Design And Construction Of A Stereo Headphone Amplifier

ABSTRACT

Headphone amplifier drives headphones instead of loudspeakers. Most commonly they are found embedded in electronic devices such as integrated amplifiers, portable music players and televisions, but standalone units are not uncommon.

Headphone amplifier can provide the voltage levels necessary to drive the headphones. Most headphone amplifiers provide power between 10 mW and 2 W depending on the specific headphone being used and the design of the amplifier. Certain high power designs can provide up to 6W of power into low impedance loads, although the benefit of such power output with headphones is unclear, as the few headphones that have sufficiently low sensitivities to function with such power levels will reach dangerously high volume levels with such amplifiers.

CHAPTER ONE

1.1                                                        INTRODUCTION

A headphone amplifier is a low-powered audio amplifier designed particularly to drive headphones worn on or in the ears, instead of loudspeakers in speaker enclosures. Most commonly, headphone amplifiers are found embedded in electronic devices that have a headphone jack, such as integrated amplifiers, portable music players (e.g., iPods), and televisions.

Effectively, a headphone amplifier is a small power amplifier that can be connected to a standard headphone jack or the line output of an audio source. Electrically, a headphone amplifier can be thought of as an amplifier that presents a very high input impedance and presents a lower output impedance and larger range of output voltages. This allows headphones of a low sensitivity to be driven louder as a result of the extra voltage provided by the amplifier. There is potential fidelity gains if headphones are driven with lower distortion than using a headphone amplifier integrated into a general purpose audio product. In practice, this most often occurs when using low impedance headphones with consumer electronics with insufficiently low output impedance.

1.2                                             OBJECTIVE OF THE PROJECT

The objective is to design a benchmark performance and low cost amplifier used in powering headphone. Headphone amplifiers are found embedded in electronic devices that have a headphone jack, such as integrated amplifiers, portable music players, and televisions.

1.3                                         SIGNIFICANCE OF THE PROJECT

Just like a good room speaker can improve when partnered with a great power amp, a headphone is a miniature speaker system that can benefit from a headphone amp to sound its best.

With headphones, an uncompressed music source and a great headphone amp, you’ll be astonished at the level of pure clarity, huge dynamic range and deep musical detail you’ll be able to hear.

Big speaker systems may out-perform headphones in terms of visceral sonic impact; great headphones can deliver much superior audio resolution and access to nuanced low-level information obscured in the recording.

1.4                                          APPLICATION OF THE PROJECT

This device is found embedded in electronic devices such as integrated amplifiers, portable music players and televisions, for the listen pleasure of the user.

1.5                                                 SCOPE OF THE PROJECT

This headphone amplifier circuit design is normally used to drive a headphone with relative low impedance. It provides one watt power output and it can also be applied as an output stage for preamplifiers in conjunction with active loudspeakers boxes. The headphone amp is composed of an OP-AMP and an additional transistor amplifier. Input signals pass through a low pass filter composed of resistor and capacitor. Its amplification together with a relatively “fast” OPAMP provides a low distortion factor.