Art Audio only sells Grade A Tubes from Sophia Electric.
Sophia Electric 6SL7 tube does not look like a typical 6SL7. By looking at the internal plate structure, it is more of a European tube structure rather than North American 6SL7. However the vintage European ECC32/33, CV181/CV1988 family of tubes are not real 6SL7 tubes. What is the story? Sophia Electric designers were smart enough to take European virtue combined with North American 6SL7 electrical tube characters, further Added with 1920's brass base accent. This is how these ST shape Sophia Electric 6SL7 tubes were born!
Sophia Electric 6SL7 would sound with a lot of more openness, more clarity and less distortion than the very best from vintage time. It just sounds bigger(better high frequency extension), louder (more drive voltage swing output), more 3-D imaging for sure (due to better testing and matching procedure applied in any tube amplifier and pre-amplifier). Hundreds of users reported Sophia Electric 6SL7 tubes are better than the vintage 6SL7 tubes being replaced, even the best from vintage time.
6SL7, like all dual triode tube, has two sections. To match two sections closely enough is hard enough; match two tubes (four sections would be much harder if high standard of matching method is applied). Note: a lot of internet vendors would only test one section of the tube due to the limitation of their vintage tube tester (like popular TV-7). So those claimed matched may be matched by one section (with assumption that the two sections would be identical). However, that assumption was false one.
This tube usually ships within 2-4 business days.