Ground loop through DC trigger cable

[jvgillow]

Hey folks,

I picked up a Denon AVR-3311ci last week which has two 12v DC trigger outputs, my last couple of receivers have not had that feature. I've got a mono 1/8" cable running from one of those outputs to the Trigger In connection on an Audiosource Amp 300. I'm getting ground loop hum on the speaker that is powered by the amplifier. The Denon receiver only has a 2-prong power plug and my amplifiers use standard 3-prong grounded cables.

If I disconnect the trigger cable from the Denon and use it to connect two of the amplifiers together (from trigger out amp #1 to trigger in amp #2) there is no hum at all, I believe because they are both grounded and the receiver is not. I'm just setting up the system from scratch, moved into a new place last week so there's no sources or CATV or displays hooked up yet. Everything connecting into one power conditioner right now.

In the past when I've used 12v trigger it's always been connected to a power conditioner that has triggered outlets.

Does anyone else have a non-grounded receiver connected to a grounded amp for DC trigger? Any noise or does it work as expected?

 

[Adam]

Hi, Jeremy. I have a receiver connected to two amps using two 12V triggers, just like you described, and I don't have an issue like that. I do have all three connected to the same power conditioner, though, so perhaps that takes care of any ground loop issues.

Did you try swapping the triggers between the amps to see if the hum followed the trigger? Perhaps there's an issue with the internal wiring of one of the triggers in the receiver. If you have the case where one of the trigger outputs works and the other hums, you could always get a splitter and just use the one trigger (unless you are triggering the amps under different conditions).

 

[cpp]

Check this out

http://www.avsforum.com/avs-vb/showthread.php?t=322698

http://www.audioholics.com/education/cables/thinking-in-isolation-2013-a-primer-on-ground-loops

http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz

 

[highfigh]

Hey folks,

I picked up a Denon AVR-3311ci last week which has two 12v DC trigger outputs, my last couple of receivers have not had that feature. I've got a mono 1/8" cable running from one of those outputs to the Trigger In connection on an Audiosource Amp 300. I'm getting ground loop hum on the speaker that is powered by the amplifier. The Denon receiver only has a 2-prong power plug and my amplifiers use standard 3-prong grounded cables.

If I disconnect the trigger cable from the Denon and use it to connect two of the amplifiers together (from trigger out amp #1 to trigger in amp #2) there is no hum at all, I believe because they are both grounded and the receiver is not. I'm just setting up the system from scratch, moved into a new place last week so there's no sources or CATV or displays hooked up yet. Everything connecting into one power conditioner right now.

In the past when I've used 12v trigger it's always been connected to a power conditioner that has triggered outlets.

Does anyone else have a non-grounded receiver connected to a grounded amp for DC trigger? Any noise or does it work as expected?

Since the Denon and AudioSource are plugged into the same power source, make sure the receptacle is wired correctly. Also, unplug the cables from the Denon to the AudioSource to find out if the noise is still there I would try another 1/8" trigger cable, too.

 

[TechB74]

Hey folks,

I picked up a Denon AVR-3311ci last week which has two 12v DC trigger outputs, my last couple of receivers have not had that feature. I've got a mono 1/8" cable running from one of those outputs to the Trigger In connection on an Audiosource Amp 300. I'm getting ground loop hum on the speaker that is powered by the amplifier. The Denon receiver only has a 2-prong power plug and my amplifiers use standard 3-prong grounded cables.

If I disconnect the trigger cable from the Denon and use it to connect two of the amplifiers together (from trigger out amp #1 to trigger in amp #2) there is no hum at all, I believe because they are both grounded and the receiver is not. I'm just setting up the system from scratch, moved into a new place last week so there's no sources or CATV or displays hooked up yet. Everything connecting into one power conditioner right now.

In the past when I've used 12v trigger it's always been connected to a power conditioner that has triggered outlets.

Does anyone else have a non-grounded receiver connected to a grounded amp for DC trigger? Any noise or does it work as expected?

