Why have one flipped cylinder magnet?

[rbkxiiowe]

Some pickups used on Watkins guitars in the 1960s had pickups that consisted of 5 cylindrical magnets with a shabby coil wrapped around them. OK. But the 4th magnet was smaller and had opposite polarity to the others. One example can be seen here www.watkinsguitars.co.uk/renovation.htm (about 3/4 down the page).

This isn't a one off. I actually have one here in front of me and it is the same.

What effect would this have? I can't really see a reason for doing it, but they obviously could.

One for the electronic engineers here to answer?

Cheers.

[sumgai]

rb,

What effect would this have?

Well, for one thing, it would reduce the hum. Sadly, it would also reduce the signal level, probably down to where everyone would describe it as "weak".

When one has gained an understanding of the "right hand rule" (google it, if necessary), one will realize that what WEM did was to force two magnets to work in opposition, which in turn caused them to cancel each other out. That left three remaining magnets to develop a usable signal, which as noted by all and sundry, isn't very much. The fact that a smaller magnet was used for the "reversed unit" means that only a partial cancellation occurs, so it's probably more like 3.5 magnets are contributing to the output signal. Still not enough, to my way of thinking.

HTH




sumgai

[rbkxiiowe]

Still don't get it...
If they wanted the effect of 3.5 magnets why not just put 3.5 magnets in there in the first place?

[sumgai]

Jul 19, 2008 11:03:22 GMT -5 rbkxiiowe said:

Still don't get it...
If they wanted the effect of 3.5 magnets why not just put 3.5 magnets in there in the first place?

Hanlon's Razor: Never attribute to malice that which can be adequately explained by stupidity.

sumgai's corollary:

"Never attribute to stupidity that which can be laid at the doorstep of Marketing."


;D


HTH




sumgai

[vonFrenchie]

Its all about magnetic fields. If you had three 1 ounce magnets and one .5 ounce magnet you'd have that "3.5 magnets" that you're talking about. But if you had four 1 ounce magnets and a .5 ounce magnet pointing in the opposite direction you would also have "3.5 magnets" but a very different magnetic field. It's that different magnetic field which makes the pickup slightly humbucking.

If you had the first set up that I mentioned you would still have the hum but close to the same output level as the second scenario.

[D2o]

Aug 4, 2008 14:22:22 GMT -5 vonFrenchie said:

... well, it doesn't really matter what you wrote, just that you wrote ...

Holy moly ... vonFrenchie! Welcome back, buddy!

DD

[rbkxiiowe]

So if I took six pole pieces from a normal strat type single coil pickup and magnetised them. Then arranged them pointing up NSNSNS. Then wrapped wire 1000 times around the first one clockwise, take the end and wrap it 1000 times around the second one ANTIclockwise, etc... would this be a humbucking pickup that sounds similar to a normal single coil?

[rbkxiiowe]

Oops. Spent too much time drawing a crappy diagram instead of working the answer out myself. I realise why that won't work now.

[sumgai]

vF?

vF??

Holy Stringbenders, Guitarman, looky there, it's vonFrenchie hisownself!!

Hey, you little shaver, you see DD842 Ver. 2.0's Title? Don't make him come down there and fetch you out..... yet again!

Nor me, for that matter! ;D


For the rest of you "newcomers", vonFrenchie is an old-timer here, so he's fair game - no respect necessary!



sumgai

[murrayatuptown]

Hi:

Hit the delete key or skip this message for any reason you like...I just came back to the top of this post because I now wonder who will find my comments of interest...at all...but you never know..

So, apologies to anyone who wonders what the (insert word of your choice) the point of this response is...


I'm new here & part-ignorant, but I also just asked someone the same or similar question - why the dirt cheap single-coil pickups I got on eBay for a why-am-I-starting-another-project? guitar project had one short magnet. I assumed it had something to do with a string that might be wound or not, but apparently I was wrong - I think it's the 3rd or 4th that some people make a choice about in some cases, my PU's have a stumpy 2nd or 5th magnet (they're not on the guitar - I hope I have enough sense to ask or look before mounting a PU backward...or would that be a lefty PU then?)

He's a guitarist AND electronics guy, I'm just the latter hoping to become both when I figure out which end of the guitar is which (OK, not that bad, but close).

He says the short magnet is one part of how they balanced the pickup's non-linear (frequency) response for all strings.

My two cents to add to this is that I believe it's not in the way one would expect a tone control and capacitor to interact with the electrical frequency response of the winding inductance, resistance and interwinding capacitance but in the magnetic properties of the pickup as a transducer - six magnetic strings that are not all the same width or mass, and not vibrating the same are all stuck inside one coil and contribute to a single combined output signal.

