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Question regarding Phantom Power

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September 24, 2004 2:44:05 PM

Archived from groups: rec.audio.pro (More info?)

Hello everyone,

I hope someone out there can answer my question, and I hope it doesn't
come across as too naieve!.

The question is regarding Phantom Power. At college, there is a 32
track mixing console, each track has an individual 'phantom power'
switch. The question arose in class that if every single track on the
mixer had phantom power enabled and phantom power runs at +48V, would
this equate to 1536V??, or isn't it as simple as that?. I realise most
mic's wouldn't draw 48V of current, but if that's the case, why is
phantom power set at 48V if the microphones don't need that much to
operate?.

I've searched for an answer to this question on the web, but I've
found no answers. Hope someone can help me!.

Thanks in advance,
Neil.

More about : question phantom power

Anonymous
September 24, 2004 6:15:38 PM

Archived from groups: rec.audio.pro (More info?)

Neil <neil.ebrey@gmail.com> wrote:
>
>The question is regarding Phantom Power. At college, there is a 32
>track mixing console, each track has an individual 'phantom power'
>switch. The question arose in class that if every single track on the
>mixer had phantom power enabled and phantom power runs at +48V, would
>this equate to 1536V??, or isn't it as simple as that?. I realise most
>mic's wouldn't draw 48V of current, but if that's the case, why is
>phantom power set at 48V if the microphones don't need that much to
>operate?.

No. Microphones don't draw 48V of current. Voltage and current are
different. Microphones draw a few milliamps of current at 48V. The
more microphones you use, the more current (in milliamps) they draw.

But they all have 48V across them, whether or not they draw any current.
(Actually, when you put a current load on them, the voltage drops a bit.)

The electrical outlets in your house all have 120V across them. You plug
in more appliances, the current demand increases but the voltage stays the
same.

>I've searched for an answer to this question on the web, but I've
>found no answers. Hope someone can help me!.

You want a good introduction to DC circuits. The Schaum's Outline is a
pretty good one, as is the first chapter of The Art Of Electronics.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
September 24, 2004 9:58:26 PM

Archived from groups: rec.audio.pro (More info?)

On 24 Sep 2004 10:44:05 -0700, neil.ebrey@gmail.com (Neil) wrote:

>Hello everyone,
>
>I hope someone out there can answer my question, and I hope it doesn't
>come across as too naieve!.
>
>The question is regarding Phantom Power. At college, there is a 32
>track mixing console, each track has an individual 'phantom power'
>switch. The question arose in class that if every single track on the
>mixer had phantom power enabled and phantom power runs at +48V, would
>this equate to 1536V??, or isn't it as simple as that?. I realise most
>mic's wouldn't draw 48V of current, but if that's the case, why is
>phantom power set at 48V if the microphones don't need that much to
>operate?.
>
>I've searched for an answer to this question on the web, but I've
>found no answers. Hope someone can help me!.
>
>Thanks in advance,
>Neil.

This is tricky - first we need to sort out your terminology a bit. 48V
isn't a current - it is a voltage. It is available to any mic that
needs it, but it is wired in a mode called parallel - that is it
doesn't add up for every mic, it is just 48V - no more than that. On
each mic channel it is fed to the mic through a pair of resistors of
about 6000 ohms (3000 ohms equivalent) so any single mic can take up
to 48/3000 or 0.016 amps (16mA). That is plenty for even the most
demanding phantom mic - most take much less. SOme need more, and they
come with their own power supply.

But the point is that all microphones are guaranteed to work off that
voltage and resistance combination, but most don't need that much.

As for the desk, if you have, say 24 mic channels, then the 48V power
supply must be able to supply 24 x .016 amps, or roughly half an amp.
So you see it is the amps, not the volts, that build up as you add
more microphones.

d
Pearce Consulting
http://www.pearce.uk.com
Related resources
Anonymous
September 24, 2004 10:04:16 PM

Archived from groups: rec.audio.pro (More info?)

In article <1eae5cc6.0409240944.89bb2b@posting.google.com> neil.ebrey@gmail.com writes:

> At college, there is a 32
> track mixing console, each track has an individual 'phantom power'
> switch. The question arose in class that if every single track on the
> mixer had phantom power enabled and phantom power runs at +48V, would
> this equate to 1536V??

Uh . . .what's the specialty at this college? Auto Mechanics? Art
History? Economics? Certainly not recording.

Excusing your errors in terminology for the moment, surely if this was
some sort of recording class, the instructor would know that the
answer was "no."

For extra credit, you can ask what might happen if you were to connect
a phantom powered mic to ALL of those 32 inputs. If it's a Mackie SR
series like the SR32-4 (although that one doesn't have 32 mic inputs)
the answer is that the voltage will drop because of the load and any
mics that require 48 volts (many will work on lower voltages) will not
get sufficient voltage. When they designed that console, to cut
corners, they didn't provide sufficient current capacity for all the
inputs to be delivering full spec phantom power simultanteously. To
give them a little credt, though, at the time the console was
designed, condenser mics costing under $400 were few and far between
so it was unlikely that anyone on the Mackie budget would own 28
condenser mics. I believe I heard that it was designed to accommodate
a 25% load at full current per mic. So that's 7 mics, more if they
draw less than 10 mA of current (the at least somewhat official
maximum), or if all the mics can run at a lower voltage.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
September 24, 2004 10:52:20 PM

Archived from groups: rec.audio.pro (More info?)

