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Review: Nugen Audio SigMod

Mid-Side, Split-Band, Dual-Mono and Parallel Processing—Added to Other Plug-Ins

I have numerous plug-ins that sound terrific but don’t offer parallel, splitband, dual-mono or mid/side processing, which I very often need. There are ways to add these capabilities to wanting plug-ins using mults, filters, summing and phase inversion, but it’s a hassle and diverts time and attention away from the mix itself. Wouldn’t it be great if there were a simple and quick way to repurpose plug-ins to have these missing capabilities?

Nugen Audio has done just that—and much more—with its SigMod utility plug-in (available in AAX, VST, VST3, AU and AudioSuite formats, and with 64- and 32-bit frameworks). Each of the 12 component modules in its GUI carries out a single utility process, but modules can be daisy-chained in different orders to execute multiple processes in one fell swoop.

To select modules and arrange their order in SigMod’s signal chain, click on the gear icon in the GUI’s bottom-right corner to show the Settings panel in the middle of the GUI (see Fig. 1). The signal flow in the panel goes from left to right. Input channels (on the far left) may be configured as either a left and right pair or as mid and side. Output channels (on the far right) automatically reflect the channel configurations wrought by inputs and the processing modules you place before the outputs.

Figure 1: SigMod’s modules are selected, and their order in the signal chain arranged, in the Settings panel. Note two instances of the Insert module are used here, to host plug-ins in two different places in the signal chain. The first Mid-Side module encodes stereo input channels to mid-side configuration, while the second decodes back to stereo after third-party processing occurs in the first Insert module.

In between the input and output modules, you can chain together up to 10 processor modules in series. Click on the ‘+’ symbol between two modules to insert a new module from the insert-module browser that appears. Click on the ‘x’ symbol below a module to remove it from the signal chain. Drag the ‘=’ symbol either left or right below a module to change the order in which the module occurs in the signal chain.

Modules with more than one function or parameter assignment have a dropdown menu situated directly above them, which you use to select their desired functionality (for example, setting the Delay module to adjust channel offsets in samples, milliseconds or bpm). Once you have selected modules and arranged their order the way you want, exit the Settings panel to return to the main display (see Fig. 2).

Figure 2: SigMod’s main display shows the same signal chain as in Fig. 1, but with actionable bypass, link and parameter controls provided for relevant modules. Plugins are instantiated here in Insert modules placed roughly at the midpoint and just before the Output module (far right) in the signal chain.

There you’ll see the same signal chain, but with channel-link and bypass buttons, and adjustable parameter fields, where applicable, on the modules you’ve chained together. You can activate or deactivate any channel in an input or output pair; an active signal path is denoted by a boldly highlighted line between input and output, while an inactive path is light gray.

The Insert module lets you insert VST2, VST3 or AU plug-ins that you own (except for virtual instruments) anywhere in your SigMod signal chain; you can add multiple instances of the Insert module. Setting a single instance of the Insert module to Dual mode allows you to insert a different mono plugin, or the same mono plug-in with different settings, on left and right channels—especially invaluable for mastering work where left and right channels need different treatment.

Insert a Mid-Side module both before and after an Insert module loaded with two mono plug-ins to make the left channel’s plug-in process the side channel instead, and the right channel’s plug-in process the mid channel (see Fig. 1). Clicking on the inserted plug-in’s name in SigMod’s main display opens its GUI so you can adjust its parameters. SigMod also provides a wet/dry control for each plug-in instance.

The Crossover module lets you apply a lowpass or highpass filter to your track—using your specified corner frequency—and then apply third-party processing (via a plug-in inserted in a following Insert module) to only the filtered signal. But you can also send the signal removed by the filter to an empty track—set to record-ready—for independent processing by inserting SigMod’s included Receive plug-in on the empty track. (Voila, split-band processing!) The Tap module works similarly, working in conjunction with SigMod’s Receive plugin to send audio—in this case, unfiltered—to another track for parallel processing.

The DC Offset module removes headroom-robbing DC from your track or full mix. Use the Delay module to align tracks that are out-of-sync by offsetting one or both channels in samples, milliseconds or bpm. (Enter values using standard protocols.)

The Protect module automatically mutes your signal chain’s output when the signal level exceeds your chosen output level (specified in dBTP, or true peak level in decibels), protecting your speakers and ears from being damaged by unexpected feedback or other loud bursts of audio. You choose how full signal level is restored: either manually (click the signal path in the GUI); automatically after 1, 2, 3 or 5 seconds; or by clicking in a pop-up window that automatically appears as a reminder that the Protect function was activated.

Other modules let you mute, solo and trim (attenuate) the left and right channels of a stereo signal independently and swap the channels; swapping left and right channels is especially valuable when checking your mix’s balance in an asymmetric room, where speaker-boundary effects can cause one monitor to sound louder or more bass-heavy than its associated mix channel really is. Check how your stereo mix sounds in mono using the Mono module. Use the Phase module to flip a channel’s phase.

Situated along the top edge of the GUI are buttons for implementing standard plug-in functions, including bypass, unlimited undo and redo, recalling (and copying settings between) A and B workspaces, and preset management. Your custom presets can be saved, named, deleted, copied or moved among multiple folders you’ve created.

SigMod made it easy for me to use some of my plug-ins in ways that surpassed their original design. Using the Mid-Side and Insert modules, I could process just the mid channel of a mix with Black Box Analog Design HG-2’s rich tube emulation, while compressing the side channel with PSP Vintage Warmer 2. Using the Crossover and Insert modules, along with the Receive plug-in on an empty track, I split a subgroup for trap drums into two frequency bands (high and low) and applied totally different Lexicon PCM Native Reverb plug-ins to each band. The Insert module’s Dual mode let me use Metric Halo’s ChannelStrip plug-in in dual-mono configuration.

Unfortunately, several of my AU plug-ins either wouldn’t reliably load into SigMod’s Insert module or caused Digital Performer to crash immediately upon doing so. SigMod’s operation manual also omits some critical information; this review fills in the most important details. I was also disappointed that the names for my custom presets were not displayed when recalled. And creating an account and authorizing SigMod was a relatively difficult process to begin with.

My criticisms notwithstanding, SigMod adds powerful mid-side, split-band, dual-mono and parallel processing to most compressors, equalizers, reverbs, saturators and other plug-ins that lack those capabilities, while also providing helpful monitoring hacks for mixing and mastering work. Costing only $49, it’s bound to find a place in many engineers’ tool kits. I’m glad I’ve included it in mine.

To hear a compressor plug-in’s delta signal (its applied gain change in isolation), first use SigMod’s Phase module to flip the phase of the unprocessed track. Mix the phase-inverted track with the un-inverted track that was processed by your compressor. The dry signal will get canceled in the summed signal, leaving only the processed effect.


COMPANY: Nugen Audio
PRICE: $49
PROS: Adds powerful mid-side, split-band, dual-mono and parallel processing capabilities to most plug-ins that lack; helpful monitoring functions; flexible daisy-chaining. Inexpensive
CONS: Insert module doesn’t always load some plug-ins, often causes DP to crash; operation manual and preset management need improvement.

Michael Cooper ([email protected]) is a Mix contributing editor. You can hear some of his productions at