yet another LM4780 pcb

zdr · 12th March 2008, 07:49 PM

I made my own PCB for bridge/parallel LM4780 setups, so decided to post it here. Bitch me now before I go ahead and order some from pcbshop. I wish I could do less power planes piercing, but I wanted to keep it compact. Dimensions are 33mmX70mm.

AndrewT · 13th March 2008, 11:16 AM

it looks like the main criteria was aesthetics.
Surely it's more important to make it electrically correct.

synthius · 13th March 2008, 03:41 PM

obviously we all would like to make the perfect electrical layout andrew......
zdr, nice job on the pcb! I can appreciate the space savings as I ran into problems with space on my last setup.

zdr · 13th March 2008, 07:23 PM

Quote:

Originally posted by AndrewT
it looks like the main criteria was aesthetics.
Surely it's more important to make it electrically correct.

No it was not and sure it is, do you see a specific electrical issue anywhere?

AndrewT · 14th March 2008, 10:59 AM

Hi,
yes, the decoupling caps are too far apart.
The shortest possible leads and the shortest possible trace lengths.
The smallest ones should aim for direct to pin attachment or on traces that go direct to pin.

BWRX · 14th March 2008, 03:21 PM

If I was forced to use the LM4780 I would make a new package that did not have through holes for the NC pins. Otherwise, I would prefer to use two LM3886's.

zdr · 14th March 2008, 07:08 PM

Quote:

Originally posted by AndrewT
Hi,
yes, the decoupling caps are too far apart.
The shortest possible leads and the shortest possible trace lengths.
The smallest ones should aim for direct to pin attachment or on traces that go direct to pin.

They are almost touching the LM4780, it does not get much closer than that? Lets assume I want to put it across the pins directly, underneath the IC. Which power pins then? There are ~4 Vcc, ~5 Vee and 2 GND pins in total, scattered all over the footprint, so how would I connect them exactly? Moreover, the rule of thumb (for <20KHz signals) is to put decoupling caps only if you have more than few inches of PS path between PS caps to IC, which is far from true in this case, so I really doubt they are needed at all.

sunrise · 24th September 2008, 08:29 PM

any progress on this one.... how does it sound if finished....???

14th March 2008, 03:21 PM	#6
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	If I was forced to use the LM4780 I would make a new package that did not have through holes for the NC pins. Otherwise, I would prefer to use two LM3886's. __________________ Brian

24th September 2008, 08:29 PM	#8
sunrise diyAudio Member Join Date: May 2005 Location: delta quadrant	any progress on this one.... how does it sound if finished....??? __________________ when you burn it - burn it good

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13th March 2008, 11:16 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	it looks like the main criteria was aesthetics. Surely it's more important to make it electrically correct.

13th March 2008, 03:41 PM	#3
synthius diyAudio Member Join Date: Nov 2007	obviously we all would like to make the perfect electrical layout andrew...... zdr, nice job on the pcb! I can appreciate the space savings as I ran into problems with space on my last setup.

14th March 2008, 10:59 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, yes, the decoupling caps are too far apart. The shortest possible leads and the shortest possible trace lengths. The smallest ones should aim for direct to pin attachment or on traces that go direct to pin.