In article <41555ef6.6943937@news.plus.net>,
donald@pearce.uk.com (Don Pearce) wrote:

> On 24 Sep 2004 10:44:05 -0700, neil.ebrey@gmail.com (Neil) wrote:
>
> >Hello everyone,
> >
> >I hope someone out there can answer my question, and I hope it doesn't
> >come across as too naieve!.
> >
> >The question is regarding Phantom Power. At college, there is a 32
> >track mixing console, each track has an individual 'phantom power'
> >switch. The question arose in class that if every single track on the
> >mixer had phantom power enabled and phantom power runs at +48V, would
> >this equate to 1536V??, or isn't it as simple as that?. I realise most
> >mic's wouldn't draw 48V of current, but if that's the case, why is
> >phantom power set at 48V if the microphones don't need that much to
> >operate?.
> >
> >I've searched for an answer to this question on the web, but I've
> >found no answers. Hope someone can help me!.
> >
> >Thanks in advance,
> >Neil.
>
you have 40(pulling a number out of my ass) 110 volt wall outlets in
your house
does this make them 4400 volt outlets if you use them all
no
they remain 110 volt outlets you just need to have enough amperage
avaiable to drive the load each outlet is drawing
George
Anonymous
September 24, 2004 10:52:21 PM

Archived from groups: rec.audio.pro (More info?)

George wrote:

> you have 40(pulling a number out of my ass) 110 volt wall outlets in
> your house


That's not a pretty image, George.

: )
September 24, 2004 11:11:30 PM

Archived from groups: rec.audio.pro (More info?)

donald@pearce.uk.com (Don Pearce) wrote in message news:<41555ef6.6943937@news.plus.net>...
> On 24 Sep 2004 10:44:05 -0700, neil.ebrey@gmail.com (Neil) wrote:
>
> >Hello everyone,
> >
> >I hope someone out there can answer my question, and I hope it doesn't
> >come across as too naieve!.
> >
> >The question is regarding Phantom Power. At college, there is a 32
> >track mixing console, each track has an individual 'phantom power'
> >switch. The question arose in class that if every single track on the
> >mixer had phantom power enabled and phantom power runs at +48V, would
> >this equate to 1536V??, or isn't it as simple as that?. I realise most
> >mic's wouldn't draw 48V of current, but if that's the case, why is
> >phantom power set at 48V if the microphones don't need that much to
> >operate?.
> >
> >I've searched for an answer to this question on the web, but I've
> >found no answers. Hope someone can help me!.
> >
> >Thanks in advance,
> >Neil.
>
> This is tricky - first we need to sort out your terminology a bit. 48V
> isn't a current - it is a voltage. It is available to any mic that
> needs it, but it is wired in a mode called parallel - that is it
> doesn't add up for every mic, it is just 48V - no more than that. On
> each mic channel it is fed to the mic through a pair of resistors of
> about 6000 ohms (3000 ohms equivalent) so any single mic can take up
> to 48/3000 or 0.016 amps (16mA). That is plenty for even the most
> demanding phantom mic - most take much less. SOme need more, and they
> come with their own power supply.
>
> But the point is that all microphones are guaranteed to work off that
> voltage and resistance combination, but most don't need that much.
>
> As for the desk, if you have, say 24 mic channels, then the 48V power
> supply must be able to supply 24 x .016 amps, or roughly half an amp.
> So you see it is the amps, not the volts, that build up as you add
> more microphones.
>
> d
> Pearce Consulting
> http://www.pearce.uk.com



Thanks very much for the reply. The reason I couldn't find out the
answer earlier is because the question is redundant! I had a feeling
it was a silly question, but I appreciate the replies.

Neil.
September 24, 2004 11:37:28 PM

Archived from groups: rec.audio.pro (More info?)

In article <415475BE.B2C005D3@comcast.net>,
Don Cooper <dcooper28800@comcast.net> wrote:

> George wrote:
>
> > you have 40(pulling a number out of my ass) 110 volt wall outlets in
> > your house
>
>
> That's not a pretty image, George.
>
> : )

ok I won't share where I keep the re20's
george
Anonymous
September 24, 2004 11:46:58 PM

Archived from groups: rec.audio.pro (More info?)

Neil wrote:
> I hope someone out there can answer my question, and I hope it doesn't
> come across as too naieve!.
>
> The question is regarding Phantom Power. At college, there is a 32
> track mixing console, each track has an individual 'phantom power'
> switch. The question arose in class that if every single track on the
> mixer had phantom power enabled and phantom power runs at +48V, would
> this equate to 1536V??, or isn't it as simple as that?. I realise most
> mic's wouldn't draw 48V of current, but if that's the case, why is
> phantom power set at 48V if the microphones don't need that much to
> operate?.

The problem is electricity is very counter-intuitive, and you have
a misunderstanding about what voltage is.

Voltage is not the same thing as power. Voltage is sometimes called
"potential" (which is short for "potential difference"). You'll
notice that "potential" and "power" represent very different ideas.

When electrons are moving from point A to point B, you've got an
electric current. But, the electrons aren't going to spontaenously
all move in one direction as a group, so in order for this to happen,
there must be a force that causes them to move. Voltage is connected
with how much force there is available to possibly make the electrons
move.

I say "possibly" because another thing that's necessary is for
there to be a path for electrons to take. Unless they are
in just the right mood, electrons don't like to just fly across
open space. (Normally this takes the form of metal, which works
because electrons can move around within metal pretty easily,
so one electron can move a little bit and nudge another electron,
which then nudges another, and then pretty soon you've a bunch
of electrons inching in one direction by tiny amounts.) Anyway,
the point is that the amount of current that flows depends on
how much the electrons "want" to move (related to voltage) *and*
on how much resistance they encounter when trying to move.
(Think of walking on a sidewalk vs. walking through very shallow
water at the beach vs. walking through waist-deep water at
the beach.)

Anyway, to relate this back to the mixer, 48V just means that
the electrons have 48V of "motivation" to work with IF they
find a suitable, easy path along which to move. It doesn't
mean that any of them are actually moving at all. If there
is a perfect path where electrons encounter no resistance
at all, and if the console has no limits on its ability to
maintain 48V, then you would have infinite current. If,
however, there is some resistance, then the current will be
lower the higher the resistance is. The person who designs
a microphone can make it get just the amount of current that
it needs by designing a circuit with just the right resistance.

