The tubes of Model_1/Model_1-300B


300B

300B is an ultimate direct-heat triode which was developed to obtain a good quality audio output of high power at the low distortion rate. In 1938 300B was announced by Western Electric Co. (WE) for the movie voice reproduction of theaters, and it was used in a lot of theaters of the world. Although WE withdrewn from the movie business afterwards, 300B was produced until 1988 for the communication and the audio high-level amplifier. In the 1980s the vacuum tube amplifier was reviewed, SUNG CHIANG Co. of China began the production of 300B. 300B used for Model 1-300B is produced by SUNG CHIANG Co. under a specially selection of material and severe quality control.

2A3

2A3 was put on the market for more high-level electric phonograph and radio from RCA(Radio Corporation of America) in 1933.The tube was produced for playback in high quality sound. In those days, listening to record sound or radio music was the best entertainment at home.2A3 succeeded as a high-power output tube for the home. And, 2A3 was produced in many countries in the world. However, the vacuum tube has not be used for consumer appliances, production of 2A3 in the United States is discontinued, and 2A3 is being produced only with SUNG CHIANG Co. of China now.
Because 2A3 had been developed as a vacuum tube for the public use, a lot of improvements were added for improving productivity and stability. 2A3 made in SUNG CHIANG Co. has a wonderful performance, which is suitably to the compilation of the improvement for many years.


6SH7

6SH7 is pentode developed by RCA for the amplification of a high frequency and small signals such as communication apparatus and radios in about 1938. 6SH7 can get a large amplification gain and high output voltage.1938 is the time immediately before World War II outbreak. An efficient and strong vacuum tube was being requested by the army. 6SH7 was used for the military at first as a tube of a complete metallic exterior(the left of the photograph). Afterwards, tubes used the general glass are produced(the center of the photograph).The right of the photograph is small tube 6AU6A developed as a succession goods of 6SH7. Electric characteristics of 6AU6A is quite the same as 6SH7. However, large-scale 6SH7 wins splendor of externals and unrestricted tone quality.Many are remaining as a large amount of produced stocks in the military use about 6SH7 though 6SH7 is not produced now.

The photograph is a piece of use 6SH7 and made of the United States Raytheon Company.It is a vacuum tube delivered to the US army in 1952.


Selection of vacuum tube


All tubes used in Model_1/Model_1-300B are measured. To use for a right and left channel of the stereo, a pair of the same characteristics tubes are selected. Our company made a special device that could inspect a pair of the tubes at the same time and same condition. We use the device for the selection. A measurement result is described in each vacuum tubes. The pair selection is done to voltage amplifier tube 6SH7 in Model1/Model 1-300B though the pair is usually selected only to the output tube.

Selection scenery from which two tubes are measured at the same time.
The left is a selection device of 300B/2A3. The right is selection device of 6SH7.

Measurement result of vacuum tube description (current value of plate).
From the left to 2A3,300B, 6SH7

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