Apologies if someone else has mentioned this...
AI notes that the L1 inverts phase and you should swap your + and - cable connections at the speaker.
I have had an L1 for many years; this makes a big difference. If you were nice and smooth with the Rotel preamp (which almost for sure doesn't invert phase) then you would swap + and - to get nice and smooth with the L1.
Because I have no idea how much experience you have with stereo fiddling I'll just say equipment off, unplugged and give it time to discharge before connecting/reconnecting any cables/wires or opening anything up to take tubes out to clean pins/sockets.
AI notes that the L1 inverts phase and you should swap your + and - cable connections at the speaker.
I have had an L1 for many years; this makes a big difference. If you were nice and smooth with the Rotel preamp (which almost for sure doesn't invert phase) then you would swap + and - to get nice and smooth with the L1.
Because I have no idea how much experience you have with stereo fiddling I'll just say equipment off, unplugged and give it time to discharge before connecting/reconnecting any cables/wires or opening anything up to take tubes out to clean pins/sockets.