Is it possible to accurately describe the tone of magnets and/or pickups?

[ken]

but what if you turn the volume way down to where most of the signal is shunted to ground?
If the volume pot is wired as a variable voltage divider (as usual), the PU always "sees" the full pot's resistance.

This is true, as *only the signal* would be attenuated by the pot slider. The total resistance of the pot would always be across the pickup.
Now would the pickup react differently if the volume pot itself was changed... say from 250K to 1M resistance?

As for what happens if you hardmount a pickup to a guitar instead of using springs or rubber tubing, EVH screwed his pickups right down to his guitar body with woodscrews.

Ken

[bbsailor]

I do not understand this. I think that the Alumitone is just a single turn pickup with a very high step up ratio.

Mike is correct about this but there is more!!!

There is another characteristic of this high turns ratio current transformer where the thick primary aluminum frame acts as a single turn string loop. It is "skin depth", something not normally discussed in relation to guitar pickups. See this chart to see skin depth of copper solid wire at various gauges. http://www.powerstream.com/Wire_Size.htm.

Note that AWG 8 is .1285" diameter and only passes full current to the wire core up to 1650Hz. This frequency goes slightly higher than the maximum guitar primary frequency at the high e string at the 24th fret at about 1448 Hz. However, upper harmonics would be affected more. Lace uses the skin effect in the aluminum frame as well as the turns ratio in the transformer coupling to affect the sound quality and output voltage level of the Alumitone pickup design. A small bundle of AWG 12 .0808" diameter wire strands for the string loop would take the frequency up to 4150Hz, typical of traditional guitar pickups and amplifier speakers. A larger bundle of AWG 18 at .0403" diameter strands would need to be used to get up to 17Khz. The actual science of this is known for radio transmissions and Litz wire but the application of this for guitar pickups is totally "in the ear of the beholder". I find that strand size and skin depth is more appropriate for use in acoustic guitar pickups where you do not want the typical "electric guitar sound" with the resonant point in the same area where the human ear is most sensitive. Since current in the primary string loop is now dependent on string and harmonics frequencies and skin effect, how much current at different frequencies can be generated and converted by the turns ratio can act as sort of an audio filter.

Joseph J. Rogowski

[Helmholtz]

In his book, Zollner shows the results of an experiment with an A5 magnet fixed in 2,5mm= 0.1" distance from the vibrating string over the neck PU position. The signal level difference caused by the presence of the magnet was around 1dB after 5 seconds.
His explanation for the small, magnet raised damping is increased hysteresis losses in the string. I consider this another plausible possibility.

He also showed that the damping caused by the player's hand-to-neck contact is much stronger than the damping caused by the magnet at realistic distances (i.e. avoiding that the vibrating string touches the magnet).

[Helmholtz]

A dead short in the coil would quickly stop the string due to eddy currents in the coil

I have some doubts, as even the short-circuit current a PU can produce is very, very small. It is limited by the DCR anyway.

but what if you turn the volume way down to where most of the signal is shunted to ground?

If the volume pot is wired as a variable voltage divider (as usual), the PU always "sees" the full pot's resistance.

[Helmholtz]

Won't the impedance of the circuit that the pickup is attached to affect the string's sustain.

Yes, I already mentioned this. The higher the PU current the stronger the damping effect.

[Helmholtz]

I do not understand this. I think that the Alumitone is just a single turn pickup with a very high step up ratio.

Yes and this very low resistance single turn in the Alumitone is shorted and hence constitutes a perfect eddy current loop. Consequently sustain will suffer if the magnetic flux is strong enough.
It looks like a potent eddy current brake.

[Chuck H]

The string is under tension so that it resonates a a set of frequencies; that is, it moves easily at those frequencies. The pickup moves very little because art is heavy and fastened to the guitar.

Yesser. I actually DO get that. But pickup mounting systems aren't all THAT secure really. Surely there is SOME movement. I admit I never thought about it before Helmholtz mentioned it. I just don't think it makes sense to ignore it. After all, we do strive for that extra five percent on this forum. If all we wanted to do was play our guitars we could ignore a lot of what's discussed here.

[Helmholtz]

I think that a magnet can cause additional damping, although I have no proof. The mechanism would be through increased string bending. Does bending cause energy loss? Of course: this is part of why higher harmonics decay faster than lower harmonics; there is more bending for given amplitude of vibration. I think that the additional bending results mostly from the two different vibrational rates you mentioned.

Yes, string bending involved in the vibration means material deformation. Though mostly elastic (non-dissipative), there is also has a lossy component in non-ideal materials. As higher harmonics bend the strings at a higher rate, they lose energy faster.
I just don't see neither a higher bending rate nor a higher bending amplitude in the presence of a magnetic force. The field just minimally shifts the equilibrium or rest position of the string in the plane perpendicular to the fingerboard.

The slightly different frequencies of up-and-down vs. sideways vibration caused by a strong magnetic field produce a beating effect as seen in the waviness of the signal decay. A local minimum in the decay means that the energy content in the up-and down vibration has momentarily decreased while the energy in the horizontal motion has correspondingly increased. This energy exchange repeats at the beat frequency. I can't think of a reason for increased losses produced in the energy exchange between the two vibrational modes. If the amplitude (and thus the bending) of one mode increases, the amplitude of the other one decreases.

