[Amps] Pin 1

[Jim Brown]

On 6/8/2013 5:14 PM, Ed K0KL wrote:
> When I was a young broadcast engineer I learned that audio shielding 
> should only be at one end of the cable. 

Yes. The reason for that was that much equipment at that time had Pin 
One Problems, but we didn't know what it was, so we opened the shield 
and it solved the problem.  It wasn't until Neil Muncy's landmark paper 
(1994) that we learned the actual cause.

AES54-1, the AES Standard for balanced interconnection of Line Level 
equipment calls for the shield to always be connected at the sending 
end, and allows for an interruption at the sending end when needed for 
compatibility with legacy equipment with Pin One Problems AES48, which 
addresses termination of external wiring inside equipment calls for the 
cable shield to go to the "shielding enclosure."

Bill Whitlock's landmark paper on balanced interfaces, on the same 
session as Neil Muncy's, showed that a balanced interface is properly 
analyzed as a Wheatstone bridge, and quite convincing showed that when a 
shield is connected at one end only, the point of connection must be at 
the sending end.

Whitlock owns Jensen Transformers, and his excellent tutorials are on 
the Jensen Transformers website.

73, Jim K9YC