Hello,

I wonder if the state-of-art stopped evolving or even deteriorated since
the old days. Are those NOS tubes genuinely better? Or do they just give
flavors liked by people?

Thanks.

Roland

Roland wrote:

Hello,

I wonder if the state-of-art stopped evolving or even deteriorated since
the old days. Are those NOS tubes genuinely better? Or do they just give
flavors liked by people?

You will get flavours with different brands of the same tube type no,
especially in amps with no NFB.
But some recent russian production sounds better than some old american
production.
That's what I have found with 6550. But its sometimes the other way around
with
other tubes, I didn't like the EH6CG7 I heard in a preamp last year.
Telefunken NOS were the best, with Mullard acceptable. Oz made 6CG7 seemed to
be very nice.

The only way to find out is to try a few different brands, but don't close the
mind by
leaping to any conclusions based on tests of just one tube.

Patrick Turner.



Thanks.

Roland

Much of the original fabrication equipment is gone along with many of the
folks who knew how to use it . . .

I don't know what constitutes state of the art now-a-days. SOTA may be one
thing in Russia and another elsewhere.

I'm sure there are good modern production tubes. I try to keep an open mind
about those things. However, I've had current Sovtek 9 pin tubes that have
lost their emissivity in short order; Chinese 5AR4s that flashed over, and
7189s that couldn't stand the original plate voltages. And we're not even
talking about how they "sound" yet -

- jon





in article , Roland at
wrote on 7/19/04 8:59 PM:

Hello,

I wonder if the state-of-art stopped evolving or even deteriorated since
the old days. Are those NOS tubes genuinely better? Or do they just give
flavors liked by people?

Thanks.

Roland

Hi Roland:

This is a very good question.

I have been tinkering with NOS and recent production tubes
(Sovtek/Electro-Harmonix, Svetlana, Ei, JJ)
since mid 1995.

My experience has been 'mixed' with mostly inconclusive results. Tube sound
quality is highly subjective to the
circuit topology and how a particular tube settles into a given DC bias and
the ensuing dynamic AC parameter
behavior.

What I can say is that there is a current trend with NOS tubes where people
use them or sell them as new and
unused when not really able to confirm whether the 30+ years were spent
inside the cardboard box, or part
of the life of the tube was already used-up and eventually re-boxed for the
next victim.

As far as the longevity of NOS tubes, there are the classic Telefunken,
Mullard, Amperex and Valvo that often
measure and perform better than new production tubes after 40 years in use.
This is of course all subject to that
all important how long has it been on test which only certain test equipment
can measure applying less than ideal
voltage levels and looking for a drop in voltage or current, indicating a
tube near it's end.

There is a distinct set of problems when using NOS tubes in Vintage
Amplifiers. Often the pin geometries
of new Russian or Yugoslavian tubes are not identical to Vintage Sockets,
resulting in less than ideal surface contact tension
and sometime no-sound altogether.

Another factor is that some Russian substitutes such as the Sovtek 7199 are
not electrically the same as NOS 7199, so
these may not work in all vintage circuits designed for true 7199's. Sovtek
7199 will hum in most Dynaco ST-70 circuits
and they did just this in my Harman Kardon A-700.

Some new production tubes are electrically different (on a data sheet side
by side comparison) to their NOS brothers. Hence
the results of using these types in Vintage Audio circuits is a subject of a
hit-and-miss tube rolling session with plenty of
music and time to experiment.

Some new production tubes do not manage the excessive grid currents from
certain designs or may require a specific
circuit topology to work properly. Other NOS tubes need to be 'cooked' a bit
prior to shocking them with full voltages
as after 40 years in the box, some precious NOS power tubes are ruined if
plugged directly into a full blown Vintage
milliamp hog and cut loose.

If one compares what new designers are doing with Bias currents, the trend
is to go for tube longevity, i.e. lower bias currents.

In the Mullard book the 5-20 amp runs each EL-34 at 32 Volts across a 470
Ohm 3 watt Cathode resistor that yields a
worrying 68 Milliamps for most New production EL-34's. The old Mullard and
Telefunkens seemed not to mind being operated
close to their plate dissipation ratings. But, try to plug a Continental
Slimmy Sovtek EL-34 WXT or Ei nipple-top EL34 into a Mullard
5-20 amp and put out the lights in the room. After about 5 minutes you will
see the plates glow a cherry-red indicating that the EL-34
is stressed out way past it's intended design bias level. These types are
happier in the 50 ma range that is more for Guitar amp Class
B circuitry.

Unfortunately most Vintage circuits ran the power tubes hard in search of
less distortion.

Current production Sovtek data sheets are non-available, (has anyone seen
these?).

Svetlana publishes it's spec sheets in pdf format regularly and in the case
of their EL-34, the evidence is there for a robust tube that handles
the Vintage Hi-Fi Bias levels most new production EL-34's fail at.

Also, the life of most tubes in Diode Rectified equipment w/o Soft Start
circuitry or current limiting circuitry will be cut short as compared
to tube rectified equipment which is a bit softer on the tubes when
powered-up, less Cathode Electron stripping.

