The Sidemen of the System
Amplifiers and preamplifiers don’t get much attention—but they’re essential to your system’s sound
Quick—name three jazz artists. Who’d you pick? Bird? Miles? Hub? It’s a pretty safe bet you didn’t pick Jimmy Cobb or Paul Chambers. Great as they are, they’re best known as sidemen. They seldom get the recognition that the hotshot saxophonists and trumpeters tend to receive.
Amplifiers and preamplifiers are like the sidemen of the stereo world. The sexier components—the speakers, the turntable and the CD player—often attract most of the attention and innovation. Meanwhile, amps and preamps often sit unnoticed in an equipment rack, humbly doing their jobs. However, amps and preamps are no less important than any other component in a system. In fact, they might even be more important than jazz sidemen. After all, you can play a gig without a drummer, but you can’t play a CD without an amp.
Nor can you put together a truly great stereo system without knowing something about amplifiers and preamplifiers. The subject might seem simple; after all, amps and preamps pretty much just boost audio signals. But there are a surprising number of differences among these products—and there’s a lot more controversy about them than you might expect.
The first thing to know about amps is that there are two basic types: amplifiers (or power amplifiers) and preamplifiers.
Amplifiers are simple in function; all they do is boost an audio signal so it can drive speakers. In fact, many amps have no controls other than a power switch. Preamplifiers are more complicated. Although they can raise an audio signal’s level a little bit, their main jobs are to control volume and to select which audio source you’re listening to.
There’s also a device called an integrated amp, which combines an amplifier and a preamp in a single box for the sake of simplicity and lower cost. Finally, there’s the receiver, which is an integrated amp with a radio tuner built in. Most of today’s receivers have surround sound built in, but for this article, we’re going to focus on stereo systems.
There’s one thing we have to clear up right now before we go any further. You will find a few crusty old coots out there who swear all amplifiers and preamplifiers sound the same. To them, they probably do. But you can also find people who say all vodkas taste the same. I once heard someone say George Benson and Wes Montgomery sound the same. There will always be those who just don’t get it, but the general consensus among audio experts is that amplifiers do sound different—and preamps do, too. Sometimes the differences can be subtle, and sometimes they are overstated, but many audiophiles consider them as important as the differences among speakers. Stop by a good high-end audio shop and listen for yourself. They’ll be happy to give you a demo.
As simple as the power amplifier may seem, it comes in a dizzying variety of types. You can buy amps that handle just the left or right channel, and amps that handle as many as 16 different channels. We’ll limit this discussion to one- and two-channel amps. Some audiophiles prefer two single-channel (or monoblock) amps to a stereo amp, to minimize any interference between the left and right channels.
The basic specification of any amplifier is its power output, which is given in watts per channel. A lot of people think you need at least 100 watts per channel for a serious stereo system, and that more is always better. But that’s like saying Hawk was better than Prez because he played louder; many of the amps most loved by audiophiles put out less than 20 watts per channel. Truth be told, you only need a watt or two of power to drive a typical speaker to a normal listening level. The big amps are usually necessary only for large listening rooms and home theaters, and for driving tower speakers with multiple large woofers.
For audiophiles, the biggest decision when choosing an amplifier is whether to go with a transistor (solid-state) model or a vacuum-tube design. Tubes are praised for a warm, natural sound, while transistors are known for a crisp, powerful sound. Through the years, the two have moved closer together—the transistor amps sound smoother, and many tube amps have become more robust. There have even been some amps that use tubes in the input stage and transistors in the output stage.
Transistor amps come in all sorts of “classes.” The differences between them are rather arcane, but here’s what you need to know. Class A amps have a reputation for the best sound, but they generally run hot and cost dearly. (A great example is Esoteric Audio’s $12,000 A-03.) Most of the amps on the market now are Class B (or AB), which is a reliable and powerful technology. Class D amps run cool but put out crazy amounts of power—1,000 watts into 4 ohms, in the case of Bel Canto’s e.One REF1000 MkII. Class G and H amps combine the sound of analog circuitry with the cool-running efficiency of Class D amps.
Tube amps come in two basic varieties: single-ended and push-pull. Single-ended means the same thing as Class A, but the term single-ended is more commonly used in the tube realm. Few of these amps produce much power; a classic example is Cary Audio’s 15-watt CAD 300SE signature monoblock, which is modeled on amps that were common in the heyday of Fletcher Henderson. In fact, some can muster only 3 to 5 watts. In most cases, you’ll need to use super-sensitive horn speakers to get usable volume from these amps. Many audiophiles consider single-ended tube amps the only true path to natural sound.
However, the majority of tube amps available today are of push-pull design, using one or more tubes for the positive half of the audio signal, and a matching complement of tubes for the negative half of the signal. Push-pull tube amps usually put out at least 30 watts per channel, and many deliver 100 watts or more.
