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The "0-Ohm" Headphone Amplifier

by John Siau December 01, 2001 1 min read

The "0-Ohm" Headphone Amplifier

The Sonic Advantages of Low-Impedance Headphone Amplifiers

- 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 essentially miniature power amplifiers.

This paper provides measurements which demonstrate the significant advantages of headphone amplifiers with very low (near 0-Ohm) output impedances. A low output impedance increases the damping factor of the amplifier-headphone system. This paper will show that a high damping factor reduces distortion at the headphone input, improves the phase response, and flattens the frequency response.

Download the White Paper:

The "0"-Ohm Headphone Amplifier - John Siau 

Additional reading:

More information on headphones and headphone amplifiers can be found here.



Also in Audio Application Notes

System Performance Calculations
System Performance Calculations

by John Siau March 02, 2023 13 min read

If an audio system is composed of multiple components, we may have detailed specifications for each component, but we will not know the performance of the combined system without doing some calculations. You may have questions such as these:

  • Will my audio system produce audible noise?
  • Will my audio system produce audible distortion?
  • How will my audio components work together as a system?
  • How loud will my audio system play?

Use Benchmark's online audio calculators to find answers!

For example, if we know the output power of an amplifier, as well as the sensitivity and impedance of our loudspeakers, we can calculate the maximum sound pressure level that our system can produce.

PEAK SPL CALCULATOR
Speaker Sensitivity: dB SPL (2.83 V, 1 M)
Amplifier Power Per Channel into 8 Ohms: Watts
RESULTS
Peak Output Level (at typical listening position): dB SPL

 

This application note provides interactive examples that help to answer the questions listed above.

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by John Siau November 29, 2022 1 min read

We have added an "Audio Calculators" section to our webpage. Click "Calculators" on the top menu to see more like these:

 

THD % to dB Converter
% THD
RESULTS
dB THD
THD dB to % Converter
dB THD
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SECRETS Q&A WITH JOHN SIAU OF BENCHMARK MEDIA SYSTEMS
SECRETS Q&A WITH JOHN SIAU OF BENCHMARK MEDIA SYSTEMS

by Benchmark Media Systems January 07, 2022 1 min read

Secrets contributor Sumit Chawla recently caught up with Benchmark’s VP and Chief Designer, John Siau to get a little more in-depth on several subjects.

John Siau, VP Engineering, Benchmark Media Systems, Inc.

Q: "Benchmark is one of the few companies that publishes an extensive set of measurements, but you also balance that with subjective testing. Can you talk about the equipment, the listening room, and the process for subjective testing?"

Q: "Was there ever a time where you learned something from a subjective test that was not captured by measurements?"

Q: "You conducted some listening tests to determine whether distortion in the “First Watt” was audible. What test material did you use for this, and what did you find?"

Q: "The AHB2 amplifier incorporates THX Audio Achromatic Amplifier technology. When and how did the partnership with THX come about?"

Q: "Linear power supplies have been and remain quite popular in high-end devices. You favor switch-mode power supplies. When and why did you make this switch?"

... and more!

Read the full interview here 

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