Add the overdrive kernel — LGW-voiced feedback soft clipper#22
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The spiritual successor to Jamoma's TTOverdrive, per the overdrive handoff brief: not a port of the old memoryless odd-function curves, but a voiced feedback clipper chasing the class of TS-lineage pedals (Mad Professor Little Green Wonder as the listening reference). - Nonlinearity inside a lowpass feedback loop, solved zero-delay with the house fast one-pass scheme (svf/ladder pattern): LF loop gain pinned so bass stays tight while mids take the full drive — the frequency-dependent clipping a static shaper cannot do. - shape() = u/sqrt(1+u^2) (smooth, rsqrt-vectorizable, LUT-able for a future fixed-point port); asymmetry bias for even harmonics; unity clean-through so the transfer never flattens; always-on DC blocker (Jamoma R = 0.9997) since asymmetry generates DC. - body voicing control: pre-clipper HP corner slide + CW upper-mid push + CCW treble lift, all linear EQ; voicing constants are by-ear placeholders pending the in-Max pass. - 1/2/4/8x oversampling (default 4x), normalized 0..1 parameters (Q-format friendly), ramped click-free setters, multichannel frame protocol. - Catch2 tests pin the design goals: gain-tilt-vs-drive, even-harmonic emergence, DC blocking, never-flat slope, alias-floor improvement, body tilt, decay to silence, determinism, clamping. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S3twSGfwUK8jnUhp5Qx6wx
Completes the house treatment for the new overdrive kernel: - tools/capi: taptools_od_* functions (create/prepare/set/oversample/ smooth/clear/process) over tap::tools::od::overdrive, mirroring the other parameter-indexed kernels; taptools_py.py gains the Overdrive ctypes class. - notebooks/overdrive.ipynb (executed): drives the shipping kernel via the C ABI and measures the design goals — the feedback loop's gain tilt growing with drive (+5/+16.3/+17.2 dB at drive 0/0.5/0.9 between 80 Hz and 4 kHz), the never-flat transfer, even harmonics vs asymmetry (H2 -151 dB at 0, -26 dB at 0.6), the alias floor at 1x vs the default 4x (folded H7 -22 -> -36 dB), the body voicing shape, and DC blocking (means ~1e-10 at full drive/asymmetry). - book: 'Distortion with a memory' (new Part VI — The pedalboard) and the machine deep-dive 'The clipper in the loop: overdrive.h' (the zero-delay solve derivation, why the unit-delay loop limit-cycles, the shaper choice, oversampling-vs-ADAA rationale, and the honestly- labeled voicing placeholders); machine part renumbered to VII; introduction and README updated. Every number in the chapters is an executed notebook cell or a kernel suite assertion. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S3twSGfwUK8jnUhp5Qx6wx
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Jul 23, 2026
The kernel PR (tap/TapTools#22) merged via rebase — main's tree is identical to the branch tip this PR previously pinned. Repointing keeps the pin reachable after kernel branch cleanup, per the kernel repo's release flow. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S3twSGfwUK8jnUhp5Qx6wx
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Summary
The spiritual successor to Jamoma's
TTOverdrive— not a port. Both legacy modes were memoryless odd-function waveshapers applied to the full spectrum; this is a voiced feedback soft clipper chasing the class of TS-lineage pedals (Mad Professor Little Green Wonder as the listening reference), per the overdrive handoff brief.include/taptools/overdrive.h(tap::tools::od):svf.hdriven-circuit /ladder.hsolver_fastone-pass scheme). The naive one-sample-delay loop limit-cycles at high drive (|J| > 1 above drive ≈ 0.9); the implicit solve is stable at any loop gain.g_fb = G/k_lf_gain − 1) so bass stays tight and near-clean at any drive while mids take the full gain — the frequency-dependent clipping a static curve cannot produce.shape(u) = u/√(1+u²): C∞ (no curvature seam to alias), monotonic, rsqrt-vectorizable, LUT-able for a future fixed-point port.asymmetrybias for even harmonics; unity clean-through so the transfer never flattens; always-on DC blocker (R = 0.9997, the TTDCBlock constant — load-bearing this time);bodyvoicing (pre-clipper HP corner slide + CW upper-mid push + CCW treble lift, all linear EQ); 1/2/4/8× oversampling (default 4×); normalized 0..1 parameters (Q15/Q31-friendly for embedded targets); ramped click-free setters; multichannel frame protocol.k_voice_*constants are by-ear placeholders pending the in-Max voicing pass against LGW demos — labeled as such in the header, the notebook, and the book.Verification layer (per house rules):
tests/overdrive_test.cpp— 11 Catch2 cases pinning the design goals: gain-tilt-grows-with-drive, even-harmonic emergence/absence, DC blocking, never-flat slope, alias-floor improvement, body tilt, decay to silence, determinism, clamping.tools/capi+taptools_py.py—taptools_od_*C ABI and theOverdrivectypes class.notebooks/overdrive.ipynb— committed executed: tilt +5/+16.3/+17.2 dB (drive 0/0.5/0.9, 80 Hz→4 kHz); H2 −151 dB → −26 dB across asymmetry; folded H7 −22 → −36 dB at 4×; DC means ~1e-10.Rebased on latest
main(integrates cleanly beside thetune.hwork: shared SUMMARY/capi/ctypes merge points resolved keep-both;submodules/dsptappin untouched vs main).Testing
ctest(including the new overdrive cases: 652k assertions).The consuming TapTools-Max PR bumps the submodule pin to this branch's head.
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https://claude.ai/code/session_01S3twSGfwUK8jnUhp5Qx6wx
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