Audio Research Dual 50 (1969-73)

Performance

Ultra-stable -

Ideally suited for complex loads such as electrostatic speakers. (May be operated into open circuit or any combination of reactive and/or resistive load.)

Unique circuitry -

Delivers superior performance under dynamics of music .

Overload Stability -

And lack of crossover distortion provides clean effective loudness of much larger amplifier.

Features

Exclusive new circuitry (U.S. Patent No. 768,460)

Conservative specifications

Quality construction

-1/8" anodized aluminum chassis

-Silicon power supply

-Thermistor controlled warmup

-Choke filtering

-Heavy duty epoxy-glass circuit board

-Conservative design

-Many precision parts

-Extra quality components

Unique guarantee

Although the information presented above provides definite clues to its outstanding performance, this amplifier employs design concepts for performance that does not readily translate from conventionally offered criteria.

Such common amplifier ills as crossover distortion, poor push-pull coupling, and power supply weaknesses are not necessarily revealed by conventional sine wave testing. In the Dual 50 design, special emphasis has been placed upon the ability to handle complex - wide dynamic range musical information into complex loads, resulting in definition previously unattainable.

Definition is not a characteristic normally associated with audio amplifiers. It cannot be measured as a identifiable quantity; it cannot be expressed in dB, watts or hertz. Definition in audio can be compared to "resolution" in photography. It is the accurate portrayal of teh original image, the faithful reproduction of both shape and texture. A high definition amplifier will reproduce the featheryhalo high of the tumpet, the delicate rasp of the violin and the sharp instantaneous attack of the piano. It will recreate characteristic tone and color not only when the instruments are played individually, but when played in combination as well, whether that combination be a jazz quartette or a full symphony orchestra.

The Dual 50 amplifier employs a partially cathode coupled output stage, providing tighter coupling and lower distortion than conventional circuitries. This is preceded by a unique new cross-coupled circuit which provides (a) very tight push-pull coupling, (b) balanced low distortiondrive, and (c) very stable long-term automatic balance. Push-pull feedback is employed around these stages. The phase inverter is also a very low-distortion automatically balancing circuit and is voltage regulated (together with the first stage of the cross-coupled circuit). It is also excluded from the overall feedback loop. Finally, an oversized power supply is used. These provisions insure its ability to perform properly regardless of signal levels or external load conditions.

Specifications

Power output: 50 watts RMS per channel, 30 Hz-15 kHz

Frequency response: 25 Hz - 20 kHz ±1 dB at 50W RMS

Input sensitivity: 1.15V RMS for 50W RMS output

Input impedance: 500 kΩ

Output taps: 4, 8 and 16 Ω

Load regulation: Approximately 1/2 dB/1 kHz - 1 dB/15 kHz

Damping factor: Approximately 14 to 1 kHz

Internal impedance: Approximately 1,1 Ω/16 Ω tap to 1 kHz

Distortion: Less than 0.1%, 1 kHz/50W RMS

Rise time: Approximately 20 µs

Hum & noise: 90 dB below rated output

Power requirements: 117 V 50/60 Hz, approximately 200 watts at idle, approximately 325 watts at full power

Tube complement: (2 matched pairs) GE6L6/KT-66/EL34, (3) 12AX7, (2) QA2, (4) 6FQ7

Dimensions (W x D x H): 16" x 9 1/4" x 7 1/2"

Weight: 38 lbs. Net, 45 lbs. Shipping