The usual stuff, mate:
Make sure your strings aren't fretting out too much; that'll kill sustain every day of the week. Raise action if need be.
Input LED green and occasionally into orange should be fine.
Try Amp Compression (not a Stomp) - that should give you more sustain, and in a pleasant way.
Make sure the global noise gate isn't set too-high.
See how you go with these for starters... 
Don’t forget that through a normal amp you have volume to help, you need to crank your speakers to get that natural resonant sustain just like with a real amp. The Kemper can help with more compression in the amp block and balancing your input sens settings.
Try Amp Compression (not a Stomp) - that should give you more sustain, and in a pleasant way.
Hi Nicky, any reason so with amp compression not stomp? I've been using the stomp compression and its...ok...so I guessing from your comments you've had better results with amp compression?
Best way to hear the effect of the amp compression is imho to plug a chord, let it ring and then to bring up and down again the compression. You'll hear the difference in sustain in the decay-phase of the chord.
Hi Nicky, any reason so with amp compression not stomp? I've been using the stomp compression and its...ok...so I guessing from your comments you've had better results with amp compression?
I find it more-transparent, V8; simple as that.
No need to futz around with attack settings or whatever, which is where I feel most compression stomps give the game away, and I'm not a fan of that signature-attack result except of course where it's "mandatory" such as in clean / edge-of-breakup, rhythmic tones such as were popular in the '80s... with tonnes of rhythmic delay, of course.
Aside from that, the OP wanted to increase sustain, that's all, so I figured recommending a stomp, whilst it should logically give him what he was after, will also mess with the attack characteristics of the resulting sound.
I haven't actually tested the stomp compression yet on the KPA 'cause the Amp Compression parameter has yielded wonderful results, and as I said, I have a bias against the way the stomp equivalents in the real world mess with attack.
I have a bias against the way the stomp equivalents in the real world mess with attack.
Need to try a Wampler EGO compressor (has an actual attack knob). It sounds gorgeous as well. 
I find it more-transparent, V8; simple as that.
Thats fab. I've never tried it so I feel some fiddling come on.
Thanks dude!!!!
No worries bud; I think you'll be impressed.
When I said, "more-transparent" I really was understating things; it's ridiculously-transparent.
No worries bud; I think you'll be impressed.
When I said, "more-transparent" I really was understating things; it's ridiculously-transparent.
Cool, got some big-ish gigs at the weekend so gonna play with this tonight!
No worries bud; I think you'll be impressed.
When I said, "more-transparent" I really was understating things; it's ridiculously-transparent.
Thanks Nicky ...I’m gonna try this. I didn’t realise it would make a big difference whichever way stomp vs amp compression but as I type it, it sort of makes sense..
Well, stomp compression is a process (as opposed to an effect), much like applying a plugin or outboard compressor to a signal.
I don't know what's going on under-the-hood with Amp Compression, but logic tells me it's not quite the same thing. I've read here previously that it doesn't do what we're talking about here 'though, so I checked the manual:
Compressor
This “Compressor” parameter is different from the Compressor effect, as it is a part of the simulated amp circuit. In other words, it allows for completely different sounds compared to compressors that are inserted before (pre) or after (post) the amp module. Distorted signals are not affected by compression; so only clean signals will be boosted. The dynamics of your playing are fully retained, allowing you to go from a crunchy sound to a compressed, clean sound, purely by the strength of your picking. The volume knob on your guitar works exactly as you would expect: for instance, reducing the volume of your guitar will transform a dynamic crunch into a clean, compressed sound with full energy.
Somehow 'though, when I crank it up using driven tones it gives me a "creamier" playing response - a smoother, seemingly-more-sustaining result. IDK why I have this impression given that the manual implies this should only be apparent using clean sounds, but hey, I love it.
Had a play last night and you are right, it does seem better. I won't know until full volume but sounds good so far!
Display MoreWell, stomp compression is a process (as opposed to an effect), much like applying a plugin or outboard compressor to a signal.
I don't know what's going on under-the-hood with Amp Compression, but logic tells me it's not quite the same thing. I've read here previously that it doesn't do what we're talking about here 'though, so I checked the manual:
Compressor
This “Compressor” parameter is different from the Compressor effect, as it is a part of the simulated amp circuit. In other words, it allows for completely different sounds compared to compressors that are inserted before (pre) or after (post) the amp module. Distorted signals are not affected by compression; so only clean signals will be boosted. The dynamics of your playing are fully retained, allowing you to go from a crunchy sound to a compressed, clean sound, purely by the strength of your picking. The volume knob on your guitar works exactly as you would expect: for instance, reducing the volume of your guitar will transform a dynamic crunch into a clean, compressed sound with full energy.
Somehow 'though, when I crank it up using driven tones it gives me a "creamier" playing response - a smoother, seemingly-more-sustaining result. IDK why I have this impression given that the manual implies this should only be apparent using clean sounds, but hey, I love it.
cheers Nicky - converted...
Just a thought, but maybe check your global noise gate too mate?
Post #2, Greg:
Make sure the global noise gate isn't set too-high.
+1 on the amp compression, I stumbled across that setting early on and love it
Post #2, Greg:
Worth saying twice 
