new LM4780 layout, any comments?

[katana2112]

YGM

[sasmit]

I have made a pcb using national's art work as a guide, it may not be upto scratch..it works without any hum hiss and sounds good too.. comments welcome..

[sasmit]

with components...not cleaned
have changed a few components after this pic..decoupling cap near IC to monolithic ceramics in place of wima films.

[454Casull]

If you attach a pic, do not preview the post, otherwise the attachment will disappear.

I also suggest that you create a new thread for better visibility.

[sasmit]

didn't want to create an exact same thread..so just posted my pics here...my apologies for disturbing this thread..

[454Casull]

Originally posted by gfiandy
Hi Brian,

You have used split bridges for the power supply for the two different rails and then shared the current paths back to the trasformer buy usign one big plane between the capacitors.

Since you have split the rectification with two bridges, the rectifier currents will flow in a loop through the capacitor C10 and 12 for the +ve rail and C9 and C11 for the -ve rail. This means that to get the minimum rectifier noise on your star point you want to split the return paths for these two rectifiers and join them back at the connection between the two rectifiers. Then a third path should join at the rectifiers to feed the rest of the amplifer star. This way none of the rectifier currents flow in copper shared with the star point, this should reduce the ripple on the ground slightly.

Since you have already had the boards made you could try this out by cutting two slots into the ground plan to isolate a path up to the "star point" OG gnd.

This is only a minor point as you already have a good design but since you are cleary wanting to get the best out of it it may give you a slight improvement.

Regards,
Andrew

Like so?

[BrianGT]

I could give that a try. I finally got around to building a new LM4780 prototype amp last night:

full size: http://www.briangt.com/gallery/lm4780r2/lm4780?full=1
ignore my lack of chassis for now

I configured the amp in stereo configuration for this one. Will try building a pair of parallel amps next.

--
Brian

[nrg2009]

Looks great Brian! How does it sound? How does it compare to your other amps?

[bmwman91]

Very cool! I have been wondering...what is the difference between the LM4780 & LM3886? They seem to be the most popular chips in here, and there's the obvious difference that the the LM4780 has 2 channels. According to their datasheets, it looks like the LM4780 has the same or less THD+N at higher power outputs. Is this correct?

I plan to build a 4ch chip amp (bi-amping some 2-way's I built a while ago), as soon as the current project is done. I opted to make some nice red oak tables for the speakers to get them off my desk...then I will move on to the DIY amp part of it.

Thanks!

[454Casull]

Got a question about the casework. I notice that the piece you've bolted to the chip will likely be a chassis panel in the future. How best to drill the holes so that everything fits? I mean, to get the spacing between the chip hole and the standoff holes correct.