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Audio distortion from Freesat HD channels by optical to a stereo amplifier

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benjaminlross's picture
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I have a Panasonic Viera TX37LZD81 that I have connected by the optical output to my stereo two channel amplifier (a Peachtree Nova). This works fine with SD television and also taking the audio from my bluray player by HDMI from the bluray player to the television. However, whenever I tune to a HD channel on the built-in Freesat tuner, all I get it distortion. I assume this is because the television is outputting a 5.1 surround sound signal when the amplifier can only receive a 2.0 signal. However, I cannot find any settings on the television to change the sound ouput to PCM. Any ideas?

Sizzers's picture
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RE: PCM Setting

 

The manual isn’t terribly clear but it appears that the PCM option is in the “HDMI  Input” settings in the Sound menu.

 

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benjaminlross's picture
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RE: PCM Setting

Fantastic - I will certainly try that! Thanks.

benjaminlross's picture
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RE: PCM Setting

Sizzers wrote:

 

The manual isn’t terribly clear but it appears that the PCM option is in the “HDMI  Input” settings in the Sound menu.

 

 

Isn't this for setting the HDMI input sound though? I wouldn't want to set my HDMI input from the bluray player as analogue - but then surely it wouldn't work anyway as HDMI is digital and so is the optical cable?

Sizzers's picture
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RE: PCM Setting

benjaminlross wrote:

Isn't this for setting the HDMI input sound though? 

Yes, but as it's only one of three mentions of "PCM" in the entire manual, and the only one which appears to have even the slightest relevance to changing the settings, is the reason for the suggestion.

Edit: Having just reconsidered my intitial thoughts it looks at though you're correct.

On my TV in the Sound menu there is a specific option for "SPDIF Selection" which you can set to PCM, so it does look as though it's not possible with your particular model.

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benjaminlross's picture
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RE: PCM Setting

Thanks for checking. I tried experimenting with the HDMI options but it's no better. It's odd that the sound should work on SD channels and blurays (not that I'm complaining) - it's only HD channels that are distorted. Any other ideas about how to set HD channels on Freesat to transmit stereo PCM sound instead of surround sound? It seems like a shame to connect phono leads to my television just to listen to HD channels.

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RE: PCM Setting

Switch to Freesat

'menu'

then 'sound menu'

then 'SPDIF selection'

toggle to 'PCM' (only two options on my Panasonic and they are 'auto' or 'pcm'

Good chance your model is similar.

EDIT. Ok it seems - reading back - you tried this.

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benjaminlross's picture
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RE: PCM Setting

Thanks Chebby. Yes unfortunately my model does not have the option of 'SPDIF selection' for some reason. It is very frustrating!

I am now in the position of having to reconnect phono leads just to listen to HD channels which makes no sense at all...

Andrew Everard's picture
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RE: PCM Setting

What you need is one of these – a DD-to-stereo downmixer with digital and analogue outputs

CYP AU-DM11

Only one problem – £150!

 

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benjaminlross's picture
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RE: PCM Setting

Thanks Andrew. Suddenly the phono cable route looks a lot more attractive!

Any idea why it is not possible to set the sound output to stereo PCM on my TV? Also, any idea why I have no problem getting sound from the Bluray through HDMI and the the opical from the TV?

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RE: PCM Setting

benjaminlross wrote:

Thanks Andrew. Suddenly the phono cable route looks a lot more attractive!

Any idea why it is not possible to set the sound output to stereo PCM on my TV? Also, any idea why I have no problem getting sound from the Bluray through HDMI and the the opical from the TV?

The Blu-ray player is probably detecting that the TV can only output stereo sound (through its own speakers), so is only sending stereo to it which the TV then passes on. Either that or you've told the blu-ray to send stereo yourself.

Andrew Everard's picture
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RE: PCM Setting

benjaminlross wrote:
Any idea why it is not possible to set the sound output to stereo PCM on my TV? Also, any idea why I have no problem getting sound from the Bluray through HDMI and the the opical from the TV?

The TV is 'telling' the Blu-ray player it can only accept stereo over HDMI, so that's what the BD player is giving it, and thus what's available over optical out. The TV designers – well at least the designers of this TV – presumably assume that if you're connecting audio out it's going to be to something able to take surround sound, hence the TV signal goes through the optical out at full fat, rather than downmixed.

I guess that's because in generalconsumerelectronicsland – which is where TVs come from – most people assume you'll be adding something home cinema to the optical out, rather than a stereo amp with a DAC in, or an external DAC.

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benjaminlross's picture
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RE: PCM Setting

That makes sense Andrew.

So no other clever ideas as to how I might get the TV to downmix or is it just unable to do it?

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RE: PCM Setting

benjaminlross wrote:
So no other clever ideas as to how I might get the TV to downmix or is it just unable to do it?

If the TV doesn't offer this option, I fear not...

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RE: PCM Setting

benjaminlross wrote:

That makes sense Andrew.

Mr Everard generally does!

Going back to the original question, I am puzzled by the problem because certainly the Freesat HD channels do not always transmit 5.1 sound, in fact I would say that they mostly transmit only 2.0 sound, at least on my Humax Freesat box. So your problem should arise only when the HD channels are actually broadcasting 5.1 sound, which is quite rarely. The BBC HD channel, when it is broadcasting the Preview loop before actual programmes start at about 4pm, does have 5.1 sound.

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RE: PCM Setting

Considering that a great majority of programmes are only delivered with a stereo mix, then that's probably why you're not getting any 5.1!

Sky seem to be the only broadcaster who actively request 5.1 mixes on their delivered masters. 

Rob