"Gemini" Dual Core Phaser project

[Ben N]

Damn shame.

[Mr. Lime]

Any chances to hear this phaser?

I'm curious how parallel and series phaseres with phaseswapped LFO sound like..

Is there a point of let's say having a 6 stage phaser where 3 stages are swept out of phase with the other 3?

Thanks!

[frequencycentral]

Any chances to hear this phaser?

Seems my Dropbox no longer plays ball. I've hosted the soudclip on my website.

http://www.frequencycentral.co.uk/wp-content/uploads/2019/10/Gemini-Montage.mp3

Is there a point of let's say having a 6 stage phaser where 3 stages are swept out of phase with the other 3?

Definitely!

I'm planning to work on a new phaser for Eurorack next year, which may have a pedal brother too. It will include a few ideas stolen from other phasers I've built over the years.

[Mark Hammer]

Thanks for the clip, pic, and "resurrection".

I made myself a Tonepad Ropez/Ross or three, and in one of them I slightly reduced the current-limiting resistor feeding the Iabc pins in the OTAs used in the circuit.  This moved the upper peak of the sweep even higher, achieving a huge range of sweep reminiscent of the phasing in the old ELO tune "Strange Magic" (see the 0:46 point here: https://www.youtube.com/watch?v=eqxigCmFRng ).

I understand that feeding too much current to OTAs can fry them, so I don't encourage reckless experimentation (especially with unsocketed chips).  But I'm curious as to whether you've experimented with use of a trimmer to achieve maximum safe range of sweep.  For instance, in the case of my Ropez, I used 9K1 for current limiting, instead of the listed 10k.  I may have gotten lucky, and perhaps other builders may be safer to use 8K2 and a 2k trimmer in series, such that they can gradually edge down from the maximum resistance to something that is tolerable and safe.

[frequencycentral]

4K7 in Gemini ;-)

[Mark Hammer]

But I gather that distributes the current over more OTA stages, right?  The Ropez has four LM13600 stages.

[Mr. Lime]

Thanks Rick!
What a gorgeous pedal!

Is there a point of havng two phasers in parallel fed by the same LFO?
I don't think that there's a difference soundwise but I might be wrong 

I listened to the Lovetone Doppelganger and the MXR 99 as well.
The series phasing with same LFO while the second phaser is out of phase with the first one sounded nice but rather subtle I would say.

What are your observations?

[Mark Hammer]

I made a dual Phase90 for myself that provides operation of two 4-stagers in series with independent LFOs or ganging both phasers to a single LFO.  The former arrangement provides a pleasing aperiodicity, while the latter offers a more "coherent" sweep.  I also wired it up such that the first 4 stages could be set for vibrato (wet only) and the second set for phasing, still ganged to the one LFO.  They both have their charms.

[PMowdes]

I made a dual Phase90 for myself that provides operation of two 4-stagers in series with independent LFOs or ganging both phasers to a single LFO.  The former arrangement provides a pleasing aperiodicity, while the latter offers a more "coherent" sweep.  I also wired it up such that the first 4 stages could be set for vibrato (wet only) and the second set for phasing, still ganged to the one LFO.  They both have their charms.

Do you have Dino's Biphase build at the moment?  Wondering what you think of that?

[frequencycentral]

But I gather that distributes the current over more OTA stages, right?  The Ropez has four LM13600 stages.

2 stages per 4K7 resistor.

[frequencycentral]

Thanks Rick!
What a gorgeous pedal!

Is there a point of havng two phasers in parallel fed by the same LFO?
I don't think that there's a difference soundwise but I might be wrong 

I listened to the Lovetone Doppelganger and the MXR 99 as well.
The series phasing with same LFO while the second phaser is out of phase with the first one sounded nice but rather subtle I would say.

What are your observations?

Thanks!

I would say the standout settings are parallel phasers with opposing LFO, as one phaser sweeps up the other sweeps down. That's awesome! And something you can't do any other way - apart from modular.

[Mark Hammer]

I made a dual Phase90 for myself that provides operation of two 4-stagers in series with independent LFOs or ganging both phasers to a single LFO.  The former arrangement provides a pleasing aperiodicity, while the latter offers a more "coherent" sweep.  I also wired it up such that the first 4 stages could be set for vibrato (wet only) and the second set for phasing, still ganged to the one LFO.  They both have their charms.

Do you have Dino's Biphase build at the moment?  Wondering what you think of that?

I reluctantly returned it to Dino.  It also gets some very vocal-like sounds.  Doesn't sweep THAT high, but the voice-range sweep is lovely.  And yes, running dual simultaneous sweeps is nice.

[Mr. Lime]

Just curious if someone ever tried to modulate the feedback R/ Regeneration control?

The phase 90 and the causality don't have a divider so a vactrol could be used easily. Might add another dimension to the sweeping?