Isolating Chassis and Audio Ground

I have a lot of RFI leaking into my circuit which I believe is a result of my grounding scheme. I'm using two ground planes, one for chassis ground and one for audio ground, and they are connected at a single point.

What would be the best way to filter the RFI from the chassis ground to the audio ground?

[quote author="Andrew"]I have a lot of RFI leaking into my circuit which I believe is a result of my grounding scheme. I'm using two ground planes, one for chassis ground and one for audio ground, and they are connected at a single point.

What would be the best way to filter the RFI from the chassis ground to the audio ground?[/quote]

I assume you're talking about two planes on your PCB? You should not have a chassis ground plane. Chassis ground is exactly that -- the enclosure.

I've done PCBs with a copper pour for PCB-mount connectors, and I've made sure that the "regular" ground plane does not go under it. The green wire that connects the chassis and mains ground to the circuit ground should suffice to ensure that your Pins 1 connected. If you're worried you could always add a discrete wire from the chassis ground pour to your single ground point.

If you don't want to do a PCB respin, try disconnecting the connector Pins 1 from the PCB ground plane and make sure they have a good enclosure connection. Then make sure the two planes are tied together.

good luck.

-a

Thanks Andy. What about putting an inductor or ferrite bead between the chassis and audio ground? Would this do anything useful?

Audio ground does not necessarily need to be bonded to chassis at all.

Shields and safety grounds get bonded, audio ground is essentially a reference node. It is good practice to have some compliance to ground, but multiple hard connections introduce potential loops, which can corrupt signals.

Of course if your dealing with single ended wiring, grounds can get rather messy and may need to be addressed systemically.

JR

Let's Rane:

http://www.rane.com/pdf/ranenotes/Grounding and Shielding Audio Devices.pdf