April showers may bring May flowers, but here in New Hampshire the showers are usually ice storms that coat all sorts of things, including power lines. Usually made of aluminum, with the weight of the ice, they do have a tendency to stretch and break. This leads to power outages. While this may be disastrous for your listening pleasure, it can be even more so for your system, as while the electricity is shutting down or turning back on, power surges of up to several hundred volts with spikes into the thousands may fry your equipment even if it is not turned on. I can still remember my grandfather back in the 1950's (yes, I'm that old) having us run around the house and unplugging all of our electrical equipment, especially our 15 inch Philco B&W television, the prized family possession.
While electronics in those days were immune to short spikes, being tubed, solid-state equipment is much less so, with even small spikes taking out integrated circuits with ease. Thus, all of you should have at least some form of protection for your whole house at the service entrance, and further protection in the room. I mention this because we had this problem in my neighborhood recently, with a couple of the neighbor's computers, stereo's and even wide screen TV's being taken out. Happily, our household suffered no more than the lights going out for a couple of hours. Of course it was at the normal time for optimal listening (i.e. 10:00 to 11:30 p.m.), but at least no damage was done. That is because I have an Environmental Potentials EP 2050 Home Protection Unit, http://www.ep2000.com/Templates/ep2050.html at the main junction box, and all of my equipment goes through either an APC S-15, Audience AdeptResponse aR12 power conditioners and/or Torus Power Isolation units in the room.
On the other hand, some of my best listening sessions have been during snow and ice storms. I don't know why it happens, but snow or ice sticking to power lines tends to decrease significantly the junk coming through them. Even with all of the electrical isolation of my system, there is still a difference in sound quality for the better at these times. Go figure.
Now on to the true topic for today; a new type of amplifier design based on so-called Class D operation. All amplifiers act as gates or valves, ( thus the English term for tubes) with a small amount of current regulating a gate to allow a much larger current through. The stronger the gate is closed by the input signal, the less output current is allowed to flow. The maximum amount of current and its quality is based on the power supply that produces the electrons pushing at the gate.
In most present-day Class A and AB amplifiers, the power supply uses a transformer to adjust the 110 voltage from the wall to that needed by the various pieces of equipment. It regulates it, and as such, provides as close to a constant voltage as possible. Then, using either tube or solid-state devices, changes the 60 Hz current to as pure a DC current as possible, with it being almost impossible to completely eradicate all of the AC current. At the 60 Hz level, this requires a large transformer and capacitor banks for storage, yielding large, heavy, and expensive amplifiers for optimum control of the signal. Also, in the process, anywhere from 50 to 80 percent of the electrical energy is lost as heat, giving only a 50 to 20 percent efficiency. Engineers have been working for years to try to design more efficient amplifiers that can completely eliminate the 60 Hz noise from the wall current. One of the systems is the so-called Class D amplifier, which takes the 60 Hz wall current and boosts it into the KHz. to GHz. range. At that point, the signal may be worked on in either a digital or an analog manner much more efficiently to get the output current.
The digital type use some form of Pulse Width or Pulse Density modulation. The input signal is converted to pulses 10 plus time greater than the highest original frequency with either the amplitude or the width of the pulse then being used to determine the amplification. One then can use a simple inductive-capacitive low pass filtering system to remove the high frequency noise produced by the process. Unhappily, like with typical analog amplifiers, one cannot perfectly remove all of this noise.
The other advance was the engineering and production of their so-called ICEamplification system. These can be purchased from B&O as a standardized module of varying power output, as customized units or as just a usage of their patent agreement. Most of the high-end companies are either buying the base units and customizing them or having B&O build them to their specifications. Only Pioneer, according to Mr. Deacon, is having B&O build them to their specifications as acknowledged by B&O at this point. This is entirely about channel format; power supply sharing and chassis fit economies and not about core sonic technology.
