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in article , Bret Ludwig
at wrote on 10/1/05 11:09 PM:

Jon Yaeger wrote:

al work-around?

Else would I be better selecting another device or topology?

Unless you are designing for nuke war-in which simply using tubes is
not enough, you have to make use of some very specific shielding and
grounding practices or small signal tubes will start losing
filaments-you would be far better off using solid state recitifiers.

Get a good book on building DC supplies that is simple and direct,
such as that bu the late Joe Carr. First build a good DC filtered A+/-
supply with either controlled warm-up time, foldback current limiting
for the steady state requirements of the tubes used, or both. Then
sequence your HT supply from the primary (line AC) supply for inrush
limiting. Easy and simple.

Derive your C- supply (you know what that is, right?) from the heater
LT side so you have it as soon as you have heater voltage. If you have
a D+ supply (an arcane term, so I will supply it-screen voltage) that
is separate it needs to come up simultaneously with or AFTER the B
supply.

Think of it like starting a jet engine-or Tony Montana's soliloquy
about, "First, you get the power..."

Thanks, Bret, that's all good general advice, but perhaps in my ignorance it
seems that your answer is somewhat peripheral to the question.

My interest in using these tubes is that they are reputed to produce the
smoothest rectification. Because the cathodes are indirectly heated, there
is an 11+ second warm-up time, which makes life easier on the cathodes
downstream. Solid state rectifiers have their advantages, but I want an
all-tube circuit here, EMP notwithstanding. With plenty of current
available but no active regulation.

You state that specific shielding is needed. Would that be different, say,
from a 5AR4, and if so, kindly elaborate . . . . .

This circuit will be using cathode bias, so C- supply considerations don't
apply. Also will have ultralinear outputs so the arcane D supply is also a
non-issue.

TIA,

Jon