– CHRISTIAAN PUNTER, hifi-advice.com

With the Evolution STA, NuPrime presents an amplifier that delivers a breakthrough in distortion reduction. To achieve this, they employ a technique they call Only Distortion Cancellation (ODC). A typical feedback error correction design inverts the output signal for summation with the original input signal to derive the negative error signal, which adds to the next cycle of the input signal to form a more accurate output signal. NuPrime’s ODC Class-D design derives the error signal from MOSFET devices and the output filter circuit directly, significantly reducing the negative feedback signal, which resulted in a substantial reduction in distortion THD+N of 0.002% @1kHz(5W), and less than 0.005% THD+N at 1KHZ (2W-100W).

Highlights include a 650KHz high-speed switching frequency to allow greater resolution, the application of the high-end NJR MUSES8820 op-amp for the preamp stage, and the Class-D oscillation circuit, a 550W high-power, ultra-thin toroidal transformer power supply with a total of 52,000uF filter capacitors. The amplifier uses low resistance terminals and is able to supply a rated RMS power of 230W at 8 Ohm and 40A of current.

After having favorably reviewed the ST-10 and the AMG-STA and having concluded that they have mutually exclusive strong areas, Jason Lim of NuPrime later mentioned that they were working on a new amplifier that would combine the strong points of both amplifiers. That new amplifier is the Evolution STA. Imagine my anticipation!

Review Context

For this review, I will use my main system, consisting in the basis of the CH C1 DAC, CH L1 preamp, CH A1.5 power amp, and Magico S1 MkII speakers with the Grimm MU-1 Music Server.

My power installation consists of a Siemens Sitor Cylindric Fuse, feeding an uninterrupted run of solid-core installation wire that ends in three wall-mounted GigaWatt G-044 Schuko Wall Sockets. These wall sockets feed three Popp/Eurolite unfiltered aluminum 8-output distributors via insulated runs of the same kind of solid-core installation wire.

Prior to starting my serious listening sessions, I made sure to leave the amp powered on for several days, and even before this, the importer also used it at home for two weeks meaning that the unit should be properly run in.

Listening

For my first listening, the Evolution STA was positioned on top of the CH A1.5, connected with the stock power cable, just like the A1.5, as the only exception in my system. While this will probably not be ideal for the amplifier, it does provide the ideal setup to compare the two amplifiers. Is there any sense in comparing the NuPrime to an amp costing over four times as much? Maybe not for prospective buyers, but for me, it is. The CH remains my reference and as such, it is a logical starting point for me. Don’t worry, though, as I will also compare the Evolution STA to the very affordable NuPrime AMG-STA and ST-10.

After having listened to a varied playlist via my regular setup, I reconnected the AudioQuest Fire RCA interlinks and the Jorma Trinity speaker cables from the CH A1.5 to the Evolution STA and adjusted the CH L1 preamp -3dB to compensate for the NuPrime’s higher gain. Even though I have not forgotten how great the AMG-STA and the ST-10 are relative to their price point, still, I prepared for the sound quality to take a few steps back with the Evolution STA compared to the CH. But that’s not exactly how it went down. Rather, my first impression was one of amazement.

The Evolution STA sounds marvelously energetic, expressive, and utterly coherent with immense neutrality but without tipping over into leanness or coolness. The amp is also very linear and quite detailed but not revealing to the point of being analytical, let alone clinical. First and foremost, it paints the complete musical picture while sounding nothing like your typical Class-D amplifier.

Between the CH and the NuPrime, certain key aspects have certainly noticeably shifted, but on the surface of it, and in an absolute sense, there is not very much to indicate that we just switched from a 31 K amplifier to one costing only 5 K. Honestly, it was more like switching from one high-end amplifier to another, invoking differences catering more to taste than to absolute quality. For instance, the Big Swiss amp remains the King of resolution and refinement. But to offset this, the NuPrime actually overshadows the CH in a couple of areas. Do read on to find out precisely how the two compare!

