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

    [​IMG]

    Here is the Quencharc RC thingy soldered to the switch, accompanied by the output wires.

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    All the necessary wires now attached and terminated with crimp rings. The cable is 16AWG PTFE 600V rated - nice, but quite stiff, making it difficult to twist nicely.
     
    struttincool likes this.
  2. fully_articulated

    fully_articulated Forum Resident Thread Starter

    [​IMG]

    This is the window cut-out for the volume control display. It had to be big enough not only for the LED numbers but also the IR receiver that sits beside.

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    And this is the red perspex insert, also produced by Front Panel Express.

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    The display itself holds the window in place, so no glue required. Unfortunately, I damaged one of the threaded holes and had to use screws in only three corners.

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    Back of the front - complete!
     
    33na3rd likes this.
  3. fully_articulated

    fully_articulated Forum Resident Thread Starter

    [​IMG]

    The LED is soldered to the attenuator PSU, and will be used for the front panel.

    In a moment of fully realised apex dunder-headedness I thought I should test the LED polarity before soldering it to the board. Grabbing a 9V battery, I pressed the leads to its terminals and the LED fizzed and smoked itself dead.

    DIY tip: An LED always needs to be preceded by a resistor. ...and buy more than one of a thing when you order parts.

    [​IMG]

    As the Khozmo attenuator was going to be screwed to the front panel the supports could be removed. They would have been in the way of the aluminium bar anyhow.

    I did however want to keep the rear strut, but needed to move the hole back a bit, so some hole widening was in order. I wanted to be careful not to get metal shavings near the finished componentry.
     
    ScottRiqui likes this.
  4. Bummer about the stripped threads. Looks like it's a blind hole. It is possible to put a thread insert (helicoil) in a blind hole, though a bit tricky. Though it looks like three bolts will hold the window and display just fine. Plus three supports for legs and feet is more audiophile than four. Last time I needed a helicoil I took the part to a local bicycle mechanic/shop that also did frame building and they were able to do it and had the tools and the right size insert (admittedly it was a bicycle part, but for something like this parts is parts).
     
    fully_articulated likes this.
  5. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Thanks, that's an interesting idea - I'll keep it in mind. You are right though, I need to maintain my audiophile cred, so three should be enough. :cool:

    The original idea was to use hex spacers, but the threads were too long so I chopped them. Every seemed fine while I was screwing the first in but it was mashing the thread the whole way down!
     
  6. fully_articulated

    fully_articulated Forum Resident Thread Starter

    [​IMG]

    After the front panel is mounted the switch is wired to the terminal block. It should really have been six terminals, and now the wiring looks a bit oddball.

    I ran out of crimp rings, so had to use an old black link wire where a red one needed to be. Will have to remember to go back and redo that at some point.

    After this a plastic protective cover was fitted, like the one in the next photo.

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    This is the other terminal block, now with a thermistor connecting the HV transformer primaries.

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    Hopefully the LED fits tight enough without needed any adhesive. Time will tell on that one.
     
  7. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Then the extension bar and knobs are fitted, and it's finally done! Let's turn it on.

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    As the volume control knob is solid aluminium and quite heavy, hopefully that won't be detrimental to the Khozmo over time.

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    The blackness of the front panel makes it difficult to shoot pictures well. This might be one of those 'looks better in person' times.

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    The red perspex works really nicely. The Khozmo display LEDs behind there are white.
     
    JMAC likes this.
  8. fully_articulated

    fully_articulated Forum Resident Thread Starter

    [​IMG]

    The triode symbol is actually a great shade of pumpkin orange. I think I may have a matching front panel made for the F6 but with a mosfet symbol on its face.

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    With the lid on. Maybe one day I'll make a tube-something that looks more tube-traditional!

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    Back end. Pretty dull back here.
     
  9. fully_articulated

    fully_articulated Forum Resident Thread Starter

    I took it outside to see if I could get any better images. It would seem not!

