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Fostex HP-A4BL (the A4 with balanced output)

Discussion in 'Headphone Amps (full-size)' started by rafa, Dec 30, 2015.
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  1. aqtaket
    Another quick question to the happy owners of this wonderful Fostex unit:
    If I hook up a DAP vis USB OTG cable+ the Fostex USB cable supplied, will it supply power to the DAP (and charge it) from its USB 2.0 port, or this port is only meant for data transfer?
  2. HungryPanda
    As far as I know the USB is only for connection to computer
  3. aqtaket
    So it wouldn't work with a DAP via OTG? Even if a DAP supports transferring data via USB OTG?
  4. HungryPanda
    I have never tried so cannot advise
  5. davehutch
    Having an issue...
    I bought an adaptor from Drop.com, the balanced XLR to 2.5mm, so that I could use my IEMS. However I get small electric shocks (tingles) from the metal shells of my IEMs.
    Any idea what's going on? I have a multimeter and if I measure between the left and right shells, there's about 19V.
    I should also add that I'm using optical in to the amp
    Can anyone help please?
  6. aqtaket
    There are differenr pinouts for 2.5mm balanced. The so-called "European", "Asian", "Fiio", "AK"....
    Looks like the pin-out of your adapter does not match the one of you male-jack in the phones..
  7. davehutch
    I also made my own adaptor cable and I get the same issue. Fostex distributor, SVC are assisting but there doesn't seem to be a pattern to it. If I measure between pins 1 and 3 I get 1 or 2 millivolts, which is fine.
    Same between pins 2 and 4
    Yesterday I plugged in and for a while it was all fine, but then I started getting shocks again.

    Can anyone else with metal bodies IEMs let me know if they experience the same issue?
  8. aqtaket
    This Fostex has only one DAC chip, but a balanced amplification part, is that correct?
    If so, that seems a bit strange to me, a balanced DAC/amp should have two DACs and two amps for true balance. What Gives balanced output in this case? Only higher power?
  9. selvakumar
    hi i tried all burson opamps v5i,v6c,v6v
  10. dsnedeco
    Can someone explain to me exactly how to uninstall the HP-A4 usb driver and install the HP-A4BL usb driver on Windos 10. I have been unable to do that. I have downloaded "FOSTEX_USB_Audio_Driver_V221.zip" It seems like no matter what I do I end up with the HP-A4. It works OK but it is not the HP-A4BL. Some where along the line months ago I had it installed. But then my computer crashed and I can't seem to get it back.
    Last edited: Sep 2, 2019
  11. davehutch
    Fostex sent me an earthed power supply. All is now fine :)
    skingg and HungryPanda like this.
  12. HungryPanda
    Glad to know all is fine
  13. gimmeheadroom
  14. RSC08
    Anyone tried this amp with the Hifiman Sundara? I'm looking to upgrade my home setup and currently deciding if I should go HP-A4 + Sennheiser HD650 or Hifiman Sundara.
  15. gimmeheadroom
    Sennheiser 600 series are at their best with a tube amp. The Fostex would not be my choice for Sennheisers. I have no idea about the Sundara.
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