help stock headunit dc on rca

[Stetsom23]

Hi guys
i have a mitsubishi lancer 2016 and i have knowledge about electronics but this is gives me a headache

try to take out the rca line from the headunit follow the lines and read the manual service of the same headunit
the first i do is solder Right, Left and Ground before reach to the IC audio amp

but there are 3 grounds!!!! and i dont know which select for the ground of the RCA. There is

AC-GND
PRE-GND (Is actually use for the rca, is this right?)
TAB

1.- I supposed is the PRE-GND the correct ground for the rca cable right???

2.- i do that and “works” but when i start the car the amplifier make a kick of DC from the rca (just 1 kick, after that works normally) and the amplifier get noise from the motor and this never happen when i use the headunit whit normal use (without external amp)

3.- i try to go more further doing this... i attached my rcas before some resistors and capacitors, even before the IC Audio Variable Volume to get more quality in the audio and i do this.
i make this kind of capacitors between ground/rca lines and series to reduce DC and the engine noise but didnt work IMAGE ATTACHED
but now is worst the dc. if i I lower or raise the glasses of the car get dc in the rcas and sounds very bad.
is not the amplifier, mine is a ORION xtr 500/2 and i try with a JL AUDIO 300/4 and do the same

4.- what is wrong? the value of capacitors and or the type of capacitors? i use ceramic between the lines and ground (i use Pre-GND LINE) to avoid engine noise and the electrolitic in series to eliminate the dc (gold capacitor shamwa)

any ideas my friend to get my project fully working without engine noise and no dc

thank you!

 

[Perry Babin]

You don't need the 0.1 bypass caps.

You need to install a 100k pulldown resistor after the DC blocking caps.

You will probably not have enough signal doing it this way but you shouldn't have noise problems.

 

[Stetsom23]

You don't need the 0.1 bypass caps.

You need to install a 100k pulldown resistor after the DC blocking caps.

You will probably not have enough signal doing it this way but you shouldn't have noise problems.

Hi sir babin thanks for answer
is correct like this. in the picture

2 caps golden serie 10uf 16v in each signal

100k resistor in each line signal


the ground Pre GND Is the correct?


thank you

 

[miniman82]

You only need one capacitor for each channel, even McIntosh used polarized caps there instead of non polar.

 

[Perry Babin]

See attached.

To add to #4, the caps don't need to be bipolar if there is DC on the input to them that will always be positive voltage.

 

[Stetsom23]

You only need one capacitor for each channel, even McIntosh used polarized caps there instead of non polar.

got it
thank you i will use just 1 capacitor by line

 

[Stetsom23]

See attached.

To add to #4, the caps don't need to be bipolar if there is DC on the input to them that will always be positive voltage.

thank you some much Sir Babin
i will.do it.like you draw it