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Positive Feedback ISSUE 68
july/august 2013


Musings on Building a Digital Music Server: Ripping Vinyl with the Apogee Duet 2 and Pure Vinyl
by Andy Schaub

"Eleanor Rigby picks up the rice in the church where a wedding has been
Lives in a dream
Waits at the window, wearing the face that she keeps in a jar by the door
Who is it for?"

—"Eleanor Rigby" by Lennon/McCartney

A friend of mine ripped his entire Decca SXL collection to hard drive at 24/192 using some very high-end equipment and some expert advice. I don't have plans to do that, partly because I don't have an entire Decca SXL collection, but also because I'd rather just clean and play the vinyl using my Transrotor Fat Bob S, SME V, and Dynavector XV-1s combination. However, I got intrigued—from a kind of an academic perspective—at the prospect of ripping vinyl using lower end equipment. So I contacted Rob at Channel D, the makers of Pure Music and Pure Vinyl, and explained that I have a backup system with a Rega P3-24, an Audio Note IQ-3 MM cartridge and an Apogee Duet 2 (i.e., the original USB version). My plan was to take the output of my Audiomat Phono 1.5 phonostage and run it into my Duet 2 breakout box using some very high-quality Cardas female RCA to male TRS (1/4") adapters; however, Rob suggested that I purchase some custom-made female RCA to male TRS (1/4") adapters with the right capacitor(s) and resister(s) for loading the cartridge, then run the IQ-3 directly into the instrument inputs of the Duet 2's breakout box, allowing the Duet 2 to act as a preamplifier and ADC then apply RIAA correction in software. He said I would get superior results that way; and I believed him. So he provided me with a license to Pure Vinyl, which is a nice albeit somewhat complex application, and the adapters, which were really necessary to make everything work.

The first time I tried it, it was a disaster. I tried sampling The Carolina Chocolate Drops' Leaving Eden and it sounded awful, no bass at all, mostly because I didn't RTFM (Read The F […] g Manual). I had effectively sampled a track or two then imported the "raw" .m4a file into iTunes without applying RIAA correction and played the whole thing back through my Audiophilleo 1 / Rega DAC combination. I actually thought I had configured the adapters with the wrong values or that the ADC in the Duet 2 just wasn't up to the task but, as I later learned, I couldn't have been more wrong. So I took the downloaded manual and very carefully read it, learning that I had left out many steps along the way and that Pure Vinyl, excellent program that it is, definitely has an intended pattern of use or "workflow", something you need to follow even if you're sampling (i.e., ripping) just one track. FWIW, I did play Leaving Eden as vinyl on the big system and the felt that the whole album was a little bright to begin with so switched to Shelby Lynne's Just a Little Lovin' on the Lost Highway label for my experiments because of its relatively lush sound, carefully cleaning it on my Clearaudio Matrix with the Disc Doctor Quick Wash solution before I began doing anything else. I should also mention that (a), I was doing all of my experiments at 24/192 and (b), Rob doesn't believe in automatic noise removal because it degrades the sound. So although Pure Vinyl can allow you to manually remove pops and ticks, it's really designed for getting rid of big clicks or removing skips. At least that's what I inferred from my email with Rob and from reading the f […] g manual.

So, I went back to square one. I did download Audio Leak from the Channel D website and measured the levels of the tracks I had recorded from Leaving Eden just to verify that the gain in the ADC in the Duet 2 was adequate and discovered that, even with the levels in Maestro 2—the control program for the Duet 2—set at 35 out of (I think) 100, my average level was equivalent to that of .m4a files I had downloaded from and that both in Maestro 2 and in Pure Vinyl the virtual meters indicated that I had adequate levels with peaks at just about the right points, so no need to increase the gain and engage the soft limiters in the Duet 2, which might also degrade the sound (an assumption on my part). The limiters are really designed for live recording anyway. So it goes. This time I did things properly, according to the manual; although, I only recorded about one track, because I was mostly interested in testing the process and seeing how good the sound quality could be, particularly on my backup system (which is still very fine, with a Tri KT-88-based tube amplifier, a pair of Micropure minimonitors, and a 12" Essex subwoofer hidden under my desk, plus all Audio Note, Stealth, and Locus Design cabling). I guess, while I'm at it, I should also mention the computer that I was using. It was a 27" quad core iMac (the original version) with 16GB of RAM and a 2TB hard drive; plus, it's been modified to boot off of a 256GB SSD with a LaCie Blu-ray drive connected via a FireWire bus. All of the recording I did in Pure Vinyl went originally to the SSD; although, when I imported the finished track(s) to iTunes, they got copied onto the 2TB magnetic drive, all of which is hypothetically backup up by Time Machine to a 4GB G-Technology RAID drive connected, again, by FireWire. I'm running Mountain Lion, iTunes 11, Pure Vinyl, Pure Music, and (mostly) Audirvana Plus for playback.

