Are these line filters any good?

[dublin78]

Hello

Do line filters like these ones offer a benefit to a CD, DAC, AMP system?

AC power line filter for Hi-Fi and Hi-END audio DIY on eBay (end time 11-Dec-10 06:22:35 GMT)

[Eric]

If you have a particular problem to solve, these may do the trick for you. The layout of the components of the board looks like a "typical" power filter: a few caps, a coil, a few more caps, a coil, a few more caps.

The price seems a bit high to me as you can purchase EIC (power entry) filters or wired "inline" filters with the same ratings for $10-20, though these are much smaller in size than the one you linked. It looks good to me, but I'd be happier with a price closer to $20-30.

Eric

[jrockhead]

Look for Corcom brand 6EHQ1 filters. I use these on all of the AC lines of my equipment. They block noise that wants to go in in either direction.

They don't get any better than this.

[dublin78]

Thanks guys for your input.

I do not have any problem to solve, I was just wondering whether it was good practice to use these filters regardless.

The 6EHQ1 look ideal, but you cannot get them in Europe. The 6EHQ3 looks even better as it incorporates an earth.

[DF96]

An ordinary IEC filtered input should be adequate. It deals with RF, which can sneak past big PSU capacitors. Any audio on the mains should be filtered by the PSU anyway - it can deal with 50Hz so 500Hz or 5kHz should be even better. That is why mains filters don't usually go that low - they don't need to! Always be wary of a salesman telling you about a problem you didn't know you had, especially if he offers just the thing to solve this 'problem'.

[Speedskater]

Jim Brown of Audio Systems Group has some papers on line filter used in audio or ham radio:

Audio Systems Group, Inc. Publications

[abraxalito]

The eBay offering looks a tad over-priced (agree with Eric) - it has a couple of common-mode chokes and a handful of X2 caps and they want $50? Much cheaper to source the components yourself and build it. Choose the CM chokes according to the current demands of your amp. For CD players, DACs etc a lower current rating will in theory give better rejection as it allows higher inductance to be used. Self-resonant frequency is though an issue - when choosing CM chokes, look for those open framed ones where the windings are segmented, these do better at rejecting RF. Filters with Y caps are a mixed blessing, depending on how good your earth connection is - they may end up polluting your earth rather than cleaning your mains