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Building the AHB2 Power Amplifier - The Poor Audiophile Interviews John Siau

July 13, 2015

AHB2 - John Siau Explains what's Inside Benchmark's Unique Amplifier

"John is a long-time audiophile. In fact, it was his love of music and audio that originally inspired his interest in electronics and prompted him to pursue a degree in electrical engineering at Syracuse University."

"“It became clear that we would not reach our goals if we designed a conventional power amplifier,” John said. “We realized that we needed to look at some unique solutions. We were very focused on eliminating crossover distortion in the output stage because we felt that this was one of the most important factors in the sonic performance of the amplifier. We began experimenting with ...”"

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Computer Audiophile Thread: Interesting Article on 24-bit depth and sampling rates from Benchmark's John Siau

August 16, 2014

In case you hadn't seen it, it's worth a quick read for those trying to stay up with some of the bit-rate/sample-rate discussions we've had here: Audio Myth - "24-bit Audio Has More Resolution Than 16-bit Audio" - sdolezalek

Join the discussion on ComputerAudiophile.com...

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Benchmark Company History

Benchmark began in 1983 as the "Benchmark Sound Company", a small operation working out of a garage in Garland, Texas. Allen H. Burdick, Founder Our founder, Allen H. Burdick, began by building very high-performance audio equipment to meet the specialized...

Is 192 kHz better or worse sounding than 96 kHz?

August 25, 2014

We would not recommend spending extra money to get the 192 kHz version if a 96 kHz version is available.

Our DAC2 D/A converter will provide exactly the same performance at either 96 kHz of 192 kHz. However, in most cases, many A/D converters (used to record the music in the studio) achieve better performance at 96 kHz than they do at 192 kHz. But, these differences will be very small.

Read the full FAQ and related posts...

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Headphone Amplifiers - Part 2

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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Star Quad Cable Demonstration - Video

February 12, 2016

Benchmark has recorded a lab demonstration that shows what happens when a standard two-wire cable is exposed to common sources of magnetic interference.

You will be able to hear the interference, see it on an oscilloscope, and view its spectrum on an FFT. A star-quad cable is exposed to the same sources of magnetic interference and the results are compared. This demonstration shows the dramatic difference between the two cables. The star-quad cable provided a 20 to 50 dB reduction in magnetic interference, keeping the interference below audible levels.

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Don't Blame the Headphones!

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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DAC1 Review - Doug Schroeder, dagogo

July 01, 2007

DAC1 - "A clean, lean digitizing machine"

"The DAC1 was created with three target users in mind: the professional studio, home use by audio professionals, and audiophiles. Indeed, the DAC1 has been well received by studios and has made inroads into the audiophile community. It is feature-laden and smartly laid out."

"It’s more than a DAC, it’s a pretty doggone good preamp too!"

"It presents hyper-nuanced, super clean sound."

"The Benchmark is a clean, lean digitizing machine. It does set the standard at its price point for pure, unadulterated digital signals coming to your nearest amp(s)."

"If you’re after the most measurably perfect CD sound and endless detail, put it on your own test bench – your audio rack."

- Doug Schroeder, dagogo

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Benchmark AHB2 Update

September 30, 2014

Live Demonstration - September 24, 2014

The AHB2 and SMS1 will be demonstrated at the Rocky Mountain Audio Fest October 10-12, 2014. Come experience this stunning combination in person. Meet Sales Manager Rory Rall and Speaker Designer Dave MacPherson. Enter to win a Benchmark DAC (1 winner per show). We will be accepting orders for the AHB2 at the show.

The AHB2 and SMS1 will be on display at the AES Convention in LA October 9-12, 2014. Stop by booth 1421 to meet John Siau and other members of the engineering team. Enter to win a Benchmark DAC (1 winner per show). We will be accepting orders for the AHB2 at the show.

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Headphone Amplifiers - Part 1

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

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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The A.H.B. Story

March 17, 2016

A.H.B.

Allen H. BurdickThe AHB2 power amplifier is named in honor of Benchmark's founder, Allen H. Burdick. Allen had a life-long passion for audio, and became one of the leading innovators in the pro-audio industry. Allen was a perfectionist and a prolific engineer. Most early Benchmark schematics bear the initials A.H.B.

