Dirty and clean signal....

[suitlandkid2005]

I'm trying to see if I got this right. Is clean signal a signal with no effects and is dirty a signal that is distorted?

[stflbn]

Essentially, yes. Dirty would be over-drive, distortion, fuzz, etc.

Some amps have clean and dirty channels directly on them.

However, there's a lot of effects that can be used and still consider the sound 'clean'.

[smo]

Yep.

Dirt = Distortion, Fuzz, Overdrive and all other distortion style effects.
A simple Volume booster can also be used to Overdrive a tube amp, but this is kinda different.

[atheos]

This is how I and pretty much everybody I know use those terms, "dirt" being equal to any kind of distortion:
Clean = No distortion/overdrive
Dirty = Any distortion/overdrive

But then these terms are also essential to know with effects, very different from clean/dirty:
Wet = Effected
Dry = Not effected (DI signal)

This means that you can have clean & wet signal (e.g. chorus, reverb) but you can't have dry & dirty because dry means having DI signal without a single effect or preamp/speaker modeling.

[suitlandkid2005]

Thanks for the info everyone.