Low power amplifier from National Semiconductor LM386.
At first glance, the amplifier on this chip is a competitor to PAM8403, and even in terms of power the LM386 is slightly inferior, but this comparison will not be correct, because Amplifiers work in different classes. This is class AB, and PAM8403 is class D, with all that it implies ...
The board has an output directly for jack3.5 headphones.
The board is also equipped with KF2510 connectors:
3pin - signal input
3pin - amplified signal output
2pin - power + micro USB power

Subjectively, the amplifier unexpectedly pleased with the quality when playing in the headphones. Easily and naturally swings any headphones even with micro USB 5V power supply.
Fairly clear and bright treble and dense bass.
Ideal if you do not have enough power output for your headphones.

Includes 2 racks with nuts and M2 bolts and a plug for connecting

In addition, the amplifier can be equipped with a cable for connecting the input signal with jack3.5 and KF2510 plugs at the ends. Cable length 90cm. Included with this cable and when powered via micro USB, the amplifier is completely ready for use with headphones and does not require any manipulation of the instrument.

Measurements
Supply voltage DC	12V
Load resistance	68 Ohm
Maximum power, W	0,6
Testing power, W	0,04
Frequency response (from 40 Hz to 15 kHz), dB	+0.07, +0.01
Noise level, dB (A)	-93,7
Dynamic range, dB (A)	93,7
THD, %	0,1330
THD + Noise, dB (A)	-55,2
IMD + Noise, %	0,1300
Stereo crosstalk, dB	-47,2
IMD at 10 kHz, %	0,1230
Measurement Page
General characteristics
Amplifier class	AB
Built-in protection	Yes
Chip	LM386
Gain	20
Module size LxWxH, mm	50x25x25
Number of channels	stereo
Supply voltage maximum (constant) DC	12V
Supply voltage minimum (constant) DC	4,5V
Weight, kg	0,025