Weather-induced amp performance variation

There is an excellent article on HiFi News current issue about how temperature affect an amp performance. It actually measures how the bias changes with different room temperature.

It may have something to do with people who notices there is a change in their hifi system in different weather.
Pretty dramatic changes in the sound of a system and amp also occur due to variations in the amounts of AC power line pollution and noise during differnt parts of the day and night, especially if you don't use a line conditioner of some kind.
I also heard that changes in the barometric pressure can cause a system, particularly the speakers, sound alittle different on different days.
Also, proper warm-up is essential, especially in solid-state amps and preamps. If they are played from a cold start, there can be huge variations and fluctuations in the sound quality as they go through their warm-up period.
Don't forget that the weather can play havoc with your sense of hearing.
Eldarthford: I guess age of the listener has much too do as age of equipment :-)
If you leave a high bias amp turned on, the device tends to stabilize temperature. It will not shift measurably unless there is a measurable shift in room temperature. Most common amps that are biased for lower level Class AB operation will undergo the greatest temperature swings, hence the bigger variations in sonics that they suffer from. Then again, going from room temperature to sustained operating temperature is still more of a swing / temperature change than going from idling but powered on up to operating temperature. On top of that, the temperature swing isn't as drastic, resulting in a slight increase in circuit stability and more consistent sonics.

Optimally, one would have a climate controlled room just for the amplifiers outside of the listening room. This would allow one to run Class A amps with enough airflow to allow them to stay cool to the touch. So long as the temperature remained consistent and the amps were adjusted in-room, both the electrical performance and sonics would be improved. I wish i was rich enough to try something like that : ) Sean
Sean, that's easy to achieve. No controlled room -- just an airconditioner at constant temp blowing on the amps 24/7. And another room for the amps. And someone to foot the electricity bill, of course... :)
At my former work at a big Aerospace outfit (I'm retired now) air conditioning with exceptionally tight specs was always provided in labs where there were big computers and other electronic equipment. When the weather got really hot, and the office AC couldn't hack it, many people migrated from their desks to the labs. I guess management thinks that their hardware is more important than their people!
Hopefully the amp manufacturers produce their products to be reasonably stable at a "range" of temperatures. The few degree swings in a normal day should not amount to much once the electronics heat up, and then settle in.

Going from a very cold room (heat turned off) to amp turn on might produce the biggest swing in thermal shock on connections, solder, caps etc. In the grand scheme of things it really should not mean too much.

The biggest effects will be on those devices that change mechanical energy into electrical energy and vice-versa, things like speakers, mics, cartridges, where very precise tolerances are required.

We did a study on microphones many years ago and found several actually sounded better "cold". It is just going to depend on all the ins and outs of your system....

Uniform temps should be better, but most homes should be 68-72 degrees. That range shouldn't mean too much.