This latest four-track recorder/mixer from the Tascam stable runs at standard speed, is portable, battery or mains operated and features switchable dbx noise reduction. Paul White took the Porta One home for a thorough evaluation.

It seems as though cassette-based multitrack recorders have been with us for as long as I can remember but the first one, the Teac 144 Portastudio, was introduced only four years ago in 1980.

Since then, the concept has been continually refined until now, there are half a dozen or so manufacturers producing machines that can record four synchronised tracks on a standard cassette.

In 1982, Tascam launched the 244 Portastudio which could record four tracks simultaneously, and by using a combination of noise reduction and twice the usual cassette tape running speed, demos of exceptionally high quality could be produced. The 244 is still a very successful machine selling in unbelievable quantities, but the new Porta One is intended to provide an affordable alternative to prospective multitrack users who either cannot afford a 244 or do not require the same level of sophistication.

Before launching into a detailed description of the Porta One, a brief general description is in order.

Primarily intended for home multitrack recording, the cost of the new machine has been kept down by sacrificing the ability to record on all four tracks simultaneously, thus saving the expense of two extra sets of record electronics. Using the Porta One, either one or two tracks may be recorded at the same time which, in the context of home multitrack, is usually quite adequate.

Unlike the 244 Portastudio, the Porta One utilises the standard cassette tape speed of 1⅞ips and, in order to retain an acceptable recording quality, the machine is biased to match chrome type tape (high bias 70ps) and incorporates switchable dbx noise reduction.

Also included in the package is a built-in four channel mixer which is used to set the level and EQ of whatever signal is being recorded, to bounce tracks, and finally to blend all four tracks together to create the stereo mix that will be recorded on your master reel-to-reel or cassette machine.

Physically, the machine is housed in an elegant plastic moulding measuring only 13" x 9 ¹³/₁₆ x 2 ³/₄ inches, weighing 7.7lb (including ten batteries). Further description is better left until the control function and layout is examined.

Why dbx?

Despite regular explanations in music and hi-fi magazines, there is still an appalling ignorance of even the most basic facts concerning noise reduction systems. When I have a band in my studio and the time comes to make a few cassette copies of the master, I always ask whether they want Dolby-encoded copies or not. Nearly always, they either don't know what Dolby is or they think that it's a 'decode-only' device that ruins the sound by removing all the treble.

All professional noise reduction systems, be they Dolby or dbx, work on what is known as an encode/decode principle, which means in practice that the tape must be both recorded and played back via the noise reduction system.

You may ask why noise reduction is necessary in the first place and what exactly is this noise that we are trying to reduce.

It's a sad fact of life but the very physical nature of recording tape makes it noisy. The tape surface is not as smooth as it looks but is, in fact, made up of tiny rod-like oxide particles which are magnetised by the record head. At any one time, there are many particles passing over the tiny gap in the record or playback head and the recorded signal strength at that instant is, in fact, a statistical summation of the magnetic field produced by each individual particle. The fewer the particles, the more inaccurate the reproduced signal will be and these statistical errors show up as noise.

Improved tape formulations with smaller, more consistently sized particles produce better results but generally speaking, the more particles that pass over the head gap in a given time, the lower the noise.

This may sound a bit involved, but what it all adds up to is that a wide tape track width running at high speed is going to give the best results and that four tracks crammed onto a narrow cassette tape running at only 1⅞ips is going to be really up against it. To prove this, just play back a new unrecorded cassette without noise reduction.

This is where dbx comes in handy, as a well designed system can reduce the background noise by as much as 30dB and give you a few dB extra headroom to stave off overload distortion into the bargain.

If you've no head for figures or dB, all this means is that the hiss generated by the tape is reduced to insignificant levels, but how does this magic system work and what side effects if any does it have?

Dbx relies on the fact that when a tape contains loud music, it conceals the noise, but when there is only quiet music, the noise can be heard. To get around this problem then, the answer is simple: record everything loud!

But wait a minute I hear you say, what about my tasteful quiet bits, does this mean that I have to give up writing ballads and take up Motorhead numbers? The answer, of course, is no; the dbx simply turns up the record volume during the quiet bits so that the levels on tape are almost as high as those during the loud bits, and this process is known as compression.