By the way, as for why it's 48V, I think that has to do with
a compromise. Higher-voltage circuits can transmit electricity
over long distances with less energy loss and with thinner
wires. Devices require various voltages, and on a DC circuit
it's much easier to cut voltage than it is to increase it.
So, 48V is high enough for most devices and it's easy to
drop down if you need to. However, high voltages also are
a little more difficult to deal with safely, and the government
makes it easier to get things approved if they are not too
high a voltage. (This is why people use "low-voltage lighting",
i.e. "Malibu lights" for their front yard to light up trees
and stuff.) So, 48V is a compromise between those factors.

- Logan
Anonymous
September 25, 2004 3:58:58 AM

Archived from groups: rec.audio.pro (More info?)

Neil wrote:

> Hello everyone,
>
> I hope someone out there can answer my question, and I hope it doesn't
> come across as too naieve!.
>
> The question is regarding Phantom Power. At college, there is a 32
> track mixing console, each track has an individual 'phantom power'
> switch. The question arose in class that if every single track on the
> mixer had phantom power enabled and phantom power runs at +48V, would
> this equate to 1536V??, or isn't it as simple as that?. I realise most
> mic's wouldn't draw 48V of current,

Volts isn't current it's *VOLTS* ! Current is *AMPS*

Do you plan a career in pro-audio or the dole queue ? If the former, I
suggest you go learn something about the fundamentals.

> but if that's the case, why is
> phantom power set at 48V if the microphones don't need that much to
> operate?.

Checks just to make sure it isn't 1 April.

What college is that ?

Was the lecturer not present and able to answer ?

I see that you're in the UK. If you had 4 x 240V power sockets in a room
would you expect the mains supply to be 960V ?

They let too many dim kids into college these days to make the numbers
look good.


Graham
Anonymous
September 25, 2004 4:52:07 AM

Archived from groups: rec.audio.pro (More info?)

<< Do you plan a career in pro-audio or the dole queue ? If the former, I
suggest you go learn something about the fundamentals. >>



Might could be that's exactly why he's in college, which, last I heard, still
allowed questions to be asked.

Scott Fraser
Anonymous
September 25, 2004 4:52:08 AM

Archived from groups: rec.audio.pro (More info?)

On 25 Sep 2004 00:52:07 GMT, ScotFraser wrote:

> << Do you plan a career in pro-audio or the dole queue ? If the former, I
> suggest you go learn something about the fundamentals. >>


>
> Might could be that's exactly why he's in college, which, last I heard, still
> allowed questions to be asked.
>
> Scott Fraser

Yeah, they're dumbed it down a lot, but there's still a thing as a stupid
question...the only thing I can say is better hit those books
Anonymous
September 25, 2004 8:41:52 AM

Archived from groups: rec.audio.pro (More info?)

ScotFraser wrote:

> << Do you plan a career in pro-audio or the dole queue ? If the former, I
> suggest you go learn something about the fundamentals. >>


>
> Might could be that's exactly why he's in college, which, last I heard, still
> allowed questions to be asked.

When I went to College/ University, you were expected to know a little bit about
the subject in advance of being allowed admission.

My UK 'A level' Physics course at school included plenty of electricity /
electronics theory. I can even recall the discussion of photo-electric emission
( energy states in electron orbits and stuff like that ).


Graham
Anonymous
September 25, 2004 8:46:17 AM

Archived from groups: rec.audio.pro (More info?)

KingMe wrote:

> On 25 Sep 2004 00:52:07 GMT, ScotFraser wrote:
>
> > << Do you plan a career in pro-audio or the dole queue ? If the former, I
> > suggest you go learn something about the fundamentals. >>


> >
> > Might could be that's exactly why he's in college, which, last I heard, still
> > allowed questions to be asked.
> >
> > Scott Fraser
>
> Yeah, they're dumbed it down a lot, but there's still a thing as a stupid
> question...the only thing I can say is better hit those books

In the UK it's been very badly dumbed down. When I went to Uni, probably no more
that 10% of the population did so. It's now 30% with a target of 50% !

I don't think you need to be a genius to see that means letting in those who really
aren't up to the former grade and it shows.

A lecturer I know ( who's involved in a pro-audio course as it happens ) admitted
that they've had to dumb down the content in order to attract students, especially
when it's a course involving real brain work like electronics related stuff.


Graham
Anonymous
September 25, 2004 8:55:50 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear wrote:
> When I went to College/ University, you were expected to know a little bit about
> the subject in advance of being allowed admission.

Oh yeah, I can definitely remember that scenario. Bummer when it's a
required class that you have absolutely NO personal interest in. (In
my own case, that was Probability I[1], although for various people
it can be English, or Government, or a wide variety of other things.)

- Logan

[1] I swear the only thing that saved me in that case was the marketing
department of The Coca-Cola Company. You see, they had this "one
free with six" promotion at the time, which basically meant that
when you got a Coke from the soda machine in the lab, you had a
1/6 chance of winning another Coke. Now, I wasn't taking probability
that semester, but my friend Omar was, so I kept pestering him
with questions, because I was sure that if you get a free Coke,
it *also* has a 1/6 chance of winning, so logically that means
that as you approach buying an infinite number of Cokes (not an
impossible proposition for a college student, mind you), that
your total earnings would be more than 1/6. Because, in 1/6 of
the cases, you'd win, and you'd have another 1/6 chance of winning
something further. Omar wasn't sure what I was getting at
(although I am used to that), so I just pondered it for a whole
semester and eventually determined that, in the same way that
1/2 + 1/4 + 1/8 + 1/16 + ... = 1, it should be the case that
1/6 + 1/36 + 1/216 + ... = 1/5, so if you buy a huge number of
Cokes, then actually you get one free with FIVE, not six. Then,
as it turns out, the final exam in Probability I was really tough,
but one of the questions involved the Starship Enterprise and a
wormhole, but conceptually it was exactly the same thing as the
Coca-Cola question, so I just answered it right away with no
trouble, whereas most of the rest of the class could be heard
after the final exam saying things like, "Man, what was that Star
Trek problem about? I had NO IDEA how to answer that one!"
But it counted for more 10% or more of the exam, so I am convinced
that through either pure luck or through divine providence, I was
able to actually pass the class and finally finish college[2].

