Atma-Sphere Music Preamplifier 3 (MP-3)
Getting back to basics pays off big time.
Review By Wayne Donnelly
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  Atma-Sphere Music Systems certainly has one of the more distinctive (and, to me, endearingly goofy) marques in high-end audio. Sometimes I think this St. Paul, Minnesota-based outfit might adopt a more directly descriptive moniker — something like "Different Drummer Audio" or "Plain is Beautiful Electronics." Atma-Sphere honcho Ralph Karsten has very clear convictions on the right way to make audio gear, and year after year he adheres unwaveringly to his approach, unswayed by technical and market trends — you know, far out stuff like remote volume control. For this writer, the company's inner-directed philosophy is by turns inspiring and slightly frustrating. How so? Read on.

Balance, Balance, Balance
The foundation of the Atma-Sphere way lies in the phrase "Balanced Differential Design^®." I was surprised a couple of years back to discover that the company had registered that familiar phrase as a trademark. I (and many other audio writers) have long flung it about as a generic descriptive term — like people casually say Coke or Kleenex for any similar product. At Atma-Sphere they mean it; every component the company builds is a fully balanced differential design.

A couple of other key factors separate the MP-3 from the general run of tube preamplifiers. The company cites the patented direct-coupled Circlotronic^® output, derived from their line of OTL amplifiers. In addition, the MP-3 employs zero feedback throughout. Taken together, those attributes are unique among tube preamplifiers in today's market, according to Atma-Sphere.

Other notable technical features include balanced passive phono equalization, which contributes materially to the fine performance of the internal phono stage. Volume control does not use a conventional potentiometer, but a precision 23-position stepped control built with 96 resistors on a custom-built switch. A front-panel toggle switch enables 180-degree phase flip (a good feature, but much more useful to this writer when remote–controllable). "Star" grounding is used throughout, a scheme that has yielded superior quietness in other units I have reviewed previously.

The depth of the company's allegiance to balanced operation is evident when examining the MP-3's rear panel. There are pairs of XLR jacks (only) for the phono and auxiliary 1 and 2 inputs, as well as the output to the amplifier. Only the two sets of tape out/monitor in circuits use RCA jacks. The tape monitor in jacks can of course be used to connect single-ended source components, but otherwise the MP–3 sticks strictly to its balanced guns.

The front panel is also unconventional. Rather than a source selection knob, we get a row of toggle switches. This scheme is unintuitive, but not hard to figure out. In lieu of a balance control knob, small knobs for level setting of the left and right channels flank the large main volume control. (I like that arrangement.)

Upgrade Options
Several extra–cost options are available to enhance the performance of the MP-3. Here is the list, with retail prices for each:

•  Power supply regulation ($600)

•  Teflon® custom coupling caps ($600)

•  Damping package ($500)

•  Caddock resistor package ($1,500)

•  Low-output MC phono step-up transformers ($750); recommended only if cartridge output is less than 0.3mV

Ralph Karsten tells me that the review unit is upgraded with power supply regulation; that brings the price of the unit as reviewed to $4,800. I suspect that the regulation contributes substantially to the MP-3's impressive dynamic control across the full frequency spectrum. My trusty adding machine tells me that a "fully loaded" MP-3 would price out at $8,150. Can't help wondering what that would sound like....

Review Setup
The MP-3 replaced my reference VTL 7.5 line stage during the review period. The analog source was my Basis 2800 TT/Graham 2.2 arm/Transfiguration Temper cartridge. The digital source was the ModWright/Denon 3910 all-format player I reviewed in July. Loudspeakers were the planar-ribbon Analysis Amphitryons, larger siblings of the Omegas I reviewed in March. Cabling included excellent power cords and cable enhancement accessories from Jack Bybee, with A Capella interconnects and speaker cables (review coming). The MP-3 drove the Spectron Musician III Class D stereo (reviewed in March) and VTL Siegfried Reference monoblock (review in progress) amplifiers. Both are true fully balanced (dare I say, differential) amplifiers, excellent partners for the balanced MP-3.

