billm90 Posted December 4, 2007 Report Share Posted December 4, 2007 I picked up a pre amp and undersaddle piezo. This preamp has a phase switch for feedback. What is it doing exactly, switching the polarity on the piezo? I would swear it makes sublte changes in tone. Quote Link to comment Share on other sites More sharing options...
Setain Posted December 5, 2007 Report Share Posted December 5, 2007 The phase switch is used prevent feedback from an amp. (I'm going to assume you know know feedback words) It causes the signal from the amp to be at the opposite phase as the instrument. The subtle changes are most likely caused by the speaker working in reverse, since the phase is opposite of normal. Quote Link to comment Share on other sites More sharing options...
Geo Posted December 10, 2007 Report Share Posted December 10, 2007 The phase switch is used prevent feedback from an amp. (I'm going to assume you know know feedback words) It causes the signal from the amp to be at the opposite phase as the instrument. The subtle changes are most likely caused by the speaker working in reverse, since the phase is opposite of normal. I think you're right that it puts the preamp output out of phase with the input. But you can't control phase between guitar and amp so easily. You would have to have the guitar positioned the correct distance from the amp, etc., to say that the strings are in phase or out of phase with the speaker. My guess is that the phase button is included to give you two options in a live setting. If you're getting feedback, put the switch on the other setting (it makes no difference whether you're going in phase > out or out of phase > in, because who knows where you're standing). It might help reduce feedback. This is why we have solidbodies... All right, I'm biased, I don't like amplified acoustics. Quote Link to comment Share on other sites More sharing options...
GregP Posted December 10, 2007 Report Share Posted December 10, 2007 And yes, you'll hear subtle differences in sound due to the way your guitar is interacting with the soundwaves pumping out of your amplication. Some degree of phasing is inevitable, and the switch doesn't really "turn it on" or "turn it off", it just changes the phase relationship between your guitar and the speaker. And it wouldn't be surprising at all if you could hear the difference when flipping that switch. Quote Link to comment Share on other sites More sharing options...
thegarehanman Posted December 10, 2007 Report Share Posted December 10, 2007 I think it's probably actually there in case you mic your guitar and use the onboard piezo simultaneously, so you don't get phase cancellation from the two signals. I say this because (at least with the LR baggs unit, meant for solidbodies), there's a phase switch that's meant to be set once and never touched again. It's there so you can assure that you don't get phase cancellation between the magnetic pickups and piezoelectric element. peace, russ Quote Link to comment Share on other sites More sharing options...
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