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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
czarivey
5,946 posts
 
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 
lewm
13,099 posts
 
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.
aolmrd1241 OP
1,042 posts
 
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.
lewm
13,099 posts
 
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? 
jperry
2,450 posts
 
"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. 
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