Crunch / analog overdrive, with IN, OUT, and a 9V power supply with an electrical outlet jack. I use it with a battery, the trap is strong and can be opened by hand if you have not cracked down like a brute.
Settings: Distortion, Filter (filter cut treble, even with a good bass) and Volume, plus On / Hard Bypass

UTILIZATION

Three knobs, hard to get any easier ...
When the manual, take my job very seriously tester, I have downloaded from the manufacturer, it has 3 settings and information on the power supply. I think it will certainly not anyone bothered to download it!

SOUND QUALITY

To start, note that I use this pedal with a LOW (active => big input level to the pedal ...)
So we will, therefore, a very good crunch to an almost distortion "fuzzesque" although in this case means more than what we played too. What a sound! : Vintage, dirty and hot (and yes even with a bass!), The crunch responds very well to the intensity of the game and the distortion is very "acid".
The sounds I get with: the crunch of Nick Oliveri on the first album of Queens of the Stone Age, or the distortion of Krist Novoselic (Nirvana) on Incesticide, even if it is not necessarily a reference.
I caught up with the lack of settings with the settings of my bass, which for players is more difficult (no preamp like an active bass ...).

Update: I now have a guitar (Fender Mustang) so I can try the Rat with (plugged into a Fender Hot Rod Deluxe). The Rat perfectly complements the amp: I use the crunch from the amp, but I prefer the Rat distortion, especially because I can put it after the wah. In any case this pedal does not have to face the shame of a grain tube distortion. Even with an output level of the lowest in the market (the microphones of the Mustang) I get a very powerful fuzz with the Rat (though less powerful in the treble). Note that after noon on the knob of distortion you feel compression Ascending; the disto food thoroughly all the dynamics, giving a very synthetic fuzz and lo-fi, which can be nice but not for everyone .

Difficult to return to its clear so it's good!

OVERALL OPINION

I've had two weeks and I'm delighted for her single grain (away from the modern types of Boss pedals, albeit in less versatility).
In short if you want to make you sound very personal, please, if you prefer the versatility, orient you rather (for bass) to the Digitech BassDriver. I also like its looks (look "East Germany" from my teacher scratching)
At 100 Euros, we are still in the initial price for an effects pedal so RAS on quality / price ratio, especially since it is manufactured in the United States.
Yes I do it again this election and I advise all bass players Alternative Rock / grunge / punk or even blues.

Update: I have now for 2 years, always satisfied, the pedal is very robust (no single scratch despite some concerts in unsavory conditions!)