Phantom power on ribbon mics.....

  • Thread starter Thread starter thajeremy
  • Start date Start date
good info.

i think the anti-phantom craze happened the same way zero-tolerance policies do. somebody screwed up and something bad happened, so the response became "never, ever, under any circumstances, ever!"

perhaps not entirely rational, but i can understand the "better safe than sorry" approach.
 
drossfile said:
i think the anti-phantom craze happened the same way zero-tolerance policies do. somebody screwed up and something bad happened, so the response became "never, ever, under any circumstances, ever!"

perhaps not entirely rational, but i can understand the "better safe than sorry" approach.
Click to expand...

As Marik pointed out in a correction to that article, historically, ribbon mics had a grounded center tap on the cable side. I'm pretty sure that applying phantom power to such a microphone would tend to permanently magnetize the transformer's core and seriously wreck the sound of the mic.

Also, with a mic wired that way, if one of the two signal wires breaks loose from the connector, you're going to get ribbon deflection when you power it on because you are now getting a sudden spike of DC on one side of the transformer and a ground on the other side.... :)

The people screaming "don't ever use phantom power with ribbons" are not wrong. If you don't know with certainty how a ribbon mic is wired, you should err on the side of caution and should not ever use phantom power with it.
 
The deflection shown in that video can occur when a ribbon is hot-patched. Whether or not that is terminal or damaging for the ribbon depends on the transformer and the construction of the ribbon.
 
mshilarious said:
The deflection shown in that video can occur when a ribbon is hot-patched. Whether or not that is terminal or damaging for the ribbon depends on the transformer and the construction of the ribbon.
Click to expand...

Do you mean with a TRS patch (in which case the plug's ring contact gets momentarily grounded out while the plug tip is connected to the ring)? If not, I'm not sure how it could happen with an XLR hot patch any more than it could happen when you turn phantom on (miswiring notwithstanding).

I see three cases:

A. Neither side of the transformer has power applied. Nothing happens.
B. Both ends of the transformer have power applied. The voltage cancels out in the transformer.
C. One end has power applied and the other end is floating. Because there is no path to ground, no inrush occurs through the transformer's cable-side windings, so you don't get any corresponding induced voltage in the ribbon-side windings.

Am I missing something fundamental? I guess if you normal your input jacks to ground in a patch panel or something, maybe.... Oh, gosh, yes, now that I think about it, I've heard of people doing that to keep noise out of the system. That would = fireworks for sure. :D
 
I'm afraid I don't have a technical explanation for you. All I know is that if you give me an XLR cable with phantom on, and a ribbon mic, I can cause excursion like that to the point of destroying a ribbon by jiggling the cable connection with the mic. Now, I will exaggerate the angle to ensure the longest difference between pin contact, which isn't typical, but XLR connectors can vary quite a bit in pin alignment. I don't know if that will destroy all ribbons, just my short, thin (2.5 micron or less) ribbons. If somebody wants to send me a ribbon to try and destroy, please feel free! I got tired of reribboning my mic, so I'm not doing more experiments. If somebody wants to send me a few square inches of 2.5 micron and 6 micron material, I can try to measure that difference, otherwise my ribbon-destroying days are over.

Again, not sure why. Collapsing secondary inductance? I really have no idea.
 
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