The first mistake I had in using Pure Vinyl was not recognizing that I needed to calibrate the "trigger" level so that it would begin recording automatically when I lowered the stylus; fortunately, that just involved setting everything up (with JUST the Duet 2 connected via USB, not the Audiophilleo 1 at the same time as well), then going into record mode—which begins paused—and clicking just one button then looking at the screen to see that the trigger level fell above the background noise produced by the IQ-3 and Duet 2 combined just a little (about -69dB). I had to fill in the metadata for the name of the artist and LP, although track editing and naming comes later, after you've finished recording the entire LP (or at least one track, as I did in my experiment). Then you record the whole LP (or, as I said, in my case, about 1 and ½ tracks). THEN you can you go into playback mode and—in my case—monitor (or playback) the recording at 24/192 through the Duet 2 using my Audio Note AN-SPx modified pair of the AKG K701's plugged directly into the Duet 2. This is one place where RIAA equalization gets applied, and I have to say it sounded really fantastic, nearly as good as a comparative direct feed from my Audiomat 1.5 going into my Tri all-tube headphone amp and into the same AKG K701's. The Audiomat might have sounded a little warmer and richer, but Pure Vinyl playback sounded cleaner and, well, purer. So RIAA EQ in software really worked! There wasn't very much record noise, mostly because I'd cleaned the vinyl; and the overall sound was very analog-like. Now came the really tricky part: editing a track. You have to go into a special edit mode in Pure Vinyl at which point you can slide the graphic of the linear-tracking tonearm back and forth, getting both sound and a graphic of the audio waveform (to make it easy to see the breaks between tracks). There is an automatic track detection function; but I have to confess that it didn't work that well for me. I would attribute it to user error or some lack of a calibration value that I didn't read about in the manual; but a friend also reported frustration with the automatic track detection functioning. No matter, track editing was actually reasonably easy when you did it manually.

In any case, I was just experimenting, so I set the beginning of the track to offset 00:00:00 (the beginning of the LP) and the end of the track to the end of my sample, which did include a few seconds of the second track on Just a Little Lovin'. It was not necessary to do it this way; but I was in a hurry and wanted to see how the whole thing would sound when I was finished and had a real .m4a file produced rather than the raw (i.e., unmarked, non-equalized version). After I had entered the metadata for the first track (really just its name, which happened to be the title track of the LP), I was able to render the file in the track editor and, low and behold, I had an ALAC file called "Just a Little Lovin'" that contained that track plus a little bit more; I could have added cover art but allowed iTunes 11 to do that automatically when I added the track to my iTunes library (which copied the .m4a file from the SSD to the internal 2TB hard drive where my iTunes library resides). I could have added the files to iTunes as a Pure Vinyl/Pure Music bookmark; but I wanted to play things back through Audirvana Plus and my Audiophilleo 1 / Rega DAC combination. Plus, my long-term goal is to sample things at 16/44.1 and copy them onto my iPod. So it made more sense to just copy a new .m4a file (even at 24/192) onto my 2TB hard drive. The bottom line is that when I unplugged my Duet 2 (after shutting down Pure Vinyl/Pure Music and iTunes), plugged in my Audiophilleo 1 (in both cases using dedicated Locus Design Axis USB cables) and launched and configured* Audirvana Plus, turned on my Tri KT-88 based push-pull amplifier and played back "Just a Little Lovin'" through my Micropure minimonitors and 12" Essex subwoofer, I was really stunned at just how great everything sounded. It would have been very difficult to distinguish the .m4a file from an actual LP played back through a conventional phonostage; and there was more than ample bass.

So what do I do now that I've mastered this technology? To quote "Eleanor Rigby", "Who is it for?" Well, for me, it's not so much about archiving my music collection, because I'm perfectly happy just cleaning and storing my precious LP's. I'd say it's more about ripping vinyl at 16/44.1 and putting it onto my iPod or burning a CD, which another friend does through an entirely different means. I could also, if I wanted, say, rip the entire Ring Cycle at 24/192 and play it back as a single long playlist through my main digital music server, which would be very convenient and probably sound just fine. That's a lot of work, though, and I don't really mind flipping records. So I'd say, for now, the whole process is mostly for fun and to prove that it's possible to rip vinyl and get excellent sound quality using just my paltry IQ-3 and Duet 2 with the right peripheral hardware and software; and that, alone, is justification enough for me.

Kindest regards,


*By "configured", I really just mean that I went into "System Preferences" under OS X and choose the Audiophilleo 1 as my audio output device for everything but sound effects, then double-checked that Audirvana Plus recognized the output device as the Audiophilleo 1 in its own setup. I didn't need to do anything special in the Audio Midi Setup application under OS X because Audirvana Plus—like Pure Music—sets the word size and sample rate automatically based on information contained in each individual track's metadata.

P. S. I know it would have been nice to resample the whole track using the output of my Audiomat 1.5 and compare that to using RIAA EQ in software but, quite frankly, I just ran out of time. Plus, I thought it was kind of cool to sample the cartridge directly. Perhaps I will write an article where I use the unloaded Cardas adapters and sample the output of the Audiomat 1.5, then do a side-by-side comparison of that with the direct cartridge sampling results.