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Zero Perceived Distortion | Master of Perfection! © Tenor Inc. 2000 -2024

Zero Perceived Distortion


Tenor amplifiers can unlock the passion and the purity lying dormant in your collection of CDs, digital music files, vinyl and tape. 

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You can finally enjoy music in its entirety - the way it was mastered and meant to be!

Tenor’s proprietary Zero Perceived Distortion technology (officially called Harmonic Structural Integrity or HSI) preserves the original fundamentals of your recording typically distorted by other amplification.  Your music is effortless, accurate and enjoyable - like your favourite performer playing live in front of you.  HSI leverages how the brain perceives distortions that occur normally in the every day listening environment of the ear and uses them in a way that can conceal what natural distortions, albeit small, a Tenor amplifier has.  With a Tenor amplifier, you hear only the music!

Sensation and Perception Hearing Loss Ear Schematic

Life’s natural sounds are so pleasurable and enjoyable.  Do you wonder why recordings of these sounds are so harsh or unnatural when played back on most audio systems … or why most CD’s simply don’t sound right - even on high end audio systems?  Amplifier distortion (source, preamp, power amplifier) contribute to a fatiguing phenomenon whereby the fundamentals of the original recording are lost!  We can listen to loud crashing waves from the ocean, strong winds whistling through the trees or rain on a hot tin roof - all without fatigue - and often considered to be melodic and calming!  

When amplifier overtones are created through distortion or feedback loops, sound quality diminishes.  The brain needs to work hard to discern true tones from overtones by relying on its library bank of "learned sounds" to correlate what it is hearing.  This is intensive work for the brain so it is not surprising when fatigue finally become unbearable with the brain saying: ‘no more’!  Interest in listening is now lost!  The music is effectively over … well, the enjoyment is!  The musical respite has now become a musical irritation!

Many thesis’ have been written on methods of lowering distortion as measured in amplifiers.  Most designers rely on either feed-back or feed-forward techniques whereby the amplifier output is connected through a return loop to the amplifier input to lower measured distortion.  The pretence is that one can actually lower the measured distortion by sharing the amplifer output with the input (or vice versa).  What most designers fail to realize is they are measuring only 2 dimensions of a 3 dimensional problem.  Unfortunately the entire industry has advocated this measuring technique as being meaningful!  Just listen to any amplifier using feedback - the musical life is gone away … but measures better than ever!  I think you see (hear) my point.

Tenor amplifiers have no global feedback.  We contend this to be the first step in great amplifier design.  

We then map the low natural distortion of our amplifiers.  This is done for every tone and overtone - at every frequency simultaneously … at every amplitude.  This allows us to understand exactly our amplifier’s dynamic nature of distortion while playing real music and not just the static measurement at a particular frequency and amplitude - the way distortion is measured by the industry today.  With this detailed mapping, we shape our amplifier circuit using Tenor’s proprietary HSI technology in a manner that the brain perceives no distortion.   What little distortion Tenor amplifiers have is now effortlessly and subconciously ignored by the brain.  This is the premise of Zero Perceived Distortion - laying bare the beautiful essence of each original master recording in all of its splendour!  

Many clients tell us that they stay up for days on end, mesmerized, addicted … listening to every single album in their collection upon receiving their Tenor amplifier.  All albums take on a lifelike immediacy never heard before - even your great artistic recordings compromised by poor sound engineering all of a sudden take on a basic perfection never realized before!

Michel Vanden Broeck, Tenor’s Chief Engineer, has spent most of his life's work in pursuit of this psychoacoustic effect using the ear-brain interface as a method to zero out distortion and free recorded music from the electronic shortcomings of the past century.  With over 40 years of combined electronics engineering and natural wonderment, Michel’s 15 years of research at Tenor labs has defied conventional industry wisdom with a truly “eureka” discovery!  

Harmonic Structural Integrity!  The essence of every Tenor product and the reason to start listening to music all over again!

What does this all mean to you?  Simply stated:  "Tenor amplifiers bring recorded music to life - like you have never heard before”!


Jim Fairhead, President, Tenor Audio, a musician & dedicated audiophile, conceived  the phrase “Zero Perceived Distortion” listening to an early Tenor amplifier.   Jim concluded that to hear recorded music properly and perfectly everyone needed the technology developed by Michel Vanden Broeck.  Jim then led a consortium of like-minded business associates / audiophiles to further develop Michel’s vision so preamplifiers and phono stages could be part of the HSI chain - allowing discriminating audiophiles everywhere the opportunity to enjoy music properly and perfectly with Tenor’s Zero Perceived Distortion technology!

Tenor amplifier products represent the "crowning point " of all amplification without reservation and will be the reason we fall in love with our music all over again!

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