Allen's DA101 distribution amplifier helped define the performance goals of the AHB2 power amplifier. The result is an amplifier that Allen would have been proud to call a "Benchmark".

 In loving memory of Allen H. Burdick (June 29, 1942 - September 27, 2013).

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The "0-Ohm" Headphone Amplifier

December 01, 2001

An Introduction to "The 0-Ohm Headphone Amplifier" White Paper

The circuits used to drive headphones are often added to a product without careful consideration of the difficult loads presented by high-quality headphones. The most common circuit is an opamp driver followed by a 30-Ohm series resistor. The series resistor provides short-circuit and overload protection while isolating the opamp from the inductance and capacitance of the headphones. The series resistor protects the opamp while keeping it stable. In contrast, today's state-of-the-art headphone amplifiers eliminate the series resistor, and use a high current driver. This change reduces distortion and flattens the frequency response when a headphone is driven. These new high-end designs are often called "0-Ohm" headphone amplifiers, and are ...

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Company Information

Benchmark ... The Measure of Excellence® As our name implies, we are committed to excellence. Benchmark products are designed and built by audio enthusiasts. We are musicians, audiophiles and audio professionals who are passionate about audio quality. We also are passionate about the...

Benchmark Announces Two New Products at RMAF 2018

October 05, 2018

PRESS RELEASE

October 5, 2018

Denver, Co.

Today at RMAF, Benchmark Media Systems announced two new products.

The first is the LA4 line amplifier/preamplifier. The second is the DAC3 B D/A converter.

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"These are the Amplifiers You are Looking For"

January 29, 2016

"These are the amplifiers that you are looking for."

Rory Rall whit the AHB2 and a Storm Trooper

Rory Rall shows a Storm Trooper the AHB2 power amplifier at the NAMM 2016 Show, and explains the new THX AAA Technology. Rory was heard to say: "These are the amplifiers that you are looking for."

 

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A Look Inside the New ES9028PRO Converter Chip and the New DAC3

November 14, 2016

ES9028PRO D/A Converter Chip - Block Diagram and Test Report

This application note examines the differences between the ES9018 and the new ES9028PRO. It also compares the Benchmark DAC2 and DAC3 to demonstrate the performance improvements that can be achieved in a commercial product. It has been a little over 7 years since ESS Technology introduced the revolutionary ES9018 audio D/A converter chip. This converter delivered a major improvement in audio conversion and, for 7 years, it has held its position as the highest performing audio D/A converter chip. But a new D/A chip has now claimed this top position. Curiously the successor did not come from a competing company; it came from ESS. On October 19, 2016, ESS Technology announced the all-new ES9028PRO 32-bit audio D/A converter. In our opinion, ESS is now two steps ahead of the competition!

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AHB2 - Driving PMC IB2S Studio Monitors

October 24, 2016

AHB2 - Driving PMC IB2S Passive Studio Monitors at AES 141

At the 141st AES conference we demonstrated two Benchmark AHB2 monoblock power amplifiers driving a pair of 4-Ohm PMC IB2S passive studio monitors (these monitor are also available in the PMC IB2SE hi-fi version).

In bridged mono, the AHB2 can deliver over 518 watts into each of these 4-Ohm speakers. This is a perfect match to PMC's 500 watt recommendation. The AHB2 easily provides the power, the output current, and the damping required by these low-impedance speakers.

"I am very impressed with the clarity and accuracy of these outstanding professional monitors. The Benchmark AHB2 and PMC IB2S are an absolutely killer combination!" - John Siau, VP, Benchmark Media Systems, Inc.

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AHB2 Crossover Distortion Measurements

March 10, 2016

Crossover Distortion - Measurements

The following measurements and scope photos demonstrate the effectiveness of the feedforward system in the AHB2.

From the first Watt to the last Watt, the AHB2 shows no evidence of crossover distortion. In contrast, all conventional class-AB amplifiers have crossover-distortion artifacts.

Dick Olsher once said that "the first Watt is the most important Watt". We agree!

 

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Amplifier Crossover Distortion

March 10, 2016

Crossover Distortion - Introduction 

Most audio power amplifiers suffer from a defect known as "crossover distortion". This distortion is particularly troublesome at low output levels. At low power levels, the crossover distortion can rise to a high percentage of the output level and become the dominant source of distortion.

