Review and Measurements of NuForce STA-200 Power Amp

[andrewinukm]

But yet you insist that you have no time to insert any real controls over your listening experience since it is only for enjoying music. How do you expect to be taken seriously on a science based forum when you will go no further than "I hear it so it is so". I have no time to debate with someone that refuses to participate in or produce any verifiable evidence for what he "thinks" he hears.

Wow. You must be the most serious person I've met on a forum. Relax man, did I not made it clear it wasn't a perfect test? Or did you get so outraged that you disregarded most of what was mentioned?

There were 4 other evaluators. I'm reporting that they heard it, and the difference was not a small difference. It's not comparing between Chinese green tea vs Japanese green tea (not easy to distinguish coz they tastes so similar at first). To put it into context, it was like drinking green tea vs oolong tea. Both tastes like tea, but very differently. That's how significant the difference were. This difference is too large to be attributed to bias alone.

Please be reminded the experiment happened in the past. I did it for myself, using simple experiment design in a casual environment. I made it clear it is not perfect, but the observation is consistent and repeatable. It confirmed certain things, and achieved my objectives. And it was done six months ago. So the data is provided as it is.

You can choose to look at it with objective curiosity, or you can doubt it and demean me. It tells a lot about how open minded a person is, and their manners.

I have no idea why is it so difficult to accept the a person who likes measurements and objective data, is also possible to enjoy and derive useful information from subjective individual observations.

 

[andrewinukm]

No, blind testing seeks to ensure that perceived differences - whether minor or drastic - are a result of real differences, as opposed to extraneous psychological factors.

There is no rule that says these extraneous factors only ever result in minor (as opposed to drastic) perceived differences, nor any evidence to support this view.

You're right.

But we also don't need blinded tests to differentiate a kick drum from a bass guitar. The difference is so observable that it's redundant to do a blind test.

 

[andreasmaaan]

You're right.

But we also don't need blinded tests to differentiate a kick drum from a bass guitar. The difference is so observable that it's redundant to do a blind test.

That’s true of course, but are you suggesting the recordings sounded like they were played on different instruments when you inserted the device in the signal chain? There’s plenty of evidence of blind testing not revealing differences that listeners thought were obvious when listening sighted. Do you consider yourself and your friends immune from normal, well-documented human psychology?

 

[andrewinukm]

All I'm saying is: the difference were significant enough and greater than the possible bias that may arise.

In any case, they were listening with a skeptical but open mind. I told them we can try, and let me know if they hear something or not, considering I may be biased. Before the test started, they do not think there will be an effect (it's digital and bits are bits). Immediately after the swap, they could hear the difference easily. If you were here, I'm pretty sure you'll hear it too.

 

[HammerSandwich]

Please note that the comments from the evaluators were: the difference is easily observable even with casual listening without focused listening. Yes, the effects are that strong that single blinded test are redundant.

And some people report similar differences between, say, USB cables...

 

[Sal1950]

And some people report similar differences between, say, USB cables...

Yea, even the wife heard it from the kitchen, "honey, what did you change, the system sounds so much clearer?".
ROTFLMAO

 

[amirm]

Yes, the effects are that strong that single blinded test are redundant. Blinded testing is only required if the effects are too minimal, and require being "blind" to control the conditions and bias.

This has been researched and is not true. Speakers have huge differences between them yet blind and sighted results vary. People are easily biased by price, looks, brand, marketing, preconceptions about design, etc. These can be powerful factors that override even large audible differences. See: http://seanolive.blogspot.com/2009/04/dishonesty-of-sighted-audio-product.html

 

[andreasmaaan]

Anyone who mixes music has likely spent minutes or even longer adjusting the EQ or the compression thresholds etc of an effect unit, certain that the changes they are implementing are having an obviously positive effect, only to discover later that the effect unit was disengaged the whole time.

 

[PIKATCHIA]

If it's needed, there could be a disclaimer for people who don't understand the implications behind powering speakers versus headphones. IFileZilla Malwarebytes Rufus don't think precision measurements should be given a handicap though. That would possibly produce backlash... tampering with published results and whatnot.

Company states THD+N of < 0.03% and we are essentially there so our testing is correct. The write-up brags about response up to 1 Mhz and such. I suspect instead of using fair amount of feedback to bring the distortion down, they have traded for wider bandwidth.

 

[1mobeau]

This is a review and detailed measurements of Optoma/NuForce STA-200 Power Amplifier. It is on kind loan from a member. I see it listed for USD $499 including Prime shipping. Looking elsewhere, it appears to have a list price of $1299.

This is one attractive enclosure that does not usually come in a $500 package:

View attachment 17048​

The finish is slightly textured and looks pretty nice.

Feature wise, there is nothing there but a set of RCA inputs and speakers. The RCA inputs are paired with speaker terminals on each end of the unit so you better have RCA cables that separate that much.

