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  • Passive summing circuit

    Reading conflicting information. It’s for a stand alone continuum center. Would appreciate any help. Thank you

  • #2
    Before or after the amplifier?

    Pretty much the same circuit either way, series resistors from the load to each channel with drastically different values. For amp level you would need perhaps 4 ohm resistors to lose as little power as possible while protecting the amp from out of phase short circuit. You will lose a significant amount of power to the resistors, so they'd need to handle lots of heat.
    Electronics engineer, woofer enthusiast, and musician.
    Wogg Music
    Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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    • #3
      It depends on what you're summing, and why.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #4
        My hope is to get it done between the amp and crossover. It’s a a center channel bagby continuum mtm

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        • #5
          Trying to sum the signal from stereo to mono before it reaches the speaker

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          • #6
            Is it possible to do this without having to buy a bridgable amp?

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            • #7
              My advise is to just use the center channel output of the AVR, and if you don't have an AVR you don't need a center channel.
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #8
                Originally posted by cornajatwa View Post
                My hope is to get it done between the amp and crossover. It’s a a center channel bagby continuum mtm
                Not sure what you're trying to achieve. If you don't have a center channel output from your amplifier - then you don't have a center channel signal. Simply summing together your stereo output to send it to a center channel is....well....kind of pointless - you're just ruining your stereo image. You can't just create a center channel from a stereo mix - center channels, just like surround channels have their own dedicated audio tracks.

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                • #9
                  Hey guys, thanks for the feedback. I need to do a better job of communicating the idea.

                  I had a 3 channel (left center right) bagby continuum setup in the living room and decided to switch to stereo by getting rid of the center channel speaker.

                  Now I have a very nice speaker without a purpose. I’d like to turn it into a portable radio.

                  One problem with that is sending a stereo signal to it. I don’t want to miss out on any part of the signal so I’d like to “sum to mono”.

                  If I can pull that off somehow I’ll be able to slap a full range plate amp (been sitting in the garage for years) on it and be good to go.

                  I have an amp and a speaker and the only thing keeping them from going to work is the stereo to mono signal problem.

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                  • #10
                    Bump
                    is this possible guys?

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                    • #11
                      Yes, before an amp this is an easy task. What's your signal source going to be?

                      For generic line level signals, you'd use a pair of resistors in series with the L and R outputs of about 1k ohm. Put a 10k ohm resistor after those to ground, the other side of which will be your mono output. The resistor values are pretty arbitrary and can have a wide range and still work fine.

                      Google "stereo to mono summing circuit", lots of schematic examples in there. Some omit the parallel resistor to ground, which would work fine too once connected to the amp input.

                      Here's one with some different values, but you should get the gist:
                      Click image for larger version

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                      Electronics engineer, woofer enthusiast, and musician.
                      Wogg Music
                      Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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                      • #12
                        Nice! Thank you! I was hoping to use a Bluetooth or, preferably, an AirPlay dingle 😬 is this still possible?

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                        • #13
                          Originally posted by cornajatwa View Post
                          Nice! Thank you! I was hoping to use a Bluetooth or, preferably, an AirPlay dingle 😬 is this still possible?
                          Sure! Put that circuit between the dingle and the amp.
                          Electronics engineer, woofer enthusiast, and musician.
                          Wogg Music
                          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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                          • #14
                            thanks wogg. is there a passive way to do this as well?

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                            • #15
                              Uh, that IS the passive way to do this.
                              Wolf
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