Another stereo question
 

I'm getting a on and off hum from my subwoofer. Wire brushed all the wire ends. changes amps move speaker wires around and wire brushed the ends. This only seems to happen when i turn up the volume. If I keep at a normal volume doesn't seem to happen. Happens with the engine running or off. The only thing I haven't done is check the battery ground to the chassis or the ohms of the sub it self. Any body else have some ideas. Head unit is clarion with rockford amps, kicker sub correct size wiring nothing fancy.

As you mentioned, triple check every connection in the ground and positive supply.
Temporarily remove the lowpass filter on the sub amplifier and go fullrange. If the hum changes in texture then the issue is likely upstream or in the input daughter board of the amplifier. A little tuner cleaner rinse might do the trick.
Losing an RCA shield ground could make a hum. Trying reseating the RCAs, try another RCA cable, or try slightly collapsing the RCA cable ground outer female for a better contact with the amplifier outer ground shield male.

Another stereo question
 

What is your gain set at?

Had a similar issue in my truck and it turned out the gain was way too high!

By chance are you running your 4 in-boat speakers off of your head unit power only?

Are you using the high-level input on your sub amp, connecting to the radio's speaker leads to get signal to the sub?


Most people will not wire a stereo this way these days, but it could still happen...

If by chance what I described above is accurate, what you are experiencing is an acoustic feedback loop. The speakers conencted to the radio might be acting literally like microphones...

If this is the case, you either need to reverse the phase of the woofer spekaer wiring, OR, you need to turn down the sub amp gain, OR both. OR, if you have RCA line level outputs on the back of the radio, use those to get signal to the amp input as opposed to tapping the high level signal at the speaker(s).

What I describe above should be a stretch for a modern boat install but you never know... :) I have fixed a few of these exact scenarios in cars over the years...

Phil
Kicker