Why Does My Bass Guitar Have A Battery?


So your bass guitar has a battery slot on the back, but you didn’t think that’s how basses work… What’s going on?

Well first of all, don’t panic! It’s fairly common to find bass guitars that use batteries, and it doesn’t mean the instrument is in any way deficient. It just means that you have an active bass, rather than a passive bass.

An active bass requires a battery to power a small pre-amplifier which is located in the body of the instrument. This pre-amplifier gives a more consistent signal and allows you to have additional EQ controls on the bass itself.

Let’s take a closer look at the difference between the two, and examine the practical and tonal pros and cons.


The Difference Between Active and Passive


Active basses require an electrical power source to function; passive basses do not. Or, put another way, active basses will have a preamp built into them somewhere.

The majority of active basses have the preamp built into the circuits within the body of the instrument, while retaining passive pickups. However, a few basses will have active pickups – that is to say, the preamp is housed inside the pickups themselves. EMG pickups are the most popular example of these.

If you have a battery in your bass, then, it’s probably powering a preamp in either the circuits or the pickups (or both, but this is neither common nor necessary). Active basses have their advantages, as I’ll explain, but they have their limitations too. First and foremost…


The Battery Does Not Replace an Amp!


At risk of stating the obvious, having a battery in your bass doesn’t mean it doesn’t need connecting to an amplifier!

If you play the strings without an amp you will hear exactly the same sound made by any other bass that isn’t plugged in: a quiet, metallic clunk.

The amp is needed to convert the input signal into the louder, electrified tone we’re after.

Even if you connect the bass to an amp via a cable or wireless transmitter, the battery in your bass will not power the amp. The amp will still need plugging into the mains – unless you have a portable amp with its own battery compartment.

So the battery on its own is insufficient to power your playing.

Does this mean that it actually isn’t necessary? Unfortunately, no. If you have an active bass guitar, then you will need the battery as well as a power supply for your amp to make it work. By extension, once the battery dies, the music stops! You’ll need to replace it before you can continue.

The battery in a bass guitar can’t power the amp, and is a minor maintenance inconvenience. A good start! What function does it actually serve, then?


The Benefits of Active Bass Guitars



The addition of a preamp within your bass gives you two main things: more power, and more control.

To illustrate this, consider a traditional, passive bass guitar. The signal coming from the pickups cannot be boosted – it can only be reduced. When the tone knob on the side of the instrument is on full, you hear what’s detected by the pickups – no more. When the knob is turned down, you cut out the higher frequencies, leaving a bassier sound, but at a lower volume.

In an active bass, the additional power the battery provides means you can boost the signal – either of particular frequencies or across the board.

You can augment the low frequencies, or the treble, or even the mid-tones, all directly from your bass guitar.

This is why active basses tend to have several control knobs on them, rather than just the volume and single tone controls found on passive basses. They allow you to tweak the sound of your bass very precisely, and very conveniently. Imagine the dials on your amp have been fitted directly onto your instrument – it’s like that!


What Does This Mean in Terms of the Sounds You Hear?


These extra tone controls naturally increase the range of sounds an active bass can produce, compared to a passive one. Boosting the treble results in a brighter, shinier tone than a passive bass will give you. Boosting the low-end results in a more powerful, deeper bass sound than normal.

You can usually tell when an active bass has been boosted in some way. It has a more ‘electrified’ feel, to put it crudely, than the warmer, more organic tones of a passive bass.

Of course, which sound you prefer is entirely a matter of personal taste – neither is innately ‘better’ than the other. Nor should you worry that having either an active or passive bass is preventing you from achieving certain tones.

If you have an active bass guitar, it will probably have a ‘bypass’ switch on it. This allows you to shift between the direct passive signal and the electrified active signal. When ‘active mode’ is turned off, you will be left with a sound much like that of a passive bass.

Bear in mind that even in ‘passive mode’ the battery is still required, and will continue to drain. The volume will therefore remain louder than on a passive bass, as the power boost is still being provided. Still, the tone will otherwise resemble that of a passive bass.

If you have a passive bass guitar, you won’t have the same power or control built into your instrument. But you can still boost and tweaks your lows, mids and highs in the traditional way: on an amp.

As long as your amp isn’t maxed out (and it’s rare that you will have your tone controls set on full) then you should be able to match the volume and tone of an active bass pretty accurately.


The Difference in Sound With Active Pickups


While the above is true for the majority of active basses, which use passive pickups, I should add a caveat where active pickups are concerned.

In these instances there is a reason why you may hear a slightly different sound, regardless of how the tone control knobs are positioned, and it’s all to do with how pickups work.

Basically, pickups work because they contain magnets. When the strings vibrate within their magnetic field, an electric current is created, which goes into the amp to produce sound.

When the pickups are closer to the string, the signal is stronger, and you get a higher fidelity sound with less distortion. However, if the pickups are too close to the strings, the magnetic field can be overpowering and actually have a negative effect on the quality of sound produced.

The solution? Use weaker magnets. Weaker magnets produce a weak electric current, which would be a problem on a bass with passive pickups. Not so on a bass with active pickups, where the battery power can boost the signal and allows the amp to produce a clean, high-fidelity tone.

The appeal of this subtle difference in tone is, once again, a matter of personal taste.

If you’re looking to buy a new bass guitar you may decide that active, EMG pickups give you exactly the tone you’re after. Otherwise, I’d suggest that your decision between active and passive might be based more on practical issues.

Does the convenience of being able to adjust the tone without touching the amp outweigh the nuisance of periodically replacing the battery? The below section may help you decide.


How Long Will the Battery Last?



I recently wrote an in-depth article on this subject which you can read here. But below is a quick summary of the key points.

Clearly, many factors will affect the lifespan of your bass guitar battery, from the brand of the battery, to how often you play, to how long you keep your bass plugged in (tip: unplug your bass after use!)

Many players report that a standard 9 volt battery will last for a year or more, and while this longevity is naturally not guaranteed for everyone, generally there should be quite a lengthy gap between battery changes.

You definitely won’t need to be replacing the battery after each practice session, and there won’t be a significant financial cost to keeping your active bass running in the long term.

The bigger danger where battery life is concerned is probably complacency. If your battery lasts for a long time you may forget that it will, eventually, need changing. There is nothing worse than a battery dying in the middle of a song at a gig!

If you are performing live, you may want to play it safe and replace the battery before each gig – or at least always have a spare at the ready.

While there’s no ‘fuel gauge’ to monitor your battery’s juice levels, you will probably get some warning when it’s on the way out. A loss of volume, a thinning of tone, signal cut-off, and distortion are all indicators that your battery may need changing.

When the battery starts to loose power you will notice a change in the strength and sound of your bass. Depending on the type and quality of the battery this could either happen rapidly or more gradually.

Rechargeable batteries, for instance, go from full to zero very quickly and so you will notice a sudden change in your bass sound. Meanwhile, a normal alkaline battery will die more slowly.

Replace the battery every few months to ensure the tone remains high quality and replace before every gig to give yourself reassurance if you need it.

Rob Wreglesworth

Rob has come to terms with the fact he will probably never be a famous rock star....but that hasn't stopped him from writing and recording music in his home studio. Rob has over 15 years experience of recording music at home.

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