StephenGiles

Why 48V for phantom power? Who started this convention?
« Reply #20 on: October 19, 2004, 02:43:24 PM »
Thanks PRR, I never knew that.
Stephen
The best place to find a helping hand is at the end of your arm!


PRR

Why 48V for phantom power? Who started this convention?
« Reply #21 on: October 19, 2004, 03:31:54 PM »
The real story is more complicated. While about 4'8" was common, everybody had a different exact size of trackage, and when railroads started to meet and merge it became a squabble.

In the US, the Civil War showed the merit of a national gauge, and Lincoln apparently picked the 4'8.5" gauge as being most-common to the northern railroads.

US railways were about that size because they expected to use UK engines, which were about that size.

But every UK railway was a little different, and Brunel was using 7' gauge. A government committee tested all the gauges, Brunel's 7' was the clear winner, which made everybody unhappy except Brunel, so of course the dolts standardized on the oddest number within the "regular" gauges, 4'8.5". (But a narrower gauge in Ireland.)

I have no idea how Lincoln and UK RR Committee came up with the same odd number. I wonder if all the public history is wrong, and some quiet guy from a RR equipment company jigged for 4'8.5" was passing out money to get his company's gauge made Standard.

The ruts at Pompey (Roman town buried alive in ash) are probably closer to 4'9", and not all uniform.

There is also a theory that 4'8.5" is one-quarter the width of the Queen's Chamber in the Great Pyramid.

http://www.trains.com/Content/Dynamic/Articles/000/000/003/011gsqfq.asp

http://infobluemountains.net.au/rail/horse-ass.htm

http://www.world-mysteries.com/gw_rellis4.htm

Smaller gauges have uses, especially outside wide-area systems. Mine and logging railways are often built narrower. There was a fad for lower-cost regional systems on (various) narrow gauges, and such oddballs persisted in Colorado, Australia, and South Africa/Rhodesia.

StephenGiles

Why 48V for phantom power? Who started this convention?
« Reply #22 on: October 19, 2004, 03:53:59 PM »
Thanks again PRR. I take it that you are a railway enthusiast. We hoped to ride the Devil's Nose Railway in Ecuador last month, which is the only working railway left in that country, but my wife became ill and we had to give it a miss. We did however see one station in a town where we stopped for lunch one day. The gauge was very narrow, which was worrying as I believe it goes up quite a few thousand feet.
Stephen
The best place to find a helping hand is at the end of your arm!

PRR

Why 48V for phantom power? Who started this convention?
« Reply #23 on: October 19, 2004, 04:52:00 PM »
> The gauge was very narrow, which was worrying as I believe it goes up quite a few thousand feet.

It follows the old donkey-trail over one of the more ragged mountain ranges in the world. And at the time, it was enough to have ANY connection; no great traffic was expected. So yeah, the gear is not a lot wider than one donkey. It is as safe as any antique machinery can be. Probably much safer than our new/improved highway bridge here: some drunk got going northbound on the southbound side and did a head-on into an SUV at 60MPH. On those little mountain railways, they don't go 60MPH and probably only have one engine in the whole system. Anyway, while I don't know that railway, similar ones are now often run as Tourist Traps ($4 for bottled water, $7 for beer, $16 for a MayaBurger), and the operators are very careful because dead tourists don't spend money.

smilinfu

Why 48V for phantom power? Who started this convention?
« Reply #24 on: October 19, 2004, 08:55:40 PM »
Oops put it in the wrong thread  :roll: he he

API

I think i know where the 48v comes from.
« Reply #25 on: June 25, 2006, 08:14:38 AM »
According to a text i read on Neumanns homepage the 48v comes from the Norwegian radio and Tv houses.
They asked Neumann to develop a microphone that could be run on 48v since they had lines for that all over their radio and Tv studios.
And apperently it was so succesfull that Neumann continued to market this concept and it later became standard everywhere.

Bo Hansen

Why 48V for phantom power? Who started this convention?
« Reply #26 on: June 25, 2006, 10:01:20 AM »
From a early investigation I have done about this matter, I find this in my archive. (cut out from the old rec.audio.pro forum)

As far as I know, it was invented by Neumann in the early 1970's when
they were trying to sell transistorized condenser mics to the broadcast
studios in Europe. No one wanted to use the existing Tonader scheme
because it would damage a dynamic or ribbon mic plugged into the same
connector. At the time Neumann was also a major supplier of broadcast
consoles so they had to solve the problem both ways -- at the mic and
at the desk.
-- joseph

It might be as simple that a large customer asked for it.
Neumann has a long history with radio and TV and has done several
things on request by them. Just look at the 48V in Phantom power, this
value comes from a request from a Norwegian radio station and was later
made into the general standard it is today.
--ghellqu

The folklore that I remember is that 48V is the highest voltage which
the European electrical inspectors will allow in a "portable" (not in
conduit) installation.
--mriv


--Bo
I met a man with a dollar, we exchanged dollars, I still had a dollar.
I met a man with an idea, we exchanged ideas, now we each had two ideas.

bcarso

Why 48V for phantom power? Who started this convention?
« Reply #27 on: June 25, 2006, 11:45:45 AM »
Note that in keeping with the answer to the Last Question of Life, The Universe, and Everything, voltages are considered hazardous, according to UL, in the US, at 42 volts.

Boswell

Why 48V for phantom power? Who started this convention?
« Reply #28 on: June 25, 2006, 02:15:20 PM »
The other half of the 48V phantom power question is why the source resistors are 6.8K Ohm in each leg. This must be a compromise between adequate available power and acceptable current in the event of a short circuit. Does anyone know any differently?

By the way:

The new vehicle supply standard is 42 volts, not 48 volts.

The standard Irish railway gauge is 5' 3", which was also the standard in parts of Australia, chiefly Victoria. Most alpine railways are metre gauge or less to allow a tighter minimum radius for corners.

BYacey

    Where dogs wear thermal underwear, Alberta, Canada
  • Posts: 769
Why 48V for phantom power? Who started this convention?
« Reply #29 on: June 26, 2006, 05:16:54 AM »
For Phantom Power / Historic Railway fans, here is an interesting link. I have been in Whitehorse and seen this train; quite an interesting history.
http://en.wikipedia.org/wiki/White_Pass_and_Yukon_Route
Bill Yacey
"Adjust R116 for least smoke"


 

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