Supply and demand. I think tube audio is gaining in popularity and they just aren't making any NOS tubes these days! :scratch2:

Exactly. If you want your amp to sound *okay* then buy the Russian/Chinese tubes. If you want it to SING then you seek out the best vintage tubes at a reasonable price. The RCA and Sylvania 6V6GT's I've picked up are a bargain for the sound they produce.

I'm still in search of the 'right' pair of TungSol 6550's. They're going for about $300/pair up to $500/pair for the good early vintage version. Most you see on eBay are beaten to within an inch of their life by the looks of the getters. And they still ask $250-350/pair for them...

There is a big difference between $500/pair and $500/each.

My "noble" Fire Bottle
 

In the world of beer making, I've always appreciated the beers made with very traditional hops, aka "Noble Hops", like Saaz, Hallertauer Mittelfruh, Tettnang, etc.

So here I present my newly tube-rolled KT-"6550" Fire Bottle with some of the heavy hitters in the vintage tube market:

Rectifier: 60's era F32 Mullard 5AR4
Driver: 60's era Telefunken E88CC
Power Tubes: 70's era Tung-Sol 6550's with matching date codes, getters that look brand new

:music:

It's in warm up mode, getting ready for a workout tonight!

http://home.comcast.net/~cryptcl/NobleFB.jpg

Nice! Would love to hear what you think about the TS 6550's. Interestingly, I got the rolling bug last night. I've been running the Pope 6v6's - gave the RCA smoked glass 6v6's a try (like the Popes better). Jumped up to 6550's. I have =C= 6550's - hmm, not bad. I tiny bit of edge in the highs. But nice range and dynamics - maybe since it would be 10wpc instead of 5 with 6v6's. Then swapped in a pair of Tung-Sol reissue 6550's - hmmm, this sounds good. I'm leaving them in a bit to see. I recall liking the TS reissues better than the =C= when I rolled between them in my conrad-johnson 11A. So the vintage Tung-Sol's should be very interesting!

BTW, still running that nice Sophia 274B and the 6N1P that Dennis supplied. I have on order the NOS "rocket" 6N1P from 1980 that gets good reviews.

I would love to find a pair of Visseaux 6L6's, but can't seem to find any. Tempted by the Mullard XF2 EL34's ($$).

A tube question......

I've heard it is less important to match power tubes in contrast with small signal tubes/pre-amp tubes.

If a pair of tubes both test close or over the "new" minimum mA rating but are different, eg, Testing result:80mA,68.2mA with 100% being 72mA. Do I need to worry about that difference of almost 12 mA?

Thanks,

It's a good question. I'd love to know the answer. My gut has always gone with "as matched as I can find". I mean, it can't be a *bad* thing if they're matched, so I default to that.

Most of the eBay tubes reference tube tester results (transconductance). But most of the power tube guys I buy from comment more on their mA output.

Can one of the techie guys comment here - it's a great question!

Peter.......This article may be of interest to you.

TubeSound » Blog Archive » Tube Matching with a Tube Tester

Interesting read, though right on my growing edge of understanding. From the writer's tone, it seems like it is not the worse thing to not match. Though he nods to the other guy - Milton, IIRC - who suggests 6% or less, preferably 3%, tolerance. My example would fall well outside that limit.

Anyway, the tubes are on ebay. They are Mazda 6L6's, which don't seem to be available anywhere anymore. They don't match well, and my emaill to the seller followed with an answer that did not inspire confidence, so I'm passing. But they are there if anyone is interested. I'd love to try a good pair in my KT150. I have a pair of RCA blackplate 6L6's on the way instead for some more rolling fun!

Peter.......The gist of Bob Putnak's article is that tube testers don't use real world amplifier voltages for their tests, so even though we have some data to compare from those tests, it is unlikely that the numbers will remain the same under actual use in an amplifier's circuit. Distortion analyzing of the amplifier's output is the only true way to determine a tube's performance. Unfortunately, the average audio enthusiast doesn't have the knowledge or equipment to analyze amplifier output distortion.

It is not a bad thing to try to purchase closely matched tubes, even though they are tested at less than realistic voltages. At least we have some data that tells us about a tube's performance under those test conditions. I guess it is better than no information at all.