How to connect two analog mixing consoles together

hello everyone and welcome to glb productions in this video we're going to look at how to connect to analog mixing consoles together this is a video that has been requested multiple times over the last one year and I'm very happy to be able to bring it to you so to begin with let's discuss why we would want to do this when would you want to connect to mixing consoles together I can think of at least two situations the first is when you run out of channels on your main mixer I'm sure that's happened to all of us you think you're nicely set up and then the drummer appears with another three rack toms or you get an unexpected string quartet or mariachi band appear you're full on your main mixer so what you do reject the job no you connect another one to give you the channels that you need now this process is called sub mixing because the main mixer is the mixer that is connected directly to the back end of the PA system in other words your system processor EQ amplifiers or powered speakers any mixes that are connected to the main mixer are known as sub mixes now the second situation that I can think of in which you need to connect two mixes together is when you're sending audio from one location to another for example you need to send a copy of the mix from the main Church sanctuary to a cry room or to an overflow room you're doing a corporate job and you have to send audio between two different conference rooms in the same building in this case you don't must always be connecting - mixes together now anytime you intend to connect to mixes together you need to work out three things the first is will you use a balanced connection using XLR or TRS cables or an unbalanced connection using normal guitar cables if you're not sure about balanced versus unbalanced connections please have a look at my di boxes part 1 video the second thing that you need to work out is will it be a line level connection meaning a signal strength of about one volt or will it be a microphone level connection a signal strength of about 0.01 to 0.1 volts and finally will it be a mono connection in other words only one signal or will it be a stereo connection stereo connection by definition uses two signals a left and a right so I'm going to begin by giving you some general answers to these questions before we start working with the gear itself when it comes to balanced versus unbalanced connections a balanced connection is always preferred because it enables better noise rejection hum buzz electromagnetic interference etc however for distances of up to five meters or 15 feet you are generally going to be okay with an unbalanced connection try it if it's fine quiet noise free you're good to go line or mic level it's important to remember that all mixers operate at line level that's why you have a gain control on the mixer because you need to bring microphone level signals up to a place where the circuitry in the mixer can deal with those signals so a line level connection is preferable to a mic level connection this avoids having to attenuate and then re amplify the signal at the other end which can cause noise remember you never want to use gain or amplification if you can avoid it you've got a line level signal coming out of the first mixer so if it all possible try and bring it into the second mixer through a line level input and the third question stereo versus mono will depend on whether you have stereo sources plugged into your sub mixer stereo sources always have two channels a left and right if all the sources in your sub mixer are mono there's no need to have a stereo connection now for certain critical jobs where it's absolutely essential that nothing goes wrong you may wish to run a second line as a form of insurance basically a redundant connection but it's important to understand that when you do that you are effectively running two mono lines it's not necessarily a stereo connection the first situation we're going to look at is when the mixers are less than five meters or 15 feet apart for example they're next to each other at front-of-house this would be common in situations where you are basically adding more channels to your main mixer using a sub mixer in situations where the mixers are relatively close together you can use an unbalanced connection because of the short distance this keeps things relatively simple and it allows you to use standard guitar cables such as the ones that I have here so the first step is to identify which output you're going to use on the sub mixer remember the sub mixer is connected to the main mixer the main mixer is connected to the back end of the PA system most mixing consoles have at least two sets of main outputs now on the Mac here you can see that it has a pair of XLR outputs on the back panel but it also has an additional pair of main outputs on the front panel and as you can see there it indicates that these can be balanced or unbalanced depending on what type of connector you use most of the time you'll be using the main connectors however it's also possible to use an auxiliary output or a subgroup output assuming that you can route the right mix of signals to these outputs I can't tell you exactly which output to use because everybody's situation is different but most of the time you'll be using either a duplicate of the main output subgroup outputs or an auxiliary output of some kind step 2 would be to identify