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DIY NAP250

Discussion in 'd.i.y.' started by Jeff Young, Jan 10, 2019.

  1. Jeff Young

    Jeff Young pfm Member

    @nootfam, there's still one project (a DIY Pass HPA-1) ahead of it in the queue. My guess is it'll be another month or so....

    Cheers,
    Jeff.
     
  2. Jeff Young

    Jeff Young pfm Member

    Having completed my HPA-1 clone (pictures here: link to diyaudio.com), I'm back on this project.

    I've decided to do my boards without solder mask and silkscreen so they look more old-school. They'll still be two-layer with plated-through holes, so not completely old-school. But care will need to be taken when soldering to check for bridges.

    Legends will be sparse (connections, test points and pots) and done in copper.

    Renderings here: link to diyaudio.com

    Anyone interested in a small group-buy? I'll be making the boards at EuroCircuits (made in EU) so they'll be more expensive than Chinese-made boards. Price will also depend heavily on volume. Figure between €10/board and €20/board.

    Also let me know if you'd be interested in the original or inverted regulator boards (or both). Note that the amp boards have jumpers so you can power either the whole amp or just the front-end from the regulators.

    Cheers,
    Jeff.
     
  3. john.luckins

    john.luckins pfm Member

    Hi Jeff, I have been watching your endeavours with interest, particularly the inverted regulators and fancy giving them a try. Had you considered "improvements" to the Amp design, such as splitting R7 and putting a cap to the -ve rail? Perhaps such changes would not be in the spirit of the exercise?

    Anyway, if possible, I'm in for a couple of the amp and inverted PSU boards as I have loads of BUV60's and BDY58R's ready to go.

    Cheers

    John
     
  4. Jeff Young

    Jeff Young pfm Member

    I also should have a few avalanche-tested (greater than 50V) BC239Cs available. I haven't matched them yet, so I don't know what the yield will be -- I might only have 2 pairs extra or it might be 4 or 6.

    Anyone know what a reasonable matching tolerance is? (I know the Avondale spec is to unbalance them by 10%, but I'm skeptical about that....)

    Cheers,
    Jeff.
     
  5. MJS

    MJS Trade: Consultant at WH Audio

    Naim used to match them by measuring the offset in an amplifier board with the DUT as one of the pair. All those with the same offset were deemed matched. It was that way for 20-odd years. They do it by micro now.
     
  6. Jeff Young

    Jeff Young pfm Member

    Huh, that's a clever way to match them at the actual operating point. Not terribly conducive to DIY, though. :cool:
     
  7. Jeff Young

    Jeff Young pfm Member

    Amp front and back:
    [​IMG]
    [​IMG]

    Regulator front and back:
    [​IMG]
    [​IMG]

    Inverted regulator front and back:
    [​IMG]
    [​IMG]
     
  8. Jeff Young

    Jeff Young pfm Member

    I've posted the BOM I'll be using for the amp board along with a stuffing guide on DIYAudio:

    NAP250 Group Buy post 16
     

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