Fosi Audio BT20A Bluetooth Stereo Amplifier

julio bonich

August 1, 2026

Un pequeño Gigante

Supero mis espectativas

Badger510

July 30, 2026

Pretty good but...

By quality of sound output I'd probably the Fosi BT20a 4 stars, especially considering the price and simplicity. I used it for KEF Q150s. They're bookshelf speakers, notorious for being low impedance, so they need an amp that is near the maximum. Compensating for that, they have amazing depth and sonority and separation of frequencies, which for me (playing a lot of classical chamber music, solo instrumentations and voice, and also small ensemble jazz) is exactly what I want. So the Fosi could have been more powerful, but they did well enough for speakers I use in my office (and that opens onto a larger den-type room). The problem is that the amp's speaker terminals (for the speaker wires) are very small, and though there's a wire hole in the post of the terminal, it's too small for 14ga wire, so I had to wrap the wires around the terminal post. But the positive/negative terminals are so small and close together that it was hard to wrap the wires tightly enough. Still, I did it. Then, over a few months, since the amp was on my desk it would inevitably get jostled every so often. Eventually, parts of the wire got loose from the terminal and connected with the wires from the opposite polarity — big, long sonic bass hiss! I tried to rewrap the wires a few times; but 1) that got to be a real pain because of the small size of the terminals and thumb screws and the tiny space between the terminals, and 2) the same thing kept happening. I finally gave up. Spent more money on a better amp. Couldn't be happier. Because now the wires fit well, and there's separation between all of them, and the amp is more powerful, perfect for the KEFs. I shouldn't have tried to save money in the first place. Penny wise, pound foolish.

Worth the price. Start here on your hi fi journey.

This is great! I have this connected to two Polk TSI100 bookshelf speakers and no issues filling the room. 14awg wire banana clips. I’m getting into the world of hi fi and started at level 1 and do not regret it. Start at the bottom and work your way up before you spend $1000 on an amp. Yes there may be better ones but at the end of the day, this works for my living apartment and I’m moving it into my office. The speakers were attached to a Bluetooth Sherwood RX 4508 and there was a faint hiss. Nothing yet with this Bluetooth amp. Again for under $100 it does the job. Great value for the money. Easy to set up. Using Spotify lossless but it’s a Bluetooth connection. Happy I bought it so far!! It fits in my hand. Tv soundbar is behind the amp.

The real deal!!!

This is the real deal. Forget all the cheaper pieces of junk. I tried to buy those but sent each one back. This sounds great. Took about 5 minutes to hook up. And sounds AMAZING! I kid you not. This is the one to get if you need something that is about as big as a large deck of cards and replaces your big stereo receiver. Of course, it’s basically just an amp and a Bluetooth receiver. But these days, what else do you need? Especially if you play from some online streaming service. A+++. Hope this helps.

0:40

Parts Express Samba MT’s love this thing!!!

I have this in my reconditioned HIFI cabinet pushing two parts express Samba MT speakers. Worth every penny. Wish it had more RCA inputs, but for this price and wattage, who’s complaining.

0:11

Xandaggo Smith

July 23, 2025

Works Great!

Works very well and as intended. Hooked it up to a pair of old bookshelf speakers and sounds fantastic. Extremely loud if you crank up the volume on the phone/laptop, 200watts is all you need. Can easily provide plenty of sound for a home theater if needed. If you need to power passive subs then get a separate unit. I suggest looking at crown amps.

Bridges The Gap

I’m an old guy with over 300 gb music on my computer. I had 2 really good Denon bookshelf speakers sitting around collecting dust. I got tired of listening to music on computer speakers and wanted an upgrade. This small amp took care of it for me. I just needed something to power the Denon speakers. This small amp is really great. Nice and simple. Plug in the speakers and a source for music and you’re done. The bluetooth feature works well as I can stream from iPad or iPhone. This is a great little amplifier that now allows me to listen to good speakers and music from my computer. I think it was a great purchase.

