Hi Bob,
> Why in the heck would anybody in their right mind even DESIGN or worse BUILD
> a voltage doubler power supply for their homebrew amplifier?
I will give you one reason, which was quite important for me, when I
built amplifiers: I wound my own power transformers, because I could get
the iron for free and the wire quite cheaply. Buying ready wound
transformers instead, or having them wound to my specifications, would
have been at least ten times as expensive. And when winding a
transformer by hand, it's a BIG advantage to design for a voltage
doubler: You need to wind only half as many turns, and the wire is twice
as thick! The time saving is obvious, and the thicker wire is easier to
handle and won't break so easily if the heavy thing slips away during
winding.
The rectifier diodes are of the same voltage rating in both cases. For a
doubler, you need half as many diodes, of twice the current rating.
Given that the smallest diodes are for 1A average current, that's enough
for the typical legal limit amp even when using a voltage doubler, so
the doubling rectifier is cheaper than a bridge. You need the same
number of capacitors, because anyway electrolytics hardly go above 450V
each. The ONLY disadvantage of a voltage doubler is that you need more
capacitance to achieve the same ripple. For me, the advantages,
specially the much easier winding work, were worth the higher cost of
filter caps.
Oh, I almost forgot: Thinner wire is more expensive by weight than
thicker one, and you need the same weight of wire for both versions of
the transformer. So there is an additional cost advantage (even if a
slight one) to partially offset the higher cost in filter caps.
When looking at commercial amps, it seems that they have generally moved
from doublers to bridges over the last few decades. I would guess that
this is related to increased automation in transformer manufacture. When
a robot winds them, the additional cost of winding twice as many turns
of half as thick a wire probably no longer balances the higher cost of
filter caps for a doubler!
Commercial manufacturers normally do things in the cheapest way that
satisfies the requirements, and will not give preference to one or the
other method just for matters of personal taste! They would soon be out
of business if they did. Unless they can sell their particular whims to
some group of golden eared hams who think they can hear a difference in
the resulting signal!
Manfred.
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Visit my hobby website!
http://ludens.cl
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