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Adapting a microphone to remote phantom power

D

David Nebenzahl

Jan 1, 1970
0
Google computer mike / mic power and you'll see how it works. Very different
from your ECM.

How is "computer mike" power different from Sony's "plug-in power"? In
both cases the DC to power the mike's electronics is carried on the
signal line. Looks, sounds, smells like phantom power to me.

You're only confusing things by saying that it's "very different from
[my] ECM". THAT'S THE GODDAMN POINT I'VE BEEN TRYING TO MAKE! The mike I
have ignores the phantom power supplied by my recorder; I'm thinking of
ways to rectify that situation. That was the whole point of this exercise.

Got it now?
 
E

Eeyore

Jan 1, 1970
0
David said:
Eeyore spake thus:

To reply to you mis-attributed post (the person you responded to is not
the owner of the Sony mike):

I know. Maybe I should have said 'This Sony mic' ?

Well, duh. Who ever claimed that Sony's
"plug-in power" scheme was standard? In fact, I've been taking
particular pains to point out just the opposite.

Doesn't change the fact that a quality ( i.e. not a Duracell AA battery ) would
be your simplest fix.

Graham
 
E

Eeyore

Jan 1, 1970
0
David said:
How is "computer mike" power different from Sony's "plug-in power"?

I'm suggesting it's probably the same thing.

In both cases the DC to power the mike's electronics is carried on the
signal line. Looks, sounds, smells like phantom power to me.

It's not TRUE phantom power. True phantom power requires a balanced signal. Read
it up. I've been trying to be practical and helpful and all you can do is bitch at
me. Go learn some FACTS !
http://en.wikipedia.org/wiki/Phantom_power

If you don't understand the above don't bother coming back to whine at others.

Graham
 
D

David Nebenzahl

Jan 1, 1970
0
David Nebenzahl said:
You're only confusing things by saying that it's "very different from
[my] ECM". THAT'S THE GODDAMN POINT I'VE BEEN TRYING TO MAKE! The mike I
have ignores the phantom power supplied by my recorder; I'm thinking of
ways to rectify that situation. That was the whole point of this
exercise.

I said much earlier on that the mic must be designed for line powering.
And presumably that Sony isn't. Since the machine supplies line powering
it's obviously designed to be used with another mic.

Obviously, yes. And as I said, it was my mistake for not buying a
powered mike, instead of mine that requires a battery (plus remembering
to turn the damn thing on when recording). It does work fine with this mike.
My feeling is there is a good reason. A couple of volts at low current
isn't going to power a good quality mike handling high SPL. It's really
restricted to lo-fi use. If you up the voltage by using an inverter inside
the mic you're then into higher current from the source which could cause
problems with the existing connectors - and the possibility of damage to a
moving coil mic used on that input.

I'm not contemplating modifying the recorder to supply higher voltage;
I'm considering rewiring the mike to use the recorder's power rather
than the mike's battery. The mike already incorporates a DC-to-DC
converter (1.5 volts--> 4.8 volts).

And as I said before, presumably a moving-coil mike wouldn't be damaged
by the 2.8 volts the recorder is sending out.
 
E

Eeyore

Jan 1, 1970
0
David said:
David Nebenzahl said:
You're only confusing things by saying that it's "very different from
[my] ECM". THAT'S THE GODDAMN POINT I'VE BEEN TRYING TO MAKE! The mike I
have ignores the phantom power supplied by my recorder; I'm thinking of
ways to rectify that situation. That was the whole point of this
exercise.

I said much earlier on that the mic must be designed for line powering.
And presumably that Sony isn't. Since the machine supplies line powering
it's obviously designed to be used with another mic.

Obviously, yes. And as I said, it was my mistake for not buying a
powered mike, instead of mine that requires a battery (plus remembering
to turn the damn thing on when recording). It does work fine with this mike.

Then you would need a phantom power supply.

