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Old 29th January 2014, 09:06 PM   #1
FOXYE is offline FOXYE  Israel
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Default Improving the LM3886 amplifier

Hello,

Currently listening with LM3886 amplifier 20,000μF for each side in the psu.

The sound is very detailed, and have dark sound signature.
But the highs is not pleasant and the mids is laid back.

In summary the sound not "live" as the great LM1875.

Are there any recommendations how to improve the LM3886?

Schematic of amplifier:

Click the image to open in full size.

Last edited by FOXYE; 31st January 2014 at 02:48 PM.
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Old 29th January 2014, 09:48 PM   #2
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Isn't R12 meant to be as close to the pins as possible?
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Old 29th January 2014, 10:03 PM   #3
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I too found the LM3886 a bit dull when compared to the true greats of the audio world. It is cheap and it is easy for those on a limited budget but it can be bettered many times over by discrete circuit designs.
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Old 29th January 2014, 10:04 PM   #4
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Quote:
Originally Posted by KatieandDad View Post
I too found the LM3886 a bit dull when compared to the true greats of the audio world. It is cheap and it is easy for those on a limited budget but it can be bettered many times over by discrete circuit designs.
I second that!
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Old 29th January 2014, 10:33 PM   #5
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Quote:
Originally Posted by KatieandDad View Post
I too found the LM3886 a bit dull when compared to the true greats of the audio world. It is cheap and it is easy for those on a limited budget but it can be bettered many times over by discrete circuit designs.
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Originally Posted by lanchile View Post
I second that!
Every thread in the Chip Amp forum has to have, by law, at least one post about discretes being better.
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Old 29th January 2014, 11:54 PM   #6
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That PCB layout looks terrible, the bypass caps are too small and too far away from the chip pins. I recommend checking for HF oscillation or transient circuit instability.

Mike
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Old 30th January 2014, 12:09 AM   #7
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Quote:
Every thread in the Chip Amp forum has to have, by law, at least one post about discretes being better.
Do you mean as in thread-jacking a thread that is only about a chip amp? Does that happen here? Surely not!

FOXYE, do you have a schematic and a photo of the entire amp?

Abs
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Old 30th January 2014, 12:18 AM   #8
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Quote:
Originally Posted by FOXYE View Post
Are there any recommendations how to improve the LM3886?
The most common mistake I've seen with chipamps is in the layout - poor gronding hygiene. Not keeping signal and power grounds separate IOW.

Show a schematic for how the decoupling caps are wired up, topologically?
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Old 30th January 2014, 12:28 AM   #9
yd1cvj is offline yd1cvj  Indonesia
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C6, input cap, you can up grade .
C11, C12 are too small , increase to 1000 microF with C for audio.

Last edited by yd1cvj; 30th January 2014 at 12:30 AM.
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Old 30th January 2014, 12:29 AM   #10
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Originally Posted by FOXYE View Post
Hello,

But the highs is not pleasant...

I've said it before and I'll say it again, this amplifier needs to have feedback compensation. Try a 27pf capacitor in parallel with R10 and see if there's an improvement.

Also, not helping things is that this layout is terrible, rip out the two small decoupling caps and place them right on the chips pins. 100nF X7R caps are perfect for this job.

I hope this helps.

How does the power supply look? Schematic please
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