AudioAmp380

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AudioAmp380-3D.png

Design[edit]

  • Pre-amp plus power amp
  • 50 Ohm input impedance matched Product Detector outputs
  • Gain trimmer potentiometer on preamp
  • External mount gain potentiometer
  • NE5534 Pre-amplifier
  • LM380 2.5W Audio Power Amplifier
  • 12V nominal power
    • 10-22V
  • Fits into 80x50x20mm extruded aluminum enclosure

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Pre-Amplifier (NE5534)[edit]

  • Low-Noise Operational Amplifiers
  • Equivalent Input Noise Voltage 3.5 nV/√Hz Typ
  • Unity-Gain Bandwidth 10 MHz Typ
  • Common-Mode Rejection Ratio 100 dB Typ
  • Wide Supply-Voltage Range ±3 V to ±20 V
  • Used as single supply

Audio Power Amplifier (LM380)[edit]

  • Wide Supply Voltage Range: 10V-22V
  • Low Quiescent Power Drain: 0.13W (VS= 18V)
  • Voltage Gain Fixed at 50 (34 dB)
  • High Peak Current Capability: 1.3A
  • Input Referenced to GND
  • High Input Impedance: 150kΩ
  • Low Distortion
  • Quiescent Output Voltage is at One-Half of the Supply Voltage

Controls[edit]

  • RV1 - trade-off gain/bandwidth - Tune for best sound
  • RV2 - volume control (after preamp and before LM380 Amp). 1x5 header wire to external pot
  • J1 - Audio In, 50 Ohms input impedance
  • J2 - Audio Out, 8 Ohm speakers
  • J3 - Power, 10V-22VDC

Rev 1 Schematic[edit]

  • (Before rework)

AudioAmp380-Rev1 Schematic.png

LM380 Equivalent Schematic[edit]

LM380 Equiv Schematic.PNG

Rev 2 Schematic[edit]

AudioAmp380-Rev2 Schematic.png

Rev 1 Rework[edit]

  • Issues
    • FPre-amp opamp has + and - reversed
    • Also hooked up the feedback to the wrong input
  • Replace R1 with wire jumper
  • Replace C9 with wire jumper
  • Remove C2
  • 5 Cuts
    • 4 on front
    • 1 on back
  • 5 jumper segments on back
    • 2 nodes

U2-2 3 Rev1 Rev2 Cuts Jumpers.png

  • Jumpers on rear side

AudioAmp380 Back Jumpers.PNG

Videos[edit]

ZL2CTM Schematic.PNG

Assembly Sheet[edit]