Church Tech Arts

Picking up from where we left off yesterday in our discussion of deciding on the best mixer…

Feature Set
What types of new features are you looking for? More groups, VCAs, a bigger Matrix, better EQ, better metering, direct outputs, mute groups, and/or automation are all found on boards at various price points. These are all great features…if you need them. If you don’t, it’s extra confusion for the people who run the board. On the other hand, don’t skip over this step. Really think through if you would be better served with groups for VCAs, and buy accordingly. 

Performance
It’s a fact that some boards sound and work better than others. If you can, get a loaner or rental board to try out in your room to see how it sounds, and how it works. Sometimes seemingly insignificant details can make the job a lot easier or a lot harder. It’s good to know that up front. Sometimes the new “upgraded” board doesn’t sound as good as the old one. If that’s the case, keep looking. 

Also consider the warranty, local and manufacturer support. One thing I really appreciate about Yamaha’s higher-end consoles is their 24/7 support. If something goes haywire with the M7 at 9 PM on Saturday, someone will answer the phone and try to talk me through a fix. If necessary, they’ll put someone on a plane to deal with the problem ASAP. Depending on your application, that might be necessary. 

I once had a Soundcraft Series Two power supply go bad at 7 PM on a Friday night. Thankfully the local shop was open on Saturday and we got the board in for repair. It took a week and I had to borrow the board out of the youth room to make church happen, but we were back up and running the next weekend, and the services went on. That’s important. Find out if your local dealer is also an authorized repair center, or if they have to send it out.

Digital or Analog
This is the first question most people ask, and it should probably be the last. Without figuring out the previous list (and I haven’t been all-inclusive in the list, there are dozens of smaller questions), you really can’t make a good decision about this. Going digital just because it’s the latest thing and all the mega churches in town are digital are not good reasons to do so. Digital has a lot of advantages, but it also carries some baggage. It’s important to know if the trade-off is worth it.

First, consider your existing complement of equipment; your snake, outboard gear, patchbays and the like. What kind of shape are they in, do you have enough, how easy is it to pull a new snake? How many stage inputs do you have now, and are they enough? Will a new snake be more cost-effective than a digital cable? Sometimes it is, believe it or not.

Think about who will be operating the board. Anyone with a reasonable amount of skill and time behind an analog board can learn a digital one–at least the lower end ones. However, who else uses it, and how easily will it be for them to make the transition? Most digital boards have permission setting ability that makes it easy to keep inexperienced operators out of trouble. But is there someone at your church who can figure out how to program the keys?

Digital boards have a lot of advantages, but they tend to be more complex to use and set up. On an analog board, it’s easy to teach someone how to use the Aux sends or EQ. It’s right there in front of you and it’s easy to visualize. A digital board has a bunch of multi-purpose encoders and it’s easy to get lost if you’re not paying attention. I’ve done a lot of mixing in my career, and once in a while I still adjust the wrong monitor mix on the M7 or select the wrong channel. Mastery of digital is by no means impossible, but it does take time. Are all the stakeholders (volunteers, leadership, board, etc.) prepared for that?

If you already have a significant investment in quality outboard gear (compressors, gates, FX, etc) and you have a decent snake installed, going digital may not make a lot of sense if all you really need are more inputs. On the other hand, if the snake is old and failing, you’re always short gates and comps and you really could use another 16 stage inputs, a digital upgrade can fit the bill perfectly.

Even with digital you have some choices. Some boards, like the Yamaha M7 and LS9 are hybrid boards; that is they are designed to be dropped into an existing analog infrastructure. You can get digital snakes for them, but they add significantly to the cost. The work great if you have an existing snake that does the job. Others, like the RSS M-400 at the low end and the Digidesign Venue and Profile at the high end, are based around a digital snake concept. Those are perfect if you need the advantages of digital and you either don’t have a snake, it’s not big enough or the one you have is failing.

Decisions, Decisions
Clearly, there are lot of questions to ask when buying a new board. I haven’t even tried to be exhaustive, but this structure will get you thinking. You really need to think it through. Then ask some people to help you think it through. Then go play with the board. Whether you’re spending $2,000, $20,000 or $50,000, it’s a big deal. That’s money that could be going to a dozen other areas of ministry, and it needs to be spent  wisely. We also need to invest for the long-term. Asking for a new board every 3 years because you chose poorly is not a way to win friends and influence people. So think it through…everyone will be better off!

Almost weekly, I receive an e-mail asking for advice on which mixer to buy. The answer, of course, is always the same; it depends. No seriously, that’s the answer. Because there is no “one” right mixer for every church. There are quite a few that hit a sweet spot in terms of a performance/value ratio, but even those are not right for every situation. So what I thought I’d do is walk through a process that I use when spec’ing out a new mixer for a church. Keep in mind that every single gear purchase is a compromise. What we try to achieve is the best compromise for the situation, with some room to grow. So with that in mind, here we go.

