A Guide to Jazzmaster Upgrades, Mods, Unique Features, and More

When Leo Fender introduced the Jazzmaster in 1958, his aspirations for the new guitar were right there in its name. Fender's Teles and Strats were already wildly successful with country pickers and rock 'n' rollers, but the company wanted to snipe some serious business from Gibson and its jazz clientele.

As you can read in Tony Bacon's "Fender Goes High-End: The Origins of the Jazzmaster," Leo wasn't about to start making arched-top jazz boxes, but he did think the Jazzmaster's pristine electronics and tonal possibilities would create some converts.

Well, the jazz players didn't really bite. But some rockers and surf guitarists found plenty to love in the Jazzmaster's unique pickups, the selector switches that allowed players to dial in two tones at once—and, of course, the wild offset shape. The vibrato system—while not to everyone's liking—was itself a new system that lent guitarists an easy way to introduce pitch-up and pitch-down vibrato. Fortunately for those that didn't like it, you could easily lock it in place.

Decades later, the guitar's second life began as Sonic Youth, Dinosaur Jr., My Bloody Valentine, and other indie rockers made Jazzmasters more popular than they'd ever been before. To this day, Jazzmasters remain a popular model, available not just with best-of-class electronics, but in all manner of budget configurations as well.

In this guide, you can learn how to get the most out of any Jazzmaster model. We'll outline the standard features first, teaching how each component should work and offering suggestions for upgrades if necessary. Then, we'll show you how you can get an inexpensive alternative—like Squier's Vintage Modified Jazzmaster—and modify it into a top-grade machine.

The Jazzmaster's Unique Features

The Offset Body

Fender Offset patent, 1958

The curious shape of the Jazzmaster initially came about because of Leo Fender's desire to attract top-shelf East Coast jazzers, who typically preferred to play sitting down. Thus, he took great pains to give the Jazzmaster a body shape that was naturally conforming to the body of a seated guitarist. As luck would have it, the offset shape also made it look really cool, and even kind of wild and dangerous.

The One-of-a-Kind Jazzmaster Pickups

Though often confused with Gibson-style P-90s or "soapbar" pickups, Jazzmaster pickups are completely unique in function and tone. Jazzmaster pickups are constructed similarly to a Strat pickup in many ways, but are much wider and flatter, in what's called a "pancake" wind.

Sonically, these physical differences make Jazzmaster pickups smoother and less mid-rangey than a P-90, while also being fatter, louder, and warmer than a typical Stratocaster pickup. As such, they are tremendously versatile, capable of delivering dulcet, jazzy cleans, Tele-like twang, and articulate, effects-friendly distorted raunch in equal measure.

The Rhythm/Lead Switch Electronics

Many players remain confused by the Jazzmaster's extra switching options, but all told, the extra controls are simple—and useful.

When the top Rhythm/Lead Switch is down, you're in the Lead position. That means the lower controls—the Volume and Tone pots and three-way toggle—function as you would expect. Just select the bridge pickup, neck pickup, or both pickups and adjust your volume and tone to taste.

Flick the top switch up, however, and you have accessed the Rhythm Circuit, in which only the neck pickup is activated. The lower controls are now bypassed completely, and a darker, bassier tone is in play. Use the black thumbwheels to adjust the Rhythm's volume and tone.

Leo's goal with this design was that, by flipping that top switch up and down, the player can access both a preset rhythm tone and a preset lead tone, instead of futzing with pots and a three-way toggle while you're playing.

Some modern-day players dislike this setting, but by rolling down the volume thumbwheel, the Rhythm/Lead Switch becomes a quick kill switch, if you prefer to craft all your tones within the (still-versatile) Lead Circuit.

The Vibrato and Bridge

Jazzmaster Bridge and Vibrato System

The Jazzmaster's floating, lockable vibrato system is often spoken of in nightmarish terms—and it does have its share of difficulties—but this is the part of the guitar that many of its most adoring adherents find they simply can't live without. It lets you wobble notes both sharp and flat and the arm is designed to let you manipulate the bar constantly while playing. This is exemplified in the playing of Kevin Shields, Nels Cline, among other devotees. That said, it's absolutely worth getting professionally set up if you plan to use the original system.

