I put my heaviest tubes in one MA1 Silver, OTK 74-76's (yes, one set of tubes is physically heavier than the others, don't argue, the scale does not lie) and I put my non =C= Sovteks in the other amp.
Here is my first observation.
There appeared to be a slight shift of balance to the side with the =C='s. I then turned everything off, and switched the 6H13C's, obviously leaving the 6SN7's. This balance abnomoly followed the tubes. Everything moved slightly towards the speaker with the =C='s. This may be explained by my second observation.
My second observation is more important.
When I went really close to the =C='s tweeter, there was slightly more extension in the upper frequencies, I could hear more of the music. Female voices especially showed this extension, with ever so slightly more articulate, everything was more focused. It is this high frequency improvement that makes me only want higher numbered OTK Svetlana's.
The differences where sutle, but they where there. To my ears anyway.
Bill