[2] Yes, I *do* realize just how long the previous footnote is.
I think there is AT LEAST a 1/6 probability that it's a
personal record.
Anonymous
September 25, 2004 12:58:37 PM

Archived from groups: rec.audio.pro (More info?)

On Fri, 24 Sep 2004 13:44:05 -0400, Neil wrote
(in article <1eae5cc6.0409240944.89bb2b@posting.google.com>):

> Hello everyone,
>
> I hope someone out there can answer my question, and I hope it doesn't
> come across as too naieve!.
>
> The question is regarding Phantom Power. At college, there is a 32
> track mixing console, each track has an individual 'phantom power'
> switch. The question arose in class that if every single track on the
> mixer had phantom power enabled and phantom power runs at +48V, would
> this equate to 1536V??, or isn't it as simple as that?. I realise most
> mic's wouldn't draw 48V of current, but if that's the case, why is
> phantom power set at 48V if the microphones don't need that much to
> operate?.
>
> I've searched for an answer to this question on the web, but I've
> found no answers. Hope someone can help me!.
>
> Thanks in advance,
> Neil.

Hi Neil,

As others may have mentioned, you need a slight tweek on your technology.
Voltage and current are different.

Ultimately, it's the combination of voltage and current (E x I = P) that
results in P (power). Some mics are more forgiving, and are able to run with
less than 48 VDC, providing enough current is there to supply the total
power.

The 48 VDC is voltage..and we assume that it's really 48 and is stabilized,
so adding more mics doesn't load the circuit down to something less than
48VDC.

The current part of the circuit should be large enough to feed all of the
mics. Different condenser mics have different power requirements. Some need
more mA (millamps) than others. Some console power supplies are not designed
to properly power all mics. The result is increased distortion and lower
headroom on the mics themselves.


Regards,

Ty Ford







-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
Anonymous
September 25, 2004 1:00:15 PM

Archived from groups: rec.audio.pro (More info?)

In article <5vq2c9uwrlph$.dlg@king.me> kingme@king.me writes:

> > Might could be that's exactly why he's in college, which, last I heard, still
> > allowed questions to be asked.

> Yeah, they're dumbed it down a lot, but there's still a thing as a stupid
> question...the only thing I can say is better hit those books

Oh, I don't think it was a stupid question, I was just surprised that
he didn't get an immediate answer about the phantom power voltage, as
well as being corrected about voltage vs. current. I'm guessing that
he didn't get an answer in class and that's why he asked here.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
September 25, 2004 1:39:19 PM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:

> In article <5vq2c9uwrlph$.dlg@king.me> kingme@king.me writes:
>
>
>>>Might could be that's exactly why he's in college, which, last I heard, still
>>>allowed questions to be asked.
>
>
>>Yeah, they're dumbed it down a lot, but there's still a thing as a stupid
>>question...the only thing I can say is better hit those books
>
>
> Oh, I don't think it was a stupid question, I was just surprised that
> he didn't get an immediate answer about the phantom power voltage, as
> well as being corrected about voltage vs. current. I'm guessing that
> he didn't get an answer in class and that's why he asked here.


Bingo. The OP did say that they had been discussing it.
Anonymous
September 25, 2004 1:56:03 PM

Archived from groups: rec.audio.pro (More info?)

In article <41555ef6.6943937@news.plus.net> in rec.audio.pro on Fri, 24
Sep 2004 17:58:26 GMT, Don Pearce <donald@pearce.uk.com> says...
> On 24 Sep 2004 10:44:05 -0700, neil.ebrey@gmail.com (Neil) wrote:
>
> >Hello everyone,
> >
> >I hope someone out there can answer my question, and I hope it doesn't
> >come across as too naieve!.
> >
> >The question is regarding Phantom Power. At college, there is a 32
> >track mixing console, each track has an individual 'phantom power'
> >switch. The question arose in class that if every single track on the
> >mixer had phantom power enabled and phantom power runs at +48V, would
> >this equate to 1536V??, or isn't it as simple as that?. I realise most
> >mic's wouldn't draw 48V of current, but if that's the case, why is
> >phantom power set at 48V if the microphones don't need that much to
> >operate?.
> >
> >I've searched for an answer to this question on the web, but I've
> >found no answers. Hope someone can help me!.
> >
> >Thanks in advance,
> >Neil.
>
> This is tricky - first we need to sort out your terminology a bit. 48V
> isn't a current - it is a voltage. It is available to any mic that
> needs it, but it is wired in a mode called parallel - that is it
> doesn't add up for every mic, it is just 48V - no more than that. On
> each mic channel it is fed to the mic through a pair of resistors of
> about 6000 ohms (3000 ohms equivalent) so any single mic can take up
> to 48/3000 or 0.016 amps (16mA). That is plenty for even the most
> demanding phantom mic - most take much less. SOme need more, and they
> come with their own power supply.
>
> But the point is that all microphones are guaranteed to work off that
> voltage and resistance combination, but most don't need that much.
>
> As for the desk, if you have, say 24 mic channels, then the 48V power
> supply must be able to supply 24 x .016 amps, or roughly half an amp.
> So you see it is the amps, not the volts, that build up as you add
> more microphones.
>

How do most power supplies handle that all too possible situation of
(a) an unintentional fault causing a short between the earth and signal
pins
(b) an intentional situation of connecting an unbalanced source that has
pin 2 connected to ground, as is standard practice but which results in
phantom shorted to earth?

I was working on a patch panel the other day. The desk was powered up and
had phantom on. Every time I touched my earthed soldering iron to the
signal pins there was a nice little blue spark from the phantom power.
Anonymous
September 25, 2004 1:56:04 PM

Archived from groups: rec.audio.pro (More info?)

