Thomas J. Norton

Aerial's new 6T loudspeaker ($6000/pair) is a 4-driver, 3-way and will be available in February. It sounded very promising: tight bass (the material didn't challenge the extreme bass, but what I did hear—bass drum—suggested more extension than you might expect from two 150mm woofers); open top end, uncolored mids; fine imaging. Typically fine sound from Aerial Acoustics.

While it is not quite accurate to say that $500/pair loudspeakers are a dime a dozen, they are by no means unusual. And since this is a price area where major design compromises are mandatory (footnote 1), the sound of such loudspeakers tends to vary all over the map, from pretty good to godawful—depending on what performance areas the designer chose to compromise and by how much.

I approached this latest half-grander with little enthusiasm, despite Siefert's persuasive literature, I have, after all, been reading such self-congratulatory hype abiout new products for longer than most Stereophile readers have been counting birthdays. This, I must admit, was ho-humsville.

When a manufacturer sets out to design and build a product, be it in high-end audio or any other field, the final retail price is usually a prime consideration. Parts and assembly are only part of the equation; there also must be enough buyers to amortize the design and development costs. If the product is to be a flagship model—something a company hopes will give a lift to its entire line—engineers will sometimes throw caution to the winds, designing a product without thought to its ultimate price, which is only set after the design is complete. When Madrigal Audio Laboratories set out to design their No.30 Reference Digital Processor, they appear to have chosen exactly this approach.

A useful test CD has recently come my way, courtesy of the Stereophile editorial staff in Santa Fe (a copy was provided to each of the contributing equipment editors). Digital Test was produced in France by Pierre Verany (PV.788031/788032, 2 CDs), and is distributed in the USA by Harmonia Mundi. It provides a wide variety of tests and useful musical selections, but the subject of special interest here is its test bands for evaluation of laser-tracking and error-correction capability.

There are two interrelated parameters which, in the absence of drop-outs or information gaps—we'll get to them shortly—can affect the ability of a player to track the CD "groove" (or "whorl," as the quaintly translated disc booklet calls it): linear "cutting velocity" and track pitch. The standards for the first establish a range of 1.2 to 1.4 meters/second (the rotation speed of the disc varies from 500 to 200rpm from the inside to the outside of the disc to maintain this linear velocity); for the second, the spacing between adjacent tracks, from 1.50 to 1.70 micrometers (µm).

Compared to the Krell KSA-300S power amplifier that I also review this month, the KRC preamp's design is, at first glance, almost conventional. But its thoroughly high-end internal design has been equally well thought-out and executed. Its main, four-layer, glass-epoxy circuit board is for the audio signal, DC power, and ground—two layers for the latter are said to minimize noise. The gain stages are pure class-A and complementary. As in the amplifier, the circuit is direct-coupled, with servo circuits controlling the DC offset. The fully regulated power supply is housed in an external chassis. Seven inputs are provided: four single-ended, two balanced, and one single-ended tape. All inputs are line-level except for the optional, single-ended phono stage. (This review will address the line stages; a Follow-Up will discuss the phono stage's operation.) There are three outputs: balanced and single-ended main outputs, and a single-ended tape output.

You'd probably be surprised to learn that headphones are the most common means for listening to music. No, I didn't get that from a book, but from personal observation. I'm referring here to personal portable stereo listening—the ubiquitous Jogman with which a whole generation has retreated into its own private world, isolated from traffic noise, muggers, and, at home, housemates or parents screaming "Turn it down!"

<A HREF="http://blog.stereophile.com/ces2009/now_thats_what_i_call_music">James Bongiorno</A>, the engineer behind the Sumo Andromeda, has enjoyed a long and colorful career as an audio amplifier designer. He has cast himself at times as an <I>enfant terrible</I>, exploding at audio critics and running scandalous advertisements (footnote 1). His best-known amplifier is the Ampzilla, produced by Great American Sound, but he also designed the Dyna 400. Currently Jim is living on a boat and serving as part-time consultant to the Sumo Company.