Installs - combination wire

[AlexD]

In my schools recording studio we have two 8 channels mixers, one is an old one and is used as a back up. We have it set up to do multi track recording, the direct outs go to a patch bay and then to a motu 828 mkii and from then to the computer. We have multicourse going to a dry room and a concert hall (so we can do ambient recordings). At the moment someone has plugged all the multi core into the backup mixer, gave me the idea of using the backup mixer to do recording for the concert hall. To this with out unplugging everything all the time, we would need to combine the dir outs of both mixers into one.
To do this I need two TRS to one stereo phono. Or a cheap combiner witch has 8x 2 in, 1 out or like this. Witch out spending loads of money of high quality combiners will this diminish the sound quality?

[AlexD]

I am also thinking that i might have to creat this cable myself. will this also diminish the sound quality if done badly?

[jkowtko]

Alex, you're referring to "splitter" or "Y" cables.

However you should not combine two powered outputs ... this is covered in other threads and is a big no-no.

If you're main goal is trying to avoid unplugging and replugging 8 TRS connectors, you might as well just label them carefully, and plug and unplug them when needed. So long as you're not doing this several times a day I don't think the plugs or jacks will wear out. Just label them well -- color code them even, to make it brain-dead simple to whoever needs to change them.

[Clifford]

A Y cable can't be used to combine signals, only to distribute them over more lines. One of the engineer types will probably say why. A hardware combiner is what the situation calls for.

Also, "which."

[museav]

So if I understand it, what you are looking at is taking a direct output of mixer A and a direct output of Mixer B and wiring both of those to the same recorder input so that you could record from either mixer. Is that correct?

[jkowtko]

Sounds like really wants a cheaper alternative to an A/B switch (e.g. Ocean Matrix | PSW-6AB 6x1 Passive Switcher, | OMX-PSW6AB | B&H
)
... maybe it's worth him trygin to build one if he can do it cheaply enough?

[AlexD]

Originally Posted by museav

So if I understand it, what you are looking at is taking a direct output of mixer A and a direct output of Mixer B and wiring both of those to the same recorder input so that you could record from either mixer. Is that correct?

Yes that is right. Though I have just found out that the interface we use has 20 inputs so we can bypass all of this and have it on separate 8 inputs. I did look at some hardwear combiners, came to about £100 for all the wires as well so not good for a school who could make do.

I’m curios though y can you not use a “Y” cable for powered singles. And dirt outs aren’t powered are they?

[FMEng]

I hope I can write this in a way that makes sense. Most output stages have a very low source impedance. Connecting two outputs together means that each one is having to drive the impedance of the other output that is much lower than it was designed to. Each output sees a load that looks almost like a dead short to it. The result is both outputs may clip (distort) at a lower level than normal, or it may have reduced low frequency response and/or distortion all of the time.

Two outputs can usually be resistively summed together through 4.7 kilohm resistors and fed into a typical high impedance input. Though I'm guessing a soldering project isn't what you had in mind. Plus, there is a noise penalty to combining because now you have two consoles contributing noise to your recording.

Or to boil this all down: You can use Y cords to drive multiple inputs from one output. But do not try driving one input from two or more outputs.

[fredthe]

Originally Posted by FMEng

Or to boil this all down: You can use Y cords to drive multiple inputs from one output. But do not try driving one input from two or more outputs.

Tell that to the sound company who just delivered the school's new portable recording setup... they included a cable to go from the stereo mixer output to the mono input of the room's sound system... I'm sure there are no resistors in there. (That's the least of the ways it's screwed up... the spec was poorly written, and they didn't listen to me when I told them how to fix it )

-Fred

[Lightguy48]

We deal with summing sources quite frequently in the broadcast business, here are a couple of companies that make 'problem solvers' for situations like this:

Henry Engineering

Radio Design Labs Product Subcategories with Product Descriptions

The nice thing about the products from these companies is their small, rugged, and easy to use. RDL has a ton of 'stick-on' products for all sorts of applications, but they are a little pricey for what some of them contain for components.