There are several types of base units. The A series has three modules of 250, 500 or 1000 watts output without a power supply. The manufacturer can then ad either a standard or a switching power supply. The ASP group output the same power levels, and have a commensurate built in switching power supply that can also power up to two additional A type units. Thus, a three-channel amplifier can be built in one chassis using one ASP and two A units. Their ASC and ASX2 units are designed for active speaker or stand-alone amplification, with the ASX2 being bridgeable, and their new ASH7 series can be used for up to seven channels, or up to three bridged channels. Thus, one can mix and match the units in one or more chassis for any power output imaginable for a system.
Each unit is on one circuit board with the ability to be true balanced or single ended from in to output. The 1000-watt unit with built-in power supply has a transformer smaller than most preamp's and the heat fins are those small indentations on the left bottom of the unit. Being energy efficient has several advantages other than improving your electrical bill.
Magnum Series Amplifiers From D-Sonic
As a part Scotsman who looks for savings at every turn and with a $300 plus electric bill every month, I've been interested in class D amplifiers with their high efficiencies for years. Unhappily, all units that have been here for evaluation have been great for subwoofer applications but tend to add a glassy sheen to any other music reproduction. There had been some buzz on the web about B&O's ICE units and about three months ago there was an advertisement at Audiogon for the D-Sonic company that is building amplifiers using these boards. Happily, Mr. Deacon, proprietor of the company, allowed me to evaluate a pair of their 500-watt monoblock units.
D-Sonic makes several units of 100 to 500 watts output in monoblocks, stereo, three channel and a seven channel unit with three front channels with 500 watts and four rear channels of 250 watts output. Varying in price from $790 for a 250-watt monoblock to $3500 for a seven-channel unit with 525 watts per channel. Any combination of channels and power in between are available. According to Mr. Deacon, many customers use the M-2500-7 with three 525-watt modules in front and four 250-watt modules for the side and rear channels for $2975.
All are built into rugged, utilitarian 14 gauge steel chassis with a black powder coat finish, with most of the construction costs going to excellent "aerospace" grade switches and "milspec" wiring. On the back, inputs are both true balanced and single ended with outputs being five-way gold plated binding posts, and an IEC AC plug, all of excellent quality. The front has a light gray turn-on switch and a small blue LED. The construction expense has been put in the proper place. Internal construction is of excellent quality. Each has a full three-year warranty for both parts and labor.
Turn-on is silent with a 20 milli-second delay before activation to allow all of the circuits to settle. Unlike other 500-watt units which usually weigh more than a bag of cement, these are lighter than my preamp and can be easily lifted with one hand. They do run cool, and even after being stressed playing almost intolerably loud movie scenes on my subwoofers, they are almost room temperature to the touch. Those are the advantages of Class D power.
So how do they sound? First, they are silent. I first used them on my mid-horn tweeters that have about 107dB/W/m efficiency and during turn-on there was some minimal hiss that could be heard while standing near the speakers. However, it turned out the hiss disappeared when the preamp was turned off. The amps themselves were almost dead silent even when my ear got within a few inches of the speakers. There was absolutely none of the "glassiness" heard with previous Class D units. With the low noise floor compared to tube and even most solid-state units, unless a disc had some hiss built in, from the listening position one could discern nothing until the music began playing. But when the music started the low-level information that allows one to determine room boundaries and space between musicians lit up, especially with analog. Unlike some other amplifiers that seem to do this by increasing tape or vinyl noise, these capture the actual hall sound through their inherent silence.
Was there a sonic signature? First, they don't sound like solid state or tube amps. Compared to the slight romanticizing effect of tubes and the slight sterility of most solid state these days, the amps seemed to be a little towards the sterile but probably more neutral sounding than any other amp I've had here. Being a tube person who likes a little romance, they are a little on the spare side, but boy did they produce a sound stage that was lifelike. The units were then placed first on my woofer horns and then on my subwoofers, and like other Class D amps, they did an excellent job in controlling bass. It was tight, impactful and somewhat more lifelike than that produced by my 750 watt per channel Crown Macro Reference Amps.
