Can I use a universal remote with my A5+s or HD6s?

Both the A5+ and the HD6 are not officially supported by any universal remotes. It is possible to use a third party remote, but that remote needs to support IR learning.  This is a feature that allows a universal remote to learn commands directly from the remote we supply. The Logitech Harmony remote, for example, is supported by the A5+s/HD6s.