Hi-Fi power amplifier circuit and power supply circuit

Hi-Fi power amplifier circuit and power supply circuit

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As indicated in the chart (from 20W to 80W RMS).

Some explanations:

- The first thing you have to do is test the amplification factor hfe or β of the last power tube. If their difference is greater than 30%, the amplifier will not give you a clear sound. I am using MJ3001 and MJ2501 transistors, their The difference is 5%.

- Before turning on the power, you must short-circuit the input, string an ammeter at the output of the amplifier, then turn on the power, adjust R13 to make the ammeter current to microampere level, if you are lucky enough, you can reach 0, the ammeter current is 10 Microamperes are easy to do.

Power amplifier circuit diagram:

Hi-Fi power amplifier circuit and power supply circuit

Power circuit:

Component and attribute table:


20 / 35 W

25 / 40 W

35 / 60 W

50 / 80 W

80 / 125 W

T1

BC546

T2

BC556

T3 (PNP Darlington)

BD898, BD678

BD896, BD676

BDX34

MJ900G

2N6052, MJ2501

T4 (NPN Darlington)

BD897, BD677

BD895, BD675

BDX33

MJ1000G

2N6059, MJ3001

C1

10 to 12 pF

C2

4.7 to 5.6 nF

C3 (no polarity capacitor)

1 to 10 uF

C4, C5

2200 uF / 35 V

4700 uF / 35 V

4700 uF / 35 V

4700 uF / 50 V

4700 uF / 50 V

R1, R2, R9, R12

10 kΩ

R3, R4, R5, R6, R14, R15

3.3 kΩ

R7, R8

680 Ω

R10

100 kΩ

R11

47 kΩ

R13 (fine tuning resistor)

10 kΩ

F1 (fast)

1,2 A

1,6 A

2 A

2,2 A

4 A

BR1

B40C1500

B40C2000

B40C2800

B40C3200

B40C5000

Cooler

4,5

2,7

2,0

1,7

1,5

Transformer secondary voltage (± 20 %)

20 + 20 V

20 + 20 V

20 + 20 V

22 + 22 V

22 + 22 V

Transformer secondary current

0,8 A

1,2 A

1,3 A

1,5 A

2,5 A

Power (RMS)

20 W

25 W

35 W

50 W

80 W

Music power

35 W

40 W

60 W

80 W

125 W

Minimum speaker impedance

8 Ω

8 Ω

8 Ω

8 Ω

4 Ω

Supply voltage (± 20 %)

± 25 V

± 25 V

± 25 V

± 30 V

± 30 V

Maximum current

0,54 A

0,85 A

1,0 A

1,15 A

2,0 A

Input voltage required for maximum power

1,8 V

1,5 V

1,7 V

1,95 V

1,7 V

input resistance

10 kΩ

Bandwidth (-3 dB)

0 – 100.000 Hz

THD at 1⁄2 P

0,04 %

THD at Psin

Max 0,18 %

Frequency response

93 dB

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