Tuesday, February 18, 2014

Tube Review: The Shuguang GEKT88 tetrode

Introduction:
The KT88 was GEC's answer to Tung Sol's big dog 6550, the most powerful consumer output tube at the time.  The '88 boasted even higher plate and screen voltages, the latter an important consideration for Ultralinear output stages.  The KT88 was used in some of the more powerful amplifiers of the time - the Dynaco Mark III, the Harman-Kardon Citation II, the Scott LK-150 - back when 50 or 60Ws was considered an insane amount of power for driving your efficient horn speakers.

Of course times goes on and new technology comes along - instead of a 60lb amplifier with massive output transformers and making enough heat to fry an egg, the consumer can get a cool running amplifier for way less money and in a considerably lighter package.  But even then there are a cohort of audiophiles who won't give up valves since they have an interest in a colorful and lively presentation when listening to their music.

The GEKT88 - also sold as a Penta KT88SC - is rumored to be Shuguangs direct copy of the now incredibly expensive GEC original.  I don't have an original on hand - this was a tube that I never had much interaction with even in the early 90s - so I can only compare by images.  Hmm... solid-plate, getters on the side, similar mica location... bulb structure is slightly different.  The rumor is that Shuguang is using the actual GEC machinery and some ancient batch of cathode emulsion.  Perhaps that's true, but how do they sound?  There was only one way to find out: I ordered a pair via Ebay and waited four weeks for them to arrive from China.

After some time in the Multi-Valve amplifier, dialed in at 70mA each, it was time to do some serious listening.

Listening Tests:
Since Neil Young - Live at the Cellar Door is one of the newest entries to my record collection, I decided to give this the first spin.  The GEKT88 proved itself right from the get go with a big clear sound with plenty of body in the guitar and piano.  The vocals are right in the middle of the speakers and project out much like the real thing.  The coughs and wheezes of the audience weren't lost in any background smear nor did they stick out in an unnatural way with some false heightened detail.  On the song Expecting to Fly, Neil really pounds those piano keys and all that power comes through in a natural way.  So far I'm quite impressed, but this is an album without bass or drums, so I thought it was time to move on to something even more dynamic.

My UK pressing of Supertramp - Crime of the Century is not as bold sounding as my U.S. one, but is a tad smoother.  With the GEKT88s in place, the bass went down real deep with plenty of impact.  Image depth was about real close to the best NOS stuff I've heard while side-to-side soundstaging was excellent.  What this new production tube seems to lack is just that last bit of true greatness I hear with vintage Tung Sol 6550s or Dutch Philips EL34s.  It's very close, but there is some faint but audible grain in the upper mids.

Fleetwood Mac - self-titled was up next.  The vocals were nice and smooth and the multi-tracking of the drums was very obvious.  Though this is a "busy" recording, it is still easy to pick out individual instruments in the mix.  Stevie Nick's voice was sublime with some real emotion coming through.  Very nice.

My promo copy of Earth, Wind & Fire - All 'N All is a hot - and I mean aggressive - recording - with plenty of top-end.  This came through with out any rolled-off treble or excessive tube "warmth"..  The bass and the thwack of the drum started and stopped without any overhang.  It was also easy to pick out different vocalists in the chorus.  A fun and engaging album, the sound came through with great clarity.  I've heard this album done better - like through the Eico HF-60s with their seemingly unlimited power - but the GEKT88s in the Multi-Valve amp were a close runner-up.

Conclusion:
As far as new production power tubes go, the GEKT88 is the best I've heard - so far.  Of course there will be other reviews coming up, so stay tuned.  Needless to say this Shuguang power tube really captures 90% of the magic of NOS, only failing at the very edges that still makes me prefer the vintage stuff.  Of course I am talking about that last bit of inner detail, liveliness, and that sense of being totally immersed in the stereo experience.  Nonetheless I give these tubes a high recommendation.


Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
Multi-Valve Stereo amplifier
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack  

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