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Old 15th August 2011, 09:08 AM   #1
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Default Single Sided LM3886

Hi Guys..Please check this Single layout for Me please

The Attachments include the pcb layout and schematic layout..Thanks in advance
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File Type: jpg lm3886_schematic.jpg (404.4 KB, 254 views)
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Old 15th August 2011, 09:53 AM   #2
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No smoothing caps?
No decoupling caps?
What are the functions of R3, R4, R5, C8, C9 and C10?
Will R1=15k, R6=1k and R7=20k lead to low offset voltage at the output?
C4 is no electrolytic. C1 should not be electrolytic, but if you use one, it will certainly have a smaller footprint.
Most traces are too narrow as are the spaces between the power and speaker traces.
Many traces are unnecessarily long and meandering about like drunk.
Signal traces should be as far as possible apart from power and speaker traces to avoid cross-talk.
Too many unnecessary jumpers.
Pads with no obvious function.
Arbitrary mounting holes.
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Old 15th August 2011, 10:46 AM   #3
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Huge lot discussions are already done on routing LM3886 PCB. search & read them, you will find lot of guidelines. and then refine your layout.
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Old 15th August 2011, 10:54 AM   #4
AndrewT is offline AndrewT  Scotland
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separate the Signal Ground from the Power Ground.

The Power Ground includes the Speaker Return and Zobel Return and Decoupling Ground and PIN7 and Mute ground and Safety Earth (on the metal Chassis) and Zero Volts. The Metal chassis must be connected directly and permanently to the mains cable PE.

The Signal ground must include the Input/Signal Return, the Rin Return, the NFB from C3 (DC blocker) and the RF attenuator (which is missing).

What is VR1?
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Old 15th August 2011, 12:52 PM   #5
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Hi guys, Thanks for replies..

I used the following schematic for my design..Im not too familiar with what some of the components do...

Ive built lm3886's before and they work fine..but for some reason, they all seem to "blow up" when I raise the volume to a certain level.

After some trials I decided to buy this board from Ebay:

LM3886TF LM3886 Amplifier Board DIY Components KIT | eBay

It Worked fine until I raised the volume again.

I dont know If the power supply is the problem, Im using the following torroid:

P042K 160VA Toroidal Transformer 0-35, 0-35 Vac Outputs | eBay

with 1000uF 50V Caps

(VR1 is a 10k Pot)
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Old 15th August 2011, 01:11 PM   #6
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Your traffo is too big. 35V rectified (35x1.41) gives you rails of near enough 50V, way higher than the chips are rated for.
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Old 15th August 2011, 01:13 PM   #7
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I would have thought so. I decided to look into building a voltage regulator..I was taught that zener diodes could be of some use but not really sure..
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Old 15th August 2011, 01:43 PM   #8
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I've never been a fan of regulating chip amps, but there are many threads here that discuss it if you search.
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