Hello all,
I'm an assistant at a very nice studio, which recently bought some vintage unbalanced microphones. This studio has some outboard preamps in the control room, and 2 Digi-pre's which are in the machine-room.
The Digi-pre's can be default-patched to some of the microphone inputs in the liveroom. These units remember their settings of the last protools session, and maintain those settings until changed in protools, or on the front of the unit. This is also the case with the +48V.
This means that a (visiting) engineer, unaware of this 'feature', could patch one of our unbalanced microphones, or vintage ribbons, directly into a phantom powered input.
In order to prevent any damage to the microphones, I thought of the following: We rewire all the vintage ribbon mics, and the unbalanced mics, with a 4-pole XLR, so it's impossible for anybody to plug them into the normal microphone inputs. We make little converter boxes, from 4-pole XLR to standard 3-pole XLR. Inside these boxes, we make this:
Mic sig (or +) --- ||+ 100uF/63V --- --- XLR +
|
|
1k Ohm
|
|
GND
Mic GND (or -) --- ||+ 100uF/63V --- --- XLR -
|
|
1k Ohm
|
|
GND
Will this be enough to protect the microphones? When +48V is applied to this circuit, the condenser won't be charged right away, so the first spike will pass through, could this spike be big enough to ruin a microphone?
Any thoughts about this would really help!
Regards
I'm an assistant at a very nice studio, which recently bought some vintage unbalanced microphones. This studio has some outboard preamps in the control room, and 2 Digi-pre's which are in the machine-room.
The Digi-pre's can be default-patched to some of the microphone inputs in the liveroom. These units remember their settings of the last protools session, and maintain those settings until changed in protools, or on the front of the unit. This is also the case with the +48V.
This means that a (visiting) engineer, unaware of this 'feature', could patch one of our unbalanced microphones, or vintage ribbons, directly into a phantom powered input.
In order to prevent any damage to the microphones, I thought of the following: We rewire all the vintage ribbon mics, and the unbalanced mics, with a 4-pole XLR, so it's impossible for anybody to plug them into the normal microphone inputs. We make little converter boxes, from 4-pole XLR to standard 3-pole XLR. Inside these boxes, we make this:
Mic sig (or +) --- ||+ 100uF/63V --- --- XLR +
|
|
1k Ohm
|
|
GND
Mic GND (or -) --- ||+ 100uF/63V --- --- XLR -
|
|
1k Ohm
|
|
GND
Will this be enough to protect the microphones? When +48V is applied to this circuit, the condenser won't be charged right away, so the first spike will pass through, could this spike be big enough to ruin a microphone?
Any thoughts about this would really help!
Regards