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Optimal sound path for TV's optical out?

razRzz

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Hello,

I have a LG CX TV.

I initially wanted to buy 2 KEF Q950 towers and a SVS/Arendal powered sub to connect to a HDMI 2.1 Yamaha/Denon AVR.

But seeing as AVRs with perfectly working HDMI 2.1 are not out yet (for gaming purposes - 4:4:4 4k120hz with ALLM, G-Sync etc.) and I being in need of an audio solution for movies/music other than my crappy TV speakers, I started considering other solutions in the meantime.

After a couple of days, I came up with this sort of solution:

TV's Optical Out -> DAC's Optical In -> DAC's XLRs Out -> Power Amp's XLRs In -> Power Amp's Binding Posts to KEF Q950s.

I was considering the following audio equipment:
DAC: Gustard X16
Power Amp: Hypex UDC400

My main problems with this setup are:
- the addition of a SVS SB-1000 or Arendal 1961 1S powered sub into the mix, without sacrificing the balanced INs/OUTs too much (they have RCA INs, RCA outs, sadly)
- the possibility to push only 80hz+ into the KEFs and keep everything under 80hz just for the sub
- movies with compressed and uncompressed 5.1+ audio and its downmixing
- I guess, volume control, due to the TV's optical out?

My options are a bit limited due to being from Romania.

What can I do to keep the sound path as clean as possible, in my situation?

Thank you.
 

abdo123

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Are you planing to use Stereo for the rest of your life time? If so, then I recommend a MiniDSP product with Toslink input and 4 outputs and to use the MiniDSP for subwoofer integration. There are many MiniDSP products with 4 outputs so pick the most expensive product you can afford.

However with the increasingly rising popularity of Dolby Atmos I really would wait for an AVR with proper HDMI 2.1 support.
 

tgray

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Can the X16 hook into the sub via RCA? I've run two channel systems for years with a sub by using a DAC that has both XLR and RCA outputs. Volume is controlled from the DAC. Both my DACS have balanced + unbalanced outputs and a volume knob.

The TV should have a setting to send just stereo out the optical output, performing down mixing if needed.

For the crossover on the main speakers, you'll have to buy a crossover, filter, or MiniDSP type solution. For my desktop system, I just don't high pass the stereo speakers and it seems fine, but I don't listen that loud.
 

Willem

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I have opted for two channel sound from my TV and Bluray player because I did not want to add many bulky speakers, and because most of my listening is to music rather than video. I use my TV's and BD player's optical stereo outputs into an RME ADI-2 (with volume control), and from there I use the ADI-2's balanced output into my power amp and the unbalanced output into my sub. This works very well. A cheaper DAC with dual outputs will do the same trick. To tame the sub I have inserted an Antimode 8033 dsp unit between the DAC/preamp and the sub
 

mdsimon2

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All good advice so far.

Not sure what the sources look like going in to the TV and cannot speak to your specific TV model, but I have measured significant performance degradation using a TV optical output. In my case the TV optical out was 40 dB worse from a SINAD perspective compared to using a HDMI extractor upstream of the TV.

Michael
 

Willem

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My only possibly comparable experience is that the loudness level from the TV's optical output is much lower.
 

abdo123

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All good advice so far.

Not sure what the sources look like going in to the TV and cannot speak to your specific TV model, but I have measured significant performance degradation using a TV optical output. In my case the TV optical out was 40 dB worse from a SINAD perspective compared to using a HDMI extractor upstream of the TV.

Michael

How can a SINAD loss occur in the digital realm?
 

mdsimon2

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How can a SINAD loss occur in the digital realm?

Elevated noise floor, looked like the TV may have been doing some rather poor resampling. I've attached some purely digital measurements which show the difference. The extractor is perfectly transparent, the TV...not so much. Also somewhat interesting that the level from the TV was 0.5 dB reduced.

Vizio TV.jpg

Extractor.jpg


Michael
 

tgray

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Cool. While the noise floor difference is striking, it's still pretty good (I think :) ).

I know my TV (Sony) gives the option of changing the volume level on the digital output when it is set to PCM, so it's obviously doing something.
 
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Willem

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I cannot find a similar option on my Panasonic plasma screen. I still have to call their support.
 

olinko

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Hello,

I have a LG CX TV.

I initially wanted to buy 2 KEF Q950 towers and a SVS/Arendal powered sub to connect to a HDMI 2.1 Yamaha/Denon AVR.

But seeing as AVRs with perfectly working HDMI 2.1 are not out yet (for gaming purposes - 4:4:4 4k120hz with ALLM, G-Sync etc.) and I being in need of an audio solution for movies/music other than my crappy TV speakers, I started considering other solutions in the meantime.

After a couple of days, I came up with this sort of solution:

TV's Optical Out -> DAC's Optical In -> DAC's XLRs Out -> Power Amp's XLRs In -> Power Amp's Binding Posts to KEF Q950s.

I was considering the following audio equipment:
DAC: Gustard X16
Power Amp: Hypex UDC400

My main problems with this setup are:
- the addition of a SVS SB-1000 or Arendal 1961 1S powered sub into the mix, without sacrificing the balanced INs/OUTs too much (they have RCA INs, RCA outs, sadly)
- the possibility to push only 80hz+ into the KEFs and keep everything under 80hz just for the sub
- movies with compressed and uncompressed 5.1+ audio and its downmixing
- I guess, volume control, due to the TV's optical out?

My options are a bit limited due to being from Romania.

What can I do to keep the sound path as clean as possible, in my situation?

Thank you.
I'm jumping in here a bit because I was trying to find more info on the LG CX's optical out and I found this.
Do you know what the sample rates are for the optical out, is it fixed or does it change depending on the source signal?
I have the CX connected to my laptop via HDMI and the TV's optical out going to my HiVi Swans D300 active speakers. I want to avoid going through my external DAC and feeding an analogue signal to my speakers because the D300 do this DSP thing where the analogue signal is first converted back to digital and then out to analogue.

So my best bet is to know what I'm dealing with in terms of the CX's optical out and then using a WASAPI event in foobar when playing my music.
 

bravomail

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TV's Optical Out -> DAC's Optical In -> DAC's XLRs Out -> Power Amp's XLRs In -> Power Amp's Binding Posts to KEF Q950s.

I was considering the following audio equipment:
DAC: Gustard X16
Power Amp: Hypex UDC400

My main problems with this setup are:
- the addition of a SVS SB-1000 or Arendal 1961 1S powered sub into the mix, without sacrificing the balanced INs/OUTs too much (they have RCA INs, RCA outs, sadly)
- the possibility to push only 80hz+ into the KEFs and keep everything under 80hz just for the sub
- movies with compressed and uncompressed 5.1+ audio and its downmixing
- I guess, volume control, due to the TV's optical out?

.
it is a logical solution. And I'm using similar setup. But be aware that TV is likely processing your sound to downmix to 2 channels, and not in a best way, even though the output is digital over optical link.
Check out miniDSP devices and Denon AVRs to solve your crossover and 5.1 downmix issues.
 
OP
R

razRzz

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Plans have changed quite a bit since I've posted the original thread.

I ended up waiting for the new revision of the Denon AVC-X3700H to be available in my country (which for me was October 8th).

This simplified everything, as expected, and I ended up connecting it to the Q950s + the Arendal 1961 1S sub.

Now I'm already thinking of the upgrades I can still make (go to 77 inch OLED, external amplifiers, add a second sub, add a center etc.).
 
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