Akai GX-77 Reel To Reel Recorder Review

The Akai GX-77 is an open-reel deck designed to use both conventional and the new EE (Extra Efficiency) chrome-type tapes, and it is the first of these units I have had an opportunity to test. A two-speed (7-1/2 and 3-3/4 inches per second), 7-inch-reel machine, the GX-77 is capable of bidirectional recording and playback. The basic advantage of the new EE tapes (currently available from TDK, Maxell, and BASF) is that, when used with recorders designed for them, performance previously attainable only at 7-1/2 ips can be achieved at 3-3/4 ips.

The formulation thus makes it possible to provide an uninterrupted 90-minute playing time (twice that of a C-90 cassette) with a standard 1,800-foot 7-inch reel and, further, an increase in the potential signal-to-noise ratio. The EE tapes, however, require increased bias and departure from the standard playback equalization. A switch on the GX-77 selects the proper parameters for either conventional or EE formulations, and a control permits a ± 30 per cent bias variation to compensate for brand-to-brand tape differences. No internal audio generator is provided to facilitate bias adjustment, though the owner’s manual suggests recommended settings for a number of different tape brands and types.

The dual-capstan transport of the GX-77 uses a servo-controlled d.c. drive motor and two d.c. reel motors. There are six tape heads—erase, record, and playback for each direction. The transport pushbuttons operate logic-controlled solenoids that prevent tape damage from rapid mode switching and permit instantaneous direction change during recording or playback at normal speeds.

Tape threading is a simple, straight-line procedure from supply to take-up reels, and the head cover is hinged to facilitate editing and routine cleaning and demagnetizing. A separate roller that glides up and down in a slot approximately 5 inches long is used both to draw the tape into the head nest and to control a digital counter that reads directly in minutes and seconds. During the threading operation the two spring-loaded tension arms are automatically retracted.

Separate left- and right-channel recording controls are supplemented by a master record knob that affects both channels simultaneously. Record and playback levels are displayed on a sixteen-segment peak-reading fluorescent indicator that is calibrated from —20 to +8 dB. An output control adjusts the level at both the front-panel headphone jack and at the regular rear-panel output jacks. Additional front-panel switches are provided for a cue/re-view function, operation from an external timer, and speed, as well as for selection of either one-direction, auto-reverse for a single cycle, or continuous repeat-play modes. The automatic-reverse functions require the addition of a short length of metal-foil sensing tape to the tape backing at the point(s) where reversal is desired.

The rear panel of the GX-77 has the usual input/output jacks plus provision for a remote-control accessory. A separate Akai MM-77 mixer (or equivalent) is required for recording with microphones.

Laboratory Measurements

The Akai GX-77 unit 1 received for testing did not include the usual manufacturer’s check-out data, nor were specific tapes indicated as having been used in the factory setup. Experimenting with various formulations, 1 achieved the best performance (by a narrow margin) with TDK SA in the EE position and with 3M Master XS in the regular mode, though essentially the same results could be achieved with a variety of alternative formulations from Maxell, BASF, and Ampex.

Playback response was tested using MRL test tapes for the standard (NAB/IEC) playback equalizations at 7-1/2 and 3-3/4 ips, as shown in the graph. EE tapes use different time constants for the two speeds (35 and 50 microseconds instead of 50 and 90 Msec), and there are, as yet, no standard playback test tapes available for this format. Using standard test tapes and mathematically calculating the response variations to be expected with the new format indicated that the playback of the GX-77 in its EE position would fall within a few tenths of a decibel of the curves shown.

The bass rise in the playback curves is not a characteristic of the recorder but results from using a full-track test tape on a quarter-track deck.

On an overall record-playback basis the advantages of EE-type tape are most obvious at the 3-3/4-ips speed when recording at a relatively high level (0 dB), as the curves in the graph indicate. In a way it is comparable to the difference between a metal-particle cassette and a good ferric or CrO2-type cassette. The difference between 7-1/2 and 3-3/4 ips is not entirely wiped out, but for most practical recording purposes it is reduced to insignificance. The curves in the graph are for the forward direction, but those made in the reverse direction did not differ by more than ±0.5 dB.

Third-harmonic distortion from a 1,000-Hz tone at an indicated 0-dB input level measured only 0.2 per cent at the 7 t/2-ips speed with the 3M tape and only 0.15 per cent with the EE TDK SA. At 3-3/4 ips the respective figures (averaging the forward-and reverse-direction measurements as before) were 0.3 per cent for both tapes. The overload margin was generous for both the regular ferric and the EE formulations at both speeds, averaging between 7.5 and 10 dB with either tape before producing 3 per cent third-harmonic distortion. At 7-1/2 ips, the signal-to-noise ratio, referred to the 3 per cent distortion point, measured 63 dB with the TDK SA and 62 dB with 3M Master XS unweighted, rising to 68 dB and 66.8 dB with IEC A-weighting. At the 3-3/4-ips speed the S/N figures were 60.6 and 60.1 dB (unweighted) and 64.7 and 64.1 dB (A-weighted) for the TDK and 3M tapes, respectively.

Averaging both directions, overall record-playback wow and flutter at 7-1/2 ips measured only 0.032 per cent on the conventional WRMS basis and 0.048 when employing the stricter DIN peak-weighted standard. At 3-3/4 ips the comparable figures were 0.04 and 0.07 per cent, respectively. Fast-forward and rewind times for a 1,200-foot reel averaged 72 seconds, and an input signal of 64 mV was required to produce a 0-dB indication. The output at this level was 0.755 volt.

Comment

The Akai GX-77 is certainly easy to operate, though some of its control knobs seem slightly small. It was capable of making truly excellent copies of audiophile discs at the 7-1/2-ips speed, and at 3-3/4 ips only the most demanding material showed any sign of high-frequency roll-off. The specific virtues of the EE format are still, to some degree, to be determined, for while high-end response and signal-to-noise ratio are definitely improved at 3-3/4 ips, modulation noise (flutter and program-responsive hiss) could still be detected by very critical listening. Nonetheless, for the home user interested in open-reel capabilities I can recommend serious consideration of the Akai GX-77.

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