Adapting a microphone to remote phantom power

[Michael A. Terrell]

Bob Larter wrote:

Michael A. Terrell wrote:
"Dave Plowman (News)" wrote:
In article <49E3C34C.CF13C6C@hotmail.com>,
Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
That wasn't possible with early phantom mics, using tube preamps.
I'm not aware of any tube based condensor mics that used phantom power
as we talk of it now. They usually had dedicated multipole connectors
rather than the now ubiquitous 3 pin XLR.
Rather obvious when you think of the technology then - and the restricted
current available with phantom power.

There's been quite a revival in valve mics and I've a feeling there may be
at least one which runs off phantom. But the majority still use a
dedicated PS and multicore cable.


I guess you never saw any of the battery powered tube hearing aids?
They used less power than a mic preamp, due to their directly heated
filaments.

I actually pulled apart a tube hearing aid as a kid. The whole hearing
aid was around the size of a packet of cigarettes, & the tubes were
maybe half the size of a cigarette. I have no idea whether or not they
did anything unusual to heat the filaments.

Directly heated filaments don't have a separate cathode, and require
a lot less current to operate. That hearing aid would be worth a lot of
money to a collector these days.

Motorola built portable two way radios with direct heated filament
tubes to extend battery life, plus the fact that they heat n a fraction
of as second, you can shut down the entire transmit section while
monitoring the base station. The US military was still using them for
the MPs into the '70s because they were rugged, and heavy. They would
survive if the MP had to subdue someone, and it hid the ground.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

--
You can't have a sense of humor, if you have no sense!

 

[Bob Larter]

Michael A. Terrell wrote:

Bob Larter wrote:
Michael A. Terrell wrote:
"Dave Plowman (News)" wrote:
In article <49E3C34C.CF13C6C@hotmail.com>,
Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
That wasn't possible with early phantom mics, using tube preamps.
I'm not aware of any tube based condensor mics that used phantom power
as we talk of it now. They usually had dedicated multipole connectors
rather than the now ubiquitous 3 pin XLR.
Rather obvious when you think of the technology then - and the restricted
current available with phantom power.

There's been quite a revival in valve mics and I've a feeling there may be
at least one which runs off phantom. But the majority still use a
dedicated PS and multicore cable.

I guess you never saw any of the battery powered tube hearing aids?
They used less power than a mic preamp, due to their directly heated
filaments.
I actually pulled apart a tube hearing aid as a kid. The whole hearing
aid was around the size of a packet of cigarettes, & the tubes were
maybe half the size of a cigarette. I have no idea whether or not they
did anything unusual to heat the filaments.


Directly heated filaments don't have a separate cathode, and require
a lot less current to operate. That hearing aid would be worth a lot of
money to a collector these days.

It's long gone, I'm afraid.

Motorola built portable two way radios with direct heated filament
tubes to extend battery life, plus the fact that they heat n a fraction
of as second, you can shut down the entire transmit section while
monitoring the base station. The US military was still using them for
the MPs into the '70s because they were rugged, and heavy. They would
survive if the MP had to subdue someone, and it hid the ground.

That's pretty impressive for a gizmo with tubes in it. ;^)


--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[Michael A. Terrell]

Bob Larter wrote:

Michael A. Terrell wrote:

Directly heated filaments don't have a separate cathode, and require
a lot less current to operate. That hearing aid would be worth a lot of
money to a collector these days.

It's long gone, I'm afraid.

I figured that. They were rare when they were new, and very few
survived when the early solid state versions hit the market.

Motorola built portable two way radios with direct heated filament
tubes to extend battery life, plus the fact that they heat n a fraction
of as second, you can shut down the entire transmit section while
monitoring the base station. The US military was still using them for
the MPs into the '70s because they were rugged, and heavy. They would
survive if the MP had to subdue someone, and it hid the ground.

That's pretty impressive for a gizmo with tubes in it. ;^)

The tubes had a small spring that shock mounted them into their
inline sockets, and the tubes were similar to those developed for early
missile guidance systems. The ones used in a missile were soldered in,
while the portable radios used special sockets. I still had a couple
sets of the sub miniature tubes from damaged radios I junked for the
potted IF filters.

Some radios even survived being used as a replacement for their
nightstick when it was taken by a suspect. Those rounded steel cases
leave nasty bruises.


--
You can't have a sense of humor, if you have no sense!