Computerized patching

[The Dark force of dance]

Y-ellow Bob 'n' all.
        As I am currently designing a device pretty close to what you're
talking about you may be interested to note. 

At 02:00 PM 10/9/97, Bob Zimmer wrote:
>What about further automation beyond just switching?
>
>I've been looking into Dallas Semiconductiors digital & audio pots and have
>been wondering if it's possible to create a MIDI driven dynamic patching,
>knob turning system using these.  Seems to my minor knowledge that it
>should be possible to multiplex them off a DAC to store values and through
>a multiplexed three wire serial line to dynamically program them realtime.

Analogue Devices manufacter, what they describe as, An 8 channel digitally
controlled stereo mixer chip. Part number SSM2163. It has 8 input channels.
Each one has a level control plus mute and can be assigned to one of two
channels. Left or Right. I'll be using 4 such devices for an 8-stereo
channel mixer across 4 stereo busses. (16 in 8 out) The devices are a
standard 3 wire interface plus a mute pin. They can be daisy chained to as
many devices as you need. No limits and still only requiring a single 3 wire
interface.

AS well as this I'll be using 4 NSC Micro-pots and 2 cross-point switches.
This will give me an extra 4 stereo channels bringing the total number of
stereo inputs to 12. However the later will only be switched across the
first two stereo output busses. Nationals also make a series of other
interesting digitally controlled audio products. Including 3 slightly
different stereo pre-amps. Each providing the usual bass, treble, balance
and volume functions. As well as features such as input selectors, enhanced
stereo, pre/post-EQ sends and the largest device also has 4 individually
controlled outputs. Designed in this case mainly for front/read stereo
adjustment but could be used to send to two different mixing busses. NSC
also make a digitally controlled 14 band graphic equalizer chip. This can be
used as anything up to a single 14 band EQ or a stereo 7 band EQ. Or any
other combination you require. 

All of these devices are standard 3 wire 'MICROWIRE' or 'INTERMETAL'
interfaces meaning they are dirt simple to control.

Harris make the Crosspoint switches although AD make some excellent
selectors. Warning. Do not use the 8 x 8 cross point switches for audio
applications as the transfer function isn't all that great. Better than a
standard B series CMOS part but still not great. However the 4 X 4 X 2, the
12 x 8 x 1 and the 16 x 8 x 1 are acceptable. Perhaps not as linear as one
of the AD selectors but linear enough. They are comparable with the industry
standard DG200 family of electronic switches which have been used in high
end/professional/broadcast audio for years. Note that it is possible to make
a 16 X 16 audio matrix with just two of these chips. However the practical
cross-talk of these devices remains to be seen. I'll keep y'all posted on
that one.

National's Micro-pots come in 3 flavors. A single channel. A dual channel
and a triple channel device. All daisy chainable and compatible with the
SSM2163's 3 wire interface.  They also feature a programmable tailored
response curve. You can adjust the pots from linear to audio taper or any
weird curve you desire. 

Hope this helps.

Be absolutely Icebox.
 _ __        _                              
| "_ \      | |         batzman at dove.mtx.net.au / aek at gist.net.au
| |_)/  __ _| |_ ____           ALL ELECTRIC KITCHEN               
|  _ \ / _` | __|___ |  The new AEK CD, Elementary Urban sanity    
| |_) | (_| | |_  / /   is out now on Transmission Communications from
|_,__/ \__,_|\__|/ /    http://brisbane.dialix.com.au:80/~com11
                / ,__   and check out http://www2.gist.net.au/~aek/
Goodfortune    |_____|       Get your SANITY and wear it out.