If the AMP1's MASTER control is turned up a bit and the AMP1 is subjected to mechanical shock (e.g. knocking on the housing or using the NoiseGate switch on the side of the case), you may hear a rattling noise. This noise comes from the tube and it is perfectly normal, because tubes are mechanically more fragile than transistors. Compared to traditional tubes, the Nanotube is even relatively insensitive.

If the rattling is actually bothering you, you can try turning down the MASTER control a little and making up for the lost volume by turning up the CLEAN VOLUME and the OVERDRIVE MASTER. But let's be honest, as tube amp players we don't really mind the tube ringing. That's how tubes are! 😉