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Asynchronous Upsampling to 110 kHz

July 01, 2010

The Advantages of Asynchronous Upsampling D/A Converters

Benchmark DAC1 converters use upsampling techniques to improve the quality of the digital to analog conversion. Benchmark’s choice of 110 kHz is slightly unorthodox. It may seem more logical to upsample by 2X or 4X and convert at standard sample rates such as 88.2 kHz, 96 kHz, 176.4 kHz or even 192 kHz. Intuition may suggest that integer ratios would produce the best results. Intuition may also suggest that higher is better, and therefore 192 kHz would be the “best” choice for an output sample rate. Unfortunately, intuition often leads us down the wrong path if it is not balanced with reason and scientific analysis. Benchmark’s analysis and testing has shown that 110 kHz offers advantages over the choices that seem more reasonable.

This paper is a short summary of the decisions that led to our choice of the 110 kHz sampling rate.

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

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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Audio Myth - "Switching Power Supplies are Noisy"

May 03, 2016

This Myth Goes Something Like This:

"Switching supplies are noisy."

"Linear power supplies are best for audio."

We disagree!

About 5 years ago, Benchmark stopped putting linear power supplies into our new products, and we replaced them with switching power supplies. We did this because linear supplies are too noisy. Yes, you read that correctly, linear supplies are noisy!

A well-designed switching power supply can be much quieter than a linear supply!

Find out why!

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Audio Myth - Balanced Headphone Amplifiers are Better

September 15, 2016

THIS MYTH GOES SOMETHING LIKE THIS:

"Balanced headphone amplifiers are better."

"If balanced line-level connections work well, balanced headphone outputs should also work well."

We disagree!

Benchmark does not offer balanced headphone outputs on any of its products. The reason for this is that a voltage-balanced interface serves no useful purpose when driving headphones. The truth is that a conventional single-ended headphone drive is technically superior to a balanced drive. This paper explains why single-ended headphone amplifiers are inherently more transparent than balanced headphone amplifiers.

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Audio Myth -"DSD Provides a Direct Stream from A/D to D/A"

August 27, 2015

This myth goes something like this:

"DSD provides a simple and direct digital path between the A/D and D/A."

"DSD is simpler than PCM."

"DSD is not PCM."

While DSD can provide spectacular audio performance, all of the statements above are false.

There are many wonderful DSD recordings, but the quality is not due to any virtues of the DSD format.

Direct Stream Digital (DSD) seems like a simple and attractive system, but it absolutely fails to deliver a "direct" path between the A/D and the D/A.

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Audio Myths - The Ultimate "Myth Buster" Video - Monty Montgomery, Xiph.Org

March 14, 2017

Digital Show & Tell, Monty Montgomery, Xiph.org

Monty Montgomery takes us into the lab and uses a series of simple demonstrations to bust some very common myths about digital audio. Test your knowledge of digital audio. This video is fun to watch and easy to understand! Monty takes some difficult concepts and demonstrates them in a clear and simple manner.

Have doubts about Nyquist? Have a fear of stairsteps? Are you worried about ringing? Ever wonder what digital audio does to the timing of transients? This video is for you!

Myth- "Digital audio has stairsteps." 

Myth- "Increased bit depths reduce the stairsteps." 

Myth- "Analog tape has more resolution than digital audio." 

Myth- "Dither masks quantization noise." 

Myth- "Signals lower than one LSB cannot be reproduced." 

Myth- "Digital filters make square waves and impulses ring." 

Myth- "Digital systems cannot resolve timing between samples."

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Audio That Goes to 11

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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Balanced vs. Unbalanced Analog Interfaces

April 23, 2018

If you look at the back of any Benchmark product, you will find balanced XLR analog-audio connectors. As a convenience, we also provide unbalanced RCA connectors on many of our products. In all cases, the balanced interfaces will provide better performance.

We build our unbalanced interfaces to the same high standards as our balanced interfaces, but the laws of physics dictate that the balanced interfaces will provide better noise performance.

This application note explains the advantages of balanced interfaces.

