Class D amp + EMI reduction

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maty tinman

maty tinman

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Joined 2012
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djpns

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Joined 2018
Well, guys I used two ferrites I've bought on the output wires of each channel (RIght and Left) of the amp. I haven't noticed any better quality of the sound. Still the same problem. But, I made something that made the sound almost perfect! I had a wire left on my kitchen and while the radio was playing, I connected the wire to one of the 4 holes that the board has on each side, I touched the antenna on her end of the wire and the sound was much better (almost great)! Is there something wrong with the grounds? I can't understand it. But I still have a little noise on the "not so strong stations".
 

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OffGridKindaGuy

OffGridKindaGuy

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Joined 2013
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..
 
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djpns

Member
Joined 2018
OffGridKindaGuy said:
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..
Click to expand...

Do you have a schematic of all these connections? It would really help me.
 
OffGridKindaGuy

OffGridKindaGuy

Member
Joined 2013
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..
 
D

djpns

Member
Joined 2018
OffGridKindaGuy said:
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..
Click to expand...

Yeap, it sounds like a task for experienced persons. And I'm not. :eek: Is there any filter board on the market that I can use?
 
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