The ABCs of Output Jacks

When it's time to replace a cranky output jack, there are several things you need to know before firing up the ol' soldering iron. The first step is to identify what kind of jack you have and what will make the best replacement.

Form and function.

Almost every type of output jack used on both acoustic and electric guitars is referred to as "a 1/4" jack," but as gearheads we have to be more specific. Here's a list of the most common types of 1/4" output jacks:

• Mono: Used in most acoustic and electric guitars with passive pickups.
• Stereo: Used in acoustic and electric guitars with stereo outputs or active electronics.
• TRS (tip-ring-sleeve): Used with active electronics, active pickup systems, or acoustic-electric guitars with two independent sound sources (such as an under-saddle transducer and onboard mic).
• Power: This is usually a stereo or TRS jack attached to a preamp.

Each of these can be found in different forms, including the open or skeleton jack, the enclosed or panel jack, the barrel jack, and the flange jack. Let's take a closer look.

Electric guitars with passive pickups typically have open jacks. I prefer the Switchcraft brand, because they have heavy-duty construction.

When it's time to replace a cranky output jack, there are several things you need to know before firing up the ol' soldering iron.

Imported guitars, especially budget models, usually come with enclosed or panel jacks. Often encased in plastic, these jacks are inexpensive and tend to wear out faster than a well-made open jack.

Acoustic-electric guitars often have a cylindrical barrel jack that passes from the inside of the instrument through the tailblock. Secured externally with a nut and threaded strap button, this jack replaces the guitar's endpin. Barrel jacks can have mono, stereo, or TRS configurations.

Takamine acoustic-electrics, as well as some other acoustic-electrics, use flange jacks. These have integrated endpins and structurally resemble barrel jacks. They too come in mono, stereo, and TRS styles.

Guitar applications.

The most common output jack for electric guitars is the mono jack. It has two lugs: One is the ground, and it's part of the jack's interior or case. The other lug is the hot or primary lead. This lug is part of the long, bent flange that connects to the tip of your instrument cable.

A stereo jack is similar to a mono jack, but it's equipped with a third lug and a second (shorter) bent flange. The latter acts as a power switch for active pickup systems by connecting and disconnecting the third lug when a standard 1/4" plug is inserted or removed from the stereo jack. For example, when the black (negative) wire of a battery snap is soldered to the third lug, inserting a 1/4" plug into the jack engages the battery by connecting the negative battery wire to ground and completing the circuit.

The TRS jack functions like a stereo jack with the addition of a fourth lug and third flange that allow you to add a second pickup source. By using a stereo cable and TRS plug, you can independently control these two sources. This is useful when you want to send each to its own preamp, direct box, or amplifier.

A common use for a TRS jack is in an acoustic guitar that has an under-saddle pickup, as well as an onboard microphone or a body sensor. For electric guitars, the TRS jack works great for using magnetic pickups in conjunction with a bridge configured with piezo-pickup saddles, like the L.R. Baggs X-Bridge.

Power jacks attach directly to a preamp and can have either a stereo or TRS configuration, and some preamps are housed within a barrel jack. Power jacks are found in many different systems, including the L.R. Baggs Active Element, Fishman Matrix, and Taylor ES1 and ES2. Because most power jacks are soldered to a printed circuit board, they are difficult to replace without damaging the electronics. If a power jack fails, your best option is to replace the entire unit.

How do I wire this thing?

With the exception of the power jack, all of these are simple to wire if you take the time to map them out. All of them will have a ground and a primary lead, but they differ in other ways. Here's a breakdown of those details:

• Mono jack: The ground lug is attached to the case and the primary lead lug connects to the bent flange (Photo 2).

• Stereo jack: The ground lug attaches to the case; the primary lead is the short lug that connects to the longer bent flange, and the long lug is the power/battery switch that connects to the short bent flange. Photo 3 shows the wiring for a stereo open jack.

And Photo 4 is a stereo barrel jack.

• TRS jack: The ground lug attaches to the case. The primary lead is the short lug connected to the bent flange, and the medium power/battery lug connects to the short bent flange. The longest lug connects the secondary pickup to an isolated output (Photo 5).

Okay, got all that? Great—someday there will be a test ... and you'll be ready.

[Updated 9/9/21]