which input you're going to use on the main mixer here you have a number of different choices given that it's a line level signal the most obvious choice would be to use the line level inputs on your mono channels these have the advantage that they give you the most control over gain EQ as well as channel routings so if you have one or two spare channels that's your best option now let's say that this doesn't apply you're completely full on your main mixer and for one reason or another you can't free up an actual input channel then you have to look for additional options one possibility would be to use a stereo input Channel now as you can see on this mixer it has two what are called hybrid channels in other words it has two channels which have both a microphone as well as stereo inputs these can be very handy for exactly this purpose again if you're going to run a mono connection you want to make sure that these channels are mono compatible meaning that they say mono left in certain cases you won't see the word mono and plugging anything in to just the left connector will result in it being sent only to the left output of the main mixer which is not good if you're going to run a mono connection another option is to return the signal into one of the effects returns now on this mixer you have two effects returns return one and return to the best way of thinking about these is line level channels which have no EQ and very limited routing options but if all you need to do is send the signal to the main mix these can be very useful they're also useful in the sense that they are stereo so it avoids tying up two channels now if you are truly desperate it is possible to connect a sub mixer to the tape input this is not recommended for a number of reasons first of all these inputs normally have extremely limited routing options typically you can send it to the left right and not much else on this particular P V mixer you can see that there is actually facility to route the tape to both of the monitor outputs which is relatively unusual the other issue is that the tape input is on RCA connectors which gives you a further connection headache so in a situation like this it may actually be better to use an RCA cable and outfit one end of it with RCA to Jack adapters this is an example of such a cable as you can see here we have an RCA cable which on one end has been fitted with RCA to TS adapters this again is not recommended simply because RCA connectors are not very secure and they're notoriously prone to breakage they're not considered professional spec connectors unlike XLR and TRS jack connectors so this should really be a last resort so now that we've explored the various options that are open to us let's make the connection on the sub mixer we will connect our guitar cables to the left output and the right output now when you do this for real it's a very good idea to actually label the connectors so that you know which one is left and which one is right now on the main mixer let's connect to the line level inputs of channels 1 and 2 so left 2 channel 1 and right 2 channel 2 once we've done this we have two set levels to ensure optimum signal-to-noise ratio between the two mixes now when you're doing this it is really best to use a steady signal source not music not your voice something like pink noise or 1 kilohertz or 440 Hertz test tone my personal preference is to use something like this this is my swiss army 6 in-1 cable tester that as you can see also has a test tone function so what I'm going to do is I'm going to enable the test tone as you can see there light on means it is a 1k tone and I'm going to connect this to the input of my sub mixer we'll just leave that there the second thing is you want to set the sub mixer such that the test stone is leaving the sub mixer at or around zero on the main meters so first thing is make sure that my gain is correct here you can see I'm at zero on my pfl so make sure the channel is unmuted bring this up and I want to make sure that I am at zero on my meters there this will present a 0 DB signal to my main mixer and I can then set gain on my main mixer accordingly so you can see that the signal levels have lit on my main mixer to indicate that it is receiving the signal I then press P FL and adjust my gain accordingly now you want it such that 0 on your sub mixer is also 0 on your main mixer that way you know that the 2 will clip at the same time this will give you the best signal-to-noise ratio obviously you want to do this for both channels just to ensure that you are at the same level there and finally seeing that we are running a stereo connection we will make sure that you pan the left channel hard left and the right channel hard right if you are running a mono signal you would just use one channel and you would set that channels pan knob to Center now just check I'm going to raise the main faders to unity game and I'm going to bring up the faders on these two now when I reach 0 on my main mixer you can see that my gain is good so when I am at 0 on my sub mixer I'll know that I'm also at zero on my main mixer this gives the best signal-to-noise ratio and it allows the two mixers to work as effectively one big gain stage now let's demonstrate how to do this gain setting procedure when running into a stereo channel as mentioned before the P V mixer has two hybrid channels which can be used either as a mono or stereo channel so let's unplug from