Boost, Distortion and Fuzz – What’s the Difference

To the ears, it’s quite easy to hear the difference between boost, distortion and fuzz.  Boost adds to the volume, generally makes your tone a bit brighter.  We’ll often use a boost during those times when the rest of the band is loud, and you need the high end of the guitar to cut through.  Sometimes it’s to emphasize a lead section, other times it’s to brighten up your tone throughout the song.  It keeps things fairly clean, just louder.

Distortion pushes the signal much more, driving it into a gritty broken-up tone.  We’ll use distortion for lead sections or for crunchy rhythm tones.  Many will leave it on all the time and it can come via a pedal or your amp.

Fuzz, on the other hand, is the extreme of distortion.  It’s often described as buzzy or harsh.  Fuzz is used for over the top, searing lead tones.  Fuzz creates driving bluesy rhythms that sound like they are going to melt the speakers.  It is never light or subdued, but raucous or insane.

But what are the technical differences?  What makes these pedals unique in terms of design?  To answer that, we must understand what is happening under the cover.

On a basic level, a boost or gain pedal needs to do a few essential things to work:

  1. Send your signal through a transistor
  2. The transistor uses a semiconductor to amplify the signal
  3. That signal approaches (in boost) or hits (in distortion/fuzz) the clipping point, which is where it distorts.

A lot of complex things happen in this rather short portion of the signal path.  Let’s break down how a transistor and semiconductor drive a signal into clipping – and how the process differs for boost, distortion and fuzz.

Transistors/Amplifiers

There are many components of a guitar pedal, but in this case, the transistor is the most crucial.  A transistor acts as an amplifier for our pedals and features three terminals; an input (called a collector), an output (emitter) and a control.  As you might imagine, the guitar signal feeds into the collector, and out the emitter.  In between, electrical current is added via the control terminal (called the base).

Basic silicon transistor

When current is fed to the base, it causes the signal to flow from the collector to the emitter.  This step is similar to turning the transistor on.  When this happens, the inner workings of the transistor start amplifying the signal.  This inner portion of the transistor is called a semiconductor.

Semiconductors in two flavors – Germanium & Silicon

Especially if you’ve shopped around for fuzz pedals, you’ve likely heard them referred to as germanium or silicon.  In either case, they are referring to the semiconductor that is sandwiched between the terminals of a transistor.  Both germanium and silicon are metalloid crystals (which is kind of like a rock made of metal).  In their normal states, they are insulators.  That is, they don’t promote the flow of electricity.  In the world of semiconductors, these elements have other elements added to change their conductive properties.  The end result is something that is between a conductor and insulator.  The process of introducing these conductive materials is called doping.

There are many transistors out there, but in the guitar world we are primarily worried about whether they’re made with germanium or silicon.  In the case of germanium, less voltage is required to make things distort.  This means we get a little smoother, warmer and more tube-like tone.  Silicon is brighter, less dynamic and kind of harsh.  Most people agree, germanium transistors sound better.

So why use silicon at all?  Well, it’s a lot cheaper.  It’s much easier to produce (a lot more effort and careful processing is required to get usable germanium).  Germanium is really temperature sensitive.  Not only is it likely to get damaged during soldering, but also even when it’s warm in the room, it won’t sound as good.  And germanium transistors just aren’t that reliable.  It’s hard to get two that sound the same, and even harder to get them to last.  But they sound great, so we put up with all of that grief anyway.

Whether we’re looking at silicon or germanium, we need to understand what a transistor does to our sound wave.  Push audio signals into clipping.

Clipping – Where the Magic Happens

All amps have a limited voltage range.  This is the point where the signal cannot get any louder.  In the simple sine wave diagram below, it’s the two horizontal lines above and below the wave.  This represents the positive and negative voltage limit.

unprocessed sine wave
unprocessed sine wave

If you continue to increase voltage beyond this point, the peaks of the signal hit that ceiling and floor point and it’s like the points of the signal are chopped off by the limit.

This is clipping.

A sine wave with some clipping
A sine wave with some clipping

Clipping is what creates distortion, as the signal is pushed further past the voltage limit, the level of distortion increases.  As we’ll outline in a moment, the waveform looks pretty dramatically different as we increase the amount of clipping.

Also, the space between the clipping point and the high/low peak of the sound wave is what’s referred to as headroom.  If headroom is increased, this allows for further signal amplification before clipping occurs.  In the case of pedals, you’ll often see overdrives that can run at 9 or 18v.  Doubling the voltage of the power supply increases the voltage limit in the transistor, keeping the signal cleaner.

So now we know the fundamentals of amplification and clipping.  How does this apply to our pedals?  Let’s start with boost.

Boost Pedals

Boost pedals started as a way to crank high frequencies and allow clean guitars to cut through the mix during earlier days of recording and live amplification.  The signal is amplified, but not to the point of clipping.  This leads to a nice clean signal coming out the other end, but louder.  However, the hotter signal may push your amp into clipping.

High frequencies get boosted more than anything else, because cranking the volume evenly across the board generally leads to muddy tones.

So we’re left with two primary uses of boost.  You can simply make things louder, helping your guitar get heard over the rest of the band.  Also, you can push an amp that’s nearly breaking up into distortion.

Distortion

Although it may seem like simply increasing the amplification would create distortion; it’s really a completely different animal.  While boost is all about creating an louder, but unclipped signal that may drive your amp into clipping – distortion is meant to clip the signal before it reaches your amp.

To this end, distortion pedals operate quite similarly to the pre-amp section of your amplifier.  The signal is clipped and the output is distorted at any volume level.

Most distortions retain a sine-wave shape, which emulates the way power tubes clip and distort.  Lower levels of distortion show smaller amounts of clipping on the actual signal, with very obvious rounded peaks like the previous example.

As distortion levels increase, clipping is far more dramatic and the resulting waveform looks a bit more square in nature like the graphic below.  However, it still retains the basic characteristics of a sine wave.

Heavily clipped sine wave
Heavily clipped sine wave

Fuzz

Fuzz is at the extreme end of distortion, but the electronic theory is roughly the same.  While distortion tries to retain a sound wave that is still fairly rounded, fuzz pushes the wave into much more of a square shape.  In some cases, fuzz pedals will actually convert the sound to a true square wave.  The result is a sound that is vastly different from the original input signal.

Square wave - some fuzz pedals get to this point, but all get close
Square wave – some fuzz pedals get to this point, but all get close

And while overdrive pedals may add voltage to increase headroom, fuzz pedals famously reduce it for the opposite effect.  You may have heard of the “starved battery” sound, which often comes from a dying battery that reduces the voltage limit, clipping the sound even more.  Modern fuzz manufacturers can achieve this effect on demand with changes in bias, which is an adjustment that can limit the number of electrons making their way through the transistor.

What about Overdrive?

Knowing what you now know, where do you think overdrive fits in the mix?  Sure you can normally hear the difference, but what about from a technical standpoint?  Is it the same thing as distortion?  If not, what do you think makes it different?