Coupla questions regarding pickup mags

[eclecticsynergy]

Okay, I have dozens of questions. But the ones at the top of my list right now fall into four areas.

1) Relative strength of the various alnico grades. First of all, I'm assuming that magnet strength correlates pretty directly with pickup output, that in a given pickup swapping to a more robust mag should increase the output a bit and vice versa. This is a safe assumption, right?

So, the prevailing wisdom seems to be rating them weakest to strongest: A3-A2-A4-A5-(A6)-A8. Yet some seem to feel A3 actually is as strong or stronger than A2- could that just be perception based on the fact that it's generally brighter overall? Also, some have said that A4 is actually the weakest of the bunch. I'm aware that there will be some variation from one manufacturer to another, possibly even from batch to batch. But in the aggregate (baaad pun, I know) the various grades must all shake out into a pretty coherent order. Can somebody with lots of experience please set this me straight on this once and for all?

2) A8s in lower winds. I have a couple of lower wind pickups that I'd love to beef up a little with an A5-to-A8 swap, but I'm seeing mixed opinions about it. At least one knowledgable voice have done it a lot and recommends it highly; others disagree. Where do you weigh in personally on this one? And among those who think it's not as great an idea as it sounds, what in your opinion is the downside? Do you think I'd be better off staying with A5 and trying roughcast/unpolished or unoriented?

3) Weaker mags with overwound coils. I have a couple of Epiphones with bridge pickups which, while adequate, to my ear sound less than ideal- slightly harsh and at the same time a bit lacking in definition. (Chinese, I think, in guitars dating from '010 and '013- DCRs read 14.0 and 13.98). Does anybody think an A4 or A3 mag might give them new life, a more articulate and dynamic voice? I don't need them to be particularly loud, since I have the PUs on these axes fairly low to better match the output of other instruments. There's room to raise 'em.

As an alternative to a mag swap, I've read somewhere that one can slightly degauss a humbucker without even taking it out of the guitar using a Neo magnet. Is this really a viable technique, and if so could mild degaussing warm them up a bit, maybe fill in the mid scoop somewhat?

[If they are a lost cause, I could be tempted to take 'em apart and try my hand at removing some winds. I'm not sure what kind of coil offset they've got and am a bit curious anyway, so it might be nice to have something pretty much disposable to experiment on. That way if I screw up it isn't a major loss.]

4) Grades/types of ceramics. I'm aware that some some overwound PUs like the DDs and SDs have extra thick ceramics, but I've also seen references to several different grades of ceramic mags, including C5 as well as the more common C8. Do these vary just in terms of strength, or do they indeed have different tonal natures- and if so, do they correspond at all to the characters of the various alnicos? Is there a C2, a C3? (And if there's a C4, is it highly explosive? Sorry, really couldn't resist that one...)

Thanks for your time. I appreciate any advice you have to offer on any or all of the above.

 

[AlexR]

Re: Coupla questions regarding pickup mags

Your strength chart is about right. There are a few contradictory posts about, but the vast majority have it in the order in your post.

Mags certainly have different strengths, and can induce more signal, but the frequencies that the signal is induced in are varied, the pickup construction is quite varied as is the wind. Then you get to the amp and how the extra signal is processed by the amp, and then how that is fed into the speaker and then lastly how our ears perceive the change.
A5 is a much stronger mag than A2 for example. But the scooped nature of the A5 can lead to a pickup that either doesn't punch through either by itself or in a band setting. A2 is a weaker mag, but its solid mids can allow it to cut through a mix, plus the mids component can drive tubes harder - leading to a pickup that actually sounds more distorted than its stronger magnet compatriot.

There is plenty of good tones from low wind+high strength magnet. I know G&L have this quite often in pickups, Gibson Tarbacks are another option. I think Bill Lawrence pickups are done this way too. They seem to be better for clarity if that is your thing.

 

[DreX]

Re: Coupla questions regarding pickup mags

1) I just ordered a bunch of magnets for testing purposes and I'm (not too) surprised to find that two of the same grade vary by up to 5 gauss. It's so relatively easy for AlNiCo to gain or lose their charge that one big reason few people on the internet might agree about how A3 should sound relative to A2 or A5 is because one guy's might be more charged than another guy's. The fact that the alloys are different plays a role also, allegedly, I'm not sure what degree of a difference alloy makeup makes compare to overall magnetic strength. I have test setup and I plan to compare different AlNiCo compositions fora given gauss, I'll post the results here. That might sort of answer question 5, but I only have a C8 on hand, no C5 (yet). If it's the case that the C5 and C8 have different gauss (magnetic strength), then they will sound different for sure.