our mono channels and connect here on this because it is a stereo channel we only have to set gain on a single knob so similar to the other ones we press P FL on this mixer you have a mic gain and a line gain so you would set the line gain use my left hand so that you can see the meters and once again we are going for zero here and zero here just to double-check release pfl raise the channel fader to unity and interestingly enough unity here is minus nine here and the reason for that is that the gain topology on this particular mixer does a little bit of subtraction from the signal when it sums the left and the right together so in this case you have a couple of options you can either leave it like we did or we can choose to raise the gain further such that when the channel fader is at unity we actually get zero here so let's try raising that and you can see there we now have zero DB on both PF Elling it you can see we're at plus six now the choice as to which of these settings to use is up to you personally I tend to be conservative with setting my game because I don't want to have to deal with distortion in the middle of a show so I would tend to trust what the PFL is telling me over what the meters say with a fader at unity so re-engaging pfl I bring my gain down until it was at zero also remember that you have an additional 10 DB of gain available at the fader itself so in my opinion it's better to have your channel gain set slightly conservative then it be set to hot and risk clipping the channel during the show now for the sake of completeness will demonstrate how to run into one of the effects returns on this particular mixer our FX returns up here we have returned one and returned to and the controls for those returns are down here you can see you have returned one send to monitor one two you have a pan and a level knob and the same for return too so let's use FX return one unplugging from the channels plug-in to our stereo return now when using a stereo return you have no game to set and you have no pfl so the only way in which you can be certain that your levels are correct is to set the faders on the main mixer at zero and then bring up the control here as you can see unity gain here is minus 3 on my meters so I have a little bit less gain on my effects returns than I would on my channels with a gain set as we did now this is okay because you're within 3 DB of the meter reading on your sub mixer if you are at zero here and say for example at +10 here you know that you need to trim your input back a little bit this is again very important because you then know that your two mixes are calibrated to one another now let's look at a situation where our mixers are more than five meters or 15 feet apart for example sending audio between different rooms in the same building or even between different buildings in this case because of the distance you have to use a balanced connection because this provides the best immunity from noise and also allows ground to be lifted to defeat ground loops you will need to use XLR cables and you may also need to use adapters on one or both ends of the cables to ensure an appropriate connection so as before you identify an appropriate output on the sub mixer in the case of our Mackie we know that this second set of main outputs can be used as both a balanced as well as an unbalanced connection the issue is that because it is a jack connection you're not going to be able to use a normal XLR connector here but you'll need to use an adapter to convert from TRS to XLR a commercially manufactured adapter such as this one or you can use an adapter cable which is a TRS plug wire through a short length of mic cable to a male XLR connector one way or another you have to convert that into an appropriate connector for your use it's worth noting that on some professional mixers like this Mackie the main output level can be switched between line level indicated by +4 and microphone level this is an extremely valuable feature to have on any mixer which might be used as a sub mixer because as you'll see later it allows you to bring the main XLR output of this mixer into a microphone channel on the main board now let's make our connection I have my XLR cables here and I'm going to connect the main output of my Mackie to the PV this time we'll be using the microphone level connectors here first our left connector and then our right connector I am pressing in the mic line level switch on behind such that the output of my Maki is now microphone level as before we need to do our level setting procedure on both boards so I still have my cable tester hooked up here which is providing a 1k test tone I want to ensure that I have a zero DB signal going out of the sub mixer which is then coming into the main mixer here I would press P FL and I would set my game to give me about zero dB now I strongly recommend that you do not run a line level signal into the mic connectors like this in order to show you why I'm going to disengage the might line setting on the back of the PV and show you what happens so as you can see we now have to clip lights which indicate that the channels are overloading obviously because our gain was set for mic level and we now have a full on line level coming in so let's repeat our gain setting procedure it's very clear that even with the gain all the way down I'm still at plus nine on my meters and without a pad switch or some other way of attenuating