Using optical digital cable switching channels sound delay or cutting in and out what would cause this?

Question

This happens with optical cable connects cable box to home theater system. Sound delay happens when changing channels or at times cuts in and out and does not seem to secure the sound. Like when channel is dolby digital or digital 5.1 or what ever. I have replaced cables and cable boxes several times and issue still persists. Any ideas. Issue does not happen with rca cable use but sounds much better and get full surround sound much better with the optical connections. So prefer to use that hookup. I have sent it in for repair under warranty twice now and they cannot find the issue.

Answer 1

Your optical cables could be too long if you are using a surround sound system. An unboosted optical signal is only really reliable up to about 5-6 meters or so, sometimes even less. Try using an optical signal booster and see if that helps, you can get them online for around $15 or so.

Answer 2

First, please make sure your optical cable that goes from the cable box to your home theater is in good condition (no dents or broken), this could be a good reason to lose signal in that kind of cable. Now, as mentioned by “42”, I also believe the problem is the box. A 3 feet long optical cable will not lose signal at all (if is not damaged) so I don’t think getting a signal booster will help.

Now, why this happens on the optical cable and not with the RCA cable? RCA cables (red and white) can only handle stereo sound so the RCA output from the cable box only sends two signals to your home theater; this action doesn’t require any “switching” in the cable box or your home theater. Optical cable can send stereo, surround and Dolby 5.1 signals through the same cable. Now, based on the fact that no all TV programs are recorded on Dolby 5.1, the box needs to switch between one sound format to another when you switch channels.

Why it happens when you switch channels? Let’s say you are watching an old movie from the 80s on channel 1, which was recorded and it is broadcast in stereo by your cable provider and then you move to channel 360, which is a HD channel, and it’s  showing Lord of The Rings (recorded on Dolby 5.1). At this point your cable box will switch the stereo signal to Dolby 5.1 and send the extra data through the optical cable to your home theater. Here is when your home theater recognizes the extra data and activates the Dolby processor inside the receiver. All these can make the home theater “confuse” and as a result, you have a delay on the sound or not sound for some seconds.

The cable box, as any other digital external receiver (say DirecTV HD receivers), uses software that handles video and audio signals helped by the hardware itself. Maybe you cable company needs to enhance the software to handle this issue. Some TVs and some cable boxes have a compensation setting that adjusts the “out of sync” sound condition. Check your cable box or home theater manuals. I hope this information helps you to resolve your problem.

Answer 3

It is the cable box, plain and simple.