By using an accurate, fast-acting compressor with a compression factor of 2:1, the input signal is treated and recorded on to the tape at a much higher average level than normal.

If we were to play this tape back on a normal cassette system, it would sound rather odd, but dbx replay electronics incorporate a circuit that reverses the effects of the compressor and restores the original dynamic range of the signal. This is called an expander and in order to work well, its characteristics must closely match those of the compressor in the record circuit.

All those quiet bits that were recorded well above their original level are now pushed back down to their natural levels, and down too goes the tape noise.

In order to get the best out of this system, another technique called pre-emphasis and de-emphasis is used, whereby the treble content of your signals is boosted during record and cut during replay. Again, in theory, this leaves you back where you started but with a subsequent reduction in high frequency tape noise.

It must be stressed that noise reduction systems of this kind only remove tape noise and possibly some of the noise produced by the internal electronics of the tape recorder. Any noise present on the input will be faithfully encoded and decoded to emerge just as obtrusive as it started out.

Of course, every miracle has its price and dbx noise reduction has side effects, the severity of which will vary depending on several factors.

For dbx to work perfectly, it must be designed with perfectly matching encode and decode circuits, otherwise errors will be introduced. Even given a theoretically perfect system, the output will only be a faithful reproduction of the input if the signal coming off tape is exactly the same in all respects to the original signal, and there are unfortunately several inevitable fundamental differences.

Firstly, loudly recorded signals on tape tend to be compressed as the tape coating starts to saturate and, when this is decoded, the amount of compression is emphasised. This can lead to a certain lack of brightness on percussive sounds but is generally not too serious as many commercial recordings are heavily compressed anyway.

More serious is 'drop-out'. If the tape surface is damaged, worn or not evenly coated in the first place, small changes in playback volume will be apparent and occasionally, large changes. Once subjected to the effects of the expander in the decode circuit, small dropouts become big ones and big ones become huge ones! So, the moral here is to choose good tape, keep the tape heads clean, and to look after the tape.

As the tape heads on all machines eventually wear, this will cause further frequency response differences between the input signal and the off-tape signal and yes, you've guessed, dbx magnifies these errors.

Despite all these warnings, dbx does work very well if you follow the rules about tape care and cleaning, and furthermore, the fact that it is applied to individual tracks rather than to the complete mix tends to mask any shortcomings.

There are many compendious tomes written on the subject of noise reduction systems and their relative evils, but what it all boils down to is that you never get anything for nothing.

Facilities

On the Porta One there are four unbalanced jack inputs, one for each channel, and these are fed to the input amplifier via the trim circuit which ostensibly allows anything from a low impedance mic to a high impedance line input to be accommodated without the need to resort to mic/line selectors or input pads.

Unlike most mixer circuits, the level fader is connected before the EQ and pan circuitry so that even with the fader down, any electronic noise from the two op amps in the signal path will be fed onto the mixing bus. Normally this practice would be frowned upon, but in this instance, it doesn't cause any apparent problems.

Next comes the EQ which is a standard Baxendall shelving circuit acting at 100Hz for the bass and 10kHz for the treble giving +/-10dB of signal boost or cut.

The last rotary control on the input channels is the pan, and all pots have recessed rubber knobs that can be easily turned with the finger tip and yet would be difficult to disturb accidentally.

The channel fader is a smoothly operating device, cleverly designed not to collect dust in the wrong places, and to the right of this is the input selector slide switch giving a choice of 'tape', 'mic/line' and 'off.

Since LEDs would cause an unacceptable power drain for battery operation, small fluorescent squares appear at the bottom of recessed windows to indicate input status, but unless you record under a sunlamp, these are very difficult to see.

Each of the four channels has a VU meter which automatically illuminates when the Porta One is powered from an 11-15 volt (½ amp) mains adaptor (not supplied), but these are sensibly extinguished during battery operation unless a non-latching pushbutton is pressed to make occasional checks. Meters one and two also monitor the left and right output levels during mixdown and the left and right bus signals during record.

Moving to the centre of the machine, we find the master section which includes a single ganged fader for level control of the main output.

