A quad of Sophia Electric blue-glass long-life KT88-ST vacuum tubes for the Leben CS600 / CS600X.
In my "Sexy Blue Tubes: The Sophia Electric EL34-ST and Aqua 274B Vacuum Tubes!" feature review article for Positive Feedback (HERE), I provided a brief history of the EL34 and 274B vacuum tube designs, and then described the various technical performance enhancements that Richard and Sue of Sophia Electric implemented in their flagship Sophia Electric EL34-ST power tubes and Aqua 274B rectifiers.
About the the Sophia Electric EL34-ST, Richard said:
"Electrically the specifications of the EL34-ST are same as the vintage Mullard, with a heater (filament) voltage of 6.3V AC, a heater current of 1.5A, a maximum plate voltage of 800V, and a maximum power dissipation of 25 watts."
Sophia Electric EL34-ST
Richard had explained to me that the shape of the glass enclosure of a vacuum tube affects its sound quality, and the ST shaped bottle sounds better than the straight glass envelope of the typical EL34:
"For the Sophia Electric EL34-ST we chose to use an ST shaped glass bottle similar to those used for 300B's, which helps give the EL34-ST a 300B-esque sound. In fact, we applied much of our 300B design and manufacturing expertise in the creation of our new EL34-ST vacuum tube. The larger ST bottle shape gives our EL34-ST tubes a sound that is more airy and live-like compared to the cheap GT glass tube."
Richard had also explained to me the blue coloring of the glass was not just for cosmetic reasons, it helps improve performance:
"The blue tint that we've added to the glass not only looks exotic, but during the voicing process we found that the blue tint of the ST shaped enclosure added more sonic impact to the presentation of the music. Vintage US military tubes often had a black metal base and/or black-grayish smoky carbon-containing paint sprayed on the inside of the glass tubes for light shielding to reduce noise. British and German military tubes often used red paint for light shielding to reduce noise. We have auditioned various light shielding possibilities, and ultimately settled on the blue tinted glass, which when combined with ST bottle shape, provided additional musicality and a distinctly better tone."
Sophia Electric blue glass KT88-ST long life vacuum tubes ($175 USD each).
About the Sophia Electric KT88-ST long life vacuum tubes, Richard told me:
"From a design point of view, the Sophia Electric KT88-ST shares similar internal metal material: grid, plate, etc., and mineral coating - in addition to ST glass - as the popular Sophia Electric Classic 300B tubes (photo below). The Sophia Electric blue glass KT88-ST tube sounds very much like a 300B tube and delivers 8x more power in a push pull KT88 amp."
Sophia Electric Classic 300B
"The same thing is true when the KT88-ST is compared to the Sophia Electric EL34-ST. Musically and sonically, this blue glass KT88-ST should be at least as good as the Sophia Electric blue glass EL34-ST, if not better."
Sophia Electric KT88-ST ($175 USD each)
I find what Richard had to say about Sophia Electric KT88-ST to be quite interesting. By analogy from what Richard said about the EL34-ST, using the blue tinted glass, for light shielding combined with the ST bottle shape should provide "additional musicality and a distinctly better tone" than your typical KT88.
Sophia Electric KT88-ST
Another aspect of the Sophia Electric KT88-ST that intrigues me is that it uses similar internal design characteristics in terms of metal material, grid, plate, mineral coating, an ST shaped glass bottle, etc., as the Sophia Electric Classic 300B tubes.
Sophia Electric Classic 300B
If find Richard's characterization of the Sophia Electric blue glass KT88-ST tube as sounding very much like a 300B tube that is eight times more powerful in a push-pull KT88 amplifier intriguing, to say the least.
Closeup of the Sophia Electric KT88-ST internal structure.
I'll be giving these Sophia Electric KT88-ST vacuum tubes a test drive in the Leben CS600 and CS600X integrated amplifiers in the near future, and reporting on the results.
The new Leben CS600X integrated amplifier.
After I get familiar with the Sophia Electric KT88-ST in the Leben CS600 / CS600X, I'll be offering some comparisons to the Sophia Electric EL34-ST for all you Leben owners out there.
A quad of Sophia Electric KT88-ST for the Leben CS600 / CS600X.
Stay tuned for a lot more Sophia Electric vacuum tube news as I proceed with listening trials in the Leben CS600 / CS600X with the Sophia Electric EL34 power tubes ...
A quad of Sophia Electric EL34-ST's for the CS-600X.
... with the Sophia Electric 12AU7 vacuum tubes ...
Sophia Electric 12AU7 vacuum tubes.
... with the Sophia Electric KT88-ST power tubes ...
A quad of Sophia Electric KT88-ST for the Leben CS600 / CS600X.
... and even some NOS Sylvania black plate 12BH7A's ...
NOS Sylvania black plate 12BH7A's.
... in the Leben CS600X.
It'll be interesting to hear how these premium Sophia Electric EL34-ST, KT88-ST, and 12AU7 tubes compare with the stock tube complement in the new Leben CS600X integrated amplifier, along with the NOS Sylvania black plate 12BH7A's I picked up so I could do a complete premium tube comparison.
As always, thanks for stopping by, and may the tone be with you!
