Phantom alone or full preamp? - the bare minimum.

[aanaddha]

Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
from condenser mics to analog stereo mini-jack or RCA ins on a given
portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
a preamp (integrated or stand alone) absolutely necessary?
What is the minimun number of sub-devices, knobs, LED's, cables,
connectors, switches, converters, wall worts, etc. to connect a
condenser mic(s) to a digital recording device for an acceptable
signal?
I would prefer techical answers over subjective ones.

Thanks,
Bill

[Arny Krueger]

"aanaddha" > wrote in message
om

> Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
> from condenser mics to analog stereo mini-jack or RCA ins on a given
> portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
> a preamp (integrated or stand alone) absolutely necessary?

Depends on what you're trying to do, what you're trying to do it with, and
what your goals are.

FWIW I have a CP8506 and have used it to make some pretty good recordings
given my rather specific requirements. I eventually switched over to using
mic preamps that had their own phantom power, mostly for convenience sake.
For the money and bulk, I'd probably first choose a small Behringer or
competitive mixer for most of the recordings that I would make of this kind.

Furthermore, a Nomad Jukebox 3 is not fully equivalent to a Sony portable
DAT. You can buy Sony portable DATs that have something that has enough gain
in the analog domain to be called a mic input. A Nomad Jukebox 3 does not. A
Nomad 3 has what are properly called line-level inputs. They do have low
enough noise that they can be *stretched* for some lower-level applications
at some likely or possible cost in sound quality.

Finally, if you pick the right mic and put it close enough to a loud enough
sound source, you can have a fairly-acceptable line-level signal with just a
phantom power box. I don't think this necessarily takes anything exotic - I
suspect that a ca. $40 Behringer ECM 8000 inside a piano or close to a drum
kit, or right in front of a loud band, or perhaps even as a close-up vocal
mic would do the deed. But, that's a narrow range of applications. OTOH if
your applications fits, then you're stylin'.

> What is the minimum number of sub-devices, knobs, LED's, cables,
> connectors, switches, converters, wall worst, etc. to connect a
> condenser mic(s) to a digital recording device for an acceptable
> signal?

Depends which mic (some condenser mics have built-in batteries) and what
digital recording device.

It was recently reported that someone was having some kind of success using
a $20 battery-powered headphone amp (with 6 dB gain, low distortion, good
frequency response and pretty low noise) as a sort of a mic preamp that in
conjunction with digital-domain amplification to make recordings with the
line-level inputs of a Nomad Jukebox 3 and some kind of a microphone.
Knowing a little something about Nomad 3 line level inputs (I own one of
those, too) I think that 6 dB of high quality analog domain gain provide a
pretty clear audible a benefit. This might actually work with a louder
source of music and/or a higher-output condenser microphone.

> I would prefer technical answers over subjective ones.

Name the mic, name the application, and name the recording device and we'll
try to get you a technical answer. If you want to get a technical answer you
often have to ask a somewhat detailed technical question.

[henryf]

aanaddha wrote:
> Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
> from condenser mics to analog stereo mini-jack or RCA ins on a given
> portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
> a preamp (integrated or stand alone) absolutely necessary?
> What is the minimun number of sub-devices, knobs, LED's, cables,
> connectors, switches, converters, wall worts, etc. to connect a
> condenser mic(s) to a digital recording device for an acceptable
> signal?

I use the AT822 stereo condenser microphone directly into a
1/8" stereo mic jack (miniDisk, miniDV) with excellent
results. This mic is powered by a single AA battery and has a
switchable high-pass filter. It comes with a passive XLR to
1/8" stereo jack adapter, and you can also use standard XLR
mic cables between the mic and the adapter. You can read more
about this mic at this Audio Technica site:
http://www.audio-technica.com/prodpro/profiles/AT822.html

You also ought to consider getting a mic stand and isolating
headphones.

[Justin Ulysses Morse]

aanaddha > wrote:

> Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
> from condenser mics to analog stereo mini-jack or RCA ins on a given
> portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
> a preamp (integrated or stand alone) absolutely necessary?
> What is the minimun number of sub-devices, knobs, LED's, cables,
> connectors, switches, converters, wall worts, etc. to connect a
> condenser mic(s) to a digital recording device for an acceptable
> signal?
> I would prefer techical answers over subjective ones.

Technically, you need the following:

1. Phantom power IF your microphone requires it.

2. Something to block the phantom power from going the other direction,
where it could damage your recorder. Any preamp will do this, wheras
some phantom supplies do and some do not. The two devices which will
serve this function are a transformer or a pair of capacitors.

3. Enough gain to bring the output signal of your microphone up to the
nominal operating level of your recorder. This will depend on the
volume of the sound hitting your microphone, the sensitivity of the
microphone, and the nominal operating level of the recorder. Total
necessary gain could be anywhere from -20dB to +80dB.

3.5 Number three above pretty much guarantees you'll need some kind of
a gain control to match the particular variables so that you don't feed
your recorder with too loud nor too quiet a signal.

