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Old 3rd January 2011, 05:46 PM  
diyAudio Member
Join Date: May 2010

LM1876 :- 80DB Channel Separation
LM4765 :- 80DB Channel Separation
LM4766 :- 60DB Channel Separation


I want Approximately 10-15 RMS watts output ,
I will be using , 20Watts RMS Speaker .

So, how help me to choose which one should I use ?
Old 4th January 2011, 09:11 AM  
diyAudio Member
Join Date: Dec 2010
Location: Bangalore
Since you have a 20W RMS speaker, I think you can go for LM1876 only (Dual 20W RMS rated).
LM4765 and LM4766 are 30W and 40W RMS respectively (if provided with rated voltage). For more info check National website links :
LM1876 - Overture Audio Power Amplifier Series Dual 20-Watt Audio Power Amplifier with Mute and Standby Modes
LM4765 - Overture Audio Power Amplifier Series Dual 30-Watt Audio Power Amplifier with Mute and Standby Modes
LM4766 - Overture Audio Power Amplifier Series Dual 40-Watt Audio Power Amplifier with Mute

Links at the top to download data-sheets as well.

BTW you never mentioned the impedence of the speakers if you intend to use 4 ohm or 8 ohm. Note that LM4765 and LM4766 are rated to be used for 8 ohms loads and LM1876 could be used with both 4 ohm or 8 ohm.
Old 4th January 2011, 05:42 PM  
diyAudio Member
Join Date: May 2008
The LM4765 is a non-isolated version of the LM1876 with improved heatsinking. Therefore it can also be used with 4 Ohm speakers, but will then not give higher output power than the LM1876. The isolated version of the LM1876 makes life easier, because you don't have to worry about electrical isolation against the heatsink.

The LM4766 is a version of the LM4780 in a different case, with lower current limit, worse heatsinking and worse channel separation. It can also work with 4 Ohm, but the current limit puts it in the same league as the LM1876, so it makes little sense to use it for such speakers.

Choose the one you can get for the lowest price which will most likely be the LM1876.
If you've always done it like that, then it's probably wrong. (Henry Ford)
Old 4th January 2011, 05:46 PM  
diyAudio Member
Join Date: May 2010
@indaudio >>

well in data-sheet both 4765 and 4766 are compatible with 4ohm speakers , at-least the data-sheet i got has something like that .
the rms rating of a chip is dependent on voltage applied to it , so having extra headroom in the chip will not matter , cause i will never apply the absolute voltage so , output will be lower ,
regarding 20watt limit , it's @ 25c , the real output of 1876 is 15w !!

what i am really interested in is , the quality of sound and cross talk ? so let me know of them have best sound quality ?

cost more or less same from where i buy these chip online , so price point is not a factor to choose the ic , just the plain quality of sound is the sole reason to choose the ic .

Last edited by horizonrays; 4th January 2011 at 05:50 PM. Reason: adding data
Old 4th January 2011, 05:58 PM  
LAJ is offline LAJ  United States
diyAudio Member
Join Date: Mar 2008
Location: Atlanta Ga. USA
Default None of the above.

I'd use 2 LM3886 chips. It is not good to put all your eggs in one basket. What happens when one side blows? You'll have to replace the whole chip just to fix one side. Besides the 3886 chips are cheap and plentiful. Probably the most popular chip amp in use today!

Last edited by LAJ; 4th January 2011 at 06:00 PM. Reason: added info
Old 4th January 2011, 06:11 PM  
diyAudio Member
Join Date: May 2010
okay laj you have got the point , i will use 4 lm3886 >
two for woofer and two for speakers , i will bi-amp the system , any other recommendation ?
Old 4th January 2011, 06:18 PM  
LAJ is offline LAJ  United States
diyAudio Member
Join Date: Mar 2008
Location: Atlanta Ga. USA
I know it is more trouble but it is worth it. The LM3886 is used in bi-amp applications by a number of manufacturers also (Mackie and Behringer are two that I can think of).
As for another recommendation, I'd put fuses on each chips supply voltages.
Old 4th January 2011, 06:29 PM  
diyAudio Member
Join Date: May 2010
@ laj what kind of power supply do you recommend ?
just filtered power-supply using diode and capacitors ? or regulated power-supply using transistors and regulators ?
i have seen the power-supply designs on this forum all use regulated power-supply without any regulator .
Old 4th January 2011, 06:47 PM  
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
no regulator.
simple: dual secondary transformer + bridge rectifier + smoothing caps for a dual polarity supply.
regards Andrew T.
Sent from my desktop computer using a keyboard
Old 4th January 2011, 07:02 PM  
diyAudio Member
Join Date: May 2010
Andrew Will 10000MFD per channel for 12watt rms be sufficient enough ?


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