Audio Devices

Configure audio input and output sources for the modem

Audio devices are the physical (or virtual) sound interfaces that graywolf’s Rust modem uses to receive and transmit audio. Each radio channel is bound to an audio device for input and optionally one for output.

Audio device cards show direction, path, sample rate, level meters, and gain controls

Detect Devices

Click Detect Devices at the top of the page to scan attached sound cards and pre-fill an entry. Adapters that graywolf recognises as a known APRS interface (Digirig, AIOC, SignaLink, and so on) are flagged as Recommended so you can pick them with one click. You can still use + Add Device to enter a device manually.

Across the top of the page graywolf tells you whether Receive and Transmit are ready. A green light on Transmit means there’s an output device configured — you also need PTT set up before the rig actually keys, and the page reminds you of that right there.

Source Types

Device Settings

Soundcard Setup

For a typical setup with a USB sound card connected to a radio, create an input device and (if transmitting) an output device. The source_path should match the ALSA device name as shown by arecord -l or aplay -l.

Channel Selection

Audio devices are always configured as mono. If your sound card only supports stereo, Graywolf automatically opens it in stereo and extracts a single channel. You can select which channel to use via the input_channel setting on the radio channel (0 = left, 1 = right). This lets you monitor two radios on a single stereo sound card by assigning each radio channel to a different stereo channel.

Test Tone

Each output device has a Test Tone button on its card. Press it to send a short test tone out the radio — useful for verifying that PTT keys, deviation is in spec, and audio reaches the air. Watch the LEVEL meter on the card while it plays.

Software Gain

The gain_db setting applies digital gain to the audio stream before it reaches the demodulator. Use this to compensate for sound cards with very low or very high output levels. Positive values amplify the signal; negative values attenuate it.

Windows: only hearing carrier when transmitting?

A common Windows-specific failure mode looks like this: PTT keys the radio, but the receiving station hears only an unmodulated carrier — no AFSK "brap" tones. The radio is being keyed correctly; the problem is that no audio is reaching the radio's mic input.

In almost every reported case the cause is one of three Windows-side volume settings being muted or set to zero, even though the device itself is enabled and selected as Graywolf's output:

1. Per-application volume. Right-click the speaker icon in the system tray and choose Open Volume mixer (or Settings → System → Sound → Volume mixer). Find the Graywolf entry under the output device you assigned to the channel and confirm it is not muted and not at zero. Windows remembers per-app volume independently of device volume, and it can silently sit at 0%.
2. Device master volume. In the same Sound panel, click the output device itself and verify its master volume is up and not muted.
3. Sound control panel "Levels" tab. Open the legacy Sound control panel (mmsys.cpl), right-click the output device, choose Properties → Levels, and confirm the slider is up and the speaker icon next to it is not crossed out.

Also worth checking: if you're using a SignaLink USB or any external interface with a hardware TX potentiometer, that pot must be turned up — rotated fully closed it produces the same "carrier only" symptom. Start with it at the 12 o'clock position and adjust from the Test Tone button on this page.

Hot Reconfiguration

Audio devices can be reconfigured without restarting graywolf. After changing device settings in the web UI, use the Reconfigure button (or POST /api/audio-devices/{id}/reconfigure) to apply changes immediately. The modem will briefly pause audio processing during reconfiguration.