This month’s Roger’s Corner focuses on the topic of tubes versus transistors which was one of Roger’s favorite topics. During his career Roger became well known for his tube circuits, but his very first commercial circuit designs were the bass amplifier and active crossover for the Beveridge 2SW loudspeaker system (the preamplifier for this system was a tubed circuit). I can recall the initial conversations that I had with Roger where he explained to me the benefits of using a solid-state amplifier for the bass frequencies on my custom woofers that I used with my QUAD ESL speakers. I had originally wanted to use a Music Reference RM-9 Special Edition, but Roger cautioned me that while it could do the job, a solid-state amplifier, even one of modest quality and cost, would be better suited to the job due to its superior damping. So, while Roger favored tube circuits (read the chapter for his reasons why), he clearly understood solid state circuits as well. Most interesting about this chapter is the discussion of various tube types and solid-state devices. After all, Roger always felt that the overall circuit design dictated the sound quality of the component, and this discussion provides interesting insights into that notion.
A Beginners Guide and Other Thoughts on Audio
Roger A. Modjeski
Chapter 7: Tubes vs. Transistors
Making both tube and transistor amplifiers allowed me to understand their differences in circuit design, as well as how their various characteristics of distortion and noise differ, and of course, how they sounded.
When we talk about tubes, we need to consider the different kinds of tubes that exist for audio purposes. Diodes were used primarily for rectifiers, triodes were the first amplifying tubes, tetrodes were rarely used, and pentodes were an improvement over tetrodes and actually very popular audio output tubes. Pentodes are also very popular in pre-amplifiers, when a great deal of gain is required. Even though pentodes are somewhat looked down upon, there are many famous tube pre-amps, both commercial and those for the public, that use pentodes, QUAD of England being one of them.
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