Building A Tube Preamp: The Aikido

Discussion in 'Audio Hardware' started by fully_articulated, Jun 13, 2019.

  1. fully_articulated

    fully_articulated Forum Resident Thread Starter

    You should post some progress pictures.:righton:
     
  2. TJF

    TJF New Member

    Location:
    Munich - Germany
    I would like to do a banaced setup, that is with 2 Aikido boards. Therefore I need 2 x PS-21 and a total of 4 of the transformers used here? Or is there a less material intensive recommendation?
     
  3. fully_articulated

    fully_articulated Forum Resident Thread Starter

    I don't know anything about balanced topology sorry. You don't mean dual-mono do you?
     
  4. TJF

    TJF New Member

    Location:
    Munich - Germany
    No. I mean balanced in- and output. Broskie describes it. You need 2 Aikidos and connect them both in symmetry. Very simple. So I assume that both boards need the appropriate power supply...
     
  5. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Broskie built the PH-2 phono stage (which is essentially two Aikidos on one board) with one power supply, so it's likely you could do the same with your project. PH-2 and LP Playback

    I wonder if the even the phono board itself could be repurposed for it?
     
  6. TJF

    TJF New Member

    Location:
    Munich - Germany
    Broskie wrote on his site (your link... at the bottom): "Thus, one board is all that is needed for stereo unbalanced use or two boards for balanced preamplification." I would like to go with the Octal Aikido :
    "Each board holds two Aikido linestage amplifiers; so, one board for stereo unbalanced or one board for one channel of balanced amplification."

    Then it's only about half the area. And here is my question again... :D
     
  7. TJF

    TJF New Member

    Location:
    Munich - Germany
  8. fully_articulated

    fully_articulated Forum Resident Thread Starter

    I'm afraid I'm not really capable enough to answer your question. My thought was that if the PH2 can be powered by two transformers plus one PS-21, then your project probably could too. I imagine you'd have to keep an eye on the current requirements and spec the transformers appropriately, hopefully not exceeding the capabilities of the PS-21.
     
  9. TJF

    TJF New Member

    Location:
    Munich - Germany
    Thank you!
     
  10. TJF

    TJF New Member

    Location:
    Munich - Germany
    You wrote:

    and in an earlier entry:

    I think my plan could work with one PS-21 and two transformers. But probably only if I would use the type 266PA14 instead of the 266L14. Or, in general, one should use 266PA14 - in your sense.
     
  11. fully_articulated

    fully_articulated Forum Resident Thread Starter

    I think you're probably right. If you use the octal Aikido board and (for example) 6SN7 tubes, that will add up to 2.4A heater current per board, but there may be other tubes which are even higher.

    Note: The PS-21 board silkscreen and manual specify the regulator as the LD1085, which is only a 3A part. However the kit itself came with the 5A LD1084. It'd be worth checking your kit is the same.
     
    TJF likes this.
  12. samurai

    samurai "See the glory, of the royal scam."

    Location:
    MINNESOTA
    I've never undertaken such a project and probably never will but
    I appreciate your posts showing what is involved.
    Nice photos too!
     
    fully_articulated likes this.
  13. TJF

    TJF New Member

    Location:
    Munich - Germany
    I'm afraid there might be a problem with the dual operation. Broskie writes about the PS-21: "The PS-21 can deliver up to 50mA of high voltage...". The Broskie table with the tube values with my tubes of choice can be seen (150 Volt): The input=6SN7 (Ik=3.0 mA), output=6H30 (because of the necessary low Z=124 Ohm) has an Ik=30.0 mA! Total gain is enough: 9.2 (19.25 dB). What do you think?
     
  14. TJF

    TJF New Member

    Location:
    Munich - Germany
    I just see that the 6H30 is a 9 pin tube ... However, to get close to the ideal Z=100 Ohm, a higher current is applied. Maybe I have to calculate this with the Noval version.
     
  15. fully_articulated

    fully_articulated Forum Resident Thread Starter

    What's the input impedance of your amplifier? Low enough to warrant such a low Zo?
     
  16. TJF

    TJF New Member

    Location:
    Munich - Germany
    I don't have the value on hand right now. But of course yes: Ideally maximum 100 Ohm output impedance of the Aikido. I think I have to change the plan to Noval Aikido to get the value approximately. I cannot find a suitable Octal tube. Matching 9-pin tubes would be the 6H30 or 5687 at 150Volt. But always a high Ik...
     
  17. TJF

    TJF New Member

    Location:
    Munich - Germany
    Whereby I would generally prefer the Octal version. In John's list I see the 6AS7 (8-Pin) at 100 Volt (!) with Z=95 Ohm, which you would probably have to mount diagonally due to space reasons. This would be ideal for the output. Has an Ik=100mA. But as far as I know, the input would have to be operated with 100 volts(?). I can't find a suitable tube for that, which provides halfway gain. The 6SN7 only really starts at 150 volts...
     
  18. Giorgi

    Giorgi Member

    Location:
    Georgia
    [​IMG]Very nice build!

    BTW: there is one error on PS-21 PCB, in particular on one low voltage regulator (see attached picture).
    On the bottom side of PCB cut trace between C14 positive and C15 and solder wire from the C15 to negative of C14. Right now C15 is shortened and make no sense.

    [​IMG]
     
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  19. Giorgi

    Giorgi Member

    Location:
    Georgia
  20. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Funny you should mention that. I noticed the same thing only a few weeks ago, and send an email to John.

    He was surprised no one had brought it to his attention before. Your fix is the same as the one he provided, but because it's not detremental to operation I've just left it.

    Thanks for reminding me!
     
  21. Giorgi

    Giorgi Member

    Location:
    Georgia
    actually, recently I receive my PS-21 and PH-2. And this wire was already fixed on PS-21
     

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