What struck me most, and I have to say that this had me a little worried, is the amplifier’s ultra-concrete solidity that makes the CH sound just a little sweet and even a little polite. The Evolution STA’s bass really is sublime and reminiscent of that of the Analog Domain M75, AVM Ovation A8.3, and Anthem STR. It is full-size, unrestrained, rock-solid, full-bodied, and weighty, but not in a thick, enriched, or loosely gripped manner as it can be with many powerhouse amplifiers, such as I feel is the case with certain Bryston amplifiers such as the 4B cubed. By the same token, the Evolution STA most definitely does not have the kind of bass that you’d expect from a Class-D amplifier, far from it actually. I have always found the bass from ICEpower, Pascal, and NCore amplifiers to be a little on the lean side, but as I found with the ST-10, NuPrime blissfully deviates from this pattern. It’s deeply saturated and full-bodied yet fast, articulate, and nimble.

With such perfectly-chiseled bass, it is not unusual for the midrange to break the spell by deviating in solidity or overall character, for instance by being too lean or too forward, or most common, to be hard or even edgy, but this is absolutely not the case here. The amp sounds very much of one piece and its midrange follows the superbly well-balanced foundation in all parameters. Just like the bass, the midrange is concrete, clean, open, and expressive, without sounding lean or being devoid of saturation or harmonics. I’d go as far as to say that this is one of the best and most supremely neutral midrange performances that I have heard. This is not a cool-sounding amp, but it also doesn’t try to hide its solid-state nature under a layer of smoothness or warmth. And it is not particularly lush or liquid. Indeed, people who prefer more of a triode tube sound will no doubt feel that the NuPrime lacks smoothness or romanticism. However, I often feel that amplifiers that do sound smoother usually do so at the expense of liveliness and immediacy. Moreover, while a nice dose of rich juiciness can be utterly seductive for a couple of songs, when an amplifier injects all the music with the same flavor I tend to get bored with it after a while. Rather than adding any kind of sweet sauce, the Evolution STA simply relays the music as unedited as it can. Meanwhile, there is excellent tonal saturation and great texturing without even a sliver of edge or hardness.

Following the bass and midrange perfectly, the Evolution STA’s treble is energetic, articulate, and direct, but again without being edgy or hard. If anything, the treble is a bit dry and ever so slightly dark. Indeed, this is one of the areas where the NuPrime cannot achieve the same lofty results as the CH, but in an absolute sense, the treble, too, is really good.

The Evolution STA strikes a visual resemblance to the ST-10, and sonically, it also reminds me strongly of it. While especially the amplifier’s bass and overall solidity are reminiscent of the ST-10, at the same time, I hear a level of linearity, refinement, and low-level detail that I do not recall having heard from the little amp. As mentioned, the Evolution STA’s is not on the same level as the A1.5 in terms of resolution, fluidity, and refinement, which is fair enough of course, but I feel that the AMG-STA also sounds airier and more refined and certainly more fluid. I think it’s fair to say that, like the ST-10, the Evolution STA is just not the most fluid amplifier on the planet. But because the amplifier is otherwise so great, I sincerely doubt that this will be a decisive factor for anyone unless one is specifically looking for tube-like warmth and liquidity and/or state-of-the-art low-level resolution.

Speed-wise, the amplifier strikes a perfect balance, it is neither slow nor fast but never slow and never speedy. It has got great PRaT, even if its immense control can sometimes make it slightly more static in its presentation. Well, strike that, it’s more fitting to say that it is just less relaxed and free-flowing than some other amplifiers. But, very importantly, this one absolutely knows how to party! While it can be less gushy or emotionally captivating with certain delicate music, the amp’s engagement factor with very nearly every other kind of music is simply off the scale. The amplifier even knows its way with classical music and even sounds remarkably convincing with massed violins and big orchestral music.

A surprising strong suit of the Evolution STA is the soundstaging. In this area, the amp miraculously performs on par with the CD A1.5, providing a wide, deep, and room-filling stage with strong focus and depth. The main difference here is that the A1.5 tends to project more to the rear while the Evolution STA projects more to the front, more in your face, if you will. As far as I am concerned, this is merely a matter of perspective and not one of quality.

When considering Class-D amplifiers, timbre or tonality is an important aspect. All too often, amplifiers of this sort sound deprived of harmonics and saturation, but here too, the Evolution STA shines. Its superbly natural timbre, combined with its exemplary solidity makes the best of piano and other percussive acoustic instruments. All too many amplifiers, even Class-AB designs, can make a grand piano sound more like a wall model or even a bit like a synthesizer, but not the Evolution STA. What this amplifier does magnificently well is to lend weight, body, and saturation to instruments, and vocals alike, and with plenty of warmth if needed, but without ever tipping over into mushiness or ever sounding colored in any way. This amplifier sounds full-bodied and it can sound smooth or warm so long as the recording dictates it. The amplifier will not overlay the music with any added softness or warmth of its own.

