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From: cejjb@marlin.jcu.edu.au (Jeffrey J Bird)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Problems finding a 8 bit D->A 14 pin chip
Message-ID: <1991May27.120644.12401@marlin.jcu.edu.au>
Date: 27 May 91 12:06:44 GMT
References: <1991May24.232649.5062@vax5.cit.cornell.edu>
Distribution: comp
Organization: James Cook University
Lines: 44

In <1991May24.232649.5062@vax5.cit.cornell.edu> u9hx@vax5.cit.cornell.edu writes:

>Has anyone out there ever built the parallel port D->A converter to listen to
>Amiga sound files?  (The circuit included in MODPY112.ZIP)?  I'm trying
>to build one, but I can't find an equivalent for the 8 bit d->a converter
>chip  ZN426E.

I also couldn't find that chip, so I just built up a R-2R D/A from a
handfull of resistors. It works very well, and the circuit is very
simple:

	      2.7K   68
	D7 ---/\/\---/\/\---+-------+--------------+--------------------
			    |       |              |
	         5.6K	    |       \              |
	D6 ------/\/\-------|       / 3.3K       --+--  .0047uF
			    |       \            --+--
              5.6K   5.6K   |       |              |
	D5 ---/\/\---/\/\---|       |             -+-
			    |       \              -
	      22K    5.6K   |       /<-+ 2K
	D4 ---/\/\---/\/\---|       \  |
			    |       +--+
	      27K    18K    |       |
	D3 ---/\/\---/\/\---|      -+-
			    |       -
	        180K	    |
	      +-/\/\-+	    |
	      |      |      |
	D2 ---+      +------|
	      | 180K |      |
	      +-/\/\-+	    |
		            |
	        180K        |
	D1 -----/\/\--------|
			    |
	      180K   180K   |
	D0 ---/\/\---/\/\---+

This circuit has pretty well the same performance (maybe a little more
distortion) and has the added advantage of not requiring an external
power supply.

			Jeff Bird