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I have two audio systems, one in my living room and one in my office. My sound system in the living room is a Teufel Concept E450 Digital which sadly isn't compatible with receivers (since it's a complete system there's a filter so external sub-in simply doesn't work - I tried everything). I currently don't have the money to upgrade my stuff to an HDMI compatible solution so I wanted to go with a budget solution: I found this tutorial for a 5.1 switch box. As of now I actually just need the front and mid/sub channel as I don't use rear on either sound system.

The tutorial is great but there's a downside: I'm certain that when I switch the channels using this and forget that one of my systems volume is up, I probably die from popping sounds.

So I'd like to avoid this. I asked a friend of my parents' who told me that I basically only need a resistor and a capacitor which compensates the voltage changes when flipping the switch. It's been a long time since I worked with electronics and I'm not really sure where to start here. Can you give me some hints what I should focus on learning (besides the basics obviously)? I'm not sure what I have to take into consideration when it comes to analog audio signals, switching them and so on.

I do have a blueprint which I don't fully understand though. I guess this project shouldn't be too difficult, but I really need to freshen up my knowledge about electronics here. So any help and hint is appreciated.

"Blueprint"

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    \$\begingroup\$ Read a couple of times but I still have no clue as to what you are trying to do. \$\endgroup\$
    – Andy aka
    Dec 23 '20 at 16:05
  • \$\begingroup\$ I want a box with some switches where I can switch my 2.1 (or 5.1 would be just another channel) input to either Output A or B without having popping noises when switching. The picture was given to me but I don't understand it especially since the units on the resistor seem to be actually those for the capactitors and those are missing them at all. I just want to understand how to do this. No need for a all-in-one solution but help understanding it would be appreciated. \$\endgroup\$
    – SharpShade
    Dec 23 '20 at 16:25
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    \$\begingroup\$ What voltages and currents are associated with inputs that you mention (2.1 (or 5.1 would be just another channel) input)? What is the purpose of switching them and what equipment are you switching those signals to (in terms of load impedance or maybe another piece of equipment). I mean $$$$ 1) I have no idea what you are trying to do and, $$$$ 2) Your circuit diagram conveys no particular meaning. $$$$ 3) What is this blueprint thing you mention? $$$$ 4) The link to a switch box doesn't tell me what the thing does. \$\endgroup\$
    – Andy aka
    Dec 23 '20 at 16:36
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The addition of the capacitors (“AC-coupling”) will solve the problem of different DC offsets that your sources boxes may or may not have. If you use a non-polarized electrolytic capacitor you don’t have to use a polarized capacitor and guess which way the DC offset may be.

This should solve any pop when switching between two idle sources with DC offsets but won’t do anything to lessen the blow when switching abruptly between two active signals.

enter image description here

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  • \$\begingroup\$ Thank you very much, that does help a lot. Is it complicated to avoid audio pops when switching between active inputs? Is there an easy way, otherwise I'll stick to that plan (no popping when idle is already something and usually I don't switch active sources anyway - would just be a nice addition) \$\endgroup\$
    – SharpShade
    Dec 23 '20 at 20:24
  • \$\begingroup\$ No, it's not easy - you'd have to add an active circuit to "duck" the audio smoothly, ramping the volume down and then back up. That is not straightforward and would add a distortion element into the audio path. \$\endgroup\$
    – td127
    Dec 23 '20 at 22:02
  • \$\begingroup\$ Okay thanks for the help, then I go with the simple solution :) That's already more than enough for my use case since I will eventually replace it with a proper receiver and a better sound system. \$\endgroup\$
    – SharpShade
    Dec 24 '20 at 8:24

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