A Story about Something I Learned About Jacks Vol. 2

Last time, I intended to talk about jacks, but somehow ended up discussing plugs instead. This time, let’s get back to jacks.

It’s common knowledge among guitarists that if you’re using a battery-powered compact effects pedal, you need to unplug the cable from the input jack when you’re not using it; otherwise, the battery will drain.

But why is that?

Most effects pedals use a stereo-type input jack.

Switchcraft / 12B

If you compare it with a mono jack, you’ll notice it has one extra terminal.

For reference, here’s a stereo plug↓

Mono plugs only have a Tip and a Sleeve, but stereo plugs have an additional terminal called Ring in the middle. It’s easy to remember since it literally forms a ring-like shape.
These terminals are also known as TRS, short for Tip, Ring, and Sleeve, and the Ring part connects to the extra terminal on the stereo jack.

This is why headphones with stereo plugs can output separate sounds for the left and right channels.

Wait a second!

Isn’t that strange?

Or am I wrong?

Guitar signals are mono, right!?

We don’t split the guitar sound into two!

Does this mean you have to use a stereo cable with your guitar?

You might think so, but don’t use a stereo cable with your guitar.

In most effects pedals, the negative (-) terminal of the battery snap is connected to the Ring terminal of the stereo jack.

Even if the battery snap is wired to the circuit board, it’s still connected through the board.

When you insert a mono plug here...

The Ring and Sleeve terminals connect!

This causes the negative (-) terminal of the battery snap connected to the Ring to ground, completing the circuit, and powering the pedal with the battery.

Conversely, when the plug is not inserted, the battery remains disconnected and doesn’t drain, which is why you should unplug it when not in use. Problem solved!
By the way, if you use a TRS stereo cable, the Ring and Sleeve won’t connect, so the pedal won’t power on. See you next time! Goodbye!

“Hold on a minute!”

“Does this mean I have to remove the battery from my fixed pedals on my pedalboard!?”

Don’t worry about that. If you connect a power supply jack to your pedal, the positive (+) side of the battery snap becomes disconnected!

The power supply jack is what everyone is familiar with.

Though some are round, the structure is the same, and this jack also has three terminals.

The terminal marked with a yellow circle in the image above connects to the circuit’s positive (+) power line. When you connect an adapter, this terminal supplies the positive power. The positive side of the battery snap is wired to the terminal marked with a red circle.

Actually, these two terminals are usually connected inside the power jack!
You can’t see it, but they’re connected!

This allows the positive current from the battery to pass through the jack and power the circuit, enabling the pedal to work (If your pedal works with an adapter but not with a battery, it could be due to a broken connection inside the power jack).

When you insert the power plug into this power jack...

The two terminals disconnect!

This causes the positive side of the battery snap to float, meaning the battery won’t drain even if a plug is inserted into the input jack.

However, for older pedals without a power jack, you’ll have to remove the plug from the input jack.

Also, for most pedals, connecting an adapter will power them on even without a plug in the input, but some models still require a plug in the input jack to turn on, even with an adapter.
Behringer’s series below is exactly like that.

Behringer / VD400 Vintage Delay Vintage Analog Delay

The wiring method discussed today is common, but it varies depending on the model, so don’t panic if the power doesn’t turn on!

Also, be aware that batteries naturally discharge over time, even when not in use, so be cautious if you’ve stockpiled batteries—they might lose some charge.

See you next time!