I have a Muff’n and a Hot Tubes. In general, both are semi noisy when cranked but here are some ideas for you to try.

1. Take off the cover over the tubes and makes sure the screw in between the two tubes is tight! This ground screw being loose can cause all sorts of issues.

2. In the Muff’n it should have 12AY7 tubes (I saw you say 12AX7 above somewhere), just fyi though I know you probably know this.

3. I remember talking to another guy who had a noisy tube pedal and it can be due to the power supply/plug in being so close to the tubes in the pedal. He removed the jack from the side and then ran it out the bottom of the pedal instead so it was further from the tubes (if you do this I would suggest just going ahead and hard wiring it!)

These are a few ideas. What effects do you use and what order do you have them in? I actually have a Behringer Tube Monster that I run at the end of my chain that has a built in nose gate so I don’t have these issues but when just using the pedals by themselves they do get quite noisy! Good luck!