Heron — User Guide | Audubon Audio

Interface Overview

Transfer Curve Display

The large graph in the center of the plugin is the most important visual in Heron. It plots input level (x-axis) against output level (y-axis) for the current saturation mode. A perfectly straight diagonal line would mean no processing — the curve bends at the top to show exactly where and how hard Heron is shaping your signal.

A small orange activity indicator moves along the curve in real time, showing the instantaneous level of the audio passing through. This tells you at a glance whether you are barely touching the saturation zone, sitting right in the sweet spot, or pushing into heavy clipping.

Heron transfer curve display with orange activity indicator moving along the curve

Input & Output Level Meters

Vertical level meters flank the transfer curve — Input on the left and Output on the right. Use the Input meter to gauge how hard you are driving the plugin before saturation. The Output meter confirms the final level after the Output Gain trim is applied. Both meters display peak hold so momentary transients are easy to catch.

Heron input and output level meters flanking the transfer curve

Mode & Core Controls

The controls arranged around the transfer curve give you precise control over how much saturation is applied and how the output is managed.

Mode — 3 dB / 6 dB

Radio buttons

3 dB mode is gentler: threshold at −6 dBFS, ceiling at −3 dBFS, +3 dB makeup. Great for subtle warmth and bus glue. 6 dB mode is more aggressive: threshold at −12 dBFS, ceiling at −6 dBFS, +6 dB makeup. Watch the curve shift when you switch — the bend point moves noticeably.

Input Gain

−12 dB to +24 dB

Controls how hard you push the signal into the saturator. More input = more saturation. Use the transfer curve's activity dot to find the right drive level rather than guessing by ear alone.

Output Gain

−24 dB to +12 dB

Trims the output level after saturation. Use this to match the processed signal to your bypass level so you can A/B compare fairly. When Auto Gain is on this is adjusted automatically.

Mix

0 – 100%

Parallel blend between the clean dry signal and the saturated wet signal. Pulling back to 30–50% is a fast way to add warmth without changing the character of transients — a classic parallel saturation technique.

Toggles & Oversampling

Three toggle switches and an oversampling dropdown round out the control set.

Auto Gain

Toggle

Automatically compensates Output Gain to keep loudness consistent as you increase Input Gain. Highly recommended when critically comparing the effect of different drive amounts — louder always sounds better, so level-matching removes that bias.

Stereo Link

Toggle

When on, the left and right channels are driven by the same gain control value, preserving the stereo image and preventing the center from wandering. Disable only if you are processing two mono sources independently on a stereo track.

Bypass

Toggle

Hard bypass for instant before/after comparison. Because it is inside the plugin rather than at the DAW level, it bypasses saturation while keeping the latency report consistent so your DAW's PDC does not shift tracks on you.

Oversample

Off / 2x / 4x / 8x

Higher oversampling reduces aliasing distortion from the nonlinear waveshaper. 2x uses a low-latency IIR filter — good default for tracking and mixing. 4x / 8x use FIR equiripple filters for mastering-grade cleanliness at the cost of additional latency.

Preset Bar

The preset bar at the top of the plugin contains left/right arrow buttons for stepping through presets, a display showing the current preset name, and a Save button. Factory presets are built into the plugin. Your own presets are saved as .heronpreset files in ~/Documents/Heron/Presets/ and appear automatically in the browser on next launch.

Reading the Transfer Curve

Why this display matters: The transfer curve shows you the exact nonlinear relationship between input and output. Rather than guessing how much saturation you are adding, you can see the shape of the distortion and watch in real time exactly where your audio sits on that curve. Drive until the activity dot lands where you want it — then stop.

Three Zones on the Curve

Think of the transfer curve as having three behavioral zones from left to right:

Gentle Zone

The lower-left section is nearly linear. Audio here passes through with minimal color — essentially transparent processing. The activity dot sitting here means you are barely touching the saturation.

Sweet Spot

The mid section where the curve begins to bend is the warmth zone. Even harmonics are generated softly here, adding density and presence without obvious distortion. This is where most mastering and bus work lives.

Hard Clip Zone

At the top right the curve flattens — this is hard saturation and clipping territory. The output ceases to grow with the input. Transients are rounded, odd harmonics increase. Useful for effect; not for transparent limiting.

Using the Activity Indicator

The orange dot traces along the curve in real time with your audio's instantaneous level. Raise Input Gain until the dot moves into the sweet spot bend — then listen. If the dot is consistently slamming the flat top of the curve you are overdriving the plugin. Back off Input Gain or reduce the source level feeding Heron.

For dynamic material like full mixes, the dot will dance across a range of the curve. That range tells you the effective working window of your saturation. If it never reaches the bend, add gain. If it never leaves the flat zone, reduce it.

Heron transfer curve with activity dot in the sweet spot zone

How the Curve Changes with Mode

Switch between 3 dB and 6 dB mode and watch the curve reshape itself. In 3 dB mode the bend is shallower and starts closer to 0 dBFS, so only the loudest peaks get shaped. In 6 dB mode the threshold drops to −12 dBFS, meaning the curve starts bending earlier — more of your signal is colored, and the effect is more audible at the same Input Gain setting.

Best Use Cases

Master Bus Warmth & Soft Limiting

Place Heron last (or second to last before a true limiter) on your master bus. Enable Auto Gain and Stereo Link. Select 3 dB mode. Raise Input Gain slowly — use the curve display to find the point where the activity dot just kisses the bend on the loudest sections. This shaves off harsh transient peaks and adds a touch of glue without audible pumping or coloration.

For mastering quality output, set Oversample to 4x or 8x. The added latency is compensated by your DAW and the aliasing reduction is significant at this stage of the chain.

Heron on master bus with Auto Gain and Stereo Link enabled

Drum Bus & Mix Bus Glue

On a drum bus or submix, try 6 dB mode with a moderate Input Gain so the activity dot settles in the sweet-spot zone during louder hits. The polynomial waveshaper adds even harmonics to the transients, making kick and snare feel more "present" in the mix without additional EQ.

Use the Mix knob at 40–70% to preserve the natural punch of the drums while still getting the cohesive, glued sound. This parallel saturation approach means you get the warmth without smearing the attack.

Heron on drum bus with Mix knob set for parallel saturation

Parallel Saturation on Vocals or Guitars

On individual tracks, Heron excels as a parallel processor. Set Mix to 20–40% and push Input Gain into the 6 dB mode sweet spot. The activity dot should be moving dynamically — staying in the warm zone on loud notes and retreating toward gentle on quiet ones. This breathing behavior adds life and harmonic richness without making quiet passages sound processed.

For vocals, keep Stereo Link on even on a mono source — it has no negative effect and avoids any accidental mono/stereo mode mismatch if the track gets doubled or widened later.

A/B Comparing with Auto Gain & Bypass

The single most important habit when using any saturation plugin: always A/B at matched loudness. Enable Auto Gain so Heron compensates its own output as you adjust drive. Then use the built-in Bypass toggle (not your DAW's plugin bypass) to flip instantly between processed and dry. Because both states share the same latency compensation state, tracks stay in sync during the comparison.

If processed sounds better even at equal loudness, the saturation is doing real work. If it sounds better only when louder, reduce Input Gain — you were just adding volume, not warmth.

Tip — Oversampling & Latency: At 2x oversampling the added latency is minimal and the IIR filter keeps it low enough for live monitoring. At 4x and 8x the FIR equiripple filters add more latency — your DAW's Plugin Delay Compensation handles this automatically during mixdown, but it may feel sluggish during live input monitoring. Switch to 2x or Off when tracking, then bump up to 4x/8x on the final mix pass.