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What's the Difference: Pre-Fade vs. Post-Fade

Today, we’re back to our What’s the Difference series. These are going to be short posts where we look at commonly misunderstood terms in the tech world. Nearly every audio console offers aux sends with a pre-fade or post-fade option, but what does that mean?

It’s the Pick Off Point Again

As we discussed in the last episode (AFL/PFL), pre-fade and post-fade are really all about the pick off point. That is to say, at what point in the channel strip is the aux send being picked off. A pre-fade aux takes the signal before (pre) the fader. So, the level of the fader has no impact on the level of the aux send. A post-fade aux takes the signal after (post) the fader so the level of the fader does impact the level of the send. Sometimes, it’s really that simple. See, I told you these were going to be short posts.

Options, We Have Options

Back in the days of analog consoles, it was often possible to change the pick off point. I remember reading the manual of our old Soundcraft Series 2 in which it described breaking solder jumpers to move the pick off from pre-fade, post-EQ to pre-fade, pre-EQ. Sometimes, it could be done with jumper blocks on the board.

With the advent of digital consoles and DSP, it’s now easier than ever to change the pick off point. For example, Digico allows for pre-fade, pre-mute; pre-fade, post-mute; and post-fade, post-mute options. Pre-fade and pre-mute are both pre-processing while post-fade is after the processing block. Even the Behringer X32 allows for each aux of each channel to be set pre-EQ, post-EQ, pre-fade, post-fade. 

I especially appreciate the signal flow diagram showing your aux options. 

I especially appreciate the signal flow diagram showing your aux options. 

You’ll have to break out the manual to see what options your board has.

Why Use Them?

Generally speaking, we use pre-fade sends for monitors and post-fade sends for FX. Post-fade sends are also useful for things like broadcast mixes, and feeds to ancillary rooms. We want monitors to be pre-fade because we don’t want to be changing the musician’s mixes each time we make a house mix adjustment. If you’re getting complaints from musicians that their mixes keep changing, make sure you’re set to pre-fade auxes. 

For FX, we want the level going to the FX processor to be tracking with the dry signal going to the mix. If you sent pre-fade signals to an FX processor, even if you pulled the channel down, the FX would still be in the mix. Similarly, if you’re using a post-fade aux bus to mix broadcast, you want the fader changes of the mix to track to the broadcast mix. 

Adding to the Confusion

Some manufacturers make analog boards with a few pre-fade auxes and a one or two knobs labeled FX. The FX knobs are simply post-fade auxes that often feed an internal FX system. Typically, there is an output on the board to use an external processor with those FX sends, so don’t be limited to the internal FX (which may or may not be any good). 

Many analog boards will let you switch the send for each aux or a pair of auxes to pre or post. Again, be sure the switches are in the right spot if you want to keep your musicians happy.

Pre-fade and post-fade is one of those concepts that is really quite simple, but can cause a lot of problems if not implemented correctly. Hopefully, this post helps with that.

“Gear

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What's the Difference: AFL-PFL

In this series, we’ll look at two things and talk about their differences. For the first installment, we’ll look at a common button on most audio consoles. The labels may vary, but the difference is important.

AFL/PFL—What’s the Difference?

AFL stands for After-Fade Listen while PFL stands for Pre-Fade Listen. Depending on the current state of your console, pressing solo in either mode may result in the same thing. Or it may be completely different. 

Both AFL and PFL are solo modes. When you press the solo button on the channel, the output of that channel is routed to the solo bus and you hear it all by itself. We use solo for auditioning an input, checking for signal, and possibly setting EQ. We’ll get to this later. 

On many consoles, you can also solo groups, VCAs and the master. So what’s the difference between AFL and PFL?

It’s All About the Pick-off Point

Pre-Fade Listen is just what it sounds like; the signal is picked off from the channel strip before the fader. Most of the time, it’s also pre-EQ, pre-dynamics and pre-Mute. You’ll have to read your manual to find out where the pick point is. Sometimes it’s after the HPF and LPF, but not always. Some digital consoles allow you to choose the PFL point, which is cool. Because PFL is pre-processing, it’s a great way to check the quality of the incoming signal before you do anything to it. 

