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2. See Number 1
3. Excessive heat can damage anything electronic. Pure Class A really produces heat.... I had an extremely modified old Sumo Nine, it is Pure Class a, Meaning no sliding bias or current and it stayed in Class A at all power levels regardless of impedance... This thing could fry an egg... I vented it and changed the fan and still left it on... Until my house was struck by lightening, it was great.
I think it is a little complicated for a categorical response.
Semiconductors do not like to be switched on and off. Neither do they like to run really hot, and some heat sink compounds can dry out.
Electrolytic caps (aka power supply caps) do not like to be turned off and on. But they really hate being hot.
All told, I think that turning on and off is better for a unit that runs hot. Especially if heat is inconvenient, or you don't own the power company.
I turn off my preamp and cd player, but leave my mono amps on all the time. The reason is that keeping the amps on causes a small amount of current to go to the speakers and acts as a 'sealing current' to the connections. The mono amps do not run hot and they are in a cool environment. The preamp and cd player take some time to warm up, but don't seem to be affected by not being on for extended time frames.
I think it really depends on what you mean by on and off. Turning your equipment on and off several times a day can not be good for it. Turning your equipment on in the am when you get up then turning it off when you go to bed, i feel is much better. I leave my solid state pre amp on all the time it does not have a stand by unless i am out of town i power it off. The same with my disc player. The screens on both units are set to go off 15 minutes after the music stops. so there is no screen burn shadow on them. The amp is in stand by if not in use and is off when out of town. I was all ways told turning them on and off does more damage than leaving them on as long as they do not run real hot. plus they sound a lot better when they are fully warmed up to go. I talked with Mark Levinson and Esoteric and this is what they recommend to me.
I have another slant on this issue. I pull the plugs on all my equipment when I leave for an extended period of time. I live in an area that is prone to severe lightning strikes and no surge protector is sufficient to prevent the dreaded blue smoke. I imagine I am shortening the life of some components of my gear but I think the trade off is worth it.
Got some good answers here. Thanks guys. Yeah, I agree it's all about the trade off. Since I almost exclusively using the units over the weekend, I believe you'll probably agree it's a good idea to turn them off over the 5 week days and turn them on Saturday morning, then, shut them off Sunday night. What I meant by "completely turning them off" is switching off the power conditioner, thus equivalent to pulling the plug. We do get thunder storms here often too in central Illinois. I think this way I minimize the heat problem, chance of electric shock, while also minimizing having to turn them off and on during the weekend.
Thanks again guys, appreciate the help.
Life of electrolytic caps is shorten by the factor of 2 for each 10degC temperature increase. It is simply drying out of electrolyte. Turning amplifier on often produces rush current, but heat amount from that is negligible. Simply, your amp will last longer when you turn it off. Also, life of semiconductors does not depend on how often you switch. The only case I know where semiconductors are getting "tired" are big SCRs (Thyristors) in welding machines. They go thru some structural changes caused by huge temperature gradients. It does not apply to small current devices. In class D amps power Mosfets are switched ON and OFF 500,000 times a second. The only drawbacks of switching on and off is shorter life of the switch (not important with a few cycles a day) and warm-up time to get the best sound.
As much as what you quote overall is true. I have found that when large filter caps are getting old, that switching them on and off very much affect their life span. When they get old, keeping them charged helps keep electrolyte from leaking and they maintain their spec very closely. Once a cap degrades to a certain condition, it is then that cycling them can damage them. I hope this makes sense. Tim
IMO the bottom line on the many tradeoffs that are involved, which certainly figure to be dependent on the designs of the particular components as well as on the particular usage patterns, simply comes down to common sense:
If the system is just being used a couple of days per week, as is the case here, and especially given that the system includes an amplifier that runs hot even in standby mode, as well as a hot-running preamp, turn it off on the rest of the days.
In situations that are at or near the other extreme, where the system is used multiple times on most days, and where everything in it is cool-running, leave it on continuously.
In circumstances that are in the middle ground between those extremes, and if the manufacturers of the particular components do not provide any specific guidance in the manuals or otherwise, flip a coin :-). It may not matter much either way.
The explained tradeofss in this thread easily compensated by owner's convenience and smaller electrical bill not only from audio power outlet, but from climate control unit as well.
If you're worried too much on healthy life and dieting as per analogy, there are also always trade-offs. I'm holding in my left hand fresh smoothie made of fresh berries and fruits not too long ago picked from farm and no sugar added; my right hand however is holding extremely tasty and sweet muffin that maybe for sure fat and having LOTs of sugar. Together it's called balance.
Czarivey, life of capacitor is reduced by factor of two for every 10degC increase over temperature that life of capacitor was specified by manufacturer. For instance capacitor rated 5k hours at 85degC will last 2.5k hours at 95degC 1.25k hours at 105degC etc, but also 10k hours at 75degC, 20k hours at 65degC, 40k hours at 55degC. At 25degC (room temperature) it would be 320k hours (37 years). Different manufacturers define end of life differently but often it is 200% of rated ESR. When capacitor dries out ESR (equivalent series resistance) increases. Increase of ESR produces, with electric current, increase in temperature. Increase in temperature produces increase in ESR leading to avalanche effect and explosion.
