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gps causing amp problem

Old 11-21-2017, 06:29 AM
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Default gps causing amp problem

I noticed when my stereo is turned off my amp puts out a very low tone pop,pop,pop,pop,pop sound. Kind of sounds like a grouse drumming in the distance. I couldn't figure out what was going on till I turned off my Garmin 7612 and the sound disappears. Any ideas?
My amp is wired directly to battery as per instructions. The garmin is wired to fuse panel in console. Transducers are a pair of gt51 th.

Last edited by barrell; 11-21-2017 at 06:35 AM.
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Old 11-21-2017, 07:32 PM
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Originally Posted by barrell View Post
I noticed when my stereo is turned off my amp puts out a very low tone pop,pop,pop,pop,pop sound. Kind of sounds like a grouse drumming in the distance. I couldn't figure out what was going on till I turned off my Garmin 7612 and the sound disappears. Any ideas?
My amp is wired directly to battery as per instructions. The garmin is wired to fuse panel in console. Transducers are a pair of gt51 th.
The head unit is probably the source. It might share ground with chart plotter.
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Old 11-23-2017, 05:25 AM
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Wire a relay to amp power line so that amp shuts off when you turn off stereo.
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Old 11-24-2017, 05:30 AM
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The popping sound is there when the head unit is on and off. Its just more obvious when the stereo is turned off. Only wat to get rid of it is to turn off gps/fishfinder. Maybe Ill experiment by pulling transducer wire out of 7612. That wont harm 7612 will it to have it on without transducer attached?
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Old 12-14-2017, 05:53 AM
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Ok so I still have this problem and by experimenting Ive narrowed the source down to the transducers. When I disconnect transducers from back of garmin 7612 the popping sound goes away even though the unit is still turned on. The power wires to the amp and the transducer wires are in the same chase back to the stern as I only have the one option.
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Old 12-14-2017, 06:51 AM
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Power wires not the issue. Its bleeding in through the rcas.
Maybe the grounds but if they are all joined then not that.
You can ground the gps chassis but doubt that will help.
Check the rcas for any knicks
Also the sonar module is in the 7612 which is what is emitting.
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Old 12-14-2017, 08:22 AM
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One of two things.
When the sounder pings the transducer, the current is momentarily much higher than when not pinging. The Amp could be seeing this small 12V reduction at the battery and makes this noise. Take a small SLA battery and run one or the other to test this theory.

The other option is that there is some radiated effect. But, look at the above scenario first.
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Old 12-15-2017, 04:07 PM
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Originally Posted by Dockholiday74 View Post
Power wires not the issue. Its bleeding in through the rcas.
Maybe the grounds but if they are all joined then not that.
You can ground the gps chassis but doubt that will help.
Check the rcas for any knicks
Also the sonar module is in the 7612 which is what is emitting.
If the sonar module is inside the 7612 and is emitting the pulse why does it go away when I pull transducer wire out of back of 7612 while its on?
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Old 12-15-2017, 06:55 PM
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when you turn the stereo off, does the amp turn off? it should...

don't pull the transducer out when the unit is powered on. or plug back in. that is how you blow things up.
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Old 12-16-2017, 05:46 AM
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Originally Posted by smac999 View Post
when you turn the stereo off, does the amp turn off? it should...

don't pull the transducer out when the unit is powered on. or plug back in. that is how you blow things up.
No I wired the amp directly to the battery as described in the manual. It comes on when I turn on battery (accessory) switch. I worried about turning on 7612 without transducer . But I did it as an experiment and it showed the transducer needs to be plugged it to cause the interference.
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Old 12-16-2017, 06:32 AM
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Originally Posted by barrell View Post
[GPS] causing amp problem...
It is completely impossible that a transmitter in a satellite in the Global Positioning System in orbit about 12,500 or more miles away is causing interference to your audio amplifier.

The more likely cause is that your SONAR is interfering. Look for the path of the electrical cables involved in the SONAR and the audio amplifier to see if they are in close proximity to each other, perhaps bundled and tied together at some point. The SONAR emits a strong electrical pulse that is carried on the cable between the display unit and the transducer. This cable should be kept physically separated and isolated from all other electrical cables on the boat. In particular, any audio cables that are unbalanced signals and carried between a source and an amplifier must be isolated from the SONAR cables.

To determine the entry point into the audio system, test to see if the strength of the interference increases when the VOLUME control of the audio amplifier is raised. If the interference increases, then the point of entry into the audio system is upstream of the volume control. If the audio interference does not change with the setting of the VOLUME control, the entry point is downstream of the volume control.
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Last edited by jhebert; 12-17-2017 at 05:54 PM.
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Old 12-16-2017, 07:23 AM
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Originally Posted by jhebert View Post
It is completely impossible that a transmitter in a satellite in the Global Positioning System in orbit about 12,500 or more miles away is causing interference to your audio amplifier.

The more likely cause is that your SONAR is interfering. Look for the path of the electrical cables involved in the SONAR and the audio amplifier to see if they are in close proximity to each other, perhaps bundled and tied together at some point. The SONAR emits a strong electrical pulse that is carried on the cable between the display unit and the transducer. This cable should be kept physically separated and isolated from all other electrical cables on the boat. In particular, any audio cables that are unbalanced signals and carried between a source and an amplifier must be isolated from the SONAR cables.

