For sale is a pair of NOS testing Matched Sylvania JHS Military Spec 5751 Black Plate triple Mica Tubes. Although they are very lightly used, they test NOS closely matching between sections at the upper end of good on my calibrated B&K 707 tester. (recently a pair of these sold on ebay for over $200).
The Sylvania 5751 JHS Black Plate is readily replaceable in most equipment with a 12AX7 tube and is often regarded as the very best sounding of the 5751/12AX7 tubes available.
JOE'S TUBE LORE QUOTE ON SYLVANIA 5751 3 MICA BLACK PLATES: "The ink used on the tubes themselves was gold and it rubs off easily, so even NOS tubes can have partial labels. Now all of this is my conjecture based on comparing the internal structures carefully and comparative listening - but after doing so I am convinced the tubes are identical. So what do you hear when these guys are in circuit? Well they have an absolutely glorious midrange - female vocals are to die for, or is it kill for? (Don't get between me and the VR6s while these are in circuit and I’m playing Jonathan Brooke's Live cd - you have been warned!). The other thing is that they have a marvelous sense of life and a tangible (almost spooky) sense of 3 dimensionality to images in the soundstage, particularly vocals. The overall effect is one of a very transparent, warm yet lively sound with a complete lack of fizz or grain and a high level of detail retrieval allied with great vocal reproduction."
SHIPPING AND PAY PAL ARE INCLUDED IN THE PRICE