Primary Objective of Upgrade
It may seem obvious, but a lot of churches are “convinced” they need a new mixer, but can’t articulate why. “Ours is old and it’s not doing the job,” is not sufficient. What part of the job is it not doing? Does it lack inputs? Is it noisy? Do some of the faders not work? Too few outputs? Too big? Don’t like the color scheme? 

Seriously, we need to consider what we are trying to fix before we can find a suitable replacement. And sometimes it really makes more sense to replace a few faders than it does to buy a new desk. Keep that in mind. But once we know what we don’t like about the old one, we can decide what features and what kind of performance we need from the new one. 

Input Count
You might think that the digital/analog question might be first, but I prefer to save that for later. First we need to determine how many inputs are currently used, what the short term (ie. 2-3 years) growth plans are and then figure in some cushion. I like to start with this question because if a church only uses 3 microphones and a CD player each week, a PM5D is probably not the best choice, even if they can afford it. Nor is an M7.

It’s important to note the number of mic inputs and line inputs. You also want to consider how many inputs you would like to be able use if you had them available. For example, if your current 16 channel mixer is full, consider what you would like to be able to do right now before you run out and buy a 24 channel. You may find that one full sooner than you expected. 

I always advise churches to count up their maximum ideal channels for weekly services (once or twice a year events are another matter), then add 8 channels to that. Start looking at consoles with that channel count at a minimum. If you end up with 30 as your ideal number (current use, planned upgrades plus 8 spares), you may find that going for a 40 channel board isn’t that much more, and might make sense. On the other hand, 32 might well be sufficient. Think it through.

Output Count
Again, this might seem obvious, but outputs get used up in a hurry. Obviously you have the mains, which usually means 1-2. Then you have monitors, 4-6 is common on smaller boards, but think about how many you’d like. If you’re still using wedges (I’ll pray for you), remember that for each monitor mix you need another channel of amplification. If you’re using ears, it’s beneficial to get everyone on their own mix, and even small bands will max out the Aux sends of smaller boards.

Don’t forget the “forgotten” outputs–cry rooms, record sends, lobby, DVD record, green room, overflow rooms–this list can get long as well. Think about how you are going to use those sends, and what makes the most sense to get them there. Sometimes, you need an Aux send, other times a matrix works better, still other times a group out makes sense. How many do you need now, what might you need, then add a few extra. 

For example, if you determine that you’d like to do 7 monitor mixes, a main left and right, a record send, a cry room, lobby and DVD record feed, don’t bother looking at a Mackie Onyx 32.4, even if you don’t need 32 inputs–you’re out of outputs on day 1.

Tomorrow we’ll consider a few other questions, and finally get to the greatest question of all–digital or analog.

In case you’re not currently aware, if you are using wireless microphones or IEMs that are operating in the 700 MHz range (698-806 MHz), you’re going to have to power them offer permanently sometime after Feb. 17, 2009. How soon is still up in the air, but they’re going to have to go away. For more information, you can read this post  and this post.

Well, either Shure feels our pain, or they figured out that they could sell some more wireless equipment by offering some pretty substantial rebates for those of us stuck getting rid of our perfectly working and soon to be perfectly obsolete 700 MHz wireless gear. The church I work at currently has 16 channels of Shure UHF wireless mics and 9 channels of PSM600 and PSM700 IEMs. Of those, let’s see, 16 of the UHF and 7 of the IEMs are in the 700 MHz band. 

To replace the UHF mics with comparable current equipment, we’d need to go with UHF-R, which runs at least $1,500 a channel (with just a pair of bodypacks–handhelds are more expensive depending on the capsule). Since we have the dual receivers, that means spending at least $3K on a rack space. With Shure’s rebate of $1,000 on a UHF-R Dual system with the return of our old UHF units, that suddenly makes the transition $8,000 more affordable. 

And they’d spot us $300 on each new PSM700, making that $2,100 more affordable. They’ll even give you a rebate if you trade in a competitor’s gear. The rebate is about 1/2 of what it would be if you currently own Shure, but it’s a nice incentive nonetheless.

The rebates vary depending on what you’re buying. Obviously, big ticket items like the UHF-R series get a bigger rebate than the less expensive SLX series. Still it’s a pretty fair percentage off.

You can get all the details of the rebate, and download the form at Shure’s website.

I had heard that Sennheiser was doing something similar, but I can’t find anything on their website that might give any details. It would be worth checking with your Sennheiser dealer (or call them directly and ask for your local rep) if you’re going that route.

Given the fact that many churches are feeling the pinch right now in their budgets, it’s a welcome bit of relief for the church sound engineer who has to explain to the board why we need to replace our wireless mics that seem to still work fine.

