Should Class A Amps be left on??

Ok- Audiogon members need some advice here. Should Solid State Class A Amps be powered all the time? Have heard two school of thoughts on this. Apparently from what I have heard this is a moot question for Class A/B amps due to the usual low biasing of A/B Amps. From what I have been to learn so far Class A Amps should be left continously on.
Leave them on.
Yes! You heard right...
In part because the temperature difference between on and off is so great, the sound does change as the components warm up. (Obviously, designers work to optimize the sound after warm up, not during.) Keep them on, and you won't have to wait for the amps to warm up for an hour and stabilize every time you listen.
I used to own a big Class A amp that I left on continously for three years. Doubled my electricity bill and warmed my placed in winter (nice) and in summer (unpleasant). Sound was great, though. Now I have a Pass X350 that can be switched to standby mode. So far I have not found much difference in sound whether I leave it on continously or switch to standby. Just not sure what the cycles of heating and cooling could do to the amp..
It's your call Ferrari!, I have class A monoblocks, and they genearate a lot of heat! But they sound good if you leave the power on all the time..
Personally, I have had Plinius SA-100 mk3 amps, and I would not leave them on in Class A idle. First they suck up electricity. Second, the hotter the temperature of an amp, the less lifespan it has. Temperature affects amplifiers like everything else, it decreases the lifespan of the amp.

Both tube and solid state amps can reach a stable operating temperature in about 15 minutes. I see no reason to leave the amp on when no one is listening just to save the warmup time. The electricity alone is enough to justify this. Didn't your parents teach you to turn off the light when you leave a room? Same goes here (and probably multiplied by a small factor if your amps are like mine: BAT VK-60). Just a few years ago we were all worried about using up the earth's resources. Whatever happened to that?

If you want to speed up the warmup process, just put a space heater under the amp. Then you only need to wait five minutes.
Hehehe, John, doesn't space heater use electricity? ;-)
We in California get our electricity from hamster power, and it is very expensive. :-)

Turn the Class A stuff off... It's not like we need heaters ;-)

I keep my solid state amps on 24/7 unless I am going out of town. The soundstage really opens up after they have been on about an hour. I turn off my tube pre-amp between sessions. It seems to warm up fairly quickly, plus I don't want to burn up my NOS tube set.

If you notice a difference and don't want to wait then leave them on all the time. If you have heat/power concerns or ocassional listening habits, then you may want to switch them on in advance of your session.

Be aware that warm up can also be significant when auditioning new equipment.

On a side note, I have 22 Bryston amps at my work that have been on for 10 years straight without failure.

hope this helps,

From a lifespan viewpoint, any heat is bad. Thermal cyclic failure is logrithmically dependant on power (half the power = 100 times more cycles before failure) so especially high power amps should not be turned on and off too often. But, if it is on all the time, the cycling effect is decreased because when you turn the volume up from idle, the device temp is not starting from room temp which increases your device lifespan compared to cold starts. The happy median point is very hard to find due to its dependancy on many factors like circuit design, layout, device type, bias, heatsink, size, weight, etc.

That said, some designs (like emitter-follower and low or zero feedback) can have thermal issues after being on for a long time like bias error which will degrade performance over time especially if extreme care in hotspot minimization was not taken. I would ask the manufacturer as to what to do (although they may be reluctant to tell you that they did not design for full thermal steady-state). If everything was taken into account in the amp design - there should be no problem in leaving it on all the time, save higher electric bill.

But as for me, I stay away from class A due to thermal problems (as I said - any heat is a problem) and because designers who like the concept of "pure" class A often tend to oversimplify the circuit to the extent that it cannot take care of itself in the long run or in extreme situations. I am always amazed how many high-priced amps have little to no protection circuits in the name of clean and pure sound, which I think is a very dumb idea. Arthur
I could be wrong about this but I thought that class A amps were least efficient when not driven. If I'm wrong I'm sure you good souls will correct me. If the first premise is true, I would think that leaving a class a amp on all the time would needlesly shorten the life of the amp, waste more electricity than any other component (perhaps as much or even more than the rest of the system combined) and have a negative effect on the enviornment. Perhaps a suitable compromise is in order.
I am an Aleph user and the class A operation on the 5 uses 300 watts, that's a lot of heat/electricity, when turned on regardless of whether there is program material.

The Aleph 5 seems to take 1 hour to warm up and become most musical and fluid, so I turn it on when I plan to listen and turn it off when not in use for longer than 6 hours. The heating and cooling cycles are no different than leaving it on continuously 24/7 I assume and quite likely better than frying forever.

As the Pass website says the aleph series like like the sun will burn brightly and when it is finished it is all over!

