Naim Audio Uniti Nova integrated amplifier-media player Measurements

Sidebar 3: Measurements

I measured the Naim Uniti Nova using my Audio Precision SYS2722 system (see the January 2008 "As We See It") and before I did so, I installed the Naim app on my iPad mini and used it to reset the Naim to the factory default settings. (The Uniti had no trouble logging on to my WiFi network.) Usually, before I test an amplifier, I precondition it with both channels driving a 1kHz tone at one-third power into 8 ohms for an hour. However, the Naim turned itself off after 15 minutes, displaying the message "Over temperature, please wait for the product to cool down." The top panel above the side-mounted heatsinks was indeed very hot, at 118.1°F (47.8°C). After the Uniti Nova had cooled down a bit, it turned itself back on and I continued the testing.

Looking first at the analog inputs, the maximum voltage gain at 1kHz from the speaker terminals into 8 ohms measured 35.35dB. The gain at the preamplifier outputs was 6.7dB. These inputs preserved absolute polarity (ie, were non-inverting) at all three sets of outputs. The input impedance was a usefully high 50k ohms at low and middle frequencies, dropping inconsequentially to 42k ohms at 20kHz.

The headphone output impedance was extremely low, at 0.5 ohms at all audio frequencies. The output impedance at the speaker terminals was 0.3 ohm at all audio frequencies; as a result, the modulation of the Naim's frequency response with our standard simulated loudspeaker was just ±0.2dB (fig.1, gray trace). The response is down by 2dB at 20kHz, and, peculiarly, it drops off very rapidly above 20kHz. When I looked at the Uniti Nova's reproduction of a 1kHz squarewave (fig.2), I understood what was happening. The overshoot and ringing indicate that the Naim converts its analog inputs to digital, apparently with a sampling rate of 48kHz. This means, of course, that a 10kHz squarewave will be reproduced as a sinewave (fig.3), all the odd-order harmonics that contribute to the square shape being stripped off by the anti-aliasing filter. The volume control operated in steps of approximately 0.4dB, with the unity-gain setting at "43" of a possible 100. However, as set the analog inputs overloaded at 2.65V, which means that source components with a maximum output level higher than this should be avoided.


Fig.1 Naim Uniti Nova, analog input, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green) (1dB/vertical div.).


Fig.2 Naim Uniti Nova, analog input, small-signal 1kHz squarewave into 8 ohms.


Fig.3 Naim Uniti Nova, analog input, small-signal 10kHz squarewave into 8 ohms.

Channel separation via the analog inputs was good rather than great, at 71dB R–L and 84dB L–R at 2kHz, decreasing by 20dB at the top of the audioband (not shown). Spectral analysis of the Naim's low-frequency noise floor (fig.4) revealed a somewhat high level of random noise, as well as AC supply components at 120 and 240Hz. (The measurements were taken with the Audio Precision's output floating and the Naim's rear-panel switch set to Grounded, the default position, which gave the lowest level of supply harmonics.) The unweighted wideband signal/noise ratio, taken with the input shorted to ground but the volume control set to its maximum, the worst case, was just 63.9dB ref. 1W into 8 ohms. This improved slightly, to 66.6dB, when the measurement bandwidth was restricted to the audioband, and to 69.3dB when A-weighted.


Fig.4 Naim Uniti Nova, analog input, spectrum of 1kHz sinewave, DC–1kHz, at 1W into 8 ohms (left channel blue, right red; linear frequency scale).

Figs. 5 and 6 plot the percentage of THD+noise in the Naim's output against power into 8 and 4 ohms. Specified as delivering 80Wpc into 8 ohms (19dBW) and 155Wpc into 4 ohms (18.9dBW), the Uniti Nova delivered 103Wpc into 8 ohms at clipping (1% THD+N) with both channels driven (20.1dBW), and 160Wpc into 4 ohms (19dBW). The wall voltage was a little high (123.8V) when I performed this test with the Naim clipping, which goes some way toward explaining why it delivered more than its specified power. I measured how the THD+N varied with frequency at a level, 20V, where I could be sure I was looking at distortion rather than noise (fig.7). While there was a rise in THD in the top two octaves, this was relatively small. The distortion itself comprised the relatively innocuous second and third harmonics (fig.8), and intermodulation distortion was respectably low in level (fig.9).


