Troubleshooting Speaker buzz/Amp? Anything else to try?

[Duranis]

So one of the classrooms has this:

Nuvo NV-WA30 Stereo Wall Mounted amplifier System: Amazon.co.uk: Electronics

 

Basically a wall mounted 30w amp with two 3.5mm inputs that you can switch between.

 

If you have something plugged into both inputs you get a really bad humming/buzzing noise. If you only have it plugged into 1 then it is fine.

 

I'm not an audio expert so was just wondering if there is some trouble shooting steps I may have missed.

 

What I have done so far:

Tested with 2 entirely different input devices and cables. The problem was the same so assume I can rule out the cables and the input sources?

Checked there were no power cables running near the box, there isn't but there are power and data cables running next to the speaker wires. Will try separating them to see if this helps but AFAIK they have always been set up like this and there has been no changes.

Took the amp off the wall, unwired it and wired it all back up again to make sure there was no lose connections.

 

Is there anything else I can do to troubleshoot this? Is it likely to be an issue with the amp?

 

Thanks!

[difinity]

What are the input sources and have you swapped the amp for one in another room to identify if it's the room/setup or the amp.

[timbo343]

You may need one of these.. http://www.amazon.co.uk/Ground-isolator-audio-noise-removal-Black/dp/B000KHBU1G ground loop isolator.

[Duranis]

What are the input sources and have you swapped the amp for one in another room to identify if it's the room/setup or the amp.

 

Input sources are:

a laptop running 3.5mm to 3.5mm on around a 3 meter cable.

A DVD Player running RCA to 3.5mm, again around a 3m cable.

 

I did replace both with an ipod and a galaxy s6 using half meter 3.5mm cables and it was doing the same thing.

 

Swapping it with another amp was on my list of things to try but have xmax fair here this afternoon so will have to wait until monday to see if there is another one of these somewhere else I can switch around.

 

You may need one of these.. Ground loop isolator audio noise hum removal: Amazon.co.uk: Electronics ground loop isolator.

 

I was looking at them. Do they go on the input source or the output?

 

Edit: PS thank you both

[timbo343]

Output, we had it on our main hall speakers and cured it.

[Arreks]

I'd suspect ground loop as @timbo343, we had something similar the other day that was causing a kind of.. heartbeat.. (there were no inputs).

[jinnantonnixx]

Do you have any hearing loops (Telecoils) switched on? Edited December 11, 2015 by jinnantonnixx

[Duranis]

I'm sure I replied to this but must have not actually hit post

 

Thanks all, I have ordered a couple of Ground Loop Isolator's to test out.

[Steve21]

They're magic pieces of kit At my old place we had some issues with buzzing so rolled them out and worked so well put one in every room ready pre-issue haha

 

Just remember that even if it doesn't fix it on first try, try plugging it on the other side too Sometimes works

 

Steve

[AJWhite1970]

One of our RE teaching staff is an ex roadie sound engineer for U2!!! One of our speakers always buzzed and he said it was because both speakers and projector (the speakers were on an in/out on the back of the projector) were on the same ring and the buzz was something to so with phase resonance. I moved the power plug of the speakers to a different ring (there were a few in that room) and the buzz instantly disappeared. I was impressed!!

 

May be totally unconnected but all I read was buzz and speaker before I started typing

 

Andrew

[clockend25]

Can these be used with the wall-mounted mini amps above? They only appear to have stereo phono inputs/outputs.

[Steve21]

Can these be used with the wall-mounted mini amps above? They only appear to have stereo phono inputs/outputs.

 

We just used use these PSG02699 - PRO SIGNAL - 3.5MM ST TO 2X PHONO, 1.8M . | CPC UK

 

And then the opposite for other side Obviously shorter cable options but being lazy

 

So one is 3.5mm jack and one is 3.5mm socket

 

Steve

[Oaktech]

One of our RE teaching staff is an ex roadie sound engineer for U2!!! One of our speakers always buzzed and he said it was because both speakers and projector (the speakers were on an in/out on the back of the projector) were on the same ring and the buzz was something to so with phase resonance. I moved the power plug of the speakers to a different ring (there were a few in that room) and the buzz instantly disappeared. I was impressed!!

 

May be totally unconnected but all I read was buzz and speaker before I started typing

 

Andrew

 

As an also ex sound engineer - although not U2 - Utah Saints was the most well known I worked for - I was about to suggest running an extension lead to ensure the amp and all sources are powered from the same source.

[clockend25]

Ah so they go on the inputs?

[Steve21]

Ah so they go on the inputs?

 

Depends where the "loop" is, but for example some of our rooms had them go PC -> cable -> isolator -> cable -> projector/amp

 

Others had it as PC -> isolator -> cable -> projector/amp

 

Sometimes a bit of testing depending on cable lengths etc

 

Steve

[Duranis]

Just as a quick follow up. I got a couple of these that just arrived today:

http://www.amazon.co.uk/Ground-Isolator-Stereo-Aux-Input-Filter/dp/B00JWJC5JE/ref=sr_1_1?ie=UTF8&qid=1452168321&sr=8-1&keywords=b00jwjc5je

 

Put on the line in socket on the amp that the laptop plugs into and problem solved. Thanks again for all the help

Edited January 7, 2016 by Duranis
Ability to type...

[Andrew_C]

 

Basically a wall mounted 30w amp with two 3.5mm inputs that you can switch between.

 

If you have something plugged into both inputs you get a really bad humming/buzzing noise. If you only have it plugged into 1 then it is fine.

TL;DR

 

Ground loop. Lift the earth on one of the AUDIO lines. (Never mains earths, whatever some Neanderthals suggest) Should fix it.

 

 

ETA,

 

Another Gotcha with some of the wall plates that have two audio inputs (one 3.5mm jack, and a pair of phonos) is that they are just connected together inside. Thus each connected source will be driving signal into the other devices output. And loosing level because of this, and possibly other effects.

Edited January 7, 2016 by Andrew_C

[Oaktech]

TL;DR

 

(Never mains earths, whatever some Neanderthals suggest)

 

Although sometimes providing one can solve issues too!

[mullet_man]

Sorry to hijack this thread, this summer we are replacing all our teacher laptops, original set up were Dell E-Docks which connect to a wall amp most are Vision Amps.

We had no major buzzing issues but we are moving to HP laptops with a USB C dock and the speakers buzz when connected to the dock when not connected to the laptop, connect to the laptop and the buzz goes away.

 

Any ideas?

[Andrew_C]

Get some isolating transformers.

 

Almost certainly down to how the ground is wired internally.

[mullet_man]

Get some isolating transformers.

 

Almost certainly down to how the ground is wired internally.

Thanks I'll have a look, we've got a lot of classrooms so would need quite a few.

 

Cheers

[DrBeaker]

I had similar with a TV, VGA and speakers in a classroom buzzing constantly. After reading similar posts and likely this very post itself - Installing one of these https://cpc.farnell.com/pulse/pls00548/ground-loop-isolator-3-5mm-p-s/dp/AV25542 solved the problem.

[mullet_man]

I had similar with a TV, VGA and speakers in a classroom buzzing constantly. After reading similar posts and likely this very post itself - Installing one of these https://cpc.farnell.com/pulse/pls00548/ground-loop-isolator-3-5mm-p-s/dp/AV25542 solved the problem.

Thanks, I might get one in and test it to make sure it works.