View Full Version : Let's talk about ground loop hums on amps
Hi guys,
I finally have been able to move in my new house, and along comes my A/V gear to be reassembled in the living room.
After I got everything wired together last night, I fired 'er up and to my surprise was a nasty grounding hum coming from all five speakers (I have a seperate two-channel amp and 5-channel amp).
Now I didn't think it was faulty wiring because I had an electrician come out a few weeks ago and run dedicated electrical lines and breakers just for the A/V stuff. The electrician showed me a test he did after installation that confirmed the outlets were wired and grounded properly.
My solution to the hum was this:
a) Install a 3->2prong "cheater" plug for the McIntosh stereo amp and
b) Install a 2->2prong "cheater" plug for the other amp which I think reversed the hot/neutral leads.
Am I causing any problems doing this? The amps are the only things on this circuit, but I suppose the problem originates from the fact that there are low-level RCAs hooked up to each from my pre-amp on another circuit.
What is your experience with this type of problem?
Sam, do you have any kind of cablevision/satellite cables connect in the chain somewhere?
Originally posted by Dave
Sam, do you have any kind of cablevision/satellite cables connect in the chain somewhere?
Yes!
I have both satellite and antenna connected. Both lines are filtered through a Panamax 5300 line conditioner for noise/RF. Do you think I'm doing any damage with the cheater plugs?
Cliff
09-27-2003, 03:32 PM
Sam, I have the same problem with my setup. The difference is only the mains are affected by the hum. I have a 5 channel amp, so it's been a rough, confusing, and frustrating ride trying to isolate the hum. When I use the Zone 2 outputs on the Lexicon, run them into the SAME two channels of amplification, the hum disappears (I switch the RCAs from Main out to Zone 2 out manually for SACD - but you know that already ;) ). If/when I find anything to be the culprit, I will certainly let you know. It's a transformer, I fear :(
JohnG
09-27-2003, 03:51 PM
cheater plugs work fine....just keep em out of harms way....back behind your equipment so they don't get jostled or something.
Originally posted by SamS
Yes!
I have both satellite and antenna connected. Both lines are filtered through a Panamax 5300 line conditioner for noise/RF. Do you think I'm doing any damage with the cheater plugs?
No I don't believe that you will be causing any damage using a cheater plug. The only exception I can think of is if you are running any tubes.
You might want to try a cheapie Radio Shack cable line RF filter in the lines themselves. I had to do this even though I was running an LC with RF protection. Cost, $10.00-$13.00 each.
I will look into those cable line filters. Do ya think that's really the bugger here? Electricity confuses me :confused:
Originally posted by SamS
I will look into those cable line filters. Do ya think that's really the bugger here? Electricity confuses me :confused:
It reasonably sounds like it could be the problem Sam. Even if it isn't you've at least eliminated any possibility that it could be RF, and at a very cheap expenditure.
Cliff
09-27-2003, 04:56 PM
Are these "cheater plugs" the adapters that take the grounds out of the PC?
Originally posted by Cliff
Are these "cheater plugs" the adapters that take the grounds out of the PC?
:confused: Are you talking computers now?
A cheater plug is a 2 pronged AC adapter, quite common in the 1960's and still available today, as opposed to a 3 prong plug with a ground. The ground just becomes null and void when you use one of these.
VU Master
09-27-2003, 06:41 PM
Disconnect satellite and cable wires and see whether the noise goes away. Then you will know whether they are causing the problem and whether a filter might help.
Originally posted by David Kulka
Disconnect satellite and cable wires and see whether the noise goes away. Then you will know whether they are causing the problem and whether a filter might help.
Thanks David, good point! :D
Cliff
09-27-2003, 10:19 PM
Originally posted by Dave
:confused: Are you talking computers now?
A cheater plug is a 2 pronged AC adapter, quite common in the 1960's and still available today, as opposed to a 3 prong plug with a ground. The ground just becomes null and void when you use one of these.
Sorry Dave. I tend to abbreviate too much. PC - Power Cord... Sorry.
But, you answered my question :) You guys don't think there's risk running an amp without the ground then? It gets rid of my system hum as well, but I was afraid to keep it on there.
