General informations

Multi channel: how & why

The multi-channel technique, born in the far fifties when the amplification systems moved from the tubes to the transistore, has had alternate successes but it remains the most satisfactory solution available today.

It's based on the division ofthe signal between two or more sound bands before the power amplification devices and it's developed around the ELECTRONIC CROSSOVER, truly the heart of the system.

This crossover (an active one) is locatedjust after the preamplifier and drives, through some amplifiers, each single loudspeaker.

Many are the technical factors that determine the high quality performance of a multi-channel system:
A) The elimination of the passive filter (with consequential increasing of the'system efficiency and real damping factor; more sharpness and better phase and resonance response).
B) The specialization of the amplifier (with improving of dynamics and reducing of real distortion).

Let's analize some of these aspects.

The absence of a passive network between amplifier and loudspeaker is very important: in fact it allows to recover the lost power due to the typical attenuation of these networks (up to 3 dB, one half of the source power) ; furthermore the resistive value of the line that joins together the amplifier and the loudspeaker is greatly lower with resulting increasing of the real damping factor.

The elimination of passive filler allows to better the phase response and the woofer fundamental resonance damping, with audible improvements. Other advantages are due to the amplifier's specialization.

As the spectral distribution of sound energy is not uniform, it's possible to utilize less powerfui and more neutral and sharp amplifiers for high frequencies and more current-capable ones for low band.

The distortion products that the above amplifiers generate during high power peaks operating are naturally attenuated by the mechanical cut that woofers have against high frequencies.

The fact that amplifiers work on limited sound ranges causes reduction of static and dynamic intermodulation distortion.

CABRE response

Thanks to a long research and planning work, CABRE managed to manufacture an extremely versatile electronic frequency dividing network, with top class technical specifications at a very low price, to make multi-channel amplification really affordable for anybody.

The AS-45 can be used either as a two way stereo crossover or as a three way mono one, allowing affordable for a bi-amplificated system easily expandible without replace the devices aiready bought. The two crossover frequencies of each channel can be selected among 24 values independently, and the output levei is variable between -∞ and +3 dB with potentiometers calibrated in decibels.

The choice to employ metal film resistors (tollerance 1%) and polipropylene film capacitors (tollerance 2%) guarantees an absolute accuracy and repeatibility of crossover values, that are selectable with DIP-SWITCHES.

The J-FET active devices utilized assure an excellent linearity on the 12 dB/oct filler slope, an elevated slew-rate and a very low noise, with consequential high signal-to-noise ratio. A switch can be configured to transfer the entire band of frequencies, making possible the headphone listening without any modification to the cable path.

For particular applications it's available a LOW version of the AS-45 that has the crossover frequencies more concentrated around the low range of the audio band.