Originally Posted by bruce108
On the Telefunken EK90s. At first, mine were not so much treble-forward as bass-light and overall a bit thin-sounding, if refined and musical (EF95). But after 40-50 hrs they became a dramatically different tube, excellent bass in quantity and quality and well-balanced through the FR. Here's the thing: they warm up more slowly than any of my other tubes, taking an hour or so to reach their optimum. Any technical reason for this?
So, I'm good for yet another 50 hour burn-in huh...? The things we do for music...
While I definitely noticed that they improve after a bit of warm-up time -most tubes do to some extent- I have haven't noticed anything as dramatic as a whole hour. I guess it's possible though, I remember thinking that even my old stock M8100 needed 15-20 minutes to sound their best.
Again, I find it pretty difficult to directly compare these heptodes together, and find myself forced to compare "lasting impressions" instead, which I usually do fairly well, but isn't exactly a fail-safe method. The fact that everyone here has different impressions of the Telefunken EH900S (regardless of gold pins, as I just saw that A11's have them and gibosi's don't, yet same comments) does strike me as odd -as in my impressions being off.
I had tested and burnt-in the Tele EH900S with the 1-7 strap until the very end, when I tried them unstrapped and concluded that was best; so, that probably influenced my impressions in and of itself (the tubes really were quite "in your face" when strapped, and I'm now pretty sure that needed way more than the 20 hours of burn-in I gave them anyway; most premium tubes do apparently). The fact that everyone says the EH900S (6BY6) and EK90 (6BE6) Telefunken are similar makes me think that they, indeed, are -which would make perfect sense as they look similar anyway- and that I just need to eventually throw the EH900S back in the sockets to confirm that. I will, at some point, after the 40h burn-in...
I do like that hard-hitting bass (not strong, just intense and punchy) on the Tele EK90 though. I still have some serious comparing to do with all those other German heptodes. Another German shootout?