12V lines on car stereo for cab audio

[stigzler]

Hi folks.

Using a car stereo in my cab. This has Battery and Switched 12V lines. Have a high amp PSU for the switched line due to current draw. However, need to keep the Battery line live in order to remember the settings, and prevent my having to redo settings every time start up cab. Thus, I'm going to use a 12V adaptor for this line

My quesiton thus: What to I wire the stereo ground to? The adaptor or PSU ground line, or both? My worry would be high amps going down the adaptor ground rathet than the PSU ground.

Would appreciate any advice

[Dawgz Rule]

Kind of hard to visualize....a drawing would help.  That aside, there should be one ground for everything.   Also, sounds pretty complicated in that you have to keep a battery on line, etc.  Why not just drop 20 bucks on PC subwoofer and speakers?  Would make things a lot simpler and easier. 

[stigzler]

One picture...

Didn't want to go down the PC speaker route. INstead 4 speakers + Sub.

Hope picture is easier to understand

Cheers

[Drnick]

Does this diagram help?

[stigzler]

Errrr.. thanks Dr NIck, but I really have no idea what all that means - just wanna know where to connect the ground on the stereo to! Both grounds on the two psus, or just one!?

Thanks anyways

[Dawgz Rule]

There is a saying we used in Electronics Technician school (many years ago)...."ground is ground all around".   All the grounds should be tied together.

[stigzler]

Cheers Dawgz. So I'll put the stereo ground to both the PSU and adaptor ground.

As a matter of interest - I'm guessing then that the high Amps (up to about 20 I think) don't run to ground, but get 'used up' by the load device instead? So doesn't matter how thin the adaptor ground wire is?

[Dawgz Rule]

Correct on the load.  As a rule of thumb, use the same size wire as the power lead.