NOS versus new production tubes

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NOS versus new production tubes

Post by øøøøøøø » Tue Dec 28, 2010 10:11 am

I've got some great info to share.

The backstory: I've been kicking around the idea of building some more microphones-- namely a "U47-inspired" mic. The U47 used a tube called a VF14 which is nearly impossible to get. They only ever made about 25,000 and most aren't good enough for mic use-- but to even "roll the dice" will cost you about $2,000... then you may or may not have a usable tube. Ouch!

This led to researching alternative tubes, and then tubes in general, from the audio engineering side of things.

Turns out there are one or two guys (one guy in particular) with such a passion for audio tubes that he knows literally more than anyone I've ever seen on the subject. His name is Oliver Archut and he's very well-respected in those circles, as the man behind TAB Funkenwerk, one of the most respected restorers of vintage microphones.

He has, in my opinion, the definitive answers about the "why do NOS tubes perform better and last longer?"

I always heard that it was foremost a difference in materials grade (I'd always heard 'laboratory grade' in the old tubes versus 'industrial grade' in the new tubes) and general build quality. Turns out that is pretty much right, but it gets deeper.

First of all, according to Archut, Mike Matthews/EH/New Sensor are generally pretty responsive to his criticism and feedback. Their tubes have improved a bit, but most still are not there. However, JJ is very stubborn and will not listen to any criticism of their tubes, and will deny all shortcomings. This is interesting to know.

After some of the new EH/New Sensor EF806 failed his 10,000 hour lifetime test, Archut wrote the following:
After the lifetime test I took all tubes apart and checked what went wrong, and aside that everything was made sloppily and not right looking, compared to a real EF806 as well as measuring, the biggest joke is the filament. The historic Telefunken EF806 had a double helix filament were the Russian samples had just a spiral one, resulting in a higher noise floor.

Even the gold plated first grid cannot make up for the sub-standard of the raw materials..... The designation EF806s is given wrongfully.

As a manufacture of mic pres I use at least 600 EF86/804/806 a year, and I have had hoped that Mike would come up with something that is at least better than the EF86 made in East Germany, but quite frankly this tube is just plain old not useable in a mic, nor mic pre, etc.
And then he goes on, with even more "meat:"
Over the last 10 years I talked numerous times with Mike, JC and even Irushka in Russi

There are two big factors with Russian tube manufactures why their tubes never can live up to old Western specimens:

the production steps they CAN NOT DO and the production steps they DO NOT WANT TO DO. Aside of that, the raw material' situation is quite poor and even tough I supplied Mike and JC with the companies' names which still make some of the material they needed, nothing happened so far.

The problems in detail:

One of the biggest problem with Russian tubes is the cathode/filament and then 2nd is the chemical procedure that applies the active coating to them.

The noise Klaus talks about is a barium coating that gets deposited onto the first grid after about 200h. This makes those tube too noisy even for simple applications with a 3 Meg Ohm grid leak; using a gold plated first grid won't help that problem- in fact it makes it even worse.

The 2nd problem is the isolation coating of the filament that deposits small traces of magnesium onto the entire tube electrodes.
When disassembling a used tube you can see those problems for yourself just by holding the grid(s) into a flame and seeing how the color turns greenish. A new tube that you take apart and subject to the same test won't show those colors)

I am still hoping that the remaining tube factories will notch up the quality so that those new tubes are useable in studio gear... But I do not see that it has happened so far.
Many of these things can and will apply to the tubes we use as well.

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Re: NOS versus new production tubes

Post by AWSchmit » Tue Dec 28, 2010 10:44 am

Though, some of this is Greek to me. It was still very interesting. Thanks for sharing.
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Re: NOS versus new production tubes

Post by øøøøøøø » Tue Dec 28, 2010 11:36 am

The long and short of it is, new production tubes from Russia, China, and eastern Europe have a long way to go in materials and construction quality (and design) when compared to the better old-stock European and American tubes.

Here's the way a tube works.

At a minimum, an amplifying tube will have the following parts: a filament (sometimes called "heater"), a cathode (sometimes part of the filament), an anode (called 'plate'), and one or more control grids.

The filament's job is to get hot. This is the part of the tube that glows.

As it gets hot, it causes the cathode to get hot. The cathode is coated with a material that releases electrons when heated.

These electrons are attracted to the anode/plate very strongly. The control grid(s) sit in between the cathode and plate. Their job is to influence the flow of electrons. When signal is applied to a grid, it controls the stream of electrons flowing between cathode and plate. This is how the tube amplifies (I've gone into greater detail before).

What Mr. Archut is describing above is as follows.