This is coming a few weeks after the fact, and some of you may already be aware of this but it’s important to note that on November 18, 2008, the FCC finally released it’s official ruling on what had been called White Space Devices (WSDs). They are now called TVBDs (TV Band Devices). While there’s no shortage of anxiety regarding these devices, at least we now know what we’re up against. Here is a summary of what we now know, and some thoughts on how it affects the church sound engineer.

There are two categories of TVBDs: Fixed and Personal/Portable. Fixed devices are permitted to operate in TV channels 2-51 (except 3, 4, and 37) at a maximum radiated power of 4W. Personal/Portable devices are permitted only in channels 21-51 at a maximum power of 100 mW (or 40 mW if operating adjacent to a TV station).

The rules stipulate that licensed wireless mics take priority over TVBDs, however there has yet to be any clarification on how a wireless mic user might get licensed. The TVBDs are supposed to use spectrum sensing technology to avoid wireless mics and TV stations, and until they can provide proof of performance that they can reliably avoid wireless mics and avoid causing interference, they must use a geolocation database to avoid permanent installations. 

In 13 major markets, there will also be 2 TV channels reserved for wireless mic use. Those channels will be the first two open channels above and below channel 37. 

So the good news is that just about anywhere in the country, we should be able to find at least 2 open channels to operate at least 16 wireless systems (8 per TV channel). I say should because there are still a lot of questions about how the geolocation database will work, and how well spectrum sensing will actually play out.

The fixed (and higher power) devices will be a known quantity, and we can frequency coordinate around them like we do with TV stations now. The bad news is that there will be any number of them coming online for the foreseeable future, and we might not know when and where they pop up. And with the portable units being banned from channels below 21, we at least have that part of the spectrum relatively free from roaming, variable interference. 

No matter how it all turns out eventually, the fact is, our wireless spectrum is shrinking, and we need to start taking steps to reduce our dependance on them. The bottom line is that there will be increasing competition for the airwaves, and since we don’t have nearly the budgets Google and Microsoft do, we’ll won’t win the battle.

I’ve been saying it for many months, and will continue to do so: If it doesn’t need to be wireless, make it wired. You’ll save yourself a lot of headaches (not to mention money and get better sound!).

Thanks to Sennheiser for their information on the ruling.

I was waiting for my daughter at middle school when the call came in. “Mike, I’m headed over to Guitar Center to listen to studio monitors for my production suite. Wanna come with?” I enjoy playing with all kinds of gear, but speakers are perhaps my favorite, mainly because the differences are so profound. The caller was Erik; our lead audio volunteer at Upper Room and CPC’s new technical director. Erik and I are both hard-core geeks, so I knew we would have fun.

I’m not normally that thrilled about hanging out at Guitar Center, but they did have a decent setup for listening to studio monitors. They had a couple of racks full of speakers, a small Rolls mixer and a selector switch. Given that we were surrounded by about $100,000 worth of other studio gear, I was a bit disappointed in the Rolls, but what are you going to do. After rounding up to GC employees to get an iPod cable hooked up, we commenced listening. Erik brought some very high bit rate files, and I had my own collection. 

Disclaimer here: This was not designed to be a test to determine absolute pristine quality. We’re not planning producing hit records with these. We were looking for monitors that were reasonably accurate, and had pleasing tone. That’s why we didn’t worry about not running them through a Manley tube pre. And the reality is, we’re normally working with compressed audio sources in our work anyway, so playing Apple lossless files was perfectly acceptable, as were the 256kps AAC’s. So no flame posts about how we weren’t using high quality sources, OK? Here’s what we heard.

GC actually had a decent selection; and we were there mainly to audition the Yamaha HS80M. Someone had recommended those to Erik, and they were priced well. But, how did they sound compared to speakers costing 2 and 3 times as much? Actually, pretty dang good. In fact, I would contend that they sounded almost as good as the most expensive monitor on that rack, the JBL LSR4328P. 

But before we got the serious listening, we had some work to do. After the GC guys left us alone, we started calibrating monitors for comparable volumes (louder speakers tend to sound “better”), and proper EQ and boundary settings. It’s always amazing to me that retail outlets generally do such a poor job at this. We even found one speaker unplugged, and another not turned on. Kind of destroys the stereo sound field when you only have one side (or one is set 8 dB lower than the other). GC, your speakers are properly set up now.

For those with short attention spans, my favorites were the HS80Ms, the Event ASP8 and the aforementioned JBL. Oddly, that’s in descending order of favorites and ascending order of price. Actually, I may have liked the ASP8s better, but they were almost 3x the price of the Yamaha’s, so it’s hard to justify.

