In article , John Phillips
wrote:
In article , Trevor Wilson wrote:
... Having said that, it is likely
that your Krell probably uses 105oC rated, computer grade main filter
caps (100,000 hours). I don't know about all the other caps, though.
Your Audiolab uses bog-standard, 85oC rated, 10,000 hour caps. How
long is 8 years, again?

To be fair, however, at 65 C ambient that 10,000 hours becomes about
40,000 hours (circa 4.5 years) for an 85 C rated electrolytic. At 60 C
it's up to about 56,000 hours (circa 6.5 years). Even that's too hot to
touch and I sincerely hope idling temperature inside a reasonable
non-class-A power amplifier isn't hotter than that.

I only have a sample of two to test but neither exceeds comfortable
external touching threshold at idle (or even in moderate use) so I am
fairly sure the internal idle temperature will not exceed 60 C [1].

Not sure of the current safety regs. However, in my day (my ghod, I must be
getting old to be able to write that! :-) ) BEAB required that no external
metal bits got too hot. Hence for the amps I tend to use the heatsinks in
normal use never get above about 35 dec C, and IIRC have thermal trips for
60 C.[1] The main heat source in use tends to be the huge transformer in
the middle of the box, and a few dropper resistors for some dc rails. No
idea how long the caps will last, but they have done 20+ years so far. I'm
keeping my fingers crossed that they will last a fair while longer. The tap
always drips in the plumber's house. :-)

Above said, one I bought second-hand had clearly had a cap failure some
time in the past. The give away is the pretty-coloured 'crud' in some
places on the internal metalwork. :-)

Of course my understanding is that the "failure" mechanism is a gradual
reduction in capacitance with time. For unregulated PSUs (i.e. for my
amps) the circuit has to cope with significant ripple voltage anyway, so
the degradation should, by design, not be great.

There may be a problem, though, that the leakage current tends to rise as
the cap deteriorates. This tends to lift the internal temperature and
provoke further deterioration.

Slainte,

Jim

[1] The IHFA (USA) used to require an amp to do 1/3rd full power sinewave
for an hour to prove it was an 'honest' power rating. Since this is about
the peak dissipation point for class AB the result tended to be the thermal
trips went every 20 mins or so for about ten mins. Like most tests, this
has nothing to do with music, though. :-)

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Stewart Pinkerton" wrote in message

On Wed, 04 Aug 2004 20:57:23 +0100, "Dave Plowman (News)"
wrote:

In article ,
Stewart Pinkerton wrote:
Anything with a valve in it (including CRTs) shouldn't be
permanently powered up,

It's not so very long ago that all broadcasting equipment was valve,
and plenty was left powered up 24/7. Indeed, a power failure could
result in lots of replacements after it was resumed.
But that equipment was designed for this task - I'm not convinced el
cheapo valve amps are.

Indeed, and early computers with up to 10,000 valves also ran 24/7,
although IIRC they required a valve change every ten minutes! Talk
about a job for life.... :-)

Given that the tubes were probably good for at least 10,000 hour MTBF, as
much as an hour's worth of sustained operation might have been possible.

I worked on radar equipment with about 400 tubes, and with luck I could keep
it going for about 24 hours at a time. My person goal was a reliable 8
hours - namely the night shift.

On Thu, 05 Aug 2004 09:46:23 GMT, "Trevor Wilson"
wrote:

**The term: "Pom", is a one of endearment. It should not be taken as an
offensive term. "Pommy *******" is also a term of great endearment. As in:

"Will ya have another beer, you Pommy *******?"

The term: "Whinging Pom" is a very severe insult.

The term: "Tight arsed Scot", is, like the term: "Miserable Scot", merely a
perfectly accurate observation and cannot possibly be taken as terms which
are offensive.

What would a whinging ocker know about it? :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Thu, 05 Aug 2004 09:41:17 GMT, "Trevor Wilson"
wrote:


"Stewart Pinkerton" wrote in message
.. .
On Wed, 04 Aug 2004 20:57:23 +0100, "Dave Plowman (News)"
wrote:

In article ,
Stewart Pinkerton wrote:
Anything with a valve in it (including CRTs) shouldn't be permanently
powered up,

It's not so very long ago that all broadcasting equipment was valve, and
plenty was left powered up 24/7. Indeed, a power failure could result in
lots of replacements after it was resumed.
But that equipment was designed for this task - I'm not convinced el
cheapo valve amps are.

Indeed, and early computers with up to 10,000 valves also ran 24/7,
although IIRC they required a valve change every ten minutes! Talk
about a job for life.... :-)

**My partner dragged out this quote from some computer guy in the 50's. It
went (to paraphrase):
"Sometime, in the future, computers will weigh less than 1.5 Tons."

Well, he was right, wasn't he? :-)

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Thu, 5 Aug 2004 12:30:22 +0100, "Keith G"
wrote:

(I believe words like '******' to be
truly non-demoninational but the phrase 'you stupid Eskimo' just doesn't
quite have that ring to it, does it....?? ;-)

Oops, yes it does - the correct term is Inuit.

