#1
hey, i just bought a digitech main squeeze compressor used for $15 to use with my bass. i have no idea how to use a compressor so could you guys give me some settings to try? the four knobs are level, attack, eq, and sustain. i play classic and hard rock. thanks.
my gear:
sansamp liverpool
sansamp gt2
fender standard strat
squire vintage modified precision bass
laguna sunburst bass
acoustic b100
ehx bass big muff pi
#2
ftp://ftp.digitech.com/pub/PDFs/Manuals/XSeries%20Manuals/MainSqueezeManualV.pdf

There's the manual to give you an idea of what the knobs do. As far as settings are concerned, it's really a case of playing around. I've heard different people playing similar genres use their compression very differently. Read through the manual, and start messing around.
#3
i just read that manual, but im still not sure what "attack" is.
my gear:
sansamp liverpool
sansamp gt2
fender standard strat
squire vintage modified precision bass
laguna sunburst bass
acoustic b100
ehx bass big muff pi
#4
attack is how soon the compressor kicks in. You set the attack to it's fastest setting and it activates as soon as it receives signal. you set it to a slower setting it waits maybe a few milliseconds before compressing the signal. If you want a really punchy sound, you would make the attack really fast, however if you want a more natural sound you might make it a little slower.

Sustain is pretty much how long the compression lasts for, as you probably gathered, and level and EQ are pretty simple.
#5
The attack and release are two separate things linked by one knob, therefore killing some of the versatility. Attack is how quickly the compressor turns the volume down. Release tells the compressor when to bring that signal back above the threshold volume (which I think is set by the level knob). If you have the attack on full, the entire signal goes under that threshold. If attack is slightly slower, then you get an initial "umph" with the note before the signal gets pushed below the threshold volume by the compressor. A long release means that the compression effect will be applied for a longer time. So with this pedal, the further anticlockwise you turn, the quicker the compression kicks in, and the longer it's applied. Go clockwise, the opposite occurs.

That's my understanding anyways.

EDIT: Threshold volume is sorted with the sustain knob.