Scott,
This is confusing me. The amp only has the speakers connected. The inputs are disconnected from the amp. I have very little noise which is good! But when I connect only one RAC cable on one channel and not connected to the preamp (i.e. only the interconnect ) I get hiss and hum. ...
If just dangling an interconnect cable from your amp input causes a radical increase in noise, then the good news is your amp is fine.
The bad news is, you're in an electrically noisy area, and the dangling interconnect is acting, in effect, as an antenna, picking up background electrical noise and feeding it to your amp. (By shorting out the center and shield, you drain off the received noise, and get silence again.)
You need to:
1) Use well shielded interconnects. Blue Jeans Cable makes nice ones that aren't hideously expensive.
2) Get the interconnect cables away from any other wiring - including wiring that might be in the walls. (Share a wall with someone that has a ham radio rig? Florescent lights? X-10 users? )
3) Never wrap interconnects (or anything else) around power supplies, near light fixtures, pipes, or anything metallic..
4) Keep the interconnect plugged into your preamp, and make sure both amp and preamp is properly grounded. In the absence of a good ground, nothing good can happen in a stereo system.
My favorite stupid trick with a good amp is to touch the center pin of an interconnect without touching the shield. This just about inevitably feeds some significant hum into an amp - and by waving your other hand at electrical appliances you can sometimes vary the kind and amount of hum. This can be a clue to what's noisy in your listening area.
