OPINIONS ON VALVES （2）

Published:2011/8/19 1:42:00 Author:Phyllis From:SeekIC

By Bernhard Vollmer

The valve microphone: physics versus emotions

The author has been actively involved in quality assurance at Schoeps, a German manufacturer of studio microphones, for nearly two decades. As a supplier to Schoeps, his company Elvo makes the model M222 valve microphone (www.m222.de).

What would music be without emotion? Should our experience, ears and sensitivity take precedence over the technical aspects? Improvements are only conceivable if well-founded understanding provides the basis for further development. Even so, comparative listening tests are always necessary along the way and for judging the end result. But what is the proper way to make comparisons? Human senses are not absolute; anyone who spares himself the trouble of making comparative tests and only listens to a single product will always fall victim to his expectations (’valve sound is warm because valves are warm’). What makes things worse is that people usually don’t realize this, so they base their work on preconceived notions.

Generally speaking, there are two questions that always have to be answered:
1. Is there a difference in sound, and if so, what is its nature?
2. Which result is better?

Prolonged listening sessions are necessary to answer these questions. Whether you find something warm or cold also depends on the temperature of your previous surroundings. Ito verify the assumption that ’A’ sounds better than ’B’, your only option is to directly compare them one after the other without any delay in between, possibly by switching back and forth between the two while the sound is playing. In this way, you can recognize whether there is any difference, how large it is, and what its nature is. Any pause between the two signals poses a large risk of false assessment.

Another important consideration in such ’A’-’B’ comparisons is that the levels of the signals being compared must be absolutely identical. People cannot hear a difference of only 0.5 dB in sound level as a difference in loudness. However, the signal with the higher level will unconsciously be judged to sound better.

A comparative test with switchable valve signal paths is pointless if there are significant measurable differences in frequency responses, or if you do not carefully match the signal levels. Measurable differences should be eliminated as much as possible before you put your ears into play. Otherwise you will only hear the prevailing differences, which you could have already demonstrated by measurement.

Many comparative tests of valve and transistor amplifiers have already been conducted, and such tests lead to comparable results if they ore done properly. To avoid going info unnecessary detail, these results can be summarized as follows.

At low signal levels, valves are noisier, but the differences in sound are small. At medium signal levels, the differences are scarcely audible. At relatively high signal levels, valves increasingly create harmonic signals, especially at low frequencies. As a result, the sound is no longer neutral as with transistors, but the result can sound more pleasant, particularly with highly impulsive sound events (such as speech and guitar music) As the harmonics of low frequencies are still low frequencies, the resulting sound is often described as being warmer or fuller. If the designers haven’t made any gross errors, the differences between valve and transistor amplifiers are much smaller than many people might think.





The Schoeps M222 valve microphone is designed for valve enthusiasts and can be used as a fixed or portable microphone in professional environments. The valve settings can be modified by the user to obtain the desired sound.

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