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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

Today's post is brought to you by DiGiCo. DiGiCo audio mixing consoles deliver solutions that provide extreme flexibility, are easy to use and have an expandable infrastructure, while still providing the best possible audio quality. Visit their website to learn more.

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CTA Review: Livestream HD500 Studio

Streaming video continues to be a hot topic amongst churches, and it’s a topic I get asked about frequently. More and more manufacturers are building turnkey solutions designed to make it easy and we’re back to look at another one. This time, from what is likely the most popular streaming destination for churches, Livestream. 

Livestream recently released a series of products called Livestream Studio. As of this writing, there are four hardware solutions along with the standalone software. We received the mid-range and highly portable HD500 model for testing, though the software is consistent across the line. 

Self-Contained and Portable

The first thing you notice about the HD500 is that it looks like a small desktop PC with a handle on top. It ships with a magical carrying bag from Tom Bihn (seriously, this bag is nice!) What sets the unit apart is that it also has a 17” 1900x1200 LCD screen built into one side, protected by a removable metal cover. Weighing just 15 pounds, it’s easy to carry around, and would certainly qualify as carry-on luggage. 

Inside the box is a six core Intel Core I7 running at 3.2 GHz. An Nvidia GForce GT520 graphics card drives the built-in display, along with an external one that can be set up as a multi-viewer. There is a 2.5” 500 GB hard drive inside, and with 7 USB 2.0 and 2 USB 3.0 ports, you have plenty of ways to add more storage. 

Each of the Livestream Studio systems are built around Blackmagic cards; in this case a Decklink Quad and a Decklink Studio. The Quad gives you 4 HD/SD SDI inputs, and the Studio can be configured for input or output for a local live mix. In output mode, one can mix four cameras (along with internal graphics) to both a stream and local video output. 

The cards support embedded audio on the SDI inputs. The Decklink Studio card will accept analog and AES inputs, or you can use a USB audio interface. The built-in audio mixer in the software allows you to mix sources or have audio follow video. 

Everything you need fits neatly into the carry bag, making this an ideal solution for portable churches even if they don’t want to stream. The latest software update to the Studio software now allows for recording of up to four video streams at once. You can select from iso camera feeds, and a pre-graphics “clean” or post-graphics “dirty” feed. 

Full-Featured Software

Rather than relying on third-party software control, Livestream built their own. It has a clean, modern interface, and is easy to learn. Whenever I test systems like this, I always try to see how far I can get without looking at a manual. With this system, I had multiple inputs configured, was able to switch both a live feed and get a stream running in about 20 minutes. 

For the demo, they also included the Livestream Studio Keyboard. It's an Apple Extended keyboard, with custom key silk screened icons for every function. In no time at all, I was switching between our four cameras, adding lower thirds, and sending video to my Livestream account. 

I’m not exactly sure why, but the latency from the HD500 to what I saw on my laptop via my Livestream page was a matter of seconds. Most streaming appliances I’ve tested add a good 20-30 seconds of latency; this was more like 2-3. Setting up my account was as simple as entering my username and password, then hitting “Stream.” 

Built-In Multi-Viewer

The built-in screen will display the four camera sources plus preview and program. The source windows are too small for accurate judgments of focus and exposure. But, the system provides both VGA or HDMI port, which allow for a configurable multi-viewer of any size. There are quite a few screen layouts to choose from, and with a simple drag-and-drop interface, you decide what goes in which box. You can even add a clock, a stream window (to verify it’s online) as well as a viewer count. 

Much to my delight, when I plugged the second display in, it was immediately recognized by the system and the multi-view window appeared. I had fully expected to at least re-start the software, if not the OS. In fact, this rather summarizes my experience with this box; everything works pretty much as you’d expect without a lot of fiddling on your part. You can pretty much plug in and go. 

Graphic Options

Livestream Studio features a two-channel graphic engine with some pretty cool features. It’s easy to build lower thirds and full screen graphics in the editor. Where it gets interesting is the dynamic features. The graphic window offers a design mode, where as you might expect, you layout your graphics, text, logos and other features. Once complete, you enter data mode, which allows you to change the content of the text boxes on the fly with minimal trouble. For example, you could build a lower third graphic with dynamic text. Then, create several possible lines of text for different pastors or speakers. Simply clicking the line makes it active. In just a few minutes, you have a full set of graphics for your staff. And there is only one layout to update with new graphics for each new series.

Moreover, the graphics can contain video windows. Thus, you can build complex multi-input picture-in-picture effects that go to air with a single click. What I like about the software is that once everything is set up, it’s easy to operate, and completely visual. While it’s not hard to set up, it would take no time at all to train a volunteer to handle fairly complex graphic overlays. 

Other Cool Features

A new feature called Remote Camera allows you to turn a computer desktop (via network) into an input. Studio will accept network camera feeds from a variety of sources. This includes Google Glass, Android and iOS devices, and Windows PCs.  This could be handy for including sermon notes on the stream or IMAG screens. Even better, imagine the interactivity you could create for special events. You can also pull in content from your Livestream account as another input source. I didn’t get a chance to test this feature, but it may make it possible to stream from one location to another easily. Quality would be my main concern—but, the quality of the stream I sent from the HD500 was quite good.

Each of the four inputs has a scaler available to it, making it easy to mix and match input formats. For my tests, I pulled in a SD SDI feed, a 1080i output from my switcher and another 1080i camera. It converted each source to 1080i as needed without issue, sync'ing everything up in the process. For IMAG systems, everything should be running genlock, and the system allows that. 

Tally is not supported directly, but a recent software update makes Studio compatible with the tally system made by metaSETZ. Tally is often forgotten with these systems, and I’m glad to see it’s available. 

While this unit is obviously made to stream to Livestream, it’s also possible to send video to UStream, or YouTube Live. You can also use any RTMP compatible server or CDN, such as Wowza Media Server, Akamai, Flash Media Server. 

Conclusion

With an MSRP of $8500, the HD500 isn’t inexpensive (though you can find it for considerably less). But, when you consider that you can walk into a venue with a bag on your shoulder and in under 5 minutes be ready to stream, switch and iso record a service, it’s a compelling option. It’s easy to use (I never once consulted a manual or help file to figure anything out), and as far as I could tell, stable. We had no problems streaming a weekend, and the video quality was quite good with minimal latency.

The inclusion of the built-in monitor makes it especially appealing for portable churches. Not having to trudge a monitor in and out each week would be a huge benefit of this system. The system comes with a year of  phone support a one year warranty and software updates are free.

Roland

Today's post is brought to you by CCI Solutions. With a reputation for excellence, technical expertise and competitive pricing, CCI Solutions has served churches across the US in their media, equipment, design and installation needs for over 35 years.

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

Today's post is brought to you by Heil Sound. Established in 1966, Heil Sound Ltd. has developed many professional audio innovations over the years, and is currently a world leader in the design and manufacture of large diaphragm dynamic, professional grade microphones for live sound, broadcast and recording.