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Optical audio signal lost when pausing or changing channels

 

Bronze Member
Username: Alderash

Post Number: 14
Registered: Jun-06
Hi,

I have a 3' optical audio cable running from my cable box to my surround receiver. The audio signal sometimes cuts out when I either change channels or pause a show. It doesn't happen all the time - maybe 50%. The only way to restore the audio is to power the receiver off/on, or change to another input and then back to the digital audio input again.

The cable is new and undamaged. I allso tested two other cables and used both optical inputs on the amp. I have also just recently replaced the cable box with a new one.

Any ideas?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17455
Registered: May-04
.

"Sometimes cuts out" is not an unusual circumstance with a digital connection that constantly moves around while the receiver is trying to lock onto it. Typically switching channels for a second or, as you say, switching the receiver's inputs back and forth is a simple fix. You can call the manufacturer of the receiver to check for any upgrades to the firmware of the receiver. That sometimes fixes the situation and sometimes, quite honestly, you just have to live with the occasional vagaries of digital media. You could also try a diffferent type of conenction to the receiver. If you've been using an optical cable for the hook up between components, try a wired type coaxial cable instead.



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Bronze Member
Username: Alderash

Post Number: 15
Registered: Jun-06
Thanks, Jan. Tried the coaxial cable with the same results. VERY frustrating!
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17462
Registered: May-04
.

It is. I had the problem occur last night during the Ranger/Orieles play off game. During a commercial break one commercial in a series of six didn't synch and the processor never caught up. Switching the processor between inputs several times finally got sound back. Turns out I would have been better off not hearing the rest of that game.
 

Gold Member
Username: Superjazzyjames

Post Number: 2054
Registered: Oct-10
When I first began to read the op, I thought it might be a problem with the cable box. Reason being, sometimes, the audio from my cable box cuts out when I switch channels or access the guide. When accessing the guide, the video often cuts out as well. I know it's the box because I connected the audio out to the TV and listened through the TV speakers. Same problem occured. In addition, neither my receiver nor the TV have digital inputs. I also tried connecting my cable box to my wife's TV. Same thing happened. She'd never had this issue with her cable. So, I connected her cable box to my system (temporarily, of course), no problem. After switching the cable boxes back, hers still works fine, mine still has delays. I never heard of a HT receiver having such an issue though. Just out of curiousity, did either of you gents try temporarily running the analog out of the cable box to your receiver just varify that there is no issue with the box?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17463
Registered: May-04
.

Yes, same problem. Each commercial or channel change requires the processor to lock onto a new set of signals. The problem appears to be in that digital "handshake" that gets dropped.
 

Gold Member
Username: Superjazzyjames

Post Number: 2056
Registered: Oct-10
I remember all the hype about how much "better" digital is than analog. Well, it ain't perfect. Not that analog is perfect either, but I never had or heard of other people having so much trouble just trying to watch TV WITH SOUND until cable & sat went digital.
 

Gold Member
Username: Magfan

USA

Post Number: 2911
Registered: Oct-07
Can't high jitter from/at the source cause such handshake problems?

To troubleshoot...I'd try connecting another digital source like a DVD player or CD player.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17464
Registered: May-04
.

My CD and DVD players have no problems communicating with the processor. But they do not have a continously variable stream of data each with a new handshake that needs to be made. And even if the CD player has not problems, what would this test prove? You can't change anything about the cable/sat receiver by proving the CD player works.



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Gold Member
Username: Magfan

USA

Post Number: 2912
Registered: Oct-07
I'm suggesting the cable box has high output jitter and would like to 'check' by using another, perhaps better, digital source.

I'm further suggesting the DAC in the receiver has low tolerance to such jitter.

Some DACs are more tolerant of such signals than others. My CA840c simply needed a pretty good signal. It'd unlock and emit an awful noise while taking the digital signal from an Airport Express and much less frequently from the DishNetwork receiver. Never with the OPPO upsampler.
My DACMagic+ has no such problems. Even the USB works fine, with a repeater and 30'+ of cable. And at 192khz, to boot.
 

