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Thöress

Thöress

Thöress 845 Power Amplifier

The most powerful amplifier of our product line...is equipped with the highly regarded 845 power triode and is capable of delivering up to 20 watts of power into a 4, 8 or 16 ohm load. The zero-feedback circuit incorporates an extraordinary single-stage driver topology employing two EL803S power pentodes operated in triode mode. The driver stage is so powerful that it could (theoretically) drive a loudspeaker with ultra-low distortion on its own. The amplifier is entirely hard-wired, while every detail of the internal construction has been given carefull attention to ensure reliability and ease of service. The sound of our “flagship” is of utmost refinement and will easily measure up to the expectations of even the most critical and experienced music enthusiast. Of special importance are several key design features which provide exceptionally noise-free performance even when highly efficient speakers are in use: DC heating is provided for the power tube, whereas any residual hum introduced by the heater circuit may be balanced out by adjusting a control knob on the rear panel of the case. Furthermore, the input sensitivity of the amplifier is relatively low, so as to keep the preamplifier’s “idle” noise within inaudible limits. (This design choice has the further benefit of avoiding the problems of channel imbalance and sub-optimal frequency response which often result when the preamplifier’s potentiometers rest at too low an angle of rotation.) Also, the mains transformer is mechanically decoupled from the amplifier case by means of damper units to prevent residual transformer vibration from interacting with sensitive parts of the amplifier.

1.Reliable output transformer with tape-wound cut core. 2.Precise 4, 8 and 16 Ohm loadspeaker load matching. Typical for all our mono power amplifiers is the following no-compromise approach: Mains transformers, output transformers and filter chokes are produced in-house to ensure the highest performance.The output transformers feature tape wound cut cores (C-cores) and allow for precise matching of a 4, 8 or 16 ohm load impedance to the power tube by way of jumpers soldered to the secondary terminals. All used rectifier diodes are of smoothly switching shottky type, while high grade foil-in-oil capacitors are used for the high-tension supply.