Studio stereo headphone amplifier

Studio Stereo Headphone Amplifier

This is a high-quality audio dual/stereo headphone amplifier built around the OPA2134. This headphone amplifier can drive high or low impedance headphones with low noise and distortion. When used with line-level signals from CD/MP3 players, only a power supply and volume potentiometer are required.

Many high-power amplifier audio designs already include headphone outputs. To support simple headphones, additional circuitry is needed by connecting two resistors in series only at the speaker output to limit the drive current and protect the headphones in case of failure.

Given its simplicity, this resistor-limited current-limiting scheme works well, although it can introduce distortion if the load is non-linear—which is likely the case for most headphones. Besides eliminating potential sources of distortion, there are several other reasons you might consider building a separate headphone amplifier.

First of all, not everyone owns a pair of headphones or even a top-of-the-line high-performance amplifier. After all, an amplifier with performance equal to or better than this new headphone amplifier would cost you a considerable amount of money!

Another reason might be its use in the latest "high-tech" audio electronics. Many headphone outputs in these devices cannot drive low-impedance headphones—or at least not to a decent listening level. Furthermore, the available output power in portable devices is intentionally limited to conserve battery power. This means that even with sensitive headphones, significant distortion can occur at higher listening levels.

One way to solve this problem is to feed the line-level output of such devices into your power amplifier and then plug low-impedance headphones into it. That works, but then you're tied to a stationary device. Furthermore, the power required to drive headphones is about 1/1000th of the power required to drive speakers, so a large power amplifier might be a bit too much for this task.