Bluetooth connected to pair of old Bose outdoor 101 Music Monitors (4 ohm) with iPhone SE, ran for 2 hours with Mo-gu @ 60% and iPhone @ 80%. No distortion, no fading, no heat issues. Filled the room with music with volume to spare. Bluetooth connected immediately with no problem, signal starts to breakup at 30-35 feet indoors with clear line of sight - acceptable for me. Speaker connectors are excellent and lock tight to bare wires. I'm sure there are mini amps out there with slightly better fidelity, longer bluetooth range or build-in mp3 players but for $30, this thing is amazing. Only wish it had a headphone jack. Note: the USB port is the micro size so if you are going to connect to a USB music source you'll need cable or adapter that gets you from micro to standard size USB. I've got so many pairs of old speakers, might need several of these F900 mini-mights.

I have a very specific use case (whole house audio) but wow... I'm very impressed! Here's my take on how I'm using it...

Whole House Audio Project:
We build our house about 11 years ago and wired it for 12 zones of audio. I have 4-wire speaker cable and CAT-5e network cable running from a central location in the basement to a single gang box in each room. Then, from the gang box, I have speaker wires running to the ceiling locations.

In the 11 years we've been here, we never pulled the trigger to purchase the "traditional" system (multi-channel amps, in wall controllers, speakers, etc.) We've been quoted well over $10,000 for all 12 zones in the past. Even a DIY solution online would run nearly $4,000 without the speakers (HTD Audio's Lync system with keypads.) That's just not worth it to me.

Being a Google fan, I set out to build a system using Google's Chromecast Audio devices, amplifiers, and in-ceiling speakers. I ended up purchasing this Mo-gu F900 amp for each zone in the house and it's been working perfectly! I'm at about $139 per zone and absolutely loving it!
I can stream to each zone (from Pandora, Spotify, Google Play Music, I Heart Radio, podcasts, etc.) and control it from an iOS device, Android device, computer, Google Home, etc. I can have different sources streaming to different zones or group any zones together. It's incredibly flexible and easy to use.

Here's the setup (per zone):
1. Google Chromecast Audio ($35)
2. Mo-gu F900 Amplifier ($31.99)
3. 82C 8-Inch In-Ceiling Speakers ($35.98 each, $72/pair - Available here on Amazon)

And here's the installation details:
1. Install the in-ceiling speakers.
2. At the gang box, connect the speaker wires running to the ceiling to the 4-wire speaker wires running to the basement
3. In the basement, connect the 4-wire speaker wires to the F900 (and plug in the F900 with the included power supply).
4. Also in the basement, connect the Chromecast Audio device to the 1/8" jack on the F900. Plug in and configure the Chromecast Audio.
5. Turn the F900 on and set the volume knob about half way up. You can use the Google Home app to adjust the final volume of course.
6. In Google Home, select the Chromecast Audio device and edit the settings. Make sure you name it to the room it's located in. Also, adjust the treble and bass settings. I put both up almost all the way. The F900 can handle the wide frequency range very well. (YMMV of course so set it to your taste!)
7. Also in Google Home, set up your groups (ie: Whole house, Downstairs, Bedrooms only, etc.) You can create as many groups as you like!
8. Using an iOS, Android, or Google Home device, cast a source to the room and enjoy!

Pros of the F900:
* Powerful - It's driving the 8" speakers a lot better than I thought it would. Even over a long distance (>60 ft). Just make sure you use the proper gauge speaker wire if you have long distances.
* Clean - We're not talking audiophile quality here but I was pleasantly surprised on how good this amp sounds.
* Simple - It's a "set it and forget it" device in my solution. I plan on keeping it on all the time and I'm not too worried about it!

Cons of the F900:
* Size - It's actually a lot smaller than I thought it would be. Not really a bad thing but it was surprising.
* Build Quality - The build quality is actually very good but the front sticker was applied a bit askew. Not a big deal though.
* Hiss - When there is no audio playing, there's a VERY SLIGHT hiss that you can hear at the speaker. I mean, VERY, VERY SLIGHT. (I only heard it when I was on the ladder putting on the speaker grills. I had to have my ear closer than 12 inches away just to hear it. I can't hear it at standing height.

Well, that's it. My cheap whole house audio solution is complete and a lot more flexible than I could have expected. Grand total for all 12 zones was approximately $1,670 (not including the speaker wire). The real beauty is that you don't have to do all of your zones at once. You can build it out zone by zone. (That definitely helps when you have to get spousal approval!)

Hope this review helps!

I needed to connect a pair of external ceiling speakers to an HDTV in our exercise room without going through the expense of a full-on AV amplifier setup. This little gem arrived promptly and took only about 5 minutes to connect. The audio fidelity is excellent and build quality of the amp is also excellent. The range of volume is impressive and i was able to equalize the external speakers to the internal speakers to my liking with volume to spare. An aspect that i found particularly impressive is that i received an email from the seller later in the day checking to verify that i received the unit and everything was 'ok'. Great customer service. Buy with confidence... this is very nice micro amplifier.

As a bluetooth / wired amp, I'd give it 3 stars. It works, it's neither particularly great nor awful. If it weren't for the deal-breaker "feature", I would have used it for its intended purpose (to drive a set of bookshelf kitchen speakers), and would have more to say about its sound quality.

The deal-breaker, for me, is the incredibly annoying start-up "tune" and greeting message. Every time you turn this thing on, it plays 4 bars of some kind of waltz tune, something reminiscent of the Hobbiton theme from Lord of the Rings (but tackier). Then it announces, in a female voice with an extremely heavy Asian accent, whether the device is in Bluetooth or AUX mode. It has similar announcements for Bluetooth pairing and disconnecting.

Unless you choose to leave the amp running 24x7 (resulting in your speakers always receiving a soft but noticeable background "hiss"), you will be greeted with this announcement every time you turn it on, blasted through your speakers at whatever volume you normally listen at. Seriously, what engineer would ever think that someone would want to hear a silly melody, and voice prompts, every time their amp is turned on? Is it really so hard just to add another LED or two to display pairing status, compared to installing an impossible-to-override audio recording in your circuitry?

For me, this stupid feature is a fatal flaw which prevents me from using this device for its intended purpose. Alas, it's not worth paying the $8-10 to return this annoying little toy back to Amazon, so I'll have to find some other use for it. It will probably be re-purposed as an occasional-use amp for my basement workshop.

Also, buyer-beware: unless you get the "combo" set, you'll need to provide your own power supply, and the power supply which comes with the combo kit doesn't appear to be powerful enough for the advertised output. I found an old laptop adapter which isn't ideal, but worked well enough for my purpose.

I am truly impressed in this tiny amplifier / Bluetooth receiver. I had to bookshelf speakers from an old stereo setup and I wanted better sound from my Echo Dot in the bedroom. This little amp did the job perfectly even using an old wall wart power supply that puts out 12V at 1A. I know that a more powerful supply should allow higher power output, but this is fine for falling asleep listening to music or environmental sounds. I easily paired the unit with my Dot's Bluetooth. There is no audible his or hum and the fidelity is good. If you have a similar application I recommend this easy to use solution.