Parallel resistor in line level output
I have a MONO LINE LEVEL OUTPUT and I want to share it with 2 devices (which will received the LINE LEVEL OUTPUT and use it for whatever reason). In one of those devices I need to use a 10K potentiometer in order to control the signal level that goes to one of those devices. See my drawing below, please.
My question is: does this 10k potentiometer affects the signal on device 1? I mean, will the signal get lower OR lose any bass? I am asking this, because as I am seeing, the potentiometer that was added is in parallel between + and -, so I think it should affect a little bit device 1 but I am not sure because I am pretty sure that devices 1 and 2 have high input impedance, so maybe this 10k resistor would not affect (less than 1%). But what do you think?
There is a resistor to the left of the + sign on the left side, and it is called the output impedance.
if the output impedance is 10k, then the signal will drop by 1/2 - which is 3dB… (or maybe 6dB as power is voltage^2). |
Honestly, 10k is a fine output impedance for gear designed for 600, but is it different? If the two devices on the right are in the 40k range, then yes. You'll be dropping the impedance a lot. Remember that parallel impedance is never higher than the smallest number. In this case though if you had 2 x 40k sources you'd start wiht a 20k effective output that then gets cut to ~ 6.7k. The formula for parallel impedance is 1 / ( ( 1/r1) + (1/r2) + (1/r...) ) |
I would run without the potentiometer if the system #2 has a volume pot. But it only might make a slight difference to the sound if the cables are getting high in capacitance. As @erik_squires mentioned… You probably want to say what the output impedance is, and what the two devices on the right have the input impedance spec at. |
