Question re: LM3886 Snubber pin connections - diyAudio
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Old 30th August 2007, 09:09 PM   #1
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Default Question re: LM3886 Snubber pin connections

I will be building an inverted LM3886 kit soon.

After I listen to the amp for a while, I plan to add Carlos Filipe's Unregulated PSU Snubber circuit. He has a very good schematic for the power supply, but he just footnotes to add a 100uF + 100pF cap across the chip's PSU pins.

My question is this: Is this how the chip side will look with the caps added to the pins?
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Old 30th August 2007, 09:18 PM   #2
troystg is offline troystg  United States
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"add a 100uF + 100pF cap across the chip's PSU pins."

I'm sure he meant in parallel not series.
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Old 30th August 2007, 09:32 PM   #3
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Thanks Troystg!

Attached is the corrected version.
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Old 30th August 2007, 10:02 PM   #4
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Sorry to correct this again, but I think you should have one between the PSU V+ and GRN and another between PSU V- and GND.

Have a look at the attached schematic of Carlos's rectifier board.
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Old 31st August 2007, 01:08 AM   #5
troystg is offline troystg  United States
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Quote:
Originally posted by salesmonster
Thanks Troystg!

Attached is the corrected version.

The way you have it now would work, but as ianpengelly said it is not the way Carlos has it drawn or implemented.

You would need another set of caps, and instead of going from rail to rail you would go pos rail to grnd and neg rail to grnd.
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Old 31st August 2007, 01:23 AM   #6
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Attached is my current understanding of the circuit. The only difference between my schematic and the original power supply side is the use of 20,000 uF of capacitance per rail. Also, the caps on the pins of the 3886 are represented in the drawing as well. Thanks for any input!

Dave
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File Type: pdf snubber.pdf (11.8 KB, 91 views)
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Old 31st August 2007, 08:15 AM   #7
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Troystg, you are correct it would work. However, is it Dave that you are tying to achieve? As far as I can see your power supply is already snubberized (though I would move the 100uF caps past the large electrolytics (i.e. closer to the output side) ont he rectifier board.

I can't see the purpose of the caps that you are suggesting near the amp itself, unless these are supposed to be the caps recommended for mounting practically on the chips legs to ensure that it operates correctly (i.e. as per the datasheet) and in which case they must go to GND.
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