There are lots of myths about tubes. Most propagated by people who have little to no understanding of them. Roger Modjeski tried to dispel tube myths for years, including the myth that tubes have a “sound”. In addition to his research with RAM Tubes which he founded after leaving Harold Beveridge, Inc. (HBI), Roger also spent considerable time visiting tube factories (Sylvania, Ei, and Siemens among others) to research tube manufacturing. We spent hours discussing how tubes were manufactured, including one story about cathode coating that may or may not have been tainted with urine as it was left in an uncovered bucket overnight while the custodian cleaned the shop floor. From those conversations one thing was clear. When the workers showed up in the morning, I can assure you the floor boss did not gather them up and say: “Okay folks get the machines set up we are making ‘warm’ tubes today.”
Another well-respected audio designer once said: “You cannot separate the sound of a tube from the circuit that it is in.” Re-read that a few times and let it sink in. Still, I am willing to bet some of you are going to misinterpret that comment. The electrical and physical characteristics of a tube interacts with the overall circuit, resulting in sound. Roger designed a circuit around a tube. Not the tubes “sound” mind you but rather using the specifications from the data sheet as a guide. Later in his career, Roger favored sweep tubes. In fact, his last circuit was based on the 26DQ5, a sweep tube (or television line output driver) specifically designed for the horizontal deflection circuits of television sets. Seriously, other than referencing temperature, no one back in the day sat in front of their vacuum tube television and described it as being “warm”.
The reality is tubes do not have a “sound”. Now some of you may reference conversations with audio designers, tube resellers, or just reading the forums and industry rags where the “sound” of tubes is discussed ad nauseum. Subjectively discussing the “sound” of tubes, replete with audiophile terminology, allows audiophiles to feel relevant and informed. Unfortunately, the industry decided it is better to speak “audiophilese” than try to properly educate audiophiles. Even more unfortunate is this is robbing audiophiles of the objective truth about tubes that would allow them to truly understand why their tube equipment sounds the way it does. I assure you Roger could have sold a lot more tubes and equipment if he did the same, but that was not in his nature. He tried to educate audiophiles right to the very end.
Why An Amplifier’s Sound Changes When You Change Tubes
By Roger A. Modjeski
Over the years, it has been noted by many astute listeners that changing tubes often produces a change in the sound of their equipment. While these changes are often attributed to the tubes alone, it is almost always a case of tube-and-unit interaction. Therefore, it is incorrect to say that a certain tube sounds a certain way. In this article we shall look at the ways in which tubes affect the equipment they go into. First, let us look at some of the problems involved in manufacturing tubes. Given a batch of tubes from a factory there will be a spread of parameters. Each manufacturers noise, microphonics, gain, and operating point will fall into a bell curve due to the nature of the machines that manufacture the tubes, the materials for the batch, and control over processes. A bell curve of gain is a good example.
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