Initial impression of the Nuprime ST-10 amp

I have a very fine McCormack DNA .05 Deluxe amp, a Don Sachs 6SN7 preamp, driving my Spatial Audio M4 Turbo S open baffle speakers and today swapped the McCormack amp for the ST10 amp.  Right out of the box, the ST10 is quite an amazing amp.  It is very powerful and yet quite delicate in its rendering of sound. To my ears, it is somewhat tipped-up in the HF compared to the McCormack amp, and at this point seems to give up a bit of the LF rendering of the sound to the McCormack amp, but overall, it has lots of inner detail and a sublime mid-range.  It has not a bit of harshness or dryness that I have heard with earlier Class D amps... it is very musical with the sound flowing effortlessly.   I will post my impressions after it has been run-in for a week. My initial impression is that for $1600, this is a very fine amplifier.  
Bad News!  Mytek is introducing a Class D amp and they are making big claims for it...

No bad news about any unproven claims.
Enjoy what you have and let us know your outcome.Put some hrs on it and it probably will smooth out on the top end.

Happy Listening,

Cool, whitestix. I really enjoy my NuPrime IDA-16. If the ST10 is anything like my IDA-16 it will take a few weeks for it to really start settling-in.

Based on my experience with the IDA-16 I believe you are in for a good time, enjoy.


Thanks for the encouragement and the reminder to be patient in the break-in process.  I never thought I would abandon tube amps for Class A/B amps, but I did and never looked back.  I was totally unhappy with the Bel Canto class D amp I had a few years ago, but clearly, this ST10 is in a whole different league.  I think Class D amps, and their modern variants, are the wave of the future.  

I will report back my impressions of the sound of this amp after 100 hours.    Cheers, Whitestix

I never thought I would abandon tube amps or class a solid state after 25 yrs and I'm not looking back either.

I'm using a red dragon s500 currently which is probably going to replace my ref600m. I haven't heard the st10 but I've read a lot of good things about them.

What bel canto Amp did you have and what preamp are you using with your st 10.

I have about 50 hours on the amp and am happy to report that it is breaking nice nicely.  It is very powerful, dead quiet, and the crystal  clarity of the sound of my Holograms is amazing.  This is nothing like the Bel Canto Class D amp I had years ago.  It adds astonishing clarity and presence to the sound of my speakers.  The LF is taut and the HF is extended.  This is an amazing amp that is probably going to be even better when it completely breaks in.  I will admit that it does sound a bit different that my Class A/B amp, but think the ST10 is much more neutral and less congested.  I will get back to you after 100 hours, but at his point, it sounds quite fine to my ears.   Whitestix

That's great. If it's anything like my IDA-16 it will continue to open up and fill out. You may have some peaks and valleys along the way. Around the 300 hour mark my amp really started to bloom. Even now passed the 500 hour mark it continues open up and settle in. Have fun.


Hello all,

I have over 500 hrs on my S-500 and thought I might comment a little about it.I think it's a step up in Sound vs nc400 and ref600m,these are the 3 class d amps that I own and I have access to more through a local audio club where we lend and or borrow equipment or occasionally listen to each other's systems.

I have been using a bel canto pre3 with all the diff. amps just to make a even playing field,the pre 3 is a pure water no coloration preamp.

The S-500 is the best class d amp I have had in my system and it has the warmest most engaging midrange with very sweet nicely extended top end that has more air and separation with the individual instruments making the entire frequency range very coherent.The bass is equally as good maybe better than my other class d amps listed.

I borrowed a Nuprime st10 to try out and found it too be a very close match to the S-500,with the nod to the S-500 for the best overall sound especially the midrange.

Offcourse this is in my system with my ears and judging the musical presentation that I prefer.

The next test will be comparison with a modwright kwa100se that I have owned for a few years but I haven't used it in about 3 years,I have loaned it out to club members though.I know it's a very good amp but can it equal or beat the S-500,only time will tell.

