NuPrime MCX-1

Maximum Headroom – The NuPrime X MCX-1 750 watt mono power amplifiers.

Given how much I liked the NuPrime-X MCX-2 stereo power amplifier, both initially and with some time to consider it in a broader context, how do the even more powerful mono versions rank?

The arrival of the NuPrime X MCX 750 watt mono amplifiers will make you revisit many of the assumptions you might hold when considering home audio components – especially amplifiers. But the first question is ‘what would you possibly do with a pair of 750 watt mono amplifiers?’

The easy answer is anything you want. OK – there is more to it than this but from the moment they were plugged these in, we’ve revelled in what the NuPrime’s can do – imagine seemingly limitless power and control, with bass like never before.

Let’s do a quick re-cap on the Nuprime X range – NuPrime originally targeted the new MCX series at the home cinema and gaming market. And I have no doubt that anyone looking to use any of the models will be blown away – they are that good. We’ve looked at them more in the context of systems that are primarily set up to play music and since reviewing the MCX-2 stereo power amplifier, I’ve been looking forward to the MCX-1s. 

But even with the foreknowledge of both the stereo model and a number of other power amplifiers that have both stereo and mono versions, I’ve been stunned by what I’m hearing. The NuPrime X MCX-2 stereo power amplifier is impressive but these babies are something else again.

The identifiable character of the MCX-2, which I’ve described as a ‘live’ sound is present and correct yet the MCX-1 is unarguably better, as much in terms of quality as much as quantity. Despite the massive power rating, this is an amplifier of considerable subtlety and refinement. But perhaps we shouldn’t use the phase ‘despite the massive power rating’ because I’m starting to think that the power might be the key…

The MCX-1 is all about the concept of headroom – this is having more power than you need so you don’t have this as a limiting factor. Which makes the MCX-1 the perfect amplifier those with large speakers and who really want to push things along.

I can certainly see the appeal of this – when I was younger, all I wanted in an audio system was to replicate the impact of live performance. Even now I’ve just shifted things a little to cater for bands such as Alien Weaponry and we’re able to go past the live performance in a crowded pub to something like the band actually letting loose in your own living room. There is that much power on tap.

Going loud is one thing, sounding great while doing it is another. And this is where NuPrime have it over everyone else.

Because I’ve already explored the sound of the MCX-2 I’m going to first talk with you about the differences between the two models –

Even from new, it’s obvious that the MCX-1 is more sophisticated — there is enhanced detail and precision and while you might not expect this, the sound is lighter, more articulate and open. The MCX-1 is considerably more transparent and better able to resolve fine detail.

Like the MCX-2, the overall sound is warm but this is now tempered with a more open presentation and easier flow. It’s more relaxed and even more listenable (which is high praise given how much I like the MCX-2)

The high gain and sensitivity means any DAC or preamp has an extremely easy load hence sounds more relaxed and fluid. So we find we are listening at what appears to be lower sound levels but what we hear is more dynamic – ie the difference between quiet and loud sections is made more obvious. But the fine detail in quiet sections is almost un-nerving.

This has always been part of the Nuprime promise – a dark deep soundstage with even the most nuanced sounds appearing with a level of clarity we have not previously experienced. On paper there should be no difference with noise floor performance between the MCX models but I’m absolutely convinced the combination of mono configuration and better internal isolation make the MCX-1s by far the best in the range.

Simple but effective – the back panel connections for the MCX-1s.

What the MCX-1s do in the bass would be more than enough to recommend them – with any good floor standing speaker you’ll gain massive amounts of authority and control. For musical genres where bass is a highlight, the MCX-1s dig deeper than any other amp I’ve heard – including NuPrime’s own Flagship Evolution Ones.

If there is one part of the performance that really comes together with time as the new amplifiers run in, this is it. From the outset it is a highlight but the gap between the MCX-2 and 1s grows by the day. 

In this era of small speakers it’s too easy to loose an appreciation of how the lower frequencies are the solid foundation upon which much music is built. But large speakers make big demands on amplifiers and so while a floor stander offers the promise, the end sound often falls short because lesser amplifiers simply run out of power. The MCX-1’s have no such limitation.

This is why some people have sub-woofers set up for music listening. The fact that most have additional amplification built in, does in part explain why. The MCX-1s deliver you the kind of power that the best subwoofers have and are a better solution in terms of providing an integrated and seamless sound from the top to the ground shaking depths.

