Fosi Audio M04 Subwoofer Amplifier for Home Theater Mono Channel Digital Class D Integrated Power Amp for Passive Speakers Subwoofer

Got this subwoofer amp to bypass the amp component of my active subwoofer which died months ago due to a peak in voltage. My amp was those that work in "stand-by" mode, so they are always powered up somehow. Replacing the board with a new one (original) was too expensive, even more expensive than what the sub costed me in the first place, so in order to not throw the box and the woofer cone to the trash, I decided to just rewire things up in order to bypass the sub's integrated amp, so I got this GREAT little FOSI amp to power my "now passive" sub.Things worked great and my sub is now back to life, shining again.The M04 Fosi Amp is a great choice as it is POWERFUL, noiseless (at least to my ear), very small and does not generate any important heat. It comes with a power adapter, so you only need the cables to connect the input signal and the output signal to the passive subwoofer. I used the convenient "bare wire connection" to hook the modified sub to the speaker output of the Fosi Amp. Worked NICELY.Quality of the M04 Fosi AMP is VERY GOOD, in a very neat, compact and ellegant BLACK enclosure. It is definitely worth the money, which is NOT AT ALL expensive, but quality exceeds by far the amount paid for this amp.Until now, i'm really loving it.

The Fosi M04 Subwoofer Amplifier was purchased as part of a computer speaker system in which the original amplifier "died of old age." The speakers were still good so it made no sense to dispose of them. Since it is not being used in a home theater system, I cannot speak to the full 100 watt output capability. My original computer speaker system (Logitech) is a 5.1 system with the amp inside the subwoofer box. I purchased a six channel amp for the surround speakers and this Fosi 04 amp for the subwoofer. All works well together. Listening to pipe organ music, which can put out some big bass sounds, the amp provides the bass that I need. (I do have a good audio system for music.Amazon has the "frequently returned" warning for this item. That's probably because people order without understanding what they need, not because the product is inferior. It produces lows from 20Hz. The item was packaged very well with foam and an attractive box, with a factory seal. I would place this in the excellent category of quality and price. (It's not junk) and has an 18 month warranty. Of course I have decades of experience building electronic devices and knew what I wanted for the purpose and budget

I'm using this amp to power a 1990 Bose Acoustimass 3 passive sub, 5-1/4" driver. The driver has dual 8-ohm coils, so I jumpered the inputs in parallel to give the amp a 4 ohm load.I'm in shock at how well this setup works. In the adjacent corner of my living room, I have a Sony 15", 200 watt sub, and down to 40 Hz, this little beast keeps up with the Sony. Very good transient response. It can make the room resonate with the Sony sub turned off, and this listening area is probably 3 times the cubic feet recommended for such a small sub. I have no idea what the RMS output is, I'll bet it's 50W or less, but it's plenty of power for the tiny Bose sub at my listening levels, which rarely go above 85 dB.Class D is nice. Stays cool, doesn't eat a lot of power.I experienced a few negatives as other reviewers mentioned.When I hooked it up stacked on top of a Kinter K2020A+ amp, there was 60 Hz hum feeding to the sub. Didn't matter if it was near the Kinter or not. Then I noticed the hum disappeared when I grabbed hold of both amps with my hand. A jumper wire between chassis screws on the amps fixed it.The power LED is ridiculously bright. It took 4 layers of 1st aid tape to tame it.It would be nice if it had a power switch separate from the volume control, so you don't have to fiddle with the volume setting every time you turn it on (with my 2-sub setup, it doesn't sound right unless both subs are at exactly the same level). But that's a minor complaint. Plugging it into a switched power strip with some of my other stuff takes care of that.We'll see how long it lasts. If it outlasts the 18-month warranty by a few years, good deal.

Purchased this to use with an old passive subwoofer from a stereo system that went bad. It was easy to set up and works perfectly, sounds great and brought new life to an otherwise perfectly good subwoofer!