{Bits of the quote removed to concentrate on the critical facts}
This combination of facts eliminates the “normal” way of routing sound for an HDMI-based signal source: Roku -> Receiver -> TV.
Your only hope (other than Obi-Wan Kenobi) would be if the TV has an audio output that is compatible with an input on your receiver. It could be a pair of RCA jacks (red and white centers, traditionally) or it could be a single digital output called S/PDIF (an RCA jack with an orange center if non-optical, or a square little socket for the optical (TOSLINK).) And I suspect that, as old as your receiver seems to be, the S/PDIF option won’t work (TOSLINK S/PDIF was introduced in 1983, so your 30-year-old receiver would probably have to have been pretty high-end to have it.)
Since we don’t know your TV’s or receiver’s model numbers, no one here can definitively tell you whether you have a workable arrangement (either digital audio out from the TV to a digital input on the receiver, or an analog audio out from the TV to a conventional input on the receiver).
Mixing home entertainment hardware from different generations is hard, and often you “cain’t get thar from here” without replacing something or buying more hardware (like format converters).
Be cautious when hooking up headphone jack out to stereo in; headphones are 16 (32?) ohms and may cause an impedance mis-match with the stereo. Could produce an overload of some sort.
Regardless of the TV’s specs, it should be possible to use an HDMI signal splitter like this which extracts audio signals from the HDMI, and passes the video signal through to the TV. Put this splitter between the Roku and the TV (i.e. HDMi cable from Roku to splitter, and HDMI cable from splitter to TV), and connect the splitter’s audio output to the receiver.
Note that the splitter’s description says it only works with 2-channel audio. Might want to check first that the Roku can be set to output 2-channel audio instead of 5.1 or whatever.
Your HDMI cable carries both audio and video signals. So an HDMI from the Roku to the TV will carry both.
You need to do either of two things:
Run another cable from the Roku audio outputs to the stereo audio inputs, if they have compatible output and input jacks.
Run another cable from the TV audio outputs to the stereo input jacks.
You may be able to buy some adaptors if the plugs on the machines are not directly compatible. There’s no way to know this without either pictures or the model numbers of your equipment.
The impedance mismatch won’t cause any problems. It’s just what impedance the little amplifier in the TV’s output is expecting to drive. The stereo input will be high impedance, so the little amplifier won’t have to put out any current to speak of.
I have my TV’s headphone jack going into my stereo amp (through a little accessory that has a 3.5 mm stereo plug going to two RCA plugs). I think that’s the best solution to the OP:
Instead of connecting your cable box to your stereo receiver with audio RCA cables, instead take the TV’s audio ouput and run that into the stereo receiver. That way, you won’t have to change any settings on your stereo when going from watching cable to watching the Roku. Again, this is exactly what I do at home. I have several TV inputs, including the antenna (coax), a Chromecast (HDMI), a Raspberry Pi (HDMI), a DVD player (HDMI), and even an old VCR (composite video plus audio). Then I take the headphone jack from the TV and send that to my stereo receiver.
We’ve already established that the Roku stick does not have separate audio output, so 2 is out. And option 1 is likely out, since most newer LG TVs don’t seem to have analog output.
So, as already pointed out, the available options are:
If the TV has optical digital audio output, get an optical-to-RCA converter, and use it to connect he TV output to the receiver
Use an HDMI signal splitter which extracts the audio channel from the HDMI signal and converts it to analog. Put the splitter between the Roku and the TV.
Welp, I got the converter and optical cable, and the cable won’t fit into the converter. I took the plastic tips off and managed to get one end into the flatscreen outlet. The other end won’t stay in the converter, and out of anger, I tried to screw the plug back and forth. It wound up breaking apart the little door in the converter.
I could run a coax to the converter, but the flatscreen’s only coax port goes to the DVR.
I could try superglue, but I’m sure it won’t work, and I want to be able to return it. Any suggestions?
I don’t see any DVR connection there and the coax is an input, not an output, so it doesn’t matter what you connect it to, it won’t carry audio from the TV to anything.
I’m not sure why you had problems with the optical cable, it should snap in to place in the appropriate ports and stay there. You did notice that it only goes in one orientation didn’t you?
Optical cables for audio come with two different kinds of ends. A square end, and a round end that looks mostly like a conventional 3.5mm audio plug. So you can buy three different sorts of cables. Square both ends, round both ends, and one of each. I rather sounds as if you might have the wrong cable.
A square end of an optical cable goes into a socket with a little square door. A round end goes into what looks like an ordinary headphone socket (but isn’t).
If you look behind the TV when it is on, you can usually see a deep red glow in the optical audio output socket.
To complicate matters, you can also send digital audio over coax, and many of the converters accept both optical and coaxial. However it is nowadays quite rare to see consumer gear with a coaxial output for digital audio. What makes things annoying and confusing is that they reused the RCA type connector for digital audio (and for video for that matter) making it far from obvious to the uninitiated what the hell is actually going on.
If the image Richard Pearse linked to is your TV, there is one, and only one way to get audio out - and that is over the optical digital output. The optical cable should, from your description, have two identical square box like connectors at each end. The connectors should just click in, maybe needing a bit of force, but certainly no twisting.
If there is any sort of setup option on the TV you must ensure that the TV is configured to output stereo PCM over the optical link. If the Roku has any audio setup menu, ensuring that it outputs 2 channel stereo only would be a good idea too. If you do get sound, but it is just insanely loud noise, it means that the TV is configured to output encoded 5.1 audio, which your converter isn’t designed to handle.
Except the “square” type isn’t really square, it’s a rectangle with two corners beveled, and a protrusion on one face. So it only goes in one way, as Richard Pearse mentioned. Trying to force it in a wrong orientation might cause damage.
Grooooannnnn… There’s 3 different types of optical audio cables? Excuse me while I get a degree in Electrical Engineering right quick. After I bang my head against the wall.
There are only three in that there are two sorts of connectors - and thus three ways you can make a cable. They all work the same. So long as you have one that has square connectors on both ends you should be fine. I was worried you had one that was round. That won’t fit.
The “round” kind is intended for small portable devices. The plug is the same size as a standard (3.5mm) headphone plug, allowing the same jack to work with both optical fiber and standard headphone cables. It’s not very common.
TVs and converter boxes will almost certainly have the larger square(ish) type. And you’d never mistake one for the other.
All you need to do is take pictures of the ports you need connected both in and out. Show them to someone who can help you at the store. Even an engineer still has to actually look at the ports to know what’s where and take note of it before buying correct cables to connect it.
