Conventional wisdom holds that DACs require "warming up" for best performance, especially multi-bit DACs like my BF2. Can someone explain this? I seem to recall the claim that temperature affects the crystal(s) for the clock(s), or something like that. I've heard the suggestion that a DAC run 24/7, and that there can be some benefit to hours or even days of operation after a "cold start". What is the physics behind this? Does it matter if my room is 65 degrees F, or 75, or 85? Is there an optimal operating temperature higher than normal ambient room temperature? Is there a temperature threshold beyond which performance degrades? Should I stack my BF2 on top of my Jot to warm it up? I've tried to give all my components a chance to "warm up" prior to an (all too infrequent) dedicated listening session, and I don't choose to have my rig running 24/7.
I'm not a EE nor do I play one on TV, so take what I am about to say with a huge block of salt!
I clearly don't remember if Schiit's multibit DACs are considered an R2R-style of DAC or not, but a while back I found an explanation of what an "R-2R" DAC is and leaving the equipment on and warmed up definitely made sense. In essence, in a digital-to-analog converter, each higher order bit adds a smaller and smaller voltage increment to each sample to recreate the voltage that was originally measured in that sample by an analog-to-digital converter. To generate that voltage, you need a voltage divider network consisting of a resistor of value R and another of value 2R. Those resistors need to be of increasingly smaller values and of increasingly greater precision to keep those resistances constant. All resistors will change value with temperature and that change is usually measured in parts-per-million. Resistors with lower temperature constants (smaller PPM) are more expensive because they're more difficult to make. So, you strike a balance between what's economical and what works satisfactorily.
What does all of this have to do with keeping your DAC turned on or not? Well, keeping it turned on allows all of the circuits within the DAC to be warmed up to a stable temperature. This stable temperature keeps temperature sensitive components at a stable value that should be close to how the unit was originally built and calibrated, thus giving you the best performance. Running your DAC right after you take it out of the box that UPS just delivered in the middle of winter probably will cause it to sound a little bit off. It probably will sound a lot better after you've given it a chance to warm up for 30 minutes. There are those who say a DAC has to be on for a week for it to sound optimal. That's their call. I, however, am skeptical because unless your DAC resides inside a perfect heatsink that pulls all heat away and never allows it to warm up, 30 minutes should be good enough to get all of those components up to operating temperature. But what do I know? I can't hear a difference between my Bifrost D/S and my Bifrost MB. I think they both sound wonderful with my equipment and am happy to have them.
I'd say do whatever you feel comfortable with and maybe do some experimentation. Play a handful of songs you're comfortable with using your system cold and then again after it's had a chance to warm up for x minutes and see if YOU can tell a difference. If you can't tell any difference, turn everything off when you're done enjoying your Schiit and save a few Watts of power. If you can, then, it's up to you whether you want to leave it on all the time or just wait for it to warm up.
And finally, we're currently getting some nice heavy, wet snow. It's covering the roofs, cars, grass, etc. but not the pavement...yet. Gotta love springtime!
