At Toms suggestion, I've tried running the Air Tight direct from the Cary 303/300 CDP once again--this time with more interesting results. It's not as brittle and hashy sounding as when I tried it before--perhaps the contribution of all my tube-rolling (in both amp and CDP)--and there is more clarity and less distortion of some kind, but there is also a definite tip up within a certain treble range. The information comes through much cleaner and, thus, I can hear what's tipped up. I'm sure it's that impedance drop in my Sonus Faber Grand Piano Home speakers below 4 ohms in the 4kHz-20kHz range.
At the suggestion of another member from another thread, I lowered the bias-settings on the Air Tight by two measure markers. He suggested lowering the bias to improve sound, particularly relating to the Air Tight's leanness and tone of being "tipped-up," as that's been his experience with his Air Tight ATM-2. He reported that, when he tube-rolled his pre, a Wavelength, the character of the ATM-2 would change, brighten in tone, and sound "tipped up and leaner." This has been my experience whatever the tubes in either pre or amp, actually, though some are better than others.
Well, I lowered the bias-setting by about two measures and the choral music I was playing was immediately slightly better--more resolving. As I listened further, I could tell there was more inner detail in the soundstage and that the voices themselves were more easily separable, creating different polyphonic lines (as they should), and coming together more cleanly in coherent harmonies (again, as they should).
Overall, judging by a handful of CDs played with the bias lowered and the CDP running direct in to the Air Tight, this results in a cleaner choral sound. And a very sweet, clear, and fast orchestral sound too.
