Leaving DAC on all the time OK?

Techs will tell you to leave all equipment powered up 24/7 except for tube amps (output tubes tend to pass a lot of current and have to be turned off to prevent excessive tube wear) and Class-A biased transistor amps (which burn too much electricity to leave on 24/7 and which produce tons of heat). It is the thermal cycles (heating up and cooling down) that result from turning equipment on and off which tends to make equipment break. Cold equipment also sounds bad in high resolution systems. This is especially true with digital processors -- you have to leave them on 24/7 if you want them to perform as the manufacturer intended.

Of course, the above poster is correct about unplugging equipment to protect against damage from electrical storms. It is also not "green" to run equipment 24/7, but if you want to increase the chance that your equipment will break and if you want it to sound like crap, turn it on and off.

PS: The light on your DAC is almost certainly an LED -- it will last forever.

Larryi: It is precisely because most modern tube preamps use solid state rectification that powering them up and down kills tubes. I agree that a soft-start circuit (CAT preamps come to mind) or using a thermistor will do a lot to ameliorate the problem, but absent such a device, I stand by my statement that small-signal tubes last much longer if left powered up in most circuits. If a person is running a big Jadis or Aesthetix preamp with tube rectification, that's one thing, but most tube pre's (or anything else that uses small-signal tubes) do not, and 24/7 will yield better tube life (and to a point, better sonics -- as I have noted in other threads on this topic, they do degrade slowly over time).

The "TIPS & ADVICE" section of the owner's manual to my VAC Renaisance 140/140 Mk. III tube amps states:

"How long should tubes last? It has long been known in professional circles (and probably now forgotten) that a tube such as the 12AX7 will display BETTER performance characteristics after TWO YEARS of CONTINUAL operation than when it was new. In normal use it is not unusual for a low level tube to last 5 years or longer. Output tubes [i.e., power tubes used in tube power amps] are another story, as they are continuously providing significant amounts of current." (Emphasis original).