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Optoma NuForce STA200 Power Amplifier

A good power amplifier design is a good power amplifier design whether it was created in 1950, 1960, 1970, or anytime thereafter. Given how long audio has been around, you can expect any list of all-time great amplifiers to have 100 entries and there would be still some worthy examples that would not make the roster. Depending on whom you ask, and who answers, the Goldmund job 225 power amplifier ($1499) could very well be one of the amps that would make it onto that list. Recently Optoma NuForce (along with Goldmund’s knowledge), introduced a new amplifier that is based on the Goldmund job 225 amplifier, called the STA200 ($1299).

How did collaboration between Goldmund and Optoma NuForce come about? According to Optoma NuForce, years ago Goldmund used to offer its customers Optoma projectors. When merger discussions between Optoma and NuForce began, the leaders of the emerging company-to-be considered how to move forward and how to expand or refresh the NuForce portfolio. At the same time Goldmund was curious to see whether younger audiophiles and audio enthusiasts would be interested in affordable high-performance equipment, and whether its own brand awareness could be expanded through NuForce. For Optoma NuForce, introducing a Class AB amplifier was a way to test the market and see whether this was a direction the company should pursue. So the STA200 power amplifier is an experiment for both firms.

Technical Tour
While the STA200 has many similarities to the Goldmund job 225 power amplifier, it is not identical. The primary difference is the power output specification. The job 225 puts out 125 watts into 8 ohms while the STA200 has only 80 watts of output into 8 ohms. This difference in power output was instituted so that the STA200 would not be a direct competitor for the job 225 (it could even be argued that for the $200 difference the job 225’s additional power offers a better value). Another difference between the job 225 and the STA200 is the latter has a slightly lower gain (34.4dB) that’s closer to a more standard figure, as opposed to the job’s 36dB gain.

According to a review by Brent Butterworth of the job 225, that amp’s Class AB design “was taken from an amplification circuit originally used in a Tektronix oscilloscope in the late 1960s.” Michel Reverchon, Goldmund’s CEO, said that the circuit has since been refined by nine generations of Goldmund engineers, and variations on the circuit were used on all of that company’s amplifiers.

The STA200 has the same wide bandwidth as the job 225, spanning the range from 10Hz to 100kHz. The STA200 also extends its high-frequency response up to 900kHz (at 3dB down). The reasoning behind such a wide bandwidth design is to eliminate phase shifts caused by the high-frequency roll-off effects.

Setup
The STA200 has all the controls you normally find on a basic power amplifier, which are not many. The only input option is a pair of single-ended RCA connections. For output the STA200 has one pair of five-way binding posts. The only other features on the back panel are the IEC AC line connection, a heatsink that takes up three-quarters of the back panel, a 115/230V AC switch, and a power output connector that can deliver power to the Optoma NuForce WDC200 streamer. The STA200’s front panel is an unadorned expanse populated by a single power on/off button located on the right side next to a small red power indicator LED.

Dimensionally the STA200 ranks as a ¾-sized cabinet. It’s 14 inches wide, only 8 inches deep, and 3¼ inches high. Even when it’s left on 24/7 the chassis only gets warm to the touch—the heatsink on the back does a good job handling all the serious heat dissipation duties.

I used the STA200 extensively during a two-month period while I was listening to and reviewing the Mytek Brooklyn DAC/preamp. The STA200 was installed in both my nearfield desktop monitoring system where it was connected to the Audience 1+1, Dali Opticon 1, ATC SCM7 II, Role Audio Sampan FTL, and Role Kayak; and in my room-based system where it drove the Spatial M3 Turbo SE loudspeakers. I did not connect the STA200 to any especially difficult-to-drive loudspeakers since I do not currently have anything with a sensitivity of less than 87dB on hand. I did find with the high-sensitivity Spatial M3 loudspeakers that the STA200 did not generate any more hiss from the tweeters than the more standard 27dB gain specification of the Bel Canto REF M600 power amplifier.

Given STA200’s extremely wide bandwidth specification I was curious if there would be any noise issues. As mentioned, during the review    period I had the amplifier in two systems, and neither displayed any noise issues that could be attributed to amplifier instability or to RFI/EMI issues affecting the amp’s performance.

Another potential sonic issue was the STA200’s higher than usual gain specification. With some preamplifiers, the STA200’s higher gain could mean that the preamplifier could be operating in a less than optimal gain range. With the Brooklyn DAC/pre I rarely got above -45 on the Brooklyn volume scale of -100 to -0). The last potential downside of an amplifier with higher gain is it can amplify the basic noise levels in an audio signal chain from inaudibility to unfortunate audibility. When the sound was muted, I had no issues with added noise from my loudspeakers in either of the systems where I used the STA200.

 

Sound
For the last couple of years I’ve been listening primarily to systems using switching (Class D) power amplifiers, so it was illuminating to go back to a linear solid-state design. I hesitate to make any gross generalizations, but listening through the STA200 provided a more organic and less coolly objective view of the music than most switching amplifiers I’ve used recently. Near the end of the review period, my venerable Pass Labs X150.3 power amplifier (circa 1996) was returned fully restored and updated by Pass Labs. Harmonically the STA200 had far more in common with the Pass X150.3 than any of the switching power amplifiers I use regularly. Perhaps there’s something to the idea that amplifiers that employ similar technologies share a certain intrinsic characteristic sound.

