Review: Slate Digital Virtual Mix Rack

Five vibe-y processors in a new wrapper
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Slate Digital—famous for plug-ins that emulate classic analog gear—has co-opted the 500 Series rack and digitized it. The company’s new Virtual Mix Rack plug-in (VMR) creates a configurable receptacle for a new line of processing modules. Included with VMR’s launch are two compressors, two equalizers, and a sonic enhancer.


VMR opens with empty rack slots, into which you can load up to eight processing modules compatible with its proprietary format . The GUI opens with four slots by default but expands automatically when you drop in five or more modules.

Some of the new compressor and equalizer modules model (with modifications) classic gear. The FG-116 module emulates the UREI 1176 Peak Limiter (Rev D); it adds a wet/dry mix knob, used to implement parallel compression. FG-401 incorporates models of several VCA compressors in its Circuit 1 mode, adds a proprietary compression algorithm (Circuit 2), and facilitates parallel compression. FG-N models the three-band Neve 1073 equalizer with high-pass filter (HPF) and Drive control (used to push the module to produce harmonic distortion); the module adds a fourth band that exactly duplicates the existing one for midrange frequencies, allowing additional control. FG-S models an SSL E Series console’s EQ, offering four bands—two parametric midrange bands and alternate shelving/bell filters for both highs and lows—and an HPF. Also included with VMR is the all-original Revival Sonic Enhancement Processor module, a two-knob affair you can use to add air and brightness to high frequencies and fatten up the bass. (Revival can be downloaded for free by anyone.) Additional VMR modules are planned for the future.

Modules can be dragged within the rack to change their order in the signal chain. You can use multiple instances of the same module in one rack. Or drag a module from a rack in one track to a rack in another, either moving or copying the module in the process.

Each module can be bypassed or soloed, either alone or together with others. You can save and recall presets for individual modules and for the entire rack’s setup (the module selection for each slot and all of the modules’ parameter settings). Rack presets can be stored in separate banks (for guitar, bass, keys, and so on) for fast search and recall.



First, the big picture: Both EQ modules are best used for relatively broad tonal sculpting. Neither one can do notch filtering, and both were ineffective at attenuating a ringing tone on a snare track.

That said, FG-N sounded great on kick drum. Unlike the Neve 1073 that it emulates sonically, the module’s frequency knobs offer many different intermediate switch settings; that allowed me to zero in on a little bell-curve boost at 3.82 kHz, bell-curve cut at 631 Hz, and shelving boost at 70.2 Hz. The result was a harmonically rich, meaty sound with nice beater click.

FG-401’s Circuit 1 mode, with the fastest attack time selected, accentuated the kick drum's attack beautifully. The slowest release time—in either mode—wasn't slow enough to appreciably lengthen the shell's sustain. But chaining FG-116 after the 401 took care of that. Selecting a 20:1 ratio and the fastest release time (which is nevertheless quite slow) increased the drum's sustain nicely. The composite effect rendered by the two compressors sounded huge and demonstrated the power of using two or more modules at once to complement each other's abilities. Adding the Revival module and liberally raising its thickness control beefed up the low end to awesome effect. I only wish the shimmer control offered a bit more range; its effect sounded relatively subtle on percussion tracks with short-lived transients.

Fig.2. VMR processes room mics for drums to create an explosive sound.I could get a fairly explosive sound on stereo room mics for drums by first boosting the bass and lower highs with FG-N (spotlighting the traps) and then slamming the track with FG-116 (see Figure 2). I jacked up FG-116’s input, selected 20:1 ratio and dialed in a slow attack time and fast release. Those settings hyped the room’s ambience beautifully without squashing drum hits. I was disappointed, however, that there was no way for me to push the sound over the top using the classic all-buttons-in mode (depressing all ratio buttons at once) for which the hardware 1176 is rightfully famous. Slate reports a new VMR module is in the works that will do that.

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On electric bass guitar, FG-N’s filters once again delivered a rich tone. Boosting the module’s line input 7 dB added just enough distortion to make the instrument growl but not break up. Activating the module’s drive control compensated for the extra gain boost to prevent clipping the plug-in’s output. Next, I placed Revival after FG-N in the rack. Boosting the thickness control even a little really flattered—make that "fat-terred"—electric bass guitar. Problem was, it also raised the level of the track enough to cause clipping. (Like the two equalizer modules, Revival has no output-level control.) I fixed that by using FG-401 as a simple level controller: Placing the compressor after Revival, I dialed in 1:1 ratio and cut the makeup gain 8 dB. The track didn’t need any compression; driving FG-N hard had already saturated the track nicely. The final touch was switching in FG-401’s transformer for some very subtle additional coloration. The bass sounded bad-ass!

Electric six-string guitar sounded great with a little boost in FG-S at 3 kHz and 200 Hz, followed by FG-401’s aggressive Circuit 1 compression algorithm. Once again, the 401’s transformer emulation added a slightly creamier tone.

I wasn’t wild about how either compressor sounded on vocals; I always reach for an optoelectronic model (or plug-in emulation of same) for the money track. But I really liked how FG-N and Revival, used together, brought lead vocals forward in the mix and made them sound bigger. And very spare amounts of Revival processing sounded excellent on a full mix, adding girth to the bottom end, silvery sparkle to highs, and a subtly wider stereo image. But again, I missed having a gain control to prevent clipping downstream, not to mention to facilitate A/B comparisons.

On acoustic guitar, FG-S sounded more delicate than FG-N. Still, it had more bark than some of my other EQ plug-ins and wouldn’t be my first choice for use on pristine acoustic instruments.



One of my regular complaints with earlier Slate products was that the coding was inefficient. I’m happy to report VMR breaks that mold. Instantiating VMR on 30 tracks—each instance loaded with at least two modules—had negligible overall effect on CPU resources, and I never observed transient CPU spikes. (I used an 8-core Mac Pro running DP 8.06 under OS X 10.9.5 during my review of VMR You can slather your entire project with vintage-flavored processing without running out of juice.

VMR offers A and B workspaces, and you can toggle between them by clicking either of their buttons (thereby avoiding the distraction of continually repositioning your mouse when making A/B comparisons). On the down side, VMR's omission of external sidechain inputs makes deessing, de-booming, ducking, and other keyed compression techniques impossible within the rack system. I also wish VMR had undo and redo functions; you can't undo multiple parameter adjustments or restore an accidentally overwritten preset or deleted bank.

I liked VMR a lot overall. FG-N was my favorite module; it always gave a beautifully rich and full sound to drums, electric instruments and vocals. Revival added impressive beef to bass instruments, including kick drum, and sounded great on full mixes when used in strict moderation. FG-401 flattered electric guitar and, especially in combination with the FG-116, kick drum.

FG-116 sounded great on room mics for drums, lending the UREI 1176’s essential character, but the omission of the all-buttons-in mode left me feeling I didn’t get the full monty. FG-S was more flexible than FG-N, but FG-N pulled tracks slightly more forward in the mix in a flattering way.

Considering all you get with VMR—with the prospect of additional modules coming down the pike soon—$199 is a very low price. That makes VMR a great buy.


Vintage vibe. Overall great sound quality. Extremely low CPU load. Low price.


FG-116 omits all-buttons- in mode. No external sidechains. Revival's shimmer control needs greater range. No undo or redo. Three modules lack output-level controls.


Michael Cooper is a recording, Mix, mastering, and post-production engineer, and a contributing editor for Mix magazine. You can reach Michael at and hear some of his mixes at