Kevin Nasky

September 4, 2024

Wow

I had managed my expectations at this price point, but it turns out this amp overdelivers. I’m using it in a small sunroom with some affordable Polk bookshelves (S15s) and I couldn’t be more pleased with the sound. I listen to a lot of jazz, and there’s a lot of warmth and clarity. But also, when playing hip hop and r&b, the bass is tight. Decent volume output. Form factor, build quality are nice. Knobs don’t feel cheap, and they have a nice consistent resistance when you turn them. Highly recommend!

Soaks up abuse and keeps going. Surprisingly loud.

I had a review of this where it was diminishing the volume. Never figured that out but I think it was a bad optical cable prior to the fosi in my system. Anyway I set this aside for a few months then fired it up in my pool driving a set of onkyo 5.25 bookshelf speakers. It has been in a 100 pool shed all summer and I’ve absolutely hammered on it with the volume cranked for 6 hr sessions and it hasn’t broken a sweat. The output of these speakers with this amp is nothing short of impressive, considering the price and footprint of the amp. I’ve used Bluetooth as the exclusive input in the pool and it actually still connects even with the phone in the house. I like that you have to select it as a pair every time you stop streaming so you don’t accidentally stay paired while trying to take a call or watching “other media” later that day.

Anyway I just wanted to update my review. This has experienced high humidity and freezing temps and it has so far just worked and worked.

Crap. Died after two years.

Just stopped working. Very disappointing.

0:10

Pushed Passive Speakers Very Well

Perfect for pushing 6ohm 130W Pioneer SP-FS52 Andrew Jones Floor Standing Speaker. Love the small hidden format, with line input or streaming Bluetooth for a very reasonable price.

0:14

J. M. Barbera

May 14, 2024

Great sound quality, plenty of power, and compact size make this one an excellent value...

I bought this because I could power it from a DeWalt power tool battery so that I could audition speakers anywhere. I was so impressed with the sound clarity and power, that I could recommend this as a main amp for many people who want a compact two channel stereo in a medium sized room.

It drives full size 10", 3 way speakers at high volume effortlessly, with no detectable distortion or noise.

The two minor issues I encountered:

1. The knobs were not indexed correctly, meaning that the tick mark pointing straight up was not the halfway point in the adjustment. This was the case for all three knobs. Setting the bass and treble to exactly halfway meant you'd need to point them to ~1:00 position. I removed them and indexed them correctly.

2. The speaker connectors were rotated at random angles. This meant that the holes for wires were oriented in a way that you could not get a wire through them from the top or bottom. I got a small drill bit and rotated them so they were correct. It's a non issue if you only use banana plugs to connect speakers.

Neither of these issues was a deal breaker for me. Still would recommend this as a great starter or garage amp, or as the basis for a portable setup. Considering a second one for just that purpose.

It's now getting a lot of use in a portable outdoor sound system powering a pair of Canton Plus S speakers.

Great sound quality, plenty of power, and compact size make this one an excellent value.

Here's a link to the parts I used to make the amp portable.

Don’t buy waste of money

Bought it for my studio monitors. Terrible investment amp squeals distorts Audio if you want an amp invest more money in another brand same issue the are you squealing and it keeps cutting in and out and just ruins my whole listening experience

0:47

Sleek, compact design and amazing customer service.

Sleek, compact design. Solid metallic construction. Great sound. The customer service is excellent! They respond quickly to emails and were easy to work with as we diagnosed the problem and methodically worked through the steps to isolate where the issue was. Once we identified that it was due to a defective unit, they sent me a new one.

Pictured is the multi-zone audio setup I've assembled to make use of the built-in speakers in my home. Each of these amps is paired with an Echo Dot 4, and the sound is excellent. Yes, I realize that Sonos and others make a device that combines the amp and the sound source; I am already in the Echo ecosystem and don't want to create another account (at Sonos), install another app (from Sonos), and create another paid membership (with Sonos). The above setup seamlessly integrates with both Alexa and Spotify.

Started smoking when I tried to hook it up and never worked

When I was setting it up, trying to attach the speaker wires, it started smoking and stopped working. I have contacted the manufacturer asking if they can refund or replce.

