Are you are beginner wanting to know what overdrive pedals do to the sound of your guitar?
Have you been using overdrives for years but want to learn more about the technical aspects of how overdrive pedals work?
In this article I’m going to answer the question “What Does an Overdrive Pedal Do?” in terms both beginners and fanatics will find interesting.
The Short Answer
An overdrive pedal amplifies, clips, and shapes the EQ of your guitar sound to create on overdriven or distorted sound. This is inspired by the sound of a loud, tube driven amplifier pushed to the point of breakup, except you can get these sounds at lower volumes.
The Long Answer
How is Overdrive Made?
Now that we know what inspires the sound of overdrive, let’s do a quick dive into the circuitry that creates the overdrive sound and what it does to your clean guitar tone.
Almost all Overdrive pedals have the following signal flow: Input Section, Gain Stage (Amplification, Clipping), EQ, Output Section
While the term “Gain” is often synonymous or misunderstood for distortion/overdrive sounds, in these terms it simply means Volume or Amplitude. This can be represented by an S-Curve on a graph.
Low Gain is represented by a smaller amplitude, aka a smaller S-curve. High Gain is represented by a larger amplitude or larger S-curve.
The Gain stage of an overdrive amplifies the volume of your guitar signal so that it can then be CLIPPED.
Clipping an amplified signal is what creates the overdrive sound. This is typically achieved in the Gain stage through the use of a component called “Diodes”. There are four terms worth knowing when it comes to clipping:
Symmetrical Clipping: Clip on both sides of the waveform.
Asymmetrical Clipping: Clip more on one side than the other
Hard Clipping: Diodes placed directly after Gain Stage
Soft Clipping: Diodes placed in feedback loop of the Gain Stage
Clipping is also responsible for the natural compression effect that overdrive pedals offer.
Overdrive pedals not only amplify and clip your signal, but they can also shape the EQ of your guitar. The most common type of EQ-curve you will see is a bump in midrange frequencies (typically between 700Hz – 1.2kHz). They also typically cut low-end.
As a result, overdrive pedals accentuate the guitar’s characteristic frequency spectrum and help you stand out in a mix.
There are two types of EQ in overdrive pedals:
Passive EQ: Found in the Tube Screamer. All the way to right, allows all frequencies thru. Turns down as you move to left
Active EQ: Found in the Klon Centaur. Add or subtract frequencies. Control at noon is neutral. Left cuts, right increases.
Where the EQ is placed makes an impact and changes the way your pedal distorts.
Another aspect of overdrive that needs to be addressed in Headroom. Headroom establishes the dynamic range of an overdrive and is affected by voltage.
Greater Voltage results in great Headroom. High headroom means greater dynamic range before hitting compression/clipping.
If your overdrive is capable of being powered by different voltages (such as 9V, 12V, 18V, or 21V) higher voltages will give you more dynamic range as a result of higher headroom.
ONLY USE HIGHER VOLTAGE IF YOUR PEDAL IS RATED TO DO SO. You can set your pedal on fire by using too much voltage.
The 5 Types of Overdrive
While there are technically more than five different types of overdrive available, the vast majority fall under one of these five types and have slight modifications that make each overdrive do something unique.
Josh Scott at JHS Pedals explains these circuits in depth in his video on the subject.
1. Soft Clipping – Tube Screamer Style
This style of overdrive is mid-heavy and was developed in the 1970’s. It was made famous by Stevie Ray Vaughan and is by far the most copied circuit ever. It is non-transparent, and the mid-hump helps push your guitar through a mix, while the soft clipping creates a smooth overdrive tone.
Recommended Soft Clipping – Tube Screamer Style Pedals
2. Soft Clipping – Blues Breaker Style
The Blues Breaker circuit was created in the 90’s to emulate a Marshall amplifier by the same name. What resulted was a new kind of soft-clipping circuit that does not shape the EQ of your guitar signal, making it the original “transparent overdrive”. The Analog Man King of Tone is a boutique pedal that made this type of overdrive famous.
Recommended Soft Clipping – Blues Breaker Style Pedals
3. Hard Clipping – 1970’s Op Amp
Hard clipping means that every part of your signal is clipped, resulting in a more intense, almost distortion level, overdrive effect. The earliest examples of this came in the 1970’s and are great for high-gain tones as well as easy to use.
Recommended Hard Clipping – 1970’s Op Amp Pedals
- DOD Overdrive Preamp 250 – Classic Op Amp Pedal
4. Hard Clipping – Klon Centaur
If you’ve heard how a Klon Centaur style pedal sounds, you may not think it to be hard clipping. By blending in your clean tone with a hard clipped signal, the Klon has achieved mythical status. These days you don’t need to spend thousands to achieve this sound, as there are a number of great clones.
Recommended Hard Clipping – Klon Centaur Style Pedals
5. Transistor Based Overdrives
The fifth kind of overdrive uses cascading transistors, similar to stacking multiple boost pedals, to create an overdrive tone like that of a tube amplifier. Most “amp-in-a-box” style overdrives are made with this circuit.
Recommended Transistor Based Overdrive Pedals
Not All Overdrives Do the Same Thing
You asked, “What does an overdrive pedal do?”
I hope that this article helped to answer that question. All overdrives share common circuits and effect your tone in similar ways, but there are a lot of unique sounding pedals out there. Not all overdrive pedals do the same thing.
Try as many as you can with your guitar and amp. Different types of overdrives work better with different setups, so don’t write off a type of overdrive.
You might just find out different drives work for different guitar/amp combinations.
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Davis Wilton Bader is a professional guitarist/writer based out of St. Louis, MO. He plays in the bands Lumet and The Outskirts.