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Fosi Audio

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

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Availability: 20 left in stock
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Arrives Monday, Sep 14
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Features

  • High-Performance Mono Amplifier:The Fosi Audio M04 is a mono amplifier designed for driving passive subwoofers or speakers. It features the Texas Instruments TPA3116 chip and NE5532 op-amp, providing an output power of 100 watts for a 2-ohm subwoofer or speaker.
  • Enhanced Bass Response:The M04 SUB amp is designed to improve the bass response of passive subwoofers. It features a selector switch that allows the user to switch between subwoofer bass amplifier and full-frequency mono amplifier modes.
  • Compact and Robust Design:This mini amp has a small and robust design with a built-in low pass filter for subwoofers and a sub frequency control, making it practical and powerful. It uses highly efficient Class D technology that remains cool under demanding loads and doesn't take up much space.
  • Superior Sound Quality:The home subwoofer amplifier can produce a deep, crisp, and clean low-frequency sound effect, making it an excellent addition to dedicated home audio receivers & amplifiers. It has been designed to enhance the sound and performance of your audio system at an affordable price.
  • Complete Package:What You Get: M04 subwoofer amp x1, 19V/4.74A power supply x1, user manual x1.

Description

Fill your device with the throbbing bass beats you want. Play low frequencies without distortion, and provide enough clean power. Fine tunes the volume level signal you wish to control. Improving the bass and the power of your music. Wide voltage input range and high efficiency. There is a switch for changing modes on the subwoofer amplifier M04. PBTL defines it as a Full-Frequency Mono amp for driving passive speakers. To SUB, it's a subwoofer amplifier used with passive subwoofers. Creating a professional sound system is easy with this mono amplifier. You can use this amp to drive most bookshelf speakers or subwoofers in your home. Amplifying Your Voice, Shaping Our Innovation Guided by our mission of "Redefining HiFi with Unmatched Value", Fosi Audio continues to fuel its passion for the Hifi industry, ramp up R&D efforts, and co-create new HiFi equipment with users. We pledge to bring more amazing Hifi gear with high value for the price, innovative design, cutting-edge technology, and premium quality, to audiophiles worldwide. Visit the Store Visit the Store

Item dimensions L x W x H: 5.2 x 3.5 x 1.4 inches


Voltage: 12 volts_of_direct_current


Manufacturer: Fosi Audio


Maximum Supply Voltage: 19 volts_of_direct_current


Minimum Supply Voltage: 19 volts_of_direct_current


Voltage: 12 volts_of_direct_current


Maximum Supply Voltage: 19 volts_of_direct_current


Minimum Supply Voltage: 19 volts_of_direct_current


Mounting Type: Freestanding


Number of Channels: 1


Output Power: 100 watts


Maximum Output Power: 100 watts


Item Dimensions: 5.2 x 3.5 x 1.4 inches


Specification Met: [Inf] Thd <= 0.04% and Frequency Range 20hz - 120hz


Manufacturer: Fosi Audio


Model: M04


Brand Name: Fosi Audio


Warranty Description: 18-month manufacturer


Unit Count: 1 Count


Included Components: Fosi Audio M04


Item Weight: 450 g


Part Number: M04


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Monday, Sep 14

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Top Amazon Reviews

    • Great little subwoofer AMP
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. ... show more
Reviewed in the United States on February 16, 2024 by ASGM
    • Nifty Little Amp - and it works!
I recently upgraded a low-budget A/V system located in a technically challenging environment - an attached greenhouse with hot tub. The previous system's receiver had a built-in amp. for the passive sub. The "new" (relocated) receiver has only line-level sub outputs, so this amp. was an obvious choice to close the "gap". I can make all the speaker and sub. adjustments including level and cross-over frequency in firmware, but it's quite convenient to have the sub volume easily adjustable on the unit itself as various sources need to be tweaked. As far as I can tell, the input jack is mono only so the mono 3.5mm plug to RCA adapter cable I bought works fine. (The photo the supplier provides in the product description shows a stereo 3.5mm plug at the input and the related consumer questions/answers on this topic are unclear.) When I first connected the system I had no sound out, but the issue was quickly traced to the speaker settings in firmware where I had declared the front L/R speakers as "Large". They need to be set to "Small" to get audio to the sub. I set the sub level in firmware to +5dB and the crossover freq. to 90Hz, but that latter will need some additional tweaking. At first experience the audio is great! Good, thunderous bass without overdriving the sub...more than I expected from this cheap system!. The unit runs cool to the touch and shows no evidence of being stressed in any way. I expect it to last a long time!. A couple of suggestions for the manufacturer: 1) consider using a less bright LED as the power on indicator - the current one is almost blinding in a darkened environment, as others have reported (the LED is dim when the volume control is switched to the OFF position then becomes very bright when switched ON) - and; 2) consider providing a standby mode when no audio signal is sensed (system power-down) like powered subs provide. I guess this latter is moot since the attached power supply would always be active and pulling some minimal power any time it's plugged-in. Otherwise, so far this seems to be a great product that will serve me well for many years...! ... show more
Reviewed in the United States on January 23, 2019 by B. Helms
    • Not LFE’s best friend. Good with speaker level input.
Had two of these for a short while now. I’ve tried my setup a few ways. If you have 4ohm speakers, this won’t push much when connected to an LFE. However, if you use speaker level output (by wiring into an rca jack), this will push plenty of sound. It’s frustrating because I want to use my receivers LFE, but cannot because little sound is achieved in that setup. The switch from full-range to sub works great. The frequency dial would be better if it had hz dial markers (around 1/2 way is close to 80hz). The volume does what it should just fine. Build quality is great. Only issue is the line-level input gets me barely any sound on the 4ohm speaker. (6.5” passive woofers in a sub enclosure which is easily getting down below 35hz.) ... show more
Reviewed in the United States on March 12, 2026 by J&E
    • Does the job. Quality feels escellent
Works perfectly. My use case doesn't push it so can't comment on the power, but it sounds good to me and does the job it is intended for.
Reviewed in the United States on May 7, 2026 by Richard W. Hepplestone
    • Great price, great sound quality
Used this to hook up a sub to a sound system for my workout room. Works exactly as expected and I’ve had no problems. Very powerful on a Sony xplode that is probably 10 years old. Great price and great sound for such a simple piece of tech. Hooked to a boss receiver.
Reviewed in the United States on September 2, 2025 by D Riley
    • Turn a passive subwoofer into active easily.
It works perfectly to power a passive subwoofer.
Reviewed in the United States on July 14, 2026 by Robert
    • Good product, make sure you send it plenty of volume from bass.
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. ... show more
Reviewed in the United States on July 3, 2026 by Jeff Stauffer
    • Powerful little amp, perfect for converting dead subs into passive ones
Review Image by ReYCangri
Review Image by ReYCangri
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. ... show more
Reviewed in the United States on July 21, 2026 by ReYCangri

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