Out of the box I noticed the massive brick adapter, which is larger and heavier than the unit itself, which I think is not acceptable by today's standards, where laptop adapters are half or one third of that size. Connected it to power and to Polk Audio S10e Signature Series speakers with no issues. Everything works immediately out of the box, and you don't need to do any special configuration. On the phone went to Bluetooth settings and it was listed there, and paired right away. I set all the knobs at 12 o'clock and played some songs. The sound was muddy, with too much of low frequency, however I adjusted it to my liking with the Treble and Bass knobs. Was enjoying some songs when I noticed that between the songs or in quiet / paused parts I can hear some noise. Cranking up the volume amplified that noise substantially.

I turned it off, upgraded my device from Android 11 to Android 12, and when I tried to play some songs next day, the device would not respond. Went to Settings and removed Fosi Audio from there, and repaired it again. It wouldn't play anything. Restarted the phone again, and luckily it reconnected. After that I noticed that I have to go to Bluetooth settings every time I switch off and on the amp and want to play songs. Again, this is unacceptable in this day and age, when all my other Bluetooth enabled devices auto-connect to my phone. After some further contemplation, decided to send it back and look for something different. It's an OK device if none of the issues I listed below bothers you. The sound is very good once you adjust it and it drives speakers very well.

Cons:
- massive brick adapter
- not clear sound on default settings, have to adjust
- does not automatically re-connect to Bluetooth, you have to select it every time in your device settings
- hiss / noise on higher volumes , audible in some (quiet) songs with pauses

I have read many reviews of similar items and decided to plump for this one. Chinese no-brands tend to amaze and disappoint in equal measure.

It arrived today, the power supply is actually wider than the amp itself. The amp is made out of metal and rather nicely finished. Incidentally the power supply is 24v 4.5 amps, 108 watts and claims to be certified by TUV and GS two highly respected German Laboratories. Even so, its probably a good idea to check the fuse in the plug is 5a if you intend to leave it left switched on. This unit claims to contain two Texas Instrument chips for amplification and one by Qualcomm, the latter presumably for Bluetooth.

I found some old QED speaker cable I had lying around and hooked it up to an old pair of Tannoy Eclipses I have owned since the eighties. I have to say, so far I am pretty amazed by this unit. It‘s very clear, detailed and loud with loads of bass. I would estimate equally it is as good as one of those £500 Japanese hifi stack systems from the eighties. Is it hi-fi? Hi-fi is as good as your hearing and to get great sound you have to pay a lot, so who knows. I would say this is a bargain and would be great to use with a couple of old speakers sitting in the loft. Certainly better than most portable speakers folk use these days.

Some have experienced a problem with the Bluetooth, well it says it supports BT5.0, i have an iPhone 13 and it sounds great, so can only presume they had a defective unit or possibly phone.
Someone suggested it really needs a remote control, well maybe if you connect via the phono sockets yes, but don't forget you can adjust the volume for bluetooth on your phone.

Altogether (and yes it’s early days) a rather terrific and great value little amplifier, it’s going in my study so I can turn it up loud without bothering the neighbours. :-)

Added 31/12/2021…. Someone criticised this for the way Bluetooth was implemented and the possibility of others having access to it. Well in theory, yes they can as there is no PIN, but there isn’t on most similar pieces of equipment. However if you switch it off and unplug, this is not a problem. My Sony headphones connect automatically when they are turned on. This amp only connects when I choose to on my iPhone, it doesn’t connect automatically once paired, which I think is a good idea for this type of device

The power supply is bigger than the amp, that's how tiny it is. The holes on the speaker terminals are a bit small if you're fitting say 4.5mm2 cable... but are an option if you want to save on banana plugs.Turning on, and you're good to go.You can either use the line in, or bluetooth, there's no mode setting, it'll just use Bluetooth if it's connected over the Line in. The bluetooth connection is easy, doesn't require a pin and won't auto connect if you just happen to walk past, which is good.Sounds is loud, and has a controls for bass and treble, so you can adjust. I can't say it's good or bad as it's driving some patio speakers, so a compromised acoustic environment.

The amp is decently clean on sound and feels well made for the money. If you’re happy with low to smooth, averagely quiet listenings then this will suit fine. But if you want the full spectrum and more beef or a bit bolder yet smoother sound and, from time to time, at strong volumes then go for the NobsoundNS-15G PRO CSR867. I ordered both and did an A-B comparison with Q acoustic concept 20s(with stands) and the Monitor Audio Bronze 2.Most people will be fine with this amp to be honest but you can have that little bit more for £12 extra.

