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#2
You will find description of possible configurations here: http://www.diyaudio.com/forums/audi...chip-amp-kits-dacs-chassis-13.html#post636565

Amp and PS as per attached schematics. The yellow foils strip inside schematic sheet supplied with a kit is for chip isolation from a heatsink.

For more general info on amp building please refer to this thread: http://www.diyaudio.com/forums/audi...cial-gainclone-kit-building-instructions.html (Please note that the diodes on LM4780 PS board are installed opposite to LM3875; just observe white stripes marking metal tabs orientation).

If you need more specific info, please post questions here.
 

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#5
I have soldered these into place but still not sure if its right...

I'm gonna join the bridges between boards coz I can do that bit.. I'm still not sure about other resistors ID yet. All the pics I can find look like different parts in places to what I have. Chill for a bit, try again soon.
 
#12
A couple of questions...

If I want to use one of the 2 LM4780 kits I have to power 2 channels (left midbass/right midbass), 4ohm impedance each, non-balanced input, which is the best configuration to run, will it require dual toroid transformers and what is the output power?



Thank you.
 
#13
It's best to use separate transformer per channel to power multiple amps.

The graph below shows power vs supply voltage with 4 ohm loads. It's for parallel configuration, but single amp will be the similar, although won't go as high due to current output limitation.
 

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#14
I think the terminology is confusing me.

Please correct me if Im wrong, and thank you for taking the time to answer my questions. This is great service !

Scenario 1:
One kit can be made to run "parallel" (also called dual mono?)which would give you two amplifier channels total, using both boards, one channel per board. This requires two transformers. Does not require balanced input.

Scenario 2:
One kit can be made to run "bridged" which would give you one amplifier channel total, using both boards. This requires one transformer, but you need to use a balanced input source.


Is that correct?

And then finally, IF that is correct than based on that power vs supply voltage graph for 4ohms, would it benefit me to use (2) 400VA 35v+35v transformers for that 2 channel parallel amp instead of the 400VA 18v+18v ?

Thank you.
 
#15
In case you are using only one kit, a single transformer is sufficient.

Also, please note that maximum allowable power supply voltage is 40V DC, so 35v + 35v transformer is out of question, as it produces DC voltage way over 40V.

With parallel setup and 4ohm speakers you'd be getting close to 160W according to graph. In such case a single 400VA transformer is sufficient for both channels. If you are adding mid and high freq amplifiers, then I would switch my recommendation to single 400VA transformer per channel.

In bridged mode, you have 2 options:

1) One kit produces two bridged channels (single amps in bridge)

2) One kit produces one channel (parallel amps in bridge).
 
#16
Peter,

I ordered your 4780 kit a few ago and am currently building it. I see that the 270R resistors are actually 220R. Is this on purpose? I didn't see it documented anywhere on the forum, hence I'm asking.

Thanks!
 
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