Bass Box v2.5.3
UTC LS-10X Transformer Emulation
The bass sound of Thriller, Billie Jean, and Off the Wall came from a handbuilt DI box that no one — not even Bruce Swedien himself — could ever recreate.
The Story: In the late 1950s, Bruce Swedien wired a UTC LS-10X transformer backwards inside a metal enclosure. This “wrong” wiring created an unrepeatable magnetic resonance between 900–2100 Hz — the signature snarl on every Michael Jackson bass track from 1979 to 2001. When Swedien later ordered a new UTC transformer to rebuild it, it sounded completely different. The original was gone forever.
What We Did: We analyzed original Thriller-era audio material, studied the physics of the UTC LS-10X transformer core, and built the first-ever software emulation of this specific device — level-dependent snarl, magnetic hysteresis, impedance coloring, and all. It took months of hard work extracting what made this box unique. This is the first and only plugin that captures what no hardware ever could again.
One-time purchase · 2 activations · Free updates
Feature Highlights
UTC LS-10X Core
Precision circuit model of the legendary transformer — frequency response, impedance simulation, and magnetic hysteresis saturation.
SOUND Panel
Drive the transformer: Input Gain, Drive, Hysteresis (magnetic memory), Mix control, harmonic Tone shaping, and Output Impedance.
SNARL Engine
Vintage transient character: attack bite, high-frequency edge, noise floor shaping, and transformer nonlinearity at your fingertips.
Synthrilla 32E EQ
6-band parametric EQ (HP, LO, MD, MD, HI, LP) inspired by classic Harrison console modules. Surgical bass sculpting.
SY-2A Compressor
Optical compression with program-dependent release, Compress/Limit toggle, and a live VU gain reduction meter.
Preset System
5 factory presets plus unlimited custom presets with export/import. Share your presets as encrypted .bbpreset files.
Signal Flow
Audio passes through a professional-grade transformer emulation chain:
The EQ and Compressor chain order can be toggled: EQ→COMP or COMP→EQ.
How It Works
SOUND Controls
| Parameter | Range | Description |
|---|---|---|
| IN (Input Gain) | −12 – +12 dB | Drives the transformer input level |
| DR (Drive) | 1.0 – 10.0 | Saturation intensity — higher = more harmonic distortion |
| HY (Hysteresis) | 0.0 – 1.0 | Magnetic memory effect, adds warmth and low-end density |
| MX (Mix) | 0 – 100% | Dry/wet blend for parallel processing |
| DU (Drive Unit) | 1 – 3 | Saturation character: soft / medium / hard |
TONE Controls
| Parameter | Description |
|---|---|
| BA (Bass) | Low-frequency boost/cut of the transformer response |
| BG (Body) | Mid-body presence, adds fullness to bass fundamentals |
| TR (Treble) | High-frequency response shaping |
CHAR Controls
| Parameter | Description |
|---|---|
| CH (Character) | Harmonic density — how much of the transformer’s harmonic fingerprint is applied |
| Z (Impedance) | Output impedance: 50 / 150 / 600 Ohm. Changes tonal color and low-end response |
Start with DR at 2–3, HY at 0.2, MX at 1.0 for subtle transformer warmth. Push DR to 6+ for aggressive saturation.
SNARL adds the vintage transient bite and nonlinear distortion artifacts of overdriven analog transformers.
| Parameter | Description |
|---|---|
| LO | Lower resonance frequency control |
| HI | Upper resonance frequency control |
| GA (Gain) | Overall SNARL output level |
| Q | Resonance / sharpness of the SNARL frequency focus |
| SA (Saturation Amount) | Intensity of nonlinear saturation |
| AT (Attack) | Transient attack bite — adds the distinctive “snarl” on note attacks |
| RE (Release) | Transient release tail character |
| NO (Noise) | Noise floor color — subtle analog hiss character |
| E/O | Harmonic character blend |
| HF (High Freq) | High-frequency trim on SNARL output |
SA + AT together create the distinctive transient bite. Try SA at 0.3, AT at 0.5 for classic transformer punch on bass guitar.
| Band | Type | Description |
|---|---|---|
| HP | High-Pass Filter | Remove subsonic rumble. Default: 25 Hz |
| LO | Low Shelf | Boost or cut bass fundamentals. Default: 98 Hz |
| MD (1) | Parametric Mid | Low-mid sculpting. Default: 722 Hz, ±1.6 dB |
| MD (2) | Parametric Mid | Upper-mid presence. Default: 710 Hz, ±0.7 dB |
| HI | High Shelf | Air and presence. Default: 3473 Hz |
| LP | Low-Pass Filter | Remove harsh high-frequency content. Default: 3440 Hz |
Toggle individual bands on/off with the HP and LP buttons at the top right of the EQ panel. Each knob adjusts gain; the frequency shown beneath indicates the center/corner frequency.
For that classic 70s bass sound: boost LO at 80 Hz (+3 dB), cut MD1 at 500 Hz (−2 dB), add presence at HI 3 kHz (+1.5 dB).
| Parameter | Range | Description |
|---|---|---|
| Peak Reduction | 0 – 100 | How hard the optical element reacts to the signal. 0 = bypassed, 100 = maximum compression |
| Gain | 0 – +40 dB | Makeup gain to compensate for gain reduction |
| Compress / Limit | Toggle | Compress = program-dependent ratio ~3:1. Limit = hard brick wall limiting |
Program-Dependent Release
Like a real LA-2A, the SY-2A’s release time breathes with the audio material. Dense passages trigger faster release; sparse signals allow the compressor to relax slowly. This is what gives optical compressors their musical, non-fatiguing quality.
