Help in amplifier grounding

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Hello,

I'm building a gainclone amp and have already the schematic design ready to make the PCB:

Schematic.png


[URL="https://plus.google.com/photos/yourphotos?banner=pwa"]https://plus.google.com/photos/yourphotos?banner=pwa[/URL]

but don't know how to deal with the grounds, if it's better to use star grounding or ground plane, and if should I take the entire system (amp supply, OPAMP supply and gainclone amp) together with only one ground or with separate grounds and how to design it in the PCB. Please if someone knows about this topic I would appreciate any advices about it.

Santiago.
 
I can't read values on your schematic.
What is the gain of your inverting chipamp?
Have you deleted the Output Thiele Network and the Output Zobel?
From where does the speaker current demand get satisfied?
No RF filter at the input to the amplifier.

I suggest you build an uncased monoblock and learn from that what you need to include inside your cased multi-channel amplifier.
 
I can't read values on your schematic.......................
No RF filter at the input to the amplifier......................

............. I do have RF filter at the amplifier input, C14 and C13 before the LM3875 input aren't it??...............
I can't read the values !!!!!!

But the point is there is NO RF FILTER at the input to the amplifier. Note INPUT !
 
Here it is :

amp.PNG


https://lh6.googleusercontent.com/-9mntd1xljuU/UcZx81pM6PI/AAAAAAAAAEQ/CCOmxWqvGN0/w834-h509-no/amp.PNG

Hope you can see the details, I think as swak that the input cap that you are talking about is C12, and the RF filter are C14 and C13 but the question is how to deal with the grounds, is it better star or ground plane grounding?? and how do I make it in a PCB, I have already designed the following PCB with a star ground but not taking into account the amp ground only for the PSU units (+24, -24 and +15, -15). In this PCB I'm leaving the ground terminals of both PSU to connect it in a star ground with cables later.

fuente.png


https://lh3.googleusercontent.com/-1AXd__Y5XFw/UcUzx8MkAGI/AAAAAAAAADk/JtXscM-aoos/w620-h553-no/fuente.png

I appreciate all of your replies. Thanks.

Santiago
 
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This is a method that worked out well. Go here, and download the assembly manual. The schematic on page 40 and overall wiring diagram on page 41 may give you some good ideas.

Akitika GT-101 Audio Power Amplifier Kit


Also, Douglas Self's power amp book has a couple good sections on grounding.

Here's also a white paper I wrote that covers some issues:

http://www.updatemydynaco.com/documents/GroundingProblemsRev1p4.pdf




Thanks a loooot for the updatedynaco pdf link. (especially page 4 of pdf)


Important!!
Tips for googlers like me looking for multichannel pcbs or being hit with hum when any source is connected.

Most people making multichannel amps (2+) are facing "Cross Channel ground loop" which has nothing to do with earthing + very very less information is available on "Hum Breaking Resistors" setup. (googling / youtubing for last 3-4 days all day long).


Most solutions on forum lead to star grounding technique, which is quite right but only half of story, because as I see in threads, everyone assumes that the hum has to be from earthing issues. (great respect for people trying to help, they are not wrong, and its very difficult to help with sometimes incomplete info).



the remaining half hum-story is due to cross channel loop, which sadly is not touched (or perhaps I have missed it in searches). If my poor assumption is right *1 *2 - no amount of start grounding will remove hum, because its in channels signal paths

Solution
A. Guaranteed: Use a line transformer, (cheapest to expensive can be bought)

youtube has many videos showng its result, but if you are an audiophile thats a whole different story, for me unless its bothering me (like a hummmmm), it wont matter and I am not 0.0000015 distortion guy (no offense :) ) so pick your solution wisely.


B. use a Hum breaking resistor as mention in pdf page 4-6
http://www.updatemydynaco.com/documents/GroundingProblemsRev1p4.pdf


and also found this later:
http://hifisonix.com/wordpress/wp-content/uploads/2018/07/How-to-wire-up-an-amplifier_2.pdf


*1 - this person was much patient to try all what was suggested for months, and settled on line transformer
Multichannel amplifier internal ground loop


*2 - tried myself, kinda in same situation like above guy, but want to exhaust all my options before going transformer way. I am into videos from pc, so I have also plans to make Hafler matrix decoding, volume normalization and digital controls to feed signal to amplifier.
 
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