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Old 31st October 2005, 04:44 PM   #1
gpapag is offline gpapag  Greece
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Default Filterless Class D

Hi all
I would like to ask if anyone has connected a Class D amp without a LP output filter to speakers as this Texas Instrument .pdf suggests www.eie.fceia.unr.edu.ar/ftp/Comunicaciones/reducing%20and%20eliminating%20class%20D%20output% 20filter.pdf

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George
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Old 31st October 2005, 05:00 PM   #2
matjans is offline matjans  Netherlands
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a friend of mine (pitch254 i think his nick is) has, a tas50xx based class d digital amp.

Tweeters managed perfectly, no probs there. Only thing was that it gave so much hf junk on the speaker lines & the internal wiring that it had trouble locking on the spdif signal when turning up te volume. even at normal listening volumes it would sometimes lose the signal.

That, and the tv & radio were completely useless when the amp was playing music
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Old 31st October 2005, 05:07 PM   #3
gpapag is offline gpapag  Greece
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matjans
the article deals (theoretically) with this problem. Some measures have to be taken during construction.
What i am interested in is the sound of the filterless versus the filtered (same) class D. Any experience?
The supplied URL does not work. Use this insteadhttp://focus.ti.com/lit/an/sloa023/sloa023.pdf

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George
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Old 31st October 2005, 05:12 PM   #4
matjans is offline matjans  Netherlands
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ah, sorry, no experience with that. I've never heard it WITH a filter
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Old 31st October 2005, 05:59 PM   #5
gpapag is offline gpapag  Greece
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Does this mean it was already agreed that it sounded better filterless?
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Old 31st October 2005, 06:04 PM   #6
gpapag is offline gpapag  Greece
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I just realised that i opened this thread in "Chip Amps" area instead of the more appropriate "Class D" area. If the moderator wishes to transfer it there , please do so.
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George
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Old 31st October 2005, 06:24 PM   #7
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Moved, and your link fixed as well!
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Old 31st October 2005, 06:45 PM   #8
gpapag is offline gpapag  Greece
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A double thanks Al.
Talking about links, here is another from Maxim dealing with (manageable) calculations for LC output filters. http://pdfserv.maxim-ic.com/en/an/AN624.pdf
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George
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Old 31st October 2005, 08:53 PM   #9
rjb is offline rjb  New Zealand
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Default Warning

Filterless Class D radiates frequencies via the speaker leads well into radio bands used by others, and you may have a man in a peaked cap knocking on your door:
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Old 1st November 2005, 08:06 AM   #10
PWMan is offline PWMan  Taiwan
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I've been measure a 2W stereo filterless class-D chip in the EMI anechonic chamber, a pair of speaker cable is only 30cm, the EMI radiation result is really bad even in the quiescence and supply voltage is only 5V, don't even think about rated power output.

Filterless type class-d is only suite for "no speaker cable outside" applications , You needs to install all componenents in a shielded case, such like a laytop PC or mobilephone.
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