I found the Yamaha’s to have a expansive sound field, very smooth vocal and mid-range response, highly detailed high end, and decent bass. If you’re mixing hip hop they may not cut it, but for everyone else, they should be sufficient. Listening to some Norah Jones, the brushes on the cymbals were plainly heard with pleasing detail and all the smoothness of her voice came through. The even revealed the hint of raspiness she sometimes brings out. The stereo sound field seemed as wide as the room itself, and the overall sound was expansive. A non-ported box, the bass was very tight and fast. One could clearly hear the subtleties of the string bass and the muffled thump of the kick. Overall, a great sound, and a great value. I’ve had Yamaha speakers in my home theater for 12 years now, and am always amazed at how clean they are, and how little I paid for them.

The ASP8s were very similar, with perhaps a tich more high end detail. They also had more low end oomph–they’re a ported enclosure–but the bass didn’t seem quite as tight and detailed as the HS80Ms. As with the Yamahas, the brushes on the cymbals came through very clear, and the vocals were pure. I’ve been a fan of Event since a buddy of mine gave me some PS8’s to demo some years ago. I actually had to buy them because I wouldn’t give them up when he came to pick them up.

I think I would have liked the JBLs more if they had actually run the auto calibration on them. Run flat, they were very detailed, and had decent bass, but the mids seemed a little over-emphasized. I think a bit of EQ could have tamed them, though. Stereo imaging was impressive, however. To me, the exhibited a bit of the classic JBL overhyped mid characteristic that gives them their impressive clarity, but can be grating if you’re not careful. These were on the edge of that. Super clear, but perhaps a little too much so. If we were interested in spending $1,500, we may have played with them more, but this is a church media department budget we’re talking about…

We also listened to the Adam A7. Those little beauties with their ribbon driver had perhaps the smoothest midrange response of anything we listened to. Norah Jones appeared to be singing right in front of us, with all the detail and grain of her voice perfectly reproduced. On the negative side, the high end was lacking in subtle detail and extension. And the string bass was barely audible. I supposed paired with a sub, that would have been corrected. I could have listened to these all day, however.

Other interesting findings were with two models from KRK. Though we weren’t really interested in these, I was curious to hear them, as I’ve heard a lot about them, but never actually listened to them. We spent a lot of time with the VXT8, mainly because they had no bass response at all. Worse than the A7 in fact. And the VXT8 has an 8″ woofer to the A7’s 6.5.” We played with EQ settings, gain, moved them around and nothing. In fact, the VXT6 had better bass extension than the 8’s. I know…weird. We honestly wonder if there was a problem with the demo models, because they just didn’t seem right. Actually, the VXT6s sounded pretty good. The stereo field wasn’t nearly as wide as the front runners, but the detail was pretty good, the mids sounded clean, and bass wasn’t bad. But at nearly 2x the price of the HS80M, they were out of the running.

Then there were the Mackies. We started with the HRT824s because they were #1 on the switch. At first blush, they were OK. If that was all we had to listen to, we might have lived with them. But when we switched to the next set (which I’m blanking on, but it doesn’t matter), it was like someone pulled a moving blanket off the sound. During the hour or so of listening, we kept going back to the 824s and a set of 624s for reference. Each time it was an, “Ewww, those just sound like we’re listening through a blanket,” moment. I know some people that love them, but I’m not one of them. They had no sound field, a barely discernible stereo stage, weak highs and lows, and the mids weren’t all that smooth. Nope, no Makies for us.

Ultimately, the Yamaha won the day. On sale for $269 apiece, they were the cheapest ones on the rack. And both of us agreed that if they weren’t the best sounding, they were in the top 2 or 3, and the other two in that short list were at least 2x if not 3x more pricey. So don’t be fooled. Just because it comes with a big price tag doesn’t mean it’s always the best. And if the price is a good deal, it doesn’t mean it’s not. Judge with your ears before you judge with your wallet.

It’s been a week since the FCC voted on the issue of White Spaces. The cynic in me believes that they chose Nov. 4 as their day to vote figuring the rest of the country would be earnestly following the other election, and they could escape any real critique. That may be, but the techies among us were just as concerned about what will happen to our wireless mic spectrum. 

Details are still coming out, but overall, it looks like generally good news for those of us who use wireless mics. I talked a bit with Chris Lyons of Shure and Kirk Longhoffer at WFX, and got a few more details. The short story is that the unlicensed white space devices will be limited to a few unused TV channels in each market, the will use spectrum sensing and geo-location to avoid other signals (which means churches can register their frequencies) and they are not allowed to use channels 14-20.

So overall, it’s good news. Kirk Longhoffer has a more detailed assessment that you can read at his site, TechnoPraxis. I just met Kirk and learned of his site at WFX, and I have to say, it’s a site to check out. Stay tuned for more details, particularly regarding the ruling on the 700 Mhz relocation plans. In the meantime, check out Kirk’s article.

