Lowering HT voltage on RS124 clone, or not?

[Winston OBoogie]

Yep. I don't know if it really is 15 - 20dB compression but, like you, I think this thing really is made for that.

An ECC189 tube giving you a bit more headroom there before you overload (cut off) the thing.

 

[abbey road d enfer]

Don't worry so much about the absolute voltages. Remember that tube equipment most of the times was built for quite variable mains voltage, sometimes with 20% variations.
The important thing is making sure the voltages are balanced where they need to be (push-pull stages in particular).

 

[Winston OBoogie]

... Irrelevant. ...