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I've been facing this problem for quite some time now: some notes sounding bad with an overdriven amp. It's a 19 years old solid body Kaman GTX-33 (the maker of the Ovation acoustic guitar), made in Korea. Practically the same as this one, but with a better PING licensed Floyd Rose bridge.

I have found a good sound example in this youtube video. Approximately at 07:43, Jack (the guy on the right) stops playing for a brief moment, switches to the neck pickup and then you hear two weird, warbling/vibrating notes, they sound almost as if they were out of tune. My guitar has this exact same issue, it annoys me so much I lose concentration, sometimes. Except in my case, it happens on the 5th string, mostly, around the 6th - 9th frets, and the 6th, towards the end of the fretboard. Does anybody know what causes that? It could be similar to the problem mentioned in this question, possibly the same, but the question didn't make it clear and also no satisfactory answer was given, so I'm really not sure.

The string is absolutely not buzzing against the frets and I've double checked and ruled out everything I could about:

  • loose parts
  • old strings
  • amp problem (happens on all of my 3 amps)
  • excessive magnetic pull
  • electronics
  • bad pickups (had them replaced just for testing, problem remained)
  • floating bridge springs vibration

Important: it only happens with overdrive. With heavier distortion, it tends to disappear. With clean sound, I can only notice it if I listen very carefully and in a very silent environment. Seems worse when using the neck pickup.

The only other possibilities I ended up with are:

  1. a vibrating truss rod (unlikely),
  2. something about my floyd rose bridge, its saddles or how it resonates, or
  3. the neck/body junction, maybe the neck and body don't "like each other"?

My theory is that there is some bad resonance or frequency beating going on, either in the wood or the bridge. It's a solid body guitar, but it never had a fantastic sustain, so to speak.

I don't have many luthier options in my area, and the last time i tried one, the guy knew less than I do (I've been playing for 24 years). I will also post a more detailed sound sample ASAP.

EDIT: here are the sound files. Notes: the first one is the neck pickup, clean. I can't hear the problem in this recording.

The second one is the neck with overdrive. I let the background noise flow for a while to illustrate to @Yorik what I was saying about hum or RF. About the sound, If you listen loud with good speakers, the problem becomes quite evident: some warbling, some unwanted vibration, some additional noise under the note, making it sound weird. I feel like it could be an excess of bad harmonics as @Andy mentioned, but I'm just not sure.

The third recording is a trick I did just for this question: I've wired neck and middle pickups in series but inverted the wiring of one of them, so they go phase cancelling and kill the background noise (I know, it kind of kills the tone, too. It's not a real humbucker, after all). In this example we can hear the problem very clearly and this removes the hum/RF possibility. The hum is gone, yet the problem remains. The pickups are pretty far away from the strings to avoid magnetic pull and there is very, little fret noise in the recordings, it was my first guess, but I don't think it is the source. I'm running out of options! I still think it's a wood resonation issue or something with the floyd rose vibrating and interfering.

  • When you get this sound with distortion, does it suddenly clean up if you turn down the tone pot on the guitar? Just thinking it might be some sort of intermodulation distortion caused by upper harmonics in the guitar's normal timbre. (Just something to try. If not, ignore this.) – Andy Nov 2 '15 at 9:08
  • Also, can you hear any problem at all when playing the guitar without an amp? – Todd Wilcox Nov 2 '15 at 11:08
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    I listened to that section of the YouTube video about 10 times and I don't hear anything strange or bothersome (to my ears) at all. I think a sample of your actual guitar making the noise in question will help a lot. – Todd Wilcox Nov 2 '15 at 12:51
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    @ToddWilcox: the only sound I hear is normal every day single-coil buzz. at 7:43. bridge pickup is a humbucker. – Yorik Nov 3 '15 at 17:50
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    @Andy, I hadn't tried that yet. It doesn't kill the problem, but certainly attenuates it. When rolled down to about 50%, whether it's the tone pot or the volume pot, will reduce the bad effect. I guess the vol pot does it because it lightens up the distortion when you lower it, and since the warbling almost doesn't happen with a clean sound... – Fractalizer Nov 4 '15 at 16:11
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Whether it actually is or not I have to say it really does sound like fret buzz to me! Listening to your clean recording I notice in looking at the waveforms produced when looking at the accompanying graphic on soundcloud, that it seems to occur more when you strike the string slightly harder, and as you know will know from experience when the string is struck harder it's vibrates more and at some point almost any string vibrating enough will contact at some point, especially with the thicker wound strings which have more mass. It's quite a familiar sound to me, as I use quite a lot of guitars with very low actions and this sort of harmonic content to the note seems to be added when some degree of contact is made with a fret - however little. On further consideration I do seem to remember hearing a similar sound produced on an electric guitar when a string seating in the saddle piece on tune-o-matic type bridge was not quite firm ie some movement of the string witinin the slot in the saddle. A simillar phenomenon can also occur when the actual saddle itself is not well seated, and can vibrate within the bridge in sympathy with a string - and this can happen at certain frequencies. I have a bridge that does this on a PRS copy at present. Hope this is of some help to you,

All the best, Dave.

PS Just listened to your Sound Cloud recordings again. The only one which is really useful is the first one without any effects on at all - adding distortion to distortion just muddy's the issue. Looking at the wave forms in detail it's very interesting to note that the distortion happens as the note starts to decay as it produces different harmonics and again this is a very familiar sound to me!

  • I guess I'll have to explore that possibility. The frets look and feel fine, but the fretboard wood is somewhat irregular (hey, it's 19 yrs old) and the neck itself is a little unstable. Since it did get a little better when I recrowned those frets, well, maybe a fretboard plaining and refret are in order. That's a little painful, because the frets are almost new, I refretted it myself about 2 years ago and it plays like a dream, but I didn't bother to plain the fretboard wood at the time. – Fractalizer Nov 11 '15 at 18:54
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tremelo tension spring with dampener

Could it be sympathetic resonance induced in the tremelo springs?

This tremelo spring is from either a Brian Moore or a Variax. Both guitars are fitted with piezo pickups and so are more sensitive to physical vibration. The illustrated precaution does however support the theory that there can be issues with spring noise. Have you tried dampening the tremelo springs?

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    Unfortunately, yes, I have them damped already (it's mentioned in the question as "flating bridge springs vibration"). I have put paper towel under the springs, up to the point that if you hit them with a screwdriver, you hear only a "click", with no vibration afterwards. – Fractalizer Nov 3 '15 at 1:15
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Sounds like a classic case of Stratitus. Try lowering your neck and middle pickups (the single coil ones) further into the body cavity. That usually helps as the strong magnets won't effect the string vibration as much.

  • Thanks, user6591, but I tried that too, they're about 15mm from the strings, I guess that would be enough, or would it? – Fractalizer Nov 4 '15 at 16:16
  • Well it really depends on the magnet strength. If you want to try experimenting, I would suggest trying a bit lower. I also have seen the suggestion to change to a heavier gauge string. But that is somewhat more of a extreme measure. Good luck! – user6591 Nov 4 '15 at 16:23

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