Here's a picture of my Jon Risch filter and DC blocker ("original" design by peranders). I used toroidal Amidon T200-26 iron powder cores but Jon Risch tells not to use toroidal or bobbin cores since there is a risk of saturation...
I also added an 1 megaohm resistor which discharges the caps. I will place the varistors right next to input.
The copper on the pcb is 105 um thick. Winding wire is 1.6 mm thick (~2 mm^2). >> total DC resistance of the filter is about 0.02 ohms. Inductor value is about 100 uH. I will place automatic fuses to the enclosure (automatic types won't add resistance).
DC blocker caps are 10000 uF and life expectancy is 250 000 hours (should be enough 😀 ) (RS No: 255-0169). It is possible to add second pair of diodes to DC blocker but for now I only need one pair as my DC offset is quite small.
http://kotiweb.kotiportti.fi/audiovideo/download/valmiit moduulit.jpg
I haven't tried these yet and in this photo the caps are placed + poles against each other. These caps have screw terminals.
I also added an 1 megaohm resistor which discharges the caps. I will place the varistors right next to input.
The copper on the pcb is 105 um thick. Winding wire is 1.6 mm thick (~2 mm^2). >> total DC resistance of the filter is about 0.02 ohms. Inductor value is about 100 uH. I will place automatic fuses to the enclosure (automatic types won't add resistance).
DC blocker caps are 10000 uF and life expectancy is 250 000 hours (should be enough 😀 ) (RS No: 255-0169). It is possible to add second pair of diodes to DC blocker but for now I only need one pair as my DC offset is quite small.
http://kotiweb.kotiportti.fi/audiovideo/download/valmiit moduulit.jpg
I haven't tried these yet and in this photo the caps are placed + poles against each other. These caps have screw terminals.
More resistance, so even lower supply impedance. Fine if you don't draw too many amps and can tolerate 5V sag or so.
TIm
TIm
Using air-core inductors you would likely pick up as much noise as you filter out. With the toroidal cores, as in the pic above, the magnetic path is closed (pretty much) so pickup is not a problem.
The use of iron powder cores gives a distributed air gap, raising the saturation flux of the core. Iron powder also becomes lossy at higher frequencies, making it even better for EMI suppression.
Layout is crucial with an EMI filter - there is little point in spending lots of $ on filter components, only to have the noise skip around the filter through parasitic capacitances.
The use of iron powder cores gives a distributed air gap, raising the saturation flux of the core. Iron powder also becomes lossy at higher frequencies, making it even better for EMI suppression.
Layout is crucial with an EMI filter - there is little point in spending lots of $ on filter components, only to have the noise skip around the filter through parasitic capacitances.
Filter
The transformer in an amplifier is already a very good low pass filter. A capacitor of 1uF in front and after the transformer will be enough. Use an X2 capacitor, special for mainvoltage use.
For any low power audio equipment you can use a isolation transformer, 220 volts in and 220 volts out. Also an 1uF cap at both sites.
I use it with good results.
The transformer in an amplifier is already a very good low pass filter. A capacitor of 1uF in front and after the transformer will be enough. Use an X2 capacitor, special for mainvoltage use.
For any low power audio equipment you can use a isolation transformer, 220 volts in and 220 volts out. Also an 1uF cap at both sites.
I use it with good results.
Re: Filter
And hence why I give engineering advice on how to make one, but won't ever bother recommending one.. 😀
Tim
Tuur said:
And hence why I give engineering advice on how to make one, but won't ever bother recommending one.. 😀Tim
DIAR said:
Experience from my days designing switchmode power supplies, and trying to get the equipment through EMI standards testing. Essentially if the inputs and outputs of the filter are too close, then the parasitic C will carry plenty on EMI across the air-space, bypassing the filter completely. In one case a simple rearrangement of the filter gave me something like 20dB improvement in the filter performance
Another thing to remember is that bigger is not always better - sometimes a smaller capacitor works better, simply because its ESR and ESL are lower!
The whole business of EMI supression is something of a black art - fundamental engineering principles get you in the ball park, but after that its build, test,modify,test,modify,test,modify ....
and thats when you have a Rhode & Shwartz conduction clamp and a $50K HP Spectrum analyser sitting on your desk!
