there is no relay and may not be. but the codec, and amp ICs have power-sleep mode... I believe that is not the case... i.e. the click is from turning the power off, or from interrupting the PCM stream, but the reason is not the audio chip itself. Did you make a Windows update after not doing so in a long time? If yes, you need to check for new audio drivers. That was a plague in the fall of 2019, when MS updated their audio subsystem and Realtek drivers failed to work properly. Since Realtek drivers are really a monstrous pile of option-protected modules with an awful mechanism of spreading configuration records int the registry, which may go astray, it may even require reinstalling windows... I.e., usually, the problem you described is related to the windows/driver updates.   BTW, If you are using digital signal, or HDMI, try connecting different receiver, since your decoder/amp may also get bad.
I have a Dell Precision T3500 with a strange problem that has started quite suddenly. When the PC starts up I hear what sounds like a relay inside being switched on, and when it shuts down I hear what sounds like the same relay switching off (it's a slightly different clicking sound). It has always done this, so I assume it's normal. What happens now however is that whenever the PC starts to play audio, I hear what sounds like the same relay (could possibly be a different one) switching on immediately. When the audio stops, I hear the relay switching off after a delay of about 10 seconds. This happens when playing a sound file, a video file (with sound), a YouTube video, or connecting to a Zoom session - anything involving sound. If I pause the sound or video file, the relay will switch off after about 10 seconds, and when I un-pause it, the relay switches back on. If I pause the audio or video for just a few seconds and then un-pause it, there will be no relay sound because the relay will not have switched off yet. This is why I suspect it's a relay behind this, since it both sounds like one and behaves like one. I'm not sure why the 10 second delay happens though. I'm hoping someone could help with ideas as to what could be causing this, since I'm worried that something is about to fail. Thanks very much for any help.
T3500 makes a clicking relay sound when starting to play audio