Mods for the RAT?

Mark Abbott · October 08, 2009, 06:17:36 AM

I have done a search and found the BYOC stuff and the Ruetz mod.

I think I have the old AMZ stuff somewhere too.

I was wondering what have you guys experimented with and what works.

I noticed Small Bear sells the LM308** metal cap IC, does this sound any different or better than the regular LM308.

Thanks for your assistance.

Yours Sincerely

Mark Abbott

Scruffie · October 08, 2009, 06:23:42 AM

I used an NE5334AP which I beleive is what the Vodka mods company uses aswell, sounded good to my ears, a switch between Diodes is something I'd reccomend, I went between 1N4148 (which gave a smooth overdrive tone) and 3mm Red LEDs (Gave a bassier more distorted tone)

Alot of people say the metal can does sound better but I couldn't comment... I wouldn't spend alot of extra money on it though and I have read that some people actually don't like it, I think from what I remember people say it gives a fuzzier sound.

Renegadrian · October 08, 2009, 08:01:43 AM

I made one with the LUBE pot and the diode switch

LUBE
adds a nice touch and interacts with both gain and tone, shaping the tone in a good way...A little less effective at higher gain settings, but it's worth yeah

Diode switch - 1N4148 and 5mm red LEDs
With the Si diodes, it has quite a VIOLENT sound!!! Yeah it's so poweful but also you can tame it down easily...
With the LEDs, I have the opposite result as Scruffie (and as I always have using LEDs) so the sound is less distorted/compressed and more "open" still distorted but with "clarity" and more volume too...

Scruffie · October 08, 2009, 08:09:12 AM

How strange we got opposite results... it was definitley the LEDs that made mine more distorted as they were lighting up when I played... they were 3mm rather than 5mm but the still had the same 2.1fV... maybe I did something wrong but hey it worked and sounded good to me.

richon · October 08, 2009, 10:48:15 AM

I use 2N7000 mosfet with a 1N60 diode for asymetric and it sounds AWESOME

beside TANTALUM coupling caps (like the firsts RAT)

oldrocker · October 09, 2009, 01:19:23 PM

Using LED's for diodes should increase volume with less distortion. This was the intention for the Turbo Rat. Although maybe not the only difference between the Turbo and the original.
The 4148's will start to clip sooner than the LED's. So you can leave the LED'S always hooked to ground with a SPST removing the SI's from ground to switch btwn the two. Having said that if you're happy with the sound don't muck with it.

frank_p · October 09, 2009, 01:40:07 PM

You could try Joe Davidson's compression discrete opamp circuit.

FlyingZ · October 09, 2009, 02:01:31 PM

I did the LED, mosfet, 47 and 560 ohm swap for pots, and the GGG buffer mods. Live and learn... it's all back to stock now with the exception of the GGG mod, which had no effect (afaik).

Just don't drill any new holes

oldrocker · October 09, 2009, 07:38:41 PM

Quote from: frank_p on October 09, 2009, 01:40:07 PM

You could try Joe Davidson's compression discrete opamp circuit.

I've thinking of trying Joe's op amp circuit. Has anyone built an effect using it?

grolschie · October 09, 2009, 08:23:57 PM

Quote from: Renegadrian on October 08, 2009, 08:01:43 AM
I made one with the LUBE pot

What is this please?

Processaurus · October 09, 2009, 09:18:02 PM

The other mod that is nice on the rat is to lift one end of the gain pot and wire in a 50K trimpot (as a variable resistor) in series with that connection. It makes it easy to consistently and quickly get the great low gain rat sound that is touchy to dial in, you'd just turn the gain down all the way and adjust the trim pot until it sounds good (or to where you can still get unity gain with the gain down all the way and the volume up all the way), then that sound is waiting for you if you quickly turn the gain knob down all the way.

frank_p · October 09, 2009, 10:48:17 PM

Quote from: oldrocker on October 09, 2009, 07:38:41 PM
Quote from: frank_p on October 09, 2009, 01:40:07 PM

You could try Joe Davidson's compression discrete opamp circuit.

I've thinking of trying Joe's op amp circuit. Has anyone built an effect using it?

I think Aron built it because he said it sounded good.

grolschie · October 10, 2009, 03:31:14 AM

Another possiblity is changing the output buffer transistor. I just swapped the 2n5458 for a 2n5457 which I think has more gain. Soulsonics mods have a 2SK117 there. I suspect that lowering the 10k resistor might increase the output volume perhaps?

Mark Abbott · October 10, 2009, 05:03:42 AM

Thanks for all the replies.

I have no idea what the LUBE mod is either.

The Musique mods are to remove the 30pF cap between pin 1 and 8 of the LM308 and replace it with a 100pF attached to pin 8 and ground The 1M resistor attached to the 1K resistor (pin 3 of IC) is reduced to 100K or 120K. These mods reduce noise.

Yours Sincerely

Mark Abbott

grolschie · October 10, 2009, 05:13:38 AM

I have a CA3130EZ in my Rat instead of the LM308N that I previously put it.

Mark Abbott · October 10, 2009, 07:50:34 PM

Unfortunately I didn't have time to post up all the mods.

The dual RC network is a bit complicated and could be reduced to a single resistor and cap. I think the cap value was 1uF.

The tone control capacitor is 0.0033uF, it was recommended that this be changed from the stock value to 0.0047uF and greater.

The change to the clipping diodes recommended is to replace one of the Si diodes with two Ge diodes in series. This would soften the sound of the RAT.

I think there was a mod to reduce the impedance of the power supply by replacing the two 100K resistors in series with two 10K resistors.

Two chips were suggested NE5534 and TL071. These were not touted as better, but different sounding.

I have tried the 0.0047uF cap and the two Ge diodes series. It introduced a bit of a Fuzz Face sound to the RAT (I like the Fuzz Face sound) and the tone control cap made the pedal sound nicer to me. All subjective things of course.

I'm sure Jack Orman has developed many more mods and twists to this circuit than what I have included here. As he did have a Fat Gnat circuit floating around for a while.

Yours Sincerely

Mark Abbott

trjones1 · October 13, 2009, 11:40:25 AM

One simple thing I'd suggest is to use an on-off-on switch for the diode switching. The middle position gives a loud crunchy sound with a lot less gain than with the diodes switched in. It sounds good.

rapmusic · December 19, 2010, 03:06:59 PM

Sorry to just jump in and revive such an old thread, but this seemed like the best place for a general Rat mod thread.
Has anyone ever tried the Ruetz or "lube" mod and replacing those two filters with a tone stack for greater control? If not, does anyone have any idea what the consequences of this would be? I recently became interested in building this pedal, but there does not seem to be anything close to a consensus on what the best variation of this mod is, so I figured why not just have a 2 or 3 band EQ on that section of the circuit?

nomorebetts · December 19, 2010, 07:11:53 PM

If this thread is about to become THE RAT MODS thread, people might find this useful:

http://www.beavisaudio.com/projects/FKR/images/MightierMouse.gif

kurtlives · December 19, 2010, 08:08:58 PM

Quote from: Mark Abbott on October 10, 2009, 05:03:42 AM
Thanks for all the replies.

I have no idea what the LUBE mod is either.

The Musique mods are to remove the 30pF cap between pin 1 and 8 of the LM308 and replace it with a 100pF attached to pin 8 and ground The 1M resistor attached to the 1K resistor (pin 3 of IC) is reduced to 100K or 120K. These mods reduce noise.

Yours Sincerely

Mark Abbott

Replacing that 1M with something lower significantly lowers your input impedance.

News:

Mods for the RAT?