Did I adress what you meant?

[Mike Sulzer]

The string is under tension so that it resonates a a set of frequencies; that is, it moves easily at those frequencies. The pickup moves very little because art is heavy and fastened to the guitar.

I keep seeing this mentioned, BUT...

The pickups mass being greater than the string is only significant if they are left to their own inertia. The string is at considerable tension and YOU pluck the string to disturb that tension. How far would a pickup move if you plucked it? My point is that the vibrating strings lower mass is considerably countered by energy. Consider that a 12 ga. bird shot load weighs a lot less than a pumpkin and perhaps reconsider the equation

EDIT: I guess for the "physics" guys I should have said "the vibrating strings lower mass is considerably countered by velocity." Resulting in the significant energy needed to impact the circumstances. Past experience has taught me that I'd better correct this here before I get flamed as a matter of semantics

[Mike Sulzer]

The eddy currents close to the strings produce a string motion-braking counter-field. The strongest contender for this would be the Alumitone as it's principle is based on eddy currents.

I do not understand this. I think that the Alumitone is just a single turn pickup with a very high step up ratio.

[Mike Sulzer]

I think that a magnet can cause additional damping, although I have no proof. The mechanism would be through increased string bending. Does bending cause energy loss? Of course: this is part of why higher harmonics decay faster than lower harmonics; there is more bending for given amplitude of vibration. I think that the additional bending results mostly from the two different vibrational rates you mentioned. This is speculative, but I do not think that it is right to dismiss the possibility of magnet induced damping with a simple physical explanation.

Thanks for your question.

As I wrote above, from the point of physics I see two possibilities to induce increased string damping by transferring/extracting vibrational energy. One is eddy currents and the other is parasitic PU vibration induced by the varying magnetic field (this could be visualized by a weak stretched rubber band between string and PU). Both effects increase with stronger fields and closer string-PU distance. (The magnetic field by itself cannot produce energy loss/absorb energy. It is purely reactive.)

The eddy currents in alnico are very small as its conductivity is relatively low, at least compared to low carbon steel. This also shows in the high unloaded resonant peaks in strat PUs. There might be some contribution, though. To completely exclude eddy currents would require to use ferrite pole pieces.
I have never read about an "eddy current break", interpreting this as an abrupt increase in eddy currents under certain conditions?(see edit below)

From the above, I still think that parasitic PU vibration might be the dominant loss effect. But without quantitative data this is admittedly speculative. It should be easy for you to verify/falsify in your test jig by mounting the PU very loosely and compare string damping.
Anyway, both damping effects seem to be rather small.

I appreciate your measuring efforts but miss some explanation of scales and data. Which software do you use?


Edit: Sorry, did you mean the eddy current "brake" effect? (had to look up this term in my dictionary, the german word is "Wirbelstrombremse") That's exactly what I meant by eddy current string damping: The eddy currents close to the strings produce a string motion-braking counter-field. The strongest contender for this would be the Alumitone as it's principle is based on eddy currents.
Theoretically there is a very weak third effect, that might induce string damping. This is the tiny counter-field produced by the signal current in the PU. It will increase with lower load resistance.

[David King]

Won't the impedance of the circuit that the pickup is attached to affect the string's sustain. A dead short in the coil would quickly stop the string due to eddy currents in the coil, I'm not sure if a 50k ohm load would have any effect but what if you turn the volume way down to where most of the signal is shunted to ground?.

[Enzo]

They pretty much gave up on the end zone at Giants Stadium. Here in Michigan, every couple years someone decides they have evidence and they dig up some poor sap's barn. The last place he was known to be was the Machus Red Fox on Telegraph, but even that is now gone.

[ken]

Some believe Hoffa was buried in a highway onramp somewhere, some believe he's part of a major league ball diamond, others believe he was made into canned dogfood or hot dogs.

Hard to say what happened to him.

[ken]

Actually, the OP's idea was a good one - to discuss *basic* differences in parts and finished pickups measurably, clearly, and distinctly. That could be useful to people like us, who need to make decisions on what parts to use in a certain product. IMO it's sorta like a cook trying to decide whether to use mild chile peppers or ghost peppers in his salsa and how much of either - the wrong amount could be a major disaster. If everybody would discuss their products in ads the OP's way, it would be a lot easier to give a customer exactly what kind of sound he or she wants to make.

The only problem is when the marketeers and engineers take over, and this entire idea flies out the window. You know... 'this pickup is potted in wax from South American killer bees for a real killer tone' or 'this pickup was wound on a machine that was buried in a time machine in Kalamazoo in 1955 right after it was used to wind the original pickups in Scotty Moore's goldtop he played with Elvis'. Or 'this pickup has a .0001db bump at 1Khz played in a 1951 Tele using 10-52 strings at 70F with 62% humidity, the player was drinking Budweiser beer and eating beans while recording this... and dont even go there about the amp'.

If your pickup sounds good, it is good. You can set quality and performance differences easily enough, and you should, but obsessing about the fifth or sixth significant digit of a measurement can be counterproductive.

Rant over

Ken