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FDP Forum / Guitar Mods, Repairs, and Projects / Evil guitar problem

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wrnchbndr
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New Jersey

I'm back with the otters again
Oct 20th, 2017 07:27 PM   Edit   Profile   Print Topic   Search Topic

Okay here's the deal and I've mentioned this problem here before. But now I have a plan.

MIM Strat. Essentially new with no mods. The neck has been tension leveled, recrowned, and polished and scrutinized beyond the capability of my inspection abilities. The trussrod is adjusted with even a little more relief than typical and the action will not approach satisfactory without fret buzz. The guitar is set up for the trem to float. It IS fretbuzz but its slightly different than typical. There is clearly a delay between from when the string is picked and when the buzz occurs -- Maybe a half second or so when this buzz happens after the initial picking of the string. The fret buzz is randomly everywhere on the fretboard and on multiple strings with no rhyme or reason. Its not the string length behind the fretted position and the buzz can be heard through the amp. I've seen this on about six guitars over 15 years. The pickups are lowered substantially below normal. I've tried switching to another brand of string in the same gauge (10-46). At one point, I installed a pair of thin Fender picks in the base of the neck pocket to slightly change the neck angle. It doesn't matter what I do.

My thoughts and I've posted this here before too. I suspect that the string energy is entering the guitar structure from either the neck or the bridge and somehow there is a reflection of energy going back into the string that disrupts the natural vibration of the string and causing a standing wave. The time it takes the standing wave to build is responsible for the delay in the buzz.

Luckily... This guitar belongs to a long time loyal client who has an extensive collection of guitars. The client has provided me another MIM strat that I have set up before and is an awesome guitar. I can swap necks, I can swap bodies, I can do what ever I want. I need to develop a strategy. I've seen this problem before and I have never been able to do anything about it.

Thoughts about strategy please... or if you've seen this exact behavior before is there something you want me to try? Does anyone have a name for it? I'm going to take my time and try to learn something.

Mick Reid
Contributing Member
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Australia

American-made in Oz!!
Oct 20th, 2017 08:10 PM   Edit   Profile   Print Topic   Search Topic

Have you considered an exorcism?

I'm sure anything I suggest you will have already tried, but...

1) Deck & block the vibrato, see if it persists.
2) Weird nut problem? Slots, loose nut or not well coupled?
3) Screws on trem block tight?
4) What kind of saddles - bent steel or solid? Saddle height screws?
5) Saddle springs?

Beyond that, I got nothin'...

I'll definitely watch this thread with interest ans hopefully also learn something.


hushnel
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North Florida

A Friend of Bill W.
Oct 20th, 2017 08:41 PM   Edit   Profile   Print Topic   Search Topic

Wow,

Have you tried round core strings? You think the strings wave form is being changed, but I can't see where the oscillation wave or radius travel could increase the peak of the wave. I'm wondering if the hex core string is resonating weirdly. Is the volume increased slightly as this happens?

Peegoo
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Enjoying

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Oct 20th, 2017 09:15 PM   Edit   Profile   Print Topic   Search Topic

I've run into this before; it's not common at (thankfully), and I think it's due to a 'spongy' neck that flexes weirdly under string tension. Sometimes it's caused by a rising tongue condition.

Sometimes the problem is impossible to correct.

When I run into this weird buzzy fret thing after a complete setup, I lightly fret each string at each fret and measure the gap between the next higher fret and the string. If I find that the gap closes up on one or more frets, that means the wood (fingerboard) is flexing upward under compression.

These problem necks are very difficult; making them behave is an exercise in frustration.

Peegoo
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Oct 20th, 2017 09:18 PM   Edit   Profile   Print Topic   Search Topic

Make dang sure there are no stow-away parts stuck to the magnets on the backs of the pickups. An extra spring in there can vibrate and sound just like fret buzz. That will drive you loony until you find it and remove it.

Te 52

Laws of Physics

strictly enforced
Oct 20th, 2017 10:16 PM   Edit   Profile   Print Topic   Search Topic

I've run into the maddening "delayed buzz" phenomenon a few times.

