Pure Acourate Sound Project: Greater Than the Sum of Its Parts

audioXpress traveled to Germany to learn about the Pure Acourate Sound Project, which aims to create the lowest distortion sound in a listening room. The initiators of the Pure Acourate Sound project are Ulrich Brüggemann, Markus Grelka, and Ralf Höllmann. The partners involved in this unique system are Purifi Audio, Okto Research, GIK Acoustics, Klippel, Roon, AudioVero, Rose Handwerk, and Joachim Gerhard. Ahead of the presentation at the May 2024 Munich High-End show, audioXpress offers a preview of the project.

In analog audio, you often must connect a source to a “receiver” unit. Pre-amp to power amp, phono preamp to an active crossover, the crossover to the power amp, that sort of stuff. Each of these units has an input impedance and an output impedance spec. I often get questions like: “My power amp has 20kΩ input impedance, my preamp has 100Ω output impedance, and maximum load is specified as 10kΩ. Will that work together or will I break something?”. Jan Didden explains all about Input-Output Impedance Matching.

Regulator Needed for Stable, Noise- and Ripple-Free DC Relationship. Does your nice circuit get what he needs from the power supply? Jan Didden explores when a regulator is a regulator. ...when it regulates, you’d think. Yet, in many online fora and discussions you see circuits that ‘do something’ but there’s absolutely no regulation taking place.

Whether it is power amplifiers, vinyl reproduction preamplifiers, active crossover filters or, as in this case, small-signal circuits for a very wide range of applications, Douglas Self is one of those authors who consistently has produced reference works about technical audio. You may think that as a fourth edition, it would just be a refinement on the three editions that went before it but Self always adds new material and new insights to make it worthwhile to get this new book.

This article details a lifetime project from audioXpress' technical editor Jan Didden. After a successful restoration project of a pair of precious ESL-63 Quad electrostatic speakers, he opted to design and build the eDD, a well-performing high voltage amplifier to directly drive electrostatic speakers. This challenging but successful DIY project with a design goal of 1500V RMS at 20mA RMS over the full audio band, took a while to complete but was a success. This article shares every step of the construction.

A loudspeaker is a mechanically moving system and like any such system, it cannot stop moving in zero time. For example, if a tone is reproduced, and the amplifier outputs a zero voltage at the end of the tone, the speaker cone will not stop immediately but will tend to keep on moving with lower and lower amplitude and eventually come to a stop. Jan Didden explores Loudspeaker Damping Factor in simple terms.

With a visit to Dutch & Dutch, Jan Didden unveils the journey of this innovative speaker manufacturer from The Netherlands. This company, founded in 2014, has so far achieved remarkable success with a single product designed to break the vicious cycle of speakers and room acoustics. The Dutch & Dutch 8c is a no-compromise active speaker designed to work together with the acoustics of the listening room.

The principles applied by Dr. Reinhold Lutz's for precise measurement of the sound pressure frequency response in the presence of room modes, are available in its AudioChiemgau Mode-Compensator solution. Jan Didden and Rens Tellers did a basic functional test to find out how well they could make it work and they were pleasantly surprised with the results. This article was originally published in audioXpress, October 2023.

audioXpress December 2023 includes a market overview of multiroom audio, Brent Butterworth writes about new ways to measure ANC earbuds, and Stuart Yaniger measured the new Axign and GaN Systems Class-D audio amplifier board. Richard Honeycutt writes about tubes, BJTs, JFETs, MOSFETs, and ICs, and Dimitri Danyuk, discusses JFETs in audio circuits. Douglas Self explains how to optimize variable-frequency tone controls, and Jan Didden shares his eDD direct-drive amplifier project.

To reproduce an audio signal faithfully over the whole audio band, your circuit needs to have a bandwidth at least as large as the audio band. But that’s not the only requirement: your circuit needs to maintain that bandwidth from the lowest to the highest signal level. That’s where the crux lies: it is relatively easy to get a nice wide bandwidth for small signals, only to have it breakdown with high signal levels due to the dreaded slew rate limiting.