the level there is a very very real chance that once the show begins I'll end up clipping these two channels so once again I strongly recommend that you do not run a line level signal into a microphone input unless you have a pad switch or something similar instead what you'll need to do is use an adapter like this you can see that this is a female XLR to TRS which will allow you to connect to the line level input and as you can see there we our channel is still pfl we have a much more reasonable gain and we can just adjust that up a little bit to give us pretty much the same game as when we were using the unbalanced connection so this is an example of having the right tools for the job and using the correct input for the correct level signal now when connecting to a stereo channel the procedure is pretty much the same as when you were using the unbalanced connectors the only difference being that you are now using a TRS instead of a TS connection one word of caution make sure that the stereo channels on your particular mixer have balanced inputs the way to detect a TRS Jack is that there will always be two clicks when you insert a jam so that is the first clip notice that the connector is still clearing the top by about a quarter of an inch that's the second click once again first click second click now if I try that same thing on this stereo channel note what happens nothing only one clip what that tells me is that these are actually unbalanced connectors and connecting a TRS jack will have no effect whatsoever was still unbalanced so these are the little things that you need to look out for when you are in the real world check your mixer manual determine whether the stereo channels have jack connectors that are balanced or unbalanced so that you can be prepared for this type of situation so far in this video we've covered how to connect to mixes together using both unbalanced as well as balanced connections we've covered situations where the mixes are next to each other as well as situations where the mixers are separated by more than 5 meters or 15 feet the last thing we're going to discuss is what if you have noise issues what if when you bring up the faders on your main mixer you have hum buzz or other forms of interference the usual reason or cause of this is a ground loop in other words the difference in the ground potential between your sub mixer and your main mixer for a full explanation of this have a look at my di boxes part one video the way to deal with ground loops is to lift the signal ground between the two mixes and the best way to do this is with an isolation transformer also known as a passive di box this will provide the galvanic isolation necessary in order to electrically isolate the two mixes from one another and it usually solves the problem these are so useful that very often professional setups will run through transformers as a matter of course just as a form of insurance so how we set this up if running mono you would use a normal DI box such as this InP 2 if running stereo you can use 2 mono di boxes or better still a dedicated stereo di box like this radio pro AV 2 which as you can see has two inputs and two outputs containing two isolation transformers which will help to reduce noise this setup is a hybrid of the first and second ones that I showed you we're going to be running line level out of this mixer and mic level in to this mixer so to begin with I'm going to get my guitar cable and I'm going to plug it into the output of this mixer and I'm going to connect that to my di box we then connect the output of the DI box to a microphone level channel on the mixer remember that running through the transformer results in what is called insertion loss so typically you will be coming out of the DI at a mic level this is useful if you need to run for example through a snake which contains other mic level signals it helps to prevent crosstalk and other forms of signal contamination so we connect to the DI box and then on our main mixer we would connect to a microphone channel how does this affect our levels our swiss army tester is still hooked up here so let's once again as you can see we are running at 0 DB u out of our Mackie let's have a look at the level on our sub mixer or rather on our main mixer so with the gain all the way down we're at minus 15 and there we are my gain here is at 11 o'clock so sort of intermediate between the two situations that we've looked at so far this is one of the reasons why it's really important to carry spare di boxes not only are they useful for running signals from the stage to your mixer they're also very useful in situations such as this if you are running a stereo connection you just double up what I've demonstrated here so that's all for this video I hope that it's been useful to you I hope that you understand how to connect to mixes together once again if you have questions or comments do please feel free to leave them in the comment section below the and I'm always happy to answer questions either here on Facebook thanks very much for watching this is Bruno loose from GLB productions and I'll see you in the next video you

Channel: GLB Productions

Views: 518,835

Keywords: Mixing Console (Invention), Sound, sound reinforcement, PA system, sound system, Audio, mixer, Mackie (Brand), Peavey Electronics (Musical Instrument Company), analog

Id: HgeVInOV1Kk

Length: 31min 52sec (1912 seconds)

Published: Sun Mar 29 2015