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Benchmark Bi-Directional 12 Volt Trigger - Technical Details

April 20, 2016

12 Volt Trigger

Link your audio products together with trigger cables

Benchmark has created a bi-directional 12 Volt trigger interface that is compatible with almost every trigger input and output. This interface can be used to connect Benchmark products together so that they will power up and down in a sequenced fashion. This same interface can be connected to the trigger inputs and outputs on other brands of audio products. This application note describes some typical configurations and it includes the full technical details of the Benchmark bi-directional trigger system.

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Benchmark DAC2 vs. DAC1 - Is There an Audible Difference?

August 06, 2015

Benchmark introduced the DAC1 in 2002 and it quickly became the best-selling 2-channel professional D/A converter. To this day, the DAC1 is a standard fixture in many recording studios, and it is also a central component in many high-end hi-fi systems. In August of 2015, Enjoy the Music.com selected the DAC1 as one of the20 most significant digital audio products from the past 20 years.

It is easy to show that the DAC2 measures better than the DAC1 in almost every way. From a marketing perspective it would be tempting to claim that all of these measured differences make audible improvements, but this just isn't the case.

One reviewer, Gary Galo, recently had the opportunity to hear a DAC1 and DAC2 side-by-side. He noted some audible differences and we agree with his conclusions. We have had a great deal of experience listening to these converters side-by-side in our own listening room and we are familiar with some subtle differences.

This paper examines the subtle audible differences between the DAC1 and the DAC2. It also includes measurements that may help to explain these differences.

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Benchmark DAC2 vs. DAC1 - Side-by-Side Measurements

August 13, 2015

There was a 10-year time span between the introduction of the Benchmark DAC1 and DAC2 audio D/A converters. The DAC1 defined the state of the art when it was introduced in 2002. Thirteen years later, Enjoy the Music.com selected the DAC1 as one of the 20 most significant digital audio products from the past 20 years. Today the DAC2 defines the state of the art in audio D/A conversion. John Atkinson said that the "DAC2 offered one of the highest resolutions I have measured". Both products set performance benchmarks when they were introduced. In a sense, they provide snapshots of technological progress.

This paper shows high-precision side-by-side measurements of the DAC1 and DAC2 converters. These measurements show how technology has improved, and they show that there may be two or three audible differences between these two products.

Travel through 10 years of audio technology, learn the significance of audio measurements, and see what has improved in our quest for transparent audio reproduction.

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

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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Calculating the Performance of an Amplifier / Speaker Combination - Example 2

October 27, 2017

Example 2 - PMC MB2S

In this application note we calculate the maximum output level and noise level produced by an amplifier/loudspeaker combination.

This application note can serve as an example for calculating the maximum sound pressure levels and noise output levels for any amplifier/speaker combination.

At the 143rd AES conference in NYC, we demonstrated two Benchmark AHB2 monoblock power amplifiers driving a pair of 4-Ohm PMC MB2S studio monitors.

We were extremely impressed by the unusually clean, distortion-free, output of these monitors. They fully compliment the distortion-free performance of the AHB2 to provide a system with outstanding clarity while delivering high sound pressure levels.

In this application note we will calculate the peak SPL produced by this system. We will also calculate the acoustic noise at a distance of 1 meter from each monitor. We will also discuss some of the unique design features of the MB2S monitors that contribute to their impressive performance.

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Calculating the Performance of an Amplifier/Speaker Combination

November 01, 2016

Example 1 - PMC IB2S

In this application note we calculate the maximum output level and noise level produced by an amplifier/loudspeaker combination. Use this example for calculating the performance of your system.

At the 141st AES conference we demonstrated two Benchmark AHB2 monoblock power amplifiers driving a pair of 4-Ohm PMC IB2S studio monitors. These monitor are also available the PMC IB2SE hi-fi version.

In bridged mono, the AHB2 can deliver over 518 watts into each of these 4-Ohm speakers. This is a perfect match to PMC's 500 watt recommendation. The AHB2 easily provides the power, the output current, and the damping required by these low-impedance speakers.

"I am very impressed with the clarity and accuracy of these outstanding professional monitors. The Benchmark AHB2 and PMC IB2S are an absolutely killer combination!" - John Siau, VP, Benchmark Media Systems, Inc.