0:05

Great value for the money

Very easy set up, amazingly balanced sound quality, coupled with the phone preamp works perfectly for me.. great value for the money, brought my 42 year old Akai turntable back to life.

0:08

great sound, questionable build quality

This little amplifier does sound quite good and powerful, for the small package and the small price, but the build quality shows some problems.

First the sound: I'm impressed. I am listening through some Dayton Audio B652-AIR bookshelf speakers. I've had two good vintage amps attached to these speakers in the same location. This Fosi amp sounds better than one, and not as good as the other. I'm mainly looking for open sound stage, low noise, and punchy, tightly articulated bass. This amp feels fairly open. There's no noise. The highs are crisp, and downright sparkly, if you use the treble knob. Excellent stereo separation. The bass is adequate, with a bit of punch, but feels a little forced and not quite as tight as with a top-notch piece of equipment. Anyway, it's quite good overall. I doubt you could do much better at this price.

Second, the build. The small metal box is simple and nice. Any smaller and the connections and knobs would feel cramped though. My problem is that the switch and knobs are a little misaligned. (See the photos.) It's a little hard to see in the photos, but the power switch is sort of bent to the right. Also, the volume knob is ever-so-slightly angled to the left. It's not bad enough for me to return this, but it is annoying. To me, this speaks either to poor engineering (i.e., a design that's difficult to assemble accurately), or poor manufacturing (just not being careful putting it together). I'd pay a small premium to be assured I don't encounter this kind of problem.

Finally, connectivity. I'm using the aux inputs fed by an old FiiO E10 DAC. The amp remains open for Bluetooth pairing regardless of whether you're using the RCA aux inputs (and whether or not you have the antenna attached). It appears impossible to completely disable Bluetooth. I've tested the Bluetooth connection briefly. Unsurprisingly, I don't think the DAC in the Fosi amp is as good as the one in my FIiO DAC. Using Bluetooth, the sound is thinner with less detail and subtlety, especially at the high end. That's my brief impression anyway. I did confirm that the range is very good. I could go roughly 30 feet away, with several walls between me and the amp without losing the Bluetooth connection to my phone. If you're sure you won't use Bluetooth, I think I'd opt for the Fosi TB10A, which appears to be the same amp, but without Bluetooth.

Great Product!!! Highly recommend!!

Great product!!! Puts out great sound!!! Highly recommend!!!!

0:27

Great Little Amp for the Great sound

Amplifier is small but it produces great sound for my speakers, I really like it. Easy installation and easy and quick to connect to a better sound system I give this little amp a 5⭐️

1:02

Great sound, small footprint!

I’ve been looking for reasonable solution to powering the outdoor speakers that the previous owner had installed. They were a sound technician and wired the whole house but it was very early 2000’s tech (definitely pre-Bluetooth) and all to a single media hub on the opposite side of the house.

I’ve never had the time or energy to invest in figuring out what the best set up was to power them from the opposite side of the house and still control media and I’ve looked into a lot of options but none seemed to be as minimalistic as I need, cost a ridiculous amount, etc.

Then this came across my random suggested items and I looked at the different levels/costs and what they did and this was perfect.

I’ve only just installed it (and will come up with a more permanent perch for it), but it was very quick and easy to hook up and pair. At only a quarter volume it’s almost loud enough to bother my neighbors and I can hear it over the traffic behind my house (I back up to a road)! So I’m sure that they will be plenty sufficient for my needs and more so. Again, only 30 minutes after installation, but I am impressed with the sound quality, the seemingly simple and sturdy construction, and the super small footprint.

Excellent small amp!

I couldn't be more happy with this little amp (Fosi BT20A).

I had this idea to hide speakers above our kitchen cabinets, and then to have an amp mounted under the cabinet which can be directly connected to, or connected through bluetooth to play music. I ended up pairing this amp with Micca OoO 3.5 inch 2-way speakers, since I wanted smaller speakers to not stick up and be seen above my cabinets. This amp/speaker combination exceeds my expectations.

