Dumping
Factor
If it is no good, why amplifier designers do the effort to make it high?
For the history of amp's, it all started with tubes. Tube amp's had low power
and low DF. They all need an output transformer to transfer high voltage / low
current, into some lower voltage and higher current.
Today, some Tube amps have more power (watts) but the DF remains low.
When
solid state (SS) was introduced, DF was one of the issues to tackle.
Amplifiers, not only audio, but in general, have a tendency to be made
with some basic spec's. to keep it ideal. The very first two are:
·
Infinite input
impedance (zero effect on source) and,
·
Zero output resistance (in
a way, an Infinite DF) that would ensure zero effect by the load.
Those
are the very basics of amplifiers in electronics.
That's
before flat FR, low noise (SNR), THD etc'. So for all who find DF (or Ro)
to be unimportant, why not look how it became a first in ideal amplification?
The
DF or output resistance can be achieved (by design) in several ways. Feedback
(FB) is one of them. Not the best way to get there, but a common one. FB is not
a bad thing in general, but may have bad
side effects when used too much or in a wrong way. One benefit of FB is to
stabilize the output at complex loads. That must be limited by FR to avoid oscillations.
The
others, are using very high current low R-on output devices (transistors) and a
very powerful power supply (PS).
Firms
like Naim, that have a method of using external PS, are paying a price on DF
with that approach. Most high power amps need more than one output device in parallel
to provide the power.
Some
designs emphasize one feature over the other, so as in life, it is difficult to
be spot on, on every parameter. When it does, it has a price.
Some
amplifiers behave bad on low speakers impedance. Most do not double output power
when load (8 Ohms) drops to half (4 Ohms) and quadruple when load drops to a quarter
(2 Ohms).
Some
would keep up even at 1 Ohm. If you think it is a good amplifier, what would
the Ro (DF) of such amp be, to keep it cool?
Amplifiers,
with different DF have different sound. Some like the laid back and relaxed
tube sound. Some (like McIntosh) would imitate it with SS topology but with an
output transformer.
For those who like it dynamic and vivid, a higher DF and power are required.
The
Amplifier – Speaker relation is more complex, as it is depends on the speaker's
load (8,4,2 Ohms!) the speaker's efficiency (dB/w/m SPL) and more. The cable
between the two are also playing
an important role. Some more and some less. The key for that role is the
amplifier's DF.
For
all who may think other, that's ok. Just be fair enough to bring a technical argument
to this conversation, rather than just a say aomething with no support. That's
an insult to intelligence.
All
those who add a link to some guru's article on the web, that support their say,
but the article has no technical support (no foundation to explain
that say), please don't. It's the same insult.
A
say with no technical support is no good on this thread. You need better.
