The Synthrilla Bass Box is the first and only software emulation of the handbuilt DI box Bruce Swedien used on every Michael Jackson bass track from Off the Wall (1979) through Invincible (2001). And it does something the hardware itself could never reliably deliver twice: it reproduces that sound — not just for real bass, but for synth bass too.
How We Got Here
In the late 1950s, Bruce Swedien wired a UTC LS-10X transformer backwards inside a metal enclosure. The result was a magnetic resonance between 900 and 2100 Hz — a level-dependent snarl that became the signature of Thriller-era bass. When Swedien later tried to rebuild the box with a replacement transformer, it sounded completely different. The original core had a batch composition and a decades-deep magnetic history that no new unit could replicate.
We spent months on this. FFT analysis of Thriller-era bass recordings. Reverse-engineering the snarl resonance across dozens of isolated stems and multitracks. Transformer physics calculations on the UTC LS-10X core — B-H curves, hysteresis loops, impedance behavior under load. Iterative DSP modeling. Then comparison listening, back to the original masters, again and again, until the snarl matched — not just spectrally, but in feel.
Swedien's Sound for Real Bass
Drop a P-Bass, a Jazz Bass, an upright DI through the Bass Box and you hear it immediately: the presence lift in the upper mids, the thick low-end with definition, that level-dependent harmonic growl when you dig in. The same signature Swedien imprinted on Billie Jean, Beat It, Don't Stop 'Til You Get Enough.
Swedien's Sound for Synth Bass
Here is where it gets interesting. Modern productions live on synth bass — Moog, Juno, MS-20, serum sub patches, sampled 808s. Out of the box these instruments are clean, controlled, DAW-direct. The Bass Box treats them the way Swedien treated every bass signal that entered his chain: through a reversed transformer that adds vintage magnetic character, program-dependent saturation, and that distinctive 900–2100 Hz snarl. A sterile synth bass becomes a recording. A modern sub fits next to real drums. The gap between "in the box" and "made in the room" closes.
Full Production Chain in One Plugin
SOUND panel: drive, hysteresis, impedance output (50/150/600 Ohm), tone shaping.
SNARL engine: vintage transient character and nonlinear distortion.
Synthrilla 32E EQ: 6-band parametric (HP, LO, MD, MD, HI, LP) based on Harrison console modules.
SY-2A optical compressor: program-dependent release, VU gain reduction metering.
Switchable signal chain: EQ→COMP or COMP→EQ.
Five factory presets ship with it — Default, Billie Jean, Thriller Bridge, Vintage Warm, Clean Clear — plus encrypted custom preset export/import.
Available Now
VST3 and AU for macOS (Universal Binary, Intel & Apple Silicon). VST3 and Standalone for Windows 10+. Two simultaneous activations per license. Free updates forever.