Focusrite Scarlett XLR inputs cannot take line-level signals; line sources must use the combo TRS input instead

On Focusrite Scarlett interfaces (at least the 2i2 and 4i4), the XLR side of the combo input is a mic preamp and cannot handle line-level signals; feeding a hot line-level source (like a DJ mixer’s record output) into it overloads the preamp and distorts. Line-level sources must instead go into the TRS side of the same combo socket, which is a line input. In practice you route the mixer’s RCA record-out through an RCA-to-TRS cable into the combo jack. This is a common miswiring error when building a DJ-into-OBS chain and it produces distortion that looks like an OBS problem but is really an input-stage mismatch.

Examples

Wrong: DJ mixer line-out via an XLR cable into the Scarlett’s XLR input → overload/distortion. Correct: DJ mixer RCA record-out → RCA-to-TRS cable → the TRS (combo) input of the Scarlett → clean line level.

Assessment

Explain why plugging a DJ mixer’s line output into a Focusrite Scarlett’s XLR input causes distortion, and specify the correct connector/input to use instead.