Subject: Re: [linux-audio-dev] Writing a driver for this card: your thoughts?
From: Lamar Owen (lamar.owen_AT_wgcr.org)
Date: Tue May 28 2002 - 23:19:48 EEST
[I may regret this... :-)]
On Tuesday 28 May 2002 01:19 pm, Tim Orford wrote:
> Lamar Owen wrote:
> > Also, due to the processing typical radio stations use in the air chain,
> > in many cases the quality of playback and record hardware for on-air use
> > must be up to the top quality of a recording studio.
> such insane amounts of compression as used by most radio stations are not
> usually related to 'quality' as understood by most poeple.
What happens is that lower quality audio is made to sound that much worse by
that very compression. Reverb is exaggerated, etc. As to the amounts being
insane -- well, that is a big point of contention in the broadcast engineer
and broadcast program director communities.
> one of the most important aspects of analogue design is a good power
> supply. Using a computer psu is going to severely limit what you are
> going to achieve. Regulators are by no means perfect.
If the output impedance of the output stage is low enough, and proper
decoupling is done at the amplifier rails, along with 'sag' compensating caps
(with low ESR! Tantalum only, and preferably sintered slug) in the proper
places, DC rail regulation becomes moot. The key is a properly designed
feedback network, with low net gain, using a high quality op amp with as high
an open loop gain as possible, and operating the output well below rail
voltage. If the output voltage goes over half rail, then all bets are off.
> also, perhaps academic here, but using balanced
> audio can actually degrade the sound by cancelling out even order
> harmonics but leaving the odd order ones, or by increasing the component
> count. Very high end stuff designed for non-hostile environments tends
> to be unbalanced.
Phase-linear balanced outputs won't cancel _any_ harmonics. Where did that
concept come from? And the Carver Silver Seven sounds better than the old
M400, too, right? :-) (audiophile humor)
> ok, back to trying to get Ardour compiled.....(does that make me
> On-Topic now?)
Hmmm. You know, a linux based broadcast compressor (on the order of an Omnia6
or Optimod 8400) would be an interesting project. Someone who wants to do
serious DSP work could have a field day doing multiband limiting and the
various other things broadcast processors must do.
But again, the hardware must be able to cancel out the enevitable RFI that is
going to be present.
-- Lamar Owen WGCR Internet Radio 1 Peter 4:11
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