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MDAC First Listen (part 00110010)

Discussion in 'audio' started by 44000khz, Aug 15, 2016.

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  1. 44000khz

    44000khz pfm Member

  2. highfi

    highfi pfm Member

    You haven't lived unless you've listened to an iPhone through ATC 100 active (oh John what am I going to suffer through before you get round to recapping my MDAC)!
  3. misterdog

    misterdog Not the canine kind

    If John had to recap all our MDAC's then many of us would not live to hear an FDAC..
  4. highfi

    highfi pfm Member

    Very true. I understood he was going to have a group of students do it. Otherwise I woudn't have sent my M-DAC. I'm also eagerly waiting for an FDAC myself. Still, the fact that it is even possible to use an iPhone like that is amazing! Of course, it makes one aware of the difference between noise-making and music -making, and makes the yearning for the FDAC all the more acute…
  5. davidismynaim

    davidismynaim pfm Member

    question for all you MDAC experts. I am considering a 300B WAD based design power amp that is very sensitive around 300mv. I am told it works best with low gain preamps. I was not planning on using a preamp (mainly as I don't have one!) I was hoping to connect the MDAC, and in the future the FDAC directly into the valve power amp. Should I be considering attenuation or a passive pre? thoughts please. Thanks.
  6. Discovery

    Discovery pfm Member


    As someone who had a pre- in one system and a passive in another, I asked John a similar question a while ago. He replied that the FDAC is intended to be connected directly to the VFETs (his intended reference quality amplifier design) as a system without the need for a pre-amp. As the FDAC/VFET combination is John's vision of audio perfection, I would assume that it will be good enough for your purposes. When John answered my question, I then chose to feed my MDAC directly into my power amp and took the pre-amp out of the equation, which works fine for now.

    You might want to get more views about the 'low gain' bit though...


  7. davidismynaim

    davidismynaim pfm Member

    Thanks Trevor, it is the gain aspect that worries me the most. Will be interesting to hear other views from folk that have similar sensitive power amps.

    DANOFDANGER pfm Member

    Well, matching systems is important because of attenuation distortion. Now as i am aware the 32bit digital volume control with the ess dac on paper may show it can provide attenuation of -35db before signal resolution starts degrading. However in reality it appears that audible distortion is heard sooner than that. I think its probably ideal to keep the signal within -20 to 0.

    With a hypersensitive input of 300mv, depending on the paired speakers. You would most likely be requiring some hefty attenuation to keep the audible levels in comfortable range. This would likely go beyond the -35db.

    Even if you had some passive -20db attenuators you would still be outside the preferred range.
  9. davidismynaim

    davidismynaim pfm Member

    thanks, I too thought the degree of attenuation afforded by the digital volume would be too much. so would a passive preamp be the answer?

    DANOFDANGER pfm Member

    Yes i should think so, no point in adding a active preamp when theres no line level amplification going on, just added circuitry to degrade the circuit.

    DANOFDANGER pfm Member

    Still however, at that input sensitivity a very high quality passive volume control may be needed due to the vast degree of attenuation. I dont know how well even a analog control could do for that sensitivity.

    Someone else will know better than me.
  12. jirij

    jirij Virtual Member

    Can we please stop calling a few resistors a "passive preamp"? :) .. There's no (pre)-amplification going on, to my best knowledge, it's just attenuation.

    I know people historically call the box between their DAC and AMP a PRE-AMP, but it's really like calling your car a horse carriage, because you used to call your vehicle transport like that before.

    (Not that it's on-topic or anything.)
  13. davidjt

    davidjt pfm Member

    Banging your head against a brick wall there, I'm afraid.

    The phrase 'that begs the question.....' is now misused so often as to have completely lost its original meaning. Mention this and you're slightly bonkers/a pedant/behind the times.
    Sooner or later you're told 'all languages (except Latin) change all the time. Get used to it.

    So we're probably stuck with the passive preamp despite its being an oxymoron. :)
  14. highfi

    highfi pfm Member

    With a passive preamp it's really important to try it in your system. It depends on system interaction between source,cable and amps to an extent far greater than active pre-amps do.
  15. highfi

    highfi pfm Member

    Regarding gain, for what it's worth, with my active speakers rated 1Vrms and the FDAC 4V RMS in balanced mode, my normal listening levels are -26 to-36 db, which is supposed to be suboptimal (not that I have any complaints with sound quality - quite the contrary).
  16. davidismynaim

    davidismynaim pfm Member

    I have some XLR 20db attenuators in a draw, will wire up a cables XLR to phono so I can use them with the 300b valve power amp to see how that works with the digital volume on the MDAC. If that is unsatisfactory guess I will be looking for a passive variable attenuator and switch box (as we can't call it a preamp anymore ;))
  17. Richard Kimber

    Richard Kimber pfm Member

    I seem to remember that there was some talk a while ago that the optical input might work at higher rates than 96k, though it's not guaranteed to.

    What about the output? If I play sample rates more than 96k, does the optical toslink provide digital output downsampled to 24/96, does it do nothing, or does it attempt to output whatever rate is being played?

    - Richard.
  18. EIffel

    EIffel Cereal Killer

    "pre" is a prefix occurring originally in loanwords from Latin, where it meant “before” ( preclude; prevent); applied freely as a prefix, with the meanings “prior to,” “in advance of,” “early,” “beforehand,” “before,” “in front of,” and with other figurative meanings ( preschool; prewar; prepay; preoral; prefrontal).

    Source: google search

    So for me a few resistors can make a pre-amplifier ;-)
  19. Discovery

    Discovery pfm Member

    At last! Thanks Eiffel - this point has been amusing me for a while but I felt it would naturally resolve itself sooner or later... :)

    Have a nice day everyone.
  20. Neil A

    Neil A pfm Member

    You haven't lived until you have listened to DSD through a dCS Debussy /ATC100ASL+ new ATC SH25-76S tweeter. Looking forward to the showdown with the FDAC :)
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