How do tweak a Phase shifter for ouboard LFO (to integrate into a modular synth)

[lowvolt]

I've recently got into building a modular synth .. well .. not ~building~ as in DIY construction, but rather *assembling* one module by module as (my limited) cash flow permits.  I'm doing up a "synthesizers dot com" modular and have had modules arriving regularly as Ebay sales of another hobby provide the cash-hish!

I see that BYOC offers a (seemingly) nice phase shifter kit these days.  I couldn't help but wonder how I could integrate the use of outboard LFOs to provide some non-standard sweep waveforms to control the phaser.  Imagine a complex LFO waveform controlling the filters!  (I'm super tired right now, forgive me if I'm a bit unclear here .... I think my meaning is fairly clear though).  Modulating the frequencies with oddball shaped waveforms, as well as the ability to sync it all up to other LFO-driven modulations sounds like fun.

So instead of (let's say) using the phaser's sine wave (or is it a triangle wave) to modulate the phaser's freqs, imagine a jack that allows patching in some other control waveform to do the same function.  A switching jack of sorts would do ... the "mechanics" of that part of this modification are the easy part ... it's tapping in to the circuit iteslf to gain access is the part I have zip-clue about.

The LFO that the modular synth I'm assembling has four simulataneously available waveforms ... all of which can be mixed togther in an infinite way to create complex waveforms for modulation purposes.  Here's a link to the VCO (this company doesn't offer a dedicated LFO, instead they simply put a "low freq" swithc on their standard VCO so that it may be used as your LFO .. jsyk).

http://www.synthesizers.com/q106.html

And the mixer ...

http://www.synthesizers.com/q161.html

Just in case you need them for reference .. it may affect you replies.

How do I provide access to these parameters of a phaser for this concept?

Thanks!  

Btw, I DID do a search for this here but wasn't able to locate anything this specific.

PS:  I see that this forum has that dreaded "jittering edit screen thing" going on ....  once I get to typing below the visible level the screen won't auto-scroll down and the danged thing jumps all over the place.  It makes writing something that is longer than the 3-inches of exposed edit screeen REALLY DIFFICULT TO DO!  I'm using Internet Explorer as a broswer... and jsyk byoc has this same issue going on.  I know that several of the members there at byoc have verified this same complaint over there.  Dunno if it ever got resolved there or not.  You basically have to type "blind" and scroll down to look at what you've typed every few dozen keystrokes .. then edit .. edit .. edit to fix the typing mistakes made from "blind typing".  Just sayin' ..

[lowvolt]

Also, I would guess the same ideas could be applied to flangers as well.  So if I get this issue figured out I may be able to integrate several modulation FX into the synth!  OH HOW COOL IS THAT!!!!

[gde]

Is this the BYOC phase royal?
The easiest way, but not exactly the most proper would be to just remove the LFO thats already in the design and add a jack to plug your desired modulation source into that end of the depth pot or go through the voltage follower right before it maybe...

Since guitar pedals use 0V, a 4.5Vref, and 9V for their supplies and modular uses +/-12V or +/-15V, you would have better luck using the phase shifter from musicfromouterspace.com in your modular. There are a bunch of other PCBs there for modular use that are very beginner friendly too. And a few standalone guitar effects as well.

I haven't used the MFOS phaser before, but it is an OTA phaser, so it will sound more like a small stone than it will an mxr.

Also, if you are interested in phaser shifters and modular synths, then Juergen Haible's (RIP) site has some cool things to look at.

[charmonder]

Check out the Rick holt of frequency central design. It uses lm13700 chips for phase stages, which are easily expandable to as many stages as you want, the best part is it uses no vactrols and no jfets. The popular vero layout cycling these parts is known as "casualty phaser" but as I recall Rick holt makes CV controlled phasers in synth modules based on the same design(? )He posts on these forums so I'll just hope he has more helpful information about it.

[lowvolt]

Hot cha cha ... 

http://www.oakleysound.com/equinox.htm

This might work!  Thanks for the suggestions ... they got me to digging deeper and checking out a few things ... the MFOS one seems pretty nice too..

http://musicfromouterspace.com/index.php?CATPARTNO=NONE&PROJARG=PHASESHIFTER2007%2FPHASESHIFTER2007.php&MAINTAB=SYNTHDIY&VPW=1266&VPH=538

Synthesizers dot com sells the blank module panels so this should be fairly easy (he said .. oh boy .. )

T'anks Mangs ..

[Processaurus]

Watch your headroom using guitar effects with modular synthesizers, guitar waveforms are about 400mV peak to peak, synthesizers can be 5-15v peak to peak.  Most guitar effects (especially those with lmited headroom, like OTA based effects) would need their audio path modified to work with higher voltage synthesizer waveforms.  An simple way to do it is to pad down the input with a resistor voltage divider and then amplify it back up again after the effect with an opamp.  Something like 10:1 would be a good starting point.

Here's a ready made version, from Ken Stone:
http://www.cgs.synth.net/modules/cgs60_sba.html

[lowvolt]

Watch your headroom using guitar effects with modular synthesizers, guitar waveforms are about 400mV peak to peak, synthesizers can be 5-15v peak to peak.  Most guitar effects (especially those with lmited headroom, like OTA based effects) would need their audio path modified to work with higher voltage synthesizer waveforms.  An simple way to do it is to pad down the input with a resistor voltage divider and then amplify it back up again after the effect with an opamp.  Something like 10:1 would be a good starting point.

Here's a ready made version, from Ken Stone:
http://www.cgs.synth.net/modules/cgs60_sba.html

I'm not planning on using the phaser for the synth audio path ... just using synth LFOs to control the phaser for guitar use.  And jsyk, any decent modular synth is outfitted with more ways of attenuating an audio signal than you can shake four or five sticks at.   There's ~signal processors~ ... ~rectifier/inverters~ ... ~voltage controlled amplifiers~ .. on and on ... the list is nearly ridiculous.

The *opposite* is true as well.  I have one module known as the "Instrument Interface" that allows the use of lo-level instruments (guitars, mics, etc ..) and easily interjects those signals into the 10 volt world of modular synths.

A well outfitted modular synth is THE best general FX unit ever made!

I think either the MFOS phaser or the Oakley that I posted there will do the job that I was attempting to *hammer and chisel* with some guitar phaser quite nicely.  I found those after someone here in this thread kinda made a casual mention of the "Music from outer space" (MFOS) unit and got me digging a bit deeper into the wabbit hole.  Either one of those two are exactly what I was trying to "reinvent" by modding the BYOC unit to do so.  (talk about trying to teach a pig to fly!  Geez!).  And both the Oakley and the MFOS are DIY units too!

Since I've got into modular synths things have changed a great deal!  I now have ... essentially .. an electronic ~lab~ that allows the creation of new ideas and designs to be hammered out with just a few patchcords.  In minutes I can prove/disprove many ideas and inventions without ever plugging in a soldering pen.  A digital VOM is easily introduced literally anywhere in the chain through banana-jack terminated probes, as well as a 2ch Hitachi scope .. so that way levels and voltages can be monitored/recorded in the event that I'm designing something for guitar-pedal use, or whatever!  I'm still learning my way around the scope .. but it's a buttload of fun, nontheless.

Thanks for making note of the signal level differences.  That info should be very helpful to others that read this nonsense that I post around here!  HAAHAA!

(Hey, if ya can't laugh at yerself you end up taking yourself entirely too seriously .. y'know whut I mean?  Then you end up in the cardiac ward at the local hospital  ).

[frequencycentral]

http://dl.dropbox.com/u/967492/M172-B.jpg