Hey guys,
I have an update to my posts #54 & #73. Regarding the hum issue, I had reported that with the original tubes there was a faint hum after 12 o'clock. It was very faint but nonetheless present. After trying to roll tubes on my own I found out that after two different pairs of 6AK5s the humming was even worse with those new tubes. The fact is that those new tubes were not matched. During that time, I have had the A1 for close to two months now, I also discovered that there was crosstalk between the two inputs of the A1. This last thing was just by chance, I wanted to check the sound of two different sources playing the same program, to my chagrin y noticed that around 1 o'clock I could hear the other channel if I paused the one I was listening to. At that point I submitted a ticket to Ryan, who as usual was very prompt in responding and taking charge of the issue. For starters, he offered to send me a matched pair of Tung-Sol 6AK5s to see if those tubes will not hum on my unit. The issue of the crosstalk was something unexpected and he had his engineer check on it, it was suspected it was coming from a ground connection in one of the resistors in the input switch, if that was the case new resistor values would need to be found to attenuate the XT. We left it at that with Ryan's assurance that as soon as the engineers found the problem he will let me know how to fix it.
Then Ryan's Tung-Sol 6AK5s arrived, I put them in and, what do you know, ALL ISSUES WERE FIXED. With these new tubes there is no hum even at 4 o'clock, my speakers are 90db, and through my Optimus LV-20 headphones (made by Koss, actually very good) I could not hear hum either, maybe a hint of ripple noise at insane volumes with no program playing.
Ryan told me that the A1 is very picky in its acceptance of tubes, they definitely need to be closely matched. I suspect the problems I was hearing arose from the stock tubes and not from the circuit itself, I am far from an expert, but my careful observations point to that direction. My advice is that if anyone wants to roll tubes, make sure they are matched.
Once again I want to commend Ryan for his outstanding commitment to his product and his uncompromising willingness to resolve issues as they arise.