While most Americans are busy watching the results of the presidential elections, those of us who regularly use wireless microphones have been anxiously awaiting the results of another vote. The FCC voted today to open up the “White Spaces” to other unlicensed devices from Google, Microsoft, Motorola and others. While this will be a boon to internet access, it is likely to be a nightmare for users of wireless mics.

So far, the white space devices have not been able to successfully detect and avoid wireless mics (and at times even TV stations) more than about 50% of the time. So over the next few years, expect to start having issues with wireless mics, even if you are properly frequency coordinated and under the 698 Mhz range. It’s a jungle out there, and it’s going to get more crowded. Don’t say I didn’t warn you…

As for the proposed 700 Mhz band relocation…well, I don’t know how that turned out yet. The final rules are not yet available. But as soon as I hear something, I’ll let you know. As we’ve been saying all along, start making a plan to move out of the 700 Mhz band, whether sooner or later. 

More to come…stay tuned!

Picking up where we left off, we’ll get back to soldering XLR cables today. This is an incredibly useful skill, as we probably use more mic cables (and break more mic cables) than any other. Today, I needed to make up a few 6-foot XLRs for our Worship Director, Jon. Jon needed to hook up his little mixer to the speakers in his office. It’s a simple job, here’s what to do.

First, assemble the tools you’ll need for the job. If you missed out on my first and second posts about soldering, you may want to go back and review. Here’s what you need. Left to right, you’ll need a soldering iron. You can find them at Radio Shack (one of the few things I buy there), or other electronics stores and of course online. You don’t need a super-fancy one with electronic temperature regulation. Just a simple 15-30 watt pencil tipped iron will do. My iron is switchable between 15 and 30 watts, though I leave it at 30 almost all the time. Next, a pair of diagonal cutters. These are the smaller ones, and spring loaded. Very handy. You’ll need solder of course, electrical grade–no plumber’s solder. The rosin inside the core is different between the two, so get the right kind. It comes in different thicknesses, and as I write this I don’t recall which I have, other than it’s the thicker kind they stock at Rac-Shack. The super-fine stuff is nice for mini-jacks, but XLRs take so much solder, the thicker variety is faster.

Also in the picture are some wire strippers. I like the kind I can adjust to strip all the way to 24 gauge wire, then count on the fact that I’ve stripped so much (wire that is) that I can tell when I’m through the insulation of thicker wire without nicking the copper. You may wish to get a wire stripper that is calibrated for different gauges of wire while you’re learning. A knife is very useful for cutting through the outer jacket of the mic cable. I use a box cutter I got when I worked at a grocery store in high school. But any sharp blade will do. Finally, there’s my vice, which is some 30 years old. It looks terrible, but is just the ticket for holding on to the connectors without burning my fingers. 

Let’s get stripping! Not so fast! Before you do anything, you want to slip the housing of the XLR connector down the end of the cable. There’s nothing worse than making a perfect solder joint on your connector, then realizing you forgot to do this step and having to de-solder the end off to put the housing on. Not that I’ve ever done that…

The first step is to carefully cut through the outer jacket of the cable. Make your slice about 1/2-5/8″ from the end. I normally try to not cut all the way through, then bend the cable at the cut and just touch the blade to the jacket at the cut line. This will split the jacket without nicking a bunch of the copper shield. Separate the copper shield from the 2 conductors, taking care to round up all the bare copper strands. Wrap them tightly together. Now if you’re using Mogami 2792 (and why wouldn’t you?) you’ll notice that both the 2 conductors are wrapped in black plastic. This black stuff is actually conductive, and it’s one of the reasons this cable is so immune to interference. Any junk that makes it past the copper shield is then shunted to ground via this conductive plastic. As great as it is, it has to go at the ends of the conductors. If you don’t take it off, you may find the cable buzzes slightly as the plastic forms a high-impedance ground to the positive and negative solder cups. So make sure you talk it off. Here, I’ve removed the coating from the red lead.

Next thing to do (after you get the black stuff off both leads) is to strip the ends of the white and red conductors. You don’t need much, just about 3/16″ should do it. Twist the copper strands together tightly, like you did for the shield. Next, we’ll tin the leads. Just like last time, put some heat on the wire, and touch the solder to the other side. Just a little bit here, you don’t need much.

You’ll notice that when you heat the wire, the insulation will melt back a little bit. That’s why you don’t need to strip too much off. Next, take your connector end, in this case a Switchcraft AAA series–my favorite, and chuck it into the vice. You need to make sure it’s not going to be moving around on you. You’ll want to fill the solder cups with solder. It should look something like this:

That’s kind of a lousy picture, but hopefully you can see the solder is coming just up to the top of the cup. Almost done now. Array the wires in the correct order for the pins. You want to make sure you follow the proper standards when building cables. With 2792, red would be hot or +, so it goes to pin 2. White is cold or -, so it goes to pin 3. The shield always goes to in 1. Switchcraft and Neutrik mold little numbers onto the ends so you know which is which. I like to start with the shield, since it’s the biggest. Heat up the solder in the cup, then drop the wire in, making sure to heat up the wire too. You want to get it all nice and hot so the solder flows together. Then remove the heat and wait. The solder will go from shiny and molten to a bit dull and solid. Then you can let go (and cool off your fingers). Do the same for the other two.

