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MDAC First Listen (part 00110111)

Discussion in 'audio' started by BigDog, May 7, 2017.

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  1. BigDog

    BigDog pfm Member

    Sorry to have mislead... I should have said "new ISO REGEN" which is on the order of $325 and which includes galvanic isolation, a redesign of the original REGEN which is still available for $175.

    Based on comments in this thread by those who I have come to know thru their posts, I have no doubt that John's DETOX will surpass the REGEN in both improved sound quality as well as construction based on number of machine screws if nothing else. :) I have less confidence in the performance of the ISO REGEN if only based on my personal experience.

    C'mon DETOX!
  2. JohnW

    JohnW Trade: Lakewest

    A standard module (CM3) will work but the CPU on the module will not be clocked-locked to the Audio Master Clock.

    My intention is to hand rework Modules under a microscope to allow external clock synchronisation - I might only do this for the P&P sponsored units (without extra cost).

    We have used an unused I/O pin on the CM3 DIMM connector as a 19.2MHz clock input (PLL'ed from the Audio Master Clocks) and I'll hand modify the module to route this pin to the CPU's XO circuit.
  3. JohnW

    JohnW Trade: Lakewest

    Sounds like you have a power amplifier with very high gain or very sensitive speakers?

    I'd not worry about it too much, there is no neat affordable solution.
  4. Richard Kimber

    Richard Kimber pfm Member

    Have I missed Fusion's view of the Detox, or hasn't he posted it yet?
  5. fusion5

    fusion5 on the dark side of hifi...

    No, you didn't miss anything. Unfortunately I have yet to deliver a final statement on the Superior DAC and the Detox.

    I'm sorry, but after my nephew was born 10 days ago, I had a lot of family business going on. This week should be calm enough for me to get more stuff done.
  6. dimedrol

    dimedrol Member

    Mine is a 200W@8Ohm power amp (input impedance 50kOhm) with no gain controls. Most listening I do is at night, hence MDAC volume has to stay below -40db and I saw people on this forum (including you) saying that this is not the best mode for the MDAC, yet it's the mode I need most. So in my situation, is there anything I could do, including opting for a different DAC etc? Or is this particular problem not worth resolving (considering the drawbacks of known approaches)?
  7. Purité Audio

    Purité Audio Trade: Purite Audio

    The whole gain of your system is too high, it is really common, with DACs having increasingly high output, a DAC with a variable analogue output would solve the problem.
  8. dimedrol

    dimedrol Member

    how is this different from a preamp?
  9. Purité Audio

    Purité Audio Trade: Purite Audio

    Analogue attenuation decreases the signal and the background noise, digital attenuation decreases the signal but not the back ground noise, that is why it is not good practise to use too much digital attenuation.
  10. misterdog

    misterdog Not the canine kind

  11. BigDog

    BigDog pfm Member

    It may be situations such as this that Mytek anticipated and made allowance for by offering jumpers to lower the gain by 6dB as required. In extreme cases, the Mytek DACs as well as others, I surmise, can overload the amp(s) resulting in distortion.
  12. Purité Audio

    Purité Audio Trade: Purite Audio

    Having the choice of output allows you to use more of your volume knob!
  13. dimedrol

    dimedrol Member

    I understand that some standalone/built-in preamps operate in analogue domain, I just don't understand how are they beneficial to in-line attenuators I already ordered. In-line attenuators are fixed level passive preamps (that is my understanding). And there's a lot of opinions on the internet about them degrading sound.
  14. JohnW

    JohnW Trade: Lakewest

    This does not apply to a decent digital front end where the significant noise contribution is basically the output impedance of the DAC array.

    The MDAC has a balanced Dynamic range of 126dB in standard form any pre-amplifier including a passive pot over most of its operating range is going to add more thermal noise.

    Where a Passive pot / "Good" pre-amplifier is going to help is that any Common Mode noise is also going to be attenuated at lower levels - where as the RF "Hush" is outputted at full level at all times with a Digital preamp.
  15. dimedrol

    dimedrol Member

    Now the question of the year is: under what condition will an analogue preamp (attenuator) be beneficial to the MDAC's digital one, provided the listening level is -40db? Are there known implementation meeting that criteria?
  16. brab

    brab pfm Member

    Relax. My situation is similar to yours. I use -15dB Rothwells. Everything sounds great.
  17. ChrisPa

    ChrisPa pfm Member

    No problem with the MDAC at -40db (or less)
    From my listening sessions with some properly implemented balanced attenuators (built by John) I (marginally) preferred the sound without, but any differences were minimal and potentially at the imaginable level.

    By all means get some attenuators and see what you think, but I wouldn't unduly worry about it
  18. timola

    timola pfm Member

    On some well produced tracks my MDAC is running at +3db ....and I still want more....:D:D:D

    (not really, the system is close to total breakdown at that sound level)...All the amps and the MDAC are really hot after a listening session....worryingly hot, but John assured me the MDAC can't go past about 38 Celsius...so maybe I imagine things.
  19. misterdog

    misterdog Not the canine kind

  20. BigDog

    BigDog pfm Member

    I am all in favor of volume settings appropriate to the genre of music being played and find that almost nothing sounds good in a whisper.

    38degC?! My Pass Class A monos idle at 60degC/140degF. Not a good thing during the warmer times of year.
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