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Old 14th May 2016, 02:41 AM   #1
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Question Questions for a Bridged LM4780 build.

I have been interested in building a LM4780 stereo amp for quite some time now. I am looking to get over 100watts into 8 ohms.

I would like to use 2 of the audiosector boards, each in bridged configuration. I will be completing the build using 2 300VA 22v transformers along with 2 of the power supply boards.

I think I read somewhere that I would need to use these transformers for bridged mode to go from unbalanced to balanced since I don't have a source with balanced output.

EDCOR - WSM Series

but with this i do not know how to make the connections to the amplifier board with the 3 conductors of the balanced connector.

Any help is appreciated!
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Old 14th May 2016, 08:55 AM   #2
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Output from pre amp goes between pins 1 and 4, it doesn't matter which way around. Input ground for both amplifiers on pin 6. Pin 5 to one amp input and pin 8 to the other. Or you could use a dual op amp and one side can invert, if you need more signal drive.
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Old 14th May 2016, 05:57 PM   #3
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Thanks for the reply Jon, but I'm still not sure that I follow.
Peter Daniel posted this schematic that he drew in this thread. Commercial Gainclone kit- building instructions

I'm just not sure how the XLR connection goes to the amplifier board depicted in this schematic
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File Type: jpg balanced.jpg (24.4 KB, 131 views)
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Old 14th May 2016, 06:17 PM   #4
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Actually i think I've got it figured out. It is wired like this? Sorry for the bad ms paint schematic
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File Type: png balancedschem.png (129.7 KB, 132 views)
File Type: png lm4780 board.PNG (79.9 KB, 131 views)

Last edited by mcarter14777; 14th May 2016 at 06:29 PM. Reason: Adding more attachments
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Old 27th June 2016, 02:01 PM   #5
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Yes, that's how it's wired. Only one SG pad should be wired as they are connected internally anyway.
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