So many very good choices out there nowadays,

The S-500 must be fine for Clayton Shaw to recommend them for his Hologram speakers.  Glad to hear you felt the ST10 compares to it.  Samac, thanks for the insight into the breaking in of the ST10... I like it now and expect I will like it even more in the future.  
@whitestix what model Bel Canto you had?
Celo, I do not recall the model of the Bel Canto amp I had maybe 5 years ago, but is was used and well run-in when I got it. My listening notes reveal that the sound of it was exceeding dry, lifeless and strident.  I flipped it in within a few days, the shortest time I have ever had a component in my system in four decades.  

That said, I will hasten to add two comments.  First, the march of technological improvement with class D circuitry has been quite amazing in the past few years.  I think it is light years better than it was just a few years back.  Secondly, if one is swapping a class D amp for a class A/B or tube amp, the listening experience takes a bit of time to adjust to.  The hyper-clarity of class D amps, with so little distortion, can initially sound rather sterile and less engaging, but I personally think with my experience with the Nuprime amp, and another class D amp in my other system, that the class D amps are distortion-less and amazingly revealing the of the sound.  It is a matter of adjustment to the sonic character of the somewhat different sound of a class D amp.  

Based on Kdudes' comments above, I ordered the Red Dragon S500 stereo amp today to compare to my ST10.  One of them will stay in my system and one will be returned.  I turned a corner and am all-in with class D amps.  However, I will not soon part with my tube preamp!  Even with my Don Sachs preamp, my speakers are absolutely dead silent on quiet passages with the ST10.  Ryan at Red Dragon has a $400 discount for his b-stock ST500 amp which swing the order for me.  
Cheers , Mark

Any word on the S500? Seems like a good choice for where your heading. I have a similar set up. Class D has been by my side for a few years. This new technology has sparked my interests.

Cheers, Kim
Funny you should ask.  I am sitting here in my living room waiting for the big brown truck to deliver the S500 at the moment. I figure I will be the last delivery of the day. 

I have been very impressed with the sound of the Nuprime amp as I have described above.  I have a 5 wpc Dennis Had EL 84 tube amp that I am selling and to make sure it is functioning properly, I swapped it out for the Nuprime amp.  Note that I am driving 94 db sensitive Spatial Audio Hologram speakers.  OMG, I was blown away with the sound of the flea-watt amp driving these speakers!  The mid-range bloom with the tube amp was just luscious, so warm and expansive.  The Nuprime amp had no such ability, but clearly excelled in LF control and HF extension.  I have had tube gear for decades and it clearly yields more warmth and sound of an euphonic nature.  If one has less efficient speakers, then these observations are not relevant as this flea-watt amp would not be compatible, but however the shoot-out between the NuPrime and Red Dragon comes out, and think I will keep one of them, I am not going to part with this venerable Dennis Had amp.  There is clearly magic in tube amps that class D's still can't match if the sound of tube amps is a sound you find appealing. 

Stay tuned.   Whitestix


Dennis makes some good little amps,I've had the pleasure of listening to most of the models and I liked the El-84 and the Kt150 versions the best.I don't blame you for keeping it you never know how many more he might produce.

The only tube amp that I kept is a Yamamoto A09s it uses the 300b tube,It took me forever to find one and I have done several upgrades to it that I would never sale it.

Anyhow back to class d land,I did a comparison of the red dragon S-500 against the Nuprime St-10 again and I prefer the S-500 overall for the same reasons as listed above in the previous post,the S-500 has a lower noise floor and conveys the micro detail and nuances of a recording a little better.

Both amps are really good examples of modern class d amps and you can't go wrong with either one in my opinion.

Next comparison will be the S-500 with a Modwright Kwa-100 SE.


I got the Red Dragon class D amp today and it sounds very good right out of the box, although not as fleshed out as the Nuprime and  bit sibilant, but only slightly so.  It has an unsightly case, as others have observed.
 Still,it might be difficult to discern the Nuprime amp from the Red Dragon sonically at the moment, but I will do that comparison with 50-60 hours on the Red Dragon to be fair.  Notwithstanding my enjoyment of my Dennis Had EL84 tube amp, the two class D amps are quite amazing in their power and performance in such a small package.  By analogy, I think that one type of amp is like a Chardonnay and the other is like a Cabernet. I like both, but neither exclusively.

