Open control for the t.racks DSP 4x4 Mini Pro over USB-OTG.
About this app
openDSP-4x4 is an open-source control app for the t.racks DSP 4x4 Mini Pro, a 4-in / 4-out XLR digital signal processor that otherwise ships with Windows-only editor software. It lets you set the DSP up from an Android phone or tablet — at the desk or on stage — connected over USB-OTG.
The control protocol was reverse-engineered clean-room, purely by observing the device's USB-HID traffic and probing it (write a known value, read it back, match the bytes). The same protocol drives a zero-install desktop web app (WebHID) and this Android build. On Android the UI runs in a WebView and reaches the device through a small native USB-host layer, because no Android browser can talk to a HID device.
Features:
* Input/output routing matrix. * Gain, mute and polarity per channel. * 7-band parametric EQ with high- and low-pass crossovers. * Compressor, gate and output delay. * Preset recall and store (7 device slots) as quick launch pads. * Live input/output meters and full device-state read-back on connect.
Privacy:
* No analytics, no telemetry, no network connections — the app talks only to the DSP over USB.
Plug the DSP into the phone with a data-capable USB-OTG cable, tap Connect, grant the USB permission, and the app reads the device's current state and is ready to edit.
Independent, clean-room interoperability project. "the t.racks" is a trademark of Thomann; this app is not affiliated with or endorsed by Thomann.
Licensed under AGPL-3.0-or-later, by Ian Williams.
What's New in v0.2.2
Imported from the F-Droid repository index.
Version history
Jun 24, 2026 · 1.6 MB · Android API 24–35 · code 6
Imported from the F-Droid repository index.
SHA-256 7a6b5f09519db1551fa6257001dcca5b87afc54d06347e0d01ad4b66987084f7
Will it run on your device?
78%
- Runs on a broad range of modern Android versions.
- ABI coverage is focused on newer 64-bit devices.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be net.opendsp.x4x4 is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
No earlier build is on record for openDSP-4x4, so there is nothing to roll back to yet. When a second version is published, this section will explain how to move between them safely.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of openDSP-4x4, and a listing is removed when the evidence for it stops holding up.
Get openDSP-4x4
Every source we list for net.opendsp.x4x4 is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
7a6b5f09519db1551fa6257001dcca5b87afc54d06347e0d01ad4b66987084f7
Signing certificate
12b4463c8a6a356c64a743ed912a047b05a210f113829de15c71b748e63fe2a1
Permissions Required
Previous Versions
No earlier build is on record — this is the first release we have listed.
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
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