4. A buffer that will provide an appropriate load impedance to load the
microphone, and an appropriate (low) source impedance to feed the
recorder. Some microphones aren't too particular about loading. Most
modern transformerless condenser mikes won't care too much as long as
they're loaded with between 1000 ohms and 100,000 ohms. These are the
same microphones which tend to have low output impedances. Other types
of microphones really want to see a transformer or an amplifier that
will apply the load they were designed to feed. Otherwise you get
frequency response anomalies that change the sound of the microphone.

5. A differential receiver, either a transformer or an amplifier, which
will amplify the balanced differential microphone output signal while
rejecting any common-mode noise picked up in the cable. This is
technically something you could get by without, sometimes. But you
generally won't know when until you're already recording and wondering
why you have so much noise in your audio.

6. You may decide you want some "features" such as switches to turn
different functions on and off (phantom power, polarity inversion,
-20dB pad), a little light to tell you the preamp's on, a light to tell
you the phantom power is on, a light to tell you the signal's too hot
to handle, a light to tell you your coffee's ready, etc.

A stand-alone mic preamp is a pretty convenient package that houses all
of these necessary features. Even if you don't need every one of them
all the time.

ulysses

[ScotFraser]

<< Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
from condenser mics to analog stereo mini-jack or RCA ins on a given
portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
a preamp (integrated or stand alone) absolutely necessary? >>

Phantom power does not provide any amplification of the mic signal. It merely
provides power to the impedance converter (in the case of electrets) or
backplate of the microphone (in the case of true capacitor mics,) without which
the mic does not work at all. Phantom power cannot be used with unbalanced mic
inputs, or line inputs. If you're plugging a condenser mic into an unbalanced
mic input you need a transformer or opamp between the phantom power source &
the input. If you're plugging into a line input you need a mic preamplifier
between the mic & the input.



Scott Fraser

[Mike Dobony]

"aanaddha" > wrote in message
om...
> Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
> from condenser mics to analog stereo mini-jack or RCA ins on a given
> portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
> a preamp (integrated or stand alone) absolutely necessary?
> What is the minimun number of sub-devices, knobs, LED's, cables,
> connectors, switches, converters, wall worts, etc. to connect a
> condenser mic(s) to a digital recording device for an acceptable
> signal?
> I would prefer techical answers over subjective ones.
>
> Thanks,
> Bill

Phantom power is totally different from preamp. Condenser mics are much
like a capacitor and needs voltage across the plates to react to sound
(overly simplified explanation). A preamp is needed to take mic level
output to line level input. The easiest and safest solution is to find a
small mixer that can supply phantom power and supply your recording device
LINE IN with line level output.

--
Mike D.

www.stopassaultnow.org

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[Mike Rivers]

In article > writes:

> Will a phantom power supply (e.g. A-T CP8506) suffice to get signal
> from condenser mics to analog stereo mini-jack or RCA ins on a given
> portable recording device (e.g. Nomad Juke3, Sony portable DAT), or is
> a preamp (integrated or stand alone) absolutely necessary?

If you have a highly sensitive microphone and you're recording loud
sources, you may not need the additional gain provided by a preamp,
but as a general answer, yes, you'll need a preamp. Given that most
preamps today provide phantom power, that both problems with one box.

> What is the minimun number of sub-devices, knobs, LED's, cables,
> connectors, switches, converters, wall worts, etc. to connect a
> condenser mic(s) to a digital recording device for an acceptable
> signal?

One cable per mic, provided the recording device has inputs that are
sensitive enough for microphone level and provides phantom power. Both
the Sony portable DAT and Jukebox are able to accommodate mic level
inputs (though the Jukebox is, to me, unacceptably noisy as a mic
input but works find as a line level input) but neither provide
phantom power.

> I would prefer techical answers over subjective ones.

You need to know the basic sensitivity of the microphone you intend to
use, in terms of millivolts out pre dB of sound pressure level (SPL).
You also need to know the SPL of the source you intend to record, and
the sensitivity of the input to which you intend to connect the
microphones. Given all of that information, you can determine whether
or not you need additional gain between the microphone and the
recorder's input. There's also the consideration of loading the
microphone properly so that its frequency response will be close to
what the designer intended. Some microphones are fussy about loading,
others are not. Some users are fussy about the sound of a microphone,
others are satisfied that they get something recorded.

If you take the square root of the inverse of the sensitivity rating
and divide it by the natural logarithm of the length of the cable in
furlongs, you'll get Finagle Factor which you can apply to the price
of the recorder you intend to purchase. For recorders between $100 and
$300, multiply the Finagle Factor by the 12th root of Pi, you'll get
the minimum microphone sensitivity required to reach -12 dBFS
recording level when placed within two cable lengths of an idling
Amtrak locomotive. For more expensive recorders, you need to use the
Sweetvodka Sliding Scale to reduce the Finagle Factor to the
appropriate value.

Is that technical enough?



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