This is a miniature 0.7W amplifier with adjustable bass boost, gain, and volume controls. Uses 1/8" (3.5mm) headphone jacks on the input and output. Powered by USB or 9v (4-12 VDC, max of 15 VDC). I designed it to use film capacitors and Nichicon audio grade electrolytic capacitors wherever possible in order to preserve the signal and reduce noise. An isolated power supply such as a battery is likely the best option for minimal noise but power output will decrease as the voltage drops. The USB port is optional and only there for the convinence of power but it is the minimum voltage in order for the amplifier to function.
Parts list for Digi-Key is attached below in an image and excel file.