Naim NAIT 5si integrated amplifier

Naim says that its NAIT 5si integrated amplifier is the company’s “introduction to high-performance integrated amplification”. After spending some time with one powering my system, I’m guessing that many people would find this “introduction” more than enough to fulfill all their high-fidelity amplification needs.

In short

  • The Naim NAIT 5si is an integrated, stereo analogue amplifier
  • Built in Salisbury, England
  • 2 x 60 watts into 8 ohms, 2 x 95 watts into 4 ohms
  • 4 x stereo analogue inputs (RCA, with parallel DIN sockets for two)
  • 1 x stereo line level output (RCA)
  • 35mm headphone output
  • Speaker outputs via banana plug sockets, wiring adaptor provided with unit
  • 432mm wide by 70mm tall by 301mm deep
  • 6.90 kilograms
  • The Naim NAIT 5si integrated amplifier is a great all-round stereo amplifier. If you have been enjoying audio on decent gear, but sense that something more is just slightly beyond what your gear can deliver, you’ll find the Naim NAIT 5si quite the revelation.
  • $3450
  • Available at fine high fidelity retail outlets, and direct from distributor's retail division (Naim NAIT 5si)
Naim NAIT 5si integrated amplifier

    More on the Naim NAIT 5si integrated amplifier

    There are a few unusual things about the Naim NAIT 5si amplifier. First, this is not a new model. Naim isn’t a company to do frequent updates so that there’s something sparkly-new on the retail shelves every year. The NAIT 5si was first released way back in 2013.

    Second, there are no holes in the case. Oh, I don’t mean its watertight. It’s just that there aren’t any cooling slots. I’m pretty sure that the amplifier isn’t Class D, yet even running it hard for a couple of hours on a warm day didn’t make it particularly hot. It seems that Naim founder Julian Vereker preferred to design what he called Class B amplifiers. I’d call it “almost Class B”. Most analogue amps are Class A/B, some are Class A and traditionally, high-fidelity enthusiasts prefer more Class A. But Vereker reckoned he could keep the bias current to a tiny amount, “just a few milliamps”. Class B runs much more efficiently than A/B, so I figure that the amp can get by with just using the nicely solid case for heat dissipation.

    Now, I’ve got to talk about power for a moment. I find that the power consumption figures printed on the back of many stereo amplifiers and home theatre receivers quite at odds with their rated power output. A seven-channel receiver rated at 100 watts per channel should presumably draw up to 700 watts, but the maximum consumption figure is typically around 300 watts. (Power input must always exceed power output in any real-world equipment.)

    Naim NAIT 5si integrated amplifier rear panel

    If it’s pushing out the maximum into low impedance loudspeakers, the Naim NAIT 5si is rated to deliver 190 watts in total. Its rated maximum power consumption is 300VA. (VA is voltage times current, which equal to or more than watts of power. It depends on the relative phases of the voltage and the current.) And indeed Naim specifies that the unit is capable of supplying transient outputs of up to 300VA. The transient power will depend on how much the loudspeaker load results in different phases for current and voltage, but that could potentially be as high as 150 watts per channel.

    We tend to specify amplifier power as continuous output, even though you never, ever listen to any music at a continuous power delivery. Music just doesn’t work like that. But we specify things that way so at least there is some comparability, unlike such “measures” as “dynamic peak power”, which are quite meaningless.

    In many cases it isn’t the amplifier output stage that’s the limiting factor in power delivery, but the ability of the power supply to provide the required current. Naim has a long reputation for excellent power supply design, and it seems that the Naim NAIT 5si is no different in that regard. A related curiosity: if you switch off power with the hard switch on the rear, the various front-panel indicator lights go out instantly, but the backlit Naim logo continues to glow. And glow. And glow. It took two minutes for it to go dark. I assume that the power supply capacitors remain connected and are allowed to discharge in this way.

    Naim NAIT 5si integrated amplifier

    Another unusual thing: while the four analogue inputs are fitted with RCAs, two of them are doubled up with 5-pin DIN sockets. That allows connections using a single cable between this and other Naim devices. Apart from Naim products, the last time I saw these in widespread use was in the early 1970s, and that was with gear dating from the 1960s. I suspect that Naim provides them for backwards compatibility, all the way backs to its very earliest models.

    You can see the overall look of the unit from the photos, but just to be clear: each of the four input selection buttons to the right has a ring around it which illuminates in a gentle green when that input is selected. The Naim logo is also backlit in the same colour, again gently so that even in a fairly dark room it isn’t obtrusive. An illuminated dot on the analogue, motorised volume control shows the level. I found that even with my fairly low sensitivity loudspeakers, the volume control spent most of its time around the 9 o’clock to 10 o’clock position, maybe 11 o’clock when I really wanted to wind it up.

    The remote control is a multi-product one, so a bunch of its keys are for other Naim products. It uses the Philips RC-5 IR protocol, so there’s a good chance that you can control things like volume with remotes from other European gear. A Cambridge Audio remote I have did indeed allow me to change the volume.

    Naim NAIT 5si integrated amplifier remote control

    There is no standby setting. If you’re going away for a while, reach over to the back to the hardwired power switch. Because of the almost Class B design, even when switched on the unit uses little power when not actually playing anything.

    Installing the Naim NAIT 5si integrated amplifier

    Installing the NAIT 5si was straightforward, or would be in most cases. You just place it on your shelf, plug your analogue outputs into the unit’s analogue inputs, plug in the speakers and plug in the power. The only small issue I had was with the plugging in of the speakers. My usual loudspeaker cables have large spade connections. I had to switch to banana-plug-equipped cables for this review. I’m not one to think that makes much of a difference, but if you would prefer spades or directly wiring up thick cable, then this may not be the amp for you.

