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RSD Studiomaster 16-4-2

Not this year's model, but its continued popularity shows that they got it pretty much right first time.

Recording Studio Design (RSD) are well established in this country providing the Studiomaster range of equipment which caters for a broad range of applications within the audio industry from backline equipment to studio quality mixers. RSD pioneered the idea of add-on expander modules and continue to offer this option with the 16:4:2 under scrutiny here. Extra input channels in groups of four may be added, more than two extra groups requiring the EP2 external power supply. Add-on patch bay modules are also available.

The Studiomaster 16:4:2 is no newcomer to the market but shows its worth by still being available, and unchanged, after nearly two years.


The mixer is thoughtfully designed and constructed with all the controls situated on a forward sloping front panel, and all the in/out sockets on a backward sloping panel which is still accessible whilst sitting in front of the mixer. Wooden end cheeks are used and a cushioned arm rest is provided along the front edge. A useful by-product of the sloping panel design is the lack of anywhere flat enough for any ignoramus to put their beer down. (So it's happened to you too has it?) Internally the modular design philosophy continues with each channel constructed on a separate PCB and all buss connections made using multiway plugs. The faders are also connected to their respective modules by plugs, making it possible to change parts without a soldering iron. The mains transformer for the internal power supply is fully screened to minimise hum pick-up and indeed none was evident. All the pots and switches are of sufficient quality to give a smooth bat positive feel during operation and the 90mm travel faders all incorporate dust covers.

Input Channels

Each of the Studiomaster's 16 input channels offers microphone, line and insert sockets. The mic inputs are made via XLR sockets and are balanced with an input impedance of 2K ohm and an optimum source impedance of 200 ohms. 48V phantom powering is available on these inputs via a switch on the far right of the socket panel. It provides power to all the mic inputs simultaneously so although a mixture of powered and non-powered balanced mics should be satisfactory, unbalanced mics should not be used whilst the phantom powering is switched on.

The line inputs are unbalanced and are made via standard ¼" jack sockets which have an input impedance of 10K ohms. The insert point sockets are stereo ¼" jacks with the send going up the tip of the jack and the return coming back via the ring. The signal for the insert point is post EQ but pre-fader. This maintains the normal operating procedure for the channel whilst providing a healthy level of signal for external signal processing without tying up any of the auxiliaries. Another advantage of break or insert points is that they can be used to take a split feed from the relevant channel as an alternative to tying up valuable patch bay space with paralleled sockets.

In the case of this mixer, by using a stereo jack plug with the tip and ring connected to the signal wire and the screen connected as usual to the sleeve, an output can be taken from the insert point without affecting the through signal to the fader. This signal can then be treated and returned through another input channel or might be used to trigger a synth (for example).

At the top of each input channel is a mic/line switch and a pad switch. The pad attenuates line signals by -18dB and microphone signals by -20dB. Below the pad switch is the input gain control offering up to 60dB of gain for microphones and up to 30dB for line signals.

As is usual amongst mixers, the EQ section is next. Unusually though, this consists of a shelving type treble control offering +16dB at 10kHz and a pair of parametrics. The middle parametric allows +16dB anywhere from 200Hz to 8kHz and the bass parametric offers the same degree of boost or cut anywhere from 25Hz to 350Hz. Under practical conditions this arrangement works very well and seems to allow you to get at all the bits you want. There is an EQ cut switch at the bottom of the EQ section which allows this whole caboodle to be by-passed, something which is worth doing if you are not actually altering the EQ or if you want to make a quick comparison. It's always best not to send an audio signal through any circuitry that it doesn't have to go through.


Further down on the input channel, we are presented with three auxiliary sends, the first and third are post and pre-fade respectively and the second is switchable and can be either. This arrangement allows for either two effects sends and one foldback or vice versa.

The final pot on the input channels is the common or garden pan, closely followed by the channel solo switch. There are many of these dotted around the Studiomaster and when any of them are pushed, their corresponding signal is routed directly to the monitor outputs muting all other signals - a boon for tracking down any stray noises or distortion. Below the solo switch are five routing switches, the first will send the input signal directly to the left and right master outputs and also to the monitor outputs. As would be expected, the channel pan control dictates the relative level of signal to either side of the master outputs. It also sets the left/right position for the monitor outputs which are in stereo. The remaining four routing switches each relate to one of the four sub-groups and can be used in conjunction with the pan control to either, route input signals exclusively to any subgroup, or to create a stereo sub-mix. If you imagine, for example, a drum kit miked up through channels 1 to 6 on the mixer, they can be mixed to a stereo sub-group and the overall level of the drums can then be adjusted using just a pair of faders instead of six. This is achieved by the fact that when the input channel pan is rotated fully to the left it feeds all the selected odd numbered sub-groups exclusively, and conversely all the even numbered sub-groups when rotated to the right. In this way, by selecting sub-groups 1 and 2, for instance, on each of the drum input channels from 1 to 6, the position of the pan control on each of these inputs will dictate the stereo position of that channel across sub-groups 1 and 2.