I believe it's caused by precession of the vibrating string. A single point on the vibrating string follows a path described by a narrow ellipe. When the string is first plucked, the long axis of the ellipse is more or less parallel with the surface of the fretboard. But under the right conditions, the elliptical path itself slowly rotates (precesses) in a plane perpendicular to the axis of the string. When the long axis of the ellipse is perpendicular to the fretboard, buzz can occur, and this can happen some time *after* the string is first plucked.

I am pressed for time right now, but take a look at the first 2:15 of the linked video for some examples of precession in vibrating bodies.

Precession is found all over in nature, including in the orbits of celestial bodies.

click

FunkyKikuchiyo

VT

Oct 20th, 2017 11:57 PM   Edit   Profile   Print Topic   Search Topic

"My thoughts and I've posted this here before too. I suspect that the string energy is entering the guitar structure from either the neck or the bridge and somehow there is a reflection of energy going back into the string that disrupts the natural vibration of the string and causing a standing wave. The time it takes the standing wave to build is responsible for the delay in the buzz."

I think you're 100% right. I've had buzzes go away by doing things like firming up the neck pocket, thereby reducing sympathetic vibrations in the neck. Removing stickers, taking down weird pieces of finish, making sure the screws aren't opening the joint when tightened, and all the other stuff. My experience is also that the thinner the neck, the more prone it is to doing this. It could also be a tuning thing. (not tuning the strings, but the resonances of the individual parts) I've had acoustics where if the tap tone of the top and back are the same, there are some really weird sounds that can come out. Shave down the top braces enough to drop the pitch and it clears up. I've done this enough times to call it more than a fluke. (I don't do this with customer guitars, don't worry!) I wonder if the tuning relationship between parts on a solid body could really make much of a difference, but it is an interesting thought.

It might be worth checking if the trem block is tight. Sometimes the mating surfaces are poorly machined and they don't really couple properly.

Therealfrogman
Contributing Member
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Pueblo, Co

illegal is a sick bird....
Oct 21st, 2017 09:22 AM   Edit   Profile   Print Topic   Search Topic

I dunno much but it makes more sense to me that the issue would be caused by one thing rather than a few different things. I really like strats that are set to float though. I would probably mess with the trem springs until I got bored, maybe the trem block angle or spring angle/tension are causing the anomaly. When the string is plucked it vibrates more intensely then it settles down and I wonder if the vibration area increases or decreases? I would think it decreases. Just thinking out loud... is there any foam dampeners in the springs?

This is way over my head, obviously.

wrnchbndr
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New Jersey

I'm back with the otters again
Oct 21st, 2017 11:07 AM   Edit   Profile   Print Topic   Search Topic

OMG finally ppl who believe me. I must have posted about this problem nearly a dozen times here or on the mimf forum. I'm quite confident that every aspect of my setup is correct when I run into this issue and I've seen severe cases of it about six times in over 9000 guitars that have crossed my bench -- thats a very conservative estimate.

As I said, I've encountered this about six times as severe cases. On three strats, a Yamaha 335 copy, and two Tom Anderson guitars. Yea, I actually remember these guitars and I don't usually remember what exactly I did yesterday.

I believe that there is some awesome knowledge to be gained if I could truly understand this problem - a sort of holy grail of solid body guitar making.

Only six guitars may seem to be a very low number but I believe that what we have here are the very worst of something that potentially exists in all guitars more or less. If you've had the experience of setting up a Les Paul where you're looking for the lowest action possible and you discover that far past what is typical for acceptable low action you can keep going lower and there still is no fret buzz until the action is so low that the guitar just feels wrong so you elevate the strings just so it feels better... I believe that this is the other end of the spectrum and I've maybe encountered this four to six times also. I've only seen this on Gibson LPs.

