Calculating the Performance of an Amplifier/Speaker Combination

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.

Our Test System - AHB2 Driving PMC IB2S Studio Monitors

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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Speaker Sensitivity

Speaker sensitivity is a measure of how loud a speaker will play at a given input power or at a given input voltage. Sensitivity is normally measured with a 1 watt power input or a 2.83 Vrms voltage input.

There have been many different speaker designs over the years and there are vast differences in speaker sensitivity. The speakers below have sensitivities ranging from about 85 dB to 109 dB.

  • What are the power requirements?
  • What are the implications for system noise?
  • How loud will each play?
  • Do they require different amplifiers?

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Audio Myths - The Ultimate "Myth Buster" Video

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

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!

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. 

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Power Amplifiers - A "First Watt" ABX Test

In Benchmark's listening room we recently demonstrated the importance of the first watt using two 100 watt stereo power amplifiers. One amplifier was a traditional class-AB amplifier, the other was Benchmark's AHB2 power amplifier with feed-forward error correction. Using a double-blind ABX test, we verified that there was a clearly audible difference when the amplifiers drove speakers at an output level of 0.01 watt.

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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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DAC2 Firmware Update 2.X

Benchmark has recently updated the firmware on the DAC2 HGC and DAC2 L audio D/A converters. This update is available as a field installable kit.

Most Benchmark products have programmable hardware. We use Xilinx FPGA devices (field-programmable gate arrays). These devices provide high-speed high-density digital signal processing, signal routing, and system control. The entire user interface is also controlled by the FPGA. This programmable-hardware architecture provides generous space for system updates, audio decoders, digital filters and other enhancements.

This application note explains the performance and feature changes in version 2.X.

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Power Supplies in Audio D/A Converters

The Benchmark DAC2 is an audio digital-to-analog converter. This application note explains the power supply configuration inside Benchmark's DAC2 D/A converter. In part 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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Digital Processing in Audio D/A Converters

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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