I'm not contemplating modifying the recorder to supply higher voltage;
I'm considering rewiring the mike to use the recorder's power rather
than the mike's battery. The mike already incorporates a DC-to-DC
converter (1.5 volts--> 4.8 volts).

And as I said before, presumably a moving-coil mike wouldn't be damaged
by the 2.8 volts the recorder is sending out.

At 1 mA or so probably not but it wouldn't work properly.

Graham
 
D

David Nebenzahl

Jan 1, 1970
0
It's not TRUE phantom power. True phantom power requires a balanced signal. Read
it up. I've been trying to be practical and helpful and all you can do is bitch at
me. Go learn some FACTS !
http://en.wikipedia.org/wiki/Phantom_power

Ah, the beauty of Wikipedia, the "encyclopedia" any junior-high-school
idiot (or electronics engineer with an axe to grind) can edit. Looking
at that article's revision history, one sees an awful lot of editing by
"anonymous IPs"; what are the chances that one of those is *you*, eh?
If you don't understand the above don't bother coming back to whine at others.

Ah, there it is: now you're stooping to throwing insults. By "you don't
understand", of course, you mean "you dare to disagree with my version
of things".

So let's see what others have to say about "phantom power", shall we? A
good starting point is to let Google sort it out: a simple search with
"define:phantom power" yields the following:

o the Wikipedia article, which agrees with you
o http://www.dramatic.com.au/glossary/glossaryp_z.htm, which says
nothing about the balanced requirement (agrees w/me)
o http://www.learnchurchsound.com/definitions/acoustical-terms.php, ditto
o http://www.woken.com.tw/internal/service/glossary.php, agrees w/you
o
http://www.britishtheatreguide.info/otherresources/glossary/glossps.htm,
which agrees w/me (except for the odd assertion that "Phantom power can
only be used when the connectors are XLR" (???)

DISCLAIMER: I make no claim that any of the above "citations" are
authoritative (least of all the Wikipedia entry). My intention is to
show that, contrary to your (and Dave Plowman's) insistent assertions,
there seems to be no general agreement that the term "phantom power" is
as restrictive as you claim it is. (See Arfa Daily's postings on the
subject for corroboration.)
 
F

Franc Zabkar

Jan 1, 1970
0
I suspect that the Walkman has an internal series resistor of around
1.8K and an O/C supply voltage of 5.0V.

WM-D6C Sony service manual:
http://esi.sony.ca/esupport/esupport/CD Rom Service Manual/042001/thiscd/sm-e/pa/995138511.pdf

Supplement:
http://esi.sony.ca/esupport/esupport/CD Rom Service Manual/042001/thiscd/sm-e/pa/995138581.pdf

The supply for each of the L and R microphone inputs is derived from a
buffered, zener regulated 2.6V source. The series resistor is 7.5K.
For comparison purposes, the condenser elements within Sony's ECM-737
mike are each powered from a 4.8V supply via 10K resistors.

I thought that the OP may be measuring the voltage while the mike was
connected, but it appears that 2.8V was the O/C voltage of the
Walkman.

This is the relevant section of the circuit:

2.6V |-- 7K5 --> L
IC201 | |
5.9V o--- R ---+---------+---- buffer -+- 1K ----+---|
| | | |
ZD --- 220uF 47uF --- |-- 7K5 --> R
HZ3ALL | --- ---
_|_ _|_ _|_
= = =

The HZ3ALL zener voltage rating is 2.5V (min) - 2.9V (max):
http://documentation.renesas.com/eng/products/diode/rej03g0183_hz_ll.pdf

- Franc Zabkar
 
D

David Nebenzahl

Jan 1, 1970
0

Franc; after this post, I have to tell you this: I think you should get
out of this newsgroup. You don't belong here.

Why? Because you

o Post helpful answers to questions asked here
o Seem extremely competent and knowledgeable about electronics
o Don't engage in insulting those you might consider beneath your
respect, or who might disagree with you
o Come up with *really* useful sources of information.

