Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.
The question I use most in framing my approach to SoundStage! Access—and budget hi‑fi as a whole—is a simple one that I’ve spelled out here before: what do you actually get for spending more money? The answer to that question is rarely “better sound,” although to be fair, sometimes it is. To be frank, in many cases the answer is a little nebulous and hard to quantify.
But since its 2025 revamp, Fosi Audio has been providing pretty clear‑cut answers to that question. My first taste of it came in the form of the BT20A MAX integrated amplifier (from US$229.99, CA$359.99, €239.99). That price only gets you a 32V/5A power supply. Add US$20 for the 48V/5A power supply, or US$40 for the 48V/5A GaN power supply my review unit came equipped with.
In terms of performance, there theoretically shouldn’t be any difference between the 48V options; the GaN adapter should be more efficient and cooler-running. Either 48V option, though, should give you more output—typically, using previous Fosi efforts as a guide, upwards of twice as much—and will be required to get close to the rated output of 180Wpc RMS and 300Wpc peak into 4 ohms. We’ll have to look at Diego’s measurements to see exactly how close it gets to that ideal.
Either way, it’s a good bit more power than you get with the original BT20A (US$79.99), which I’m using in my budget outdoor audio system, and you get oodles of features not found on either the BT20A or the newer BT20A Pro (US$99.99 to $149.99, depending on the power supply you opt for).
The MAX, for example, benefits from an upgrade to the newer Qualcomm QCC3095 Bluetooth 6.0 chip, features an additional stereo line‑level in (RCA) for a total of two, boasts a legit subwoofer output along with a selectable 80Hz high‑pass filter for the speaker‑level outs, has a remote control and a motorized volume knob, and supports pretty much all of the relevant Bluetooth codecs, including SBC, AAC, aptX, aptX HD, aptX Adaptive, aptX Lossless, and LDAC. What’s more, it’s the first of its siblings to feature PFFB (post-filter feedback), which promises to lower noise and distortion, and also decrease (or eliminate) load dependency.
None of that conveys Fosi Audio’s new aesthetic, which hits the BT20A series for the first time with the arrival of the MAX. It’s a much more refined look overall, with better fit and finish, better-feeling buttons, an eye-catching mix of gloss and matte finishes, and a few touches you might not be inclined to describe as “refined,” such as the metallic-orange accents, including on the cooling vents. The exhaust vent is also stylized as the letters MAX, making it clear that you’re not the type to settle for anything less.
Setting up and dialing in the BT20A MAX
The beauty of a Bluetooth integrated amp like the BT20A MAX is that there really isn’t much to think about in terms of setup. The Bluetooth pairing worked without hiccups, in my experience, pairing with my iPhone 16 Pro Max, iPad Air, and PC quickly and easily. I also connected my reference iFi Audio Zen One Signature DAC to one of the Fosi amplifier’s analog inputs, just so I could do some sound-quality comparisons, isolate what might be related to BT compression, if anything, and also figure out if the BT20A MAX’s reconstruction filter is doing anything stupid. (It isn’t.) For a second RCA source, I connected my U‑Turn Audio Orbit Theory turntable with its own internal phono preamp engaged, although I didn’t do any critical listening to that source, since there wasn’t much to learn from doing so.
For speakers, I relied primarily on my reference Paradigm Studio 100 v.5 towers, connected via a pair of SVS SoundPath Ultra speaker cables. I also had my SVS PB‑1000 Pro subwoofer on standby as backup, and used it for testing the BT20A MAX’s bass-management capabilities, which again amount to a switch that engages or disengages an 80Hz HPF for the speaker-level outputs.
How does the BT20A MAX perform?
Before we talk about sound performance, let’s talk about Bluetooth performance, because I’ll admit I underestimated the stubby little antenna of the BT20A MAX. I maintain the Wirecutter guide to Bluetooth receivers and have tested a gazillion of them in and around my house. I keep a map showing the points where all the receivers I test start to drop signal. And of all those I’ve tested, only one—the iFi Audio Zen Blue V2—bested the range of the MAX, and it tied for second place with the newer iFi Audio Zen Air Blue 2. What this means in real terms is that I had to move to a spot 43 feet in a direct line away from the MAX to reach its limits, which put four interior walls and two brick exterior walls between me and the little antenna that could. Top marks there.
