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The S9 is an integrated stereo amplifier with an output power stage that is a single-ended parallel design in pure class A. The output power is about 35 watt per channel.
The output power valves for this amplifier are the SV572 from the Russian manufacturer Svetlana. At Unison Research, we believe this may be the best factory for valves.
The SV 572 has a directly-heated thoriated tungsten filament for a soft glow and a warm sound. Other characteristics include a hard glass envelope with white ceramic base, low microphonic construction with ceramic internal spacers, a graphite plate with titanium coating for extremely high power capability and a relatively small physical size. The bias of output stage is manually controlled for each tube, obtained with the aid of a precision analogic mA meter.
The output transformers have been carefully designed and produced in our factory to extract the most out of the exceptional sound characteristics of the SV572. The total negative feedback of S9 is very low–about 9 dB–nonetheless the bandwidth is from 30Hz to 50kHz. The anodic power supply, more than 1kV, is supported with 8.000 uF capacitors filters! The filaments of each of the power valves has supplied with a dedicated power supply with Shotky diodes. |
