Black Diamond Distortion

About Black Diamond Distortion

Black Diamond Distortion is the first plugin from Aspen Instruments — a flexible distortion engine that covers everything from subtle preamp-style warmth to aggressive modern waveshaping. Start from a curated library of presets, including classic hardware-inspired designs, or build your own from first principles by combining four editing modes (Harmonic, Spline, Brush, and Equation) through a multi-lane mixer that blends, scans, or stacks them in series.

New in v1.1: physics-based simulations of magnetic hysteresis and diode surge that interact with the curves you design. Here’s a top-to-bottom tour of how it’s laid out.

The Top Panel

From the top panel you undo, redo, set system-level options like the color scheme — and open the Preset Browser.

Preset Browser showing the local library and online community presets

The Preset Browser

Search your local library or connect to an online community where users share presets and curves. Every preset carries metadata — artist, title, tags and category, description — and all of it is searchable.

Online presets can be previewed in memory and downloaded to your user folder. Local presets support subdirectories so you can organize your collection any way you like. Click the upload button to share your own work back to the community. Browsing, previewing, and downloading are free with no account required; uploading requires an account.

Curves nest inside a system preset the way oscillator waveforms nest inside a synth patch — one level deeper, with their own browser inside the curve editor below.

Mixer view showing multiple curves loaded in parallel lanes

The Mixer

In v1.1, every mode loads into a multi-lane mixer. Each lane holds its own curve and can be edited independently. The mixer combines the lanes three ways: Blend crossfades between them, Scan sweeps through them like a wavetable, and Series stacks them end-to-end for a more aggressive sound.

Previously, only Harmonic Mode had a mixer — for blending individual harmonics — and every other mode was a single curve. The mixer is now always present, and any combination of Harmonic, Spline, Brush, and Equation curves can share the lanes.

Add a new lane with +, remove the selected lane with Del, and double-click any lane label to rename it.

The Morph knob behaves differently per mode — it sets crossfade depth in Blend, scans the wavetable in Scan, and adjusts gain in Series. It can also drive animations defined inside the Curve Editor (gesture playback for Spline, sweeping a constant for Equation — see below).

The Curve Editor

Each mixer lane has its own curve. Click a lane label to open the editor, then pick a tool: Harmonic Exciter, Curve Browser, Spline, Brush, or Equation.

Curve Editor showing per-lane curve customization and tool selection

Harmonic Exciter

The Harmonic Exciter uses trigonometric identities to excite specific harmonics, similar to Chebyshev polynomials. Strictly speaking, these are precise harmonic exciters only for 0 dB sine waves: sin(x) → sin(Nx). Feed in any signal for harmonically rich results, but for precise harmonic behavior, enable Autonormalize in the Bottom Panel — it conditions the input to a 0 dB sine wave.

Stacking different harmonic exciters across the mixing lanes is a quick way to dial in a unique distortion — it's also the Init preset's starting state.

Harmonic Exciter editor showing harmonic sliders and waveform preview

Curve Browser

Click the folder icon to load curve presets (.tfunc files) from your local library or browse online. The flow mirrors the system preset browser — searchable metadata, free preview and download, account required to upload.

Spline

Spline mode shapes the transfer curve through anchor points. You manipulate the curve directly by dragging the anchors in the editor.

The spline-fitting algorithm is optimized to use as few anchors as possible, which makes each anchor extremely powerful. A single adjustment can reshape large portions of the waveform, encouraging broad, intentional changes rather than tedious micro-editing.

Arm the Morph Dial button, drag an anchor to record a gesture, and the Morph knob plays it back from start to end.

Brush

Brush mode adds texture and irregularity to the distortion. The standard brush lets you draw the curve pixel by pixel — and because humans aren't particularly good at drawing smooth curves, the result is often "broken" in interesting ways.

The Roller Brush smooths the curve as you draw, flattening jagged edges that can otherwise lead to brittle or unstable distortion.

Several texture brushes introduce controlled noise into the curve, creating subtle randomness that's especially fun to experiment with.

Brush editor showing a hand-drawn distortion curve

Equation

Equation mode is the core of Black Diamond. You define the distortion directly by entering the mathematical equation that computes it.

For users willing to learn a small amount of signal processing, this becomes an extremely powerful tool. Math describes nonlinear behavior far more precisely than manual curve drawing ever could. In fact, equations are the foundation of the Harmonic Exciter — Equation mode simply removes the guardrails. This opens the door to experimenting with an effectively infinite range of distortion algorithms.

Reference the constant m in your equation and the Morph knob sweeps it from 0 to 1, animating the curve in real time.

The Bottom Panel

The bottom panel houses the global controls that shape how the plugin behaves around your curves.

Modulators and conditioning. Oversampling and a DC-blocking filter sit on the left, alongside an envelope (audio) follower and LFOs. Clicking any modulator opens its controls and reveals the destinations it can drive.

Hysteresis. The Hysteresis control enables a Jiles-Atherton magnetic hysteresis simulation — virtual analog with a twist. The static saturation building block (the anhysteretic magnetization in the physics literature) is replaced with the waveshaper you designed upstairs, while nonlinear differential equations around it emulate the feedback and memory that make magnetic components "sticky" — once magnetized, they resist returning. It's a small control at the bottom of the plugin, but a big idea — colliding the worlds of virtual analog with modern waveshaping.

Gain section. Input and output gain are independent by default. Enable gain linking and the output compensates automatically when you turn the input up or down — useful for A/B-ing distortion characters at matched loudness.

Autonormalize. Autonormalize strips the envelope before the waveshaper and restores it after. Mathematically, an input A(t)·sin(t) becomes sin(t) before distortion, then Distorted(sin(t)) after, and A(t)·Distorted(sin(t)) at the output. Like any automatic feature, envelope detection isn't perfect on every signal — use with awareness. It pairs especially well with the Harmonic Exciter — that tool always produces harmonically rich results, but feeding it a normalized 0 dB sine wave unlocks the precise sin(x) → sin(Nx) mapping its math is built around.

Bottom panel showing modulators, hysteresis, gain section, and autonormalize controls

Black Diamond Probe

Our free companion plugin, Black Diamond Probe, allows you to reverse-engineer almost any hardware or software distortion, provided it is memoryless.

The Probe works by scanning a unit under test and extracting the nonlinear transfer function that defines its behavior. Once captured, this curve can be imported into Black Diamond Distortion’s preset library. If you enjoy cloning gear and dissecting nonlinear systems, this is where things get dangerous—in a good way.

Formats

Operating Systems