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:
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:
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):
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:
Likely the mains intrusion is the cause (which would vary from installation to installation).
Sweeping input level and measuring IMD we get:
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:
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):
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.
This is one attractive enclosure that does not usually come in a $500 package:
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:
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):
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:
Likely the mains intrusion is the cause (which would vary from installation to installation).
Sweeping input level and measuring IMD we get:
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:
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):
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.
