MBL Noble Line N11 line preamplifier Measurements

Sidebar 4: Measurements

I measured the MBL Noble Line N11's performance with my Audio Precision SYS2722 system (see the January 2008 "As We See It"), repeating some of the tests with a loan sample of Audio Precision's more-recent, higher-performance APx555 system. As advised in the manual, using the front-panel menu, I deactivated all the N11's inputs other than one of the balanced inputs and the unbalanced CD1 input for the measurements. I performed all the testing with the N11 set to its recommended Unity Gain mode and its volume control set to its maximum in that mode, "70." I then repeated some of the tests with the preamp set to apply its maximum gain with the volume control set to "100."

In Unity Gain mode, the maximum gain for the balanced input to the balanced output was identical, at 0.34dB. The maximum gain for the unbalanced input to the unbalanced output was similar, at 0.59dB. In Gain mode, the maximum gain was 10dB for both sets of inputs and outputs, this slightly higher than the specified 8dB. The preamplifier preserved absolute polarity (ie, was noninverting) with both balanced and unbalanced inputs and outputs. The XLR jacks are wired with pin 2 hot, the AES convention.

The N11's balanced input impedance is specified at 10k ohms, which was confirmed by my measurements at all frequencies from 20Hz to 20kHz. The unbalanced input impedance for CD1 was low, at 2.3k ohms, but this is again the specified figure. The unbalanced Aux inputs are specified as having an input impedance of 50k ohms—I activated this input just for this measurement and measured 47k ohms from 20Hz to 20kHz. The balanced output impedance was a low 198 ohms, the unbalanced impedance 100 ohms; both values were consistent across the audioband and conformed to the specification.

The preamplifier's frequency response in both balanced and unbalanced modes was flat from 10Hz to 200kHz, both into the high 100k ohm load (fig.1, blue and red traces) and into 600 ohms (cyan, magenta). Fig.1 was taken with the N11's volume control at its maximum setting; both the response and the superb channel matching were identical at lower settings of the control. Channel separation (not shown) was excellent, at >100dB in both directions below 2kHz. It decreased to 80dB at 20kHz, presumably due to low-level capacitive coupling between the channels.


Fig.1 MBL N11, Unity Gain Mode, balanced frequency response with volume control set to "70" at 1V into: 100k ohms (left channel blue, right red), 600 ohms (left cyan, right magenta) (0.5dB/vertical div.).

From balanced inputs to balanced output, the MBL preamp offered extremely low noise, with virtually no power-supply–related spuriae in its output (fig.2). The wideband, un-weighted signal/noise ratio, measured with the balanced input shorted to ground but the volume control set to its maximum in Unity Gain mode, was a very high 93.4dB, left channel, and 97.5dB, right, both ratios ref. 1V output. Restricting the measurement bandwidth to the audioband increased the S/N ratio to an extraordinary 112.6dB for both channels, while switching an A-weighting filter into circuit further improved this ratio, to 114.4dB! Repeating the S/N ratio measurements in Maximum Gain mode, with the volume control set to "100," degraded these ratios by 2–3dB, but in either mode, this is the quietest preamplifier I have encountered. I fed the N11 a balanced 1kHz tone at 10mV and averaged 16 captures calculated with a 1.2M FFT length, the longest offered by the APx555. The FFT bins all lay below –117dB, referenced to the low signal level (fig.3), which again is extraordinary.


Fig.2 MBL N11, Unity Gain Mode, balanced spectrum of 1kHz sinewave, DC–1kHz, at 1V into 100k ohms (left channel blue, right red) and with no signal (left cyan, right magenta) (linear frequency scale).


Fig.3 MBL N11, Unity Gain Mode, AP555x measurement, balanced spectrum of 1kHz sinewave, 20Hz–20kHz, at 10mV into 100k ohms (left channel blue, right red) (linear frequency scale).

Fig.4 plots the percentage of THD+noise in the N11's balanced output into 100k ohms. The THD+N is very low between 2V and 9V. (It rises below 2V output, due to the fixed level of noise becoming an increasing percentage of the signal level.) Neither the N11's balanced nor unbalanced output clips (ie, when the THD+N reaches 1%) until a very high 10.5V. Reducing the load to a punishing 600 ohms reduced the maximum balanced output level to 8.1V (fig.5), which is still much higher than will be needed to drive a power amplifier into clipping.


Fig.4 MBL N11, Unity Gain Mode, balanced distortion (%) vs 1kHz output voltage into 100k ohms.


Fig.5 MBL N11, Unity Gain Mode, balanced distortion (%) vs 1kHz output voltage into 600 ohms.

