Can temperature fluctuations affect audio gear?

I agree with Elizabeth. I wouldn't worry about the possibility of damage, if that was the point to your question.

I would add, though, that from a technical standpoint it does seem conceivable to me that a 25 or 30 degreeF difference in ambient temperature could result in sonic differences, at least to a subtle degree. But I would expect those differences, if any, to be equipment-dependent and unpredictable.

Also, it wouldn't surprise me if a temperature difference of that magnitude caused differences in your own hearing mechanisms as well. :-)

Regards,
-- Al

Magfan & Bigbucks, I'll say first that thermodynamics was definitely not one of the shining successes among the courses I took in college, but pending further info from Magfan's PhD friend I believe that Bigbucks is correct.

Magfan: In SS, for example, you have a max temp possible....say the junction temp of the devices. In a hot room wont' the difference drop as the room temp approaches junction temp? Or will the junction keep getting hotter until failure? Isn't there an upper limit to the temp of an amp?

The maximum rated junction temperature of a semiconductor device, less some derating (margin), is the maximum temperature that is safely allowable. It is by no means the maximum temperature that is "possible." And yes, it can keep getting hotter until its mtbf (mean time between failure) is severely degraded, or until immediate failure occurs.

Think of it this way: If everything has been turned off for a while, everything (including internal device junction temperatures) will be at the room ambient temperature. The energy that is fed into each device, less whatever amount of energy the device outputs to other devices, and less whatever amount of heat is conducted or radiated away from it, can only have the effect of heating the device up from that starting temperature.

Best regards,
-- Al

Heat does indeed kill electronics, or at least reduce mtbf. However, if the equipment is well designed from a thermal management/heat sinking standpoint, and if parts such as electrolytic capacitors whose mtbf may be particularly heat sensitive are well chosen, the effects of heat will not become significant until temperatures are reached that are much higher than might be expected.

Those are very big "if's," of course. And I would not expect that small manufacturers of high end equipment will always or even usually have thermal design specialists on staff, not to mention that providing conservative design margins will tend to increase the cost of the product.

But to provide some perspective, commercial grade integrated circuits are most commonly rated for ambient operating temperatures of 0 to 70 degC, that being conditional in the case of higher powered devices on heat sinking provisions that maintain reasonable junction temperatures. 70 degC = 158 degF! Specifications for integrated circuits used in military avionics usually require an ambient operating temperature range of -55 to +125 degC. 125 degC = 257 degF! (Although keep in mind that "ambient" for each device means the nearby temperature inside the case of the equipment, not the external air temperature).

Devices that consume large amounts of power, such as computer cpu's, usually have considerably lower ambient temperature ratings than those numbers, but they are still higher than one might expect. Current Intel quad-core desktop cpu's have a TDP (thermal design power) of 130 watts. It boggles my mind that so much power can be dissipated in such a small package, even with the special heat sink and fan that is required. Consider how hot a 100W light bulb gets, the bulb being considerably larger than a cpu chip!

Addressing Magfan's point about the fact that computer enthusiasts (I am one one of them) pursue exotic cooling solutions, the reason for that is not to extend life but to optimize overclocking ability (running the cpu at faster than its rated speed, which enthusiast-oriented motherboards make possible). Faster speed = higher power consumption and higher internal temperatures, and higher internal temperatures will limit the maximum speed at which the cpu can be operated without crashes.

Overclocked cpu's utilizing good aftermarket cooling devices typically run reliably for many years with internal junction temperatures in the area of 40 degC (104 degF) when idle, and 75 degC (167 degF) to 90 degC (194 degF) when performing intensive processing.

Best regards,
-- Al

That strikes me as a good datasheet to use for purposes of focusing the discussion, Magfan.

It's interesting to note, extrapolating from the data that is provided, that its maximum rated power dissipation of 115 watts at a case temperature of 25 degC/77 degF (commonly referred to as "room ambient") does not drop off by a factor of 2 (to 57.5 watts) until the case temperature has risen to 112.5 degC/234.5 degF! And it can go considerably higher than that, as well, if the power that it is called upon to dissipate is reduced such that the junction temperature is kept below the rated maximum of 200 degC/392 degF!

Some related things that should be kept in mind, though:

1)The numbers provided are "maximum" ratings, commonly referred to in other datasheets as "absolute maximum" ratings. Those are the ratings which if exceeded stand a good chance of causing immediate failure. A good design will provide a very large margin between those ratings and the actual operating conditions. As noted in the reference you provided earlier, a rough rule of thumb is that each 10 degC reduction in junction temperature doubles mtbf.

2)"Derating" can refer to two different things. It is used in the datasheet to refer to the falloff in MAXIMUM power handling capability that occurs as case temperature increases. "Derating" is also used to refer to the amount of margin that the design provides between the rated maximums and the actual operating conditions.

3)The amounts by which both case temperature and junction temperature rise above ambient temperature will depend on the adequacy of the heat sinking that is provided, and on how much power the circuit application requires the device to dissipate.

Best regards,
-- Al