Tech Audio

Miscellaneous

Some interesting papers and utilities - collected with no clear plan, just caught when I came across them! 

Remember the circlotron amplifier design concept? I came across a delightful little book from 1962, in Dutch (my native language) where a full chapter was dedicated to theory and practical designs of circlotron amplifiers. Curiously, there is no mentioning of an author anywhere in the book, There is mentioning of a 'Videlleer amplifier', and Videlleer is a wel-know designer from that period, so maybe he is the author. But I digress.

John Atkinson on negative feedback

I also found out that in 1997, John Atkinson of Stereophile referenced an article of me in Audio Amateur "Negative feedback - curse or blessing". I seem to support no one less than Martin Colloms! ;-)

We visit Mundorf

We visit Mundorf is the report of my visit to the Mundorf brothers, on the request of Ed Dell, when Mundorf was still trying to counquer a spot for themselves in the audio scene.

Novel feedback topology obviates the need for high loop gain

My one and only AES publication: Novel feedback topology obviates the need for high loop gain, J. M. Didden, AES preprint 4597, 103rd Convention, Sept 1997. In hindsight, it wasn't really brilliant, but as they say, participation is more important than winning ;-)

On FFT and Distortion Measurement

Distortion analysis with FFT.

On SPICE simulation

For many yeares I have been ussing a paid-for circuit simulator, part of the Proteus package from Labcenter in the UK. In 2017 I decided to give the free LTspice from (then still) Linear Technology a run, liked it and switched over.

Fast-forward to mid-2019: Spectrum Software's MicroCap (uC) simulator is now distributed free of charge! Accordoing to online sources this would be the best circuit- simulator ever, so I will give that a try soon. I do see a potential disavantage to free software, that it will no longer be kept up-to-date. But we'll see.

Yet more on power supply decoupling

A great series of on-line articles articles by analog and digital guru Kendall Castor-Perry, aka The Filter Wizzard ....

Thermal transient variation of power amp quiescent current

This Linear Audio article is made available as free download for a limited time.

Thermal transient variation of power amp quiescent current - Instrumentation and findings, Jan Didden, Linear Audio Volume 9

Balanced Phono-Amps

I usually do not discuss audio books here, I used to publish reviews in Linear Audio. But this book is unique and needs some attention, so there!

Readers of Linear Audio will be familiar with author Burkhard Vogel; he heas written extensively about tube and low-noise design, and has several books published by the prestigeous Springer Nature publishers of Germany. This book, Balanced Phono-Amps has everything you might ever need to ask about the subject. In his tradition, Burkhard combines simulation, calculation and MathCad for cross-verification and confirmation.

On Safe Operating Area Issues

Thermal issues in MOSFETs operating in linear mode.

During the development of my electrostatic Direct Drive amplifier I ran into SOA issues with the 4.5kV high-voltage MOSFETs. Several people pointed me to pertinent papers on this subject, and I decided to post them here for whoever has the same issues.

Feedback, feedforward & Error Correction

Recently I ran into the issue of input Common Mode (CM) distortion in opamps. Especially in non-inverting series feedback configurations, both inputs of an opamp can show appreciable signal swing even when the input signal difference is very small, in linear operation. The large input swing in bipolar opamps causes relatively large non-linear input current swings, and in FET opamps it causes large voltage swings and thus non-linear input currents due to non-linear input capacitances.

Nostalgia Lane: The Philbrick K2-X

On one of my Saturday-morning visits to Helmut Singer in Aachen, Germany I spotted a small box behind the counter that immediately got my attention. I had heard before about the legendary tube-based opamps designed by George Philbrick in the 50-ies. I had never seen one, and this was my chance to get one. Herr Singer graciously parted with it for a quite reasonable fee - about the same as the original amount in dollars from 50 years ago. I felt like a kid that had just cleaned out the candy store.

The State of Audio

The State of Audio "The scientific method is a method or procedure that has characterized natural science since the 17th century. It consists of systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses." - Oxford English Dictionary. "Audio as a hobby is dying, largely by its own hand.

Cyril Bateman's Capacitor Sound articles

Update April 2017: I was made aware of another large zip-repository of Cyril's work. Thanks to Kevin Thompson and Sebastion Veyrin-Forrer. 

During 2002 and 2003 Electronics World published a slew of articles by Cyril Bateman on capacitor distortion, dielectric absorption and several other subjects. The series also detailed his purpose-build test equipment and was published under the title 'Capacitor Sound'.

MathCad resources for the audio enthousiast

MathCad resources for the audio enthousiast Update 5 July 2012: Mason Green send me some info on an alternative to MathCad/MatLab: 'Scientific Python' ;He included a link to an excellent tutorial on Scientific Python. For an example of a practical application of Scientific Python, see Mason's PORC (Python Open Room Correction) project. Thank you Mason!   There have been several articles in Linear Audio supported by MathCad calculations and graphs; Burkhard Vogel's articles come to mind.

Comments on distortion in Power Amplifiers

Comments on distortion in Power Amplifiers Baxandall Peter   In 1995, Peter Baxandall wrote a long (35 pages) personal letter to Douglas Self. In the letter, which has never been published before, Peter comments on Douglas' series of articles on power amplifier design. But more than just comments, he expands on the various issues, adds his own views and clarifies many issues in a very clear and concise manner. Thirty-five pages of typewritten text interspersed with hand-drawn graphs and schematics. A must-read jewel!