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Old August 29th, 2008, 02:09 AM   #1
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In line attenuators: can they be used with Phantom power?

In line attenuators are useful for padding down a line level signal to your input where you have only mic level in, such as with the MixPre. But another application which I have been wondering about is if you use one in line from your microphone when recording a very noisy thing, like a jet engine. The resistor network in the attenuator is (in mine) like an H, where there are five resistors, one on each leg above and below the crossbar, and on the crossbar itself. Now I'm pretty sure that the crossbar resistor would rule out using a T power microphone as it would leak across the two signal legs that power the mic. But has anyone used an in line attenuator with Phantom powered mics?
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Old August 29th, 2008, 04:39 AM   #2
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In line attenuators are useful for padding down a line level signal to your input where you have only mic level in, such as with the MixPre. But another application which I have been wondering about is if you use one in line from your microphone when recording a very noisy thing, like a jet engine. The resistor network in the attenuator is (in mine) like an H, where there are five resistors, one on each leg above and below the crossbar, and on the crossbar itself. Now I'm pretty sure that the crossbar resistor would rule out using a T power microphone as it would leak across the two signal legs that power the mic. But has anyone used an in line attenuator with Phantom powered mics?
Since both legs of the signal line are at the same potential with regard to the phantom voltage, the 'crossbar' has no effect. You are correct that they won't work with T-power. Shure explicitly states in their info on the A15AS pad, which is a pretty typical model, that it passes phantom without a problem.
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Old August 29th, 2008, 07:16 AM   #3
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Thanks Steve. The real answer to recording loud noises I suppose is to use a less sensitive microphone, a moving coil job such as a AKG D25 in its globe-shaped windgag. That that assumes that you have been briefed fully on the job before you set out! A -60dB and a -20dB pad would seem to be useful things to carry for emergencies. Now all I have to do is to flog my T powered mics and replace them with Phantoms!
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Old August 29th, 2008, 07:31 AM   #4
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Thanks Steve. The real answer to recording loud noises I suppose is to use a less sensitive microphone, a moving coil job such as a AKG D25 in its globe-shaped windgag. That that assumes that you have been briefed fully on the job before you set out! A -60dB and a -20dB pad would seem to be useful things to carry for emergencies. Now all I have to do is to flog my T powered mics and replace them with Phantoms!

O get a phantom to t-power inline converter such as this unit from Sennheiser

http://www.bhphotovideo.com/c/produc...V_Phantom.html

or this from Canford

http://www.canford.co.uk/Products/49-224.aspx

Then be sure you're connected up in the order ... mixer --> pad --> converter --> mic
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Old August 29th, 2008, 09:34 AM   #5
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Steve, you're a genius! I already have a P to T converter for my MixPre - the only drawback is that it stipulates no more than 15V in from the mixer; but that's no problem as the MixPre does 15v and 48v. Thanks a lot again.
Nick
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Old August 29th, 2008, 10:45 AM   #6
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Steve, you're a genius! I already have a P to T converter for my MixPre - the only drawback is that it stipulates no more than 15V in from the mixer; but that's no problem as the MixPre does 15v and 48v. Thanks a lot again.
Nick
Strange that your converter only go up to 15v input since 48 is the norm
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Old August 29th, 2008, 11:52 AM   #7
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Yes indeed! Strange and irritating! It came with the mixer from the Sound Devices dealer. It means, of course, that I can't use it with my other two mixers, both of which supply Phantom power only at the normal 48V. Such is life.
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