Do you leave CD players with tube outputs on?

Hi Abe,

Thank you for the polite nature of your questions, but I'm not able to answer them particularly knowledgeably.

Yes, I would think that a suitable high-current thermistor, suitably placed somewhere in the path between ac inputs and tube filaments, would be an effective means of inrush current limiting. I know that is commonly done in power supply designs, although I don't have a feel for how widespread their use is in audio.

I'm not sure I understand your reference to shorting of caps, but that would seem to only be relevant to designs that incorporate a dc filament supply, not to those that drive the filaments with low voltage ac directly from the transformer.

Re cathode stripping, as I indicated its significance with respect to small signal tubes is a matter of some controversy, and I have no particular feel for its degree of significance myself. But given the possibility of it being significant, it would seem to be good practice to design a tube component to bring up the B+ slowly.

Regards,
-- Al

A1,

Thanks a lot! I am glad that you accomodated my request.
Thanks for your time answering my inquiries. I learned something today!

Best regards,

Abe

Tubes reach the point of normal operation faster than semiconductors thus require shorter time to worm up (for the small signal tubes near 2min. Why bother to keep them on??

I think a lot depends on your unit. Some take longer to warm up than others, also some are a little more "blunt" with how they power up. If Telefunken 12ax7s last 10,000 hours, you do the math....
I tend to leave my system on all weekend if I'm listening a lot. But, if I'm not going to listen for a day or two, it gets turned off.

From conrad johnson's web-site........

"To obtain maximum tube life, vacuum-tube products should be switched off when not in use. A good general rule for is that if you will not be listening for more than an hour, turn any tube component off. Conrad-Johnson solid-state preamps (including Sonographe and Motif), on the other hand, are designed to be left on at all times. We recommend switching power amps off when unattended and over night."

How long do tubes last?
A. That varies depending on the type of tube, the number of hours of use and the type of use they have had. Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time.