A Preamp Plus EQ from SAE
SAE Model 2900 stereo preamplifier in rack-mount case. Dimensions: 19 by 5 1/4 inches (front panel), 3 3/4 inches deep plus clearance for controls and connections. Price: $500.
Warranty: "limited," five years parts and labor.
Manufacturer: Scientific Audio Electronics, Inc., 701 E. Macy St., Los Angeles, Calif. 90012, USA.
With the exception of a few designs in which their omission is explained either as economy or purism (depending upon the price point), tone controls have traditionally been a standard feature of preamplifiers. As graphic and parametric equalizers gained in popularity, some companies-SAE a notable example--began to substitute them for conventional tone controls. Many of these preamp-cum-equalizer designs are complex, bristling with more levers than most people would dare to shake a stick--or twitch a finger--at. And they tend to be expensive besides.
In the Model 2900, SAE has apparently sought a middle ground: Its parametric equalizer is more than a bass and a treble knob and yet is not so elaborate as to strain either the user's understanding or budget. But the equalizer has not shrunk to minuscule proportions, either; its controls occupy virtually half of the front panel.
Viewed as a basic preamp, the 2900 is quite a solid piece of work. Though TIM sleuths may look askance at the fact that the figure for 20 kHz is just about double that at midband, the percentage of total harmonic distortion plus noise in the output is tiny indeed. Measured by the conventional procedure, IM distortion turns out to be less than THD. With respect to the 2-volt output level at which these data are taken (with the volume control adjusted so that a 0.5-volt input is required), the Model 2900 is capable of more than 14 1/2 dB of headroom before clipping.
For all practical purposes, the frequency response curve of the preamp can be drawn with a ruler held horizontally, the corner frequencies (-3 dB points) being below 10 Hz and above 100 kHz. All of the various inputs demonstrate good sensitivity and very good weighted signal-to-noise ratios. The overload point of the phono stage is adequately high, and the RIAA equalization is close enough to the target to preclude offending anyone's ears.
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SAE Model 2900 Preamp/Equalizer
Output at clipping (channels driven simultaneously)
L ch 11.0 volts
R ch 11.0 volts
Frequency response + 0,-1. dB, 10 Hz to 20 kHz +0,-2'/: dB, below 10 Hz to 100 kHz
RIAA equalization + 1,-'h dB, 20 Hz to 20 kHz
Input characteristics (re 0.5 V; noise A-weighted)
Sensitivity S/N ratio phono 1, 2 0.58 mV 75 dB tuner, aux 32.5 mV 86 dB tape 1, 2 32.5 mV 86 dB Phono overload (clipping at max. gain) 195 mV at 1 kHz
THD + N (at 2 volts output) <0.012%, 20 Hz to 20 kHz
IM distortion (at 2 volts output) 0.0035% 100-Hz filter -3 dB at 100 Hz; 6 dB/octave 30-Hz filter-3 dB at 30 Hz; 12 dB/octave
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The input selector and OUTPUT CONTROL, both operated via pushbuttons, are functional and easy to use. The output controls are a bit unconventional: They allow a choice among normal stereo, mono left channel, mono right channel, mono sum, and reverse stereo, depending on the combination of buttons pushed. Additional buttons cut the EQ section in and out of the line and tape outputs as well as engage the low-frequency filters. The sliding potentiometers that serve to control volume and balance and to adjust the parameters of the EQ section respond easily to the touch of a finger and are noise-free in operation. True, the Model 2900 as a control center can take getting used to: The layout of the panel is unusual and the markings of the controls strike us as just a little busy and cluttered.
But the feature of the preamp that commands the lion's share of one's attention is the parametric equalizer, which like others of its type consists of several sections-two in this case-each adjustable for amplitude, center frequency, and bandwidth. The two sections partition the audio band at 1.2 kHz, the treble operating above that and the bass below. Indicated center frequencies are reasonably accurate, though not exact, and so are the indicated degrees of boost and cut. Calibrated (somewhat cryptically) in octaves and fractions thereof, the bandwidth controls, set as narrow as possible, yield ±3-dB boost/cut points two octaves or less apart in all cases of maximum boost or cut; the widest setting separates these points by something in excess of six octaves. Clearly, a high degree of flexibility has been provided.
Laying aside our lab data and putting our ears to work for a time, we found the basic performance of this preamp unimpeachable. It interfaces well with phono cartridges, and with two-way tape dubbing and two sets of MAIN OUT jacks, the interconnection and control possibilities look flexible indeed.
The low-frequency filters, on the other hand, are problematical: The lower one, with its 30-Hz turnover and a nice, sharp slope, is about one octave too high to deal with troublesome infrasonic without taking an audible bite out of bass-drum pulses and organ pedals. The upper filter, turning over at 100 Hz with a gradual slope, amounts to a tone-control function; its effect on the underpinnings of the music would be hard not to notice.
More likely as a result of our inexperience than because of any problem with the unit, we had difficulty with the parametric equalizer, principally in relating the settings of the controls to what we heard. The hardest control to use by ear is BANDWIDTH, which has an effect that few nonprofessional users are conversant with. We suspect that someone who just wants to tweak up the treble a bit on a dull recording or restore the bass that a low listening level seems to take away will be happier with conventional tone controls.
But the Model 2900 is surely not targeted at people whose interests end there. It decidedly wants to be in the hands of someone who will put it to work-fixing up dubs, taking the chaff out of old, treasured recordings, excising hum from some recalcitrant component, improving a loudspeaker system. And we'd bet that folks like this will not only willingly learn how to use it, but lore it besides.
NEW MEASUREMENT STANDARDS
In making comparisons between current reports and those published in the past, readers are cautioned to pay particular attention to the reference levels and similar test criteria cited. S/N ratios for electronics, in particular, are measured very differently now that we have adopted salient features of the new HF amplifier-measurement standard. While we believe that the new technique i which also implies a saner approach to loading of all inputs and outputs) will result in measurements that more perfectly reflect audible, in-use effects, they cannot be compared directly to the numbers resulting from the former, more conventional lab measurements.
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(High Fidelity, Jan. 1979)
Also see:
Marantz Model 5030B cassette deck (review, Jan. 1979)
JVC turntables (ad, Nov. 1977)
Sansui DC amplifier (ad, Jan. 1979)