24
The electrostatic treble unit
Electrostatic units are amongst the oldest loudspeaker
technologies. In its basic form a featherlight membrane
(in our electrostatic units only a few µm thick) is charged
electrically and held between two electrodes, to which
the music signal is fed at a high voltage.
The foil is driven homogeneously over its entire surface,
and for this reason is free of any tendency towards parti-
al vibration. With its low mass the foil is practically iner-
tia-free, endowing the electrostatic device with a virtually
perfect transient response. The extremely high upper
limit frequency (> 70,000 Hz) of these systems is almost
beyond the reach of conventional dynamic loudspeaker
systems.
These are the reasons why
has developed an
electrostatic treble unit, which is built using sophisticated
precision tooling. In this speaker the potential
advantages of all electrostatic drivers - superb dynamic
characteristics, transparency, lightness and luminosity -
are brought fully to fruition.
The curvature of the foil membrane produces a linear
frequency response even under large off-axis listening
angles of up to +/- 30°.
Electrostatic drivers require a power supply to charge up
the foil membrane, and that is why the
TCI
1 RE
and
TCI
2 E
feature a mains power input. In the
TCI
2 E
the
amplifier signal is driven to high voltage using a repeater,
whereas in the
TCI
1 RE
a new valve output stage drives
it directly.
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
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 suspen-
sion 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 deterio-
ration in the valves, which therefore have no adverse
consequences on performance. Thanks to this innovative
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 per-
formance of the
TCI
1 RE
.
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