Above the faders are the left and right bus switches which again incorporate non-illuminated fluorescent status indicators. The left hand switch selects record track 1, record track 3 or safe, and the right selects record track 2, record track 4 or safe.

Further up the panel is a two-way switch for remix or cue which affects only the headphone output. In the 'remix' position, the headphones monitor the left/right programme busses and the headphone level is affected by both the master output fader and the phones level control.

In the 'cue' position, the phones receive a combination of the master left/right output plus the mono tape cue signals, each track having its own cue level control above the cassette section. These cue controls monitor only previously recorded tracks and consequently receive no signal if the track is set to record. There are no sync problems, of course, as the Porta One uses the same head to both play and record.

Directly below the cue knobs is a laterally mounted slider for tape varispeed (+/-15%) and the manual very honestly points out that a tape recorded at one speed and played at another will suffer some mistracking of the dbx encode/decode process, but in practice, these side effects should not upset anyone and indeed are difficult to detect.

The cassette section itself does not have soft-touch microswitch controls but rather easy-to-press mechanical switches, and pressing the record button automatically operates the play switch. This makes for simple one finger recording but it is also possible to accidentally enter record. The mechanical tape counter has a zero return facility which, when engaged, causes the tape to stop at or just before zero in the fast rewind mode only.

On the left hand edge of the case are located the four line outputs for the individual channels as well as the stereo mix out and these are, of course, phono connectors. Also on this panel is the socket for connecting an external power supply, an invaluable feature when you weigh up the cost of ten batteries.

The front edge of the case houses the four signal inputs, the headphone output and the remote punch-in socket. This latter feature is invaluable to the solo recordist who can drop in and out of record mode using an optional footswitch for tight punch-ins.

That's a brief look at the hardware then, so what happens when we try to record some music.

In Use

Let's start by plugging our drum machine or whatever into channel one and connecting the left and right line outputs to the domestic hi-fi stereo Aux input.

Ready for the pre-flight checks? OK.

Power on - check.

Input selector to 'mic/line' (channel one) - check.

Spare channels to 'off' - check.

Set channel fader to about 7 - check.

Alright so far?

We must now use the pan control to route the signal to the left bus as tracks 1 and 3 are recorded from the left bus and 2 and 4 from the right.

Next, start up the drum machine and set the trim control for a sensible meter deflection. By altering the position of the master fader, the level fed to the monitor system (hi-fi set - remember) may be adjusted for a comfortable listening level. Slide the left bus selector to the channel one position and the red light will begin to flash, warning you that one push on the record button will do something irrevocable.

Push record, wait for the leader to wind off your cassette and restart the drum machine. When the track has finished, rewind the tape (making use of the return to zero facility), set the record selector to 'safe' and set channel one input selector to 'tape'. Hopefully, playing the tape will reveal a perfectly recorded drum track.

Normally you would fill up two or three tracks in this way and bounce the results down onto a spare track, possibly adding another part live as you did so. The manual charmingly calls this 'ping-ponging' or 'collapsing' tracks.

If you are collapsing onto channel four, the pan controls on the first three channels must be turned clockwise and the right bus selector set ready to record channel four. The input selectors are set to 'tape', except channel four which is set to 'mic/line', and all faders are set around 7.

Play the tape and adjust the levels for the desired balance, monitoring the level on meter two (the right bus meter). If you want to add a new part live as you bounce these tracks down, this may be done by plugging the new source into channel four input (making sure the pan is fully clockwise) and simply balancing its level with the recorded material before pressing record and doing it for real.

One slightly confusing thing about the two bus system is that when you are recording on channel four, the meter reading comes up on the channel two meter which is monitoring the right bus.

Fortunately, the Porta One obligingly turns off the illumination in the last two meters to encourage you to look in the right direction. Eventually, when all the tracks are full, it's time to mix down.

This is simply a matter of setting all the tracks to 'safe', setting all the input selectors to 'tape', and using the level and pan controls to achieve the desired balance. This mix is then transferred to your mastering machine (cassette or reel-to-reel) after its input level has been optimised.

Punch-Ins

That all sounds fairly straightforward and indeed it is, but at some stage you'll play a duff note and want to punch in a short passage to rectify matters. This can be done using the tape transport keys or by means of a footswitch, the latter being much more convenient for the musician working on his or her own.

