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

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  1. Slater
    What is the battery capacity/runtime?
     
    DBaldock9 likes this.
  2. xrk971
    Using a 3000mAhr 3.7v LiPo cell and boosting to 16v should give about 4hrs. I need to test duration of run.
     
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  3. xrk971
    In addition to a LiPo and DC step up and Cap Mx, would having BT 4.0 or a built in DAC be more of a desired feature?
     
  4. BucketInABucket
    Not for me, it's a dedicated amp and should stay one imo. :)
     
    DBaldock9 and polandro like this.
  5. DBaldock9
    If you're designing the circuit board, considering future upgrades, maybe you could add a header, for a "Digital Audio" daughter-board?
     
  6. xrk971
    I’m designing a new desktop preamp/headphone amp that will have a DAC and BT. But a header for future expansion is certainly a good feature. I currently use headers for core amplifier daughter boards on the group but Aksa Lender Preamp. It lets one swap boards for different gain, bias, even output devices. Daughter boards are inexpensive and allow ultimate flexibility of main amp.

    More info here:
    http://www.diyaudio.com/forums/group-buys/315521-aksas-lender-preamp-40vpp-ouput-gb.html

    Here is one of the daughter boards:
    [​IMG]

    This is the sort of distortion this amp achieves for 20vpp:
    [​IMG]

    The new Pocket amp will be Class A of course but with topology similar to Aksa Lender for lower distortion. Will have LiPo, DC step up, cap multiplier, BT, and am working on adding a DAC even. Won’t really have room for expansion cards - as it will be pretty compact and still pocket sized with custom CNC case.
     
    Last edited: Jan 12, 2018
    DBaldock9 likes this.
  7. xrk971
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  8. DBaldock9
    Will you be offering a USB rechargeable Li-Po battery pack, for the Class A NHB Amplifier?
     
  9. xrk971
    There is a DIY solution you can follow just like I did using a small cap Mx board, a DC boost board, and a LiPo pack. It requires cutting a trace on the PCB and some wiring.
    The details can be found here:
    http://www.diyaudio.com/forums/group-buys/302859-xrk971-pocket-class-headamp-gb-144.html

    [​IMG]

    [​IMG]

    Looks like this laid out flat:
    [​IMG]

    And like this all packaged up:
    [​IMG]

    If there is enough demand, maybe I can make an integrated board that has the DC step up, cap Mx, CRCRC, and battery holder all on one board. But that still requires surgery to the main PCB and I don't know how many people are willing to do that.

    I am working on an all new design with a CNC case and integrated LiPo USB power charge system though - but that is kind of down the road.
     
    DBaldock9 likes this.
  10. Slater
    Or better yet, let this accept a USB battery power pack (all output 5v 1A, and they even have them with 5v 2.4A nowdays). You can buy the power packs in almost infinite capacities and case configurations, from single 18650 "lipstick" tube style (usually around 1500-2000mAh), all the way to 20,000mAh (and even larger). That way, it's up to the user to decide what amplifier runtime they want.

    You'd just need to have a female microusb port on the amp as the power input (as well as the built-in boost and power filtering circuitry obviously).
     
  11. MyPants
    Welp, I'm extremely interested in one of these, but I'm torn on whether or not to take the NHB plunge. Decisions decisions...
     
  12. xrk971
    You can be certain that the amp will sound excellent and is sure to please. Everyone who has listened to one or reviewed it has loved it. Even the last review by Brooko, he liked it so much he bought it despite the fact that I gave him a free sample to keep.

    What cans or IEMs are you using? I can custom tune the amp for best performance with your headphone or earphone.
     
  13. MyPants
    I just read Brooko's review before my post, and I tend to trust his impressions, so I'm confident that either version will indeed satisfy. I'd be using the amp primarily with the HE400i, Fostex T20RP MK3, and LZ A4 iems.
     
  14. xrk971
    The LZ A4 will be an excellent match with high sensitivity and 16ohms. The Fostex can work but sensitivity is on low side so may not get as loud as you want. Given that it is 93dB and 50ohms which is about the borderline of what can be driven by this amp. The HE400i being 32ohms and 91dB is too low of sensitivity and low impedance and will probably not sound it’s best. I have not personally listened but will guess that it’s going to be a struggle. I use 55ohm and 96dB OB-1’s and that works great. 91dB and 250ohms would be fine for example.

    Anyhow, that’s just a limitation of the amp in not being a high current amp.
     
  15. MyPants
    Hmm, two questions then;

    1. Considering that my current mobile amp is a 9v cMoyBB kit from JDS that I put together, would the NHB version of your amp perform at least as well or better than the cMoy with my sub-optimally paired planar cans?

    and

    2. I also have a 600ohm set of DT880s, and the extremely sensitive NuForce Primo8. Any better luck with these two as far as pairing goes?
     
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