I'm curious. I just got a new condenser mic which is powered exclusively by
phantom power. I'm using a midiman audio buddy preamp to feed the signal
into my pc. I'm just curious because I want to make sure my new mic is not
defective--after not using the preamp for some time, it usually takes a good
4 seconds after switching on the phantom power before the mic is active.
Afterit's been in use, and then shut off and then turned right back on,
everything starts up right away; it's only when the equipment has been shut
down for some time that I notice this. Is this caused by the preamp or the
mic? I assume it's normal but I want to be sure--can someone help?

I'm curious. I just got a new condenser mic which is powered exclusively by
phantom power. I'm using a midiman audio buddy preamp to feed the signal
into my pc. I'm just curious because I want to make sure my new mic is not
defective--after not using the preamp for some time, it usually takes a good
4 seconds after switching on the phantom power before the mic is active.
Afterit's been in use, and then shut off and then turned right back on,
everything starts up right away; it's only when the equipment has been shut
down for some time that I notice this. Is this caused by the preamp or the
mic? I assume it's normal but I want to be sure--can someone help?

I suspect that it's normal, and is due to the design of the preamp.
The Audio Buddy is powered by a 9-volt AC adapter. If I recall
correctly, phantom power is 48 volts DC, which you can't develop
directly from a 9 VAC source. This implies that the preamp must have
some sort of voltage step-up circuitry (possibly a small transformer,
possibly a DC-to-DC converter). The need for low noise levels would
require that the phantom power be very well filtered, to keep AC hum
or converter noise out of the audio. Phantom power requires very
little current.

So, my guess is that the preamp's voltage step-up circuitry includes
one or more stages of RC (resistive/capacitive) filtering, with a
fairly large R value and a large C value (and thus a long time
constant). This would result in excellent filtering of the noise, but
it would require some amount of time for the filter capacitors to
charge up and for the output voltage to rise up enough to power the
mic. As a beneficial side effect, this slow rise in the voltage would
minimize the turn-on THUMP.

If you power the Buddy off and then on again fairly quickly, the
filter caps in the phantom-power circuit would not have had time to
discharge, and you'd get audio immediately.

In short, it's very probably normal behavior for this preamp and is
nothing to worry about.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article , TheKeith wrote:
I'm curious. I just got a new condenser mic which is powered exclusively by
phantom power. I'm using a midiman audio buddy preamp to feed the signal
into my pc. I'm just curious because I want to make sure my new mic is not
defective--after not using the preamp for some time, it usually takes a good
4 seconds after switching on the phantom power before the mic is active.
Afterit's been in use, and then shut off and then turned right back on,
everything starts up right away; it's only when the equipment has been shut
down for some time that I notice this. Is this caused by the preamp or the
mic? I assume it's normal but I want to be sure--can someone help?

All those bypass capacitors and coupling capacitors take a while to charge
up. Could take as much as five minutes for everything to completely stabilize.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"TheKeith" wrote:

I'm curious. I just got a new condenser mic which is powered
exclusively by phantom power. I'm using a midiman audio buddy preamp
to feed the signal into my pc.

Uh oh. The "Audio Buddy" preamp has completely non-standard phantom
powering--only around 30 Volts (open circuit), last sample I measured,
instead of the 48 Volts (open circuit) which most mikes are made for.
Most high-quality condenser microphones will not function properly with
that preamp--you can get reduced sensitivity, altered frequency response
and reduced maximum SPL handling ability (perhaps drastically so).

In addition, the inputs of the "Audio Buddy" overload at about 110 mV
(way too low), and the "Clip" LED doesn't indicate input overload; it
lights only if the _output_ of the circuit is pushed into clipping.
That's a very risky setup for live recording with condenser microphones.


I'm just curious because I want to make sure my new mic is not
defective--after not using the preamp for some time, it usually
takes a good 4 seconds after switching on the phantom power before
the mic is active.

That in itself is nothing to worry about. The preamp generates its
phantom supply voltage through a voltage multiplier, which has to charge
up some capacitors through some diodes. That ordinarily takes a bit of
time. Then inside your microphone (depending on what brand and model it
is, which you didn't say), there may be another DC/DC converter which
may take time to rev up--perhaps all the more so since as I said, the
phantom powering circuit in the "Audio Buddy" doesn't offer the 48 Volts
that most phantom-powered condenser microphones expect.

Some microphones--some electrets and even some externally polarized
condensers--will operate properly with that supply voltage. But you
can't rely on it for general use. The "Audio Buddy" is a nice enough
little preamp for semi-pro or amateur use with dynamic and electret
microphones (only). M Audio makes a serious two-channel preamp called
the "DMP3" which does have proper phantom powering at 48 Volts; I'd
strongly recommend using that model instead, or something else that
halfway respects the phantom powering standard.

"David Satz" wrote in message
om
"TheKeith" wrote:

I'm curious. I just got a new condenser mic which is powered
exclusively by phantom power. I'm using a midiman audio buddy preamp
to feed the signal into my pc.

