Seymour Duncan JB & Jazz Neck, Analysis & Review

[antigua]

The JB bridge / Jazz neck combo has been marketed by Seymour Duncan as a good pairing, ever since they set was introduced in the very early 80's.

The JB is essentially a highly over wound PAF, while the neck is essentially a PAF-like neck pickup. At 8 henries, the JB has around twice the inductance of the Jazz neck, which shows 3.9 henries inductance. It appears that all the same parts are used for the two pickups, including plastic spacers, AlNiCo 5 magnets, 4 conductor wire, a polyester tape, etc. The only difference appears to be the wire gauge used for the coils, and the wind count, achieving a great difference in inductance. Both appear to use the same wire insulation, which is fairly transparent, so the coils are copper-colored, probably a polyester or poly nylon. From the images below, they are impossible to tell apart, aside from the stickers that are affixed.

I had previously measured a Jazz bridge and neck here , but that set from from the Custom Shop where as these are production floor pickups. The Custom Shop Jazz neck showed a slightly higher inductance. The electrical values of the Jazz neck are pretty close to that of the '59 neck, most likely within the range of production tolerance. The loaded peaks of both Jazz neck samples and the '59 I've tested land right around 3.0Hz. It appears that the idea was to have a neck pickup that performs like a PAF neck, but shares all the same production components of the JB, either for aesthetic reasons or cost reasons.

The JB has a loaded peak frequency of 1.96kHz, which is similar to many of the P-90 style pickups measured. Having no metal cover should help increase the Q factor, but the higher DC resistance brings it down to 1.6dB, roughly the same amplitude at resonance you get when you put a nickel silver cover over a typical PAF pickup. The Jazz neck, by contrast, has a resonant amplitude of 2.9dB.



Seymour Duncan JB I1IXQ SH-4 20161011

DC Resistance: K
- series:  16.80k ohms
- parallel: 4.20k ohms
= screw:    8.22k ohms (red & green)
- slug:     8.06k ohms (black & white)
Inductance:
- series:   8.059H
- parallel: 2.013H
= screw:    3.535H
- slug:     3.516H
Calculated C:
- series:   128pF (138-10)
- parallel: 243pF (253-10)

Resonant Peak:
- series:   dV: 8.0dB f: 4.78kHz black
- parallel: dV: 8.7dB f: 7.05kHz red
- screw:    dV: 8.7dB f: 6.89kHz green
- slug:     dV: 10.0dB f: 6.97kHz gray
Loaded Peaks (200k ohms & 470pF):
- series:   dV: 1.6dB f: 1.96kHz black
- parallel: dV: 4.6dB f: 4.08kHz red
- screw:    dV: 3.1dB f: 3.28kHz green
- slug:     dV: 4.1dB f: 3.28kHz gray

Gauss at screw / slug tops at center: 370G/365G





Comparison of output voltages for different wiring modes:






Seymour Duncan Jazz SH-2N I6N46 SH-2N 20091116

DC Resistance: K
- series:   7.76k ohms (measured 7.48k w/ Custom Shop sample)
- parallel: 1.93k ohms
= screw:    3.90k ohms (red & green)
- slug:     3.85k ohms (white & black)
Inductance:
- series:   3.922H (measured 4.255H w/ Custom Shop sample)
- parallel: 0.980H
= screw:    1.672H
- slug:     1.726H
Calculated C:
- series:   112pF (122-10) (99pF w/ Custom Shop sample)
- parallel: 204pF (214-10)

Resonant Peak:
- series:   dV: 7.4dB f: 7.29kHz black (6.0dB f: 7.63kHz w/ CS sample)
- parallel: dV: 7.8dB f: 11.0 kHz red
- screw:    dV: 8.0dB f: 11.5 kHz green
- slug:     dV: 7.5dB f: 10.6 kHz gray
Loaded Peaks (200k ohms & 470pF):
- series:   dV: 2.9dB f: 3.17kHz black (dV: 2.0dB f: 3.06kH w/ CS sample)
- parallel: dV: 5.3dB f: 6.36kHz red
- screw:    dV: 3.9dB f: 5.36kHz green
- slug:     dV: 5.3dB f: 4.95kHz gray

