Audio Technica AT-PHA50BT bluetooth amp modifications

  1. AudioCats
    ** Starting a new thread to document the modding of this little amp. Maybe somebody else can find the info useful somewhere down the road.
    The goal of this mod is to (hopefully) improve the sound quality to the level of Creative Sound Blaster E3. Some sound impression/ comparison of PHA50 vs E3 is in the E3-mod thread.
    To disassemble the A50, lift the top cover off (it is made of plastic, with snap tabs)
    undo the four little screws, the bottom cover can be separated from the main body.
    Most of the electronics are on the bottom side.
    * in the picture above: next to the volume dial and mic is a chip marked "AIG BAK", it has a greenish SMD film cap next it it, chip is 3mmx3mm with 16 leads, maybe it is a headphone amp chip similar to a max97220?
    *The chip above it is marked "NLAS, 4634, GAZD", maybe an analog signal-switching chip?
    in this picture below: To the left of the big chip is a chip marked "uP60028", maybe a power control chip? ( it is close to the battery terminals)
    The big chip is the processor chip, marked "MSP430, G2855, TI A52K" ; next to it is the flex ribbon for the display.
    The battery pack is 3.7v 240mAh. Available space in the battery compartment is 22.7mm x 31.5mm x 5mm
    Top side of the board has a CSR bluetooth chip and four purple-ish SMD coupling caps.
    The four caps are probably for coupling between the DAC differential output and the headphone amp. They are 1.8mmx3.5mm long, measured around 1.8uF in-circuit, likely polyester caps (I don't think the 1.8uf PPS caps can get this small, unless they are special low-voltage PPS caps; 50v 1.5uf SMD PPS cap from Kemet is 12.7x11.5x6.7mm). Upgrading these four caps might be a viable SQ upgrade option.
    ***the DC voltage across these film caps is about 0.77v, the + end is toward the CSR chip.
    teknojack66 likes this.
  2. AudioCats
    took the four purple film caps off and soldered on some 28awg wires. The film caps did not break during the desoldering (used a pair of thermal tweezers).
  3. teknojack66
    Hello Audiocats!

    Thanks for posting this. I am awaiting delivery of my very own AT-PHA50BT, and really looking forward to putting it through its paces. I wonder, is there room in the AT for a larger LiPo?
    Last edited: Aug 20, 2017
  4. 0x6170
    Does the PHA50 have a seperate DAC?
    Or is it just direct connection [Bluetooth chip] -> [Amplifier] -> [Headphone jack] ?
  5. Mad Max
    "AIG BAK"
    TPA6130, no doubt
    Circuit layout there also looks like what TPA6130 would need.

    A battery with even less capacity than a Sansa Clip's. Wow.

    I guess that this could be considered a "fatter Fiio E5" and with bluetooth connectivity added?
    Last edited: Apr 21, 2018

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