Category Archives: Whats New Shutting Down

This notice is to inform all users of this website about important changes.

The and the associated blog site, will be ceasing operation in July of this year.

1) Future Communications: With this event, all email addresses which now end in will stop operating. New email addresses ending in will thereafter be the functional replacement, i.e., “” becomes “”.

2) Future Content: All the PDFs associated with the original site will be retained offline. What is not guaranteed to be available after this shutdown are the interactive “glue” pages, which presently make up Those interested in this content should avail themselves of it now, prior to the shutdown.

Thanks to everyone for the interest and support over the years!


June 8, 2018

It has been noticed that an unauthorized posting of this website’s PDF content has been made. A request has been filed that this be removed.

In due time, I plan to provide some access to the archival PDFs, but on my terms.

Walt Jung

The unauthorized posting of this website’s PDF content has now been removed, thanks.


Calling All (older) Correspondents

Having lately been involved in the archiving of old articles and various correspondence, some frustration has been noted. My contact info is not up-to-date! But this is understandable, as the associated time periods predate email and today’s Internet.

So, I’d love to hear from anyone with whom I shared letters way back when, especially from the 1980s and later.  Please pass on this note if you know anyone in this category (email contact here).

I was especially reminded of this, when I read Michael Wilcox’s note of February 9th, about a passive eq RIAA preamp, which had origins within my 1980 AES paper.

Many thanks in advance!

Walt Jung



Walt’s Blog is back!

This notice is to inform the users of this website about current and or pending changes to Walt’s Blog. It is back!

The blog site ceased operation over the past months, with most if not all PDF content moved into an archival format. This content will continue to be available, via the Site Pages link at

We are happy to note some recent Walt Jung articles, just below. Click the highlighted link to download a copy. Comments are welcome.

Most Recent Articles

2017: ‘A Sources 101 Update’ Is a new and updated article related to the original ‘Sources 101’ as referenced below. It appeared in AudioXpress in June 2017, and includes detailed analysis of the test methodology. It also includes both SPICE results and new high performance circuits with their associated lab results. Note that the Sources 101 Kit (below) includes all relevant materials, including LTSpice test files.

2016: ‘Sources 101 Kit’ Is a ZIPfile summary of ‘Sources 101’ and the related follow-up letters from AudioXpress; April 2007, May 2007, September 2007, and April 2009. Download this for a complete summary.

Watch these blog pages for additional content of importance.

Walt Jung


Pending Changes to Waltsblog

This notice is to inform the users of this website about pending changes to Waltsblog.

The blog site will gradually cease operation over the next few months, with most if not all PDF content moving to an archival format.

A good deal of this PDF content is available right now, via the Site Pages link at

My sincere thanks to everyone for their interest in the website, and in my work.

Walt Jung


A Useful ADI Book Collection

I recently received a very interesting email from Walt Kester, my friend and former co-worker at Analog Devices Inc. (ADI). In it he was announcing the online availability of about 30 ADI books. I am paraphrasing his note as follows:

This link will take you to a PDF file that allows you to download material out of any or all these books:

The PDF file has active links to the table of contents and the actual files for all the books published over the 50 year history of ADI, including a collection of op amp articles by Ray Stata from the 1960s.

Thanks for assembling such a powerful collection, Walt! I’m sure many readers will find this most useful.

GLED431: An Ultra Low Noise LED Reference Cell

Looking for a low noise reference circuit for an audio regulator, at 2.5V? But you’ve found bandgap circuits too noisy? Read on!

This GLED431 circuit is very simple, and works as a 2.5V shunt reference with ultra low noise.

Consider the simple circuit to the right, which I call the GLED431. Just 3 low cost parts, all easy to get. It acts like an extremely low noise 2.5V zener. On my setup, noise measures around 2nV/√Hz, so if you take out the measuring system noise, the actual noise is likely below 1nV/√Hz. Really quite good. We’ll have more on this later on, in 2016.

While the GLED431 performance is very high for noise, you will need to apply about 5mA (or more) to make it work. Yes indeed, this current threshold is much higher than that of the TL431. But, it also has around 1/100 the noise! Caveat(1): The voltage won’t be as tight as typical bandgap ICs, nor as low for temperature drift. Those are conscious tradeoffs.

Here are some Vout measurements on a sample set of 5 LTL-4231Ns, in the lab prototype shown, after 1 minute warmup:

#1: 2.5094V, #2: 2.5093V, #3: 2.5069V, #4: 2.5019V, #5: 2.5062V

Not too shabby! In the schematic, the leftmost R values are just as shown from lab tests, as trimmed for the  2.500V target Vout. Obviously, just use a single 150Ω RN60D unit for this R. Note that the forward voltage of the LTL-4231N green LED (LiteOn) and the Vbe of the ZTX951 (Diodes Inc.) conveniently add, producing the desired Vout of 2.5V. Caveat(2): These two parts should not be changed if you expect to get close to 2.500V!

In use, if you are building say, a 5V regulator, select a series resistor so that 5mA is supplied to the GLED431 cell (499Ω). With this, also be sure to select a very low noise op amp, and reduce all the surrounding resistances, so as to minimize their noise contributions.  Finally, be careful to minimize capacitive loading.

I am now releasing this simple version, as a Christmas present to the readers. Stay tuned for more, have fun with the GLED431, and have a great holiday!

Walt Jung

December 24, 2015


Gary Galo AudioXpress preamp series

We are pleased to note that Gary Galo has recently made a very large Guest Contribution to this website. This is in the form of a series of his notable preamp modification articles, that appeared in AudioXpress. The articles are listed below in the sequence they appeared. Click the individual link for a given article. A ZIPfile with all the articles is available as well, at the end.

The four (+) part series on modifications to the Adcom GFP565 preamp:

Part one, from the 11/03 issue of AudioXpress.

Part two, from the 12/03 issue of AudioXpress.

Part three, from the 01/04 issue of AudioXpress.

Part four, from the 02/04 issue of AudioXpress.

A follow up, from the 12/04 issue of AudioXpress.

Miscellaneous letters and corrections.

Another preamp article, on Gary’s design of a music library preamp, for the Crane School of Music, SUNY Potsdam.

A zipped file with all seven articles (~12megs). 

It is a real pleasure to be able to make this landmark series of preamp articles available to the readers of this website.

Our thanks to Gary for making all of this possible, and for executing some superb examples of true DIY craftsmanship!

Walt Jung




Making Web Comments

After fighting various forms of SPAM comments for way too long, we’ve decided to try a new system for comments from users. It is effective now, and will enable a comment sent via email, on any aspect of this website.

Simply use MakeWebComment at as your target email, after changing the ” at ” appropriately (no spaces, subbing an uppercase 2). That’s it. Write on!