Walky phantom power

[vendettav]

sooo yeah. I'm being asked to record some movie audio and some of it is outside so I want to have the ability to walk with my boom mic.

What I have now is my condenser mic goign into my behringer mixer and then the mixer going into my iRig which is going into my iPod recording 44.1 khz wav format audio. Awesome quality for the setup gotta say. It'll do for the movie well too, the movie is an indie movie and I'm not being payed too much so this is all good.

what I'm looking for is a means to not plug my mic into a mixer and to have a portable phantom power preamp box kidn of thingy. working on a 9v battery I guess

possible? I've seen the iRig Pre. and they managed it with that product so may be we can do it too?

[Jdansti]

If I understand correctly, you just need portable power for your condenser mic.

This would probably work:



The circuit would be smaller than the 9V battery.

[Crontox102098]

If I understand correctly, you just need portable power for your condenser mic.

This would probably work:



The circuit would be smaller than the 9V battery.

I recommend this diagram, as I use it on my acoustic guitar pedal with a Piezoelectro inside her:

[ashcat_lt]

What mic is it?  You're sure it wont take a battery?  Not trying to be insulting, but sometimes we overlook the simple and/or obvious.

[Gus]

Phantom power often is 48VDC with two 6.8k matched resistors to pins 2 and 3 with pin one being ground
There are also other phantom power specifications
http://en.wikipedia.org/wiki/Phantom_power

I would guess you are using 48VDC phantom
What microphone are you using?
You will need a blimp or something else for wind noise.

[Jdansti]

Maybe PRR will chime in. I understand that be has a lot of experience with condenser mics.

[vendettav]

Hey guys it's an MXL 441 pen mic.

It doesnt have a battery capability.

What I need I guess is not just phantom power but a preamp with it.


I am plugging it to a behringer xenyx 802 mixer by the way so may be I thought I can get somethign that'll transform the car power to 220v or 110v. Mixer is 110v and I use a 220 to 110 adapter since Im in Armenia now

so anyways. Any possible solutions to recording on the street? Even if I could at least get away by just getting power for my mixer from a car

[PRR]

Does the iPod have a mike? Trade that studio junk for a large cardboard box. Make three diagonal cuts around one corner to make the largest-possible 3-sided "cone". Get a iPod car-mount (you know you need one). Mount the iPod in the corner, with the mike-hole as-close-as-possible to the corner (within 2 inches). If the large end of the cone is over a foot across, this will give very significant directivity, possibly better than Cardioid in the critical speech bands. And it's light. And if the iPod stays in the mount, fairly drop-proof (the cardboard will crumple).

If you must use a *studio* mike on location....

Go battery. What, a 2-hour movie? 10:1 shooting ratio? 2:1 setup/shoot ratio? You only need it to run 40 hours total. One 9V can supply 10mA for 30+ hours to 5.4V; say 10 hours for Phantom work. Need five batteries per pack, four packs per entire movie, 20 9V batts. Home Despot will sell you six for $10, so $40 for the project. (Less if you can see the camera tally-light and turn-off ASAP; less if the shooting-ratio is lower.)

Given a hot condenser and the iRig, I think all you need is RadioShack 274-016 modded to inject your 45V battery via 2x6K8 to the XLR jack terminals.

[vendettav]

you see the bad part is that my iRig is for guitar, meaning it doesnt have a preamp for the mic. so I'd need a preamp. I actually figured i'm gonna borrow my friend's interface which can take power from USB only and also provide phantom power. This is so far the easiest solution, I'll have to have long cables to walk with the mic but given the cables are balanced, they dont really provide any worries

[Jdansti]

^ Maybe not. Using the schematic I provided above, I've powered a condenser and run it through my guitar amp and it worked fine without a preamp.

[PRR]

I've often run mikes through guitar amps. The classic 1940 guitar amp IS the mike input on a small PA amp. Lo-Z mikes favor step-up such as that RS transformer.

[vendettav]

alright well then it's gonna be ok, but the schematic has only a single input and output. my mics are balanced actually.

oh also would there be a way to get 48v from a laptop usb? like the audio interfaces do?

[Jdansti]

For reference, here's your mic: http://www.mxlmics.com/microphones/Kits/440-441/

Here's an excerpt from http://www.epanorama.net/circuits/microphone_powering.htm:
----------------------
"Obtaining the +48V power supply for phantom power.
In mixing consoles the phantom power voltage is usually made using a separate transformer output or using a DC/DC converter. One example of such DC/DC-converter circuit can be found at http://www.epanorama.net/counter.php?url=http://www.paia.com/phantsch.gif (circui diagram of one microphone preamplifier kit from PAiA Electronics).  [old link doesn't work-JD]

If you are operating using batteries then it might be useful to know that many phantom powered micks will work fine on less than 48v, try 9v and work up till you get good results, 27v would be 3 9v batterys and a lot simpler than a DC to DC converter. Remeber that some microphones do not work properly or sound different when run on too low voltage. Five 9v batteries in series is 45 volts which should be enough for any phantom power microphone.

If you do use batteries, put a capacitor around them because batteries do make noise. Filtering of battery noise can be done for exammple by using 10 uF and a .1 uF in parallel with the batteries. Another option is to decouple batteries with a 100 ohm resistor and 100uF 63V capacitor."
---------------------------
Here are a couple of off-the-shelf interfaces that will provide 48v from a laptop, but I've read that they can quickly drain laptop's battery:

M-Audio MobilePre USB Audio Interface
PreSonus FireStudio Mobile

Another thought: how mobile does your rig have to be?  Will your laptop be carried by hand, in a backpack, or in a wagon. The reason I ask is if you use a kiddie wagon or something similar, you could expand your power supply options and use a small UPS (uninterruptible power supply). If you do this, pick one that doesn't beep when unplugged, or else you might have to do a beeperectomy.

[PRR]

> my mics are balanced actually

A transformer like RS 274-016 will take balanced input, can isolate the Phantom from the iRig, and give 1:7 step-up.

> "many phantom powered micks will work fine on less than 48v"

Some do some don't. The earliest needed a good 40V to polarize the capsule. Later there were high-buck mikes with internal voltage converters; AKG 414 is perfectly happy at 9V. With the rise of $99 mikes and near-universal P48 we again find mikes that expect over 40V for capsule polarization because its a buck cheaper.

Be conservative in complications. The more stuff you have, the more can/will go WRONG.