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Kirchhoff-EQ is an ultimate 32-band parametric EQ plugin built for all critical professional applications. It has refined sound quality, analogue-matched curves, 15 filter types with continuously variable shape and 32 vintage EQ types modeled from real-world devices. The builtin dynamic processing functions are highly flexible and have ultra-low distorion. All these push Kirchhoff-EQ to a next-generation standard.

Equalizers will never be the same again.

Ultimate Sound Quality

Robust Nyquist-matched Transform

Through originally developed "Robust Nyquist-matched Transform", Kirchhoff-EQ has made digital-domain frequency response more approximate to its analogue counterparts without high frequency cramping as in regular IIR (infinite impulse response) equalizers. This technique is applied on all filter types in Kirchhoff-EQ.

Frequency response of analogue prototype (blue) and common digital filters (red).

Frequency response of analogue prototype (blue) and Kirchhoff-EQ (red).

High-Precision Processing

64-bit is mandatory and it's not negotiable. The internal processing of Kirchhoff-EQ is always in 64-bit (or 117-bit), regardless of host DAW's current working precision.

Psychoacoustic Adaptive Filter Topologies

All linear filter structures should have the same sound on paper. However in real-world application, round-off errors make every filter structure sound differently: some better in low frequencies, some better in high frequencies.

A technology called "Psychoacoustic Adaptive Filter Topologies" has been deployed in Kirchhoff-EQ. Filter structures change themselves to a "best fitting" state along with corresponding band frequency changes, resulting in optimized sound quality in both low and high frequencies.

Quantization noise of raising 6 dB at 1000 Hz of a very famous EQ.

Quantization noise of raising 6 dB at 1000 Hz of Kirchhoff-EQ.

Click here to know more about how Psychoacoustic Adaptive Filter Topologies work.

Switchable Ultra-High 117-bit Processing

Since there's already 64-bit, why not go further? Kirchhoff-EQ uses a technique called "Double-Double" to make precision of internal processing reach 117 bits! This is the first equalizer in the world to reach such precision. You can switch between 64-bit and 117-bit at any time. It satisfies the most demanding ears.

* Linear-phase mode always uses 64-bit as it is an FIR(finite impulse response) filter, and does not support 117-bit.

Filter Types

15 Unique Filter Types

  • low pass, high pass, band pass: continuously variable from 0 dB/oct to 96 dB/oct;
  • bell, notch: continuously variable from 12 dB/oct to 96 dB/oct;
  • low shelf, high shelf, tilt shelf: continuously variable from 6 dB/oct to 96 dB/oct;
  • flat tilt and flat top;
  • sword: has sharper slope than bell, specifically designed to "dig" out resonances.
  • brickwall low pass, brickwall high pass, allpass low and allpass high.

Continuously Variable Slopes Filters

The slope of most filter types can be continuously changed from 0 dB/oct, 6 dB/oct or 12 dB/oct up to 96 dB/oct. Would you like to try a 8.125 dB/oct highpass?

32 Filter Types Modeled from Historic Vintage EQs!

Get vintage and modern at same time! We modeled 9 vintage EQ hardware units as a total of 32 EQ types implemented in Kirchhoff-EQ. Benefit from Robust Nyquist-Matched Transform, every EQ type precisely matches the original hardware and won't cramp near Nyquist frequency. For a further step, unlike the original hardware that only allows to choose between several frequency positions, we modified the DSP model to make adjustable frequency points for all these types! Every type in these models can be used together with regular EQ types or other modeled types, and can be applied with dynamic functions (except lowpass and highpass types). This brings you more freedom and convenient operations.

* No non-linear behaviors were modeled. All vintage filter types only contain ideal linear parts of their physical model.

Click here to know how circuit modeling works in Kirchhoff-EQ.

Zero-Latency/Analogue/Linear/Mixed Phase Modes

The phase mode of Kirchhoff-EQ is switchable between zero-latency mode, analogue mode, linear phase mode and mixed phase mode, in order to meet all your phase relationship needs.

* No matter which phase mode currently in, if dynamic functions is turned on for a filter band, it will work on minimum-phase mode (won't affect other bands).

Mixed Phase Mode

The zero-latency and linear phase modes have a very different sound. Kirchhoff-EQ provides a mixed mode that uses zero-latency when the band frequency point is low, and uses linear phase when it is high. Each band could be changed smoothly between minimum and linear phase mode according to their frequency.

* There is no noticeable crossover between filter types while in mixed phase mode, transition is seamless.

Phase response tends to be linear as frequency increases.

Flexible Dynamic EQ Functions

Dynamic functions in Kirchhoff-EQ are not just a bonus, they provide the richest functions you have ever seen. Enabling you to achieve unlimited possibilities of dynamic EQ functions. All filter types (except low/high pass, band pass and notch), even these vintage-modeled ones, can be applied with dynamic functions.

