Part 2 – Digital and Conclusions.
In Part One we examined the performance of the NuPrime AMG PRA preamplifier in analogue systems. Now we bring digital into the mix.
Digital is all about certainty – there is nothing like the variability of setup associated with analogue and the performance tends to remain consistent over time. Which is of course part of why it has taken off. Not to mention the vastness of available music across a broad range of digital formats.
The NuPrime AMG PRA might, at its heart be an analogue component, yet it weaves magic into digital replay and shows us that music is what matters regardless of how it is stored or delivered. So now in Part Two and you’ll learn how the PRA works with digital sources, how it compares to other options, and advice on matching with power amplifiers and cables.
The PRA is outstanding in terms of making music sound better in any separates system for both digital and analogue sources.
The PRA is also an unequivocal improvement on all previous Nuprime and NuForce preamplifiers and combined DAC/Preamplifiers.
There is no better way to illustrate this than in the context of NuPrime’s flagship system – the Evolution DAC running directly into a pair of the Evolution One mono amplifiers. The inclusion of the AMG PRA between the DAC and power amps (with the DAC switched to fixed output), is superior in every way. This is astonishing given the comparatively low cost of this preamplifier – it literally cost less than one of the sets of interconnecting cables used yet gave a far greater and immediate improvement. The sound is richer, imaging more tangible, resolution and detail enhanced, and the dynamics and bass better to the point of being just a bit scary.
It’s a little crazy that the affordably priced PRA can have such a significant effect in a high end system. What’s even better news is that the improvement wrought in more modest systems is even greater.
I’ll admit to being taken aback by this. In theory the Evolution DAC and Monos ‘should’ be perfectly matched and the imposition of another component could be expected to have a downside. The Evolution Ones feature the same 1M Ohm input impedance as the PRA and the preamp section of the DAC is convincingly better than other models with great attention being paid to the power supply especially. So obviously there is more going on than just simple transmission of sound from A to B.
In Part One I wasn’t able to give a definitive answer as to if the PRA is full Class A – the answer from NuPrime is that yes, it absolutely is. Unlike the previous HPA-9 it’s not having to run a separate and higher powered headphone section and so it doesn’t get as warm – but I tend to cover ours with a dust cloth at nights in the vain hope of discouraging our cat from nesting on it as he does with many warm amps, and this does confirm that there is a modest amount of warmth dissipating from the top cover. Electrical efficiency is at the heart of many NuPrime designs so it’s not overly obvious but the sound is certainly consistent with Class A operation.
A preamplifier is very much the heart of a music playing system. (With integrated amplifiers the preamp is a section within your amplifier), but as the PRA illustrates, it is the most important when it comes to determining the delivered sound quality.
It follows that you are highly likely to have more than one source and so our next question is how does the NuPrime treat different inputs? With digital this will include wireless options such as Bluetooth, direct connection such as USB from a laptop or streamer. And of course the original digital formats of CD and DVD.
Why the PRA works
Although our first example of what the PRA does with digital is the NuPrime Evolution DAC, all other NuPrime DACs show even greater improvements. This is because the differences between the digital sections and DAC chips used, while significant and audible, are qualitatively less obvious than the improvement made by the PRA to the output stage. In all DACs with a variable output, we either switch to fixed, or if this isn’t an option, take the volume up to full. This ensures the PRA can extract every last ounce of performance.
Note that with many DACs the volume control is just an attenuator and this has a profoundly negative effect especially at lower volumes – that’s why the sound often goes flat and lifeless. It’s not a problem with digital – it’s a preamp issue, and that’s exactly what the PRA solves.
Unlike analogue systems where there is often residual background noise, the PRA is operating with vanishingly low levels with digital. And somehow it digs into what we’d previously heard as an amorphous silence and extricates detail that we never knew was there. Until you hear your system with the PRA included you actually have no idea at all as to what you have been missing.
The PRA is far more than addition to an already high performing system. It also enables unprecedented performance from some amazing low cost components that have started to come through.
Better performance for less
The little NuPrime uDSD headphone DAC exists at the opposite end of the range to the Evolution – it’s around 1/20th of the cost and was primarily designed for desktop use with a laptop given the single USB input. The trick is that it also features a pair of high quality fixed RCA outputs and when connected via these to the PRA the results are completely out of proportion to the cost.
