[Toon]

Gents,
I have very little experience with tubes but, based on all the good raps for the BTs, bought a Grade A matched pair (in the fancy box) from a reputable US vendor. Don't plan to use them until the preamp is fully burned in and I've determined exactly what the standard tubes sound like, but thought it best at least to check that they were working ... which they are! The only concern I have is that there's a high-pitched rattling sound coming from both of them, heard when they're tapped or knocked gently while moving the amp around - is that normal?

One other observation - the handwritten spec sheets that come with the tubes were suspiciously identical, and besides there's no way to determine which tube each sheet refers to. I also found a photo on a Chinese vendor's eBay listing, showing spec sheets with a different batch number but the same datestamp and the exact same set of values as mine! Can these spec sheets be trusted?   

[JohnR]

How much were they?

[Dracule1]

I have the BT CV-181s.  I have not had any microphonic issues with my pair.  I have not tapped on them while they're on, but they are very quiet tubes when left alone.  Have you tried using tube dampeners?

As far as eBay sellers go, it's kind of a crap shoot on how they select and match their tubes.  You'll be lucky if you get an intelligible response to any technical question. The values that come on the tube/box are transconductance values which is only one of the criteria to match a pair of tubes.  I could be wrong here, but I was told this by a tube seller I have used.  Grant Fidelity and thetubestore are two reliable trusted tube sellers in North America.  GF is by far the most expensive if you want their premium tubes.  I got mine from thetubestore.com.  They basically match their tubes the same way GF does but are less expensive.  Hope this helps.

[richidoo]

Could be counterfeit, any high priced commodity made in China is at risk. Talk about it with the seller. The tubes should not be that microphonic.

Bunky has recommended this seller for BT tubes, is this is who you are using?
http://stores.ebay.com/Hanshare-Electronics

I have received good BT power tubes from Grant Fidelity.

[TomS]

I have the BT CV-181s.  I have not had any microphonic issues with my pair.  I have not tapped on them while they're on, but they are very quiet tubes when left alone.  Have you tried using tube dampeners?

As far as eBay sellers go, it's kind of a crap shoot on how they select and match their tubes.  You'll be lucky if you get an intelligible response to any technical question. The values that come on the tube/box are transconductance values which is only one of the criteria to match a pair of tubes.  I could be wrong here, but I was told this by a tube seller I have used.  Grant Fidelity and thetubestore are two reliable trusted tube sellers in North America.  GF is by far the most expensive if you want their premium tubes.  I got mine from thetubestore.com.  They basically match their tubes the same way GF does but are less expensive.  Hope this helps.

I also got my matched CV181's from www.thetubestore.com with good results and they were reasonably priced.

[Toon]

Grateful for the feedback, guys. A mate got them for me - we combined orders to save on shipping - and I think (but am not certain) they came from thetubestore. Guess I can take it up with the vendor, just wanted to establish whether rattling was normal ... apparently not. Thanks again.

[MarkM]

I have had the Black Treasure CV-181 for over a year now.  Purchased from Grant Fidelity, two pairs actually.  Preamp and phase splitter in my power amp.   One was their highest matching, the other a notch below that.  Dead quiet, no issues what so ever from noise, microphonics etc. The best 6SN7 tube you can buy imho.