Tonight was my first practice with my assembled rig, a GK 1001RBII, with an Alesis 3630 in the effects loop. I played a P bass, and throughout the night, I was experiencing slight clips when digging in. I have 2 questions... First, how much clipping is too much clipping? I was getting one little blip every few seconds. Second, would a compressor in the effects loop affect the input clipping? I don't think it would, as I was getting the clip even with the compressors output turned way down. I played a Jazz through the same amp and had no clipping issues. Do I just have a really hot P bass? It's a stock MII Squier. I want to make sure that I don't fry this amp. It's not expensive or rare, but I still don't like breaking stuff. BTW, it sounds absolutely thunderous through an 810E!
Yes, compressor or any effect that can boost the output can cause clipping if the output is higher than input. Does the amp get louder or quieter when you bypass the compressor without touching anything else? You can also lower the amp's input gain if it has one or toggle a pad switch. Or just lower the volume from the bass. On the other hand, clipping is not ALWAYS bad - it's bad only if it sounds bad. Of course the extra distortion is not the best thing for speakers but slight peak clipping is not the worst thing you can do to your tone.
From what you described, it does sorta sound like you've narrowed it down to the input stage clipping. I'm not familiar with that GK - how do you know when it clips? I assume there is an led indicating it? I'm running that same compressor in the effects loop on my Ashdown. I was having some problems when I first hooked it up with some audible clipping somewhere in the chain, which I fixed by switching the level on the back to +4dBu. (It sounded horrible at -10 dBv) None of that helps with the input clipping I suppose, but then again it might help to try both settings. Passive P pickups can be pretty loud. I've had a few P's over the years, some active (EMG's) and some passive. Right now I have one loaded with a Quarterpounder that I'd say is a touch louder than the EMG that it replaced. Where's the input gain at the amp set? Is there a "low" gain input? Maybe try lowering the pickup? It doesn't sound to me like you need to worry about damaging the amp if it's just once every few seconds when you're really digging in as you say. It's probably irritating to have to worry about it while you're trying to play, more than anything.
If you don't like the sound of the clipping, turn down the intput gain (volume) and turn up the output stage (woofer). I believe the clipping light pertains to the input gain stage only (volume). The output boost can also cause distortion so you should experiment with that setting too.
Doh! Why didn't I think of that? Turn down the input, raise the output to compensate. What would I do without TB? I'm not used to seeing clip lights, it must have made me lose my mind for a minute. Thanks!
Just one other thought -- I've noticed with GK heads that some effects including compression just seem to sound better when they're NOT in the amp's effect loop.