EMC Filtered Power Inlet

[Faber65]

The place I live has not a very good power supply and I was considering to replace the stock IEC power entry with something filtered like the Schurter 5200-0243-1 or similar.

Any donwside that I should consider?

Thanks and regards
F.

[Paul Birkeland]

The first issue that you'll have is that those parts won't fit the hole in the chassis.

Filters like those are great at creating a barrier for high frequency noise, both to get into the device they are connected to, and potentially to keep that noise from migrating out of the device back into the powerline.  In the case of the Crack, the EI type power transformer used is also very good in this role, so additional high frequency filtering tends not to be particularly helpful.

[Doc B.]

Your description is not really giving enough info for us to be able to offer a useful suggestion. Is the line noisy? If so, what is the noise like, and do you know the source? Or does your mains voltage fluctuate? A filter won't help with that. It could be that more effective grounding would have more impact that a line filter.

When you look at filters you want to focus on what the noise issue you have is and what frequency range the filter works in. The type of filter that is built into the power entry is usually designed to work in the tens to hundreds of MHz range. That might help to block spurious line noise from digital sources, but it's not going to do much down near the audio band. A filter that comes in around 10kHz is probably going to be more useful that one that doesn't work below 1MHz. Something like the Corcom Q series for switching power supplies might be more effective.

[Paul Joppa]

Some few years ago, I looked at what was around and thought the Corcom EC series, said to have "...the highest attenuation of any available standard inlet filter." It begins to attenuate around 100kHz, but doesn't get really effective until a few hundred kHz; the more typical ones don't start until 10MHz.  I even bought a couple, but then I got distracted onto another project. So I don't have any actual experience. Best bet is to download spec sheets and study them carefully.

Long ago the late John "Buddha" Camille published some thoughts on the subject. Kind of intense, but some good stuff. It was in the old VALVE magazine - v6n3 and v6n4 1999 - the article title was "Buddhafied Afterglow." Following his ideas, I was going to add a CLCLC filter with common-mode chokes, to extend the attenuation band down to around 30kHz.

I should probably put the parts together in a separate box and give it a listen.