The Capacitance Multiplier

In this article for audioXpress, Bill Reeve helps us to make sense of a misunderstood circuit. A capacitance multiplier is useful as a power supply low-pass filter. It is commonly said that, like Miller capacitance, the capacitor’s value in this circuit is “multiplied” by the transistor gain (β) to lower the filter’s pole frequency. The transistor-enhanced filter does that and more, as the article explains in detail. This article, an excellent tutorial on analog circuit design, was originally published in audioXpress, August 2012.

B&K Precision continues to deliver on its promise of delivering reliable and cost-effective test and measurement instruments and announced the expansion of its bench LCR meter family with the addition of two new models that extend the family's test frequencies up to 1 MHz. B&K Precision's new 894 and 895 bench LCR meters provide test frequencies from 20 Hz to 500 kHz and 20 Hz to 1 MHz, respectively, and can measure inductance, capacitance and resistance with 0.05% basic impedance accuracy.

This design by Joseph Norwood Still is a control unit that the author described as offering “lifelike concert-hall performance for a modest cost”. A great tube-based amplifier for phono and line sources, featuring a very subtle bass enhancement control using negative feedback to enhance only selected frequencies, below 400Hz. As the author described, a great project for discriminating audiophiles.

Linear Integrated Systems, a full-service manufacturer of specialty linear semiconductors, now offers the LSK 489, a 1.8-nV at 1-kHz, low-capacitance, N-channel monolithic dual JFET. The LSK 489 is part of a family of ultra-low-noise, dual JFETs specifically designed to provide users with less expensive solutions for obtaining tighter drain-source saturation current (IDSS) matching and better thermal tracking.