High Quality unit. No need for a preamplifier.
Circuit diagram
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 1uF 63V Polyester Capacitor
- C2,C3,C4 100uF 25V Electrolytic Capacitors
- C5 22pF 63V Polystyrene or Ceramic Capacitor
- C6 22uF 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
- R7 2K2 1/4W Resistor
- C7,C8 2200uF 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
- 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.
- 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