The Fosi Audio P3 combines the distinctive character of tube amplification with a compact and versatile design. The preamplifier circuit raises the operating voltage of the tubes to 54 volts, allowing them to function as full amplification components during signal processing.

The tube preamplification is designed to reproduce clear treble, a full-bodied midrange, and deep, rhythmic bass with a natural presentation. The P3 can be used with both analogue and wireless sources while serving as either a preamplifier or a headphone amplifier within an audio system.

The P3 preamplifier circuit provides a 54-volt operating voltage for the vacuum tubes. This allows the tubes to actively participate in amplifying the audio signal and produce the warm, rich sound character associated with tube technology.

The 20 Hz to 20 kHz frequency response with a ±1 dB deviation covers the audible range. A 103 dB signal-to-noise ratio, 104 dB dynamic range, and total harmonic distortion of no more than 0.02% support clean and detailed signal transmission.

The built-in Qualcomm QCC3031 chip provides Bluetooth 5.1 connectivity for compatible smartphones, tablets, and other wireless audio sources. Support for SBC, AAC, aptX, aptX HD, and aptX LL codecs makes the P3 preamplifier suitable for use with a wide range of playback devices.

aptX HD supports higher-resolution wireless audio transmission, while aptX LL supports low-latency connectivity. The Bluetooth range is 10 metres, and the device uses a flashing blue indicator during pairing and a steady blue light once the connection has been established.

The internal design of the P3 uses high-quality Japanese ELNA capacitors and an A-taper potentiometer. These audiophile-grade components support stable operation and clean signal transmission throughout the preamplifier’s signal path.

The front-panel bass and treble controls allow the sound character to be adjusted to suit the system, listening room, and individual preferences. Both controls feature a centre detent, allowing a setting without additional tone emphasis to be selected in the centre position.

The 3.5 mm headphone output supports wired headphones with impedances ranging from 16 to 300 ohms. Output power depends on the impedance of the connected headphones, so different power levels are available for lower- and higher-impedance models.

The manufacturer-specified RMS output is 250 mW into 16 ohms, 150 mW into 32 ohms, 32 mW into 250 ohms, and 20 mW into 300 ohms. The P3 can therefore be used for personal listening without a separate headphone amplifier.

The Fosi Audio P3 provides Bluetooth and RCA inputs together with RCA, AUX, and 3.5 mm headphone outputs. Its wired and wireless inputs make it suitable for use with conventional analogue sources and compatible Bluetooth devices.

The RCA and AUX outputs allow the P3 to be connected to active speakers, an amplifier, or an active subwoofer. A 2.1-channel audio system can also be created by simultaneously connecting an amplifier or active speakers and a subwoofer.

The P3 accepts seven-pin vacuum tubes, and the factory-supplied tubes can be replaced with compatible alternatives. Supported models include the 6K4, 6J1, 6J4, GE5654, and 6AK5.

Replacement allows the tube system to be customised and different compatible tubes to be tried. Before installation, each pin must be carefully aligned with its corresponding socket opening, and the procedure must only be performed when the device is switched off, disconnected from power, and cool.

The P3 enclosure is manufactured using integrated CNC machining. The precision production process is complemented by fine sandblasting and meticulous detailing, giving the preamplifier a compact and cohesive appearance.

The design combines modern electronic solutions with the natural visual character of vacuum tubes. Its compact size makes the device easy to place in a desktop headphone system, alongside active speakers, or as a preamplifier for a separate power amplifier.

The Fosi Audio P3 can be used with a 12 V DC power supply capable of delivering 1.5–3 A. The device is supplied with a 12 V / 1.5 A power adapter, which provides the power required for the factory configuration.

The available power supply headroom depends on the current-delivery capability of the selected power supply.