Preamps: Down and Around
“I push the first valve down
The music goes down and around
And it comes out here.”
(R. Hodgson, E. Farley, M. Riley, Copyright 1935, Chappell & Company)
This snip from a classic tune (a variation of which I first heard in a Three Stooges film) effectively expresses the simple desire of all horn players to make music come out of their instruments. A small amount of air pressure manipulated by a few valves and coils of brass should exit the bell as a pleasing, perhaps even moving, musical expression. In the same way, a small amount of electrical current from a turntable, CD player or video source enters a preamplifier-let’s equate this to the valves in a horn (in British parlance, valve is the word for vacuum tube)-and goes round and round until it is strong enough to enter the amplifier (i.e., the length of brass tubing) where the current is boosted once more, this time to the point that the electricity has the potency to make a speaker cone vibrate in a manner faithful to the sound that went in way back when-like the bell of a horn.
Just as incorrect fingering of the valves can create some mighty strange and messy music, a poorly designed preamp can cause a perfectly good signal derived from a CD or LP to come out edgy and difficult to listen to, unmusical, since a poor preamp may very well be adding unwanted distortion as it does its duty preamplifying.
But we need these potentially dastardly preamps, not just to boost those initially weak electronic pulses, but, via the input selectors, to help organize signals from the various components we want to include in our systems (including matching their electrical qualities like resistance and voltage) and to offer some sort of volume and balance control.
So what does a good preamp do? According to Keith Herron, principal designer and proprietor at Herron Audio in St. Louis, Mo., a company known for very clean and very quiet electronics, a worthy preamp does its job without getting in the way of the music.
“A good preamp performs its functions in a neutral way,” Herron says. “Here neutrality means not coloring the sound of the music with characteristic sounds made by the equipment itself. Sonic colorations such as brightness or warmth distort the sense of timing and ultimately defocus the musical experience. A good neutral and very low distortion preamp will have great clarity and articulate events as they happen in time without loss of musical expression or rhythm.
“If a preamp is not neutral, it will add or subtract something and initially that brightness or warmth might be appealing like sugar. One might enjoy having a little sugar added to one’s breakfast cereal, but that sugar probably would not be as palatable on a filet mignon. The sonic colorations added by a particular piece of audio equipment may have a similar effect by stripping away much of the emotion and rhythm from the musical listening experience and by making different recordings sound in many ways very much the same. Listening under these conditions can get old after a while.”
Herron should know about amplifying music. For many years he was director of research and development at St. Louis Music Inc., makers of Ampeg and Crate musical instrument amplifiers. But he admits that designing a component to translate music accurately is not easy.
“A good preamp,” he says, “will provide adequate gain and impedance matching by using amplifying devices such as tubes or transistors in a way that transparently lets the music get through without adding characteristic sounds of its own. The circuits must be carefully engineered and components must be selected that will not contaminate the original signal. Amplifying sound is a relatively easy task for an electrical engineer today. Amplifying music is not. It is an arcane mixture of science and art.”
Mark O’Brien, owner and designer at Rogue Audio, an innovative new company that offers simple, tube-based designs exclusively, agrees with Herron. “A good preamp should be as transparent as possible to the audio signal passing through it. It should serve as the control center for the audio system but should not add or subtract anything from the music. The more complex the preamplifier becomes, the less likely that it will remain faithful to the original audio signal.
“A well-designed preamp will not color the music in any way,” O’Brien continues, his words still echoing Herron’s. “Some designers will soften the presentation, which can be appealing but not very realistic. Other preamps can sound harsh or grainy, leading to listener fatigue rather than a relaxing musical experience. A good preamp will have a natural sound that is both detailed and musical at the same time.”
