I've been running this SC-35 for a month or so now, and have been quite pleased. I'm using it mostly for TV and music, through a pair of Dynaco A25s. My B+ is running comfortably at about 355V.
Now that things are settling down, I'm noticing some muddy sound in the ~300 Hz range, when running through my TV (Samsung 46a650). Sadly, my only real option for TV sound is to feed through a headphone port, which may be the cause of the problem, since my ipod sound a whole lot better. Even then, the problem really only shows up when I'm listening to music which is busy in that area (specifically, Air is tough to listen to).
I have plenty of headroom, since I rarely run it anywhere near the 100% volume setting, so I wouldn't mind cutting back the gain if it would clean up the sound.
Does anyone here have any ideas on why this one frequency would be bothersome? I've heard the ST35's downfall is it's tendency of favor one frequency. Could biasing be a problem? I've tried different tubes in all spots and haven't noticed a significant change.
I'm still new to tube amps, and my first guess would be that the headphone out on the TV is a bit too loud, pushing the amp into some kind of clipping, creating an abundance of harmonics.
I don't really have a good way to test the TV output, as I have no scope. If you all agree that the TV out is too loud, I may put together a stereo pad and see if that helps, otherwise, I'll just avoid the problem.
Thanks all for the help.