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Posts posted by hyperma

  1. Hello everyone, hope everything doing very well today.

    Few days ago I found two transformers in my dungeon, which named by my wife. I mentioned it has 16V out and double 110V in, so I guess perhaps could make something like stax srd-7.

    Then I made a pcb and give most places to voltage doubling rectifier, as same as srd-7, and... it works.

    Well somehow the bias unable to reach 580V, only around 490V, the sound quality, of course, bass section bit weak, so I have to turn the EQ on, then everything fantastic.






     2 30W transformers 110-0-110 in 16V out, 1 50W transformer 220V in 110V out.

    1 fuse @200ma

    6 0.1uf 630V caps

    1 0.01uf 630v cap

    6 1n4007 diodes

    4 speaker connectors

    2 2M2 resistors @ 2W (for safety consideration no less than 1/2W)

    1 15k resistors ( to light up led)

    2 5R resistors @5W for dummy load

    1 1M resistor

    1 stax standard electrostatic can connector

    Infact if I could spend enough time on it, hand wired construction must be better and cheaper.

    So I call this project "Ghetto SRD-7".





    • Like 2

    On 2/28/2020 at 4:47 AM, simmconn said:

    I was wondering... why the first and second stages are designed at such low operating points. 12AU7 is at 1.2mA and 12AX7 at 0.5mA. Wouldn't higher operating points give better distortion and lower output impedance and hence better frequency response at the higher end?

    Probably because it's an electrostatic amplifier, the first stage needs provide 24db gain to drive pair 12au7s ,otherwise unable to reach amplititude.

  3. On 2019/8/21 at PM3点42分, jose said:

    I understand but precisely the price difference is what should make you suspect and now you have to spend twice as much to replace the defective components. Then this will be more expensive.

    On the other hand, we are handling voltages and amperages that are highly dangerous. IMO trying to save money here is not recommended.
    Pay attention to Blueman (SRX-P thead), his experience is quite instructive.

    It's true, for diyer, Mouser, RS , Element14 or TME etc are best choice.

    Few month ago,I have bought some FAKE PCM1704s, of course they didn't work. The best way to find out who they are , is disassembling.....by fire, on microscope , I saw HC574 and TI mark on the die.......What a joke.

    Another example was my personal favorite op LM4562, I got some on same way, and matched their dies with AD744, remarked for sure. Also funny is in China AD744 is more expensive than LM4562 now.

    8 hours ago, Blueman2 said:

    HERE is what happens when you buy parts from eBay.  Never, never, never again.  

    Hell......but seems Kevin already known everything about fake parts.?

  4. 33 minutes ago, jose said:

    I'm not sure what advantage have when buying components in places like ebay, tobao ...   when It´s a current production component so it´s easy to obtain in official distributors.

    The price ..... worth that risk, AK4497  $35per/100pcs  and $5 a package of TIP122(500 pcs).

  5. On 8/15/2019 at 6:12 PM, Hirsch2k said:

    Ok that is understadable... The fat C2M, Caps and Heatsinks are probably not very enjoyable with lead-free. 

    I am collecting more components for my second mouser order and thinking about the on/off switch on the front. What do you think, is it critical or will transients and spikes be completely filtered in the PSU and one can workwith an ordinary push button switch?

    I thought about ordering the Amb epsilon 24 with transformer but that will set me back  ~40 dollars in shipping alone ?

    To be honest, I don't have much EXP on this, but 40 USD is enough to afford the alumium amplifier case with heatsink......few weeks ago I took a relay pcb from garbage bin,it's working on Carbon(or more carbon) now, don't you want to make your own one?

  6. Finally, well, I have fixed the "KG Carbon - more carbon" ......,in beginning I wanna make a "more carbon and lots cheaper version",but see what I got:

    DN2540 and IXCP10m90s I have bought from taobao.com......are fake, now show you guys photo:

    Fake DN2540(yes, I have bought all of them for testing):



    simply them didn't work ,that's all , I can read 455V from multimeter though probe touch the headsink,but....nothing happened, until I replaced the replica silicon:

    Mouser version:



    Taobao -  Save your broken heart also bit expensive version:



    Now the IXCP10M90S time:

    Left: mouser

    Right:You don't know who I am version



    • Thanks 1
  7. 27 minutes ago, kevin gilmore said:

    With those diodes is there any unregulated voltage on the first big cap?

    the rms volt of transformer is 348v ,  I cant reach the cap due to parallel installed pcb ,measured 450v from 10m90s and c2ms  drain by multimeter. On monday I will bring oscilloscope to studio.

  8. 1 hour ago, Pars said:

    Regarding the diodes, the pinout is the same... seems like it should be superior to the STTH512 and work?

    I didn't think the Toshiba 2SK389BL was available in SMT? Only thru hole. The Linear Systems replacement K389 is available as an SOIC8, but aren't marked like that. Where did you get these?

     I will replace all bridge diodes by stth512s on Monday, just noticed something.

    I bought smt k389 from taobao , they are made by linear.sys , cost 45rmb or 5 pounds , mint choice.

  9. Replaced STTH512 by infineon IDH10S120 on PSU ..... Hmmmm.....no output voltage.

    I'v chosen this diode for making a "more carbon version KG Carbon", and the performance of IDH10s120 way better than STTH512 on paper but donno what happened.


    On 8/8/2019 at 9:12 PM, mwl168 said:

    The LSK389B for the Carbon - it's equivalent of the 2SK170 BL grade.

    I bought some SMT version of 2SK389 for better thermal coupling and way cheaper......hope it works.


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