On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
<patrickdunford@nomail.invalid> wrote:

>In article <41555ef6.6943937@news.plus.net> in rec.audio.pro on Fri, 24
>Sep 2004 17:58:26 GMT, Don Pearce <donald@pearce.uk.com> says...
>> On 24 Sep 2004 10:44:05 -0700, neil.ebrey@gmail.com (Neil) wrote:
>>
>> >Hello everyone,
>> >
>> >I hope someone out there can answer my question, and I hope it doesn't
>> >come across as too naieve!.
>> >
>> >The question is regarding Phantom Power. At college, there is a 32
>> >track mixing console, each track has an individual 'phantom power'
>> >switch. The question arose in class that if every single track on the
>> >mixer had phantom power enabled and phantom power runs at +48V, would
>> >this equate to 1536V??, or isn't it as simple as that?. I realise most
>> >mic's wouldn't draw 48V of current, but if that's the case, why is
>> >phantom power set at 48V if the microphones don't need that much to
>> >operate?.
>> >
>> >I've searched for an answer to this question on the web, but I've
>> >found no answers. Hope someone can help me!.
>> >
>> >Thanks in advance,
>> >Neil.
>>
>> This is tricky - first we need to sort out your terminology a bit. 48V
>> isn't a current - it is a voltage. It is available to any mic that
>> needs it, but it is wired in a mode called parallel - that is it
>> doesn't add up for every mic, it is just 48V - no more than that. On
>> each mic channel it is fed to the mic through a pair of resistors of
>> about 6000 ohms (3000 ohms equivalent) so any single mic can take up
>> to 48/3000 or 0.016 amps (16mA). That is plenty for even the most
>> demanding phantom mic - most take much less. SOme need more, and they
>> come with their own power supply.
>>
>> But the point is that all microphones are guaranteed to work off that
>> voltage and resistance combination, but most don't need that much.
>>
>> As for the desk, if you have, say 24 mic channels, then the 48V power
>> supply must be able to supply 24 x .016 amps, or roughly half an amp.
>> So you see it is the amps, not the volts, that build up as you add
>> more microphones.
>>
>
>How do most power supplies handle that all too possible situation of
>(a) an unintentional fault causing a short between the earth and signal
>pins
>(b) an intentional situation of connecting an unbalanced source that has
>pin 2 connected to ground, as is standard practice but which results in
>phantom shorted to earth?
>
>I was working on a patch panel the other day. The desk was powered up and
>had phantom on. Every time I touched my earthed soldering iron to the
>signal pins there was a nice little blue spark from the phantom power.

The maximum current that can flow even in a dead short is the result
of the full 48 volts appearing across the 3000 ohms built into the
system - that is 16mA and will do no harm.

The little sparks you saw were the result of the 48volts. Pretty, but
probably not a good thing to do during a session! (Hint: you can
always switch the phantom off on the connectors you are working on ;-)

Connecting one pin to ground is not a problem - as far as phantom
power is concerned, the two mic pins are entirely separate.

d
Pearce Consulting
http://www.pearce.uk.com
Anonymous
September 25, 2004 1:56:04 PM

Archived from groups: rec.audio.pro (More info?)

On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
<patrickdunford@nomail.invalid> wrote:

>I was working on a patch panel the other day. The desk was powered up and
>had phantom on. Every time I touched my earthed soldering iron to the
>signal pins there was a nice little blue spark from the phantom power.

Never solder in a powered circuit. In fact, there's good reason to not
solder in an earth grounded circuit.

Chris Hornbeck
Anonymous
September 25, 2004 1:56:04 PM

Archived from groups: rec.audio.pro (More info?)

In article <MPG.1bbf5f18601fc7eb98a4ea@news.paradise.net.nz> patrickdunford@nomail.invalid writes:

> How do most power supplies handle that all too possible situation of
> (a) an unintentional fault causing a short between the earth and signal
> pins
> (b) an intentional situation of connecting an unbalanced source that has
> pin 2 connected to ground, as is standard practice but which results in
> phantom shorted to earth?

The standard phantom power circuit puts a 6800 ohm resistor in series
with the voltage going to each signal pin of the XLR connector.
Shorting one (or even both) pins to Pin 1 causes a current of
48V/6800ê or a fraction over 7 mA. That's just a little more than the
worst case microphone. Assuming the power supply is "stiff" enough,
this won't cause a change in the phantom power supplied to any other
mics fed from the same supply.

> I was working on a patch panel the other day. The desk was powered up and
> had phantom on. Every time I touched my earthed soldering iron to the
> signal pins there was a nice little blue spark from the phantom power.

It was only a tiny spark, hopefully. No damage done, probably, but why
not turn off the phantom power? Or use an ungrounded soldering iron?

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
September 25, 2004 1:58:07 PM

Archived from groups: rec.audio.pro (More info?)

In article <SQ_4d.163$W21.34@fe2.texas.rr.com> in rec.audio.pro on Fri,
24 Sep 2004 19:46:58 GMT, Logan Shaw <lshaw-usenet@austin.rr.com> says...

> By the way, as for why it's 48V, I think that has to do with
> a compromise.

No, like the 600 ohms impedance, 48V comes to us from telephone
technology. That is the voltage that phantom power on your telephone line
uses.
Anonymous
September 25, 2004 1:58:08 PM

Archived from groups: rec.audio.pro (More info?)

> In article <SQ_4d.163$W21.34@fe2.texas.rr.com> in rec.audio.pro on Fri,
> 24 Sep 2004 19:46:58 GMT, Logan Shaw <lshaw-usenet@austin.rr.com> says...
>
> > By the way, as for why it's 48V, I think that has to do with
> > a compromise.

In article <MPG.1bbf5f98130c58a498a4eb@news.paradise.net.nz> patrickdunford@nomail.invalid writes:

> No, like the 600 ohms impedance, 48V comes to us from telephone
> technology. That is the voltage that phantom power on your telephone line
> uses.

