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  • 10 Tips for Mixing in a Plug-In World

    By Anderton |

    To your CPU, plug-ins can be the ultimate power trip


    By Craig Anderton


    You gotta love effects and virtual instrument plug-ins, but they’ve changed the rules of mixing. In the hardware days, the issue was whether you had enough hardware to deal with all your tracks. Now that you can insert the same plug-in into multiple tracks, the question is whether your processor can handle all of them.

    Does it matter? After all, mixing is about music, balance, and emotional impact—not processing or synthesizer/sampler sounds. But it’s also about fidelity, because you want good sound. And that’s where Mr. Practical gets into a fight with Mr. Power.



    Plug-ins require CPU power. CPUs can’t supply infinite amounts of power. Get the picture? Run too many plug-ins, and your CPU will act like an overdrawn bank account. You’ll hear the results: Audio gapping, stuttering, and maybe even a complete audio engine nervous breakdown.

    And in a cruel irony, the best-sounding plug-ins often drain the most CPU power. This isn’t an ironclad rule; some poorly-written plug-ins are so inefficient they draw huge amounts of power, while some designers have developed ultra-efficient algorithms that sound great and don’t place too many demands on your CPU. But in general, it holds true.

    Fortunately, modern CPUs are quite powerful and don't place the same kind of processing limitations on plug-ins we used to have to endure in the past. Regardless, everything has limits; and sometimes you'll need to use an older machine, or a laptop that doesn't have the same power capacity as your desktop. Also, lower CPU power means you can spend the power you do have on other things, like low latency or having several programs open simultaneously.

    So the bottom line is if you need to use lots of plug-ins in your mix, you want as much available power as possible. Here are the Top Ten tips to help you make that happen.



    Let’s get the most expensive option out of the way first. Because plug-ins eat CPU cycles, the faster your processor can execute commands, the more plug-ins it can handle. Although there are a few other variables, as a rule of thumb higher clock speeds = more power for plug-ins. Cool bonus: Pretty much everything else will happen faster, too.



    And in the spirit of equal time, here’s the least expensive option: Increase your system latency. When you’re recording, especially if you’re doing real-time processing (e.g., playing guitar through a guitar amp simulation plug-in) or playing soft synths via keyboard, low latency is essential so that there’s minimal delay between playing a note and hearing it. However, that forces your CPU to work a lot harder. Mixing is a different deal: You’ll never really notice 10 or even 25ms of latency. The higher the latency, the more plug-ins you’ll be able to run. Some apps let you adjust latency from a slider, found under something like “Preferences.” Or, you may need to adjust it in an applet that comes with your sound card or audio interface (Fig. 1).


    Fig.1: A latency increase might be just the ticket to running more plug-ins. This applet controls a Line 6 interface; the ASIO buffer size is being increased from 128 samples to 512 samples.



    When CPUs didn't have the power they have today, outboard DSP cards from companies like Digidesign (now Avid) and Creamware were a popular solution for adding more power to a computer system. It was assumed that over time, native systems would become so powerful extra hardware assitance wouldn't be needed, but that didn't take into account that software developers were more than happy to use the extra power to create more powerful plug-ins.

    As a result, we still have external hardware solutions like audio interfaces with built-in DSP, or "heavy hitters" like Universal Audio's Powered Plug-Ins and Sonic Core's SCOPE system (formerly from Creamware), These either insert into your computer (like Universal Audio's UAD-2 OCTO), or connect to it via a fast interface, like FireWire or Thunderbolt. The cards run their own proprietary plug-ins (although the SCOPE system enjoys third-party support), so the plugs don’t load down the host CPU—the hardware does the heavy lifting (Fig. 2).


    Fig. 2: Universal Audio's Satellite card connects to desktops or laptops via FireWire to boost the computer's processing capabilities - as well as deliver some fine-sounding plug-ins.


    Although these boards will eventually say no mas! as well, one advantage compared to CPU-based processing is you have a finite, known amount of power so you can “red-line” the DSP without fear. With your CPU, sometimes running too close to the edge will cause a meltdown when the CPU has to perform that one extra function. Cool bonus: Hardware-based plug-ins are often platform-independent.



    Inserting one effect in an aux bus is much more efficient than inserting multiple instances of an effect in multiple tracks (Fig. 3). Of course, there are some cases where an effect must be limited to a single track. But for something like reverb, which tends to draw a lot of juice, see if it isn’t possible to do the aux bus option instead.