Realistically? Hack the filter out of a PC power supply 😀
The comment about the transfomer forming a low-pass filter is quite valid for differential noise, less so for common-mode noise.
Two Spoons
Have had the same issues with PWM controllers for treadmills.
a big issue is that a line filter is load dependent. Add this to all the previous posts and it becomes a challenge of the worst sort. This is why lab time for CE/FCC testing is $1500/day.
I've had good luck here in the states using a 220/110 transformer. Our 220 is 2 phase and then earthing one side of the secondary. It kills most common mode noise but it isn't cheap to do.
Mike
Have had the same issues with PWM controllers for treadmills.
a big issue is that a line filter is load dependent. Add this to all the previous posts and it becomes a challenge of the worst sort. This is why lab time for CE/FCC testing is $1500/day.
I've had good luck here in the states using a 220/110 transformer. Our 220 is 2 phase and then earthing one side of the secondary. It kills most common mode noise but it isn't cheap to do.
Mike
1 megohm to discharge the caps sounds too high because the time constant will be very long. As an example 10K uF discharged by a 1 meg resistor will take 10000 seconds to loose only 33% of its charge.
RS sells up to 4.7 uF X-caps. My filter is made by these instructions:
http://www.geocities.com/jonrisch/surge.htm
http://www.geocities.com/jonrisch/surge.htm
promitheus []
50 Hz is too low to filter. the parts needs to be giant, thats the reason most good filters start from 1-2 KHz. And these are big.
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Hi Promitheos excellent thread youve started my Friend
i dont include such filter in my amps, should I?, your input
would be appreciated
thanks
50 Hz is too low to filter. the parts needs to be giant, thats the reason most good filters start from 1-2 KHz. And these are big.
----------------------------------
Hi Promitheos excellent thread youve started my Friend
i dont include such filter in my amps, should I?, your input
would be appreciated
thanks
Hello there,
good this thread is coming alive again.
I found these new filters here.
They are very good quality and they shouldnt supress dynamics of power amplifiers because the series resistance of the coils is extra low.
http://www.diycable.com/main/product_info.php?cPath=21&products_id=536
good this thread is coming alive again.
I found these new filters here.
They are very good quality and they shouldnt supress dynamics of power amplifiers because the series resistance of the coils is extra low.
http://www.diycable.com/main/product_info.php?cPath=21&products_id=536
aleph 1.2's to AX100
Has anyone designed a dc blocking circuit for incoming AC for 120 volts US operation? I would like to put this circuit inside my power amp. I already have RF and EMI filter. thanks, dave
Has anyone designed a dc blocking circuit for incoming AC for 120 volts US operation? I would like to put this circuit inside my power amp. I already have RF and EMI filter. thanks, dave
Re: aleph 1.2's to AX100
Notice also that if you don't have any problems with DC on the mains you don't have to fix it. DC on the mains creates only an accoustical problem, nothing else.
DIAR, are you awre of that inductors are usually winded on a single core, "common mode inductor". It's also essential to keep the filter compact in order to get the highest filtering properties.
The filter looks exactly the same. The caps value is determined by the max continous current.daly41k said:
Notice also that if you don't have any problems with DC on the mains you don't have to fix it. DC on the mains creates only an accoustical problem, nothing else.
DIAR, are you awre of that inductors are usually winded on a single core, "common mode inductor". It's also essential to keep the filter compact in order to get the highest filtering properties.
aleph 1.2's to AX100
thanks, Peranders,
The problem that I am having is that my 2kva torroids in my Aleph 1.2's buzz or mechanically hum. It could be the transformers themselves. They are Plitron brand and their spec sheet says that they can handle up to 250mv of dc on their primaries before making noise (on a 120 volt line). I just want to eliminate it as a concern. My amps are class A and draw about 5 amps AC from the wall outlet. Knowing this, how would I size the caps? dave
thanks, Peranders,
The problem that I am having is that my 2kva torroids in my Aleph 1.2's buzz or mechanically hum. It could be the transformers themselves. They are Plitron brand and their spec sheet says that they can handle up to 250mv of dc on their primaries before making noise (on a 120 volt line). I just want to eliminate it as a concern. My amps are class A and draw about 5 amps AC from the wall outlet. Knowing this, how would I size the caps? dave
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