SA610 ABB SA610 Power Supply ABB SA610 ABB SA610 ABB SA610

ABB SA610 Power Supply
 

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The 54,-610 features a 3-stage direct-coupled equalizer amplifier for greater reduction of noise and distortion. Besides the use of an ultra low-noise transistor (25C26O2) in the first stage, the adoption of low impedance input resistance and equalizer circuit has contributed to an S/N ratio of at least 82dB (at 2.5mV input, IHF-A).

This all stage direct-coupled pure complemen- taly SEPP circuit features a current mirror load differential amplifier in the first stage, and incor- porates the tone control circuit in the NFB loop.

Although the incorporation of the tone control circuits in the power amplifier stage reduces the number of elements that the signal has to pass through, and thereby further reduces noise, dis- tortion, and cost, the power stage does require a higher gain and a higher degtee of stability. In the SA-610, this high gain and high stability are achieved by a cunent mirror load differential amplifier in the first stage and by the use of a constant current circuit for the load of the pre- driver stage. Furthermore, the tendency for the pre-driver stage capacitance impedance load to cause deterioration in the high end frequency response is suppressed by inserting a capacitor (C) between the emitter of the pre-driver stage (Q2) and the base of the constant current circuit (Q1) as shown in Fig. 7-1. At frequencies where the reactance of this capacitor may be ignored, the push-pull action of Ql and Q2 serves to counteract the high end frequency response deterioration.

The power amplifier stage is a complementary 2-stage' Darlington connection, resulting in an output power rating of 45W + 45W (8Q, 20Hz- 2OkHz, harmonic distortion of less than O.O37o (20H2 20kHz at rated output), and output power bandwidth of 5Hz - 50kHz (0.O3% THD). Certainly a superb performance for an amplifier of this class is obtained.

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