Hopefully everyone who takes the time out to visit these pages can appreciate the effort that went into the design and implementation of this website. The whole purpose of these pages was to make you want to learn and really think about your favorite tube guitar amplifiers. We need to develop our intuitive reasoning skills, and by expanding your scope and learning related subjects, we can think through most myths and legends. Always keep in mind that we are talking about guitar amplifiers; not stereophonic equipment, not radar missile systems, but guitar amplifiers. Sometimes this intuitive reasoning will answer one question with more questions, and that’s OK. Borrowing a great quote from the book Tesla: Man Out Of Time (Margaret Cheney) which addresses the issue of commonly held myths and beliefs; “Errors once committed to print are stubborn.” We all know many printed myths and false legends. Columbus ‘discovering’ America is one. Who ‘invented’ the radio? Who ‘invented’ the telephone? I think you get the idea; there are commonly held beliefs and then there are the ‘corrected’ accounts of history. When it comes to tube guitar amplifiers, I wish some of the commonly held myths were true. It would certainly help me in building a better tube guitar amplifier. And no matter how many vintage tube theory books you have in your library, none seem to have a chapter entitled ‘Listening to Capacitors’ (I wonder why?). So you are left to believe in cult shamen who are on a par with the psychic mediums of the early 20th century. You may recall stories of these charlatans who, in darkened rooms, professed to have contacted the spirits of your dear, departed loved ones as tables and chairs spun about the room (Yikes!). Many people believed in these heartless fraud artists, and paid their life savings just to ask dead Uncle Joe where the hell he hid his car keys. I don’t think I am joining the ‘Flat Earth Society’ by not acknowledging the recently discovered secrets to vintage tone, because there are no secrets. To be fair, maybe some people honestly believe they can hear a discernible difference in the wood or in different types of capacitors. Most likely they just don’t want to admit that they can’t hear any difference and appear tone deaf, so they ‘play along’. If you really believe you can hear any difference between capacitors/resistors/wire, you won’t hurt anything but your pocketbook by splurging for these ‘designer’ parts. And if they don’t happen to cost any more than Brand ‘X’, then all the better. But, before you buy any capacitor, try to imagine and rationalize the theory about why these parts would sound different. You should conclude…
Unfortunately, these ‘myths’ can live long and fruitful lives because there is no concentrated effort to dispel them; they are harmless after all, right? With other ‘fads’ and ‘fallacies’ throughout history, there was a constant tug-of-war between the zealot believers and the zealot skeptics. Information, theories and experiments were freely exchanged each trying to prove or disprove a point. Whether it was the shape of the Earth or the credibility of the Shroud Of Turin, there was equal amounts of research and published data to support each side of the argument. Sadly, with tube guitar amplifiers, there is no such balance of arguments. I believe that this is because most of the educated old-timers are long passed, and the few left to defend the truth simply aren’t aware of the hyperbole surrounding the issue, or don’t really care to get involved. With even the best research, reading can sometimes be a dangerous thing, when what you read is not taken into the proper context. Take for example the popular Radiotron Designer’s Handbook. Here we can actually read sections about voltage ratings for resistors (something few ever mention), the effects of temperature on resistance, the effects of applied voltage on resistance (something no one ever mentions), capacitance/inductance of resistors, and the effects of frequency on resistance (something published on one website). This is a lot of information to read and comprehend. What is forgotten, perhaps because it is buried amongst all the data, is that this all comes into play above 4MHz. Even an interleaved output transformer can’t have a frequency response that high. The Radiotron Designer’s Handbook was mostly written for radio engineers, and too many guitar amplifier gurus miss that point.
Remember, we are not designing a nuclear missile system; these are simple guitar amplifiers.
Hopefully you’ve ‘learned’ quite a bit during your visit to the Tone lounge. Of course there is still much more to learn. I have spent decades learning as much as I have, befriending as many ‘old timers’ as I could find along my journey. I suggest you do likewise. They are a great untapped source of knowledge. Read everything you can get your hands on. Ask a lot of questions, and do a lot of experimenting. Remember that some of the prevalent myths do have at least a grain of truth to them, as it has been said that even a broken watch tells the correct time at least twice a day! Vintage electronics/tube theory textbooks are available from antique book dealers such as NEW WIRELESS PIONEERS/BRAMPTON BOOKS (1-716-681-3186). Other suggestions;
- start up a little ‘nerd’ group of like minded filament heads in your area, and get together once a month or so and exchange ideas.
- frequent ham radio flea markets.
- locate elder/retired radio/TV repairmen and/or ‘hams’ (see above) and make a new friend who may ‘donate’ any theory books he may have to you.
