Contour

An on-the-go EQ manager for the CrinEar Protocol Micro, Protocol Max, FiiO KA15 and FiiO K13 R2R. Keep all your EQ profiles on your phone, plug the dongle in, pick one and send it. Plug in, send, unplug - that is the whole routine.

Website: contoureq.app - a 1.5-minute demo film, the full guide film and the install page.

  

Why it exists

The Protocol Micro, Protocol Max, KA15 and K13 R2R have a parametric EQ built into the DAC itself. Whatever EQ a DAC holds works with every app and every device you plug it into - no system equaliser, no app running in the background. But the official way to change it on the Protocol dongles is CrinEar's browser tool at eq.hangout.audio, which the maker lists for desktop (PC and macOS) browsers. There is no official mobile app, and phone browsers lack the WebHID support the tool relies on - so in practice you need a computer nearby.

Contour puts that on your phone. It is deliberately a small, simple tool:

• Your EQs are saved. One profile per pair of earphones, or per mood. They live on the phone, ready whenever the dongle is plugged in.
• Sending takes seconds. Plug the dongle in, tap a profile, hold HOLD TO SEND. Contour writes it, reads it back to check every value, and stores it in the dongle's memory.
• Then the phone is out of the picture. Unplug the dongle and use it with your laptop, another phone or anything else. The EQ stays in it until you send another one.
• Real examples to start from. The first launch includes NIGHTFALL, the maintainer's own tuning for the CrinEar Nightfall, and DUSK, the default curve of Moondrop's DSP cable for the Moondrop x Crinacle DUSK (so the analog cable sounds like the DSP one), next to a flat PROFILE 1.
• You can still tune on the go. Drag bands on the graph, fine-tune with sliders, paste an AutoEQ profile from the clipboard, or read the current EQ off the dongle.

Contour does not process audio, does not need the internet and has no accounts. It only talks to the dongle.

Watch the guide: every function of the app in a 6-minute film, with chapters and the full text.

Supported hardware

• CrinEar Protocol Micro (USB 3302:C20F, WalkPlay chip): 8 bands, PEAK, LOW SHELF and HIGH SHELF, gain -10 to +10 dB, Q 0.1 to 10, 20 Hz to 20 kHz, preamp -30 to 0 dB in whole dB. Tested on the developer's own hardware.
• CrinEar Protocol Max (USB 3302:43CC, WalkPlay chip): 10 bands, PEAK, LOW SHELF and HIGH SHELF as native filters, gain -10 to +10 dB, Q 0.1 to 10, 20 Hz to 20 kHz, preamp -30 to 0 dB in whole dB, computed and sent by the app. Tested by a Reddit community member on a real Protocol Max (8 bands, peak and shelf filters, no crashes). Large HIGH SHELF boosts at lower frequencies don't fit the Max's filter format; since 1.4.0 Contour refuses them with a message instead of sending them.
• FiiO KA15 (USB 2972:0104, FiiO protocol): 10 bands, PEAK, LOW SHELF and HIGH SHELF, gain -12 to +12 dB, Q 0.1 to 10 (shelves up to 7.07), 20 Hz to 20 kHz, preamp -24 to 0 dB. Pick USER1, USER2 or USER3 above HOLD TO SEND; Contour writes the profile to that slot and names the slot after it (up to 7 letters and digits). Long-press a slot to rename it. The KA15 answers only while audio is streaming to it, so Contour plays a silent stream to it while it reads or writes (no audio focus, your music keeps playing). Tested on the developer's own hardware. The KA15 plays its shelf filters with a Q 1.41 times lower than the value it stores, and every USER preset 12 dB quieter than EQ off. Since 1.3.3 Contour compensates both, so the curve and preamp you see are what it plays (measured on the device, see research/protocol/PROTOCOL.md). The FiiO app shows the stored values, so its shelf Q and preamp look higher.
• FiiO K13 R2R (USB 2972:0120, FiiO protocol, desktop DAC/amp): 10 bands, PEAK, LOW SHELF and HIGH SHELF, gain -24 to +12 dB, Q 0.1 to 10, 20 Hz to 20 kHz, preamp -24 to +12 dB. Pick USER1 to USER10 above HOLD TO SEND; Contour writes the profile to that slot and makes it the active one. The slots keep their USER names (Contour does not rename K13 slots). The K13 always holds ten bands, so a shorter profile is filled up with flat 0 dB bands. Writes are paced 300 ms apart, so a send takes about five seconds: faster writes read back fine but did not survive turning the K13 off. BYPASS and the stock presets are chosen on the K13 itself. Tested on the developer's own hardware; the read-back checks the stored values, the sound has not been measured yet.

Contour is unofficial and not affiliated with CrinEar or FiiO. Other WalkPlay and FiiO dongles are possible later (see ROADMAP.md); they are not enabled until someone confirms one on real hardware.

Needs Android 9 or newer and a phone with USB host (USB OTG) support.