The STA200 displayed exemplary dimensionality. Lateral image placement was as precise as I’ve heard from any amplifier. Depth delineation was equal to the Pass Labs X150.3, and on some selections I felt the STA200 did a better job of defining the edges of each instrument or vocalist than the Pass could. The Bel Canto REF M600 did an even slightly better job of defining image edges and produced an even larger soundstage, but it did not better the STA200 in overall dimensionality. The REF M600 was slightly inferior in depth recreation compared to the STA200. In comparison, the REF M600’s soundstage was wider, but less deep than the STA200’s.

The STA200 had a darker than absolutely neutral harmonic balance that is quite similar to the Pass X150.3. Depending on the other components in your system you might find, as I did, that I preferred this less spotlighted upper midrange on modern pop, but on some classical and vintage jazz I preferred the Bel Canto REF M600’s slightly brighter harmonic rendering. I must stress this wasn’t a radical difference, but it was enough be readily identifiable.

One particular performance area where the STA200’s sonics were closer to those of the Bel Canto REF M600 than the Pass X150.3’s was dynamic speed and agility. Here the Pass seemed a bit less fleet. It lacked some precision in its transient attack and decay that both the REF M600 and the STA200 had little trouble traversing. Perhaps this sonic difference could be attributed to the REF M600’s and STA200’s S/N figures, which both bettered those of the Pass.

In bass control and definition the STA200 displayed a nimbleness that matched the best amplifiers I’ve heard. The bass rendition was definitely tighter and better defined in the STA200 than in the Pass X150.3, where the lower octaves were fluffier and slower by comparison. Once more I found the STA200’s basic low-frequency personality closer to that of the Bel Canto REF M600.

Currently I have the Spatial M3 Turbo SE loudspeakers set up so they receive a full-range signal with no crossover-set bass roll-off. This system also has a pair of JL Audio Fathom f112 subwoofers configured for a 45Hz, 24dB-per-octave crossover slope. Both the STA200 and the Bel Canto REF M600 generated fast, tight bass that melded well with the Fathom f112.

On my own recordings played back through my nearfield system I found the STA200 was among the more truthful amplifiers I’ve used. I did some A/B testing where I compared it with the NuForce ST-10 amplifier. I found the NuForce produced a bit larger soundstage, but it was a dead heat between the two amps in image specificity, low-level detail, dynamic contrast, and bass extension.

Conclusion
Basic solid-state power amplifiers are not, due to their essential nature as boxes with parts inside, sexy objects that inspire a lot of audiophile lust. Perhaps that is why so many manufacturers feel the need to tart up their basic power amplifiers with thick front panels, cool meters, or artistically sculpted, rad-colored enclosures. The STA200 will never be accused of looking sexy or especially stylish—unless you are into stark minimalism. But if sound quality and solid-state reliability are your primary purchasing criteria, the STA200 should be on your radar. You may not be blown away by the STA200’s looks, but its sound turns it into one sexy beast.

Specs & Pricing

Type: Solid-state, Class AB
Output power: 80Wpc into 8 ohms
Input: RCA analog (single-ended)
Input impedance: 51k ohms
Output impedance: 30m ohm
Dimensions: 14″ x 3.4″ x 8.8″
Weight: 13 lbs
Price: $1299

OPTOMA USA
3178 Laurelview Ct.
Fremont, CA 94538
(510) 897-8600
optomausa.com/soundproducts

Associated Equipment
Source devices: A 2013 MacPro Desktop with a 3.7GHz Quad-Core Intel Xeon E5 processor with 16GB of memory and OS 10.11.5, running iTunes 12.4 and Amarra Symphony 3.3, Pure Music 3.0.1, Audirvana+ 2.5, Roon 1.2, and Tidal 1.3.
Analog sources: VPI TNT III w/Graham 1.1 tonearm and ClearAudio Victory II cart; VPI HW-19 with Souther SLA-3 tonearm and Denon 103/van den Hul cartridge
Phono preamps: Vendetta Research SCP-2B and Vinnie Rossi LIO
DACs: Mytek Brooklyn, PS Audio DirectStream Jr. DAC, Cary Audio DMC-600SE Music Hub, Grace m9xx
Amplifiers: Bel Canto REF M600, April Music S-1 monoblocks, NuPrime ST-10, Pass Labs X150.3
Speakers: Spatial M-3 Turbo SE with two JL Audio Fathom f112 subwoofers; Audience 1+1, Role Audio Sampan FTL, Dali Opticon 1, ATC SCM7 II, with one Velodyne DD 10+ subwoofer
Cables and accessories: WireWorld Silver Starlight USB cable, WireWorld Eclipse 7 balanced interconnect, AudioQuest Carbon USB cable; AudioQuest Colorado single-ended RCA interconnect, Kimber KCAG single-ended and balanced interconnect, Audience Speaker Au24e speaker cables, PS Audio Quintet, Dectet, Octet, and Premier power conditioners

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