Can too many components on one outlet affect the sound of an amp?

I am running a few amps, a receiver, tv and a few more components on the same outlet. I am using a power conditioner. My main issue is - I recently noticed that when I'm only running my McIntosh MC275, a pre-amp and a cd player, I seem to be getting better bass compared to having more components on. Is it just my imagination? Or is it possible? Everything is running on a 15 amp circuit.