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gpapag 31st October 2005 03:44 PM

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 20filter.pdf


matjans 31st October 2005 04:00 PM

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 :smash:

gpapag 31st October 2005 04:07 PM

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 instead


matjans 31st October 2005 04:12 PM

ah, sorry, no experience with that. I've never heard it WITH a filter ;)

gpapag 31st October 2005 04:59 PM

Does this mean it was already agreed that it sounded better filterless?

gpapag 31st October 2005 05:04 PM

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.

pinkmouse 31st October 2005 05:24 PM

Moved, and your link fixed as well! ;)

gpapag 31st October 2005 05:45 PM

A double thanks Al.
Talking about links, here is another from Maxim dealing with (manageable) calculations for LC output filters.

rjb 31st October 2005 07:53 PM

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:

PWMan 1st November 2005 07:06 AM

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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