earth hum

I had exactly the same problem with a nait3 - I took it back to my dealer who performed a mod (I'm unsure what) to eliminate the problem.

Now I get a hum whenever the thing is *not* connected to a receiver, but since it's currently the rear amp in an A/V setup that's less of a problem :-)

I had this exact problem. I tracked it down to the fact that when I removed the sky cable it went (clearly the sky dish had a different ground). I take it you are only getting hum from your nait and not any of the speakers connected to your rotel av processor? If so then the problem is easily fixed. Get one of these:

http://www.beststuff.co.uk/xitel_ground_loop_isolator.htm

Basically it cuts the earth between the two bits of equipment it is connecting (the signal still gets through fine). This is better than some ground loop isolators which can alter the signal. It cured the problem completely for me.


regards,

Tam

This will be a frequent problem now that Naim systems are being connected to AV systems. It arises because we earth signal to ground at the CD player. The AV components often reference to another ground potential - this being most common through a SKY box or distributed aerial system in blocks of flats.

You need to speak to your dealer or SKY installor to get an isolator. This should be fitted inline in the correct position within the AV system (probably the aerial lead to the television) to prevent there being two earth points at differing potentials.

Adam and co.

It can also be due to the A/V receiver via it's pre-out sockets. I had a Denon and got hum via it in "Unity gain" mode. I happened to switch to a Sony and the problem went away. I can only assume the earthing arrangements in the two receivers were different.

regards
GEOFF

Adam,

As you thanked Marc Evans for the tip are you suggesting I send the Nait (it's a Nait 5 - not i - BTW) back to Naim for a mod - or did you mean to thank Tam for his suggestion of the ground loop isolator?

Geoff P,
which Denon reciever did you use, and how did you identify the problem?

andy c!

quote:

---

Originally posted by woody:
Adam,

As you thanked Marc Evans for the tip are you suggesting I send the Nait (it's a Nait 5 - not i - BTW) back to Naim for a mod - or did you mean to thank Tam for his suggestion of the ground loop isolator?

---

Whoops - missed that - should have been Tam.
The Ground Loop Isolator - or similar.
Earthing problems are difficult to solve "remotely" and you would be better using the isolator to (err) isolate the problem rather than do things to the amplifier to compensate for a problem properly identified as being elsewhere.

Guys, I tried the Xitel ground loop isolator between the processor preouts and the Nait AV input but it appeared to make the problem much worse. I've currently managed to reduce it by plugging the nait, processor and TV into the same mains block. It seems to be the TV that is the problem. Any more ideas?

Hi,
i identified the TV as the earthing problem in my set up (Denon 2805 reciever, Denon 2910 DVD player, Philips 32PF9986 LCD TV - the pre outs on the denon feeding the 282's unity gain).

This in effect electrically isolated the 2805 from the other av equipment, allowing the unity gain earthing to do its job properly.

I got round this by using optical leads from the DVD and Sky+ into the Denon 2805, and not using any video switching the 2805 has (as bit of a waste but my 2 channel is more important). I used the isolators for the DVD-a output of the 2910 - you cannot use the isolator for the digital coaxial signal as it does not work!

hope this helps,

andy c!

quote:

Originally posted by woody:
It seems to be the TV that is the problem. Any more ideas?

Woody,

It sounds like you have a ground loop between your electric supply and the your cable television ground. You will need a ground loop isolator for your sky cable to eliminate the problem.

John

quote:

It sounds like you have a ground loop between your electric supply and the your cable television ground.

The easy but long winded way to sort this out is to disconnect everything from the Naim kit, and then connect and disconnect individual bits to identify the item causing the buzz. In my st up the Sky or DVD , when not connected to the Tv, did 'not' induce a buzz. As soon as the tv was connected the buzz was there, hence the isolation of the reciever by using optical leads.

andy c!

PS one thing for certain - these problems are a right pain.

I needed two of those thingies, to get rid of the hum:

http://www.monacor.ch/int/en/produktseite_suche.php?artid=4864&spr=EN&typ=full

One for the tuner and one for the tv. Both are plugged in the broadband cable feed (not in the rca/phono cable).
Sometimes you'll have to check different positions, until you get the best results: directly on the wall plug, at the input of the first device, at the output of first device, at the input of the second... It doesn't seem to be exact science there!?

Silence is golden, golden :-)
Adrian

Adrian,

It may well be the aerial but currently I'm not using satellite/cable just simple old analogue (UHF). Could I have problems from the aerial?