Somewhat out of character is a traditional extruded aluminum heatsink poking out the back. I guess this avoids having to put the heatsink inside and having to vent the enclosure. The heatsink is pretty small though and it was cooking even when testing the unit at just 5 watts/channel. I worry about its ability to run OK at full power for any extended amount of time.

Rated power is 80 watts/channel with 8 ohm load. My testing was at 4 ohm however.

Let's get into measurements and see how she does.

Measurements
As with my previous amplifier tests, let's start with a dashboard view of the unit while it was outputting 5 watts:

View attachment 17049

Boy, this is disappointing. We have tons of mains and power supply components (which I reduced somewhat by grounding one leg of the speaker terminals to my AP analyzer). The dominant distortion components are the cause of poor SINAD though with the second harmonic peaking up to nearly -70 dB. So even if the rest were not there, the SINAD would remain the same.

Company states THD+N of < 0.03% and we are essentially there so our testing is correct. The write-up brags about response up to 1 Mhz and such. I suspect instead of using fair amount of feedback to bring the distortion down, they have traded for wider bandwidth.

Looking at the power rating versus distortion, the STA-200 doesn't bring much to the party over the much cheaper Topping TP60 ($199):

View attachment 17050

Yes, there is less noise at lower power levels but by the time we get to 1 watt, they equalize in performance and at limit, the Topping TP60 (red) actually has less distortion.

The spec says the signal to noise ratio is 100 dB. My measurements fall somewhat short of that:
View attachment 17051

Likely the mains intrusion is the cause (which would vary from installation to installation).

Sweeping input level and measuring IMD we get:
View attachment 17052

As with THD, the STA200 has good bit less noise than Topping TP-60 but then suddenly clips and clips badly. Looking at the gain we see why:
View attachment 17053

This is a lot of gain for a low power amplifier. No wonder sensitivity is spec'ed at just 0.45 volt (versus nominal 2 volts). This means if you may have to significantly turn down the volume in your pre-amp/dac+pre. This would make for an amp that plays loud due to its high gain and perhaps that is a conscious choice.

Frequency response is reasonable to 40 kHz (0.3 dB down):
View attachment 17054

Anyway, I think we have enough here to know the merits of this amplifier.

Conclusions
I was pretty depressed when I reviewed the Topping TP60 and FX Audio FX502SPro and had high hopes that the NuForce STA200 would easily outperform them. Such was not the case. The Topping TP60 at less than half the price essentially matches its performance. It also runs substantially cooler than this unit. It doesn't look quite as nice though although it has a more manageable desktop form factor if that is how you use it.

The NuForce ST-200 seems to cater the audiophile myth of "fast" and high-bandwidth amplifiers, sacrificing fidelity to get there. This is a poor trade off in my book when just about all the content we play is quite band limited.

Why is this review/test accepted as a valid evaluation, since according to the reviewer/tester, the amplifier was tested using a 4 ohm load. This is not a recommended load to be used with this amplifier according to the manufacturer.

 

[amirm]

Why is this review/test accepted as a valid evaluation, since according to the reviewer/tester, the amplifier was tested using a 4 ohm load. This is not a recommended load to be used with this amplifier according to the manufacturer.

Where do you see such an admonition? I just looked up the spec and manual and neither says anything about not using 4 Ohm. The question was asked on Amazon and three people said they are using it with 4 ohm. Not a word from the manufacturer or seller saying otherwise there.

 

[OShag]

Greetings. I took up the offer notice on this website to join and just registered.

With respect to this topic - the NuForce ST200 - interesting analysis, but I am experiencing a very different sound than these measurements you present would indicate. I am not in a position to challenge your measurements, as I have not measured the amp myself.

You may know that this amp is designed by Goldmund (they partnered with NuForce on this). It is virtually identical to the Job 225. The Job 225 and this ST220 are essentially the same amp albeit the ST220 has been slightly detuned (for marketing /brand purposes I’m sure Goldmund didn’t want the ST200 to appear to be as good as the in-house Goldmund version). The power ratings of this amp are 80watts per channel whereas the Job is 120watts.

I can give you some insight into the sound of the ST200 as I own one. I am somewhat familiar with the sound of some very high end amps eg Soulution, Constellation, Audio Research, Mark Levinson and more. Additionally I’ve heard and in the past owned a number of excellent mid-fi ht processor/amp separates and Receivers.

i bought this little amp because of its Goldmund design, and the fact that it has some NuForce heritage too and because it is an absurdly good bargain. I highly doubt you will find an amp of such capability and sound performance at anywhere close to this price. The ST200 was originally intended to sell for 1,499.00 I believe. At $499? Well, I think they are just ‘giving it away’ to finish the final stock. My advice is to not hesitate and buy it. They will not last long I think.

