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Chip Amps Amplifiers based on integrated circuits

Chip Amp guide
Chip Amp guide
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Old 30th March 2012, 07:28 AM   #1
blue eagle is offline blue eagle  United Kingdom
diyAudio Member
Join Date: Aug 2011
Default Chip Amp guide

Hi all,

I've put together something of a guide to building chip amps which covers my LM3886 based amp. I found it difficult to find accurate information from so many sources on the internet so wanted to document what has worked for me.

I'd like to share it here as I received a lot of help from your members and I will be open to feedback on things that are incorrect or unclear. It is still a work in progress and I'm sure there are things that could be expanded or things that have been missed completely.

. ... Link taken down until I make some changes

(Nb, It isn't supposed to give the best methods, but just the methods that worked for me. So I'm more interested in technical accuracy than engineering excellence)

Last edited by blue eagle; 31st March 2012 at 11:41 AM.
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Old 30th March 2012, 06:47 PM   #2
raudio1969 is offline raudio1969  United States
diyAudio Member
Join Date: Sep 2007
Location: N38
Quote from bottom of page 8:

"Note, if using bare metal remember the metal tag on the top of the LM3886 is connected to GND, so will not electrocute you, but do not let anything apart from ground touch the heat-sink. It would be
wise to paint it."

I would like to point out that on the exposed metal tab version of the LM3886, the tab is connected to V- and not ground. Also, painting the heat sink will increase the thermal resistance of the IC to the heat sink. It is common practice to use a mica insulator on the back side of the IC and a shoulder washer on the front side to isolate the exposed tab from the heat sink.

- Richard
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Old 30th March 2012, 07:49 PM   #3
blue eagle is offline blue eagle  United Kingdom
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Join Date: Aug 2011
Thanks, corrected and since I quoted you, I added your name username at the bottom
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Old 31st March 2012, 07:36 AM   #4
pacificblue is offline pacificblue  Germany
diyAudio Member
Join Date: May 2008
Your power supply schematic is a bit out of the ordinary. You usually combine a centre-tapped transformer with a single rectifier from rail to rail and the centre tap connects to ground. To make things worse BR2 is drawn the wrong way round and if it weren't for the shorts produced by that, you would have two positive rails.

What is the purpose of D1?

C3 should not connect to the centre tap, but between D7 and R17.

I strongly recommend to add fuses to the transformer secondaries.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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Old 31st March 2012, 11:33 AM   #5
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
Blue Eagle.
You are a danger to anyone daft enough to follow your build guide.

No PE/Safety Earth connection.
Figs2 & 5 wrong.
regards Andrew T.
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