The complexity of variables in the electrical circuitry of an electric guitar is explained nicely by probably a number of people, but

buildyourguitar.com/resources/lemme/

is one I have read and found helpful/interesting...I had some trouble finding the English language version of this a 2nd time, but here it is.

Anyway, the number of electrical variables that model (mathematically explain) electric guitar function is abstract enough to deal with, and is out of the realm and interest of many readers.

The magnetic 'circuit' is a whole different beast...much of which is difficult to even be practically measured without affecting the response. The electrical properties are measureable but hard to understand for many people because it's 'invisible'. Magnetism is another level deeper into the 'invisible' realm because any measurements are made by proximity and not a contact or connection whose effect can be minimized

This stuff is outside my brain's ability to process...I finished all the math in an electrical engineering curriculum but didn't complete my degree. I think it falls into the category some people call 'black magic'. There is a certain amount of predictabilty and limitations to theory... fine-tuning by sophisticated approximation and repeated experimental changes are necessary (empirical results).

All part of why there are so many pickup designs, magnet options, Lollar's custom magnet degaussing, etc. It's not just how strong or long or wide heavy a magnet is...the concentration of and shape of the magnetic flux lines, the interaction of adjacent magnets (the end magnets don't have one on both sides, etc.).

I may even be wrong about some of this, but I am confident it's a pretty specialized field to analyze.

I thought they were supposed to have adjustment screws, so I guess the non-adjustable ones have to be installed at the right height (I decided I better not make my own guitar body for a first project).

I actually thought it would be cool to make my own pickups (saw an old 50's article on building one's own steel guitar with pickup), but $4.72 + shipping for 7 pickups cut me off from that idea...no matter how krappy they are, they are probably better than my own random results.

I'll try to stay on-topic and type less in the future.

-

Uh, the future is here, I have something to add...

There's no law that says the magnets have to be uniform throughout the entire length or width...magnetizing can be far more complex than just magnetized/demagnetized, there can be a tailored profile (a number of variables). This is the stuff that gets kept out of patents and makes copying someone's design EXACTLY harder to do.

[newey]

Murrayatuptown-

Hello and welcome!

I think you and rbkxiiowe may be talking apples and oranges here. The original post was a reference to a particular type of vintage pickup from a Watkins guitar. Now, I've never seen one of these, but from rbkx's description, it had one magnet which was not only shorter but of reversed polarity to the others.

You are apparently referring to pickups with what are referred to as "staggered pole pieces". There are many varieties of these, and differing sized poles are used as you suggest, to sort of "fine-tune" the magnetics for differing response on different strings. This does not imply that the shorter ones are of opposite polarity, nor that any hum-reduction is occurring, as in the Watkins pickups.

Sumgai's comments about marketing apply in either case; much of the hype on pole pieces being staggered is just that, hype. In the end, only your ears can be the judge.

[ChrisK]

He says the short magnet is one part of how they balanced the pickup's non-linear (frequency) response for all strings.

It's how they balance the differing string magnetic mass velocity response for each string. Slug AlNiCo magnets are generally non-machinable and hence, one can only balance the response by either varying the magnetization of each (one must pay close attention in manufacturing) or the height of each (mass production is).


The work of Helmuth E. W. Lemme is critical in understanding the physics of pickups. I "leaned" heavily on his work in the past (Pickup Coil Response Tuning). (Of course, it didn't hurt that pSpice graphically shows such effects easily.)

The magnetic 'circuit' is a whole different beast...much of which is difficult to even be practically measured without affecting the response. The electrical properties are measurable but hard to understand for many people because it's 'invisible'. Magnetism is another level deeper into the 'invisible' realm because any measurements are made by proximity and not a contact or connection whose effect can be minimized

This stuff is outside my brain's ability to process...I finished all the math in an electrical engineering curriculum but didn't complete my degree. I think it falls into the category some people call 'black magic'. There is a certain amount of predictability and limitations to theory... fine-tuning by sophisticated approximation and repeated experimental changes are necessary (empirical results).

Oh, you mean classical electrodynamics?

Or, the real truth, quantum electrodynamics.

This is the stuff that gets kept out of patents and makes copying someone's design EXACTLY harder to do.

Of course. There's money involved, it's a business.

The secret of business is OPM; Other People's Money, Other People's Margin.

Once a patent application is published by the Patent Office, the world gets to see what's afoot. We often choose to not file for a patent if we think that we won't be easily able to discern if someone is actually infringing. What's the point of spending the money for a patent if all you did was elevate the playing field?

These are kept sub-rosa and called "Trade Secrets"! We give nice plaques to our inventors for these too.


Patents are used (as a license to sue) to prevent others from practicing your inventions. While you describe/teach preferred embodiment(s) and wildly claim all that is cosmically possible, you try to refrain from enabling the world with all of the secret (trade) sauce.

Stupidity isn't.