Siemens CCa Finest 6922 tube

Listing for a pair of Siemens CCa tubes. All show various amount of wear to printing. Rarest and finest sounding e88cc tube. 2 pairs for sale. These I bought from a dealer 5 years ago as part of a lot of 16 tubes and held as a backup for a phono preamp I recently sold. Just tested by Tyler at Chelsea Tubes, including for noise and microphonics. All tubes tested very strong. Actual test results followed by Tyler's comments: 


1) 14.6 11,540/14.8 11,200 2) 14.0 11,600/15.4 12,000 3) 13.2 10,800/12.8 10,400 4) 13.0 11,000/11.8 10,400      

Tyler & Chelsea tctubes.com <[email protected]> May 12 (3 days ago)

to me

Hi Ralph,

I've finished testing your tubes. I wrote down the test scores based on actual

readings taken from the AT1000 testers under the following conditions:

90vdc plate

-1.2vdc bias

Expecting 10mA and 10,000Gm or better. I would not recommend using/selling

tubes

that test at or below 8mA or 8,000Gm.

There is a large range of acceptable scores for this type from about 9mA and

9,000Gm up to as much as 20mA and 15,000Gm.

To unambiguously qualify as testing "as new" I'd use 10mA and 11,000Gm or

better.

Given all of that, here's how your tubes did:

CCA tubes:

mA scores ranged from 10.8mA to 17.8mA

Gm scores ranged from 10,000Gm to 13,200Gm

All solid testing tubes but not all have matched sections.

All of the tubes were acceptable in my phono stage which uses 6DJ8/6922 tubes.

There are probably more sensitive applications out there, but this is a good

sign in terms of noise screening. You will find that a few of the tubes were

marked as having a bit of microphonics. That showed up on the AT1000 testers

but not in my phono as I don't tap the tubes directly on the phono stage. I just

flip switches as it would normally be used.

Thanks,

CCa = LOW-NOISE E88CC "6922" = PREMIUM QUALITY GOLD PIN E88CC:

The "CCa" is an E88CC specially selected for "Post Germany" in the 1950's -60's, they were a special low noise, low microphonic, long-life E88CC / 6922.  Philips had similar "designations" for the "Dutch Post", some tubes that were selected had "PTT" * and "BP" lettering or etched designations, but they were the same as a top specification E88CC.  The "German and Dutch Post" consisted of telephone, telegraph, telex, and the postal system "tube" technologies which required LOW-NOISE E88CC / 6922.  A CCa is the same as a 6922 but was tested and certified with high mA, RP, and Mu and lowest-noise audio threshold - the same proceedure the Tube Museum New York certifies tubes by today.  Much of the telephone centrals used vacuum tube technology equipment for telephone equipment requiring a "noise-free" enviroment.  The letters "CC" probabably equates to "double triode", and for a special low-noise design - the "frame-grid" inner construction, which was actually invented by Amperex USA, and became ubiquitous - Present, appearing, or found everywhere in the 6922/E88CC design of the day, including Siemens Halske, Telefunken, Amperex, Philips, and many others.  Internally the inner construction of the CCa is identical to Siemens Halske E88CC - why? Because the only difference is the cosmetic-lettering and ofcourse the "special selection" of the best and quietist specimens.  In addition, the suppliers of the day, wanted a sure method of identifing the tubes they provided, as the very tubes sold to these companies. It could have been very easy to swap with a current different E88CC in the day, if it wasn't uniquily labeled, simply by walking down to the local radio shop and purchasing a different tube.  The CCa factory markings identified the original supplied tubes as the ones guaranteed by the Siemens "Klingarm" Division ( "Klingarm" is the term for low microphonics. You often see Telefunken EF12K or AC701K, the K means Klingarm) whom charged a premium for selected low-noise high mA specimens for industrial customers.