Interlinks

So far, I’ve listened to the Evolution STA using a stock power cable and the AudioQuest Fire interlinks, neither of which I guess are very likely to be used by prospective buyers. Not the former because I know that the other NuPrime amplifiers that I tested before sure benefitted from better power cables and not the latter because the Fire is even more expensive than this amplifier. But since they are my references, they had to be my starting point.

Changing the full and robust-sounding Fire interlink for the leaner and more refined, but also very neutral-sounding Driade Flow Link Reference 808 RCA cable, the balance shifts noticeably, and more toward sounding more like the A1.5 amplifier. With this interlink, the Evolution STA’s treble gains more fluidity and becomes a little bit airier while the cable’s slightly leaner yet highly articulate bass works well with the amp’s inherent solidity and fullness. On balance, the sound remains quite solid but is now slightly leaner. On the one hand, this makes the amplifier come across as more transparent but on the other hand, the fullness of timbre suffers slightly. But I think I know just what to do about that… 

Power Cables

Swapping the stock power cable for a Belden 19364 with Bals schuko and Oyaide C-004 IEC does indeed deliver what I expect from it and restores the overall balance with the proper fullness and even better authority, along with just a nice bit of extra delicacy, compared to the sound with the stock power cable and the Fire interlink. Another huge benefit of the Belden over the stock cable is that of an even more realistic timbre and an even wider and deeper soundstage.

I was already a fan, but when integrated this way, with the Driade interlinks and the Belden power cable, the Evolution STA sounds positively fantastic. But while I’m at it, why not also try the amplifier’s balanced input. As fortune has it, I also have the balanced version of the Driade Flow Link Reference 808 cable. With the preamp adjusted -6dB to adjust for the differences in gain, believe it or not, the amplifier provides even wider soundstaging, and without creating a hole in the middle. The focus remains solid. While balanced interlinks usually tend to sound wider than single-ended connections, the difference here is larger than what I am used to hearing between the two connections. Additionally, I feel that the amplifier sounds just a bit crispier and cleaner, as well as even more authoritative and realistic when using its balanced inputs. On the other hand, the RCA inputs lend a slightly smoother touch to the sound, with the Driade cables at least. All in all, I’d say that the NuPrime amplifier’s two inputs provide equally good performance, but with slightly different perspectives.

Speaker Cables

While the Jorma Trinity has thus far remained my favorite and my main speaker cable, we shouldn’t rule out the Driade Flow 405 speaker cable. Unlike the Driade interlinks, this speaker cable has a smooth, warm, and mellow character, coupled with fantastic fluidity and refinement and very good resolution. In the past, I have found it to work particularly well with the ST-10 and the same proves to be true for the Evolution STA. The nice amount of liquidity that the cable brings to the table works well with the concrete-sounding amplifier, providing a sweeter and more forgiving sound with greatly enhanced lushness and flow and an arguably more seductive delivery, without losing too much propulsion or control.

Mad Scientist Black Magic

Simultaneously in for review are new speaker cables by Mad Scientist. To me, this manufacturer is known to be different from the rest and, just like NuPrime, to deliver products with a very good cost to performance ratio. While the Black Magic cables are not cheap, they do still deliver great value for money. As it turns out, these speaker cables have very similar strengths as the NuPrime amplifier. As such, they enhance the bass impact, solidity, and dynamics, making the amp even more of a rock star.

The more affordable 2-Core version adds a remarkable tightness and coherence and makes the amp sound even more exciting but it is also a little lean and forward and it narrows the width of the soundstage compared to the Jorma and the Driade cables. The more expensive 4-Core variant, however, sounds tonally considerably richer, is wider in soundstaging and makes the NuPrime sound extremely well-balanced, in addition to incredibly engaging.

