Steve Macatee started the ball rolling by reviewing basic electricity concepts to define resistance and reactance; comparing them to the familiar water analogy. Then he went over several dictionary definitions of impedance, and finally the nature of alternating current (AC), audio waves, and acoustic waves.

Colin Isler then focused on the typical audio interface and what those impedance specs all mean. He spoke about the historical development of modern audio circuits from the earlier telegraph and telephone circuitry through to more familiar solid-state devices. Originally, most audio devices used tubes, and were designed to maximize power transfer, thus impedances of input and output stages needed to be as close to identical as possible. Colin explained the need to reconsider the once sacred notion of "matching" impedance between stages, since solid state devices, hence most modern equipment, are voltage driven rather than power driven. Ideal voltage transfer calls for impedance bridging - the practice of ensuring the impedance of the input stage of a circuit is several orders of magnitude higher than the output impedance of the previous stage. This concept of the difference between impedance matching and bridging remains a confusing one for some in the industry. He went on to describe balanced and unbalanced circuit topology, and to talk in more depth about the physical construction of devices, and the unexpected sources of impedance in real world circuits, including capacitive and inductive reactance resulting from the physical construction of cables and connectors.

After a break including a delicious cake, cookies and some time to chat, the group reassembled in the studio for the awarding of door prizes:

• Rob Baum won a "Resistance is Futile" t-shirt, courtesy Rick Chinn and Uneeda Audio
• Gerard Hranek and Ron Riggs won Fluke Volt Lights, courtesy Rick Rodriguez/Fluke
• Scott Holden, won an Amprobe DMM, also courtesy Rick Rodriguez/Fluke
• Chris Hunting won Mac computer memory modules, courtesy Dr. Mike Matesky and Opus 4 Studios
• jon.metrosound at yahoo.com won a CAT 5 cable prep tool, courtesy Belden/Steve Lampen
• Nikhil Das won a mini drumsticks keyring, courtesy Paiste via Gary Louie

Finally, Mark Rogers put a point on the discussion by describing several real-world situations where systems designers got into trouble by failing to take into account the impedance and resistance offered by the interconnection wire itself - and reminded us that most tables listing the loss in electrical cables fail to communicate that they list only the impedance of ONE conductor, when in reality we must always remember that it's the ROUND-TRIP we need to consider - a 300' run means a 600' round trip path to be calculated.