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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 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
Contributing Member
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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.

Peegoo
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Oct 22nd, 2017 03:04 PM   Edit   Profile   Print Topic   Search Topic

Hmmm

You could build a simple test jig that contains two pickup coils: one coil on the X axis, the other coil on the Y axis, and the string on the Z axis. Hook each pickup coil to its own channel on your O-scope, and measure voltages produced by the plucked string.

You should observe a decreasing 'see-saw' voltage from one channel to the other as the string's vibration pattern oscillates 90 degrees.

The difficult part will be to get the pickups in close to each other, at the same location on the string. A small, single-pole "button" pickup would be easy enough to make.

Here's a quick sketch of the eye-deer. Science!

Peegoo
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Oct 22nd, 2017 04:29 PM   Edit   Profile   Print Topic   Search Topic

I wonder if the phenomenon is created by counter-propagating waves in the length of the string, because--per the first law of thermodynamics--a string that is plucked cannot create more energy than is initially put into it by the pluck. So how is the string vibrating more *after* it is plucked?

That "extra energy" necessary to cause a delayed fret buzz has come from somewhere else, or has to be collected in a shorter segment of the string and cause an increase in amplitude of vibration within that short segment. That may be what's happening here.

What I mean is if you put X energy (vibration) into a string, X may not always be present in the entire length of the string. Certain portions of the string may become quiescent (energy loss) and certain portions may exhibit a larger amplitude of movement (energy gained) via constructive interference.

I think it's probably due to the same physical processes at work which are best demonstrated by Young's constructive/destructive interference experiment (the "double slit" experiment) that proves light travels in waves.

First...standing waves and counter-propagation: a paper

Peegoo
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Enjoying

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Oct 22nd, 2017 04:31 PM   Edit   Profile   Print Topic   Search Topic

Here's a link to a video I started a thread on a few months back, simply because the double-slit experiment is

just so damn fascinating. Physics!

Leftee
Contributing Member
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VA

One foot on the brake, one on the GAS
Oct 22nd, 2017 04:53 PM   Edit   Profile   Print Topic   Search Topic

I got nuttin.

I’m just here for the videos.

.

Peegoo
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Enjoying

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Oct 22nd, 2017 06:48 PM   Edit   Profile   Print Topic   Search Topic

Here's more. Is light a wave? Or is it a particle?

These same principles can be applied to a guitar string. Is this a New String Theory wrnchbndr has uncovered?

One photon at a time. I'm going to try this with a laser. Pics to follow!

wrnchbndr
Contributing Member
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New Jersey

I'm back with the otters again
Oct 23rd, 2017 11:38 AM   Edit   Profile   Print Topic   Search Topic

Don't get me started on watching youtube videos. I just won't stop and now half the day is gone by and I haven't done anything at all.

I've considered the deer eye pickups at 90 degree orientation but won't the magnetic fields interact and skew the observation? It might be better to have four of these pickups with the poles reversed at 90 degrees. Not sure about the reverse pole or even reverse winding but I do know that once you figured that out, you could plug one axis into the vertical and the other into the horizontal input of an oscope and get a really cool representation of the string action on the screen.

FunkyKikuchiyo

VT

Oct 23rd, 2017 01:07 PM   Edit   Profile   Print Topic   Search Topic

Yeah, I've seen optical pickups in vague prototype form (they end up sounding kinda like piezos) that would probably be perfect for it. Not sure how to go about getting some for such a project.

Te 52

Laws of Physics

strictly enforced
Oct 23rd, 2017 04:16 PM   Edit   Profile   Print Topic   Search Topic

I would think a capacitive or inductive non-contact proximity sensor would be a better choice. You'd want one with a diameter somewhat larger than the anticipated envelope of the string at the sensed point.

If you have two such sensors mounted at right angles to one another and run the output of one into the X-axis of an oscilloscope and the output of the other into the Y-axis, the screen display will actually show the cross-sectional view of the path of the sensed point. Such figures are called Lissajous curves (link).

click

(This message was last edited by Te 52 at 06:17 PM, Oct 23rd, 2017)

Previous 20 Messages  

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




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