Re_Mike: [sdiy] SAD1024 different modes

[Scott Stites]

Hi JH,

Actually there were two versions of the A/DA - one used the SAD1024 and the other used the MN3010.  Not sure, but I believe the SAD1024 version pre-dated the MN3010 version?  If not, I guess it was the other way around =-).

Cheers,
Scott

-----Original Message-----
From: "JH." <jhaible at debitel.net>
Sent: Aug 29, 2005 2:31 PM
To: "Mike I." <mikei at marketbridge.ca>
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re_Mike: [sdiy] SAD1024 different modes

Hi Mike,

> The way Eventide does it in the plugin delay card for the Instant Flanger
> seems like a good solution. Each 512-stage section is
differentially-driven,

This I don't unterstand. How can each 512stage section be differentially
driven - I only see one input ?! I thought for differential driving you
already
need both halves of the chip ...

> the two sections are operated in parallel-multiplex, and the n, n-1
outputs
> within each section  are resistively summed and fed to the inputs of a
> single diff amp at the output.

... does this mean they drive the two sections with inverted signals *and*
with swapped clocks ... now that is interesting!
Would be very nice to take a look at these schemos, too. 8-)



> I think this is the main advantage of parallel multiplex -  for a given
> clock rate the resulting sample rate is 2 x clock.

Yes ...

> If many sections are
> operated in a "multiphase multiplexed" arrangement the ratio of S.R. to
> clock becomes even larger. What this does is allow you to extend the the
max
> delay time without changing the minimum delay time... increasing the
max/min
> ratio.

I think I can see how multiplexing many lines allow for increased bandwidth
of the input
(anti aliasing) filter: You won't get aliasing even when the signal spectrum
exceeds
the sampling rate, if 4 devices are used. But on the output, the remains of
the clock
will be in-band then, won't it? (speaking of the spikes that remain from
non-ideal
cancellation)

> The Marshall Time Modulator probably  took full advantage of  differential
> operation and n x parallel multiplexing.

Another box for which I haven't seen schemos yet. Guess I'm a bit behind
with my
BBD circuit collection. (;->)

JH.



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