Sub wiring help, high level speaker terminal to RCA line level Sub inputs

A Y-splitter coming out of the pre-amp to connect the amp and the sub will probably work just fine. Doing it that way the pre-amp will see the input impedance of the sub and amp. Where now it sees only the amp. Should not matter but not knowing any of those its impossible to know in advance. The bigger concern I would have, and still not much but it is bigger, is this puts a splitter in the signal path to the amp. More to the point, it puts an additional connection in the signal path. No matter how high quality a splitter you get, or how great the connection, there simply is no getting around the fact you're degrading the signal. Whereas using the power amp speaker path leaves your signal path pristine, untouched.

Frankly this is probably more a theoretical than practical concern. In all reality you will probably never hear the difference. But it will be there. That for me is enough to not even want to try, and is why I suggested the LOC instead.

I completely agree, that's the main reason I didn't want to go with any kind of adapter/splitter and just figure out some way to get a direct connection. It bugs me to spend money on better speaker cables and then terminate them with a Y-splitter.

Just for discussion using the resistors, is it possible to get unwanted feedback back into the pre-amp that can cause some other kind of distortion?

Not sure I understand your question in the post just above. Regarding the first paragraph, a y-splitter would not be used to terminate the speaker cables. Regarding the second paragraph, the resistors would not be connected to the preamp.

In any event, the resistors themselves would not cause any kind of feedback into the power amp to which they would be connected, aside from what is known as Johnson noise which would almost certainly be audibly inconsequential in this situation. And in the unlikely event that the sub itself sent some sort of feedback to the power amp, that might have audible consequences as a result of being injected into the amp’s feedback loop (assuming the amp has a feedback loop), the presence of the resistors would reduce any such effects, not increase them. And likewise with respect to any RFI/EMI that may be picked up by whatever wiring is between the resistors and the sub.

Regards,
-- Al

@almarg I understand I meant terminate as just the end of the cable. You're right I miss-spoke saying pre-amp, I meant power amp. Thanks for the explanation!

Wanted to post a follow up. I've spoken to all 3 companies in the mix, Rythmic, Cambridge Audio, and Schiit, they all said to use the RCA line out with a Y splitter. They said the speaker post connection would at best sound the same, but have the side affect of potential distortion so there's no real point in using that connection unless the sub was made to use them.

I tried using the amps speaker post output anyway, the volume levels were not incredibly different, they were about 25% louder than the RCA line out. In the end I couldn't really notice any difference in sound quality between either one when volume matched. So I'm going to stick with the RCA line outs using a Y split for peace of mind.

Now I have one last question, I've been using BJC LC-1 cables to my power amp, but for now only had left over cheapo component video cables I was testing to the subwoofer. I would like to get RCA's that are Y split themselves to not have to use an added Y adapter. However BJC cannot make the LC-1 cables in Y configurations, only their MSA-1 cables which don't have the same gauge, shielding, etc..

So I'm not sure if it would be best now to use 2 higher quality LC-1 cables attached to the separate Y-adapter, or use 2 lesser quality MSA-1 cables already Y split and eliminate the use of the adapter.

Or is there another cable company that can make better quality custom Y cables for the same price as BJC?