I’m using a Fryette PS-2 with an unpowered Rack and it sounds great to my ears. I run to a celestion f12-x200 in a thiele cab for monitor and also direct to FOH. The PS-2 uses 6L6s, but I’m never at a monitor volume to push those hard at all. I don’t notice them coloring the Kemper’s sound at the level I’m running, but of course everyone’s ears are different. I already had the Fryette from using it with my tube amps - if I hadn’t I would have likely found a good solid state amp that was lighter (or maybe would have bought a powered Rack).
Agreed, I tried to buy a powered rack mount Kemper here locally but the seller wouldn't budge on the price and I found a good deal on the unpowered rack, foot swtich and expression pedal combo so I jumped on it figuring to use the PS100 for power. I wouldn't say that the Kemper sounded bad with the PS100, but it's just not the same. I don't have the eloquent vocabulary that many others have when it comes to describing what I'm hearing.. So, "alive" is the best I could come up with. LOL
I did notice that the Carvin power amp had "presence" controls on the back for each channel. I adjusted them "in the blind" before putting the amp in the rack (basically setting them strait up the middle) so I'm sure that probably has some impact on how it sounds. The PS power side is supposed to be supplying a "clean" power source for the amplifier being attenuated so I really didn't figure it would be coloring the overall tone that much but also moving from 6550's to 5881's may be some of the difference too.
Interesting to see how many different options people are using though!