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Author Topic: Hardwired or Passive vs Transformer Isolated Splits  (Read 4620 times)

Samuel Rees

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Hardwired or Passive vs Transformer Isolated Splits
« on: April 26, 2012, 11:04:20 pm »

Preface - I know this has been discussed for years on this forum. I have been reading threads for about an hour. Someone turned what I thought I know about splits on its head the other day, and reading the archives only seems to confuse me more.

The question(s):

For small format FOH/MON configurations or IEM rack, is a hardwired snake (ex: EWI poorman's splitter) appropriate and/or safe? If yes, what are the downsides and risks? If no, is transformer isolated the only other option, and are there downsides to transformer isolated?

I previously believed that a transformer isolated split was essentially the only option, because passive splits could damage the secondary console by hitting it with phantom and that phantom from the secondary console could damage microphones. There would also be the non-damaging but annoying effects from gain changes console-console. I have never used a passive product for this reason.

Some people said things in the archives that seemed to confirm this for me. Others seemed to say the opposite, describing problems I didn't totally understand from trans-iso systems. Additionally, there are passive splits being sold all over the place - which confused me previously as I thought they were dangerous and and largely useless.

Can someone straighten me out? This is so simple I'm embarrassed I can't figure it out!

Thanks...

« Last Edit: April 26, 2012, 11:07:07 pm by Samuel Rees »
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brian maddox

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #1 on: April 26, 2012, 11:43:18 pm »

Preface - I know this has been discussed for years on this forum. I have been reading threads for about an hour. Someone turned what I thought I know about splits on its head the other day, and reading the archives only seems to confuse me more.

The question(s):

For small format FOH/MON configurations or IEM rack, is a hardwired snake (ex: EWI poorman's splitter) appropriate and/or safe? If yes, what are the downsides and risks? If no, is transformer isolated the only other option, and are there downsides to transformer isolated?

I previously believed that a transformer isolated split was essentially the only option, because passive splits could damage the secondary console by hitting it with phantom and that phantom from the secondary console could damage microphones. There would also be the non-damaging but annoying effects from gain changes console-console. I have never used a passive product for this reason.

Some people said things in the archives that seemed to confirm this for me. Others seemed to say the opposite, describing problems I didn't totally understand from trans-iso systems. Additionally, there are passive splits being sold all over the place - which confused me previously as I thought they were dangerous and and largely useless.

Can someone straighten me out? This is so simple I'm embarrassed I can't figure it out!

Thanks...

okay, there are others who can go on and on about the technical aspects of this.  i'm just gonna weigh in with my 20+ years in the trenches.  take it FWIW..

by way of history, i started using passive splits with shared grounds.  ewww.  then we had nice custom built passive splits.  then we had a 3-way jensen transformer split.  i've used all 3 of these in quite literally hundreds of shows in all sorts of situations.  here's what i found to be true.

passive splits can, possibly, maybe, in certain very specific situation, cause issues based on the fact that it's nothing more than a big y cable.  however, out in the real world i have NEVER had a passive split damage anything, and I've had them hooked up wrong and double phantomed and wet with ribbon mics and all sorts of stupid things.  i've occasionally had issues with ground loops, usually where there were unbalanced connections involved, either intentionally, or not. but i've never had them 'break' anything.  and i can only think of a handful of times i wished i had the transformer split.  as to there being issues with gain changes interacting across a passive split, i've never had that experience or even heard of it.  if it happens, it's so minute a problem as to have escaped me entirely.

 transformer splits give you a physical disconnect between the two destinations.  and that's great.  but they also introduce the 'sound' of the transformer, the potential of magnetic fields to induce hum in them, the inability to pass comm, and several other pesky issues.  frankly, i've had far more times that i had the transformer split, and wished i didn't, than the other way around.  and honestly, most of times that we used it, it was because it was spec'd and we were meeting the contract.

none of this even includes the cost factor.  my 2 cents is, if you need a splitter, get a good, well-built passive one with pin1 lifts on every channel.  you may have the rare occasion where you'll wish you had transformers.  but you're gonna be hard pressed to find yourself in a situation where this will ruin your day.
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brian maddox
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Samuel Rees

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #2 on: April 27, 2012, 12:01:29 am »

Thanks Brian, I really appreciate the boots on the ground info. The fact that they sell passive splits like the ones from EWI in large amounts was contradictory to my understanding that they were largely a bad idea. I've spent most of my short career working for venues with isolated splits I never gave a second thought. I wonder know if some of them were even hardwired and I assumed they were isolated.

