“Audio Considerations for a TV broadcast station”,

 presented by

AES member Mr. Vinayak Deo.

The Section met on 14^th February, 2004 at S.N.D.T. University committee room at 4 p.m. There were 15 members present. The topic was “Audio Considerations for a TV broadcast station”, presented by AES member Mr. Vinayak Deo.

Mr. Deo first explained the basic set up of the TV channel station- in this case a news channel in Bangladesh, where he was acting as a consultant. While setting the audio, he had a few problems and how he tackled them formed the main body of this interesting meeting.

They had a Behringer  DDX 3216 mixer as the main routing device, which is an analog board. All the operation is digital otherwise. So Behringer suggested a A/D and D/A converter breakout box at the output. The mixer was fed by CD player, DAT and several microphones. The output of the A/D converter was incorporated with the picture for broadcast, and  as input to D/A. D/A was used to monitor mixer output on amplispeakers.

The problem arose when a lapel cabled condenser mike was connected, with 48 V phantom power from the mixer, there was a noise only on the amplispeakers connected to D/A converter but not on the mixer’s HP out and on the output of the A/D, checked with the amplispeaker with AES/EBU input. The signal chain was checked many times but did not show any problem anywhere.

Hence, in an effort to solve the problem, the lapel condenser microphone was disconnected and a dynamic microphone was used instead. And the sound came clean without any noise. So it was found out that the problem was indeed in the phantom supply of the mixer. It was not possible to check the waveform of Phantom supply for ripples and other inconsistencies. It is being taken up with Berringher.

Another peculiar problem was about digital interconnect.

The D/A converter is situated in a different (monitoring) room, and was fed with the Video sync. Whereas the A/D converter is in the production room and was without any sync feed. When they fed the mixer out to the system, there was no output from D/A converter, whereas there was digital audio available at the Digi out of the A/D converter.

A strange thing noticed was when they connected the CD player out direct to the A/D converter the sound was available everywhere.

The debate went on between members present about the digital AES/EBU connections, the sync clock sent on along with the digital audio, the position of the selector on the digital devices etc.It was fairly singular conclusion that the sending device acts as master and receiving device locks to the incoming clock. Otherwise there has to be a house sync or Video Reference clock fed to all the digital devices in the studio, which will be a full proof solution.

It was a very informative & interactive session and members felt the need for more such programs with real life situations.Mr. Oak thanked Mr. Deo and the members for making the session so very lively and interesting.

                                                                                                            Avinash Oak