Shuguang's Black Treasure KT-88 tubes are being run-in on my Cary amp at the moment.
Visually striking, these tubes are classy. Launched to commemorate the 50th anniversary of Shuguang, the Black Treasure tubes are said to have 60 differences compared to their normal line. The most obvious is the black high polymer compound carbon coating inside.
Initial testing upon power up resulted in a loud crackling distortion that lasted about 2 seconds before disappearing one one channel. It never happened again, so I would not put too much into that.
Trawling the internet revealed user accounts of long tedious burn in (200-600 hours), with an accompanying roller coaster ride in quality in the process. It kinds of reminds me of my Mundorf Silver-in-oil burn-in experience.
Thankfully, the Black Treasure sounded quite good from the outset. With about 10 hours under their belt, initial impressions are that of exquisite refinement and quietness. Compared to the Genalex re-issues that preceded them, the Black Treasures had less bass bloom, but a more refined midrange and treble. The Genalex has more prominent bass, with a fatter upper bass that gives music solidity and heft. The Black Treasure is arguably tighter and more controlled.
The Back Treasure really differentiates itself on the midrange and treble. Apart from its inky black background, the dynamic contrast, and low level resolution were world class. Holographic presentation of instruments and voices, and the accompanying acoustic space were superb. The only fly in the ointment was the extension and air of high frequencies. Compared to the Genalex, the Black Treasures sounded restrained, and simply unable to let go. The local dealer and another hi-fi friend assures me that this would disappear upon extended run-in.
The highs eventually opened up. There was no "ah-ha" moment where the dark clouds parted, and the sun shone down on my humble abode. Rather, there was a slow and progressive opening up of the sound, with everything coming together quite well at about the 50 hour mark.
I checked the tubes every few weeks, and bias remained spot on. Sadly, one tube died on me after about a year of use (approximately 300 hours of usage).
Oh yes, please peel of the stickers affixed to the base of the tubes. They will drop off at the most inconvenient moment possible, and if you are really unlucky, fall inside your amp, or on some hot component. Across the six Treasure Tubes I used (from two different batches), I can guarantee you that this will happen as a matter of certainty.
Black Treasure tubes are available in Singapore from Live Acoustics, www.liveacoustics.com.sg