Musical amp, part 2

[Tachikoma]

http://www.head-case.org/forums/headphone-amplification/7028-mysteriously-musical-amplifier-moth-300b-problem.html

Well, I'm hearing the same symptoms on my Stax T1S now. This amp has no output transformers so... what's going on here <.<

And no, its not just the new Shuguang CV181-Z that's doing this, the tube I was using before this was doing it too, albeit less audibly (probably because its only half the size).