[sdiy] How droopy is too droopy in a S & H?

[johnspeth at yahoo.com]

For VCO pitch control applications, 2 mv is exacly 2 cents of pitch with a 1v/oct control.  My ear's less than perfect sense of pitch is able to hear about 5 cents error.  I wonder if I'd be able hear a periodic refreshing of a S/H at a 1 second refresh interval.

That's the numbers but of course it's all about the ear.  I think 2 mv/second will probably work in most synth apps with the right refresh rate.

JJS


----- Original Message ----
From: mark verbos <mverbos at earthlink.net>
To: Synth DIY <synth-diy at dropmix.xs4all.nl>
Sent: Monday, January 26, 2009 10:08:46 AM
Subject: [sdiy] How droopy is too droopy in a S & H?

I have been seduced by the Analog Devices SMP04 quad sample and hold chip. It has 4 independent S&H circuits with built in capacitors, in a 16 pin chip. I claims a "low droop rate" of 2 mV per Second. Doesn't that seem like a lot? How much does a normal sample & hold droop? How much does an LF398 with polystyrene caps droop? Is this a waste of time and money? The AD684 seems to be about 10 time better, but also $50! It's hard to tell because they don't use the same units for measuring the specs on all the chips...


Mark
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