From: tom@cpac.washington.edu (Tom May)
Newsgroups: rec.music.makers.bass,rec.music.makers.guitar
Subject: Re: what exactly is a "small stone"?
Date: 24 Jan 93 10:59:53 GMT
Organization: The name of the band is Slip.
	<1993Jan23.235630.5445@cronkite.ocis.temple.edu>
NNTP-Posting-Host: bailey.cpac.washington.edu
In-reply-to: christen@astro.ocis.temple.edu's message of 23 Jan 93 23:56:30 GMT

In article <1993Jan23.235630.5445@cronkite.ocis.temple.edu> christen@astro.ocis.temple.edu (Carl Christensen) writes:

>john.s.pfaff (pfaff@cbnewsi.cb.att.com) wrote:
>: my guitar player has one of those old electro-harmonix "small stones",
>: which has a really cool "underwater" sound.  i'd like to get one for
>: my bass, but i doubt the actual small stones are still available.
>: what is the technical/functional name of this thing?  i imagine the
>: effect is available under some other name.  any ideas?

>I don't think Electro-Harmonix makes the "Small Stone" anymore.  I used
>to have one way back when I was an undergrad.  The effect name is
>a PHASOR, and they're still available from various companies.  A
>FLANGER is also a nice effect to use on a bass.  You can get a
>combination CHORUS/FLANGER/PHASOR from most companies also to
>get the best of all worlds.

You can get chorus/flanger/phasor in a multi-effects box that also
provides additional goodies, but can you get it all in one little
stomp box?  Even some multi-effects boxes provide chorus/flanger, but
not phasor.  Here's why:

Chorus and flanger (and delay/echo, too) are variations on the same
theme (and very easy to implement digitally), but a phasor (aka phase
shifter) is a different sort of thing.  Flanger etc. work by delaying
the signal a certain amount and mixing it with the undelayed signal.
The old MXR flanger I have uses a Reticon SAD-1024 analog bucket
brigade chip as a delay device.  More modern effects use digital
delays.  A very small delay (~1ms) gets you a flanger, a somewhat
longer delay gets you a chorus, and a delay so long it is audible gets
you an echo.  The delay time is usually modulated in a flanger and
chorus to get a dynamic sound.  Some portion of the delayed signal
will also typically be fed back to the input of the delay stage.  Note
that the time delay is not dependent on the signal frequency.

Phase shifters are not part of the flanger/chorus/echo family.  A
phase shifter also delays the signal, mixes it back in, uses feedback,
and has a modulated delay, BUT the delay is achieved with an opamp
unity-gain phase-shift circuit which produces a DIFFERENT amount of
delay for different frequency components (actually, there are usually
six of these circuits in series).  This produces a much different
sound from chorus/flange, although both flange and phase are comb
filters, it's just that the comb looks different.  Since a phase
shifter is not just a tweak on the flanger theme, I don't have the
foggiest idea how they simulate it in digital multi-effects boxes, and
I wouldn't expect to see a unit that did only flange/chorus AND phase.

I did see an article in the Journal of the Audio Engineering Society
which said that a phase shifter approached a flanger as the number of
phase-shift circuits in series went to infinity, or something like that.

The Small Stone is the one with the "color" switch, right?  Does anybody
know what that switch did in technical terms?
--
Tom
Newsgroups: rec.music.makers.bass