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Audio amplifier grounding Answered

How to make proper grounding in audio amplifier circuit? How to have separate signal and power grounds?


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2 years ago

Having them seperate is exactly what most try to prevent when setting up high end audio equippment.
A "hanging" ground is always source of unwanted signals and even less wanted interference.
Been there too many times back in the vinyl glory days ;)

You have two camps, the purists, going analog and the new age going digital.
For the later fibre optic connections provide fully ungrounded operations with no real interference of any kind.
On the other side most high end and almost all analog systems do require a common ground or better EARTH to work within audio quality specs.

If you have a signal in- and output at different ground levels then you literally have two independent "batteries" so to speak.
One side has to make up for the difference, in the worst case by blowing up some parts.
And once you connect the signals you create a path for those two batteries.
In a good audio system EARTH and common ground are only seperated by filters.
Meaning that if you measure you should see no voltage at all at any time between audio gorund and EARTH.
The filters make sure that no interference enters the audio signal that originated from the outside, like the power supply area.
If you then connect the audio signals without sharing EARTH connections on the device the audio line becomes the transmitter for everything in interference that differs from one device to the other.

Only way I know to avoid this crosstalking and interference build up is to add a suitable filter between audio input and audio output.
Whatever frequency the speakers can handle is allowed through the rest is blocked.
Downside is a certain quality loss and a slight powerloss of the signal when passing through the filter.
So it could really help to get much more detailed info on the problem from your end if that is possible!?