Glass Audio

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A Quality Dynamic Headphone Tube Amplifier
by Helmut Becker and Michael Oberesch
Glass Audio 01-0-1988

Only a few of us are privileged to listen to music at a volume comparable to the original performance. It's not because we lack appropriate equipment, but rather the neighbors force us to reduce the volume. There are two answers to this problem. We can either move to an apartment far away from civilization, or we can use headphones. The second option is definitely less expensive and offers an additional advantage: for quality sound, no loudspeaker can compete with headphones.

Most stereo manufacturers seem to ignore the fact that headphones are among the best transducers. Nearly all amplifiers have a headphone jack, but this output is often inadequate at best.

Plain, Bad, Simple

Usually, headphones are connected in parallel with the loudspeakers, where, as an option, the loudspeakers may be switched off. Headphone systems are available with impedance from 8 to 2kΩ, but usually a resistor with approximately 300Ω is connected in series with the headphones.

This prevents overloading from too high a voltage at the 8Ω loudspeaker output. When connected to high impedance systems, this resistor causes only a negligible voltage drop.