For Bluetooth the new iFi Zen Blue delivers an equally impressive result for a similar price. Likewise their Zen DAC offers a slightly different flavour to the NuPrime uDSD. For the technically inclined the NuPrime and Zen Blue both use Sabre DACs whereas the Zen DAC favours the Burr Brown model. Not only does the PRA wring out every last bit of performance from these sources – it also makes the differences in character between them far more obvious.
Just to throw another real world example in I recently had a client visit who uses their iPad directly connected into a power amp – yep this works just fine as it’s got full volume control and the results are not too bad at all. But insert the PRA and it’s a whole different ballgame.
We all understand that there are some compromises made with smartphones and other source devices yet for many of us they are a part of daily life. From the introduction of the very first iPod we’ve always sort to find ways to connect and improve these. Cables, docks, small DACs and better quality headphones. The PRA builds upon this again – To say the improvements made by connecting your smartphone to the PRA via either the headphone output or and intermediary DAC are obvious is an understatement.
As an aside and something I should have covered in more detail in Part One: the PRA has the same effect with various phono stages. The new little Cambridge Solo phono is in exactly the same ballpark as the 3 digital components mentioned so the Nuprime has applications in an almost bewilderingly wide range of settings.
So you can see, these options all show why it’s been such a good idea to keep the PRA simple and just concentrate on the performance – plenty of other talented designers have already done all the hard work on these little source components and you can just select the one or two that best suit your needs – everything is optimised and nothing is wasted.
This also hammers home the advantages of separate components – no brand has a monopoly on sound quality and the NuPrime PRA enables to to select the best options for your own system and tastes. Even more importantly it keeps the door open for future improvements. No-one is likely to be upset if a better $300 DAC comes along and with the PRA you’ll be able to change digital sources in the same way that turntable owners can upgrade styli or cartridges.
The other side to this is, that while the PRA does wickedly well with entry level sources, you’ll hear even greater improvements as you work your way up the hierarchy. Even with NuPrime’s own DACs – the uDSD, DAC-9, DAC-10 and Evolution, the magnitude of improvement between the models is magnified by the insertion of the PRA.
And it doesn’t render them redundant or obsolete. Rather it enhances their best qualities and improves every other source within your system to a similar degree. Having now spent over a year in the company of NuPrime’s very best DAC I’m still in awe of what it does – every improvement made at source is obvious, it responds to better cables and it handles every type of input and format that I could ever want. The ability to subtly fine tune the sound with easy control of upsampling and digital filters will satisfy the most demanding and the quality and power of the output stage with full variable volume control will light up almost any breed of power amplifier. And yet the PRA makes it even better. Not a little, but a lot.
When the Evolution DAC was introduced the question was asked as to why it didn’t have analogue inputs like NuPrime’s other DACs and integrated amplifiers. The answer was that this would have compromised the performance of the DAC and added cost. We all understand that there is no such thing as a free lunch so could live with this. But the PRA not only solves this issue for Evo DAC owners (and there are a good number of other brands out there facing the same limitation) – it also greatly improves the performance across the board with all sources and formats.
The positive effect of the PRA on a system’s sources is mirrored by the performance gain with power amplifiers.
In every case, when compared to other preamps or a directly fed DAC, the PRA makes power amplifiers sound bigger and more controlled. And not by a small margin.
Within many brands you’ll have a choice of power amplifiers and often the jump in cost between models will be at a similar level to the PRA. Having made these comparisons many times in the past, the move to a larger power amp can be more subtle than you might expect with a large percentage increase in power. Because of the way our hearing works, twice the power won’t give you anything like twice the volume. The quality of the input signal will remain also unchanged.
In contrast, with the PRA a the perceived increase in power, dynamics and bass control will be greater AND you also get an equivalent increase in detail, resolution, all round music making ability – yes, you can have both quantity and quality.
OK – the real available output from your power amp hasn’t increased but what you are hearing is a much more lifelike, open and expansive rendition that will make the previous sound compressed and flat. It’s an across the board improvement.
I’ve now done this comparison many times – both for myself and with clients. Seldom have I found a single component that makes such and obvious and positive difference at any price. Even within NuPrime’s ecosystem of amplifiers, the PRA is a real stand out.
