[sdiy] Multi-voice architecture without CV parameters: mechanical replication of settings?

[cheater cheater]

Welp, the technology has progressed, we have CV and other stuff now -
but the thing is, with adding CV capability we have also changed the
sound. I guess this is for people who like the old sound :-) For one
thing the new SEM specifically kept everything non-CV-able.

D.

On Tue, Apr 6, 2010 at 12:33, ChristianH <chris at chrismusic.de> wrote:
> For a minute I thought I was back in the early 70s, when people
> really considered crude and awkward mechanical stuff like that to be
> practical...
> Except back then it sometimes was the only way to do things at all.
>
> Chris
>
>
>
> On Sat, 3 Apr 2010 14:45:05 +0200 cheater cheater <cheater00 at gmail.com>
> wrote:
>
>> Hi guys,
>> I was recently considering older synthesizers, such as the SEM, and
>> also other designs where a lot of the settings are not
>> voltage-controlled. One problem many people mention is having toturn 8
>> knobs (in an 8-voice system) to change one sound parameter.
>>
>> I was wondering what ideas you guys had for solving this problem?
>>
>> The obvious way of having one 'knob' control multiple resistances is
>> to have a multigang potentiometer. However these aren't very popular:
>> even 2-gang potentiometers can be difficult to find for some
>> resistances/transfer functions.
>>
>> One other way to do this is to have separate potentiometers arranged
>> around a worm drive (if someone doesn't know what I'm refering to,
>> have a quick look here: http://en.wikipedia.org/wiki/Worm_drive ). You
>> could have one long worm shaft (the screw-like gear) connected to
>> multiple potentiometers with cogs on their shafts, instead of knobs.
>>
>> Of course this has its own problems:
>>
>> - the worm drive has to be precisely placed so that the axis of
>> rotation is in the right distance to the axis of each of the 'worm
>> wheels', i.e. the gears fixated on the pots. If the worm drive shaft
>> is not perfect (it is slightly bowed) or the axis is a bit off(and
>> hence not equally distant to the axes of the pot gears), a pot gear
>> could have less contact with it and presumably start skipping; This
>> can be helped by using a spring to press the pot's gear against the
>> worm gear, but that could lower the life of the system, especially the
>> shaft of the potentiometer which is not built for constant force
>> applied perpendicularly to its axis of rotation.
>>
>> - the worm drive will inevitably have a ratio lower than 1, which
>> means the knob will be multi-turn and hence 'slower' than normally.
>> Some people might not like that
>> - more force has to be used to turn the knob
>> - mechanically difficult assembly which makes it expensive
>>
>> Another way is to use a cam shaft drive like the hammond novachord.
>> You can see on youtube (I cannot use it right now so can't find the
>> exact link) a demonstration of how its 'brightness' knob works.
>>
>> Another way would be to make your own multi-gang potentiometers. I
>> guess in a typical potentiometer the shaft could go through a hole in
>> the resistive element and out the back. I guess you could make such
>> potentiometers without a shaft, but with a keyed hole for receiving
>> the shaft; then you could take one long shaft and just line up as many
>> potentiometers on it as you wanted. Sound like a good idea? I wonder
>> if any currently existing potentiometers could be modified for that.
>>
>> Of course all multi-potentiometer setups inevitably have the issue of
>> differences in resistance at a given position; but this isn't an issue
>> of concern if you're taking this approach; you can accept this as a
>> way of making the sound 'more lively'.
>>
>> Thoughts? :-)
>> D.
>
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