Single sided gainclone pcb

mateo88 · 1st July 2004, 09:34 PM

I was reading Idefixes thread, and wanted to design a gainclone pcb that is single sided and easy to make at home. This is my first attempt at a pcb layout, so will someone please critique it? It's based on Briangt's schematic. Thanks!

BTW there will be a 22K resistor between pins 3 and 8.

moving_electron · 1st July 2004, 11:46 PM

mateo88,

It looks like you meant to attach a image. But I don't see it. Was it too large by chance?

jackinnj · 2nd July 2004, 02:40 AM

you mean like this:
http://www.tech-diy.com/lm3875_board.jpg

mateo88 · 2nd July 2004, 01:15 PM

Yes, I did intend on attatching an image...

zagisrule! · 2nd July 2004, 01:26 PM

That Tech/DIY PCB leaves alot to be desired. With the chip mounted so far in from the edge, how does one ever hope to mount it in a clean fashion? Look at how spread out the parts are, with sharp acute bends...a no-no in PCB design.

Just so room for improvement is all I am saying.

-Matt

mateo88 · 2nd July 2004, 01:35 PM

Hmmmm.... Perhaps because I am still "under moderation" the images will not be attatched. When I clicked "view contents of this post," however, the attatchment showed up. I'm not really sure what's going on, but the image is only 48k or so.

jackinnj · 2nd July 2004, 02:21 PM

Quote:

Originally posted by zagisrule!
That Tech/DIY PCB leaves alot to be desired. With the chip mounted so far in from the edge, how does one ever hope to mount it in a clean fashion? Look at how spread out the parts are, with sharp acute bends...a no-no in PCB design.

Just so room for improvement is all I am saying.

-Matt

mounting the chip is a compromise necessitated by keeping the power supply trace to the V-, V+ pins as wide as possible -- it has to be at least 150 mils to handle the current.

the bends aren't "acute" -- If you have a Gerber viewer, take a look at the Gerber files on Nat Semi's "Overture" design page. (the image below is an X-Ray of the LM4730 board which illustrates how National's engineers layed out the board for their 18W stereo chip)

even if you hard-wired the resistors directly to the chip you wouldn't be able to get them any closer to the pins of the LM3875 -- and I have tried!

I am using 6 of these boards right now. i had no trouble mounting them on an 11 inch Thermalloy extrusion with a (quiet) 200 cfm blower.

jackinnj · 2nd July 2004, 02:57 PM

Quote:

Originally posted by mateo88
Yes, I did intend on attatching an image...

Mattt -- the pins on the LM3875 do not "snap to" a normal grid (a la www.expresspcb.com 's software) -- they are spaced 67 mils apart. the front to back spacing is 200 mils. if you are using expressPCB you should disable the "snap" function on their software (I am using Ultiboard 7 and just designed a custom "part" for the LM3875, LM3886, etc. -- i have used expressPCB in the past, however.)

sss · 2nd July 2004, 03:05 PM

mateo88 :

what is that wire between the connectors of C1? is that the input signal ? imho u should put it somewhere else

ps
whats up with those resistors connected directly to the chip ? c'mon guys +-1cm wont do any difference

sss · 2nd July 2004, 03:07 PM

oh thats the out

well i think it should be thicker and i still dont like the location

1st July 2004, 11:46 PM	#2
moving_electron diyAudio Member Join Date: Jan 2004 Location: Where the rain does fall but the trees grow tall	Re: Single sided gainclone pcb mateo88, It looks like you meant to attach a image. But I don't see it. Was it too large by chance?

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2nd July 2004, 02:40 AM	#3
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	you mean like this: http://www.tech-diy.com/lm3875_board.jpg

2nd July 2004, 01:26 PM	#5
zagisrule! diyAudio Member Join Date: Apr 2004 Location: Edgewood, NM	That Tech/DIY PCB leaves alot to be desired. With the chip mounted so far in from the edge, how does one ever hope to mount it in a clean fashion? Look at how spread out the parts are, with sharp acute bends...a no-no in PCB design. Just so room for improvement is all I am saying. -Matt

2nd July 2004, 01:35 PM	#6
mateo88 diyAudio Member Join Date: May 2004 Location: Argyle, Texas	Hmmmm.... Perhaps because I am still "under moderation" the images will not be attatched. When I clicked "view contents of this post," however, the attatchment showed up. I'm not really sure what's going on, but the image is only 48k or so.

2nd July 2004, 03:05 PM	#9
sss diyAudio Member Join Date: Jul 2003 Location: Israel , haifa	mateo88 : what is that wire between the connectors of C1? is that the input signal ? imho u should put it somewhere else ps whats up with those resistors connected directly to the chip ? c'mon guys +-1cm wont do any difference

2nd July 2004, 03:07 PM	#10
sss diyAudio Member Join Date: Jul 2003 Location: Israel , haifa	oh thats the out well i think it should be thicker and i still dont like the location

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