Again something tantalising and interesting from the CS PORT, Japan. Playing pleasure of life-like listening..

"You can not escape from distortion as long as you use amplifying elements. The countermeasure is whether to use a device with good linearity or reduce the number of gain stages. C3PR uses highly reliable, high linear  C3g tube, developed by Deutsche Telekom for triode connection. It consists only of amplifying tube 2 balls, suppressing harmonic distortion and intermodulation distortion to a minimum while returning non-return.

A negative feedback circuit was invented in 1927, and the performance of the amplifiers was improved markedly. When looking at microscopically, the negative feedback circuit (servo control) returns the signals that have gone too far to +, unnecessary vibration that restores the signals that have gone too far back to - and causes intermodulation with the audio signal. It that way is different from the original sound. In order not to cause this oscillation, it is necessary to perform ideal servo control, or use non linearity good for the components such as amplifying element and capacitor with no feedback.

Intermodulation distortion is more harmful than harmonic distortion. Harmonic distortion means that when a signal passes through the element,  signal of an integral multiple is output, and in a sense, it can be heard comfortably for humans. Among the distortion, it is intermodulation distortion that is scary, generating uncorrelated signals that are not in the original signal, resulting in an unpleasant sound. For example, when a signal of 1 kHz and a signal of 1.1 kHz pass through a rectifier or an amplification element, a sum signal and a difference signal of the respective signals are generated. 100 Hz and 2.1 kHz were not found in the original signal. The audio signal is a collection of many frequency components, and the frequency component of noise also causes intermodulation and invades the audio signal. This phenomenon occurring at MHz outside the audio band also causes noise to enter the audio band."

Outstanding noise processing technology

Contacts in rectifiers and circuits used for power supply are sources of noise. Since these noises are sharp rising noises, they occur over a band of 50 hz to several hundred MHz, causing intermodulation and entering the audio band, thus making the sound cloudy. Of course switching power supply as well as noise is greatly generated, the same thing happens. CS port noise processing technology based on years of switching power supply design suppresses / cuts unnecessary noise and achieves a clear sound. C3PR has a particularly high ability to eliminate common mode noise, and it also has a noise reduction effect of the front unit.

Switching power supply + analog power supply

It is no exaggeration to say that the sound of the amplifier is determined by the power supply. C3PR stabilizes all the power supplies appropriately for the reference machine, such as insulation with AC line in multiple stages, and does not cause turbidity of sound. The voltage is stabilized by the switching power supply and further rectified by the high-speed response non-feedback analog power supply. From there you can hear a sound like a clear stream of the Alps.

Attenator determines the value of the preamp

Resistor switching ladder type, constant impedance attenuator. For variable resistors with contacts sliding on the resistive element, point contact diodes are formed at the contacts, and noise is generated when sound signals pass through, which is the basis of distortion. In C3PR, resistance ladder is switched by a high reliability relay with crossbar gold twin structure · platinum contact, and attenuation from 0 dB to -60 dB is performed. It can be adjusted in 0.5 dB from 0 dB to -38 dB, and from 1 dB in 5 dB units from -38 dB to -60 dB. By further pushing the knob it is possible to squeeze it down to -70 dB, and you can adjust the volume in 107 stages as a total.
0 db >>> - 70 dB

Large viewable display

The display of the attenuator level of character (25 mm) can be clearly seen from the listening position which is far away. The display brightness can be varied in 5 steps, and it can be adjusted to the brightness of the room.

Balance adjustment

You can adjust the left and right balance to ± 3.5 dB in 0.5 dB step.

Bass boost

Three levels of bass boost can be done in 2 dB steps.

Remote controller

All operations except POWER SW are possible from the listening point with remote control. Because it adopts rechargeable battery, it is unnecessary to replace for over 5 years. You can charge from the USB terminal of the personal computer.
Product Specifications

Model C3PR
Method input, output transformer mounted vacuum tube type non-feedback preamplifier
Configuration Input Transformer -C3g3 Connected FET Driver - 3g3 Connected FET Driver Output Transformer
Frequency response 20 Hz to 20 kHz + 0 -1 dB
Gain 16 dB
Maximum input voltage 4 V / 1 kHz
Maximum output voltage 4 V / 1 kHz
Input impedance 7 kΩ or more * 1
Output / impedance 50 Ω or less
Minimum load impedance 600 Ω
S / N ratio 80 dB / ATT 0 dB 100 dB / ATT - 20 dB
Total harmonic distortion factor 0.05% 1 kHz 250 mV
Balance adjustment ± 3.5 dB
Compensator + 2 dB 3 steps 100 Hz
Remote control by infrared remote control
Power supply voltage AC 100/120/200/240 V 50/60 Hz
Power consumption 30 W 60 VA
Size 470 W × 90 H × 400 D Containing part not included
Weight 14 kg
Finish Silver alumite and precious rosewood veneer
Accessories AC power cable · Remote control · USB cable for charging

Warranty period 5 years (excluding expendable items) registration is required

* 1: Please use the item whose output impedance of the former stage equipment is 1.5 KΩ or less.