Can phantom power damage condenser mic over unbalanced XLR cable?

PavelK

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Jul 7, 2017
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Hi,
I bought Chord CM05 microphone on amazon - it looked as reasonably quality mic for a good price. Since it is my first condenser mic, I just wanted to try it and bought a cheap phantom power from aliexpress.
Unfortunately I realised that the XLR cable I had (just spare one, I never used it before) is unbalanced one - only two wires, pin 1&3 interconnected. That means Chord mic got 48V on pin 2 and 0V on pin 3 and 1. I realized it soon (under one minute) after I didn't hear anything on the output.

When I obtained correct, balanced cable, I'm hearing only noise when I switch phantom power on, no other sound. I checked that there is really 48V on both pins 2 and 3 (to pin 1 of course) and I measured approx 10kohms between pins 2&3 on mic side of PhPwr (while turned off) which restricts current to about 10mA on each pin. I also tried a dynamic mic which passes sound through phantom power supply.

Mic spec mentions FET preamp inside, can it be damaged by 48V difference between pins 2&3 ? How can I find it out?

My testing setup is:

Mic - balanced XLR cable - Phantom Pwr Supply - XLRto3.5mmJack - mobile phone with recording app

This setup works with dynamic mic (with or without PhPwr). I intendcto buy something better (phantom power & recorder or PC interface), but I am on budget, so I go step by step, began with mic...

Thank you for any idea.
 

shrapnel_indie

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Jan 21, 2010
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This may help some: http://www.prosoundweb.com/channels/church/primer_on_phantom_power_for_condenser_microphones/


According to DIN standard 45596, phantom powering is a positive voltage (12-48V DC) on XLR pins 2 and 3 with respect to pin 1. The cable shield is the supply return. There is no voltage between pins 2 and 3. Pin 1 is ground; pin 2 is audio in-polarity, and pin 3 is audio opposite-polarity.

Also, pin 1 has 0 volts; pin 2 has a positive voltage, and pin 3 has the same positive voltage as pin 2. The phantom on/off switch in many consoles is labeled “P48” to signify “phantom power 48 volts.”

Some microphones or mic capsules work on DC bias rather than phantom power. A separate wire supplies B+ to the mic capsule. You’ll see this arrangement in lavalier mics or choir mics between the mic capsule and its XLR connector. The mic capsule itself runs off DC bias, while the XLR connector houses a circuit that runs off phantom power. That circuit converts phantom power to DC bias for the mic capsule, and balances the signal.
A condenser Mic definitely needs a true 3-pin XLR line from start to end... it also helps in reducing noise from them.
 
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