[sdiy] Digital echo chip

[harry]

ADM is "Adaptive Delta Modulation"... the method used by DeltaLab
for their digital delays.

The way it works is that the bit referrs to the sign of the incomming
signal...
and the sign is integrated and compared with in input.

If the sign remains the same for consecutive clock cycles, the integrator
current
is progressively stepped up. So 1 bit in a row is a small step, 2 in a row is
a larger
step... etc.

The technique works very well with a very high clock frequency. For that
reason,
the amount you can vary the delay (by clock rate) is somewhat limited. Its
best to
add and delete RAM to get the times you want. Echo is no problem.

Let us know how it works !

H^) harry

Scott Gravenhorst wrote:

> It's another of Murpy's Laws that says the site you
> looked at casually yesterday will be down today simply
> because now you NEED it.
>
> The data sheet talks about "1 bit digitized" as "ADM"
> modulated, and they don't define "ADM" per se.  The DRAM
> needed is single bit wide.  I wonder if this is some
> kind of PCM ??  They don't describe the digitization much
> other than that, so it's hard to know what digital resolution
> is attained.  They call it "low distortion", but show
> different distortion specs, one is 3% THD, the other
> 0.4% THD.
>
> But who knows, for $3.95 it could be fun at least and
> might well be better than Happy Harry's nemesis, the BBD.
>
> If you get one and play with it, I for one would like to
> hear about your discoveries with it.
>
> Scott Bernardi <sbernardi at attbi.com> wrote:
> >I came across the PT2935 (Princeton Technology) digital echo IC at
> >Jameco (www.jameco.com) for $3.95.  The delay can be continuously
> >variable with a resistor. You can supposedly get up to 800msec of delay
> >with an external 256k DRAM chip in extended delay mode. There was a very
> >minimal datasheet on the Jameco page. I got to the manufacturer's
> >website yesterday but today it seems to be down (www.princeton.com.tw).
> >Anybody have any experience with this chip?  It looks pretty
> >interesting, and it's cheap enough.
> >
> >--
> >Scott Bernardi
> >sbernardi at attbi.com
> >
> >
> >
>
> =========================================================
> - Government: The other religion.
> - The media's credibility should always be questioned.
> - Lambs who lie down with lions are lunch.
>
> -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> -- Linux Rex         | RedWebMail by RedStarWare
> -- FatMan: home1.GTE.NET/res0658s/TekLab_FatMan_WebSite/index.html

--
Jihad Terrorism Conspiracy New World Order
Revolution Black Helicopters Freedom of
Speech First Amendment Rights: Carnivore Bait
go ahead and READ my e-mail I have nothing to
hide... how about YOU ???