When I reviewed the Portico II Master Buss Processor hardware for Tape Op #89 in 2012, I was fortunate to get my hands on one just as I was mastering a modern rock album that I had tracked and mixed. The producer and I were immediately struck by the MBP’s ability to increase the power, energy, and apparent loudness of the masters without sacrificing tonality or introducing obvious distortion. This was a box I could get along with! Over the years, I seriously considered investing in the hardware, but having relied primarily on an in-the-box workflow for almost two decades, I couldn’t quite justify the investment. Still, every once in a while I would think back to that first experience with the MBP. Fast-forward to 2026, when my friends at Rupert Neve Designs whispered to me that they had developed a plug-in version of the Master Buss Processor in a rare collaboration with McDSP. Naturally, I was excited to try it. Spoiler alert: I found the same excitement, energy, and power in the plug-in as I had the rack unit.
When I reviewed the hardware, I was struck by the sophisticated actions of its analog stages. Today, we have come to expect another level of sophistication – and sometimes a little magic – from plug-ins, so rather than revisit every detail of the original circuitry, I’ll focus on what’s new in the plug-in and, more importantly, how it sounds. During the past few weeks, I’ve used it on mixing and mastering projects ranging from indie folk to metal to traditional jazz. In every genre, the Master Buss Processor proved useful, whether mastering a stereo mix, processing a drum bus, shaping and widening a subgroup, or simply adding a touch of Silk coloration to a vocal bus.
Users of the hardware will find the plug-in immediately familiar, with a few notable differences. In addition to conventional stereo operation, the plug-in adds mid/side functionality. The compressor’s sidechain high-pass filter is sweepable up to 350 Hz rather than fixed, and an external sidechain bus allows any DAW signal to control the compressor. In stereo mode, the right-channel dynamics controls are grayed out, leaving the left channel to control both channels. While the hardware relies on detented controls for repeatability, the plug-in provides continuously variable adjustment with fine resolution, and double-clicking a knob allows precise values to be entered directly.
This processor really shines for stereo mastering. The compressor offers feed-forward or feedback operation along with Peak or RMS detection. Attack and release times are optimized for bus processing, with useful ranges that make it difficult to get into trouble – unless you want to. Ratios range from invisibly low to crushingly high (40:1), providing everything from subtle leveling to aggressive dynamic effects. A Blend control enables parallel compression by mixing the dry and compressed signals in any proportion.
The compressor is suited for mixing and mastering, easily providing gentle level control and mix glue in feedback mode at low ratios. Switch to feed-forward operation, and it can create considerably more movement, pumping, and envelope shaping. The limiter can provide anything from gentle peak control to drum bus crush that competes with my favorite aggressive FET and VCA compressors. The sidechain filter and external sidechain further expand the range of possible compression effects, from transparent to explosive.
The compressor’s makeup Gain precedes the limiter, allowing the two processors to function as a particularly effective loudness maximizer, producing loud, punchy, controlled mixes with almost no artifacts. Just set the limiter ceiling and increase Gain to drive the program into it. The soft-clip limiter, with its automatic release behavior, remains surprisingly transparent while controlling peaks, yet it can also be driven hard enough to become an obvious effect.
For me, the compressor and limiter section alone justify the price of admission. I never failed to find a dynamics setting that improved a mix bus or master, regardless of musical style. On the indie folk master, I gently squeezed the dynamics, bringing out low-level details without pushing the loudness anywhere near Top 40 territory. On the metal project, I was able to achieve extreme loudness while retaining definition within the mix and maintaining a smooth overall presentation. On an acoustic pop track that arrived somewhat over-compressed, the feed-forward compressor imparted just enough movement to make the track feel alive again.
Once the dynamics have been tamed, the Silk section offers a wide range of tonal shaping. Blue mode emphasizes lower-frequency transformer harmonics, while Red emphasizes the upper mids and highs, and Off removes the Silk coloration. The Texture control adjusts the amount, or drive, of the selected transformer saturation. In my sessions, the Silk modes proved extremely useful. Blue added weight and harmonic density to the bottom end of a hip-hop or R&B groove, while Red increased the presence and intensity of a pop mix as an alternative to EQ.
The final processing section is the SFE, or Stereo Field Editor, which manipulates the depth and width of a stereo signal. The Depth control adjusts the center information, while Width adjusts the sides. Either can operate across the entire spectrum or focus on one of four frequency ranges. The SFE can be positioned before or after the dynamics processing, as compression and stereo-width processing often interact.
As much as I love the dynamic section, the SFE may be the MBP’s secret weapon. Increasing Depth can bring a lead vocal, kick, snare, or bass guitar into clearer focus, while Width can bring out stereo guitars, drum overheads, and ambience, or simply make an entire mix feel larger. Just as importantly, frequency-selective Width processing can pull the low-frequency information toward the center, cleaning up a mix with too much stereo bass.
Plenty of processors excel at one particular trick. The MBP moves easily between transparent dynamics control, aggressive compression, limiting, harmonic coloration, mid/side manipulation, and stereo enhancement without feeling like a collection of unrelated processors. Back in 2012, I wrote that the hardware could take a good mix and turn it into a great master. Fourteen years later, that is still the best way I can describe the Portico II Master Buss Processor. The difference is that I can now open it in a session, recall every setting, and use as many instances as I need.
For anyone looking for a processor that truly makes a mix sound like a record, the MBP plug-in belongs on the short list. It is available for Mac and Windows (AU, VST3, AAX); and Pro Tools HDX, Venue, and Carbon users will appreciate that both AAX DSP and native versions are included.