CA-72 0.3.1

Cleaner driven HI output and LO filter modulation, lower CPU use in ULTRA, and fixes for contour solves, Windows stack use and quality switching.

Install

Close CA-72 and your DAW before installing, then rescan plug-ins. Back up important projects before updating: the DSP changes below can change their rendered sound. The Windows installer is unsigned; Windows may require More info → Run anyway. Installation details are in the README.

Changes

• ULTRA uses High Fidelity numerics to reduce CPU use, with No Compromises retained as the
  lab reference. ULTRA is not bit-identical to 0.3.0; nonlinear feedback can diverge.
• HI reduces high-note and driven-output aliasing by running its open-loop VCA at 2x
  between decimator stages. FEEDBACK closes through the exact circuit preamplifier at 4x.
  HI uses more CPU than 0.3.0, especially with FEEDBACK. The 2x path retains more driven
  aliasing than the experimental 4x path, while improving substantially over 0.3.0.
• LO reduces aliasing from audio-rate filter modulation by evaluating its nonlinear
  cutoff law at 2x, and keeps the resonance limit intact across DRIVE updates.
• Contour and V-trig solves converge without the previous solver-limit spikes and caps.
  This corrects numerical behavior; the note-priority and retrigger policy stays the same.
• The circuit preamplifier eliminates linear-only nodes before solving its nonlinear
  system. Exact oscillator conversion caching and other calculation savings reduce
  repeated work without replacing the circuit equations.
• Factory HI AUTO GAIN curves are measured again. Shared HI/ULTRA curves also change the
  level of some newly selected ULTRA factory presets. Preset LEVEL values stay as set;
  saved projects retain their saved curves and settings, but the DSP changes above can
  still change their rendered sound.
• Worker-template cloning uses less stack on Windows, including when a host starts an
  instance on a thread with only 256 KB of stack.
• Switching HI and ULTRA during a held note transfers the active VCA state and warms
  its entering output history, avoiding a dropout from resuming an idle signal path.
• RETRIGGER's tooltip explains its interaction with NOTE PRIORITY. Reported latency stays
  86 samples in every quality mode.

CPU improvements depend on the patch, quality, voice count and computer. Dense ULTRA
feedback patches can still exceed the available callback time; this release does not
guarantee a particular real-time voice count.

Known issue

REAPER VST3 parameter editing (#146): a report against version 0.3 describes knobs reverting when the mouse is released in REAPER 7.83. This release does not include a fix; standalone and CLAP were reported unaffected. The operating system and root cause are not yet established. Use CLAP in REAPER if affected.

Verification and sources

The release source is commit 5090ae873430ae018ef869096625cacb113325ce. Its tree matches the signed Mac candidate tested by the owner. Platform CI, Mac signature/notarization checks and the installer smoke test passed.

SHA256SUMS.txt lists checksums for the installers, Windows ZIP, retired presets and dependency-sources archive. THIRD-PARTY-NOTICES.txt contains third-party licenses. CA-72-0.3.1-git-sources.tar.gz contains the git-pinned dependency sources; CA-72's own source is this repository at v0.3.1.

Free software under the GNU General Public License, version 3 or later. Copyright © 2026 Idle Foundry Ltd.