When NOS is NOT NOS

[printer2]

I have had good luck buying NOS tubes from Ebay but most of the stuff I bought was non standard, 12BK5's, 15CW5, 12AQ5, 6AQ5, 6AK6, 12AT6, 12V6, 25L6. Original boxes, did have a bum NOS 6AQ5 but that happens. Mainly bought from sellers that had lots of sales and good feedback. I expect NOS to be exactly that. I have some tubes that tests NOS but they were still sold as used. New is new.

[Firestorm]

If the price is right, you can do well on eBay from sellers who don't claim to know anything about what they've got. I scored a NOS pair of Tung Sol 5881s from a guy who didn't have any way to test them and made no claims. It's a crap shoot though.

[rp]

I agree that NOS should offer no latitude and should be just that. Some dealers will use ANOS which can be broad but more honest. Some beat looking tubes might even be NOS but just sat in a damp basement or in a drafty garage etc for 60 years so it's hard to always tell. Lots of folks in the old days would replace tubes on a schedule and stick the fine looking, 1/2 worn tube in the new crisp box of the new tube, and that then went into a pulls box in the garage... to be found 50 years later to be sold on ebay as NOS. It's all very hit or miss on ebay, but I've done ok there - if buying NOS bid ANOS. If a dealer has a large quantity of that one tube then it's more likely NOS.

If I get a tube that test excellent and looks ANOS even if labeled NOS I don't complain. Handle enough and you get a good tube vibe when one's in your hand. Anyway, IMO even an old tube w/ markings half gone testing Good is better than new stuff as long as you didn't pay too much.

[pula58]

The guys who sold me the used tube as NOS are a major tube parts dealer. I am surprised at their policies.

[cbass]

Bought two 5U4GB rectifiers sold as "NOS."
One of them was clearly used.
I call the seller, they say that if a used tube tests as fully meeting its specs, they sell it as "NOS."

Well, I was surprised about that!

Shouldn't the tubes have been called ANOS? But certainly not NOS?

What do you folks think about this?

That's a bunch of crap new is new.who was the seller?

[Invertiguy]

This is exactly why I love messing with old TV tubes instead of standard audio types. When tube TVs went the way of the dinosaurs, there was a huge surplus of unused tubes laying around that just got stashed away, and since they weren't common audio types, most never got used (except for the illegal CB radio amplifiers that used and ate a few types of sweep tubes, thus making them rare and driving up the price, but that's a different story). As a result, there's a much higher likelihood that what is called NOS is actually NOS, but you still end up with the occasional tube that shows a bit of wear. It's not as big of a deal when the tubes cost $5 a piece or less, though.

[boots]

I agree that NOS should mean old but unused. But that is not how most tube dealers define it.

There is a definition of what constitutes NOS, and I've seen it posted on some of the tube dealers' websites. If a tube meets certain criteria, i.e., if it tests within a certain percent of what a new tube would, it can be called "NOS". NOS is definitely a misused term, but I guess that's how it is.

I have had great luck with used, vintage tubes, and I will continue to seek them out. There are so many used vintage tubes available that it seems pointless to me to pay huge bucks for "NOS" tubes that are probably used anyway.

But I'm still searching for that mother lode of 50 year old NIB's!

[Structo]

I buy from a seller that does not claim NOS.
Most are pulls and they do not say they are NOS.

They post the Gm, so you know if you are getting a balanced tube or how worn out it is.

Most popular audio NOS tubes are history but wouldn't it be great to find a warehouse full of guitar NOS tubes, pristine in their original boxes?

Like 1 million 12ax7's and 6L6's among other desirable tubes.

Gold mine!

[dynaman]

Well, the tubes ARE old stock. And they're new to YOU.

Wow, now I can sell off my duds under a new acronym...NTYOS!

[73GTV]

Invertiguy:
This is exactly why I love messing with old TV tubes instead of standard audio types.

(Great Point) It would be worth starting another post on this subject of which TV tubes would work for making a different type (based on tube type and Voltages) of amplifier circuit.

Based on what I have been reading from old tube manuals. Back a few years ago I started buying a stash of odd tubes and when I first started collecting, ended up with a few old sets of TV tubes.

I kind of wanted to see if there was a good use for these, since a lot of them were NOS.

Just food for thought.

[Invertiguy]

There are a TON of TV tubes that will work in a guitar amplifier if you're designing an amp from scratch, way too many to list in a single post, and that's not even including all the odd filament versions intended for use in series-string sets. But overall, except for a few specialized tube types such as HV rectifiers and regulators, you can probably find a way to use most of them in an amp. Vertical-sweep tubes make very linear audio amps, since distortion in the vertical sweep circuit would lead to distortion in the picture. These usually are either dissimilar triodes or triode-power pentodes. A few types off the top of my head are the 6LU8, 6LR8, 6KY8, 6EM7, and 6GF7. Just avoid the ones that have a common cathode.

Horizontal-sweep tubes, which were responsible for sweeping the electron beam across the screen as well as generating the HV for the CRT, make very robust power pentodes in an audio amp. They are typically rated extremely conservatively as far as plate dissipation goes due to the severe service that these tubes served (full RMS power for hours a day inside a cramped, poorly-ventilated box with a bunch of other tubes putting off heat), so in a guitar amp you may be able to get away with exceeding the specs by 50% or more in some types. Note that for the same tube type there were often several different constructions, though, and not all of them take kindly to being pushed. A few favorites are the 6BG6 (which is basically a 6L6 with a different pinout and a top cap), 6BQ6, 6DQ6, 6CD6, 6LR6, and the mighty 6LW6, some of which will handle 90+ watts of dissipation per tube without red-plating.

Damper diodes, which were used to damp high frequency ringing on the horizontal deflection coils and generate the boost voltage for certain parts of the set, make good power rectifiers. They usually only have one diode per bottle, so you'll need 2 of them to make a full wave rectifier, but on the plus side they can use the same filament supply as the rest of the amp due to a separate cathode connection and a high Vhk rating. A few examples are the 6CJ3, 6AL3, 6AX4, 6BL4, and the 6DL3.

As far as the small signal types go, you'll typically find various triodes and pentodes (often in the same bottle), sometimes with a few diodes thrown in for good measure (but hey, you can always use them for some extra clipping if that's your thing). Most of them can be treated as you would any other triode/pentode when it comes to designing a gain stage, with the exception of dual-control pentodes and remote-cutoff pentodes. Dual-control pentodes can be made to work with the application of a slightly positive voltage on g3, otherwise they're pretty non-linear. Remote cutoff pentodes can be used as a compressor, but will result in non-linear distortion when used as an audio amp (which you may find you like anyway). A few types I can think of to try would be the 6KE8, 6GH8, 6CM8, and 6DJ6.

A few links to help you on your journey:
http://www.diyaudio.com/forums/tubes-va ... tubes.html
http://www.junkbox.com/electronics/Comp ... ndex.shtml
http://www.diyaudio.com/forums/tubes-va ... utput.html

As a final note, and as you can probably tell from the links, the guys over at DIY Audio have done some amazing things with old TV tubes. Some of the members there have forgotten more about tubes than I could ever hope to learn. There is a gold mine of information about using unconventional tubes on that site if you're willing to dig.

Hope that helps!
-Matt