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I have a Krell KST 100W amp and KST Pre amp with internal phono stage, all solid state. They date back to 1992. I really wonder how well these guys age. That's 24 years. I notice little things like the channel balance being a bit off but that is also source dependent. Scratchy pots. The left channel cannot be shut off completely, so even with the volume at zero I can still hear music through the left (but not the right) channel. And I have read the capacitors especially can lose their spec qualities over time. What I can't do is go back in time and compare them to a brand new amp. It would be simple enough to simply compare them to new amps on the market but we all know where that might lead!
Along those lines my DAC is also the same vintage, a Theta DS Pro Prime II. I imagine that in addition to component aging the technology of DAC's has improved over the years.
If I decide to shop (listen) around I am most interested in modern integrated solid state amps like the Hegel and Quad with high power outputs and built in DAC's which can also play high res downloads. This is something I have no experience with.
Speakers are Harbeth SHL5+ sources a VPI TT and Musical Fidelity transport. And maybe my Mac Air.
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All electronics age.
Oil caps may 'dry'. PS caps are generally conceeded to have a max life of 30 years.
Semiconductors, both power and stuff like opamps and CPU are subject to a phenom called ElectroMigration. This is when the current basically carries some metal along WITH it. Where current density is at Maximum, so too, is the effect. Eventually the current 'fuses' the thinning connection and the device fails.
Proper fabrication (including design) and lifetime testing by the device manufacturer ensures a long life. But not 'forever'.
I would NOT worry about semiconductor lifetime.
Copper will oxidize and turn green. Copper Oxide is a semiconductor and nasty.
Some parts may absorb moisture over long time periods and have 'value' changes which effect OTHER devices, stability and performance.
Photo Diodes have a fairly short lifespan, when used as 'laser pickups' in the likes of CD players. I do NOT know what the particular failure mechanism is. You may also have proble with the LASER LED. Same issues.
All that being said, my OLD Kenwood KA-7100 which I bought in the late / mid '70s is still being used by my nephew. I want it BACK but don't know how to pry it out of his hot little PAWS. My Garage needs MUSIC!
Too much is never enough
I would tend to agree that every 10 years, one should "service" any power amp.
Here's some information on Harbeth's website regarding amp aging..
An often overlooked characteristic of power amplifiers is 'ageing'. That means that the performance of the amplifier will permanently drift away from the 'as new' specification with the passing of time due to the ageing characteristics of the components especially when the amplifier runs hot.
Amplifiers should be re-tuned during their working life - perhaps every 5-10 years? - to be sure that the frequency response, distortion and noise specs are as intended. Some designs have self-tuning circuitry and are less effected by ageing, but wet-type capacitors do inevitably dry out and this can not be fully self-corrected. Vintage amplifiers can be great fun to own but common sense says that after 25 or more years all electronic systems need specialist servicing to return them (close) to original specification.
Generally, the better built the amplifier (solid state or tube), the better they will handle the aging process.
Still, an electrolytic cap will usually last 20-30 years, no matter how well built the amp is.
Steve
In theory at least :-) Power Supply Caps DO age /time out... 10/15 years is a good life span expectation.
Especially those that run Class A.
Also the rectifier diodes need replacing with a PS recap.
That said: Caps and Diodes are Cheapish
Foolish not to renew them
If they are designed conservatively and don't have heat issues, they can last indefinitely. Many studios have mic preamps, consoles, and amplifiers from the 1970s that are still making great recordings.
Forty-year-old Neve mic preamps stand up to anything new. Electronics in the great Studer tape decks have not been bettered and, providing the electrolytics are replaced every 25 years or so, sound just like new. The great Mac and Marantz tube amps can sound great for decades to come.
Tube gear should last forever, providing the trannys aren't damaged from misuse, and the 'lytics are updated. S/S gear can be a problem when transistors fail, as there are some transistors which are no longer made and for which there are no substitutes. It's pretty rare though - you can *almost* always find substitutes.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
Solid-state amps don't "age" like tube amps. As with all electronics, though, the greatest enemy is heat. As long as the internals get adequate ventilation, it's likely that cleaning pots and jacks is all you'll have to do on a solid-state unit.
If there's failure, though, it will be unmistakable. You won't have to guess.
I have a 44yo Lafayette amp I got when I was a kid. I've had to do 2 maintenance chores on that amp since 1972: replace a fuse and clean the pots. That's it.
