This is a review and detailed measurements of the Naim Uniti Atom streamer, DAC and integrated amplifier. It is on kind loan from a member and costs US $3,799.
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The overall industry design is attractive and has a high-end look to it. Alas, every part of the unit has an ultra sharp edge from heatsinks to edges of the plexiglass (?) front panel. It is a heavy box which makes you really feel those sharp edges as if they are going to tear into your skin. It was unpleasant every time I had to move or rotate the unit.
The front panel is large and sharp which I like. Alas, and strangely so, it is not a touch screen. In this day and age and at this price, a touchscreen is a requirement in my opinion. A very large rotary control managed the volume. It seem to have some kind of acceleration but wasn't very intuitive.
Here is the back panel:
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I was surprised to see the compact binding posts that are made only for banana plugs. Likewise there is no USB B to use the unit as a DAC. Maybe you can use the type-A connector for that but even so, it is very unusual choice. Nice to see a floating ground switch. In my testing, it only impacted the networked tests. Otherwise it had no effect.
Inclusion of HDMI is very important to allow sound from TV to be piped into it.
Upon booting and with Ethernet cable plugged in, it nicely told me there is new firmware. It took something like 10 minutes to download the image and then went into a seemingly infinity cycles of booting, dark screen, non-descript progress bar and power button that would fade on or off or solid on. I left there for probably half hour when it finally seem to be ready.
There is the usual app to control it but I opted for the included remote control. It too has very sharp edges but otherwise functional.
Naim Uniti Atom DAC Measurements
I started by testing the unit using Coax due to lack of type-B or type-c USB port. Here is our usual dashboard:
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Distortion dominates causing our SINAD (noise+distortion) to barely reach into "fair" category:
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Distortion rises into the noise floor of even 16 bit content so not a good first showing. As noted, changing the grounding mode made no difference in any of these measurements.
The output stage is capable of higher voltage which is nice:
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Good to see the output does not become all distorted once the internal amplifier is pushed beyond clipping.
Noise performance is not competitive with even budget DACs but almost good enough for 16-bit playback:
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Multitone distortion was quite high:
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Jitter display looks clean but noise floor is high and is masking interference patterns:
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Levels of those spurious tones though is quite low and inaudible (-128 dB).
We have a rather odd filter response:
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This partially contributes to rather poor noise+distortion relative to frequency:
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Finally, linearity matches the fair performance of the rest of the system:
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Naim Uniti Atom Amplifier Measurement
Given the choice of analog or digital input, I tested both which producing 5 watts:
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Performance is very close so I opted to use analog in as that makes the comparison to other amps easier. Notice the high power supply noise at 120 Hz (double mains frequency in US). Overall ranking is well below average:
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Frequency response test with analog input shows a brick wall filter which indicates input is being digitized:
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Shame then that no DSP functionality is provided. The roll off filter in the ADC causes some drooping in the high frequencies.
Crosstalk response was kind of shaky but overall good:
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Multitone test once again shows less than optimal performance:
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Rated power is low and that is what we see:
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Sweeping the frequency for power measurement we get orderly response:
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Notice the typical sharp drop in power at 20 Hz. This is why you need more powerful amplifier than you think you are getting. Power is needed in bass but the reservoir capacitors in the power supply get depleted and you don't get as much output.
Naim Unit Headphone Amplifier Measurements
I expected the headphone output to be "junk" but it actually is not:
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That is plenty of output for satisfactory response of high impedance headphones. Noise floor is not competitive with any modern/recommended headphone amp but could have been far worse. At 32 ohm though, available power is much more limited:
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Sweeping the load we see that the headphone amplifier is not capable of much current delivery:
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So best to stay with high impedance headphones.
Naim Uniti Atom Streaming Measurements
I ran the streaming tests a day later and here, I noticed noise bleeding into the output:
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So I tried the ground lift switch and it remedied that:
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SINAD though is dominated by high distortion so didn't matter one way or the other. And performance is the same as local/coax S/PDIF input.
Conclusions
Performance of Naim Atom ranges from fair/adequate to rather poor. Shame that when you pay so much for a piece of audio, not much design hygiene is included. I suspect more went into software development and enclosure design than making sure the hardware is performant. I hope for a version 2 the company works to substantially improve the performance of these subsystems. I am sure many buy a Naim product thinking they are getting great audio performance.
I can't recommend the Naim Uniti Atom streaming amplifier.
P.S. I was going to give the mailman panther rating to the unit but he is out making deliveries......
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