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Trident VFM Modular Mixing Systems

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16/8/2 mixer review


In 1968 Malcolm Toft, a sound mixing engineer at the Wardour Street, London based Trident Studios, was fortunate to be involved with the recording of the Beatles 'Hey Jude'. Fortunate, because Trident was the only studio outside of EMI to be used by The Beatles. It was the first 8-track studio in the U.K. and in those early days recorded David Bowie, T. Rex (with Tony Visconti producing) and other bands like The Nice (for their last album).

Malcolm was promoted to Studio Manager in 1971 and, in the studio's equipment, found a need for a different mixing console unobtainable at the time. Over the next year he worked with a designer on the production of Trident A-Series (the forerunner of today's top of the range TSM consoles). Even then, it contained 28 inputs for 24-track recording and 4-band graphic EQ. Later on, Chipping Norton Studios took one of the first B-Series consoles. So the mixer production venture soon became important enough for a separate company to be established in 1972 within the Trident group called Trident Audio Developments Ltd, with Malcolm Toft as Managing Director. After four years the company had outgrown its original premises and moved to its present location at Shepperton, Middlesex.

Trident Audio is now selling its products internationally for TV, broadcast and theatre applications. Many London theatres use Trident's Trimix for sound reinforcement, including Drury Lane, Barbican and the National Theatre. As well as for plays with Royal Shakespeare Company, recent musical productions such as Cats, Evita, Chorus Line, Annie, Grease and The Beatles were all mixed through Trident consoles.

The range starts with the new VFM systems from around £1,000, to Trimix at £3,000, Series 70 at £10,000, Series 80/B at £18,000, to the TSM Series at £50,000. There's also Trident's own professional multi-track recorder, the T.S.R. Series, at £18,000.


The VFM (Value for Money) systems have been out nearly a year and recently underwent a small facelift with its end pieces and front buffer rail changed for natural pine wood finish. They are aimed at the semi-professional end of the market, offering a completely modular construction, with versions for either Recording or PA.

The Recording mixers are 16-8-2, 16-4-2 and 20-8-16 types. The first two have echo returns on the group outputs and can monitor and meter the output of a 2-track recorder for mixdown. The 16-track has the same monitoring facilities but, instead of group echo returns and talk to foldback, can record and monitor on a 16-track recorder directly (without parallelling of feeds or using channel inputs for tape replay monitoring).

The PA mixers are 16-8-2, 16-4-2 and 20-4-2 types and have EQ on output groups and master foldback send, with only one group echo return and no 2-track monitoring — but these are not usually necessary for sound reinforcement.

All versions use identical Input modules, a selection of three Output modules, two Master modules and a standard power supply module. The 16-track also has a special monitor module.

Construction



The console is made from one metal base plate, with four protrusions acting as feet having screwhole fixing if desired, and the individual modules on 2mm aluminium increase the rigidity considerably. The pine end and front pieces are reasonably well finished and contrast the black panel modules and brightly coloured fader and control tops. Knobs are low cost black moulded plastic types with insert tops, coloured to match the function: red for input and monitoring, blue for EQ, green for echo sends, grey for foldback and yellow for pan. All pots operated smoothly with sufficient stiffness for setting, although unfortunately no centre detent types are used — these are always useful for EQ and pan controls. The coloured latching switch buttons are also all one type, operating quietly, but are a little awkward in ascertaining on or off mode without LED indication. Long throw faders have yellow plastic tops for input, red for output groups and blue for stereo/monitoring. A small scratchpad area is provided at the base of every module for your own track comments. The supplied faders are reasonable quality types that can be upgraded to Trident 'professional' versions if desired. They work smoothly, although excessive pressure on the tops will push them in contact with the module plate. Legending is clear on all modules except for the output faders which could benefit from setting points on both sides of the control. Some slight difference in positioning of the printing is also noticeable but not really a problem. (It does mean that sliders are not exactly in line at the same setting. For some reason, there are no channel input numbers on the rear sloping end of the modules for quick identification. Certainly the angled shape makes connection changes much easier. Standard mono and stereo jacks are used on all connections except mic inputs and stereo master and monitor outputs, which are XLR types.

