NJM386 Headphone Amplifier

This headphone amplifier circuit is based around the NJM386 audio amplifier IC manufactured by the New Japan Radio Corporation. The 386 designation may be familiar to you and remind you of the LM386, because both have identical pinout arrangements with gain and bypass options.

In comparison, their internal circuitry is very different with the NJM386 IC having a greater transistors count that is almost double that of LM386. I also find that the NJM version is also more stable and has better performance due to the internal circuitry. Interestingly, their price is almost the same at auction sites.

What makes this high-end headphone amplifier circuit unique is how the output is fed back to the inverting input which helps with improving the stability, thereby allowing for a wide range of load conditions. This IC will operate on as little as 4 V and accepts up to 12 V, and has an operating current rating of 3 mA, making it ideal for battery powered applications.

In this circuit, pins 1 and 8, for setting the gain to 200 are not used and instead we use the internally set gain of 20 which is sufficient for headphone amplifier applications. A huge advantage of this IC is that the output is internally biased thereby reducing the external component count.

Board Layout

Component List