# XLR Y Cable



## jonhall5446 (Aug 4, 2009)

Hello all,

I have a rack with 3 Marcrotech 2400 amps. Typically we only use two of them, splitting the signal with an XLR Y cable. We are powering 2 18" Subs per amp. 

I would like to add a single XLR patch to the back of the rack case and parallel the signal to all three of the amps. Is there a way to accomplish this without purchasing some sort of splitter? Can I build a Y cable that runs to three amps?

thanks!


----------



## Derrick (Aug 4, 2009)

Yes, that would be fine.

You might also look into using the XLR input jacks to connect the amps together. 

Example:

Here I am assuming that you are operating these in "parallel mono"

Main input to amp 1 XLR channel 1. Connect a MALE XLR from the XLR "input" jack on channel 2. Connect this to the channel 1 XLR input on amp 2. Which will also be a MALE XLR.

Connect a MALE XLR to amp 2 channel 2 "input" then connect to amp 3 channel 1 with another MALE XLR.

Amp 1 channel 1 would be the main input.
Amp 1 channel 2 feeds to amp 2 channel 1
Amp 2 channel 2 feeds to amp 3 channel 1

These interconnecting cable will be MALE XLR to MALE XLR.

Oh, and it doesn't matter if you choose to use amp 3 channel 2 as the main input or an extra output. At this point all inputs are in parallel. Again, I am assuming you are operating these in "parallel mono"

D


----------



## jonhall5446 (Aug 4, 2009)

Thanks for the reply. Would daisy chaining these amps cause any sort of unwanted gain staging?

and they would be operating in parallel mono


----------



## Derrick (Aug 4, 2009)

Nope, none. The two input XLRs are only in parallel. Channel 1 only controls channel 1 and the channel 2, only channel 2. These WILL NOT change what appears at the associated "input" XLR only the associated amp / channel OUTPUT at the speaker terminals.

I am reading the manual for this amp as I type this. Instead opf using the XLRs to daisy chain these, you might have to use the 1/4" jack for channel 1.

It seems that Crown parallels the signal after the XLR jacks. But the 1/4" is actually hard-wired to the XLR. The QSC amps I use are not like this, sorry.

So here is the clarified setup. The only XLR you would use would be the AMP 1 CHANNEL 1 Input. Using a 1/4" TRS plug connect the channel 1 1/4" jack to AMP 2 CHANNEL 1 XLR. Then from AMP 2 1/4" jack to AMP 3 XLR.

The statement regarding the LEVEL controls still holds true.

Sorry for the confusion. But you need two 1/4" TRS to XLR MALE cables. 
The pinout for these cables is:

1/4" TRS -to- XLR
TIP -to- 2
RING -to- 3
SHIELD -to- 1


----------



## jonhall5446 (Aug 4, 2009)

Thanks so much for your help. I'll give it a go!


----------



## Chris15 (Aug 5, 2009)

Directly paralleling XLRs on an input stage is not a normal practice, there would normally be a buffer etc.

I've made 4 way W splits before, there is no real issue when talking about line level and within a rack...


----------



## Derrick (Aug 5, 2009)

The way I read it, he wants to split ONE signal source to his three amps within the rack. A splitter is just fine for that. No buffer needed. The same can be accomplished by utilizing both the XLR and 1/4" "input" connections on the amp.

If he were asking about paralleling two signals into one, such as a L & R output from a mixer, cd, mp3, tape deck, phono or any other two output source, then yes some sort of a summing device either active or passive would be the correct way. 

Never "Y" two OUTPUTS into one.


----------



## Chris15 (Aug 7, 2009)

Derrick said:


> The way I read it, he wants to split ONE signal source to his three amps within the rack. A splitter is just fine for that. No buffer needed. The same can be accomplished by utilizing both the XLR and 1/4" "input" connections on the amp.
> 
> If he were asking about paralleling two signals into one, such as a L & R output from a mixer, cd, mp3, tape deck, phono or any other two output source, then yes some sort of a summing device either active or passive would be the correct way.
> 
> Never "Y" two OUTPUTS into one.



Agreed splitting it should be fine.

But using M-M link leads between amps means something funky is going on with that amp and it isn't buffering it's inputs - it's paralleling them which is not a sound design principle...


----------



## Derrick (Aug 7, 2009)

From the Crown operator's manual for the MT2400, page 12:

L. Balanced XLR Inputs
The factory-installed PIP2-FXQ provides a three-pin
female XLR connector for balanced input to each channel.
The XLR inputs are connected in parallel with the
amplifier's phone jack inputs. Because the PIP2-FXQ
does not have any active circuitry, its XLR connectors
can also be used as "daisy chain" outputs to connect signals
from phone jack inputs to multiple amplifiers. Caution:
The Channel 2 input should NOT be used in either
Bridge-Mono or Parallel-Mono mode.