Originally posted by Cliff
Sorry Dave. I tend to abbreviate too much. PC - Power Cord... Sorry.
But, you answered my question :) You guys don't think there's risk running an amp without the ground then? It gets rid of my system hum as well, but I was afraid to keep it on there.
Cliff, I've been running mine this way for 5 years now continuously on 24/7 with no problems what so ever.
Cliff
09-27-2003, 10:25 PM
Originally posted by Dave
Cliff, I've been running mine this way for 5 years now continuously on 24/7 with no problems what so ever.
Thanks, Dave. Guess what I'm doing tomorrow :D
I take it you too, have system hum then?
Originally posted by Cliff
Thanks, Dave. Guess what I'm doing tomorrow :D
I take it you too, have system hum then?
You mean had about 5 years ago, don't you Cliff? ;)
Cliff
09-27-2003, 10:46 PM
Originally posted by Dave
You mean had about 5 years ago, don't you Cliff? ;)
Ahh, yep :p
mne563
09-28-2003, 04:18 AM
Originally posted by David Kulka
Disconnect satellite and cable wires and see whether the noise goes away. Then you will know whether they are causing the problem and whether a filter might help.
I agree with David's comment here; satellite or cable is your problem. The satellite cable itself should be grounded before entering the house. Disconnect these completely and the hum will (probably!) stop.
I had the same problem with two big amps, put a cheater on only one of the amps and the hum stopped. I haven't grounded the satellite cable yet 'cause I'll be moving that cable soon (it's buried in the ground).
petzi
09-28-2003, 07:16 PM
I don't recommend lifting the ground of the mains. It may be dangerous.
Did you check if removing any cable TV or antenna connection mitigates your problem while keeping your mains connected to the ground? If so, then you should try to solve the problem there. There are little pluggable isolating RF transformers available for this, they will galvanically separate your equipment from the ground of your cable/antenna setup.
KeithH
09-29-2003, 04:08 AM
Sam, I had this problem when I got my Sony SCD-777ES SACD player a few years ago. It came with a three-prong power cord. I have cable TV in the same set-up, and since there was no way around that, I simply used the cheater plug that came with the '777ES to stop the hum. That's all there was to it.
Originally posted by petzi
I don't recommend lifting the ground of the mains. It may be dangerous.
Did you check if removing any cable TV or antenna connection mitigates your problem while keeping your mains connected to the ground? If so, then you should try to solve the problem there. There are little pluggable isolating RF transformers available for this, they will galvanically separate your equipment from the ground of your cable/antenna setup.
petzi, If I were living in Europe I would agree with you 100%, but here in N. America being 120V it's not really a concern unless you are running a tube system.
petzi
09-29-2003, 11:50 AM
AC is considered lethal at voltages above 48V.
DC is considered lethal from 100V on, but that's not what comes out of your outlet.
I acknowledge that 120V AC is not as dangerous as 230V AC, but IMHO that is compensated for by a much laxer handling of those voltages.
My point here was, that you shouldn't disable safety measures in your gear by lifting ground from the mains with a "cheater plug", when you can solve the ground loop in the antenna connection.
Thanks for all the responses here so far guys.
My satellite lines are grounded before they come in the house, but I'm realizing now the antenna is in the attic and not grounded--it just runs straight down the wall to the power conditioner.
The problem was solved by just using one cheater plug on my McIntosh stereo (3-prong) amp. Just by using this cheater, the hum on the other amp went away as well. Weird, huh?
Cliff
09-30-2003, 09:21 AM
Originally posted by SamS
Thanks for all the responses here so far guys.
My satellite lines are grounded before they come in the house, but I'm realizing now the antenna is in the attic and not grounded--it just runs straight down the wall to the power conditioner.
The problem was solved by just using one cheater plug on my McIntosh stereo (3-prong) amp. Just by using this cheater, the hum on the other amp went away as well. Weird, huh?
Congrats, Sam. Glad you solved the hum problem with a cheater plug :) I tried the cheater plug the other day, and the hum is still there :mad:
mikelakers
10-01-2003, 12:16 PM
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