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Old 19th April 2014, 08:05 PM   #1
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Default Preamp grounding

I am designing a simple pre-reg that will be feeding the K-Multiplier that resides directly on the pre-amp main board. The two will be housed in seperate enclosures. I am trying to determine if one of these layouts is better in terms of grounding than the other or are they both wrong. The actual star ground is not created until the two rails come together on the main board.
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Old 19th April 2014, 09:26 PM   #2
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Star grounding is good.
Especially in regards smoothing capacitor charging pulses.

I designed USB mixer and just laid the tracks as they came out of the schematic.
I had about 1 volt of hum on the output !!!
The problem turned out to be the power supply part of the design was not star grounded.
I proved this by removing the power supply to an external power supply on veroboard and the hum stopped.
I reworked the pcb with the smoothing capacitors ground taken right back to the star ground and it was very quiet.
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Old 19th April 2014, 10:00 PM   #3
Zen Mod is offline Zen Mod  Serbia
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just make it more elegant
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Old 22nd April 2014, 04:46 PM   #4
AndrewT is offline AndrewT  Scotland
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Zen Mod's is much closer.

The input to the dual capacitors must be at the opposite end to the output from the dual capacitors.
The final output must be fed to that single cap on the right and the output must come from that final cap.
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Old 23rd April 2014, 02:03 AM   #5
6L6 is online now 6L6  United States
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You mean like this? (Sorry for the crude drawing)
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Old 23rd April 2014, 08:15 AM   #6
AndrewT is offline AndrewT  Scotland
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You need to "sort" the exit from the second capacitor.
In on one side and out on the other side.
The long spread of feeders from the first to second cap is wrong.
There are four capacitor pins that show the correct way.
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Old 23rd April 2014, 09:18 AM   #7
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This is what I etched. We will see if it is quiet or not.
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Old 23rd April 2014, 09:26 AM   #8
AndrewT is offline AndrewT  Scotland
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The electro at the bottom is not doing anything useful.
It has a common in/out. When located at the end of a a high impedance trace it's performance will be dominated by the trace impedance.
There is a film capacitor just above it.
It too has a long link back to the power supply. What does that film capacitor do? Will that long high impedance link interfere with what it is required to do?
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Old 23rd April 2014, 10:19 AM   #9
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The film cap is simply a bypass for the elco and should lower the overall Zo. Some say they heaer an improvement with such additions. I have seen them in some successful designs and had the caps to do it, so i went ahead and included them....in ignorance of their affect. I would be interested in seeing how you would lay it out, as i do not understand completely some of things you are referring to.
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Old 23rd April 2014, 10:24 AM   #10
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Here is a redarw of the negative rail( on the left). Are these the changes you were referring to?
Million dollar question. Will I observe or hear a difference in the two?
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