A different view of the guitar tone circuit

[FunkyKikuchiyo]

Tonestack - it is my experience (and subsequent theory) that perceptions of compression usually come from the envelope qualities of the note as relayed by the pickups rather than actual compression. If you think of the note as "attack-sustain-decay-release" like in MIDI parlance, then you're in territory that can be easy to hear with a trained ear, but extremely hard to measure. Things like changing magnets, pickup proximity, magnet placement, and form factor can play huge roles. Guitar strings don't vibrate in the same way for all 360 degrees, and the direction perpendicular to the fingerboard tends to have more "pop" and volume, not unlike a "rest stroke" on a classical guitar. This tends to give the impression of broad dynamics, for example. So, take a strat pickup with A5 rod magnets. The "flux" goes largely perpendicular, is relatively strong, and is fairly sensitive to changes in distance. At the neck pickup (where the string moves a lot) the volume can change an awful lot based on pick attack, and the sound is often very percussive. This is consistent with those ideas, so it seems to work intellectually, but I am not sure how one would go about testing it empirically. Envelope is very difficult to measure, and when playing technique comes in as an important variable, it all becomes nearly impossible.

My guess is that pretty much any amplifier would compress hard long before the pickup. Any time I've had way too much "input" to a pickup (using a source other than a guitar string - a small speaker or a tuning fork for example) all of the distortion I hear is typical amplifier distortion. I don't hear anything new from the pickups. Then again, I don't quite know what I'm listening for, either.

[Steve Conner]

You're right, there is no physical way for a pickup to "compress" the signal. The fluctuations caused by the string are tiny compared to the saturation flux density.

[fieldwrangler]

You're right, there is no physical way for a pickup to "compress" the signal. The fluctuations caused by the string are tiny compared to the saturation flux density.

True enough, but anomalous behavior during the initial transient could be described by some as "compression."

Bob Palmieri

[Tonestack]

I figured that it would be difficult to saturate the magnetic core using only the small field that is generated by the AC current flowing through the coil. However, is the signal strong enough to momentarily affect the B field, which, in turn, would momentarily affect the amount of AC current being generated for a given string oscillation frequency and amplitude?

Something else that I have been pondering for a while is magnetic hysteresis. Is it possible for a pickup to have memory? Does the person using a guitar pickup alter its magnetic field over time, even if the change in atomic dipole alignment is tiny?

I know that a lot of pickup builders could care less about understanding electromagnetism at this level. They arrive at their secret sauces empirically. However, my father used to say that I was part of the "Why Generation" because I would always ask him "why" after he showed me how something worked.

[FunkyKikuchiyo]

Something else that I have been pondering for a while is magnetic hysteresis. Is it possible for a pickup to have memory? Does the person using a guitar pickup alter its magnetic field over time, even if the change in atomic dipole alignment is tiny?

It has been theorized before as a "why old pickups sound great" explanation, but I'm not aware of any hard data.

[CRU JONES]

I figured that it would be difficult to saturate the magnetic core using only the small field that is generated by the AC current flowing through the coil. However, is the signal strong enough to momentarily affect the B field, which, in turn, would momentarily affect the amount of AC current being generated for a given string oscillation frequency and amplitude?

The X axis is H, which is the coercive force of an external magnetic field. During rest, a pickup sits at H = 0 and Br, H, the external field is the string.

The coercive force of the string would then, as you are imagining, effect B. The moving strings coercive force would move about either side of H = 0. If you know what the coercive force of the string is, you could follow how much B changes. The problem is: not much the interesting thing might be that the slope of permeability is very curved for some magnets. This may or may not be significant, but it is interesting. And I think your thoughts are interesting

Something else that I have been pondering for a while is magnetic hysteresis. Is it possible for a pickup to have memory? Does the person using a guitar pickup alter its magnetic field over time, even if the change in atomic dipole alignment is tiny?

So, this goes back to the very tiny coercive force that the string actually generates. The hysteresis loop looks like an amazing transfer function for creating distortion, doesn't it? Seriously! Look up the B-H curves for some low coercivity magnet and see how much of the curve gets traced by a force of .0068 Oersted... Maybe add a couple more zeros if it looks exciting

I know that a lot of pickup builders could care less about understanding electromagnetism at this level. They arrive at their secret sauces empirically. However, my father used to say that I was part of the "Why Generation" because I would always ask him "why" after he showed me how something worked.

I care! I care a lot! I want to understand this stuff! I also really admire Joe Gwinn, Mike Sulzer, Steve Conner, Bob Palmieri, and if I left you out, its because I don't want to misspell your name. But who I mean, are people that help know this stuff, have educations or not, and share. I try to hit the "like" button when I can. You can't overlook the guys that just put in a ton of years worth of winding that are actually going to be able to get you some righteous tone. I do object to the idea that only schooled engineers or technicians will understand this stuff. That is complete non-sense. I don't think any of the professional winders out here lack an understanding of this electro-magnetics stuff. Education or no.

No way around learning most of this stuff empirically. For instance, staying on topic, how is one to tell if there is a direct favorable sonic correlation between high coercivity magnets and low coercivity magnets? You have to separate a few variables out of that one. Algebra or not, I have been messing about with that one for quite sometime and only THINK I know what kind of magnets I like.

At any rate, if you want to saturate the $h!t out of some permeable materials you are my kind of guy

Peace,
Ethan

[David Schwab]

Do you really use tone settings near zero?

I do. I generally have the tone control on 10 or zero. I like that resonant hump you get with it at zero, and generally have less use for it to just dull the tone, but do eery now and then.

Small value caps (.01 - .02µF) are better for using the control on zero.

[big_teee]

I use the tone control more than the volume.
I like the vol. on 10, and usually turn the amp up and down.
Depending on the guitar, and pickup arrangement what cap I use.
I usually run it 0-5.
I like 0 on certain Leads.
Keep Rockin!
T

[Mike Sulzer]

Mark, David, Big_tee,

Thanks for the replies. I think then the nonlinear response of the amp then fills in the harmonics and adds some cross products.

I use the tone control more than the volume.
I like the vol. on 10, and usually turn the amp up and down.
Depending on the guitar, and pickup arrangement what cap I use.
I usually run it 0-5.
I like 0 on certain Leads.
Keep Rockin!
T

[fieldwrangler]

I do. I generally have the tone control on 10 or zero. I like that resonant hump you get with it at zero, and generally have less use for it to just dull the tone, but do eery now and then.

Small value caps (.01 - .02µF) are better for using the control on zero.

For guitars with fairly conventional pickups. I do in fact find myself using .015 caps suspiciously often. I find them to be better for pretty much any setting on the tone control for what I and most people I work with want from that dial.

Bob Palmieri