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Old 31st May 2004, 02:00 PM   #1
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Default Summing inputs...

I have built a couple of BrianGT's kits and the second one is integrated with a volume pot, thus eliminating my preamp. I am running some line arrays with the PE Pioneed 4 ' drivers and I would like to use a powered sub.

How can I sum the inputs of the source to have a input level output on the GC? This would be used to feed the sub woofer amp.
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Old 31st May 2004, 02:12 PM   #2
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To sum the inputs, you would need an additional opamp or two.
Why not sum the outputs of the amps?
a 1k resistor from the output of each channel into a 10k pot will do the trick nicely.
This is known as passive summing and works well as long as the source impedance (the output of your chip amps) is low.
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Old 31st May 2004, 03:42 PM   #3
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Thanks... and that's a 10K each side to the wiper of a 10K pot, right? That will give me mV output signal then?
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Old 1st June 2004, 04:23 PM   #4
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You don't need an opamp to combine line level outputs.
What frank said will work, and it will keep your volume control working for your sub. But just to be a pain , Id like to add an alternative method of summing.

http://www.epanorama.n et/circuits/linesum.html

Also see this for more info on converting speaker level to signal level
http://www.epanorama.net/circuits/speaker_to_line.html
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