In short, you're out of step with the program here.

All joking aside: many thanks for this very useful information.
 
D

David Nebenzahl

Jan 1, 1970
0
Phantom powering for mics is a tightly defined standard.

Line powering can mean anything.

You keep saying this, which doesn't make it any more or less true.

Can you quote a reliable, authoritative source that defines phantom
power so? (And puleeze, don't even *think* about using Wikipedia!) One
which says that phantom power (R)(TM) *must* include the use of balanced
inputs, etc., as you've been claiming?

If there exists such a definition online, that could settle the whole
matter pretty easily.
 
F

Franc Zabkar

Jan 1, 1970
0
So let's see what others have to say about "phantom power", shall we? A
good starting point is to let Google sort it out: a simple search with
"define:phantom power" yields the following:

o the Wikipedia article, which agrees with you
o http://www.dramatic.com.au/glossary/glossaryp_z.htm, which says
nothing about the balanced requirement (agrees w/me)
o http://www.learnchurchsound.com/definitions/acoustical-terms.php, ditto
o http://www.woken.com.tw/internal/service/glossary.php, agrees w/you
o
http://www.britishtheatreguide.info/otherresources/glossary/glossps.htm,
which agrees w/me (except for the odd assertion that "Phantom power can
only be used when the connectors are XLR" (???)

DISCLAIMER: I make no claim that any of the above "citations" are
authoritative (least of all the Wikipedia entry). My intention is to
show that, contrary to your (and Dave Plowman's) insistent assertions,
there seems to be no general agreement that the term "phantom power" is
as restrictive as you claim it is. (See Arfa Daily's postings on the
subject for corroboration.)

I was curious as to what a microphone manufacturer had to say.

For example, Shure considers that "phantom power" and "bias" are two
different concepts:
http://www.shure.com/ProAudio/Products/us_pro_ea_phantom

Sennheiser also appears to differentiate between phantom power (48V)
and T or A-B power (12V):
http://www.sennheiserusa.com/faq/faq.asp?transid0=0005

And then there's this site:
http://www.epanorama.net/circuits/microphone_powering.html

Phantom power now appears to be defined by a prevailing standard, DIN
EN 61938, July 97, formerly DIN IEC 268-15 and DIN 45 596.

That said, I'd always used the terms "phantom power" and "bias"
interchangeably, but my knowledge of microphones is essentially zero.

There are other systems where power is supplied to the remote device
via the signal cable, eg a masthead amp, or a video camera, or an LNB
for a satellite dish. I think these are generally referred to as being
*line* powered. Instead of a resistor, the series element is an
inductor. This has a low impedance at DC, or AC mains frequency, but a
high impedance at video frequencies.

Then there are those devices which can be considered to be *signal*
powered, eg serial mice which rob power from the DTR and RTS signals
(?) of an RS232 port.

So I guess the moral of the story is that one has to be aware that not
everyone speaks the same language, whether or not they are correct.
However I'd tend to lean towards a definition that is incorporated
into an accepted standard. Unfortunately DIN/EN 61938 does not appear
to be available as a free download. :-(

The funny thing is that telephones can be considered to be phantom
powered, yet I'd never heard the term used in that context until I
read the Wikipedia article on the subject.

- Franc Zabkar
 
D

David Nebenzahl

Jan 1, 1970
0
I get some 197,000 hits when I Google for phantom power. And can't be
bothered wading through all of them.

Lets just say it's an album from Super Furry Animals if Google is your
source of things technical.


I've a feeling if I gave you such a site you'd just rubbish it as you do
Wikipedia if it doesn't agree with you.

In other words, I can't be bothered to come up with a fucking citation
to back myself up.

Why didn't you just say so? Fewer electrons would've been tortured in
the process.
 
F

Franc Zabkar

Jan 1, 1970
0
Anywhere that sold phantom powered mics would require you to know what
they were when buying, otherwise you might end up with one which didn't
work to your requirements.