Fig.5 Naim Uniti Nova, analog input, distortion (%) vs 1kHz continuous output power into 8 ohms.


Fig.6 Naim Uniti Nova, analog input, distortion (%) vs 1kHz continuous output power into 4 ohms.


Fig.7 Naim Uniti Nova, analog input, THD+N (%) vs frequency at 20V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta).


Fig.8 Naim Uniti Nova, analog input, spectrum of 50Hz sinewave, DC–1kHz, at 40W into 4 ohms (left channel blue, right red; linear frequency scale).


Fig.9 Naim Uniti Nova, analog input, HF intermodulation spectrum, DC–24kHz, 19+20kHz at 40W peak into 4 ohms (left channel blue, right red; linear frequency scale).

Turning to the Uniti Nova's behavior with digital data, I tested it using the Audio Precision's TosLink and coaxial S/PDIF inputs, and repeated the tests with WAV, AIFF, and DSD files stored on an SDcard that I plugged into the rear-panel port. The Naim successfully played PCM data sampled up to 384kHz, as well as both DSD64 and DSD128 files. With the volume control set to "100," a 1kHz tone at –20dBFS gave rise to an output of 558mV at the preamplifier outputs, 158mV from the headphone jack, and 15.23V from the speaker outputs, the latter equivalent to 29W into 8 ohms. As the amplifier clips at 28.7V, this suggests that the volume control not be set above "65" with digital sources. With all but the low-level tests, I measured the Uniti Nova's digital performance at the preamplifier outputs, but with the volume control set to avoid clipping at the speaker terminals.

The Naim's impulse response with 44.1kHz data (fig.10) indicates that the reconstruction filter is a minimum-phase type, with all the ringing following the single sample at 0dBFS. With 44.1kHz-sampled white noise (fig.11, red and magenta traces), the Uniti Nova's response didn't start to roll off until just below half the sample rate (vertical green line). An alias at 25kHz of a full-scale tone at 19.1kHz (blue and cyan traces) is therefore visible. Distortion harmonics of this tone are also visible, the second harmonic being the highest in level at –66dB (0.05%).


Fig.10 Naim Uniti Nova, digital input, impulse response (one sample at 0dBFS, 44.1kHz sampling, 4ms time window).


Fig.11 Naim Uniti Nova, digital input, wideband spectrum of white noise at –4dBFS (left channel red, right magenta) and 19.1kHz tone at 0dBFS (left blue, right cyan), with data sampled at 44.1kHz (20dB/vertical div.).

When I examined the Naim's digital frequency response with S/PDIF data, I got what appeared to be anomalous results (fig.12). With 44.1kHz data (gray and green traces) the output stopped just above 20kHz, but with data sampled at 96kHz (cyan, magenta) and 192kHz (blue, red) the ultrasonic response was down by 9dB at 29kHz. These responses were measured at the preamplifier outputs; repeating them at the speaker terminals gave the same result, other than the rolloff above 20kHz being slightly faster. As a check, I measured the responses again using WAV files stored on an SD card, but found no differences from S/PDIF data. The Uniti Nova's Burr-Brown DAC chip does function at sample rates up to 192kHz; I suspect that the Uniti Nova downsamples high-resolution data so that its DSP can be applied to those data.


Fig.12 Naim Uniti Nova, digital input, frequency response at –12dBFS into 100k ohms with data sampled at: 44.1kHz (left channel green, right gray), 96kHz (left cyan, right magenta), 192kHz (left blue, right red) (1dB/vertical div.).

