耳机放大器电路(HeadphoneAmplifier)

耳机放大器电路 (Headphone Amplifier)

Amplifier parts:

P1_____________22K Log.Potentiometer (Dual-gang for stereo)

R1____________560R 1/4W Resistor
R2,R3__________10K 1/4W Resistors
R4_____________12K 1/4W Resistor
R5,R6___________2R2 1/4W Resistor
R7_____________22R 1/2W Resistor

C1______________1F 63V Polyester Capacitor
C2,C3,C4______100F 25V Electrolytic Capacitors
C5_____________22pF 63V Polystyrene or Ceramic Capacitor
C6_____________22F 25V Electrolytic Capacitor

IC1___________LM833 or NE5532 Low noise Dual Op-amp

Q1,Q3_________BC337 45V 800mA NPN Transistors
Q2,Q4_________BC327 45V 800mA PNP Transistors

J1______________RCA audio input socket

Power supply parts:

R7______________2K2 1/4W Resistor

C7,C8________2200F 25V Electrolytic Capacitors

D1____________100V 1A Diode bridge
D2____________5mm. or 3mm. Red LED

IC2___________7815 15V 1A Positive voltage regulator IC
IC3___________7915 15V 1A Negative voltage regulator IC

T1____________220V Primary, 15 + 15V Secondary 5VA Mains transformer

PL1___________Male Mains plug

SW1___________SPST Mains switch

Notes:

Can be directly connected to CD players, tuners and tape recorders.

Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 2000 Ohms.

Can drive old 8 Ohms impedance headphones, but these obsolete devices are not recommended.

Schematic shows left channel and power supply.

Numbers in parentheses show IC1 right channel pin connections.

A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of J1, P1, C2, C3 C4. Then connect separately the input and output grounds at the power supply ground.

Technical data:

Output voltage: Well above 5V RMS on all loads

Sensitivity: 250mV input for 5V RMS output

Frequency response: Flat from 30Hz to 20KHz

Total harmonic distortion @ 1KHz 10KHz: Below 0.005% on 32 Ohms load and up to 4V RMS output (typical 0.003%)
Total harmonic distortion @ 1KHz 10KHz: Below 0.005% on 100 to 2000 Ohms load and up to 5V RMS output (typical 0.003%)

Unconditionally stable on capacitive loads