Bad NOS tubes...


I just want to put this out there...as much as I would not like to...my head says otherwise. Tube buyers beware!!!

On 3/7/16 I bought 6 NOS Mullard 12au7 4003 tubes for my preamp from a vender out of Minesing, Ontario Canada... under the store front name of ’mullard.com’ http://www.mullardtubes.com/Mullard-ECC82-12AU7-CV4003/?ID=0&ProductID=153 and ’ tube products.com’ http://www.tubeaudioproducts.com/Mullard-Brimar/ProductDetail.aspx?CatID=65&ProductID=153#

The owner is one Alfred Kayser. On his site/sites he states all of his tubes are tested and matched for best performance values. Well,I went ahead and ordered and received said tubes. After 2-3 months of use I started to hear unacceptable levels of noise from my speakers,you know, the dirty sound of that dreaded tube noise of a scratching, distorted, dirty volume pot type of noise,which totally infringes upon the music. I went ahead and called Alfred and asked him about it and he just responded there is "nothing he could do" for me. Hey,no problem,but he advertised full-up tested tubes. If it was only one bad tube,I could understand,I’m a realist...things happen.

But!!!

Long story short,I came to find out that four of the six tubes are defective and are not what I paid for. Two are fine. So the moral of this story is...When buying tubes,do not go the cheaper route,find and use a "reputable" tube vender and save yourself some time,money and aggravation. Of course I will never use this guy again for any of my audio needs... Hope this is of some help to the Audiogon membership.

Convert?fit=crop&h=128&rotate=exif&w=128aolmrd1241
The long story short, 
If you're onto NOS tubes, have a tube tester and shop for'em at thrift stores selling old tube radios for cheap. Purchasing them from dealer is big risk.
Purchasing NOS on internet is risky no matter how reputable the seller is.
Another useful tool to use NOS tubes is VARIAC transformer to bring NOS tubes SLOWLY up to operating voltages when you mount them first time no matter how good these tubes test.

Other than that, there are plenty of options to void NOS and to purchase just brand new tubes 
In fairness to the vendor, any tube that tests well on a given day might be prone to early failure that cannot be predicted based on those favorable test results.  However, I do also empathize with you in that to have 4 out of 6 fail so early is way beyond the laws of chance.  So, I have to wonder about the state of your preamplifier.  Before you pop in yet more new and expensive tubes, perhaps you should have a competent technician check out the unit.  What you've experienced simply should not happen, even if the seller were a charlatan, and I am not ready to conclude that he is.  And by the way, a bad switch or volume control can indeed cause the symptom you describe, so did you check out those elements? So, check the pots and switches, and check the voltages at critical points in your preamplifier.
Hello,and thanks for the replys. I put the stock tubes back in place that came with the pre and have had not so much as a burp from them. The two good nos tubes have seen time in the driver stage and are quiet as a mouse. So I do believe the four bad nos tubes are very much defective.
The driver stage is typically low stress, and, since there is no gain in the driver stage, most likely to be "quiet".  Try the "bad" tubes in the driver stage and let us know what happens.  What is the vintage and brand of the original set of "stock" tubes? 
"aolmrd1241, So the moral of this story is...When buying tubes,do not go the cheaper route,find and use a "reputable" tube vender and save yourself some time,money and aggravation."

Absolutely true, it is tempting because the prices from reliable vendors is not inexpensive, but the value is there when you use the right vendor. 
You used the tubes and they functioned properly for HOW LONG? I have no problem at all, with the idea that those tubes tested and sounded, "NOS", when checked by the seller. How is he supposed to know what they will do, in your equipment, after sixty to ninety days? If there exists a tube vendor, that will warranty NOS, small signal tubes after that length of time, I want to know their name. I’ll be purchasing from them too.
Periodic problems with tubes - including both noise and catastrophic failure - are inherent in their use. While getting only two or three months from a tube seems like poor service, it does happen. It's happened to me. Over the long term, there's probably no avoiding such a result unless you're very, very lucky.

Users who don't have the patience, budget or disposition to cope with tube problems probably should avoid tube products altogether, imo. They'd be happier that way.

Last month, I replaced a failed 6550 in my preamp after only 260 hours of service. Oh well!
lewm said..."The driver stage is typically low stress, and, since there is no gain in the driver stage, most likely to be "quiet". Try the "bad" tubes in the driver stage and let us know what happens. What is the vintage and brand of the original set of "stock" tubes?"  

