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Stuart Charles here, HomeStudioBasics.com helping YOU make sound decisions, so…
In the realm of audio quality, where the pursuit of pure and accurate sound reigns supreme, one critical concept takes center stage: Total Harmonic Distortion (THD).
Like a shadow cast upon the clarity of an audio signal, THD measures the extent to which unwanted alterations and distortions seep into the realm of pristine sound reproduction.
As we delve into the world of headphones and headphone amplifiers, we uncover the significance of THD in shaping the sonic landscapes that envelop our ears, exploring how this concept influences our perception of sound quality and the technologies designed to mitigate its impact.
Join me on a journey through the realm of THD, where precision and fidelity strive to harmonize with the symphony of audio excellence.
What is Total Harmonic Distortion?
FiiO’s K11
Total Harmonic Distortion (THD) is a measurement that quantifies the amount of distortion present in an audio signal.
Huge shocker there, right?
Distortion in audio refers to any unwanted alteration or modification of the original waveform of a sound signal.
THD specifically focuses on harmonic distortion, which is the introduction of additional frequency components that are multiples of the original signal’s frequency (harmonics).
These harmonics can create a sound that is not present in the original signal and can result in an undesirable listening experience.
The THD percentage is calculated by summing the powers of all harmonics present in the audio signal, and then dividing this sum by the power of the fundamental frequency.
The result is multiplied by 100 to express it as a percentage. This value gives insight into the level of distortion introduced by harmonics relative to the original signal’s strength.
The lower the THD percentage, the cleaner and more accurate the audio signal is considered to be, as it closely resembles the original input.
Now, let’s discuss THD in the context of headphone headphone amplifiers:
Headphone Amplifiers
Headphone amplifiers play a critical role in driving headphones with sufficient power and ensuring that the audio signal remains clean and undistorted.
A headphone amplifier’s THD becomes relevant when it starts to introduce additional distortion to the signal as it amplifies it.
High-quality headphone amplifiers are designed to have very low THD values, minimizing the distortion introduced during amplification.
This is especially important when dealing with sensitive headphones or high-impedance headphones that require more power to reach their optimal performance.
A good headphone amplifier will strive to keep THD as low as possible, typically well below 1%.
Some premium amplifiers might even advertise THD values in the range of 0.001% or lower, indicating a high level of audio fidelity – but that also can come at a cost.
More on that later. Stick around!
It’s worth noting that while THD is an important consideration, it’s not the only factor that determines the audio quality of headphones and amplifiers.
Other factors, such as signal-to-noise ratio, crosstalk, and intermodulation distortion, also play a role in the overall sound quality.
The Numbers
When interpreting Total Harmonic Distortion (THD) numbers and percentages, it’s important to understand the scale of distortion and its impact on audio quality.
THD is usually expressed as a percentage and represents the amount of harmonic distortion relative to the original signal.
Here’s a breakdown of what constitutes good and bad THD values:
Good THD Values
In the context of audio equipment like headphones and headphone amplifiers, lower THD values are generally considered better.
THD values that are typically regarded as good and indicative of high-quality audio reproduction fall below 1%. As previously mentioned, some premium audio gear might even boast THD values well below 0.1% or even closer to 0.01%.
At these low levels of THD, the distortion introduced is often imperceptible to the human ear.
This means that the audio signal remains close to its original state, resulting in a clear, accurate, and enjoyable listening experience.
Moderate THD Values
THD values between 1% and 3% might not be considered excellent but are still within an acceptable range, especially for mid-range audio equipment.
In some cases, a THD value of around 1% might be barely noticeable, while a THD value approaching 3% might lead to a slightly perceptible alteration in sound quality.
High THD Values
THD values above 3% are generally considered high and can have a noticeable negative impact on audio quality.
As THD increases, the distortion becomes more apparent, leading to a degradation of the original audio signal.
High THD can result in a muddied or “muffled” sound with a lack of clarity and precision.
Very High THD Values
THD values exceeding 10% are exceptionally high and typically associated with poor-quality audio equipment.
At these levels, the distortion is substantial and can significantly alter the character of the sound, making it highly undesirable for accurate sound reproduction.
When choosing headphones or headphone amplifiers, it’s a good practice to consider THD values in conjunction with the source file followed by the headphones/speakers.
Ultimately, the goal is to strike a balance between low THD and other factors that collectively contribute to an enjoyable and accurate audio experience.
Unintended Consequences
The pursuit of extremely low Total Harmonic Distortion (THD) values can sometimes lead to unintended consequences in audio equipment, particularly in headphone amplifiers.
While lower THD percentages generally suggest better audio fidelity, it’s essential to strike a balance with other factors that contribute to the overall listening experience.
The Chord Hugo 2, a highly regarded portable DAC and headphone amplifier, serves as a prime example of this phenomenon.
The Hugo 2 is known for its cutting-edge technology and exceptional audio performance.
However, some audiophiles and reviewers have noted that its incredibly low THD figures, often approaching or even reaching the vanishingly low range of 0.001%, can lead to a sonic characteristic that some describe as overly “clinical,” “sterile,” or “analytical.”
In the pursuit of minimizing THD, designers of audio equipment like the Hugo 2 may inadvertently create a sound signature that lacks warmth, musicality, and the organic nuances that give music its emotional depth.
When THD is pushed to such extremely low levels, the audio signal can become technically accurate but may lose the subtle harmonics and colorations that make music feel alive and immersive.
This can result in a sound that some listeners perceive as “soulless” or devoid of the emotional connection that music can evoke.
Ultimately, the perception of audio quality is subjective, and different listeners have varying preferences.
While some listeners might appreciate the utmost precision and analytical nature of gear like the Hugo 2, others may find it lacking the emotional engagement they seek in their music.
Myself?
I do tend to gravitate towards neutral, but the Hugo was a clear (no pun intended) exception.
Per my experience, it made music sound really lifeless and overly sterile/dry, but that could have simply been my imagination, knowing it has such low percentages; both in THD as well as its very low, almost minuscule Output Impedance.
That said, I firmly believe that the SINAD standard (Signal-to-noise and distortion exceeds 90dB) is the most important component in evaluating whether or not a DAC will perform well, and fortunately for us, 99.9% of them do; often exceeding the standard by at least 20-30dB.
Now that we understand the most critical consideration, let’s choose one.
Well, that’s about it for today folks! I hope you’ve enjoyed this What is Total Harmonic Distortion? discussion and gained some valuable insight.
Questions? Comments? Requests? Did I miss the mark on something? Please let me know down below or Contact me!!
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Do you believe that a super low THD percentage can suck the life out of music? I’d love to hear from you. Until next time…
All the best and God bless,
-Stu
