How can I add a 1.5ms time delay (not echo) to one channel?

[steve]

You can do that with this “Echo” effect: https://forum.audacityteam.org/t/new-plug-in-stereo-echo/15997/1

Set the left and right delay times as you want them.
Set “Feedback” to 0%.
Set “Effect Mix” to 100%.

Installation instructions are here: http://wiki.audacityteam.org/wiki/Download_Nyquist_Plug-ins#Installing_Plug-ins