The Dragonfly Red is stated to provide a maximum output level of 2.1 volts, and it has a low enough output impedance to drive headphones. So it shouldn’t have any problem driving a line-level input of most preamps in most systems.
You’ll just need a cable providing a 3.5 millimeter stereo plug at one end and a pair of RCA plugs at the other end. Such as many of the ones shown on the following page. (But be sure to carefully read the description of whichever of them you may consider, as at least a couple of them combine left and right channels into mono):
https://www.bhphotovideo.com/c/buy/Mini-To-RCA-Cables/ci/4244/N/3992462199
Regards,
-- Al
You’ll just need a cable providing a 3.5 millimeter stereo plug at one end and a pair of RCA plugs at the other end. Such as many of the ones shown on the following page. (But be sure to carefully read the description of whichever of them you may consider, as at least a couple of them combine left and right channels into mono):
https://www.bhphotovideo.com/c/buy/Mini-To-RCA-Cables/ci/4244/N/3992462199
Regards,
-- Al