The valve output stage

In contrast to conventional transistor power amplifiers, valve output stages can be used to process the high voltages required by the electrostatic unit directly. If valve technology is employed, repeaters are not required to convert the low output voltage of transistor output stages.

For this reason it is only logical that T+A has developed a completely new push-pull Class A valve output stage for use with the electrostatic driver fitted to the TCI 1 RE. The output stage employs the EL34 pentode valve, renowned for its superbly linear response and its fantastically high-quality, harmonious sound character.

The tremendous transparency and lightness of the electrostatic treble unit’s sound can only be exploited to the full by this superb new valve-based output stage. The unbeatable speed of valve technology is reflected in the output stage’s sensational slew rate of 400 V/µs. This value is better than the figures achieved by current transistor amplifiers by a factor of around 10.

The valve output stage is de-coupled from all external influences by a highly sophisticated mechanical suspension system (spring sub-chassis with three graduated levels of spatial clearance).

The working point of the output valves is monitored and automatically corrected by a precision regulatory circuit. This circuit compensates for ageing effects and deterioration in the valves, which therefore have no adverse consequences on performance. Thanks to this innovative T+A development the valves can be used right to the end of their life (approx. 10 ... 15 years) without any danger of changes to the sound.

The unique combination of outstanding characteristics derived from the valve output stage and the electrostatic driver is the key to the unparalleled high-frequency performance of the TCI 1 RE.