Hi Jeremy,

I have a Denon 3312 with a Russound amp for the 3rd Zone (unamplified), and I am having the same problem as you. The second amp (Russound) can be triggered when it detects audio input but this does not work well when listening at low volumes. However no hum/deep buzz is heard in this way. When I connect the 12v trigger cable I get a hum from the speakers supplied by the Russound amp. Lowering the volume on the Russound amp also lowers the hum. Disconnecting the RCA cables between the Denon and the Russound also eliminates the hum. The Russound had a ground pin the Denon doesn't. Any suggestions would be greatly appreciated.

 

[highfigh]

Hi Jeremy,

I have a Denon 3312 with a Russound amp for the 3rd Zone (unamplified), and I am having the same problem as you. The second amp (Russound) can be triggered when it detects audio input but this does not work well when listening at low volumes. However no hum/deep buzz is heard in this way. When I connect the 12v trigger cable I get a hum from the speakers supplied by the Russound amp. Lowering the volume on the Russound amp also lowers the hum. Disconnecting the RCA cables between the Denon and the Russound also eliminates the hum. The Russound had a ground pin the Denon doesn't. Any suggestions would be greatly appreciated.

Are you using analog audio to feed the Russound? If so, you shouldn't hear any difference with/without the trigger cable because the analog inputs are also at chassis potential.

If the Russound has a threshold adjustment, set it lower so the amp turns on more easily. Otherwise, you'll need to turn the volume up briefly to turn it on and then decrease the level. If the Denon and Russound are in two different locations, have a good electrician check the wiring and if possible, have all receptacles with connected equipment assigned to the same circuit, or at least the same phase. If the house is old, have new wiring run so the ground and neutral are unbroken from the panel to the receptacles. A little resistance on a neutral or ground will cause all kinds of problems.

 

[TechB74]

Are you using analog audio to feed the Russound? If so, you shouldn't hear any difference with/without the trigger cable because the analog inputs are also at chassis potential.

If the Russound has a threshold adjustment, set it lower so the amp turns on more easily. Otherwise, you'll need to turn the volume up briefly to turn it on and then decrease the level. If the Denon and Russound are in two different locations, have a good electrician check the wiring and if possible, have all receptacles with connected equipment assigned to the same circuit, or at least the same phase. If the house is old, have new wiring run so the ground and neutral are unbroken from the panel to the receptacles. A little resistance on a neutral or ground will cause all kinds of problems.

Hello highfigh,

Thanks for taking the time to help me out with this. The signal is analog using L & R RCA cable. The Russound doesn't have anysettings except L and R gain, volume knobs basically. I already do that trick with the volume, it will turn on but when the music goes quiet or there is a pause the Russound goes into standby. I use it a lot for relaxation music, especially at night which tends to be softer/quieter. Both amps are in the same cabinet. Setting the volume lower on the Russound also lowers the volume of the buzzing hum, no hum when trigger cable is removed and RCA's are connected (how I have been using it the past), and no hum when trigger cable is connected but RCA connections to Denon are disconnected. Don't know if this information helps any. Thanks again.

 

[TLS Guy]

Hey folks,

I picked up a Denon AVR-3311ci last week which has two 12v DC trigger outputs, my last couple of receivers have not had that feature. I've got a mono 1/8" cable running from one of those outputs to the Trigger In connection on an Audiosource Amp 300. I'm getting ground loop hum on the speaker that is powered by the amplifier. The Denon receiver only has a 2-prong power plug and my amplifiers use standard 3-prong grounded cables.

If I disconnect the trigger cable from the Denon and use it to connect two of the amplifiers together (from trigger out amp #1 to trigger in amp #2) there is no hum at all, I believe because they are both grounded and the receiver is not. I'm just setting up the system from scratch, moved into a new place last week so there's no sources or CATV or displays hooked up yet. Everything connecting into one power conditioner right now.

In the past when I've used 12v trigger it's always been connected to a power conditioner that has triggered outlets.

Does anyone else have a non-grounded receiver connected to a grounded amp for DC trigger? Any noise or does it work as expected?

I think you know what a ground loop is and you have one.

This is a very common problem with power amps.

