During the four years that I’ve reviewed for Stereophile, I’ve had the privilege of evaluating products from some of the world’s best-known audiophile companies: Audio Research, Bel Canto, CH Precision, dCS, D’Agostino, Dynaudio, EMM Labs, Jadis, Krell, Nordost, and Wilson, among others. But one long-standing manufacturer whose exhibits at audio shows invariably inspire ecstatic reports, Germany’s MBL, has remained outside my purview.
It thus came as a delightful surprise when MBL North America’s Jeremy Bryan informed Jim Austin and me that the MBL N11 solid-state line preamplifier ($14,600) was available for review. Part of the company’s middle-level Noble Line of electronics, the N11 differs from the Reference Line’s 6010 preamp in one key respect: the notion—specifically, designer Jürgen Reis’s notion—of how it should sound.
In a series of Skype interviews, Reis explained, “The lines don’t differ very much in measurements. In the 35 years I’ve developed preamps, I’ve had a lot of experience with different audiophiles. I have spent a lot of time at the homes of Reference Line customers, and I know their taste, how they’ve constructed their living rooms, and the sound they prefer. The typical Noble Line customer has a different living room and different taste. Therefore, the answer to the question, ‘Which is the better preamp?’ is, ‘The preamp that works the best for you in your room.’
“I know the sound of every resistor, every capacitor—everything. I know what tonal balance will be created when I mix this with that. So, when I started to develop the N11, I had a sound in my head. I made the schematic, optimized the layout to measure well, and then began listening and tuning with small parts. I adjusted the capacitor contacts, chose the correct parts for the desired sound, and determined what kind of silk screen on the printed circuit board would create the sound that would best fit Noble Line target customers.
“Some of my work involved tuning the power supply. It may come as a surprise to learn that you can change tonality without even touching the signal path, because the signal originates from the power supply. The impedance curve of the N11’s power supply is absolutely homogenous from DC to 200kHz, which creates a very balanced sound. I also tuned the resistors for the voltage gain, using a mix of carbon and metal resistors to create a neutral balance. There are a lot of preamps that claim to be ‘neutral’ or ‘in balance,’ but there are different shades of ‘neutral.’ If you have a tube preamp, for example, ‘neutral’ is at a different level than solid-state; it’s not better or worse, but it is different. It took a lot of work to find the tonal balance I like a lot that measures well, with low noise, and fits very well in the Noble Line.”
“I won’t tell anyone that the N11 is the ‘best’ preamp for their system, but I will say that it matches perfectly with other Noble Line components, and its sound is different than the sound of the preamp section of the Noble Line N51 Integrated amp. The goal is to choose components that work well together to achieve optimal synergy. They don’t have to be the ‘best’ products or all from the same company, but they have to work optimally with your other components, your room, and your taste. This is the biggest challenge for a dealer: To get to know a customer well enough to be able to find the best combination for them.”
“Unity Gain”
A unique aspect of the N11 is its “Unity Gain” feature, which can be engaged or disengaged easily via the preamp’s control panel or remote control. “When you have components whose specifications are within the normal range, eg, a digital source with an analog feed of around 2V and a power amp that delivers its maximum power around 2V, then it makes the most sense to have a preamp or control unit that works best at 2V,” Reis told me. “If you set our preamp to Unity Gain, the music flows the easiest way, without impediment, from the DAC to the power amp. This gives the highest transparency and lowest distortion.”
This is, Reis confirmed in a series of emails, a matter of reducing the preamp’s gain so that the signal isn’t amplified excessively and then attenuated. With “Unity Gain” activated, a 2V input signal—full-scale according to the CD Standard—results in a 2V signal to the power amp with the N11’s volume set to 70. Two volts is close to the input voltage at which most power amplifiers achieve their maximum power: max-in = max-out, or vice versa, depending on your perspective.
While 2V is the CD Standard, many digital source components have full-scale output that’s as much as several volts higher—and yet most preamps have more gain than the N11 with Unity Gain activated, which means more attenuation is needed to achieve the optimal volume level. “By unnecessarily reducing the level and then amplifying it, dynamics and resolution are lost, while noise and distortion increase—factors that one desperately wants to avoid with high performance, high resolution systems,” Reis told me. Of course, the N11 can also be used, with Unity Gain on or off, with source components that don’t adhere to this standard—just reduce or increase the volume setting to compensate—but in that case, the system is less than perfectly optimized.