So getting the negative out of the way, the gain is really high. This poses a problem for the preamp as it will get a bit loud for easy low-level listening with only two or three clicks on the gain knob. Therefore it is best to have a DAC that has variable level so the signal volume can be reduced. Not to say the results won’t be just right in fixed level mode, but that the volume may be too loud for later night hifi easy listening. That is the only negative as far as I can find.

Power output is more than acceptable. My speakers are rated at 88db (actually they are 87.6db). While rated at 4ohms, because of the sealed cabinet design, these speakers provide a challenging load at certain frequencies, going down as low as 1.6ohms. What I can tell you is there is more than enough juice to get my speakers to throw a massive sound that is very loud and without any audible distortion.

What is important is the sound. This little amp is a lovely sounding amp. It gets so much right. Its a Class AB amp that has the virtues of Class D but with more bloom and ‘warmth’. By Class D virtues I mean that it is super transparent, clear as a bell, and very resolving. The transient performance is terrific with lots of PRaT (although I have another amp that is faster and others (Class D) that are as fast.

The presentation is very engaging (unlike many other amps). The center image and main sound focus is not set too far back. The sound is not too forward either, but just right. Sound is very balanced with excellent clean highs, deep powerful bass, and a lovely open midrange (a must for me). Superb dynamics with no smearing or fuzziness. The soundstage is big / room-filling even in this large room, with generous true to life scale and massive bass that you feel and hear. Plenty of height, width and depth. Imaging is excellent. From DAC direct the sound is very transparent and resolved. But with a good preamp, the sound becomes astonishingly good in terms of increased engagement, and lighting up all the frequencies for the full ‘live’ experience. This little amp qualifies as HiFi / Hi-end with the high price.

This is a link to a quick vid so you can hear the sound. Use headphones. Source was a video of the making of ‘Hey Now’ by London Grammar, so the voices at the end - “thats a wrap” - are from the video. You will also hear someone opening the french doors immediately behind me. They are sticking so they have to be forcefully opened : ). The voices at the end sound close to real and is a testament to how good this little amp is. Also keep in mind that this was video’d on an iPhone and as good as the iPhone is, it cannot record full range stereo sound like a proper stereo mic recorder. This vid does not sound close to as good as what it actually sounds like in room. Also I have just checked. The bit rate on icloud is reduced so it will not sound as good on the iCloud link. But you should get an idea. Cheers, OShag

https://share.icloud.com/photos/0m4yOUGOqqRgEmU6SzK34KtVw#Anaheim

 

[OShag]

Just checked that icloud link. Sounds dreadful grainy unclear and small - nothing like the original recording. Apple’s compression decimated it. At least it may give an impression.

the room by the way is 19ft x 16ft with a 25ft high ceiling.

 

[maxxevv]

Greetings. I took up the offer notice on this website to join and just registered.

With respect to this topic - the NuForce ST200 - interesting analysis, but I am experiencing a very different sound than these measurements you present would indicate. I am not in a position to challenge your measurements, as I have not measured the amp myself.

You may know that this amp is designed by Goldmund (they partnered with NuForce on this). It is virtually identical to the Job 225. The Job 225 and this ST220 are essentially the same amp albeit the ST220 has been slightly detuned (for marketing /brand purposes I’m sure Goldmund didn’t want the ST200 to appear to be as good as the in-house Goldmund version). The power ratings of this amp are 80watts per channel whereas the Job is 120watts.

I can give you some insight into the sound of the ST200 as I own one. I am somewhat familiar with the sound of some very high end amps eg Soulution, Constellation, Audio Research, Mark Levinson and more. Additionally I’ve heard and in the past owned a number of excellent mid-fi ht processor/amp separates and Receivers.

i bought this little amp because of its Goldmund design, and the fact that it has some NuForce heritage too and because it is an absurdly good bargain. I highly doubt you will find an amp of such capability and sound performance at anywhere close to this price. The ST200 was originally intended to sell for 1,499.00 I believe. At $499? Well, I think they are just ‘giving it away’ to finish the final stock. My advice is to not hesitate and buy it. They will not last long I think.

So getting the negative out of the way, the gain is really high. This poses a problem for the preamp as it will get a bit loud for easy low-level listening with only two or three clicks on the gain knob. Therefore it is best to have a DAC that has variable level so the signal volume can be reduced. Not to say the results won’t be just right in fixed level mode, but that the volume may be too loud for later night hifi easy listening. That is the only negative as far as I can find.

Power output is more than acceptable. My speakers are rated at 88db (actually they are 87.6db). While rated at 4ohms, because of the sealed cabinet design, these speakers provide a challenging load at certain frequencies, going down as low as 1.6ohms. What I can tell you is there is more than enough juice to get my speakers to throw a massive sound that is very loud and without any audible distortion.

