--- product_id: 58115674 title: "M04" brand: "fosi audio" price: "NZ$179" currency: NZD in_stock: true reviews_count: 13 category: "Fosi Audio" url: https://www.desertcart.nz/products/58115674-m04 store_origin: NZ region: New Zealand --- # 100W output power Cool-running Class D tech Adjustable low-pass filter M04 **Brand:** fosi audio **Price:** NZ$179 **Availability:** βœ… In Stock ## Summary > 🎡 Elevate your bass game with power and precision β€” don’t let your subwoofer miss out! ## Quick Answers - **What is this?** M04 by fosi audio - **How much does it cost?** NZ$179 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.nz](https://www.desertcart.nz/products/58115674-m04) ## Best For - fosi audio enthusiasts ## Why This Product - Trusted fosi audio brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - β€’ **Compact & Cool:** Sleek mini design with efficient Class D amplification keeps it cool and discreet. - β€’ **Plug & Play Upgrade:** Breathe new life into old passive subs without the hassle of buying new powered units. - β€’ **Powerful 100W Output:** Drive your passive subwoofer with clean, punchy bass that fills your space. - β€’ **Precision Bass Control:** Fine-tune your low frequencies effortlessly with the dedicated low-pass filter knob. - β€’ **Versatile Mono Channel:** Switch between subwoofer and full-frequency modes to match your audio setup perfectly. ## Overview The Fosi Audio M04 is a compact, high-performance mono subwoofer amplifier delivering 100 watts of clean power via a Texas Instruments TPA3116 chip and NE5532 op-amp. Featuring a user-friendly low-pass filter and sub frequency control, it enhances bass response for passive subwoofers with minimal heat output thanks to efficient Class D technology. Ideal for upgrading or repurposing existing passive subs, it offers professional-grade sound quality in a sleek, space-saving design. ## Description Buy Fosi Audio M04 Subwoofer Amplifier for Home Theater Mono Channel Digital Class D Integrated Power Amp for Passive Speakers Subwoofer: Amplifiers - desertcart.com βœ“ FREE DELIVERY possible on eligible purchases Review: perfect little amp to repurpose a passive htib sub - 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. Review: Powerful little amp, perfect for converting dead subs into passive ones - 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. ## 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. ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B07942M4MC | | Best Sellers Rank | #15,985 in Electronics ( See Top 100 in Electronics ) #74 in Audio Component Amplifiers | | Brand Name | Fosi Audio | | Customer Reviews | 4.4 out of 5 stars 564 Reviews | | Included Components | Fosi Audio M04 | | Item Dimensions | 5.2 x 3.5 x 1.4 inches | | Item Weight | 450 g | | Item dimensions L x W x H | 5.2 x 3.5 x 1.4 inches | | Manufacturer | Fosi Audio | | Maximum Output Power | 100 watts | | Maximum Supply Voltage | 19 volts_of_direct_current | | Minimum Supply Voltage | 19 volts_of_direct_current | | Model | M04 | | Mounting Type | Freestanding | | Number of Channels | 1 | | Number of Items | 1 | | Output Power | 100 watts | | Part Number | M04 | | Specification Met | [Inf] Thd <= 0.04% and Frequency Range 20hz - 120hz | | Unit Count | 1 Count | | Voltage | 12 volts_of_direct_current | | Warranty Description | 18-month manufacturer | ## Product Details - **Item dimensions L x W x H:** 5.2 x 3.5 x 1.4 inches - **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 ## Images ![M04 - Image 1](https://m.media-amazon.com/images/I/51ghuLx4kZL.jpg) ## Questions & Answers **Q: Will this power up passive subwoofers ?** A: Yes, absolutely. That's the reason I bought it and it works just fine without spending a whole lot of money. **Q: How hot does this amp run? The unit I currently use is very hot to the touch even after a short while.** A: This thing seems cool no issues **Q: What is the input voltage range?** A: Not sure what your question is about. If you mean input power, it's spec'd. at 12-24 vdc. It comes with a power brick rated at 19 vdc, 4.47 amps. Input sensitivity is =< 280 mv... **Q: I have a Harman Kardon reciver with a single rca sub connection. What cables do i need to hook my sub to this amp and the amp to my reciever** A: You need 1/8 audio plug to RCA adapter .. ## Customer Reviews ### ⭐⭐⭐⭐⭐ perfect little amp to repurpose a passive htib sub *by M***L on September 4, 2026* 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. ### ⭐⭐⭐⭐⭐ Powerful little amp, perfect for converting dead subs into passive ones *by R***I on July 21, 2026* 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. ### ⭐⭐⭐⭐ Good quality and sound *by C***R on August 21, 2026* Works great clean sound lil under powered why 4 stars but for the value good unit good power. ## Frequently Bought Together - Fosi Audio M04 Subwoofer Amplifier for Home Theater Mono Channel Digital Class D Integrated Power Amp for Passive Speakers Subwoofer - FosPower RCA Y-Adapter (3 Feet), 1 RCA Male to 2 RCA Male Short Y Splitter Digital Stereo Audio Cable for Subwoofer, Home Theater, Hi-Fi - Dual Shielded | 24K Gold Plated - Tan QY 2RCA to 2RCA Cable 3Ft, Gold-Plated 2 RCA Male to 2 RCA Male Stereo Audio Cable for Home Theater, HDTV, Gaming Consoles, Hi-Fi Systems (3Ft/1M) --- ## Why Shop on Desertcart? - πŸ›’ **Trusted by 1.3+ Million Shoppers** β€” Serving international shoppers since 2016 - 🌍 **Shop Globally** β€” Access 737+ million products across 21 categories - πŸ’° **No Hidden Fees** β€” All customs, duties, and taxes included in the price - πŸ”„ **15-Day Free Returns** β€” Hassle-free returns (30 days for PRO members) - πŸ”’ **Secure Payments** β€” Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** β€” Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.nz/products/58115674-m04](https://www.desertcart.nz/products/58115674-m04) --- *Product available on Desertcart New Zealand* *Store origin: NZ* *Last updated: 2026-10-04*