Yamamoto Sound CraftCA-03 Vacuum tube phono preamplifier

The ripple filter of the power supply is divided separately from the rectifier circuit for each stage, and each stage is supplied from an independent power supply. The rectifier circuit is double-wave rectifier to improve regulation. The ignition of the Telefunken 6AK5W heater has an independent rectifier circuit for each of the six vacuum tubes, eliminating interference between the tubes with each other. The amplifier circuit achieves both large gain and noise reduction by setting the operating point to the optimal point.


The gain of the equalizer amplifier is 58dB at 1kHz. The gain of a normal equalizer amplifier is about 34dB, so it is set 24dB more. By reducing the noise to 2.3 mV, the signal-to-noise ratio was achieved to 110 dB. The company's equalizer amplifier is very simple and provides gain with only two vacuum tubes, so there is no lack of information. Although it is a CR type circuit configuration, it achieves a fairly good signal-to-noise ratio. Since the maximum output is about 28V, it can be used not only for MC cartridges, but also for MM cartridges with large output and MC cartridges with high output. The company's MC cartridges YC-03S and YC-03M (output is 0.25 mV) can be directly connected to the system and can be used without using a step-up transformer. The sound of the MC cartridge, which does not pass through a step-up 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 100 Ω.

《Line Amplifier》

Vacuum tubes used	Telefunken 6AK5W x6
Maximum Output	8V
Frequency response	10-150kHz/-0.5dB
Output impedance	1.6kΩ
Line Amplifier Gain	14dB (approx. 5 times)
Residual noise	0.13mV
SNR	92dB

《Equalizer Amplifier》

Maximum Output	28V
Frequency response	30-15kHz/+-0.5dB
Input impedance	47kΩ,1kΩ,100Ω
Output impedance	4.8kΩ
Amplification factor	58dB/1kHz
Residual noise	2.3mV
SNR	110dB
size	420(W)290(D)94(H)mm
weight	6.3kg