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Oct 22 2003
Location - Forge Recording
Speaker - Doug Fearn
Topic - Tubes vs. Transistors
Forge Recording Studios in
their newly designed room and new building in Oreland, Pa hosted the October
meeting of the Philadelphia Chapter of AES. Doug Fearn of D.W. Fearn, who
presented "Vacuum Tubes in the Twenty-first Century." This was a reprise of the
talk he gave at the AES 115th Convention in New York earlier in October.
Fearn's primary point was that there is a difference between the harmonic
distortions produced by tubes vs. transistors. To demonstrate the difference,
the sine waveform and spectrum of a vacuum tube and solid-state microphone
preamplifier were viewed, and the resulting audio was played. The vacuum tube
distortion was mostly second harmonic while the solid-state distortion was
predominantly third harmonic. The second harmonic distortion was far less
audible and more acceptable compared to the third harmonic. Many real-world
recording situations result in peak microphone levels that exceed the headroom
of microphone preamps, particularly on the transient peaks at the start of a
percussive sound. This can dramatically alter the overall audio impression.
Other differences between the operation and sound of tube microphone
preamplifiers and their solid-state versions were discussed. The attendees had
excellent questions and the meeting went into overtime.
Doug Fearn
After meeting calm down
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