Quick clarification on the below:

by way of history, i started using passive splits with shared grounds.  ewww.  then we had nice custom built passive splits.  then we had a 3-way jensen transformer split.  i've used all 3 of these in quite literally hundreds of shows in all sorts of situations.  here's what i found to be true.
..........................
my 2 cents is, if you need a splitter, get a good, well-built passive one with pin1 lifts on every channel.  you may have the rare occasion where you'll wish you had transformers.  but you're gonna be hard pressed to find yourself in a situation where this will ruin your day.

Can you clarify the "passive splits with shared grounds" to "nice custom built passive splits" spectrum? I assume the EWI Poorman's Splitter would be the former. What would be the latter? Do you just mean generally better quality or some technical difference (like a pin1 lift switches?)
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Tim Perry

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #3 on: April 27, 2012, 12:49:59 am »

Look at it this way; if a console is capable of producing phantom power, applying phantom power externally is not going to damage it.

You can also look at it this way; If a mixer input can be damaged by external application of phantom power, it deserved to die anyway <g>



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Geoff Doane

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #4 on: April 27, 2012, 09:16:39 am »


You can also look at it this way; If a mixer input can be damaged by external application of phantom power, it deserved to die anyway <g>

Yeah.  My sentiments too!  :)

I think Brian is correct, that a "passive" split with ground lifts will work in almost all situations, at least that has been my experience over 20+ years.  That's particularly true, if you have control over the complete system, both consoles, and power distribution to them.  And the chances are even better that it will work now, rather than 20 years ago, because "pin 1 problems" are better understood by the manufacturers, and console grounding schemes are better.

However, if you don't have control over the complete system, or the setup is not always the same, transformers can be a show saver.  Part of my day job involves looking after a remote recording truck, and we learned fairly early on that the only way to get clean recordings in certain situations was to have transformer isolation.  And I can't remember a single instance in over 20 years of using transformer splitters, that there was a hum problem that couldn't be solved with the ground lift switches.  There have been problems with bent or broken multipins, but that was operator error, not poor design.

It's true that you have to plan carefully how to run com and condenser mics that may only be going to the recording console (audience mics), if transformers are involved.  Splitter transformers are also optimized for mic level signals, and may introduce distortion if line level with significant low end is run through them.  Sometimes the only practical way to do that is to run another snake, but that's just the cost of doing business.

Also keep in mind that adding splits is effectively the same thing as adding cable capacitance to each microphone.  The load on each mic is also doubled once another console is added.  Most splitter transformers are 1:1, so electrically they behave pretty much the same as a hard wired split.  The Whirlwind 3-way transformers, and perhaps others, have a 3 dB voltage loss on each of the two secondaries.  That reduces the impedance and capacitive loading effect, at the cost of some signal level on those outputs.

Maybe I should also add that technically, hard wired and transformer splits are both "passive".  A real active split is another step up, although it adds even more complications, besides the greatly increased cost.  The ones I've seen had options for transformer isolation on at least some of the outputs, so a split can be active and transformer isolated at the same time.  Like an active DI, the active split is useful when you need to drive long lines, because the microphones don't see all that extra capacitance.

The last remote I worked on had an interesting combination of technologies.  There was a passive 3-way split on stage.  One split went to the analog inputs of the M7 on stage, another went to the Yamaha stage boxes, and then CAT6 to the FOH M7, and the third split went to our SSL stage box, and then fibre to the truck. Other than one suspect channel in the split, which the PA company had already found before we got there, it all went together flawlessly, and worked on the first try.

