Plugins built where engineering meets the creative process.
091Audio is a small plugin project built at the intersection of software engineering and music production. The plugins come from different places — some from hardware behaviors worth translating into DSP, some from production problems worth solving differently. What they share: a focus on the creative phase, and on staying out of the way.
Conversations with producers and other developers shape what gets built — HighpassDoctor, the first release, started exactly that way.HPDoctor is the first release from 091Audio — a free highpass filter plugin with seven selectable filter types. It came out of a conversation with Ronny Pries, who needed more flexibility than existing tools offered... more.I'm also available for freelance audio software projects — plugin development, DSP consulting, or custom tools. Details on the about page.
Plugins
Precision low-frequency processing — 1 to 150 Hz.
Most high-pass filters stop at 20 Hz and offer a limited set of slopes and filter types. HPDoctor goes down to 1 Hz, covers fractional slopes from 1 dB/oct up to 24 dB/oct, and includes seven filter types for different sonic and phase characteristics. A focused utility for situations where a regular HPF isn't precise enough.The idea and the design was provided by Ronny Pries.Applications
- Removing DC offset without touching the audible low end
- Cleaning up subsonic energy before compressors
- Shaping kicks and bass with resonance around the cutoff
- Console-style high-pass emulation
- Mastering cleanup where precision matters
- Phase manipulation and alignment via the allpass modeFeatures
- Frequency range: 1–150 Hz
Slopes from 1 dB/oct up to 24 dB/oct (type-dependent)
- Seven filter types: Butterworth, Elliptic, Chebyshev I, Chebyshev II, Bessel, Ladder, Allpass
- Optional "Const -3 dB" mode for consistent cutoff behavior across filter types
- Full 64-bit double-precision internal processing
- Click-free transitions for all parameter and filter changes
- Formats: VST3, AU
- Platforms: Windows, macOS (signed), LinuxMany thanks for testing and feedback to:
JoaChip https://www.robotplanet.dk/
Mattias Fridell https://mattiasfridellmastering.com
About
091Audio is the audio plugin project of Andy Leuckert from Chemnitz. As a software developer working in post-processing of measurement data, bringing my engineering background and my passion for music production together has been a long-term goal. Parts of my day job touch DSP as well — where accuracy is critical and artifacts are problems to eliminate. Audio is the complementary space where some of those "imperfections" can become musically useful.As a musician I always wanted to understand how effects actually work under the hood. Plugin development is where those two worlds meet for me.
The plugins are built from real production needs, often refined through discussions with the audio community.
The focus is on the creative phase — reducing distractions and avoiding overly technical decision-making.
I'd be grateful if my plugins made your creative life a little easier or more fun.Freelance work
Alongside the plugins, I'm open to freelance projects in audio — plugin development, DSP consulting, custom synth or sound design work, and audio analysis. If something like that fits your needs, feel free to get in touch. If something like that fits your needs, feel free to get in touch
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Contact me
Looking to collaborate or have a question?Feel free to write to me using the form below. I read and reply to all my emails.