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Old 4th April 2008, 11:56 AM   #21
Nordic is offline Nordic  South Africa
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Hi Guys, I am almost done, also picked up two of the chips to do a prototype with. I was well on my way when I saw Daniel's request to be able to fit diffirent input caps.

I won't bother with SMD feedback resistors, lets keep this boards simple (I know SMD is too, but it is scary for the newer guys).

As you know I have made up to 250W RMS amps and those have feedback paths orders of magnitude longer without any adverse effects.

The only places you need to take care on these chipamp boards is the high impendance connections...(around the inputs)

Daniel nice to see you takeing up PCB layout... on your last board, there is something you can learn... look at the schematic, at the bit above the 10R ground lift resistor, see how those connections can aslo form a star (Signal ground star) so each can refference the same ground point voltage. Now translate that to your traces...
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Old 4th April 2008, 12:42 PM   #22
Paswa is offline Paswa  India
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daniel,

I've modofied my PCB as you said and added your name coz u helped me a very kinda way
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Old 4th April 2008, 02:30 PM   #23
Nordic is offline Nordic  South Africa
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Move your large electrolytics next to each other...
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Old 4th April 2008, 04:41 PM   #24
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Nordic, Paswa:

If you are having this PCB built - please add a few and set-up a wiki for us to buy.

I'm interested in at least 6 single-channel boards.

And if you can add the PS to a single board this would be heaven!

thanks
Bob
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Old 4th April 2008, 04:56 PM   #25
Paswa is offline Paswa  India
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Yeh! I've done it, friends. Now check.......
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Old 4th April 2008, 06:01 PM   #26
Nordic is offline Nordic  South Africa
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Click the image to open in full size.

I measuered the fuses, they are not worth wile takeing out I think, you gain a handful of mm at best.

I tried a few layout, each have their own issues, like mounting holes etc...

This one seems to be the best, good routing, can accommodate a number of diffirent caps by drilling hole in inline trace... and on input cap you can choose between two points for connecting one of the leads, by cutting through the other trace with a blade.
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Old 4th April 2008, 06:14 PM   #27
Nordic is offline Nordic  South Africa
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here is the pdf
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Old 4th April 2008, 06:32 PM   #28
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Quote:
Originally posted by Paswa
daniel,

I've modofied my PCB as you said and added your name coz u helped me a very kinda way
Thank you for the kind remarks. If you put my name on then it appears that Nordic needs credit too.
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Old 4th April 2008, 06:36 PM   #29
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Quote:
Originally posted by Nordic
. . .
Daniel nice to see you takeing up PCB layout... on your last board, there is something you can learn... look at the schematic, at the bit above the 10R ground lift resistor, see how those connections can aslo form a star (Signal ground star) so each can refference the same ground point voltage. Now translate that to your traces...
I do wish I knew what that meant. Can you make a photo or quickie pencil sketch?

EDIT2: I think I realized it. The NFB needs a stronger ground than the input so the trace, currently containing a 1m, could run straight up to the NFB. . . and then the 1m could go on the outboard side?

OH, please doublecheck your power caps and terminal block polarity. Pin3 (center) is "-25v" and the negative stripe on the cap will also be onto the "-" trace.

EDIT:
Thanks for the nice comments!!
But, I have more editing skill than creating skill. The first time I made a PCB "from scratch," I was puzzled for half the day.
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Old 5th April 2008, 08:28 AM   #30
Paswa is offline Paswa  India
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for Nordic for post #26,

The center pin or pin 3 is negative or Vee point of LM1875. Nordic, just see it, that the + and - has reversed in your PCB. Otherwise the PCB is the best and so good-looking gal.
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