Clipping Markbass F500 only when slapping - suggestions?

Do you HEAR it clipping or just see the light coming on? It's OK if it blinks occasionally as long as you can't hear it. Also, are you turning up the volume with the compressor louder than without it?

 

Have you tried a faster attack time on the compressor? And a higher ratio?

With an 18V pre, you might be getting some pretty hot transients, playing slap.

 

I haven't used that compressor, and the panel graphics aren't intuitive to me! Best to check the manual to see which way to turn the knobs.

But try lowering the threshold and speeding up the attack. That'll squash more of the transients in your signal; the compressor will grab 'em quicker. You might increase the ratio a bit, too. It'll do more gain reduction.

 

I had to send mine in
They replaced two capacitors according the repair ticket

 

I’m not familiar with this particular compressor - but, it looks like assuming you have the gain ok the threshold looks about right or maybe a little low - you want it kicking in on peaks, the ratio looks like it might be about a 2:1? with a fast attack and fast release, but assuming 12 noon on the output (volume) 0 is center it does look like your boosting the output about 3dB? May be try making the attack a little faster, tweak the threshold up a little, and back down the output (volume) a tad? Also, it could be your bass - IE, strings smacking pickups etc when you slap.