Yamamoto Sound Craft CA-03 Preamplifier with built-in vacuum tube phonoeco

The power supply ripple filter is divided into each stage separately from the rectifier circuit, and each stage is supplied from an independent power source. The rectifier circuit has been made into double-wave rectification to improve regulation. The heater of the vacuum tube Telefunken 6AK5W was ignited with independent rectifier circuits for each of the six vacuum tubes, eliminating the interference of each vacuum tube. The amplifier circuit has achieved both a large gain and a reduction in noise by setting the operating point at the optimum point.


The equalizer amplifier has a high gain type, with a gain of 58dB at 1kHz. The gain of a normal equalizer amplifier is around 34dB, so it is set to be 24dB larger. By reducing the noise to 2.3mV, the signal-to-noise ratio was achieved to 110dB. The company's equalizer amplifiers are extremely simple, and are extremely simple to get gains from just two vacuum tubes, so there is no lack of information. Although it has a CR-type circuit configuration, it achieves a fairly good signal-to-noise ratio. The maximum output is approximately 28V, so it can be used not only for MC cartridges, but also for large output MM cartridges and high output MC cartridges. The company's MC cartridges YC-03S and YC-03M (output is 0.25mV) are directly connected to the company to be used without using a booster transformer. The sound of the MC cartridge, which does not pass through the boost transformer, is fresh and the amount of information is greatly improved. The optimal input impedance of the equalizer section of an amplifier such as the CA-03 is 100Ω.

《Line amplifier section》

{Equalizer amplifier section}