KA-10SH - Reasonably priced transformer coupled ECC88 amp from Japan

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by borrego, Aug 18, 2016.

  1. borrego

    borrego Incessant Audio-GD #1 Fan Boy

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    Made by the Japanese transformer specialist Kasuga:
    Kit:
    https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http://www.e-kasuga.net/goods.asp?id=1231
    https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http://www.e-kasuga.net/goods.asp?id=1220

    Assembled:
    https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http://www.e-kasuga.net/goods.asp?id=981

    [​IMG]

    While the low impedance output is on the 2nd winding of the OPT, the high impedance output to on the 1st winding (as autoformer) of the OPT. Very special.

    I have won a fully modified version of the amp from yahoo auction Japan last week. Awaiting delivery :D
    https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http://dirtyponpoko.blogspot.hk/2014/03/ka-10sh-limited-version.html
     
    Last edited: Aug 19, 2016
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  2. bazelio

    bazelio Friend

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    You got the "remodeled" version with Jensen caps, Z201 resistors, WBT jacks etc? That's a pretty nice BOM, just not sure about the OPT quality (or WTF they're talking about vis-a-vis the secondary taps). What'd it cost?

    PS, Hope they used a 120V mains transformer if you're in the US. :)
     
    Last edited: Aug 18, 2016
  3. borrego

    borrego Incessant Audio-GD #1 Fan Boy

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    The highly modified unit I won from yahoo Japan auction was a used unit. It has all the Jensen/Nichicon caps, Vishay Z201/Dale resistors, Tokyo Ko-On Denpa volume pod, silver shielded internal wire mods as mentioned on that DIY webpage. The only mods it does not have are the WBT jacks and the EIZZI telfon tube sockets.

    The MK3 version of the amp has bigger OPT with increased bass response (30ma max current on primary winding instead of 20ma, and 12H inductance instead of 8H). I bought a pair of the MK3 OPT (https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http://www.e-kasuga.net/goods.asp?id=36) for swapping later

    This Kasuga shop has high reputation in Japan making high quality transformers. There is a premium version of the amp with even better transformers, with frequency response down to 10Hz: https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http://www.e-kasuga.net/goods.asp?id=1127

    The PT of the amp only support 100V AC. I have to use a external 220V-100V step down transformer to use the amp.
     
    Last edited: Aug 18, 2016
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  4. borrego

    borrego Incessant Audio-GD #1 Fan Boy

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    Will try the following tubes with the amp. All inexpensive (the most expensive 6H23n costs me US$8 each)

    Left:
    GE 5670W, CCCP 6H3NE (90 & 84), Beijing 6H3-T . These need adapters
    Right:
    CCCP 6H23N. It is pin compatible to 6DJ8

    [​IMG]
     
  5. borrego

    borrego Incessant Audio-GD #1 Fan Boy

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    6H3П-EB on adapters. These CCCP era tubes takes long time to burn in before not sounding like AM radio.
    [​IMG]
     
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  6. borrego

    borrego Incessant Audio-GD #1 Fan Boy

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    Circuit Diagram. Note the high 132V anode plate voltage to the tube. On mine it actually was measured at 143V. This is part of the reason I choose to use 5670, 6H3П and 6H23П tube variance for now.
    [​IMG]
     
  7. borrego

    borrego Incessant Audio-GD #1 Fan Boy

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    After 3 months of tubes burn in, it is confirmed the Voskhod 6H23П sounds the best (resolution, air, extension, imaging)

    The 6N3-EP is warmer and has less treble extension and sound stage, and needs at least over 30+ on/off heat cycle to sound reasonably good.

    The GE 5670 sounded at first with good details, but eventually lost out to the 6N3. It sounds flat and compressed.
     
    Last edited: Dec 21, 2016

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