I'm starting this thread with the intent it can be referenced from the archives, so I'm looking for info about how/why to identify and correctly match impedances of various equipment. Example #1: High impedance inputs for passive bass pickups Example #2: Preamp 1/4" TS unbalanced out to Power Amp in. Example #3: Preamp XLR balanced out to Power Amp in. Example #4: Preamp 1/4" TS unbalanced out to Sound Card in. #1: Passive pickups require a high impedance input, or the tone degrades. Multiple pickups, volume and tone pots in a passive circuit reduces the impedance and degrades the tone. #2: QSC specifies input impedance as 6K unbalanced, and 12k balanced. How does a typical unbalanced preamp-out operate with this? #3: Rane typically uses a 20K input impedance, but only a 100 ohm output impedance. How does this 100-ohm output impedance interact with the 12k input of the QSC PLX? #4: Going DI from the preamp into a high quality sound card should sound good, but often does not. Is the problem simply a voltage mismatch, or is there also an impedance issue? Pro audio and consumer equipment use different dB systems. Matching voltages is only part of it. How are they interfaced correctly?