Chuck Fry 🏳️‍🌈Dec 3, 2022
So among many other hobbsessions, I play some electric #guitar for fun. A couple of years ago, I bought a B-stock L*s P**l clone from Rondo Music. It had some finish issues that were invisible from more than 2 feet away, but was otherwise in great shape. It plays really nicely for a US$300 guitar. My only "complaint" was that the pickups in it are nothing special. So I set out to fix that... 1/?
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Sweetwater Sound had a Black Friday 25% off sale on DiMarzio #guitar #pickups. DiMarzio is one of the 2 best known makers of aftermarket pickups, Seymour Duncan being the other. Both have been at it since the 1970s.

I wanted pickups that were hotter, but not too hot, and better balanced than the originals. So I ordered an Air Norton for the neck and a Satchur8 for the bridge. They showed up yesterday... 2/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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#Geek that I am, and knowing enough about #electronics to be dangerous, I got out an LCR meter to get a feel for what these #pickups are about. (How many other #guitarists do this??)

Guitar pickups are, in essence, nothing more than coils of wire wrapped around a magnetic structure. The technical term is "variable reluctance sensor". Since most guitarists don't know jack about electronics, there's a lot of mumbo-jumbo and cargo-cult mystique about pickups... 3/?

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Hum from magnetic fields generated by AC power wiring is a problem with #guitar #pickups. A clever engineer in the 1950s put two similar coils next to each other, but reversed the magnetic and electric polarity on one of the coils ,and connected them in series. The result is that the hum signal is "bucked", or canceled, and the desired musical signal is doubled. "Humbucking" pickups or #humbuckers are in most electric guitars made today... 4/?

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#Guitar #pickups are relatively big inductors, with very lumpy frequency responses. We'd like to know the output transfer curve, but there's no easy way to measure it, and too many variables.

It's easy to measure series resistance (R in #electronics speak). But it has almost no bearing on the output characteristics. Inductance (L) has a direct bearing on output, but requires fancier measurement gear.... 5/?

Dec 3, 2022 at 9:14pmWeb
Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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Back up a bit: a pure inductor (L) has no resistance (R) or capacitance (C). Real inductors have both. The result can be characterized as an RLC resonant circuit. It's easy to measure R, not as easy to measure L, and tricky to measure C, but you can infer C from the resonant frequency.

I picked up a Chinese RLC meter some time ago for other projects. So I dragged it out to get some measurements on the new DiMarzio #guitar #pickups.... 6/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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OK, let's cut to the chase. I don't have a rig for measuring resonant frequency, but I did get inductance and series resistance numbers for both #pickups.

Each pickup has two coils. I measured them individually, in series (the usual #humbucker configuration), and in parallel.

The Air Norton:
coil 1, 2.80 Henrys (inductance), 6.90k Ohms (resistance)
coil 2, 2.70 H, 5.35 kΩ
series: 6.41 H, 12.3 kΩ
parallel: 1.61 H, 3.02 kΩ

... 7/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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The Satchur8:
coil 1, 2.88 H, 5.77 kΩ
coil 2, 2.89 H, 7.22 kΩ
series, 6.64 H, 13.0 kΩ
parallel, 1.68 H, 3.21 kΩ

What's interesting about these numbers? DiMarzio claims that both of these #guitar #pickups (and many others they make) have coils with deliberately different resonant frequencies. And you can see this in the numbers.

The two coils of a #humbucker have to have the same inductance, or the hum canceling is diminished (i.e. more hum gets through).... 8/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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So since L must be constant, something else has to change. The clue is the series resistance. Higher R means finer wire was used, and because the coils are now packed more tightly, it also increases C. The result is a lower resonant frequency (duller sound). Conversely, lower R means lower C, and a higher resonant frequency (brighter sound).

As I said, I don't have a setup for measuring resonant frequency. But I took R, L, and Z readings over a range from 120 to 10k Hz... 9/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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And the Z (impedance) and phi (phase) over that range give a hint about resonances. Phase is + while L dominates, 0 at resonance, and - once C becomes dominant.

Coil 1 of the Air Norton resonates1 somewhere just under 10 kHz; phase is positive at 4k, slightly negative at 10k. Coil 2 is somewhat above 10 kHz; phase is still positive at that point. The series resonance is a fair bit lower than coil 1, I'll take a SWAG and call it 6-ish kHz. Parallel is pretty much at 10k... 10/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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The Satchur8 is unusual. Coil 1 resonates above 10 kHz. Coil 2 I'll SWAG about 5 kHz; it is the only coil tested with a lower Z at 10k than 4k. In series, I'll SWAG 7.5-ish kHz. In parallel, it's closer to 6 kHz. Parallel resonance is usually higher than series, so this is an unexpected result.

Caveat: You'll never see these numbers in actual use, because a #guitar cable adds signficant capacitance, dropping the resonant frequency quite a bit.... 11/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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What do these #guitar #pickups sound like? I don't know yet; I haven't installed them. Here's what the numbers suggest.

Guitar strings move further at the neck pickup than at the bridge pickup. So ideally the bridge pickup should be more sensitive, or "hotter".

The Air Norton and the Satchur8 have similar total inductance. That would suggest similar sensitivity. But the magnetic structures are quite different. The "Air" in Air Norton refers to a gap in the structure.... 12/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

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DiMarzio's advertised output figures suggest the Satchur8 #guitar #pickup is about 40% hotter than the Air Norton. That's likely due to the magnetic structures.

A typical pickup's output curve will have a very sharp peak at resonance, and fall off steeply at higher frequencies. Not these. I'd expect the Air Norton to have a flatter peak, an extended high frequency response. I'd expect the Satchur8 to have a bit of a "double-hump" shape due to the 2nd coil's response... 13/?

Show threadChuck Fry 🏳️‍🌈Dec 3, 2022

... concluded...

So why am I still typing when I should be soldering these pickups into my guitar?? I hope to have a followup report once I've put some time on them.

Links (disclaimer: I pay them, not vice versa):

DiMarzio: https://www.dimarzio.com/ - #guitar #pickup maker
Rondo Music: https://www.rondomusic.com/ - well made #guitars, cheap
Sweetwater Sound: https://www.sweetwater.com/ - everything musical

14/fin

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