Headphone Amplifier

There is little doubt that the headphone amplifier de- scribed here belongs in the so- called high end class of audio equipment, and is, therefore, perfect for incorporation in, or adding to, the Top-of-the-range Preamplifier described in (1), although it is also suitable as an autonomous, high quality, unit. The circuit diagram of the head- phone amplifier appears in Fig. 1. The unit is based on Type OP-50 power operational amplifiers, whose technical features are summarized in Table 1. Clearly, everything feasible has been done by the manufacturers, Precision Mono- lithics Inc., to ensure optimum operation of the device, and it is with this in mind that the re- mainder of the amplifier was designed. Both supply rails to the ampli- fier ICs are adequately decoupled and filtered with a small series resistor, (R4-R5) and a combination of an electrolytic and a solid capacitor (C4-C2 and Cs-C3). With reference to the upper of the two identical chan- nels, preset P2 enables com- pensa...