3) weaker magnet in a hotter wind is a bad mix, IME, it results in a strange, chewy dynamic. If they lack in definition with what is presumably a charged A5 bar, you're probably not going to get more definition out of them with an other sort of magnet. If those are the stock pickups, I think you have to perhaps try another pickup in order to differentiate how much blame lies in the pickups versus the guitar itself. A DC resistance of 13~ sounds like a rather hot pickup anyway, not exactly PAF, if that's what you're looking for.

3.b) you don't want to degauss a magnet with just one neodymium because the magnetic flux shape of the charging magnet will be donut shaped, so the discharge will be uneven across the length of the bar. That's why you only charge or discharge with two neodymium magnets, because between the two of them you will get a straight across flux pattern which will charge the bar evenly, did I explain that clearly?

 

[eclecticsynergy]

Re: Coupla questions regarding pickup mags

Yah, thanks guys.

AlexR, I agree about the differences in frequency balance between various mags making for apparent volume differences in the end result. And thanks for the reassurance about strong mags in lower wind pickups. I will order a couple of A8s and give it a try.

Drex, I'm eager to read about your alnico comparisons when you've done them. About ceramics, assuming different grades are made of different compounds, I'm quite curious to learn how (or if) they mirror the characteristics of the various alnico alloys. Please post if and when you have a chance to compare your C8 with C5, or anytime you have more to share about different ceramics.

Thanks also for your advice about weak mag/hot wind. I expected there'd be good reasons why that combination isn't much in evidence, but I had to ask. The pickups in question aren't awful, they just don't compare well with my others, which are better quality. I kinda like these Epi's woodwise (especially the '010, which is all Korina) and feel they deserve better bridge pickups at least. But they aren't front-line guitars.

About the neo degaussing, yes, you explained it well and I get it. That really was only a passing thought, rather than something I was actually planning. I do appreciate the info though.

 

[AlexR]

Re: Coupla questions regarding pickup mags

You can degauss a mag by running a stronger one across the pickup while its in the guitar. If you sit the mag (maybe that A8) on the strings with the pickup at normal height, then this will do a slight degauss....you just wipe it across to and fro maybe 4 or 5 times. You may well hear the difference in that one set of swipes, but you can go for more if needed. Remember, its harder to recharge than degauss.

 

[DreX]

Re: Coupla questions regarding pickup mags

Drex, I'm eager to read about your alnico comparisons when you've done them. About ceramics, assuming different grades are made of different compounds, I'm quite curious to learn how (or if) they mirror the characteristics of the various alnico alloys.

I've been experimenting with them tonight. I have a setup that lets me perform string strikes in a consistent way, a plucking arm is pulled down by gravity, same pressure, same angle of attack. I put the different bars into a neck '59, record six strikes, crop them, normalize them (because I care about tonal differences, not overall volume differences), then average the frequency response with FFT analysis.

In the FFT analysis, the A5 rough cast was sort of an out-liar, especially in the 6k-9kHz range but everything else was surprisingly close. I guess the question is, are those differences audible even though

For the sake of comparison, here's how series/parallel/split differed:



What was much more noticeably different was the amplitude change over time in the recordings. It's still a bit hard to tell the difference, but if you use the horizontal lines as a reference, you can see that, for example, the C8 with a gauss of 52 drops in amplitude faster than the A4 with the gauss of 30, and the A5 is in between, even though it has the same gauss as the A4. The overall shape of the crests and troughs are noticeably different, there's a big hump that occurs sooner with the C8 and later with the A4 and A5.

So if I were flying strictly on instruments, I guess that the variation in magnets might have more impact on the bloom characteristics, how the sound changes as it decays, because I can actually see a real signature differences there. The eternal question is, if you can see a difference in an electronic measurement, can it also be heard? If little to no difference is seen, does it mean our ears are somehow more sensitive than the electronic measurement, or are we allowing our hopes and expectation to decide that we hear a difference?

Here's my test rig, I've done a bunch of experiments already with it and ultimately plan to compare woods after I've become confident in a testing methodology. When I test magnets and nickel covers and barely see any difference, I get wary.

 

[eclecticsynergy]

Re: Coupla questions regarding pickup mags

Cool stuff, DreX! It'll be interesting to see how A2s, A3s, and A8s compare.

 

[GuitarStv]

Re: Coupla questions regarding pickup mags

That's some great information Drex! What FFT algorithm are you using? I recall from my university testing that playing around with some of the parameters can drastically change the smoothing of the data you get, and those frequency analysis charts look heavily smoothed.

 

[Demanic]

Re: Coupla questions regarding pickup mags

^^
I was thinking that maybe you should run a graph from non-normalized signals, since those volume differences, coupled with the various attack and decay rates, could play a big difference in perceived tonal differences between magnets.

