[mresseguie]

Alan

I just looked and it's there.

Jack,

If you scroll down to the bottom of the page, you'll see the separate 'Sonic Characteristics' graph (below the photograph of the Evolution One). The Evolution STA has not yet been added.

[JackD]

I was referring to the big grid.

[mresseguie]

Greetings Michael.  Many thanks for sharing your experience.  I appreciate it.  I returned to edit my post to characterize SPL preferences but was happy to find your response. 
You're welcome!

  To SPL I should say I need to keep the volume down for reasons similar to yours but, for critical listening, absolute numbers are less important than life size SPL.  Single, close mic’d front row acoustic guitar expectations are different than mid row concert hall symphony.
Agreed. I listen to a ton of 'simple' music - solo acoustic instruments, girl & a guitar, Jazz trio/quartets, etc. at low level SPL, but turn up the volume for orchestral music, Led Zeppelin, and similar music (but not as often as I did in my youth).

  Besides a 60 year old back, the inefficiency of a full time 200W space heater is the primary reason I hesitate to jump on Class A.  A west facing room in the middle of a NC summer is uncomfortable enough.  I’m also both a cheap SOB and (more than) a bit irrational.  I spend more on LED bulbs than we’re ever likely to save in electricity usage but I’m an engineer who’s obsessed (to a fault) with efficiency. 

I see we have a lot in common - and I don't just mean LED bulbs. My back is about 1.5 years older than yours, but who's quibbling? My living room is east facing, so my KT88 comes in handy during winter mornings.

  So the more I think seriously about amps the more I consider the value in finding that just right combination of performance, efficiency, and what I can only describe as topographical artistry. 
  In my limited experience I believe many Class A or A/B designs are owned end to end by the designer and reflect their values.  Class D seems to be a relatively new art form with most designers choosing a paint by numbers approach.  Constrained by the same picture, they’re left with primary color selection being their most significant differentiator.  Perhaps this is an overly harsh and ill informed characterization and genuinely unfair to those who passionately labor in this art form.  If you are one of those or one of their adherents please accept my humble apologies.  I mean no disrespect.
  Perhaps it’s premature for me to consider this, but what little I’ve learned about NuPrime in the past few hours suggests they are to Class D what someone like Nelson Pass is to Class A - at least in values.  Bruno Putzeys and others will certainly come to mind but I’m thinking only of end to end design.

I suspect Jason will happily accept the compliment. I've followed Nuprime's Class D amp progression from the release of their 'cute' little IDA-8 all-in-one amp to their newest Evo STA, and have been impressed by most of their amps that I've gotten to try. I'd still have my IDA-8 if I hadn't gifted it to my son and daughter-in-law as a house warming gift. [I eased my pain by buying an Omnia A300.  ]

Michael

[AllanS]

Alan

I just looked and it's there.

I see it in the first table “Relative Ranking of Power Amps” but not the second “Sonic Characteristic” table below the Evo One top view.

[John Casler]

Some may find our New Zealand Dealers evaluation valuable to the EVO STA

https://totallywired.nz/nuprime-2/nuprime-evolution-sta/

[rustydoglim]

I think he is referring to the bottom table.  I forgot to update.
The bottom table is simply a summary from the product page.

[AllanS]

The bottom table is simply a summary from the product page.

Thank you Rusty.

With that in mind would you please help me understand one choice in particular?  I’m coming from a place of technical ignorance and am really trying to understand the technology and implications.

I haven’t found a reference that helps me help understand the significance in choosing an op amp over a Class A Transistor Module.

From the Sonic Characteristic section I found this statement:  Practically all the amp products on the market use Op Amp for preamp stage. Only a few very high end products use discrete transistors design.

From the Evo STA product page I found these statements:
- The Evolution STA offers a breakthrough in distortion reduction (Only Distortion Cancellation) and rivals the Evolution One in sound quality.
- Preamp stage and Class D oscillation circuit utilizing high-end NJR MUSES8820 op-amp.
- Hybrid Class-D technology that retains the merits of both Class-A and Class-D amplification.

  I hope you understand that someone like me who isn’t as well informed as some could read into these statements that the STA rivals the One but uses a preamp stage is that is somehow inferior to that used in the One. 

   Does the STA rival the One in sound quality by trading the Class A Transistor Module for Only Distortion Cancellation?

  From the descriptions I’ve found, op amps sound like the Class A Transistor Module packaged into a single device.  Is that how or why the STA is considered a hybrid?

Thank you.  I appreciate your help and patience.
Allan

Edit to add:   If accurate, a reread of the NZ dealer review you posted before helped to understand the why of preamp choice - an evolution of the ST10.  Still very interested in trade offs in preamp choice.   Thanks again.

https://totallywired.nz/nuprime-2/nuprime-evolution-sta/

[rustydoglim]

Op Amp is a circuit that amplifies signal.


Op Amp modules are off-the-shelf parts that perform the above purpose. These modules are transistors packaged in a chip for commercial sales.
The Op Amp modules range in price and performance. Some like the MUSES8820 is expensive and very good.
Instead of using these off-the-shelf parts, an Op Amp circuit can be designed using transistors.
Very few high end audio companies in the world have engineer that can design custom Op Amp circuit that can create different sound characteristic. This is a very specialised skill.  Some of you have heard about people swapping Op Amp to change the sound, that's the idea. But we are doing it at a whole different level and complexity.

