Technical information

the phono preamplifier of the playback equipment reverses this EQ, boosting the
bass back to its proper level and handily cutting the treble. This last has the
welcome effect of substantially reducing the hiss produced by the scraping of the
stylus within the groove. Note: old-style ceramic cartridges did not require this
second step of reversing the EQ because their frequency response characteristics
roughly approximated this anyway.
RMS Root Mean Square. A measure of voltage or (incorrectly) power output.
The latter is often quoted in the specifications for an amplifier or home theatre
receiver. Measuring voltage is simple with direct current, even if it varies in level.
You can simply average the values over time. But alternating current, when
arithmetically averaged, gives you a value of zero or close to zero. If you square
each value (multiply it by itself) before taking the average, and then take the
square root of that average, you not only get a reasonable representation of the
voltage, but a value that provides effectively the same amount of power as a
similar DC voltage into a resistive load. What is called 'RMS power output' for
amplifiers is calculated using the RMS voltage delivered by the amplifier to test
loads, so in that sense the term is not entirely misleading (however something like
'average sine wave power output' is far less irritating). Such figures should include
a measure for the amount of distortion generated at that power. This should be
well under 0.5%. If the figure is 10% (often used with home entertainment
systems) the figure should be discounted substantially.
Rumble Low frequency noise, usually from a turntable. Given that RIAA
equalization boosts the bass signal from a cartridge by an enormous amount
(17dB at 50 hertz), the highest quality bearings and excellent isolation from the
turntable's motor are required to control rumble.
Running in An often recommended process for the installation of new Hi-Fi
equipment. Essentially, running in is operating the new equipment for some
hours, or tens, or hundreds of hours, to bring it up to peak performance.
Loudspeakers are physical systems with suspensions and surrounds that do
definitely benefit from being run in. Running in cables does seem to improve their
performance, and it is certainly true that capacitors and some other components
in electrical circuits sound ‘better’ when run in for some time. None of this is
measurable and there are sceptics who say this is all baloney. Use your own ears
to decide!
S