When the Uniti decoded dithered 16- and 24-bit data representing a 1kHz tone at –90dBFS, with the volume control set to "100" to minimize the effect of its selfnoise, the increase in bit depth dropped the noise floor by around 20dB (fig.13), which implies resolution of greater than 19 bits. With an undithered 16-bit tone at exactly–90.31dBFS (fig.14) the waveform was symmetrical, but the three DC voltage levels described by the data are somewhat obscured by high-frequency noise. With undithered 24-bit data (fig.15) the result was a somewhat noisy sinewave.


Fig.13 Naim Uniti Nova, digital input, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data (left blue, right red) (20dB/vertical div.).


Fig.14 Naim Uniti Nova, digital input, waveform of undithered 1kHz sinewave at –90.31dBFS, 16-bit TosLink data (left channel blue, right red).


Fig.15 Naim Uniti Nova, digital input, waveform of undithered 1kHz sinewave at –90.31dBFS, 24-bit TosLink data (left channel blue, right red).

As suggested by fig.11, the digital inputs' distortion signature was primarily the subjectively benign second harmonic (fig.16), and while actual intermodulation distortion was low in level (fig.17), the noise floor didn't look random. With 16-bit J-Test data, the resultant spectra (fig.18) were identical, whether I fed the Naim optical or coaxial S/PDIF data, or played the same data stored on the SDcard. A slight widening of the spectral spike that represents the high-level tone at one-quarter the sample rate can be seen, but all the odd-order harmonics of the LSB-level, low-frequency squarewave are reproduced at the correct levels (slanting green line). However, a pair of sidebands at ±120Hz can be seen in the left channel's output, these obviously related to the power supply. These sidebands are also evident with 24-bit J-Test data (fig.19), though the spectrum is otherwise superbly clean.


Fig.16 Naim Uniti Nova, digital input, spectrum of 50Hz sinewave, DC–1kHz, at 0dBFS (left channel blue, right red; linear frequency scale).


Fig.17 Naim Uniti Nova, digital input, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 0dBFS into 100k ohms, 44.1kHz data (left channel blue, right red; linear frequency scale).


Fig.18 digital input, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 16-bit TosLink data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.


Fig.19 digital input, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit TosLink data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

Other than its idiosyncratic behavior with high-sample-rate data, the Naim Uniti Nova's measured performance reveals it to be well sorted, as they say in the UK.—John Atkinson

Naim Audio Ltd.
US distributor: Audio Plus Services Inc.
156 Lawrence Paquette Drive
Champlain, NY 12919
(800) 663-9352

fetuso's picture

nice review. I was just downtown this morning, wish I had known about Hi-tech hifi. I was recently in the market for a new integrated and toyed with the idea of a vintage receiver. I also considered some used naim amps. I ended up getting a great deal on a used Yamaha as2100 integrated and I love it.

supamark's picture

that the Guardians soundtrack sales were as much about collectors and novelty as anything. I still can't get my head around a cassette revival. I get vinyl, it has a sound that's appealing. Mass produced cassettes are just awful sounding - cassette is to vinyl as mp3 is to CD, and very few cassette decks ever had the azimuth adjustment (and bias adj. plus 3 heads for recording) needed to get the most out of the medium.

Also, Naim's Mu-so Qb facinates me, though I've no idea how it sounds.

ok's picture

Ten years ago someone stole my beautifull red hatchback, newly serviced, freshly washed and filled up with my decades-old, obscurely sourced collection of cassette tapes. Now, don’t get me wrong, I really missed that car; but what I wished for back then was that the scumbag who stole it had been kind enough to return those precious cassette tapes.

ken mac's picture

I feel your pain.

jporter's picture

No practicality at all. The NAD C368 is a bargain. I think there has to be a # Me too movement for these kind of reviews. "he said it was a bargain, but I felt violated and small"...Shame, Shame, Shame...lmfao..and Cheers!

ken mac's picture

The NAIM is extremely practical, does everything well and sounds fantastic.
The NAD 368 a giant killer? We shall see, review forthcoming.

supamark's picture

the tension building music... dun Dun DUN!

tonykaz's picture

I mean : instead of a Mono Phono Cartridge, for gods sake.