It should look like the above. Notice the solder is just up to the top of the cup, and everything is nice and neat. You don’t want solder dripping all over the place, and you especially don’t want any stray copper or solder connecting any two pins. 

Finally slide the housing up (you may have a few other parts if you’re using Neutrik NC3 series). But this is why I love the Switchcraft AAA series. There are two parts to the connector, and when you’re done soldering, slide it up, screw it together and you’re done.

That’s it! You’ve just successfully soldered an XLR connector on the end of some mic cable. Just make sure if you put a male on one end, you put the female on the other. Not that I’ve ever made that mistake…

If you missed the earlier posts on where to get supplies, or how to do unbalanced speaker connections, you can find them here and here. 

I made this cable for $6.80. It’s all top quality material, and it took less than 5 minutes (including picture taking). Buying one of comparable quality would set me (actually, the church) back at least $15-20. And it’s just plain fun. So go make some cables, huh?

In the previous post, we got started talking about groups. Most church sound boards have groups. Some have VCAs. As a church sound volunteer, it’s important to know what they do and how to use them. To recap, Groups are additional mix busses on your board that allow you to collect inputs and make them controllable by a single fader. That’s the vast over-simplified version anyway. A more elegant way to accomplish that task is with a VCA.

So now, picking up where we left off…

The VCA Masters from a Yamaha PM5000 (click to enlarge)

VCAs
VCA stands for Voltage Controlled Amplifier. The clears it all up, no? Well, how about this: According to Wikipedia, “A voltage-controlled amplifier is an electronic amplifier that varies its gain depending on a control voltage.” In other words, rather than controlling the level of a signal through a resistance network, the way a typical fader control does, a VCA uses changes in control voltage (which is adjusted by fader movement up and down) to control an amplifier that alters the level of the signal. In a non-VCA fader, the audio signal actually runs through the resistance network of the fader and the level is altered based on how much resistance to signal flow there is. Lowering the fader raises the resistance, lowering the level of the signal.

In a VCA desk, when you raise and lower the fader, you’re actually raising and lowering the control voltage that tells the amplifier to raise or lower the level of the signal. It’s kind of like the difference between a switch and a relay. A switch has the signal (say 110 volts of AC to power your light) flowing right through it. When you turn off the switch, you directly break the connection. A relay however is controlled by another switch. Flip the switch, and the control voltage tells the relay to close and let signal through. Hopefully, this is making sense.

VCAs have several advantages over regular faders. First, they last longer and are less prone to get “scratchy” because of wear and dust. Second, because the fader is not processing the signal, VCAs can be more accurate and precise. Finally, because a VCA is sort of like a remote control, they can be remote-remote controlled. Enter what is known as the VCA (really, they’re VCA Groups).

For the purposes of illustration, let’s assume that we’re using a 1K tone as our signal source, and that we have adjusted the head amp (or trim, or preamp, or gain, or whatever your board calls it) so that the channel, when in PFL (or solo) mode reads 0 dBu.

Let’s say you turn up channel 1 to 0 dBu, or unity. That tells the amplifier in channel 1 to let the signal flow with no gain or cut applied to the signal. When you lower the fader to -10, that tells the amplifier to apply 10 dB of cut to the signal.

Now, let’s say we assign channel 1 to VCA Group 1 (more commonly known as VCA 1). And let’s turn channel 1 back to 0. If we were to now lower VCA 1 to -10, that would tell the amplifier in channel 1 to apply 10 dB of cut to channel 1 [above left]. And if we now dial the fader of channel 1 back to -10, that tells the amplifier in channel 1 to apply another 10 dB of cut to the signal [above right]. “Madness!” You might say, “Lowering the signal twice!” That’s true, but it’s also highly useful. 

Consider this; we can accomplish the same thing, level-wise, with a group. However, we’re sending the signal through 2 amplification stages. And once the signal leaves the group, it goes through a third amplification stage at the main faders. With a VCA, there is a single amp stage on each channel. The channel faders and the VCA faders simply tell that amp what to do. At no point does the signal pass through the VCA group, because there is no “group.” I said it gets interesting, so here’s how it could play out.

