Connect a pair of passive speakers and stream music from a compatible phone, or use the 3.5mm AUX input for wired audio. The ZK-502MT combines a compact Class-D stereo amplifier with separate bass, treble and volume controls for desktop, bookshelf and workshop audio projects.
50W + 50W*
Advertised stereo output
Bluetooth 5.0 + AUX
Wireless or wired audio
4–8Ω speakers
One passive speaker per channel
Bass · Treble · Volume
Three onboard controls
*Actual output depends on power-supply voltage, speaker impedance, cooling and distortion. The advertised figure is not a guaranteed continuous output in every setup.
Before you buy: this is a DIY amplifier kit. Fit the supplied plates and knobs, then connect your own power supply and speakers. It has two stereo outputs; choose a 2.1-channel board if you need a separate subwoofer channel.
Included in the box
- ZK-502MT amplifier board and heatsink
- Three control knobs
- Top and bottom protective plates
- Mounting screws and spacers
- Screwdriver and DC connector adapter
Customer assembly required. Ensure the heatsink is correctly fitted before use.
What you need separately
- One suitable regulated DC power supply
- Two 4–8Ω passive speakers
- Speaker wire and suitable DC wiring
- Speaker enclosures for bare drivers
- AUX cable if using wired audio
The included DC connector adapter is a wiring connector, not a power supply.
Choose your power supply
Recommended: 24V 5A regulated SMPS. Provides more output headroom for your stereo build.
View 24V 5A supply.
Alternative: 12V 10A regulated SMPS. Suitable when lower maximum output is sufficient.
View 12V 10A supply.
RoboGears has checked operation with both options. Choose one supply. These industrial SMPS units require mains wiring by a competent installer; they are not plug-and-play wall adapters.
Technical specifications
| Model / SKU |
ZK-502MT / 1049410
Listing reference: CA-502MT / ZK-502MT |
| Amplifier |
Class-D, 2.0-channel stereo; left and right outputs |
| Advertised output |
50W + 50W, subject to operating conditions* |
| Audio inputs |
Bluetooth 5.0 and 3.5mm AUX |
| DC input |
9–24V regulated DC; maximum 24V |
| DC socket |
5.5 × 2.5mm; check polarity on the actual board |
| Speaker load |
4–8Ω passive speaker per channel |
| Controls |
Bass, treble and master volume |
| HSN |
85437099 |
Assembly & wiring guide
- Disconnect power. Identify DC polarity and the actual L+/L− and R+/R− markings.
- Fit the hardware. Ensure correct heatsink contact, fit plates and spacers without shorting the PCB, then fit the three knobs.
- Connect speakers. Connect one 4–8Ω passive speaker to each output pair. Remove stray copper strands.
- Check the supply. Verify voltage and polarity before connection. Use one regulated DC supply and do not exceed 24V.
- Start at low volume. Set bass and treble near the middle, connect Bluetooth or AUX, then increase volume gradually.
Wiring essentials: keep speaker-negative terminals separate from each other and from DC ground. Do not bridge the outputs. Use wires and connectors rated for the actual current.
For an industrial SMPS, provide protective earth, covered mains terminals, strain relief and ventilation. Disconnect mains before working on wiring.
Troubleshooting & engineering tips
- No sound: check supply voltage/polarity, speaker connections and source volume. Try a known working AUX source.
- Bluetooth pairing: disconnect previously paired devices nearby, move closer and select the name broadcast by the actual board.
- Distortion or cutouts: reduce volume and bass boost. Check for shorts, voltage sag, loads below 4Ω and restricted heatsink airflow.
- AUX hum: use a short shielded cable and route it away from power wiring. Never remove protective earth.
RoboGears engineering tip: use short, suitably thick DC leads and a speaker enclosure suited to your drivers. Measure the actual board before preparing an enclosure or drilling template.
Optional woofer drivers for custom speaker builds
The Belson 8-inch 4Ω 50W woofer is an optional driver for a custom speaker project. Use one per stereo channel.
It is a woofer rather than a complete full-range speaker. For balanced full-range sound, use a suitable speaker system or design an appropriate enclosure, tweeter and crossover combination. Keep the complete speaker load within 4–8Ω.
Buying questions
Does it include a power supply or speakers?
No. You receive the amplifier kit and the assembly accessories listed above. Power supply, speakers and hookup wires are purchased separately.
Which speakers can I connect?
Connect one 4–8Ω passive speaker to each channel. Choose suitable power handling for your intended listening level. Do not connect two 4Ω speakers in parallel on one channel, as this creates a 2Ω load.
Should I choose 24V 5A or 12V 10A?
Choose 24V 5A for greater maximum output headroom. The 12V 10A option works at lower output. Although both supplies are rated 120W DC, supply voltage limits how much voltage the amplifier can deliver to the speakers.
Will it deliver 50W + 50W in every setup?
No. This is the advertised output figure. Actual audio power depends on supply voltage, speaker impedance, cooling and distortion. Functional testing with the two supplies is not a measured continuous-power test.
Can I use it for a separate subwoofer channel?
The ZK-502MT has two stereo outputs and no dedicated subwoofer channel or subwoofer-frequency control. Choose a 2.1-channel amplifier if you need left, right and separately controlled subwoofer outputs. Do not bridge this board’s outputs.
Is it ready to use out of the box?
Basic assembly is required to fit the supplied plates and knobs. Ensure the heatsink is correctly fitted, then connect a suitable power supply and speakers. The stock DC socket is 5.5 × 2.5mm.
