The reason I ask is because I'm setting up a bedroom system and I'm using a Sherwood S-5000. I used to use this in a larger room with efficient Klipsch Quartets, and was able to get decent volume out of the speakers while keeping the volume knob fairly low on the Sherwood. I would like to use it with a pair of inefficient speakers (AR 4x) as they fit much better in the bedroom, but are much less efficient. I have to turn the volume knob up halfway, instead of a quarter of the way to get the same volume with the Quartets. Is pairing a tube amp with inefficient speakers harmful to the amp, and does having to increase the volume on the amp wear tubes out any faster? Thank you
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Does higher volume wear tubes faster?
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Just enjoy it. You should be good!
If you were to operate the amplifiers at continuous power output levels that on average represents 75% of the amplifier's capability versus the same amplifiers only developing 10% of it's capability on average for the same period of time, then the tubes would be expended earlier all else being equal, at a rate that would be noticeable. After all, for the amplifiers to produce more power output, the tubes have to conduct more current, so there is a definite relationship between output tube current flow and power output, although it is not exactly a linear relationship. For your purposes however, unless you're going to keep the neighbors awake night after night till all hours of the morning with disco music sound levels, I wouldn't give it much thought.
Dave
Dave
linuxslate
Well-Known Member
Here's one, possibly over simplified, way to think of it.
The cathode has to be hot in order to efficiently boil off large quantities of electrons. That is what the heater (filament) does. The heaters account for the vast majority of heat in a tube amp, and thus the electrical power used.
The rest of the power and heating is basically the same as a transistor amp. I'll even go as far as to say that it is more efficient than a classic BJT (Bipolar Junction Transistor) -- more like a MOSFET. (A MOSFET in a regular analog circuit. I'm not talking about class-D.)
Also, for those out there thinking about commenting, the explanation is clearer in the case of a push pull amp (tube or transistor).
A transistor amp run at high power will run hotter than when run at low power, and thus reduce the life of the power transistors.
In a tube amp, the plate is unintentionally heated by it's proximity to the filament, but it is also heated by the current running through it. Just like the transistor, this current is due to the program content (music) ( and bias). The louder the music, the more plate current from program content. But in a tube, the part of the plate heating from the music content is a small fraction of the total temperature.
The cathode has to be hot in order to efficiently boil off large quantities of electrons. That is what the heater (filament) does. The heaters account for the vast majority of heat in a tube amp, and thus the electrical power used.
The rest of the power and heating is basically the same as a transistor amp. I'll even go as far as to say that it is more efficient than a classic BJT (Bipolar Junction Transistor) -- more like a MOSFET. (A MOSFET in a regular analog circuit. I'm not talking about class-D.)
Also, for those out there thinking about commenting, the explanation is clearer in the case of a push pull amp (tube or transistor).
A transistor amp run at high power will run hotter than when run at low power, and thus reduce the life of the power transistors.
In a tube amp, the plate is unintentionally heated by it's proximity to the filament, but it is also heated by the current running through it. Just like the transistor, this current is due to the program content (music) ( and bias). The louder the music, the more plate current from program content. But in a tube, the part of the plate heating from the music content is a small fraction of the total temperature.
Retrovert
Addicted Member
Ummm, no.
Power transistors do not have lifespans reduced by from higher power output PROVIDED the junction temperature remains within design limits.
I am specifically ignoring over-current situations from poor design such as thermal runaway, junction melting, junction damage from electrostatic discharge. As well as physical failures in packaging, including tin plating growing whiskers inside a transistor housing, nichrome links regrowing in fusible link PROMs, electromigration, etc.. The lifespan of a transistor is essentially forever. The power rating for a transistor is a function of temperature and thus die size, color inside the lines and the device will never fail because it passed high current.
The lifespan of a transistor, particularly in an integrated circuit, may be significantly reduced, even significantly so, by excessive heating; e.g. overclocking in modern processors. Such transistors are far from power devices used in audio, and are quite fragile. Fragile junctions may be punctured by ESD, damaged from overcurrent (particularly sourcing current vs. sinking), excessive junction temperature, etc. Germanium devices are well-known to be subject to thermal runaway, i.e. resistance falls with temperature so the device better conducts the hotter it gets, raising its temperature until failure. A MOSFET may be damaged by spikes in junction voltage. Even bipolar transistors may become hot enough to physically crack the die. Radiation will also degrade transistors, as can be seen by the short lifespan of the remote-control cars and robots used to navigate Chernobyl and Fukushima. Integrated circuits can suffer from electromigration, i.e. metal atoms are physically dragged from high current, similar to electroplating. Such movement increases with current.
