New Phaser Design - “Causality 4” – Built with you in mind!

[bluebunny]

I use the causality 6. Great phaser.

Small bump-ette to say that Rich was quite right.  I (finally) got around to building one:

     (more snaps in the main Pictures thread)

[frequencycentral]

I love it Mark! Very smart. Nice to know this design is still being built. I'm just about to retire the Eurorack version, as the advent of reissue/clones of CEM3320 (Alfa AS3320) means 4 stages are possible on one chip. With a charge pump these could be used in a pedal too I suppose. Alfa are also doing a 4 OTA variant of the LM13700 (AS13704) which is ripe for some phaser action, and should run on 9V. I've been been thinking a lot about phasers again recently.....

[Mark Hammer]

Why use up CEM3320 clones?  Leave 'em for the synth gang.  SSM2164 clones are cheap and available.  And if a quad 13700 becomes available, so much the better.

Mike Irwin once demonstrated a phaser for me that used 2-pole allpass filter stages (most OTA-based phasers use 1-pole stages).  Interestingly, the notches were closer together than what we're familiar with.  Because of that, even without much feedback used, the sound is more "focussed" as the tighter cluster of notches moves around.

I think some sort of aperiodic sweep is desirable.  That could be from 2 unsynced LFOs being mixed, or some other variation.  Anything that removes the up-and-down-and-up-and-down monotony makes the effect something you don't mind leaving on.  Of course, there are times when you want the sweep to sync with something pertaining to the flow of a tune, so I guess the "periodic option" is still worth retaining.

[bluebunny]

Thanks Rick.  I have one more phaser of yours in the pipeline... 

I've been been thinking a lot about phasers again recently.....

Of course!  It's the law, right?   

[bluebunny]

P.S. I can post my vero layout if anyone's interested?  I can't remember if there's one in this thread already (and is still online and not blurred).

[anotherjim]

Did anyone try an Ensemble phasor - a similar idea as a Solina triple BBD chorus but with phasor stages?
Using an MCU, it would be possible to have tailored multi-phase LFO sweep waveforms that also supports tap tempo. For guitar, only dual-channel might suffice. I read somewhere that Donald Fagin liked to use a pair of Phase45's with his Rhodes piano for a fake stereo effect.

[Ben N]

After a brief scan of a few pages of the thread, it seems like the old perf and pcb layouts are ph[otob]uck[et]ed. Are there any legible ones for late versions of the Causality family available?

[Axldeziak]

There is a way to see the photobucketed pics but it's a pain. First right click and tell it to view image, then save the pic locally. The file can then be opened and will not have the blur or photobucket banner on it.

[bluebunny]

Hopefully with Rick's blessing, here's what I have in my stash for the Causality 4 and Causality 6 designs.  (@Rick: let me know if you would prefer me to pull this post.)

original schematic, perf layout and PCB:
       

Mk. II schematics and PCB:
   

LED wax'n'wane mod:


daughterboard for extra stages:
 

Mk. II V2:
 

Causality 6 schematics, original and rev. 2:
 

And here's the slightly simplified C6 version I built along with my vero layout:
 

[Berger]

Thanks for posting these! I've been looking for them for a while. I have the old layouts but no schematics to go with them.

[Kevin Mitchell]

Alfa are also doing a 4 OTA variant of the LM13700 (AS13704) which is ripe for some phaser action, and should run on 9V. I've been been thinking a lot about phasers again recently.....

That's a fine idea 
And some motivation to give SMD work a try.

I recently gave away my CA3094 Small Stone clone so I've been itching for another OTA phaser.

-KM

[Mark Hammer]

Note that OTA-based phasers permit the wonderful phase-filter mod.  Flip one end of the cap in a stage from the input to ground, and the stage converts from allpass to lowpass.  See the SSM2040 appnotes or issue 4 of DEVICE, that I posted on my old Ampage site ( http://hammer.ampage.org/files/Device1-4.PDF ).

[Ben N]

Thanks, Marc (& Mark).

[tubegeek]

Hopefully with Rick's blessing, here's what I have in my stash for the Causality 4 and Causality 6 designs.

