Posted on 
Nov 16, 2007 02:57 pm I think that you're on the right track for both devices.
The threshold on your compressor tells the device "how loud does the signal have to get before I decide to turn it down?". A good method for setting the threshold for light compression and peak clipping is to do as you say: turn the threshold to 0 dB and slowly turn it down until its blinking intermittently. If you want heavy compression to squish the signal, keep turning down the threshold until the LED is always on.
The ratio means "how severely do I want to compress the signal?". Lower ratios like 1.5:1, 2:1 or even 3:1 are relatively low and work good for when you want your compression to sound transparent. Like for vocals, acoustic instruments and drum overheads. Higher ratios like 5:1 and above are for those instances when you want the compression more as an effect. Extremely high ratios (infinity:1) are for hard limiting your signal.
Attack and release are the hardest to give advice on. They differ for each instrument/sound source and for each different type of application. It just means "how quickly do I turn down the signal once it breaks my set threshold" (attack) and "how quickly do I return the signal to its normal amplitude after I've turned it down" (release).
For instruments like kick and snare drums, you generally want to set the attack so that it lets the initial "crack" or "pop" through, but so that it'll still clamp down to dampen the "ring" or "boom". This gives you a nice, punchy sound. Set the release long enough so that it doesn't release while the "ring" or "boom" is still sounding.
And that's my over-caffinated, personal opinion essay for the day :)
