ProCo Rat

I hate to be a stickler, but there have been a LOT of threads on the ProCo RAT, Turbo RAT, and other variations... it's worth taking a look if you have the time.

The search function is your friend.

But I'll gladly get you started on what to expect:

The general consensus on the regular RAT: great, gritty, distorted tone, but significant low end loss (enough that not even modding them for more bass can help much). The Turbo RAT and RAT II are the ones which get more love, from what I've seen here, because they retain bass much better, but the tone is a bit different from the original RAT.

IIRC, Justin Chancellor (of Tool) currently uses a Turbo RAT in a bi-amp setup for some of his gritty distorted tones, in order to maintain more bottom end via having that second rig be clean (or doused with other effects). Don't quote me on that, but I think that's the one he uses. The previous threads have more to say than I remember.

As for that "bass" version of the RAT... you're most likely thinking of the made-for-bass ProCo Juggernaut, which gets poor fanfare here. Another one worth reading about, though, just to see why (I can't remember the reasons off the top of my head).

 

I have used the RAT II on bass. It takes the bass out of the mix. Listen to Breather Resist of Young Widows and that's what your tone will sound like with the RAT II at full distortion and no filter. At full distortion, full filter, you would get a extremely muddy, low pass filter sound out of the pedal.

I currently have, use, and love my Vintage ProCo RAT. With the LM308 chip (not in RAT II), it pulls the bass response up A LOT! You can keep a dirty, gritty sound that still has bass response. As with other RATs, as you roll up the filter, the muddier your sound gets.

I have not used the BRAT, TurboRAT, or Juggernaut.

I would recommend any RAT w/ the LM308 chip in it if you want good distortion, well, good RAT distortion. If you want more fuzz, look into a Big Muff clone (General Guitar Gadgets' GGG/Bluebeard specs are the best IMHO).

 

I had a Turbo Rat as the only distortion on my board for over a year. Fabulous pedal. It does retain the bass reasonably well, but not completely; there is still some loss. In the end, I ended up doing a clean blend with it, and found it to be damn near the perfect distortion in that setup. Gritty, angry distortion.

And yes, Justin Chancellor from Tool has used a Turbo Rat for his entire time with Tool. On Aenima, he used it for his main distorted tone in H., jimmy and Third Eye (at the minimum, maybe others that slip my mind now). Now he indeed uses it in a separate channel from all his other effects, and its always on (at least live). His main channel distortion sound now is a Sansamp GT2, and he also has a Colorsound Tonebender for fuzz.