A couple of professional studio players have pointed out on numerous occasions that the middle range of tube recordings is very clear, each instrument has presence, even at very low playback levels. Transistor recordings tend to emphasize the sibilants and cymbals, especially at low levels. Two people commented that transistors added a lot of musically unrelated harmonics or white noise, especially on attack transients. It was generally agreed that tubes did not have this problem because they overloaded gently. Tube records jump out of the speaker at you. . . .
Transistors have highs and lows but there is no punch to the sound.
When we heard an unusually loud and clear popuar-music studio recording, we tried to trace its origin. In almost every case we found that the recording console had vacuum- tube preamplifiers. We are specific in mentioning preamplifiers because in many cases we found hybrid systems. Both are applications where there is a mechanical-electrical interface. As the preliminary basis for our further investigation we decided to look into microphones and preamplifier signal levels under actual studio operating conditions.