Commercial vs. industrial tubes

[David Axt]

How do "industrial" vacuum tubes compare to "commercial" tubes? Are they more rugged? Less noise? Are they less quality because they are intended to be used in industrial applications not audio applications?

For example there are a lot of industrial equivalents (5751, 6057, 6681, 7025, 7494, 7729) to the 12AX7 tube. How are they different?

Thanks,

David

[Fred Nachbaur]

David Axt wrote:

> How do "industrial" vacuum tubes compare to "commercial" tubes? Are
> they more rugged?

Sometimes, depends on the tube, and what it was optimized for.

> Less noise?

Same answer.

> Are they less quality because they are
> intended to be used in industrial applications not audio applications?

Depends what you mean by "quality." Industrial and military devices tend
to be optimized for ruggedness and long life. In general, how close they
are to "bogey tube" values used to derive the characteristics and curves
were *not* particularly important. So if by "quality" you mean
"matching," then there probably won't be much of a difference. If you
mean abstract or subjective properties like "soundstage transparency,"
then you're on your own. ;-)

> For example there are a lot of industrial equivalents (5751, 6057, 6681,
> 7025, 7494, 7729) to the 12AX7 tube. How are they different?

IIRC, 5751 was optimized for ruggedness, but has a lower published gain
figure than 12AX7. 7025 was optimized for low noise. 6681 was a mobile
communications version, so would again be optimized for ruggedness (and
possibly low microphonics, and high tolerance to filament voltage
changes.) The rest I don't know about. If you can find the actual spec
sheets for the tubes you're interested in, they will usually state what
the intended application was, or other clues as to what they were
optimized for.

Cheers,
Fred
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[Casino]

Actually, some of the so called "scientific", "medical" or "military"
grade tubes were really low-level consumer grade products that were
just labelled as such. It was scam that was used by several
well-known tube manufacturers like GE, Tung-Sol, Philips, RCA, etc.
I've ripped apart a lot of scientific and medical electronics
instruments, both tube-type and solid state (I wasn't aware that a few
were still in-use when I removed them from institutions; not my
fault), and was quite surprised to discover that cheapest available
components were used and were of very poor quality. However, chassis
and outer shells (enclusure boxes) were built like tanks.

Oh yeah, this reminds me of a project: I have a metal outer case from
some old tube-type spectrometer instrument (device was found at school
in working order and was still in-use till I came along and thought it
was junk) into which I'm going to build a tube-type FRS transciever.

Regards,

C.W.

Fred Nachbaur > wrote in message >...
> David Axt wrote:
>
> > How do "industrial" vacuum tubes compare to "commercial" tubes? Are
> > they more rugged?
>
> Sometimes, depends on the tube, and what it was optimized for.
>