Aiwa AD-S950 Cassette Deck Review

The AD-S950 is Aiwa’s top-of-the-line analog cassette deck. With a three-head, dual-capstan design, the AD-S950 incorporates Dolby HX Pro headroom expansion together with the full complement of Dolby B, Dolby C, and the more sophisticated Dolby S noise-reduction systems. In addition to automatic selection of bias and equalization for the different tape types, the AD-S950 provides the manual bias-optimizing and tape-sensitivity controls required by Dolby S.

Separate record and playback heads in the AD-S950 allow users to compare the incoming signal directly with the recorded result. The heads are mounted in a common case and use pure-copper coils to minimize residual noise. The two capstans are belt-driven by a DC servomotor. A second DC motor handles the reel drive and shifts the heads and pinch-roller assembly into position.

The window in the cassette-well door of the AD-S950 is rather narrow, and while the relative amount of tape on each reel can be gauged by eye, the labels are not visible. The inner side of the door contains a spring-loaded tape-stabilizer mechanism to damp vibrations that might muddy the sound. The door is not removable, however, which makes cleaning the heads and demagnetizing the heads and capstans somewhat awkward.

When a cassette is inserted, the machine initially emits four loud mechanical thumps, which can be unnerving. These are caused by the operation of the automatic tape-tensioning system, however, and are nothing to worry about.

A calibration button switches in the bias fine-tuning circuit, which uses adjustment tones of 400 Hz and 10 kHz. To optimize performance the user has only to adjust the bias control for equal indications on the signal-level display and then turn the sensitivity trimmer so that the display deflects to a designated mark. After switching the calibration circuit off, the tape must then be rewound to the start of the procedure so that the test tones will be erased at the beginning of a new recording.

Signal levels are shown on a fifteen-segment-per-channel peak-reading fluorescent display, which is calibrated from -35 to +10 dB. Dolby level is marked at -2 dB, but it measured at -4 dB with our calibrated tape. Tape position is read out in minutes and seconds on a four-digit elapsed-time display that automatically blinks when approximately 3 minutes remain on the side. In conjunction with the counter reset, a Zero Return button helps you find a given place on the tape during fast-wind modes.

Light-touch solenoids operate the usual tape-transport functions, which also include cue and review. An MPX button activates a filter to prevent any residual stereo-multiplex components from affecting the accuracy of the noise-reduction systems while recording from FM radio. The usual pause and record-mute buttons are also provided, as is a switch for turning on the deck with an external timer. The wireless remote-control unit supplied with the AD-S950 permits controlling its transport functions from a distance and dimming the control display.

Small front-panel knobs control the bias and record sensitivity along with record channel balance and headphone playback level. A single large knob sets the overall record level. The deck's rear panel carries the record and playback jacks.

As is clear from the accompanying graph, the measured playback response of the AD-S950 was very good. With our ferric and CrO2 IEC-calibrated BASF tapes, response fell by less than 3 dB at 18 kHz and only 1 dB at 31.5 Hz. Between those points the variation was less than ±0.5 dB.

On an overall record/playback basis, response with our metal tape (TDK MA) was extraordinarily flat — within ± 1 dB from 20 Hz to 20 kHz — at the usual -20-dB recording level. Our ferric (TDK D) and chrome-equivalent (Maxell XL-II) samples dropped slightly (2 to 3 dB) at the 20-Hz bass end and more appreciably in the top half octave. At a level of 0 dB the extreme treble range ran into the usual saturation problems, but with Dolby S and metal tape the loss was only 1.5 dB at 18 kHz.

Signal-to-noise ratio (S/N) was very good, ranging from 66.6 dB (ferric tape, Dolby B, A-weighting) to an excellent 82.5 dB (metal tape, Dolby S, CCIR weighting). Wow-and-flutter was 0.085 percent (rated 0.1 percent) on the IEC peak-weighted basis, and 0.046 percent WRMS (rated 0.035 percent) on the JIS standard. Dolby tracking error measured only 0.5 dB with our chrome-equivalent tape, and the worst-case error was 2.7 dB, using Dolby S with ferric tape, better figures than we normally obtain.

The AD-S950, if slightly boxy in appearance, was easy to use, and its calibration feature worked perfectly with a variety of tapes we tried on it. Except for its initial thumps whenever it adjusted the tension for a newly inserted cassette, the deck ran quietly and without fuss. The controls are well laid out and well marked, and the display is crystal clear.

With both prerecorded cassettes and those we made ourselves, we found the sonic qualities of the AD-S950 to be very good indeed. Frequency response was broad and smooth, noise was audible only at extremely high playback levels, and wow-and-flutter was inaudibly low.

The Dolby S noise-reduction system is designed to give cassette users the same audible performance they can get from CD’s, and in the Aiwa AD-S950 this hope is very nearly realized. Tape users still without Dolby S are well advised to try it on a deck like the AD-S950: Record a cassette with no input signal and play it back at a very high volume level while successively switching from no Dolby to Dolby B, Dolby C, and, finally, Dolby S. At each stage the unwanted noise components will shrink dramatically, with Dolby S knocking out the last remaining low-frequency “grunge.”

No analog copy is absolutely perfect, however, and we found that we could — barely — distinguish the original from the copy, at least with solo-piano recordings. There was also a very slight loss of definition and ambience-produced soundstage width. That’s a small price to pay for extending the enjoyable life of a medium long dear to music lovers, and I’m happy to recommend the Aiwa AD-S950 to anyone looking for solid value in a medium-price cassette deck.

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