Phantom power and SM57/58's

[amanise]

Quicky about SM57 and SM58 mics when you have phantom power switched on for something like a Rode NT1.

My Mackie 802-VLZ3 phantom switch enables phantom power for mic input 1-3. If I used an NT1 on ch1 and, say, an SM57 on ch2 - would the SM57 be affected by the phantom power it would 'have available to it'?

(I have read the manual - apparently a ribbon mic would be upset!)
Cheers
Adrian

[James Perrett]

No, the SM57/58 wouldn't worry at all about phantom power. Neither would most properly designed ribbon mics. The only mics that you need to worry about are just a few ribbon mics designed with a centre tapped transformer which should mainly be old mics rather than current mics (though I wouldn't put it past some boutique manufacturer to use an old design for "authenticity"). If a modern mic can't take phantom power then it is poorly designed.

[amanise]

No, the SM57/58 wouldn't worry at all about phantom power. Neither would most properly designed ribbon mics. The only mics that you need to worry about are just a few ribbon mics designed with a centre tapped transformer which should mainly be old mics rather than current mics (though I wouldn't put it past some boutique manufacturer to use an old design for "authenticity"). If a modern mic can't take phantom power then it is poorly designed.

Wonderful - thanks very much James!

[MarkOne]

I did read that the tie-lines between studio floor and control rooms at the old television centre had 48v permanently enabled on the floor boxes.

[Hugh Robjohns]

Yes, thats true... it was done that way to allow mic patching on a standard (PO316 B-guage) patchbay without having phantom across the sockets.

It also meant that ALL mic plugging/unplugging on the studio floor was 'hot plugging' with phantom permanently on the lines.

[Hugh Robjohns]

Quicky about SM57 and SM58 mics when you have phantom power switched on for something like a Rode NT1.

Not an issue. The two ends of the moving coil element in the SM57/58 are wired to XLR pins 2 and 3.

The body is wired to pin 1 (screen). Phantom puts 48V on both pins 2/3 returning to pin 1.

So as far as the moving coil mic is concerned, its got no voltage difference across the coil (48V at both ends) and no connection between the coil and pin 1, so no phantom current can flow.

Essentially, the SM57/58 has no idea phantom is present at all.

I have read the manual - apparently a ribbon mic would be upset!

It would be a rubbish ribbon mic if it was... but there are some about (mostly very ancient ribbons) that genuinely don't like phantom. Not something I've ever worried about, thought and I happily use Coles and AEA ribbons with phantom on the lines.

[amanise]

[ef37a]

Small point, do make sure XLR cables are in good order. A poorly soldered joint on the screen on pin one will introduce crackles and pops in ANY mic!

Dave.

[amanise]

Small point, do make sure XLR cables are in good order. A poorly soldered joint on the screen on pin one will introduce crackles and pops in ANY mic!

Dave.