[[email protected]]

I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC. I made this measurement because I haven't used this device in some time and it is probably 30 years old. Before I connect a condenser mic I thought I'd ask on this group if I might be at risk of damaging my microphone. Is it possible 54 Volts is normal given there is no load on the circuit?

Gary V

[Scott Dorsey]

wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC. I made=
this measurement because I haven't used this device in some time and it is=
probably 30 years old. Before I connect a condenser mic I thought I'd ask =
on this group if I might be at risk of damaging my microphone. Is it possib=
le 54 Volts is normal given there is no load on the circuit?

Gary V

That's out of spec, but it's only 9% high.

I don't think it will damage your microphone, but it implies the regulator
circuit inside (which I think is just a shunt zener on these things) is
bad. If that is the case you are apt to get insane hum.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers[_2_]]

On 7/10/2015 12:52 PM, wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC.

The official spec is 48 v +/-10%. The N-62E has a 51 v 5% Zener diode
for the voltage regulation so your power supply is just barely out of
spec for the worst case of the diode. There's a 6.8k resistor from the
Zener in series with the 6.8 k "phantom" resistors, so with a mic that
draws 10 mA (also part of the phantom power spec) you'll lose another
0.68 v across that.

I don't think you'll have anything to worry about unless the Zener is
open, and with the terminal voltage measuring as close to the Zener's
specified voltage, it's probably OK. But check for hum before you need
to use the supply.

--
For a good time, visit http://mikeriversaudio.wordpress.com

[[email protected]]

There's a 6.8k resistor from the
Zener in series with the 6.8 k "phantom" resistors, so with a mic that
draws 10 mA (also part of the phantom power spec) you'll lose another
0.68 v across that.

10 mA through 6.8k = 68V

Mark

[JackA]

On Friday, July 10, 2015 at 5:16:20 PM UTC-4, wrote:
There's a 6.8k resistor from the
Zener in series with the 6.8 k "phantom" resistors, so with a mic that
draws 10 mA (also part of the phantom power spec) you'll lose another
0.68 v across that.

10 mA through 6.8k = 68V

Mark

E = I x R

68 = .010 x 6800

I think Mark has a point!

Jack

[Les Cargill[_4_]]

wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC.
I made this measurement because I haven't used this device in some
time and it is probably 30 years old. Before I connect a condenser
mic I thought I'd ask on this group if I might be at risk of damaging
my microphone. Is it possible 54 Volts is normal given there is no
load on the circuit?

Gary V


Do these things, like batteries, measure high unless they are under load?

Is it under load when you measure it?


The lcklassic is a car battery @ 13.2 V 110% of nominal.

48 + 4.8 is 52.8 - not that very far from the 54V figure given.

--
Les Cargill

[JackA]

On Friday, July 10, 2015 at 7:31:55 PM UTC-4, Les Cargill wrote:
wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC.
I made this measurement because I haven't used this device in some
time and it is probably 30 years old. Before I connect a condenser
mic I thought I'd ask on this group if I might be at risk of damaging
my microphone. Is it possible 54 Volts is normal given there is no
load on the circuit?

Gary V


Do these things, like batteries, measure high unless they are under load?

Is it under load when you measure it?


The lcklassic is a car battery @ 13.2 V 110% of nominal.

48 + 4.8 is 52.8 - not that very far from the 54V figure given.

--
Les Cargill

Les, from a schematic I saw, it has a regulated supply. My guess, it has little voltage change, no load to full load. May have had incorrect schematic, but Mike's mention of a zener diode, makes me believe I was close.

Jack

[None]

"Les Cargill" wrote in message
...
wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts
DC.
I made this measurement because I haven't used this device in some
time and it is probably 30 years old. Before I connect a condenser
mic I thought I'd ask on this group if I might be at risk of
damaging
my microphone. Is it possible 54 Volts is normal given there is no
load on the circuit?

Gary V


Do these things, like batteries, measure high unless they are under
load?

Is it under load when you measure it?

I would think the voltage measured, say, across pins 1 & 2 of the
microphone cable, would depend on the amount of current being drawn.
If the power supply puts 48 V on the power-supply side of the series
resistors, and the microphone is drawing the full 10 A, then the
voltage across the microphone-side of the resistors, pins 1 & 2, would
be less than 15 V, I think. Or maybe I'm off by a factor of 2. But the
mic won't be seeing 48 V.



The lcklassic is a car battery @ 13.2 V 110% of nominal.

48 + 4.8 is 52.8 - not that very far from the 54V figure given.

--
Les Cargill

[John Williamson]

On 11/07/2015 00:32, Les Cargill wrote:
wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC.
I made this measurement because I haven't used this device in some
time and it is probably 30 years old. Before I connect a condenser
mic I thought I'd ask on this group if I might be at risk of damaging
my microphone. Is it possible 54 Volts is normal given there is no
load on the circuit?

Gary V


Do these things, like batteries, measure high unless they are under load?

Is it under load when you measure it?


The lcklassic is a car battery @ 13.2 V 110% of nominal.

