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HDTV has no "Analog Audio Output"

My oldest son has a similar problem with a Sony set. We're trying to
figure out the least complex way to get the "optical" audio into a TV
modulator for distribution throughout the house.

You need a Toslink receiver for the optical and an S/PDIF reveiver IC
(or a small FPGA) and a DAC.

Fun fact: with a few resistor changes to the input, you can put the
electrical S/PDIF signal through one of those video sender transmitters
and pull decodeable S/PDIF out the receiver - bandwidth is about the
same as video but the levels are different. Nice clean digital
distribution without noise, until someone microwaves popcorn to go with
the movie, in which case at least it cuts off cleanly.
 
P

Pooh Bear

Jan 1, 1970
0
You need a Toslink receiver for the optical and an S/PDIF reveiver IC
(or a small FPGA) and a DAC.

Fun fact: with a few resistor changes to the input, you can put the
electrical S/PDIF signal through one of those video sender transmitters
and pull decodeable S/PDIF out the receiver - bandwidth is about the
same as video but the levels are different. Nice clean digital
distribution without noise, until someone microwaves popcorn to go with
the movie, in which case at least it cuts off cleanly.

S/PDIF only carries 2 channels.

Is that the format of the digital out ?

Graham
 
Pooh said:
S/PDIF only carries 2 channels.

Is that the format of the digital out ?

Yes, but you can run Dolby AC-3 5.1 surround (a compressed format) over
the same signalling at the same data rate, with receivers that can
handle both autodetecting either AC-3 or PCM. It's true that if using
a 'dumb' PCM S/PDIF receiver IC you'd have to make sure the TV is
always outputting that and not some compressed format.

FYI, you can get a test (PCM) S/PDIF signal off a header on the back of
most current CDROM drives. Terminate it into 75 ohms and look at it on
a scope (but you probably can't tell the difference between a PCM and
an AC3 signal without being able to capture and examine the frame
header)
 
P

Pooh Bear

Jan 1, 1970
0
Yes, but you can run Dolby AC-3 5.1 surround (a compressed format) over
the same signalling at the same data rate, with receivers that can
handle both autodetecting either AC-3 or PCM. It's true that if using
a 'dumb' PCM S/PDIF receiver IC you'd have to make sure the TV is
always outputting that and not some compressed format.

FYI, you can get a test (PCM) S/PDIF signal off a header on the back of
most current CDROM drives. Terminate it into 75 ohms and look at it on
a scope (but you probably can't tell the difference between a PCM and
an AC3 signal without being able to capture and examine the frame
header)

The data rate is ~ the same but the difference is in the frame header ?

I didn't know that.

I know what it looks like btw. My CD player has digital out. And I've
worked with AES format too.

Graham
 
J

Joseph2k

Jan 1, 1970
0
Pooh said:
Jim said:
Hi Guys


My friend has a 42" LG Plasma HDTV (DU 42PX12X) it has only one audio
output via digital "optical" output. I am trying to help him connect it
to his amplified speaker system. The HDTV has one extra monitor RCA
audio output but only works when you are watching standard TV and
processor disconnects it on HDTV channels.

[snip]

My oldest son has a similar problem with a Sony set. We're trying to
figure out the least complex way to get the "optical" audio into a TV
modulator for distribution throughout the house.

...Jim Thompson
What is so hard about puting it through the SPDIF chip from any current
home entertainment "receiver" and using the output of that?
Oh hell, is everything but the RF and PA on one chip?

The presumption being that you have to have a 'home entertainment
receiver' in the first place !

Graham
With home theater receivers costing about 1/10th or less that of the 42"
palsma tv is venture that it is not an unreasonable estimate of likely
equipment available.
 
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