Class A Amp- Leave On For Intermittent Listening?

[James Edward]

I almost always left my class AB amps on all the time; they certainly sounded better after several hours, and didn't use much power at idle. Throw in the oft stated wisdom that the turn on/off cycles were detrimental, and the choice was easy.
Now I use a Class A integrated; it sounds great after 15 minutes of being on, but as you know, they are always drawing pretty much full power. And it gets and stays hot- not crazy hot by any means, but mighty warm. I no longer leave it on 24/7, but wonder how the heat and design affect the longevity of the amp.
The question is this- if I know I'll be listening again in 2,3,4 hours or so, should I leave it on, or turn it off. I guess I am wondering which does more damage: the on/off cycles, or the heat from the always on class A transistors.
No, I'm not losing any sleep over this, but I wonder if there is any accepted wisdom regarding this slightly different beast.
Thanks.

[steve]

I almost always left my class AB amps on all the time; they certainly sounded better after several hours, and didn't use much power at idle. Throw in the oft stated wisdom that the turn on/off cycles were detrimental, and the choice was easy.
Now I use a Class A integrated; it sounds great after 15 minutes of being on, but as you know, they are always drawing pretty much full power. And it gets and stays hot- not crazy hot by any means, but mighty warm. I no longer leave it on 24/7, but wonder how the heat and design affect the longevity of the amp.
The question is this- if I know I'll be listening again in 2,3,4 hours or so, should I leave it on, or turn it off. I guess I am wondering which does more damage: the on/off cycles, or the heat from the always on class A transistors.
No, I'm not losing any sleep over this, but I wonder if there is any accepted wisdom regarding this slightly different beast.
Thanks.

Heat deteriorates nearly everything, especially electrolytic capacitors. The general rule is that a capacitor's life shortens by half for every 20 degree increase in temperature.

Another effect on electrolytic capacitor life is the ripple current; the higher the ripple current the shorter the life.

I have seen transistors change characteristics over time, so that is a consideration.

I understand about time period on for improved sonics, as test equipment, audio equipment requires time to settle down electrically. This includes temperarture stabilization. I warm my components at least 2 hours, preferably 3 before a test listening session. Otherwise, speaker placement will need to be upgraded when the components and parts are optimized.

As one can see, this is all very scientific in nature, and known for decades. Relatively recently, higher temperature electrolytic capacitors have been introduced. However, the same general rule applies. The Radiotron Designers Handbook, publish by 26+ engineers for RCA, 1960 edition discusses temperature effects of parts etc in some detail.

steve

[tmazz]

My father was an electrical engineer that designed military radar systems. On occasion he would bring me into work with him when he had to go in on a Saturday. Thus usually involved him having to check on tests being done on some kind of prototype. I remember tubed electronics being baked in some kind of ovens. Of course I asked him why they were trying to cook the equipment and he explained that sometimes Army bases were located in some very hot places and he had to make sure that the equipment would work even after sitting for long times in the hot sun. Back then that was about all than my little 8 year old brain could handle, but I now realize that they were testing to see if the component values shifted in the heat far enough to adversely effect the operation of the circuitry. What I wouldn't give to have the opportunity to sit down with him and talk shop, engineer to engineer, but unfortunately he passed away when I was only 12. 

But several years ago I did find on the net, a copy of a patent he was awarded for work on a radar unjamming system. This unit would detect an incoming radar jamming system and send out a counterattacking signal that would in a sense jam the jammer, thereby allowing the pilot to continue using his navigation instruments even in the face of enemy jamming efforts. That was really cool to read, and what was even cooler was that I actually understood what they were saying, 

[Triode Pete]

My father was an electrical engineer that designed military radar systems. On occasion he would bring me into work with him when he had to go in on a Saturday. Thus usually involved him having to check on tests being done on some kind of prototype. I remember tubed electronics being baked in some kind of ovens. Of course I asked him why they were trying to cook the equipment and he explained that sometimes Army bases were located in some very hot places and he had to make sure that the equipment would work even after sitting for long times in the hot sun. Back then that was about all than my little 8 year old brain could handle, but I now realize that they were testing to see if the component values shifted in the heat far enough to adversely effect the operation of the circuitry. What I wouldn't give to have the opportunity to sit down with him and talk shop, engineer to engineer, but unfortunately he passed away when I was only 12. 

But several years ago I did find on the net, a copy of a patent he was awarded for work on a radar unjamming system. This unit would detect an incoming radar jamming system and send out a counterattacking signal that would in a sense jam the jammer, thereby allowing the pilot to continue using his navigation instruments even in the face of enemy jamming efforts. That was really cool to read, and what was even cooler was that I actually understood what they were saying, 

Tom - Great story (except him leaving you so soon... )! I guess electrical engineers run in your family! Cool!

Cheers,
Pete

[Nick B]

My father was an electrical engineer that designed military radar systems. On occasion he would bring me into work with him when he had to go in on a Saturday. Thus usually involved him having to check on tests being done on some kind of prototype. I remember tubed electronics being baked in some kind of ovens. Of course I asked him why they were trying to cook the equipment and he explained that sometimes Army bases were located in some very hot places and he had to make sure that the equipment would work even after sitting for long times in the hot sun. Back then that was about all than my little 8 year old brain could handle, but I now realize that they were testing to see if the component values shifted in the heat far enough to adversely effect the operation of the circuitry. What I wouldn't give to have the opportunity to sit down with him and talk shop, engineer to engineer, but unfortunately he passed away when I was only 12. 

But several years ago I did find on the net, a copy of a patent he was awarded for work on a radar unjamming system. This unit would detect an incoming radar jamming system and send out a counterattacking signal that would in a sense jam the jammer, thereby allowing the pilot to continue using his navigation instruments even in the face of enemy jamming efforts. That was really cool to read, and what was even cooler was that I actually understood what they were saying, 

Great story, Tom. My dad passed when I was 16. He repaired typewriters, adding machines etc. and was teaching himself basic electronics. It would have been great fun to learn from him as he could already read schematics, a skill which I don't have. That's another reason it's nice to have this forum as knowledge is so readily shared
Nick

[rollo]

  A heart warming story Tom. Besides heat damage to parts. Tube life will suffer as well. A good [2] hours of warm up is just fine.


charles