Nuprime ST10 audio stereo power amplifier at Totally Wired

NuPrime ST-10 stereo power amplifier – NZ$2850

The NuPrime ST-10 is a breath of the proverbial fresh air in the audio world- every part of conventional power amplifier design is questioned and new approaches and technologies are embraced. It’s the perfect time to look at a new power amplifier. If you already own a pre/power combination or are looking to upgrade from integrated the ST-10 sounds so much better than any other power amplifier at this price.

Cool Power

All about the new NuPrime ST-10 Reference LE Stereo Power Amplifier.

85% efficiency means you don’t need to get rid of a whole lot of heat – so the ST-10 is smaller – which allows shorter, lower noise signal paths. The actual power supply is only as big as it needs to be, so costs much less and produces far less unwanted interference. All the savings made can be channeled back into better quality components where it really matters. The long term reliability and working life is extended. This is why the ST-10 sounds so much better than any other power amplifier at this price and almost all beyond.

Up until recently, power amplifiers were all about muscle – big and expensive, highly rated, hot and heavy. But possibly not all that smart.

We all know Apple now pack more computing power into an iPhone than you could fit in a room a decade ago. And the same thing is happening with amplifiers. You’ll remember that NuForce did some amazing things with their ultra compact Icon integrated amplifiers and DACs. What you might not know is where technology in these products originally came from and how that is now being perfected.

Before NuForce was represented in New Zealand, they gained a great reputation in the USA with their Reference series power amplifiers –

“The Reference 18 is hands down the finest amplifier NuForce has made, and I think it is good enough that it deserves to be included in most any discussion of top-tier amplifiers. Even if you have heard (and perhaps disliked) Class D amplifiers in the past, this is one I think you will find worthy of your time and consideration. Above all, the Reference 18 keeps faith with the truth of the recording itself, which is all anyone might ask of a fine power amplifier.” The Absolute Sound 218

The NuForce amplifiers evolved at a frenetic rate – the first reference series product we got to hear for ourselves was the ST8.5 V3 which sold almost immediately. In the short time we had, it was apparent that these were very special designs, breath-taking in power and remarkably rich in sound. Yet compact, cool running and by no means costly. NuPrime provide continuity for the best of these NuForce branded products.

NuPrime DAC-10 and ST-10 at Totally Wired

With the transition from NuForce to NuPrime, things have jumped forward again. The first product – the IDA-16 remains our best sounding and most powerful integrated option. The new DAC-10 converter and analogue preamp extends the levels of resolution and fidelity. And now we have the matching new ST-10 Reference LE stereo power amplifier.

This looks similar to the NuForce ST-8.5 V3, but has been extensively re-worked. Pictures of the internals show a vastly different amplifier, built to a higher standard with a completely different power supply.

The fourth generation (V4 amplifier module) of this patented amplifier design significantly outperforms its predecessor in several key aspects:

It lowers the noise floor by an astounding 20dB to deliver exquisite low-level detail, and a fully revealed, fully dimensional sound stage against a backdrop of mile-deep silence. Shortened circuit pathways result in a 20% improvement in through-put. You will literally hear things that any other amplifier will obscure.

The ST10 elevates the output stage to 85% efficiency. This is vastly better than any conventional amplifier and is why the NuPrime runs cool yet is so powerful. We’ll discuss the important benefits of this shortly.

Increased switching frequency to 600 KHz and an improved musical sampling rate. Most switching amplifiers – often labeled Class D – switch at 300 kHz. By pushing up to over twice this level, the NuPrime can deliver a lucidity and and smoothness that confounds any preconceptions as to how this design should sound.

The new linear power supply with a high-efficiency toroidal transformer is a significant departure from the switched mode power supplies in previous designs with reduced high-frequency noise and strengthened low-frequency performance. The high efficiency of the output stage allows the transformer to be both smaller and of higher quality than would be the case otherwise. The end result is an ideal balance of richly textured timbres and harmonics, bottom-end authority, startling dynamics.

What was a class leading design has been taken to a whole new level, up with the very best, most costly power amplifiers in any genre. That any other amplifier designer could make such rapid progress. This isn’t just our opinion.

