Build Your Own Hi-Fi Bluetooth Amp for the Price of a Sandwich

There are plenty of audio amplification modules out there that you can buy for a few dollars to add sound to your electronics projects. Many of them even offer Bluetooth connectivity. But one thing these modules do not offer is high-quality audio output. They get the job done for most applications, but if you are building a smart speaker or other device where sound quality really matters, you need to look elsewhere.

If you don’t mind putting in a little elbow grease, Amply is worth checking out. It is a high-quality audio amplifier and Bluetooth receiver that can be built from about $10 worth of widely available parts. For another few dollars, you can order a custom PCB to make the circuit more reliable and durable.

Amply delivers up to 2×10 watts into 8-ohm speakers while running from a standard USB-C power adapter. The project was created to address a common frustration among electronics hobbyists: inexpensive Bluetooth amplifier boards are easy to find, but few of them offer genuinely clean and balanced audio reproduction.

The circuit is built around the classic NE5532 operational amplifier, a decades-old chip that remains popular in audio applications because of its low noise and excellent linearity. According to the project documentation, the amplifier achieves total harmonic distortion figures below 0.015%, with simulations showing performance as low as 0.009% at full output power. The circuit also includes a gentle high-frequency roll-off intended to soften harshness when paired with small desktop speakers.

Rather than relying on a modern Class D amplifier chip, Amply uses a more traditional Class AB topology with discrete output transistors arranged in Sziklai pairs. This approach increases complexity slightly, but it offers improved linearity and avoids some of the switching artifacts associated with cheaper amplifier modules. Biasing minimizes crossover distortion while keeping idle power consumption low enough that heatsinks are often unnecessary when driving 8-ohm speakers.

The amplifier operates from a single positive supply rail, simplifying construction and allowing it to work directly from USB-C Power Delivery adapters. A low-cost USB-PD trigger board negotiates voltages of 9 volts or higher from compatible chargers. The design also supports conventional DC power supplies ranging from 9 to 30 volts.

Bluetooth connectivity is handled by an inexpensive MH-M18 receiver module, chosen partly because it omits the loud voice prompts that plague many budget Bluetooth boards. Builders who prefer wired audio can omit the wireless circuitry entirely, along with the onboard 5-volt regulator.

The project includes PCB files for a custom 100×100 mm circuit board and a matching 3D-printable enclosure. The PCB design incorporates a solid ground plane to reduce hum and interference, helping the amplifier maintain clean audio performance despite its modest cost. Full details are available in the project write-up.