At the bottom of each input channel inevitably comes the fader which is calibrated logarithmically from infinity (fully faded) up to 0 to give accurate relative level indications, and beside each fader is a red overload LED which fires at 3dB below dipping to warn you if you are about to bump you head. The block diagram shows this overload detector to be post EQ and in use it gives an obvious indication of how easy it can be to upset things by over-zealous use of EQ.


At the top of each of the four sub-groups is a monitor control. This adjusts the level of signal from the sub-group to the stereo monitor outputs and to the left and right master outputs. Each of these four monitor controls has an associated Tape switch. When pressed, this switch routes the outputs from the multitrack tape (which come into the mixer via the first four line inputs on input channels 1 to 4) directly into the monitor bus, bypassing the input channel completely.

Each sub-group has an auxiliary 3 send which in this case is post-fade as opposed to its pre-fade status on the input channels. Below this is the sub-group pan which determines the left/right balance of the sub-group signal to the stereo monitor and master left and right outputs. More solo switches are available here, one for each sub-group, and in common with the operation of all the other solo switches, when pressed a solo LED indicator illuminates below meter number four. This meter then exclusively shows the level of the selected solo signal.

The four sub-group faders are labelled slightly differently to the input channel faders in that they go from infinity to +10. They determine the final signal level available at the four unbalanced jack sub-group outputs on the rear panel as well as to the post fader sub-group busses. Above the fader for sub-group four is a 1 kHz line up oscillator. This tone may be fed to all 4 sub-groups simultaneously and also bussed through to the master outputs by use of the sub-group monitor controls. This useful feature allows rapid line-up of recording levels, tape slating, and system continuity checks.

Above the sub-groups are the master controls relating to the auxiliary outputs and above sub-groups one to three are the auxiliary one to three master sends with their associated solo buttons. Above sub-group four is the master control for the stereo monitor output level. Two stereo jack monitor output sockets are provided on the rear panel, one at 8 ohms for headphones and one at 600 ohms to feed the monitor amp. Although the master monitor control is used to adjust the overall level of volume heard from the monitor speakers, it does not affect the level of signal bussed to the master left and right outputs from the group monitor controls. Also positioned above sub-group four is the talkback to auxiliary three level control and 'press to talk' switch. As its label implies, by plugging an unbalanced mic into the appropriate XLR socket on the rear panel of the mixer, this facility can be used to communicate via the stage monitoring system during PA applications, or to the studio when recording. A 2-track to monitor switch sits above the talkback controls and this allows playback of the 2-track master into the monitor system via a pair of unbalanced 2-track return jack sockets on the rear panel.

Metering on the Studiomaster is taken care of by 6 LED meters, calibrated from -20dB to +3dB, positioned one above each sub-group and master output. They use green LEDs below 0dB and red above.

As previously mentioned, the meter above group four doubles as the level indicator for any solo selection.


The faders for the left and right master outputs are calibrated in the same manner as the group faders and are situated on the far right of the mixer. They feed a pair of unbalanced XLRs at a level of +4dB and a pair of unbalanced jack sockets at a level of -10dB. This admirably sensible arrangement will cater for the vast majority of applications, with most PA and professional recording equipment suiting the +4dB level and most semi-pro gear matching the -10dB level. It can be taken pretty much as read these days that these levels are referenced to a 0dB voltage of 0.775V RMS giving a +4dB real life voltage of 1.23V and -10dB materialising as 0.3V, but even so it is good to note that the Studiomaster hand-book does go to the trouble of spelling it out.

Each of the master faders feeds the outside world via a three band EQ network. These operate over different ranges to the input channel EQ and are not parametric. The treble and bass are shelving types operating at the extremes of the audio band, 20kHz and 20Hz respectively. The middle control offers a reciprocal curve (peak or dip) of 16dB boost or cut at 1.5kHz. The areas in which these equalisers operate would indicate that they have been chosen for corrective rather than creative measures. Being able to roll off the extreme top and bottom will often prove very useful for PA work but I would like to have seen EQ by-pass switches provided for the recording purists.

