Pass Labs preamp with Krell Evo amp. Anyone..??

The specs for the two models do indicate that they differ signficantly. Note that the 402 burns a LOT more power, even in standby, indicating that it's biased more heavily into class A.

On the other hand, the 302's slew rate is faster, and it has a higher damping factor.

So it does make sense that they should sound different.

Also note that at $0.10/kWH, the 302 costs $130 per year in standby, while the 402 costs $320 per year. Not much money compared to the amps themselves though :)

302
Power consumption
Standby: 150 W
Idle: 320 W
Maximum: 3400 W
Slew rate
120 V/µs
Damping Factor (referred to 8 ohms)
>200 at 20 Hz, referred to 8 Ω
>150, 20 Hz to 20 kHz, referred to 8 Ω

402
Power consumption
Standby: 370 W
Idle: 570 W
Maximum: 3800 W
Slew rate
100 V/µs
Damping Factor (referred to 8 ohms)
>145 at 20 Hz, referred to 8 Ω
>125, 20 Hz to 20 kHz, referred to 8 Ω

Turns out the 402's standby and idle power consumption was overstated due to a typo. Krell has updated their site:

402
Power consumption
Standby: 260 W
Idle: 390 W
Maximum: 3800 W
Slew rate
100 V/µs
Damping Factor (referred to 8 ohms)
>145 at 20 Hz, referred to 8 Ω
>125, 20 Hz to 20 kHz, referred to 8 Ω

Mert,
More does not mean it is better. I see you have an EVO 402 and it is a fine amp and I am sure it makes your speakers sing. In most cases it is easier to make a less powerful amp sound good as opposed to more powerul amp. The more output devices and more complex an amp design is the more difficult it is to make sound good. That is why many of the pure class a biased amps are low wattage with lots of current. Simple is best and less sometime is more. Since my last posting I have been able to put some ear time on a Krell Evo 302 and it is better than the 402 in my opinion. It is much more musical and I liked what it does in the bass and if I did not own a Pass Labs X350.5 I would probably buy an Evo 302.