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I bought some months ago a slightly used Acoustic Fender. I tested it with amplification a couple of times and only noticed a very loud response when palm-hitting the bridge, for rythmic purposes. I didnt care much at the time. Yesterday I performed live for the first time and I noticed a couple of things. First of all I played right next to the speaker box, and I know that may have been the reason, just checking. 1. I had this growing humming sound with the volume on, just touching the D string went away. 2. (most concerning) Playing open D string played the note with a growing reverberating sound almost like a feedback. rendered useless playing that note.

My questions are (of course without testing it not close to the speaker) if those problems are only related to sympathetic humming or if there could actually be a problem in the electronics specifically with that string. And if so, what simple solution could I apply. I live in a country where I cannot count on taking it to any repair shop and even a economic, used acoustic like this costed like halaf a year salary, so a repairment is necessary, jaja.

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... growing humming sound with the volume on, just touching the D string went away ...

Playing open D string played the note with a growing reverberating sound almost like a feedback ...

It sounds like the guitar/amp combination settles nicely into a feedback loop with open D, and likely any fretted D notes that you might play as well.

It can be hard to control the feedback of an acoustic guitar that is plugged in to a nearby, loud amplifier. When the amplifier is operating, the sound waves it produces can resonate with the soundboard of your guitar, and any strings that are at an interval of the broadcast frequency. This imparts energy to the strings/soundboard, which can then continue to vibrate at that frequency, and there you have a feedback loop.

One way you can attempt to thwart that behavior would be to apply some muting to the open strings, either by having a plush/fuzzy thing going over the strings; or I have also put some cloth/fuzzy stuff under the strings, going across the fretboard, snugged up close to the nut. Having some soft physical material there will give the strings something to dump their energy into aside from just the soundboard, and should help to reduce the feedback issue for you.

Other than that, you might want to try aiming the amplifier away from where you'll be standing, and/or try to be out of the "line of fire". The closer you get to the amp, the easier it'll be for the feedback to do what it wants to.

  • Thansk a lot sir. I will try other location and come back with the results. – Earendil Oct 19 at 17:13
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Went back and played away from the speaker. No feedback loop, buuuut.

Things got nasty mid session. Guy operating the audio thought he didnt heard the guitar enough (me either) and lifted the levels. It went through the roof. I think I have a very sensitive pick up, because all other guitars Ive seen there are not so temperamental. I still think we have to fiddle with the right settings, someone told something about impedance, but that is as far as I go.

  • If you have an Electric/Acoustic guitar with a built in preamp, then the preamp onboard has already corrected for impedance, and the output impedance should be quite low. If the amp you are using has a High/Low set inputs, that generally refers to impedance, and you should plug in to the 'Low' one. Your onboard preamp may also have a phase selector, trying a different phase may help some. – whofferbert Oct 21 at 21:16

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