Extension box with EMI/RFI filter

[keith_correa]

I think the connections made are fine. There is a dedicated earth terminal and that is wired correctly.

 

[Love4sound]

I think the connections made are fine. There is a dedicated earth terminal and that is wired correctly.

Yes in the input side. Output has only line and neutral. The earth line for both input and output are looped and connected to the terminal

 

[Subbu68]

I think the connections made are fine. There is a dedicated earth terminal and that is wired correctly.

From the circuit of the filter what I made out is the earth of line side remains isolated from load. The EMI from line would be attenuated and common mode interference "drain" through the two caps connected to the earth. Load side EMI will be blocked by the LC loop formed there.



These filters do an impedance mismatch to block the EMI frequencies, don't they? Something new for me to study further. Must make a log of what all I learnt after joining this forum

View attachment 72401

 

[mbhangui]

From the circuit of the filter what I made out is the earth of line side remains isolated from load. The EMI from line would be attenuated and common mode interference "drain" through the two caps connected to the earth. Load side EMI will be blocked by the LC loop formed there.
View attachment 72402


These filters do an impedance mismatch to block the EMI frequencies, don't they? Something new for me to study further. Must make a log of what all I learnt after joining this forum

View attachment 72401

You have a point. I too have made the mistake of connecting the earth from the output side back to the input. The issue that I'm wondering is about the loss of safety earth if we want to keep the EMI generated on the output flowing back to the input side

 

[Subbu68]

You have a point. I too have made the mistake of connecting the earth from the output side back to the input. The issue that I'm wondering is about the loss of safety earth if we want to keep the EMI generated on the output flowing back to the input side

If the equipment are double insulated (like the amps, AVRs, CDPs are) safety earth is not required.

Still most of them provide the three pin plug like over here in UAE due to the regulation that bans two pin plugs. We have no two pin sockets here. People defeat the earth interlock with a screwdriver or use those Chinese multipin adaptors and insert EU style plugs that have two pin with scraping earth into the British sockets and use the devices without earth. I think EU plugs can go into Indian 6A sockets and again without earth.

Similarly, in India there may be a regulation to supply with 3 pin IS plugs even if the equipment is double insulated. In such cases, earth pin a dummy pin. But if you have body earth, then using EMI filter and connecting body to earth wire of the line may be defeating the purpose.

Most AV equipment may not create EMI as they have in-built step down transformers that would isolate the internal circuitry from mains. But class D amps may produce EMIs?

 

[mbhangui]

Most AV equipment may not create EMI as they have in-built step down transformers that would isolate the internal circuitry from mains. But class D amps may produce EMIs?

Because of euro regulations enforcing that equipment draw very little power in standby state, most manufacturers have an efficient standby SMPS supply to supply power to the remote control circuit and standby LED so that the equipment can be turned on using a remote control. Transformer based supplies are not efficient and hence this standby SMPS to power the equipment in standby state. Even AMPS now have a small SMPS supply. When you switch on the AMP, the remote control circuit turns on a relay which then turns on the mains power to the main transformer. So some amoiunt of EMI is generated by these equipment because of this standby SMPS. Any equipment that can be turned on and off using a remote have a standby SMPS.

 

[Love4sound]

From the circuit of the filter what I made out is the earth of line side remains isolated from load. The EMI from line would be attenuated and common mode interference "drain" through the two caps connected to the earth. Load side EMI will be blocked by the LC loop formed there.
View attachment 72402


These filters do an impedance mismatch to block the EMI frequencies, don't they? Something new for me to study further. Must make a log of what all I learnt after joining this forum

View attachment 72401

If I disconnect earth at the load side how will the equipment’s get earth? Is this emi filter supposed to have the load side earth isolated?

 

[Love4sound]

You have a point. I too have made the mistake of connecting the earth from the output side back to the input. The issue that I'm wondering is about the loss of safety earth if we want to keep the EMI generated on the output flowing back to the input side

Are we supposed to leave the load without earth?

 

[mbhangui]

Are we supposed to leave the load without earth?

Yes. Not a big deal. As per my understanding most equipments with safety certifications are now designed to fail safe and now come with 2 pins

 

[Love4sound]

Yes. Not a big deal. As per my understanding most equipments with safety certifications are now designed to fail safe and now come with 2 pins

All my equipment’s work only with two pins. But what if you have gears that work with three pin and requires earth?

 

[mbhangui]

All my equipment’s work only with two pins. But what if you have gears that work with three pin and requires earth?

Connect those 3 pin equipment directly and not to the output of the EMI filter. Or have another EMI filter for 3 pin equipments. What say @Subbu68 ?

 

[Love4sound]

Connect those 3 pin equipment directly and not to the output of the EMI filter. Or have another EMI filter for 3 pin equipments. What say @Subbu68 ?

