The attenuator can replace the speaker cabinet. You can run the head without a cabinet connected if there is an attenuator (they have line out). A volume in the loop always need a cabinet connected to the amp.
The 1960 does not have master volume so I would not use the PS1.
What is it you want to do? Change/Delete Presets? There a several ways to "reset" the IPD. Different levels of reset. Tell me your problem and I will try and help you out.
Best Regards, Robert
Hello! I have had the exact same problem for a while. I have changed just about everything. New cables, shorter cables, outlets from other rooms, mains filters, isolation transformers, an alligator clip on the bridge to ground etc. The only thing that made a big difference was when I unconnected the monitor speaker cables from my audio interface. I also tried to run my pedals on battery only. Other than that I have just "accepted" it and for now I always run the macbook on battery and that solves it for me. Sorry I could not help more.