darTZeel Audio NHB-108 B version - Manual (Page 33)

darTZeel NHB-108 model one
User Manual, version B 1.0 Page 33 of 35
What is far less known is the mathematical relation-
ship between expected lifespan and high tempera-
ture exposure.
Many studies have shown that for each 5°C in-
crease, lifespan is halved! Sorry about not convert-
ing into Fahrenheit - the law doesn’t work out so
easily. Sometimes the metric system is not so bad,
especially when one wants to launch a probe to
Mars… But that’s another story.
Back to our story. If a component lifetime is given
for 10 years at 20°C, it will only last one day if
permanently exposed to 80°C! This very same
component will last for 40 years if ambient tem-
perature is only 10°C…
This law does not take all parameters into account,
but it is close enough to reality to rely on it when
designing electronic circuits.
We see then that while it is very important to
choose components designed to resist high tempera-
tures, it is always preferable to stop the problem at
source, by simply ensuring that components do not
overheat.
In continuous round the clock domestic use – but is
this still domestic use? – provided you respect the
location advice mentioned in the first section of this
manual, the NHB-108 model one stabilizes at
around 50°C on its heat sinks. As bipolar transistors
can work as high as 120°C, the margin is comfort-
able here.
The internal temperature, on the mother plate mod-
ule, is around 40°C. At this crucial place are in-
stalled the very expensive filtering capacitors. Do
not be worried too much: at 40°C, 24/24, their es-
timated span life is… 40 years.
Just imagine: a poorer design – we will not mention
any name – subject to an internal temperature of
60°C would imply a change of capacitors every 2
and a half years!
Furthermore, in normal use, say if you sometime
power OFF your machine, capacitors’ life span can
be easily doubled, or even quadrupled.
As soon as we realize that working temperature is
the most long lasting factor, it becomes easier to
choose components for their sonic attributes first.
Another factor, even less known but very interest-
ing, is that of sustaining bias powering. A given
component, being active or passive, lasts longer if
some voltage, however low it is, remains applied to
its terminals. For electrolytic capacitors, this small
"polarizing" voltage even keeps their internal elec-
trolyte in perfect chemical working condition,
greatly reducing the "warming time" usually needed
with other gear.
All these reasons led us to keep the darTZeel
NHB-108 model one
powered at around 2 volts
(instead of 60), even when shut OFF, by pressing
the Power Nose. Your amplifier is then always
gently permanently energized, extending even fur-
ther its life span, and attaining much more quickly
the full performance the amplifier can deliver to
your ears.
It is also the reason why you can still hear some
music through the NHB-108 model one even
when it is powered OFF. Incidentally, the fact that
the amp can sing with such a low voltage demon-
strates how simple the audio circuit really is…
In case you are worried about this, the power con-
sumption of the "power OFF" mode is around 2
watts. It represents around $5.33 per year, assuming
that a kilowatt/hour costs $0.33. This means $160
after 30 years. It is not too high a price to pay com-
pared to changing the capacitors more frequently!
Bear in mind that producing new capacitors pol-
lutes more than keeping them energized… With all
sonic benefits.
T9.2. Long term availability
T9.2.1. Spare parts
To own a darTZeel NHB-108 model one must
not only give you musical pleasure.
You must also benefit from a first class customer
service, whatever the problem encountered.
Whether it is a failed component, or a broken heat
sink due to an unfortunate accident – not dropped
on your feet we hope – all parts need to be avail-
able, at anytime.
If, as we think, your machine only requires mainte-
nance every 30 or 40 years, we will ensure that
parts availability will last far beyond that.
We at darTZeel, always stock all "non perishable"
components in sufficient quantity for – very – long
term operation.
Semiconductors and passive components with no
instable material inside are stocked, and will be
available at any time, in brand new working condi-
tion.
As for electrolytic capacitors, however, their pres-
ervation is much more delicate when one tries to
stock them for 30 or 40 years in brand new working
condition, their life span being limited even when
not in use.
Fortunately, we have chosen industrial models, of
the highest quality, from one of the world’s biggest
and longest established manufacturers. We can bet
that they will still be there in 100 years, and that
they will continue to offer equally outstanding ca-
pacitors, or perhaps even better ones.