Preamp, Equalizer, Handling | Hughes & Kettner QC 421, QC 412

Quantum -combo Manual

1. Preamp

1.1 Tube Touch Circuit™

1.1 Connections:

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

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.

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.

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.

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 figure above shows the BASS EQ’s
the pre filter with PUNCH activated.	curve when boosting (top curve) and
	cutting (bottom curve) frequencies.

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).