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ribbon mic phantom isolation
Old 29th June 2017
  #1
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Thread Starter
ribbon mic phantom isolation

Irrespective of the many ribbon mics today with onboard preamps making use of phantom power, it's general wisdom that applying phantom power to ribbons is not a good thing !

Is there such a device as a phantom blocker, that could perhaps be incorporated into an XLR female connector, which always travels with and remains dedicated to a ribbon mic ? Thus if inadvertantly connected to phantom 48V, it would harmlessly dissipate/absorb it rather than passing it on the the ribbon and damaging it ? I suspect such a circuit doesn't exist, otherwise it would routinely be built into the xlr socketry of ribbon mics already ?

Many small (and larger) mixers have global phantom power (or at least in switched banks of 4 or 8), and it's too easy to connect up a ribbon mic amongst a few condensors and hurried apply global phantom.......sssss !

Is the circuitry involved complex in nature..or is the notion of shunting phantom power harmlessly away simply not feasible ?
Old 29th June 2017
  #2
cloudlifter would do that, plus add 25db of clean gain, so I have read.
Old 29th June 2017
  #3
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Matti's Avatar
Old 29th June 2017
  #4
Gear Addict
If you only need phantom protection can't you just use an XLR ground lift
adapter (that lifts pin 1)?
I believe that phantom power sends power out on pins 2 and 3 and returns on pin 1. So no pin 1 then no phantom
current.
Old 29th June 2017
  #5
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Matti's Avatar
Quote:
Originally Posted by Folkie View Post
If you only need phantom protection can't you just use an XLR ground lift
adapter (that lifts pin 1)?
I believe that phantom power sends power out on pins 2 and 3 and returns on pin 1. So no pin 1 then no phantom
current.
- and get no protection against hum AND the phantom current still goes to the mic.

Matti
Old 29th June 2017
  #6
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Thread Starter
Thanks Matti and Adam, both good solutions ! I just found another online as well: http://www.sescom.com/product.asp?item=SES-IL-PPB

I'd be using a DAV preamp close to the mic stand, so the advantage of either the CloudLifter or FETHead in boosting the mic signal at the source end, would be minimized.

The DAV has 26dB - 59dB gain in 3dB steps., so it's hard to know if the mic would require the additional gain that either of these can provide ? With a mic of sensitivity: > -52 dBu (ref 1v/pa) I'm wondering if the extra gain is necessary ?
Old 29th June 2017
  #7
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Interesting, so that's why the AEA RPQ Pre has separate XLRs for 48v and passive. Always thought it was just annoying until now, thanks! I'm glad I never had the urge to try the BM5 with anything else cause that would have blown for sure and been a real nuisance to find a replacement that looks and sounds like it should. Prob would get the Royer clone if I lost the B&O.
Old 29th June 2017
  #8
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jimjazzdad's Avatar
Quote:
Originally Posted by studer58 View Post
Thanks Matti and Adam, both good solutions ! I just found another online as well: Sescom SES-IL-PPB XLR Inline Phantom Power Blocker

I'd be using a DAV preamp close to the mic stand, so the advantage of either the CloudLifter or FETHead in boosting the mic signal at the source end, would be minimized.

The DAV has 26dB - 59dB gain in 3dB steps., so it's hard to know if the mic would require the additional gain that either of these can provide ? With a mic of sensitivity: > -52 dBu (ref 1v/pa) I'm wondering if the extra gain is necessary ?
A high quality pre like the DAV may give you enough clean gain at max (59 dB), depending on the source level, but my rather limited experience with passive ribbons suggests that you want a high gain preamp like the AEA RPQ (80 dB) or something like a Fethead or Cloudlifter. YMMV.
Old 29th June 2017
  #9
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Matti's Avatar
Ditto

Matti
Old 29th June 2017
  #10
Our passive ribbons often receive phantom power. No issues.
Old 29th June 2017
  #11
RPC
Gear Maniac
 

I just last weekend connected my SAMAR VL37s to my ULN8 which had phantom power turned on - oops. Nothing (bad) happened. In my experience, phantom power and ribbons require one more ingredient to be a really bad mix: patchbays, or in general any TRS connection between the mike and source of phantom.

To the OPs original question: you could easily wire up two capacitors and two bleed resistors in an XLR barrel. I'm not going to venture into the audibility of capacitors and resistors and connectors here!
Old 29th June 2017
  #12
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Matti's Avatar
Often discused subject....
There is the possibilyty to short connections in patchbay or broken cables that happens in due time

Matti
Old 30th June 2017
  #13
Gear Nut
 
PuebloAudio's Avatar
 

Generally, a phantom blocking protection circuit will only reduce fidelity and increase phase distortion. It may (note the implied, non-guarantee meaning of the word "may") protect the ribbon element during preconnected-phantom-on instanances.

It will surely not protect from phantom-on-then-connect casualties because distructive currents can flow due to non-instantaneous pin 2/3 (tip/ring) contact.

Just be careful and in control of implementation.
Don't prescribe to guard-rail philosophy.

Never lost a ribbon under my watch in the last 30 years.
Old 1st July 2017
  #14
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boojum's Avatar
Just be super, super careful and remember to turn off P48 on your ribbon channels. That is the best way to do it. Set it before you go to the venue, check it when you get there and check it before you switch on the recorder. Kind of like the carpenter's "measure twice, cut once."

Last edited by boojum; 4th July 2017 at 07:15 AM.. Reason: spelling
Old 2nd July 2017
  #15
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grrrayson's Avatar
 

I've seen an RCA 44bx, Royer SF-1, and Coles 4038 all get phantom just fine.

The DAV has individual phantom so what are you worried about?

It's like being a classical musician: just don't mess up.
Old 2nd July 2017
  #16
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Yannick's Avatar
 

IMO this falls into the category of how not to press STOP during record.

Of course, sometimes stress can get the better of us
Old 4th July 2017
  #17
Gear Head
 

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