Active filter ground pour

Mfly · 26th March 2012, 12:38 PM

Dear all,

I made a PCB design for an active subwoofer filter. It will be a 2 layer board. Because it has several potentiometers on the board edge, quite a few signal traces will end up in the ground layer.

In this situation would it be preferable to still use a single ground pour like this:

Bottom:
SubWooferFilter_PCB_1pour_Bottom.png

Top:
SubWooferFilter_PCB_1pour_Top.png

Or is it better to have ground pours in both layers like this:

Bottom:
SubWooferFilter_PCB_2pours_Bottom.png

Top:
SubWooferFilter_PCB_2pours_Top.png

Or doesn't it really matter in a situation like this (low frequency audio)?

Thank you for your input.

Cheers, Maarten

Osvaldo de Banfield · 26th March 2012, 12:44 PM

I personally prefer to have such a big ground plane as can be done. I made several hand wrote PCB´s and using soft like autotrax for DOS, and use large ground planes, for two reasons: less copper and acid waste, and quicklier acid attack, and electrically is also better.

marce · 26th March 2012, 01:38 PM

Bothn layers withground pours and stiching vias between the two pours, to join them together at multiple points.

mickeymoose · 26th March 2012, 02:13 PM

Nice looking boards!
I do not use ground-planes in line-level based audio circuits. I prefer to keep the physical dimensions of the board to its minimum and pc traces as short as posasible with the maximum number of traces on the solder side. E

marce · 27th March 2012, 11:35 AM

Ground planes for low level analogue do help keep noise down, I have seen them used on analogue designs for 27 years, and in't old days we wouldn't dreem of doing an analogue board without ground planes, pours.
The traces that are not power could be reduced in width a bit, they all look around 0.050".

mickeymoose · 27th March 2012, 02:41 PM

marce: I agree that ground planes should be used on low-level signals. I use them there and also on high-gain narrow filter circuits. This one seems to be line-level with a gentle filter. Poorly implemented ground planes can all to easily end up as antennae. E

marce · 27th March 2012, 08:51 PM

Yes, it is important to add stiching vias to at least both ends of a long thin strip of a copper pour, often overlooked or missed. I put my vias in a different colour to the copper and step through the design, visually checking there are vias in the right places.

Mfly · 28th March 2012, 07:52 AM

Thank you all for your input. I'll go for the double ground pour then. Stitching vias shouldn't be a problem as the board will be manufactured by a PCB manufacturer and as such all ground connections will be plated through. I'll look into placing some extra via's on long thin stretches of copper to get a good connection between the two planes throughout the board.

26th March 2012, 12:38 PM	#1
Mfly diyAudio Member Join Date: Feb 2008 Location: Utrecht	Active filter ground pour Dear all, I made a PCB design for an active subwoofer filter. It will be a 2 layer board. Because it has several potentiometers on the board edge, quite a few signal traces will end up in the ground layer. In this situation would it be preferable to still use a single ground pour like this: Bottom: SubWooferFilter_PCB_1pour_Bottom.png Top: SubWooferFilter_PCB_1pour_Top.png Or is it better to have ground pours in both layers like this: Bottom: SubWooferFilter_PCB_2pours_Bottom.png Top: SubWooferFilter_PCB_2pours_Top.png Or doesn't it really matter in a situation like this (low frequency audio)? Thank you for your input. Cheers, Maarten

26th March 2012, 12:44 PM	#2
Osvaldo de Banfield diyAudio Member Join Date: Dec 2011 Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina	I personally prefer to have such a big ground plane as can be done. I made several hand wrote PCB´s and using soft like autotrax for DOS, and use large ground planes, for two reasons: less copper and acid waste, and quicklier acid attack, and electrically is also better. __________________ LW1DSE

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26th March 2012, 01:38 PM	#3
marce diyAudio Member Join Date: Jun 2007 Location: Blackburn, Lancs	Bothn layers withground pours and stiching vias between the two pours, to join them together at multiple points.

26th March 2012, 02:13 PM	#4
mickeymoose diyAudio Member Join Date: Nov 2008	Nice looking boards! I do not use ground-planes in line-level based audio circuits. I prefer to keep the physical dimensions of the board to its minimum and pc traces as short as posasible with the maximum number of traces on the solder side. E

27th March 2012, 11:35 AM	#5
marce diyAudio Member Join Date: Jun 2007 Location: Blackburn, Lancs	Ground planes for low level analogue do help keep noise down, I have seen them used on analogue designs for 27 years, and in't old days we wouldn't dreem of doing an analogue board without ground planes, pours. The traces that are not power could be reduced in width a bit, they all look around 0.050".

27th March 2012, 02:41 PM	#6
mickeymoose diyAudio Member Join Date: Nov 2008	marce: I agree that ground planes should be used on low-level signals. I use them there and also on high-gain narrow filter circuits. This one seems to be line-level with a gentle filter. Poorly implemented ground planes can all to easily end up as antennae. E

27th March 2012, 08:51 PM	#7
marce diyAudio Member Join Date: Jun 2007 Location: Blackburn, Lancs	Yes, it is important to add stiching vias to at least both ends of a long thin strip of a copper pour, often overlooked or missed. I put my vias in a different colour to the copper and step through the design, visually checking there are vias in the right places.

28th March 2012, 07:52 AM	#8
Mfly diyAudio Member Join Date: Feb 2008 Location: Utrecht	Thank you all for your input. I'll go for the double ground pour then. Stitching vias shouldn't be a problem as the board will be manufactured by a PCB manufacturer and as such all ground connections will be plated through. I'll look into placing some extra via's on long thin stretches of copper to get a good connection between the two planes throughout the board.