Uh oh. The "Audio Buddy" preamp has completely non-standard phantom
powering--only around 30 Volts (open circuit), last sample I measured,
instead of the 48 Volts (open circuit) which most mikes are made for.

Most high-quality condenser microphones will not function properly
with that preamp--you can get reduced sensitivity, altered frequency
response and reduced maximum SPL handling ability (perhaps
drastically so).

The 48 volt *standard* isn't without exceptions, as you say.

The phantom voltage coming out of a Rolls MP13 is just under 30 volts. The
good news is that the clipping indicator seems to be more representative.

There also seem to be a number of mic preamps and mics that use phantom
power in the range of 12 volts. Benchmark Media comes to mind. Is this a
broadcast thing?

....not to mention cheap electret mics that require only about 3 volts.

"David Satz" wrote in message
om...
"TheKeith" wrote:

I'm curious. I just got a new condenser mic which is powered
exclusively by phantom power. I'm using a midiman audio buddy preamp
to feed the signal into my pc.

Uh oh. The "Audio Buddy" preamp has completely non-standard phantom
powering--only around 30 Volts (open circuit), last sample I measured,
instead of the 48 Volts (open circuit) which most mikes are made for.
Most high-quality condenser microphones will not function properly with
that preamp--you can get reduced sensitivity, altered frequency response
and reduced maximum SPL handling ability (perhaps drastically so).

In addition, the inputs of the "Audio Buddy" overload at about 110 mV
(way too low), and the "Clip" LED doesn't indicate input overload; it
lights only if the _output_ of the circuit is pushed into clipping.
That's a very risky setup for live recording with condenser microphones.


I'm just curious because I want to make sure my new mic is not
defective--after not using the preamp for some time, it usually
takes a good 4 seconds after switching on the phantom power before
the mic is active.

That in itself is nothing to worry about. The preamp generates its
phantom supply voltage through a voltage multiplier, which has to charge
up some capacitors through some diodes. That ordinarily takes a bit of
time. Then inside your microphone (depending on what brand and model it
is, which you didn't say), there may be another DC/DC converter which
may take time to rev up--perhaps all the more so since as I said, the
phantom powering circuit in the "Audio Buddy" doesn't offer the 48 Volts
that most phantom-powered condenser microphones expect.

Some microphones--some electrets and even some externally polarized
condensers--will operate properly with that supply voltage. But you
can't rely on it for general use. The "Audio Buddy" is a nice enough
little preamp for semi-pro or amateur use with dynamic and electret
microphones (only). M Audio makes a serious two-channel preamp called
the "DMP3" which does have proper phantom powering at 48 Volts; I'd
strongly recommend using that model instead, or something else that
halfway respects the phantom powering standard.


thanks everyone for your help. The audio buddy's underpowered phantom power
cannot harm the mic at all can it?

"David Satz" wrote in message
om...
"TheKeith" wrote:

I'm curious. I just got a new condenser mic which is powered
exclusively by phantom power. I'm using a midiman audio buddy preamp
to feed the signal into my pc.

Uh oh. The "Audio Buddy" preamp has completely non-standard phantom
powering--only around 30 Volts (open circuit), last sample I measured,
instead of the 48 Volts (open circuit) which most mikes are made for.
Most high-quality condenser microphones will not function properly with
that preamp--you can get reduced sensitivity, altered frequency response
and reduced maximum SPL handling ability (perhaps drastically so).

In addition, the inputs of the "Audio Buddy" overload at about 110 mV
(way too low), and the "Clip" LED doesn't indicate input overload; it
lights only if the _output_ of the circuit is pushed into clipping.
That's a very risky setup for live recording with condenser microphones.


I'm just curious because I want to make sure my new mic is not
defective--after not using the preamp for some time, it usually
takes a good 4 seconds after switching on the phantom power before
the mic is active.

That in itself is nothing to worry about. The preamp generates its
phantom supply voltage through a voltage multiplier, which has to charge
up some capacitors through some diodes. That ordinarily takes a bit of
time. Then inside your microphone (depending on what brand and model it
is, which you didn't say), there may be another DC/DC converter which
may take time to rev up--perhaps all the more so since as I said, the
phantom powering circuit in the "Audio Buddy" doesn't offer the 48 Volts
that most phantom-powered condenser microphones expect.

Some microphones--some electrets and even some externally polarized
condensers--will operate properly with that supply voltage. But you
can't rely on it for general use. The "Audio Buddy" is a nice enough
little preamp for semi-pro or amateur use with dynamic and electret
microphones (only). M Audio makes a serious two-channel preamp called
the "DMP3" which does have proper phantom powering at 48 Volts; I'd
strongly recommend using that model instead, or something else that
halfway respects the phantom powering standard.

