Siemens CCa: Gray and Silver riser differences

11-06-07: Imin2u
The silver risers are the older, and much better sounding, tubes.

No. Grey risers are the older...and generally better sounding tubes. No question about it.

Why? CCa grey riser tubes were manufactured in the late 50s and early 60s, before the silver riser versions manufactured in the late 60s through early 80s. The 60s grey riser tubes were manufactured before transistors took over...and therefore tight tolerances made a difference.

Why do CCa grey riser tubes sound better than the shiny riser versions? This is open to debate, and I have yet to read a convincing explanation.

Slightly off-topic, but not really too far....Does anyone have a link to a diagram of a tube with various parts named; IOW a guide to tube anatomy.

I also have never read a reasonable explanation as to why the early grey riser versions bettered the later silver risers. Doing a search on the Tubes Asylum, I read that some have said that the early versions had a .028 diameter frame grid. Who knows if this was the main difference. I have recently put the question up on the tube asylum asking why and how regarding the differences, so maybe someone will give a good explanation. We'll see.

Tvad,

Can you recommend a reliable source for grey riser CCas?
Do those that tend to the microphonic react this way in all amps? Aside from microphonics could one expect consistent quality from all grey shields or are there best of the best versions in your view (again, perhaps by virture of date)?

11-07-07: Anacrusis
Tvad,

Can you recommend a reliable source for grey riser CCas?

None other than the usual suspects found in Audiogon listings and mentioned in threads.

All grey riser (not grey shield as you wrote) have sounded similar to me. I am unable to decipher the Siemens date code.