MANUFACTURER'S SPECIFICATIONS
Speeds: 7 1/2, 3 3/4, 1 7/8 ips.
Motors: Three, induction type.
Controls: Directional levers for OFF, STANDBY, and PLAY, and for REWIND, STOP, and FAST FORWARD. Speed selector. Playback Frequency Response: 40 to 18,000 Hz ± 3 dB at 7 1/2 ips. S/N Ratio: 50 dB. Crosstalk: 55 dB at 1000 Hz.
Head: Four-channel, in line, compatible for two or four channel play.
Wow and Flutter: Less than 0.2% at 7 1/2, 0.25% at 3 3/4.
Output: 1.4 mV at 1000 Hz.
Counter: Four digit, pushbutton reset.
Brakes: Electro-dynamic.
Finish: Black and silver trim in walnut base.
Size: 11 by 16 1/2 by 6 1/4 inches.
Price: $249.95, with take-up reel, four patch cords, and ground cable.
The Telex Quad/Sonic 2 + 2 is a quadraphonic tape deck intended for use with an amplifier which can also provide the necessary equalization-in other words, output is taken directly from the heads. No recording facilities are provided but the 2 + 2 can also play two-channel stereo as the heads are in-line quarter track. Three motors are used, all induction types, and there is a choice of three speeds, 1 7/8, 3 3/4, and 7 1/2ips.
Fig. 1.
Looking at Fig. 1, we see a digital counter on the left and just under this is the speed change lever. On the right is the ON-OFF, STANDBY, and PLAY Switch, and under that is a similar switch controlling rewind direction. In the center is a pilot light which indicates whether power is on. Figure 2 shows the tape head and capstan, and Figure 3 shows the view from underneath. Note the large, dynamically balanced flywheel which weighs two pounds!
Fig. 2--Showing the tape head and capstan.
Fig. 3--Underneath view.
Measurements
The frequency response curves are shown in Fig. 4. Ampex standard tapes were used for the 3 3/4 and 7 1/2 ips speeds but the response at 1 7/8 ips was made with a tape made on a Tandberg recorder. It will be noted that very little, if any, treble boost is necessary for playback compensation and a response up to 20 kHz at 3 3/4 and 7 1/2 ips should be easily realized with low distortion. It must be remembered that almost unlimited treble boost can be used to compensate for poor heads-at the expense of high distortion and poor signal/noise ratio.
This is why (in terms of frequency response) a $99.95 deck can have the same specifications as one costing over $1000.00! The head in the Telex 2 + 2 is a professional-grade type made by Nortronics, which of course is not cheap. Output from the 7 1/2 ips standard tape was 1.1 mV at 1000 Hz (10 dB below operating level). No signal/noise measurements were taken by us, as these will depend on the amplifier, matching, equalization, and so on. Wow and flutter came out at 0.11% at 7 1/2, 0.2% at 3 3/4, and just under 0.25% at 1 7/8 ips-better than the rather conservative specifications.
Fig. 4--Frequency response at the three speeds.
Performance
On test, the 2 + 2 came well up to expectations. The controls, which are simple but functional, worked smoothly and were extremely easy to use. Mechanical noise was low and the electro-dynamic brakes were really positive. No four-channel receiver or amplifier with tape head inputs was available so two Fisher 700 receivers were pressed into service, and it was found that equalization was not far out. No actual measurements were made but the standard Vanguard VSS-1 quadraphonic demonstration tape certainly sounded well-balanced with solid bass and silky-smooth treble. The Vanguard recording of the Mahler 9th was also most impressive. Some conventional two-channel tapes were played, with every satisfaction. Summing up, the Telex 2 + 2 can be recommended for the attention of those who want a relatively inexpensive deck for playback only.
Fig. 5--Close up view of some of the controls.
-T.A.
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(Adapted from Audio magazine, Jan. 1972)
Also see:
Wollensak Model 6364 Two/Four Channel Tape Recorder (Feb. 1972)
TEAC 3340 Open-reel tape recorder (Equip. Profile, Mar. 1973)
Teac X-20R Open-Reel Recorder (Equip. Profile, Mar. 1982)
TEAC Model C-1 Cassette Deck (Dec. 1979)
Technics SV-P100 Digital Audio Cassette Recorder (Apr. 1982)
Technics Model RS-616 Cassette Deck (Feb. 1979)
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