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Virtual Audio Cables

RFWhisper emits clean audio to a virtual audio cable. WSJT-X, fldigi, JS8Call, your rig's logging software, or your headphones then read from that cable.

Picking one​

OSRecommendation
WindowsVB-Cable (free donationware). Add Voicemeeter if you want multi-app routing.
macOSBlackHole 2ch (brew install blackhole-2ch).
Linux (PipeWire)Native loopback via pw-loopback.
Linux (JACK)qjackctl + JACK modules.
Linux (classic ALSA)sudo modprobe snd-aloop.

Windows · VB-Cable​

  1. Download from https://vb-audio.com/Cable/. Run installer as Administrator.
  2. Reboot (VB-Cable installs a kernel audio device).
  3. In Sound settings, set CABLE Input as RFWhisper's output device.
  4. In WSJT-X → Settings → Audio → Input: pick CABLE Output.
  5. To hear it yourself: in Sound Settings → CABLE Output → Properties → Listen → Listen to this device → Speakers.

Multi-app routing​

For more than one listener app (WSJT-X + JS8Call + speakers), install VB-Voicemeeter Banana and use its virtual I/O bus. RFWhisper emits to a Voicemeeter input; each app reads from a dedicated Voicemeeter output.

macOS · BlackHole​

  1. brew install blackhole-2ch (or download from the site).
  2. Open Audio MIDI Setup.
  3. + → Create Multi-Output Device, check BlackHole 2ch and MacBook Pro Speakers (or your external DAC).
  4. Rename to RFW-Listen.
  5. Select RFW-Listen as the system output when you want to hear RFWhisper through your speakers as well.
  6. In RFWhisper: --out "BlackHole 2ch".
  7. In WSJT-X: Input = BlackHole 2ch.

BlackHole 16ch​

Install the 16-channel variant if you want to run multiple independent RFWhisper pipelines simultaneously (e.g. HF SSB and VHF FM denoisers side by side).

Linux · PipeWire​

Modern distros ship PipeWire. Create a virtual sink:

pw-loopback \
  --capture-props='media.class=Audio/Sink'   \
  --playback-props='media.class=Audio/Source' \
  &

Then:

rfwhisper denoise-live --in hw:0,0 --out "loopback" --profile ssb

WSJT-X will see the loopback as a normal input.

Linux · JACK​

  1. sudo apt install qjackctl jackd2 pulseaudio-module-jack
  2. Start QjackCtl → Start.
  3. Create a virtual output port (RFW → WSJT-X).
  4. RFWhisper uses PortAudio's JACK backend automatically if JACK is running.

Linux · snd-aloop​

Lightweight, zero dependencies:

sudo modprobe snd-aloop enable=1 index=10
# Now two devices: Loopback,0 (playback) and Loopback,1 (capture) — symmetric

rfwhisper denoise-live --in hw:0,0 --out hw:10,0,0 --profile ssb
# WSJT-X input = hw:10,1,0

Persist across reboots by adding snd-aloop to /etc/modules-load.d/snd-aloop.conf.

Why not just use the system default?​

Because:

  1. You'd lose the ability to hear raw audio simultaneously (for A/B).
  2. The denoise → decoder chain would fight whatever system mixer is doing in the background.
  3. Many decoder apps only accept a specific input device, not the system default.

A virtual cable is 2 minutes of setup and you get it back tenfold in reliability.

Troubleshooting​

  • Silent output — check sample rate of the virtual cable matches RFWhisper (48 kHz).
  • Crackles / dropouts — raise blocksize (--blocksize 960), confirm nothing else on the machine is grabbing real-time scheduler priority.
  • Double audio — one of the listeners has loopback monitoring enabled; turn it off in that app's settings.