Stereo Power Amplifier
Incredible Power Amp Featuring 20 Pentodes
The 20A was the first Technics-brand power amp. This vacuum-tube amp featured an OTL (Output Transformer Less)/OCL (Output Capacitor Less) system. Five 50HB26 beam tubes were used in the output stage, and they were connected in parallel so ordinary speakers could be connected directly. Distortion before negative feedback (NF) was minimised, and the amount of NF in the main loop was maintained below 30 dB to successfully reduce distortion. The load resistance was also reduced to minimum in each stage to ensure stable high-frequency characteristics of beyond 200 kHz without NF. Pentodes with superb high-frequency characteristics were used in all stages to provide distortion-free, high output across the entire frequency range. The two-stage output selector enabled the use of only half of the 20 output tubes when the user wished to use the amp at a low output with reduced power consumption and heat generation.
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