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Old 18th June 2008, 06:19 PM   #1
thoronx is offline thoronx  Yugoslavia
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Default 1 input to 4 amp ?

Hi,

I want to make 2 stereo gc amp in one case to drive four speakers in two different room in My house, and to have individual volume control for 2 speakers in My living room , and another individual volume control for the other two speakers located in the dining room

My Plan:
to build 4 monoblicks based on lm3875 (NI configuration) each stereo pair has its own pot for volume control

is it possible to connect these 4 monoblocks to one input source, if it is, how ? with simple parallel connection of the inputs of gc amp ? have I need to increase the input resistor of those monoblocks ?
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Old 18th June 2008, 08:18 PM   #2
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Default Re: 1 input to 4 amp ?

Quote:
Originally posted by thoronx
Hi,


My Plan:
to build 4 monoblicks based on lm3875 (NI configuration) each stereo pair has its own pot for volume control

is it possible to connect these 4 monoblocks to one input source, if it is, how ? with simple parallel connection of the inputs of gc amp ? have I need to increase the input resistor of those monoblocks ?
You can put a dual op amp buffer in front of or use two dual (one quad op amp) buffer after the pots. If using buffers after pots,least 20k pots should be used.

Use at least one power transformers per stereo pair.
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Old 19th June 2008, 01:31 PM   #3
thoronx is offline thoronx  Yugoslavia
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jaudio - can You suggest some schematic for this buffer ?
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Old 19th June 2008, 02:10 PM   #4
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this is a plain buffer,just add a resistor from + signal input to ground.

http://webpages.ursinus.edu/lriley/r...its/node5.html fig26

With the Lm3875 at a gain of 10 add some gain. A gain of 3 would do.
fig.26

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Old 19th June 2008, 02:24 PM   #5
thoronx is offline thoronx  Yugoslavia
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thx.
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Old 19th June 2008, 02:35 PM   #6
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If it not cost, why not use two separate boxes. You can use the buffer before the pot in the amp located in main listening area. Split each output in two, one (L+R) goes to pot of main amp and the other (L+R) output at the back of the main amp. This way each amp has its own volume control. Change volume without going from room to room.
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