"Gregg" wrote

When talking about regulated DC for heaters, CC makes more sense
to me
than CV - it is even more gentle to the heaters :-)

Tom

Yes, I remember that from your GeeK ZonE posts. I'll have to try
that!

Also more efficient cos regulator drop is lower proportion of
voltage. And you can use thinner wire.

But all the heaters end up at different potentials, and all valves
in the chain must have same heater current requirements. This latter
point is a fundamental problem, because requirements tend to be for
increasing perveance valves from input to output. Higher perveance
tends to mean higher heater current.

Also heater current spec is not as reliable as voltage spec. Morgan
Jones did some testing on this. He advocates series supply but warns
that you need to be careful. Is the current rating of ECC88 really
different from E88CC, for example?

So I use series (I reg) for the four power valves, and parallel (V
reg) for the little chappies. Both are easily made switchable to
half power in standby if adjustable regs are used.

cheers, Ian