From analogue-request@magnus.acs.ohio-state.edu Thu Apr  8 12:19:20 1993
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Date: Thu, 8 Apr 93 09:18:58 PDT
From: rogoff@teradyne.com (David Rogoff x4627)
Message-Id: <9304081618.AA03836@midas.teradyne.com>
To: analogue@magnus.acs.ohio-state.edu
Subject: Re: great "universal midi box" project
Status: OR

<inc> 
<inc> Here we're touching an interesting subject for us into analogue synth
<inc> electronics. Just two thoughts from the back of my head...
<inc> 1. The Matrix-6/6R and Cheetah MS-6 use two sample and hold circuits for
<inc> each analog CV. One of them has a much longer time constant, so the
<inc> CPU can decide how fast it wants the CV to move, and avoid zipper noise.
<inc> 2. In my own synth I use integrators to actually generate ramps between
<inc> CV increments in the EG's and LFO's. Result: no zipper (but more complicated
<inc> s&h's).
<inc> 
<inc> /Ricard
<inc> 
This is great for real VCOs.  Eventually I want to use digital oscillators,
so there is no sample/hold or integrator.  That's why I need to know how
fast I can jump the frequency - to make the integrator in software, if you
will.

David

From analogue-request@magnus.acs.ohio-state.edu Thu Apr  8 04:35:38 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Thu, 8 Apr 93 09:35:04 MET DST
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To: rogoff@teradyne.com (David Rogoff x4627)
Subject: Re: great "universal midi box" project
Cc: analogue@magnus.acs.ohio-state.edu
Status: OR

> 
> Forrest Cook writes:
> >P.S. The great "universal midi box" project is coming along, I've figured out
> Forrest,
>
> you are in a great position to test something that has bothered me
> (and hopefully other analog types interested in new analogish-
> digital stuff):  what DAC step size and/or sample rate is required
> to avoid the "zipper" effect on glide/portamento.
> 
> On any synth I've listened to (D70, JD-800, Vintage Keys etc..) if
> you set portamento to a fast value (~1/4 sec for five octaves) and
> then rapidly alternate between high and low keys, you will hear
> this zipped or stair-case effect.  
> 
> Could you write alter your code to add portamento in the HC11 and play
> with timing loops to hear the effect of different update rates?
> It would be great to have this info to figure out what kind of
> horsepower a digital synth would have to have to control 32 or more
> voices.

Here we're touching an interesting subject for us into analogue synth
electronics. Just two thoughts from the back of my head...
1. The Matrix-6/6R and Cheetah MS-6 use two sample and hold circuits for
each analog CV. One of them has a much longer time constant, so the
CPU can decide how fast it wants the CV to move, and avoid zipper noise.
2. In my own synth I use integrators to actually generate ramps between
CV increments in the EG's and LFO's. Result: no zipper (but more complicated
s&h's).

/Ricard

-- 
Ricard Wolf                   / | \  / | /-           email: ricard@axis.se
Axis Communications AB       /__|  \/  | \__          uucp:  axisab.se!ricard
S - 223 70 LUND             /   |  /\  |    \         Tel:   +46 46 19 18 63
SWEDEN                     /    | /  \ | \__/         Fax:   +46 46 13 61 30
                 -- "Sweet dreams are made of this" --

From analogue-request@magnus.acs.ohio-state.edu Wed Apr  7 19:40:00 1993
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Date: Wed, 7 Apr 93 16:39:24 PDT
From: rogoff@teradyne.com (David Rogoff x4627)
Message-Id: <9304072339.AA01790@midas.teradyne.com>
To: analogue@magnus.acs.ohio-state.edu
Subject: great "universal midi box" project
Status: OR


Forrest Cook writes:

>P.S. The great "universal midi box" project is coming along, I've figured out
>how to get the 68HC11 to interpret MIDI data and deal with running status.
>My old ARP Odyssey really plays well when connected to a decent keyboard.

Forrest,

you are in a great position to test something that has bothered me
(and hopefully other analog types interested in new analogish-
digital stuff):  what DAC step size and/or sample rate is required
to avoid the "zipper" effect on glide/portamento.

On any synth I've listened to (D70, JD-800, Vintage Keys etc..) if
you set portamento to a fast value (~1/4 sec for five octaves) and
then rapidly alternate between high and low keys, you will hear
this zipped or stair-case effect.  

Could you write alter your code to add portamento in the HC11 and play
with timing loops to hear the effect of different update rates?
It would be great to have this info to figure out what kind of
horsepower a digital synth would have to have to control 32 or more
voices.

Thanks,

 David

  David Rogoff,  Teradyne Semiconductor Test Division 
   teradyne!rogoff@ism.isc.com
    rogoff@teradyne.com
      818-991-2900 x4627




From dacc@cmp-rt.music.uiuc.edu Wed Apr  7 23:48:52 1993
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From: dacc@cmp-rt.music.uiuc.edu (Andrew C. Crowell)
Message-Id: <9304080347.AA17212@cmp-rt.music.uiuc.edu>
To: analogue-request@magnus.acs.ohio-state.edu
Subject: Modular MIDI?
Status: OR

	Hey, gang...I need some advice on MIDI applications with modular
analog gear. More specifically, I'm looking for interfaces that'll allow
MIDI->CV control of modules that use the standard 1v/8va convention for
CV scaling, even better if I can find controllers that'll allow control of
non-standard CV scaling implementations. Ideas/devices, anyone?

D.A.C. Crowell
Computer Music Project/School of Music
University of Illinois at Urbana/Champaign
(dacc@cmp-rt.music.uiuc.edu)

