The NuPrime STA-9 is a stereo power amplifier with hybrid technology, combining a Class A preamplification stage with a Class D power stage. It delivers 2 x 120 watts into 4 to 8 ohms in stereo mode and can be configured in mono mode to reach 290 watts. Its even-order harmonic circuit is designed to reproduce a sound signature close to tube amplifiers while maintaining the precision and speed characteristics of digital technologies. The 550 kHz switching frequency and the linear power supply with a toroidal transformer aim to optimize audio signal reproduction in a compact format.
At the heart of the NuPrime STA-9 lies an ULCAM (Ultra Linear Class A Module) design combined with a Class D power stage. This hybrid architecture, first introduced in NuPrime’s IDA-8, pairs a powerful single-ended high-impedance amplification circuit in the preamplifier stage with a seamlessly integrated Class D power stage. The result is an amplifier capable of reproducing the harmonic richness and warmth of tube amplifiers while offering the speed, precision, and energy efficiency characteristic of digital amplifiers.
The STA-9’s front circuit uses a single-ended JFET structure that primarily simulates the sonic characteristics of a triode by adding second harmonics. This approach achieves the sought-after musical qualities of tube amplifiers without their usual drawbacks: fragility, heat generation, regular maintenance, and limited lifespan. This results in a spacious, transparent, and luxuriously textured soundstage, with particularly moving vocal reproduction.
The amplifier switches at an exceptionally high frequency of 550 kHz, far beyond the 44.1 kHz sampling rate of CDs and significantly higher than the 300 kHz typically found in conventional Class D amplifiers. This technical feature contributes to more precise musical signal reproduction and enables an extended frequency response up to 50 kHz, resulting in a more faithful rendering of upper harmonics and an enhanced sense of space.
Despite its impressive power, the NuPrime STA-9 stands out with its compact size (235 × 55 × 281 mm) and lightweight design of 4.75 kg. Its minimalist and elegant design, available in a black finish, integrates harmoniously into any environment. The clean front panel reflects NuPrime’s philosophy: focusing on essentials to deliver the best possible sound quality.
The special isolation feet developed by NuPrime (patent pending) play a crucial role in the device’s performance. They effectively absorb and cancel vibrations that could degrade audio performance. This attention to detail reflects NuPrime’s holistic approach to designing high-end amplifiers.
The STA-9’s power supply deserves special attention. NuPrime has opted for a linear power supply with a high-efficiency toroidal transformer, which helps reduce high-frequency noise and enhances low-frequency performance. This meticulous power supply design results in better dynamics and reduced distortion, especially during complex musical passages.
The rear panel of the STA-9 reveals its versatility. The amplifier features a stereo RCA input and a stereo XLR input, allowing it to connect to a wide range of preamplifiers and sources. Two small switches near the inputs make it easy to switch from stereo to mono mode, offering remarkable flexibility.
This ability to switch from stereo to mono mode opens up numerous possibilities for evolving your audio system. You can start with a single STA-9 in stereo configuration, then add a second unit for bi-amplification, with each amplifier dedicated to one channel. This approach provides better channel separation, increased dynamics, and a more precise soundstage.
Alternatively, you can use each STA-9 in mono mode to achieve higher power output (290 watts per channel), ideal for driving particularly demanding speakers or for sound systems in large rooms. This modularity makes the STA-9 a long-term investment, capable of evolving with your audio system over time.
The NuPrime STA-9 stands out for its ability to combine the sound qualities typically associated with different amplification technologies. On the one hand, it offers the warmth, harmonic richness, and sound depth typical of tube amplifiers. On the other hand, it retains the precision, speed, and speaker control characteristic of the best transistor amplifiers.
This duality results in a soundstage that is both spacious and precise, where each instrument finds its natural place. Vocals benefit from a particular presence, with texture and emotion rarely achieved in this price range. The upper registers of instruments are rendered with finesse, faithfully reproducing the shimmer of live performances.
In the low frequencies, the STA-9 demonstrates remarkable authority for an amplifier of this size. The toroidal transformer and linear power supply contribute to delivering deep, articulated, and perfectly controlled bass. The exceptional transient speed and almost striking dynamic impact allow for faithful reproduction of the most complex passages, from orchestral explosions to the subtle nuances of a jazz trio.
Compared to traditional tube amplifiers, the NuPrime STA-9 offers several significant advantages. It does not require a warm-up period, powers on instantly, and reaches optimal performance immediately. It does not generate excessive heat, which extends its lifespan and reduces the risk of failure. Finally, it does not require periodic component replacement, unlike tubes that wear out over time.
Compared to conventional Class D amplifiers, the STA-9 stands out for its musicality and harmonic richness. The higher switching frequency (550 kHz versus the usual 300 kHz) contributes to better musical signal reproduction, with fewer digital artifacts. The Class A input stage brings warmth and sonic texture generally absent in pure digital amplifiers.
Compared to traditional class AB amplifiers, the STA-9 offers the advantage of better energy efficiency, reduced heat dissipation, and a more compact design for equivalent power. Its hybrid design allows it to deliver the musicality of the best analog amplifiers while retaining the practical benefits of modern technologies.
With the STA-9, NuPrime offers an amplifier with a sleek aesthetic and excellent sound performance thanks to exclusive and high-performance electronics, earning it our Qobuzissime award.
The STA-9’s class A+D technology combines a pure class A input stage (ULCAM) with a class D power stage. The class A stage provides harmonic richness and warm sound, while the class D stage ensures energy efficiency and power. A standard class D amplifier lacks this class A input stage and tends to produce a more clinical sound, less rich in harmonics. Additionally, the STA-9 operates at an exceptionally high switching frequency (550 kHz), far above the usual 300 kHz of conventional class D amplifiers.
The bridged mode combines the two channels of the amplifier into a single, more powerful channel (290W instead of 2x120W). To activate this mode, simply use the switches located on the back of the device. This mode is particularly useful for driving speakers with high current demands or for sound reinforcement in large rooms. It is also ideal in a bi-amplification setup, where each STA-9 is dedicated to one channel (left or right).
Absolutely. The STA-9 can be used to power the main speakers (left and right) of a home theater system. For a complete setup, you can use multiple STA-9 units: one in stereo for the surround channels, one in mono for the center channel, and another in mono for the subwoofer. This configuration ensures sound consistency across all channels, with the same sound signature for all speakers.
To set up bi-amplification, you will need two STA-9 units and compatible speakers (with separate input terminals for bass and treble). Configure each STA-9 in stereo mode. Connect the first amplifier to the bass speaker terminals of your speakers (left and right), and the second to the treble speaker terminals. This setup provides better frequency separation, increased dynamics, and a more precise soundstage.
Mickael
Product conforms to the specification, sounds like tubes.
Quality product.
Comment from April 18, 2026 — Experience from February 06, 2022
Jean-marc
Nothing to report, quality product
Comment from January 02, 2026 — Experience from January 31, 2022
Laurent
1. Advantage: amplifier in a small case, which means space saving, overall very convincing sound, no harshness, maybe a slight lack of instantaneous dynamics, currently works very well hooked up to a home-cinema amp, powers the left and right speakers.
2. Advantage: can double as a space heater!! Gets very hot, let it breathe. Needs a few hours of break-in to really open up!
Comment from December 05, 2025 — Experience from November 22, 2025
