Felston DD740 Lip-Sync Corrector (Delays Digital Audio via Remote Control)

Digital Audio Lip-Sync Correction

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

The DD740 is inserted in the digital audio path between your video source (STB, DVD, DVR, etc.) and your AV receiver (or sound bar)  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 such as Dolby and DTS at both 48 KHz and 96 KHz. 

Since there is nothing in the video or audio signal to define when they were ever 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 in 1 ms steps (1/3 in fine mode) 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 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. That assumes your TV allows you to turn OFF any audio delay it adds. Samsung and Vizio allow setting audio delay to zero but Sony, Panasonic, Toshiba, etc. usually don't so in those cases you should route digital audio directly from each source to your DD740 bypassing the TV. 

The DD740's output is optical and/or coax digital and therefore compatible with most AV receivers as well as "most" soundbars.  Please note it is NOT analog so if you need an analog stereo output you will need a digital to analog converter (DAC). We offer an excellent one on : https://www..com/itm/15-1242-Stereo-Analog-Digital-Converter-A-to-D-New-as-low-as-9-95/124485550427

Note: The first photo of a poster we used at our INFOCOMM booth shows our DD540 which has two inputs.  Our DD740 not only has 4 inputs but features direct numeric input of delay values as well as a fine mode which adjusts in 1/3 ms increments.