Acceptable level of hum at max volume?

so i am noticing a faint hum when i set my amp to full volume. not sure if it's been there all along but i was tinkering around and noticed it. here is my setup: rega p3-24 w/ttpsu and herbie mat into jolida jd 9 into decware mini torii. if i switch the mini torii to the second input via the switch i get no hum, but when i switch back to the phono i can hear it. mind you this is at FULL VOLUME. my question is, is there an acceptable level of hum at these outrageous volumes. it's not present in the music at normal or even loud listening levels it's just something i noticed while dickering around. i've tried all the usual solutions to eliminating hum like cheater plugs and moving components and swapping cables. i even have a line conditioner. what say you enthusiasts?