Timlub, I'm not sure why keeping them charged stops them from leaking. Perhaps some capacitors are not properly sealed, to start with, and would eventually leak. Keeping them on will most likely increase their temperature (since electronics dissipates heat) drying out electrolyte faster, hence thickening it (and reducing capacitors' performance). Company I work for has a lot of obsolete electrolytic caps in stock, often 30 years, and I never heard of any of them leaking. They are unusable, in my opinion, but it is not my decision to toss them out. Keeping fully charged might extend life of some batteries, but not capacitors AFAIK. The only negative effect turning electronics off is reduction in breakdown voltage of the aluminum capacitor. Without voltage electrolyte eats out dielectric - aluminum oxide, reducing breakdown voltage. Presence of voltage rebuilds dielectric. We're talking >5years of keeping gear unpowered.
I am only speaking from personal experience and the way my feeble brain see's it. I've been around a whole bunch of Amps being built and modified in my time and have developed my perceptions.
When caps are charged and the electrolyte is active within them it somewhat pressurizes the inside of the cap. This pressure helps maintain the seal along with the electrolyte keeping the seal from drying out.
The problem comes when a cap is powered down and seals weaken.... I have seen caps leak.. or even explode when suddenly powered up. It is for this reason that on very old gear that hasn't been run that we always have brought their voltage up slowly on a variac to reform the caps and to protect the amp. It has been a problem is a few brands.... I believe that Mark Levinson had this problem at one time.
Again, this is simply my feeble perception... I'm a speaker guy.
Timlub, caps unused for very long time, as I mentioned before, loose their rated breakdown voltage, but it takes very long time. Caps might explode because of this, but often when caps are getting very old and dry the avalanche effect (High ESR=heat, heat=higher ESR), can build-up pressure and explode the cap.
I'm not sure if charged capacitor has more pressure inside, but I'm pretty sure that warm capacitor does, so it might improve the seal, I agree. I've seen few capacitors leaking, but it was decades ago when capacitors were not up to current design, materials and production standards.
Also, there were some very poor quality electrolytic caps made in China few years ago exploding in computer power supplies. I would not be surprised to find them also leaking. A lot of parts are made in China, including pretty much all ceramic caps and quality is excellent, but some Chinese companies might take shortcuts. I would feel safe with electrolytic caps as long as the are branded by well known companies. That way my home state "Illinois Capacitor" (now part of Cornell Dubilier) might have factories in China still being very reputable company.
The reason electrolytics need to be brought up slowly after a long sleep is because they will exhibit leakage current which multiplied by whatever voltage will produce some watts of heat. I dont think ESR is the main factor in caps exploding. It is best to form caps with a constant current which is sized to the cap. You can then watch a 350 volt cap charge rapidly to 200, slow down and grow to 350 in several minutes and then past its rated voltage to its surge voltage where things stop. Good caps can have this top voltage be 20-50% higher than the rated voltage. What voltage a cap was made to is not always what is on the label. I talked to an old timer at P R Mallory and got the good scoop on all this. Its the water in the caps that turns to steam that causes them to explode. Its also this water that dries over time and increases ESR. But even is ESR doubles I would not think that is a big contributor to heat.
When you form a cap you are actually rebuilding the aluminum oxide layer to its original level. BTW this is why high voltage caps cost more because they need more plating time in the bath when being made. The plating process slows and cuts itself off at about 600 volts. That's why you dont see higher voltage caps. The surge has to be about 20-30% higher than the operating voltage for several reasons.
I use a current of about 1 mA per 100 uf. depending on the physical size and the voltage I am going to. My examples are higher voltage because I make tube amps.
Brown tolex and knobs, and weirdly somewhat underpowered not quite matching the supposed output rating…I've seen this exact thing in other Deluxes of that model, consequently it made a great recording or harmonica amp (miked of course), but even with an efficient speaker (like a JBL or Altec) you couldn't use it with a drummer unless it was pointed right at your head. A real grease fest with great tremolo.
The Deluxe was suppose to produce 28 watts, but at what percent distortion? The cream and brown tolex Deluxe had somewhat different circuitry than the later black tolex (but still blackface control panel) version, with more overdrive/tube distortion at the same volume. It’s loud enough with the "right" drummer---like me ;-). I worked with a couple of guys who wouldn’t play out of anything but a Deluxe, Evan Johns being one (playing a Tele). The Deluxe Reverb had a tube tank, but the stand-alone Fender Reverb unit was better. They’re worth a lotta money now. I played with a guy whose set-up was a reverb tank into a brown Tolex Pro, halfway between the Deluxe and Twin, an amp I really dislike. Too loud, very piercing. And I have the tinnitus to prove it!
Guitar amp power is usually measured at 5% THD. At low powers they can be quite clean. The older brown face Fenders were really clean. This was before Hendrix and the craze for overdrive, which is just another name for clipping/limiting, turning everything into square waves. If you know how a limiter works in an FM tuner, thats what they did.