Reverb Pedal creating phase invert

[gereva87]

First time poster.

I've bought a reverb pedal, decent brand from a recognised manufacturer. Not an acoustic specific pedal. Hitting the footswitch inverts the phase. When I put the reverb mix and decay to nil it and flick the switch it is very noticeable. It does this with the pedal in isolation and when it is daisy chained to other pedals.

I'm not sure if this is just, from what I have read, the sound from my speaker interacting with the acoustic nature of the guitar and causing phase cancellation but it is bothers me that the tone changes like this. It is the same difference as when I flick the phase switch on the preamp system in the guitar.

Should the pedal do this? Do other reverb pedals do this?
Seems strange...

[Doug Young]

Seems odd, but more investigation would be needed to know for sure what's going on. What pedal is this?


But likely what you're hearing is the phase cancellation from hearing both the amplified sound and your direct guitar. An audience won't hear that. To test that, record your sound and play it back as you switch on and off, or listen thru headphones, or try it with an electric guitar where you don't hear much direct sound from the instrument. Then see if it bothers you - likely you won't even hear it.

[gereva87]

Originally Posted by Doug Young

Seems odd, but more investigation would be needed to know for sure what's going on. What pedal is this?


But likely what you're hearing is the phase cancellation from hearing both the amplified sound and your direct guitar. An audience won't hear that. To test that, record your sound and play it back as you switch on and off, or listen thru headphones, or try it with an electric guitar where you don't hear much direct sound from the instrument. Then see if it bothers you - likely you won't even hear it.

It's a JHS series 3 reverb. No I don't hear the difference when recording. Only when tracking. So I assume that there is a phase switch happening when the pedal is engaged or disengaged and my other question is whether other reverb pedals will do this (which they proabably do but shy of testing them in the same scenario I probably won't know)?

I'm completely happy with the pedal otherwise but I guess I would prefer one that didn't do this. Other pedals I have don't do this.

And the take away is that there is no actual difference in the tone in front of the speaker unless the sound of my guitar would be heard out of phase with the sound from the speaker.

[Doug Young]

Originally Posted by gereva87

I my other question is whether other reverb pedals will do this (which they proabably do but shy of testing them in the same scenario I probably won't know)? .

I haven't noticed this with any reverb's I've tried, but keep in mind that many digital pedals these days will have some latency - delay. These pedals have to do analog to digital conversion, do their thing, then do digital to analog back, all of which takes some tiny amount of time that you might be hearing as a phase shift. Some pedals may pass the dry signal thru all analog, so minimal or no delay, while others may do the conversion on the dry signal as well. It wouldn't just be reverbs, it'd be any pedal that does digital processing. I know TC's Hall of Fame advertises analog passthru, but it can be hard to determine this info unless the manufacturer touts it.

[gereva87]

Originally Posted by Doug Young

These pedals have to do analog to digital conversion, do their thing, then do digital to analog back, all of which takes some tiny amount of time that you might be hearing as a phase shift. Some pedals may pass the dry signal thru all analog, so minimal or no delay, while others may do the conversion on the dry signal as well.

So in essence it is likely that this pedal is converting the signal more than once adding delay whereas an analogue pass thru pedal will do something like add a digital layer to the analog signal.

Thanks for your help in understanding.

[jonfields45]

It’s not out of the question. The low end SonicIR pedal inverts as I’ve previously posted (for which I’ve not taken the trouble to fix in my IRs). If you have a stereo audio interface for your PC make a short recording, reverb level at zero, of the guitar and pedal output. Open it in your DAW and zoom in to check.

[Rudy4]

Originally Posted by jonfields45

It’s not out of the question. The low end SonicIR pedal inverts as I’ve previously posted (for which I’ve not taken the trouble to fix in my IRs). If you have a stereo audio interface for your PC make a short recording, reverb level at zero, of the guitar and pedal output. Open it in your DAW and zoom in to check.

Sounds like a good idea, although I'd try summing them to mono and listening to the A/B'ed signal. Something as complex as a verbed waveform would be difficult for me to follow, I do better with listening rather than visually trying to decipher. YMMV, of course.

I wonder how a digital verb's delay would compare to the propagation time of a signal through a mechanical spring reverb?

[gereva87]

Originally Posted by jonfields45

The low end SonicIR pedal inverts as I’ve previously posted.

I don't understand.

Originally Posted by jonfields45

If you have a stereo audio interface for your PC make a short recording, reverb level at zero, of the guitar and pedal output. Open it in your DAW and zoom in to check.

You mean record guitar through a mic and the signal through a pedal simultaneously and then visually check the waveform?

Would I hear the phase cancellation listening to both tracks?

[jonfields45]

Some pedals phase invert. Probably a minor design error. Not likely something your pedal does.

I have a Scarlett 2i2. I plug the guitar into the channel 1 input on the 2i2. I take the channel 1 line output and plug that into the pedal under test. I plug the pedal output into the channel 2 input on the Scarlett.

Set the levels to not clip, and in this case minimize the reverb in the pedal output. Make a short stereo recording.

Open that recording in a DAW (I like the free Audacity for ease of use) and zoom in until the waveform is easily visible. The right channel waveform should look identical and slightly delayed. If it looks upside down, the pedal phase inverts.

[H165]

If I thought this was true phase inversion, the first thing I'd do is get out my soldering stuff, reverse the leads on one of the cables in my signal chain, and listen to whatever happens.

[Mobilemike]

Originally Posted by gereva87

Hitting the footswitch inverts the phase...

It is the same difference as when I flick the phase switch on the preamp system in the guitar.

What happens if you hit the footswitch on the pedal and then flick the phase switch on the preamp too? If it is true phase inversion it should go back to normal with both engaged. If it doesn't go back to normal, probably something else is going on.

[gereva87]

I contacted the manufacturer, they said that this pedal and a few others in the series don't switch phase. They also said that it is an Analog to digital to analog conversion for the signal.

Originally Posted by Mobilemike

What happens if you hit the footswitch on the pedal and then flick the phase switch on the preamp too?

It basically reverses what it happening.
So the signal will sound the same. It will just switch to the other side of the pedal being disengaged or engaged if that makes sense.

Originally Posted by Mobilemike

If it is true phase inversion it should go back to normal with both engaged. If it doesn't go back to normal, probably something else is going on.

Wouldn't audible phase cancellation happen regardless of whether it was delay or phase inversion? I mean are they not essentially the same thing? I.e the waves of the two sounds are opposing just via a different method?