Tubelab is both our name, and the name we gave our vacuum tube prototyping environment several years ago.
What is the purpose of the Tubelab web site?
I am creating this web site for two reasons. First, I have spent countless hours looking at the vacuum tube sites that currently exist on the web. I have found a few sources of unique information, authored by knowledgeable people. They are listed on the information page. I have found many sites that repeat the same old designs over and over with a few small differences. These are not bad designs (I have built most of them), they just don’t need to be repeated again. I have created this web site to share my ideas, the ideas of my friends, and some of our crazy theories, with any one who can make use of them. I believe that these ideas should be put into the public domain, rather than patented for private profit.
The plan is for the web site and related activities become self sufficient in 2006 (still didn’t happen, maybe in 2007), and generate some income later in retirement. At this time the web site hosting and related development activities are funded entirely out of my own pocket. Operating funds have been generated by selling some of my amplifiers, since I can’t possibly use them all. We are cleaning out the warehouse and selling the stuff that we don’t have time for locally and on E-bay. Our E-bay ID is tubelab*com. There are thousands of oddball tubes and components and several old amplifiers that are being sold. The proceeds from these items are used to fund the web site and development of more vacuum tube projects.
Since I am working 50+ hours per week at my full time job, I have limited time to devote to this web site and tubes in general. In this case new content will be added as I develop new designs. Minor updates will be added each month. I originally planned to also feature vacuum tube designs created by a fellow engineer, but he lost his job and had to move away to find employment.
Why vacuum tube audio?
I have been designing and servicing amplifiers for over 35 years. I played in a rock and roll band in junior high school. The guitar amp that I had at the time was made out of an old Magnavox tube hi-fi set. I eventually built my own tube powered guitar amp using parts from old televisions and radios. Someone liked the sound, offered to buy it, and I have building audio equipment (and other electronics) ever since. That was in 1965. As solid state devices became available I started experimenting with them. Loud rock was becoming popular and musicians wanted power, lots of it. Around 1970 I found a large quantity of RCA 2N3055 transistors at a surplus store in Miami. With these I could build really powerful amps. Then the quest for power began, first 100 Watts then 200, the largest amp I built with 2N3055’s put out over 600 Watts into a 2 ohm load. The 600 Watt amp was used as a PA for a local rock band for several years (I got it back, and still have it). I found a large military surplus heat sink in a scrap yard with 24 2N3773 transistors already mounted. This became the most powerful audio amp that I have ever created (it went to the rock band). Over 1200 Watts into a 4 ohm load (a lot of power in 1971). All of these solid state amps shared the same schematic, which is on this site (note the similarity to the totem pole vacuum tube output stage). Whatever stereo equipment, and guitar electronics that I had was either home made, or it was something that I rescued from the trash and repaired. When I got tired of it I usually sold it and built another.
About 12 years ago I was given an old Scott Laboratory Standard amplifier. After I fixed it up I was amazed at the sound that this amp could produce. Once I had listened to that amp for a few days, I became convinced that a well designed tube amplifier could produce awesome sound. I have built only one solid state amp since that day, and it was a digital subwoofer amp. The National Semiconductor sales rep had just given me a set of their latest digital audio chips and I just had to try them. Even though a tube amp produces great sound, many of them fall short below 100Hz. A solid state subwoofer can be used to extend the bass if you desire.
Working in a high tech facility with several hundred engineers often brings the question, why do you use those “obsolete” vacuum tubes? I found that the question is best answered by loaning the person a vacuum tube amp. I have sold a few amps that way. Does everyone who auditions a tube amp like the sound? No, most of the listeners that I have approached (mostly 20 something year old engineers) still prefer their solid state wall shaking home theater systems. It depends largely on the type of music that you listen to. Loud rap music or home theater movie sound with strong bass content does not go well with most (but not all) tube amps. Add a solid state subwoofer. Female vocals and classical music seem to sound more alive through a good tube amp. Electric guitar players usually prefer the sound of a tube amp. The reasons for buying a solid state amp usually involve cost, availability, or reliability concerns. If you think a tube amp is for you find someone who has one, or go to an audio store where both solid state and tube amps are sold. Bring some of your favorite music and have a listen. If you like a particular tube amp, find out as much as you can about its construction. Then if you decide to build your own, you will know where to start.
E-mail to Tubelab
We get several e-mails per week. Some of the e-mail is asking my opinion. Often it is asking for my opinion about something I have never tried. I try to answer these e-mails politely but this requires substantial time. These questions are better asked on one of the audio forums. Unfortunately some of the audio forums are frequented by “experts” that will gladly give (or sell) you their opinion as fact. Some of these people can become quite rude to anyone who does not agree with them. I refused to participate in any of the audio forums for several years because I thought that they were all like that. About a year ago I discovered the diyAudio forums. So far I have only had one encounter with one of these “experts”. This forum seems to be well behaved, and welcomes newbies and advanced users alike. There are sections for just about every type of audio device that could be home built.
There have been a few e-mails blasting me for corrupting vacuum tube amplifiers with solid state devices. I even got an e-mail telling me to change my name to transistorlab! Ok, you are entitled to your opinion, and I really don’t mind if you share it with me. I am trying to solve some of the design issues that have been associated with vacuum tubes since the beginning of time and I will use whatever device best fills the need. If there is no new innovation we will be building the same old amplifier designs forever. Many of them are excellent amplifiers, but how many different ways can you connect a 6SN7 to a 300B?
There are only a few engineers left in this field that are trying to create new designs, and many of them will patent their wares and keep them out of the public domain. I will publish my ideas and designs here. You are free to use them in non – commercial designs.
A lot of the e-mail that I receive is related to the SE amp designs, so that is where I will concentrate my effort for now. I didn’t understand what all of the SE hype was about until I started building these things. Now I know. I have not abandoned push pull tube amplifiers, in fact I have a screen driven push pull amplifier on my Tubelab3 prototyping system as this is written.
The PowerDrive circuit has become the most popular topic of in my e-mail lately. I get e-mail complementing me for the concept, saying that it really wakes up their amp. I also got a few e-mails criticizing me for using silicon. Many write asking for component values for their particular amplifier design. I can’t possibly calculate the values for everybody’s design and test them, so I am doing the next best thing. I am working up a cookbook approach to assist you in perfecting your own PowerDrive circuit.
I get 1 or 2 e-mails a week asking me to design a particular amplifier. I welcome these as suggestions, however, with my current schedule, I can’t possibly finish my own projects. It is simply not possible for me to even research the requirements and make suggestions for all of these requests. I have tried to politely answer these requests, but several went unanswered during periods of time when I was busy at work, or out of town. This is unavoidable sometimes. If you write about something that is on this web site, I will try to get back to you. If you were the guy that asked me to design an amplifier that used 2N3055’s, I ignored you. I have been called transistorlab already.
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.