splitter isolation confusion

jenkel16 · 23rd October 2006

Last night I recorded a band at a local venue and after getting setup connecting the snake 1-1 to the preamps I had to do some repatching and when I pulled a line with phantom from the FOH desk on it the PA popped. I was using a spare transformer isolated Monitor split and none of my outputs were going to the PA. Any ideas why this happened?
I'm at a loss and it's nagging at me a bit because I can't think of why this could happen.

Thanks in advance
Graham

**Remoteness** · 23rd October 2006

Audio passes through the transformers. If you plug or unplug a connector at FOH, MON or REC everyone else is going to hear it.

The transformer only isolates the chassis grounds from the different audio systems.

Also, on another note, (depending on the design) pin one is only lifted when you use the ground lift switch.

jenkel16 · 24th October 2006

Good to know Steve, but I pulled 4 or 5 before it happened and it was a channel that was muted on the desk and unassigned to the mix.

**Remoteness** · 24th October 2006

Now that's strange.

jenkel16 · 24th October 2006

Alright then.

Jim vanBergen · 24th October 2006

Do you know whose brand splitter it was, and what consoles were being used?

A few thoughts, righht or wrong:

1. Monitor path could have been up to a pre-fade or AFL channel in the cue wedge

2. Aux sends can be set up pre-mute on some cheap desks (which is VERY bad!) like Crest or A&H, but I experienced a Midas Verona that did the same thing. After an hour of tracing, I found a junction where pin3 bonded to pin 1. Ooops!

3. Direct outs are often used to feed verbs, record desks, or monitor paths. Any chance?

4. Many installed splitter systems and house PAs have a shared ground as specified by the NEC. One bonded path can really ruin someone's day! I found a lovely Clair Brothers installation that had 48 split pairs and 8 lines designed for returns (that were bonded, not split) but are often used for vocal mic inputs (and Beta 87s, KMS104s, Shure KSM9s, etc being used) . Guess what happpens when you pull one of them with +48 on them.... POW!

Hope these thoughts help.

JvB

jenkel16 · 25th October 2006

Jim,
I have no idea what brand the snake was. FOH was a Series 5, monitors were run from it so there was no other console, and I'm pretty sure the Series 5 doesn't count as cheap

. Then mains were what popped and the mic was in the desk only so that it could receive phantom, it was a room mic and was there specifically for recording.

I pulled 4 key lines and the low Tabla before the room mics and as I'm typing this I realize that the DI's were active and phantom powered as well, but did nothing.

Oh so strange.

Graham

23rd October 2006	#1
jenkel16 Gear nut Joined: Oct 2005 Posts: 144 Thread Starter	splitter isolation confusion Last night I recorded a band at a local venue and after getting setup connecting the snake 1-1 to the preamps I had to do some repatching and when I pulled a line with phantom from the FOH desk on it the PA popped. I was using a spare transformer isolated Monitor split and none of my outputs were going to the PA. Any ideas why this happened? I'm at a loss and it's nagging at me a bit because I can't think of why this could happen. Thanks in advance Graham

23rd October 2006	#2
Remoteness Super Moderator Joined: Aug 2002 Location: NYC Posts: 7,405	Audio passes through the transformers. If you plug or unplug a connector at FOH, MON or REC everyone else is going to hear it. The transformer only isolates the chassis grounds from the different audio systems. Also, on another note, (depending on the design) pin one is only lifted when you use the ground lift switch. __________________ Steve Remote AuraSonicLtd.com the home of ASL Mobile & Location Production Remoteness on the Linkedin Network What about my Facebook Profile? Remoteness on Myspace

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread starter	Forum	Replies	Last Post
Helios confusion...	Mattsson	High end	0	3rd August 2006 08:21 PM
Help me out with this confusion	RainbowStorm	So much gear, so little time!	0	10th May 2006 10:15 AM
Next purchase confusion!!!	VO-Guy	So much gear, so little time!	3	8th October 2005 05:02 PM
DI confusion!	monsterz	So much gear, so little time!	5	22nd September 2005 11:46 PM
Splitter / Splitter-Snake	jazzbutcher	Remote Possibilities in Acoustic Music & Location Recording	10	21st November 2003 12:30 AM

24th October 2006	#3
jenkel16 Gear nut Joined: Oct 2005 Posts: 144 Thread Starter	Good to know Steve, but I pulled 4 or 5 before it happened and it was a channel that was muted on the desk and unassigned to the mix.

24th October 2006	#6
Jim vanBergen Lives for gear Joined: Apr 2005 Location: New York Friggin' City Posts: 2,562	Do you know whose brand splitter it was, and what consoles were being used? A few thoughts, righht or wrong: 1. Monitor path could have been up to a pre-fade or AFL channel in the cue wedge 2. Aux sends can be set up pre-mute on some cheap desks (which is VERY bad!) like Crest or A&H, but I experienced a Midas Verona that did the same thing. After an hour of tracing, I found a junction where pin3 bonded to pin 1. Ooops! 3. Direct outs are often used to feed verbs, record desks, or monitor paths. Any chance? 4. Many installed splitter systems and house PAs have a shared ground as specified by the NEC. One bonded path can really ruin someone's day! I found a lovely Clair Brothers installation that had 48 split pairs and 8 lines designed for returns (that were bonded, not split) but are often used for vocal mic inputs (and Beta 87s, KMS104s, Shure KSM9s, etc being used) . Guess what happpens when you pull one of them with +48 on them.... POW! Hope these thoughts help. JvB

25th October 2006	#7
jenkel16 Gear nut Joined: Oct 2005 Posts: 144 Thread Starter	Jim, I have no idea what brand the snake was. FOH was a Series 5, monitors were run from it so there was no other console, and I'm pretty sure the Series 5 doesn't count as cheap . Then mains were what popped and the mic was in the desk only so that it could receive phantom, it was a room mic and was there specifically for recording. I pulled 4 key lines and the low Tabla before the room mics and as I'm typing this I realize that the DI's were active and phantom powered as well, but did nothing. Oh so strange. Graham