resistor is right next to the 47ohm.
Compared my modified RAT to some stock 90's version. Mine had less gain and output but worked much better through the range of the distortion knob. Before I only used my RAT with full distortion but now it also sounds good with a bit less drive.
You can give your comments by clicking the link below. Also, feel free to email me.