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[Joseph Meditz]

In studying schematics I see CKTs with filament voltages of 6V for the
signal path tubes while the rectifier's filament voltage is 5 V. Why is
it that the filament voltage of the rectifier differs from that of the
other tubes especially since rectifiers with 6V filaments are
available?

Joe

[Phil Allison]

"Joseph Meditz"

[Joseph Meditz]

Thank you very much Phil.

Joe

[Guest]

The first tubes in consumer applications were made with 6.3 or 12.6
volt heaters or filaments because that was the nominal voltage of a 3
or 6 cell lead acid battery. They were battery radios that needed two
batteries, an "A" supply for filament voltage (which was often a car
battery) and a B supply for the plate voltage. When radios that ran on
AC voltage came out they had 2.5 volt filaments, as that was quieter.
The rectifiers had a separate winding and were 5 volt filaments (no
heater/cathode) as that way the transformer manufacturers could put on
windings that could be seriesed for a 5 volt center tapped winding or
used separately-or if bifilar wound, in parallel-for the 2.5 volt
supply.

6.3 volt heater cathode rectifiers have specially insulated heaters so
a large voltage difference is OK. But by the time they were
introduced, the 5 volt rectifier tube had been the standard for 25
years and tube rectifiers were on the way out-and all the rest of the
tubes were to follow shortly thereafter.

Unless EMP/ESD is a critical issue (you are building for a bomb
shelter), I think tube rectifiers should be foregone in new build tube
equipment. Soft start can be better engineered with modern components
than relying on a tube rectifier, and sonically I believe silicon
rectifiers properly shielded and filtered/bypassed simply sound a lot
better.

[Rich Sherman]

Good explanation, I did not know these facts about the history
rectifiers.

As far as the sonic benefits of tube versus diode rectification
this is a subjective subject.

I think otherwise. For my ear tube rectifiers are sonically superior
to diode rectifiers in most vintage preamplifier applications.

But in power amps, diode technology has improved so much as
to eclipse the benefits of a tube rectifier's inherent soft start
characteristics.

Diode rectification does away with the need for an additional
secondary section in a given power transformer saving the need
for a tube socket, a rectifier tube, heat, and chassis space.

There are several interesting studies about the sonics of
tube rectification as compared to silicon, germanium and/or
similar solid state material.

For sure that these studies can open up a 'pandoras box'
for lengthy discussions and a slew of follow up posts.

Excellent information, thank heavens that we are
beyond the battery thing today.

Thanks,

Rich

calcerise@hotmail.com wrote in article
<1105568589.019284.178480@f14g2000cwb.googlegroups.com>...

[Guest]

Joseph Meditz wrote:

[John Stewart]

Joseph Meditz wrote:

[Guest]

In the case of both, I think having the power supply off the chassis
is the best possible "upgrade". Whether a tube or solid state rectifier
is used, having the power transformer, rectifiers, and filters on a
separate chassis and passing DC on a cable is a quieter approach.

For tube power amps, I think choke filtering with swinging and
smoothing chokes is the genuinely significant "upgrade".

In the case of a preamp, using a regulated supply helps, although I
think that in cases where the CD is the main signal source, directly
driving a power amp from the CD player with a good volume control and
sufficient output level is a better idea. Really, or in other words,
all stereo amps should be "integrateds". McIntosh has in effect done
this with their big power amps,a lot of them have volume controls-all
they lack is multiple switched input jacks.

[John Byrns]

In article <41E5BF9B.538FA49D@sympatico.ca>, jh.stewart@sympatico.ca wrote:

[Alan Douglas]

Hi,
Sylvania made Philco's tubes, but Philco called the shots. In 1934
for instance Philco sold 1,250,000 radios, to RCA's 500,000. John is
quite right: RCA wanted heater voltages in 2.5V increments but Philco
adopted 6.3V and that was that.

73, Alan

[John Stewart]

John Byrns wrote:

[Joseph Meditz]

Thanks for the responses. They were very informative and unexpectedly
interesting!

Joe

[Ruud Broens]

"John Stewart" <jh.stewart@sympatico.ca> wrote in message
news:41E5D525.D88D15F4@sympatico.ca...
:
: Gerald F J Tynes book 'Saga of the Vacuum Tube' shows Philco manufacturing
tubes
: at Lansdale Tube Co, Division of Philco Corp. at Lansdale, Pennsylvania in
1928.
:
: Oddly, to me anyway, the first experience I ever had with LED's was when my
: supervisor at U of Toronto Physics, Prof RW McKay suggested we should try some
of
: the then new fangled devices. I pursued the lead & found they were being made
in
: Lansdale, but my recollection is that the supplier was by RCA. The connexion
made
: me wonder, could these two companies have been somehow joined or simply a
: contract to build parts? As many of us know some of these companies were
nothing
: more than marketing & sales, just as Sears or Wal-Mart is today. They
: manufactured nothing.
:
: Anyway, the going price was something like $60 per LED which taking into
account
: inflation was a lot of money. By chance I have the conversion at hand since
: someone a while ago posted all the inflationary figures from 2003 back to
1920.
: The multiplier for 1960 is 6.19 so that is about $370 in todays money. We
passed
: on the LED.
:
: Next time I saw LED's was as an HP salesman. By the late 60's the price was
down
: a lot but not cheap. They were all hermetically sealed. Fabrication was still
: expensive. By the time I left HP in 1984 we were getting something like 8
cents
: per copy in 100K lots. They must be a lot less today. And a lot better!!

Yep, in small numbers, about 10 eurocents will get you LED's that will have an
output
of several Candela's at 10-15 mA, nowadays :-))
Rudy


: Cheers, John Stewart
:
:

[Tom Schlangen]

Hi calcerise,