2. analog
  3. 125078-1452

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.

aolmrd1241
czarivey
4,494 posts
 
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!
jea48
2,944 posts
 

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/[

dover
1,165 posts
 
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 
jea48
2,944 posts
 

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


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