r2r

Cayin RU6

Cayin RU6 is the first, portable R-2R dongle. It features a balanced output, and it costs $249.

Hifiman Deva Pro

Hifiman Deva Pro is an open-back, planar-magnetic headphone that can be used both wired and via Bluetooth, thanks to its Bluemini R2R module. It is priced at $329.