Life expectancy of Stereomour components

[crooner12]

Hey guys,

Just curious if anyone knows the life expectancy of the Stereomour. More specifically, which parts are more prone to failure (e.g. caps, resistors, etc.) and how long before they need replacement? Are there "service intervals"?

Also, how often should one check the hum balance levels?

Otherwise, it's been several months and my amp has worked flawlessly. Both a testament to the build quality and triple checking my work.

I'm having a lot of fun comparing the Stereomour to "brand name" manufactured amps (tube and SS) that cost several multiples in price, yet sound just as good (or sometimes worse) than this thing. Gotta love the law of diminishing returns!

[Paul Birkeland]

The black electrolytic capacitors have a lifetime somewhere around 20 years (+/-5). 
The volume pot will wear out eventually from general use.  I'd expect this to be right around when the caps are going south.
The Sovtek 2A3 tubes supplied with the kit have a lifetime in the tens of thousands of hours.  I would rebalance the hum pots when you replace these tubes.
The used old stock 12AT7's provided with the kit have a variable bit of life left in them, it could be anywhere between 10,000-100,000 hours.

The rest of the parts may outlive all of us.

-PB

[crooner12]

Wow, so basically I'm good for a while 

[porcupunctis]

I recently pulled an RCA radio out of my father-in-laws closet.  It's an AM radio from about 1950.  I doubt that it has been used in the last 40 years but I know it got a lot of use in the 50's and early 60's.  I brought it home, plugged it in and was listening to a station as soon as the tubes warmed up.

It could use some TLC.  There are some old paper caps in there that I know are not what they used to be and I'm sure the tubes could stand a refresh.  As of now, I plan on leaving it as it is.  A real testament to point-to-point wiring and simple tube design.

I figure my Bottlehead gear will outlast me by a long shot.  Especially if I can find someone in the family that will appreciate them properly.  If they do need any work, it will probably be because of an "iffy" solder joint that I will be solely responsible for. 

The caps may get a little off and the attenuator contacts may get a little scratchy but they will still sing.

One of the reasons I was attracted to the Bottlehead gear was that I was tired of trying to maintain and repair vintage SS amps.  A lot more work and a lot less reward in my opinion. 

Once you get them "right", they just stay that way.  It's like Newton's 4th law:  A Bottlehead amp that works today will keep working for a long, long time.

[earwaxxer]

Like Paul said, we will probably be dead before this stuff wears out. Enjoy it. When our circuits wear out there is no replacement.

[Paul Joppa]

I recently did some studying up on capacitor life expectancy. Traditionally, electrolytic caps are the first thing to go, after tubes. But like tubes, they can last a long time if they are not abused.

For the caps, it's heat that kills. Caps are specified for a certain lifetime at rated voltage, temperature, and ripple current. Most of our caps are specified for 2000 or 3000 hours - sounds pretty bad, doesn't it?  :^)  But that's at 85 degrees C - that's 185 F, which is plenty hot enough to curdle your Hollandaise. At 45C (113F) that's 32,000 hours, or 8 hours a day for 10 years. I have not made enough measurements to make a claim about the under-hood temperatures, but the caps are easily felt to be cooler that the transformer core, and even our hottest transformers are less than 140F (65C). I have designed for 60C under the hood but I think - at least for the more recent amps with cooling slots - 45C is a good guess.

The most serious long-life electrolytic caps are rated at 125C and sealed in welded stainless steel cases. They'll supposedly last a million hours at 45C - and for only $200 each!

Those are of course the predicted lifetimes based on engineering studies. Those who read the papers might have heard about the new Boeing 787 and it's battery problems. The real world does not always work exactly like the engineering models.

[Comity]

Hi Guys....I am the audio nut who after hearing my friend Andy's Stereomour (which he hauled almost 1000 miles to my house) knew right away that it was a special amp and I built one over the holidays.  I couldn't be happier!!.  Anyway, your discussion of component lifetimes reminded me of a question I have regarding cap lifetimes.  I am using  Klipschorns that were made in 1978 (incidentally they were from the estate of Bill Johnson of AR) but used very little.  I have been told by several people that I should replace the caps because of their age and that the caps 'dry out' over time.  These speakers were like new when I got them and were obviously rarely played, so if it is a function of use then they obviously wouldn't need to be replaced.  Any opinions?

Thanks,
Greg K.

 

[Paul Joppa]

It depends on what the capacitor is. If it's nonpolar electrolytic for example, then it is built to leak very very slightly, so that the hydrogen can escape when the dielectric repairs itself. That means the electrolyte will eventually leak its water molecules as well.

Some other capacitor types were not built  to last decades - paper in oil that is not tightly sealed for example. Most modern capacitors are better built because of advances in plastics.

There is an active forum on the Klipsch website, and I believe Bob Crites is a well-regarded source of crossovers, parts, and good advice. Here's a link from that site that you might find interesting; I believe from the dates you have teh Type AA crossover:

http://www.critesspeakers.com/rebuilding_a_set_of_type_aa.html

I have no connection and no Klipsch experience myself, just going on what I hear around the web.

[Comity]

Thanks Paul for the information. I will check out the Crites Speakers site and also figure out what type of caps I have in the crossover.  I would think a change in caps should be very straightforward.

I really appreciate your input.

Greg

[corndog71]

Rebuilding your crossovers is a great idea and a cheap way to breathe new life into your old speakers.  I've refreshed a pair of Klipsch Heresey IIs with new crossovers.  You can expect a clearer presentation, better resolution, and improved dynamics.

I second recommending Bob Crites. 

[Comity]

Thanks Rob...I appreciate your input.  It sounds like that is next on my list of upgrades!

Greg

[Follow the white rabbit]

Hi, I put a 12V fan (ran with 10V and very quiet) under the hood to cool everything down! The resisters do radiate heat and this heat goes to the caps and all...

[Chris]

Ok, so this kind of answers my question.. I am planning to make a computer sytem based around the Kef LS50 speaker.. I just heard it and it is superb.. I would love a stereomour for it but i was worried about the power, however, after seeing the video of the guy playing his through NHT super zeros and it was plenty loud, I think power wont be a problem.. i will be playing nearfield and quite low so not be distracted when working on the computer.. the other concern is about just burning up 2A3 tubes and thus money only for mainly low volume music "background" really... But it sounds like i may get not 2 thousand hours , but maybe around 10 thousand hours on the tubes, if that is the case, then the worry of throwing money out the window for "overkill" sound quality is not a factor then...solid state may be the most practical for this application, but, I just cannot bring myself to do it.. The stereomour is such an incredible value and the thought of a 2A3 amp doing computer music duties is too good to pass up... Does the amp heat up a room much?

[Paul Birkeland]

Does the amp heat up a room much?

If you put the amplifier in a closet, it will heat up the closet.  In your listening room, you will heat up the room more than the Steremour.

-PB 

[Chris]

Dammit Paul, how did you know I was fat??!!     Ok, thank you , Great news then... This is why, I ruled out the Pass gear (class A solid state) and any OTL (Lots of tubes) type amps cooking me nearby... The stereomour is just the screaming choice for computer nearfield applications FOR ME... Thank you again