Post by antigua on Feb 12, 2018 23:15:22 GMT -5
I've had my eye on Fender offset guitars for a while, but there are none in stock at any nearby guitar stores, and I was hesitant to buy one, knowing that they've been much less popular than Strats or Teles on a consistent basis for decades. Then I saw that there is a well reviewed Squier Jazzmaster for not much money, so I ordered one, and here I have analysed the Duncan Design pickups that came with it.
A lot of people see Jazzmaster pickups and think P-90, but the truth is these pickups have far fewer turns of wire than a P-90, and generate only half the inductance of a typical P-90, and so they sound brighter, more comparable to a Strat and Tele pickup. Fender's frequent combination of a low inductances and AlNiCo rod pole pieces results in a characteristic that is often described as "Fendery". As can be seen from the pics below, the Jazzmaster pickup is actually even wider and flatter than a P-90. It's said that Leo Fender tried this form factor in the hopes of getting a "wider spectrum" and "warmer tone", though there's no physics based justification for that analysis.
Although these pickups use AlNiCo 5 pole pieces, the flux density at the pole tops is about 30% weaker than that of AlNiCo 5 Strat pickups, because the pole pieces are only 12mm in height, where as a Stratocaster pickup's pole pieces range from 16mm to 18mm in height. The strength of AlNiCo is highly dependant on the shape of the magnet, which is much less true of neodymium or ceramic magnets.
The bridge pickup is wound very hot, nearly 6 henries inductance and a DC resistance of nearly 12k . My understanding is that the original Jazzmasters had two identical pickups that were wound to 6k to 7k range, so this "hot" bridge is definitely a "custom" appointment, probably meant to make the guitar more "rock 'n' roll" ready. So, while Jazzmaster pickups are not really intended to sound P-90'ish, this much overwound bridge pickup gets fairly close to a P-90. The Squier Jaguar, which also come loaded with Duncan Design pickups, also features a similarly hot bridge.
The neck pickup's DC resistance of 6.65k and inductance of 3.0H is near identical to what Fender lists for their Pure Vintage Jazzmaster set, so had they used two Duncan Designed neck pickups, this Squier would sound very close to the $2,000
AMERICAN VINTAGE '65 JAZZMASTER, which comes equipped with said Pure Vintage pickups. The loaded resonant peak of 3.85kHz is near identical to that of a Seymour Duncan SSL-1, for comparison sake.
Duncan Designed Jazzmaster Bridge (JM101B-ADWH BRIDGE 1610)
- DC Resistance: 11.75K ohms
- Measured L: 5.872H
- Calculated C: 44pF (54 - 10)
- Gauss: 750G
Duncan Designed Jazzmaster Neck (JM101N-ADWH NECK 1610)
- DC Resistance: 6.65K ohms
- Measured L: 3.044H
- Calculated C: 46pF (56 - 10)
- Gauss: 750G
Bridge unloaded: dV 20.4dB f: 8.95kHz (black)
Bridge loaded (200k & 470pF): dV 4.4dB f: 2.64kHz (blue)
Neck unloaded: dV 20.9dB f: 12.2kHz (red)
Neck loaded (200k & 470pF): dV 7.0dB f: 3.85kHz (green)
Pole piece height: 12.13mm
A couple interesting things can be seen from these specs.
First, for the intrinsic capacitance of these coils is very low, only 44pF and 46pF capacitance. It seems that the wide, flat coil cross section results in much less intrinsic capacitance than the more "square" cross section of a typical pickup coil. On the flip side, the inductance is higher. For 6.7k ohms of wire on the neck pickup, the inductance comes in around 3.0 henries, where as a Stratocaster coil wound to this DC resistance typically has an inductance closer to 2.6 henres. Therefore, what is lost in capacitance is gained in inductance, and as the resonant peak is a product of both the inductance and the capacitance, the resonant peak of the neck pickup comes out to 3.85kHz, which is spot on for a Strat pickup of similar DC resistance, but with a lower inductance of 2.6H and a higher capacitance of 120pF.
Another interesting aspect is that the Q factor is very high. The unloaded peak produces a ridiculous +20dBV, higher than I've seen from any other pickup. The next closest was the Jazz Bass split pickup, with +15dBV at resonance. This high Q is true of both the normal neck and the "hot" bridge, though under 200k ohms load, the resonance of the hot bridge drops to a typical +4.4dBV, probably due in part to the high DC resistance, though the loaded neck shows +7dBV, which is very high for a Fender pickup, or any other kind of pickup. I'm not exactly sure what accounts for the higher Q factor, but one factor is that the AlNiCo pole pieces are smaller than usual, and I would also guess is that the wider coil means that a greater portion of the magnetic flux path travels through air, as opposed to core material, reducing eddy current losses.
Making the Q factor even more extreme, the Jazzmaster comes equipped with 1 meg tone and volume pots, so the in-situ Q factor will be a lot higher than what is seen from a 200k test load. A 1 meg tone and 1 meg volume would combine to become a higher 500k load. A higher Q factor makes for a more nasal treble, or a more squawky mid range, depending on the peak frequency. The Q factor can be reduced with the tone knob, so this just means you might have to set the tone knob to 8 or 9 to get a treble response that is similar to a Strat or a Tele in the same rig.
Also note that, according to the plot, the "hot" bridge does increase the output by 3.0dB. Not too bad, but it comes at the expense of treble response much beyond 2.6kHz, depending on the guitar cable.
About the guitar...
At first I wasn't digging the loose and rattly bridge, but I installed a "Buzz Stop" on the trem unit to tighten the strings down, and now I'd enjoying it a lot. The controls looked complicated, but if you ignore the switch and two knobs on the upper bow, the controls basically amount to 1 tone, 1 vol, and a 3 way pickup selector, very simple.
Compared to a Strat's pickup placement, the bridge pickup's pole pieces correspond to the pole piece that is nearer to the bridge, straight across, so that lack of angle means there will be less bass response from the Jazzmaster bridge pickup. The Jazzmaster neck pickup's pole pieces are about 10mm closer to the bridge, compared to the neck pickup of a Strat or a Tele, so the Jazzmaster neck pickup's voicing is a bit less "chimey" and a little more "quack". The Jazzmaster neck pickup's pole pieces are not directly below the 4th harmonic node, and is instead shifted closer to the 5th harmonic node, and so it imparts some of the harmonic response associated with a middle pickup. PAF type neck humbuckers in a Gibson generally have a similar quality, since the inner coil's row of pole pieces is 18mm closer to bridge.
I'd say the neck pickup placement is probably the #1 thing that restricts the Jazzmaster's ability to cover all of the popular music recorded with Stratocasters and Telecasters. Without the "Buzz Stop" accessory, the bridge feels like it can't take nearly the abuse that a Strat or Tele can withstand. It feels almost like playing a solid body guitar that came equiped with a floating archtop and bigsby. With the Buzz Stop, it feels more solid and reliable. The body contours are all around similar to that of a Strat, but the larger body size restricts your movement somewhat.
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