I raaaathhhhre like this design.

This brit stuff is decidedly not "hair shirt" type gear, which will probably make it a 'slow seller' on the Audiophile Shop Sales Floor.

It's ( pretty ) like a nice vintage B&O tabletop piece.

Now, all we'd need is a brushed al-u-mini-mum Plinth for our LP-12 and we'll be all-set.

I could love this thing sitting near-by my Green Leather Lazyboy and Book Reading gear.

Thank you Stereophile for this Review, you remind us that there is another viable music system World ( Planet ) out there.

Tony in Michigan

spacehound's picture

I would have purchased a Naim 'digital' box years ago.

But except for the DAC-V1 (which is a DAC only), they consistently refuse to put a 'computer' USB socket on any of them including this one.

So, sadly, very nice but no thanks.

tonykaz's picture

this naim has two USBs, one on the Front and one on the rear.

Wudea think about those Woo Fireflies?

Tony in Michigan

ps. a weak attempt to spell out a Yorkshire pronouncing of "What do you"

ps.2 are you lads "allowed" to get PS Audio Electronics ?

spacehound's picture

We once imported a PS audio preamp that COULD be made to sound good but it was very sensitive to varying inputs and outputs so you had to be careful what you connected. Not even their own power amp worked well with it.
Few bothered so PS Audio wasn't here long.

A UK distributor now half-heartedly imports the modern PS Audio stuff but none of it has received notably good reviews.

And the UK mags are fairly honest, particularly 'Hifi News and Record Review' which does very detailed measurements too. But only afterwards so the reviewer is not influenced.

Woo Fireflies. I'm not interested in headphone stuff.

(Only Boeing, IBM, Ford, and Harley-Davidson seem to make any significant 'US effort' in the UK.They all do quite well. GM recently vanished, as did Jeep. Apple try, but can't really be said to 'succeed'. I think all that applies to most of Europe)

mrkaic's picture

Predictably, the comments ignored the elephant in the room -- the fact that the unit overheated so badly it had to shut down. Was that just a bad unit or a systemic/design issue? (Even one bad unit seems quite bad to me, though.)

tonykaz's picture

This isn't a Miller Welding Machine, is it ???

It's just a little 80 Watt'r with an Engineered Thermal Shut-down to protect the owner from having to ship the darn thing back to Wales.

Of course they could've used Fuses instead of Breakers but they probably couldn't afford "Proper" German Audiophile Fuses.

My Cuisinart Coffee Grinder overheats ( and shuts down ) when I grind more than one Pound of Beans.

Thermal shut-downs are a very good thing, no Thermal shut down quickly destroys lots of things.

Tony in Michigan

mrkaic's picture

They should have used bigger heat sinks and/or (a more powerful) fan in the first place. Shutdown is a preventive measure and it's fine they have it, but the unit should never overheat under normal(!) operation, i.e. setting any combination of inputs by the user.

I suspect the class AB amp inside is biased too hot to reduce distortion. But they seem to have gone too far with it. In this context, the review could have said what kind of circuit design measures and components they used to guard against thermal runaway. (For example, ThermalTrak transistors were most likely not used, were they?)

Indydan's picture

I wonder if JA had the speaker cables plugged into the Naim, and the speaker cables plugged into speakers during his test.

With Naim amps, the following usually applies:

"Naim amplifiers do not have extra inductance networks in the output, Naim prefer to use the speaker cable to provide the correct inductance and capacitance."

If no speaker cable is attached to the amp (or a very incompatible speaker cable), the amp could overheat.

John Atkinson's picture
Indydan wrote:
I wonder if JA had the speaker cables plugged into the Naim, and the speaker cables plugged into speakers during his test...If no speaker cable is attached to the amp (or a very incompatible speaker cable), the amp could overheat.

I thought it clear from my text that yes, I did have the amplifier connected to the load during the preconditioning test.

