Will NOS tubes kill my OT/Amp?

sirshackleton

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I realize I'm probably not listing all the needed info here, but there might be just enough to provide some advice:

I picked up a matched pair of smoked glass NOS RCA 6V6GT VT-107A blackplates a little over two years ago and have been running in them my workhorse amp, a Wooly Coats Spanky (a BF-inspired 1x12 combo that runs about 18 watts or so). It's a well-built, fairly clean, high-headroom amp and I love it. Fell had over heels the first time I played one.

The amp sounds great with them and I've put a lot of hours on it the past year...gigs, rehearsals, etc. I'm guessing if there was an issue it would've emerged by now, but I was going down the rabbit hole last night on a related topic and read that old NOS tubes aren't necessarily capable of handling modern voltages like some current production tubes are, which can strain the OT. Is that true? I don't know.

I'm not able to find specific info on the OT, but I believe it's a Heyboer and is intended to be somewhat "overbuilt." As mentioned before, it's got a lot of headroom and doesn't crunch or compression that easily on it's own.

I don't have any data on plate voltages and things like that and I did not re-bias when I installed these; I just popped them in and gave them a go. The manual states the amp is configured/biased/setup specifically for JJ 6V6s. So I'm wondering if I'm cooking these old tubes to the detriment of my amp. Thoughts?
 

schmee

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IME many NOS tubes will not put up with the high voltages in some vintage amps.

One example is my BFDR about 14 years ago. I had spent the day putting in a pair of NOS RCA 6V6 in it. I had a couple sets at the time so I got a set all biased up and ready for the gig. One hour into the gig a tube blew taking out the original Output Tranny in the DR. That amp ran 460V+ on the plates as do many old BFDR's.
After an OT replacement, I tried new Electro Harmonic 6V6's and I thought they actually sounded very good. The first set lasted 3 months of fairly regular gigging. The second set lasted 3 months also.
By now JJ had solved their "small tube pin" issues and I heard they were up to the task. I have used JJ's ever since.

6V6's seem to be the only NOS ones that may not hold up as far as I know. The NOS 6L6's seem to do fine in the old 6L6 amps. For some reason it seems many of the old 6V6 based amps run very high on voltage. But not all.
There may be some EL84 amps that do also, but I have not used enough vintage EL84 tubes to know if they fail much or not.

For the OP with a newer amp, I would imagine it's made with the voltages under control somewhat...?
 

nickmm

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IME many NOS tubes will not put up with the high voltages in some vintage amps.

One example is my BFDR about 14 years ago. I had spent the day putting in a pair of NOS RCA 6V6 in it. I had a couple sets at the time so I got a set all biased up and ready for the gig. One hour into the gig a tube blew taking out the original Output Tranny in the DR. That amp ran 460V+ on the plates as do many old BFDR's.
After an OT replacement, I tried new Electro Harmonic 6V6's and I thought they actually sounded very good. The first set lasted 3 months of fairly regular gigging. The second set lasted 3 months also.
By now JJ had solved their "small tube pin" issues and I heard they were up to the task. I have used JJ's ever since.

6V6's seem to be the only NOS ones that may not hold up as far as I know. The NOS 6L6's seem to do fine in the old 6L6 amps. For some reason it seems many of the old 6V6 based amps run very high on voltage. But not all.
There may be some EL84 amps that do also, but I have not used enough vintage EL84 tubes to know if they fail much or not.

For the OP with a newer amp, I would imagine it's made with the voltages under control somewhat...?
Exact opposite for me.
Old Musicman running (el34) at 700 dc old tubes were fine. New ones would red plate at the same dissipation.
Old Vox running (el84) over spec voltages same deal.

Both amps had to run cooler to maintain reliability of new tubes.
Problem with the old valves was there were physical problems they rattled.. not red plating.
 
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schmee

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Exact opposite for me.
Old Musicman running (el34) at 700 dc old tubes were fine. New ones would red plate at the same dissipation.
Old Vox running (el84) over spec voltages same deal.

Both amps had to run cooler to maintain reliability of new tubes.
Problem with the old valves was there were physical problems they rattled.. not red plating.
"Red plating" is all about bias setting.
 

sirshackleton

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Thanks all for the help!

