[sdiy] DACs for Arp-style quantizer

[harrybissell]

No... I've done both.

If you increment the counter on the rising edge of the clock...
and run the comparator to a D flip-flop and clock that on the
falling edge...

... it does not matter about the ripple count. Presumably any
glitches will have settled by then, and the comparator output
will have a half-clock cycle to stabilize.

The big trouble with the whole ARP thing is its slow. You don't
get very good accuracy anyway, so why not use a cheap A/D - D/A
like Grant suggested.

I did the qunatized Theremin that way, eventually getting rid of the
MiniWave electronics.  Grant wanted to clock the unit at a very high
rate...
I needed it to run a scan every 5ms or so, or it would just dither
like crazy.

Its an interesting problem.

H^) harry

scottnoanh at peoplepc.com wrote:
> 
> Whoa - talk about blonde mode.  I read a post from the archives where you
> were talking about latching, but I understood it to mean latching the output
> of the counter (which would make sense if a ripple counter were being used),
> but you were talking about latching the signal from the comparator to the
> LF398?
> 
> Blonde in Kansas
> 
> ----- Original Message -----
> From: "harrybissell" <harrybissell at prodigy.net>
> To: "Grant Richter" <grichter at asapnet.net>
> Cc: "Tim Parkhurst" <tim.parkhurst at gmail.com>; "BrightBoy"
> <jdec at mindspring.com>; "synth-diy" <synth-diy at dropmix.xs4all.nl>
> Sent: Tuesday, January 31, 2006 6:58 PM
> Subject: Re: [sdiy] DACs for Arp-style quantizer
> 
> > <blonde mode on>
> >
> > uhhh... hello...?
> >
> > Haven't you heard of the "Wiard MiniWave" ???   :^P
> >
> > H^) harry  (pay no attention to the man behind the curtain :^)
> >
> > Seriously... I was going to build a programmable scale
> > quantizer, but buying the MiniWave was quicker. Finally I DID
> > build a quantizer, freeing up the Minwave to be a wavetable
> > oscillator (as it is better suited).
> >
> > The ARP design is 'ok' if you make some changes... namely
> > you want to add a latch between the comparator output and
> > clock it on the opposite edge of the D/A clock... so that
> > you have 1/2 clock cycle for the comparator to stabilize before
> > clocking the LF398
> >
> > H^) harry again
> >
> >
> >
> > Grant Richter wrote:
> > >
> > > Of course an ADC followed by a DAC only uses 2 chips costing about $4
> > > now a days.
> > >
> > > If you put an EPROM between them, you can have multiple scales.