Minor update USPS rate increase, fixed some broken links 3-19-12, major update coming soon
Welcome to the TUBELAB home page
Dedicated to advancing the state of the art in affordable high end audio.
The USPS has raised their rates. Effective immediately I must increase the shipping charge for international orders. See the board ordering page for details.
A Simple P-P Amp (almost finished)
The navigation features generated by Front Page are hopelessly busted, so I will resort to this! The board assembly part of the Simple P-P manual is here. More will be posted as is is ready.
The communications industry has been hit hard by the economic downturn with hundreds of layoffs in the plant where I work. I am usually at work 10 to 12 hours a day lately doing my best to stay employed. Unfortunately no job is totally secure, and the expenses associated with Sherri's mom have forced a careful optimization of Tubelab's expenses. So for now, Tubelab is operating with a fraction of my time, none of Sherri's, and limited funds. The budget for new projects is very limited so except for small parts, all development projects in the near future will come from my "junk box" which fortunately is well stocked. There is no budget for transformers or other costly parts.
When the economy started to slow down, sales of PC boards dwindled too. This forced the delay in the launch of the Simple P-P. The Simple P-P is shipping now, and there is also a parts kit available too. For now future products must wait until the current new project (Simple P-P) pays for itself.
I get a lot of email asking similar questions, and of course there are plenty of questions about the SimpleP-P.
The Simple P-P is shipping now, and there is also a parts kit available too.
It has also been the subject of some extensive experimentation. In fact I decided to build another one, and then three more were assembled so that I could shoot all of the pictures for the manual.
The board assembly part of the Simple P-P manual is here.
All of the pictures have been taken for the manual and I am currently putting it all together on my laptop while travelling. I have discovered a few photos than must be redone once I return home. We have ordered the parts for a small parts kit which will consist of everything needed to populate the PC board. Both should be ready within two weeks of my return to Florida.
The next step in the "not quite so Simple P-P" is a P-P Driver board. The design goals are simple, it needs to be capable of driving a pair of tubes to full power in P-P. It should be capable of driving anything from a pair of 6V6's or 6L6 type tubes in conventional grid drive up or cranking a pair of sweep tubes to near meltdown in screen drive or even cathode follower mode. This board must be able to drop in to the original 300Beast amplifier, replacing its driver board while offering equal or better sound quality.
OK, writing down some lofty goals on paper (or in the computer) is easy. Building the circuit and getting it to work is not. This project has been alive since before there was a Tubelab web site. In many ways it has evolved from my 300Beast amplifier. It incorporates a lot of the 300Beast design and many techniques that I have learned since the 300Beast was built.
I laid out this prototype PC board in a hospital waiting room in Pittsburgh during the Christmas (2008) holidays. I started building it when I got back to Florida. When I completed it and powered it up I found that I had swapped the top and bottom layers when making the board, resulting in a mirror image of what I laid out. After nearly tossing it in the trash, I realized that all I needed to do was solder a set of tube sockets on the back of the board. The board is alive and working now. More details are on the Universal Driver Board page.
I have received numerous requests for an amplifier using all octal tubes. Octal tubes use up more board space than miniature tubes and are usually more expensive, so I have not done a completely octal amplifier yet. I decided that a complete P-P amplifier would not fit on a single PC board if it used octal tubes, so an octal tube amp must be broken up into blocks. While working on the Universal Driver Board a thread developed on the diyAudio forum dealing with designing an amplifier using 6L6GC's in AB2. The thread originator desired to use 6SN7's for the driver tubes. I was assisting in a "paper design" effort by modifying a Universal Driver Board for this project. I got a little carried away and 350 forum posts later I had a working a prototype amplifier that used all octal tubes.
See the Octal Driver Board page for more details.
I have developed another future product, the Spud SE. This is a "really simple SE". It started out as an email conversation about "Spud Amps" and evolved into this. There was very little interest in this project until lately. In the past two months there have been a few questions about the availability of this board, unfortunately I don't have the time to work on it right now, and I am not sure that it would ever pay back the initial PC board design costs in today's economy. This one is on hold for now.
MiniTron (no update)
I got a lot of email about the MiniTron. Some called it cool, some thought it was criminal, most was positive though. Either way, the MiniTron and its derivatives will have to wait until I have more time. Circuit Cellar asked me to write an article about it for their magazine. That article is in the current issue of Circuit Cellar (Oct. 2009). I don't have the time right now to do any further development on the software. The MiniTron now sits, lonely, all alone in the closet, waiting for some attention.
Due to legal issues the amp formerly known by the name "Simple" and the common abbreviation for the term "Single Ended" is now called the SSE. I can no longer use the word combination together in print. I ask that you refrain from using them together to describe this project as well. Some search engines detect this word combination as a trademarked name for another company's audio / home theater product. Searching for their product produced more pictures of proudly built SSE's than references to their product. They were justifiably unhappy about this.