To be sure that the reading was not dominated by noise, I measured how the N11's distortion changed with frequency at 2V output. The THD+N percentage was extremely low throughout the audioband both into 100k ohms (0.0004%, fig.6, blue and red traces) and 600 ohms (0.0005%, cyan, magenta traces). What is unusual about this graph is that the very low THD+N percentage doesn't increase toward the top of the audioband, which implies that the N11's circuit has an extremely high open-loop bandwidth.


Fig.6 MBL N11, Unity Gain Mode, balanced distortion (%) vs frequency at 2V into: 100k ohms (left channel blue, right red), 600 ohms (left cyan, right magenta).

I examined the spectrum of the distortion at the same balanced output level (fig.7). Although the second, third, and fifth harmonics can be seen, these are still below –120dB (0.0001%), which is close to the residual level of these harmonics in my Audio Precision SYS2722's analog signal generator. I repeated the spectral analysis with the APx555 system, whose signal generator features even lower distortion: the second harmonic lay at –130dB in the left channel, –136dB in the right; the third harmonic lay at –135dB in both channels; and the fifth harmonic lay at –128dB in both channels. I offer these results for completeness's sake; these levels are so extraordinarily low that they are of academic interest only.


Fig.7 MBL N11, balanced spectrum of 50Hz sinewave, DC–1kHz, at 2V into 100k ohms (left channel blue, right red; linear frequency scale).

Tested for intermodulation distortion in balanced Unity Gain mode with an equal mix of 19 and 20kHz tones at a peak level of 2V, the second-order difference product at 1kHz lay at just –136dB, and the higher-order products all lay at or below –126dB (fig.8). Commendably, these products didn't rise at the same level into 600 ohms.


Fig.8 MBL N11, balanced HF intermodulation spectrum, DC–30kHz, 19+20kHz at 5V into 100k ohms (left channel blue, right red; linear frequency scale).

I concluded my measurements of the Benchmark LA4 preamplifier in the January 2020 issue by writing "Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered." Its performance on the test bench reveals that MBL's N11 now takes that crown.—John Atkinson

MBL Akustikgerate GmbH & Co. KG
US Distributor: MBL North America, Inc.
217 N. Seacrest Blvd. #276
Boynton Beach, FL 33425
(561) 735-9300

Bogolu Haranath's picture

Some preamplifiers like the Parasound JC2 BP come with input gain controls ...... Also, some power amplifiers like the Parasound Halo JC-5 come with input gain controls ....... Do those pre-amps and power amps work similar to the 'unity gain' controls like the MBL N11 pre-amp? ..... May be JA1 could shed some light on this matter :-) ........

Bogolu Haranath's picture

Distortion levels 0.0005% ..... SNR better than 20 Bits :-) ......

Shahram's picture

I mean seriously. Chrome Gold? Yuck. I guess that appeals to the 70 year old audiophile.

Jason Victor Serinus's picture

And adds nothing of value. For the record, the version I reviewed, on which I based my visual assessment, was black and chrome.

Long-time listener's picture

You're right Jason. Ageism, like racism, is ignorant and offensive.

Having said that, putting a single knob or dial in the middle of a component's front face is pretty much the definition of design dullness (like the Cambridge Audio Edge). And MBL has made it not only dull, but ungainly, and gratuitously bling-ey as well. Not good moves.

And here we have a $14,600 pre-amp that you can't be sure will work well with whatever your DAC is. What a wonderful world we modern audiophiles are living in!

Jason Victor Serinus's picture

First and foremost, thank you. Ordinarily I do not call people out for stuff. But you're right on. These divisions of rank and privilege based on age, race, gender, sexual orientation, nationality, religion / spiritual path / or lack thereof, country of origin, and all the rest must be addressed and named for what they are.

We all have our differences in taste and aesthetics, which I respect. Even if you think this preamplifier is ugly as sin, you are not my enemy, and neither of us need defend our opinions. As with many products these days, the N11's front is minimal because, unless you use the remote, all functions are controlled by that one knob and six buttons, and displayed on the big screen. Some would say designs of the nature beat 4 knobs, 8 toggle switches, and the like, but others would not. Diversity is what makes the world go round.

However, the issue of what preamp will or will not work well with your DAC or amps or speakers or whatever is one of system synergy. System synergy is always an issue with audio components, whether audiophile quality or not. It's just that when we have little money to spend-there was a time when all I could afford was a used turntable, basic cartridge, used $25 headphone amp, and some aging and not very costly Sennheiser headphones-many of us see ourselves as "beggars can't be choosers." Undoubtedly there were more harmonious pairings of $25 or $30 headphone amps and Sennheiser or Koss or whatever headphones out there, but I never even knew that a simple change of one or the other could make an audible difference. When it comes to naïveté, I was "in the garden," so to speak, albeit not the one that Joni Mitchell sang about in "Woodstock."

