Hughes & Kettner Quantaum Combos QC 412 - Manual (Page 7)

7
ENGLISH
Quantum TM -combo Manual
Low Mid:
Turning this knob up boosts a broad range of frequencies neighbo-
ring the center frequency of 400 HZ (up to +12 dB), adding presence
and punch to the bass signal. This parallel circuit does not squawk;
even high settings do not elicit the annoying honk that serial EQs
are infamous for. By backing off lower frequencies, you can dial in
sounds similar to Jaco’s trademark woody tone. Note that this con-
trol is like a notch filter – its slope is very steep, ranging all the way
down to -25 dB. By carefully dampening select frequencies, you can
dial in punchy sounds with a distinct hi-fi flavor.
High Mid:
This knob works along the same lines, boosting frequencies in a
broad band and cutting them in a narrow band. This EQ’s center
frequency on amps loaded with 10" speakers is 850 hertz; on amps
loaded with 1x 12" and 1x 15", the center frequency is 1.2 kHz.
The figure above shows the HIGH MID EQ’s curve when boosting
(top curve) and cutting (bottom curve) frequencies.
HF-Character:
The knob HF-CHARACTER is divided into two control ranges.
When twisted clockwise from the center position, it works just like
a tube power amp’s presence knob. PRESENCE generates soft,
glossy top-end frequencies while rolling off harsher-sounding
frequencies found at the low end of the high frequency range.
This yields a sonic image very similar to that of a "soft" tweeter.
The effect is particularly prominent in the high-end response of
basses sporting active circuitry. If your instrument is equipped with
passive pickups (or its strings are very old), you may find that this
effect is hardly audible because there are few high-range frequencies
in the instrument’s signal. When twisted counterclockwise from the
center position, it works just like a normal TREBLE knob, affecting
the lower end of the high-range frequency spectrum. In contrast to
the PRESENCE function, dialing into the TREBLE control range
yields a wiry kind of sound that you
might expect from a bass combo that
is not loaded with an HF horn.
Frequencies lying above the TREBLE
control range’s center frequency are
dampened, which emphasizes the
character of this voicing control.
Pushing the PUNCH button clearly
enhances the HF-CHARACTER
knob’s effect.
The figure above shows the LOW MID
EQ’s curve when boosting (top curve)
and cutting (bottom curve) frequencies.
The illustration shows the curves
for PRESENCE (top curve) and
TREBLE (bottom curve) at extreme
HF-CHARACTER knob settings.
The figure above shows the HIGH MID
EQ’s curve when boosting (top curve)
and cutting (bottom curve) frequencies.
3. Tube Growl
3.1 Tube Saturation & Compression
More than merely a means to determine saturation levels, the
TUBE GROWL knob is a complex circuit that controls peaks like a
tube preamp does, converting the energy of spikes into overtones
rather than allowing it to dissipate. TUBE GROWL is comparable
to a string that generates a fundamental frequency and a series of
harmonics generated by half the string, a third, a quarter and so
forth. The relative levels of harmonics are decisive in shaping tone,
so it takes the right mix to please the human ear.
The figure shows the harmonic overtone
spectrum generated for a fundamental
tone of 500 hertz.
Serving to harness distortion is an intelligent compressor that
grants you precision control over tube saturation. It keeps your
string attack up front without undesirable spikes in volume, while
avoiding all the pitfalls of conventional compressors. This circuit
does not mask attack, generate pumping sounds, or any other sonic
side effects. But it does deliver truckloads of sustain, making your
instrument easier and more fun to play.
3.2 Handling:
Tube Growl:
The TUBE GROWL knob is a particularly handy feature, allowing
you dial in natural compression and tube effects: This tool puts at
your fingertips the means to control the compressor parameters
threshold, ratio, make-up gain, and attack and release, as well as
tube saturation levels.
Quantum_Combos_Manual_1.3 29.10.2003 14:59 Uhr Seite 7