Hooking up an integrated to a subwoofer

Let me first say, I used to know how to do this, but have forgotten.

Im hooking up a friend’s NAD 320 to a subwoofer, Running it full range, so am NOT connecting the sub to the speakers (same manufacturer, Nola). I have two Audioquest Hard RCA splitters to use for the hookup. (1 male and 2 female ends on each splitter.

I have unplugged the bus bars that connect the "preamp out/amp in" settings, so now the preamp-outs are free. I have Y splitters (2), but I can’t remember the actual hookup. if I plug in the male part of the splitters - one into the right channel and one in the left - and run the right and left channels of the sub into the splitters, I will have one (female) RCA empty on the preamp end. What am I forgetting here?
The right splitter goes to the sub in and also to the amp in on the NAD. Same thing for the left splitter. You have to feed both the sub and the amp from the preamp outs on both channels ,if you don’t do that the main speakers will not work. Take a look at page 9 in this manual and you should see how to hook up a subwoofer the way you are doing it!

The simplest way would be to use a Y adapter like this,


Remove the jumper between "preamp out/amp in" , then connect the 2 males of the Y adapter to the 2 females (preamp out/amp in). Use the female of the Y adapter for connecting a cable to the subwoofer input. Use another Y adapter and do the same on the other channel.

Just a word of caution and a suggestion to email Almarg through A/gon mailer and see what he has to say on this type of set up  ... 

What I've gained from his posts and comments is ... if you try to split the preamp out signal to both the sub's plate amp and the main speaker's amp simultaneously ... the preamp will see the input impedances of both the Sub amp and the Main amp  

Here's where I forgot exactly what happens and why I ask you to contact him for clarification ... by splitting the signal from the preamp it either reduce the input impedance as seen by the preamp to the lower of the two amp's input impedance's or it reduces the input impedance as seen by the preamp in half ... I forget which one it does 

Sub amps usually have a very low input impedances and can either drag down the main amp's impedance that the preamp sees or reduce by half the impedances that the preamp sees  

If the subwoofer's plate amp has a 12K ohm input impedance and the main amp has a 47K ohm input impedance ... they can either both be reduced by half or be seen as the lower of the two reducing the main amp's input impedance to 12K ohm  

This may make it difficult for the preamp to drive both  into these lower amp input impedance's ... 

I looked at the SVS manual listed and it doesn't give the spec for their plate amp's input impedance ... but I would not be surprised if it is about 12K ohm  

The same thing can occur with a two channel preamp that has two separate outputs that are not buffered from each other  

A way around this would be to use a buffer to the main amp so it's input impedance is protected from the much lower sub plate amp's low impedance shifting everything around  

In  HT the processor or AVR's Sub Out connection by design are usually buffered from it's Main outs as in HT it is expected that your main amp and sub's plate amp may has a wide difference in input impedances  

In a stereo two channel preamp with two main outs ... I think they were designed to drive separate mono blocks having the same input impedances .. so it's not a problem  

Just a word of caution an a referral to a higher more knowledgeable authority

Enter your text ...
Thanks, yogi boy, with your help (and my reconstruction of the last time I did it), I got it to work fine.