"Hi Stew, glad to hear the hissing sound was not present last night. In my experience, tube noise can be intermittent - from one listening session to another. It can be a little unnerving. I've made a practice of taking a deep breath, powering down the system, and coming back a few hours later or the next day. Sometimes the noise completely disappears, sometimes not. I once lived with a really irritating noise in a driver stage tube of my amplifier for a couple of weeks, then it completely disappeared and never came back. What you're hearing is more likely an intermittent problem with a tube than a problem with the unit itself."
I had the same experience with my Callisto.
From the beginning I had a noise ( hiss ), but after some hours of tube burning it went away ( after a few days of use. Possible, that one or the other tube can be very sensitive at the beginning.)
Later I ordered NOS tubes and these worked fine from the very first moment.
I had the same experience with my Callisto.
From the beginning I had a noise ( hiss ), but after some hours of tube burning it went away ( after a few days of use. Possible, that one or the other tube can be very sensitive at the beginning.)
Later I ordered NOS tubes and these worked fine from the very first moment.