SPDIF Audio Experience...what are your thoughts...

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
Situation: A couple years ago, the audio out from the headphone jack on my wall mounted TV failed. The internal speakers, such as they are, still work but sound very poor. Wanting better audio, and since the TV has a SPDIF output connector, I bought this device: Digital to Analog Audio Converter which has the SPDIF input. I route that to an 18 watt stereo audio amp. The audio amp is a pretty neat little device just perfect for my needs.

Issue: I am accustomed to seeing the SPDIF outputs on equipment and read about it but this was my first experience with the hardware. And I'm less than impressed. Right off it was difficult to get any audio from the TV to the amp via the converter. I can see a red glow at the end of the cable when the TV is on, I plug it into that Converter and sometimes it works right off. Other times I really have to worry it into place, wiggling it around because I don't get audio right away. The sockets or the plugs on either end just aren't designed well it seems. The positive locks seem more of a Meh lock. Weak. So what happens is every time I want to watch that TV, I'm worrying the connections of the SPDIF trying to get audio because it seems to die between uses. This doesn't seem right.

Question: Does anyone have a bunch of experience with these SPDIF setups? Do they work better then mine does? Why do I need to worry the ends of the cable into just the perfect position for there to be audio out? Why is the connection so loose? Is it just the setup I bought or are they all this poorly made? The plug does seem to be more solid in the TV socket then the converter socket but it often comes loose on it's own too. The stiffness of the fiber optic cable doesn't help as it often fights staying in place when I close the door of the cabinet the TV is attached to.

Thanks! for any insight on how to proceed. Should I toss the now out of warranty Converter and buy new, or go to the trouble of fixing the audio device in the Vizio TV instead because no SPDIF device works well? I am not sure exactly what's wrong at this point but if these SPDIF systems are all prone to poor connections I'll just dump it and move to some other method.
 

Papabravo

Joined Feb 24, 2006
17,299
The SPDIF format can be used with TOSLINK, optical fiber, coax, and twisted pair. You can purchase ready made cables, which in my experience have always worked well, always fit snugly and never caused a problem. Our technicians did become minimally proficient at terminating optical fiber with the use of dedicated materials and tools, but they hated the results. Coax and twisted pair were less problematical.

Can you provide more details on the media and connectors that you are using?
 

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
@Papabravo: So your techs had problems with the SPDIF system setup? Hmm. More details on the media & connectors? Not really, the link shows about all I know other then they look the same as all the others I've ever inspected over the years. This is my first use of the SPDIF system though.

@Audioguru again: So you're saying that the cheap converter is the problem? And any SPDIF receptacles you've used have been solid?
 

Papabravo

Joined Feb 24, 2006
17,299
@Papabravo: So your techs had problems with the SPDIF system setup? Hmm. More details on the media & connectors? Not really, the link shows about all I know other then they look the same as all the others I've ever inspected over the years. This is my first use of the SPDIF system though.

@Audioguru again: So you're saying that the cheap converter is the problem? And any SPDIF receptacles you've used have been solid?
There was no problem with the SPDIF method of encoding and decoding audio data. The problem they had was taking raw optical glass or plastic fiber, and terminating each end with an appropriate connector. It took considerable skill and practice to cut, polish, and attach connectors to both ends to make a custom optical fiber cable. It was far more effective to purchase machine made cables in standard lengths. I thought I made that ABUNDENTLY clear in my original post. The cables are fabricated in such a way that there is very little attenuation of the digital signal along considerable lengths such as might exist in a home theater installation.

SPDIF over coax and twisted pair also work very well with differential transmitters and receivers at each end.

This was one of the products I worked on:
Layout 1 (wadia.com)
 

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
Ah, I see. It was clear after I re-read your post. I'm getting distracted by neighbors needing help with a sewage problem. Yuk.

The cable came with the converter and is commercially made. Seems to be well made. I think the problem lays with the receptacle. I think I'll take it apart again and though I didn't find anything that appeared out of order the 1st time I looked, this time I'll look closer.

And I just realized I can move the setup to my main TV and plug it in there to see if the problem follows the converter or not.

Later: Doesn't work there either. Really seems to be the funky cable. It just doesn't fit into the female receptacles well at all. Either end, either TV or in the converter. The tiny led on the ends of the fiber optic cable seems to be out too far and too large. And it barely resembles a Toslink cable #1. That's my only cable so I'll have to order a different brand to test my evaluation. Mine resembles this one: Toslink Cable #2

OH FOR FREAKS SAKE! The ends of my cable that came with the converter has a tiny little plastic COVER/CAP on the very ends of the cable...the part that pokes inside the receptacle. Jeese!! That's why they wouldn't plug all the way in. Pull the caps off and they plug in solidly and boom, I have excellent audio. Can't believe that I missed that, only noticed that one eBay supplier showed the cable both with them and without them depending on the length. What the what!!!???

Well, I might be dumb, but luckily I'm good lookin'.

Okay, so maybe Toslink isn't that bad after all.

Thanks.
 
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Papabravo

Joined Feb 24, 2006
17,299
Ah, I see. It was clear after I re-read your post. I'm getting distracted by neighbors needing help with a sewage problem. Yuk.

The cable came with the converter and is commercially made. Seems to be well made. I think the problem lays with the receptacle. I think I'll take it apart again and though I didn't find anything that appeared out of order the 1st time I looked, this time I'll look closer.
From my time in the saddle, I don't remember ever having to deal with pieces parts from China. That might be the big difference between then (ca. 2007) and now.
 

