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Author Topic: 3 way passive splitter with 2 ISO,, not passing Phantom  (Read 2958 times)

Oakie Pitakskul

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3 way passive splitter with 2 ISO,, not passing Phantom
« on: November 10, 2015, 01:48:56 am »

Greetings,

2 questions

Q1.
We have 56 channels of the EWI MST-412 4 Channel, 3 way,  transformer iso splitter. They are great units and work well for us. Recently a few channels started not to work. When used with regular dynamics mics they work fine, but with Condensers. only the direct outs work the ISO outs do not work (with pressing 48V on the ISO outs)

Q2
What do you guys usually do?  FOH on Direct outs and ISO out for Monitor World? or vice versa?  or do you put  both FOH and MON on separate ISO outs?



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Steve M Smith

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #1 on: November 10, 2015, 02:53:38 am »

When used with regular dynamics mics they work fine, but with Condensers. only the direct outs work the ISO outs do not work (with pressing 48V on the ISO outs)
As there is no direct connection between each side of a transformer, you will not get phantom power from the transformer isolated inputs, only from the direct inputs.

This is normal.  Apply phantom power from the mixer connected to the direct side (or both just to be sure).


Steve.
« Last Edit: November 10, 2015, 02:55:55 am by Steve M Smith »
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Jordan Wolf

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #2 on: November 10, 2015, 07:35:16 am »

Transformers won't pass the phantom power; I would use an ISO for MONs and keep an ISO open for record/broadcast situations where you want that physical isolation between devices on different power setups (shore power vs generator, different panels, etc.).


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Dave Pluke

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #3 on: November 10, 2015, 11:12:45 am »

Apply phantom power from the mixer connected to the direct side (or both just to be sure).

Assuming cable lengths are shorter to the Monitor Console, would it not make sense to provide phantom power there (i.e. less voltage drop)?

Dave
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Steve M Smith

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #4 on: November 10, 2015, 11:18:50 am »

Assuming cable lengths are shorter to the Monitor Console, would it not make sense to provide phantom power there (i.e. less voltage drop)?
Each line (pin 2 and pin 3) has a 6K8 resistor at the mixer to the +48 volt supply and anything which uses phantom power has another pair of 6K8 resistors summed back together to give the phantom supply.

If we assume that there is a 24 volt zener diode there to regulate (as there often is) that means that there is 12 volts dropped across the resistors in the mixer and another 12 volts dropped across the resistors in the device (mic or DI).  Any voltage drop in the cable will be much less than that.

Phantom power cannot supply much more than 4 to 5mA.

If your cables have a high enough resistance that they can affect that, you have bigger problems than getting phantom power to something.


 

Steve.
« Last Edit: November 10, 2015, 11:27:32 am by Steve M Smith »
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Mac Kerr

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #5 on: November 10, 2015, 11:51:35 am »

Q1.
We have 56 channels of the EWI MST-412 4 Channel, 3 way,  transformer iso splitter. They are great units and work well for us. Recently a few channels started not to work. When used with regular dynamics mics they work fine, but with Condensers. only the direct outs work the ISO outs do not work (with pressing 48V on the ISO outs)
Only the direct out will pass phantom to the inputs. The ISO outs are, how shall I put this... ISOlated from the inputs, direct outputs, and each other.
Quote
Q2
What do you guys usually do?  FOH on Direct outs and ISO out for Monitor World? or vice versa?  or do you put  both FOH and MON on separate ISO outs?
The console that has all the mics or DIs that require phantom needs to supply the phantom. Often this is the FOH console, although there is a good argument to be made for monitors supplying phantom since they are right there on stage and will know when to kill phantom before someone unplugs a mic and blows up the mains with the loud pop.

Mac
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John Sulek

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #6 on: November 10, 2015, 11:55:02 am »

Assuming cable lengths are shorter to the Monitor Console, would it not make sense to provide phantom power there (i.e. less voltage drop)?

Dave

Voltage drop is not a big issue, but there are a couple of other reasons to put the monitor console on the direct side of things...

Closer to the action on stage so easier to communicate the need for phantom when things change in the patch.

Before digital, there would be a lot less cable involved before mics and DI's saw signal ground. Could be a lot less noisy, especially with certain brands of FOH console.
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Elliot Carroll

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #7 on: November 21, 2015, 12:43:57 pm »

Check your ground/lift situation.  If it's just happening on a few select channels...

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William Schnake

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #8 on: November 21, 2015, 05:18:28 pm »

Only the direct out will pass phantom to the inputs. The ISO outs are, how shall I put this... ISOlated from the inputs, direct outputs, and each other.

Mac
Mac, you are 100% right.  I ran into the same thing with a Horizon 48 channel ISO snake.  I couldn't get phantom from FOH.  Then it dawned on me...it's an ISO snake stupid.  Now we do all of our phantom from the monitor console when we use that analog snake.  Works for us, but when I rent the snake I have to remember to tell the renter prior to them picking it up.

Bill
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Keith Broughton

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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #9 on: November 22, 2015, 06:26:07 am »

Check your ground/lift situation.  If it's just happening on a few select channels...
On the split snakes I have seen , the ground lifts are on the output side(s) of the splits and not on the "direct" side so they should not play a part in phantom supply grounding.
The "direct" side is connected to the console supplying phantom.
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Re: 3 way passive splitter with 2 ISO,, not passing Phantom
« Reply #9 on: November 22, 2015, 06:26:07 am »


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