The GAT Preamplifier is a vacuum-tube, line-stage preamplifier that looks as good as it sounds. It is also notable for convenience and ease of use. The unit features input selection and level adjustment by microprocessor-controlled relays. Level and balance can be adjusted in 100 steps of approximately .7 dB per step. All functions can be controlled by the hand-held wireless remote control.
The circuitry of the GAT Preamplifier is elegant in its simplicity. The audio circuit consists of a single amplifier stage incorporating one composite triode comprised of paralleled sections of a high-transconductance miniature dual triode vacuum tube. This amplifier stage is coupled to the preamplifier outputs through a high-current MOSFET buffer, which achieves a very low output impedance, making the GAT extremely flexible in the choice of interconnect cables and amplifiers. DC voltage is supplied to the circuit by our latest discrete voltage regulator that isolates the audio circuit from the power line by maintaining negligible impedance across the audio frequency band. Infrasonic noise is minimized by operating the tube filaments (heaters) on a dc voltage supplied by another discrete regulated power supply.
Considerable care and attention have been paid to the physical aspects of the design as well.
Microprocessor controlled relays, used for selecting sources and level setting, are located right at the input connectors, keeping signal paths short to minimize crosstalk between channels and inputs. The vacuum-tubes are isolated by a suspension system designed to minimize microphonics. The dramatic casework features attractive clear Lucite tube guards outside the chassis, allowing for easy access for tube replacement.
At conrad-johnson we have long appreciated that the full potential of any circuit can only be realized by using the finest available parts.
Each part for the GAT has been selected on the basis of both sonic performance and durability.
The audio circuit (including the level control) is executed entirely with precision metal foil resistors and proprietary CJD Teflon capacitors. Tubes have been carefully hand selected for minimum noise and microphonics. The dc regulated power supplies use the same quality resistors as the audio circuits. Capacitors for the power supplies are exclusively polypropylene and Teflon – there are no electrolytic capacitors in the audio circuits or their related power supplies. All signal switching is done by special relays designed for signal applications. These relays are sealed and have gold plated silver contacts. Input and output connectors are machined from oxygen free copper, and are gold plated. The GAT is built without compromise to achieve a new standard in musical performance, and it is built to last.