Thank you very much.

Tayda just got LM13700's back in stock. Coincidence? I think not!

[Mr. Lime]

How does the Causality phaser differ from the Maestro phaser soundwise? Do they have a lot in common? Both are OTA based and both have the resonance fed back from the 5. stage..

How to discribe the difference from sweeping stages to fixed ones? The Maesto 5 stager sounds great but would it benefit from 2 extra fixed stages on the front and back like the Causality offers?

Probably someone already discribed it but I can't find it in detail..

[Scruffie]

I love it Mark! Very smart. Nice to know this design is still being built. I'm just about to retire the Eurorack version, as the advent of reissue/clones of CEM3320 (Alfa AS3320) means 4 stages are possible on one chip. With a charge pump these could be used in a pedal too I suppose. Alfa are also doing a 4 OTA variant of the LM13700 (AS13704) which is ripe for some phaser action, and should run on 9V. I've been been thinking a lot about phasers again recently.....

I breadboarded a 3320 phaser up a few months back, I found that if you're using the full sweep capability (which is a big part of the appeal) as it sweeps so high they get pretty noisy for guitar use, the S/N specs are about as bad as a BBD so the space benefits of 4 stages on a chip quickly disappeared with the charge pump and additional support circuitry.

[Mark Hammer]

I love it Mark! Very smart. Nice to know this design is still being built. I'm just about to retire the Eurorack version, as the advent of reissue/clones of CEM3320 (Alfa AS3320) means 4 stages are possible on one chip. With a charge pump these could be used in a pedal too I suppose. Alfa are also doing a 4 OTA variant of the LM13700 (AS13704) which is ripe for some phaser action, and should run on 9V. I've been been thinking a lot about phasers again recently.....

I breadboarded a 3320 phaser up a few months back, I found that if you're using the full sweep capability (which is a big part of the appeal) as it sweeps so high they get pretty noisy for guitar use, the S/N specs are about as bad as a BBD so the space benefits of 4 stages on a chip quickly disappeared with the charge pump and additional support circuitry.

Maybe that's why the Boss PH-2 and RPH-10 both use companding.  OTAs have gotten much better over the years, but they still aren't as intrinsically immune to noise and distortion as LDR-based phasers.

[Scruffie]

I love it Mark! Very smart. Nice to know this design is still being built. I'm just about to retire the Eurorack version, as the advent of reissue/clones of CEM3320 (Alfa AS3320) means 4 stages are possible on one chip. With a charge pump these could be used in a pedal too I suppose. Alfa are also doing a 4 OTA variant of the LM13700 (AS13704) which is ripe for some phaser action, and should run on 9V. I've been been thinking a lot about phasers again recently.....

I breadboarded a 3320 phaser up a few months back, I found that if you're using the full sweep capability (which is a big part of the appeal) as it sweeps so high they get pretty noisy for guitar use, the S/N specs are about as bad as a BBD so the space benefits of 4 stages on a chip quickly disappeared with the charge pump and additional support circuitry.

Maybe that's why the Boss PH-2 and RPH-10 both use companding.  OTAs have gotten much better over the years, but they still aren't as intrinsically immune to noise and distortion as LDR-based phasers.

Even with companding and an emphasis network it still had more background noise than a small stone with the colour on.

Don't get me wrong, makes a nice phaser but I wouldn't call it a 1590B friendly chip.

[bluebunny]

How does the Causality phaser differ from the Maestro phaser soundwise?

I don't have the adjectives to describe it, but they are quite different.  I might venture that the Stage Fright is almost flanger-like, but not.  (No helicopters.)  And the C6 is very phaser-y.  I'm not helping, am I?      If I were to mimic the Stage Fright vocally, my face would be comically contorted!   

[Mark Hammer]

There are going to be a few things that make two phasers sound fairly different from each other, even though they might have very similar designs:
1) Component tolerances in the phase-shift stages  This can affect how wide the sweep is, how focussed or diffuse it is, and where in the spectrum notches might occur.
2)  Component tolerances in the modulation part.  This can affect how wide it tells the allpass stages to sweep, where it tells them to start from, and the shape of the sweep.