Some ideas to a 12v custom noice filter.

Hi Forum.

I hope that some of you guys can give me some inspiration to a high-end noice filter that operates in 12v DC.

This project of mine, is making a true HIGH-END automitve audio system, so i use some parts i know sounds grate, from our home systems.

Ive made a drawing, which you can take a look on - it isn't with the right symbols, but i can read diagrams, so if any of you has an idea, to a filter / Ground Loop ect. then you will be a fantastic help.

as you can see from the drawing, the DAC has to be switched on with the engine from the car, it shall not have power directly from the acc. The Transport and the Router, gets power directly from the acc, and one thing to be aware of, is that the Transport needs 12v aswell as 5v.

Best Regards.

Jesper, Denmark.
One of the problems in a car if you're going to be running a DAC is that you'll need a preamp as well because a DAC has no volume control.

What are you planning to use for amplifiers?

What have you used for speakers?

What are you doing to control the resonances of the body panels?

I've built sound quality cars before, and the improvement from running a seperate DAC vs a quality head unit is minimal compared to the other questions I've raised. Until you've maxed the setup of amp, speakers, sub enclosure and properly deadened, stiffened and insulated the car you're wasting your time.

John C.
Hi John.

Thanks for your reply.

Yes, im aware that the DAC needs a Preamp :-) This project is just an extra gimmic to the car, not the main system.

But i think that this will sound way better than the headunit of the car, because most 2-DIN Headunits isn't born with serious audio circuit. If i chose to built in a normal 1-DIN the opurtunities would be much better.. But the look of the cabin woulden be the same.

Here is a list of components.

AMP. Genesis Five Ch. S3
Headunit. Pioneer AVIC-F10BT
Speakers. Rainbow Germanium (german)
Sub. JL-Audio 12w6
Dynamat all over
Damping Fibre on the other site.

all of the car has been isolated with 2 layers of resonance damping material.. ( in the car four )

i am just asking to find a proper way to make a 12v noice filter.


I ment 4 layers in the door, like a sandwich construction. First Heavy material, then light material, damping mid and high freq - this is done both on the inner door panels, and on the outer door metal.

Thee roof is hardned from fabric, and i found no reason to give it more weight - it is stiff as a rock.

The trunk has applyed heavy material aswell as the backside of the instrument panel.
Jesper, DC noise filters can be implemented passively with shielding, more capacitance or inductance (a choke).

I do not recommend any form of voltage regulation, because a car batery is nominally rated for 12 V, but in reality most batteries operate around 14 Volts. Regulating to 12 Volts will reduce the power output of your power amps.

So, if you hear engine noise through the system, you need suppressor spark plug cables and a choke inline with the 12V DC feed to your DAC and head unit.
Most car audio stores sell the chokes (even Radio Schack sells a nice one).

Capacitance provides additonal filtering and also serves as a very stable power supply. Several vendors make 1 Farad capacitors for powerful car audio systems. These are usually needed for Nascar SPL contests and extremely powerful amps, anyway, a large cap makes an excellent noise filter, even if you listen at low volumes.

Lastly, make sure your interconects and the digital cable between head unit and DAC are double-shielded and do not run speaker cables near any IC.

I hope this helps