But as long as a solid-state device is not operated in an environment deleterious to the junction (heat, ESD, radiation, etc.) the lifespan of the silicon is forever. This includes transistors used in amplifiers. What kills solid-state equipment is the failure of electrolytic capacitors, devices with notoriously short lifespans which further exponentially degrade with heat.
As an example of how solid-state devices function in extreme environments, consider that Voyager 1, built in 1977, is still operating FORTY-TWO YEARS LATER. It will finally die when the Radioisotope Thermoelectric Generators (RTG) finally run out of power, not because the transistors "wore out". This is a tribute to the quality of American engineering and what humans can build when permitted. All of the transistors are run well within the design limits.
Power devices operating inside the design rating do NOT degrade with use or power output. This is the great advantage of solid state: it never wears out.
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Destructor
Super Member
Voyager will eventually begin sterilizing imperfections.
Interesting Retro -- So the 100,000 hour rating so often seen for SS devices must be akin to the expiration date on Twinkies -- put there to satisfy some bureaucrat's job description, but actually will last forever when handled properly.........
Dave
Dave
I'd play a 500 year old Solid State Amp or receiver, but eat 500 YEAR OLD TWINKIES???? NO WAY!! The Last ones I ate were in 1976 and I still have the DUNLOP that was the Result.
Retrovert
Addicted Member
To clarify I did not address the entirety of solid-state devices in all circumstances. I wrote, concerning transistors:
The lifespan of a transistor is essentially forever. The power rating for a transistor is a function of temperature and thus die size, color inside the lines and the device will never fail because it passed high current.
I did not, however, address LEDs, rectifiers, MOVs (which soon fail), etc. More on those in a bit.
If transistors really failed after a mere 11.4 years of solid use we'd damn well know about it. A crash plan would have been developed to replace those pesky and unreliable devices. Because planes would be falling out of the sky, medical devices would be failing, and phones would not work, etc.
Look at large-scale transistorized installations which run 24-7-365, such as the phone company, air traffic control system, military systems (including air force and navy), and, oh, the list goes on and on.
Utterly bogus expiration numbers are placed on products to evade lawsuits and make more money. Drugs and nutritional supplements are like the latter. Most never expire. (Aspirin, however, sort of does. The acetyl group cracks off in the presence of moisture to yield salicylic acid and acetic acid, i.e. vinegar. But it isn't clear that the tiny amount which has degraded is an issue; the salicylic acid is irritating to the stomach and causes greater bleeding. The human nose can detect vanishingly small amounts of acetic acid.)
Now, LEDs are a different matter. Over-driving a solid-state LED with excessive current or voltage increases light output but decreases lifespan. This is routinely done. Most LED bulbs fail after maybe ten thousand hours, well, the light reduces to 50% of nominal, because the junctions are overdriven (excessive voltage or current) to increase lumen output, poor thermal management increases the junction temperature (biggest part of an LED bulb is the heatsink), the packaging materials degrade, the seals are poor permitting the ingress of moisture, etc. Plus the ones which contain capacitors have those fail. Organic LEDs, such as those in OLED TVs, degrade from oxygen and moisture. This is why I have not yet upgraded to an OLED TV. Well, that and the cost is rapidly dropping.
I studied this when trying to understand LED ballasts for the tubes I used to replace my fluorescent plant lights. (I am growing tropicals, not weed, so no need to call the DEA on me.) The lumen output and lifespan vary with the ballast. I eventually opted for the 105% ballast to up the lumens / watt, as the bulb cost is quite low and will be even lower in another five years. The ballast for two bulbs cost twice as much as the bulbs.
The MOV which is solid state, being a metal oxide, fails because current paths through the device from voltage spikes create lower-resistance paths. Over time the resistance drops low enough to conduct at mains voltage, not merely excessive voltage.
Rectifiers which are run with excessive voltage or current also suffer junction damage, just like transistors will.