The meter bar displays are formed from vertical rows of 12 rectangular LEDs fitting flush to the module plate. These give good visual indication at scaled points from -20 to +8dB in all conditions. However, the single red LED on the input channels for peak/overload indication is poorly lit and needs subdued light to catch your attention. Distortion occurs once the LED is fully on, so correct input level setting is fairly critical.

Circuitry



Components are mounted on glass fibre PCBs and the construction is of good quality throughout. The low noise of the mixer is due to good layout and the use of TL071 op-amps. The circuitry is commendable because it uses the minimum of components to achieve its control and allows Trident to keep the final costs down: the input module only uses three TL071 and four transistors! PCB mounted pots and switches are used throughout. A very neat linking arrangement between modules is made with a single ribbon cable having socket connectors spaced along its length. A foam strip grips the back of each PCB mounted at right angles to the front panel, and metal foil completes pot earthing.

Built-in power supply module.

The LED display also has an interesting circuit based on one IC not generally used for this application. Single preset adjustment makes own requirements easy to set up, once a module is removed by loosening four screws, and following the instructions in the informative manual supplied, the mixer can be quickly set to -10 record/replay for semi-pro equipment instead of +4dBm used in pro recording studios.

The PSU module runs off 110 or 220V AC and uses two IC voltage regulators (1½ amp), bridge rectifier, 4700 capacitors and a toroidal transformer for clean +/-18V supply, shown by two red LEDs on the panel. The mixer is hum-free and generally very quiet in operation.

Input Module



Input module circuit board.

The provision of mic/line switching and variable input gain control allows most signals to be accommodated. A resistor Pad can also be switched in to reduce input gain by approx. 20dB. It is useful to have separate mic and line sockets and the mic input is for 1200 ohms balanced line with maximum gain of +70dB. The use of unbalanced mics is not recommended. Line input is 50k unbalanced with gain between -15dB and +30dB. Both inputs cover a frequency range of +/-1dB 25Hz to 20kHz.

In practice, mic or line gain settings were best kept below 3/4, with the overload LED indicator near the fader occasionally lit on loud passages. Incidentally, the LED's simple rectifier operation did not produce any signal interference. The module also has a Send/Return stereo jack for external signal processing with effects or limiter/compressors etc.



Equalisation is always switched in and covers four ranges: High and Low affect frequencies above 12kHz and below 60Hz, with 'shelving' (i.e. giving equal boost and cut for 12k-20kHz and 60-20Hz). Mid 1 and Mid 2 are peaking types with boost and cut at 600 and 5kHz respectively. Quite reasonable results are obtained with this section, although some interaction does take place. Mid 2 will give brighter instruments and vocals, leaving High to bring up cymbals etc — the shelving characteristic does mean that tape hiss may also be accentuated. Bass problems can usually be tidied up provided the input signal is hum free. EQ knobs are the only ones with numbered scaling.

Next actually comes the Foldback send level because it operates prior to the channel fader (Pre-fade). Then Echo 1 and 2 are postfade controls, with the channel fader having an extra 10dB gain before the overload LED and Pan control. The latter has a slight jump from its extreme positions as it is moved, with virtually centre pan covering a significant part of its range.

Four routing switches coloured alternately white and green send the channel signal to output groups 1-2, 3-4, 5-6 and 7-8 depending on the position of the Pan control. A slight drop in volume occurs on the output as more groups are switched in. There's also a Pre-Fade Listen (PFL) switch with the routing switches. Because there's no LED indication of routing or PFL selection, a little more attention has to be paid to switch settings.

Rear panel output sockets.


Rear panel input sockets.


Output Groups



The mixer under test was the 16-8-2 recording version and contained one Output module with Talkback and seven others without. A Talkback level control is provided for assessing the Foldback output so that the mixing engineer can communicate directly to the musicians using headphones. An on/off switch allows a level to be set without further adjustment and the female XLR input socket will take a low impedance unbalanced mic (600-2k ohms).

With one or more input channels routed to a particular output group, the group fader sets final volume (plus a 5dB boost stage) to the group output socket at the top of the module.

Close-up of switchbuttons.

Normally echo and other processor effects outputs would be sent to an input channel for routing (without Echo Send level up as it would cause feedback). An alternative Echo Return input and level control is also sent to the group output.

