Upgrading Jazzmaster Electronics: Unleash The Potential of Your Offset

Lots of players have a hankering for a Jazzmaster these days, and a limited budget shouldn’t stand in the way. Why not buy a low- or medium-priced model and upgrade it with new pickups and wiring?

Take a look at the stock Squier Vintage Modified Jazzmaster. It’s already an excellent bargain at $300. A few key changes, though, can transform it into a serviceable instrument with vintage-spec parts that sounds great.

There are two main issues with the instrument: electronics and setup. Both can be rectified, but we’ll concentrate on the former.

The Case for Upgrading

Pickups

The Squier comes with a pair of Duncan Designed single-coil pickups and budget electronic components. In general, the Duncan pickups are hotter and brighter than vintage Jazzmaster pickups, and the bridge pickup likely will sound too harsh for those with vintage tastes.

Pots

The following two photographs depict stock Squier electronics, which are clearly of lesser quality than those found on higher-end instruments.

stock squier Jazzmaster electronics

Stock Squier Electronics

stock squier Jazzmaster electronics

A Closer Look at the Stock Electronics

If you rotate the volume pot any lower than 9 ½ when playing a Squier Jazzmaster, it rolls off too much high end. We’re going to fix that with a simple treble-bleed mod, which I will demonstrate below.

Squier Jazzmaster Control Cavity

Squier’s Control Cavity

Shielding

Also, note that the factory didn’t shield the pickguard. That’s an issue because Jazzmasters have a loud 60-cycle hum. It’s caused by single-coil pickups and exacerbated by the long wire runs required to cover the large surface area of the instrument. Surprisingly, the Squier’s control cavity (pictured right) is shielded with conductive paint, which is a nice bonus.

Choosing Replacement Parts

Aftermarket Pickups

Curtis Novak Pickups

Curtis Novak JM-FAT Pickups

Your choice of pickups will have an enormous effect on your tone. While there are a lot of good options available, I chose a set from Curtis Novak. Novak’s pickups not only sound amazing but offer a great deal of variety to boot. His secret lies in the artistry of his hand-winding technique, coupled with his vast knowledge of pickup designs, which he has developed over more than 25 years in the business.

One of his most popular sets is the JM-FAT bridge pickup paired with a JM-V neck pickup. The JM-V is modeled after vintage Fender pickups and hand-wound just as they were. The JM-FAT is designed to give more body and fewer mids, offering a more bell-like tone.

Other Replacement Components

Depicted below are the components you’ll need in an electronics upgrade, which ideally would include vintage style 22 AWG cloth wire and the higher-quality CTS pots. The pot values and taper, as per vintage specifications, should be:

Wiring Kit for squier jazzmaster

Wiring Kit

  • Lead circuit volume pot: 1 meg linear taper
  • Lead circuit tone pot: 1 meg audio taper
  • Rhythm circuit volume pot: 1 meg linear taper
  • Rhythm circuit tone pot: 50k linear taper
  • For the switches and jack, I recommend Switchcraft products, the de facto standard

For the capacitors, use the value .033 MFD in the lead circuit and .022 MFD in the rhythm circuit. Of the many suitable brands and types of capacitors available, I chose a high-end Uptone Audio Film & Foil Musicap in the lead circuit and a Mallory 150 Series in the rhythm circuit.

Shielding the Pickguard

To shield the pickguard, use either a Fender aluminum shield or Rothstein Guitars copper shield. The Fender shield fits only the Fender AVRI pickguards. The Rothstein copper shield was patterned after an original 1962 Jazzmaster pickguard, but it’s universal and can be trimmed up to fit any available pickguards, including the Squier.

Rothstein Guitars Copper Shield

Rothstein Guitars Copper Shield

Copper Shield Applied to jazzmaster

Copper Shield Applied

Tools needed to install the copper shield include an awl, Exacto blade and spray adhesive. To reuse the original Squier pickguard, you’ll need to enlarge the lead circuit’s pot holes with a hand reamer for the slightly larger CTS pots.

Wiring it Together

Wiring will be straightforward for anyone with basic soldering tools and skills. Below is a traditional Jazzmaster wiring diagram. If you’re new to soldering, go experiment on some disposable parts until you get the hang of it. Here’s a good primer on using a soldering iron.

Traditional Jazzmaster Wiring Diagram

Traditional Jazzmaster Wiring Diagram

A completed lead circuit is depicted below. Observe the liberal use of heat-shrink tubing, which is optional but can prevent the inadvertent “ground-outs” that may occur when installing the wiring harness into the guitar. That can happen when a “hot” connection inadvertently makes contact with a ground point.

Completed Lead Circuit on jazzmaster

Completed Lead Circuit

Optional features include a treble-bleed mod, also known as a “volume kit.” It can prevent the loss of highs experienced with a lower volume pot. One variation that works well is a .001 MFD capacitor in parallel with a 150K resistor, wired across the wiper and outer lug of the volume pot, as depicted below.

The following photograph shows the completed rhythm circuit. Insulate the tone capacitor with heat shrink tubing to prevent ground-outs.

Treble-Bleed Mod on jazzmaster

Treble-Bleed Mod

Completed Rhythm Circuit on jazzmaster

Completed Rhythm Circuit

The last step connects the guitar’s bridge ground and shield wires to the wiring harness ground. The wires are labeled A, B and C in the photograph below. Points A and B connect to the cavity shielding, and point C is the bridge ground. Twist the ends of the three wires together and solder them to the casing of the volume pot, as displayed in the photograph.

Connect to the Wiring Harness Ground on jazzmaster

Connect to the Wiring Harness Ground

Soldered to the Casing of the Volume Pot on jazzmaster

Soldered to the Casing of the Volume Pot

Depicted below is the final wiring harness, ready to be mounted into your guitar. Plug it in and enjoy the dramatic improvement in tone!

Final Wiring Harness on jazzmaster

Final Wiring Harness

Completed Wiring mod on jazzmaster

Finished & Assembled

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ABOUT THE AUTHOR: Andy Rothstein

Andy Rothstein has been a guitarist for 35 years. He owns and operates Rothstein Guitars, which specializes in guitar wiring. He has recorded two solo Jazz Fusion albums, Wit of the Staircase and Voodoo Tone.


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