Every emi filter has earth only at the line side. Load side has only line and neutral in every models. I feel the filter working fine with the earth connection looped.I think I’ll leave it as it is since none of my equipment’s are using 3 pin. Also I have an isolation transformer that’s already blocking most of the interference. If still earthing has to be disconnected I will just cut the earth wire in the load side

 

[Subbu68]

Because of euro regulations enforcing that equipment draw very little power in standby state, most manufacturers have an efficient standby SMPS supply to supply power to the remote control circuit and standby LED so that the equipment can be turned on using a remote control. Transformer based supplies are not efficient and hence this standby SMPS to power the equipment in standby state. Even AMPS now have a small SMPS supply. When you switch on the AMP, the remote control circuit turns on a relay which then turns on the mains power to the main transformer. So some amoiunt of EMI is generated by these equipment because of this standby SMPS. Any equipment that can be turned on and off using a remote have a standby SMPS.

That's something new I learnt today. Never opened up my old amp or bothered to analyze the circuits.
Those SMPS must be like wall wart chargers and generating very little EMI?

 

[Subbu68]

All my equipment’s work only with two pins. But what if you have gears that work with three pin and requires earth?

Connect those 3 pin equipment directly and not to the output of the EMI filter. Or have another EMI filter for 3 pin equipments. What say @Subbu68 ?

Check the continuity between the earth pin and body of equipment. If no connection, use it with EMI filter. Else as @mbhangui wrote, use it directly on mains.

I use my Mac Mini on the same socket array as my valve amp as a source. I can't hear anything more of whining sound or disturbance as without the Mac. Those devices designed properly may be having filters inside.

In the case in India with all jugads in the network and with lots of inverter based equipment it may be an issue I believe.

 

[Hari Iyer]

Every emi filter has earth only at the line side. Load side has only line and neutral in every models. I feel the filter working fine with the earth connection looped.I think I’ll leave it as it is since none of my equipment’s are using 3 pin. Also I have an isolation transformer that’s already blocking most of the interference. If still earthing has to be disconnected I will just cut the earth wire in the load side

I wish to listen a setup without any EMI/RF filter or an isolation transformer to just understand the noise aspect. None of my equipments use any of these and I have not yet faced any issues. Hence always keep wondering what you guys are talking about....

 

[keith_correa]

Hence always keep wondering what you guys are talking about....

Me too!

Also, I really don't understand this thing about earth at the load end or at the other end or isolated at any end. It's earth and needs to go there from any end if applicable.

 

[Subbu68]

I wish to listen a setup without any EMI/RF filter or an isolation transformer to just understand the noise aspect. None of my equipments use any of these and I have not yet faced any issues. Hence always keep wondering what you guys are talking about....

Not sure if one can hear any difference, but if you have more than 3-4% harmonics in the line feeding into a transformer inside an equipment these harmonics can throw it off - overheat and die later if there is no overload capacity designed into the core and winding. Most commercial equipment may have a tight design to cut costs so the overload factor may be just not enough.

Even I do not have any isolation trafo or EMI filter for my audio. But on switching on the TV and if connected to the amp directly I had it - bees buzzing around. I use a Optical DAC to isolate. My wife who uses the TV most is not worried much about sound. So I don't give an input for her TV shows or films.

 

[Love4sound]

I wish to listen a setup without any EMI/RF filter or an isolation transformer to just understand the noise aspect. None of my equipments use any of these and I have not yet faced any issues. Hence always keep wondering what you guys are talking about....

I have lot of issues and hence using an isolation transformer. If I connect my system directly to a socket the transformer in my PA screams like a motor and vibrates. Speakers hum very loud as well.The source for this is my tv. So I have connected my tv directly to a socket and all other equipment’s to the isolation transformer. Also at times there is a huge potential rise in the neutral line.

Check the continuity between the earth pin and body of equipment. If no connection, use it with EMI filter. Else as @mbhangui wrote, use it directly on mains.

The avr even though work with two pin it has the body earthed and has a provision to earth for using it with turn table. Since the tester glows in the avr, tv and shield I have earthed my avr and through avr all the other equipment’s get earth and solves the tester glowing.

 

[Subbu68]

I have lot of issues and hence using an isolation transformer. If I connect my system directly to a socket the transformer in my PA screams like a motor and vibrates. Speakers hum very loud as well.The source for this is my tv. So I have connected my tv directly to a socket and all other equipment’s to the isolation transformer. Also at times there is a huge potential rise in the neutral line.

The avr even though work with two pin it has the body earthed and has a provision to earth for using it with turn table. Since the tester glows in the avr, tv and shield I have earthed my avr and through avr all the other equipment’s get earth and solves the tester glowing.

Some manufacturer's resort to virtual earth through the neutral. Technically your neutral is also grounded at the transformer but not safe to use as safety ground as there is a chance of potential rise due to unbalanced loads or network faults like you had earlier.

 

[Love4sound]

Some manufacturer's resort to virtual earth through the neutral. Technically your neutral is also grounded at the transformer but not safe to use as safety ground as there is a chance of potential rise due to unbalanced loads or network faults like you had earlier.

I still do have faults. Day time seems to be stable and voltage is around 230-240v and potential in neutral is within 6v. Night after 8 or 9 it’s very unstable.Good for nothing EB. Voltage is very high and at times 250-260v and there is a raise of potential in the neutral 6-17v.