Pat Amer and Jim Boak Dynaco ST150 Mods

November 25th, 2013

In The Audio Amateur issue 2 of 1981, two Dynaco ST150 amp modification articles appeared. One was titled ‘The ST-150-BJ-1 A Boak-Jung Modification of the Dynaco Stereo 150 Amplifier’, and it was authored by Pat Amer. This article was on the general ST150 modification process, and it included both circuit upgrades and a set of power regulation mods. The specific power mods were developed by Jim Boak, who also wrote a related article, titled ‘Power Modifications for the ST-150-BJ-1‘. This second article is definitely Dyna ST150 oriented, but Jim also wrote a more general version, within The Audio Amateur issue 1 of 1980, titled ‘A Family of Power Amplifier Regulated Power Supplies‘.

Not only do the articles describe a useful mod path for the Dyna ST150, but they are still generally applicable within almost any power amp, especially the power mods. Many thanks to Pat and Jim for their help in making these articles available.

We are happy to be able to make these three articles once more available, under the category of Guest Contributions. And, it is also a pleasure to renew contact with both Pat and Jim, after 30-plus years!

Mike Sulzer 1980/1981 Regulator Articles

October 17th, 2013

We are very pleased to be able to have available here in PDF format Mike Sulzer’s classic articles from The Audio Amateur, issues 2/1980 and 1/1981. These two articles are: A High Quality Power Supply Regulator for Operational Amplifier Preamplifiers (published in TAA issue 2/80), and Regulators Revisited (published in TAA issue 1/81). A  ZIPfile package of these two articles is available, for fastest downloads.

These two articles are unquestionably classic mileposts among DIY audiophiles, and essentially started the serious development of quality regulation as an integral part of higher performance audio schemes.

Our sincere thanks go to Guest Contribution author Mike Sulzer for responding to the initial request from Waltsblog reader Nikolaos Baxevanakis, and making these articles available. So, enjoy the articles Nikolaos!

Of course, we hope that many other readers (and re-readers) may also do so.

New ‘By Request’ Entry on Gain Control Chip

April 26th, 2013

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).

A Dynamic Range and Clipping Indicator

March 31st, 2013

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!

Morrey’s Super Oscillator

March 31st, 2013

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)

New Guest Contribution Added

March 30th, 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.

Edward T. Dell Jr. — Remembering an Audiophile’s Editor/Publisher

March 1st, 2013

Edward T. Dell Jr.
(2009 photo courtesy Chad Dell)

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!

In 2011 Ed Dell sold his publishing assets to the Elektor group, which today publishes audioXpress. They recently published an online memorial, Edward T. Dell, Jr.: In Memoriam.

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.

Walt Jung

New ‘Guest Contributions’ Page Added:

February 5th, 2013

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.

A ‘By Request’ Entry Triggered by AX Interview

November 15th, 2012

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!

 

Jack Walton Audio Regulator Test Article in Linear Audio V4

October 18th, 2012

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!