There have been a few questions related to the construction of amps. Many builders request an exact parts list with part numbers and transformer recommendations for the "standard configurations" It is impossible to cover all of the possible combinations, but I have added specific transformer and configuration information to the tubes and transformers page. There have been numerous inquiries about a small parts kit for this board. I have decided to offer a kit containing all of the parts to populate the PC board later this year. It was delayed from late 2009 due to the worldwide parts shortage. 500 volt electrolytics were just not available and Panasonic ceased their production.
Tubelab SE update
There have been far more questions about the Tubelab SE. The parts list has been modified to reflect the changes outlined below.
If you have a Tubelab SE and it is working OK, leave it alone. If you have any instability, or have experienced blown mosfets, make these changes. If you are starting a new build, or in the process of building one, make the following changes.
Increase the grid stopper resistors on the 5842 (R31 and R32) from 1K to 4.7K ohm. These resistors should be carbon composition if at all possible. The 5842 will oscillate if given the opportunity. The higher stopper resistor value will help. If you are using a volume pot on the board, make sure that the case of the pot is grounded. The cable from the board to the input jacks should be connected to ground on the PC board, and connected to ground at the input jacks. All ground connections to the chassis should be made at the input jacks. See the wiring diagrams for the Simple SE for details. The oscillation occurs in the 100KHz range which is inaudible, but may be heard as a hum or buzz. It can also cause the output tube current to rise unexpectedly.
R14 and R25 set the operating current for the mosfets. The parts list shows a value of 20K ohms. This is good for boards that operate from 275 to 325 volts of B+. Boards that operate from 325 to 360 volts should use 30K ohms. Boards that operate from 360 volts to 400 volts should use 36K ohms. This will reduce the dissipation at higher voltages. The B+ voltage may be considerably higher than normal during the time that the tubes are warming up. This is especially true with low cost power transformers. Voltages of 450 volts and higher have been seen, which combined with high mosfet current can lead to blown mosfets on power up.
C6 should be rated for the full B+ voltage, and the expected rise on power up. This means a 350 volt cap is OK for 45 amps that run at 275 to 325 volts. A 400 volt cap should be used if your B+ is from 325 to 360 volts, and a 450 volt cap is needed for boards that run from 360 to 400 volts. It is unlikely that a 100uF cap that will fit the PC board can be found in the higher voltages. It is OK to use an 82 or 68 uF cap.
What about kits?
Sherri started working on the first non PC board product for Tubelab last year. It is a "bag of parts" for the Simple SE. It contains all of the components that go on the PC board. The parts have been ordered for the Simple SE and the Simple P-P. They will be "kitted" when she returns. (mid November)
The MiniTron amplifier was designed for entry into the Circuit Cellar / Microchip design contest. In a sea of microprocessor powered IC based gizmos this vacuum tube amplifier WON ONE OF THE CATEGORY PRIZES!!! It is featured in the Oct 2009 issue of Circuit Cellar magazine, and is currently on their web site. I will be posting much more information about this design in the coming months. You don't care anything about an amplifier that has more chips than tubes? I don't blame you, but this project has taught me a lot about the distortion producing mechanisms in vacuum tube circuits. I am using this information to design some radically new vacuum tube circuitry, that is silicon free, as well as some unique hybrid designs. Unfortunately the events outlined below have severely slowed down the progress. The amplifier you see above was completed in early October, and hasn't been touched since.
Progress has resumed slowly with the design of an all tube cathode follower amp incorporating some of the technology developed during the development of the MiniTron. A new page for this design will be created soon. One component of the MiniTron is the cathode follower amplifier, which still has its own page. The complete contest submission including schematics, source code, and design details can be found here:
Boards can be ordered using PayPal or by sending a money order through the mail. Details are on the PC board ordering page.
More pictures have been added to the page of users amps. If you have built an amplifier using either of our boards, and you want the whole world to see it, send me pictures, and any details via email. Indicate if you want your name used. (the following two links are not on my web site) A Simple SE amp built by a customer was shown at the Burning Amp Festival in San Fransisco. The pictures are here.
I have started revising the Tubelab SE assembly manual. A new parts list has been added, the Tubes and Transformers page has been fixed and updated with transformer information, and some other pages have been revised. More will be added as soon as I have time. New checkout instructions for both amplifiers are next.
I have begun to reorganize the web site in preparation for the eventual conversion from Microsoft Front Page to Microsoft Expression Web. I didn't realize how disorganized this web site has become. The Assembly manuals for the PC boards are now located on the Our PC boards page. The manuals illustrate how to assemble and checkout the PC board itself. A separate section has been started to illustrate the assembly of an amplifier using our boards. This is done because some amplifier designs could use either board, and more are coming.
