[sdiy] Telharmonium motors, perhaps?

[Ken Stone]

Personally, I don't think a single disk could be used successfully - there
would either be too many inacuracies, or too fine a resolution on the disk
for easy manufacture. Early Compton units did it with two rotors, according
to one web site, and they later went for twelve separate rotors anyway. Note
however, they
use a single motor with the twelve rotors  - it is the diameter or the
rotors that they vary.

As for using one as a VCO, the flywheel effect was too great on the one I
played with, though a really enthusiastic person may consider adding brakes
(mechanical or by shorting the motor) to encourange quicker speed reduction,
and whopping great surges to rapidly speed it up.

Have fun!

Ken

>A TOG (top octave generator) can derive 12 pitches from one master
>frequency, so I say that yes, one rotating disk could contain 12
>optical pitch tracks, BUT... the numbers are not very encouraging.
>Remember that we need high frequencies (we must accomodate the *top*
>octave, after all). A turntable is way too slow.
>
>Take a look at the TOG divisor ratios:
>    http://www.organservice.com/crm/topdividers.htm#Fig6
>
>Visualize a protractor and you can picture 360 divisions per circle.
>One revolution = 1 cycle.
>
>Enough rambling for now...
>--
>john
>
>
>----- Original Message ----- 
>From: "Glen" <mclilith at charter.net>
>To: "Michael Baxter" <mab at cruzio.com>; "Gene Stopp" <gene at ixiacom.com>
>Cc: <synth-diy at dropmix.xs4all.nl>
>Sent: Monday, November 22, 2004 8:46 PM
>Subject: RE: [sdiy] Telharmonium motors, perhaps?
>
>
>> At 08:09 PM 11/22/04 , Michael Baxter wrote:
>>
>> >This then leads to a motor speed controller and phase-locked loop,
>and
>> >then eventually 12 motorized speed controllers for an
>equal-tempered
>> >octave, with 12-16 VCAs per voice ...
>>
>> I wonder if you would really have to use 12 motors? Perhaps you
>could get
>> more than one of the 12 notes of the scale on the same disk? If the
>disk is
>> larger, it would be easier to fit more notes on it. If you use
>opaque
>> printing with reflective sensors, you can also use printing on both
>sides
>> of the disc. If you could manage to cram all 12 notes of the scale
>onto one
>> disc, you would automatically guarantee that the unit would always
>be in
>> tune with itself, without the need of servos or PLLs. I wonder if a
>special
>> disc could be printed and adapted for a common vinyl record
>turntable?  :)
>>
>> It would certainly be a cheap way to experiment with the concept,
>and it
>> might be of some research value, even if you eventually decide to do
>> something far more elaborate.
>>
>>
>> take care,
>> Glen
>
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>