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Creating a High-Resolution 5.1 Music Server

April 21, 2015

Blu-ray disks often contain high-resolution audio formats. Dolby TrueHD and DTS-HD are two Blu-ray audio encoding formats that support lossless high-resolution audio. These systems support up to 8 channels of 24-bit, 96kHz audio, or up to 6 channels of 24-bit 192 kHz audio.

Blu-ray disks may seem like an ideal solution for the distribution of high-resolution audio, but there are problems. It is not easy to gain access to the high-resolution audio stored on these disks.

Our solution was to set up a PC-based music (and video) server. We used a Blu-ray equipped PC running Windows 7 and the JRiver MediaCenter software.

This application note provides a guide for setting up a music server that can play the lossless high-resolution audio tracks found on DVD and Blu-ray disks.

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Feed-Forward Error Correction

October 11, 2018

The Benchmark AHB2 power amplifier and HPA4 headphone amplifier both feature feed-forward error correction. This correction system is an important subset of the patented THX-AAA™ (Achromatic Audio Amplifier) technology. It is one of the systems that keeps these Benchmark amplifiers virtually distortion free when driving heavy loads. It is also the reason that these amplifiers can support 500 kHz bandwidths without risk of instability when driving reactive loads.

This paper explains the differences between feedback and feed-forward systems. As you read this paper, you will discover that you already understand the benefits of feed-forward correction because you use it instinctively to improve a feedback system commonly found in your automobile. If feed-forward correction can improve your driving experience, it may also improve your listening experience!

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Headphone Impedance and Sensitivity

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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High-Resolution Audio - Bit Depth

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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High-Resolution Audio - Sample Rate

March 19, 2015

Sample Rate

Digital recordings are now available in a variety of sample rates. The CD uses a 44.1 kHz sample rate, but high-resolution audio recordings are now available in sample rates of 96 kHz and 192 kHz. What are the advantages of higher sample rates? How high a sample rate do we really need?

Digital audio systems take instantaneous snapshots or "samples" of an analog audio signal and then store each of these samples as numeric values. The digital samples can be stored and transmitted without any loss of quality, but these samples must be used to reconstruct an analog signal before we can listen to the audio. The sample rate places very specific limitations ...

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History of the AHB2 Power Amplifier

March 17, 2016

The DA101 - Inspiration for the AHB2

Benchmark DA101About 33 years ago, Benchmark's founder, Allen H. Burdick,  began building analog audio distribution amplifiers for television networks. This application demanded an audio amplifier with a very wide frequency response, very low noise, and very low distortion. The Benchmark DA101 distribution amplifier had a 160 kHz bandwidth, THD+N of 0.00044%, and a SNR of 130 dB, but the power output was only about 40 watts in bridged mono.

For many years, we used our distribution amplifiers to drive the speakers in our listening room. We couldn't buy an amplifier that came close to the performance of our distribution amplifiers, and Allen had often talked about building a bigger amplifier that could match the performance of the DA101.

In 2011 we began to talk about making Allen's dream for a power amp a reality. The goal was to meet or exceed the performance of Allen's DA101, while scaling up the power by a factor of 10.

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How Should I Buy an Audio System?

February 26, 2016

Two Distinct Types of Audio Products - Understand the Difference Before You Buy!

2013 Porsche 911 Carrera 4S (991) (9626546987)

Make your own choice!

"Buying an audio product is much like buying a car"

There are two distinct types of audio products. Some audio products are designed to be transparent while others are designed to provide a euphonic experience. These types are as different as a Porsche and a Cadillac.

There is not a right and wrong type of car. Likewise there is not a right and wrong type of audio product. The choice belongs to the user, but the user must be fully aware of the differences before they buy.

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Inside the DAC2 - Part 1 - Analog Processing

June 04, 2016

The DAC2 is an audio digital-to-analog converter. Most people focus on the word "digital" and assume that all of the "magic" happens in the digital processing, but nothing could be further from the truth! A look inside most audio converters would show that about 90% of the components are analog!

This application note takes a look at the analog processing in Benchmark's DAC2 D/A converter.