I've got a good stash of matched JJ 6V6 pairs, including the ones that originally came with the amp, and decided to pop the old set back in for the heck of it. Still a great sounding amp and many more similarities in tone and performance than differences between those old RCAs and the modern JJs. I may stash the RCAs for the time being until I can get an amp tech to take a look, but I may find the JJs suit my needs just fine and tamp down my worries about blowing something up.

For those keeping score: to my ears the RCAs seemed to firm up the overall midrange voice while the JJs sound/feel just a little bit softer there (which is actually nice because the mid control feels like it gained a little more useful range...makes sense, given the design is probably tailored to JJs!). That said, that's with me listening very carefully and intentionally for audible differences.
 

RetiredUnit1

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I check the bias half an hour after installing NOS tubes. Many times I end up resetting the bias up to 3 times before it stops drifting. I also check it a week later just to be sure.
 

Wally

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I realize I'm probably not listing all the needed info here, but there might be just enough to provide some advice:

I picked up a matched pair of smoked glass NOS RCA 6V6GT VT-107A blackplates a little over two years ago and have been running in them my workhorse amp, a Wooly Coats Spanky (a BF-inspired 1x12 combo that runs about 18 watts or so). It's a well-built, fairly clean, high-headroom amp and I love it. Fell had over heels the first time I played one.

The amp sounds great with them and I've put a lot of hours on it the past year...gigs, rehearsals, etc. I'm guessing if there was an issue it would've emerged by now, but I was going down the rabbit hole last night on a related topic and read that old NOS tubes aren't necessarily capable of handling modern voltages like some current production tubes are, which can strain the OT. Is that true? I don't know.

I'm not able to find specific info on the OT, but I believe it's a Heyboer and is intended to be somewhat "overbuilt." As mentioned before, it's got a lot of headroom and doesn't crunch or compression that easily on it's own.

I don't have any data on plate voltages and things like that and I did not re-bias when I installed these; I just popped them in and gave them a go. The manual states the amp is configured/biased/setup specifically for JJ 6V6s. So I'm wondering if I'm cooking these old tubes to the detriment of my amp. Thoughts?
Thanks all for the help!

I've got a good stash of matched JJ 6V6 pairs, including the ones that originally came with the amp, and decided to pop the old set back in for the heck of it. Still a great sounding amp and many more similarities in tone and performance than differences between those old RCAs and the modern JJs. I may stash the RCAs for the time being until I can get an amp tech to take a look, but I may find the JJs suit my needs just fine and tamp down my worries about blowing something up.

For those keeping score: to my ears the RCAs seemed to firm up the overall midrange voice while the JJs sound/feel just a little bit softer there (which is actually nice because the mid control feels like it gained a little more useful range...makes sense, given the design is probably tailored to JJs!). That said, that's with me listening very carefully and intentionally for audible differences.

without knowing the voltages and bias numbers with each set of power tubes, imho comparisons are not valid.
 

dan40

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I trust NOS tubes far more than the new production stuff. Any tube, NOS or new production can fail without warning but I get far more hours out of the older stuff than any of the new production tubes. You can still find Fender amps from the 50's that are still running on their original pair of power tubes even though higher wall voltages these days are creating higher B+ voltages throughout the amp. Just like modern tubes, any NOS tube can suffer infant mortality in it's first few hours of use but once they make it past that, they seem to hold up far longer.

Some of the earliest variants of 6v6's were not designed to handle higher plate voltages so care must be taken if your amp runs at 400vdc and above. Once you get into the 6v6's with the "GT", "GTA" and "GTY" suffixes, they hold up just fine in most tube amps.
 

AxemanVR

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I trust NOS tubes far more than the new production stuff.

The main reason I don’t trust so-called “New” Old Stock tubes is, how can anyone be absolutely sure if what they’re getting are truly “unused” tubes.

It stands to reason that the NOS market has been around long enough now that a significant chunk of new/unused tubes has to be fairly depleted.

Even reputable suppliers have to replenish their stock from a wide variety of sources. How can they possibly verify each tube as accurately being NOS other than checking them for physical appearance (which is sometimes misleading) and rating them based on a generalized testing machine - which certainly can’t predict whether a tube is about to fail.

None of this would be a big deal if the price of NOS tubes weren’t so astronomical (for certain brands).

Plus, I feel that a great amp design overcomes many tube deficiencies anyway.

