Teac C-3RX Cassette Deck Review

The Teac C-3RX is a front-loading, three-head, two-motor cassette deck that includes both dbx and Dolby-B noise-reduction systems. Its tape transport operates under logic-controlled solenoids activated by light-touch pushbuttons. The capstan of the C-3RX is belt-driven by a servo-controlled d.c. motor. A mechanical sensing arm in the tape path responds to tape tension and feeds this information to circuitry controlling the d.c. hub motor. The record and playback head elements are separate units contained within a single case, and the sensing arrangement, together with the pressure pad, helps maintain proper tape-to-head contact.

Cassettes are loaded, tape openings downward, into slides behind the transparent cassette-well door, and rear illumination is provided so the amount of tape remaining on a side can be easily seen. The record, rec mute, and pause pushbuttons have LED status indicators. There is a three-position switch (play, out, rec) for an external timer and a similar memory-rewind switch (play, off, stop).

The record-playback indicators of the C-3RX are illuminated, peak-reading meters calibrated from —20 to +5 dB. While no specific Dolby-level marking is provided, we found it corresponded in both channels to the indicated 0 dB. The left- and right-channel record-level controls are interlocked behind the front panel by a gearing mechanism so that turning one (to change the balance between channels) automatically turns the other unless it is firmly held. The single output-level control affects both the headphone volume and the signal at the rear jacks, though not the playback indications on the meters.

Separate three-position bias and equalization lever switches are provided for normal, CrO2, and metal tapes. These work in conjunction with a preset/adjust pushbutton that permits the user to optimize the record bias and 0-dB record-level indication on the meters for specific tapes using four (two per channel) front-panel screwdriver-adjustable controls. A LED indicates when the adjust option has been selected. The adjustment procedure requires the use of an external audio generator (Teac makes a suitable accessory, Model TO-8) and is a little more complicated than most such “optimizing” techniques, but because the built-in dbx noise-reduction system is sensitive to frequency-response variations the procedure should be mastered if you intend to use a wide variety of tape types.

Additional lever switches are used to select between source and tape monitoring; between Dolby, dbx, or no noise-reduction system; and between microphone, line, or test inputs. The test input uses the regular rear-panel line jacks but provides the meters with an additional 20-dB gain so that they can be read with the low-level generator signals used in the bias/level-adjustment procedure. Microphone and line-input signals cannot be mixed without an external mixer.

The rear panel of the C-3RX contains the normal line-input and -output jacks, plus a multi-pin connector intended for use with Teac’s RC-90 accessory remote-control unit. Overall, the deck measures 17 inches wide (19 inches with the supplied rack-mounting adaptor), approximately 13-1/2 inches deep, and 5-3/4 inches high. The feet on the bottom may be removed so that the unit will fit into a standard 5-1/4-inch rack-mounting space. Weight is approximately 21 pounds. Price: $690.

Laboratory Measurements. Our sample of the C-3RX was not supplied with the specific tapes used in its factory set-up, so we experimented with a wide variety of tapes within each basic type. Among the metal tapes, we obtained flattest response from Fuji Metal, with Memorex Metal IV a close second. Very good performance was also achieved with Sony Metallic and TDK MA. We selected TDK SA-X as the best performer on the C-3RX among the CrO2-type tapes, though Maxell XLII-S was also extremely good. BASF Professional II is a good alternative, and, with bias readjustment, 3M Master II and TDK SA would also yield comparable results. In the ferric (“normal”) switch positions, best response was obtained from Maxell XLI-S and TDK AD (a tossup; we chose the former for our reference), with essentially equivalent results being obtained from 3M Master I, Loran Ferric, Memorex MRX-I, and Fuji FX-I.

Playback response was checked using Teac MTT-216 (ferric) and MTT-316 (CrO2/metal) test tapes. As indicated in the accompanying graph, maximum deviation from ideal response was less than +2, — 1.5 dB throughout the covered range (31.5 Hz to 14 kHz) and was generally much closer still.

Overall record-playback frequency response, measured at the usual —20-dB level and using our selected tapes, extended to 20 kHz ( — 3 dB) with Fuji Metal and TDK SA-X, and it was down 3 dB at 16 kHz with the ferric Maxell XLI-S. With all the tapes we tested, the bass rolloff took place in two stages: a gentle drop of about 3 dB in the 100- to 50-Hz octave, followed by flat response for another half-octave, with a final steeper drop for frequencies below about 35 Hz. At the 0-dB recording level the curves for metal, Cr02-type, and ferric formulations show their relative high-frequency storage capacity very clearly. In comparing these curves with those of other decks we have tested, readers should bear in mind that a 0-dB record level on the Teac C-3RX is about 2 dB higher than that used by many deck manufacturers, so the high-frequency rolloffs naturally begin at slightly lower frequencies.

