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The cross-over unit
A very sophisticated, low-loss passive FSR cross-over
unit (FSR = Fast Signal Response) adjusts the combina-
tion of electrostatic unit and valve output stage
(TCI 1 RE), and of electrostatic unit and repeater
(TCI 2 E), to match the output of the other sub-systems
in the loudspeaker.
The circuit boards of these cross-over units feature a
large-area copper layer on the top surface whose sole
purpose is to act as the earth conductor.
The copper tracks on the underside connect the compo-
nents with each other. This layout ensures that the criti-
cal earth reference potential is not falsified by the large
signal currents which flow. The usual voltage losses
caused by narrow conductor tracks do not occur in this
design, which means that much higher currents can
safely be used. Undesired effects on signals such as
inter-modulation or cross-talk between the individual
tracks are also minimised.
The components of the cross-over unit are extremely
low-resistance types, and are designed to minimise los-
ses.
The large capacitance required is implemented in the
form of several small capacitors wired in parallel, as this
arrangement reduces series inductivity and resistance,
and also improves slew rates. All these design features
are aimed at obtaining maximum possible signal fidelity.
To reduce the distortion which can arise with large cur-
rents, virtually all the coils are of the air-core type.
High-quality cable is employed for all internal wiring
inside the cabinets.