Different designs of filaments can cause different amounts of noise/interference within the tube itself. Sometimes they're straight wire, sometimes they're spiral wound, and sometimes it's a double-helix. I think the double helix is supposed to give the best noise rejection. Substituting one for another will change the noise floor of the tube, particularly if the heaters are run with AC (most common) as opposed to DC.

Gold-plating the grids is something tube manufacturers of old sometimes did (I believe the vaunted original Tung Sol 5881 had gold grids, as well as others), and new manufacturers are starting to do on select tubes. Gold is very resistant to corrosion in free air, but I'm not sure what properties it possesses that might help performance in a vacuum. In any case, the grid is the part of the tube where the input signal is applied, so it's a very critical part. It's literally the part which controls the entire flow of electrons in the tube-- it is the "valve" that varies the amount of electrons allowed to pass, which is why tubes are sometimes called "valves."

As for other raw materials, this is important. If purity is compromised, it can allow 'rogue' elements inside the tube that can sabotage the performance of other elements. Mr. Archut mentions observing a coating of magnesium on the electrodes which we can only presume is a result of compromised purity in cathode or anode material. If the grid is coated in magnesium, it cannot perform 100% as intended. If the anode is coated in magnesium, I'd speculate that its operation might be compromised, as well-- the high positive charge on the anode is the 'engine' that makes the tube run.

He also mentions a barium coating that is a byproduct of a poor type of cathode manufacture. This barium can get on the grid after some hours of operation and compromise it, causing spurious noises, higher noise floor, etc.

The implication, of course, is that the better old tubes (Telefunken, Amperex, Mullard, RCA, Tung Sol, etc.) did not exhibit these problems. Additionally, the implication is that tubes from those vaunted manufacturers were more carefully constructed. This, of course, is obvious to anyone who's ever casually looked through the glass on an old tube and compared it to a modern production tube.

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Re: NOS versus new production tubes

Post by Professor Plum » Tue Dec 28, 2010 2:58 pm

interesting. thats cool reading. if anything ever happened with the tech tubes guys, i would have said to try to get them connected with this dude... but at this point even the techtube website is dead.

on a side note, one of my biggest studio gear lusts is the V72S pre that he builds. :? :? :? i dont have anything else recording-wise that would make a pre of that caliber worthwhile but of the stuff that would go in my dream studio setup its near the top.
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Re: NOS versus new production tubes

Post by sookwinder » Tue Dec 28, 2010 7:04 pm

Brad ... great thread ... where did you read these comments by Oliver Archut ?
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Re: NOS versus new production tubes

Post by øøøøøøø » Tue Dec 28, 2010 7:10 pm

I saw a thread on Klaus Heyne's microphone forum on prosoundweb.com where Klaus mentioned that Oliver Archut was the guy who knew in great detail the differences between NOS and new production tubes. This piqued my interest, so I just plugged in some Google search strings with his name trying to find info. I think most of the quotes above came from one thread, but I've closed that browser window and don't know the link anymore. :)

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Re: NOS versus new production tubes

Post by øøøøøøø » Tue Dec 28, 2010 9:19 pm

More insight from Oliver:
Ei has lots of the original Philips/Mullard and Telefunken machinery and their tubes are far from NOS ones.

GT provided over the years an incredible service for pre-screening tubes, their warranty policy is absolute the best, but even they can not remake the entire tube raw material support industry.

And that is the biggest problem to make tubes, the raw material, companies like "International Nickel" here in the US, Hoesch in Germany do not make the needed special alloys anymore, and this is one of the biggest secrets of NOS tubes.

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Re: NOS versus new production tubes

Post by alfal013 » Wed Dec 29, 2010 12:49 am

Brad, you never cease to amaze me with your general knowledge of pretty much everything. This was a great read. Thanks for sharing.
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Re: NOS versus new production tubes

Post by zhivago » Wed Dec 29, 2010 4:12 am

AWSchmit wrote:Though, some of this is Greek to me. It was still very interesting. Thanks for sharing.

hmmm...I dunno...I'm fluent in Greek, and still didn't get it! ;D
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Re: NOS versus new production tubes

Post by zhivago » Wed Dec 29, 2010 4:17 am

joking aside, I have purposely stayed off the NOS tube "dance" as I just can't afford it...I've been pretty happy with normal production tubes...

...the only reason being, I have avoided being spoiled forever by playing a good set of NOS tubes...especially in something as a tweed deluxe, which is my main amp, and also a circuit very sensitive to tube changes.

for what it's worth, I prefer the sound of Tung Sol ones to JJs, for some reason that I can't really explain.


what is the best new production tube at the moment?
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Re: NOS versus new production tubes

Post by øøøøøøø » Wed Dec 29, 2010 2:24 pm

Opinions will vary. Consensus is that it depends on the tube type.

