Re: Citation II Rebuild Project
- From: "West" <west@xxxxxxxxxxx>
- Date: Tue, 04 Mar 2008 23:46:16 GMT
"Ian Iveson" <IanIveson.home@xxxxxxxxxxxxxxxx> wrote in message
news:9dQwj.112731$LD6.77360@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
Jon said:
Actually, Trevor, West may have a point. However, the
"problem" with adding
a lot of capacitance to a power supply isn't that it might
degrade the
transient response, in terms of how we measure it with lab
gear.
Adding excessive capacitance may indeed alter the
"musicality" of an amp --
which is subjective. There isn't agreement on ways to
measure subtle
changes in "musicality" -- if indeed it can be quantified.
Some people describe the effect of to many MFDs as
"slowing down the amp" on
the passages that include transient, high frequency, or
high slew rate
signals. One fellow I know who has built amps all of his
life, and is a
walking encyclopedia of technology and methods says an
amplifier is like a
musical instrument, and too much capacitance can
over-dampen or degrade the
instrument. No, I can't prove it, but it is plausible.
Where lots of capacitance improves matters is during high
demand periods
with low frequencies, by providing a reserve of current.
IMHO, tube
amplifiers tend to suffer on the low end compared to their
SS cousins.
My friend firmly disagrees with Jim McShane's capacitor
upgrade
recommendations for the aforementioned reasons. He says
it will improve the
bottom end of the amp to the detriment of the top.
We shall see. Fortunately, Jim's scheme puts the caps in
parallel so I can
easily clip a good bit of it out of circuit.
Too bad Stu Hegeman and most of the "pioneers" aren't
around to ask them why
they didn't just add a bunch more capacitance if their
goal was to get the
best sound. Surely the added cost and weight of the
electros would not be
the only factors to exclude them -- especially for those
who would spare no
expense.
I don't like this transient-as-a-noun thing, as I've said
before. In the phrase "transient response", the word is an
adjective. It refers to that part of a system's response
which is transient, or as a text book might put it, that
part of a system's response that would be zero after an
infinite time. Hence, although "transient response" may be
related in practice to the system's response to what many
people call "a transient", the relationship is not necessary
to the meaning of the phrase.
In this proper meaning of the phrase, an identical amplifier
fitted with a larger PS filter cap may have a slower
transient response. That is, if you disturb it, perhaps with
a step at the input, then it may take longer for it to
settle. However, at signal levels that the amp can sustain
indefinitely, the filter cap's contribution to the total
transient response is very small, and so perhaps not
significant.
At higher levels, such as brief excursions into overdrive,
PS sag will be slower for the amp with the bigger cap. This
applies to both onset and recovery, which go hand in hand,
unfortunately.
So it's a matter of judgement. The bigger cap may enable the
amp to nail, and sustain for longer, an overdrive excursion,
but at the expense of taking longer to recover from the
event. The smaller capped amp may fluff the leading edge of
the envelope, but recover faster.
Just a train of thought...could be wrong.
I absolutely agree with the musical instrument thing,
although for me it is the system...sources, amps and
speakers...that is the instrument. Where's your friend? I
think there may be just two of us left.
Ian
Can you define instantaneous power demand?
west
.
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