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    Once again thank all of you for joining me on my journey, especially those that commented or liked. It was good to know I wasn't just a guy talking to himself. :laugh:

    If anyone wants more, this is the full gallery of the entire build: https://imgur.com/a/Gs2TVQ1

    Hopefully I'll get some decent time to give it a damn good testing! Stay tuned...
     
    Kray, jmpsmash, Echo and 4 others like this.
  10. fully_articulated

    fully_articulated Forum Resident Thread Starter

  11. djost

    djost Senior Member

    Location:
    Dallas, TX
  12. WntrMute2

    WntrMute2 Forum Resident

    Great build. Nice to see the extra care you took. So, how does it sound?!
     
  13. JMAC

    JMAC Forum Resident

    Location:
    PDX, OR, USA
    The red is really slick!
     
  14. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Let's agree to agree on that. ;) I think black and red is my favourite front panel combo. Blue lights be damned!
     
    Echo and JMAC like this.
  15. fully_articulated

    fully_articulated Forum Resident Thread Starter

    I'm going to have to equivocate for a while on that question. It doesn't hum, so that's a major battle won.

    If I can quote Broskie from this link New Aikido Stereo Noval PCB & CCA where he introduces this particular board:

    [​IMG]

    At this moment I find myself being almost desperate to like what I'm hearing and afraid that it was all a waste of time, so can't make any concrete declarations. They would be too affected.

    What I can say is that it seems quite neutral - not tubey, tubby or even lush. It has, as one would hope from a piece of tube equipment, elevated the sense of 'realness' in the music.
     
  16. fully_articulated

    fully_articulated Forum Resident Thread Starter

    A little more on the early sound impressions.

    In the first few hours it sounded slightly wonky. I think when you listen to something familiar, whether on a full stereo system, headphones, car radio, or whatever, that even though the quality may be different the core of the presentation doesn't really change, and you can recognise it in equipment that is new to you. This was a bit weird sounding, but I couldn't really fix on why.

    At first I thought maybe I'd mixed up left and right channels when hooking it up. Things weren't quite imaging in quite the same way I was used to. I confirmed that wasn't the case, but it did make me recollect something: the Aikido circuit inverts absolute phase.

    Swapping the speaker cable plugs out of the amplifier seemed to immediately make the soundstage more coherent, or more recognisable at least. But then again, as JB says, I am the easiest person to fool.

    The other problem is this - how do I know how much of what I'm hearing is the sound of the tubes or the circuit? I suppose only tube-rolling will tell, but I may wait some time to do that, not least because there's eight screws between me and the interior.
     
  17. WntrMute2

    WntrMute2 Forum Resident

    I agree on the placebo effect being a powerful one. I've built my own DHT amps, phono-stages, crossovers, resurrected a TD-124 and it is indeed hard to separate your efforts from the actual performance of the rig.
     
  18. fully_articulated

    fully_articulated Forum Resident Thread Starter

    I find the worst thing I've been doing is trying to imagine what other people would say about the sound, even though I'm the only person who listens to my stereo. I need an audio Freud to explain that!
     
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  19. fully_articulated

    fully_articulated Forum Resident Thread Starter

    One of the things I've kinda learned with DIY is that everything is a compromise. I'm not sure it's not the same with listening as well.

    If I understand the concept of imaging correctly, this thing images like a monster. The resolution of voices and instruments, and their placement within the soundstage, is really something. I suppose this is transparency?

    This serves background sounds well, not bringing them forward but defining them in their own space, so you can appreciate that Guiro being stroked quietly in the corner or the muted piano accompaniment to a vocal.

    I've always been a bit lost at sea with lyrics, never being able to easily decipher the words many vocalists are singing. The Aikido appears to bring them out nicely. Also, it has been easier to pick out individuals when singing in chorus, or when two vocalists are singing in close harmony perhaps into one microphone.

