Audio Electronics: Cascodes, Folded Cascodes, and Current Mirrors (Part 1)

For this audio electronics article, Morty Tarr wrote a fascinating exploration of circuit topologies that are used to provide specific functions for an amplifier design. Cascodes, folded cascodes, and current mirrors are some of these topologies, intended to improve the performance of the devices, but which also add complications. In the first of a three-part series, the author discusses cascodes and folded cascodes, useful to improve high-frequency response and device linearity.

While Voice Coil Test Bench reviews only make use of the Large Signal Identification (LSI) data from the Klippel analyzer, the reality is that there is an amazing list of 30 modules available for the KA3 that are seriously valuable for transducer and system development. As space permits, I will be covering a number of these modules in future issue of Voice Coil. The first module in this series is the Time Frequency Analysis (TFA) module. This article was originally published in Voice Coil, October 2021

The Megaclite 4.0 UH-R2040 is a reference design based on USound's Achelous UT-P2018 MEMS drivers, comparable in length and width to smaller balanced armatures, but thinner. They’re SMT reflow-compatible, so easy to incorporate into automatic assembly processes. Brent Butterworth listened, measured, and compared the performance of this new design against conventional in-ear products using established driver technologies. This article was originally published in audioXpress, October 2021.

In this article Geoff Hill completes the Tetrahedral Test Chamber story, a concept born out of necessity, simple wavelength theory and Beranek's wedges, measurement theory, and building upon experience gained in designing chambers in Europe, US, and Asia. These chambers are now in use throughout the world, providing consistent, reliable, and accurate measurements of loudspeaker transducers and loudspeaker systems. This article was originally published in audioXpress, October 2021.

This Test Bench focuses on Eighteen Sound’s latest ND2T, a 1.4” neodymium compression driver, combined for characterization with the XT1464 elliptical-shaped horn, also from Eighteen Sound. This ultra-compact compression driver features a 2.4” diameter edge-wound voice coil wound with aluminum wire on a non-conducting Nomex former with a proprietary treatment. This assembly drives a field-replaceable pure titanium diaphragm and proprietary tangerine radial phase plug design. This article was originally published in Voice Coil, October 2021.

This Test Bench explication characterizes the 15DS100 15” professional subwoofer from B&C Speakers. This new transducer from the Italian company is a very high power handling design, able to deliver 3kW continuous (1.6W nominal), thanks to B&C's latest generation of very long voice coils - a great asset in applications from discreet PA subwoofers to three-way PA speakers. The B&C 15DS100-4 uses a proprietary 12-spoke cast aluminum frame with cooling vents for the neodymium FEA motor, which uses a 4” four-layer voice coil wound with round aluminum wire on a non-conducting glass fiber former. This article was originally published in Voice Coil, October 2021.

The October 2021 edition of Voice Coil discusses "The State of Loudspeaker Magnetics," with an annual overview of these critical industry components and materials for loudspeakers, complemented with an updated industry directory focused on Integrated Electronics. James Croft covers a patent awarded to Coastal Source for the variable waveguide speaker control, while Vance Dickason characterizes the powerful 15DS100 professional subwoofer from B&C Speakers, and Eighteen Sound's latest ND2T 1.4” neodymium compression driver. Now available in print, immediate online access or download.

The October 2021 edition of audioXpress is now available in print and digital. This edition offers a balanced mix of content, starting with our annual market update report on home theater, and associated residential technologies. Brent Butterworth reviews a MEMS earphone design from USound, Geoff Hill completes his Tetrahedral Test Chamber Story, and Bruce Heran writes about refurbishing Altec Lansing Vintage Speakers. Diving into audio electronics, Morgan Jones writes about Ultra-Linear Design; Morty Tarr discusses Cascodes and Folded Cascodes; and Richard Honeycutt talks about the Effects of Negative Feedback. Jump right in!