So what is it that this magical mixture of science and art does to the electrical impulses generated by Sonny Rollins playing “Way Out West”? What is the music going round and round in, anyway? O’Brien explains, “A typical preamp consists of several sections. First there is a set of inputs, usually from four to six, for hooking up the different source components. These inputs are then routed through a selector switch used for choosing the music source. Next are the balance and volume controls, usually potentiometers, used for adjusting the signal level. These are followed by an amplifying stage or stages. The amplifying section consists of the amplifying device-either a tube, transistor or integrated circuit. This active portion of the preamp circuit requires a power supply, the quality of which is critical to the audio performance. After amplification, the signal is sent to the preamp outputs for connection to the power amplifier.”
Sounds simple, but it obviously isn’t. I have heard preamps that make even Trane sound syrupy and others that make Ella sound almost as screechy as Alvin and the Chipmunks. You gotta be careful out there in the cruel world of hi-fi!
Having heard both the Herron Audio and Rogue Audio products, I can assure you that these guys practice what they preach. Each preamp was amazingly free of coloration and noise and performed the daunting task of creating holographic images of the musicians in question. Herron’s design, the VTSP-1A ($3,995), incorporates four tubes maximized for low noise and low distortion, short signal paths in the wiring that also help to preserve the original intent of the music, and a balance control that, if set at zero, stays almost totally out of the way of the signal, another secret to keeping that signal as clean as possible.
The Rogue Sixty-Six ($1,295), another winner in the neutrality corner, also features tubes in critical parts of the circuit, but features a phono section-quite a deal when you consider the price. (Herron also offers a couple of separate, critically acclaimed phono preamps as add-ons to the VTSP-1A, for an additional $2,750 or $3,250.) O’Brien, like Herron, uses the best parts he can find and has packed a lot into this audio bargain-the resulting sound is convincing evidence of that. The Sixty-Six is well worth a listen if you are shopping for a preamp, and if nothing else, its styling will make you certain this thing is way underpriced.
Another unit I have had the pleasure to audition is the Art Audio VPS ($3,350). This one also sports tubes in its guts and features a no-feedback option that can increase openness, clarity and definition (most preamps and amps include some degree of feedback in the circuit as a sort of error correction but this feedback can degrade the sound ever so slightly). It also offers dead silence when there is no music running through the system. But since the VPS sounds so lifelike, I rarely let it operate without something pumping through its veins. Principal designer Joe Fratus credits the unit’s sound, or lack of same, to its dual mono design consisting of a separate circuit board, transformer, et cetera for the left and right channels. Its ultraquiet separate volume controls for each channel-handmade stepped attenuators with gold contacts-as well as the tube-regulated power supply and the use of other premium parts (like Hovland capacitors) contribute to the transparency of the VPS. Another winner from Art Audio.
There are certainly more preamps out there worth considering: check out Audio Research, a pioneer in modern tube circuitry, Sonic Frontiers, Krell, Classé, Convergent Audio Technologies, Adcom, Hovland, Musical Fidelity, NAD, Anthem, Blue Circle, Cambridge Audio, Arcam, Onkyo and Rotel, among others. Some of these companies offer very affordable preamps, some fall into the cost-is-no-object range, but all will help open new windows on the music you already love.
O’Brien has some advice when shopping, words which should sound familiar to regular readers of this column: “When auditioning your preamp, have your local dealer put together a demo that is similar to your home system. Some dealers may even be willing to let you take home a demo preamp and try it out in your own system. Either way, be sure to have plenty of discs on hand that you are familiar with. Do the instruments and voices sound natural? Do the highs sound correct or are they bright or rolled off? Does the music sound overly warm or does it sound grainy or harsh? For jazz listeners in particular,” O’Brien sums up, “the tube preamp’s combination of tonal accuracy and rich yet detailed sound is quite appealing.”
But Herron says it all in a few words: “If music coming through the preamp makes you feel good and makes you tap your foot, it must be doing something right.”
And if it makes you holler “Whoa-ho-ho-ho-ho-ho,” when it comes out “there,” you are approaching musical nirvana.