The Absolute Sound “…over the years I’ve reviewed and used plenty of digital power amplifiers from Bel Canto, Wyred4Sound, April Music, and others, and I appreciate what a well-designed model can bring to a system. And it happens that the ST-10 is the best digital power amplifier I’ve heard to date”…- Steven Stone, editor.

Yet the NuPrime ST-10 is startlingly affordable. In our own long experience with New Zealand made it is far less costly but outperforms all Perreaux and Plinius models.

How they do this goes back to the design and the efficiency is the key.

Wasting power make no sense on any level. There is the ongoing cost of running. The cost of building in extensive heat sinks to get rid of heat, the cost of building in large power supplies that only ever provide a small percentage of the output to making music. There is the thermal ageing of capacitors due to heating and the noise and unreliability that are inevitable with age. The noise and hum from RF interference generated by the over sized power supplies with excess voltage and current. The weight and material costs, the design compromises. Crazy. Costly.

The NuPrime ST-10 is a breath of the proverbial fresh air in the audio world- every part of conventional power amplifier design is questioned and new approaches and technologies are embraced. 85% efficiency means you don’t need to get rid of a whole lot of heat – so the ST-10 is smaller – which allows shorter, lower noise signal paths. The actual power supply is only as big as it needs to be, so costs much less and produces far less unwanted interference. All the savings made can be channeled back into better quality components where it really matters. The long term reliability and working life is extended. This is why the ST-10 sounds so much better than any other power amplifier at this price and almost all beyond.

So why doesn’t everyone do this? Most companies are wedded to old technologies, are continually trying to incrementally engineer out problems and only make small gains. It continually costs them more to build the same, let alone build better. The writing is on the wall.

“I was especially impressed by the ST-10’s performance at the top and bottom of its range. The bass was taut and tuneful. Conversely, the upper midrange and treble were airy yet accurate. On recordings with exaggerated upper midrange or treble energy I was aware of the additional musical information, but it was never emphasised to the point of harshness.

After living with the ST-10 for a while I can understand why NuPrime draws attention in its sales literature to the ST-10’s ‘tube-like’ upper-frequency characteristics. While the ST- 10 certainly doesn’t soften or roll those off in the manner of classic tube designs, it brings to its upper frequencies the kind of ease and sweetness that are usually found in power amplifiers that employ tubes somewhere in their circuitry.

Depth recreation, dimensionality, and image specificity were also exemplary through the ST-10. On my live 128x DSD recordings of the Boulder Philharmonic, the soundstage was accurately portrayed with the spaces between the instruments elucidated with a level of specificity that was equal to the best I’ve heard from any amplifier in my systems.” The Absolute Sound

So there is no doubt that this is a very fine sounding and powerful amplifier – how will it work in your system? In almost all existing systems it will just plug straight in and perform. You have the choice of both RCA and balanced inputs and it sports a meaty set of speaker binding posts that will take banana plugs, spades or raw cable.

When we first heard the Nuprime ST-10 in the shop, it was in tandem with the DAC-10 – this obviously makes a lot of sense as a combination. It’s clearly a step up from the big IDA-16 integrated amplifier – we found it at once smoother, more detailed and richer sounding. The IDA-16 has a higher power rating and does seem to have a bit more of a growl to it which is a lot of fun – and there is a significant price difference between the two combinations – especially when you take interconnecting cables into account, so the IDA-16 should by no means be seen as lesser value.

Likewise the entry level NuPrime intergrated – the IDA-8 gives you a hint of how the Reference level separates will sound, but the power and weight of the ST-10 is made doubly obvious by this comparison. We found the ST-10 really likes full sized floor standing speakers – it’s got awesome levels of control and can really energize the air in the room when you have bass heavy tracks. We’ve had great fun with many different speakers and have never felt like we are testing the limits of the ST-10s output. All our digital files sounded better than we have heard them in any system.

