Tone controls, treble, bass, and sometimes midrange, have been
with us since the first full-featured tube table radio in the 1930’s. But
perhaps it’s finally time to retire these features since tone controls are
about useful (and precise) as a button marked “more.”
What is a tone control? Basically, it’s a volume boost at a
pre-selected frequency point with a fixed Q.
The pre-selected point is pretty easy to understand, but what is Q? It’s
a way to quantify the severity of the slope and range of a tone control. But
what I’ve described also applies to a single bank of a multi-bank equalizer
circuit, such as what you’ll find on many audio devices, including iTunes.
Actually iTunes has a pretty sophisticated group of tone
controls and pre-set EQ settings built into it. Also you can link tone settings
to particular songs, so when you play them these settings will be automatically
activated. In other words you can, if so inclined, have individual tone control
settings for each and every song in your iTunes library.
If you use Pure Music as your primary playback software you can
install multiple EQs in Pure Music’s plug-in control pane. Amarra also has
provisions for tone or EQ adjustment via three variable-point, variable Q
equalization channels built into its interface. Tone controls can, and probably
should, be handled in software, where not only the EQ parameters can be more
precise, but also group delay and phase-shift issues caused by the EQ
adjustments can also be addressed.
The best set of tone controls I’ve used on a preamp were on the
Quad 44 preamp. Unlike almost every other set of tone controls, the Quad
permitted changing the parameters of the EQ curve, especially on the bass. In
comparison your average tone controls, with their permanent frequency points
and fixed Q are very much a hit-or-miss proposition.
Many receivers and Pre/pros now include sophisticated
room-correction and EQ features that make tone controls seem as quaint as 45-RPM
record adapter. Unless the tone controls are adjustable both in frequency and
Q, manufacturers would be better off leaving them out.