Zero Delta Amplifiers

Zero Delta amplifiers are ultra low distortion amplifiers.

The most significant advantage of Zero Delta amplifiers is low distortion. Other advantages are high efficiency and automatic biasing which eliminates the need for bias alignment. The advantages come at a cost of high component count.

It is common for high end amplifier designers to substantially eliminate distortion caused by symmetrical input signals. They test this with test sets that inject sine waves. However distortion caused by asymmetrical input signals is not reduced by any of the measures used by amplifier designers and does not show up in distortion measurements based on sine wave input signals.

In the real world, amplifiers are fed with music or movie sound tracks which are substantially asymmetrical. If, for example, with a conventional amplifier, one cycle is biased towards the positive the positive device will instantaneously heat more than the negative device causing a different bias current during each part of the cycle. The result is distortion which in high end amplifiers is typically much greater than the measured distortion. The thermal feedback mechanism in conventional amplifiers is of the order of seconds and so has no chance of correcting the problem.

In Zero Delta amplifiers bias current is instantaneously corrected so that regardless of asymmetrical input signals output devices receive identical bias currents regardless of their individual die temperatures. Zero Delta amplifiers have a control system that utilises a feedback signal with low harmonic content so that the control is well within the gain bandwidth constraints of the control circuit to ensure high accuracy.

With conventional high end amplifiers asymmetrical distortion manifests as loss of definition particularly with short duration percussive sounds. With Zero Delta amplifiers the improvement in clarity is significant.