12V Trigger buzz

[TomekNet]

I've connected SVS sub to my Denon 3700 AVR with a 6-meter mono mini-jack cable and I hear a buzz in all speakers.
After I disconnect the trigger cable buzz stops.
Is there a way to solve this?
All equipment is connected to a single wall socket via the strip, btw.

 

[peng]

I've connected SVS sub to my Denon 3700 AVR with a 6-meter mono mini-jack cable and I hear a buzz in all speakers.
After I disconnect the trigger cable buzz stops.
Is there a way to solve this?
All equipment is connected to a single wall socket via the strip, btw.

Without being there, I would suggest one quick fix would be to not use the trigger on the sub, just use the auto sensing feature. I have never found a need to trigger the sub. Trigger an ext. amp yes, if it does not have auto sensing.

 

[oupee]

Denon or SVS seems to have cheated something. Or both. The trigger should operate via an optocoupler.

 

[DonH56]

I've heard this a few times, wherein the trigger cable creates a ground loop. Vexing. Plugging everything into a single outlet (strip) often helps but is not a cure all of the time. I would use a line-level isolator on the signal cable to the sub, or try something like a Hum-X on the AVR (maybe the sub but check the power line rating for the sub -- the Hum-X is only good for 6 A, ~720 W, I think.)

Signal isolators: https://smile.amazon.com/s?k=ground...fix=ground+is,aps,190&ref=nb_sb_ss_ts-a-p_1_9
Hum-X: https://smile.amazon.com/Ebtech-Hum...s=Hum-X+ground+isolator&qid=1610296964&sr=8-3 (probably cheaper elsewhere)

 

[tvrgeek]

Have you tried lifting the ground on the trigger cable?

 

[TomekNet]

I will try the auto sense feature for now on the SVS as @peng suggests. Previously I had a bad luck with this in the SVS but it was perhaps Yamaha AVR fault. With Denon it seems to work fine for now (better pre-outs probably)

Anyway I'd like to know if I can solve it in terms of triggering a power amp in the future.
@tvrgeek : what does it mean to "lift the ground" exactly? English is not my native language.

 

[tvrgeek]

The 12 V trigger is two lines. 12V and ground. If you have a ground loop as the signal lines also have ground, the test I suggest is to disconnect the ground on the trigger cable. Of course that means slicing open the cable to cut it so if it did not work, you trashed a cable.

I use auto-sense on my subs. ( Old O-Audio BASH plates) and it works fine. The auto sense on my Parasound main amp is a bit slow.

I guarantee you, your English is a lot better than my Spanish or German!

 

[wwenze]

12V trigger is usually just a minijack? You can just tape over the ground.

 

[bigguyca]

I will try the auto sense feature for now on the SVS as @peng suggests. Previously I had a bad luck with this in the SVS but it was perhaps Yamaha AVR fault. With Denon it seems to work fine for now (better pre-outs probably)

Anyway I'd like to know if I can solve it in terms of triggering a power amp in the future.
@tvrgeek : what does it mean to "lift the ground" exactly? English is not my native language.

As with many subjects, a quick Google search will provide lots of sites that cover "lift the ground."

 

[Adam_M]

I had a similar problem, and the optocoupler solved the issue. I don't remember the exact device I used, but I soldered up the reference design for whatever coupler it was, put it inline with the trigger, and solved the issue. There's a ton of them.

 

[TomekNet]

The 12 V trigger is two lines. 12V and ground. If you have a ground loop as the signal lines also have ground, the test I suggest is to disconnect the ground on the trigger cable. Of course that means slicing open the cable to cut it so if it did not work, you trashed a cable.

I went this way, eventually. I've unscrewed the mini-jack plug, disconnected and isolated the ground/shield. Works perfectly, both with SVS sub and NAD C298 power amp. So it seems ground is was provided from Denon to those components (or vice versa) both over low level interconnects and the trigger cable, what created the loop. Thanks, @tvrgeek.

By the way, Emotiva ET-3 trigger expansion module does not isolate the grounds between the input and the outputs. Pitty, it might do that easily as there is external 12V power provided.