MAX083

[Arthur Harrison]

I tried the MAX083 when it came out, as a 7 octave audio
sine wave source for a theremin, but it had a lot of frequency
jitter.  I followed the applications notes, used a ground plate,
did everything by the book, but there was still audible jitter.
I resorted to the good ol' integrator/hysteretic comparitor method.

Your comment re: lead inductance just might have been the
problem!

-----Original Message-----
From: Tony Allgood <oakley at techrepairs.freeserve.co.uk>
To: synth diy <synth-diy at mailhost.bpa.nl>
Date: Wednesday, November 04, 1998 1:14 PM
Subject: MAX083


>Hi there,
>
>It was scheduled to be a quiet day in the office so I decided I would have
a
>go at upgrading my home-made signal generator. This was based on the old
LFO
>idea of integrator/schmitt trigger with a few waveshapers to get some
>different wave outputs. But slew rate was crap and sinewave distortion was
>not good. So I bought a MAX083. Looks great on paper, both for a VCLFO or
>signal generator. But beware, because it is designed to be really fast...
>20MHz and up... it was a real pain to stabilise. Honks all over the shop,
>couldn't get my ground clean... but then again I was using stripboard. The
>sync output is real sharp edged little thing, that put glitches over the
>ground and output. The data sheet warns you of this, and they are not
>kidding. However, you can disable this function... and I did. Current
>consumption is high (around 50mA0 and not constant either so your power
>lines will be noisy without some decent filtering/decoupling. And it runs
>off split rail 5 volt, not exactly handy for me I can tell you. Be careful
>if you decide to have a selection of timing caps to switch in. The
>inductance in the leads to the switch will cause instability of the sine
and
>triangle outs. Not the square though. Very fussy of output load as well.
For
>our purposes you will need a voltage follower/amplifier of some sort.
>
>In the end it makes a nice sig gen with a very good sinewave. The
mark/space
>can be changed for all the output waveforms with only a small change in
>frequency. As for VCLFO it may be useful, with a control range of 300:1.
>
>Regards,
>
>Tony Allgood, Cumbria, UK
>
>e-mail: oakley at techrepairs.freeserve.co.uk
>
>Rack mounted Moog VCF module. Details to be found at...
>
>http://aupe.phys.andrews.edu/diy_archive/schematics/effects/filter.html
>
>
>