Question Ground loop insanity.

No Naim

Novice Member
Joined
Jul 15, 2014
Messages
6
Reaction score
1
Points
27
Age
41
Location
Bristol, UK
Hi all!

My first post but a long time user of the forums knowledge base. I am having quite a frustrating time with what I believe to be a ground loop in my new AV/hifi system. I will try to supply all relevant details. It is as follows

Yamaha RX775 AV Receiver connected via pre-outs to Naim Nait 5i AV input.

Into the receiver I have via HDMI - sky box, Apple TV. Hdmi out to TV.

Into the Nait 5i I also have a Rega Dac.

I have a BK subwoofer connected to the AV receiver and also connected on the high level input directly to the speaker posts on the back of my speakers - as per Naims instructions.


So.. To begin with I had a hum through the front speakers on ALL inputs on the Nait. After help from Naim I connected a small piece of wire from a chassis screw on the Nait to the outer of one of its unused RCA sockets. Bingo! It cleared up all hum on all inputs *except* the AV input. When I remove the interconnects between AV receiver and Nait it disappears.

I tried running an additional second piece of wire from Nait chassis to the phono ground post on the AV receiver and that cleared it up just a bit but not completely. I have also tried a maplin Ground loop isolator between amp and av receiver but it didn't really help at all.

I have tried plugging, unplugging every single component of my system and starting with the bare bones. All I can conclude is that the hum is there even when there is nothing plugged into the AV receiver and the only connection is to the Nait. I *think* The hum does change a bit and can get better or worse depending on what else is plugged into the AV receiver but it definitely is there when the only connection is to the Nait via preouts.

I have also tried experimenting with all combinations of using the same/different wall sockets to no avail.

Therefore, I really am at the limit of what I feel I can try next. I'm wondering about getting a different receiver but not even sure if that would help. If anybody could offer any help and save my sanity I would be extremely grateful.

Many thanks in advance

James
 
I had a similar problem and never solved it... Very annoying but am moving soon now so I'll have another go at it!

One thing that was suggested to me that I didn't try was (if I remember correctly) adding a couple of resistors to the speaker wire (or something!!) to essentially drop the output volume which could lower the noise floor.

This would work in my case as the noise I experience is constant no matter the volume / level of amplification. So the amp would be running at a slightly higher level but the noise would be masked...

Maybe I'll find the thread at some point, or someone else will know what I mean and explain it better! Careful not to short your amp!

P.s I also tried isolation things like you mentioned about maplin products - none worked, some made it worse, I think this was down to the cheap quality rather than the isolation.
 
I had a similar problem and never solved it... Very annoying but am moving soon now so I'll have another go at it!

Moving house - that's one thing I haven't tried yet! I hope the hum goes for you this time and thanks for the speaker resistor suggestions, I'll keep that in my locker as something to try.

I found that for me, the hum can only be heard when the integrated amp is near max volume. Why would I have it at max volume you say? Well I got this particular amp because it has the Unity Gain or "HT passthrough" feature on the AV input, which means the amps volume control is disabled on this input and I just use the AV receivers volume control. It's a nice feature. When the intregrated amp is acting just like a power amp like this, it's own volume is automatically set at near maximum. At this massive volume, the amp reveals all sorts of hum and noise.


Yes the maplin ground loop isolator seems pretty poor - I'm not sure why Naim recommend it. I haven't totally given up on isolators yet, since yesterday I was giving it another go and found that the thing acts like an antenna for mains noise. When it was resting near my 8 way mains block the Hum was LOUD, when I moved it up onto the top shelf of the AV rack it became quite quiet. I'm not totally sure why but it's given me some hope!

All the best,

James
 
Since yours is due to near max volume you will definitely have noise and will struggle to get rid, your down to all sorts of tweaks to try and improve it.

The resistor thing in this case would be counter intuitive.

Perhaps there is some noise coming through the power cable? Use an isolating power supply / mains conditioner? Try to plug it into its own wall outlet first and maybe even turn off everything in your house like fridges etc, see if this affects the noise at all, if so you know the mains might be carrying the noise.

How long are you interconnects and speaker cable? Also try to get some really shorts connections as it may be your cables allowing static in. Perhaps you have a spare bit of speaker wire you can try at about half a meter each, see if that helps?

Obviously unplug everything else from your system in order to isolate the problem.

Good luck but I think you will struggle and may need to rethink why your using max volume.
 
Is all equipment plugged into the same main supply?
Ideally have a socket strip that everything goes into.
 
Great tips, thank you for the I formative reply.

I definitely do have noisey mains. I also live above a butchers and they have industrial sized refrigeration going 24/7 - I guess this can't help the situation!

If I don't use unity gain ill need to recalibrate the AV receiver with the intregrated amps volume set at around 12 o'clock. At this volume I know at some point I'll switch to a different input and blow my head off!

I think you are right it's a matter of tweaking and I'll go through the steps you describe. I have tried a tacima power conditioner block and it made no difference unfortunately.

As I mentioned, when I use the ground loop isolator and make sure the isolator itself is well away from all mains sources I get almost zero hum at max volume. So I just need to find a neat arrangement to do this and I should be golden! Why this is the case I'm not totally sure - is it because the isolator redefines where the signal ground is and then picks up mains noise itself?
 
Is all equipment plugged into the same main supply?
Ideally have a socket strip that everything goes into.


Hi trollslayer

Yep everything goes to the same supply. I've tried (I think) every combination of sockets and power strips. but so far no difference.

I will keep experimenting.

Cheers!
 
I had a very similar problem recently and found that one piece of equipment was causing a hum, even when it wasn't switched on.

The culprit in my case was a Cambridge Audio DAB tuner.
During the "test every connection" process, I found that the hum vanished when I disconnected the stereo phono lead from my DAB to my receiver.

The solution was to replace the phono connection with an optical (toslink) one.
 
Thanks Roohster - that's interesting that the DAB didn't even need to be turned on!

Unfortunately my hum is between AV receiver and Amp even when nothing else is connected.

However I have had success today with a better ground loop isolator - the Ebtech Hum Eliminator. Reduced the hum to almost nothing. I would have to have my ear pressed to the speaker to hear it very faintly now. It only has 1/4" jack inputs and outputs so I used RCA to jack adapters. No degradation to sound quality. It's a quality unit, well built and I'm really pleased with the results.

Sweet sweet humless silence.
 
Glad to hear you sorted it out :)
 

The latest video from AVForums

TV Buying Guide - Which TV Is Best For You?
Subscribe to our YouTube channel
Back
Top Bottom