Lewm,I did just that,checking all of them through the drive stage. Four were noisy and two were quiet. I own a Prima Luna Dialogue Premium  preamp purchased on 5/28/15. The preamp came with  Primaluna stock tubes all around. They are all as quiet as a tomb... with roughly 600-700 hours on them. The NOS may have 125 hours of use. 
The NOS may have 125 hours of use.
Is there any sort of odometer in vintage NOS tubes?
czarivey. The vendor is/was selling them as new,never used nos tubes. My estimate of 125 hours is from my point of view,all things being equal. Could they have been used before I got them? Know body knows that except the seller. And if they were used being sold as new...well,shame on him.
I always test tubes before installing.  If they test "new" then fail 2 months later I would be very inclined to have my pre-amp checked out.  4 tubes going bad at once is very unlikely unless your pre-amp is burning them up.  Keep in mind that your new production tubes may simply be more durable?

czarivey-I've never heard of bringing tubes up to voltage on a variac?  What's the point?  It's like turning on a light bulb with a dimmer switch only.  Yes, if the pre-amp spikes the voltage upon turn-on you can damage things.  That's why this pre-amp probably needs to go into the shop.
Elevick.I never said any of the nos tubes failed,they still work and make music. The problem is...distortion. So now we must have tube testing equipment to make sure we are getting what we pay? 

Elevick. Also in concern of a durability issue with the tubes in question. The 4003 Mullards are a military version of the 12au7. The Primalunas are a standard Chineese 12au7 tube with nothing special about them...as far as I know. One would have to assume the Mullards would be far more robust in design and production quality standards than the stock Primalunas. Looking at them side by side definitly confirms this to be a correct assumption.

Try cleaning the pins on the tubes/sockets.  Chances of 4 out of 6 tubes defective????  Maybe the plate voltage is high and mullards do not like it.
Disclaimer: This is my opinion only based on years of my own experience with both new tubes and so-called NOS and used vintage tubes from a variety of sources.

My personal opinion, for what it is worth, and that may not be anything at all, but, based from much personal experience owning tube audio components from a number of well regarded tube manufacturers, is that NOS and used vintage tubes offer absolutely no=zero=nothing=zilch=null=nada=nyet sonic or other advantage or value to the listening experience in pre/phono/power/guitar amps that I have owned, listened to or built. They are a waste of time and money while chasing a "holy grail" that simply doesn’t exist. For that reason, I am happy buying inexpensive new tubes from the Tubestore or the Tube Depot. I have NOS Mullards, Telefunkens, RCA, Sylvanias, etc., that I paid good money for along with new JJ’s, EH, Tung-Sol and Sovtek’s that, after much careful listening and comparing, hair-tearing and swearing, are as sonically fulfilling as any NOS or vintage tubes, despite what the "snake oil" sales guys or dealers will lead you to believe.

Again, this my personal opinion only from my own (possibly defective) ears and long term listening experience. Your mileage may (will) vary, of course. ;-)
OH, how I WISH I couldn't hear all the differences between NOS tubes and the stuff being cranked out these days!    Could'a saved so many Dollars and..and.......  NAH!
OH, how I WISH I couldn't hear all the differences between NOS tubes and the stuff being cranked out these days!    Could'a saved so many Dollars and..and.......  NAH!
Yeah, me too.

I am somewhat with stevecham on this one, not that I can't tell the difference in sound, but it is not a sure thing that NOS will always outperform current production tubes.

I believe, like many things in audio, it is just a matter of matching. Different brands of tubes (NOS or current production) do have different sound, so the users have to match them to their systems. For example, in one of my amps, I prefer the plain EH6922 to NOS Amperex 7308.

Think about it, most current tube amp manufacturers are probably tuning the sound of their amps with current production tubes, so NOS tubes probably don’t have any advantages.

Add me to the list of those who can hear differences between tubes and who enjoy fine tuning the sound of their systems with old stock tubes.

aol, Talk to Kevin Deal at Upscale Audio. He is the importer of PrimaLuna amps and the expert on them. He also has a great selection of NOS and current production tubes that are priced from very reasonable  on up.

He can probably tell you if there is a possibility that the tubes that went bad on you were not right for your preamp or if you just got some bad tubes, as you suspect.

Before you talk with him give the stock tubes a good listen and decide what kind of change in sound you want to hear with a change of tubes. He will give you his honest opinion, even if it’s not what you want to hear, which causes people to rant about him on this forum from time to time.

