Two mixers, one PA

[Imagine]

OK peeps, probably a really silly question but one I've searched the interweb for and I'm sure the answer's really dead simples.

My current setup:
Main playout: Laptop into VMS4.1 which in turn goes out to powered subs and tops (nothing complicated there).
Backup playout: Laptop into Mixtrack Pro II which can also be wired into the powered subs/tops

(Connections are obviously XLR with the exception of the back of the Mixtrack which has phono connectors on it - I have the conversion leads to XLR for this).

So, the silly question.....both of these run standalone, the idea being if the main playout fails, I plug the speakers into the backup with minimal dead air and away we go.....is there a way to have them both connected and yet standalone at the same time?

I've seen XLR splitters on the web which to my mind would be the obvious solution (so both desks go into the splitter cable and then on to the powered PA).....can anyone see any issues with this idea or am I likely to blow something up in the process?

[Nakatomi]

OK peeps, probably a really silly question but one I've searched the interweb for and I'm sure the answer's really dead simples.

My current setup:
Main playout: Laptop into VMS4.1 which in turn goes out to powered subs and tops (nothing complicated there).
Backup playout: Laptop into Mixtrack Pro II which can also be wired into the powered subs/tops

(Connections are obviously XLR with the exception of the back of the Mixtrack which has phono connectors on it - I have the conversion leads to XLR for this).

So, the silly question.....both of these run standalone, the idea being if the main playout fails, I plug the speakers into the backup with minimal dead air and away we go.....is there a way to have them both connected and yet standalone at the same time?

I've seen XLR splitters on the web which to my mind would be the obvious solution (so both desks go into the splitter cable and then on to the powered PA).....can anyone see any issues with this idea or am I likely to blow something up in the process?

Due to outputs of equipment generally being fairly low impedance you can't really get away with just wiring outputs in parallel with a 'cable' & hoping for the best. It might work, but it might not sound good or be good for the output stages of one or more pieces of your gear.

The easiest way to connect two outputs together is with a passive mixer/combiner/splitter. The only side effect you get using one of those is it'll attenuate (i.e. quieten) both of the outputs you're combining. Such passive (passive meaning they don't need a power supply) devices use resistors - better quality ones use transformers to couple the signals together to one output.

Here's a single channel (two inputs to one output) one..

https://www.studiospares.com/Microph...ner_458220.htm

and a dual channel one (two inputs to one ouptut x 2) here:

https://www.studiospares.com/Microph...ner_255300.htm

FWIW the amount the signal is attenuated using a good quality passive combiner shouldn't be too bad. Your PA likely has more than enough headroom to compensate for any loss through those combiners

Active mixer/combiners buffer each of their inputs and mix them - just like an ordinary mixer except without gain or other controls. These need to be powered though. If you're considering something like this, you may as well run unbalanced audio from both mixers into the final mixer & split its balanced outputs. And since you're doing this for backup - would you really want another active device which could fail, in the way of both primary and your backup playout?

[Imagine]

Somehow I knew it wasn't going to be as easy as I thought

Thanks for the link - looking at that one now

[DJColsie]

Couldn't you feed the phono outputs from the mixtrack into one of the line inputs on the VMS4?

The VMS4 acts as a standalone mixer so even if the laptop for the VMS4 failed, the line inputes (ie your back up laptop and mixtrack) would still work through the VMS4.

[Nakatomi]

Couldn't you feed the phono outputs from the mixtrack into one of the line inputs on the VMS4?

The VMS4 acts as a standalone mixer so even if the laptop for the VMS4 failed, the line inputes (ie your back up laptop and mixtrack) would still work through the VMS4.

Wayne could, for sure, do that.

But what if the VMS4 went bad, say if its internal PSU failed? Wayne would be stuck having to swap cables over, still. Okay by the law of averages, a laptop is much more likely to fail than a mixer but I've been working alongside a 'famous' DJ in a club where the main PA mixer failed & a spare had to be hurriedly ripped out of a neighbouring bar owned by the same company.

[Imagine]

Couldn't you feed the phono outputs from the mixtrack into one of the line inputs on the VMS4?

The VMS4 acts as a standalone mixer so even if the laptop for the VMS4 failed, the line inputes (ie your back up laptop and mixtrack) would still work through the VMS4.

I could (indeed for CD output I plug my old CDMix into it in exactly this way) - but I'm trying to make the system bomb-proof. What happens if something goes wrong on the VMS? I'm probably being over paranoid, but just want it to run as two stand-alones so that I can recover from any problems (not had any yet....touch wood) as quickly and with as little fuss and dead air as possible if that makes sense.

[Excalibur]

Wayne could, for sure, do that.

But what if the VMS4 went bad, say if its internal PSU failed?

Unlikely. It has an external PSU.

Yes, I'm having a whimsy, but Juski is absolutely correct. I actually carry a spare PSU.

The other possible solution is to feed both controllers into another mixer, eg an FOH mixer. We're heading rapidly into overkill territory, unless you want to use the FOH mixer to run microphones.

[Hugh Jarse]

Build your own "10k ohm mixer" (cheap) I use it to combine outputs of my MC 6000 and Karaoke mixer
you can build it into an existing XLR Y splitter or build your own...after all its only adding some 10k ohm resistors. (diagrams in link)
http://www.epanorama.net/circuits/linesum.html

[Nakatomi]

Unlikely. It has an external PSU.

Yes, I'm having a whimsy, but Juski is absolutely correct. I actually carry a spare PSU.

The other possible solution is to feed both controllers into another mixer, eg an FOH mixer. We're heading rapidly into overkill territory, unless you want to use the FOH mixer to run microphones.

Ugh, an external PSU? Minus one point for that, ADJ. But yeah I'd carry a spare PSU too.

[DazzyD]

Build your own "10k ohm mixer" (cheap) I use it to combine outputs of my MC 6000 and Karaoke mixer
you can build it into an existing XLR Y splitter or build your own...after all its only adding some 10k ohm resistors. (diagrams in link)
http://www.epanorama.net/circuits/linesum.html

Hi John!

Welcome to the forum and it seems like your knowledge could be very valuable when shared with other forums members. Can I ask you to pop across to our "Newbies" section and give us a little introduction about yourself as, to be honest, we're a nosey bunch and we like to know a bit about who we're talking with!!

You can find all the relevant info here:

linky