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Chip Amps Amplifiers based on integrated circuits

LM3886 with some problems
LM3886 with some problems
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Old 30th January 2013, 02:13 AM   #21
silver1omo is offline silver1omo  Mexico
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Join Date: Jan 2011
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Quote:
Originally Posted by JMFahey View Post
Which leg?
Connected to what?
Following the first schematic, the one with r6 and c4, I believe it is the speaker return. And connect to star ground.
It is fixed now. I needed to separate signal and power ground.
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Old 30th January 2013, 02:42 AM   #22
Oliphant is offline Oliphant  New Zealand
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LM3886 with some problems
You may also want to add a small (something in the 10's of picofarads range) capacitor in parallel with your feedback resistor R3. This will compensate for high frequency oscillations. You'll notice the sound get a lot smoother.

Start with 4p7 and increase from there. If you have an oscilloscope, put a square wave through it and if your square wave has a jagged edge increase the capacitance to 10pF etc, repeat until the output wave is as smooth as the input wave.

You can also do this by ear if you don't have a scope, just listen out for extended "sss's" when people sing or harsh high notes, when those become silky smooth, you've got the right cap value.
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Old 30th January 2013, 08:24 AM   #23
Oliphant is offline Oliphant  New Zealand
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LM3886 with some problems
I've just checked my own gainclone and I've used a 27pF cap across the 22k feedback resistor
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Old 30th January 2013, 08:42 PM   #24
silver1omo is offline silver1omo  Mexico
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Thanks Oliphant, I'll wait until I have it in a case properly grounded before modding.
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