Have Hiss-Need Help ASAP

while using a cheater plug can, in theory, be dangerous, the *path* for ground woltage is generally dissapated thru the interconnects. using a cheater plug is basically dangerous when the equipment it's used on is not connected to anything else. i've had hum problems in the past, and i've tried the suggestion to hook wires between the chassis' to no avail - perhaps cuz they're awreddy connected, w/the interconnects? re: using a circuit thester, this sounds like a great idea, as ewe seem to be having the problem regardless of what combination yure using...

doug s.

Get a new cat!

No need for new cat, just get a muzzle for the current puss. ha, ha.

It is correct that many components share a common ground via the interconnect grounds, but not all circuits are also referenced to the chassis ground. In other words the IC's may create a ground only between the circuit boards while the boards may be floating and not referenced to the chassis. The externally added ground wire will make sure the two chassis have the same ground reference.

A good way to tell if the RCA jacks and corresponding circuit are referenced to chassis ground or isolated is to look closely at the RCA jacks. If you can see the metal of the jack making a direct metal-to-metal contact with the chassis and doesn't have any insulated washers or shoulder washers around it, then you have a chassis grounded jack.

Now, even though the RCA jack is grounded directly to the chassis originally, there is no guarantee that the ground aspect of the connection is still good after time. Aluminum corrodes, steel rusts, copper oxidizes, and powder coatings can interfere with a good electrical ground contact. Look for star type washers that have teeth that penetrate the chassis metal for the best and longest lasting connection in this situation.

laywer, what ya say is true - about the grounds, that is - dunno about the muzzle! ;~) of course, while there may be exceptions, my experience has been that this sharing of common ground via the interconnects, is a major cause of system-induced hum. if the i/c's are floating, odds are ewe won't *have* a hum problem. in fact, one amp i had a hum problem with, i had a technician float the ground instead of using a cheater plug. woila - no more hum.

doug s.

Yes, exactly. That is why so many high priced interconnects have three conductors even in the single-ended RCA termination. The inner conductors are the signal and return path. The shield is then only grounded at one end since it is no longer needed as part of the circuit. With the shield acting as a shield only, it no longer transfers ungrounded chassis hum hissss EMI RFI downstream to the next component for even more amplification.