Hello.I recently got a new pair of active speakers (S1000DB), and I'm using both analog (PC) as well as optical (TV). The speakers have two analog inputs, however. One RCA pair is "700mv" and is labeled "AUX", the other is "900mv" and is labeled "PC." My analog source is a PC with a Xonar D1 sound card. I'm not sure which RCA pair to use to connect the 3.5mm line out from the Xonar to the speakers. I would assume I should connect it to the "PC" RCA pair, since the source is a PC, but this produces a quieter signal than the "AUX" and optical inputs.The specs of the Xonar say:Output/Input Full-Scale Voltage, 2 Vrms (5.65 Vp-p)But I don't know what that means... What I can say for sure, however, is that when I connect the optical out of the Xonar to the speakers at the same time as the analog out and switch between the sources, the 900mv PC connector is much quieter compared to the 700mv AUX connector. The 700mv AUX connector is in fact exactly as loud as the optical connector, which (perhaps naively?) makes me believe that's what should be used here, even though the source is a PC sound card.Does someone know which is the correct RCA pair to use here?Edit:The full specs of the sound card are listed here: https://www.asus.com/us/Sound-Cards/Xonar_D1/specifications
The difference between 700 mv sensitivity and 900 mv sensitivity is about 2 dB which is rarely enough to make a significant difference. The one with the higher voltage is going to be little louder all things considered, but you may not be able to reliably hear the difference with rapidly varying audio signals like music. You should be able to use them interchangeably.