Balanced Modulator for Pan?

Started by varialbender, May 06, 2006, 04:22:18 PM

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varialbender

Anyone ever tried this?
It seems that if you split the output from the multiplier and inverted the phase of one of them and mixed them both with dry, you'd get normal pan.
Makes sense to me because when you mix 50/50, it'd be just like any stereo amplitude modulation with inverted oscillator signals.
Example:
Multiplier left output:    1         0        -1         0
Multiplier right output: -1         0         1         0
Dry:                            1         1         1         1
Left sum:                  .5+.5    0+.5  -.5+.5    0+.5
            :                     1         0.5      0         0.5
Right sum:                -.5+.5   0+.5   .5+.5    0+.5
              :                   0         0.5      1         0.5

The only problem is that at fully wet, they'll always be opposite phase, and if I corrected that phase and inverted the dry, then the dry would be out of phase...
Is there any good solution to this problem, or do I need to put one or two phase switches on this thing?
Any insight much appreciated.
Thanks

varialbender

Does this make sense?
Is it common?
Has it been done?
Thanks

PS bump

R.G.

It's a reasonable idea. It's been done, although not (that I'm aware of) for effects.

The principal problem is the complexity. If you have a stable multiplier that has a tight enough multiplication to give good cancellation, chances are that the simpler thing to do is to use two multipliers to give a pan effect. That prevents any problems with inverting phases, mixing, etc.

But there's nothing really wrong with your reasoning.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

varialbender

#3
I just got a couple AD633s, and I'll be testing this soon.
I'm not sure how using two would be simpler though.
I think the phase stuff can be dealt with one 3-pos switch:
mult dry ; -mult dry ; mult -dry.
I'd leave out the case where both the dry and multiplier out are inverted, as that would just give two opposite waveforms the whole time.
The other cases look as if they'd give interesting cancellations.
I'll try to make a simple graph and post it.
Thanks a lot R.G.

Edit: here are the graphs.
The top one shows mult dry and -mult dry.
Dry is the top black bar, mult is blue, -mult is green. Blending the two gives the red, and I've shown 3 different points: 1/4 blend, half blend, and 3/4 blend, the dry being 0 blend and mult and -mult being full blend.
The bottom one shows mult dry and mult -dry
If you understood the top one, this one should be easy to follow.
Hopefully this is understandable, I don't know how else to show that many cases without being confusing.
Thanks again.

varialbender


R.G.

It's worth a try - go build one and see!
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.