VU Meter
The horizontal VU meter shows live gain reduction:
- 0 VU to −3 dB: Amber — light compression
- −3 to −10 dB: Green — moderate compression
- Below −10 dB: Blue — heavy limiting
Peak Reduction 30–50 + Makeup Gain 6–12 dB is the classic optical compression setting for bass. The VU should breathe visibly but stay mostly in the amber zone.
5 factory presets are embedded directly in the plugin binary — no external files needed.
| Preset | Character |
|---|---|
| Default | Flat response, transparent transformer pass-through |
| Billie Jean | Subtle saturation, punchy low-mid, clean high-end |
| Thriller Bridge | Warm drive with SNARL bite, classic 80s bass character |
| Vintage Warm | Heavy hysteresis, rounded transients, full low-end |
| Clean Clear | Minimal saturation, impedance coloring only, wide mix |
- Export / Import — Share presets as .bbpreset files or back up your custom presets
- < > arrows — Step through presets in order
- Browse button — Open full preset browser with search
- Factory presets marked (F), custom presets marked (C)
- All parameters saved including EQ, Compressor settings, and chain order (EQ→COMP or COMP→EQ)
System Requirements
Frequently Asked Questions
The UTC LS-10X is a professional transformer unit used in recording studios and famously by engineer Bruce Swedien for the bass sound on Michael Jackson’s Thriller album. Transformers color the sound through magnetic saturation, impedance interaction, and frequency response shaping. The Bass Box emulates all of these characteristics in software.
The SOUND panel is the transformer emulation core. Drive controls how hard you push the magnetic core (more drive = more harmonic distortion). Hysteresis adds magnetic memory — the slow, warm saturation that builds up with sustained notes. Mix blends the processed signal with dry. The Tone section shapes the frequency response of the transformer itself, just as different transformers have different tonal signatures.
SNARL is the character engine that adds vintage transient bite and analog nonlinearity. At low values it adds subtle warmth and presence; higher values introduce the gritty, aggressive character of overdriven transformers. The AT (Attack) control shapes the transient snap on note attacks — this is the distinctive "snarl" that gives the engine its name.
Yes. Between the 32E EQ and SY-2A panels there is a chain separator with a toggle button. Click it to switch between EQ→COMP and COMP→EQ processing order. EQ-first changes what frequency content the compressor "hears", resulting in different dynamic behavior. Both orders are valid and produce different sounds. The current chain order is saved with presets.
VST3 and AU (Audio Unit) on macOS 11+ as a Universal Binary (native on Intel and Apple Silicon). VST3 and Standalone application on Windows 10+ (64-bit).
Tested with Cubase, Logic Pro, Ableton Live, FL Studio, Reaper, Studio One, and Bitwig. Any DAW supporting VST3 or AU should work.
Each license supports 2 simultaneous activations, so you can use the Bass Box on your studio machine and laptop. Activation requires an internet connection. You can deactivate and move the license to a new machine at any time.
Yes, all updates are free. Download the new version and run the installer — your custom presets and settings are preserved.
Version History
- Improved user interface: brighter labels, better readability across all panels
- EQ layout follows Harrison 32C channel strip order (LP top, HP bottom)
- Added HP enable button and animated filter response curves for LP and HP
- Bell/Shelf toggle icons now clearly visible with white curve symbols
- Refined knob textures with organic turbulence overlay
- Improved envelope algorithm — bass transients cut through the mix with more definition and warmth
- Enhanced analog noise character with natural high-frequency air
- Encrypted preset format — .bbpreset files are now protected against reverse engineering
- Preset export/import — share and back up your custom presets
- Preset overwrite warning when saving over existing presets
- Improved preset metadata loading performance
- macOS PKG v2.5.1 (signed + notarized) and Windows installer v2.5.1
- Animated transformer glow — drive/snarl-reactive overlay, up to 90% opacity at full drive
- Fader shaft background texture — hardware-style vertical fader graphics
- EQ gain knob color indicators — real-time color feedback (blue → orange → red)
- Preset state restoration — correct preset name restored on DAW project reload
- macOS PKG v1.0.0 (notarized) and Windows installer v1.0.0 with all 5 factory presets
- Synthrilla 32E EQ panel — 6-band parametric with Harrison-style knobs
- SY-2A Optical Compressor with program-dependent release and VU meter
- Chain Toggle: switch EQ→COMP or COMP→EQ processing order
- Windows installer (NSIS) with VST3, Standalone, and factory presets
- 5 factory presets embedded in plugin binary (no external files)
- Preset Browser modal with search and (F)/(C) prefix display
- Initial release: UTC LS-10X transformer emulation core
- SOUND panel (Drive, Hysteresis, Tone, Impedance)
- SNARL engine for vintage character and transient shaping
- macOS Universal Binary (VST3 + AU) and Windows VST3
- License system with 2-activation support
Add Transformer Warmth to Your Bass
The UTC LS-10X sound that shaped Thriller — now in your DAW.
One-time purchase · Free updates · macOS & Windows
Instant download after purchase · License key via email
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