Nuprime Evolution STA SE black

NuPrime Evolution STA-SE, 400 watts per channel in Class D

Doubling, or nearly doubling, an amplifier’s power without making its enclosure heavier: it all comes down to the power supply. The STA-SE takes the Evolution STA stereo power amplifier and swaps its linear transformer for a gallium nitride power supply. The result fits into a 9 kg chassis: 400 watts per channel, a silent noise floor, and the warm tonal character that NuPrime cultivates across its entire Evolution range.

Nearly double the power

The original Evolution STA delivered 230 watts into 8 ohms and 310 watts into 4 ohms. The STA-SE raises these figures to 400 watts per channel, nearly 75% more power. This increase does not come from a larger transformer, but from a complete change of power supply. NuPrime reserves this upgrade for its workshop: an Evolution STA already in use is transformed into an STA-SE through a factory service, not by adding a board yourself.

A GaN power supply that cancels its own noise

The power supply is what most clearly separates the STA-SE from its predecessor. Instead of the linear toroidal transformer, NuPrime installs a gallium nitride (GaN) module, a semiconductor that switches much faster than conventional silicon. Two mechanisms work together. The first continuously monitors the mains supply and generates an out-of-phase signal to eliminate noise and ripple, following the principle of active noise-cancelling headphones. The second distributes conversion across two interleaved phases, smoothing the current supplied. GaN’s switching speed provides an almost instantaneous current reserve of up to 40 amps, along with a power factor close to ideal, while remaining cool even with a low-impedance load. The benefit is also physical: this module takes up around one quarter of the volume of an equivalent transformer-based power supply and weighs five times less, while retaining 52,000 µF of filtering capacitance.

NuPrime’s proprietary distortion cancellation

The amplification section retains the in-house Class D design, called ODC (Only Distortion Cancellation). A Class D amplifier normally corrects its deviations through a global feedback loop. NuPrime instead takes its error signal directly from the output transistors and the output filter, therefore including the final stage in the loop. Two correction paths keep switching stable at 650 kHz and reduce distortion across the entire 5 Hz-50 kHz range. Total harmonic distortion plus noise drops to around 0.002%, measured at 0.0025% at 5 watts and 0.01% at 100 watts. These values rise slightly with power, as expected from a stage of this type.

Two mono blocks in one chassis

The STA-SE is a stereo amplifier with a dual-mono structure: each channel has its own power supply and amplification path, with no sharing between left and right. This reduces crosstalk and improves stereo image stability. In terms of power, the 400 watts per channel represent an RMS maximum, which explains the identical figure into both 8 and 4 ohms: the amplifier does not double its power as impedance drops, it maintains its maximum and relies on its 40-amp reserve to handle difficult loads. The stated output impedance of 4 milliohms corresponds to a damping factor of around 2,000 into 8 ohms, ensuring firm control over speaker bass. Input sensitivity is 2 Vrms for a ×21 gain, or around 26 dB, a fairly high value that may require lowering the level of the preamplifier with high-output sources.

Controlled bass, warm midrange, airy treble

The signature remains faithful to the Evolution line: warm tonal character and a silent background rather than analytical showmanship. Bass comes through with control and weight, supported by the current reserve. The midrange gets its character from the NJR MUSES8820 op-amp, used in the preamplification stage as well as in the Class D oscillator, whose dense rendering brings playback closer to a Class A tonal character. Treble is fluid and extended, without the harshness sometimes associated with high-power Class D amplifiers. The soundstage develops in width and depth, with good clarity in the most distant layers.

Furutech connectors and copper traces

Input is via Furutech FP900 RCA connectors, in unbalanced operation only: the STA-SE does not offer a balanced XLR input. Output is via high-conductivity Eichmann binding posts. Inside, the connection between the power supply and amplification circuits uses copper traces etched onto the printed circuit board rather than wires, to limit current losses. The enclosure rests on in-house anti-vibration isolation feet and is only 57 mm high, measuring 430 mm wide and 375 mm deep, at 9 kg. Two finishes are available, black or silver. A 115 / 230 V voltage selector and a pair of trigger sockets, input and output, complete the rear panel.

In hi-fi as in home theater

Without volume control or an extended source selector, the STA-SE requires a preamplifier or a converter with variable output upstream; within the range, the Evolution DAC-2 fulfils this role. In a hi-fi system, it drives a pair of demanding speakers, including low-impedance loads or electrostatic panels requiring substantial current. Connected to the preamplified outputs of a home theater processor, it handles the front channels with dedicated power, alongside the channels managed by the AV receiver. Its low heat output and reduced height make installation in a cabinet easier.

Technical Specifications

Overview

• High-end NuPrime Evolution STA-SE stereo power amplifier
• Available in black or silver

Power and Performance

• Output power: 400 W × 2 RMS into 8 Ω and 4 Ω
• Instantaneous current up to 40 A for excellent speaker control
• Total harmonic distortion + noise (THD+N): as low as 0.002% at 5 W
• Switching frequency: 650 kHz for fast, detailed reproduction

Proprietary Technologies

• ODC (Only Distortion Cancellation) technology for extremely low distortion
• Dual-Mono architecture for optimal channel separation and precise stereo imaging
• Class D preamplifier and oscillator stage equipped with an NJR MUSES8820

Power Supply

• Ultra-low-noise ANC GaN (gallium nitride) power supply
  • Active Noise Cancellation technology to reduce power supply noise and ripple
  • Optimized power factor thanks to GaN PFC technology
  • Compact format: approximately ¼ of the volume and 20% of the weight of an equivalent traditional power supply
• Filtering capacity: 52,000 µF

Connectivity and Internal Wiring

• Furutech FP900 RCA inputs
• High-conductivity Eichmann speaker terminals
• Internal connections via copper traces to optimize current transmission
• Trigger In / Out

Electrical Specifications

• Output impedance: 4 mΩ
• Input impedance: 47 kΩ
• Gain: ×21
• Sensitivity: 2 Vrms
• Frequency response: 10 Hz – 50 kHz (-3 dB)

Sound Reproduction

• Bass: fast, powerful, and perfectly controlled
• Midrange: rich, natural, and warm, with a signature close to Class A
• Treble: detailed, airy, and extended
• Dynamics: high impact capability and excellent micro-detail reproduction
• Soundstage: wide, deep, and precise
• Sound signature: a combination of warmth, transparency, precision, and power

Physical Characteristics

• NuPrime anti-vibration isolation feet
• Dimensions (H × W × D): 57 × 430 × 375 mm
• Weight: 9 kg