Are there any recognized problems between the h90 and the power attenuators, because the H90 works very poorly with the Boss Waza Tube Amp Expander, especially the distortions which are terrible to hear, whether in front or in the effects loop
The H90 works brilliantly with the TAE. Absolutely no problems.
Note I don’t use the effects loop in the TAE. Half of the H90 is switched by my ES8 to be anywhere in the chain before the amp input. The other half is in the loop of my amp. You could argue that my delays and reverbs are going into my power amp distortion but I don’t run the master high and it sounds great. If that worried me I would probably use the reverbs and delays in the TAE occasionally to free up effects on the H90.
Bear in mind that your amp will colour the tone in its own way. My set up sounds completely different through the full stack speakers compared to the TAE going via USB straight into the Mac and through my studio monitors and with cab emulations/IRs.