It is a compromise of sorts. In some countries in Europe, 48V is the
highest voltage they'll allow for a temporary (not-in-conduit)
installation. Imagine having to run your PA snake through conduit to
set up your system in a club.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
September 25, 2004 1:58:09 PM

Archived from groups: rec.audio.pro (More info?)

In article <znr1096063987k@trad>, mrivers@d-and-d.com (Mike Rivers)
wrote:

> > In article <SQ_4d.163$W21.34@fe2.texas.rr.com> in rec.audio.pro on Fri,
> > 24 Sep 2004 19:46:58 GMT, Logan Shaw <lshaw-usenet@austin.rr.com> says...
> >
> > > By the way, as for why it's 48V, I think that has to do with
> > > a compromise.
>
> In article <MPG.1bbf5f98130c58a498a4eb@news.paradise.net.nz>
> patrickdunford@nomail.invalid writes:
>
> > No, like the 600 ohms impedance, 48V comes to us from telephone
> > technology. That is the voltage that phantom power on your telephone line
> > uses.
>
> It is a compromise of sorts. In some countries in Europe, 48V is the
> highest voltage they'll allow for a temporary (not-in-conduit)
> installation. Imagine having to run your PA snake through conduit to
> set up your system in a club.
>
many of my outdoor(jam band festival in the feild sites) venues requrie
me to pull the snake through underground conduit, often 12 inch pvc pipe
George
Anonymous
September 25, 2004 1:58:10 PM

Archived from groups: rec.audio.pro (More info?)

In article <g.p.gleason-F93BBF.21241224092004@netnews.worldnet.att.net> g.p.gleason@worldnet.att.net writes:

> many of my outdoor(jam band festival in the feild sites) venues requrie
> me to pull the snake through underground conduit, often 12 inch pvc pipe

That's certainly an reasonable alternative to stringing it overhead.
Obviously they (and you) don't want it laying along the ground. Hope
they have the pipe installed already, or pay you well to install it.

I recall reading about a huge festival in California several years,
maybe the Us Festival, where they laid contuit, probably concrete
sewer pipe, that was large enough to crawl through without too much
contortion. They used it to get between the house console and the
stage without fighting through a sea of people.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
September 25, 2004 5:22:24 PM

Archived from groups: rec.audio.pro (More info?)

In article <znr1096110202k@trad>, mrivers@d-and-d.com (Mike Rivers)
wrote:

> In article <g.p.gleason-F93BBF.21241224092004@netnews.worldnet.att.net>
> g.p.gleason@worldnet.att.net writes:
>
> > many of my outdoor(jam band festival in the feild sites) venues requrie
> > me to pull the snake through underground conduit, often 12 inch pvc pipe
>
> That's certainly an reasonable alternative to stringing it overhead.
> Obviously they (and you) don't want it laying along the ground. Hope
> they have the pipe installed already, or pay you well to install it.
>

yes they installed it
G
Anonymous
September 25, 2004 7:35:44 PM

Archived from groups: rec.audio.pro (More info?)

In article <yMKdndZm3JTg9sjcRVn-ug@comcast.com> tyreeford@comcast.net writes:

> The 48 VDC is voltage..and we assume that it's really 48 and is stabilized,
> so adding more mics doesn't load the circuit down to something less than
> 48VDC.

> Different condenser mics have different power requirements. Some need
> more mA (millamps) than others. Some console power supplies are not designed
> to properly power all mics. The result is increased distortion and lower
> headroom on the mics themselves.

It's not hard to build a power supply with sufficient current capacity
to handle any reasonable number of microphones, and most well designed
consoles are so equipped. However, when it comes to budget-priced
consoles, often the 48 volt supply is a low power DC-DC converter
running off the op-amp power supply. This is considerably less
expensive than using a separate power transformer or a transformer
with a separate winding for the 48V power supply (wall-wart power is a
dead giveaway) but rarely provides enough current for a "full house"
of microphones.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
September 25, 2004 8:26:38 PM

Archived from groups: rec.audio.pro (More info?)

On 24 Sep 2004 10:44:05 -0700, in rec.audio.pro you wrote:

>Hello everyone,
>
>I hope someone out there can answer my question, and I hope it doesn't
>come across as too naieve!.
>
>The question is regarding Phantom Power. At college, there is a 32
>track mixing console, each track has an individual 'phantom power'
>switch. The question arose in class that if every single track on the
>mixer had phantom power enabled and phantom power runs at +48V, would
>this equate to 1536V??, or isn't it as simple as that?. I realise most
>mic's wouldn't draw 48V of current, but if that's the case, why is
>phantom power set at 48V if the microphones don't need that much to
>operate?.
>
>I've searched for an answer to this question on the web, but I've
>found no answers. Hope someone can help me!.
>
>Thanks in advance,
>Neil.
Hi Neil

a good site is

http://www.microphone-data.com/library.asp



martin

Serious error.
All shortcuts have disappeared.
Screen. Mind. Both are blank.
Anonymous
September 25, 2004 8:41:44 PM

Archived from groups: rec.audio.pro (More info?)

<< I'm guessing that
he didn't get an answer in class and that's why he asked here.
>>



Yeah, unfortunately some self-certified superior being had to slam the kid for
not already knowing the answer to the question he was asking.

Scott Fraser
Anonymous
September 26, 2004 5:31:18 AM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:

> In article <yMKdndZm3JTg9sjcRVn-ug@comcast.com> tyreeford@comcast.net writes:
>
> > The 48 VDC is voltage..and we assume that it's really 48 and is stabilized,
> > so adding more mics doesn't load the circuit down to something less than
> > 48VDC.
>
> > Different condenser mics have different power requirements. Some need
> > more mA (millamps) than others. Some console power supplies are not designed
> > to properly power all mics. The result is increased distortion and lower
> > headroom on the mics themselves.
>
> It's not hard to build a power supply with sufficient current capacity
> to handle any reasonable number of microphones, and most well designed
> consoles are so equipped. However, when it comes to budget-priced
> consoles, often the 48 volt supply is a low power DC-DC converter
> running off the op-amp power supply.

