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  #11  
Old 10-20-2013, 07:39 PM
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David Analog David Analog is offline
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Originally Posted by JimN View Post
Beside cost, if this is a better way to shield, why don't the manufacturers break the shield and use a small value cap, in series? It would still act as an AC/RF shield, but there would be no DC connection (unless they're using the shield as THE ground).

I don't remember the last time I heard of a shield that was acting to cause this kind of problem when the cabling was routed correctly (away from major noise sources).
That's a good question. I suspect that it has something to do with capacitors normally being used in parallel as an electrical shunt to send any AC noise component to ground rather than in series applications. Also, the capacitor may not function in series and still allow the full shielding function not to mention there may be a problem with it not being linear, interrupting the DC, but still passing the AC components.

In noise issues, rarely do I see cabling that is adequately shielded being a proximity issue related to other wiring with a fluxuating magnetic field. Most often it is a potential difference causing the DC current to find a path to circumvent the isolation. When the lowest resistance path happens to be a connecting ground shield or other wire between two items in the signal path, then you have DC present on that line. And that DC current always carries the AC ripple that is there in every car or boat, whether from the alternator, management module, or a power supply.

Auxilary inputs can be a common noise problem when using a separate ipod or phone power supply (plugs into cigar lighter, etc.). Again, this is a conflict in the ground potential causing the flow of DC current down the shield that was intended to protect the center conductors carrying the audio signal from induced noise. But now it is actually acting as the noise transmitter. Kind of like the fox protecting the hen house. The noise usually disappears once you go to the ipod battery power and end the conflict in ground potential. Or, a ground loop isolator (using small isolation transformers on the ground shield) normally does the trick.

I'm not a fan of using a ground loop isolator as a bandaid while the core problem is left intact. But there are just a few instances when it is the best solution.
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  #12  
Old 10-20-2013, 07:48 PM
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http://www.mastercraft.com/teamtalk/...ad.php?t=42059

I had the same problem. hope you can get some info!
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  #13  
Old 10-20-2013, 09:14 PM
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Originally Posted by David Analog View Post
That's a good question. I suspect that it has something to do with capacitors normally being used in parallel as an electrical shunt to send any AC noise component to ground rather than in series applications. Also, the capacitor may not function in series and still allow the full shielding function not to mention there may be a problem with it not being linear, interrupting the DC, but still passing the AC components to ground.

The AC ripple riding on the DC voltage is a good case for the power and ground wires being twisted and parallel for better common mode noise rejection, as long as they're of adequate gauge to reach from battery to equipment and avoid voltage drop.

In noise issues, rarely do I see cabling that is adequately shielded being a proximity issue related to other wiring with a fluxuating magnetic field. Most often it is a potential difference causing the DC current to find a path to circumvent the isolation. When the lowest resistance path happens to be a connecting ground shield or other wire between two items in the signal path, then you have DC present on that line. And that DC current always carries the AC ripple that is there in every car or boat, whether from the alternator, management module, or a power supply.

Auxilary inputs can be a common noise problem when using a separate ipod or phone power supply (plugs into cigar lighter, etc.). Again, this is a conflict in the ground potential causing the flow of DC current down the shield that was intended to protect the center conductors carrying the audio signal from induced noise. But now it is actually acting as the noise transmitter. Kind of like the fox protecting the hen house. The noise usually disappears once you go to the ipod battery power and end the conflict in ground potential. Or, a ground loop isolator (using small isolation transformers on the ground shield) normally does the trick.

I'm not a fan of using a ground loop isolator as a bandaid while the core problem is left intact. But there are just a few instances when it is the best solution.
Re: the cap used to shunt noise- if that's causing the problem, star grounding is usually considered "best practice", but obviously, exceptions sometimes work as well/better. Maybe breaking the shield and using an R-C to provide a poor DC connection and a good AC shunt would work unless, again, the shield is used for the ground. Foil and braid shielding might cost more than the manufacturer wants to pay.

I'd like to see a full diagram of all equipment/accessories and the wire routing. The vast majority of noise problems I have seen were caused by resistance on ground/neutral (ask me why I was working yesterday!) and sometimes, using the recommended methods doesn't work. I have also seen metal objects act as secondary radiators for noise and this goes back to the late-'70s, when I began to do car audio. Cable routing was usually the easiest way to cure this, although some GM cars had interesting causes- the Chevy Celebrity had a power wire for the blower that passed directly behind the radio and when a cassette deck was installed, noise was induced because the tape head wasn't magnetically shielded. The Cavalier problem was usually because the hood hinge bolts weren't the right ones and/or the hood's bonding clip had been removed.