Because the MP-3's phono jacks are XLR, and my Graham phono cables are RCA — like, I would guess, probably 99 percent of the phono cables in use today — I briefly used a pair of RCA-to-XLR adapters to do some "ballpark" comparisons among the MP-3's phono section, my reference Thor TA-3000 Mk. II (tubed) and the superb solid-state Ray Samuels Emmeline XR-10B phono preamplifiers. As I expected, both of the far more expensive separate phono stages (costing as much or more than the entire MP-3) clearly outpointed the MP-3 — although less decisively than I expected. But I knew that using those adapters to connect to the MP-3 put the latter at a disadvantage. So, for the serious review listening sessions I replaced my Graham phono cables with a set of DIN-to-XLR cables supplied by Atma-Sphere. The improvement from that change was easily audible. The descriptions of phono performance below are based only on listening through the Atma-Sphere XLR phono cable.

Phono Performance
As near as I can recall (can't find the literature), my particular version of the Transfiguration Temper cartridge outputs around .3 to .4mV. That's on the low side, but within the range specified by Atma-Sphere for use with the MP-3's phono section.

Considering the cartridge's lowish output, the MP-3 was surprisingly quiet on phono, especially since the section uses seven 12AT7 tubes and no step-up transformer. Tube noise was discernible, but not very obtrusive--really noticeable only on quiet, intimate recordings. (Bill Evans' Waltz for Debby comes to mind.) Records with big dynamics — orchestral blockbusters (such as the Classic Records reissue of the great Dorati/LSO Firebird on single-sided 200-gram pressing), or large jazz ensembles (such as Gil Evans' Out of the Cool), were consistently exciting to hear. And great rock LPs — especially live ones such as the Stones' Get Yer Ya-Yas Out or The Band's The Last Waltz — seemed to leap out of the speakers and take over the room. Fun fun fun!

This excellent-sounding phono section adds just $550 to the price of a line-stage-only MP-3. I suspect it would be hard to find a separate phono stage near that price that would deliver the impressive combination of glorious dynamics, timbral fidelity, imaging precision and voluminous soundscaping that I heard from the MP-3 with record after record.

Line Stage Performance
My CD player does not provide for balanced output, so I connected it to the MP-3 through tape monitor RCA jacks. Despite that "handicap," the sound of various types of silver discs through the MP-3 seemed more like than unlike the qualities I so admired in the phono presentation.

Especially impressive was the unit's control over dynamic scaling. The microdynamic elements in particular benefited from the MP-3's very quiet line section and excellent detail retrieval. The Michael Tilson Thomas/San Francisco Mahler Second Symphony SACD has become one of my favorite review discs, partly because its dynamic range is as wide as any CD I can think of. On one hand, it contains barely audible moments of ethereal delicacy. On the other, this is the only disc with which I have managed to blow the circuit breakers powering the 800-watt VTL Siegfrieds. (Gotta get those dedicated 20-Ampre outlets installed in my listening room!)

From Mahler to Gershwin to Verdi to Miles, to Aimee Mann to Roseanne Cash to Dylan to Horowitz to… well, you get the picture. The MP-3 consistently dug into the heart of the music and brought me into intense emotional involvement with virtually every recording. No, I didn't like having to cross my darkened room to adjust the volume or verify polarity at the preamplifier, but the musical presentation left little to complain about. Some audio components are just instruments; the MP-3 is a true music maker.

Bottom Line
I love my VTL 7.5 preamp. It sounds great, looks great, and offers degrees of flexible functionality and ergonomic ease that can be matched by very few competitors. In the couple of years I have owned it, the 7.5 has proven itself an ideal reviewer's tool. But after a recent price increase, it now retails for a cool $15,000. The MP-3 comes very close to the sonic performance of the VTL, at one-third the price. No bells, whistles, or remote controls, not much flexibility, and it is hardly an example of audio jewelry. Back to basics with a vengeance.

Specifications
Type: Tubed preamplifier with moving coil and moving magnet (MC / MM) phonostage

Tube Complement: seven 12AT7 (phono section)
                                  two  6SN7GT (output section)
                                  two 12AU7 (line stage)

Frequency Response: 0.2Hz to 200KHz (+0dB, -2dB)

Gain: ~15dB linestage, ~50dB for phonostage

Phono Section Frequency Response: 0.5Hz to 90KHz

RIAA Accuracy: 0.1dB

RIAA Phono Sensitivity: for 0.5V @ 1KHz = 0.2mV

Minimum Recommended Phono Input: 0.3mV

Phono Input Overload: 500mv

Warranty: 3 years

Price as reviewed: $4,800

Company Information
Atma-Sphere Music Systems, Inc. 
160 South Wheeler
St. Paul, MN 55105

Voice: 1.651.690.2246
Fax: 1.651.699.1175
E-mail: Ralph@atma-sphere.com
Website: www.atma-sphere.com