Buying old stock tubes does have risk. You can minimize the risk by buying from an established seller with a good reputation. Don’t let your bad experience sour you on tubes. They can definitely improve the sound of your system, IMHO.

Here are some other good sellers:

Tubemonger

Vintage Tube Services

Jim McShane

Brent Jessee

Talk to Andy bowman at vintage tube services.  He will take care of you.
Guys, Here are the facts as I see them:
(1) The OP bought 12AU7s for a preamplifier that presumably uses 12AU7s, so there is no question that he bought the right tube type. In terms of operating parameters, all 12AU7s are alike. (The OP should report to us if he changed tube types, but he did not say that he did.)
(2) A tube that looks good on a tester can only be relied upon to have been good at that moment. Tubes can fail unexpectedly and prematurely, whether NOS or current manufacture, but the hooker here is that 4 out of 6 tubes appear to have gone bad in such a short time. That defies the law of averages for tube lifespan, when tubes are used within the recommended limiting parameters.
(3) For this reason, we suggested that the OP might want to check out the voltages in his preamplifier; one cause of such a catastrophe would be abuse of the tubes, for sure. They DID last for more than a month before showing signs of early death.
(4) Against this hypothesis, the OP also tells us that his set of OEM tubes, presumably also 12AU7s, are all working fine after many more hours of use in the very same preamplifier. Moreover, he re-installed the OEM tubes and they are sounding fine.
(5) So, if we want to exonerate the vendor, one more hypothesis remains tenable: Perhaps something went bad in the preamplifier subsequent to the installation of the new tubes, something that killed 4/6 of them prematurely. If this is so, then the OEM tubes ought to go bad too, after a while. To test this hypothesis, I advise the OP to continue listening with the OEM tube set for a month or two longer; see how that works. Some or all of them will fail as well, if the preamplifier has developed a power supply problem. (This could involve either the filament supply or the B+ supply.) OR, take the unit now to a good technician for a check-up.

Peace. Out.


aolmrd1241 said:

"After 2-3 months of use I started to hear unacceptable levels of noise from my speakers,you know, the dirty sound of that dreaded tube noise of a scratching, distorted, dirty volume pot type of noise,which totally infringes upon the music. "

~~

As someone earlier said the tube pins could be dirty. I would clean the tube pins with Isopropyl Alcohol. Then try them again.

I would like to know how the OP was able to determine all 4 tubes are defective.

I would suggest he find someone in his area to check the tubes.

I can't imagine buying vintage tubes and not owning a tube tester.

~~ 

The OP said he reinstalled 4 of the original tubes that came with the amp and the amp sounds fine again. I wonder if he then pulled one of the good tubes and then installed one of the bad tubes in it's place and then took a listen? (After cleaning the tube pins first).... If that tube did sound bad then pull it and try another supposedly bad tube and then listen to it again. Repeat the process until he has gone through all 4 tubes.

(Note: I don't know if this amp requires closely matched pairs of driver tubes. Or  closely match sections of each driver tube.)

~~

To the OP. I suggest you send an email to the tube vender you bought the tubes from with a Link to this thread. I think it's only fair the guy should have the right to defend himself.



  

Pins were clean. I swapped nos tubes one at a time and then listened...one at a time. Like I said 4 good and 2 noisy.  I have the 2 good nos Mullards running in the driver sockets and 4 stock ones in the 4  gain sockets  with another 12 hours of play time since I posted... Quiet as a mouse!


Post removed 
Oops!  I mean 4 noisy and 2 good.
Post removed 
well i mostly deal with solid states, not tubes and once i've ordered a set of NOS transistors via ebay. they came to me with clear signs of being mounted onto the heatsink(dry traces of heat sink compound!) so it looks like NOS isn't really NOS but perhaps UOS with unknown hours.

Czarivey, For a source of truly NOS discrete transistors that may have been discontinued, try James Electronics in California.  They had every transistor I needed for rebuild of my Beveridge direct-drive amplifiers (ca 1980 vintage), when no one else could supply them.

aolmrd1241 said:

Pins were clean.

Did you clean them?

When were the tubes manufactured? Gold plated steel pins I assume?

How tight do the pins of the tubes fit the tube socket female contacts?


Did your tubes come boxed like this?


Copy and paste between the brackets.

]https://www.youtube.com/watch?v=YfBTlJBWoGw[

Jea48 asked...

Did you clean them?....Yes I did.

When were the tubes manufactured?..... I don't know the manufacture date.

