I've compared a lot of different 6922 tubes for my older Spoiler DAC design. By far the best tube I found was the Siemens CCA grey-plate. A pair of these is expensive, particularly strong ones. These were top performers made for the German phone company in the late 50s. They have finer grids than other tubes for superb extension. I tried these in a modded Lyr and they were great.
Can anyone break down the CCA thing for me? If I understand right its a marker for 'low noise'. Now we're talking about low noise in relation to the gain curve, as opposed to noise floor correct? There is this and military spec versions which I assume are just simply more rugged builds, designed initially to take more physical abuse in their respective environment. I grabbed a pair of non-cca Simmens which were much cheaper, but effectively German DOD grade (BWB). At this point I'm basically taste testing different makes trying to find out what I like, so I went with a buy now $100 pair. All I have to do is break them in to see if they were worth the purchase. The boxes and internal structure so far as I can tell are definitely the real deal - ie the internal date stamps can't be replicated.
There's another pair up for grabs here: http://www.ebay.ca/itm/281066852578?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
I think the $20 shipping was worth it. 4days from Germany.
The CCA versions of this tube are crazy expensive. Not as much as a pair of E188CC Telefunkens mind you. My question I guess is this... are the ones I picked up going to give me a good idea of what the CCA versions are like? Or are they completely different beasts?
A swap program would be nice. :) Trust is a problem though. Yikes. I can't imagine having to give up your borrowed dream tubes. 