Ever seen a Malibu ski boat with this kind of noise, in about 1999-2001? They ALL had it and Malibu was paying 3 hours of labor at shop rate for every one of them. The head unit was mounted in the driver's side panel with the main harness directly behind it. Also, they bundled the audio, speaker and radio power wires with the main boat harness BEFORE it reached the dash. When I asked who was doing their installs, the service manager told me "they had a guy who's good with this stuff". I said "No, he's not!" and explained why.
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  #14  
Old 10-20-2013, 09:51 PM
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I do not have other accessories or processors other than the Wetsounds 420sq.
The stock X30 system with the Clarion CDM6 and JL 600/6 always had a slight high pitch hum that did not vary with rpm or radio volume. I added 2 more JL amps to upgrade. The hum did not change in intensity or tone. After I added the Wetsounds EQ, the hum got about 30% Louder. My RCAs are good quality jl x 3 and wetsounds x 1. If I remove the CDM6 source RCA at the 420SQ, the hum remains. If I remove in boat and/or tower Amplifier RCAs at the wetsounds and short the RCAs, the hum disappears. This makes me also think there is a ground issue between the BIG computer and the stereo system. I will post results on further trouble shooting this week. Also note that the hum is present and the same whether playing the FM radio or iPhone aux.
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  #15  
Old 10-20-2013, 10:38 PM
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Originally Posted by djue View Post
I do not have other accessories or processors other than the Wetsounds 420sq.
The stock X30 system with the Clarion CDM6 and JL 600/6 always had a slight high pitch hum that did not vary with rpm or radio volume. I added 2 more JL amps to upgrade. The hum did not change in intensity or tone. After I added the Wetsounds EQ, the hum got about 30% Louder. My RCAs are good quality jl x 3 and wetsounds x 1. If I remove the CDM6 source RCA at the 420SQ, the hum remains. If I remove in boat and/or tower Amplifier RCAs at the wetsounds and short the RCAs, the hum disappears. This makes me also think there is a ground issue between the BIG computer and the stereo system. I will post results on further trouble shooting this week. Also note that the hum is present and the same whether playing the FM radio or iPhone aux.
Just for grins, take a piece of wire and connect it from the head unit's case to the shielding ring of the audio cables' RCA plug. If the noise goes away, solder the wire to the shield of the cable, crimp/solder a ring terminal to the wire (cut it to reach the stud on the back of the head unit) and attach it to the head unit. If it doesn't work, do the same at the amplifier end, connecting it to the ground terminal of the amp, rather than the head unit. If it goes away, solder the wire to the shield of the plug, as described before and connect it to the amp's ground wire.
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  #16  
Old 10-20-2013, 11:50 PM
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Ok. I am going to chime in with some not do technical info on here. The Wetsounds 420 is notorious for creating / amping up noise when induced in a system. The new 420sq has dialed down the noise when compared to the older model, but it is still present. Did you adjust all your gains properly with tge addition of the 420? It takes some gain adjustments and tinkering to get it right. Lot of guys have used an arc audio line driver between the head unit and 420sq to alleviate the noise with success. Just another simple solution to try. Seems like it more of a constant hiss white noise that us amplified with the 420 correct?

I don't have nearly the vast knowledge of Jim or David, but so know this can be a problem in some systems when a 420 is introduced.
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  #17  
Old 10-21-2013, 08:17 AM
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Originally Posted by swatguy View Post
Ok. I am going to chime in with some not do technical info on here. The Wetsounds 420 is notorious for creating / amping up noise when induced in a system. The new 420sq has dialed down the noise when compared to the older model, but it is still present. Did you adjust all your gains properly with tge addition of the 420? It takes some gain adjustments and tinkering to get it right. Lot of guys have used an arc audio line driver between the head unit and 420sq to alleviate the noise with success. Just another simple solution to try. Seems like it more of a constant hiss white noise that us amplified with the 420 correct?

