I actually succeeded in getting a friend to adopt a DSP in his tube/turntable system

Because - it works - and he admits that. But he still loves to tinker with the tuning of his turntable.
Also got two others to include an old style equalizer in their turntable system, to counter their troubled sound - also because - it was not digital - you know - the enemy - the dark side

Usually, if you can convince them, that you only alter the bass, and don't interfere with the midrange/tweeter - they soften up
You have got to leave them just a little "magic", so there's something to fiddle with