I thought I'd try putting the KPA in the FX loop of my amp just to see how it sounded today, especially after all the talk of how glorious the KPA sounds through a real guitar cab, and I'll be honest it was an eye opening experience, but not for the right reasons.
Some background - my rig for this was a Mesa Express 5:25 Combo amp, this offers a standard straight FX loop without the usual Mesa Mix parameter that only has a 90% throw, I know this amp pretty well and before trying the KPA had spent a half an hour or so just noodling on it, then I set it to a very clean sound with tone controls at midday before putting the KPA in it's loop (I used the KPA's monitor output for the loop). The profiles I tried included the Andertons profiles, several of the standard profiles that come with the unit some of Andy's and of course my own of this very amp, I tried with and without the cabinet section enabled on most amps and various EQ settings just to be sure of the results.
First up noise floor. Can you say holy crap that's a lot of noise? This is known to be a "noisy" Mesa amp to begin with, but this was as loud as a vacuum in the room with me. I tried the various lifts and volume adjustments to little joy, though I may go back and try again to see if i can trouble shoot this because it was just obscene.
Second problem, aliasing. Something that's just not very apparent through studio monitors is apparently amplified (if you'll pardon the pun) when being driven by a real tube power amp through a real guitar speaker. I have to apologize to Radley as maybe this is how he's been hearing this all along. But notes that are usually silky smooth on the amp are just full of the most horrific atonal harmonics and ghost notes, the thing is after I've heard them so prominently once I went back to playing through the studio monitors I could really hear them as compared to playing through my real amp and it's kinda spoilt the fun.
Third is feel, the KPA just wasn't as spongy. Now bear in mind that the KPA is basically replacing the amps own preamp and we're still using the amps power section, this was like I'd slammed a limiter inbetween the pre and power amps. Playing through studio monitors doesn't exhibit this problem, the sound is much more lively, but through the amp while the sound was still passable it just lost that liveliness completely and felt like an old solid state amp. No amount of fiddling with gain or levels could bring this back.
Fourth was sound. As was expected most of the profiles sounded pretty alike through the guitar cab, but even with a profile of the this very amp the sound was out, far too much treble/presence a really biting sound even when I dialed that far down on the KPA (the input and output lLED's were all green in case you were wondering), the distortion far less rich and complex. Again when I went back to the studio monitor with the KPA the result was much closer to the real amps sound and complexity, but through the amp itself somehow it turned into a much too smooth fuzz style distortion.
TBH I'm pretty disappointed, I'd expected a better showing, but this just didn't feel any better than any other amp sim in that situation and worse when it came to the so called aliasing (which I should point out started to be very noticeable at well below the 12th fret on the upper strings). Of course it was just a quick test and I need to do a lot more, but I was surprised at just how extreme some of the issues were, they weren't subtle problems at all when compared to the amps real tone or the KPA through studio monitors.
Anyhow, there is always the possibility that I did something horribly wrong, but I checked everything twice and all the components involves are working fine and the settings should be good, I'll have to try it again another day when I have more time maybe in a different configuration (any suggestions?). If this is just the way things are then I'm not expecting much to be done about this, and please don't think I'm bashing the unit because I do love my KPA, but I'm just feeling a little glum about the outcome of this particular experiment this time On the other hand I don't need to use the KPA in this configuration I can carry on using it through the studio monitors and be happy (apart from really noticing the artifacts now, and the extreme treble/upper mids transient peaks). But hey you've gotta try these things out at least, right?