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My new Journey carbon fiber acoustic guitar is a joy to play, and sounds way above average when played unamplified. But if I plug it into an amp, the piezo pickups sound so bad (muddy, can’t hear any single notes clearly) that I can’t stand to listen to it. Stranger still, if I turn the volume on the amp up to a moderate level and stand anywhere near the amp, I get the dreaded feedback howl that you would get from a mic. Right away I wondered how could a piezo pickup – which picks up only vibrations from the guitar body – act like a mic and generate feedback. After a bit of Googling, I found that this does sometimes happen when guitarists are on stage and their amp is turned up very loud. Their solution is to block the hole in the guitar with a “feedback buster”.
None of my wood electric-acoustics have this problem, and they all sound great when plugged into an amp. I can only assume that somehow the carbon fiber body is acting like a giant microphone, so that the sound coming from the amp causes the guitar body to vibrate, and the piezos pick up that vibration and amplify it, resulting in a loud feedback howl.
Am I the only AM member who has never heard of or experienced this sort of thing before?
Sunjamr Steve
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Interesting question. I have an acoustic Traveler guitar and a pocket amp that I use with it at my work office. The guitar has an internal built-in piezo pickup. If I turn the amp on in front of the guitar it causes an ear-piercing feedback. I just thought it was because of the crappy amp. By the way, that Traveler guitar has no body and thus no sound hole.
🎸JoLa
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That’s it! If I turn on an amp while holding my guitar, the feedback quickly becomes so loud it causes a panic reaction in my brain. If I turn it on while the guitar is far away from the amp, there is no immediate feedback. But if I carry the guitar anywhere near the amp, it starts up again. This never happens with any of my other guitars, only the carbon fiber one.
Sunjamr Steve
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Steve maybe it is to do with the pressure on the pickup. I know some types lie under the bridge and the pickup sensor is compressed between the bridge and the base of the bridge slot. Maybe that if this is not sufficiently pinched could it perhaps cause a problem, I dont know its just a suggestion. But an area I would take a look at if it were mine. Possibly some dirt, friction or poor fit is interfering in the feed back of the vibration from strings to sensor.
JohnStrat -
Steve maybe it is to do with the pressure on the pickup. I know some types lie under the bridge and the pickup sensor is compressed between the bridge and the base of the bridge slot. Maybe that if this is not sufficiently pinched could it perhaps cause a problem, I dont know its just a suggestion. But an area I would take a look at if it were mine. Possibly some dirt, friction or poor fit is interfering in the feed back of the vibration from strings to sensor.
JohnStratThe rogue noise goes round and round in a loop starting from the amp, into the guitar and then back to the amp on a continuous cycle and each cycle gets louder and louder, The guitar doesn’t even need to be played for feed back to occur.
Possibly a poor earth at the Jack or poor solder join, But I still go back to my earlier thoughts on this and adding a pre-amp.
Hopefully Steve remedies this soon so we can find out the cause....Billy..
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Billy, Initially he says the tones are muddy and no clarity of single notes and thus I wonder if the correct compression is on the sensor. Clearly at any volume, but especially the low end it should be picking up without obvious distortion. I can quite imagine that if that is the case or perhaps a duff sensor that higher volume would only create a feed back loop.
ATB
JohnStrat-
Yes, thats what feed back does. Kinda like a never ending echo that gets louder and muddier when the strings are hit.when the strings are not hit then the screeching becomes louder and louder as the feedback intensifies.
I see Steve is going back into lockdown so he’ll have plenty time to figure it out…..Billy..
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Thanks for the thoughts and advice, everyone. What happens is just as Jola described, so I am happy to know that I am not the only person to experience this. BTW, it happens on either an acoustic amp or a gender neutral amp. The piezo pickups consist of 3 individual pickups about the size of a small coin, glued to the underside (inside) of the body near the bridge. I just emailed Journey Guitars and here is what I said:
“OK, I have used a mirror and light to peer inside the guitar, and what I see are 3 piezos glued to the underside of the face, which appear to be wired in parallel to the jack. All wires are intact and well attached. Here’s what I suspect: I know that piezos have polarity, and if two piezos are wired in a non-polar manner, the sound will be muddy and quite unpleasant, which is just what I hear. So I plan to remove the jack and verify that the 3 piezos are correctly wired with respect to polarity. If this is not possible, I could cut the wires on two of the three piezos and just use a single piezo as the pickup. That way polarity would not be an issue.”
Sunjamr Steve
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Steve Sounds like K & K pickups they are very good by reputation but more basic than Bags etc. I have one to install but its sat in its box for a while now. I seem to recall that they recommend gluing the Microphones to the underside of the bridge as preferable to self adhesive pads which they supply for ease. The rigidity being advantageous. I wonder if one is not fixed so well and causing some phase shift issue? It will indeed be interesting to here what they say. If they are attached to the under side of the sound board it is no wonder that it becomes a bit microphonic I would have thought.
Did you see Justin Johnston’s hi Tec bluetooth Guitar?
JohnStrat -
Wont cutting one of them off then distort the sound as the piezo pickups are arranged so they pick up the bass, middle, and treble?.
There is a soundhole plug on the market which a lot of players use to stop the feedback reaching the piezos..
Just another thought though, where do you stand your amp, right, left or in front of your guitar?...Billy..
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