The other level controls are for Foldback, Monitor and Pan, the latter sending the stereo position of the group outputs to the stereo master outputs and monitor. There's a Tape-Return socket and on/off switch for direct playback from a multitrack recorder for overdubbing, plus a PFL switch. One scaled 12-segment LED display completes the module and will show tape playback or group output level. The display has PPM ballistics and is scaled from +8 to -20dB.

Monitoring



The final Master module prior to the PSU outputs everything except the separate group outputs.

Foldback is well arranged to send both individual input, group and tape playback tracks to musicians' headphones, although it's preferable to use group rather than input foldback if a lot of overdubbing is to be done. A Master Foldback level control with PFL switch is provided and a 5dB boost stage is added just before the stereo jack socket on the module.

Actual monitoring is taken from the stereo mix created at the group outputs with Monitor Level and Pan controls, and adjusted with Monitor Master. The monitor output is via an XLR socket. A PFL/Normal switch offers mono PFL on the monitor output and the dual LED displays will respond to the switch setting. Some care, as is often the case, has to be taken when more than one PFL switch is used as not only will signal output be increased, but the LED meters will easily move into the red overload section. The PFL system does give 'soloing' facilities for monitoring one or more channels in isolation.

This recording version of the VFM has the 8 Group Outputs feeding a multitrack recorder and these are also very useful for 'sub-grouping' instruments like a mic'd up drum kit into one or two group faders.

During the mixdown process from the multitrack recorder, or direct from the channel inputs, the VFM has a Master Output send for the stereo tape recorder. Once again, after the left and right faders containing the stereo mix, there's a 5dB boost stage before the XLR output socket.

Instant monitoring of the stereo tape recorder output is obtained by connecting this to the 2-track return socket and pressing the 2-track switch.

Completing the module are Echo 1 and 2 Master level controls and output send sockets plus separate PFL switches.


Operation



Input modules.

The 16-8-2 mixer is straightforward in use and contains all the basic requirements for a small studio multitrack/stereo recording situation. The sloped case and coloured controls provide nice visual contact with all the controls and the LED displays have a good response and clear overall indication from green -20 to -1dB, yellow 0dB and red +1 to +8 segments.

There are no real drawbacks to the mixer operation and the first time user of this kind of console will not miss the cost saving omissions, as these do not restrict the basic recording process. In fact, there are quite a few hidden extras. For example, during mixdown, it's possible to use the Foldback Send as an additional treatment output, along with Echo 1 & 2. However, since Foldback is not a switchable pre/postfade signal on the input module, its fixed pre-fade mode has to be considered before use. 'Phantom echo', where only the echo signal is to be monitored, can be obtained by returning the echo device output to a Tape Return socket on one of the group modules, and pressing its Tape switch. This can also be heard on the normal foldback system by setting the appropriate group Foldback Level control.

Overdubbing is particularly easy via the Tape Return sockets just mentioned, although during mixdown it is often desirable to re-route one or more of the multitrack outputs to individual channel inputs for tailoring, especially for 'ping-pong' track bouncing techniques.

One particular routing that took some getting used to was that the Monitor level control on the group output modules also had to be used for setting the stereo mix as well as the L/R master faders in the Master module. But it's necessary to allow the same monitoring levels to be received and also to set up a different level mix from the group outputs.

The more experienced sound engineer may notice certain limitations of the VFM systems, such as lack of 48V phantom power, oscillator tone, EQ cut-out, EQ on tape returns and muting. There's no multiway socket for expanding the system as it's designed to be a completely interchangeable modular system that will not become obsolete as you move from 4 track to 8 and then 16 track recording. As your work turns towards PA rather than studio recording, you can easily change a few modules to update the VFM.

The VFM systems do offer what they claim - a reasonably low cost mixer range that contain the basic functions for PA and recording. The cost cutting lies primarily in the circuitry and therefore I would recommend that you try the VFM out with a local dealer. In terms of quality, the system is quiet in operation and, providing the facilities are sufficient for your requirements, the VFM is well worth the money.

The mixers are competitively priced as follows (ex VAT) 16-4-2 PA and Studio £1,050, 16-8-2 PA and Studio £1,200, 20-4-2 PA version £1,300, 20-8-16 Studio version £1,850.

The Trident VFM MKII mixers are sold in the UK ex-factory by Trident Audio Developments Ltd, (Contact Details). For further details telephone (Contact Details).



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Studio Sound Techniques

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Studio Focus


Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Jul 1983

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