Super high precision clocks drift with temperature. Not much, but when you need the precision you notice it. Computers etc. are designed binary so minor errors either don't matter or are checked and weeded out, but it matters for analog.
Temperature change on clocks is an important part, but there is another. DAC chips generate less jitter when they are warm, and I do mean warm as in higher temperature. All chips generate current pulses on their power and ground traces in the die and on the package bond wires. These variation in PS voltages create jitter due to threshold change in the chip. The amplitude of the current pulses a given piece of circuitry depends on how fast that circuit changes state. Total amount of charge transferred stays constant, so if the circuit is faster, the current is higher, which creates more jitter.
It turns out that as CMOS circuits heat up they get slower, thus generate less internal jitter. The hotter it gets the less jitter, up til the speed gets so slow the chip fails to operate. I have done several studies on this and found that hot chips DO sound better. This is part of the reason I design my DACs to be warm, they just plain sound better. Heat can also decrease chip life so there is a tradeoff here. Run a DAC warm but not HOT.
John S.
