Begin at the source output
A passive guitar pickup and a keyboard’s line output present different signals to an interface. The interface may offer a shared jack with selectable line and instrument modes, or separate inputs. PreSonus distinguishes these signal levels in its input guidance; the correct mode must match the source. The plug fitting into the socket does not decide which mode is correct.
Read the output label and manual of the source. A synthesizer, mixer, or effects unit may provide line-level audio, while a guitar connected directly generally needs the appropriate instrument input. A pedal chain can complicate the answer, so check the final device in the chain rather than assuming everything attached to a guitar remains the same kind of output.
Make the channel assignment explicit
For a stereo keyboard, connect its left and right outputs to two suitable line channels if stereo recording is intended. Select those channels correctly in the application. A single balanced mono input is not a stereo input just because it accepts a TRS plug. Use the source’s documented mono output arrangement if recording only one channel.
With the correct mode selected, set gain during the loudest expected passage. If the signal is weak or distorted, verify the source’s output setting and cable wiring before changing modes as a workaround. A mismatch can remain even when a gain knob makes the meter look plausible.
Keep a record of mixed-source sessions
When one interface channel records a guitar and another records a keyboard, label the channels and note their modes. Some interfaces display the selected channel’s settings rather than every setting at once. Confirm each channel individually before recording. Recheck after recalling a preset or connecting a different instrument.
Do not connect a power amplifier’s speaker output to either input type. Speaker-level signals need a specifically supported recording arrangement, not a line/instrument switch. For ordinary home sessions, a simple source-to-input note prevents most confusion: name the device, its output, the cable, and the interface mode. That is more reliable than remembering where the gain knob happened to be last time.
