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Vol 4-0

Brian Lenharth commented on Les Bordelon's article in Vol 4 on DAC design. His comment was specifically aimed at Les' classification of DACs as R-2R or Sigma-Delta. Between them, Brian and Les eventually agreed and added some additional information regarding differences between varies DACs.

Vol 4-1

Both Ian Hegglun's article (Towards Reconciliation of Measurements and Listening Tests) and Hans van Maanen's Guest Editorial (The Case for Subjective Listening Tests) in Vol 4 drew comments and some interesting additional information from prolific author Burkhard Vogel. His comments and the replies by both Ian and Hans are here.

The reply from Ian Hegglun also contains several corrections to his Vol 4 article.

(Note: updated 1 Jan 2013)

Vol 4-2

Marcel van de Gevel and Bob Cordell had a lengthy exchange regarding some noise issues in Bob's VinylTrak article in Vol 4. Bob placed a large section of additional material on his website covering the exchanges as well as other areas of the design. Marcel's initial letter is here.

Vol 4-3

Letter from Walt Jung to Jack Walton on V4 article on power supply measurement and listening tests

Jack's article drew comments from the man who started much of the interest in power supply impact on audio circuits in the 80-ies, Walt Jung. On Walt's request Jack provides some additional information on the transformer and rectifier configurations, and takes some of Walts suggestions for an eventually follow-up test. Their exchange can be downloaded here.

Vol 3-1

Letter from Burkhard Vogel to the review of his book by Ovidiu Popa

Burkhard Vogel, the author of The Sound of Silence, commented on the review of his book by Ovidiu Popa in Vol 3. Mr. Vogel offers some additional information about applying very-low-noise BJTs in phono preamps.

Vol 3-2

I received several letters commenting on articles in Volume 3, notably to the articles by Samuel Groner (low noise lab-grade measurement amp), Steven van Raalte (correcting transducer response with inverse filter) and Robert Munnig Schmidt (mechatronics approach to subwoofer design).

These comments (some extend to several exchanges) can be downloaded here.
The comments were in some cases accompanied by the following LTspice files, referenced in the text: jm-1.txt; jm-2.txt; rms-1.txt; rms-2.txt and finally jm-3.pdf (in French).
Be sure to rename the .txt to .asc.

Vol 1-0

Menno van der Veen commented to Bruno Putzeys' article in Vol 1 "The F-word - or, why there is no such thing as too much feedback". In replying to Menno, Bruno en passant comes up with a conclusion in which way feedback really decreases distortion. Read it here.

Vol 1-1

Burkhard Vogel from Stuttgart, Germany commented to Ovidiu Popa's article in Vol 1 "On the Noise performance of Low Noise Input Stages", and to Brad Wood's letter to the same article. Vogel's letter contains a complete MathCad noise analysis and the MathCad worksheet is also available for download from within the letter. The full document including Ovidiu's reply can be found here. This is the MathCad worksheet referred to.

Vol 1-2

Another comment to Bruno Putzeys' article in Vol 1 "The F-word - or, why there is no such thing as too much feedback", this time from Marcel van de Gevel. Marcel adds a few pieces to the puzzle on where the 'feedback is bad' story originated. His comments and Bruno's reply is here.

Vol 1-3

Dr. Ramkumar Ramaswamy wrote a nice article for Linear Audio "A universal Continuous-Time active filter", Vol 1, pp 77. I had an intersting discussion with Ramkumar about the meaning of the  "Characteristic Frequency" of a filter. As a follow-up, Ramkumar has written "On the Characteristic Frequency of a Filter". This article is available online.

Vol 1-4

Cyril Bateman commented on Ed Simon's article on resistor non-linearity in Vol 1. Cyril recalled some vintage testequipment documentation and application notes for measuring passive device non-linearities. He has graciously provided PDF copies of these documents. The document links are in his comment.

Vol 1-5

Brad Wood from Canoga Park, CA, USA, commented to the article by Ovidiu Popa in Vol 1 "On the Noise performance of Low Noise Input Stages". Ovidiu replied to each comment here.

Vol 1-6

Samuel Groner from Zurich, Switzerland, commented on Ed Simon's article in Vol 1 "Resistor non-linearity - there's more to Ohm than meets the eye". The comments, along with Ed's reply, can be found here.

Vol 0-1

Christopher Paul from Bayport, NY, USA commented on Stuart Yanigers article in Vol 0: "Split the Difference: The Truth about the Humble Cathodyne". Here are his views and Stuart's reply.