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gain 28th October 2008 12:06 AM

quick solid state amp question
form a component durability standpoint (especially OPS transistors), when not listing to music, is it better to:

- leave your amp in hot standby (power on no signal applied but idling)
- power it off

i always thought that it was the thermal cycles (heat up then cool down) that wore out components, so i have always left my amps on continuously. but i was talking to a stereo guy i met recently and he advised to always turn amp off because its the heat itself that kills, not the cycling between hot and cold.

which is right?

hitsware 28th October 2008 12:14 AM

If your amp runs (idles) at a comfortable, slight, warmness then leaving it on is better. If it runs real warm or hot (you can get a whiff of warm parts) then turn it off. Amps (like lightbulbs) do tend to blow at turnon so if in doubt, leave it on.

gain 28th October 2008 01:30 AM

hey thanks for the reply. yeah it idles pretty cool when i touch the heatsinks when nothing's been playing for a while i barely feel warmth. just enough to let me know its on. in fact, i use the 3 second rule on all of my amps ... if i can't keep my fingers comfortably on the component for 3 seconds without pain, its too hot.

some may say thats overly conservative but i like my stuff to run cool enough to touch.

Nico Ras 28th October 2008 05:10 PM


Originally posted by hitsware
If your amp runs (idles) at a comfortable, slight, warmness then leaving it on is better. If it runs real warm or hot (you can get a whiff of warm parts) then turn it off. Amps (like lightbulbs) do tend to blow at turnon so if in doubt, leave it on.

I agree with you that leaving an amp on it is always ready to play. My trusty 50 watt class A is hot to touch but has never been turned off in eight years. I guess it will fail one day.:bawling:


Jan Dupont 29th October 2008 05:13 AM

There is a term called "Working hours lifetime" for all components.

It may be better to leave your amp on for a short time (few hours) if you know that you will be listening again very soon, however if the design is made right, the transistors won't suffer from switching the amp On/Off when not listening.

Much worse is it for the electrolytic caps (PSU caps etc.)! These have normally only a working lifetime of 2000 hours, so by leaving your amp On all the time quickly eats up the caps lifetime.

PMA 29th October 2008 11:04 AM

Jan, 2000 hours is at maximum operating temperature, i.e. +85C or +105C, according to type used. At some 40-50C, the cap life time is much much longer.

CBS240 29th October 2008 01:48 PM

What about metal fatigue, would it be an issue particularly the bonding wires that connect the pins to the die? Hot/cold/hot/cold ect will take a toll on the wire bond strength, just like the filament in a light bulb. Incandescence bulbs tend to last longer if they are left on continuously compared to intermittent use. I saw a program once about an old firehouse light bulb that has been on for like 75 years. Nobody dares turn it off because the filament may break from temperature change and age and no one wants to be the one responsible for its death.:D They just don't make 'em like they use to anymore.:smash:

Jan Dupont 29th October 2008 02:02 PM

Pavel :)
You are absolutely right ;)
I was not really awake when I replied to this thread :sleep:

h_a 29th October 2008 02:31 PM

It depends a bit on the amp.

ClassB-amp: no thermal cycling to speak of when switching on/off; only thermal cycling is caused by listening to music. Leaving it on all the time will hurt your power supply caps (as ACD already wrote).

(By the way there's the old rule for temperature: every 10C temperature increase cut lifetime of the part in half. So a 85C cap with 2000 hours lifetime translate into 32000 hours at 45C - in about 4 years permanent on the caps are outside their specified lifetime.)

ClassA-amp: thermal cycling due to Class A; however there's not much benefit again for leaving it on as the caps have to endure high ripple current and higher ambient temperature. Both reduce lifetime.

In short: switch it off at least for the night.

Have fun, Hannes

AMV8 29th October 2008 05:40 PM


I guess I go along with ha and ACD.

In practice I have found that the longest use I have had from a piece of equipment was from a Sony professional tv. That lasted 20 years. If you assume 2 hours per day that gives 600 hours per year ( time off for hols ) or 12,000 hours.

I have also assumed that electrolytic caps dry out slowly over the years and this is exascerbated by keeping them warm. ( find thaty electrolytics last a long time if stored in a sealed plastic bag.)

I switch equipment off at nights.


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