I recently got to spend some time listening and using a Fosi Audio BT20A Pro Amplifier and here are my thoughts.
I guess I'll cut to the chase: The Fosi Audio BT20A Pro is a small Class D amplifier with Bluetooth that turns out to be a solid, clean-sounding amp performing well above its low price. For under $100, the BT20A Pro delivers crisp, controlled sound with plenty of power on tap. It works great as a desktop amp or backup power amp, and gets even better when paired with good upstream gear. The amp stays true to your source material without adding its own flavor - it stays honest and reliable.
I wanted to test the Fosi BT20A Pro as if I was building a new system, piece by piece, improving and changing and seeing how it fit into different scenarios. My testing started simple: SMSL VMV PL100 CD player >> BT20A Pro >> Polk Audio Monitor 5Bs. Here, the BT20A Pro worked as a single-input integrated amp, making use of its volume, treble, and bass controls to manage the amp's output.
My impressions of the amp during this scenario were good. The amp produced a clean sound that showed detail without being harsh. While not offering any sort of "sweetened" signal, it worked well with an honest, straight presentation that let music come through unchanged. The Monitor 5Bs let the BT20A Pro show how well it could present healthy bass, with good grip and clarity across all frequencies.
Scenarion 2 put the BT20A Pro into a desktop / nearfield listening setup. Switching to JVC SP-UX7000 speakers (with upgraded drivers) proved the amp worked well for desktop use. While the Polks clearly offered better full-range sound, the small setup showed how well the BT20A Pro could drive smaller speakers with control at proper desktop levels.
The third scenario employed the Fosi Audio BT20A Pro as a power amp. The biggest step up came when adding a Fosi Audio ZD3 DAC/preamp to the chain (PL100 via digital coax >> ZD3 >> BT20A Pro >> Polk 5Bs). Setting the BT20A Pro's volume wide open (more or less) turned it into a straight power amp, while the ZD3 took over tone shaping and volume duties. This setup worked much better for a listening space (a full-sized room), with both the PL100 and ZD3 offering remote control features. More importantly, it lets each piece do what it does best. The ZD3 became the main tone-shaping part in the chain, while the BT20A Pro focused purely on clean power.
I changed scenario #3 by adding Streaming to the mix. Adding a Bluesound NODE 2 streamer built a flexible system that could handle CD playback,
streaming, and TV hookup through the ZD3's HDMI ARC input. Through all these setups, the BT20A Pro delivered consistent, quality sound.
Looking around at my other gear, I decided to forgoe the donvenience of all remote control and sacrifice comfort for sound quality. In that spirit, I decided to add some tube warmth to the signal chain and was pleased with the results. This final combination involved using a Fosi Audio GR70 tube headphone amp as a preamp between the ZD3 and BT20A Pro. This setup lets the ZD3 run in component mode (bypassing the volume control with the output fixed and turned up to the maximum). I decided to run the ZD3 in component mode to keep things simple and to eliminate a redundant volume control. The tube preamp was, maybe a little rounder and warmer? I always ask if adding vacuume tubes is a placebo effect or if it is a real, measurable difference and most often I decide I don't care. If it is a placebo effect I'll keep enjoying my placeboes. All the opinions are just that. If you don't love tubes, you may choose to not use an antiquated music platform. My feelings won't be hurt. That said, the improvement in sound quality was immediately apparent. Where earlier setups focused on accuracy and showing detail, this tube-enhanced signal chain gave a sweet, musical tone that made listening much more enjoyable. Paired with the upgraded JVC desktop speakers, this became an outstanding desktop listening system - arguably the most enjoyable setup tested. The trade-off was practical rather than sonic: losing remote volume control meant going back to manual adjustment at the GR70. For dedicated desktop listening sessions, this small hassle was easily offset by the superior tone. However, for multimedia uses where remote control is important, the GR70 would have to go. This tube-warmed setup is how I would set up the BT20A Pro for my prefered desktop listening.
