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LM3875 KIT from ebay

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2010-08-04 9:27 pm
I got the Power Amplifier KIT 56W rms Audio HiFi Amp Low THD K331 from ebay and had some questions which are not addressed by the instructions.
1. There are five outlets on the left extrem side of the pcb not very clearly marked. Can you confirm that they are V+,V-,Sup Gnd, Out Gnd, Out from top to bottom.

2. There are 2 further inlets at the bottom center labeled GND and IN - I assume they are for the signal input?

3. Iam trying to build a non inverting amp. For this, the cap C1 I assume is the Epcos polyester film of 1uF ? pl. confirm. Can you please confirm if C4 and C6 should be the .47 Epcos polyester film or the surface mount capacitor? or can they be either?

4. C10 and C11 appear on the pcb but no parts supplied nor referenced in the supplied circuit. Are they to be left open?

5. Just above R2 there are 3 holes no indication of what needs to happen here there is a plus sign in the box? There is another small hole to the left of this seris of holes. No idea of what is to be done here. some more holes below R2.
6. A small box with 4 holes between C7 and C11. and 2 holes just below this box. No idea of what is required here.
7. What is the significance of the star placed above R2?

For mounting the surface mount caps, I assume I need to use the side which does not have any labelling and other components will be on the labelled side?
I have attached an image of the pcb with the points in question.

Will a 25V x 2 (200VA) transformer be ok or should I bring it down to 22V?

Any answers, guidelines will be much appreciated.



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As an update, I did get the amp to work and its actually very good. I have been spending more time on it than I want to!!
The link to the store can be found at
gainclone items - Get great deals on opamp, microcontroller items on eBay.co.uk Shops!
This is NOT Peter Daniels site by the way. The seller could do better in terms of prompt communications and a more detailed construction instruction leaflet but is generally good. Also got a powersupply pcb and thermistors from them.

All of them boxed in a broken down amp brought cheap for a few pound on ebay auction. Used a 200VA torrid 2 x 25V from Canterbury windings. DC voltage is a little high at 36V.
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