NuPrime STA-9X Power Amplifier - Black

NuPrime STA-9X Power Amplifier — Black

What It Does in Your System

130 Watts a Side, or 330 as a Monoblock

The STA-9X is a stereo power amplifier that delivers 130 watts per channel into 8 ohms. Flip a switch and it becomes a 330-watt monoblock, which means you can start with one and add a second later to run a pair of monoblocks.

That upgrade path is unusual at this size and price, and it makes the STA-9X a sensible first serious power amplifier — you are not replacing it when you want more, you are buying its twin.

Class A Front End, Class D Output

NuPrime calls this an A+D design. The input stage is a single-ended Class A circuit with no negative feedback, and it feeds a dual-feedback Class D power stage.

The reasoning is to get the tonal character people like from Class A and tubes — helped along by a circuit that shapes even-order harmonics — while keeping the efficiency, low heat, and grip of Class D. NuPrime derived this arrangement from their higher-end AMG STA amplifier.

A 750kHz Switching Frequency

Class D amplifiers work by switching very rapidly. The faster they switch, the further the switching noise sits above the audible range and the easier it is to filter out cleanly.

Most Class D designs switch at 300kHz or below. The STA-9X runs at 750kHz — faster than anything else in NuPrime's own lineup, including their Evolution models. Frequency response reaches to 50kHz, and the signal path avoids coupling capacitors entirely.

Is This Right for You?

Three things to consider:

• You need a preamplifier or a preamp output. This is a power amplifier with no volume control and no source switching. It connects to a preamp, an integrated amp's pre-out, or a processor.
• Your speakers dip low in impedance. The STA-9X has 130% more output current capability than the STA-9 it replaces, and NuPrime states the output stays stable regardless of speaker impedance. That matters with demanding loads.
• You want a small amplifier. Class D means far less heat and a far smaller box than a comparable Class A or A/B design. If you want something that will disappear onto a shelf, that is a real advantage.

Setup & Installation

Connect your preamplifier to the RCA or XLR inputs on the rear panel — both are provided. Connect your speakers to the appropriate outputs, noting that stereo and monoblock modes use different terminals. Check the voltage selector switch matches your supply before powering up.

If your other components have 12V trigger connections, wire the trigger in and out so everything powers up and down together. The main power switch is on the rear panel, and the front indicator lights when the amplifier is on. NuPrime's own isolation feet are already fitted.

Features & Specifications

Switchable Stereo or Monoblock Operation
130 watts per channel in stereo, or 330 watts as a bridged monoblock.

Class A Input Stage, Class D Output Stage
Single-ended non-negative-feedback Class A feeding a dual-feedback Class D power stage, derived from NuPrime's AMG STA.

750kHz Switching Frequency
The highest in NuPrime's range, pushing switching artifacts well clear of the audio band.

Linear Power Supply with Toroidal Transformer
A high-efficiency toroidal design intended to lower high-frequency noise and firm up the bass.

Specifications

• Output power, stereo: 2 x 130W into 8 ohms
• Output power, monoblock: 330W bridged
• Amplifier class: Class A input stage with Class D output stage
• Switching frequency: 750kHz
• Frequency response: To 50kHz
• Inputs: RCA and XLR
• Outputs: Stereo and monoblock speaker terminals
• Trigger: 12V in and out
• Power supply: Linear, high-efficiency toroidal transformer
• Protection: Enhanced short circuit protection, stable under no-load
• Feet: NuPrime isolation feet
• Finish: Black

Frequently Asked Questions

How is the STA-9X different from the STA-9?
More power — 130 watts against 120 in stereo, 330 against 290 bridged. A faster switching frequency, 750kHz against 550kHz. And 130% more output current capability, which helps with speakers that drop to low impedance.

Can I add a second one later?
Yes, and that is the intended path. Two STA-9X units in monoblock mode give each speaker its own 330-watt amplifier. Start with one in stereo and add the second when you are ready.

Does Class D sound like Class A?
They are different technologies and people hear them differently. NuPrime's approach is a Class A input stage plus even-order harmonic shaping, aiming for a warmer character than Class D is usually credited with. Whether it lands for you is worth hearing in your own system.

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