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
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cleeds
5,723 posts
 
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!
aolmrd1241 OP
1,023 posts
 
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. 
czarivey
5,756 posts
 
The NOS may have 125 hours of use.
Is there any sort of odometer in vintage NOS tubes?
aolmrd1241 OP
1,023 posts
 
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.
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.
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