Virtual audio cable

Why it is needed

An operating system really only understands one concept: the default output device. If a translation tool plays into the default speakers, the audio either gets recaptured by the microphone (creating a feedback loop) or never reaches OBS at all.

A virtual cable provides a dedicated path so translated audio goes precisely to OBS and disturbs nothing else.

Common implementations

• Windows. VB-Audio Virtual Cable is the de facto standard. It ships as donationware and installs one cable (CABLE Input and CABLE Output); the A+B and C+D cables VB-Audio also publishes are separate installers, not extra channels on the first one.
• macOS. BlackHole, with the 2ch build being sufficient. Its repository states plainly that it requires no kernel extension and no changes to system security settings — the driver installs as a HAL plug-in under /Library/Audio/Plug-Ins/HAL/. Pair it with a Multi-Output Device in Audio MIDI Setup if you also want to monitor.
• Linux. PulseAudio and PipeWire provide null sinks natively, so nothing extra is required.

Two configuration mistakes to avoid

Sample rate mismatch. The virtual cable’s playback and recording ends, the translation tool’s output and OBS should all sit at the same rate. Agreement is what matters; which value you pick matters much less, since platform requirements are not uniform and copying someone else’s number is no substitute for aligning your own chain. Mismatches cost you needless resampling and show up as drift over a long broadcast.

Multi-Output Device drift on macOS. BlackHole’s FAQ is specific: enable drift correction on every device in the aggregate except the clock source, and keep the built-in output at the top of the list. Get it wrong and you hear artefacts creeping in half an hour into a stream — easily misdiagnosed as a network problem.