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

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Peegoo
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Enjoying

the downtime
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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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
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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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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
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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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