The JB Jr is the attempt to get the legendary tone of the original JB Model into a single-space slot.
This design falls in to what I refer to as a “rail” type. Although not all that externally visually similar to the Hot Rail, it’s a more expedient designation than explaining “humbucker in a single coil”. LOL! On the surface, the JB Jr looks like the Little 59, the Li’l Screamin’ Demon, the Red Devil, and so on.
As a reminder of the architecture of this design, let’s take another peek with the cover removed:
There is basically a blade in the middle of each coil that goes down to connect with the actual magnet at the bottom. As it gets toward the business end at the top of the coil, that blade has a bit of a “sawtooth” action going on. Each pole piece goes in to the end/tip of each “tooth”. If you remove one of those screws, you will see the pole is pretty short. Nothing at all that goes all the way down to make a physical connection to the magnet in the same sense as a traditional humbucker. So, in essence, the blades are hauling the load of the magnetic information. In other words, this design is more like a “rail” than one might assume.
Some of the history of the earlier rail types appears to have fallen between the cracks in the sidewalk. HaHa! But all indications suggest that the JB Jr originally came out in the very late 80s or early 90s. The “rail” series gets a redesign in 2005. They were even nice enough to publish variances in the specs. As you can see, the differences aren’t enough to ruffle any tail feathers.
Another part of the redesign is that they are a little bit taller than the original version. They still clearly fit in a Stratocaster. If you are going off the reservation, maybe check the design specs of all the parts to make sure you are good.
For this article, we are going to be talking about the current version. Again, I think the tonal difference are not worth losing any sleep over.
For this testing, the install is in a 1990 American Standard Strat with maple neck and board. The same as in the bulk of coverage of single coil and rail sets. I am using the Mojotone Solderless Strat Harness for the install. It is set up for all-series operation, although the JB Jr set does have 4-con lead wire. The guitar has 09-42 strings and is in E standard tuning. This guitar is also one of the test subjects for the new AxLabs Tone Claw Locking Spring Claw.
Is it really a JB?
What do most people ask? Does it sound like the JB Model? Nope. It does not.
Well, in as much as what is in the Seymour Duncan “rail” series that sounds the “most like” a JB Model? OK then, it will be this one. Or if you’re one of the people that considers the full-size JB Model to have too many upper-mids, you’re going to like the JB Jr.
Yes, the resonant peak is shifted down a little in the JB Jr. Along with the nature of the physical parameters of the rail bobbins, you’re getting something slightly more compressed with a smidge more beef. Nothing over the top, mind you. Imagine something between the original JB Model and the Hot Rail and you’ll be there.
If you want to turn your Strat in to a high-performance hot-rod, this is the starting line. As a complete set, you are going to be able to cover the lion’s share of genres from classic rock to metal.
A real hidden gem is the guitar’s middle position, in my opinion. I think that’s a great spot for a JB Jr bridge model. Hear me out. You get a little more definition for rhythm playing and a little more grind for heavier lead tones. This can work great in a HSS configuration with a hot bridge humbucker. In a similar sense, you can get the same result in a SSS with a Hot Rail bridge or a JB Jr bridge in the bridge slot.
Speaking of Hot Rail bridge, there is a demo here in a minute of the Dave Murray set. It has a Hot Rail bridge, a JB Jr neck/middle in the middle, and a Hot Rail neck.
The JB Jr neck delivers a bit of a surprise. It is actually voiced much better for punch and clarity in a neck position that one might expect. Sort of that sweet spot if you think the Hot Rail neck has too much brawn and the Little 59 neck has too much spank.
While as a full set in the test Strat, everything is all in series. However, I do have other harness variations in other guitars and other pickup combinations. While technically on the hot side, the JB Jr can play really well with a clean amp channel when in split or parallel mode(s). Actually, parallel wiring is another trick with a “rail” type. You get the more polite voice and the hum-cancelling. But the single-width size focuses the magnetic field more precisely for the slight flavor of a single coil or even P90, if you catch my meaning.
The pool is a little shallow on official demo videos for the JB Jr. What the company does have is a demo of the Everything Axe Set, which has the JB Jr bridge.
For a fun comparison, here is an official demo of the Dave Murray (Iron Maiden) set. This has a Hot Rail bridge, a JB Jr neck/middle in the middle, and a Hot Rail neck/middle in the neck.
JB Jr Bridge
Series – 15.376 K
Inductance – 10.235 H
Res. Peak – 2.9 KHz (advertised)
Split – 7.864 K
Split – 7.551 K
Parallel – 3.855 K
Magnet – Ceramic
JB Jr Neck/Middle
Series – 9.605 K
Inductance – 5.58 H
Res. Peak – 3.79 KHz (advertised)
Split – 4.802 K
Split – 4.815 K
Parallel – 2.402 K
Magnet – Ceramic
The JB Jr for Strat players include Mike Scott (formerly of Prince), Todd Wolfe (Sheryl Crow), Joe Perry (Aerosmith), Nick Lashley (Alanis Morissette), Brian Baker (Bad Religion), John Popper (Blues Traveler), Robbie Allen (Candlebox), Janick Gers and Dave Murray (Iron Maiden), Paul Pesco (Jennifer Lopez, Madonna, Janet Jackson), James Pennebaker (Lee Roy Parnell), Tommy Bolan, and Kevin Hunter (Shania Twain). So it’s going to be good for hard rock, garage, punk, progressive rock, fusion, shred, country, pop, 80s metal, heavy rock, thrash, hardcore, and more.
For reference, this Seymour Duncan JB Jr for Strat humbucker set evaluation was conducted with a Fractal Axe-Fx II XL+ featuring Celestion Impluse Responses and Fractal MFC-101 MIDI Foot Controller. In addition, real cabs in use are Marshall 1960B, Mojotone British, and Peavey 6505 cabs loaded with Celestion Classic Series Vintage 30s and Classic Series G12M Greenbacks.
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