I've discussed this idea with a friend and done some Google searching.
Apparently the sync signal consists of two square wave tones at 1200
and 2400Hz. The 2400Hz tone denotes a clock pulse, and the 1200Hz tone
is used for the lead-in (where the drum machine picks up sync at the
start of the tape) and to fill up the rest of the space on the tape.

So it should be fairly easy to fake this up using a square wave output
from a microcontroller, and add a knob and readout for tempo.

This is something that could be integrated into the Clockbox project
from the MIDIbox Hardware Platform at ucapps.de

http://www.midibox.org/dokuwiki/doku.php id=clockbox


--- clae < clae13@... > wrote:

> I've noticed a fair bit of tempo drift as well. I think it's a
> problem
> that varies from one 707 to another, and maybe has something to do
> with
> aging components.
>
> From memory, when the 707 is in "master" mode, it's actually in tape
> sync mode. So perhaps an external device could be hacked up to
> output
> a fake tape sync audio signal, with a more accurate tempo control.
>
> Or it might be easier to analyse the problem on the 707 and repair or
> upgrade it onboard.
>
> --- "Olivier.b" < club_cuisine@... > wrote:
>
> > right when i slave my atari to the 707 i can notice some slight
> tempo
> > shifting...but i think the overall tempo is still pretty steady.
> what
> > I complain about is the unpreciseness of the tempo knob .
> > anyway i think it is better to have the rythm machines in sync as
> > slaves, just a question of dynamics, i work a lot with samples and
> > it's nice to have the beats a little late..and being able to reach
> a
> > tempo up to the 0.001th BPM from an external clocking device (i
> still
> > haven't found better than my atari 1040)
> >
> > but yeah it would definitely be the best machine if the 707 sent
> the
> > sync signal in midislave mode...i know some people on the tr707
> yahoo
> > group are electronic wizards and maybe on day someone will come up
> > with a hack or mod
> >
> >
> >
> >
> > walterdsil < orangeattack@... > a écrit :
>
> > Hi there,
> >
> > Midi works together with sync, but only when your 707 is master.
> >
> > I use this function a lot on order to synchronise my 101, 202, 303
> > and
> > 909 with my other midi gear and computer.
> >
> > It works fine like this. I heard people say the 707 isnt a good
> > constant master, but i havent experienced this in person!
> >
> > hope this helps
> >
> >
> >
> >
> >
> >
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