 

[DreX]

Re: Coupla questions regarding pickup mags

That's some great information Drex! What FFT algorithm are you using? I recall from my university testing that playing around with some of the parameters can drastically change the smoothing of the data you get, and those frequency analysis charts look heavily smoothed.

The window type is Hann and the FFT size is 64, and it's averaged over 12 seconds six two-second strikes, you can see those in the multitrack screenshot above. If the FFT size is increased (decreased) to 8192, then the individual harmonics can be seen (tuned to an open D)

Here's an example of a six plucks analyzed as three sets of two

FFT size 8192 shows individual harmonic spikes, but it's hard to see trends this way

Here's the same thing with an FFT size of 64 (and zoomed in a bit to show how tight the lines are), it averages the difference between 64 FFT blocks instead of 8192, so end result looks more like an intelligible EQ curve, and shows that the end result is rather consistent.

If the plucking were done by hand, those lines would be less congruent since it would be plucked in a different location, at a different angle and with a different intensity, which would mean different amplitudes at different frequencies.

 

[DreX]

Re: Coupla questions regarding pickup mags

^^
I was thinking that maybe you should run a graph from non-normalized signals, since those volume differences, coupled with the various attack and decay rates, could play a big difference in perceived tonal differences between magnets.

If I don't normalize the amplitude, then I can see the volume differences, but it makes the frequency response differences harder to see, especially when comparing many lines at the same time, since you have to try and align all then curves in your mind. I'm more interested in whether something changes the EQ profile rather than the overall amplitude. I still have the non-normalized recordings, so I can specifically compare that later.

Regarding varied pick attack, I screwed the plucker into the board real good so that it wouldn't move even a little, so moving it around would be a chore, and I don't have reason to believe there would be characteristics that would be entirely hidden by a certain way of plucking, because there is full harmonic content, and plucking in different spots with different strengths just change how much of it there is, so if you pluck the same way each time, you get enough information across the whole spectrum, and it's a consistent baseline for comparison. It's possible, maybe even probable, that by having it tuned to a D3 I'm losing details that stick out below 147 Hz, but that's just a limitation of the experiment, and tuning any lower might have other drawbacks in turn.

 

[SJ318]

Re: Coupla questions regarding pickup mags

DreX,
While almost all of the content on this thread is over my head, I must give you your "props" if people still say that, for a lot of good hard work putting this all together. I must remark on some of the graphs the sounds look to be almost exactly the same. So whoever said maybe our ears are more sensitive, or, the power of suggestion is at work here.
If it could be proved, I guess a blindfold the would do the trick, I did go through A2,3,4,5,8, some RC, some UORC,
the A8 I had a pre-conceived idea of it and it did not do what I expected, and a couple I couldn't tell the difference, as I've said many times, the A4 really sounded good, different, and well EQ'd for me to tweak. So I guess I'd put my money on what my ear says, but not much money, as I admit I am a suggestible guy. So I guess I am fairly agnostic on this point, but still leaning toward the ear as the final arbiter.
Good work,
SJBuffington.

 

[DreX]

Re: Coupla questions regarding pickup mags

I'm going to try lowering the pickup away from the string and see if that makes a difference. I had it pretty close, like 3mm away, to get as much signal as possible.

There clearly is some sort of measured difference between the bars. The frequency response of the different bars are slightly divergent and those amplitude decay profiles show differences, so the question is how to magnify the difference. I'll try applying a linear EQ boost to see if I can make that steep downward slope more horizontal and easier to visualize like an EQ curve, and I'll let the neodymium monsters out of their cage so I can fully charge the bars, so that weak charges can't be blamed for differences.

Here's a curious thing to look at, notice the dip in series/parallel between 6kHz and 9 kHz? I believe that's caused by the fact that when you have the two coils going at once, any frequency width where the downward wave is over, say, the screws, while the corresponding upward wave is over the slugs, the positive and negative will cancel each-other out, making for a "dent" in the frequency response (this is a fact, I'm not taking a guess). The frequencies for which that will happen is dictated by by the width of the pole pieces of the two coils, which is about 18mm, and the length of the string, and the placement of the pickup, since all this factors into which nodes fall where. I see that suspicious "dent", but I'm not 100% sure that side-by-side coil +/- node cancellation is the cause there.

 

[AlexR]

Re: Coupla questions regarding pickup mags

Are you going to do a test with the mags charged fully - I mean part of the frequency distribution of mags is due to the charge (and therefore field shape/size) that they have.

 

[LtKojak]

Re: Coupla questions regarding pickup mags

DreX, first I'd like to thank you for the time and effort put into publishing the results of your research. Much appreciated!

Having said that, I'm having trouble interpretating the graphs... I really don't know what to make of them.

