Step 6: Buses (subgroups), Main mix, VCA's

Picture of Buses (subgroups), Main mix, VCA's
Almost all decent sized mixers have at least one bus, or subgroup, many have up to 10 or more. Buses are, simply put, a routing system. There will be buttons near the fader on each channel for each subgroup, allowing you to assign that channel to one or more of these subgroups. Think of the buses is mini-mixes.
One very common use of a bus is to assign all the drum channels (floor tom, kick, hi-lo tom, hi-hat, snare, etc.) to one bus. This way, the engineer can change the volume of the drumset in the total mix without having to change each fader on each channel. Other uses include groups of singers (girls, boys; leads, harmony), instruments (main, backup; brass, woodwind, percussion), etc.
Just remember that changing the fader on a bus is NOT equivalent to changing the faders on all of its assigned channels. It simply changes the volume of that particular mix of channels relative to the entire mix. Channels can be assigned to multiple buses, and changing the volume of one bus with channel 6 in it will not change the volume of channel 6 in any other subgroups.

Each of the subgroups also has a button allowing assignment to the main mix. In most cases, you will want everything combined into the main mix so that you can control the total volume of everything with one setting. Sometimes, however, you may leave one subgroup by itself; independent of the main mix, for whatever reason may apply. Usually each subgroup will have a left and a right fader, allowing for individual adjustment of the left and right aspects of that mini-mix. The main mix will also probably be stereo. There will be two outputs on the back of the board for left and right mix.

However, some mixers have another button to assign the main mix and any and all subgroups to a "mono" fader. This is another output on the back that is a single bridged out between the right and left of the mix out. This allows you to have a huge amount of possibilities of setups depending on where you have channels and busses assigned and what you have plugged in to the back. The mono will "bridge" the left and right channels, causing all sounds in each to be played in both. It will also, however, leave alone any left/right settings set before it.

VCA's are confusingly similar to buses. However, it helps to remember that buses route, and VCAs are simply a control mechanism. Contrary to subgroups, a change in a VCA will be exactly like moving the faders of all its assigned channels. Thus, any post-fader outs will be affected: post-fader auxes, the level of that channel in any subgroups, etc. If post-fader auxes are used for other main speakers like subwoofers, than a VCA will allow change in those too; where a subgroup would not.
VCA's are found only in larger boards.
joeltan1115 years ago
I love this tutorial....
going to use it for teaching purposes. 
But, i wish to ask if there are any guides or tutorials which detail the operation of a digital board, as this guide is focused on a analogue board.

This response is 4 years to late, but as of right now it would be difficult to create a guide like this for digital mixers as they are all different. If you want to use a digital one then you will need to find information specifically for that board.

_Basse_6 years ago
Can anyone recommend a "begginer" Soundboard ?
It all depends on what kind of things you are looking for the board to be doing, if you give me some sort of idea what you want and I can give you some recommendations.

07511 664218
Braedenb133 years ago
Hey, I run a tech booth at church and we want to start recording sermons and putting them on the Church Website for home-bound seniors. We have our computer and we have a 16-channel soundboard. If i wanted to record it, could i but a XLR cable that converts to a 3.5mm Jack and plug it into the microhone jack in the computer, and record it that way in Audacity, and upload it to the Website? I just want to know before i buy the cable.

