Russell Hughes takes time off from his job in the recording department of Jones and Crossland's music store to write a few lines for HSR.

Over the past few months the man in the street (or the studio as the case may be), has started to realise the importance of devices such as compressor/limiters and noise gates. The trend towards very clever digital effects is gradually slowing down, and home recordists are starting to look for other ways of making their recordings sound more like those coming from 'pro studios'. If you are looking to get away from the gimmicks and would like just to obtain a good tight sound, then this relatively new product from Vesta Fire may be just what you're searching for. If you can cast your minds back to the Nov 84 issue of HSR, you may remember Martin Sheehan reviewed the Vesta Fire SL020 dual compressor/limiter. The SL200 supercedes the SL020 and incorporates a few design improvements. The operation and application of compressor/limiters has been covered in some depth within these pages recently and so I won't go into this aspect of the subject in too much depth.

The most obvious use of a compressor is to restrict the dynamic range of programme material, vocals being a prime application. Another of its functions is to tighten up the sound of individual instruments such as drums, bass, guitar and keyboards, though it can also be used to increase the sustain of an instrument. This is done simply by applying a high degree of compression so that the level of the instrument is in effect turned up during its natural decay period.

Now that we have established the basics of the comp/limiter, lets take a look at the SL200 and see what it can do for you the user.

Construction

The unit is built in the now standard (and increasingly familiar) 1U 19" rack mounted case, and the controls are laid out in much the same way as the older SL020. From left to right, the first control selects stereo or dual mode. This enables the SL200 to be used as either a stereo unit or two independent mono units. The stereo mode ensures a stable stereo image when you process a complete stereo mix, avoiding the problem where one channel activates the limiter more than the other and moves the sound, which should be balanced in the centre, towards the other channel. Without a stereo mode of operation, this type of problem would be inevitable unless control settings on both channels were identical. The mono mode comes in handy if you need to treat two independent sound sources where the unit functions as two completely separate compressors.

Next we come to the attack control. This determines the time it takes for gain reduction to occur after the threshold point is exceeded. This is variable from 0.1msec to 10msec. The release control follows, which sets the time it takes the system to return to its normal gain setting once the input signal has fallen below the threshold. The release range is 0.7sec to 1.5sec. Release is used to give a more unobtrusive compression effect. If the compressor action was stopped abruptly it would give a very unnatural change in the audio signal which can be heard as gain pumping. The release solves this problem by introducing a variable decay time which can be set with regard to the natural decay characteristics of the programme material.

Threshold is third in line, and this controls the level at which the compression will begin. It features two ranges; 40dB to 20dB in unbalanced operation and 20dB to 0dB in balanced.

Next comes the ratio selector. A compression ratio of 1:1 means no compression, but a compression ratio of 4:1 means if the input signal is increased by 4dB,the corresponding output increase will be only 1 dB. The ratio is variable from 1:1 to infinity: 1. Incidentally a compression ratio of infinity: 1 means that however much the input threshold is exceeded, the output level will remain unchanged.

Finally we have an output control, as you will have guessed this controls the output level of the compressed signal. Situated on each channel we have an effect on/off switch in the form of a mini toggle, which is handy for doing A/B comparisons and above that are six LEDs which indicate the amount of gain reduction from 4dB to 24dB. Channel two is identical in its layout, apart from the power on/off switch on the far right with a LED status indicator above it.

The Back Panel

As soon as I took a look around the back, I realised the first improvement the SL200 has over its predecessor. Not only has it got the standard ¼" unbalanced jack sockets for its inputs and outputs, but it also features balanced XLR connections for truly professional use, operating at +4dB. I can imagine these being very useful in PA rigs as well as studios where nearly all mixers and power amps have XLR connections. Also on the rear we have two sockets per channel marked Detector in/out. If a connection is made via a graphic equaliser, it is possible to choose the frequency affected by the compressor, and it's also possible to pick an instrument out from a mix by 'detecting' its frequency characteristics. On the far left is a small switch marked GND, which is a ground lift facility - helpful for sorting out earth loop problems.

In Use

Most home studios incorporate a drum machine of some sort, a bass, guitar and/or a synth. I decided to try the SL200 on all of the above plus a few other things to see how it coped.

After a short amount of time spent experimenting, a punchy bass drum sound was achieved giving a good click and a more defined bottom end - no trouble there. Snare sounds were given more life and using my Roland TR909, I obtained an amazingly realistic snare drum sound - very deep and crisp. Hi-hats also had a startling crispness, thus enabling me to drop their level in the mix, and the toms reacted in much the same way as the bass drum, becoming more punchy and giving better definition in a drum fill. Altogether I was very pleased with the results on drum machine.

Bass guitar was the next victim of the SL200 and again I was much impressed with the way the unit handled it. With the current trend for slap bass playing, it can be a nightmare to obtain a good, even bass sound, but the SL200 worked like a dream. It turned the usual 'Boom Clank' syndrome into a smooth and well balanced bass line.

Guitar is one of those instruments we find relatively easy to record but some further improvement can be achieved using compression. With the SL200 connected to my Strat, all the notes became more defined and the overall clarity of the guitar was considerably improved. I managed to achieve that glass-like tone on my strings, which you may have noticed when playing your guitar through a Rockman which uses a lot of compression to achieve its sound. Also sustain can help to improve single notes lines in raunchy lead breaks and those Nile Rodgers funk riffs.

The synth used to test the SL200 was the Roland JX3P, and I was interested to see the results on brass and strings settings.

It performed well on brass sounds. I set a ratio of about 2:1 just to discourage the bottom end from overpowering the higher frequencies. The overall result was very subtle but almost definitely worth considering in both live and studio situations. Strings, especially those with a long attack were constrained into a smaller dynamic range, making them far easier to record, and the electric piano performed in much the same way as the brass with the SL200 just helping to level out the overall sound. Immediately after using the SL200 with synth, I realised the possibilities of using the detector loop to compensate for unwanted frequencies within certain sounds; of course that does require an additional equaliser...

As far as vocals were concerned, setting quite a high threshold level and a compression ratio of about 4:1, annoying peaks were removed and with the release set to give a natural decay, the vocal sound improved tremendously. It retained its correct perspective within the final mix and made the recording of my vocals less of a headache in general.

Finally when all your sounds have been committed to tape you almost invariably want to mix them down onto a 2-track master machine. Again the SL200 comes to the rescue, helping to make the overall mix far more appealing. On the mix I tried, the drums and bass were quite 'boomy' and the SL200 soon sorted that out - a useful salvage treatment. The lead guitar also had an annoying grating sound (try taking the plectrum out of the strings - Ed) but that was soon singing sweetly after a little treatment.

Conclusions

As you probably realised by now, the Vesta Fire SL200 compressor/limiter was a welcome addition to my studio.

The gripes? Well nothing that could cause any problem to your sound. I would like to see a slightly more detailed manual as to the SL200 application and perhaps some suggested settings. It's alright for HSR readers but some people have nowhere to turn for guidance.

The SL200 is slightly cheaper than its older brother and the only place I could imagine savings being made was on the exterior of the unit. The presentation is not as attractive as the old SL020, losing is nicely colour coded knobs and the bright red power on switch, but then who's going to see those on your finished recording? Well, with a S/N ratio of 90dB, a frequency response of 20Hz-20kHz, balanced inputs and outputs and a RRP of £283.00 inc. VAT, what more can you ask for?

Trying to tell you the improvements it would make to your sound would be like trying to tell a non-HSR reader what good taste is, so check it out for yourself - you won't be disappointed.