I too have the same problem with the HUM issues described above with the Raleigh Audio Line stage preamp. This is a fully balanced output transformer coupled preamp but with my V-5x it gives a very low level hum. At the listing position its not audible but distinct few feet away. Initially I was blaming the preamp and tried all grounding schemes but it was the amp that was causing this HUM.
Other than this issue, the V5x is a great amp, very musical.
Other than this issue, the V5x is a great amp, very musical.