Ground loop problem.

J

jackal

Guest
Sinnce I bought my Denon, this has reared its ugly head, and only when the amp is in standby, with both subs popping and whooshing away. It seems to be getting worse and no amount of Russ Andrews is working.

Question is, is this a problem that a regular electrician could come out and sort?
 

HiFiRuss71

Distinguished Member
Are you using pukka double screened coaxial sub cables, like the Mark Grant ones in the cable power buys?

Russell
 
J

jackal

Guest
Yup, I am using a specially made phono splitter cable made by Chord (based on odyssey cable, and MonsterBass 400 there on. It was never a problem with my Tag processor.
 

HiFiRuss71

Distinguished Member
Have you tried disconnecting the earth cable to the REL?

<only advisable if it has the CE double square symbol somewhere on the amp plate>

Russell
 
J

jackal

Guest
Would I need to do that on the B&W as well? To be honest I am a bit worried about frying them. Is it a problem that could be solved electrically?

Edit: Hit the post button by mistake.

I mean would an electrician be able to earth all the sockets on the cinema room circuit in such a way that this could be solved (star earthing?)? I don't want to pay a huge callout fee for some plonker to say "errrrrrrrrrrr.............".

I understand it could be an issue of double earthing between amp and subs, hence I understand the clipping of the earth connection, but I would prefer to find an external solution if possible. Thanks for your help so far.
 

Coolit

Active Member

HiFiRuss71

Distinguished Member
An electrician could run a separate spur from the main breaker board to the sockets the AV kit is specifically plugged into.

I think the key is to separate the spur they're on from all the other electrically noisy items plugged into the same ring.

Have you tried turning off the fridge/freezer, washing machine, dishwasher, cooker, etc to see if the intereference is generated from within your own house? If so, I think you may have an answer as to whether a separate mains spur is worth it.

When I put my new kitchen in I had 'leckys' in and they wanted an extra &#163;200 to install a separate spur to the living room AV sockets, pull through speaker cables in the walls AND install speaker wall sockets for the side and rear surrounds.

Well worth the money, but even prior to this, I'd never had serious hum problems (with the exception of the BFD) so I can't claim it actually soved anything, but it certainly hasn't hurt.

I'd try disconnecting the earth from the sub just to see if there's any mileage in geting a separate spur installed though. It'll certainly be cheaper than throwing cash at that shiester Russ Andrews!

If you don't fancy any of the above, it may be worth considering 'home brew' mains leads based around ferite cores, like those on TNT Audio.

I know a reviewer on that site who suffered mains interference and solved his problems with the Merlino.

Russell
 
J

jackal

Guest
Cheers Russell,

Isolating the noise source would be a nightmare as this place is 5200 Sq/ft. I think I'll go the dedicated mains spur route.

Don't tell anyone, but I am using Merlin black widow and Russ andrews P cables on everything (Ian J will kill/ban me as I told another forum member they were useless and not to waste their money - ahem:suicide: ). I also have 5 Isotek neoplugs and two RA Silencers around the house - no good.

It is funny that only the subs are afffected, Even if I unplug the input RCAs the B&W still carries on (REL goes quiet). Power up the amp andf all goes quiet:confused:
 
K

kstrain

Guest
Cheers Russell,

It is funny that only the subs are afffected, Even if I unplug the input RCAs the B&W still carries on (REL goes quiet). Power up the amp andf all goes quiet:confused:

Not a ground loop then. For it to be a ground loop the grounds must have a loop. So there must be two connections to the offending component (one through the mains lead and one through signal ground, for example).

If I understand you correctly, your B&W still hums with no signal input, so the only ground connection is the mains lead. In this case the problem is pickup somewhere in the sub.

So why does it go when the amp comes out of standby? Although I don't know that model, it seems probable that the output goes high impedance when on standby, but very low when on, thereby shorting out the hum.

If the problem is gradually increasing (another thing that does not happen with normal ground loops) the sub is likely developing a fault. Unless, that is, you have recently moved something with a mains transformer closer to the sub, or rotated said thing close to the sub.

You did not say which end of the cable you disconnected: information that may also give a clue.

Ken

ps. for those who have real ground loops due to mains wiring (like me) a cheap solution is to run extension leads from one mains double socket to all components following the same path as the signal leads (loosely spiralling around them in my case) that reduces the enclosed area of the loop to near zero - and the hum is much reduced (about 30 dB in my case). Probably a few percent of the cost of rewiring.
 

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