Revolutionary Actilinear

Tandberg has introduced two new tape machines that incorporate a revolutionary recording system, known as Actilinear. The machines can be used with all currently-available recording tapes, and the new system is said to offer improved reproduction of transient signals — no worries about sudden peaks being clipped because the record amplifier can't track the changes fast enough — plus a dramatic increase in headroom, which means that higher levels can be put on to tape without overload or distortion. All of which results in an increased signal-to-noise ratio, because average recording levels can be significantly higher than those possible with a 'conventional' tape machine, and hence kept further away from inherent tape noise.

As if all that wasn't astounding enough, with slight modification the new machines equipped with Actilinear will be able to record signals on the new 3M Metafine 'pure iron' tape. This new recording material offers up to 6dB increase in output level over the entire audio frequency range, resulting in a radically improved signal-to-noise ratio over the normal Ferric, Ferri-chrome, Chromium-dioxide and other such tapes. Claims are being made, quite reasonably I suspect, that a cassette machine equipped with Dolby B noise reduction running at 1⅞in/s, will offer a performance comparable to that of a reel-to-reel machine turning at 7½in/s.

The heart of the new Actilinear system is what Tandberg refer to as a 'transconductance converter'. No, it didn't mean much to me either until it was explained that most conventional tape machines make use of a combined equalisation amplifier and passive recording output stage. The value of the resistor is kept high to isolate the head from the amplifier, but this high value also reduces the amount of signal that can be passed to the tape head. In the Actilinear system the resistor is replaced by an active output stage (the so-called transconductance converter) that provides a buffer between the amplifier and the tape head and also prevents feedback of bias signals into the amplifier. Furthermore, unlike conventional designs the active output stage compensates for the changes in electrical impedance of the head with frequency. The end result is that higher level signals can be recorded on to tape with significantly less distortion.

This increase in headroom is particularly useful for the new high-output tapes that offer greater signal-to-noise ratios by operating at elevated recording levels, but which many conventional tape machines cannot handle properly because their recording amplifiers can only produce high output levels with corresponding high levels of distortion. A higher recording level is also essential for the new miracle Metafine tape which, by its very composition of precipitated iron rather that iron oxide (and hybrids thereof), is very much more reluctant to be magnetised and hence needs a far stronger signal at the record head. Actilinear scores again.

The new TC20A stereo reel-to-reel machine (A standing for Actilinear) features full motion sensing and logic control of transport functions, with provision for remote control of all the common modes of operation. Four motors are used: two for forward and reverse spooling; a synchronous capstan motor and belt drive to a large flywheel assembly; plus a fourth motor to engage the pinch wheel and tape guide mechanism — not a solenoid in sight. The machine will accommodate 10½in NAB reels, with a front-panel switch providing the correct tension for large and small size reels. Two models are available with speeds of 3¾ and 7½in/s or 7½ and 15 in/s, both in half-track or quarter-track versions. Other features include separate mic and line inputs with mixing between input pairs; full sel-sync (rather a luxury on a stereo machine but useful for sound-on-sound and reverb); separate output level controls; and very useful front-panel bias controls. No built-in noise reduction has been provided, although this is not unusual with reel-to-reel machines. Price in the UK is a very reasonable £532.

The new TCD340A cassette machine is derived from the much-respected TCD330 - and with which it shares a strong external appearance — and features three heads and a three-motor, dual-capstan closed loop transport design. Like the TD20A reel-to-reel machine all deck functions are logic controlled, enabling full remote control of most transport modes. This is very useful if your cassette is mounted across the control room and you don't want to have to keep getting out of your seat to stop and start it. (After all, we expect full remote control on reel-to-reel machines so why not on cassettes?) Another really useful feature is a manual azimuth adjustment control that works in conjunction with a 10KHz tone recorded by the machine on to the right-hand channel. The control is adjusted to give maximum output, which corresponds to correct azimuth. Neat touch that, and also useful for keeping an eye on head cleanliness and wear. Since the maximum signal should remain stable for a particular type or brand of tape, a gradual drop in this value will indicate that the heads need attention. The three-motor, dual-capstan closed loop transport ensures impeccable tape handling and low wow and flutter values.

Separate mic and line inputs are provided, with output level being controlled by two large faders. Level monitoring is handled by two elegant peak-reading meters. Dolby B noise reduction had been incorporated, selectable on front panel pushbuttons between 'normal' encode/decode and 'FM' Dolby for decoding programmes broadcast in that format. A further pushbutton selects combined bias and equalisation for Type I (Ferric and Ferri-chrome) and Type II (Chromium-dioxide and 'Pseudochrome') tapes. The 'stop-at-zero' facility is more useful on the TCD340A because of its fast acting logic-controlled transport. Not surprisingly, the UK price of such an advanced machine is rather high at £488.

As mentioned earlier, Tandberg recently demonstrated a prototype machine based on the 340A that will record signals on to 3M Metafine tape. Obviously the extra level available with the Actilinear recording system makes Tandberg machines the logical — and at present the only — choice for the new material, and both companies are reported to have been actively engaged in research for several years in this area of mutual interest. But technology aside, the results were quite staggering. The demonstration I attended comprised a direct-cut recording that had been copied onto Metafine tape with Dolby B noise reduction. The lack of noise and hiss on replay was such that even at quite moderate monitoring levels it was possible to detect the point at which the stylus had been lowered on to the record.

That is to say the inherent tape noise on tape with Dolby B was less than that of a direct-cut record. In terms of numbers then, it looks - and sounds - as if Metafine recordings with Dolby B (at 1⅞in/s, don't forget) will offer a signal-to-noise ratio of some 65-70dB, compared with around 55 dB for a conventional tape or 60-65 dB for a stereo reel-to-reel machine running at 15 in/s. Goodness only knows what Metafine will sound like on a reel-to-reel; we will have to wait until Tandberg and 3M get it together with a suitable machine and supplies of £inch and wider tape. Perhaps there is still some life left in analogue recording after all, and the inevitable takeover by digital technology won't happen for a few years yet.

Further details about the new machines can be obtained from: Tandbergs Radiofabrikk A/S, (Contact Details); UK: Tandberg (UK) Ltd, (Contact Details); US: Tandberg of America Inc, (Contact Details). And if you want to know more about Metafine tape contact: 3M Company, (Contact Details). UK: 3M House, (Contact Details).

The death of the Who's drummer, Keith Moon is not only sad in its own right, but also means the end of what we at SI unanimously feel was the world's best performing rock band. As Moon could hardly be imagined with any other band, so no-one else could possibly be a Who drummer.

Moon's apparent indestructibility makes his death sadder. He was in our experience a kind, friendly and honest man as well as being the eccentric extrovert of his legend. Certainly he was unique.