Here's my notes of important issues that may interest people:

There is no "pop" when I turn on the amp, or when I switch tracks, and also there is no "hiss" coming from the speakers at any time.

* I have cranked the volume for long periods of time and there was no distortion of sound from increasing the bass or treble.

* I can't really detect any difference in sound between playing music with a direct connection, or a Blue Tooth connection with my iPhone 5S.

* The 3 control knobs feel solid/high quality, and I love the bass and treble response.

* In general, I always just have the volume on my iPhone "two clicks" from the highest volume setting, and the volume on the amp is always at about 50% (knob straight up). I then can decrease the volume on the amp to ~30%, or increase the volume on the amp up to 75%, which is really loud!

I have to say, that before I placed my order, I was hesitant because of some of the negative reviews, but it seemed like the best solution for me. There were other decent small amps that could be mounted under a cabinet, but they were only 50W, and this one is 100W. But now that I have it, I honestly feel that the people in the comments who had issues had a defective amp...or else I just got really lucky. I just wanted to report my own experience with this item as it was really good. I'm very satisfied with the performance of the amp (volume, bass, treble, bluetooth range and behavior, overall quality).

JH

March 7, 2021

Surprisingly good

I did not have high expectations for this device, but what the heck it was going to power my garage system. So for the price I was game.

First off, my main system consists of class A/B components. Bryston amp &preamp, B&W speakers, Phillips CD 880 player, Technics turntable. I have an old set of Cambridge SoundWorks bookshelf speakers I refinished. My thought was to power these puppies with the FosiAudio amp. When I opened the box I was surprised by the size of this unit. I could put this in my pocket.

Hooked things up and linked to my iPhone 11. Easy enough. This is amazingly good for the price paid. Will it play loud enough to rattle your windows, no. But it will definitely fill a good size room with decent quality audio. My plan is to cable this to an Echo Dot I have. I am going to have fun with this unit and highly recommend it as a inexpensive power source for good music. Enjoy!

Surprisingly effective, breathes new life into silent speakers

I don't write reviews anymore lately but I've had a good experience with the Fosi BT20A that I feel is worth sharing.

I purchased the BT20A because I had a long-silent pair of Signet SL-260 speakers from over a decade ago that were great budget audiophile speakers but had sat unused. I just didn't have any more 2-channel or AV systems in the house that needed a set of speakers.

So I figured that I'd bring them fully into the future-present by integrating them into my Alexa ecosystem. This consists of quite a few Echo Dots situated around the house, including my office. I had been using a twinkie-sized BT speaker with the Dot in my office and you can imagine that the sound quality was unimpressive to say the least. Based on research, the BT20A seemed exactly what I needed, a reasonably powerful Bluetooth enabled device that could directly drive unpowered speakers with a quality signal at reasonable levels of volume.

As for this goal, the BT20A met my needs exactly and fully. Now I can listen to my music at high quality. Very satisfying.

I should note one quirk of the system. The BT20A was able to quickly be detected and linked using my iPhone 12 Pro, but initially I could not get the Alexa app or the Echo Dot directly to find the BT20A. Internet and forum searches here were fruitless. Finally, I tried something unusual. Thinking that maybe for whatever reason the Echo Dot's search wasn't triggering the BT linking capability of the BT20A, i tried it again at the same time as I put another BT speaker into linkup mode. Immediately, the Alexa app showed that my Echo Dot now saw the BT speaker AND the Fosi. From there I selected the Fosi and from that point on, the Dot and BT20A could find each other any time I wanted to use the system. Odd but works. Fosi support actually responded within 10 hrs of my help request and were pleasant but I solved this one on my own.

Never would I have imagined that there was such a device as this, but now that I've found it, I can bring high quality sound anywhere around the house I want without having to move stereo components or settle for typical BT portable speakers. And at a cost that's actually an amazing value. I love it!

I have included a picture of my super little system. Super happy overall with the sound for dollar punch these little components.

Michael Johnson Jr., Ph.D.

January 18, 2021

A Tiny BEAST!!!

