Just because the company switched from an au to an at doesn't mean that you can. I'd bet they changed something or determined that more gain was needed and made the modifications. As Hovland before you even consider it.
As far as lasting 1 year, these tubes should last 3000 to 5000 hours. Unless you are leaving it on 24/7, you should get many years out of these. Even if they are wearing out, they shouldn't get noisy so easily. Usually your dynamics will just flatten out?
As far as lasting 1 year, these tubes should last 3000 to 5000 hours. Unless you are leaving it on 24/7, you should get many years out of these. Even if they are wearing out, they shouldn't get noisy so easily. Usually your dynamics will just flatten out?