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Inside the DAC2 - Part 2 - Digital Processing

June 24, 2016

The Benchmark DAC2 is an audio digital-to-analog converter. This application note explains the proprietary digital processing inside Benchmark's DAC2 D/A converter. In part 1 of this series we made the case that 90% of the components in an audio converter are analog, and that about 90% of the "magic" happens in the analog processing. Nevertheless the 10% that is digital still makes an audible contribution to the sound of an audio D/A converter. This is especially true when the digital processing is complemented by a very pure and clean analog section. With a highly transparent analog section, some of the subtleties of the digital processing can become apparent.

Take a tour of the digital processing chain in the DAC2.

 

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Inside the DAC2 - Part 3 - Power Supplies

July 13, 2016

The Benchmark DAC2 is an audio digital-to-analog converter. This application note explains the power supply configuration inside Benchmark'sDAC2 D/A converter. Inpart 1 of this series we discussed the importance of the analog section of an audio converter. In part 2 we discussed the unique high-headroom digital processing chain inside the DAC2. The analog and digital systems each contribute toward Benchmark's overall goal of transparent musical reproduction, but this goal can only be reached when these systems are supported by a well-designed power supply system. In many cases, classic solutions (linear power supplies, line-frequency transformers, and large banks of capacitors) fail to deliver adequate performance. The DAC2 takes a radically different approach.

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Interpreting THD Measurements - Think dB not Percent!

November 15, 2017

Distortion measurements (THD, THD+N and IMD) are traditionally expressed in terms of percent. But what do 1%, 0.1%, 0.01% or 0.001% mean in terms of loudness or audibility?

If you are like most people you just know that 0.001% is the best of the three numbers listed above. If you are a well-trained geek you will recognize that each added leading zero represents a 20 dB improvement. 0.01% is 20 dB lower than 0.1% and 40 dB lower than 1%. The well-trained geek will convert % to dB in order to give meaning to these numbers.

When THD is expressed in terms of dB, we can easily determine how loud the distortion will be in our playback system.

Will my audio electronics produce audible distortion?

Will the distortion produced by my audio electronics be inaudible?

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Intersample Overs in CD Recordings

February 10, 2017

Intersample Overs are a Common Occurrence in CD Recordings

We have frequently used Steely Dan's Gaslighting Abbie from Two Against Nature in our listening tests. This is a spectacular CD recording with lots of dynamics and a low noise floor. Nevertheless, in a little over 5 minutes, this track has 559 intersample overs on the left track and 570 on the right track for a total of 1129. This means that there are about 3.7 intersample overs per second. The highest intersample over measures +0.8 dBFS. The track itself is not clipped, the 44.1 kHz sampling has simply captured peaks that exceed 0 dBFS. The following image shows the track with the intersample overs highlighted in red:

This track can be played cleanly by the Benchmark DAC2 and DAC3 converters. These converters accurately render the intersample peaks that were captured in the recording process. In contrast, conventional converters will clip each of the peaks highlighted in red. In this track the peaks coincide with hits to the snare drum. Converters that clip these peaks add a false brightness to the snare drum and alter its sound.

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Is MQA DOA?

May 05, 2016

The truth is that we may add MQA to the list of audio formats that have come and gone. This list includes HDCD, DVDA, and DSD. All three of these claimed to deliver some sort of sonic improvement, but all three have suffered from a lack of content. HDCD and the DVDA are dead while DSD may be on its death bed. All three were supported by hardware but have died due to a lack of recordings in these formats. It should be noted that the DVDA did bring us high resolution audio formats and these have survived while the DVDA itself has died. Two dead, one dying ... is MQA next?

It is curious that most of the claimed sonic advantages of these formats have never been proven. There are plenty of anecdotal accounts of miraculous improvements in the sound, but there is no hard evidence that people could tell the difference. If the differences are real, they are so small that they can only be resolved by the very best playback systems. Consequently, to the average music lover, the letters all blend together into some sort of meaningless alphabet soup: HDCDDVDADSDMQA...

To those of us who are interested in the best possible musical playback, the small details are important. The promise of "improved sound" always catches our attention ...

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Jitter and its Effects

February 07, 2002

By John Siau and Allen H. Burdick

 

This paper addresses these questions:

  • How and where do I measure jitter, and how do I eliminate it?
  • How does sample clock jitter relate to interface jitter measured at digital output connectors?
  • How can we accurately measure jitter?
  • Why does sample clock jitter have to be so low?

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