Through high school I worked at a music store, mostly in the guitar department. I can’t tell you how many times a client would bring in a relatively new acoustic guitar, complaining that it was distorting or had no sound coming out. A familiar call and answer would then ensue:
Me: “did you check the battery?”
Customer: “it has a battery?!”
Me: “that’ll be $4.20 plus tax.”
It’s easy to forget there’s a chemical cell wedged into the guitar body somewhere, harnessing ion migrations for current, becoming weaker by the minute. Acoustic guitar batteries and their bass guitar counterparts tend to last a really long time! Long battery life may sound like a good thing, but in practice it makes them very easy to neglect until it’s too late.
As a battery wears down it supplies less voltage. If you know a bit about audio electronics, you’ll know that higher voltages allow for more headroom. Headroom is the ability to reproduce a clean audio wave with lots of dynamic range. The preamp on a guitar is designed to produce enough headroom with 9 volts of electricity. But as the voltage drops to, say, 6 volts, the circuit can no longer amplify the audio signal cleanly and it starts to introduce clipping distortion. The distortion is subtle at first, but at some point it becomes really noticeable. Before you know it, your acoustic guitar sounds like a garbled mess.
It should be noted that not all acoustic guitars with pickups have batteries. Most do, but there are passive pickup systems as well. And bass guitars are about half and half. Passive pickups are still really common on basses.
As a guitar player and an audio tech, I have a vested interest in avoiding this all-too common problem. So here are my suggestions:
Change your battery regularly – you (hopefully) change your smoke detector batteries every year. Your guitar battery should be one step down on the same priority list! Every pickup system is different, but if you’re not playing multiple times per week, you’re probably fine changing the battery just once per year. So put it on the calendar.
[note to spouses and parents: 9V batteries make great stocking stuffers.]
Use good batteries – you usually get what you pay for with batteries, especially 9V ones. I won’t weigh with a brand preference, but I will suggest the dollar store is not the right place to buy your batteries.
Unplug your instrument – your active pickup system switches on automatically when a cable is inserted into the jack. So a simple way to conserve battery life is to unplug it when it’s not in use. There’s no need to go crazy, you can go ahead and leave it plugged in between sets, but if you’re leaving it plugged in overnight you’ll drain the battery pretty quick.
Pay attention – a dying battery doesn’t always sound awful at first. Sometimes it’s just a little spongy or it just sounds “different.” Unfortunately, acoustic guitar pickups never sound fantastic in the first place [see this post] but soloing the channel in headphones may help you troubleshoot the situation.
But what if I ignore all the advice in this brilliant blog post and I find myself in the middle of a performance with a dying battery? Is there hope for me?
Yes! Understanding what happens as a battery fades can help mitigate the situation. There are no guarantees, but here are three ways to rage against the dying of the light:
Strum (or pick) lighter – I’m listing this option first because it’s possible do immediately upon noticing the dying battery sound. Strumming or picking lightly produces quieter sounds (I know–amazing) which don’t require as much “juice” for the preamp to handle.
Turn down the volume at the guitar – once again, reducing the volume at the guitar will reduce the battery draw and may get you by for a little longer as your battery fades. How much do you need to turn it down?
Turn down the bass control at the guitar – low frequencies use more power. Turning down the bass on an active circuit should reduce the amount of headroom needed to give the same apparent volume.
All three of these options have implications for audio techs. You will need to boost the gain or change the EQ at the console to compensate, but the end result should be better than letting the battery die through the sound system. One more thing for sound people: use your best judgment, but at some point you may have to cut your losses and take the acoustic out of the mix completely. A dying acoustic guitar in its final stages sounds horrendous and will be more distracting than none at all.
Good luck, have fun, and may your batteries always be fresh!