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AC Line Filter
AC Line Filter
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Old 30th April 2012, 11:59 AM   #11
AndrewT is online now AndrewT  Scotland
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It is just possible that an amplifier may sound different with and without an external AC line filter.

Why?

I will start the suggestion list with:

The amplifier is marginally stable, due to bad design and this results in non linear amplification when short term transients enter the amplifier, either via the PSU, or via the conventional input nodes.

How to avoid this misbehaviour in the amplifier - design it properly !

How many other reasons are there?

Discuss please.
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Old 30th April 2012, 12:21 PM   #12
Alexontherocks is offline Alexontherocks  Italy
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Could the "clearer" and "more alive" perception be somehow related to the same phenomenon described by some when using AC to power directly heated tubes vs DC?
Some swear that DHT with AC do actually sound more dynamic and alive than DC heated tubes
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Old 30th April 2012, 12:34 PM   #13
doctordata is offline doctordata  Australia
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AC Line Filter
Interesting !
What about the other way around , suppose you have a class D amp (or 5 of them ) and a SMPS switching like hell , does the line filter do any good keeping all this nasty Mega and Kilohertzes away from your beloved DVD player and preamp and or processor ??

Cheers ,

Rens
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Old 30th April 2012, 12:36 PM   #14
AndrewT is online now AndrewT  Scotland
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The integrated IEC socket filter, filters in both directions.
It is better (more attenuation) in the forward direction.
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Old 30th April 2012, 12:40 PM   #15
kaputt is online now kaputt  Germany
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Keep posting. The motivation to hook my scope up to the powersupply and measure with different sockets might bloom. Might....
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Old 30th April 2012, 12:45 PM   #16
trobbins is offline trobbins  Australia
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How many short term transients do you think occur during a song (or whatever is being listening to). How many of those transients are of a size that cause a 'change' - or vice-versa get clipped. Imho - zilch.

The emi filter could decrease the stiffness of the AC supply (due to series resistance and a titch of inductance). An isolation transformer would have a similar characteristic.

The capacitance to earth in the filter could lead to noise between the amp earth and the earth use by other connected equipments.
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Old 30th April 2012, 12:48 PM   #17
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by trobbins View Post
How many short term transients do you think occur during a song ......
My guess, a million.
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Old 30th April 2012, 01:19 PM   #18
TheGimp is offline TheGimp  United States
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I think you are conservative.

Every CFL is producing hash. Refrigerators and other motors produce sizable surges. This stuff is not just from YOUR house, but will come in on the power line from outside as well.

And now the power grid is being used for communications between intelligent power meters and the power company computers.

Power lines are gigantic antennas. They radiate and pick up.

Power is nasty.
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Old 30th April 2012, 01:22 PM   #19
Alexontherocks is offline Alexontherocks  Italy
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DIY power station is the way to go.
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Old 30th April 2012, 01:51 PM   #20
trobbins is offline trobbins  Australia
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How much 50/60Hz do you hear through your speakers??? Is that coming via the AC mains rms level?! Do you think your power supply has similar attenuation for other frequencies, or does it magically lose all filter performance at other audio frequencies?

I suggest you look for other entry paths in to the audio chain for refridgerator and other 'hash' than via conducted mains signals. And if you do have a poor refridgerator, then putting a filter at the amp is the least effective management path for that source of noise.
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