Rat build/mods

[JohnnyCrash]

I'm starting my Rat clone distortion pedal build...

Any thoughts? Tips? Most importantly, any mods you'd recommend?

This sucker has a lot of caps in it...

[Guitar_Ninja]

Attaching the clipping diodes to a switch is a pretty popular mod.

The classic Rat uses 1N914/1N4148 diodes, the Turbo Rat uses 3mm Red LEDs. Gets you a nice variety between lower gain, fuzzier distortion with the silicon diodes and a higher gain, more overdriven sound with the LEDs.

[richon]

1.- no 2.2uF caps in FBloop og LM308
2.- LM308 for sure
3.- tants caps for coupling caps (like vintage original rat)
4.- 2N7000 mosfet clipers (or even with a ASYMETRIC 1N60 germanium diode)
5.- 50K pot for GAIN and 100K pot for FILTER
6.- 4,7K resistor as minimun gain resistor (before the GAIN pot)

that's it... and ENJOY!!!

[JohnnyCrash]

Originally Posted by richon

1.- no 2.2uF caps in FBloop og LM308

How does omitting the 2.2uF caps change the sound? Darker, less gain?

Originally Posted by richon

2.- LM308 for sure
3.- tants caps for coupling caps (like vintage original rat)
4.- 2N7000 mosfet clipers (or even with a ASYMETRIC 1N60 germanium diode)

I've got a LM308N. The caps are box types (poly film), except for the bigger ones. I have 1N914 clippers as per the GGG schematic... I might put the clippers on sockets so I can swap back and forth. Thanks for the tips on the mosfets.

Originally Posted by richon

5.- 50K pot for GAIN and 100K pot for FILTER
6.- 4,7K resistor as minimun gain resistor (before the GAIN pot)

I'm broke, so I have to settle for 100k pots all around. The GGG schem calls for 100k pots and a 1k gain resistor. What differences in tone should I expect?

[dalandan]

how about a pot for the ruetz mod? try looking for the mods done on the grandlaff mo'd that are supposed to make the pedal a bit clearer.

[Higgs F. Boson]

Originally Posted by dalandan

how about a pot for the ruetz mod? try looking for the mods done on the grandlaff mo'd that are supposed to make the pedal a bit clearer.

Mine (late 90's RAT2) is currently Reutz-clipped, and when I have the time I'm going to add a switch or pot to get that sound, which is HUGE, and the stock RAT as well.

Not to hijack the thread, but on the subject of RATs, would the LM741CN op amp I picked up from Radio Shack be an improvement over the stock Texas Instruments op-amp? The name is at least similar to the LM308N...

[JohnnyCrash]

Originally Posted by Higgs F. Boson

Mine (late 90's RAT2) is currently Reutz-clipped, and when I have the time I'm going to add a switch or pot to get that sound, which is HUGE, and the stock RAT as well.

Not to hijack the thread, but on the subject of RATs, would the LM741CN op amp I picked up from Radio Shack be an improvement over the stock Texas Instruments op-amp? The name is at least similar to the LM308N...

I've had too many Scotches and beers and it's 1:30am, but so far looking at both datasheets, they look a little different.

I'm soldering a chip socket onto my board so I can swap different chips to taste-test... maybe this would be an option for you too?

If I can scrape together the dimes, I'll try the chip you mentioned...

[JohnnyCrash]

Originally Posted by dalandan

how about a pot for the ruetz mod? try looking for the mods done on the grandlaff mo'd that are supposed to make the pedal a bit clearer.

This sounds similar to what richon was suggesting....

I've already got a TS808 overdrive and a Clean Boost, then I've got a Red Llama overdrive in the works. I think I may keep the Rat a little closer to stock and cover my distortion bases a little more.

I've got my OD's and boosts covered... I've got my fuzzes and germanium OD's covered too (Big Muff and a Rangemaster), but only a Guvnor and DS-1 for dist.

[richon]

Originally Posted by JohnnyCrash

How does omitting the 2.2uF caps change the sound? Darker, less gain?