What is important is the sound. This little amp is a lovely sounding amp. It gets so much right. Its a Class AB amp that has the virtues of Class D but with more bloom and ‘warmth’. By Class D virtues I mean that it is super transparent, clear as a bell, and very resolving. The transient performance is terrific with lots of PRaT (although I have another amp that is faster and others (Class D) that are as fast.

The presentation is very engaging (unlike many other amps). The center image and main sound focus is not set too far back. The sound is not too forward either, but just right. Sound is very balanced with excellent clean highs, deep powerful bass, and a lovely open midrange (a must for me). Superb dynamics with no smearing or fuzziness. The soundstage is big / room-filling even in this large room, with generous true to life scale and massive bass that you feel and hear. Plenty of height, width and depth. Imaging is excellent. From DAC direct the sound is very transparent and resolved. But with a good preamp, the sound becomes astonishingly good in terms of increased engagement, and lighting up all the frequencies for the full ‘live’ experience. This little amp qualifies as HiFi / Hi-end with the high price.

This is a link to a quick vid so you can hear the sound. Use headphones. Source was a video of the making of ‘Hey Now’ by London Grammar, so the voices at the end - “thats a wrap” - are from the video. You will also hear someone opening the french doors immediately behind me. They are sticking so they have to be forcefully opened : ). The voices at the end sound close to real and is a testament to how good this little amp is. Also keep in mind that this was video’d on an iPhone and as good as the iPhone is, it cannot record full range stereo sound like a proper stereo mic recorder. This vid does not sound close to as good as what it actually sounds like in room. Also I have just checked. The bit rate on icloud is reduced so it will not sound as good on the iCloud link. But you should get an idea. Cheers, OShag

https://share.icloud.com/photos/0m4yOUGOqqRgEmU6SzK34KtVw#Anaheim

.
You obviously don't know what you're doing despite the effusively nice prose and praise for the amp.

....

 

[OShag]

I’m sorry, can you explain? How do you mean I don’t know what I am doing? Are you insulted by my effusive praise? If so I apologize. Please explain so I can more fully understand your point of view. I just meant to say that this amp sounds really good to my ears compared to other far more expensive amps I’ve heard.

 

[audimus]

Given that NuForce is virtually defunct, units are not being manufactured any more in case you need a replacement and these units are getting cleared out by a retailer who only gives lifetime technical assistance rather than a warranty, products from this company has had some very mixed results when measured, why would anybody consider these regardless of how they sound or not sound?

You don’t work for HiFiHeaven do you?

 

[OShag]

No I don’t work for HiFi Heaven. Actually as of two weeks ago I became unemployed (not for long hopefully). But I do see your point and it is valid. It is terrible to get stuck with electronics that fail in a short time without recourse for repair or return/refund. However should I say the same about my Oppo UDP-203 and UDP-205? At the end of the day, the amp sounds...sorry to be effusive..awesome.

 

[digicidal]

 

[OShag]

By the way, Audimus, is HiFiHeaven a bad company?

 

[digicidal]

I’m sorry, can you explain? How do you mean I don’t know what I am doing? Are you insulted by my effusive praise? If so I apologize. Please explain so I can more fully understand your point of view. I just meant to say that this amp sounds really good to my ears compared to other far more expensive amps I’ve heard.

I understand the principle behind what you're saying and it could very well be true - it might (subjectively) sound better to you than other far more expensive amps. However, not only is that useless for anyone else - it's not even provably true for yourself (stay with me on this - it's not an attack).

If you didn't compare those other amps directly (preferrably blind, but at least level-matched with fast switching) then all you could compare were memories. Memories, especially short-term and auditory ones, are subject to levels of noise and distortion the likes of which make this amp seem flawless in every regard. What you're most likely expressing is this:
"I've heard expensive amps which sounded good to me. I own this amp and it sounds good to me. I would qualify the sound of this amp as being as good or better than the others - and it's cheaper - so what's not to love?"

None of that statement is "wrong" - it can't be, it's your opinion. However, it also does not in any way determine the actual performance of the amp in question. The reality is that, like good digital sources, the amp shouldn't sound like anything at all (just providing gain) - this one actually can (and that's what's not good about it, ironically). If you take a look through the reviews, there seems to be a trend in high-end audio... in general it doesn't necessarily perform well at all - especially in comparison to more "pedestrian" alternatives.

So while I find it entirely possible that this amp sounds different to other amps (it should if compared to a transparent one) and I also find it possible that other high-end amps you've heard also sounded distinctly different. The greater likelihood is that they were even less transparent than this one, or that you simply like a high level of noise/distortion products in your signal chain. Nothing wrong with that preference IMO - but it's not hifi - key being FIDELITY. It's just textured sound which is pleasing to you but doesn't accurately reproduce the input signal perfectly.