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<blockquote data-quote="Mike Sokol" data-source="post: 64784" data-attributes="member: 1989">Re: Complete the DC circuit?If you&#039;re referring to the separate ground planes found in my many audio devices with digitally switched supplies, then that&#039;s pretty simple. For instance, in many Sony professional video cameras there are 3 separated ground planes; one for the chassis (external) ground tied to the safety (earth) ground if you&#039;re plugged into a wall outlet, one for the analog audio (XLR pin 1), and one for the on-board switcher supplies that provide all sorts of voltage from the 12-volt DC battery pack. Both the audio and switcher power supply ground planes are tied to the chassis via a capacitor/inductor/resistor network. Essentially this form a high-pass shorting filter somewhere in the 1K Hz area if memory serves (via that series capacitor) with a small leakage current (series resistor) to keep the ground planes in the same general potential voltage. Some also include a small inductor to low-pass filter the highest frequencies of the switcher supply and keep sub-harmonics out of the audio ground (and sound)&nbsp; &nbsp; &nbsp;if you accidentally plug in a male XLR mic cable with the shell tied to pin-1, you&#039;ll short audio audio ground plane to the chassis ground plane, and you&#039;ll hear the switcher supply sub-harmonics leaking into your audio (and how do I know this? :lol: )So when troubleshooting these things, you can&#039;t think that all grounds are the same. Cross connecting them accidentally usually won&#039;t cause any physical circuit damage, but will introduce switching power supply noise into your audio, which can drive you CRAZY!!!Is that what you&#039;re asking about?</blockquote>

[QUOTE="Mike Sokol, post: 64784, member: 1989"] Re: Complete the DC circuit? If you're referring to the separate ground planes found in my many audio devices with digitally switched supplies, then that's pretty simple. For instance, in many Sony professional video cameras there are 3 separated ground planes; one for the chassis (external) ground tied to the safety (earth) ground if you're plugged into a wall outlet, one for the analog audio (XLR pin 1), and one for the on-board switcher supplies that provide all sorts of voltage from the 12-volt DC battery pack. Both the audio and switcher power supply ground planes are tied to the chassis via a capacitor/inductor/resistor network. Essentially this form a high-pass shorting filter somewhere in the 1K Hz area if memory serves (via that series capacitor) with a small leakage current (series resistor) to keep the ground planes in the same general potential voltage. Some also include a small inductor to low-pass filter the highest frequencies of the switcher supply and keep sub-harmonics out of the audio ground (and sound) if you accidentally plug in a male XLR mic cable with the shell tied to pin-1, you'll short audio audio ground plane to the chassis ground plane, and you'll hear the switcher supply sub-harmonics leaking into your audio (and how do I know this? :lol: ) So when troubleshooting these things, you can't think that all grounds are the same. Cross connecting them accidentally usually won't cause any physical circuit damage, but will introduce switching power supply noise into your audio, which can drive you CRAZY!!! Is that what you're asking about? [/QUOTE]

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