Posted by thebordas (A) on September 26, 2010 at 07:31:03

In Reply to: RE: Sunfire vs. McIntosh Amp for Magnepan 3.6 posted by pictureguy on September 25, 2010 at 23:58:13

A “high-current” amplifier is capable of delivering power into low impedance loads (speakers)
without going into protection and/or shutting down. Ideally, an amplifier’s output power would double
every time the load presented at its output is halved. For example, an “ideal” amplifier rated 250
Watts @ 8 Ohms would deliver 500 Watts @ 4 Ohms, noting that the load has halved and the
power has doubled. In actuality, a “real-world” high-current amplifier capable of 250 Watts @ 8
Ohms might be delivering about 425 Watts @ 4 Ohms.
An easy way to identify a “high-current” amplifier for use with home consumer electronics is
to look at what happens to the power rating as the impedance of its load (speakers) drops. The
closer the amplifier comes to approaching the “ideal” amplifier scenario, the more current the
amplifier is capable of delivering and the better the sound reproduced by the speaker.
In a typical amplifier-speaker circuit, voltage and current are delivered to a very complex load
consisting of speaker drivers, resistors, inductors, and capacitors. Voltage may be thought of as the
potential to do work, and current as what actually flows to do the work. Although basic power may
be calculated by the simple multiplication of voltage and current, it is the delivery of the power from
the amplifier to the complex speaker load that accounts for why two amplifiers may have the same
power rating into identical impedances (speaker loads), but still be significantly different from one
another in sound quality. Some of these sound quality differences may include perceived loudness,
depth, and clarity. Amplifiers that are designed to operate with high voltage as opposed to high
current are typically much better suited to high impedance loads, typically 8 Ohms and higher.
Lower current rated amplifiers have been said to sound dynamically limited and “harsh” at high
listening levels.
High quality “audiophile” speakers can have nominal impedances from 8 – 2 Ohms, and
during very dynamic passages in source material can easily dip below 2 Ohms. These super low
impedance drops can easily choke a high voltage amplifier with limited power storage capacity. For
a high-voltage amplifier, this will likely cause problems and trigger its protection, not to mention the
less than nice sound it may produce. A high-current amplifier operates with much less effort and
typically does not have any problem with these types of speakers.
High current amplifiers offer large amounts of capacitive power
storage. Modern high current amplifiers can handle nominal impedance of 4 Ohms, as well as dips below 1
Ohm while remaining stable, loud and clear with deep bass and good three-dimensionality. A good
example of a “real-world” situation being very close to an “ideal” situation would be our Reference
200.1 mono amplifier. Rated 250 Watts @ 8 Ohms with 150 peak-peak Amps of current, it is quite
the powerhouse. When used with a 4 Ohm load the Reference 200.1 kicks out a cool 425 Watts!
That’s about as close to perfect as one could expect.
So, what’s the bottom line? For use with lower impedance speakers, high-current amplifiers
sound louder, cleaner, and provide more depth than their high-voltage counterparts. High-current
amplifiers will not shut down when the speaker presents a difficult load due to varying dynamics in
source material.

Not my writing (B&K's), but get's the message across. I've owned Levinson, Krell, ARC and Macintosh mostly. Large power supplies and storage capacitance combined with High Current capability just sound clearer, more dynamic and maintain control under complex signal demands. Equating potential HCC Amps of an amplifier to Arc welding is missing the point completely. High current capability reflects internal stability and the amps ability to reproduce complex musical signals during large impedance swings. kinda like having extra power reserves are always better for a speaker, no matter how efficient it is....the results will be less distortion, better dynamics, increased transient speed and better articulation. The HC amp sounds bolder, faster, cleaner and more "alive".
dave_b