I'm hardly an expert on this, but in debates over the merits of various
rectifier tubes for my phono stage power supply, one well informed industry
person brought up the topic of voltage drop or sag. I know anecdotally
about this from the musical instrument amplifier world- guitarists often want
a tube that that ultimately compresses when pushed, to give it a distinct
(albeit distorted) sound. One of the differences, for example, between a re-
creation Marshall guitar amp that has solid state rectification and one that
still uses a tube. For hi-fi, you don't want that. :)
In any event, some of the differences in sound may be attributable to such
characteristics. Differences in circuit design as it applies to this are beyond
my pay grade. There are various sources for rectifier tube data sheets free
on the Net. You should consult the manufacturer of your equipment too if
there are questions.
From what I have been able to determine the NOS Mullard I am using (first
series fat base) has different voltage characteristics than other vintage
Mullard tubes.
Also, don't assume that because the tubes of different designations can be
swapped, that they are appropriate for your particular device. Again,
beyond my competence, but a little due diligence on various tube
charactistics may be advisable, as well as consulting with your
manufacturer.
If someone else here has more knowledge on the last subject, they are
welcome to chime in.