Gauss at screw / slug tops at center: 380G/360G





Comparison of output voltages for different wiring modes:






product link: www.seymourduncan.com/pickup/hot-rodded-humbucker-set




JB pics:













SH-2 Jazz pics

[frankfalbo]

Oct 29, 2017 16:34:49 GMT -5 antigua said:

The JB bridge / Jazz neck combo has been marketed by Seymour Duncan as a good pairing, ever since they set was introduced in the very early 80's.

Seymour made these in the 70s before he even launched the company, and they were among the first two models to exist. They weren't sold together as a set until much later.

Oct 29, 2017 16:34:49 GMT -5 antigua said:

It appears that the idea was to have a neck pickup that performs like a PAF neck, but shares all the same production components of the JB, either for aesthetic reasons or cost reasons.

No. Seymour chooses wire for the sound they produce. By the time these became models, Seymour had already wound pickups for people like Jimmy Page with Plain Enamel, and Jeff Beck with poly. Consolidating wire insulation types was not a consideration.

[roadtonever]

I read somewhere that the Duncan Distortion is the same pickup with a ceramic magnet. So if you are not digging the JB you can mod it into another very popular pickup model with a magnet swap.

[gpdb]

I've been doing some investigation on my Seymour Duncan Jazz pickup as well, and my theory is that each coil uses a different wire gauge. On the SD website, it mentions that the Jazz has a "special coil wind". Here's the quote (https://www.seymourduncan.com/single-product/jazz-model): 

"The Jazz Model bridge features its own unique coil wind to deliver a bridge tone with extra treble emphasis, a nice tight bottom, and a hushed midrange." This description is in line with what I've heard about mismatched coils, but I can't confirm the validity of that.

I came to the same conclusion as Antigua that the 59 neck and Jazz neck have identical specs from what is listed, and have been testing both models. So either they are the same pickup, or there is something different. This mention about a special coil wind seems to be the only difference that is noted on the website. I took mine apart and noticed that the South coil appeared to have more wire on it than the North coil. It's small, but when I measured with my digital calipers, I consistently got the same result. However they both read very similar resistance values. So if it's not more wire, than it could only be a different gauge. To confirm a tonal difference I created a loaded frequency plot for series, north, and south coil individually. If the north and south coil were identical, I would have assumed them to be more identical in shape and output, but that's not what I'm seeing. The only thing I'm not accounting for in this would be pole pieces as one side is screws, and the other is slugs. I haven't done enough testing to know what effect that would cause. I'd love to get anyone's thoughts on what I might be missing, or if this is correct. If this is correct, then it would be very similar to Dimarzio's Dual Resonance patent.

	DCR (kOhms)	Inductance @1khz (H)	Coil Width (mm)
Jazz Series	7.36	3.73
Jazz North	3.6	1.67	13.8
Jazz South	3.7	1.57	14.17

[antigua]

Feb 20, 2022 13:42:08 GMT -5 gpdb said:

I've been doing some investigation on my Seymour Duncan Jazz pickup as well, and my theory is that each coil uses a different wire gauge. On the SD website, it mentions that the Jazz has a "special coil wind". Here's the quote (https://www.seymourduncan.com/single-product/jazz-model): 

"The Jazz Model bridge features its own unique coil wind to deliver a bridge tone with extra treble emphasis, a nice tight bottom, and a hushed midrange." This description is in line with what I've heard about mismatched coils, but I can't confirm the validity of that.