Nelson Pass expects 20 years or so from the Alephs because they "run hard". As energy consumption is also importantly an issue, I too try to flip my 30 amp switch on my ACME cry0-outleted junction box with my toe about an hour or two before listening...or listen to FM background before CD.
I'm hoping that this 10-15% on-time leverages my Aleph MTBF to at least 25 years (I'll be 75). We'll see....
Sometimes I think it takes mybe 2-3 hours for the Aleph 2 monos (300w idle each) to get liquid and VERY resolving.
But it could be my (our) hearing apparatus acclimating to the listening environment, like occurs at a live concert.
Yeah, I guess I could afford to leave them on 24/7, especially in the winter, but I'd still feel like they'd age due to thermal load. I have them each sitting in holey
plastic 1 ft-cube milk cartons, hanging a foot under the basement floor joists, so they get convection cooling from UNDERNEITH, too. Hope it helps....
Many thanks to all the respondents of this thread. I have found this one draws 1 amp and 120 Watts at idle. According to the manufacturer,(I just found out)Can be turned on and off as well as left on constantly. If possible keep turned on. If going on vacation or away for a period of time turn the system off.
Leave them on and make sure that they have adequate airflow. Sean
Based upon advice here and from other sources. The amp has been on for a solid ten days now. There is no comparision between turning off and leaving on. Clearly Class A amps,whose output operates in Class A definitely sound better being left on. This amp has really come into its own now and is quite impressive to say the least.
You da man. :-)
After reading all the threads posted I agree that leaving the amp on is the way to go sonically. I have a Audible Illusions S-120 and it sounds great when left on. However I would like to turn the tube pre(AE-3 Cary) off to keep the Sylvania's in top shape. My question is how do I turn the pre off while not damaging the amp. Dosen't the amp need to see a load while on? Many thanks.
South43, be REALLY CAREFULL when you turn on the preamp. I know a gentlemen, damage his speakers because he left the power amp on, and turn of the pre the way you do. When you turn on the pre the load will goes through the power amp and out to your speakers. I damage my speakers twice because the power disrupted.
From "Audio Power Amplifier Design Handbook" 2nd ed. by Douglas Self page 362 final paragpraph:

"Readers of hi-fi magazines are frequently advised to leave amplifiers permanently powered for optimal performance. Unless your equipment is afflicted with truly doubtful control over its own internal workings, this is quite unnecessary. (And if it is so afflicted, personally I'd turn it off now) While there should be no real safety risk in leaving a soundly constructed power amplifier powered permanentley, I see no point and some potential risk in leaving unattended equipment powered; in Class-A mode there may of course be an impact on your electricity bill."
No offense Ezmeralda, but Doug Self can listen to his system how he wants. Regardless of who has how many books published, his thoughts and opinions on the subject are simply that, his thoughts and opinions. Personally, i think that he is FAR more hung up on measuring things than to listening to them. Personally, i do not know how well his designs work, as i've never used, heard or even seen one of them.

I suggest that one try leaving the system powered up and listening as you normally would. One should obviously take precautions when leaving the system unattended, but one should do that anyway. If you don't notice any difference after a few days ( at least 72 hours of continuous power ), then go back to powering it up and down as needed. Nothing lost except for a small amount of electricity and a few pennies.

My findings are that very richly biased AB amps and those that truly are Class A sound best after 2 - 3 days of continuous power. Amps of low bias AB design or models using some type of switching supply typically sound as good as they are going to get after a half an hour or so.

As far as tubes go, i would put preamps into standby mode and leave them on. Tube power amps should be powered down and fired up as needed unless the system is used most of the time.

Obviously, these are only suggestions based on past experience, just like those of Mr Self's. Sean
No do not leave them on all the time. The heat generated will lead to pre mature failer.I have owned several Class A biased amps and they need about an hour of warm up to sound good.Also youd be wasting electricity.
Does "standby" count as being on? I've left mine in standby mostly since I did not want to run the internal fans continuously. I figure that these would be the first bits to go. Any thoughts?
Well, I have tried leaving my Aleph 5 on for extended periods after all of this discussion and I must add that...

It is incredible how removed the amp becomes and music forward after one, two and even three days of power on. I am now sold on not turning off the amp overnight and only turning off for longer than 36 hour periods.

Other than the power bill the only downside I have come to experience is the desire for more dynamics that micro fade after extended power up periods.

In a word how does the Class A Aleph 5 perform after extended periods of power up, Incredible!
Sayas: Thanks for the follow-up. Hopefully, your posting of honest findings based on first hand experience will encourage others to check things out for themselves. It is good to see that, even though you initially thought your system sounded quite good, it sounds even better now. As you've found, it sometimes pays to have an open mind and experiment : )

As to the slight fading of dynamics that you are experiencing, i have to wonder if your amp is receiving adequate aiflow. It sounds as if the amp is running TOO hot, which can make them sound dynamically constricted in my experience. How much open space do you have on top of and around the amp ? I know that the Aleph's are all heat-sink, but anything that you can do to let the heat naturally dissipate through convection will only help the matter. Sean
Sean, the 5 is in a basement on concrete, underpad & carpet and marble slab with nothing surrounding it for 4'. Airflow, cool air is as good as it gets. The listening room is 70F or cooler.
I am confident that the convection factor is as good as I can make it.
Leave them on...most decent Class A amps are designed with this in mind...if you have reservations....and want to turn them off...give them 10-15 minutes of "warm UP" when turning back on...and dont stack other componets on top!
If you have the old MF can make some chicken fajitas while listening to Mahler..awesome!