Have Hiss-Need Help ASAP

Hi Steve,
Are the units tube or solid state? If they are tubes, then you need to change them (tubes). Tubes, once they have reached their "life expectancy", tend to throw a slight to medium audible "hiss". The solid state is a little more complex. It could be anything from a faulty capacitor, to dirty power. I would recommend changing your power cord(s) to a "higher grade" like the Harmonic Tech Pro AC11 and get a power conditioner. That combo greatly reduces background noise.

Have you tried putting in a different or cheaper pair of speakers? With multiple amp and preamp changes it can't be them. Also how loud is the hiss and does it change (as it should) with phono and high (CD) outputs? Almost all systems will hiss at the speaker position especially with some volume, but how far away can you casually hear it? If you can hear it at your listening position (say 5 feet away), then you have a problem. Cables are easy, just switch 'em. Also you have not mentioned is this just a straight stereo system or are there HT components (surround processor) involved as well? Btw if you do have an HT setup you also need to think about cable TV lines and their effect on your system. But if you are without HT then by logic you are left with the speakers or the cables.

steve, ewe could also be experiencing ground-loop hum - try a cheater plug between the amp & the wall, & see if the hum goes away...

doug s.

Steve: Are you married? It could be your wife. Mine sucks her tongue a lot (which makes a funny noise) when I pay too much attention to the gear.

Get a three prong male "Receptacle Tester" from Radio Shack or your local hardware store for $4 to $8 cost. Check all your outlets to make sure they are wired correctly. Sometimes the Neutral & Ground wires are reversed causing a ground loop problem due to ground differential. All the gear works with the wires reversed, but you get the hissss.

Step two is to use a piece of wire to connect the component chassis together to help equalize their ground potential. Connect the wire from chassis bolt on component A to a chassis bolt on component B. If the hissss goes down you can come back and fashion a better chassis-to-chassis ground jumper with the advice of a pro.

Defeating the ground wire on the AC cord with a "cheater plug" can be dangerous. Sometimes that ground wire is used to ground out voltage that may be present on the chassis. Without the ground wire the voltage is still there waiting for a "path". You could become the path by touching two components at once and get yourself a little love shock or in some cases a real doozie up to 120volts.

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.