Assembled Premium Class A Headphone Amplifier Ref Audio-Technic HA5000 For Head-Fi

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Assembled premium class A headphone amplifier refer to Audio-Technic HA5000 for Head-Fi,For headphones from 32Ohm to 600 Ohm.

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Assembled Premium Class A Headphone Amplifier Refer To Audio-Technic HA5000 4 Head-Fi

Fully assembled,Just hook it up with power transformer to run


Hight light

Input stage is single differcial circuit with 2SK370 mosfet transistor,Very silky sound.

Outpu stage is powered by K2955 and J554 high power mos-fet transistor.

Selectable gain with a DIP selector, Set it at 00 for low impendence headphone below 600 Ohm, Set it at 11 for 600 Ohm headphone or speaker.



  • Output mos-fet K2955 J554 have been discontinued, So the K2955 J554 transistors are used but tested good
  • ALPS Potentiometer is not included,The amplifier is compatible with type 16 an 27 potentiometer
  • Power transformer and aluminum enclosure are available,Pls select in drop-down list.

Adjustment for working point

Measure the voltage drop on Pin 1 and Pin 3 one the white KOA resistor,Rotate the variable resistor to make voltage between 40-50mv to set static current is between 100-200ma,It works at class A mode.


PCB size: 130mm * 106mm

Distance between ceter of headphone jack and potentiometer is 45mm


Packing List:

  • One assemble headphone amplifier board refer to HA5000.

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