48 + 4.8 is 52.8 - not that very far from the 54V figure given.

How accurate is the meter being used? Some cheap ones are only
guaranteed to be accurate to +-5%

--
Tciao for Now!

John.

[Scott Dorsey]

Les Cargill wrote:

Do these things, like batteries, measure high unless they are under load?

No. They need to be a solid, regulated 48V supply (+/- 10% to meet the
AES specification, but +/- 2% in order to meet Neumann's spec), driving
two 6.8K breakout resistors.

So... if you measure the unloaded supply with a meter that has a much higher
impedance than the breakout resistor, what you measure is the regulated supply
itself.

Now... when you plug the microphone in, the voltage will drop somewhat
and how much depends on the microphone. With 48V through a 6.8K resistor,
the short circuit current is only 7mA per side (14mA total). If you draw
the maximum the spec allows of 10mA, your voltage drops down to something
like 14V because of the breakout resistor.

In most cases the breakout resistor in the supply is being used as part of
the output stage of the amplifier circuit, so you shouldn't panic when you
measure 35V under load or even less, because the supply is still producing
48V on the other side of those breakout resistors.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Gareth Magennis]

"Scott Dorsey" wrote in message ...

Les Cargill wrote:

Do these things, like batteries, measure high unless they are under load?

No. They need to be a solid, regulated 48V supply (+/- 10% to meet the
AES specification, but +/- 2% in order to meet Neumann's spec), driving
two 6.8K breakout resistors.

So... if you measure the unloaded supply with a meter that has a much higher
impedance than the breakout resistor, what you measure is the regulated
supply
itself.

Now... when you plug the microphone in, the voltage will drop somewhat
and how much depends on the microphone. With 48V through a 6.8K resistor,
the short circuit current is only 7mA per side (14mA total). If you draw
the maximum the spec allows of 10mA, your voltage drops down to something
like 14V because of the breakout resistor.

In most cases the breakout resistor in the supply is being used as part of
the output stage of the amplifier circuit, so you shouldn't panic when you
measure 35V under load or even less, because the supply is still producing
48V on the other side of those breakout resistors.
--scott
--


This from the AKG PSU manual he
http://lcweb2.loc.gov/master/mbrs/re...T,%20N-66E.pdf


On the other hand, using another manufacturer's microphone exceeding the
N-66E's specified current limitations may cause low operating voltage at the
power-supply output(s) feeding that microphone. In such cases, it may be
necessary to " jump" or "short-out" the internal 6 .8k-ohm series resistor
at the affected output(s) as required (R7, Rl0, R13, R16, R19, R22 in the
Schematics section).



Gareth.

[Gareth Magennis]

wrote in message
...

I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC. I made
this measurement because I haven't used this device in some time and it is
probably 30 years old. Before I connect a condenser mic I thought I'd ask on
this group if I might be at risk of damaging my microphone. Is it possible
54 Volts is normal given there is no load on the circuit?

Gary V





Change the Zener, they often go faulty. Its a few cents, and your voltage
readings (or multimeter) appear out of spec.

51v + 5% = 53.55v. Subtract the 0.6v Base Emitter junction buffer
transistor = 53v absolute max.

Apply the -5% variance to the Zener and you get 47.85v.


Gareth.

[Scott Dorsey]

wrote:
Yes, I found the exact part number on the DigiKey site, but how does
one buy parts like this that are only a few cents? Even if I ordered 10
the total part cost is probably 50 cents.

Order a bunch of 10uF film capacitors, and some 47k resistors, a roll of
solder, some machined pin DIP sockets. There are plenty of things from
digi-key you need, you just don't know you need them yet.

Also, since another poster questioned my meter, I tried a couple of
other preamps with this meter and both were very close to 48 VDC,
so I'm guessing the meter reading is correct.

Probably. When in doubt, use a carbon-zinc D cell and it should be
1.56V unloaded. Reference good to two places.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Gareth Magennis]

wrote in message
...

On Saturday, July 11, 2015 at 1:57:12 PM UTC-7, Gareth Magennis wrote:
wrote in message
...

I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC. I
made
this measurement because I haven't used this device in some time and it is
probably 30 years old. Before I connect a condenser mic I thought I'd ask
on
this group if I might be at risk of damaging my microphone. Is it possible
54 Volts is normal given there is no load on the circuit?

Gary V





Change the Zener, they often go faulty. Its a few cents, and your voltage
readings (or multimeter) appear out of spec.

51v + 5% = 53.55v. Subtract the 0.6v Base Emitter junction buffer
transistor = 53v absolute max.

Apply the -5% variance to the Zener and you get 47.85v.


Gareth.

Yes, I found the exact part number on the DigiKey site, but how does
one buy parts like this that are only a few cents? Even if I ordered 10
the total part cost is probably 50 cents.

Also, since another poster questioned my meter, I tried a couple of
other preamps with this meter and both were very close to 48 VDC,
so I'm guessing the meter reading is correct.

Gary V





I would guess the same.