I NEVER write reviews BUT THIS little black box is a BEAST!! Worked flawlessly from the moment I plugged it in. It appears right away on my iPhone 11, and, when it pairs successfully to Bluetooth it makes a satisfying audible “click”. The status light on the front will appear red to indicate it has power - but when connected via Bluetooth, it switches to blue.

It’s about the size of a grown man’s palm, VERY sturdily built in an all metal case. And everything about it’s build - from the volume/treble/bass knobs on the front, to the connectors on the rear - all feel like solid and appear to be quality built.

I’ve had it for a day and so far, not the slightest problem or disappointment. All I’ve used it for is to connect my Aperion Versus III Bookshelf speakers with my iPhone. The connection is strong and the 50ft distance seems to work without any problems. And I’ve had it running on and off all day long and it’s only mildly warm to the touch.

Needless to say I’m IMPRESSED.

I’ll update if there any issues arise. I strongly suggest you try this bad boy out!!! 5 Stars!!!

Absolutely. Fantastic.

I was a LITTLE CONCERNED that this small unit wouldn't do what I needed it to do.

For the record, I am definitely not an audio equipment snot.

I am literally going iPhone>>Bluetooth>>Fosi>>KlipshCornwall with this setup. I'm pushing signal from my phone to this little amp to see if it can drive some really serious cabinets.

The image attached here isn't of my place, it's just to give you a sense of how big the speakers I inherited are...and how massive the challenge was for the little Fosi amp.

The New York Times has a gadget column curated by experts that recommended this tiny unit, and I still wasn't convinced.

The Klipsch's are passively powered. They operate in the 100-400W range, and this little amp is just 100W.

Just to be clear, at 400W, my speakers can produce 119Db. That's 'threshold of pain' loud, with perfect fidelity, enough to fill the Hollywood Bowl.

So I went ahead and bought this little Fosi, and hooked it up to my horns.

Boy...was I wrong about this little amp.

I can't put the volume up above 50% without knocking the back wall off of my apartment. That something SO small can drive speakers THAT big, and with total clarity...is just astonishing.

We live in the future.

If you're thinking about buying this, stop thinking and just do it. Hope that helps.

The Cheap Audioman

March 4, 2020

One of the best purchases I’ve made

Well, I couldn’t recommend this highly enough. I bought this based mainly on all of the positive reviews. I’m glad I did. I bought this mainly for the power ratings. I have somewhat of an unorthodox set up. I have an Oppo blue ray player I’m using as a CD transport and a Rasberry Pi with a HIFI hat for a Spotify connect node running into a Schiit Modi 3 and then into the Fosi. Sound is detailed and full. For speakers I have a set of Bookshelf kits from I believe MT audio that I got from parts express and a small powered Polk sub I’m using with speaker level inputs. As another reviewer mentioned, this setup has made the inadequacies of my other audio systems apparent. I like this thing so much that I bought a non Bluetooth version to add a pair of rear channels. I’ll run the same setup but use the Schiit Magni headphone/preamp and split the rca connections between the amps. So I’ll have independent volume and bass and treble control for both channels. I just wanted a slightly more immersive experience. I’ll update once I receive it as I had to order it from the Fosi website. As for the Bluetooth connection, it connected well and had a good range. Although I really didn’t buy this for the Bluetooth as I wanted to run an external DAC and stream directly to it for quality purposes. Just an amazing little amp. I’m sure it’s the same board as some other mini amps have but I’m impressed with Fosi. Just get it. I’d recommend an external DAC but for $70 and $200 for the DAC and preamp from Schiit you’ve got a hell of a system for less than $300.

Leagues better than the lepai2020a+

I'm a little disappointed with this product because will it does sound great and gets really loud its held back by several design choices. This review will have lots of technical language. TLDR Great amp, gets loud, sounds clean, bluetooth needs work, and will really only do half of the advertised power out of the box. If you dont need bluetooth save yourself 8 bucks and get the Fosi Audio TB10A.

The bluetooth is basically useless while the paring is fast and easy it has so much distortion I don't bother with it I don't know if its the board they chose or interference with other components/environment but it sounds TERRIBLE even at low volumes.