There is one thing that I find dismaying about the comments so far. People have focused on words, attitude, income, cost, and looks. But no one seems to have paid much attention to this:

"I concluded my measurements of the Benchmark LA4 preamplifier in the January 2020 issue by writing 'Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered.' Its performance on the test bench reveals that MBL's N11 now takes that crown.—John Atkinson"

Although, subjectively speaking, the N11 may not be the most neutral or mind-blowing preamp I have ever auditioned, it is the best-measuring preamp that John Atkinson has ever had on his test bench. We're talking about four decades of testing. This is a major component, and worthy of consideration as a Best of the Year. John wasn't as impressed, measurement-wise, with the D'Agostino Momentum HD preamp I reviewed, but I consider it another worthy contender for all the reasons I detail in that review.

This, ultimately, is the reason why my reply is so long. This preamp is worthy of consideration by anyone who can afford it and who likes its looks and sound. It could very well be "the" preamp for many Stereophile readers.

One more comment. In the last two years, I've reviewed products that cost between $600 and $52,000. I kinda lose track of what review will be published in what issue,, but I think that my next product review is of a DAC that costs 1/4 - 1/3 the price of the MBL N11 (depending upon whether you purchase the DACs optional outboard power supply). I like the sound of that DAC a lot.

By nature, I do not automatically resent people who have more $ than I do, who drive nicer and newer cars than my '94 Toyota Corolla DX, or who retired when they were 30 years younger than I am now. I do have strong feelings about people who make their money by exploiting others, but that's a completely other issue in my book. I know people who work just as hard or far less hard than I who nonetheless make or who have made far more money through honest labor that serves humanity's highest good. Some of those people can afford and care about the five-figure products I sometimes review. I wish them all the happiness in the world.

Stay safe, my friend, and be well. And I say that to everyone, even my harshest critics and those who are contributing to the spread of COVID-19.

Long-time listener's picture

I appreciate all that you say. As far as whether I "automatically resent people who have more $ than I do," I don't. What I resent is that money seems to dictate what is popular, or even ideologically or politically correct, with respect to stereo stuff -- such as tone controls or balance controls -- and that leaves a lot of us out of the game. Tone controls for example are prevalent on cheap receivers, but rarely, if ever, on expensive equipment, and there is no justification for that in audio terms. Those of us who want to use them (I use then rarely, but occasionally they're very helpful) of course understand that there may be some tiny price to pay in terms of distortion or noise, but we consider it worth it. Yet the idea of "signal purity" is used to reject tone controls even by the same kind of people who put up with high levels of distortion in tube equipment. These things are not dictated by consumer needs, but by fashion, or ideology, or audio political correctness, and it's obviously the high end that is dictating those things, not the mass market. There actually was one pre-amp in recent years, by Luxman, that did have wonderfully versatile tone controls, and I would like to buy it but at $5,000, I can't really afford it (and I don't like messing with tubes). Actually I could afford it if I hadn't already bought the $4,000 NAD M32 which came "highly recommended" in Class A by John Atkinson. After buying it I found that (in addition to the tone controls I wanted) it had hard, brittle sound that made it fatiguing and unlistenable to me. So now I know that I can't trust Atkinson's ears and I ignore that aspect of his reviews, even if I find his measurements invaluable and I read them religiously. I applaud the fine measurements of the MBL. And resentment of money isn't the issue here. It's the stupidity and narrow-mindedness that makes people like me feel left out that creates resentment. And the casual recommendations of reviewers who don't really care about items that aren't in the stratospheric range of components they normally listen to and they don't care to live with them long enough to find out how they really sound. (I know what you're going to say in his defense -- whatever.) LTL

Jason Victor Serinus's picture

Hello L-t L,

Please understand that when I was discussing resentment on the part of people who can afford equipment we can't afford, I was not thinking about you personally (or impersonally, since I have no idea who you are). I was making an observation about a recurring trend I see in the comments section.

Your comment about tone controls is interesting, because I just reviewed an integrated with tone controls. It will take two months for that review to appear here, and less for it to appear in print (and available, along with recording reviews and comments and letters that are not available online, to subscribers for a whole $12.95/year). I didn't like the effects of those tone controls at all. I'm rather relieved that in my discussion, I didn't invoke "signal purity." The thought wasn't even in Ms. Ivory Snow's mind. I just know what I heard.

