Chris Paul asked a question on an old NE570/571 gain control application, causing some digging on my part to resurrect the 1977 Ham Radio article. The results are posted as the most recent By Request entry (right).
Back in Audio Amateur issue 1 of 1980 David M. White Jr. published a very worthwhile system tool project, titled A Dynamic Range and Clipping Indicator. With a full instruction set including PCB layout, parts list, and a detailed schematic, this design uses an LED array for display of dynamic signal peaks.
Dave recently upgraded the original hardware, as part of a complete system restoration. He has retired to a new home, and is now busy on the listening room and upgrading his home-built electrostatic arrays along with the associated complex crossover and drivers. As for the Clipping Indicator, he has indicated that all parts are still available, but today’s modern LEDs should provide longer lifetimes than did the old parts. Thanks for sharing a useful design with us once again, Dave!
Recently, we had an occasion to review some very old Audio Amateur articles, dating all the way back to issue 4 of 1975. Among them was Morrey’s Super Oscillator, by Walter T. Morrey. This article was a landmark piece in a couple of regards. It provided a comprehensive update for the Heath IG-18 sine wave oscillator, a popular test bench instrument of the period. In it Walt Morrey lays out numerous IG-18 improvements, going far beyond the typical DIY “tweaks”. The replacement op amp topology used for the IG-18 is just as sound today as it was in 1975 (setting device availability as a side-issue). In fact, some of the cascoding features used within individual stages were not only superior then, but also remain so today.
It would be interesting to see someone develop this op amp circuit into a discrete part modern realization, using some of today’s improved complementary SMD active parts. Thanks to Walt Morrey for sharing this classic with us!
(originally posted Feb 2013)
We’ve added another entry under ‘Guest Contributions’, as a new category. See right most column. This time it is a useful article by Dave White, on his dynamic system LED display.
Audio editor and publisher Edward T. Dell Jr. passed on last week, not long after celebrating his 90th birthday with his family and friends, including many from his local parish, All Saints’ Church, in Peterborough, NH. His funeral will take place at 11AM on Saturday, March 9, at All Saints Church.
Ed was born February 12, 1923, and died February 25, 2013. He was very well known among audiophiles, having published thousands of their articles in his various audio-related publications — The Audio Amateur (TAA), AudioXpress, Audio Electronics, Speaker Builder, and Glass Audio. These audio publications began back in 1970 with TAA, in Swarthmore, PA. Later on Ed moved his Audio Amateur, Inc. operations to Peterborough, NH. He was recognized by the Greater Peterborough Chamber of Commerce in 2010 as one of their “Legends of Business: Publishing Pioneers”.
Over the past 40 years, I was fortunate to write many articles for Ed’s various magazines, beginning in TAA issue 2/1973. That was the start of a long and fruitful relationship. Ed Dell was a pleasure to work with on those articles. Today, this is a satisfying thing to me, knowing that many of them are here as web versions, hopefully useful for some time yet.
It is difficult to write a concise summary of a person’s work spanning more than four decades, and capture the essence in a couple of sentences. Shortly after learning of Ed’s passing, I exchanged some emails with fellow author Jan Didden, on the influence of Ed’s work. I said this to Jan: “Ed Dell certainly did leave large footprints along the path towards better audio, especially our DIY audio, where he was really the one who did the most. He was simply a great enabler for folks like you and me.”
Well, I think that’s a true statement centered on Ed’s greatest contribution; he enabled and encouraged many people to tell stories of their audio designs, especially with home built equipment. Yes, he was also a great editor, and one learned lots of useful insights on audio technical writing working with him. But the combination of a skillful editor sharing your own objective of making better audio working on your articles was, to me at least, a most invaluable thing. I’m sure that many other authors feel the same way. Ed’s love of audio was the same as mine, and this was perceived mutually!
Jan Didden interviewed Ed Dell for the pages of audioXpress in October of 2011, and has kindly made this available on the web. Jan has also started an “Ed Dell memorial” thread on DIYAudio, which can be found here. Understandably, one can find many comments there underscoring the value of Ed Dell’s audio efforts. Waltsblog readers can also leave comments here as well, should they wish (just register first). I especially want to encourage any of Ed’s many authors over the years to do so.
Our audiophile editor/publisher friend Ed Dell deserves honor for all the good work he did for so many years. He’ll be missed here, as well I’m sure in many other places populated by audio nuts. He has left truly a great tangible legacy within all those audiophile magazines, for forty-plus years. So, I’d advise you to hang onto them!
Condolences to Ed’s family on their loss. And, thanks to son Chad Dell, who helped with several details of this memorial.
Thank you so much for everything, Ed.
We’ve added a new feature to the site, ‘Guest Contributions’. This is to provide access to noteworthy articles and papers of other authors. It is accessible via the link to the right, under ‘Categories’.
Guest Contributions leads off with a gem by Walter T. Morrey, on his Heathkit IG-18 modifications.
In the recent audioXpress interview, I mentioned Gary Galo’s Part 4 article, from the 1995 “Regulators for High-Performance Audio” series. I myself have been remiss in not making this valuable article available until now (not Gary). Fortunately, Gary has graciously agreed to do so, and a PDF of it is now available, either via this link, or via the ‘By Request’ page.
Consistent with this, the References & Regulators page has been updated, and now appears at the right as a blog page. Note — The old page is still available, as References & Regulators (old), under Meta links, but will not be updated further.
Thanks to Larry Burk for asking about it, and to Gary Galo for agreeing that it should be made available along with the other three parts. With the 2000 Improved Regulators, readers will now have a rather comprehensive set of ideas and circuit details on audio regulators. All good reading, but you might also wish to add Jack Walton’s testing article to your list. Enjoy!
For all those audiophiles interested in clean power for your circuits, I call your attention to Jack Walton’s recent article in Linear Audio, Volume 4. The title is “A Comparative Overview of Power Supply Regulator Designs with Listening Tests”. The five published volumes of Linear Audio are available for purchase at www.linearaudio.net.
I made some follow on comments to this article, which also appear on the Linearaudio.net website as a Letter-to-the-Editor, along with Jack’s response. Good stuff!
I am pleased to announce that audioXpress has just published an interview with yours truly, as conducted by Shannon Becker. It appeared in their October issue on page 32, and I hope folks will find it a good read. It was fun doing it, with all of the pulling together of so many experiences over 50+ years with my audio and other electronic work.
This interview is available here as a PDF, through the courtesy of audioXpress. Thanks to audioXpress for this opportunity, and for those audiophile friends helpful in the process. Note: see comment #1 below, if you get an “error 109″ using IE9.
Note that the above PDF file has active links, and many of the articles mentioned can be accessed simply by clicking on the embedded link.
Here are links to some of the other articles mentioned within the interview, accessible directly from this web site:
On page 32 — “Those Long-Lost Hi-Fi Kits,” appeared in The Audiophile Voice, Vol. 10, #4, 2005.
On Page 34 — “Walt’s Tools and Tips columns on audio” are available here, on a special page.
On page 34 — Operating op-amps in a transconductance mode, from my 1980 AES paper appendix.
On page 35 — The “Baxandall Super Pair” forum thread on DIYaudio website. Note the specific post #103, correcting typos re authors Baxandall – Shallow.
On page 36 — Parts 1-3 of the 1995 regulator series appearing in TAA is available here, along with many other regulator and reference related articles.
On page 36 — The DN2540 MOSFET cascode pair writeup is also available here.
We have added a new page, one dedicated to a special Electronic Design archive of ‘Walt’s Tools and Tips’ columns. All of the 26 ED columns within this 1997-1998 series are available here. Click on the title to bring up the searchable PDF of that column.