Tube Life

Right, a tube rectifier helps to protect the downstream tubes from simultaneous application of filament and plate voltages. The plate voltages will come up slowly. Also the simple use of a thermistor in the filament transformer primaries will protect both the transformer and the tubes from rapid application of filament current. Most modern gear, even including tube gear, uses SS rectification and so does not afford the natural protection of a tube rectifier. However, it is a simple matter to employ a relay device that effects a time delay between application of filament voltage (first) and plate voltage (second).

I would not want to have to go hunting for ECC803S TFKs on an annual basis.

Having an extra reference set to compare to is the best way to know for sure how another set is performing.

Or else you might just trust your ears enough to detect a problem that matters when it sneeks in.

I have TFK 12ax7s in a lot of places and 50% could mean 10 more years depending on the circuit. Trust your ears and the poster above who said older tubes become sleepy I think is right with regard to phono stage tubes.

VAC recommends leaving their Signature-type preamps on 24/7 unless you're going to be away from the system for an extended period. That's what they do. I was told to expect to change tubes every 5 years using this regimen. Clearly, they expect a lot of tube life in their circuit. YMMV.

Definitely diggin' it!
Thank you all for your time and experience. Apparently, the ears have it. I was a mite suspicious before posting this and I swapped a set of electro-harmonix in for the telefunkens. While the telefunkens beat the electro-harmonixs originally it was no longer the case with age. What to do with the telefunkens that are now a bit slow. Alas.....

Sincerely,