At a glance

Two pages, switched with the bar at the bottom or by swiping: EQ and LIBRARY.

• EQ edits the current profile: drag, tap, double-tap and pinch band nodes on the graph; PEAK, LOW SHELF and HIGH SHELF filters; FREQ, GAIN and Q sliders that are fine when you drag slowly and cover the whole range when you drag fast; tap any number to type it; tap the selected band chip again to bypass or delete the band, or delete it with the minus chip; PREAMP with a MANUAL / AUTO anti-clipping bar; A/B to hear the curve off and on at the same volume (the preamp stays; Protocol Micro only for now).
• HOLD TO SEND (0.7 s hold) writes the profile to the dongle, reads it back, compares every register and only then saves it to the dongle's memory. The button then shows ON DAC.
• Undo and redo work like Ctrl+Z: one touch is one step, up to 100 steps per profile, kept after closing the app. CLEAR EQ leaves one flat band and is an undo step too. LAST SENT appears when the profile differs from what the dongle holds, and goes back to that version.
• LIBRARY keeps your profiles: tap to open, long-press to rename, change the icon, duplicate or share; swipe to archive or delete, with UNDO. New profiles start flat, come from the clipboard or a .txt file (Equalizer APO, AutoEQ, squig.link or graph.hangout.audio parametric text, or EQ by Ear JSON; Contour also shows up in Open with and Share for .txt files) or are read from the dongle. SAVE .TXT saves a profile as a file in the squig.link format.

On the Protocol Micro only, HIGH SHELF bands are sent as a mirrored LOW SHELF plus preamp, which gives exactly the same curve shape (the Protocol Max, KA15 and K13 R2R have native shelf filters and need no mirroring) (the maths is in android/core/src/main/kotlin/io/github/chronosauros/contour/core/Device.kt).

Safety

Contour writes to the DAC only when you hold HOLD TO SEND (or confirm an action on the service screen). It sends only commands documented in research/protocol/PROTOCOL.md, checked on a real device, and verifies every write by reading it back. Every value is rounded toward quieter, never louder, and a band or preamp the dongle can't store as asked is refused before anything is sent. Still, this is an unofficial tool talking to hardware: use it at your own risk (see the warranty disclaimer in LICENSE).

Install

Step-by-step instructions: contoureq.app/install

• Obtainium (recommended, updates itself): in Obtainium tap Add app and paste https://github.com/Chronosauros/contour, or on your phone tap Add Contour to Obtainium.
• APK: download contour-<version>.apk from the latest release and open it on your phone (Android asks you to allow installs from that source).

Every official build is signed by the same key: package io.github.chronosauros.contour, certificate SHA-256 C8:C8:CA:EA:76:16:28:ED:9D:50:5F:F0:73:42:EE:5E:A0:D4:66:A4:AD:71:8D:0D:B0:77:42:2B:A3:F7:E6:01 (CN=Chronosaur). Each release also lists the APK's SHA-256. The guide takes it from there.

Build

Requirements: JDK 21 and the Android SDK (platform 37.2, build-tools 36 or newer).

cd android
./gradlew :core:test            # protocol and codec parity test
./gradlew :app:assembleRelease  # unsigned release APK in app/build/outputs/apk/release/
./gradlew :app:assemblePerf     # review build (package ...contour.perf, debug-signed, profileable)

android/wsl-build.sh wraps the same tasks for Linux / WSL with the paths from android/toolchain.env (copy toolchain.env.example). The release APK is unsigned unless you pass your own key, see android/app/build.gradle.kts.

Code layout:

• android/core - pure Kotlin/JVM: profile model, DSP, text codecs, the WalkPlay and FiiO (KA15, K13 R2R) device protocols;
• android/app - the Jetpack Compose app, USB HID transport, storage;
• research/protocol - protocol notes, Python reference tools and the device captures the parity test checks against.

Privacy

Contour has no internet permission, no analytics and no accounts. Profiles stay on the phone. See PRIVACY.md.

Contributing

Issues and pull requests are welcome, especially reports from other WalkPlay-based DACs. Read CONTRIBUTING.md first.

Licence and credits

Contour is licensed under the Apache License, Version 2.0 (LICENSE).

The WalkPlay and FiiO protocols and the biquad coefficient maths are ported from devicePEQ by Jerome O'Flaherty (0BSD). Every third-party component and its licence is listed in THIRD_PARTY_NOTICES.md; attributions are in NOTICE. The DUSK example profile uses the DUSK-Default DSP curve published by Crinacle. In the app, all of this is under ABOUT & LICENCES at the bottom of the Library.

Contour is an unofficial project, not affiliated with or endorsed by CrinEar, FiiO or any other brand. CrinEar, Protocol Micro, Protocol Max, FiiO, KA15, K13, Nightfall, WalkPlay, Moondrop, Crinacle, DUSK and other product names belong to their owners and are used only to say what Contour works with.