Head units sub outputs
 

Hey I am shopping for a 5 channel amplifier and I had a few questions about sub outs. I have an Alpine Head unit with a 3rd RCA pre-out for a sub. The vast majority of 5 channel amps have the 3rd set of RCA inputs, but some have just a single RCA input for the subwoofer. So for example the last generation Eclipse and Memphis Belle 5 channel amps have 2 sets of RCA ins for the speakers and a single RCA for the sub. I am wondering what gives with this? I have never seen a head unit with just a single wire RCA. The only place I have seen single wire RCA's for subwoofers is with Home entertainment amps and active subwoofers. This leads me to beleive these amps are intended for specific Head units, mainly that specific manufacturers head units? Can I just plug one end of the RCA into the subwoofer in on the amp and plug the two ends on the other end of the RCA into the RCA out on the head unit?

I believe this is because subs are mono (not stereo) and only require one channel. I might be wrong though.

Just use a Y splitter. They can be had for like under $10 made by Alpine. Just make sure you have the right ends (male female) Plug into amp and use normal set of rcas off the deck its all going to be mono in the end anyways right?

OK great, I thought that was the case. Will I lose any RCA voltage or signal clarity at all?

Y them together at the HU output, then you need only 1 RCA cable to the amp. Combining them means they add together, won't hurt a thing.
Yes, you need both. 99.9% of sub is mono, but once in a while......