Gold plated steel pins I assume?..... Steel pins,no gold plating.

How tight do the pins of the tubes fit the tube socket female contacts?.....Extremly tight.

Did your tubes come boxed like this?..... Yes.

Jea48, Gold-plated pins are a sure sign of recently manufactured tubes.  Vintage tubes of the good old days rarely had gold-plated pins unless specified by the type. For example, some milspec 6900s had gold-plated pins but most did not.  GE 5-star tubes sometimes had gold-plated pins. Other than those two instances, I have never encountered true vintage tubes with gold-plated pins.  And the pins are not usually made of steel.  They're probably brass or other copper alloy (which is why they oxidize and may need cleaning) or rolled "sheet metal" in most cases, although which tubes have what pins is an interesting question.  Just not steel.
I agree with the op.

I bought a refurbished set of Mark iiis that came with nice new Tung Sol 6550s and I had bought a nice old Pas 2 from Gold Sound on South Broadway in Denver (Englewood technically ), and it sounded really nice.

I got some nice nos EIA 12ax7s from my brother for the Pass 2, a nice NOS Hammond  driver tube and nicely matched Svetlana 6550s for my mark iiis, and wow.  

Not that it sounded like mud before,  it really didn't. 

As far as the nos vs brand new tubes, I'm not going to dog some audiophile's religion. I just don't have the time.  Let YOUR ears be your guide.

I also hear that really good nos or highly tested used old stock tubes last way longer than the new stuff.

So there's another opinion for ya, based on my own experience,  of course.

lewm,

Here is some reading material for you.

http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#6DJ8


Post removed 
To be fair: Two months ago, I also purchased a matched pair of NOS Mullard’s 12au7/CV4003/M8136 - from the same vendor Albert Kayser. They sound great! In my preamp, they are extremely quiet - and have no issues at all. They sound just like Albert described them. He was 100% professional. I’m a very satisfied customer.

OTOH: For tube-rolling experimenting, I also purchase a matched pair of La RadioTechnique 12au7/6189 from Watford Valves in England. Noisy as hell. After a several weeks, they’ve calmed down a little bit - but nowhere near as quiet as the Mullard’s from Albert.

It’s very easy to discern the different sonic signatures of the two brands. Each has its advantages and disadvantages. It’s been a great learning curve for tuning my system. Curiously, one of the tube-sellers recommend earlier in this thread, gave me very poor advice. He was simply trying to sell what he had in stock. It’s a crap shoot!

Being an owner of a tube preamp and tube mono-blocks, I’ve resigned myself to this relationship which requires attention and expense. But, it can be so good when all is working.
steakster said... "To be fair: Two months ago, I also purchased a matched pair of NOS Mullard’s 12au7/CV4003/M8136 - from the same vendor Albert Kayser. They sound great! In my preamp, they are extremely quiet - and have no issues at all."

The two good mullards that I am using now in my preamp drive stage are just as you say...very quiet and sound great. My problem are with the remaining four... that do not make the grade with their noise issues. Believe me,I wish they did make the grade.
Jea48, First, I apologize for sounding so pedantic.  Your post actually prompted me to do some research on the metals used in tube pins.  In the URL you provided, are you referring to this passage?: "The 6DJ8 family was originally developed by Amperex. The first tube in the family was the steel pinned 6DJ8 followed by the gold pinned 6922 and 7308. These latter two were premium versions rated as 10,000 hour life tubes. The 6922 was a premium industrial version and the 7308 was the top of the line guaranteed low noise version. Frankly, I’ve measured & listened to a lot of these and there is no correlation between model # and sound quality."

Based on the brief bit of researching I did do, my first thought is that this guy is incorrect as regards the composition of the pins and that he used the word "steel" without really thinking about it.  Moreover, I think any one of us would say that no tube ever made has "gold" pins (as he describes them, carelessly); at best sometimes pins are gold-plated.  Pure gold would be a terrible choice for a tube pin, because it is so soft. You cannot easily plate steel in the first place.  So the notion of gold-plated steel does not make sense, either.  And finally, this is a piece about the 6922 and its many related tube types.  These are frame grid tubes that were only developed at the very end of the "vacuum tube era", mostly for use in instruments and TVs.  So generalizing from the 6922 back to the tubes from the golden era of audio tube technology is dangerous, even if some 6922s do have "steel" pins.  But it's a good question, and there is not much solid info on the internet.  I do believe that older octal based tube types, like 6SN7s probably have brass pins that were plated, maybe with nickel. My NOS 12AX7s and 12AU7s seem to have some copper containing alloy that is tinned.  If I polish a pin with my Dremel tool, it eventually reveals a copper-y color.
Post removed 
lewm
06-18-2016 2:39pm
Jea48, Gold-plated pins are a sure sign of recently manufactured tubes
This statement is completely misleading and not correct. I have many vintage tubes with gold plated pins - from Telefunkin, Mullard, Siemens and many others dating back to the 50’s
lewm
06-19-2016 6:10am
I think any one of us would say that no tube ever made has "gold" pins (as he describes them, carelessly)
No it is not careless, most experienced tube collectors refer to gold plated pins as "gold pins".

