LM4780 Paraclone

[jackinnj]

I reworked my bridged LM4780 amplifier, changing the 4.7uF polypropylene caps to 47uF NP electrolytics, put in some load balancing resistors, kept the soft-start circuitry:



the PCB is a tad smaller -- gonna burn me some boards this evening.

jack

[pinkmouse]

It's a bit hard tracking the circuit with those pcb colours, do you have a schematic?

How are you implementing your soft start? I'm playing with a transistor and an RC circuit.

[jackinnj]

the schematic is on page 6 of the National PDF for the '4780 -- i have found that the folks at National have done a pretty good job in the various configurations of the 4780, 3886, 3875.

this image might be a little clearer, but is large:

[Gcollier]

Originally posted by jackinnj
the schematic is on page 6 of the National PDF for the '4780 -- i have found that the folks at National have done a pretty good job in the various configurations of the 4780, 3886, 3875.

this image might be a little clearer, but is large:

Looks like your + and - supply rails are touching at the upper left near the chip...probably don't want to do this

[RCBandwidth]

National Semi provides the gerber files for the LM4780 on their website.I used them with good results.With a little rework you can reconfigure for bridge or parallel operation. RC

[jackinnj]

Originally posted by RCBandwidth
National Semi provides the gerber files for the LM4780 on their website.I used them with good results.With a little rework you can reconfigure for bridge or parallel operation. RC

National doesn't pay attention to star-grounding in their layout, the space for the caps is smaller than the polypropylene ones used in real life and they also use a socket for the LM4780.

i cleaned up the layout, but the old GIF was over-written with the new one, sorry.

[jackinnj]

well, the boards just came back from the proto-shop -- here's the first one I've assembled:


the fit of parts is a bit snugger than I would like -- so when I have boards made it will be a bit more relaxed. the boards measure about 3.00 X 2.75"

[reever]

Hey Fellow Jerseyite.....

Just curious, but will you be offering these boards to the masses?
And what type of supply configuration will you be using?
I'm a curious newbie to this site, drooling over all of the different chipamp possibilities. Currently handwiring the 3875tf, but my heart is thumpin' o do the 4780

reever

[jackinnj]

yeah, the people's republic of New Jersey --

I usually make up some boards for my own use and to figure out what needs fixin' -- then have a few hundred or so made with silk screen and soldermask and sell them at a little over cost -- the immediate imperfections I noted are that the trace for the mute function is too close to the mounting hole, there is a need to separate the caps by a few 0.010" so they seat themselves squarely, and the zobel and decoupling resistors could be spaced a bit more comfortably.

i am using my "generic" power supply board -- an easy single sided board -- with a quad of MUR860's and 10,000 uF filtration. i've had quite a few requests for a regulated version of this supply, so this might be in the works, along with a "quiet" switching supply for auto use. stay tuned, nothing goes onto my website until it's been thoroughly tested.

[Lsharptec1]

Jack,

I might be interested as well. I too am a resident of NJ.

Some time ago, I obtained two LM4780 chip samples from National Semiconductor.

I thought about using BrianGT's PCB, but I wanted a "bridged" configuration.

Let me know if you do run off some extras.

Larry