syme6 years ago
Hi brilliant set of instruction was slightly confused by you saying about set the gain by putting the channel fader to 0 dB and the main and use a uV monitor I thought you could use the pfl button to assign the channels signal to the led volume indicator on the main mix then tune that accordingly till it reaches zero level on that LED indicator or use the zero level light alongside the gain knob of am I incorrect at thinking that also while I'm at it got a mackie CFX 16 mixer however the inbuilt processor's clip is contently overloaded even if no signal is being sent to the processor and if the main effects send and "to main Mix " etc. are all set low it still overloads, am I right in thinking that the clip is something that stores the signal to be processed like some kind of cache or am I totally out by thinking that??
Markusaurelius (author)  syme6 years ago
You could use any meter you want to use the gains to get unity (all the channels being the same volume if their faders are the same volume), or just your ears. Clipping occurs when more voltage (due to high audio levels) is sent to a component than it is designed to handle. It is a very broad term. On a console, this means that wherever in the signal's path the clipping occurs, there's too much audio for that component. For example, your power amplifiers driving the speakers are set to low volumes, so all the channels are turned up to compensate. Each channel may be clip-free, but once they are summed (technical term for mixed) in the Mono or Mix output, the levels are too much for the components thereafter. You would see clipping lights above the main mix faders, or a VU meter reaching the very top red bar. Sometimes if your gain is set too high, that channel alone clips - often the indicator light for this is the same as the PFL light. If your console is clipping with suspiciously low audio levels, this probably means an electrical problem within the console. It might be remotely possible that some powerful unwanted signals outside of hearing range are making there way into the signal path before the console (like in a broken cable or something), so I would check for that first, since it would be a much less expensive fix.
Congrats on a thorough and well written Instructable. You covered all the basics nicely! I run an MH3 as a freshman at my school regularly. You need to be careful in your definition of Gain, as it is NOT to be confused with a gate. It's not so much to filter out the soft sounds (like a gate) as it is to control preamplification, or in some cases attenuation of the input signal.
Markusaurelius (author)  inquisitivegoat7 years ago
Yes, good thing to point out. I guess what I really should have said is that a low gain will result in a loss of softer frequencies, which is sometimes good and sometimes bad. When it is bad (I.E. mic'ing electric guitar amps, where you need the softer frequencies to sound right), it is called (or at least I call it) undergained. Gates don't really take out softer frequencies, they mute the whole channel when the signal is softer than a certain desired level. I'm sure that's what you meant, just wanted to elaborate. :)
That's a good point, perhaps my argument is flawed. Micing amps is an interesting science. The different response of different microphones can lead to good or bad effects. Perhaps an Instructable on that is in order. Have you ever done any work on a Vi6 or Vi4 console?
Markusaurelius (author)  inquisitivegoat7 years ago
As I told someone else, I'm actually just a high school student, although I've been trained; so I don't have much experience on different consoles, just the ones around my church and school (which are in the same building). So even though I know stuff, I haven't done much stuff, if that makes sense :) My church's consoles are Soundcraft Spirit LX7's - pretty old, but work (32 inputs). They have an MH2 I think in the new Worship Center, but only certain people are allowed to touch that, which is a whole other debate....
I too am a high schooler, a freshman actually. The thing I miss on the MH2 is the fully parametric EQ on the Hi-Mid and Low-Mid (which the MH3 does have). The MH2 has a sweep bandpass EQ with a fixed Q of 1.5. The ability to adjust the Q in the Mids is very helpful when equalizing almost anything and I rarely leave it set at home. The MH3 has to be by far the best analogue console I have ever used. I don't care for the MH4's nested pots, and the MH2's limited EQ is a drawback. For everything I have ever used an analogue console for I have found the MH3's mix of signal processing and outputs adequate. (although I have found uses for all four matrices and wished for more) At my church we have a MACKIE TT24 which, due to it's extensive DSP power, has fully parametric EQ with an adjustable Q on all four bands. (not to mention the onboard compressors / gates / expanders / patchbay / etc, digital has endless power)
Markusaurelius (author)  inquisitivegoat7 years ago
Yeah, I really wish I had Q on the consoles I use; especially since I'm working with really cheap mic's. Did you know you can buy PG58's in Hastings? Any sound equipment you can by in a book store can't be to nice....
That's a good thought. My favorite dynamic vocal has got to be the Shure Beta 58, or in the Audio-Technica realm I like the AE6100. I tend to lean towards AT for vocals, my favorite condenser being the AE5400. We have two of those in a 5000-series wireless transmitter at my school. For wired vocals at school I tend to use the Shure Beta 87A. I would love the chance to use a few KSM9's but I don't think we will be getting any new mics in the next year or two because the ones we have now are in excellent condition. As far as instrumental/amp pickup I typically use SM57's for amps and toms. For cymbals, drum overhead, brass/woodwind overhead, grand piano, acoustic guitar, etc. I usually use the SM81. I've used a pair of KSM44's extensively for recording and even for amplification of about 15 vocals in a gospel band. Sometime I think it would be cool to use them to amplify a grand piano or a (very high-quality) guitar amp. Unfortunately the only pair I have access to at the moment belong to a teacher who retired at the end of this year.
Markusaurelius (author)  inquisitivegoat7 years ago
Everyone loves the SM57 and SM81 - great mic's; as well as the SM58 - which I prefer a lot over the Beta 58. We use Beta58's at our church too, and their so muddy - I always have to almost kill somewhere around 400hz, depending on the person. If you go to Shure's website you can see the difference in low-end response between the SM and Beta. I can't say I've ever got to use any of the KSM's - way over our church's budget (for the two rooms in which I get to work at least). When they built the new worship center, all the budget and good stuff got put down there...
I think heavy bass is pretty common among the Beta series. It is evident between the SM and Beta 58, like you said, and you hear the same thing between the SM and Beta 57. At school we don't have any subs, so really low end stuff becomes really obsolete really fast. Our in-house center cluster sounds like a speaker in a tin can, but for most of the year we had additional cabinets hanging in left and right positions that really enhanced the sound in the room. We had Skillet come in, and they brought their own line arrays and some really low drivers. At church we have a relatively small sanctuary with seating for only about 600. We have a single 18-inch sub hanging center up front which makes bass very evident and has the power to rattle things sitting on the desk in the sound booth. We use all Audio-Technica mic's at church, so I have never gotten to experiment with different Shure sounds where I can hear very low bass response.
Markusaurelius (author)  inquisitivegoat7 years ago
It's not so much sub-range sound as it is just plain muddiness that I get with the Beta 58, which is quite nasty, but easily fixed with a parametric low-mid band. I still would rather have a Beta 58 over a PG58 any day :)
soundgod2197 years ago
Fantastic! Can I use this to teach other people the "how-to's"?
Markusaurelius (author)  soundgod2197 years ago
Sure. I'm not a big copyright fan, so use it all you want.
Thank you soooo Much! I've been looking for a good tutorial on soundboards. I'm learning the one at my church and have been needing something in writing. Now that I've actually read through it, its really, a lot clearer. Thanks again! Really great. -Roxie