Some nationalities/countries/races (?) lend themselves to a nickname and
some don't. For example, we have 'Yanks' in the 'US of A'

Let's not forget Gringos!

and, er,
'Canadians' in 'Canada'...???

Canucks, shurely? Or Loonies?

(Interesting also that no-one objects to the
term 'Jap' - as opposed to 'Japanese'...???)

Actually, this is a pretty common objection.

And so it goes on....

FWIW, while I'm on, I would add that I don't give a FF what colour a person
is but I would admit that I'm getting fed up with seeing my own native
country sagging under the weight of imported Cheap Labour who, due to
increasing weight of numbers, have started to 'feel their oats' and have now
got opinions on what people like me think, say and do. (I'm also getting a
bit fed up of 'ethnics' reporting our news and I don't much care for 'dis,
dat, ting, fink, axe, nutter mean, innit' etc...)

Ah, the good old days of Beeb Beeb Ceeb English as she should be
spoke!

What ethnic groups need to realise is that they will get/have already got
'nicknames' and what those nicknames mean is *earned* their by their own
behaviour, attitudes and actions - for instance, where I come from the early
negro immigrants were called 'Darkies', now other terms are deemed more
fitting by some......

See my point?

Well, negro is simply Spanish for black, and black is a generally
accepted term the se days. I wonder what's acceptable in
Spanish-speaking countries? :-)

BTW, there's really nothing so pathetically PC as 'African-American',
or indeed 'Native American'. Also, real Africans can't stand black
Americans! Or of course, each other...................

To get back on topic - I've got absolutely no problem with Chinky gear and
welcome the opportunity for a) skint Brits to acquire very decent products
like DVDPs at silly cheap prices (which is rendered necessary by them not
having a job due to the imported Cheap Labour - see above) and b) other 'Joe
Ordinaires' like me in other countries get the chance to earn a few bob and
buy the same DVDP for themselves....

You wouldn't say that if you owned any patents on stuff the Chinese
are ripping off!

One last point (a deep one, consider it carefully) - with all this
'multicultural society' BS think how arse-grindingly boring this planet will
become when we *do* have 'coffee-coloured people' everywhere, eating,
drinking, playing, listening to, watching, wearing, driving, riding,
worshipping, thinking *exactly* the same stuff......

But none of use will be allowed to wear mink - even a blue one!

(If the bugs or 'an asteroid the size of Texas' don't get us all
first....!!! ;-)

Didn't the Bugs launch those asteroids at us?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Thu, 5 Aug 2004 10:51:01 +0100, "Keith G"
wrote:


"Tat Chan" wrote in message
...
Andy Evans wrote:


I think we bottleheads are ultimately going to become rarities, but the
sound
of valves lives on - musicians love them and use them, and a number of
musical
listeners, as you say, find they come closest to the sound they find
represents
the "musical experience".

If valves are used for musical *production*, then the distortion forms
part of the art (which is fine, since musicians are making new music)

However, for musical *reproduction*, the valves would distort the signal
being reproduced, and taken to its extreme, a valve amp would then act
as a signal processor, wouldn't it?

This sort of post never fails to amaze me - like ss kit *doesn't* distort
the signal FFS!!!

Good SS kit doesn't *audibly* distort the signal, which is what
matters. That of course is why all competent amps sound the same -
even valve ones.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Trevor Wilson" wrote


Neither is farting, but I doubt it's a major issue.

**Every bit helps. As they used to say: "Think globally, act locally."
Think
of the money, Stewart.


Jeez, I thought farting was the one pleasure left that didn't cost money!

(I must owe fekkin' millions..... :-)

"Don Pearce" wrote


"Believe" = accept without proof
"Know" = accept on the basis of proof


There you go, man, keep as cool as you can,
Face piles of trials with smiles.

It riles them to believe that you perceive the web they weave
And keep on thinking free....

(Dan dan dan daaaan....)

:-)


Extreme danger of "golden-ageism" here.


Always.


What you like is what you like.


Yep! - Even if we don't know it!

;-)

"Andy Evans" wrote in message
...
This sort of post never fails to amaze me - like ss kit *doesn't* distort
the signal FFS!!!

Hang on here, Keith - ss kit measures .00000000001% distortion because
it's
sonically transparent. Never mind what it sounds like. And anyway, most
people
use ss kit so it must be better. Who are we to remain unconvinced by such
arguments.


So true.......

"Tat Chan" wrote in message
...
Keith G wrote:

"Tat Chan" wrote in message
...


If valves are used for musical *production*, then the distortion forms
part of the art (which is fine, since musicians are making new music)

However, for musical *reproduction*, the valves would distort the signal
being reproduced, and taken to its extreme, a valve amp would then act
as a signal processor, wouldn't it?

This sort of post never fails to amaze me - like ss kit *doesn't*
distort
the signal FFS!!!


well, it was a sweeping generalisation. But if I was a betting man, I
would
wager that a similarly priced SS amp would have less distortion than a
valve amp.


Very likely - strong chance it wouldn't be Class A tho......


Keith, I'm not taking a dig at valve preferences, since there are no right
or
wrong preferences.


Agreed