I don't think our article implied that Op Amp modules are always inferior to custom Op Amp circuit. Obviously custom circuit is much more expensive and time consuming to design. The "Class D with a Soul" section of this article https://nuprimeaudio.com/guides/amp-design/ talks about what I just said here. When our chief engineer design the op amp circuit, it is the preamp stage of the Class D topology, so he has to consider the entire design, so that he achieves the sound characteristic for the specific product.  This is very complex. To design something like Evolution STA from the ground up, I think there are less than a handful of engineers in the world who can do that.  The engineer must know analog design, Class D, and just happen to be an audiophile. 

[AllanS]

Op Amp is a circuit that amplifies signal.


Op Amp modules are off-the-shelf parts that perform the above purpose. These modules are transistors packaged in a chip for commercial sales.
The Op Amp modules range in price and performance. Some like the MUSES8820 is expensive and very good.
Instead of using these off-the-shelf parts, an Op Amp circuit can be designed using transistors.
Very few high end audio companies in the world have engineer that can design custom Op Amp circuit that can create different sound characteristic. This is a very specialised skill.  Some of you have heard about people swapping Op Amp to change the sound, that's the idea. But we are doing it at a whole different level and complexity.

I don't think our article implied that Op Amp modules are always inferior to custom Op Amp circuit. Obviously custom circuit is much more expensive and time consuming to design. The "Class D with a Soul" section of this article https://nuprimeaudio.com/guides/amp-design/ talks about what I just said here. When our chief engineer design the op amp circuit, it is the preamp stage of the Class D topology, so he has to consider the entire design, so that he achieves the sound characteristic for the specific product.  This is very complex. To design something like Evolution STA from the ground up, I think there are less than a handful of engineers in the world who can do that.  The engineer must know analog design, Class D, and just happen to be an audiophile. 

Many thanks Rusty.  I appreciate the explanation.  It’s starting to make sense.

[rustydoglim]

I found out more information about the linear power supply design in Evo STA.
There are two identical windings for two identical power outputs. Therefore Evo STA is really two mono amps in a box.
We design all our power supplies. Other features for EVO STA LPS:
- dual wires for each winding for low noise
- iron core is selected for low noise

[seikosha]

I found out more information about the linear power supply design in Evo STA.
There are two identical windings for two identical power outputs. Therefore Evo STA is really two mono amps in a box.
We design all our power supplies. Other features for EVO STA LPS:
- dual wires for each winding for low noise
- iron core is selected for low noise

Two mono amps in one box?  Are there two power cords?  😉

[rustydoglim]

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!

https://www.hifi-advice.com/blog/amplifier-reviews/power-amplifier-reviews/nuprime-evolution-sta-stereo-power-amplifier/


This review is very detailed.  We are very appreciative of Christiaan's reviews because in each one, he precisely pointed out the best qualities and areas for improvement.  So in Evolution STA, we set out to combine the best qualities of AMG STA and ST-10M and I think we did a good job. 

[AllanS]

Indeed.  Very nice write up.  Thanks much for posting.  Thanks also for the power supply details, which I suppose supports the dual mono statement on the product page.

[Soffer]

So if the amp uses an op amp as the input section instead of a class A version as with some of the other Nuprime amp offerings, is it true to say that the amp never heats up at all? And if that's true, does it mean that the Evolution STA runs more efficiently than if it had a class A input section?

Thank you.

[mresseguie]

So if the amp uses an op amp as the input section instead of a class A version as with some of the other Nuprime amp offerings, is it true to say that the amp never heats up at all? And if that's true, does it mean that the Evolution STA runs more efficiently than if it had a class A input section?

Thank you.

I can't answer the other question, but this is one cool running amp. A room heater it is not. The top case of mine barely feels warm.

Michael

[Soffer]

Thanks Michael.  I am still interested in the efficiency value of this amplifier if anyone knows the answer.  Thank you.

Edit: Removed a comment to Michael that was off topic.

[rustydoglim]

We started to use linear power supplies for most of our amps, so the efficiency is between a pure class D (i.e. Class D with switching power supply) and Class A amp.  We don't measure efficiency anymore.

[Soffer]

Thank you.

[Mystic Dragon]

Due to covid travel restrictions throughout Asia, I haven't been able to listen to Evo STA out of Taiwan factory.  But I don't need to listen to it for myself, I can rely on the chief engineer.  HiFi Advice has been reviewing our amps and we come close to challenge the reference CH A1.5 ($39,500). I think Evo STA has a shot at matching any class A reference amp.

Hi Jason,
I am using a ST-10 to to drive a pair of Martin Logan ESL11A speakers.
Currently looking for an amp that sounds warmer and smoother.
Is the Evo STA warmer and smoother sounding than the ST10?
Is there a review of the Evo STA somewhere?
How can I get hold of a demonstration unit in Australia?
Thanks.


 

[mresseguie]

Toward the top of this page, you'll discover this review:

https://www.hifi-advice.com/blog/amplifier-reviews/power-amplifier-reviews/nuprime-evolution-sta-stereo-power-amplifier/


This review is very detailed.  We are very appreciative of Christiaan's reviews because in each one, he precisely pointed out the best qualities and areas for improvement.  So in Evolution STA, we set out to combine the best qualities of AMG STA and ST-10M and I think we did a good job.