Attenuator for high RMS signal tests

Hello everybody, this is my first post on the QA forum about my great QA401 analyzer.
I’m an italian audio tube DIYer and, although I had been told that it was not created to be used for high voltage devices, I bought it and carefully used it… cap coupled. No problems so far. I’ve been careful enough not to fry it. Yet.
I need to test signals over 100V RMS (an 845 amp will soon follow). What’s the best path to follow?
Thank you in advance!

Hi @Fralippo, take a look at the link below. it walks through building a load and including an attenuator. And then feel free to post your design if you want some eyes looking at it!