After-Fade Listen is a pick-off point after the fader. Typically, it’s also after EQ, dynamics and mute. So that means anything you’ve done to the signal with any of those processing blocks will be reflected in the solo output. In AFL mode, you will hear the effects of EQ, dynamics and filters. If the fader is off on a channel that you AFL, you won’t hear anything. It’s after the fader, remmember. 

When To Use Them?

PFL is most useful for checking signal. When I line check a stage, I set the console to PFL and use the headphones to verify each input. Most of the time, the faders are all down (or turned off with VCAs), so nothing comes through the house. But I can hear it clearly with PFL. It’s also useful for verifying signal of a muted mic during a service. It’s not a bad idea to PFL your pastor’s mic a few minutes before he goes up to be sure you have signal. This has saved me many times. 

AFL is useful for seeing if what you’re doing is helping or hurting the sound. If you’re trying to zero in on an offending frequency on an instrument, a quick AFL while you check the EQ can save you a lot of time. Many of my FOH friends and I generally prefer to EQ channels in the context of the mix—because it is a mix after all—but sometimes some isolation is helpful to solve a particular problem.

AFL is also useful to hear the blend of a group of instruments or vocals. I use it often on the BGV VCA to hear how my vocals are blending. Because the AFL happens after faders, I hear the blend based on the fader position. A quick AFL of the VCA can make short work of getting your vocals or drum mic’s blended.

Bonus: Solo In Place

This is known by a few other names, but what it does is the same. When SIP is pressed, instead of routing the PFL’d or AFL’d signal to the headphones or solo outputs, it routes it to the main L&R buss. That means everything but the solo’d channel is shut off and all you hear is that solo signal.

This can be useful or incredibly dangerous, depending on the situation. When you’re running a rehearsal, SIP can be helpful to identify a channel that might be lighting up a room resonance or something similar. But during a service, it can be devastating. It’s so dangerous that Digico requires you to press the SIP button for full two seconds just to engage it, and then it blinks red the entire time. 

Don’t try out SIP during a service—ever! I rarely use SIP as I much prefer to EQ and alter dynamics within the context of the mix. But that’s what it does. Proceed with caution.

“Gear

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The Secrets of My Success, Pt. 2

Last time, I gave you the first two secrets of acquiring knowledge. I’ve employed the crazy tactic of reading the manual and reading online help for years and learned a ton. But sometimes, the answer you’re searching for is not there, or you are still not getting the results you want. At that point, you have to expand your search radius. 

Image courtesy of Jacob Bøtter

Image courtesy of Jacob Bøtter

Contact Tech Support

This goes overlooked more than it should. It’s true that some companies have terrible phone support (we’re looking at you, Blackmagic…) but others are stellar. I’ve had some tech support staff help troubleshoot problems that turned out to not be theirs. One even contacted support at another company and helped me solve a tricky problem between platforms. 

I have learned so much by talking with good tech support reps. Often times, I learn not only about their product, but about a protocol, system or just how something works. Good tech support teams are invaluable and when you find them, you want to keep their number close. 

Use Your Network

I put this last for a reason. I’m a big fan of having a network of people I can call when I get stuck. But I usually only call on them after I exhausted the above options. The reason for this is simply time. Most often, I can find an answer quicker in the manual, online or with Google than I can from a friend. My friends are great, but they’re also busy. I don’t expect them to drop everything and help me solve a problem.

Sometimes I’ll shoot a quick text to a friend with a question, but if I don’t hear back right away, I’ll work through the previous steps. Many times, by the time they get back to me, I have my answer. There are times that I can’t find an answer, or the question is so specific that I really do need advice or counsel from a friend, and that’s really the best use of your network. 

If I want to know how to invert a selection in Photoshop, I’m not going to ask my friend Ken—even though he could surely tell me. I can find that on Google in under a second. But if I’m trying to decide if I should upgrade to Photoshop CC or stick with CS5, we’re going to have a conversation. See the difference?

Bonus Round: Use the Search Box

This is something else I get all the time; someone will ask me, “Hey, I think you wrote an article on thus and so a while back. Do you know where it is?” Chances are, the answer is no, I have no idea. I write well over 200 articles a year and have been doing so for 7 years. Even if I did remember writing the post—which I probably don’t—I couldn’t tell you the URL. 