One thing to keep in mind with tube amps is that tubes don’t last forever. They eventually burn out—in a year if you run them hard, or maybe five if you pamper them. Then you’ll need to replace them, which is a task you can handle. Manufacturers such as VTL even include circuitry that tells you which tube is faulty. Many audiophiles engage in a practice called “tube rolling,” in which they experiment with different tubes in pursuit of better sound.
The only feature you normally need to be concerned about in a power amp is its inputs. All amps designed for home use have RCA (unbalanced) input jacks. Some also have XLR (balanced) input jacks, like the microphone inputs you see on a mixer. If your preamp offers XLR outputs, you’ll probably want an amp with XLR inputs.
Amps are available at all sorts of prices, from a couple hundred dollars to tens of thousands. Because there aren’t usually any features associated with amps, what you’re paying for when you pay more is generally more power and better sound quality.
Preamp Ps and Qs
Choosing a preamp can be less critical than choosing an amplifier. There are no power ratings to worry about. You can choose from tube and transistor amps, but that’s just a sonic preference. Single-ended or Class A preamps are common, and they don’t present the downsides that single-ended or Class A power amps do. And the tubes in preamps don’t carry much power, so they tend to last a long time; I got 10 years of life out of a set of tubes in a lovely old Conrad-Johnson preamp I once owned.
Once you’ve made the tubes vs. transistors decision, your next concern is the preamp’s features. What features you need depends on what sources are in your system. You’ll need at least one input per source device (i.e., CD player, AM/FM tuner, computer, etc.), plus one or two spare inputs in case you add more sources. If you have a record player, you may want to get a preamp with a built-in phono stage. (If you fall in love with a preamp that doesn’t offer that option, don’t worry—outboard phono stages are available.) If your CD player or phono stage has XLR balanced outputs, you’ll probably want a preamp with XLR inputs to match, such as Parasound’s Halo P3. Watch this year for a new crop of preamps that can even dock directly with an iPod, an iPhone or a computer.
All preamps come with a volume control, but surprisingly, there’s a big difference among volume controls. Traditional preamps use a potentiometer, or variable resistor, as the volume control. Some high-end preamps use a multiposition switch that accesses individual resistors; many audiophiles feel this delivers better sound. Still, others control volume with a digital volume control, which switches resistors through a digital multiprocessor.
As we stated above, many preamps have a balance control and some have tone controls. Most include a remote control. Some have outputs for headphones or a subwoofer. For most people, none of these features is really a must-have, but they might prove convenient for you.
Audiophiles generally prefer to keep all of their components separate, but not all of us have the space or budget for separates. Fortunately, the audio industry offers simpler, less-costly options: the integrated amp and the receiver. Although both products have some compromises—for example, the amp and the preamp use the same power supply—many of them deliver superb sound. And why not? If Rahsaan Roland Kirk could play three instruments at once, why can’t a single-chassis audio product provide both power and control?
Shopping for an integrated amp or receiver is like shopping for an amp and a preamp at the same time. You’ll be concerned about whether it uses tubes or transistors; how powerful the amplifier section is; how many and what type of inputs the preamp section has; and whether or not the preamp has a phono stage. The radio sections of most receivers are pretty much the same—most use generic radio tuning chips and offer enough station-memory presets for anyone.
Many people started their journey into audiophilia with NAD’s small, inexpensive 3020 integrated amp, which debuted the same year Wynton Marsalis did (1978, if you don’t remember). The 3020’s 28-watt-per-channel amp section didn’t shake any floors, but its clean sound won it a lot of fans. NAD’s new $349 C315BEE looks much like later versions of the 3020, but ups the power to 40 watts a side. It makes the perfect pint-sized power source for an entry-level audio system.
Although the 3020 and similar products gave the integrated amp a rep for anemic power, many of today’s integrateds deliver enough juice to drive practically any speaker. A great example is Krell’s S-300i, which puts out 150 watts per channel—and includes an iPod interface to boot. I’ve found the S-300i adequate to drive my 200-pound tower speakers to deafening volumes.
Stereo receivers used to dominate the hi-fi market, but the growth of surround sound nearly eliminated them as a product category. But surprisingly, stereo receivers have seen a renaissance recently, with many new models such as the art deco-styled Outlaw Audio RR2150. Marantz is one of the few manufacturers that never gave up on the category; its latest stereo receiver is the SR4023, an 80-watt-per-channel receiver that at $499 is surprisingly affordable.
You can get decent sound out of any good amplifier, but audiophiles and dealers agree that the best systems are those that match the sound qualities of the speakers with the sound qualities of the amp, preamp, CD player, etc. Whether you base your system around a favorite speaker or around a classic tube amp you just can’t resist, talk to your dealer or chat on some of the audiophile forums to find the most synergistic systems. You’ll find that choosing the right amp and preamp can be just as important as choosing the right bass player and drummer.