Maybe a "Graph interpretation for Dummies" gudeline is in order for people like myself?

Yours very truly,

 

[Dahla]

Coupla questions regarding pickup mags

Awesome DreX!

Edit: (deleted) Nevermind!

 

[DreX]

Re: Coupla questions regarding pickup mags

Are you going to do a test with the mags charged fully - I mean part of the frequency distribution of mags is due to the charge (and therefore field shape/size) that they have.

I just tested them as I received them. I'll charge the up and test again, but I'm not sure what the maximum gauss is for those various alnicos. I listed the gauss in that graph above so that there would be no mysteries in that regard. I have about ten magnets in all, so there's a lot left to do, including comparing a full strength versus a deliberately weakened magnet. I bet a lot of people order and use these magnets without even realizing they're degaussed to some extent.

 

[MacBradley]

Re: Coupla questions regarding pickup mags

Great experimenting Drex! Some interesting stuff here.

 

[DreX]

Re: Coupla questions regarding pickup mags

Having said that, I'm having trouble interpretating the graphs... I really don't know what to make of them.

I recorded a neck '59 with various magnets and with various wiring modes, using a gravity compelled plucking arm so that the plucks are uniform, then cropped the recordings so that they are all identical in length, then averaged the frequency amplitudes picked up throughout the duration of the recording. For the graph with the lines, the X axis is frequency, the Y is amplitude, so if one magnet produces more mids then for that magnet's line, there should be a hump in the line in the line near the mids frequencies near 800 kHz, when compared to a magnet that doesn't produce as many mids. A subjective aspect is that the plucks are allowed to decay for only two seconds. I recorded them in five second samples originally, but trimmed them back to two, because I figure that's the most relevant to real-life usage. Most of the time we're not letting the notes ring out for five whole seconds.

Then there's the multitrack view, which shows the amplitude for those string strikes. Those are normalized, meaning the whole thing is amplified until the loudest point is at 0 dB, and the purpose of that was just to show that the decay characteristics actually varied a bit between the different magnets, which I was not expecting. The C8 clearly decays at a faster rate than the A4 or A5. I'm wondering if that's due to magnetic dampening, it's 52 gauss where as the A4 and A5 are 30 gauss, so I'll move the pickup farther away from the strings and give it another try. I though that was only an issue with Strat pickups that had the ends of the magnets right up to the strings.

I'm still working on making the measurements easier to read, and I need to fully charge the magnets and record them again, because I received pairs of all the various types, and noticed many of them had different strengths, even though they were the same alloy and were stuck together when they arrived. The results so far just show that there is a difference, and how wide the differences tend to be, but they aren't to the point yet where a clear statement can be made about how one magnet differs from another (given the specific conditions of this test setup, anyway).

 

[LtKojak]

Re: Coupla questions regarding pickup mags

I recorded a neck '59 with various magnets and with various wiring modes, using a gravity compelled plucking arm so that the plucks are uniform, then cropped the recordings so that they are all identical in length, then averaged the frequency amplitudes picked up throughout the duration of the recording. For the graph with the lines, the X axis is frequency, the Y is amplitude, so if one magnet produces more mids then for that magnet's line, there should be a hump in the line in the line near the mids frequencies near 800 kHz, when compared to a magnet that doesn't produce as many mids. A subjective aspect is that the plucks are allowed to decay for only two seconds. I recorded them in five second samples originally, but trimmed them back to two, because I figure that's the most relevant to real-life usage. Most of the time we're not letting the notes ring out for five whole seconds.

Then there's the multitrack view, which shows the amplitude for those string strikes. Those are normalized, meaning the whole thing is amplified until the loudest point is at 0 dB, and the purpose of that was just to show that the decay characteristics actually varied a bit between the different magnets, which I was not expecting. The C8 clearly decays at a faster rate than the A4 or A5. I'm wondering if that's due to magnetic dampening, it's 52 gauss where as the A4 and A5 are 30 gauss, so I'll move the pickup farther away from the strings and give it another try. I though that was only an issue with Strat pickups that had the ends of the magnets right up to the strings.

I'm still working on making the measurements easier to read, and I need to fully charge the magnets and record them again, because I received pairs of all the various types, and noticed many of them had different strengths, even though they were the same alloy and were stuck together when they arrived. The results so far just show that there is a difference, and how wide the differences tend to be, but they aren't to the point yet where a clear statement can be made about how one magnet differs from another (given the specific conditions of this test setup, anyway).

Got it, thank you! I'm going to need some time to digest all of this info, but you've been clear and thorough with the explanation, so it's only a matter of time.. I'd hope! LOL!

BTW, how do you charge the mags, with a couple of Neos in a jig or you have a zapper?