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Chip Amps Amplifiers based on integrated circuits

What is this additional capacitor added to PAM8403 Audio Amplifier Board for?
What is this additional capacitor added to PAM8403 Audio Amplifier Board for?
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Old 18th August 2019, 07:34 PM   #1
spiatrie is offline spiatrie
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Default What is this additional capacitor added to PAM8403 Audio Amplifier Board for?

Can someone please enlighten me about the addition of a large electrolytic capacitor to a High-Power 2-Channel 3W PAM8403 Audio Super Mini Digital Red Amplifier Board ?

I came across an instructable to build a Bluetooth boombox and the design incorporates two High-Power 2-Channel 3W PAM8403 Audio Super Mini Digital Red Amplifier Boards. The instructable makes no mention of adding an electrolytic capacitor to the board but one is clearly visible in one of the pictures (shown - pic 1). Looking at the board (pic 2) it appears to have been added to C8 on the top side of the board. The underside of the board (pic 3) appears to illustrate solder points for an additional capacitor 'marked C7', but I can find nothing on the web to confirm this assumption, nor to clearly explain why the designer of the boombox has added one where he has.

Can someone please explain?

This is a link to the instructable:
DIY Tough Bluetooth Boombox (Lasts 20hrs!): 12 Steps (with Pictures)
Attached Images
File Type: jpg PAM8403 Audio Amplifier Board 01.jpg (174.1 KB, 111 views)
File Type: jpg PAM8403 Audio Amplifier Board 02.jpg (26.2 KB, 108 views)
File Type: jpg PAM8403 Audio Amplifier Board 03.jpg (20.4 KB, 106 views)
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Old 18th August 2019, 09:36 PM   #2
PRR is offline PRR  United States
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Any efficient audio Power amp needs a power storage reservoir. If it is "close" to the AC power supply that unit's filter cap can do the job. If there are long wires between, it is conventional to put some local storage "AT" the power amp.

> I can find nothing on the web to confirm

Try the spec-sheet. https://www.diodes.com/assets/Datasheets/PAM8403.pdf
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File Type: gif PAM8403.gif (8.9 KB, 103 views)
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Old 19th August 2019, 01:56 AM   #3
abraxalito is offline abraxalito  United Kingdom
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Lowering the LF impedance of the PSU improves the subjective bass quality. Works on pretty much all chipamps, classD or classAB.
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Old 19th August 2019, 07:55 AM   #4
spiatrie is offline spiatrie
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I read about reducing EMI by putting a large capacitor at the power supply terminal, but the capacitor attached to the board in the picture didn't look to be that so I was confused.

Should I solder the cap to the back of the board where the line drawing is, or should I copy what the boombox designer did and solder it across C8?
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Old 19th August 2019, 08:43 AM   #5
ubergeeknz is offline ubergeeknz  New Zealand
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Quote:
Originally Posted by spiatrie View Post
I read about reducing EMI by putting a large capacitor at the power supply terminal, but the capacitor attached to the board in the picture didn't look to be that so I was confused.

Should I solder the cap to the back of the board where the line drawing is, or should I copy what the boombox designer did and solder it across C8?
Either will work, up to you. Just be sure and get the polarity correct unless you like the smell of freshly baked electrolytics What is this additional capacitor added to PAM8403 Audio Amplifier Board for?
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Old 19th August 2019, 09:11 AM   #6
spiatrie is offline spiatrie
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LOL
Thanks. I'll avoid doing it half-cut!
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Old 19th August 2019, 09:15 AM   #7
ubergeeknz is offline ubergeeknz  New Zealand
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Quote:
Originally Posted by spiatrie View Post
LOL
Thanks. I'll avoid doing it half-cut!
Also wise What is this additional capacitor added to PAM8403 Audio Amplifier Board for?
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Old 19th August 2019, 09:20 AM   #8
jean-paul is offline jean-paul  Netherlands
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The first picture is an example of wrong wiring/soldering skills.Wires should be put in the holes and then soldered.

BTW PAM8406 boards perform better and have slightly higher output power. This one even has output filtering and film caps at the input:

5wx2 stereo dual channel digital amplifier board pam8406 audio amplifier module 5v class d amplifier Sale - Banggood.com

IMO the PAM8406 sounds better than the PAM8403.
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Last edited by jean-paul; 19th August 2019 at 09:23 AM.
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Old 19th August 2019, 10:06 AM   #9
anti is offline anti  Slovakia
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Quote:
Originally Posted by abraxalito View Post
Lowering the LF impedance of the PSU improves the subjective bass quality.
BS.
OBJECTIVELY (!) you get more and better boom. Boom-boom, you know?
Your guts will tell you the objective truth.
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Old 19th August 2019, 11:30 AM   #10
spiatrie is offline spiatrie
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Quote:
Originally Posted by jean-paul View Post
BTW PAM8406 boards perform better and have slightly higher output power. This one even has output filtering and film caps at the input:PAM8403.
Mmm OK. Anything which improves performance is worth serious consideration.

Does using the board you recommend negate the need for the extra 470uF cap? That would be another bonus.
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