True Stereo in/out Pedals

[mcasey1]

I have a Prophet 6 synth with stereo outputs and a great pan spread function that sends each new voice played to the opposite side of the stereo field than the last.  I want to run the stereo outputs through some modulation effects like chorus, flanger, or phaser.  However, it is difficult to find any of these effects with true stereo ins and outs.  Therefore, I'm looking into building my own.  I would assume that to have a stereo in/stereo out pedal with no summing to mono you would basically have to have two circuits in parallel, controlled by one set of pots and switches with a separate in and out jack for each side.  Is this true?  Also, in the case of a modulation effect like chorus, wouldn't the two independent sides of the circuit be out of sync with one another in regards to their sweep?  Maybe I'm making it more complicated than it is.  If it's feasible and not too complex, I will be making a set of stereo in/out modulation effects.  I'd rather not go rackmount, even though there are definitely some units out there that accomplish what I want.  Thanks everyone!   

[Mark Hammer]

There are actually a lot of stereo effect pedals.  Many of the various multi-FX floor units have stereo ins and outs.  The Line 6 M5 sells for around $150 or so, and is stereo in and out.  It has something like 128 different effects, including just about everything included in the various LIne 6 modeller pedals.  Many of Boss's delays are stereo in and out.

Some commercial pedals that are one in and two out are not what you are seeking in the way of stereo.  So, some delay-based pedals, whether straight echo or chorus, send dry out one jack and wet out the other.  In other instances, one output is dry+wet while the other is dry-wet.  Each output sounds fine on its own and is different, but run them both at the same time and the effect either cancels out if fed to the same amp, or else cancels out in the air if fed to two separate amps/cabs.

If you are seeking to make the two outputs of the synth have the same effect, but provide a bigger-sounding stereo spread, you really need something that functions as two independent versions of the same effect,

Do the two versions have to function in complementary fashion?  For example, as one goes up, the other goes down, or as one gets louder the other gets quieter.  They could, but they don't have to.  Strictly reciprocal stereo effects can sometimes be too distracting.  I sense from your query that what you want is something that provides some animation, rather than something that forces the listener to pay attention over here, now over here, now over here.

[mcasey1]

I would definitely prefer to have the modulation occur in the same way on both channels simultaneously.  So for a flanger, as it sweeps down on the left channel I would prefer it do the same on the right channel and vice versa.  I suppose I might be looking to make two PCBs of the same effect and connect one set of pots and the switch to both.  Maybe the LFO would need to be affecting both channels rather than two separate LFOs in order to get identical sweep on left and right.

[hymenoptera]

Watching this discussion because I'm hoping to do some of the same stuff. Starting with pairs of distortions first. The ganged pots and double pole switches is the easy part. Anything with FET buffers will require matching. Certain fuzz circuits will require even more intense scrutiny.

Modulation is another story. Might have to slave one board off the other's control voltage, clock, or whatever, depending on which circuit. Some will be trickier than others. Since I'm relatively new to the world of DIY pedals I'm curious which ones will be the most receptive to stereo functionality.

I too want this for synths, drum machines, etc. so I'm curious where this leads to

[roseblood11]

NUX Mod Force!!! Dead cheap, 9 Presets, true stereo, and you can use two different effects simultaneously, in series or parallel!

https://www.youtube.com/watch?v=4mvXs9u_-to

[boogietone]

For modulation effects, I would use the same lfo for each. You could build a second lfo that you could switch into one half if you wanted the flexibility.

[hymenoptera]

I've got 4 of the old Alesis ModFX "pedals" (not really pedals, more like pedal-sized table-top processors) which are all stereo. They're all pretty slick. I've got the phaser, the flanger, the vibrato/trem one, and the compressor, and they're pretty crazy on the old Ensoniq. Would love to get the colection, but some of them are more collectable that others and harder to find.

[Mark Hammer]

I got the flanger one in that series.  Some interesting modulation possibilities, but I think I like the Tonecore Liqui-flange better.  Never had a chance to check out the shared bus, since there's only one unit.  Pity they never really caught on.

[hymenoptera]

I really want the bit crusher and the filter one, but they usually go for like $60 and up, and I'm a cheap-ass when it comes to ebay.

There's a rackmount unit with all of them in one, but you don't have access to every parameter (only three of the knobs, and no tap tempo, but it does have midi ins) the way you do with the pedals, but it's still a pretty unique processor as far as cheap 1RU multi effects go, which in my experience, the low end units are all pretty much the same sounding. Unlike my Kurzweil Mangler, which is freaking insane! If you get the itch for a cheap rack box, check out the Alesis Akira, and it usually goes for like $80, so it's a pretty slick buy for something different. I'll probably never sell mine.

Then there's the Alesis Ineko, which is the all-in-one desktop version. Haven't used it, so can't comment on it.

It's true, it's a shame they didn't sell more. I guess they were ahead of their time. The "desktop set" gig with glitch, 8-bit, no-input, etc electronics music didn't really catch on until early 2000's. Today a box like those would probably fly off the shelves!

Oh, and the link isn't all that great IMO, it just lets each box to the right share the box to the left's tap tempo LFO, and of course saves you a bunch of patch cables!  Maybe I'll dig em out again this weeken and play with them some more.

[blackieNYC]

A stereo tremolo, where the two channels modulate together, or invert the polarity from the lfo to one channel and the sound sweeps back and forth. Crazy stereo sound.