Welcome to the VacuumTubeAudio.info Web site. Please also see the McGraw-Hill Web site for more information on this title.

About this Site

This site supports The TAB Guide to Vacuum Tube Audio in a number of ways, including the following:

• Parts lists for the projects described in the book as downloadable Microsoft Word or Excel files
• PWB layout resources
• Additional supporting information and commentary on the projects contained in the book
• Corrections and errata from the first printing
• Additional audio projects using vacuum tubes, including downloadable files and supporting documents
• Other resources relating to vacuum tube audio applications

For more detailed information about the book see the Table of Contents and the Preface.

This book was written in 2010 and published in 2011. At the time, the only way to build a vacuum tube amplifier was to settle on a design, acquire the parts, prepare the chassis, assemble the unit, and test the final product. These steps are outlined in some detail in the book and on this site.

After the book was published, a revival of interest in vacuum tube amplifiers—driven in some part by a revival of interest in vinyl records—resulted in companies building new vacuum tube amplifiers for consumers, both in assembled and kit versions. The kits can be found for sale in any number of places—Amazon and eBay, to name just two. These kits appear to be of high quality, and generally speaking are very inexpensive compared to the build-it-from-scratch option. The good news is that audio enthusiasts have many options now with regard to building a vacuum tube amplifier. People who want to build it from scratch can still do that, of course.

This site serves as an archive resource for readers. It has been up for more than 10 years; at some point the site will come down. Until then, we hope the resources here will helpful to builders of vacuum tube amplifiers.

In an effort to provide as much useful information as possible on this site, hyperlinks to various sources are included. Hyperlinks to external web sites can change over time. Our apologies in advance if any are no longer functional.

Corrections and Errata

Unfortunately, errors can creep into a book as it works its way through the writing, editing, production, and printing process. The following items are known issues from the first printing:

• Page 56, Figure 3.5. Two traces are given for three different cathode temperatures. The upper curve for each trace should be dashed, as described in the figure cutline. This replacement figure shows the dashed lines correctly.
• Page 61, first equation on the page: some weird font issue is at play here. The equation should read mu = delta Eb divided by delta Ec1.
• Page 61, fourth equation (total cathode current of an ideal triode) is missing the quantity K (a constant determined by tube dimensions). The quantity inside the brackets is multiplied by K. When K = 1, the term falls out. The corrected page 61 equations are shown here.
• Page 69, Figure 3.17; disregard the dot on the plate (no idea where that came from).
• Page 73, at the bottom of the page the last line says “heather-cathode”; it should read “heater-cathode”.
• Page 191, the last sentence on the page explains that pins 3 and 6 of the 5651A should not be used; the sentence reads "5615A" but should read "5651A".
• Page 202, the text describing the Final Power Supply Design refers to an "R24"; it should be "R23" (there is no R24 on the parts list or on the schematic).
• Page 262, Figure 10.5, the terminal post "RVHa" should read "5VHa."
• Page 311, paragraph 7 (counting the numbered list), the third sentence reads "Table 8.7 list typical..."; it should read "Table 8.6..."
• Page 312, Figure 12.11 lists the tube type for V2 incorrectly as "7876." This, of course, should be 7868 as described in Chapter 11.

My apologies for these errors. If you see anything else that doesn't look right, please let the author know.

A Personal Comment

A funny thing happened after I finished the book and put a couple of the projects (the stereo preamp and the 25 W stereo amplifier) in my home office: I began collecting (well, recollecting) vinyl records.

Regretting it now, I got rid of my LP collection many years ago (OK, decades). CDs were new and modern and convenient and sounded better...or so it seemed.

Viewed with some perspective now, there were some very good vinyl pressings, and some bad ones too. Fortunately for tube enthusiasts, many record labels have begun re-issuing 180 gram vinyl LPs. Between the newly issued and old stock records, the selection of LPs available today is quite good.

So, after collecting some LPs, I began playing them. Much to my surprise my wife (and sometimes even the kids) sat down to listen. It has since become a bit of a ritual to pour as glass of wine (not for the kids, of course) and put on an LP. There is a certain appeal in listening to a great classic LP out loud—not just ear buds—in a group setting.

The ultimate endorsement came when my wife suggested I move the equipment to the living room so we can turn it up really loud.

Tube Talk at NAB

Each year, the National Association of Broadcasters holds its annual convention in Las Vegas. During the show, more than a hundred highly technical presentations are given on leading audio, video, and transmission technologies. I have attended the NAB Convention for the past 30 years, and given perhaps two dozen talks. In 2012, I had the opportunity to do a short presentation on the topic of vacuum tubes and vinyl records at the SBE Ennes Conference. The presentation was intended as a broad overview of the subject matter. The presentation was titled "The Tube Sound: Fact or Fiction?" I hope you enjoy it.

Update: At the invitation of the Wisconsin Broadcasters Association, I gave an expanded version of the NAB talk at a Society of Broadcast Engineers meeting during the WBA Broadcasters Clinic, October 9-11, 2012, in Madison. This version goes into a little more detail, and led some interesting question-and-answer discussion afterward. (download Acrobat file)

Disclaimer (the Fine Print )

Although the following text probably reads like boilerplate disclaimer language, the intent here is to clearly state some important (although perhaps obvious) points regarding material provided on this web site.

• Through publication of this web site, the author is not rendering professional engineering services.
• The projects and circuits detailed on this site are intended for use by hobbyists and audio enthusiasts with some basic experience in electronics projects. If the reader believes that a project may be too advanced, he/she is discouraged from attempting to build it.
• While every effort has been made to ensure that all drawings, tables, figures, layouts, documents, and other data contained on this site are complete and accurate, no warranties can be made that they are perfect or otherwise without error.
• All plans, drawings, circuit descriptions, and parts lists are provided as-is. No warranty is implied or stated.
• Beyond publication of this web site and the advice contained therein, no other form of technical support is implied or stated.
• In an effort to make the task of acquiring the parts necessary for construction of the projects described on this site, the author has included part numbers and in some cases hyperlinks to various vendors. These are strictly for the convenience of the reader. The author does not endorse the use of any particular vendor, or discourage the use of any vendor not mentioned on the site.
• The reader acknowledges that working with electrical devices carries potential harm. The circuits described on this site utilize voltages sufficient to result in injury or death.
• Some components may run sufficiently hot to result in burns to the skin.
• Anyone working the electronic circuits should use proper safety precautions at all times.