Between the master output faders and their respective EQ sections are the level controls and routing switches for the auxiliary one and two returns. They are routed to the sub-groups and master outputs in a similar manner to the input channel signals using a pan pot and left-right, 1-2, 3-4 routing switches. Each return also has a solo button.


Once we get to this level of sophistication in a mixer, one would hope that such mundane facts as low noise levels can be taken for granted; but just to be on the safe side...

I first tried an average output, unbalanced, dynamic microphone and got acceptable results, problems only arising when miking from a distance. Not the fault of the mixer, I hasten to add, but a bit of hum and noise induced into the microphone and cable themselves. Switching the microphone cable and plug to ones which allowed the same microphone to be used in balanced mode eliminated this problem and indicated the effective operation of the mixers balancing/unbalancing circuitry. Further tests with condenser mics and line inputs all gave the trouble free results which should be expected.

I particularly like the EQ section on the Studiomaster. The provision of parametric, or should I say sweep equalisers for the mid and bottom allow a good degree of fine tuning. Also, the fact that the bottom parametric can be taken down to 25Hz enables this very low frequency area to be removed thus reducing microphone rumblings without taking out any of the body in a voice for example. The mid parametric extends up to 8kHz so even with the treble EQ fixed at 10kHz, a fair amount of tweaking is still available at the the top end.

Apart from any corrective measures, having two parametrics which can both operate around the lower mid area allows for a good degree of creative twiddling in picking out and highlighting particular points in a sound.

No matter how many auxiliaries are available on a mixer, uses can always be found for more. The three found on the Studiomaster, with one being pre/post switchable, is a sensible arrangement and coupled with the provision of insert points it should offer sufficient versatility for the majority of users.

All mixers have their little idiosyncrasies in terms of routing and layout and two points which caused me to think twice were the placing of the auxiliary sends in line with the sub-groups and the positioning of the returns between the master faders and their respective EQ sections. Having said this, after a bit of use you find your fingers starting to move in the right directions, as I'm sure they eventually would for any layout that was at least semi-logical. So long as everything is within easy reach I think it all boils down to familiarity in the end.

No matter how many outputs your mixer has, and how many patch bays you own, I'm sure most of us small studio owners still find ourselves having to do the odd bit of re-plugging of mixer leads. I found the ease of access to the Studiomaster sockets most helpful, especially as under review conditions far more replugging than usual is going on.

In Use

Once you get involved in routing and sub-groups, the options open to the recordist soar in number. It would be an article in itself to attempt to cover the number of ways in which a 16:4:2 mixer can be used and abused. Suffice it to say the Studiomaster will provide all the ins and outs you will need for any 4-track system without requiring any re-plugging for overdubs or mixdown. There are even choices open as to the way in which you dub or mix, some signals going via sub-groups, some direct to the masters, auxiliaries coming back to groups or masters or through input channels for further treatment, monitoring from source or tape... the list goes on. All the more common modes of operation are available on the Studiomaster and it is hoped that the explanation of the functions and routings for each section, and the inclusion of the block diagram, will make it possible to work out if the mixer is capable of some particularly bohemian requirement you may have.


It is the emergence of equipment such as this which further blurs the already hazy line between semi-pro and professional equipment. On the one hand the Studiomaster 16:4:2 will be within the price range of some serious semi-pros, whilst on the other it offers a performance good enough to satisfy many professional applications.

There is some fairly heavy competition amongst mixers in this section of the market with more than half a dozen manufacturers offering products with similar performance capabilities. It is also amazing the influence that having the letter 'S' as an initial can have... Studiomaster, Soundcraft, Star Sound, Soundtracs, System 8, Sterling Series, Seck. Even up against this lot, at an all in price of £1167.251 think the Studiomaster 16:4:2 represents good value for money.

The Studiomaster 16:4:2 mixer retails for £1167.25 including VAT. For further details contact:- RSD Studiomaster, (Contact Details).

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Logitech CSDD1 Sampling Delay

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Things That Go Boing In The Night

Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.


Home & Studio Recording - Dec 1985

Donated & scanned by: Mike Gorman

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Mixer > Studiomaster > 16:4:2

Review by Martin Sheehan

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