Path: utzoo!attcan!uunet!munnari.oz.au!csc.anu.oz.au!csis!rackland
From: rackland@csis.dit.csiro.au (Ross Ackland)
Newsgroups: sci.electronics
Subject: Audio from a VGA card
Message-ID: <1990Nov12.235118.29947@csis.dit.csiro.au>
Date: 12 Nov 90 23:51:18 GMT
Organization: CSIRO Div of Inf Tech
Lines: 33

The other day, an idea struck me from the twilight zone. It seemed stupid
at first but the more I thought about it the more it seemed feasible.

The video DAC's on a VGA card (IBM-PC) are good for quite a few MHz, 
so would it be possible to generate audio from them in the form of music 
or speech?

I guess a low pass filter would help. You would cut one or two lines going 
to the monitor and stick them into an amplifier. Hey, the video signal should 
be well above the audio range, what about video and audio at the same time 
(that would be impressive!).

Or, we could even modulate the audio (using the palette registers) and build
an AM  transmitter!!!! What happens to the signal during vertical and 
horizontal retrace? I don't know enough about programming VGA's at the 
register level (I wish I did).

I'm beginining to get out of control on this one and my days of undergraduate
Elec Eng and signal theory are long gone.

Don't flame me for this, if its beyond the ridiculous then let me die a 
natural death, if you think its feasible then lets hear your ideas...

Ross Ackland

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