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Author Topic: Having trouble deciding between 48v Phantom blockers  (Read 4102 times)

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Offline tim in jersey

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Having trouble deciding between 48v Phantom blockers
« on: July 04, 2014, 02:48:38 AM »
DISCLAIMER: Wasn't sure if I should have posted this in the
Cables
Microphones & Setup
or
Battery Boxes, Preamps, Mixers, ADCs, and Processors

Sub-boards...

Mods: feel free to relocate...

Long story short, I'm doing a lot more AUD+SBD recording. I have a Patchbox and I'm pretty good at making sure the "patchers" have 48v Phantom switched off, but you just never know. I want to block Phantom from burning out a trusted source. I've googled Phantom blocking and come up with these 2 sources:

http://www.sescom.com/product.asp?item=SES-IL-PPB
http://tritonaudio.com/index.php?option=com_content&task=category&sectionid=4&id=23&Itemid=43

Any Ideas on either of these items?

Offline TSNéa

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #1 on: July 04, 2014, 05:31:41 AM »
What about this:
http://naiant.com/itpspecification.html

Unless I misunderstand something... And it can also be used as a mic preamp. But let's Jon explain the tech stuff.  :)

Offline JD

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #2 on: July 05, 2014, 03:08:21 PM »
Where do you intend to put the blockers in the chain?
Between the patchbay and the source would protect the source, but I would think the P48 could still back-feed to all the decks plugged into the patchbay. You might need blocker for each of the balanced outputs on the patchbay.

FWIW, I have the same patchbox you have, although a generation or two older. When I bought it used off of ebay, two of the XLRs outputs were dead. Upon further investigation, I found that there were some resistors burned open on the circuit board, an easy fix. I always suspected that someone plugged into it with 48P on and toasted those outputs.... http://www.henryeng.com/pdf_MANUALS/PIIM.pdf

You have me thinking about modding my patchbay to choke any accidental P48 on all the balanced outputs. There is plenty of room to add some circuitry inside those Henry Engineering boxes... :hmmm:


Fortunately, 99% of my patchers plug in with RCA's so phantom isn't an issue.
Mics: DPA 4022, 4060; Nevaton MC51, MCE400; Gefell sms2000, m20, m21, m27
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Offline ScoobieKW

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #3 on: July 05, 2014, 03:33:03 PM »
Transformer isolated splits are the industry standard in this situation. Here's an example of a pro press box. Each output is transformer isolated and ground lifted. I'm sure Whirlwind will build this in a 2 input config for stereo recording.

http://www.markertek.com/Audio-Equipment/Audio-Interface/Press-Boxes/Whirlwind/PB06.xhtml

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Offline TSNéa

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #4 on: July 05, 2014, 11:50:20 PM »
Thanks, Jon!

Offline tim in jersey

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #5 on: July 06, 2014, 12:54:05 AM »
Transformer isolated splits are the industry standard in this situation. Here's an example of a pro press box. Each output is transformer isolated and ground lifted. I'm sure Whirlwind will build this in a 2 input config for stereo recording.

http://www.markertek.com/Audio-Equipment/Audio-Interface/Press-Boxes/Whirlwind/PB06.xhtml

My initial search which eventually led me to the HE Patchbox was for a press box.

I'm located near Trenton, NJ and I've been the local sound guy for several gubernatorial elections and many other state, county, and municipal functions. I'm not sure why it never dawned on me to ask Whirlwind to spec a box for stereo feeds.  :facepalm:

Offline tim in jersey

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #6 on: July 06, 2014, 01:18:32 AM »
Where do you intend to put the blockers in the chain?
Between the patchbay and the source would protect the source


I want to put the protection between the Patchbox and the SBD. I've worked too hard to get SBD access and don't want to burn any bridges/screw over any of my fellow FOH and/or BOH compadres and the gear they use to make a living.

Thanks for raising the subject of incurring incidental damage to my own gear, specifically the Patchbox and/or my own deck, Jamie. I never considered that. I'm going to be wicked militant about who can and can not patch out of me going forward. Most of my taper buddies with P48 know the deal already, and I know I can trust them, but I'm gonna *insist* they prove to me P48 is *OFF* before they plug in...

Online Gutbucket

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #7 on: July 08, 2014, 09:45:29 AM »
I only know enough electronics to be dangerous and not trust myself without consulting others.  What am I missing here?

Couldn't someone simply modify the passive HE patch box by inserting series capacitors in just the pin 1 & 2 input lines (to protect the input alone from DC applied to any of the outputs), or on all the output signal lines (to protect all outputs from DC applied to any of them)?  Wouldn't that form a DC blocking high-pass filter?

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Re: Having trouble deciding between 48v Phantom blockers
« Reply #8 on: July 08, 2014, 12:30:18 PM »
Ah, I didn't realize the problem is more complex than simply blocking the straight 48VDC.  Okay I get it now.   Thanks for the learnin!
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

 

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