Rat, Turbo Rat & LM308

johnnyseven · Post by **johnnyseven** » Mon Sep 06, 2010 10:24 am

I have a Rat with a metal can LM308 in it and it sounds ace. I also have a Turbo Rat which doesn't have an LM308 in it. I hear that sticking one of these chips into a Turbo Rat makes it sound better, does anyone know if this is the case? Or will it just make my Turbo Rat sound like my Rat, which isn't what I want.

If it is going to improve my Turbo Rat i'll look into getting an LM308. Anyone know where I can get one and is fitting one easy? Bearing in mind I have no soldering skills whatsoever.

Post by **Mike** » Mon Sep 06, 2010 10:28 am

It won't make your Turbo RAT sound like your RAT since the Turbo RAT has LED clippers which is the main difference.

Will it make it sound better? Debatable.

Is it simple? Nope. You have to desolder the current chip from the PCB which is not an easy task even for the skilled solderer (I don't offer this type of work anymore as it's tedious and prone to issues) without damage to the PCB pads meaning the chip replacement can be impossible.

I don't think you would gain anything that anyone but you could hear in a bedroom. Rehearsal or Live? Forgetaboutit.

But do I build RATs with LM308Ns in even though they might not make all that much difference? Of course, because that (rightly or wrongly) is what people want.

Simon · Post by **Simon** » Mon Sep 06, 2010 10:35 am

I've got a Turbo RAT with the LM308 chip in and it sounds like the sex. I also had a RAT with the chip in before selling it to Doog, that also sounded like the sex, but in a totally different way. Two completely different beasts.

Post by **Doog** » Mon Sep 06, 2010 10:40 am

Time to wheel out this stalwart:

[youtube][/youtube]
Stick it on 480p for the clearest sound possible.

The '92 RAT 2 I bought off Mr Winter indeed sounds very different to the current production (Russ from CAUTIONHORSES has one based on my recommendation and it's pretty nasty), but based on the above video, I'm pretty sure it's down to the whole list of components rather than just the MAGIC MOJO op amp.

Russ is actually coming around on Saturday to do some songwriting, it'll get him to bring it along and I'll do some A/B demo action.

johnnyseven · Post by **johnnyseven** » Mon Sep 06, 2010 10:43 am

Mike wrote:It won't make your Turbo RAT sound like your RAT since the Turbo RAT has LED clippers which is the main difference.

Will it make it sound better? Debatable.

Is it simple? Nope. You have to desolder the current chip from the PCB which is not an easy task even for the skilled solderer (I don't offer this type of work anymore as it's tedious and prone to issues) without damage to the PCB pads meaning the chip replacement can be impossible.

I don't think you would gain anything that anyone but you could hear in a bedroom. Rehearsal or Live? Forgetaboutit.

But do I build RATs with LM308Ns in even though they might not make all that much difference? Of course, because that (rightly or wrongly) is what people want.

I think you've just persuaded me not to do it. If it was going to make a big difference and was easy to do then i'd think about it but as it's going to be the opposite I shall leave it as it is. Thanks to both of you for your comments though.

Post by **Mike** » Mon Sep 06, 2010 10:53 am

Doog wrote:The '92 RAT 2 I bought off Mr Winter indeed sounds very different to the current production (Russ from CAUTIONHORSES has one based on my recommendation and it's pretty nasty), but based on the above video, I'm pretty sure it's down to the whole list of components rather than just the MAGIC MOJO op amp.

Russ is actually coming around on Saturday to do some songwriting, it'll get him to bring it along and I'll do some A/B demo action.

They shouldn't really have any circuit differences as far as I know. I thought a 90s Rat was pretty much identical to a current model save the op-amp.

Personally I don't believe that Op-Amp video because I make pedals and in some designs op-amps sound way different.

TL082s for example have a much better high frequency response than TL072s and even moreseo TL062s.

As a result, the wrong match for a circuit can yield ice picky highs or a muffled response with no presence whatsoever.

So, just bear that in mind. Your man is trying to sell you Visual Sound pedals after all - and the pedal they use is a Tubescreamer derivative. Not all pedals are created equal, much less the fucking TUBESCREAMER. Blerugh.

johnnyseven · Post by **johnnyseven** » Mon Sep 06, 2010 10:59 am

Can anyone explain the difference between a metal can LM308 and a LM308N?