Harmonic Shifted Envelope

All dynamic EQ have odd- and non-integral harmonics, that’s the laws of physics. By using advanced DSP techniques, Kirchhoff-EQ now "shifts" most energy of odd-harmonics into even-harmonics, creating an ultra-low noise floor and enhanced sound. Now you can use dynamic functions with freedom without worrying about smashing your sounds.

Frequency response of a very famous dynamic EQ working at 1000 Hz. Note the rich odd-time harmonics.

Dynamic function of Kirchhoff-EQ. Note that overall harmonic distortion is decreased whilst new even-time harmonics are generated.

Click here to know more about how Harmonic Shifted Envelope Detection works.

Two-Way Threshold

You can now control how dynamics react to the portion of the signal above/below threshold concurrently. In Kirchhoff-EQ, the "Above" stage works as a compressor or upward-expander, and the "Below" stage works as an expander or upward-compressor. For example, you can raise the signal below the threshold AND compress the signal above the threshold to "stabilize" a band.

Detect/Relative Envelope Detection

Let us imagine a simple case: we are playing an audio clip in which sounds around 1khz are 9 dB. You may think "The 1khz range is over powering, We should reduce at 1khz." But we should also consider the overall level. If the whole audio is 30 dB, you would not feel that 1khz is too much, instead you may feel it's not enough. The better criteria to determine whether a band's volume is high or low is its relative portion in overall volume envelope, instead of only its absolute dB value.

Thereby we introduce "Detect/Relative Envelope Detection" in Kirchhoff-EQ. The dynamics are affected by both current frequency band and relative portion to a "Relative" band. The contribution of Relative Envelope Detection to dynamics is also adjustable: when set to 0%, it degrades as a normal dynamic EQ; and when set to 100%, the amount of dynamics is fully calculated from the relative portion.

The “detect” band is set according to the frequency and Q of the band by default, “Relative” is the whole audio envelope by default. But they can be set freely.

The detecting band and relative band have a freely adjustable frequency point and Q value. Or enable “S.C.” mode to use “Detect” or “Relative” with a sidechain signal.

Onsets Detection Mix

By turning on "Onsets" mix, the envelope detector reacts more specifically to transients inside of the envelope. So you can fine-tune the tone of transients. For better adjustability, you can "mix" envelope detector and onsets detector. For example, you can compress the high frequencies just a little bit whilst compressing the sudden increase of high frequencies more aggressively.

Reviews & Tutorials

More Details

Spectrum Grab

Kirchhoff-EQ allows you to locate a specific frequency peak rapidly by directly grabbing on spectrum.

Switchable 2x Oversampling

Kirchhoff-EQ has builtin 2x oversampling that can be freely turned on/off.

Per-Band Directional EQ

Each band can be set as mid/side or left/right processing, so you can pan a band left or right, or adjust Mid/Side, or just left, right, mid and side separately.

Global left/right/mid/side Monitoring

4 independent buttons were added to help you to switch left/right/mid/side monitoring more smoothly.


Lookahead is not a feature that can always be found in an EQ plugin. But it's considered necessary for Kirchhoff-EQ's various dynamic functions.

Global Stereo Width Control

2 ways of stereo width control are implemented in addition to global output gain and pan. You can adjust the ratio between Mid and Side or gain the Side channel individually.

Band List

Operational list helps you to check and adjust the basic parameters of every band. Drag an item to arrange the order, or sort them by frequency with 1-click.

Extreme CPU Optimization

Through hand-written assembly code commands, Kirchhoff-EQ achieves ultra low CPU workload. Never fear to use hundreds of instances!

Low Clicking Noise

We did our best to reduce clicking noises while performing parameter changes, type switching, bypass on/off and enter/leave solo listening mode.

GPU Accelerated GUI

We are dedicated to smoothness in operating, speed to open/close UI and operation latency. To achieve better rendering efficiency, the GUI of Kirchhoff-EQ is rendered using OpenGL.

Visual-Comfort Spectrometer

The spectrum panel of Kirchhoff-EQ is carefully optimized for visuals and is freely configurable. You can adjust its decibel range, refresh speed, resolution, frequency scaling and brightness. You can even directly specify its center frequency.

User-Customizable Settings

How to trigger war on a forum? Ask them if a Q value shall increase/decrease when mouse wheels up. To help speed-up your workflow, Kirchhoff-EQ provides a rich set of options allowing you to cast it to your own handy tool.

Choose your favourite from various GUI themes, or just make a new one only for yourself! Any visual requirements will be satisfied by the highly customizable GUI.

