On 18 Dec 2003 at 10:19, David Stinson wrote: > Has anyone ever used a regulated DC supply for the BC-221 filaments? > Results worth the work? Hmmm....interesting thought. I have not found my BC-221 to be anything other than stable and accurate with AC on the filaments. However, there is a bit of hum in the headphones despite adequate filtering in the PS. Ken W7EKB