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Author Topic: Should I buy this kit?  (Read 1339 times)

exztinct01

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Should I buy this kit?
« on: September 04, 2016, 08:19:03 PM »
I was planning to buy a board from ESP but was still hesitant because of the cost.
Then, I found this kit. It is being sold here in the Philippines and costs only Php457 (about US$ 9.5). Reason for considering a kit is because I think it is easier to work with professionally made boards and that kit is so affordable.
Problem is, it says the Zobel network which is supposed to make it stable does the opposite so it removed those. Also, supply bypass caps are both 3300 uF (is this too large or any values will do?). Luckily, the board still has the holes for the Zobel RC.
Any comment on this kit?
Link is http://e-gizmo.com/oc/kits%20documents/LM3886%20audio%20amplifier/68WPowerAmpLM3886.pdf
~ Stephen

J M Fahey

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Re: Should I buy this kit?
« Reply #1 on: September 05, 2016, 08:14:35 AM »
R1 C5 Zobel IS required, definitely.
If he found it produces instability is because the PCB is poorly designed, period.

Now R2 C6 are wrong, wonder why he added them in the first place.

LM3886 is far from unity gain stable, it needs gain >20X so NFB values 20k/1k are already on he edge, typical suggested value (in the datasheet itself) is 20k/680 ohms, exactly because of that.

R2 C6 lower gain even below 20X and of course cause unstability.

So you are getting a professionally *made*  PCB but that does not mean it´s professionally *designed* , not the same thing.

exztinct01

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Re: Should I buy this kit?
« Reply #2 on: September 05, 2016, 08:47:53 PM »
Great!
~ Stephen

 

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