New happening on the converted head to combo... Once in the cabinet, and just inches from the raging V30 speaker, I started to hear a rattle on certain notes. At first I thought it was something near the amp, but the more I traced, the more it became clear the sound was originating from inside the rear of the amp. I started with the preamp tube spring coves; a common culprit. But removing the covers and putting pressure on the tube produced no change. In case you’ve never chased a rattle like this, it’s comical to watch, but not fun to do. You’re trying to hold a guitar, fingering a note on a particular fret location because that’s where the ring happens, and it only happens for a second or two! There is never anyone around to assist when this happens. So trying not to bash my brand new, beautiful, most expensive guitar I’ve ever bought on hard things in the area, picking the note just right while contorting as needed to quickly reach inside an amp with scorching hot tubes everywhere, must have been quite the funny sight. I finally found that the power tube closest to the speaker would resonate at certain frequencies. Nothing affecting the sound of the tube... just an annoying metallic rattle that was audible on the outside. Touching it stopped the sound. These are German-made Siemens tubes, so it wasn’t poorly made innards rattling around. I’d seen people put o-rings on tubes until they looked like the Michelin Man to dampen vibration. Checking around, my old friends at Eurotubes had a more substantial, square section ring that they said would just take one per tube to dampen sympathetic vibrations. I received the dampers very quickly after ordering via Reverb, and worked one over each tube. With the amp up loud, the tubes were dead quiet. I’ve had this issue on other combo amps, such as my Road King II, so I’m going to add a selection of these for pre/power tube sizes to my tool kit for the future. I thought I’d share in case anyone else experiences this issue and needs a good quality product to fix it. The HXDA Experience continues!