Hissing in tower speakers, but not cabin

[Bogusdogs]

Had an install of a JL M6 10" amp and a JL M1000 5ch amp on my 14 SAN230 with the stock Polk system. The new JL amp powers 4 Roswell horns on the tower and the M6 10" sub. The stock amp powers the 4 Polk in cabin speakers. The hiss only happens on the tower speakers when the engine is running. Otherwise all good. There wasn't a hiss before with the old amp that powered 2 Roswell horns and the 4 stock Polk in boat speakers. So I can only assume that there is something messed up with the new amp/sub/horn wiring configuration or levels/gains.

Like most hissing, it is simply too much. I understand that there can be some his...if you put your ear up to it...but this is significant hissing.

I take it back in to the shop this week for them to look at. I thought before I do, I would reach out and see if people have some direction that I can point them before they start wasting too much of everyone's time...and money.

[bturner]

Poor grounding or ground loop. Did they change the cable to the amps out to the recommended gauge? Are the grounds for the stereo and both amps tied to the same ground?
You could also try installing a ground loop isolator on the inputs to the amp.

[Bogusdogs]

Poor grounding or ground loop. Did they change the cable to the amps out to the recommended gauge? Are the grounds for the stereo and both amps tied to the same ground?
You could also try installing a ground loop isolator on the inputs to the amp.

Thanks for the reply. All great questions and I don't have the answer to any of them.
Are the grounds for the stereo and both amps supposed to be tied to the same ground? I don't know the answer, but when I ask, not sure if you were suggesting they need to be.
I will ask about a ground loop isolator ad well.

The fact that it doesn't hiss when the engine isn't running, seems to suggest a bad ground, yes?

[bturner]

All the grounds need to be tied together so they're at the same ground potential. This is typically done by using bus bars. When I install high power stereos with multiple amps I like to run a single heavy gauge cable to the area where the amps/head unit will be installed and terminate it into a distribution block. I'll then break the individual power cables out from there to the components. This insures that power and grounding is at the absolute same potential. If I can't do a single run I'll do multiple runs directly to a bus bar by the battery and take the feeds directly from there. In general you want as close to a direct link to the battery as possible. Avoid any connections that are "linked" through multiple bus bars or connections.

On the cable gauge..... Look in your manual that came with the amp to see what the recommended gauge is then go to the boat and see what is going to the amp. The cable should be equal to or heavier than what is spec'd by the manufacture. This is a typical short cut area used by a bad or lazy installer.

Also check to see that the polarity of the speaker cables were connected correctly. Sounds crazy but I've seen weird problems here as well. Make sure the positive/negative wires are attached to the positive/negative connectors on the speakers. This is another typical sloppy installation area that I've seen before.

And yes the hiss when running typically is a ground or ground loop issue.

[MLA]

Just to clarify, You stated no his with "There wasn't a hiss before with the old amp that powered 2 Roswell horns" So one amp was removed and the new 5 channel amp was installed in its place? Same power cabling and and RCA? Or did the existing OEM 4 chnl power the 4 in-boats and existing 2 towers. And now existing amp only powers the in-boats and new amp was installed from scratch to power the woofer and all 4 towers?

Just an FYI, ground is not the only place to get ground loop. Takes two (circuits) to tango.

If your shop wants to solve by installing a ground loop isolator, find a new shop.