Actually Mike, I know of no such instance and I'm pretty familiar with the 'usual
suspects' in the low cost console arena.

Truth is, a DC-DC converter tends to be quite expensive.

It's much easier/cheaper to put an extra tap on the power supply transformer or
use a 'charge pump' arrangement to derive a 'high voltage' from the AC used for
the op-amp supplies.


> This is considerably less
> expensive than using a separate power transformer or a transformer
> with a separate winding for the 48V power supply (wall-wart power is a
> dead giveaway) but rarely provides enough current for a "full house"
> of microphones.

Errr.. it seems I disagree ( have never seen this - the dc to dc converter - used
in any of the major brands of budget desks ).

The charge pump is historically popular and is the arrangment usually least likely
to be able to power many mics due to its poor regulation of the ( pre 48V
regulator ic ) unregulated high voltage supply vs load current ( supply droop ).


Graham
Anonymous
September 26, 2004 5:39:48 AM

Archived from groups: rec.audio.pro (More info?)

ScotFraser wrote:

> << I'm guessing that
> he didn't get an answer in class and that's why he asked here.
> >>


>
> Yeah, unfortunately some self-certified superior being had to slam the kid for
> not already knowing the answer to the question he was asking.

In the UK ( where the OP posted from ) - it's normal to have passed some relevant
exams before going to college.

I think there's a difference between UK and US usage here. I believe that in the
US you can go to 'college' at an earlier age with less academic knowledge.

We don't have compatible schemes of education and assessment of ability but I
would expect anyone attending one of the very few UK audio courses to be (a) lucky
to be there (b) to have some knowledge of electricity that already includes volts
and amps.

The absence, apparently, of (b) reinforces my opinion that UK higher education is
going to the dogs.


Graham
Anonymous
September 26, 2004 5:42:42 AM

Archived from groups: rec.audio.pro (More info?)

Patrick Dunford wrote:

> In article <SQ_4d.163$W21.34@fe2.texas.rr.com> in rec.audio.pro on Fri,
> 24 Sep 2004 19:46:58 GMT, Logan Shaw <lshaw-usenet@austin.rr.com> says...
>
> > By the way, as for why it's 48V, I think that has to do with
> > a compromise.
>
> No, like the 600 ohms impedance, 48V comes to us from telephone
> technology. That is the voltage that phantom power on your telephone line
> uses.

There's nothing *phantom* about it - lol !

Only 2 wires used in telephony :-)


Graham
Anonymous
September 26, 2004 5:48:27 AM

Archived from groups: rec.audio.pro (More info?)

ScotFraser wrote:

> << I'm guessing that
> he didn't get an answer in class and that's why he asked here.
> >>


>
> Yeah, unfortunately some self-certified superior being had to slam the kid for
> not already knowing the answer to the question he was asking.

Yeah - and if doesn't know his volts from his amps - all those long winded
explanations about V=IR will be lost on him

I hate to see good education wasted on those who clearly don't have a clue about
the subject.

Education was once seen as a privilege - not an excuse for lame timewasters with
no clue to act the dosser.


Graham
Anonymous
September 26, 2004 12:10:49 PM

Archived from groups: rec.audio.pro (More info?)

<< I hate to see good education wasted on those who clearly don't have a clue
about
the subject.>>

This would appear to be a perfect example of the previously mentioned
difference between US & UK notions of higher education. In the US the
assumption is one attends college to learn what one doesn't already know. Seems
the UK version is more of an advanced degree in a subject already mastered.

<<Education was once seen as a privilege - not an excuse for lame timewasters
with
no clue to act the dosser.>>

We don't have dossers in the US, but it's generally the lame timewasters who
DON'T attend college (with the prominent exception of GW Bush.)


Scott Fraser
Anonymous
September 26, 2004 5:27:05 PM

Archived from groups: rec.audio.pro (More info?)

In article <41560DD6.9AF6279C@hotmail.com> rabbitsfriendsandrelations@hotmail.com writes:

> Errr.. it seems I disagree ( have never seen this - the dc to dc converter -
> used
> in any of the major brands of budget desks ).
>
> The charge pump is historically popular and is the arrangment usually least
> likely
> to be able to power many mics due to its poor regulation of the ( pre 48V
> regulator ic ) unregulated high voltage supply vs load current ( supply droop
> ).

I'm not familiar with the term "charge pump" but that's probably what
I was thinking of when I said "DC-to-DC Converter." I haven't seen the
classic oscillator/transformer/rectifier circuit used in this
application, but I have seen tricks where the op-amp power supply has
been goosed up without transformers.

I'll defer to your detailed answer on this one.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
September 26, 2004 5:27:06 PM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:


> I'm not familiar with the term "charge pump" but that's probably what
> I was thinking of when I said "DC-to-DC Converter." I haven't seen the
> classic oscillator/transformer/rectifier circuit used in this
> application, but I have seen tricks where the op-amp power supply has
> been goosed up without transformers.


A voltage multiplier circuit, the one with the cleverly-arranged caps
and diodes. It doesn't need a transformer, so it's frequently a
square-wave generator going to an electrolytic which charges through one
diode then discharges through another diode into another cap. It can be
cascaded to make triplers, quadruplers, etc, or negative supplies.
Maxim makes EIA-232 driver chips that have this built in, to make +/-
12v from +5v. If you follow the electrons around the circuit over
several cycles, a mental image of a positive-displacement water pump may
appear, hence the name.
Anonymous
September 26, 2004 5:54:45 PM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" wrote ...
> I'm not familiar with the term "charge pump" but that's probably
> what I was thinking of when I said "DC-to-DC Converter."

a.k.a. "voltage multiplier", a clever series of capacitors and diodes
explained: http://www.tpub.com/neets/book7/27m.htm et. al.
Anonymous
September 26, 2004 11:00:15 PM

Archived from groups: rec.audio.pro (More info?)