I came to the same conclusion as Antigua that the 59 neck and Jazz neck have identical specs from what is listed, and have been testing both models. So either they are the same pickup, or there is something different. This mention about a special coil wind seems to be the only difference that is noted on the website. I took mine apart and noticed that the South coil appeared to have more wire on it than the North coil. It's small, but when I measured with my digital calipers, I consistently got the same result. However they both read very similar resistance values. So if it's not more wire, than it could only be a different gauge. To confirm a tonal difference I created a loaded frequency plot for series, north, and south coil individually. If the north and south coil were identical, I would have assumed them to be more identical in shape and output, but that's not what I'm seeing. The only thing I'm not accounting for in this would be pole pieces as one side is screws, and the other is slugs. I haven't done enough testing to know what effect that would cause. I'd love to get anyone's thoughts on what I might be missing, or if this is correct. If this is correct, then it would be very similar to Dimarzio's Dual Resonance patent.

	DCR (kOhms)	Inductance @1khz (H)	Coil Width (mm)
Jazz Series	7.36	3.73
Jazz North	3.6	1.67	13.8
Jazz South	3.7	1.57	14.17

Those numbers are pretty close, within margins of error. If they used different wire gauges for the slug and screw coils, the DC resistance and inductance would be somewhat farther apart for the same inductance, and vice versa.

I don't put much thought into what the company says about the product itself, they have to come up with creative ways to justify a lot of products that are essentially indistinguishable from one to the next. Mismatching the coils will cause a higher noise ratio, which they likely see as a bigger drawback than any subjective tonal benefit.

DiMarzio mismatches coils, and makes lots of claims of supposed benefits, but at the end of the day they still give them matched inductances, presumptively to get optimal noise cancellation. DiMarzio's Dual Resonance is all marketing mumbo jumbo. You can see for yourself that when the two coils are in series, you get but one resonant peak. The inductances combine in series, the capacitances combine in parallel, and from that you get one resonant peak. It's possible that when they were applying for the patent they didn't even understand this point of physics. The USPTO might not have understood the underlying physics, either, so a patent could be issued that is based on an false premise. 

[gpdb]

Feb 21, 2022 15:50:09 GMT -5 antigua said:

Feb 20, 2022 13:42:08 GMT -5 gpdb said:

I've been doing some investigation on my Seymour Duncan Jazz pickup as well, and my theory is that each coil uses a different wire gauge. On the SD website, it mentions that the Jazz has a "special coil wind". Here's the quote (https://www.seymourduncan.com/single-product/jazz-model): 

"The Jazz Model bridge features its own unique coil wind to deliver a bridge tone with extra treble emphasis, a nice tight bottom, and a hushed midrange." This description is in line with what I've heard about mismatched coils, but I can't confirm the validity of that.

I came to the same conclusion as Antigua that the 59 neck and Jazz neck have identical specs from what is listed, and have been testing both models. So either they are the same pickup, or there is something different. This mention about a special coil wind seems to be the only difference that is noted on the website. I took mine apart and noticed that the South coil appeared to have more wire on it than the North coil. It's small, but when I measured with my digital calipers, I consistently got the same result. However they both read very similar resistance values. So if it's not more wire, than it could only be a different gauge. To confirm a tonal difference I created a loaded frequency plot for series, north, and south coil individually. If the north and south coil were identical, I would have assumed them to be more identical in shape and output, but that's not what I'm seeing. The only thing I'm not accounting for in this would be pole pieces as one side is screws, and the other is slugs. I haven't done enough testing to know what effect that would cause. I'd love to get anyone's thoughts on what I might be missing, or if this is correct. If this is correct, then it would be very similar to Dimarzio's Dual Resonance patent.

	DCR (kOhms)	Inductance @1khz (H)	Coil Width (mm)
Jazz Series	7.36	3.73
Jazz North	3.6	1.67	13.8
Jazz South	3.7	1.57	14.17

Those numbers are pretty close, within margins of error. If they used different wire gauges for the slug and screw coils, the DC resistance and inductance would be somewhat farther apart for the same inductance, and vice versa.

I don't put much thought into what the company says about the product itself, they have to come up with creative ways to justify a lot of products that are essentially indistinguishable from one to the next. Mismatching the coils will cause a higher noise ratio, which they likely see as a bigger drawback than any subjective tonal benefit.

