Radi0Kit RK-318 Value is a stereo RIAA phono preamplifier kit that uses electronic valves. You may use it in order to connect your turntable with an audio amplifier or preamplifier. The purpose of the kit is to amplify and adapt the signal of a moving magnet phono cartridge to a line-in input of an amplifier or preamplifier. RK-318 Value does not only amplify the signal of the phono cartridge but it also applies the RIAA equalization curve, so that it counterbalances the inverse RIAA curve that is applied during the construction of the master that is used to produce vinyl disks.

During the design process of RK-318 Value all the factors that are important, so that the quality of the kit and of the final sound stand at a high level, were taken into consideration. For this exact reason electronic valves were chosen to be the active components of the kit. They not only add their distinctive tone in the final audio outcome but they also make the whole construction look and feel pleasant and original. The electronic valve, used for each channel, to amplify the phono cartridge signal so that it can drive the line input of any amplifier or preamplifier is ECC83 or 12AX7 as is it's American designation. It is a double triode valve that uses 12.6 or 6.3V heater supply according to the connection layout used. The current drawn by each anode is very low and there is no need to use very high voltage so that good signal amplification is achieved. All the individual components (resistors, capacitors etc) were chosen so that the highest possible audio quality and the correct application of the RIAA curve are achieved. The height of all the components used has been taken into consideration so that the preamplifier board is easily placed under a chassis, in a way that only the valves protrude from the upper side. The high tension and heater voltages, from the power supply, are connected on the board by the means of PCB terminals. Audio inputs and outputs are connected by means of PCB RCA connectors, provided with the kit, or PCB pin terminals which are also provided with the kit. You may choose which ones to use according to the way you are going to install the board in a metal box or a chassis.


The voltages that the preamplifier needs are two. The high tension voltage which is 250V DC and the heater voltage which is 12.6V DC. The total current drawn by the high tension circuit is about 2mA while the current drawn by the heaters is 300mA. You may use Radi0Kit PS-318 to supply the appropriate voltages. It's a power supply kit designed for use with this certain preamplifier but it can also be used with other similar boards that draw up to 10mA at the high tension circuit and up to 1A at the heater circuit. During the design process of the preamplifier board high tension voltages were taken into consideration and were needed the PCB lines have enough distance between them, so that safety rules are followed. For all needed PCB connections the appropriate connectors, terminals and pins are provided with the kit. For the high tension (B+) and heater voltages PCB screw terminals are provided. The polarity of these two voltages is printed on the PCB by using the (+, -) symbols. As mentioned before for connecting audio inputs and outputs on the kit's PCB you may opt to use RCA terminals or PCB pins. All the indications concerning the correct application of audio signals are printed on the board. The right and left channel audio inputs are marked as R-IN and L-IN with the symbols (+, -) designating their polarity while the audio outputs are marked as R-OUT and L-OUT. On the center of the board you will find the main ground (GND) connection of the preamplifier. It can be used as the only common ground signal and power connection of the board with the chassis or the box inside which you will install it. This way we may avoid ground loops which are the cause of many problems with the construction of high amplification stages.

 

TECHNICAL SPECIFICATIONS

Input impedance:

47kΩ

Output Impedance:

45kΩ

Gain at 1KHz:

47db

Sensitivity (500mV output):

2.25mV

THD:

<0.03%

RIAA response accuracy:

+/- 0.8db

Operating voltages:

250V DC
12.6V DC

Operating currents:

3.2mA at 250V
300mA at 12.6V


BE CAREFUL!!! HIGH TENSION VOLTAGES THAT CAN BE DANGEROUS OR LETHAL ARE USED IN THIS KIT. DO NOT TRY TO CONSTRUCT IT IF YOU LACK THE EXPERIENCE OR IF YOUR WORK IS NOT OVERSEEN BY AN EXPERIENCED CONSTRUCTOR OR ELECTRONICS ENGINEER. ALWAYS FOLLOW THE SAFETY RULES THAT APPLY IN YOUR REGION.


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