Homemade summing box?
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- audio school
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Homemade summing box?
Has anyone made a homemade summing box? I seem to remember that if you
-take plain resistors,
-put them in series with the hot wire of audio outputs, and
-tie the leads of the resistors together on the side of the resistors opposite the input - the wire from the audio output,
you can combine several outputs without having interaction between them. In other words, mix them.
Has anybody tried this?
-take plain resistors,
-put them in series with the hot wire of audio outputs, and
-tie the leads of the resistors together on the side of the resistors opposite the input - the wire from the audio output,
you can combine several outputs without having interaction between them. In other words, mix them.
Has anybody tried this?
robertm2000
Re: Homemade summing box?
Tons of gear "sums" signals together like this internally. It's called passive summing. It's a perfectly fine way to do it, assuming there's some sort of makeup gain available afterwards if you need it.robertm2000 wrote:
Has anybody tried this?
An even better way to do it is to add an active summing stage so you've got a low-impedance output to drive the next piece of gear. An inverting summing amplifier would be the best choice as the Thevenin equivalent resistance of one channel doesn't effect the level of the other channels, unlike a non-inverting summing amplifier. You can then put another inverting amplifier after it to bring it back to the correct polarity and make it variable to adjust the makeup gain. Pretty simple with one dual opamp.
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- gettin' sounds
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I used this web thread to build mine:
http://www.groupdiy.com/index.php?topic=16731.0
It works as advertised on complex mixes (I used Millennia Media pres to bring it back up to level). Small mixes, say a jazz combo, didn't seem to benefit. Also, in one environment I've used it, it developed a ground hum. Not sure why, there may have been something in the electricity or air causing that - I just mention it so you're informed.
Honestly, for what I do, I'm not sure I'd replace it if it was lost.
http://www.groupdiy.com/index.php?topic=16731.0
It works as advertised on complex mixes (I used Millennia Media pres to bring it back up to level). Small mixes, say a jazz combo, didn't seem to benefit. Also, in one environment I've used it, it developed a ground hum. Not sure why, there may have been something in the electricity or air causing that - I just mention it so you're informed.
Honestly, for what I do, I'm not sure I'd replace it if it was lost.
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- audio school
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- Joined: Fri Oct 21, 2011 12:50 pm
- Location: Longview WA
Here's mine:
10 pairs of unbalanced ins. It's got a passive output which gets the signals before it hits the onboard makeup gain stage, then a variable gain stage, then a set of four independent outputs each with its own volume control. It takes 12VAC wallwart power and internally converts to +/-12VDC bipolar supply for itself, with two "aux power" outputs. It's pretty specifically built for my situation, but works pretty well.
10 pairs of unbalanced ins. It's got a passive output which gets the signals before it hits the onboard makeup gain stage, then a variable gain stage, then a set of four independent outputs each with its own volume control. It takes 12VAC wallwart power and internally converts to +/-12VDC bipolar supply for itself, with two "aux power" outputs. It's pretty specifically built for my situation, but works pretty well.
- digitaldrummer
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I built two of them based on this:
http://www.forsselltech.com/media/attac ... hsum_2.pdf
the pictures in the group DIY link look nice and clean! much better than my first attempt that's for sure.
and since I had room in the box, I also added a monitor switcher (for active or self-powered monitors). In one of the units I used a toggle switch (so you can choose between two pairs of monitors), and on the other I used a 3-way rotary switch so I can select from 3 different pair. That is the unit I use in my studio today.
Mike
http://www.forsselltech.com/media/attac ... hsum_2.pdf
the pictures in the group DIY link look nice and clean! much better than my first attempt that's for sure.
and since I had room in the box, I also added a monitor switcher (for active or self-powered monitors). In one of the units I used a toggle switch (so you can choose between two pairs of monitors), and on the other I used a 3-way rotary switch so I can select from 3 different pair. That is the unit I use in my studio today.
Mike
Last edited by digitaldrummer on Mon Oct 01, 2012 2:28 pm, edited 1 time in total.
- digitaldrummer
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don't forget about this one too:
http://www.diyrecordingequipment.com/st ... mming-kit/
simple and cheap.
Mike
http://www.diyrecordingequipment.com/st ... mming-kit/
simple and cheap.
Mike
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