> In the last years of serious tube research and design there was a new type of > cathode created, which was as efficient as previous types, but was immune to > this effect. Most of tubes designed to be used in digital circuits were > designed with long times with no anode current flowing.
There are a lot of myths about this, some disparaging metallurgy in the 1950s and 60s, referring to cathode impurities. They are false. The tube business, like any business, focussed on volume and cost cutting. Early on, the tube manufacturers determined that adding a small amount of silicon to the (nickel) cathode sleeve accelerated the activation process, saving time and money. Later, when computer applications came around, the "sleeping sickness" problem arose, where cathode interface would raise the cathode (and tube) impedance during long periods of cut-off operation. A little research revealed that this was caused by the added silicon. The tube manufacturers responded by offering "computer" tubes which were produced without the added silicon, and therefore required the longer (and more expensive) activation. This worked fine. To save money, the manufacturers would often use older tooling for the computer tubes, as linearity was not important. Amusingly, a few modern audiophiles prefer the computer tubes, figuring they must be "better", but in some case, the computer rated tubes will be made with older tooling and have less linearity than the non-computer versions. - John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/DDFCB36F-4145-4E5B-906B-2215878CCACF%40mac.com. For more options, visit https://groups.google.com/d/optout.
