Should an audio system be left on at all times?

You won't fint MTBF on any datasheet of any transitor, diode, IC (digital or analog) etc. - probably because it is in order od few hundred years.

Yes, but when you combine hundreds or thousands of devices into a system, the several hundred year mtbf of an individual device essentially gets divided down by the number of devices (with each device receiving greater or lesser weight in the overall calculation depending on its individual mtbf).

There is an entire branch of engineering that deals with this, known as Reliability Engineering. MIL-HDBK-217F, that I linked to above, provides an inkling of how involved it can be.

Regards,
-- Al

Almarg - when you have hundreds of thousand od devices you increase chance that one, or connection between them, might be faulty. If number of devices should decide alone on reliability then Pentium processor that contains milions of transistors should fail every day. What about system that contain thousand of Pentiums - it should fail constantly.

It is not even relevent to audio gear that contains small amount of components. Stress done to wires inside of IC caused by current flow cannot be that bad since we have some of ICs working (and often in bad environment) for about 50 years (and first ones were poorly made).

If you believe that SS amp is more prone to failure from switching on and off - please tell me what fails!!!
(Don't count cases when you turn system off to modify something - like shorting speaker wires and then turn amp on again with failure.)

Kijanki -- I was NOT one of those who said that a ss amp is more prone to fail if switched on and off -- please re-read the posts I have made in this thread.

Audio gear does not contain a small number of components. A typical high-end system will contain hundreds, and perhaps thousands, of components, especially if you include passive components such as decoupling capacitors (not electrolytics), resistors, etc.

One of the fundamental advantages of integrated circuit technology is that it is integrated, meaning that an integrated circuit containing millions of transistors will have VASTLY greater reliability, and longer mtbf, than a circuit containing a corresponding number of discrete transistors.

A supercomputer containing thousands of Pentiums WILL experience failures somewhere in the system almost constantly, perhaps daily, and a great deal of thought goes into their design to provide redundancy that can overcome the low overall reliability.

If you do not, or will not, understand the concept that system mtbf is reduced as a function of the number of devices in the system, I can only tell you that you are wrong and you should research the matter further, including in MIL-HDBK-217F.

Again, I did not say, and I do not believe, that a solid state amp is necessarily more prone to failure if switched on and off regularly. In fact, most of my previous comments are probably closer to being consistent with yours than most of the comments posted by others in this thread.

Regards,
-- Al

Almarg - Supercomputers don't fail daily, otherwise we would have serious security problems (unless you talking about software crashes). Audio gear does not contain thousands of components - give me example of one. You will be lucky to find one that contains couple of hundred.

What is interesting about electronics commonly used is that if it does not fail in the first year most likely it won't fail for next 20 years (just opposite to MTBF) and when it does it's usually because of lightning or mechanical failure (switch, relay, motor, plug etc).
Hard discs that have MTBF in order of at least 5 years have 99.9% of time mechanical failure in spite of having a lot of electronics (ICs) on them.

MTBF does not apply to audio gear and probably should not be mentioned (unless we try to predict statistical failure in 500 years). Remember saying about lies big lies and statistics? Statistics already has proven that motorcycle accidents are caused by tatoos.

Kijanki -- What I meant about supercomputers was that a failure will occur somewhere in the system frequently, perhaps daily, but the systems are designed with redundancy that allows them to continue to function despite the failure, and while the failure is being isolated and repaired. In fact I believe some of them have associated diagnostic computers, whose only function is to detect and diagnose failures.

When I mentioned hundreds or possibly thousands of components, I was referring to the system as a whole, not to any one individual component. And I was including capacitors, resistors, etc., which these days are very small and can be very numerous.

I don't have schematics for any recent audio components. To some extent I'm extrapolating from my knowledge of computer motherboards, which typically contain zillions of tiny components and are probably somewhat indicative of the digital, microprocessor-based, parts of many modern audio components. But besides that, if you have ever looked under the chassis of a quality analog FM tuner, new or old, you will see many hundreds of discrete components. The ultimate example is probably the Marantz 10B of the 1960's, which I have seen the underside of, and it contains more components than I would want to count.

Your comment about not failing for 20 years or so after the first year is exactly what I was referring to earlier about failure rates being non-linear functions of device age. Failure rates are greatest during infancy and old age. They are much lower during the period following infancy and through middle age. That is well recognized in Reliability Engineering. But my point is that the relatively low failure rate during middle age can still be significant, because it will be degraded at the system level as a function of the number of devices (and potentially also by many other things, such as operating temperatures and the specific circuit designs).

The quote about there being lies, damned lies, and statistics, was actually originated by Mark Twain, and is one of my favorites. I hadn't heard the one about motorcycle accidents before -- good one!

Regards,
-- Al