Phase inversion in stompboxes... should we care?

[earthtonesaudio]

Coming from a recording background, I have a habit of keeping track of the phase of signals as they go from source to speaker.  The stompbox world seems to not care too much about this, and the sheer number of one-transistor boost pedals seems to confirm this.

Obviously it's not a problem in many, many situations, but when you start doing things like parallel processing, or recording and doubling tracks, you can run into phase related problems.  Bass players especially.

So is it worth the extra effort to add on a phase inversion stage to boost pedals and the like? 

[slacker]

Personally I've never worried about it.  If you were parallel mixing effects I can see why you might want them all to be in phase, but then again mixing them out of phase might sound good as well, so from a creative point of view a phase switch might be useful.
As far as recording goes if you're using mics can't you can just move them to get the phase relationship you want?

[bool]

Techically, phase relations should matter after the "delivery point"; i.e. after d.i.ed and miced signals go into recording gear.

All these "booster" phase inversions are affecting and coloring the signal before delivery points, so it all becomes part of the "sound".



Unless you decide to reamp the bastard with "boosters" later on ...

[earthtonesaudio]

Yeah, that's one of the few scenarios I can think of where it would matter.  Either parallel processing or re-amping/double tracking, (when recording direct).


I think that settles it for me.  Definitely not worth the extra effort to keep the signal in phase with a boost pedal, especially considering how they are used and the fact that the extra stage would make it unnecessarily complicated.

[DougH]

I think if you have deliberate plans to do parallel mixing and etc, IOW in a circumstance where you do need to worry about it, then you should. If you're just doing typical simple single-string guitar->pedal->amp stuff, it's not worth worrying about IMO.

[chicago_mike]

It is a concern for us bassist who use pedals. Especially filters and such that invert the phase. We have to use a blend pedal or use the filter as the last pedal in the chain.

But how much would moding a pedal to "correct" phase destroy the origional sound?

[dschwartz]

i wonder if inverted phase has an influence on feedback..i know some acoustic guitars have an inverting switch to avoid feedback..but usually on elec guitar, controlled feedback is a nice thing to have..

if the magnetic field induced on the PU´s by the string is positive, and the magnetic field produced by the speaker is negative, then they may cancell out and/or produce an harmonic, but cutting sustain (as fernandes sustainer works)..

probably at bedroom levels it doesn´t make a difference..but at decent volumes may be noticeable..


well, i´m just gessing here..
someone with more free time could make a switchable phase inverter and test  the difference..

[Ed G.]

In high-gain pedals, having the output out-of-phase with the input makes it easier to avoid oscillations.

[Processaurus]

In high-gain pedals, having the output out-of-phase with the input makes it easier to avoid oscillations.

Absolutely.  That was the  only way I could get rid of oscillations in my high gain Big cheese clone.  Tried everything and changing the phase was the only hands down solution.

Phase inversion is undesirable in general audio design though, if there is ever a situation where you needed to split the signal (like with recording, recording two sounds so you can choose  between or mix the two later on). It can be really annoying in that case if you hit a pedal that inverts the phase in one signal chain on and off during a song, because you'd have to correct the phase by hand while mixing.

Just thought of a possible good niche utility box for recording or complicated guitar rigs: a true bypass loop with a phase inverting buffer in it, to switch to a inverting pedal, but always keep your output in phase, whether the loop is in or not.

i wonder if inverted phase has an influence on feedback..i know some acoustic guitars have an inverting switch to avoid feedback..but usually on elec guitar, controlled feedback is a nice thing to have..

I've felt that when playing loud with distortion and my ross compressor, sometimes it feels like it chokes the acoustic feedback in an odd, unnatural way.  Unnatchural, I say.

[earthtonesaudio]

Maybe the best thing to do would be to just label the phase inverting pedals as such, so that you always know which way is up. 

[darron]

i like the idea of the final speaker production being the same as my pickup's phase, but i'd be confident that it shouldn't matter too much.

hope it's not OT, but i was wondering if you should invert your phase for your personal monitor as it faces a different direction to the audience and their speakers? if you imagine the sound waves they would all work together that way. i should ask a sound tech.

[earthtonesaudio]

i like the idea of the final speaker production being the same as my pickup's phase, but i'd be confident that it shouldn't matter too much.

hope it's not OT, but i was wondering if you should invert your phase for your personal monitor as it faces a different direction to the audience and their speakers? if you imagine the sound waves they would all work together that way. i should ask a sound tech.

I agree with Processaurus that as a general rule, it's better to not have to even think about phase inversion, and everything should be phase-correct at all points in a signal chain. 
But it seems like it only really matters if you're parallel processing, and you'd probably only notice it as a problem if you're in the studio.  Live, the sound is affected by so many variables (venue shape, objects/people present, etc.) that it would be next to impossible to predict phase response.

[Steben]

I got splendid controllable feedback (string as well as field) with my Valve Jr. Guitar in Speaker out. Does the Output transformer invert? If not, the guitar and the speaker are in fact OUT of phase (3 inverting class A stages).

[Mark Hammer]

Phase inversion is something you only have to do once, no matter how many pedals you may have.  I can't think of a better use for a 1590A-sized chassis than a simple phase inversion stage.  You don't need a stompswitch, and the circuit itself is painfully easy and small.  Since it is the sort of thing you'd only intermittently use, and the current requirements are minimal (no status indication required because it is always "on"), you could easily power it from a couple of button-sized batteries.