    Fig. 3: In this screen shot from Ableton Live, tracks 7 and 9 are sending signal into Send A. This feeds a single reverb plug-in, which is more efficient than inserting separate reverbs as an insert effect in both tracks 7 and 9. 


    Sometimes, even EQ can work as a bus effect; this may let you use a high-quality "mastering" EQ that takes a lot of CPU instead of individual, lower-power EQs. For example, suppose you miked a bunch of acoustic percussion, and feel all the percussion tracks need to be brightened up a bit. Send them to a stereo bus, and insert a single EQ into that bus.



    Anything that’s active is making demands on your CPU. Using only one band of a four-band EQ? See if you can turn off the other bands. Even input and output drivers drain your CPU. When you’re mixing, you probably don’t need any of your sound card’s input drivers to be active (with an exception we’ll cover next) and only one output driver—go ahead and disable them (Fig. 4).



    Fig. 4: Disabling any I/O that's not needed will save CPU power. In this example, all of Roland's VS-700 interface inputs are turned off except for the main stereo outputs.


    Although any one of these changes won't make much difference, when added together the difference can be significant.



    Reverb is one of the most CPU-intensive effects. A native, high-quality convolution reverb that sounds good will show no mercy to your CPU, which is why some of the best reverbs come from hardware-based plug-ins. But you can also use an external hardware processor. Dedicate one of your sound card output buses to feeding the reverb, and bring it back into an input. Although there will be some latency going into the reverb, think of it as free pre-delay - you probably won't even notice a difference. (If you do, then record the reverb to a track and shift it ahead in time.) Cool bonus: several programs make using external hardware pretty painless (Fig. 5), and compensate for latency.
    Fig. 5: Cubase is one of several programs that makes it easy to use external effects.

    A digital mixer can be an important adjunct to a DAW's setup, not only because it’s useful while tracking, but because it can also serve as a control surface if you can send individual channels or even "stems" (groups of channels) from your DAW to the mixer. One way to do this is if the mixer has a FireWire or USB connection suitable for connecting to your computer (e.g., PreSonus StudioLive series), but mixers with ADAT light pipe inputs are also suitable if your audio interface has ADAT light pipe outputs. Either return the mixer output back to the host, or with some projects, you can do your mixing in the mixer itself, using that old school “move the faders” technique. Cool bonus: The outboard mixer’s aux bus is an ideal place for putting a reverb. And, you get to mix with real faders.



    Soft synths, especially ones that sound good, can really suck power; “aastering quality” signal processing plug-ins also like to drink at the CPU power bar. So, use your host’s “freeze” function to convert tracks that use real-time plug-ins into hard disk tracks, which are far more efficient.



    Plug-ins aren’t the only elements that stress out your CPU: Complex, real-time automation can also eat CPU cycles. So, simplifying your automation curves will leave more power available for the CPU to run plugs. Your host may have a “thinning” algorithm; use it, as you generally don’t need that much automation data to do the job (particularly if you did real-time automation with fader moves, which will add quite a few extraneous automation nodes). But the ultimate CPU saver is using snapshot automation (which in many cases is all you really need anyway) instead of continuous curves. This process basically takes a “snapshot” of all the settings at a particular point on the DAW’s timeline, and when the DAW passes through that time, the settings are recalled and applied.



    Our last tip doesn’t relate to saving CPU power, but to preserving sound quality. Many plug-ins and soft synths offer multiple ways to automate: By recording the motion of on-screen controls, driving with MIDI controller data, using host automation (like VST), etc. However, not all automation methods are created equal. For example, moving panel controls may give higher internal resolution than driving via MIDI, which may be quantized into 128 steps. Using the right automation can make for smoother filter sweeps, less stair-stepping, and other benefits.


    Okay . . . there are your Top Ten tips, but here’s a bonus one: Any time you start to insert a plug-in, ask yourself if you really need to use it. A lot of people start their mix a track at a time, and optimize the sound for that track by adding EQ, reverb, etc. Then they bring in other tracks and optimize those. Eventually, you end up with an overprocessed, overdone sound that’s just plain annoying. Instead, try setting up a mix first with your instruments more or less “naked.” Only then, start analyzing where any problems might lie, then go about fixing them. Often tracks that may not sound that great in isolation mesh well when played together.


    5318e81deba22.jpg.2e2804bd4558e113d03195abaaaa8f26.jpgCraig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.

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