Just moved and now I have a HUMMMMMMMM

[jbl_daddy]

At last I hooked up my theater system last night and there is a humm. I have changed out all the cables wiggled all the cords and it still is there??? The humm only exists on two of the six power amps??? The rack consists of two Croen K1's, one K2 (No Humm) and three Crown DC300 II's, two of the three have a humm??? I was showing my wife this morning and she said just get more K1's and I told her that was not cost efective when you have just purchased a new house. What should I try next to kill the hum???

[Triumph Don]

http://www.psaudio.com/ps/how-to/finding-and-fixing-hum

[HCSGuy]

The most common hum I've found is a ground loop with your Cable or Satellite service. Either way, turn on the system until you get hum, then unscrew the coax cable/cables that feed the system. If the hum goes away and you have cable, get a ground isolation transformer (Jensen transformers makes the best, I haven't had any luck with the cheap capacitive ground blockers Comcast will give you). If you have satellite, you need to bridge the ground between your equipment and your dish or possibly move the dish ground to the equipment ground, if it can be done to code.

The second common cause I've seen in larger systems is having equipment plugged into multiple circuits, especially if the circuits are on different phases of your incoming power. Find the breaker that powers the main equipment and turn it off - does everything turn off? If not, continue to turn off breakers until you find the one that kills the remaining equipment (hopefully there is only one; if there is more things may get difficult). Once you have found all the breakers, turn the main equipment back on with the others off. Does it hum? If so, and you've unplugged the coax, it's probably time to shop for a new house (just kidding, but it's going to be harder to find, and may be an interconnect problem). If the equipment doesn't hum with only the one circuit on, turn on the next - if the hum comes back, unplug the equipment on that circuit and plug them into the main circuit using extension cords. If the hum goes away, that circuit may be on the other side of the breaker panel from the main one - you or an electrician can try wiring the circuit to a breaker on the same side/phase as the main equipment and see if that takes care of it, or can run a new circuit. If your equipment still hums, check all of your interconnect cables - unplug them one at a time until the hum goes away - you may have a bad cable.

I hope this helps - the coax ground loop with cable is the most common one we see and the easiest to fix. If not, you may be embarking on one of the longest, most unrewarding parts of this hobby. Let us know what you find!

[boputnam]

HSGuy had some great points.

There are a number of threads here dealing with ground loops (GL). Search.

Do make sure all your gear - ALL - is into the same AC circuit.

Definately disconnect your cable connection, if you use one, until you figure out what is going on. There is often a bad ground in a neighbor's down the street that is contaminating everyone.

If this does nothing, you need to work backwards, upstream, toward your sources. Start with everything disconnected. Plug the amps into the speakers and turn them on - no hum?, then add your HT processor. No hum, then one-by-one, connect each device individually and test for hum. Unplug when that device is not the problem, and try another.

You are looking for a device that is finding two sources to ground, due to different grounding schemes. That is leaking into your signal path, and it sucks. When you find the problem, we can help you isolate that without compromising the entire system.

btw, I think your wife is great! :bouncy:

[lgvenable]

I have 12 amps hooked up; and solved all ground loop issues by installing a separate transformer, with an independent ground isolated from my home electrical panel. I out in an 80amp breaker to a separate panel., grounded to the transformer case. I grounded the transformer secondary circuit through my garage floor to a 6 foot cooper ground rod. Then, I ran a line up to the theater room in conduit, and placed 4 20 amp breakers on it. Using that effectively isolated my amps from my pre-amp, and having amps with balanced outputs have completely eliminated ground loop issues.

I'm running 9.2 on an Integra DHC 80.2 with 11 BGW 250D's or 250E's which are bridged to mono though three sets of L100T's, L100A's, 8830's and 8840's and a set of Control 28's (front-lft right upper channels..with a Dolby Pro Logic IIZ. Absolutely no hum whatsoever; and before the transformer...they had hum like a mother.

Less expensive route:
If its just one or amps, get a couple of Behringer HD400 hum destroyers, which use rca > phono>unbalanced>balanced>phono>rca; the use of these $25 unbalanced > balanced > unbalanced converters will also eliminate ground loop by isolating the amps ground from the source ground; voila hum too.;)

[1audiohack]

Here is a "never fails" if you don't mind a little reading, nine pages is all, go to

jensen transformers.com

open the applications page, then open white papers and read the Jensen System Trouble

Shooting Guide by Bill Whitlock. I suggest you read it all. There is a lot of good information on this site.

A systematic approach will get it done in short order, everytime.