NOS versus new production tubes

[zhivago]

got some RCA 6V6s on the way too!

[sookwinder]

Hey Brad, I suspoect you and I unintentionally have helped turn Yannis into a NOS valve ....

[zhivago]

my woman has ALREADY left me...

[Stratelejazzuar]

haha, you just made me think:





You guys and your NOS tube pr0n is giving me major GAS, too, btw

[zhivago]

some more just arrived...RCA 6V6GTAs...







there will be more this week, and then the experimenting will begin!

[Jaguar018]

I'd be willing to take your zhivago seconds...

[zhivago]

I'd be willing to take your zhivago seconds...

I'll see what happens after the shootout, and let everyone know how the spares will roll

[Jaguar018]

I'll see what happens after the shootout, and let everyone know how the spares will roll

Cool. Whenever I read stuff on tube comparisons, there tend to be stand outs. Often second or third place is almost as good, or just has a different element to the sound that the tester person subjectively does not enjoy as much as the #1.

[zhivago]

very true!

this arrived today...










....and more to come in the next few days...

[NoiseAnnoys]

I didn't really buy into the NOS hype until I picked up an old Harmony amp that had the original RCA 6V6's in it. They really do sound amazing. I'm going to have to buy a stash while prices are still reasonable. Yannis, I'm curious to see which ones are your favorites.

I still use JJ's though for things like my Vox AC50, because it just chews up tubes as is and I'd hate to spend the coin on NOS EL34s to keep it going. Plus, I feel this weird kind of ethnic duty to them for having a plant in Slovakia. In the end, I suppose I could get NOS for them, but the AC50 was my road amp (and hopefully will be going on tour in the next few years) and I hated the thought of carrying $300+ worth of tubes around as replacements in case something went wrong.

[zhivago]

I found this explanation of tube name/designation aliases online on another forum, that I thought we could have here too...

12AX7 numbered variants:

7025 - spiral wound filaments for reduced hum. Most 12AX7s after the mid 50s will have this as a standard feature.

6681 - mobile-rated 12AX7. Filaments perform well with a wider range of voltages.

6057 - Brimar's special quality 12AX7.

7729 - CBS/Raytheon's instrumentation grade 12AX7, with heavily gold plated pins.

CV492, CV4004, M8137 - British Military designators. Typically Mullard or Brimar.

B339 - Another British equivalent, most of these are regular Mullard ECC83s branded Marconi or MWT.

B759 - The Genalex "custom" 12AX7, a selected, tested Mullard ECC83.


12AU7: 5814, 5963, 6067, 6189, 6680, 7316, 7730, CV491, CV4003, M8136, B329, B749

12AT7: 6060, 6201, 7728, CV455, CV4024, M8162, B309, B739

12AY7: 6072

[NoiseAnnoys]

I'm going to bump this for a question, primarily directed at Theta or anyone else who knows a bunch about this subject:

So, I have this vintage Vox AC50, right? And it positively chews up EL34s, even biased a little cooler than AC50s typically are. Approximately how much more life could I expect out of a set of NOS EL34s (or any other equivalent) since the amp is running so hot? I've been using JJ's, but if I'm going gain a lot more performance out of it, I might as well consider switching and laying in a stock of NOS while I can.

[jetset]

Thirdly, consider that modern wall voltages have crept up and up over the years. When the voltage gets transformed upward for plate voltage, the difference of 5 or 10 volts at the wall can be very significant... it can become 30 or 50 volts different on the secondary side of the transformer. If tubes were already being run "at the edge," this can prematurely put them under in some cases. Stick a meter in your wall and find out what you're getting out. If it's significantly higher than what's printed on the back of the amp as the input voltage (usually 117 in the USA, probably something close to 220 or 240 in Europe), then consider getting a source of regulated, steady power.

+1 on this. I have an old Vox AC15, and I had the guy who restored it (Matt @ JMJ amps) include power scaling to be able to dial in the right voltage. A lot of guys also get a step up transformer and run their Vox or other British amps that have voltage selectors on the 245V (UK) setting. Some say they sound better that way. If you have a tube rectifier (which most ac50's don't) you may also be able to adjust things with a tube substitution. Not sure about that.

[NoiseAnnoys]

Thanks Theta and Jetset. I'll have to look into the line-voltage. The amp has been frankensteined a bit, so that the voltage selector isn't easily accessible anymore (the previous owner took its big-box AC50 chassis and transplanted it into a narrow-box AC100 shell), but it's still there. I'll ask my tech about it next time I take it in.

That's a bummer that there's no EL34s even remotely close to old specs around.

[jetset]

the voltage selector isn't easily accessible anymore but it's still there. I'll ask my tech about it next time I take it in.(

If you want to go the step up transformer route, you could have him wire up the 245 tap directly, and bypass the selector. Those vox voltage selector gizmos are kind of sketchy anyway.
-J