Many players' problems with this design start with the bridge, which has a tendency to buzz, rattle, and allow strings to pop out of its shallow saddle grooves during hard playing. There are a number of fixes for this, though.

Many players will swap the stock bridge for a Fender Mustang bridge, which is similar in design but has deeper grooves and is less prone to rattling (though not immune). When browsing used Jazzmaster listings on Reverb, you'll often find models with the Mustang bridge already installed. Another option is the very popular aftermarket Mastery Bridge, a brilliantly engineered piece of hardware endorsed by many of today's masters of jazz. (You can also find Mastery-equipped used and vintage Jazzmasters on Reverb.)

As it was designed for jazz guitarists, the Jazzmaster was originally intended to be strung with heavy-gauge flatwound strings. Thus, the stock bridge can often work quite well after a switch to a set of 11s, 12s, or 13s (not necessarily flatwound), and a good, professional setup. This option also has the benefit of retaining all of the Jazzmaster's sonic idiosyncrasies, which are often muted by some of the more popular modern day modifications.

How to Upgrade Jazzmaster Electronics

Lots of players have a hankering for a Jazzmaster—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?

Start with a Budget Jazzmaster

Take a look at the stock Squier Vintage Modified Jazzmaster. It's already an excellent bargain at $300. And a few key changes can transform it into a great instrument with vintage-spec parts. Other affordable versions include Fender's Classic Series '60s Jazzmaster and Classic Player Jazzmaster. (You can also find deals on Fender's higher-end but discontinued Vintage Reissue Jazzmasters, both US- and Japan-made, which are already historically spec'd.)

Swapping the Pickups

Curtis Novak JM-FAT Pickups

The Squier comes with a pair of Seymour 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.

Your choice of pickups will have an enormous effect on your tone. There are a lot of good options available, particularly Curtis Novak's. His 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.

That said, Seymour Duncan makes its own vintage-spec replacement pickups, the Seymour Duncan Antiquity II for Jazzmasters, and browsing through Reverb's aftermarket Jazzmaster pickups will yield more options.

Replacing the Wiring and Pots

Wiring Kit

To complete your electronics upgrade, you'll ideally include vintage-style 22 AWG cloth wire and higher-quality CTS pots, as opposed to the lesser-quality pots and wiring used in budget models. The pot values and taper, as per vintage specifications, should be:

  • 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, Switchcraft products are the de facto standard

For the capacitors, use the value .033 MFD in the Lead Circuit and .022 MFD in the Rhythm Circuit.

Replacing the Wiring and Pots

Squier's Control Cavity

Squiers and some other budget Jazzmaster models may not have any shielding on the pickguard, which will be a very noticeable issue when you're plugged into an amp. 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, but you'll still want to properly shield the pickguard.

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

Stock Squier pickguard and shield
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 All Together

Wiring will be straightforward for anyone with basic soldering tools and skills. You can find a traditional Jazzmaster wiring diagram on Rothstein's site here.

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

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
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
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
Finished & Assembled
Additional Jazzmaster Mods for Adventurous DIYers

Above, we discussed ways to upgrade a stock Squier Vintage Modified Jazzmaster. Here we'll lay out some wiring mods that can give your offset more versatility and put the Rhythm Circuit to good use.

Jazzmaster with Dual Volumes

One mod reconfigures the Lead Circuit to make the guitar more like a Les Paul by employing two independent volume controls, one for each pickup. That way, players can blend a percentage of neck pickup with the bridge pickup—or vice versa. I would recommend sticking with the stock value of 1 meg pots.

Below is a diagram showing how to wire the Lead Circuit with dual volume controls.

Jazzmaster Lead Circuit with dual volume controls. Click to view full size.

Leo Fender’s Passive Treble and Bass System

Some continue the Les Paul wiring approach by assigning an independent tone control to each of the two independent volume knobs.

However, a really cool and useful alternative borrows the passive treble bass tone stack (PTB) Leo Fender developed for G&L Guitars.

  • One control cuts treble and the other cuts bass.
  • Both are configured as “master” controls, meaning they affect all pickup switch positions.

The treble-cut control, which is a low-pass filter, functions like a standard tone control. A low-pass filter allows frequencies lower than the cutoff frequency to pass, and higher frequencies are rolled off. The cutoff frequency is controlled by the capacitor and resistor values.

