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What Is Intermodulation Distortion? Exploring Audio Imperfections

by Stuart Charles Black
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Greetings mate and Welcome aboard!

Stuart Charles here, HomeStudioBasics.com helping YOU make sound decisions, so…

What is Intermodulation Distortion?

JDS Labs Atom vs. Objective 2

The venerable Objective 2 had a 0.002% IMD.

Intermodulation distortion (IMD) is a phenomenon that occurs in electronic systems, including headphone amplifiers, where the nonlinear behavior of components leads to the creation of unwanted signals at frequencies that are not present in the original input signal.

In the context of headphone amps, IMD refers to the generation of new frequencies as a result of the interaction between multiple input frequencies, which can degrade the quality of the amplified audio signal.

When you feed a headphone amplifier with two or more different frequencies simultaneously, the nonlinear characteristics of the amplifier’s components can cause these frequencies to mix and produce additional frequencies that were not part of the original audio signal.

These new frequencies are usually the sum and difference of the original frequencies and their harmonics.

For example, let’s say you have two audio tones of 100 Hz and 200 Hz.

In a linear system, the output would be the same frequencies, just amplified. However, in a system with IMD, you might also observe frequencies at 100 Hz + 200 Hz = 300 Hz and 200 Hz – 100 Hz = 100 Hz, which are not present in the original signal.

These additional frequencies can lead to distortion and alter the quality of the audio.

IMD is typically quantified using parameters like Total Harmonic Distortion (THD) and Intermodulation Distortion (IMD) measurements.

THD measures the ratio of the power of harmonics to the power of the fundamental frequency, while IMD measures the presence of additional frequencies resulting from the interaction between two or more input frequencies.

In the context of headphone amplifiers, IMD can lead to an audible degradation of audio quality, causing unwanted artifacts and distortion.

High-quality headphone amplifiers are designed to minimize IMD by using linear components and careful circuit design to maintain the integrity of the audio signal and avoid the creation of unwanted frequencies.

Intermodulation Distortion (IMD) is typically measured as a percentage and is denoted as a ratio between the power of the unwanted intermodulation products and the power of the original input signals. This measurement is often expressed as IMD percentage or IMD level.

In the context of audio amplifiers, especially high-quality headphone amps, a lower IMD percentage is desirable because it indicates that the amplifier is generating fewer unwanted frequencies and preserving the integrity of the original audio signal.

A good IMD performance indicates that the amplifier is producing minimal distortion and maintaining the clarity and fidelity of the audio.

When considering IMD levels in amplifiers, there are a few general guidelines to keep in mind:

Good IMD Performance

iFi Zen DAC/Amp + Zen CAN Amp (Stack) vs. iFi Zen CAN Signature 6XX Stack

iFi’s Zen CAN (top left) advertises an IMD of 0.0098%.

A high-quality amplifier will typically have an IMD percentage well below 1%.

This means that the generated intermodulation products contribute very little to the overall audio signal and are unlikely to be perceptible to most listeners.

Acceptable Range

Amplifiers with IMD percentages in the range of 0.1% to 0.5% are considered to be very good in terms of distortion performance.

These levels of distortion are often imperceptible to the human ear and contribute minimally to the overall sound quality.

Poor IMD Performance

Amplifiers with IMD percentages above 1% can be considered to have poor IMD performance.

Distortion at this level might start to become audible, particularly with complex audio signals or at higher volumes.

The audio may sound less clear and detailed due to the presence of additional frequencies.

It’s important to note that while IMD is a crucial factor in evaluating audio equipment like headphone amplifiers, it’s not the only consideration.

Total Harmonic Distortion (THD), signal-to-noise ratio (SNR), and other factors also play a role in determining the overall audio quality an amplifier can provide.

Additionally, personal preferences can vary, and some listeners might be more sensitive to distortion than others.

When selecting an amplifier, it’s advisable to look for specifications provided by the manufacturer that detail the IMD performance.

However, keep in mind that the real-world listening experience is also influenced by the quality of the source audio, headphones, and the environment in which you’re listening.

If possible, auditioning equipment or consulting with knowledgeable professionals such as myself can help you make an informed decision based on your specific preferences and requirements.

Well that’s about it for today my friend! I hope you’ve enjoyed this What is Intermodulation Distortion? discussion and came away with some valuable insight.

Questions? Comments? Requests? Did I miss the mark on something? Please let me know down below or Contact me!!

Is Intermodulation Distortion important? I would love to hear from you. Until next time..

All the best and God bless,





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