The reason is that the MCX-1s avoid the all the problems and discontinuities created by a subwoofer – the differences in amplifiers and signal paths, the additional crossover elements, the differing driver brands and materials with their inevitable sonic signatures, phasing issues due to placement and mono operation.

The solidity of sound generated by the MCX-1s amazing. It makes the differences in bass extension between speakers more obvious than any other amplifier I’ve dealt with. There is no downside to this – with a smaller speaker the performance is as good as it can be with control but also subtlety – there is no extra overhang or coloration that would suggest artificially boosted bass. But go to something bigger and the increased depth enabled by larger drivers and cabinet capacity become immediately apparent.

In the past we’ve only ever had a very limited range of extremely costly amplifiers that might have approached what the MCX-1s can do. They were brute force solutions and had multiple issues with heat, noise and unreliability that Nuprime have completely bypassed with this design. In doing this NuPrime also open up the range of speakers with which you can partner the MCX-1s.

Any moderately sized floor stander such as the New Zealand made Images will come to life in a way you have never heard before. The Monitor Audio models seem to be an especially good match with the warmth of MCX series doing wonderful things with the very slight edge the ribbon tweeters can sometime produce. There is literally a whole world of speakers just waiting for the MCX-1s to unleash their potential.

On the front end you are similarly free to match a wide variety of sources – as we’ve have detailed the combination of benign impedance, high sensitivity and high gain all allow even modest DAC/preamps and other components to deliver their best and happily drive the MCX-1s to full rated output. 

Just to put this all in context – if you match something like the NuPrime DAC-9 preamp to MCX-1s you have a highly capable 3 box 750 watt per channel amplifier system that will do pretty much everything you could ever want for just on NZ$6000. And obviously the MCX-2 with 550 watts at $3800 makes for an even better value option for many. Both of these put many integrated amps, which as supposed to be a value for money option, to shame in performance, price and power.

Remember that you can just tuck the power amps away as they are cool running. Stacking the MCX-1s on each other is just fine. And they have a 12v trigger so will switch in and out of standby in tandem with the rest of your system if you have this choice.

In many ways the already high level of capability that the MCX-2 exhibits makes it a harder sell to move up to the MCX-1s – after all they cost exactly twice as much since you have to have two. 

Yet the benefits they deliver make this a lot easier – the improvement in quality afford by better isolation, both within the MCX-1 ( produced by the greater physical separation of power supply and amp sections) but also the complete isolation of channels and reduction of cross talk, the doubling of power supply and storage to well beyond the limits of the amp sections rated output, are there to be heard and if you are able to make the most of this via either large or challenging speakers, you’ll be well rewarded.

Inside the MCX-1

The NuPrime X MCX-1 is an amplifier that is both remarkable and unique – which given NuPrime’s already innovative approach – is really saying something.

The technology that enables the excellent sound of the other established Nuprime models such as the Nuprime ST-10 power amp and the Evolution Ones is there in the MCX-1s but with some important differences.

Like these other models, the MCX utilises NuPrime’s Class A+D hybrid amplification design deliver the substance and warmth of Class A amplification and the efficiency and speed of Class D. 

But within the amplifier module’s design there are some interesting twists – the amplifier board within the MCX-1 has two identical circuits which (if the information I’ve gleaned from NuPrime is correct) operate in a ‘half bridged’ mode – this would go some way explain the 750 watt rating as even the Evolution Ones are only rated at 240 watts into 8 ohms.

What is the difference between hard bridged and full bridged? I suspect what it does mean is that the MCX-1 is more tolerant of lower impedances that would be the case otherwise. But more interestingly, Nuprime amps often specify lower distortion levels when they are bridged which is the opposite of conventional designs and I think this makes a contribution to what we are hearing.

The amplifier section is in turn is powered by a 1000W switched mode power supply running into a 33,000 uF CMA capacitor array which allows the MCX-1 to fully exploit the Class A+D design’s ability to deliver massive amounts of power and speed.

So you can see that the MCX-1’s power rating provides two levels of headroom – the first of 750 watts per channels which means you’ll be unlikely to ever use the full output but even more importantly, the 1000 watt power supply behind it means that even if full amplifier output is used, the MCX-1 remains well within it’s performance envelope. 

Another point of difference with the NuPrime design is stability of output regardless of speaker impedance – while it may seem like a good thing to have higher power ratings at 4 ohms, this is often accompanied by higher levels of distortion and greater demands on the power supply. Of course with 750 watts as a starting point as well as an over specified power supply, few other amps will ever come close. The MCX amps are designed to handle a wide range of speaker impedance from 2 Ohms to greater than 16 Ohms.