DiMarzio mismatches coils, and makes lots of claims of supposed benefits, but at the end of the day they still give them matched inductances, presumptively to get optimal noise cancellation. DiMarzio's Dual Resonance is all marketing mumbo jumbo. You can see for yourself that when the two coils are in series, you get but one resonant peak. The inductances combine in series, the capacitances combine in parallel, and from that you get one resonant peak. It's possible that when they were applying for the patent they didn't even understand this point of physics. The USPTO might not have understood the underlying physics, either, so a patent could be issued that is based on an false premise. 

Do you have any experience measuring coils with different wire gauges? I'm curious if there is a way to identify the wire gauge based on the chart or other factors. Clearly with the Jazz set in full epoxy, there's no way I could measure the actual wire without absolutely destroying it. As far as the numbers, my DE-5000 should be coming in this week so I'll have more reliable numbers moving forward, the inductance reading I provided might be off.

I hear what you're saying, but to blatantly lie that obviously about a pickups design seems unlikely. Maybe I'm an optimist. I still can't get past the measured coil widths being different. Unless the epoxy is what is actually wider, but I had others look and they came to the same conclusion. Maybe there's a way to determine a coil's wire gauge based on expected capacitance at a certain DCR? I thought the main difference with two coils of equal DCR having different wire gauges would be the capacitance, but I could be mistaken. The difference between the 59 and Jazz seems to be large enough to justify some type of difference.


I actually play a set of Dimarzio Utopia pickups (which have dual resonance), and they do sound/feel different than normal pickups I've played. Whether that's psychosomatic or real, I'd like to find out. I haven't measured them yet.

The larger theory that I have for Seymour Duncan is that they essentially have a few different "platforms" that a lot of their pickups stem from - that being the JB, the Custom, and the Jazz. When you look at all of their pickups reported specs next to each other, it's pretty easy to see. They seem to all be the same coil winds, but with different pole pieces or magnets. The custom platform is obvious as they make it fairly clear, but I think the Full Shred is also part of that one. 

JB platform models (not including Dimebucker or Stag Mag):


Custom platform models:



Jazz platform models:

[antigua]

> Do you have any experience measuring coils with different wire gauges?

Yeah I've tested hand made pickups of varied gauges as well as pickups that happen to have varied gauges. For example, the Air Norton guitarnuts2.proboards.com/thread/7757/dimarzio-air-norton-analysis-review , obviously different wire gauges, but the inductances are about the same, within 150mH of one another.

 > I'm curious if there is a way to identify the wire gauge based on the chart or other factors

Sort of, I made this reference: 

To convert 42 AWG to 43 AWG equivalent, you multiply the resistance by 1.29 ( 2143 / 1659 )
To convert 42 AWG to 44 AWG equivalent, you multiply the resistance by 1.56 ( 2593 / 1659 )

To convert 43 AWG to 42 AWG equivalent, you multiply the resistance by 0.77 ( 1659 / 2143 )
To convert 43 AWG to 44 AWG equivalent, you multiply the resistance by 1.21 ( 2593 / 2143 )

To convert 44 AWG to 42 AWG equivalent, you multiply the resistance by 0.64 ( 1659 / 2593 )
To convert 44 AWG to 43 AWG equivalent, you multiply the resistance by 0.83 ( 2143 / 2593 )

If the inductances of the two coils are the same, then you can assume they have a very similar turn count, since turn count tracks with inductance. Then measure the DC resistance, and use the reference above to see if you can guess what gauges were used based on the difference between them. The Air Norton's coils measures 5.21k and 6.66k, a ratio of 0.78, which is rather close to the difference between 43 and 42 AWG. I wouldn't take that to the bank, but it's a reasonable guess. You can determine a lot by comparing the unknown target to some known reference.

>  Clearly with the Jazz set in full epoxy,

 You have a Jazz pickup that is epoxied? I never heard of that being the case.

> I hear what you're saying, but to blatantly lie that obviously about a pickups design seems unlikely.

