ACOUSTIC RESEARCH X10 POWER SECTION

ACOUSTIC RESEARCH X10 is a name of an AM/FM receiver that include a Power Amplifier inside. Its able to amplify up to 100 Watts of audio power at 8 Ohm loads.

FM radio, which is has a better character than AM radio, was the best folk entertainment in mainland Europe and the United States in the 80’s.
Of course Ausio Research participated in making this equippment to entertain people.

SCHEMATIC DIAGRAM

After getting the schematic, I must to redraw the receiver’s schematic because they are blurry image quality wasn’t that great.

Here is a redraw of this amplifier with a few edits.

From this schematic we can see that the power amplifier circuit has a circuit blocks:

Preamplifier, with transistor C2259 as differential amplifier.

Q503 as a current mirror transistor to deliver current to Q9.

At the VAS output we could see that there is a pair of zener diodes (ZD503 and ZD506) whose job is to reduce the voltage between the two VAS transistors (Q5 and Q9).

After that, Q507 is a servo driver transistor located in the same heatsink of the power transistor as act to prevent overheating of the Final power transistor.

Next is the amplifier driver block whose their job is to amplify the current from the Voltage Amplifier Stages at a higher current: Q511 and Q513.

The last is the transistor power amplifier Q518 to Q521 which uses 2 pairs of power transistors C3519A and A1386A.

NOTE

The GAIN of this circuit is determined by R547 and (R517+R519).

It using a 22 VDC voltage stabilizer for the preamp circuit by zener diode ZD501.

By using a 52VDC supply on the power amplifier, it is possible for the transistor to produce up to 122 Watts of audio power at a load of 8 Ohms per channel or 240 Watts at a load of 4 Ohms per channel.

The power transistors they use have a power of up to 130 Watts or 260 Watts in total power output.

( DATASHEETS )