NDX hissing noise from Optical input

Posted by: bretth on 13 June 2011

Hi

Im using my NDX as a DAC from my TV, Bluray player and Freeview box, connected via optical SPDIF, i have set all the devices to output Stereo PCM, thereby removing any AC3 etc, but after a few minutes i get a hissing noise around the actual sound, so silent parts are still silent, it is very noticable on speach, its terrible,

 

What am i doing wrong?, surley this isnt normal?

 

Thanks

Posted on: 13 June 2011 by DavidDever
Try an audio-only device (no surround) and see if the problem persists - there is no guarantee that your optical or coaxial outputs are not streaming AC3 while your HDMI outputs are streaming PCM.
Posted on: 13 June 2011 by bretth
Originally Posted by DavidDever:
Try an audio-only device (no surround) and see if the problem persists - there is no guarantee that your optical or coaxial outputs are not streaming AC3 while your HDMI outputs are streaming PCM.

Hi

 

I also tried an Apple Airport express, streaming audio from iTunes, which is definatly not surround sound (AC3), and the same problem occurs, intrestingly, stopping and restaring the playback in iTunes corrects the problem for a few minutes, but it then comes back, kind of like the clock is drifting.

 

But playing back the same MP3 files from uPNP is fine, i never get the hissing problem

 

Regarding your question, i have sent all my devices to output stereo PCM from all their HDMI and Optical outputs, although i cant be sure they are actually doing this, i have some confidence that they probably are.

 

any ideas?

 

Thanks

Posted on: 13 June 2011 by Hook

Hi Bretth -

 

No clue if this will help, but the NDX manual, section 4.3.6, shows an option for

S/PDIF input called "Unstable source", which can be set to Yes or No:

 

"...Select No unless the NDX has problems locking to a digital signal. Selecting Yes will enable the NDX to lock to unstable digital signals, however sound quality will be slightly degraded..."

 

If you are using a Mac to run iTunes, and if you have a Toslink-to-Mini-Toslink cable, then you could test directly that way as well.  If you are using a PC, then a USB-to-S/PDIF converter would do the trick as well.   Just following Dave's advice, and trying to think of an easy-ish way to testing a basic, direct-connected audio only source.

 

Good luck.

 

Hook

Posted on: 14 June 2011 by bretth

I have attached a recording of the noise, i dont think my comment regarding hissing is correct, please take a listen to the noise around the guy speaking on the attached file, does this narrow the issue down?

 

I aslo tried setting the input to "Unstable source" as instructed above, but that didnt make any difference, still the noise continued

 

Thanks

Brett

Posted on: 14 June 2011 by BigH47

I get  a similar sound when signal is overloaded.

Posted on: 18 June 2011 by bretth

Hi


They are all standard devices, could they all really be outputting to high a signal?, i dont think so

 

Thanks

Posted on: 18 June 2011 by Hook

Bretth -

 

As Dave suggested above, do you own, or can you perhaps borrow a simple audio-only device like a CD player?  This is a logical first step to determine whether or not the NDX itself has a problem. 

 

If a CD player plays just fine, then that would tell us that the issue lies with your other source devices.  If this is not easily done, then I suggest you take your NDX back to your Naim dealer for testing.

 

Hook

Posted on: 25 June 2011 by bretth

Hi

 

I finally got around to hooking the NDX up to my laptop via optical SPDIF, and sure enough no problems with hissing etc

 

So why are all my other devices causing this?, if it is being over driven then how do i stop this?

Thanks

Posted on: 25 June 2011 by garyi

time to contact your dealer.