For a final scenario, I decided to test the BT20A Proin a final real-world test. I used the BT20A Pro as a replacement amp in my main system: HiFiman
Serenade wireless DAC/digital switching >> NAD 1300 preamp >> BT20A Pro >> Monitor 5Bs. This mimics what would happen if a main amp died and needed quick replacement. People who enjoy vintage gear face these kinds of pproblems all the time. The BT20A Pro proved perfectly useful in this role, running cool even during demanding listening sessions, though with some expected limits. While lacking the authority and high-current delivery of my usual NAD 2200PE Class A/B amp, it delivered solid performance that would satisfy in a pinch. The amp stayed true to its uncolored character, letting the better DAC and preamp upstream shine through and shape the overall tone. The main caution in this setup was how easily the BT20A Pro could be overdriven compared to the high-current NAD. Careful attention to volume levels was needed to keep the amp s performance clean and appealing. Still, for temporary replacement duty or as a backup amp, it will serve well.
The BT20A Pro's greatest strength lies in its abundance of inexpensive power. When working at reasonable volumes in a small listening space, the amp never showed signs of strain or harshness. This generous power reserve kept connected speakers well-behaved and added to an overall controlled, effortless presentation that stayed engaging without fatigue.
Wrapping up, the Fosi BT20A Pro succeeds as both an entry-level integrated amp and a capable power amp in more sophisticated systems. Its clean, revealing character, solid build quality, and ample power make it suitable for desktop listening or small room uses. Without adding any kind of "sweetened" signal, its honest presentation and reasonable price make it a solid pick for budget-conscious audio fans seeking reliable performance.
One note on power supplies: This testing was done using Fosi Audio's 32V 5A power supply (model JYH11Z-3200500-BF), which is actually the lowest voltage option in their lineup. Given the excellent output level and control shown even with this base-level supply, upgrading to their 48V 5A or 48V 5A GaN power supplies would likely lift an already capable amp to even higher performance levels.
A last note (promise) on Bluetooth: You may have noticed that I focused on wired connections only throughout this review. Despite the "BT" in the name, I skipped the Bluetooth testing due to sound quality concerns with wireless transmission. For serious listening, wired connections are the way to go with this amp.
I guess I'll cut to the chase: The Fosi Audio BT20A Pro is a small Class D amplifier with Bluetooth that turns out to be a solid, clean-sounding amp performing well above its low price. For under $100, the BT20A Pro delivers crisp, controlled sound with plenty of power on tap. It works great as a desktop amp or backup power amp, and gets even better when paired with good upstream gear. The amp stays true to your source material without adding its own flavor - it stays honest and reliable.
I wanted to test the Fosi BT20A Pro as if I was building a new system, piece by piece, improving and changing and seeing how it fit into different scenarios. My testing started simple: SMSL VMV PL100 CD player >> BT20A Pro >> Polk Audio Monitor 5Bs. Here, the BT20A Pro worked as a single-input integrated amp, making use of its volume, treble, and bass controls to manage the amp's output.
My impressions of the amp during this scenario were good. The amp produced a clean sound that showed detail without being harsh. While not offering any sort of "sweetened" signal, it worked well with an honest, straight presentation that let music come through unchanged. The Monitor 5Bs let the BT20A Pro show how well it could present healthy bass, with good grip and clarity across all frequencies.
Scenarion 2 put the BT20A Pro into a desktop / nearfield listening setup. Switching to JVC SP-UX7000 speakers (with upgraded drivers) proved the amp worked well for desktop use. While the Polks clearly offered better full-range sound, the small setup showed how well the BT20A Pro could drive smaller speakers with control at proper desktop levels.
The third scenario employed the Fosi Audio BT20A Pro as a power amp. The biggest step up came when adding a Fosi Audio ZD3 DAC/preamp to the chain (PL100 via digital coax >> ZD3 >> BT20A Pro >> Polk 5Bs). Setting the BT20A Pro's volume wide open (more or less) turned it into a straight power amp, while the ZD3 took over tone shaping and volume duties. This setup worked much better for a listening space (a full-sized room), with both the PL100 and ZD3 offering remote control features. More importantly, it lets each piece do what it does best. The ZD3 became the main tone-shaping part in the chain, while the BT20A Pro focused purely on clean power.
