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  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
elevick
2,636 posts
 
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.
aolmrd1241 OP
1,011 posts
 
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? 

aolmrd1241 OP
1,011 posts
 
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.

tomwh
150 posts
 
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.
stevecham
3,340 posts
 
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. ;-)
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