De-syncing half-waves: what's it sound like? worth it? Paul, any opinions?

[Mark Hammer]

The traditional approach, or rather one of them, to producing octave-up from guitar is to somehow split the positive and negative half-cycles up and invert one of the half-cycles so that what used to be a dip now becomes a bump, and with double the number of "bumps" you hear double the frequency.

That splitting of negative and positive half-cycles can be done in a multitude of ways, but the thing that unifies them all is that the two half cycles are always maintained in sync.  That is there is no phase lag or lead introduced (at least not deliberately), and the location of the "bump" on the scope is exactly where the maximum dip would have shown up on the scope, except higher up on the screen.

I forget how it happened (mornings are like that), but I was having murky fleeting thoughts about crossover distortion or something, and I started wondering what would happen if after the phase split one of the half-waves was shifted over a bit so that the sync was lost/corrupted.  The simplest implementation of this that I can think of is to take a single transistor phase splitter (equal value resistors on the emitter and collector) like you see on the Green Ringer and tack an allpass stage after one of the outputs (either emitter OR collector; no real difference which, as near as I can tell). before combining them. 

(Note that in order to work with each half cycle independently, you need to stick a diode in series with each transistor output, like you see here on the Green Ringer - http://www.generalguitargadgets.com/diagrams/gringer_sc.gif - except that you'd need to reverse the orientation of one of the diodes.  Remember, we're not trying to make a frequency-doubler here, just treat the two half-cycles differently.  So, there's no need to invert the half-cycle.  Reversing one of the diodes will simply mean that what comes out one diode is the positive half cycle and what ciomes out the other is the negative half-cycle.)

The allpass stage could be variable OR fixed.  Keep in mind that making it variable does not produce the same degree of lead/lag across the spectrum.  Rather, it would simply determine where the phase maxima occurs, such that full 90-degrees might not occur until, say, 1000hz or it might occur at 400hz or 6khz, etc., depending on component values.  The ley thing, though is that it be only modest amounts of phase-shift, so as to introduce a sort of crossover distortion.

Does this sound like it might be a productive tangent to go off on?  Paul (Perry), you must have some opinions on something like this and may have even tinkered with it.  I'd do the legwork myself but we have a big office potluck at our home to prepare for this week and my evenings are pretty much spoken for until Sunday.

[A.S.P.]

patented by B*hr*nger...

[Mark Hammer]

You'll forgive my puzzlement, but is that being said in jest or seriousness?

[A.S.P.]

seriously!

(I`ve been busy to find a way around it since about 7 months,
and I think I found a way by the words/laws of that patent`s claims,
although the sound/effect will be 99.9% equal...)

It`s one of those patent files, that will guys like J.O. and R.G. (plus a few others `round here...) drive mad and roll their eyes.

{details soon}

[Processaurus]

Thats a real innaresting notion,  the closest thing I've seen isn't the same at all, but is kinda novel, its the Schumann electronics two face fuzz, which uses a different fuzz face for the top and bottom half of the signal.  Thats just asymetrical distortion, though.

Hey, how about a box that splits the top and bottom halves of the signal, and has an effects loop for each?  Phase vibrato the top half, fuzz out the bottom?  EQ the top, wah the bottom?

[Paul Perry (Frostwave)]

Simply moving on lot of half waves relative to the other doesn't give an interesting effect (in my opinion), it just has the effect of changing the harmonic ratios. Which is equivalent to applying EQ.
If you vary the half wave displacement, then you get a wahish effect (as the various harmonics add and subtract) plus, I imagine there would be some phasing as well.
It would be a hell of a mess on chords.
As to 'prior art', I guess it is a matter of looking at a million organ tone generation hacks from the 50s....

[Transmogrifox]

This makes me think of the synths that provide 2 oscillators that can be phase-shifted with respect to one another. 

[A.S.P.]

http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=EP0420948&F=0

tube-version:
http://v3.espacenet.com/origdoc?DB=EPODOC&IDX=DE19631892&F=0&QPN=DE19631892

http://v3.espacenet.com/origdoc?DB=EPODOC&IDX=US2001033667&F=0&QPN=US2001033667

it`s all in the claims...

[cd]

Here are a couple of files for anyone who wants to play around with the idea in Adobe Audition or whatnot.

chopped.wav - stereo file, L channel has positive portion of wave, R channel has negative portion of wave <- apply shift and mix down to mono
nonchooped.wav - stereo file, complete (dual mono) demo
mixed.wav - positive portion of chopped.wav left alone, 120ms delay applied to negative, mixed down to mono
mixed10ms.wav - same as mixed.wav but with a 10ms delay


96khz, 32bit WAV files

http://www.box.net/public/5xfuetcc0g

Notice how the chopped one has distortion already where the halves are "chopped".