MASS-Kobo Headphone Amp. model404

Discussion in 'Portable Headphone Amps' started by seeteeyou, Feb 8, 2015.
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  1. seeteeyou
    It's already shipped on Wednesday but the online tracking didn't show any changes at all since Thursday

    2015/04/02 02:42    国際交換局から発送        中部国際郵便局    愛知県

    04/02/2015 02:42    Dispatch from outward office of exchange        CHUBU INT    AICHI

    It's Rudi's birthday tomorrow as well as Easter Sunday, hopefully he's getting his own 404 soon but mine should arrive on Tuesday since Monday will be a public holiday here.
  2. mrmax
    Unboxing, what's inside, initial set up

  3. zniper2984
    Any impression on these amp?
  4. seeteeyou
    Rudi posted his impressions on Facebook and it's a winner

  5. mrmax
    At a hotel.

    Seeteeyou, got yours? Wanted to ask a few q about your unit.

    Basically, would you know if i can plug in usb ext charger while there're are (rechargeable batteries inside?
    The instructions showed that the trrs bal 2.5mm input is different from the output trrs configuration. Is it the same wih your unit?

    Some random shot....

  6. seeteeyou
    Yes, it's delivered last Friday.
    According to the instructions, we need batteries that are providing 5V / 1A (i.e. at least 5 watts) in order to power the amp up. Check the manual of your batteries and most likely we'll have at least 1A unless it's a really old one.
    Sometimes the batteries might not be deliver precisely 5.0V since that particular value could fluctuate just a little bit. The bare minimum should be 4.6V as mentioned in the manual:
    If the voltage were 4.6V or above, the power indicator on the upper-right corner should be in green color.
    If the voltage were below 4.6V, the power indicator on the upper-right corner should be in red color and that's NO GOOD.
    Basically stick with brand name batteries and they should be fine with the appropriate power requirements. Stay away from generic ones that are really cheap because they might even explode or something.

    If you don't mind spending more for much better batteries and carry them with you, here are some options


    Masuda-san sent everyone an e-mail and asked each owner to specify the balanced input / output type respectively.
    He gave us 4 choices and I picked the last one:
    Input = AK240 2.5-mm
    Output = AK240 2.5-mm
    AK240 2.5-mm should look just like this, T / R / R / S = R- / R+ / L+ / L-

    I only have the TRRS plugs from Nakamura but no cables yet, my only source with balanced output is AlgoRhythm Solo -dB but I can't test my 2.5-mm balanced connections without a cable.
    My LCD-X worked fine with XLR balanced output and I was feeding the amp with the single-ended output of Tera-Player. The amp was able to convert single-ended input into balanced output successfully.
  7. rudi0504

    Thank you Frankie for sharIng
    Now I use Note 4 , i don't know how to post big pictures to Head Fi
  8. rudi0504

    Congrats for your new Mass Ko Bo 404
  9. mrmax

    Thanks rudi. Love the power and transparency of the 404.
  10. seeteeyou
    Brief intro from Jaben Singapore


  11. mrmax
    Using ak240 --> whiplash 2.5 bal --> mass ko bo 404 --> jvc fxz-200 (using 3.5 hp out)

    Liking it. No hiss.

    I don't think i've yet had 50 hours on the amp

    Highs, mids and lows are tight. Mids are a bit lacking only a bit but i believe thats from the jvc's.

    Haven't used the jvc's for quite a while but it's now reminding me why i've kept it.

    I also had an option to choose between 8 wire silver or gold coated silver. Chose the silver for the details.
  12. Angular Mo
    Is there an English language Web site?

    I could be interested in the unbalanced version.

    Though AA batteries?
  13. seeteeyou
    Just a few pages in English so far
    395 here

  14. seeteeyou
    Voltage accepted should be between 9V ~ 7.2V with 6 pieces of AA batteries

    消費電流(無信号時) :0.13A(電池9V時)、0.14A(電池7.2V時)、0.21A(USB 5V)
    (最大出力時) :0.27A(電池9V時)、0.33A(電池7.2V時)、0.7A(USB 5V)

    14500 batteries are rated between 4.2V ~ 3.7V so combining 2 pieces of 14500 batteries (8.4V ~ 7.4V) and 4 pieces of battery place holders (0V) should give us:
    4.2 + 0 + 0 + 0 + 0 + 4.2 = 8.4V (highest)
    3.7 + 0 + 0 + 0 + 0 + 3.7 = 7.4V (lowest)
    8.4V ~ 7.4V

    2 pieces of 14500 batteries
    4 pieces of battery place holders

    6 pieces will yield between 8.4V ~ 7.4V and that's staying between 9V ~ 7.2V
  15. sfoclt
    Do you remember the other options?
    Are the other options still possibilities or was one configuration settled upon?
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