Post by **Mike** » Mon Sep 06, 2010 11:02 am

m@j@

Metal cans used to be what Op-Amps were made in before people design the Dual In Line (DIL) packages they come in these days.

johnnyseven · Post by **johnnyseven** » Mon Sep 06, 2010 11:06 am

I take it they're pretty much the same thing then.

Post by **Doog** » Mon Sep 06, 2010 12:35 pm

Mike wrote:
Doog wrote:The '92 RAT 2 I bought off Mr Winter indeed sounds very different to the current production (Russ from CAUTIONHORSES has one based on my recommendation and it's pretty nasty), but based on the above video, I'm pretty sure it's down to the whole list of components rather than just the MAGIC MOJO op amp.

Russ is actually coming around on Saturday to do some songwriting, it'll get him to bring it along and I'll do some A/B demo action.
They shouldn't really have any circuit differences as far as I know. I thought a 90s Rat was pretty much identical to a current model save the op-amp.

Personally I don't believe that Op-Amp video because I make pedals and in some designs op-amps sound way different.

Fair enough, I'm always up for being proven wrong. Defo gonna A/B those two RATs just in the name of science, see whaaat haaaapppen.

Bill Oakley · Post by **Bill Oakley** » Wed Sep 08, 2010 2:11 am

I'm one of the few (I'm guessing) that doesn't like the LM308. I like the newer OP chip. To me the LM308 is very hissy/noisy. I think the Rat would be better off with a TL070 in there. It is externally compensated like the LM308 so you can probably get the same slew rate by replacing the 33pf compensating cap with a 180pf and it will be a lot quieter. Just my 2 cents.

aen · Post by **aen** » Wed Sep 08, 2010 3:26 am

Meh. I just built a rat clone, Im assuming with the "easy to find" chip. It sounds like it should: like a hundred dollar distortion pedal with a one pot tone control. Totally usable in a variety of contexts, good variation in gain, not remarkable in these days of ten trillion distortion pedals (yes i know, i part of the problem). Normal distortion. Satisfied.

johnnyseven · Post by **johnnyseven** » Wed Sep 08, 2010 10:52 am

After going on a journey round various fancy distortion/drive pedals for the last couple of years i've decided that I like sound of cheap pedals rather than ones that are supposed to sound like an actual Marshall or whatever. So now i'm back where I started with a Rat, Turbo Rat and Big Muff (plus a couple of others), I just need to get a DS1 now and I really will be back where I started.

sp3k · Post by **sp3k** » Wed Sep 08, 2010 2:45 pm

Do the reutz mod, it will turn the pedal from a nice one to a awesome one

johnnyseven · Post by **johnnyseven** » Wed Sep 08, 2010 3:04 pm

Does that work on a Turbo Rat? I thought that was just for a regular Rat2.

Bill Oakley · Post by **Bill Oakley** » Wed Sep 08, 2010 3:12 pm

It should work on all Rats.

johnnyseven · Post by **johnnyseven** » Wed Sep 08, 2010 3:31 pm

My Rat2 has a metal can LM308 chip in it, will the Reutz mod recognisably improve the sound?

Bill Oakley · Post by **Bill Oakley** » Wed Sep 08, 2010 3:47 pm

Yes, it changes the gain frequency. Try it and report back here. That's the best way and you'll be helping other people out.

Post by **Doog** » Wed Sep 08, 2010 3:48 pm

It reduces the gain by about a third, but improves low-end frequency response as you turn down the distortion dial. A great mod if you prefer medium gain sounds, I'm not sure it really alters the FULL GAIN AHEAD sound, aside from reducing the maximum level of distortion available. I did the mod on my '91 RAT 2 to cop the sounds of my previous modded RAT 2 but preferred having more gain on tap, so undid it.

Either way, it's an easy mod to undo if you cut the resistor in question in the right place, allowing you to reconnect its wires with solder.

James · Post by **James** » Wed Sep 08, 2010 3:57 pm

Doog wrote:It reduces the gain by about 15%...