splitting line level signals on the cheap

[S&L]

I have 2 scenarios in mind:

1. I do this regularly -- single line level out of mixing desk, split to two amp channels using :

http://cpc.farnell.com/pulse/pls00257/XLR-splitter-lead/dp/AV14537?crosssellid=AV14537&crosssell=true&in_merch=true&

and then on to two monitors replicating the signal.

2. a colleague of mine wanted to split the signal into two to serve 2 PA systems and 'wasn't sure you could do this with balanced lines'

 

this set me thinking - am I losing any signal level before the amp by splitting in this way - and if so would the same be true if you took 2 seperate signals from a desk tht had 2 versions of the same signal available (typically one a jack and one a XLR).

Have I just been getting away with it for monitors?

I ask because as a field practitioner I don't have enough theoretical knowledge to work through this - I do know it works in practice (either 2 connections at the desk OR a splitter).

I have a practical application for this on Saturday so await your comments/observations eagerly!

[laolu]

Dear S&L,

 

 

Normally the output impedance of your mixing desk is low enough (a few hundred Ohms, +/-) to be able able to drive two power-amps whose input impedance should be in the area of tens of kiloOhms or more. Assuming the polarity of your XLR-out is the same as that of the balanced phone-jack. But usually, they are.

 

A line mixer/splitter (like the Rane SM26 or Behringer Ultralink) would be a bit more elegant but also a lot more expensive than your Y-cable.

 

I'd say: If it works, just do it. :D

 

 

Norbert

[pete10uk]

I too don't really have the theoretical knowledge but I have always been told that its not the best way and can understand why if you look at it in the following way.

 

It's all about the impedance, the signal will choose the path of least resistance, if you connect 2 identical lenght cables to 2 identical peices of kit then the signal will split equally but if you for instance, connect one output or one side of your split to a much longer cable run or kit with a higher resistance, most of the signal will take the least line of resistance.

 

Adding a mixer or proper spliter is just ensuring that both legs have a controllable resistance.

 

I have seen some real what I would call bodge jobs in the past when it comes to splitting, but in reality If it works for that particular application why do you need to do it any other way.

 

If say try it out, if you are short of time do it right first time but If you have the time, try it the easy way and or the results arn't brilliant correct the bodges.

[DrV]

Norbert's right. Given the relative impedances of the mixer output, the cables and the amp inputs you are going to get almost the same level into two amps as into one.

Dave

[Jivemaster]

Elegant and expensive answer -one distribution amplifier output per channel needed.

 

Practical answer, plug in a few items by Y-split, downside you will lose a little signal level and faults in the Y-split may affect all or some amplifiers.

 

If it isn't broke don't fix it.

[paulears]

Consider the humble patchbay in most studios and broadcast installations. hot patching an output to a new destination is routinely half-normalled, so is a straight split - the original destination being still connected. It's a tried and tested way of doing it, and very rarely causes issues.

[Mixermend]

Balanced outputs should be capable of driving a true 600 ohm load - or possibly even lower, without losing level or suffering an increase in harmonic distortion.

 

Certainly most mixing desks can do this - and it is a test I carry out frequently when repairing items, as it can point to faults if an output cannot drive a low load.

 

This means that one balanced output can happily drive many power amplifier inputs - I would expect no problem at all driving 10 input loads, possibly many more.

[Jivemaster]

With a wired parallel split the first unbalanced input on an amp unbalances everything. Consider whether this would matter in your application.

[Doug Siddons]

2. a colleague of mine wanted to split the signal into two to serve 2 PA systems and 'wasn't sure you could do this with balanced lines'

 

 

 

 

Just a quick heads up on this, if your outputting from one PA system and feeding it into the desk of the other make sure phantom power is off on the split or the channel your feeding into

[Bazz339]

A great many amplifier racks have either a male XLR parallel wired to the input female XLR to allow "daisy chaining" whereby one output from the desk (say) feeds an input which is then linked to another input an then another.

 

Some have switches instead or as well usually to link left an right inputs of an amp so that no cable is needed.

 

It is good practice not to link too many together but one output ought to be able to feed 4 inputs without problem and maybe more.

[revbobuk]

Equally common is for amps to have XLR and TRS inputs which are paralleled - so use the XLR as input, then run from the TRS into the next amp's XLR. Just check that the jack input is TRS balanced, not TS unbalanced.

[Bazz339]

Equally common is for amps to have XLR and TRS inputs which are paralleled - so use the XLR as input, then run from the TRS into the next amp's XLR. Just check that the jack input is TRS balanced, not TS unbalanced.

 

And that it does not break the signal path from the XLR.

[S&L]

I just wanted to say thanks for all the replies and input.

as I said in initial post, I have used y splitters in the past. what I didn't say was that I used to use a patchbay with pre amps and that worked fine but was a bit cumbersome unless racked as a permentent solution.

the colleague I'm working with asked me to discuss the issue with a well known national hire company who are supplying the monitors for this weekend's show.

'why aren't you just using y splitters?' came the response ' we use them all the time for this.'

fair enough.

I explained that my colleague has concerns and was there anything small he could offer. off the shelves came and Alice 6-2 distribution amplifier, adding £8 to the weekend's hire cost. So to keep the peace I went with that. but at least when I'm working on my own, I wouldn't be afraid of using y splitters again.

[Bazz339]

An audio distribution amplifier with isolated outputs like the Alice is especially useful when you are providing feeds to multiple unknown destinations like at press conference where you made be feeding a variety of recorders some balanced, some not, some cables in good repair, some not etc.

[revbobuk]

If you want something in the rack to cover situations like this, then the Behringer Ultralink mentioned above - this one - is useful and works well. Can double up as a submixer as well.