Class A+D Stereo Amp bridgeable into a 290W mono amp
The NuPrime STA-9, a 2 X 120W Class A+D stereo amp, bridgeable into a 290W mono amp, is designed with enhanced even-order harmonic circuitry that mimics the most attractive features of tubed-amp sound without incurring tubes’ drawbacks and limitations. The STA-9's spacious, transparent, dynamic and luxuriously textured soundstage has to be heard to believed.
The STA-9 amplifier is derived from the ULCAM (Ultra Linear Class A Module)+Class D design first introduced in the IDA-8. By joining a powerful high impedance singled ended amplifier circuit in the preamp stage with a well integrated Class-D power stage, the STA-9 delivers a rich tube-like sound with the remarkable speed and clarity of NuPrime Class-D design. Audio enthusiasts are bound to be impressed.
The NuPrime amp circuit improves on traditional Class-D design by using a self-oscillating circuit to generate pulse-width modulation. The amplifier switches at a frequency of 550kHz, well beyond the compact disc’s 44.1kHz sampling rate. Most class-D amps switch at 300kHz or lower. Completing the ensemble is NuPrime's new linear power supply with its high-efficiency toroidal transformer for reduced high-frequency noise and strengthened low-frequency performance. The damping effect of the NuPrime isolation feet (patent pending) absorbs and cancels vibrations that degrade audio performance. The overall result is unprecedented transient speed and an almost shocking level of dynamic impact.
The STA-9's frequency response to 50 kHz elevates vocals into emotional experiences; similarly, instrumental upper registers mimic a live performance’s shimmering heights.
- Single End Class A + D amplifier design
- Bridgeable allowing switch between stereo or mono mode.
- Enhanced even-order harmonic (H2) circuitry resembling the most attractive features of tubed-amp sound without its drawbacks and limitations.
- Highly reliable under no-load condition and enhanced short circuit protection.
- High output current drive capability for low impedance speakers.
- 550 KHz switching frequency for accurate reproduction of musical signal.
- New linear power supply with a high-efficiency toroidal transformer. Reduced high-frequency noise and strengthened low-frequency performance.
- Signal path avoids cross-linking capacitors, thus achieving a frequency response at DC level for pure musical enjoyment.
How did STA-9 achieve tubed-amp sound?
The front-end circuit of the STA-9 employs the same structure as that of the HPA-9: a single-end JFET structure that mainly simulates the sound characteristics of a triode by the addition of 2nd harmonics. The 2nd harmonic of a vacuum tube and STA-9 are high, resulting in an SNR measured value > 90DB. This does not mean that the STA-9 produces audible noise; rather, it is the effect of 2nd harmonic’s appealing coloration. The bandwidth of the front-end circuits of the STA-9 and HPA-9 are up to 300KHZ, which produce a more natural sound. With very low negative feedback, the sound is smooth and relaxed rather than harsh.
How did STA-9 mono achieve better sonic characteristic, in addition to more power than STA-9 stereo ?
The standard method for bridging a stereo amp into mono employs a series of op amps (OPA) in order to invert the input signals to one of the stereo amp, thereby creating an opposite phase, which can then be combined to increase power. Conversely, the STA-9’s innovative bridging circuit utilises a design we call Single-Ended Direct-Inject Bridge Technology, in which the mono mode, in addition to acquiring more than double the power, sounds livelier and more dynamic.
The NuPrime Sound
- Vast soundstage
- Wide, lightning-fast dynamics
- Ultra-low distortion and noise
- Music emerges from a pristine background, with delicate details and nuances intact
In summary, NuPrime’s sonic character stands well apart from – and indeed above – the soft, cushy sound we often associate with most tubed amplification or the dry, clinically edgy sound we often associate with solid-state and switching technology. Rarely does an amp achieve an ideal balance of richly textured timbres and harmonics, bottom-end authority, startling dynamics, exquisite low-level detail, and a fully revealed, fully dimensional soundstage against a backdrop of mile-deep silence.
- RCA: Un-Balanced input x 1
- XLR: Balanced input x 1
- Stereo Speaker Out x 1 or
- Mono Speaker Out x 1
- Power: 2 X 120W / 1 X 290W @ 8 & 4 Ohms
- Peak Output Power: 2 X 280W / 1 X 320W @ 8 & 4 Ohms
- Input Impedance: 47k Ohms
- Input sensitivity: 232.8mV, 1W @ 8 Ohms; 1.4V to rated power
- Gain: x 22
- Signal to Noise Ratio: < -95dB at 1W, 10W, 100W
- THD+N: 0.02% (Stereo) / 0.01% (Mono)
- Frequency Response: 10Hz to 50kHz
- Worldwide AC voltage: (115 VAC / 230 VAC) with Voltage Select Switch
- AC Fuse: Slow-blow, 3A, 250VAC
- Dimension: 235 mm W x 281 mm D x 55 mm H (including feet)
- Weight: 4.75 kg
- Color: Black or Silver
- In a 110V outlet, the idle-power consumption is below 14W. In a 230V outlet, the idle-power consumption is below 16W.
First off, Aamir has the DNA of an Audio boutique Store out of the late 70s. I will always remember as a kid being treated with respect as I plunked down my hard-earned cash from delivering papers. Aamir treats you with that same respect. He is knowledgeable, and he actually cares about his customers. He could have tried to sell me something else. However, we decided on this amp primarily because I could purchase a second when I had the money and more than double my power. I was so worried about it being a class D though. My experience with class D like a lot of people was not great. However, he was so confident that I try this amplifier I decided to purchase it. I got it delivered, opened the box, set it up and left it running for about four hours. I sat down and listened to my favourite selection of high def music. I was floored. Simply floored. This does not sound like a class D amplifier. This bloody thing sounds like a class A amplifier. Smooth, but does not lack in clarity. I should mention I am familiar with class A amps as I had them before they were stolen.
This is truly an amazing amplifier that punches WAY above its price point. The design of the amplifier is well, elegant. And I believe that's the best word to describe the sound. One thing I noticed right off the bat, the amplifier weighs way more than any class D I have encountered. Then I saw a review where they had opened the amplifier up. Holy crap! The Toroidal power supply on this amp is HUGE. I have yet to see a Class D with such a large power supply. Is that part of the "special sauce" that makes this amplifier so good. Who knows? I know that I will be calling Aamir and plunk down my hard-earned cash once again as soon as I have enough to purchase a second amp. And there is no Company that comes close to Summit Audio's service! Thanks again Aamir.
Love the unit, tons of power in stereo and I like the fact that I can and another and use them as monoblocks, very versatile. Solidly built too!
Sounds is very clean on the warm side. Tight bass. I’m using it with a DAC-9H preamp/dac as well as monitor audio bronze 2 and a svs sb1000 sub in my office. Sonic bliss.
Will get relatively hot but thats normal. Awesome service and feedback from summit hifi staff. Buy with confidence.
Love this power amp . Small footprint but big sound.
I bought this for a desktop setup but I am using it in my main system. I must say as well , summit Hifi were awesome all the way.
NuPrime STA-9 Power Amplifier - 120W x 2 (8 Ohms) & 290W Mono ( Oh My! )
Having never really heard of NuPrime previously and never having considered Class D amps I was pleasantly surprised by this relatively small amp.
It sure packs a punch though, at 120wpc, it pairs perfectly with my KEF Q350 speakers. It gets plenty loud, there's no hiss or hum, bass is tight, midrange is great and the soundstage is big. It sounds a little warm but if you aren't into that a bit of EQ would easily fix it.
The only complaint I have is that it was shipped with a EU power cord instead of a US one but Aamir offered to ship the correct cord without any hesitation.