lewm
06-19-2016 6:10am
You cannot easily plate steel in the first place. So the notion of gold-plated steel does not make sense, either.
Again this is not correct. My understanding is that to gold plate steel you simply do a nickel plate process first and then flash gold plate over the top of the nickel base.

lewm said:

"Based on the brief bit of researching I did do, my first thought is that this guy is incorrect as regards the composition of the pins and that he used the word "steel" without really thinking about it. Moreover, I think any one of us would say that no tube ever made has "gold" pins (as he describes them, carelessly); at best sometimes pins are gold-plated. Pure gold would be a terrible choice for a tube pin, because it is so soft. You cannot easily plate steel in the first place. So the notion of gold-plated steel does not make sense, either. "


WOW, right out of the gate you trash the man.

I am sure Joe S is quite aware the tube pin is gold plated. Just guessing he figured anyone reading his post knew that. Apparently not all though.

Joe’s Tube Lore

http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html

A lot of guys just say gold pins instead of gold plated pins. Surely you don’t think, they think, the pins are solid gold?

>>>>>>>>>>>>>>>


As for exactly what the base metal of the 9 pin miniature signal tube pins are made from all I have ever heard, when specking of the pin is steel. Why don’t you supply a credible Web Link what the pins are actually made from if not steel.


Note below these guys also refer to the pins as gold pins. I would be willing to bet a hundred bucks they know the pins are gold plated and not actually solid gold.

>>>>>>>

Brent Jessee

Quote:

"This is one of two premium versions of the 6DJ8 tube. First of all, it is the same tube as the 6DJ8, and will work wherever a 6DJ8 is needed. It has premium features such as low noise, low microphonics, and usually a longer lifespan. Sylvania made a version that is JAN military spec without gold pins. Amperex made all of theirs with gold plated pins and most have the PQ shield logo, standing for Premium Quality. See note below about Amperex 6922 and Bugle Boy tubes. Some of the later gold pin Amperex have the orange world logo."

http://www.audiotubes.com/6dj8.htm


Notice Brent did say gold plated once, and just gold pins twice. I am pretty sure he knows the pins on Sylvania are gold plated and not solid gold.

>>>>>>>>>>>

"Amperex "PQ" 6922 - Super super rare gold pin 6922 with tall bottle made in 1960"

http://www.upscaleaudio.com/6922-6dj8-7308-pcc88/amperex-6922-tall-bottle-1960-s-vintage-made-in-usa...


I would be willing to bet Kevin knows the pins are plated and not solid gold.

>>>>>>>>>>>>

New Sensor

Standard Electro-Harmonic 12au7EH

http://www.newsensor.com/ProductHighLight.aspx?ProId=30


Electro-Harmonic-Gold

http://www.newsensor.com/ProductHighLight.aspx?ProId=32


New Sensor just says gold.

>>>>>>>


Best regards,

jea48

Several points:

From Jim McShane (an excellent tube dealer) on AA:

"Do yourself a favor - clean the tube pins and sockets every time you change tubes. A bottle of DeOxit D5 and a handful of good old fashioned pipe cleaners works great for octals and other large pin sockets; for the miniatures, D5 and the little tiny dental brushes for cleaning between your teeth (another drug store item) do a solid job. BTW, D5 is good to 400F - so don’t lose sleep over it because of something you read on the "Hi-Fi Hysteria" forum. And it doesn’t gum up either. Spray some in a paper cup and let it evaporate - you’ll be able to see for yourself.

Sometimes you swap a tube and the new tube is okay. so the tube you removed must be bad, right? NO! Sometimes the scraping action of removing and reinstalling a tube in that socket is enough to temporarily restore contact - and fool you into thinking you have a bad tube! KEEP YOUR SOCKETS CLEAN!!"

