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...

SUMMER MUSINGS: What are the most important audio components? Domains / dimensions of the audiophile pursuit.

[Available as audio podcast summary.]

The other day, I came upon another common question we run into within the audiophile forum communities. The thread topic on the Steve Hoffman Forums read: "What is more important? The quality of the source devices or the quality of the amp and speakers?"

Among the pages, in response to the question, there was this one listing items as such:

1 (tie). Source material, i.e. the recording, the mix and master, etc.
1 (tie). Speakers
3. Your hearing
4. Analog source playback device
5. Your room
6. Your mood
7 (tie). Digital source playback device
7 (tie). Amplification

A good list to start with! Let's spend some time in this post thinking more about this, adding more details, and broadening it out. Clearly, this (and variants of this) topic is one of those "classic" big-picture questions that demand a more nuanced and complete take. Specifically, let's make sure to contextualize the response with what I believe are relevant dimensions or domains to include.

2.5Gbps Ethernet in the Sound Room... (D-Link DMS-106XT & GigaPlus S25-0802 2.5G Smart Switch). And a quick peek in the Headphone Bar & Red Cat Records.

On occasion, I get a kick out of reading the audiophile media's review of ethernet switches. These are perhaps some of the most hilarious pseudo-infomercials out there as companies try to justify their highly expensive network switches in the hopes of capturing the interest of the few audiophiles who still somehow do not realize that there's no benefit to these devices (even Paul McGowan agrees, imagine that!).

Feel free to check out the reviews of such things like the Silent Angel Bonn NX Pro Ethernet Switch (asking US$4000!), or filters like the Network Acoustic Muon Pro (asking £1,329.17!). There are also now Chinese companies that make these things for audiophiles - Gustard N18 (US$370 - only 2 ethernet ports + 1 gigabit SFP) and N18 Pro (US$530 - 5 ethernet + 1 gigabit SFP) for example; sure, they're cheaper but that's still quite a bit for what you get which is just a nice looking ethernet switch with integrated power supply and an essentially meaningless 10MHz clock input! (Timing is essential inside the DAC for precise conversion to analog output, not the network switch.)

A few years ago (2020), I talked about the Netgear Nighthawk S8000 as a great choice for a high quality ethernet switch which affords features including port priority. Hey, it's still a great little switch and I see that sometimes there's still stock available on Amazon.  Over the years, I've upgraded my home network beyond 1Gbps (and update here) so I figured let's find faster switches to try out for the sound/media room.

Here are two easily available and not expensive options: the D-Link DMS-106XT (US$200), with 10GbE high-speed port to connect to your main network plus 5 x 2.5GbE ports for downstream devices with user-defined port priority, and the very inexpensive GigaPlus S25-0802 2.5G Smart Switch (US$80), an 8-port 2.5GbE switch with 2 x 10Gbps SFP+ for those who want to use fiber networking, or possibly 10GbE RJ45 multigigabit transceivers (some very inexpensive like this).

Both are fanless - essential for the sound room.

AudioVero Acourate v3.1 - room correction with bass pre-filtering and Inter-Channel Phase Alignment (ICPA).

After writing the post on Audiolense recently, I thought it would be good to have another peek after a few years now at AudioVero's Acourate (€416 non-EU countries); the latest version 3.1 released in June 2024.

For years, Acourate has been the room-correction filter toolbox I've used (at least since 2016, updated 2019, plus discussion on partial correction in 2021). Now that it has been half a decade plus a pandemic (!) since the step-by-step 2019 update, let's look at the latest version which has brought with it changes in the user interface as well as the Inter-Channel Phase Alignment (ICPA) feature released in version 2 which I had not discussed previously.

Before getting started, a big thanks to Mitch Barnett of Accurate Sound for his YouTube video a couple years back using Acourate 2 showing the technique around pre-filtering and ICPA. I've taken inspiration from his video, applying it to my home set-up, and converting those steps into a written blog format for the current Acourate version. If what I'm doing here is not clear, make sure to also check out the video since Mitch might have already covered your questions/issues there.

Let's get started!