At home through much smaller stand mount Sonus fabers, the finer parts of the character of the DAC-10/ST-10 combination became more apparent. With an analogue source there was an immediate lucidity and clarity that left our own amplifier standing – the NuPrime sound is almost liquid in the best style of tube amplifiers but it also seems more open and lighter. There is a real subtlety there that we didn’t expect with the power that first caught our attention in the shop. While some NuForce products have tended to have a bit of a push in the midrange, the DAC-10/ST-10 is much more even handed – vocals are well handled with lyrics remarkably clear. The top end is extended with no hint of roll-off and stays remarkably smooth even at levels that are seriously loud – Nuprime don’t get smoothness confused with syrup, so we do get the idea that this amplifier should be teamed with products that compliment this character.

The bass with our small speakers was less pronounced than with our resident amplifier – but also faster, more controlled and ultimately more accurate. At the time of listening we were also dealing with 3 new components including a set of the the KLEI gZero10 interconnects – experience has taught us that hey have an extended run in and I’m very much getting the feeling that the NuPrime electronics are likewise . Over the course of several days, the bass gained a richer quality and I’d love to hear where it ends up.

The ST-10 has slightly more gain than most power amplifiers – this will deliver an immediate improvement in dynamics and also means it will easily match with many lower output devices such as passive preamplifiers and source components with variable volume levels. Initially I felt that the high gain setting on the DAC-10 was required to drive the ST-10 but with more listening I settled on the low gain and was able to use the wide range of the volume control to its best – if you are used to systems where all the power is in the first half turn, the NuPrime will take a little getting used to – you may well find your volume control at 90/100. This is not a bad thing as the ST-10 has vanishingly low noise levels – provided the rest of your system is as well sorted.

NuPrime ST-10 rear at Totally Wired

Choose your interconnecting cable carefully -The KLEI gZero range is the best we have found in this regard and the care taken with grounding means that you’ll really hear the benefits of the ST-10s low noise floor – silence where there should be and detail in music that you’ve never heard before. The ST-10 also features balanced inputs.

I haven’t played around with power cables with the ST-10. Unlike most of the previous NuForce products, this power amplifier does have a toroidal transformer in its power supply, yet with the class leading efficiency there will be very little current draw. The cable provided is better than many anyway. There also seems to be little reason to look for mains filtering – we have none in our own system and there hasn’t been a hint of any noise with the ST-10 – not even the tiniest click.

Time for change?

In the past you might have been impressed by the brutality of some big name amplifiers – they had the size, the weight and certainly knocked my speakers about. But without exception they all had a lot of issues – far more hum and noise than I could live with, the inevitable heat dissipation requirements and most of them were a lot more expensive than the NuPrime. You may well be living with one of these – most aren’t aging that well with increasing noise levels and a gradual increase in what might be best described as opacity – the sound just won’t be grabbing you like it used to. So why not investigate the ST-10?

We’ve also seen a lot of progress with Class D amplifiers – Rotel’s cool running high power slimline models may not have been that popular but they did impress us far more than their heavyweight models. The NuPrime ST-10 takes what we liked about those and improves upon it in every respect but remarkably comes in at around half the cost – for an undeniably superior result.

On the basis of what we have heard for ourselves the only sonic competitive amplifiers on our horizon are the new NZ made Pure Audio models. Yet these are around four times as much.

So you’ve read the reviews and our take on it – how about comments from one of our clients who has just gone to NuPrime after auditioning the DAC-10 and ST-10 against his 5 year old (and far more costly) Plinius M8 and SA-103 combination:

‘Hi John,
You’ll be pleased to know that I think the ST-10 does everything as claimed, and in combination with the DAC-10 it’s obviously a formidable component. Everything the DAC-10 began — extended soundstage, extended and enriched bass, more contoured and detailed sound — is simply augmented and consolidated. This power amp exercises an authority and control that I hadn’t experienced with the Plinius, and I begin to see why the company stresses the effects of sound emerging from silence: with the right music it’s an awesome effect. I’ve tested the ST-10 mostly with big orchestral sound where the extended and detailed soundstage has been stunning, but it also imposed an authority and balance on chamber music, particularly string quartets, that I didn’t expect, providing a naturalness and warmth I haven’t heard before from digital sources.

