Nuforce STA200

I am curious about the Nuforce STA200 amplifier  If anyone has experience with the amp it would be appreciated if you would share your listening impressions, both good and bad.  Some of the descriptions I have read classify it as a class AB amp and others a class D amp.  I am not technical savvy about these things, can a single amplifier be both? 
Thanks randy, I am hoping someone owns/has owned the little amp and could share their experience, but does not seem very popular.
I just hooked mine up with a Classe CP-35 preamp and after a few hours I'm very impressed with the sound... especially at the close out prices a great value...
Thanks jl35, that is good to know.  If you don't mind give your thoughts after break in is complete.
Hi jl35, would be great to read your thoughts about this amp,  there is no so much information out there. 
Very clear and warm. Good depth and dynamics. Did not use with speakers that had deep bass. I think the TAS review was quite accurate. I think Audio Advisor still has them new for $500
I saw that Audio Advisor only had 8 left. I just ordered one. As I update my main system with a much higher end amp and pre, I'll be building a system in out master bedroom. My Nova pre will make the move. However, wife says that my B&k st140 will not make the move. The Nuforce will blend in nicely. I'm sure it will do fine for what I need it for. 
The amp arrived yesterday and I started listening. I have not fully broken in.
This amp is quite heavy for its size and built like a tank. Soundstage goes beyond speakers. So much better than my old B&K.
Sounds lika a veil lifted off the sound. The Nuforce sounds great for both the Older and modern music (My B&K sounded dull for modern music). The highs are not brittle, which is what I was afraid of with my Zu Omen tweeters.

The low end is deep and tight. You can feel the lowest of the notes. The B&k had a loose, bloated low end which worked quite well for old material. This is with the Zu's known for slightly shy bass. 
Cranked compression or strain. I feel I could give it much more (101db efficient speakers). The amp is dead quite. Background is black.

This amp is truly, in my opinion, is a $1300 amp ( original msrp). The $499 price is a STEAL. I suggest pick one up before they are all gone.

I believe the amp is class a/b...not D 

Thanks  jl35 and aberyclarck for sharing  your experiences I guess would be very helpful for  some people 
I'm happy with the way it sounds out of the box. I'll be curious , after more hours of usage, how characteristics will improve. 
After 24 hours of continuous power and background music playing, I did another round of listening. I was thrilled with the amp out of the box. The amp seems to be slightly more "silky" and the low end seems to have "blossomed" FLOABT. I did not think the amp would improve any. However, there is an improvement OR my ears have adjusted differently. Anyway, I did my late night listening with my EQ turned on (I use the eq as a loudness switch for late night listening-slight low end boost). I quickly bypassed the eq off since the low end now seemed too much. I'm at the point now where I may just remove the EQ out of the system. I did do a slight speaker position adjustment to compensate for the much wider soundstage the Nuforce has over my old B&K.

My Zu's are 101db, this amp is dead quiet. Solo piano music seems to come from nowhere.

I'm really thrilled with this amp and can only imagine how much better  the right higher end amp (and Pre) will sound when I shop for one this fall/winter.

Again, I'm coming from a 30+ year old differences may not be as drastic with something newer. 

It will improve for another week or two. It's an exceptional amp and bargain 
It will improve for another week or two. It’s an exceptional amp and bargain
I was totally surprised with how the low end seemed to go deeper and wider. In the past when I have purchased equipment, I’ve noticed a slight high end "taming" (especially speakers) but never low end improvements.
It's cool you could find a replacement for the old B&K.  My former B&K FET amps sounded great for a few decades and I'm not sure if parts inside degraded over time due to heat or what but I replaced my 2ch/3ch dual mono amps with Outlaw Audio on my HT system and like you said, "a veil got lifted off" for home theater and general listening, but not the same for dedicated 2ch listening.  Will be interesting how the NuForce works for you over the next few years, and if it sounds nice for $499, quite a steal.  I'd be tempted to try it with a nice tube preamp in front of it to see how it does. When I want to save the tubes on my tube amps, I run a Cary solid state amp behind my tube preamp and its quite amazing.  Maybe something to try with the Nuance to see what you think.  Good luck. 
I am now shopping for a high end pre amp-power amp for my main system (the STA 200 is in main system until ---then it moves to a second system with my NOVA Pre). I slightly adjusted speaker position for the wider soundstage that the Nuforce brings. After a few days the amp seems much more silkier and the deep low end has gotten more focused and deep. I'm sure some may be due to the slight speaker adjustments. The STA really makes me want to listen to music so much more than the old B&K. 
After a week of playing, I think the amp has probavly leveled off as far as break in is concerned. The amp is totally superb. Even if I paid $1300 ( original msrp), i would have been thrilled. 

I really cranked it up the other day to uncomfortable levels and no distortion or compressed sound whatsoever. Im sure lots of the "loudness" for an 80 watt ss amp has to do with my efficient speakers. 

One thing this amp does, it has gotten me more aware iquietness. This amp is pitch black, however, I hear a slight hiss with static with my Nova Pre in the loop. I changed the pre amp input ( removed Peachtree) to both my Oppo and Bluesound Node 2 ( changed both voulumes to variable) and the noise was gone. On the Nova Tree, bypassing the gimmicky tube made no difference. 

