MTX Soundcraftsmen P100 Preamplifier Review

The Soundscraftsmen name has been associated with quality American-made audio components for more than twenty-four years. The California-based firm, now known as MTX Soundcraftsmen, recently announced a new line of components consisting of a preamplifier and several power amplifiers, including the A200 amplifier(a tuner and other products are also planned).

The P100 preamplifier is a low-profile unit measuring 17 inches wide, 10-7/8 inches deep, and only 1-3/4 inches high. Though not starkly minimalist, it provides only the basic preamplifier functions of source selection, volume, balance, and tone control, tape monitoring, and headphone output.

Finished entirely in black, the P100 has black knobs and pushbuttons, the latter for power switching and tape-monitor selection, clearly marked with white characters. The top and bottom edges of the panel, as well as the controls, are beveled, relieving the otherwise austere appearance. The source selections are marked CD, tuner, phono, and A/V (all of them except phono are interchangeable line-level inputs).

On the back panel are phono-type jacks for the various inputs, plus line and tape outputs. One of the two AC outlets is switched. The unusually high total rating of 1,150 watts enables the P100 to switch almost any power amplifier likely to be used with it.

The P100’s specifications include a frequency response of 20 to 20,000 Hz ±0.5 dB, less than 0.008 percent harmonic or intermodulation (IM) distortion (at an unspecified output level), and a maximum output of 8 volts at less than 0.02 percent harmonic distortion. The A-weighted noise level is specified as 100 dB below full output (presumably 8 volts), which would be 74 dB below the EIA reference output of 0.5 volt. The phono-input capacitance is stated as 200 picofarads (pF). The tone-control range is specified as ±10 dB at 50 and 10,000 Hz.

Complementary metal-oxide semiconductor (CMOS) electronic signal switching is used in the P100 so that the switches can be located close to the circuits that they control, thereby minimizing noise and interchannel crosstalk.

In our tests, the P100’s basic frequency response measured within ±0.1 dB from 20 to 20,000 Hz. With the balance control at its center detent, the channel levels differed by about 0.4 dB over much of the audio range. RIAA phono equalization was accurate within 0.5 dB above 1,000 Hz, but the response sloped off below that frequency to — 2 dB at 20 Hz. The bass tone control met its rated range of ± 10 dB at 50 Hz, but the treble control was a trifle shy of the stated range at 10,000 Hz, where it varied the output by ±9 dB. The treble curves were hinged at 3,500 Hz, and the bass control had a sliding turnover frequency from approximately 50 to 200 Hz. The midrange, from 300 to 2,000 Hz, was unaffected by tone-control settings.

The P100’s output clipped at about 9 volts. Total harmonic distortion (THD) plus noise was 0.006 to 0.008 percent from 1 to 2 volts output, increasing to 0.033 percent just before clipping. The A-weighted noise level, referred to a 0.5 volt output, was -98.4 dB through a high-level input and — 86.7 dB through the phono input. A spectrum analysis of the preamplifier output at levels of 0.5, 2, and 5 volts at 1,000 Hz showed six or seven odd harmonics at each level, with a total RMS value of 0.004 percent.

Sensitivity, for a reference output of 0.5 volt, was 123 millivolts (mV) for the high-level inputs and 1.95 mV for the phono input. The phono preamplifier overloaded at 1,000-Hz-equiva-lent inputs of 134 mV at 20 Hz, 100 mV at 1,000 Hz, and 85 mV at 20,000 Hz. Phono-input impedance was 46,000 ohms at 1,000 Hz.

The Soundcraftsmen P100 provides very good performance at one of the lowest current prices for a good separate preamplifier. The most obvious measurable differences between it and most higher-price preamps are in the accuracy and precision of its components and circuits (such as the RIAA phono-equalization error below 1,000 Hz and the slight channel imbalance).

Its sound quality left little to be desired. Noise and distortion were totally inaudible, the controls operated with a positive action and smooth rotation, and there were no audible switching transients. Headphone volume from the front-panel jack was adequate (with medium-impedance phones) but not the equal of a headphone output driven from a power-amplifier stage, as in a receiver or integrated amplifier.

The P100’s appearance, compactness, and general performance, combined with its smooth operation and bargain price, make it a fine value in today’s market.

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