Summing inputs...

chipco3434 · 31st May 2004, 02:00 PM

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.

Frank Berry · 31st May 2004, 02:12 PM

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.

chipco3434 · 31st May 2004, 03:42 PM

Thanks... and that's a 10K each side to the wiper of a 10K pot, right? That will give me mV output signal then?

officeboy · 1st June 2004, 04:23 PM

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

, I’d 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

31st May 2004, 02:00 PM	#1
chipco3434 diyAudio Member Join Date: Feb 2004 Location: Racine, Wisconsin	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.

31st May 2004, 02:12 PM	#2
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	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. __________________ Frank

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31st May 2004, 03:42 PM	#3
chipco3434 diyAudio Member Join Date: Feb 2004 Location: Racine, Wisconsin	Thanks... and that's a 10K each side to the wiper of a 10K pot, right? That will give me mV output signal then?

1st June 2004, 04:23 PM	#4
officeboy diyAudio Member Join Date: Nov 2003 Location: NW Washington	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 , I’d 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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