You can but something is going to fry. Your amp will be feeding your loudspeakers and your amp. Not designed to do that.
Using one set of speakers with AV receiver and Lamp amplifier
I have NAD T778 setup for my home theater with Vienna Acoustics bookshelf speakers. I want to buy two floorstanding B&W 803 speakers and mid range two channel tube amplifier. Can I switch floorstanding speakers from tube amplifier to NAD and vice versa if I use secondary posts on the B&W speakers. Thank you in advance.