Other Features

Piano roll display

Customizable knob speed

My favorite filter types

Apple silicon native support

  • Solo mode
  • Phase invert
  • Automatic gain compensation
  • Gain scale
  • Adjustable spectrum center frequency
  • Resizable interface
  • Full-screen mode
  • MacOS Retina and Windows high-DPI support
  • User-defined default settings
  • Pre-EQ/post-EQ/both spectrum
  • Multi-band selection
  • Multiple display ranges: 3dB, 6dB, 12dB, 18dB, 30dB
  • Output level meter
  • Preset selector
  • 40+ presets for mixing and mastering
  • Undo/redo and A/B switching
  • VST2, VST3, Audio Unit, AAX Native (64-bit)


Minimum System Requirements
  • Intel or AMD CPU with SSE 4.1 instruction set, or Apple Silicon.
  • macOS 11 / Windows 10.
  • 2GB RAM and 300MB disk space.
Plugin Formats Provided
  • 64-bit VST2, VST3, AAX and Audio Unit.
Download & Trial

Activating Kirchhoff-EQ requires you to have a account. If you don't have one, SIGN UP HERE.

After installing Kirchhoff-EQ and logged in with your Plugin Alliance account, you can choose to start a 14-day free trial. A trial license is fully-functional, so you can enjoy all the features of Kirchhoff-EQ. It will be active for 14 days after the first activation. If you are satisfied with the trial, and would like to support us, please come back to Three-Body Tech to get a full license! Learn More.

User Manual
Click to download

Version 1.7.0 (Jul 9, 2024)


- Improved performance on touchscreens.

- New vector font.

- New pitch display in spectrum grab mode.

- Default filter types created by dragging at low and high frequencies now can also be customized.

- Optimized Tilt's edit section.

- Optimized performances of some popup windows.

- Completely revised settings menu.

- New 'Factory Reset Default State' button in settings menu.

- 'Initialize' now renamed to more accurate 'Clear All Bands'; new 'Reset to Default' function.

Bug Fixes

- Fixed an issue that freezes the render thread in certain cases.

- Fixed the issue that corrupted default state file might disable the plugin.

- All knobs and sliders now respond to the 'reverse mouse wheel' setting.

- Operations on Lookahead switch, Output Gain knob and Output Pan knob now can be correctly undo/redo or saved between A/B switching.

- Fixed the audio glitch that might occur following adjustments on band's pan in non-minimum phase modes.

- Fixed the issue that when monitoring certain types of bands, the monitored frequency range won't change along with the Q value.

- Fixed the issue that in full screen mode, removing tracks or plugins in the DAW might cause a crash.

- Fixed multiple display issues in full screen mode.

- Fixed the issue that full screen mode won't be on top in certain DAW's.

- Fixed incorrect scales of menus and popup windows under certain display settings.

- Fixed incorrect mouse dragging behavior on knobs under certain screen resolutions.

- Fixed an issue that the actual cursor position might be inconsistent with the position the plugin responded to when used on multiple screens with different display scales.

- Fixed incorrect spectrum refresh rates in certain special cases.

- Fixed multiple issues under Rosetta translation environment on macOS.

Version 1.6.4 (Mar 28, 2023)

New Features

- Now AAX plugin is available for native Apple Silicon.

- Allow to customize spectrum refresh rate in Global tab of settings menu.

The available values are between 30FPS and the highest refresh rate of your monitor(s). Changes on this setting would affect Kirchhoff-EQ on all instances in real time.

- Added 7 preset themes.


- Rebuilt OpenGL rendering scheme that improves software stability on integrated graphics cards.

Bug Fixes

- Now global scale applies to all menus.

- Now the user manual could be opened correctly through PA licensing toobar.

- Fixed unexpected refresh rate changes when making mouse operations on spectrum panel.

Version 1.6.2 (Mar 08, 2023)


- The inactive knobs of the current filter type are grayed out.

- Sharper Q value of monitoring.

- Slightly improved GUI rendering speed.

- Improved stability in native ARM64 Logic Pro.

- Show CPU type in About page to distinguish native/rosetta translated version.

Bug Fixes

- Fixed the issue that certain parameters does not respond to DAW's automation.

- Fixed occasional high CPU consumption in audio thread.

- Fixed incorrect panel backgrounds.

- Fixed the issue that manually typed output gain and pan values cannot be correctly applied.

- Fixed the issue that copied band cannot be correctly pasted on certain devices.

- Fixed the issue that minus values cannot be typed into certain text boxes.

- Fixed default path for background image customization on Mac.

- Fixed improper popup window in Ableton Live that causes missing plugin.

- Changing Q with mouse dragging now behaves the same with mouse wheel.

Version 1.6.0

- Initial PA Release

List Price: $299

Now $129.99

14-day Free Trial