Note that Magnepan did have a response to it's stance on Class D here is a quote form them "
- 4 Ohm capacity is important in amplifier design (more on that later).
Customers are always surprised that we don't know which brands and models are the best choices. We have a very small staff and none of us have the time to test amplifiers. But, we have decades of experience with a class of amplifiers that work well with Magneplanars. If you follow these guidelines, you are in the right "ball park".
The short answer is direct-coupled, class A/B designs with high current capability. But to learn more, you'll need to read further.
First, let's address a misconception: The more expensive Maggies require better amplifiers.
It is true that most customers use better electronics on our more expensive models. But technically, it is not because the more expensive models are more demanding on the amplifier. The loads and efficiencies are very similar. Typically, the customer has a larger budget for amplifiers and, of course, the speakers respond with better sound.
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.
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 ratio of the power at 8 ohms and 4 ohms defines the quality of the sound probably more than any other aspect of the sonic performance. Typically, if the engineers got this right, they probably did a good job in other areas of the design.
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.) In the final analysis, buy an amplifier that comes as close to doubling the power at 4 ohms as your budget will allow.
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 and will only offer a 6 ohm power rating. 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. Quite frankly, some sound very poor on Maggies. However, more recent designs of high-end models 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. Direct-coupled, class A/B designs with high current capability have proven a good choice for many decades."
I can say that I like my Rotel amps that are class D and there are some much better expensive models and some cheaper I tested a Crown XLS1500 Class D amp for a friend and it doubles it's rating at 4 ohms and it had plenty of juice to push my 1.7I's