I often buy the odd individual part from Ebay, which usually incur
reasonable postage.
I am in the UK and know which Ebay suppliers I trust and those I don't,
maybe someone else in North America can better help you here.

(I assume this is where you live, as you haven't specified)



Gareth.

[Trevor]

On 11/07/2015 3:38 PM, John Williamson wrote:
On 11/07/2015 00:32, Les Cargill wrote:
wrote:
I have an AKG N-62E Phantom Power Supply which measures 54 Volts DC.
I made this measurement because I haven't used this device in some
time and it is probably 30 years old. Before I connect a condenser
mic I thought I'd ask on this group if I might be at risk of damaging
my microphone. Is it possible 54 Volts is normal given there is no
load on the circuit?

Gary V


Do these things, like batteries, measure high unless they are under load?

Is it under load when you measure it?


The lcklassic is a car battery @ 13.2 V 110% of nominal.

48 + 4.8 is 52.8 - not that very far from the 54V figure given.

How accurate is the meter being used? Some cheap ones are only
guaranteed to be accurate to +-5%

The cheap ones are NOT "guaranteed" to be accurate at all! Their spec
may indicate +/-5%, (and some may actually meet the spec) but that's
another matter.

Trevor.

[Trevor]

On 12/07/2015 9:57 AM, Scott Dorsey wrote:
wrote:
Yes, I found the exact part number on the DigiKey site, but how does
one buy parts like this that are only a few cents? Even if I ordered 10
the total part cost is probably 50 cents.

Try a supplier who deals in small quantity instead.

Also, since another poster questioned my meter, I tried a couple of
other preamps with this meter and both were very close to 48 VDC,
so I'm guessing the meter reading is correct.

Probably. When in doubt, use a carbon-zinc D cell and it should be
1.56V unloaded. Reference good to two places.

Even if you could actually rely on that (and you can't) it would NOT
help much with calibration at 50V.

Trevor.

[Mike Rivers]

On Saturday, July 11, 2015 at 12:03:21 AM UTC-4, None wrote:

I would think the voltage measured, say, across pins 1 & 2 of the
microphone cable, would depend on the amount of current being drawn.
If the power supply puts 48 V on the power-supply side of the series
resistors

It does, and that's why we measure (and specify) phantom power as an open circuit voltage. The other part of the specification says that it also needs to be able to supply 10 mA into a short circuit. The unspecified part is that the microphone that claims to be powered with a standard phantom supply has to be able to work with the voltage it gets, allowing for the voltage drop across the power supply's internal resistors.

(I think) Les wrote:
The classic is a car battery @ 13.2 V 110% of nominal.

Batteries have internal resistance too. You may have heard tales of guitarist Eric Johnson being able to tell the difference between different brands of batteries used in his effect pedals. Differences in internal resistance and how they age (in theory, can) make a difference in the amount of headroom that the device they'e powering has, which can affect the sound.

[Don Pearce[_3_]]

On Sun, 12 Jul 2015 05:25:36 -0700 (PDT), Mike Rivers
wrote:

On Saturday, July 11, 2015 at 12:03:21 AM UTC-4, None wrote:

I would think the voltage measured, say, across pins 1 & 2 of the
microphone cable, would depend on the amount of current being drawn.
If the power supply puts 48 V on the power-supply side of the series
resistors

It does, and that's why we measure (and specify) phantom power as an open circuit voltage. The other part of the specification says that it also needs to be able to supply 10 mA into a short circuit. The unspecified part is that the microphone that claims to be powered with a standard phantom supply has to be able to work with the voltage it gets, allowing for the voltage drop across the power supply's internal resistors.

(I think) Les wrote:
The classic is a car battery @ 13.2 V 110% of nominal.

Batteries have internal resistance too. You may have heard tales of guitarist Eric Johnson being able to tell the difference between different brands of batteries used in his effect pedals. Differences in internal resistance and how they age (in theory, can) make a difference in the amount of headroom that the device they'e powering has, which can affect the sound.

Most phantom power seems to be delivered via a pair of 6800 ohm
resistors. Between them they will supply 14mA from a 48 volt supply,
which is plenty of margin to the spec. Any microphone manufacturer
should be able to deal with that.

d

[Scott Dorsey]

Don Pearce wrote:
Most phantom power seems to be delivered via a pair of 6800 ohm
resistors. Between them they will supply 14mA from a 48 volt supply,
which is plenty of margin to the spec. Any microphone manufacturer
should be able to deal with that.

There is an actual standard for this stuff, IEC 61988, which specifies
a current source able to deliver at least 10mA into a pair of 6800 ohm
resistors.

Most modern phantom supplies are able to deliver more than 10mA, but
you will find some supplies from the seventies which are not able to
deliver more than a couple mA because they predate the actual standard
and were intended for use with specific vendors' products.

But the thing is, there's a standard, and everything today is built to
the standard, and so it's all interoperable. You will occasionally find
older stuff not built to the standard or poorly-designed stuff where someone
skimped (like the Mackie boards that couldn't handle more than half the
channels drawing phantom, etc.).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."