LM3886 Layout ok?

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Hello,

I´ve just finished my first PCB layout for my LM3886 Amp and i want to ask you if it´s ok?

The schematics I´ve used are more or less exactly the same as those from chipamp.com

The 0,1µF Caps in parallel to the two 2200µF Caps will get soldered directly to the pins of these; Rfeedback will also geht soldered directly to the LM3886s pins!

An externally hosted image should be here but it was not working when we last tested it.
 
I never like the speaker output to be anywhere near power tracks.Think that with only a small solder bridge, stray bit of wire etc, your speaker can end up directly connected to +V = bye bye speaker. Try to isolate it. I'd suggest skipping the track to pin 5, and instead put a wire jumper between the two.

I also find that the Zobel components RZ and CZ work just as well if you put them across your speaker terminals instead of on the PCB. That will give you a little more room. My own LM3886 is stable without the Zobel though, if you wish to try that.

edit: I just noticed there is a component missing - there is no feeback resistor between the output and the inverting input. I guess you are planning to add this by hand between the pins?
 
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So... now I´ve done the following things:

- correctly dissabled the thermals
- removed the connection from Pin1 to Pin5; will solder it on the LMs Pins, as suggested
- Output is now directly under Pin3
- thickend the "track" from Pin3 to Output

An externally hosted image should be here but it was not working when we last tested it.


I want to use the Zobel-Network, but I´ve got to ask, if the tracks to Rz an Cz have to be as thick as the one from Pin3 to Out?

And yes, Rf will get soldered directly to the Chip :)
 
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i've no problem with you basing the design on mine :)

Mine does not have the Zobel on board as previously mentioned. It has the L-C (thiele network?) in place, resistors R6 and R12 should have some 1mm diameter enamelled wire coiled around them as shown here. The zobel is across the speaker terminals (I used 10 ohms 1W + 100nF mylar "Greencap" type)
 
It can have it´s "sizeable" heatsink, even if the Board´s that small :)
If there´s no need to make it bigger - then why should I make it bigger? Of course making it that small makes it much more complicated - but that´s why I am here, requesting your help :D

Because you can allow space on the PCB for the heatsink to sit on rather than hanging loose. Of course it all depends on the lay out, you may have a big metal plate you intend to mount everything on instead? Did I mention I used a fan at the end to keep things cool ? :)
 
@akis: I will mount the PCB onto the heatsink, not the heatsink onto the PCB I think :) So I thought it would be better to make the PCB as small as possible...

@AndrewT: The missing caps an Rf will get soldered directly to the correct pins.
Where should I connect R2 an Signal-Gnd to then? :confused:

@all: L-C-effect? :D
 
separate the dirty (power) from the audio grounds, separate the high current audio from the low current audio grounds.
Then connect them at a single point.

the L of the L//R can go in the route from PCB to output terminals.
The final R+C can go across the terminals.
The first R+C must be located very close to the chipamp, to minimise the L of the interconnecting traces.
 
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