Now i know to shop for a quiet preamp. Maybe oassive is the way to go since my speakers are so sensative. 
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Let us know how the passive and  the STA200 match us sound wise. Im considering a passive pre myself
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Thanks again jl35 and aberyclark for providing your listening experiences.  
No problem. The amp is really special IMO. I was amazed how deep the low end goes (not in a bloated way). The top end is very smooth. I would say its maybe just a small tad on the warm side of neutral. Which is great for my ZU "super" tweeters. I’m now shopping for a pre to replace my Nova pre. 
Does anybody have compared this Nuforce with the job 225?? Despite the power and price difference,  do they sound the same? If not Wich is better? It is worth the price  difference considering the Nuforce is selling for 499?
You could probably google. The issue is if the Job is $1200 better which I doubt. 

For the Money of $499 It is fantastic value. I bought two of them on a whim about a year ago, one is still unopened waiting for ancillaries to be added If I can get any other equipment  in the house and set up unnoticed (lol), the other is teamed with a Quad Vena used as a Pre Amp listening to the excellent  Bireli Lagrene 'Standards' CD as I type and it sounds very good. All said and done it is great value at whatever the original price was ($1299)?, at $499 It is exceptional value to my ears. I could quite happily live with (and do) with the STA200. High End performance for pennies.  IMHO. Is there a better Amp for $499?
Purchased one in April of ’17, for shits and giggles. Sold many of my " expensive " amps, because after a few months of this little guy breaking in, it bettered many of them. My only negative issue, because of it’s high gain, I do get a small amount of hum from my 104 db sensitive speakers, which was bothersome at some point. Hum is at constant level, does not increase with volume. Have not even done my AVM mod to it yet ( which I do to almost everything ). An amazing amplifier.
NuForce uses a hybrid approach, very similar to Carver's idea, and << cough >> borrowed by Yamaha in the EEEngine design. Not sure if Yamaha ever licensed it or waited for patents to expire.

The voltage + and - rails are Class D, and they swing up and down. In between the rails is a Class A or A/B (not sure) linear amplifier.

It's quite clever. By keeping the voltage rails from deviating too much from each other, the power dissipation in between is always limited to a few watts compared to a linear power amp of the same output.

For instance, a 120 W amplifier might have +- 50 V rails. The amp between has to dissipate a lot of heat as a result of the 100V difference. But if the voltage between the two rails is kept small, say 30V, then the heat and size of the amplifier can be made much smaller, with much less wasted power.


@erik_squires My understanding about the STA 200, is, it is a conventional AB design, taken from a circuit developed by Goldmund, also used in the Job 225. But yes, Nuforce ( Nuprime ) does use designs in other models in which you speak of.
Ordered a pair of Goldenjacks 10 db attenuators. Will see if it reduces the hum, without affecting the sonics ( doubtful ). If this does not work, might need to go back to passive ( never liked ), change to a lower gain preamp, or a different amp ( although I do like the STA 200 ). I gave up on tubes a while ago.
Just do what i did. I have a tube pre amp and the high gain causes the hiss to become louder thAn normal. I have zu 101 db speakers. Order the Schiit $49 passive preamp and place between pre and nuforce. Adjust the schiit volume to an accepttable level where hum is not heard at sitting position. Very transparent and better than attenuators. I tried attenuators and the sound was slightly smeared. No noticable sound quality reduction with the Schiit. 
@aberyclark Thanks for the recommendation. I will try the attenuators when they arrive, and allow them break in time. Hopefully, they do not smear the sound much. If they do not work out, I will see what to do next. Thx. 
Has anyone tried a passive unit with the STA 200 ? ( @aberyclark , did you happen to listen to your Schiit sys direct, w/o preamp ? ). Thanks
I picked up the NuForce a couple weeks ago and was planning to have my CEntrance dacmini modded to variable outs.  When that was a no go, I ordered a Luminous Audio Axiom ii passive preamp.  Luminous Audio takes the specs on your amp and speakers (as well as the dac) and designs the preamp accordingly.  Put it all together today, and even tho it’s just a few hours out of the box I’m pretty blown away.  Excellent soundstage and imaging, bass is tight, excellent midrange and the background is dead quiet.  I highly recommend the Axiom—about $220.00 with the upgraded Caddock Resistor.
Looks like the Nuforce has finally been discontinued. Too bad....I really love mine
I purchased a Luminous Audio Walker Mod, single ended, 3 in, 2 out remote unit about a month ago, and all I can say is, I will never use a preamp again. And, the STA 200 is amazing, and such a joy to listen through. Enjoy ! MrD.
mrdecibel, I purchased a STA200 about a month ago when Audio Advisor received them back in inventory again.  As was discussed previously, the amps high gain resulted in me only being able to turn up the volume on my tube preamp about 1/3 of usual.  At someone's recommendation, I purchased the Schitt Sys passive for less than $60 including shipping and put it between my pre out and amp, and that did the trick perfectly.  I have had only tube amps for a long time, but I am enjoying the STA200 quite a lot.  At $499 I am quite happy.
jetter, I did try some 10db attenuators and did not like them. I also borrowed an inexpensive passive unit to go between my pre and amp. Did not like it either, with a 2'ndary volume control and an additional set of cables. Tried the cheap passive direct, and found it better in some ways to the preamp. So bit the bullet and am enjoying high end passive. I am glad, after a year, you bit the bullet, purchased, and are enjoying your STA200. Enjoy ! MrD. 
Has anyone switched out the PC on the STA200?  I have a Transparent Audio Premium PC coming tomorrow- curious to see what other folks are using.
I use that cord on my STA200 as well as Nuprime DAC-9 and CDT-8 and that combo sounds great   Salk SongTowers complete the system 
Did not do any comparisons, but sounded great with a Signal Cable PC. I'm sure a better PC will bring better performance. 

It opens up nicely with a superior power cord, especially over the stock cord. Enjoy ! MrD.