In our now almost complete transition into the digital world, there is one general tendency that I uphold as true: Many things that were incredibly complicated to make in the past are not anymore. At the same time our ever-tinkering audiophile mind craves incredibly complicated and difficult products to make. Complexity and effort that go into a solution are examples of having done the exceptional to reach the subliminal. As odd as it may sound, our audiophile line of loudspeakers and sound systems would probably sell even better if they were only more expensive and difficult to make.
To begin with, it's important to state that, for the purposes of this article: An amplifier's job is arguably not to sound ''a certain way.'' Creating the sound and reflecting the artist's intention is the recording engineer's job.. The end user can influence the sound to his or her preference by using equalization, but an amplifier, once again for the purposes of this article, is something that takes a weak signal and turns it into a similar but stronger signal as faithfully as it possibly can.
Audio amplifiers are a case where analog complexity has faded into digital simplicity, but our mind still craves the idea that what we own should be uniquely difficult to build obtain, and operate. Up until the fifties all amplifiers were tube amplifiers. Such amplifier, simply put, heat a charged plate called the cathode inside a vacuum tube until it starts to emit a constant stream of electrons that fly towards another plate with opposite charge, called the anode. To reach their goal they have to pass a control grid. This grid acts as a goalkeeper of sorts and by applying an increasing voltage to it, an increasing number of electrons are sent back to the cathode from where they came.. The amount of electrons thus reaching the anode is inversely proportional to that voltage. Flow of electrons is called current, and since the current is large and the control voltage small, we have ourselves an amplifier; a hot, powerless, inefficient, glow in the dark, beautiful thing that triggers a similar sense of being at home as does a warm chimney.
Good tube amps are rather difficult to make and I have the highest respect for the enthusiast crowd that keeps this technology alive. All over the world an increasing number of people get together to exchange tubes and listen to the different sounds they make in what is known as ''tube rolling.'' Tube amps are so difficult to make, that many manufacturers make gross exaggerations about their capabilities, especially when it comes to power output. The only customers we have had who thought they needed an additional subwoofer despite our speakers more than sufficient bass output were those who believed their tube amplifier manufacturers' highly optimistic claims regarding low frequency power.
Tube amps are said to sound ''warmer.'' Getting back to the premise of the article, ''warmth'' is the job of the recording engineer, not the amplifier, and what is really going on is that because most tube amps are so difficult build to put out any significant amount of power that they are operating at their limits where they start to distort. Distortion is what happens when the amplified signal does not recreate the original signal faithfully anymore, usually because it is operating at or near its power limit. In a tube amplifier distortion at moderate levels sounds absolutely lovely, warm, and ''vintage.'' An underpowered digital or solid-state amplifier however turns into an outright death machine. Such amplifiers when they reach their maximum signal strength, rather suddenly flatten the waveform in what is known as clipping. This leads to tremendous acceleration and thus large forces on the loudspeakers. If you are going to get an underpowered amplifier, by all means get a tube amplifier. Inversely if you do get a tube amplifier, be generous on the specifications and assume that it will be underpowered. Now, a good recording engineer knows how to do ''lovely, warm and vintage'' if that is what he or she wants the recording to sound like. Listening to a mildly distorting tube amplifier is a little like looking at the Mona Lisa through pink sunglasses. Also fun, but not what Leonardo Da Vinci had in mind. Try Edgar Degas if you like pink.
What about amplifiers that are powerful enough though? Allow me to introduce Robert Carver. Mr. Carver is a curious fellow, a stout physicist and engineer who in the eighties devised a method to copy the sound of some of the most expensive amplifiers of the time with one that was only a fraction of their cost but much more powerful. His method was delightful. He simply built a very good amplifier that had a very linear response. It most certainly did not sound “lovely, warm and vintage”. He set it up next to a highly regarded amplifier and gave both an equal but opposite signal. After the amplification, he then fed both signals together and in a perfect world they would cancel each other out. In reality they did not and Carver then used devices called distortion pots to introduce distortion which was present in the much more expensive amplifiers but wasn't that wasn’t present in his less expensive cheaper ones. (Dont use the word cheap in conjunction with a quality product like Carver, it can also mean poorly built, which Carver amps are definitely not)After careful tuning, the output would be identical, and he had copied the acclaimed sound of expensive amplifiers by making his better amp technically worse.
Carver caused quite a stir in the audio industry and was very clever in his ways; he challenged Hi-Fi magazines to have him ''copy'' the sound of any amplifier they chose at any price point and then perform double blind testing to see if anyone could reliably hear the difference. They could not. Bob Carver would then sell such deliberately deteriorated amps as model M1.5T. ’s, or ''transfer function modified'' that had been proven to sound just like a $12,000 Mark Levinson ML-2; a highly regarded mono-block amp that produced just 25 watts. The copied M1.5T sounded just the same but had a whopping 350 watts per channel.
What becomes clear here is that expensive amplifiers aren't technically better, they cater to a given preference in sound and thus second-guess the intention of the recording artist. While this is perfectly legitimate, the idea of perfection in amplification being reflected in price is now probably obsolete.
The digital wave continues to roll and over recent years Class D amplifiers have made a great break through. They are very efficient, technically close to perfect, outright tiny. And they keep a digital signal digital all the way to the loudspeakers. They do that by converting the bits and bits that correspond to a waveform into what is called a pulse width modulated signal. Here, a very fast clock turns a maximum voltage on and off a usually around 300,000 times a second. The relationship between the times the signal is on, compared to off encodes the strength of the musical signal at any point in time. Since this happens so fast and there are some very mild filters that smoothen out the waveform, what the loudspeaker sees is an amplified voltage that very faithfully reflects the input signal. These amplifiers are rather easy to get technically perfect as they are usually designed to prevent clipping through digital protection. And just like Robert Carver in the 1980s, if an amplifier designer wants to get a sound that is a little more ''lovely, warm and vintage'' they know how to do that at little or no additional cost. Class D amplifiers can be outright tiny with our MicroFidelity amps being only a little bigger than a deck of cards.
Today we live in a time where making a truly audiophile sound system available at a much lower price is a distinct possibility. Fortunately for us as a loudspeaker company, the competition that targets low cost usually tends to push the limits on size and materials just a little bit too much to be truly audiophile. This creates a rather nice niche were a new generation that was raised on tiny boom boxes can enter the wondrous world of high fidelity music without breaking the bank.
Arved Deecke is founder of the Danish / Mexican Loudspeaker company KVART & BØLGE that makes audiophile quarter wave loudspeakers and sound systems at a price anyone can afford. In his free time he blogs about all things related to sound, music and audio.
