For four decades, the conrad-johnson design team has been dedicated to creating audio components that do credit to music performances. Through meticulous engineering, careful specification of only the finest available component parts, and a painstaking attention to construction, they have created a line-stage without rival in its class: the ET7-S2 Enhanced-Triode Preamplifier Designed to incorporate the advances made with the Series 2 upgrade to their flagship GAT into a more affordable model, the ET7-S2 also boasts the GATs convenience and ease of use. The unit features input selection and level adjustment by microprocessor-controlled relays, with controls available both at the front panel and via a full-function remote. All control functions of the ET7-S2 operate through microprocessor-controlled relays. For the level control, the relays select combinations from a network of precision, low-noise metal foil resistors to effect loudness and balance changes in 100 steps of approximately .7dB per step. All switching and adjustment can be controlled by the units remote control. A Theater Mode, which passes the input signal through at unity gain, makes it simple to incorporate the ET7-S2 into a high quality home theater system without compromising its two-channel performance. The circuitry of the ET7-S2 closely follows that of the GAT Series 2. The audio circuit is elegant in its simplicity. An audio amplifier stage consisting of a single-ended triode amplifier provides the voltage gain. This amplifier stage is connected to the preamplifier outputs through a high-current MOSFET buffer, which achieves a very low output impedance, making the ET7-S2 extremely flexible in the choice of interconnect cables and amplifiers. DC voltage is supplied to the circuit by the revised discrete voltage regulator developed for the GAT Series 2. It isolates the audio circuit from the power line by maintaining negligible impedance across the audio frequency band. Infra-sonic noise is minimized by operating the tube filaments (heaters) on a dc voltage supplied by a separate regulated power supply. Like its bigger brother, the GAT Series 2, the ET7-S2 is constructed from the highest quality, carefully selected parts for unrivaled sonic performance and reliability. Tubes have been selected for minimum noise and microphonics. CJD Teflon capacitors are used in the ET7-S2 for output coupling and post-regulator power supply storage. In the power supplies, all capacitors are of polypropylene or Teflonthere are no electrolytic capacitors anywhere in the audio circuits or their DC power supplies. The resistors in these circuits (including the two dozen level control resistors) are special low inductance, high-precision laser-trimmed metal foil resistors. Switches are sealed relays with gold-plated silver contacts. Input and output connectors are machined from oxygen-free copper, and are gold plated. As Alan Sircom (hifi+) says: The ET7-S2 is a remarkable improvement over the ET7; one that takes the performance even closer to that of the GAT-S2. The baby GAT is all growed up and it isnt a baby anymore. The improvements brought about by the additional power supply (and presumably the connectors) give an already graceful sounding preamplifier prima ballerina poise but coupled with an ability to thwack and growl with the best of them when needed. Its good enough that prospective GAT-S2 owners might ask themselves some very difficult questions before paying much more for the big hitter Read Alan Sircoms review of the ET7-S2 line stage preamplifier in Issue 179 of HiFi+.
