Preamp; Tube Touch Circuit; Connections: Active And Passive; Handling: Gain - Hughes & Kettner QC 421 Manual De Instrucciones

TM
Quantum -combo Manual
section plays a pivotal role in the overall design of a bass amp.
The interface between bass player and instrument on one side
and the amp and power circuitry on the other, it shapes both the
amp's response to your attack and the instrument's sonic spectrum.

2. Equalizer

2.1 Pure Parallel™ Technology
Pure Parallel EQ is a technology based on a breed of circuitry other-
wise found exclusively in high-end studio gear. In conventional
EQs, filters are cascaded in serial array and signals are routed
through all filtering stages. This is known to seriously degrade
signal quality. In contrast, the Quantum EQ's filters are arrayed in
a parallel circuit. The signal is distributed to the filters for all four
bands. In addition, the original signal is routed through via a passive
circuit. This means that the signal not interrupted as it passes through
the EQ! The filters for the respective bands are arrayed in parallel to
this circuit. They process only the targeted frequencies, which are
then added to the original signal. This ensures extremely effective
signal processing, with the tweaked signal that is faithful to the
original signal - apart from the selectively processed frequencies,
of course. The characteristic curve of the low and high frequency
bands is unlike that of a serial equalizer. Much like the legendary
Pultec EQs, this EQ boosts the targeted frequency and cuts neighbo-
ring frequencies and vice versa. This instills warmth and punch into
low end frequencies without muddying them, and introduces brilli-
ance and transparency to high end signals without adding a harsh
or obtrusive note. This EQ boasts yet another hip feature:
The Q-factor (that is, the filter quality or the bandwidth affected
by a given tweaking operation) is adapted automatically so that fre-
quencies are boosted in a wider band and cut in a narrower band.
This dramatically reduces undesirable filtering effects, transforming
the four-band EQ into an effective sound-sculpting tool - intuitive
tweaking and superior bass tone guaranteed.
6

1. Preamp

1.1 Tube Touch Circuit™

Quantum™ amps' inputs feature the
Tube Touch Circuit™. Extraordinarily
resistant to high gain saturation, it's
the real deal in feel, offering remark-
ably natural and phenomenally direct
response to your touch. The preamp
1.1 Connections:
Active:
Connect basses equipped with active circuitry to this port.
Passive:
Connect basses equipped with passive circuitry to this port.
1.3 Handling:
Gain:
The Quantum amp's GAIN knob does more than merely determine
input level. It also controls the preamp's tube characteristics.
The figure above shows a sophisticated parallel EQ
circuit in comparison to a simple serial circuit. Note
the bands' parallel array and the passive circuit that
carries the original signal.
2.2 Handling:
Punch:
Pushing the PUNCH button is akin to activating a passive tube-
driven tone control located in front of the EQ. This filter's curve is
shaped like that of a tube amp set up to deliver clean sounds (for
example, for slap techniques). Unlike conventional pre filters, which
cut midrange frequencies so that loss of loudness is inevitable, the
PUNCH circuit's frequency response is tweaked to ensure that
there is no audible change in overall level.
This figure above shows the curve of
the pre filter with PUNCH activated.
Bass:
Turning this knob up boosts frequencies ranging from 40 to 120 Hz
(with a center frequency of 75 Hz), while scooping mids from 300 Hz
to 500 Hz. This emphasizes low-end frequencies without drastic
changes in overall level. Note that tweaking these frequencies agrees
with the kick drum, beefing up the sound of your entire band
without stepping all over other instruments' frequency spectrum.
Turning the knob down raises the lower of the two limiting frequen-
cies, giving the speaker more room to breathe (for example,
to boost low mids).
The figure above shows the BASS EQ's
curve when boosting (top curve) and
cutting (bottom curve) frequencies.