NAD owners: help with speaker selector problem


I own an NAD c-740 receiver. Today I hooked it up to a cheap speaker selector I bought on Ebay. I bought the selector mainly to be able to switch from the NAD to my 1981 Onkyo TX-5000 when I wanted more wattage or a better tuner. As it turns out, only the Onkyo worked. The NAD has something called "impedance sensing circuitry". Could this be the source of the problem? Is this impedance sensor throwing the NAD a signal it doesn't know how to handle? If yes, is there a simple way to circumvent the circuitry. If not, what do you recommend to accomplish the switching I mentioned? I'd really like to be able to use both receivers with the flick of a switch.

Dave are you trying to use the speaker selector switch *backwards*? Selector switches are normally connected with a single source component (receiver) as the input, & then you'll have two or three pairs or speakers on the switched output sides.
It sounds here like you are trying to drive a single pair of speakers from two separate receivers? You can probably do that too, but everything will have to be setup backwards. By that, I mean the speakers would have to be wired to the input side of the switcher. Then the two receivers would be wired to the output sides (A & B respectively) of the switcher. To play receiver A you switch to A & to play receiver B you switch to B. As a precaution you should probably not simultaneously have both receivers powered up & driving their outputs at a high level, perhaps not powered up at all when switching between them. If the switcher contacts don't break before make then you could have some serious smoke.
No. I am not reversing the set up. This speaker selector also has an A/B switch to switch between two amps/receivers. Any ideas? Anyone???