A Closer Look at Sony PHA-2 (Part 2)


TPA6120 OFF!

When measure the voltage across the +-ve pins of the TPA6120, I found it was 0V. OMG! I'd killed this amp...! I checked the power, pins and buttons over and over. Finally, I found 6120 was turned off due to the OUTPUT SELECT was switched to "LINE OUT". There is a relation between the TPA6120 and LM49860. When the OUTPUT SELECT Position is "PHONES", TPA6120 is on and LM49860 is off. If you switch it back, these chips' on off status will switch accordingly. This help to reduce the battery drains for the unused chip during the "PHONES" or "LINE OUT" mode. Besides, this help to reduce the noise coming from each other.





LINE OUT

Benefit from the +-10V operating voltage, PHA-2 has 2Vrms output voltage swing (2Vrms is the typical standard for CD player). In general, portable media player has lower operating voltage is due to battery powered without step up. This led to lower the signal swing. The higher the dynamic range and signal to noise ratio you want, the higher the signal swing is needed since receivers typically have a fixed amount of noise floor. Therefore, you could treat it as a decent DAC when you are not using the headphones.


More Photos


Upper layer PCB



Lithium battery



Summary

Goods:
  • Pleasant sound
  • Improve portable player sound quality
  • Rubber belt for fastening portable player to it
  • Rack mount like metal protector for preventing volume changed accidentally
Bads:
  • Difficult to put into the bag when connecting to iPod or Walkman through digital inputs
  • Volume control could be more linear
  • Left right channel is not balance at 8-9 o'clock
  • Gain could be set lower for IEMs

1 comment:

  1. Nice tear down and article you have here! I pretty surprised to see through hole Nichicon Gold capacitors here, presumably for output filtering/DC offset blocking? I thought they would try to reduce labour costs by going SMD as much as possible.

    Do you happen to know what IC was used to provide the USB to I2S interface? Thanks!

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