K A L
Kichijoji Audio Laboratory
Line Preamplifier PRE ONE
PRE ONE is a line preamplifier produced with KAL’s original audio technologies integrated into a body. Its sound is warm due to using vacuum tubes as the amplifying elements but is also exceedingly realistic due to the high performance by which even sound with very small acoustic energy can be perfectly presented. The amplifier has hybrid amplifying units with the vacuum tubes that are 6DJ8’s equivalents and semiconductor devices. By its hybrid circuit, the outstanding linearity of the tube, not shown in any other amplifying elements, can be utilized to extremes. An appropriate gain of the amplifier can be chosen from six steps according to an input level and so on. For example, to select a gain ranging from 8 to 14dB is recommended when the input level is about 2Vrms as is a standard value of output levels of CD players or digital-to-analog converters.
MAIN SPECS
- input：RCA 3 channels
- output：RCA 1 channel
- gain：switched to 2, 5, 8, 11, 14 or 18db
- volume: valiable from －∞ to ＋0dB
- input impedance: more than 10kΩ
- output impedance: less than 200Ω
- phase：positive (Input/output signals have the same phase.)
- size：463mm(w)×105mm(h)×200mm(d) protuberances included
- power supply voltage: 100V AC
FEATURES OF PRE ONE
KAL has clarified that an important function of a preamplifier is to remove an interference with the former stages from a power amplifier. In many cases, using a passive attenuator instead of an active preamplifier cannot show a good result, because the passive attenuator has no ability to remove the interference. PRE ONE is designed with the intention of maximizing the ability, making an ideal condition in which the true performance of the power amplifier is revealed. The ideal condition will present the reproduced sound as if the performance of the power amplifier was drastically improved.
In designing an audio amplifier, to control resonances in circuits is generally an important technical issue. In PRE ONE, the method with which Q-value of every parts of circuits even in the high frequency range are reduced enough is thoroughly adopted for getting extremely open sound same as live sound.
From the perspective of product credibility and sound quality, high-accuracy metal foil resistors made by Vishay, a high-accuracy and long life wire-wound-resistor-type potentiometer, high quality rotary switches, high reliability RCA jacks, high-performance line transformers are used. And, silver wirings are applied to signal lines instead of wirings formed on a wiring board. From all of the parts influence sound quality, metal film resistors and carbon resistors are excluded, and only the metal foil resistor or a wire wound resistor produces higher quality sound is mounted on each of the parts.
By a protective circuit that increases plate currents by gradation after power is turned on, a damage to the vacuum tubes can be avoided.
Adopting the circuit structure where a volume adjusting circuit is connected to the post-stage side of the amplifying unit gets a practically very high SN ratio.