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Old 25th August 2003, 12:39 PM   #21
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hmmm...can we get a bread board layout?? Thanks in advance...they have got so many pins~! and most of them are for power connections...wonder why they need so many??
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Old 25th August 2003, 08:02 PM   #22
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100Watts is a lot of juice to ram thru such a small package really, probably they simply needed more paths so it get directly to where it is needed instead of travelling thru internal wires
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Old 25th August 2003, 08:15 PM   #23
PRR is offline PRR  United States
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> anybody tried a LM4780? think it could possibly sound good like a 3875?

Sure looks to me like a dual LM3886, with maybe some small 20KHz difference in bias or stray coupling.

Also looks to me like it may not really be out yet. There may be one production run for sampling, and they may not make any more unless somebody places a Big Order.

That is a lot of pins and they are VERY close together (0.040"). And this thing will need a HEAVY heatsink base to pass 125 Watts of dissipation. It almost makes more sense to use two LM3886. Easier to wire, and you don't have all that heat coming down in one place.

As a PA amp: it works great up to a point. Start paralleling speakers down to low-Z, and the Overture amps will clip and shut-down where a good PA amp will huff and puff and keep putting out most of rated power or more. You can't beat dozens of devices.
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Old 25th August 2003, 10:04 PM   #24
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Quote:
Originally posted by li_gangyi
hmmm...can we get a bread board layout?? Thanks in advance...they have got so many pins~! and most of them are for power connections...wonder why they need so many??

unfortunately the stereo 50 and 60W chips have too many pins to fit in a veroboard/breadboard with a standard track pitch even if you bend the pins significantly (not recommended)

see here
http://oc4free.scalded.net/amplifier/amp3.html
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Old 26th August 2003, 11:55 AM   #25
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okie...how 'bout a cheap pcb??
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Old 28th August 2003, 02:20 PM   #26
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I got some samples from national of the 4780's. It has been a real pain wiring it up. The pins are smaller and a lighter gauge that one would expect. I carefully clipped all of the NC pins off and then very carefully bent them to plug into a more usually spaced protoboard.

Results? Not sure yet as I just got it playing. I would not want to go through doing it again. SO if someone builds a bog-standard PCB for these, I will buy 4 of them.
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Old 28th August 2003, 02:21 PM   #27
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Perhaps you can take a few pictures and let us have a look...I do have the samples...the pins are so damn small...
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Old 28th August 2003, 03:11 PM   #28
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Yeah, I have the same problem with the last lot of OPA549s I bought. I mistyped the order code and ended up with surface mount versions with very thin closely spaced pins. I'm sure I'll find a use for them, but it will definately involve a PCB I think.
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Old 21st September 2003, 01:54 AM   #29
ukram is offline ukram  Finland
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Got the LM4780:s, designed the PCB, and i have almost all parts soldered on the board.

I had to ask a friend in Canada to order the samples, because it was impossible to get the samples direct to Finland...

The package is nonstandard (as far as i know). Hopefully "mt200" type mica washer can be used.

My LM4780 page is here:

http://hepso.dna.fi/misc/LM4780/lm4780_amplifier.html

Picture, showing the board in real life:

http://hepso.dna.fi/misc/LM4780/lm4780.jpg
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Old 21st September 2003, 01:56 AM   #30
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Looking good from here...perhaps you might want to try an inverted mode sometime after u have done this...
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