At the 0-dB input level (with no noise reduction), third-harmonic distortion measured 0.86, 0.46, and 0.42 per cent with the Maxell XLI-S, TDK SA-X, and Fuji Metal tapes, respectively. The overload margin for the three tapes (the increased signal over 0-dB needed to raise distortion to the 3 per cent point) was 7.8, 5.4, and 6 dB. On an unweighted basis, without Dolby or dbx, signal-to-noise ratios measured 57.2 dB for the ferric Maxell XLI-S and 59.0 dB for the chrome-equivalent TDK SA-X and Fuji Metal. Using Dolby-B noise reduction and IEC A-weighting curves resulted in S/Ns of 61 and 62.5 dB, respectively.

As we found on a previous occasion, using dbx noise reduction completely alters the testing profile. Basically a 2:1 linear compander (compressor-expander), the dbx system reduces a 90-dB dynamic range to a much more manageable 45 dB during recording, then expands it back to the original 90 dB during playback. Since any good-quality tape can handle 45 dB, the stress is placed on the electronics of the tape deck (and those of the dbx system itself) rather than on the tape. It was not surprising, therefore, that even with an input signal level of a little over + 17 dB, at which point the C-3RX input stages began to overload, the distortion on the tape itself was barely over 1 per cent. Indeed, at a 0-dB level, and with the dbx system switched on, tape distortion for our three representative tape types was less than half that previously measured: approximately 0.2 per cent for the metal and Cr02-type formulations and 0.38 per cent for the ferric-oxide. Noise measurements were similarly difficult to make with the dbx system switched in, for the noise voltage drops to a level close to the internal electronic noise of our test instruments. With dbx noise reduction, the C-3RX produced A-weighted signal-to-noise ratios well in excess of 80 dB from all the tapes we used.

We checked the frequency-response tracking of both the Dolby-B and the dbx noise-reduction systems at levels of —20, — 30, and —40 dB. The accuracy of the Dolby system was excellent—within 1 dB— up to 15 kHz, above which it fell off very sharply, probably indicating the presence of a built-in FM multiplex filter. The tracking of the dbx system was far more dependent on the tape’s interaction with the C-3RX itself. Where the frequency response was absolutely flat, so was the dbx tracking, but every departure from flat response was magnified by the 2:1 compander ratio: a 50-Hz tone that measured —2.5 dB without noise-reduction would register — 5 dB with the dbx system switched in.

An input level (1,000 Hz) of 70 millivolts (0.07 volt) was sufficient to produce a 0-dB record-level indication on the meters, and the corresponding output at this level was 560 mV. At the microphone jacks the 0-dB sensitivity measured 0.28 mV, and evidence of microphone-input overload required an input level of 31 mV. Wow-and-flutter measured 0.055 per cent (wrms) and 0.07 per cent (DIN peak-weighted) using both TDK AC-342 and Teac MTT-111 test tapes. On short tone bursts the peak-reading meters tended to deflect 1 or 2 dB higher than the true value of the signal, a minor error. Fast-forward and rewind speeds were 77 and 79 seconds for a C-60 cassette.

Comment. Sonically, the C-3RX performed every bit as well as its measurements would suggest. With FM and disc sources it was able to make copies so nearly indistinguishable from the original that without the instantaneous comparison its three-head design affords it would be hard to know whether one was listening to the original or to the dub. With extremely wide-range materials the high-frequency limitations of the Dolby-B circuit and of the ferric tape (compared with metal) could be detected, but our experience indicates there is every reason to doubt the significance of even this small audible difference in any normal application.

Using the built-in dbx system so completely eliminates tape noise that any further improvement in that direction would be superfluous. We tried a number of music and noise sources to make the system misbehave, but as long as the frequency response of the tape was flat on the C-3RX (or could be adjusted to be so) we failed. When we used tapes that were not flat, however, the defects were noticeable in A-B comparisons, though in most cases they would probably be inconsequential for normal listening purposes. In short, we found the Teac C-3RX to be an excellent performer that stands up to the most demanding scrutiny.

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