Gold Member
Username: Superjazzyjames

Post Number: 2057
Registered: Oct-10
Basically Leo, I don't think trouble shooting is necessary. It seems that the problem has been identified and hopefully cable and sat signals and boxes will improve over the next few years.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17466
Registered: May-04
.

"I'm suggesting the cable box has high output jitter and would like to 'check' by using another, perhaps better, digital source."



I don't know that "jitter" is the culprit in this case, just a lousy digital stream that constantly moves around while the processor is blindly looking around to find it. Like the "joke" of holding out your hand for a handshake and then at the last minute pulling it away. Wasn't funny in person, it's even less funny in digital audio. The problem is once the processor has extended its hand, if there's nothing there, it eventually just stops trying to find the new hand.

There certainly shoudn't be a problem with a dedicated audio stream from something like a CD/DVD player, the player provides a constant source for the processor to lock onto. Therefore, verifying that fact seems pointless to me. The problem is in the constantly moving stream, if the processor misses one micro-second of the codes, you're done. This appears to be a not so uncommon issue with digital TV receivers and multi-channel processors.

I don't see the point of confirming something we already know to be a problem. Nor do I see a simple solution should we "prove" the two components to be having problems existing with each other. There are only so many options for digital TV receivers and I'm not ready to re-buy another $1k processor just to solve this particular problem. The op could send back the reciever in exchange for another, but in all likelyhood, the problem will remain. Either a software/firmware update helps, or I'll live with the situation I have and an occasional annoyance. Cripes, it's not like digital anything has made my life easier.



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Gold Member
Username: Superjazzyjames

Post Number: 2058
Registered: Oct-10
Well, I was having all kinds of fun trying to watch the Texans/Jets game last night. Sometimes, I'd lose audio. Sometimes video and sometimes both. Other times, the picture would freeze. These things would always happen during a crucial point in a play, like when the Texans intercepted what would've been a touchdown pass.
 

Bronze Member
Username: Alderash

Post Number: 16
Registered: Jun-06
I switched to standard red and white analog RCAs, and of course have no problems with audio delays or drops. I could live with this setup if it wasn't for the annoying hum I'm now getting. Ground loop problem? Not sure. Don't have the hum with digital connections.

Any ideas on how to eliminate the hum? It's a brand new high-quality RCA audio cable. Also tried another cable and still get the hum.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17470
Registered: May-04
.

Interconnect cables are seldom the cause of ground loop hums unless they are damaged in some way. Hum is the result of ground loop problems elsewhere in the system.

The first thing it resolve is the severity of the problem. Is this a noise you hear from a few feet away from the speakers when no other signal is present? If so, this might be something you want to live with as that represents an other than normal situation.

Otherwise, there are no specific instructions for resolving grounding problems. It is a hunt and peck issue resolution which is likely to vary from one system to the next. The overriding issue is typically a set of components connected by single ended interconnects - RCA to RCA - where the individual components are not sharing a common AC ground plane. The AC ground plane exists at the AC outlet termination from your wall.

If the components showing this behavior are plugged into a common AC extension strip, moving the positions toward each other sometimes helps. Other times, if you have an accessory AC outlet on the back of the receiver, plugging the satellite/cable box into the receiver will be the fix. On occasion, the problem is with the grounding system used by the cable provider. Here you would want to call your cable service company and ask them to resolve the problem.


There are numerous threads on the forum which deal with ground loops. You can check those out for further instructions. You can also enter something on the order of "curing cable receiver ground loops" into a search engine for more complete instructions. As I said, there typically is no one single cure but, since the problem has a common cause, many solutions are relevant to many systems.


Good luck, be prepared to devote some time to tracing the cause and then resolving the problem.




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Bronze Member
Username: Alderash

Post Number: 17
Registered: Jun-06
Thanks, Jan - much appreciated!
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