In the world of audio amplifiers, there is a wide range of types, from semiconductor amplifiers to vacuum tube amplifiers, each of which has its own advantages and can be enjoyed as a hobby for audios. In particular, there are several vacuum tube power amplifiers, such as 2A3 and 300B, which are known for their sound quality and are called "famous valves." Their sound quality has a quality that cannot be expressed by semiconductor amplifiers, and they are still strongly supported even today. This year, we have developed the MA-5000 as a monaural power amplifier to respond to the desire to experience the highest quality sound from a 211 amplifier. It uses highly reputed vacuum tube 211 at a parallel single output use, also uses 300B for the driver stage to drive the 211 powerfully by a transformer coupling.
PSVANE WE-211 parallel single output stage with a fixed bias and pure class-A operation
The PSVANE WE-211 is a single pure class-A operation with two separate and dedicated fixed bias power supplies that ensure optimal and stable operation. It is a configuration that can demonstrate the inherent qualities of WE-211 in its simplest operation and achieved a powerful speaker drivability of over 45W output power by parallel operation. In addition, with combining the power supply timer control (1 minute) when the power is turned on, high-reliability operation and high-quality sound are achieved.
Output tube PSVANE WE-211 optimally is driven by transformer-coupled PSVANE WE-300B
The PSVANE WE-300B, which has a good reputation as an output tube, is used as the driver for WE-211 in transformer coupling, and by setting the WE-300B to the optimum operating point, the WE-211 parallel independent fixed bias DC stability is improved and driving the speaker with unwavering stability.
Non-feedback amplifier configuration with triode tubes in all stages
The amplifier circuit is composed of an ECC803 + 300B + WE211 triode tube in all stages to achieve the dynamic and expressive unique music playing capability that is only possible with a non-feedback circuit.
Adoption of the output transformer and interstage transformer made by Lundahl, Sweden
The Lundahl interstage and output transformers were selected as the most suitable for MA-5000’s composition and the sound quality we are aiming for. In the interstage transformer, with utilizing the independent winding structure on the secondary side, a fixed bias circuit is provided to each WE-211, and the optimum operating point setting and stable operation are ensured by direct reading of the meter. In addition, for the output transformer, we have prepared a specially designed transformer that can optimally drive a speaker impedance of 4 to 8Ω.
Balanced input supported with adapting the transformer type attenuator
The input terminals are provided both balanced and unbalanced, and a transformer type attenuator that also serves as a balanced to unbalanced converter is built in. The gain can be adjusted by -3, -6, and -10 dB compared to the standard gain, and an input OFF position of negative infinity can be set to facilitate the speaker output off when changing cable connections and so forth.
Independent dual power transformer configuration
The driver stage (300B) and power stage (WE-211 parallel-single) are each powered by independent power transformers to eliminate mutual interference between the input signal amplification circuit and the speaker driving output circuit in order to amplify the signal levels from minute to high-power level clearly. Furthermore, the power transformer is floating from the chassis with anti-vibration rubber. It suppresses unnecessary vibration from being transmitted to the chassis, contributing to further reduction of the noise level.
Thorough low noise design
For the high-voltage power supply, two 5R4G rectifier tubes which in principle do not generate switching noises, are connected in parallel, and a large enough rectification circuit due to a double choke transformer is used. The heater is a DC ignition due to a full DC power supply for all vacuum tubes and is designed to be thoroughly at low noise.
The timer indicator and the appearance
It is equipped with a two-color LED indicator that changes to red when the timer is in standby mode and to blue when the amplifier starts operating after one minute. The front and left/right panels are made of 10mm-thick aluminum to ensure rigidity, and TAOC cast iron insulators are used to the feet to suppress unwanted vibrations. The speaker output terminals use Furutech audio grade products with torque limiters to minimize the adverse effects of conducting and contacting resistance. The impressive front glass tube cover is decorated with a Japanese traditional design called "cloisonne" to give the unit a dignified appearance.
