Earth loop-power conditioners

[Groovertb]

Hi guys
Hoping someone can help me out.

I've just bought a tv. I have my studio set up in my living room and plugging the tv into the aerial socket has, from my research so far, caused an earth loop and is creating a hum on my monitors.

When I unplug the aerial lead, the hum stops.

Someone suggested trying a power conditioner, but for what I understand that will fix the hum and not the earth loop. As I'm in a block of flats it seems my options for fixing the earth loop are zero.

Has anyone had experience of this problem? How did you fix it?

On the power conditioner front I was thinking of the Samson powerbrite. I'm only using in the home, so I'm guessing nothing too fancy is required.

http://www.dv247.com/studio-equipment/samson-powerbrite-pb10-rackmount-power-conditioner-and-distribution-unit--47392Samson power rite

[James Perrett]

Have you got your TV connected to your recording setup? What is the aerial cable connected to - some kind of amplifier or distribution system?

Power conditioners are rarely needed - especially in the UK where mains power is pretty clean already. I'd save your money and methodically check out how the ground loop is occuring. You may need an isolator between your TV and your recording system if you want to hook them together but you might get away with just changing the cables.

[Hugh Robjohns]

I've just bought a tv. I have my studio set up in my living room and plugging the tv into the aerial socket has, from my research so far, caused an earth loop and is creating a hum on my monitors.

Quite possibly. I presume you have connected the audio outputs of your TV to the studio gear. If that is the case, you will need to install a line-level transformer isolator between the TV and the studio gear. ART's DTI is one solution with very convenient connector options.

http://artproaudio.com/artcessories/audio_solutions/product/...

Or Orchid's dual transformer isolator if you can cope with TS/TRS plugs.

http://www.orchid-electronics.co.uk/dual_isolator.htm

Someone suggested trying a power conditioner, but for what I understand that will fix the hum and not the earth loop.

It won't do either. The hum is caused entirely by the ground loop. Condition the mains feed will make no difference at all, other than emptying your wallet.

As I'm in a block of flats it seems my options for fixing the earth loop are zero.

It's incredibly simple to break a ground loop, as described above, and the fact that you are in a block of flats has nothing to do with it.

Perhaps if you can provide more information about your set up we can be more precise about the optimal solution. It is possible that a more appropriate solution would be an RF 'Braid Breaker' in the aerial cable rather than an audio transformer in the audio leads.

H

[Groovertb]

Thanks for getting back to me guys

My monitors aren't connected into the TV at all. I've an MBP, to an Apogee Duet to Yamaha HS80s and HS10.

The aerial lead goes from the socket straight to the TV. The TV is not connected to the monitors.

The TV and one of the HS80s is connected to a socket on one side of the room, the hs10 and the other hs80 on the other suing surge protected extensions.

I've already unplugged everything and the thing that makes the biggest difference is disconnecting the aerial lead from the socket as it kills the hum. There is a little hiss, but nothing that is noticeable unless I have my ear right next to the speaker.

Hugh, the aerial lead you suggested looks a good place to start. I've nay just gotten a tv after a 3 year break from it, so I've just had the mac connected up, and never had this problem until now.

[Hugh Robjohns]

The TV and one of the HS80s is connected to a socket on one side of the room, the hs10 and the other hs80 on the other suing surge protected extensions.

Ah -- OK. In that case I suspect that the screen of the aerial socket is connected to a ground elsewhere in the building, and that is then forming a loop with one wall socket safety earth through the TV.

Can I suggest you try powering the HS80 (that currently shares a socket with the TV) from the same wall outlet as the rest of the studio gear. I think that if you run all the studio gear from a single wall outlet (not the one the TV is plugged into), using decent plug-boards as necessary, this problem will go away.

If it doesn't, then the TV aerial braid-breaker leads is the next thing to try.

H

[Groovertb]

I've already tried running all the speakers off one side and it made no difference, but would it be worth running it like that anyway?

I've ordered the aerial lead, so I shall let you know what happens when it turns up.

[Hugh Robjohns]

I've already tried running all the speakers off one side and it made no difference, but would it be worth running it like that anyway? .

Always!

Interesting that running everything off one socket made no difference. That suggests its not a simple ground loop at all. Intriguing! Let us know what happens with the braid breaker!

H

[Groovertb]

Talk about speedy service. The lead with the bead just turned up and it's gotten rid of the hum almost completely. I can still hear it if I put my head right up to the monitors. There's been a hiss on them since I got them, which is still there, but again I need to put my head up close to hear it.

I'm guessing routing all the audio stuff off to one socket should help with the last little bit?

Thanks again Hugh

[Hugh Robjohns]

Glad that's solved your problem.

It's always best to power all the audio equipment from the same wall socket where possible, as that minimises the likelihood and audibility of any ground loops.

It's quite normal to hear some hiss from the tweeter when your ear is right next to it. The totally silent amplifier hasn't been invented! But you shouldn't be aware of it at all when listening from a normal distance.

There shouldn't be any audible hum at all from the amplifier... but interference getting into the system earlier in the chain or minor ground loops can cause problems like this. Again, if you can't hear it when listening at a normal distance I wouldn't worry about it.

H

[Groovertb]

That's good news then

Thanks again for your help Hugh