NOS Rocks in New amps....wait...What????

[Guitar-Sam]

K guys I've been loving NOS valves for a few 6 or so yrs.
Recently I've been gigging(& recording with)a little Orange Tiny Terror.
I've been running all NOS in it since I removed the JJs a month after I got it a couple years back.
Recently I got my new co-guitarist into the joys of tube swapping.In that he got me screwing around again with my amp,I let him try a few and he let me try some of his new production stuff that was in his amps.Most were lifeless and harsh.........till I got to a New Sensor Mule 12ax7 in the PI and surprisingly I not only liked it,it was the smoothest out of anytube I've tried in that spot(Tele,Mule,RFT,Tungsram included).Hummm weird??? So he gives me a couple sets of el84s to try an old GE set nicer than my Polems hum???? Then I try a set of TAD el84-str to amuse myself......WTF........they sound smoother than my Polems,GEs,the Tungsreams I had ,RFTs I had and of course the stock JJs.Both these swaps fixed problems I thought I was gonna have to mod out of my amp.The new production tubes (power & PI) while having less lowend and complexity were still the smoothest as far as making the amps playabilitie best.
NOS is still my only choice for V1 for full smooth balanced sweet tone but,What the hell is goin on in the power section??
Is it that newer amps are built around these newer tubes??Anyone else find this in any of there newer and/or el84 amps??
TT would be ashamed of me.

[soundguruman]

V1 is always the critical tube, and should probably have a feed back circuit installed on it to stop it from ringing.
(example: a 6 pf 1000V cap between plate and grid)
the Sino Chinese 12AX7 also sold as GT12ax7CH, is doing just fine in place of NOS tubes. It has plenty of gain, much more than most others, lots of crunch, moderate sizzle, and will work just dandy with a feedback circuit on V1, like I said , to stop it from ringing. It has a sound reminiscent of an old Mullard.
Now most people would be skeptical that this Chinese tube would live up to rock and roll, but be prepared to be surprised. This tube does rock.

Power output tubes have been upgraded over the years, and are much different from NOS output tubes. The new tubes produce more power, with higher voltages, Of course the new amps are designed for the new tubes.
For example, a vintage Marshall super lead has no screen grid resistors. A new one MUST have screen grid resistors, the new EL34 tube draws WAY more current. You MUST install the resistors in the old amp to run the new EL34 tubes, or the HT fuse will blow.
That's only one example.

[Kevin]

As far as I know, even the earliest Superleads had screen grid resistors - the light-gray RS pieces. Sure, many have been replaced over the years with the cement-block types, which might lead one to believe that they were added later. I think that the vintage 50-watters were the only ones to come out of the factory without screen grid resistors.

And, I don't know that new EL34s necessarily draw more screen current than vintage ones. There was a discussion a few years back about choke current ratings and Larry measured the screen current draw by various EL34s. RFTs were the highest of the tested tubes, followed by Mullards (xf4s, IIRC), and JJs. I repeated the experiment with various tubes (no JJs, though ) in an attempt to shed some light on my own ghosting issues, and didn't find that newer tubes draw more current in general. They were all pretty close and the difference in current draw between tube types didn't have much effect on ghosting. I have since started using 1k5 screen grid resistors - and even 2k resistors on higher-voltage amps - for tube-life and against ghosting. Maybe some new tubes draw more current than some older ones, but I don't think it's a general rule.