CHAPTER 20
Headphone Amplifiers
Driving Heavy Loads
This chapter focuses on techniques for driving loads heavier than can be handled by a single 5532 or LM4562 opamp –basically any impedance less than 500 Ω. This is typically a headphone load, the impedance of headphones varying widely from 600 Ω to 16 Ω or less, with sensitivity inversely related so the higher impedance models need more drive voltage. The need to drive impedances below 500 Ω is also likely to arise in very-low-noise designs, so that special measures have to be taken just to drive the next stage. A good example is my Preamp 2012 design for Elektor. [1] It is assumed here that the heavy loads must be driven to the same high standards of noise and distortion that are required ...