S O'Neill <nopsam@nospam.net> wrote:
>Mike Rivers wrote:
>
>> I'm not familiar with the term "charge pump" but that's probably what
>> I was thinking of when I said "DC-to-DC Converter." I haven't seen the
>> classic oscillator/transformer/rectifier circuit used in this
>> application, but I have seen tricks where the op-amp power supply has
>> been goosed up without transformers.
>
>A voltage multiplier circuit, the one with the cleverly-arranged caps
>and diodes. It doesn't need a transformer, so it's frequently a
>square-wave generator going to an electrolytic which charges through one
>diode then discharges through another diode into another cap. It can be
>cascaded to make triplers, quadruplers, etc, or negative supplies.
>Maxim makes EIA-232 driver chips that have this built in, to make +/-
>12v from +5v. If you follow the electrons around the circuit over
>several cycles, a mental image of a positive-displacement water pump may
>appear, hence the name.

This is also very commonly built with a 555 timer in order to get small
amounts of higher voltages without using a hybrid converter module. Many
microphones use similar circuits inside to crank the 48V phantom up to
a higher voltage to polarize the capsule.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
September 26, 2004 11:55:25 PM

Archived from groups: rec.audio.pro (More info?)

In article <18-dnbVs_LD6nMrcRVn-gw@omsoft.com> nopsam@nospam.net writes:

> A voltage multiplier circuit, the one with the cleverly-arranged caps
> and diodes.

OK, I know what that is. Just never heard the term "charge pump."


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
September 27, 2004 5:39:50 AM

Archived from groups: rec.audio.pro (More info?)

ScotFraser wrote:

> << I hate to see good education wasted on those who clearly don't have a clue
> about
> the subject.>>
>
> This would appear to be a perfect example of the previously mentioned
> difference between US & UK notions of higher education. In the US the
> assumption is one attends college to learn what one doesn't already know. Seems
> the UK version is more of an advanced degree in a subject already mastered.

In the UK it would tend to be more of an advanced course at college in a subject
that the student already has some knowledge of.


> <<Education was once seen as a privilege - not an excuse for lame timewasters
> with
> no clue to act the dosser.>>
>
> We don't have dossers in the US, but it's generally the lame timewasters who
> DON'T attend college (with the prominent exception of GW Bush.)

We get that too but here, sadly, college / university education is no longer the
province of those who intend to use it to further their career opportunities.

A degree is also certainly not anything like an almost guaranteed job ticket
anymore. Of those I know who have passed degrees in recent years - not *one* has
obtained a job in the subject studied. Some have simply become bar or shop staff.
This is what happens when you devaluate further education.


Graham
Anonymous
September 27, 2004 5:43:48 AM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:

> In article <41560DD6.9AF6279C@hotmail.com> rabbitsfriendsandrelations@hotmail.com writes:
>
> > Errr.. it seems I disagree ( have never seen this - the dc to dc converter -
> > used
> > in any of the major brands of budget desks ).
> >
> > The charge pump is historically popular and is the arrangment usually least
> > likely
> > to be able to power many mics due to its poor regulation of the ( pre 48V
> > regulator ic ) unregulated high voltage supply vs load current ( supply droop
> > ).
>
> I'm not familiar with the term "charge pump" but that's probably what
> I was thinking of when I said "DC-to-DC Converter." I haven't seen the
> classic oscillator/transformer/rectifier circuit used in this
> application, but I have seen tricks where the op-amp power supply has
> been goosed up without transformers.

That'll be the classic 'voltage doubler ( tripler) ' that uses capacitive coupling of the ac
input to a further rectifier stage that 'sits on top of' the + rail bulk reservoir cap. A.k.a
charge pump.

No oscillator/transformer as you say.


Graham
Anonymous
September 27, 2004 4:39:42 PM

Archived from groups: rec.audio.pro (More info?)

In article <41561082.FC498D9A@hotmail.com> in rec.audio.pro on Sun, 26
Sep 2004 01:42:42 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> says...
> Patrick Dunford wrote:
>
> > In article <SQ_4d.163$W21.34@fe2.texas.rr.com> in rec.audio.pro on Fri,
> > 24 Sep 2004 19:46:58 GMT, Logan Shaw <lshaw-usenet@austin.rr.com> says...
> >
> > > By the way, as for why it's 48V, I think that has to do with
> > > a compromise.
> >
> > No, like the 600 ohms impedance, 48V comes to us from telephone
> > technology. That is the voltage that phantom power on your telephone line
> > uses.
>
> There's nothing *phantom* about it - lol !
>
> Only 2 wires used in telephony :-)

It's called phantom in both cases because it doesn't use extra wires to
carry the power.
Anonymous
September 27, 2004 4:39:43 PM

Archived from groups: rec.audio.pro (More info?)

Patrick Dunford <patrickdunford@nomail.invalid> wrote:
>In article <41561082.FC498D9A@hotmail.com> in rec.audio.pro on Sun, 26
>Sep 2004 01:42:42 +0100, Pooh Bear
><rabbitsfriendsandrelations@hotmail.com> says...
>> Patrick Dunford wrote:
>>
>> > In article <SQ_4d.163$W21.34@fe2.texas.rr.com> in rec.audio.pro on Fri,
>> > 24 Sep 2004 19:46:58 GMT, Logan Shaw <lshaw-usenet@austin.rr.com> says...
>> >
>> > > By the way, as for why it's 48V, I think that has to do with
>> > > a compromise.
>> >
>> > No, like the 600 ohms impedance, 48V comes to us from telephone
>> > technology. That is the voltage that phantom power on your telephone line
>> > uses.
>>
>> There's nothing *phantom* about it - lol !
>>
>> Only 2 wires used in telephony :-)
>
>It's called phantom in both cases because it doesn't use extra wires to
>carry the power.

Well, originally the notion was to "phantom" a telegraph line in top of
a telephone circuit by DC signalling between ground and both sides of the
telephone line.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!