To punch in using the keys, the offending track is set to 'ready' and the performance monitored via the headphone outlet or the monitor speakers. Start the tape in play mode and just before you start to play the corrected phrase, press 'record'. When the passage is complete, press 'stop' and check your handiwork.

The procedure using a footswitch is very similar, the tape is set in motion and the switch depressed just before the faulty section. This causes the machine to enter the record mode and pressing the switch a second time exits record without stopping the tape.

All these techniques are thoroughly described in the manual, complete with illustrations, circuit diagrams and helpful advice on maintenance.

So much then for the procedure but how well does it work?

Performance

Despite my earlier warnings on the evils of noise reduction, this system performed surprisingly well with only the slightest trace of high frequency loss when making direct tape/source comparisons.

My digital drums came through unscathed apart from a little tape compression and this is inevitable when using cassettes. Subjectively, this test showed the machine to perform as well as a high quality hi-fi cassette deck so no complaints here. As for tape noise, well that was negligible compared to the noise generated by the instruments that I recorded. A quick check without dbx gave predictably hissy results but the sound quality was otherwise very similar.

Next came the tubular bells, courtesy of the Editor's Yamaha DX7, and these remained bright, a good test of any noise reduction system. Vocals and lead guitar never show up many problems anyway, but a soft bass guitar is guaranteed to find any noise pumping effects caused by the noise reduction. Inevitably, the slight breathing as the noise faded up and down with the volume of the bass was audible, but not obtrusive, and is certainly preferable to the constant hiss of unprocessed material.

So, the dbx gets the seal of approval; even with wild use of the varispeed, no unpleasant effects were apparent.

After a few track bouncing sessions, the sound quality begins to deteriorate but providing that you record at sensible levels, second and third generation bounces are quite acceptable.

Drop-ins caused no noticeable punch-in clicks but it's good practice to drop in on a snare drum beat if possible to disguise any sudden level changes. Also, the erase head is a quarter of a second or so upstream from the combined record/play head so there is bound to be a little overlap when dropping in and a gap when dropping out. This should be allowed for when planning drop-ins and this is also true of multitrack reel-to-reel recorders, though at high tape speeds, the problem is less acute.

To maintain this standard of performance, it is necessary to use fairly new tapes and to keep the tape path clean and demagnetised. TDK SA cassettes were used for our tests though Tascam understandably recommend their own Teac tapes.

Summing Up

The Porta One performed reassuringly well, regardless of what we threw at it and the dbx handled most types of programme material without unpleasant side effects.

I found that the operating system was reasonably flexible and easy to use but I did find that the lack of anywhere to plug in external effects was limiting. The mitigating factor in this case is that Tascam have fitted line outputs to all four channels and so the Porta One can be connected to a conventional mixer for final mixing if this flexibility is required. The fluorescent status markers were difficult to see and could have been larger.

A selection of microphones from about 200 ohms impedance upwards all worked satisfactorily as did line level inputs, but high levels of gain and trim setting were required with low impedance mics. This could lead to noise problems when recording quiet vocalists, and high impedance mics would probably be a better choice in this instance.

The Porta One is provided with a secure carrying strap for portable use but the fact that it can only record two tracks at a time precludes it from being used to record live gigs with a view to mixing down the four tracks later.

For the solo songwriter, the Porta One is an efficient and compact tool for testing ideas or producing good demos and the 1⅞ips tape speed and track format means that it can be used to play standard stereo music cassettes. In this respect, the dbx noise reduction is a hindrance as not many pre-recorded cassettes are compatible with this system and so the more common Dolby B tapes cannot be decoded. By turning the treble down, Dolby B tapes can be made to sound passable, but it's hardly hi-fi.

If you're new to recording, it can be a bit daunting deciding on what recording level is best for a given sound source but the manual gives practical advice in this and many other areas that should get you off to a very good start.

Conclusion

It seems that in designing what is, in effect, a budget Portastudio, Tascam have made all the right compromises and come up with a system that offers all the facilities needed by the songwriter/home recordist in one very attractive and affordable package.

Recommended selling price of the Porta One Ministudio is £439 inc VAT.

Further details from Tascam stockists or Harman UK Ltd. (Contact Details).