David Christensen wrote: > On 9/20/26 18:46, Roy J. Tellason, Sr. wrote: > > On Saturday 19 September 2026 03:59:18 pm David Christensen wrote: > > > ... > > > When using analog audio devices, ensure that the impedance is matched > > > for all devices in the signal chain. ... > > > > ... It's not a matter of impedance but more what signal levels are > > expected to be found at a given point. > > > To me, the term "signal level" covers voltage and application (e.g. > "consumer audio", "pro audio", etc.); while the term "impedance" covers > voltage and current, and is more fundamental to all electrical circuits:
The two are related here: a change in the impedance will cause a frequency-dependent change in the power of the circuit, which can in practice as well as in theory change the audible frequency response. The article: https://en.wikipedia.org/wiki/Line_level should be of use. Second paragraph: Generally, line-level signals sit in the middle of the hierarchy of signal levels in audio engineering. There are weaker signals, such as those from microphones (Mic Level/Microphone Level) and instrument pickups (Instrument Level), and stronger signals, such as those used to drive headphones and loudspeakers (Speaker Level). The strength of these various signals does not necessarily refer to the output voltage of the source device; it also depends on its output impedance and output power capability. A headphone output is typically handled by a volume control which affects the voltage swing. Headphones and most cheap powered speaker systems want this, mostly via 1/8" (3.5mm) stereo jacks. A "line-out" will not have a volume control and should always provide a full "line-level" signal. If you are feeding to a powered speaker system with its own volume control, or a preamplifier (or integrated amplifier or receiver), line-level is what it will be expecting. The PC side is likely to be another 1/8" (3.5mm) jack, but sometimes it is a pair of RCA jacks. The receiving end is almost always using RCA jacks. Nobody has recently been silly enough to put a speaker-level power amplifier inside a PC case, so that won't be of concern. -dsr-