The bass-cut control is another animal entirely. It’s a high-pass filter, which is the opposite of a low-pass filter. A high-pass filter allows frequencies higher than the cutoff frequency to pass, and lower frequencies are rolled off. The ability to dial out some of the low frequencies is useful, particularly to help overdriven sounds “pop” and cut through a mix. I like to think of it as a “sharpen” control.

What does it sound like? Check out the following three sound samples. I performed all of them with a Squier Vintage Modified Jazzmaster with electronics upgraded using the mods described here and Curtis Novak pickups (JM-FAT bridge and JM-V neck). The samples were recorded by mic’ing a Egnater Rebel 30 using the amp’s overdrive channel. I didn’t use pedals or audio plugins.

  • In the first sample, both controls are rotated fully clockwise on 10, and therefore disengaged.
  • In the second sample, the bass cut pot has been rolled down to the 2–3 range, so you hear a somewhat sharper sound provided by the bass cut.
  • In the third sample, both pots have been rotated almost fully counterclockwise. It’s an unusual effect that emphasizes the lower mid-range.

Component selection is important for the bass-cut control. Leo Fender’s design calls for a 1 meg reverse taper pot with a .002 MFD capacitor. You can experiment with the capacitor value in the range of .001 MFD to .003 MFD. The smaller the capacitor value, the more pronounced the bass cut. For example, a .001 MFD capacitor provides a more dramatic bass cut, and a .003 MFD is more subtle. For the pot value, stick with 1 meg, and the reverse taper is critical for the pot to provide a gradual bass roll-off.

There’s plenty of flexibility with component selection for the treble-cut control, but I prefer to stick with the standard values used on the primary tone pot in vintage Jazzmaster wiring, namely a 1 meg audio taper pot with a .033 MFD capacitor.

The diagram below shows how to incorporate the PTB tone stack into the initial diagram. Note that with the treble cut control, the capacitor is directed to ground, whereas with the bass cut control the capacitor is in line with the signal.

Jazzmaster Lead Circuit with Dual Volume Controls and G&L Style PTB Tone Stack Click to view full size

The photo includes a closeup of the bass and treble tone controls. Note the liberal use of heat shrink tubing to prevent ground-outs during installation.

PTB tone stack

Jazzmaster with Series/Parallel Switching

A useful mod for the slide switch is series/parallel switching. In traditional Jazzmaster wiring, when the two pickups are combined via the toggle switch, they are in parallel. Rewiring the slide switch can engage a series connection, which yields a significantly different sound.

  • Series will sound more humbucker-like, with louder, darker, and more-pronounced mids.
  • In contrast, the parallel will sound brighter, with scooped mids and exhibiting more “quack” and twang.

In the following sound sample, you can hear the same pattern, first in parallel and then in series.

Putting it all together, this wiring diagram combines all three mods: dual volume controls, a PTB tone stack, and series/parallel switching.

Here’s a closeup of the completed rhythm circuit, followed by the final wiring harness, ready for mounting on a guitar:

Completed Rhythm Circuit

Completed rhythm circuit

Jazzmaster Lead Circuit with Dual Volume Controls

Final wiring harness

Jazzmaster Kill Switch and a Variation

This wiring scheme produces an unexpected byproduct. When the series connection is engaged, the toggle switch in the bridge position yields no sound at all. To some, it’s a “happy accident” that provides a kill switch effect as an added bonus. Others dislike having a dead toggle switch position when in series mode.

For the latter group, here’s an easy fix. You’ll need an extra pole on the slide switch. Each set of solder lugs is referred to as a pole. The traditional Jazzmaster slide switch is a double-pole double-throw (DPDT) switch, and therefore has two poles.

You need a three-pole double-throw switch (3PDT), which is available from mouser electronics (Swithcraft brand, part #50209LX). You can find a detailed diagram depicting the extra third pole on the slide switch here.


Now, hopefully at this point you've absolutely mastered your Jazzmaster. If you have more tips and techniques for getting the most out of your Jazzmaster, let us know in the comments.

Contributors to this article include Jamie Wolfert and Rothstein Guitar's Andy Rothstein.

Buying Guide: Jazzmasters
Learn everything you need to know to choose the right Jazzmaster for you.
Learn More
comments powered by Disqus