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Registered Member #941
Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
MAX913, but LT1016 and AD8561 will drop right in with no changes, downside is that LT1016 is ridicolously expensive, so when i build more of these i will have to go with AD8561 as it is the cheapest as well as the only one i can get in PDIP at a reasonable price(around 4 euros).
Registered Member #941
Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
UNACCEPTABLE!!! Building in shielded cans is just sweeping the problem under the carpet.
If class d modules from Hypex and Anaview/Abletec can be run without shielded cans in the same box as a AM/FM tuner with no interference what so ever, i want my diy to have the same ability.
Therefore i put class d on the shelf until i come up with a board layout that fullfills this requirement. Until then, no more class d will be produced.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The Coldamp module I had used a few tricks: A second stage of filtering on the output, a RC snubber on the switching node to suppress ringing, and it was shipped with some small ferrite chokes to be inserted in the power supply wires if you had any trouble. Using it as a bass guitar amp, I mostly had trouble with switching noise getting back into the preamp input, causing gross-sounding distortion. I had to limit the bandwidth of the preamp quite a bit.
RC or LC filters will only be effective if the filter capacitor is grounded to a low-impedance ground. Putting the whole circuit in a metal box and grounding the EMI filter caps directly to the box where the wires pass through is a brute force technique, pretty much guaranteed to work. The box forms a Faraday cage and all the return currents from the caps are confined to the inside.
I would be very surprised if any Class-D amp module could be used in the same box as an AM tuner without some pretty epic levels of shielding and filtering. Or nowadays a clever noise shaping algorithm connected to the tuner, that moves the noise energy away from whatever station you're listening to
Registered Member #941
Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
My boards did use a ground plane.
I took these pics for a troubleshooting thread at diyaudio:
And i stayed up late last night and drew this, but im gonna assume its just as terrible as the previous one, if not worse. Worse or better ? you decide:
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