[sdiy] Niche ACM-1 how's this thing work?

Mike Bryant mbryant at futurehorizons.com
Tue Mar 21 16:03:30 CET 2023

With a 10 bit MDAC or DPOT, any zipper noise should be 60dB down on full house.  Now of course we don't operate at full house so you have to take your headroom off that but chosen carefully it shouldn't be hugely annoying.  But if it is there are some DPOTS with zero crossing switching included so they only change gain as you pass through zero, eliminating most annoyances.
From: Tom Wiltshire <tom at electricdruid.net>
Sent: 21 March 2023 14:56
To: Roman Sowa <modular at go2.pl>
Cc: Mike Bryant <mbryant at futurehorizons.com>; synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Niche ACM-1 how's this thing work?

This is a good point. MDACs or even digital pots work best in situations where you set a value and then leave it. That's ok for quite a lot of programmable stuff, but it doesn't suit things where there's an element of performance control likely. For that, a DAC controlling a VCA is a better bet, since the VCA's CV can be heavily smoothed to avoid any zippering. A mixing desk is a bit of both depending on how you use it, so it's a tricky one.

The old Sequential Pro-FX 500 system I was looking into some months ago used plenty of MDACs ( the 7524, 8-bit, still available) for audio level control. It was probably a top-end solution at the time.

On 21 Mar 2023, at 14:38, Roman Sowa <modular at go2.pl<mailto:modular at go2.pl>> wrote:

This may not going to work in every application though. Imagine Buzz Lightyear talking to Woody: "glitches and zipper noise, glitches and zipper noise everywhere"

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