Likewise with many power amplifiers there will be a bridging or bi-amping option and we have always found this beneficial and obvious in effect. Yet the PRA betters this and more. And as the icing on the cake if you do subsequently bridge with the PRA and two power amps the gain will even greater again as you’ll be feeding both amps a much better signal and the PRA has ample capacity to drive.
Not just for NuPrime
The sonic qualities of the PRA and it’s ability to fine tune bass performance works wonders with many older power amplifiers – the warmer overall sound when the settings are applied brings a real tube like glow to what might be slightly clinical sounding solid state amps and the extra resolution at the top end ensures that you get an improvement from one end of the frequency spectrum to the other. The dynamics greatly improve with amplifiers that might have previously sounded a bit flat and uninspiring.
Over the past 30 years I’ve enjoyed listening to a vast number of different amplifier brands and models. Time and time again the importance of preamplifier quality to the end sound has been proven. This applies across the board, being equally valid for both New Zealand made and imported models. Just as you would have no problems in matching a different brand to your amplifiers when selecting source or speakers, the same applies with the NuPrime AMG PRA as a preamplifier. The ability to switch gain levels, phase and bass response, plus having both balanced and RCA inputs and outputs, all allow you to better match any existing power amplifiers on a practical level. But most importantly if you greatly improve the quality going in, you will make any power amplifier sound vastly better. No-one else has even tried to come up with such an ambitious analogue-only product in this digitally oriented time and so regardless of what brand of power amplifier you presently have, the NuPrime is highly likely to be your best solution.
Also remember that the NuPrime design is uniquely suited to matching many different brands on the input side. The extremely high-input impedance effectively eliminates matching issues that may have previously occurred, allowing each and every source, be it a cheap and cheerful or seriously high end, to perform at it’s full potential.
With the NuPrime power amps
With the latest generation of power amplifiers from NuPrime the PRA really emphasises the innate character of each and the differences between them. The resolving power of the Evolution Ones takes off to another level with the PRA. The high power and live signature of the MCX series becomes even more impressive to the point of being just a bit scary, The PRA has, for the first time allowed me to find the limit of the MCX-2 when a friend who really should know better wound our system right out to the point that the protection started to activate – this has never happened previously but clearly showed there is more than enough output.
The NuPrime STA-9 is easy to underestimate because of its modest price and small size. But remember that there are 120 watts on tap and with PRA you’ll be making the most of all it’s talents. Even more so if you already have made the jump to bridging with two. Exactly the same applies with the little Nuprime’s predecessor – the NuForce ST-100.
All this is leading to a review the matching AMG STA power amplifier – the same casework as the PRA, same price, balanced and RCA in, 130 watts a side but also with 1M Ohm input and a wickedly fast 700kHz switching speed – essentially a small stereo version of the Evolution Ones. And bridgeable to boot.
In combination with the PRA, this represents a staggeringly good amplifier option with analogue performance well beyond any similarly priced combination or integrated model, plus digital performance that’s only limited by the quality of input. The two boxes together, either side by side or stacked, are smaller than most integrated options.
You’ll see that the PRA has a pair both balanced inputs and outputs. While I have been a firm advocate of the KLEI cables which are almost all RCA terminated there is a really strong case to consider balanced with the PRA- especially for the pre-power connection.
There are some good quality low cost balanced options from Kimber – the 1m Tonik Balanced is just on $200 a pair and the 3 conductor braided construction is ideal in this setting. I’ve found the sound of these to be excellent when used between the PRA and a number of NuPrime power amplifiers which also feature balanced in and it’s certainly my preference as an affordable option.
There is a school of thought that suggest the use of balanced tends to minimise cable differences and likewise that some of what is heard when comparing RCA cables is the effect of either better or worse matching with regard to impedance. It is possible that the PRA (on the input side especially), may well be solving issues like this. But what I’m also finding, especially on the output side going into power amplifiers is that the benefits of better cabling are made doubly obvious. I would suggest this is because the PRA simply provides considerably more information and hence there is more to be gained in this link.
It’s also worth noting that both balanced and RCA outputs are continually active so if required to allows you to easily run a second stereo power amplifier or subwoofer.
