Noise over unity gain
Posted by: tvh3ad on 16 December 2010
Hi Folks - I'm relatively new to Naim; have been lurking for awhile and enjoying the crowd.
I have a NAC202/NAP250.2 with olive hicap and napsc.
I'm using the 'unity gain' AV input on the 202 in conjunction with my HT setup (recent Denon receiver), and I have a noise question..
Specifically, when the Denon is placed in standby and the 202 is still set to the AV input, I get a fair bit of noise through the speakers -- sort of a midrangey sizzle plus a bit of mains hum. With the Denon powered up, the noise is mostly but not entirely gone (you have to put your ear up to the speaker to hear it). If the Denon is muted, the noise goes away completely.
Other things to know / things I have tried:
- I am using balanced power (equitech) and shielded AC mains cables on a dedicated circuit.
- I do not have traditional cable TV
- I have tried every possible permutation of connecting/disconnecting equipment. I can affect the noise level or timbre slightly, but that's about it.
- I have tried using two different RCA-to-DIN cables between the Denon and the 202. A Chord was much noisier. The one in there now was made up by Naim USA and has the shield lifted, I believe. It's better but not perfect.
I would appreciate any ideas - I'm fresh out.
Take care,
Marc
Posted on: 16 December 2010 by Richard Dane
Marc, short of fitting an in-line isolator (sometimes necessary) check with Naim USA whether they slugged the interconnect between the Denon and NAC202. I can't recall the exact value but this usually improves things markedly. Putting the Denon into standby will usually create noise issues - not unusual where you have one item with a floating earth connected in to a properly earthed Naim system.
Do you get the noise even when there's nothing else plugged in to the Denon.
Have a chat with Dave at Naim USA, he's quite familiar with such issues.
I've moved this one to the Home Theatre Room, as appropriate.
Posted on: 16 December 2010 by Geoff P
Marc
If you cancel 'unity gain' on the 202 do the problems go away?
If so I can suggest a way to run the Denon A/V without having 'unity gain' enabled
regards
Geoff
Posted on: 16 December 2010 by tvh3ad
quote:
Originally posted by Richard Dane:
check with Naim USA whether they slugged the interconnect between the Denon and NAC202. I can't recall the exact value but this usually improves things markedly.
Do you get the noise even when there's nothing else plugged in to the Denon.
Do you mean a ferrite slug? No, the cable is straightforward wire. I have a couple of ferrite slugs..I'll try one and see if it helps.
I do get the noise even with nothing else plugged in.
Posted on: 16 December 2010 by tvh3ad
quote:
Originally posted by Geoff P:
I can suggest a way to run the Denon A/V without having 'unity gain' enabled
regards
Geoff
Sounds interesting.. how?
Posted on: 16 December 2010 by Richard Dane
No, by "slugged" I mean a resistor fitted to the i/c. This has cured similar symptoms in the past where a long length of i/c has been used, but it depends upon what exactly is causing the problem... By all means try a ferrite clamp but I don't think that will help here, as they're better on interference.
Have you tried earthing the chassis or the outer edge of the RCAs on the Denon?
Posted on: 16 December 2010 by Geoff P
OK nothing magical:
1) Turn off Unity gain.
2) To use in A/V mode select a volume setting on the 202 that is easy to reset like 9.00 or if you are brave enough even better 12.00 ( you will have to remember to turn it back down when finished)
3) If you have an Audessey setup mic just run the setup as normal. Audessey will automatically boost the volume setting in the Denon on the channels running to the 202 and reduce volume on the others so the volume is balanced as normal.
4) Use the Denon as normal to control the volume of all channels.
5) Whenever you want to use the Denon just set the 202 to the volume value you chose in 2) above.
If you set gain in dB on the Denon using a dB meter, start by boosting the 202 channels to the top of the setting range ( say + 10 dB ) then balance the volume of the others which will probably need settings like -6 to -8 dB.
Either way you can get the same effect as normal without needing 'unity gain'.
regards
Geoff
Posted on: 16 December 2010 by tvh3ad
quote:
Originally posted by Geoff P:
OK nothing magical:
1) Turn off Unity gain.
2) To use in A/V mode select a volume setting on the 202 that is easy to reset like 9.00 or if you are brave enough even better 12.00 ( you will have to remember to turn it back down when finished)
3) If you have an Audessey setup mic just run the setup as normal. Audessey will automatically boost the volume setting in the Denon on the channels running to the 202 and reduce volume on the others so the volume is balanced as normal.
4) Use the Denon as normal to control the volume of all channels.
5) Whenever you want to use the Denon just set the 202 to the volume value you chose in 2) above.
If you set gain in dB on the Denon using a dB meter, start by boosting the 202 channels to the top of the setting range ( say + 10 dB ) then balance the volume of the others which will probably need settings like -6 to -8 dB.
Either way you can get the same effect as normal without needing 'unity gain'.
regards
Geoff
Gotcha...this solution would work if it was just me, but my wife and kids use the same system, so the config needs to be a simple as possible (as in, press one button to watch TV).
Thanks.
Posted on: 16 December 2010 by tvh3ad
quote:
Originally posted by Richard Dane:
No, by "slugged" I mean a resistor fitted to the i/c. This has cured similar symptoms in the past where a long length of i/c has been used, but it depends upon what exactly is causing the problem... By all means try a ferrite clamp but I don't think that will help here, as they're better on interference.
Have you tried earthing the chassis or the outer edge of the RCAs on the Denon?
I'm pretty sure there are no resistors. The cable is short - about 1 meter. I did try earthing the chassis and the interconnect shield, but both of those connections increased the noise level.
Posted on: 16 December 2010 by Richard Dane
Hmmm, OK, sounds like the problem has been cured as best as it can. If you can only just hear anything when your ear is by the speaker then that's a "cure" in most anyone's book. Only other thing would be to send back the Denon and ask them to put a properly earthed PSU inside... (they'd have to totally re-design it and probably double or triple the selling price, but still..)
Anyway, jesting apart, as I say, a noise when the Denon is in standby with parts asleep and parts still active is probably quite normal, in much the same way as if you put an AV procesor to sleep but leave the active subwoofer awake you can get a loud hum. If it's annoying then just remember to either mute the pre-amp or change input. Or leave the Denon powered up but muted.
