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Floating Ground Adapter for Car audio line level signal?
#1
I have a an Audi that uses the Bose external amplifier. Bose/Audi designed the system to use a single common between the head unit line out and the Bose amplifier line input, so it is four wires (FR+, FL+, RR+, RL+, Common) with the common not tied to ground, it is a floating common. However, new car audio electronics use a common that is tied to ground, with both the head unit and external amplifiers tying the ground to the line level common.
One explanation I've read, and I have no confidence in the accuracy, is that Bose uses some sort of capacitor filtering on the line level input in order to filter the "pops" that a head unit creates when switching inputs. However, now with a new head unit that uses the ground tied common for it's line level output I now hear a pop when the unit switches inputs, changes radio stations etc. One explanation is that apparently with the ground tied common the filtering capacitors in the Bose amplifier get tied to ground during the input changes of the head unit and discharge to ground.
What most I've found on the internet says to use is a "Floating Ground Adapter" (FGA) between the head unit and the amplifier. Being the electrical engineer I am I'm wondering if anyone has any familiarity with these car audio systems and could help me design a FGA, or come up with some other way to decouple the ground in such a way as to prevent these pops while, hopefully, not affecting the audio quality?
Thanks!
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#2
(03-03-2017, 03:10 AM)jisoo Wrote: I have a an Audi that uses the Bose external amplifier. Bose/Audi designed the system to use a single common between the head unit line out and the Bose amplifier line input, so it is four wires (FR+, FL+, RR+, RL+, Common) with the common not tied to ground, it is a floating common. However, new car audio electronics use a common that is tied to ground, with both the head unit and external amplifiers tying the ground to the line level common.
One explanation I've read, and I have no confidence in the accuracy, is that Bose uses some sort of capacitor filtering on the line level input in order to filter the "pops" that a head unit creates when switching inputs. However, now with a new head unit that uses the ground tied common for it's line level output I now hear a pop when the unit switches inputs, changes radio stations etc. One explanation is that apparently with the ground tied common the filtering capacitors in the Bose amplifier get tied to ground during the input changes of the head unit and discharge to ground.
What most I've found on the internet says to use is a "Floating Ground Adapter" (FGA) between the head unit and the amplifier. Being the electrical engineer I am I'm wondering if anyone has any familiarity with these car audio systems and could help me design a FGA, or come up with some other way to decouple the ground in such a way as to prevent these pops while, hopefully, not affecting the audio quality?
Thanks!

I had this problem in my Mk2 P38 Range Rover.   The car has Harmon Kardon amplifiers in all 4 doors, plus subwoofer.  The amps are balanced inputs, so I used 5 x Z1604 audio transformers from RS Components.   Z1604 Transformer

Avoid the cheaper audio transformers, because they have crappy freq-response.
 
Now the Line-Out from Joying sounds great in the car, and no buzz or hum at all.

Pete
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