|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
83.84.141.120
I've encountered a lot of different constructions of the Sylvania 12ax7 here on the tube asylum and elsewhere but I have never seen this one before. It looks to be the same construction as the grey long plate Sylvania's introduced in 1959, but with black plates. I've searched high and low and can't find any info on them. So I took the plunge and got 2 pairs on eBay which I will audition in about a week, when they arrive.
The description said that they have datecode 439 which would translate to week 39 of 1964 which seems unlikely for a 12ax7 black plate. Or maybe Sylvania made a special batch on request of Baldwin?
Has anyone auditioned these and compared them to the regular grey plate version? I'm very curious..
Follow Ups:
That Sylvania date code would be the 39th week of 1954 I believe. That said, I have several samples of Sylvania black plate 12ax7s and they all have bent square getters. Tube Mongers library also shows several pictures of Sylvania 12ax7 black plates and they all have square getters. Also all early Raytheon and RCA black plate 12ax7s have square getters. Only latter Raytheon black plates from 1960 and 1961 have the halo getters. That's what your tubes look like.
All great tubes by the way!
Thanks for the suggestions, but I don't think this is a Raytheon make. Please take a good look at the plate structure and the crimps. I've made a little comparison pic with a typical Sylvania 1960s 12ax7 grey plate.
As you can see it has the narrow bump in the middle (unlike RCA/Raytheon black plates which have wider bumps) and it has many plate holes (probably 6 per plate) where a Raytheon would only have 2 per plate.
Those look kinda like some RCA BP 6681 I once owned --- you know, I think a couple are in an amp, somewhere around here. 8^)I have no idea what the difference is between the 12AX7 and the 6681.
Edits: 10/03/16
6681s are tough to find in quads or even pairs. Black plate 6681s are considered unobtainium. BTW, The 6679/12AT7 and 6680/12AU7 are also ruggedized for mobile operation and > 13VDC filament capable...
Got to look around for my stock. Think I have some 7729 tubes, too.
Maybe, Raytheon (Made in Japan?) 12AX7. Very good tubes.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: