Intense feedback as gain turned up and I'm not playing anything

[mgray]

Excuse my obvious newbie question concerning feedback. But I'm trying to get an understanding how it works and how to prevent it.

 

I'm trying out a California Blonde II with my Martin HD-28V. There's been a few times that as I'm setting the gain and volume, not playing the guitar, howling feedback just starts on its own. The first time I think was because all the tone controls on the K&K preamp were set full, but even after I turned them down, at high enough volumes the guitar will start to feedback on it's own without me even playing anything. Even if I mute the strings with my hand, the feedback will continue.

 

Is this my guitars natural feedback frequency causing me trouble? Is this normal?

 

With my electric Strat, I can get feedback when I play loud, but I can control it easily with location and can stop it instantly by muting the strings with my hand.

[Coaster]

a guy goes to the doctor and says "doc, everytime i move my arm like this it hurts, what should i do?" doc says "dont move your arm like that"

 

you have reached the point of no more Gain Before Feedback (GBF). thats it, all, said and done. there are things you can do to improve this though, like eq, distance between your guitar and speaker. i'm not familiar with a HD-28v and i'm not going to look it up but i assume it is an acoustic guitar? you can get feedback busters for the hole of acoustics and that does halp a lot but mostly IME with 500-900hz troubles, is this the trouble you're having?

[RoadRanger]

The kinda invented the solid body just because of this . There's some thing you can stick in the sound hole to help - I'm sure someone will be along shortly that knows more about that .

 

EDIT> http://www.amazon.com/Ultra-Feedback-Buster-Acoustic-Guitars/dp/B0009WPMQG

[allexcosta]

Cover the soundhole with clear adhesive tape.

[RoadRanger]

Cover the soundhole with clear adhesive tape.

That'd be a rather blasphemous thing to do to a Martin !

[Bobby1Note]

mgray,

 

Is that a Shenandoah series Martin? (D-28v)

 

In any case, muting the strings will not necessariliy help. If you lightly touch the top of the guitar with a finger-tip, you'll probably feel a vibration in the guitar body(body resonance??). The P/A can trigger this vibration, and you have to notch it out with your EQ. Just for the heck of it, try applying the palm of your hand to the top of the guitar to prevent it from vibrating, and see if the feedback goes away.

 

You probably have three things to consider;

1. Gain level

2. EQ setting

3. placement of speakers, relative to the guitar. Try pointing the speakers away from the guitar (not behind you, or too close to the side)

 

A soundhole plug can help.

[TimmyP]

What pickup system is in the guitar?

 

Is there a preamp of any sort in the guitar?

[mgray]

Hey thanks all for the replies! Yes it's a lightly braced, forward shifted scalloped braced rosewood dreadnaught acoustic with K&K pure mini. Probably not the best loud live setup.

 

From what I've been reading, sounds like my issue is the natural body resonense of the guitar. I guess as gain goes up, so does that frequency causing the feedback, even if the strings are muted. I'll try muting the body next time, because yeah if I tap the body, even lightly at high gain it will start to howl.

[agedhorse]

You have reachd the point of maximum gain before feedback. Provided you can't improve this by using the polarity switch on the amp (does the CA Blonde II have one), or a little eq corection, the only practical thing to do is to turn the gain/volume down a little bit until it stops being a problem.

 

This giutar may not be set up as the ideal live gigging guitar.