Audioengine D3 is a portable USB-stick micro DAC and headphones amplifier build for those looking for an instant audiophile quality upgrade to their Mac’s headphone output. The D3 plugs directly to the USB port and has a 3.5mm audio out to connect to music systems or to a headphones. It bypass your Mac’s internal audio and convert them using its high fidelity 24-bit digital-to-analog converter at up to 96kHz. With a build-in headphones amplifier, it can push all but the hardest-to-drive headphones. Audioengine D3 is priced at USD $189 and is as good as some DAC that cost much more.