A system with standardized input voltage and Unity Gain mimics systems used in mastering studios—first by better exploiting a system’s available gain and second by allowing output levels to be calibrated. “When you set a stereo system at the same volume level as a mastering system, a unity-gain preamp will bring you the closest to what the mastering engineer heard,” Reis told me. “In my mastering setup, I follow the guidelines set down by Bob Katz in his book, Mastering Audio: The Art and the Science. Each channel should measure 83dB average; this is the level where, when music is played back, it sounds as it sounded during a mastering session conducted by a certified mastering engineer.” (footnote 1) In such a system, if the track you’re listening to has a dynamic range rating of DR14 (footnote 2)—very wide—the peak signal level will be 101dB, which is also optimal.” (footnote 3)
In the green room
Some may not consider my opinions on visual aesthetics worth the price of beans—especially with beans being hoarded during the COVID-19 pandemic. Be that as it may, when it perches on the top left shelf of my Grand Prix Monza rack, the N11’s unique black-and-silver profile cut a handsome figure in the company of dCS’s Rossini DAC, Clock, and CD/SACD Transport; EMM Labs’ DV2 integrated DAC; Roon’s Nucleus+ with the HDPlex linear power supply; two Nordost QX4 noise suppressors; and AudioQuest’s Niagara 5000 power conditioner.
Besides its Unity Gain option and unique remote control (round, heavy, well-considered), the N11’s features are decidedly up-to-date. Its front is dominated by a 5″ color TFT display, easily read from 12′ away, that can be used in place of the remote to access the menu, display options, and control basic functions. Also on the front panel are a standby button and six “smart keys”—function buttons—three on each side of the display. These easily depressed buttons—in the sense that they don’t require much force, not that they have a tendency to be morose—can, among other things, activate or deactivate inputs and outputs, set maximum volume at power-on (50 is the default), restore factory defaults, turn Unity Gain on and off, and mute or unmute. As your hand approaches the N11, a sensor automatically switches the screen from playback mode to interface mode and displays the settings available with the soft keys; otherwise, the screen displays the volume level, which input is activated (RCA or XLR), which outputs are deactivated, and whether Unity Gain is engaged.
On the rear, the N11 has five pairs of RCA (single-ended) inputs, two pairs of XLR (balanced) inputs, and one set of inputs that can be, optionally, either an RCA pair for a moving-coil phono cartridge or a third XLR pair; the review sample had the XLR pair. Five pairs of variable outputs are divided in two groups, each with a mixture of RCA and XLR. There are two fixed outputs, one RCA and one XLR. There’s a ground terminal for a turntable, two MBL SmartLinks (for other MBL products, which I didn’t have), an Update interface (which I didn’t use), and your basic fuse bracket/IEC inlet/power switch. The top has an illumined circular logo that doubles as a brightness control for the display. It’s all laid out well and makes sense.
Footnote 1: Many readers know that the ear’s sensitivity depends on frequency—pitch—and that this dependence varies with volume. So the tonal balance of music sounds different at different volume settings.
Footnote 2: Reis is referring to the “crest-factor” dynamic-range scale from the Pleasurize Music Foundation and implemented by MAAT—not the D128 standard whose ratings are displayed, for example, in Roon. MAAT has a tool you can buy for measuring this dynamic range, here.—Editor
Footnote 3: Ideal calibration of volume-vs-input level also depends on having an ideal combination of amplifier gain and loudspeaker sensitivity.—Editor
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COMPANY INFO
MBL Akustikgerate GmbH & Co. KG
US Distributor: MBL North America, Inc.
217 N. Seacrest Blvd. #276
Boynton Beach, FL 33425
(561) 735-9300
mbl-northamerica.com
ARTICLE CONTENTS
Page 1
Page 2
MBL Chief Engineer Jürgen Reis
Specifications
Associated Equipment
Measurements
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