D-Sonic peak current output compared to other

There is an interesting reading in Magnepan's website regarding amplifiers current output.

Link:
http://www.magnepan.com/faq#receivers

Quote:
"What is the best amplifier for Magneplanars? [top]

Some individuals assume we won't make product or amplifier recommendations for "political" reasons. Not true. We CAN'T make specific recommendations because WE DON'T KNOW. It is too much work to keep up with changing models and the vast number of products. As it is, our small staff is not getting all of our work done. However, the following guidelines will be helpful. Class A/B amplifier designs that come close to doubling power at 4 ohms have a long and successful track record.

There are 2 features or aspects of a receiver or amplifier that will enhance your music or experience-- High current power supplies (ability to drive 4 ohm loads) and adjustable crossover points in the bass management menu for home-theater.

The most common question is about the amount of recommended power for Magneplanars, but, first, it is important to understand the role of current and the power supply. High current and the capability of the power supply is a good indicator of the QUALITY of the amplifier. The amount of power you will need is a matter of QUANTITY. High current and total power are two separate issues.

The power supply is "what separates the men from the boys." A receiver is very efficient and cost-effective way to get is all in one package, but there are "issues". Unfortunately, consumers want all the "bells and whistles" without understanding the importance of power supply. Many manufacturers offer the "bells and whistles", but, compromise the power supply to be price competitive. There are a few manufacturers that are the exception.

Everyone understands they need plenty of power, but the role of power supply is not understood. There is one important concept you need to understand when shopping for an amplifier or receiver---and it is somewhat like understanding "good" and "bad" cholesterol. The ratio is very important. An Gold Standard for an amplifier would be to double the power at 4 ohms. This concept is important even if you are buying an 8 ohm speaker. If the amplifier is rated at 80 watts at 8 ohms, it should (ideally) produce 160 watts at 4 ohms (or close to it). None of the receivers will do that. However, this is the benchmark of a good amplifier design. A 10 watt amplifier that produces 20 watts at 4 ohms "speaks volumes" about the PHILOSOPHY of the designer. (But, of course, it does not tell you if a 10 watt amplifier is enough for your room.)

A good receiver might produce 30-40% more power at 4 ohms. Most receiver manufacturers don't want to talk about 4 ohm ratings because they have cut the "guts" out of their products to keep the cost down. Some receivers produce the same power at 4 ohms as the 8 ohm ratings. Or they use a switch on the back for 4 ohms to reduce the power and to prevent the receiver from self destructing. Others warn against 4 ohm speakers. Regardless of what speaker you buy, we don't recommend any of these receivers. There are a few manufacturers making receivers with good 4 ohm capability. But, we can't keep up with who's doing what. All you have to remember is to ask-- "What is the 4 ohm power rating?" If the 4 ohm rating isn't available, find another model or brand. It may take some digging to find the 4 ohm rating, but there are a number of receivers on the market that are rated for 4 ohms. For example, the THX rating requires that the amplifier section must be able to drive 4 ohms continuously. Even an inexpensive receiver like the 50 watt NAD C725 BEE (suggested retail of $799) is advertised to be stable with impedances down to 1 ohm and has peak power of 200 watts. So, don't be fooled by pretty front panels. Its what is on the inside that counts.

A new type of amplifier (Class D) has become more popular because it is a "green" design and uses less power plus it is smaller in size compared to conventional amplifier designs. We have heard reports of Class D amplifiers shutting down when driving 4 ohm loads or sound quality that is less-than-desirable. Some, more recent designs are much better. Because we do not have the time to determine which models of Class D designs are compatible with Maggies, we must take a conservative approach. Class A/B designs with high current capability have proven a good choice for many decades.

Adjustable crossover points- If you are shopping for a receiver or processor, you will want a model with adjustable crossover points for "small" speakers in the bass management menu. This is very important to the design of a Magneplanar home-theater system. Adjustable crossover points up to 250 Hz are desirable.

Most ribbon or electrostatic center channel speakers incorporate a dynamic midbass driver since the rather small ribbon or electrostatic elements can not produce midbass. This seems like a mistake to us. The does approximately 60% of the "heavy lifting" for movies. Why compromise such a critical ribbon speaker with a dynamic woofer?

Magneplanar center channel speakers are also small (relative to our full range models) and cannot produce adequate midbass-- by themselves. Our strategy is to utilize the front left/right Magneplanars (or one of the new Magneplanar Woofers) to produce the center channel midbass/bass. When optimally setup, the illusion is of a big Maggie in the middle. However, it requires one of several solutions for getting center channel midbass/bass. Adjustable crossover points in the bass management menu is one of the easiest solutions. If your receiver or processor only has an 80 Hz crossover point for "small" center channel, there are other options. Please call us and we will be happy to discuss your installation requirements."

The above quote is from Magnapan's website.

This is a video explaining why current output is so important in audio playback:
http://www.youtube.com/watch?v=Y_22XOakyxM&feature=player_embedded

Not sure I buy the explanation in the video. It needs elaboration to know what he is trying to say.

