Can I use simple A/D for TV's "Optical Digital Audio Out"?

[larrym]

I want to connect my LG 42LK520 TV's audio--"OPTICAL DIGITAL AUDIO OUT--to external speakers. Old external speakers. I'm trying to improve the TV's audio, and save money, so want to pipe the audio from the TV to my old analog receiver that includes RCA input connectors and is wired to speakers. I run a Blueray player and Comcast Cable into the TV, never over the air.

I see a $23 (http://www.monoprice.com/Product?c_id=104&cp_id=10423&cs_id=1042302&p_id=6884&seq=1&format=2 ) "Digital Coax & Optical Toslink to R/L Stereo Audio Converter" but it has a big note, "IMPORTANT NOTE! This device will NOT decode 5.1-channel signals. It will ONLY convert 2-channel digital stereo (PCM) input signals to analog stereo output. This will not work with TVs that only output 5.1-channel digital signals!"

I don't know what the output of this mysterious TV connector is, doesn't show online or in the owner's manual. I would hate to buy the A/D device then find it doesn't work.

I realize I could buy a more modern soundbar or AV setup, but that's probably 10X the cost of this.

Does anyone know what the output of this TV connector is, or have other ideas to connect my TV to an analog receiver? Thanks![/B]

[jagabo]

I just opened up the TV, disconnected the internal speakers, and ran the wires out to external speakers.

[newpball]

Alternatively get an old receiver with optical input from craigslist or similar site.
That should set you back perhaps $30-$50.

[pippas]

I see a $23 (http://www.monoprice.com/Product?c_id=104&cp_id=10423&cs_id=1042302&p_id=6884&seq=1&format=2 ) "Digital Coax & Optical Toslink to R/L Stereo Audio Converter" but it has a big note, "IMPORTANT NOTE! This device will NOT decode 5.1-channel signals. It will ONLY convert 2-channel digital stereo (PCM) input signals to analog stereo output. This will not work with TVs that only output 5.1-channel digital signals!"

I don't know what the output of this mysterious TV connector is, doesn't show online or in the owner's manual. I would hate to buy the A/D device then find it doesn't work.

Couple of points:

- Firstly, you are looking for a D/A device not an A/D device, as you described above.
You've linked to a D/A device, so it's probably just a typo. However there are A/D units that look identical.. so make sure you order a D/A device.

- The device you linked to is re-badged and sold by many different companies. You can find it a lot cheaper than that
(See here for example : http://www.amazon.com/Portta-PETDTAP-Digital-Optical-Converter/dp/B005DIRI6I/ref=pd_cp_pc_2 )

- Although your manual doesn't mention 5.1 or stereo for the optical Toslink output, I would be amazed if the output from the TV was not stereo.
Plus, if you buy it from Amazon you could return it in the unlikely event that your TV optical output is 5.1....

[usually_quiet]

In this case, there may be be no audio available via optical Toslink. Sometimes the Toslink out from a TV only works if the TV's digital tuner is used, and the OP isn't using it.

[larrym]

Thanks, Jagabo, Newpball, Pippas and Usually_quiet! Good information. A couple of follow-up questions, please:

--Is there any way to know in advance if there is an audio signal coming out of the Toslink port? Or do I just need to hook it up and try it?

--Assuming there is a stereo signal, do you think this D/A conversion will provide good audio? I see the following specs on the converter:

Supports sampling rate at 32, 44.1, 48 and 96 KHz
24-bit S/PDIF incoming bit stream on left and right channels

Thanks again for your great help!

Larry

[Cornucopia]

Most LG TVs do have audio passthrough in the TOSlink out port (mine does and it's just a middle-of-the-road model), and that is for ALL incoming signals.

Assuming good components in the DA circuitry (depends greatly on mftr), it SHOULD be fine-to-great. YMMV, however, if you go the cheap route.

Scott

[pippas]

--Assuming there is a stereo signal, do you think this D/A conversion will provide good audio? I see the following specs on the converter:

Supports sampling rate at 32, 44.1, 48 and 96 KHz
24-bit S/PDIF incoming bit stream on left and right channels

As I mentioned in my earlier post, these D/A devices all seem to be from a common (Chinese) source. The only difference between the several units I've seen is the screen printed words on the enclosure, and the type of external 5V DC PSU supplied with the unit.

Internally they all appear use a Cirrus Logic 8416 DIA receiver (see here http://www.cirrus.com/en/pubs/proDatasheet/CS8416_F3.pdf )

... and a 4344 DAC (see here http://www.cirrus.com/en/pubs/proDatasheet/CS4344-45-48_F2.pdf )

From those specs, you can see that the audio quality from those devices is pretty good. The PCB layout is also a pretty standard SMD layout, so shouldn't give any problems.

The only unknown is the quality of the 5V DC power supply that comes with these units. Most are OK... but they are generic cheap Chinese wall warts, and, I suspect, may even vary from batch to batch from the same supplier!

The D/A unit uses an internal (AM117 ) voltage regulator, so most power supply deficiencies should be dealt with OK.
I have on occasion though, had an external power supply which is a bit noisy. So, possibly a bit of 'luck of the draw' on that one. You'll probably be fine.....

[fritzi93]

Most LG TVs do have audio passthrough in the TOSlink out port (mine does and it's just a middle-of-the-road model), and that is for ALL incoming signals.

Assuming good components in the DA circuitry (depends greatly on mftr), it SHOULD be fine-to-great. YMMV, however, if you go the cheap route.

Scott

Yes, my LG TV does DD 5.1 passthrough from all sources (65LW6500). It was their flagship TV in 2011; dunno if their cheaper TVs do, but I should think so.

[EDIT] I just checked the audio settings on my TV, also the manual, and I see no way to set the toslink output to stereo PCM.

Maybe you can set your Blu-Ray player and cable box to output stereo PCM to be sure it will work with the converter? I know I can do it with my BD players (2 different models), but am unsure about Comcast cable boxes. We cut the cord last year, so I can't check. As I recall, on the cable box, first turn it off, then hit menu. Check the options there.

Alternatively, there's the headphone jack. For a while I used a 3.5 mm minijack/RCA splitter to an old soundbar without toslink input.

[usually_quiet]

My guess is that all Comcast HD cable boxes can be set up to output two-channel LPCM audio. It is probably the default setting for HDMI audio.

There is a hidden menu with a selection controlling HDMI audio output. Selecting AC3 passthough or LPCM is allowed. The menu is accessed by turning off the cable box and quickly pressing the Menu button on the remote. For my box the menu option is called "HDMI Settings", but that might not be true for all Comcast HD boxes.

[larrym]

Thanks to all of you for the great advice! I will buy a cheap D/A and try it. I understand the issues you've outlined, but for $20, worth a shot!

Larry