Integrated tube amp has no bass Cayin A50T

Hi folks,

So I just bought a Cayin A50T (used, but well looked after), I have set it up at home and found that there is extremely little low end. it's very very noticeable.

Im powering Energy pro series 3.5 bookshelf speakers so nothing too crazy.

I'm very new to this hobby so I would greatly appreciate some help. I doubt the seller will take the amp back.

Thanks in advance for your help!

Nick