Why mono? 

If NuPrime have the MCX-2 stereo amp why didn’t they just make a bigger version? By physically separating the left and right hand channels you gain much better electrical and RF isolation. And with two separate power supplies we make further gains by eliminating interaction and resonance as well as exactly doubling the available power. 

The MCX power amplifiers are effectively modular – the 4 models all look the same from the front and have what appears to be the same power supply but have a choice of 1,2,3 or 4 channels of output. The 3 multichannel models all have two amplifier boards inside but the MCX-1 only has the single module. This answered the obvious technical question, being was the MCX-1 just a bridged version of the MCX-2? It isn’t. 

With just the one amplifier module, MCX-1 has the greatest amount of free space inside and the 3 boards – power supply, capacitor bank and amplifier board are well separated. I think this also contributes significantly to the sound quality we hear.

Then there are the simple economies of scale – the MCX series are effectively all reconfigured versions of the same design so the more you build in the same casework, the lower the unit cost. And really, the two MCX-1s are still more compact, lighter, cooler running and more affordable than many 100 watt stereo amplifiers.

SMPS – the Switch Mode Power Supply.

Most audio amplifiers employ a conventional transformer, often toroidal (donut shaped) for their power supply – these are not without issue being costly (much copper wire), limited in output and prone to creating interference from their strong EM fields. And they run at mains frequency – that’s 50 hertz so you often get a very particular hum, even more so with powerful units – this can be either audible from the amplifier itself or through your speakers.

The MCX range use a switched mode power supply which takes the incoming AC but kicks the frequency up far beyond 50 hertz. The trick is that the higher the frequency used, the smaller the transformer can become. Likewise when making the conversion from AC to DC the parts can be much smaller and higher in tolerance and specification. So when you look at the power supply section, if you can even recognise the transformers, they are tiny.

So the primary benefit of the SMPS is speed – by operating at a much higher frequency than the mains power supply it can respond to the music’s demands. 

NuPrime aren’t the first people to use switched mode power supplies and for may of their earlier designs used off the shelf units.What sets the NuPrime MCX power amps apart is that they have produced a dedicated SMPS – it’s a complex board but you can see it in the internal pictures. Again, this appears to be derived from the original MCH-K38 and what previously pushed 8 channels is now fully allocated to just one in the MCX-1.

I want to also re-iterate that both the amplifier modules and power supply sections are all Nuprime’s own work – most class D amplifiers employ some variant of the Hypex or ICE amplifier modules and either an off the shelf torrid or SMPS. So while these ones don’t have to re-invent the wheel, they are limited to what someone else’s technology can do; the slower switching speeds – 300kHz are an obvious limitation. The MCX-1s switch at 550kHz

The almost direct relationship between power supply and output of the MCX amplifier really is the key to their performance – only an SMPS has both the speed and power to keep up with the demands of the amplifier section with the capacitor bank providing a degree of isolation and storage.

How do the MCX-1s compare with NuPrime’s other Mono amplifiers?

The obvious question is how do the Evolution Ones improve upon the MCX-1s. The appreciably higher switching speed of the Evolutions (750kHz vs 550) do give them a real advantage in terms of speed, absolute resolution, noise performance and transparency. The much more costly build, use of premium parts and linear power supply, not to mention the 1000kOhm input impedance all contribute further. 

Yet with the much higher rated output, the MCX’s can open the sound out and deliver a warmer character with subterranean bass that will make them a better choice in some systems regardless of cost. I’ll also point out that if any of this significant saving is diverted into better source components the balance can shift even further in the MCX-1’s favour. 

So you do have to look at the choice in the context of a complete system.

The choice between the MCX-1s and NuPrimes similarly priced ST10Ms is rather more pragmatic – smaller speakers, especially if used in near field or smaller rooms will just be overwhelmed by both the power and high gain and depending on the characteristics of the source. In this setting the ST-10Ms are more appropriate and accurate. But if you have the room and larger speakers, I’d be heading straight to the MCX-1s.

Conclusion.

The NuPrime X MCX-1 mono power amplifiers offer an unmatched mix of both power and quality at a surprisingly affordable price. While the 750 watt per channel rating may at first appear daunting, it allows an ease of delivery combined rich warm bass that makes for enjoyable listening at any level. Best matched with larger speakers to fully explore their potential, the MCX-1s are a star product in NuPrimes ever expanding portfolio of high end electronics.

Nuprime X MCX-1 750 watt per channel mono amplifiers NZ$2350 each including GST and delivery.

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