Tuning Into Tuners
The public airwaves, as congested with aural garbage as they may be, can still be a wonderful resource for listening to music, even jazz. These days there are reasonably decent public-radio stations scattered generously across the United States. I always search for those tuneful oasises as I drive across the country, and I never fail to find something to keep me entertained and informed, often uncovering new artists who end up becoming long-term faves. After all, as omniscient as we pundits think we are, we can’t really be aware of everything that comes out in every genre of music. So an FM tuner and antenna in the home are indispensable to maintain a real sense of currency-unless you are a traveling salesperson or trucker. (National Public Radio continues to provide some fantastic jazz programming ranging from the long-lived Piano Jazz one-on-one sessions hosted by Marian McPartland to Billy Taylor’s Jazz at the Kennedy Center; check its Web site at www.nprjazz.org.)
Vince Stables of Magnum Dynalab offers some advice on selecting a tuner. “When looking for a tuner, pay attention to the adjacent channel specification. The higher the numeric value the better the adjacent channel performance. This is one of the most important specs for a tuner’s performance. It measures the tuner’s ability to isolate the station you are listening to from the station next to it. In urban areas where there are stations every 200Khz on the dial (91.1 to 91.3 for example), this is critical. And look at capture ratio. The lower the numeric value of this spec the better the tuner’s ability to lock onto the stronger signal when two signals are on the same frequency.
Stables continues, “The performance of a good-sounding tuner begins with a properly aligned front end with good adjacent channel specifications and a clean path to the audio output. Mass-marketed tuners are not aligned individually; they are at the mercy of the microprocessor that does your fine tuning.”
But just as important as the tuner is the antenna. “A tuner is completely dependent on its antenna to receive the FM signal,” says Stables. “If you have an antenna the size of a thimble then you can only offer so much frequency bandwidth to the tuner. Therefore bass goes away; high frequencies can become rolled or chopped off. An antenna is very much like a record player’s cartridge: It is the first contact with your music.”
There are countless tuners to choose from, but in the high-end community Magnum Dynalab is generally recognized as producing some of the best tuners on the market. The MD 90, at $995, is its least expensive, but that aside, this baby is everything you want and more in a tuner. It is ultrasensitive, and the thing I like best is the analog tuning mechanism which, because it isn’t limited to modern, electrically present frequency jumps, allows the listener to slightly detune any given station to dial out unwanted noise and to maximize stereo separation. This would be the selling point for me. I also spent time with the Cambridge Audio T500, not quite as sensitive as the Magnum Dynalab, but at only $300 you can’t ask for perfection-I was still able to pull in my favorite Portuguese station (50 miles away) as long as my antenna was set up properly. The Cambridge is well beyond what you find in the typical receiver and an ideal tuner for most folks, excellent sound and sensitivity for the money, but if you can afford it, the MD 90 is a hands-down winner.
Amplified antennas have become popular of late, but sometimes the amplification of unwanted signals can cause more harm than good. I had a chance to play with a few decent antennas recently: the Magnum Dynalab whip-style one-half wave commercial quality antenna; the ST-2; the cute tabletop Terk AM/FM Q; and the Terk FM Pro, which is a much-lauded powered unit. The small Terk AM/FM Q works great if you are blessed with relatively close broadcasters and even has circuitry to help cut down noise and interference from unwanted stations. But if you are trying to pick up distant stations, try one of the other two choices. They both served to pick up stations 40 to 50 miles from my house that I had trouble receiving previously (though the Terk FM Pro worked better for me with its power supply shut off). But it is important to follow the manufacturer’s instructions-most call for outdoor installation for best reception.
“If you can’t put it outdoors, get your antenna close to a window,” says Stables. “If you have the antenna buried away in a closet not much signal is allowed to reach the antenna. You can hide the antenna behind a drape. I recommend purchasing an antenna from a dealer that has a good return policy since you may need to try different types of antennas to maximize your results. The best option for getting distant stations is a half-wave wave design, omnidirectional antenna mounted as high as you can, hanging the antenna near a window in the highest point of your home. If you are in a bungalow and have access to your attic, mount it at the peak of your roof.”
Preamps: Down and Around