AES San Francisco 2012
Product Design Session PD3
Friday, October 26, 4:00 pm — 6:00 pm (Room 130)
PD3 - Don't Make Your Product a Noise NightmarePresenter:
William E. Whitlock, Jensen Transformers, Inc. - Chatsworth, CA, USA; Whitlock Consulting - Oxnard, CA, USA
Audio systems that operate on AC power will experience interference in the form of ground voltage differences, magnetic fields, and electric fields. Although, theoretically, balanced interfaces are immune to such interference, realizing high immunity in real-world, mass-produced equipment is not trivial. Designers who use ordinary balanced input stages fail to recognize the critical importance of very high common-mode impedances, which are the advantage of transformers. Because legacy test methods don’t account for signal sources, most modern audio gear has poor immunity in real-world systems. The new IEC test for CMRR is explained as well as excellent alternatives to ordinary input stages. Other ubiquitous design errors, such as the “pin 1 problem” and the “power-line prima donna” syndrome are described as well as avoidance measures.