China ax7s

[TUBEDUDE]

is it the plate structure that is the limiting factor? maybe it's the cathode coating.

[Stevem]

I don't know, but if you look at output tubes where the cathode is strong enough to power the tube into red plating , then maybe not!

[FUCHSAUDIO]

I have spoken with TAD who buys, matches and grades Shu 12AX7's and other tubes. They claim these are the "closest to old real 12AX7 specs" of all the current production tubes. I have not plotted them out yet, but would like to compare on something like a Maxi-Matcher to confirm this.

I've dealt with for years and didn't get the sense they were blowing smoke up my butt. Their power tubes have become stock in Marshall, Engl and many other brands (often labeled for the maker) and have proven pretty robust and reliable.

I suspect that shield may be for rigidity and possibly to isolate the tube halves from one another. In some amps the signal can leak from one side of the tube to another, these don't seem to do that.

[Matt D]

For what its worth I've tested (literally) thousands of JJ preamp tubes on an Amplitrex and and the ECC83-types come in within 10% of spec about 90% of the time. The higher-current tubes like the 12AT7 and 12AU7 seem a little harder to get dialed in to dead-spec, though they are most often within the manufacturing tolerances and sound fine in amps. I have hundreds of vintage tubes and notice the same trends generally with high and low current tubes. I don't have tons of experience with the Shugangs but a similar trend is not surprising.

[Stevem]

Thanks for the info on the Shu AX7s Andy!
In my work over the last 4 years I have yanked out more than 600 hundred new Shu AX7s and also tested in my spare time some 300.

Most of them test out very good, and maybe 10% of them test out way too good , but still will not have the pure current output of a JJ brand that comes in at even only 95%!

Just for kicks I have checked some 12AT7 groovetubes out of brand new Fenders we have on the show room floor here at work and they are very sub par also!

Hey Andy, I have no problem with NJ, lol!

[FUCHSAUDIO]

Cool steveM...!!

[Turbojunkie]

I couldn't get in touch with an acquaintance who has lots of experience with Chinese 12AX7's, he had a large stash of them, I think most were purchased from Magic Parts (Ruby? not sure) quite a while ago.... a great player with great ears, he swears by them in his JMP/JCM 800 Master Vol Marshalls over any other 12AX7's from any time period. They didn't last nearly as long as tubes from other countries, but it wasn't a big deal because they were so inexpensive and readily available....I thought they sucked in the amps I played at the time.
I do remember that those shiny metal structures between the plates are for stiffening purposes.

[Stevem]

Well from my testing of hundreds of them I can see why some say they do not sound good, as many have tested out killer on one side and useless on the other!
I like the sound of them in stages where they will not be over driven too far , but I have also found that it can hinge on the plate voltage applyed to them.

That said , yes they do not last as long as other brands!