Key Kim of The StereoTimes:
"...they feature a unique parallel push-pull Class-A design using six beam power pentode tubes per channel. The Challenger can be used with EL-34s, 6550s, or KT88s, and it produces a powerful 115 to 180 watts per channel. This is made possible by its revolutionary and proprietary Automatic Bias Regulator (ABR) circuitry, which monitors, biases and controls each tube independently. Brilliantly, it makes tube replacement very economical and simple, there is no need for tube matching to get the best sound. My review pair was equipped with the EL-34s and they rendered music with power and authority, transparency and beautiful tonality..." (the full review is in the making).
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