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Class D Switching Power Amplifiers and Power D/A conversion

Class D amp + EMI reduction
Class D amp + EMI reduction
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Old 17th March 2018, 11:28 AM   #31
maty tinman is offline maty tinman  Spain
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Many years ago a friend told me a phrase that I always remember when I have no explanation: electronics is very mysterious
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Old 17th March 2018, 11:35 AM   #32
djpns is offline djpns
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Originally Posted by maty tinman View Post
Many years ago a friend told me a phrase that I always remember when I have no explanation: electronics is very mysterious
Hahaha you're so right my friend! That's why I love Electronics
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Old 17th March 2018, 12:31 PM   #33
OffGridKindaGuy is offline OffGridKindaGuy  United States
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Originally Posted by maty tinman View Post
Many years ago a friend told me a phrase that I always remember when I have no explanation: electronics is very mysterious


Yup.. Them thar RF's are strange critters..
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Old 17th March 2018, 12:51 PM   #34
maty tinman is offline maty tinman  Spain
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My problem/confusion was that I was thinking about the problems I had with my class AB amplifier and I did not realize that Class D works internally with a higher bandwidth.
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Old 17th March 2018, 01:00 PM   #35
OffGridKindaGuy is offline OffGridKindaGuy  United States
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I've used an RC low pass tank circuit with good results. Cut a foil and insert a 60 ohm resistor, bridging the cut, close to the solder pad. Add a 20pF cap after the resistor to ground. (Using surface mount components)


I've done this right at the wire connections on the board. Cut the signal trace right at the solder pad and bridge with the resistor. Install the cap across the wire solder pads, shorting them out with the cap. This provides a low pass circuit that will filter everything above ~130 MHz


I discovered this on a 2.1 amp and the trash from the chip was getting into the sub level control. I installed this filter on the board at the solder pads for the control and the problem went away.


This could be used on the power input also with low current draw demands. 60 ohms isn't going to drop much voltage. Many times that is where the crap is getting into the receiver..

Last edited by OffGridKindaGuy; 17th March 2018 at 01:10 PM. Reason: 'cause I could..
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Old 17th March 2018, 04:45 PM   #36
djpns is offline djpns
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Originally Posted by OffGridKindaGuy View Post
I've used an RC low pass tank circuit with good results. Cut a foil and insert a 60 ohm resistor, bridging the cut, close to the solder pad. Add a 20pF cap after the resistor to ground. (Using surface mount components)


I've done this right at the wire connections on the board. Cut the signal trace right at the solder pad and bridge with the resistor. Install the cap across the wire solder pads, shorting them out with the cap. This provides a low pass circuit that will filter everything above ~130 MHz


I discovered this on a 2.1 amp and the trash from the chip was getting into the sub level control. I installed this filter on the board at the solder pads for the control and the problem went away.


This could be used on the power input also with low current draw demands. 60 ohms isn't going to drop much voltage. Many times that is where the crap is getting into the receiver..
Do you have a schematic of all these connections? It would really help me.
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Old 17th March 2018, 07:34 PM   #37
OffGridKindaGuy is offline OffGridKindaGuy  United States
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No schematic. All boards are different. The mods I refer to are on/near the outside connections to the board. (plugs/sockets, solder points for external wiring, ect..)


Follow the board traces to the external connections on the board. Cut the trace and jump the cut with a surface mount resistor as close to the edge as possible. Most cases are at the point of which the trace ends at the solder pad for an external connection. The +/- pads are usually close enough to solder a cap across them. Short the pads with a cap..


Soldering a resistor to the cut trace might be difficult for someone who doesn't have lots of experience in soldering. The trace needs scraped to get rid of the insulation so the solder can stick and not destroy the trace. Also, not to scrape any near by traces to avoid bridges. Not a task for a novice..
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Old 17th March 2018, 07:40 PM   #38
djpns is offline djpns
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Originally Posted by OffGridKindaGuy View Post
No schematic. All boards are different. The mods I refer to are on/near the outside connections to the board. (plugs/sockets, solder points for external wiring, ect..)


Follow the board traces to the external connections on the board. Cut the trace and jump the cut with a surface mount resistor as close to the edge as possible. Most cases are at the point of which the trace ends at the solder pad for an external connection. The +/- pads are usually close enough to solder a cap across them. Short the pads with a cap..


Soldering a resistor to the cut trace might be difficult for someone who doesn't have lots of experience in soldering. The trace needs scraped to get rid of the insulation so the solder can stick and not destroy the trace. Also, not to scrape any near by traces to avoid bridges. Not a task for a novice..
Yeap, it sounds like a task for experienced persons. And I'm not. Is there any filter board on the market that I can use?
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