ZK-MT21 2.1 Channel Bluetooth Subwoofer Amplifier Board Module

Our review of the ZK-MT21 2.1 Channel Bluetooth Subwoofer Amplifier Board finds it best suited for DIY speaker builders and hobbyists who need a compact, highpower board with flexible tone control. The single biggest reason to buy is straightforward: it packs true 2 x 50W stereo plus a 100W subwoofer output in a palmsized PCB with Bluetooth 5.0 and AUX input, making it easy to upgrade bookshelf or custom enclosures without a bulky receiver. Installers will appreciate the builtin protections and adjustable treble and bass for fine tuning.

Key Features

• 2.1 Channel Output: Delivers 2 x 50W to left/right channels plus a 100W subwoofer channel for clear stereo and impactful low end.
• Bluetooth 5.0 and AUX: Provides fast, stable wireless streaming and a wired AUX option so it works with phones, media players, and legacy sources.
• Adjustable Tone and Volume: Independent treble, bass, frequency and volume controls let the user tailor sound for different enclosures and speaker sizes.
• Protection Circuits: Antireverse connection, overheating, overcurrent and short circuit protection protect the board and connected drivers during setup and use.
• Compact and Compatible: Small 93 x 90 x 22mm PCB and support for 15-100W, 4-8 ohm speakers make it a flexible dropin for many DIY projects.
• Complete Kit: Ships with cover, bottom plate, adapter, screws and knob caps to simplify installation and finishing.

Who It's For

The ZK-MT21 is ideal for DIY audio enthusiasts building custom 2.1 bookshelf systems, small powered multimedia speakers, or refurbishing vintage cabinets where a compact amplifier with a sub output is required. Its tone controls and protection features make it practical for makers who want adjustability without external DSP or complex cabling.

It is less suited to users who need network streaming, multiroom synchronization, or an integrated display and full remote control; for those use cases a full AV receiver or streaming amplifier would be a better choice.

Pros & Cons

Pros

• Compact 2.1 design with a strong 100W sub output for good bass extension in small enclosures.
• Bluetooth 5.0 ensures a stable wireless connection alongside AUX for wired sources.
• Builtin protections reduce the risk of damage from wiring mistakes or thermal stress during testing.

Cons

• No builtin network streaming, remote, or display, so control is basic compared with full receivers.

Specifications

Model	ZK-MT21
Channels	2.1 Channels
Output Power	2 x 50W + 100W subwoofer
Bluetooth	BT 5.0
Inputs	Bluetooth and AUX (support AUX+BT)
Speaker Compatibility	15-100W, 4-8 ohm speakers
Protection	Antireverse, overheating, overcurrent, short circuit

Our Verdict

The ZK-MT21 is a compact, wellprotected 2.1 amplifier board that offers significant value for DIY builders who want Bluetooth streaming plus a dedicated subwoofer output. With flexible tone controls and a full accessory kit, it is a practical choice when space is limited and performance matters, though those wanting advanced streaming features should look elsewhere.

Frequently Asked Questions

Can this board drive passive subwoofers?
Yes, it provides a dedicated 100W subwoofer output suitable for passive subwoofers rated in the compatible power and impedance ranges.

What power supply range is required?
The board runs on DC12-24V as supplied and listed, so choose an adapter that matches the voltage and current needs of your speaker load.

Does it support tone adjustment?
Yes, it includes adjustable frequency, treble, bass and volume controls for tuning the system.