To determine the entry point into the audio system, test to see if the strength of the interference increases when the VOLUME control of the audio amplifier is raised. If the interference increases, then the point of entry into the audio system is upstream of the volume control. If the audio interference does not change with the setting of the VOLUME control, the entry point is downstream of the volume control.
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ReRead the post its when the transducer is hooked up
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Old 12-16-2017, 08:01 PM
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Originally Posted by barrell View Post
No I wired the amp directly to the battery as described in the manual. It comes on when I turn on battery (accessory) switch. I worried about turning on 7612 without transducer . But I did it as an experiment and it showed the transducer needs to be plugged it to cause the interference.
stereo amps have a 3rd remote wire that connects to the stereo. the amp turns on and off with the stereo.

turning the unit on with no transducer is fine. you said you pulled it out while it was on, which is a big no no.


if the RCA cables and transducer cable is in the same pipe, and that is the only pipe. there is likly nothing you can do. you can try rca inline noise filters.

hook up the stereo / amp correctly. so when the stereo is off, there is no amp noise. that will fix half your problem.
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Old 12-17-2017, 05:29 AM
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My earlier reply elicited this comment:

Originally Posted by prowlersfish View Post
Re[-r]ead the post [.] [The interference occurs] when the transducer is hooked up
I don't need to re-read "the post". I already read all prior posts in this thread.

My recommendation remains the same. The SONAR is the source of the interference, and the mechanism is via the proximity of the electrical cables for the SONAR and the audio amplifier to each other.

The cessation of the interference when the SONAR transducer is disconnected is an affirmation of my recommendation that the SONAR is the cause. There are two possible interpretations of the relationship between the transducer being connected and the interference occurring:

--when the transducer is disconnected the SONAR stops trying to generate an initial pulse to excite the transducer and the interference it was causing then stops; or

--the SONAR continues to generate an initial pulse to excite the transducer, but since it is not connected, the mechanism to introduce the interference into the audio amplifier is removed because the transducer cable is no longer carrying the initial pulse signal.

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Old 01-05-2018, 07:02 AM
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Ok, I fixed it. After calling airmar, who were very help full even after informing me they did not build the th51 transducers, garmin did. Although their info was incorrect. They said I needed to add rfi filters to the power wires of both the jbl amp and the garmin 7612.
I was on hold with garmin for 3 days with no one picking up.
JBL bounced me around to different departments in 8 emails with no one willing to talk to me.
It was catroonz car stereo shop in vero beach that finally pointed me in the right direction. He told me to pull the RCA jacks off of the amp while the head unit was off to see if I needed to add a rfi filter to the rca wires.
Turns out that stopped the drumbeat because there was some defect in the RCA wires. By simply replacing the wires with a fresh set I got rid of the interference coming from the transducers.
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Old 01-05-2018, 07:10 AM
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Originally Posted by barrell View Post
Ok, I fixed it. After calling airmar, who were very help full even after informing me they did not build the th51 transducers, garmin did. Although their info was incorrect. They said I needed to add rfi filters to the power wires of both the jbl amp and the garmin 7612.
I was on hold with garmin for 3 days with no one picking up.
JBL bounced me around to different departments in 8 emails with no one willing to talk to me.
It was catroonz car stereo shop in vero beach that finally pointed me in the right direction. He told me to pull the RCA jacks off of the amp while the head unit was off to see if I needed to add a rfi filter to the rca wires.
Turns out that stopped the drumbeat because there was some defect in the RCA wires. By simply replacing the wires with a fresh set I got rid of the interference coming from the transducers.
Yep. There you go. Modern electronics are so well shielded that its rare you have any bleed anymore. Long gone are the big rfi tubes on power cables. The ground in the rca was probably broken. Glad you figured it out!
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Old 01-05-2018, 09:15 AM
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Originally Posted by barrell View Post
Ok, I fixed it. After calling airmar, who were very help full even after informing me they did not build the th51 transducers, garmin did. Although their info was incorrect. They said I needed to add rfi filters to the power wires of both the jbl amp and the garmin 7612.
I was on hold with garmin for 3 days with no one picking up.
JBL bounced me around to different departments in 8 emails with no one willing to talk to me.
It was catroonz car stereo shop in vero beach that finally pointed me in the right direction. He told me to pull the RCA jacks off of the amp while the head unit was off to see if I needed to add a rfi filter to the rca wires.
Turns out that stopped the drumbeat because there was some defect in the RCA wires. By simply replacing the wires with a fresh set I got rid of the interference coming from the transducers.
Yep shielded wires don't work well unless they're grounded on both ends.
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Old 01-05-2018, 07:18 PM
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I wouldn't discard the cables you removed until you try then on something else or ohm them out. They may be bad but maybe not.

The fix could be as simple as when you rerouted the new cables they aren't in the same proximity as to allow cross talk as the other set was.
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Old 01-06-2018, 11:25 AM
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Originally Posted by Grunts N Grits View Post
I wouldn't discard the cables you removed until you try then on something else or ohm them out. They may be bad but maybe not.

The fix could be as simple as when you rerouted the new cables they aren't in the same proximity as to allow cross talk as the other set was.
No, I tried moving the old RCA cable all over the place And only after, did I try replacing it. Theese are just the cheapo RCA cables you get when you buy a dvd player. Im going to look around for a marine grade RCA cable.
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Old 01-06-2018, 02:10 PM
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Originally Posted by barrell View Post
No, I tried moving the old RCA cable all over the place And only after, did I try replacing it. Theese are just the cheapo RCA cables you get when you buy a dvd player. Im going to look around for a marine grade RCA cable.
Buy some stinger marine rcas. Good price, single jacket and easy to find.
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