In the never ending quest for better SQ, this HE-6 owner removed the two Mills 10 ohm resistors connected in parallel to the 8 ohm speaker taps of the auto-biasing BAT VK-55SE. There was absolutely no improvement whatsoever.
In fact, the opposite was the case. At least one tube in the left channel went microphonic and the center image "wandered". These traits became apparent almost immediately and lasted over the entire 7 minutes the amp was subjected to this impedance mismatch.
Needless to say, the Mills have been reinstalled and apparently no permanent damage was done. Once again enjoying the synergy of these cans with the BAT and the Calypso linestage.
In my amp driving the HE-6 I can definitely hear the change in sound with the resistors in now that I have my Wadia transport back working in a semi state (trying to find a new unobtainium laser).
Listening to Holy Cole- I can see clearly now- with the resistor the bass is stronger (I like the more solid thwack of the kick drum -Ben Webster at the REnaissance- Georgia on my mind and other cuts- Analogue Productions) and the sound stage is slightly collapsed, everything is a bit rounder and there is more sibilance and it is clearly evident in the first two lines. So without the resistors the sound is more transparent, almost no sibilance and the piano has more decay time and the most important more air around the instruments. Tho I must admit on some (CD's) recordings the resistors do take the edge off more so when listening to Flac files off my computer. So a real quagmire to decide.
And I am surprised that the BAT had problems without the resistors- tho the 6C33B tubes tend to be very finicky.