Speaking to well known radio broadcast-studio engineer Poul Kirk at the CBAA conference recently, radioinfo picked his brains about the benefits of digital on-air broadcast desks.
Poul Kirk’s company Elan Audio has a new digital broadcast desk available, The Italian AEV Energya (pictured), which he had on show at the trade exhibition adjoining the CBAA conference. But before a station buys any digital desk, Poul Kirk urges them to think about how digital desks work so they get the most benefit from them.
While not being critical of any digital desks, Poul Kirk said that a digital desk is not necessarily important for the transition to Digital Radio Broadcasting (DRB). They can in fact be a hinderance to the integration of digital playback components due to the many different sampling rates and audio compression methods used.
He suggested that in some cases an analog desk might be as good or better than a digital desk because conversion and compression are only done once, at the end of the whole output process, giving less opportunity for problems with the sound quality.
There are still some issues to be faced with digital gear, which Kirk wants to encourage all radio engineers and producers to think about as they approach the era of digital desks.
For instance CDs sample at 44.1 kHz and use a special 16 bit digital format; Wav files sample at 32 or 48 kHz in 16, 20 or 24 bit; MPEG 2 and mp3 use audio compression at various sampling rates.
Current trends for Recording Studios are moving to a 24 bit, 96 kHz sample rate.
When each of these signals goes into a digital desk it has to be “squashed or expanded to make the numbers add up,” according to Kirk. So you get already compressed signals being uncompressed or recompressed time and again as the signal is made suitable to go into and out of the desk. “Sometimes it sounds like crap!”
“Compression removes the subtleties and can change the voice. It destroys classical music,” says Poul Kirk.
”I heard about one major network that recently was transferring material around to its different stations using ISDN lines – the promos went through 5 conversions. From mp3 in the raw voiceover, to Wav in the production area, then to another format for ISDN transfer, then another format in production and another for the on air desks. No wonder the voice did not sound like the original by the time it got to air,” he said.
“With digital you can still hear the voice clearly, which is a plus, but there
is no guarantee that it sounds the same as when it was originally produced by the time it has gone through so many format transfers.”
“Digital desks will be good when all these things are sorted out, but people
need to be thinking about them now,” said Kirk.
“The benefits of digital
broadcast desks are great – you can configure them to whatever fader combination you need, but there are still issues to be thought through – it is not such a simple solution as you might originally think.”
Currently the most popular digital mixing systems for major radio stations seem to be the Klotz and Logitek Digital on-air mixing systems.