Audio Application Notes

High-Resolution Audio - Bit Depth

High-Resolution Audio - Bit Depth

by John Siau February 24, 2015

Bit Depth

We now have 16-bit CDs and 24-bit high-resolution recordings available to us. What are the advantages of a24-bitword length? Are 24-bit recordings better? How many bits do we really need?

Bit depth (also known as word length) indicates how many bits are used to represent each sample in a digital sampling system. Each sample is a snapshot of a signal or voltage at an instant in time. The CD uses 16 bits to represent the voltage of an audio waveform at each instant in time. Other digital audio systems use different bit depths ranging from 1 to 64 bits. It is important to understand the relationship between bit depth and audio quality. The bit depth sets ...

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Box-to-Box Phase Accuracy of Benchmark DAC1 and DAC2 Converters

Box-to-Box Phase Accuracy of Benchmark DAC1 and DAC2 Converters

by John Siau October 03, 2014

Phase Accurate Multi-Channel D/A Conversion

- Using Multiple DAC1 or DAC2 Converters

Two or more Benchmark DAC1 or DAC2 converters can be used together in phase-coherent multichannel audio systems even though their internal clocks are not synchronized. This seems to defy logic, but an examination of the system details reveals why this is possible.

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Jitter in A/D Converters

Jitter in A/D Converters

by John Siau October 03, 2014

All A/D converters have two forms of jitter: Conversion clock jitter, and interface jitter. These two forms of jitter are very different and have very different consequences. Conversion clock jitter...
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What High-Resolution Audio is NOT

What High-Resolution Audio is NOT

by John Siau August 27, 2014

"Low-Resolution Hardware Cannot Deliver High-Resolution Audio"

The music industry is struggling to define High-Resolution Audio or "HRA". In doing so, most have focused on the delivery formats - analog vs. digital, 24-bits vs. 16-bits, 1X vs. 2X and 4X sample rates, PCM vs. DSD, uncompressed vs. compressed.

But, High-Resolution Audio is much more than the delivery format ...

"High-Resolution Audio Requires High-Resolution Performance at all Stages of the Recording and Playback Chain"

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Audio Myth -

Audio Myth - "24-bit Audio Has More Resolution Than 16-bit Audio"

by John Siau August 14, 2014

This myth goes something like this:

"Analog audio has infinite amplitude resolution."

"Digital audio is limited to a finite number of steps."

"24-bit audio has more resolution than 16-bit audio."

While it is true that digital systems quantize the amplitude of the audio signal to the nearest step in the digital encoding system, this does not necessarily mean that digital systems cannot have infinite resolution. Contrary to popular belief, digital systems can provide infinite amplitude resolution if they are properly dithered. 

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The AHB2 - A Radical Approach to Audio Power Amplification

The AHB2 - A Radical Approach to Audio Power Amplification

by John Siau July 30, 2014

Radical!

The performance of the AHB2 would not have been achievable without taking a radical approach to power amplification. In many ways, the AHB2 is a complete 180 degree departure from traditional high-end amplifier designs. There is nothing ordinary about the Benchmark AHB2!

Take a look inside this unique audio power amplifier! 

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Don't Blame the Headphones!

Don't Blame the Headphones!

by John Siau July 25, 2014

Headphones Sounding Bad? It Could be Your Headphone Amplifier!

It is easy to build a headphone amplifier that produces sound.  It is an entirely different matter to produce an amplifier that is clear, clean, and enjoyable.  

Headphone amplifiers need to provide enough voltage and current to achieve a suitable listening level. They must also be able to cleanly deliver the required output. Furthermore, they need to be able to control the transducers.

If these goals are not achieved, a good set of headphones can sound bad.

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The Mac Mini as a High-Resolution Audio Server

The Mac Mini as a High-Resolution Audio Server

by Benchmark Media Systems June 27, 2014

A "Mini" Server for High-Resolution Audio

Mastering and Recording Engineer, Mark Waldrep (A.K.A. Dr. AIX) recently published an excellent application note titled "My First Server". This is a step-by-step guide for setting up a High-Resolution Audio (HRA) server. He chose a Mac Mini, a Benchmark DAC2 HGC, and the highly-acclaimed Amarra playback software to bring studio-quality playback to his own living room.

With his simple guide, you can join Mark, and enjoy mastering-quality High-Resolution Audio in your room.

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The CE Mark - A Photo-Tour of Immunity Testing

The CE Mark - A Photo-Tour of Immunity Testing

by John Siau June 25, 2014

Testing for Immunity to Interference

Most people have seen the CE mark on electronic equipment, but few have had the opportunity to witness the tests that are required to conform to the CE specifications. This post takes the reader on a behind-the-scenes photo-tour of the CE tests of Benchmark's new AHB2 power amplifier.

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The CE Mark - What Does it Mean, and Why Should I Care?

The CE Mark - What Does it Mean, and Why Should I Care?

by John Siau June 17, 2014

Why is the CE Mark Important?

Many electronic products have a "CE" mark affixed to the product. This mark is mandatory in European markets, but is not required on products sold elsewhere. Few people understand what this mark means and why it is important. It is often a good idea to look for this mark when purchasing a product. It is also important to understand the differences between professional and consumer audio products (as defined in the CE standards).
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Headphone Impedance and Sensitivity

Headphone Impedance and Sensitivity

by John Siau May 05, 2014

  • Is headphone impedance important? 
  • What is headphone sensitivity?
  • Which headphones will work best with my new headphone amplifier? 
  • Which headphones will work best with my portable device? 

