Recent content by xrk971
  1. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    New thread on DIYA to discuss technical aspects of the new HPA with battery management system. Amp will be called the Hakuin HPA. Block diagram of LiPo and wall-plug power management system: https://www.diyaudio.com/forums/headphone-systems/345851-hakuin-se-class-hp-amp.html
  2. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    3D printed case version with 5000 mAhr battery.
  3. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    I am looking at option to provide the 3D printed case for a nominal cost circa $30 - depending on how many people interested. There are many onlOne 3D printing services that will print for you if you provide a file. We may be able to leverage more units to bring costs down.
  4. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Dbaldock, Cool! Please respond in the DIYA thread to show interest.
  5. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Hi Folks, I haven’t been here for a while but thought you all might be interested in a new project brewing over on DIYA. It’s going to be a new PCA Mk II. This time fully assembled and tested and ready to run (RTR) all SMT design. You just need to install in your own mint tin or 3D printed...
  6. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Here’s the new Muscle Amp - uses eight OPA1622 in parallel. Can drive speakers even down to 4ohms. About 10w into 8ohms. Tested T 47ohms and listening with 50ohm HE400i. Fantastic dynamics. Zero noise or background. Powered with 25va 15v trafo through a cap multiplier for low noise power source...
  7. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    New Balanced Drive 2 Transistor SE Class A Headphone Amp with beautiful harmonic profile and ability to drive 50ohm cans. https://www.diyaudio.com/forums/headphone-systems/338656-balanced-drive-2-transistor-se-class-headphone-amp.html Measured FFT for 2Vpp itno 49ohms:
  8. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Here’s a new spin on this amp. Using an ultra low 117uA bias current in the JFET (via new DC setpoint resistors), the sound is sweeter (lower third harmonic relative to second) and lower overall THD, and more dynamic through higher gain. It seems that the input signal had to control a much lower...
  9. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    I was wondering when you were going to build the balanced DCA’s. Do you have 6 boards?
  10. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Simply a matter of parts running out of stock - I can order more of there is interest. I will put it back as soon as parts arrive in a week. Or he can preorder.
  11. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    No, it will have optional single ended input (which only gives single ended output.). Will follow diagram posted above.
  12. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    That’s a pretty lame way to bump a thread (worse than people who actually say “bump”). At least add some new info. I am thinking of offering my Pocket Amp, reconfigured as a balanced input / output amp as a transportable desktop amp. Contact me if you are interested - it will be on a custom...
  13. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Dbaldock9, I think I have a much simpler passive solution for you. It's detailed over on DIYA thread for DCA, but I will repeat here: You might be able to do this via passive "switching" on the input/output TRS or XLR jacks. Here is one approach to try... when using balanced, require a 4 pin...
  14. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Mypants, Sorry, don't understand your last post is referring to?
  15. xrk971

    New Portable Amp - "Pocket Class A" by xrk971 - now available as complete PCB

    Yes, I have matched FETs for DCA. However my basement just got flooded so finding things may take me a few days.
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