About measuring electrical properties guitar pickups

[tizimor71]

Hi everybody

I have been following this forum for years but this is the first time I write and I wanted to congratulate you on all the information you have shared.

Unfortunately I have no knowledge in electrical engineering and as you will notice also in English but your forum gave me the impetus to deepen the topics covered and I hope to make a small contribution in the future.

I started testing pickups thanks to the information in this thread by Antigua guitarnuts2.proboards.com/thread/7723/measuring-electrical-properties-guitar-pickups

This is my setup :

M-Audio Fast Track Pro soundcard
Test coil 2mH and 104 ohm
Crocodile clips capacitance about 25 pF
Drive coil tension 1V PP





The integrator was built thanks to the information available by Stratotarts kenwillmott.com/blog/archives/323.
The only variant is the addition of a selector (JP1 to JP6) for add a different type of resistor and capacitors and a jack connector input.





First I took a sets of Fender Pure Vintage 65 to compare the results with Antigua database.
The inductance and resistance are measured by Extech 380193 and the capacitance by Ken Wilmott method.

Here the results




I get a resonance peak about 2 dB higher and loaded resonance frequency 200 Hz lower.

I try to change the soundcard because from M-Audio Fast Track datasheet the input impedance is > 220 Kohm, so I try another soundcard (Native Audio Komplete 6 with 1 Mohm input impedance), but the result is the same




I try to change the test coil






In this case I find an increase of dB with lower test coil inductance value but with 0,450 mH and 2mH the value are the same.

So I took a second set of pickup Fender Texas special (testing with 2mH test coil inductance).









In this case I get a resonance peak about from 0,6 to 0,9 db higher and loaded resonance frequency 200 Hz lower.

Are these deviations acceptable? Or are there other factors beyond the test method (USB oscilloscope or soundcard) or pickup tolerances that I haven't considered?

I hope I have not been too confusing in proposing my first topic

Thank you in advance for any suggestion on the matter

[stratotarts]

Your schematic appears to be behind a registration wall. Could you possibly move it here, or host it publically?

[tizimor71]

Hi Stratotart , sorry but my English is at school level.
What do you mean by "your schematic appears to be behind a recording wall" do you intend to do better the set up photo or the integrator schematic?



Thank you

[Yogi B]

Jun 20, 2021 11:26:43 GMT -5 stratotarts said:

Your schematic appears to be behind a registration wall. Could you possibly move it here, or host it publically?

I think that's just Postimages being unhelpful, as about maybe 50% (?) of the time for reasons unknown to me the BBCode it spits out links to their homepage rather than to the image. Although in the specific case of the above post it's 5/6 that link to the home page.

Right clicking the image & opening it in a new tab takes you to the correct page, however the image isn't any larger. I don't know if this is also a weird Postimages issue, because it's not the first time that I've seen people post oddly small images via this method.

[tizimor71]

Thanks for the help,

I hope I have added the photos with a correct size, sooner or later I will understand how to do the right things, be patient ....

I look forward to your comments



See you soon

[antigua]

tizimor71, thanks a lot for setting up a test rig and joining in on the fun. Yeah, those deviations looks typical. There is a lot of variability in Fender pickups, especially when the pickups are made in different years, because they have different productions runs, and in each production run, they will make the pickups a little differently. Unfortunately, it would be expensive for any one of us to buy many of the same pickup, so it's difficult to tell whether the deviation is because our test setups have slight differences, or if the pickups themselves are different, but I have had two sets of many pickups, such as Texas Specials, the 57/62, Original Vintage Telecaster pickups, and a difference of 100mH, or more, between them is not uncommon.

[tizimor71]

Hi Antigua,


Thanks for the reply, and first of all I would like to thank all the forum members. When I started reading it, I didn't know what was a resistance .

Do you still think that the variations in terms of dB detected on the resonance peak are also due to the variability of the Fender pickups?

In your opinion which of the single coils you have already analyzed would you recommend me to test for a further comparison?

[antigua]

Jun 22, 2021 14:15:35 GMT -5 tizimor71 said:

Hi Antigua,


Thanks for the reply, and first of all I would like to thank all the forum members. When I started reading it, I didn't know what was a resistance .

Do you still think that the variations in terms of dB detected on the resonance peak are also due to the variability of the Fender pickups?

In your opinion which of the single coils you have already analyzed would you recommend me to test for a further comparison?

The differences could easily be explained by manufacturing differences. The thing is, even if they use identical turn counts, the wire spools onto the pickup bobbins randomly, and that creates a variation is turn-to-turn inductive coupling, because the turns are not perfectly aligned on the axis, the turns of wire all all have slightly varied axis. Physical electrical components always have non-ideal aspects, such as unwanted resistance, capacitance and inductance, and because the way a guitar coil is wound in a relatively sloppy matter, guitar pickups are especially non-ideal. I've only seen a high degree of consistency with some imported pickups from China. The more  machines involved, the less that is left to chance, the more electrically consistent pickups will be. 

I'm not sure there is a standard that can be relied upon, but we have often used the Seymour Duncan SSL-1 and Seymour Duncan '59 neck humbucker as test subjects, because they're among the most common aftermarket pickups, and they seem to be made fairly consistently. They still vary enough that we can't used them as a calibration reference. 

I think it's safe to say your test rig is working properly and capable of capturing usable data as it is now. The only thing to maybe look at is that 200k and 470 capacitor for testing load are in fact within ~1% of 200k and 470pF, tested with an LCR meter, because if they are off by 5%. For our 200k and 470pF dummy loads, we try to make sure they're as close as possible to the nominal values.  

[tizimor71]

Thanks Antingua,

Your answer was very complete.

I will make the measurements you indicated and let you know.

See you soon