bridging gainclone lm3875 type amps

jamie1107 · 8th February 2008, 03:51 PM

hi
i have just built 4 gainclones for a couple of systems and they sound great i used the pre made pcb s from chip amp . com and the lm3875 chips all fine what i want to do next is bridge 4 or g of those to gether for each channel of a power amp i have seen some people have done this before but i cant find any info on the builds anyone have any ideas i see one of them uses a ballanced line driver on the input is this overkill or nessacary when bridging chip amps
any info would be good
many thanks

Puffin · 9th February 2008, 11:03 AM

Have you looked at this :-

http://www.national.com/an/AN/AN-1192.pdf

There may be one specific to the LM3875. I used this and have just finished a pair.
I see the pin outs are different but it should work for teh LM3875. I dont know if balanced connection is neccessary.

BWRX · 10th February 2008, 12:35 AM

An inverting and non-inverting input buffer will give you the signals needed for each half of the bridge and will provide a good low impedance drive for the LM3875 chips.

ionomolo · 10th February 2008, 12:46 AM

LM3875 is not rated to drive 4 ohms loads and should not be bridged without paralleling too!

8th February 2008, 03:51 PM	#1
jamie1107 diyAudio Member Join Date: Jan 2008	bridging gainclone lm3875 type amps hi i have just built 4 gainclones for a couple of systems and they sound great i used the pre made pcb s from chip amp . com and the lm3875 chips all fine what i want to do next is bridge 4 or g of those to gether for each channel of a power amp i have seen some people have done this before but i cant find any info on the builds anyone have any ideas i see one of them uses a ballanced line driver on the input is this overkill or nessacary when bridging chip amps any info would be good many thanks

10th February 2008, 12:35 AM	#3
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	Re: bridging gainclone lm3875 type amps An inverting and non-inverting input buffer will give you the signals needed for each half of the bridge and will provide a good low impedance drive for the LM3875 chips. __________________ Brian

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9th February 2008, 11:03 AM	#2
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Have you looked at this :- http://www.national.com/an/AN/AN-1192.pdf There may be one specific to the LM3875. I used this and have just finished a pair. I see the pin outs are different but it should work for teh LM3875. I dont know if balanced connection is neccessary.

10th February 2008, 12:46 AM	#4
ionomolo diyAudio Member Join Date: May 2007 Location: Los Angeles	LM3875 is not rated to drive 4 ohms loads and should not be bridged without paralleling too!

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