The exert below is very clear and it is consistent with basic electronics course content.

This is an exert from The Complete Guide to High-End Audio as published for free by The Absolute Sound at AVguide.com

This link has the free download guide to electronics 2012. The section of this exert is on page 13.

http://media.avguide.com/BG_Audio_Electronics_2012.pdf

"
Excerpted and adapted from The Complete
Guide to High-End Audio (fourth edition).
Copyright © 1994–2012 by Robert Harley.

Why Amplifier Output Current Matters

Some amplifiers barely increase their output
power when driving 4 ohms; others can double
it. This means that not all “100Wpc” amplifiers
are created equal. One “100Wpc” amplifier
might put out 150W into 2 ohms, while another
might deliver 400Wpc into 2 ohms. This ability
to drive low-impedance loads (specifically, to
deliver lots of current) has a large influence on an
amplifier’s sound and subjective power capability.
Loudspeakers have dips in their impedances at
certain frequencies, which puts greater currentdelivery
demands on the power amplifier.

This difference has real-world consequences.
The ability to increase output power into low
impedances indicates how much current the
amplifier can deliver to the loudspeaker. It is
current flow through the loudspeakers’ voice
coils (in dynamic loudspeakers) that creates the
electromagnetic force that causes the cones
and domes to move, and thus produce sound. If
current flow through the voice coil is constrained,
so is the music.

An analog is helpful to understanding this
concept. Think of a power amplifier driving a
loudspeaker as a water faucet and a hose; the
water pressure is voltage, the flow of water through
the hose is electrical current, and squeezing the
hose forms a resistance (impedance) to the flow.
In this analogy, the loudspeaker’s impedance is
the resistance in the hose that impedes the flow
of water. The lower the loudspeaker’s impedance,
the less the resistance to current flow from the
amplifier, and the harder the amplifier must
work to deliver current to the loudspeaker. If the
impedance is halved (say, from 8 ohms to 4 ohms),
the amplifier is asked to deliver double the current
to the loudspeaker (all other factors being equal).

If the amplifier isn’t up to the job, the musical
result is strain or even distortion on musical
peaks, weak bass, loss of dynamics, hardening
of timbre, and a collapsing soundstage. In short,
we can hear the amplifier give up as it runs out
of power. Conversely, amplifiers that can continue
increasing their output power as the impedance
drops generally have very deep, extended, and
powerful bass, virtually unlimited dynamics, a
sense of ease and grace during musical peaks,
and the ability to maintain correct timbre and
soundstaging, even during loud passages. If you
have relatively high-impedance loudspeakers
with no severe impedance dips, you’re much less
likely to encounter sonic problems, even with
modest power amplifiers; the loudspeaker simply
demands less current from the power amplifier.

Amplifiers with high current capability (indicated
by their ability to increase output power into low
impedances) are often large and expensive. Their
current capability comes from massive power
transformers, huge power supplies, and lots of
output transistors—all expensive items.

Keep in mind, however, that not all systems
require large power amplifiers. If you have sensitive
loudspeakers with a fairly high impedance, the
loudspeaker’s current demands are vastly lower.
Consequently, smaller amplifiers work just fine.
Single-ended triode amplifiers with as little as
3Wpc and very limited ability to deliver current
can sound highly musical when driving a load-appropriate
loudspeaker.

Excerpted and adapted from The Complete
Guide to High-End Audio (fourth edition).
Copyright © 1994–2012 by Robert Harley.
"

There are a number of things in the excerpt above that are patently false (despite the source) but are indeed widely-held opinion in the form of myth.

For example the ability to play deep effortless bass has nothing at all to do with the ability of the amplifier to double its power as impedance is halved.

If you would like an example of this, try that of a Sound Lab ESL being driven by a transistor amplifier. The tendency is for the amp to be bass-shy on that speaker while also being too bright.

What in fact is far more important is the relationship between the amp and speaker, as well as the intention of the designer of the speaker. Very closely related to this fact is the experience of seeing 'good' specs on paper, but also knowing full well that the specs will not tell you how that amp will sound in your system.

Here is an easy to read article about what is going on:
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

Most box speakers have a woofer in that box that makes the bass. The woofer has a resonance in that box that is expressed by a peak in the impedance curve. This usually shows up in most designs right near the low frequency cutoff of the speaker itself. So you can see that the comment:

amplifiers that can continue increasing their output power as the impedance drops generally have very deep, extended, and powerful bass

is not really true at all. In fact making deep bass has nothing to do with 'tons of current', since at the resonant peak in the box, the speaker's impedance will be high, not low, forcing the amp to make *less* power, not more! Obviously something else is at play in the way amps make good bass.

It is true that lots of capacity in the power supply (which is the source of the 'amplifier' current that generated this thread) is generally associated with the better amplifiers made. But it is the relationship between the amp and the speaker that actually governs the things we hear from them. Understanding that fact is how you avoid flushing large amounts of dollars down the loo.