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Class D Switching Power Amplifiers and Power D/A conversion

Infineon MA12070 Class D
Infineon MA12070 Class D
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Old 18th January 2021, 06:18 AM   #341
jean-paul is offline jean-paul  Netherlands
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I mean why the connection of the middle pin to GND (with or without cap) at all?
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Old 18th January 2021, 06:25 AM   #342
abraxalito is offline abraxalito  United Kingdom
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If you just put the +ve and -ve phases of the trafo to the two (+/-) inputs then the CM voltage isn't well defined at AC. Adding the cap provides a low AC CM impedance. Without the cap, it might still work, depending on how well matched the impedances are at the two inputs but I prefer to ensure its going to work.

Also CM rejection of a trafo isn't perfect, the cap to CT helps with that too.
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Old 18th January 2021, 06:27 AM   #343
jean-paul is offline jean-paul  Netherlands
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It worked well with other circuits in the past where inputs were more or less equal and it ensures galvanic separation. I admit having not used transformers (except for power) for some time now and no practical experience in combination with MA12070 yet.
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Last edited by jean-paul; 18th January 2021 at 06:39 AM.
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Old 18th January 2021, 10:04 AM   #344
Toku is offline Toku  Japan
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Quote:
Originally Posted by jealcuna View Post
you can use 3e audio dsp adau1701 which has balanced output and you can take advantage of the dsp and a high performance from analog device IC. Even you can use sigma estudio to enable some filters.
I had no idea of using the 3e audio adau1701. The price is cheap and you can study DSP in common with the SY-DAP2002 that you have already purchased. I will consider purchasing. Thank you for your ideas.
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Old 18th January 2021, 10:22 AM   #345
commstech is offline commstech  Singapore
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Originally Posted by abraxalito View Post
I connected the CT pins of the trafos to GND via an electrolytic cap as the DC potential isn't 0V. I used 2700uF/6.3V

Here's a pic of how I wired up the AVDD caps - bit of a gash job I must admit. There are polymer caps close to the IC (for low ESR) and those bulky Panasonic 15000uFs further away.
woah, looks kind of challenging. How did you manage to solder it the pin17?
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Old 18th January 2021, 10:25 AM   #346
commstech is offline commstech  Singapore
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Quote:
Originally Posted by jean-paul View Post
I mean why the connection of the middle pin to GND (with or without cap) at all?
i tried disconnecting the middle pin to ground yesterday. Resulted in some squealing and rushing noise. Not very loud but audible from 1m away from my speakers. Putting back the middle pin to ground immediately removed the noise . I did not use any caps like Abraxalito do.
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Old 18th January 2021, 10:26 AM   #347
abraxalito is offline abraxalito  United Kingdom
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I didn't solder directly to pin17, rather I made a connection to the decoupling cap on pin17.
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Old 18th January 2021, 10:30 AM   #348
commstech is offline commstech  Singapore
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Tks abraxalito, i will try to locate this cap that you mentioned. I am really keen to try this mod.
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Old Yesterday, 03:17 AM   #349
ricky005 is offline ricky005
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Are the builds looking promising. or will it take some more time to perfect?
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