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From: "Haible J. ZFE BT SE 42" <Juergen.Haible@zfe.siemens.de>
To: "'analogue'" <analogue@magnus.acs.ohio-state.edu>
Subject: AW: Quantized output info...
Date: Wed, 20 Jul 94 09:18:00 PDT
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>
>I'm looking for info on how the output of an analog sequencer could be
>quantized.  I know that the old ARP sequencer had that feature, so I'd
>like to get a schematic diagram of how it was done on that machine.  I'm
>interested in any other sources as well.
>

I don't know how it's done in the ARP. But it would be easy to do this with
a simple ADC -> DAC chain. If you only want chromatic quantisation, it's
simply connecting the outputs of the ADC to the inputs of the DAC. The
trick is to use converters with a sufficient high resolution to get the 
required
accuracy (12bit should be far enough, but even 10 or 8 bits should work),
*but* only connect some of the higher significant bits to get the 
quantisation
effect. Fine adjustment should be done by adjusting the gain of simple
analogue amplifiers before the ADC and after the DAC. (You could
adjust the converters' reference voltages as well.) What you need are
steps of 1/12 Volt.
If you want more complex quantisation (major or minor scales etc.) or
you want to switch between different quantisations, you'll need a simple
EPROM between ADC and DAC, which filters out the steps that should
be suppressed.
There are other possibilities: If you use an EPROM, You could use all bits
of the DAC and make the whole quantisation in the EPROM. You could
also use converters with less accuracy and program the EPROM in a
way to correct the convertors' errors ... but this last one would be far too 

difficult for a DIY, I think.

Hope that helped,

JH.


PS.: There was a DIY in ELEKTOR many years ago. But please don't ask
me in which issue - I don't know. But if You have luck, they still sell the
EPROMs ...