This application note addresses these common questions and presents some guidelines for selecting headphones with the proper impedance and sensitivity.

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Why

Why "Audio Goes to 11"

by John Siau April 17, 2014

Intersample Overs - Part 2

In my last post, "Audio that Goes to 11", I made the bold assertion that most of our audio recordings contain peaks that exceed the limits of our digital hardware. In this post I will show how this happens, and explain why this is a problem in PCM audio systems.

Do we throw out PCM and move to DSD?

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Audio That Goes to 11

Audio That Goes to 11

by John Siau April 10, 2014

Intersample Overs - Part 1

It's on your iPhone, your Android and your computer. It's even on those CDs you put on a shelf somewhere. Audio that goes to 11.  If 10 is the clip point of digital audio, you actually have digital recordings that go to 11. Nigel Tufnel of Spinal Tap was on to something in 1984 when he explained that his Marshal amps "go to 11".

But, it's not just Spinal Tap recordings that go to 11, every recording you own may also go to 11! How is this possible? If 10 is the clip point of digital audio, how can there possibly be an 11? And, if we use Nigel's logic; if 10 is good, why isn't 11 better?

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What is High-Resolution Audio? - Part 2

What is High-Resolution Audio? - Part 2

by John Siau April 03, 2014

Is there Life Beyond 20 kHz?

High-Resolution Audio systems offer the promise of an extended high-frequency range. High-Resolution digital systems now operate at 2 to 4 times the sample rate of the standard CD. This means that these systems have the capability of extending the playback frequency range well above the 22 kHz limit of the standard CD. Does this added high-frequency range improve our listening experience? How high is high enough?  Do we really need anything over 20 kHz?

If we want to accurately reproduce 20 kHz audio, the frequency response of each component must extend well beyond 20 kHz.

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What is High-Resolution Audio? - Part 1

What is High-Resolution Audio? - Part 1

by John Siau March 27, 2014

Eliminate the Noise!

There is a raging debate over the definition of "High-Resolution Audio". The focus of this debate has been misdirected by a lot of marketing hype. High-Resolution Audio will only truly arrive when the sum total of all defects in the audio chain become inaudible. We are not there yet, but we are getting close. The final chapter will not be higher sample rates and more bits. The final chapter will be achieving the necessary improvements to critical components in the signal chain.

If your playback system can't resolve anything better than CD quality, then "High-Resolution Audio" will remain an illusion.

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Headphone Amplifiers - Part 2

Headphone Amplifiers - Part 2

by John Siau March 20, 2014

It's all about control! - Headphone Output Impedance

The movement of headphone transducers must be well controlled in order to produce high-quality audio. It is easy to build a headphone amplifier that produces sound. It is an entirely different matter to produce an amplifier that is clear, clean, and enjoyable.  

Headphone amplifiers need power and accuracy to achieve control. They also need to be protected from short circuits and overload conditions. The cheap, dirty, and common way to protect the amplifier is to add a series resistor between the amplifier and the headphone jack. This simple solution protects the amplifier from short circuits and overloads. Unfortunately, the resistor isolates the headphones from the amplifier, causing a loss of control. This ...

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Headphone Amplifiers - Part 1

Headphone Amplifiers - Part 1

by John Siau March 14, 2014

Headphones do not Behave Like a Resistor - Beware of Misleading Specifications!

A couple years ago, some of us at Benchmark noticed a weird discrepancy between our HPA2  headphone amp (built into our DAC1 and DAC2) and some comparably-priced headphone amps. The advertised specifications of all the amps were basically the same, but they sounded noticeably different. Benchmark launched a detailed investigation to identify the differences. The results were surprising and are detailed in a white paper...
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An Examination of Headphone Amplifier Performance Specifications

An Examination of Headphone Amplifier Performance Specifications

by John Siau November 11, 2011

Headphone Amplifier Whitepaper

Recording Engineers and Audiophiles often distrust audio measurements and specifications. It is not uncommon to hear claims that a product measures poorly but sounds good. Occasionally we also hear claims that a product measures well but sounds bad.

This whitepaper documents significant differences between three headphone amplifiers that have nearly identical published specifications.

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iPad Streams High-Resolution Audio to Benchmark DAC1

iPad Streams High-Resolution Audio to Benchmark DAC1

by Benchmark Media Systems June 24, 2011

iPad Music Server

A simple USB adapter made by Apple can enable the iPad to connect directly to a Benchmark DAC1.

Using this adapter, the iPad can transparently stream high-resolution digital audio to the USB input of Benchmark converters. Once this connection is established, it is also possible to wirelessly stream a 96-kHz, 24-bit audio to the iPad and out to the DAC without losing sonic quality.

This application note explains the simple set-up and shows proof of performance.

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UltraLockDDS™ Clock System

UltraLockDDS™ Clock System

by John Siau November 01, 2010

UltraLockDDS™

- A Low-Jitter Direct-Digital-Synthesis Clock System

The ADC16 is equipped with Benchmark’s new UltraLockDDS™ clock system. This system utilizes the latest low-jitter clock technology developed for high-frequency RF communications systems. 

The master oscillator is a low phase-noise, temperature-compensated, fixed-frequency crystal oscillator with a +/- 2 PPM frequency accuracy. This oscillator drives a 500 MHz Direct Digital Synthesis (DDS) system. 

Jitter attenuation is achieved with digital filters in a custom FPGA that controls the DDS system. All jitter-induced distortion artifacts are well below audibility under all operating conditions.

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