Hi Eric,
-
As your probably finding out, the traditional 572 and later
572b are similar and sometimes called "upgraded" 811a
type tubes.
-
re the 572b...
They handle higher plate voltages and have much more
plate dissipation... about double from memory and the
various data sheets. .
-
In RF Amplifiers...
Unless you are a serious "lock to talk" type, their
installation in an original equipped 811a chassis is not
going to net a great deal. There are good and bad points
for doing said, different Cin and Cout values might
require tuned circuit tweaking.
You should also revisit the power supply ratings to
help determine if it's just plain worth it.
572b tubes tend to be pricey... 811a are still found NOS
for under $20 each, quite the bargain.
The Svetlana fun starts when you order, be advised they
make (or used to) a few different versions of the 572b,
one or more has the plate connection at the base. There
were some issues about early production run problems
that were reported worked out.
I would hope any decent quality RF rated 572b would
work, just make sure to get the right type and external
plate connection (at the top). People have purchased
the audio tube for use in RF and wondered "where the
top of the tube went..."
If you have an existing amplifier with 572b's on board,
it's probably best to use replacement 572b's when
replacement is required... pretty obvious.
IMO, it is not worth the trouble, nor cost effective to
replace original equipment - 811a tubes with 572b
tubes unless you need the duty cycle or just have
the money to burn.
You can't get a lot more out of the power supply by
changing tubes if it's already at or near its limits...
cheers
skipp
--------- Forwarded message ----------
From: EVonvaltie@aol.com
Does anyone have any REAL information which shows any significant
difference
between the 811A and the SV-572. I have looked at the curves for both
tubes
and the curves quack like the same duck to me.
Is this really another tube PR scam like the ones tube mfrs. have been
running on the audio business for years?
Eric von Valtier K8LV
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