Author Topic: is one buffer enough to split to two outputs?  (Read 7823 times)

GibsonGM

Re: is one buffer enough to split to two outputs?
« Reply #20 on: August 15, 2014, 07:34:47 PM »
Sure. I've been meaning to breadboard or just build that thing for a long time now, but never get around to it.  It looks awesome, in that it is so simple but 'you can tell' it's effective.   Like a phaser version of the Easyvibe, even easier!  Looks as complicated as a basic BMP....
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PRR

Re: is one buffer enough to split to two outputs?
« Reply #21 on: August 16, 2014, 12:00:04 AM »
> full bandwidth variable phase adjustment isn't very commonplace huh?

It is incredibly difficult. And open to ambiguity. (In the recording studio we more often need uniform delay than phase-shift.)

> running two dirt pedals in parallel and reversing the phase on one end i still had plenty of volume

Subtraction cancels if both paths are "linear". Clean. Dirt-pedals are NOT clean. Their output has little to do with their inputs.

Let's say I have a boat-mold, and mold a boat from it. When I put the boat back in the mold, there is zero space between them, the negative mold and positive boat "cancel" the space.

Now say I roll over the boat with my tractor, and throw the mold off the cliff. When I bring them back together, the cancellation will fail. Boat twisted this way, mold bent another way, huge gaps between.
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ashcat_lt

Re: is one buffer enough to split to two outputs?
« Reply #22 on: August 16, 2014, 11:34:00 AM »
Subtraction cancels if both paths are "linear". Clean.
I would take this a step back to say that cancellation requires coherence.  That is, the signals need to be otherwise exactly the same in order to cancel completely.  It is theoretically possible (really possible in digital) to apply exactly the same non-linearity to the two signals and get them to cancel perfectly.  But that won't happen except by accident in the analog world.

People who want to sound smart will throw this one out any chance they get, but I think that it actually has become important in this thread:

Phase is NOT Polarity.

A true phase change requires a delay, and that delay is always frequency dependent.  It is very difficult to change the phase of every frequency in the signal by the same angle at the same time.  But really, if you managed it, and mixed it with the original, you'd get broadband attenuation or boost.  No notches.

There are boxes found in studios meant for "phase correction", one is actually called In Between Phase.  These are all(!) static variable all-pass filters.  They do not change the phase of all frequencies equally.  It's exactly like a stage or two from a phaser pedal.

pinkjimiphoton

Re: is one buffer enough to split to two outputs?
« Reply #23 on: August 16, 2014, 07:06:07 PM »
thanks ash, that makes sense .... i mean, you can tell when it's happening, but it doesn't sound like a "phaser" to me. so ya need a delay as well to make it happen?
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PRR

Re: is one buffer enough to split to two outputs?
« Reply #24 on: August 17, 2014, 06:55:35 PM »
> exactly the same non-linearity to the two signals and get them to cancel perfectly.

This is true.

I didn't mean to claim that the *only* way to cancel was two linear paths.

But as you note, two *identical* non-linear paths is nearly impossible. Especially at stompbox accuracy? Also seems rather pointless?

Your points about broadband audio "phase" are spot-on and well said.
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ashcat_lt

Re: is one buffer enough to split to two outputs?
« Reply #25 on: August 17, 2014, 07:26:37 PM »
> exactly the same non-linearity to the two signals and get them to cancel perfectly.

This is true.

I didn't mean to claim that the *only* way to cancel was two linear paths.

But as you note, two *identical* non-linear paths is nearly impossible. Especially at stompbox accuracy? Also seems rather pointless?

Your points about broadband audio "phase" are spot-on and well said.
Thanks.  I knew you knew what you meant.  ;)
Quote from: pinkjimiphoton
thanks ash, that makes sense .... i mean, you can tell when it's happening, but it doesn't sound like a "phaser" to me. so ya need a delay as well to make it happen?
I'm glad I could help, but I'm not completely sure what you're shooting for.  If you want something like a "stuck phaser" then build any phaser you prefer and replace the LFO with a DC voltage through a pot.

pee-j

Re: is one buffer enough to split to two outputs?
« Reply #26 on: May 27, 2022, 06:22:42 AM »
truly a great thread

when, if ever, a sticky (all about) buffers post is created,
this thread should be linked in it...
with this post / thread:   

https://www.diystompboxes.com/smfforum/index.php?topic=102554.msg909664#msg909664
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https://www.diystompboxes.com/smfforum/index.php?topic=102554.msg909664