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      05-01-2019, 02:21 PM   #1
tonksie93
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Ground loop help

I have base audio and i have fitted aftermarket amplifiers and a DSP. I have a static high pitched buzz when my cars engine is on. My headunit, DSP and both amplifiers all ground straight to the battery. When i unplug ONE of the RCAís going into my DSPís input the buzz stops. But when both RCAís are connected the buzz is there, when both RCAís are disconnected the buzz stops too. I also rerouted the right input cable thinking it could be getting interferrence from the 12v alternator cable running down the right hand side of the car, still no luck.

Any ideas?

Last edited by tonksie93; 05-01-2019 at 02:26 PM..
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      05-01-2019, 05:38 PM   #2
Kevin @ Integral Audio
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I think your two issues are related. Tell us more about the wiring...
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      05-01-2019, 09:23 PM   #3
Billfitz
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Didn't I reply to this in another thread? This explains cause and cures of ground loops:
http://www.rane.com/note110.html
Since you know plugging both RCAs into the DSP causes buzz options to try are lifting the ground from the RCA connector on one cable, and if that doesn't work isolation transformers before the DSP.
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      05-02-2019, 04:41 AM   #4
tonksie93
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Quote:
Originally Posted by Kevin @ Integral Audio View Post
I think your two issues are related. Tell us more about the wiring...
I have the base stereo which i have coded to HIFI so it now outputs low level signals (checked with multimeter at full volume). I used the technics 2/4 harness to get an input from the connectors that plug into the underseat woofers. I then connected some RCAís to the other side of the cables so i can plug them into the low level inputs on my DSP.
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      05-02-2019, 04:46 AM   #5
tonksie93
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Quote:
Originally Posted by Billfitz View Post
Didn't I reply to this in another thread? This explains cause and cures of ground loops:
http://www.rane.com/note110.html
Since you know plugging both RCAs into the DSP causes buzz options to try are lifting the ground from the RCA connector on one cable, and if that doesn't work isolation transformers before the DSP.

I wasnít sure whether to start a new thread or not as my main issue in the previous one was resolved.

Yeah when one RCA is connected fully, and i lift the ground on the second one the noise is still there. The noise starts when i insert the middle contact on the second RCA.
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      05-02-2019, 07:46 AM   #6
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In that case transformer isolation is probably required. Search to find something like this on your side of the pond:
https://www.amazon.com/Isolator-BOSS...YVRRA9KRN&th=1
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      05-16-2019, 02:03 AM   #7
fackamato
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Quote:
Originally Posted by Billfitz View Post
In that case transformer isolation is probably required. Search to find something like this on your side of the pond:
https://www.amazon.com/Isolator-BOSS...YVRRA9KRN&th=1
Unfortunately that affects the sound, at least according to one review:

Quote:
The frequency response of the Boss converter is perfectly linear from 20kHz to around 100Hz with a very gradual fall off, and 50Hz being only 4% down in output, 30Hz 7-8% down, and 20Hz about 50% down compared to the (100%) 20kHz to 100Hz range. This diminishment is not noticeable with the Dynaudio speakers, but the converter is less suited below 30Hz.
The sensitivity adjustment of each output is through a 3/4 turn of a set-screw, clockwise for higher gain. I used a sine-wave generator and an oscilloscope + a multimeter for the measurements and settings, but a 1volt 50 or 60Hz signal plus an ac multimeter with a 1000mV range would suffice for setting the sensitivity, because the setting at 50Hz is valid throughout the frequency range.
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      05-16-2019, 07:22 AM   #8
Billfitz
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What happens below 30Hz is of no consequence in auto sound. For that matter it wouldn't matter in at least 90% of relatively high end home theaters.
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