Your receiver has no ground plug and so its ground is at a potential somewhere around the potential of the neutral at the outlet. Your amp is grounded and is at the potential of the ground at the outlet.

These potentials are different in your case which is frequently the case. In your case this is how the ground loop is created.

In a building grounds and neutral are daisy chained from outlet to outlet, and there is frequently a small voltage on neutral and ground is seldom true ground.

The first thing to try is to link your receiver and the amp with No 4 gauge copper. If that does not work create a ground to your receiver with heavy gauge wire to the AC outlet. If you get hum them leave the new receiver ground in place and lift the amp grounds.

In professional practice you do not ground power amps. You ground the preamps, or mix desk.

If I ground my power amps I get hum no matter what. Even though the amps have three pin sockets, Peter Walker always supplied the Quad 405 series with two pin power cords. The Quad 909s come with a three pin power cords, but the there is no connection to the ground pins. So what the eye does not see the heart does nor grieve over.

I personally never ground power amps and never will, it just causes trouble.

 

[TechB74]

Hello highfigh,

Thanks for taking the time to help me out with this. The signal is analog using L & R RCA cable. The Russound doesn't have anysettings except L and R gain, volume knobs basically. I already do that trick with the volume, it will turn on but when the music goes quiet or there is a pause the Russound goes into standby. I use it a lot for relaxation music, especially at night which tends to be softer/quieter. Both amps are in the same cabinet. Setting the volume lower on the Russound also lowers the volume of the buzzing hum, no hum when trigger cable is removed and RCA's are connected (how I have been using it the past), and no hum when trigger cable is connected but RCA connections to Denon are disconnected. Don't know if this information helps any. Thanks again.

Hi Jeremy,

I have a Denon 3312 with a Russound amp for the 3rd Zone (unamplified), and I am having the same problem as you. The second amp (Russound) can be triggered when it detects audio input but this does not work well when listening at low volumes. However no hum/deep buzz is heard in this way. When I connect the 12v trigger cable I get a hum from the speakers supplied by the Russound amp. Lowering the volume on the Russound amp also lowers the hum. Disconnecting the RCA cables between the Denon and the Russound also eliminates the hum. The Russound had a ground pin the Denon doesn't. Any suggestions would be greatly appreciated.

Should I somehow isolate the 12v trigger with a relay of some sort?

 

[TechB74]

Problem Solved

Hi just thought I should post my solution to this problem to help anyone else who might experience this. Basically I had a friend help me out. When I described the problem he said it was a signal ground loop and suggested cutting the ground on the 12v trigger. I did that and soldered the positive wire back together and all is working fine. Denon triggers second amp with no hum.

 

[Reclaimist]

Old post bump... I just ran into this issue as well, but rather than chop up the trigger cable's braided shield, I merely added a short (3") ground wire between the trigger cable input on my receiver and its ground screw. The trigger cable input was isolated by a coloured plastic ring preventing contact between the subwoofer cable and the receiver, so they weren't sharing a common.

 

[Jbrunwa]

Old post bump... I just ran into this issue as well, but rather than chop up the trigger cable's braided shield, I merely added a short (3") ground wire between the trigger cable input on my receiver and its ground screw. The trigger cable input was isolated by a coloured plastic ring preventing contact between the subwoofer cable and the receiver, so they weren't sharing a common.

Thanks for posting this solution. I had the same issue with a Marantz SR6014. Your solution worked perfectly.

 

[SDplinker]

Old post bump... I just ran into this issue as well, but rather than chop up the trigger cable's braided shield, I merely added a short (3") ground wire between the trigger cable input on my receiver and its ground screw. The trigger cable input was isolated by a coloured plastic ring preventing contact between the subwoofer cable and the receiver, so they weren't sharing a common.
View attachment 43920
View attachment 43921

Another old thread follow-up. I have the same buzz triggering my Monolith amp from my Denon x3700h. I made the same cable but still have buzz. I missed the part about the plastic ring isolator.
Does this go under the ground connector (fork) on the Denon, the trigger out (ring connector) on the Denon or under the trigger in jack on the amp?