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MDAC First Listen (part 00111010)

Discussion in 'audio' started by JohnW, Jun 9, 2018.

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  1. JohnW

    JohnW pfm member

    To help suppress external / internal RF interference within the MDAC2 / FDAC the critical circuit blocks are internally shielded from each other via small screened enclosures... These enclosures help to reduce and control the internal RF environment which is very important to achieve the high Jitter attenuation and low phase noise of the audio clock and sub systems...

    These internal screened sections effectively allow multiple internal enclosures to subdivide the critical circuit sections...
    ti33er likes this.
  2. ti33er

    ti33er pfm Member

    I always wanted my ‘Detox’ internal ...I used to love having my rack/s littered with bling hardware and interconnects, but nowadays the minimalist approach is my preference ...definitely, I’m most happy for my Detox contribution to go into the MDAC2 pool instead

    There are others that wanted external Detox though ...could they not just receive a Detox Board and try house it themselves (as the perfectionist case is what’s holding John back as far as I recall) ?
  3. BigDog

    BigDog pfm Member

    FWIW (and I HAVE pictures), the CNC DETOX chassis as designed had individual shielding compartments for each of the 3 decrapifier stages as well as other pieces of the circuitry, part of its distinction from realized competitive designs. I expect trying to do that with a garden variety build-box would be a bit of a challenge.

    Not to speak for others in the cue for a standalone DETOX but IF the enhanced DETOX planned for the "X"DAC is going to exist as a separate board within the DAC chassis which had the potential for adequate EMI/RFI shielding, I WOULD be interested in that compromise in order to get a SOTA DETOX hand!
  4. mike9876

    mike9876 Well-Known Member

    I will be happy to take what comes first, I am happy we have gone back to using the MDAC as the donor unit, it's only cost what is a worry because not everybody is high earners. I budgeted £1200 for this project and now it's going higher and higher. I am happy to pay extra for the dexot to be included and I am very happy that ESS Dacs are not being used, I always thought they had their limitations. I just hope when the final bill comes I can afford it.
    JohnW likes this.
  5. Bob L

    Bob L pfm Member

    John, I'm quite certain that any power supply that I might build would fail any safety regulations, even those in post-Brexit ERG Freedomland, and might not be an improvement on your internal supply. However, mainly out of curiosity, what will an external supply need to provide?
  6. jirij

    jirij Virtual Member

    Hello everyone, it's been a while and I see we have a new forum engine, but besides that, not much has changed. :)

    From reading the last few pages, I can only support the decision to scale back the ultimate vision to smaller steps, starting with the donor chassis. Like I was saying years ago, iteration and smaller milestones are the goal to success, not one grandiose premiere, in my opinion. The world is full of dead visionaries that never managed to finish their magnum opus because it was not ready yet.

    Over the last few years, I got into additive manufacturing ("3d printing") and subtractive as well (CNC mill) and will be building a steel-capable DIY router soon (actually my 3rd), so if you need some chassis (plural) milled, I may be able to prototype a few parts (not now, in a few months). Probably the cheapest approach would be casting the rough shape + machining the surfaces. Anodizing is a bit tricky on the chemical side, but logistically not that hard. Also, aluminium is boring, make it out of some alloy like aluminium bronze - no anodizing required or wanted, hehe.
    Anyway, no point in making the chassis if there's no board yet. :)

    Keep dreaming on! ... But don't let life stop you ..
    Mark Dirac, misterdog and ti33er like this.
  7. JohnW

    JohnW pfm member


    Sorry for the late reply, I'ts been crazy busy this week.

    I do worry that the more advanced optioned boards will require higher current then the 30VA of the MDAC transformer so will have to find a suitable solution - the deign is far more efficient then the original MDAC, but it now also far more features (Streamer / Tube options etc).

    The basic MDAC2 option will be Ok with the standard PSU, but I'll have to figure a PSU solution for the more advanced optioned boards.
  8. iansr

    iansr pfm Member

    John, I’m one Of those who used the Calex PS units to create a direct 5 rail supply for their MDAC. This bypassed the power input board. I wasn’t alone in thinking that this brought about a very significant improvement in SQ. This suggests that the aforementioned input board is a major weak link in the MDAC, so I’m really hoping that the MDAC2 will not be reusing that board -?
    I also hope that the design will make it easy to opt for a high quality DIY PS rather than the standard MDAC PS.
  9. ti33er

    ti33er pfm Member

    Hi JiriJ

    How expensive is it to make bespoke cases that may be fit for purpose here?

    Thanks :)
    Mark Dirac likes this.
  10. JohnW

    JohnW pfm member


    No problem to reuse the Calex PS - I'll work with you on a connection diagram.
  11. GWM

    GWM Lost in the 70's

    John if there's a tube option won't this need a higher voltage supply?
  12. paulski

    paulski pfm Member

    That’ll only be in the FDAC which will have a dedicated power supply.
  13. JohnW

    JohnW pfm member

    The Tube option will be also available in the MDAC2 chassis - the HV supply is not an issue but rather the relatively High current required for the tube heaters...
  14. davidjt

    davidjt pfm Member


    If you're going to use pm to avoid clogging up this thread, I'd be grateful if you'd copy me in.
    Many thanks.
    JohnW likes this.
  15. paulski

    paulski pfm Member

    There’s room in there for valves?!?
  16. davidjt

    davidjt pfm Member

    Well, perhaps not for a pair of 813s . :)
  17. paulski

    paulski pfm Member

    Yeah, they’d be a bit snug!

    I’m more concerned about the heat build tbh with valves in such a small space.
  18. russel

    russel ./_dazed_and_confused

    OK, so so long as an improved PSU has the voltages and currents of the original MDAC2 it will be fine for the basic MDAC2.
  19. davidjt

    davidjt pfm Member

    Are you buying or building? Or do you have one already?
    The Swagman (as recommended by JemHayward of this parish) uses 2 x 50VA transformers, one for the analogue and one for the digital supply. So way more than the original 30VA MDAC lump. Gilding the lily now that John has sweated blood over new internal psus, but whether or not you hear a difference at least you'll know the transformers can cope.
    If you've built something Calex-based you might chuck another one on the pile if they're still available. Or simply make a 50-60VA MDAC lump of your own.
  20. jirij

    jirij Virtual Member

    That depends on many things, milling it out of a single cast block, ~15 GBP just for the material (of which 80% gets removed) for a detox-sized box - casting the rough shape + finishing the surfaces would be probably cheaper. Don't want to go on long writing sprees here, but one could probably make it easily within 80 GBP with all the panels, both halves, finishing, engraving, work, etc., especially if making say 10 or more pieces. Maybe cheaper.
    I don't have any business so I would probably make only a few and for "free" (materials + running cost + shipping) for the pfm friends here if it gets to it. We could make it personalized for each piece with custom engraved names/drawings/etc. I'll probably try to prototype something once the MDAC2 is out.
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