I've got a LM308N. The caps are box types (poly film), except for the bigger ones. I have 1N914 clippers as per the GGG schematic... I might put the clippers on sockets so I can swap back and forth. Thanks for the tips on the mosfets.

I'm broke, so I have to settle for 100k pots all around. The GGG schem calls for 100k pots and a 1k gain resistor. What differences in tone should I expect?

The way the RAT works adds two GAIN frecuencys in different GAIN.... without the 2.2uF the RAT loose the extrem high frecuency GAIN sound, becoming CLEARER (not DARKER ) and with a little less GAIN

LM308N is the way to go

Poly's are fine (but do try TANTS, please... the add character to the sound, and even a little more clear guitar sound through)

100K are fine... I used 50K for GAIN pot to have a even more controlable OVERDRIVE (before DISTORTION) sound.

the 4.7K gain resistor , that i was talking about, is adding it to one leg of the GAIN pot to set the minimun GAIN the pot controls.

you know, the RAT at CERO gain, doesn't sound really good.

[11 Gauge]

I don't like tantalums in dirt boxes, but must admit that they sound really good in a Rat.

I will also repeat that the LM308N is a special chip for two reasons - it has horrible slewing capabilities, and it's externally compensated. Looks bad on paper and for hi fi applications, but is magic in this pedal.

When you clip part of the dual tail on a stock Rat, you're also killing part of it's essential character. The high pass filter that's around 1.5KHz is necessary to get those classic tones, IMO. When you hear them on the Jeff Beck stuff for example, I just couldn't imagine it w/o them.

I like to reduce the compensation cap, which really opens up a Rat, but doesn't lose the core character. You can go as low as roughly 3pF, but I find 10pF to work pretty well. Lotsa people miss this aspect altogether.

The part that's removed with the Ruetz mod I swap with a 100 ohm/1uF pair, which makes it a little less overt.

Clippers again are a taste thing. I've personally found that when the compensation cap is reduced (in conjunction with tweaking the ~1.5KHz high pass), that the stock silicon diodes work very well.

I also personally prefer running a 20K pot with a .018uF cap for the Filter circuit, but you can get a multitude of sweeps with different pot and cap combinations.

The Soul Sonic mods are some of the better ones that I've tried, and you can check them out here. Just bear in mind that Martin is very picky about caps, and has a stash of stuff that most tweakers do not! He's also got a sound clip of it here.

[Higgs F. Boson]

Originally Posted by 11 Gauge

The part that's removed with the Ruetz mod I swap with a 100 ohm/1uF pair, which makes it a little less overt.

Newbie question: do you mean that, in place of the clipped resistor, you wire 2 100 ohm/1uF resistors in parallel? Or series?

[Higgs F. Boson]

Originally Posted by JohnnyCrash

I've had too many Scotches and beers and it's 1:30am, but so far looking at both datasheets, they look a little different.

I'm soldering a chip socket onto my board so I can swap different chips to taste-test... maybe this would be an option for you too?

If I can scrape together the dimes, I'll try the chip you mentioned...

Thanks - don't feel any obligation to, unless you just want to; I'm going to add a socket when I do the Ruetz switch, and I'm planning to order an LM308N too.

[11 Gauge]

Originally Posted by Higgs F. Boson

Newbie question: do you mean that, in place of the clipped resistor, you wire 2 100 ohm/1uF resistors in parallel? Or series?

I replace the 2.2uF cap with a 1uF unit, and the 47 ohm resistor with a 100 ohm one. This gives you the same upper midrange high pass filtering, but at a serious gain reduction, on that side only.

[ibobunot]

Beavis Audio

The Four Knob Rat

Two Rats In A Rack

[limbe]

Scott Burnham,who constructed the original RAT,put a 47 ohm resistor in the prototype by mistake instead of a 470 ohm(he misread the colour of the multiplier).Since the chip couldn´t handle that amount of gain he got slewing distortion.That sound is unique for the RAT and separates it from all other distortion boxes which "11 Gauge" has pointed out.I find it ironic that the Ruetz mod take this resistor out of the circuit.