    There is another side to all that however. With the voices being so well defined, there's a tendency toward more unwanted sibilance. The expanded soundstage can make the rest of the presentation feel a bit thin - at least not as thick or rich as I'm used to - and maybe less focused.

    Most of this was solved after I re-measured and adjusted my room correction EQ. My curve is (I believe) much the same as the Harman curve - a straight line tilted downward from bass to treble decreasing about 1dB per octave. Someone correct on that if I'm wrong. Mine is slightly more tilted (about 1.4dB per octave) meaning basically a bit more bass and a bit less treble.

    That means I can't really categorise the Aikido as far as frequency response goes - although it's safe to say it's not dull or dark. The tubes I'm using are JJ's and Electro Harmonix, so nothing with a large amount of pedigree.
     
    33na3rd likes this.
  20. Just Walking

    Just Walking Forum Resident

    Location:
    Abingdon UK
    Thanks for a great build thread - a real joy to read. And first rate detail and build quality!
     
  21. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Cheers, I'm glad you enjoyed it!
     
  22. MrKovo

    MrKovo New Member

    Location:
    Oakland, ca
    Hello, brand new forum member--have been a lurker for many years--doing what brand new members do: dredge up old threads.

    fully_articulated, now that you've had your Aikido build completed for almost a year, care on providing an update on the sound? Great build thread, by the way. I am sure I will be revisiting it often.

    I am currently, and slowly, populating a PS-21 board with the intent of using it to power a an octal Aikido board. Will be using 12sn7 tubes and two toroidal transformers to power the three power supplies. My first foray into DIY audio.
     
  23. fully_articulated

    fully_articulated Forum Resident Thread Starter

    Quite a challenging first project I would say, so good luck! And thanks for viewing my thread.

    As for the Aikido, it has been a real pleasure since I built it. Initially I found it a bit hard in the upper midrange or something like that - transparent and open but slightly affronting also. It's difficult to describe.

    I'm not sure how much a believer I am in break-in, but I was relatively patient with it as the output caps especially had a reputation for needing some long hours before sounding the way they should. Rolling in some NOS 6N23P tubes helped some, and either my ears or the Aikido started to settle.

    However, it was trying the Russian 6N6P tubes in the input section that really gave me what I was searching for. They took whatever edge I was experiencing away without sacrificing the detail or transparency. A bit warmer in the bass, a bit softer (yet more realistic) up top, smoother through the midrange. Although they could probably use a bit more plate voltage and current, the Aikido sounds so good now I haven't yet been bothered to go back and fiddle with anything like that. There's also some Mundorf output caps that I bought to install as well. Maybe one day.

    There's been only one main 'problem' with the build. The 6.3V winding on the main transformer really isn't enough for the 5V regulated remote power supply. In the year since being built, it has maybe lost power to the volume control 5 times shortly after turn-on. Not too bad though - turning it off and on fixes that.

    The other thing is I wish I'd specced a higher current heater transformer. 2 amps per winding was fine with the intended 6922 tubes, but the 6CG7 & 6N5P are 600mA, and the 6N6P IS 750mA! Can't run those in both the input and output sections even if I wanted to.
     
  24. MrKovo

    MrKovo New Member

    Location:
    Oakland, ca
    A bit of hubris mixed with ambition, I suppose. Really trying to take my time, double checking orientations and being patient with my soldering. I have a feeling chassis work and wiring will really be where the rubber meets the road.

    Appreciate your thoughts. Glad to hear it settled in and you're enjoying it!
     
  25. BillWojo

    BillWojo Forum Resident

    Location:
    Burlington, NJ
    I had an earlier Aikido factory built preamp with 12AX7 tubes that I purchased used. It was the biggest improvement in my system I had ever done. The increased detail and soundstage was amazing. It took an Audio Research SP8 to unseat it.
    They are a lot of bang for the buck!

    BillWojo
     
    fully_articulated likes this.

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