At Upper Room, we have our VCAs (well, technically they’re DCAs, but they act essentially the same) set up like this: 1–Kick & Bass; 2–The rest of the drum kit; 3–Guitars; 4–Keys; 5–All Band; 6–Vocals; 7–FX; 8 Speech mics. VCAs 1-4 act like groups for us, in that we can quickly adjust the entire drum kit up and down, add or subtract keys, whatever. However, we also have the whole band on another VCA. So that means that every channel that is assigned to VCA’s 1-4 is also assigned to VCA 5. That allows us to take the level of the entire band up and down on one fader, without altering the relative levels between each of those channels. If during the set the band gets crankin’ and starts to overpower the vocals, we turn down the band VCA. That’s it, the whole band comes down.

Where this is very elegant is that the signal is processed strictly in the channel amp; it’s not going through multiple amp stages of gain/cut to get there. So let’s play this out.

Take the kick, channel 1 in our setup. Let’s say on the fader, it’s set to -5 dBu. So at the channel level, we’ve knocked 5 dB off the level (relative to 0, or unity, which is determined by the head-amp control). Now, as part of the drum kit, it’s assigned to VCA 1. And we might run that at -2. That knocks another 2 dB off the level for a total cut of 7 dB. As part of the band, it’s also assigned to VCA 5, which we might run at -5 also. That’s 5 more off, for a final level of -12 dB. And again, all of this level changing is done on the channel strip itself, in a single amp stage; it’s not going through multiple stages at each VCA. The VCA groups simply alter the control voltage of that channel’s amp.

By definition, and unlike a group, a VCA group can never overload. This is because it’s simply a “master remote control” for a bunch of inputs. Even if you push your VCA group fader to +10, you’re merely telling all the channels assigned to that VCA group to add 10 dB of level to their respective signals. At that point an individual channel might clip, but the “group” never will because it’s really more of a virtual group.

We should also note that by lowering VCA 1 (kick & bass) to -2, it also tells channel 9 (bass) to turn down by 2 dB as well. And by setting the VCA 5 at -5, it tells all of the band channels (basically 1-14) to lower by 5 dB. But each individual channel can be adjusted relative to each other, so the mix is preserved.

You do have to be careful with VCAs, however. Because you are remotely controlling a channel (for lack of a better term), you could be tempted to over-drive your input channels with too much signal. This could happen in the above example very easily. Let’s say someone wasn’t paying attention and set VCA 1 (kick & bass) to -20, and VCA 5 (the whole band) to -30. That would lower the signal of the drum mics by 50 dB. That would be pretty low in most systems. You would probably want to hear more drums than that, and even if your channel fader is already at +10, the total output of the channel is -40 (+10 plus -20 plus -30). So you might be tempted to turn up the head amp control to get more level. However, you would quickly drive the head amp into distortion. When using VCAs, getting good gain structure is more important than ever.

Still, that shouldn’t dissuade you from using them. Their much cleaner than groups, and the level of control is far greater. You also have more options for control, as shown above. Moreover, when you mute a VCA group, you also mute the channels. On most boards, this will have the effect of shutting off the Aux sends as well, which keeps you’re monitors quiet when you want them quite. Another benefit of VCAs. 

DCAs
DCA stands for Digital Controlled Amplifier. Essentially, they are the same thing as a VCA, but on a digital board. Every digital board I’ve seen has DCAs, which makes sense because the signal is already in the digital domain, and it’s just a simple matter of programming to make a DCA group behave the same as a VCA group. So there’s not really any more to see here. Move along.

You do have to pay attention to your DCAs on a digital board, however, because most of the time they’re on a separate layer. So it’s really easy to have the scenario I illustrated above play out (40 dB of cut applied without you knowing where it came from). As always, proper gain structure is important.

I hope this has shed some light on the concept of Groups versus VCAs/DCAs. While they can all have the same ultimate effect on the signal, they go about it differently. And when you use one versus the other depends mainly on your board. If you have both, use VCAs for your channel “grouping” and groups for sending mixes somewhere else besides the main speakers. They are great for “submixes” for an Aviom system for example. If all you have are groups, break your band up into logical “groups” and control them as described. Most of all, I want to encourage you to explore what your mixer can do. It probably has more power than you thought. To paraphrase my favorite foodie, Alton Brown, “Get out there and play with your mixer” (preferably during non-service times…)

Picking up where we left off, today we’ll talk a little bit about how digital consoles are changing the way we think about a matrix mix. Perviously, we discussed what a matrix is, and how to use it. Rather than try to give a completely illustrated guide to every digital console and how it works (which I can’t because I’ve not used them all), I’m going to pick out a few desks that represent, at least in broad strokes, how a matrix functions in the digital realm. 

Yamaha PM5D
While the PM5D is a digital desk, it handles the matrix pretty much the same way an analog desk does. The PM5D has 24 mix busses, plus LCR. It really doesn’t do groups, you simply assign your channels to the mix busses. Any of the mix busses can feed into a matrix mix, as can the LCR mixes. Once you’re at this level of a board, the set up gets complicated fairly quickly. As I’ve not spent much time at all behind a 5D, I won’t attempt to suggest a variety of options. Suffice it to say if you have a 5D at your church, you should have someone on staff who knows how to use it.

