Hello Everyone,
I’m thinking of building a box to house main filter (using John Risch’s design), plus a DC blocker (using Rod Elliott’s design). This will sit between the mains from the wall and my solid state amp.
Question is, from the mains from wall, should the DC blocker first or the main filter first?
Any thoughts much appreciated.
I’m thinking of building a box to house main filter (using John Risch’s design), plus a DC blocker (using Rod Elliott’s design). This will sit between the mains from the wall and my solid state amp.
Question is, from the mains from wall, should the DC blocker first or the main filter first?
Any thoughts much appreciated.
Why do you think its the other way around ?
There is a logical reason for that choice , think of what you are dealing with normally in a electrical mains supply and the different frequencies of them as well as pulse /spikes and what electrical effect would happen to any interface between the mains socket and the amplifier if those components had a self resonance with just ONE of those various frequency it would amplify the interference making it much harder to remove the HF oscillations .
Anyway your post caused me to check it out and I think one enterprising dealer is selling a unit combining the two which would make it easier to test for interaction before selling the combined unit.
But I look forward to your rebuttal .
I am looking at a circuit of a power conditioner that is build-able but contains many components but even there self resonance is mentioned but it is not a DC blocker which does only one job --block DC its the fact it contains electrical components that interface the amplifier before ( in your opinion ) before the mains filter .
There is a logical reason for that choice , think of what you are dealing with normally in a electrical mains supply and the different frequencies of them as well as pulse /spikes and what electrical effect would happen to any interface between the mains socket and the amplifier if those components had a self resonance with just ONE of those various frequency it would amplify the interference making it much harder to remove the HF oscillations .
Anyway your post caused me to check it out and I think one enterprising dealer is selling a unit combining the two which would make it easier to test for interaction before selling the combined unit.
But I look forward to your rebuttal .
I am looking at a circuit of a power conditioner that is build-able but contains many components but even there self resonance is mentioned but it is not a DC blocker which does only one job --block DC its the fact it contains electrical components that interface the amplifier before ( in your opinion ) before the mains filter .
I do not know why it should make any difference which comes first. Since they are in series between the source and the load, the current through both of them will be identical at all times, regardless of which is first in line. The only way a difference could happen is if the filter or DC blocker has more than just an input and an output connection, such as a connection to earth. Maybe it's time for a little SPICE session.
As the DC blocker is only blocking DC and isn't a filter all the mains noise goes through it and can be amplified by the circuit if the self resonance of components is achieved.
This was purely a question because I tried to think about it and could not come up with a reason for before or after. So sorry, no rebuttal here 😀
In an attempt to clarify things further - do you mean the series resonance of the DC blocking cap? I tried to do a quick mouser search to find out the ESL of a 10000u/16V cap, could not find any caps that specify ESL after a few tries. Do you have an estimation in what ballpark the ESL will be for such big aluminium electrolytic caps and where the self resonant frequency might be?
Makes no difference which is first. Draw up an actual diagram, LTSpice it and you can see for yourself.
As a matter of common sense electronics theory, the only exception would be if the filter circuit can't handle DC, or the blocker can't handle normal garbage in the mains. Either would be unusual and you would only know if you had the schematics of both.
As a matter of common sense electronics theory, the only exception would be if the filter circuit can't handle DC, or the blocker can't handle normal garbage in the mains. Either would be unusual and you would only know if you had the schematics of both.
Can be amplified by which "circuit"? The blocker circuit? Ummm... I would have to see the schematic of a blocker capable of amplifying mains noise. Show me.
So what you are saying is that every known interference frequency via the mains supply is known to you in every household and there is zero chance of ANY of them resonating with electronic components in every DC blocker ?
Are you going to guarantee that ?
Are you going to guarantee that ?
What I'm saying was stated very clearly, in English. No need for you to interpret.
You don't need to "know" the frequency of interference. You can assume all frequencies are possible. If you can show that a blocker has an anomaly (peaking) anywhere in it's frequency response, do so. Otherwise it can't resonate. Very easy to do a sim and see.
Or, better yet, don't buy a blocker at all. Wait until you actually have DC in your mains. You will die of old age. We already had that discussion.
You don't need to "know" the frequency of interference. You can assume all frequencies are possible. If you can show that a blocker has an anomaly (peaking) anywhere in it's frequency response, do so. Otherwise it can't resonate. Very easy to do a sim and see.
