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Mac mini to DAC Settings

Discussion in 'audio' started by deebster, May 14, 2019.

  1. deebster

    deebster Half Man Half Biscuit

    Been using an old Mac mini (Core Duo 1.83 c2007 I think but can check when back home) to stream my ripped CDs from iTunes to an Audiolab Q-DAC via its optical input and it all works fine, just wondering if I could do better on connections and settings.

    From reading other threads it seems most folks use USB rather than optical and I've used that in the past with no problems but tried optical a couple of years ago and stuck with it. Might've been down to sound quality but honestly can't remember.

    I favour my LP12 as a source but of course there is plenty of stuff that never made it to vinyl so need both, but now I'm interested in getting as much as I can out of the digital side. Granted the Q-DAC isn't much loved and I get that, but for now it's the Mac to DAC settings I'm interested in. A new DAC can follow maybe.

    No need for any streaming service or music suggestions, hence why I've stuck with iTunes. All its sound enhancer / equalizer settings are turned off and I only have ripped CDs, so no hi-res files. Am I right in thinking here the best setting is native CD format 16/44.1?

    The other question I have is USB vs optical. Is this more dependent on the Mac's / DAC's relative performance on each output/ input, or is there more to it than that?

    Apologies as I'm sure these questions have come up plenty of times before, but would appreciate any pointers on the above or anything else I should consider
  2. JensenHealey

    JensenHealey pfm Member

    My Mac Mini is USB connected to a Cambridge Audio 100. All good, running Roon with music attached on a USB drive. Roon runs headless with control on a PC laptop. The Cambridge Audio box has its optical input connected to the TV.
  3. tuga

    tuga European

    Computers produce electrical noise. If you use a wired connection to the DAC then you will be sending that noise along. Some DACs are better isolated whilst others are very sensitive. Using an optical interface prevents this.

    The optical interface has two disadvantages: the computer is not slaved by the DAC and this increases jitter (sensitivity depends on the DAC), and the Apple Toslink optical is as far as I know limited to 24-bit/96kHz.
    USB usually performs better in terms of jitter and currently allows 32-bit/768kHz and DSD2048. Why does this matter?

    There are two approaches to using the computer as transport:
    - send the file as is and rely on the DAC's internal ASRC and filtering
    - upsample and filter with the computer with (in most cases) higher performance software then feed the resulting stream to the DAC


    For CD/Redbook(16-bit/44.1kHz) playback.
    On the Mac Mini, open Midi, then select 16-bit 44.1kHz for the optical output.

    There's a useful and very affordable add-on for iTunes called BitPerfect which will add features and increase performance, namely allow you to upsample and try different filters.
  4. deebster

    deebster Half Man Half Biscuit

    Cheers Tuga

    So assuming I don't need any sampling then it's a trade-off of noiseless but potentially jittery optical, vs noisy but jitterless USB?

    Which I guess then means try it and listen.

    Will check out BitPerfect though. I've read it's not working on the latest OS X but then I'm on a very old version (Lion IIRC) so may be OK
  5. notevenclose

    notevenclose pfm Member

    There are a number of third-party sound-processing options available for the Mac. I've used BitPerfect in the past, it's okay, but there are better options available, of which my favourite for quite a while has been Audirvana.

    Virtually all of them have a free trial period so you can test whether or not you think they bring anything to the party without it costing you anything other than a few hours listening.

    Like you, the vast majority of the music I store on a Mac is rips from my own CDs and as such the whole 'hi-res' thing is of minimal interest. Truth be told I have around 120 tracks in hi-res format and I actually prefer the RedBook rip, but that's another story.

    Generally USB, flawed though it is, will potentially offer better sound than Toslink, but they're not 'night and day' differences, so as you say, listen and make your own mind up. Generally I've come to think of file-based replay as best thought of as a 'system' (source, cables, DAC) in the same manner as motor unit, arm and cartridge, so often it's not so much about the merit of individual components as finding those which work optimally together.

    All that said, physical media still sounds better... ;-)
  6. tuga

    tuga European

    If you wish to go the extra mile then I agree that there aet better players/processors than iTunes, such as JRiver, Audirvana, Amarra or HQ Player (my favourite).

    In an attempt to provide the DAC with the cleanest signal I read my music files from a NAS, process them on a laptop with HQ Player Desktop and then feed the stream to a Cubox with the HQ Player NAA (which works as an endpoint/buffer). The three are connected with Ethernet to take advantage of the galvanic isolation.
    The LPSU-powered Cubox, a low-power NUC that produces very little electrical noise, is connected to the DAC with a short 1'' USB M/F adapter but there's a USB Y-splitter before the DAC which severes the power leg of the USB connection coming from the Cubox and injects clean 5V from a linear PSU.
    All the upconverting (PCM to DSD128), filtering and noise-shapping is performed on the laptop, the DAC is in Non-Oversampling Digital-Filterless mode (doing what it's supposed to, D/A conversion).

    This effort has taken the performance of my file playing system above that of physical media.
  7. tuga

    tuga European

    P.S. I also add a touch of EQ to a couple of modes below 100Hz.

    Of course a 10 year old Mac Mini doesn't have enough processing power to perform these very demanding tasks.
  8. notevenclose

    notevenclose pfm Member

    Thank goodness you didn't go down one of the more complicated routes...
  9. notevenclose

    notevenclose pfm Member

    You probably just need a better CD player. ;-)
  10. tuga

    tuga European

    I have a really nice modified PD-91. Hard to beat.

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