John Atkinson
Editor, Stereophile

Indydan's picture

Thanks for the answer. Were you using Naim's NAC A5 speaker cable? I know that speaker cable in a twisted pair design can cause problems. Naim recommends low capacitance cables of moderate inductance.

Capacitance: 16pF per metre
Resistance: 9 milliohms per metre
Inductance: 1uH per metre

It is possible to use other speaker cables than Naim's, but it must be reasonably compatible. If not, it could cause the amp to over heat. I use Naim's NAC A5 cable with my Naim integrated, and it runs cold even when pushed hard.

John Atkinson's picture
Indydan wrote:
Were you using Naim's NAC A5 speaker cable? I know that speaker cable in a twisted pair design can cause problems.

No, but I was using a similar spaced-pair cable with moderate inductance and low capacitance. The overheating with the 1/3-power test, which is maximally demanding on a class-AB amplifier's ability to rid itself of heat, was due to the Uniti Nova's industrial design undersizing the heatsinks.

John Atkinson
Editor, Stereophile

tonykaz's picture

Someone from Naim should be explaining things by now.

This is a rather good example of where PS Audio's Paul McGowan "shines".

We consumers no longer have well informed Dealers to walk us thru the Ownership experience.

Of course, Stereophile's technical people seem to be reaching-out with "helpful" information.

Still, where is Naim when we need them ?

Digital 4K Video Cameras ( some ) are overheating and shutting down.

We might have a Case where this Naim Digital Device's Computer is what's overheating and stopping as a result.

Hello Naim, what's going on?, is there an V2.7 upgrade?

Tony in Michigan

audiodoctornj's picture

Ken first of all I want to thank you for such a glowing review of one of our favortie products, namely the Naim Uniti Line.

One of the things that makes the Naim Uniti line so special wasn't mentioned at all and even if it was, it was not spelled out in big bold letters.

Yes we agree that the Nova sounds fantastic, and is a joy to use, the Naim sound hits all the factors that we find important, the gear is extremely practical, and sounds engaging, the Nova as well as the Star and the Atom all draw you into the music in a way that many more expensive brands and products just don't.

The point that comes up with the entire Uniti line as a retailor, is that this is a line of real high end products that are highly enjoyable, elegantly styled, easy to use, and that these products can get non audiophils into our hobby and into the passion of hearing the joys of realisitc music reproduction in their lives.

I can imagine how many audiophiles with big rigs of separates with tubes and vinyl and no digital sources miss the point that their neophyte friends would never go down that same path no matter how good that type of system performs no matter how hard they try to convince them.

Is is any wonder that Sonos is a Billion dollar company? Even though their products are under performing compared their higher end varients?

We actually start our showroom tour with the Naim Muso a $900 all in one streaming box from Naim, and then show people that a Uniti Atom, $3,000.00 streaming amp/dac with a pair of $1,000.00-$2,500.00 loudspeakers makes a real music system and they can easily hear the difference.

The fact that the Naim app can control a Muso a $900 streaming box, an Atom a $3,000.00 streaming box, going up to as high as a NAC 272 streaming dac/preamp along with a NAP 250 power amp a $13,000.00 package, is a very powerful tool that can transform a starter music lover into a true audiophile!

I know of no other company in the high end audio industry that offers such a wide range of products that are all tied together into one echo system.

So a perspetive client can start with a Muso and then build up to a Naim streaming amp, or conversely they can start with a Naim Streaming Amp/DAC live the Nova and then decide to add a room such as a Kitchen or a Study and just purchase a Naim streaming speaker.

The only other contender is NAD with their Blue Sound line which is excellent but aims at a less lofty world than the ultimate levels of sound quality that the higher end Naim products represent.

Ken if you are in our area, Jersey City NJ, you should come in and visit our store, we have the Naim Muso, the Naim Muso QB, the Atom, the Nova, the NAC 272/250DR setup throught the store in one seemless room to room streaming display. Our clients love it.

Thanks again Ken, I am delighted that you appreciate just how speical the Nova is.