I bought this mini amp after trying two expensive soundbars and being disappointed with the quality and depth of the sound. Of course it helps that I was able to hook this up to a couple of decent bookshelf speakers, but I wasn't prepared for the quality of sound that this little baby produces. It is a doddle to set up (banana plugs recommended, naturally) and within a minute I was up and running. I was blown away by the volume this unit can achieve, and with bass and treble controls you can tweak settings as required.

You simply can't beat this unit for price, especially if you have a couple of bookshelf speakers sitting redundant in your loft. Even if you have to buy new speakers, the cost of that setup is much more value for money than some powered computer speakers or a soundbar.

I had intended this as a present to myself when I get my garden office in a few weeks, but having experienced what the Fosi Audio BT20A can do I'm afraid my family is going to have to put up with my overly-loud music until that point from my broom cupboard.

I bought this as an experiment, in place of a £400 hi-fi amplifier. I wasn't expecting much at the price, but it amazed me - it drives my 8ohm vintage speakers as loud as the amp it replaced, and with a better, more open sound quality. The Bluetooth works well. The only inconveniences are that Bluetooth and RCA inputs are exclusive - you can only have one active at a time; there's only one RCA input so you need a small analog mixer if you have several analog sources (mine cost only £18); and there's no headphone output. With the mixer and a mini preamp for my vinyl record turntable, I've built a new system that sounds better than what it replaced for under £100!

The sound is poor for the relatively high price and the silver sprayed case looks cheap. Remember that this is a tiny case with with a few simple buttons so the amp in there should be of pretty good quality, which it isn't (I've connected it to high quality Canton Plus S speakers). I would say that the sound of my 70 pounds John Lewis Radio is not any worse, but comes with a radio and two speakers for that price, if you get my point. If you want to connect old speakers then you're better off by buying a used "classic" amp. Alternatively invest your money in a (used) Bang & Olufsen Beoplay A1 first generation (no mic).

This review would be good, except for the fact that this product has a SERIOUS design flaw with the Bluetooth connectivity. I’ll get straight to it: there’s no password protection on the Bluetooth and connecting via Bluetooth OVERRIDES RCA input. Why is this a flaw? Because if you’re using it with RCA, ANYONE connecting via Bluetooth will override that and assume Bluetooth control. There is NO WAY to stop it. We tested this by using the unit with RCA input, then asking a neighbour next door to find the device and connect to it - they were able to play whatever they wanted through it, and we could not take back control without killing power or them disconnecting first. If you’ve bought this amp as a small unit for a child’s bedroom (as we have) this opens a whole can of bad actor possibilities. Removing the Bluetooth antenna helped a bit with range but they were still able to assume control. This problem could be completely solved by adding a Bluetooth password and a Bluetooth off switch!! This is a SERIOUS SERIOUS flaw, and I would suggest the product be recalled!

On a value for money basis this clearly deserves 5 stars. The unit itself is tiny, but it packs a mighty punch, plenty loud enough for an average sized room. Set-up was straight forward, but I'd advise buying some 'banana plugs' for hassle free connection of speakers. Blue tooth connectivity is good and, unlike other reviewers, I can discern no difference in sound quality when compared to CD player via the RCA option. When connecting a lap-top via bluetooth I find I have to switch bluetooth off, then on again in order for the unit to find a connection, but this is a minor point. I don't seem able to make a connection with my Android phone at all, but maybe that's something I'm doing wrong. Audiophiles, or those with a very discerning ear might detect some minor 'wooliness' in sound quality. Personally, I listen to rock music so for me it's not an issue at all really - for a purchase price of a mere £63 I think you have to be prepared for a few imperfections. I was about to fork out nearly £600 for an amp with bluetooth connectivity. Absolutely no regrets that I took a chance on this instead.

I was looking to replace a very old mini hifi stack so did a fair bit of research before selecting this item. I was looking for ok sound for a small room using existing old speakers. I was pleasantly surprised by the build quality which is well finished metal. The connections and switches are all good quality. I used the BT connection to Spotify and it was super quick and stable. I haven't given the amp a thorough run through yet so 4 stars on sound quality. I did connect a small recently purchased mini valve pre zmp as I have a turntable and was pretty blown away by the sound quality of this combi especially for the price and size of the units. All round a very good bit of kit.