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MDAC First Listen (part 00111000)

Discussion in 'audio' started by PhilCTTE, Jun 20, 2017.

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  1. Bob L

    Bob L pfm Member

    The MCRU unit, and the similar Swagman,are only "3-rail" supplies, like my home-assembled dual Calex supply, and connect via the original 9-way DIN connector on the back panel. Fancier versions ( see my comment above about 5- rail supplies) have to work with the outer sleeve removed, and some dangling wires (see Miterdog's "plydac" pictures a week or so back).

    John commented earlier that the PS input to the MDAC-2 is a D- connector, "to make it easier for Home builders" (maybe not his exact words) to connect on their own supplies, but I think this means at least a "5-rail" supply. You and I are in the same position- when we get the MDAC-2, all we can do is entrust our old supplies to the mercy of e-Bay.
     
  2. misterdog

    misterdog Not the canine kind

    I'm aiming for a neater final solution though. :D

    [​IMG]

    Decent power supply makes for a BIG difference in SQ. with the Mdac so I assume it will also do so with Mdac 2.
     
  3. JohnW

    JohnW Trade: Lakewest

    1. The AC linear supply cannot supply the required power for the MDAC2.

    2. It does not provide isolate for the Digital and Analogue sections

    3. Has no isolated tapping for the Streamer PCB

    4. External PSU's (with the internal PSU PCB modified / bypassed) on the MDAC brings a significant step improvement. The MDAC's non optimal Grounding arrangement on its Mini-Din due to lack of contact poles significantly degrees the MDAC's performance. Adding an external PSU without resolving this limitations does not help much (such as adding the MRCU).

    The PSU is the foundation of any audio product - compromising here is a sure recipe for failure.
     
  4. JohnW

    JohnW Trade: Lakewest

    In fact the MCRU is only a 2 rail supply.
     
  5. JohnW

    JohnW Trade: Lakewest

    In theory all USB drives should work, but some drives have VERY high / nasty current peaks during seek that can trigger the USB current limit - this is especially true with cheaper drives from China that compromise on the internal PSU bulk decoupling - or have non optimised servo control loops (peak seek current is a consideration when optimising the servo circuit coefficients).
     
  6. timola

    timola pfm Member

    What a mess! modern art?
     
  7. JohnW

    JohnW Trade: Lakewest

    The MCRU upsets me somewhat as its expensive to my eyes - but to be far its "typical" of HiFi industry charges, but if you compare the engineering, internal component count and the amount man hours that has gone into the MDAC2 over these past years - then I'm being stupid for not taking the same path!

    If I where to ponder if, I'd get depressed as I pump everything into my work, and it takes its toll... I've just spent over GBP40K on a mini SMT line, yet can ill afford to take Renata on a holiday... on top of that we are kitting out a 3rd bench position for a yet to be found engineer to help with production. This means "duplicating" the test equipment required as I cannot pull equipment of Jareks or my lab bench.

    When I see a simple PSU sold for so much - I feel stupid for always taking the hard route!

    In answer to your question, the MCRU is only a dual rail PSU - we need 7 PSU rails for the MDAC2 with decent current for the Streamer board (12V 1.5V to 2A max).

    Also the Digital and Analogue PSUs sections need to be galvanically isolated.
     
  8. JohnW

    JohnW Trade: Lakewest

    Arh the good old days of Rats Nest point to point wiring! :)
     
  9. YNWOAN

    YNWOAN 100% Analogue

    No wonder some valve gear goes up in flames with matches wired into them....
     
  10. Bob L

    Bob L pfm Member

    Thanks John- I shouldn't have reported my guess as fact...

    Cheers

    Bob

    p.s. Just to amplify your point about the costs of other LPS supplies, I think this means that the MCRU at £360 does more or less the same as a single Calex, which cost me £20 (but it does look much nicer...)
     
