How to send phantom power to an electret mic - UK Vintage Radio Repair and Restoration Discussion Forum

znortaudio · 19th Nov 2008, 9:01 pm

Hello everybody! I've recently bought two electret vintage microphones (Grundig GCMS 333), wich come with 6-pin DIN connector and need electric power to work.
My idea is to build a little box with DIN input connectors, XLR (or TRS) output connectors, and supply the voltage trough the phantom power of a mic preamp (48 V). The question is, the mics need a maximum of 20 V, so I have to make a voltage divider too. I've made one, but it doesn't work (!!), so could somebody help me with an specific-for audio purposes voltage divider scheme?
Thanx and cheers from Spain!

Tim · 19th Nov 2008, 11:18 pm

Phantoms for mics are supplied via mic transformers. Haven't done anything serious with mics for nearly 20 years, but ISTR it had to do with centre taps and balanced lines.

Explanation here

http://www.soundonsound.com/sos/mar0....htm?print=yes

arjoll · 20th Nov 2008, 3:26 am

Phantom power is 48V fed down both hot and cold on a balanced line, so there is no voltage across the mic itself.

Some information on how to power a mic that needs power but is not designed for Phantom power (i.e. 48V) is here.

Tim · 21st Nov 2008, 12:19 am

Thanks,that's a handy one Arjoll. Added to my Bookmarks..............

19th Nov 2008, 9:01 pm	#1
znortaudio Diode Join Date: Nov 2008 Location: Madrid, Spain Posts: 1	How to send phantom power to an electret mic Hello everybody! I've recently bought two electret vintage microphones (Grundig GCMS 333), wich come with 6-pin DIN connector and need electric power to work. My idea is to build a little box with DIN input connectors, XLR (or TRS) output connectors, and supply the voltage trough the phantom power of a mic preamp (48 V). The question is, the mics need a maximum of 20 V, so I have to make a voltage divider too. I've made one, but it doesn't work (!!), so could somebody help me with an specific-for audio purposes voltage divider scheme? Thanx and cheers from Spain!

19th Nov 2008, 11:18 pm	#2
Tim Nonode Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire. Posts: 2,291	Re: How to send phantom power to an electret mic Phantoms for mics are supplied via mic transformers. Haven't done anything serious with mics for nearly 20 years, but ISTR it had to do with centre taps and balanced lines. Explanation here http://www.soundonsound.com/sos/mar0....htm?print=yes __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

20th Nov 2008, 3:26 am	#3
arjoll Octode Join Date: May 2006 Location: Invercargill, New Zealand Posts: 1,203	Re: How to send phantom power to an electret mic Phantom power is 48V fed down both hot and cold on a balanced line, so there is no voltage across the mic itself. Some information on how to power a mic that needs power but is not designed for Phantom power (i.e. 48V) is here.

21st Nov 2008, 12:19 am	#4
Tim Nonode Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire. Posts: 2,291	Re: How to send phantom power to an electret mic Thanks,that's a handy one Arjoll. Added to my Bookmarks.............. __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."