Yamaha LS9
This board is becoming increasingly popular in the church arena. It’s small, has a high feature set and is very affordable. The LS9 has 16 mix busses (plus L, R & Mono and Monitor L,C & R), and 8 matrix mixes. Like the 5D, the matrix is fed from the other mix busses. In a church setting, the matrix mixes are going to be primarily used for recording sends, cry rooms & lobby feeds and things like that. With only 16 mix busses at your disposal, you will probably be feeding the main mix into your matrix most of the time. The matrix mixes then become a level control for your various outputs. 

If you are not running stereo IEMs (which consume mix busses pretty quickly), you might be able to do some quasi grouping with a few leftover mix busses and use them to feed into a matrix for various mixes as we discussed on Tuesday. If you even separated the band into 2 mix busses, and used a third for vocals, you could come up with a combination of “external” feeds for recording, cry rooms, etc. using those mix busses and matrix mixes. Though the LS9 only has 16 Omni outs, you can add additional outputs using the MY-Card slots. Those outputs can be fed from the matrix to give you some more output capability.

RSS M-400V Mixer
Roland’s entry into the digital mixer game is an interesting one. While I’ve not mixed on it yet, I’ve played around with the software, and I’m impressed. The M-400 is very well integrated with the REAC digital snake, which provides plenty of configuration and I/O options. I’m not entirely sure I have a full grasp on what it can do, but it seems quite powerful. Like the LS9, the M-400 has 16 mix busses, L, R & Mono. It also has 8 matrix mixes. And while the matrix mixes are fed primarily by the mix busses and L&R, you can also pick any two other input channels and put them into any of the matrix mixes.

This starts to get really interesting. For example, for a recording feed, to make up for the fact that the music is always going to be a lot louder than the pastor speaking, you could send L&R to a matrix, then also add in the pastor’s channel. That would bring the level up to a more comparable level with the music.

How useful this is depends a lot on how you set up your mix busses. But certainly, the ability to directly add a channel (or two) into a matrix mix could come in handy. This is a board I want to spend some more time with at WFX in November. It has some great functionality that and a price point that would work well for many churches under 1000.

In some ways, using a matrix mix on a digital board is a little less useful than an analog board because you don’t really have groups to derive your matrix mixes from. Because every digital board I can think of uses DCAs (a topic for another post), you don’t need to group say, the drums, the keys, the guitars, etc.. You can do it all with DCAs and with better sonic purity. The cost is that the matrix becomes less useful. That is, unless you’re driving an M7…

Yamaha M7CL
In many ways, I saved the best for last. I’ve said before that I believe the M7 is just about the ideal all-around console for churches between “large enough to need digital” and several thousand. And once you cross that 3000-4000 attender threshold, you probably have someone on staff who can efficiently drive a Venue or a 5D–that is, if you really the need additional capabilities of those boards.

The M7 breaks new ground with it’s approach to the matrix. At first glance, it appears to be set up just like the LS9–16 mix busses plus L, R & Mono. It also has 8 matrix mixes. What makes the M7 unique (for just about every digital desk I could find) is that you can assign anything to the matrix mix, right down to the channel level. This effectively makes the M7 a 24 mix bus board, only better. It’s better because you can assign mix busses to the matrix; L, R & Mono to the matrix and individual channels to the matrix. 

Because you can stereo link matrix mix pairs, you could create an additional 4 stereo monitor mixes. Or stereo record mixes. You can use it to break out record sends to different places if you want. At Upper Room, I use Matrix 1 as my video record send, and use Studio Manager to mix it on the fly without affecting the FOH engineer. You can read more about that here. We also have another record send that goes to the cassette recorder & HD24 fed by Matrix 2. Because we don’t have the time to deal with that mix much, it’s fed mostly by the mono mix, with a little extra pastors mic for good measure. 

In a sense, the matrix becomes another “layer” of mix busses on the desk. For mixing the CPC contemporary service, we use a matrix to feed the ButtKicker for the bass player. We have matrix mixes set up for wedges when we need them. When thinking about how to use a matrix mix on the M7, just think, “What would I use a mix bus for,” and you can use a matrix for it as well. 

I originally thought the LS9 had this functionality, but it doesn’t. So far, it’s unique to the M7. I don’t know if it would be a simple software update to enable this on an LS9, or if it’s a matter of processing power. Either way, until the LS9 can do this, the M7 remains my favorite all-around church board.

Hopefully, these three posts give you a little more insight into the strange and wonderful world of the matrix. While not exhaustive, I tried to give an overview of what you can do with these useful tools we have at our disposal. Happy mixing. Next up, VCAs and DCAs…