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Cordell Bob
 Bob Cordell has been deeply involved in audio since his adventures with vacuum tube designs in his teen years. He is an equal-opportunity designer to this day, having built amplifiers with vacuum tubes, bipolar transistors and MOSFETs. Bob is also a prolific designer of audio test equipment, including a high-performance THD analyzer and many purpose-built pieces of audio gear. He has published numerous articles and papers on power amplifier design and distortion measurement in the popular press and in the Journal of the Audio Engineering Society. Bob is a member of the JAES Review Board. He was the first to publish and demonstrate a power amplifier design combining vertical power MOSFETs with error correction, achieving unprecedented distortion levels of less than 0.001% at 20 kHz, full power in 1983. Bob is also an avid DIY loudspeaker builder, and has combined this endeavor with his electronic interests in the design of powered audiophile loudspeaker systems. Bob and some colleagues have presented audiophile listening and measurement workshops at The Rocky Mountain Audio Fest and the Home Entertainment Show.
As an Electrical Engineer, he has worked at Bell Laboratories and other telecommunications companies, where his designs have included integrated circuits and fiber optic communications systems. Bob maintains an audiophile website at http://www.cordellaudio.com where diverse material on audio electronics, loudspeakers and instrumentation can be found. |
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VinylTrak – A full-featured MM/MC phono preamp
Bob Cordell
 After spending many years to write an encyclopedic tome on audio power amplifier design, Bob Cordell decided to turn his considerable talent to the design of a phono preamplifier. Strictly solid state, his design using the best device for each position: jFETs for the input stages, BJTs for current sources and amplifying stages, and operational amplifiers for the output stages. Here, Bob proposes a different approach to achieve the 75uS hf RIAA roll-off that eliminates the cartridge electrical resonance and extends the electrical response well into the ultrasonic range. The design is single ended in and balanced out, and uses fully separate preamp channels for MM and MC cartridges.
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Cordell Bob
