Optical audio

I

IncenseMan

New Member
I have been using a Humax Freesat HDD box for some time with no problems... but I've now added a soundbar to my system, and using the optical output from the Freesat box there's an annoying whistle at about 500Hz under the audio. It doesn't happen on the standard electrical outputs. Any ideas how to get rid of it?
 
Think about this logically: the whole point of a digital audio feed is to eliminate interference and signal degradation point-to-point. With the optical connection to your sound bar, you have a digital transmission path from the broadcaster right through to the sound bar itself.

So, you are postulating, either the broadcaster is injecting a whistle into the audio data at source, or the Humax is somehow adding a whistle component to the audio stream (bearing in mind that there is a conversion process if you have selected stereo digital audio rather than multi-channel).

Neither of those possibilities seem very likely to me, so I would blame the sound bar.
 
The whistle is only apparent when the soundbar (a Hitachi model) is connected to the Freesat box. As soon as I unplug the optical connection, it vanishes, even though the soundbar is still in optical mode. There is no problem using the soundbar with the standard electrical connection. In any case I'm not necessarily blaming the Freesat box, I don't care WHERE the whistle is coming from, I just want to get rid of it!
 
Sony Mini Disc players have optical, got one hiding in the back of a draw?

A lot of A/V amps, DVD players, etc have optical.

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But it's an 'a/v amp' that's causing the problem in conjunction to an optical audio source.
Substitution is a recognised, albeit sometimes risky (although not in this case), fault finding technique, and you don't necessarily need to know how it works to diagnose that 'it's not working properly'. But it's best if you do.:)
 
Quite correct about the Sony, but my separate Hi-Fi Tascam MD has in and out; useful for recording off my hummy.

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OK, I think I have now ascertained that the offending whistle IS coming from the Humax Freesat box's optical output, as there is no evidence of it from the optical outputs of either my Blu-Ray player or DAB tuner. So... any suggestions as to what might be causing it, and how to rectify it? (Unfortunately the Freesat box is out of warranty, so I can't return it for a replacement.)
 
I can't think of any reason for it - not that I have a huge experience of digital audio, but from first principles...
 
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