AW: Phasers

[Haible Juergen]

	>There is one design I've been wondering about. Everyone
	>always says that the SSM2040 is the best sounding filter
	>chip. In an old Polyphony article, Tom Henry uses an
	>SSM2040 to build a phasor. I've wondered if it sounds
	>as great used in this application as it does as a low
	>pass. And if so, could JH's SSM2040 clone be adapted.

I have never tried to build a phaser with the SSM2040. But the circuit
is straight forward, and I see no reason why it should not work with 
my discreet version as well. I just cannot say if the the famous
2040 output clipping would have an advantage here or not.
(In the LPF case, the clipping of the first stage(s) is filtered by
the next stages ...)
But for the normal SSM2040 data sheet phaser application, I'd
say go ahead, it should work.

Cascading more than 4 of these stages might be interesting, too.
But stability might become an issue at one point. Or maybe not.
(I've tried to build a 16-stage phaser from 4 CEM3320's once,
but I didn't get it quiet with all the bypass caps you can think of -
but then this is a very different chip ...)

If your "ultimate" phaser is one that has a very pronounced sound
(subtle ones have their benefits as well ...), I recommend the
Phaser of the ARP Quadra. 14-stage circuit, stereo, noise
reduction circuit, built from cheap chips, and very pleasant
sound at high feedback that cuts thru but never gets too nasty.
(well, nasty can be a good thing too ...)

I have schemos and a PCB layout published at 
<http://www.synthfool.com/diy/hj_sch.html>
if you're interested. (It's slightly adapted to work as a stand alone
unit.)

JH.