Technics RS-B100 Cassette Deck Review

Aside from offering three noise-reduction systems (Dolby B, Dolby C, and dbx), three heads, and a dual-capstan transport, Technic’s RS-B100 includes some “hidden” features in its circuitry. While they may not have immediately obvious sonic advantages, they indicate the extent to which the Technics designers have pondered the problems of cassette recording.

For example, every analog recorder introduces quite extensive phase shifts to the signal (these come mainly from the record and playback equalization circuits). The RS-B100 is unique among home cassette decks we have examined in that it contains phase-compensa-tion circuits to correct for these phase shifts. If nothing else, the circuits permit much more accurate recording and playback of square waves. The manufacturer’s literature says the effects of the phase compensation become more audible when tapes are copied since the cumulative phase distortion is drastically reduced. Other circuit features of the RS-B100 include a direct-coupled play back amplifier utilizing dual FET’s (field-effect transistors) for lower noise.

The separate record and playback heads of the RS-B100 allow the user to make instant quality comparisons between source and tape. They also enable the use of appropriately different head-gap widths for recording (2.5 micrometers) and playback (0.8 Mm). Both head elements are contained in a single case and are made from an amorphous (non-crystalline) metal alloy that combines extremely good magnetic characteristics with high wear resistance. The tape transport uses a direct-drive d.c. servomotor to turn the leading capstan, which is belt-coupled to a trailing capstan of a different size. The dual closed-loop capstans isolate the tape from any additional wow/flutter-producing sources as it crosses the heads. A separate d.c. motor turns the reel hubs, and a third is used to position the head block.

The cassette well has better rear illumination than do most, and its clear door (removable for head cleaning) affords a full view of the cassette label and the amount of tape remaining on the side. Detectors inside the well automatically switch equalization and record bias for the different tape types. The tape optimization facilities include both 400-Hz and 12-kHz oscillators, for tape-sensitivity and bias adjustments, respectively, and while the procedure is being run the resolution of the fluorescent record-level indicators is temporarily increased to show small 1 -dB changes. During regular operation the indicators read levels from —40 dB to +18 dB, and signal peaks are held for approximately two seconds to facilitate reading.

The overall dimensions of the RS-B100 are 17 inches wide (19 inches with rack adaptors installed), 3-3/4 inches high, and 10-1/4 inches deep. The unit weighs slightly over 12 pounds. Price: $800.

Lab Tests

Playback frequency response, checked with our IEC calibrated tapes, showed a slight, smooth dip in the upper midrange (—1.9 dB at 4 kHz) with both the 120-microsec-ond (ferric) and 70-μs (chrome and metal) tapes. Above this point, however, the 70-ms tape rose steadily to + 3 dB at 18 kHz, while the ferric (120-μs) tape dropped slowly to — 3.7 dB at the same frequency. From the variations we observed at the highest frequencies of the ferric test tape, we suspect that a combination of tolerances between the tape and the deck resulted in an azimuth error that caused the high-end losses shown. Certainly we did not hear the problem while playing other tapes, and it did not show up in the overall record-playback response curves.

Our sample of the RS-B100 was supplied with the three tapes used in its factory checkout (TDK AD, TDK SA-X, and TDK MA-R), which are representative of today’s premium-grade formulations. With these tapes, overall record-playback frequency response, measured at 20 dB below the 250 nanoweber/meter international standard “0-dB” level, was within +1, — 2 dB from approximately 32 Hz to 20 kHz, which is extremely good performance. At the IEC 0-dB level, which corresponded to a reading of +4 on the RS-B 100’s indicators, the advantage of metal tape in high-frequency storage potential was clear: the response at 20 kHz was down by only 4 dB. Indeed, with the Dolby C system in use, response at 20 kHz was flat within 1.5 dB.

Because the dbx noise-reduction system (unlike Dolby) operates as a 2:1 compressor-expander, both distortion at the IEC 0-dB level and headroom up to the 3-percent distortion point (normally used in signal-to-noise ratio measurements) were considerably affected when dbx was used. Even at input/output signal levels above the + 18-dB limit of the fluorescent display we could not reach 3-percent distortion with any tape, though at +20 dB the unit’s amplifiers gave audible evidence (confirmed by our oscilloscope) of the onset of overload. We used this level, therefore, in our signal-to-noise ratio (S/N) measurements with the dbx system, though it is considerably higher than we would recommend allowing signal peaks to reach (even with dbx). Part of the advantage of using dbx derives from the fact that all of its potential need not be used for hiss reduction: some can be used to lower distortion generally and to increase the high-frequency handling capacity of the tape.

The wow and flutter readings on the RS-B 100 were extremely low, and speed was exact. Dolby tracking error, measured at —20- and —30-dB levels, was about average, as were the high-speed winding times and line sensitivity.

Comments

Listening both to prerecorded and dubbed tapes on the RS-B 100, we were impressed with the fine musical quality of the sound. Whether this is to be attributed to the special phase-compensation circuitry the deck incorporates, to the low wow and flutter, or to a combination of still other factors is not clear, but what is important is that the upper tones of piano recordings, for example, had an entirely commendable clarity. Moreover, at least with the selections we used, the dbx system manifested no audible “breathing” or “pumping”; it did not have a “sound” different from that of the Dolby C system, though it did provide a lower noise “floor” with very low-level inputs.

In a unit so physically small, it is not possible to make all the knobs as large as one might like, but the size of the main record-level control (both silver and black knobs are supplied) is certainly adequate. One minor caution about the rack-mounting adaptor is in order, however: EIA-standard rack components must all have vertical heights that are a multiple of 1-3/4 inch, and the RS-B 100 is 1/4 inch too high to fit a standard equipment opening. With the continuously variable heights accepted by most furniture-type audio racks, however, this is not a problem.

In all, we found the Technics RS-B100 a very fine cassette deck that we can recommend without hesitation.

Read all

Technics reviews

Read all