Dave Lalin,
Audio Doctor NJ

Indydan's picture

Please address the overheating, or forward it to Naim for a reply. Is Atkinson's test a reliable indicator of how the Nova will be used?

John Atkinson's picture
Indydan wrote:
Please address the overheating, or forward it to Naim for a reply.

Naim were sent a preprint of the review prior to publication. They didn't comment on the Uniti Nova turning itself off during the preconditioning due to "over temperature."

Indydan wrote:
Is Atkinson's test a reliable indicator of how the Nova will be used?

This test is a worst-case situation for a class-AB or -B amplifier. It was introduced by the IHF in the 1970s and reveals how effective an amplifier's heatsinking is. If all you play is wide dynamic-range classical music, the Naim will never turn itself off. But if you play music with limited dynamic range such as modern rock at party levels, an amplifier that fails the preconditioning test may well be stressed.

The heatsink is one of the costliest parts in an amplifier so the designer has to decide whether to use a large (and costly) enough heatsink so the amplifier will never shut off or compromise on the assumption that the amplifier will be okay for 95% of the situations it will face in normal use.

John Atkinson
Editor, Stereophile

tonykaz's picture

When talking Naim, everyone misses many key points.

Naim is not an Entry level type Company.

I keep hearing about how Naim lets each of it's builders complete the assy. of every individual piece. ( something like Aston engine builders building and signing the completed engines ).

Naim has a fascinating Story to tell.

as do LINN and Focal, PS Audio and a good number of other outfits.

You might pass along Paul McGowan's YouTube daily Vlog work as a useful example of keeping your customer base enthusiastically informed about all things.

Naim is one of those rare Companys we all seem to admire.

Tony in Michigan

ps. I've never owned a Naim product but would've...., Naim is like a nice Swiss Watch on the wrist of a successful Banker.

audiodoctornj's picture

Dear Tony,

You have raised some excellent points. All the companies you have mentioned have interesting stories and make excellent products.

We have been Naim fans for years, but what really got us to pursue a dealership was the Uniti products.

When you have been selling equipment for 30 years you can sometimes see paradigm shifting products. The original Naim Uniti was just that.

Nowdays there are numerous other companies that make great sounding intergrated amp/dac/streamers.

It is the complete echo system by having a streaming speaker system that is affordable the $899 Muso, a $3,000.00 Streaming amp/dac and then having upper level even greater sounding products the Uniti Star and Nova which in our mind make the Naim produt line so compelling.

We wonder why the industry is dying, too often it is the fact that we are trying to shoehorn our ideas of what is compelling to neophyes whose eyes glass over and they run away in terror at the prospect of having great sound in many large boxes which in their minds becomes something they would never consider owning.

If you show a prospective buyer that for $899 you can get a better sounding product than a Sonos okay it does cost nearly double, but one that sounds better and is made out of wood, aluminium, and acrylic.

The Muso, is simple and elegant, compact and easy to use, and sounds good, to move a Sonos buyer into a better experience and the fact that the Naim Muso offers a compelling musical sound may start someone on a journey to discover what better sound is all about.

So Naim isn't only for Bankers, Naim is for everyone yearning for better music.

Dave Lalin,
Audio Doctor NJ

tonykaz's picture

I just-now had a look-see at various YouTube presentations of the Mu-So Active Loudspeaker system.

It kinda looks like an "Architectural Digest" type of Table Top music system. Sure, I could have one sitting on my Office Credenza. Is it just under $1,500 Retail. I'll bet it plays from my iTunes or iPhone.

Naim seems to be worthy of your loyalty.

Tony in Michigan

tonykaz's picture

I just had a closer look at these Naim Products and must say that they are impressive. ( gorgeous )

Naim is now on my short list of things needing a decision.

Gotta see and hear one of these : maybe the Atom.

Tony in Michigan

hifiluver's picture

where has great sensible British engineering gone?

spinsLPs's picture

The Nova currently sells for $5990.00, not $6995.00 as stated in the article. Price on January 1, 2022, will go up to $6899.00.