Yamamoto Sound Craft EQB-01 Vacuum Tube Phono Equalizer Amplifier

The EQB-01 amplifier circuit has been completely revised to significantly improve the signal-to-noise ratio of the amplifier.

The EQB-01 is a unique circuit system that uses a pentapole tube for the amplifier section.

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 improves regulation with both wave rectification. 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. Furthermore, while maintaining the same basic circuitry, the amplifier circuit has been able to achieve both a large gain and a reduction in noise by re-setting the operating point to the optimum point.



The equalizer amplifier has a high gain type, 58dB. The gain of a normal equalizer amplifier is around 34dB, so it is 24dB larger than the standard. The residual noise in this state was 2.3mV, resulting in a signal-to-noise ratio of 110dB. The gain is obtained using only two vacuum tubes, so it is very simple and does not lack information. Although the CR-type circuit configuration is generally considered to be disadvantageous in terms of SN ratio, it has proven that it can achieve a fairly good SN ratio depending on the method of use. 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 MC cartridges YC-03S and YC-03M are connected directly to the level that can be used without using a booster transformer. The YC-03S output is 0.25mV, so most MC cartridges can be used directly. 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 optimum input impedance of the equalizer section of the company's CA-03 amplifier is 100Ω.
The EQB-01 is configured with the line amplifier section omitted from CA-03 and CA-03L, and the input volume and selector switch omitted. The thickness of the copper foil is 70μ gold plating to improve the sound quality.
{Equalizer amplifier section}