For a while my 04 STi was full of audio equipment that I do not sell / offer... yet is supposed to be my demo car (had all the equipment from before I started the business). I am in the process of slowly changing it all out as I sell off my current stuff. Last week I sold off my Polk components and replaced them with a set of Alpine Type R components. I wanted to make sure I was getting the most out of the speakers so instead of connecting them to my current Kicker 700.5 5 channel, I decided to take an Alpine MRV-F300 that has been sitting in my inventory for a while (was ordered to replace what was believed to be a blown amp in a customers car... but I found out that it was simply a poor installation and a bad ground connection... so the amp has been sitting ever since). I opted to bridge the Alpine 4 channel amp to maximize the output to my fronts and then also bridged the 4 channels of the Kicker to my rears. I was hesitant with bridging the Kicker because I heard mixed reviews on whether it could be bridged stereo or only mono... but it seems to be working great. Anyways, from what I could find, the Alpine and the Kicker still required all 4 RCA inputs to be connected so I had to use a few splitters to complete the task.
The problem is that I now have very slight backfeed (alt. whine) coming through the speakers. It exists regardless of whether the engine is running or not. Since the only thing that I changed was adding a power wire from my cap to the Alpine, a ground from a ground distribution block to the Alpine, and the RCA splitters, I would have to assume that the splitters are the culprit.
My over-all plan is to eventually run 2 of the same Alpine MRV-F300 amps (both bridged for now until I have the time / money to do a 4 speaker rear deck lid). So when the time comes, am I better to split the rca's behind the head unit and run 2 sets of 4 channel rca's back to the amps or keep it split at the amps and try to move them around so they are furter from the power wires at the amps??? Moving them will be tough because they only really come together when they get near the amp (maybe the last 12" or so). As far as money goes, I can get decent RCA cables for a good price so if I will get better sound by running 2 separate 4 channel rca's then I'd rather do that. I really don't want a demo vehicle with alternator whine... lol.
Before anyone asks, I have a true 1/0 awg ground from a solid point (sanded down seat belt bolt) to the dist. blow then 4 awg to each amp. The cap is there simply because I had it, and it works well as a dist. block for the power. I will probably end up removing it when I re-do the setup. The car also has all new 'Big 3' wiring and even a couple extra grounds to make it perfect. Up until adding the new amp, I never had any hint of back-feeding.
On a final note, yes I know this is probably a dumb post to be coming from a shop owner, but ever since my C.City days, I've always been more into the remote start / convenience / etc. aspect of installations and never really did much with audio other than the standard everyday installations. But now that I am a shop owner, I am starting to get more into the audio aspect and want to make sure that I am doing everything in my power to get my customers set up correctly the first time... but training is a long work in progress.
Sorry for the long post, but to those who read through it, I applaud and thank you!!
Kenny
Owner / Technician
KKD Garage LLC
Albany, NY 12205