Schematic Request EH Polyphase.

[Mark Hammer]

Another possibility is that the 4 swept stages are in common (and it sounds like a 4-stager, rather than 2 stager), but two fixed stages are added to the input of one mixing stage, such that it pans between a 4-stage phaser on one side and a 6-stage uit on the other.

Again, it's the sort of guessing that comes about when you have only modest information about the pedal and limited choice/control over soundclips.  We might both be way off.  I'd work my way through all the posted soudclips, but it takes a while to download them and I know from past communicatuion with that webmaster that too much traffic and bandwiodth charges has been a sticky point, so I only listened to a few.

[Gripp]

Interesting.
The ARP Quadra does exactly that. Mixes wet with one in phase and one out of phase dry (wet+dry & wet-dry). In itself this gives a panning effect when running both outputs left and right in stereo. It also gives a loopsided pan that I have thought a lot about trying to correct only to realize that it's probably just mother nature trying to tell me something. How loopsided it appears to be seems to depend on what frequencies you are sweeping, how much feedback there is and other things. This makes sense.
I did some FFT of the quadra using noise input and this really gives a clear picture.  The two channels are not mirror images with peaks exactly the same shape/size as where the other had valleys, they differ in shape and actual cut/boost. This gives a loopsided feel in a lot of settings. My unit has 1% MF mixing resistors so I don't think that the mix is that off.

A picture.....
Noise input from M-audio Firewire 410 generated in reaktor, directly in to the 410 and recorded in reaktor. Upper channel wet+dry, lower channel wet-dry. Zero feedback, no sweep, just a frozen phase with manual lowish. No normalizing either so don't mind the actual dB's, just look at it relative. FFT done with Sound Forge.

 

Best!
Pelle G

Just imagine sweeping this and you got it.

[Mark Hammer]

Thanks for the info.  Interesting and informative.

One of the things to consider about sum-vs-difference phasing is that you end up with different overall amplitudes for sum and difference, especially if there is any feedback/regeneration applied.  Use of 1% mixing resistors will not avoid that issue.  Unless one is able to adjust the balance of the output levels, any such wet-panning would be "lopsided".  Happily, the adjustment is rather trivial and can be as simple as adjustment of two feedback resistors in each op-amp stage, or perhaps adjustment of the ground leg resistance with one single pot (wiper to ground) in a pair of noninverting op-amp stages after the mixing stage.

Of course, since a great many stereo phasers (I have a DOD FX20) are used by folks who tend not to process in stereo, but rather use the one output or the other(i.e., either sum OR difference), this problem doesn't come up very often.  If you DO process in stereo, though, you'll notice it.  I didn't particularly notice it in the modezero samples, but I wasn't listening all that closely or under favourable conditions.

[Gripp]

One of the things to consider about sum-vs-difference phasing is that you end up with different overall amplitudes for sum and difference, especially if there is any feedback/regeneration applied.

Exactly! I've tried to offset this by adjusting the gains of the different channels on my headphone amp (just for testing) , but it really never worked well. So hard to find a happy medium. Feedback changes things too much and sweeping a different part of the spectrum changes the appearent left or right boost yet again. You'd have to adjust that gain control too often (really in sync with the sweep some times) so  I think I'll just live with it and call it a feature. Actually, when feedback/regeneration is low, modulation isn't that wide and the sweep is centered in the middle, you get an almost even panning feel. This is a very nice stereo sound that in some cases can replace a stereo chorus for me. 

[notchboy]

Mark, I know the guy who runs modezero.com, and from my understanding of their hosting setup, I really doubt if you have to limit your mp3 consumption that severely...

[Mark Hammer]

Well, I haven't corresponded with him in a year or so, and at last contact the fact that he was ending up having to pay his ISP more because of the large bandwidth demands that all the pictures and soundclips were creating sort of rankled him.  Perhaps that has improved.  Just trying to look out for a guy who has provided an extremely useful source of information out of the goodness of his heart.