It only took me around an hour to establish all this, and that, as claimed by reviewers, the bass end is enriched in texture and timbre and the top end is controlled and pure. But it’s then taken me ages to decide whether I prefer the low or high gain from the DAC-10. I think finally you’re right and the low gain allows greater purity and richness of sound, presumably coming closer to the original source, but there are differences depending on the source and I haven’t always been immediately convinced that low gain provided the best result (I suppose what it was doing in some cases was revealing source limits, when a microphone for example might be placed too close to strings, retaining the squeaks of fingers on strings, or when, occasionally, the effect of high strings seemed too sweet). Still, there’s no question for me that the NuPrime combination is brilliant and that the ST-10’s post-switching design outperforms class A amplifiers of the order of my 5-year old Plinius — all of which you suggested of course in your website report.

So thanks again for all your wonderful descriptions and suggestions about products. I’m very happy indeed with the NuPrime amps and look forward to many more hours of pleasurable listening, now with sound even closer to the originals (and in some cases possibly even better than being in a concert hall). My meagre knowledge of the amplifier scene suggests this really is a revolution, developing a design that produces better sound reproduction than the heavy, hot, class A amps (I think my Plinius generated the heat of a 500watt heater), and at a lower cost. For me, they have achieved what they claim in their manual: ‘an ideal balance of richly textured timbres and harmonics, bottom-end authority, startling dynamics, exquisite low-level detail, and a fully revealed, fully dimensional soundstage against a backdrop of mile-deep silence.’

I have a CD of the Kirov Orchestra playing the Tchaikovsky 6th in Finland from the late 90s. It was one of Gergiev’s earlier recordings where he was establishing his conducting fame with this revitalised orchestra, and has received high praise as a performance. It has deep sonorities in the opening passages with rich bass strings, and later in climactic passages distinctive Russian brass playing. With the Plinius I heard solid deep, and, in the high brass, bright sound, but with the NuPrime I hear also the crunch of bow on string and its instrumental resonance, adding texture and timbre to solid and deep, and textured tone as well as brightness in the upper brass. And the improved soundstage also brings the sound forward from the speakers in a way that the Plinius didn’t (this was already noticeable with the DAC-10). All this is noticeable in large group sound, but as I said last time there’s an even more noticeable effect with small groups. In a full orchestra the collective sound of a section of violins or cellos blends into a harmonious whole whose richness will depend on the quality of the contributing players, but in chamber groups the individual instruments and players all retain their distinctive qualities. The NuPrime system, with the Sonus Faber Olympicas which must be helping here, is allowing that individual distinctiveness to be heard, reproducing both the quality and texture of separate instruments as well as the resulting combined performance. The naturalness of that effect is quite remarkable.

Anyway, sorry to keep going on, but I’m glad to be a fan. And you have now led me, gently and entirely without coercion, to a complete change in my stereo system! Not one wire or plug is left intact (actually, no, there are still the speaker cables, but as soon as we change our carpet I’ll change those!) My friends know you as my personal hi-fidelity adviser in Dunedin.’

And this is what NuPrime are all about – by being really smart about how they build things, they have managed to produce an amplifier that is up with the very best. Because the ST-10 is both affordable and broadly compatible it can be added to many systems – while our evaluation is primarily with the NuPrime DAC-10, there are plenty of other settings it will fit straight into.

Anyone with an existing pre/power combination should consider the NuPrime ST-10. It really is one of the very best power amplifiers we’ve ever heard, regardless of price. There will be very few systems that won’t sound appreciably better with its inclusion, regardless of the size or original cost of the power amplifier it is replacing – you’ll gain power, control and a massive improvement in resolution. And you’ll get rid of size, heat, hiss and hum.

The NuPrime ST-10 has driving abilities that are completely at odds with its physical size. The first ST-8 we sold ended up powering an absurdly large and complicated US made speaker system with reactive electrostatic tweeters. The ST-10 is a more capable beast again with a high damping factor and enhanced protection allowing it to deal the largest and most demanding speakers. Yet the levels of subtlety it brings to systems with small but perfectly formed monitors make it a quality option for the most astute listeners.

Why not try the ST-10 out for yourself and see?