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
Those male connectors are in the receptacles so tightly now that those protective caps are removed that I have to use a freakin' tool to extract them. Whoa.
 
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Papabravo

Joined Feb 24, 2006
17,299
As a kid I remember reading about the TV service people who made house calls. The solution to the most common complaint they received was to plug the line cord into the wall socket. At least we have evolved from that stage.
 

BobTPH

Joined Jun 5, 2013
4,049
You are not alone. When I saw your post I vaguely remembered having a bit of trouble when I first plugged in an optical cable, it didn’t seem to fit. Wish I had remembered in time to help you.

Bob
 

MisterBill2

Joined Jan 23, 2018
9,844
I am wondering what would be so difficult about replacing the headphone connector on a TV set.

And as for any product from amazon, the only information they can provide is price and shipping weight. And not always shipping weight.
 

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
I am wondering what would be so difficult about replacing the headphone connector on a TV set.

And as for any product from amazon, the only information they can provide is price and shipping weight. And not always shipping weight.
I DID replace the headphone connector. The OEM connector attached to the mobo was physically broken so needed to be replaced. I did that with one I had in stock but it's not the original OEM form factor, which I couldn't find at the time....so the one I used pokes out of the case of the TV hanging on the wires (tug test proves they are all still connected). But several months afterwards the sound from the headphone amp died too. So I needed to find another method and the SPDIF seemed a lot easier then tearing into the TV, finding the offending component on the mobo and replacing it (or replacing the mobo which is often the easiest) since I was traveling at the time (this equipment is in my RV). I could have interconnected with the speakers too if I'd wanted to bother with it but playing with a new-2-me Toslink setup at under $10 appealed to my curious and frugal nature more then hacking the TV. Much less work too. I did have to cross my fingers that the Toslink still worked but turned out it did.

As far as Amazon products not showing 'specs' that we need goes, finding that to be difficult these days IS NOT A NEW THING. I'd been in the industry designing industrial or consumer products for 50 years before I retired and it was the same 50-40-30-20 years ago, I'd choose a component from a 'distributor' and then sometimes I'd have to work on finding specs for it. Often would have to contact the OEM themselves for more concise specs. Of course back then I kept an extensive library of semiconductor handbooks but even those don't always cover everything. Not to mention 10's of distributor's catalogs. It seemed everything I ever designed had a quirk and I'd need to see if the part would fit or had that certain function I needed, or some listed spec just wasn't clear. Unfortunately, I no longer have the room to store all those books and catalogs so I depend on the internet...which often fails me these days what with all the freakin' ads for unrelated parts in the way of real info.
 
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crutschow

Joined Mar 14, 2008
28,204
sometimes I'd have to work on finding specs for it.
I had an interesting example of that recently.
I was looking up semiconductor heatsinks on Amazon, and did not find one that listed its thermal resistance value.
Tell me, how can you design with a heatsink if you don't know that fundamental information about it? :confused:
 

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
Easy. Build a prototype of the circuit around the power device using breadboard and point-to-point wiring. Leave plenty of room for different sizes and styles of heatsinks. Go to the next Electronics trade show in a nearby big city and pick up every heatsink the various manufacturers offer - they will be free, unless trade shows have changed a lot over the years. Then using your thermal gun test the various heatsinks with 2X the expected current and freq paying attention to ambient. Choose the best heatsink that does the job...there will be several so it's a choice based on experience and expected form factor of the case the device will go into. Boom, done designing. See? Easy. (Also, I have a cheat sheet for heat sinks and I just get dims from that and order the heatsink that matches the size I need).
 

bassbindevil

Joined Jan 23, 2014
203
Changing a TV set connector is more difficult if it's on a densely populated multilayer circuit board. I'd approach it by breaking up the old jack and removing one pin at a time.
 

Thread Starter

Jim@HiTek

Joined Jul 30, 2017
50
Changing a TV set connector is more difficult if it's on a densely populated multilayer circuit board. I'd approach it by breaking up the old jack and removing one pin at a time.
Great minds think alike as that's exactly what I did. After breaking it up the rest of the way since it was already broken, and unsoldering the pins, I soldered leads to the through hole pads and extended them outside the case. Then soldered them to a stereo receptacle I had in stock. So it became a dangler.

And that worked to provide issue free audio for almost 8 months and then one day, no audio. Now at that point, I could have opened the case of the TV again and rooted around in there trying to find the defective part (or even a bad solder joint), but I wanted to play with Toslink as I've been eyeing the receptacles on equipment for years but had never worked with the SPDIF system. Plus the Toslink to RCA converter was so inexpensive, under $10, that I thought, hey, why not? Even if it didn't fix the issue, I could always use it somewhere, sometime.

And now that I've figured out that there's little caps on the ends of the Toslink cables, I know it works well, makes solid connections on both ends of the cable and except for the stiffness of the light pipe, it's a pretty neat way to transfer audio. Handier and less bulky then ol' time RCA cables. AND those tiny light pipes can be long enough generally, "TOSLINK cables are usually limited to 5 meters in length, with a technical maximum of 10 meters, for reliable transmission without the use of a signal booster or a repeater." That's only 16 feet so an RCA cable beats it by many many feet (up to 200 feet), but at the price of being big and bulky when used for stereo.

But still, the Toslink system is pretty cool!
 
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