Pretty standard practice. This is using the internal connection between the XLR and the 1/4"TRS to accomplish the same result as making a 3 split xlr. Only in this case, if you had a rack of 10, 15, 20 etc...amps and all these amplifiers sources are the same, needing the same DSP, EQ etc... Then how much easier would it be to daisy chain using M-M that have a splitter cable or perhaps a splitter "box". The only drawback to daisy chaining is that if you have an amp fail in mid-show, in order to "swap it out" you must interrupt the signal at that point. However most likely you will have a "not on line spare" already cabled up and you can just move the speaker leads over to the spare amp, turn it on and bring it up. And no, If the amp in mid daisy fails it does not interrupt the signal flow to the remaining amps. Only in the event it should explode and actually break the hard-wired soldered connection between the XLR and 1/4" would you have a signal loss.


----------



## Chris15 (Aug 8, 2009)

Derrick said:


> Caution:
> The Channel 2 input should NOT be used in either
> Bridge-Mono or Parallel-Mono mode.
> -snip-
> ...



Respectfully, you've just contradicted yourself. You've quoted that nothing should be connected to the channel 2 input and then wanted to connect another male to it to loop through...

And you don't need an amp to explode to kill your signal chain, a mere dry joint will cause grief galore...

Please tell me an application where you would want 20 amps being fed the exact same signal and being in the same rack...


----------



## museav (Aug 8, 2009)

Chris15 said:


> Please tell me an application where you would want 20 amps being fed the exact same signal and being in the same rack...


Well, maybe two racks for twenty amps but how about an arena with many larger speakers or an airport/convention center type system for general announcements and background music? I've done it for both of those type of applications. Especially when using amps that have onboard DSP, sending the same signal to many amp channels is not that unusual.

In fact, because the 1/4" TRS jacks on the MA-2400 are in parallel after the PIP input module slot, for the IQ-PIP-USP2 input card that provided DSP, monitoring, etc. capability at the amp had its own set of parallel XLR jacks that were intended solely to support daisy-chaining, in fact the data sheet refers to them as "Audio Daisy Chain Output" and the manual states "*Balanced Daisy Outputs - *A male XLR connector is provided for balanced audio daisy chaining for each channel. Each daisy output connector can be set to pass processed or unprocessed signal from its respective channel via jumper settings." This is exactly how I approached the system in one arena, multiple MA series amps with IQ-PIP-USP2 input modules daisy-chaining pre-processed signal.

As far as the "Caution: The Channel 2 input should NOT be used in either
Bridge-Mono or Parallel-Mono mode." comment, that warning has to do with the amp operating mode, in Bridge-Mono or Parallel-Mono operating modes the Channel 2 input is not to be used, and is not specific to daisy-chaining. Looping from Channel 1 to Channel 2 is acceptable in stereo/two channel mode where you would normally use both inputs.

Daisy-chaining amp inputs, or device inputs in general, is both an acceptable and common approach. While one of the advantages of low impedance outputs to high impedance inputs is maximum voltage transfer, another is that with high impedance inputs you can connect to multiple parallel destinations and still have an effective impedance ratio.


----------



## Chris15 (Aug 8, 2009)

museav said:


> Well, maybe two racks for twenty amps but how about an arena with many larger speakers or an airport/convention center type system for general announcements and background music? I've done it for both of those type of applications. Especially when using amps that have onboard DSP, sending the same signal to many amp channels is not that unusual.



Amps with inbuilt DSP are the exception to the above statement.
An arena - If it's a PA it is unlikely to be 20 amps feeding the same hang and thus will need different DSP settings.
Airports - I shoudl have thought you'd be looking at way smaller zones to localise paging to the relevant gate and then feeding it off PageMatrix with Media Matrix or a similar solution.


museav said:


> In fact, because the 1/4" TRS jacks on the MA-2400 are in parallel after the PIP input module slot, for the IQ-PIP-USP2 input card that provided DSP, monitoring, etc. capability at the amp had its own set of parallel XLR jacks that were intended solely to support daisy-chaining, in fact the data sheet refers to them as "Audio Daisy Chain Output" and the manual states "*Balanced Daisy Outputs - *A male XLR connector is provided for balanced audio daisy chaining for each channel. Each daisy output connector can be set to pass processed or unprocessed signal from its respective channel via jumper settings." This is exactly how I approached the system in one arena, multiple MA series amps with IQ-PIP-USP2 input modules daisy-chaining pre-processed signal.
> 
> As far as the "Caution: The Channel 2 input should NOT be used in either
> Bridge-Mono or Parallel-Mono mode." comment, that warning has to do with the amp operating mode, in Bridge-Mono or Parallel-Mono operating modes the Channel 2 input is not to be used, and is not specific to daisy-chaining. Looping from Channel 1 to Channel 2 is acceptable in stereo/two channel mode where you would normally use both inputs.
> ...



