[sdiy] Stereo Phasing With the 32 Stage MultiPhase Project

[Scott Stites]

René Schmitz wrote:

>I just listened to some of the the older sounds for the first time, and 
>the difference between triangle and hypertriange was an eye opener.

It certainly helped getting some of the smaller stage numbers to sound 'tighter'.  In practice, I find as the number of stages increases, I start leaning more heavily in the direction of 'normal' triangles.

>I especially liked the percussive pulse and triangle modulation, thats 
>something which one would miss out in a phaser that is limited to a 
>single LFO for modulation. Might be interesting to be able to use and 
>envelope generator for sweeping as well.

Yes, I love the percussive sound of resonant phase shifters - I really should try 'ringing' the phase shifter with a pulse input, but have never gotten around to it.

The envelope generator is an excellent idea as well.  The external CV could cover that, but it would be nice to have one built in that could be triggered/gated from the audio source.

>One thought occurred, how to make all these possibilities available, 
>once that design leaves the breadboard?

That's the million dollar question =-D.  I've been scratching on paper and scratching my head recently on this aspect of the thing.  It's either going to be one huge phase shifter or I'll have to start trimming some things out.  As usual, the hardest part is to decide what can fit on the front panel. I'm hoping I can fit nearly everything on a 4U rack panel.  I know that's pretty big for a phase shifter, but this is something I can see using a lot (not just for phase shifting - the control signals will be useful, too).

One approach would be to make it modular, sort of like Doepfer did with theirs, but I'm really not wild about that idea - I'd rather make this a standard rack effect.

The phase and regen stages can be selected with rotary switches, though I have been considering using DGXXX type audio switch IC's with momentary switch selection.  I think the audio path would be improved by this, but I don't see the approach as a means for conserving panel space if one wants to devise a visual feedback system that wouldn't be too cryptic.  CV and regen attenuation and inversion can be handled with single bipolar attenuation controls.  Even/odd input and regen stages can be handled with DPDT ON-ON-ON toggle switches.  Wet/Dry blend for each section can be handled with a single control per section.  Parallel/cascade operation can probably be handled with switching jacks.  A switch will be necessary to pass the regen from the B section to the A input if one wants more than 16 stages of regen in cascade mode.

The real consumer of panel space will be the control section. Not only do I have the LFO/ExtCV/and EF controls to worry about, but I'm looking at having a set of master controls so that both phase sections can be operated from a single set of controls.  The fact that one would *not* want to invert master center voltage and hypertriangular LFO's while everything else is invertable complicates that a bit.

I haven't even touched on the wet signal crossfaders yet =0).

Cheers,
Scott


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