Message-ID: <249@gitpyr.UUCP>
Date: Fri, 28-Sep-84 16:37:54 EDT
Article-I.D.: gitpyr.249
Posted: Fri Sep 28 16:37:54 1984
Date-Received: Sat, 29-Sep-84 10:19:46 EDT
Distribution: net
Organization: Georgia Institute of Technology
Lines: 42



Help!  I'm in the final planning stages of constructing a
micro-based music generation system.  I'll be generating samples in
software and sending them to a D/A converter.  Is there anyone out
there who can offer some advice and guidance with respect DACs?  I'd
like to use the new 512K Mac (great graphics, and you just can't beat
the mouse... I know, I know, I'll wait till I see a good programing
language out there.), but it's only contact with the outside world 
is an RS-422 serial port.  My questions:

      1)  I'll be generating samples at 10K-40K Samples per second.
	  I'd like to use a 14/16 bit converter, so I'll need to
	  talk to te DAC at 160K-640K bits/sec.  Can the RS-422 do
	  it?  (I'm assuming for the sake of argument that the Mac
	  will be able to send them fast enough.  I won't know for
	  sure until I see a real C or Pascal compiler, or an
	  assembler...)

      2)  The DAC will need the following features:
	    a)  fast enough conversion

	    b)  ability to talk 'serially'

	    c)  14/16 bit conversion

	    d) (optional)  I'd like to have a stereo output. (I realize
	       that my sample rate just doubled...)Are reasonably
	       priced multiplexed DACs out there?
	    
	    e)  The converted signal will have to be filtered at
		half the sample rate.  Since I'll be varying the
		sample rate from time to time, it would be nice to
		have this cutoff frequency set from software.
		Is it possible to get a filter onboard the DAC?

You may have gathered that I'm not very conversant with I/O. I'd
appreciate any help or suggestions.

      Steve Tynor
      Georgia Institute of Technology
      ...{ihnp4, harpo}!gatech!gitpyr!tynor