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Guru of Grounding

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Principal Engineer

Bill Whitlock has designed analog electronics since 1972, specializing in high dynamic range professional audio equipment and systems. He is president and chief engineer of Jensen Transformers, Inc., Chatsworth, CA, www.jensen-transformers.com, and also does consulting work as time permits. His landmark paper on balanced interfaces appears in the June 1995 Audio Engineering Society Journal, now the most popular ever printed. Other writings include chapters for several books, Jensen white papers, and numerous magazine articles. He presents seminars at trade shows, professional meetings, and universities, including MIT in 2007. NSCA students voted him technical instructor of the year in 2009 and 2010. Bill is also active in standards work for AES, UL, and IEC. His four patents include the InGenius® balanced line receiver IC by THAT Corp. He's a Life Fellow of the AES and a Life Senior Member of the IEEE.


Guru of Grounding

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  • 08.25.2010
  • Why is NASA audio so bad?
  • I think what's being overlooked here is that the channel is for voice communications in noisy backgrounds. Well before World War II, research had shown that, under extreme noise conditions (think airplane cockpits), voices are more intelligible if the audio is high-pass filtered, hard-clipped, and then low-pass filtered. It sure isn't "hi-fi" but it vastly boosts voice intelligibility. I'll assume they were smart enough to do this on purpose. Just because it's "old school" doesn't mean it's bad ... neither is digital always better!
  • 08.25.2010
  • Flickering bulbs clue to signal integrity problem
  • If shielded wires solved the problem, then it was not a magnetic field coupling issue but an electric field issue. At power frequencies, "shielded" cables do absolutely nothing to combat magnetic field coupling. The extremely low operating current of the NE-2 means that a long wire could easily couple (capacitively) enough energy from nearby high-voltage wiring to make it glow.
  • 08.12.2010
  • Water hammer
  • What a great analogy!! I teach seminars to professional audio system designers and technicians about grounding and interfacing in AV systems (you know, that "mysterious" hum and buzz stuff). One of the most difficult concepts to explain (in simple, non-mathematical terms) is inductance. I will incorporate this analogy into my seminars ASAP. Many thanks!
  • 07.22.2010
  • Consulting engineer sinks teeth into problematic ultrasonic toothbrush
  • This sounds like a product that went into production way, way too fast. Just because one prototype worked well, doesn't mean it's ready for production. An engineer who thinks even slightly outside the box should have realized the transducer sub-system is a high-Q thing!
  • 07.22.2010
  • Do we have to make the reliability versus repair tradeoff?
  • Personally, I loathe this "throw-away" attitude that pervades marketing-driven manufacturing. And what about the "green" implications? Wouldn't we be far, far better off as a society if products really had a long useful lifetime ... and could even be repaired. A classic example is wristwatches that lasted so long they were frequently family heirlooms. Then along came the Timex (first popular jewel-less watch) ... essentially a throw-away watch. And, of course, this "unrepairable" philosophy forces us to replace entire circuit boards (or even entire products) because it's so hard to find and/or replace a 5-cent resistor!
  • 06.11.2010
  • Goodbye, incandescent bulb--or maybe not?
  • The rush to make us "green" involuntarily is often thoughtless (like many other causes politicians pile onto). For example, one unintended consequence of LED traffic signals has been quite a few traffic deaths in snowy climates - when the light is obscured by snow stuck to the lens. The old incandescent bulbs also kept the lens warm.
  • 03.04.2010
  • Toyota, drive by wire, and our failure to learn from experience
  • Excellent summary! I've maintained from the beginning that the "sticky gas pedal" was a subterfuge. Although I'm an analog guy, I think the transition from writing machine code to writing untestable "bloatware" has given all engineers, and the profession, a black eye. What would truly scare me is to find that Microsoft wrote the software for the cruise control in my car!

  • 02.04.2010
  • Way too cool
  • You say "when our government talks about nationwide health care, I think we should try it for a while in one state first to see whether it works." It's been done, for about 40 years now, in Hawaii ... and it works fine by all accounts. What I don't understand is why the media continues to ignore this example of so-called "evil socialized medicine." One of my current consulting projects is a simple, elegant solution to the LED traffic light problem. IMHO, one of the biggest problems with younger engineers is that their thinking rarely goes beyond the immediate "gee-whiz" ... this LED problem should have been obvious!

  • 09.03.2009
  • Draw the line: Isolation shields systems from shocking surprises
  • I have several disagreements with the authors. I dislike the term "earth ground" when referring to the 3rd prong of standard ac power plugs. This implies that its safety arises from its connection to soil. Safety (from equipment faults, the main threat) arises from its connection to NEUTRAL at the main disconnect panel. This protection mechanism works regardless of whether a soil connection exists! For that reason, I always refer to the 3rd prong as "safety ground". Regarding audio folks and star grounding. If your signals of interest include 50/60 Hz and its harmonics, star grounding is the only way to guarantee that signal currents and ground currents don't mix via common-impedance coupling. EMI susceptibility is another issue that's properly dealt with by shielding and low-pass filtering of all cables that penetrate the shielded space, just as in any other discipline. I, for one, am tired of being dictated to by the telecom and IT industries - whose signals don't extend to 20 Hz and are happy with 40 dB of dynamic range. Designing a system for 20 Hz to 20 kHz flat response, near-zero phase distortion, and 120 dB dynamic range is anything but trivial! ... Bill Whitlock, president & chief engineer, Jensen Transformers, Inc., www.jensen-transformers.com, Audio Engineering Society Life Fellow and IEEE Life Senior