I find John's ears extremely acute. I wouldn't be surprised if his recent Esenvalds recording, to which I gave a RotM and which Gramophone praised highly for its engineering, scores a Grammy nomination in the engineering department. It is possible, however, that the NAD was a far better match for his system than for yours. This could lead to a whole discussion of the "absolute sound" of components. But a simple mention of that myth is more than sufficient, as far as I'm concerned.

Time to go running before the rain hits. Be well,

Long-time listener's picture

Good for you. I think he needs to be a little more thoughtful in his reviews, and ask himself if what he is hearing is something he would really want to live with himself. Recommending the Aerial 5T for Class A, after describing how difficult it was to set it up to get good bass response -- and how he did that only by ignoring manufacturer placement recommendations, and only by using a $20,000 amp known for its bass control -- is one example. Also, I tried the NAD M32 with three different sets of speakers (one being his "Class A" Aerials), so sorry, it's not just that it was a poor match for my "system." With each of the three it sounded hard and digital relative to a (less expensive) solid state amp with the same power rating.

And again you express your dislike for tone controls. In every single review they are either ignored, or disparaged. Reviewers always say something like, "And then I got out my Reference Recording pressing of Bruckner's 9th by [fill in the name of an orchestra and conductor not known for playing Bruckner, since it's not really the music that counts here], which allowed me to hear the delicately filigreed highs..." Duh. Of course we never see: "And then I got out my 1939 Toscanini Beethoven 9th (or my 1958 Miles Davis "Miles Ahead," or my early '80s digital Karajan Bruckner), where the wonderful tone controls of the Luxman allowed me to tame the steely highs, and to hear more realistically proportioned weight in the bass." No, that will never happen. You'd rather "hold your ears and grit your teeth," or however it was that you once described it. That's not the audiophile experience all of us want to have. But we often don't have much choice in the matter.

Bogolu Haranath's picture

May be JVS could review the two chassis flag-ship tube pre-amp, Mcintosh C1100 ($13,000) ...... Hi-Fi News measured 0.00009% - 0.0005% distortion levels for C1100 :-) .......

glamanna's picture

QUOTE: // “These divisions of rank and privilege based on age, race, gender, sexual orientation, nationality, religion / spiritual path / or lack thereof, country of origin, and all the rest must be addressed and named for what they are.” //

You read all of that into a comment about styling of an audio component? The comment you condemn as somehow “divisive” is actually an accurate assessment of the audio component’s 1970s look. So now saying that a house is “turn of the century” is akin to lynching minorities or pushing grandma over the cliff?

Do you really believe this? Because if you do, you are the one perpetuating all of this “isms” you listed and showing that they exist primarily between your ears. Certainly not in reality.

Ask yourself who benefits from the feigned victim hood of manufactured divisiveness. Victim hood is Big Bisiness and the cornerstone of Fascist and Marxist revolutionary theory. Just saying ….

glamanna's picture

Looks like a discoteche threw it up.

tonykaz's picture

"purview" is 'Scope of Influence'

Jason Victor Serinus's picture

There is a wider definition of "purview." You may want to look at this one: https://www.merriam-webster.com/dictionary/purview.

tonykaz's picture

Purview is legal terminology typically associated with being outside the limits of your Job, authority or knowledge. i.e. a plumber offering legal advice.

Considering that the MBL person did the majority of the important parts of the review, this MBL review may very well have been outside your purview. I found his insights helpful and necessary.

Tony in Venice

ps. Oxford English Dictionary is the Standard. The 20 Volume Edition is appropriate for writers.

tonykaz's picture

"purview" is 'Scope of Influence'

Bogolu Haranath's picture

Anybody who can afford Wilsons, D'Agostinos, dCS, Nordost cables and Grand Prix Monza racks is 'privileged' :-) .......

tonykaz's picture

and a bit of a snub to lesser peer groups.

There is an implied 'Velvet Rope' divider with this sort of attitude.


MBL is super nice sounding, gaudy gear that is probably hell on the cleaning lady. The entire MBL System is Jaw Dropingly stunning in appearance and Sound Quality ( if you are "privileged" enough to be in the Same Room with it playing Lang-Lang ).

Tony in Venice

Anton's picture

1) That MBL preamp is stone cold guaranteed to match well will your Nagel prints! How’s that for synergy?

2) Anybody remember when the reference was “the absolute sound” and not comparative differences between pieces of gear? This has been a quantum shift that was discussed 40 years ago as a pathway we should be wary of. Now, we compare gear to gear.

Jason Victor Serinus's picture

Score two points for the Gipper.

