25 Watt Audio Amplifier Circuits Diagram

25 Watt Audio Amplifier Circuits Diagram

Parts:

R1,R4_________47K  1/4W Resistors

R2____________4K7  1/4W Resistor

R3____________1K5  1/4W Resistor

R5__________390R   1/4W Resistor

R6__________470R   1/4W Resistor

R7___________33K   1/4W Resistor

R8__________150K   1/4W Resistor

R9___________15K   1/4W Resistor

R10__________27R   1/4W Resistor

R11_________500R   1/2W Trimmer Cermet

R12,R13,R16__10R   1/4W Resistors

R14,R15_____220R   1/4W Resistors

R17___________8R2    2W Resistor

R18____________R22   4W Resistor (wirewound)

C1___________470nF  63V Polyester Capacitor

C2___________330pF  63V Polystyrene Capacitor

C3,C5________470µF  63V Electrolytic Capacitors

C4,C6,C8,C11_100nF  63V Polyester Capacitors

C7___________100µF  25V Electrolytic Capacitor

C9____________10pF  63V Polystyrene Capacitor

C10____________1µF  63V Polyester Capacitor

Q1-Q5______BC560C   45V 100mA Low noise High gain PNP Transistors

Q6_________BD140    80V 1.5A PNP Transistor

Q7_________BD139    80V 1.5A NPN Transistor

Q8_________IRF530  100V 14A N-Channel Hexfet Transistor

Q9_________IRF9530 100V 12A P-Channel Hexfet Transistor

Power supply circuit diagram

Parts:

R1____________3K3  1/2W Resistor C1___________10nF 1000V Polyester CapacitorC2,C3______4700µF   50V Electrolytic CapacitorsC4,C5_______100nF   63V Polyester Capacitors D1__________200V 8A Diode bridgeD2__________5mm. Red LED F1,F2_______3.15A Fuses with sockets T1__________220V Primary, 25 + 25V Secondary 120VA Mains transformer PL1_________Male Mains plug SW1_________SPST Mains switch

Notes:

• Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need.
• Q6 & Q7 must have a small U-shaped heatsink.
• Q8 & Q9 must be mounted on heatsink.
• Adjust R11 to set quiescent current at 100mA (best measured with an Avo-meter connected in series to Q8 Drain) with no input signal.
• A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 to output ground. Then connect separately the input and output grounds to power supply ground.
• An earlier prototype of this amplifier was recently inspected and tested again after 15 years of use.

Technical data:

Output power:

well in excess of 25 Watt RMS @ 8 Ohm (1KHz sine wave)

Sensitivity:

200mV input for 25W output

Frequency response:

30Hz to 20KHz -1dB

Total harmonic distortion @ 1KHz:

0.1W 0.014% 1W 0.006% 10W 0.006% 20W 0.007% 25W 0.01%

Total harmonic distortion @10KHz:

0.1W 0.024% 1W 0.016% 10W 0.02% 20W 0.045% 25W 0.07%

Unconditionally stable on capacitive loads

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