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-   -   Lm4780 SS PCB (http://www.diyaudio.com/forums/chip-amps/78142-lm4780-ss-pcb.html)

pinkmouse 21st April 2006 10:25 AM

Lm4780 SS PCB
 
2 Attachment(s)
I just had to knock this up for my own use as a single sided, dual mono board for home manufacture, but I thought I'd post it here just in case it's any use to anyone else. It's based loosely on the work of Brian GT and Peter Daniel, but I've added the soft start mute enable circuit shown in the datasheet. If anyone's interested, I'll post the Eagle files.

Upupa Epops 21st April 2006 11:16 AM

Too thin rails and output lines, too big capacity at rails ( fuses blows by switch on ), Al.... ;)

pinkmouse 21st April 2006 11:41 AM

Well, it runs fine Pavel! :)

I've got one pumping out Massive Attack on the bench as we speak. I'd post a pic but my sister has borrowed my camera.

Mmne 21st April 2006 12:56 PM

I just sapled a couple of lm4780's to play around with and would like to study your eagle files. I'm also interessed in your powersupply solution. Would be nice if you could describe it too.
Cheers

Wynand 21st April 2006 01:24 PM

I don't know if it will be forward to ask but can I have a copy of your pcb file ( maybe schematic also ). I'm trying to make a guitar amp using the LM4780 and a circuit from ESP. This will fit PERFECTLY!!

Thanks.
Wynand.

sivan_and 21st April 2006 02:54 PM

If u can post a high res pic or email..will be appreciated..Thanks

dfdye 21st April 2006 09:48 PM

Dumb question, but will hooking up both of the power ground connectors create a ground loop?

Either way, thanks for sharing! I especially like the softstart mute addition. Is that working well?

pinkmouse 21st April 2006 10:16 PM

I'll post the Eagle files for you all tomorrow, I'm not at home right now.

dfdye, the soft start works well, I used it because I will be using active crossovers and I didn't want any start up twinges in them getting through to the speakers. The power rails are laid out like that because I am using twin rectifiers, so the ground connections at the bottom are for connection purely the a star ground on the chassis.

Mmne, the schematic is virtually exactly the same as the datasheet, so if you download that you will have all the info you need. The PSU is eight MBR10100s in a split bridge configuration, and four 1000Uf Rubicon ZLs. It was one I made a while back, so I didn't do a PCB.

Arius 21st April 2006 11:10 PM

Looks very nice and simple.

I don't get why Upupa said the rail traces were too thin. They look to be at least 60 mils to me. Short 60mil traces won't drop much with 3A or so going through them.

Heh, I remember someone's GC using 10,000uF rail caps :)

Question: Isn't 4 X 1000uF of rail cap a bit on the low side for a 2 X 60W amplifier? It is so wierd that the same folks who use weeny PSU caps on their GC's turn to giant banks of PSU caps for their Aleph clones.

pinkmouse 21st April 2006 11:20 PM

My implementation will use the LMs for mid and treble, and an exixting mosfet amp for bass, so I'm not expecting huge demands on the chips, and the highs are better with lower capacitance in the rails. If you were using them full range, then you could usefully go up to about 10000uf per rail, bass would improve, but the top end suffers a little.


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