Noise From Speakers

[Coop]

Just upgraded from a Wet Sounds 420 to a 420SQ. Initially, I had an issue with the tower speakers cutting out (addressed in different thread), which seems to have been resolved with a re-tune of the system (thanks for the advice on that, Tim).

Now, though, I'm getting high pitched noise through the speakers even when the volume is down entirely. On the tower, it seems to be worse in the Pro-60's and less so in the MB's. It's also coming from the 650's in the boat. It's worse when the engine is running, but I also get some noise when in ACC mode.

Any thoughts on cause/diagnostics? Thank you.

[Bill25]

Hi there, I have this same issue. James Walker was out a few weeks ago and
gave me the insight. Apparently, you have to double ground the 420. One standard ground
and then one home runned to the battery directly. That should solve your issue. I have not
Done it yet but that's my plan in the next week or two.

[chpthril]

Where did you grab the red B+ and black B- for the 420SQ? Make sure the all the RCA cables are fully seated.

@ Bill, the 420 does not need redundant (double) grounds, just a single solid ground to the best place. Even though boats only have a common ground, there are some advantages to ground audio gear in the signal path, at the amp(s). But even more important, is where the B+ is terminated. ALL audio gear has to share the same battery reference. If not, this creates a ground loop. Yes, a ground loop has little to with the equipment's ground.

[Bill25]

I agree. I heard the same thing your saying this past weekend. That's why I prefaced it with what I was told by James Walker. I going to get into it in the next week or two and figure it out. I can say I had my entire wet sounds system professionally installed and they missed it; can't tell you if the did it your way however. Thanks for the info. I will share my findings/fix upon completion.

[Coop]

Where did you grab the red B+ and black B- for the 420SQ? Make sure the all the RCA cables are fully seated.

@ Bill, the 420 does not need redundant (double) grounds, just a single solid ground to the best place. Even though boats only have a common ground, there are some advantages to ground audio gear in the signal path, at the amp(s). But even more important, is where the B+ is terminated. ALL audio gear has to share the same battery reference. If not, this creates a ground loop. Yes, a ground loop has little to with the equipment's ground.

Mike -- Sorry for the delayed response on this. I'm finally taking the boat in to have them look at this issue. I don't know the answer to your first question regarding the red B+ and black B- for the 420 SQ, but I will ask. Where should they? I did check the RCA cables. Thanks.

[chpthril]

All the audio gear needs to share the same battery reference.

[ChrisSnow]

Where did you grab the red B+ and black B- for the 420SQ? Make sure the all the RCA cables are fully seated.

@ Bill, the 420 does not need redundant (double) grounds, just a single solid ground to the best place. Even though boats only have a common ground, there are some advantages to ground audio gear in the signal path, at the amp(s). But even more important, is where the B+ is terminated. ALL audio gear has to share the same battery reference. If not, this creates a ground loop. Yes, a ground loop has little to with the equipment's ground.

As an electronics engineer I'm curious why you think the +12V has more of an influence on ground loops than the ground?

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[chpthril]

As an electronics engineer I'm curious why you think the +12V has more of an influence on ground loops than the ground?

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Sent a PM

[philwsailz]

As an electronics engineer I'm curious why you think the +12V has more of an influence on ground loops than the ground?

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I'll jump on here, just to get a chance to respond over here, (haven't done so in a while )

Short answer: "Two things, supply voltage differences and noise from other electronics that share the same power circuit in a standard-wired boat"

When considering 12-volt audio electronics typically found on a boat, any interconnected devices have a potential to create a path for noise when there is a voltage difference between the two devices. Voltage potential will induce current, regardless whether it is on the B+ leg or the B- leg. Voltage potential on either will create noise typically associated with "ground loops".

Historically, we have seen head units / radios wired into the same B+ and B- connections in the harness that goes to the dash and helm area. We historically have also seen, typically with wake boats, that the battery and amps share the space forward of the observer's seat. This combination presents the following issues:

* The amp is close to the battery, (batteries) and has a short run essentially straight to the battery. As a result voltage measured at the amp terminal's will most closely approximate voltage measured at the battery, (batteries).

* The head unit is some distance away from the battery, (batteries) and some distance further along the wiring harness' path.

Ground (B-) conductor to helm:
Length of the harness to the helm and wire gauge of the harness will affect the B- ground. Connections, good or bad, will also add resistance. The "ground" the head unit sees will have a resistance between the radio's B- connection and the battery B- connection. As a result there will be a voltage difference that is easily measured when one measures between the head unit's black wire and the amp's B- terminal. I think we all grasp this clearly. What we miss is that other stuff is also connected to this same ground. The boat's nav light circuit, tachometer, digital dash, etc... noise....