Or, better yet, don't buy a blocker at all. Wait until you actually have DC in your mains. You will die of old age. We already had that discussion.
Dont you remember the OP asking which one should be first because THAT is what THIS thread is all about .
I said Filter first so you are saying put the DC blocker first ?
What makes you think I use a DC blocker --I don't - no DC on my mains .
The OP hasn't come back and said he is doing it your way- DC blocker first .
You have just read my posts later on and ignored posts #1 & post #2 & post #3 .
I said Filter first so you are saying put the DC blocker first ?
What makes you think I use a DC blocker --I don't - no DC on my mains .
The OP hasn't come back and said he is doing it your way- DC blocker first .
You have just read my posts later on and ignored posts #1 & post #2 & post #3 .
Hello DGAT,
Good to know that you live in an area with no DC in your mains, but I guess I'm one of the unfortunate ones.
I have measured the DC from my mains and it reads ~60mVDC in normal days and some times it could be as high as ~90mVDC. My transformer produced a "ring" when I turn on my main and it does vibrates. I have tried other transformers and so far only one of the few I tried don't suffer from this problem - not sure why.
But surely this is a problem and I have read that a DC blocker should solved the problem hence I want to incorporate a DC blocker onto my main filter that I am building.
As the filter and DC blocker have to be in series, the question is of course which comes first.
I will still take Duncan's suggestion to have the filter first. I may try the other way around after I complete this one and hope nothing blows up 🙂
Good to know that you live in an area with no DC in your mains, but I guess I'm one of the unfortunate ones.
I have measured the DC from my mains and it reads ~60mVDC in normal days and some times it could be as high as ~90mVDC. My transformer produced a "ring" when I turn on my main and it does vibrates. I have tried other transformers and so far only one of the few I tried don't suffer from this problem - not sure why.
But surely this is a problem and I have read that a DC blocker should solved the problem hence I want to incorporate a DC blocker onto my main filter that I am building.
As the filter and DC blocker have to be in series, the question is of course which comes first.
I will still take Duncan's suggestion to have the filter first. I may try the other way around after I complete this one and hope nothing blows up 🙂
A friend who is an electrician came over and did the measurement. He used a Fluke metre to test and also plugged in some kind of filter and measure from there (I think it was a low pass filter IIRC).
A few round he did and he thought the result (DC) was too high and actually called the power company to feedback.
Anyhow it’s obvious that there is a problem and affecting the transformer, so my thought is to throw in a DC blocker and the one suggested by Elliott Sound looks simple enough.
Filter first is correct.
The reason. All cables into the box can carry unwanted interference, this you want to stop before internal cabling can radiate this further into other components. Like wise, noise/interference from the inside should be stopped from coming out on same cable. Having filter near as possible where cables come in/out of box is best b/c if there is a length long enough internally after the filter, the noise may couple to that length of cable/wire.
This all assumes the chassis is used as a shield. If it is not, interference may couple anywhere and it matters not which order the filter is placed.
The reason. All cables into the box can carry unwanted interference, this you want to stop before internal cabling can radiate this further into other components. Like wise, noise/interference from the inside should be stopped from coming out on same cable. Having filter near as possible where cables come in/out of box is best b/c if there is a length long enough internally after the filter, the noise may couple to that length of cable/wire.
This all assumes the chassis is used as a shield. If it is not, interference may couple anywhere and it matters not which order the filter is placed.
There are best practices for proper EMI filter installation. See as example this handy reference: EMI Filter Installation Best Practices | Astrodyne TDI. Wiring placement is important. I once failed a EMI compliance test due to the wiring bundle from the IEC power outlet to the EMI filter that was placed too close to the SMPS transformer.
This is correct for an internal filter/blocker but you didn't read the OP.
He is proposing to build the filter and blocker into a separate box, to be placed between the mains and the amp. A stand-alone power conditioner. As such,
1. one would hope the box is properly designed (shielded), in which case there is nothing escaping the box so it makes no difference,
or
2. The box is not properly shielded. But it's far away from the amp compared to the internal wiring dimensions of the conditioner to make a difference in EM coupling to the amp. In fact, the physical orientation of the conditioner w/respect to the amp will make a greater difference than the order of the 2 filters.