I'm not sure I like the HD650 more with the Amperex tubes. They aren't as crisp sounding as the GEs, though they are more revealing somehow? At least on my DT880. But there were some songs that I listened to on my HD650 last night where I was listening for one specific part in a song that is a little hard to hear, and I swear it was smoothed right over. Like it wasn't even there. Vocals didn't really seem any better, either. I do like the sound on my DT880 but it will take some getting used to with my HD650.
That statement is quite nebulous. What are they? Where were they made? Era? Getters?