But properly manufactured transistors, i.e. not Chinese counterfeits, operated well inside the design specifications so the junction doesn't overheat? If those actually failed after 11.4 years, we would know about it.
Retrovert
Addicted Member
Fish have circadian rhythms and need downtime, as do the plants. On my tanks I use a standard timer for about 10 hours of daylight.
Retrovert
Addicted Member
It's not the oxygen, it's the water vapor because it permits oxidation of the metalization layer and the lead in the solder. Without water vapor the oxygen isn't an issue.
Epoxy resin is oxygen permeable, so if oxygen truly were a problem we'd see failures in plastic-packaged transistors and plastic-packaged integrated circuits, and we do not.
The germanium transistor failures from the 1960s resulted from the growth of tin whiskers on the interior plating, not oxidation or corrosion, or failure of the germanium itself. Amazing how the lies and fabrications of one professor resurrected that ancient demon and needlessly filled landfills with electronic waste.
Epoxy resin is oxygen permeable, so if oxygen truly were a problem we'd see failures in plastic-packaged transistors and plastic-packaged integrated circuits, and we do not.
The germanium transistor failures from the 1960s resulted from the growth of tin whiskers on the interior plating, not oxidation or corrosion, or failure of the germanium itself. Amazing how the lies and fabrications of one professor resurrected that ancient demon and needlessly filled landfills with electronic waste.
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I've had silicon transistors in assorted packaging from the 60s get noisy. Not sure if it was moisture, or eventual failure because of impurities in the materials used to build it 50 years ago, abuse, or whatever. I expect that what NASA put in Voyager is a little better quality than what Sherwood put in their early integrated amps though.
Retrovert
Addicted Member
Are you certain it is the transistors and not the passive components, i.e. resistors and capacitors, which are noisy or out of specification?
To what heat stress were the transistors subjected? What were the current and voltage relative to the datasheet?
What was the original noise? Where are the measurements?
Lots of unknowns.
Again, if transistors were actually decaying over time papers would be published on the subject. The aerospace and military users would have standards governing transistor replacement to prevent mission-critical failure, particularly for avionics. None of these apparently exist!
Where are these (missing) peer-reviewed papers showing small lifespan for transistors?
To what heat stress were the transistors subjected? What were the current and voltage relative to the datasheet?
What was the original noise? Where are the measurements?
Lots of unknowns.
Again, if transistors were actually decaying over time papers would be published on the subject. The aerospace and military users would have standards governing transistor replacement to prevent mission-critical failure, particularly for avionics. None of these apparently exist!
Where are these (missing) peer-reviewed papers showing small lifespan for transistors?
linuxslate
Well-Known Member
Not all consumer (or worse) grade SS electronics have adequate heatsinking, and not all transistors have good coupling from the junction to the case.
I've replaced lots of horizontal output transistors in early SS TVs. I've also replaced numerous examples of those MOSFET audio amp ICs in professional sound equipment, and the 12vdc amps that the other kids used to like to put in their trunks.
I made a good living regularly replacing banks of power BJT's in large laser power supplies -- and in some cases they were on water cooled heatsinks.
Yes, it's gotten better in the last few decades.
Yes, there are XXX Billion transistors in an Intel Core i7. If each transistor had an average failure rare of 1 in a thousand years, a brand new i7 wouldn't last 10 minutes. I get it with respect to the statistics Retrovert is referring to.
Never the less transistors (specifically BJT's and power MOSFET s) in consumer electronics (not rad hardened, selected lot, aerospace stuff) will fail sooner if run hard and hot.
I've replaced lots of horizontal output transistors in early SS TVs. I've also replaced numerous examples of those MOSFET audio amp ICs in professional sound equipment, and the 12vdc amps that the other kids used to like to put in their trunks.
I made a good living regularly replacing banks of power BJT's in large laser power supplies -- and in some cases they were on water cooled heatsinks.
Yes, it's gotten better in the last few decades.
Yes, there are XXX Billion transistors in an Intel Core i7. If each transistor had an average failure rare of 1 in a thousand years, a brand new i7 wouldn't last 10 minutes. I get it with respect to the statistics Retrovert is referring to.
Never the less transistors (specifically BJT's and power MOSFET s) in consumer electronics (not rad hardened, selected lot, aerospace stuff) will fail sooner if run hard and hot.