Marantz PM-94 Amplifier

One quick look at the Marantz PM-94 integrated amplifier, and I am reminded of the kinds of components that first propelled Saul Marantz and his company to the pinnacle of the high-end audio realm in the 1950s and 1960s. The sheer elegance of the gold front panel (it's available in black, if you insist), the solid look and feel, and, yes, the high price of this integrated amp all bring back memories of such Marantz classics as the Model 10 B tuner. Of course, Saul Marantz hasn't been involved with the company in many years, but with products such as this superb-sounding amplifier, it's clear that present management is attempting to recapture the company's original image.

The PM-94 incorporates four separate power supplies. Each channel has a separate supply for the low-level voltage-amplifying circuitry and another for the MOS-FET output stage. Separate windings on a toroidal power transformer ensure adequate current capacity when driving low-impedance loads and also help to reduce hum and interchannel crosstalk.

The PM-94 features circuitry which Marantz calls "Quarter A" operation. This term denotes that the amplifier operates in pure Class A until power output reaches approximately a quarter of its rated value. The output stage changes to Class-AB operation only at high signal levels. This would explain the heavy weight of the PM-94 (51 pounds) as well as the extensive open grille work on its top surface. Class-A operation means high idling current, even in the absence of signal, which, in turn, means an amplifier that will run warm and therefore require adequate ventilation. Since average power levels in music are at least 10 dB (and often more) below short-term peaks, the PM-94 operates in Class A nearly all of the time.

Examination of the inside of this amplifier revealed the use of extremely high-grade components. The chassis is copper plated, and, according to Marantz, oxygen-free copper wiring is used for all critical signal-handling connections. All connectors are gold plated for positive, corrosion-free contact. Another reminder of earlier Marantz preamps and amps is the use of separate bass and treble controls for each channel. And, as if to satisfy all factions, Marantz designed this amp so that CD and phono inputs can be routed directly to amplifying circuits, bypassing the tape-dubbing and tone-control circuitry. This feature should please those who eschew tone controls altogether. For other program sources, the tone-control circuitry can also be selectively defeated.

The phono section offers three separate input levels (MM and low- and high-level MC), and a high-quality transformer is employed for the moving-coil cartridge inputs. A separate pair of preamp output jacks permits you to connect a second amp for a biamplified system. The sample that I tested had a rose-gold colored front panel and hand-rubbed rosewood side panels. Should you prefer the satin-black front-panel finish, that version comes with oak side panels.

Control Layout

The symmetrical layout of the PM-94's front panel includes four gold-colored rotary knobs at the left, for independent left- and right-channel bass and treble control, and four matching knobs at the right. These four knobs handle master volume, selection of the phono input (MM and two MC gain settings), selection of major signal inputs (CD, phono, tuner, AUX 1, or AUX 2), and tape-copying modes.

Below the four rotary knobs at the left end of the panel are a "Power" on/off button, a stereo headphone jack, and two speaker-selector pushbuttons. Below the four rotary controls at the right are subsonic filter on/off and stereo/mono pushbuttons, a small rotary balance control, and a "CD/ Phono Direct" button which, when pressed, minimizes the signal path from input to main amplifier stages.

The center section of the panel is elegantly bare, except for a vertical bank of tiny indicator lights that show which program source has been selected, whether the "CD/Phono Direct" button has been pressed, and whether the amp is in one of its several tape-monitor modes. Six additional nonprotruding square pushbuttons, along the bottom of the panel's center section, include four tape-monitor switches (for one of two tape decks or DAT recorders, the audio loop of a Hi-Fi VCR, and to select "Source"). The remaining two switches are "Tone Defeat" and "Muting."

The rear panel has four pairs of color-coded speaker terminals of the type that securely lock the stripped ends of speaker cables in place. There are three a.c. receptacles for the power cords of associated components (two switched, one unswitched), the usual array of gold-plated phono and high-level inputs, the preamp out and main amp in jacks, three sets of tape-monitor in and out jacks, and a chassis ground terminal for use with turntables. A fuse-holder completes the rear panel.

As mentioned earlier, large open grille areas atop the cabinet allow for dissipation of the increased heat associated with Class-A operation, and the owner's manual warns not to obstruct these openings or those beneath the cabinet. You can expect the grilles to get quite warm when the amp is operating, regardless of volume-control setting or whether a signal is even being applied to one of the inputs.

Use and Listening Tests

I've had the Marantz PM-94 mounted in my system for the better part of a week now, and during all that time, while playing everything from some of my older LPs to my latest CD and DAT acquisitions, the amplifier has been able to drive my reference Infinity RS 9 Kappa speakers with no difficulty. I can report that the "CD/Phono Direct" switch is no mere gimmick. Although I detected little or no difference between the direct mode and the regular mode (with tone controls defeated) when playing LPs and cassettes via the CD input, there seemed to be a definite firming up of the image when I listened to some of my more recently acquired CDs. Vocals were more solidly positioned between my speakers, and it seemed somewhat easier to pinpoint and concentrate on individual musical instruments of orchestral selections.

If you want to put an amplifier such as this through its paces, I recommend playing straight through Telarc's new CD sampler, Sampler Five Plus (CD-80005). It's got everything on it from Vivaldi to Liza Minnelli. In addition to 65 or so minutes of music of every genre and of widely differing dynamic ranges, the "Plus" in the title refers to a few minutes of sound effects such as pistol and rifle shots, cannons, and aerial explosions-all taken from sound-effects tracks of earlier Telarc LPs and CDs. The Marantz PM-94 handled the sound effects with as much aplomb as it did the musical selections, though I was careful to start my effects listening at low level settings-as cautioned by Telarc in the notes accompanying the sampler.

The clarity of sound reproduced by the PM-94, particularly during quieter passages, seemed to confirm at least some of the advantages of Class-A operation. I must confess, too, that when sudden loud passages were reproduced, I was not conscious of any sort of artifacts caused by the amplifier's switching between Class A and Class AB. Whether this is because such switching transients would be masked by the levels involved or because Marantz has figured out a way to have the switching occur in a totally seamless manner is academic, so long as the system doesn't intrude on musical integrity and enjoyment.

I am told that vintage Marantz products built in the early years of the company's history, if in working condition, can bring a high price here and a very high one abroad. If that's the case, then the rather high price of this Marantz "limited-production" amplifier may well be thought of as an investment for the future. Meanwhile, as you wait for its value to appreciate, you can enjoy the PM-94 as a central component in your present-day audio system.

Marantz PM-94 Amplifier photo