But, Squarespace has this great search tool. The search box is right over there on the right, and you too can do exactly what I’m going to do; type some keywords into the search box and see what comes up. Again, you could email me and wait 2-4 weeks for me to do a quick search on my site and send you the result, or you could do it yourself. Not that I mind hearing from all of you, but you can probably get the answer faster on your own. 

So that’s it. That’s how I look so smart all the time. I learned a while ago that I don’t need to know all the answers, I just need to know where to find them. Today, that’s easier than ever. And you can do it from your phone. To be fair, I am really good at seeing how a whole bunch of disparate information fits together in a cohesive whole. That’s a natural talent that I’ve worked hard to hone. But you too can learn this skill. It all starts with a quick glance around the old inter-webs.

Roland

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The Secrets of My Success, Pt. 1

I get a lot of questions from other tech leaders. And I’m OK with that. I really do enjoy helping people and solving problems. But I’m only one person, and I’m a busy one at that. Sometimes, emails and twitter questions can pile up and go weeks without being answered. I generally get to them eventually, but I feel bad when it take so long. 

In the interest of spreading the wealth (of knowledge), I’m going to share with you the secret to acquiring knowledge. Learning new things has been one of my keys for staying employed, and I think it’s one thing that makes me good at what I do. So here you go; some of the secrets I’ve employed to learning more about this crazy trade.

Read the Manual

Yes, I know. Most of us pride ourselves on being able to take any new piece of gear out of the box and start using it without reading the manual. Well-designed equipment will even make that possible—at least to some extent. But when you start getting into the technical details of how to do something, often the fastest way to figure it out is read the manual. 

I can’t tell you how many questions I’ve answered from people by simple downloading the manual for the product they’re having trouble with and reading it. Sometimes, I even cut and paste the relevant section in my answer. 

Often, you will even discover cool features of a product that you didn’t know existed by reading the manual. I don’t even know how many times I’ve thought to myself, “I wish this box would do …” only to find it does because I read the manual.

I will acknowledge that many manuals are not worth the paper they’re not printed on (everything is a PDF now, right?) I’ve seen a manual for a mixer say, “The PFL button engages PFL mode,” and nothing more about it. Well, now that’s super-helpful isn’t it. I sort of figured pushing a button labeled PFL would do something related to PFL. And if you’re familiar with what PFL is, you probably don’t need that less than helpful sentence. But if you don’t know what PFL is, you need to go searching. 

Use Online Help

More and more software is coming with built-in help that is actually useful. Just the other day, we were trying to figure out how to run a particular report in our new system-design software. We knew what we wanted was possible, but it wasn’t immediately obvious. So I hit the big ? button. It took me to online help section that eventually led me to the solution. 

More and more, companies are using YouTube for really helpful instruction videos. I was trying to learn some new to me lighting software a while back, and discovered a whole slew of videos from the creator of the software. My learning curve shortened dramatically.

Again, I’ve done this for others. Many times, when I get a question about software, I’ll either launch my copy or download a demo and look for help. It’s amazing how many times the answer is right there. But sometimes the answer is there, but it doesn’t work. I was trying to convince a Blackmagic routing switcher to work the other day and while the manual told me what to do, I wasn’t getting the result I wanted. In that case, it’s time to pull out the big guns.

Use the Google

Google is probably the single greatest technical resource for a technical director today. You really should learn how to use it. Seriously. I’ve had questions come in and I’ve literally typed the question into Google and sent out a response based on my findings. 

See, here’s the thing. Chances are, someone else has already needed to do what you’re trying to do. And they’ve probably already written something about it online. And Google knows where it is. Now, you could email me and ask, or you could just go to Google. Google is faster, by the way. 

Google has become really good at taking in natural language questions and giving you good results. I was going to give you an example, but I do it so regularly that it’s become like breathing; I don’t even think about it. Just try it. 

Someone asked me once if I had any online resources for training volunteers. You know what I did? I used the Google (and reminded them about this cool site called ChurchTechArts). When someone asks if I’ve heard about an obscure product, I use the Google. Do I remember where an article by someone is on a particular topic? Use the Google.

Next time, more top tips for acquiring knowledge!

“Gear

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