Part II: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [Power, Distortion, and Subjective Impressions.] And on rejoicing over "Solved Problems" in audio.

Gotta love those Nordost-like flat speaker cables from AliExpress. The 90° locking banana connectors are a bit on the large side however. 😉

As we saw last week in Part I, I started reviewing the Fosi Audio V3 Mono amplifier, early August 2024 retail release, in the form of the stereo with 48V/10A power supply kit. We've already had an extensive look externally and inside the device, seen the benefit of PFFB for load invariance as well as discussed a couple of the issues I ran into (inverted polarity and the ground noise with 2 amps connected to one battery).

This time in Part II, let's proceed deeper into the measurements to explore the amount of power this little amplifier can provide, some details on distortion characteristics, and as usual, ending off with subjective impressions and summary of the product.

Part I: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [With initial measurements.]

Over the last few months, I've been hearing a lot about this Fosi Audio Mono V3 (~US$140) amplifier which is typically sold as an individual unit with 48V/5A power supply, or as dual amps with 48V/10A supply, DC filter, and splitter cable (currently ~US$280).

I have already seen a number of reviews and YouTube videos typically with the pre-release product supplied by the company; honestly guys, many of the reviews seem superficial with essentially "Trust me, bro!" opinions rather than presentation of facts. For this review, let me grab the 2 amps + single 48V/10A kit from the Amazon retail pipeline to have a look at the final product. This review is not sponsored by Fosi Audio. With measurements, I believe this would be as bias-free as a review can be.

As you might already be aware, this inexpensive amplifier represents an evolution of their TI TPA3255 Class D "chip amp" product line. The company incorporated community feedback and developed this as a monoblock design (through Kickstarter funding, as usual due diligence needed when participating in crowd-funding) with no volume control so as to optimize resolution, accepts true balanced (XLR/TRS) input, and also incorporates Post-Filter Feedback (PFFB) to lower output impedance (increase damping factor) for load independence.

The company publishes a power rating of 240W into 4Ω, 1% THD; 120W into 8Ω. That should be more than enough for most reasonably efficient speakers of normal load, in normal smallish listening rooms.

Let's take a good look...