I probably shouldn't mention this, as this was not an actual evaluation session, but they were taken to Maurice Schmir's house where Wally Malewicz was setting up his new WAM speakers. They were used for a very short listening session as the new speakers were still being voiced by Wally, but compared to his Accuphase amplifiers, they sounded slightly sterile, but, again that was only over a short listening session with speakers that weren't completely set up.
So what sort of adjectives could be used for the amplifiers. First, NEUTRAL comes to mind. Second, QUIET. Third, VALUE for the MONEY. The Magnum 500M go for $975 each, and one can get the stereo equivalent for $1475. Their least expensive stereo 100 watters cost $875 and their most expensive7 channel unit for $3500.
In summary, if one is interested in neutrality, quietness, and value, these amps will be hard to beat. I know that a recent Absolute Sound article gave several other Class D amps less than favorable reviews, but they were digital rather than analog variants. Also, with these boards being sold OEM by B&O, they'll certainly be other manufacturers out there building variants of variable quality. I do think that these type of amps will be the future of audio considering the cost of electricity, the greening of society, and their obvious quality.
And Now A Few Words From Mr. Deacon
ICEPOWER 100ASC and 250, 500, 1000ASP Performance Description
Here is a description of the ICEpower technology in what I hope the readers consider plain English. This is condensed from several B&O sources for the most part. B&O does not elaborate on their designs too much beyond what you see here unless you are a development partner. An abbreviation/acronym list is shown at the end of this page.
ICEpower amplification is not digital, as many believe. The amplifier output stage is MOSFET transistor based, similar to other linear Class A and AB solid-state products. There is no digital methodology used in the switching power supply (PAM) which is the heart and soul of this relatively new technology also known as class D. B&O controls this process with their patented MECC chip. Each component on the various modules has been carefully chosen to match the low-heat thermal characteristics of each other to enhance efficiency and life of part. This high switching frequency of 320 to 380KHZ is what allows the modules to use very small power supplies, transformers and capacitors compared to conventional units due to their high efficiency rate of 83% vs 20% and 48% for class A and AB respectively, which translates into large heat sinks or fans to dissipate the heat from the waste power. The only exception I am aware of to this is the down tracking conversion technology developed by Bob Carver for his various amplifiers. They do not match the ICEpower products in this area but are an impressive step in the right direction.
Another key ICEpower technology is the patented COM chipset that presents a relatively constant resistance load to the amplifier output regardless of variation in the loudspeaker impedance. A very low output impedance of 5mOHMS also makes the units less performance dependent upon speaker load. They are stable into any known speaker resistance. If a module overheats, or is directly shorted out for any reason, the amplifier shuts down until temperature stabilizes or the short is removed whereby the module automatically resets to restore power. Clipping control slowly starts rounding off the top of any wave form that distorts beyond 1% so that even when heavily overdriven, the loudspeaker drivers are at low risk of damage.
Some amplifier manufacturers are adding different buffer circuits or trans-formers to the module inputs to raise the input impedance. This was originally done to be a better match to some experimental tube preamplifiers, but is now being offered as a major improvement to the entire sonic palette. We originally offered this circuit as an option but dropped it after determining that it made no sonic difference, even with our tube preamp customers. Others are modifying the module components. This immediately negates the B&O warranty and possibly degrades the performance and efficiency specifications (see paragraph two). I would like to see an independent lab check this out.
Lastly, ICEpower modules are not subject to the 60HZ AC hum cancellation /reinforcement issues that affect conventional amplifiers. I believe this is one reason that they sound so clear in the upper base to lower midrange area where the musical sounds begin to take on the chunk, snap and crack of cello, percussion, horns, etc.
I hope this information has been helpful. If anyone has any differences with, or additions to what has been presented by me, please make contact through the D-Sonic website to discuss any issues.
COM: Controlled Oscillation Modulator;