- check with your local college library about old electronics texts that are no longer used.
- older, less ‘up-to-date’ public libraries may have the books you need on tube theory, etc.
- older (<1960) back issues of magazines such as Popular Electronics, Radio Electronics, and Radio and TV Experimenter are a great source of information as to how things were done back in the good old days.
When you find your old-time ham radio operator, offer buy his ARRL book. Look for the logo shown above. The American Radio Relay League put out a huge book every year since about 1923 tutoring the novice ham radio operator, and the books didn’t change much until the late 1960’s, when solid state theory took over the electronics primer at the beginning of each book. The year is always listed at the top of every book, and you should buy at least one, from any year up until about 1971. After 1971, check it out first and see if the theory primer is on tubes or solid state. There is a marvelous section at the front of these books dealing with basic electronic theory, moving on to resistance, capacitance, inductance, etc. Then we learn about vacuum tube amplifiers, and class A, B, AB, and C power amplifiers, and a nifty section covers cathode circuits and grid bias! The rest of any typical AARL book deals with construction plans and troubleshooting hints on receivers and transmitters, and has catalog advertising at the back for electronics suppliers. This is after all a book trying to teach you how to build your own ham radio transceiver. It is also the only book I have ever read that comes out and says in print that AC signal does not pass through any tube (e.g. 42nd Edition (1965), page 62). We should know this, but until you actually read it, it may not sink in! So how can one 6L6 sound different from another?
Ask any old-time TV repairman if an RCA tube as the burst amplifier in the chroma circuit will give him a ‘better’ picture than a Sylvania tube.
Be very careful, however, in completely trusting one old-timer exclusively. It may be extremely difficult to find that one mentor, let alone two or three. I have met more than a few experienced electronics men that were excellent service technicians, but very theory illiterate. Be careful not to walk away from one of these men with even more misinformation than you arrived with! Most of the servicing theory books I have procured over the years don’t delve deeply into the theory of output transformer operation or how a paraphase phase inverter circuit works, as examples, but instead have statement written in them similar to the following…
… we learned how to test the power-supply stage… (and) in a manner of minutes, a serviceman can determine that the tubes light and that the hum level and B voltages are normal. Thereafter, no further checks are necessary, and the radioman goes on…
From the book Practical Radio Servicing/Marcus & Levy, 1956
In other words, speed and efficiency in the repair was paramount, and not the ability to sit there and analyze the Thevenin equivalent of the coupling circuit. Mention to these men the ESR of a filter capacitor (the most common argument I get as to why filter capacitors sound different. Sure.) or ask if the output transformer in that radio is interleaved and the most likely answer will be a blank stare. The old time ‘Ham Radio’ operator is usually much more fluent in tube theory, and has considerable experience building circuits ‘from scratch’ as well.
The amplifiers we have all come to covet were simple designs using ‘light-duty’ transformers and speakers. Early manufacturers never dreamed that we would play their amplifiers on ’10’, and actually love the resultant distortion! These amplifiers were built with production techniques and practices that were common to their time period. In my own personal opinion, when the parts industry geared towards the guitar amplifier industry, the amplifiers didn’t sound ‘as good’. Engineers decided what parts ‘quality’ would be required/manufactured, and all of the wonderful distortion disappeared. So we are left to enjoy the ‘crude beauty’ in the tone of a tweed covered Bassman. Just don’t deify it. The result of this ‘blind faith’ is all the BS circulating today. Thankfully, a few myths have died a quiet death. Tag boards vs. PC boards and the cloth covered wire hyperbole have come and gone. A Texas-based guru has stopped telling his readers that new filter capacitors sound ‘better’ when formed slowly (like you were basting a chicken on the grill). Hopefully this website will contribute to the demise of other fairy tales. Dissuading potential customers away from a Tone-Lizard amplifier in a pine box takes a lot of patience. Sure, I could do it, and charge more. But I have a conscience. Besides, I’m lazy, and I can’t gather up the energy to keep up to date with all the latest bullshit. I’d rather just remember the truth.
If you have any questions/comments about this series of ‘Lessons’, please don’t hesitate to forward them to me! There is a constant state of ‘updating’ done to these pages, and most changes occur because of feedback from you, the reader. Please try to keep the criticism to a constructive level, OK?
It maybe an exaggeration to describe myself as an everlasting fountain of knowledge, but I am definitely an unstoppable leak.
Share what you know and learn what you don’t! And, whenever possible, please have reference material information available (the book you are ‘quoting’ to pick apart the ideas presented here) to help support your counter-claim. This will help us all in the long run.