Positive Feedback ISSUE 71
january/february 2014


Musings on Building a Digital Music Server: When Lo-Res is High-Res and How to Best Down Sample Your Music
by Andy Schaub


"If I ventured in the slipstream
Between the viaducts of your dream
Where immobile steel rims crack
And the ditch in the back roads stop
Could you find me?"

—"Astral Weeks" by Van Morrison

OK, you already know I'm crazy or at least perverse in the sense that, while everyone else is screaming for more and more resolution, I actually bought a very high-end DAC that sounds best at 44.1kHz. I'm not saying high-resolution is a bad thing. In fact, I've often found that 24/192 files down sampled to 24/44.1 sound better than files I get at 24/44.1 and definitely better than files I get at 16/44.1. The trick is how you down sample them. I'm going to discuss three methods. I'm sure there are more; but I want to keep things simple and use tools with which I am familiar. So I am using two applications: Pure Music and Audirvana Plus; and I'm trying three different methods of down sampling: real time in Pure Music, offline in Pure Music (in other words, using PM as an engine to down sample files without actually trying to play them then using those downsampled files as if they had always been at 24/44.1), and real time in Audirvana Plus. My tendency is to do the third one because I find A+ a little simpler to use than PM (albeit less flexible) and I don't have to get on my 27" iMac, which I use as a kind of mastering station with its own stereo system and everything, and load PM, put it in file conversion mode, drag and drop a bunch of files to the appropriate location, then wait for them to get down sampled and saved with unique file names in the same location that the original, say 24/192 files, came from. I'm not saying it's a bad thing, particularly if it sounds better; but it is a bit hassle to have two copies of all (or some) of my albums on my Mac mini in the digital music server having been transferred, usually by thumb drive, from the 27" iMac where they came into existence.


In any case, as I last indicated, I've been very happy with new arrangement, which consists of an older Mac mini (now running Mavericks) with a third-party SSD in it all acting as an engine for the music, which is stored via a FireWire connection on a LaCie RAID drive. I use the Synergistic Research Active SE USB cable with the Galileo MPC and the black enigma tuning bullet, all feeding a first generation Sonicweld Diverter HR, then sending the S/PDIF signal via a five-meter Apogee Wyde Eye S/PDIF cable into the jaw-droppingly amazing Audio Note 4.1x Balanced Signature DAC, designed to operate primarily at 16/44.1 but capable of going to 24/96, just sounding best at 44.1kHz then running the whole thing into my mostly Audio Note system. The first sample I'm going to work with is the 24/192 download of Astral Weeks by Van Morrison from hdtracks.com. I'm playing it now, down sampled—as usual—in real time by Audirvana Plus. It sounds very sweet, quite clear, and the strings have a nice shimmer to them. It doesn't sound as good as vinyl (which is rather unfortunate, given the dCS Vivaldi-ish price of the Audio Note DAC); but it sounds extremely good. Next, I'm switching to real time down sampling in Pure Music. I have to confess that, although it's a bit more difficult to operate, the real time down sampling in Pure Music (which is proprietary) sounds quite a bit more open and natural than the iZotope-based down sampling offered by Audirvana Plus. The occasional bell has a much more natural ring to it and, overall, percussion is better. Vocals are also clearer. There is a bit less shimmer to the strings, and I miss that, but I think that, overall, I'm getting better, more neutral sound by using the real time down sampling in Pure Music over that of Audirvana Plus. I guess the truth of the matter is that the main thing that draws me to Audirvana Plus is its simpler, more intuitive (dare I say more Mac-like?) user interface even though, overall, it is more limited in what it can do. I'm not slamming Pure Music. It's just that it has a lot of options and you really need to RTFM (Read the F […] g Manual) before trying to do much with it.

So what's next? Well, of course it would be listening to the 24/44.1 down sample of the same album that I made using the non-real-time mode of Pure Music. Using this method, while intrinsically a bit of a hassle not because of anything PM does wrong, should result in the best sound because rather than trying to minimize CPU, RAM, or disk usage to accommodate the limits of the Mac mini in real time, it simply takes its time and the all the resources it needs to down sample the music offline, then gives you a set of (in this case) 24/44.1 files sourced from the 24/192 files that I purchased via HDtracks.com. I have to say that it really does sound much, much better this way, so much so that I may become addicted to it. It comes very close to the sound quality that I would get from listening to a vinyl album, which is the whole reason I bought the Audio Note DAC 4.1x Balanced Signature to begin with. I won't go into a detailed account of the differences I hear in the sound because it's pretty much everything. It's just much gentler, more detailed, perhaps a tad bit warmer, and everything is in its proper place with just the right amount of ambience on Van Morrison's voice. Particularly now that I have a new 27" quad-core iMac with a faster processor, 32GB of RAM, and a 3TB fusion drive with Pure Vinyl installed on it (Pure Vinyl containing Pure Music) artfully setup by Rob at Pure Music via a remote session, I don't think creating offline down samples of my favorite albums and copying them—through some means—onto my Mac mini is going to be nearly so cumbersome as it has been in the past and even if it were, I would do it because the sound is just so damned much better.

I guess one thing I wanted to try was playing the pre-down-sampled files through Audirvana Plus as well as through Pure Music. So I did that. It didn't sound quite as good as playing the pre-down-sampled files through PM, but it certainly sounded better than any real time down sampling that I tried. It was just a little veiled, a little less close to a vinyl LP. I have to be careful here because I like both products very much and I haven't even included Amarra or any of a number of other Mac-based music playing applications that are out there. However, I am really glad to say that the pre-down-sampled files played through Pure Music in Memory Play mode, etc., etc., do come strikingly close to the sound of playing a vinyl album; and that makes me happy.


I conducted a similar experiment with the 24/88.2 download of Like Minds by Chick Corea et al, acquired from HDtracks.com. Although this time the difference was a bit subtler, perhaps because I was starting from a lower resolution set of files, there's no doubt that the non-real-time conversions, played through Pure Music with Memory Play, etc., turned on, sounded more analog-like and that same gentler quality with better ambience and spatial arrangement. I can't say it sounded like my actual vinyl copy of that album (a double LP) played on my Transrotor Fat Bob S, SME V, Dynavector XV-1s combination, but it sounded much closer than anything else I've heard coming out of a computer and I would happily listen to it all day long and not feel any regret for having wasted my time with "digital", much less, "a computer". Now I just have to find a chunk of time to offline down sample my favorite albums so that I have a whole library of near-analog-sounding music on the computer. I feel bad about abandoning PM in favor of A+ and now going back again, but, as Joni Mitchell sings, "Everything comes and goes, marked by lovers and styles of clothes."

Kindest regards,