Thanks for the explanation, David.  I sensed that a common ground (or
ground to chassis) would damage the power transistors but didn't know if
the damage might only occur at high loads (e.g., when I'm cranking up
Springsteen's live "Tenth Avenue Freeze Out" on a Forest Service road).
Good to know that it shouldn't be done period.

Mark

On Sat, 14 Jul 2007 08:30:09 -0700, David Kao <dtkao0205@YAHOO.COM> wrote:

>Mark:
>
>There are two types of power amplifiers among car stereos. One has single
ended
>output, the other has differential output. Single ended has one hot wire
and
>a grounded one that is truly grounded to the metal chassis. For the
differential
>type both wires are hot and never grounded. When the signal in one swings
>positively the other will swing negatively. It's like push pulling.
>It is capable of much higher power output. But you can not share a common
>grounded wire. Each channel (left and right, and front and rear) has to
have
>its own pair of wiring. Never ground (connect to metal chassis) any of the
>two wires. That will cause damage to the power amplifier of the stereo.
>The power transistors will burn out almost instantly.
>
>David
>
>
>