NOTES FROM THE TEST BENCH
By Bruce Hofer
I have been extremely busy for the past several months getting our new APx555 ready for production. That, plus a very heavy travel schedule to Germany, Austria, Denmark, South Korea, Japan and Taiwan (not to mention a brief vacation to Florida to celebrate my 40th wedding anniversary), has left me with no time to write my "notes from the Bench" column...until now.
Therefore, I would like to devote this edition to our new APx555. In case you missed its introduction on September 9, I strongly encourage you to check outwww.ap.com for more details and information.
The APx555 is a major new product that will have significant repercussions within our industry. It is quite simply the ultimate in terms of performance among all commercially available audio analyzers. With residual THD+N specifications that totally eclipse all previous analyzers, it sets a new standard that is likely to be unchallenged for a long time. Indeed, the residual THD+N performance of our previous standard-bearer, the 11-year old SYS-2722, has yet to be equaled by other competitive analyzers! The following graph clearly tells the story:
So how did we do it? There is no simple answer because state-of-the-art performance is the result of many factors, years of research, experimentation and careful optimization. I have discussed or hinted at several important analog design factors in past editions of my "Notes from the Bench." For example, the linearity of the individual resistors and capacitors that make up the analog signal processing circuits is paramount. Circuit layout, grounding and power supply decoupling are also very important. Beyond that, I really cannot disclose any of our new circuit tricks or designs for obvious reasons.
The development of the APx555 was a team effort by many highly qualified engineers and support staff. My own work on the analog portions of the APx555 represents the culmination of 35 years in the field of audio test and measurement, and over 44 years as an analog design engineer. (In many ways I consider it to be the "magnum opus" of my career.) However, the APx555 also includes improvements in other areas such as DSP, control software and user interfaces (it has two). Well done, Team AP!
To anyone who really cares about the accuracy of their audio measurements, I invite you to arrange for a demonstration of the APx555, or to visit us at an upcoming tradeshow. Perhaps I will see you there....
Audio Precision co-founder and Chief Analog Engineer