11 Jul
2023
11 Jul
'23
9:33 a.m.
You might try looking for Data Translation products. I know some of the later ad and da
modules were made by them for DEC
On July 11, 2023 12:28:43 p.m. EDT, Douglas Taylor via cctalk
<cctalk(a)classiccmp.org> wrote:
The DACs on the AAV11-C board are not marked in any
revealing way. I think they are Burr Brown DAC80, 24 pin, but I'm not sure. I
wasn't sure if they were working and was looking for a replacement.
Looking at the spec sheets DAC's seem to come in Voltage or Current versions. Life
got more complicated.
This started out as a simple exercise into verifying the AAV11-C operation using PDP11GUI
to program up a basic program to run all the codes thru the DAC. It worked, got a ramp
out. Now, I'm starting to look at the KWV11-C and how to use that to send values to
the DAC at a controllable rate.
Doug
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On 7/11/2023 11:41 AM, Mike Katz via cctalk wrote:
I originally used R-2R DACs but I was lucky
enough to be able to buy a couple of DAC08 chips at Radio Shack and built a circuit using
74LS244 latching buffers so that I could drive both channels of a single 8-bit parallel
port and 2 extra control lines (Select and Strobe).
On 7/11/2023 6:43 AM, steven(a)malikoff.com steven--- via cctalk wrote:
On
07/10/2023 11:31 PM AEST Mike Katz via cctalk <cctalk(a)classiccmp.org> wrote:
Way back in the 80's I was able to do stereo 4 part harmony on a 2 MHZ
6809 using two 8-bit D/A converters.
Much the same here. I recounted this on VCFed a few months ago about building a
simple 2-chip 8-bit ladder DAC with one-transistor amplifier for my Applied Technology
DG680 S100 machine back in the early 80s from this absolutely excellent BYTE article on
how to do polyphonic synthesis on a microcomputer (KIM-1):
https://archive.org/details/byte-magazine-1977-09/page/n63/mode/2up
A schoolfriend who had an Apple ][ and had not done any Z80 machine code before asked for
me to hand him my Zaks book, upon which he wrote out one attempt in Z80, crossed it out
and wrote a second version. Which worked perfectly. For the music piece I got it to play
four-voice polyphony after painstakingly encoding Bach's Praeludium in C Major from my
mothers' collection of piano music scores.
A few years ago I had thoughts about porting the 6502 code to the PDP-11 and use the same
sort of ladder DAC. Not sure if the slimline 11/05 would be fast enough for anything too
high frequency, but if it was, the slimline 05's power supply could then temporarily
come out and be perhaps be powered off some beefy batteries in that space, along with a
small 1970s transistor amp and 1970s headphones topped off with a leather shoulder strap
to lug it around like a giant Walkman.