Line 6 LowDown LD-15 - Manual (Page 11)

Saving
To store your own “snapshot” of all knob positions
(except Master Volume), press and hold the current
model button for two seconds. The LED flashes twice
when the save is complete.
CD/MP3
Connect a CD player, MP3 player, drum machine or
other device here, and you’ll hear it from LowDown’s
speaker or headphone output. Very handy for jamming
along! The instrument input must have a plug inserted
to allow the input from the CD/MP3 player to be
heard. Use the output volume control on the connected
device to set its level.
Phones
Connect your stereo headphones here to listen to your
bass and/or your favorite CD and jam along for working
on your favorite licks. Plugging in headphones disables
your speaker output.