The Felston digital audio delays solve lip-sync error by allowing you to delay the digital audio signal to match the delay* in the video signal thereby restoring perfect lip-sync.

The delay unit is inserted in the digital audio path between your video source (DVD, DVR, etc.) and your AV receiver as in the diagram above. Since the DD740's "bit-perfect reproduction" does not change the digital audio signal, it is compatible with PCM and all present and future s/pdif surround sound formats at both 48 KHz and 96 KHz.

Since there is nothing in the video or audio signal to define when they are in sync it is a subjective adjustment and this is where the remote control excels. It remembers the last delay setting used on each input and includes 36 presets where common delays can be stored for instant recall. But most importantly, the + and - buttons allow dynamic "on-the-fly" delay adjustments while watching with no image disturbance - an essential feature allowing tweaking for "perfect-sync". These are necessary features for true lip-sync correction and not generally available on even the most expensive AV receivers that claim a lip-sync delay feature.

* Normally lip-sync error is due to video delays in both the arriving signal as well as in the display allowing audio to arrive too soon but when broadcasters over-correct for the video delay they added the arriving signal might have audio delayed instead of video.

At first thought it might appear the DD740 audio delay could not correct for "already delayed audio in the arriving signal"  but in conjunction with the video delay of your LCD, DLP, or plasma display it actually can - up to the display's video delay. That is, if your display delays video 100 ms your DD740 will correct lip-sync errors from 100 ms audio lagging to 580 ms audio leading.

For a more detailed explanation CLICK HERE.