Selecting Electrolytic Capacitors for Lowest Distortion

Douglas Self shares real experiments when selecting electrolytic capacitors to achieve the lowest distortion. An experiment inspired by his recent audioXpress article, "Optimizing Variable-Frequency Tone Controls," available online. This short piece is an interesting closer examination on the subject for audio circuit designers. Originally published in The Audio Voice newsletter, #453, January 11, 2024.

Designing Audio Circuits and Systems will have its 1st Edition published in April 2024, and advanced copies are being sent to reviewers, which includes audioXpress. Bob Cordell, wrote this new book as a comprehensive guide to audio circuits and systems design, beginning with analog audio basics, all the way through to in-depth design techniques for home and professional audio preamps, amplifiers, filters, equalizers, and even headphone amplifiers and DACs.

Many audioXpress readers will be familiar with Peter Dieleman from his books on the theory and practice of tube amplifiers. In this article he debunks some of the myths, such as load (mis) match in output stages, which is by definition perceived as a bad thing, when that might not be necessarily the case. Another myth example regards the efficiency of a triode output stage versus a pentode.

TDK Corporation has announced its latest compact noise suppression filters MAF1005FR series, measuring 1mm (L) x 0.5mm (W) x 0.5mm (H). These multilayer chip components are designed to improve sound quality and reduce noise interference in the audio lines (sound lines) of smartphones, portable devices, and wearables. Mass production of the new EMC components series started in November 2023.

There are many aspects of negative feedback in audio that are the subject of continued discussion. Jan Didden continues to debunk more Audio Myths. This article addresses re-entrant distortion. The idea is that, since negative feedback sends some of the distorted output signal back to the input, this already-distorted signal would only get more distorted by going through the nonlinear amplifier, over and over again.

Hegel has introduced their reference integrated amplifier. The H600 is rated for 303 watts in 8 ohms, with a damping factor of 4000, and 2 ohms drive capability - core specifications that Hegel considers are key for an amplifier to drive any speaker with confidence and ease. In line with the company's obsession of dual everything, the amplifier is a dual mono design. It also boasts a state-of-the-art preamplifier with the same extremely precise volume attenuator found in the Hegel reference P30A amplifier.

This article expands the conversation around feedback theory for electronic circuits and audio amplifiers. Do we "really" need wideband open loop in audio amplifiers? The subject came up at the 154th Audio Engineering Society (AES) convention in Helsinki, Finland. Looking at the frequency domain, not necessarily, Jan Didden argued. In this article he looks at the question in the Time Domain. Narrow Bandwidth, High Open Loop Gain Amplifier versus a Wide Bandwidth, Low Open Loop Gain Amplifier in the Time Domain.

Interested in accurately simulating the noise of op-amp circuits? Audio electronics expert Burkhard Vogel wrote a book that addresses this relevant topic for any audio circuit designer that doesn't want to rely just on manufacturers own models. In this review, Marcel van de Gevel explored the full book after he read Vogel's introduction, explaining that some manufacturer-supplied simulation models are way off.

Although feedback theory for electronic circuits has been established for over a century, it is still a subject for discussion. This short essay is an attempt to shed some light on one of those recurring controversies. The subject came up at the 154th Audio Engineering Society (AES) convention in Helsinki, Finland. Audio amplifiers are basically integrators or, if you will, low-pass filters. That means that at some frequency, their open-loop gain starts to fall off. With that, the loop gain available for feedback also starts to fall off, leading to a diminishing of the curative effects of feedback: distortion starts to rise, gain accuracy starts to drop, output impedance starts to go up, etcetera.

Nanusens has announced that it has successfully created a fully digital circuit design to measure the capacitance of its nanosensors. This means that both the sensor structure and its detection circuitry can be made at the same time within a chip using standard CMOS processes on whatever process node is required. As a result, ASICs can now be made with several different sensors embedded within them, helping to expand MEMS applications in hearables.