Headphone Amplifier Trail Diagram
Parts
P1_____________50K Log. Potentiometer (or 47K)
(twin concentric-spindle dual gang for stereo)
R1,R2__________47K 1/4W Resistors
R3____________100K 1/4W Resistor
R4______________8K2 1/4W Resistor
R5____________470R 1/4W Resistor
R6______________2K7 1/4W Resistor
R7______________1K 1/4W Resistor
R8____________560R 1/4W Resistor
R9____________100R 1/4W Resistor
R10____________10R 1/4W Resistor
R11____________22R 1/2W Resistor
C1____________470nF 63V Polyester Capacitor
C2_____________47µF 25V Electrolytic Capacitor
C3,C6,C7______220µF 25V Electrolytic Capacitors
C4____________100µF 25V Electrolytic Capacitor
C5_____________47pF 63V Polystyrene or Ceramic Capacitor
Q1___________BC560C 45V 100mA Low noise High gain PNP Transistor
Q2___________BC337 45V 800mA NPN Transistor
Q3,Q4________BD437 45V 4A NPN Transistors
The extreme simplicity of the 7W Class-A Audio Amplifier Trail Projects, leads invariably to think that it could be naturally converted into a Headphone Amplifier. So, this was immediately done and as a result, a 500mW into 32 Ohms load Headphone Amplifier was obtained, featuring ultra low THD, about 100mA current drawing per channel and small heatsinks for the output transistors
Power Supply Trail Diagram
Power Supply for the Single ended Class-A Headphone Amplifier
Power Supply Parts
R1_______________2K7 1/2W Resistor
R2_______________6K8 1/4W Resistor
R3______________18K 1/4W Resistor
R4_____________270R 1/4W Resistor
C1____________3300µF 35V or 50V Electrolytic Capacitor
C2______________10µF 25V Electrolytic Capacitor
D1_____Diode bridge 100 to 400V, 1A
D2______________LED Any type and color
IC1___________LM317 3-Terminal Adjustable Regulator 1.5A
SW1_____________SPST Mains switch
T1______________230V Primary, 24V Secondary,
7-10VA or 290 to 400mA, Mains transformer
PL1_____________Male Mains plug with cord
Notes
The regulated power supply circuit is straightforward and employs an LM317 3-Terminal Adjustable Regulator IC. Parts values suggested are suited to power a stereo version of this design.
Total current drawing of each amplifier is about 100mA and should not require adjustment.
Use small, U-shaped heatsinks for Q3 and Q4. A similar heatsink could be used also for IC1, though in most cases it is not necessary.
Author By : Red Free