Best cable placement

In my experience, it all depends on the synergy. In most cases in my system(and different variations of it), the best cable made the biggest difference between preamp and amp. But because it can also reveal the shortcomings upstream, experiment and hear for yourself what it does and where it sounds best. 

OP…There’s no right or wrong way to do it. It’s what creates better synergy and sounds best to you.

Here’s an example…

Acoustic Zen Matrix Ref II vs Silver Ref II. Or Acoustic Zen Silver Ref II vs Acoustic Zen Absolute Copper. I am talking about same make cables here. In both cases the Silver Ref sounded best between source and preamp. And it is not because the Silver Ref II is a better cable than the Matrix or the Absolute. It is because in that configuration in my system that was the best synergy. Having the Silver between preamp and amp was too hot. In both cases the copper set balanced out what tge silver had to offer and made the best out of it. So just experiment and go by what sounds best to you and hit us up with your findings