Replacing the audio system - Amp & Helm Volume Control questions

[Dave Lester F27PC]

My F27PC has a new Kenwood AM/FM/CD/BT radio, which I installed to replace its predecessor, when it stopped putting out volume.

The new one produced the same nothing. I pulled the two (Kenwood) cabin speakers and two JVC speakers from the arch. The Kenwoods were visibly deteriorated. I'm not sure about the JVCs. but again, none of them were emitting sound. All four are being replaced with Sony 65W RMS Marine Speakers.

From various blogs in this forum, I could see that the original problem (no sound) is most likely to be either fuses to the amps, or the twin Kenwood amps themselves. The original Kenwood KAC-424 2-channel amps have been discontinued, with no (recommended) direct replacements. At the recommendation of another trusted audiologist, I have ordered a single 4-channel Kenwood KAC-M3004 amp to replace the original twins.

Here is my first concern: When I wire the new Amp, based on which (of the two sets of) wires I use, will I have helm control that changes the volume or no helm volume control over the arch speakers? [Note: I have no documentation for the original audio system wiring for this boat.]

When I receive my replace equipment, (amp and speakers) I will be back in the boat and checking the fuses (and wire continuity), before replacing the original 2-channel amps with the single four channel amp. Major question number two is: Where are the amplifier fuses?

I look forward to hearing from anyone who has had this issue and made this system upgrade.

Best regards,


Dave Lester

 

[Sanmiam]

The head unit will control volume to amps via the RCA cables used to connect them. Basically the HU will adjust the signal strength out on the RCAs. More signal/more volume.

You will need to set the gains on the amps to match with the signal being received. There are tons of explanations with a google search, but cliff notes: Turn gain on amp all the way down. Turn HU on an adjust volume to about 80%. Play a song on the radio. Slowly turn up gain until you get the either A)the point at which the speakers start to distort - then turn it back down just a hair, or B) the loudest you would potentially want the system to play. You may ask "Why 80%". Well, after that point the most HUs will start to distort, so you really don't want to move past this mark. Not really going to hurt anything if you do (unless you start clipping the speakers), but you are not getting clean sound so why bother?

Amp fuses will be a breaker from Formula, and again on the amp itself (with standard bus fuses). Reach out to formula for a wiring diagram of your boat for reference. Basically, if the LED on the amp lights up your fuses are good. You can certainly pin it using a multimeter as well if you want additional confirmation.

I have been messing with this stuff for 20+ years. If you shoot me a PM I would be happy to send my cell number to provide a lifeline in case you get stuck.

EDIT: mistakenly noted voltage rather than signal in first paragraph of my initial response. Voltage output remains constant, it is the signal that is modulated by the head unit. Concept remains the same, but wanted to update for accuracy.