Both cables complement the Evolution STA in its strong areas but what these very neutral and very honest cables do not do is enhance the refinement or fluidity. And while the Jorma’s inherent refinement and fluidity add a gentle amount of forgiving friendliness, the Black Magic cables simply tell it like it is, warts and all. While that may not make them the ideal cables for everyone, I must admit that they have blown me away with the immensely energetic, toe-tapping, dynamic, and joyful presentation that they elicit from both the NuPrime and the CH A1.5.

Just as I experienced with the Evolution versus the CH A1.5, the Black Magic speaker cables make the Jorma speaker cables sound a little polite. A separate review will be forthcoming and meanwhile, I’ll have something to think about.

ST-10

Adding the ST-10 for a direct comparison, to my surprise, the little amp turns in an even more savagely growling bass, but admittedly in a decidedly less detailed manner. And indeed, across its entire range, the small beast cannot keep up with its bigger brother in the areas of linearity, resolution, transparency, refinement, and openness. The only area where it is competitive is in its dynamic delivery of power. And perhaps due to its “squarer” and less refined delivery, the ST-10 also has a slightly more urgent bounce in its step. Not that the Evolution STA is lacking in that department.

Thinking of the Evolution One, when I reviewed it, I found that it sounded a little too controlled, its presentation verging in the direction of cerebral rather than particularly gushing or singing. I’m glad to report that with the Evolution STA, this is no longer the case. I’m not sure if the manufacturer has intended to position it above the Evolution One, but if you ask me, the Evolution STA is a more satisfying amplifier.

And now that I am making a direct comparison between the Evolution STA and the ST-10, it is very clear that the amplifiers are rightfully positioned in different price categories, the higher-end model indeed being considerably more transparent and more nuanced. This not only manifests in greater fluidity and more refined treble but also in a wider and deeper soundstage in which the instruments float more freely and with more air around them.

As far as the ST-10 is concerned, it’s clear that the new amplifier has not only inherited all its strong points, but it has added to this significantly, while it seems that it has also integrated some aspects of the AMG-STA.

AMG-STA

Pulling out the AMG-STA for a final direct comparison, it becomes clear that this amp is quite different still. The AMG-STA sure does not have the concrete authority or the sonorous robustness of the ST-10 and Evolution STA, not their timbral fullness, but it does actually come closer to the CH A1.5 in terms of fluidity and refinement. While it is less expressive and more polite, the AMG-STA does have very nice flow and the PRaT also remains pretty good.

On balance, while I still enjoy the ultra-bouncy kind of loud-mouth ST-10 and I respect the heck out of the AMG-STA each at their friendly price points, the Evolution STA is most definitely superior to both.

It has been suggested to me that a fair comparison would be to use two AMG-STA amplifiers in mono mode and I guess the same is true for the ST-10 versus the ST-10 M. I have followed up on this and a second AMG-STA is actually on its way, but already knowing what the pair brings in addition to a single AMG-STA, I don’t feel that this would alter my conclusion. When the amp arrives I will certainly try it in a mono configuration and if this shifts the balance in a meaningful way, I will add my findings to this review.

Conclusion

With the Evolution STA, NuPrime has delivered an amplifier that manages to strike a beautiful balance between the strong qualities of the ST-10 and the AMG-STA, while raising the overall performance even further.

The amplifier strikes a visual resemblance to the ST-10, and while especially the amplifier’s bass and overall solidity are strongly reminiscent of the ST-10, at the same time, I hear a new level of linearity, refinement, and low-level detail.

The Evolution STA is extremely neutral but never lean or clinical. What it does magnificently well is to lend weight, body, and saturation to instruments, and vocals alike, and with plenty of warmth if needed, but without ever tipping over into mushiness or ever sounding colored in any way. This amplifier sounds full-bodied and it can certainly sound smooth, warm, or romantic but only if the recording dictates it. It will not overlay the music with any added softness or warmth of its own.

For all of its solidity and enthusiasm, the amp is a little on the dry side and it could do with just a little bit more refinement. But as I have often found (and as evidenced within the NuPrime range), extra refinement often comes at the cost of some dynamic impact and expression. And if I had to choose between these two options, I for one would opt for the one that provides the most fun and engagement, which is the Evolution STA.

Link to the review -->https://www.hifi-advice.com/blog/amplifier-reviews/power-amplifier-reviews/nuprime-evolution-sta-stereo-power-amplifier/