Oliver seems to think that the Chinese tubes sound the best for very many types, but their reliability can be poorest of all. I prefer the sound of selected new Chinese 6L6s to any other new 6L6, for whatever that's worth, and I haven't personally found their reliability to be too much poorer than other makes-- although that isn't based on extremely broad experience.

EH/New Sensor stuff (all their brands from Sovtek, EH, to Tung Sol and Mullard) seem to be making good progress.

JJ looked promising at first, but they've had problems and in my opinion, it seems that they may have even regressed in quality.

Other than that, who knows. I can't manage to make myself buy new production tubes anymore enough to find out.

The NOS stuff lasts 3x as long at least, and sounds way better-- so paying 3x as much in the short run doesn't seem like that bad of a deal, to me.

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Re: NOS versus new production tubes

Post by Joeleo » Wed Dec 29, 2010 3:32 pm

Do you recommend any places online to find NOS tubes? My Twin is due for a retube, and i wouldn't mind at least checking out prices.

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Re: NOS versus new production tubes

Post by øøøøøøø » Wed Dec 29, 2010 3:50 pm

Joeleo wrote:Do you recommend any places online to find NOS tubes? My Twin is due for a retube, and i wouldn't mind at least checking out prices.
Here's what I'd do with your Twin.

If any or all tubes are old American manufacture and have escaped the dreaded and nonsensical phenomenon of the preventative "retube" all these years, DO NOT assume that anything needs to be changed at all. The word "retube" was invented by guys that sell tubes, and nobody ever heard it until the late 1980s (at the earliest) when Groove Tubes and other companies came on the scene and unreliable communist bloc tubes began to dominate the market. Think about it. Standard M.O. with ALL tube gear for YEARS was "when one quits working, replace the broken one only." I tend to replace power tubes in pairs, but other than that, I still apply that thinking, at least when it comes to quality tubes-- and it has served me well.

For power tubes, get either JAN/Philips 5881 (more on this later) or Chinese Ruby/TAD/Etc. 6L6GCs.

A 5881 is rated for lower V(a) than a 6L6GC and normally would not be up to the job, but the JAN/Philips 5881 is actually internally identical to a 6L6GC. This is a "dirty little secret." They're the only cost-effective NOS 6L6GC (or substitute)... almost all others are prohibitively expensive. I'd advise against putting ANY OTHER (true) 5881 in a Twin Reverb. Note that the Sovtek "5881" isn't actually a 5881.

Fpr preamp tubes, I'd grab a blackplate RCA for V2 (assuming you mainly use the 'vibrato' channel), an RCA, GE, Sylvania or something 'nice enough but not ridiculously expensive' for V4 (1/2 of which is reverb recovery, 1/2 of which is extra gain stage), and something decent for the phase inverter (V6), such as an RCA 12AT7 (cheap enough and plentiful) or a Mullard CV-4024 (same as 12AT7) which is also cheap enough.

That's it. I'd leave all other tubes alone.

As for retailers, there are many. There's thetubestore, tubedepot, kcanostubes, watfordvalves, tejastubes, etc. Put www. and .com fore and aft of any of those names and you'll get there.

Good luck.

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Re: NOS versus new production tubes

Post by sookwinder » Wed Dec 29, 2010 6:34 pm

zhivago wrote:joking aside, I have purposely stayed off the NOS tube "dance" as I just can't afford it...I've been pretty happy with normal production tubes...
I was like this, but then I did "hear" the marked differences (improvement) when I used NOS 1960s 6V6s in my Champs. Now NOS 6V6s can be bought readily cheaply on ebay if you wait (RCA, GE, sylvania) so I put them into my PR and DR and woooooww what an improvement.

I also managed to source a bunch of NOS preamp valves which will last me "a life time" and are the "sound" I want.

But unfortuneately 6L6s and EL34s are not as cheap as 6V6s these days on ebay, but then again for me I don't have any high powered amps that require a bank of EL34s or 6L6s
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Re: NOS versus new production tubes

Post by jgs61 » Thu Dec 30, 2010 4:32 am

Interesting thread Brad. Thanks for posting!

I actually just got some JJs that I plan on trying. I'm not too happy to hear they might have digressed, but at least they were really cheap.

I will add that I like all the Tung Sol 12AX7s and 6V6s I've played. I'll be interested to see how long they last. NOS is still the way to go when I can afford it.

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