Accuphase A 30 Brochure

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Accuphase A 30 Brochure

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lower, so that each device is driven only in its low- power range where linearity is excellent. A music signal consists of a continuous succession of pulse waveforms. To prevent clipping on occasional momentary high-level pulses, the maximum clipping level of the A-30 is set to 50 watts per channel into 8 ohms (sine wave output). Current feedback circuit topology assures excellent phase characteristics in high range In the A-30, the signal current rather than the more conventionally used voltage is used for feedback. Since the impedance at the current feedback point (current adder in Figure 3) is very low, there is almost BufferCurrent adder I-V converter Trans-impedance amplifier Amplifier Output Current NFB network – Input Buffer + Input Gain(Large) (High) Frequency no phase shift. Phase compensation therefore can be kept at a minimum. A minimal amount of NFB results in maximum improvement of circuit parameters. The result is excellent transient response and superb sonic transparency,coupled with utterly natural energy balance. Figure 4 shows frequency response for different gain settings of the current feedback amplifier. The graphs demonstrate that response remains uniform over a wide range. Robust power supply with large power transformer and high filtering capacity In any amplifier, the power supply plays a vital role since it acts as the original source for the output delivered to the speaker. The A-30 employs a large and highly efficient 400 VA power transformer. It ishoused in an enclosure filled with a material that transmits heat and absorbs vibrations. This completely prevents any adverse influences on other circuit parts. Two aluminum electrolytic capacitors rated for 47,000 µF each serve to smooth out the pulsating direct current from the rectifier, providing more than ample filtering capacity. Fig. 3 Principle of current feedback amplifier Fig. 4 Frequency response with current feedback(Response remains uniform also when gain changes) n Power amplifier assembly with three parallel push-pull power MOS-FET pairs per channel mounted directly to large heat sink, MCS+ circuitry, and current feedback amplifier