1. The document shows a circuit diagram for a high end headphone amplifier with inputs for left and right audio channels. 2. It uses operational amplifiers, transistors, resistors, and capacitors to regulate voltage and amplify the audio signal for output to headphones. 3. The amplifier can run on either 240V or 120V input and provides adjusted voltage outputs of +12V, 0V, and -12V to power the circuitry and drive the headphones.

1. 1 2 3 4 5 6 7 8
CN1 F1 T1
Live
A LK1 A
IC1
BR1
LM2940CT-12
LK2 +12V
In Out
LK3
G
+ + + +
C9 C11
C1 C2 C3 C7
100n 100n R21
1000u 1000u 1000u 4700u
CN2 22K
Neutral
240V Input = LK3 0V + + + +
120V Input = LK1 + LK2 LED1
C10 C12
C4 C5 C6 C8
100n 100n
1000u 1000u 1000u 4700u
G
In Out
-12V
IC2
L7912CP
+12V +12V
B B
R6 D9 R16
D3 47R 47R
D10
D4
TR1 TR5
BC557 BC557
+12V TR3 +12V TR7
R4 R14
2N5551 2N5551
1K 1K
CN3 C18 CN5 C25
Left Input + R1 100n Right Input + R11 100n
R2 0V R12 0V D7
1K 0V D1 R8 1K 0V R18
3K3 3K3
10R 10R
7
7
C13 0.5W C20 0.5W
VR1A 3 VR1B 3
CN4 C17 CN6 C24
50K 6 R10 50K 6 R20
Left Input - Right Input -
+
+
470n C14 2 470n C21 2
IC3 47R IC4 47R
100p R22 100p R23
0V 0V LME49710HA 470u 2W 0V 0V LME49710HA 470u 2W
100K R9 100K R19
0V 25V 0V 25V
4
4
R3 10R R13 10R
1K 0.5W 1K D8 0.5W
0V D2 0V
C19 C26
100n 0V R5 100n 0V R15
+
TR4 +
TR8
1K 1K
C C15 C16 -12V 0V 2N5401 C22 C23 -12V 0V 2N5401 C
10n 470u 10n 470u
35V 35V
TR2 TR6
0V 0V
BC547 BC547
D11
D5
R7 R17
47R D12 47R
D6
-12V -12V
CN7
1/4" Headphone Socket
0V
PCB ref: 00000268
Heatsink Wakefield Engineering
637-10ABPE
D D
Title
High End Headphone Amplifier
Size: A3 Date: 08/08/09 Revision 1.1
Kelvyn Shaw Sheet 1 Of 1
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