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in reducing the inherently low output impedance of the output stage in the usual way, being
unaffected by the addition of the displacer.
So while the constant-current displacement method is simple and effective, the push-pull version of
crossover displacement has many advantageous and was preferred for the best linearity and
efficiency; the extra control circuitry developed was relatively simple and works at low power so
adding relatively minimally to total amplifier cost.
Performance
Measurements are presented here to demonstrate how the crossover displacement principle
reduces distortion in reality.
Fig 9: THD vs. frequency for a Class B amplifier at 30W/8 Ohm. (604b)
Firstly, as a reference, the results obtainable from well-implemented Class B amplifier, Fig 9 shows
THD vs. frequency for a Class B amplifier giving 30W into 8 Ohms. The distortion shown only
emerges from the noise floor at 2 kHz, and is wholly due to the inherent crossover artefacts; the
bias is optimal, so this is essentially as good as Class B gets. The distortion only gets really clear