Bogolu Haranath's picture

That MBL pre-amp also matches well with the round meters on the Progression amps :-) ........

davip's picture

What is the point of this 'pre'-amplifier (indeed, all line-level pre-amps)? No digital source that I'm aware of requires pre-amplification to provide levels suitable to drive a power amp, and the only source that does require pre-amplification -- a phono one -- is not catered for in this pre-amp by the absence of a phono input. So what point this device?

All the rattling about "Unity-gain" being better than a competitor's over (pre-)amplified pre-amp is a straw-man argument as it side-steps the obvious (and usually $0, unless you want to spend $5K on an auto-former) option of having no pre-amp AND better sound.

While I don't question the ability of a $14K pre-amp to show a clean pair of heels to a $140 one, I do question whether there is any digital medium of any bit- or sampling-rate whose sound quality merits such expenditure or such a wide-window as will only throw the faults of that medium into sharper relief. Spend the $14K on sealed vinyl and play it through the $140 amp -- guess which will sound better.

Let's not get into the whole "...things sounded better with the pre- in-circuit than a passive ... more 'drive' etc" thing. If transparency and fidelity are the goal, then assuming appropriate impedance matching no preamplifier is better than a pre-amplifier that isn't needed when dealing with line-level sources. In a world where companies are falling over themselves NOT to offer phono inputs, why the hell does anyone make pre-amps anymore (and who the hell buys them?!)?

And yes, it's blingy and fugly. Looks like it belongs in a financial-adviser's kitchen...

At risk of being censored, here in the UK we would say that this is kit for "wankers", irrespective of the depth of their pockets.

directdriver's picture

"If transparency and fidelity are the goal, then assuming appropriate impedance matching no preamplifier is better than a pre-amplifier that isn't needed when dealing with line-level sources."

Err... Not really for me. Maybe it is for Stereophile. I just want coloration to enhance the recording so I can enjoy the music more, unless I only listen to audiophile recordings. I don't. Obviously I'm not a neutral or absolute sound type of audiophile. Other than that I agree with your assessment of this gear. It's really ugly. At least it has good engineering and measurements.

Canadianwalker's picture

I can't help but mention the Schiit Magni Heresy headphone amplifier. It costs 100usd and has a preamp output. It is unity gain or has a switch for higher gain. It's distortion measurements are close to the MBL and does the same job, minus the switching and any phono preamp.

So basically, for digital it can do the same job. I think part of the difference in sound you are hearing between a DAC that has a volume control and using the MBL may be attributable to most of the DAC volume controls being digital. That makes for perfect matching between channels etc but you are listening to a must reduced dynamic range and possibly the low level detail is lost or distorted by comparison to full scale digital reduced in volume by a unity gain stage with an analog volume control. Something to consider anyway.

krahbeknudsen's picture

I certainly agree that the design is an acquired taste. Moreover, I would assume that most people would buy such a pre-amp for the long term. In that respect, I would be worried about the durability of the colour LCD screen and the possibility of getting a replacement after say 6-8 years.

Fruff1976's picture

That was the first thing that crossed my mind. Not only from a replacement standpoint, but the graphics alone could make it look dated. It already sort of looks like Sega Genesis.

hb72's picture

very interesting article, especially the interview. I must confess, I was not aware footers would allow as much tuning toward ones own preferences, as e.g. the choice of cables (IC & power). I always thought there is a more general i.e. uniform gain in SQ by reducing component vibrations.

Charles E Flynn's picture

From https://gearpatrol.com/2020/06/30/whats-actually-the-difference-between-a-cheap-and-expensive-stereo-receiver/ :

In general, the bigger and better the speakers you have, the more powerful the stereo receiver you’re going to need to drive them. But power isn’t everything. For example, the Yamaha R-S202BL and the more expensive Cambridge Audio AXR100 can both deliver 100-watts per channel, but what makes the Cambridge Audio AXR100 better is the build quality of the built-in amplifiers. Not only are the components higher-grade, but the AXR100 also has both right and left channels, which contributes to more accurate sound.

Jason Victor Serinus's picture

50 per channel.

Bogolu Haranath's picture

Mark Levinson 5805 integrated amp is specified as 125 WPC into 8 Ohms, by the manufacturer ..... Stereophile measurements show, it can also drive 2 Ohm loads with 370 Watts :-) ........

Glotz's picture

As I just bought the Benchmark HPA4 (line section the same as LA4), and sighed to myself, a bit deflated, but still smiling. It held the crown for a few scant months.. lol.

I love MBL designs, and I'm sure I would love silver and that white variant (I forget the color name). Otherwise a bit too blingy for my tastes.

That being said it sounds like it's a superlative preamp... though I would go with their speakers as a first purchase choice to...pretty much anything extant.

Great review as always, Jason.