LM4780 SS Pcb - Page 5

dj_zibi · 7th December 2006, 12:41 PM

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?

pinkmouse · 7th December 2006, 03:04 PM

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.

dj_zibi · 7th December 2006, 05:51 PM

In my amplifier. LM4780 in parallel version worked on power supply +-34V on 4R. It was OK. Radiator had 45-50 * C.

baskiria · 11th December 2006, 12:13 PM

dj_zibi: can you please post the eagle files for your board? I would be grateful!

jaste · 11th December 2006, 01:03 PM

Do all resistors have to be with 0.1% tollerence if you want to go parallel?

pinkmouse · 11th December 2006, 01:12 PM

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.

jaste · 11th December 2006, 02:00 PM

true, I just hope my elcheapo DMM got a o,1% tolerence....

mhennessy · 11th December 2006, 02:58 PM

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.

CarlosT · 11th December 2006, 03:05 PM

Da**! I've never seen .1% resistors...you guys sure you're not talking about 1%?

jaste · 11th December 2006, 03:11 PM

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?

7th December 2006, 03:04 PM	#42
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	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. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

11th December 2006, 01:12 PM	#46
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	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. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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7th December 2006, 12:41 PM	#41
dj_zibi diyAudio Member Join Date: Mar 2005 Location: Wroc³aw/poland	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?

7th December 2006, 05:51 PM	#43
dj_zibi diyAudio Member Join Date: Mar 2005 Location: Wroc³aw/poland	In my amplifier. LM4780 in parallel version worked on power supply +-34V on 4R. It was OK. Radiator had 45-50 * C.

11th December 2006, 12:13 PM	#44
baskiria diyAudio Member Join Date: Jan 2006 Location: budapest	dj_zibi: can you please post the eagle files for your board? I would be grateful!

11th December 2006, 01:03 PM	#45
jaste diyAudio Member Join Date: Dec 2005 Location: Stockholm	Do all resistors have to be with 0.1% tollerence if you want to go parallel?

11th December 2006, 02:00 PM	#47
jaste diyAudio Member Join Date: Dec 2005 Location: Stockholm	true, I just hope my elcheapo DMM got a o,1% tolerence....

11th December 2006, 03:05 PM	#49
CarlosT diyAudio Member Join Date: Oct 2006	Da**! I've never seen .1% resistors...you guys sure you're not talking about 1%?

11th December 2006, 03:11 PM	#50
jaste diyAudio Member Join Date: Dec 2005 Location: Stockholm	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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