A word about this site:
This web site is here to present the amplifier designs and circuit ideas that I have developed. Much of the information is intended for experienced tube amp builders. We do not intend to cover basic electronics or vacuum tube theory. Neither will we devote much time to the classic designs that are already well covered on the web. I have initially focused on circuits and ideas that are unique, or have the potential to reduce the cost of high end sound. It is assumed that the reader has the basic tools (digital meter, soldering iron, chassis punch, drill, and perhaps access to an oscilloscope) and the knowledge to use them.
Due to the many requests, I have attempted to add content that is useful to a vacuum tube beginner. I will attempt to write new content such that it can be understood by a beginner, but this is often impossible when dealing with advanced topics. I have recently designed an amplifier that could be built by a beginner, but is still useful to an advanced user. I have added a color coded icon to each page that attempts to demonstrate the skill level that is required by a project or a concept.
This icon indicates that this project or concept could be attempted by people of all skill levels. The reader should still understand the risks involved, and the safety required with the voltages involved in vacuum tube electronics.
This icon indicates that some knowledge of vacuum tube electronics is assumed for understanding of the concepts presented, OR that some previous vacuum tube project construction experience is needed to build the project.
This icon indicates a project or concept that requires considerable knowledge or experience to complete. Often this is because complete construction details are not presented.
This icon is used to indicate a project that involves very high voltages, or a concept that has little chance of success without considerable experimentation.
All material and schematics on these pages are (c) Copyright 1999-2007 by George Anderson and Tubelab Inc. The information presented here is intended for the personal use of the reader. You may freely use the information contained in this site to build your own equipment. You should not use this information to produce commercial equipment without a licensing agreement. It is my intention to freely share all of the designs that I have. I will not attempt to patent any of the unique designs or keep them out of the public domain.
My only feedback about this site is e-mail from the readers and the statistics from the web hosting company. Several changes have been made in response to your suggestions. The site is being simplified. Pages that were visited infrequently have been combined or eliminated. Many pages are being updated to answer recurring questions. The automotive pages (mostly pictures) have been expanded due to reader requests.
We will begin selling some of the "stuff" (over 100,000 tubes and other treasures) that is in our warehouses on Ebay (Ebay id = tubelab*com) to offset the web site and development costs.
I have limited time to devote to this web site since I work a full time (45 to 60 hours per week) at a large electronics company. Many of my friends who I have worked with for 20 to 30 years have been laid off. I must make my job priority #1. Work on this site happens in my spare time. I have a list of requests from readers for specific projects. Distilled down from that list is the list of my next few amplifier designs. The next one will be a plug and play SE amp mentioned above.
A word about safety:
This web site deals with audio amplifier design using vacuum tubes and high voltage solid state devices. The voltage and current levels associated with the designs presented in this web site are potentially lethal. If you have no experience working with high voltages, please enlist the help of a qualified technician who has experience with vacuum tubes. We are presenting information for use by qualified individuals for educational purposes. We are not responsible for accidents, acts of random stupidity, burning your house down, exploding parts, and other undesired actions (all of which are possible) resulting from the use of ANY information on this web site. Should you decide to attempt to build any equipment based upon information provided by this web site, you are doing so at your own risk. If this sounds serious, it is! All vacuum tube circuits operate at dangerous voltage levels. The 845SE and other powerful tube amplifiers operate at over 1000 volts. Accidental contact with an energized circuit of this nature would likely be instantly lethal.
It has become obvious to me that there are warning messages like the one above on most vacuum tube web sites, but very little information related to electrical safety. In fact I found essentially no information specific to vacuum tube experimentation. At the same time "fear of frying" has become the topic of many emails that I have received lately. Setting up a new amp and testing it seems to evoke the most fear. This is justified, since that is where the most risk is. A few have expressed the need for a good source of information, and I actually got a request for a tube amplifier design that couldn't shock you because it ran on batteries. With this in mind I have started a new section of the site devoted to electrical safety, and safe practices. I have included information outlining how to set up your bench and work on tube equipment while minimizing the risk of electrical shock. There is a section on how to use multiple meters to set up a new amp that virtually eliminates the shock risk. PLEASE READ THEM! Do not proceed unless you (or your mentor) understands the information presented here. IT MAY SAVE YOUR LIFE.
We welcome your ideas, circuits, suggestions, and questions that relate to the material presented on this site. I can't help you decide which amp, speakers, tubes, or components to buy. Those questions ask for an opinion based upon personal choice. My personal choice is likely to be different than yours. I will try to answer e-mails when I can, and discuss recurring topics on this site.