It's not really a lie, it's just creative use of descriptions and adjectives. And there has been blatant lying in the past. For example, one pickup maker claimed they discovered a way to wind wind single coils in such a way that reduced noise. It's also hard to know if they realize what they're saying is contrary to physics. They might really believe it.

> I thought the main difference with two coils of equal DCR having different wire gauges would be the capacitance, but I could be mistaken.

The inductance will vary a lot if the DCR is the same. The capacitance doesn't track with wire gauge as much, because capacitance owes to proximities, dielectric constants, and complex electrical gradients across the entire coil. It's possible for a pattern to be seen, but it won't nearly reliable as inductance.

> The difference between the 59 and Jazz seems to be large enough to justify some type of difference.

The 59 uses enamel wire and the Jazz uses some more modern coating, I forget the name, and I'm sure the reason is because the Jazz is sold as a companion to the JB, which uses the same materials. The difference you see could be attributed to manufacturing tolerances. The Jazz and 59 neck are so close that whether they tried to make them the same or not is less important than the fact that they just are nearly the same.


> I actually play a set of Dimarzio Utopia pickups (which have dual resonance), and they do sound/feel different than normal pickups I've played. Whether that's psychosomatic or real, I'd like to find out. I haven't measured them yet.

You won't see a dual resonance, I can tell you that. 

> The larger theory that I have for Seymour Duncan is that they essentially have a few different "platforms" that a lot of their pickups stem from - that being the JB, the Custom, and the Jazz. When you look at all of their pickups reported specs next to each other, it's pretty easy to see. They seem to all be the same coil winds, but with different pole pieces or magnets. The custom platform is obvious as they make it fairly clear, but I think the Full Shred is also part of that one.


They have admitted that the only difference between many of their pickups is the type of magnet they load into it. There have been various employees from the company on their SDUGF forum, some have been more plain spoken and honest than others.

[gpdb]

I have an Air Norton on the way to for measurement, I'll have to compare my results with yours. I agree it's likely 42 and 43. And that conversion chart will be really useful, thanks for sharing. 

If turn count = inductance, then I would expect Dimarzio's dual resonance coils to have the same because their patent specifically states, "The coils have substantially the same number of turns of electrically conducting wire wound thereon, and the wires constituting the coils are of different gauges." My thought here was that instead of the same number of turns, it was the same DCR for each wire gauge. 

> You have a Jazz pickup that is epoxied? I never heard of that being the case.

I'm still new at taking these pickups apart, so it could be waxed. It just felt much harder and didn't scrape like other wax I've felt so far. There might be some clear tape around it that's making it not scrape. The coils look just like your pictures.

> The inductance will vary a lot if the DCR is the same.
Is there a conversion for this too? Once my meter comes tomorrow I can check for more reliable inductance readings from each coil. 


> The 59 uses enamel wire and the Jazz uses some more modern coating, I forget the name, and I'm sure the reason is because the Jazz is sold as a companion to the JB, which uses the same materials. The difference you see could be attributed to manufacturing tolerances. The Jazz and 59 neck are so close that whether they tried to make them the same or not is less important than the fact that they just are nearly the same.
Probably a polysol or polyurethane coating is what I see it referenced as. It could be possible that's the only difference... wouldn't that be boring!

[antigua]

> I'm still new at taking these pickups apart, so it could be waxed. It just felt much harder and didn't scrape like other wax I've felt so far. There might be some clear tape around it that's making it not scrape. The coils look just like your pictures.

Probably wax, but they do epoxy their Little 59 and active pickups. The epoxy usually has a glossy black look, they seem to use it for pickups with plastic covers. Even some import Strat single coils with the "Duncan Designed" moniker have had epoxy in them.


> Probably a polysol or polyurethane coating is what I see it referenced as. It could be possible that's the only difference... wouldn't that be boring!

I've tried to find dielectric values for polysol and enamel, and the best I could tell both were in the area of 3 to 4, and the capacitance values never vary by much, and in either case it's halved by the series wiring of the humbucker, so I have good reason to state that it's functionally irrelevant.