M04

picked this up to drive a leftover passive samsung sub from an old htib system down in the basement. paired it with a 2006 panasonic receiver running polk bookshelf speakers, feeding the receiver's sub out directly into this unit via rca. it provides plenty of clean power to drive the sub without breaking a sweat. having the dedicated low-pass filter knob makes dialing in the crossover with the polks painless so the low end blends smoothly instead of muddying up the mids. it runs cool, has a tiny footprint on the shelf, and makes zero hum or turn-on pop. definitely the cheapest and most effective way to breathe new life into a passive sub you already have laying around instead of buying a whole new powered unit. solid little workhorse.

This little guy packs a punch! The sub for my Onkyo home theater system died due to a lightning strike nearby and I had no luck finding a replacement board for the SKW-593 and this is where this little guy came into play. I was able to convert the dead sub from active (powered) into a passive sub very easily, I simply clipped the leads to the driver (closer to the old amp board as the cables are short), then I extended those two cables by soldering extended cables together; you could probably accomplish this with T-taps or just plain old electrical tape but I wanted it secure and protected with shrink tubing. I then removed the plate off of the old amp board so I could re-use it to cover the hole, then I routed the cables out to the Fosi M04 and plugged all of the screw holes on the metal plate to prevent distortion from air trying to scape the box. This little sub is more than sufficient, and though technically the 100 watts it outputs I lower than the original amp circuit which output 120 watts, I cannot hear any difference as I’d have to bump my volume close to the max to reach that power level, which I don’t do. Overall I’m very satisfied, the quality is great and I’m happy that I get to continue using my sub instead of scrapping it and buying a new one.

Works great clean sound lil under powered why 4 stars but for the value good unit good power.

This was the perfect amp for my passive subwoffer that was in the set of surround sound speakers. Using with a Yamaha RX300A receiver. The included power supply was great for this price point. Hooked it up and everything works perfectly.

Seems like a good product. I used this amp to replace the amp that failed in my subwoofer. At first I was not sure it worked but discovered the output level on my system was set too low, so once I raised the bass up it started working, it seemed to almost over power my speaker. the controls on the front of the amp help keep the balance with the other speakers in my system. sound quality was nice, simple to connect.

This is NOT a subwoofer amplifier. I'm attaching the REW measurements as proof. A) With the sub function off it measures reasonably flat. B) turning the sub function on REMOVES bass under 120 HZ! C) turning the frequency knob does not change the frequency. That knob changes the amount of cutoff. D) it's not shown, but I checked if the switch is labeled wrong but it's not. The sub knob has no effect when in the other position E) THIS IS THE REVERSE OF A SUB AMP!!! I like Fosi products but this is a 110% fail.

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.

I have a large 12" subwoofer enclosure for my home theater system that had its 150W power supply die. I decided to try out this amp to see if it'd work well my subwoofer. I was a little concerned that this is a 90W (with the power supply it comes with) amp and that it wouldn't drive the subwoofer as well, not that it'd usually be high enough to hit 150W. I was expected that at best this would sound the same as the old amp. Which is fine because it worked just fine with the old amp. But this amp surprisingly sounds quite a bit better than the sub's built-in amp though. I swear it seems to handle <60Hz better. I've turned music or a movie action sequence way up and this unit easily has more power than I'll ever use. There are a few downsides but they are all manageable. 1. I really wish the volume control and power switch were separate. 2. I wish it had an 'auto-off' feature, although the class D amp uses very little power. 3. Make sure you have a 3.5mm to male RCA plugs cable, or a 3.5mm to female RCA + an RCA cable. I wish it used regular RCA jacks really. Mostly because the 3.5mm jack isn't *that* secure so if the amp ever moves (and it is tiny and light weight so it is easy to accidentally move it) you hear a lot of loud static. #2 isn't that big of a deal really, and #1 & #3 aren't really an issue once you are done setting it up though. I'd buy it again, or recommend it to a friend who needs a subwoofer amp.

Bought this to replace the buttkicker gamer 2 amps that is 16x larger. This little amp works so well and has less delay between Rumble and press time also much more defined Rumble. Great little sub amp for buttkicker.

El producto es de muy buena calidad. Es increíble que un dispositivo tan pequeño te de mucha potencia. Lo tengo instalado en un woofer de 6. 5 a 6 ohms y lo mue e perfectamente bien. Se escucha genial

Good

Funciona perfectamente bien, alimentando 2 woofers de 10".

It is as it is 👍🏻