I laugh when I hear latter-day tube fans ask, "Gee, why did the audio world switch to solid-state tech?" Why do we have quartz and LCD watches now instead of the wind-up ones that have to be periodically fixed at the jeweler's?
[Anticipated response from some Inmate: "Well, I've got a wind-up watch from the Wars of the Roses that keeps time better than any atomic clock! Because I say so and, anyway, you have to look beyond the measurements! You are SO BURNED, man!"]
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It's amazing that hipsters who insist they can hear sampling remnants in interpolated 24/96 digital waveforms can somehow fail to detect surface noise from their own vinyl LPs.
I have a Krell KST 100 too, same vintage and never a problem. I go through the amp every 10 years and do routine maintenance. You see people who use McIntosh amps for 40 years and they're still running, if you maintain it why not Krell? If you had a 1992 car and just put gas in it and never serviced it would you expect it to run good as new? Sure you can throw out your gear every 10 years and buy new but this hobby is about music not buying gear.The other point is you're right Krell does make class A amps and they do run hot but the KST 100 isn't one of them. The KST 100 is a class A/B amp it runs warm not hot. The difference is you can leave your hand on top of it indefinitely with no fear of getting burned. In addition it has adequate heat sinking because it was designed right. Give it adequate ventilation and service it and it WILL out last you.
Edits: 02/07/16
Yeah, it is unbelievable how hot the KST amp runs, and for all these years too.
Wait till you need a new FET or BJT. Solid state parts go in and out of production about as frequently as computer CPU's, so it wouldn't be the caps I would worry about!
That's why I stay away from Class A solid state amps! :)
My Edge M8 was damaged by a GAS Theadra preamp back in the early 2000s. The preamp passed a high DC Offset of -2.7vdc that took out the whole output stage. The output transistors were the Toshiba 2SC 3281 and were out of production. The Edge technician said they couldn't get the original parts any more cause Toshiba stopped making them. So he replaced them with the ON Semi 2SC 3281's they sound just as good as the original Toshiba's.
So there was replacements but just from another manufacturer. The 2SC 3281 is a bipolar transistor though. If it had been a lateral mosfet output stage I really would have been in a serious bind. Those would have been nearly impossible to find in to have had the output stages replaced. My Edge M8 is the original black model that was made back in the 90's.
You guys need to understand the SemiConductor industry. A company will begin manufacture of a than NEW device. Sales go up and new circuits are designed and utilize this new device. Production of the device at some point plateues and the company may stock or the distributors maintain a stock of spares. Production levels off to actual demand.
At some point the line of product is NOT profitable or falls below the profit line of the original company. THAN the line is sold to a 2nd string manufacturer.
International Rectifier did just that about 5 or 6 years ago. Certain products had a lower than desired profit margin. They sold the ENTIRE LINE of dozens of devices and the underlying PROCESS ot Vishay. We built stuff FOR Vishay for maybe a year than we did what's called a 'build out' where we slowly turned OFF the line. At that point, the entire 40,000sq ft facility was gutted and re-equipped for NEWER and more profitable devices. That process took maybe a year or MORE. At one point, I had responsibilities at BOTH end of what was about a 2 acre (90,000 sq ft) fabrication facility.
We had a piece of equipment which had a special DELCO transistor. I have NO idea who made it, but it was a PIA to get replaced. The 'new' part number was made by somebody else but it was NEVER quite the same.
You also need to understand the difference between a DEVICE and the PROCESS. A Device is made using a process. That process with SLIGHT variation (like implant dose) can be used to make DOZENS of different devices. Take 'em apart with like a SEM or other reverse engineering and you will see they are ALL similar. But ALL made on the same line with the same equipment using the same or related recipes.
When replacing something like ONE of pair of output devices, I'd replace BOTH. For multiple output devices, I'd replace ALL. Different manufacturers may optimize the process for a different parameter and while the devices MAY work in the same circuit, ONE-AT-A-TIME, it is possible that another measurable is far enough off between the original and remade that it could cause a problem.
Too much is never enough
How hard you push them. I know Krell amps run in class A and should be serviced every 10 years to be safe if using them quite often. Class A amps run hot and in time wears out the caps and other components internally faster than class A/B ampsYou should have your Krell gear service and brought back up to like NEW operation.
I have a friend that has the Krell KSA series and he is having all kinds of issues with one of his mono blocks but he can't afford to have both of his KSA amp sent back to Krell for servicing plus the cost of bringing them back up to spec.
Edits: 02/06/16
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