My Shuttlemax 9.2 is hissing like sid on the tube channel, but oddly, ( or not ? ) kicking in the compressor on my Zoom B3 increases this a lot. In fact i tried 4 different compressors on the Zoom to see if it was one in particular , but they all did it.
There's a lot less hissing sid on the FET channel. The hissing on the tube channel is loud enough to be annoying, and as said above, the compressor kicking it makes it even more so.
There's a guy on TB ( think its AgedDonkey or something ) who does Genz support and have read that he thinks this could be a dodgy valve. First trick to try was re-seating but that did nothing. Next is to replace it, which i think is next on the list. It has the stock Ruby 12AX7 Select in it right now.
I shall give Watford Valves a bell and see what he recommends - any body swapped there's out , perchance ?