[LAU] ground loop hell

[David Christensen]

On 02/15/2015 04:50 PM, Roger wrote:
> On 11/02/15 13:58, David Christensen wrote:
>> On 02/10/2015 05:43 PM, Len Ovens wrote:
>>> Right now there is a TS plugged directly into a TRS mixer
>>> output which means the signal minus is grounded.
>> I wouldn't plug a TS cable into an balanced TRS output.  First, you
>> are shorting one half of the balanced driver output circuit. Second,
>> you are injecting chassis ground noise into the audio circuits.
> Agreed. If you run balanced -> unbalanced, it's probably best to run
> shielded twisted core from the output and just leave the shield
> disconnected at the input. It's discussed in those Rane docs I posted.

Those are good documents -- I finally finished reading through them last 
night.


Some output driver circuits/ chips can handle shorting the signal 
negative pin to the signal ground pin.  Others cannot.  If you are 
certain your sending equipment can do this, then a custom cable might 
work.  If you're sending equipment cannot handle this, or if you are not 
certain, then you either need an isolation transformer or a suitable 
balanced-to-unbalanced converter circuit.


David