[Amps] World's worst coax connectors

[Jim Brown]

On 4/20/2023 11:47 AM, Paul Christensen wrote:
>   Most preassembled XLR cables I've seen do not bond Pin 1 to the shell.  1/4" and 3.5 mm are poor designs as the signal pins typically rely on a single-point of contact.  They also don't guarantee a shield before signal connection.

That's because AES Standards define Pin 1 as the designated shield 
contact, with no connection to the shell. They call for Pin 1 to be 
bonded to the shielding enclosure at the point of entry to ACTIVE 
equipment, but to have NO connection for tie lines. See AES48, AES54-1, 
AES54-2, and AES54-3, of which I am a principal author. These Standards 
were developed by WG members from broadcasting in both EU and NA, 
recording studios, and large and small scale sound reinforcement. They 
were developed between about 1996 and 2003, and apply to balanced analog 
audio at both mic and line levels.

There's a very good reason for this -- cable shields bonded to power 
system grounds at different locations in a building, or to a recording 
or broadcast truck, can carry very large currents as a result of power 
distribution. One of the members of the WG who was an engineer at ABC-TV 
in Manhattan spoke of very large differences in ground potential between 
buildings across the street from each other; these tie lines were 
transformer isolated, and ran at line level.

It's been at least three decades since transformers have been standard 
on the vast majority of production audio mixers. In 1994, Bill Whitlock, 
then owner and chief engineer at Jensen transformers, published a 
landmark paper analyzing the balanced interface as a Wheatstone bridge, 
and tutorial work showing that, with properly wired tie lines, a 
balanced electronic interface was just fine for most applications.The 
IEEE Standard for measurement of CMRR was revised to reflect his work.

73, Jim K9YC