"300B" and "2A3" are very similar in appearance, but due to the difference in filament voltage and operating point, it is necessary to switch the supply voltage. The TU-8900 automatically detects which vacuum tube is installed, and automatically sets the filament voltage and B voltage to suit each vacuum tube. When 300B is installed, the left and right sides of the volume will glow blue, and when 2A3 is installed, it will glow green. In addition, due to an abnormality in the vacuum tube, etc., when an excessive current flows, the abnormal channel side glows red, and the current is shut down for protection. The windings of the power transformer are separately wound on the left and right sides to suppress interference between channels as much as possible. The latest DC-DC converter with ultr.
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