And now for the bits you really came here for.
For whatever reason, there are pieces of gear that enter my rack and almost immediately make me want to try and break them. I’m not sure if that sounds like a compliment, but it’s intended as such. The BT20A MAX is one of those products.
I could have gone either of two routes on the road to attempted destruction, but I tried the metaphorical path first. Relying on the second-most basic Bluetooth codec to which I have access, and the one I rely on the most—AAC, that is—what would I be giving up here? What would be lost? What nuances would fail to make it through?
I’m a somewhat recent Boards of Canada convert, and I’ve been exploring their back catalog lately. One great imaging test track I’ve stumbled upon is “Zoetrope” from In a Beautiful Place Out in the Country – EP (16‑bit/44.1kHz ALAC, Warp Records / Apple Music). The track might not be to everyone’s taste, consisting as it does of repeated arpeggios played on a keyboard or keyboards—it isn’t easy to tell—then run through an analog delay, then manipulated on analog tape. True to its name, there’s a hypnotic, circular thing going on here. But for our purposes, it’s simply a fascinating mix, whether you dig the tune or not. (I do, for what it’s worth.)
What makes it fascinating is that it’s never quite centered. The mix wiggles and warbles around, never quite landing at 0 degrees for more than a microsecond. What’s more, when frequencies above, oh, 5kHz or so are wiggling and warbling and wobbling left, the frequencies below, I dunno, 1kHz are wandering over to the right, and vice versa. But the little globules of delayed, decaying tinkling that really give the cut its sense of space create a spray of ephemeral points in space around the center of high-frequency mass, meaning you really want a system capable of incredible imaging specificity if you want to do this one justice.
The BT20A MAX totally did it justice, with utter precision and also really lovely tonal balance. This is a song I shy away from when listening via my Sonos system, as it can sound a little harsh and brittle. Not so through the Fosi and Paradigms. Granted, there’s practically nothing going on below 80Hz in this track, so it wasn’t really a torture test for the amp in that regard. But still. Lovely.
The real torture test, indeed the first real attempt to literally break the MAX instead of merely breaking its will, came with “Go (feat. Q-Tip)” from the Chemical Brothers’ Born in the Echoes: Deluxe Edition (16/44.1 ALAC, EMI / Apple Music). It may not have the deepest bottom end in the history of electronic dance music, but the beat in this one is as hard-hitting as it is complex, and the bass line plays around in the frequency range where my speakers start to thin out if not fed sufficient current. At anything resembling reasonable listening levels, the BT20A MAX held its composure beautifully, with chest-slamming, pants-flapping low frequencies, great vocal clarity, and all the excellent soundstaging and imaging you’d expect if you’d read the preceding three paragraphs.
Now things got a little iffy when I pushed past the point of reasonable listening levels, which I defined as 110dB peaks at my listening position roughly six feet away, because that was way past the point when I had to put in my Zounds earplugs to even tolerate being in the same room with the system. For the brief moment I could tolerate it, though, I could hear that the bass and vocals were starting to get a little warmer than I liked, and the higher-frequency percussion got a little (a lot) too sharp. Plus, I lost some bass in the areas in which my speakers are prone to such, making me question whether the MAX is as load-independent as it claims to be, at least at the extremes of its performance range. But easing the volume back to the point of hitting 108dB peaks nipped these issues in the bud. Then again, so did adding a sub.
Another great track with most of its bass energy concentrated in the frequency range where my speakers have a big impedance dip is “Blue Sky” from the Allman Brothers Band’s Eat a Peach (24/96 ALAC, Mercury Records / Apple Music). This is one of the tracks that tripped up the otherwise-excellent Vincent Audio SV‑500MK I reviewed a few months back. Whether due to a lack of current or low damping factor, but that amp thinned out a lot with this song at reasonable listening levels. And again, if I pushed the little Fosi hard—way too hard for my comfort—I could get it to thin out a little, though never to the degree I remember hearing with the Vincent.