I don't have nearly the vast knowledge of Jim or David, but so know this can be a problem in some systems when a 420 is introduced.
I seem to remember reading about excessive hiss and that's why I offered the definitions for hum and buzz. This is an important distinction, too- if the OP has hiss, there's no point in trying to fix a ground loop because none would exist. If it's hum or buzz, it's usually a grounding/shielding/bundling/equipment proximity issue.

Back in the late '80s and early '90s, car audio systems with an Alpine head unit, Audio Control EQ/crossover and ADS amp(s) were the perfect mix for alternator noise and it was very important to make sure grounding was perfect, not just 'good'. Also, the levels needed to be set differently from the past and at that time, high output head units became more common. Cranking up the input sensitivity on the amp(s) and setting the EQ/crossover at more of a medium level is a great way to hear all kinds of noise. Finding the max clean output for the head unit and then the intermediate pieces has to be done first, then raise the input sensitivity on the amp(s) until the max clean output (or max needed) should be done, but I think the equipment manufacturers should come up with a way to achieve this more easily, using a green LED for a good level and a red for overload. Some commercial/pro audio equipment has this and it makes level setting much easier. It also doesn't force the user/installer to use an oscilloscope or put up with noise and distortion.
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  #18  
Old 10-21-2013, 09:19 AM
djue djue is offline
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This is not a hiss, but a definite high pitch hum. When the boat engine/computers are off or the clarion remote wire is disconnected, the system is whisper quiet without hum/buzz/hiss.
I will add the RCA grounding to my to do list! Thank goodness for this forum and all of your help-learning a lot of good info and may get a noise free system
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  #19  
Old 10-21-2013, 10:07 AM
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Quote:
Originally Posted by djue View Post
This is not a hiss, but a definite high pitch hum. When the boat engine/computers are off or the clarion remote wire is disconnected, the system is whisper quiet without hum/buzz/hiss.
I will add the RCA grounding to my to do list! Thank goodness for this forum and all of your help-learning a lot of good info and may get a noise free system
A "high pitch hum" that is constant and does not change with the rpms. So we know it's not alternator whine if the pitch does not change. A boat management module could be the likely culprit. Noise is always there and normal. However, the noise actually getting into the audio system is not the norm.
There would appear to be a conflict in your description. If the noise is still there when the EQ is unattached from the HU, and the HU is the only audio electronics connected to the boat electronics, then this would seem to eliminate the HU to boat relationship as the cause. You also said that when you unplug the boat electronics to HU Din cable the noise goes away. I now suspect that neither the HU nor the EQ are properly grounded if all statements are true.

Also, keep in mind that a single bad RCA cable can induce noise into all amplifier channels.

An EQ adds gain so it's automatic that the existing noise would increase.

In more contemporary electronics the RCA and amplifier speaker output ground is typically common throughout the signal chain but 'above true ground'. In other words, intentionally there is significant isolation resistance between signal or shield ground and power supply ground. As a means of effective noise isolation this signal ground chain is intended to only terminate and ground back at the source electronics. The old Sony/Audio Control/ads relationships had issues precisely because this combination of equipement did not share the same approach to the signal ground to supply ground isolation. Most contemporary electronics have moved past this and grounding an RCA shield would be counter-productive. However, the Wetsounds WS420SQ version does have an internal switch that allows you to change the signal ground relationship. It's worth a flip of the switch AFTER you have made some headway.

With noise diagnosis you begin with the very last device in the audio signal chain and work backwards in the path. I would start the process over. When you plug in that one cable or component that introduces the noise, stop there, and fully focus on that relationship until you have a hard conclusion.
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  #20  
Old 10-27-2013, 12:29 AM
djue djue is offline
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Update on diagnostics

Grounding the RCAs between the Wet Sounds EQ and amps almost completely silences the hum. Note that grounding the RCA between the source unit and wet sounds EQ does nothing. And of course disconnecting the clarion remote from the Big computer completely resolves the noise with RCAs grounded or not. For those that are interested, the noise is originating from the Ilmor 5.7 throttle position sensor. The same piezo type hum can be heard direct from the sensor area. The sensor evidently calibrates for 2 -3 seconds when the ignition is moved to start. Then shuts down until the engine is started. You can hear the noise through the stereo in those 3 seconds then it goes away until engine start. When I disconnect the TPS wires, the noise is gone.
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