GTD

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brian maddox

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #5 on: April 27, 2012, 09:33:33 am »

Can you clarify the "passive splits with shared grounds" to "nice custom built passive splits" spectrum? I assume the EWI Poorman's Splitter would be the former. What would be the latter? Do you just mean generally better quality or some technical difference (like a pin1 lift switches?)

actually, by 'passive split with common ground' i was referring to the splitters i used when i first got into the business in the early 90s.  the company i worked for had these splitters they had made ten years prior that used a 27 pair and a 19 pair snake together to get 46 channels.  ALL the shields were tied together and went through one big switch on the split output.  this was NOT ideal to say the least and i think you'd be hard pressed to find anyone doing this now.  after a few years of suffering through that system, we had built for us a modern style 56 channel 3-way splitter with pin1 lifts on all channels independently.  while pin1 lifting the whole thing was a bit tedious [switching all 56 switches] it was world's more reliable.  a few years later we got a 3-way jensen transformer split based on the same design as our non-transformer one.  so those are the 3 different configurations i was referring to.

geoff makes some excellent points.  transformers can absolutely save you when you can't control all the variables.  and the drawbacks can be dealt with if you understand what they are.  and he is absolutely correct in saying that all these options are actually 'passive' splits.  i've had  the privilege on rare occasion to use true active splitters [BSS units as i recall] and it really was a treat.  they have their own issues as well, cost perhaps being number one on the hit parade, but in the right circumstance they are wonderful things to have...

my bottom line is still that in 99.8 percent of cases you're gonna get totally satisfactory results out of a good ol' fashioned non-transformer split with individual pin1 lifts.  and if i was doing PA work, and i was spending my money, that's what i'd buy...
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brian maddox
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Charlie Zureki

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #6 on: April 27, 2012, 09:40:34 am »


geoff makes some excellent points.  transformers can absolutely save you when you can't control all the variables.  and the drawbacks can be dealt with if you understand what they are.

my bottom line is still that in 99.8 percent of cases you're gonna get totally satisfactory results out of a good ol' fashioned non-transformer split with individual pin1 lifts.  and if i was doing PA work, and i was spending my money, that's what i'd buy...

   +1

   and for any pesky problems, buy a few in-line iso transormers to keep on hand.

   Cheers,
   Hammer
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Brad Weber

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #7 on: April 27, 2012, 09:47:25 am »

Look at it this way; if a console is capable of producing phantom power, applying phantom power externally is not going to damage it.
 
You can also look at it this way; If a mixer input can be damaged by external application of phantom power, it deserved to die anyway <g>
.
Good in theory, but I have seen it fail in practice.  Phantom power in a hardwired split should not damage a properly design, professional live sound console, but I once encountered issues with a direct coupled split to a broadcast console that resulted in all the splits carrying phantom from the house mixer causing the correpsonding channels to fail on the broadcast mixer.
 
I'd also think twice about hardiwred splits if you are feeding something like a broadcast or production truck running off different power such as their own generator.  That's a situation where the transformer isolation may be warranted.
 
For a more technical discussion on microphone splitters try http://www.audiosystemsgroup.com/Mic_Splitters.pdf and http://www.audiosystemsgroup.com/AESPaperSplittersASGWeb.pdf.
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George Dougherty

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #8 on: April 27, 2012, 11:21:07 am »

Any recommendations on where to get a decent priced splitter for a band that's looking to carry their own monitor console?  Ground lifts would definitely be nice.  Though, I've always seen phantom supplied by FOH as the arrangement when I've used a splitter.  Would it be enough to hard lift pin 1 on the feed to the monitor console off something like the EWI poor man's splitters?
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Samuel Rees

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Re: Hardwired or Passive vs Transformer Isolated Splits
« Reply #9 on: April 27, 2012, 12:04:45 pm »

George you took the words right out of my mouth just there. EWI's snakes, which have seemed to be the budget favorite in the past, don't appear to have ground switches on any of their models. Any recs?

My app is all rock&roll use. Splitting from house console to my SiC or an LS9.

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