Concerning solid state equipment, there have been endless discussions of this question over the years, concerning audio equipment, computer equipment, and all kinds of other electronic things, with no definitive answers, even among electrical design engineers (I am one, and I've discussed this question with others).
My own feeling is that the answer will be dependent on the design of the particular item, both the circuit design and the characteristics and quality of the particular parts that are chosen. Doing an analysis to definitively answer the question even for one particular design would be a formidable task, and could only be done if complete documentation on the design were available.
My bottom line suggestion for solid state gear is simply a common sense one -- if you use it frequently (e.g., two sessions or perhaps even one session per day) leave it on all the time; if you don't use it frequently turn it off.
Regards,
-- Al |
I guarantee that ANY electronics will have a much higher failure rate when turned On/Off vs leaving it on.
Your guarantee is a considerable over-generalization at best. For starters, your guarantee totally ignores how often the equipment is turned on and off, how long it is left on when it is on, and how long it is left off when it is off. Your guarantee also evidently extrapolates from your experiences with certain equipment to all other possible equipment designs, part qualities, usage patterns, and environments, which is, to use your term, "bs". All electronic and electromechanical parts, whether resistor, capacitor, inductor, transistor, analog integrated circuit, digital integrated circuit, relay, even printed circuit boards, have finite MTBF's (mean time between failure) if left on all the time. The MTBF is typically non-linear with the age of the component (i.e., older components fail more frequently). New components also fail more frequently, especially if they are not adequately screened and burned in by the manufacturer. As has been noted in some of the posts above, MTBF is typically temperature dependent, and will be shortened as operating temperatures increase. It will also typically be shortened due to the thermal stress of being powered up and powered down repeatedly, which is apparently a key basis of your statements. As I indicated in my earlier post, an analysis that would balance and combine all of these factors for all of the parts in a piece of equipment, and define an optimum power-up/power-down duty cycle for even one specific design, is essentially an impossible task. Most of the responses above, including yours, are based on perspectives that just address a limited number of these factors, for a limited number of part types in a limited number of designs, and understandably don't present any quantitative trade offs. As I said in my earlier post, as an experienced electronics design engineer I believe that the best approach (for solid state gear) is simply the common sense one of turning the system off if you don't use it frequently, and leaving it on if you do. If like many of us you are somewhere in the middle, and use the system neither very frequently nor very infrequently, then you won't be going very far wrong with either approach. Regards, -- Al |
semiconductors, resistors, capacitors etc don't have MTBF (not in our lifetime). They operate practically forever (except electrolytic caps). Not true at all, unless you are referring to a single part operating by itself, which you are not. The combined mtbf of the hundreds or thousands of semiconductor and passive devices (even excluding electrolytic capacitors) in a typical sophisticated audio system will be measured in decades at most, and quite conceivably in years (less than one decade). That is especially true when you consider the sharp increase in failure rate that occurs with older components, according to accepted reliability models, and is even more true when you consider that many amplifier designs intentionally run semiconductors at high junction temperatures in the interests of improving the sound quality. Please take a quick look at some of the 205 pages of MIL-HDBK-217F, linked to below, which is the guideline document for reliability calculations for military systems. Note that it addresses just about every conceivable type of electronic component. And keep in mind also that these are typically components that are manufactured, burned in, tested, and screened vastly more rigorously than anything in most consumer audio systems. http://assist.daps.dla.mil/docimages/A/0000/0005/3939/000000041349_000000020839_BTJRBUHXWM.PDF?CFID=18958726&CFTOKEN=fdbcdd5971174382-FEB22389-1372-548A-D368EF4CD631E514&jsessionid=063010dbe387801aa415Regards, -- Al |
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 |
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 |
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 |
Kijanki -- Good questions.
I don't want to get into non-electronic things, because I'm not particularly knowledgeable about them.
But consider a transistor or integrated circuit. Envision a plot of failure rate vs. component age, based on the assumption that it is being operated within its specifications (not always the case). A plot of failure rate vs. age will start out at some relatively high value (infant mortality), which in turn will depend on the degree of screening, burn-in, quality control, etc. (which is better for military gear than for consumer gear -- one reason consumer gear is so much cheaper). The curve will then go down to a lower level following the infancy period, and remain relatively constant until old age, when it will rise considerably.
What is most relevant to the questions we have been discussing is the middle period, where the failure rate is lowest, and is fairly constant over a considerable number of years (as you have pointed out). If we consider only that period, where the failure rate is essentially constant, then yes, if that failure rate at that point on the age curve is, say one failure per 100 years, and we have 100 components of that type, then we can expect one of those components to fail each year, on average. One set of 100 components may do better than average, and last 5 years without a single failure. Another set of 100 components may do worse than average, and have a failure within a month. But averaged across a large number of sets of 100 components, there will be 1 failure per year per set, based on the assumptions of constant linear failure rate, mtbf of 100 years, and 100 components.
If the failure rate vs. age curve is not linear and constant, such as during infancy and old age, the analysis is more complex. And as I indicated earlier, calculation of system mtbf has to take into account and properly weight the mtbf's of the different types of components, as well as their relative quantities in the system.
Hope that clarifies things more than it confuses them!
Regards,
-- Al |
Is the general consensus that I should keep everything except the tube preamp on at all times due to the high frequency of usage? I'm hesitant to declare that we have a general consensus. But in terms of reliability I would say the diversity of opinion we have seen is consistent with the opinion I expressed that, considering your frequent but not extreme usage patterns, you won't be going too far wrong either way. In terms of sound quality, optimal warmup time is going to be system dependent, and probably listener dependent as well, so if you choose to have your system off during the day see if you notice continued improvement in sound quality following whatever warmup period you choose to use initially. Perhaps this is a bit of an anticlimactic conclusion in view of all that has been said, but I think that any conclusions beyond these simple ones are unprovable, are probably not universal, and in terms of longevity probably don't make a lot of difference anyway. Regards, -- Al |
Also, complex systems are LESS fault tolerant than simple systems. I'd add the words "everything else being equal" to that statement. The complex system might have redundancy and fault tolerance designed into it, while the simple system might not. And I'm not certain that the statement is true even with that qualification. For instance, if anything in the signal path of a very simple amplifier goes, the system doesn't work. Regards, -- Al |
