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-   -   ADVC-G1 Audio Out Greatly Reduced (http://forum.grassvalley.com/forum/showthread.php?t=39827)

wcardone 05-09-2017 03:02 PM

ADVC-G1 Audio Out Greatly Reduced
 
Product: ADVC-G1 Any In to SDI

Input: 480i video/audio
Video Port: Y/CVBS

Problem Statement:
The audio output embedded in the SDI OUT is objectionably reduced. I don't remember the numerical magnitude but would estimate it is -18 to -20dB. The audio can be restored to 0dB in post using any ordinary audio editing tool and appears to be satisfactory.

I have confirmed that the problem is not with the original audio source by downloading the same video using another device (ADVC-300).

The ADVC-G1 +4dB DIP switch option is engaged. If it makes a difference it is too small to see without careful editing inspection.

Note: the G1 BNC output is being fed to an Epiphan AV.io-SDI device which delivers USB 3.0 video. I have not confirmed that the loss does not occur in this device. it just didn't occur to me to check but I would not expect it to be the source of the problem.

wcardone 06-14-2017 10:44 PM

That was back in May when I posted this. Still nobody has anything to say.

The DIP switch 4 allows a selection of +0dBu or +4dBu audio gain. The position of this switch makes no difference in the captured audio.

We've got to do better than this, folks.

wcardone 06-15-2017 01:28 AM

MY WORKAROUND:

Some might call this a solution but I will call it figuring out how to make something deficient provide satisfactory results.

I insert a stereo amplifier between the G1 and the A2D converter. It was actually a mixer board not intended to provide any gain so I am wondering if we are talking an impedance mismatch.

Anyhow, I don't have to normalize the audio as a second step after the download.

GrassValley_PS 06-15-2017 05:20 AM

I am guessing that very few people here have that device. I do have it and have never had any audio problem with it.

antonsvideo 06-15-2017 05:54 AM

if using analog audio inputs from semi pro or domestic decks, 0db will give you a much louder capture sound than +4db

+4db is suitable for pro and broadcast players that have XLR balanced output only

wcardone 12-04-2018 03:23 PM

I am wondering if this is a problem or flaw with my G1 unit not observed on other units.

The problem suggests an input impedance anomaly since my workaround is to route the audio through an audio mixer at 0dB gain. In theory there should be no difference in the ADVC G1 audio output whether the audio in comes from for example a VHS (or camcorder) audio line out or my mixer line out fed from the VHS with 0dB gain.

This unit has also been giving me random freeze-frame anomalies from the very start as if the video stream input has ended. It is impossible to repeat these. They are random showing up once every one or two hours of use.

dpalomaki 12-10-2018 03:01 PM

I believe that the ADVC300 is designed for consumer-type audio sources with a nominal output level of -10 dBV. It also offers some audio gain adjustment.

The G1 is for professional sources with nominal outputs of 0 or +4 dBU. Thus the audio embedded in the digital stream will be on the order of 10 dB lower with the G1 given the same source. Perhaps more depending on the output impedance of the source.

Many current consumer line outputs have a source impedance on the order of 1K to 2K ohms, but older gear may be higher. Not sure what the input impedance of the G1 is but I would expect it to be around 10k.

Depending on the mixer it may have a nominal line output of +4 dBu at 0dB on the meters with around 18 dB of headroom and a 120 ohm output impedance. Also it may consider 0 dB for a RCA consumer line input to be -10 dBV signal. It will depend on how it is configured.


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