The 440A is a HH SCOTT ‘S audio amplifier in the late 70’s.

With a symmetrical 47VDC supply voltage this amp is able to produce the audio up to 55 Watts of power at a load of 8 Ohms.

INFO

The amplifier is a luxury amp of its era with many interesting accessories. VU Diplay is mounted on the front box of this amplifier for monitoring the output power of the amplifier.

Tone control consists of 3 potentiometers to adjust the TREBLE, MIDDLE and BASS tones.

Amplifier already has a protection feature against DC voltage to the speaker as well as protection against overcurrent on the power transistor.

SCHEMATIC

Berikut ini adalah skema hasil pangkasan dan edit dari skema aslinya.

Power Section of HH SCOTT 440A

The input signal goes to transistor Q1 ( 2SA798).

Furthermore, from the collector Q1 goes to Q7 which serves as a VAS.

This signal will then be amplified by the Q17 Q19 transistor which serves as the amplifier driver.

While Q9, Q11, Q13 and Q15 are transistors whose job is to keep excess current from the final amplifier transistor.

The last boosters are Q21 and Q23.

NOTE

The GAIN of the amplifier is determined by the ratio of the feedback resistor ( R11 ) to the input resistor ( R11 ).

This amp uses 2 supply voltages, the first is symmetric 47VDC for the Driver ,Power blocks and secondly is 22 VDC asymmetrical to provide supply to the differential amplifier preamp block.

The 2SD588 and 2SB618 are able of producing until 80 Watts of output power ( SOURCE ).

2SD688 2SB618

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