For instance, my 2019 Fender ‘57 Custom Deluxe sounds great with just about any tubes I put in it. To me the gain structure, component choices and even the Alnico speaker play a greater role than the tubes themselves, and, even then, the preamp tubes affect the tone far more than the power tubes.

So I’m not saying tubes don’t make a difference, but I’ve heard some great sounding modern tubes and some lousy vintage tubes (after much tube swapping I ended up keeping the original Groove Tubes in my Deluxe) which makes it exceedingly difficult to justify spending a boatload of my hard earned cash on something that may or may not yield superior results…


 
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InstantCoffeeBlue

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NOS are overrated and new components are more likely to be at the spec.
JJ 6V6 are designed to take high voltages.

Also, as tube stashes become more and more picked over,"NOS" has become an almost meaningless catch-all marketing phrase for "old" tubes. It used to mean something, now every used-up tube on ebay can be "NOS".
 

Wally

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Also, as tube stashes become more and more picked over,"NOS" has become an almost meaningless catch-all marketing phrase for "old" tubes. It used to mean something, now every used-up tube on ebay can be "NOS".

Such would be an unethical use of the NOS label in a dubious marketing ploy. Unless I get the tubes in their original boxes, I do not use the NOS Label. I may in fact have some NOS that I cannot claim as such because I bought a small stash of military tubes that had been mishandled by people who did not know what they had. Some of the tubes’ boxes remained intact….others did not. I bought the stash to get a couple of 18-tube sleeves of boxed GE JAN 5751s from the late 1950s.
 

PhoenixBill

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Yet, as we all know, there are far too many sellers who have no qualms about “stretching the truth” when it comes to selling their product. On top of that, just because a tube is in an original box doesn’t mean it is a truly unused tube that came in that box. I have bought a couple of tube caddies containing hundreds of tubes. On a couple of occasions I have taken a tube out of a box expecting to find a brand new tube, only to find a tube of a different maker in that box—even the tube might look new, it was obviously tried or something. I have heard of old repair guys that get a service call out to a house and sometimes swap a tube to see if that solved an issue, but then seeing that the old tube was still usable they would save it for the next repair where they might again have to try swapping a tube (and perhaps billing the second customer for a “new” tube).
 

Wally

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On a couple of occasions I have taken a tube out of a box expecting to find a brand new tube, only to find a tube of a different maker in that box—even the tube might look new, it was obviously tried or something.

been there…. However, there are times when one opens up such a box and it is obvious that the use in the box left the factory in that box. Such is the case with he GE 5751s I mentioned above. The date codes on the tubE’s match the dates on the boxes, all of the tubes were produced at about the same time…there are three codes on the tubes to prove that, and all of the boxes have he exact same shipping dates handwritten on them. They left the factory in these boxes and in these large sleeves.
I also was,lucky enough to get hold of some RCA 6v6GTs that were in the original shipping box. Sometimes it is easy to know that tubes are NOS. Sometimes that status cannot be known…and should not be claimed.
 
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dan40

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The main reason I don’t trust so-called “New” Old Stock tubes is, how can anyone be absolutely sure if what they’re getting are truly “unused” tubes.

I use the term "NOS" loosely because most of the tubes that I have gotten over the years had seen some use before I received them and were priced accordingly. Even with the previous use, they have stilled tested out great and continue to last far longer than some of the newer stuff I have purchased. Much of the older equipment that ran tubes back in the day (excluding guitar amps) ran a much more conservative B+ and bias setting, so many of the ANOS tubes still have years of life left in them.

I have been lucky enough to find a few pairs of power tubes that were true NOS but the prices for those is often more than I'm willing to pay. The first thing I look for when considering a purchase is the color of the glass down at the bottom of the tube. Unused tubes will normally have nice clear glass at the base whereas a used tube will often show a darkening of the glass due to heat. The pins are also a telltale sign. Any scratches or bent pins is a dead giveaway that the tube has been in a socket or two over it's lifetime. Most sellers will run the tube through a tester first but hopefully they are careful enough not to bend the pins. The getter flashing should also be full and shiny but some of the brands did come with a darker flashing so it can be tricky identifying it. I wouldn't consider purchasing anything labeled as true "NOS" unless it met all of those criteria and even then, it would have to be exceptionally well priced before I would take the chance.
 




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