Интегральные усилители — Fosi Audio V3

The V3 is a compact stereo Class D amplifier from Fosi Audio, the Chinese maker of small desktop amplifiers and DACs, launched around May 2023. It is sold without a power supply at USD 69.99, or bundled with a 32 V 5 A supply at USD 89.99, a 48 V 5 A supply at USD 109.99 or a 48 V 5 A GaN supply at USD 139.99. Fosi also makes the V3 Mono monoblock and the ZA3 balanced stereo amplifier on related platforms. The V3 is essentially a power amplifier with a volume control and a single line input.

Key specs that matter

The amplifier chip is the Texas Instruments TPA3255. Fosi rates maximum output at 300 W per channel into 4 ohm, and loads from 2 to 8 ohm are supported. The only input is RCA, and the outputs are speaker terminals and a preamplifier output with volume control. Frequency response is 20 Hz to 20 kHz ±0.1 dB, SINAD is 88 dB, THD is 0.003%, signal to noise ratio is at least 110 dB and the noise floor is 140 µV. The supply input accepts 24 to 48 V DC. The case measures about 165 x 104 x 36 mm, and Fosi gives a 24-month warranty.

Engineering and use context

The TPA3255 is a Class D power stage that switches its output transistors at high frequency, which keeps losses low and allows high output from a very small case. Maximum power depends on the supply voltage, so the higher-voltage supply options allow the V3 to reach higher output. The input stage uses two swappable NE5532-type dual op-amps in 8-pin sockets, and owners can replace them with types such as the SS3602, MUSES02 or OPA2134PA. Components include Sumida inductors in the output filter, NCC filter capacitors, WIMA output capacitors and ELNA capacitors. The volume control is a logarithmic taper-A potentiometer, so level changes evenly across the rotation. The power rating is a maximum, and continuous output depends on the load and on the power supply chosen. The amplifier chip's heat sink is bonded to the case, so the whole enclosure dissipates heat, with vents on the top and bottom. The preamplifier output follows the volume control and can feed a subwoofer or a second amplifier.

Pairing

With the higher-voltage supply, the V3 drives bookshelf and floorstanding speakers on a desk or in a room of about 20 m2. Sources such as DACs, streamers and phones with adapters connect through RCA, and the preamplifier output adds a powered subwoofer.

Alternatives

The Fosi Audio V3 Mono uses the same TPA3255 platform as a monoblock with balanced XLR input.