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Old 2nd November 2009, 12:38 PM   #1
GregH2 is offline GregH2  Australia
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Default PCB Ground planes

Hi All,

I'm designing a gainclone PCB and I'm just interested to know if PCB ground planes should be connected to the signal or chassis (power) ground?

Thanks for your help!
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Old 2nd November 2009, 01:38 PM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
audio gets little if any benefit from a ground plane.
You are more likely to screw up the grounding by using a ground plane than to improve the audio quality.

Delete the ground plane from all your audio PCBs.
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Old 2nd November 2009, 02:18 PM   #3
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I'm for groundplanes also for audio.

You can check my QRP02, scroll down the page and you can see how I have separated the power side and the signal side of the ground plane.
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Old 2nd November 2009, 03:04 PM   #4
h_a is offline h_a  Europe
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Use what you prefer - in very most amps noise is dominated anyway by other factors, like magnetic induction, wiring, grounding, ripple...

@swordfishy: depends on your grounding scheme ;-) Usually one defines separate signal and power grounds. Alternatively, pour a ground plane that does not cover power devices and connect it to signal ground. The power parts get their own ground (or go balanced and forget about this issue).

As that's a chipamp, I think you shouldn't have problems connecting a full plane to signal ground. I wouldn't reference signal input to power ground.

Have fun, Hannes
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Old 2nd November 2009, 04:33 PM   #5
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Quote:
Originally Posted by AndrewT View Post
Hi,
audio gets little if any benefit from a ground plane.
This thread puts a different slant on that.

dave
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Old 2nd November 2009, 05:58 PM   #6
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by planet10 View Post
This thread[/URL] puts a different slant on that.
looks like you have given me quite a bit of homework to complete, before I can offer any further advice.
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Old 2nd November 2009, 06:43 PM   #7
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It is hard to believe that the little pigtails can possibly have any affect on anything...

dave
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Old 2nd November 2009, 07:04 PM   #8
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Quote:
Originally Posted by planet10 View Post
It is hard to believe...
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Old 3rd November 2009, 03:49 AM   #9
GregH2 is offline GregH2  Australia
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Thanks all for your responses.

Regards,

Greg.
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Old 3rd November 2009, 01:53 PM   #10
h_a is offline h_a  Europe
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Quote:
This thread puts a different slant on that.
There's not much magic about ground planes vs. star grounding.

One trades low impedance against capacitance to ground, that's it. The higher the frequencies to be transmitted, the more important are reactive components of the ground impedance. Consequently, for analog Mhz signals the shortest path is (often) not the path of lowest impedance.

A solid ground plane increases capacitive coupling to ground by some pf/cm^2, which forms a low pass filter. That's usually not a big deal, though. There are hatched variants of ground planes, but these again trade lower coupling for higher impedance.

Most DIY pcbs are double-sided as that's widely available. Most designs need already both sides for proper routing, so an additional ground plane is usually largely compromised with large holes.

In my view, a ground plane comes handy for high speed (MHz) signals or multilayer designs (beyond 2 layers).

For audio, star ground gave me always excellent results.

Have fun, Hannes

For more details, I refer to dozens of application notes that are freely available, among:
Linear AN47
Analog AN-202
Circuit layout techniques and tips 1-6, Bonnie Baker, Microchip
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