How to Overdrive Your Guitar Amp (And Still Be Friends With Your Neighbors)
You know the sound of that crunch. The tooth-shaking rumble of a distorted power chord or the whine of a searing solo. For many of us, this was the siren call that drew us to the electric guitar. We wanted to rock. Yet when you plug in your amp for the first time, getting that overdriven sound can be a little daunting. You probably turned one knob only to be attacked by a raging wall of volume that sent you scurrying behind the couch. Getting an overdriven sound is pretty easy, however, once you understand what creates it and the tools you are using.
What is Overdrive?
An amplifier begins to overdrive when the amplitude (volume) of the wave exceeds the capacity of the amplifier components to produce it. Thus the sine wave begins to “clip” or round off at the threshold of production, creating a rounded or squared waveform. How much the wave clips is determined by the amount the amplitude exceeds the threshold. Unfortunately, the volume at which most tube amps begin to overdrive is way too high for any bedroom players who are not practicing in a bomb shelter. To fix this problem, amplifier manufacturers began producing models with separate controls for the preamp and power amp stages. This way, players can overdrive the preamp tubes (using a knob typically labeled gain or pre) while using the power amp tubes (using a knob typically labeled master or post) to control the overall volume.
Finding Your Amp’s Headroom (In Your Bedroom)
The term “headroom” refers to the volume an amplifier can produce before it begins to distort. Most musicians seek amplification with a lot of clean headroom, but guitarists are unique in seeking amplifiers that deliberately overdrive. The point just before an amp begins to distort will produce the fullest and warmest tone, so knowing where that “sweet spot” lies is very useful whether or not you play in a style with a lot of distortion. Your headroom will depend on the amp and guitar you are using, therefore it is useful to experiment.
To find your headroom without blowing out your windows, plug your guitar into your amp and turn the guitar to full volume. Most amps now have a master volume and a gain control, though these may be separated into their own overdrive channel, in which case you will need to toggle to that channel. The master volume knob (or post on some amps) will control the output of the power tubes and thus the overall volume. The gain (or pre) knob will control the preamp tubes and by increasing its level, we can send the preamp tubes into overdrive without distorting the power amp tubes. After setting the master volume at a reasonable level, begin strumming a chord while slowly turning up the gain knob on your amplifier. When the sound begins to crunch, you have exceeded your headroom and are traveling into overdrive territory. If you continue turning the knob, the signal will become more distorted as the preamp tubes are pushed harder. To combat the increase in volume this produces, you can begin to roll back the master volume. If you turn the preamp knob back to right where the signal becomes clean again, you’ll have found the sweet spot that gives you the fullest clean tone.
Once you know where your amp overdrives, you can use it to color your tone. Here are a few ways you can use this to your advantage:
- Set the amp to the sweet spot using a single-coil pickup and switch to a humbucker to overdrive the amp. As I discussed in my blog on pickups, a single-coil pickup has a lower output than a humbucker. If you find the sweet spot with the single-coil, you can overdrive it with the humbucker (though there will be some change it tone due to the change in pickup).
- Set the amp to the sweet spot and use a clean boost pedal to send the amp into overdrive. If you want to switch from a clean amplifier tone to an overdriven one, set the amp into the sweet spot and then put a clean boost pedal in your effects chain. When you stomp on the pedal, it will increase the signal sent to the amp, overdriving the tubes.
- Set the amp into overdrive and use the volume knob on your guitar to roll it back into a clean sound. This is the opposite of the boost pedal method. If you set the amp into slightly overdriven territory with the guitar volume on 10, rolling back the guitar volume with reduce the signal being fed into the tubes.