As far as musicality is concerned, there are many new production tubes that
offer marvelous performance at beer budget prices.
The Sovtek 2A3 Single Plate tubes is one of these, it can take a higher
plate dissipation than the original bi-plate 2A3, although
I still am seeking a spec sheet for this tube.

With NOS availability dwindling, and the 8417 gone the way of the dinosaur,
the best tubes to use are those that can be bought
by the dozen and not break the bank. The Russians have been very kind in
re-issuing the 7591, despite the fact that it is not
a true 7591 in size and the performance is close but does not match the
original.

There are so many disappointed people that spend a fortune on KT-77 and
KT-88 Genalex, etc. only to find
that their investment has resulted in a microphonic tubes or worse yet, they
fall victims to tube fraudsters that sell bogus
NOS to buyers on Ebay that do not know how to tell the difference.

In one case, there were Amperex 6550 tubes for sale on Ebay. Amperex never
made a 6550, and the tubes were Chinese 6550
placed in White-Boxes with Color-Photo copies of Amperes labels and fake
labeling on the tubes.

I see so many NOS Made in Germany tubes in Sylvania and RCA boxes, including
my latest find of Sovtek 5U4G in National Union
boxes and labeling. Only to find that they are Chinese or Russian tubes with
makeup, not quite perfume on a pig so to speak.

Unless one really needs to get NOS tubes for a particular restoration, it's
probably best to spend the money on the new production tubes
that have proven themselves worthy. Or buy tested NOS tubes from a reputable
dealer where the extra money spent will guarantee
a satisfied customer whether it works well or needs to be returned or
exchanged for something more compatible.

Some Russian tubes out perform NOS types. But this is not generally the
case. Also one must be wary of the famous "Tube Substitution Handbooks".
There are significant errors in some of these publications. In one case, a
EF86/6227 is listed as a 6BQ5 - EL-84 substitute.

If you plug an EL-84 into a EF86 socket at hit the power switch, good luck!

NOS can be nice, but it takes lots of experimentation to see whether these
can work well in modern tube equipment. As the supply of
NOS tubes is now nearing it's end-of-life period, what is left may not be
the best that was available and often are the reboxed rejects
accumulated and sold as NOS tube lots ending up sold at a premium to
unsuspecting enthusiasts who may have been under the
impression that they made a killing on those vintage 6SL7's with smoked
glass!

It's all about testing, listening and choosing the best for the money. If it
looks to good to be true, it probably is.
In my opinion NOS is best served at liquidation prices in lots, where the
buyer can weed through dozens and find the one or
two killer tubes in a lot of used, microphonic, or weak examples.

BR/
Rich Sherman





"Roland" wrote in message
om...
Hello,

I wonder if the state-of-art stopped evolving or even deteriorated since
the old days. Are those NOS tubes genuinely better? Or do they just give
flavors liked by people?

Thanks.

Roland

This is a neverending argument here. The problem is just (as someone
already pointed out) which NOS and which new one.
Apart from restoring antique equipments where true NOS are needed for a
matter of "collectible" value, I'd say:

- NOS are the best if You are a true tube freak, if You love the smell of
dust and age, and You can afford the prices of a professional tube seller
(Uncle Ned Carlson is one of these, but there are some others on RAT) who
can test 'em and guarantee that even the 50+ yrs old tubes he sells are not
pulls from some scrapped Army stuff or rejected by teh original manufacturer
as 3rd choice items. Sometimes even good suppliers can be fooled, because
the oldest types can be erratic. Some times ago I bought a couple of 45
triodes from AES (who's an absolutely dependable supplier too) but one of
them turned out to be weak, when installed. After all it had been made by
Zenith before WW II, what could You pretend?
Sure, if You have a Leak "point one" and You can get true Philips 6J7,
Mullard ECC33, Philips GZ34, GEC KT66 and so on, You probably will hear a
difference, and if the tubes are really OK they will last so long You'll
never have to re-tube. In fact, no new tube comes close to TFK or Valvo
manufacturing care, but sound does not need necessarily to shape mica
spacers in an "artistic" way....
- new tubes are generally good, cost a sensible price and come in matched
couples/quads/howmanyyoulike. As I often write on RAT, I tried to swap JAN
Philips 7581A and Svetlana 6L6GC on my bigger amp and I cannot tell them
apart. Sure, You have to look for "good" ones like Svets, JJ or premium
Sovteks (as an example the Sovtek 6B4G or its twin 2A3 is a great tube at a
very sensible price). When I think of a new project I try to use only
current valves, that can later be replaced with NOS if I manage to get a
real deal.
- there are NOS Russian too: did You know that You can find Svetlanas
6B4Gs, dual-plate, for some 20$ each? Just "google" for 6C4C or 6S4S, its
CCCP tag. It's a top quality tube, at the price of a light bulb.

But, after all, it's a matter of feeling and individual taste, as it happens
with many of the finest things in life. Swapping tubes is fun, like playing
with Lego bricks when I was in my 6th year, just more expensive and
dangerous.

Ciao

Fabio

"Roland" ha scritto nel messaggio
om...
Hello,

I wonder if the state-of-art stopped evolving or even deteriorated since
the old days. Are those NOS tubes genuinely better? Or do they just give
flavors liked by people?

Thanks.

Roland