By default I have chosen to listen to the PRA with good quality audio AC power cables from KLEI. The PRA does come with a reasonably heavy AC cable as standard. Previous experiences with the NuPrime HPA-9, DAC-10 and NuForce HAP-100 all suggest that the KLEI is a worthwhile and cost effective upgrade to performance. But it’s also important to understand that the scale of improvement I’m hearing with the PRA over these other preamplifiers far exceeds that made by any AC cable I’ve heard to date. This isn’t surprising given how much is obviously going on inside the PRA. But previous to this point I’d come to the conclusion that the best of these cables delivered an improvement often better than a component change. Clearly the PRA is a game changer.
NuPrime AMG PRA preamplifier NZ$3600 including GST and delivery.
Despite the delayed release and recent global disruption, we’ve got good new stocks of the NuPrime AMG PRA preamplifier here now and ready to ship directly to you. You can purchase from our on-line store here. Call or e mail us for a more personal response with any questions you may have as regards the performance, operation or matching with any other components. We’re happy to consider trade ins – especially NuPrime and NuForce if it makes it easier for you to move to the PRA. Also talk to us about connection recommendations with both signal and mains cables to make the most of your new preamplifier.
John Ransley – www.totallywired.nz March 2020
Declaration of interest: Totally Wired is an independent specialist audio dealership based in Dunedin, New Zealand. We are Authorised NuPrime resellers but strive to maintain independence and objectivity with all our reviews based on over 30 years of experience with multiple brands and agencies from both New Zealand and overseas. We welcome your feedback and questions regardless of location.
All my writing on the AMG models has been in a comparative vacuum – especially so given the year from hell 2020 has proven to be. There have been no other reviews to reference and I’ve come to conclusions based only on my own listening. So just after I’d finished the article above, it’s fascinating to get a review from Christiaan Punter, the owner of Hifi-Advice.com.
Christiaan is an amazing enthusiast and an obviously astute listener who has access to a range of componentry that most of us can only dream of. Yet, like me he’s got a huge respect for the NuPrime designs and is first and foremost into listening to music for pleasure rather than being hung up on specification.
In his review it’s obvious we’ve found common ground in our assessment of the AMG STA and its qualities – ‘I will agree that the amp is unusually fluid and refined not only for a Class-D design but even if it were a Class AB amplifier. But I never had the impression that the AMG STA is in any way coloured. Rather, it is very pure and neutral and utterly linear, with just a hint of sweetness.‘
Christiaan’s comparisons with more costly designs go far further than mine as do his expectations of the AMG STA in terms of working with some seriously costly and demanding speaker systems. So you can trust what he says and add it to what I’ve written and I strongly recommend you do take the time to read his articles as I know just how much he has poured into them.
John Ransley – December 2020
Further updates – March 2021
In a follow up to the above review Christiaan explores both the AMG PRA and bridged STA’s .
“The AMG-PRA + AMG-STA form a beautiful combo, not only visually, but also in terms of sonic synergy, the preamp’s robust and full sound perfectly complimenting the power amp’s slightly leaner balance. The combined result is a musically always engaging sound that is solid and full-bodied, smooth and refined yet highly detailed and transparent, with perfect pacing, and great dynamics. Honestly, at 3200 euro, I haven’t heard a better amplifier, either integrated or separates.
As great as the combo is, the AMG-STA power amplifier really is the star of the show. On its own, it is capable of performing on a level that is well and truly beyond what might be expected from an amplifier at its price point. To be more precise: if the preamp already performs at a level that belies its price sticker, the power amp steals the show as it has the ability to perform on the level of amplifiers that typically cost multiples of its modest 1.595-Euro price. I am not kidding!
Combine the AMG-STA with a great volume-controlled DAC and you’ll have a nearly unbeatable system. Between single and dual amps, if ever there was a no-brainer decision, this is it. The pair simply raises the performance in each and every audiophile parameter, without harming the emotional involvement.
As should be clear by now, I am definitely impressed by NuPrime power amplifiers. First, the ST-10 proved to be a keeper, then the ST-10 Monos proved that the concept could be taken further, then the AMG-STA proved that Class-D can be as “analog” and as refined as the best linear power amplifiers, and now, the pair of AMG-STA’s have further raised the bar. Although the ST10 and ST10 Monos still have their unique flair, as of now, the pair of AMG-STA’s are my personal reference in the field of affordable power amplifiers with true high-end aspirations.
Whether used as a single stereo model or as a double-mono pair, the AMG-HPA is an absolute HFA Favorite.”