I changed scenario #3 by adding Streaming to the mix. Adding a Bluesound NODE 2 streamer built a flexible system that could handle CD playback,
streaming, and TV hookup through the ZD3's HDMI ARC input. Through all these setups, the BT20A Pro delivered consistent, quality sound.
Looking around at my other gear, I decided to forgoe the donvenience of all remote control and sacrifice comfort for sound quality. In that spirit, I decided to add some tube warmth to the signal chain and was pleased with the results. This final combination involved using a Fosi Audio GR70 tube headphone amp as a preamp between the ZD3 and BT20A Pro. This setup lets the ZD3 run in component mode (bypassing the volume control with the output fixed and turned up to the maximum). I decided to run the ZD3 in component mode to keep things simple and to eliminate a redundant volume control. The tube preamp was, maybe a little rounder and warmer? I always ask if adding vacuume tubes is a placebo effect or if it is a real, measurable difference and most often I decide I don't care. If it is a placebo effect I'll keep enjoying my placeboes. All the opinions are just that. If you don't love tubes, you may choose to not use an antiquated music platform. My feelings won't be hurt. That said, the improvement in sound quality was immediately apparent. Where earlier setups focused on accuracy and showing detail, this tube-enhanced signal chain gave a sweet, musical tone that made listening much more enjoyable. Paired with the upgraded JVC desktop speakers, this became an outstanding desktop listening system - arguably the most enjoyable setup tested. The trade-off was practical rather than sonic: losing remote volume control meant going back to manual adjustment at the GR70. For dedicated desktop listening sessions, this small hassle was easily offset by the superior tone. However, for multimedia uses where remote control is important, the GR70 would have to go. This tube-warmed setup is how I would set up the BT20A Pro for my prefered desktop listening.
For a final scenario, I decided to test the BT20A Proin a final real-world test. I used the BT20A Pro as a replacement amp in my main system: HiFiman
Serenade wireless DAC/digital switching >> NAD 1300 preamp >> BT20A Pro >> Monitor 5Bs. This mimics what would happen if a main amp died and needed quick replacement. People who enjoy vintage gear face these kinds of pproblems all the time. The BT20A Pro proved perfectly useful in this role, running cool even during demanding listening sessions, though with some expected limits. While lacking the authority and high-current delivery of my usual NAD 2200PE Class A/B amp, it delivered solid performance that would satisfy in a pinch. The amp stayed true to its uncolored character, letting the better DAC and preamp upstream shine through and shape the overall tone. The main caution in this setup was how easily the BT20A Pro could be overdriven compared to the high-current NAD. Careful attention to volume levels was needed to keep the amp s performance clean and appealing. Still, for temporary replacement duty or as a backup amp, it will serve well.
The BT20A Pro's greatest strength lies in its abundance of inexpensive power. When working at reasonable volumes in a small listening space, the amp never showed signs of strain or harshness. This generous power reserve kept connected speakers well-behaved and added to an overall controlled, effortless presentation that stayed engaging without fatigue.
Wrapping up, the Fosi BT20A Pro succeeds as both an entry-level integrated amp and a capable power amp in more sophisticated systems. Its clean, revealing character, solid build quality, and ample power make it suitable for desktop listening or small room uses. Without adding any kind of "sweetened" signal, its honest presentation and reasonable price make it a solid pick for budget-conscious audio fans seeking reliable performance.
One note on power supplies: This testing was done using Fosi Audio's 32V 5A power supply (model JYH11Z-3200500-BF), which is actually the lowest voltage option in their lineup. Given the excellent output level and control shown even with this base-level supply, upgrading to their 48V 5A or 48V 5A GaN power supplies would likely lift an already capable amp to even higher performance levels.
A last note (promise) on Bluetooth: You may have noticed that I focused on wired connections only throughout this review. Despite the "BT" in the name, I skipped the Bluetooth testing due to sound quality concerns with wireless transmission. For serious listening, wired connections are the way to go with this amp.
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