Positive (B+) conductor to helm:
Similarly, there is a length associated with the B+ power wire that creates a voltage drop. That voltage drop may be the same as the B- voltage drop or it may be different. Truth is though, it is usually different. Many random factors at play here, but you will measure a voltage difference between the head unit's red or yellow wire and the amp's B+ terminal. The B+ wire is also connected to all the stuff mentioned above.

Where does a "ground loop" live?
We usually only think about the ground conductors as the key issue when we talk about "ground loops", but this is an over-simplification due to a lack of general understanding in the public eye. Radios and amps in a boat are thought of as DC devices but we don't listen to DC. These devices create AC voltage at their outputs.... Consider this: connect a speaker to a DC voltage source. Past the initial pop, all you hear is silence..... An AC circuit does not have an earth-ground reference, as at any given moment the AC output on the speaker + wire can be swinging to negative... just like AC voltage in the walls of your house. a "ground loop" talks about an AC phenomenon, yet we inadvertently attribute it solely to the DC ground side of the supply circuit.


What is often not considered is the fact that as soon as you connect an RCA cable between the amp and the radio is that you completed a straight-shot common-connection between head unit and amp that is ONLY connected between the radio, (or EQ) and the amp. It is NOT connected to other things in the helm that are creating noise on the B+and B- power wires. The RCA connection becomes a voltage reference between head unit and amp that the power and ground hover somewhere above or below from a voltage standpoint. Adding an RCA cable that creates a buzz or noise does not mean the cable is at fault. It is only giving you the magnifying glass and the audible clue that your system itself has wiring issues.

So now with this knowledge, take your digital volt meter and with your voltage meter set to DC, probe the voltage between the RCA cable's shield and both the B+ and B- conductor. Note the DC offset. Note how the RCA shield floats with respect to the head unit ground. Now switch your meter to AC and do the same thing. Turn the boat on, start the motor, watch... Got an O-scope? That will really make it make sense.

With a typical stock boat with the head unit in the helm wired to helm wiring there is voltage potential all over the place. B+ to RCA shield, B- to RCA shield, Amp B+ to head unit B+ etc. We have two separate circuits established with reference to the RCA cable, both of which will now flow current. When you have voltage potential and a closed circuit you will have noise.

The Fix. Yes, You Need to do Black AND Yellow, (and Red) Power Wires
The way to eliminate the AC issue known as a "ground loop" is to eliminate voltage differences between your electrical components by ensuring all equipment sees the same ground AND supply voltage; you need to mimic the RCA point-to-point connections for both B+ and B-. The easiest way to do this is to not only take a ground wire from your head unit straight to your battery, (batteries) but ALSO take at least the yellow wire, (I do the red as well; I'm OCD) and run it straight to the battery, (or batt switch). In my opinion, it is even better to wire it straight to your biggest amp. Here's why: When you consider there are some pretty large capacitors just inside the amp, next to the power terminals, and they are parallel to the power connectors, (hence parallel to the battery) it seems reasonable that you will get a little voltage smoothing and filtering from these power supply caps... Some might argue this, but for me for now, I prefer to do it this way. It works, so hey????

There is the long answer for why B+ matters. Get all your audio system operating at the same B+ voltage with a common ground that also has zero voltage potential and you remove the rest of the boat's ability to create noise. At that point you can focus on your equipment itself... Adjusting gains, (read: turning them down) and other controls to get the best sound possible.

Anyway, there is my long post.

Phil
Kicker

[lee]

So, are you saying to run the radio's black, yellow and red to the amp inputs?

[chpthril]

Black and yellow but red can stay on the ignition if one chooses.

[99bison]

So after the yellow, black, red are on the same power source... What's next to determine if hu or tt is the noise source?

[chpthril]

Isolate the noise so you can determine where in the signal path, the noise is coming in. If you take the head-unit out of the chain and the noise is still there, you know its down stream.

[99bison]

Yes, it's upstream from amps, take out hu and go directly to amps and its no noise.

[chpthril]

Is the noise present in all modes of the head-unit like CD, tuner, USB, blue tooth, etc?

If you are using an MP3 of some type, make sure its not plugged in to a 12V source for charging

Try with a new RCA and just run it direct from the h/u to amp. dont tie it up to the harness or anything.

So after the yellow, black, red are on the same power source.

exactly where did you terminal the black and yellow, so they are seeing the same battery source as the amp(s)?