Stereo Power Amplifier (1974)
Unique design features incorporated into the Model 500D make it virtually fail-safe and free from accidental damage caused by human error in audio service.
A fast acting SCR (silicon controlled rectifier) crow bar is employed as a safeguard for your speakers.
The sophisticated sensing circuitry for the crow bar constantly samples the individual outputs of each channel.
The outputs of each channel are integrated and passed through an absolute value detector.
The output of the detector is connected to a comparator which is activated by the presence of a large DC component.
If such a value is present, the comparator in turn triggers a fast discharge pulse circuit which gates the SCR crow bar.
The crow bar is essentially a direct short placed across the two power supplies and this activates the circuit breaker.
Power output: 200 watts per channel into 8Ω (stereo), 501W into 8Ω (mono)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.1%
Damping factor: 200
Gain: 26 dB
Input sensitivity: 2V
Signal to noise ratio: 110dB
Speaker load impedance: 2Ω (minimum)
Semiconductors: 2 x IC, 37 x transistors, 1 x unijunction transistor, 1 x thyristor, 5 x zener diodes, 19 x diodes
Dimensions: 7 x 19 x 12 inches
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