Plug-ins have become so affordable, flexible, and downright good that it’s easy to forget that plenty of hardware gear can provide functions that are unobtainable “inside the box.” Fortunately most DAWs can provide easy interfacing to external hardware, which we’ll learn how to take advantage of in this column.
Fig. 1. External audio insert configuration setups, from top: Avid Pro Tools 10, MagixSamplitude Pro X, and Steinberg Cubase 6.
Benefits and Challenges
Cool applications of routing an audio track from your DAW to an external effects processor or synthesizer include:
- Integrating rack processors and stompboxes with DAWs.
- Creating feedback loops, which many DAWs won’t allow. (A favorite technique: Loop through a graphic EQ, moving the sliders to fade tones in and out.)
- Sending a track’s output into a hardware synth’s external input, bringing its output back into the DAW, thus making the synth a playable signal processor.
However, note that there are some limitations and demands with external hardware, such as:
- You’ll need enough inputs and outputs on your audio interface. Your software may dedicate a stereo pair to this function so with a monaural outboard device, it may or may not be possible to use the stereo pair’s other half for something else.
- Looping through the interface adds latency. Some programs “ping” to measure this delay and compensate for it. For the best accuracy, bypass any internal track effects that introduce latency, like limiters with a look-ahead function.
- Latency compensation isn’t always perfect. For example, the delay on a chorus varies, so you may need to trim manually.
- Bounces through hardware must be in real time. Faster-than-real-time calculations work only for processes happening inside the computer. Track freezing can also be iffy. Once your setup and processing is finalized, bounce the processed signal in real time to an audio track.
There are three main ways DAWs can insert external effects.
- Manually: Assign track or bus outputs to I/O that feeds the effect, and assign inputs to receive from I/O that connects to the effect outputs. All DAWs can do this.
- As part of the DAW’s I/O setup that dedicates particular buses to particular effects (see Figure 1 above). You can then call up the “effects bus” as an insert that behaves like a plug-in.
- Via a dedicated insert plug-in that specifies connections and sets levels to external hardware (see Figure 2 below).
Fig. 2. External audio insert plug-ins, clockwise from top: PreSonus Studio One Pro 2.5, Ableton Live 9, Cakewalk Sonar X3, and Apple Logic Pro X.
MOTU’s Digital Performer uses the first approach. Open the Mixing Board window, assign a track’s send to the I/O patched into your effect, and optimize output levels with the send level. Then create an aux track, assign its input to the I/O where the effect returns, and adjust levels if needed. You can compensate for latency with the Edit > Shift option to move a track in time.
Avid Pro Tools, Steinberg Cubase, and Magix Samplitude use a dedicated I/O configuration. You define the interface I/O (which you can name) that’s dedicated to a particular effect, then insert this external I/O connection into a track or bus the same way you’d insert a plug-in. Pro Tools has an additional tab for hardware insert delay.
Steinberg Cubase sets up multiple parameters in the VST Connections window’s External FX tab. It works like adding standard buses, but includes additional fields so you can compensate for latency, as well as change the send and return gain levels. Magix Samplitude uses a similar approach where you again create an External FX Setup in a separate window.
Cakewalk Sonar X3 and Apple Logic Pro X take similar plug-in-based approaches. You can assign send and return connections to your interface, adjust levels going to and from the effect, and ping the amount of delay for automatic latency compensation (correcting manually if needed). Most parameters are automatable, and plug-in settings are savable as a preset. The only major differences are that Sonar includes a phase invert button for one return, and Logic has three I/O plug-ins (stereo, mono, and mono in/stereo out). Although Sonar can send the left, right, or both channels to a stereo pair, you can’t use the stereo pair as two separate mono channels; the return can be stereo, or mono from either channel.
PreSonus Studio One Pro’s plug-in has similar parameters (including a phase reverse button) and while not automatable, the plug-in displays the results of the ping and compensation graphically. This helps considerably when doing “fine tuning” with the manual offset control. Ableton Live 9’s insert plug-in adds a dry/wet control to mix the original signal in with the one being processed through the insert (you compensate for delay manually). However, Ableton assigns interface I/O to numbers that may not correlate to how your actual interface names them. For example, if your interface has Main and Sub outs then outs called 1+2, Live may identify the Main as 1+2, Sub as 3+4, and 1+2 as 5+6—so make sure to mentally correlate Ableton’s nomenclature to that of your interface.
The Synth Factor
One of my favorite applications is using hardware synths that have external audio inputs as playable effects processors. You can do the functional equivalent by using a soft synth’s external input with a general-purpose controller to control its parameters, but the hardware synth is already a controller that’s optimized for the task at hand, and may have features no soft synth has.
Fig. 3: The External input block from Casio’s XW-P1 editor software.
As one example of why this is cool, Casio’s XW-P1 performance synth has a Solo Synth section with an External Input option that offers many unusual functions. I was surprised when I saw an “Osc On” button for the external input (see Figure 3 above)—how could an external input have an oscillator? But this allows you to treat the input signal as an oscillator, and transpose it in real time from the keyboard. The fidelity is lo-fi, but has a uniquely strange personality. You can even use the XW-P1’s phrase capability or the arpeggiator to trigger phrases. Of course, the XW-P1’s effects (check out the ring modulator) are exposed as well, as are the same pitch, filter, and amp modules as the Synth and PCM Tone blocks. You can also do legato and portamento effects on the external input . . . the mind boggles.
Indeed, there are definitely some rewards for thinking “outside the box.”