Now that we’ve gotten through our beginner and intermediate mods, we’ve finally made it to the fun stuff. We’ll be talking about series/parallel switching in general and how to implement this feature in your Strat, Tele, and Les Paul. Many considerations for this mod were covered in the previous mod, so you’ll benefit from what you learned last time. All you need for the series/parallel switching mod is a DPDT switching device and to move some wires. Sure, it’s more wires than the previous mods, but you can do it.

The Mod: Series Wiring
This parallel/series switching mod is about wiring two pickups, regardless of what type they are, together—not parallel/series switching of humbuckers, so take care not to mix it up.

On most guitars with more than one pickup installed, you have the choice to play through any one pickup by itself or through combinations of the pickups. The standard way to connect multiple pickups together is to wire them in parallel, which is the industry standard today. This is also the tone our ears know from countless records, when someone uses the in-between pickup positions—bridge and middle or middle and neck—of a Strat. Only a few guitars use series wiring for their pickups as a standard, the most popular examples are the Brian May “Red Special” and, of course, almost all Danelectro guitars.

Why would you want to wire your pickups in series? There are a lot of good reasons for this. If you’re looking for more volume and midrange out of your pickups, the parallel/series switching may be the perfect option for you. As mentioned before, parallel wiring of two pickups is what you are used to by now. It’s used in most guitars to add transparency and clarity to the tone. Series wiring of two pickups produces a longer path with increased resistance, adding volume and preventing the highest frequencies from getting through, allowing more low- and midrange to pass through the circuit. With series wiring the output of one pickup goes into the input of another pickup, while with standard parallel wiring each pickup takes its own path to the output. So the series wiring will be noticeably louder, with prominent low- and midrange—a perfect combination to drive any tube amp into saturation without any external help of a booster. Series wiring on a Telecaster is a standard mod, but series wiring is not very common on Strats and Les Pauls.

Please note that series wiring has no effect when one pickup is played alone. In this case, parallel and series wiring will sound the same. The series wiring only takes effect when a pickup combination is engaged—same as with the out-of-phase wiring from the intermediate mod.

Here is an example, to show the difference between standard parallel and series wiring of two pickups:

In the first diagram the two pickups are wired in parallel, so all of the pickup inputs are connected together, and all of the outputs are connected together. This is one of the main reasons why a Strat or Tele usually has a very bright tone—this wiring allows the signal from each pickup to reach the output jack by the shortest possible route. The result is that the high frequencies reach the output jack almost unchecked, giving your Strat and Tele the sparkling sound qualities we all love so much.

In the second diagram, the two pickups are wired in series. The theory behind series wiring is that the ground wire of one pickup is connected to the hot wire of the other pickup. They become a kind of compound-pickup, one ground and one hot for both. When wired in series, the pickups’ impedance (resistance) is added together and the output is very high. If one of the involved pickups is a reverse wound/reverse polarity type (aka “RWRP”) you will receive the same humbucking effect as with the pickups wired in parallel, so you won’t notice a change.

When pickups are wired in series, a good portion of the treble frequencies are lost because the long pickup wire works like a resistor. As you know from guitar cables, the longer the wire, the higher the resistance, and the more treble gets lost. Any resistor in the signal path will suppress the signal. In addition, higher frequencies are attenuated more by a resistor than lower frequencies. This is the reason for the prominent low and midrange when pickups are wired in series. The signal has to travel through twice as much pickup wire to reach the output jack compared with parallel wiring.

Now you know why series wiring produces a different tone with less high-end, but why is it louder, ending up in a beefy, meaty tone? Let’s have a look at the output signal of your guitar and assume that each pickup puts out 100 percent of its power. When wiring two pickups in parallel, each pickup loses 3/4 of its output! The total parallel output of the two pickups will be 25 percent plus another 25 percent from the second pickup, resulting in a total of 50 percent. This is the reason why pickup combinations don’t sound as loud as a single pickup played individually. With the same pickups wired in series, the output of the first pickup will be the full 100 percent plus another 100 percent from the second pickup, resulting in a total of 200 percent. Because the two pickups are wired one into another, the output from the first pickup is added to the output from the second one, resulting in a much louder tone.

But don’t worry—this doesn’t mean that the two pickups wired in parallel are only half as loud as a single pickup, or that the two pickups wired in series are double as loud as one pickup. Our human hearing doesn’t work this simple way, but I don’t want to bore you to death with all of that theory.

