What are the differences between the 3875, 3886, and 4780? - diyAudio
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Old 24th January 2006, 01:16 AM   #1
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Default What are the differences between the 3875, 3886, and 4780?

Is it just power output?

I haven't been around this forum for awhile I picked up the briangt kit on the very first group buy and I finally got it working just last week, two 50k pots fixed my buzzing problems. Anyways I noticed there is a two new additions to the chipamp group but I know nothing about them. I am in the process of building up a 7 channel gainclone 3875 but I wonder if I should have waited for the other two.
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Old 24th January 2006, 02:46 AM   #2
lineup is offline lineup  Sweden
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I beginning there was LM1875
and .....


National Semiconductor calls this series of amps Overture.
Here, at National website, you can compare all those audio amplifier chips:

National Audio Amplifier IC - Overview and data page
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Old 24th January 2006, 04:02 AM   #3
lineup is offline lineup  Sweden
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Default Re: What are the differences between the 3875, 3886, and 4780?

Quote:
Originally posted by AJ Bertelson

What are the differences between the 3875, 3886, and 4780?
Is it just power output?
no it is not just power

LM3875 is a very good and stable IC for 4/8 Ohm.
Good for first project, to get some experience.
I prefer the standard setup schematic in datasheet.
You've got to love this IC!


LM3886 can put out more current than LM3875, almost twice as much,
before Current Limit is activated (SPiKe protection).
This makes LM3886 better suited for 4 Ohm at higher powers.
LM3886 is also faster than LM3875.
Higher slewrate. (If you are unlucky you can get oscillation.)

LM4780 is judging from data two LM3886 in same chip.
This gives a bit reduced high power performance, compared to two LM3886.
Mainly because 2 chips can cool better, than one chip. (Larger cooling surface)
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Old 24th January 2006, 05:28 AM   #4
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Well if you bridge up two 3875's would they be equal to one 3886?
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Old 24th January 2006, 06:43 AM   #5
Nordic is offline Nordic  South Africa
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I would suggest you just try a plain LM3875... with the right speakers they get pretty loud.

I see you have tried the Brian GTs, I have the fortune of haveing quite old speakers (in the good old days they made some nice and efficient speakers that the average Joe could afford), Now even if the single chip is not quite as loud as you seem to like.. imagine a handfull of them driving speakers.. I'm sure it will get quite intense.

One of the benefits I see to 3875 is lower power demands = cheaper PSUs.

Output from 3875 is about 75% of 3886
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Old 24th January 2006, 07:47 PM   #6
dfdye is offline dfdye  United States
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While this thread is active, I have a set of speakers that average ~6 ohms but dip to just under 4 in a couple of spots. When gaguing which chips to use, should I use assume a 6 or 4 ohm load for the chips?

My gut says 6, but I figured you guys would be the folks to ask.
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