OPINIONS ON VALVES （1）

Published:2011/8/19 1:29:00 Author:Phyllis From:SeekIC

Valves versus transistors

We have two audio amplifier design articles in this issue: one with valves and the other with transistors. They are just as different as people’s opinions on the issue of valves versus transistors.

Does it make sense to go back to the amplifier technology of our grandparents? Is there really such a thing as the ’legendary valve sound’? Or is this only a question of our emotions refusing to bow to physical measurements? We attempt to resolve this issue by viewing it from three different perspectives. One belongs to a designer in our own Elektor Electronics lab, a second one belongs to the world of professional studio engineering, and a third one combines the physical and musical aspects.

The audio designer: no emotions

For many years now. Ton Giesberts has been a stalwart of the small but tight-knit team that mans the Elektor Electronics laboratory. During this time he has become a specialist in audio circuitry. He has been responsible for most of the major audio designs we have published in Elektor Electronics, such as the All Solid-State Preamplifier (1989), the Medium Power AF Amplifier (1990), the Output Amplifier for Ribbon Loudspeakers (1992), the Bartery-Operated Preamplifier (1997), the Titan 2000 (1999) and the Crescendo ME (2001) to mention but a few. This very issue features his latest creation, which ’naturally’ uses transistors: the splendid, compact ’High-end Power Amplifier’.

Given the never-ending dispute between valve and transistor enthusiasts over what sounds better, and in light of the fact that we feature both types of amplifiers in this issue, we naturally would like to hear Ton’s thoughts on this subject. We should start by saying that Ton is an absolute stickler for technical quality, so DIY designs with poor performance figures haven’t a chance of leaving the audio lab with his approval.

Ton has a clear-cut opinion of valve amplifiers: "They’re simply no good! They color the sound, and they have poor damping, which degrades the sound. A transistor amplifier does a much better job of keeping the speakers under control, and it adds almost nothing to the sound." According to him, that’s not actually the fault of the valves, but instead comes from the fact that most valve amplifiers are poorly designed. What’s more, the output transformer in a valve output stage forms an additional obstacle to efforts to obtain realistic reproduction. He bases his opinion on the many measurements he has made on valve amplifiers over the years. Ton doesn’t have anything against valves as such. He thinks that excellent designs can be made using them, but his experience is limited to transistor designs, so he’s reluctant to tackle designing a valve amplifier. "Thai’s the wrong challenge for me; I definitely belong to the silicon generation."

According to Ton, there are some other serious drawbacks to valve amplifiers besides their sound quality. "In our age of environmental awareness, how can you justify marketing an amplifier with such poor efficiency? And what’s more, valves have a relatively short life, and I wonder if they don’t contain poisonous substances. Maybe they should be treated as hazardous waste!" As you can imagine, Ton would never build or buy a valve amplifier. He thinks it’s perfectly possible to design valve amplifiers and transistor amplifiers with equally good characteristics, but it’s a lot harder to do so using valves. "If someone chooses a valve amplifier for its ’warm’ or ’natural’ sound, that’s fine with me, as long as he or she is happy with it. But I want a system that adds as little as possible to the original sound; the output signal must be the best possible copy of the input signal."

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