Here is a general schematic of how to wire two pickups in parallel, with the option to put them together in series as well.

The switch is a normal DPDT (aka "2PDT"). In the down position, both pickups are connected together in standard parallel wiring for maximum chime and twang. With the toggle in the up position, the ground of pickup No. 2 is lifted and no longer connected to ground, instead it is connected to the hot output of pickup No. 1, with the red jumper-wire on the toggle switch making the connection. It’s the same principle as in the intermediate mod with the out-of-phase switch. The pickups have to be connected via the additional series/parallel switch and from there to the rest of the circuit, where everything else stays the same.

There is really nothing special to consider on a Strat, you will have to decide which of the two pickups you want to connect in series: the bridge plus the middle or the middle plus the neck pickup. Usually this mod sounds best with the bridge and the middle pickup on a Strat. With the middle and the neck pickup, the sound on many Strats can get muddy and boomy—something you don’t want for a solo part. If you want to have the possibility to use both pickup combinations in series and parallel wiring, the easiest way is to use two switches, but as I said, the middle plus neck combination in series is not very desirable on a Strat.

Setting up the parallel/series option on a Telecaster is not too special either, but there are a few more things to keep in mind. As shown in the intermediate part for the out-of-phase switching, you will have to unground and reground one of the pickups, preferably the neck pickup. We described this in detail previously, but to summarize: on a typical Telecaster neck pickup, there is a metal cover. One of its mounting tabs, folded under the coil, usually has a small, short jumper to the eyelet on the pickup’s chassis that connects the coil to the negative wire. To unground and reground the cover, all you need to do is carefully clip that little jumper, breaking the connection, and then add a new insulated wire from the cover's tab into the control cavity, where you can attach it to any given ground spot (e.g., the back of a pot). Don’t forget to insulate your new soldering spot with some tape or heat-shrink tubing to avoid any unwanted connections.

Besides using a series/parallel switch on a Telecaster, another option is available for this guitar breed, the so-called "4-way switch," available from numerous companies. Besides the normal 3-way switch functions, this offers a fourth switching position, ideal for series connection of both pickups. Using such a switch as a substitute for a standard 3-way switch has become a standard mod for a Telecaster, and I recommend it. On a Telecaster, this additional switching position sounds really good and is a perfect addition to the Telecaster’s standard tonal palette. Here is the wiring diagram and how to use the 4-way switch. Remember, you will have to first mod your neck pickup as described above.

Wiring diagram courtesy of Seymour Duncan Pickups and used by permission. Seymour Duncan and the stylized S are registered trademarks of Seymour Duncan Pickups, with which Premier Guitar magazine is not affiliated.

Les Paul (also SG or ES-335)
Series wiring for Les Paul guitars is not seen very often. The main reason is that the tonal result will depend a lot on the pickups, and can vary from pretty cool to completely useless. If you have vintage-flavored, low-output PAF style humbuckers or P-90/P-94 pickups in your guitar, chances are good that series wiring of them will sound excellent. If you have modern high-gain humbuckers in your guitar, the result may be less than appealing—too much bass and too muddy. Remember, when you have two humbuckers with 14k output each in your guitar, this will result in 28k series output, which is close to insane output. It’s always worth a try, though—this is an easy mod to reverse.

How easy or how difficult it is to pull off with your Les Paul, depends on the pickups you have in your axe, with the same considerations as in the intermediate out-of-phase part. If you have single-coil P-90/P-94s or humbuckers with 4-conductor wiring, simply follow the color code from the manufacturer and solder along.

If you have a two-conductor wiring on your humbucker and/or braided shield wiring, you will have to consider some more things, described in detail in the previous mod. Again, if you don’t have the skills and tools to convert your pickup to 4-conductor wiring, leave it alone and get this work done by someone who knows how to do it, or get a replacement pickup with factory installed 4-conductor wiring.

That concludes our “3 Mods for 3 Guitars” series, from easy to difficult. I hope you had some fun and found some useable and doable mods to enhance your personal tonal palette!

Dirk Wacker lives in Germany and is fascinated by anything related to old Fender guitars and amps. He plays country, rockabilly, and surf music in two bands, works regularly as a session musician for a local studio, and writes for several guitar mags. He’s also a hardcore guitar and amp DIY-er who runs an extensive website——on the subject.