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Old 7th December 2006, 11:41 AM   #41
dj_zibi is offline dj_zibi  Poland
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pinkmouse I wants to make PCB under two LM4780. I. TWO lm4780 ( every parallel) I want to make in bridge version.

What about this do you think?
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Old 7th December 2006, 02:04 PM   #42
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I would be a bit wary about running the 4780 bridged if you want any real power out of it. At 4 Ohm it gets quite warm, and the package isn't as good as transfering heat as two 3866s. However, if you use a nice big heatsink, 30-35V rails max, and make sure it never drives less than an 8 Ohm speaker then you should be able to get away with it.
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Old 7th December 2006, 04:51 PM   #43
dj_zibi is offline dj_zibi  Poland
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In my amplifier. LM4780 in parallel version worked on power supply +-34V on 4R. It was OK. Radiator had 45-50 * C.
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Old 11th December 2006, 11:13 AM   #44
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dj_zibi: can you please post the eagle files for your board? I would be grateful!
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Old 11th December 2006, 12:03 PM   #45
jaste is offline jaste  Sweden
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Do all resistors have to be with 0.1% tollerence if you want to go parallel?
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Old 11th December 2006, 12:12 PM   #46
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It's best, but you don't have to buy them that way, get more than you need and you can match them with a DMM yourself.
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Old 11th December 2006, 01:00 PM   #47
jaste is offline jaste  Sweden
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true, I just hope my elcheapo DMM got a o,1% tolerence....
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Old 11th December 2006, 01:58 PM   #48
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Quote:
Originally posted by jaste
true, I just hope my elcheapo DMM got a o,1% tolerence....
It's not about absolute accuracy, rather the resolution. Even a cheap 3.5 digit dvm will measure 10K with 10 ohms resolution (10.00). Although there will always be +/-1 digit uncertainty. As a percentage, 10 ohms in 10,000 ohms is 0.1%

Measuring the low-value output resistors is another matter!

Re heat, I agree with PM. Better to bridge with two LM4780s, each running in parallel mode.
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Old 11th December 2006, 02:05 PM   #49
CarlosT is offline CarlosT  United States
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Da**! I've never seen .1% resistors...you guys sure you're not talking about 1%?
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Old 11th December 2006, 02:11 PM   #50
jaste is offline jaste  Sweden
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So the low-value output resistor is hard to meashure, maybe I“ll get that one from 0.1% department rigth away tehn, or do the even exist in that tolerance?
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