    The only other issue I had was just getting used to how Naim does things. The remote had marked keys (eg, “CD”, “Tun”) which I took to be input selection buttons. In fact, they were remote control mode buttons for which device you want to control (“Pre” is appropriate for this unit). You make your input selections using the number keys.

    Naim NAIT 5si integrated amplifier

    Listening with the Naim NAIT 5si

    Playback equipment:

    Well, time to sit down and do some listening. I hit the vinyl first, starting with Legend, the best of Bob Marley and the Wailers. And, oh, what a fine experience it was. It was clear from the opening seconds that the Naim NAIT 5si was exercising absolute control over the Dynaudio Contour 20i loudspeakers, including into the bass. The sound was so clean, I found myself advancing the volume beyond my accustomed levels. And even at quite extreme levels, the sound remained relaxed and effortless.

    The thump of the drum in the live version of “No Woman No Cry” presented on this album had a real presence in my listening room, thanks to both its coherent presentation with all the frequencies constituting the sound presented as a unified wavefront, along with the non-harmonic elements of the strike. The stereo image was gorgeously rounded, with the instruments layered and Marley himself clearly sitting back just a little in the mix, surrounded by his backing vocalists.

    Back to the studio for “Could You Be Loved”, the rhythm was immaculate, the sound driving yet with every subtlety revealed. Again, the timing was simply perfect, not just between instruments but again with all the tonal components of each instruments presented as a whole.

    Naim NAIT 5si integrated amplifier rear panel

    Even though I was listening to that on a recent 180 gram pressing, the recordings themselves are old, dating back to the 1970s. So, moving forwards in time I went to Laura Marling’s Once I Was An Eagle, released in 2013. This combination of voice and small ensemble can be very revealing of any problems. Well, there were none. Marling’s vocals are close-miked on this album to the point of stress, and were present up front and centre as they ought to have been, while the acoustic instruments occupied their correct places across the stereo stage, and again were presented with depth. There was a lovely richness to whole thing, accompanied by some bass notes of which I’d been previously unaware, despite having played this album on both digital and vinyl several dozens of times.

    And I keep coming back to the coherence of the percussion.

    Staying on vinyl and analogue instruments, but upsizing radically in scale, I moved to a 1981 recording of Tchaikovsky’s Fifth Symphony, with Eugene Ormandy conduction The Philadelphia Orchestra. (You know the 5th, popularised in the 1970s in Australia by Paul Hogan in a cigarette commercial; “Let ’er rip Boris”.) The version I have – I would have bought it not long after its release – was a Soundstream digital recording. That was one of the early systems, also used by Telarc for many of its most famous releases. It employed a 50kHz sample rate and 16 bits, so slightly higher spec than the CD. The recording was by means of three microphones mixed to two channels.

    It has been a while since I’ve played this record, but I do remember that the overall performance seemed a little restrained. In fact, fairly boring which is why I haven’t played it for a long time. Well, there was none of that this time around. I wound up the playback level – hey, with a full orchestra, you simply must – and let her, er, rip. The delivery was exciting, truly exciting. I don’t think I’ve heard an orchestral recording played with such clarity, with such a clear presentation that every instrumental section was distinct and easily picked by ear. The double basses were distinct presences in my room, the violins were also a clear presence, but leaning towards sweetness rather than steeliness. As the tympani came in during the leadup to the second movement crescendo, it hit properly, but didn’t outstay its welcome, with the Naim NAIT 5si ensuring that the woofers did exactly what they were supposed to do with no overhang.

    Naim doesn’t specify things like damping factor, but surely it is a very high number in this model.

    I listened to plenty of other music from various digital sources as well, but there’s really nothing more to add. The performance was exemplary in all cases.


    The Naim NAIT 5si has a proper 6.35mm headphone socket on the front. Plug in a headphone and the speaker outputs are switched off. I confess, I’m somewhat leery of headphone outputs on things like integrated amplifiers and home theatre receivers, due to the fact that so many of them simply switch their main amplifiers to that output, as required, and manage the output level by placing a largish resistor in the way of the output. That can provide fine results in some circumstances but can in others produce unpredictable frequency balance problems with many headphone models.

    Naim NAIT 5si integrated amplifier

    Well, it turns out that Naim has provided a discrete headphone amp in this unit. My measurements showed a clean output well in excess of a volt regardless of headphone impedance, and a very low output impedance (which always warms my heart). I calculated an average output impedance of 0.44 ohms across my half-dozen tests. There was some variation, but the highest test still came in at well under one ohm (0.85 ohms).

    And that means – as my headphone listening confirmed – the Naim NAIT 5si amplifier will deliver a neutral tonal balance to your headphones, regardless of any impedance variations they may undergo across the audible frequency spectrum.

    The amplifier will deliver almost 10mW into a 300-ohm load, which is almost 10dB above the usual headphone sensitivity rating, and 95mW or almost 20dB into a 16-ohm load. This amplifier will drive any low to medium impedance headphones to whatever level you desire. However, if you have particularly high-impedance headphones (say, 600 ohms) which are of low sensitivity, the amp may run out of oomph.


    That stuff about the headphones really quite surprised me. I’ve reviewed plenty of integrated amplifiers in which the headphone output is, at best, an afterthought. Perhaps 99 percent of headphones are going to love the headphone output on this amplifier.

    As for the main game – loudspeakers – the Naim NAIT 5si is a glorious performer. It is a true audiophile amplifier that provided plenty of performance even for my low sensitivity, four-ohm Dynaudios. And, remember, this is the baby Naim amp! Do find a Naim retailer and listen for yourself.

    Integrated amplifiersNaim audio