My concern all along has not been using a provided loop output or with daisy chaining within normal circumstances - within a rack and with a reasonable number of outputs. I would be looking at a DA if distance were involved. My concern was with the comment that got tossed in earlier about using the panel female of channel 2 while in parallel mode and connecting an XLRM - XLRM jumper lead, reproduced here:

> Example:
> 
> Here I am assuming that you are operating these in "parallel mono"
> 
> ...



I know a company that has owned a 48 way Y split, admittedly they had set it up as a ring to help minimise the voltage drop. They used it to test consoles...


----------



## museav (Aug 8, 2009)

Chris15 said:


> Amps with inbuilt DSP are the exception to the above statement.


Because DSP is so flexible and relatively inexpensive today, it is probably more common to independently process every channel. In the past it was probably more common to have a minimal number of processing chains and to daisy-chain their output to multiple amplifier channels.


Chris15 said:


> An arena - If it's a PA it is unlikely to be 20 amps feeding the same hang and thus will need different DSP settings.


Yes, but multiple larger satellite arrays that each cover a different area of the seating but are otherwise virtually identical is a very common approach for arenas, stadia, raceways, etc. Here's an example of a recent one locally, Danley Sound Labs | Portfolio. The larger Genesis horns are rated at 1,400W continuous and in one picture there are I believe nineteen identical such speakers shown (it's hard to see the ones painted green to match the wall) with each mounted the same, the same relationship to the listeners, etc., only covering different areas of the seating. That is the kind of application where you might have several amps daisy-chaining the same signal, especially in the days before lower cost DSP processing was available.


Chris15 said:


> Airports - I should have thought you'd be looking at way smaller zones to localise paging to the relevant gate and then feeding it off PageMatrix with Media Matrix or a similar solution.


While IED is my preference for those applications, that is true. However, you still run into facilities where there are large zones that require multiple amplifiers. On a simple level, think of paging the passenger loading and unloading zones or the parking lot at a major airport, those may be one zone using the same speakers mounted the same, etc. but that requires multiple amplifiers.


----------



## Derrick (Aug 8, 2009)

In jonhall's first post he posed a question, can he build a 3 split. In answering his question I figured I would elaborate on other ways within the industry, of accomplishing the same result. It is presented in my first post to the thread.

He then asks a question regarding "unwanted gain staging". I conclude two things. ONE- he must be talking about CH1 level affecting the CH2 "output" and vice versa, TWO- (no disrespect to you jonhall) He is lacking knowledge of the industry and that the information given to him should be in a non-confusing manner.

In post number 4, I outright answer his direct question. Knowing he needs the correct information and that I use QSC amps, I wanted to be sure of my "daisy chain" answer with direct application to the MT2400. I download the manual and discover that the MT2400 amp is not like any of my QSC amps.

At this point CHANNEL 2 on any of the amps, is removed from the equation.
The omly mistake here was that I stated, "The only XLR you would use..." I should have correctly stated, "The INPUT XLR you would use..."

Chris, you then come in on post 6, " Directly paralleling XLRs on an input stage is not a normal practice, there would normally be a buffer etc."

My response was, "The way I read it, he wants to split ONE signal source to his three amps within the rack. A splitter is just fine for that. No buffer needed. The same can be accomplished by utilizing both the XLR and 1/4" "input" connections on the amp."

The next post, #8, got my attention. "But using M-M link leads between amps means something funky is going on with that amp and it isn't buffering it's inputs - it's paralleling them which is not a sound design principle..."

Chris, I then in answer to your statements and responses. Knowing full well that jonhall might very well be reading and getting concerned and or confused, I copied a page from the manual and posted it. Crown themselves state that this is an acceptable way of connecting signal from one amp to another.

I then elaborated more. In an effort to keep things clear for jonhall, I used the example of the "rack of ten". Then by use of hyperbole, I expressed, for jonhall, that it did not matter how many amps you wanted to do this with.