I don't believe that there is a single explanation for this. I believe that the recipe of a solid mahogany body with a maple top and a set mahogany neck is a good foundation to begin with but have no real facts about this at all -- only observations. I haven't encountered a PRS that'll achieve the stupid low action even though the construction is quite similar and the craftsmanship is superior.

I believe that deep in the bowels of Gibson there is some knowledge about this. I've encountered the odd LP where the tunematic posts were threaded into plastic or hard rubber inserts. Like WTF were they trying to do? Some sort of isolation of the string energy to prevent energy feedback or improve the sustain?? Nylon tunematic saddles???

If you're into this and would like to collaborate on ideas or methods of measuring this phenomena send me an email. I'm thinking about trying to cobble together some type of recording spectrum analyzer and maybe catch a glimpse of the problem -- we need a name for this.



FunkyKikuchiyo

VT

Oct 21st, 2017 01:06 PM   Edit   Profile   Print Topic   Search Topic

One thing of relevance I think is that a les Paul neck is shorter than a strat neck, which is shorter than a prs neck, so less length to create the sympathetic vibrations. Note that i am talking about neck length NOT scale length. I have other thoughts on it, but am on my phone now so I'll post more later...

Te 52

Laws of Physics

strictly enforced
Oct 21st, 2017 02:26 PM   Edit   Profile   Print Topic   Search Topic

If you can get your hands on a stroboscope, it would be most interesting to observe the plucked string and see if that yields any insights.

A big problem with studying this problem is the extremely low rate of incidence. Six guitars out of 9,000 makes it very hard to find candidates, and then any theory has to be confirmed on other instruments.

LeftRightOut
Contributing Member
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Australia

too many guitars and not enough hands
Oct 21st, 2017 03:10 PM   Edit   Profile   Print Topic   Search Topic

just throwing it out there could it be possibly the truss rod vibrating? a sympathetic vibration transferred through the neck

or some one dropped a bit of metal in the truss rod route and its vibrating against the truss rod?

Or its just and evil guitar that was put on this earth to do your head in?



Cal-Woody

USA/California

Why do I keep fixing things that work?
Oct 21st, 2017 03:51 PM   Edit   Profile   Print Topic   Search Topic

Input jack loose, or any cavity varmits?

Maybe a poor angle over string saddles.

Or maybe the springs behind the saddles are rattling because of the saddles being so far forward that they are loose and you finally hear them after the string is plucked?

Like what was mentioned earlier, check the trem block for proper mating and/or if needed, file it flush to mate firmly to the bridge base. ......

So many thoughts come to mind but I'll wait to see which get flushed out before I say anything further. ...

Best of luck to you and hope you find the culprit soon!

Te 52

Laws of Physics

strictly enforced
Oct 21st, 2017 04:12 PM   Edit   Profile   Print Topic   Search Topic

Random neuron firing: Does the phenomenon change if you add some mass to the headstock, e.g., a C-clamp?

wrnchbndr
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New Jersey

I'm back with the otters again
Oct 21st, 2017 04:40 PM   Edit   Profile   Print Topic   Search Topic

Te: No. Tried it - no change.

FunkyKikuchiyo

VT

Oct 21st, 2017 07:36 PM   Edit   Profile   Print Topic   Search Topic

... another one that comes to mind that has had this issue for me was a custom made bass that had LEDs in the fingerboard. Very cool instrument, but odd phantom buzzes all over. It was incredibly prone to odd back buzzes, and different notes that would go out of control. My working theory on that was that it was more or less a chambered neck because of the wiring needed for the LEDs. Who knows how conservative they were in removing wood for it, and it might have been little more than a tube for all I know.

"A big problem with studying this problem is the extremely low rate of incidence."

Certainly, though I'd have to agree with wrnch's hypothesis that this phenomenon exists on nearly all instruments, just to varying degrees. I do know it increases in magnitude with: maple necks, one piece construction (or, single piece neck w/fingerboard vs. multi-piece neck), thin necks, long necks (again, I'm talking the "stick" of the neck, not the scale length) and quality of the neck joint. I've played guitars where everything is wrong but it seems okay and vice versa, but these elements have strong correlations in my experience.

