CD Player/Transport Reviews

JA returned to the MBL N31 in December 2020 (Vol.43 No.12):

In Stereophile's February 2018 issue, I reviewed the MBL Noble Line N31, a baroque-styled CD player and D/A processor from German manufacturer MBL. The N31 is expensive, at $15,400, but, as I said in my review's conclusion, digital audio engineering doesn't get any better and neither does digital sound quality. However, I also wrote that the N31's absence of a volume control might be a problem for those who've sold their preamplifiers, as will be the lack of a network port for those who've banished their noisy NAS drives from the listening room. (The N31 does have a USB port—two, actually—which I used with Roon running on a Mac mini.) I also wished that the MBL's reconstruction filter—the N31 offers a choice of three: Fast and Slow linear-phase filters and a minimum-phase filter—could be selected with the remote control.

At the start of 2020, MBL North America's Jeremy Bryan let me know that an update for the N31 was available that would address these practical concerns. The N31 can now have a Roon Ready Input Module installed, either in production, which increases the price to $16,420, or retrofitted to existing N31s for $1062 plus the cost of field installation by a qualified technician (footnote 1). Bryan warned that some of the oldest N31s, including my review sample (serial number 0034), would have to be returned to the factory for the upgrade.

COVID delayed the return of 0034. When I finally received it back from Germany, I installed it in my system, connecting the new Ethernet port to my router so it could receive audio data from my Roon Nucleus+ server. I connected its balanced outputs directly to either the Parasound Halo JC 1+ monoblocks I reviewed in June 2020 or to the Lamm M1.2 Reference monoblocks. Loudspeakers were the Göbel Divin Marquis floorstanders, followed by three standmounted models: the Marten Oscar Duo, my long-term reference KEF LS50, and the Bowers & Wilkins 705 Signature that I review elsewhere in this issue.

Roon recognized the network-connected N31 as "Roon Ready"—the Roon endpoint firmware version was listed as 0.2.71, which was subsequently updated automatically to 0.2.73—and I activated it as a playback zone with the app's Settings-Audio menu. But there was another N31 listed by Roon in "Other Network Devices," labeled "N31-CD-DAC (ShairportSync)." I asked MBL chief designer Jürgen Reis what this was?

Shairport, he explained, is intended to send audio data from an iOS Device to the N31. It is lossless but limited to 16/44.1 resolution, as this is the resolution of Apple's Airplay protocol. However, unlike the original Airport, which used a jitter-prone adaptive protocol, MBL's Shairport input uses an asynchronous protocol, so it should be freer from jitter.

Reis recommended that I not enable the Shairport backdoor in Roon. I didn't. But I did play CD-resolution files from iTunes on my iPad mini with the N31, via Wi-Fi. I could also play the audio from YouTube videos from a browser window on my Mac mini by selecting "M31-CD-DAC" as the output device. In both cases, the sound quality was excellent and with YouTube better than I expected. For example, streaming the video of the title track from the Portland State Chamber Choir's 2020 album on Naxos, Translations, which I had engineered and mastered, the presentation of the soundstage was basically the same as that on the CD.

Returning to using Roon with the N31, the maximum sample rate available for PCM files was 192kHz. The N31 also plays DSD64 files. (Roon downsampled DSD128 files to DSD64.) With the USB connection, which I had used with my 2018 review, "Device Volume" was fixed at 0dB; now, with Ethernet added, the N31 allows its volume to be controlled by Roon. Reis explained that control of volume—without losing effective resolution—is applied in the N31's ESS Sabre 9018 DAC chip immediately before the modulator, where it will also work with native DSD data without first transcoding those data to PCM.

Something I had not mentioned in my original review was that a certain button on MBL's "intelligent remote control"—the period-with-a-circle "option" button—can be customized to change the display brightness (footnote 2), repeat a CD, change the digital source, or switch between digital filters. I set the remote to switch between filters so that I could easily compare them without leaving my seat (footnote 3).

Initially, I had a problem with Roon controlling the N31. If I paused playback in Roon, the music stopped and the Pause symbol appeared on the N31's screen—all good. But then, when I then pressed play, the Pause symbol was replaced by the album cover art but the music didn't play and the message "Roon lost control of the audio device" appeared on the Roon screen. If I waited for 10–20 minutes or rebooted the N31, then selected play with Roon, the music started up correctly. This only happened occasionally, and hasn't for a while now, since I installed a new router. I blame my usual bad network kharma.

The N31's sound quality with Roon-sourced network data was identical to what I had described with the USB connection. Rather than rely on memory, I checked this by inserting an NHT balanced Passive Volume Control before the power amplifiers so that I could set the volume control to 0dB in Roon for network playback. I then made a second connection between the N31 and the Nucleus+ via USB, and this connection appeared in Roon's "Settings-Audio" menu. As long as I only enabled one of the two N31 zones at a time, I could compare the sound of the USB and network connections.

As with USB, the networked MBL rendered music with an excellent sense of overall drive and low-frequency impact. Low-level recorded detail, such as the reverberation on the Translations album, was well resolved, especially when I reverted to the direct connection to the amplifiers and controlled volume with Roon. As before, I found the minimum-phase filter to sound the most musically natural of the three reconstruction filters, giving the best balance between the presentation of detail and listenability, particularly with CD-resolution files.

Although the volume control in Roon worked well with the N31 feeding the power amplifiers directly, CD playback still requires external control of volume. The obvious solution was MBL's Noble Line N11 preamplifier, which Jason Victor Serinus reviewed in February 2020. The MBL had been one of the two finest-measuring preamplifiers I had measured for the magazine (the other was Benchmark's LA4), so I asked Jason to ship the N11 to me when he had finished comparing it with the Audio Research Reference 6SE preamplifier he reviewed for the November 2020 issue.

I performed all the listening with the N11 set to its recommended Unity Gain mode and with unused inputs deactivated. I initially thought that there was a very slight loss of clarity with the preamplifier in the system. However, repeated listening convinced me that all the low-level detail was present but that it was set a little farther back in the soundstage.

I was not expecting an increased sense of palpability to the acoustic objects within that soundstage, particularly vocals, but that is what I heard. As Jason wrote in his review, "the N11 preamp's intrinsic sonic signature brought a velvety smooth, subtly warm, and immensely pleasurable finish to the sound of both my reference DACs and made listening a joy." Amen to that sentiment, Mr. S.—but how can inserting an active device with vanishingly low levels of noise and distortion result in improved sound quality? Obviously, there are more things in heaven and Earth than are dreamt of in my philosophy (footnote 4).

I very much enjoyed my time with MBL's updated N31. As I purchased a lifetime subscription to Roon after I bought my Nucleus+, I found that the Roon Ready module makes this superb-sounding, superbly well-engineered processor even more desirable.—John Atkinson

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Footnote 1: The Roon module can be ordered, for $1020, as a factory-installed option on new N31s.

Footnote 2: If you gently hold two fingers on the white-illuminated logo on top of the N31 for a few seconds, the light turns off and the standby button on the faceplate is illuminated blue. With the lowest brightness setting, the display goes dark after a few seconds, unless you get close to the player or use the remote. Jeremy Bryan told me that on earlier models, the brighter setting could affect the N31's sound quality, but this has been corrected in newer models: Current N31s should sound the same regardless of the brightness setting.

Footnote 3: The option key on the remote can also be programmed for the N11 preamplifier. To avoid confusing the two components, you can set one to respond to short pushes on the button and the other to long pushes.

Footnote 4: For more about Hamlet and preamps, see my review of the PS Audio BHK preamplifier.—Editor