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Discussion Starter · #1 ·
Hi,


I have an integrated amp that has L/R pre-amp outputs that I would like to use for a subwoofer, but my sub only has a single input. Is there a simple way to combine the L/R outputs into a mono signal so that the sub gets all the info, not just one channel?


Thanks

Jared
 

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Quote:
Originally Posted by taoggniklat /forum/post/19602736


Hi,


I have an integrated amp that has L/R pre-amp outputs that I would like to use for a subwoofer, but my sub only has a single input. Is there a simple way to combine the L/R outputs into a mono signal so that the sub gets all the info, not just one channel?


Thanks

Jared
Quote:
Originally Posted by SycamoreSeej /forum/post/19602850

http://www.computercablestore.com/5_..._C_PID459.aspx


Got 3 bucks?

Probably won't work. Simple Y-connectors will also shunt the L/R for the main channels in the integrated amp unless the outputs are separately buffered and that is rare. The OP can try it (for $3) and see if he still has stereo separation on the main outputs. If not, he needs to add a pair of resistors to the Y connector or get one with the resistors built in.
 

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^^^ Nope, this is a much better idea.




Make each Rmix the same as the input impedance of the plate amp and obviously you only need the two of them. Build it into a small plastic jiffy (component) box and add leads each side to connect to the integrated and the plate amp.


EDIT: Kal beat me to it as I was typing whilst I cooked breakfast. My ^^^ refers to post 2.
 

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Quote:
Originally Posted by A9X-308 /forum/post/19602989


^^^ Nope, this is a much better idea.




Make each Rmix the same as the input impedance of the plate amp and obviously you only need the two of them. Build it into a small plastic jiffy (component) box and add leads each side to connect to the integrated and the plate amp.

Yup.
 

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wrong execution. Use a small METAL enclosure, not plastic and the resistors are usually 47k 1/2 watt the 1/2 watt rating is not for electrical requirements just for ease in physical handling and assembly for novices.
 

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Bollocks Giz, a metal enclosure isn't going to make a tad of difference unless the shielding is correctly applied through it and including it.
 

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Show me a commercial audio device with ground paths through plastic. Even a noob should know a ground path via the shielding is required in an unbalanced audio path.


BTW, simply mounting the typical metal sleeved RCA jacks in the wall of a metal enclosure WILL provide the required ground return.


Your naivete in this amazes me.
 

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Quote:
Originally Posted by Gizmologist /forum/post/19603970


Show me a commercial audio device with ground paths through plastic.

That wasn't my original idea...
Quote:
Originally Posted by Gizmologist /forum/post/19603970


Even a noob should know a ground path via the shielding is required in an unbalanced audio path.

I don't have such confidence (apologies to OP as I have no idea of what he can do, but most newbs mess it up)

Quote:
Originally Posted by Gizmologist /forum/post/19603970


BTW, simply mounting the typical metal sleeved RCA jacks in the wall of a metal enclosure WILL provide the required ground return.

What I intended earlier was similar to my in cable (see below) just made easier inside a protective case using no extra sockets and soldering the resistors onto a tag strip, suing flying leads for cables.

Quote:
Originally Posted by Gizmologist /forum/post/19603970


Your naivete in this amazes me.

I've made so many attenuators/passive mixers in cables by cutting them and soldering in resistors series/shunt with nothing more than shrinkwrap and had them work without issue in all sorts of harsh environments, I don't see it as an issue.
 

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I too have made thousands of passive summing devices, signal splitters, mic splitters and combiners and impedance pads, T-pads, H-pads, etc and I too have slapped together adapters etc in cable form, covered in electrical tape, masking tape, gaffers tape, and heat shrink.


However, if you are not faced with an emergency "get it going no matter how" situation, making a small investment in a RS or similar metal enclosure is the preferred method, especially considering the nature of the "anality" of some of the members here with regards to cabling.
 

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For the OP: When in doubt, go with the advice from the audio pro.



If you’re not into a DIY solution, you can always get something like this . A more elegant solution would be to get a project mixer like the Behringer ZENYX 502. It will combine a stereo input down to a mono output.


My only concern is whether or not the combining (by any means) will have an effect on the imaging of your stereo system. I don’t know one way or the other.


Regards,

Wayne A. Pflughaupt
 

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Some of the circuits shown will also work HOWEVER the XLR combining network is incorrectly drawn. Pin 1 (signal ground/shield) is NOT located in the position shown and if wired this way will not work. Also 1k (475+475 and unavailable value) shunts between L/R channels will remove most all the separation. These circuits will NOT maintain the max channel separation the OP is trying to achieve.
 

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Quote:
Originally Posted by Gizmologist /forum/post/19611405


Some of the circuits shown will also work HOWEVER the XLR combining network is incorrectly drawn. Pin 1 (signal ground/shield) is NOT located in the position shown and if wired this way will not work. ...

I agree one probably shouldn't use a graphic that somewhat conflicts with what the graphic is trying to represent. But, afaik, it does work if you go by the pinout numbers does it not.
 

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Quote:
Originally Posted by whoaru99 /forum/post/19613049


I agree one probably shouldn't use a graphic that somewhat conflicts with what the graphic is trying to represent. But, afaik, it does work if you go by the pinout numbers does it not.

These circuits will work if you are using a stereo mix desk and are not trying to maintain maximum channel separation such as most Pro AV suppliers use for standard PA mic mixers. We use stereo desks not for stereo necessarily but for a multitude of mix and main output busses and the stereo desks have a much greater capability of on board EQ and trim adjustments.


Essentially these circuits are Y cables with only 1k isolation between them. This will create an almost full mono combination emanating from BOTH discrete channels and the desired mono SW feed. The OP wants as much channel separation as possible while passively creating a SW output.
 

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The correct thing to do, I would say, is put it through something like a Hafler matrix & connect the sum channel to the sub (which may require hanging a dummy load of the same impedance as the sub on the difference channel). Otherwise you're going to lose stereo channel separation. This could be solved in the resistor-based mixers by adding a passive low-pass filter before the mixer, though.


Another solution would be to use a circuit with an active component, like an op-amp based adder, but that's more applicable to line level — you don't want to do it after the amp.
 
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