Adcom GTP-450 w/B&K REF 4430 w/Klipsch RF-63's

I just put together this 2-channel system. Any experiences with this combo or a variation of the three? I was using an Onkyo TX-SR705 as a preamp with the B&K until I found the Adcom for $100.00. Wow, what a difference. Cleaner,more dynamic, very detailed. When using a receiver as a preamp, does it send the signal out untouched or is there a slight bit of processing before going out to the amp? Don't get me wrong the Onkyo sounds great w/the RF-63's when used in HT configuration. I just want to know why it sounds so much better.

The main problem with using a receiver as a preamp is that it is really three components in one box sharing a common transformer and power supply: a tuner, a preamp and an amp. There's just a lot of STUFF in there and a lot of opportunity for noise and interference not to mention the fact that the power supply and transformer are doing triple duty. As you found out, a dedicated preamp is a much better solution for 2-channel music.

As for processing, unless you've selected a processing mode, it should be outputting only a 2-channel stereo signal.