  11. davidismynaim

    davidismynaim pfm Member

    John, so sorry this triggered such remorse with your approach. I do hope that you can look back at your last few years with pride and hopefully designs and products that can result in a decent financial return for you. Staying true to your principals is a worthy endevour, I just hope you find commercial outlets that can be rewarding too, striking a balance is never easy.

    Btw, this is my friends psu, that I have on long term loan, so I was just interested in whether it had any role to play with MDAC2.

    Do let me know if I need to contribute anymore based on my desired configuration of MDAC2-Streamer-ADC for analogue input so I can avoid the need for a preamp. Thanks
     
  12. misterdog

    misterdog Not the canine kind

    The Calex supply is £ 96 now it has an ROHS sticker.

    I find it amazing that people will spend £ 360 on a LPSU for a £ 600 DAC.

    The benefit of the full 5 rail supply probably warrants such but the benefits of swapping out the supplied power brick brought minimal gains.
     
  13. misterdog

    misterdog Not the canine kind

    Imagine trying to design a pick and place machine to do that :D
     
  14. stephengrenfell

    stephengrenfell pfm Member

    Hi John,

    For those folks who have ordered Detox (before the streamer option existed), but now plan to use only the steamer and not USB into MDAC2, what do we do ?.

    Personally : I don't care about loosing the DETOX development fees (this is part of the deal), but I don't particularly want to splash out on the Detox manufacturing fees if I no longer need it and will likely not use it.

    Thanks
     
  15. Dark Energy

    Dark Energy pfm Member

    Replacing the MDAC PSU can give you a small improvement but you can do it simply enough, I think a zener (or similar) referenced capacitance multiplier/gyrator would be as good as anything. While I no longer have an MDAC I do have the service manual, super regulators are overkill here. There are some expensive power supplies being offered with "over enthusiastic" performance claims. You could tweak a Hi-Cap to work, it's not ideal, the regs would run hot and the input/output differential on the LM317K wouldn't look nice, but you know how "complex" a Hi-Cap is, so building something more appropriate isn't too difficult.
     
  16. timola

    timola pfm Member

    You're talking about me!....I have a MRCU power supply....:(

    I reported here several years ago that it made little difference if any IME (My review was never published by MRCU although I spent much time testing and writing it). When pushed, I said maybe a max of 5% improvement which was being generous.

    It is however very well built (the blue led could light a runway its so bright...so mine is black taped). It went wrong last year and was repaired completely free of charge...which was very nice. I replaced the fuse once too after if blew.

    The reason I bought it was:...like John just said, the power supply is very important in HiFi and I just guessed the original external one was a budget model, although it was heavy for it's size....we live to learn, i suppose.

    This is why I have always been incredulous here why people complain about the costs of these projects and how John is costing these projects to the bare knuckle, without any headroom.

    I do understand that John is developing products that may benefit LakeWest in the long run....initially without getting bank loans and taking huge risks.
    John has now risked over £40K of his own money without counting his time and trouble (I think he is enjoying it though :D).

    I'm confident these products will be a success and if we all spread the word, John could market these products at a decent profit in the future i hope.

    In fact I think it's important that LakeWest make a decent profit in the long run......on purely selfish grounds....I want top quality LakeWest products in the future. :D:D:D
     
  17. BigDog

    BigDog pfm Member

    Really...?! It DOES have an abstract art quality to it!

    [​IMG]
     
  18. iansr

    iansr pfm Member

    In contrast several of us found that using 3 x Calex to make a direct 5 rail supply and bypassing the MDAC's PS board makes a BIG difference. I think it's difficult to over estimate just how important the PS is for all hi fi components.
     
  19. misterdog

    misterdog Not the canine kind

    The Calex has 5mv of ripple and noise where a good regulator can be down to 0.4 mv.
     
  20. iansr

    iansr pfm Member

    Well Radiohead were great but Chic have just blown everybody else away. Absolutely bloody fantastic 😀😀
     
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