Alcohol really isn’t enough to clean with. Old tube pins also often really need to be scrapped. A dental brush can work but sometimes I use a small Exacto knife. You’d be surprised what occasionally comes off.

On the other hand, I’ve tried more than half a dozen NOS Mullards (purchased from several sources) in the pre-amp section of my Cronus Magnum (which takes just one pre-amp tube) and all have started to get noisy within a month or so. Various short plates, long plates, 12AU7s, CV4003s, from various factories; it hasn’t mattered.

I also tried NOS Amperex and Radiotechnique (both, like the Mullards, made by Philips). The Amperex also started to get noisy: the RT (platinum grade from Upscale Audio: several over several years) have stayed quiet. Some of the Mullard CV4003s were Platinum Plus ("CJ Test") grade tubes from Upscale. Supposed to stay quiet in hard on tube pre-amps from the likes of CJ, Rogue and Sonic Frontiers. They didn’t. I don’t blame Kevin. I’ve just come to the conclusion that the Cronus and NOS Mullard are incompatible: I don’t know why. They certainly work in other pre-amps owned by many people. (For the record, NOS RCA/Raytheon 12AU7 black-plates and RCA/GE 5814s also stay quiet).

In addition, I’ve purchased tubes from Alfred Kayser and found him knowledgeable and fair. The very short plate CV4003s he sold me also started to get noisy in the Cronus pre-amp slot - but they took longer than even the Upscale Platinum Plus. Luckily the 12AU7 driver section of the Cronus has a significant effect on the sound and all of the Mullards that didn’t make it in the pre-amp slot went to the former section over time and sound(ed) great there. I also bought several NOS Mullard rectifiers from Alfred (back when I had gear that took them; mostly Modwright) and they all performed perfectly.



Sometimes you swap a tube and the new tube is okay. so the tube you removed must be bad, right? NO! Sometimes the scraping action of removing and reinstalling a tube in that socket is enough to temporarily restore contact - and fool you into thinking you have a bad tube! KEEP YOUR SOCKETS CLEAN!!"

Once a blond girl goes into her nice bmw coupe and it does not start. She wiggles key back-forth pushes pedals jerks shift knob, but no success.
Another blond girl comes by and asks what's the problem....
Than she asked:
-- Did you wipe your dashboard?
-- Yes
-- Did you wipe your headlights and bumper?
-- Yes
-- Did you wipe your wheels and shined your tires?
-- Yes
-- I'm sorry I have no idea why it doesn't start than!

From Upscale Audio

Quote:

"I have a brand new tube that’s noisy. When I put my old tubes back they worked fine. This tube is defective.

Okay... I know this one’s not really a "question" but we get it so often that it needs to be addressed anyway. Many times when a piece of tubed equipment is noisy, the cause is a bad connection between a tube and the socket, not a noisy tube. In fact, the majority of tubes we have returned to us for warranty replacement, are not noisy at all!

Remember: Tube stockets are not highly reliable connectors! If the sockets are dirty or not tight enough, or if the pins are slightly "thinner" than your original tubes, or have a little grime on them, it can cause one or more pins be unable to make solid contact. This can result in noise.

So... make sure your tube pins are clean before plugging them in. Also, make sure your sockets are clean and tight. Many times, just the act of removing a tube and re-seating it, either in another position or back into its original spot, can alleviate the problem. You might also try gently twisting the tube in its socket, to make sure it’s getting a solid connection on all the pins."


Copy and paste between brackets.

]http://www.upscaleaudio.com/technical-help/tube-faq/[

Further to the above post, it can be useful to tighten (tension) the individual pin sockets in the tube sockets if they have been opened up over time by a bent or oversized valve pin. Better connectivity can reduce noise significantly.

Post removed 

It appears the pins on a miniature tube are made of Kovar.

I posted a message asking the question and here is one of the responses I received.

The term "steel" doesn’t always get used in the strictest metallurgical sense. I think steel is commonly used to describe the pins because they’re usually quite magnetic. The material I’ve seen referenced in tube manuals and such is "kovar", a nickel/cobalt/iron alloy with coef of thermal expansion similar to borosilicate glass. The alloy also bonds well to glass and is apparently magnetic too. Seems if one believes magnetic conductors distort music signals, tubes should not be in the signal path...LOL.


http://www.audioasylum.com/audio/tubes/messages/26/269123.html


http://www.audioasylum.com/audio/tubes/messages/26/269119.html