But within any sane range of SPLs, the BT20A MAX sounded as beautifully balanced as you could hope for. Furthermore, the little tones and textures that define this recording for me—from the bronzy texture of the acoustic-guitar strings being strummed to the unique valve saturation of Dickey and Duane’s Fender ’62 Super amps—were all rendered unmistakably and gorgeously, even via lowly AAC.
I didn’t notice any meaningful difference between the sound of the DAC built into the Fosi when compared to the iFi DAC routed into one of the BT20A MAX’s analog ins. I did, on the other hand, notice that the MAX runs a little toasty, even with its cooling fan running. Not hot, mind you. But toasty. Sitting at idle for a day or so, the top of the chassis gets up to around 105°F (40.5°C). Crank it for a bit, and it only climbs to around 108.5°F (42.5°C). So your cats will love using it as a chaise longue, but nobody’s gonna burn their hand on the thing. And although the cooling fan was always running, I couldn’t hear it from more than a foot or so away, even without music playing.
What else might you consider in this price range?
As whackadoodle as its frequency response was, I really loved the Dayton Audio HTA200, so if I had about this much money to spend, I’d also be looking at its little sibling, the HTA100, which sells for closer to US$269.99. It doesn’t have nearly as much power, and its BT codecs are limited to SBC and AAC (fine by me, but you might have different priorities), but it has loads more inputs, including a phono stage.
As much as I hate to be this guy, though—the guy who says, “Oh, your budget is $X? Have you considered spending $1.5X instead?”—I think Fosi Audio has a much more interesting value proposition in its own lineup. For US$179.99, you could get yourself a Fosi Audio ZD3 Fully Balanced Desktop DAC, then add a Fosi ZA3 Balanced Stereo Amplifier for US$149.99, bringing you up to just shy of $330. Fosi often sells bundles at a significant discount, and as I was wrapping up this review, I built such a bundle and added a power supply, bringing the total up to US$306.49. Either way, what does that extra $35 to $60-ish get you? A lot in terms of connectivity, including an HDMI ARC port, a USB‑B DAC input, and a coaxial digital in. You also get a display, balanced XLR out, and both a 12V trigger input and output. What do you give up? One line-level stereo RCA input and real bass management, making it less than ideal for 2.1-channel setups, especially those relying on smaller satellite speakers.
TL;DR: Is the BT20A MAX worth the money?
In my opinion, the Fosi Audio BT20A MAX does only two things wrong: its bass-management capabilities would be more complete with a low-pass filter on the sub output accompanying the high-pass on the speaker outputs; and the amp’s output capabilities would be a hell of a lot more impressive if Fosi didn’t fudge the numbers—or, at the very least, I wish the company would give a more detailed breakdown of how much output you get for each compatible power supply, with both 4- and 8-ohm nominal loads.
If the thing cost $500 or $1000, I might be more inclined to care about these little issues. The fact of the matter is, for $270 all in, the BT20A MAX could get away with a lot more by way of imperfections before its value proposition started to look iffy. As long as you don’t expect to reach concert-level SPLs with big, inefficient speakers in a big room, this thing has plenty of usable power. It’s got a great DAC and an amazing BT receiver, its line-level inputs sound excellent, and it’s got something most gear in this price class sorely lacks: really great-feeling knobs. Like, seriously super nice feeling. And a fully featured remote.
Frankly, it’s almost insulting to ask if this thing is a good value. It’s a stupendous value.
. . . Dennis Burger
dennisb@soundstagenetwork.com
Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.
Associated Equipment
- Speakers: Paradigm Studio 100 v.5
- Subwoofer: SVS PB‑1000 Pro
- Sources: U‑Turn Audio Orbit Theory turntable; iPhone 16 Pro Max; iPad Air; custom-built PC running Pop!_OS with Cosmic Desktop 1.9.0
- Speaker cables: SVS SoundPath Ultra
- Interconnects: Monoprice subwoofer cable
- Power conditioner: SurgeX XR115
Fosi Audio BT20A MAX integrated amplifier
Price: From US$229.99, CA$359.99, €239.99 (with 32V/5A power supply); US$269.95, as tested (with 48V/5A GaN power supply)
Warranty: Two years
Fosi Audio
Aohua Building
Dalang Street
Longhua District
Shenzhen, 518116
Guangdong, China
WhatsApp: +86 17722625601
Website: www.fosiaudio.com
