Meeting Review, November 1999
|other meeting reports||11/14/99 Meeting Highlights
by Marty Reiling
Review: Neil Muncy, Grounding, Shielding, Hums, Buzzes, and Things that Go ZAP! in Audio Signal Processing Systems
The Chicago Section's November meeting was an all day workshop, "Grounding, Shielding and Things that Go ZAP! In Audio Signal Processing Systems," presented by well-known grounding and shielding guru, Neil Muncy of Muncy Associates, Toronto, Canada. Neil graciously donated his time and knowledge to the approximately 70 attendees who enjoyed his straightforward explanations of common audio system problems and great demonstrations.
The Chicago section would like to extend its thanks to Neil and also to the others who worked hard to offer a great workshop, especially Jim Brown, Committee member, who gets credit for the workshop idea and a lot of the work that went into organizing it, and Ron Steinberg of Rent Com, who offered the use of Rent Com's facilities and equipment. Neil, Jim, Ron, and the Rent Com staff put in a lot of hours preparing for the day's events. Thanks!
The section would also like to thank the following additional sponsors who supplied demonstration equipment.
· New Frontier Electronics, Inc.: surge suppressors
· Rane Corporation
· WaveNet, Inc.: Audio Precision, System Two
Neil began the workshop with a comparison of the state of audio systems in 1947 compared to 1999. The 40 dB increase in dynamic range of audio systems over the last 50 years has resulted in the need for better grounding and shielding practices. He then reviewed common problems with AC distribution, technical grounding and safety issues and continued with discussions and demonstrations of capacitive, inductive, common impedance and differential coupling of noise into an audio system. Methods to minimize these problems such as proper shielding, minimization of loops and separation of noise sources and receivers were demonstrated. Neil used various types of audio cable in his demonstrations and noted the effect of the cable construction on its noise immunity.
Many times sound system problems arise when new equipment is added or even when the individual components of the system are first connected. Some of these problems can be attributed to construction of the equipment and some to the connections between the equipment. Neil discussed the "pin 1 problem" which results from connecting the shield of input/output connectors to the PC board audio ground and then to chassis ground rather than immediately to chassis ground. With his "generic mixer" and "Hummer," he was able to demonstrate the advantages of connecting pin 1 to either point. He continued with a discussion of correct bonding of audio cable shields for connection between various types of equipment.
Neil closed the day with a discussion balanced AC power, series mode power line surge suppression, star ground for power distribution, and minimization of loop area for AC and audio grounds.
Thanks again to Neil, those who helped with the workshop arrangements and facilities setup, the workshop sponsors, and the support of the attendees.