AW: To earth, or not to earth...

[Paul Perry]

At 12:25 AM 2/12/97 -0500, MARK PEACE OUT :)wrote:
>At 6:25 PM +0100 12/01/97, Haible Juergen wrote:
>>	>The trouble with using banana (EVEN Serge) is that you are
>>relying on a ground loop (Bad!) for >your
>>	>audio signals. This will allow 50/60Hz hum to enter the system.
>>I thougt just the opposite was true. With bananas, you *avoid* ground
>>loops, and hum, but you *might* get crosstalk as all your signals share a part
>>of the GND connection.
>
>This is true.  You are trading off sheilding for a simpler ground path. 
....I could be wrong, but if shielding is an issue, shouldn't the shield be
connected at one end only of the cable?
 
>My understanding of banana patching systems is that they use voltages and
>input impedances that are high enough that RF isn't much of a problem.
>This is what Serge told me about their system.
.....actually it is a matter of keeping the impedances low, so any intercepted
stray signals can't develop much of a voltage across the inputs

  Crosstalk of audio signals
>seems a possible problem with a shared signal ground.
.....earthing and noise is very complex....a search for 'grounding, FAQ' and
similar might turn up some of the raves I have seen on the net on the topic
>
>Perhaps a good compromise would be to have unsheilded stackable banana
>plugs for control voltages and sheilded  1/4" or 1/8" cables for audio
>signals
........PLEASE DON"T!  The beauty of modular systems is that there is no
intrinsic difference between control and audio signals, hence posibility of
ring mod inputs from DC to 30KHz, FM by audio etc....having a two-teir
system would make interesting patches more difficult and less obvious.

 Due to typical impedances, for audio it is OK to mult outputs but
>not inputs.  
.....this is true, and I hope I am not confusing the issue by urging people
to put multiple summing inputs on everything they can (it only costs one
resistor and socket usually). Don't worry about the space, size is everything;)

paul perry melbourne australia