Condenser Microphone Phantom Power

[VK2CSW]

Hi All,

A bit of a left field question.

Does anyone use condenser microphones? If so, how do you supply the power?

The obvious ways (from a sound engineers view) is to run it from a desk with the MixOut as the audio source for the radio, or to use a mic preamp - either way you will get the phantom power.

Without going to these lengths, as both solutions have interference concerns around HF, how do you power the mic?

Do modern radio's have issues with phantom power and balanced mic's? I guess a transformer would isolate the DC ok.

[VK4TI]

if the radio doesn't have simple power available then add a voltage phantom and a 9v battery somewhere I guess

[VK2CSW]

if the radio doesn't have simple power available then add a voltage phantom and a 9v battery somewhere I guess

I am not sure a 9v battery will cut it.

The spec for phantom power is from DIN Specification 45 595, dated August 31, 1976. Voltage is rated at 48 Vdc and the maximum phantom power current is rated at 7 mA, (Which usually works as 48 Vdc supplied through a 6.8 kOhm limiting resistor).

Time for a few experiments.

This is another Sunday afternoon thought experiment gone physical. I turned up an old studio condenser mic in a box of stuff from a previous life - I thought it would look groovy in the shack. The issues are that it is a) a balanced mic - not hard to over come and b) requires phantom power.

Now where is that mixing desk, that should let me at least test the mic to see if it works...

[VK3MIX]

I've seen portable phantom power units using a couple 9v batteries. I dont think it has to be 48 volts, my thinking is 48 volts is the standard to over come voltage drop over the distance of a microphone cable which could be a hundred feet or more.

A quick google gave me these links ...
http://shure.custhelp.com/app/answers/d ... ced-output
http://www.songsofthecosmos.com/encyclo ... power.html

[VK4TI]

Yup old std 9v battery and some circuit to make it run the mic , http://www.epanorama.net/circuits/micro ... ering.html should help as its easy , just remember to bring spares in a contest

[VK4APN]

Hi All,

A bit of a left field question.

Does anyone use condenser microphones? If so, how do you supply the power?

The obvious ways (from a sound engineers view) is to run it from a desk with the MixOut as the audio source for the radio, or to use a mic preamp - either way you will get the phantom power.

Without going to these lengths, as both solutions have interference concerns around HF, how do you power the mic?

Do modern radio's have issues with phantom power and balanced mic's? I guess a transformer would isolate the DC ok.

I use one through a cheap mixer - from memory a Behringer 802? This supplies the 48v phantom power. As a bonus it allows you to tailor your audio (simple equaliser) and listen to the changes via headphones, also setting levels is easy to do with it.

Paul

[VK3ALB]

Hi All,

A bit of a left field question.

Does anyone use condenser microphones? If so, how do you supply the power?

The obvious ways (from a sound engineers view) is to run it from a desk with the MixOut as the audio source for the radio, or to use a mic preamp - either way you will get the phantom power.

Without going to these lengths, as both solutions have interference concerns around HF, how do you power the mic?

Do modern radio's have issues with phantom power and balanced mic's? I guess a transformer would isolate the DC ok.

Yes I used condenser microphones and I can't say that either of the options you suggested do have interference issues if you take a few simple precautions. Running mic signals at line level is not a bad thing as long as you use a suitable attenuator (40dB from memory) at the radio. You're right to think about transformer coupling and you can find suitable transformers in old modems. Others have already pointed you to solutions for providing power to your microphone. Don't forget to use decoupling capacitors around the place.

[VK2CSW]

Thanks for the replies.

It seems the mic in question is being a little recalcitrant.

I haven't given up, just yet. At least it gives me a couple of fiddling around projects!
(I just wish this working for a living lark would stop getting in the way)

One question for Paul - I take it you used the mic gain on that channel to attenuate the levels being fed to the radio? (In addition to judicious setting of the MixOut level).

[VK4APN]

One question for Paul - I take it you used the mic gain on that channel to attenuate the levels being fed to the radio? (In addition to judicious setting of the MixOut level).

Yes exactly, very easy to get levels correct. Especially if you have radios that require quite different mic levels.
Paul vk4apn