I confess I'm ignorant about professional audio gear. I've always
thought of phantom power as a generic term, and it appears that many
people do likewise.

In fact the Wikipedia article recognises this:

=====================================================================
The low-current 3 to 5 V supply provided at the microphone jack of
some consumer equipment, such as portable recorders and computer sound
cards, is sometimes called "phantom power."
=====================================================================

I can see a parallel in the definition of USB standards:
http://www.usb.org/developers/packaging/:

=====================================================================
Because the USB 2.0 Specification encompasses all USB data transfer
speeds, low (1.5Mb/s), full (12Mb/s) and high (480Mb/s), it is
important that vendors clearly communicate the type of product on
packaging and in marketing and advertising materials. Inconsistent use
of terminology in combination with the existing general misconception
that USB 2.0 is synonymous with Hi-Speed USB ... creates confusion in
the marketplace.
=====================================================================

One would think that low, full, and high speed are loose, generic
terms, but in the USB context they have particular numbers associated
with them.
No - telephones are line powered. True phantom power was however first
used in the telephone industry for other purposes.

A telephone line is balanced - but if you apply an AVO to that line you'll
see the DC. Do the same to a balanced mic line with phantom power present
and you won't.

OK, I see now ...
http://www.mediacollege.com/audio/phantom-power/

- Franc Zabkar
 
E

Eeyore

Jan 1, 1970
0
David said:
Eeyore spake thus:

Ah, the beauty of Wikipedia, the "encyclopedia" any junior-high-school
idiot (or electronics engineer with an axe to grind) can edit. Looking
at that article's revision history, one sees an awful lot of editing by
"anonymous IPs"; what are the chances that one of those is *you*, eh?


Ah, there it is: now you're stooping to throwing insults. By "you don't
understand", of course, you mean "you dare to disagree with my version
of things".

So let's see what others have to say about "phantom power", shall we?

Irrelevant. The term is regularly abused. I have explained in considerable detail why
it's a no-go and still you whine.

Graham
 
E

Eeyore

Jan 1, 1970
0
Franc said:
There are other systems where power is supplied to the remote device
via the signal cable, eg a masthead amp, or a video camera, or an LNB
for a satellite dish. I think these are generally referred to as being
*line* powered.

That is the term I would use too. It is NOT phantom power'.

Graham
 
E

Eeyore

Jan 1, 1970
0
Franc said:
I confess I'm ignorant about professional audio gear. I've always
thought of phantom power as a generic term, and it appears that many
people do likewise.

In fact the Wikipedia article recognises this:

=====================================================================
The low-current 3 to 5 V supply provided at the microphone jack of
some consumer equipment, such as portable recorders and computer sound
cards, is sometimes called "phantom power."
=====================================================================

Classic 'dumbing down'.

Graham
 
E

Eeyore

Jan 1, 1970
0
Michael A. Terrell said:
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.

Graham
 
D

David Nebenzahl

Jan 1, 1970
0
Seems there may well be lots of people who use the term without knowing
what it means.



Yes. Wonder who added that to the original article?

You can easily find out: just check the "history" tab and trace it back.
(But it'll probably turn out to be an "anonymous IP", meaning that it
could be anybody, qualified or not.)

And there's really no such thing as an "original article" on Wikipedia,
as all articles are constantly undergoing rewriting for better or worse
(often the latter).
 
E

Eeyore

Jan 1, 1970
0
Dave Plowman (News) said:
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.

Yup, I've seen a few. Usually the PSU is finished in that Hammerite style
paint in a silver grey.

Graham
 
E

Eeyore

Jan 1, 1970
0
Dave Plowman (News) said:
Well you can take it from me the current explanation is pretty decent and
rather better than many others you'll find.

I've amended the entry slightly to make it clearer.

Graaham
 
D

David Nebenzahl

Jan 1, 1970
0
I've amended the entry slightly to make it clearer.

Aha! So much for relying on Wikipedia as a reliable source of information.
 
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