Sorry I forgot to mention that my mic is an mxl 990
(http://tinyurl.com/zon2, one of those cheap low-cost chinese-made
ones--sounds great though). I actually do not need a 2-channel at all--I
only need one. I was just doing a little digging around on the music sites,
and discovered that there are a bunch of single channel preamps (one of
which is half the price of the audio buddy) that actually specify the +48V
which the midiman for some reason does not. Why would midiman implement a
non-standard phantom power voltage on the audio buddy? I don't get it?

Anyway, would you recommend one of the top few preamps on this page instead
of the audio buddy: http://tinyurl.com/zomq - All I do is some occasional
voice stuff for my flash animations. If I bought one of these cheaper ones,
I would just sell the audio buddy on ebay or something. Thanks.

"TheKeith" wrote ...
Sorry I forgot to mention that my mic is an mxl 990,
one of those cheap low-cost chinese-made ones--
sounds great though).

Most of those "Shanghai" mics use the phantom voltage
directly on the condenser capsule as the polarization potential.
Using a voltage lower than 48v will likely make the microphone
less capable of handling loud sounds before distorting. But
perhaps you don't need that capability for your application?

I actually do not need a 2-channel at all--I only need one.
I was just doing a little digging around on the music sites,
and discovered that there are a bunch of single channel
preamps (one of which is half the price of the audio buddy)
that actually specify the +48V which the midiman for some
reason does not.

Perhaps because the Midiman doesn't DO 48v?

Why would midiman implement a non-standard phantom
power voltage on the audio buddy? I don't get it?

It is easier/cheaper. Nothing more complicated than that.
Many condenser mics (like electrets) need only 12v or
even less.

Arny Krueger wrote:

There also seem to be a number of mic preamps and mics that use phantom
power in the range of 12 volts. Benchmark Media comes to mind. Is this a
broadcast thing?

The DIN standard for phantom powering defined systems for phantom powering
at 12 Volts, 24 Volts and 48 Volts. 12 VDC was proposed because it can
nearly always be obtained fairly easily from most recording equipment.

48 VDC was advanced by Neumann because back when the maximum current was
2 mA, it was compatible with power supplies for tube mikes containing the
AC 701 tube (standard with German radio, with +120 VDC plate supplies),
and because it was originally improvised to work with a particular set of
fixed installations in Norway, if I recall the history correctly, where
a regulated 48 Volt DC supply happened to be available.

Unfortunately the capsules of most tube condenser microphones of the
time were designed for 60 Volt polarization and required either some
redesign or some loss in performance when polarized at only 48 Volts
(or what's left of that after it passes through the phantom feed
resistors and the filtering inside the microphone).

Sound Devices is another manufacturer that offers 12-Volt phantom powering
in some of its portable preamps and mixers, and Nagras had it 30 years ago.
If I remember correctly the Aeta portable preamp offers it, too (a nice
little French device that I never see mentioned here).

As you may know, Schoeps offers a 12-Volt phantom-powered amplifier in
the modular "Colette" microphone series--the model CMC 3--and also an
amplifier version called the CMC 6 which switches automatically between
48 and 12 Volt phantom powering, depending on what voltage it senses.
That's useful because if the supply is at 48 Volts, that mode of the
circuit will draw far less current than a microphone designed purely for
12 Volt phantom powering would try to draw under the same circumstances.

The proposal for 24 Volt phantom powering had real merit, but it came along
so late (1979) that a kind of reverse chicken-and-egg situation was created:
no one wanted to make microphones that ran only on 24 Volt phantom powering,
since 48 Volts was already so well established, and no one wanted to make
mixing consoles or preamps with 24 Volt phantom because all phantom powered
mikes could be supported by supporting 12 and 48 Volts.

"P 12" was carried over to the IEC specification along with "P 48," but
"P 24" is either gone now or is about to be--I forget exactly which.

P 48: supply resistors = 2 x 6.8 kOhm
P 24: supply resistors = 2 x 1.2 kOhm
P 12: supply resistors = 2 x 680 Ohm

I know of only one microphone which was explicitly engineered to support
P 24 powering: the original, discrete-transistor version of the Neumann
TLM 170 (i.e. not the present-day model TLM 170 R). But it also worked
with 48-Volt phantom powering, so ...

TheKeith wrote:

I was just doing a little digging around on the music sites, and
discovered that there are a bunch of single channel preamps (one of
which is half the price of the audio buddy) that actually specify the
+48V which the midiman for some reason does not.

Of the preamps on that page, I have tested the 48 Volt phantom powering
implementation in the lowest-cost version of the Art Tube MP and the small
dbx preamp which so strongly resembles it. BUT both those preamps had
surprisingly high distortion levels and odd gain structures which made
them easy to overload inadvertently. I really can't recommend either of
them, unfortunately. You may want to try a Sound Devices MP-1, a JoeMeek
VC3Q (conceivably--they're quirky), or an Event EMP-1 if you can find one.

I have the feeling that I'm forgetting another good choice, so if I think
of it after my Tae Kwon Do class that I have to leave for now, I'll post
again later.

There are also higher-end choices (John Hardy; Grace) but they're beyond
your price range, I suspect.

--best regards