I guess I need to spend an evening plugging and unplugging things

quote:

Originally posted by woody:
Guys, I tried the Xitel ground loop isolator between the processor preouts and the Nait AV input but it appeared to make the problem much worse. I've currently managed to reduce it by plugging the nait, processor and TV into the same mains block. It seems to be the TV that is the problem. Any more ideas?

This is really weird - perhaps it was faulty - mine cured the ground loop perfectly as it should (cutting the the ground between the two). Maybe I'm being silly, but I can't understand how it could make things worse. I'm sure if you get it in the right place it will work, assuming of course your problem is a ground loop.

First thing, as already been said, start unplugging things until you know exactly what is the cause. It could well be the aerial (again, I had this problem with the aerial connection to my NAT 101), in which case one of these should do the trick:

http://www.simplyautomate.co.uk/productDisplay.asp?prodId=5346

Annoyingly, it has f-type connectors (as opposed to the more normal coax ones here), so you'd need adaptors, but I've been unable to find one that didn't.

It's worth noting that these don't seem to work on sky cables (I think sky actually need the ground unbroken - anyway connect one of these and I get no signal).

Sorry my initial suggestion wasn't more use.


regards,

Tam

Tam, don't worry about it!

Now, the thing is when I have the Xitel between the pre-outs of the processor and the AV input of the Nait I get a really terrible noise - the same noise as when, with a given input selected, connecting an RCA lead before it's connected properly. If that makes sense.

Without the Xitel there's hum but it's not that bad! So at the moment I've removed the Xitel completely.

I made sure everything was powered down (incl. switching off at mains wall socket) before connecting it up.

Maybe the Xitel is faulty?

The problem appears to be when anything is connected to the TV. Currently I have RGB SCART from DVD player to TV and that's it. If I disconnect the SCART lead the problem disappears. However, clearly I need to use this as without it it's kind of difficult to watch movies(!)

If I use the Xitel between the analogue out of the DVD player (Denon 2200) and the processor it makes no difference.

Oh, one more thing...the TV seems to chuck out a huge amount of RFI even when on standby. Is there anyway to minimise this? (one of those isotek jobbies?)

Any advice most appreciated.

Sounds to me like it's your tv aerial. This is easily confirmed by having everything else connected up and the disconnecting this (and see if the hum vanishes) - make sure you disconnect it where it enters the system (i.e. at the vcr if the aerial loops through this).

If this does the trick, then putting an isolator like the second one I mentioned has worked well for me (but then so did the xitel)

If the xitel isn't causing problems between the dvd and the av processor then that suggests it isn't faulty, but I don't know (there's not exactly much in there to go wrong).

One temporary measure I've used in the past to minimise this problem, until I can cure it, is to adjust the speaker output levels for center and surround on the processor so they're as low as possible, that way, instead of using unity gain, I can have the naim volume control down fairly low (and still have a good balance between all the speakers) however the hum should be much less audible.

You can try an isotek thing, although it it's a ground loop these won't help (perhaps it isn't and that's why the xitel won't work). Worse, I've found they only serve to make the rest of the system sound much, much worse.



regards,

Tam

Tam, disconnecting the TV aerial makes no difference

Hmmm (no pun intended), now I'm really stumped.

What is the connection between your dvd and the processor? Is is the tv connected to the processor as well? Are you using any other av sources, e.g. vcr?

At this point it's possibly worth pointing out that ground loops are one of the blackest of the black arts (something you may already have gathered).


regards,

Tam

Tam,

Connection between DVD player and processor is:
- coax for DD/DTS
- 2 x analogue RCAs for CD/SACD/DVD-A (it's a universal player - not that I use them much as the CD5 slaughters it)
- 1 x composite video (for setting things up).

TV is connected to processor via a composite connection to VCR. VCR connects to TV via SCART. DVD connects to TV via SCART and composite (via processor) as discussed.

I have a VCR and xbox (which I know doesn't cause the problem as I had the problem before the xbox).

Complex eh?

Did you sort out the problem in the end?

I sorted out my mates Nait 5 hum problem by connecting a single wire from the case of his DVD player (I just used one of the case screws to fix it) to one of the screws that holds the power socket onto the metal back-box which is itself earthed.

Sorted the hum immediately and for zero cost

I have just cured the earth hum problem that I experienced from the cable that connects to my NTL box.

Previously I had to unscrew the cable from the box when I wanted to play music.

As Adrian recommends earlier in this thread I bought a RF isolating transformer from Cybermarket....sales@cybermarket.co.uk and fitted it into my NTL cable this cured my earth hum problem.

Part No Monacor RFT-3.

This cost me £11.44 inc p&p.