Hi-Fi power amplifier circuit (with BOM)
This is a simple low success rate amplifier. You can complete her in 5 ways, as indicated in the chart (from 20W to 80W RMS).
Explanatory notes:-The first thing you have to do is to test the amplification factor of the final power tube hfe or β. If their difference is greater than 30%, the amplifier will not provide you with a clear sound, I use MJ3001 and MJ2501 transistors , Their difference is 5%.
-Before turning on the power, you must short-circuit the input terminal, connect an ammeter to the output of the amplifier, and then turn on the power, adjust R13 to make the ammeter current to microampere level, if you are lucky enough, you may be able to reach 0, the ammeter current is 10 Microamps are easy to do.
Power amplifier circuit diagram:
Power circuit:
Components and parameter 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 ～ 12 pF | ||||
C2 | 4.7 to 5.6 nF | ||||
C3 (non-polarized capacitor) | 1 ～ 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 (trimmer 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 |
Required input voltage at 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 ½ P | 0,04% | ||||
THD at Psin | max 0,18% | ||||
Frequency response | 93 dB | ||||
This amplifier has very good sound quality.
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