Burned Out


I recently got caught up in the tube swapping craze. I have a tubed amp and preamp. I researched things as well as I could for only having access to the internet and forums like this. I also was in contact with the owner of a very well known vintage tube dealer. I bought two tubes from eBay from dealers with a long history on eBay and high customer review rating. Both tubes from eBay were for my preamp, one  was a Brimar and the other Melz 1578 6sn7 tubes manufactured in the 50’s or 60’s. The Brimar only played through one channel and at first dealer tried dispute the fact that it malfunctioned and then contacted me saying he was now having the same issue. The Melz red plated on me and was very microphonic. The dealer is in the Ukraine so I’m waiting to see if I will get my refund. And, last but not least one of the most reputable dealers recommended a tube RCA and has stated he stands behind his product. But, what happens when his product causes damage to your preamp? My preamp now plays only through one channel. When I called up the dealer about the noise the tube was making, I was told follow the instructions regarding microphonics and that there was no way the tube would damage my equipment. There was a recommended break in period of around 48 hrs. Well long story short, my preamp is not functioning and has to be sent back to manufacturer and as of on out $115 for the tube. So my question is are NOS tubes worth all the risk? Are the newer tubes that bad that I have to sacrifice the working condition of my gear for a possible sound improvement? I would like to know your thoughts. Are tubes the Shuguang Black treasure, Northern Electric, a safer risk. I’m venting right now, but looking for answers
sidog1460
@inefficient
I believe the OP said the Melz 1578 came from a Ukraine dealer. The Brimar came from a well-known US dealer.

Based on my experiences buying Melz tubes from Russia
I doubt they have been tested.

The short story is, it was a rca vt231 gray glass tube. Highly recommended. Placed the tube in my preamp, which only requires one tube. Right away I had some concerns about the noise. Called the dealer who advised me how to deal w the issue and that I couldn’t do any damage to my system. And, the rest is history the noise continued and my preamps volumne can’t be increased without the a deafening static like roar. And, yes I removed the tube in question and placed the original back in and got the same result. Manufacturer of preamp has to inspect for location of the damage. No more tube rolling with NOS tubes for me. 
this is an opening for me to repeat my advice, buy a simple tube tester, test them when you receive them. Verify bad when a problem occurs, verify good, annual check .... take it to your friend's house, loan it to those you trust.

Not big high quality one, just a basic one.

My basic one always agrees with my big Hickock, I don’t even bother with the big one anymore. It’s good, no short, has more than enough strength, and if I bought ’matched’ the same strength as it’s twin? Yes!

my simple one, with original instruction book

https://www.ebay.com/itm/Vtg-Accurate-Instrument-Co-Vacuum-Tube-Tester-Model-151-W-Instruction-manua...

some simple testers do NOT have sockets for some less popular tube types, you can ask seller if your tubes are listed in the manual, or, if you can return it, no big risk.

also get a tube substitution book

mine is downstairs, something like this, has english #s also

https://www.ebay.com/itm/1967-HOWARD-W-SAMS-RADIO-VACUUM-TUBE-SUBSTITUTION-BOOK-AUDIO-2A3-12AX7-6V6-...
I spent some time in Odessa, Ukraine. I don’t know if I’d buy products there unless I went through someone I knew personally. I’ve seen shops there that lasted only a few weeks before they either moved or disappeared altogether. Most folks in Ukraine are struggling to buy food though of course there are some who have some wealth but buying from Ukraine isn’t like buying from the UK or Germany. That aside, I do love Ukraine. Anyway, I bought about $350.00 worth of NOS military grade Telefunken’s on eBay for an HH Scott FM Multiplex and they transformed the tone and musicality of my tuner but the seller was here in the states. He even made sure I got a matched pair and swore they were all tested. I can’t remember the name of the tube tester but it was the Rolls Royce of testers. I’m sorry your pre amp was damaged. I would try to have it repaired and then look for a seller here in the US.