Regarding the signal path opening up by way of the amp exploding, again hyperbole. How many of us have actually had a catastrophic failure in which the amps case actually exploded. Yes I have had and they will make some pretty wicked sounds at the point of failure. But I have never seen one in it's proper use actually "explode". At far as the solder connection, well I use QSC for a reason. QUALITY. Crown is a good name, not knocking them, just don't use that many of their products.

In post 10 you state that I have contradicted myself. Sir, respectfully, go back and read post 4.

I will let Brad's post speak for itself. Researched, concise and accurate.

Chris in post 12 you go back AGAIN and state,

"My concern all along has not been using a provided loop output or with daisy chaining within normal circumstances - within a rack and with a reasonable number of outputs. I would be looking at a DA if distance were involved. My concern was with the comment that got tossed in earlier about using the panel female of channel 2 while in parallel mode and connecting an XLRM - XLRM jumper lead, reproduced here:

Quote:
Example:

Here I am assuming that you are operating these in "parallel mono"

Main input to amp 1 XLR channel 1. Connect a MALE XLR from the XLR "input" jack on channel 2. Connect this to the channel 1 XLR input on amp 2. Which will also be a MALE XLR.

Connect a MALE XLR to amp 2 channel 2 "input" then connect to amp 3 channel 1 with another MALE XLR. 

Again go back and read post 4. You have posted this comment TWICE.

And by the way, It is a sound design for the parallel switch to actually connect the CH1 and CH2 inputs together. If anybody wishes, you can go study the QSC schematics here:

QSC - Schematics, Amplifiers

I am sure Crown has a source for schematics also. 

For all reading this or on any other board. READ THE ENTIRE THREAD BEFORE COMMENTING.

There is a wealth of knowledge here and I can see many new folks are arriving each day with limited knowledge wanting to learn. I am all about breaking it down for the general layperson to understand. I do not like having to write an epistle to correct a knowledgeable person's lack of reading the thread. 

Jonhall, make your cable, use with confidence and have fun!!


----------



## Chris15 (Aug 9, 2009)

OK, so there's been a lot of misinterpretation here.

Yes you can Y split, to any reasonable number of devices. Consider alternatives when splitting mic level to more than 2 devices, when you need a high level of redundancy or when you are dealing with multiple power sources, especially if they have different grounding paths.

In an effort to avoid confusing people, I suggest we stick to Y splitting or using provided male chassis or TRS connectors for daisy chaining.
Some maunfacturers may choose to link input XLRs when monoing the amp, I tend to think it bad design - introducing noise etc as well as an additional way for people to stuff things up - bump the switch and stuff goes nasty. I'd prefer a mono switch was configured with the amp input on the wiper and the channels on the outer, literally switching the input of channel 2 across to 1 and disconnecting 2 in the process. I'd suggest post buffer would be better, but either way would work.
At least until, if ever, you meet the handful of other times, there are only 2 uses for gender benders, ergo M-M or F-F cables / adapters - 1 is when you need to run backwards down a piece of core / installed cabling etc. 2 is a legacy from the days of XLR speaker cables, where you needed m-M joiner for the F-F speaker cables. Beyond that, let's not tryt connecting inputs to inputs and outputs to outputs, it mucks up the impedances in most cases (yes these QSCs might behave, other things won't).

Note that a Y split will probably end up cheaper than lots of link leads, purely on connector numbers. I would conend it can be easier to trace, but that very much depends on the topography of the amp rack; link jumpers may be tidier.

Yes there will be cases where large racks of amps are needed, few of those will show up in a high school. Given the price of copper, to maintain acceptable power losses, cable is going to keep getting more pricey and I suspect we might see amps becoming more distributed, so much is Ethernet monitorable these days, it's physical location becomes less important. Air con is also now the norm not the exception. And comms rooms are dotted around building to work with the cable limits of Ethernet.

As we start using more and more amps with DSP inbuilt, we are also doing much more of our signal distribution with AES or network based protocols. And you won't get pleasant results if you throw a Y split into an AES line...

In things like the airports, carparks etc Brad mentioned, most of these PA systems also perform duty as an evacuation PA system, and so redundancy becomes a big thing, single points of failure are bad and so link leads could potentially be more risky than Y splits, but in all cases, if the master input dry joints you are stuffed. (That's why you would run primary and secondary masters).

I think a lot of this could have been avoided by not assuming that all amps will link inputs directly and 'most all of the conjecture has derived from that.

For what it may be worth, I've always seen it done with Y splits, you will always have an input, whether you get a loop out is up to the manufacturer and is often omitted for real estate or cost reasons...

And yes, amps DO explode in the real world, used by comptent professionals. It happens and since everything is going cheap as they can in manufacturing, it will happen more with newer stuff.


----------

