Sometimes it's hard to sidestep quiet habits. I was laying out a pre, and in my haste decided to wire up the 5687 cathode follower faux pentode with AC heaters.The parts truck was late delivering my late-ordered parts for the DC supply, and I was impatient. I was quite suprised when it was quiet on AC. That's a first for a 5687 pre for me.
cheers,
Douglas