Warmoth style necks are less buzz prone, and this is good supporting bit of data. Warmoth necks tend to be at the high end of tolerances for size - pegheads are thicker, fingerboards are thicker, truss rods are heavier, and the thickness at the heel is pretty much always the full 1". If you've done a replacement, you probably had the experience of the replacement just feeling more substantial. Frankly, the straightness/trueness of the fingerboard plane isn't anything special on them, and comparable to a lot of other things out there if you get a straight edge on them and really compare, so I think it comes from somewhere else.

Wrnch: humor me with my own observations... the LPs you speak of that went below 1/32" and still sounded fine... Standards? Customs? 60s neck? 50s?

(Yeah, I'm really into this thread. Get over it. ;) )

Peegoo
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Oct 21st, 2017 08:22 PM   Edit   Profile   Print Topic   Search Topic

I've never run across this on a long-scale (34"+) bass.

vomer
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Broke Down

in the Brassicas
Oct 22nd, 2017 05:20 AM   Edit   Profile   Print Topic   Search Topic

Wrnch, you said you can change necks and bodies, have you tried swapping anything out yet, saddles, bridge etc?

I had a buzz on a Spongebob Squarepants hardtail strat copy recently and it took me a while to figure it out. I don't recall if the timing was exactly as you described, but the buzz was definitely noticeable a bit later. The problem was that the saddle screws weren't sitting in firm contact with the bridge plate. The holes in the vertical part of the bridge plate were not cut well and didn't allow the intonation adjust screws to angle downwards when the saddles were low, lifting the saddles away from the body. By coincidence or Murphy's Law it was impossible to see with the set up I was aiming for, and I only noticed it in feeling a hint of a movement on pressing down on a saddle. In preference to filing out the intonation screw holes, with a shim in the neck pocket and a higher saddle position it went away.

I would assume MIM bridges would be better made than this, but I thought I'd throw it out there. I like Te's precession idea and wonder what a strobe would show up.



Peegoo
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Oct 22nd, 2017 09:06 AM   Edit   Profile   Print Topic   Search Topic

I posted that link to Matt's vid a few days ago because I noticed fret buzz was different when a guitar was laying flat on the bench, compared to when held vertical in the playing position. I did know that a string vibrates in a figure-of-eight pattern that axially oscillates 90 degrees based on its frequency, so I went looking for some slo-mo close-ups of vibrating strings. There's not a lot out there on this topic. There is a lot of speculation.

It is strange that a string seems to not be as loud when the guitar is played flat on its back. Further research is needed...

wrnchbndr
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New Jersey

I'm back with the otters again
Oct 22nd, 2017 12:47 PM   Edit   Profile   Print Topic   Search Topic

Funky: The LPs were all standards or customs at least 10 years old when they crossed my bench. But I was thinking about this yesterday. Only guitars that are in need of service cross my bench. Guitars without a problem or that belong to someone who knows how to address problems will never come in to my shop. What I see in my shop is not an accurate sampling of what is being produced. Additionally, I often get guitars where the only requested service is to replace a worn out or broken component such as an output jack and I do not address setup issues at all. Its only in the process of doing a full setup that I'll encounter these hyper low action instruments.

Peegoo: In my experience, a guitar laying on its back (neck sitting in a neck rest) is going to be slightly out of normal geometry due to the weight of the guitar stressing the neck joint and the neck itself. This is a real factor when doing fret leveling along with the weight of your arms, hands and tools. Additionally, both the neck and the body are in contact with an energy absorbing work surface (the work bench and the neck rest) (probably something soft and spongy/rubbery) and this is much different than the normal playing position either sitting or standing. I have no idea what the result of dampening the potential resonance of the guitar structure does to volume of the guitar but I'd imagine that there is an effect.

I haven't been able to start experimenting yet. I'm looking at PC based spec analyzers. I want to look at both the pickup output and the signal generated by a clamp-on piezo transducer.

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