Don’t Mess With The Music: Designers’ Secrets for Great Preamps

Posted on by Mike Quinn

“I push the first valve down
The music goes down and around
Whoa-ho-ho-ho-ho-ho
And it comes out here.”
(R Hodgson, E Farley, M Riley, Copyright 1935, Chappel & Company)

This snip from an old classic tune I first heard in a Three Stooges film effectively expresses the desire of all horn players to make music come out of their instrument. 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 (coincidentally, in British parlance, valve is the word for vacuum tube), and goes round and round until it is strong enough to enter the amplifier (the length of brass tubing, if you will) 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. The music comes out here.

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 (www.herronaudio.com) in St. Louis, a company known for very clean and very quiet electronics, a worthy preamp does its job without getting in the way of the music.

Keith Herron, Herron Audio

“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 will 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 continues, “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 (www.rogueaudio.com), an innovative company which 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.

O’Brien continues, his words still echoing Herron’s, “A well-designed preamp will not color the music in any way. 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 it that the music is 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 Coltrane sound syrupy, and others that make Ella Fitzgerald sound almost as screechy as Alvin and the Chipmunks. Ya gotta be careful out there in the cruel world of hi-fi!

Herron Audio VTSP-3A Preamplifier

Having heard both the Herron Audio and Rogue Audio products, I can assure you that these guys practice what they preach. Each was amazingly free of coloration and noise and performed the daunting task of creating holographic images of the musicians in question. Herron’s design, his VTSP-3A ($6550/list) incorporates vacuum tubes maximized for low noise and low distortion, short signal paths in the wiring which also helps 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.

Rogue Audio Perseus Preamplifier

The Rogue Perseus ($1895/list) is also a 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 separate, critically acclaimed phono preamp, the VTPH-2 as an outboard add-on to the VTSP-3A, for an additional $3650.)  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 Perseus 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 under-priced.

Art Audio VPS Preamplifier

Another unit I have had the pleasure to audition of late is the Art Audio VPS ($4500 www.artaudio.com). Surprise! this one also sports tubes in its guts, features a no-feedback option which 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) and offers dead silence when there is no music running through the system. But since it 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, etcetera for the left and right channels. Its ultra-quiet 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, Krell, Classé, Shindo, Convergent Audio Technologies, Hovland, NAD, Blue Circle, Arcam, 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 website:  “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,” the RogueMeister 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.

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