zipper noise was: digital control

[Brousseau, Paul E (Paul)]

A lot of people have brought up glide curcuits, etc., but the high bitcount
DAC seems glanced over.  What are the pros and cons of that?  The only
immediate con I can imagine is that anything beyonf 7 (8?) bits is out of
MIDI resolution.  I would propose that solved by using two MIDI signals, a
"course" resolution and a "fine" resolution.  What am I missing?

(After a moments thought...)  Using two MIDI signals would make things
difficult for external control, I suppose.  It would be nearly impossible to
spin two knobs to achieve a continuous sweep through a broad band.  Spinning
just the fine control knob wouldn't do very much, and spinning just the
course control knob would just introduce the zipper effect again.  The
usefulness of two controls, then, would be limited to patch storage.  The
module could be designed to use one knob locally.

A relevant question, then, is "Is 14 (16?) bits enough?"  Also, how fast
would one need to clock?

--PBr

> -----Original Message-----
> From:	harrybissell at prodigy.net [SMTP:harrybissell at prodigy.net]
> Sent:	Wednesday, January 12, 2000 7:47 AM
> To:	DCMagnuson at aol.com
> Cc:	synth-diy at mailhost.bpa.nl
> Subject:	Re: zipper noise was: digital control
> 
> Yes... you can put a "glide circuit" or lowpass filter on the DAC output.
> The trouble is... what rate to filter at. If you do a very slow (manual)
> filter sweep... you need a very long time constant. If you "whip" the dial
> quickly... the long sweep will fight you.
> 
> You could detect how fast the dial is moving and filter slow or fast
> (either digital of analog) or have so many bits and clock so fast that
> no-one can hear it.
> 
> The Studio Electronics AT1 (???) the "tone chamelion" model with the
> single "Alpha Dial" is the only hybrid synth I have ever heard that does
> not have zipper noise... Even at high resonance settings it is dead
> smooth. I'd consider buying it just for that reason. I wonder how they did
> it ???
>