At the end of the day, I think one trades crystal clarity of the music, LF control, and dead silent background with the class D amps for the gloriously expansive, and palpable mid-range bloom of a tube amp. Neither can completely do what the other can do, yet.  Gents, at the price point of any of my amps, there is no such thing as the “absolute sound”.  Tube biasing and running big honking KT88’s in the summer heat of Sacramento would tilt me to the class D amp, but the Had amp with its four EL 84 tubes runs reasonably cool and needs no biasing, a hassle that I disliked with my Harmon Kardon gear.  My Spatial Audio Holograms are ~93 db efficient and it bears noting that the 5 wpc Had tube amp is no less engaging than that the 250-wpc Red Dragon amp. I run the volume pot on my Don Sachs tube preamp at 12:00 with the Had amp, while the volume pot runs at 9:00 for the same SPL with both the class D amps.  I have plenty of gain with any of the amps.    Obviously, if you have much less efficient speakers, my discussion of the comparison with my Had amp would be irrelevant to your situation, but not with respect to the sonic differences of a tube vs. class D amp.   My ears are 63 years old so take that into account. I would encourage any of you readers to compare, contrast, or refute my impressions.

The appeal of class D amplification is very easy to understand for the reasons described above.  If 10 years ago I somebody had told me that class D amps would sound this excellent, I would have been dubious. Yet, to my ears, such sonic performance is easily attainable for less than $2K, or a few hundred more with the Channel Island Audio mono-blocks, which I have heard and are excellent. Several audio companies have outstanding class D integrated amps, including NAD, that provide outstanding “one component” performance.  
Just my take,

There is no perfect Amp at least I haven't found one yet.
They all have their own sound characteristics as you are finding out.
That's why I like trying different ones and comparing and most of them I could live with and use a long time and be happy with.

You may want to give the red dragon at least 100 hrs or more before you judge It's true character.You did get a S-500 is that correct.

Red dragon doesn't have the best looking cases that's how they keep their price down compared to others, I have a black one and It's not as noticeable for me.

As I tell a lot of people you need to figure out what kind of sound presentation you desire and go from there.That's the best way that I know how to describe It.


Right you are, Kenny.  I will run in the new amp for the requisite hours and then compare them.  I do have the S500 and like you, the black case is no bother to my eyes.  The ST10 has a main on/off switch on the back and a standby on/off switch on the front.  It is a bit of a bother having to reach to the back end to switch it on and off, but that is a trifling matter. 

I reckon in time the class D amps might be able to mimic the euphonic sound of tube amps and keep the speed and LF control.  My pal has the Nuforce/Nuprime Ref 9V3 mono blocks and for them he has retired his high end Krell amp, much preferring the REF 9.  Now, even further up the food chain of Nuprime is the Ref 18 and 20 mono blocks and I would expect that they are incrementally better than the ST10 I have.  Cheers, Mark

I can relate to you about what you are saying about the various Amp differences.

"I reckon in time the class D amps might be able to mimic the euphonic sound of tube amps and keep the speed and LF control. "

There is some of the upper models that can do this to some degree at a price.There is a very fine line in design of class d to have these kinda qualities,mainly you would have to add distortions and colorations to get those euphonic tube like qualities but then you lose clarity,detail,inner detail and the perception of speed and LF control.

Class d has certainly come a long way but I kinda look at like analog vs digital,we have had digital music for a long time know and today we have better dac's than ever but It still sounds different than analog.Now don't get me wrong I enjoy both formats equally.

Maybe It's the same with speakers,there is some qualities I like about OB's but I never have had a pair and since moving in to our smaller house I don't have the right room for them anyway or panels either.It's just a trade off I quess,no perfect speaker either but we do have some very good ones.