They chose to use 2 of the "TI TPA3116D2" Chips, the spec sheets of said chips claim 50w per channel or 100w bridged (both channels together) so with two chips bridged this is were they get 100w per channel. The description is misleading because while this amp is, on paper, capable of that the included power supply is, at best, capable of delivering 108w of power. This means with the amplifier chips they have chosen at 90% efficiency each speaker channel will be seeing 48.6w and all of these numbers are with 4ohm impedance speakers as you go higher the power output will be less. This may not be entirely bad however as the chips share a heatsink heat dissipation could be the limiting factor and they planned for that to only run each chip at half there potential. So why not just use one chip not bridged and run it a full potential and save on pcb space and complexity. If heat is not a concern they could have just not spent money on the bluetooth receiver and antenna and put that into a better power supply to really have a beast of an amp in a tiny form factor. All this to say I think this amp has some hidden potential I might update this in the future after I try some mods on it.

The sound quality with the RCA input is fantastic you can basically max the knob out without it distorting this could because of what I described above running at half potential or a conservative limiting on Fosi's part when they designed the pcb and set the gains. The build quality is pretty good as well, all the seams are clean, no gaps, all aluminum construction, and hex cap screws on the front face. all the knobs turn smooth and the treble/bass adjustment is an awesome feature.

The aesthetics are more subjective but I love the two tone black and raw aluminium with three equally sized knobs just super minimal looks good with all the other black equipment.

I would say 7 out of 10, fix the bluetooth or include a better power supply for more volume and easily be 9 out of 10.

dallase

June 15, 2019

More wattage but broken bluetooth

I was using the fosi 50x2, and decided I wanted a bit more wattage, so I moved up to the 100x2 version with bluetooth.

The 100x2 has a larger power supply giving you 24v power instead of 19v power. Both the 50x2 and the 100x2 will spark when you plug in the connector on the back which is scary. If you plug it in first, then plug in the power block to the outlet it will not spark.

The 100x2 has individual controls for Bass, Treble and Volume. The 50x2 only has volume control.

The 100x2 has bluetooth. When I bluetooth my iphone xs to it and play via my Music app, the sound is terrible. Everything sounds great when I play my TV audio via the toslink->rca via a DAC. But when I sync my phone on bluetooth, its so bad. I will record a video of it later and update my review.

For the extra money, its worth having more wattage and bass/treble control. But dont buy for the bluetooth. This unit was $77.

I run a Nobsound NS-15G PRO CSR8675. It comes with a 19v adapter, but I replaced that with a 24v 4.5A adapter that I had laying around, and it works much better delivering more power to the speakers.

BT20A vs BT30A

Both are great products! See the video for a few key differences between the units.

3:02

Probably need to leave unplugged when not in use

Love the form factor of this amp: small and mighty. I wired it to a set of Sony 100w bookshelfers running a toslink signal from my television. Lush, full sound with plenty of air and clarity, whether streaming audio, digital files or Blu-Ray. Ideal for someone building a hi-fi rig in a small space (I compute, game and watch movies on my small couch with a 40 inch hd screen in a 200 square foot room).

HOWEVER, the amp stopped working at just over a month of ownership. This doesn't seem to be the fault of the amp's interior construction either. The front switch (and how it is labeled) is misleading. It's for the bluetooth, not the amp's power. Nowhere is this made clear in the instructions either. Point is: you probably need to unplug this thing when you're not using it because you risk running it into the ground. And don't dare disconnect the power cord from the unit because that oft-mentioned spark is terrifying as the pop from a can of biscuits.

I'm sending it back and getting a refund. May purchase again but I'm not sure. I still own a Pyle 120wx2 PCAU46A (see second photo), which does the job of several components: speakers, tone control, headphones, even plays audio from a USB if you like (and for less money). The problem: it's just an ugly, bulky amplifier with a slightly worse sound and recurring quirk is that you gotta reset your RCA jacks every time you power them on.

Such is the struggle for getting quality audio on a budget. You're gonna get quirks somewhere and this Fosi Mini Amp is no exception.